Photomask Design Minimizing Thermal Stress via Segmented Phase Shift Regions

Solution Overview

Problem

Photomasks in lithography processes generate thermal stress due to heat absorption, leading to deformation and overlay errors during the exposure step, as light-blocking patterns and phase shift patterns absorb optical energy, causing heat and distortion in the light transmission substrate and lenses.

Innovation Solution

The photomask design incorporates light-blocking and phase shift regions with specific patterns that minimize light absorption, using exposed regions with narrower widths than the resolution limit to reduce heat generation, thereby preventing thermal stress and deformation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If light-blocking patterns and phase shift patterns are used to transfer patterns onto photoresist, then pattern formation is achieved, but thermal stress and deformation occur due to heat absorption

Engineering Contradiction:

Improvepattern accuracyVSAvoidthermal stress

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The photomask is divided into multiple functional regions: light-transmitting regions for pattern transfer, phase shift regions for phase control, and exposed regions with narrower widths than the resolution limit to minimize light absorption. This segmentation allows each region to serve its specific function while controlling overall heat generation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the photomask are designed with different properties: the light-transmitting regions have high light transmission for accurate pattern transfer, the phase shift regions have specific phase shift characteristics, and the exposed regions have minimized light absorption. This local differentiation optimizes both pattern accuracy and thermal management.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If light-blocking patterns absorb optical energy to block light, then light control is achieved, but heat generation causes deformation

Engineering Contradiction:

Improvelight controlVSAvoidheat generation

Core Design Contradiction:

Illumination intensityVSTemperature

Solution Approach 1:

The patent converts the harmful heat generation from light-blocking patterns into a beneficial design feature by strategically placing exposed regions with minimized light absorption. These exposed regions act as thermal sinks that distribute heat more uniformly, preventing localized overheating and deformation while maintaining effective light blocking in other regions.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Manufacturing precision

If phase shift patterns are used to improve pattern transfer, then manufacturing precision is improved, but thermal stress increases

Engineering Contradiction:

Improveoverlay precisionVSAvoidthermal stress

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The photomask is divided into multiple functional regions: light-transmitting regions for pattern transfer, phase shift regions for phase control, and exposed regions with narrower widths than the resolution limit to minimize light absorption. This segmentation allows each region to serve its specific function while controlling overall heat generation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the photomask are designed with different properties: the light-transmitting regions have high light transmission for accurate pattern transfer, the phase shift regions have specific phase shift characteristics, and the exposed regions have minimized light absorption. This local differentiation optimizes both pattern accuracy and thermal management.

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 design effectively reduces thermal stress and deformation of the photomask and lenses, maintaining pattern accuracy and overlay precision by minimizing light absorption and heat generation during the exposure process.

Implementation Method 1

a light transmission substrate having a transfer region and a frame region, a light-transmitting region exposing a portion of the light transmission substrate in the transfer region

Methodology Applied

Scientific EffectLight transmission: Light

Implementation Method 2

a phase shift region surrounding the light-transmitting region in the transfer region. The phase shift region includes a first phase shift region surrounding the light-transmitting region and a second phase shift region surrounding the first phase shift region

Methodology Applied

Scientific EffectPhase shift: Phase Modulation

Data Source

PatentUS9841668B2Photomasks for reducing thermal stress generated by heat

Publication Date: 2017.12.12 SK HYNIX INC

AI summary

A photomask includes a light transmission substrate having a transfer region and a frame region, a light-transmitting region exposing a portion of the light transmission substrate in the transfer region corresponding to a transfer pattern, a phase shift region surrounding the light-transmitting region in the transfer region. The phase shift region includes a first phase shift region surrounding the light-transmitting region and a second phase shift region surrounding the first phase shift region. A first phase shift pattern is disposed on the light transmission substrate in the first phase shift region, and a plurality of second phase shift patterns are disposed on the light transmission substrate in the second phase shift region.