Wrap-Around Source/Drain Contacts for Backside Power Delivery
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Solution Overview
Problem
The challenge in fabricating integrated circuits with high-density, high-performance transistors is the limited contact area and manufacturing flexibility due to the small dimensions of source/drain regions and channel regions, which affects the efficiency of backside and frontside contacts.
Innovation Solution
A monolithic semiconductor structure with both backside and frontside source/drain contacts is developed, where metal source/drain sidewall contacts and backside contacts are formed to directly contact the side wall and bottom surfaces of the source/drain regions, enhancing contact areas and facilitating wrap-around contact structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If only frontside contacts are used, then contact spacing is reduced, but contact area and power delivery capability are limited
Solution Approach 1:
The patent extends contacts from a single plane (frontside only) to multiple dimensions by adding backside contacts. This allows current to flow through additional pathways by contacting source/drain regions from both the front and back surfaces of the semiconductor device, effectively increasing the total contact area without increasing the footprint on a single plane.
Solution Approach 2:
The contact structure is divided into multiple segments: frontside contacts, backside contacts, and sidewall contacts. Each segment contacts different portions of the source/drain regions, allowing the total contact area to be distributed across multiple locations and planes, thereby increasing overall contact area while maintaining manageable individual contact structures.
2Productivity
If component dimensions are shrunk, then capacitance and resistance are reduced, but contact spacing becomes more critical and difficult to maintain
Solution Approach 1:
By utilizing the vertical dimension and adding backside contacts, the patent creates additional current pathways that are spatially separated from frontside contacts. This three-dimensional contact architecture allows for adequate spacing between contacts on each surface while maintaining high current density through the combined contact area, thus supporting scaled dimensions without compromising manufacturing precision.
Solution Approach 2:
The contact structure employs nested configurations where sidewall contacts wrap around source/drain regions and connect to both frontside and backside contacts. This nested arrangement maximizes the use of available space around scaled components, providing multiple contact points without requiring excessive lateral spacing, thereby maintaining manufacturing precision in scaled devices.
3Power
If backside contacts are added, then power delivery capability is improved, but fabrication process complexity increases
Solution Approach 1:
The patent performs preliminary actions by forming sidewall contacts and preparing backside contact regions during earlier fabrication stages before final assembly. The sidewall contacts are formed conformally on source/drain regions, and backside contact holes are defined in advance, allowing subsequent backside contact formation to proceed more efficiently and reducing overall process complexity.
Solution Approach 2:
The sidewall contacts serve multiple functions: they provide electrical connection from the frontside to the backside, act as spacers during patterning processes, and contribute to the overall contact area. This multi-functionality reduces the need for separate dedicated structures, thereby simplifying the overall fabrication process despite the added backside contacts.
4Ease of manufacture
If contact spacing is increased, then manufacturing is easier, but contact area per unit footprint is reduced
Solution Approach 1:
The patent resolves this contradiction by moving part of the contact area to the vertical dimension through backside contacts. This allows adequate lateral spacing between contacts on the front surface for easy manufacturing, while compensating for the reduced in-plane contact density by adding contact area on the back surface, thereby maintaining high total contact area density within the device footprint.
Data Source
AI summary
Backside and frontside contact structures wrapping around source/drain regions provide increased contact areas for electrical connections and allow increased silicide areas. Sidewall metallization of epitaxially grown source/drain regions provides source/drain sidewall contacts that enable wrap-around contact formation on both the front side and the back side of a semiconductor device layer. Front side and back side contact metallization over the source/drain sidewall contacts allows wrap-around contact structures on both sides of the device layer.