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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

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

VR02103C

PLASMA

SUBSTRATE

POWER SUPPLY

Thin Metal Layer

CATHODE

ANODE

METAL

ATOMS

VR02103D

Photoresist Mask

Thin Film to be etched

Substrate

BEFORE

AFTER