JP2018157469A - Frequency adjustment method of piezoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frequency adjustment method of a piezoelectric transducer in which a difference of a prediction processing rate and an actual measurement rate.SOLUTION: A frequency adjustment method of a piezoelectric transducer, comprises: a first frequency adjustment step of adjusting a frequency of the piezoelectric transducer by removing a frequency adjustment film by a constant amount on the basis of a first prediction processing rate; and a second frequency adjustment step of adjusting the frequency of the piezoelectric transducer by removing the frequency adjustment film by the constant amount on the basis of a second prediction processing rate after the first frequency adjustment step. When the second prediction processing rate in the second frequency adjustment step is YR2, an average value of an actual measurement processing rate in the second frequency adjustment step executed in the past is AR2, the actual measurement processing rate in the first frequency adjustment step executed just before this is R1, and the average value of the actual measurement processing rate in the first frequency adjustment step executed in the past is AR1, the following equation is satisfied: YR2=AR2×A^(In the equation A=R1/AR1).SELECTED DRAWING: Figure 7

Description

  The present invention relates to a frequency adjusting method for a piezoelectric vibrator.

  Conventionally, as a frequency adjustment method for a piezoelectric vibrator, a frequency adjustment metal film (frequency adjustment film) made of Au or the like previously attached to the surface of the piezoelectric vibrator is fixed by a laser or a particle beam (ion beam or the like). A method of adjusting the frequency is taken by removing the amount (etching) and reducing the mass of the deposited metal film.

  As one of such methods, before scraping the metal film for frequency adjustment, the speed (etching rate) at which the metal film is scraped is predicted in advance, and the piezoelectric vibrator is based on the predicted etching rate. A technique called a predictive processing method is generally known in which a metal film is irradiated with a laser or particle beam for a certain period of time until the desired frequency reaches the target frequency. (For example, see Patent Document 1)

  In the predictive machining method, normally, in order to adjust the frequency of one piezoelectric vibrator, laser and particle beam irradiation is performed in multiple steps in stages, and the frequency is gradually driven to a target value. Specifically, it is as follows, for example.

  FIG. 1 is a conceptual diagram showing a general system of a predictive machining method, FIG. 2 is a diagram showing a relationship between a predicted machining rate and an actual machining rate in a conventional predictive machining method, and FIG. 3 is a piezoelectric wafer on which a plurality of piezoelectric vibrators are formed. 4 is a top view showing the piezoelectric vibrator, FIG. 5 is a cross-sectional view of the portion where the metal film for frequency adjustment is formed, and FIG. 6 is a state in which a mask is arranged on the metal film for frequency adjustment FIG. A plurality of piezoelectric vibrators 2 are formed in the piezoelectric material wafer 1, and a Cr film 5 as a metal film 3 for frequency adjustment is formed on the surface of a piezoelectric vibrating piece 6 that is a base material of each piezoelectric vibrator 2. A laminated film of the Au film 4 is formed. When adjusting the frequency of the piezoelectric vibrator 2, a mask 7 having a circular opening is placed on the metal film 3, and an ion beam is irradiated from above the mask 7 for a predetermined time, thereby opening the mask 7. A part of the metal film 3 exposed through the part is removed (etched). The ion beam irradiation is performed in three times for one region, and in the first (Step. 1) and second (Step. 2) irradiation, the upper Au film 4 is mainly removed and continues. In the third irradiation (Step 3), the lower Cr film 5 is mainly removed.

  The irradiation time of the ion beam is calculated based on the etching rate (predicted processing rate) of the metal film 3 predicted in advance, and the predicted processing rate is determined as follows.

  In the first frequency adjustment step (Step 1), the average value of the actually measured machining rates in the first frequency adjustment step performed in the past is determined as the predicted machining rate of the first frequency adjustment step. For example, as shown in FIG. 2, when the first frequency adjustment process is performed on the third piezoelectric vibrator (work No. 3), the first frequency adjustment process is performed before that. The average value (55 [ppm / sec] of the actually measured machining rate (50 [ppm / sec]) of the first piezoelectric vibrator and the second actually measured machining rate (60 [ppm / sec]) of the second piezoelectric vibrator. ]) Is calculated, and the average value is set as the predicted machining rate (predicted rate 1) in the first frequency adjustment step for the third piezoelectric vibrator.

  In the second frequency adjustment step (Step 2), the average value of the actually measured machining rates in the second frequency adjustment step performed in the past is determined as the predicted machining rate of the second frequency adjustment step. For example, as shown in FIG. 2, when the second frequency adjustment process is performed on the third piezoelectric vibrator (work No. 3), the second frequency adjustment process is performed before that. The measured machining rate (60 [ppm / sec]) of the first piezoelectric vibrator (work No. 1) and the measured machining rate (70 [ppm / sec] of the second piezoelectric vibrator (work No. 2)). sec]) average value (65 [ppm / sec]) is calculated, and the average value is set as the predicted processing rate (predicted rate 2) in the second frequency adjustment step for the third piezoelectric vibrator.

  In the third frequency adjustment step (Step 3), the value of the actually measured machining rate in the second frequency adjustment step performed immediately before is determined as it is as the predicted machining rate of the third frequency adjustment step. For example, as shown in FIG. 2, when the third frequency adjustment process is performed on the third piezoelectric vibrator (work No. 3), the third piezoelectric vibrator is immediately before the third piezoelectric vibrator. The measured machining rate (67 [ppm / sec]) in the second frequency adjustment step performed in the above is directly used as the predicted machining rate (predicted rate 3) in the third frequency adjustment step for the third piezoelectric vibrator.

JP 2006-86702 A

  In the related art described above, when etching the metal film 3 for frequency adjustment, the upper Au film 4 is first scraped, and then the lower Cr film 5 is traced. Since the etching rate is greatly different between the Au film and the Cr film (Cr has a higher etching rate), the etching rate is low in the second etching in which the vicinity of the interface between the Au film 4 and the Cr film 5 is etched. If the actual etching rate (actual processing rate) is high in the first etching, the actual processing rate tends to be high in the subsequent second etching. However, in the conventional method for calculating the predicted machining rate, such a tendency is not taken into account, and there is still a large error between the predicted machining rate and the measured machining rate, leaving room for improvement. Such a tendency is not limited to the case where the frequency adjustment film is composed of an Au film and a Cr film, but when the frequency adjustment film is composed of other materials and the lower layer has a higher etching rate than the upper layer. Is shown as well.

  The present invention has been made in view of the above problems, and an object thereof is to provide a frequency adjustment method for a piezoelectric vibrator in which an error between a predicted machining rate and an actually measured machining rate is small.

The piezoelectric vibration includes a lower layer and an upper layer formed on the surface of the piezoelectric vibrator, and the lower layer has a processing rate higher than that of the upper layer, and is removed stepwise from the upper layer in a plurality of steps. A method for adjusting a frequency of a piezoelectric vibrator for adjusting a frequency of a child, wherein the frequency of the piezoelectric vibrator is adjusted by removing a certain amount of the frequency adjustment film based on a first predicted processing rate. An adjustment step; and a second frequency adjustment step of adjusting the frequency of the piezoelectric vibrator by removing a certain amount of the frequency adjustment film based on a second predicted processing rate after the first frequency adjustment step. YR2 for the second predicted machining rate in the second frequency adjustment step, and the average value of the actually measured machining rate in the second frequency adjustment step performed in the past When R2 is R1, the measured machining rate in the first frequency adjustment process performed immediately before is R1, and the average value of the measured machining rate in the first frequency adjustment process performed in the past is AR1, the following equation holds. The frequency adjustment method of the piezoelectric vibrator is used.
YR2 = AR2 × A ^ ^A (where A = R1 / AR1)

  In the first frequency adjustment step, the frequency of the piezoelectric vibrator is adjusted by removing the frequency adjustment film only during the removal time of the frequency adjustment film calculated based on the first predicted processing rate. In the second frequency adjustment step, the frequency of the piezoelectric vibrator is removed by removing the frequency adjustment film only during the removal time of the frequency adjustment film calculated based on the second predicted processing rate. A frequency adjustment method of a piezoelectric vibrator that adjusts the frequency may be used.

  The first predicted machining rate may be a frequency adjustment method of a piezoelectric vibrator that is an average value of an actually measured machining rate in the first frequency adjustment step performed in the past.

  A third frequency adjusting step for adjusting the frequency of the piezoelectric vibrator by removing a predetermined amount of the frequency adjusting film based on a third predicted processing rate after the second frequency adjusting step; The third predicted machining rate may be the frequency adjustment method of the piezoelectric vibrator that is the same as the actually measured machining rate in the second frequency adjustment step performed immediately before.

  The lower layer may include a layer composed of Cr, and the upper layer may be a frequency adjustment method of a piezoelectric vibrator including a layer composed of Au.

  A frequency adjustment method for a piezoelectric vibrator in which the frequency adjustment film is removed by a laser or a particle beam may be used.

  According to the present invention, the predicted machining rate and the actual measurement at the second frequency adjustment are reflected in the formula for calculating the predicted machining rate at the second frequency adjustment by reflecting the value of the actual machining rate at the first frequency adjustment. Since the error from the processing rate is reduced, the accuracy of frequency adjustment can be improved.

Conceptual diagram showing the general system of predictive machining Diagram showing the relationship between the predicted machining rate and the actual machining rate in the conventional predictive machining method Top view showing a piezoelectric material wafer on which a plurality of piezoelectric vibrators are formed Top view showing a piezoelectric vibrator Sectional view of the part where the metal film for frequency adjustment is formed Top view showing a state in which a mask is placed on a metal film for frequency adjustment The figure which shows the relationship between the prediction processing rate and the measurement processing rate in the prediction processing system of this invention Conceptual diagram showing the situation where etching is performed by applying the calculated predicted processing rate in individual units Conceptual diagram showing the situation where etching is performed by applying the calculated predicted processing rate in units of rows Conceptual diagram showing the situation where etching is performed by applying the calculated predicted processing rate in wafer units

  FIG. 7 is a diagram showing the relationship between the predicted machining rate and the actual machining rate in the predictive machining method of the present invention, and FIG. 8 is a conceptual diagram showing a situation where etching is performed by applying the calculated predicted machining rate in individual units. In one embodiment of the present invention, for a plurality of piezoelectric vibrators 2 integrally formed in a piezoelectric material wafer 1, a metal film for frequency adjustment formed in advance on those vibrating parts (tips of tuning forks). The frequency is adjusted by etching 3. The metal film 3 for frequency adjustment is composed of a laminated film of a Cr film 5 and an Au film 4, and when adjusting the frequency, a mask 7 having a circular opening is disposed on the metal film 3. The Au film 4 and the Cr film 5 are sequentially etched by irradiating a laser beam or a particle beam (such as an ion beam) from above. In consideration of the difference in etching rate between the Cr film 5 and the Au film 4, the etching of the metal film 3 is divided into three steps (Steps 1 to 3) for each piezoelectric vibrator 2. Do. The configuration up to here is the same as that of the prior art.

  A feature of the present invention resides in a method of calculating a predicted processing rate when performing the second etching on the metal film 3 for frequency adjustment. Specifically, it is as follows.

  In the first frequency adjustment step (Step 1), the average value of the actually measured machining rates in the first frequency adjustment step performed in the past is used as the predicted machining rate in the first frequency adjustment step. For example, as shown in FIG. 7, when the first frequency adjustment process is performed on the third piezoelectric vibrator (work No. 3), the first frequency adjustment process is performed before that. The actually measured machining rate (50 [ppm / sec]) of the first piezoelectric vibrator (work No. 1) and the actually measured machining rate (60 [ppm / sec] of the second piezoelectric vibrator (work No. 2)). sec]) is calculated as an average value (55 [ppm / sec]), and the average value is set as a predicted processing rate (predicted rate 1) in the first frequency adjustment step for the third piezoelectric vibrator.

In the second frequency adjustment step (Step 2), the average value of the actually measured machining rate in the first frequency adjustment step performed in the past is AR1, and the value of the actually measured machining rate in the first frequency adjustment step performed immediately before is R1. The ratio is calculated as R1 / AR1 = A, and a value obtained by multiplying the average value (AR2) of the actually measured machining rate in the second frequency adjustment step performed in the past by the square of the ratio A (A ^ ^A ) ( AR2 × A ^ ^A ) is assumed to be a prediction rate (YR2) in the second frequency adjustment step (YR2 = AR2 * A ^ ^A ). For example, as shown in FIG. 7, when the second frequency adjustment process is performed on the third piezoelectric vibrator (work No. 3), R1 = 55 [ppm / sec], AR1 = ( 50 + 60) / 2 = 55 [ppm / sec], A = 1, A ^ ^A = 1, AR2 = (60 + 70) / 2 = 65 [ppm / sec], so that the predicted processing rate in the second frequency adjustment step (YR2) is 65 × 1 = 65 [ppm / sec] (predicted rate 2). When the second frequency adjustment process is performed on the second piezoelectric vibrator (work No. 2), R1 = 60 [ppm / sec], AR1 = 50 [ppm / sec], A ^{= 1.2, a ^ a ≒ 1.245} , AR2 = 60 because it is [ppm / sec], the prediction processing rate in the second frequency adjustment step (YR2) is, 60 × 1.245 = 74.7 [ ppm / sec] (predicted rate 2).

  In the third frequency adjustment step (Step 3), the value of the actually measured machining rate in the second frequency adjustment step performed immediately before is directly determined as the predicted machining rate in the third frequency adjustment step. For example, as shown in FIG. 7, when the third frequency adjustment process is performed on the third piezoelectric vibrator (work No. 3), the third piezoelectric vibrator is immediately before the third piezoelectric vibrator. The measured machining rate (67 [ppm / sec]) in the second frequency adjustment step performed in the above is directly used as the predicted machining rate (predicted rate 3) in the third frequency adjustment step for the third piezoelectric vibrator.

  Note that the method of calculating the predicted machining rate by the above process is preferably applied to all the piezoelectric vibrators subject to frequency adjustment, but may be applied to only some of the piezoelectric vibrators. Absent.

  The etching time in each step (frequency adjustment process) is obtained by dividing the adjustment amount (remaining amount) up to the target frequency determined for each step by the predicted processing rate calculated individually in each of the three times. . That is, when the predicted processing rate at the n-th etching is R, and the adjustment amount (remaining amount) up to the target frequency at the time of performing the n-1th etching is F, the n-th etching time is F It is represented by the formula / R. For example, as shown in FIG. 7, for the third piezoelectric vibrator (work No. 3), the remaining amount up to the target frequency immediately before the first frequency adjustment step (Step 1) is performed. If F1 [ppm], the etching time [sec] in the first frequency adjustment step is F1 [ppm] / 55 [ppm / sec], and immediately before the second frequency adjustment step (Step 2) is performed. If the remaining amount up to the target frequency in F2 is F2 [ppm], the etching time [sec] in the second frequency adjustment step is F2 [ppm] / 65 [ppm / sec], and the third frequency adjustment step ( If the remaining amount up to the target frequency immediately before performing Step 3) is F3 [ppm], the etching time [sec] in the third frequency adjustment step is F3 [ppm]. 67 the [ppm / sec].

  FIG. 9 is a conceptual diagram illustrating a situation in which etching is performed by applying the calculated predicted processing rate in units of rows, and FIG. 10 is a conceptual diagram illustrating a state in which etching is performed by applying the calculated predicted processing rate in units of wafers. In the above-described embodiment, as shown in FIG. 8, the frequency adjustment film is etched by applying a specific predicted processing rate for each piezoelectric vibrator. However, the number of piezoelectric vibrators to be etched at one time is limited. For example, as shown in FIG. 9, a plurality of piezoelectric vibrators are etched simultaneously by applying a specific predicted processing rate in units of rows and columns of piezoelectric vibrators arranged in a piezoelectric material wafer. As shown in FIG. 10, a specific predicted processing rate may be applied to each wafer as shown in FIG. 10, and a plurality of piezoelectric vibrators may be etched at the same time, according to the required frequency adjustment accuracy. The best method can be selected as appropriate.

  In the above embodiment, the frequency adjustment film is a metal film made of Cr and Au. However, for example, a metal film containing other materials or a film made of a material other than metal may be used. .

  The means for etching the frequency adjusting film is not limited to laser or particle beam (ion beam, electron beam, neutron beam, etc.), and other means can be used.

  In addition, the present invention is not limited to the case where the frequency adjustment film is composed of a laminated film in which films of different materials are laminated. For example, the frequency adjustment film is composed of a single layer film, and the upper layer and the lower layer are included in the film. The present invention can also be applied to a case where there is a difference in the etching rate (upper layer etching rate <lower layer etching rate).

  Further, the piezoelectric material constituting the piezoelectric vibrator is, for example, quartz, but other materials may be used.

  Moreover, in the above-mentioned embodiment, although the average value of the actually measured machining rate in the first frequency adjustment step performed in the past is used as the predicted machining rate in the first frequency adjustment step, other values are used as the first frequency adjustment. It is also possible to use the predicted processing rate in the process.

  Moreover, in the above-mentioned embodiment, although the 3rd frequency adjustment process is implemented after the 2nd frequency adjustment process, it is also possible to abbreviate | omit the 3rd frequency adjustment process.

DESCRIPTION OF SYMBOLS 1 Piezoelectric material wafer 2 Piezoelectric vibrator 3 Metal film for frequency adjustment 4 Au film 5 Cr film 6 Piezoelectric vibrating piece 7 Mask

Claims (6)

The piezoelectric vibration includes a lower layer and an upper layer formed on the surface of the piezoelectric vibrator, and the lower layer has a processing rate higher than that of the upper layer, and is removed stepwise from the upper layer in a plurality of steps. A frequency adjustment method for a piezoelectric vibrator that adjusts the frequency of a child,
A first frequency adjusting step of adjusting the frequency of the piezoelectric vibrator by removing a certain amount of the frequency adjusting film based on a first predicted processing rate;
After the first frequency adjustment step, a second frequency adjustment step of adjusting the frequency of the piezoelectric vibrator by removing a certain amount of the frequency adjustment film based on a second predicted processing rate,
The second predicted machining rate in the second frequency adjustment step is YR2, the average value of the actually measured machining rates in the second frequency adjustment step performed in the past is AR2, and the first frequency adjustment step performed immediately before. A frequency adjustment method for a piezoelectric vibrator, wherein the following equation is established, where R1 is an actually measured machining rate and AR1 is an average value of the actually measured machining rates in the first frequency adjustment step performed in the past.

YR2 = AR2 × A ^ ^A (where A = R1 / AR1)
  In the first frequency adjustment step, the frequency of the piezoelectric vibrator is adjusted by removing the frequency adjustment film only during the removal time of the frequency adjustment film calculated based on the first predicted processing rate. In the second frequency adjustment step, the frequency of the piezoelectric vibrator is removed by removing the frequency adjustment film only during the removal time of the frequency adjustment film calculated based on the second predicted processing rate. The method of adjusting the frequency of the piezoelectric vibrator according to claim 1, wherein the frequency is adjusted.   3. The frequency adjustment method for a piezoelectric vibrator according to claim 1, wherein the first predicted machining rate is an average value of actually measured machining rates in the first frequency adjustment step performed in the past.   A third frequency adjusting step for adjusting the frequency of the piezoelectric vibrator by removing a predetermined amount of the frequency adjusting film based on a third predicted processing rate after the second frequency adjusting step; 3. The frequency adjustment of the piezoelectric vibrator according to claim 1, wherein the third predicted machining rate is the same as the actually measured machining rate in the second frequency adjustment step performed immediately before. Method.   5. The frequency adjustment method for a piezoelectric vibrator according to claim 1, wherein the lower layer includes a layer composed of Cr, and the upper layer includes a layer composed of Au. .   The frequency adjusting method for a piezoelectric vibrator according to claim 1, wherein the frequency adjusting film is removed by a laser or a particle beam.

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