GaN Device Spalling via Stressor Layer
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Solution Overview
Problem
Current methods for manufacturing gallium nitride (GaN) devices are limited by the high cost and complexity of processing brittle substrates, and there is a need for efficient methods to produce novel thin layers of semiconductor materials for device manufacture.
Innovation Solution
The method involves forming a GaN substrate with metal contacts and an insulating GaN layer, applying a stressor layer to induce spalling, separating the GaN layer, bonding it to a thermally conductive substrate, and creating vertical channels to define device structures, which allows for the production of GaN devices with improved electrical isolation and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If controlled spalling technology is used to remove surface layers from GaN substrates, then manufacturing cost is reduced and process simplicity is improved, but substrate breakage and processing-induced defects increase
Solution Approach 1:
A stressor layer is applied to the GaN substrate surface before the spalling process to pre-induce tensile stress. This preliminary action controls where and how the substrate will fracture, enabling precise removal of the active layer while minimizing uncontrolled breakage and defects in the remaining substrate.
Solution Approach 2:
A handle substrate is introduced as an intermediary element during the spalling process. This handle substrate provides mechanical support and control during layer separation, allowing the active GaN layer to be cleanly detached from the base substrate while maintaining integrity of both the detached layer and the remaining substrate.
2Productivity
If thin layers of GaN are separated through spalling, then material cost is reduced and device manufacturing efficiency is improved, but electrical isolation between device structures becomes more difficult to achieve
Solution Approach 1:
The insulating GaN layer is formed with spatially varying properties - it has different thickness and insulation characteristics in different regions. The layer provides enhanced electrical isolation in areas where device structures are adjacent, while maintaining appropriate conductivity where contacts are needed, thus achieving both high productivity and precise electrical isolation.
3Manufacturing precision
If vertical channels are formed through the insulating GaN layer, then device structure definition is improved and electrical isolation is enhanced, but processing complexity and potential defects increase
Solution Approach 1:
The insulating GaN layer is formed on the substrate surface before the vertical channels are etched. This preliminary formation of the insulating layer simplifies the subsequent channel formation process by providing a pre-defined insulation barrier, reducing the need for complex multi-step processing to achieve both isolation and structure definition.
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 cost-effective manufacture of GaN devices with enhanced electrical isolation and thermal conductivity, suitable for high-power and high-frequency applications, while minimizing substrate breakage and processing-induced defects.
Implementation Method 1
The tensile stressor layer has a combined thickness and stress that is sufficient to induce spalling mode fracture in the base substrate
Implementation Method 2
bonding the first surface of the stressor layer to a thermally conductive substrate
Data Source
AI summary
A method of making a GaN device includes: forming a GaN substrate; forming a plurality of spaced-apart first metal contacts directly on the GaN substrate; forming a layer of insulating GaN on the exposed portions of the upper surface; forming a stressor layer on the contacts and the layer of insulating GaN; forming a handle substrate on the first surface of the stressor layer; spalling the GaN substrate that is located beneath the stressor layer to separate a layer of GaN and removing the handle substrate; bonding the stressor layer to a thermally conductive substrate; forming a plurality of vertical channels through the GaN to define a plurality of device structures; removing the exposed portions of the layer of insulating GaN to electrically isolate the device structures; forming an ohmic contact layer on the second surface; and forming second metal contacts on the ohmic contact layer.