High-Resolution Transmission Electron Microscopy (HRTEM) Imaging of ALD Films.

Isotropic etch profiles are crucial for semiconductors. This case study done by Infinitalab reports highly accurate and statistically significant measurement of sub-nanometer level thickness variations to evaluate the etch profile uniformity of atomic layer deposited (ALD) films, by HRTEM imaging.

High-resolution TEM imaging of the trench cross-sections is used to reveal the etch profile of atomic layer deposited (ALD) films. Sub-nanometer level thickness variations can affect properties of ALD films and therefore highly accurate measurements across ALD films are required. We have developed an image processing program that can rapidly measure grayscale variations across these layers, precisely, down to a pixel. As many as 100 of such measurements are made across each trench and analyzed to accurately determine the average film thickness and the etch profile’s uniformity.

Sub-nanometer accuracy is achieved by making 100s of measurements at different locations of the trench. Since visually identifying the start and end location of the film can introduce errors, a semi-automatic method of picking out the start and the endpoint from the intensity profile (See Fig. 1) across the film is used. Average and standard deviations are plotted against location (Fig. 2) to provide a visual map of highly accurate and statistically significant sub-nanometer variations of the film for each trench.

*Fig. 1. Cross-sectional TEM images of Al2O3 deposited and etched on 3D Si trench structures. Reference [1]*

*Fig. 2. An example of film thickness measurements on a trench. Each point is an average of 10 measurements. Error bars represent standard deviation.*

*Fig. 3. TEM of ALD film etch profile (a) top of the trench (b) Side of the trench. Reference [2]*

Isotropic etch profiles are crucial in semiconductor wafers, PCB and IC manufacturing. Infinita Lab’s vast network of materials testing labs and experts enables us to produce reliable, reproducible, high-precision measurements in these smaller technology nodes using cutting-edge meteorology techniques.

[1] Isotropic plasma atomic layer etching of Al2O3 using a fluorine containing plasma and Al(CH3)3, Appl. Phys. Lett. 117, 162107 (2020)

[2] Status and prospects of plasma-assisted atomic layer deposition featured, Journal of Vacuum Science & Technology A 37, 030902 (2019)