The influence of ultrasonic vibrations on material removal in the silicon wafer polishing using DDCAMRF: Experimental investigations and process optimization

Abstract

The present experimental investigation attempts to understand and address the effect of ultrasonic vibrations on material removal in the polishing of silicon wafers (1 0 0). The requisite finishing experimentations were performed on an indigenously developed experimental arrangement of double-disc chemical assisted magnetorheological finishing (DDCAMRF) process with longitudinal vibrations. The MR fluid used in the experiments consists of a water-based suspension prepared by mixing suitable amounts of carbonyl iron particles (CIPs), abrasive particles, and additives or stabilizers. The prepared MR fluid uses both mechanics and chemistry to finish the silicon surface. Mechanics is mainly responsible for micro-scratching of silicon surface, which gets “softened” by hydration utilizing DI water in the MR fluid. In this study, the ‘response surface methodology (RSM)’ was chosen for designing the experiments to evaluate the significance of different process factors, namely polishing speed, abrasive concentration, and ultrasonic power on the material removal rate (MRR) in DDCAMRF process. The material removed from the wafer surface was measured using the precision digital weighing balance. It was observed that the MRR was found to increase with the increase in various process factors used. Further, analysis of variance (i.e., ANOVA) technique with a 95% confidence interval was performed to analyze the significant contribution of different process factors on MRR. The validation of developed model was done by performing experiments on random and optimized set of process factors. From, the statistical investigation it was discovered that ultrasonic power has highest contribution of 57.9% on MRR, followed by the polishing speed (13.3%), and abrasive concentration (12.5%). Furthermore, a genetic algorithm optimization tool was utilized to obtain optimum set of process parameters to maximize MRR.

Ultrasonic vibration assisted double disc chemo-magnetorheological finishing of silicon wafer: Experimental investigations and optimization for surface roughness

“…The MRR increased with speed and abrasive concentration and directly impacted the surface quality. Srivastava and Pandey 31 reported a similar effect for using MRF to polish silicon wafers using ultrasonic-vibration assistance.…”

“…It was caused by the increased centrifugal force splashing abrasive particles. 31,[38][39][40] The abrasive particles could not be held in the CIP chains at a higher rotational speed due to the magnetic disc rotation applied centrifugal force. The number of cutting edges required to perform the finishing operation per unit area was increased by increasing the abrasive concentration.…”

“…The deep finishing marks and less time required for finishing were noted with vibration assistance. Recently, Srivastava and Pandey 30 and Srivastava et al 31 explored the double-disc chemo-MRF of silicon wafers. The results promised a better surface finish than double-disc MAF.…”

Effect of sintering routes on CIP/EIP – Al2O3 composite magnetic abrasive for chemo-mechanical magneto-rheological finishing of aluminium 6061

“…13 Furthermore, loosely mixed abrasive was embedded over the metal surface, creating surface irregularities. 14 The alternative solution is magnetic abrasive in the form of composite powder, which essentially bonded the ferromagnetic material and ceramic abrasives. 15 For the fabrication of magnetic abrasive in composite form, several methods have been available, including adhesive-based, gel-based, mechanically alloyed, plasma spraying, atomised and so on.…”