Etching of Silicon Nitrides
Challenge
Remove/etch Silicon Nitride from a variety of substrates in the photovoltaic production process.
Deposition
Silicon Nitrides
Substrate
Stainless Steel, Carbon Fiber and Graphite
Results
We were able to demonstrate our selective etching of Silicon Nitride without the use of Hydrofluoric Acid, which the customer utilized soon after at their facilities. Our solution allowed the use of the stainless steel components between 10 to 15 times longer than the process that we replaced.
Several of our clients, that are involved in cleaning precision parts, asked us to come up with a concept of etching photovoltaic deposition of silicon nitrides from stainless steel and/or carbon fiber carriers (CFC) and/or graphite precision parts, without the use of hydrofluoric acid.
Since hydrofluoric acid (HF) is a gas dissolved in water, its fumes always stay in pores of CFCs and/or graphite, which can produce outgassing of the components in the vacuum chamber prior to the coating step. This increases the time to optimum vacuum to start the pretreatment and coating process for both PVD and CVD systems.
It is also very aggressive and destroys stainless steel fasteners (bolts, screws, washers, nuts, rivets, etc.) on the CFC frames so they need to be replaced right after the deposition is etched away.
We were given the task to develop a technology that would avoid using hydrofluoric acid and after some trial experiments we came up with two novel technologies.
We assisted in scaling up the less expensive one. This technology saves production time while increasing the productivity during the production of photovoltaic films significantly. Since the etching mix is not as aggressive as the mix with hydrofluoric acid (HF), the precision parts cleaned by this technology last between ten to fifteen times longer than those with cleaned by the previous cleaning HF cleaning method.
The extraction of chromium from stainless steel treated by hydrofluoric acid (HF) was measured and we found that the amount of chromium extracted by hydrofluoric acid is ten times higher than for the stainless steel precision part that had been treated by our non-HF technology.
All the customers switched from the HF technology to our non-HF novel technology right after their trial tests.