Self-Aligned Common Gate Contact for Stacked Transistor Alignment
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Solution Overview
Problem
Current designs for stacked transistors with common gate contacts face challenges such as increased resistance and misalignment due to separate wiring and complex fabrication processes, which hinder efficient integration and performance.
Innovation Solution
A self-aligned gate contact is introduced that electrically connects both the top and bottom gate conductors, using a single contact formed through a self-aligned process, ensuring alignment and reducing resistance by sharing the same conductive material and barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate gate contacts are used for top and bottom transistors, then alignment can be achieved through separate fabrication processes, but resistance increases and device complexity increases
Solution Approach 1:
The patent merges the gate contacts of the top and bottom transistors into a single common gate contact structure. This single contact is formed through a self-aligned process that simultaneously contacts both gate conductors, eliminating the need for separate contacts. The merging reduces the number of interfaces and contact resistance points while improving alignment precision through the self-aligned fabrication approach.
2Ease of manufacture
If separate gate contacts are used for top and bottom transistors, then each contact can be independently fabricated, but device complexity and fabrication complexity increase
Solution Approach 1:
The patent combines the fabrication of two separate gate contacts into a single self-aligned contact formation process. The self-aligned process allows the single contact to be precisely positioned relative to both gate conductors without requiring separate alignment steps, thereby reducing fabrication process complexity while maintaining ease of manufacture.
Solution Approach 2:
The self-aligned contact structure is formed in advance during the gate conductor formation process itself, rather than as a subsequent separate step. This preliminary action integrates the contact formation into the existing fabrication flow, reducing overall process complexity while maintaining manufacturing ease.
3Reliability
If a single common gate contact is used, then resistance is reduced and alignment is improved, but fabrication complexity increases
Solution Approach 1:
The gate contact structure is self-aligned, meaning it automatically positions itself relative to the gate conductors during fabrication without requiring external alignment steps. The self-aligned process uses the gate conductor structure itself as the reference for contact positioning, eliminating the need for complex alignment procedures and reducing fabrication complexity while maintaining low resistance and precise alignment.
Data Source
AI summary
A stacked semiconductor structure including a top transistor stacked above a bottom transistor, and a single gate contact in electrical contact with a top gate conductor of the top transistor and a bottom gate conductor of the bottom transistor.