Backside Metal Gate Layout for Threshold Voltage Tuning
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Solution Overview
Problem
The existing manufacturing processes for semiconductor structures require multiple photomasks to form transistors with different threshold voltages, increasing complexity and cost.
Innovation Solution
A semiconductor structure design where transistors are positioned on the front side of a substrate with metal gates on the back side, allowing for adjustment of threshold voltages by applying voltage to the metal gates, reducing the need for multiple photomasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple photomasks are used to form pocket doped regions with different doping concentrations, then transistors with different threshold voltages can be formed, but the manufacturing process complexity and cost increase
Solution Approach 1:
The patent moves the gate structure from the front surface to the back surface of the semiconductor substrate, utilizing the third dimension (depth/vertical position) to achieve threshold voltage control. By forming metal gates at different positions on the back surface, the patent can adjust threshold voltages without requiring multiple photomasks on the front surface, thus resolving the contradiction between adaptability and manufacturing complexity
Solution Approach 2:
The patent changes the physical parameters of the gate structure by using metal gates with different work functions and positioning them at different depths on the back surface. This allows continuous adjustment of threshold voltages through parameter variation rather than discrete doping concentration changes requiring multiple photomasks
2Adaptability or versatility
If multiple photomasks are used to form pocket doped regions with different doping concentrations, then transistors with different threshold voltages can be formed, but the manufacturing cost increases
Solution Approach 1:
By transitioning to back-surface gating, the patent eliminates the need for multiple front-surface photomasks, directly reducing manufacturing costs while maintaining threshold voltage adjustability through vertical positioning and material selection
3Device complexity
If metal gates are formed on the back side of the substrate, then the number of photomasks is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent segments the gate formation process into separate steps: forming first metal gates at a first position and second metal gates at a second position on the back surface. This segmentation allows independent optimization of each gate region and simplifies the overall manufacturing process by avoiding complex multi-layer photomask alignment
Data Source
AI summary
A semiconductor structure including a substrate, a first transistor, and a first metal gate is provided. The substrate has a front side and a back side opposite to each other. The first transistor is located on the front side. The first transistor includes a first channel region. The first metal gate is located on the back side and aligned with the first channel region.