[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).