Warning! This is the archived 1999 Fabweb site! Here is the latest site
In the IC Fabrication Experiment," ECE 344 students are given bare silicon wafers and the guidance to help
them fabricate some simple devices and circuits on them.
The emphasis is on "guidance". The students do practically everything by
themselves. The equipment is all manually operated so that when the
students are finished, they will have a thorough grasp of what was done
at every stage of the fabrication. Highly automated fab equipment is actually
rather undesireable for education since the purpose here is to remove the
mystery ICs often have for students. In ECE 344, the students can see the
wafer during every step.
Here are cross sections of a P-channel Metal Oxide Semiconductor Field
Effect Transistor(P-MOSFET) and an NPN Bipolar Junction Transistor (BJT) at several
significant points during processing.
This is a basic overview of what happens during the ece344 process. Layers are
not to scale. Also, silicon consumption
during oxidation and undercutting during etching are not shown.
1. RCA Clean: Over an hour is spent cleaning a bare silicon wafer in preparation for the
first oxidation. Except for a few parts per billion of phosphorus, the silicon
is a near perfect crystal with all four valence electrons covalently bonded to
neighbors. Phosphorus has 5 electrons in it's valence
shell causing one of the electrons to be available for conduction of electricity.
Since electrons were assigned a negative charge, this is called N-type silicon.
All unintentional impurities must be kept at even lower levels.
2. Initial Oxidation: About 1500 Angstroms of silicon dioxide is grown on the wafer in an 1100 degree Celcius
furnace with pure oxygen flowing. During part of the oxidation, hydrogen is injected into the furnace along
with the oxygen
to speed up the oxidation.
This screen is maintained by
Kevin Beernink - U of Illinois ECE Dept. - beernink@uiuc.edu
E-mail comments and suggestions to ece344@uiuc.edu or use the
FEEDBACK FORM.
overview.html
Warning! This is the archived 1999 Fabweb site! Here is the latest site