GaN Substrate Surface Waviness Control for Uniform Large Devices
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Solution Overview
Problem
As Group-III element nitride semiconductor substrates increase in size, device characteristics degrade, and variations in device characteristics between devices on the same substrate increase, leading to unsatisfactory performance in high-frequency/high-power electronic devices.
Innovation Solution
A Group-III element nitride semiconductor substrate with a first surface having a maximum height Wz of the surface waviness profile of 150 nm or less, a root mean square height Wq of 25 nm or less, and an average length WSm of surface waviness profile elements of 0.5 mm or more, achieved through mirror processing and surface roughening treatments, ensuring reduced surface roughness and waviness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the substrate size is increased to accommodate larger devices for high-frequency and high-power applications, then the device power handling capability is improved, but the device characteristics degrade and variations in device characteristics increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling surface roughness parameters (Ra≤5nm, Rms≤2nm, Rz≤10nm) and substrate curvature radius (R≥10m) to maintain device characteristic consistency on large-diameter substrates. This resolves the contradiction by optimizing surface quality parameters to compensate for the challenges of larger substrate sizes.
2Manufacturing precision
If the surface roughness is reduced to achieve satisfactory crystallinity and device performance, then the epitaxial growth quality is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by performing surface roughening treatment on the substrate before epitaxial growth to pre-establish the required surface quality (Ra≤5nm, Rms≤2nm, Rz≤10nm). This preliminary surface preparation ensures satisfactory epitaxial growth quality while managing manufacturing complexity through systematic pre-processing.
Solution Approach 2:
The patent controls specific surface roughness parameters (Ra, Rms, Rz) within defined ranges to achieve satisfactory crystallinity. By specifying quantitative parameter ranges, the patent transforms the complex surface quality requirement into measurable and controllable parameters, resolving the contradiction between manufacturing precision and device complexity.
3Length of moving object
If the substrate diameter is increased from 2 inches to 4 inches or more, then the device size is increased for high-power applications, but the total thickness variation and surface flatness deteriorate
Solution Approach 1:
The patent applies parameter changes by specifying a minimum substrate curvature radius (R≥10m) and controlling total thickness variation (TTV≤10μm) on large-diameter substrates. These quantitative parameter specifications enable the substrate to maintain adequate flatness and thickness uniformity even when the diameter is increased to 4 inches or more, resolving the contradiction between substrate size and manufacturing precision.
Data Source
AI summary
There is provided a Group-III element nitride semiconductor substrate including a first surface and a second surface, in which even when devices to be produced on the first surface are increased in size, variations in device characteristics between the devices in the same substrate are suppressed. A Group-III element nitride semiconductor substrate includes a first surface and a second surface. The Group-III element nitride semiconductor substrate satisfies at least one of the following items (1) to (3): (1) The main surface has a maximum height Wz of a surface waviness profile of 150 nm or less; (2) The main surface has a root mean square height Wq of the surface waviness profile of 25 nm or less; (3) The main surface has an average length WSm of surface waviness profile elements of 0.5 mm or more.