阅读说明：本技术 一种氮化镓基功率器件的新型制备方法 (Novel preparation method of gallium nitride-based power device ) 是由 郝惠莲 于 2020-11-19 设计创作，主要内容包括：本发明属于半导体的技术领域,公开了一种氮化镓基功率器件的新型制备方法,在衬底上生长氮化镓外延层,然后,在所述氮化镓外延层上依次生长第一氮化镓铝外延层、第二氮化镓铝外延层,再利用刻蚀停止工艺对第一氮化镓铝外延层进行刻蚀形成表面平整的栅极凹槽,刻蚀停止在第二氮化镓铝外延层上,最后,制备漏电极、源电极和栅电极,完成器件制备。本发明的制备方法优化的外延生长方案,同时搭配刻蚀停止技术,既能加快刻蚀过程,又能保证刻蚀深度均匀、一致,从而使整个晶圆上的器件得到均匀的阈值电压分布,对凹槽法的产业化应用提供了更好的选择。(The invention belongs to the technical field of semiconductors, and discloses a novel preparation method of a gallium nitride-based power device. The epitaxial growth scheme optimized by the preparation method is matched with the etching stopping technology, so that the etching process can be accelerated, and the uniform and consistent etching depth can be ensured, so that devices on the whole wafer can obtain uniform threshold voltage distribution, and a better choice is provided for the industrial application of the groove method.)

1. A novel preparation method of a gallium nitride-based power device is characterized by comprising the following steps: growing a gallium nitride epitaxial layer on a substrate, then sequentially growing a first gallium nitride aluminum epitaxial layer and a second gallium nitride aluminum epitaxial layer on the gallium nitride epitaxial layer, etching the first gallium nitride aluminum epitaxial layer by utilizing an etching stopping process to form a grid groove with a smooth surface, stopping etching on the second gallium nitride aluminum epitaxial layer, and finally preparing a drain electrode, a source electrode and a grid electrode to finish the preparation of the device.

2. The novel method of fabricating a gallium nitride-based power device according to claim 1, wherein: the aluminum component content of the first gallium nitride aluminum epitaxial layer is smaller than that of the second gallium nitride aluminum epitaxial layer, the etching stopping process is set to be a dry etching process which uses gas combination gas of chlorine, oxygen and argon as etching gas to etch the first gallium nitride aluminum epitaxial layer to form a grid groove, and the etching is stopped on the second gallium nitride aluminum epitaxial layer.

3. The novel method of fabricating a gallium nitride-based power device according to claim 2, characterized in that: the aluminum component content of the second gallium aluminum nitride epitaxial layer is more than 20%, and the thickness of the second gallium aluminum nitride epitaxial layer is set to be 1-30 nm; the aluminum component content of the first gallium aluminum nitride epitaxial layer is less than 20%, and the thickness of the first gallium aluminum nitride epitaxial layer is set to be 1-100 nm.

4. The novel method of fabricating a gallium nitride-based power device according to claim 1, wherein: and covering a gate dielectric layer on the gate groove, and then preparing a gate electrode.

5. The novel preparation method of the gallium nitride-based power device according to claim 1, characterized by comprising the steps of:

the method comprises the following steps that firstly, a gallium nitride epitaxial layer, a first gallium nitride aluminum epitaxial layer and a second gallium nitride aluminum epitaxial layer are epitaxially grown on a substrate in sequence, photoetching is carried out, and then edge parts of the first gallium nitride aluminum epitaxial layer and the second gallium nitride aluminum epitaxial layer are etched to the gallium nitride epitaxial layer;

etching the first gallium aluminum nitride epitaxial layer by using an etching stopping process to form a grid groove with a smooth surface, and stopping etching on the second gallium aluminum nitride epitaxial layer;

step three, preparing a source electrode, a drain electrode and a gate electrode;

and step four, depositing a passivation layer, then carrying out photoetching, and etching to remove the passivation layer on the source electrode, the drain electrode and the gate electrode to finish the preparation of the device.

6. The novel preparation method of the gallium nitride-based power device according to claim 5, characterized in that: and etching the first gallium nitride aluminum epitaxial layer by adopting a dry etching process taking gas combination gas of chlorine, oxygen and argon as etching gas to form a gate groove, and stopping etching on the second gallium nitride aluminum epitaxial layer.

7. The novel preparation method of the gallium nitride-based power device according to claim 5, characterized in that: the substrate is made of Si, sapphire or SiC materials.

8. The novel preparation method of the gallium nitride-based power device according to claim 5, characterized in that: the source electrode, the drain electrode and the gate electrode are all made by evaporation of electron beam evaporation equipment, the source electrode and the drain electrode are ohmic contact electrodes and are made of Ti/Al/Ti/Au or Ti/Al/Ni/Au metal materials, and the gate electrode is a Schottky contact electrode and is made of Ni/Au or Ni/Pt/Au metal materials.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a novel preparation method of a gallium nitride-based power device.

Background

Compared with a silicon Si material, the third-generation semiconductor material gallium nitride GaN has larger forbidden bandwidth and higher breakdown field strength, and is an outstanding representative of the third-generation semiconductor material. Different from the traditional Si-based semiconductor device, the AlGaN/GaN High Electron Mobility Transistor (HEMT) based on the GaN material can obtain high electron concentration, high electron mobility and high saturated electron drift velocity at a heterojunction interface by utilizing the polarization effect in a GaN heterojunction, thereby realizing the conduction of the device. These excellent electrical characteristics determine that AlGaN/GaN HEMT devices have great industrial potential in the power semiconductor field of high frequency, high voltage, and high power density.

Because the AlGaN/GaN heterojunction structure has a naturally conducted two-dimensional electron gas channel, the conventional AlGaN/GaN HEMT has a depletion-type switching characteristic, and from an application perspective, only the enhancement-type HEMT can be widely accepted by the conventional power electronics industry. The existing groove gate etching technology mainly adopts dry etching and wet oxidation etching, and aims to etch a part of an AlGaN barrier layer positioned in a gate region in a gallium nitride GaN heterojunction structure, so that the concentration of two-dimensional electron gas at the position is low enough, the concentration of the two-dimensional electron gas is small enough to be ignored under the condition of not applying gate voltage, and the device is in a turn-off state. The conductive channel can be restored after positive gate voltage is applied, and the conduction of the device is realized, namely the characteristic of the enhanced device is realized. The dry etching scheme generally adopts ICP or RIE to etch the AlGaN layer below the grid so as to form a groove, the etching speed of the method is high, but the problem of discrete threshold voltage distribution of devices on the whole wafer due to the fact that the etching depth of the whole wafer is not uniform exists; the wet oxidation etching is to oxidize the surface of the AlGaN layer below the grid and then remove the oxide layer by using acid or alkaline solution to form a groove.

Disclosure of Invention

The invention aims to overcome the defect that the threshold voltage distribution of a device on the whole wafer is easy to be discrete due to uneven etching depth of a grid electrode groove in the prior art, and provides a novel preparation method of a gallium nitride-based power device.

In order to achieve the purpose, the invention provides the following technical scheme:

a novel preparation method of a gallium nitride-based power device comprises the steps of growing a gallium nitride epitaxial layer on a substrate, sequentially growing a first gallium nitride aluminum epitaxial layer and a second gallium nitride aluminum epitaxial layer on the gallium nitride epitaxial layer, etching the first gallium nitride aluminum epitaxial layer by utilizing an etching stopping process to form a grid groove with a smooth surface, stopping etching on the second gallium nitride aluminum epitaxial layer, and finally preparing a drain electrode, a source electrode and a grid electrode to finish the preparation of the device.

Further, the aluminum component content of the first aluminum gallium nitride epitaxial layer is less than that of the second aluminum gallium nitride epitaxial layer, the etching stopping process is set to be a dry etching process which uses a gas combination gas of chlorine, oxygen and argon as an etching gas to etch the first aluminum gallium nitride epitaxial layer to form a gate groove, and the etching is stopped on the second aluminum gallium nitride epitaxial layer.

Further, the aluminum component content of the second gallium aluminum nitride epitaxial layer is more than 20%, and the thickness of the second gallium aluminum nitride epitaxial layer is set to be 1-30 nm; the aluminum component content of the first gallium aluminum nitride epitaxial layer is less than 20%, and the thickness of the first gallium aluminum nitride epitaxial layer is set to be 1-100 nm.

Further, after a gate dielectric layer is covered on the gate groove, a gate electrode is prepared.

Further, the method comprises the following steps:

the method comprises the following steps that firstly, a gallium nitride epitaxial layer, a first gallium nitride aluminum epitaxial layer and a second gallium nitride aluminum epitaxial layer are epitaxially grown on a substrate in sequence, photoetching is carried out, and then edge parts of the first gallium nitride aluminum epitaxial layer and the second gallium nitride aluminum epitaxial layer are etched to the gallium nitride epitaxial layer;

etching the first gallium aluminum nitride epitaxial layer by using an etching stopping process to form a grid groove, and stopping etching on the second gallium aluminum nitride epitaxial layer;

step three, preparing a source electrode, a drain electrode and a gate electrode;

and step four, depositing a passivation layer, then carrying out photoetching, and etching to remove the passivation layer on the source electrode, the drain electrode and the gate electrode to finish the preparation of the device.

And further, etching the first gallium aluminum nitride epitaxial layer by adopting a dry etching process taking a gas combination gas of chlorine, oxygen and argon as an etching gas to form a grid groove with a smooth surface, and stopping etching on the second gallium aluminum nitride epitaxial layer.

Further, the substrate is made of Si, sapphire or SiC materials.

Further, the source electrode, the drain electrode and the gate electrode are all made of electron beam evaporation equipment through evaporation, the source electrode and the drain electrode are arranged to be ohmic contact electrodes and are made of Ti/Al/Ti/Au or Ti/Al/Ni/Au metal materials, the gate electrode is arranged to be a Schottky contact electrode and is made of Ni/Au or Ni/Pt/Au metal materials.

The beneficial technical effects of the invention are as follows:

two gallium aluminum nitride epitaxial layers grow on a substrate firstly, preparation is made for a subsequent etching stopping process, then a grid groove with a smooth surface is formed on a second gallium aluminum nitride epitaxial layer by etching by using the etching stopping process, the etching depth is ensured to be uniform and consistent, uniform threshold voltage distribution is obtained, the uniform threshold voltage distribution of devices on the whole wafer is ensured, and a better choice is provided for the industrial application of a groove method. The preparation method disclosed by the invention is simple to operate, low in cost, high in efficiency, strong in adaptability and extremely wide in application prospect.

Drawings

FIG. 1 is a schematic overall flow diagram of the present invention;

FIG. 2 is a schematic diagram showing the preparation method of the present invention.

Detailed Description

The following detailed description of the preferred embodiments will be made with reference to the accompanying drawings.

The invention combines the advantages and disadvantages of dry etching and wet etching, and provides a novel preparation method of a gallium nitride-based power device, as shown in figure 1, a gallium nitride epitaxial layer grows on a substrate, then a first gallium nitride aluminum epitaxial layer and a second gallium nitride aluminum epitaxial layer sequentially grow on the gallium nitride epitaxial layer, then the first gallium nitride aluminum epitaxial layer is etched by using an etching stopping process to form a grid groove with a smooth surface, the etching is stopped on the second gallium nitride aluminum epitaxial layer, and finally, a drain electrode, a source electrode and a grid electrode are prepared, and the preparation of the device is completed. Thus, two gallium aluminum nitride epitaxial layers are grown on the substrate by optimizing the epitaxial growth method, preparation is made for a subsequent etching stop process, and then a grid groove with a smooth surface is formed on the second gallium aluminum nitride epitaxial layer by etching by using the etching stop process, so that the etching depth is ensured to be uniform and consistent, uniform threshold voltage distribution is obtained, uniform threshold voltage distribution of devices on the whole wafer is ensured, a better choice is provided for industrial application of a groove method, and the method has a great application prospect.

In order to improve the etching efficiency and the convenience of process execution, the dry etching is used as a basis, the etching speed is accelerated by the dry etching, but plasma bombardment exists, so that the surface is rough, interface state defects are introduced, and the electrical performance of a device is damaged. For example, the aluminum component content of the first aluminum gallium nitride epitaxial layer is set to be less than that of the second aluminum gallium nitride epitaxial layer, and chlorine Cl is selected₂Oxygen O₂And argon Ar as etching gas to etch the first aluminum gallium nitride epitaxial layer, and when etching to the surface of the second aluminum gallium nitride epitaxial layer, Al is formed on the surface of the second aluminum gallium nitride epitaxial layer with high aluminum composition due to high aluminum composition₂O₃And AlGaO, prevents the plasma from continuing to etch downwards, therefore, the etching can be stopped on the surface of the second gallium aluminum nitride epitaxial layer with high aluminum component, thus the depth of the grooves of the devices on the whole wafer can be consistent, the threshold voltage distribution of the devices on the whole wafer is ensured to be uniform, and the groove preparation only adopts dry etching, so that the speed is high, and the method is suitable for industrial production.

Referring to fig. 2, the novel preparation method of the gallium nitride-based power device of the invention comprises the following steps:

the method comprises the following steps of firstly, epitaxially growing a gallium nitride layer, a first gallium aluminum nitride epitaxial layer and a second gallium aluminum nitride epitaxial layer on a substrate in sequence, carrying out epitaxial growth by using MOCVD equipment, carrying out photoetching, and etching the edge parts of the first gallium aluminum nitride epitaxial layer and the second gallium aluminum nitride epitaxial layer to the gallium nitride layer by using ICP equipment so as to block two-dimensional electron gas; the substrate may be made of Si, sapphire or SiC material.

Etching the first gallium aluminum nitride epitaxial layer by using an etching stopping process to form a grid groove with a smooth surface, and stopping etching on the second gallium aluminum nitride epitaxial layer;

specifically, by adjusting the dry etching process, an etching stop technique can be realized, that is, the first aluminum gallium nitride epitaxial layer is etched off and stopped on the surface of the second aluminum gallium nitride epitaxial layer. The aluminum component content of the second gallium nitride aluminum epitaxial layer can be set to be higher than 20%, and the thickness of the second gallium nitride aluminum epitaxial layer is set to be 1-30 nm; the first GaN-Al epitaxial layer has low Al content (less than 20%) and thickness of 1-100nm, and is prepared with chlorine Cl₂Oxygen O₂And the combined gas of argon and Ar is etching gas to etch the first gallium aluminum nitride epitaxial layer with low aluminum composition, and when the surface of the second gallium aluminum nitride epitaxial layer with high aluminum composition is etched, because the aluminum composition is high, a metal oxide Al can be formed on the surface of the second gallium aluminum nitride epitaxial layer with high aluminum composition₂O₃And AlGaO, which prevents the plasma from continuing to etch downwards, therefore, the etching can be stopped on the surface of the second gallium aluminum nitride epitaxial layer with high aluminum composition, thus the depth of the grooves of the devices on the whole wafer can be consistent, and the threshold voltage distribution of the devices on the whole wafer can be ensured to be uniform. And because the groove preparation adopts dry etching, the speed is high, and the method is suitable for industrial production.

And step three, preparing a source electrode, a drain electrode and a gate electrode.

And photoetching is carried out, the first gallium aluminum nitride epitaxial layer and the second gallium aluminum nitride epitaxial layer in the source region and the drain region are etched to remove the source region and the drain region, then a source electrode and a drain electrode are prepared in the source region and the drain region, both of which are ohmic contact electrodes, the source electrode and the drain electrode can be evaporated by utilizing electron beam evaporation equipment, and the source electrode and the drain electrode are both composed of multilayer metals, such as Ti/Al/Ti/Au, Ti/Al/Ni/Au and the like.

Then, photolithography is performed again, and a gate electrode is deposited by an electron beam evaporation apparatus in the gate recess region, and the gate electrode is a schottky contact electrode and is also provided with a multilayer metal, which may be a combination of metals such as Ni/Au or Ni/Pt/Au. Of course, the gate electrode can also be prepared after the groove structure is covered with a gate dielectric layer.

And fourthly, depositing a passivation layer on the surface of the device by utilizing a PECVD process, etching the passivation layer on the surfaces of the source electrode, the drain electrode and the gate electrode, and only leaving the passivation layer in the region among the electrodes to finish the preparation of the device.

The above description is only a preferred embodiment of the present invention, and the embodiment is not intended to limit the scope of the present invention, so that all equivalent structural changes made by using the contents of the specification and the drawings of the present invention should be included in the scope of the appended claims.