Semiconductor Gate Electrode Design for Dual-Metal-Process Simplification
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Solution Overview
Problem
The complexity and increased cost of manufacturing processes in semiconductor devices with dual-metal-gate CMIS structures, where different metal materials are used for n-channel and p-channel MIS transistors, necessitate a simplification of the manufacturing processes while maintaining the required effective work function differences.
Innovation Solution
A semiconductor device design featuring n-channel and p-channel MIS transistors with gate electrodes composed of a Ta—C alloy, where the lower layer gate electrode is 1 monolayer or more and 3 nm or less thick, and the upper layer has a different average electronegativity, allowing for collective etching and reduced material complexity, with the sum of absolute electronegativity differences between layers being 0.1 or more to achieve the necessary effective work function differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different metal materials are used for the gate electrode of the n-channel MIS transistor and that of the p-channel MIS transistor, then the effective work function difference is achieved, but the manufacturing process becomes complex and manufacturing cost increases
Solution Approach 1:
The patent merges the gate electrode formation process for both n-channel and p-channel MIS transistors by using the same metal material (molybdenum) for both gate electrodes. This allows simultaneous formation and processing of both gate electrodes, eliminating the need for separate processing steps that would be required if different metal materials were used, thereby simplifying the manufacturing process while achieving the required effective work function difference through selective carbon introduction
Solution Approach 2:
The patent applies local quality by introducing carbon selectively into one of the gate electrodes (either the n-channel or p-channel gate electrode) while keeping the other gate electrode as pure molybdenum. This localized modification changes the work function of only the affected gate electrode, creating the necessary effective work function difference between the two transistors without requiring different metal materials for each gate electrode
2Reliability
If different metal materials are used for the gate electrode of the n-channel MIS transistor and that of the p-channel MIS transistor, then the effective work function difference is achieved, but the manufacturing cost increases
Solution Approach 1:
The patent merges the gate electrode formation process for both n-channel and p-channel MIS transistors by using the same metal material (molybdenum) for both gate electrodes. This allows simultaneous formation and processing of both gate electrodes, eliminating the need for separate processing steps that would be required if different metal materials were used, thereby simplifying the manufacturing process while achieving the required effective work function difference through selective carbon introduction
Solution Approach 2:
The patent applies local quality by introducing carbon selectively into one of the gate electrodes (either the n-channel or p-channel gate electrode) while keeping the other gate electrode as pure molybdenum. This localized modification changes the work function of only the affected gate electrode, creating the necessary effective work function difference between the two transistors without requiring different metal materials for each gate electrode
3Reliability
If carbon is introduced into one of the gate electrodes to achieve different work functions, then the effective work function difference is achieved, but the manufacturing process becomes complicated
Solution Approach 1:
The patent applies local quality by introducing carbon selectively into one of the gate electrodes (either the n-channel or p-channel gate electrode) while keeping the other gate electrode as pure molybdenum. This localized modification changes the work function of only the affected gate electrode, creating the necessary effective work function difference between the two transistors without requiring different metal materials for each gate electrode
Solution Approach 2:
The patent applies preliminary action by forming both gate electrodes from the same metal material (molybdenum) before selectively introducing carbon into one of them. This sequence allows the gate electrodes to be formed simultaneously using the same deposition process, and the carbon introduction is performed as a subsequent selective modification step, thereby simplifying the overall manufacturing process compared to forming different metal materials separately
Data Source
AI summary
A semiconductor device has an n-channel MIS transistor and a p-channel MIS transistor on a substrate. The n-channel MIS transistor includes a p-type semiconductor region formed on the substrate, a lower layer gate electrode which is formed via a gate insulating film above the p-type semiconductor region and which is one monolayer or more and 3 nm or less in thickness, and an upper layer gate electrode which is formed on the lower layer gate electrode, whose average electronegativity is 0.1 or more smaller than the average electronegativity of the lower layer gate electrode. The p-channel MIS transistor includes an n-type semiconductor region formed on the substrate and a gate electrode which is formed via a gate insulating film above the n-type semiconductor region and is made of the same metal material as that of the upper layer gate electrode.