Resist Slimming for DSA Lithography Pattern Alignment

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Solution Overview

Problem

The directed self-assembly (DSA) technique for semiconductor lithography often fails to form patterns accurately due to issues with resist pattern thinness leading to tapered recessed portions and misalignment of microphase separation patterns.

Innovation Solution

A pattern forming method involving the formation of a resist pattern, etching a recessed portion in an under-layer, slimming the resist pattern to increase affinity for specific polymers, forming a block copolymer film that undergoes microphase separation, and selectively removing one portion to achieve a precise microphase separation pattern with high dimensional accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the resist pattern is made thin to achieve finer patterns, then the pattern resolution is improved, but the resist pattern becomes tapered and loses dimensional accuracy

Engineering Contradiction:

Improvepattern resolutionVSAvoidresist pattern shape

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

The patent applies preliminary action by forming a recessed portion in the under-layer before applying the block copolymer film. This pre-prepared recessed structure provides a stable foundation that prevents the thin resist pattern from tapering during subsequent processing, thereby maintaining dimensional accuracy while enabling fine pattern formation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a neutral layer as an intermediary between the under-layer and the block copolymer film. This neutral layer acts as a mediator that protects the thin resist pattern from direct interaction with the block copolymer, preventing deformation and maintaining the rectangular shape throughout the microphase separation process.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If the resist pattern width is reduced to form finer features, then the pattern fineness is improved, but the microphase separation pattern becomes misaligned

Engineering Contradiction:

Improvepattern finenessVSAvoidpattern alignment

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent establishes the position of the microphase separation pattern in advance by forming the recessed portion in the under-layer before applying the block copolymer. This preliminary positioning ensures that even when the resist pattern is made very thin, the resulting microphase separation pattern remains properly aligned with the underlying structure.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If conventional DSA lithography is used to form fine patterns, then pattern formation is attempted, but the patterns cannot be formed accurately

Engineering Contradiction:

Improvepattern formation accuracyVSAvoidpattern formation reliability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent forms the recessed portion in the under-layer as a preliminary step before applying the block copolymer film. This pre-formed recessed structure serves as a reliable template that guides the microphase separation process, ensuring accurate and reliable pattern formation even at fine dimensions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The neutral layer acts as an intermediary that ensures reliable interaction between the under-layer and block copolymer film. This intermediate layer provides a controlled interface that enhances the reliability of pattern formation by preventing direct, uncontrolled interactions between the resist pattern and block copolymer.

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 method ensures accurate formation of microphase separation patterns with excellent shape and dimensional accuracy by adjusting the relationship between resist pattern widths, pitches, and block copolymer arrangements, preventing disarrangement of polymers and maintaining the rectangular shape of resist patterns during etching.

Implementation Method 1

forming a microphase separation pattern comprising a first portion formed of the first polymer and a second portion formed of the second polymer by applying microphase separation processing to the block copolymer film

Methodology Applied

Scientific EffectMicrophase separation:

Implementation Method 2

forming a recessed portion in the under layer by etching the under-layer using the resist pattern as a mask

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS9696628B2Pattern forming method

Publication Date: 2017.07.04 KIOXIA CORP

AI summary

According to one embodiment, a pattern forming method includes forming a resist pattern on an under-layer, forming a recessed portion in the under-layer by etching the under-layer using the resist pattern as a mask, slimming the resist pattern, forming a neutral layer having an affinity for first and second polymers on a region of the under-layer not covered with the slimmed resist pattern, forming a block copolymer film containing the first polymer and the second polymer on the slimmed resist pattern and the neutral layer, and forming a microphase separation pattern comprising a first portion formed of the first polymer and a second portion formed of the second polymer by applying microphase separation processing to the block copolymer film.