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Solid State Watch: May 9-15, 2014

Friday, May 16th, 2014
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Blog review May 5, 2014

Monday, May 5th, 2014

Jeremy Read of Applied Materials writes that while some consumer IoT applications will require semiconductors manufactured using cutting-edge technologies the vast majority of chips will be used in client-side applications. These chips, such as a sensor monitoring room temperature in a connected HVAC system, require processing capabilities that can be met using legacy process (90 and 45nm) technologies manufactured on 200mm wafers.

Ali Khakifirooz of Spansion notes that body biasing has been long considered as an effective and relatively easy way to compensate for some of the process variations. Not only does it lead to a tighter performance distribution and better yield, but also by mitigating the guardband requirements for process corners and temperature variation, it leads to better performance and faster design cycle.

Frank Feng of Mentor Graphics blogs that transistor and gate levels of library design are normally delivered fully vetted for reliability issues such as electrostatic discharge (ESD), latch-up, electrical overstress (EOS), and dielectric breakdown. However, when designers assemble transistors and gates into intellectual property (IP), blocks, or whole chip designs, they encounter a variety of reliability problems generated across interconnect layers or across device regions of PSUB and NWELL bodies.

Phil Garrou has not been predicting the end of the world, but rather the end of electronics as we know it, i.e.,relying on CMOS scaling. He blogs that it was with great anticipation that he perused the 2013 ITRS roadmap that was released a few weeks ago. He is happy to tell you they are facing the challenges head on although the ultimate solutions are, as we might expect, not yet crystal clear.

Pete Singer writes that the newly revamped International Technology Roadmap for Semiconductors was released in early April. It’s actually called the 2013 ITRS, which makes it seem already out of date, but that’s the way the numbering has always been. The latest ITRS highlights 3D power scaling, system level integration and a new chapter on big data.

Blog review March 31, 2014

Monday, March 31st, 2014

Ofer Adan of Applied Materials blogs about his keynote presentation at the recent SPIE Advanced Lithography conference, which focused on how improvements in metrology, multi-patterning techniques and materials can enable 3D memory and the critical dimension (CD) scaling of device designs to sub-10nm nodes.

Soitec’s Bich-Yen Nguyen and Christophe Maleville detail why the fully-depleted SOI device/circuit is a unique option that can satisfy all the requirements of smart handheld devices and remote data storage “in the cloud.” Devices that are almost always on and driven by needs of high data transmission rate, instant access/connection and long battery life. Demonstrated benefits of FDSOI, including simpler fabrication and scalability are covered.

This year’s IMAPS Device Packaging Conference in Ft McDowell, AZ had a series of excellent keynote talks. Phil Garrou takes a look at some of those and several key presentations from the conference. Steve Bezuk, Sr. Dir. of Package Engineering for Qualcomm discussed “challenges and directions in mobile device packaging”. Qualcomm expects 7 billion smartphone units to be shipped between 2012 and 2017.

Karen Lightman of the MEMS Industry Group writes about the recent MEMS Executive Congress Europe 2014. She describes how every panelist shared not only the “everything’s-coming-up-MEMS” perspective but also some real honest discussion about the remaining challenges of getting MEMS devices to market on-time, and at (or below) cost.

Pete Singer shares some details of the upcoming R&D Panel Session at The ConFab this year. The session, to be moderated by Scott Jones of Alix Partners, will include panelists Rory McInerny of Intel, Chris Danely of JP Morgan, Mike Noonen of Silicon Catalyst and Lode Lauwers of imec.

Roll over flat panel displays

Tuesday, March 25th, 2014

By Sara Ver-Bruggen, contributing editor

Flexible displays is a technological field that has been in R&D and pre-commercial development for several years, but what needs to happen to make volume production a reality, in areas including substrates, materials and production processes? Semiconductor Manufacturing & Design discussed the issues with Max McDaniel, Director and Chief Marketing Officer, Display Business Group, Applied Materials, Michael Ciesinski, MD of the Flextech Alliance, and Keri Goodwin, Principal Scientist from the Centre for Process Innovation (CPI), in the UK.

SemiMD: Taking a step back and looking at the timeline for flexible display R&D and achievements so far, where is the industry in terms of entering volume production – how close is the industry to resolving those outstanding challenges to volume production, such as cost-effective barrier technologies, for example?

McDaniel: Curved displays are here as evidenced by several curved smartphones and TVs showcased at the Consumer Electronics Show (CES) in January 2014. People are ready for flexible displays, but production volume will take some more time. As the smartphone market matures, brands are embattled in a ‘resolution arms race’. The key challenge for the brand makers is to come up with the next big thing that will differentiate their products and spur new demand from consumers. The display plays a key role in defining the device, and a new form factor – like flexible displays – can bring new opportunities to the market, but the technology is not ready for the mass market because of cost and technology challenges.

Ciesinski: FlexTech initiated its R&D program into flexible displays in 1998 with substantial project funding beginning in 2002 and continuing today. We’ve worked with companies and R&D organizations in the areas of substrates, encapsulation, barrier coating, roll-to-roll (R2R) manufacturing and other key areas. Generally, the supply chain for flexible electronics is adequate but not yet robust, which will occur once large volume production is achieved. In building flat panel displays (FPDs) that industry could build on IC manufacturing strengths and simply scale the equipment. For volume manufacturing on a flexible substrate, many new tools and processes have to be developed from scratch, such as metrology, as experts must build a system to account for a substrate that can shrink or expand depending on temperature, and move in multiple directions. As for barriers, several solutions are available and ready for production. The extreme requirements for OLED thin film barriers have been achieved in production and the main focus now is on cost reduction. The materials industry is quite competitive and ready for volume. In order to obtain better utilization of these materials in production new printing equipment is being developed.

Goodwin: There are still significant challenges to overcome in flexible display volume production. A cost-effective flexible barrier with a very low water transmission vapor rate (WVTR) is still to be developed, this will be required if OLED frontplanes are to be used. Typically these barriers are still multilayer structures with a mix of inorganic and organic coatings to minimize defect levels. While this can be achieved R2R, perhaps via a combination of sputter deposition and solution processing such as slot die, the cost will ultimately be set by the number of multiple coatings required.

An alternative method may be to use R2R atomic layer deposition (ALD), which should yield a significantly lower level of defects, thereby improving the barrier capability of a single layer and reducing, or removing, the need for multiple coatings. However, process scale up is required. CPI envisages that R2R ALD will play important roles in various aspects of flexible printable electronics, where highly conformal nanoscale thin films are required. CPI has been evaluating ALD technology for several years and recently signed an agreement with Beneq to deliver an ALD system to CPI for pilot scale production.

Layer-to-layer registration is another major challenge to overcome in volume production with flexible substrates typically distorting during processing. This issue can be overcome in several ways such as development of lower temperature processes or development of lamination materials to allow sheet-to-sheet (S2S) production without distortion.

And, in terms of commercialization for flexible (as opposed to curved) displays what time frame are we talking?

McDaniel: The approach for early adopters of flexible displays has been a production process that adheres the flexible substrate onto glass, running it through what’s mostly the normal rigid OLED processing, and then delaminating that flexible substrate from the rigid one at the end of processing. What remains is a flexible substrate that has all the transistor structures built onto it. However, this is still a complex process, and due to the cost and complexity involved in manufacturing on a high-volume scale, it is still a ways off from full mass production.

Goodwin: Overall, there are multiple approaches to volume production of flexible displays but all require scale up towards a commercialization solution, therefore it would be expected that the timeline for a product is still five years away. What is important in the short term is to demonstrate controlled processes that can yield products with good lifetime and performance, which then can be scaled up for commercialization.

Ciesinski: Displays in a conformable format have been produced and exhibited; a truly flexible and foldable display is much more than that and there are many approaches to achieving this result in the next few years.

Various flexible display R&D has focused on different substrates, different thin film transistor (TFT) materials and so on. Is there likely to be one approach that will make it to volume production?

Ciesinski: Multiple approaches are currently being considered by the market. For example, plastic substrate films from DuPont Teijin and other suppliers have a strong a presence. Corning’s introduction of flexible glass provides a competitive choice. As for the display technology, LCDs, OLEDs and electrophoretic displays have all been built in a flexible format. Materials will continue to improve and there will be multiple TFT materials for the next few years.

McDaniel: Materials have a key role to play in the R&D efforts for enabling flexible displays. OLED is promising as the rigid glass encapsulation required to protect the organic material from moisture and air can be replaced by thin film. You can make flexible LCD displays but maintaining the required cell gap between the color filter and backplane is very difficult to do. Both OLED and LCD require a TFT backplane. A major challenge for the industry is how to move away from rigid glass while not compromising the operation of the TFT when flexed, folded, or bent.

We have discussed the backplane and encapsulation; but for OLED to get to mass production (especially in large sizes); the industry also has to address challenges in EL evaporation such as lifetime of organic materials, low deposition efficiency, low yield from defects and scalability of evaporation technology which affect the cost of volume production but are not necessarily related to the issues around flexibility. All display technologies, including OLED displays, require very high levels of precision in film uniformity and particle control to maintain yield. There is the potential for OLED display production to become less expensive, and Applied Materials is leveraging its expertise in precision materials engineering to help solve these technology hurdles to reduce the cost and complexity.

Goodwin: It is likely that there will be multiple options for volume production. This will depend on final product requirements, such as limits of flexibility, level of resolution of display and cost of display. For example, metal oxide-based TFT displays already demonstrate high performance in terms of the TFT, and therefore can achieve high resolution displays, but ultimately will be very limited in the flexibility.

Organic electronics show excellent flexibility, but historically have tended to have a lower performance for OLED display backplanes and therefore may not achieve the same level of display resolution as metal oxide in the short term. More recently this gap in performance has been closed substantially making organic TFT backplanes a good candidate for a wide variety of display formats and resolutions. In addition OTFT backplanes may ultimately be a lower cost of production. Overall, it is likely that the different TFT technologies will independently develop the substrate types suitable for their processes, for example metal oxide on high temperature substrates and for organics the substrates are likely to be more flexible and suitable for lower temperature processes.

SemiMD: In terms of production equipment and tool advances, which technologies are most promising for enabling volume production of flexible displays?

Goodwin: Metal oxide is currently deposited via industrially used techniques/tools in the display industry, such as sputter deposition. This makes it a likely candidate for early adoption in the display industry, with moderate investment required to enable scale-up. However, solution-processing of organic based materials is likely to provide a lower cost of manufacture via the route of additive printing and R2R manufacture. CPI is working with a number of SMEs in building scale up capability across a range of printed and plastic electronics technology areas such as OLED, OTFT and barrier encapsulation, to help take forward new research ideas into technology prototypes and then into manufacturing demonstrators.

McDaniel: Flexible and other future bendable form factors in display will require precision engineered materials including thin film technologies that deliver performance with stringent uniformity and defect requirements at lower cost and less power. Advances in CVD and PVD systems for LTPS and metal oxide will play an important role in achieving high resolution but even these processes will require materials modification to support the full promise of flexible displays. One example of a required modification is indium tin oxide (ITO), a mainstay process step in TFT-LCD but as a material may prove to be too brittle in the production of more flexible displays.

Applied is also looking to help display makers mass produce larger scale, more efficient manufacturing processes and advanced materials as a means of gaining economies of scale at the factory.

Ciesinksi: FlexTech has funded and successfully completed projects for key steps in flex display manufacturing, such as lithography and deposition. Clearly various printing technologies and RTR additive manufacturing processes are capable of achieving major advances in flexible display production which will be seen over the next few years.

SemiMD: New display technologies that commercialise successfully have done so because they have enabled new products. The mass volume production of LCDs has helped to initiate smart phones, tablet devices, for example, while e-paper (E-Ink) display technology is largely responsible for e-reader devices such as the ubiquitous Kindle. So what potential new class of consumer/portable electronic device might flexible display technology enable? On the other hand, will the technology, in the nearer term, be more beneficial for enabling rugged/unbreakable display-based electronic devices?

McDaniel: There is a lot of potential. Think about what our phones looked like six or seven years ago. Now we’re seeing HD-quality screens on a device we can slip into our pockets. We could see flexible displays enabling devices that can be rolled up or folded into more compact shapes. Some studies have said that for a tablet, people prefer semi-rigid displays to something that is flopping around, to provide structure while they’re reading it. In the public environment flexible could bring the possibility of more immersive or interactive displays at airports or on billboards, or even on the sides of buildings. There are a lot of possibilities.

Goodwin: Rugged displays are likely to have military applications and so may attract funding support from this sector and therefore this may be a route to the first marketable products. However, the learning from the production of those rugged displays can likely be used within new mainstream product development. Many major display manufacturers are already trying to patent areas of interest such as smart watches and early products may focus on these smaller displays. Ultimately, if volume production is possible and large area displays can be produced then there is a vast range of products that can be envisaged from clothing applications, rollable/foldable phones, large scale advertising hoarding or even replacement of aircraft windows with lightweight displays.

Ciesinski: Technology adopters fall into several categories. For example, early adopters are those with the first cellular phone, the first tablet, etc. These users are willing to sacrifice elegance or product maturity for functionality. Other adopters waited until smart phones became fully functional before consolidating to a primary device from a combination of a PC, cell phone, and pager. Wearable electronics, as a class, represents a game-changing technology. A wearable device – even with limited functionality – is attractive, for example, to competitive athletes if it can help improve performance even modestly. Once wearable technology matures, it can explode into other markets to monitor the chronically ill, aged/infirm, or paediatric patients. Then, it jumps to the packaging or automotive or aerospace markets in the form of sensors.

Once flexible display technologies reach volume production, how fast might the technology establish itself – evolve from niche to mainstream?

Ciesinski: Successful technologies ramp quickly and displace incumbent technologies ruthlessly. Just consider the displacement of CRTs by FPDs or CCFL backlights by LED backlights. FlexTech believes that flexible electronics – of which flexible displays is a subset – will grow rapidly in multiple markets, led by disposable and wearable electronics. Our recent user survey indicated substantial purchases of flexible electronics by key end users within three years; adoption by large contract manufacturers is already taking place due to their customer demands.

Goodwin: This is likely to be dependent on the product uptake. For example the rise of tablets and smart phones drove the development of OLED frontplane and materials development. The same is likely to happen with flexible displays. Early products may have limited flexibility, for example the already available curved display products from LG and Samsung, but later products will need to show the truly flexible nature of these advanced displays. Once market pull is established a range of products are likely to be developed that will aid the flexible display to become a mainstream product. CPI can play a vital role in the move from niche to mainstream by providing the infrastructure and environment for companies to de-risk and scale up their innovative ideas from concept to market.

McDaniel: Five years ago, when display manufacturers wanted to start bending and curving the design, they faced a new set of struggles. Applied Materials had insights on where the market was heading and was already working on technologies to address the challenges. We have seen similar waves of technology with laptops and smartphones, and the acceleration of flexible or curved display devices or other form factors could take off in a similar manner. Display analyst firms are anticipating strong growth for the flexible and curved displays market over the next several years. For instance, Touch Display Research has forecast flexible and curved displays to achieve 16% of the global display revenue market by 2023 compared with 1% in 2013.

The Week in Review: March 21, 2014

Friday, March 21st, 2014

Research from University of California, Berkeley scientists sponsored by Semiconductor Research Corporation (SRC) promises to revolutionize portable radio frequency (RF) electronics and communication systems via advancements in on-chip inductors by leveraging embedded nanomagnets. The UC Berkeley research focuses on using insulated nano-composite magnetic materials as the filling material to shrink the size and improve the performance of high frequency on-chip inductors, thereby enabling a new wave of miniaturized electronics and wireless communications devices.

North America-based manufacturers of semiconductor equipment posted $1.29 billion in orders worldwide in February 2014 (three-month average basis) and a book-to-bill ratio of 1.00, according to the February EMDS Book-to-Bill Report published today by SEMI.   A book-to-bill of 1.00 means that $100 worth of orders were received for every $100 of product billed for the month.

Dr. Tzu-Yin Chiu, Chief Executive Officer & Executive Director of SMIC presented the SEMICON China 2014 opening keynote yesterday and was given a SEMI Outstanding EHS Achievement Award.

EV Group (EVG), a supplier of wafer bonding and lithography equipment for the MEMS, nanotechnology and semiconductor markets, today announced that it has opened a new, wholly owned subsidiary in Shanghai, called EV Group China Ltd., which will serve as regional headquarters for all of EVG’s operations in China.  The new subsidiary, which houses a local service center and spare parts management facility, will further strengthen EVG’s presence in the region and support the company’s ongoing efforts to improve service and response times to local customers.

ChaoLogix, Inc., a semiconductor technology provider focused on developing embedded security and low-power design intellectual property, today introduced ChaoSecure technology that deters side channel attacks on semiconductor chips and contributes a superior layer of security compared to existing solutions. ChaoLogix’s ChaoSecure technology is a hardware-based solution designed to provide optimal performance at the nexus of security and power. Proven in silicon and validated by an independent security lab, ChaoSecure is a secure standard cell library that can be easily integrated into an existing integrated circuit (IC) — making it the ideal security solution in terms of cost and performance for designing complex applications ranging from smart cards to smart phones.

Applied Materials, Inc. this week announced that it was named a 2014 World’s Most Ethical Company by the Ethisphere Institute, an independent center of research promoting best practices in corporate ethics and governance. This is the third consecutive year Applied Materials has received the annual award, which recognizes organizations that continue to demonstrate ethical leadership and corporate behavior.

Blog review March 17, 2014

Monday, March 17th, 2014

Pete Singer is delighted to report that Dr. Roawen Chen, Senior Vice Present of global operations at Qualcomm, has accepted our invitation to deliver the keynote talk at The ConFab, on Monday June 23rd. As previously announced, Dr. Gary Patton, Vice President of IBM’s Semiconductor Research and Development Center in East Fishkill, New York, will deliver the keynote on the second day, on Tuesday June 24th.

Phil Garrou takes a look at what was reported at SEMI’s 2.5/3D IC Summit held in Grenoble, focusing on presentations from Gartner, GLOBALFOUNDRIES, TSMC and imec. He writes that GLOBALFOUNDRIES has been detailing their imminent commercialization of 2.5/3D IC for several years, and provide a chart showing the current status report. TSMC offered a definition of their supply chain model where OSATS are now integrated.

Bharat Ramakrishnan of Applied Materials writes about the importance of wearable electronics in the Internet of Things (IoT) era, and the role that precision materials engineering will play. He note that one key part of the wearables ecosystem that is still in need of new innovations is the battery. Two of the biggest challenges to overcome are the thick form factor due to battery size, and the lack of adequate battery life, thus requiring frequent recharging.

Blog review March 10, 2014

Monday, March 10th, 2014

Pete Singer is pleased to announce that IBM’s Dr. Gary Patton will provide the keynote talk at The ConFab on Tuesday, June 24th. Gary is Vice President of IBM’s Semiconductor Research and Development Center in East Fishkill, New York, and has responsibility for IBM’s semiconductor R&D roadmap, operations, and technology development alliances.

Nag Patibandla of Applied Materials describes a half-day workshop at Lawrence Berkeley Lab that assembled experts to discuss challenges and identify opportunities for collaboration in semiconductor manufacturing including EUV lithography, advanced etch techniques, compound semiconductors, energy storage and materials engineering.

Adele Hars of Advanced Substrate News reports on a presentation by ST’s Joël Hartmann (EVP of Manufacturing and Process R&D, Embedded Processing Solutions) during SEMI’s recent ISS Europe Symposium. FD-SOI is significantly cheaper, outdoes planar bulk and matches bulk FinFET in the performance/power ratio, and keeps the industry on track with Moore’s Law, she writes.

Phil Garrou reports on the RTI- Architectures for Semiconductor Integration & Packaging (ASIP) conference, which is focused on commercial 3DIC technology. Timed for release at RTI ASIP was the announcement that Novati had purchased the Ziptronix facility outside RTP NC. Tezzaron had been a licensee of the Ziptronix’s direct bonding technologies, ZiBond™ and DBI® and they now have control of the Ziptronix facility to serve as a second source for their processing. In addition Tezzaron’s Robert Patti announced that they were partnering with Invensas on 2.5 and 3DIC assembly.

Vivek Bakshi, EUV Litho, Inc., blogs that most of the papers at this year’s EUVL Conference during SPIE’s 2014 Advanced Lithography program focused on topics relating to EUVL’s entrance into high volume manufacturing (HVM).

On March 2, 2014 SIA announced that worldwide sales of semiconductors reached $26.3 billion for the month of January 2014, an increase of 8.8% from January 2013 when sales were $24.2 billion. After adding in semiconductor sales from excluded companies such as Apple and Sandisk, that total is even higher, marking the industry’s highest-ever January sales total and the largest year-to-year increase in nearly three years. These results are in-line with the Semico IPI index which has been projecting strong semiconductor revenue growth for the 1st and 2nd quarters of 2014.

Experts At The Table: Commercial potential and production challenges for 3D NAND memory technology

Thursday, February 6th, 2014

The last six months have seen several developments concerning 3D memory concepts moving into production, from companies such as Samsung, Micron, Toshiba and Sandisk. What follows are excerpts from a roundtable discussion with SemiMD, Samsung Electronics (SE) in South Korea, which has begun production of its proprietary 3D NAND technology, Bradley Howard, Vice President of Advanced Technology Group, Etch Business Unit, at Applied Materials and Jim Handy from Objective Analysis, which specialises in coverage of the memory industry.

SemiMD: Where does 3D NAND fit into the long-term roadmap for memory technology and is there one technology most likely to dominate?

SE: We successfully came out with the industry’s first 3D NAND (V-NAND) in August 2013, which offers 128 GB on a chip and vertically stacks cell layers that make use of charge trap flash (CTF) technology. The V-NAND has already been used in 960 GB solid state drives (SSDs) for server and enterprise applications.

The V-NAND technology is expected to replace planar NAND market gradually, starting from the high-end enterprise market. We will continue to come up with more advanced V-NAND products with higher density and reliability. The company has also been working on a diversity of next-generation memory technologies including RRAM (or ReRAM) while strengthening its future business competence.

Howard: All major memory customers have 3D NAND transition in their roadmap. We’ll soon see the first generation of 24-layer 3D cell array devices enter the market. RRAM and STT-MRAM technologies are further out from the market as there are still critical process and manufacturing challenges for both the materials and patterning.

Handy: NAND will dominate. 3D NAND is less disruptive than alternative technologies, like RRAM, since it involves the same materials that have been used to produce NAND for its entire lifetime, while RRAM, MRAM, FRAM and so on require new materials that are not as well understood. After 3D NAND has reached a limit and can no longer place increasing numbers of transistors onto a wafer then the door is opened for alternative technologies like RRAM, but that won’t happen until 2023.

How is the semi industry (such as foundries and designers) preparing for the transition to 3D memory?

Handy: The bulk of the semiconductor industry doesn’t need to transition since these technologies are only being used for the highest-density discrete memory chips. The most significant impact should be to the capital equipment market, where a move to 3D could increase materials equipment usage while decreasing spending on lithography tools.

SE: We are working closely with global IT companies in a wide range of fields to expand the market base and application of 3D V-NAND, and we expect that the market will grow rapidly throughout the year. The 3D V-NAND is expected to be adopted in many different applications including SSDs, high-density memory cards and other applications for consumer electronics. While Samsung will work on more V-NAND based applications, the company also will contribute to global IT companies’ development of next-generation IT systems using our 3D V-NAND products.

Are there specific tooling challenges that must be overcome?

SE: The key technologies for V-NAND would be applying 3D CTF structure for individual cells and constructing vertically interconnected cell arrays. We have mastered these technological challenges and will continue to come up with more advanced V-NAND products.

Howard: Fabricating vertically to build multilayer stacks of 3D NAND cells reduces the historical reliance on lithography as the dominant and limiting factor in scaling, and increases the role of materials-enabled deposition and etch to drive vertical scaling. This shift brings formidable device performance and yield challenges for deposition and etch technologies including distortion-free high aspect ratio etching, complex staircase patterning with precise step-width control, and uniform and repeatable deposition.

From a 3D NAND fab perspective, the changing balance of tool types toward significantly more deposition and etch equipment will have a substantial impact on tool footprint and fab layout to enable optimum manufacturing efficiency. Moreover, this new tool balance compromises the capability to adjust manufacturing capacity between NAND and DRAM since planar NAND and DRAM share a high level of commonality with regard to the balance of tool types and lithography.

Handy: For 3D NAND there are significant challenges in putting down layers that have uniform thickness across the entire wafer. There are also issues with pull-back etching for stairsteps that currently increase the lithography load more than was originally anticipated, but this issue should eventually be solved. For alternative technologies there will be issues in bringing new materials into the fab, some of which are antagonistic to the underlying silicon.

To what extent can 3D memory chips be scaled and what challenges does this pose?

Howard: Scaling for the first few generations, from 32 to 48 to 64 and higher cell layer stacks will largely be a matter of adding more vertical layers. The general consensus is that this is sustainable to around 100 device layers, and this will likely require some amount of reduction on the layer thicknesses to control the aspect ratios that must be etched. Even small reductions in thickness are critical, because any reduction gets multiplied by the number of layers. Scaling beyond this will likely require more effort towards thinning the layers through advancements on the device architecture.

Lithographic-based horizontal scaling will continue, but instead of the historical 15-20 percent CD reduction per generation, we expect planar scaling to slow dramatically, equivalent to a CD shrink more on the order of ~5 percent per generation. In addition, layout changes in the peripheral circuits to achieve more efficiency, along with more efficient designs for the complex staircase structure to allow for access to the different layers, are expected. These will all play a role in overall die size efficiency.

For deposition, major challenges to effectively scale vertically are advanced thickness and uniformity controls layer to layer. Any non-uniformity in a film layer will propagate throughout the stack as subsequent layers are deposited on top of it. With more layers in the device stack, this results is more devices potentially impacted by topography.

The challenge for etch is growing high aspect ratios despite a thinning down of individual layers in the stack. Aspect ratios today are already at 60:1. Achieving etch fidelity at such aspect ratios puts pressure on getting higher selectivity to the mask material which already is very thick. In some cases, the aspect ratio for the hard mask is already greater than 20:1, and this is the aspect ratio before even starting the etch into the device stack. While thinning the hard mask layer reduces the overall aspect ratio of the feature, new more resilient patterning films will be required. Higher selectivity will be through a combination of new materials with higher etch resistance and improvements to the etch process chemistry.

SE: We have core technologies to develop more advanced high-density V-NAND devices and are seeking to define manufacturing technologies for stacking more than 24-cell-layer structure which was applied to our first 3D V-NAND device.

The most advanced process technology for conventional NAND using floating gate would be 10 nm-class technology. However, process technology refers to the width of integrated circuitry that is used for NAND on a conventional planar structure. Applying the same considerations to our V-NAND would not be appropriate because the cell array structure has been totally changed.

For example, if we compare the wafer productivity of Samsung’s new 128 GB V-NAND to previous products, it has the approximate chip size of a conventional NAND that was built using approximately mid-10nm-class process technology.

The 3D V-NAND has its strength in scalability. There are plans to continue developing more advanced V-NAND products and applications including 1 TB and higher-density SSDs for servers and enterprise systems and other next-generation memory storage which should lead to the growth of the overall NAND flash market.

Handy: 3D NAND is expected to scale in height, from 16-bit-tall strings to string heights of more than 128 bits. Meanwhile NAND makers will probably find ways of placing these strings closer to each other through more aggressive lithography. There is a lot of room for scaling in 3D.

Everything in 3D is a significant challenge. With vertical scaling the challenges include etching high aspect ratio holes, with the aspect ratio doubling with each doubling of layers. These holes must have absolutely parallel walls or scaling and device operation may be compromised. If the layers are thinned then the atomic layer deposition (ALD) of the layers must be able to apply a constant thickness layer across the entire wafer. This is also true of the layers that are deposited on the walls of the hole. The entire issue of 3D is its phenomenal complexity.

3D NAND: To 10nm and beyond

Wednesday, January 29th, 2014

By Sara Ver-Bruggen, contributing editor

In launching the iPod music player, Apple bumped consumption of NAND flash – a type of non-volatile storage device – driving down cost and paving the way for the growth of the memory technology into what is now a multibillion dollar market, supplying cost-effective storage for smart phones, tablets and other consumer electronic gadgets that do not have high density requirements.

The current iteration of NAND flash technology, 2D – or planar – NAND, is reaching its limits. In August 2013, South Korean consumer electronics brand Samsung announced the launch of its 3D NAND storage technology, in the form of a 24-layer, 128 GB chip. In 2014, memory chipmakers Micron and also SK Hynix will follow suit, heralding the arrival of a much-anticipated and debated technology during various industry conferences in recent years. Other companies, including Sandisk, are all working on 3D NAND flash technology.

Like floors in a tower block, in 3D NAND devices memory cells are stacked on top of each other, as opposed to being spread out on a two-dimensional (2D), horizontal grid like bungalows. Over the last few decades as 2D NAND technology has scaled, the X and Y dimensions have shrunk in order to go to each chip generation. But scaling, as process nodes dip below 20nm and on the path towards 10nm, is proving challenging as physical constraints begin to impinge on the performance of the basic memory cell design. While 2D NAND has yet to hit a wall, it is a matter of time.

Transition to mass production

But despite the potential of 3D NAND and announcements by the leading players in the industry, transferring 3D NAND technology into mass production is very challenging to do. As Jim Handy, from Objective Analysis, points out: “The entire issue of 3D NAND is its phenomenal complexity, and that is why no one has yet shipped a 3D NAND chip yet.” Mass production of Samsung’s device will happen this year. With 3D NAND there is the potential for vertical scaling, going from 16-bit-tall strings to string heights of more than 128 bits.

But while 3D NAND does not require leading-edge lithography, eventually resulting in manufacturing costs that are lower than they would be for the extension of planar NAND, new deposition and etch technologies are required for high-aspect-ratio etch processes. This “staircase” etching requires very precise contact landing. In 3D NAND manufacturing depositing layers of uniform thickness across the entire wafer presents issues with pull-back etching for these “stair steps” that currently increase the lithography load more than was originally anticipated.

Staircase etching requires very precise contact landing.

“Everything in 3D is a significant challenge. With vertical scaling the challenges include etching high aspect ratio holes, with the aspect ratio doubling with each doubling of layers. These holes must have absolutely parallel walls or scaling and device operation may be compromised. If the layers are thinned then the atomic-layer deposition (ALD) of the layers must be able to apply a constant thickness layer across the entire wafer, which is also true of the layers that are deposited on the walls of the hole,” according to Handy.

Indeed, while the best combination of cost, power and performance will be found in 3D NAND architectures, there still remain issues concerning cost, especially. These issues, in the context of their respective memory technology roadmaps, were discussed by memory chipmakers, including Sandisk, SK Hynix and Micron, at a forum organized and sponsored by semiconductor industry equipment manufacturer Applied Materials in December 2013, while the equipment supplier provided some in-depth discussion on 3D NAND manufacturing considerations and challenges. The session was hosted by Gill Lee, Senior Director and Principal Member of Technical Staff Silicon Systems Group at Applied Materials.

Sandisk plays its 2D hand for as long as possible

Ritu Shrivastava, Vice President Technology Development, at Sandisk Corporation, set out the challenge. “Whenever you talk about technology, it has to be in relation to the objectives of your company. In our case we have a $38 billion total available market projected to 2016 and any technology choices that we make have to serve that market.” Examples of products he was referring to include smart phones and tablets. “Our goal is to choose technologies that are most cost-effective and deliver in terms of performance.”

Sandisk has a joint NAND fab investment with Toshiba and the two have had a 128 GB 2D NAND flash chip using 19 nm lithography in production for a while now. They have also previously announced plans to build a semiconductor fab for 16-17 nm flash memory.

”One of our goals is to extend the life of 2D NAND technologies as far as possible because it reflects the huge investment that we have made in fabs and the technology, over the number of years,” said Shrivastava. “Of course, 3D NAND is extremely important and when it becomes cost-effective then it will move into production.” Sandisk plans to start producing its 3D NAND chips in 2016.

“We are travelling in what we think is the lowest cost path in every technology generation, going from 19 nm to 1Y where we at the limit with lithography, and then we will scale to 1Z, which is our next-generation 2D NAND technology. We believe that this scaling path gives us the lowest cost structure in each of the nodes and in terms of cumulative investment.”

But it is not just achieving the smallest die size, it is the cost involved in scaling. Capital equipment investment is what determines success in the market, according to Shrivastava. “Even though we are saying that 3D NAND is a reality there are a couple of things that we need to keep in mind. It leverages existing infrastructure, which is good, but there are still a lot of challenges. 3D NAND devices use TFT as opposed to the floating gate devices commonly used in 2D NAND chips. New controller schemes and boards will be required also.”

So while, according to Shrivastava, 3D NAND is looking very promising, there is a big ‘but’ for a company such as Sandisk, which produces some of the most cost-competitive flash memory devices on the market. “2D NAND still continues to be more cost-effective than 3D NAND and 3D NAND is not yet proven in volume manufacturing. Every new technology takes some time. Getting to mass manufacturing will take time. Our goal is to extend 2D NAND as long as possible, continue to work on 3D NAND and introduce it when it becomes cost-effective.”

Shrivastava sees 2D and 3D NAND technologies co-existing for the rest of the decade. Beyond 3D NAND the company is developing a 3D resistive RAM (RRAM) as the future technology beyond 3D NAND.

From 3D DRAM to 3D NAND

Next Chuck Dennison, Senior Director Process Integration, from Micron, provided an overview of where the company is today in terms of its own NAND memory technology roadmap.

“Our current generation is 16nm NAND that is now in production and we’re showing that it is getting to be a very competitive and very cost-effective technology,” according to Dennison. Micron’s new 16nm NAND process provides the greatest number of bits per sq mm at the lowest cost of any multilayer cell (MLC) device. Eight of these die can hold 128 GB of data. The 16nm storage technology will be released on next-generation solid state drives (SSDs) during 2014. SSDs consist of interconnected flash memory chips as opposed to platters with a magnetic coating used in conventional hard disk drives (HDDs).

Micron 16nm NAND die

“Our next node is a 256 GB class of the NAND memory. Technically it could be extended before taking the full step to 3D NAND.”

Today NAND is the lowest cost-per-bit memory technology and this continued cost-per-bit reduction is really driving the whole of the NAND industry, according to Dennison. It is why NAND replaced DRAM in terms of total dollars and has continued to proliferate across various applications, and is responsible for continued innovation in portable consumer electronics, such as tablets, where so much functionality enabling photography, video recording, storage of an entire music library, and so on, can be packed into one device.

Outlining Micron’s technology scaling path, Dennison explained: “We went to high-K/metal gate to 20 nm and we used the same technology to extend us to 16nm. From there, the company is moving to a vertical channel 3D NAND for a 256 GB class.

“In terms of capital expenditure (CapEx) per wafer it all looks very cost-effective, with a little bit of transition going to 20 nm,” explained Dennison, because of the high-K metal gate, but with minimal increase going to 16nm. “But when you go to 3D NAND it is expensive, per wafer. So if you are increasing your wafer costs by X amount you need a much higher amount of GB per cm sq, so the density we are choosing to go with is a 256 GB class. And when you start actively looking at 3D NAND there are a lot similarities between 3D NAND and DRAM,” he explained, referring to the stacked capacitor of DRAM. “There is a lot planarization, you are etching very high aspect ratio contacts where you need to be very controlled, in terms of how you define your control and CD uniformity. Then there are a lot of additional modules requiring ALD deposition. So we think that there is a lot of opportunity to utilize our DRAM expertise.”

He outlined an inflection point going from 16nm, again. “We’re transitioning to go to the 256 GB density. We think that when we do this it will make financial sense and it will be a cost-effective solution despite the high Capex. And then from there we will continue. With the majority, or bulk, of the market we’ll see vertical NAND continuing to scale with a couple of us scaling fast for that market.”

Dennison also touched on longer term advances in classes of flash memory, in the form of 3D cross-point technology. These are memories stacked in cross-point arrays over CMOS logic to enable memory technology with speed features akin to DRAM but the density and cost effectiveness of NAND. The 3D stacked memory arrays in 3D cross-point technology would make these devices suitable, for future, in very high density computing and even biological systems.

“But, to conclude, NAND will not be replaced and will continue to be the lowest cost, it’s going to be the largest market in tablets, phones and so on. It’s not the best memory technology – it has poor cycling endurance and it has a terrible latency – but it is very low cost at very high density so it is the most cost-effective solution. We think that 3D cross-point absolutely has a market in terms of displacing DRAM and will selectively displace some NAND in very high performance applications but we will stay with NAND and go to 3D NAND.”

Soek-Kiu Lee, VP and Head of the Flash Device Technology Group, at SK Hynix brought the audience up to speed on his company’s NAND technology. Every year SK Hynix has increased bit density per area by around 50%. The company’s 16nm 64 GB MLC NAND flash, based on floating gate technology, has been in production since mid-2013 with SK Hynix now entering full scale mass production of 16nm chips. SK Hynix will start to ship samples of its 3D NAND chips this year with mass production happening later in 2014.

Like Shrivastava, Lee expects that 2D NAND and 3D NAND will co-exist and compete with each other in terms of reliability, performance and density, for some time and that the big challenges facing the transition to 3D NAND architectures include stabilization of multi-stack patterning to improve yields, better metrology and defect monitoring in the 3D structure itself.

Head for heights

Lastly, Applied Materials was able to provide some insight into manufacturing the more complex structures that moving to 3D NAND device architecture entails. Very simplistically, to make 3D NAND flash devices requires building extremely tall multilayer structures. Every layer in the device requires an insulating layer, so – for example – a 32-layer device is really a 64-layer device. As a result of this, aspect ratios of the structure being etched are getting to be very high and the challenge that this poses is nothing less than a game-changer for etch and deposition, according to Applied Materials’ Vice President, Advanced Technology Group Etch Business Unit, Bradley Howard.

“Historically, if you look at how scaling has gone, it has been limited by lithography on getting to the next node down, now we getting to the point where scaling is being driven by deposition and etching because as the scaling is now going in a vertical direction you’ve eased out the design rules.” The reality is that lithography is still important, Howard said, listing off control, good uniformity and other factors. ‘Everything that you had to have from lithography before still needs to be there but it just does not need to be the limiting factor for scaling.”

High aspect ratios present lots of challenges. Standard photolithography will not hold up for the long etches required for etching such deep features so hard mask layers are needed. “Depositioning is transitioning from single layer depositions in typically thinner films to multilayer stacks where you go and deposit alternating stacks of films and then also very thick films for both device and the hard mask,” said Howard.

Howard addressed the gates axis, an alternating stack of materials built up with alternating layers. “You need to have very precise control and very low defectivity. Historically, if you had a defect come in on a film it affected that bit, or that area. Now if you get a defect that gets deposited on your first layer down at the bottom it becomes a propagating defect that goes up the entire stack and it is going up in regions , which means that the defect density on deposition is becoming more important.”

Howard then moved on to hard masks. “We are going to have thicker hard masks because the aspect ratios of what you are trying to etch are getting very extreme as well as the amount of depth you have to etch. Having a micron or a micron-and-a-half of hard mask is not unusual. In effect, the hard mask that you are forming is its own high aspect ratio feature and then it is forming a high aspect ratio feature below it. In addition, there are various challenges on the isolation on getting the gap filled between the features and also into these very complex three dimensional structures.

“On the etch side high aspect ratio is really the key. There are multiple features, contacts in the array, there are contacts coming out of the staircase, and 60: 1 aspect ratios are becoming the common target here.

“At the edge of the array access still has to be made at each one of the layers, so a staircase structure is made to enable different landing pads for contacts to come down. But some of the contacts – towards the top – are very shallow and the ones at the bottom are extremely deep.

“You might think it might be achieved by doing a litho step and an etch step and a litho step and an etch step and doing that 32, 64, or whatever number of times, but what happens is that you are starting out with a feature and you etch down into the feature then you pull back the resist and then you etch again and then you pull back the resist and so you start to form your ‘steps’ that way and you do that as many times as you can get away with, depending on the amount of resist that you have. So, you can envision that you are trying to pull this resist back really fast. The problem is the resist is now determining the CD for the cell, so you need to have good control in place.” Howard summarized the challenges as being about sequential processes for both deposition and etching, thick films – whether it be the alternating stack of films or the thick films that are done to separate out the different arrays – and, finally, defect densities – especially with deposition – which are becoming more critical than ever before because of the additive effect on the deposition.

The panellists:

Dr Ritu Shrivastava, Vice President Technology Development, at SanDisk Corporation

Chuck Dennison, Senior Director, Process Integration, at Micron

Dr Soek-Kiu Lee, VP and Head of the Flash Device Technology Group, at SK Hynix

Hang-Ting Liu, Deputy Director Nanotechnology R&D Division, at Macronix International Co.

Dr Bradley Howard, Vice President, Advanced Technology Group Etch Business Unit, at Applied Materials

Experts At The Table: Exploring the relationship between board-level design and 3D, and stacked, dies

Tuesday, December 17th, 2013

By Sara Verbruggen

SemiMD discussed what board level design can tell us about chip-level (three-dimensional) 3D and stacked dies with Sesh Ramaswami, Applied Materials’ Managing Director, TSV and Advanced Packaging, Advanced Product Technology Development, and Kevin Rinebold, Cadence’s Senior Product Marketing Manager. What follows are excerpts of that conversation.

SemiMD: What key, or major, challenge does the transition to 3D and stacked dies – and increasingly ‘advanced packaging’ – present when it comes to board-level design?

Ramaswami: The three-layer system architecture comprising the printed circuit board (PCB) system board, organic packaging substrate and silicon die offers the greatest integration flexibility. From a design perspective, this configuration places the most intensive co-design challenges on the die and substrate layers. On the substrate, the primary challenges are dielectric material, copper (Cu) line spacing and via scaling. However, when the packaged die attaches to the PCB through the ball grid array (BGA), surface-mount packaging, used for used for integrated circuits for devices such as microprocessors, the design challenges are more considerable. For example, they include limitations on chip size (I/O density), warpage and worries about co-efficient of thermal expansion mismatch between the materials.

Rinebold: Any advanced ‘BGA style’ package, regardless if it is three-dimensional (3D) or flat can have a significant impact on PCB layer count, route complexity, as well as cost. Efficient package ball pad net assignment and patterning of power and ground pins can make the difference between a four-layer and a six-layer PCB. Arriving at the optimal ball pad assignment necessitates coordinated planning across the entire interconnect chain from chip level macros to board level components. This planning requires new tools and flows capable of delivering a multi-fabric view of the system hierarchy while providing access to domain specific data like macro placement, I/O pad ring devices, bump patterns, ball pad assignments, and placement of critical PCB components and connectors.

SemiMD: 3D chip stacking and stacked die chip-scale packaging is favoured by the consumer electronics industry to enable better performing mobile electronics – in terms of faster performance, less power hungry devices, and so forth – but how do PCB design and testing tools need to adapt?

Rinebold: One benefit of these package formats is that they entail moving most of the high-performance interconnect and components off the PCB onto their own dedicated substrate. With increasing data rates and lower voltages there is little margin for error across the entire system placing a premium on signal quality and power delivery between the board and package.

In addition to high-speed constraints and checking, design tools must provide innovative functionality to assist the designer in implementing high-performance interconnect. In some situations complete automation (like auto-routing) cannot provide satisfactory results and still enforce the number of diverse and sometime ambiguous constraints. Designers will require auto-interactive tools that enable them to apply their experience and intuition supported by semi-automatic route engines for efficient implementation of constraints and interconnect. Example of such tools include the ability to plan and implement break-out on two ends of an interface connecting to high pin count BGAs to reduce route time and via counts. Without such tools the time to route high pin count BGAs can increase significantly.

Methodologies must adapt to incorporate electrical performance assessment (EPA) into the design process. EPA enables designers to evaluate electrical quality and performance throughout the design process helping avoid the backend analysis crunch – possibly jeopardizing product delivery. It utilizes extraction technology in a manner that provides actionable feedback to the designer helping identify and avoid issues related to impedance discontinuities, timing, coupling, or direct current (DC) current density.

SemiMD: More specifically, what impact will this trend towards greater compactness – i.e. smaller PCB footprint, but with more stacked dies and complex packaging – have on interconnection technologies?

Ramaswami: The trend towards better quality, higher-component density PCBs capable of supporting a wide range of die has significant implications for interconnect design. An additional challenge, is attaching complex chips on both sides of a board. Furthermore, with PCBs going thinner to fit the thin form factor requirements for mobile devices, dimensional stability and warpage must be addressed.

Rinebold: In some regards stacked applications simplify board level layout by moving high-bandwidth interconnect off the PCB and consolidating it on smaller, high density advanced package substrates. However, decreasing package ball pad pitch and increased pin density will drive use of build-up substrate technology for the PCB. This high density interconnect (HDI) enables smaller feature sizes and manufacturing accuracy necessary to support the fan-out routing requirements of these advanced package formats. Design tools must support HDI constraints and rules to ensure manufacturability along with functionality to define and manipulate the associated structures like microvias.

SemiMD: How will PCB manufacturing processes, tools and materials need to change to address this challenge?

Ramaswami: To manufacture a more robust integrated 3D stack, I think several fundamental innovations are needed. These include improving defect density and developing new materials such as low warpage laminates and less hygroscopic dielectrics. Another essential requirement is supporting finer copper line/spacing. Important considerations here are maintaining good adhesion while watching out for corrosion. Finally, for creating the necessary smaller vias, the industry needs new etching techniques to replace mechanical drilling techniques.

SemiMD: So as 3D chip stacking and stacked dies become more mainstream technologies, how will board level design need to develop, in the years to come?

Rinebold: One challenge will be visibility and consideration of the PCB during chip-level floor-planning and awareness of how decisions made early on impact downstream performance and cost. New tools that deliver a multi-fabric view of the system hierarchy while providing access to domain specific data will facilitate the necessary visibility for coordinated decision making. However these planning tools are just one component of an integrated flow encompassing logic definition, implementation, analysis, and sign-off for the chip, package, and PCB.

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