Double Patterning Alignment Marks for Sub-25nm CD Control

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Solution Overview

Problem

The semiconductor manufacturing industry faces challenges in accurately forming features smaller than 25-30 nm with high precision and uniformity, particularly with the limitations of existing photolithography tools and the need for double patterning techniques to achieve smaller feature sizes, which demands precise alignment and critical dimension control across the wafer.

Innovation Solution

The introduction of a test structure and pattern recognition marks designed for double patterning techniques, featuring a grating pattern with first and second line features of different lengths, and a pattern recognition mark with intersecting sides, to analyze critical dimension variations and ensure alignment accuracy, using a double patterning process involving two patterned photoresist mask layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If single-exposure photolithography is used to form features, then the manufacturing process is simple and fast, but the minimum feature size is limited to about 25-30 nm

Engineering Contradiction:

Improveminimum feature sizeVSAvoidphotolithography process complexity

Core Design Contradiction:

Length of moving objectVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the single photolithography exposure process into two separate exposure steps, each forming a portion of the final pattern. This allows the minimum feature size to be reduced below the single-exposure limit while managing process complexity through structured segmentation of the patterning workflow.

Inventive Principle:

Principle #1Segmentation

2Length of moving object

If double patterning techniques are used to form smaller features, then the minimum feature size is reduced below 25-30 nm, but the alignment precision requirement increases

Engineering Contradiction:

Improveminimum feature sizeVSAvoidalignment precision

Core Design Contradiction:

Length of moving objectVSMeasurement precision

Solution Approach 1:

The patent introduces alignment mark structures as intermediary reference elements that facilitate precise alignment between the two exposure steps. These marks serve as mediators that enable measurement and correction of alignment errors, thereby achieving the required sub-25 nm feature size with controlled alignment precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct mechanical or manual alignment methods with optical measurement and feedback systems. By using alignment marks and optical measurement techniques, the system achieves higher precision alignment without relying on mechanical positioning accuracy alone.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Length of moving object

If double patterning techniques are used to form smaller features, then the minimum feature size is reduced below 25-30 nm, but the manufacturing precision requirement increases

Engineering Contradiction:

Improveminimum feature sizeVSAvoidcritical dimension uniformity

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

The patent implements feedback mechanisms by incorporating test structures and alignment marks that allow measurement of critical dimension variations. This feedback enables process adjustment and control, ensuring that CD uniformity is maintained within specification even when producing sub-25 nm features through double patterning.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies preliminary action by forming test structures and alignment marks before the main production patterning. These preliminary structures allow characterization and optimization of the double patterning process parameters, ensuring that subsequent production features meet the required manufacturing precision and critical dimension uniformity.

Inventive Principle:

Principle #10Preliminary action

4Productivity

If feature size is reduced to increase device functionality, then more features can be packed in a given area, but the photolithography tool capability becomes insufficient

Engineering Contradiction:

Improvedevice functionality densityVSAvoidphotolithography process complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the patterning process into two separate exposure and development steps, allowing each step to work within the capabilities of existing photolithography tools while achieving overall feature sizes and densities that exceed single-tool limitations. This enables increased device functionality density without requiring beyond-state-of-the-art photolithography equipment.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8932961B2Critical dimension and pattern recognition structures for devices manufactured using double patterning techniques

Publication Date: 2015.01.13 GLOBALFOUNDRIES INC

AI summary

An illustrative test structure is disclosed herein that includes a plurality of first line features and a plurality of second line features. In this embodiment, each of the second line features have first and second opposing ends and the first and second line features are arranged in a grating pattern such that the first ends of the first line features are aligned to define a first side of the grating structure and the second ends of the first features are aligned to define a second side of the grating structure that is opposite the first side of the grating structure. The first end of the second line features has a first end that extends beyond the first side of the grating structure while the second end of the second line features has a first end that extends beyond the second side of the grating structure.