Exposure Mask with Multi-Plane Focus Structures
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Solution Overview
Problem
Conventional methods for determining optimal exposure geometry in semiconductor manufacturing are time-consuming and costly, requiring extensive use of test wafers and manual intervention, which prolongs throughput times and increases defect rates due to the difficulty in ensuring proper focus during the exposure process.
Innovation Solution
An exposure mask with multiple structure planes and focus-sensitive exposure structures allows for inline determination and control of focus settings, enabling simultaneous exposure of reference and product structures without varying the focus, thereby reducing batch logistics and rework by using a topographical staircase with focus-sensitive patterns on the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If test wafers are used for reference exposures with varied exposure geometries to determine optimal focus, then exposure quality can be optimized, but throughput time increases and process complexity increases
Solution Approach 1:
The patent combines reference exposure structures and product exposure structures onto a single exposure mask. This merging eliminates the need for separate test wafers, allowing focus determination to be integrated into the normal production exposure process, thereby maintaining exposure quality optimization while significantly reducing throughput time and process complexity
Solution Approach 2:
The reference exposure structures are pre-configured on the exposure mask with known geometric relationships to the product structures. This preliminary arrangement enables automatic focus determination during each exposure run without requiring subsequent test measurements, allowing real-time focus optimization without extending process time
2Measurement precision
If multiple test wafers are used for focus determination, then measurement precision improves, but loss of time increases
Solution Approach 1:
Multiple reference exposure structures with different geometries are merged onto a single mask, enabling multiple focus measurements to be obtained simultaneously from one exposure run. This eliminates the need for sequential testing with multiple wafers, maintaining high measurement precision while reducing time loss
Solution Approach 2:
The reference exposure structures enable continuous focus monitoring and determination during every production exposure run. This continuous measurement approach replaces discrete, time-consuming test wafer sequences, maintaining precision through repeated measurements without interrupting the production flow
3Measurement precision
If manual evaluation of test wafers is performed to determine optimal exposure geometry, then measurement accuracy can be ensured, but device complexity and operational complexity increase
Solution Approach 1:
The reference exposure structures are designed to automatically indicate focus quality through their imaging characteristics on the wafer. The system self-evaluates focus accuracy through the geometric relationships of the exposed patterns, eliminating the need for manual intervention while maintaining measurement precision through inherent structural indicators
Solution Approach 2:
The reference exposure structures provide immediate feedback on focus quality by producing distinguishable pattern variations that directly indicate whether optimal focus was achieved. This automated feedback mechanism replaces manual evaluation, maintaining measurement accuracy while significantly reducing operational complexity
4Manufacturing precision
If focus verification is performed after exposure of multiple wafers, then exposure quality can be confirmed, but defect rates increase due to delayed detection
Solution Approach 1:
The reference exposure structures enable focus verification to be performed preliminarily and automatically with every exposure run, rather than after batches of wafers. This immediate verification prevents defective exposures from propagating, reducing defect rates while maintaining quality confirmation
Solution Approach 2:
The reference structures provide real-time feedback on focus quality for each exposure run, enabling immediate detection and correction of focus deviations. This continuous feedback loop prevents defective product structures from being produced, improving reliability without compromising quality verification
Data Source
AI summary
In various embodiments, an exposure mask may include a carrier, a first exposure structure in a first structure plane of the carrier, and a second exposure structure in a second structure plane of the carrier. The two structure planes differ from one another.