Thin film bulk acoustic wave device heterogeneous integrated structure and preparation method thereof

Abstract

The invention discloses a thin film bulk acoustic wave device heterogeneous integrated structure and a preparation method thereof, the thin film bulk acoustic wave device heterogeneous integrated structure arranges a passive device in a cavity required by the work of a thin film bulk acoustic wave device, and realizes the high integration of a packaging device, thereby releasing more cover plate space, improving the utilization rate of a packaging cover plate, and improving the reliability of the packaging device. And meanwhile, in the preparation method, the preparation of the second electrode of the passive device and the TSV adhesion layer are combined into the same process, so that the preparation process of the device is simplified, the use frequency of precious metal is reduced, and the manufacturing cost of the device is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS devices, and in particular to a thin film bulk acoustic wave device heterogeneous integrated structure and a preparation method thereof. Background Art

[0002] With the rapid development of mobile communication technology, the market demand for highly integrated, high-performance filters is increasing. Patent document CN201210345115.5 discloses a structure combining a thin film bulk acoustic wave device and a passive device package. The patent proposes to introduce mutual inductance between the inductors connecting the thin film bulk acoustic wave device, adjust the position of the transmission zero point of the thin film bulk acoustic wave device, and improve the high-frequency performance of the filter.

[0003] At present, there are many studies on the structure of the combination of thin film bulk acoustic wave devices and passive device packaging. There is a design that directly connects the passive device chip on the back of the package cover or the back of the thin film bulk acoustic wave device substrate. This design will inevitably increase the overall thickness of the chip, which is not conducive to the miniaturization of the chip. There are also passive devices formed on the surface of the cover, and then a protective layer is deposited to isolate the passive devices, and the gap left after bonding with a thicker bonding layer is used as the cavity required for the operation of the thin film bulk acoustic wave device, or a very thick isolation layer is deposited, and then a cavity is prepared on the isolation layer. In actual device packaging, in addition to TSV through holes, pad holes are also arranged on the cover to increase the bonding strength of the device. These pad holes will occupy a part of the cover space. There may be other devices and thin film bulk acoustic wave devices integrated in the future, which is a test for the utilization rate of the cover. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention proposes a thin film bulk acoustic wave device heterogeneous integrated structure and a preparation method thereof, which can significantly improve the performance of the thin film bulk acoustic wave device while reducing the production cost required to achieve similar performance improvement.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a heterogeneous integrated structure of a thin film bulk acoustic wave device, the method comprising the following steps:

[0007] Step 1: Cleaning the cover substrate;

[0008] Step 2: forming a first cavity on the cover substrate by dry etching;

[0009] Step 3: depositing a layer of first metal on the cover substrate processed in step 2, and dry-etching the deposited first metal to form a first electrode; wherein the first electrode comprises an electrode pattern located in the first cavity and a wire located outside the first cavity;

[0010] Step 4: depositing a dielectric layer metal on the cover substrate obtained in step 3, and dry-etching the deposited dielectric layer metal to retain only the dielectric layer metal covering the electrode pattern in the first cavity, thereby forming a dielectric layer;

[0011] Step 5: etching at least two countersunk holes on the cover substrate processed in step 4 by using a deep silicon etching process;

[0012] Step 6: Continue to deposit a layer of second metal on the cover substrate processed in step 5 as an adhesion layer, and process the deposited adhesion layer to remove a portion of the second metal located on the first electrode and not covered by the dielectric layer, so that the adhesion layer is divided into two unconnected left and right parts, and ensure that the adhesion layer on one side is connected to the first electrode; the portion of the adhesion layer on the other side located on the dielectric layer serves as the second electrode; the first electrode, the dielectric layer and the second electrode constitute a passive device; at this time, the preparation of the packaging cover of the passive device is completed;

[0013] Step 7: bonding the package cover plate with passive components obtained in step 6 to the thin film filter to be bonded by a bonding method;

[0014] Step 8: removing the back side of the bonded cover substrate by mechanical grinding to expose the adhesion layer deposited in the countersunk hole;

[0015] Step nine: fill the countersunk holes with electroplating, and etch the electroplating material between the two countersunk holes with dry etching or wet etching to form a pad.

[0016] Furthermore, the metal is deposited in step three, step four and step six by thermal evaporation or magnetron sputtering.

[0017] Furthermore, in the step six, when the adhesion layer is processed, plasma etching, lift-off or wet etching is used to form a pattern.

[0018] A heterogeneous integrated structure of a thin film bulk acoustic wave device obtained by the above-mentioned preparation method comprises a package cover plate with a passive device and a thin film filter bonded together, wherein the passive device is located in a first cavity inside the package cover plate;

[0019] The package cover plate includes a cover plate substrate, a first electrode, a dielectric layer, a second electrode, and an adhesion layer;

[0020] A first cavity is formed in the middle of the cover substrate, and at least two through holes are formed at the end of the cover substrate;

[0021] The first electrode is deposited on the cover substrate, and includes an electrode pattern located in the first cavity and a wire located outside the first cavity;

[0022] The dielectric layer is deposited on the first electrode and covers the electrode pattern;

[0023] The adhesion layer is deposited on the cover substrate, and includes two unconnected left and right parts, one of which covers at least one through hole of the cover substrate and is connected to the first electrode; the other part covers another through hole of the cover substrate, and the part of the adhesion layer located on the dielectric layer serves as the second electrode; the first electrode, the dielectric layer and the second electrode constitute a passive device.

[0024] The thin film filter to be bonded includes a substrate, a cavity, a piezoelectric oscillator stack, and a metal pad layer. The substrate is the base for preparing the device; the cavity is between the substrate and the piezoelectric oscillator stack, and the piezoelectric oscillator stack includes a piezoelectric layer and two layers of electrodes; the metal pad is to thicken the two layers of electrodes as a solder joint for subsequent packaging bonding.

[0025] Furthermore, the cover substrate is selected from one of silicon, silicon carbide, sapphire, ceramic or any combination thereof.

[0026] Furthermore, the first cavity of the cover substrate is in the shape of a trapezoid, a triangle, a rectangle, a square or any combination thereof, with a lateral width of 40-500 μm and a depth of 1 μm-10 μm.

[0027] Furthermore, the material of the first electrode is one of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten, nickel or any combination thereof, with a thickness of 50-500 nm. The designed pattern is formed by plasma etching, wet etching and other methods, and the first electrode is a lead on the surface of the cover substrate, which does not occupy too much use area of ​​the cover substrate. The wiring of the first electrode in the first cavity is of any shape, and generally does not cover the first cavity.

[0028] Furthermore, the material of the adhesion layer is selected from one of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten, nickel or any combination thereof, with a thickness of 1 μm-10 μm. The depth of the countersunk hole is 100-400 μm, and the lateral width is 20-200 μm.

[0029] Furthermore, the material of the dielectric layer is selected from one of aluminum nitride, doped aluminum nitride, silicon oxide, doped silicon oxide, silicon nitride, doped silicon nitride or any combination thereof, and the thickness is 0.1-5 μm.

[0030] Furthermore, the passive device is a capacitor, an inductor or any combination thereof, and the lateral width of the device is 1 μm-500 μm.

[0031] Furthermore, the package cover plate with passive components and the thin film filter are bonded together by alloy bonding or ultrasonic bonding. The material of the pad is selected from one of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten, nickel or any combination thereof, with a thickness of 1 μm-10 μm, and the designed pattern is formed by plasma etching, wet etching and other methods.

[0032] The beneficial effects of the present invention are as follows:

[0033] The present invention achieves high integration of packaged devices by arranging passive devices into the cavity required for the operation of thin film bulk acoustic wave devices, thereby releasing more cover plate space and improving the utilization rate of the package cover plate. At the same time, in the preparation method, the preparation of the second electrode of the passive device and the TSV through-hole adhesion layer are combined into the same process, which simplifies the device preparation process and reduces the frequency of use of precious metals, thereby reducing the device manufacturing cost. The present invention can significantly improve the performance of thin film bulk acoustic wave devices while reducing the manufacturing cost required to achieve similar performance improvements. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. 1 is a schematic diagram of forming a first cavity on a cover substrate.

[0035] Figure 2 Schematic diagram of depositing a first metal on a cover substrate and etching to form a first electrode.

[0036] Figure 3 It is a schematic diagram after a dielectric layer is formed on the cover substrate.

[0037] Figure 4 Schematic diagram of etching two countersunk holes on the cover substrate.

[0038] Figure 5 Schematic diagram of depositing an adhesion layer on a cover substrate.

[0039] Figure 6 Schematic diagram of the thin film filter to be bonded.

[0040] Figure 7 It is a schematic diagram of the package cover after bonding and the thin film filter to be bonded.

[0041] Figure 8 Schematic diagram of thinning the back side of the package cover to expose the TSV through-hole adhesion layer.

[0042] Fig. 9 Schematic diagram of filling metal holes and forming pads 108.

[0043] Among them, 100 is a cover substrate, 101 is a first cavity, 102 is a first electrode, 103 is a dielectric layer, 104 is a countersunk hole, 105 is an adhesion layer, 106 is a passive device, 107 is a bonding layer, 108 is a pad, and 200 is a thin film filter to be bonded. DETAILED DESCRIPTION

[0044] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] (1) The cover substrate 100 is ultrasonically cleaned using an SPM solution.

[0046] (2) A first cavity 101 is formed in the silicon substrate 100 by using a dry etching process, such as Figure 1 As shown, the etching process of the first cavity 101 is RF power 1000 / 200W, chamber pressure 10mT, etching gas SF6 / O2 flow rate 100 / 60sccm, etching rate about 1μm / min, the lateral width of the first cavity 101 is 300μm, and the depth is 3μm. In this embodiment, the first cavity 101 is trapezoidal.

[0047] (3) Depositing 200 nm of metal molybdenum on the cover substrate 100 by thermal evaporation or magnetron sputtering, and forming the first electrode 102 of the passive device by dry etching. The etching process of the first electrode 102 is RF power 500 / 100 W, chamber pressure 7 mT, etching gas Cl2 flow rate 40 sccm, etching rate about 70 nm / min, the lateral width of the first electrode 102 of the passive device is 200 μm, the electrode pattern of the first electrode 102 is located in the first cavity 101, and the wire is located outside the first cavity 101, as shown in FIG. Figure 2 shown.

[0048] (4) A 500 nm thick silicon nitride film is deposited on the cover substrate 100 by magnetron sputtering or MOCVD, and dry etching is performed to retain only the dielectric layer metal covering the electrode pattern in the first cavity 101, thereby forming a dielectric layer 103 of the passive device. Figure 3 The etching process of the dielectric layer 103 is as follows: RF power 800 / 100 W, chamber pressure 20 mT, etching gas CF4 / O2 flow rate 400 / 20 sccm, etching rate about 200 nm / min, and the lateral width of the dielectric layer 103 is 250 μm.

[0049] (5) At least two TSV countersunk holes 104 are etched on the cover substrate 100 using a deep silicon etching process, such as Figure 4As shown, the Bosch etching process has an RF power of 3000 / 150W, a chamber pressure of 5mT, an etching gas O2 / SF6 flow rate of 100 / 200sccm, and an etching rate of about 7μm / min. The depth of the TSV sink hole 104 is 300μm.

[0050] (6) Use thermal evaporation or magnetron sputtering to deposit 1.4 μm of gold on the cover substrate 100 as the adhesion layer 105. Use dry etching or wet etching to remove a portion of the second metal located on the first electrode 102 and not covered by the dielectric layer, so that the adhesion layer 105 is divided into two unconnected left and right parts, and ensure that the adhesion layer on one side is connected to the first electrode 102, and the portion of the adhesion layer on the other side located on the dielectric layer serves as the second electrode of the passive device. The adhesion layer is filled in at least two TSV countersunk holes 104 at the same time. The first electrode 102, the dielectric layer 103 and the second electrode are combined into a passive device 106 prepared in the first cavity. The passive device 106 can be a capacitor or an inductor or any combination thereof. The lateral width of the passive device 106 is 1 μm-500 μm. At this time, the preparation of the packaging cover of the passive device is completed, such as Figure 5 shown.

[0051] (7) Using a bonding method, the package cover plate with the passive device prepared in the first cavity is bonded to the thin film filter 200 (such as Figure 6 As shown) bonded into shape, such as Figure 7 As shown, 107 is the bonding layer after bonding molding.

[0052] (8) Mechanical grinding is used to remove the back side of the bonded chip cover substrate 100 to expose the adhesion layer deposited in the TSV countersunk hole, such as Figure 8 shown.

[0053] (9) The TSV countersunk hole is filled by electroplating, and the pad 108 is formed by dry etching or wet etching. Fig. 9 shown.

[0054] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A method for preparing a heterogeneous integrated structure of a thin film bulk acoustic wave device, It is characterized in that The preparation method comprises the following steps: Step 1: cleaning the cover substrate (100); Step 2: forming a first cavity (101) on the cover substrate (100) by using a dry etching process; Step three: depositing a layer of first metal on the cover substrate (100) processed in step two, and dry-etching the deposited first metal to form a first electrode (102); wherein the first electrode (102) comprises an electrode pattern located in the first cavity (101) and a wire located outside the first cavity (101); Step 4: depositing a dielectric layer metal on the cover substrate (100) obtained in step 3, and dry-etching the deposited dielectric layer metal to retain only the dielectric layer metal covering the electrode pattern in the first cavity (101), thereby forming a dielectric layer (103); Step 5: using a deep silicon etching process to etch at least two countersunk holes (104) on the cover substrate (100) processed in step 4; Step 6: Continue to deposit a layer of second metal on the cover substrate (100) processed in step 5 as an adhesion layer, and process the deposited adhesion layer to remove a portion of the second metal located on the first electrode (102) and not covered by the dielectric layer, so that the adhesion layer is divided into two unconnected left and right parts, and ensure that the adhesion layer on one side is connected to the first electrode (102); the portion of the adhesion layer on the other side located on the dielectric layer serves as the second electrode; the first electrode (102), the dielectric layer (103) and the second electrode constitute a passive device; at this time, the preparation of the packaging cover of the passive device is completed; Step 7: bonding the package cover plate with passive components obtained in step 6 to the thin film filter to be bonded by a bonding method; Step eight: removing the back side of the bonded cover substrate (100) by mechanical grinding to expose the adhesion layer deposited in the countersunk hole; Step nine: Fill the countersunk holes with electroplating, and etch the electroplating material between the two countersunk holes with dry etching or wet etching to form a pad (108).

2. The method for preparing the heterogeneous integrated structure of the thin film bulk acoustic wave device according to claim 1, It is characterized in that The metal is deposited in step three, step four and step six by thermal evaporation or magnetron sputtering.

3. The method for preparing the heterogeneous integrated structure of the thin film bulk acoustic wave device according to claim 1, It is characterized in that In the step six, when the adhesion layer is processed, plasma etching, lift-off or wet etching is used to form a pattern.

4. A heterogeneous integrated structure of a thin film bulk acoustic wave device obtained by the preparation method according to claim 1, It is characterized in that It comprises a package cover plate with a passive device and a thin film filter bonded together, wherein the passive device is located in a first cavity inside the package cover plate; The packaging cover plate comprises a cover plate substrate (100), a first electrode (102), a dielectric layer (103), a second electrode, and an adhesion layer (105); A first cavity is provided in the middle of the cover substrate (100), and at least two through holes are provided at the end of the cover substrate (100); The first electrode (102) is deposited on the cover substrate (100), and comprises an electrode pattern located in the first cavity (101) and a wire located outside the first cavity (101); The dielectric layer (103) is deposited on the first electrode (102) and covers the electrode pattern; The adhesion layer (105) is deposited on the cover substrate (100), and comprises two unconnected left and right parts, wherein one part covers at least one through hole of the cover substrate (100) and is connected to the first electrode (102); the other part covers another through hole of the cover substrate (100), and the part of the adhesion layer (105) located on the dielectric layer (103) serves as a second electrode; the first electrode (102), the dielectric layer (103) and the second electrode constitute a passive device.

5. The heterogeneous integrated structure of thin film bulk acoustic wave devices according to claim 4, It is characterized in that The cover substrate (100) is selected from silicon, silicon carbide, sapphire, ceramic or any combination thereof.

6. The heterogeneous integrated structure of thin film bulk acoustic wave devices according to claim 4, It is characterized in that The first cavity of the cover substrate (100) is in the shape of a trapezoid, a triangle, a rectangle, a square or any combination thereof, with a lateral width of 40-500 μm and a depth of 1 μm-10 μm.

7. The heterogeneous integrated structure of thin film bulk acoustic wave devices according to claim 4, It is characterized in that The material of the first electrode (102) is one of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten, nickel or any combination thereof, and the thickness is 50-500 nm.

8. The heterogeneous integrated structure of thin film bulk acoustic wave devices according to claim 4, It is characterized in that The material of the adhesion layer (105) is selected from one of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten, nickel or any combination thereof, and has a thickness of 1 μm-10 μm.

9. The heterogeneous integrated structure of thin film bulk acoustic wave devices according to claim 4, It is characterized in that The material of the dielectric layer (103) is selected from one of aluminum nitride, doped aluminum nitride, silicon oxide, doped silicon oxide, silicon nitride, doped silicon nitride or any combination thereof, and has a thickness of 0.1-5 μm.

10. The heterogeneous integrated structure of thin film bulk acoustic wave devices according to claim 4, It is characterized in that The passive device is a capacitor, an inductor or any combination thereof.

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