Let's First Start With the Basics of How
Semiconductors
Are Manufactured
Semiconductors are manufactured on large silicon wafers, which
are eventually sliced into what are commonly called “chips”.
Each “chip” is a complete, electronic device that
is individually packaged, tested and is then installed in everything
from toys to virtually all manufactured consumer, communications
/ cell phone and computer products.
WHAT HAPPENS TO THE SILICON WAFERS IN MAKING
THESE CHIPS?
Silicon wafers are placed in specialized manufacturing equipment
called “Plasma Chambers”. Inside these chambers,
high power RF (radio frequency) equipment is utilized for converting
materials (such as metals, insulators, etc) into a gas type “plasma".
This plasma then evenly deposits the desired materials on the
wafers. After this deposition process, hundreds to thousands
of miniature electronic circuits are then projected (exposed)
on to the surface of the wafer through another process called “photolithography”.
The wafers are once again subjected to a plasma process that
chemically selects and etches the excess materials away to
allow for only the new electronic circuit to appear. (This
process is very similar to the process of exposing film in
a standard, hand-held camera. When the film is later developed,
as with the miniature electronic circuit, only the exposed
part of the picture shows up on the picture negative. The excess
material has been washed or etched away in the development
or “etching” process.)
This “deposition / etching process” is repeated over
and over until all of the device circuits are completed. The
wafer can then be tested and sent off to be “diced” into “chips”.
These “chips” are then individually packaged into
completed devices, ready for installation. They are then marked
and tested, and shipped to various electronic product and equipment
manufacturers.
SO, WHAT'S THIS GOT TO DO WITH AN AIM
NETWORK?
For the plasma deposition or etching applications as stated
above, high frequency RF process power must be utilized. With
the complex impedance of the plasma chambers varying with different
process conditions, the transfer of power from the RF Generator
to the chamber requires that the plasma load must “match” the
impedance of the RF generator.
This matching can be achieved in a number of methods. One of
the most common is the utilization of transformers. However,
for applications that require greater than 1 megahertz (MHz),
transformers are not adequate. The industry standard RF for semiconductor
manufacturing is 13.56 MHz, therefore an impedance matching network
or “tuner” is required.
In order for the “chip” manufacturing process within
the chamber to operate correctly, the plasma RF generator must
operate in a 50 ohm environment. Unfortunately, the impedance
load inside the wafer process chamber is never a consistent 50
ohms. By using an “Automatic” Impedance Matching
Network, the 13.56 MHz network automatically “tunes” to
maintain the standard 50 ohm impedance of the RF generator. In
other words, the AIM Network allows the load inside of the chamber
to appear to match the RF generator’s 50 ohm impedance.
Without this “Matching”, it would be impossible to
deliver all of the power from the generator to the process chamber.
Therefore, the AIM Network provides the proper environment for
the process tool to offer a consistent level of plasma deposition
across the silicon wafers.
CONCLUSION
High power, Automatic Impedance Matching Networks
are critical subsystems used in the manufacturing of semiconductors. |
