Alloying and Annealing
After the metallized interconnections have been deposited and etched, a final step of alloying and annealing may be performed. To perform alloying, the metallized substrate is placed in a low-temperature diffusion furnace. Usually aluminum is placed in the furnace to form a low-resistance contact between the aluminum metal and silicon substrate. Finally, either during the alloy step or following it, the wafers are often exposed to a gas mixture containing hydrogen in a diffusion furnace at 400-500ºC. This annealing step is designed to optimize and stabilize the characteristics of the device by combining hydrogen with uncommitted atoms at or near the silicon-silicon dioxide interface.
The following are the potential hazards of alloying and annealing.
- Possible employee exposure to various metals, aluminum being the most common.
- Identify metal hazards and perform appropriate exposure evaluations.
- Perform exposure measurements for the compounds used.
- Keep exposures below acceptable exposure levels.
- Address all dermal exposures.
- Provide appropriate ventilation to reduce metals concentration levels in the air.
- Provide PPE as appropriate to prevent contact. [29 CFR 1910 Subpart I]
- Use respiratory protection when necessary to further reduce exposure and protect employees. [29 CFR 1910.134]
- Maintain adequate housekeeping to remove unwanted metals and reduce concentration levels.
OSHA Safety and Health Topics Pages:
- Dermal Exposure
- Personal Protective Equipment (PPE)
- Respiratory Protection
- Sampling and Analysis
- Toxic Metals