GaN HEMT Gate Structure for Interface Stress Relief
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Solution Overview
Problem
High electron mobility transistors (HEMTs) using GaN-based semiconductor materials face challenges in achieving uniformity and reliability due to lattice mismatch and stress at heterojunction interfaces, leading to poor electrical performance.
Innovation Solution
A semiconductor device structure comprising a substrate, buffer layer, channel layer, barrier layer, and gate structure with specific protection patterns and spacers is developed, including a gate layer, gate electrode layer, first protection pattern layer, and second protection spacers, to alleviate stress and improve interface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If GaN-based semiconductor materials are used to form HEMTs, then high-frequency and high-temperature operating performance is improved, but lattice mismatch and stress at heterojunction interfaces cause poor uniformity and reliability
Solution Approach 1:
The patent introduces an etch stop layer between the AlGaN barrier layer and the GaN channel layer, segmenting the heterojunction structure into distinct regions. This segmentation allows independent optimization of each layer's thickness and composition, reducing the cumulative effect of lattice mismatch and stress while maintaining the beneficial high-temperature performance of GaN-based materials.
Solution Approach 2:
The etch stop layer acts as an intermediary layer between the AlGaN barrier layer and the GaN channel layer. This intermediate layer buffers the lattice mismatch and stress between the two adjacent layers, preventing defect propagation and improving interface quality, thereby enhancing device reliability without compromising the high-temperature operating performance.
2Ease of manufacture
If conventional gate structure formation processes are used, then manufacturing simplicity is maintained, but interface defects and stress lead to poor electrical performance
Solution Approach 1:
The etch stop layer is formed preliminarily before the gate structure fabrication process. This preliminary action establishes a stable interface foundation that prevents stress-induced defects during subsequent gate patterning and metallization steps, ensuring high interface uniformity without adding significant process complexity.
Solution Approach 2:
The etch stop layer provides local quality improvement at the critical heterojunction interface between the barrier layer and channel layer. By targeting only this specific interface region with enhanced structural stability, the patent improves interface uniformity and electrical performance without requiring modification of the entire device structure or process flow.
3Speed
If multiple material layers with different energy gaps are stacked to form HEMT, then high electron mobility is achieved, but stress and defects at interfaces degrade electrical performance
Solution Approach 1:
The etch stop layer serves as an intermediary between the AlGaN barrier layer and the GaN channel layer, mediating the stress and lattice mismatch between these two materials with different energy gaps. This intermediary structure allows the formation of high electron mobility 2DEG at the interface while preventing stress-induced defects from degrading the interface quality.
Solution Approach 2:
The patent employs a composite material structure consisting of AlGaN barrier layer, etch stop layer, and GaN channel layer. This composite structure combines materials with different energy gaps and physical properties to achieve high electron mobility while managing stress and defects through the carefully designed multi-layer configuration.
Data Source
AI summary
A semiconductor device and a method for forming the same are provided. The semiconductor device includes a substrate, a buffer layer on the substrate, a channel layer on the buffer layer, a barrier layer on the channel layer and a gate structure on the barrier layer. The gate structure includes a gate layer, a gate electrode layer, a first protection pattern layer and second protection spacers. The gate electrode layer covers the gate layer. The first protection pattern layer covers a first top surface of the gate electrode layer. The second protection spacers cover first side surfaces of the gate electrode layer, second side surfaces of the first protection pattern layer and a portion of the gate layer. First interfaces between the second protection spacers and the gate layer are coplanar with a second interface, which is between the gate electrode layer and the gate layer.