Stress in chromium thin films deposited by DC magnetron sputtering on grounded cupper and stainless-steel substrate holders

TL;DR

This study investigates how substrate material and film thickness influence the intrinsic stress in chromium thin films deposited by DC magnetron sputtering, revealing substrate-dependent stress variations and effects of annealing.

Contribution

It provides new insights into substrate-dependent stress behavior and the impact of annealing on chromium thin films, highlighting the role of substrate conductivity and growth mechanisms.

Findings

Stress decreases with increasing film thickness.

Higher stress observed on copper substrate holders.

Stress increases after annealing due to diffusion and relaxation.

Abstract

Chromium thin films deposited on silicon substrates by DC magnetron sputtering were systematically investigated as a function of film thickness, using a DC power of 50 W and a post-deposition annealing temperature of 200 C. Two types of grounded substrate holders, copper and stainless steel, were employed to assess substrate-dependent effects. The intrinsic stress, determined by the wafer curvature method, decreases with increasing film thickness but increases with the annealing temperature. It is observed that for thinner as-deposited chromium films, the stress showed a pronounced irreversible increase when measured immediately after deposition and after several days of aging. Films deposited on copper holders consistently exhibited higher stress values than those grown on stainless steel holders. These observations suggest that the intrinsic stress in as-deposited films is linked to the growth mechanism, while the stress increase after annealing may be related to thermally active diffusion and structural relaxation. The higher stress in films grown on copper substrate holder can likely be associated with enhanced ion bombardment due to the higher electrical conductivity of copper.