Alright even. I've worked in the semiconductor industry for most
of my working life so I'll try to explain very briefly and simply
how integrated circuits are made. Silicon wafers are thin slices
of highly pure silicon, made by MEMC and others. The chip makers
take these wafers and implant ions, called impurities, which change
the electrical nature of the silicon in local areas. These areas
are what make the transistors, or active devices, in the silicon.
That is IN THE WAFER, not on it. These are high temperature steps
which are controlled with quite sophisticated control equipment.
Once the active regions in the wafer are created they must be
connected together properly to create a circuit. This is done
using thin layers of polysilicon and metal which are growth ON THE
TOP OF THE WAFER after it is covered with an insulator dielectric
called Silicon Dioxide. After the first interconnect layer, each
subsequent interconnect layer is grown over additional layers of
insulator so the layers don't short to each other, except as desired.
The way these layers are defined is by generating a pattern for
every layer to make a single chip design. Each chip is square or
rectangular. The pattern for a chip is repeated in an array across
the wafer to create as many chip locations (called die) as possible
on the wafer. Once these wafers have completed processing each die
is tested. The wafers are cut by diamond saw or laser along the
edges of the die locations. The good die are packaged and retested
(some are damaged), then sold. Very simplistic explanation!
My apologies to the many of you who are intimately familiar with the
business, but Mephisto's post was so full of errors that is grated
my nerves reading it.
Mephisto, if after reading other sources you still feel you just
must know more please contact me by e-mail to keep this thread on
it's intended subject. I won't write a book or spend a lot of
time on this, but I will be willing to help you out some - but I
hope you do some homework on your own instead of just leaning on
others for information. You'll get a much better understanding
than you can get from anyone posting short notes to you.
The bottom line for WFR is that they just supply "raw materials"
for the chip companies. As long as wafer demand remains strong
enough for their bookings to hold WFR should be in good shape.
More DRAM production is good for WFR. However, if computers and
other electronic systems sales start to slip in growth, then chip
volumes won't grow, so wafer volumes won't grow - so watch out if
PC sales don't pick up.
Ed Miller |
