HEMT Recess Depth Control via AlN Etch Stop Layer
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Solution Overview
Problem
Existing high electron mobility transistors (HEMTs) face challenges in accurately controlling their characteristics, such as threshold voltage and withstand voltage, due to difficulties in uniformly maintaining the depth of the recess region during the etching process, leading to inconsistent device performance.
Innovation Solution
The implementation of a multilayer channel supply layer structure with an etch stop layer and an upper layer, where the etch stop layer and upper layer have different materials like AlGaN and AlInN, allows for precise control of the recess region depth through selective etching, improving the control over HEMT characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-layer channel supply layer is used, then the manufacturing process is simple, but the control of recess region depth and HEMT characteristics is inaccurate
Solution Approach 1:
The channel supply layer is divided into multiple sub-layers (first channel supply layer, second channel supply layer, third channel supply layer) with different materials and thicknesses. Each sub-layer serves a specific function: the first layer (AlN) provides high etch selectivity, the second layer (AlGaN) controls electron supply, and the third layer (AlInN) adjusts polarization. This segmentation enables precise control of recess depth and HEMT characteristics while maintaining manageable manufacturing complexity.
Solution Approach 2:
The patent employs a composite channel supply layer structure combining different nitride materials (AlN, AlGaN, AlInN) with distinct properties. AlN offers superior etch resistance, AlGaN provides high electron mobility, and AlInN enables polarization control. The composite structure leverages the advantages of each material to achieve accurate HEMT characteristic control that cannot be obtained with a single material.
2Manufacturing precision
If the recess region depth is not uniformly controlled, then the manufacturing process is simpler, but the HEMT characteristics such as threshold voltage and withstand voltage are inconsistent
Solution Approach 1:
The first channel supply layer made of AlN serves as an intermediary etch stop layer between the upper AlInN layer and the underlying channel layer. During etching, this AlN layer provides a distinct etch endpoint that enables precise control of recess depth. The intermediary layer acts as a buffer that simplifies the etching process by providing a clear visual and measurement reference for when to stop etching, ensuring uniform depth across all devices.
Solution Approach 2:
The patent utilizes optical property changes during the etching process to detect when the AlN etch stop layer is reached. The AlN layer has distinct optical characteristics that change when exposed, providing a visual indicator for etch endpoint detection. This allows operators to precisely control recess depth by monitoring optical changes during etching, ensuring consistency without requiring complex real-time measurement systems.
3Reliability
If conventional HEMT structures are used, then the device design is straightforward, but the withstand voltage performance is insufficient
Solution Approach 1:
The patent applies local quality by creating regions with different electron concentrations and material compositions within the channel supply layer. The AlInN layer specifically targets regions requiring enhanced polarization control, while the AlGaN layer focuses on electron mobility enhancement. This localized optimization of material properties in specific regions improves overall withstand voltage performance without requiring complete structural redesign throughout the entire device.
Solution Approach 2:
The patent introduces a vertical dimensionality change by stacking multiple channel supply layers with different materials and thicknesses. This multi-layer vertical structure creates distinct functional zones that control electron transport in the vertical direction, enhancing breakdown voltage and withstand voltage performance. The dimensional approach allows independent optimization of different voltage characteristics without increasing lateral device complexity.
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 approach enables easy and accurate control of HEMT characteristics, enhancing threshold voltage control and withstand voltage performance, leading to improved device reliability and performance.
Implementation Method 1
A high electron mobility transistor (HEMT) may include semiconductors with different electric polarization characteristics. In a HEMT, a semiconductor layer of relatively high polarizability may induce a 2-dimensional electron gas (2DEG) in another semiconductor layer adhered to the semiconductor layer.
Data Source
AI summary
High electron mobility transistors (HEMTs) and methods of manufacturing the same. A HEMT may include a channel layer and a channel supply layer, and the channel supply layer may be a multilayer structure. The channel supply layer may include an etch stop layer and an upper layer on the etch stop layer. A recess region may be in the upper layer. The recess region may be a region recessed to an interface between the upper layer and the etch stop layer. A gate electrode may be on the recess region.