A displacement field coupled ohmic contact and method of making the same

Abstract

The application discloses a displacement field coupled ohmic contact and a preparation method thereof, which comprises a substrate layer, a bottom gate, a gate dielectric layer and a heterostructure arranged on the substrate layer in sequence, a plurality of sources and drains, all of which are arranged on the surface of the heterostructure and connected by air bridges, and each drain is surrounded by a plurality of sources, a plurality of TSV through holes, each of which penetrates the heterostructure and reaches the bottom gate, and a TSV dielectric layer is arranged on the inner wall of the TSV through hole and an interconnection metal is arranged in the TSV through hole, a plurality of TSV lead-out gates, each of which is arranged on a TSV through hole and in contact with the interconnection metal in the TSV through hole, and the effective width of each source and drain and the distance between adjacent sources and between an adjacent source and a drain are determined by Maxwell electromagnetic theory. The application realizes displacement field transportation, so that the ohmic contact has higher stability and reliability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor, and particularly relates to a displacement field coupled ohmic contact and a preparation method thereof. BACKGROUND

[0002] The third generation compound semiconductor GaN has superior material performance, and is very suitable for manufacturing high-frequency and high-power devices. The devices and circuits have wide application prospects in military and civilian fields. Due to the unique two-dimensional electron gas density of GaN heterojunction, GaN HEMT has very superior microwave power and noise characteristics. The high-power, high-frequency and low-noise GaN devices and circuits have wide application prospects in military and civilian fields. At present, GaN HEMT has become a research focus and hotspot.

[0003] GaN HEMT provides many superior performances, including high-frequency operation, high power density, high-temperature stability and high electric field strength. However, in order to fully utilize these characteristics, it is necessary to reduce the ohmic contact resistance in GaN HEMT as much as possible.

[0004] The ohmic contact resistance is the resistance of the contact area between the metal and the semiconductor of the source and the drain of the semiconductor device, and the size of the resistance directly affects the electrical performance of the device. Low ohmic contact resistance plays a crucial role in achieving excellent device electrical characteristics, such as high transconductance and high saturation current. The prior art solution, i.e. the Ti (titanium) / Al (aluminum) / Ni (nickel) / Au (gold) ohmic metal solution, is a traditional metallization solution for GaN HEMT ohmic contact. The Ti layer acts as a hard surface metal layer, which forms a stable titanium nitride phase through reaction with GaN, and generates a large number of N vacancies in the barrier layer, promoting the combination of metal and GaN and enhancing the conductivity; the Al layer acts as a sacrificial layer, which mainly reacts with titanium to form TiAlX compound during the annealing process to produce low impedance ohmic contact; the Ni layer acts as a barrier layer to prevent Au atoms from diffusing to the nitride interface during the annealing process, and this layer also improves linearity and reliability; the Au layer acts as a top layer, which is mainly responsible for providing good oxidation resistance. The Ti / Al / Ni / Au ohmic metallization solution involves main processes such as electron beam evaporation, sputtering and photolithography during implementation, and good low ohmic contact performance is obtained after a series of annealing processes, and it is widely used in the preparation process of GaN HEMT. After years of practice, it has been proved to have good performance in low contact resistance and high reliability.

[0005] However, since GaN HEMT works in extreme environments of high temperature, high voltage and high power, the stability and reliability of the ohmic contact are required to be higher, so it is imperative to design new ohmic metal solutions and preparation techniques to obtain higher stability and reliability. SUMMARY

[0006] In order to solve the above problems in the prior art, the present application provides a displacement field coupled ohmic contact and a preparation method thereof. The technical problem to be solved by the present application is achieved by the following technical scheme:

[0007] In a first aspect, the present application provides a displacement field coupled ohmic contact, which comprises:

[0008] a substrate layer, a bottom gate, a gate dielectric layer and a heterostructure which are sequentially located on the substrate layer;

[0009] a plurality of sources, each of which is located on a surface of the heterostructure, and all the sources are connected by air bridges;

[0010] a plurality of drains, each of which is located on the surface of the heterostructure, and all the drains are connected by air bridges; wherein each drain is surrounded by a plurality of sources;

[0011] a plurality of TSV through holes, each of which penetrates the heterostructure and reaches the upper surface of the bottom gate, and a TSV dielectric layer is arranged on the inner wall of the TSV through hole, and an interconnection metal is arranged in the TSV through hole;

[0012] a plurality of TSV gate leads, each of which is located on a TSV through hole and contacts the interconnection metal in the TSV through hole;

[0013] wherein the effective width of each source and drain, and the distance between adjacent sources and between adjacent sources and drains are obtained by solving Maxwell's equations, so that the coupling between the radio frequency field and the two-dimensional electron gas generated by the heterostructure is realized based on Maxwell's electromagnetic theory, and the effect of displacement field control is achieved.

[0014] In an embodiment of the present application, each source and drain is a regular polygon structure or a circular structure.

[0015] In an embodiment of the present application, the regular polygon structure includes an equilateral triangle and an equilateral hexagon.

[0016] In an embodiment of the present application, the effective width of each source and drain is 1-3 μm.

[0017] In an embodiment of the present application, the distance between adjacent sources and between adjacent sources and drains is 200-500 nm.

[0018] In an embodiment of the present application, the heterostructure is a thin barrier structure, and the thickness of the barrier layer in the heterostructure is 3-10 nm.

[0019] In one embodiment of the present application, the shape of each source and drain, and the distance between adjacent sources, between adjacent sources and drains is obtained by solving Maxwell equations, including:

[0020] According to Maxwell electromagnetic theory, Maxwell equations at the barrier layer in the heterostructure are established;

[0021] According to the requirement of current continuity in the heterostructure, the Maxwell equations are rewritten;

[0022] The rewritten Maxwell equations are solved, and when the vertical component of the electric field at the barrier layer in the heterostructure is 0, the effective width of each source and drain, and the distance between adjacent sources, between adjacent sources and drains are obtained;

[0023] The rewritten Maxwell equation is expressed as:

[0024]

[0025] Wherein, E Z represents the vertical component of the electric field at the barrier layer in the heterostructure, represents the second order derivative of E Z , j represents the imaginary unit, ω represents the angular frequency, ε represents the dielectric constant of the barrier layer, R sh represents the surface resistance of each source and drain, R sh is calculated by the effective width of each source and drain, d represents the thickness of the barrier layer, E Z is calculated by the distance between adjacent sources, between adjacent sources and drains.

[0026] In one embodiment of the present application, the channel resistance of the heterostructure is calculated by the formula:

[0027] R ch = gw -1 R sh ;

[0028] Wherein, R ch represents the channel resistance of the heterostructure, g represents the distance between adjacent sources, between adjacent sources and drains, w represents the effective width of each source and drain, R sh represents the surface resistance of each source and drain, R sh is calculated by the effective width of each source and drain.

[0029] In the second aspect, the embodiments of the present application provide a preparation method of displacement field coupled ohmic contact, and the preparation method comprises:

[0030] A bottom gate is made on a substrate layer;

[0031] growing a gate dielectric layer on the bottom gate;

[0032] growing a heterostructure on the gate dielectric layer;

[0033] lithographing a plurality of source regions and a plurality of drain regions on the heterostructure, fabricating a source on each source region and a drain on each drain region respectively; wherein each drain is surrounded by a plurality of sources;

[0034] etching the heterostructure until the upper surface of the bottom gate to form a plurality of TSV through holes, and leading out the bottom gate by each TSV through hole;

[0035] fabricating air bridges between all the sources and between all the drains respectively by air bridge process, so that all the sources are common-sourced and all the drains are common-drained by air bridges;

[0036] wherein during the preparation process, the effective width of each source and drain, and the distance between adjacent sources and between adjacent sources and drains are obtained by solving Maxwell's equations, so as to realize the coupling of the radio frequency field and the two-dimensional electron gas generated by the heterostructure based on Maxwell's electromagnetic theory, and achieve the effect of displacement field control.

[0037] In an embodiment of the present application, before growing the heterostructure on the gate dielectric layer, further comprising:

[0038] performing planarization treatment on the surface of the gate dielectric layer.

[0039] Advantages of the present application:

[0040] The displacement field coupled ohmic contact proposed in the present application replaces the traditional tunnel transport mechanism with displacement field transport mechanism, and is verified by calculation according to Maxwell's electromagnetic theory. By changing the voltage on the source and drain, the radio frequency field can be micro-operated, so that the radio frequency field can be coupled with the two-dimensional electron gas generated by the heterostructure. Therefore, the displacement field transport mechanism replaces the traditional device tunnel transport mechanism, so that the on-state resistance close to the theoretical quantum limit can be obtained, and the trade-off between the on-state resistance and the off-state capacitance of the conventional device is broken. Through strong electric field coupling between the metal electrode and the two-dimensional electron gas of the heterostructure, the contact resistance and parasitic effects can be reduced, and high linearity can be obtained. Since the carriers no longer reach the metal electrode by tunneling, there is no loss problem, so more sources and drains can be made to realize the transmission of larger current. At the same time, the resistance between the ohmic metal and the heterostructure is extremely small and can be ignored, and the actual effective resistance is mostly from the channel resistance, so the distance between the source and the drain, and the distance between the source and the source, that is, the channel width, is limited to achieve a smaller channel resistance. In summary, the ohmic contact proposed in the present application has higher stability and reliability.

[0041] The application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a structure schematic diagram of a displacement field coupled ohmic contact provided by an embodiment of the application;

[0043] Figure 2 is a top view schematic diagram of a single regular hexagon source-drain combined unit (including a TSV through-hole leading gate) provided by an embodiment of the application;

[0044] Figure 3 is a back view schematic diagram of a single regular hexagon source-drain combined unit (including a bottom layer gate) provided by an embodiment of the application;

[0045] Figure 4 is a top view structure schematic diagram of a plurality of regular hexagon source-drain units expansion provided by an embodiment of the application;

[0046] Figure 5 is a top view structure schematic diagram of a plurality of circular source-drain units expansion provided by an embodiment of the application;

[0047] Figure 6 is a top view structure schematic diagram of a plurality of regular triangle source-drain units expansion provided by an embodiment of the application;

[0048] Figure 7 is a schematic diagram of metal electrode plate edge electromagnetic field distribution provided by an embodiment of the application;

[0049] Figure 8 is a schematic diagram of reaching displacement field control effect after metal-two-dimensional electron gas coupling provided by an embodiment of the application;

[0050] Figure 9 is a top view structure schematic diagram of leading out source-drain-gate three terminals in GSG form provided by an embodiment of the application;

[0051] Figure 10 is a flow schematic diagram of a preparation method of a displacement field coupled ohmic contact provided by an embodiment of the application;

[0052] Figures 11(a) to 11(f) is a corresponding structure schematic diagram of a preparation process of a displacement field coupled ohmic contact provided by an embodiment of the application. DETAILED DESCRIPTION

[0053] The application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0054] The traditional ohmic metal scheme conducts current by forming an ohmic contact between the metal and the semiconductor layer, because a potential barrier is generated when the metal and the semiconductor layer are in contact, and the carriers pass through the potential barrier to the other side by two mechanisms, i.e., thermal emission and tunneling, to achieve the purpose of conducting current. When the voltage on the source and drain is not very large, the energy obtained by the carriers in the barrier channel from the electric field is not enough for them to directly cross the barrier, i.e., the thermal emission mechanism, at this time the carrier transport mechanism is tunneling, i.e., the carriers directly pass through the barrier to the other side with a certain probability to form a current. Since not all the excited carriers can tunnel to the other side of the barrier to form a current, there will be a relatively large resistance. Since the above phenomenon occurs when each drain and semiconductor layer are in contact, the traditional device will not have multiple drains, which will double the number of carriers that cannot tunnel through the barrier, thereby making the ohmic characteristics of the device worse. Therefore, how to still have good ohmic characteristics on the basis of making more drains is a technical difficulty to be overcome.

[0055] Based on the above problems, the embodiment of the present application proposes a displacement field coupled ohmic contact and a preparation method thereof based on a relatively novel carrier transport mechanism.

[0056] In a first aspect, referring to Figure 1 The embodiment of the present application provides a displacement field coupled ohmic contact, which comprises:

[0057] a substrate layer, a bottom gate, a gate dielectric layer and a heterostructure which are sequentially located on the substrate layer;

[0058] a plurality of source electrodes, each of which is located on the surface of the heterostructure, and all the source electrodes are connected by air bridges;

[0059] a plurality of drain electrodes, each of which is located on the surface of the heterostructure, and all the drain electrodes are connected by air bridges; wherein each drain electrode is surrounded by a plurality of source electrodes;

[0060] a plurality of TSV through holes, each of which penetrates the heterostructure to the upper surface of the bottom gate, and a TSV dielectric layer is arranged on the inner wall of the TSV through hole, and an interconnection metal is arranged in the TSV through hole;

[0061] a plurality of TSV gate leads, each of which is located on a TSV through hole and in contact with the interconnection metal in the TSV through hole.

[0062] The embodiment of the present application adopts a bottom gate structure, which is located below the heterostructure, and thus a TSV (Through Silicon Via) via hole is designed to lead out the bottom gate through the TSV via hole. The gate material selected for the bottom gate should have good interface characteristics, be able to form a good Schottky contact between the gate material and the semiconductor material, have high conductivity, be able to ensure effective control of the bottom gate on the device channel switch, and have good stability and processability, its chemical stability and corrosion resistance, and be able to effectively resist stress and deformation caused by thermal expansion, and be able to adapt to more complex working environments. Preferably, the gate electrode material is Au, and the thickness is 200 nm to 500 nm, more preferably the thickness is 400 nm.

[0063] The gate dielectric layer of the embodiment of the present application should have good insulation performance, be able to effectively isolate the gate electrode and the source-drain region, prevent current leakage and electron loss, and improve the insulation effect of the device; and the dielectric constant of the gate dielectric layer is usually low, which helps to reduce the capacitance and loss, and improve the high-frequency performance of the device, and its heat resistance and reliability are very good, and it can adapt to different working environments. Preferably, the gate dielectric layer material is SiO2, and the thickness is 100 nm to 300 nm, more preferably the thickness is 100 nm.

[0064] The heterostructure of the embodiment of the present application is a thin barrier structure, which includes a channel layer and a barrier layer from bottom to top; the thickness of the barrier layer in the heterostructure is 3 nm to 10 nm, more preferably the thickness of the barrier layer is 7 nm, and the thickness of the channel layer is 10 nm to 50 nm, more preferably the thickness of the channel layer is 30 nm. The heterostructure is preferably a GaN-based and GaAs-based heterostructure, because the GaN-based and GaAs-based heterostructure has high electron mobility and two-dimensional electron gas density and low sheet resistance, and the heterostructure has good matching degree in lattice matching. This advantage makes it possible to realize low stress and deformation during growth, which is beneficial to improve the quality of the material and the integrity of the crystal structure. For example, when the heterostructure is a GaN-based heterostructure, it can be AlGaN / GaN, AlInN / GaN, AlN / GaN, ScAlN / GaN, AlGaN / InGaN, AlInN / InGaN, etc.; when the heterostructure is a GaAs-based heterostructure, it can be AlGaAs / GaAs, InAlAs / GaAs, AlGaAs / InGaAs, etc. In order to improve the polarization strength, the heterostructure of the embodiment of the present application further includes an insertion layer located between the channel layer and the barrier layer, and the material can be AlN, and the thickness is 1 nm to 5 nm, more preferably the thickness of the insertion layer is 3 nm.

[0065] The source-drain metal selected for the drain and source of the embodiment of the present application should have high conductivity to ensure effective transmission of current and reduce resistance and power consumption. The contact between the drain metal and the GaN material should be good, with low contact resistance and high interface quality, to ensure smooth electron transmission and improve device performance. The preferred source-drain metal is Ti, with a thickness of 100-300 nm, more preferably 120 nm.

[0066] The source and drain of the embodiment of the present application are regular polygon structures or circular structures; more preferably, the regular polygon structures include equilateral triangles and regular hexagons; more preferably still, the regular polygon structure is a regular hexagon. If a regular hexagon is used as the source and drain pattern, Figure 2 The top view structure of a single regular hexagonal source-drain combination unit is shown, and Figure 2 The case where the bottom gate is led out through a TSV via is also shown, Figure 3 The back view structure of a single regular hexagonal source-drain combination unit is shown, and Figure 3 The shape and position of the bottom gate are also shown, Figure 4 The top view structure of multiple regular hexagonal source-drain combination units is shown, and Figure 4 It can be seen that the source and drain can be extended indefinitely in a honeycomb shape, thereby further improving the performance of the device. Figure 5 The top view structure of multiple circular source-drain combination units is shown, Figure 6 The top view structure of multiple triangular source-drain combination units is shown, illustrating that the ohmic contact proposed in the present application can use other regular patterns as the source-drain electrode scheme.

[0067] Since the ohmic contact structure proposed in the embodiment of the present application is scalable, there may be problems such as difficulty in leading out the source and drain, crosstalk between the leads, etc. when performing S-parameter measurement on a large-scale device. Therefore, the sources and the drains are respectively connected by air bridges to achieve common source and common drain. The air bridge can reduce the impact of crosstalk to some extent. In addition, since the air bridge structure is erected on the surface of the device and does not change the device structure, it can avoid parasitic effects. At the same time, since the medium below the air bridge is air, the air bridge structure can effectively reduce the capacitive load, thereby improving the high-frequency performance and speed of the device, making it more stable and efficient at high frequencies.

[0068] After the three ports of the source-drain gate of the device are led out in the embodiment of the present application, as shown in Figure 7 The GSG (Ground-Signal-Ground) probe can be used to measure the radio frequency parameters of the device more conveniently. How to use the GSG probe for measurement can use the prior art, and will not be described in detail here. Figures 2 to 7 In the formula, S represents the source, and D represents the drain,Figure 3 In the formula, G represents the bottom gate.

[0069] The effective width of each source and drain and the distance between adjacent sources and between adjacent sources and drains is obtained by solving Maxwell equations, so that the radio frequency field is coupled with the two-dimensional electron gas generated by the heterostructure based on Maxwell electromagnetic theory, and the effect of displacement field control is achieved. Figure 2 As shown in the regular hexagonal source and drain, the effective width w is the length of the diagonal top point line, and the distance g is the shortest distance between adjacent sources and between adjacent sources and drains. Figure 5 As shown in the circular source and drain, the effective width w is the length of the diameter of the circle, and the distance g is the shortest distance between adjacent sources and between adjacent sources and drains. Figure 6 As shown in the triangular source and drain, the effective width w is the length of the vertical distance from one vertex to the opposite side, and the distance g is the shortest distance between adjacent sources and between adjacent sources and drains.

[0070] The embodiment of the application provides a process for obtaining the shape of each source and drain and the distance between adjacent sources and between adjacent sources and drains by solving Maxwell equations, comprising:

[0071] According to Maxwell electromagnetic theory, Maxwell equations at the barrier layer in the heterostructure are established; the Maxwell equations are rewritten according to the current continuity requirement in the heterostructure; the rewritten Maxwell equations are solved, and when the vertical component of the electric field at the barrier layer in the heterostructure is 0, the effective width of each source and drain and the distance between adjacent sources and between adjacent sources and drains are obtained; wherein, the formula of the rewritten Maxwell equations is:

[0072]

[0073] wherein, E Z represents the vertical component of the electric field at the barrier layer in the heterostructure, represents the second-order derivative of E Z , j represents the imaginary unit, ω represents the angular frequency, ε represents the dielectric constant of the barrier layer, R sh represents the surface resistance of each source and drain, R sh is calculated by the effective width of each source and drain, d represents the thickness of the barrier layer, E Z is calculated by the distance between adjacent sources and between adjacent sources and drains. More specifically:

[0074] For the structure shown in Figure 1, a barrier layer with thickness d, dielectric constant ε, and permeability μ0 is sandwiched between the top metal and a semiconductor layer (channel layer) with thickness d0 and resistivity ρ. Assuming the electric field is symmetrical along the y-direction, and based on Maxwell's electromagnetic theory, Maxwell's equations at the barrier layer in the heterostructure are established, expressed as:

[0075]

[0076] Among them, E Z J represents the vertical component of the electric field at the barrier layer in a heterostructure. x This represents the current density at the channel layer in a heterostructure. Indicates E Z Find the second derivative. Indicates J x Find the first derivative. For the case where ρ→0, equation (1) can be simplified to the ordinary Helmholtz equation with transverse electromagnetic mode solutions. However, for the case of non-zero ρ and small d, the second term in equation (1) The third item ε can be replaced. 2 E Z In this case, considering the current continuity requirement in the heterostructure, we can obtain:

[0077]

[0078] If we consider the geometry of the source and drain, and pattern the stripes with oscillating subwavelength lengths to form a metastructure, then in this embodiment of the invention, each source and drain needs to be a regular polygonal or circular structure. In this case, the gaps in the semiconductor structure are the distances between adjacent sources and between adjacent sources and drains, rather than the direct gaps between electrodes in conventional semiconductor structures. Therefore, E Z It also satisfies the equation:

[0079]

[0080] Where, k m This represents the effective wavenumber of the oscillating subwavelength mode, from which E can be obtained. Z It is a sine function with x as the independent variable. In this embodiment of the invention, x corresponds to the distance g between adjacent sources and between adjacent sources and drains. In this case, E can be controlled by adjusting the distance g. Z , making such Figure 1 The structure shown exhibits an almost zero E at the edge of the metal field plate. Z ,like Figure 8 The values ​​marked as x (i.e., g) represent the ideal coupling values, thus generating ideal metal-two-dimensional electron gas coupling and achieving displacement field manipulation, as shown below. Figure 9 As shown,Figure 9 In the formula, E represents the electric field at the barrier layer in the heterostructure, and Current represents the current. It can be seen that the current is injected from the drain to the source. For a conventional device, since the channel stripes between the metal electrodes are not patterned, the Maxwell equation, i.e. formula (1), cannot be simplified to the form of formula (3), and at most can be simplified to the form of formula (2), which leads to the fact that the electric field E Z at the boundary position of the metal electrode is not 0, such as Figure 8 indicated by the mark, which is the boundary position of the metal electrode in the general case, cannot reach the ideal coupling condition. At the same time, for the displacement field manipulation, excellent characteristics of signal transmission between the two sides of the electrode are also provided, because the two electric fields have the same direction, and the current is injected from one electrode to the other electrode. In addition to the same polarity of E Z in the two adjacent electrodes, compared with the case of the straight gap device, the amplitude is also significantly reduced. In this case, the effective potential difference on both sides of the barrier layer and the gap will offset each other, thereby generating excellent metal-semiconductor coupling. Finally, in the embodiment of the present application, the channel resistance of the heterostructure is calculated as:

[0081] R ch = g w -1 R sh (4);

[0082] wherein R ch represents the channel resistance of the heterostructure, g represents the distance between adjacent source electrodes and between adjacent source electrodes and the drain electrode, w represents the effective width of each source electrode and drain electrode, R sh represents the surface resistance of each source electrode and drain electrode, and R sh is calculated by the effective width of each source electrode and drain electrode. According to the derivation formula of the channel resistance, in order to ensure a small channel resistance, the effective width w of the source electrode and the drain electrode in the embodiment of the present application should be large, and the value of w is preferably 1 μm to 3 μm, and the distance g between the source electrode and the drain electrode and between the source electrodes should be as small as possible, and the value of g is preferably 200 nm to 500 nm.

[0083] In summary, the displacement field coupled ohmic contact provided by the embodiment of the present application replaces the traditional tunnel transport mechanism with the displacement field transport mechanism, and the calculation and verification are based on the Maxwell electromagnetic theory. The micro-operation on the radio frequency field is achieved by changing the voltage on the source and drain, so that the radio frequency field can be coupled with the two-dimensional electron gas generated by the heterostructure, and thus the displacement field transport mechanism replaces the traditional device tunnel transport mechanism, thereby obtaining an open-state resistance close to the theoretical quantum limit and breaking the trade-off between the open-state resistance and the off-state capacitance of the conventional device. Through the strong electric field coupling between the metal electrode and the two-dimensional electron gas of the heterostructure, the contact resistance and the parasitic effect can be reduced, and high linearity can be obtained. Since the carriers no longer pass through the tunnel to reach the metal electrode, there is no loss problem, so more source and drain electrodes can be made to realize the transmission of larger current to achieve the purpose of effectively controlling the radio frequency field. At the same time, the resistance between the ohmic metal and the heterostructure is extremely small and can be ignored, and the actual effective resistance is mostly from the channel resistance, so the distance between the source and the drain, that is, the channel width, is limited to achieve a smaller channel resistance. In summary, the ohmic contact provided by the present application has higher stability and reliability.

[0084] In a second aspect, referring to Figure 10 The embodiment of the present application provides a preparation method of the displacement field coupled ohmic contact, and the preparation method comprises the following steps:

[0085] S10, a bottom gate is made on a substrate layer.

[0086] The embodiment of the present application can use an electron beam evaporation technology to make the bottom gate, as shown in FIG. 11(a).

[0087] S20, a gate dielectric layer is grown on the bottom gate.

[0088] The embodiment of the present application can use a PECVD (Plasma Enhanced Chemical Vapor Deposition, Plasma Enhanced Chemical Vapor Deposition) process to grow the gate dielectric layer, as shown in FIG. 11(b).

[0089] In addition, after the growth of the gate dielectric layer and before the growth of the heterostructure, the embodiment of the present application further comprises a planarization treatment on the surface of the gate dielectric layer. The planarization treatment can polish the surface of the gate dielectric layer by using a chemical mechanical polishing (CMP) process, so that the surface is very smooth and the surface roughness is less than 0.4 nm. The planarization treatment can make the protrusions generated in the deposition process of the gate dielectric layer caused by the bottom gate smooth, thereby ensuring good contact with the heterostructure.

[0090] S30, a heterostructure is grown on the gate dielectric layer.

[0091] The heterostructure of the embodiment of the present application can be made by MOCVD (Metal-organic Chemical Vapor Deposition) process, or directly selected from existing integrated heterostructures, as shown in Fig. 11 (c).

[0092] S40, photoetching a plurality of source regions and a plurality of drain regions on the heterostructure, respectively making a source electrode in each source region and a drain electrode in each drain region; wherein each drain electrode is surrounded by a plurality of source electrodes; in the preparation process, the effective width of each source electrode and drain electrode, and the distance between adjacent source electrodes and between adjacent source electrodes and drain electrodes are obtained by solving Maxwell's equations, so as to realize the coupling of the radio frequency field and the two-dimensional electron gas generated by the heterostructure based on Maxwell's electromagnetic theory, and achieve the effect of displacement field control.

[0093] The embodiment of the present application can use electron beam evaporation technology to make a plurality of drain electrodes and a plurality of source electrodes, as shown in Fig. 11 (d), which only shows one drain electrode and two source electrodes. The shape of the source electrode and the drain electrode on the heterostructure should be a regular polygon structure or a circular structure, and the drain electrode should be in the center position, and the plurality of source electrodes should be arranged around the drain electrode, and sufficient space should be reserved for the next step of TSV process to lead out the bottom gate electrode when making the source electrode and the drain electrode.

[0094] Considering that the number of channels between the source electrode and the drain electrode should be as many as possible, and the structure needs to be scalable, the optimal electrode pattern is a regular hexagon, and in the preparation process, the effective width of each source electrode and drain electrode, and the distance between adjacent source electrodes and between adjacent source electrodes and drain electrodes are determined by Maxwell's electromagnetic theory, so that the radio frequency field and the two-dimensional electron gas generated by the heterostructure are coupled, and the effect of displacement field control is achieved.

[0095] S50, etching the heterostructure until the upper surface of the bottom gate electrode forms a plurality of TSV through holes, and using each TSV through hole to lead out the bottom gate electrode.

[0096] In order to obtain the S parameters of the radio frequency device, the source-drain-gate electrodes of the device need to be led out, and for the leading out of the bottom gate electrode, the embodiment of the present application uses TSV technology to achieve, specifically: using ICP (Inductively Coupled Plasma) process to dry etch the heterostructure until the upper surface of the bottom gate electrode to form a plurality of TSV through holes, and each TSV through hole is used to lead out the bottom gate.

[0097] Then, a PECVD process is used to grow a TSV dielectric layer on the inner wall of each TSV via, and an electron beam evaporation technique is used to grow an interconnection metal in each TSV via. The TSV dielectric layer electrically isolates the interconnection metal in the TSV via from the main body of the device, and the material of the TSV dielectric layer is preferably SiO2; the interconnection metal is used to lead out the bottom gate, and the material of the interconnection metal is preferably W (tungsten) or Cu (copper).

[0098] Finally, a TSV lead-out gate is made on the interconnection metal at each TSV via, as shown in Fig. 11 (e).

[0099] S60, air bridges are made between all the sources and between all the drains respectively by using an air bridge process, so that all the sources are connected to form a common source through the air bridges, and all the drains are connected to form a common drain through the air bridges.

[0100] For the lead-out of the sources and the drains, the embodiment of the present application interconnects and leads out by using the air bridge process, in particular:

[0101] First, a bridge pier is photoetched to define a bridge pier shape for supporting the air bridge structure, and then source-drain metal sputtering is immediately performed; then a bridge surface is photoetched to define a bridge surface pattern, and the bridge body is made by Au electroplating; finally, the source-drain metal is etched and the photoresist is removed, to complete the making of the air bridge, as shown in Fig. 11 (f). The sources and the drains are connected to form a common source and a common drain respectively through the air bridges, and Fig. 11 (f) only shows that the sources and the drains can be connected through the air bridges, but not that the sources and the drains are connected through the air bridges.

[0102] For the preparation method example of the second aspect, since it is basically similar to the structural example of the first aspect, the description is relatively simple, and the relevant parts refer to the part of the description of the structural example of the first aspect.

[0103] In the description of the present application, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0104] Although the present application has been described in connection with certain embodiments, persons skilled in the art will understand and appreciate that many modifications can be made to the described embodiments and these modifications can be made without departing from the scope of the application in practical matter. Throughout the specification, the word "comprising" does not exclude the presence of other elements or additional steps. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. It is further noted that certain measures can be described as being implemented in software even though they are not specifically mentioned in this respect. It is believed that the applicant has invented other inventions which are not specifically described herein. It is intended that the claims shall cover all inventions which fall within the scope of the present application and its equivalents.

[0105] The above description is further detailed in connection with specific preferred embodiments of the application, and it is not intended to limit the specific implementation of the application to these descriptions. For those skilled in the art, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, and all of them should be considered as falling within the scope of the present application.

Claims

1. A displacement field coupled ohmic contact, comprising: The ohmic contact comprises: a substrate layer; a bottom gate, a gate dielectric layer and a heterostructure successively on the substrate layer; a plurality of sources, each on a surface of the heterostructure, all the sources being connected by air bridges; a plurality of drains, each on the surface of the heterostructure, all the drains being connected by air bridges; wherein each drain is surrounded by a plurality of sources; a plurality of TSV through holes, each TSV through hole penetrating the heterostructure to the upper surface of the bottom gate, and a TSV dielectric layer being arranged on the inner wall of the TSV through hole, and an interconnection metal being arranged in the TSV through hole; a plurality of TSV gate leads, each TSV gate lead being arranged on a TSV through hole and contacting the interconnection metal in the TSV through hole; wherein each source and drain is a regular polygon structure or a circular structure; the effective width of each source and drain, and the distance between adjacent sources and between adjacent sources and drains are obtained by solving Maxwell's equations, so that the radio frequency field and the two-dimensional electron gas generated by the heterostructure are coupled based on Maxwell's electromagnetic theory, and the effect of displacement field control is achieved; the process of obtaining the shape of each source and drain, and the distance between adjacent sources and between adjacent sources and drains by solving Maxwell's equations comprises: establishing Maxwell's equations at the barrier layer in the heterostructure according to Maxwell's electromagnetic theory; rewriting Maxwell's equations according to the current continuity requirement in the heterostructure; solving the rewritten Maxwell's equations, and obtaining the effective width of each source and drain, and the distance between adjacent sources and between adjacent sources and drains when the vertical component of the electric field at the barrier layer in the heterostructure is 0; wherein the formula of the rewritten Maxwell's equations is: ； wherein represents a vertical component of the electric field at the barrier layer in the heterostructure, represents the second derivative of with respect to represents the imaginary unit, represents the angular frequency, represents the dielectric constant of the barrier layer, represents the surface resistance of each source and drain electrode, is calculated by the effective width of each source and drain electrode, represents the thickness of the barrier layer, is calculated by the distance between adjacent source electrodes, between adjacent source and drain electrodes.

2. The displacement field coupled ohmic contact of claim 1, wherein, the regular polygon structure comprises an equilateral triangle and an equilateral hexagon.

3. The displacement field coupled ohmic contact of claim 1, wherein, The effective width of each source and drain is 1 μm to 3 μm.

4. The displacement field coupled ohmic contact of claim 1, wherein, The distance between adjacent sources and between adjacent sources and drains is 200 nm to 500 nm.

5. The displacement field coupled ohmic contact of claim 1, wherein, The heterostructure is a thin barrier structure; the thickness of the barrier layer in the heterostructure is 3 nm to 10 nm.

6. The displacement field coupled ohmic contact of claim 1, wherein, The channel resistance of the heterostructure is calculated according to the formula: ； wherein, represents the channel resistance of the heterostructure, represents the distance between adjacent sources, between adjacent sources and the drain, represents the effective width of each source and drain, represents the surface resistance of each source and drain, calculated by the effective width of each source and drain.

7. A method of fabricating a displacement field coupled ohmic contact, comprising: The preparation of the ohmic contact for the displacement field coupling according to any one of claims 1 to 6 comprises: manufacturing a bottom gate on a substrate layer; growing a gate dielectric layer on the bottom gate; growing a heterostructure on the gate dielectric layer; photolithographing a plurality of source regions and a plurality of drain regions on the heterostructure, manufacturing a source in each source region, and manufacturing a drain in each drain region; wherein each drain is surrounded by a plurality of sources; etching the heterostructure to the upper surface of the bottom gate to form a plurality of TSV through holes, and leading out the bottom gate by each TSV through hole; manufacturing air bridges between all the sources and between all the drains by an air bridge process, so that all the sources are common sources and all the drains are common drains by the air bridges; In the preparation process, the effective width of each source and drain, and the distance between adjacent sources and between adjacent source and drain are obtained by solving Maxwell equations, so that the radio frequency field and the two-dimensional electron gas generated by the heterostructure are coupled based on Maxwell electromagnetic theory, and the effect of displacement field control is achieved.

8. The method of claim 7, wherein the method further comprises: Before growing the heterostructure on the gate dielectric layer, further comprising: The surface of the gate dielectric layer is subjected to a planarization treatment.

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