GaN HEMT Threshold Voltage Control via Multi-Depth Recesses
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Solution Overview
Problem
Existing semiconductor devices face challenges in precisely controlling the threshold voltage without affecting the breakdown voltage, particularly in high-electron mobility transistors, and require additional implantation processes.
Innovation Solution
The semiconductor device features an upper recess and a lower recess in an aluminum gallium nitride layer, where the gallium nitride layer is filled, creating a step-shaped bottom surface with varying thicknesses, allowing for precise control of the threshold voltage without additional implantation processes, by forming a first gallium nitride layer on a semiconductor substrate, an aluminum gallium nitride layer, and a gate structure on the gallium nitride layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional implantation processes are used to control threshold voltage, then threshold voltage control precision is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies local quality by creating recesses with different depths (first recess and second recess) in the aluminum gallium nitride layer, where the second recess extends deeper than the first recess. This localized structural variation allows different regions to provide different electrical characteristics, enabling precise threshold voltage control through the step-shaped gallium nitride layer configuration without requiring additional implantation processes.
Solution Approach 2:
The patent transitions from controlling threshold voltage through material composition or doping (traditional approaches) to controlling it through structural dimensionality - specifically by creating multi-level recesses at different depths in the aluminum gallium nitride layer. This dimensional approach (first recess at one depth, second recess at greater depth) provides a new degree of freedom for threshold voltage control that simplifies the manufacturing process.
2Ease of manufacture
If threshold voltage is controlled by traditional methods, then manufacturing process is simpler, but breakdown voltage is adversely affected
Solution Approach 1:
The patent uses local quality by implementing selectively positioned and depth-controlled recesses in the aluminum gallium nitride layer. The first recess and second recess (extending deeper) are strategically located to modulate the electric field distribution locally, enabling threshold voltage control without compromising the overall breakdown voltage characteristics of the device structure.
Solution Approach 2:
The patent changes the geometric parameters of the aluminum gallium nitride layer by creating recesses with controlled depths and widths. By adjusting the depth of the second recess relative to the first recess, and controlling the fill characteristics of the gallium nitride layer, the threshold voltage can be precisely tuned while maintaining adequate breakdown voltage through proper parameter selection.
3Ease of manufacture
If single-depth recesses are used in aluminum gallium nitride layer, then manufacturing is simpler, but threshold voltage control precision is insufficient
Solution Approach 1:
The patent applies segmentation by dividing the single recess structure into multiple recesses at different depths - specifically a first recess and a second recess that extends deeper into the aluminum gallium nitride layer. This segmented approach creates a step-shaped configuration of the gallium nitride layer, providing multiple zones for electric field modulation and enabling finer control over threshold voltage while remaining manufacturable through sequential etching processes.
Solution Approach 2:
The patent introduces depth dimensionality by creating recesses at two distinct depth levels within the aluminum gallium nitride layer. The first recess sits at one depth level while the second recess extends to a greater depth, creating a vertically stratified structure. This multi-level depth configuration provides additional control parameters for threshold voltage adjustment without significantly complicating the manufacturing process.
Data Source
AI summary
A semiconductor device includes a first gallium nitride layer disposed on a semiconductor substrate, and an aluminum gallium nitride layer disposed on the first gallium nitride layer. The semiconductor device also includes an upper recess and a lower recess disposed in the aluminum gallium nitride layer, wherein the upper recess adjoins the lower recess, and the upper recess has a width that is greater than that of the lower recess. The semiconductor device further includes a second gallium nitride layer disposed in the first recess and the second recess, and a gate structure disposed on the second gallium nitride layer. In addition, the semiconductor device includes a source electrode and a drain electrode disposed on the aluminum gallium nitride layer.