Low-Defect, High-Quality Simox Produced By Multiple Oxygen Implantation with Substoichiometric Total Dose
- PDF / 2,236,177 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 20 Downloads / 151 Views
LOW-DEFECT, HIGH-QUALITY SIMOX PRODUCED BY MULTIPLE OXYGEN IMPLANTATION WITH SUBSTOICHIOMETRIC TOTAL DOSE* F.
NAMAVAR,
E.
CORTESI,
Spire Corporation,
and P.
SIOSHANSI
Patriots Park, Bedford, MA 01730
ABSTRACT This work addresses the formation of Separation by IMplantation of OXygen (SIMOX) structures by multiple oxygen implantation into silicon and high temperature annealing. We observed no threading dislocation defects in the several plane view TEM and XTEM micro graphs of each of the samples implanted with a single dose of up to 8 x 1017 O+/cm2 . We also demonstrated that with a multiple low-dose (3 to 4 x 1017 O+/cm2 ) oxygen implantation and high temperature annealing process, we are able to produce continuous and uniform buried Si0 2 layers with a total dose of 1.1 x 1018 O+/cm2 (about 60% of the total dose for standard SIMOX). The density of defects is about 10 5 /cm 2 . There are no silicon islands in the buried layer, no Si02 precipitates in the silicon top layer, and the Si-SiO2 interfaces are sharp and smooth. SIMOX material with a high-quality Si top layer and a continuous buried layer has been produced with a total dose of 7 x 1017 O+/cm2 (40% of the total dose for standard SIMOX) and a two-step process. However, in this case there are a few Si islands present in the buried Si0 2 layer. INTRODUCTION The SIMOX process for formation of silicon-on-insulator (SOI) material has been studied extensively in recent years because of the technological importance of the material [1-5]. Standard commercially available SIMOX wafers are produced with a single implantation of 1.6 to 1.8 x 1018 0+/cm2 by means of high current implanters. A post-implant anneal is required to regrow the silicon and redistribute the oxygen [6,7]. Recent results indicate that very high temperature anneals, between 1250°C [8] and 1405°C, [9] are required in order to increase the oxygen mobility sufficiently to completely getter all oxygen to the Si-SiO2 interfaces. The standard SIMOX wafer typically has a silicon surface layer about 1400 to 1500 A thick and a buried layer about 4000 A thick. The interfaces are generally smooth and sharp, but there are some silicon islands in the buried oxide layer even when annealed at temperatures as high as 1405*C [9]. In general, for annealing temperatures >1250°C, Si02 precipitates in the Si top layer disappear. However, threading dislocation defects in the silicon top layer continue to exist. The density of defects in2 this material has typically been observed at a level of about 108 to 1010/cm [2,9,10]. Although in some cases we have observed defect densities as low as 10 6 /cm 2 , a large sampling of our own standard wafers by plane view TEM has shown that the defect density is typically 108 to 10 9 /cm2. For the most part, these defects do not seem to play an important part from the point of view of CMOS device fabrication. However, they are considered detrimental for bipolar structures. For some time, we have studied [11] two methods to reduce the defect density in SIMOX wafers: (1) prevent
Data Loading...
