Compound Semiconductor Substrate Surface Treatment and Inspection
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Solution Overview
Problem
Existing methods for inspecting and treating compound semiconductor substrates fail to effectively reduce surface impurities and surface roughness at the atomic level, leading to increased costs and contamination issues.
Innovation Solution
An inspection method using an atomic force microscope (AFM) with a pitch of not more than 0.4 nm to measure surface roughness Rms, combined with a surface treatment process involving acid and alkaline solutions, and reducing agents to reduce surface impurities and roughness, thereby minimizing the need for heating processes and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical inspection methods are used to measure surface roughness, then measurement can be performed over large areas, but the measurement precision is insufficient to detect atomic-level unevenness
Solution Approach 1:
The patent divides the measurement task into two levels: optical inspection for large-area screening and AFM for localized atomic-level measurement. The AFM measures a small representative area (e.g., 10μm x 10μm) with atomic-level precision, while optical methods cover the entire wafer surface. This segmentation allows both large area coverage and high precision to be achieved without requiring the entire surface to be measured at atomic resolution.
Solution Approach 2:
The patent replaces optical measurement (electromagnetic field-based) with mechanical probe measurement (AFM) for the critical atomic-level surface roughness assessment. The AFM's mechanical tip can resolve atomic-level height variations that optical methods cannot detect, providing the necessary measurement precision for evaluating substrate quality for epitaxial growth.
2Ease of manufacture
If conventional washing methods are used to reduce surface impurities, then the process is simple, but oxygen and other impurities remain adsorbed on the surface
Solution Approach 1:
The patent changes the chemical parameters of the washing solution by using acid solutions (such as dilute hydrochloric acid, dilute sulfuric acid, or dilute nitric acid) instead of conventional neutral or basic cleaners. The acid treatment chemically reacts with and removes adsorbed oxygen and other impurities from the semiconductor substrate surface, achieving superior surface cleanliness while maintaining operational simplicity.
Solution Approach 2:
The patent employs acid solutions that act as strong oxidizing agents to chemically remove adsorbed impurities from the substrate surface. The acid treatment oxidizes and eliminates oxygen molecules and other contaminants that conventional washing methods cannot effectively remove, thereby improving surface cleanliness and reducing impurity adsorption.
3Object-affected harmful factors
If LB films and polymer films are used to protect wafer surfaces, then surface protection is provided, but surface-active agents and particles contaminate the surface
Solution Approach 1:
The patent extracts and eliminates the need for LB films and polymer films by implementing acid washing treatment that provides surface protection without introducing contamination. The acid-treated surface forms a protective layer through chemical modification rather than physical film deposition, thereby avoiding the introduction of surface-active agents and particles that would otherwise be present from film-based protection methods.
Solution Approach 2:
The patent uses acid solution as an intermediary treatment that chemically modifies the substrate surface to create a protected state without requiring physical film layers. The acid treatment creates a chemically stable surface that resists impurity adsorption, serving as a mediator between the substrate and the environment without introducing the contamination problems associated with LB and polymer films.
4Manufacturing precision
If deionized water at low temperature is used to reduce haze level, then surface quality improves, but the equipment complexity and cost increase
Solution Approach 1:
The patent changes the chemical parameter (pH and composition) of the washing solution by using acid solutions instead of relying on temperature control of deionized water. This chemical approach achieves haze reduction and surface quality improvement without requiring complex temperature control equipment, thereby maintaining manufacturing precision while reducing device complexity and cost.
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
The method reliably detects surface unevenness at the atomic level, reduces impurity adhesion, and lowers surface roughness to below 0.2 nm, resulting in higher-quality crystal growth and reduced production costs.
Implementation Method 1
surface roughness Rms is measured using an atomic force microscope at a pitch of not more than 0.4 nm
Implementation Method 2
washing the substrate with an acid solution including at least one of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid
Implementation Method 3
washing the substrate with an acid-mixed alkaline solution of at least 8.0 in pH, having acid ions added
Implementation Method 4
polishing or washing the compound semiconductor substrate using a reducing agent immediately after the polishing step
Data Source
AI summary
There are provided an inspection method of a compound semiconductor substrate that can have the amount of impurities at the surface of the compound semiconductor substrate reduced, a compound semiconductor substrate, a surface treatment method of a compound semiconductor substrate, and a method of producing a compound semiconductor crystal. In the inspection method of the surface of the compound semiconductor substrate, the surface roughness Rms of the compound semiconductor substrate is measured using an atomic force microscope at the pitch of not more than 0.4 nm in a scope of not more than 0.2 μm square. The surface roughness Rms of the compound semiconductor substrate measured by the inspection method is not more than 0.2 nm.