MOSFET Source/Drain Delta Doping Layer for Contact Resistance

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Solution Overview

Problem

In-situ high n-type III-V doping using metalorganic chemical vapor deposition (MOCVD) is challenging, resulting in lower n-type III-V source/drain terminals with higher contact resistance and reduced device performance.

Innovation Solution

The transistor architecture incorporates a layered configuration for the source and drain terminals, featuring a terminal layer with an intervening layer oriented perpendicular to current flow, using a common semiconductive compound and dopant, where the dopant concentration in the intervening layer is over ten times that in the terminal layer, effectively reducing contact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If in-situ high n-type III-V doping is attempted using MOCVD, then device performance should improve, but the doping concentration cannot be achieved due to process limitations

Engineering Contradiction:

Improvedevice performanceVSAvoiddoping concentration

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent introduces an intervening layer with locally concentrated dopant within the terminal layer, creating a non-uniform doping profile. This localized high-concentration dopant region (exceeding 1×10^20/cm³) addresses the MOCVD process limitation by providing the necessary high doping concentration in a specific region rather than attempting uniform doping throughout the entire terminal layer.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the doping parameter distribution by creating a layered structure with an intervening layer that has dopant concentration over ten times higher than the average terminal layer concentration. This parameter change from uniform to non-uniform doping enables achieving the required high n-type doping level that is otherwise difficult to obtain through conventional MOCVD processes.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If lower n-type III-V source/drain terminals are used, then manufacturing is easier, but contact resistance increases and device performance decreases

Engineering Contradiction:

Improvedoping processVSAvoidcontact resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The terminal layer is segmented into multiple regions by introducing an intervening layer. This segmentation creates distinct doping zones: a lower-doped terminal layer region and a high-doped intervening layer region. This segmentation allows the manufacturing process to work with achievable doping concentrations while still achieving the functional equivalent of high-doped terminals through the combined structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The terminal structure is designed as a composite of the terminal layer material and the intervening layer material with different doping concentrations. This composite structure combines the advantages of easier manufacturing (using achievable doping levels in the terminal layer) with the performance benefits of high doping concentration (achieved in the intervening layer), thereby reducing contact resistance while maintaining ease of manufacture.

Inventive Principle:

Principle #40Composite materials

3Reliability

If dopant concentration is increased to reduce contact resistance, then device performance improves, but the required dopant concentration exceeds MOCVD capabilities

Engineering Contradiction:

Improvecontact resistanceVSAvoiddoping concentration

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent transitions from considering doping concentration as a single-dimensional parameter to a multi-dimensional approach by introducing spatial distribution through the intervening layer. Instead of requiring the entire terminal layer to achieve ultra-high doping concentration, the high concentration is concentrated in the intervening layer dimension, while the terminal layer maintains manufacturable doping levels. This dimensional approach to doping distribution resolves the contradiction between achieving low contact resistance and maintaining MOCVD process capabilities.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

This configuration reduces contact resistance and enhances device performance by modulating the band structure and increasing electron tunnel probability, making in-situ doping more cost-effective with less dopant required and no additional processing steps.

Implementation Method 1

increasing electron tunnel probability

Methodology Applied

Scientific EffectElectron tunneling:

Data Source

PatentUS9166035B2Delta doping layer in MOSFET source/drain region

Publication Date: 2015.10.20 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A transistor includes a gate terminal, a source terminal and a drain terminal. At least one of the source and drain terminals has a layered configuration that includes a terminal layer and an intervening layer. The terminal layer has a top surface and a bottom surface. The intervening layer is located within the terminal layer, between and spaced from the top and bottom surfaces, is oriented to be perpendicular to current flow, and is less than one tenth the thickness of the terminal layer. The terminal layer and the intervening layer include a common semiconductive compound and a common dopant, with a concentration of the dopant in the intervening layer being over ten times an average concentration of the dopant in the terminal layer.