Resist Sidewall Modification for Minute Hole Patterns

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Solution Overview

Problem

Conventional methods struggle to form minute hole patterns due to insufficient optical image contrast using dark field masks, as negative development tends to dissolve intermediate exposed portions more easily than positive development, leading to incomplete pattern formation.

Innovation Solution

A pattern forming method using a bright field mask for exposure, followed by negative development to remove unexposed portions, modifying the sidewall to reduce solubility in a second developer, and then performing positive development to remove exposed portions, which includes reacting the sidewall with ammonia, organic bases, or amino group-containing silane coupling agents to enhance solubility reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If dark field mask is used for exposure, then hole pattern formation is attempted, but optical image contrast is insufficient leading to poor pattern formation

Engineering Contradiction:

Improveoptical image contrastVSAvoidpattern formation quality

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional approach by using bright field mask instead of dark field mask, and by performing negative development first followed by positive development, rather than the conventional positive then negative development sequence. This inversion resolves the optical contrast issue while achieving the desired hole pattern formation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent performs preliminary negative development to remove unexposed portions before performing positive development. This preliminary action creates intermediate exposed portions that serve as templates for the final hole pattern, enabling precise pattern formation that cannot be achieved with conventional single-step development.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If negative development is performed to remove unexposed portions, then unexposed portions are removed, but intermediate exposed portions are dissolved leading to incomplete pattern formation

Engineering Contradiction:

Improvepattern formation processVSAvoidintermediate exposed portion retention

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent performs preliminary negative development to remove unexposed portions while retaining intermediate exposed portions. This preliminary action creates a scaffold structure that guides subsequent positive development, ensuring complete pattern formation without dissolving critical intermediate portions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the development process into two distinct stages: negative development followed by positive development. This segmentation allows each development step to perform its specific function optimally, with negative development removing unexposed portions and positive development removing exposed portions, thereby preserving intermediate exposed portions throughout the process.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If conventional single development is performed, then process is simple, but pattern resolution is insufficient for minute hole patterns

Engineering Contradiction:

Improvedevelopment process stepsVSAvoidpattern resolution

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent divides the development process into two segmented stages: negative development followed by positive development. This segmentation enables achieving high pattern resolution for minute hole patterns by allowing each development step to selectively remove specific portions while preserving intermediate exposed portions, which would not be possible with a single development step.

Inventive Principle:

Principle #1Segmentation

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 effectively forms a minute hole pattern with improved optical image contrast and resolution, allowing for the retention of intermediate exposed portions and the formation of patterns with narrower pitches than the exposure mask.

Implementation Method 1

exposing the resist film using a bright field mask

Methodology Applied

Scientific EffectPhotochemical reaction: Photopolymerisation

Implementation Method 2

reacting the sidewall with ammonia, organic bases, or amino group-containing silane coupling agents to enhance solubility reduction

Methodology Applied

Scientific EffectChemical reaction with ammonia: Chemical Bonding

Implementation Method 3

modifying the sidewall to reduce solubility in a second developer

Methodology Applied

Scientific EffectSolubility modification: Solvation

Data Source

PatentUS10539876B2Pattern forming method

Publication Date: 2020.01.21 TOKYO ELECTRON LTD

AI summary

Provided is a method for forming a hole pattern in a resist film. The method includes forming a resist film on a workpiece; exposing the resist film using a bright field mask; removing an unexposed portion of the resist film by supplying a first developer to the resist film and performing a negative development after the exposing the resist film; modifying a sidewall portion of the resist film after the removing the unexposed portion of the resist film; and removing an exposed portion of the resist film by supplying a second developer to the resist film and performing a positive development after the modifying the sidewall portion of the resist film. The modifying the sidewall portion of the resist film is a processing of reducing solubility of the sidewall portion of the resist film in the second developer.