Mesa Structure Passivation via Conformal Cladding and Anisotropic Etching

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Solution Overview

Problem

Existing methods for passivating the side faces of mesa structures in optoelectronic semiconductor components require significant adjustments and result in yield reductions due to the need for precise etching masks and tolerances, especially when dealing with inclined side faces.

Innovation Solution

A method involving a conformal coating of a semiconductor layer sequence with a cladding, followed by anisotropic etching to create a flank coating that encloses the mesa structure without an additional etching mask, allowing for selective passivation of side faces with a tolerance of up to 200% of the mean thickness, ensuring complete coverage while avoiding radiation exit surfaces and trenches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional passivation methods with etching masks are used, then precise coverage can be achieved, but device complexity and adjustment outlay increase significantly

Engineering Contradiction:

Improvepassivation coverage precisionVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent removes the etching mask step from the conventional passivation process. By applying cladding material conformally to cover all free surfaces and then using anisotropic etching to selectively remove cladding from horizontal surfaces, the method achieves precise side face passivation without requiring etching masks, thereby reducing process complexity while maintaining precision

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using an etching mask to define where passivation should occur, the patent inverts the approach by applying cladding everywhere and then selectively removing it from areas where passivation is not desired (horizontal surfaces). This reverse methodology simplifies the process by eliminating mask preparation and alignment steps

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If conformal coating with anisotropic etching is used, then adjustment outlay is reduced, but manufacturing precision must be maintained within 200% tolerance

Engineering Contradiction:

Improveadjustment outlayVSAvoidflank coating tolerance

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the etching parameters to achieve anisotropic etching behavior, where the etching rate differs significantly between vertical and horizontal surfaces. By controlling the etching chemistry and process conditions, the method achieves selective removal of cladding from horizontal surfaces while preserving it on vertical side faces, maintaining precision within the specified 200% tolerance range

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If additional etching masks are used for anisotropic etching, then manufacturing precision improves, but productivity decreases due to additional process steps

Engineering Contradiction:

Improveside face coverage accuracyVSAvoidproduction yield

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent extracts the etching mask step from the process entirely. By relying on the self-aligned nature of conformal coating and the directional selectivity of anisotropic etching, the method achieves accurate side face coverage without the need for additional masks, thereby improving productivity and production yield by reducing the number of process steps

Inventive Principle:

Principle #2Taking out (Extraction)

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 enables efficient and precise passivation of side faces without adjustment tolerances, allowing for the production of high-yield optoelectronic semiconductor components, including LEDs, with the flank coating completely enclosing the mesa structure and protecting the active zone, even on inclined surfaces.

Implementation Method 1

applying at least a portion of a cladding to the semiconductor layer sequence with the mesa structure by a conformal coating method such that all free surfaces are covered by the cladding

Methodology Applied

Scientific EffectConformal coating: Deposition (physical)

Implementation Method 2

anisotropically etching the cladding such that a flank coating is created from the cladding, which coating is limited with a tolerance of at most 200% of a mean thickness of the flank coating to the side faces of the mesa structure

Methodology Applied

Scientific EffectAnisotropic etching:

Data Source

PatentUS10158042B2Method of producing optoelectronic semiconductor components and optoelectronic semiconductor component

Publication Date: 2018.12.18 OSRAM OLED

AI summary

A method of producing optoelectronic semiconductor components includes A) providing a semiconductor layer sequence on a carrier top of a carrier, B) patterning the semiconductor layer sequence such that at least one mesa structure is formed with side faces, C) applying at least a portion of a cladding to the semiconductor layer sequence with the mesa structure by a conformal coating method such that all free surfaces are covered by the cladding), and D) anisotropically etching the cladding such that a flank coating is created from the cladding, which coating is limited with a tolerance of at most 200% of a mean thickness of the flank coating to the side faces of the mesa structure and completely encloses the mesa structure, wherein step D) takes place without an additional etching mask for the anisotropic etching.