Oxygen Precipitation in N + Silicon
- PDF / 830,795 Bytes
- 8 Pages / 417.6 x 639 pts Page_size
- 71 Downloads / 242 Views
OXYGEN PRECIPITATION
W. DYSON*^ AND J.
IN N+ SILICON
MAKOVSKY**
* Monsanto Electronic Materials Co. Highway 79, St. Peters, ** Intel Corp. 3601 Juliette Lane, Santa Clara, CA 95051
Current address,
3601 Juliette Lane,
Santa Clara,
MO 63376
CA 95051
INTRODUCTION: The advantages of oxygen precipitation in terms of intrinsic gettering to reduce oxidation induced surface defect densities and improve minority carrier generation lifetimes ( T) are well documented in the literature (1-3). Various gettering cycles to establish oxygen precipitation in n type and p type nondegenerate substrates have been developed (4-6), based on homogeneous nucleation theory. For nondegenerate silicon no differences in oxygen precipitation kinetics related to the dopant type have been reported. However, with the increasing interest in both p/p+ and n/n+ epitaxial layers for CMOS devices (7), work on the precipitation of oxygen in both p+ and n+ degenerate silicon substrates has revealed a dependence of oxygen precipitation kinetics on dopant type ( 8-11). In the case of p+ silicon the differences in precipitation kinetics are small when compared to p- silicon (10,11). For n+ silicon it has been reported (8-11) that the dopant concentration plays a major role and that a significant retardation of oxygen precipitation is observed. There are currently two different explanations for the difficulty encountered in producing sufficient oxygen precipitation in n+ Si. These are the failure to incorporate sufficient oxygen into the crystal during crystal growth (12) and an interaction between intrinsic point defects and the n type dopant, which influences the oxygen precipitation kinetics (8,13). In order to understand the impact of initial oxygen concentration (IntOx) on precipitation in n+ silicon it is necessary to use well characterized (for oxygen) starting material. Once the IntOx has been determined its relationship to precipitation can be studied. In this paper we will report results on oxygen incorporation in n+ crystals and the impact of IntOx on precipitation for Low-High, High-Low-High and Multistep intrinsic gettering cycles. Results which demonstrate the relationship between oxygen precipitation or rather bulk defect densities (BDD) due to oxygen precipitation and minority carrier generation lifetimes will also be presented.
EXPERIMENTALi Two n+ (100), 100mm diameter, Sb doped (Rho=0.018-0.011 Ohm-cm.) crystals were grown using a growth process that when used for p- crystal growth produces initial oxygen values between 40 to 28ppma (ASTM F121-79) from seed to tail respectively. These crystals were sliced and axial position maintained during fabrication. Wafers spaced no more than 50 wafers apart were used for oxygen measurement by Secondary Ion Mass Spectroscopy (SIMS). In this way an inventory of characterized wafers was provided for subsequent precipitation studies which allowed comparison of precipitation behavior as a function of known IntOx. Wafers from various ingot positions were fabricated with either chemically etche
Data Loading...
