Self-Aligned Backside Via Structure for Low-Resistance Power Rails
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the inefficient electrical connection between source/drain contacts and backside power components, leading to decreased performance due to small contact areas and increased resistance in high-performance transistors.
Innovation Solution
A self-aligned backside via (BSRV) with dielectric sidewalls and a conductive core is used to connect source/drain contacts to a backside power rail, enhancing the connection area and reducing resistance, while maintaining isolation from adjacent components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional connection methods are used between source/drain contacts and backside power components, then the manufacturing process is simple, but the contact area is small and resistance is high
Solution Approach 1:
The patent transitions from planar 2D connections to 3D vertical connections by forming via holes through the substrate thickness. This dimensional change enables direct connection between frontside source/drain contacts and backside power components, dramatically increasing the effective contact area and reducing resistance while managing the increased structural complexity through precise vertical alignment.
Solution Approach 2:
The via structure is nested within the substrate, with the conductive fill material positioned precisely within the etched via hole. This nesting approach maximizes the use of available space within the substrate thickness, allowing direct vertical connections without occupying additional lateral area, thus improving electrical connection quality without excessive increase in overall device footprint.
2Reliability
If the contact area between source/drain and power components is increased, then resistance is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The via holes are formed and positioned using the existing source/drain contact locations as reference points before final power component placement. This preliminary positioning action ensures that the via alignment is predetermined and controlled, reducing the precision requirements for subsequent steps while maintaining large contact areas for low resistance connections.
Solution Approach 2:
The via structure utilizes the substrate's own thickness and existing contact locations to define its position and dimensions. The via automatically aligns with the source/drain contacts through self-aligned formation processes, eliminating the need for separate high-precision alignment steps and reducing manufacturing precision requirements while achieving large contact areas.
3Reliability
If via holes are formed through the substrate, then direct connection is achieved, but the substrate integrity is compromised
Solution Approach 1:
The via walls are lined with thin film conformal dielectric layers that coat the via sidewalls, providing mechanical support and structural reinforcement to the substrate around the via holes. These thin film shells maintain substrate integrity while allowing the via to penetrate through the substrate for direct electrical connection, preventing crack propagation and maintaining structural strength.
Solution Approach 2:
The via structure employs composite construction with multiple materials: conductive fill material for electrical connection, conformal dielectric liners for structural support, and barrier layers for adhesion. This composite approach distributes mechanical stresses across different materials with complementary properties, maintaining substrate integrity while enabling through-substrate connections for improved electrical reliability.
Data Source
AI summary
Embodiments disclosed herein include a semiconductor structure. The semiconductor structure may include a source/drain (S/D) contact, a backside power rail (RB); and a self-aligned backside via (BSRV). The BSRV may include dielectric sidewalls and a conductive core. The BSRV may electrically connect the S/D contact to the RB.