Composite Wafer Grinding With Thickness Mapping for Uniform Chips

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Solution Overview

Problem

Existing grinding methods for chip-on-wafer packages result in inconsistent thickness of chips due to variations in support wafer thickness, leading to non-uniformity among multiple packages.

Innovation Solution

A method involving contactless thickness measurement and pattern recognition to set specified areas for precise grinding, ensuring uniform thickness by using a contactless thickness measurement device to measure and adjust the thickness of chips or device wafers on a support wafer, followed by grinding until the specified thickness is achieved.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional grinding methods are used to grind chip-on-wafer packages, then the support wafer can be processed, but the thickness of chips becomes inconsistent due to variations in support wafer thickness

Engineering Contradiction:

Improvethickness uniformity of chipsVSAvoidhandling of support wafer thickness variations

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent performs preliminary thickness measurement of the support wafer before the grinding process. By measuring the thickness distribution in advance and creating a thickness map, the system can determine the precise grinding amount needed for each location, ensuring uniform chip thickness despite variations in support wafer thickness

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the measured support wafer thickness data is used to control the grinding process. The system continuously monitors thickness during grinding and adjusts grinding parameters in real-time to maintain uniform chip thickness across the wafer

Inventive Principle:

Principle #23Feedback

2Measurement precision

If contactless thickness measurement is used to measure chip thickness, then measurement precision is improved, but the device complexity increases

Engineering Contradiction:

Improvethickness measurement accuracyVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses the support wafer itself as an intermediary measurement surface. By measuring the thickness of the support wafer (which has a flat, accessible top surface) rather than directly measuring the chip thickness, the system achieves high measurement precision while avoiding the complexity of direct chip measurement

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct mechanical contact measurement of chips with contactless optical measurement of the support wafer. This substitution eliminates the complexity of positioning and contacting small chips while maintaining high measurement precision through optical interferometry

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method ensures uniform thickness of chips or device wafers across multiple packages, even when support wafer thickness varies, by accurately measuring and controlling the thickness of specified areas using contactless measurement and grinding techniques.

Implementation Method 1

a contactless thickness measurement device to measure the thickness of a composite wafer

Methodology Applied

Scientific EffectOptical measurement: Light

Implementation Method 2

grinding a top surface of the composite wafer by a grinding stone until a measured thickness becomes equal to a finished thickness

Methodology Applied

Scientific EffectAbrasion: Abrasion

Data Source

PatentUS20250323049A1Method of grinding composite wafer and method of grinding chip-on-wafer package

Publication Date: 2025.10.16 DISCO CORP

AI summary

A method of grinding a composite wafer includes the steps of: holding a support wafer of the composite wafer by a chuck table; the chuck table in a radial direction of the chuck table, measuring the thickness of an area which is part of the composite wafer and whose thickness is measured at least during finishing grinding, and storing the measured thickness and XY coordinates of a point of measurement of thickness on a horizontal surface, as thickness data; setting a specified area which is an area whose thickness is specified during the finishing grinding, by using the stored thickness data; and measuring the thickness of the specified area by using the XY coordinates of the specified area, and grinding a top surface of the composite wafer by a grinding stone until a measured thickness becomes equal to a finished thickness set in advance.