High resolution X-ray diffraction study of proton irradiated silicon crystals

Abstract

Radiation-induced modification of semiconductors is achieved by controlled introduction of intrinsic structural and impurity defects. Conventionally, introduction of radiation-induced defects is used as an efficient tool for controlling the lifetime of metastable carriers in local areas of silicon based devices and supporting mechanisms of avalanche-like breakdown through radiation-induced defect levels. Desired parameters of damaged layers are typically achieved during post-implantation heat treatment. There are recent applications of proton irradiation in silicon technology. A significant growth of luminescence was observed in proton irradiated silicon and attributed to the formation of special rod-shaped clusters of interstitial type radiation defects. We have studied the transformation of radiation-induced defects forming as a result of proton implantation into n silicon crystals with a resistivity of 100 Ω cm using high resolution X-ray diffraction and shown that sequential implantation of 100, 200 and 300 keV protons with a fluence of 2.1016 cm−2 causes the formation of a 2.4 μm thick damaged layer with a greater lattice parameter. The layer forms simultaneously with intrinsic clusters of vacancy and interstitial type radiation-induced defects. Vacuum annealing of the irradiated crystals at 600 °C increases the power of the radiation-induced defects of both types and reduces their quantity. Interstitial type defects dominate after annealing at 1100 °C. We have assessed the power of the defects at every transformation stage.

Keywords

• Silicon
• H+ implantation
• Annealing
• High-resolution X-ray diffractometry