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Posts Tagged ‘22nm’

Solid Doping for Bulk FinFETs

Monday, January 5th, 2015


By Ed Korczynski, Sr. Technical Editor

In another example of the old one-liner that “all that is old is new again,” the old technique of solid-source doping is being used by Intel for a critical process step in so-called “14nm node” finFET manufacturing. In the 7th presentation in the 3rd session of this year’s IEDM, a late news paper written by 52 co-authors from Intel titled “A 14nm Logic Technology Featuring 2nd-Generation FinFET Transistors, Air-Gapped Interconnects, Self-Aligned Double Patterning and a 0.0588m2 SRAM Cell Size” disclosed that solid source doping was used under the fins.

As reported by Dick James of Chipworks in his blog coverage of IEDM this year, the fins have a more vertical profile compared to the prior “22nm node” and are merely 8nm wide (Fig. 1). Since Intel is still using bulk silicon wafers instead of silicon-on-insulator (SOI), to prevent leakage through the substrate these 8nm fins required a new process to make punch-through stopper junctions, and the new sub-fin doping technique uses solid glass sources. Idsat is claimed to improve by 15% for NMOS and 41% for PMOS over the prior node, and Idlin by 30% for NMOS and 38% for PMOS.

FIGURE: Intel Corp’s “14nm node” finFETs show (in the left SEM) 8nm wide and 42nm high fins in cross-section, below which are located the punch-through stopper junctions. (Source: IEDM 2014, Late News 3.7)

Solid glass sources of boron (B) and phosphorous (P) dopants have been used for decades in the industry. In a typical application, a lithographically defined silicon-nitride hard-mask protects areas from a blanket deposition in a tube furnace of an amorphous layer containing the desired dopant. Additional annealing before stripping off the dopant layer allows for an additional degree of freedom in activating dopants and forming junctions.

In recent years, On Semiconductor published how solid-source doping on the sidewalls of Vertical DMOS transistors enable a highly phosphorous doped path for the drain current to be brought back to the silicon surface. The company shows that phosphorous-oxy-chloride (POCl) and phospho-silicate glass (PSG) sources can both be used to form heavily doped junctions 1-2 microns deep.

The challenge for solid-source doping of 8nm wide silicon fins is how to scale processes that were developed for 1-2 microns to be able to form repeatable junctions 1-2 nm in scale. Self-aligned lithographic techniques could be used to mask the tops of fins, and various glass sources could be used. It is likely that ultra-fast annealing is needed to form stable ultra-shallow junctions.

Intel is notoriously protective of process Intellectual Property (IP) and so has almost certainly ensured that any equipment and materials suppliers who work on the solid-source doping process sign Non-Disclosure Agreements (NDA) with amendments that forbid acknowledging signing the NDA itself, so it is pointless to directly ask for any further details at this point. However, slides from John Borland’s recent presentation at the NCCAVS Junction Technology Users Group meeting provide a great overview of the publicly available information on finFET junction formation, and include the following:

…higher dopant activation can be realized at low temperatures if the junction is amorphous and recrystalized by using SPE (solid phase epitaxy) recrystalization of the junction as also shown in the data by Intel.

Also seen at IEDM this year in the 7th presentation of the Advanced Process Modules section, Taiwanese researchers—National Nano Device Laboratories, National Chiao Tung University, and National Cheng Kung University—joined with Californian consultants—Current Scientific, Evans Analytical Group—to show “A Novel Junctionless FinFET Structure with Sub-5nm Shell Doping Profile by Molecular Monolayer Doping and Microwave Annealing.” They claim an ideal subthreshold swing (~60 mV/dec) at a high doping level. Poly-Si n & p JLFinFETs (W/L=10/20 nm) with SDP experimentally exhibit superior gate control (Ion/Ioff >10E6) and improved device variation.


The Week in Review: Dec. 20, 2013

Friday, December 20th, 2013

3DIC memory, and therefore all of 2.5/3D technology, took one step closer to full commercialization last week with the HBM joint development announcement from AMD and Hynix at the RTI 3D ASIP meeting in Burlingame, CA. Bryan Black, Sr Fellow and 3D program manager at AMD noted that while die stacking has caught on in FPGAs and image sensors “..there is nothing yet in mainstream computing CPUs, GPUs or APUs” but that “HBM (high bandwidth memory) will change this.”  Black continued,  “Getting 3D going will take a BOLD move and AMD is ready to make that move.” Black announced that AMD is co-developing HBM with SK Hynix which is currently sampling the HBM memory stacks and that AMD “…is ready to work with customers.”

ABI Research verified that Intel has a leading position in the mobile processor technology race; launching the first 22nm mobile application processor. The 22nm quad-core application processor (Intel Z3740D) was found in a Dell tablet that was recently launched for the Christmas season. “2013 saw a number of new processor launches with 32nm and 28nm technology (most from fabless companies) but Intel has used one of its core advantages [process technology] to pass them all,” Jim Mielke, VP of engineering at ABI Research, commented. “The 22nm process node used for the Z3740D is not just the smallest geometry in a mobile device today; it also introduces a new transistor. The core transistor structure used in the 22nm Z3740D is quite different than structures used in previous generations. The core transistor found in the device ABI Research analyzed has a gate that surrounds source/drain diffusion fins on three sides giving it the name tri-gate or 3D transistor.

North America-based manufacturers of semiconductor equipment posted $1.24 billion in orders worldwide in November 2013 (three-month average basis) and a book-to-bill ratio of 1.11, according to the November EMDS Book-to-Bill Report published today by SEMI.   A book-to-bill of 1.11 means that $111 worth of orders were received for every $100 of product billed for the month. “The continuing rise in equipment bookings clearly points to year-end order activity that is substantially stronger compared to one year ago,” said Denny McGuirk, president and CEO of SEMI.  ”This trend supports the current outlook showing a rebound in equipment spending for 2014.”

Soitec and CEA have renewed their partnership for the next five years. This new contract aims to support Soitec’s strategy for the electronics, solar energy and lighting markets. It will focus on engineered substrates and materials offering higher performances and energy savings at a competitive cost. As the new partnership is putting in place a powerful R&D ecosystem, time from research to product will be considerably reduced. Thanks to the strengths of CEA-Leti in electronic materials, multi-domain research and its pre-industrialization infrastructure, competitive R&D sample prototyping will be enabled thru a common platform, reducing time to market and R&D costs for Soitec and its customers.

Micron Technology, Inc. announced its collaboration with Broadcom Corporation to develop the industry’s first solution designed for customers challenged by an intrinsic DDR3 timing parameter called tFAW, or four activate window.

EUV Flare And Proximity Modeling And Model-Based Correction

Thursday, May 16th, 2013

The introduction of EUV lithography into the semiconductor fabrication process will enable a continuation of Moore’s law below the 22 nm technology node. EUV lithography will, however, introduce new and unwanted sources of patterning distortions which must be accurately modeled and corrected on the reticle. Flare caused by scattered light in the projection optics is expected to result in several nanometers of on-wafer dimensional variation, if left uncorrected. Previous work by the authors has focused on combinations of model-based and rules-based approaches to modeling and correction of flare in EUV lithography. This paper focuses on the development of an all model-based approach to compensation of both flare and proximity effects in EUV lithography. The advantages of such an approach in terms of both model and OPC accuracy will be discussed. In addition, the authors will discuss the benefits and tradeoffs associated with hybrid OPC approaches which mix both rules-based.

To view this white paper, click here.