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Suprem-III User´s Manual
50. Example 2: Bipolar Polysilicon Doped Emitter.
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Presented here is an example of the simulation of a bipolar process with a polysilicon doped emitter. Two
vertical cross-sections are simulated, one through the emitter region, and other through the isolation region.
The structure was simulated using five input files. The first file simulates the processing in the active region
of the device up to the point of the isolation oxidation. The second file starts with the result of this first file and
completes the processing in the active region. The third file performs an electrical parameter calculation on the resulting
structure. As in the first example, the fourth file is similar to the first one, except that the processing in the
isolation region is simulated. The fifth file completes the isolation region processing.
The processing sequence used is listed below.
1. The process begins with a high resistivity, , p-type substrate.
2. Thermally oxidize the substrate, growing approximately one micron of silicon dioxide.
3. Remove the oxide layer from the areas where the buried layers are to be placed.
4. Ion implant antimony at a dose of 10ˆ15/cmˆ2. Drive in the buried layer for five hours
at 1150 degrees Centigrade.
5. Etch the silicon dioxide from the surface.
6. Epitaxial growth of 1.6 microns of arsenic doped silicon.
7. Thermally grow a 400 Angstrom pad oxide.
8. Deposit 800 Angstroms of silicon nitride.
9. Etch the nitride and oxide from the isolation regions.
10. Etch the silicon halfway through the epi-layer.
11. Ion implant boron in the field regions to increase the surface p doping. Use a dose of
10ˆ13/cmˆ2 and an implant energy of 50 KeV.
12. Thermally oxidize the field regions to an oxide thickness equal to approximately onehalf
that of the epi-layer.
13. Strip the nitride layer.
14. Using a photoresist mask, implant the base region. Use boron at a dose of 10ˆ14/cmˆ2
and an energy of 50KeV.
15. Etch the oxide from the emitter region.
16. Deposit arsenic doped polysilicon.
17. Remove the polysilicon from the non-emitter regions.
18. Anneal to drive-in the emitter and activate the base diffusion.