Silicon wafers are among the most fragile products found in semiconductor manufacturing services. Subject to many different potential concerns, one of the most prominent is surface contamination, which can occur simply as a result of silicon wafers being exposed to organic particles in the air. Due to electrostatic force, contaminants will bond directly to silicon wafers, causing them to function improperly unless thoroughly cleaned prior to implementation.
Fortunately, experts in semiconductor manufacturing services have developed a solution for this all too common issue—here’s how it works.
Step #1: Cleaning with Solvents
When it comes to cleaning the surfaces of silicon wafers, nothing beats the effectiveness of solvents. Acetone is commonly employed for this purpose, as it can easily remove organic residues, oils and more from wafers without causing additional issues. Since solvents themselves can contribute to wafer residue, a two-step process is often employed in which the wafers are cleaned with methanol after being bathed in acetone. Finally, the wafers are rinsed with deionized water and blow-dried with nitrogen.
Step #2: RCA Clean
Though solvents play a crucial role in the silicon wafer cleaning process, an additional RCA clean is also typically performed. This step in the procedure adds a thin layer of oxidation to the silicon, protecting the surface so that buildup of contaminants is no longer able to occur on the actual surface of the wafer. After the RCA bath is complete, the wafers are once again cleaned with multiple changes of deionized water and then rinsed under a constant flow to discourage water residue from sticking to the surface.
Step #3 HF Dip
The third and final step in the wafer cleaning process involves dipping the silicon into hydrofluoric acid (HF), which serves the purpose of removing silicon dioxide from the surface of the chip. Once dipped for a period of two minutes, the chips are then tested for “wettability,” with manufacturers looking for beads to roll off and not stick—an indication of a hydrophobic, oxide-free surface. Hydrofluoric acid is a very dangerous chemical, and great care must be taken throughout this step in the process.
The Importance of Cleanroom Manufacturing for Wafer Cleaning Components
When conducted properly, the wafer cleaning process can be extremely effective—that is, if components being used in the process are designed in a clean environment. Particle-free systems are essential throughout every step of the semiconductor component manufacturing process, from wafer cleaning to the handling of gases/liquids and everything in between. Axenics maintains a Level 100 Cleanroom, ensuring that all weldments, manifolds, gas boxes, tubing kits and other components are free of contamination.
With 30+ years of experience producing particle-free cleanroom welding, piping, tubing, and bends for the semiconductor industry, Axenics helps create solutions for even the most complex challenges faced by today’s engineers.