GaN Wafer Separation Using Etchable Layers Instead of Grinding
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Solution Overview
Problem
Conventional wafer thinning processes for semiconductor manufacturing, such as grinding, introduce mechanical stress and scratches, which can lead to stress-induced defects in gallium nitride (GaN) materials.
Innovation Solution
A wafer-scale method involving a GaN wafer with a GaN material layer, a non-crystalline substrate, and etchable intermediate layers, where trenches are formed, tether material layers are deposited, and the intermediate layers are etched to release the GaN material layer without physical grinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wafer thinning is performed using conventional grinding processes, then the desired amount of material is removed to produce ultra-thin wafers, but mechanical stress and scratches are introduced causing stress-induced defects in the material
Solution Approach 1:
The patent extracts and removes the harmful intermediate layers (nucleation layer, buffer layer, etchable layer) from the wafer structure through selective etching processes. This extraction eliminates the need for mechanical grinding of the GaN layer, thereby preventing stress-induced defects and scratches while achieving the desired thin wafer structure
Solution Approach 2:
The patent replaces the mechanical grinding system with a chemical etching system. Instead of using abrasive mechanical forces to remove material, the invention uses chemical etchants to selectively remove intermediate layers, thereby achieving wafer thinning without introducing mechanical stress or scratches that cause defects
2Reliability
If intermediate layers are removed via etching, then the GaN material layer is exposed without mechanical stress, but selective etching processes and etchable intermediate layers must be introduced
Solution Approach 1:
The patent applies preliminary action by forming etchable intermediate layers (such as aluminum nitride buffer layers or silicon oxide etchable layers) during the initial wafer growth process. These layers are specifically designed to be removable by chemical etching, enabling subsequent stress-free exposure of the GaN material layer without requiring complex post-growth modifications
Solution Approach 2:
The patent introduces intermediary etchable layers (aluminum nitride buffer layers, silicon oxide layers) that serve as mediators between the GaN material and the substrate. These intermediary layers can be selectively removed through chemical etching, allowing the GaN layer to be exposed and transferred without mechanical stress while maintaining a relatively simple overall process
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 the production of GaN device dies with an ultra-smooth surface and high thermal conductivity, avoiding the damage and stress associated with traditional wafer thinning processes, and eliminating the thermal boundary resistance from a GaN/SiC interface.
Implementation Method 1
removing the at least one etchable intermediate layer to expose a second side of the GaN material layer
Data Source
AI summary
A wafer-scale method of making gallium nitride (GaN) device die is provided. In embodiments, the method includes: providing a GaN wafer including a GaN material layer, a non-crystalline substrate, and at least one etchable intermediate layer between the GaN material layer and the non-crystalline substrate; forming trenches through the GaN material layer and at least partially through the at least one etchable intermediate layer; forming one or more tether material layers on a first side of the GaN material layer and through portions of the trenches, thereby forming a set of tethers between the GaN material layer and the non-crystalline substrate; and removing the at least one etchable intermediate layer to expose a second side of the GaN material layer. In implementations, the resulting exposed second side of the GaN material layer has a surface roughness of less than 1 nanometers (nm) Root Mean Square (RMS).