Page 165 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

146 H Chapter Fourteen

After the wafer has
cooled, it is coated with a
thin layer of organic re~ist,~
which is first dried and then
baked to form an impervious
layer (Figure 14-5).

Organic resist A mask is created and
ultraviolet light is applied.
Silicon
(su bstrate) Silicon dioxide The ionizing ultraviolet
radiation passes through the
Figure 14-5. Apply a layer of organic resist
transparent areas of the
mask into the resist, silicon
Ultraviolet
radiation source dioxide, and silicon. The ultraviolet breaks
down the molecular structure of the resist, but

does not have any effect on the silicon dioxide
or the pure silicon (Figure 14-6).

As was previously noted, the small area
I of the mask shown here is associated with a
single transistor. The full mask for an inte-
Mask grated circuit can consist of

millions of similar patterns.
After the area under the
mask has been exposed, the
wafer is moved, and the
process is repeated until the
pattern has been replicated
Organic resist across the wafer’s entire
surface, once for each inte-
Sili& Silicon dioxide grated circuit. The wafer is
(su bstrate)
then bathed in an organic
Figure 14-6. The exposed resist is degraded solvent to dissolve the
by the ultraviolet light degraded resist. Thus, the

The term “organic” is used because this type of resist is a carbon-based compound, and carbon
is the key element for life as we know it.