16 February 2012

Silicon Wafer Processing


The processing of Silicon wafers to produce integrated circuits involves a good deal of chemistry and
physics. In order to alter the surface conditions and properties, it is necessary to use both inert and toxic
chemicals, specific and unusual conditions, and to manipulate those conditions with both plasma-state
elements and with RF (Radio Frequency) energies. Starting with thin, round wafers of silicon crystal, in
diameters of 150, 200, and 300mm, the processes described here build up a succession of layers of
materials and geometries to produce thousands of electronic devices at tiny sizes, which together
function as integrated circuits (ICs). The devices which now occupy the surface of a one-inch square IC
would have occupied the better part of a medium-sized room 20 years ago, when all these devices
(transistors, resistors, capacitors, and so on) were only available as discreet units.
The conditions under which these processes can work to successfully transform the silicon into ICs
require an absolute absence of contaminants. Thus, the process chambers normally operate under
vacuum, with elemental, molecular, and other particulate contaminants rigorously controlled. In order to
understand these processes, then, we will begin the study of semiconductor processing with an overview
of vacuum systems and theory, of gas systems and theory, as applied specifically to these tools, and of
clean room processes and procedures
The semiconductor industry reflects and serves an extraordinary revolution in both materials science and
in data processing and storage. As recently as 1980, most individuals had no idea that computers would
ever impact their personal lives. Today, many families own one or two computers, and use many other
computers and dedicated processor systems in their appliances and automobiles. The intrusion of
electronics and computer technology into our lives and the devices we use daily is growing at an
exponential rate, and Moore’s Law still applied in the computer world. This is one of the few markets in
which, as time passes, the power and capacity of the products grows steadily, while the cost of that
power and capacity drops.
Today, only twenty years later, we are continually pushing the envelope of capabilities of the data
processing and storage systems that are now in the mainstream. Ingenuity and creativity, along with
great strides in quality control, process control, and worker productivity, are leading daily to new ideas
about how to further reduce device size and data density. On the horizon are visions of biochemicallybased
devices which will be far smaller, work faster, and generate less heat than current devices. It is
worth spending some time imagining where this evolving technology will take us, and the society we
live in.

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