Multilayer SiN Mask Blank for ArF Light Fastness and EB Repair

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Solution Overview

Problem

The challenge is to create a mask blank with a light-shielding film that has a laminate structure of high and low nitrided layers to improve ArF light fastness and reduce the occurrence of steps in the side wall pattern during electron beam defect repair, while ensuring accurate detection of the end point between the light-shielding film and the transparent substrate.

Innovation Solution

A mask blank with a light-shielding film comprising three or more laminate structures of high and low nitrided layers, where the high nitrided layer has a nitrogen content of 50 atom % or more and a thickness of 10 nm or less, and the low nitrided layer has a nitrogen content of less than 50 atom % with a thickness twice that of the high nitrided layer, formed on a transparent substrate, allowing for enhanced detection of the end point and reduced step formation during electron beam defect repair.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thin film formed of a SiN-based material with reduced nitrogen content is applied as a light-shielding film, then ArF light fastness is improved and optical density is achieved with smaller thickness, but it becomes difficult to detect the etching end point during EB defect repair

Engineering Contradiction:

ImproveArF light fastnessVSAvoidend point detection during EB defect repair

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The light-shielding film is segmented into multiple thin films with different nitrogen contents. The first thin film has high nitrogen content (50 atom % or more) for easy end point detection, while the second thin film has reduced nitrogen content for high ArF light fastness. This segmentation allows each layer to fulfill its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the light-shielding film structure are assigned different nitrogen contents based on their functional requirements. The first thin film (near the transparent substrate) has high nitrogen content optimized for detection, while the second thin film (outer layer) has reduced nitrogen content optimized for light fastness. This local quality differentiation resolves the contradiction between detectability and performance.

Inventive Principle:

Principle #3Local quality

2Reliability

If a single layer structure of SiN-based material with reduced nitrogen content is used, then ArF light fastness is improved, but excessive etching into the transparent substrate occurs during EB defect repair

Engineering Contradiction:

ImproveArF light fastnessVSAvoidetching precision during EB defect repair

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The light-shielding film is divided into two thin films with different nitrogen contents. The first thin film with high nitrogen content acts as a protective layer that limits etching depth during EB defect repair, preventing excessive etching into the transparent substrate. The second thin film with reduced nitrogen content provides the desired ArF light fastness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first thin film with high nitrogen content serves as a cushioning layer that is intentionally designed to be etched first during EB defect repair. This layer protects the transparent substrate from excessive etching by providing a buffer zone, thereby preventing manufacturing precision issues before they occur.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Difficulty of detecting and measuring

If a light-shielding film with high nitrogen content is used, then end point detection during EB defect repair is easy, but ArF light fastness is reduced

Engineering Contradiction:

Improveend point detection during EB defect repairVSAvoidArF light fastness

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The light-shielding film is segmented into two thin films with different nitrogen contents. The first thin film has high nitrogen content for easy end point detection, while the second thin film has reduced nitrogen content for high ArF light fastness. This segmentation allows each layer to fulfill its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #3Local quality

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 configuration enhances ArF light fastness and improves the accuracy of electron beam defect repair by allowing easier detection of the end point and minimizing excessive etching into the transparent substrate, resulting in higher transfer accuracy and reduced step formation in the pattern.

Implementation Method 1

irradiating the opaque defect portion with an electron beam to etch the opaque defect portion

Methodology Applied

Scientific EffectElectron beam: Electron Beam

Implementation Method 2

when Auger electrons emitted from the portion subjected to irradiation with an electron beam are detected

Methodology Applied

Scientific EffectAuger electrons: Auger Effect

Implementation Method 3

a light-shielding film having an optical density for ArF excimer laser exposure light of 2.5 or more

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Implementation Method 4

irradiating the opaque defect portion with an electron beam to etch the opaque defect portion, to thereby remove the opaque defect portion

Methodology Applied

Scientific EffectElectron beam etching: Electron Beam

Data Source

PatentUS10712655B2Mask blank, transfer mask, method for manufacturing transfer mask, and method for manufacturing semiconductor device

Publication Date: 2020.07.14 HOYA CORPORATION

AI summary

This mask blank is provided with a light blocking film on a light transmitting substrate. The light blocking film has an optical density of 2.5 or more with respect to ArF excimer laser exposure light, and has a structure that comprises three or more multilayer structures, each of which is composed of a high nitride layer and a low nitride layer. The high nitride layer and the low nitride layer are formed from a material that is composed of silicon and nitrogen or a material that contains one or more elements selected from among semimetal elements and non-metal elements in addition to silicon and nitrogen. The high nitride layer has a nitrogen content of 50 atom % or more, and has a thickness of 10 nm or more. The low nitride layer has a nitrogen content of less than 50 atom %, and has a thickness that is not less than twice the thickness of the high nitride layer.