Reflective Exposure Mask With Stepped Surface for Local Focus Control
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Solution Overview
Problem
In semiconductor device manufacturing, reflective exposure masks struggle to uniformly focus light on photoresist layers with local film thickness differences, leading to difficulties in achieving precise pattern formation across regions with varying distances from the exposure mask.
Innovation Solution
The exposure mask features a reflective layer with varying surface heights and an absorption layer, allowing for precise focusing on photoresist layers by adjusting the substrate's thickness and step angles to match the local steps on the wafer, ensuring uniform light reflection and absorption across the entire exposed region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a reflective exposure mask is used with a fixed distance to the wafer, then light can be uniformly focused on a photoresist layer with uniform film thickness, but it becomes difficult to focus light uniformly on photoresist layers with local film thickness differences
Solution Approach 1:
The reflective layer is designed with different surface heights in different regions (first region with first height, second region with second height) to correspond to local film thickness variations on the wafer. This local variation in the reflective layer's surface height enables each region to focus light at the appropriate depth, solving the problem of non-uniform focusing on photoresist layers with local thickness differences.
Solution Approach 2:
The invention introduces a height dimension variation in the reflective layer structure by forming steps or different thickness regions. This dimensional change allows the exposure mask to compensate for film thickness variations in the photoresist layer, enabling uniform light focusing across regions that previously could not be focused uniformly due to thickness differences.
2Manufacturing precision
If the distance from the exposure mask to the wafer is adjusted to focus on regions with local steps, then focus can be achieved on those specific regions, but uniform focusing across the entire exposed region is compromised
Solution Approach 1:
The reflective layer is designed with different surface heights in different regions (first region with first height, second region with second height) to correspond to local film thickness variations on the wafer. This local variation in the reflective layer's surface height enables each region to focus light at the appropriate depth, solving the problem of non-uniform focusing on photoresist layers with local thickness differences.
Solution Approach 2:
The reflective layer is divided into multiple regions (first region and second region) with different surface heights, where each region is optimized for focusing on photoresist layers of different thicknesses. This segmentation allows simultaneous uniform focusing across the entire exposed region, including areas with local film thickness steps.
3Ease of manufacture
If a conventional reflective exposure mask with uniform surface is used, then the structure is simple and easy to manufacture, but it cannot achieve high-precision pattern transfer on wafers with local film thickness variations
Solution Approach 1:
The reflective layer is designed with different surface heights in different regions (first region with first height, second region with second height) to correspond to local film thickness variations on the wafer. This local variation in the reflective layer's surface height enables each region to focus light at the appropriate depth, solving the problem of non-uniform focusing on photoresist layers with local thickness differences.
Solution Approach 2:
The surface height parameter of the reflective layer is varied across different regions to match the local film thickness variations on the wafer. By changing the height parameter locally rather than maintaining a uniform height, the mask achieves high-precision pattern transfer on wafers with local film thickness variations while maintaining a relatively simple manufacturing approach.
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 configuration enables high-precision pattern transfer and improved focus margin, allowing for accurate formation of patterns on photoresist layers with local steps, enhancing the manufacturing process by ensuring light is focused on the entire region of the photoresist layer.
Implementation Method 1
a reflective layer that is provided on the first main surface side and reflects exposure light
Implementation Method 2
an absorption layer that is provided with a predetermined pattern on the first main surface side via the reflective layer and absorbs the exposure light
Data Source
AI summary
An exposure mask includes a substrate having a first main surface and a second main surface, a reflective layer that is provided on the first main surface side and reflects exposure light, and an absorption layer that is provided with a predetermined pattern on the first main surface side via the reflective layer and absorbs the exposure light, in which the reflective layer includes a first region of which a surface height from the second main surface is a first height, and a second region which is adjacent to the first region via a first step on a surface of the reflective layer, and of which a surface height from the second main surface is a second height higher than the first height, and the absorption layer is provided in each of the first region and the second region.