Characterization of Ion-Implanted SiO 2 Properties Applicable to Laser Processing
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Inc.
Laser and Electron-Beam Solid Interactions
391
and Materials Processing
CHARACTERIZATION OF ION-IMPLANTED SiO2 PROPERTIES APPLICABLE TO LASER PROCESSING T. C. TENG, Y. SHIAU, Y. S. CHEN, C. National Semiconductor, Santa Clara,
SKINNER California
J. D. PENG, L. J. PALKUTI Advanced Research and Applications Corp.,
Sunnyvale,
California
ABSTRACT The use of an antireflection oxide film applicable to laser annealing process has been investigated. The optical properties of the antireflection oxide film are changed by ion implantation although the antireflection characteristics are similar to calculations based on nominal optical constants. Implantation annealing can be achieved at powers lower than predicted by calculations. Using the antireflection(AR) technique, n+-p junction diodes were fabricated. Reverse bias junction leakage is around 10-9 A/cm2 , comparable to those annealed thermally. Short channel MOS devices were also fabricated and indicated much better resistance to the short channel effect than those thermally annealed. INTRODUCTION The CW argon laser can activate high-dose ion implantation in silicon without diffusion (1,2). This feature is attractive for fabricating small geometry devices. Short-channel polysilicon gate MOSFET's with arsenic-implanted and laser processed source and drain regions were successfully fabricated without the deposition of a protective layer. No cracking or delamination was observed in either the Si0 2 or polysilicon films (3). The diodes formed in these early experiments exhibited higher reverse-bias leakage than similar devices formed using standard thermal annealing. TEM investigation indicated that this increased leakage was caused by damage introduced around the n+-field oxide perimeter during the laser processing (4). This damage was attributed to enhanced optical energy absorption at the sloped edge of the field oxide around the device perimeter (5,6). If a uniform antireflection coating is applied over the n+ region (see Fig. 1), then the absorption efficiency of laser power into the n+ region can be maximized. Hence, the incident laser power necessary for annealing is minimized, and thus the laser-induced damage region along the junction perimeter can be eliminated. Using such a technique, n+-p junctions have been successfully fabricated by CW argon laser annealing, exhibiting a junction quality comparable to or better than those annealed thermally (7). To determine the thickness and uniformity requirements of the AR coating needed in an NMOS fabrication sequence that incorporates laser processing, experiments were conducted on the usefulness of
392 both thermal and plasma CVD oxides for such an AR coating. Since a high-temperature process is required for thermal oxidation, this AR coating must be grown prior to ion-implantation, while the plasma CVD oxide coating can be deposited after ion-implantation. Ion-implantation changes Si0 2 and substrate optical properties and, as such, may modify the AR requirements. In this paper, we describe Si0 2 properties
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