Cl. Wang et al., THE VIABILITY OF GEH4-BASED IN-SITU CLEAN FOR LOW-TEMPERATURE SILICONEPITAXIAL-GROWTH, Journal of the Electrochemical Society, 143(7), 1996, pp. 2387-2391
Several groups have reported on the use of GeH4 for in situ cleaning o
f the silicon surface prior to the epitaxial growth of silicon. Howeve
r, questions remain as to the extent to which the surface oxide can be
removed from the silicon surface by GeH4. We report here our results
from the study of an in. situ GeH4-based clean in the temperature rang
e of 500 to 700 degrees C with 10 to 100 ppm GeH4 in H-2. For comparis
on, a H-2 bake in. situ clean was also examined in the temperature ran
ge of 600 to 950 degrees C. The results showed that surface oxide coul
d not be removed by GeH, to an adequate level before excessive Ge depo
sits which causes epitaxial stacking fault. A 120 s H-2 bake at 850 de
grees C of an HF dipped surface results in no detectable oxygen based
on secondary ion mass spectroscopy. Also, we demonstrate that the qual
ity of the epitaxial layer grown after the clean is not necessarily a
good indication of the effectiveness of the clean when the surface oxy
gen coverage is below a certain value. We conclude that due to the com
petition between the surface oxide removal and the Ge deposition, GeH4
-based clean is not suitable for high quality Si epitaxial growth by c
hemical vapor deposition techniques.