A method to reduce the parasitic capacitance of millimeter-wave algan/gan HEMT gate

Abstract

A method for reducing the parasitic capacitance of a millimeter-wave AlGaN / GaN HEMT gate. The main structure of the microwave millimeter-wave chip includes a SiC substrate, an epitaxial channel, a barrier layer, a source-drain electrode and a T-type gate. The T-type gate structure Prepared by one-step electron beam forming, the method for reducing the parasitic capacitance of a millimeter-wave AlGaN / GaN HEMT gate includes the following steps: stripping off the gate metal, passivating the gate structure, and the passivated dense dielectric has the property of resisting the corrosion of BOE solution; growing Capacitive medium; photolithography process is used to expose the gate and the capacitor structure is protected by glue; use BOE solution to corrode the capacitive medium, control the time to remove the capacitive medium on both sides of the gate and retain the passivation medium. Different dielectrics are used as passivation and capacitor dielectrics to selectively remove parasitic capacitances on both sides of the gate. This method uses high-density high-temperature SiN dielectrics for gate passivation, and uses low-density low-temperature SiN dielectrics as capacitors. The difference in BOE corrosion rate between gate passivation and capacitor removal removes the capacitor dielectric on both sides of the gate to reduce the gate parasitic capacitance.

Description

technical field [0001] The invention relates to a gate preparation process, in particular to a method for reducing parasitic capacitance of a millimeter-wave AlGaN / GaN HEMT gate. Background technique [0002] The three generations of semiconductors have broad application prospects in the high frequency field of microwave and millimeter wave chips. Millimeter-wave GaN HEMT devices have the advantages of high operating voltage, output power above watt level, high power density and operating frequency up to 100GHz. A major process bottleneck that restricts the development of high-frequency devices is the parasitic problem associated with small-size gates. At present, the gate process of GaN millimeter-wave HEMT devices is generally based on "T" gate or "Y" gate based on electron beam direct writing. However, the bare gate process is commonly used in the gate process for preparing a "T"-shaped gate or a "Y"-shaped gate. The so-called bare gate process means that no medium is ...

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Problems solved by technology

Therefore, the direct use of the bare gate process is not suitable for the preparation of GaN HEMT devices

In addition, the bare gate process itself has certain shortcomings: the bare gate structure has no dielectric assistance during the gate forming process, the stripping is easy to reverse the gate, and the stability of the subsequent process is not high

For the stacked gate process, its disadvantages are: 1. Two steam gate process plus three photolithography or electron beam direct writing process plus one etching process, the steps are complicated and the process cost increases; 2. Photolithography or electron beam It is difficult to ensure overlay in the step of direct writing dielectric etching, especially for small-sized gates; 3. The thickness of the passivation dielectric in the stacked gate process will increase the corresponding parasitic capacitance.

[0004] In summary, a single "T" gate or "Y" gate process is insufficient for millimeter-wave GaN HEMT devices at high frequencies.

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