Fence-Shaped Overlay Mark for Double Patterning Alignment

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Solution Overview

Problem

The existing double patterning process in electronic device manufacturing results in a weak signal for alignment due to the small area and insufficient contrast provided by circular spacers left after photoresist layer removal, making alignment challenging.

Innovation Solution

A method of forming a fence-shaped overlay mark by creating photoresist patterns with first and second strips arranged in parallel, followed by anisotropically etching a spacer material layer to form islands on the sidewalls, which are left as dot-type strip patterns to serve as the overlay mark, enhancing contrast and signal strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a circular spacer is used as the overlay mark after photoresist removal, then the manufacturing process is simple, but the signal strength is weak and alignment is difficult

Engineering Contradiction:

Improveprocess simplicityVSAvoidalignment difficulty

Core Design Contradiction:

Ease of manufactureVSDifficulty of detecting and measuring

Solution Approach 1:

The overlay mark is segmented into multiple dot-type strip patterns arranged in a fence shape, where each strip contains multiple dots. This segmentation increases the total area and contrast of the overlay mark while maintaining ease of manufacture through systematic patterning

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The overlay mark transitions from a two-dimensional circular spacer to a three-dimensional dot-type strip pattern with vertical sidewalls. This dimensional change increases the effective area and provides better contrast for alignment detection

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Difficulty of detecting and measuring

If the overlay mark area is increased to improve signal strength, then alignment becomes easier, but the photoresist pattern complexity increases

Engineering Contradiction:

Improvealignment easeVSAvoidphotoresist pattern complexity

Core Design Contradiction:

Difficulty of detecting and measuringVSDevice complexity

Solution Approach 1:

The increased area is achieved by segmenting the overlay mark into multiple strips with multiple dots each, arranged in a fence pattern. This segmentation allows area expansion while maintaining manageable pattern complexity through systematic repetition

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple dots are nested within each strip, and multiple strips are arranged within the fence-shaped photoresist pattern. This nested structure efficiently increases the overlay mark area while organizing complexity in a hierarchical manner

Inventive Principle:

Principle #7Nested doll (Nesting)

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

The proposed method provides sufficient contrast and strengthens the alignment signal, facilitating easier alignment in the existing double patterning process by creating a more visible overlay mark through the formation of dot-type strip patterns with larger spacers.

Implementation Method 1

the spacer material layer is anisotropically etched to form a plurality of spacers on a sidewall of the photoresist patterns and in each of the gaps

Methodology Applied

Scientific EffectAnisotropic etching:

Data Source

PatentUS9017926B2Overlay mark and method of forming the same

Publication Date: 2015.04.28 NAN YA TECH

AI summary

A method of forming an overlay mark is provided. A plurality of photoresist patterns are formed on a substrate. Each of the photoresist patterns includes a first strip and a plurality of second strips arranged in parallel. The first strip crosses the second strips to form a fence shape. Further, there is a space between two adjacent photoresist patterns, and the space is fence-shaped. A plurality of islands are formed in each of the spaces to form dot type strip patterns. The photoresist patterns are removed, and the dot type strip patterns serve as the overlay mark.