Nickel phosphorus coated substrate micro-defect reduction through chemical mechanical planarization process optimization

Abstract

Chemical mechanical planarization (CMP) was known as a process to gain superfine surface finish with high precision mechanical parameters. It widely used within semiconductors wafer manufacturing and hard disk (HDD) industries. There’re very few research done in HDD compared with silicon wafer. Micro defect formation caused by first step polishing in multistep polishing reducing the “good sector” and areal density in HDD substrate platter. In this study, micro defect reduction became the main objectives and as main response with others parameters including material removal rate and micro waviness. A 2 level 4 factor fractional factorial with center points Resolution IV, Design of Experiment (DOE) with total of 12 experimental runs was chosen for main effect and interaction screening purposes. All key factors such as platen rotation speed (rpm), applied pressure (g/cm2), slurry distribution points and slurry flow rate (ml/min) were then being optimized using Response Surface Method (RSM) setup of a set of full factorial 4 factors with center point, single replicate, 8 axial point and 2 alpha significance value with total 31 random runs. Results shows that all the input factors were affecting MRR and MD count except micro waviness which not respond to all input factors applied. Optimum input parameter setup were then established with setup of applied pressure (103.1 g/cm2), slurry distribution points (4/5 points), slurry flow rate (381.6 ml/min) and platen rotation speed (15.7 rpm). Predicted composite desirability gained to be 0.998, which can be satisfactory accepted. Verification runs from the parameter setup shows and concluded that the desired MD and MRR successfully achieved with 1.688% variation.