Trouble Shooting

Troubleshooting
Page 3

1 - 2 - 3

Problems with Silicon Wafers

Problem	Probable Cause	Suggested Solution	Comments
Silicon Damage	Excessive glass transfer	Use correct source for deposition temp.	(7)
	Residual photoresist	Use "RCA Clean" immediately after stripping resist	(8)
	Moisture in tube	Avoid backstreaming Clean boats in dil. HF Use improved storage techniques	Ambient Gases Storage (2)
	Moisture absorbed by deposited glass after dep.	Keep silicon dry by cooling in elephant Immediately etch off deposited glass with dilute HF Immediately rinse silicon in DI water and dry	(9)
	Insufficient Oxygen in gas	Use 1/4-3% when dep. temp. is above 1000°C Use trace amounts of oxygen (ie 1000ppm) when dep. temp is low Use argon gas instead of nitrogen	Ambient Gases
	Thermal gradients in silicon wafers	Decrease push/pull temp. and rates Decrease ramp rates Cool in elephant	Processing Parameters
	Failure to remove boron- silicon phase (stain)	Use LTO and etch before drive	Ambient Gases

Field Oxide Damage After Drive	Moisture absorbed by deposited glass after dep.	Keep silicon dry by cooling in elephant Immediately etch off deposited glass with dilute HF Immediately rinse silicon in DI water and dry	(9)

Silicon Warping	High thermal gradients across silicon wafer	Decrease push/pull temps. and rates Decrease ramp rates Cool in Elephant	Processing Parameters

Staining	Excessive boron-silicon phase on silicon surface	Increase oxygen in carrier gas Use high temp source Use LTO	Ambient Gases (7)

Low Minority Carrier Lifetime	Impurities from boat, tube, sources, etc	Use gettering (TCA, phosphorus dep., back surface damage, etc.) Induce minor surface damage by decreasing oxygen in carrier gas Age sources	Ambient Gases (10),(11)
Low Minority Carrier Lifetime	Process-induced defects in silicon wafers	Slowly anneal doped silicon wafers	(12)

Increasing Beta or Variable Beta	Moisture absorption of PhosPlus® sources	Insert sources in diffusion tube to dry Store in dry environment	(13)

Rough Polysilicon Surfaces	Overdoping poly with phosphorus	Decrease amount of phosphorus depositing on silicon

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.

1 - 2 - 3