US Patent 11935746 Pattern formation through mask stress management and resulting structures

As deposited, hard mask thin films have internal stress components which are an artifact of the material, thickness, deposition process of the mask layer as well as of the underlying materials and topography. This internal stress can cause distortion and twisting of the mask layer when it is patterned, especially when sub-micron critical dimensions are being patterned. A stress-compensating process is employed to reduce the impact of this internal stress. Heat treatment can be employed to relax the stress, as an example. In another example, a second mask layer with an opposite internal stress component is employed to offset the internal stress component in the hard mask layer.