GaN Wafer Polishing via Photoelectrochemical Oxidation
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Solution Overview
Problem
Conventional polishing methods, such as photoelectrochemical etching and chemical mechanical polishing, are inefficient in processing and flattening Ga element-containing compound semiconductor substrates like GaN, as they lack sufficient flattening capability and are prone to surface damage, especially in achieving high surface accuracy and processing rate.
Innovation Solution
A polishing method involving a neutral pH buffer solution with Ga ions, where the substrate is irradiated with light or subjected to a bias potential to form Ga oxide, which is then selectively removed using a polishing tool, allowing for precise removal of raised portions while inhibiting dissolution in recessed areas, thereby shortening processing time and improving surface flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polishing methods (photoelectrochemical etching or CMP) are used on GaN substrates, then surface processing can be performed, but the processing rate is insufficient and surface flatness cannot be achieved
Solution Approach 1:
The patent changes the chemical environment parameters by using a neutral pH buffer solution containing Ga ions instead of conventional acidic or basic solutions. This parameter change enables simultaneous achievement of high processing rate and surface flatness by controlling the dissolution behavior of Ga oxide through the specific chemical composition and pH conditions of the buffer solution
Solution Approach 2:
The patent employs a composite processing approach combining photoelectrochemical oxidation (to form Ga oxide) with chemical dissolution (in the neutral pH buffer solution). This composite method integrates two different mechanisms - oxidation for selective formation and chemical dissolution for controlled removal - to achieve both high productivity and manufacturing precision
2Productivity
If CMP is used to increase processing rate, then mechanical removal is faster, but lattice defects are generated and surface damage occurs
Solution Approach 1:
The patent replaces the mechanical action of CMP with a photoelectrochemical method. Instead of using abrasive mechanical removal, the invention uses light irradiation to induce photoelectrochemical oxidation followed by chemical dissolution, thereby eliminating mechanical surface damage while maintaining efficient processing rates
3Object-affected harmful factors
If photoelectrochemical etching is used to avoid surface damage, then lattice defects are minimized, but the method lacks flattening capability and processing rate is low
Solution Approach 1:
The patent applies preliminary photoelectrochemical oxidation to form Ga oxide on the substrate surface before dissolution. This preliminary action creates a reactive oxide layer that dissolves rapidly in the neutral pH buffer solution, thereby increasing the overall processing rate while maintaining the gentle, non-mechanical nature of the process that avoids surface damage
4Productivity
If Ga oxide is formed on the substrate surface through light irradiation or bias potential, then chemical processing rate increases, but excessive Ga oxide growth occurs and surface flatness deteriorates
Solution Approach 1:
The patent uses the neutral pH buffer solution containing Ga ions as a feedback-controlled environment. The buffer solution maintains stable pH conditions and provides Ga ions that suppress excessive oxide growth by establishing an equilibrium, thereby automatically regulating the dissolution rate to match oxide formation rate and maintain surface flatness while preserving high processing 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 method enables efficient and accurate polishing of Ga element-containing compound semiconductor substrates, significantly reducing processing time while maintaining high surface accuracy and preventing excessive Ga oxide growth, thus enhancing the flatness and quality of the substrate surface.
Implementation Method 1
irradiating a surface of the substrate with light or applying a bias potential to the substrate, or applying a bias potential to the substrate while irradiating the surface of the substrate with light, thereby forming Ga oxide on the surface of the substrate
Implementation Method 2
simultaneously moving the substrate and the polishing tool relative to each other to polish and remove the Ga oxide formed on the surface of the substrate
Data Source
AI summary
A polishing method can process and flatten, in a practical processing time and with high surface accuracy, a surface of a substrate of a Ga element-containing compound semiconductor. The polishing method includes: bringing a Ga element-containing compound semiconductor substrate (16) into contact with a polishing tool (10) in the presence of a processing solution (14) comprising a neutral pH buffer solution containing Ga ions; irradiating a surface of the substrate with light or applying a bias potential to the substrate, or applying a bias potential to the substrate while irradiating the surface of the substrate with light, thereby forming Ga oxide (16a) on the surface of the substrate; and simultaneously moving the substrate and the polishing tool relative to each other to polish and remove the Ga oxide formed on the surface of the substrate.