Photomask Inspection via Wafer Virtual Pattern Overlap
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Solution Overview
Problem
Current photomask inspection methods are offline, time-consuming, and costly, leading to inaccurate pattern transfer during the photolithography process due to haze formation on photomasks, which affects the semiconductor manufacturing process.
Innovation Solution
A real-time online method for inspecting photomasks by defining virtual pattern regions on wafers and performing overlap comparisons to detect haze, allowing for continuous photolithography processing without removing the photomask from the equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offline photomask inspection is performed using a photomask inspecting tool, then measurement precision is improved, but loss of time and productivity are worsened due to removing the photomask from equipment and waiting for inspection results
Solution Approach 1:
The patent introduces an intermediary inspection method by using the wafer itself as the inspection medium. Instead of directly inspecting the photomask, the system inspects the pattern transferred to the wafer, which serves as an indirect indicator of photomask quality. This intermediary approach allows inspection to occur during normal production without stopping the photolithography process.
Solution Approach 2:
The system performs self-inspection by using the wafer processing equipment to automatically inspect the pattern on the wafer. The inspection is integrated into the existing production flow, allowing the system to monitor photomask quality without external intervention or dedicated inspection equipment, thereby eliminating the need to remove the photomask from the chamber.
2Manufacturing precision
If offline photomask inspection is performed, then manufacturing precision is maintained by detecting haze, but device complexity and cost are worsened due to expensive photomask inspecting tools
Solution Approach 1:
The patent makes the wafer processing equipment multi-functional by enabling it to perform both production and inspection functions. The same equipment that processes wafers also inspects the patterns on wafers, eliminating the need for separate, expensive photomask inspection equipment. This universal approach reduces device complexity and cost while maintaining manufacturing precision.
Solution Approach 2:
Instead of directly inspecting the photomask, the system inspects a copy of the pattern that has been transferred to the wafer. This indirect inspection method allows the use of simpler, less expensive equipment while still detecting photomask defects such as haze, thereby reducing the need for complex and costly dedicated inspection tools.
3Productivity
If continuous photolithography processing is performed without inspection, then productivity is improved, but reliability is worsened due to undetected haze affecting pattern accuracy
Solution Approach 1:
The patent maintains continuous photolithography processing by integrating inspection into the production flow. The inspection occurs during normal processing without stopping the photolithography cycle, allowing continuous production while simultaneously monitoring for defects. This ensures both high productivity and reliable pattern transfer through real-time detection.
Solution Approach 2:
The system implements feedback by continuously monitoring the pattern on wafers and using this information to detect photomask degradation. When haze or other defects are detected, the system can provide feedback to adjust processing parameters or alert operators, ensuring reliable pattern transfer while maintaining continuous production.
Data Source
AI summary
A method for inspecting a photomask is provided, which is applicable for the photomask with a pattern region and a blank region. First, a wafer is performed a photolithography process by the photomask. The wafer includes a plurality of exposure regions, each of which has a component pattern region. Each component pattern region is surrounded by a scribe line region. Each component pattern region corresponds to the pattern region of the photomask, while the scribe line region corresponds to the blank region of the photomask. Afterwards, the scribe line region is divided into a plurality of virtual pattern regions. The virtual pattern regions are processed by an overlap comparison step one by one. As at least one of the virtual pattern regions overlaps the others incompletely, a part of the blank region on the photomask corresponding to the incompletely-overlapping virtual pattern region has a haze.