Mask Fabrication Phase Shift Layer CD Control
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Solution Overview
Problem
The challenge in photolithography is the variation in Critical Dimension (CD) of the phase shift layer pattern during the cleaning process, which can lead to exposure defects and render masks unusable, due to excessive corrosion and the difficulty in maintaining the CD within process tolerance as the pattern size becomes finer.
Innovation Solution
The method involves forming oxide side walls on the phase shift layer pattern by oxidizing the side faces with oxygen plasma before cleaning, and using a polymer layer to protect the pattern from corrosion, allowing for the use of cleaning solutions with high detergency while preventing CD loss and maintaining the CD within the target tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cleaning process with high detergency is used to remove byproducts and foreign substances, then cleaning effectiveness is improved, but the phase shift layer pattern is excessively corroded or lost causing CD variation
Solution Approach 1:
A polymer layer is deposited as an intermediary protective coating on the phase shift layer pattern before cleaning. This polymer layer acts as a mediator that shields the phase shift layer from direct contact with the high-detergency cleaning solution, preventing excessive corrosion while allowing effective removal of byproducts and foreign substances. The polymer layer is subsequently removed without affecting the underlying phase shift layer pattern.
Solution Approach 2:
The polymer layer is deposited in advance before the cleaning process to pre-protect the phase shift layer pattern. This preliminary protective action ensures that when the high-detergency cleaning solution is applied, the phase shift layer is already shielded and will not be excessively corroded or lost, thereby maintaining CD size within process tolerance.
2Measurement precision
If the phase shift layer pattern is made finer to achieve higher resolution, then pattern resolution is improved, but the pattern becomes more susceptible to corrosion and loss during cleaning
Solution Approach 1:
The polymer layer serves as a protective intermediary that specifically shields finer phase shift layer patterns from corrosion during cleaning. This intermediary protection is crucial for fine patterns as they have smaller cross-sections and are more vulnerable to complete removal. The polymer layer prevents direct interaction between the cleaning solution and the fine pattern features, maintaining their integrity.
Solution Approach 2:
The invention changes the physical and chemical parameters of the cleaning process by introducing the polymer layer, which alters the interaction between the cleaning solution and the phase shift layer pattern. This parameter change allows the use of high-detergency cleaning solutions without the adverse effects on fine patterns, effectively decoupling cleaning effectiveness from pattern damage risk.
3Manufacturing precision
If a cleaning solution with weak detergency is used to protect the phase shift layer pattern, then pattern integrity is maintained, but foreign substances and particles remain on the mask surface
Solution Approach 1:
The polymer layer acts as a sacrificial intermediary that enables the use of high-detergency cleaning solutions. It absorbs the harmful effects of strong cleaning agents, allowing thorough removal of foreign substances and particles from the mask surface while the phase shift layer pattern remains protected underneath. After cleaning, the polymer layer is removed, leaving a clean surface without pattern damage.
Solution Approach 2:
The invention converts the potentially harmful effect of high-detergency cleaning solutions into a benefit by using the polymer layer as a protective buffer. The cleaning solution's strong detergency is redirected to remove contaminants from the mask surface rather than corroding the phase shift layer pattern, effectively transforming a harmful factor into a useful cleaning mechanism.
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 effectively prevents excessive loss of the phase shift layer pattern during cleaning, ensuring the CD remains within the process tolerance, enabling the use of high-detergency cleaning solutions and reducing defects, thus maintaining the mask's usability and pattern accuracy.
Implementation Method 1
forming oxide side walls on the phase shift layer pattern by oxidizing the side faces with oxygen plasma
Implementation Method 2
oxidizing the side faces with oxygen plasma
Data Source
AI summary
A method of fabricating a mask includes sequentially depositing a phase shift layer and a light shielding layer on a transparent substrate; forming a light shielding layer pattern and a phase shift layer pattern by selectively etching the light shielding layer and the phase shift layer; forming side walls on side faces of the phase shift layer pattern; cleaning the substrate formed with the side walls; and selectively removing a portion of the light shielding layer. The side wall can be formed of an oxide formed by oxidizing the side faces of the phase shift layer pattern.