Nitride Crystal Substrate Carrier Concentration Uniformity
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Solution Overview
Problem
Conventional methods for manufacturing nitride crystal substrates result in non-uniform carrier concentration and mobility distributions, leading to variations in device properties among semiconductor devices, due to issues like crystal warpage, dislocation density, and unintentional impurity incorporation, which affect the accuracy of carrier concentration measurements using reflection-type Fourier Transform Infrared Spectroscopy (FTIR).
Innovation Solution
A nitride crystal substrate with a main surface formed of group-III nitride crystal, where the carrier concentration and mobility are controlled to satisfy specific ratios (0.5≤NIR/NElec≤1.5 and 0.6≤μIR/μElec≤1.4) using feedback-controlled impurity addition during crystal growth, measured by optical and electrical methods, to achieve uniform distribution and improved crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to manufacture nitride crystal substrates, then manufacturing process is simple, but carrier concentration and mobility distribution becomes non-uniform
Solution Approach 1:
The patent implements feedback control by measuring the carrier concentration on the crystal growth surface during growth and adjusting the impurity addition amount accordingly. This closed-loop control system ensures uniform carrier concentration distribution while maintaining a manageable manufacturing process through real-time monitoring and adjustment.
Solution Approach 2:
The patent changes the growth parameters dynamically during crystal growth, specifically adjusting the impurity addition rate based on measured carrier concentration values. By modifying these parameters in real-time, the system achieves uniform carrier concentration distribution without requiring fundamentally complex manufacturing equipment.
2Manufacturing precision
If impurity addition is increased to control carrier concentration, then carrier concentration uniformity improves, but unintentional impurity incorporation increases
Solution Approach 1:
The feedback control mechanism measures the actual carrier concentration on the growth surface and adjusts impurity addition precisely to achieve the target concentration. This prevents both under-doping and over-doping, thereby reducing unintentional impurity incorporation while maintaining accurate carrier concentration control.
Solution Approach 2:
The system uses the crystal growth surface itself as the measurement location, obtaining carrier concentration data directly from where it is needed. This self-service approach ensures that impurity addition is controlled based on actual local conditions, minimizing unnecessary impurity incorporation.
3Productivity
If crystal growth rate is increased to improve productivity, then manufacturing efficiency improves, but carrier concentration uniformity deteriorates
Solution Approach 1:
The feedback control system continuously monitors carrier concentration during growth and adjusts impurity addition rate accordingly. This allows the system to maintain uniform carrier concentration distribution even at higher growth rates, decoupling productivity improvements from precision deterioration.
Solution Approach 2:
The patent makes the impurity addition process dynamic by continuously adjusting the addition rate based on real-time measurements. This dynamic control enables the system to adapt to changing growth conditions, maintaining uniform carrier concentration distribution regardless of the overall growth rate.
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 solution ensures approximately uniform carrier concentration and mobility across the substrate, enhancing the accuracy of FTIR measurements and reducing device property variations among semiconductor devices, while minimizing crystal strain and impurity-related issues.
Implementation Method 1
a carrier concentration NIR at a center of the main surface to a carrier concentration NElec... NIR is the carrier concentration on the main surface side of the nitride crystal substrate obtained based on a reflectance of the main surface measured by a reflection type Fourier transform infrared spectroscopy
Implementation Method 2
measured by a reflection type Fourier transform infrared spectroscopy
Implementation Method 3
NElec is the carrier concentration in the nitride crystal substrate obtained based on a specific resistance of the nitride crystal substrate and a mobility of the nitride crystal substrate measured by an eddy current method
Data Source
AI summary
There is provided a nitride crystal substrate having a main surface and formed of group-III nitride crystal, wherein NIR/NElec, satisfies formula (1) below, which is a ratio of a carrier concentration NIR at a center of the main surface relative to a carrier concentration NElec: 0.5≤NIR/NElec≤1.5 . . . (1) where NIR is the carrier concentration on the main surface side of the nitride crystal substrate obtained based on a reflectance of the main surface measured by a reflection type Fourier transform infrared spectroscopy, and NElec is the carrier concentration in the nitride crystal substrate obtained based on a specific resistance of the nitride crystal substrate and a mobility of the nitride crystal substrate measured by an eddy current method.