Ferroelectric Recessed HEMT Structure for High Threshold Voltage
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Solution Overview
Problem
Existing III-V compound semiconductor transistors, such as gallium nitride or gallium oxide, are normally-on devices with negative threshold voltages, leading to unnecessary power loss and instability due to extra power consumption and potential abnormal turn-on at high bias voltages, and current methods to increase threshold voltage result in parasitic effects and increased manufacturing costs.
Innovation Solution
A semiconductor device structure is developed with a recessed barrier layer and ferroelectric material layers to trap charges and alter bandgaps, increasing the threshold voltage beyond 6V, using materials like BaTiO3, KH2PO4, HfZrO2, SrBi2Ta2O9, and PbZrTiO3, and employing deposition methods like plasma enhanced atomic layer deposition to form dielectric and ferroelectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods (ion implantation, thinning gallium nitride layer, or using p-type gallium oxide) are used to increase threshold voltage, then the threshold voltage can be increased to above 0V, but the threshold voltage cannot reach more than 6V and additional circuits are required which cause parasitic effects and energy loss
Solution Approach 1:
The patent changes the material parameters by introducing ferroelectric materials (such as Pb(Zr,Ti)O3 or Pb1-xLaxZr1-yTiyO3 with specific composition ratios) into the transistor structure. By controlling the ferroelectric material's polarization state and composition, the threshold voltage is directly tuned to be greater than 6V without requiring additional control circuits, thus resolving the contradiction between reliability and device complexity
Solution Approach 2:
The patent employs composite material structures combining gallium nitride semiconductor layers with ferroelectric material layers. The composite structure leverages the strong polarization effect of ferroelectric materials to achieve high threshold voltage (>6V) while maintaining the high electron mobility characteristics of gallium nitride, eliminating the need for parasitic additional circuits and reducing energy loss
2Reliability
If the threshold voltage is increased to prevent abnormal turn-on, then circuit stability is improved, but manufacturing cost increases due to additional circuits and complex processes
Solution Approach 1:
The patent achieves circuit stability through parameter changes in the material composition and structure. By controlling the ferroelectric material's crystal orientation, thickness, and polarization state, the threshold voltage is optimized to be >6V, providing inherent stability without additional circuits, thus improving ease of manufacture while maintaining reliability
Solution Approach 2:
The patent extracts and eliminates the need for additional threshold voltage control circuits by directly integrating the threshold voltage control function into the transistor's material structure through ferroelectric materials. This extraction of the control function from separate circuits to the device structure itself reduces manufacturing complexity and cost while maintaining circuit stability
3Power
If gallium nitride or gallium oxide is used as semiconductor material, then high electron mobility and high power capability are achieved, but the transistor becomes normally-on with negative threshold voltage causing power loss
Solution Approach 1:
The patent utilizes the phase transition特性 of ferroelectric materials - the ability to switch between positive and negative polarization states. By controlling the polarization direction of the ferroelectric layer, the transistor can switch between on and off states with threshold voltage >6V, enabling normally-off operation that eliminates power loss while preserving the high power capability of gallium nitride materials
Solution Approach 2:
The patent creates a composite structure where ferroelectric material layers are integrated with gallium nitride semiconductor layers. The ferroelectric component provides the normally-off characteristic with high threshold voltage, while the gallium nitride component maintains high electron mobility and power handling capability, thus achieving both high power and low energy loss simultaneously
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
The structure achieves a normally-off high electron mobility transistor with enhanced threshold voltage, reducing power loss and improving circuit stability by maintaining high output current and preventing abnormal turn-on.
Implementation Method 1
forming a first ferroelectric material layer on the charge trapping layer; forming a second dielectric layer on the first ferroelectric material layer; forming a second ferroelectric material layer on the second dielectric layer
Implementation Method 2
forming a charge trapping layer on the first dielectric layer
Implementation Method 3
employing deposition methods like plasma enhanced atomic layer deposition to form dielectric and ferroelectric layers
Data Source
AI summary
A method of manufacturing a semiconductor device includes providing a substrate. A channel layer is formed on the substrate. A barrier layer is formed on the channel layer. A source and a drain are formed on the barrier layer. A recess is formed in the barrier layer, in which the recess has a bottom surface, and a portion of the barrier underneath the recess has a thickness. A first dielectric layer is formed to cover the bottom surface of the recess. A charge trapping layer is formed on the first dielectric layer. A first ferroelectric material layer is formed on the charge trapping layer. A second dielectric layer is formed on the first ferroelectric material layer. A second ferroelectric material layer is formed on the second dielectric layer. A gate is formed over the second ferroelectric material layer.