Trouble Shooting

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	Processing Parameters
	Source fusing to boat	(See "Sticking") Periodically rotate sources within slots	Carrier Design
	Tight Slots	See "Sticking"	Carrier Design
	No silicon between sources	Always have silicon between sources during use	Aging

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	Aging
	Incorrect boat design	Etch or recut slots Increase distance across side rails	Carrier Design
	Excessive B₂O₃ or P₂O₅ on boat and inside slots	Clean boat in dilute HF Periodically rotate sources within slots	Storage

Breakage	Excessive warpage	Check "warpage" and "sticking" problems
	No silicon between sources	Always have silicon between sources during use	Aging
	Thermal shock	Decrease push/pull temps. and rates Decrease ramp rates	Processing Parameters

Black Spots	Cutting fluid in surface imperfections	Reage in 25-100% oxygen	Aging Cleaning: BoronPlus Cleaning: PhosPlus

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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