Stealth Laser Wafer Edge Trimming for Precise Bonded Wafer Alignment

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Solution Overview

Problem

The existing wafer edge trimming processes face challenges in precision and accuracy, leading to potential damage and peeling issues during the bonding of semiconductor wafers, as conventional methods rely on scanning cameras for alignment, which can be imprecise and cause defects.

Innovation Solution

The use of infrared alignment with a stealth laser apparatus and a blade trimming process, where the stealth laser forms a controlled damage region within the wafer, allowing the blade to remove outer edges without direct contact, followed by grinding to minimize defects and improve alignment accuracy from 500 micrometers to 3 micrometers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If scanning camera alignment is used for wafer edge trimming, then the alignment process is simple, but the alignment precision is poor (500 micrometers accuracy)

Engineering Contradiction:

Improvealignment precisionVSAvoidalignment system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical scanning camera alignment system with an optical infrared alignment system. The infrared camera captures images of alignment marks on the wafer, and image processing algorithms calculate precise positions, achieving 3 micrometer accuracy instead of 500 micrometer mechanical alignment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses alignment marks that are copied from the photolithography process onto the wafer. These marks serve as reference patterns that the infrared camera detects and uses for precise alignment calculations, eliminating the need for direct mechanical measurement.

Inventive Principle:

Principle #26Copying

2Reliability

If blade trimming is used to remove outer edges, then material removal is effective, but damage and peeling occur due to direct contact

Engineering Contradiction:

Improvewafer integrityVSAvoidblade contact damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary laser damage to the wafer outer edge before blade trimming. The laser creates a damaged region that extends partially through the wafer thickness, which then guides the blade to remove only the damaged outer portion without contacting the intact inner region, preventing peeling and damage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces laser-damaged material as an intermediary between the blade and the intact wafer. The laser creates a sacrificial damaged layer that the blade removes, protecting the underlying healthy wafer material from direct blade contact and associated mechanical damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If conventional trimming methods are used, then the process is straightforward, but peeling and defects occur during bonding and subsequent processing

Engineering Contradiction:

Improveedge qualityVSAvoidpeeling and defects

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by creating a gradient of damage in the wafer outer edge through laser treatment. The damage is concentrated in the outer region that needs removal, while the inner region remains intact. This localized damage pattern enables precise control over what material is removed and what remains, ensuring high edge quality without defects.

Inventive Principle:

Principle #3Local quality

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 enhances the precision and reliability of wafer edge trimming, reducing peeling risks and achieving smooth, defect-free edges, thereby improving the integrity of bonded wafers for further processing steps like packaging and dicing.

Implementation Method 1

aligning the stealth laser apparatus and the blade on the second wafer using an infrared camera integrated in the wafer edge trimming apparatus

Methodology Applied

Scientific EffectInfrared radiation detection: Infrared Radiation

Implementation Method 2

using the stealth laser apparatus to form a damage region within the wafer that separates an outer region of the wafer from an inner region of the wafer

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS12183571B2Integrated aligned stealth laser for wafer edge trimming process

Publication Date: 2024.12.31 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

In some embodiments, the present disclosure relates to an integrated chip fabrication device. The device includes a stealth laser apparatus arranged over a chuck configured to hold a substrate. An infrared camera is arranged over the chuck and configured to detect an alignment mark below the substrate. The alignment mark is used to align the stealth laser apparatus over the chuck. Control circuitry is configured to operate the stealth laser apparatus to form a stealth damage region at a location within the substrate that is determined based upon the alignment mark. The stealth damage region separates an inner region of the substrate from an outer region of the substrate.