Investigation on S-136 steel surface planarization by chemical mechanical polishing

• The CMP behavior of S-136 mold steel was investigated in this paper.
• Optimized process parameters of CMP were proposed for S-136 steel.
• The RMS roughness and MRR were 3.01 nm and 187 nm/min in optimized condition.
• The CMP mechanism of S-136 steel was discussed in detail.

S-136 (STAVAX ESR) steel has been widely applied in the mold manufacturing industry. Commercially available S-136 steel possesses high surface roughness, which exerts negative effects on the device performance. In this paper, S-136 steel surface planarization using chemical mechanical polishing (CMP) was investigated and the process parameters included down pressure, platen speed, slurry pH and abrasive category. The results demonstrated that the relationship of material removal rate (MRR) with respect to the multiply of pressure and platen speed was in accordance with a modified Preston equation: MRR = (KP + B0) V + R0. With the variation of pH, the MRR changed rapidly. Compared with initial root mean square (RMS) roughness of 37.47 nm, the ultra-smooth surface with RMS roughness 3.01 nm was obtained under optimized condition with MRR as high as 187 nm/min. Finally, optimized CMP process parameters for S-136 steel were proposed and its CMP mechanism was discussed in detail.

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