Photomask Pattern Correction for Overlay Error Reduction
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Solution Overview
Problem
The increasing pattern density and reduction in size on semiconductor wafers have made overlay control more challenging, leading to higher overlay errors and misalignment issues during the photo-etching process, which can result in short circuits and connection failures, impacting fabrication yield and profit margins.
Innovation Solution
A method for correcting the photomask pattern involves expanding and rotating mask holes to form contact patterns, with verification of device gaps and overlay margins to ensure precise alignment, using optical proximity correction techniques to adjust the mask patterns and prevent misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pattern size is reduced and pattern density is increased to improve device integration, then manufacturing precision deteriorates due to higher overlay errors
Solution Approach 1:
The patent applies optical proximity correction (OPC) to pre-adjust the mask pattern before fabrication. This preliminary action compensates for expected overlay errors by modifying the mask design, thereby ensuring that even with reduced pattern sizes and increased density, the final fabricated patterns achieve the required alignment precision.
Solution Approach 2:
The patent modifies geometric parameters of the mask pattern, specifically expanding hole sizes along the horizontal direction and rotating mask holes. These parameter changes are designed to compensate for overlay errors that occur during fabrication, thereby maintaining manufacturing precision despite smaller feature sizes and higher pattern density.
2Manufacturing precision
If hole size is expanded to reduce overlay error, then device gap verification becomes more challenging
Solution Approach 1:
The patent applies different modifications to different parts of the mask pattern. Specifically, hole sizes are expanded along the horizontal direction where overlay errors are most critical, while other dimensions are adjusted differently. This localized quality adjustment optimizes overlay correction without uniformly increasing all dimensions, thereby maintaining measurability of device gaps.
3Manufacturing precision
If mask pattern is rotated and expanded to correct overlay, then fabrication complexity increases
Solution Approach 1:
The patent performs all necessary mask pattern adjustments (expansion and rotation) during the mask design and verification stage, before actual fabrication. This preliminary action consolidates the complexity into the design phase, allowing the fabrication process itself to proceed with standard procedures, thereby managing overall fabrication complexity while achieving high alignment precision.
Data Source
AI summary
A method of correcting a designed pattern of a photomask for fabricating a semiconductor device is provided. A substrate is provided. A first mask pattern of the photomask designed to form a first contact pattern on the substrate is conceived. The first mask pattern includes a plurality of mask holes each having a hole size. The first mask pattern is adjusted to expand the hole size along a horizontal direction and rotate the mask holes for conceiving a second mask pattern of the photomask designed to form a second contact pattern having a plurality of contact holes. A plurality of device gaps between the contact holes is verified, and an overlay margin between the second contact pattern and an adjacent pattern in the semiconductor device is verified for determining whether the second contact pattern is the designed pattern of the photomask.