Chuck Table Holding Surface Shaping for Uniform Wafer Thickness

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Solution Overview

Problem

The existing methods for shaping the holding surface of a chuck table for TAIKO grinding often result in uneven wafer thickness due to differences in grinding wheel diameters, leading to difficulties in performing TAIKO grinding and potential formation of steps on the chuck table surface.

Innovation Solution

A method that involves grinding the chuck table surface to create a concentrically slanted region, with the outer circumferential edge being progressively deeper towards a central region, and adjusting the tilt and movement of the grinding wheel to ensure uniform depth without forming steps, using a grinding wheel with an outside diameter smaller than the chuck table radius.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the holding surface of the chuck table is ground to curve the entire surface by making the grinding wheel outside diameter larger than the chuck table radius, then the wafer can be properly supported, but the wafer thickness becomes non-uniform due to the difference between grinding wheel and TAIKO grinding wheel diameters

Engineering Contradiction:

Improvewafer thickness uniformityVSAvoiddifficulty in performing TAIKO grinding

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The holding surface is divided into different regions with different curvatures: a first region with a first curvature radius and a second region with a second curvature radius. This local differentiation allows the surface to be optimized for both wafer support and uniform thickness while accommodating the TAIKO grinding wheel's specific diameter requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The holding surface grinding process is segmented into multiple regions with different curvature characteristics. The grinding wheel is tilted at different angles for different regions, creating a multi-zone surface geometry that resolves the conflict between overall wafer support and local thickness uniformity.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the holding surface is ground flat by using a grinding wheel with outside diameter smaller than the chuck table radius, then the wafer outer edge can be supported, but the wafer center region becomes thicker causing uneven thickness

Engineering Contradiction:

Improvewafer thickness uniformityVSAvoidholding surface geometry

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

Instead of grinding the holding surface completely flat, the invention applies a controlled curvature to specific regions. The first region has a first curvature radius and the second region has a second curvature radius, creating a smoothly varying surface profile that ensures uniform wafer thickness while maintaining proper outer edge support.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Object-affected harmful factors

If the rotational shaft of the TAIKO grinding wheel is tilted with respect to the rotational shaft of the chuck table, then surface burning and iris-shaped marks are prevented, but the wafer develops non-uniform thickness with thicker center and edge portions

Engineering Contradiction:

Improvesurface burning and grinding marksVSAvoidwafer thickness uniformity

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The holding surface is pre-shaped with specific curvature profiles before TAIKO grinding is performed. This preliminary surface preparation compensates for the thickness non-uniformity that will occur during tilted-axis TAIKO grinding, ensuring that the final wafer achieves uniform thickness despite the necessary tilt for preventing surface defects.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for a smooth, uniformly shaped chuck table surface suitable for TAIKO grinding, preventing step formation and ensuring consistent wafer thickness during the grinding process.

Implementation Method 1

a region of the holding surface of the chuck table that underlies the recess is ground by a grinding wheel

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 2

the wafer may have its surface blackened, i.e., burned, due to frictional engagement with the grindstones

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS20240261926A1Method of shaping holding surface of chuck table

Publication Date: 2024.08.08 DISCO CORP

AI summary

A second relative speed where a spindle and a center of a holding surface are brought together in a grinding step is established such that the spindle and the outer circumferential edge of a surrounding region of the holding surface start being brought together other along a first direction and the spindle's rotational shaft and the holding surface's center start being brought together along a second direction simultaneously and that the spindle and the outer circumferential edge of the surrounding region finish being brought together along the first direction and the spindle's rotational shaft and the holding surface's center finish being brought together along the second direction simultaneously. Specifically, the second relative speed is established in view of parameters that are established as desired and the worn-off amount of the grindstones that is grasped prior to or during the grinding step (i.e., a change in thickness of the grindstones).