AN900 Datasheet, PDF (5/15 Pages) STMicroelectronics – INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY

INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY
Metal deposition is used to put down a metal layer on the wafer surface. There are two ways
to do that. The process shown on the graph below is called sputtering. It consists first in cre-
ating a plasma with argon ions. These ions bump into the target surface (composed of a metal,
usually aluminium) and rip metal atoms from the target. Then, atoms are projected in all the di-
rections and most of them condense on the substrate surface.
Figure 4. Metal Deposition Process
POWER SUPPLY
CATHODE
PLASMA
METAL
ATOMS
Thin Metal Layer
SUBSTRATE
ANODE
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Etching process is used to etch into a specific layer the circuit pattern that has been defined
during the photomasking process. Etching process usually occurs after deposition of the layer
that has to be etched. For instance, the poly gates of a transistor are obtained by etching the
poly layer. A second example are the aluminium connections obtained after etching of the alu-
minium layer.
Figure 5. Etching Process
Photoresist Mask
BEFORE
Thin Film to be etched
Substrate
AFTER
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