Photomask Hard Mask Pattern Critical Dimension Correction
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Solution Overview
Problem
The existing methods for fabricating semiconductor photomasks face challenges in achieving accurate critical dimension (CD) accuracy due to margin reduction and foreign materials in the etching process, leading to increased processing time and cost, as well as degraded quality and reproducibility issues.
Innovation Solution
A method that forms a light blocking layer, hard mask layer, and resist layer on a transparent substrate, allowing for selective exposure and etching to create a hard mask pattern, which is then used to correct the CD by etching the light blocking layer, eliminating the need for a separate correction mask, thereby reducing processing time and cost while enhancing pattern reproducibility and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a separate correction mask is used for CD correction, then CD accuracy can be improved, but processing time and fabrication cost increase
Solution Approach 1:
The patent merges the CD correction function into the main photomask fabrication process by using the hard mask pattern itself as the correction reference. The etching conditions are adjusted to achieve the target CD directly, eliminating the need for a separate correction mask and its associated resist coating, exposure, and development processes.
Solution Approach 2:
The hard mask layer serves multiple functions: it acts as both the pattern definition layer and the CD correction reference. By controlling the etching process to achieve the target CD in the hard mask pattern, the same pattern is used for subsequent light blocking layer etching, making the hard mask multi-functional and eliminating redundant correction steps.
2Manufacturing precision
If a separate correction mask is used for CD correction, then CD accuracy can be improved, but fabrication cost increases
Solution Approach 1:
The patent combines the CD correction function into the main fabrication process, eliminating the need for separate correction mask materials and processing steps. This reduces material costs and process complexity while maintaining CD accuracy through controlled etching parameters.
Solution Approach 2:
The patent extracts the CD correction function from the separate correction mask process and integrates it into the hard mask fabrication step. By taking out the redundant correction mask requirement and using the hard mask itself as the correction reference, the process becomes more cost-effective.
3Manufacturing precision
If additional etching processes are performed for CD correction, then CD accuracy can be improved, but foreign materials may degrade photomask quality
Solution Approach 1:
The patent merges the CD correction into the primary etching process by using the hard mask pattern as the reference. This eliminates additional etching steps that would introduce foreign materials, as the correction is achieved through controlled etching parameters rather than separate correction processes.
4Manufacturing precision
If additional resist coating and exposure processes are performed for correction, then CD accuracy can be improved, but pattern reproducibility becomes difficult to ensure
Solution Approach 1:
The patent combines the CD correction function into the hard mask fabrication process itself. By using the hard mask pattern as the correction reference and controlling etching conditions, the process eliminates variable-sensitive steps like resist coating and exposure, thereby improving pattern reproducibility while maintaining CD 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
This method improves CD accuracy and reproducibility in photomask fabrication by integrating CD correction directly into the process without additional masks, reducing processing time and cost, and ensuring pattern quality.
Implementation Method 1
forming a resist pattern to selectively expose the hard mask layer by removing the resist layer selectively
Implementation Method 2
forming a resist pattern to selectively expose the hard mask layer by removing the resist layer selectively
Implementation Method 3
forming a hard mask pattern by etching the exposed hard mask layer using the resist pattern as an etch mask
Data Source
AI summary
A method for fabricating a photomask includes forming a light blocking layer, a hard mask layer, and a resist layer on a transparent substrate, forming a resist pattern to selectively expose the hard mask layer by removing the resist layer selectively, forming a hard mask pattern by etching the exposed hard mask layer using the resist pattern as an etch mask, exposing the hard mask pattern by removing the resist pattern; measuring a critical dimension of the exposed hard mask pattern, correcting the measured critical dimension of the hard mask pattern to correspond to a critical dimension of a target pattern, forming a light blocking pattern by etching the exposed light blocking layer using the corrected hard mask pattern as an etch mask, and removing the hard mask pattern.