Backside Contact Structure Geometry for Void-Free Metal Filling
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Solution Overview
Problem
The existing backside power distribution network (BSPDN) structures in semiconductor devices face challenges with routing complexity and excessive IR drop at the front side, particularly due to incomplete filling of backside contact structures, leading to insufficient metal connection between source/drain regions and backside contact structures, which degrades device performance.
Innovation Solution
A semiconductor device with a backside contact structure is designed, where the width of the upper portion is smaller than the lower portion in a 1st-direction cross-section view, and both portions have uniform widths in a 2nd-direction cross-section view, with a side surface in a positive slope from the bottom surface, to facilitate complete metal filling and improve connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a backside contact structure is used to connect source/drain regions to backside metal lines, then routing complexity is reduced and IR drop is prevented, but incomplete filling of the contact structure occurs leading to insufficient metal connection
Solution Approach 1:
The backside contact structure employs an asymmetric geometry where the top opening width is greater than the bottom width, creating a tapered shape. This asymmetric design ensures that the opening is sufficiently wide to allow complete metal filling during fabrication, while the bottom remains narrow enough to maintain structural integrity and provide effective electrical connection to the source/drain regions.
Solution Approach 2:
The invention modifies the geometric parameters of the backside contact structure by establishing a specific width relationship between the top opening and bottom portion. By controlling the width parameters such that the top width exceeds the bottom width, the structure enables complete metal infiltration while maintaining connection reliability, thus resolving the filling incompleteness issue through parameter optimization.
2Ease of manufacture
If the backside contact structure has uniform width throughout, then manufacturing is simplified, but metal filling may be incomplete leading to void formation
Solution Approach 1:
Rather than using a uniform width design, the invention applies asymmetric geometry with a wider top opening and narrower bottom portion. This asymmetric configuration facilitates complete metal filling by providing sufficient opening width for metal infiltration, while the tapered shape prevents void formation that would occur with uniform width structures.
3Productivity
If the backside contact structure has a narrow opening, then routing density is improved, but metal filling becomes difficult causing insufficient connection
Solution Approach 1:
The asymmetric design with wider top opening and narrower bottom allows the structure to achieve both high routing density and complete metal filling. The wider top opening ensures metal can fully infiltrate the contact structure, while the narrower bottom portion maintains compact footprint for high routing density, effectively resolving the contradiction between these two requirements.
Data Source
AI summary
Provided is a semiconductor device including: a channel structure; source/drain regions connected by the channel structure; and a backside contact structure formed below at least one of the source/drain region, wherein, in a 1st-direction cross section view, a width of an upper portion of the backside contact structure close to the source/drain region is smaller than a width of a lower portion of the backside contact structure distant from the source/drain region, wherein, in a 2nd-direction cross-section view, widths of the upper portion and the lower portion of the backside contact structure are substantially uniform along a vertical downward direction, and wherein the 1st direction intersects the 2nd direction.