Semiconductor Epitaxial Structure with Sacrificial Dopant Removal

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Solution Overview

Problem

In semiconductor device preparation, doping elements like iron or magnesium precipitate upward into upper-layer epitaxial structures, reducing electron mobility and device performance due to their 'memory effect'.

Innovation Solution

A method involving the formation of a sacrificial layer on a doped first epitaxial structure, followed by etching to gather and remove dopant atoms, preventing their precipitation into upper layers, and optionally using a protective layer to minimize damage to the epitaxial structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If doping elements (iron or magnesium) are added to the first epitaxial structure to increase resistivity and reduce electrical leakage, then the resistivity of the epitaxial layer is improved, but the doping elements precipitate upward into the upper-layer structure, reducing electron mobility and device performance

Engineering Contradiction:

Improveelectrical leakage reductionVSAvoiddoping element distribution control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

A sacrificial layer is introduced as an intermediary between the doped first epitaxial structure and the upper-layer epitaxial structure. This sacrificial layer acts as a mediator that captures and retains the doping elements (iron or magnesium) that would otherwise precipitate upward into the upper layer. The sacrificial layer is subsequently removed, having served its purpose of preventing dopant contamination of the upper layer while allowing the beneficial electrical properties of the doped lower layer to be maintained.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful doping elements (iron or magnesium) that have precipitated into the sacrificial layer are extracted and removed from the overall structure through sacrificial layer etching. This extraction process eliminates the source of electron mobility degradation in the upper-layer structure while preserving the electrical leakage reduction benefits in the lower-layer structure.

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If multiple cycles of sacrificial layer formation and etching are performed to reduce doping element concentration below a preset value, then the electron mobility of the upper-layer epitaxial structure is ensured, but the manufacturing complexity and process time increase

Engineering Contradiction:

Improvedoping element concentration controlVSAvoidprocess steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent employs periodic action by repeating the cycles of sacrificial layer formation and etching multiple times. Each cycle reduces the doping element concentration in the first epitaxial structure further, with the repetition continuing until the concentration falls below a preset threshold value. This periodic process ensures precise control over dopant distribution while providing a systematic approach to achieving the desired concentration level.

Inventive Principle:

Principle #19Periodic action

3Strength

If a protective layer is added between the first epitaxial structure and the sacrificial layer to minimize damage during etching, then the integrity of the epitaxial structure is improved, but the device complexity and manufacturing steps increase

Engineering Contradiction:

Improveepitaxial structure integrityVSAvoidlayer structure

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

A protective layer is deposited beforehand between the first epitaxial structure and the sacrificial layer to cushion and protect the epitaxial structure during the subsequent etching process. This protective layer prevents potential damage to the epitaxial structure from the etching chemicals or mechanical stress, ensuring its integrity is maintained throughout the sacrificial layer removal process.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 method effectively reduces the concentration of dopant atoms in the first epitaxial structure below a preset value, enhancing electron mobility and device performance by preventing dopant precipitation into upper-layer structures.

Implementation Method 1

S3: etching the sacrificial layer

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

continuing to grow a second epitaxial structure on the first epitaxial structure

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Data Source

PatentUS12183576B2Preparation method for semiconductor structure

Publication Date: 2024.12.31 ENKRIS SEMICON

AI summary

Disclosed is a preparation method for a semiconductor structure. The semiconductor structure includes: a substrate; an epitaxial layer and an epitaxial structure that are stacked on the substrate in sequence. The epitaxial layer is doped with a doping element. In the forming process, a sacrificial layer is formed on the epitaxial layer, and the sacrificial layer is repeatedly etched, such that a concentration of the doping element in the epitaxial layer is lower than a preset value. In this application, the sacrificial layer is formed on the epitaxial layer, and the sacrificial layer is repeatedly etched, such that the concentration of the doping element in the epitaxial layer is lower than the preset value, so as to prevent the doping element in the epitaxial layer from being precipitated upward into an upper-layer structure, ensure the mobility of electrons in a channel layer, and improve the performance of a device.