Formation of SiC, Si 3 N 4 , and SiO 2 by High-Dose Ion Implantation and Laser Annealing
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FORMATION OF SiC, ANNEALING
Si3N
407
AND SiO2 BY HIGH-DOSE ION IMPLANTATION AND LASER
S.W. CHIANG, Y.S. LIU, AND R.F. REIHL General Electric Corporate Research and Development Schenectady, New York, 12301, USA
ABSTRACT -2 + + 17 Hiqh-dose ion implantation (10 ions-cm ) of C , N and 0 at 50 KeV into silicon followed by pulsed laser annealing at 1.06 pm was studied. Formation of SiC, Si N4 , and SiO2 has been observed and investigated using Transmission Electron Microscopy (TEM) and Differential Fourier-Transform Infrared (FT-IR) Spectroscopy. Furthermore, in N -implanted and laser-annealed silicon samples, we have observed a celllike structure which has been identified to be spheroidal polycrystalline silicon formed by the rapid laser irradiation.
INTRODUCTION It has been shown that silicon compound layers can be formed by high-dose ion implantation and thermal annealing [1-5 ]. Ion implantation offers the advantages of controlled depth and high purity. The formation of SiO 2 , Si N4 . and SiC compound layers are of particular interest because of their elec ronic device applidation. However, the post-implant annealing temperature required 0 for the formation of these compounds is in the range of 850-1200 C [1-5]. For some applications, e.g., oxidation of multi-layer devices, high temperature could degrade the device performance. The present work has been motivated by the need to find a low-temperature process and to investigate the feasibility of using a localized laser beam for fabricating compound layers, especially for the three-dimensional devices. In the present study, we have demonstrated 1 he formation of SiC, Si N., and SiO films by high-dose ion implantation (_10 ions-cm ) and pulsed-laser anneahing at 1.06 Pm. EXPERIMENTAL METHOD P-type (100) silicon wafers, 3-5 a-cm, were implanted with 5T 7 KeV C, N+, or 0 at liquid nitrogen temperature. Ion fluences were 1 x 10 cm and the ion beam2 luxej were -3 WA-cm . This resulted in a peak concentration of - 8 x 190 cm3 at a depth of -0.12 pm, with the concentration falling below -4 x 10 cm at a depth of less than 0.03 pm. Laser annealing was carried out with a 70-nsec Nd:Glass laser pulse at 1.06 im which has a spot size of 2 26 mm. The laser energy density was varied in the range from 2.0 to 3.6 J-cm Samples for transmission electron microscopy (TEM) were chemically etched from the silicon back surfaces with a nitric and hydrofluoric acid solution. TEM and differential Fourier-transform infrared (FT-IR) spectroscopy have been employed to study the ion-implanted and laser-annealed samples.
408 RESULTS + Amorphous silicon formed by the high-dose ion implantation of C+, 0, and N was observed with TEM; no compound was found in the as-implanted samples. The surface of the laser-annealed repions exhibited a color change. The diameter of the color-changed areas in C -implanted sampes was +about twice of that in N - or 0 -implanted samples. Visible damage on N - or 0 -implanted surfaces 2 was observed at an energy density of about 2.3 j_m- . The C+-implanted •ampl
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