CN112382718A - C-axis vertical preferred orientation AlN piezoelectric film and preparation method thereof - Google Patents

C-axis vertical preferred orientation AlN piezoelectric film and preparation method thereof Download PDF

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CN112382718A
CN112382718A CN202011262292.8A CN202011262292A CN112382718A CN 112382718 A CN112382718 A CN 112382718A CN 202011262292 A CN202011262292 A CN 202011262292A CN 112382718 A CN112382718 A CN 112382718A
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aln
thin film
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preferred orientation
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郑泽渔
赵雪梅
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CETC 26 Research Institute
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    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
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Abstract

The invention relates to the technical field of thin film material preparation, in particular to a C-axis vertical preferred orientation AlN piezoelectric thin film and a preparation method thereof, wherein the preparation method comprises the following steps: preparing an AlN thin film, a metal electrode layer and an AlN piezoelectric thin film from a buffer layer on the sapphire or YAG crystal in sequence. And inducing the orientation of the metal electrode layer from the buffer layer AlN thin film to realize the preparation of the high-C-axis preferred orientation AlN thin film on the electrode layer. The sapphire or YAG crystal and the high-purity sputtering target form a 45-degree angle, the energy of migration motion of sputtered atomic groups parallel to the surface of the substrate after reaching the substrate is effectively regulated, the growth of a growth buffer layer and the preferred orientation of the C axis of the AlN piezoelectric film is facilitated, and the piezoelectric response and the electromechanical coupling coefficient of the film are improved. The method can realize the growth of the C-axis preferred orientation AlN film by utilizing the magnetron sputtering technology at a lower temperature, and the obtained AlN film has high crystallinity and higher piezoelectric response coefficient and electromechanical coupling coefficient.

Description

C-axis vertical preferred orientation AlN piezoelectric film and preparation method thereof
Technical Field
The invention relates to the technical field of thin film material preparation, in particular to a C-axis vertical preferred orientation AlN piezoelectric thin film and a preparation method thereof.
Background
The body wave (BAW) device is mainly applied to radio communication and radar systems and mainly comprises a BAW delay line, a BAW resonator, a BAW filter and the like, wherein the thin-film BAW delay line (BAWDL) is a very high frequency device which is rapidly researched and applied in recent years, has the advantages of small volume, light weight, no margin and the like in a microwave frequency band, and is widely applied to systems such as airborne and missile-borne wireless altimeters and the like.
The traditional BAWDL usually adopts a zinc oxide (ZnO) film, ZnO is amphoteric oxide, can react with acid and alkali, is sensitive to the environmental humidity, and in the preparation process, the oxygen defect of the ZnO film is difficult to control, and the AlN (AlN) piezoelectric film material has high sound wave transmission speed, good chemical stability and small frequency dispersion, thereby being an ideal key material for preparing BAW devices. For AlN material, the AlN crystal structure is shown in fig. 1, since the C-axis (002) direction has the largest piezoelectric response coefficient. Whether the C-axis preferred orientation AlN film can be prepared is the key of the application of the AlN film to the bulk acoustic wave device. Because high particle energy is needed for forming nitrogen-aluminum bonds in the C-axis direction, but the ion energy is too large, the corresponding B2 bonds are easy to break, and the film is very easy to form other preferred orientation (100) or non-preferred orientation, so that the preparation of high-quality C-axis preferred orientation AlN film is difficult.
Magnetron sputtering is a commonly used thin film deposition technique in semiconductor processes and can be used for preparing AlN thin films. The traditional AlN film magnetron sputtering deposition process is that a substrate and a sputtering target are oppositely arranged in a vacuum cavity (the substrate and the sputtering target are horizontally arranged), the substrate is heated to a certain temperature through a base, reaction gases (nitrogen and argon) with a certain proportion are introduced into the vacuum cavity, and high voltage is applied to the sputtering target to ionize the gases to form plasma; the plasma bombards the sputtering target, particles generated by sputtering leave the surface of the target in a certain direction and energy, reach the surface of the substrate, reach an equilibrium position through horizontal diffusion, and continuously grow to form a film. Although the traditional magnetron sputtering process can be used for preparing the AlN thin film, the traditional magnetron sputtering process has the problems of low motion energy of sputtered particles reaching the surface of the substrate in the horizontal direction, large surface roughness of the thin film, large internal stress between the thin film and the substrate, lattice mismatch and the like, and is not easy to form the high-quality AlN thin film with the preferred orientation of the C axis.
Disclosure of Invention
In order to solve the problems, the invention provides a C-axis vertical preferred orientation AlN piezoelectric film and a preparation method thereof. The preparation method of the AlN piezoelectric film can continuously grow the seed layer, the metal electrode layer and the high-C-axis preferred orientation AlN film by utilizing the magnetron sputtering technology, improve the crystallization degree of the AlN film and prepare the high-quality C-axis preferred orientation AlN film.
A C-axis vertical preferred orientation AlN piezoelectric film comprises a substrate and an AlN thin film layer, wherein the substrate adopts a sapphire or YAG substrate; an AlN seed thin film layer and a metal electrode thin film layer are arranged between the substrate and the AlN thin film layer.
A preparation method of a C-axis vertical preferred orientation AlN piezoelectric film comprises the following steps of continuously growing an AlN seed film layer, a metal electrode film layer and a high C-axis preferred orientation AlN film layer on a substrate by adopting a magnetron sputtering process, wherein the substrate adopts a sapphire or YAG substrate, and the preparation method comprises the following steps:
s1, preparing an AlN seed thin film layer on the sapphire or YAG substrate: horizontally placing a sapphire or YAG substrate in a cavity, and obliquely placing a high-purity material for preparing an AlN seed thin film layer (AlN target), a metal electrode layer (metal electrode target) and an AlN thin film material (AlN target) around the sapphire or the substrate as a sputtering target material; vacuumizing the vacuum cavity of the magnetron sputtering equipment to 3 multiplied by 10-4Introducing argon and nitrogen into the vacuum cavity below Pa, applying 400-700V of voltage to a high-purity sputtering target for preparing the AlN seed thin film layer for magnetron sputtering, and disconnecting the voltage after certain magnetron sputtering time to obtain the AlN seed thin film layer with certain thickness;
s2, inducing on the AlN seed thin film layerPreparing a metal electrode thin film layer with preferred orientation: maintaining the vacuum chamber of the magnetron sputtering device at 3X 10-4Introducing argon into the vacuum cavity below Pa, and applying a voltage of 400-700V to a high-purity metal sputtering target for preparing a metal electrode layer for magnetron sputtering to induce generation of a metal electrode film with preferred orientation;
s3, preparing an AlN thin film layer with growth height and preferred C-axis orientation on the metal electrode thin film layer by induction: maintaining the vacuum chamber of the magnetron sputtering device at 3X 10-4And introducing argon and nitrogen into the vacuum chamber below Pa, and applying a voltage of 400-700V to a high-purity AlN sputtering target for preparing the AlN film with the height C-axis preferred orientation for magnetron sputtering to obtain the AlN film with the height C-axis preferred orientation and a certain thickness.
Furthermore, the structure of the sputtering target material is an asymmetric inclined target, the sputtering target material is a distributed multi-target, and the connecting line of the upper edge of the high-purity sputtering target and the edge of the sapphire substrate forms an included angle of 45 degrees relative to the target material direction.
Further, the sputtering target material for preparing the metal electrode layer comprises any one of molybdenum, gold or platinum; the metal electrode layer is made of any one of molybdenum, gold or platinum.
Further, in step S1 and step S3, the volume ratio of argon gas to nitrogen gas introduced into the vacuum chamber is greater than or equal to 0 and less than or equal to 2/3.
Further, in the process of plating the AlN seed thin film layer, the metal electrode thin film layer and the AlN thin film layer with the height of the C-axis preferred orientation by a magnetron sputtering method, the sapphire or YAG substrate rotates around the center at 200-300 r/min, the magnetron sputtering time is 2-4 hours, and the temperature of the sapphire or YAG substrate is 350-450 ℃.
Furthermore, the surface roughness of the sapphire or YAG substrate is less than 9nm, and the thickness of the sapphire or YAG substrate is 2-6 mm.
Further, the surface roughness of the AlN seed thin film layer is less than 9nm, and the thickness of the AlN seed thin film layer is 30-60 nm.
Furthermore, the surface roughness of the metal electrode layer is less than 9nm, and the thickness of the metal electrode layer is 30-100 nm.
Furthermore, the surface roughness of the AlN thin film with the preferred height C axis orientation is less than 9nm, and the thickness of the AlN thin film with the preferred height C axis orientation is 200-1000 nm.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a C-axis vertical preferred orientation AlN piezoelectric film and a method for preparing a self-buffer layer, a metal electrode layer and a C-axis preferred orientation AlN piezoelectric film in a continuous growth mode based on magnetron sputtering, wherein the traditional magnetron sputtering process only grows one AlN film, aims to solve the problems of large internal stress, lattice mismatch, poor crystallinity and low C-axis orientation degree and is beneficial to forming a buffer layer film and the C-axis orientation AlN piezoelectric film, adopts a target material placing structure as an asymmetric inclined target, the included angle of a connecting line between the upper edge of a high-purity sputtering target and the edge of a sapphire or YAG (acoustic crystal) substrate relative to the direction of a target material is 45 degrees, the target material is distributed multi-target, a plurality of target materials can be loaded into a vacuum cavity at one time, a subsequent continuous growth mode is adopted, and the continuous uninterrupted preparation process in the whole process is greatly simplified, the preparation cost is low.
The included angle between the sapphire or YAG substrate and the high-purity sputtering target is 45 degrees, the energy of migration motion of sputtered atomic groups parallel to the surface of the substrate after reaching the substrate can be effectively regulated, the preferred orientation growth of a buffer layer film and an AlN film C axis is facilitated, the internal stress of the film is greatly reduced, and the piezoelectric response and the electromechanical coupling coefficient of the film are improved.
The method adopts a mode of secondarily inducing and growing the film, namely, firstly growing the AlN seed film layer to form a seed layer, utilizing a self-buffer layer to induce and grow the metal electrode with certain preferred orientation, and finally growing the AlN film with the C-axis height preferred orientation, so that the finally obtained AlN film has small internal stress, small roughness, high crystallinity and high orientation degree.
The temperature of the sapphire substrate is controlled to be 350-450 ℃, so that the substrate material and the device performance are not influenced, and the growth of the C-axis preferred orientation AlN thin film by utilizing the magnetron sputtering technology at a lower temperature is realized.
The method provided by the invention is simple to operate and is easy to be compatible with large-scale integrated circuit process equipment.
The AlN polycrystalline film with the buffer layer prepared by the method provided by the invention has higher C-axis preferred orientation and can be used as a chip material to be applied to a bulk acoustic wave delay line.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic diagram of an AlN crystal structure;
FIG. 2 is a schematic structural diagram of a C-axis vertical preferred orientation AlN piezoelectric film according to an embodiment;
FIG. 3 is a schematic structural diagram of a distributed target used in magnetron sputtering provided by an embodiment;
FIG. 4 is an XRD diffraction pattern diagram of a Mo electrode film grown on an AlN seed film layer by using sapphire as a substrate in the example;
FIG. 5 is an XRD diffraction pattern diagram of a highly preferred orientation AlN/Mo/AlN composite piezoelectric film grown on a sapphire substrate in an example;
FIG. 6 is an atomic force microscope photograph of an AlN/Mo/AlN composite film grown on a substrate of the example.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in FIG. 1-2, a C-axis vertical preferred orientation AlN piezoelectric film comprises a substrate and an AlN thin film layer, wherein an AlN seed thin film layer and a metal electrode thin film layer are arranged between the substrate and the AlN thin film layer. The sequence of each film layer comprises: the following steps are sequentially performed from the bottom to the top of the substrate: an AlN seed thin film layer, a metal electrode thin film layer and an AlN thin film layer.
The substrate adopts any one of a sapphire substrate or a YAG substrate.
In one embodiment, a sapphire substrate is used as the substrate, the sapphire substrate having a surface roughness of less than 9nm, more preferably less than 6 nm; the thickness of sapphire substrate is 2 ~ 6mm, and more preferably, the thickness of sapphire substrate is 5 mm.
In one embodiment, a YAG substrate is used as the substrate, the surface roughness of the YAG substrate being less than 9nm, more preferably less than 6 nm; the thickness of the YAG substrate is 2-6 mm, and more preferably, the thickness of the YAG substrate is 3 mm.
Preferably, the surface roughness of the AlN seed thin film layer is less than 9nm, and the thickness of the AlN seed thin film layer is 30-60 nm.
Preferably, the surface roughness of the metal electrode layer is less than 9nm, and the thickness of the metal electrode layer is 30-100 nm.
The AlN thin film layer is an AlN thin film with a preferred height C axis orientation, the surface roughness of the AlN thin film layer with the preferred height C axis orientation is less than 9nm, and the thickness of the AlN thin film layer with the preferred height C axis orientation is 200-1000 nm.
A preparation method of a C-axis vertical preferred orientation AlN piezoelectric film is characterized in that the whole film growth process is continuous growth, a target does not need to be replaced midway, specifically, an AlN seed film layer, a metal electrode film layer and a high C-axis preferred orientation AlN film layer are continuously grown on a substrate by adopting a magnetron sputtering process, the substrate adopts a sapphire or YAG substrate, and the preparation method comprises the following steps of:
(1) preparing an AlN seed thin film layer on a sapphire or YAG substrate: the sapphire or YAG substrate is horizontally placed in a vacuum cavity of a magnetron sputtering device, and a high-purity material for preparing an AlN seed thin film layer (AlN target), a metal electrode layer (metal electrode target) and an AlN thin film material (AlN target) is obliquely placed around the sapphire or YAG substrate as a sputtering target material.
The structure of the sputtering target material is an asymmetric inclined target, as shown in fig. 3, the target material is a distributed multi-target, and the connecting line of the upper edge of the high-purity sputtering target and the edge of the sapphire substrate forms an included angle of 45 degrees relative to the target material direction.
Vacuum chamber is pumped to 3 × 10-4And introducing argon and nitrogen below Pa, and applying a voltage of 400-700V to a high-purity sputtering target for preparing the AlN seed thin film layer for magnetron sputtering for 2-4 hours to obtain the AlN seed thin film layer with a certain thickness.
In the process of growing the AlN seed thin film layer by adopting a magnetron sputtering method, the sapphire or YAG substrate rotates around the center at 200-300 r/min, and the temperature of the sapphire or YAG substrate is 300-450 ℃.
In a preferred embodiment, a sapphire substrate is used as a substrate to grow an AlN seed thin film layer, the temperature of the sapphire substrate for growing the AlN seed thin film layer is set to be 300-400 ℃ in the magnetron sputtering process, the sputtering power range is 90-140W, the volume ratio of nitrogen to argon introduced into a vacuum cavity is greater than or equal to 0 and less than or equal to 2/3, and the magnetron sputtering time is 2 hours.
In a preferred embodiment, a YAG substrate is used as a substrate to grow an AlN seed thin film layer, the temperature of the YAG substrate for growing the AlN seed thin film layer is set to be 300-400 ℃ in the magnetron sputtering process, the sputtering power range is 90-140W, the volume ratio of the nitrogen gas/argon gas introduced into a vacuum cavity is more than or equal to 0 and less than or equal to 2/3, and the magnetron sputtering time is 2 hours.
(2) Continuously preparing a metal electrode thin film layer (metal electrode layer) on the AlN seed thin film layer: vacuum chamber is pumped to 3 × 10-4And introducing argon into the vacuum cavity below Pa, and applying a voltage of 400-700V to a high-purity metal sputtering target for preparing the metal electrode layer for magnetron sputtering to induce and generate a metal electrode film with preferred orientation.
In a preferred embodiment, in the process of preparing the metal electrode thin film layer by the magnetron sputtering method, the sapphire or YAG substrate rotates around the center at 200-300 r/min, the magnetron sputtering time is 2-4 hours, and the temperature of the sapphire or YAG substrate is 350-450 ℃.
Preferably, the sputtering target material for preparing the metal electrode layer comprises any one of molybdenum, gold or platinum; the metal electrode layer is made of any one of molybdenum, gold or platinum.
Preferably, the substrate temperature of the metal electrode layer is set to 400 ℃.
In an optional embodiment, the substrate temperature of the gold electrode layer is set to be 400 ℃, the sputtering power is in a range of 90-140W, and the magnetron sputtering time is 2 hours.
In an optional embodiment, the substrate temperature of the molybdenum electrode layer is set to be 400 ℃, the sputtering power is in a range of 90-140W, and the magnetron sputtering time is 2 hours.
In an optional embodiment, the substrate temperature of the platinum electrode layer is set to be 360 ℃, the sputtering power range is 90-140W, and the magnetron sputtering time is 2 hours.
(3) Continuously growing an AlN film with preferred height C axis orientation on the metal electrode film layer: vacuum chamber is pumped to 3 × 10-4And introducing argon and nitrogen into the vacuum chamber below Pa, and applying a voltage of 400-700V to a high-purity AlN sputtering target for preparing the AlN film with the height C-axis preferred orientation for magnetron sputtering to obtain the AlN film with the height C-axis preferred orientation and a certain thickness.
Preferably, when growing the AlN film with the height C-axis oriented preferentially, the volume ratio of argon gas and nitrogen gas introduced into the vacuum chamber is 0 or more and 2/3 or less.
In a preferred embodiment, in the process of plating the AlN thin film layer with the preferred orientation of the height C axis by a magnetron sputtering method, the sapphire or YAG substrate rotates around the center at 200-300 r/min, the magnetron sputtering time is 2-4 hours, and the temperature of the sapphire or YAG substrate is 350-450 ℃.
In an alternative embodiment, the temperature of the substrate for growing the AlN on the gold electrode layer is 400 ℃, the sputtering power is in a range of 90-140W, and the magnetron sputtering time is 2 hours.
In an optional embodiment, the temperature of the substrate for growing the AlN on the molybdenum electrode layer is 400 ℃, the sputtering power is in a range of 90-140W, and the magnetron sputtering time is 2 hours.
In an optional embodiment, the temperature of the substrate for growing the AlN on the platinum electrode layer is 360 ℃, the sputtering power range is 90-140W, and the magnetron sputtering time is 2 hours; the volume ratio of nitrogen to argon is greater than or equal to 0 and less than or equal to 2/3.
(5) And taking the AlN thin film out of the cavity and annealing.
Preferably, the surface roughness of the sapphire or YAG substrate is less than 9nm, more preferably less than 6 nm.
Preferably, the thickness of the sapphire substrate is 2-6 mm, and more preferably, the thickness of the sapphire substrate is 5 mm.
Preferably, the thickness of the YAG substrate is 2-6 mm, and more preferably, the thickness of the YAG substrate is 3 mm.
Preferably, the surface roughness of the AlN seed thin film layer is less than 9nm, and the thickness of the AlN seed thin film layer is 30-60 nm.
Preferably, the surface roughness of the metal electrode layer is less than 9nm, and the thickness of the metal electrode layer is 30-100 nm.
Preferably, the surface roughness of the AlN thin film with the preferred height C axis orientation is less than 9nm, and the thickness of the AlN thin film with the preferred height C axis orientation is 200-1000 nm.
In the preparation method of the C-axis vertical preferred orientation AlN piezoelectric film, the whole process is continuous from the preparation of the buffer layer, the metal layer to the final preferred orientation AlN piezoelectric film layer. The action condition generated in the magnetron sputtering process is specifically as follows: applying high voltage on the high-purity sputtering target, and ionizing argon or nitrogen to generate plasma; bombarding the surface of the sputtering target by plasma to generate a large amount of target atomic groups (metal electrode atoms or Al); most of atomic groups incident to the surface of the substrate are inclined at a certain angle with the normal direction of the surface of the substrate, and the horizontal kinetic energy is far larger than that of the atomic groups vertically incident to the surface of the substrate; the high-energy target atomic group can reach the high-energy position of the atomic structure on the surface of the substrate and react with the reaction gas to form the preferred orientation AlN polycrystalline film with the C axis vertical to the surface of the substrate.
The method provided by the invention can utilize the magnetron sputtering technology to grow the C-axis preferred orientation AlN film with the buffer layer, and the obtained AlN film has small internal stress, small roughness, high crystallinity and good preferred orientation. In addition, the method provided by the invention is simple to operate, good in consistency and easy to be compatible with large-scale integrated circuit process equipment. The AlN polycrystalline film provided by the invention has higher preferred orientation of a C axis, and can be used as a chip material to be applied to a bulk acoustic wave delay line.
In order to make the method for preparing the C-axis preferred orientation AlN film with a buffer layer by magnetron sputtering more clear and complete, the following will further describe by taking continuous growth of an AlN/Mo/AlN composite piezoelectric film on a sapphire substrate as an example, but they should not be construed as limiting the scope of the present invention.
Preparing a high-C-axis preferred orientation AlN/Mo/AlN composite piezoelectric film on a sapphire substrate by using magnetron sputtering equipment, wherein the preparation method comprises the following steps:
the adopted substrate is a 2-inch sapphire substrate, the thickness of the sapphire substrate is 3.36mm, and the surface polishing roughness of the sapphire substrate is less than 6 nm; horizontally placing the sapphire substrate on a sample table in a vacuum chamber, wherein the sample table can rotate around the center, and the sample table controls the temperature of the sapphire substrate to be 320 ℃ so as to prepare an AlN seed thin film layer;
vertically distributing a high-purity aluminum target on a sample table (the normal direction of the surface of a substrate is vertical to the normal direction of the surface of the high-purity sputtering aluminum target), wherein the diameter of the sputtering aluminum target is 279mm and is 120mm higher than the surface of the substrate;
the vacuum cavity is vacuumized to reach 3 multiplied by 10-4Less than Pa; introducing nitrogen of 60sccm and argon of 150sccm into the vacuum cavity, applying 600V high voltage on the sputtering aluminum target, and ionizing the gas to generate plasma; the plasma bombards and sputters the surface of the aluminum target to generate a large amount of high-energy atomic groups; the high-energy atomic group reaches a high-energy position of an atomic structure on the surface of the substrate and reacts with the reaction gas to form a seed layer film on the surface of the sapphire substrate;
after the continuous growth for 1 hour, the growth was stopped and the high purity aluminum target was switched to the high purity molybdenum target.
Vertically and evenly distributing the high-purity sputtering molybdenum targets around the sample table (the normal direction of the surface of the substrate is vertical to the normal direction of the surface of the high-purity sputtering molybdenum targets), wherein the diameter of the sputtering molybdenum targets is 60mm and is 180mm higher than the surface of the substrate;
the vacuum cavity is vacuumized to 1 x 10-4Less than Pa; argon gas of 150sccm is introduced into the vacuum chamber, and molybdenum is sputteredApplying 700V high voltage on the target, and ionizing the gas to generate plasma; the plasma bombards and sputters the surface of the molybdenum target to generate a large amount of high-energy atomic groups; the high-energy atomic group reaches a high-energy position of an atomic structure on the surface of the substrate, reacts with the reaction gas and forms a Mo electrode film with a certain preferred orientation on the seed layer;
after the continuous growth for 1 hour, the growth was stopped, and the high-purity molybdenum target was switched to a high-purity aluminum target.
Vertically and evenly distributing the high-purity sputtering aluminum targets around the sample table (the normal direction of the surface of the substrate is vertical to the normal direction of the surface of the high-purity sputtering aluminum target), wherein the diameter of the sputtering aluminum target is 279mm and is 120mm higher than the surface of the substrate;
the vacuum cavity is vacuumized to 1 x 10-4Less than Pa; introducing 30sccm of nitrogen and 150sccm of argon into the vacuum cavity, applying 700V high voltage on the sputtering molybdenum target, and ionizing the gas to generate plasma; the plasma bombards and sputters the surface of the molybdenum target to generate a large amount of high-energy atomic groups; the high-energy atomic group reaches a high-energy position of an atomic structure on the surface of the substrate, reacts with the reaction gas and forms an AlN film with high C-axis preferred orientation on the molybdenum electrode layer;
and stopping after continuous growth for 2 hours, and taking the AlN/Mo/AlN composite piezoelectric film out of the cavity.
FIG. 4 is an X-ray diffraction pattern of a Mo electrode film grown on an AlN seed thin film layer with sapphire as a substrate in the example, and it can be known from FIG. 4 that only Mo peaks appear, which shows that the grown AlN seed thin film layer can well induce the growth of a Mo metal layer, and the Mo thin film has good preferred orientation and high crystallinity.
FIG. 5 is an X-ray diffraction pattern of an AlN thin film grown on a substrate, and as can be seen from FIG. 4, only the (002) peak and the Mo peak of AlN appear, indicating that the AlN thin film is oriented preferentially with respect to the C height axis, and that the intensity of the (002) peak is high and the half-value width is narrow, indicating that the AlN thin film has a very high crystallinity.
FIG. 6 is an atomic force microscope photomicrograph of an AlN thin film grown on a substrate, the AlN thin film having a smooth surface, a grain diameter of about 70nm and a roughness of 3.8nm as measured by an atomic force microscope.
The method realizes the preparation of the high-C-axis preferred orientation AlN thin film on the electrode layer by inducing the orientation of the metal electrode layer from the buffer layer AlN thin film. The sapphire or YAG crystal and the high-purity sputtering target form a 45-degree angle, the energy of migration motion of sputtered atomic groups parallel to the surface of the substrate after reaching the substrate can be effectively regulated, the growth of a growth buffer layer and the preferred orientation of the C axis of the AlN piezoelectric film is facilitated, and the piezoelectric response and the electromechanical coupling coefficient of the film are improved. The buffer layer and the AlN piezoelectric film layer are prepared in a continuous growth mode, the operation is simple, and the consistency is high. An AlN thin film is continuously grown on the buffer layer, and the thin film has the advantages of small internal stress, small lattice mismatch, small roughness and high crystallinity; the method provided by the invention can realize the growth of the C-axis preferred orientation AlN film by utilizing the magnetron sputtering technology at a lower temperature, the obtained AlN film has high crystallinity and higher piezoelectric response coefficient and electromechanical coupling coefficient, and the obtained high-quality AlN film can be applied to high-quality BAW delay line devices.
When introducing elements of various embodiments of the present application, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.
It should be noted that, as one of ordinary skill in the art would understand, all or part of the processes of the above method embodiments may be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when executed, the computer program may include the processes of the above method embodiments. The storage medium may be a magnetic disk, an optical disk, a Read-0nly Memory (ROM), a Random Access Memory (RAM), or the like.
The foregoing is directed to embodiments of the present invention and it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (10)

1. A C-axis vertical preferred orientation AlN piezoelectric film comprises a substrate and an AlN thin film layer, and is characterized in that the substrate adopts a sapphire or YAG substrate; an AlN seed thin film layer and a metal electrode thin film layer are arranged between the substrate and the AlN thin film layer.
2. The preparation method of the C-axis vertical preferred orientation AlN piezoelectric film according to claim 1, wherein an AlN seed film layer, a metal electrode film layer and a highly C-axis preferred orientation AlN film layer are continuously grown on a substrate by adopting a magnetron sputtering process, and the method is characterized in that the substrate adopts a sapphire or YAG substrate and comprises the following steps:
s1, preparing an AlN seed thin film layer on the sapphire or YAG substrate: horizontally placing a sapphire or YAG substrate in a cavity, and obliquely placing a high-purity material for preparing an AlN seed thin film layer (AlN target), a metal electrode layer (metal electrode target) and an AlN thin film material (AlN target) around the sapphire or the substrate as a sputtering target material; vacuumizing the vacuum cavity of the magnetron sputtering equipment to 3 multiplied by 10-4Introducing argon and nitrogen into the vacuum cavity below Pa, applying 400-700V of voltage to a high-purity sputtering target for preparing the AlN seed thin film layer for magnetron sputtering, and disconnecting the voltage after certain magnetron sputtering time to obtain the AlN seed thin film layer with certain thickness;
s2, preparing a metal electrode thin film layer with preferred orientation on the AlN seed thin film layer by induction: maintaining the vacuum chamber of the magnetron sputtering device at 3X 10-4Introducing argon into the vacuum cavity below Pa, and applying a voltage of 400-700V to a high-purity metal sputtering target for preparing a metal electrode layer for magnetron sputtering to induce generation of a metal electrode film with preferred orientation;
s3, preparing an AlN thin film layer with growth height and preferred C-axis orientation on the metal electrode thin film layer by induction: maintaining the vacuum chamber of the magnetron sputtering device at 3X 10-4Introducing argon and nitrogen into the vacuum chamber below Pa, and applying a voltage of 400-700V to a high-purity AlN sputtering target for preparing an AlN film with a preferred orientation of the height C axis for magnetron sputtering to obtain a certain valueAnd the height C axis of the thickness of the AlN thin film is preferred to be oriented.
3. The method for preparing the AlN piezoelectric film with the C-axis vertical preferred orientation according to claim 2, wherein the sputtering target material is placed in an asymmetric inclined target structure, the sputtering target material is a distributed multi-target, and the connecting line of the upper edge of the high-purity sputtering target and the edge of the sapphire substrate forms an included angle of 45 degrees with respect to the direction of the target material.
4. The method for preparing the AlN piezoelectric film with the C-axis vertical preferred orientation according to claim 2, wherein the sputtering target for preparing the metal electrode layer comprises any one of molybdenum, gold or platinum; the metal electrode layer is made of any one of molybdenum, gold or platinum.
5. The method of claim 2, wherein in steps S1 and S3, the volume ratio of argon to nitrogen introduced into the vacuum chamber is greater than or equal to 0 and less than or equal to 2/3.
6. The method for preparing the AlN piezoelectric film with the preferred C-axis vertical orientation is characterized in that in the process of plating the AlN seed film layer, the metal electrode film layer and the AlN film layer with the preferred C-axis height orientation by the magnetron sputtering method, the sapphire or YAG substrate rotates around the center at 200-300 r/min, the magnetron sputtering time is 2-4 hours, and the temperature of the sapphire or YAG substrate is 350-450 ℃.
7. The method for preparing the AlN piezoelectric film with the C-axis vertical preferred orientation according to any one of claims 2, 3 or 6, wherein the surface roughness of the sapphire or YAG substrate is less than 9nm, and the thickness of the sapphire or YAG substrate is 2-6 mm.
8. The method for preparing the AlN piezoelectric film with the C-axis vertical preferred orientation according to claim 2, wherein the surface roughness of the AlN seed film layer is less than 9nm, and the thickness of the AlN seed film layer is 30-60 nm.
9. The method for preparing the AlN piezoelectric film with the C-axis vertical preferred orientation according to claim 2 or 4, wherein the surface roughness of the metal electrode layer is less than 9nm, and the thickness of the metal electrode layer is 30-100 nm.
10. The method for preparing the AlN piezoelectric film with the C-axis vertical preferred orientation is characterized in that the surface roughness of the AlN piezoelectric film with the height of the C-axis preferred orientation is less than 9nm, and the thickness of the AlN piezoelectric film with the height of the C-axis preferred orientation is 200-1000 nm.
CN202011262292.8A 2020-11-12 2020-11-12 C-axis vertical preferred orientation AlN piezoelectric film and preparation method thereof Pending CN112382718A (en)

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