Temperature Effects on Internal Stress in Molybdenum Thin Films on Single-Crystal Silicon Substrates

Abstract

Molybdenum thin films were deposited with an electron beam gun onto (100)- oriented silicon substrates. The samples were then annealed in vacuum, and the internal stresses in the molybdenum thin films were studied as functions both of the annealing temperature and of the substrate temperature during deposition. Silicide formation and the film thickness after annealing were monitored by the Rutherford backscattering spectrometry technique, and the stress was determined from the substrate curvature which was measured from Newton's ring interference fringes. It was found that, when the substrate temperature was kept at 400°C during deposition, MoSi2 was formed after annealing at temperatures above 500 °C. This MoSi2 exhibited large tensile stresses of about 2 × 1010 dyn cm−2 for annealing above 700 °C, whereas at the lower annealing temperature of 500 °C the stresses were compressive. No detectable silicides were observed when the substrates were kept at temperatures below 150 °C. The Mo-Si film stresses were tensile for substrates kept at room temperature during deposition and compressive for substrates kept at 150 °C.