Crystallization of PECVD-deposited Amorphous Silicon Thin Films Using the Aluminum-induced Crystallization Technique

Abstract

The investigation of polycrystalline silicon made on glass and carbon coated nickel substrates by aluminum-induced crystallization of amorphous silicon (a-Si) is reported. Aluminum was sputtered onto a-Si films deposited in an ultra-high-vacuum plasma-enhanced chemical vapor deposition (PECVD) system to form Al/a-Si substrate structures. These samples were then vacuum annealed for 30 min. at temperatures in the range 150°C -350°C. X-ray diffractometry (XRD) and transmission electron microscopy (TEM) were utilized to determine the crystallization temperature. Annealing at 200°C resulted in the formation of crystalline Si as observed by TEM, and at 275°C as observed by XRD. These different results obtained by these two techniques are discussed and explained. Scanning electron microscopy (SEM) was used to study the surface morphology. SEM pictures of the interacted film surface of Al/a-Si structures annealed above the crystallization temperature clearly show hillocks or bumps distributed all over the surface. The presence of these hillocks or bumps after annealing at 275°C and above confirms that the a-Si has been crystallized.