Photoresist Surface Layer Segregation for Defect Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Negative tone development processes in photolithography suffer from surface inhibition issues such as 'necking' and 'T-topping' in contact holes and line/trench patterns, leading to poor process windows, depth of focus, and exposure latitude, resulting in defects like missing contact holes and micro-bridging.

Innovation Solution

A photoresist composition comprising a matrix polymer with acid-labile groups, an additive polymer with a lower surface energy, and a photoacid generator, which segregates during coating to form a surface layer that controls stray light and reduces patterning defects, allowing for improved focus and exposure latitude without a topcoat layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If negative tone development is used to achieve superior imaging quality, then pattern formation capability is improved, but surface inhibition effects (necking and T-topping) occur

Engineering Contradiction:

Improvepattern formation capabilityVSAvoidsurface inhibition effects

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies local quality by introducing a surface treatment layer with different chemical properties (lower surface energy) than the bulk resist. This creates a gradient where the surface layer has enhanced properties for preventing necking and T-topping, while the bulk resist maintains its photoacid generator functionality for pattern formation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses composite materials by combining the base photoresist polymer with a surface treatment polymer that has lower surface energy. This composite structure allows the surface layer to exhibit different solubility and surface energy characteristics, effectively suppressing surface inhibition effects while maintaining the overall resist's photoacid generator capability.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If photoacid generator is added to enhance photoacid formation, then exposure sensitivity is improved, but surface inhibition and stray light diffusion increase

Engineering Contradiction:

Improveexposure sensitivityVSAvoidsurface inhibition and stray light

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the photoacid generator from the surface layer and places it in the bulk resist layer. By removing the PAG from the surface treatment layer, the invention eliminates the source of harmful photoacid formation at the surface that causes necking and T-topping, while maintaining exposure sensitivity through the PAG in the bulk resist.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The surface treatment layer acts as an intermediary between the bulk resist and the environment. It provides a protective function by preventing stray light diffusion and suppressing surface inhibition effects, while allowing the bulk resist to contain the photoacid generator for controlled photoacid formation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If topcoat layer is added to suppress surface inhibition, then pattern quality is improved, but device complexity increases

Engineering Contradiction:

Improvepattern qualityVSAvoidresist layer structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the surface treatment function with the bulk resist by incorporating a surface treatment polymer directly into the resist composition. This eliminates the need for a separate topcoat layer, reducing structural complexity while maintaining pattern quality through the integrated surface layer with lower surface energy.

Inventive Principle:

Principle #5Merging (Combining)

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 solution provides uniform resist patterns with reduced defects, improved focus and exposure latitude, and minimized necking and T-topping, enhancing the yield of electronic devices by effectively addressing surface inhibition issues in negative tone development.

Implementation Method 1

Exposure to actinic radiation causes the photoacid generator to form an acid

Methodology Applied

Scientific EffectPhotoacid generation: Photopolymerisation

Implementation Method 2

a second polymer having a lower surface energy than a surface energy of the first polymer

Methodology Applied

Scientific EffectSurface energy differentiation: Surface Tension

Implementation Method 3

a difference in solubility characteristics in organic developers is created between exposed and unexposed regions of the resist

Methodology Applied

Scientific EffectDifferential solubility: Solvation

Data Source

PatentUS9482945B2Photoresist compositions and methods of forming photolithographic patterns

Publication Date: 2016.11.01 DUPONT ELECTRONIC MATERIALS INT LLC

AI summary

Provided are photoresist compositions useful in forming photolithographic patterns by a negative tone development process. Also provided are methods of forming photolithographic patterns by a negative tone development process and substrates coated with the photoresist compositions. The photoresist compositions include one or more polymer additive that contains a basic moiety and which is substantially non-miscible with a resin component of the resist. The compositions, methods and coated substrates find particular applicability in the manufacture of semiconductor devices.