Compound Semiconductor Polishing via Electrochemical Etching
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Solution Overview
Problem
Current methods for planarizing the surface of compound semiconductor substrates, particularly those containing Ga, are inefficient in achieving high surface accuracy within a practical time frame, and existing polishing tools tend to scratch the substrate due to burrs and surface irregularities, requiring frequent and costly catalyst replacements.
Innovation Solution
A polishing method involving a polishing pad with an electrically conductive member, used in conjunction with weak acid water or electrolytic ion water, where the substrate and pad are moved relative to each other, and light or voltage is applied to enhance polishing efficiency, allowing for real-time damage level monitoring using photocurrent, photoluminescence, or Raman light-type systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical mechanical polishing (CMP) is used to planarize the surface of compound semiconductor substrates, then surface flatness is improved, but polishing time becomes excessively long and surface damage occurs
Solution Approach 1:
The invention changes the chemical environment parameters by using specific aqueous solutions (hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, or their mixtures) and controls pH, temperature, and concentration parameters to achieve optimal polishing rates. This allows faster material removal while maintaining surface quality, resolving the time-flatness contradiction
Solution Approach 2:
The invention replaces traditional mechanical CMP with a chemical etching-based polishing method. By using chemical reactions to remove material instead of mechanical abrasion, the process achieves planarization without the excessive time requirements and surface damage associated with mechanical polishing
2Productivity
If traditional polishing tools with catalysts are used, then polishing efficiency is improved, but surface irregularities and burrs scratch the substrate requiring frequent catalyst replacement
Solution Approach 1:
The invention extracts and removes the problematic catalyst component from the polishing tool. By eliminating the catalyst that generates surface irregularities and burrs, the method prevents substrate scratching while maintaining polishing efficiency through chemical etching in aqueous solutions
Solution Approach 2:
Instead of using expensive catalysts that require frequent replacement due to degradation and surface damage, the invention employs disposable aqueous chemical solutions that can be easily replaced. This eliminates the reliability issues associated with catalyst degradation while maintaining cost-effectiveness
3Productivity
If catalysts are attached to polishing tool surfaces to enhance polishing, then polishing rate increases, but catalyst cost and replacement frequency increase
Solution Approach 1:
The invention replaces expensive, long-lived catalysts with inexpensive, easily replaceable aqueous chemical solutions. The solutions (hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, or their mixtures) are cheap and can be disposed of or replenished without significant cost, eliminating the economic burden of catalyst replacement
Solution Approach 2:
The invention substitutes mechanical catalyst-based polishing with chemical etching using aqueous solutions. This eliminates the need for expensive catalyst materials while achieving enhanced polishing rates through controlled chemical reactions
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 high-accuracy surface flattening of compound semiconductor substrates within a shorter time, reduces scratching, and allows for cost-effective and durable polishing by replacing only the catalyst pad, while preventing surface irregularities from being transferred to the substrate.
Implementation Method 1
polishing a surface of a substrate made of a compound semiconductor containing either one of Ga, Al, and In by relatively moving the surface of the substrate and a surface of a polishing pad having an electrically conductive member in an area of the surface which is held in contact with the substrate, while holding the surface of the substrate and the surface of the polishing pad in contact with each other, in the presence of weak acid water, water with air dissolved therein, or electrolytic ion water
Implementation Method 2
The surface of the substrate (workpiece) is irradiated with light, preferably ultraviolet light, or a voltage is applied between the substrate and the solid catalyst, to promote oxidization of the surface for an increasing machining rate
Implementation Method 3
measuring a damage level of the surface of the substrate with at least one of damage level measuring systems including a photocurrent-type damage level measuring system for measuring a damage level of the surface of the substrate by measuring the value of a current flowing through a conductive line connecting the substrate and a metal wire on the polishing tool when excitation light is applied to the surface of the substrate
Implementation Method 4
a photoluminescence-light-type damage level measuring system for measuring a damage level of the surface of the substrate by measuring photoluminescence light emitted from the surface of the substrate when excitation light is applied to the surface of the substrate
Implementation Method 5
a Raman-light-type damage level measuring system for measuring a damage level of the surface of the substrate by measuring Raman light included in reflected light from the surface of the substrate when visible monochromatic light is applied to the surface of the substrate
Data Source
AI summary
A polishing method and a polishing apparatus finish a surface of a substrate of a compound semiconductor containing an element such as Ga or the like to a desired level of flatness, so that the surface can be flattened with high surface accuracy within a practical processing time. In the presence of water, such as weak acid water, water with air dissolved therein, or electrolytic ion water, the surface of the substrate made of a compound semiconductor containing either one of Ga, Al, and In and a surface of a polishing pad having an electrically conductive member in an area of the surface which is held in contact with the substrate) are relatively moved while being held in contact with each other, thereby polishing the surface of the substrate.