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DEEP LEVEL GENERATION-ANNIHILATION IN NITROGEN DOPED FZ CRYSTALS T. ABE, H. HARADA, N. OZAWA, and K. ADOMI Shin-Etsu Handotai Co., 2-13-1 Isobe, Annaka-Shi Gunma-Ken 379-01 Japan ABSTRACT Nitrogen atoms exist in silicon as non-reactive nitrogen molecules. This is concluded frw fo I-R absorption experiments: one is the nitrogen isotope effects on N- N pairs and the other is silicon isotope shifts at 10 K. Intrinsic resistivities (over 20 K ohm-cm) are obtained by annealing at 0 1000 C, 1 min. in N2 in both p- and n-type nitrogen doped thin wafers. Resistivity increases are due to deep- level generations: 0.66 eV above the valence band for p-type and mainly 0.44 eV below the conduction band for n-type material. These deep levels are considered to be formed by nitrogen pairs and divacancies which are incorporated during growth. Since divacancies are easy to out diffuse to the wafers surface, the deep levels are also irreversibly removed. Diffusion coefficient of Si intersititialswici'ch are annihilated with divacancies in the lattice are calculated as 6x10-/"c s and 2xW0 cm /s at 900 C and 1000 C respectively. Migration energy of Si interstitials is about 4.5 eV. INTRODUCTION The intrinsic gettering (IG)[l] and strengthening [2] techniques by controlling the interstitial oxygen concentration are popular in VLSI processes these days. These discoveries changed the traditional ways from the crystallographyically ideal crystals into the perfect crystals for the electronic devices. Owing to the lack of these two effects, FZ crystals having the superiority in hyperpurity are used rarely for VLSI processes. The new effects [3,4], however, have been reported by intentionally doping nitrogen into FZ crystals during growth: 1. The crystals are 1 strejigthened by the incorporation of a low concentration (lxlO /cm ) of nitrogen [5]. 2. Swirls and D-defects can be diminisyd J6] within the low concentration of the detection limit (2xlO /cm ) by IR. In order to understand such anomalous behavior of nitrogen in silicon, nitrogen configuration in the latticel esh 5 be studied at first. Recently, Stein [7] presentej 5 the existence of N- N pairs, which are formed by ion implant.i 1 .Nand N simultaneously. In this paper, we confirm existence of these N- N pairs in FZ crystals and these pairs are almost isolated from silicon lattice, and moreover, deep levels are generated with interaction between these pairs and divacancies which are incorporated into crystals during growth. EXPERIMENTAL 1. Double doping of 1 4 N and 1 5 N SiN is produced as the result og reaction between nitrogen gas N and the fees rod surface overheated 1200 C. Then the Si 3 N4 is melted, ang finally incorporated into crtals in FZ groy~h process. In this experiment, nitrogen isotope gas N2 followed by N2 are used for the 100 crystal

Mat. Res. Soc. Symp. Proc. Vol. 59. *ý1986 Materials Research Society

538

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