Monitoring Testkey for Semiconductor CDU and Electrical Uniformity
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Solution Overview
Problem
Current semiconductor fabrication techniques face challenges in achieving uniformity of both critical dimension (CD) and electrical characteristics across different positions on a wafer, particularly with existing exposure-dose control systems like DoseMapper, which do not adequately address variations in on-state current.
Innovation Solution
A monitoring testkey is introduced, comprising MOS transistors of different conductivity types and orientations, with a common gate pad and separate source and drain pads, along with a monitoring pattern of bar-shaped structures, allowing for the measurement of CD variations and on-state current, enabling precise adjustment of exposure and process parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If exposure-dose control system (DoseMapper) is used to improve critical dimension uniformity, then CDU is improved, but uniformity of electrical characteristics at different positions of wafer is not adequately addressed
Solution Approach 1:
The monitoring testkey structure integrates multiple measurement functions into a single device: it simultaneously measures critical dimension (via bar-shaped structure widths) and electrical characteristics (via MOS transistor on-state currents). This multi-functional approach allows both CDU and electrical uniformity to be monitored together, resolving the contradiction by making one measurement system serve multiple purposes.
Solution Approach 2:
The patent introduces a dedicated monitoring testkey as an intermediary measurement structure that bridges the gap between exposure process control and electrical characteristic verification. This intermediary structure provides real-time feedback on both CD and electrical parameters, enabling process adjustments that simultaneously optimize both aspects without interfering with functional circuit layouts.
2Measurement precision
If monitoring structures are added to measure both CD and electrical characteristics, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent combines CD measurement bars and electrical characteristic measurement transistors into a single integrated monitoring testkey structure. The bar-shaped structures for CD measurement are positioned adjacent to MOS transistors for electrical measurement, sharing common fabrication processes and measurement procedures. This merging reduces overall device complexity compared to separate measurement systems while maintaining comprehensive measurement capability.
Solution Approach 2:
The monitoring testkey serves multiple measurement functions simultaneously: it measures critical dimension through bar structure widths, electrical characteristics through MOS transistor currents, and both can be used for process control. This multi-functionality reduces the need for separate measurement structures, thereby reducing overall device complexity while improving measurement precision.
Data Source
AI summary
A monitoring testkey for a wafer is provided. The monitoring testkey includes a first metal oxide semiconductor (MOS) transistor having a channel extending in a first direction, a second MOS transistor having a channel extending in a second direction, a common gate pad electrically connected to gate electrodes of the first MOS transistor and the second MOS transistor, a first source pad electrically connected to source electrodes of the first MOS transistor and the second MOS transistor, a first drain pad electrically connected to a drain electrode of the first MOS transistor, and a second drain pad electrically connected to a drain electrode of the second MOS transistor. The monitoring testkey helps to improve the critical dimension uniformity and electrical characteristics uniformity of elements in a wafer.