Semiconductor thin film components represent critical technological interfaces where microscopic contamination can dramatically impact performance and reliability. Leftover particulates can act as a nucleation site for non-uniform film growth, create localized cavities in film thickness and introduce microscopic surface imperfections.
Thin film deposition is a widely used method to coat Silicon, GaAs, GaN and SiC wafers (substrate material). However, during the coating process, the intended substrate is not the only material that receives the desired thin film. The PVD system chamber walls (Shielding) can receive most of the thin film deposition. The shielding components are generally stainless-steel parts, that can have sensitive welding and surface areas. Consequently, these stainless-steel components can be costly to manufacture.
Due to the requirements of modern semiconductor manufacturing, advanced cleaning techniques have become essential in maintaining the exceptional standards of these Shield Components.
Key Cleaning Methodologies
Chemical and Mechanical Removal
Two key methods to effectively remove the thin film deposition that has coated PVD chamber shielding.
- We use a variety of chemistries to effectively and safely remove the thin film deposition from our customers shielding. The selected chemistries are based on the thin film stack and the substrate material. Depending on the thickness of the coating, these parts may be required to go through the chemical process multiple times. While this can be time consuming, the chemical processes help increase the lifetime of these expensive components.
- Mechanical removal is done with both blast media and special tooling to help undercut the thin film deposition without damaging the Components. The mechanical process is used in concert with the chemical process, to help penetrate difficult metal stacks.
TWAS (Twin Wire Arc Spraying) & Plasma Spraying
These deposition techniques are not used to remove particulate but they do play an important part in the overall cleaning process. Both are applied after the Shield Components are cleaned.
- TWAS (typically Aluminum) Layer
Used a sacrificial layer between the deposited thin film and the Shield Components. We can undercut the TWAS layer with various chemistries and reduce the amount of mechanical removal. TWAS gives us the ability to customize coating to improve tool performance (example: lower PC’s, improved chamber life, leading to reduced tool downtime) - Plasma Spray (typically Al2O3 or Y2O3) Coatings
Used to help collect the thin film deposition and protect the costly Shield Components from extreme heat coming from the ignited plasma.
Ultrasonic Precision Cleaning
Used to help remove contamination that may be left over from the cleaning techniques.
Utilizing high-frequency sound waves, ultrasonic cleaning helps in:
- Microscopic cleaning for complex geometries
- Minimal mechanical stress on delicate components
- Effective removal of particulate and residual contamination
- Consistent cleaning across intricate surface structures
Heat Treatment
These processes are then used to remove any moisture. We use various time and temperature-controlled ovens to bake out any residual water that may be trapped in textured, TWAS’ed or Plasma Sprayed surfaces.
Inspection and Clean Room Packaging
The final steps of processing the Shield Components. Our final inspection and packaging are both completed in a Class 100 clean room, double bagged in an inert atmosphere.
Advanced cleaning techniques represent a critical intersection of chemistry, physics, and precision engineering. As semiconductor technologies become increasingly complex, cleaning methodologies must simultaneously become more sophisticated and more nuanced.
Interested in precious metals reclamation? Read more.