A MEMS monolithic integrated circuit and its preparation method

Abstract

The present application discloses a MEMS monolithic integrated circuit and a method for preparing the same, the method comprising: preparing a substrate, forming a diamond layer on the substrate; forming an aluminum nitride layer on the diamond layer; making a MEMS device and a matching circuit on the aluminum nitride layer; making a first interconnection structure inside the matching circuit, and a second interconnection structure between the MEMS device and the matching circuit. The present application forms a diamond layer on a substrate, uses aluminum nitride as a piezoelectric material, forms a MEMS integrated device, and achieves the technical effect of improving the operating frequency and bandwidth of the MEMS device.

Description

Technical Field

[0001] The present application relates to the field of wireless communication technology, and in particular to a MEMS monolithic integrated circuit and a method for preparing the same. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) is a small device or structural system that may include integrated mechanical and electronic devices, which can sense immediate or local environmental changes; or perform some physical interaction with the immediate or local environment when there is a corresponding signal input.

[0003] SAW (Surface Acoustic Wave) filters are RF (Radio Frequency) related applications in MEMS and are commonly found in electronic products. Currently, surface acoustic wave filters are usually made of lithium tantalate and lithium niobate materials. The operating frequency of filters made of these two materials is below 3GHz, which cannot meet the requirements of 5G and future communications. Summary of the invention

[0004] The main purpose of the present application is to provide a MEMS monolithic integrated circuit and a method for manufacturing the same, aiming to solve the problem of low operating frequency and bandwidth of MEMS devices.

[0005] To achieve the above object, the present application provides a method for preparing a MEMS monolithic integrated circuit, the method comprising:

[0006] preparing a substrate and forming a diamond layer on the substrate;

[0007] forming an aluminum nitride layer on the diamond layer;

[0008] Fabricating a MEMS device and a matching circuit on the aluminum nitride layer;

[0009] A first interconnection structure inside the matching circuit and a second interconnection structure between the MEMS device and the matching circuit are manufactured.

[0010] Optionally, the step of forming a diamond layer on the substrate comprises:

[0011] polishing and cleaning the substrate;

[0012] forming a diamond layer on the cleaned substrate by chemical vapor deposition;

[0013] The surface of the diamond layer is polished.

[0014] Optionally, before the step of forming an aluminum nitride layer on the diamond layer, the method further comprises:

[0015] forming a seed layer on the diamond layer;

[0016] The seed layer is annealed.

[0017] Optionally, the step of forming an aluminum nitride layer on the diamond layer comprises:

[0018] An aluminum nitride layer is sputtered on the diamond layer by a reactive magnetron sputtering method.

[0019] Optionally, after the step of forming an aluminum nitride layer on the diamond layer, the method further comprises:

[0020] The aluminum nitride layer is doped, wherein the doping element is at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, chromium, zirconium, manganese and magnesium, and the doping concentration is 1at%-50at%.

[0021] Optionally, the step of manufacturing a MEMS device on the aluminum nitride layer includes:

[0022] Evaporating or sputtering a metal material on the aluminum nitride layer to form a metal layer, wherein the metal material is gold, platinum, copper, aluminum, molybdenum, tungsten, titanium or tantalum;

[0023] The metal layer is sequentially subjected to coating, alignment, exposure, development, etching, degumming and cleaning processes, and a reflective grating and an interdigital transducer are manufactured on the metal layer.

[0024] Optionally, after the step of manufacturing a MEMS device on the aluminum nitride layer, the method further includes:

[0025] A passivation layer is deposited on the metal layer, and the material used for the passivation layer is silicon oxide, silicon nitride, aluminum oxide or gallium oxide.

[0026] Optionally, the step of fabricating a matching circuit on the aluminum nitride layer includes:

[0027] Inductors, capacitors and resistors are manufactured on the aluminum nitride layer. The inductors include inductor metal windings, inductor metal inter-dielectric layers, inductor through-holes and inductor metal connections. The capacitors include capacitor metal electrodes, capacitor dielectric layers, capacitor metal inter-dielectric layers, capacitor through-holes and capacitor metal connections. The resistors include thin-film resistors, resistor metal inter-dielectric layers, resistor through-holes and resistor metal connections.

[0028] Optionally, before the step of manufacturing a MEMS device and a matching circuit on the aluminum nitride layer, the method further comprises:

[0029] The aluminum nitride layer is etched to provide an isolation zone between the MEMS device and the matching circuit.

[0030] In addition, to achieve the above-mentioned purpose, the present application also provides a MEMS monolithic integrated circuit, which is prepared by the MEMS monolithic integrated circuit preparation method described above.

[0031] The present application makes the piezoelectric material aluminum nitride on the surface of the diamond layer, combines the excellent piezoelectric properties of the aluminum nitride material with the high acoustic wave transmission speed of diamond, and produces a high-frequency surface acoustic wave MEMS device. At the same time, the surface acoustic wave MEMS device and the matching circuit are integrated on the same chip to form a MEMS monolithic integrated circuit, thereby achieving the purpose of increasing bandwidth, improving chip performance, reducing chip area, and reducing manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic flow chart of a first embodiment of a method for preparing a MEMS monolithic integrated circuit of the present application;

[0033] Figure 2 A schematic diagram of manufacturing a diamond layer for the method of manufacturing a MEMS monolithic integrated circuit of the present application;

[0034] Figure 3 A schematic diagram of manufacturing an aluminum nitride layer according to the method for preparing a MEMS monolithic integrated circuit of the present application;

[0035] Figure 4 Schematic diagram of a SAW resonator based on AlN material;

[0036] Figure 5a A schematic diagram of manufacturing a metal layer in the method for manufacturing a MEMS monolithic integrated circuit of the present application;

[0037] Figure 5b A schematic diagram of a SAW resonator produced by the method for producing a MEMS monolithic integrated circuit of the present application;

[0038] Figure 5c A schematic diagram of etching a metal layer and an aluminum nitride layer in the method for preparing a MEMS monolithic integrated circuit of the present application;

[0039] Figure 6 It is a schematic diagram of the structure of a MEMS monolithic integrated circuit;

[0040] Figure 7 A schematic diagram of making a seed layer for the method of preparing a MEMS monolithic integrated circuit of the present application;

[0041] Figure 8a A schematic diagram of manufacturing a SAW resonator according to a third embodiment of the method for manufacturing a MEMS monolithic integrated circuit of the present application;

[0042] Figure 8b A schematic diagram of manufacturing an aluminum nitride layer according to a third embodiment of the method for manufacturing a MEMS monolithic integrated circuit of the present application;

[0043] Fig. 9 This is a connection diagram of the MEMS monolithic integrated circuit of this application;

[0044] Fig.10 Schematic diagram of the wafer produced for this application.

[0045] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, and back), such directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0048] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text is to include three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. The technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0049] The present application embodiment provides a method for preparing a MEMS monolithic integrated circuit, referring to Figure 1 , Figure 1 This is a flow chart of a first embodiment of a method for manufacturing a MEMS monolithic integrated circuit of the present application.

[0050] In this embodiment, the method for preparing the MEMS monolithic integrated circuit includes:

[0051] Step S10, preparing a substrate, and forming a diamond layer on the substrate;

[0052] Figure 2 This is a schematic diagram of making a diamond layer on a substrate. The material of the substrate can be silicon (including silicon-on-insulator SOI), SiC, sapphire, glass or other substrates. The size of the substrate is determined by the material, generally 2 inches to 6 inches. For a silicon substrate, the size can be 4 inches to 12 inches.

[0053] The substrate is polished and cleaned; a diamond layer is formed on the cleaned substrate by chemical vapor deposition; and the surface of the diamond layer is polished.

[0054] The substrate is first polished to form a smooth surface. The surface is ultrasonically cleaned with acetone or other solutions and mounted on a molybdenum substrate holder to ensure uniform temperature.

[0055] There are many methods for producing diamond materials. Commonly used methods include High Pressure High Temperature (HPHT) method and Chemical Vapor Deposition (CVD) technology.

[0056] The high-pressure and high-temperature synthesis method generally requires a pressure and temperature of 10GPa and above 3000℃ to transform graphite into diamond. If a metal catalyst is involved (such as Fe, Ni, Mn, Co, etc. and their alloys), the temperature and pressure conditions required for graphite to become diamond will be greatly reduced, so the current high-temperature and high-pressure synthesis of diamonds all involve metal catalysts. The metal catalyst as a solvent is between the carbon source (generally graphite) and the diamond seed crystal. The carbon source is at the high-temperature end and the seed crystal is at the low-temperature end. Since the solubility of the carbon source at the high-temperature end is greater than that at the low-temperature end, the solubility difference caused by the temperature difference becomes the driving force for the carbon source to diffuse from the high-temperature end to the low-temperature end. The carbon source gradually precipitates at the seed crystal, and the diamond crystal gradually grows. Since the driving force for crystal growth is caused by the temperature difference, this method is also called the temperature difference method.

[0057] Chemical vapor deposition technology introduces gas into a vacuum chamber, and then uses plasma or microwaves to activate and decompose gas molecules, causing carbon atoms to accumulate on the substrate to form diamonds. Chemical vapor deposition can be divided into: Plasma Enhanced Chemical Vapor Deposition (PECVD) and Microwave Plasma Chemical Vapor Deposition (MPCVD).

[0058] When producing diamond using PECVD technology, methane (CH4) and hydrogen (H2) are usually used as feed gas streams at temperatures between 600°C and 1000°C in a proprietary reactor system. Diamond films are deposited by passing a methane and hydrogen gas mixture through a reaction zone. Decomposition of these gases occurs at the substrate surface by plasma bombardment. Using the mixed gas, the H atoms contribute to the dissociation of double or triple bonds of carbon. During deposition, the concentration of methane in the mixed gas is between 1vol%-2vol%, the mixed gas pressure is 1kPa-10kPa, the mixed gas flow rate is 10sccm-100sccm, and the temperature of the substrate is 800°C-1000°C.

[0059] The diamond layer is formed by MPCVD method, with a power of 1kW-10kW, a microwave frequency of 2.45GHz, a pressure of 5kPa-200kPa in the reaction chamber, CH4 and H2 as reaction gases, a small amount of nitrogen is added to the reaction gas to increase the growth rate, the gas ratio of N2 / CH4 is 1vol%-5vol%, and the temperature is 1000°C-1500°C. The thickness of the produced diamond layer is 0.2μm-5μm.

[0060] Step S20, forming an aluminum nitride layer on the diamond layer;

[0061] Figure 3Schematic diagram of making aluminum nitride layer. The aluminum nitride (AlN) layer is located above the diamond layer and serves as a piezoelectric layer. The aluminum nitride film in the aluminum nitride layer can be single crystal or polycrystalline. The method of making the AlN layer can be, for example, molecular beam epitaxy (MBE), chemical vapor deposition (CVD), plasma assisted chemical vapor deposition (PACVD), laser chemical vapor deposition (LCVD), metal organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), and magnetron reaction sputtering (MRS).

[0062] Magnetron reactive sputtering combines the advantages of magnetron sputtering and reactive sputtering. Magnetron sputtering refers to applying a magnetic field in a direction parallel to the target surface, using the magnetron principle that the electric field and the magnetic field are orthogonal to reduce the bombardment of electrons on the substrate, and achieving high-speed and low-temperature sputtering. This embodiment preferentially uses magnetron sputtering to grow polycrystalline AlN material as the aluminum nitride layer. When preparing AlN, a metal aluminum target is used, and nitrogen is filled as a reaction gas. The thickness of the produced aluminum nitride layer is 100nm-5μm.

[0063] In order to improve the piezoelectric coefficient of the aluminum nitride film, and thus improve the electromechanical coupling coefficient of the resonator using aluminum nitride as the piezoelectric material, the aluminum nitride layer can be doped. The doping element can be at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, chromium, zirconium, manganese and magnesium, and the doping concentration is 1at%-50at%.

[0064] Taking Sc as an example, after doping, Sc atoms replace some Al atoms to form scandium nitride (ScN). Scandium nitride is a non-polar III-V nitride with a rock salt structure, while aluminum nitride is a polar wurtzite structure III-V nitride. After Sc doping of AlN, a transition region between the wurtzite structure and the rock salt structure is formed, thereby improving the piezoelectric coefficient of the aluminum nitride layer. Appropriate Sc doping can increase the piezoelectric coefficient of the AlN film by 100%-500%.

[0065] The doping method is illustrated by doping with scandium (Sc). When AlN thin film is doped with high concentration of Sc to form ScAlN, two separate targets and two separate magnetrons are used: one is pure aluminum and the other is pure Sc. The difference in power is used to compensate for the huge difference in sputtering rate and obtain the chemical composition of the two materials. The target material can also be a mixed target of Sc and Al made in a certain proportion. When preparing ScAlN thin film by sputtering, a mixed target material is used and nitrogen is filled as the reaction gas to produce Sc doped in a certain proportion. x Al （1-x） N thin film, where x is (1-50) at%.

[0066] In addition to doping with one metal element, two or more elements can also be doped. For example, Sc and Cr can be doped at the same time. Multiple targets can be used, such as pure aluminum, pure scandium, and pure chromium. When sputtering at the same time, nitrogen can be filled in as a reaction gas to produce a multi-doped ScCrAlN film. A mixed target can also be used, a mixed target of Sc, Cr, and Al made in a certain proportion. When preparing a doped AlN film by sputtering, a mixed target is used and nitrogen is filled in as a reaction gas to produce a ScCrAlN film doped in a certain proportion. x Cr y Al （1-x-y） N film. Where x = (1-50) at%, y = (1-50) at%, x + y < 50 at%.

[0067] Step S30, manufacturing a MEMS device and a matching circuit on the aluminum nitride layer;

[0068] Figure 4 Schematic diagram of a SAW resonator based on AlN material. The MEMS device in this embodiment may be a SAW resonator. The resonator may be composed of one IDT (Interdigital Transducer) structure or two IDT structures. Figure 4The resonator shown is a dual-port structure. The left side is the input IDT and the right side is the output IDT. The surface acoustic wave device is made of two interdigital transducers on a piezoelectric substrate to achieve the conversion of acoustic energy and electrical energy. The transducer on the left end (input transducer) converts the input electrical signal into an acoustic wave through the inverse piezoelectric effect. This acoustic wave propagates along the surface of the substrate and is finally converted into an electrical signal for output by the transducer on the right side of the substrate (output transducer). The function of the entire surface acoustic wave device is achieved by performing various processing on the acoustic wave propagating on the piezoelectric substrate and utilizing the characteristics of the acoustic-electric transducer. Reflection gratings are made on the left and right sides respectively, and their function is to reflect energy back to the interdigital transducer, thereby reducing energy loss. The above resonator can be used to make a variety of devices, temperature and pressure sensors, gas detectors, radiation detectors, energy harvesters, energy converters, acoustic wave filters, etc.

[0069] Figure 5a , Figure 5b and Figure 5c Figure 1 is a schematic diagram of making a SAW resonator. Figure 5a As shown, when making a resonator, a metal material can be first evaporated or sputtered on the aluminum nitride layer to form a metal layer, wherein the metal material can be gold, platinum, copper, aluminum, molybdenum, tungsten, titanium or tantalum; the metal layer is sequentially coated with glue, aligned, exposed, developed, etched, debonded, and cleaned, and a reflective grating and an interdigital transducer are made on the metal layer. The positions of the reflective grating and the interdigital transducer are as shown in FIG. Figure 5b As shown. The number of reflectors and interdigitated fingers is determined by the specific application. The thickness of the metal layer is 100nm-1μm.

[0070] When making IDT and reflector, metal stripping process can be used, or dry or wet etching process can be used to etch the metal layer. For example, when the material used for the metal layer is aluminum, plasma dry etching is used, and the gases used can be Cl2 and BCl3. By optimizing equipment and process conditions, such as power, bias power, pressure, gas flow and other parameters, and adding other gases (such as oxygen), the etching selectivity of Al and AlN can be improved to achieve the etching of metal Al, while minimizing the damage to the AlN layer.

[0071] As another embodiment, when manufacturing the interdigital transducer and the reflective grating, the metal layer and the aluminum nitride layer may be etched simultaneously. Figure 5c This is a schematic diagram of etching the metal layer and the aluminum nitride layer. When the metal layer material is aluminum, plasma dry etching is adopted. The gases used can be Cl2 and BCl3. The same gas can also etch the AlN material and complete the etching of the metal layer and the aluminum nitride layer at the same time.

[0072] After the MEMS device is manufactured, a passivation layer can be deposited on the metal layer to protect the metal layer. The method for depositing the passivation layer can be plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD, Atomic Layer Deposition) and other methods. Silicon oxide and silicon nitride can be produced by plasma enhanced chemical vapor deposition (PECVD), and the thickness of the produced passivation layer is 10nm-500nm. When using atomic layer deposition, the material of the passivation layer can be silicon oxide, silicon nitride, aluminum oxide, gallium oxide, etc., with a thickness of 0.5nm-20nm.

[0073] MEMS devices can be integrated with matching circuits on aluminum nitride or passivation layers. Inductors, capacitors and resistors are made on aluminum nitride or passivation layers. Inductors include inductor metal windings, inductor metal inter-layer dielectric layers, inductor through-holes and inductor metal connections. Capacitors include capacitor metal electrodes, capacitor dielectric layers, capacitor metal inter-layer dielectric layers, capacitor through-holes and capacitor metal connections. Capacitor metal electrodes include lower metal electrodes and upper metal electrodes. Resistors include thin-film resistors, resistor metal inter-layer dielectric layers, resistor through-holes and resistor metal connections.

[0074] A base dielectric layer may also be grown on the aluminum nitride or passivation layer before the MEMS device is integrated with the matching circuit.

[0075] Figure 6 It is a schematic diagram of the structure of a MEMS monolithic integrated circuit. Figure 6 As shown, the base dielectric layer, the intermetallic dielectric layer and the through-hole etching can be carried out simultaneously. In a specific implementation, the inductor, capacitor and resistor can be arranged around the resonator at any position on the chip to optimize the chip performance and chip area. The material used for the inductor metal can be at least one of Au, Al, Cu, Fe, Ni or their alloys. The capacitor dielectric can be silicon nitride, silicon oxide, or other dielectric materials, such as high dielectric constant hafnium silicate, zirconium silicate, hafnium dioxide and zirconium dioxide, etc., to further increase the capacitance density and reduce the area of ​​the capacitor. The capacitor metal electrode material is generally Au, Al, Cu, or other metals or alloys. The thickness of the capacitor dielectric and metal, as well as the size and shape of the capacitor are determined by the specific application and design. The optional materials for the thin film resistor include Ni-Co series, Ta series, Si series, metal ceramic series resistor film and Au-Cr, Ni-P and other resistor films, and the commonly used ones are NiCr and TaN.

[0076] like Figure 6As shown, an isolation zone can be set between the MEMS device and the matching circuit. The aluminum nitride layer is etched between the area where the MEMS device is located and the area where the matching circuit is located. The isolation zone after etching can be empty to form air isolation, or it can be filled with isolation material.

[0077] Step S40: fabricating a first interconnection structure inside the matching circuit and a second interconnection structure between the MEMS device and the matching circuit.

[0078] like Figure 6 As shown, the first interconnection structure may be a metal interconnection between any two of the inductor, capacitor and resistor, and the second interconnection structure may be a metal interconnection between the MEMS device and the inductor, a metal interconnection between the MEMS device and the capacitor and / or a metal interconnection between the MEMS device and the resistor. The metal interconnection may be interconnected or connected via an air bridge.

[0079] In this embodiment, the piezoelectric material aluminum nitride is made on the surface of the diamond layer, and the excellent piezoelectric properties of the aluminum nitride material and the high acoustic wave transmission speed of diamond are combined to produce a high-frequency surface acoustic wave MEMS device. At the same time, the surface acoustic wave MEMS device and the matching circuit are integrated on the same chip to form a MEMS monolithic integrated circuit, thereby achieving the purpose of increasing bandwidth, improving chip performance, reducing chip area, and reducing manufacturing costs.

[0080] Further, in the second embodiment of the method for preparing the MEMS monolithic integrated circuit of the present application, referring to Figure 7 Before forming the aluminum nitride layer, a seed layer is formed on the diamond layer. The seed layer can be AlN, GaN or other materials. The thickness of the seed layer is 1nm-10nm.

[0081] The seed layer can be deposited at a relatively low temperature (400°C-700°C) by using metal organic chemical vapor deposition (MOCVD). By optimizing the process parameters such as temperature and gas flow, high-quality films can be obtained. The preparation of AlN film is to use hydrogen to send metal organic compound vapor (trimethylaluminum, TMA, Trimethylaluminium) and gaseous non-metallic hydride (NH3) into the reaction chamber, and then heat to decompose the compound. The overall reaction formula is as follows:

[0082]

[0083] If GaN is used as the seed layer, metal organic compound vapor (trimethylgallium, TMG) ​​and gaseous non-metal hydride (NH3) are introduced into the reaction chamber using hydrogen, and then heated to decompose the compounds.

[0084] A seed layer can also be made using atomic layer deposition (ALD). ALD is a thin film deposition technique based on the continuous use of gas phase chemical processes, which is a subclass of chemical vapor deposition. Most ALD reactions use two chemical species called precursors. These precursors react with the material surface one at a time in a continuous, self-limiting manner. Through repeated exposure to different precursors, the film is slowly deposited and grown.

[0085] Aluminum nitride films are deposited on diamond surfaces from trimethylaluminum (TMA) and ammonia (NH3) by thermal atomic layer deposition (Thermal ALD or thermal ALD) and plasma enhanced atomic layer deposition (PE-ALD, Plasma Enhanced Atomic Layer Deposition). For thermal ALD and PE-ALD, the deposition rate increases significantly with the deposition temperature. Plasma significantly increases the deposition rate of AlN films.

[0086] Plasma-enhanced atomic layer deposition (PE-ALD) allows the growth of AlN thin films at low temperatures between 100°C and 300°C. Gaseous precursors and oxidants are applied to the substrate in separate pulses, with each pulse adsorbing at most a full monolayer. Therefore, one layer of atoms is deposited in each pulse. ALD deposition of AlN is based on the use of trimethylaluminum (TMA) or aluminum chloride (AlCl4) as aluminum sources. Using TMA as an aluminum precursor allows higher deposition rates and lower doses to reach saturation, which means more uniform nucleation on the substrate surface in the first cycle of deposition. This will lead to higher crystallinity when growing AlN. Crystal growth of AlN thin films can be achieved by PE-ALD using TMA and NH3 as aluminum and nitrogen sources, respectively. This can be optimized by adjusting different parameters such as temperature, pressure, pulse time, etc.

[0087] In addition, after the film growth is completed, an annealing process can be performed to further improve the crystallinity of the AlN film. The annealing temperature can be 700°C-1100°C, and the annealing time can be 30 sec-10 min.

[0088] If GaN is used as a seed layer, trimethyl gallium (TMG) and ammonia (NH3) are deposited on a silicon wafer by thermal atomic layer deposition (Thermal ALD or thermal ALD) and plasma enhanced atomic layer deposition (PE-ALD), and then annealed. The annealing temperature can be 700°C-1100°C and the annealing time can be 30sec-10min.

[0089] In this embodiment, a seed layer with atomic-level thickness can be controlled and synthesized on the diamond layer to form a nanomaterial film, thereby improving the growth quality of the subsequent aluminum nitride layer.

[0090] Further, in the third embodiment of the method for preparing a MEMS monolithic integrated circuit of the present application, referring to Figure 8a and Figure 8b , when making MEMS devices, such as Figure 8a As shown, a metal layer is first formed on the diamond layer to make a reflection grating and an interdigital transducer, such as Figure 8b As shown, an aluminum nitride layer is then formed, and the thickness of the aluminum nitride layer is greater than that of the metal layer.

[0091] The method for making the diamond layer is the same as that in the above-mentioned embodiment. A metal layer is deposited on the diamond layer, and then the metal layer is subjected to the process steps of gluing, aligning, exposing, developing, etching, degumming, and cleaning to make a reflective grating and an interdigital transducer. The metal layer material can be Au, Pt, Cu, Al, Mo, W, Ti, or Ta. The thickness of the metal layer is 100nm-1μm. An aluminum nitride layer is prepared based on the completed metal layer. The preparation method of the aluminum nitride layer refers to the above-mentioned embodiment and will not be repeated here. The thickness of the aluminum nitride layer is 200nm-2μm. After the aluminum nitride layer is made, the same method as in the first embodiment can be used. Figure 5c The corresponding method etches the metal layer and the aluminum nitride layer simultaneously.

[0092] In this embodiment, the reflection grating and the interdigital transducer are in direct contact with the diamond layer, so that the sound wave can propagate on the surface of the diamond layer, and the surface sound velocity of the diamond layer is high, so the frequency of the manufactured MEMS device can be increased.

[0093] The present application also provides a MEMS monolithic integrated circuit, referring to Fig. 9 , Fig. 9 This is a connection diagram of a MEMS monolithic integrated circuit according to an embodiment of the present application. Fig. 9 The circuits shown in the figure are for illustrative purposes only and do not constitute limitations on the circuit design.

[0094] like Fig. 9 As shown, a MEMS monolithic integrated circuit may include a MEMS device and a matching circuit. in Indicates voltage input, V out represents voltage output, C represents capacitance, L represents inductance, and the connection between MEMS devices, inductors, capacitors, and resistors can be in series or in parallel. The number of components in a MEMS monolithic integration, such as resonators, inductors, capacitors, and resistors, depends on the specific design and can be zero (such as resistors).

[0095] The MEMS monolithic integrated circuit may include a substrate, a diamond layer, and an aluminum nitride layer that are stacked in sequence, a MEMS device and a matching circuit are arranged on the aluminum nitride layer, a first interconnection structure is arranged inside the matching circuit, and a second interconnection structure is arranged between the MEMS device and the matching circuit. A seed layer may also be arranged between the diamond layer and the aluminum nitride layer. The aluminum nitride material in the aluminum nitride layer may be doped aluminum nitride. For the MEMS device part, the stacking order of the aluminum nitride layer and the MEMS device may be swapped. An isolation zone may be arranged between the MEMS device and the matching circuit. A passivation layer may also be arranged above the layer where the MEMS device is located.

[0096] Fabricating a diamond layer on a substrate, and fabricating an AlN layer on the diamond layer as a piezoelectric material to fabricate a surface acoustic wave (SAW) resonator and filter can improve the operating frequency and quality factor of the device. The propagation speed of sound waves on the surface of AlN material is 6000 m / s, and the propagation speed on the surface of diamond is 13000 m / s. The relationship between the frequency and the speed of sound of the device is: v=λ / f, where f is the frequency, v is the propagation speed of sound waves, and λ is the spacing of the IDT. Therefore, under the same IDT spacing (same process capability), the operating frequency of the device will increase by more than 2 times.

[0097] In addition to frequency, another major indicator of communication devices is bandwidth. In order to further improve the bandwidth, the MEMS monolithic integrated circuit provided in this embodiment integrates the MEMS device with the RLC circuit to form a MEMS MMIC (Monolithic Microwave Integrated Circuit). The RLC circuit serves as a matching circuit for the MEMS device and forms multiple functions. For example, the RLC matching circuit can form a bandpass filter, which is integrated with the SAW filter on the same chip, which can improve the bandwidth of the filter, while increasing the device concentration, reducing power consumption, and reducing chip area and manufacturing costs.

[0098] Fig.10 The schematic diagram of the wafer manufactured according to this application. The chip products in the wafer can be SAW resonators, SAW filters, SAW MMIC (SAW monolithic integrated circuit). In wireless communication systems, such as wireless base stations, mobile phones, WIFI and other smart terminal devices, this wafer product has a higher frequency and a larger bandwidth, and can be widely used in the field of wireless communication. At the same time, the SAW resonator manufactured according to this application can also be used in various sensors, such as temperature sensors, pressure sensors, mass sensors, chemical sensors, biosensors, etc.

[0099] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0100] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a MEMS monolithic integrated circuit, characterized in that: The preparation method comprises the following steps: preparing a substrate and forming a diamond layer on the substrate; forming an aluminum nitride layer on the diamond layer; Etching the aluminum nitride layer to set an isolation zone between the MEMS device and the matching circuit; Fabricating a MEMS device and a matching circuit on the aluminum nitride layer, wherein the matching circuit includes an inductor, a capacitor, and a resistor; A first interconnection structure inside the matching circuit and a second interconnection structure between the MEMS device and the matching circuit are manufactured, wherein the first interconnection structure is a metal interconnection between any two of the inductance, capacitance and resistance, and the second interconnection structure is a metal interconnection between the MEMS device and the inductance, a metal interconnection between the MEMS device and the capacitor and / or a metal interconnection between the MEMS device and the resistance.

2. The method for preparing a MEMS monolithic integrated circuit according to claim 1, characterized in that: The step of forming a diamond layer on the substrate comprises: polishing and cleaning the substrate; forming a diamond layer on the cleaned substrate by chemical vapor deposition; The surface of the diamond layer is polished.

3. The method for preparing a MEMS monolithic integrated circuit according to claim 1, characterized in that: Before the step of forming an aluminum nitride layer on the diamond layer, the method further comprises: forming a seed layer on the diamond layer; The seed layer is annealed.

4. The method for preparing a MEMS monolithic integrated circuit according to claim 1, characterized in that: The step of forming an aluminum nitride layer on the diamond layer comprises: An aluminum nitride layer is sputtered on the diamond layer by a reactive magnetron sputtering method.

5. The method for preparing a MEMS monolithic integrated circuit according to claim 1, characterized in that: After the step of forming an aluminum nitride layer on the diamond layer, the method further comprises: The aluminum nitride layer is doped, wherein the doping element is at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, chromium, zirconium, manganese and magnesium, and the doping concentration is 1at%-50at%.

6. The method for preparing a MEMS monolithic integrated circuit according to claim 1, characterized in that: The step of manufacturing a MEMS device on the aluminum nitride layer comprises: Evaporating or sputtering a metal material on the aluminum nitride layer to form a metal layer, wherein the metal material is gold, platinum, copper, aluminum, molybdenum, tungsten, titanium or tantalum; The metal layer is sequentially subjected to coating, alignment, exposure, development, etching, degumming and cleaning processes, and a reflective grating and an interdigital transducer are manufactured on the metal layer.

7. The method for preparing a MEMS monolithic integrated circuit according to claim 6, characterized in that: After the step of manufacturing a MEMS device on the aluminum nitride layer, the method further includes: A passivation layer is deposited on the metal layer, and the material used for the passivation layer is silicon oxide, silicon nitride, aluminum oxide or gallium oxide.

8. The method for preparing a MEMS monolithic integrated circuit according to claim 1, characterized in that: The step of making a matching circuit on the aluminum nitride layer comprises: Inductors, capacitors and resistors are manufactured on the aluminum nitride layer. The inductors include inductor metal windings, inductor metal inter-dielectric layers, inductor through-holes and inductor metal connections. The capacitors include capacitor metal electrodes, capacitor dielectric layers, capacitor metal inter-dielectric layers, capacitor through-holes and capacitor metal connections. The resistors include thin-film resistors, resistor metal inter-dielectric layers, resistor through-holes and resistor metal connections.

9. A MEMS monolithic integrated circuit, characterized in that: Prepared by the preparation method of a MEMS monolithic integrated circuit according to any one of claims 1 to 8; the MEMS monolithic integrated circuit comprises a substrate, a diamond layer and an aluminum nitride layer which are designed to be stacked in sequence, a MEMS device and a matching circuit are arranged on the aluminum nitride layer, an isolation zone is arranged between the MEMS device and the matching circuit, the matching circuit comprises an inductor, a capacitor and a resistor, a first interconnection structure is arranged inside the matching circuit, a second interconnection structure is arranged between the MEMS device and the matching circuit, the first interconnection structure is a metal interconnection between any two of the inductor, the capacitor and the resistor, and the second interconnection structure is a metal interconnection between the MEMS device and the inductor, a metal interconnection between the MEMS device and the capacitor and / or a metal interconnection between the MEMS device and the resistor.

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