Photo Mask Mark Pattern for Semiconductor Alignment Measurement

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Solution Overview

Problem

In semiconductor fabrication, the increasing fineness of patterns poses a challenge for alignment and superposition measurement due to sidewall patterns formed below the resolution limit of exposure and measuring light, making it difficult to measure and focus using optical microscopes.

Innovation Solution

A photo mask with a mark pattern and a regular pattern is used, where the regular pattern is smaller in size and pitch than the mark pattern, allowing for the formation of a concave mark pattern that can be measured by an optical microscope, even when the mark pattern is formed below the resolution limit of the exposure light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If sidewall manufacturing process is used to form patterns below resolution limit, then pattern fineness is improved, but measurement capability deteriorates

Engineering Contradiction:

Improvepattern finenessVSAvoidmeasurement capability

Core Design Contradiction:

Manufacturing precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The invention divides the mark structure into two functional parts: a core mark pattern for measurement and a surrounding sidewall pattern for fine feature definition. This segmentation allows the core to serve as a measurable reference while the sidewalls provide the ultra-fine pattern structure that would otherwise be unmeasurable.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The core mark pattern acts as an intermediary element that enables measurement of the otherwise unmeasurable sidewall patterns. By placing a measurable core at the center of the sidewall structure, the system gains the ability to locate and measure positions even for features below the optical resolution limit.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If core film pattern is removed in sidewall manufacturing process, then ultra-fine pattern formation is achieved, but mark measurability is lost

Engineering Contradiction:

Improveultra-fine pattern formationVSAvoidmark measurability

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The core mark pattern is designed and positioned in advance as a permanent reference structure that will remain after the sidewall manufacturing process. This preliminary placement ensures that even after removing the core material used for sidewall formation, a measurable reference remains in the correct position.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of removing the entire core pattern as in conventional sidewall manufacturing, the invention inverts the approach by preserving a central core mark while using surrounding material removal to form the sidewall pattern. This inversion maintains measurability while achieving ultra-fine features.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8790851B2Mask and method for fabricating semiconductor device

Publication Date: 2014.07.29 KIOXIA CORP

AI summary

A photo mask for exposing according to an embodiment includes a mark pattern arranged in a mark region that is different from an effective region to form a semiconductor device; and a regular pattern arranged in the mark region and around the mark pattern and smaller than the mark pattern in size and pitch.