The Role of Plasma in Wafer Processing

by | Jan 24, 2025

The semiconductor industry supplies crucial components for everything from cars to smartphones. Silicon wafers are the main components in producing semiconductor devices, including integrated circuits (ICs), diodes and transistors.

Learn more about the role of plasma in semiconductor wafer manufacturing and how argon-based atmospheric plasma can improve critical procedures such as surface cleaning.

Which Materials Are Essential for Wafer Processing?

Wafers are processed using various materials, such as silicon, gallium arsenide and germanium. Today, most wafers are made from silicon, which undergoes processing and purification to form a crystalline structure, creating the foundation on which semiconductor devices are built.

The role of materials in semiconductor production is significant:

  • Germanium: This element was one of the first semiconductor materials used to manufacture transistors in numerous electronic devices. However, silicon has replaced its use, as germanium wafers have a melting point of 158 degrees Fahrenheit and are prone to breakage. Germanium is also scarce — there are approximately 1.3 parts per million elements in the crust of the Earth. 
  • Gallium arsenide: Wafers made from a compound of gallium and arsenic have a faster electron velocity and higher electron mobility, making them ideal for specialized applications such as telecommunications, aerospace and high-frequency circuits. However, gallium arsenide can be expensive, is challenging to produce and involves toxic chemicals.
  • Silicon: Compared to germanium, silicon wafers are more heat resistant and can withstand temperatures around 300 degrees Fahrenheit without suffering heat damage. Additionally, silicon is the second most abundant element, accounting for 27.7% of the mass of the Earth’s crust. Because of its abundance, silicon wafers are more cost-effective than those made from germanium and gallium arsenide. Due to its affordability, manufacturers prefer this element for mass-produced consumer devices.

What Are the Steps in the Wafer Fabrication Process?

Wafer fabrication is a highly intricate procedure paramount to semiconductor manufacturing processes. It involves the following steps, transforming raw silicon into structures that are ready to form the foundation of devices like ICs:

  1. Growing: The first step is ingot growth, where manufacturers place a small silicon seed crystal into a quartz crucible containing molten polysilicon. The crucible is slowly drawn away from the silicon, acting as a mold for the polysilicon to form one cylindrical crystal ingot.
  2. Slicing: Manufacturers slice the ingot into hundreds of thin disks using a saw with a diamond blade. These disks have a thickness between 500 and 900 microns.
  3. Grinding: As slicing causes tiny cracks and other flaws in the wafer’s circumference, manufacturers grind the edges to smooth them out. This involves using a grinding wheel to remove a small strip of material, leaving behind a clean edge around the wafer’s periphery.
  4. Lapping: The lapping process flattens the wafer’s surface by gently spinning the disks between two rotating cast iron plates, each coated with an abrasive slurry. These plates remove some material from both sides of the wafer until the front and back are flat and level. In addition to bringing the wafer closer to the thickness required for device production, lapping removes the saw marks that result from slicing.
  5. Etching: This step removes any remaining surface imperfections and contaminants caused by previous processes. Etching uses wet or dry chemicals to selectively strip microns away from the wafer’s surface to eliminate flaws, revealing an immaculate layer beneath.
  6. Polishing: Next, manufacturers polish the wafers via a mechanical-chemical process. They use a silica slurry to oxidize the disk’s silicon surface and, with the help of a soft pad, physically scrape it away with abrasive particles. This polishing method creates a smooth and pristine surface, which is vital for semiconductor manufacturing steps like photolithography.
  7. Cleaning: Finally, manufacturers thoroughly clean the wafers to eliminate particles, metal impurities and organic contaminants from their surfaces. As semiconductor manufacturing demands exceptional surface purity, this step upholds the industry’s cleanliness standards.

What Is the Role of Plasma in Wafer Processing?

Plasma is indispensable in the etching and cleaning steps involved in wafer processing. Known as the fourth state of matter, this neutral ionized gas consists of positive and negative ions and free electrons. It’s produced by directing energy to a gas, causing electrons to depart from the atomic shell and ionize the gas.

While plasma has existed naturally for millennia, technological advancements have cemented its place in production processes.

Plasma in Wafer Cleaning

Surface cleaning is one of the most common ways manufacturers use plasma. During wafer fabrication or an assembly process at a later stage, manufacturers must remove microscopic contaminants from all surfaces to improve the yield, dependability and function of ICs. Plasma cleaning is highly effective for removing inorganic and organic impurities and surface oxidation.

While this method thoroughly cleans surfaces, it’s still gentle enough to preserve materials’ performance and integrity. As a result, plasma is ideal for applications such as the semiconductor wafer cleaning process. The benefits of using plasma in cleaning include: 

  • Better adhesion: Plasma cleaning can ensure proper adhesion for bonds created at later stages in semiconductor manufacturing. This process removes external impurities from the substrate so contaminants can’t interfere with the bond. Manufacturers can also modify the cleaning process to focus on targeted contaminants and materials.
  • Decreased waste: Along with adhesion problems, contaminants can lead to bubbling. Such issues may result in unusable wafers, which causes waste and negatively impacts the manufacturer’s bottom line. Plasma cleaning can overcome these obstacles, helping to increase the yield.
  • Increased eco-friendliness: Volatile organic compounds and harsh chemicals can negatively affect the environment, yet these are unnecessary with plasma cleaning.

Challenges and Opportunities in the Semiconductor Industry

Manufacturers have traditionally performed plasma cleaning in vacuum chambers, adding gases like oxygen, argon, helium or hydrogen to a chamber and introducing an electrical field or energy. Another conventional approach is high-voltage atmospheric plasma, in which extremely reactive radicals and energetic electrons interact with the surface.

However, the industry faces challenges with both these approaches. The ion bombardment inherent in vacuum plasma cleaning can damage the surface of delicate components like wafers. In addition, high-voltage atmospheric plasma creates interactions with electrons that can result in an electrostatic discharge (ESD) event, which can also harm electrically sensitive parts. 

A newer, more modern method for plasma cleaning mitigates these challenges. At Surfx Technologies, we create argon plasma via a mixture of oxygen process gas at atmospheric pressure. As there’s no need for a vacuum chamber or the risk of ESD, argon plasma presents an opportunity for the semiconductor industry to improve manufacturing processes. The weak ionization of our argon plasma also differentiates it from open-air systems.

Here are the benefits of atmospheric pressure plasma cleaning:

  • Extended uptime: Cleaning batches inside a chamber can result in considerable downtime. Instead, wafers can be processed without interruption, increasing uptime. 
  • Nondamaging procedures: Due to the atmospheric pressure and weakly ionized plasma, Surfx Technologies’ argon plasma can clean surfaces without harm.

Integrate Atmospheric Argon Plasma Into Your Wafer Fabrication Processes

While using plasma in the etching and cleaning steps of wafer fabrication can improve production, argon plasma produced at atmospheric pressure elevates these processes to a higher standard. Surfx Technologies’ range of argon-based atmospheric plasmas is excellent for high-volume wafer manufacturing. We also provide cutting-edge plasma machines, accelerating the speed of surface treatments, enhancing precision and reducing the chance of damage. 

Contact us to discover how our patented plasma solutions can enhance wafer processing, or request a demo to witness the potential yourself.