JP2009055128A - Method for manufacturing thin film piezoelectric resonator and thin film piezoelectric resonator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin film piezoelectric resonator capable of preventing a lower electrode from being damaged resulting from dry etching during forming a piezoelectric thin film pattern. <P>SOLUTION: After forming a pattern of a lower electrode made of metal on the surface of a substrate, an etching stop layer made of material different from that of the lower electrode is formed on the surface of the pattern of the lower electrode, which is an area including an area that is not covered by a piezoelectric thin film. The etching stop layer is made of material, the etching-proof property of which is large against etchant in plasma so as to be able to protect the lower electrode when the piezoelectric thin film is eliminated by etching. Then, there is no possibility that the lower electrode is etched by plasma when plasmatizing reactive gas for dry etching to form a pattern of the piezoelectric thin film by etching the piezoelectric thin film by the plasma. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a thin film piezoelectric resonator and a thin film piezoelectric resonator, and more particularly to a thin film piezoelectric resonator manufactured by a dry etching (reactive ion etching) method using a reactive gas and a manufacturing method thereof.

  Thin film piezoelectric resonators include a resonator using longitudinal vibration in the film thickness direction of a piezoelectric thin film and a resonator using contour mode vibration determined by the shape of the piezoelectric thin film. The former is also called an FBAR (Film Bulk Acoustic Resonator) or a BAW (Bulk Acoustic Wave) element, and its resonance frequency is determined by the sound speed and film thickness of the piezoelectric thin film. For example, when AlN or ZnO is used as the piezoelectric thin film, a resonance frequency of 2 to 5 GHz is obtained with a film thickness of 0.4 to 2 μm (in inverse proportion to the film thickness). The latter is a resonator suitable for a filter application in which a plurality of resonators having different resonance frequencies need to be combined since the resonance frequency can be defined by the outer shape and size of the piezoelectric thin film (see, for example, Non-Patent Document 1). Since both have the features of high Q value and low impedance in the GHz band, they are promising as high-frequency oscillators and filter resonators. Furthermore, thin-film piezoelectric resonators can be formed on a silicon substrate instead of a piezoelectric single crystal substrate like SAW (surface acoustic wave) resonators, so integration with LSI (Large Scale Integration) (one-chip integration) ) And can contribute to the miniaturization and modularization of the RF front end of mobile communication terminals.

  The FBAR thin film piezoelectric resonator that uses the longitudinal vibration in the film thickness direction of the piezoelectric thin film and the contour vibration thin film piezoelectric resonator that uses the contour mode vibration determined by the shape of the piezoelectric thin film differ only in the vibration mode. The same element structure is the same, and it has a structure in which a laminated body sandwiching a piezoelectric thin film between upper and lower electrodes is floated. Therefore, the FBAR type thin film piezoelectric resonator will be described below.

  Patent Document 1 discloses a structure of a typical FBAR type thin film piezoelectric resonator and a manufacturing method thereof. An example of the structure of an FBAR thin film piezoelectric resonator having the element structure of Patent Document 1 is shown in FIG. In the thin film piezoelectric resonator shown in FIG. 10, a recess 11 is formed at a substantially central portion of the surface of a substrate 10 such as silicon, and the lower electrode 12, the piezoelectric thin film 13, and the upper electrode 14 are arranged in this order so as to cover the recess 11. A laminated body 15 is formed, and the lower electrode 12 and the upper electrode 14 are drawn to the external connection terminals (electrode pads) 16a and 16b. Further, the concave portion 11 formed on the surface of the substrate 10 is covered with the laminated body 15 to form a void portion (cavity) 17. The elastic vibration excited in the thickness direction of the thin film piezoelectric resonator is reflected at the boundary surface between the upper electrode 14 and air and the boundary surface between the lower electrode 12 and the cavity 17, and the electrode films 12, 14, the piezoelectric thin film 13 and those. Resonance occurs at a resonance frequency determined by the film thickness.

  The lower electrode and the upper electrodes 12 and 14 of the thin film piezoelectric resonator are made of a metal having a large acoustic impedance such as molybdenum (Mo) and tungsten (W), and the piezoelectric thin film 13 is made of aluminum nitride (AlN) or zinc oxide ( A piezoelectric polycrystalline film such as ZnO) is used.

  The thin film piezoelectric resonator is manufactured as follows. First, a recess (recess 11) is formed on the surface of the silicon (Si) substrate 10 using anisotropic etching, and then a sacrificial layer is formed on the substrate 10. As the sacrificial layer, for example, a silicate glass (BPSG) layer doped with boron (B) and phosphorus (P) is used. Thereafter, as shown in FIG. 3 in an embodiment described later, the surface of the sacrificial layer is polished until the surface of the silicon substrate 10 is exposed, and the surface of the sacrificial layer is flattened. As a result, the sacrificial layer is buried in the depression formed in advance in the silicon substrate 10, and the surface of the silicon substrate 10 can be exposed in the periphery thereof. Subsequently, the lower electrode 12, the piezoelectric thin film 13, and the upper electrode 14 are sequentially formed and patterned on the sacrificial layer to form a laminate 15 with the piezoelectric thin film 13 sandwiched between the upper and lower electrodes 12 and 14. . Thereafter, a hole is drilled until the sacrificial layer is reached, and the sacrificial layer is removed by selective etching through the hole to form a cavity (cavity) 17 corresponding to a depression formed in advance between the silicon substrate 10 and the lower electrode 12. . Through these series of manufacturing steps, an FBAR type thin film piezoelectric resonator is completed.

  The cavity does not need to be formed by digging the surface side of the substrate 10. For example, an air gap type having a convex cavity described in Patent Document 2 or an opening provided from the back surface of the substrate disclosed in Patent Document 3, for example. It may be a membrane-type cavity. In addition, there is an FBAR type thin film piezoelectric resonator called SMR (Solidly Mounted Resonator) using an acoustic multilayer film (also called an acoustic mirror or a Bragg reflector) instead of providing a cavity.

  The patterning of the thin film piezoelectric resonator is carried out by a wet etching method using a chemical solution or a dry etching (reactive ion etching) method using a reactive gas with a resist pattern formed on the thin film by an exposure (lithography) process as a mask. Is called. In dry etching, a plasma of a reactive gas containing a halogen atom such as fluorine or chlorine is generated, and etching proceeds by making a material to be etched a volatile product by radicals and ions generated in the plasma.

  In general, since wet etching using a chemical solution proceeds isotropically, an undercut is generated at the lower portion of the resist mask end, and the pattern dimension of the material to be etched is smaller than the resist pattern dimension. Further, the end of the resist mask is tapered, and the cross-sectional shape of the resist pattern tends to be trapezoid. That is, in wet etching, when the resist pattern dimension is small, it is difficult to control the dimension and shape of the resist pattern. In addition, since the etching rate varies depending on the concentration of the chemical and the liquid temperature, it is not easy to perform etching with good reproducibility.

  On the other hand, the dry etching method has an advantage that anisotropic etching can be performed by adjusting various types of etching parameters during gas etching and ion etching. That is, in dry etching, not only the pattern dimension of the resist mask is faithfully transferred but also the cross-sectional shape of the pattern can be made rectangular, so that complex patterns and fine patterns can be formed. Conventionally, in the manufacture of thin film piezoelectric resonators, patterns by wet etching have been performed, but high-precision control of the dimensions and shape of the element pattern is required, for example, to suppress spurious noise, which is an unnecessary vibration mode. Patterning by a dry etching method has come to be performed.

As the reactive gas for dry etching which is suitable for the upper electrode 13 and lower electrode 11 and piezoelectric thin film 12 constituting the thin film piezoelectric resonators, for example, Mo (or W) to the electrode film carbon tetrafluoride (CF ₄ ), Chlorine (Cl ₂ ) gas or a gas containing chlorine atoms, such as boron trichloride (BCl ₃ ), is suitable for the AlN piezoelectric film. However, in the patterning process of the AlN piezoelectric film, when dry etching is performed with, for example, chlorine plasma obtained by converting Cl ₂ gas into plasma, Mo is more reactive to active species of chlorine than AlN, that is, the chlorine gas is activated. Since the etching selectivity between the Mo electrode film and the AlN piezoelectric film due to the converted plasma is approximate, unless the etching end point of AlN can be detected with high accuracy, the lower electrode 11 is also etched following the piezoelectric thin film 12, There is a problem that the film thickness of the electrode 11 becomes thin and the wiring resistance increases. In addition, at the place where the piezoelectric thin film 13 is not formed on the surface of the lower electrode 11, the Mo electrode film of the lead portion to the external terminal not masked with the resist is etched almost simultaneously with the etching of AlN. The film thickness of the electrode film becomes thin, and in an extreme case, there arises a problem that this portion disappears.

G. Piazza and A.P. Pisano, "Dry-Released Post-CMOS Compatible Contour-Mode Aluminum Nitride Micromechanical Resonators for VHF Applications," Technical Digest of Solid-State Sensor, Actuator and Microsystems Workshop, pp. 37-40 (2004). JP 2000-69594 A JP 2005-109702 A Table 2004/1964 JP 2004-235886 A

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of manufacturing a thin film piezoelectric resonator and a thin film piezoelectric resonator capable of preventing damage to a lower electrode due to dry etching when forming a piezoelectric thin film pattern. It is to provide.

The present invention provides a method for manufacturing a thin film piezoelectric resonator in which a lower electrode, a piezoelectric thin film, and an upper electrode are laminated in this order on a substrate.
Forming a pattern of a lower electrode made of metal on the surface of the substrate;
Forming an etching stop layer made of a material different from that of the lower electrode in a region including a region not covered with the piezoelectric thin film on the surface of the pattern of the lower electrode;
Next, forming a piezoelectric thin film on the surface of the substrate;
Forming a resist mask patterned into a predetermined shape on the surface of the piezoelectric thin film;
Thereafter, the reactive gas for dry etching is turned into plasma, and the piezoelectric thin film is etched with this plasma to form a pattern of the piezoelectric thin film;
Then, forming a pattern of the upper electrode on the surface of the piezoelectric thin film,
The etching stop layer is made of a material having a high etching resistance to the etchant in the plasma so that the lower electrode can be protected when the piezoelectric thin film is removed by etching.

  In the above-described thin film piezoelectric resonator, the lower electrode is a metal selected from, for example, molybdenum, niobium, tantalum, tungsten and ruthenium, and an etchant in plasma for etching the piezoelectric thin film is, for example, chlorine. An active species is preferred. The etching stop layer is preferably one selected from, for example, chromium, iron, cobalt, nickel, copper, platinum, or an alloy composed of these elements. The piezoelectric thin film is preferably made of, for example, aluminum nitride or zinc oxide.

The present invention also relates to a thin film piezoelectric resonator in which a lower electrode, a piezoelectric thin film, and an upper electrode are laminated in this order on a substrate.
The lower electrode is made of a metal whose volatility with chlorine is volatile,
A metal that is different from the lower electrode and does not exhibit volatility of a compound with chlorine is formed on the surface of the lower electrode pattern, including a region that is not covered with the piezoelectric thin film. It is characterized by.
In the above-described thin film piezoelectric resonator, the lower electrode is preferably a metal selected from, for example, molybdenum, niobium, tantalum, tungsten, and ruthenium. Moreover, it is preferable that the metal in which the compound with chlorine does not show volatility is, for example, one selected from chromium, iron, cobalt, nickel, copper and platinum, or an alloy composed of these elements. Moreover, it is preferable that the film thickness of the metal in which the said compound with chlorine does not show volatility is 1 nm or more and 100 nm or less, for example.

  According to the present invention, since a lower electrode is protected by an etching stop layer when a piezoelectric thin film is dry etched, a method for manufacturing a thin film piezoelectric resonator suitable for manufacturing by a dry etching method and a thin film piezoelectric resonator are provided. Can do. In the thin-film piezoelectric resonator, spurious due to unnecessary vibration mode appears near the resonance frequency of the main vibration mode, especially in the case of the contour vibration mode, but if the shape (shape, dimension) of the piezoelectric body changes. Resulting in. Therefore, the etching for determining the shape greatly affects the element characteristics. According to the present invention, since a thin film piezoelectric resonator having a fine and highly accurate element shape and element size can be manufactured, it is possible to provide a thin film piezoelectric resonator free of spurious which is an unnecessary vibration mode.

  An example of a thin film piezoelectric resonator manufactured by the manufacturing method according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing a thin film piezoelectric resonator according to the present embodiment, and FIG. 2 is a plan view. In FIG. 1, reference numeral 30 denotes a rectangular silicon substrate, and a tapered recess 31 having a size that protrudes slightly to the left and right of the lateral width of a piezoelectric thin film 33 described later is provided at a substantially central portion of the surface of the substrate 30. Is formed. A lower electrode 32 is formed on the surface of the substrate 30, and in this example, a region where the lower electrode 32 is formed is located at a position slightly beyond the other edge side of the recess 31 across the recess 31 from one end of the substrate 30. Is formed. As shown in FIG. 2, the lower electrode 32 does not cover the entire recess 31 but is formed so that a part of the recess 31 is exposed. An etching stop layer 6 is formed on the entire surface of the lower electrode 32 in order to prevent etching of the lower electrode 32 by dry etching when the pattern of the piezoelectric thin film 33 is formed, as will be described later. The etching stop layer 6 will be described later in detail.

  In addition, a rectangular piezoelectric thin film 33 is formed on the surface of the substrate 30 on which the lower electrode 32 and the etching stop layer 6 are formed, and the formation region of the piezoelectric thin film 33 is the other end side of the substrate 30 in this example. To the one end side of the recess 31 across the recess 31. Further, an upper electrode 34 is formed on the surface of the piezoelectric thin film 33, and the formation region of the upper electrode 34 is formed from one end side to the other end side of the piezoelectric thin film 33 in this example. As described above, since the laminated body of the lower electrode 32, the piezoelectric thin film 33, and the upper electrode 34 is positioned on the concave portion 31, a cavity 36 is formed below the laminated body. Further, an electrode pad 35 a is formed on the surface of the upper electrode 35 located on the other end side of the piezoelectric thin film 33, and an electrode pad 35 b is formed on the surface of the etching stop layer 6 located on one end side of the substrate 30. Has been. When the thin film piezoelectric resonator shown in FIG. 1 is electrically connected to adjacent circuit elements in the same wafer, the electrode pads 35a and 35b are not necessarily required.

  Specifically, the lower electrode 32 is made of a metal such as molybdenum (Mo), tungsten (W), tantalum (Ta), niobium (Nb), or ruthenium (Ru) having high acoustic impedance. As the piezoelectric thin film 33, for example, aluminum nitride (AlN) or zinc oxide (ZnO) is used.

  In addition, the etching stop layer 6 is provided with respect to an etchant in the plasma, which will be described later, so that the lower electrode 32 can be protected from the plasma used for the etching after the portions other than the pattern of the piezoelectric thin film 33 are etched. It consists of a material with high etching resistance. In this example, since the piezoelectric thin film 33 is etched with an active species of chlorine as will be described later, the etching stop layer 6 is made of a metal whose compound with chlorine does not exhibit volatility. Specifically, one selected from chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), platinum (Pt), or an alloy composed of these elements. Etc. In FIG. 1, the etching stop layer 6 and the lower electrode 11 overlap in the same pattern, but the pattern of the etching stop layer 6 may be larger than the pattern of the lower electrode 11. The film thickness of the etching stop layer 6 is preferably at least 1 nm or more in order to function as a stop layer for dry etching at the time of forming a piezoelectric thin film pattern to be described later. Or if it is the film thickness range which does not affect a piezoelectric material thin film, it will not restrict | limit in particular, Preferably it is 100 nm or less.

  In the oscillation operation of the thin film piezoelectric resonator configured as described above, the elastic vibration excited in the thickness direction of the piezoelectric thin film 33 by applying a voltage between the upper electrode 34 and the lower electrode 32 causes the upper electrode 34 and the air to be oscillated. And the boundary surface between the lower electrode 32 and the gap 36, and resonance occurs at a resonance frequency determined by the film thickness of the piezoelectric thin film 33.

Next, a method for manufacturing the thin film piezoelectric resonator shown in FIG. 1 will be described with reference to FIGS. First, a resist is applied on the silicon (100) substrate 30 with the thermal oxide film 41, and the thermal oxide film 41 is patterned in a rectangular size corresponding to the opening of the cavity 36 by photolithography (FIG. 3A). Next, when the silicon substrate 30 is etched from the opening of the thermal oxide film 41 using potassium hydroxide (KOH) aqueous solution or TMAH (4-methyl ammonium hydroxide) which is an anisotropic etchant of silicon, FIG. A concave portion 31 with a taper as shown in FIG. Here, if a hydrofluoric acid aqueous solution which is an isotropic etchant of silicon is used, the concave portion 31 having a rectangular cross section can be formed. Further, the recess 31 may be formed by reactive ion etching using SF ₆ or the like.

Next, a recess 31 formed on the silicon substrate 30 by forming a SiO ₂ -based sacrificial layer 42 typified by a silicate gas (BPSG) doped with boron (B) and phosphorus (P) by CVD. Is completely buried (FIG. 3C), and the surface of the sacrificial layer 42 is polished by CMP (Chemical Mechanical Polishing) until the surface of the thermal oxide film 41 or the surface of the silicon substrate 30 is exposed to flatten the surface of the sacrificial layer 42. (FIG. 3 (d)).

  Next, a metal thin film having high acoustic impedance such as Mo, W, Ta, Nb, and Ru is formed on the planarized silicon substrate 30 surface by magnetron sputtering or the like as described above, and lithography and nitric acid are used. The lower electrode 32 is formed by patterning by wet etching (FIG. 3E). In addition, in order to ensure adhesion between the lower electrode 32 and the substrate 30, titanium (Ti), chromium (Cr), or the like may be formed as a base film prior to the formation of the lower electrode 32. The film thickness of the lower electrode 32 is desirably about 0.1 to 0.3 μm.

  Next, as described above, a metal in which the compound with chlorine does not exhibit volatility, for example, Cr, Fe, Co, Ni, Cu, Pt, or an alloy made of these elements is formed as an etching stop layer, An etching stop layer 6 is formed by patterning using lithography and a wet etchant suitable for each (FIG. 4A). The etching stop layer 6 is patterned so as to cover the pattern of the lower electrode 32 so as to be the same as or overlapping with the pattern of the lower electrode 32. In FIG. 4A, the etching stop layer 6 is patterned so as to overlap the pattern of the lower electrode 32.

Next, a piezoelectric thin film 33 such as AlN or ZnO having a film thickness of 0.8 to 1.5 μm, for example, is formed on the entire surface of the substrate 30 by RF magnetron sputtering (FIG. 4B). In this example, AlN is used. Then, a resist film 47 is formed on the entire surface of the piezoelectric thin film 33 (FIG. 4C), and the resist film 47 other than the resist film 47 which becomes the pattern of the piezoelectric thin film 33 is peeled off by photolithography (FIG. 4 ( d)). Subsequently, the piezoelectric thin film 33 that is not covered with the resist film 47 is etched (dry etching (reactivity) by plasma (hereinafter referred to as “chlorine plasma”) obtained by converting chlorine (Cl ₂ ) gas into plasma using the resist film 47 as a mask. Ion etching)) to form a pattern of the piezoelectric thin film 33 (FIG. 4E).

  Here, the formation of the pattern of the piezoelectric thin film 33 by dry etching will be described in detail. The layer located under the piezoelectric thin film 33 not covered with the resist film 47 is simultaneously etched with the pattern of the piezoelectric thin film 33. Exposure to chlorine plasma. Since the metal used for the lower electrode 32 is etched by the active species of chlorine, that is, the compound with chlorine has volatility, in other words, the lower electrode 32 and the piezoelectric thin film 33 formed by chlorine plasma. Therefore, if the lower electrode 32 is exposed when the etching of the pattern of the piezoelectric thin film 33 is completed, the lower electrode 32 is instantaneously etched by chlorine plasma. Therefore, in the present invention, as shown in FIG. 4A, the etching stop layer 6 in which the compound with chlorine does not exhibit volatility is formed on the entire surface of the lower electrode 33. Since the electrode 32 is protected, the contact between the chlorine plasma and the lower electrode 32 can be blocked.

After the patterning of the piezoelectric thin film 33, the upper electrode such as Mo is formed by magnetron sputtering or the like in the same manner as the lower electrode, and lithography and wet etching using an etchant such as nitric acid or dry using a reactive gas such as CF ₄ are performed. Patterning is performed by etching (FIG. 5A).
Next, if necessary, electrode pads 35a and 35b for electrical connection to the outside are formed by a lift-off method (FIG. 5B). Finally, a resist pattern having an opening for etching the silicate glass sacrificial layer 42 embedded in the cavity 36 is formed by lithography, and the silicate glass sacrificial layer 42 is etched by buffered hydrofluoric acid (FIG. 5C). . Thus, the cavity 36 is formed under the lower electrode 32, and the thin film piezoelectric resonator shown in FIG. 1 is completed.

  According to the above-described embodiment, as shown in FIG. 4A, the etching stop layer 6 is formed on the entire surface of the lower electrode 32 to protect the lower electrode 32. Therefore, as shown in FIG. Thus, in the pattern forming process of the piezoelectric thin film 33 by dry etching, the etching stop layer 6 can block the contact between the active species of chlorine and the lower electrode 32, and the lower part in which the compound with chlorine exhibits volatility. There is no fear that the electrode 32 is etched.

  Next, another embodiment of the thin film piezoelectric resonator of the present invention will be described with reference to FIGS. FIG. 6 is a cross-sectional view schematically showing the thin film piezoelectric resonator according to the present embodiment, and FIG. 7 is a plan view. In FIGS. 6 and 7, the same components as those of the thin film piezoelectric resonator described with reference to FIG. As shown in FIG. 6, the etching stop layer 6 is covered only in a region of the lower electrode 32 that is not covered with the piezoelectric thin film 33. However, a part of the etching stop layer 6 extends into the piezoelectric thin film 33, and a part of the etching stop layer 6 and an end of the piezoelectric thin film 33 have an overlapping portion. The length of the overlapping portion is not particularly limited, but a few μm to 10 μm is sufficient.

  The manufacturing method of the thin film piezoelectric resonator in this embodiment is the same as the manufacturing method described above except that the pattern of the etching stop layer 6 is different in the step of forming the etching stop layer 6. In the pattern forming process of the piezoelectric thin film 33, the end of the piezoelectric thin film 33 covers a part of the etching stop layer 6. In this embodiment, the pattern of the piezoelectric thin film 33 is formed at least on the surface of the lower electrode 32 that is not covered with the etching stop layer 6. That is, the lower electrode 32 is covered with the etching stop layer 6 and the piezoelectric thin film 33. Even if it is this form, the effect similar to the above-mentioned is acquired.

Further, as shown in FIG. 8, acoustics are also obtained in an SMR type thin film piezoelectric resonator in which an acoustic multilayer film 5 made of tantalum pentoxide (Ta ₂ O ₅ ) and silicon dioxide (SiO ₂ ) is formed on the surface of the substrate 30 by vapor deposition. The etching stop layer 6 may be formed on the entire surface of the lower electrode 32 formed on the multilayer film 5, or only the region of the lower electrode 32 that is not covered with the piezoelectric thin film 33 as shown in FIG. Alternatively, the etching stop layer 6 may be formed. Also in this embodiment, a thin film piezoelectric resonator is manufactured in the same manner as the manufacturing method described above except that the acoustic multilayer film 5 is formed on the surface of the substrate 30 and then the lower electrode 32 is formed on the acoustic multilayer film 5. The Even if it is such a form, the effect similar to the above can be acquired. 8 and 9 are cross-sectional views schematically showing the thin film piezoelectric resonator. In FIG. 8 and FIG. 9, the same components as those of the thin film piezoelectric resonator described with reference to FIG. It is attached.

The film thickness of the acoustic multilayer film (Ta ₂ O ₅ / SiO ₂ ) 5 is λ / 4, where λ is the wavelength of the bulk acoustic wave calculated from the resonance frequency and sound velocity of the desired thin film piezoelectric resonator. is there. When the combination of Ta ₂ O ₅ / SiO ₂ is defined as one cycle, in order to confine the thickness vibration excited inside the piezoelectric thin film 33, it is necessary to stack at least two cycles, preferably three cycles or more. The acoustic multilayer film 5 is not limited to Ta ₂ O ₅ / SiO ₂ , and a high acoustic impedance material and a low acoustic impedance material may be combined. For example, Mo / Al, W / SiO _2, etc. It may be. Further, the film formation method is not limited to the vapor deposition method, and an optimum film formation method may be employed depending on the material to be used.

In the above-described embodiment, the FBAR type thin film piezoelectric resonator in which the cavity 36 of the recess 31 is formed on the surface of the substrate 30 and the SMR type thin film piezoelectric resonator using the acoustic multilayer film have been described. It may be an air gap type having a membrane or a membrane type thin film piezoelectric resonator in which a cavity is formed from the back surface of the substrate.
In the above description, the case where the present invention is applied to an FBAR type thin film piezoelectric resonator using the longitudinal vibration in the film thickness direction of the piezoelectric thin film has been described. However, the contour vibration type using the contour mode vibration determined by the shape of the piezoelectric thin film. The present invention can also be applied to a thin film piezoelectric resonator.

It is sectional drawing of the thin film piezoelectric resonator which concerns on embodiment of this invention. 1 is a plan view of a thin film piezoelectric resonator according to an embodiment of the present invention. It is explanatory drawing of the manufacturing process of the said thin film piezoelectric resonator. It is 2nd explanatory drawing of the said manufacturing process. It is 3rd explanatory drawing of the said manufacturing process. It is sectional drawing which shows the other form of the thin film piezoelectric resonator of this invention. It is a top view which shows the other form of the thin film piezoelectric resonator of this invention. It is sectional drawing which shows the other form of the thin film piezoelectric resonator of this invention. It is sectional drawing which shows the other form of the thin film piezoelectric resonator of this invention. It is sectional drawing of a thin film piezoelectric resonator.

Explanation of symbols

30 Substrate 31 Recess 32 Lower electrode 33 Piezoelectric thin film 34 Upper electrode 35a, 35b Electrode pad 36 Gap 37 Gap 41 Thermal oxide film 42 Sacrificial layer 47 Resist film
6 Etching stop layer

Claims (8)

In a method of manufacturing a thin film piezoelectric resonator in which a lower electrode, a piezoelectric thin film, and an upper electrode are laminated in this order on a substrate,
Forming a pattern of a lower electrode made of metal on the surface of the substrate;
Forming an etching stop layer made of a material different from that of the lower electrode in a region including a region not covered with the piezoelectric thin film on the surface of the pattern of the lower electrode;
Next, forming a piezoelectric thin film on the surface of the substrate;
Forming a resist mask patterned into a predetermined shape on the surface of the piezoelectric thin film;
Thereafter, the reactive gas for dry etching is turned into plasma, and the piezoelectric thin film is etched with this plasma to form a pattern of the piezoelectric thin film;
Then, forming a pattern of the upper electrode on the surface of the piezoelectric thin film,
The etching stop layer is made of a material having a high etching resistance to an etchant in the plasma so that the lower electrode can be protected when the piezoelectric thin film is removed by etching. A method for manufacturing a resonator.   The lower electrode is a metal selected from molybdenum, niobium, tantalum, tungsten, and ruthenium, and an etchant in plasma for etching the piezoelectric thin film is an active species of chlorine. 2. A method for manufacturing a thin film piezoelectric resonator as described in 1.   3. The thin film piezoelectric resonator according to claim 2, wherein the etching stop layer is one selected from chromium, iron, cobalt, nickel, copper, and platinum, or an alloy composed of these elements. Manufacturing method.   4. The method of manufacturing a thin film piezoelectric resonator according to claim 2, wherein the piezoelectric thin film is made of aluminum nitride or zinc oxide. In a thin film piezoelectric resonator formed by laminating a lower electrode, a piezoelectric thin film, and an upper electrode in this order on a substrate,
The lower electrode is made of a metal whose volatility with chlorine is volatile,
A metal that is different from the lower electrode and does not exhibit volatility of a compound with chlorine is formed on the surface of the lower electrode pattern, including a region that is not covered with the piezoelectric thin film. A thin film piezoelectric resonator characterized by the above.   The thin film piezoelectric resonator according to claim 5, wherein the lower electrode is molybdenum, niobium, tantalum, tungsten, and ruthenium.   The metal in which the compound with chlorine does not exhibit volatility is one selected from chromium, iron, cobalt, nickel, copper, and platinum, or an alloy composed of these elements. 6. The thin film piezoelectric resonator as described in 6.   The thin film piezoelectric resonator according to any one of claims 5 to 7, wherein a film thickness of the metal in which the compound with chlorine does not exhibit volatility is 1 nm or more and 100 nm or less.

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