Al2O3 one side deposition with carrier wafer and clamps

Sometimes, we need material to work as masks for the Deep Silicon Etch. The available masks are Al2O3, SiO2, PR, and Cr. If we want to etch about 500 microns, Al2O3 masks are the ideal ones. It’s because Al2O3 is simple to be deposited using the ALD Banerjee. However, there’s another question we have to take into consideration: one-side Al2O3 deposition. Because Al2O3 is appropriate to work as a hard mask, Al2O3 is hard to remove. For example, we normally use BOE to wet-etch SiO2; while the BOE chemical hardly works on Al2O3 removal. I only know Oxford ICP RIE 100 is able to dry-etch so far.

Thus, one-side Al2O3 deposition is one of the essential processes.

Generally, Yoonho uses 4 clamps to combine the sample wafer with one other dummy wafer, and then he can get the one-side Al2O3 deposition.

Yoonho’s method to do one-side Al2O3 deposition. I got the screenshot from Yoonho’s Harman Update document.

According to Yoonho’s job, I imitate the method and repeat it

Yoonho’s method to do one-side Al2O3 deposition. I got the screenshot from Yoonho’s Harman Update document.

According to Yoonho’s job, I imitate the method and repeat it.

The left one is the sample wafer’s backside. We don’t want Al2O3 to be deposited at the backside. So, you can see only there is some Al2O3 at the edge. The right one is the dummy wafer. The dummy wafer works as a substrate contacting the chuck of the ALD Banerjee. Because there is some space between the dummy wafer and the chuck, some Al2O3 is deposited on the backside of the dummy wafer.