Asymmetric Mandrel Structures for Precise Slanted Trench Angles

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Solution Overview

Problem

Current methods for fabricating slanted trench features in semiconductor substrates, such as those used in augmented reality devices, face limitations in angle control and depth achievement due to redeposition issues and low etch selectivity, restricting the formation of mandrel structures with varied angles and orientations.

Innovation Solution

A semiconductor structure and method for forming mandrel structures with asymmetric profiles, allowing controlled inclination angles, using a combination of epitaxial layers with graded compositions and angled ion implantation to create mandrel structures suitable for nanoimprint lithography and optical waveguides.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If reactive ion beam etching (RIBE) is used to produce slanted trenches, then slanted features can be formed, but only at a single angle and single direction

Engineering Contradiction:

Improveangle varietyVSAvoidfabrication process

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The fabrication process is segmented into multiple sequential steps: forming initial vertical mandrels, depositing spacer material, selectively removing mandrels, and repeating the process. This segmentation enables creation of mandrels with different inclination angles (first plurality with first angle, second plurality with second angle) that would be impossible to achieve in a single etching step

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Vertical mandrel structures are formed preliminarily before the final slanted features are created. These preliminary vertical mandrels serve as templates that guide subsequent spacer deposition, which ultimately forms the slanted mandrels with desired inclination angles

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If conventional etching techniques are used, then fabrication can proceed with standard processes, but redeposition issues and low etch selectivity prevent precise angle control

Engineering Contradiction:

Improveangle controlVSAvoidfabrication difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

A spacer material layer is introduced as an intermediary between the vertical mandrels and the final slanted structure. This spacer material (different from both the mandrel and substrate materials) enables precise angle control during deposition and can be selectively removed, solving the redeposition and selectivity issues of conventional etching

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes material parameters by using three distinct materials with different properties: mandrel material, spacer material, and substrate material. This material differentiation enables selective etching and deposition processes that achieve precise angle control without the redeposition problems of conventional techniques

Inventive Principle:

Principle #35Parameter changes

3Reliability

If slanted gratings are fabricated for high efficiency light coupling, then optical performance is improved, but fabrication requires high etch selectivity between SiO2 and metal mask

Engineering Contradiction:

Improveoptical efficiencyVSAvoidetch selectivity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The structure uses composite material layers including dielectric layers, metallic layers, and spacer materials with distinct properties. This composite approach enables high optical efficiency for light coupling while maintaining manufacturability through selective processing of each material layer

Inventive Principle:

Principle #40Composite materials

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

Enables the formation of mandrel structures with precise and varied angles, facilitating efficient mass production of complex micro- and nano-scale structures for augmented reality displays and optical sensors, overcoming redeposition and selectivity challenges.

Implementation Method 1

using a combination of epitaxial layers with graded compositions

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 2

angled ion implantation to create mandrel structures suitable for nanoimprint lithography

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentUS12558835B1Fabrication of asymmetric mandrel structures in semiconductor device

Publication Date: 2026.02.24 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A semiconductor structure includes a first plurality of mandrel structures extending outwardly from a substrate. Each of the first plurality of mandrel structures includes a first side at a first inclination angle with respect to a surface plane of the substrate and a second side at a second inclination angle with respect to the surface plane of the substrate. A second plurality of mandrel structures extend outwardly from the substrate. Each of the second plurality of mandrel structures include a third side at a third inclination angle with respect to the surface plane of the substrate and a fourth side at a fourth inclination angle with respect to the surface plane of the substrate. A template structure for an imprint mask is formed by the first plurality of mandrel structures and the second plurality of mandrel structures.