Warping of silicon wafers subjected to back-grinding process

• Characteristic of wafer holding mechanic on a vacuum chuck in grinding is revealed.
• Mechanism of wafer warp in diamond thinning is revealed based on elasticity theory.
• A mathematical model is established for predicting wafer warp in diamond thinning.

This study investigates warping of silicon wafers in ultra-precision grinding-based back-thinning process. By analyzing the interactions between the wafer and the vacuum chuck, together with the machining stress distributions in damage layer of ground wafer, the study establishes a mathematical model to describe wafer warping during the thinning process using the elasticity theory. The model correlates wafer warping with machining stresses, wafer final thickness, damage layer thickness, and the mechanical properties of the monocrystalline silicon. The maximum warp and the warp profile are measured on the wafers thinned to various thicknesses under different grinding conditions, and are used to verify the modeling results.

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