DEFECTS IN SILICON AFTER B- A STUDY USING A POSITRON-BEAM TECHNIQUE, RUTHERFORD BACKSCATTERING, SECONDARY NEUTRAL MASS-SPECTROSCOPY, AND INFRARED-ABSORPTION SPECTROSCOPY( IMPLANTATION )

The distribution of defects in Si (100), (110), and (111) after boron implantation and annealing processes was measured by means of differen t methods. Boron implantation was carried out at 300 K with three ener gies (50, 150, and 300 keV or 30, 90, and 180 keV) in multiple mode to obtain a homogeneously damaged layer. Ion fluences ranged from 10(14) to 10(16) B+ cm(-2). The profile of vacancy-type defects was detected by variable energy positron annihilation spectroscopy (VEPAS). The de fect concentration increases proportionally to root phi, where phi, is the ion fluence. It was found that the line-shape parameter S of the positron-electron annihilation peak in the implanted layer increases w ith phi. The divacancy (2 upsilon) concentration observed by infrared absorption spectroscopy (IRAS) was nearly constant in all samples (abo ut 1.8 X 10(19) cm(-3)). It can be concluded that divacancies are not the main vacancy-type defect and the increasing S parameter must be at tributed to additional defects of larger open volume. A value S-defect /S-bulk = 1.048 was fitted for the dominating defect, where S-2 upsilo n/S-bulk = 1. 04 Rutherford backscattering (RBS) measurements were car ried out to detect the distribution of displaced lattice atoms. The de fect-production rate was proportional to root phi again. The concentra tion profiles of implanted ions were measured with sputtered neutral m ass spectrometry (SNMS). In addition, Monte Carlo calculations were do ne with the TRIM code. The nearly homogenous defect distributions up t o a depth of 1 mu m found by VEPAS, TRIM, and RBS are in very good acc ordance. The samples were annealed up to 1150 K. It was found that the annealing behavior of vacancylike defects depends on the implantation dose and on the sample material under investigation. The divacancies are annealed at 470 K as measured by IRAS. An annealing stage of vacan cy clusters at 725 K was observed in all samples by VEPAS. In Czochral ski material, a decrease of the S parameter below the value of defect- free Si was observed after annealing at about 750 K. This can only be explained by the appearance of a different defect type, most likely an oxygen-vacancy complex. At high ion fluences (10(16) B+ cm(-2)), an i ncrease of the S parameter above the defect value at room temperature was observed after annealing at 700 K in a region 100 nm below the sur face. This high S parameter is caused by the creation of larger vacanc y clusters. These defects remain stable after annealing at 850 K. Corr elated RBS and SNMS measurements were done at identically implanted sa mples for all annealing stages.