Growth of Hydrogenated Amorphous Silicon (A-Si:H) on Patterned Substrates for Increased Mechanical Stability

Residual stress in hydrogenated amorphous silicon (a-Si:H) film has been studied. Deposition on square island pattern reduced the stress when the lateral dimension of the islands became comparable to the film thickness. The overall stress was reduced by approximately 40% when the lateral dimension was decreased to 40 μm, but the adhesion was not improved much. However, substrates having a 2-dimensional array of inversed pyramids of 200 μm in lateral dimension produced overall stress 3∼4 times lower than that on the normal substrates. The inversed pyramid structure also had other advantages including minimized delamination and increased effective thickness. Computer simulation confirmed that the overall stress can be reduced by deposition on the pyramidal structure.