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OXYGEN-RELATED DEFECTS IN SILICON J. LENNART LINDSTROM AND BENGT G. SVENSSON National Defense Research Institute P.O. Box 1165 S-581 11 Linkoping, Sweden

ABSTRACT In this review we focus on oxygen-related defects created by electron irradiation (vacancy-oxygen defects) and subsequent thermal treatments. The annealing of the vacancy-oxygen pair (VO-center) at 300 - 350 OC is discussed as well as results from the formation and annealing of the successors to VO, the V02 and V03 -centers. It -s found that V02 is formed by diffusion of a vacancy-oxygen pair to an interstitial oxygen atom.

It is suggested that V03

is formed by the diffusion o- -nterstitial oxygen to a V02 -center (in the temperature range 450 - 485 OC).

At continued annealing at these temperatures

V03 is transferred to a new defect V04 by attaching one more oxygen. Simultaneously thermal donors are developing in a normal way i.e. as in an unirradiated sample. It

is therefore concluded that V02 is not an important core for

thermal donors but a possible nucleus for oxygen precipitation.

INTRODUCTION

The study of oxygen in silicon is a wide research field, including electrical,

structural and mechanical properties of the host crystal.

As the

silicon used in the fabrication of integrated circuits is grown by the Czochralski method, and contains typically about 1018 oxygen atoms cm- 3 , oxygen is a dominant impurity in these materials. Many oxygen related defects both present in as-grown material and introduced by different treatments have been found. The high demands on base materials used today and the development of new processing methods for VLSIcircuits have lately increased the research efforts to identify and understand these defects. in this review we shall focus on oxygen-related defects created by electron irradiation (vacancy-oxygen defects) and the annealing of these defects. We will also shortly discuss the effects of carbon on oxygen-defect formation and a suggested relation between vacancy-oxygen defects and thermal donors (at 450 OC).

Mat. Res. Soc. Symp. Proc- Vol. 59. 1986 Materials Research Society

46

OXYGEN IN SILICON Isolated oxygen exists as a bonded interstitial, 01, in a puckered bond centered configuration,

[1, 2, 3] which can be viewed as a Si 2 0 molecule bon-

ded in the silicon lattice. The presence of oxygen is revealed by observation at room temperature of an infrared (IR) absorption band at 1107 cm-1 [4, 5, 6]. There have been several studies of the strength of this band and its correlation with the oxygen content of silicon materials [7, 8]. For the results presented in this paper we have used

[Oil = 2.45 x 101 7a 1 1 07 3 where [Oi] is the interstitial oxygen concentration in at/cm and a 1 1 0 7 is

the absorption coefficient of the 1107 cm-1 band in cm-1.

[A recent investi-

gation [9] suggests that 2.45 should be changed to 3.00.] At low temperatures the 1107 cm-1 band shifts to higher frequencies and splits up into several bands. Some of them are assigned to an isotopic shift in frequency of Si 20 molecu