Microscratch testing method for systematic evaluation of the adhesion of atomic layer deposited thin films on silicon

Abstract

The scratch test method is widely used for adhesion evaluation of thin films and coatings. Usual critical load criteria designed for scratch testing of coatings were not applicable to thin atomic layer deposition (ALD) films on silicon wafers. Thus, the bases for critical load evaluation were established and the critical loads suitable for ALD coating adhesion evaluation on silicon wafers were determined in this paper as LCSi1, LCSi2, LCALD1, and LCALD2, representing the failure points of the silicon substrate and the coating delamination points of the ALD coating. The adhesion performance of the ALD Al2O3, TiO2, TiN, and TaCN+Ru coatings with a thickness range between 20 and 600 nm and deposition temperature between 30 and 410 °C on silicon wafers was investigated. In addition, the impact of the annealing process after deposition on adhesion was evaluated for selected cases. The tests carried out using scratch and Scotch tape test showed that the coating deposition and annealing temperature, thickness of the coating, and surface pretreatments of the Si wafer had an impact on the adhesion performance of the ALD coatings on the silicon wafer. There was also an improved load carrying capacity due to Al2O3, the magnitude of which depended on the coating thickness and the deposition temperature. The tape tests were carried out for selected coatings as a comparison. The results show that the scratch test is a useful and applicable tool for adhesion evaluation of ALD coatings, even when carried out for thin (20 nm thick) coatings.

Aluminum oxide/titanium dioxide nanolaminates grown by atomic layer deposition: Growth and mechanical properties

“…This is related to the previously reported finding that the TiO2 films grown at 250 °C and higher have lower critical loads in scratch testing than ALD Al2O3, behaviour most likely caused by crystallinity of the films grown in higher temperatures. 50 No significant difference was found between the critical load values nor the delamination behaviour of TAO when compared to ATO laminate (both grown at 200 °C, TiO2 fraction 60%, and total thickness 100 nm). Therefore both Al2O3 and TiO2 can be used as the starting layers of ALD growth on RCA-cleaned silicon.…”

“…49 Mechanical properties such as elastic modulus and hardness has been studied as a function of bilayer thickness using nanoindentation for films grown at 200 °C 39 and elastic modulus by bulge and shaft loading test. 49 The Al2O3 / TiO2 nanolaminate adhesion has been studied by indentation on stainless steel substrate, 41,40 and for reference ALD Al2O3 and ALD TiO2 materials on silicon 50 and on polymeric substrate. 51 Since there is no systematic data on residual stress, adhesion and mechanical properties of Al2O3 / TiO2…”

“…Four critical loads for adhesion were determined as described in Ref. 50 , namely LCSi1, LCSi2, LCALD1, LCALD2 representing the critical loads for the silicon substrate failure and the film delamination.…”

Molecular layer deposition builds biocompatible substrates for epithelial cells

“…By doing this, gas phase reactions are avoided and uniform coverage even on complex three‐dimensional substrates can be achieved. The cyclic nature of the process also enables monolayer control of the deposited films and provides the possibility to vary the type of building units as the film grows, ensuring control on the molecular level …”

“…The cyclic nature of the process also enables monolayer control of the deposited films and provides the possibility to vary the type of building units as the film grows, ensuring control on the molecular level. [16][17][18][19][20] While other coating techniques, such as physical vapor deposition, have been used for deposition of biomaterials, for example, as corrosion resistance materials in artificial joints, 21 design of bioinert and bioactive surfaces is a vast field where ALD/MLD is in its infancy. Recently, attempts have been made to produce biocompatible structures using ALD including deposition of biocompatible hydroxyapatite thin films 22 and hydrophilic ALD-deposited alumina thin films.…”