EUV Reticle Defect Correction via Second Exposure
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Solution Overview
Problem
The semiconductor industry faces challenges in obtaining defect-free EUV reticles due to inherent blank defectivity, leading to costly and time-consuming processes for defect correction, especially for EUV technology nodes below 20 nm, where reticle defects and OPC weak spots require replacement reticles and redesign, causing yield loss and increased setup time.
Innovation Solution
A method involving a second exposure using a correction reticle or a repair pattern, either on the original reticle or with a programmed electron beam/laser writer, to address defects and weak spots without the need for a new reticle, utilizing alignment marks and metrology structures to monitor and adjust the exposure process, allowing for defect correction in a single additional exposure step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a replacement reticle is written to correct all reticle defects, then defect-free wafer patterning is achieved, but manufacturing cost and setup time increase significantly
Solution Approach 1:
The correction reticle is segmented to contain only the specific defect patterns that need correction, rather than containing the complete design pattern. This segmentation allows the correction reticle to be manufactured more quickly and cheaply, while still achieving defect-free wafer patterning when combined with the original reticle through multiple exposures.
Solution Approach 2:
Defects are detected and mapped on the original reticle before manufacturing the correction reticle. This preliminary defect detection allows the correction reticle to be precisely tailored to correct only the identified defects, reducing manufacturing complexity and time while ensuring reliable defect correction.
2Ease of repair
If the pellicle is removed to repair detected defects, then defect correction is possible, but the process takes time and may damage the reticle
Solution Approach 1:
Instead of physically repairing defects on the original reticle by removing and reattaching the pellicle, a correction reticle is created that contains optical copies (patterns) of the defects. These defect patterns on the correction reticle optically compensate for the actual physical defects during wafer exposure, achieving defect correction without mechanical manipulation that could damage the reticle.
3Reliability
If EUV blanks are manufactured with higher precision to reduce inherent defects, then reticle quality improves, but manufacturing cost and time increase
Solution Approach 1:
The defect correction function is extracted from the original reticle manufacturing process. Instead of requiring perfectly defect-free EUV blanks, the system accepts blanks with inherent defects and separately creates a correction reticle that contains only the necessary defect patterns. This extraction allows standard EUV blank manufacturing to be used while still achieving high reticle quality through the added correction step.
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 enables cost-effective and time-efficient correction of reticle defects and OPC weak spots, reducing the risk of yield loss and setup time, while minimizing the impact of blank defectivity, by using a cheaper correction reticle or repair patterns, and allowing for defect-free wafer patterning without complete reticle rewrites.
Implementation Method 1
programming an e-beam or laser writer to expose the wafer in the regions corresponding to the defects and/or design/OPC weak spots on the reticle
Implementation Method 2
programming an e-beam or laser writer to expose the wafer in the regions corresponding to the defects and/or design/OPC weak spots on the reticle
Implementation Method 3
exposing a resist covered wafer using the first and second patterns
Data Source
AI summary
Correction of reticle defects, such as EUV reticle defects, is accomplished with a second exposure. Embodiments include obtaining a reticle with a first pattern corresponding to a design for a wafer pattern, detecting dark defects and/or design/OPC weak spots in the first pattern, exposing a resist covered wafer using the reticle, and exposing the wafer using a second reticle with a second pattern or a second image field with openings corresponding to the dark defects, with a repair pattern on the reticle or on another reticle, or with a programmed e-beam or laser writer.