SOI Sidewall Oxide Spacers for Epitaxial Growth Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing semiconductor manufacturing processes face challenges in preventing the formation of SOI sidewalls during epitaxial growth, which leads to increased integration complexity and crystalline defectivity, particularly in Dual Substrate Orientation (DSO) and Bulk on SOI (BOS) integrations, and complicates the Shallow Trench Isolation (STI) etch process.

Innovation Solution

The formation of SOI sidewall oxide spacers through thermal oxidation prevents epitaxial growth on SOI sidewalls, allowing for their easy removal during the STI etch process, thereby simplifying the integration and reducing defectivity by oxidizing the SOI sidewalls in a trench opening to create spacers that can be trimmed and removed without complex etch chemistry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If nitride sidewall spacers are formed to prevent epitaxial growth on SOI sidewalls, then crystalline defectivity is reduced, but device complexity and STI etch process complexity increase

Engineering Contradiction:

Improvecrystalline defectivityVSAvoidintegration complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent changes the material parameter of the sidewall spacer from nitride (complex to etch) to oxide (simple to etch). This parameter change allows the spacer to be formed through thermal oxidation rather than deposition and anisotropic etching, significantly simplifying the subsequent STI etch process while maintaining the function of preventing epitaxial growth on SOI sidewalls.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The oxide sidewall spacer serves as a temporary protective structure that is easily removed during the STI etch process. Unlike nitride spacers that require complex chemistry to remove, the oxide spacers are readily etched away with standard STI etch chemistry, making them a disposable element that simplifies the overall manufacturing process.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Manufacturing precision

If nitride sidewall spacers are used to define STI etch regions, then epitaxial growth is controlled, but STI etch chemistry selection becomes complex

Engineering Contradiction:

Improveepitaxial growth controlVSAvoidSTI etch process simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent changes the chemical composition parameter of the sidewall spacer from nitride to oxide. This enables the use of standard STI etch chemistry (such as buffered HF) that can easily remove oxide spacers along with the SOI layer, eliminating the need to develop complex multi-selective etch chemistry required when nitride spacers are present.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If thermal oxidation is used to form sidewall spacers, then integration complexity is reduced and STI etch is simplified, but epitaxial growth on SOI sidewalls is prevented

Engineering Contradiction:

Improveintegration complexityVSAvoidepitaxial growth control

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent converts the potentially harmful effect of thermal oxidation (which could damage the structure) into a beneficial process. By applying thermal oxidation to form the sidewall spacers, the process simultaneously protects the SOI sidewalls from unwanted epitaxial growth while simplifying subsequent manufacturing steps. The oxidation process creates a protective oxide layer that is easily removed later.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach promotes planarization and simplifies the integration of DSO and BOS substrates, reducing crystalline defectivity and complexity in the STI etch process, enabling the fabrication of high-performance CMOS devices with optimized electron and hole mobility.

Implementation Method 1

oxidizing the SOI sidewalls in a trench opening to create spacers

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

epitaxial growth to form one of the crystal surface orientations

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Data Source

PatentUS7790528B2Dual substrate orientation or bulk on SOI integrations using oxidation for silicon epitaxy spacer formation

Publication Date: 2010.09.07 NXP USA INC

AI summary

A semiconductor process and apparatus provide a planarized hybrid substrate (15) by thermally oxidizing SOI sidewalls (90) in a trench opening (93) to form SOI sidewall oxide spacers (94) which are trimmed while etching through a buried oxide layer (80) to expose the underlying bulk substrate (70) for subsequent epitaxial growth of an epitaxial semiconductor layer (96). In this way, SOI sidewall oxide spacers (94) are formed that prevent epitaxial SOI sidewalls from being formed in the trench opening (93) during the epitaxial growth step, and that can be readily removed during any subsequent STI etch process