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 challenges.

Innovation Solution

A semiconductor device with a polysilicon stack and contact structure is developed, featuring undoped and doped polysilicon layers, a barrier layer, and a conductive layer, which reduces contact resistance and enhances device performance by forming the polysilicon stack between the source/drain structure and the contact structure, and using an anisotropic deposition process for a void-free conductive layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If manufacturing and integration steps are increased to provide greater functionality, then device functionality and integrated circuitry amount increase, but manufacturing complexity and process deficiencies increase

Engineering Contradiction:

Improvedevice functionalityVSAvoidmanufacturing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The contact structure is segmented into multiple functional layers: a polysilicon stack with doped and undoped regions, a barrier layer, and a conductive layer. This segmentation allows each layer to perform its specific function optimally while reducing overall manufacturing complexity by breaking down the complex contact formation into manageable steps.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The polysilicon stack acts as an intermediary structure between the source/drain structure and the contact structure. It mediates the electrical connection while providing controlled resistance through its doped and undoped regions, simplifying the integration process by providing a standardized intermediate component.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If contact resistance is reduced to enhance device performance, then electrical conductivity improves, but manufacturing precision requirements increase

Engineering Contradiction:

Improvecontact resistanceVSAvoiddeposition precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The polysilicon stack employs local quality by having different doping concentrations in different regions. The doped polysilicon layer provides high conductivity where needed, while the undoped polysilicon layer provides controlled resistance in other regions. This local differentiation achieves optimal contact resistance without requiring extreme manufacturing precision throughout the entire structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The contact structure uses composite materials combining polysilicon with different doping levels, barrier layer materials, and conductive materials. This composite approach allows the structure to achieve low contact resistance through material properties rather than relying solely on precise geometric dimensions, thereby reducing manufacturing precision requirements.

Inventive Principle:

Principle #40Composite materials

3Reliability

If barrier layer thickness is increased to prevent diffusion, then material diffusion control improves, but conductive layer formation difficulty increases due to voids

Engineering Contradiction:

Improvediffusion controlVSAvoidconductive layer formation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The barrier layer thickness is optimized to provide sufficient diffusion control while maintaining compatibility with subsequent conductive layer formation processes. The local quality of the barrier layer is matched with the local requirements of the contact structure, ensuring adequate protection without creating excessive thickness that would prevent proper conductive layer deposition.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively reduces contact resistance and improves device performance by forming a polysilicon stack between the source/drain and contact structures, and ensures a void-free conductive layer through differential barrier layer thicknesses, thereby enhancing the semiconductor device's functionality.

Implementation Method 1

using an anisotropic deposition process for a void-free conductive layer

Methodology Applied

Scientific EffectAnisotropic deposition: Anisotropy

Implementation Method 2

The second polysilicon layer is doped

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS11935834B2Method for preparing semiconductor device with contact structure

Publication Date: 2024.03.19 NAN YA TECH

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.