Immersion Lithography Image Sensor Protective Layer Design

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Solution Overview

Problem

Image sensors in immersion lithography systems face degradation due to exposure to deep ultraviolet radiation, leading to undesirable particle generation and imaging errors, as well as reduced coating effectiveness over time.

Innovation Solution

An image sensor design featuring a grating with an absorber layer configured to absorb radiation, a protective layer less reactive to immersion liquids, and a hydrophobic coating at the surface to minimize liquid interaction and prevent degradation, where the protective layer is deposited between the absorber and hydrophobic layers to shield the absorber from immersion liquid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the absorber layer is exposed to immersion liquid, then the sensor can function in immersion lithography, but the absorber layer degrades due to chemical reactivity

Engineering Contradiction:

Improvesensor durabilityVSAvoidchemical degradation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A protective layer is introduced between the absorber layer and the immersion liquid to act as an intermediary barrier. This protective layer prevents direct contact between the reactive absorber layer and the immersion liquid, thereby eliminating chemical degradation while allowing the sensor to function in immersion lithography.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The image sensor employs a composite structure with multiple layers including the absorber layer and the protective layer. This composite material approach combines materials with different properties - the absorber layer for radiation absorption and the protective layer for chemical resistance - to achieve both functionality and durability.

Inventive Principle:

Principle #40Composite materials

2Loss of substance

If the liquidphobic coating is applied directly on the absorber layer, then liquid loss is reduced, but the absorber layer degrades from liquid contact

Engineering Contradiction:

Improveliquid lossVSAvoidcoating stability

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The protective layer serves as an intermediary between the liquidphobic coating and the absorber layer. It allows the liquidphobic coating to perform its function of reducing liquid loss while preventing the immersion liquid from contacting and degrading the absorber layer directly.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Different layers of the coating structure have different local qualities - the outer liquidphobic layer provides liquid repellency while the inner protective layer provides chemical resistance. This local differentiation of properties allows each layer to perform its specific function optimally.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If multiple thin film layers are deposited on the substrate table, then sensor functionality is enhanced, but upper layers degrade from radiation exposure

Engineering Contradiction:

Improvesensor functionalityVSAvoidcoating lifespan

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The protective layer acts as a mediator that shields the absorber layer from radiation exposure while allowing the upper liquidphobic coating to maintain sensor functionality. This intermediary layer protects the sensitive absorber layer from degradation caused by radiation and chemical exposure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protective layer provides beforehand cushioning against both chemical and radiation degradation. By placing this protective barrier in advance, the absorber layer is pre-protected from harmful effects before they can cause degradation, extending the overall lifespan of the multi-layer structure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 enhances the resistance of the image sensor to degradation, reducing overlay inaccuracy and increasing productivity by preventing oxidation and delamination, thus maintaining accurate focus and yield in lithographic processes.

Implementation Method 1

an absorber layer on the grating, the absorber layer configured to absorb radiation

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

a liquidphobic coating at an upper surface of the image sensor

Methodology Applied

Scientific EffectHydrophobic effect: Hydrophobe

Data Source

PatentUS11774868B2Image sensor for immersion lithography

Publication Date: 2023.10.03 ASML NETHERLANDS BV

AI summary

An image sensor for immersion lithography, the image sensor including: a grating; an absorber layer on the grating, the absorber layer configured to absorb radiation; and a liquidphobic coating at an upper surface of the image sensor, wherein a protective layer is provided between the absorber layer and the liquidphobic layer, the protective layer being less reactive than the absorber layer to an immersion liquid.