Phase Shift Photomask Etching for Cr Residue Removal
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Solution Overview
Problem
The existing methods for manufacturing phase shift photo masks face challenges in efficiently removing chromium (Cr) residues during the etching process, leading to increased manufacturing costs and turnaround time due to the need for repeated photolithography and etching operations to achieve acceptable defect levels.
Innovation Solution
A novel etching operation using a detachable ceramic etching hard cover that covers the opaque border region, allowing for the selective removal of the light blocking layer in the pattern region without etching it, thereby reducing the number of lithography operations and effectively eliminating Cr residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If repeated photolithography and etching operations are performed to remove Cr residues, then Cr defect density is reduced, but manufacturing cost and turnaround time increase
Solution Approach 1:
The mask blank is divided into two distinct regions: a pattern region where the light blocking layer is completely removed, and an opaque border region where the light blocking layer is retained. This segmentation allows different processing treatments for different regions, eliminating the need for repeated etching operations to remove Cr residues from the entire mask.
Solution Approach 2:
The harmful Cr residues are extracted selectively from the pattern region through complete removal of the light blocking layer, while the opaque border region serves as a protective zone that prevents Cr residue generation in the first place. This extraction approach eliminates the need for repeated cleaning operations.
2Manufacturing precision
If repeated photolithography and etching operations are performed to remove Cr residues, then Cr defect density is reduced, but manufacturing cost increases
Solution Approach 1:
The mask blank is divided into two distinct regions: a pattern region where the light blocking layer is completely removed, and an opaque border region where the light blocking layer is retained. This segmentation allows different processing treatments for different regions, eliminating the need for repeated etching operations to remove Cr residues from the entire mask.
Solution Approach 2:
The harmful Cr residues are extracted selectively from the pattern region through complete removal of the light blocking layer, while the opaque border region serves as a protective zone that prevents Cr residue generation in the first place. This extraction approach eliminates the need for repeated cleaning operations.
3Manufacturing precision
If the light blocking layer is completely removed from the entire mask, then Cr residues are eliminated, but the opaque border region cannot serve its protective function
Solution Approach 1:
The mask blank is divided into two distinct regions: a pattern region where the light blocking layer is completely removed, and an opaque border region where the light blocking layer is retained. This segmentation allows different processing treatments for different regions, eliminating the need for repeated etching operations to remove Cr residues from the entire mask.
Solution Approach 2:
Different regions of the mask blank are given different properties: the pattern region has complete light blocking layer removal for Cr residue elimination, while the opaque border region maintains the light blocking layer for protective functionality. This local differentiation optimizes both manufacturing precision and reliability.
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 approach reduces the manufacturing costs and turnaround time by allowing for the efficient removal of Cr residues in a single etching operation, improving the defect density of phase shift photo masks and enhancing the overall manufacturing process.
Implementation Method 1
phase shift masks have been developed where the phase of the wavefronts of light passing through alternating portions of the reticle pattern are shifted out of phase with respect to light passing through adjacent portions to produce destructively interfering wavefronts
Implementation Method 2
produce destructively interfering wavefronts to reduce undesired exposure of the wafer photoresist due to diffraction of light at feature edges of the reticle pattern
Implementation Method 3
A novel etching operation using a detachable ceramic etching hard cover that covers the opaque border region, allowing for the selective removal of the light blocking layer in the pattern region without etching it
Data Source
AI summary
In a method of manufacturing a photo mask, a resist layer is formed over a mask blank, which includes a mask substrate, a phase shift layer disposed on the mask substrate and a light blocking layer disposed on the phase shift layer. A resist pattern is formed by using a lithographic operation. The light blocking layer is patterned by using the resist pattern as an etching mask. The phase shift layer is patterned by using the patterned light blocking layer as an etching mask. A border region of the mask substrate is covered with an etching hard cover, while a pattern region of the mask substrate is opened. The patterned light blocking layer in the pattern region is patterned through the opening of the etching hard cover. A photo-etching operation is performed on the pattern region to remove residues of the light blocking layer.