Analysis of buried oxide layer formation and mechanism of threading dislocation generation in the substoichiometric oxyg
- PDF / 2,019,303 Bytes
- 12 Pages / 576 x 792 pts Page_size
- 88 Downloads / 159 Views
The structure of SIMOX wafers implanted at 180 keV with doses of 0.1 X 10 18 -2.0 X 1018 16 O + cm"2 at 550 °C, followed by annealing over the temperature range of 1050-1350 °C, has been investigated using cross-sectional transmission electron microscopy and a chemical etching. With doses of 0.35 X 10 18 -0.4 X 1018 cm"2, a continuous buried oxide layer having no Si island inside is formed by high-temperature annealing at 1350 °C. At a dose of 0.7 X 1018 cnr 2 , multilayered oxide striations appear in the as-implanted wafer. These striations grow into multiple buried oxide layers after annealing at 1150 °C. The multiple layers lead to a discontinuous buried oxide layer, resulting in the formation of a number of Si micropaths between the top Si layer and the Si substrate when the wafer is annealed at 1350 °C. These Si paths cause the breakdown electric field strength of the buried oxide layer to deteriorate. With doses of 0.2 X 10 1 8 -0.3 X 1018 cm"2 and of higher than 1.3 X 1018 cm"2, an extremely high density of threading dislocations is generated in the top Si layer after annealing at 1350 °C. The dislocation density is greatly reduced to less than 103 cm"2 when the oxygen dose falls in the range of 0.35 X 10 18 -1.2 X 1018 c m 2 . Here we propose a mechanism that accounts for the threading dislocation generation at substoichiometric oxygen doses of less than 1.2 X 1018 cm"2.
I. INTRODUCTION 1
SIMOX, one of the silicon-on-insulator (SOI) technologies, has been applied to high-speed CMOS, intelligent-power CMOS, and radiation-hardened CMOS LSI's. 2 " 4 Among the SOI technologies, it is emerging as one of the most promising candidates for fabricating high-performance ULSI's using ultrathin-film CMOS/SOI.5 Much effort has been expanded over the past decade to reduce the threading dislocation density in the top Si layer of SIMOX wafers, in order to improve reliability in LSI's. A threading dislocation is defined as a defect spanning the top Si layer, from the buried oxide layer to the surface. A couple of methods6"8 have already been proposed for producing high-quality wafers with a low density of threading dislocations. Of these methods, wafers produced by low-dose oxygen implantation and subsequent high-temperature annealing promise to be the most useful approach because it is compatible with a greatly increased production throughput of SIMOX wafers.6 In addition, a thinner buried oxide layer formed by the low-dose implant effectively suppresses the short-channel effect of MOSFET's. 9 Therefore, this method should open the way to practical fabrication of ULSI's/SIMOX. However, details of the formation mechanism of the high-quality SIMOX wafers are still unclear. J. Mater. Res., Vol. 8, No. 3, Mar 1993 http://journals.cambridge.org
Downloaded: 13 Mar 2015
This paper describes the analysis of buried oxide layer formation using cross-sectional transmission electron microscopy (XTEM). Particular attention has been focused on the threading dislocation generation mechanism in the substoichiometric oxygen dose region
Data Loading...
