Film and surface stress during Al2O3 thermal atomic layer etching using; in situ; wafer curvature measurements Journal Article uri icon

Overview

abstract

  • In situ wafer curvature measurements were employed to monitor film and surface stress during Al2O3 thermal atomic layer etching (ALE). The Al2O3 thermal ALE was performed using fluorination and ligand-exchange reactions using sequential hydrogen fluoride (HF) and trimethylaluminum [TMA, Al(CH3)3] exposures at temperatures from 250 to 300 °C. The initial Al2O3 films were grown using Al2O3 atomic layer deposition (ALD) with TMA and H2O as the reactants. These Al2O3 ALD films are known to be under tensile stress. The progressive decrease in stress-thickness versus Al2O3 thermal ALE cycles was consistent with the linear removal of the Al2O3 ALD film that contains tensile stress. The results indicated that ALE can be used as a layer removal method to determine the stress distribution in a thin film. The reduction of the stress-thickness by Al2O3 thermal ALE at 250, 275, and 300 °C was consistent with the Al2O3 etch rates at these temperatures. Surface stresses corresponding to the fluorination and ligand-exchange reactions were also monitored during Al2O3 thermal ALE. The TMA reaction resulted in an average negative stress-thickness change of −0.50 ± 0.07 N/m that was consistent with a compressive surface stress. This negative stress-thickness change was attributed to repulsive interactions between surface methyl groups. The subsequent HF reaction then produced a positive stress-thickness change by releasing the compressive stress from the TMA reaction. The fluorination of the initial Al2O3 ALD film by HF led to a negative stress-thickness change that was consistent with a gain in compressive stress. The amount of this negative stress-thickness change depended on the thickness of the initial Al2O3 ALD film. The average negative stress-thickness change of −0.52 ± 0.08 N/m after >8 Al2O3 ALD cycles suggested that the fluorination depth during HF exposure to Al2O3 was approximately 9–10 Å.

publication date

  • May 1, 2026

Date in CU Experts

  • April 30, 2026 3:05 AM

Full Author List

  • Vanfleet RB; Bright VM; George SM

author count

  • 3

Other Profiles

International Standard Serial Number (ISSN)

  • 0734-2101

Electronic International Standard Serial Number (EISSN)

  • 1520-8559

Additional Document Info

volume

  • 44

issue

  • 3

number

  • 032605