Insulation Trench Depth Control via Localized Doping and Selective Etching

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Solution Overview

Problem

Existing methods for producing isolation trenches in semiconductor on insulator substrates face challenges in precisely controlling trench depth, leading to issues such as incomplete trench formation, excessive etching, and increased electrical resistance.

Innovation Solution

A method involving localized doping and selective etching of the insulating layer, followed by anisotropic etching and protective layer formation, allows for precise control of trench depth by selectively removing the insulating layer while protecting the semiconductor layer, ensuring the trench bottom stops at the interface between the insulating and semiconductor layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If selective etching of the insulating layer is performed to stop precisely at the interface with the semiconductor support layer, then trench depth precision is improved, but the etching process tends to continue into areas beyond the interface causing over-etching

Engineering Contradiction:

Improvetrench depth precisionVSAvoidover-etching

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

A protective layer is deposited on the semiconductor support layer before the etching process. This protective layer acts as a barrier that prevents the etching process from continuing beyond the desired interface, thereby eliminating over-etching while maintaining precise trench depth control.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective layer serves as an intermediary element between the etching process and the semiconductor support layer. It allows the etching to proceed precisely to the interface without penetrating into the semiconductor layer, thus mediating the interaction between the etchant and the substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If trenches are etched deeper to reach the interface between insulating layer and semiconductor layer, then isolation effectiveness is improved, but electrical resistance of the semiconductor support layer increases

Engineering Contradiction:

Improveisolation effectivenessVSAvoidelectrical resistance increase

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The protective layer is deposited in advance to define the exact etching boundary. This allows the trenches to reach precisely to the interface without excessive depth, thereby achieving effective isolation while avoiding the creation of high-resistance regions in the semiconductor support layer.

Inventive Principle:

Principle #10Preliminary action

3Object-generated harmful factors

If trenches are etched shallower to avoid over-etching, then semiconductor layer protection is improved, but trench depth uniformity deteriorates

Engineering Contradiction:

Improvesemiconductor layer protectionVSAvoidtrench depth uniformity

Core Design Contradiction:

Object-generated harmful factorsVSManufacturing precision

Solution Approach 1:

The protective layer acts as a uniform intermediary that provides a consistent stopping point for the etching process across the entire substrate. This ensures that all trenches reach the same depth with high uniformity while preventing any penetration into the semiconductor layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical control of trench depth through precise etching parameters is replaced by a chemical/physical barrier (the protective layer). This substitution provides more reliable and uniform depth control, as the protective layer thickness can be precisely controlled during deposition.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables the production of trenches with precise depth control, preventing over-etching and reducing electrical resistance, facilitating effective filling with dielectric material and ensuring uniformity in trench depth for both shallow and deep isolation trenches.

Implementation Method 1

localised doping of a given portion of said insulating layer through an opening in a masking layer resting on the fine semiconductor layer

Methodology Applied

Scientific EffectDoping: Dopants

Implementation Method 2

selective removal of said given doped area at the bottom of said opening. This selective removal is effected by selective etching of said doped area vis-à-vis the given dielectric material of said insulating layer

Methodology Applied

Scientific EffectSelective etching:

Implementation Method 3

Prior to step a), a step of anisotropic etching of a thickness of the insulating layer through at least one opening in a masking layer resting on the fine semiconductor layer can be performed

Methodology Applied

Scientific EffectAnisotropic etching:

Data Source

PatentUS8735259B2Method of producing insulation trenches in a semiconductor on insulator substrate

Publication Date: 2014.05.27 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

A method for producing one or plural trenches in a device comprising a substrate of the semiconductor on insulator type formed by a semiconductive support layer, an insulating layer resting on the support layer and a semiconductive layer resting on said insulating layer, the method comprising steps of: a) localised doping of a given portion of said insulating layer through an opening in a masking layer resting on the fine semiconductive layer, b) selective removal of said given doped area at the bottom of said opening.