Multi-Mask Lithography Stitching Control for Accurate Pattern Transfer

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Solution Overview

Problem

In the process of multiple-mask multiple-exposure patterning for integrated circuit fabrication, the stitching region where the exposure areas of adjacent masks overlap can lead to double exposure and interference with pattern transfer, affecting the accuracy and reliability of the circuit patterns.

Innovation Solution

The design of the masks includes a stitching region with an opaque region that corresponds to the mask feature of the adjacent mask, ensuring that the corresponding area is unexposed during the first lithographic exposure and exposed during the second exposure, preventing double exposure and allowing for accurate pattern transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If multiple masks are used for large chip area patterning, then the coverage area is improved, but double exposure in stitching regions causes pattern transfer interference

Engineering Contradiction:

Improvechip area coverageVSAvoidpattern transfer accuracy

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The harmful stitching region is extracted and isolated using an isolated stitching region mask that covers only the stitching area. This allows the stitching region to be treated separately from the main die region, preventing double exposure interference while maintaining large chip area coverage through multiple mask exposures.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Different mask regions are assigned different functions: the main die region mask covers functional circuit areas, while the isolated stitching region mask specifically covers only the stitching region. This local differentiation ensures that each region receives appropriate exposure control, preventing pattern transfer interference in stitching areas while maintaining accuracy in functional regions.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If stitching region is covered in first exposure, then alignment is simplified, but double exposure occurs and interferes with pattern transfer

Engineering Contradiction:

Improvealignment simplicityVSAvoidpattern transfer reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The lithographic process is segmented into two distinct exposure steps: first exposure for the main die region and second exposure for the isolated stitching region. This segmentation allows each exposure to be optimized independently, ensuring alignment simplicity in the first exposure while preventing double exposure interference in the second exposure through the use of an isolated stitching region mask.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The main die region is exposed first in the first lithographic exposure, establishing the primary pattern. The stitching region is then addressed in a subsequent second lithographic exposure using the isolated stitching region mask, ensuring that stitching area patterns are transferred without interference from the first exposure.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If opaque region is added to mask stitching region, then double exposure is prevented, but mask complexity increases

Engineering Contradiction:

Improvepattern transfer accuracyVSAvoidmask structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

An isolated stitching region mask serves as an intermediary tool that specifically addresses the stitching region without affecting the main die region. This intermediary mask contains opaque regions only in the stitching area, preventing double exposure interference while maintaining simplicity in the main die region mask design.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution effectively prevents the influence of the stitching region on pattern transfer, ensuring that the desired patterns are accurately and reliably transferred onto the integrated circuit workpiece, even in large chip areas.

Implementation Method 1

The photoresist includes one or more components that undergo a chemical transition when exposed to radiation

Methodology Applied

Scientific EffectPhotochemical reaction: Photopolymerisation

Implementation Method 2

a stitching region with an opaque region that corresponds to the mask feature of the adjacent mask, ensuring that the corresponding area is unexposed during the first lithographic exposure

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS12298667B2Lithography

Publication Date: 2025.05.13 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes the following steps. A photoresist is exposed to a first light-exposure through a first mask, wherein the first mask includes a first stitching region, and a first portion of the photoresist corresponding to a first opaque portion of the first stitching region is unexposed. The photoresist is exposed to a second light-exposure through a second mask, wherein the second mask includes a second stitching region, and a second portion of the photoresist corresponding to a second opaque portion of the second stitching region is unexposed and is overlapping with the first portion of the photoresist.