B+, P+, As+ and Si+ Ion Implantation Induced Defects in Silicon Studied by a Variable-Energy Positron Bean
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B+,P+,As+ AND Si+ ION IMPLANTATION INDUCED DEFECTS IN SILICON STUDIED BY A VARIABLE-ENERGY POSITRON BEAN JUN SUGIURA*, MAKOTO OGASAVARA*,' AKIRA UEDONO**, LONG VEI*** AND SHOICHIRO TANIGAWA*** *Hitachi Ltd., Device Development Center, Tokyo 198, Japan **University of Tokyo, dept. of Industrial Chemistry, Tokyo 113, Japan ***University of Tsukuba,
Institute of Materials Science,
Ibaraki 305, Japan
ABSTRACT Vacancy type defects introduced by As+, P+, Si+ and B+ Ion implantations into Si(100) single crystals were studied by a variable-energy Depth distributions of the defects were obtained from positron beam. measurements of Doppler broadening profiles of the positron annihilation as The results showed that this techa function of incident positron energy. nique Is sensitive not only to a vacancy type defect but to formation of The defects introduced by lower doses were identified as amorphous regions. By higher doses vacancy clusters from isochronal annealing experiments. 2 4 such as 5x101 /cm , amorphous layers were formed for l50KeV As+, 15OKeV P+, and 200KeV Si+ ions, and it was not formed for 8OKeV B+ by the dose of 15 /cm 2 . These results are consistent with the calculated critical 5x10 was observed with higher In the case of B+, pre-amorphous formation doses. 5 2 Ion beam current over 5mA and a dose of 5x101 /cm . INTRODUCTION Ion implantation technique is widely used for changing a surface Accurate control of depth property of semiconductors in selected regions. and quantity is the advantage of this technique, but defect production In an Many fundamental implanted substrate is one of the major side effects. studies on the defect behavior have been reported, but they are still the subject of controversy because of the lack of effective methods to observe The use of a variable-energy positron beam has emerged as a point defects. non-destructive and sensitive tool for studying vacancy-type defects in a Details of this technique would sub-surface region and a muitilayer system. In the present paper, we will report the study of be found In ref. l. defects in Si single crystal introduced by As+, P+., Si+, and B+ Ion Implantat ion. An individual implanted positron undergoes scattering events with electrons and atoms in a condensed material, reducing the energy until it Then a positron annihilates with an electron, and comes to thermal energy. A Doppler produces two annihilation photons with energies of 511KeV. broadened profile of these photons provides the momentum distribution of the A positron is repelled from positively charged ion annihilated electron. In a perfect material the Doppler broadened cores by a coulomb Interaction. energy spectrum consists of both a narrower parabolic part corresponding to the annihilation with conduction electrons or valence electrons and a In a material containing vacancy-type broader one with core electrons. defects, a positron is attracted to the defects and annihilates with an As a result, the annihilation probability with core electron at the place. electrons is reduced beca
