GaN Layer Thickness Control via Metal Stop Marker
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Solution Overview
Problem
The manufacturing of semiconductor devices with nitride semiconductor layers, such as GaN, faces challenges in achieving high-precision thickness due to the high polishing rate on the −c plane during Chemical Mechanical Processing (CMP), making it difficult to reliably stop the polishing process and resulting in potential stress concentration and surface cracks.
Innovation Solution
The method involves forming a GaN layer with a +c face on a substrate, creating trenches, burying them with a metal layer, and then polishing the −c face until the metal layer is exposed, which significantly reduces the polishing rate, allowing for precise control and stopping of the CMP process, ensuring the GaN layer achieves the desired thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CMP is performed on the −c face of the GaN layer, then a higher polishing rate is obtained, but it becomes difficult to reliably stop the CMP in a predetermined position, resulting in poor thickness precision
Solution Approach 1:
A metal layer is formed in advance at a predetermined position within the GaN layer before polishing. This metal layer serves as a pre-positioned stop marker that indicates when the polishing process should be terminated, allowing the high polishing rate to be maintained while ensuring precise thickness control.
Solution Approach 2:
The metal layer acts as an intermediary element between the polishing process and the GaN layer thickness control. By polishing until the metal layer is exposed, the metal layer mediates the stopping point of the polishing process, providing a reliable and precise termination signal that resolves the contradiction between high polishing rate and thickness precision.
2Productivity
If the nitride semiconductor layer is separated from the base-material substrate by laser beam application, then separation is achieved efficiently, but stress concentration and surface cracks occur in the joined part
Solution Approach 1:
The damaged layer caused by laser separation is extracted and removed through CMP processing. By removing this problematic surface layer that contains stress concentrations and cracks, the reliability of the separated nitride semiconductor layer is improved while maintaining the efficiency of laser-based separation.
Solution Approach 2:
The surface condition of the nitride semiconductor layer is changed by removing the damaged surface layer through CMP. This parameter change (from damaged surface to polished surface) eliminates stress concentration and crack formation, improving reliability without affecting the separation efficiency.
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 efficient and precise fabrication of GaN layers with high-precision thickness, reducing the risk of stress concentration and surface cracks, and improving the manufacturing process for semiconductor devices like light emitting diodes.
Implementation Method 1
the nitride semiconductor layer and the base-material substrate are separated by applying a laser beam having predetermined strength to the interface between the nitride semiconductor layer and the base-material substrate to locally heat and sublimate the laser beam applied part
Implementation Method 2
when CMP is performed, a higher polishing rate is obtained on a −c plane than on a +c plane
Data Source
AI summary
A method of manufacturing a semiconductor device including a nitride semiconductor layer having high-precision thickness is provided. The method includes steps of: forming a gallium nitride (GaN) layer whose main face is a +c face on a substrate; forming a trench by selectively etching down a partial region in the +c face of the GaN layer; forming a metal layer so as to bury the trench; and separating the substrate and the GaN layer, after that, polishing a −c face of the GaN layer until the metal layer is exposed, and removing a part in a thickness direction of the GaN layer.