Wafer Alignment via Front-Side Marks for Backside Sawing

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Solution Overview

Problem

Accurate alignment of scribe lines during the die-sawing process in semiconductor wafer fabrication is challenging, as existing methods may damage semiconductor dies and require complex alignment procedures, increasing manufacturing costs and complexity.

Innovation Solution

The formation of alignment marks on the wafer's front surface, which extend through to the back surface after grinding, allowing for precise determination and cutting through scribe lines during backside sawing, reducing the need for additional alignment steps and manufacturing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If complex alignment procedures are used to accurately locate scribe lines, then manufacturing precision is improved, but device complexity and manufacturing costs increase

Engineering Contradiction:

Improvescribe line alignment accuracyVSAvoidalignment procedure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Alignment marks are formed on the front surface of the wafer before the wafer is flipped for backside sawing. These marks serve as pre-established reference points that guide the saw blade alignment, eliminating the need for complex real-time alignment procedures during the sawing process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The alignment marks are created as simplified copies or representations of the scribe line positions. By forming these marks through opening formation and selective removal, the complex task of locating precise scribe lines is replaced with the simpler task of aligning to the clearly visible marks

Inventive Principle:

Principle #26Copying

2Manufacturing precision

If complex alignment procedures are used to accurately locate scribe lines, then manufacturing precision is improved, but manufacturing costs increase

Engineering Contradiction:

Improvescribe line alignment accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The alignment marks are formed in advance on the front surface using standard photolithography and opening formation techniques. This preliminary action integrates seamlessly into the existing manufacturing flow without requiring expensive specialized equipment or additional complex process steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The method extracts the alignment function from the sawing process itself and separates it into a distinct pre-processing step. By forming alignment marks independently before flipping the wafer, the complex alignment requirements are removed from the critical sawing operation, reducing overall manufacturing complexity and cost

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If conventional alignment methods are used during sawing, then scribe line positioning accuracy is improved, but the risk of damaging semiconductor dies increases

Engineering Contradiction:

Improvescribe line positioning accuracyVSAvoiddamage to semiconductor dies

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

Instead of aligning the wafer to the scribe lines during sawing, the method inverts the approach by forming alignment marks on the front surface that correspond to scribe line positions, then flipping the wafer to perform sawing from the backside. This inversion allows alignment to be established before the wafer is flipped, eliminating the risk of die damage during alignment operations

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

All alignment mark formation and positioning actions are completed preliminarily on the front surface before the wafer is flipped for backside sawing. This ensures that alignment is established when the dies are still protected on the front surface, eliminating the risk of damage that would occur if alignment operations were performed on the exposed backside

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10090254B2Wafer alignment methods in die sawing process

Publication Date: 2018.10.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes forming a molding compound molding a lower portion of an electrical connector of a wafer therein. The molding compound is at a front surface of the wafer. The molding compound covers a center region of the wafer, and leaves an edge ring of the wafer not covered. An opening is formed to extend from the front surface of the wafer into the wafer, wherein the opening is in the edge ring of the wafer. A backside grinding is performed on the wafer until the opening is revealed through a back surface of the wafer. The method further includes determining a position of a scribe line of the wafer using the opening as an alignment mark, and sawing the wafer from a backside of the wafer by sawing through the scribe line.