Focus Position Adjusting Apparatus for Semiconductor Exposure
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Solution Overview
Problem
In semiconductor device manufacturing, the miniaturization of devices leads to a shortened depth of focus, making it difficult to secure best focus for all regions during the exposure process, resulting in insufficient process margin and potential defective products due to step differences between arithmetic, storage, and peripheral circuits.
Innovation Solution
A focus position adjusting apparatus that includes a step difference estimation unit, an assist pattern generation unit, and a spherical aberration conversion unit, which adds assist patterns with varying sensitivity to spherical aberration to the mask pattern based on processing layer step differences, allowing for the conversion of these differences into spherical aberration to optimize the best focus position across the semiconductor chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the depth of focus is shortened according to miniaturization of the semiconductor device, then the resolution and miniaturization capability are improved, but the focus position cannot be secured for all regions due to step differences, resulting in insufficient process margin
Solution Approach 1:
The patent applies local quality by adding assist patterns with different sensitivities to spherical aberration in different regions of the mask pattern. Specifically, assist patterns are added to regions with step differences (such as around via holes or in different circuit regions) with sensitivities tailored to their local step difference characteristics, while regions without step differences use standard assist patterns. This localized differentiation allows each region to be optimized for its specific conditions, maintaining focus quality across the entire chip despite varying step differences.
Solution Approach 2:
The patent utilizes parameter changes by converting step differences (height variations) into equivalent spherical aberration parameters. The spherical aberration conversion unit calculates the spherical aberration value corresponding to each step difference and adjusts the exposure conditions or mask design parameters accordingly. This parameter transformation allows the system to compensate for focus position shifts caused by step differences, effectively extending the usable depth of focus while maintaining miniaturization benefits.
2Reliability
If assist patterns are added to the mask pattern to compensate for step differences, then the focus position can be adjusted for different regions, but the mask pattern complexity increases
Solution Approach 1:
The patent applies local quality by adding assist patterns with different sensitivities to spherical aberration in different regions of the mask pattern. Specifically, assist patterns are added to regions with step differences (such as around via holes or in different circuit regions) with sensitivities tailored to their local step difference characteristics, while regions without step differences use standard assist patterns. This localized differentiation allows each region to be optimized for its specific conditions, maintaining focus quality across the entire chip despite varying step differences.
Solution Approach 2:
The patent applies partial action by selectively adding assist patterns only to specific regions where step differences exist, rather than uniformly across the entire mask. The assist pattern generation unit identifies regions requiring compensation (such as around via holes, in different circuit blocks, or where step differences exceed thresholds) and adds assist patterns only to those areas. This selective approach compensates for step differences while minimizing the overall increase in mask complexity.
3Manufacturing precision
If the best focus position is optimized for one region, then the manufacturing precision for that region is improved, but other regions with step differences cannot achieve best focus
Solution Approach 1:
The patent applies local quality by adding assist patterns with different sensitivities to spherical aberration in different regions of the mask pattern. Specifically, assist patterns are added to regions with step differences (such as around via holes or in different circuit regions) with sensitivities tailored to their local step difference characteristics, while regions without step differences use standard assist patterns. This localized differentiation allows each region to be optimized for its specific conditions, maintaining focus quality across the entire chip despite varying step differences.
Solution Approach 2:
The patent utilizes parameter changes by converting step differences (height variations) into equivalent spherical aberration parameters. The spherical aberration conversion unit calculates the spherical aberration value corresponding to each step difference and adjusts the exposure conditions or mask design parameters accordingly. This parameter transformation allows the system to compensate for focus position shifts caused by step differences, effectively extending the usable depth of focus while maintaining miniaturization benefits.
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 solution enables the securement of process margin across all regions by adjusting the focus position, reducing defective products by ensuring accurate alignment and dimensionality of resist patterns despite height differences in the processing layer, thereby improving the manufacturing yield of semiconductor devices.
Implementation Method 1
a spherical aberration conversion unit that converts the step difference of the processing layer into the spherical aberration
Data Source
AI summary
According to one embodiment, a step difference estimation unit, an assist pattern generation unit, and a spherical aberration conversion unit are installed. The step difference estimation unit estimates step difference of a processing layer. The assist pattern generation unit adds an assist pattern having different sensitivity to spherical aberration in an exposure process to a mask pattern based on the step difference of the processing layer. The spherical aberration conversion unit converts the step difference of the processing layer into the spherical aberration.