Carbon-containing dual-doped aluminum nitride piezoelectric film, preparation method and application

Abstract

The invention provides a carbon-containing dual-doped aluminum nitride piezoelectric film, a preparation method and an application thereof. By first-principles calculation and starting from the interatomic binding energy, an AlN piezoelectric film dual-doped with C element and X element is designed, and no complicated modification of equipment is required, thereby proposing an efficient and simple technical means. The carbon-containing dual-doped aluminum nitride piezoelectric film is prepared by magnetron sputtering technology, wherein dual-target or triple-target sputtering is adopted, and the doping concentrations of C element and X element can be accurately controlled by separating the target materials, and the stoichiometric ratio of 1:1 is always maintained as much as possible, so that a uniformly doped film can be obtained in the crossover region; single-target sputtering is adopted, so that the operation is simple and the film preparation is convenient and fast; thus, the aluminum nitride piezoelectric film with high piezoelectric performance can be prepared by the invention.

Description

Technical Field

[0001] The invention belongs to the field of piezoelectric films and relates to a carbon-containing dual-doped aluminum nitride piezoelectric film, a preparation method and an application thereof. Background Art

[0002] With the rapid development of micro-electromechanical system (MEMS) manufacturing technology, micro devices led by sensors, filters and actuators have quickly occupied the market. Therefore, piezoelectric materials that can be integrated with complementary metal oxide semiconductor (CMOS) technology have become a key research topic for scientists.

[0003] Aluminum nitride (AlN) film is considered to be one of the most promising piezoelectric thin film materials for acoustic wave devices due to its extremely high longitudinal acoustic wave velocity (10400m / s), low material intrinsic loss, excellent thermal stability, and ability to be integrated with CMOS technology. However, studies have found that the piezoelectric stress constant (e) of wurtzite phase AlN is 33 ) is 1.29C / m 2 ~1.80C / m 2 , its electromechanical coupling coefficient Kt 2 It is 6.1%, which is still at a relatively low level compared to other common piezoelectric materials such as ZnO and PZT, which limits its wide application in the field of acoustic wave devices to a certain extent. Therefore, it is a common method to improve the piezoelectric properties of AlN by doping with other elements. Among them, doping with Sc (scandium) elements can increase the piezoelectric stress constant e of AlN films. 33 , but it will lead to the piezoelectric constant (d 33 ) increases, and the Sc element is a transition element with high cost, which will cause a waste of resources.

[0004] Therefore, it is necessary to provide a carbon-containing dual-doped aluminum nitride piezoelectric film, a preparation method and an application thereof. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a carbon-containing dual-doped aluminum nitride piezoelectric film, a preparation method and an application, so as to solve the problem that it is difficult to prepare aluminum nitride piezoelectric films with high piezoelectric properties in the prior art.

[0006] To achieve the above objectives and other related objectives, the present invention provides a carbon-containing dual-doped aluminum nitride piezoelectric film, wherein the aluminum nitride piezoelectric film is composed of C element, X element and AlN, and the X element is one or a combination of Mg, Zn, Ca and Be.

[0007] Optionally, the molecular formula of the carbon-doped aluminum nitride piezoelectric film is C m X m Al 1-2m N,0<m≤0.3.

[0008] Optionally, the molecular formula of the carbon-doped aluminum nitride piezoelectric film is C m X m Al 1-2m N, 0.125≤m≤0.3.

[0009] The present invention also provides a method for preparing a carbon-containing dual-doped aluminum nitride piezoelectric film, which is prepared by a PVD three-target sputtering method, wherein the three targets are a C target or a CN target, an X target, and an Al target, respectively. The preparation of the carbon-containing dual-doped aluminum nitride piezoelectric film comprises the following steps:

[0010] After cleaning and drying the substrate material, place it in a vacuum chamber with an air pressure of 10 -7 Pa;

[0011] Argon and nitrogen were introduced, and the gas volume flow rates of argon and nitrogen were maintained at 35 sccm and 15 sccm respectively, and the pressure of the vacuum chamber was maintained at 3 Pa;

[0012] Apply RF power to the C target or CN target and adjust the power to 150W. Add DC power to the X target and Al target and adjust the power to 150W-200W. Co-sputter for 2 hours to prepare the carbon-containing dual-doped aluminum nitride piezoelectric film on the substrate.

[0013] Optionally, three sputtering targets are installed on the top of the vacuum chamber at an angle of 45° relative to the longitudinal symmetry axis of the vacuum chamber, and the distance between the center of the target and the center of the substrate stage is 150 mm.

[0014] The present invention also provides a method for preparing a carbon-containing dual-doped aluminum nitride piezoelectric film, which is prepared by a PVD dual-target sputtering method, wherein one of the dual targets is a C target or a CN target, and the other is a corresponding XAl alloy target or an Al target. The preparation of the carbon-containing dual-doped aluminum nitride piezoelectric film comprises the following steps:

[0015] After cleaning and drying the substrate material, place it in a vacuum chamber with an air pressure of 10 -7 Pa;

[0016] Argon and nitrogen were introduced, and the gas volume flow rates of argon and nitrogen were maintained at 35 sccm and 15 sccm respectively, and the pressure of the vacuum chamber was maintained at 3 Pa;

[0017] Apply radio frequency power to the C target or CN target, adjust the power to 150W, and add direct current power to the XAl alloy target or Al target, adjust the power to 150W-200W, and perform co-sputtering for 2h to prepare the carbon-containing dual-doped aluminum nitride piezoelectric film on the substrate.

[0018] Optionally, two sputtering targets are respectively installed at positions parallel to the longitudinal symmetry axis of the vacuum chamber, and the distance from the center of the sputtering target to the center of the substrate stage is 150 mm.

[0019] The present invention also provides a method for preparing a carbon-containing dual-doped aluminum nitride piezoelectric film, which is prepared by a PVD single-target sputtering method, and the target material is a CXAl alloy target.

[0020] The present invention also provides an acoustic wave resonator, comprising the above-mentioned carbon-containing dual-doped aluminum nitride piezoelectric film.

[0021] The present invention also provides a filter, comprising the above-mentioned carbon-containing dual-doped aluminum nitride piezoelectric film.

[0022] As described above, the carbon-containing dual-doped aluminum nitride piezoelectric film, preparation method and application of the present invention, through first-principles calculation, starting from the interatomic binding energy, designs an AlN piezoelectric film dual-doped with C element and X element, without the need for complex modification of the equipment, and proposes an efficient and simple technical means; the carbon-containing dual-doped aluminum nitride piezoelectric film is prepared by magnetron sputtering technology, wherein dual-target or triple-target sputtering is adopted, and the doping concentrations of C element and X element can be accurately controlled by separating the target materials, and the stoichiometric ratio of 1:1 is always maintained as much as possible, and a uniformly doped film can be obtained in the intersection area; single-target sputtering is adopted, which is simple to operate and convenient for rapid preparation of the film; thus, the present invention can prepare an aluminum nitride piezoelectric film with high piezoelectric performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is shown as C calculated by first principles in the embodiment of the present invention. m X m Al 1-2m The piezoelectric stress constant (e 33 ) and elastic constant (C 33 ).

[0024] Figure 2 It is shown as C calculated by first principles in the embodiment of the present invention. m X m Al 1-2m The piezoelectric constant (d 33 ). DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] Through first-principles calculations, it is found that the addition of 12.5% ​​Sc can increase the piezoelectric stress constant (e) of the AlN piezoelectric film. 33 1.8075C / m 2 ), but through COHP analysis, further research on the properties of covalent bonds in metal-N pairs shows that the ICOHP value of the Sc-N bond (-3.56eV) is significantly smaller than that of the Al-N bond (-5.22eV), indicating that the covalent bond energy of Sc-N is weaker than that of Al-N, so the Sc-N bond length is longer than that of Al-N, so the lattice constant and volume increase after adding the Sc element. Although Sc replacing Al will cause unit cell distortion and increase the piezoelectric stress constant e of the material, 33 However, the Sc-N covalent bond slightly increases the unit cell volume, resulting in elastic softening. Therefore, the addition of Sc into AlN will reduce the elastic constant (C 33 3029KBar), increasing the piezoelectric stress constant e 33 , but finally leads to the piezoelectric constant d 33 Moreover, Sc is a transition element with high cost, and its addition will increase material cost and cause waste of resources.

[0027] In order to overcome the above shortcomings, the applicant provides a carbon-containing dual-doped aluminum nitride piezoelectric film, wherein the aluminum nitride piezoelectric film is composed of C element, X element and AlN, and the X element is one or a combination of Mg, Zn, Ca and Be.

[0028] As an example, the molecular formula of the carbon-doped aluminum nitride piezoelectric film is C m X m Al 1-2m N, 0<m≤0.3, preferably 0.125≤m≤0.3.

[0029] Specifically, with the addition of C and X elements, the piezoelectric properties of AlN materials can be greatly improved. When the doping concentrations of C and X are both below 30%, that is, m≤0.3, the prepared piezoelectric material has a high piezoelectric constant and good performance. Figure 1 and Figure 2 , which shows the carbon-containing dual-doped aluminum nitride piezoelectric film C obtained by first-principles calculation when m=0.0625, m=0.125 and m=0.25 and the X element is Mg. m X m Al 1-2m The elastic constant C corresponding to N 33 , piezoelectric stress constant e 33 and piezoelectric constant d 33However, the value of m is not limited thereto, for example, the value of m may also be 0.1, 0.2, 0.3, etc., and the X element is not limited to the Mg element, but may also be one of the Zn element, the Ca element, the Be element, or a combination of the Mg element and the Zn element, the Ca element, and the Be element.

[0030] Through first-principles calculations, it was found that with the incorporation of X element, X will replace Al position and form covalent bonds with surrounding N atoms containing weak ionic bonds. The bond energy of XN bond is weaker than that of Al-N, which reduces the elastic stiffness coefficient of the material. Traditionally, the bond energy of CN bond is relatively strong, and the stiffness coefficient of the material will increase after the incorporation of AlN. However, the strong electronegativity of C will attract the electrons of the surrounding Al-N bonding, resulting in the weakening of the bond energy of the surrounding Al-N bonds, and there will be a small amount of antibonding electrons above the bottom of the CN bonding conduction band that affect the bonding. Therefore, when the concentration of doped C reaches a certain level, the elastic constant of the material decreases instead, resulting in elastic softening. At the same time, with the doping of X element and C element, the strain sensitivity of the lattice along the C axis will increase significantly, resulting in the piezoelectric stress constant e of the dual-doped AlN of X element and C element. 33 Much larger than pure AlN. So through first-principles calculations, it is found that Figure 1 and Figure 2 As shown in the figure, when the C and Mg doping concentrations are both 12.5%, that is, when m is 0.125, the lattice will produce obvious elastic softening, resulting in the elastic constant C 33 Significantly reduced (C 33 is 2474Kbar), and the piezoelectric stress constant e 33 Producing amazing growth (e 33 3.25C / m 2 ), resulting in a piezoelectric constant d 33 (d 33 13pC / N) is 4-5 times that of ordinary pure AlN. Therefore, by doping AlN materials with C and X elements, AlN piezoelectric composite films with high piezoelectric constant and high electromechanical coupling coefficient can be prepared.

[0031] This embodiment uses first-principles calculations to design the carbon-containing dual-doped aluminum nitride piezoelectric film, and this embodiment also provides a method for preparing the carbon-containing dual-doped aluminum nitride piezoelectric film. The above-mentioned carbon-containing dual-doped aluminum nitride piezoelectric film can be prepared by the following method, but is not limited to this.

[0032] As an example, the carbon-containing dual-doped aluminum nitride piezoelectric film may be prepared by a PVD three-target sputtering method, wherein the three targets may be a C target or a CN target, an X target, and an Al target, respectively. The preparation of the carbon-containing dual-doped aluminum nitride piezoelectric film includes the following steps:

[0033] After cleaning and drying the substrate material, place it in a vacuum chamber with an air pressure of 10-7 Pa;

[0034] Argon and nitrogen were introduced, and the gas volume flow rates of argon and nitrogen were maintained at 35 sccm and 15 sccm respectively, and the pressure of the vacuum chamber was maintained at 3 Pa;

[0035] Apply RF power to the C target or CN target and adjust the power to 150W. Add DC power to the X target and Al target and adjust the power to 150W-200W, such as 150W, 160W, 180W, 200W, etc., and perform co-sputtering for 2 hours to prepare the carbon-containing dual-doped aluminum nitride piezoelectric film on the substrate.

[0036] Specifically, by using three-target sputtering, the C element, X element, and Al element are sputtered separately, so that the doping concentration of the C element and the X element can be precisely controlled, and the stoichiometric ratio of 1:1 is always maintained as much as possible to avoid charge imbalance, thereby avoiding more electrons from presenting an anti-bonded state. In addition, the C element is preferably doped with a high-purity C target or CN target, and the concentration of the doped C can be directly controlled by controlling the power supply.

[0037] Furthermore, three sputtering targets are installed on the top of the vacuum chamber at an angle of 45° relative to the longitudinal symmetry axis of the vacuum chamber, and the distance between the center of the target and the center of the substrate stage is 150 mm, so that the doped film can be more uniform in the intersection area of ​​the three-target sputtering.

[0038] Specifically, in addition to the three-target PVD sputtering process, the preparation process of the carbon-containing dual-doped aluminum nitride piezoelectric film can also adopt dual-target sputtering or single-target sputtering. Among them, in the dual-target sputtering process, one of the targets can be selected as a high-purity C target or a CN target, and the other target can be replaced with an XAl alloy target. In the single-target sputtering process, the target material can be selected as a CXAl alloy target for sputtering, and other process parameters can be fine-tuned.

[0039] As an example, when the carbon-containing dual-doped aluminum nitride piezoelectric film is prepared by a PVD dual-target sputtering method, one of the dual targets is a C target or a CN target, and the other is a corresponding XAl alloy target or an Al target. The preparation of the carbon-containing dual-doped aluminum nitride piezoelectric film includes the following steps:

[0040] After cleaning and drying the substrate material, place it in a vacuum chamber with an air pressure of 10 -7 Pa;

[0041] Argon and nitrogen were introduced, and the gas volume flow rates of argon and nitrogen were maintained at 35 sccm and 15 sccm respectively, and the pressure of the vacuum chamber was maintained at 3 Pa;

[0042] Apply RF power to the C target or CN target and adjust the power to 150W. Add DC power to the XAl alloy target or Al target and adjust the power to 150W-200W. Co-sputter for 2 hours to prepare the carbon-containing dual-doped aluminum nitride piezoelectric film on the substrate.

[0043] Specifically, by using dual-target sputtering, the C element and the X element are sputtered separately, so that the doping concentration of the C element and the X element can be precisely controlled, and the stoichiometric ratio of 1:1 is always maintained as much as possible to avoid charge imbalance, thereby avoiding more electrons from being in an anti-bonded state. In addition, the C element is preferably doped with a high-purity C target or CN target, and the concentration of the doped C can be directly controlled by controlling the power supply.

[0044] Furthermore, two sputtering targets are installed at positions parallel to the longitudinal symmetry axis of the vacuum chamber, and the distance from the center of the sputtering target to the center of the substrate stage is 150 mm, so that the doped film can be more uniform in the intersection area of ​​the three-target sputtering.

[0045] As an example, when the PVD single-target sputtering method is used to prepare the carbon-containing dual-doped aluminum nitride piezoelectric film, the target material is a CXAl alloy target, and single-target sputtering is used, which is easy to operate and facilitates rapid preparation of the film.

[0046] This embodiment also provides an acoustic wave resonator, which includes the carbon-containing dual-doped aluminum nitride piezoelectric film; this embodiment also provides a filter, which includes the carbon-containing dual-doped aluminum nitride piezoelectric film. The types and preparation of the acoustic wave resonator and the filter are not limited here.

[0047] In summary, the carbon-containing dual-doped aluminum nitride piezoelectric film, preparation method and application of the present invention, through first-principles calculation, starting from the interatomic binding energy, designs an AlN piezoelectric film dual-doped with C element and X element, without the need for complex modification of the equipment, and proposes an efficient and simple technical means; the carbon-containing dual-doped aluminum nitride piezoelectric film is prepared by magnetron sputtering technology, wherein dual-target or triple-target sputtering is adopted, and the target materials are separated to accurately control the doping concentrations of C element and X element, and the stoichiometric ratio of 1:1 is always maintained as much as possible, and a uniformly doped film can be obtained in the intersection area; single-target sputtering is adopted, which is simple to operate and convenient for rapid preparation of the film; thus, the present invention can prepare an aluminum nitride piezoelectric film with high piezoelectric performance.

[0048] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A carbon-doped aluminum nitride piezoelectric film, characterized in that: The aluminum nitride piezoelectric film is composed of C element, X element and AlN, wherein the X element is one or a combination of Mg, Zn, Ca and Be, and the molecular formula of the carbon-doped aluminum nitride piezoelectric film is C m X m Al 1-2m N, 0.125≤m≤0.

3.

2. A method for preparing the carbon-doped aluminum nitride piezoelectric film as claimed in claim 1, characterized in that: The PVD three-target sputtering method is adopted, wherein the three targets are C target or CN target, X target and Al target respectively, and the preparation of the carbon-containing dual-doped aluminum nitride piezoelectric film includes the following steps: After cleaning and drying the substrate material, place it in a vacuum chamber with an air pressure of 10 -7 Pa; Argon and nitrogen were introduced, and the gas volume flow rates of argon and nitrogen were maintained at 35 sccm and 15 sccm respectively, and the pressure of the vacuum chamber was maintained at 3 Pa; Apply RF power to the C target or CN target and adjust the power to 150W. Add DC power to the X target and Al target and adjust the power to 150W-200W. Co-sputtering is performed for 2 hours to prepare the carbon-containing dual-doped aluminum nitride piezoelectric film on the substrate.

3. The method for preparing the carbon-doped aluminum nitride piezoelectric film according to claim 2, characterized in that: The three sputtering targets were installed on the top of the vacuum chamber at an angle of 45° relative to the longitudinal symmetry axis of the vacuum chamber, and the distance between the center of the target and the center of the substrate stage was 150 mm.

4. A method for preparing the carbon-doped aluminum nitride piezoelectric film as claimed in claim 1, characterized in that: The PVD double-target sputtering method is adopted, one of the double targets is a C target or a CN target, and the other is a corresponding XAl alloy target. The preparation of the carbon-containing double-doped aluminum nitride piezoelectric film includes the following steps: After cleaning and drying the substrate material, place it in a vacuum chamber with an air pressure of 10 -7 Pa; Argon and nitrogen were introduced, and the gas volume flow rates of argon and nitrogen were maintained at 35 sccm and 15 sccm respectively, and the pressure of the vacuum chamber was maintained at 3 Pa; Apply RF power to the C target or CN target and adjust the power to 150 W. Add DC power to the XAl alloy target and adjust the power to 150 W to 200 W. Co-sputter for 2 hours to prepare the carbon-containing dual-doped aluminum nitride piezoelectric film on the substrate.

5. The method for preparing the carbon-doped aluminum nitride piezoelectric film according to claim 4, characterized in that: The two sputtering targets are respectively installed at positions parallel to the longitudinal symmetry axis of the vacuum chamber, and the distance from the center of the sputtering target to the center of the substrate stage is 150 mm.

6. A method for preparing the carbon-doped aluminum nitride piezoelectric film as claimed in claim 1, characterized in that: The target material is CXAl alloy target and prepared by PVD single target sputtering method.

7. An acoustic wave resonator, characterized in that: The invention comprises the carbon-doped aluminum nitride piezoelectric film as claimed in claim 1.

8. A filter, characterized in that: The invention comprises the carbon-doped aluminum nitride piezoelectric film as claimed in claim 1.

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