CN113113478B - GaN-based radio frequency power device based on ohmic regrowth and preparation method thereof - Google Patents
GaN-based radio frequency power device based on ohmic regrowth and preparation method thereof Download PDFInfo
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- 238000001312 dry etching Methods 0.000 claims abstract description 24
- 238000002161 passivation Methods 0.000 claims abstract description 18
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- 238000009616 inductively coupled plasma Methods 0.000 claims description 35
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- H01L29/66446—Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET]
- H01L29/66462—Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET] with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
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Abstract
The invention relates to a GaN-based radio frequency power device based on ohmic regrowth and a preparation method thereof, wherein the method comprises the following steps: s1: growing a GaN-based heterojunction on a substrate; s2: etching the ohmic region of the GaN-based heterojunction by adopting a dry etching process to form an ohmic regrowth region for ohmic regrowth; s3: epitaxially growing n on the surface of the device + A GaN layer; s4: using dry etching process to n + The GaN layer is self-terminated etched to remove n between ohmic regrowth regions + A GaN layer; s5: forming isolation regions on both sides of the device by using ion implantation equipment; s6: at n + Depositing metal on the GaN layer to form a source electrode and a drain electrode; s7: forming a passivation layer on the surface of the device; s8: and etching the passivation layer of the gate region by adopting a dry etching process to form a gate groove, and depositing metal in the gate groove to form a gate. The preparation method simplifies the preparation process of ohmic regrowth, and simultaneously continues the advantages of the conventional ohmic regrowth technology.
Description
Technical Field
The invention belongs to the technical field of semiconductor devices, and particularly relates to a GaN-based radio frequency power device based on ohmic regrowth and a preparation method thereof.
Background
The III group nitride semiconductor heterojunction is a preferred material for preparing high-temperature-resistant, radiation-resistant and high-frequency high-power electronic devices by virtue of large forbidden bandwidth, high two-dimensional electron gas density, high electron saturation drift velocity and large critical breakdown electric field, and the electronic devices mainly comprise High Electron Mobility Transistors (HEMTs) and Schottky Barrier Diodes (SBDs) and are respectively applied to radio frequency power amplifiers and power switch modules. Among them, gaN-based high-frequency (microwave, millimeter wave) high-power HEMT devices are generally applied to key fields such as satellites, radars, base stations and the like.
With the improvement of nitride material growth technology and device process level, the radio frequency power characteristics of the GaN-based HEMT device are continuously improved, specifically, the radio frequency power characteristics include higher cut-off frequency and working frequency, higher output power and higher power added efficiency. With the advent of the 5G era and the introduction of 6G, the operating frequency of GaN rf power devices is required to be further increased, and the output power and efficiency at high operating frequency need to be improved at the same time, and reducing the parasitic resistance of the devices is one of the most fundamental solutions. Specific methods include reducing device contact resistance, heterojunction sheet resistance, and device size. For the preparation of the GaN-based HEMT device, the method for reducing the contact resistance comprises the following steps: optimizing a conventional rapid thermal annealing process; upgrading ohmic laminated metal; before ohmic metal evaporation, ge/Si dopant is deposited, and ohmic region n-type doping is formed after annealing; and n-type heavy doping of the ohmic region is realized by an ion implantation technology or an ohmic regrowth technology. In the method, the ohmic regrowth technology can realize the lowest ohmic contact resistance, and simultaneously, the good ohmic appearance can be ensured without annealing or low-temperature annealing, thereby being beneficial to further reducing the source-drain distance of the device.
However, conventional ohmic regrowth techniques rely on SiO 2 Masks, film-depositions thereofAccumulation, film patterning and wet etching make the device preparation process more complicated. In addition, the wet etching has higher requirements on the concentration, the etching temperature and the etching time of BOE etching solution, which directly leads to the increase of the difficulty of the conventional ohmic regrowth technology.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a GaN-based radio frequency power device based on ohmic regrowth and a preparation method thereof. The technical problem to be solved by the invention is realized by the following technical scheme:
the invention provides a preparation method of a GaN-based radio frequency power device based on ohmic regrowth, which comprises the following steps:
s1: growing a GaN-based heterojunction on a substrate;
s2: etching the ohmic region of the GaN-based heterojunction by adopting a dry etching process until the position of at least 20nm below the interface of the GaN-based heterojunction is etched to form an ohmic regrowth region for ohmic regrowth;
s3: epitaxially growing n on the surface of the device + A GaN layer;
s4: applying dry etching process to n + The GaN layer is self-terminated etched to remove n between the ohmic regrowth regions + A GaN layer;
s5: forming isolation regions on both sides of the device by using ion implantation equipment;
s6: at the n + Depositing metal on the GaN layer to form a source electrode and a drain electrode;
s7: forming a passivation layer on the surface of the device;
s8: and etching the passivation layer of the gate region by adopting a dry etching process to form a gate groove, and depositing metal in the gate groove to form a gate.
In one embodiment of the present invention, the S1 includes: sequentially stacking and growing a GaN buffer layer and a barrier layer on the substrate from bottom to top by using MOCVD equipment, wherein,
the GaN buffer layer comprises an Fe or C doped GaN layer and an unintended doped GaN layer which are sequentially stacked from bottom to top;
the barrier layer is one of AlN, scAlN, inAlN or AlGaN, and the Al component of the AlGaN is more than 50%.
In one embodiment of the present invention, the S2 includes:
s21: coating photoresist on the barrier layer, and exposing and developing two sides of the top surface of the device to form an etching area;
s22: etching the etching region by using an ICP (inductively coupled plasma) etching device by using a dry etching process until the etching region is etched to at least 20nm below the interface of the GaN buffer layer and the barrier layer to form an ohmic regrowth region for ohmic regrowth, wherein the etching gas is BCl 3 And Cl 2 And (4) mixing the gases.
In one embodiment of the present invention, in the S3, the n + The doping concentration of the GaN layer is 5 x 10 19 cm -3 -5×10 20 cm -3 。
In one embodiment of the present invention, the S4 includes:
s41: at said n + Coating photoresist on the GaN layer, and exposing and developing between the ohm regrowth areas to form a self-termination etching area;
s42: utilizing ICP etching equipment and adopting dry etching process to etch n of the self-termination etching area + The GaN layer is self-terminated etched to remove n between the ohmic regrowth regions + And a GaN layer.
In one embodiment of the present invention, the self-terminating etch gas is SF 6 And BCl 3 Wherein, SF 6 And BCl 3 The gas flow ratio of (1) 6 The gas flow rate of (b) is 5-15sccm 3 The flow rate is 15-45sccm;
the parameters of the etching process are as follows: the power of an electrode on the ICP is 160-240W, the power of an electrode under the ICP is 24-36W, and the pressure is 2-8mTorr.
In one embodiment of the present invention, the S6 includes: using electron beam evaporation equipment at n + And depositing Ti/Al/Ni/Au ohmic laminated metal on the GaN layer to form a source electrode and a drain electrode.
The invention provides a GaN-based radio frequency power device based on ohmic regrowth, which is prepared by adopting the preparation method of any one of the embodiments, and the GaN-based radio frequency power device comprises:
the substrate layer, the buffer layer and the barrier layer are sequentially stacked from bottom to top;
n + the GaN ohmic region is arranged in the buffer layer and the barrier layer and positioned on two sides of the device;
a source and a drain respectively disposed at the n + A GaN ohmic region;
the grid electrode is arranged on the barrier layer and is positioned between the source electrode and the drain electrode;
and the passivation layer is arranged on the surface of the device between the source electrode and the grid electrode and between the drain electrode and the grid electrode.
In one embodiment of the invention, the buffer layer comprises an Fe or C doped GaN layer and an unintentional doped GaN layer which are sequentially stacked from bottom to top;
the barrier layer is one of AlN, scAlN, inAlN or AlGaN, and the Al component of the AlGaN is more than 50%.
In one embodiment of the invention, said n + The doping concentration of GaN ohmic region is 5 × 10 19 cm -3 -5×10 20 cm -3 。
Compared with the prior art, the invention has the beneficial effects that:
1. the preparation method of the GaN-based radio frequency power device based on ohmic regrowth is based on the self-termination etching technology, can process the device structure with the same essence as the conventional ohmic regrowth technology, and does not depend on SiO compared with the conventional ohmic regrowth technology 2 The mask simplifies the preparation process and simultaneously continues the advantages of the conventional ohmic regrowth technology.
2. The GaN-based radio frequency power device based on ohmic regrowth has low ohmic contact resistance and good ohmic appearance, and the good ohmic appearance is used for further reducing the source-drain size of the device, thereby being beneficial to realizing ultra-low parasitic resistance and improving the radio frequency power characteristic of the device.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following preferred embodiments are described in detail with reference to the accompanying drawings.
Drawings
Fig. 1 is a flowchart of a method for manufacturing a GaN-based rf power device based on ohmic regrowth according to an embodiment of the present invention;
FIGS. 2a to 2j are schematic diagrams of a process for manufacturing a GaN-based RF power device based on ohmic regrowth according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a GaN-based rf power device based on ohmic regrowth according to an embodiment of the present invention.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, a GaN-based rf power device based on ohmic regrowth and a method for fabricating the same according to the present invention will be described in detail with reference to the accompanying drawings and the detailed description.
The foregoing and other technical matters, features and effects of the present invention will be apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying drawings. The technical means and effects of the present invention adopted to achieve the predetermined purpose can be more deeply and specifically understood through the description of the specific embodiments, however, the attached drawings are provided for reference and description only and are not used for limiting the technical scheme of the present invention.
Example one
Referring to fig. 1, fig. 1 is a flowchart of a method for manufacturing a GaN-based rf power device based on ohmic regrowth according to an embodiment of the present invention. As shown in the figure, the method for manufacturing a GaN-based rf power device based on ohmic regrowth of this embodiment includes:
s1: growing a GaN-based heterojunction on a substrate;
specifically, the method comprises the following steps:
and sequentially stacking and growing a GaN buffer layer and a barrier layer on the substrate from bottom to top by using MOCVD equipment. Wherein the content of the first and second substances,
optionally, the substrate is a SiC or Si substrate material.
Optionally, the GaN buffer layer includes an Fe or C doped GaN layer and an unintentionally doped GaN layer stacked in this order from bottom to top.
Optionally, the barrier layer is one of AlN, scAlN, inAlN, or AlGaN, and the Al composition of AlGaN is greater than 50%.
In this embodiment, the barrier layer is a high-polarization-strength barrier layer, and the GaN buffer layer and the barrier layer constitute a low-sheet-resistance heterojunction material.
As for the barrier layer, the higher its Al composition, the higher its polarization strength, for example: the Al component of AlN is 100%, the Al component of lattice-matched ScAlN is 82%, and the Al component of lattice-matched InAlN is 83%. The Al composition of conventional AlGaN is 20 to 30%, and in this embodiment, if the barrier layer is AlGaN, alGaN with a high Al composition, i.e., alGaN with an Al composition greater than 50%, needs to be selected.
Furthermore, it should be noted that these high polarization barriers usually have typical layer thickness values, such as: alN is 2-6nm, lattice-matched ScAlN is 2-15nm, lattice-matched InAlN is 3-15nm, and high Al component AlGaN is 7-25nm.
S2: etching the ohmic region of the GaN-based heterojunction by adopting a dry etching process until the position of at least 20nm below the interface of the GaN-based heterojunction is etched to form an ohmic regrowth region for ohmic regrowth;
specifically, the method comprises the following steps:
s21: coating photoresist on the barrier layer, and exposing and developing the two sides of the top surface of the device to form an etching area;
s22: etching the etching region by using an ICP (inductively coupled plasma) etching device by adopting a dry etching process until the etching region is etched to at least 20nm below the interface of the GaN buffer layer and the barrier layer to form an ohmic regrowth region for ohmic regrowth, wherein the GaN HEMT (high Electron mobility transistor) device relies on a 2DEG channel for conducting electricity, and the distribution range of the 2DEG is generally considered to be within the range from a heterojunction interface to 10nm below the heterojunction interfaceN within the enclosure, in order to regrow ohmic regions + The GaN is in effective contact with the 2DEG, thus ensuring etching to at least 20nm below the interface of the GaN buffer layer and the barrier layer. Wherein the etching gas is BCl 3 And Cl 2 And (4) mixing the gases.
In this embodiment, BCl 3 And Cl 2 The flow rate of the mixed gas is respectively 20/8sccm, and the etching process parameters are as follows: the electrode power on ICP was 51W, the electrode power under ICP was 14W, and the pressure was 5mTorr.
S3: epitaxially growing n on the surface of the device + A GaN layer;
specifically, performing low-temperature epitaxy on the surface of the device by using MBE equipment + And the GaN layer adopts a low-temperature epitaxy process to avoid barrier quality degradation caused by high-temperature epitaxy.
In this embodiment, the re-growth of heavily doped GaN is realized by in-situ doping with Si + The doping concentration of the GaN layer is 5 x 10 19 cm -3 -5×10 20 cm -3 . The doping concentration in this range is chosen because lower doping concentrations do not easily achieve low n + GaN sheet resistance, higher doping concentration although low n is easily achieved + GaN sheet resistance, however n + The GaN crystal quality may deteriorate. Therefore, the doping concentration is 5X 10 19 cm -3 -5×10 20 cm -3 。
N is + The thickness of the GaN layer is typically twice the depth of the nitride etch of the ohmic region.
S4: using dry etching process to n + The GaN layer is self-terminated etched to remove n between ohmic regrowth regions + A GaN layer;
specifically, the method comprises the following steps:
s41: at n + Coating photoresist on the GaN layer, and exposing and developing between the ohmic regrowth regions to form a self-termination etching region;
s42: utilizing ICP etching equipment, adopting dry etching process to etch n of self-termination etching region + Self-terminating etching is carried out on the GaN layer, and n between the ohm regrowth areas is removed + And a GaN layer.
In this embodiment, the self-stop etching gas is SF 6 And BCl 3 Wherein, SF 6 And BCl 3 The gas flow ratio of (1) 6 The gas flow rate of (b) is 5-15sccm 3 The flow rate is 15-45sccm.
Further, the etching process parameters are as follows: the power of an electrode on the ICP is 160-240W, the power of an electrode under the ICP is 24-36W in order to ensure that the etching gas forms a plasma state, certain bombardment etching capacity is given to the plasma, and the pressure is 2-8mTorr.
In this embodiment, SF 6 And BCl 3 Mixed gas pair n of + Etching the GaN layer at n + After the GaN layer is etched, when SF is added 6 Contact reaction with barrier layer containing Al to form AlF 3 Can block SF 6 And BCl 3 The self-termination etching is realized by etching the barrier layer by the mixed gas.
S5: forming isolation regions on two sides of the device by using ion implantation equipment;
specifically, by using ion implantation equipment, B or Ar and the like are implanted into two sides of the device to form an isolation region, thereby realizing device isolation.
S6: at n + Depositing metal on the GaN layer to form a source electrode and a drain electrode;
in particular, using electron beam evaporation equipment at n + And depositing Ti/Al/Ni/Au ohmic laminated metal on the GaN layer to form a source electrode and a drain electrode.
S7: forming a passivation layer on the surface of the device;
specifically, firstly, a PECVD device is used for depositing a SiN passivation layer on the surface of the device, and then an ICP etching device is used for removing the SiN passivation layer on the source electrode and the drain electrode by adopting a dry etching process, wherein the etching gas is CF 4 And O 2 The gas flow rate of the mixed gas (2) is 25/5sccm, the chamber pressure is 5mTorr, the ICP upper electrode power is 80W, and the ICP lower electrode power is 10W.
S8: and etching the passivation layer of the gate region by adopting a dry etching process to form a gate groove, and depositing metal in the gate groove to form a gate.
In this embodiment, first, an ICP etching apparatus is used to etch the SiN passivation layer in the gate region by using a dry etching process to form a gate groove, where an etching gas is CF 4 And O 2 The gas flow rate of the mixed gas is respectively 25/5sccm, the chamber pressure is 5mTorr, the ICP upper electrode power is 80W, and the ICP lower electrode power is 10W; then, a Ni/Au laminated metal is deposited on the grid groove by using an electron beam evaporation device to form a grid.
The preparation method of the GaN-based radio frequency power device based on ohmic regrowth of the embodiment is based on the self-termination etching technology, can process and obtain the device structure which is the same as the device structure of the conventional ohmic regrowth technology, and does not depend on SiO compared with the conventional ohmic regrowth technology 2 The mask simplifies the preparation process and simultaneously continues the advantages of the conventional ohmic regrowth technology.
Example two
Taking InAlN/GaN heterojunction as an example, the method for manufacturing the GaN-based rf power device based on ohmic regrowth of this embodiment will be specifically described. Referring to fig. 2a to fig. 2j in combination, fig. 2a to fig. 2j are schematic views illustrating a process for manufacturing a GaN-based rf power device based on ohmic regrowth according to an embodiment of the present invention.
The preparation method comprises the following specific steps:
the method comprises the following steps: a GaN layer 202 and an InAlN layer 203 are sequentially stacked and grown on the SiC substrate 201 by using an MOCVD apparatus, wherein the GaN layer 202 is composed of Fe or C doped high-resistance GaN and UID-GaN (unintentionally doped-GaN) from bottom to top, as shown in fig. 2 a.
Step two: coating photoresist PR on the InAlN layer 203, and exposing and developing the two sides of the top surface of the device to form etching regions 204 as shown in FIG. 2 b;
step three: etching the etching region 204 by using an ICP etching apparatus and a dry etching process until the position of at least 20nm below the interface of the GaN layer 202 and the InAlN layer 203, an ohmic regrowth region is formed for ohmic regrowth, as shown in fig. 2 c.
Wherein the etching gas is BCl 3 And Cl 2 The flow rate of the mixed gas is 20/8sccm respectively, and the pressure of the chamber5mTorr, ICP upper electrode power 51W, lower electrode power 14W.
Step four: low temperature epitaxial n on device surface using MBE equipment + GaN layer 205, as shown in fig. 2 d.
Step five: at n + A photoresist PR is applied over the GaN layer 205 and exposed to develop between the ohmic regrowth regions to form self-terminating etch regions 206 as shown in figure 2 e.
Step six: etching n of region 206 by dry etching using an ICP etching apparatus + The GaN layer 205 is self-terminating etched to remove n between ohmic regrowth regions + GaN layer 205, as shown in fig. 2 f.
In this embodiment, the self-stop etching gas is SF 6 And BCl 3 Wherein, SF 6 The gas flow rate was 10sccm, BCl 3 The flow rate was 30sccm. The parameters of the etching process are as follows: the electrode power on ICP is 200W, the electrode power under ICP is 30W, and the pressure is 5mTorr.
Step seven: and (5) injecting B or Ar and the like into two sides of the device by using ion injection equipment to form an isolation region so as to realize device isolation, as shown in figure 2 g.
Step eight: using electron beam evaporation equipment at n + A Ti/Al/Ni/Au ohmic stack metal is deposited on the GaN layer 205 to form a source electrode 207 and a drain electrode 208 as shown in fig. 2 h.
Step nine: and depositing a SiN passivation layer 209 on the surface of the device by using a PECVD (plasma enhanced chemical vapor deposition) device, and then removing the SiN passivation layer 209 on the source electrode 207 and the drain electrode 208 by using an ICP (inductively coupled plasma) etching device through a dry etching process, as shown in FIG. 2 i.
Wherein the etching gas is CF 4 And O 2 The gas flow rate of the mixed gas (2) is 25/5sccm, the chamber pressure is 5mTorr, the ICP upper electrode power is 80W, and the ICP lower electrode power is 10W.
Step ten: the SiN passivation layer 209 in the gate region is etched by using an ICP etching apparatus through a dry etching process to form a gate groove, and then a Ni/Au stacked metal is deposited in the gate groove by using an electron beam evaporation apparatus to form a gate 210, as shown in fig. 2j, in this embodiment, the gate 210 is a T-shaped gate.
Wherein the etching gas is CF 4 And O 2 The gas flow rate of the mixed gas (2) is 25/5sccm, the chamber pressure is 5mTorr, the ICP upper electrode power is 80W, and the ICP lower electrode power is 10W.
EXAMPLE III
The embodiment provides a GaN-based radio frequency power device based on ohmic regrowth, which is prepared by adopting the preparation method of any embodiment. Referring to fig. 3, fig. 3 is a schematic structural diagram of a GaN-based rf power device based on ohmic regrowth according to an embodiment of the present invention. As shown in the figure, the GaN-based rf power device of the present embodiment includes: substrate layer 301, buffer layer 302, barrier layer 303, n + GaN ohmic region 304, source 305, drain 306, gate 307, and passivation layer 308. The substrate layer 301, the buffer layer 302, and the barrier layer 303 are stacked in this order from the bottom to the top. n is + GaN ohmic regions 304 are disposed inside the buffer layer 302 and the barrier layer 303, and on both sides of the device. A source 305 and a drain 306 are respectively arranged at n + On the GaN ohmic region 304. And a gate 307 disposed on the barrier layer 303 and between the source 305 and the drain 306. A passivation layer 308 is disposed on the device surface between the source 305 and gate 307 and between the drain 306 and gate 307.
Optionally, the buffer layer 302 includes an Fe or C doped GaN layer and an unintentionally doped GaN layer stacked in sequence from bottom to top; the barrier layer 303 is one of AlN, scAlN, inAlN or AlGaN, and the Al component of the AlGaN is more than 50%.
In this embodiment, the barrier layer 303 is a high-polarization-strength barrier layer, and the buffer layer 302 and the barrier layer 303 constitute a low-sheet-resistance heterojunction material.
In the present embodiment, n + The GaN ohmic region 304 has a doping concentration of 5 × 10 19 cm -3 -5×10 20 cm -3 。
The GaN-based radio frequency power device based on ohmic regrowth has low ohmic contact resistance and good ohmic morphology, the source-drain size of the device is further reduced through the good ohmic morphology, the ultra-low parasitic resistance is favorably realized, and the radio frequency power characteristic of the device is improved.
It should be noted that, in this document, the terms "comprises", "comprising" or any other variation are intended to cover a non-exclusive inclusion, so that an article or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed. Without further limitation, an element defined by the phrases "comprising one of \8230;" does not exclude the presence of additional like elements in an article or device comprising the element. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The directional or positional relationships indicated by "up", "down", "left", "right", etc., are based on the directional or positional relationships shown in the drawings, are merely for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be taken as limiting the invention.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, numerous simple deductions or substitutions may be made without departing from the spirit of the invention, which shall be deemed to belong to the scope of the invention.
Claims (8)
1. A preparation method of a GaN-based radio frequency power device based on ohmic regrowth is characterized by comprising the following steps:
s1: growing a GaN-based heterojunction on a substrate, comprising: sequentially stacking and growing a GaN buffer layer and a barrier layer on the substrate from bottom to top by using MOCVD equipment;
s2: etching the ohmic region of the GaN-based heterojunction by adopting a dry etching process until the position of at least 20nm below the interface of the GaN-based heterojunction is etched to form an ohmic regrowth region for ohmic regrowth; the method comprises the following steps:
s21: coating photoresist on the barrier layer, and exposing and developing the two sides of the top surface of the device to form an etching area;
s22: etching the etching region by using an ICP (inductively coupled plasma) etching device by adopting a dry etching process until the etching region is at least 20nm below the interface of the GaN buffer layer and the barrier layer to form an ohmic regrowth region for ohmic regrowth, wherein the etching gas is BCl 3 And Cl 2 Mixing the gas;
s3: epitaxially growing n on the surface of the device + A GaN layer;
s4: applying dry etching process to n + The GaN layer is self-terminated etched to remove n between the ohmic regrowth regions + A GaN layer; the method comprises the following steps:
s41: at the n + Coating photoresist on the GaN layer, and exposing and developing between the ohm regrowth areas to form a self-termination etching area;
s42: utilizing ICP etching equipment and adopting dry etching process to etch n of the self-termination etching area + The GaN layer is self-terminated etched to remove n between the ohmic regrowth regions + GaN layer of n between ohmic regrowth regions + The middle part of the GaN layer is removed, and n at the two end parts + The GaN layer is remained on the barrier layer;
s5: forming isolation regions on both sides of the device by using ion implantation equipment;
s6: n in the ohmic regrowth region + Depositing metal on the GaN layer to form a source electrode and a drain electrode;
s7: forming a passivation layer on the surface of the device;
s8: and etching the passivation layer of the grid region by adopting a dry etching process to form a grid groove, and depositing metal in the grid groove to form a grid.
2. The method of claim 1, wherein the GaN buffer layer comprises an Fe-or C-doped GaN layer and an unintentionally doped GaN layer stacked in sequence from bottom to top;
the barrier layer is one of AlN, scAlN, inAlN or AlGaN, and the Al component of the AlGaN is more than 50%.
3. The method of claim 1, wherein in S3, n is + The doping concentration of the GaN layer is 5 × 10 19 cm -3 -5×10 20 cm -3 。
4. The method of claim 1, wherein the self-terminating etch gas is SF 6 And BCl 3 Wherein, SF 6 And BCl 3 The gas flow ratio of (1) 6 The gas flow rate of (B) is 5-15sccm 3 The flow rate is 15-45sccm;
the parameters of the etching process are as follows: the power of an electrode on the ICP is 160-240W, the power of an electrode under the ICP is 24-36W, and the pressure is 2-8mTorr.
5. The method of claim 1, wherein the S6 comprises: n in the ohmic regrowth region using electron beam evaporation equipment + And depositing Ti/Al/Ni/Au ohmic laminated metal on the GaN layer to form a source electrode and a drain electrode.
6. A GaN-based rf power device based on ohmic regrowth, characterized by being prepared by the preparation method of any one of claims 1-5, comprising:
the substrate layer, the buffer layer and the barrier layer are sequentially stacked from bottom to top;
n + the GaN ohmic region is arranged in the buffer layer and the barrier layer and positioned on two sides of the device; n is + N is provided on both ends of the barrier layer between the GaN ohmic regions + A GaN layer of which n + GaN layer and corresponding n + GaN ohmic region contact;
a source and a drain respectively disposed at the n + A GaN ohmic region;
the grid electrode is arranged on the barrier layer and is positioned between the source electrode and the drain electrode;
and the passivation layer is arranged on the surface of the device between the source electrode and the grid electrode and between the drain electrode and the grid electrode.
7. The ohmic-regrowth-based GaN-based radio frequency power device of claim 6, wherein the buffer layer comprises an Fe-or C-doped GaN layer and an unintentionally doped GaN layer stacked in this order from bottom to top;
the barrier layer is one of AlN, scAlN, inAlN or AlGaN, and the Al component of the AlGaN is more than 50%.
8. The ohmic-regrowth-based GaN-based radio frequency power device of claim 6, wherein the n + The doping concentration of GaN ohmic region is 5 × 10 19 cm -3 -5×10 20 cm -3 。
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