Polysilicon Contact Stack for Low-Resistance Semiconductor Contacts
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Solution Overview
Problem
The complexity of manufacturing and integration in semiconductor devices leads to deficiencies, necessitating improvements in the manufacturing process to address these issues.
Innovation Solution
A semiconductor device with a polysilicon stack comprising undoped and doped layers, surrounded by a dielectric layer, and a contact structure including a barrier and conductive layer, is developed. This configuration reduces contact resistance and enhances device performance by forming the polysilicon stack between the source/drain structure and the contact structure, and using a barrier layer with varying thicknesses to ensure void-free conductive layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact structure is formed directly over the source/drain structure, then the manufacturing process is simpler, but the contact resistance is higher
Solution Approach 1:
The contact structure is segmented into multiple polysilicon layers with different doping concentrations. The undoped polysilicon layer is formed first, followed by a doped polysilicon layer, creating a stacked structure that reduces contact resistance while maintaining manufacturability
Solution Approach 2:
Different regions of the contact structure have different doping concentrations optimized for their specific functions. The undoped region provides low resistance contact to the source/drain, while the doped region provides better interface properties with the dielectric layer, achieving local optimization of electrical properties
2Reliability
If the barrier layer has uniform thickness, then the deposition process is simpler, but voids form in the conductive layer
Solution Approach 1:
The barrier layer is designed with non-uniform thickness, being thinner at the sidewalls and thicker at the bottom of the contact hole. This local variation in thickness prevents void formation in the conductive layer while maintaining deposition feasibility
Solution Approach 2:
The thickness parameter of the barrier layer is changed spatially across different locations. By controlling the deposition process to create thickness gradients, the structure accommodates the conductive material without forming voids, solving the manufacturing challenge
Data Source
AI summary
The present disclosure relates to a semiconductor device with a contact structure and a method for preparing the semiconductor device. The semiconductor device includes a source/drain structure disposed over a semiconductor substrate, and a dielectric layer disposed over the source/drain structure. The semiconductor device also includes a polysilicon stack disposed over the source/drain structure and surrounded by the dielectric layer. The polysilicon stack includes a first polysilicon layer and a second polysilicon layer disposed over the first polysilicon layer. The first polysilicon layer is undoped, and the second polysilicon layer is doped. The semiconductor device further includes a contact structure disposed directly over the polysilicon stack and surrounded by the dielectric layer.