Nitride Semiconductor Laminate IR Reflection for Homoepitaxial Film Quality
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Solution Overview
Problem
Current methods, such as Fourier transform infrared spectroscopy (FT-IR), face challenges in non-destructively and non-contactly inspecting the physical properties of homoepitaxial films of group III nitride semiconductor crystals, particularly due to high dislocation scattering and lack of infrared absorption coefficient difference at low carrier concentrations.
Innovation Solution
A method involving the growth of a nitride semiconductor laminate with a substrate having a dislocation density of 5×10^6 pieces/cm² or less, low oxygen concentration, and controlled impurity levels, where the film quality is inspected by analyzing deviations in reflected light within specific wavenumber ranges using infrared light, and a calculated reflection spectrum is fitted to an optical model to determine carrier concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FT-IR method is used to inspect homoepitaxial film, then non-contact and non-destructive inspection is achieved, but measurement precision deteriorates due to large dislocation scattering and no absorption coefficient difference
Solution Approach 1:
The invention changes the measurement parameters by selecting specific wavenumber ranges (1,600-1,700 cm⁻¹ and 3,000-3,500 cm⁻¹) where absorption coefficient differences exist between homoepitaxial and substrate regions, enabling detection despite low carrier concentration and dislocation scattering
Solution Approach 2:
The invention introduces an intermediary approach by using reflection spectrum analysis with specific wavenumber selection as a mediator between the infrared light and the homoepitaxial film, allowing indirect detection of film properties through absorption characteristics at selected frequencies
2Reliability
If substrate with low dislocation density is used, then film quality inspection becomes feasible, but manufacturing precision requirements increase
Solution Approach 1:
The invention applies preliminary action by establishing strict substrate quality criteria (dislocation density ≤5×10⁶ cm⁻², oxygen concentration <1×10¹⁷ cm⁻³, impurity concentration <1×10¹⁷ cm⁻³) before epitaxial growth to ensure the substrate is suitable for high-precision inspection
Solution Approach 2:
The invention applies local quality by specifying particular property thresholds for the substrate (dislocation density, oxygen concentration, impurity concentration) that must be controlled to enable successful film quality inspection
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
Enables non-destructive and non-contact inspection of film quality, overcoming the limitations of existing techniques by accurately measuring film thickness and quality even at low carrier concentrations, thereby improving the reliability of semiconductor devices.
Implementation Method 1
detecting a deviation of an amount of reflected light at a predetermined wavenumber determined in a range of 1,600 cm−1 or more and 1,700 cm−1 or less in a reflection spectrum obtained by irradiating the thin film on the substrate with infrared light
Implementation Method 2
there is no difference in an absorption coefficient in an infrared region (IR), especially at low carrier concentration of 1×1017 cm−3 or less
Data Source
AI summary
There is provided a method for producing a nitride semiconductor laminate in which a thin film is homoepitaxially grown on a substrate comprising group III nitride semiconductor crystals, the method including: homoepitaxially growing a thin film on a substrate, using the substrate in which a dislocation density on its main surface is 5×106 pieces/cm2 or less, a concentration of oxygen therein is less than 1×1017 at·cm−3, and a concentration of impurities therein other than n-type impurity is less than 1×1017 at ·cm−3; and inspecting a film quality of the thin film formed on the substrate, wherein in the inspection of the film quality, the film quality of the thin film is inspected by detecting a deviation of an amount of reflected light at a predetermined wavenumber determined in a range of 1,600 cm−1 or more and 1,700 cm−1 or less in a reflection spectrum obtained by irradiating the thin film on the substrate with infrared light, from an amount of reflected light at the predetermined wavenumber determined according to a film thickness of the thin film, a carrier concentration of the substrate, and a carrier concentration of the thin film.