Material Removal Model for Lapping Process Based on Spiral Groove Density

Abstract

The increasing demand for single-crystal wafers combined with the increase in diameter of semiconductor wafers has warranted further improvements in thickness variation and material removal rate during lapping to ensure price competitiveness of wafers; consequently, the lapping process has gained the attention of researchers. However, there is insufficient research on the effect of platen grooves on the lapping process. In this study, the parameters to describe grooves were defined in order to understand their influence on the lapping process, and a material removal model was suggested based on indentation theory and subsequently experimentally validated. The results indicate that changes in groove density affect the lubrication condition at the contact interface as well as the probability of abrasive participation by varying the oil film thickness. When fabricating the groove for a lapping platen, a groove density at the critical groove density (CGD) or higher should be selected. The higher the groove density, the easier it is to avoid the CGD, and the higher is the material removal rate. The results of this study will enable engineers to design lapping platen grooves that are suitable for the production of modern semiconductor wafers.

Sapphire as a Single-Crystal Cutting Tool for Machining Ferrous-Based Optics

“…Fig. 3 shows the polishing 6 µm diamond slurry is used on the Kemet copper lap with lapping load of 10N [6].…”

Fabrication, characterization, and testing of a sharp cutting-edge radius sapphire tool for ultra-precision machining

“…Parks et al [9] reported lapping of sapphire wafers with #400 boron carbide (BC) abrasives on a cast-iron plate, observed a high material removal rate of 5-10 µm/min and achieved a surface roughness of 400-600 nm. Taekyung et al [10] used Kemet copper lap having grooves to hold the diamond slurry for longer durations, reported a low material removal rate of 0.5-1 µm/min, this improved the surface roughness of the wafer and obtained 10-20 nm Ra. Aida et al [11] reported chemical mechanical polishing of sapphire using poly urethane pad and colloidal silica as the slurry, achieved an excellent surface nish of 10-20 Å Ra and the material removal rate was very low 50 nm/hr.…”