Troubleshooting
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Periodically a diffusion engineer will experience certain difficulties while using the BoronPlus® or PhosPlus® sources in his/her diffusion system. If this occurs, it has been our experience that slight modifications of the current processing parameters and procedures will usually bring the process back within specifications. With this in mind, the following table was compiled. It lists some of the problems that are often experienced by the diffusion engineer, it outlines the common causes of these problems, and it contains a number of suggestions that often solve the problems.

Please keep in mind that the information contained in this bulletin is very general and should only be used as a guide to troubleshooting a system. If any problem continues to persist, the process engineer is encouraged to contact us for additional assistance.

Source Problems
Problem
Probable Cause
Suggested Solution
Comments*
Warpage
Excessive temp. for
source type
Use correct
source
Excessive temp. gradients across sources
  • Decrease push/pull
    temps. and rates
  • Decrease ramp rate
  • Cool in elephant
  • Periodically rotate quartz boats
Source fusing to boat
(See "Sticking")
Periodically rotate sources within slots
Tight Slots
See "Sticking"
No silicon between sources
Always have silicon between sources during use
       
Sticking
(look for tiny
pieces of boat
on source or pieces of source on boat)
Excessive temp. for source type
Use correct source
Aging sources too long too high of a temp.
Follow aging recommendations
Incorrect boat design
  • Etch or recut slots
  • Increase distance across side rails
Excessive B2O3 or P2O5 on
boat and inside slots
  • Clean boat in dilute HF
  • Periodically rotate sources within slots
       
Breakage
Excessive warpage
Check "warpage" and "sticking" problems
No silicon between sources
Always have silicon between sources
during use
Thermal shock
  • Decrease push/pull temps. and rates
  • Decrease ramp rates
       
Black Spots
Cutting fluid in surface imperfections
Reage in 25-100% oxygen

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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