Takuya Futase

Pattern-Independent PMD Layer Planarization by Controlling its Volume Before CMP

We achieved excellent planarization for a pre-metal dielectric (PMD) layer regardless of its pattern density distribution by making the distribution uniform before chemical mechanical polishing (CMP) without any stopper layer. The distribution control was done by lithography using a checkered reticle on the high-density PMD area followed by etching of the PMD layer to uniformize the CMP rates at both areas. After this planarization, the PMD layer was flattened in the local and global regions. The PMD step-height within chip was approximately 8 nm (approximately 1% of PMD height), which is a variation of less than one tenth compared with conventional planarization, and the non-uniformity of PMD thickness within wafer was approximately 2%. The planarized PMD layer suppressed the defocusing in lithography for contact hole formation on the layer, thus dramatically reducing contact-open failures in a chip of approximately 50 × 110 nm in diameter with 620-nm high-contact holes. The number of defects was one-thousandth that of a conventionally planarized PMD layer.