JP4987684B2 - Method for manufacturing gyro sensor element - Google Patents

Method for manufacturing gyro sensor element Download PDF

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JP4987684B2
JP4987684B2 JP2007326876A JP2007326876A JP4987684B2 JP 4987684 B2 JP4987684 B2 JP 4987684B2 JP 2007326876 A JP2007326876 A JP 2007326876A JP 2007326876 A JP2007326876 A JP 2007326876A JP 4987684 B2 JP4987684 B2 JP 4987684B2
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vibration
crystal
electrode
crystal piece
gyro sensor
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JP2009150678A (en
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晶子 加藤
池田  智夫
真紀 滝沢
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シチズンホールディングス株式会社
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  The present invention relates to a method for manufacturing a high-precision and small-sized gyro sensor element using crystal, and further relates to a method for manufacturing a gyro sensor element that is less likely to cause defects and has high productivity and excellent reliability.
  In recent years, there has been an increasing demand for gyro sensor elements used for angular velocity detection of automobile navigation systems and angular velocity detection of camera shake correction systems such as digital cameras and digital videos. In particular, a gyro sensor element using a quartz crystal has attracted attention because of its superior frequency temperature characteristics and high reliability compared to a gyro sensor element using a ceramic material.
  Conventionally, a manufacturing method as described below has been used in order to manufacture a gyro sensor element using this highly reliable quartz (see, for example, Patent Document 1).
  FIG. 10 is a diagram showing a configuration of a conventional gyro sensor element having four drive vibration legs and two detection vibration legs. As shown in FIG. 10, the conventional gyro sensor element 20 includes a crystal piece 105 made of crystal, an electrode 205, and a weight portion 600. The crystal piece 105 includes a connection leg 125, four drive vibration legs 115 extending in a direction perpendicular to the connection leg 125, and two detection vibration legs 116. The drive vibration leg 115 and the detection vibration leg 116 include The electrode 205 and the weight part 600 are formed in each.
  The crystal piece 105 having such a shape is formed by an etching method, and the electrode 205 on the crystal piece 105 is patterned into a predetermined shape by a photolithography method after forming a metal film by a sputtering method or a vapor deposition method. The weight part 600 formed at the tip of the drive vibration leg 115 and the detection vibration leg 116 is made of gold (Au) in order to increase the mass, and is formed thick with a thickness of about several microns by plating or vapor deposition.
  FIG. 11 is a diagram schematically showing a vibration operation of a gyro sensor element having four conventional drive vibration legs and two detection vibration legs. In FIG. 11, each leg portion is simplified and represented by a line for easy understanding of the vibration operation.
  When the gyro sensor element 20 is in a non-rotating state, as shown in FIG. 11A, only the four driving vibration legs 115 have a predetermined frequency between the vibration state indicated by the solid line and the vibration state indicated by the alternate long and short dash line. The other detection vibrating legs 116 and the connecting legs 125 hardly vibrate.
  When the rotational state is applied and the angular velocity ω is applied, as shown in FIG. 11B, a Coriolis force is applied to the vibrating drive vibration leg 115, and thereby the detection vibration leg 116 is in a vibration state indicated by a solid line and a one-dot chain line. It vibrates at a predetermined frequency between the vibration modes shown. The gyro sensor 20 recognizes the angular velocity ω by electrically outputting the vibration of the detection vibration leg 116 through the electrode 205 (not shown in FIG. 11).
In the gyro sensor element 20 shown in FIG. 10, in order to detect the angular velocity with high sensitivity and high reliability, the degree of detuning, which is the difference between the resonance frequency of the drive vibration leg 115 and the resonance frequency of the detection vibration leg 116, is uniform. It needs to be as designed. However, since dimensional variations due to processing errors occur in the manufacturing process, the resonance frequencies of the drive vibration legs 115 and the detection vibration legs 116 are not always as designed. As a result, the degree of detuning (the difference between the resonance frequency of the driving vibration leg 115 and the resonance frequency of the detection vibration leg 116) does not become as designed, and as it is, the angular velocity cannot be detected with high sensitivity and high reliability.
  Therefore, in the conventional gyro sensor element 20, the weight portion 600 is sequentially removed by a laser processing method or the like to adjust the resonance frequency of the driving vibration leg 115 and the resonance frequency of the detection vibration leg 116, and the degree of detuning becomes as designed. It was like that.
  In addition, a method has been proposed in which the detuning degree of the gyro sensor element is adjusted by adjusting the etching time for forming the crystal piece while measuring the degree of detuning using a monitor crystal piece (for example, Patent Document 2). reference.).
  FIG. 12 is a diagram showing the configuration and vibration operation of a conventional gyro sensor element having a pair of vibrating legs. A conventional gyro sensor element 30 shown in FIG. 12 includes a crystal piece 101 including a pair of vibrating legs 110 having the same shape, and an electrode 210 formed on the crystal piece 101 in a predetermined shape.
  When the gyro sensor element 30 having such a configuration is in a non-rotating state, as shown in FIG. 12 (a), when one vibrating leg 110 is excited, the other vibrating leg 110 resonates accordingly, As a result, the two vibrating legs 110 vibrate in the horizontal direction (drive vibration fd).
  When the rotational state is reached and the angular velocity ω is applied, as shown in FIG. 12B, Coriolis force acts on each vibration leg 110 and starts to vibrate in the opposite direction (detection vibration fs). The gyro sensor 30 recognizes the angular velocity ω by electrically outputting the detected vibration fs of the vibrating leg 110.
  In the gyro sensor element 30 that performs such a vibration operation, the sensitivity increases as the resonance frequency of the drive vibration fd (drive vibration frequency fd1) and the resonance frequency of the detection vibration fs (detection vibration frequency fs1) are closer. It becomes more susceptible to disturbances and becomes less reliable. Therefore, the conventional gyro sensor element 30 is made by separating the drive vibration frequency fd1 and the detection vibration frequency fs1 within an optimum range based on experiments. In the gyro sensor element 30, the difference between the drive vibration frequency fd1 and the detected vibration frequency fs1 is referred to as a detuning degree.
  In order to manufacture the gyro sensor element 30 with high accuracy and reliability, the gyro sensor element 30 must be manufactured so that the degree of detuning is within an optimum range. For this purpose, a manufacturing method as described below has been conventionally used.
  FIG. 13 is a view showing a conventional method for manufacturing a gyro sensor element having a pair of vibrating legs. First, as shown in FIG. 13A, a mask layer 400 made of metal is formed in a desired shape on both sides of a quartz wafer 1000. The desired shape in this step is a shape obtained by projecting the crystal piece 101 having the pair of vibrating legs 110.
  Next, as shown in FIG. 13B, the crystal wafer 1000 on which the mask layer 400 is formed is put into an etching solution, for example, buffered hydrofluoric acid (BHF) solution, and wet etching is performed to form a crystal piece 151. To do.
  FIG. 14 is a view showing a state in which a monitor crystal piece is broken from a crystal piece substrate formed by a method of manufacturing a gyro sensor element having a pair of conventional vibration legs. A large number of crystal pieces 151 formed in FIG. 13B are connected to the crystal piece substrate 1500 as shown in FIG. Since a large number of crystal pieces 151 can be formed simultaneously in one process, the productivity up to this process is very high.
  As shown in FIG. 14, after the crystal piece 151 is formed in FIG. 13B, the mask layer 400 exists on the crystal piece substrate 1500 almost before the wet etching.
  In the conventional method of manufacturing the gyro sensor element 30, as shown in FIG. 14, one or several of the crystal pieces 151 connected to the crystal piece substrate 1500 are folded, and a monitor crystal piece for vibration measurement is obtained. Used as 152. The mask crystal 400 is peeled off from the broken monitor crystal piece 152 to form an electrode.
  FIG. 15 is a diagram showing a configuration of a monitor crystal piece used in a conventional method for manufacturing a gyro sensor element and a state during vibration measurement. As shown in FIG. 15A, the monitor crystal piece 152 performs vibration measurement after the electrode 215 is formed in a predetermined shape after the mask layer 400 is peeled off.
  When the vibration of the monitor crystal piece 152 is measured, the drive vibration frequency fd2 and the detected vibration frequency fs2 can be measured as shown in FIG. Ideally, it is desirable that the drive vibration frequency fd2 and the detected vibration frequency fs2 coincide with the values of the drive vibration frequency fd1 and the detected vibration frequency fs1 as designed. Therefore, the drive vibration frequency fd2 and the detected vibration frequency fs2 which are different from the designed drive vibration frequency fd1 and the detected vibration frequency fs1 are often obtained.
  Therefore, in the conventional method of manufacturing the gyro sensor element 30, the design drive vibration frequency fd1 and the detected vibration frequency fs1 and the difference between the drive vibration frequency fd2 measured by the monitor crystal piece 152 and the detected vibration frequency fs2 are used. The additional time of the wet etching process is calculated.
  Then, the crystal piece substrate 1500 to which the crystal pieces 151 that have not been broken are connected is wet-etched again for the calculated etching time. Since the upper and lower surfaces of the crystal piece 151 connected to the crystal piece substrate 1500 are left with the mask layer 400 formed, only the side surface is etched, and as shown in FIG. A crystal piece 101 having a narrow width is formed.
  After that, as shown in FIG. 13D, the electrode 210 is formed after the mask layer 400 on the crystal piece 101 is peeled off, and the vibration leg 110 vibrates at the drive vibration frequency fd1 and the detection vibration frequency fs1 as designed, The gyro sensor element 30 having the designed detuning degree (difference between the drive vibration frequency fd1 and the detected vibration frequency fs1) is completed.
JP 2006-258527 A (page 6, FIG. 1) JP 2003-28645 A (page 3, FIG. 3)
  In the case of the conventional method of manufacturing the gyro sensor 20 that adjusts the degree of detuning by sequentially removing the weight portion 600 formed at the tip of the driving vibration leg 115 and the detection vibration leg 116 by a laser processing method or the like, in order to adjust the degree of detuning. Therefore, the weight portion 600 must be formed only, and the number of manufacturing processes is large and the productivity is very poor.
  Further, in order to increase the adjustment amount of the degree of detuning, it is necessary to increase the mass by forming the weight portion 600 thick, and therefore the time required for the film formation process of the weight portion 600 becomes longer. Productivity deteriorates.
  In addition, the electrode 205 is wired in the vicinity of the weight portion 600 processed by the laser, and there are many cases where a defect that causes the electrode 205 to be disconnected accidentally occurs due to the laser processing. As a result, the conventional manufacturing method of adjusting the degree of detuning by sequentially removing the weight portion 600 by a laser processing method or the like has low reliability.
  Further, when the gyro sensor element 20 is downsized, the area where the weight portion 600 can be formed becomes narrow and the amount of adjustment of the detuning degree is reduced, which is not suitable for downsizing.
  On the other hand, based on the measurement result of the detuning degree of the monitor crystal piece 152 broken from the crystal piece substrate 1500, the conventional gyro sensor 30 is manufactured by wet-etching the crystal piece substrate 1500 again to adjust the detuning degree. In the case of the method, the broken monitor crystal piece 152 is discarded without being used as a defective product, so that the production efficiency is poor.
  Further, when the number of monitor crystal pieces 152 is reduced in order to improve production efficiency, the average detuning degree of the crystal pieces 151 connected to the crystal piece substrate 1500 may show a far-off value. is there.
  If the measurement result of the monitor crystal piece 152 is far from the average detuning degree of the crystal piece 151, the optimum etching time cannot be calculated, so that the accuracy of the detuning degree adjustment becomes very poor and the reliability becomes low. Further, in the worst case, the etching is excessively necessary, and all of the remaining crystal pieces 151 connected to the crystal piece substrate 1500 may be defective.
  The electrode 215 formed on the monitor crystal piece 152 is formed after being broken off from the crystal piece substrate 1500, whereas the electrode 210 formed on the crystal piece 101 in the final step is formed on the crystal piece substrate 1500. Since they are formed in a connected state, the electrode 215 and the electrode 210 are not necessarily formed at the same position in the same shape. Depending on the formation state of the electrode 210, the degree of detuning may deviate from the design value.
  Further, when the gyro sensor element 30 is downsized and the monitor crystal piece 152 becomes very small, it is very difficult to form an electrode on the broken monitor crystal piece 152 and is not suitable for downsizing.
  An object of the present invention is to provide a method for manufacturing a highly accurate and small gyro sensor element, and further to provide a method for manufacturing a gyro sensor element that is less prone to defects and has high productivity and excellent reliability. There is.
In order to solve the above problems, in the method for manufacturing a gyro sensor element of the present invention, an electrode for inputting / outputting an electric signal, a driving vibration leg that vibrates by the input of the electric signal from the electrode, and a Coriolis force generated by a rotational motion. A gyro sensor element comprising a crystal piece having a detection vibration leg for detecting
A mask layer patterning step for forming a mask layer of a desired shape on a quartz wafer;
A crystal piece substrate forming step of etching a crystal wafer on which a mask layer is formed and forming a crystal piece substrate in which a plurality of crystal pieces are connected, and
A vibration measurement electrode forming step of forming vibration measurement electrodes on a plurality of crystal pieces connected to the crystal piece substrate;
A vibration measurement step of exciting a crystal piece connected to the crystal piece substrate and forming a vibration measurement electrode, and measuring a driving vibration frequency and a detected vibration frequency of the crystal piece connected to the crystal piece substrate;
A vibration measurement electrode peeling step for removing the vibration measurement electrode from the crystal piece connected to the crystal piece substrate;
An additional etching step of etching a crystal piece substrate provided with a crystal piece from which the electrode for vibration measurement is peeled off by wet etching;
After the additional etching step, an electrode forming step of forming the electrode on a plurality of crystal pieces connected to the crystal piece substrate;
A crystal piece separation step for separating the crystal piece on which the electrode is formed from the crystal piece substrate.
  Further, it is desirable that the vibration measurement electrode and the electrode are formed in alignment with an alignment mark provided on the quartz piece substrate.
  Further, in the vibration measurement electrode forming step, it is desirable to process the conductive mask layer into a predetermined shape to form the vibration measurement electrode.
(Function)
In the above-mentioned means of the present invention, first, a mask layer formed on a quartz wafer is used as an etching protective film, and a crystal piece is formed on a quartz piece substrate by etching an exposed portion not covered by the mask layer of the quartz wafer. To do. The etching method can be finely processed with high accuracy compared to the cutting method or the like, and is suitable for downsizing. Furthermore, since a large number of crystal pieces can be formed simultaneously, the productivity is excellent.
  In addition, since a plurality of crystal pieces are connected to a single crystal piece substrate, it is possible to perform a vibration measurement electrode and an electrode forming process for each crystal piece substrate. As a result, the vibration measurement electrodes and electrodes can be simultaneously formed on a large number of crystal pieces at the same time, which is excellent in productivity. Further, even if the gyro sensor element is downsized and the size of the crystal piece is reduced, the work can be performed with the size of the crystal piece substrate.
  Further, in the present invention, the drive vibration frequency and the detected vibration frequency of the crystal piece on which the vibration measurement electrode is formed are measured while being connected to the crystal piece substrate. Since vibration measurement is performed without breaking off the quartz piece substrate, the quartz piece is not wasted and the production efficiency can be increased.
  Furthermore, since the crystal piece is not broken and wasted, it is possible to measure many crystal pieces from one crystal piece substrate. For example, vibration measurement of all crystal pieces may be performed. As a result, the number of measurements can be increased, so that the average driving vibration frequency and the detection vibration frequency of all the crystal pieces in the crystal piece substrate and the average detuning degree that is the difference between them can be accurately predicted. can do.
  As a result, it is possible to accurately calculate the additional etching time required to adjust the detuning degree (the difference between the drive vibration frequency and the detected vibration frequency) as optimally designed, and within the crystal piece substrate after the additional etching process. Most crystal pieces can be adjusted to the degree of detuning close to the design. For the above reasons, the present invention can achieve both high reliability and high productivity.
  Further, in the present invention, the quartz piece is separated from the quartz piece substrate in the last step, and the gyro sensor element is completed. For this reason, almost all the steps can be carried out in the size of the quartz piece substrate, so that workability is good and it is suitable for miniaturization.
  Since the additional etching step in the manufacturing method of the present invention is performed after the vibration measuring electrode peeling step, it is performed in a state where the entire surface of the crystal piece is exposed. Therefore, each vibrating leg of the crystal piece is etched in all directions of the width direction, the length direction, and the thickness direction, but the etching rate is not constant depending on the direction of the crystal plane of the crystal. In general, when a Z-cut quartz wafer is used, etching proceeds faster in the thickness direction than in the width direction and the length direction.
  In the present invention, by utilizing the crystal etching characteristics in which etching proceeds rapidly in the thickness direction, a difference occurs between the change amount of the drive vibration frequency and the change amount of the detection vibration frequency. The degree of detuning, which is the difference, can be changed by an additional etching process.
  Further, the manufacturing method of the present invention includes a step of forming a vibration measurement electrode on a quartz piece substrate and a step of forming an electrode. However, it is preferable to form the vibration measurement electrode and the electrode at the same position as much as possible. Adjustment reliability increases. This is because the vibration characteristics slightly differ depending on the electrode positional relationship. Therefore, in the present invention, an alignment mark is formed in advance on the quartz piece substrate, and the vibration measurement electrode and the electrode are formed in alignment with the alignment mark. Since the position of the alignment mark does not change before and after the additional etching step, the vibration measurement electrode and the electrode can be formed at the same position.
  In the present invention, the vibration measurement electrode can be formed by forming the mask layer from a conductive material and processing the mask layer into a desired shape. By doing so, the labor of newly forming a conductive film for the formation of the vibration measurement electrode can be saved, and the productivity is further improved.
  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the gyro sensor element excellent in production efficiency and high productivity can be provided. Furthermore, it is possible to provide a method for manufacturing a gyro sensor element suitable for miniaturization. Furthermore, it is possible to provide a method for manufacturing a gyro sensor element having high sensitivity and excellent reliability.
(First embodiment)
FIG. 9 is a diagram showing the configuration and vibration operation of the gyro sensor element of the present invention. The gyro sensor element 10 of the present invention shown in FIG. 9 is composed of a crystal piece 100 made of crystal, which is a material having excellent temperature characteristics, and an electrode 200 formed on the crystal piece 100 and for inputting and outputting electric signals. Yes.
  The crystal piece 100 used in the gyro sensor element 10 of the present invention includes two drive vibration legs 111 having the same shape and one detection vibration leg 112 having a leg width narrower than that of the drive vibration leg 111. It has a protruding fork shape.
  The gyro sensor element 10 having such a configuration detects the angular velocity ω as described below. First, the two drive vibration legs 111 are excited to vibrate the two drive vibration legs 111 in the horizontal direction (drive vibration fd). In the non-rotating state, as shown in FIG. 9A, the two drive vibration legs 111 vibrate, but the remaining one detection vibration leg 112 does not vibrate.
  When the rotation state is applied and the angular velocity ω is applied, as shown in FIG. 9B, the Coriolis force acts on the vibrating drive vibration leg 111, and the vibration (detection vibration fs) starts in the opposite direction to each other. . At this time, the detection vibration leg 112 is designed to vibrate in resonance with the vertical vibration (detection vibration fs). As a result, the detection vibration leg 112 vibrates (detection vibration fs) only in the rotating state. To do. In the gyro sensor 10 of the present invention, the angular velocity ω is recognized by electrically outputting the detection vibration fs of the detection vibration leg 112.
  In the gyro sensor element 10 that performs such a vibration operation, the sensitivity increases as the resonance frequency of the drive vibration fd (drive vibration frequency fd1) and the resonance frequency of the detection vibration fs (detection vibration frequency fs1) are closer, but if it is too close It becomes more susceptible to disturbances and becomes less reliable.
  Therefore, in order to achieve both high sensitivity and high reliability, the gyro sensor element 10 of the present invention is made by separating the drive vibration frequency fd1 and the detection vibration frequency fs1 within an optimum range based on experiments. In the gyro sensor element 10, the difference between the drive vibration frequency fd1 and the detected vibration frequency fs1 is referred to as a detuning degree Δf.
  In the present embodiment, in order to form the gyro sensor element 10 having high sensitivity and high reliability, the degree of detuning Δf is set in a range of about 300 to 500 Hz, and the drive vibrating leg 111 is set to have this degree of detuning Δf. Designed to be 0.15 mm wide x 0.16 mm thick x 2.3 mm long, and the shape of the detection vibration leg 112 is 0.05 mm wide x 0.16 mm thick x 2.4 mm long. It was.
    FIG. 1 is a view showing a method for manufacturing a gyro sensor element of the present invention. A method for manufacturing the gyro sensor element 10 of the present invention will be described below. First, as shown in FIG. 1A, a mask layer 400 having a desired external shape of a crystal piece 100 is formed on a plane of a crystal wafer 1000 having a plate thickness of 160 μm. In the manufacturing method of the present invention, this step is referred to as a mask layer patterning step.
  FIG. 2 is a view showing a state after the mask layer patterning step in the method for manufacturing a gyro sensor element of the present invention. As shown in FIG. 2, a mask layer 400 having a plurality of crystal piece patterns 410, a frame pattern 420 to which the crystal piece patterns are connected, and an alignment mark 2100 is formed on the front and back surfaces of the crystal wafer 1000 (see FIG. 2). In FIG. 2, the mask layer 400 on the back side is not visible.)
  In the present embodiment, a chromium (Cr) film is formed on the crystal wafer 1000 using a sputtering method, which is one of vacuum film forming methods, and a gold (Au) film is further formed on the Cr film. Thereafter, a mask layer 400 was formed by a photolithography method. Photolithographic methods are generally widely used in the LSI field, and it is generally known that patterning can be performed with very high precision of micron or less, and is suitable for miniaturization.
  Next, as shown in FIG. 1B, the quartz wafer 1000 is processed by an etching method using the mask layer 400 as a mask, and then the mask layer 400 is removed as shown in FIG. 1C. Thus, the crystal piece 150 of the two drive vibration legs 113 and the one detection vibration leg 114 is completed.
  The etching method used in this step is a processing method that can be finely processed with high accuracy compared to a cutting method or the like, and a very small crystal piece 150 can be formed. Therefore, the gyro sensor element 10 is very suitable for downsizing. In the manufacturing method of the present invention, the process from FIG. 1B to FIG. 1C is referred to as a quartz piece substrate forming process.
  FIG. 3 is a view showing a state after the crystal piece substrate forming step in the method for manufacturing a gyro sensor element of the present invention. FIG. 1C partially shows only one of a plurality of crystal pieces 150 formed by etching a single crystal wafer 1000, and as a whole, as shown in FIG. In addition, a single crystal piece substrate 1500 in which a plurality of crystal pieces 150 are connected by a frame portion 1550 is formed.
  In this way, since a plurality of crystal pieces 150 can be simultaneously formed, it can be said that this process is excellent in productivity. In this step, the alignment mark 2100 formed on the mask layer 400 is also transferred, and the alignment mark 2000 engraved on the quartz piece substrate 1500 is formed at the same position.
  In this embodiment, a quartz wafer 1000 having a plate thickness of 160 μm is subjected to a wet etching process for 4 hours with buffered hydrofluoric acid (BHF) at 70 ° C., and then the mask layer 400 with an etching solution of Au and an etching solution of Cr. Was removed to form a quartz piece substrate 1500 in which a plurality of quartz pieces 150 were connected.
  In this embodiment, the crystal piece substrate 1500 is formed by the wet etching method. However, it is possible to form the crystal piece substrate 1500 in the same manner by the dry etching method. In the quartz crystal substrate forming step in the manufacturing method of the present invention, even if the wet etching method is used, there is no problem using the dry etching method.
  Next, as shown in FIG. 1D, the vibration measurement electrode 300 is formed on the crystal piece 150. In the present invention, this step is referred to as a vibration measurement electrode forming step. Further, by applying an electric field to the crystal piece 150 through the vibration measurement electrode 300, the drive vibration leg 113 and the detection vibration leg 114 are vibrated, and the drive vibration frequency fd2 and the detection vibration frequency fs2 of the drive vibration leg 113 are measured. In the present invention, this process is referred to as a vibration measurement process.
  FIG. 4 is a view showing a state after the vibration measurement electrode forming step in the method for manufacturing a gyro sensor element of the present invention. In the vibration measurement electrode forming step of the present invention, as shown in FIG. 4, the vibration measurement electrode 300 is formed on a crystal piece substrate 1500 in which a plurality of crystal pieces 150 are connected via a frame portion 1550.
  The formation process of the vibration measurement electrode 300 can be processed for each crystal piece substrate 1500, and the vibration measurement electrodes 300 can be simultaneously formed on a large number of crystal pieces 150, so that the productivity is very good. . Even if the gyro sensor element 10 is downsized and the size of the crystal piece 150 is reduced, the work can be performed with the size of the crystal piece substrate 1500, so that the workability is good and the size is reduced.
  The vibration measurement electrode 300 is accurately formed at a predetermined position of the crystal piece 150 by aligning and forming the vibration measurement electrode 300 with the alignment mark 2000 formed on the crystal piece substrate 1500 as a guide. can do.
  Furthermore, the vibration measurement process of the present invention is also characterized in that the drive vibration frequency fd2 and the detected vibration frequency fs2 of the crystal piece 150 are measured while being connected to the crystal piece substrate 1500 shown in FIG. Since vibration measurement is performed without breaking the crystal piece substrate 1500, it is not necessary to waste the crystal piece 150 measured as in the conventional manufacturing method (the monitor crystal piece 152 in the conventional manufacturing method), thereby improving the production efficiency. Can be high.
  Further, since the crystal piece 150 is not broken and discarded, many crystal pieces 150 can be measured from one crystal piece substrate 1500. For example, it is possible to perform vibration measurement on all the crystal pieces 150 connected to the crystal piece substrate 1500. Since the number of measurements can be increased in this way, the average drive vibration frequency fd2 and the detected vibration frequency fs2 of all the crystal pieces 150 in the crystal piece substrate 1500 can be predicted with high accuracy.
  In this embodiment, a vibration measurement electrode 300 is formed by patterning a laminated film made of a Cr film having a lower layer of 0.03 μm thickness and an Au film having an upper layer of 0.15 μm thickness on a quartz piece substrate 1500 by a photolithography method. did. Then, a voltage is applied to the vibration measuring electrode 300 from the outside, the driving vibration frequency fd2 and the detected vibration frequency fs2 of each crystal piece 150 are measured, and before adjustment, which is the difference between the driving vibration frequency fd2 and the detected vibration frequency fs2. The degree of detuning Δf2 was examined. As a result, in this embodiment, the pre-adjustment detuning degree Δf2 of each crystal piece 150 in the crystal piece substrate 1500 was in the range of 400 Hz to 600 Hz.
  Next, as shown in FIG. 1E, after removing the vibration measurement electrode 300, the crystal piece 150 is wet-etched, and the difference between the drive vibration frequency fd1 of the drive vibration leg 111 and the detected vibration frequency fs1, that is, Adjustment is performed so that the post-adjustment degree of detuning Δf1 is in an optimum range, for example, about 300 to 500 Hz in the present embodiment. This adjustment step is referred to as an additional etching step in the present invention.
  Since the additional etching process is performed after the vibration measuring electrode 300 is removed, the additional etching process is performed with the entire surface of the crystal piece 150 exposed. Therefore, each vibration leg (the drive vibration leg 113 and the detection vibration leg 114) of the crystal piece 150 is etched in all directions of the width direction, the length direction, and the thickness direction. However, when the quartz is wet etched, the etching rate is not constant due to the influence of the crystal plane. In general, when a Z-cut quartz wafer is used, it is known that etching proceeds faster in the thickness direction than in the width direction and the length direction.
  When etching progresses rapidly in the thickness direction due to the crystal etching characteristics, the detected vibration frequency fs2 changes greatly, and the drive vibration frequency fd2 does not change so much. As a result, a difference occurs between the amount of change in the drive vibration frequency fd2 and the amount of change in the detected vibration frequency fs2, and the degree of detuning Δf changes greatly.
  The adjustment of the degree of detuning Δf in this additional etching step is performed by adjusting the degree of detuning before adjustment Δf2 (= driving vibration frequency fd2−detected vibration frequency fs2) of the crystal piece 150 and the desired degree of detuning Δf1 (= driving vibration). The wet etching time is calculated from the difference between the frequency fd1 and the detection vibration frequency fs1), and the quartz piece substrate 1500 is etched by the calculated wet etching time.
  Therefore, the higher the measurement accuracy of the pre-adjustment detuning degree Δf2 obtained by measurement in advance, the higher the accuracy of adjustment to the post-adjustment detuning degree Δf1 as designed. In the present invention, since the number of measurements can be increased in the vibration measurement process as described above, the measurement accuracy of the pre-adjustment detuning degree Δf2 can be increased, and as a result, the vibration frequency can be adjusted with very high accuracy. it can.
  FIG. 5 is a view showing a state after the additional etching step in the method for manufacturing the gyro sensor element of the present invention. If the number of measurements is increased in the previous vibration measurement step, the average pre-adjustment detuning degree Δf2 of all the crystal pieces 150 in the crystal piece substrate 1500 can be accurately predicted.
  If the wet etching time calculated based on this average pre-adjustment detuning degree Δf2 is used, almost all of the crystal pieces 100 connected to the crystal piece substrate 1500 are driven vibration legs 111 having the adjusted detuning degree Δf1 as designed. And the detection vibration leg 112. As a result, adjustment failures in one quartz piece substrate 1500 can be reduced, and productivity is remarkably improved.
  In this embodiment, the pre-adjustment detuning degree Δf2 of the crystal piece 150 measured in the vibration measurement process was about 400 Hz to 600 Hz, and thus was about 100 Hz larger than the desired post-adjustment detuning degree Δf1 (300 to 500 Hz). Therefore, an additional etching process was performed for several minutes with 50 ° C. buffered hydrofluoric acid (BHF).
Thereafter, as shown in FIG. 1 (f), an electrode 200 is formed on the newly formed crystal piece 100 (referred to as an electrode forming step), and again the drive vibration frequency fd1 and the detected vibration of the drive vibration leg 111 are detected. The frequency fs1 is measured, and it is confirmed that the frequency is adjusted to the desired post-adjustment detuning degree Δf1. In addition, when adjustment is insufficient at this time, it is also possible to peel the electrode 200 again and to perform an additional etching process.
  In the present invention, it is not necessary to fold the crystal piece 100 as in the conventional manufacturing method, so that the additional etching process can be performed any number of times without wasting the crystal piece 100.
  FIG. 6 is a view showing a state after the electrode forming step in the method for manufacturing a gyro sensor element of the present invention. In the electrode forming process of the present invention, as shown in FIG. 6, the electrode 200 is formed on a crystal piece substrate 1500 to which a plurality of crystal pieces 100 are connected. Since the formation process of the electrode 200 can be processed for each crystal piece substrate 1500 and the electrodes 200 can be formed on a large number of crystal pieces 100 at the same time, the productivity is very good.
  Further, even if the gyro sensor element 10 is downsized and the crystal piece 100 is reduced in size, the work can be performed with the size of the crystal piece substrate 1500, so that the workability is good and suitable for downsizing. Note that the electrode 200 can be accurately formed at a predetermined position of the crystal piece 100 by aligning and forming the electrode 200 with the alignment mark 2000 formed on the crystal piece substrate 1500 as a guide.
  Further, by using the same alignment mark 2000 in the vibration measurement electrode formation step and the electrode formation step, the vibration measurement electrode 300 and the electrode 200 can be formed at substantially the same position. Therefore, the reliability of the detuning adjustment can be improved.
  In this embodiment, a laminated film made of a Cr film having a lower layer of 0.03 μm thickness and an Au film having an upper layer of 0.15 μm thickness is formed on a quartz piece substrate 1500 by a sputtering method, and then patterned by a photolithography method. Thus, the electrode 200 was formed.
  Then, when an external voltage is applied to the electrode 200 and the driving vibration frequency fd1 and the detection vibration frequency fs1 of each crystal piece 100 are measured, the adjusted detuning degree, which is the difference between the driving vibration frequency fd1 and the detection vibration frequency fs1. Δf1 was in the range of 400 Hz to 600 Hz as designed. As described above, the degree of detuning Δf could be adjusted within a desired optimum range.
  Finally, as shown in FIG. 7, the quartz piece 100 on which the electrode 200 is formed is divided from the quartz piece substrate 1500, and the gyro sensor element 10 is completed. This step is referred to as a crystal piece separation step. Note that any method may be used as the dividing method, but in this embodiment, the crystal piece 100 is divided by a laser processing method.
  Even in the case where the crystal piece separation step is performed by the laser processing method, if the alignment mark 2000 formed on the crystal piece substrate 1500 is used as a guide, the laser can be accurately irradiated to a predetermined position, and the break-off position can be determined. Defects can be reduced as much as possible.
  As described above, in the present embodiment, the small gyro sensor element 10 having high accuracy and high reliability can be manufactured. Further, when the gyro sensor element 10 is manufactured, a large amount of gyro sensor elements 10 can be produced at one time, and the occurrence of defects can be reduced, so that productivity can be greatly improved.
(Second Embodiment)
FIG. 8 shows a method for manufacturing a gyro sensor element using the mask layer of the present invention as an electrode for vibration measurement. This embodiment is an example in which a conductive mask layer 400 is used and the mask layer 400 is also used as the vibration measurement electrode 350.
  The manufacturing method will be described below. First, as shown in FIG. 8A, a conductive mask layer 400 having a desired external shape of the crystal piece 100 is formed on the plane of the crystal wafer 1000 (mask layer forming step). Further, a resist pattern 500 is formed on the mask layer 400 in the shape of the vibration measurement electrode 350.
  In this embodiment, a 0.03 μm-thick chromium (Cr) film and then a 0.15 μm-thick gold (Au) film are formed on a quartz wafer 1000 having a plate thickness of 160 μm by sputtering, A mask layer 400 was formed by a lithography method. Further, a photosensitive resist was applied on the mask layer 400, and a resist pattern 500 was formed by photolithography.
  Next, as shown in FIG. 8B, the crystal wafer 1000 is processed by an etching method using the mask layer 400 as a mask to form a crystal piece 150 (crystal piece forming step).
  In this embodiment, a quartz wafer 1000 having a plate thickness of 160 μm is subjected to a wet etching process for 4 hours with buffered hydrofluoric acid (BHF) at 70 ° C. to form a quartz piece substrate 1500 in which a plurality of quartz pieces 150 are connected. . At this time, since the resist pattern 500 has corrosion resistance against buffered hydrofluoric acid (BHF), an etching solution of Au, and an etching solution of Cr, the shape was not broken.
  Next, in the present embodiment, as shown in FIG. 8C, the mask layer 400 is patterned by an etching method using the resist pattern 500 as a mask to form a vibration measurement electrode 350 (vibration measurement electrode formation). Process). Thereafter, the resist pattern 500 is removed to expose the vibration measurement electrode 350, and a current is passed through the vibration measurement electrode 350 to vibrate the drive vibration legs 113 and the detection vibration legs 114 of the crystal piece 150, thereby driving vibration legs 113. Drive vibration frequency fd2 and detected vibration frequency fs2 are measured (vibration measurement step).
  As described above, in the vibration measurement electrode forming step of the present embodiment, it is possible to save the trouble of newly forming a conductive film for forming the vibration measurement electrode. Therefore, productivity can be further improved.
  Next, as shown in FIG. 8D, after removing the vibration measurement electrode 350, the crystal piece 150 is wet-etched to form the crystal piece 100 having the drive vibration leg 111 and the detection vibration leg 112 (additional). Etching process). The wet etching processing time at this time is the pre-adjustment detuning degree Δf2 (difference between the drive vibration frequency fd2 and the detected vibration frequency fs2) obtained in the vibration measurement step, and the desired post-adjustment detuning degree Δf1 (drive vibration frequency fd1). And the detected vibration frequency fs1).
In the present embodiment, the pre-adjustment detuning degree Δf2 of the crystal piece 150 measured in the vibration measurement process is about 400 Hz to 600 Hz. Since the desired post-adjustment detuning degree Δf1 (300 to 500 Hz) was about 100 Hz larger, additional etching treatment was performed for several minutes with 50 ° C. buffered hydrofluoric acid (BHF).
  Thereafter, as shown in FIG. 8E, the electrode 200 is formed on the newly formed crystal piece 100 (electrode forming step), and the drive vibration frequency fd1 and the detection vibration frequency fs1 of the drive vibration leg 111 are again set. Measure and confirm that it is adjusted to the desired post-adjustment detuning degree Δf1.
In this embodiment, the lower layer is a Cr film having a thickness of 0.03 μm on the crystal piece 100 and the upper layer is 0.15.
A laminated film made of a Au film having a thickness of μm was formed by a sputtering method, and then patterned by a photolithography method to form the electrode 200.
  Then, when an external voltage is applied to the electrode 200 and the driving vibration frequency fd1 and the detection vibration frequency fs1 of each crystal piece 100 are measured, the adjusted detuning degree, which is the difference between the driving vibration frequency fd1 and the detection vibration frequency fs1. Δf1 was in the range of 400 Hz to 600 Hz as designed. As described above, the degree of detuning Δf can be adjusted within the optimum range in design.
    Finally, as shown in FIG. 7, the crystal piece 100 on which the electrode 200 is formed is divided from the crystal piece substrate 1500 to complete the gyro sensor element 10 (crystal piece separation step).
It is the figure which showed the manufacturing method of the gyro sensor element of this invention. It is the figure which showed the state after the mask layer patterning process in the manufacturing method of the gyro sensor element of this invention. It is the figure which showed the state after the crystal piece board | substrate formation process in the manufacturing method of the gyro sensor element of this invention. It is the figure which showed the state after the electrode formation process for vibration measurement in the manufacturing method of the gyro sensor element of this invention. It is the figure which showed the state after the additional etching process in the manufacturing method of the gyro sensor element of this invention. It is the figure which showed the state after the electrode formation process in the manufacturing method of the gyro sensor element of this invention. It is the figure which showed the crystal piece separation process in the manufacturing method of the gyro sensor element of this invention. It is the figure which showed the manufacturing method of the gyro sensor element which uses the mask layer of this invention as the electrode for a vibration measurement. It is the figure which showed the structure and vibration operation | movement of the gyro sensor element of this invention. It is the figure which showed the structure of the conventional gyro sensor element which has four drive vibration legs and two detection vibration legs. It is the figure which showed typically the vibration operation | movement of the gyro sensor element which has the conventional four drive vibration legs and two detection vibration legs. It is the figure which showed the structure and vibration operation | movement of the gyro sensor element which has a pair of conventional vibration leg. It is the figure which showed the manufacturing method of the gyro sensor element which has a conventional pair of vibration leg. It is the figure which showed the state which broke off the monitor crystal piece from the crystal piece substrate formed with the manufacturing method of the gyro sensor element which has a conventional pair of vibration leg. It is the figure which showed the structure and state at the time of vibration measurement of the monitor crystal piece used for the manufacturing method of the conventional gyro sensor element.
Explanation of symbols
10, 20, 30 Gyro sensor element 100, 101, 105, 150, 151 Crystal piece 110 Vibration leg 111, 113, 115 Drive vibration leg 112, 114, 116 Detection vibration leg 120 Base 125 Connecting leg 152 Monitor crystal piece 200, 205 , 210, 215 Electrode 300, 350 Vibration measurement electrode 400 Mask layer 410 Crystal piece pattern 420 Frame pattern 500 Resist pattern 600 Weight portion 1000 Crystal wafer 1500 Crystal piece substrate 1550 Frame portion 2000, 2100 Alignment mark

Claims (3)

  1. A method for manufacturing a gyro sensor element, comprising: an electrode for inputting / outputting an electric signal; a driving vibration leg that vibrates by the input of the electric signal from the electrode; and a crystal piece having a detection vibration leg that detects a Coriolis force generated by a rotational motion. Because
    A mask layer patterning step for forming a mask layer of a desired shape on a quartz wafer;
    A crystal wafer substrate forming step of etching the crystal wafer on which the mask layer is formed and forming a crystal wafer substrate in which a plurality of crystal chips are connected, and
    A vibration measurement electrode forming step of forming a vibration measurement electrode on the plurality of crystal pieces;
    A vibration measuring step of exciting the crystal piece on which the electrode for vibration measurement is formed, and measuring a driving vibration frequency and a detected vibration frequency of the crystal piece;
    A vibration measurement electrode peeling step for removing the vibration measurement electrode from the crystal piece;
    An additional etching step of etching the quartz crystal substrate, which is provided by connecting the quartz crystal strips from which the electrodes for vibration measurement are connected, by a wet etching method;
    After this additional etching step, an electrode forming step of forming the electrodes on a plurality of crystal pieces connected to the crystal piece substrate;
    A quartz piece separating step of separating the quartz piece on which the electrode is formed from the quartz piece substrate;
    A method for manufacturing a gyro sensor element, comprising:
  2. 2. The method for manufacturing a gyro sensor element according to claim 1, wherein the vibration measuring electrode and the electrode are formed by being aligned with an alignment mark provided on the quartz piece substrate.
  3. The mask layer is formed of a conductive material having conductivity, and the vibration measurement electrode is formed by processing the mask layer having conductivity into a predetermined shape in the vibration measurement electrode formation step. A method for manufacturing a gyro sensor element according to claim 1 or 2.
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