JP2006242931A - Manufacturing method for oscillation gyro sensor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain a piezoelectric thin film from separated out of an upper layer electrode film, in an oscillation type gyro sensor. <P>SOLUTION: This manufacturing method forms an oscillation type gyro sensor element 100 provided with a cantilever-shaped oscillator 110 comprising a piezoelectric oscillation body formed with a driving electrode 106a and detecting electrodes 106b, 106c, on a surface, by a thin film process. Recrystallization heat treatment is carried out at a temperature lower by 50°C or more than a heat treatment temperature when forming the piezoelectric substance thin film, after forming a lower electrode, a piezoelectric layer and an upper layer electrode pattern. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a vibration type gyro sensor element including a cantilever-shaped vibrator including a piezoelectric ceramic vibrator having a driving electrode and a detection electrode formed on a surface thereof.

  In recent years, it has been easy for camera shake to occur in recorded images due to the high zoom ratio of video cameras and the lack of retainability associated with the miniaturization of cameras. As a countermeasure, image information capture positions such as CCD image sensors can be captured. A mechanism for correcting camera shake by changing the position of the camera is used.

  This correction may be performed by matching the position shift itself on the time axis of the image, but it is corrected using a sensor that detects actual camera shake to prevent malfunctions when the captured image is tilted. A method of acquiring an amount and correcting image jitter due to camera shake is mainly used.

  As a sensor for such applications, a gyro sensor is used. The gyro sensor is a sensor that detects a rotation angle in a holding state of a video camera, for example, and outputs a corresponding angular velocity, and a detection mechanism. As such, there are those using a vibrating body, those using a rotating body, and those using light. Among them, those using a vibrating body have become the mainstream as a small and inexpensive sensor because of their simple mechanism and short start-up time, and are often used in the aforementioned video cameras.

  Conventionally, as an angular velocity sensor for consumer use, there is a vibration type gyro sensor that detects an angular velocity by vibrating a rod-like vibrator at a predetermined resonance frequency and detecting a Coriolis force generated by the influence of the angular velocity with a piezoelectric element or the like. Widely used.

JP-A-10-332379 JP 2000-131077 A

Conventionally, as this vibration type gyro sensor, a piezoelectric material was cut out by mechanical processing and shaped, but a vibrator was used. However, along with the downsizing of video cameras, the sensor itself has become smaller, higher performance, and other uses. There is a demand for combination with other sensors.
However, as the piezoelectric material and the electrode are formed of a sputtered film due to downsizing, there is a problem that the upper electrode film is peeled off.

  Accordingly, an object of the present invention is to suppress peeling of the piezoelectric thin film and the upper electrode film in the vibration type gyro sensor in view of the conventional problems as described above.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

  In order to suppress the peeling of the upper layer electrode, it is necessary to eliminate the peeling element in the process while keeping the deterioration of the piezoelectric characteristics to a minimum. One of the peeling elements is Pb deposition from the piezoelectric material, and the recrystallization heat treatment temperature after forming the lower electrode, piezoelectric material, and upper electrode pattern is 50 ° C. or more lower than the heat treatment temperature at the time of forming the piezoelectric thin film. Can be avoided. In addition, when there is a resist on the upper electrode, stress due to heat is also a peeling element, but also in this regard, by controlling the heat treatment temperature after resist formation to 120 ° C. or more and 140 ° C. or less, peeling can be performed. Can be avoided.

  Accordingly, the present invention is a method for manufacturing a vibration type gyro sensor element comprising a cantilever-shaped vibrator formed by forming a lower electrode film, a piezoelectric material, and an upper electrode film on a substrate serving as a base having a beam shape. And a recrystallization heat treatment step in which the recrystallization heat treatment after forming the lower electrode, the piezoelectric material, and the upper layer electrode pattern is performed at a temperature lower by 50 ° C. or more than the heat treatment temperature at the time of forming the piezoelectric thin film.

  Moreover, the manufacturing method of the vibration type gyro sensor element according to the present invention includes a heat treatment step of performing heat treatment at 120 ° C. or more and 140 ° C. or less after forming the resist pattern of the upper electrode.

  Furthermore, the manufacturing method of the vibration type gyro sensor element according to the present invention includes a heat treatment step of performing heat treatment at 120 ° C. or more and 140 ° C. or less after forming the resist pattern of the lower electrode.

  According to the present invention, in a thin film gyro having an ultra-small vibrator, deterioration of piezoelectric characteristics can be kept to a minimum, and peeling of the upper electrode can be avoided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.

  FIG. 1 is an external perspective view of a vibration type gyro sensor element 100 provided in an angular velocity sensor to which the present invention is applied.

  As shown in FIGS. 1A and 1B, the vibration gyro sensor element 100 includes a so-called cantilever vibrator 110 cut out from a silicon single crystal substrate. The vibrator 110 is formed in a quadrangular prism shape whose cross-sectional shape when cut along a plane perpendicular to the longitudinal direction is a right quadrilateral.

  The vibration type gyro sensor element 100 has an approximate size of an element thickness t1 of 300 μm, an element length t2 of 3 mm, and an element width t3 of 1 mm. Further, as the size of the vibrating beam that actually vibrates, that is, the vibrator 110, the vibrating beam thickness t4 is set to 100 μm, the vibrating beam length t5 is set to 2.0 mm, and the vibrating beam width t6 is set to 100 μm. When the vibrating beam is vibrated in this shape, the resonance frequency is about 40 kHz. The above numerical values are examples, and can be arbitrarily set according to the frequency to be used and the size of the target element.

  A plan view of the vibration gyro sensor element 100 is shown in FIG. In the vibrator 110, a reference electrode 104a and a piezoelectric body 105a are sequentially stacked. Further, a driving electrode 106a and a pair of detection electrodes 106b and 106c sandwiching the driving electrode 106a are arranged on the piezoelectric body 5a. They are formed so as to be parallel to each other and not in contact with each other. The drive electrode 106a, the detection electrodes 106b and 106c, and the reference electrode 104a are provided with wiring connection terminals 101A, 101B, 101C, and 101D, respectively.

The piezoelectric body 105a is a thin film made of, for example, piezoelectric ceramics such as lead zirconate titanate (PZT), crystal, piezoelectric single crystal such as LaTaO _3, and the like.

  The vibration type gyro sensor element 100 operates by being connected to the IC circuit 40 shown in FIG. 3, and functions as an angular velocity sensor 50 that detects Coriolis force generated according to the angular velocity.

  The IC circuit 40 includes an adder circuit 41, an amplifier circuit 42, a phase shift circuit 43, an AGC (Automatic Gain Control) 44, a differential amplifier circuit 45, a synchronous detection circuit 46, and a smoothing circuit 47. Yes.

  The pair of detection electrodes 106b and 106c of the vibration type gyro sensor element 100 are connected to the adder circuit 41 and the differential amplifier circuit 45 via the wiring connection terminals 101B and 101C, respectively. The drive electrode 106 a of the vibration type gyro sensor element 100 is connected to the output end of the AGC 44.

  In the angular velocity sensor 50, a so-called phase shift oscillation circuit is configured by the adder circuit 41, the amplifier circuit 42, the phase shift circuit 43, the AGC 44 and the vibration type gyro sensor element 100, and the vibration type gyro sensor element 100 is constituted by this phase shift oscillation circuit. A voltage is applied between the reference electrode 104a and the drive electrode 106a to cause the vibrator 110 to self-oscillate. The vibration direction of the vibrator 110 is the thickness direction of the vibrator 110.

  Further, in the angular velocity sensor 50, the output terminal of the adder circuit 41 and the differential amplifier circuit 45 in which the pair of detection electrodes 106b and 106c are connected via the wiring connection terminals 101B and 101C are connected to the synchronous detection circuit 46, The synchronous detection circuit 46 is connected to the smoothing circuit 47, and these and the piezoelectric body 105a function as a detection unit that detects the angular velocity of the vibrator 110.

  That is, in the angular velocity sensor 50 shown in FIG. 2, the angular velocity is applied in the longitudinal direction of the vibrator 110 when the vibrator 110 of the vibration type gyro sensor element 100 is self-excited by the phase-shift oscillation circuit described above. The Coriolis force generated in the direction perpendicular to the vibration direction is detected by the piezoelectric body 105 a, output as signals having opposite polarities from the detection electrodes 106 b and 106 c, and input to the differential amplifier circuit 45. The output amplified by the differential amplifier circuit 45 is input to the synchronous detection circuit 46, where synchronous detection is performed. At this time, the output from the adder 41 is supplied to the synchronous detection circuit 46 as a synchronous signal in order to perform synchronous detection. The output from the synchronous detection circuit 46 is output as an angular velocity signal that is a DC signal obtained by detecting the Coriolis force generated in the vibrator 110 via the smoothing circuit 47.

  As described above, in the angular velocity sensor 50, the vibrator 110 is vibrated using the piezoelectric body 105a, the Coriolis force generated in the vibrator 110 is detected by the piezoelectric body 105a, and the Coriolis force detected by the piezoelectric body 105a is detected. Based on this, the angular velocity can be detected.

  The vibration gyro sensor element 100 was manufactured as a piezoelectric thin film sensor using a thin film process as follows.

First, a Si substrate 1 as shown in FIGS. 4 and 5 is prepared. The size of the substrate 1 is arbitrarily set according to the line of the thin film process that is owned, and in this embodiment, a wafer having a diameter of 4 inches is used. Although the thickness of the substrate 1 is determined by workability and the price of the substrate, it may be finally equal to or greater than the thickness of the vibrator, and in this embodiment, the thickness is 300 μm. Thermal oxide films (SiO ₂ films) 2A and 2B formed by thermal oxidation serving as protective masks during anisotropic wet etching are formed on both sides of the Si substrate 1. Although the thickness of the thermal oxide films 2A and 2B is arbitrary, it is set to about 0.3 μm in the present embodiment. Further, although the N type is adopted for the Si substrate 1, the selection is arbitrary. However, the azimuth plane of the Si substrate 1 is precisely defined, and the substrate is cut out so that the wide-mouth plane of the substrate shown in FIG. 1 is the (100) azimuth plane and the plane of FIG. Need to do.

  Next, as shown in FIGS. 6 and 7, in order to remove a part of the thermal oxide film 2 </ b> B on the back surface of the substrate 1, a resist pattern film 3 having an opening as a part to be removed is formed.

  FIG. 7 is a cross-sectional view taken along the line X-X ′ of FIG.

  As a forming method, a so-called photolithography technique usually used in a semiconductor thin film process is used. As the resist film 3, OFPR-8600 manufactured by Tokyo Ohka Co., Ltd. was used, but the type of the resist film 3 is arbitrary. The photolithography process is a technique generally used in a thin film process such as resist film coating, pre-baking, exposure, and development, and details thereof are omitted here. Photolithography technology is also used in future processes, but general steps are omitted except for special usage methods. Each of the openings shown in FIG. 5 becomes one element.

  The shape of the opening is determined by the final beam shape, the thickness of the substrate 1, and the etching width when the beam shape is formed. The etching width will be described later with reference to FIGS. 39 to 41, but here it is 50 μm.

  First, with respect to the width direction (diaphragm width t9), the required width is the vibrating beam width t6 + etching width t7 × 2 (left and right), and the thickness of the substrate 1 is 300 μm in this embodiment and the vibrating beam thickness is 100 μm. As will be described later, when a substrate thickness of 300 μm is shaved to 100 μm by a wet etching method, as shown in FIG. 10, there is a feature of being ground at an angle of 55 °, so that width (300-100) μm. Xtan 55 ° = 140 μm needs to be added to the left and right. Eventually, the diaphragm width t9 = t6 + t7 × 2 + 140 × 2 = 100 + 50 × 2 + 140 × 2 = 480 μm. Similarly, diaphragm length t8 = vibrating beam length t5 + beam space width t7 + 140 × 2 = 2000 + 50 + 140 × 2 = 2330 μm.

  Next, as shown in FIGS. 8 and 9, the portion of the thermal oxide film 2 </ b> B corresponding to the opening portion is removed. The removal method may be physical etching such as ion etching or wet etching, but considering the smoothness of the interface of the substrate 1, wet etching in which only the thermal oxide film 2B is removed is suitable. In this embodiment, ammonium fluoride is used as a chemical solution for wet etching. However, in the case of wet etching, when etching is performed for a long time, so-called side etching in which etching proceeds from the side surface of the opening becomes large, and therefore it is necessary to terminate the etching when only the opening of the thermal oxide film 2B is removed.

  Next, as shown in FIGS. 10, 11, and 12, wet etching is performed on the substrate 1 exposed as an opening portion until the thickness of the substrate 1 in the opening portion reaches a desired vibration beam thickness t4. Sharpen. In this embodiment, a TMAH 20% solution is used to etch the substrate 1 made of Si. At this time, the liquid temperature is kept at 80 ° C. and immersion etching is performed. FIG. 12 is an enlarged view of portion A in FIG. Under the above conditions, the etching amount (approximately 6 hours is required to set the diaphragm depth t10 to 200 μm. Further, the shape of the substrate 1 in the opening portion is wet etching angle as shown in FIG. In addition to TMAH, KOH or the like is generally used as such a wet etching chemical, but in this embodiment, etching with the thermal oxide films 2A and 2B is performed. TMAH, which has a higher rate selection ratio, was adopted.

  By the way, in this embodiment, wet etching utilizing the characteristics of Si is employed for substrate grinding until the thickness of the vibrating beam is reached, but the grinding method is arbitrary and is not limited to this method.

  A diaphragm is formed in the opening by the above method. The diaphragm thickness t11 left by wet etching finally becomes equal to the vibrating beam thickness t4.

  Hereinafter, in the description of the manufacturing method of the vibration type gyro sensor element 100 of the present embodiment, one element indicated by W in FIGS. 13 and 14 will be described in an enlarged manner. Moreover, in order to make the explanation easy to understand in the figure, the actual dimensional ratio may be different.

  Further, as shown in FIG. 15 and FIG. 16, the description will be made with the opening formed with the above-described diaphragm and the thermal oxide film 2B facing downward.

  Next, as shown in FIGS. 17 and 18, a lower electrode film 4, a piezoelectric film 5, and an upper electrode film 6 are formed. The lower electrode film 4 is made of Ti: 50 nm + Pt: 100 nm in order to improve the characteristics of the piezoelectric film. First, a Ti film having a thickness of 50 nm was formed by a magnetron sputtering apparatus, and a Pt film having a thickness of 200 nm was formed on the i. Ti and Pt were formed with a gas pressure of 0.3 Pa and RF power of 1.0 kW and 0.1 kW, respectively. Next, using a Pb1 + x (Zr0.53Ti0.47) O3-y oxide target in a magnetron sputtering apparatus, a piezoelectric body under conditions of normal temperature, Ar / O2 ratio 1/1, gas pressure 0.7 Pa, and RF power 1.0 kW. A thin film was formed to 1 μm. Thereafter, crystallization heat treatment was performed at 700 ° C. for 30 minutes in an oxygen atmosphere using an electric furnace. Thereafter, 300 nm of Pt was formed as an upper electrode film on the surface of the piezoelectric thin film. The Pt film was formed by a magnetron sputtering apparatus under conditions of a gas pressure of 0.3 Pa and an RF power of 0.3 kW.

  Next, as shown in FIGS. 19 and 20, the upper electrode 6 is formed. The upper electrode 6 is divided into three parts as shown in FIG. The center thereof is a drive electrode 6A for generating power for driving the vibrating beam, and detection electrodes 6B and 6C for detecting Coriolis force are provided on the left and right sides thereof. In the width direction, the center of the drive part coincides with the center of the vibrating beam, and the left and right are placed in contrast. Further, as shown in FIG. 19, the base of the vibrating beam and the end of the straight portion of the upper electrode film 6 are placed at the same position, and a wiring connection portion is provided from the end.

  In this embodiment, the drive electrode width t13 is 50 μm, the detection electrode width t14 is 10 μm, the upper electrode length t12 is 1.8 mm, and the distance between the drive electrode 6A and the detection electrodes 6B and 6C is 5 μm. This size is arbitrary, but it must be within the range of the final vibrating beam size. In addition, the shape of the connection portion with the wiring pattern to be described later is also arbitrary, and in this embodiment, the connection portion width t16 is 50 μm and the connection portion length t15 is 50 μm.

  The upper electrode 6 was formed by forming a desired resist film pattern using a photolithographic technique, then performing a heat treatment at 130 ° C. for 3 minutes, and removing an unnecessary portion of the upper electrode film by ion etching. . If the heat treatment temperature after forming the resist film pattern is less than 120 ° C., the resist wall surface does not have a sufficient taper angle and etching burrs are generated, and if it exceeds 140 ° C., the upper layer electrode is peeled off due to the stress of the resist.

  Next, the piezoelectric film 5 shown in FIGS. 21 and 22 is formed. The shape of the piezoelectric film 5 is arbitrary as long as it completely covers the upper electrode film 6. In the present embodiment, the piezoelectric film length t17 is 1.85 mm, and the piezoelectric film width t18 is 90 μm. Here, the center of the piezoelectric film width coincides with the center of the vibrating beam, and the lower end portion thereof coincides with the root line. The piezoelectric film width t18 needs to be less than or equal to the width t4 of the vibrating beam. The piezoelectric films 5 of the connection portions 6a, 6b, 6c of the upper electrode film 6 were formed with a width of 5 μm from the outer periphery of the connection portion of the upper electrode film 6. This width is arbitrarily set according to the shape size of the entire element.

  As the above piezoelectric part forming method, a resist film pattern having a piezoelectric part shape is formed using a photolithography technique, and then removed by wet etching with a hydrofluoric acid solution in this embodiment. The removal method is arbitrary, and removal by physical ion etching or chemical removal by RIE (Reactive Ion Etching) can be considered.

  Next, as shown in FIGS. 23 and 24, the lower layer electrode 4 is formed. The shape of the lower electrode 4 is arbitrary as long as it completely covers the piezoelectric film 5 like the piezoelectric portion. In the present embodiment, the lower layer electrode length t19 is 1.9 mm, and the lower layer electrode width t20 is 94 μm. Here, the center of the lower electrode width coincides with the center of the vibrating beam, and the lower end coincides with the root line. The lower electrode width t20 needs to be less than or equal to the width t4 of the vibrating beam. Further, the lower layer electrode 4 of the connection part was formed by waiting for a width of 5 μm from the outer periphery of the connection part of the piezoelectric film 5. This width is arbitrarily set according to the shape size of the entire element. Further, in order to electrically connect the lower electrode film 4 to the outside, a lower electrode bonding portion 4A is provided as shown in FIG. The lower electrode joint portion 4A needs to secure an area that can be subsequently drawn out by the wiring pattern, and the lower electrode joint length t21 is 50 μm and the lower electrode joint width t22 is 100 μm.

  As the above lower electrode part formation method, after forming the resist film pattern of a lower electrode part shape using a photolithographic technique, it forms by removing an unnecessary part by ion etching. This method is also arbitrary and is not limited to ion etching.

  In the above lower electrode portion forming method, a resist film pattern having a lower electrode portion shape is formed by using a photolithography technique, followed by heat treatment at 130 ° C. for 3 minutes, and unnecessary portions are removed by ion etching. When the heat treatment temperature after forming the resist film pattern is less than 120 ° C., the resist wall surface does not have a sufficient taper angle and etching burrs are generated, and when it exceeds 140 ° C., the upper layer electrode peels off due to the stress of the resist.

  Here, since the piezoelectric characteristics were deteriorated by repeating the etching, crystallization heat treatment was performed again in an oxygen atmosphere using an electric furnace. The heat treatment is preferably performed at a high temperature, but if heated above the heat treatment temperature at the time of forming the piezoelectric thin film, the upper electrode may be peeled off. In this embodiment, the heat treatment is performed at 650 ° C. for 30 minutes. did.

  Next, as shown in FIGS. 25 and 26, a wiring base film 7 is formed. This purpose is to ensure the adhesion of the wiring film 9 described later, and an insulating material is a prerequisite. If the wiring base film 7 is formed on the vibrator other than the electrode connection portions 6a, 6b, 6c and the etching area around the vibrator, the shape of the wiring base film 7 is arbitrary. In the present embodiment, each of the upper electrode film 6 and the lower electrode film 4 and the wiring base film have an overlap of 5 μm in order to improve the adhesion of the electrode film.

  The wiring base film 7 is formed by forming a resist film pattern having an opening with a desired shape by a photolithography technique, forming a wiring electrode film by sputtering, and applying the sputtered film attached to unnecessary portions to the resist. The film was formed by a so-called lift-off method in which the film was removed simultaneously with removal. Alumina was selected as the material, and 75 nm was deposited. However, the material and the forming method of the wiring film are arbitrary and are not limited to the above forming method and material.

  Next, as shown in FIGS. 27 and 28, a planarizing resist film 8 is provided on the electrode connecting portions 6a, 6b, 6c. The purpose of the planarizing resist film 8 is to smoothly perform electrical bonding between a wiring film 9 and an upper electrode film 6 described later. When the wiring film 9 and the upper electrode film 6 are physically joined, they must pass through the end portions of the piezoelectric film 5 and the lower electrode film 4, but the piezoelectric film 5 is wet-etched in this embodiment. The formed end portion is reversely tapered or substantially vertical, and if wiring is performed without installing the planarizing resist film 8, there is a risk of disconnection at the end portion. Further, since the lower electrode film 4 is exposed, an electrical short-circuit occurs unless insulation is taken with the planarizing resist film. From the above viewpoint, the planarizing resist film 8 is provided.

  The shape of the flattening resist film 8 is arbitrary as long as it covers a wiring film 9 described later. In this embodiment, the flattening resist film width t23 is 200 μm and the flattening resist film length t24 is 50 μm.

  The planarizing resist film 8 is formed by patterning the resist film into a desired shape by a photolithography technique and then curing the patterned resist film by applying a heat treatment of about 280 to 300 ° C. At this time, although the thickness of the resist film is about 2 μm in this embodiment, the thickness is changed according to the thickness of the piezoelectric film 5 and the lower electrode film 4 and is approximately equal to or greater than the total thickness of both. It is desirable to have

  In this embodiment mode, a resist film is used for the purpose of the above planarization, but this material is not limited to this. Any non-conductive material that meets the above-mentioned purpose is arbitrary including its formation method.

  Next, as shown in FIGS. 29 and 30, a wiring film 9 is formed in order to connect the upper electrode film 6 to the outside. This is for facilitating electrical connection with the outside, and the wiring film 9 passes through the upper surface of the planarizing resist film 8 and comes into contact with the junction of the upper electrode film 6. The shape of the upper electrode connecting portions 6a, 6b, and 6c is arbitrary, but is preferably 5 μm square or more in order to reduce electrical contact resistance. Further, in this embodiment, the electrical connection with the outside is premised on the bonding method by Au bump + flip chip, so that electrodes PAD101a, 101b, 101c, and 101d are formed on each electrode as shown in FIG. The Au bump area is secured. The electrodes PAD101a, 101b, 101c, and 101d need an area where Au bumps can be formed. In this embodiment, the electrode PAD portion length t25 is 120 μm and the electrode PAD portion width t26 is 120 μm. Further, since the drive electrode 6A, the left and right detection electrodes 6B and 6C, and the lower layer electrode 4 that are the upper electrode film 6 need to be electrically connected to the outside, respectively, the wiring film 9 also has these four. The wiring PADs 101a, 101b, 101c, and 101d are premised on being in the element area AR.

  In this process, a polarization rail is also formed at the same time. The vibrator according to the present embodiment is finally polarized to stabilize the piezoelectric characteristics, but in order to make the polarization work more efficient, the elements in the same row are collectively performed. In order to perform this simultaneous polarization, wirings on the voltage application side and the GND side must be formed in advance. Here, the polarization rails 111 and 112 are formed in a horizontal straight line as shown in FIG. At this time, the element and the rail are independent, but the wiring on the application side and the GND side are connected by the formation of the Cu polarization line 11 described later.

  The wiring film 9 is formed by forming a resist film pattern having an opening with a desired shape by a photolithography technique, then forming a wiring electrode film by sputtering, and applying the sputtered film attached to unnecessary portions to the resist film. It was formed by a so-called lift-off method in which removal was performed at the same time as removal of the film. As a wiring film material, 20 nm of Ti was deposited to improve adhesion, and then 500 nm of Au was deposited to facilitate Au bumps. However, the material and the forming method of the wiring film are arbitrary and are not limited to the above forming method and material.

  Next, as shown in FIGS. 32 and 33, the insulating protective film 10 is formed on the vibrating beam and the wiring. The purpose is to prevent leakage between electrodes due to external factors such as humidity, and also to prevent oxidation of the electrode film. The condition is that the vibrator upper protective film width t27 is wider than the lower electrode width t20 and narrower than the vibrating beam width t6, and in this embodiment, t27 is set to 98 μm. The condition is that the vibrator upper protective film length t28 is longer than the lower electrode length t19 and shorter than the vibrator length t5. In this embodiment, t28 is 1.95 mm. The protective film 10 on the wiring film 9 is a pattern that covers the entire surface. However, the protective film is selectively prevented from being attached at the four electrode PAD locations where Au bumps are formed and at the four connection portions with the Cu wiring 11. There is a need.

The protective film 10 is formed by forming a resist film pattern having a desired shape as an opening by a photolithography technique, forming a protective film by sputtering, and applying the sputtered film attached to unnecessary portions to the resist film. It was formed by a so-called lift-off method that is removed simultaneously with removal. As a material for the protective film 10, Al ₂ O ₃ is deposited to a thickness of 50 nm in order to improve adhesion, and then a highly insulating SiO ₂ is deposited to a thickness of 750 nm. In order to improve the thickness, Al ₂ O ₃ was deposited to 50 nm. The SiO ₂ functioning as an insulating protective film needs to be at least twice the thickness of the upper electrode. However, when the thickness is 1 μm or more, burrs are likely to occur during lift-off. Moreover, in order to increase the film density during the SiO ₂ film formation, the Ar pressure was set at 0.4 Pa, which is the lower limit of the discharge limit.

  Next, as shown in FIGS. 34 and 35, a Cu wiring 11 is formed. The Cu wiring 11 connects the driving electrode 6A of the upper electrode film 6 and the left and right detection electrodes 6B and 6C to the rail 111 on the voltage application side, and the lower layer electrode 4 to the rail 112 on the GND side. As shown in FIG. 36, the Cu wiring 11 is similarly connected in all elements. The reason why this wiring is made Cu is that it is easily dissolved by wet etching after polarization, and the device can be made independent again without damaging the device. Therefore, any material can be used as long as it is a conductor that can be easily lost without damaging the element. The wiring width is preferably 30 μm or more in order to ensure conduction during polarization.

  The Cu wiring 11 is formed by forming a resist film pattern having a desired shape as an opening by a photolithography technique, forming Cu by sputtering, and removing the sputtered film adhering to unnecessary portions by removing the resist film. At the same time, it was formed by a so-called lift-off method. The Cu film thickness was set to 400 nm to ensure conduction during polarization. The method for forming the wiring film is arbitrary and is not limited to the above-described forming method.

Next, as shown in FIGS. 37 and 38, the back surface stopper film 12 is formed. The purpose is to prevent edge shape defects due to plasma concentration on the lowermost surface when through etching is performed in the formation of a vibrating beam described later. In this embodiment, SiO ₂ is formed with a thickness of 500 nm on the entire back surface by sputtering.

  Next, as shown in FIGS. 39, 40 and 41, the beam space is removed to form a vibrating beam. 40 is a cross-sectional view taken along the line YY ′ of FIG. 39, and FIG. 41 is a cross-sectional view taken along the line XX ′ of FIG.

As a method for forming the beam space, a resist film pattern having the through portion 13 as an opening is formed by a photolithography technique, the thermal oxide film (SiO ₂ ) 2A is removed by ion etching, and etching is performed until the substrate 1 is penetrated. . The removal of the thermal oxide film 2A can be performed by wet etching, but ion etching is preferable in consideration of a dimensional error due to side etching. In order to penetrate Si of the substrate 1, the vibration beam thickness t14 (diaphragm thickness t11) is 100 μm in this embodiment, and this amount needs to be removed by etching. In normal ion etching or the like, the selectivity with the resist film cannot be obtained, and it is difficult to leave it as a vertical wall surface. In this embodiment, a Bosch process (SF ₆ during etching, C ₄ during film formation) that repeats etching and sidewall protective film formation in an apparatus equipped with ICP (Inductively Coupled Plasma) used in MEMS technology. F ₈ gas) by using, was formed of the vibrating beam with vertical immediate wall. The technology for grinding the Si material vertically is generally established, and this embodiment is also performed by a commercially available apparatus. However, the method for removing the beam space is arbitrary and is not limited to the above method. The etching width t7 needs to be a width that can be etched by ICP, and is 50 μm in this embodiment. Further, since the Cu wiring bridge width t29 is on the line of the Cu wiring, it is prevented from penetrating. However, in the structure of the present embodiment, the element is divided by cutting along the Cu wiring bridge portion in element cutting described later, so that the Cu wiring bridge width t29 is equal to or less than the cutting wheel width. Become. In the present embodiment, the Cu wiring bridge width t29 is set to 32 μm.

  After completion of etching by ICP, the back surface stopper film 12 is removed. The removal method is arbitrary, but in this embodiment, the removal is performed by wet etching with ammonium fluoride. At this time, if the penetration pattern resist is removed before the stopper film 12 is removed, the insulating protective film 10 disappears. Therefore, the resist is removed after the stopper film is removed. The stopper film 12 and the resist after removal are shown in FIGS.

  With the above process, the main steps of piezoelectric element formation, shape formation, and wiring formation are completed with respect to the formation of the piezoelectric thin film sensor. As shown in FIG. 45, a plurality of vibration type gyro sensor elements 100 as piezoelectric thin film sensors are formed in the substrate 1. In FIG. 45, it is represented by 5 × 5 columns, but the number is determined by the size of the element to be designed and the pitch to be listed.

  Next, the element shown in FIGS. 46 and 47 is subjected to a polarization process for stabilizing the piezoelectric characteristics. In order to collectively polarize the elements in the same row, they are connected to an external power source via the application side PAD and the GND side PAD. Although the connection method and the polarization method are arbitrary, in this embodiment, the connection is made to an external power source by wire bonding, and the polarization treatment is performed at 20 V for 10 minutes.

  Next, as shown in FIGS. 48 and 49, the Cu wiring 11 that is no longer necessary after the polarization process is removed. If the element is cut with the Cu wiring 11 left, the Cu wiring 11 and the substrate 1 leak electrically at the cut surface, so it is desirable to remove them chemically. In this embodiment, in order not to damage the element, wet etching was performed using an Enstrip solution manufactured by Meltex Co., and the element was eliminated.

  Next, as shown in FIGS. 50 and 51, Au bumps 14 for performing flip chip are formed. The Au bumps 14 are formed on the four electrode PADs.

  Next, as shown in FIGS. 52 and 53, the fifteen vibration type gyro sensor elements 100 formed as piezoelectric thin film sensors on the substrate 1 are individually divided. At the time of cutting, it is necessary to cut with a grindstone having a width of 32 μm or more in the Cu wiring bridge portion, and in this embodiment, cutting is performed by dicing with a grindstone having a width of 40 μm. As shown in FIG. 53, cutting is performed along cutting lines L1 to L3 according to the element size. In this case, the cutting lines L1 and L2 must be cut on the Cu wiring bridge portion. As a result, the vibration type gyro sensor element 100 as the piezoelectric thin film sensor shown in FIG. Is completed, and the portion C shown in FIG. 53 becomes an unnecessary portion.

  As described above, the vibration type gyro sensor element 100 is formed by a thin film process, and a plurality of thin film gyroscopes are polarized at a time through the thin film wiring formed by the thin film process, so that a large number of thin film gyroscopes can be manufactured inexpensively and stably. Can be formed.

Then, the individually divided vibration type gyro sensor elements 100 are attached to the IC substrate by a flip chip technique, for example, as shown in FIG. The IC substrate is designed in advance so that the electrical connection is completed according to the arrangement of the elements. In the example of FIG. 55, the biaxial acceleration sensor 150 including the two vibration gyro sensor elements 100X and 100Y is formed by attaching the vibration gyro sensor elements 100 one by one in the X direction and the Y direction.
As shown in FIG. 56, the acceleration sensor 150 is protected by a cover material 15 in order to eliminate contact between elements and circuits and the outside. The material of the cover material 15 is arbitrary, but it is desirable to have a shielding effect such as metal in consideration of the influence of external noise. Further, the cover material 15 has a shape that does not hinder the vibration of the vibrating beam.

It is a perspective view of a vibration type gyro sensor element shown as the best mode for carrying out the present invention. It is a top view of the said vibration type gyro sensor element. It is a block diagram which shows the structure of the drive detection circuit of the said vibration type gyro sensor element. It is a top view of the single crystal silicon substrate used when manufacturing the said vibration type gyro sensor element. FIG. 6 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 5. It is a top view which shows a mode that the resist film pattern was formed in the said single crystal silicon substrate. FIG. 7 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 6. It is a top view which shows a mode when the thermal oxide film of the said single crystal silicon substrate is removed. FIG. 9 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 8. It is a top view which shows a mode that the crystal anisotropic etching was given to the said single crystal silicon substrate. FIG. 11 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 10. It is sectional drawing which expanded and showed the area | region A shown in FIG. 11 of the said single crystal silicon substrate. It is the top view which showed the mode of the surface side of the said single crystal silicon substrate. FIG. 14 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 13. It is the top view which showed the mode of the back surface side of the said single crystal silicon substrate. FIG. 16 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 15. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the lower layer electrode film, the piezoelectric film, and the lower layer electrode film were formed. FIG. 18 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 17. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the drive electrode and the detection electrode were formed. FIG. 20 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 19. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the piezoelectric film was formed. FIG. 21 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 20. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the lower layer electrode was formed. FIG. 24 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ in FIG. 23. It is a top view which expands and shows the mode of the single crystal silicon substrate in which the wiring base film was formed. FIG. 26 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 25. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the planarization resist film was formed. FIG. 28 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 27. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the wiring connection terminal was formed. FIG. 30 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 29. It is a top view which shows the mode of the said single crystal silicon substrate in which the polarization rail was formed. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the insulating protective film was formed. FIG. 33 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 32. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which Cu wiring was formed. FIG. 35 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 34. It is a top view of the whole said single crystal silicon substrate in which Cu wiring was formed. It is a top view which expands and shows the mode of the said single crystal silicon substrate in which the back surface stopper film | membrane was formed. FIG. 38 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 37. It is a top view which expands and shows the mode of the said single crystal silicon substrate from which the beam space was removed and the vibration beam was formed. FIG. 38 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 37. FIG. 38 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ of FIG. 37. It is a top view which expands and shows the mode of the said single crystal silicon substrate which removed the stopper film | membrane. FIG. 43 is a cross-sectional view of the single crystal silicon substrate taken along line YY ′ of FIG. 42. FIG. 44 is a cross-sectional view of the single crystal silicon substrate taken along line XX ′ of FIG. 43. It is a top view of the whole said single crystal silicon substrate in which a plurality of vibration type gyro sensor elements were formed as piezoelectric thin film sensors. It is a top view of the said single crystal silicon substrate whole which performs the polarization process for stabilizing a piezoelectric characteristic. It is a top view which expands and shows the said single crystal silicon substrate which performs the polarization process for stabilizing a piezoelectric characteristic. It is a top view of the said single crystal silicon substrate whole which removed the Cu wiring which became unnecessary after the polarization process. It is a top view which expands and shows the said single crystal silicon substrate from which the said Cu wiring was removed. It is a top view of the said single crystal silicon substrate whole in which Au bump for performing a flip chip was formed. It is a top view which expands and shows the said single crystal silicon substrate in which the said Au bump was formed. It is the top view of the said single crystal silicon substrate whole which showed the cutting line at the time of dividing | segmenting 15 vibration type gyro sensor elements formed as a piezoelectric thin film sensor individually. It is a top view which expands and shows the said single-crystal silicon substrate which shows a mode that the said vibration type gyro sensor element is divided | segmented separately. It is a top view of a vibration type gyro sensor element formed as a piezoelectric thin film sensor. It is a top view which shows a mode when a vibration type gyro sensor element is affixed on an IC substrate. It is a top view which shows a mode when a cover material is attached to the angular velocity sensor provided with a vibration type gyro sensor element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 2A thermal oxide film, 2B thermal oxide film, 3 resist pattern film, 4 lower layer electrode, 4A lower layer electrode junction part, 5 piezoelectric film, 6 upper electrode film, 6A drive electrode, 6B, 6C right and left detection electrode, 6a, 6b, 6c Upper electrode connection portion, 7 Wiring base film, 8 Planarization resist film, 9 Wiring film, 10 Insulating protective film, 11 Cu wiring, 12 Back stopper film, 13 Through portion, 14 Au bump, 15 Cover material, 40 IC circuit, 41 adder circuit, 42 amplifier circuit, 43 phase shift circuit, 44 AGC, 45 differential amplifier circuit, 46 synchronous detection circuit, 47 smoothing circuit, 100, 100X, 100Y vibration type gyro sensor element, 101a, 101b, 101c , 101d electrode PAD, 101A, 101B, 101C, 101D wiring connection terminal, 104a reference electrode, 105a pressure Body, 106a drive electrodes, 106b, 106c detection electrode, 110 oscillator, 111 a voltage application side of the rail, 112 GND side of the rail, 50,150 acceleration sensor, L1 to L3 cutting line

Claims (3)

A method for manufacturing a vibration type gyro sensor element comprising a cantilever-shaped vibrator formed by forming a lower electrode film, a piezoelectric material, and an upper electrode film on a substrate that forms a beam shape,
A vibration type gyro sensor element comprising a recrystallization heat treatment step in which a recrystallization heat treatment after formation of a lower electrode, a piezoelectric material, and an upper electrode pattern is performed at a temperature lower than the heat treatment temperature at the time of forming a piezoelectric thin film by 50 ° C. or more Manufacturing method.   2. The method of manufacturing a vibration type gyro sensor element according to claim 1, further comprising a heat treatment step of performing heat treatment at 120 ° C. or more and 140 ° C. or less after forming the resist pattern of the upper electrode.   2. The method of manufacturing a vibration type gyro sensor element according to claim 1, further comprising a heat treatment step of performing heat treatment at 120 ° C. or more and 140 ° C. or less after forming the resist pattern of the lower electrode.

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