Pellicle Mounting Apparatus with Elevated Dummy Plate
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Solution Overview
Problem
The existing pellicle mounting process in optical projection lithography introduces distortion and registration errors due to pressure-induced stress, causing flatness degradation and overlay inaccuracies in the mask system.
Innovation Solution
A pellicle mounting apparatus with a dummy plate featuring an elevated portion that distributes and absorbs mounting pressure, maintaining mask flatness by acting as a stress-relieving feature between the pellicle frame and the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pressure is applied to create adhesive bond between pellicle frame and mask, then bonding strength is improved, but mask flatness deteriorates causing registration errors
Solution Approach 1:
A dummy plate is introduced as an intermediary component between the pellicle frame and the mask. The dummy plate absorbs excess mounting pressure through its elevated portion, preventing direct stress transmission to the mask while still enabling adequate bonding of the pellicle frame to the mask structure.
Solution Approach 2:
The dummy plate with its elevated portion serves as a pre-positioned stress-absorbing element that cushions the mask from mounting pressures before the bonding process completes. This prevents pressure-induced distortion from occurring in the first place, rather than attempting to correct it afterward.
2Reliability
If pressure is applied to seal pellicle to mask, then sealing effectiveness is improved, but overlay accuracy deteriorates due to stress-induced distortion
Solution Approach 1:
The dummy plate acts as a mediator that enables effective sealing between the pellicle frame and mask while protecting the mask from stress-induced distortion. The elevated portion of the dummy plate absorbs mounting pressure, allowing the seal to form without compromising overlay accuracy.
3Ease of operation
If pellicle is mounted using conventional pressure method, then mounting simplicity is maintained, but mask flatness degrades causing lateral pattern positioning errors
Solution Approach 1:
The dummy plate is integrated into the existing mounting process as an additional component that requires no change to the basic operating procedure. It automatically performs stress absorption during the conventional pressure mounting process, maintaining simplicity while improving positioning accuracy.
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 effectively reduces or eliminates distortion and overlay errors, preserving the flatness of the mask and improving the accuracy of pattern positioning during the lithography process.
Implementation Method 1
the stress due to pellicle mounting can contribute between 10 and 32 nm of inconsistent lateral pattern positioning at the mask
Data Source
AI summary
An apparatus for mounting a pellicle onto a mask is provided. In one embodiment, the apparatus comprises a base provided with a track; a dummy plate holder coupled to the base, the dummy plate holder for receiving a dummy plate having an elevated portion on one side thereof; a mask holder for receiving a mask, the mask holder slidably coupled to the base; a pellicle holder for receiving a pellicle frame, the pellicle holder slidably coupled to the base; and drive means being adapted to drive the pellicle holder along the track towards the dummy plate holder, wherein during operation when the pellicle frame is mounted onto the mask causing the mask to contact the dummy plate, the mounting pressure in the mask is distributed by way of the elevated portion in the dummy plate, thus reducing distortion in the mask.