Preparation method of AlScN film, FBAR filter film and FBAR filter

Abstract

The invention discloses an AlScN film and a preparation method thereof, an AlScN intermediate and an FBAR filter, and relates to the field of semiconductor materials. The preparation method of the AlScN film provided by the invention comprises the following steps: S100, growing an AlN epitaxial layer on a heterogeneous substrate; s200, forming a graphene layer on the surface of the AlN layer by using a CVD (Chemical Vapor Deposition) technology; and S300, sputtering and depositing an AlScN film on the surface of the graphene layer by using a PVD (Physical Vapor Deposition) technology. According to the preparation method, the AlScN film which is high in crystal quality and easy to peel can be prepared, and the AlScN film can be used for improving the performance of an FBAR filter in a high frequency band.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor materials, and in particular to a preparation method of an AlScN film, an FBAR filter film and an FBAR filter. BACKGROUND

[0002] An FBAR (Film Bulk Acoustic Resonator) filter is a trusted radio frequency device for high frequency communication, and is one of the most ideal filter devices applied in the Sub 6G field after a SAW (Surface Acoustic Wave) filter. AlScN (aluminum scandium nitride) can be used to manufacture an FBAR filter, and AlScN has good acoustic velocity (up to 10700 m / s) and higher thermal stability, which has a significant impact on the performance of the FBAR filter.

[0003] At present, a magnetron sputtering method is generally used to deposit an AlScN film on a silicon substrate or other heterogeneous substrates. However, the AlScN film formed by using this method has poor crystal quality and is difficult to improve (especially for an AlScN film with a large thickness), and cannot meet the performance requirements of a high-frequency FBAR filter. Moreover, this process not only has a relatively high requirement for the warping degree of the silicon substrate, but also makes it difficult to separate the deposited AlScN film from the silicon substrate, and the separation needs to be performed through a plasma etching or wet cleaning stripping process, resulting in a low production efficiency of the AlScN film. SUMMARY

[0004] The present application provides an AlScN film, a preparation method of the AlScN film, an AlScN intermediate and an FBAR filter, and the AlScN film with high crystal quality can be prepared, and the prepared AlScN film is easy to be separated from a substrate, and the production efficiency can be improved.

[0005] In a first aspect, the present application provides a preparation method of an AlScN film, including the following steps: S100, growing an AlN epitaxial layer on a heterogeneous substrate; S200, forming a graphene layer on the surface of the AlN layer by using a CVD technology; and S300, sputtering and depositing an AlScN film on the surface of the graphene layer by using a PVD technology.

[0006] Based on the preparation method of the AlScN film of the present application, an AlScN film with high crystal quality and easy to peel can be obtained. In the embodiment of the present application, the AlN epitaxial layer first formed on the surface of the substrate can ensure that the AlScN film formed subsequently does not directly contact the heterogeneous substrate, and the AlScN film will not crack or affect the crystal quality of the AlScN film due to lattice mismatch and thermal mismatch with the heterogeneous substrate. In addition, the inventors found that since there is a graphene layer made using CVD technology between the AlScN film and the AlN epitaxial layer, the atoms in the graphene layer are arranged in a hexagonal pattern, and the arrangement is similar to that of c-plane AlN and ScAlN, and the graphene layer can even form a single atomic layer, which has very little effect on the lattice arrangement between AlN and ScAlN. Therefore, the AlN epitaxial layer will directly affect the AlScN film. Since the lattice difference between AlN and AlScN is small, it can not only ensure that the AlScN film will not reduce the crystal quality due to lattice mismatch and thermal mismatch, but also promote the crystallization of AlScN. In addition, since the graphene layer and the AlN epitaxial layer, and the graphene layer and the AlScN film deposited using CVD technology are bonded together only by van der Waals forces, the AlScN film does not form metallic bonds or covalent bonds with the AlN epitaxial layer or the substrate, which makes the AlScN film very easy to peel off, and can even detach on its own, without the need for plasma etching or wet cleaning and other peeling processes for separation. Therefore, in the preparation method of the present application, the graphene layer deposited using CVD technology can reduce the difficulty of peeling the AlScN film without substantially affecting the crystal quality of the AlScN film, and the AlScN film deposited by sputtering using PVD technology can also significantly improve its own crystal quality under the inherited effect of the AlN epitaxial layer with good crystal quality.

[0007] In some embodiments, the half-maximum width of the (002) crystal plane of the AlN epitaxial layer is I A arcsec, meeting: 600≤I A ≤1500, and / or the thickness of the graphene layer is 0.334nm~3.5nm.

[0008] Based on the above embodiment, when the AlN epitaxial layer meets the above conditions, its crystal quality is high, which facilitates the deposition of an AlScN film with higher crystal quality. Furthermore, because the graphene layer is located between the AlN epitaxial layer and the AlScN film, the AlN epitaxial layer can more effectively promote the formation of an AlScN film with higher crystal quality when the exfoliation layer is no greater than 3.5 nm. Furthermore, since the thickness of a single layer of graphene is only 0.334 nm, the thickness of the graphene layer must also be 0.334 nm or greater; otherwise, it will not be able to separate the AlN epitaxial layer (also called the "seed layer") from the AlScN film. When both the AlN epitaxial layer and the graphene layer meet the above conditions, the resulting AlScN film has higher crystal quality and is easier to exfoliate.

[0009] In some embodiments, in the CVD technology of step S200, the reaction temperature is 900° C. to 1100° C., the gas pressure is 0.01 to 10 Torr, and the flow ratio of methane to hydrogen is 1:50 to 1:10.

[0010] Based on the above embodiments, a suitable temperature range can ensure that the stone forms a continuous graphene layer. Too low a temperature may easily cause discontinuous layer structure, and too high a temperature may easily cause desorption of the generated graphene layer. A suitable air pressure range and air flow ratio can ensure the efficiency of graphene preparation while preventing excessive growth caused by excessive air pressure, which may prevent the formation of a continuous film at a specific thickness.

[0011] In some embodiments, the thickness of the AlN epitaxial layer is 50 nm to 150 nm.

[0012] Based on the above embodiments, the thickness of the AlN epitaxial layer is controlled within a suitable range, and the quality of the prepared AlScN film is better and less prone to cracking.

[0013] In some embodiments, the thickness of the AlScN film is 300-1000 nm.

[0014] Based on the above embodiments, the thickness range of the AlScN film can well meet the material thickness requirements of mainstream frequency filters.

[0015] In some embodiments, in the PVD technology of step S300, the sputtering power is 1500W~3000W, the gas pressure is 2mtorr~6mtorr, the temperature is 200~700°C, and the flow ratio of the introduced argon gas and nitrogen gas is 1:2~1:7.

[0016] Based on the above embodiments, the appropriate sputtering power can prevent the deterioration of crystal quality caused by too low or too high power; the appropriate gas pressure value can ensure process efficiency while preventing the deterioration of crystal quality caused by too high gas pressure; the appropriate sputtering temperature can ensure the quality of thin film crystals while preventing excessive temperature from reducing the service life of the heating module. Argon is used as a sputtering gas to form a plasma under the action of accelerated electrons, and is accelerated to bombard the ScAl alloy target under the action of a strong electric field. The sputtered Sc / Al atoms combine with nitrogen to form a ScAlN ternary alloy. Therefore, the appropriate gas ratio can ensure that argon gas efficiently acts on the target material, ensure process efficiency, and prevent the proportion of argon gas from being too high, which increases the probability of Al and Sc atoms being scattered, resulting in low energy of Al and Sc atoms, thereby reducing the crystal quality of ScAlN.

[0017] In some embodiments, the foreign substrate is a silicon substrate.

[0018] Based on the above embodiments, the silicon substrate is cheap and has a low preparation cost, and it is easier to form an AlN epitaxial layer with good crystal quality on the silicon substrate and the sapphire substrate.

[0019] In a second aspect, the present application provides an FBAR filter membrane, which includes a substrate and an AlScN film stacked in sequence, the substrate and the AlScN film are bonded by intermolecular forces, the substrate includes an AlN epitaxial layer and a graphene layer stacked, and the graphene layer is located between the AlN epitaxial layer and the AlScN film.

[0020] Based on the FBAR filter membrane in this application, since the graphene layer belongs to a single atomic layer and the atoms are arranged in a hexagonal pattern, the arrangement is similar to that of c-plane AlN and ScAlN, and the effect on the lattice arrangement between AlN and ScAlN is very small. The graphene layer in the substrate and the AlScN film are bonded together by intermolecular forces. The weak intermolecular forces result in weak adhesion between the layers. Therefore, the AlScN film can be easily peeled off without the need for plasma etching or wet cleaning.

[0021] In some of the embodiments, the AlScN film is prepared by the above-mentioned AlScN film preparation method.

[0022] Based on the above embodiments, the AlScN film produced has high crystal quality and is easy to peel off.

[0023] In a third aspect, the present application provides an FBAR filter comprising the above-mentioned AlScN film. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the following examples are used to further illustrate the present application. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0025] In the prior art, it is difficult to prepare an AlScN film with high crystal quality to meet the needs of high-frequency FBAR filters, and the prior art also needs to separate the prepared AlScN film through a stripping process such as plasma etching or wet cleaning, resulting in low production efficiency of the AlScN film.

[0026] In order to solve the above technical problems, the present application provides a preparation method of an AlScN film, which is specifically as follows: S100, growing an AlN epitaxial layer on the surface of a heterogeneous substrate.

[0027] The AlN epitaxial layer formed in this step can avoid the AlScN film formed subsequently from being in direct contact with the heterogeneous substrate, and can determine the crystal quality of the AlScN film formed subsequently, so a good crystal quality of the AlN epitaxial layer is very important. The method for preparing a seed crystal layer with good crystal quality includes but is not limited to metal-organic chemical vapor deposition (MOCVD), physical vapor deposition (PVD), hydride vapor phase epitaxy (HVPE), and any one or a combination of two or more methods, and the heterogeneous substrate can be any one of a silicon substrate, a sapphire substrate, a silicon carbide substrate, and a metal substrate.

[0028] As an example, in the embodiments of the present application, the AlN epitaxial layer is grown by using the MOCVD method. Compared with other methods, MOCVD can guarantee the process efficiency while preparing a high-quality AlN epitaxial layer on a Si substrate. In this step, the AlN epitaxial layer is prepared by using the MOCVD method, and the group III metal source is trimethylaluminum (TMAl) and the group V gas source is ammonia (HN3). The process flow is as follows: S110, high-temperature hydrogen cleaning of the Si substrate in the reaction cavity; this step is usually performed at a temperature of 1050°C to 1150°C, which can well clean the impurities and oxides on the surface of the heterogeneous substrate.

[0029] S120, pre-depositing an Al atomic layer on the Si substrate.

[0030] S130, growing an AlN nucleation layer; this step can improve the overall crystal quality of the AlN epitaxial layer.

[0031] S140, growing an AlN high-temperature layer.

[0032] The generated Al atomic layer, AlN nucleation layer, and AlN high-temperature layer are superimposed to form the AlN epitaxial layer.

[0033] The specific process data are as follows:

[0034] In some implementations of the present application, the half-maximum width of the AlN epitaxial layer (002) crystal plane obtained in this step is I A arcsec, meeting: 600≤I A ≤1500, so that the crystal quality of the AlN epitaxial layer is high, which is conducive to the deposition of AlScN films with better crystal quality. In addition, in some embodiments of the present application, the thickness of the AlN epitaxial layer is 50nm~150nm, so that the quality of the subsequently produced AlScN film is better and less prone to cracking.

[0035] Of course, other processes can also be used to obtain the AlN epitaxial layer of the required quality. Therefore, this application does not specifically limit the preparation process of the AlN epitaxial layer, as long as it can meet the purpose of this application.

[0036] S200: forming a graphene layer on the surface of the AlN layer using a CVD (Chemical Vapor Deposition) technique.

[0037] In this step, the graphene layer formed by the CVD technique does not contain any substance that can form a chemical bond such as a metallic bond or a covalent bond. Therefore, the graphene is bonded to the AlN nucleation layer by van der Waals forces, and is also bonded to the subsequently formed AlScN film by van der Waals forces. In addition, as an example, the thickness of the graphene layer formed by the deposition in this step is preferably not greater than 3.5 nm, so that it is less likely to affect the promoting effect of the AlN epitaxial layer on the crystal quality of the AlScN film. In addition, since the standard thickness of a single layer of graphene is 0.334 nm, the thickness of the graphene layer will also be 0.334 nm and above, so that the graphene layer can more effectively separate the AlN epitaxial layer and the AlScN film, which is more conducive to reducing the difficulty of peeling the AlScN film. As an example, the specific experimental process of this step is as follows: Methane and hydrogen are introduced into the reaction chamber at a flow ratio of 1:10 to 1:50, the pressure is maintained at 0.01 to 10 Torr, and the reaction is carried out at 900 to 1100°C.

[0038] S300, sputtering and depositing an AlScN film on the surface of the graphene layer using PVD technology.

[0039] This step can form AlScN films of various thicknesses, ranging from 300nm to 1000nm. Furthermore, the AlScN films formed by the method in the embodiments of the present application have a particularly significant improvement in crystal quality when the thickness is not less than 300nm compared to the prior art. Furthermore, as an example, this step forms an AlScN film on the surface of a graphene layer using PVD technology under the following conditions: a sputtering power of 1500W to 3000W, a gas pressure of 2mtorr to 6mtorr, a temperature of 200°C to 700°C, and a flow ratio of argon to nitrogen of 1:2 to 1:7.

[0040] The present application also provides an FBAR filter membrane, which comprises a three-layer structure comprising an AlN epitaxial layer, a graphene layer, and an AlScN film, wherein the three layers have not yet been peeled off. In this case, the structure formed by the superposition of the AlN epitaxial layer and the graphene layer serves as a substrate. Furthermore, the AlN epitaxial layer and the graphene layer are bonded to each other via intermolecular forces, and the graphene layer and the AlScN film are bonded to each other via intermolecular forces. The AlScN film in this FBAR filter membrane can be easily peeled off without the need for plasma etching or wet cleaning.

[0041] The FBAR filter membrane prepared using the above preparation method can be used in the FBAR filter, thereby improving the performance of the FBAR filter in the high frequency band.

[0042] The AlScN film and its preparation method are further described in detail below with reference to the examples. Where specific conditions are not specified in the examples, conventional conditions or those recommended by the manufacturer were followed. Reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0043] Example 1 This embodiment provides an AlScN film, and the preparation method thereof is as follows: (1) Growth of AlN epitaxial layer: The AlN epitaxial layer is grown using MOCVD. The specific process data are as follows:

[0044] The XRD (002) half-maximum width of the AlN epitaxial layer prepared in the above manner is 1020 arcsec.

[0045] (2) Depositing a graphene layer on the surface of the AlN layer using CVD technology: Methane and hydrogen were introduced into the reaction chamber at a flow rate ratio of 1:10, and reacted at 900°C to deposit a graphene layer (i.e., single-layer graphene) with a thickness of 0.334 nm on the surface of the AlN epitaxial layer.

[0046] (3) Using PVD technology to sputter-deposit AlScN film on the surface of the graphene layer: Under the conditions of a sputtering power of 1500W, a gas pressure of 2mtorr, and a temperature of 200°C, argon and nitrogen with a flow ratio of 1:2 were introduced to sputter-deposit an AlScN film with a thickness of 300nm on the surface of the graphene layer.

[0047] Example 2 This embodiment provides an AlScN film, and the preparation method thereof is as follows: (1) Growth of AlN epitaxial layer: The AlN epitaxial layer prepared by the same process as in Example 1 has an XRD (002) half-width of 1045 arcsec.

[0048] (2) Depositing a graphene layer on the surface of the AlN layer using CVD technology: Methane and hydrogen were introduced into the reaction chamber at a flow ratio of 1:50, and the reaction was carried out at 1100°C for 40 minutes, thereby depositing a graphene layer with a thickness of 3.4 nm (i.e., 10 layers of graphene) on the surface of the AlN epitaxial layer.

[0049] (3) Using PVD technology to sputter-deposit AlScN film on the surface of the graphene layer: Under the conditions of a sputtering power of 3000W, a gas pressure of 6mtorr, and a temperature of 700°C, argon and nitrogen with a flow ratio of 1:7 were introduced to sputter-deposit an AlScN film with a thickness of 1000nm on the surface of the graphene layer.

[0050] Example 3 This embodiment provides an AlScN film, the preparation of which is different from that of Example 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1039 arcsec; and the thickness of the graphene layer formed in step (2) is 7.8 nm (i.e., 20 layers of graphene).

[0051] Example 4 This embodiment provides an AlScN film, the preparation of which is different from that of embodiment 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1024 arcsec; and the temperature of step (2) is 700°C.

[0052] Example 5 This embodiment provides an AlScN film, the preparation of which is different from that of embodiment 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1067 arcsec; and the temperature of step (2) is 1200°C.

[0053] Example 6 This embodiment provides an AlScN film, the preparation of which is different from that of Example 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1086 arcsec; and the ratio of methane to hydrogen in step (2) is 1:5.

[0054] Example 7 This embodiment provides an AlScN film, the preparation of which is different from that of embodiment 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1041 arcsec; and the gas pressure in step (2) is 200 Torr.

[0055] Example 8 This embodiment provides an AlScN film, the preparation of which is different from that of embodiment 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1053 arcsec; and the sputtering power in step (3) is 800W.

[0056] Example 9 This embodiment provides an AlScN film, the preparation of which is different from that of embodiment 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1055 arcsec; and the sputtering power in step (3) is 4000W.

[0057] Example 10 This embodiment provides an AlScN film, the preparation of which is different from that of embodiment 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1072 arcsec; and the gas pressure in step (3) is 10 mbar.

[0058] Example 11 This embodiment provides an AlScN film, the preparation of which is different from that of embodiment 1 in that: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1012 arcsec; and the sputtering temperature in step (3) is 50°C.

[0059] Example 12 This embodiment provides an AlScN film, and the main differences in its preparation compared with Example 1 are: the half-maximum width of the prepared AlN epitaxial layer XRD (002) is 1038 arcsec; and the ratio of argon to argon in step (3) is 2:1.

[0060] Comparative Example 1 This comparative example provides an AlScN film, and the preparation method thereof is different from that of Example 1 in that: step (2) is not included, and an AlScN film of the same thickness is directly sputter-deposited on the surface of the AlN epitaxial layer.

[0061] Performance Testing Peel strength test The AlScN films in each embodiment and comparative example were peeled off by hand. The experimental results show that the AlScN films in the embodiments can be successfully peeled off, and the AlScN films in Examples 2 and 3 can even fall off by themselves. The AlScN film in the comparative example cannot be peeled off by hand and can only be peeled off by subsequent plasma etching.

[0062] Crystal quality test The AlScN films peeled off in the embodiment and the comparative example were tested using XRD (X-ray diffraction) technology. The test results are shown in Table 1.

[0063] Table 1 Crystal quality of AlScN films in various examples and comparative examples

[0064] It can be seen from Table 1 and the above-mentioned peeling test results that the AlScN film prepared by the preparation method in the embodiment of the present application has high crystal quality and is easy to peel off.

[0065] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing an AlScN film, characterized in that: It includes the following steps: S100, growing an AlN epitaxial layer on a foreign substrate; S200, depositing a graphene layer on the surface of the AlN layer using a CVD technique; S300 , sputter-depositing an AlScN film on the surface of the graphene layer using PVD technology.

2. The method for preparing an AlScN film according to claim 1, wherein: The half-maximum width of the (002) crystal plane of the AlN epitaxial layer is I A arcsec, meeting: 600≤I A ≤1500; And / or, the thickness of the graphene layer is 0.334 nm to 3.5 nm.

3. The method for preparing an AlScN film according to claim 1 or 2, wherein: In the CVD technology of step S200, the reaction temperature is 900° C. to 1100° C., the gas pressure is 0.01 to 10 Torr, and the flow ratio of methane to hydrogen is 1:50 to 1:

10.

4. The method for preparing an AlScN film according to claim 1 or 2, wherein: The thickness of the AlN epitaxial layer is 50nm-150nm.

5. The method for preparing an AlScN film according to claim 1, wherein: The thickness of the AlScN film is 300nm~1000nm.

6. The method for preparing an AlScN film according to claim 1 or 5, characterized in that: In the PVD technology of step S300, the sputtering power is 1500W~3000W, the gas pressure is 2mtorr~6mtorr, the temperature is 200~700℃, and the flow ratio of the argon gas and the nitrogen gas is 1:2~1:

7.

7. The method for preparing an AlScN film according to claim 1, wherein: The foreign substrate is a silicon substrate.

8. An FBAR filter membrane, characterized in that: The invention comprises a substrate and an AlScN film which are stacked in sequence, wherein the substrate and the AlScN film are bonded by intermolecular forces, the substrate comprises an AlN epitaxial layer and a graphene layer which are stacked, and the graphene layer is located between the AlN epitaxial layer and the AlScN film.

9. The FBAR filter film according to claim 8, characterized in that The AlScN film is prepared by the AlScN film preparation method according to any one of claims 1 to 7.

10. An FBAR filter, characterized in that: It contains the AlScN film according to claim 9.

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