Integrated Circuits

In much the same way as we make a printed circuit board we can now etch away the parts of the aluminium we do not need and in this way create tracks that direct the current. The finished work will look something like this:

If we wished to have crossover sections then we can either do so by an n+ region which we would have to diffuse at the same time as the others, or we could add a layer of silicon dioxide to the above and use that to cross. Either way it needs careful consideration as we may introduce stray capacitance that will affect the workings.
We could now backlap the wafer, which means grinding it down from the non-circuit side to make the substrate thinner. This leads to smaller profiles of the finished IC.
Remember that we have made dozens of these on a single wafer cut from a boule. Now we need a method of testing them.