Pellicle Frame Recess Locking Mechanism for Photomask Protection

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Solution Overview

Problem

The semiconductor industry faces challenges in photolithographic processes due to contamination from pellicle removal and the inadequacy of traditional pellicle materials under deep ultraviolet (DUV) and extreme ultraviolet (EUV) illumination, which leads to particulate contamination and material breakdown.

Innovation Solution

A pellicle frame with a recess and locking member secures a non-adhesive membrane to a photomask, allowing for secure attachment and easy removal without adhesive residue, and using high-transmissivity materials that can withstand EUV illumination without distorting radiation, enabling secure photomask protection during inspection and exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If traditional adhesive-based pellicles are used to protect the photomask, then the photomask is protected from particulate contamination, but adhesive residue and particulates are generated during pellicle removal

Engineering Contradiction:

Improveparticulate contamination on photomaskVSAvoidadhesive residue and particulates from pellicle removal

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent extracts the adhesive function from the pellicle attachment mechanism. The pellicle frame includes attachment members that mechanically engage with the photomask frame without using adhesives, thereby eliminating adhesive residue and associated particulate contamination while maintaining effective photomask protection

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary mechanical attachment system between the pellicle frame and photomask frame. The attachment members with engagement features (protrusions, recesses, or magnetic components) serve as a mediator that provides secure attachment during use but allows clean removal without contamination

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If organic pellicle membranes are used for traditional photolithography, then they provide effective protection, but they break down under DUV and EUV illumination

Engineering Contradiction:

Improvepellicle protection effectivenessVSAvoidpellicle material stability under illumination

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the material parameters of the pellicle membrane to withstand higher energy illumination. The membrane is made from materials with appropriate bandgap energies and chemical stability to resist breakdown under DUV (193 nm, 248 nm) and EUV (13.5 nm) wavelengths while maintaining optical transparency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures combining the pellicle frame (metal or polymer), adhesive-free attachment members, and specialized membrane materials. This composite approach allows each component to be optimized for its specific function: mechanical support, clean attachment, and radiation-resistant optical protection

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If metal mesh pellicles are used for EUV illumination, then they can withstand the radiation, but they are brittle and difficult to manufacture and clean

Engineering Contradiction:

Improveresistance to EUV illuminationVSAvoidmanufacturing and cleaning complexity

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The patent replaces rigid metal mesh with flexible thin film membranes that can be manufactured using standard thin-film deposition techniques. These membranes maintain EUV radiation resistance while being more flexible, easier to manufacture, and simpler to clean compared to rigid metal mesh structures

Inventive Principle:

Principle #30Flexible shells and thin films

4Measurement precision

If pellicles are removed from photomasks for inspection, then defects can be detected, but particulate contamination and mask damage risk increase

Engineering Contradiction:

Improvedefect detection accuracyVSAvoidparticulate contamination and mask damage

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the source of contamination by eliminating adhesive-based attachment. The mechanical attachment system allows pellicle removal for inspection without generating adhesive residue or particulates, and the pellicle can be reattached without risking mask damage from adhesive application

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8968971B2Pellicles with reduced particulates

Publication Date: 2015.03.03 MICRO LITHOGRAPHY INC(US)

AI summary

Pellicles for photomasks used in photolithographic manufacturing are described. A frame of a pellicle may include a recess formed in a side member and a locking member dimensioned to secure a membrane to the frame when the membrane is disposed between the recess and the locking member. A pellicle may be secured to a photomask using non-adhesive attachment members that contact a side surface of the photomask.