Low temperature deformation mechanism of semiconductor single crystal and molding of Ge microlens array by direct electrical heating

Kai Tokuhiro,Yasuhiko Shimotsuma,Satoru Hachinohe,Makoto Okano,Masahiro Shimizu,Kiyotaka Miura

doi:10.1063/5.0003218

Abstract

Although deforming a silicon single crystal at a temperature of about 600 °C lower than its melting point (1414 °C) by direct electrical heating was successfully demonstrated, the mechanism has still not been fully clarified. In this paper, we propose a model for the low temperature deformation of a semiconductor single crystal by direct electrical heating. The thermographic observation during direct electrical heating reveals that the local temperature is higher at the region where dense dislocation occurred in the semiconductor single crystal by uniaxial pressing. This is interpreted in terms of the scattering of an electron by the dislocation leading to an increase in the electrical resistivity. Finally, the deformation temperature of the semiconductor single crystal apparently becomes low due to the occurrence of such hot spots. We have also demonstrated an application to mold a microlens array composed of a germanium single crystal with a focal length of 25 µm.

Highlights

It is well known that semiconductors such as silicon (Si) and germanium (Ge) are brittle materials because they have strong chemical bond anisotropy
We confirmed that the temperature of the region with many dislocations in the Si single crystal was higher than that of the region with few dislocations during direct electrical heating
Since the electrical resistivity increased with an increase in number of dislocations, the drift electrons were scattered by the dislocations, leading to a temperature that was locally hot

Summary

Introduction

It is well known that semiconductors such as silicon (Si) and germanium (Ge) are brittle materials because they have strong chemical bond anisotropy. We have demonstrated the deformation of the Si single crystal at a temperature of about 600 ○C lower than its melting point (1414 ○C) by direct electrical heating with a pulsed current.. The mechanism of the deformation of the Si single crystal at a temperature hundreds of degrees below its melting point by direct electrical heating has not been fully understood. The phenomenon in which the plastic deformation or dislocation movement is promoted by the electric current has been reported for alloys and phase change materials and is called the electroplastic effect.. The phenomenon in which the plastic deformation or dislocation movement is promoted by the electric current has been reported for alloys and phase change materials and is called the electroplastic effect.5–7 Such an electroplastic effect is mainly explained by the following two models. The first model is that the electrons are scattered by dislocations and the dislocations become locally hot. The second is that the electrons collide with dislocations and give the dislocations momentum, which is called the electrical wind force.

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Conclusion