Pellicle Adhesive Layer Flatness Control
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Solution Overview
Problem
Conventional pellicle frames for photolithography cause irregularities in the mask surface due to their own flatness issues, leading to unfocused light exposure and compromised pattern quality, especially when using shorter wavelength ultraviolet light for high-resolution semiconductor manufacturing.
Innovation Solution
A pellicle with a pressure-sensitive adhesive layer of at least 0.4 mm thickness and an elastic modulus not exceeding 0.5 MPa is used to absorb the irregularities of the pellicle frame, maintaining the flatness of the mask surface by effectively reducing the impact of the frame's irregularities on the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pellicle frame with conventional thickness is used, then the pellicle can be attached to the mask, but the frame's irregularities cause mask surface flatness to deteriorate
Solution Approach 1:
The patent applies a flexible pressure-sensitive adhesive layer (thickness ≥0.4mm) between the rigid pellicle frame and the mask. This adhesive layer acts as a compliant interface that absorbs the frame's irregularities through its elasticity (modulus ≤0.5MPa), preventing transmission of frame defects to the mask surface while maintaining secure attachment.
Solution Approach 2:
The patent changes the physical parameters of the adhesive layer by specifying minimum thickness (≥0.4mm) and maximum elastic modulus (≤0.5MPa). These parameter changes ensure the adhesive is sufficiently thick to absorb irregularities yet maintains appropriate mechanical properties for bonding, resolving the contradiction between attachment reliability and surface flatness.
2Manufacturing precision
If a thicker pressure-sensitive adhesive layer is used, then frame irregularities are absorbed better, but the attachment strength may be compromised
Solution Approach 1:
The patent optimizes the adhesive layer parameters by setting minimum thickness (≥0.4mm) for irregularity absorption and maximum elastic modulus (≤0.5MPa) for maintaining bonding strength. This parameter control ensures the adhesive remains sufficiently compliant to absorb frame irregularities while retaining adequate attachment strength.
Solution Approach 2:
The patent creates a composite structure combining the rigid pellicle frame, compliant pressure-sensitive adhesive layer, and rigid mask. This composite design allows each material to perform its optimal function - the frame provides structural support, the adhesive absorbs irregularities through its compliance, and the mask maintains pattern precision.
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 ensures that the flatness of the mask remains within acceptable limits, even when attaching a pellicle with substantial irregularities, thereby maintaining the quality of pattern transfer and enabling successful exposure to short-wavelength ultraviolet light.
Implementation Method 1
a layer of pressure-sensitive adhesive coated on an opposite end face of the frame, wherein the pressure-sensitive adhesive layer has a thickness of at least 0.4 mm
Data Source
AI summary
In a photolithographic pellicle for dustproof protection of a photomask for photolithographic patterning by mounting thereon with the aid of a pressure-sensitive adhesive layer on one end surface of the pellicle frame, the adverse influence on the flatness of the photomask caused by mounting the pellicle can be minimized when the thickness of the pressure-sensitive adhesive layer is 0.4 mm or larger or when the elastic modulus of the layer does not exceed 0.5 MPa.