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Integrated circuit begins same as other semiconductors: ingot
of monocrystalline silicon, "grown" at 1425°C (melt point) in oxygen-free atmosphere.
Diffusion steps in IC fabrication:
After the first diffusion, following step is to deposit a crystal layer over
entire silicon slice. A smooth epitaxial layer is produced this way.
Next, isolation diffusions - to keep electronic signals from leaking from one
segment to another - are developed in the integrated chip.
Other diffusion steps develop a number of transistors, diodes, and resistors.
Each element is an integral part of original chip.
Still more steps are needed in the diffusion process to complete development
of circuit portions. Result is a chip full of active elements.
Evaporation apparatus like this is used for depositing interconnects.
IC chips are soldered to headers, and thin connecting wires are
welded from the bonding points on each integrated-circuit chip to the termination
points on the headers. There are different shapes of headers, depending on what
style of final packaging is to be used for the integrated microcircuit. Girl above
is moving integrated-circuit chip into position for spot-welding the tiny wire leads
to the bonding pads at the outer perimeter of the chip - a delicate task that requires
of the assembly operator precision, especial care and coordination.
... of the TO-5 variety. The flat package is already finding
considerable use in computers, and will undoubtedly be put into consumer products
when micro-circuits become available that need the additional connections. As you
can see from the preceding photographs, the means for producing cheap microcircuits
is already available. It now remains only for the designers to develop new IC's
and ways to use them in consumer goods.
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Slices of silicon are coated with a layer of photosensitive material
and exposed to ultra-violet light passing through a mask. The patterns which are
thus impressed on the silicon substrate form shapes which will then be etched away,
leaving behind areas for the many diffusions that are part of the manufacturing
process. Mask alignment is simplified by projection-type magnifying viewers shown
being used here in IC production.
Diffusion is in quartz-tube furnaces. Special gases react with
the silicon material to create the desired electrical qualities in the chip.
Metallic deposits over and among elements link IC components.
Finished chips rest in honeycomb-like carrier awaiting packaging.
Powerful microscope for viewing, and special equipment for handling,
make final assembly job easier for workers.
The familiar TO-5 transistor can is frequently used as housing
for IC's, This packaging is ordinarily merely for convenience in mounting, since
a typical integrated circuit chip is tiny in comparison; if there were room for
leads, a dozen IC's could be enclosed in a single TO-5 package. The one pictured
above is an epoxy-plastic housing placed over a ceramic base. In quantities, integrated
circuits in these package types can be sold for considerably less than $5. The "dual-in-line"
at right was developed for handling IC's whose lead requirements are greater than
can be adapted easily to a package. ...
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