Troubleshooting
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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
  • Decrease oxygen in carrier gas
  • Check calibration of mass flow meters
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
  • Reduce flow rate
  • Periodically rotate sources in boat
  • Use oversize sources

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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