Phase Shift Mask Lift-Off Process for Uniform Transmittance
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Solution Overview
Problem
The manufacturing process of phase shift (halftone) masks is prone to uneven thin film thickness and increased defects due to etching, leading to low yield and higher costs compared to conventional binary masks.
Innovation Solution
A mask manufacturing method using a lift-off process to form phase shift (halftone) layers, allowing for the creation of masks with varying transmittance by using different materials and thicknesses for the transmitting layers, thereby avoiding uneven thickness issues and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an etching process is used to form phase shift (halftone) layers, then the mask can achieve phase shift functionality, but uneven thin film thickness occurs leading to low yield
Solution Approach 1:
Instead of removing material through etching to create phase shift layers, the invention deposits transmitting layers only in desired regions using photoresist masks. This inverted approach—adding material rather than removing it—eliminates etching-induced thickness variations and achieves uniform phase shift properties.
Solution Approach 2:
The invention applies photoresist layers before depositing transmitting layers to define precise patterns. This preliminary masking action ensures that transmitting layers are deposited only in required areas with controlled thickness, preventing the unevenness problems that would arise from subsequent etching processes.
2Reliability
If a phase shift (halftone) mask is manufactured using conventional methods, then phase shift functionality is achieved, but manufacturing cost increases due to complicated procedures
Solution Approach 1:
The invention combines multiple manufacturing steps into a more integrated process. By depositing transmitting layers directly onto photoresist masks and using the photoresist as both pattern definition and protective layer, the method reduces the number of separate etching and deposition cycles required, thereby lowering manufacturing complexity and cost.
Solution Approach 2:
The invention uses photoresist patterns as templates to guide the deposition of transmitting layers. This copying approach allows the phase shift pattern to be defined by the photoresist structure itself, eliminating the need for complex etching masks and reducing manufacturing steps while maintaining functional accuracy.
3Ease of manufacture
If etching is used to remove phase shift (halftone) thin film, then pattern transfer is achieved, but defects increase due to uneven etching
Solution Approach 1:
Instead of transferring patterns by removing material through etching, the invention creates patterns by selectively depositing transmitting layers onto photoresist masks. This inverted material addition approach eliminates etching-related defects such as uneven removal, over-etching, and pattern distortion, achieving defect-free pattern transfer.
Solution Approach 2:
The photoresist layer serves as an intermediary that facilitates pattern transfer without requiring etching. The transmitting layers are deposited onto the photoresist mask, which acts as a protective intermediary layer. This eliminates direct etching of the phase shift material, preventing etching-induced defects while achieving complete pattern transfer.
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 method results in phase shift (halftone) masks with even transmittance and phase angles, reducing manufacturing costs and improving yield by eliminating defects associated with etching, while also enabling the remanufacturing of masks from recycled binary masks.
Implementation Method 1
by exposing and developing in certain areas, part of the photoresist layer is removed to expose the metal layer thereunder
Implementation Method 2
the transmittance of phase shift (halftone) thin film depends on the film material, film thickness, and phase angle
Data Source
AI summary
A mask including a transparent substrate, a non-transmitting layer, a first transmitting layer and a second transmitting layer is provided. The transparent substrate has a first region, a second region, and a third region. The non-transmitting layer is disposed in the first region of the transparent substrate. The first transmitting layer is disposed in the second region and the third region of the transparent substrate. The second transmitting layer is disposed on the first transmitting layer in the third region.