Top-Side Contact Structure for Semiconductor Substrates
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Solution Overview
Problem
Conventional techniques for forming top-side contacts to semiconductor substrates face challenges such as high thermal budgets, complex processes, and difficulty in achieving low resistance contacts, particularly in vertically-conducting power devices.
Innovation Solution
A semiconductor structure is created with a recessed portion filled with a semiconductor material, where a dielectric spacer prevents lateral growth and a highly conductive interconnect layer forms a top-side contact to the substrate, reducing thermal budget and silicon area consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heavily doped diffused region is used to extend through the substrate to reach the substrate region, then a top-side contact is formed, but a high temperature drive-in process is required leading to wide lateral out-diffusion and high thermal budget
Solution Approach 1:
A dielectric spacer is introduced as an intermediary element between the semiconductor material and the substrate. This spacer enables the formation of a low resistance contact path without requiring high temperature drive-in processes, thus reducing thermal budget while maintaining contact reliability
Solution Approach 2:
The contact structure is segmented into distinct functional regions: a recessed portion filled with semiconductor material, a dielectric spacer layer, and an interconnect layer. This segmentation allows each component to be optimized independently, achieving low resistance contact without excessive thermal exposure
2Reliability
If a deep trench is formed through the substrate and filled with conductive material to make top-side contact, then contact is achieved, but the process becomes complicated and highly doped polysilicon is difficult to obtain
Solution Approach 1:
The problematic deep trench formation step is extracted and replaced with a simpler recessed portion approach. Instead of forming a deep trench through the entire substrate, a shallower recessed portion is created and filled with semiconductor material, significantly simplifying the manufacturing process while achieving the same low resistance contact objective
Solution Approach 2:
The geometry parameters of the contact structure are changed: instead of a deep narrow trench, a wider shallower recessed portion is used. This parameter change facilitates easier material filling and doping, reducing process complexity while maintaining low contact resistance
3Reliability
If conventional top-side contact techniques are used, then contact is formed, but silicon area is consumed and back-side contacts become impediments for applications like Chip-Scale Packaging
Solution Approach 1:
The contact structure utilizes vertical dimensionality with the dielectric spacer extending vertically between the semiconductor material and substrate. This vertical arrangement allows compact integration, reducing the horizontal silicon area consumed while maintaining effective electrical contact
Data Source
AI summary
A semiconductor structure includes a starting semiconductor substrate having a recessed portion. A semiconductor material is formed in the recessed portion, and has a higher resistivity than the starting semiconductor substrate. A body region extends in the semiconductor material, and has a conductivity type opposite that of the semiconductor material. Source regions extend in the body region, and have a conductivity type opposite that of the body region. A gate electrode extends adjacent to but is insulated from the body region. A first interconnect layer extends over and is in contact with a non-recessed portion of the starting semiconductor substrate. The first interconnect layer and the non-recessed portion provide a top-side electrical contact to portions of the starting semiconductor substrate underlying the semiconductor material.