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INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY

Figure 2. Diffusion and Ionic Implantation Processes

Photomasking (or masking) is an operation that is repeated many times during the process.

This operation is described on the above graph. This step is called photomasking because the

wafer is “masked” in some areas (using a specific pattern), in the same way one “masks out”

or protects the windscreens of a car before painting the body. But even if the process is some-

what similar to the painting of a car body, in the case of a silicon chip the dimensions are

measured in tenth of microns. The photoresist will replicate this pattern on the wafer. The ex-

posed part of the photoresist is then rinsed off with a solvent (usually hydrofluoric or phos-

phoric acid).

Figure 3. Photomasking Process

VR02103B

DIFFUSION PROCESS

IONIC IMPLANTATION

IONIC IMPLANTER

Electron Beam

HIGH TEMPERATURE

DIFFUSION FURNACE

Doping atoms

PROCESS

OXIDE GROWTH

DOPING

DOPING

Oxygen (O )

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