28nm Planar Flow

Device Context and Integration Logic

The AA Hardmask Deposition step is positioned after pad oxide growth and pad nitride deposition to introduce an additional, more etch-resistant masking layer that decouples lithographic pattern fidelity from subsequent aggressive plasma etching steps used in STI formation [A1].The pad oxide and pad nitride primarily serve to buffer mechanical stress and protect the silicon surface, but their etch selectivity and thickness scalability alone are insuffici…

• [High] Hardmask Erosion During STI Etch: Insufficient film density or weak bonding leads to accelerated chemical or ion-induced erosion during anisotropic trench etching, resulting in CD loss and distorted trench profiles that degrade isolation effectiveness [P3].- [High] Stress-Induced Cracking or Delamination: Excessive intrinsic tensile or compressive stress in the hardmask can accumulate with underlying pad nitride stress, causing microcracks or interfacial delamination that propag…