MBC Transistor Blocking Features for Drive Current Tuning
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Solution Overview
Problem
Existing methods for forming multi-bridge-channel (MBC) transistors are not satisfactory in all aspects, particularly in modulating effective resistance, capacitance, and drive current, which are crucial for advanced semiconductor devices.
Innovation Solution
A method involving the formation of blocking features after inner spacer features to selectively shut off channel members, modulating the effective resistance, capacitance, or drive current of MBC transistors, by using a blocking feature formation process that includes forming inner spacer features and blocking features to isolate specific channel members, allowing for the creation of MBC transistors with varying effective channel widths and resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing methods for forming MBC transistors are used, then the gate control is improved by increasing gate-channel coupling, but the effective channel width modulation is insufficient leading to suboptimal drive current performance
Solution Approach 1:
The patent segments the channel members into multiple individual bridges (first channel member, second channel member, third channel member) that are spatially separated. This segmentation allows independent control and optimization of each channel member's contribution to drive current while maintaining overall gate control through the common gate structure wrapping around all bridges.
Solution Approach 2:
The patent transitions from a planar channel structure to a three-dimensional multi-bridge-channel configuration where channel members are arranged in multiple dimensions (laterally separated bridges with vertical height). This dimensional change increases the effective channel width and surface area for carrier transport, thereby improving drive current performance while the gate structure wraps around to maintain electrostatic control.
2Productivity
If multiple channel members are used to increase effective channel width, then drive current performance is improved, but the complexity of processing and manufacturing ICs increases
Solution Approach 1:
The patent employs a universal gate structure that simultaneously wraps around and controls multiple channel members (first, second, and third channel members). This multi-functional gate structure provides electrostatic control over all channel bridges through a single formation process, reducing manufacturing complexity compared to forming separate gates for each channel member.
Solution Approach 2:
The patent merges multiple channel members into a unified multi-bridge-channel device under a single gate structure. By combining the channel members laterally while maintaining their individual identities, the device achieves increased effective channel width and drive current performance without proportionally increasing manufacturing steps, as all channels are processed and controlled together.
3Reliability
If channel members are closely packed to maximize gate-channel coupling, then gate control is improved, but the ability to modulate effective channel width is reduced
Solution Approach 1:
The patent applies local quality by creating distinct spatial regions for different channel members (first channel member in a first region, second channel member in a second region, etc.). This local differentiation allows selective modulation of effective channel width by controlling which specific channel members are active, while each local region maintains strong gate-channel coupling through the wrapping gate structure.
Data Source
AI summary
The present disclosure provides semiconductor devices and methods of forming the same. A semiconductor device of the present disclosure includes a first source/drain feature and a second source/drain feature over a substrate, a plurality of channel members extending between the first source/drain feature and the second source/drain feature, a gate structure wrapping around each of the plurality of channel members, and at least one blocking feature. At least one of the plurality of channel members is isolated from the first source/drain feature and the second source/drain feature by the at least one blocking feature.