Semiconductor Test Structure for Photoresist Residue Detection
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Solution Overview
Problem
The challenge in current semiconductor manufacturing is the difficulty in detecting photoresist residue on source/drain regions of transistors during the implantation process, which is critical for maintaining device quality, due to stringent photolithography requirements and the limitations of visual inspection methods.
Innovation Solution
A novel test key structure is introduced in the scribe line area of a semiconductor wafer, comprising a series-connected first and second transistor test units with defined source and drain regions, connected via a photoresist pattern, allowing for electrical performance monitoring to identify photoresist residue through drain-source on-resistance comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection methods are used to detect photoresist residue, then the inspection process is simple, but the detection precision is insufficient due to stringent photolithography requirements
Solution Approach 1:
The patent replaces visual inspection methods with electrical measurement methods. Specifically, it uses drain-source on-resistance measurements to detect photoresist residue, substituting optical/mechanical inspection with electrical field-based detection that provides higher precision suitable for stringent photolithography requirements
Solution Approach 2:
The patent introduces test transistor structures as intermediary elements between the photoresist processing and the detection system. These test transistors serve as mediators that convert the presence of photoresist residue into measurable electrical parameter changes (drain-source on-resistance), enabling indirect but precise detection
2Measurement precision
If test structures are added to monitor photoresist residue, then detection capability is improved, but the scribe line area occupies more space
Solution Approach 1:
The patent segments the test structure into multiple transistor test units arranged in series within the scribe line area. This segmentation allows the test functionality to be distributed across available space, enabling comprehensive detection while optimizing the use of limited scribe line real estate
Solution Approach 2:
The patent utilizes the vertical dimension and multi-layer structure to accommodate test transistor units. By stacking and arranging transistors in three-dimensional space rather than only horizontal plane, the design achieves adequate detection capability while minimizing the footprint in the scribe line area
3Measurement precision
If series-connected transistor test units are used, then detection accuracy is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent designs the transistor test units to use the same fabrication processes and materials as the main circuit devices. This universality allows the test structures to be manufactured alongside production devices without requiring separate or specialized process steps, thereby improving ease of manufacture while maintaining detection accuracy
Solution Approach 2:
The patent optimizes the electrical parameters of the test transistors (such as channel width, length, and doping concentrations) to enhance sensitivity to photoresist residue while keeping the structures compatible with standard fabrication capabilities. This parameter optimization achieves high detection precision within the constraints of existing manufacturing processes
Data Source
AI summary
A semiconductor structure is provided. The semiconductor structure includes a semiconductor wafer, a test structure, and a photoresist pattern. The semiconductor wafer has a substrate with die areas separated by a scribe line area. The test structure disposed in the scribe line area includes first and second transistor test units. The photoresist pattern is arranged between the first and second transistor test units. The first gate structures of the first and second transistor test units are electrically connected to each other. The second gate structures of the first and second transistor test units are electrically connected to each other. A first drain region of the first transistor test unit is electrically connected to a first source region of the second transistor test unit. A second drain region of the first transistor test unit is electrically connected to a second source region of the second transistor test unit.