Epitaxial Semiconductor Material With Enhanced Local Isotropy

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Solution Overview

Problem

Existing field-effect transistor structures face challenges in achieving adequate silicidation and isotropic capping layer growth due to anisotropic epitaxial growth of the capping layer on facets, leading to insufficient thickness and conductivity issues.

Innovation Solution

A structure and method involving a first epitaxial layer with inclined surfaces, a surface layer with higher dopant concentration, and a second epitaxial layer grown over the surface layer, which catalyzes the growth of a capping layer with improved thickness and isotropy, enhancing silicidation and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If process parameters are adjusted to maintain selectivity of epitaxial growth, then selectivity is improved, but the growth rate on facets becomes negligible leading to insufficient capping layer thickness

Engineering Contradiction:

ImproveselectivityVSAvoidcapping layer thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

A surface layer is introduced as an intermediary between the faceted semiconductor material and the capping layer. This surface layer has enhanced dopant concentration that catalyzes the epitaxial growth of the capping layer on facet surfaces, enabling adequate thickness while preserving selectivity. The surface layer acts as a mediator that facilitates capping layer formation on facets without requiring compromise to selectivity parameters.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The dopant concentration parameter is changed in the surface layer relative to the underlying semiconductor material. By increasing the dopant concentration in the surface layer, the epitaxial growth rate of the capping layer on facet surfaces is enhanced, allowing sufficient thickness to be achieved while maintaining the process parameters needed for selectivity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If selective epitaxial growth is used to form raised source and drain, then selectivity is improved, but anisotropic growth leads to faceting that prevents uniform capping layer formation

Engineering Contradiction:

ImproveselectivityVSAvoidcapping layer uniformity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The surface layer serves as an intermediary that addresses the anisotropy problem. It has enhanced dopant concentration that promotes uniform epitaxial growth of the capping layer across all facet orientations. This mediator layer enables the capping layer to form uniformly over the faceted structure without requiring changes to the selective growth process that created the facets in the first place.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If capping layer thickness is increased to support silicidation, then silicidation is improved, but growth on facets remains insufficient due to anisotropic growth rates

Engineering Contradiction:

Improvesilicidation qualityVSAvoidcapping layer thickness on facets

Core Design Contradiction:

Manufacturing precisionVSLength of stationary object

Solution Approach 1:

The dopant concentration in the surface layer is increased relative to the bulk semiconductor material. This parameter change catalyzes the epitaxial growth of the capping layer on facet surfaces, enabling sufficient thickness to be achieved for proper silicidation support. The enhanced dopant concentration in the surface layer specifically targets the facet growth limitation.

Inventive Principle:

Principle #35Parameter changes

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 proposed solution ensures adequate silicidation and isotropic growth of the capping layer, addressing the conductivity and thickness issues in field-effect transistors, thereby improving the overall performance of the transistors.

Implementation Method 1

epitaxially growing a second epitaxial layer arranged over the surface layer on the first surface and the second surface of the first epitaxial layer

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 2

which catalyzes the growth of a capping layer with improved thickness and isotropy

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 3

The surface layer contains a second concentration of the dopant that is greater than the first concentration of the dopant in the portion of the first epitaxial layer

Methodology Applied

Scientific EffectDopant concentration gradient: Dopants

Data Source

PatentUS10763328B2Epitaxial semiconductor material grown with enhanced local isotropy

Publication Date: 2020.09.01 GLOBALFOUNDRIES US INC

AI summary

Structures for a field-effect transistor and methods for fabricating a structure for a field-effect transistor. A first epitaxial layer has a first surface and a second surface inclined relative to the first surface. A surface layer is arranged on the first and second surfaces of the first epitaxial layer. A second epitaxial layer is arranged over the surface layer on the first and second surfaces of the first epitaxial layer. A portion of the first epitaxial layer defines an interface with the surface layer. The portion of the first epitaxial layer contains a first concentration of a dopant. The surface layer contains a second concentration of the dopant that is greater than the first concentration of the dopant in the portion of the first epitaxial layer.