Multi-Layer Chromium Mask Blank Etching Anisotropy

Solution Overview

Problem

In dry etching of chromium-based light shielding films, the use of chlorine-based gases with oxygen leads to low anisotropy etching, resulting in significant side etching and difficulty in maintaining pattern accuracy and optical characteristics, particularly in multi-layer structures where chromium content and oxygen levels vary across layers.

Innovation Solution

A mask blank with a three-layer light shielding film structure on a transparent substrate, where the intermediate layer has the highest chromium content and includes metallic elements like indium or tin, and the upper and lower layers have lower chromium content and varying oxygen levels, optimized for dry etching using chlorine-based gases under high-bias conditions to minimize side etching and maintain optical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If chlorine-based gas containing oxygen is used as etching gas for dry etching of chromium-based light shielding film, then etching rate is improved, but anisotropy of etching decreases and side etching increases

Engineering Contradiction:

Improveetching rateVSAvoidpattern accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a multi-layer light shielding film structure where each layer has different chromium content and composition. The intermediate layer has highest chromium content with metallic elements (In, Sn, Mo) to provide high etching rate and anisotropy, while upper and lower layers have lower chromium content to maintain optical characteristics. This localized differentiation of material properties throughout the film thickness enables selective etching behavior in different regions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining chromium-based compounds with metallic elements (indium, tin, or molybdenum) in the intermediate layer. This composite structure provides synergistic effects: chromium ensures light shielding performance and etchability, while the added metallic elements enhance etching anisotropy and rate. The composite light shielding film thus achieves both high productivity in etching and maintained manufacturing precision through the tailored composition of each layer.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If high bias voltage is applied to increase anisotropy etching, then side etching is reduced, but etching rate decreases

Engineering Contradiction:

Improveside etching controlVSAvoidetching rate

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent applies local quality by creating a multi-layer light shielding film structure where each layer has different chromium content and composition. The intermediate layer has highest chromium content with metallic elements (In, Sn, Mo) to provide high etching rate and anisotropy, while upper and lower layers have lower chromium content to maintain optical characteristics. This localized differentiation of material properties throughout the film thickness enables selective etching behavior in different regions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining chromium-based compounds with metallic elements (indium, tin, or molybdenum) in the intermediate layer. This composite structure provides synergistic effects: chromium ensures light shielding performance and etchability, while the added metallic elements enhance etching anisotropy and rate. The composite light shielding film thus achieves both high productivity in etching and maintained manufacturing precision through the tailored composition of each layer.

Inventive Principle:

Principle #40Composite materials

3Reliability

If multi-layer structure with varying chromium content is used, then optical characteristics are maintained, but etching anisotropy becomes difficult to control uniformly

Engineering Contradiction:

Improveoptical characteristicsVSAvoidetching uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a multi-layer light shielding film structure where each layer has different chromium content and composition. The intermediate layer has highest chromium content with metallic elements (In, Sn, Mo) to provide high etching rate and anisotropy, while upper and lower layers have lower chromium content to maintain optical characteristics. This localized differentiation of material properties throughout the film thickness enables selective etching behavior in different regions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining chromium-based compounds with metallic elements (indium, tin, or molybdenum) in the intermediate layer. This composite structure provides synergistic effects: chromium ensures light shielding performance and etchability, while the added metallic elements enhance etching anisotropy and rate. The composite light shielding film thus achieves both high productivity in etching and maintained manufacturing precision through the tailored composition of each layer.

Inventive Principle:

Principle #40Composite materials

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 enables precise pattern formation with reduced side etching and maintained optical characteristics, improving the accuracy and form quality of the phase shift mask and semiconductor device manufacturing process.

Implementation Method 1

the intermediate layer having a highest content of chromium in the light shielding film, and containing at least one metallic element selected from indium, tin, and molybdenum

Methodology Applied

Scientific EffectAnisotropy: Anisotropy

Implementation Method 2

the upper layer having a lowest content of chromium in the light shielding film

Methodology Applied

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

Data Source

PatentUS10088744B2Mask blank, method of manufacturing phase shift mask, phase shift mask, and method of manufacturing semiconductor device

Publication Date: 2018.10.02 HOYA CORPORATION

AI summary

A mask blank having a structure in which, on a transparent substrate, a light shielding film and a hard mask film are laminated in the stated order from the transparent substrate side. The hard mask film is formed of a material containing at least one element selected from silicon and tantalum, and the light shielding film is formed of a material containing chromium. The mask blank has a structure of three layers wherein a lower layer, an intermediate layer, and an upper layer are laminated in the stated order from the transparent substrate side. The upper layer has a lowest content of chromium in the light shielding film, the intermediate layer has a highest content of chromium in the light shielding film. It contains at least one metallic element selected from indium, tin, and molybdenum.