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New Materials: A Paradox of the Unknown

Thursday, March 17th, 2016


By Pete Singer, Editor-in-Chief

The semiconductor industry has slowly been implementing a growing array of new materials in an effort to boost speed and performance, reduce power consumption and reduce leakage. From the 1960s through the 1990s, only a handful of materials were used, most notably silicon, silicon oxide, silicon nitride and aluminum. Soon, by 2020, more than 40 different materials will be in high-volume production, including more exotic materials such as hafnium, ruthenium, zirconium, strontium, complex III-Vs (such as InGaAs), cobalt and SiC (Figure 1).

Figure 1

At the same time, semiconductor manufacturing processes are executed at the atomic level. Atomic layer deposition, atomic layer etching and atomic layer epitaxy are now common.

One of the challenges with new materials and atomic-level processing is that new and unexpected reactions can occur due to the trace impurities in the gases used during production. These impurities may be organic materials or trace levels of oxygen, nitrogen or other elements.

Jean-Charles Cigal

Jean-Charles Cigal, market development manager at Linde in Pullach, Germany, said a growing concern is that gases that have the same specification as before suddenly are not working the same way. “There are a lot of impurities that weren’t a problem before. They are now reacting because you have new materials on the wafer,” he said. “Process engineers don’t know what to look at in terms of impurities. That’s the paradox of the unknown.”

To help customers avoid such problems, gas supplier Linde has implemented tools commonly used in the semiconductor industry, including statistical process control (SPC), statistical quality control (SQC) and a lab information management system (LIMS). “The advantage of having this statistical process strategy is the ability to more rapidly correct any quality issue,” Cigal said.

A “fingerprinting” strategy also comes into play. “We’re using broad spectrum analyzers to get a lot of data and check everything possible. We want to do detection and correction of any quality issue before it reaches the fab,” Cigal said. If an unexpected quality issue is later identified at the fab, Linde can step in with forensic analysis using a database of information.

It is not cost-effective to simply specify higher and higher levels of purity. Instead, Cigal says targeted specifications are now the norm. “In the past, people were asking for the highest purity. Give me a 7.0 silane. Now they are saying OK, give me a silane with 5.0 but I don’t want this organic material,” he said. Linde’s HiQ portfolio offers more than 100 different pure gases such as HiQ Nitrogen 5.0 and HiQ Argon 6.0. Purity is commonly expressed as a two digit number. For example, Helium with a purity of 99.9996% would be described as HiQ Helium 5.6 with the 5 representing the number of nines, while the 6 represents the first digit following the nines.

“What we want ultimately is to get a full picture of what is inside (the gas) and to make the customer aware,” Cigal said. “We don’t know everything about the customers’ processes, but Linde is building large database that will help electronics manufacturers identify what impurities might react in certain processes.”

Customers are now asking for specifications just under the detection limits. We are continuously acquiring analytical tools that will help them to better understand the composition of their materials, which ultimately helps to improve their manufacturing yield.

The semiconductor industry demands very high-purity materials and yet electronics materials suppliers often receive raw materials of very low quality. To ensure that customers get the high-quality materials they require, Linde takes on the responsibility of being the quality gate keeper and controls the whole supply chain – from the source, through purification, and transportation.

Editor’s Note: Jean-Charles Cigal is currently Market Development Manager at Linde Electronics. In his role, Jean-Charles supports electronics customers and equipment manufacturers to achieve their roadmap with the introduction of new processes and materials. He joined Linde as principal technologist in 2009, where he was technology consultant for the semiconductor and the photovoltaic industry.  Prior to joining the Linde Group, Jean-Charles worked several years as senior process engineer in the semiconductor industry. He owns a M.Sc. in Applied Physics from Pierre et Marie Curie University, Paris, France, and a PhD in Applied Physics from Eindhoven University of Technology, the Netherlands.

Sustainability through Materials Recovery

Wednesday, July 16th, 2014

By Paul Stockman, Linde Electronics

Increased costs of development and manufacturing are challenging the continuation of Moore’s Law. Manufacturing processes are dependent on critical materials supplied by complex, global supply chains. Additionally, regulations are increasing and there is more of a demand for and focus on green manufacturing. To stay competitive and lay the foundation for sustainable manufacturing processes, electronics manufacturers need supply chain security, flexible logistical solutions, and a lower carbon footprint.

Because manufacturing plants are often located far from the source of materials, some materials are rare and/or difficult to procure, and being good environmental stewards is imperative to companies, recovering and reusing materials is becoming an increasingly essential consideration in order to ensure consistent quality, a stable supply of materials, and lower costs.

Linde offers three main types of material recovery solutions:

  1. On-site, closed-loop recovery – Materials are recovered on site, purified, and are available for re-use in the manufacturing process.
  2. On-site, open-loop recovery – Materials are recovered on site and are available for use in other applications.
  3. Off-site recovery – High-cost materials are recovered, shipped off site, and purified at an external facility for re-use.

Helium, argon, sulfuric acid, and xenon are vital to electronics manufacturing and are among the materials that offer real value when recovered.

On-site, closed-loop recovery

Helium, fairly rare on earth and a finite resource, is the second lightest element and the coldest liquid, making it useful in electronics manufacturing for cooling, plasma processing, and leak detection.

Several core technologies can be combined in a hybridized plant to separate, purify, and optionally liquefy helium and extend helium recovery to electronics applications, where the waste streams are often more diluted and contaminated. Groups of large fabs clustered in one major site can realize the greatest cost advantages of a helium recovery system.

The benefits of an on-site helium, closed-loop recovery system are steady access to a finite resource at lower costs.

Linde helium recovery and liquefaction plant in Skikda, Algeria

Argon: There are sufficient supplies of argon, a gas that makes up 1% of the air, to meet global demand, but users are often located far from the sources of this heavily-used material, making it challenging to get materials on time and on budget. Argon has applications in the electronics industry in the deep UV lithography lasers used to pattern the smallest features in semiconductor chips and in plasma deposition and etching processes.

Two applications use so much argon that they alone make on-site recovery worthwhile. Large amounts of argon are used daily in the manufacture of silicon wafers to protect the silicon crystal from reactions with oxygen and nitrogen while it is being grown at temperatures > 1400 o C. In addition, small drops of liquid argon are used with tools to clean debris from minute, fragile chip structures.

Argon can be recovered most economically through on-site Air Separation Units (ASUs). The process recovers 80% of the original argon, takes only minutes, and is nearly identical to the process used in the original production of argon.

The benefits of an on-site, closed-loop argon recovery system are reduced transportation costs and logistics challenges and a steady supply of argon.

On-site, open-loop recovery

Sulfuric acid: Due to its strong oxidizing properties, sulfuric acid is highly corrosive to metals, making it ideal for removing extraneous particles and cleaning semiconductors. Stringent regulations surround the disposal of sulfuric acid due to its capacity to destroy other materials and cause severe burns in humans. At very large semiconductor sites, traffic congestion can occur with the constant delivery of fresh sulfuric acid and removal of the waste.

One option is to dispose of the sulfuric acid waste by neutralizing and diluting it until it reaches acceptable, regulated levels for discharge to general waste water. Another option is to cleanse the waste for re-use, which can be done at an on-site system. This allows recovery of a high percentage of the sulfuric acid from the waste material, which is purified for re-use in electronics manufacturing¾or other¾processes.

The benefits of an on-site, open-loop recovery system are reduced disposal costs and associated demands for fresh water and waste water volumes, lower environmental impact, and decreased logistics complications and traffic.

Off-site recovery

Xenon, a very rare gas in the air, is obtained as a byproduct of the liquefaction and separation of air. It is used in electronics manufacturing in small amounts in lithography lasers and in higher amounts and concentrations in etch applications. Xenon can be used alone or as the fluorinated compound xenon difluoride in plasma etching.

Because of the low availability and high cost of xenon¾only about 10 million liters are made each year due to the low starting concentration¾it is prudent to capture the after-use, residual xenon and ship it to a rare gas manufacturing center for re-purification and packaging. The submitting fab then receives a credit for the xenon recovered at their site toward future purchases of xenon.

The benefits of recovering xenon are that it facilitates the increase in supply of the rare gas and stabilizes the cost of xenon for larger users.

Materials recovery innovations and sustainability in manufacturing processes

To meet the high demands of today and to build a sustainable future, electronics manufacturers must not only be cutting-edge in their technology, but also in their manufacturing processes. One way to do this is through implementing one or more of these materials recovery systems, which are offered by Linde. By doing so, not only will electronics manufacturers lessen the strain on natural resources, but they will also reduce their own costs, secure a steady supply of materials, and mitigate complex logistics problems.

For more information, contact Francesca Brava:

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