Experimental Study on the Role of Bond Elasticity and Wafer Toughness in Back Grinding of Single-Crystal Wafers

TL;DR

This study explores how bond elasticity and wafer toughness affect the back grinding of semiconductor wafers, offering practical insights for optimizing the process.

Contribution

The study derives a log-linear empirical model linking diamond protrusion height to bond elasticity and wafer toughness, validated experimentally.

Findings

A log-linear relationship between diamond protrusion height and bond elasticity and wafer toughness was experimentally verified.

Increasing bond modulus from 95.24 to 131.38 GPa reduced diamond protrusion height for SiC wafers.

Optimal grinding conditions were identified to balance removal rate, surface quality, and subsurface damage.

Abstract

Grinding semiconductor wafers with high hardness, such as SiC, remains a significant challenge due to the need to maximize material removal rates while minimizing subsurface damage. In the back-grinding process, two key parameters—the elastic modulus (Eb) of the grinding wheel bond and the fracture toughness (KIC) of the wafer—play a critical role in governing the behavior of diamond and the extent of wafer damage. This study systematically investigated the effect of Eb and KIC on diamond protrusion height (hp), surface roughness (Ra), grinding forces, and the morphology of generated debris. The study encompassed four wafer types—Si, GaP, sapphire, and ground SiC—using five Back-Grinding Wheels (BGWs), with Eb ranging from 95.24 to 131.38 GPa. A log–linear empirical relationship linking hp to Eb and KIC was derived and experimentally verified, demonstrating high predictive accuracy across all wafer–wheel combinations. Surface roughness (Ra) was measured in the range of 0.486–1.118 μm, debris size ranged from 1.41 to 14.74 μm, and the material removal rate, expressed as a thickness rate, varied from 555 to 1546 μm/h (equivalent to 75−209 mm3/min using an effective processed area of 81.07 cm2;). For SiC, increasing the bond modulus from 95.24 to 131.38 GPa raised the average hp from 9.0 to 1.2 μm; the removal rate peaked at 122.07 GPa, where subsurface damage (SSD) was minimized, defining a practical grindability window. These findings offer practical guidance for selecting grinding wheel bond compositions and configuring process parameters. In particular, applying a higher Eb is recommended for harder wafers to ensure sufficient diamond protrusion, while an appropriate dressing must be employed to prevent adverse effects from excessive stiffness. By balancing removal rate, surface quality, and subsurface damage constraints, the results support industrial process development. Furthermore, the protrusion model proposed in this study serves as a valuable framework for optimizing bond design and grinding conditions for both current and next-generation semiconductor wafers.

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