Comparison between Bosch and STiGer Processes for Deep Silicon Etching

Area of Science:

• Materials Science
• Microtechnology
• Plasma Physics

Background:

• Cryogenic etching is crucial for creating high aspect ratio silicon features with smooth sidewalls.
• The Bosch process is a widely used time-multiplexed cryogenic etching technique.
• The STiGer process, developed in 2006, offers an alternative cryogenic etching method.

Purpose of the Study:

• To evaluate the STiGer process for silicon etching.
• To compare the performance and profile quality of STiGer against the Bosch process.
• To assess the advantages of STiGer's polymer-free passivation chemistry.

Main Methods:

• Utilized a time-multiplexed cryogenic etching process (STiGer).
• Employed cycles of isotropic etching followed by SiF4/O2 plasma passivation at cryogenic temperatures.
• Analyzed etched silicon feature profiles and performance metrics.

Main Results:

• The STiGer process demonstrated equivalent profiles and performances to the Bosch process.
• Sidewall passivation was achieved using a polymer-free plasma chemistry (SiOxFy deposition).
• The absence of polymers necessitates less frequent chamber cleaning.

Conclusions:

• STiGer is a viable alternative to the Bosch process for high aspect ratio silicon etching.
• The polymer-free passivation offers a significant advantage in reduced maintenance and increased throughput.
• This process is suitable for microfabrication applications requiring precise silicon feature etching.