Category Archives: CVD Source Materials


By Pete Singer, Editor-in-Chief

N2O, or Nitrous Oxide, also known as laughing gas, is a weak anesthetic gas that has been in use since the late 18th century. Most people have experienced nitrous in the context of dentistry, but it’s also used to make whipped cream, in auto racing, deep sea diving, or – in the semiconductor industry — as the oxygen source for chemical vapor deposition (CVD) of silicon oxy-nitride (doped or undoped) or silicon dioxide, where it is used in conjunction with deposition gases such as silane. It’s also used in diffusion, rapid thermal processing and for process chamber treatments.

The problem – and why it’s no laughing matter – is that after CO2 and CH4, N2O is the 3rd most impactful man-induced greenhouse gas (GHG), accounting for 7% of emissions. According to the U.S. Environmental Protection Agency, 5% of U.S. N2O originates from industrial manufacturing, largely semiconductor manufacturing. “It’s very much of interest because of its high global warming potential, combined with its long atmospheric lifetime of over 100 years,” said Mike Czerniak Environmental Solutions Business Development Manager, Edwards. “After PFCs, this is one of the most impactful gases from semiconductor manufacturing.” With a TLV of 50ppm, N20 is also poses a health risk.

There are two ways to get rid of N2O: reducing and oxidizing. “Reducing means getting rid of the oxygen in it so you just drive it down to be nitrogen, or you can oxidize it and add additional oxygen to it,” Czerniak explained.

Oxidizing is the easier approach in that it involves putting the gas through an ordinary flame. “The problem with doing this is you then make nitrogen oxides, NOx, and that generally is very bad because that’s the gas that’s the acid rain contributor and it also does nasty things to people,” Czerniak said. When NOx and volatile organic compounds (VOCs) react in the presence of sunlight, they form photochemical smog, a significant form of air pollution, especially in the summer. “If you do make NOx, then you probably want to do some additional treatment to try and get rid of the NOx that you’ve generated,” Czerniak said.

Reduction, therefore, is preferable. N2O can be catalytically reduced to H20 + N2. A reducing flame can be used in a combustor; this requires the presence of a reducing agent, such as methane (a commonly used fuel gas) or even a hydrogen-containing process gas such as silane. “You can avoid forming NOx if you use low temperatures, moderate amounts of oxygen, and you add a reducing agent like methane,” Czerniak said.

Edwards presently offers the Atlas series of inward-fired combustion gas abatement solutions. Atlas systems have low fuel consumption compared with previous-generation gas abatement devices and utilize proven Alzeta inward-fired combustor technology to achieve significantly reduced costs of ownership. With one to six inlets with a number of options, including a temperature management system (TMS), they can reach a flow capacity of up to 600 slm and they offer enhanced ease-of-use and more efficient maintenance.

After CO2 and CH4, N2O is the 3rd most impactful man-induced greenhouse gas (GHG). Source: Climate Analysis Indicators Tool, World Resources Institute.

After CO2 and CH4, N2O is the 3rd most impactful man-induced greenhouse gas (GHG). Source: Climate Analysis Indicators Tool, World Resources Institute.

CVD Source Materials

December 17, 2015

Reaction materials for chemical vapor deposition (CVD) and atomic layer deposition (ALD) are typically delivered into the chamber in a gaseous form. CVD polycrystalline silicon, for example, is deposited from trichlorosilane (SiHCl3) or silane (SiH4), using the following reactions:

SiH3Cl → Si + H2 + HCl
SiH4 → Si + 2 H2

This reaction is usually performed in LPCVD systems, with either pure silane feedstock, or a solution of silane with 70–80% nitrogen. Polysilicon may be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber.

Silicon dioxide (usually called simply “oxide” in the semiconductor industry) may be deposited by several different processes. Common source gases include silane and oxygen, dichlorosilane (SiCl2H2) and nitrous oxide (N2O), or tetraethylorthosilicate (TEOS; Si(OC2H5)4). The reactions are as follows:

SiH4 + O2 → SiO2 + 2 H2
SiCl2H2 + 2 N2O → SiO2 + 2 N2 + 2 HCl
Si(OC2H5)4 → SiO2 + byproducts

CVD source materials are typically gases, such as silane and nitrogen, but can also be liquids: There are now a larger variety of liquid sources used in the semiconductor, FPD and PV manufacturing processes.

CVD Sources

The graph above shows the different possible states of matter. There are two ways to get from a liquid to a gaseous state. The first method involves increasing the temperature while holding the pressure steady, as indicated by the arrow with the broken line. This method is commonly used in everyday settings—to boil water and convert it to steam, for example. Heating a liquid takes time, however, which makes rapid vaporization difficult. On the other hand, one can also heat the liquid in advance and then abruptly reduce the pressure, as illustrated by the arrow with the solid line. The pressure in the vaporization section of the injector can be reduced instantaneously, and this makes it possible to vaporize a liquid source instantaneously.

Chemical Vapor Deposition

December 11, 2015

Chemical vapor deposition (CVD) is used to produce high-purity thin films. In a typical CVD process, the wafer (substrate) is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. Frequently, volatile byproducts are also produced, which are removed by gas flow through the reaction chamber.

Microfabrication processes widely use CVD to deposit materials in various forms, including: monocrystalline, polycrystalline, amorphous, and epitaxial. These materials include: silicon, carbon fiber, filaments, carbon nanotubes, SiO2, silicon-germanium, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, and various high-k dielectrics. The CVD process is also used to produce synthetic diamonds.

Applications include shallow-trench isolation, pre-metal dielectric, inter-metal dielectric, and passivation. CVD processes are also important in strain engineering that uses compressive or tensile stress films to enhance transistor performance through improved conductivity.

Additional Reading

Taking 2D materials from lab to fab, and to technology

New materials require new approaches

Deposition equipment market witnesses a year of significant change

By Jeff Dorsch, Contributing Editor

There are four main segments in the thin-layer deposition equipment market – atomic layer deposition, chemical vapor deposition, epitaxy, and physical vapor deposition, also known as sputtering.

As the semiconductor industry powers through the 14-nanometer process generation, interest is keen on how researchers and suppliers will improve the current crop of deposition equipment to meet the requirements of the 10nm and 7 nm nodes.

The long-pending merger of Applied Materials and Tokyo Electron into a company to be called Eteris, called off in April due to regulatory issues, would have created a mighty deposition vendor, holding nearly 60% of the worldwide market. Applied still holds a commanding share of the deposition market, yet will have to contend with Lam Research (which acquired Novellus Systems in 2012), AIXTRON, ASM International, and other competitors.

Global Industry Analysts (GIA) forecasts the global deposition equipment market will hit $13.6 billion by 2020. Atomic layer deposition (ALD) will be the fastest growing segment, with a compound annual growth rate of 19.9 percent, the market research firm estimates.

Chemical vapor deposition (CVD) will be the second largest deposition segment through the end of this decade, followed by physical vapor deposition (PVD) and epitaxy, according to GIA. Japanese vendors, namely Hitachi Kokusai Electric/Kokusai Semiconductor Equipment and Tokyo Electron, dominate the worldwide CVD market, with significant market shares held by Applied Materials, ASM International, and Lam Research, the market research firm states.

Taiwan is the world’s largest market for deposition equipment, Global Industry Analysts says. That’s not surprising, since SEMI estimates that Taiwanese semiconductor manufacturers will spend about $10.5 billion on wafer fabrication equipment this year, representing nearly 30 percent of worldwide spending on fab equipment in 2015. GIA sees China being among the fastest-growing markets for deposition, with a CAGR of 15.1 percent.

In May, Applied Materials introduced the Applied Endura Cirrus HTX PVD system for making titanium nitride hardmask films, targeting applications in fabricating semiconductors with 10nm and 7nm features.

A year ago at SEMICON West, the company debuted the Applied Producer XP Precision CVD system, which it said supports the industry transition to 3D NAND flash memory devices by providing nanometer-level layer-to-layer film thickness control for critical-dimension uniformity across a wafer.

July of 2014 also saw Lam Research unveil its VECTOR ALD Oxide system to produce conformal dielectric films defining critical pattern dimensions in multiple patterning.

SEMICON West 2015 is expected to see announcements on new products and research in the deposition equipment field.