Self Annealing Ion Implantation in thin Silicon Films
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SELF ANNEALING ION IMPLANTATION IN THIN SILICON FILMS
J. D. Rubio, R. P. Vijay and R. R. Hart Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843
ABSTRACT The self annealing phenomenon was studied utilizing 1 cm diameter, 1 lm thick, oriented silicon films. Previous results established the viability of the self annealing process for medium energy argon beams incident on similar targets [1]. In the current work, doubly aligned backscatter spectra were obtained to improve the sensitivity of the residual lattice damage measurements. In addition, some implantations were performed at elevated temperatures to independently determine the effect of the flux and the sample temperature on the self annealing process. The results showed strong correlations between the implantation flux, sample temperature and the residual lattice damage. Two distinct temperature regions were observed above and below 330 °C with corresponding activation energies of 1.5 eV and 0.1 eV. INTRODUCTION Ion implantation has become an essential tool in the production of semiconductor devices. A disadvantage of the implantation process, however, is that nuclear collisions between the implanted ions and the lattice atoms can severely damage the crystalline structure of the semiconductor material. Consequently, an annealing treatment is needed to repair the implantation damage and incorporate the implanted dopants onto electrically active substitutional lattice sites. Currently, conventional annealing processes require implanted semiconductor wafers to be placed in a furnace at temperatures of 1000 °C for times on the order of 30 minutes. The high temperature of the annealing process may have deleterious effects on device quality and performance. Alternative annealing techniques using laser and electron beams can reduce the annealing time to less than 1 second but require high cost equipment [2-4]. Self annealing ion implantation combines ion implantation and annealing into a single, low temperature process step. The viability of this process has been proven using thin silicon films as targets [1]. In the current investigation, the sensitivity of RBS measurements to residual lattice damage was increased by using a double alignment technique. In addition, the temperature and flux dependence of the self annealing process was studied by performing implantations inside a radiative oven at elevated temperatures.
Mat. Res. Soc. Symp. Proc. Vol. 201. c 1991 Materials Research Society
254
EXPERIMENTAL PROCEDURE The sample properties, dimensions and method of preparation are described in reference [1]. Double alignment RBS spectra were obtained before and after ion implantation by aligning the incident 120 keV proton beam with the axis of the sample and the backscatter particle detector with the axis. The random to aligned yield ratios thus obtained were on the order of 100:1. 1 The samples were then implanted with 120 keV Ar+ to fluences of 1x10 4 2 13 14 2 ions/cm with fluxes varying between 4.2x10 -1.3x10 Ar/seccm and analyz
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