[aivisol]

I have some doubts about step 15: I used to work in a post-Soviet lab which produced chips in early 90s and as far as i remember etching happened in a high temperature (was it 1200C ?) environment where you would pass some chlorine type gas over the wafers. The temperature was achieved by induction heating with 8kHz AC passing through water cooled copper coils. The generators were mechanic, big water cooled machines placed in the basement of the building due to the noise they generated. Another reason for placing them in a basement was that water leaks were common. I was responsible for maintaining the heating setup and transitioning to electronic, thyristor based generators. The job was kind of electronic-engineer-plumber type of duty.

[PawgerZ]

> etching happened in a high temperature (was it 1200C ?) environment where you would pass some chlorine type gas over the wafers.

This is plasma etching or dry etching.

Step 15 shows acid etching or wet-chemical etching.

I don't know the pros/cons of each, but both have been used as viable options to etch a circuit.

[aivisol]

You are probably right. What I remember there was this chlorine gas, and there was some other gas (oxygen?). And in between them we had to flush everything with lots of nitrogen to prevent formation of potentially explosive mixture. The wafers would be placed on a graphite support, which was heated by that induction coil (as copper itself would melt at that temperature I guess).