Etching apparatus and etching method

Abstract

An etching apparatus and an etching method are provided that can suppress variations in the outer dimensions of a workpiece by measuring the etching rate with high accuracy. [Solution] An etching device 100 immerses a workpiece 3 and a measurement substrate 2 in an etching bath 1 and performs etching. The measurement substrate 2 has a wiring 10a formed in a narrow portion 7 formed between multiple openings 9a, 9b, and is equipped with a power source 5 that passes current through the wiring 10a, a break detection means 6 that detects when the wiring 10a is broken, and a calculation means that calculates the etching rate of the workpiece 3 from the time it takes for the break detection means 6 to detect the break in the wiring 10a.

Description

[Technical Field]

[0001] The present invention relates to an etching apparatus and an etching method for manufacturing tuning fork type crystal resonators and the like by etching. [Background technology]

[0002] Tuning fork type piezoelectric vibrators, especially tuning fork type quartz crystal vibrators made from quartz crystal, are widely used as low-power clocks in electronic devices such as mobile phones, smart watches, smart rings, voice recorders, and action cameras. As these devices become smaller, there is a demand for miniaturization of the vibrators as well. A tuning fork crystal unit typically consists of a tuning fork-shaped quartz crystal element hermetically housed in a vacuum-sealed container consisting of a ceramic base and a metal lid. This tuning fork crystal element is a key component that determines the characteristics of the tuning fork crystal unit, and reducing manufacturing variations in tuning fork crystal elements is one of the key technical challenges in achieving miniaturization while maintaining the performance of tuning fork crystal units. In particular, the external dimensions of the tuning fork crystal element determine the frequency of the tuning fork crystal unit, so variations in these dimensions have a significant impact on the characteristics, and the more miniaturized the tuning fork crystal element is, the greater this impact becomes.

[0003] In recent years, as tuning fork crystal elements have become increasingly miniaturized, they are generally manufactured by using photolithography and wet etching techniques to create a quartz substrate. To manufacture a tuning fork crystal element, a gold mask pattern for etching the crystal is created on the quartz substrate using photolithography, and then the quartz substrate is etched using an etching solution such as buffered hydrofluoric acid to form the quartz tuning fork's outer shape. While manufacturing variations in the outer shape of tuning fork crystal elements are caused by the photolithography resist coating, exposure, development, and etching processes, variations in the amount of etching of the quartz substrate are one of the main causes of dimensional variations in the quartz tuning fork's outer shape.

[0004] Furthermore, the etching of quartz substrates involves placing several dozen quartz substrates in an etching bath at once, but it has been confirmed that the amount of etching varies for each batch. This lot-to-lot variation is influenced by some variable factors of the etching solution, such as the concentration, temperature, and agitation state of the etching solution. However, the relationships between these variable factors are complex, and there are limits to how much lot-to-lot variation can be suppressed by simply managing each variable factor individually. Therefore, an effective means of suppressing lot-to-lot variation is needed.

[0005] Here, measuring the amount of quartz crystal etched by the etching solution per unit time as the etching rate is effective in suppressing variations in the amount of quartz crystal etching. For example, various methods have been proposed to date (see, for example, Patent Documents 1 and 2) based on the idea of ​​forming an area on the quartz crystal substrate for checking the etching rate, calculating the etching rate from the dimensional change of that area, and determining the etching time for processing tuning fork quartz crystal elements based on that etching rate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-207510 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-195134 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 discloses a method for etching a thin portion of a substrate, calculating an etching rate from the time it takes for the thin portion to penetrate and the thickness of the thin portion, and determining the etching time required to obtain a desired quartz crystal element. In Patent Document 1, the thin portion is formed in the thickness direction of the substrate, and the etching rate in the thickness direction of the substrate is calculated from the thickness of the thin portion and the etching time, and this value is converted to an etching rate in the in-plane direction of the substrate. Because the tuning fork shape of a tuning fork-type quartz crystal element is formed in the in-plane direction of the substrate, its outer dimensions are significantly affected by the in-plane etching rate. Therefore, the method disclosed in Patent Document 1, which indirectly measures the in-plane etching rate rather than directly, has the problem of introducing errors into the in-plane etching rate.

[0008] Furthermore, since the determination of whether the thin-walled portion has been penetrated is made by the amount of light transmitted through the thin-walled portion when irradiated from outside the etching tank onto the thin-walled portion, a large space is required in the etching tank to ensure an optical path when a large number of substrates to be processed are placed into the etching tank at the same time, which also poses the problem of the etching tank becoming larger.

[0009] Patent Document 2 also discloses a method of forming a corrosion-resistant film on a dimension measurement section of a substrate, and determining the etching time required to obtain a desired quartz crystal element based on the amount of dimensional change in the in-plane direction of the corrosion-resistant film due to etching and the etching time. The amount of change in the corrosion-resistant film is detected by actual measurement of the dimensions, but since it is not possible to measure the dimensions during etching, it is necessary to temporarily interrupt the etching, remove the substrate from the etching bath, and then measure the dimensions after processes such as cleaning and drying. Furthermore, because the etching solution remains on the substrate during the period from removal from the etching bath to cleaning, it is difficult to accurately determine the etching time of the substrate. Therefore, there is a problem that the etching rate measured by the method disclosed in Patent Document 2 also contains errors.

[0010] In view of the above problems, an object of the present invention is to provide an etching apparatus and an etching method that can suppress variations in the outer dimensions of a material to be etched by measuring the etching rate with high accuracy. [Means for solving the problem]

[0011] In order to achieve the above object, the etching apparatus of the present invention is an etching apparatus that etches a workpiece by immersing it in an etching bath containing an etching solution, The etching apparatus includes a measurement substrate at least a portion of which can be accommodated in the etching tank and having wiring formed on its surface, a power source for passing current through the wiring, a disconnection detection means for detecting disconnection of the wiring, and a calculation means for calculating the etching rate of the workpiece from the time taken for the disconnection detection means to detect disconnection of the wiring. The measurement substrate may be an etching device having a pair of openings and a narrow portion formed between the pair of openings, and the wiring is formed in the narrow portion. The wiring may also be formed in the narrow portion at a predetermined distance from the outer edge of the narrow portion, and the etching apparatus may include an exposed portion between the outer edge of the narrow portion and the wiring, where the surface of the measurement substrate is exposed. Furthermore, the etching apparatus may include a plurality of narrow portions with the same or different predetermined intervals. The opening may have an opening width equal to or greater than the thickness of the measurement substrate. The opening may have an opening length at least four times the predetermined interval. The measurement substrate may be made of the same material as the workpiece.

[0012] The etching method of the present invention is an etching method in which a workpiece is immersed in an etching solution and etched, in which a measurement substrate having wiring formed on its surface and the workpiece are immersed in the etching solution, an etching rate of the workpiece is calculated from the time it takes for the wiring to break as the measurement substrate is etched, and an etching time for the workpiece is determined based on the etching rate. Furthermore, the etching method may include providing a plurality of the wirings on the measurement substrate, and performing linear regression analysis on the relationship between the disconnection time of each of the plurality of wirings and the amount of etching of the measurement substrate until the wiring is disconnected. [Effects of the Invention]

[0013] The etching rate of the workpiece can be measured with high accuracy, and variations in the outer dimensions of the workpiece can be suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram for explaining an embodiment of an etching apparatus and an etching method according to the present invention; [Figure 2] FIG. [Figure 3] 2A and 2B are diagrams showing the Z cross section of the measurement substrate 2 in FIG. 1, in which (a) shows the state before etching and (b) shows the state during etching. [Figure 4] FIG. 2 is a diagram showing an element substrate 3. [Figure 5] 1A to 1C are diagrams illustrating an etching method of the present invention. [Figure 6] 10 is a diagram showing the relationship between a disconnection signal of a disconnection detector and time when a wiring portion is disconnected; FIG. [Figure 7] FIG. 10 is a diagram showing the relationship between the time from when the measurement substrate is placed in the etching bath 1 until the wiring portion is broken (disconnection time) and the width of the exposed portion in the narrow portion in this example. [Figure 8] FIG. 10 is a diagram showing the relationship between the etching rate and the correction time. DETAILED DESCRIPTION OF THE INVENTION

[0015] In this example, the etching apparatus and method of the present invention will be described using an apparatus and method for manufacturing a tuning fork-type quartz crystal element by etching a quartz crystal substrate as an example. Figure 1 is a schematic diagram for explaining one embodiment of the etching apparatus and etching method of the present invention. The etching apparatus 100 includes an etching tank 1, a measurement substrate 2 that can be accommodated in the etching tank 1, a wire break detector 6 connected to the measurement substrate 2, and a power supply 5 connected to the measurement substrate 2 and the wire break detector 6. The etching apparatus 100 performs etching by immersing an element substrate 3, which is the target of etching, in an etching solution (not shown) filled in the etching tank 1. The etching process of the element substrate 3 by the etching device 100 is performed by immersing the measurement substrate 2 together with the element substrate 3 in the etching solution in the etching tank 1, calculating the etching rate from the etching state of the measurement substrate 2, and determining the etching time of the element substrate 3 based on the calculated etching rate. The etching rate of the measurement substrate 2 is determined by measuring the time until the wiring provided on the measurement substrate 2 is broken due to the progress of etching of the wiring substrate 2 using the wire breakage detector 6.

[0016] (etching bath) The etching tank 1 is made of a material that is resistant to corrosion and heat from the etching solution, and is a tank for holding the etching solution and etching the material to be etched. In this embodiment, the etching tank 1 contains buffered hydrofluoric acid as the etching solution. Although not shown, the etching tank 1 is connected by a pipe to a storage tank for the etching solution that is provided separately from the etching tank 1, and the etching solution is circulated between the etching tank 1 and the storage tank while the temperature of the etching solution is kept constant using a liquid temperature sensor and a heater.

[0017] (measurement board) FIG. 2 is a diagram showing the measurement substrate 2. FIG. 3 is a diagram showing the Z-section of the measurement substrate 2 in FIG. 1, where (a) shows the state before etching and (b) shows the state during etching. The measurement substrate 2 is a substrate whose base material is quartz, and whose main surface is an approximately XY plane of a rectangular crystal consisting of two sides parallel to the quartz crystal's X-axis and two sides parallel to an axis obtained by rotating the crystal's Y-axis by several degrees around the X-axis, and whose thickness direction is approximately parallel to the crystal's Z-axis. The measurement substrate 2 is configured to have the same material, crystal orientation, and thickness as the element substrate 3, which is the material to be etched in this embodiment. Note that in the following description, for simplicity's sake, when a crystal axis or crystal plane approximately coincides with a specific crystal axis or crystal plane, the approximately coincident crystal axis or crystal plane will be omitted as the specific crystal axis or crystal plane.

[0018] The measurement substrate 2 includes a pair of through holes 9, each consisting of a pair of through holes 9a, 9b that communicates between the front and back main surfaces, and a plurality of narrow portions 7 located between each of the through holes 9a, 9b of the pair of through holes 9. In this embodiment, the measurement substrate 2 includes four pairs of through holes 9 and narrow portions 7. The through holes 9a, 9b that make up the pair of through holes 9 are holes with rectangular openings having long sides with a length Q along the crystal Y-axis direction and short sides with a length P along the crystal X-axis. When viewed from above from the main surface side of the measurement substrate 2, the narrow portions 7 located between the through holes 9a, 9b are rectangular with their long sides aligned with the crystal Y-axis and their short sides aligned with the crystal X-axis. The four pairs of through holes 9 are spaced apart at different intervals, and the four narrow portions 7 located between the through holes 9a, 9b have different widths.

[0019] Furthermore, a conductive corrosion-resistant film 10 that is resistant to corrosion by etching solutions is formed on the front principal surface, the back principal surface, and part of the side surface connecting the front and back principal surfaces of the measurement substrate 2. The corrosion-resistant film 10 is a laminated film with a thickness of approximately 100 nm, which is made up of a chromium film formed as an adhesive layer to the surface of the measurement substrate 2 and a gold film formed on the chromium film.

[0020] The corrosion-resistant film 10 is disposed on the front principal surface of the measurement substrate 2 in the narrow portion 7. The wiring portion 10a has a wiring width E that passes through the center of the narrow portion 7 and is parallel to the crystal Y axis, and a first contact portion 10b connected to one end of the wiring portion 10a. Furthermore, the corrosion-resistant film 10 is provided with a second contact portion 10c that is connected to the other end of the wiring portion 10a disposed in the narrow portion 7 and is disposed on the front principal surface so as not to contact the wiring portion 10a excluding the other end of the wiring portion 10a and the first contact portion 10b. In other words, the first contact portion 10b and the second contact portion 10c of the corrosion-resistant film 10 are disposed so as to be electrically connected only via the wiring portion 10a. In this embodiment, the second contact portion 10c, the portion excluding the other end of the wiring portion 10a, and the first contact portion 10b are spaced apart by approximately 10 μm, and the wiring width E is 3 μm. The distance between the second contact portion 10c and the portion of the wiring portion 10a excluding the other end thereof and the first contact portion 10b, the wiring width E, and the thickness of the corrosion-resistant film 10 can be changed as appropriate, and for example, the wiring width E can be selected from a predetermined value within the range of 3 to 5 μm. The corrosion-resistant film 10 is also formed on the entire back main surface of the measurement substrate 2 and on the entire side surface of the measurement substrate 2 at its outermost shape, but is not formed on the side surface (inner surface) of the through-hole 9.

[0021] Here, the wiring portion 10a is arranged away from the end of the narrow portion 7 (the opening end of the through holes 9a, 9b). In other words, the measurement substrate 2 has an exposed portion that is not covered by the wiring portion 10a arranged to pass through the center of the narrow portion 7 and is exposed to the outside. In this embodiment, the widths of the four narrow portions 7 are different, and the wiring portions 10a provided in each narrow portion 7 have the same width E, so the widths Wa, Wb, Wc, and Wd of the exposed portions provided in each of the four narrow portions 7 are different (see FIG. 3(a)). In this embodiment shown in FIG. 3(a), the relationship in the size of the widths of the exposed portions is Wa <Wb<Wc<Wdである。

[0022] It is preferable that the length Q of the through holes 9a, 9b be at least four times the maximum width Wd of the widths Wa to Wd of the exposed portions of the narrow portion 7. In this embodiment, the length Q of the through holes 9a, 9b is four times the maximum width Wd of the exposed portions. By making the length Q of the through holes 9a, 9b sufficiently larger than the width of the exposed portions in this way, it is possible to ignore the effect of etching residues that occur on the short sides of the through holes 9a, 9b due to etching that progresses in the length direction, particularly in the central portion of the narrow portion 7 in the length direction, and it is possible to identify etching that progresses in the width direction of the through holes 9a, 9b as the main cause of disconnection of the wiring portion 10a.

[0023] Furthermore, the width P of the through holes 9a, 9b is preferably at least one time the thickness of the measurement substrate 2. This is to suppress the effect on the etching rate of the widening of the openings of the through holes 9a, 9b that occurs as the exposed portion of the narrow portion 7 is dissolved by etching. In this example, the width P of the through holes 9a, 9b was set to be the same as the thickness of the measurement substrate 2.

[0024] (Measurement substrate preparation process) Next, we will explain the preparation process of the measurement substrate 2. The measurement substrate 2 needs to be produced in a preparation process before etching the element substrate 3 using the etching apparatus 100 explained above. The measurement substrate 2 is produced by photolithography and etching in the following procedure.

[0025] Step 1: A metal film that will become the corrosion-resistant film 10 is formed by sputtering or the like on the entire front and back principal surfaces and side surfaces of the quartz substrate. In this example, the metal film is a laminated film of a chromium film and a gold film. Step 2: After removing the metal film at positions corresponding to the through holes 9a and 9b by photolithography to expose the surface of the quartz substrate, the through holes 9a and 9b are formed in the quartz substrate by quartz etching. Step 3: A cutout pattern is formed in the metal film by photolithography, and the wiring portion 10a, the first contact portion 10b, and the second contact portion 10c of the corrosion-resistant film 10 are formed.

[0026] (break detector and power supply) The wire break detector 6 is a device for detecting a wire break in the wiring portion 10a of the measurement board 2. It is connected to the positive voltage side of the power supply 5 via the connection wiring 16 and to the ground side of the power supply 5 via the connection wiring 15, the first contact portion 10b of the measurement board 2, the wiring portion 10a, and the second contact portion 10c. The power supply 5 supplies the necessary power to the wire break detector 6 and the measurement board 2. The etching apparatus 100 of this embodiment is configured so that the measurement board 2 has a pair of through holes 9, a narrow portion 7, and four sets of wiring portions 10a and first contact portions 10b of the corrosion-resistant film 10. It also has four wire break detectors 6. In this case, each of the four wire break detectors 6 is connected to one of the four first contact portions 10b. There is only one power supply 5, and one power supply 5 is connected to the second contact portion 10c of the measurement board 2. In this way, when there are multiple wiring sections 10a, by connecting one open circuit detector 6 to each wiring section 10a, it is possible to independently detect the continuity and open circuit of each of the multiple wiring sections 10a.

[0027] The open circuit detector 6 includes one or more of a current sensor, a voltage sensor, and a resistance sensor, which monitor the electrical characteristics of the wiring portion 10a and generate a signal if an abnormality is detected. The generated signal is then sent to a processor, which analyzes the data from the sensor and determines that an open circuit has occurred if a preset threshold is exceeded.

[0028] (Etching rate calculation means) A data processing device (not shown) for calculating the etching rate is connected to the disconnection detector 6. The data processing device includes an insertion time recording means for recording time information when the measurement substrate 2 is inserted into the etching solution in the etching tank 1, and a disconnection time recording means for recording time information when a disconnection occurs based on a signal sent from the disconnection detector 6 when an abnormality (disconnection) occurs in the wiring portion 10a of the measurement substrate 2. The data processing device also includes a processor for measuring the time until the wiring portion 10a is disconnected from the insertion time information and the disconnection time information, and for calculating the etching rate V in the width direction of the measurement substrate 2 as the quotient obtained by dividing the preset width of the exposed portion of the narrow portion 7 by the time until the disconnection.

[0029] (element substrate) Here, we will explain the structure of the element substrate 3, which is the target of processing in this embodiment. FIG. 4 is a diagram showing the element substrate 3. Like the measurement substrate 2, the element substrate 3 is a quartz substrate with X- and Y-axes as its edges and a Z-axis as its thickness direction. A corrosion-resistant film 31 is formed on the front and back principal surfaces and side surfaces of the element substrate 3 by sputtering or the like. The corrosion-resistant film 31 remains on the front and back principal surfaces of the element substrate 3 in areas corresponding to the tuning fork shapes 11 of the tuning fork-type quartz element. The corrosion-resistant film 31 is made of a material that is resistant to quartz etching solutions. In this embodiment, it is a laminated film made of chromium and a gold film formed thereon. The element substrate 3 prepared in this manner is etched using the etching apparatus 100 of the present invention, dissolving the periphery of the tuning fork shapes 11 and leaving the tuning fork shapes 11. Note that FIG. 3 shows an example in which one tuning fork shape 11 is formed in the element substrate 3. However, it is also common to form multiple tuning fork shapes 11, for example, 1,000 tuning fork shapes, on a single element substrate 3. However, since the etching process is essentially the same whether there is one tuning fork shape 11 on the element substrate 3 or multiple tuning forks, the present embodiment illustrates the case where there is one tuning fork shape 11.

[0030] Next, the etching method of the present invention will be described. 5 is a diagram for explaining the etching method of the present invention. The crystal etching process of the present invention is carried out in the procedure shown in FIG. (Step 1: Start etching the element substrate and measurement substrate) First, the element substrate 3 and the measurement substrate 2 are placed in the etching tank 1 and immersed in the etching solution, and etching of the element substrate 3 and the measurement substrate 2 begins. The element substrate 3 and the measurement substrate 2 are placed in the etching tank 1 by mounting the measurement substrate 2 and the element substrate 3 on a carrier. In this embodiment, two element substrates 3 and one measurement substrate 2 are mounted on a carrier and placed in the etching tank 1. However, several or even several tens of element substrates 3 may be placed in the etching tank 1 at once to perform etching. The measurement substrate 2 and the element substrate 3 mounted on the carrier are held in a spaced-apart state on the carrier to ensure equal access to the etching solution on the entire surface of each substrate and to maintain a constant flow of the etching solution. The measurement substrate 2 is also placed in the etching tank 1 while connected to the open circuit detector 6 and power supply 5. When the measurement substrate 2 and the element substrate 3 are placed in the etching tank 1, the time of placement of the measurement substrate 2 is recorded in the placement time recording means of the data processing device.

[0031] (Step 2: Detecting disconnections in the wiring of the measurement board) When the element substrate 3 and the measurement substrate 2 are placed in the etching bath 1, etching begins. Then, over time, the exposed portion of the narrow portion 7 of the measurement substrate 2 is etched, and as time passes, the etching progresses to the portion of the narrow portion 7 that is covered by the wiring portion 10a, causing the wiring portion 10a to break. When the disconnection detector 6 detects a disconnection in the wiring portion 10a, it outputs a signal (disconnection signal) indicating that the wiring portion 10a has been disconnected to the data processing device, and the data processing device records the time of the disconnection using a disconnection time recording means.

[0032] The time until the wiring part 10a breaks is dependent on the widths Wa to Wd of the exposed parts of the narrow part 7. FIG. 3(b) is a cross-sectional view showing the state during the etching process of the measurement substrate 2, and shows the state of the Z cross-section of the measurement substrate 2 at the time when the wiring part 10a provided on the narrow part 7 with the smallest width of the exposed part breaks. In the exposed part of the narrow part 7, the front main surface side where the wiring part 10a is formed by the etching process is thinner than the back main surface side. Since the widths of the respective exposed parts are in the relationship of Wa < Wb < Wc < Wd, when the wiring part 10a provided in the narrow part 7 having the exposed part with the width Wa breaks, only the wiring 10a of the narrow part 7 having the exposed part with the smallest width Wa is in a state of having broken, and the wiring parts 10a of the narrow parts 7 having the exposed parts with the widths Wb to Wd are not in a state of having broken. As time further passes from here, in the narrow parts 7 having exposed parts with large widths, the wiring parts 10a also break in order of increasing width. FIG. 6 is a diagram showing the relationship between the disconnection signal of the disconnection detector 6 and time when the wiring part 10a breaks. When the disconnection times of the respective wiring parts 10a formed in the respective narrow parts 7 having the widths Wa, Wb, Wc, Wd of the exposed parts of the narrow part 7 are ta, tb, tc, td respectively, the disconnection times are in the relationship of ta < tb < tc < td.

[0033] (Step 3: Calculation of etching rate) Next, the relationship between the disconnection times ta-td, calculated from the insertion time and disconnection time recorded by the data processing device, and the widths Wa-Wd of the exposed portions of each narrow portion 7, is calculated using a regression equation. Figure 7 shows the relationship between the time from insertion of the measurement substrate 2 into the etching bath 1 until the wiring portion 10a is disconnected (disconnection time) and the width of the exposed portion in the narrow portion 7 in this example. As shown in Figure 7, by plotting the disconnection time on the horizontal axis and the width of the exposed portion on the vertical axis, a regression curve can be drawn using the regression equation shown by the dashed line in the figure. In this example, the relationship between the two is calculated using linear regression. In this linear regression, the slope of the line can be used as the etching rate V of the measurement substrate 2 in the width direction. Furthermore, since the measurement substrate 2 and the element substrate 3 are constructed of the same material and have the same crystal orientation, the calculated etching rate V of the measurement substrate 2 is the same as the etching rate of the element substrate 3 in the width direction. In this example, the etching rate V was calculated to be 0.123 μm / min.

[0034] In the preparation process of the measurement substrate 2, certain processing errors occur in the outer shape and etching rate of the corrosion-resistant film 10, and the width of the exposed portion of the narrow portion 7 also includes processing errors. Therefore, the time it takes for the exposed portion of the narrow portion 7 to be etched and the wiring portion 10a to be broken is also affected by these processing errors. However, as in this embodiment, by providing a configuration in which multiple narrow portions 7 with different exposed widths are provided and calculating the etching rate based on the results of regression analysis of data on the width of the exposed portion and the time to break, it is possible to calculate the etching rate V with high accuracy without being affected by processing errors, such as when the multiple narrow portions 7 are uniformly large in the preparation process of the measurement substrate 2.

[0035] (Step 4: Determine the etching end time) Next, the time to complete the etching of the element substrate 3 is calculated from the etching rate V obtained in step 3. To calculate the etching completion time, first, a plurality of quartz substrates are etched in advance to determine the etching rates, and then a corrected etching time is calculated based on the relationship between the etching rate and the time required to obtain the desired etching amount (hereinafter referred to as "processing amount A") for the element substrate 3. Here, the corrected etching time represents the difference between the etching time required to process the processing amount A at the etching rate V measured using the measurement substrate 2 and the standard etching time t0, where V0 is a specific etching rate measured in advance in the etching of a plurality of quartz substrates, and t0 is the etching time required to process the processing amount A at the standard etching rate V. The corrected etching time can be calculated by multiplying the difference between the etching rate V and the standard etching rate V0 by the standard etching time.

[0036] FIG. 8 is a diagram showing the relationship between the etching rate and the correction time. In FIG. 8, an etching rate of 0.125 μm / min is defined as the standard etching rate V0, and the etching time required to process the processing amount A at that time is defined as the standard etching time (the correction time is zero). The etching rate V in this embodiment is 0.123 μm / min, and the correction time for the standard etching time is 2.8 minutes. Therefore, the etching time for the element substrate 3 in this embodiment is determined by adding the correction time of 2.8 minutes to the standard etching time. In this way, by comparing the etching rate and etching time measured in advance with the etching rate V obtained when the element substrate 3 is actually processed and adding the correction time for the standard etching time, the etching time can be easily determined even when processing multiple lots.

[0037] (Step 5: End of etching) Next, after the etching time determined in step 4 has elapsed, the measurement substrate 2 and the element substrate 3 are removed from the etching bath 1 . (Step 6: Cleaning) Then, the measurement substrate 2 and element substrate 3 are lifted up and washed and dried, completing a series of etching steps.

[0038] According to the etching apparatus 100 and etching method of this embodiment, the element substrate 3 and the measurement substrate 2 are simultaneously immersed in the same etching bath 1, and the etching rate is calculated by detecting breaks in the wiring portion 10a provided on the measurement substrate 3. This eliminates the need to interrupt the etching process by removing the substrate for measuring the etching rate from the etching bath 1 to check the etching status of the substrate, and allows for accurate calculation of the etching rate, enabling highly accurate processing. Furthermore, by arranging the wiring portion 10a of the measurement substrate 2 so that it breaks as etching progresses in the in-plane direction of the substrate, the etching rate in the in-plane direction of the substrate, which directly affects the external dimensions of the tuning fork crystal element, can be directly calculated, enabling highly accurate processing.

[0039] Although the etching apparatus and etching method of the present invention have been described above, the present invention is not limited to the embodiments. For example, in the embodiment, the measurement substrate 2 is configured with four narrow portions 7 having different exposed portion widths. However, the number of narrow portions 7 is not necessarily limited to four. The etching rate can also be calculated using narrow portions 7 having one or more different exposed portion widths. Considering variations in the width of the exposed portion during processing and variations in the time to disconnection of the wiring portion 10a, it is preferable to provide a large number of narrow portions having different widths, as this improves the accuracy of the regression analysis used to calculate the etching rate. Alternatively, multiple narrow portions 7 having the same exposed portion width may be provided, and the etching rate may be calculated from the average of the times to disconnection of each wiring portion 10a.

[0040] Furthermore, although the measurement substrate 2 is produced by photolithography in the example shown, it may also be produced by methods other than photolithography, such as machining. However, producing the measurement substrate 2 by photolithography is advantageous because it does not increase the production cost due to an increase in the number of narrow portions 7 provided on one measurement substrate 2, and it is easy to provide a necessary and sufficient number of narrow portions 7.

[0041] In this embodiment, a linear regression equation is used in the regression analysis to calculate the etching rate V, but the method is not limited to a linear regression equation and may be a higher-order regression equation or a non-parametric method. For example, the etching rate may be calculated by deep reinforcement learning, or a corrected etching time may be obtained.

[0042] In addition, while the embodiments have shown an apparatus and method for etching a quartz crystal substrate to manufacture a tuning fork-type quartz crystal element, the present invention can be used to process other materials and shapes as long as it involves etching. For example, it can be applied to a corrosion-resistant film etching process for forming a corrosion-resistant film for etching a substrate. [Industrial Applicability]

[0043] As described above, the etching apparatus and etching method of the present invention are capable of controlling the amount of etching with high precision, and are therefore advantageous for miniaturizing tuning-fork type quartz crystal resonators, and are suitable as a manufacturing apparatus and manufacturing method for tuning-fork type quartz crystal resonators used in portable electronic devices such as mobile phones and electronic devices with a high degree of integration of circuit components. [Explanation of symbols]

[0044] 100 Etching equipment 1 Etching bath 2 Measurement board 3 Element substrate 5 Power supply 6. Wire break detector 7 Narrow area 9, 9a, 9b through hole 10 Corrosion resistant membrane 10a Wiring section 10b 1st contact part 10c 2nd contact part 11 Tuning fork shape 15 Connection wiring 16 Connection wiring 31 Corrosion resistant membrane

Claims

1. In an etching apparatus for etching a workpiece by immersing it in an etching tank containing an etching solution, a measurement substrate having wiring formed on its surface, the measurement substrate being at least partially accommodated in the etching tank; a power source that applies a current to the wiring; a disconnection detection means for detecting a disconnection of the wiring; a calculation means for calculating an etching rate of the workpiece from the time it takes for the disconnection detection means to detect a disconnection of the wiring; An etching apparatus comprising:

2. the measurement substrate has a pair of openings and a narrow portion formed between the pair of openings, and the wiring is formed in the narrow portion; 2. The etching apparatus according to claim 1.

3. the wiring is disposed in the narrow portion at a predetermined distance from the outer edge of the narrow portion, and an exposed portion where the surface of the measurement substrate is exposed is provided between the outer edge of the narrow portion and the wiring.

3. The etching apparatus according to claim 2.

4. The narrow portion has a plurality of narrow portions, the predetermined intervals of which may be the same or different.

4. The etching apparatus according to claim 3.

5. The opening has an opening width equal to or greater than the thickness of the measurement substrate.

3. The etching apparatus according to claim 2.

6. The opening has an opening length at least four times the predetermined interval.

4. The etching apparatus according to claim 3.

7. The measurement substrate is made of the same material as the workpiece.

7. The etching apparatus according to claim 1, wherein the etching apparatus is a gas-permeable gas.

8. In an etching method in which a workpiece is immersed in an etching solution and etched, Immerse the measurement substrate having wiring formed on its surface and the workpiece in the etching solution; calculating an etching rate of the workpiece from the time it takes for the wiring to be broken due to etching of the measurement substrate; determining an etching time for the workpiece based on the etching rate; An etching method characterized by:

9. a plurality of the wirings are provided on the measurement substrate, and the etching rate is determined by performing a linear regression analysis on the relationship between the breakage time of each of the plurality of wirings and the etching amount of the measurement substrate until the wiring breaks; 9. The etching method according to claim 8.

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