Photomask Ring Areas for High-Contrast Overlay Marks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current photomask technologies for double patterning in IC manufacturing face challenges in achieving precise alignment due to low contrast and difficulty in identifying overlay marks, particularly because the conventional spacers and hollow cylinders have similar thin thicknesses, making metrology processes cumbersome.
Innovation Solution
A photomask with ring areas and inner areas of different light transmittance is used, along with a method involving a photoresist layer, exposure, development, and etching to form thick spacers that create high-contrast overlay marks, facilitating precise alignment in double patterning processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional spacers and hollow cylinders are used with similar thin thicknesses, then the manufacturing process is simpler, but the contrast is low and overlay marks are difficult to identify
Solution Approach 1:
The patent applies local quality by creating regions with different light transmittance properties. The photomask contains first regions with first light transmittance and second regions with second light transmittance, where the light transmittance differs between regions. This creates high-contrast overlay marks that are easily distinguishable during metrology processes, resolving the contradiction between manufacturing simplicity and mark identifiability.
Solution Approach 2:
The patent uses optical property changes (analogous to color changes) by varying light transmittance in different regions of the photomask. The first regions and second regions have different light transmittance values, creating visual contrast that enables easy identification of overlay marks during alignment and metrology, while maintaining a relatively simple manufacturing process.
2Ease of manufacture
If photomask patterns with uniform light transmittance are used, then the manufacturing process is simpler, but alignment precision is insufficient
Solution Approach 1:
The patent implements local quality by dividing the photomask into first regions and second regions with different light transmittance properties. This regional differentiation enables precise alignment through high-contrast overlay marks while keeping the overall manufacturing process relatively simple, thus resolving the contradiction between manufacturing simplicity and alignment precision.
Solution Approach 2:
The patent applies parameter changes by varying the light transmittance parameter across different regions of the photomask. The first regions have a first light transmittance value and the second regions have a second light transmittance value, creating distinguishable features that improve alignment precision without significantly complicating the manufacturing process.
3Ease of manufacture
If overlay marks with low contrast are used, then the manufacturing cost is lower, but metrology processes become cumbersome and time-consuming
Solution Approach 1:
The patent uses optical contrast enhancement (analogous to color changes) by creating regions with different light transmittance. The first regions and second regions have distinct light transmittance values that produce high-contrast overlay marks, making them easily identifiable during metrology processes and significantly reducing measurement time while maintaining cost-effectiveness.
Solution Approach 2:
The patent applies local quality by creating spatially differentiated regions with varying light transmittance properties. This produces high-contrast overlay marks that are easily distinguishable during metrology, reducing the time required for alignment verification while keeping the manufacturing process and costs relatively low.
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
The high-contrast overlay marks enable easier identification and improved alignment precision, ensuring successful patternization by maintaining a thickness range that enhances visibility during metrology processes.
Implementation Method 1
the light transmittancy of the ring areas is different from that of the inner areas
Implementation Method 2
performing an exposure and development process, so that the photoresist layer has a plurality of mark patterns
Implementation Method 3
etching the substrate to form an overlay mark corresponding to the thick spacers
Data Source
AI summary
The present invention relates to a photomask and a method for forming an overlay mark in a substrate using the same. The photomask comprises a plurality of patterns. At least one of the patterns comprises a plurality of ring areas and a plurality of inner areas enclosed by the ring areas, wherein the light transmittancy of the ring areas is different from that of the inner areas. When the photomask is applied in a photolithography process, the formed overlay mark has a large thickness. Therefore, the contrast is high when a metrology process is performed, and it is easy to find the overlay mark.