Multilayered Nitride Semiconductor Wafer Buffer Structure
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Solution Overview
Problem
Nitride semiconductor layers on silicon or sapphire substrates face significant strain and crystal quality degradation due to lattice mismatch, leading to cracks and hardening, which complicates device design and increases film thickness requirements, exacerbating crack issues.
Innovation Solution
A semiconductor wafer structure featuring alternately laminated nondoped first and second nitride semiconductor layers with a larger lattice constant, and a nondoped third nitride semiconductor layer, providing conductivity in the film-thickness direction, which acts as a buffer layer to reduce crystal defects and enhance film thickness without cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impurity doping is used to generate conducting carriers in the nitride semiconductor layer, then conductivity is improved, but crystal quality degrades and cracks become more likely due to crystal hardening
Solution Approach 1:
A multilayered buffer structure consisting of alternating nondoped first nitride semiconductor layers and nondoped second nitride semiconductor layers with different lattice constants is introduced as an intermediary between the silicon substrate and the nitride semiconductor layer. This buffer structure mediates the lattice mismatch and strain, enabling the formation of high-quality thick nitride semiconductor layers without impurity doping-induced crystal hardening and cracking.
Solution Approach 2:
The invention changes the lattice constant parameter by using second nitride semiconductor layers with larger lattice constants than the first nitride semiconductor layers. This parameter variation in the buffer structure allows for strain management and enables the growth of thick nondoped nitride semiconductor layers with maintained crystal quality and inherent conductivity.
2Manufacturing precision
If the film thickness of the nitride semiconductor layer is increased to improve element characteristics, then crystal quality is improved, but the film thickness of the buffer layer must also be increased, making cracks more serious
Solution Approach 1:
The buffer layer is segmented into a multilayered structure with alternating first and second nitride semiconductor layers having different lattice constants. This segmentation allows the buffer to accommodate strain through the lattice constant difference between layers, enabling the support of thick nitride semiconductor functional layers (500 nm to several micrometers) without crack formation, thereby improving crystal quality while maintaining structural integrity.
3Reliability
If a thick buffer layer is used to support thick nitride semiconductor functional layers, then element characteristics are improved, but crack formation becomes more serious
Solution Approach 1:
The buffer layer is constructed as a composite multilayered structure combining first nitride semiconductor layers and second nitride semiconductor layers with different lattice constants. This composite structure provides both the thickness needed to support thick nitride semiconductor functional layers and the strain management capability to prevent crack formation, thereby improving element characteristics while maintaining crack resistance.
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 structure inhibits crystal quality degradation and crack formation, enabling the production of high-quality, thick nitride semiconductor layers with reduced dislocation density and improved conductivity, facilitating the manufacture of reliable semiconductor devices like light-emitting diodes and high electron mobility transistors.
Implementation Method 1
the lattice constants of such semiconductor substrates and that of a nitride semiconductor layer are greatly different from each other, and coefficients of thermal expansion thereof also differ from each other. Therefore, a large strain is generated in a nitride semiconductor layer formed by epitaxial growth on a sapphire substrate or a silicon substrate
Implementation Method 2
nondoped first nitride semiconductor layers and nondoped second nitride semiconductor layers with a larger lattice constant than the first nitride semiconductor layer are laminated alternately, and a nondoped third nitride semiconductor layer which is located on the multilayered film and has a larger lattice constant than the first nitride semiconductor layer, wherein the semiconductor wafer has conductivity in a film-thickness direction
Data Source
AI summary
A semiconductor wafer includes a multilayered film having a structure in which nondoped first nitride semiconductor layers and nondoped second nitride semiconductor layers with a larger lattice constant than the first nitride semiconductor layer are laminated alternately, and a nondoped third nitride semiconductor layer which is located on the multilayered film and has a larger lattice constant than the first nitride semiconductor layer, wherein the semiconductor wafer has conductivity in a film-thickness direction.