AN900 Datasheet, PDF (4/15 Pages) STMicroelectronics – INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY

INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY
Figure 2. Diffusion and Ionic Implantation Processes
DIFFUSION PROCESS
IONIC IMPLANTATION
PROCESS
OXIDE GROWTH
Oxygen (O ₂)
SiO 2
DOPING
HIGH TEMPERATURE
Doping atoms
DOPING
Electron Beam
VACUUM
DIFFUSION FURNACE
IONIC IMPLANTER
VR02103B
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
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