Measurement and empirical equation of critical stresses for slip generation from oxide precipitates in silicon wafers

Abstract

The behavior of slip dislocations generated from oxide precipitates or bulk microdefects (BMDs) in Czochralski silicon wafers with different BMD sizes and oxygen concentrations has been studied using three-point bending tests at high temperatures (700-850 °C). We have developed a method of measuring critical stresses for slip generation caused by BMD growth. It has been found that not only the locking effect of residual oxygen on dislocations but also other factors such as BMD size are important for critical stress to generate and mobilize slip dislocations on {111} crystallographic planes, especially in high temperature ranges. An empirical equation for the estimation of the critical stress has also been produced using a simple model and the experimental results obtained in this study. The formulation enables us to accurately estimate the behavior of slip deformation under various thermal stress conditions.

Effect of Surface Oxygen Concentration on Wafer Strength in Floating Zone Si Wafers

“…Effect of interstitial oxygen atoms on critical shear stress.-It is well known that oxygen atoms affect critical shear stress through locking effect. 5,10,19,20,[28][29][30][31][32] The locking stress can be expressed by the following;…”

“…Stress analysis.-Similar to previous studies, 10,20 the hightemperature three-point bending test was carried out using a Shimadzu AG-X universal testing machine equipped with a thermal treatment furnace. The specimen in the thermal treatment furnace was bent by a rod with a load cell.…”

“…One is the occurrence of slips due to oxygen precipitates. [10][11][12][13][14][15][16][17] When large thermal stress is applied to oxygen precipitates in the wafer, slip dislocations are generated at the precipitates, resulting in the bending of the wafer. However, wafers with low oxygen concentrations, such as FZ wafers, do not contain oxygen precipitates.…”

“…The cleaved specimens were pre-annealed at 1373 and 1423 K for 30 min, 2 h and 5 h, after which indents were introduced with a 10,20 Specimen width b is 14 mm and the distance between support pins L is 30 mm. Indents introduced by Vickers hardness tester on the specimen surface are placed at 0.5 mm pitch.…”

“…Figure 1. Schematic representation of the three-point bending test as shown in previous reports by Fujise et al10,20 Specimen width b is 14 mm and the distance between support pins L is 30 mm. Indents introduced by Vickers hardness tester on the specimen surface are placed at 0.5 mm pitch.…”