Multilayer Photomask Blank Structure for Cleaning-Resistant Resolution

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Solution Overview

Problem

Existing photomasks, particularly those with multi-layer light shielding films, face degradation in resolution due to damage from cleaning processes, especially at interlayer boundaries, leading to non-uniform optical properties and reduced durability.

Innovation Solution

A photomask design with a multi-layer light shielding film structure, including a first and second light shielding film with controlled surface roughness and an adhesion strengthening layer, enhances durability and maintains optical properties by limiting roughness variation before and after cleaning processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a multi-layer light shielding film is used to improve light shielding performance, then the photomask can form refined minute patterns, but the interlayer boundaries become vulnerable to cleaning solution damage causing resolution degradation

Engineering Contradiction:

Improvepattern resolutionVSAvoiddurability against cleaning solution

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by forming a protective layer on the side surfaces of the multi-layer light shielding film before the cleaning process. This protective layer (formed by soaking in SC-1 solution and ozone water treatment) creates a pre-established protection mechanism that prevents cleaning solution from attacking the interlayer boundaries, thereby resolving the contradiction between maintaining high pattern resolution and ensuring durability during cleaning

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary substance (protective layer formed through chemical treatment) that mediates between the cleaning solution and the light shielding film. This intermediary layer acts as a buffer that allows the cleaning process to occur while protecting the vulnerable interlayer boundaries, thus enabling both effective cleaning and preservation of pattern resolution

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the photomask is soaked in SC-1 solution for extended periods to improve cleaning effectiveness, then organic contaminants are removed, but the light shielding film deteriorates and roughness increases

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidsurface roughness uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-forming a protective layer on the light shielding film before cleaning. This pre-established protection allows the photomask to undergo extended SC-1 soaking (800 seconds or more) for thorough cleaning while the protective layer prevents excessive roughness development, thus resolving the contradiction between cleaning effectiveness and surface uniformity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements beforehand cushioning by creating a protective barrier that cushions the light shielding film against the harsh cleaning environment. This cushioning effect allows aggressive cleaning protocols to be used without causing damage to the film's surface roughness, enabling both thorough contaminant removal and maintenance of manufacturing precision

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 design improves the photomask's resistance to cleaning solutions, maintaining resolution and optical uniformity, thereby ensuring stable pattern development on semiconductor wafers.

Implementation Method 1

a side surface of the multi-layer light shielding pattern film includes a measuring zone corresponding to a zone between a first spot spaced apart from a first point on an upper boundary of the first light shielding film in a direction to a lower boundary of the first light shielding film and a second spot spaced apart from a second point on a lower boundary of the second light shielding film in a direction to an upper boundary of the second light shielding film, wherein a surface roughness Wr of the measuring zone satisfies Equation 1 below: 0 nm≤Wr−Wo≤3 nm

Methodology Applied

Scientific EffectSurface roughness control:

Implementation Method 2

The design improves the photomask's resistance to cleaning solutions, maintaining resolution and optical uniformity, thereby ensuring stable pattern development on semiconductor wafers

Methodology Applied

Scientific EffectChemical resistance:

Data Source

PatentUS12529952B2Photomask blank and photomask using the same

Publication Date: 2026.01.20 LUMINAMASK CO LTD

AI summary

Disclosed is a photomask comprising: a transparent substrate; and a multi-layer light shielding pattern film disposed on the transparent substrate, wherein the multi-layer light shielding pattern film comprises: a first light shielding film; and a second light shielding film disposed on the first light shielding film and comprising a transition metal and at least one selected from the group consisting of oxygen and nitrogen, and wherein a surface roughness Wr of the measuring zone satisfies Equation 1 below:0 nm<Wr−Wo≤3 nm [Equation 1]where, in the Equation 1 above, Wo is a surface roughness of the measuring zone before soaking and washing processes, Wr is a surface roughness of the measuring zone after soaking in SC-1 (standard clean-1) solution and washing with ozone water, and the SC-1 solution comprises NH4OH, H2O2, and H2O.