Reticle Stitching Metal Lines With Angled Overlap for Overlay Errors
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Solution Overview
Problem
Existing reticle stitching methods face challenges with limited overlay margin due to placement errors, distortion, and other errors, leading to thin, high-resistance metal lines or disconnections in semiconductor fabrication.
Innovation Solution
Incorporating angled or crossed portions in the metal lines during reticle stitching to increase overlay tolerance, allowing for misalignment accommodation and preventing short circuits or gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard lithographic reticle stitching is used to connect adjacent fields, then metal lines can be formed across field boundaries, but overlay errors cause thin, high-resistance metal lines or disconnections
Solution Approach 1:
The patent applies curvature by replacing straight metal line segments at field boundaries with angled segments. The angled portions create an overlapping merged region that accommodates overlay misalignment, transforming the vulnerable straight-line connection into a robust angled connection that tolerates positional variations during lithographic stitching.
Solution Approach 2:
The patent changes the geometric parameters of metal lines at stitch regions by introducing angled portions with specific angles (e.g., 45 degrees) instead of straight segments. This parameter modification increases the effective overlap area and creates a merged portion that compensates for overlay errors, directly improving connection reliability despite precision limitations.
2Area of stationary object
If multiple lithographic fields are used on a wafer to save computational resources, then larger die sizes can be achieved, but reticle stitching complexity increases
Solution Approach 1:
The patent segments the metal line structure at field boundaries into distinct portions: a first portion in the first field, a second portion in the second field, and an intermediate merged portion at the boundary. This segmentation allows each segment to be independently optimized and processed, simplifying the overall stitching process while enabling larger die sizes through multiple fields.
Solution Approach 2:
The patent performs preliminary design of the angled portions and merged regions during the reticle pattern definition stage. By pre-configuring the metal line geometry at stitch boundaries with angled segments that anticipate overlay variations, the actual lithographic stitching process becomes more robust and less complex, as the compensation mechanism is built into the pattern itself rather than requiring complex real-time alignment corrections.
Data Source
AI summary
A semiconductor device includes a first field and a second field connected to the first field across a stitch region by a metal line. A merged portion within the stitch region connects portions of the metal line between the first field and the second field. The portions of the metal line each include angled portions that extend beyond a width of the metal line.