Strained Semiconductor Structure Formation via Low-Temperature HCl Etching

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Solution Overview

Problem

Existing methods for forming strained semiconductor structures face challenges such as surface roughness and defect formation due to oxide residues and high-temperature processing, which affect device performance.

Innovation Solution

The use of a sacrificial layer on top of the strain relaxed buffer layer, which can be etched to expose the underlying buffer layer, allowing for improved oxide removal and regrowth of the strained semiconductor structure without high-temperature baking, using gases like HCl for etching and epitaxial growth to control the environment and prevent oxidation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If high-temperature baking (700-800°C) is used to remove oxides from SiGe surface, then oxide removal is achieved, but surface roughening and Ge-migration occur

Engineering Contradiction:

Improveoxide removalVSAvoidsurface roughness

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The invention changes the temperature parameter from high (700-800°C) to low temperature processing, and changes the chemical environment from oxidizing to reducing atmosphere using HCl gas, which enables oxide removal without the harmful effects of high-temperature baking

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the thermal field (high-temperature baking) with a chemical field (HCl gas treatment), substituting thermal energy with chemical reaction energy to achieve oxide removal through chemical etching rather than thermal decomposition

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If high-temperature baking is used for oxide removal, then oxide removal is achieved, but Ge coalescence and device performance reduction occur

Engineering Contradiction:

Improveoxide removalVSAvoiddevice performance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If conventional oxide removal methods are used, then oxide removal is achieved, but complicated pre-cleaning and high temperature baking steps are required

Engineering Contradiction:

Improveoxide removalVSAvoidprocess complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the high-temperature baking step from the conventional multi-step process, achieving oxide removal through a single low-temperature HCl gas treatment step, thereby simplifying the overall fabrication process

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the temperature parameter from high to low and introduces HCl gas as the processing medium, transforming a complex multi-step high-temperature process into a simpler low-temperature chemical treatment

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If the SRB layer is exposed without protection, then oxide formation occurs on the SRB layer, but this leads to surface roughness and defects

Engineering Contradiction:

Improveoxide formation controlVSAvoidsurface quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention creates a reducing atmosphere using HCl gas that prevents oxide formation on the SRB layer while enabling controlled oxide removal from the sacrificial layer, thereby maintaining surface quality without requiring the SRB layer to remain protected

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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 provides well-controlled trench recess formation and improved surface quality, reducing defects and enhancing the performance of strained semiconductor devices by preventing oxide formation and atom migration.

Implementation Method 1

etching through the sacrificial layer such that a portion of the strain relaxed buffer layer is exposed

Methodology Applied

Scientific EffectChemical etching: Chemical Bonding

Implementation Method 2

forming the strained semiconductor structure on the exposed portion of the strain relaxed buffer layer

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Data Source

PatentEP2819154B1Method for forming a strained semiconductor structure

Publication Date: 2021.04.21 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

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AI summary

The present invention relates to a method (100) for forming a strained semiconductor structure (212, 312). The method comprises providing (102) a strain relaxed buffer layer (204), forming (104) a sacrificial layer (206, 306) on said strain relaxed buffer layer (204), forming (106) a shallow trench isolation structure (208) through said sacrificial layer (206, 306), removing (108) at least a portion (210) of an oxide layer on said sacrificial layer (206, 306), etching (110) through said sacrificial layer (206, 306) such that a portion of said strain relaxed buffer layer (204) is exposed (110), forming said strained semiconductor structure (212, 312) on said exposed portion (210) of said strain relaxed buffer layer (204).