阅读说明：本技术 氮化镓压力传感器及其制备方法 (Gallium nitride pressure sensor and preparation method thereof ) 是由 刘泽文 孙剑文 于 2021-10-11 设计创作，主要内容包括：本发明公开了氮化镓压力传感器及其制备方法,所述氮化镓压力传感器包括：第一衬底、第二衬底、外延结构、源极、漏极、栅极和凹槽,所述源极、所述漏极和所述栅极位于所述外延结构远离所述第二衬底的一侧,所述源极和所述漏极分别位于所述栅极相对的两侧,所述栅极的数量为大于等于2的正整数,所述源极和所述漏极之间具有沟道区域。由此,本发明的氮化镓压力传感器具有两个以上的栅极,通过在栅极上施加电压调控沟道宽度,实现了沟道宽度的调控,可以对氮化镓压力传感器的检测范围、精度以及灵敏度等进行二次调整优化,扩大了工艺制备窗口,扩展了压力传感器的应用范围。(The invention discloses a gallium nitride pressure sensor and a preparation method thereof, wherein the gallium nitride pressure sensor comprises: the transistor comprises a first substrate, a second substrate, an epitaxial structure, a source electrode, a drain electrode, a grid electrode and a groove, wherein the source electrode, the drain electrode and the grid electrode are located on one side, far away from the second substrate, of the epitaxial structure, the source electrode and the drain electrode are respectively located on two opposite sides of the grid electrode, the number of the grid electrodes is a positive integer larger than or equal to 2, and a channel region is arranged between the source electrode and the drain electrode. Therefore, the gallium nitride pressure sensor provided by the invention has more than two grids, the channel width is regulated and controlled by applying voltage on the grids, the regulation and control of the channel width are realized, the detection range, the precision, the sensitivity and the like of the gallium nitride pressure sensor can be secondarily regulated and optimized, the process preparation window is expanded, and the application range of the pressure sensor is expanded.)

1. A gallium nitride pressure sensor, characterized in that the gallium nitride pressure sensor comprises:

a first substrate;

a second substrate located at one side of the first substrate;

the epitaxial structure is positioned on one side, away from the first substrate, of the second substrate and comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are arranged in a stacked mode, and the GaN buffer layer is positioned on the surface of one side of the second substrate;

the source electrode, the drain electrode and the grid electrode are positioned on one side, far away from the second substrate, of the epitaxial structure, the source electrode and the drain electrode are respectively positioned on two opposite sides of the grid electrode, the number of the grid electrodes is a positive integer larger than or equal to 2, and a channel region is arranged between the source electrode and the drain electrode;

a groove located on the second substrate, an orthographic projection of the channel region on the first substrate at least partially overlapping an orthographic projection of the groove on the first substrate.

2. The gallium nitride pressure sensor according to claim 1, wherein the second substrate comprises a base layer, an insulating layer, and a silicon layer arranged in a stack, the base layer being located on a side close to the first substrate.

3. The gallium nitride pressure sensor according to claim 2, wherein the base layer has a thickness of 100-500 μm;

the thickness of the insulating layer is 0.5-5.5 μm;

the thickness of the silicon layer is 0.5-100 μm.

4. Gallium nitride pressure sensor according to claim 2, wherein the groove is located on the base layer, and the opening of the groove is located on a side of the base layer away from the insulating layer.

5. The gallium nitride pressure sensor according to claim 4, wherein the depth of the groove is 100-500 μm.

6. The gallium nitride pressure sensor according to claim 1, wherein the GaN buffer layer has a thickness of 0.5-5 μm, the GaN channel layer has a thickness of 0.2-5 μm, the AlN insertion layer has a thickness of 0.5-3nm, the AlGaN barrier layer has a thickness of 10-100nm, and the GaN cap layer has a thickness of 1-10 nm.

7. The gallium nitride pressure sensor according to claim 1, wherein the material forming the source and drain electrodes comprises at least one of Ti, Al, Ni, Au;

the material for forming the grid electrode comprises at least one of Ti, Cr, Ni, Pt and Au.

8. The gallium nitride pressure sensor according to claim 1, wherein the epitaxial structure is an enhancement mode HEMT structure or a depletion mode HEMT structure.

9. A method of making a gallium nitride pressure sensor, the method comprising:

forming an epitaxial structure on one side of a second substrate, wherein the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are arranged in a stacked mode, and the GaN buffer layer is located on the surface of one side of the second substrate;

forming a source electrode, a drain electrode and a grid electrode on one side of the epitaxial structure far away from the second substrate, wherein the source electrode and the drain electrode are respectively positioned on two opposite sides of the grid electrode, and the number of the grid electrodes is a positive integer greater than or equal to 2; a channel region is arranged between the source electrode and the drain electrode;

etching one side of the second substrate, which is far away from the epitaxial structure, to form a groove;

and forming a first substrate on the side of the second substrate far away from the epitaxial structure, wherein the orthographic projection of the channel region on the first substrate at least partially overlaps with the orthographic projection of the groove on the first substrate.

10. The method of claim 9, wherein the forming the source, the drain, and the gate comprises:

etching the epitaxial structure to form an etching table-board;

depositing a first metal layer and a second metal layer on the etching table-board to form a source electrode and a drain electrode;

and depositing a third metal layer on the etching table-board to form a grid.

Technical Field

The invention belongs to the technical field of semiconductors, and particularly relates to a gallium nitride pressure sensor and a preparation method thereof.

Background

The semiconductor pressure sensor is a semiconductor transducer for converting pressure signals into electrical signals, and is widely applied to the application fields of industry, medical treatment, automotive electronics, consumer and the like. The traditional silicon-based piezoresistive pressure sensor adopts diffused silicon resistors to form piezoresistors, but the piezoresistors drift along with temperature change, and the silicon-based piezoresistive pressure sensor can only work below 120 ℃. Gallium nitride is a wide-bandgap semiconductor material, the working temperature of the pressure sensor based on the gallium nitride technology can reach 600 ℃, and the pressure sensor has wide application prospect in the field of high-temperature pressure detection. The AlGaN/GaN heterostructure forms two-dimensional electron gas (2DEG) with high concentration and high electron mobility on the surface of a GaN channel layer due to piezoelectric polarization and self-polarization effect, is very sensitive to external pressure change, and is suitable for being used as a high-sensitivity pressure sensor.

However, the pressure detection range and sensitivity of the existing gallium nitride pressure sensor are designed according to the size and thickness of the chip suspension film, once the pressure sensor is prepared, the pressure detection range, accuracy and sensitivity are fixed, and secondary adjustment cannot be performed. That is, in the prior art, the pressure detection range, accuracy, sensitivity and other performances of the pressure sensor cannot be secondarily adjusted. For the pressure sensor with high requirement on consistency, the corresponding preparation process is also high in consistency, small in process window and low in yield.

Therefore, there is a need for improvements to existing gallium nitride pressure sensors.

Disclosure of Invention

In order to solve the above technical problem, the present invention provides a gallium nitride pressure sensor, including: a first substrate; a second substrate located at one side of the first substrate; the epitaxial structure is positioned on one side, away from the first substrate, of the second substrate and comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are arranged in a stacked mode, and the GaN buffer layer is positioned on the surface of one side of the second substrate; the source electrode, the drain electrode and the grid electrode are positioned on one side, far away from the second substrate, of the epitaxial structure, the source electrode and the drain electrode are respectively positioned on two opposite sides of the grid electrode, the number of the grid electrodes is a positive integer larger than or equal to 2, and a channel region is arranged between the source electrode and the drain electrode; a groove located on the second substrate, an orthographic projection of the channel region on the first substrate at least partially overlapping an orthographic projection of the groove on the first substrate. Therefore, the gallium nitride pressure sensor is provided with more than two grids, the channel width is regulated and controlled by applying voltage to the grids, the regulation and control of the channel width are realized, and the problem that the performance of the pressure sensor cannot be secondarily regulated and optimized after the pressure sensor is prepared is solved. The invention can carry out secondary adjustment and optimization on the detection range, precision, sensitivity and the like of the gallium nitride pressure sensor, enlarges the process preparation window and expands the application range of the pressure sensor.

According to an embodiment of the present invention, the second substrate includes a base layer, an insulating layer, and a silicon layer, which are stacked, and the base layer is located on a side close to the first substrate.

According to the embodiment of the invention, the thickness of the base layer is 100-500 μm; the thickness of the insulating layer is 0.5-5.5 μm; the thickness of the silicon layer is 0.5-100 μm. The thickness of the pressure sensitive film of the pressure sensor can be regulated and controlled through the thickness of the silicon layer, so that the pressure detection range of the pressure sensor is regulated, and meanwhile, the consistency of the preparation process of the gallium nitride pressure sensor can be improved.

According to the embodiment of the invention, the groove is positioned on the base layer, and the opening of the groove is positioned on the side of the base layer away from the insulating layer.

According to the embodiment of the invention, the depth of the groove is 100-500 μm.

According to an embodiment of the present invention, the thickness of the GaN buffer layer is 0.5 to 5 μm, the thickness of the GaN channel layer is 0.2 to 5 μm, the thickness of the AlN insertion layer is 0.5 to 3nm, the thickness of the AlGaN barrier layer is 10 to 100nm, and the thickness of the GaN cap layer is 1 to 10 nm.

According to the embodiment of the invention, the material forming the source electrode and the drain electrode comprises at least one of Ti, Al, Ni and Au; the material for forming the grid electrode comprises at least one of Ti, Cr, Ni, Pt and Au.

According to an embodiment of the invention, the epitaxial structure is an enhancement mode HEMT structure or a depletion mode HEMT structure.

The invention also provides a preparation method of the gallium nitride pressure sensor, which comprises the following steps: forming an epitaxial structure on one side of a second substrate, wherein the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are arranged in a stacked mode, and the GaN buffer layer is located on the surface of one side of the second substrate; forming a source electrode, a drain electrode and a grid electrode on one side of the epitaxial structure far away from the second substrate, wherein the source electrode and the drain electrode are respectively positioned on two opposite sides of the grid electrode, and the number of the grid electrodes is a positive integer greater than or equal to 2; a channel region is arranged between the source electrode and the drain electrode; etching one side of the second substrate, which is far away from the epitaxial structure, to form a groove; and forming a first substrate on the side of the second substrate far away from the epitaxial structure, wherein the orthographic projection of the channel region on the first substrate at least partially overlaps with the orthographic projection of the groove on the first substrate.

According to some embodiments of the present invention, the gallium nitride pressure sensor prepared by the method has all the features and advantages of the gallium nitride pressure sensor described above, and thus, the detailed description thereof is omitted. Generally speaking, the gallium nitride pressure sensor prepared by the method has more than two grids, the width of a channel is regulated and controlled by applying voltage on the grids, so that the output current between a source electrode and a drain electrode is regulated and controlled, the pressure detection range of the pressure sensor can be expanded, and the precision and the sensitivity of the pressure sensor are improved.

According to an embodiment of the present invention, the forming the source, the drain and the gate includes: etching the epitaxial structure to form an etching table-board; depositing a first metal layer and a second metal layer on the etching table-board to form a source electrode and a drain electrode; and depositing a third metal layer on the etching table-board to form a grid.

Drawings

FIG. 1 is a schematic diagram of a gallium nitride pressure sensor according to an embodiment of the present invention;

FIG. 2 shows a gate voltage V according to an embodiment of the present invention_GS1＝V_GS2Depression of gallium nitride pressure sensor at 0VView of wherein V_GS1And V_GS2Respectively representing the voltages applied by the two grids;

FIG. 3 is a cross-sectional view taken along the direction AA' of FIG. 2;

FIG. 4 shows a gate voltage V according to an embodiment of the present invention_GS1<V_TAnd V_GS2<V_TA top view of the gallium nitride pressure sensor, wherein V_TIs the threshold voltage of the HEMT;

FIG. 5 is a cross-sectional view taken along the direction AA' of FIG. 4;

fig. 6 is a schematic diagram of the structure of the second substrate in one embodiment of the invention.

FIG. 7 is a schematic diagram of a channel width tunable gallium nitride pressure sensor configuration having a Wheatstone bridge configuration;

FIG. 8 is a flow chart of a method for fabricating a gallium nitride pressure sensor, in accordance with an embodiment of the present invention;

FIG. 9 is a flow chart of a method for fabricating a source, a drain and a gate in accordance with an embodiment of the present invention;

fig. 10 is a schematic diagram of a structure for forming a source and a drain on an etched mesa in accordance with an embodiment of the present invention.

Description of reference numerals:

100-a first substrate, 200-a second substrate, 210-a base layer, 220-an insulating layer, 230-a silicon layer, 211-a groove, 300-an epitaxial structure, 300 a-an etching table, 310-a GaN buffer layer, 320-a GaN channel layer, 330-an insertion layer, 340-an AlGaN barrier layer, 350-a GaN cap layer, 400-a drain electrode, 500-a source electrode, 600-a grid electrode, 700-a channel region, 800-a grid electrode regulation region and 900-a support film.

Detailed Description

Embodiments of the present application are described in detail below. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents used are not indicated by manufacturers, and are all conventional products available on the market.

The pressure detection range and sensitivity of the existing gallium nitride pressure sensor are designed according to the size and thickness of a chip suspension film, once the pressure sensor is prepared, the pressure detection range, the precision and the sensitivity are fixed, and secondary adjustment cannot be performed.

In order to solve the above technical problem, the present invention provides a gallium nitride pressure sensor, and referring to fig. 1, the gallium nitride pressure sensor includes: the epitaxial structure comprises a first substrate 100, a second substrate 200, an epitaxial structure 300, a drain 400, a source 500, a gate 600 and a groove (not shown in the figure), wherein the second substrate 200 is positioned on one side of the first substrate 100; the epitaxial structure 300 is located on the side of the second substrate 200 far away from the first substrate 100, the epitaxial structure 300 comprises a stacked GaN buffer layer 310, a GaN channel layer 320, an AlN insertion layer 330, an AlGaN barrier layer 340 and a GaN cap layer 350, and the GaN buffer layer 310 is located on the surface of the side of the second substrate 200; the source electrode 500, the drain electrode 400 and the gate electrode 600 are positioned on one side of the epitaxial structure 300 far away from the second substrate 200, the source electrode 500 and the drain electrode 400 are respectively positioned on two opposite sides of the gate electrode 600, the number of the gate electrodes 600 is a positive integer greater than or equal to 2, and a channel region 700 is arranged between the source electrode 500 and the drain electrode 400; the recess is located on the second substrate 200 and the orthographic projection of the channel region on the first substrate 100 at least partially overlaps the orthographic projection of the recess on the first substrate 100. Therefore, the High Electron Mobility Transistor (HEMT) unit has more than two gates 600, the channel width is regulated by applying voltage on the gates 600, specifically, the carrier transport of two-dimensional electron gas (2DEG) in the AlGaN/GaN heterostructure below the HEMT can be controlled by applying driving voltage on the gates 600, the channel width between the source electrode 500 and the drain electrode 400 is regulated, so that the output current between the source electrode 500 and the drain electrode 400 is regulated, the pressure detection range of the pressure sensor can be expanded, and the precision and the sensitivity of the pressure sensor can be improved.

The invention can carry out secondary adjustment and optimization on the pressure detection range, the precision, the sensitivity and other properties of the pressure sensor, solves the consistency problem caused by process errors in the process, expands the process preparation window and also expands the application range of the pressure sensor.

According to the embodiment of the present invention, when the gan pressure sensor has more than two gates 600, each gate 600 can be controlled separately, and the voltages applied to different gates 600 may be equal or unequal.

When the number of gates is 2, V_GS1And V_GS2Respectively, the voltages applied to the two gates 600 when the gate voltage V is applied_GS1＝V_GS2Referring to fig. 2 and 3, when V is 0V, a high concentration, high electron mobility two-dimensional electron gas is formed on the upper surface of the GaN channel layer 320 due to spontaneous polarization and piezoelectric polarization effects of the AlGaN barrier layer 340 and the GaN channel layer 320 in the AlGaN/GaN heterostructure, when V is_GS0V, the two-dimensional electron gas is distributed on the entire upper surface of the GaN channel layer 320, and the channel width of the transistor is a design value W₁。

V_TIs the threshold voltage of HEMT when the gate voltage V_GS1<V_TAnd V is_GS2<V_TReferring to fig. 4 and 5, a gate control region 800 is near the gate 600 and is controlled according to the voltage of the gate 600. Two-dimensional electron gas just under and at the edge portion of the gate electrode 600 region is exhausted, and the equivalent channel width between the source electrode 500 and the drain electrode 400 becomes W₂。

If two gates 600 are placed closer to each other or more than two gates 600 are used, the channel width can be achieved from 0 to the longest W₁And (4) regulation and control.

When the number of the gates 600 is 2, two gates 600 may adopt a symmetrical distribution or an asymmetrical distribution.

The change of the transistor channel width correspondingly changes the stress distribution position of the transistor on the support film, thereby realizing the secondary adjustment optimization of the sensitivity and the precision. The support film 900 refers to a structure located above the recess 211, the support film 900 includes the silicon layer 230 and the epitaxial structure 300, and the support film 900 is used for sensing a pressure change. When external pressure is applied to the gallium nitride pressure sensor, the piezoelectric polarization electric field is changed, so that the charge density of two-dimensional electron gas is changed, channel current is changed, but channel saturation currents under the control of different grid 600 voltages are different, so that pressure detection ranges are different, and secondary adjustment and optimization of the pressure detection ranges are realized. In a word, the gallium nitride pressure sensor with the adjustable channel width can perform secondary adjustment and optimization on the pressure detection range, the precision, the sensitivity and other properties of the pressure sensor, solves the consistency problem caused by errors in the technological process, expands the technological preparation window and also expands the application range of the pressure sensor.

According to an embodiment of the present invention, referring to fig. 6, the second substrate 200 includes a base layer 210, an insulating layer 220, and a silicon layer 230, which are stacked, the base layer 210 being located at a side close to the first substrate 100.

According to an embodiment of the present invention, the thickness of the base layer 210 is 100-500 μm, such as 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm. If the thickness of the base layer is too large, cost and process complexity may increase. If the thickness of the base layer is too small, there is a risk of splintering, and handling is not easy.

The thickness of the insulating layer 220 is 0.5 to 5.5 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm. The insulating layer is a stop layer of an etching process, and if the thickness of the insulating layer is too large, the process is not easy to realize, and the cost is high. If the thickness of the insulating layer is too small, the handling is not easy.

The thickness of the silicon layer 230 is 0.5-100 μm, for example 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm. The thickness of the silicon layer can be designed according to the pressure measurement range of the pressure sensor. And the thickness of the silicon layer is large, so that the pressure measurement range is large. The small thickness of the silicon layer provides a high sensitivity of the pressure sensor.

The thickness of the pressure sensitive film of the pressure sensor can be regulated and controlled by selecting the thickness of the silicon layer 230, so that the pressure detection range of the pressure sensor is regulated, and the consistency of the preparation process of the gallium nitride pressure sensor is improved. Specifically, the pressure sensor can be designed with pressure measuring range by changing the thickness of the silicon layer before preparation, and can also be secondarily regulated by the grid after preparation.

Fig. 7 is a schematic structural diagram of a wheatstone bridge type gallium nitride pressure sensor with adjustable channel width, and referring to fig. 7, the wheatstone bridge can be selected as a wheatstone full bridge or a wheatstone half bridge, so as to improve the accuracy and sensitivity of the sensor. By applying voltage control on the gate, the channel width of the transistor is regulated, and the change of the channel width of the transistor correspondingly changes the stress distribution position of the transistor on the support film 900, thereby realizing secondary adjustment optimization of sensitivity and precision. Further, in a wheatstone bridge configuration, the electrical signal of the diagonal legs increases or decreases as the pressure increases.

According to the embodiment of the invention, the groove 211 is located on the substrate layer 210, and the opening of the groove 211 is located on the side of the substrate layer 210 away from the insulating layer 220. Therefore, the reference pressure can be set, so that a pressure difference is formed above and below the support film, and when the external pressure changes, the pressure difference changes, thereby influencing the output characteristic of the transistor.

According to an embodiment of the present invention, the depth of the recess 211 is 100-500 μm, such as 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm. The depth of the groove can be designed into different pressure range. If the depth of the groove is too large, the deviation of the design value is large due to the angle influence of the deep silicon etching process.

According to an embodiment of the present invention, the groove 211 formed on the second substrate 200 may serve as a reference pressure chamber after the second substrate 200 is bonded to the first substrate 100.

According to an embodiment of the present invention, the thickness of the GaN buffer layer 310 is 0.5-5 μm, such as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm. Through the GaN buffer layer, the stress matching problem between the gallium nitride layer and the silicon layer can be reduced. If the thickness of the GaN buffer layer is too large, the stress of the buffer layer is large. If the thickness of the GaN buffer layer is too small, a large dislocation density of the epitaxial layer may result.

The thickness of the GaN channel layer 320 is 0.2-5 μm, such as 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm. If the thickness of the GaN channel layer is too large, the stress distribution may be non-uniform. If the thickness of the GaN channel layer is excessively small, the two-dimensional electron gas cannot be formed or the concentration of the two-dimensional electron gas is low.

The AlN insertion layer 330 has a thickness of 0.5 to 3nm, for example, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3 nm. The AlN insert layer mainly has the function of forming a high potential barrier and improving the concentration of two-dimensional electron gas. If the AlN insert layer is too small in thickness, the implementation is not easy, and the concentration of the two-dimensional electron gas cannot be effectively increased. If the AlN insertion layer is too thick, extreme stress may be introduced, degrading the epitaxial quality of the AlGaN barrier layer, resulting in reduced mobility.

The AlGaN barrier layer 340 has a thickness of 10 to 100nm, for example, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, or 100 nm. If the thickness of the AlGaN barrier layer is too small, a two-dimensional electron gas cannot be formed or the density of the two-dimensional electron gas may be low; if the thickness of the AlGaN barrier layer is too large, the concentration of the two-dimensional electron gas becomes saturated, possibly resulting in a decrease in mobility.

The thickness of the GaN cap layer 350 is 1-10nm, such as 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10 nm. If the thickness of the GaN cap layer is too small, the carrier concentration may be reduced; if the thickness of the GaN cap layer is too large, contact resistance may increase, reducing mobility of the two-dimensional electron gas.

According to an embodiment of the present invention, the material forming the source and drain electrodes 500 and 400 includes at least one of Ti, Al, Ni, and Au. It should be noted that the material for forming the source electrode 500 and the material for forming the drain electrode 400 may be the same or different, and those skilled in the art can select them according to the usage requirement.

The material forming the gate electrode 600 includes at least one of Ti, Cr, Ni, Pt, and Au.

According to an embodiment of the present invention, the epitaxial structure 300 is an enhancement mode HEMT structure or a depletion mode HEMT structure. The enhancement mode HEMT structure is a normally-off device with a threshold voltage greater than 0. And the depletion type HEMT structure is a normally-on device, and the threshold voltage is less than 0.

The invention also provides a preparation method of the gallium nitride pressure sensor, and referring to fig. 8, the method comprises the following steps:

s100, forming an epitaxial structure 300 on one side of a second substrate 200;

the epitaxial structure 300 includes a GaN buffer layer 310, a GaN channel layer 320, an AlN insertion layer 330, an AlGaN barrier layer 340, and a GaN cap layer 350, which are stacked, and the GaN buffer layer 310 is located on the surface of the second substrate 200 on one side.

S200, forming a source electrode 500, a drain electrode 400 and a grid electrode 600 on one side of the epitaxial structure 300 far away from the second substrate 200;

the source 500 and the drain 400 are respectively located at two opposite sides of the gate 600, and the number of the gates 600 is a positive integer greater than or equal to 2; the source electrode 500 and the drain electrode 400 have a channel region therebetween.

According to an embodiment of the present invention, referring to fig. 9, the forming of the source electrode 500, the drain electrode 400, and the gate electrode 600 includes:

s210, etching the epitaxial structure 300 to form an etching table;

s220, depositing a first metal layer and a second metal layer on the etching table to form a source electrode 500 and a drain electrode 400;

according to an embodiment of the present invention, referring to fig. 10, a first metal layer and a second metal layer are deposited on the etched mesa 300a, and alloyed by selecting a suitable annealing condition, a source electrode 500 and a drain electrode 400 may be formed.

It should be noted that the material of the first metal layer and the material of the second metal layer may be the same or different, and those skilled in the art can select them according to the use requirement. Further, the material of the first metal layer and the material of the second metal layer are independently selected from at least one of Ti, Al, Ni, Au.

And S230, depositing a third metal layer on the etching table to form a grid 600.

According to the embodiment of the invention, a third metal layer is deposited in the region between the source electrode 500 and the drain electrode 400, and two or more gate electrodes 600 are prepared, so as to form a structure with adjustable channel width.

Further, the material of the third metal layer is selected from at least one of Ti, Cr, Ni, Pt, and Au.

S300, etching one side, far away from the epitaxial structure 300, of the second substrate 200 to form a groove 211;

further, the recess 211 is located below the channel region 700, i.e. the recess 211 is located at a side of the channel region 700 close to the first substrate 100.

And S400, forming the first substrate 100 on the side, away from the epitaxial structure 300, of the second substrate 200.

Wherein an orthographic projection of the channel region 700 on the first substrate 100 at least partially overlaps with an orthographic projection of the recess 211 on the first substrate 100.

According to an embodiment of the present invention, after the second substrate 200 and the first substrate 100 are bonded, the groove 211 is located between the first substrate 100 and the second substrate 200, and the groove 211 may serve as a pressure reference chamber.

According to some embodiments of the present invention, the gallium nitride pressure sensor prepared by the method has all the features and advantages of the gallium nitride pressure sensor described above, and thus, the detailed description thereof is omitted.

The examples described below in this application, unless otherwise indicated, all materials used are either commercially available or can be prepared by the methods described in this application.

Example 1

1) Selecting a second substrate 200, wherein the thickness of the silicon layer 230 is 20 μm, the thickness of the insulating layer 220 is 1 μm, the thickness of the base layer 210 is 350 μm, pretreating the surface of the second substrate 200, and sequentially growing a GaN buffer layer 310 with the thickness of 1 μm, a GaN channel layer 320 with the thickness of 2 μm, an AlN insertion layer 330 with the thickness of 2nm, an AlGaN barrier layer 340 with the thickness of 30nm and a GaN cap layer 350 with the thickness of 3nm on the second substrate 200 to form an epitaxial structure 300;

2) selectively etching the epitaxial structure 300 by using an Inductively Coupled Plasma (ICP) etching device to form an etched mesa;

3) depositing a metal layer Ti/Al/Ni/Au on the etching table, and selecting proper annealing conditions for alloying to prepare a source electrode 500 and a drain electrode 400;

4) depositing a metal layer Ni/Au on two sides between the source electrode 500 and the drain electrode 400, and preparing two grid electrodes 600 to form a structure with adjustable channel width;

5) selectively etching the base layer 210 of the second substrate 200 below the source-drain channel region 700 of the HEMT device by a deep silicon etching process to form a groove 211, wherein the etching depth is 350 μm;

6) the first substrate 100 is bonded on the side of the second substrate 200 remote from the epitaxial structure 300 such that the recess 211 is located between the first substrate 100 and the second substrate 200, the recess 211 serving as a pressure reference chamber.

It should be noted that the terms "first", "second", "third" and "fourth" in this specification are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. In the description of the present application, the terms "upper", "lower", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present application but do not require that the present application must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present application.

In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.