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Non-Uniform Sheet Resistivity
Problem |
Probable Cause |
Suggested Solution |
Comments* |
High
at Gas
Inlet End |
Gas flow too high |
- Reduce gas flow
- Use dummy sources at gas
inlet end of boat
|
|
Upstream source
depleted |
- Replace sources
- Periodically reverse boat
|
|
Deposition time too short |
Increase dep. time |
|
| |
|
|
|
High
at Gas
Exhaust End |
Moisture/air
backstreaming into tube |
- Increase gas flow
- Improve seal of tube
|
|
Insufficient time at temp.
for downstream sources |
- Tilt furnace profile
- Use ramping instead of direct insertion
|
|
Deposition time
too short |
Increase dep.
time |
|
| |
|
|
|
High
at both
Ends |
Sources nearing end
of lifetime |
Replace sources |
|
Deposition time
too short |
Increase dep.
time |
|
Quartz boats outside
flat zone |
Recheck furnace profile |
|
| |
|
|
|
Gradually
Increasing on
all Silicon |
Oxide growth on
silicon |
|
|
Source nearing end of
lifetime |
Replace sources |
|
Deposition time
too short |
Increase dep.
time |
|
| |
|
|
|
Suddenly
Increasing on
all Silicon |
Sources exposed to moisture |
-
Reage sources
-
Replace sources
|
|
Air leak, broken
tube |
Check fittings
and tube |
|
Sources exposed to
acids, etc. |
Replace sources |
Cleaning:
BoronPlus
Cleaning: PhosPlus |
| |
|
|
|
Non-Uniform
Run-to-run |
Improper storage |
Improve storage |
|
Moisture in tube or
carrier gas |
Check fittings, check for cracked
tube |
|
Deposition time
too short |
Increase dep.
time |
|
| |
|
|
|
Rapidly
Changing Early
in Life of
Sources |
Equilibrium evolution rate
not established |
Increase aging time as necessary |
|
| |
|
|
|
High on Edge
of Silicon |
Gas flow too high |
Reduce flow rate |
|
| |
|
|
|
High on One
Edge of Silicon |
Partial depletion of edge
of source |
|
|
References:
1. “Hydrogen Peroxide Solutions for Silicon Wafer Cleaning”,
RCA Engineer, vol. 28-4, July/Aug 1983, pp. 99-105.
2. Hur-Ling Hsiu, “Effect of Solid
Source Impurities on Silicon Devices”, Thesis at Arizona
State University, Dec. 1988.
3. “Processed-Induced Defects in
Borosilicate Glass-Diffused Silicon”, O. Aina and R.
Kennedy, J. Electrochem. Soc., vol. 131, no. 8, pp 1884-1887.
4. J.E. Rapp, “The Planar Diffusion
Technique”, Semicon Technology Asia 1998/9, Nordica
International. 3.F Block B, Quarry Bay, Hong Kong, p.33.
5. T.A. Carbone, “Solid Source Doping
of a Double Polysilicon Capacitor”, Semiconductor International,
Nov. (1997) p. 89-95.
6. J.E. Rapp and T. A. Carbone, “Surface
Roughness of Polysilicon Layers Doped with Solid Sources”,
Presented at SEMICON® China 99 Technical Symposium, March
17, 1999, Beijing.
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