Strained Epitaxial Layer Structure for Semiconductor Device Strain Delivery

Solution Overview

Problem

Scaling down semiconductor devices to smaller technology nodes makes it difficult to achieve enhanced carrier mobility due to challenges in delivering strain to the channel region, leading to device instability and potential failure.

Innovation Solution

A method for fabricating a semiconductor device with a strained structure involves forming recess cavities in a substrate, growing strained silicon germanium material within these cavities using selective epitaxy, and applying a cap layer to confine and redistribute the strain effectively, enhancing carrier mobility and device performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If gate length and spacing are decreased to scale down devices, then device density increases, but strain delivery to the channel region becomes difficult leading to device failure

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies local quality by creating a second epitaxial layer with specific properties (grown at a second temperature) that is localized directly over the channel region. This layer is specifically designed to confine and deliver strain locally to where it is needed in the scaled-down device, ensuring effective strain delivery despite reduced gate length and spacing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements a nested structure where the second epitaxial layer is grown over and confines the first epitaxial layer. This nested arrangement allows the outer second layer to protect and deliver the strain generated by the inner first layer into the channel region, enabling effective strain delivery in scaled devices through a multi-layer nested configuration.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 method effectively confines compressive stress in the channel region, improving carrier mobility and reducing the likelihood of device instability and failure, while allowing for enhanced performance in semiconductor devices.

Implementation Method 1

growing a first epitaxial (epi) material in the cavity

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 2

growing a second epi material on the first epi material

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 3

treating the second epi material, wherein treating the second epi material comprises causing the second upper surface to transform to a second crystal plane different from the first crystal plane

Methodology Applied

Scientific EffectPhase transformation: Phase Change

Data Source

PatentUS11257951B2Method of making semiconductor device having first and second epitaxial materials

Publication Date: 2022.02.22

AI summary

A method of manufacturing a semiconductor device includes forming a first gate stack over a substrate. The method further includes etching the substrate to define a cavity. The method further includes growing a first epitaxial (epi) material in the cavity, wherein the first epi material includes a first upper surface having a first crystal plane. The method further includes growing a second epi material on the first epi material, wherein the second epi material includes a second upper surface having the first crystal plane. The method further includes treating the second epi material, wherein treating the second epi material comprises causing the second upper surface to transform to a second crystal plane different from the first crystal plane.