Ge Photodetector Barrier Layer for Lower Dark Current

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Solution Overview

Problem

Conventional photodetector sensors with germanium (Ge) detection regions over a semiconductor substrate face limitations in device resolution and complexity due to the need for multiple Ge layers, which can lead to increased dark current sensitivity and device size, and the diffusion of halogen species from etchant gases into the Ge material.

Innovation Solution

A method involving the formation of recesses in the semiconductor substrate using a first halogen series etchant, followed by a second etchant to create a barrier layer, allowing for epitaxial growth of Ge detection regions directly in the substrate, thereby reducing halogen diffusion and enhancing device resolution and complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If multiple Ge layers are integrated into the device to improve device resolution, then device resolution is improved, but device size and complexity increase

Engineering Contradiction:

Improvedevice resolutionVSAvoiddevice complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges multiple Ge detection regions into a single integrated structure formed within a recess of the semiconductor substrate. Instead of stacking multiple separate Ge layers, the invention combines their functionality into one unified Ge detection region that achieves high resolution while reducing device complexity and size.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent transitions from a vertical stacking approach (multiple layers in the z-dimension) to a lateral integration approach (single region with extended area in the x-y plane). The Ge detection region is formed within a recess that extends laterally, achieving high resolution through increased detection area rather than through multiple stacked layers.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If multiple Ge layers are used to improve device resolution, then device resolution is improved, but device size increases

Engineering Contradiction:

Improvedevice resolutionVSAvoiddevice size

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If a first halogen series etchant is used to form recesses, then recesses are formed in the semiconductor substrate, but halogen species diffuse into the Ge material causing contamination

Engineering Contradiction:

Improverecess formationVSAvoidhalogen contamination

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary barrier layer composed of a second halogen series between the first halogen series etchant and the Ge detection region. This barrier layer acts as a protective intermediary that prevents direct diffusion of the first halogen species into the Ge material, thereby eliminating contamination while maintaining the ability to form recesses effectively.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies preliminary anti-action by forming a barrier layer of a second halogen series before the Ge detection region is exposed to the first halogen series etchant. This pre-established barrier prevents the harmful diffusion of first halogen species into the Ge material, counteracting the potential contamination before it can occur.

Inventive Principle:

Principle #9Preliminary anti-action

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 reduces dark current sensitivity and improves device resolution and complexity by forming Ge detection regions with minimal halogen contamination, resulting in more efficient and accurate photodetector sensors.

Implementation Method 1

performing a first etching process to form a recess in an exposed portion of the semiconductor substrate, using a first etchant comprising a first halogen species

Methodology Applied

Scientific EffectChemical etching:

Implementation Method 2

performing a second etching process using a second etchant comprising a second halogen species, such that the second halogen species forms a barrier layer in the semiconductor substrate, surrounding the recess

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 3

growing a detection region in the recess using an epitaxial growth process

Methodology Applied

Scientific EffectEpitaxial growth: Epitaxy

Data Source

PatentUS12191328B2Photodetector with reduced dark current sensitivity and methods of forming the same

Publication Date: 2025.01.07 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of forming a semiconductor device includes: forming a patterned hard mask layer on a semiconductor substrate; performing a first etching process to form a recess in an exposed portion of the semiconductor substrate, using a first etchant that includes a first halogen species; performing a second etching process using a second etchant that includes a second halogen species, such that the second halogen species forms a barrier layer in the semiconductor substrate, surrounding the recess; and growing a detection region in the recess using an epitaxial growth process. The barrier layer is configured to reduce diffusion of the first halogen species into the detection region.