Inverted Mark Patterns for Overlay Accuracy in Semiconductor Masks
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Solution Overview
Problem
In multiple exposure lithography processes for semiconductor device manufacturing, achieving high overlay accuracy between masks is challenging due to the need for precise positional accuracy of device patterns, which is compromised by the formation of mark patterns close to the device patterns, leading to potential defects such as mark pattern peeling and reduced accuracy.
Innovation Solution
The use of a mask set with first and second masks, where the mark patterns on each mask are formed at a dimension equal to or larger than the resolution limit and are inverted relative to each other, allowing for improved positional inspection without transferring onto the substrate, thus maintaining accuracy and preventing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mark patterns are formed close to device patterns for positional inspection, then measurement precision is improved, but manufacturing precision deteriorates due to mark pattern peeling and defects
Solution Approach 1:
The patent introduces an auxiliary pattern as an intermediary element that enables positional inspection without requiring mark patterns close to the device pattern. The auxiliary pattern, formed at a distance from the device pattern, serves as a reference for overlay inspection while preventing the peeling and defect issues that occur with closely placed mark patterns.
Solution Approach 2:
The patent separates the inspection function from the device pattern by placing auxiliary patterns at a distance. This segmentation allows the positional inspection to be performed using the auxiliary patterns while the device patterns remain undisturbed, preventing the manufacturing precision deterioration caused by mark pattern peeling.
2Area of stationary object
If mark patterns are formed at small dimensions for close placement, then area is reduced allowing closer positioning, but reliability deteriorates due to increased peeling risk
Solution Approach 1:
The auxiliary pattern acts as an intermediary that provides inspection functionality without requiring small-dimensional mark patterns. By using the auxiliary pattern formed at a distance, the system maintains reliability while achieving the inspection function, eliminating the need to reduce mark pattern dimensions to the point of instability.
3Manufacturing precision
If multiple exposure is performed with high overlay accuracy requirements, then manufacturing precision is improved, but device complexity increases due to stringent alignment requirements
Solution Approach 1:
The auxiliary pattern serves as an intermediary reference that simplifies the alignment process in multiple exposure. By providing a dedicated inspection pattern at a distance from the device pattern, the system achieves high overlay accuracy without increasing the complexity of the alignment system, as the auxiliary patterns provide clear reference points for measurement.
Data Source
AI summary
According to one embodiment, there is provided a mask set including a first mask and a second mask. The first mask includes a first device pattern and a first mark pattern. The first mark pattern is used for an inspection of a position of the first device pattern on a surface of the first mask. The second mask is used to perform multiple exposure on a substrate together with the first mask. The second mask includes a second device pattern and a second mark pattern. The second mark pattern is used for an inspection of a position of the second device pattern on a surface of the second mask. The second mark pattern includes a pattern corresponding to a pattern obtained by inverting the first mark pattern.