JP3888107B2 - Etching method of piezoelectric diaphragm for piezoelectric vibrating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present inventionPiezoelectric diaphragm for piezoelectric vibration deviceEtching methodTo the lawRelated. In particular, the present invention relates to measures for improving the efficiency of molding operations and improving the quality of molded products.
[0002]
[Prior art]
With the increase in the frequency of communication equipment and the increase in the operating frequency of microcomputers, piezoelectric vibration devices such as crystal resonators and crystal filters are also required to have higher frequencies. In general, as a crystal wafer (crystal plate) corresponding to higher frequency, the AT-shear crystal plate thickness shear vibration is often used. As is well known, the frequency is determined by the thickness, and the frequency and the thickness are inversely proportional to each other. . For example, when an attempt is made to obtain 600 MHz as the fundamental vibration frequency, an extremely thin piezoelectric diaphragm of 3 μm or less is required. Such processing of an ultra-thin plate is difficult to polish and it has been difficult to improve the manufacturing yield.
[0003]
In order to solve this problem, as shown in FIG. 25, a concave portion b is provided in the central portion of the crystal wafer a, and a thinned vibration region c is set at the bottom of the concave portion b, and the thickening of the surroundings is reinforced. A so-called inverted mesa configuration in which the vibration region c is reinforced by the portion d has been proposed. This type of quartz diaphragm has a configuration in which an excitation electrode and an extraction electrode (not shown) are formed on a quartz wafer a having a thinned vibration region c and a reinforcing portion d formed therearound. By adopting such a configuration, the vibration region c can be made considerably thinner than the conventional one, and the yield can be improved. This type of quartz wafer is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-341064.
[0004]
Further, as one type of the inverted mesa type crystal diaphragm, by forming a stepped step portion e between the vibration region c and the reinforcing portion d, as shown in a cross section in FIG. It is also known that the mechanical strength of the crystal wafer a is improved and the external force is propagated to the vibration region c. Hereinafter, the molding operation of the inverted mesa type quartz diaphragm having the stepped portion e will be described.
[0005]
As shown in FIG. 26A (a diagram showing a cross section of the crystal wafer and the mask layer), a mask layer (resist is formed on the entire lower surface and a part of the upper surface of the crystal wafer a1 whose upper and lower surfaces are mirror-finished by polishing. Membrane) R is formed. This mask layer R has a two-layer structure of, for example, chromium (Cr) and gold (Au). In addition, the formation region of the mask layer R on the upper surface is the entire region except the portion where the vibration region c is formed. Specifically, the mask layer R is formed on the entire upper surface, and the mask layer R at a position corresponding to the vibration region c is selectively removed by a photolithography technique or the like.
[0006]
Then, using the mask layer R remaining on the quartz wafer a1 as a mask, the quartz wafer a1 is immersed in an etching solution such as hydrofluoric acid + ammonium fluoride solution, and the first wet etching is performed. FIG. 26B shows a state at the end of the first wet etching. As a result, a first step e1 is formed.
[0007]
Next, part of the remaining mask layer R is further selectively removed. The removal region of the mask layer R is a region where a second step portion e2 is formed as shown in FIG. Thereafter, the second wet etching with the etching solution is performed in the same manner as described above. FIG. 26D shows a state at the end of the second wet etching. As a result, a second step portion e2 is formed.
[0008]
Further, a part of the remaining mask layer R is selectively removed. The removal region of the mask layer R is a region where a third stepped portion e3 is formed as shown in FIG. Thereafter, a third wet etching with an etching solution is performed in the same manner as described above. FIG. 26F shows a state at the end of the third wet etching. As a result, a third step portion e3 is formed.
[0009]
After a plurality of etching steps in this way, all the mask layers R on the upper and lower surfaces are removed, thereby forming a stepped shape between the vibration region c and the reinforcing portion d as shown in FIG. A crystal wafer a having a step e is formed. A crystal resonator is manufactured by forming predetermined electrodes on the upper and lower surfaces of the vibration region c.
[0010]
In addition, as shown in FIG. 27G, a so-called mesa type crystal wafer in which the thickness dimension of the central portion of the crystal wafer a is set larger than the thickness dimension of the outer edge portion is also etched by substantially the same etching method as described above. Can be molded. That is, as shown in FIG. 27A, the mask layer R is formed only on a portion of the quartz wafer a1 whose upper and lower surfaces are mirror-finished by polishing, excluding the outer edge portions of the upper and lower surfaces. Using this mask layer R as a mask, the quartz wafer a1 is immersed in an etching solution such as a hydrofluoric acid + ammonium fluoride solution, and the first wet etching is performed. FIG. 27B shows a state at the end of the first wet etching.
[0011]
Next, as shown in FIG. 27C, the outer edge portion of the remaining mask layer R is removed. Thereafter, the second wet etching with the etching solution is performed in the same manner as described above. FIG. 27D shows a state at the end of the second wet etching.
[0012]
Further, as shown in FIG. 27E, the outer edge portion of the remaining mask layer R is removed. Thereafter, a third wet etching with an etching solution is performed in the same manner as described above. FIG. 27F shows a state at the end of the third wet etching.
[0013]
After a plurality of etching steps in this way, all the mask layers on the upper and lower surfaces are removed, so that the thickness dimension of the central portion of the crystal wafer a becomes the outer edge portion as shown in FIG. A crystal wafer a which is set to be larger than the thickness dimension and has a stepped step portion e between the central portion and the outer edge portion is formed.
[0014]
[Problems to be solved by the invention]
However, the molding operation of each crystal wafer as described above requires a plurality of etching steps, and the step of immersing the crystal wafer in the etching solution and the step of drying the crystal wafer must be repeated a plurality of times. For this reason, the work is complicated and requires a long work time, and the surface of the crystal wafer may be roughened by repeating the dipping process and the drying process. One of the causes of this surface roughness is that dust or the like adheres to the surface of the vibration region in the drying step, and moves to the dipping step without being removed. When such surface roughness occurs, particularly in the inverted mesa type, there is a possibility of adversely affecting the performance of the crystal resonator (such as variations in fundamental frequency). In addition, in the dipping process after the drying process, there is a possibility that air may exist near the step portion that has already been formed.In this case, the etching solution does not flow around the step portion, leading to etching failure, There is also a possibility that the crystal wafer cannot be formed into a predetermined shape. Furthermore, in the final stage of the multiple dipping processes, there will be a part with a very thin wall thickness on the quartz wafer, and cracks etc. in this thin part and its peripheral part during the dipping process and drying process. There is a possibility that damage may occur, leading to deterioration in yield.
[0016]
  The present invention has been made in view of such points, and the object of the present invention is to form a crystal wafer having a predetermined shape (for example, a shape having the above-described stepped portion) by only one etching process. As a result, it is possible to prevent surface roughness of the quartz wafer, avoid etching defects, and prevent damage to the thin-walled portion and its peripheral portion.Piezoelectric diaphragm for piezoelectric vibration deviceEtching methodThe lawIt is to provide.
[0017]
[Means for Solving the Problems]
-Summary of invention-
In order to achieve the above-described object, the present invention provides an etching amount in various places using a plurality of mask layers having different etching rates when a molded object such as a quartz wafer is formed into a predetermined shape by etching. There is a difference.
[0018]
    -Solution-
  Specifically, it is an etching method for etching a piezoelectric vibration plate for a piezoelectric vibration device into a predetermined shape. In this method for etching a piezoelectric vibration plate for a piezoelectric vibration device, the surface of the portion that becomes the piezoelectric vibration region of the piezoelectric vibration plate is not masked by the mask layer, and the outer surface of the portion that becomes the piezoelectric vibration region is not masked. For each placeEach otherBy mask layer made of the same materialRespectivelyAfter masking, the piezoelectric vibration region is subjected to a process that lowers the etching rate only for the constituent material of the mask layer in a region other than the region adjacent to the outer peripheral side of the piezoelectric vibration region where the etching amount may be small, After that, the piezoelectric diaphragm is etched by a wet etching method, so that the portion of the piezoelectric diaphragm that is not masked, the portion that is masked by the mask layer that is not subjected to the treatment, and the mask layer that is subjected to the treatment are used. The etching amount of each masked portion is made different from each other, and the piezoelectric vibration plate is etched into a predetermined shape while the mask layer in the region adjacent to the outer periphery of the piezoelectric vibration region is completely melted during the etching process. ing.
  More specifically, the treatment for the constituent material of the mask layer in the portion where the etching amount may be small in the piezoelectric diaphragm is an oxidation treatment.
[0019]
BookAccording to the invention, a mask layer having a high etching rate (It is a mask layer that has not been subjected to a treatment that reduces the etching rateSince the etching operation is started early in the portion masked by the mask layer that is easily dissolved in the etching solution, the etching amount increases, and conversely, the mask layer having a low etching rate (A mask layer that has been processed to reduce the etching rate.Since the start of the etching operation is delayed in the portion masked by the mask layer that is hardly dissolved in the etching solution, the amount of etching is reduced. Thus, it becomes possible to form the piezoelectric diaphragm for a piezoelectric vibrating device into an arbitrary shape by utilizing the difference in etching amount due to the difference in the mask layer, and the above-mentioned step portion can be molded with high efficiency and high accuracy. Can be done.
[0020]
That is, since an etching molded product having a predetermined shape can be obtained by one etching process, the conventional problem of surface roughness caused by repeating the dipping process in the etching solution and the drying process a plurality of times is avoided. Further, with this repeated operation, air does not exist in the vicinity of the stepped portion so that the etching solution does not circulate, and one of the causes of the etching failure can be eliminated. Furthermore, since it is not necessary to repeat the dipping process and the drying process in a state where the etched molded product is thinned by etching, damage to the etched molded product can be prevented, and the yield can be improved.
[0023]
  In addition, the following may be cited as other means for solving. An etching method for etching a piezoelectric vibration plate for a piezoelectric vibration device into a predetermined shape, wherein the surface of a portion to be a piezoelectric vibration region in the piezoelectric vibration plate is not masked by a mask layer, and the piezoelectric For each part on the outer circumference side of the part that becomes the vibration areaEach otherBy mask layer made of the same materialRespectivelyAfter masking and oxidizing the entire surface of the mask layer, the material constituting the mask layer in the region adjacent to the piezoelectric vibration region on the outer peripheral side and requiring a large amount of etching Only the reduction treatment was performed, and then the piezoelectric diaphragm was etched by a wet etching method, and the piezoelectric diaphragm was masked by the mask layer that was subjected to both the oxidation treatment and the reduction treatment in the portion where the masking was not performed. The etching amount of each portion masked by the mask layer subjected to only the oxidation treatment is different from each other, and the mask layer in the region adjacent to the piezoelectric vibration region on the outer peripheral side is completely melted during the etching treatment. However, the piezoelectric diaphragm is etched into a predetermined shape.
[0024]
  like thisIn maWhen the process is performed on the mask layer, for example, even when a mask layer with an extremely low etching rate is required, there is no restriction on the selection of the material constituting the mask layer. For example, Au is known as a constituent material of a mask layer (resist film) having a very low etching rate, but according to the present invention, a process for increasing the thickness of the mask layer or reducing the etching rate is performed. By doing so, a mask layer having an extremely low etching rate can be obtained without using expensive Au, and the manufacturing cost of the etched molded product can be reduced.
[0025]
  An etching method for etching a piezoelectric vibration plate for a piezoelectric vibration device into a predetermined shape without masking the surface of a portion to be a piezoelectric vibration region in the piezoelectric vibration plate with a mask layer, and The area adjacent to the piezoelectric vibration area on the outer peripheral side and masking the area that requires a large amount of etching is masked by the inner mask layer. The piezoelectric vibration plate is etched by the wet etching method in a state where the mask is masked by the outer mask layer which is lower than the etching rate of the inner mask layer, so that the piezoelectric vibration according to the magnitude of the etching rate of each mask layer is obtained. The etching amount of each part of the plate is made different from each other so that the piezoelectric vibration region After etching the piezoelectric vibration plate in a predetermined shape while completely melt the mask layer adjacent regions in the middle of the etching process at its outer periphery to, eachFurther reduction in thickness can be achieved by performing a process of thinning the entire piezoelectric diaphragm by etching the entire piezoelectric diaphragm evenly in the absence of the mask layer. In particular, when applied to a piezoelectric vibration device such as a crystal resonator or a crystal filter, the frequency can be further increased.Here, the material having a high etching rate means a material that is easily dissolved in an etching solution. Conversely, a material having a low etching rate is a material that is difficult to dissolve in an etching solution. Depending on the type of etchant, for example, when using hydrofluoric acid + ammonium fluoride solution as the etchant and using Cr and electrolessly plated Ni as the mask layer, Cr is more electrolessly plated. It becomes a material whose etching rate is lower than Ni.
[0026]
  An etching method for etching a piezoelectric vibration plate for a piezoelectric vibration device into a predetermined shape, comprising:By etching the piezoelectric diaphragm from both the front and back sides with a mask layer having a different etching rate on each of the front and back surfaces of the piezoelectric diaphragm, the etching rate of each mask layer can be increased. Depending on the thickness, the etching amount from the front side of the piezoelectric diaphragm and the etching amount from the back side are made different from each other.After processing, the surface of the piezoelectric vibration region in the piezoelectric vibration plate is not masked by the mask layer, and is the region adjacent to the piezoelectric vibration region on the outer peripheral side and the etching amount. Masking a portion that requires a large amount with the inner mask layer, and masking a portion where the etching amount may be small in other regions with an outer mask layer whose etching rate is lower than the etching rate of the inner mask layer Then, by etching the piezoelectric diaphragm by the wet etching method, the etching amount at each part of the piezoelectric diaphragm is made different according to the magnitude of the etching rate of each mask layer. The mask layer in the adjacent area on the outer peripheral side is completely melted during the etching process. The reluctant piezoelectric diaphragm is to be etched into a predetermined shape.For example, when the piezoelectric diaphragm before etching is polished, a certain amount of processing strain layer exists on the front and back surfaces. When the processing strain layer on one surface of the front and back surfaces is thick, if the same etching is performed from both the front and back surfaces, the processing strain layer on one surface may not be completely removed. On the other hand, if the present invention is used, the etching amount on the side where the processing strain layer is thick can be set to be particularly large, and the entire surface of the piezoelectric diaphragm is suppressed to the necessary minimum, while each side of the front and back surfaces. It becomes possible to completely remove the processed strain layer.
[0027]
  An etching method for etching a piezoelectric vibration plate for a piezoelectric vibration device into a predetermined shape, comprising:Part of piezoelectric diaphragmonlyHave been processed to reduce the thickness,Thereafter, the surface of the piezoelectric vibration region in the piezoelectric vibration plate and the thinned portion are not masked by the mask layer and are adjacent to the piezoelectric vibration region on the outer peripheral side thereof. The area where the etching amount is required is masked by the inner mask layer, and the other area where the etching amount may be small is outside the etching rate lower than the etching rate of the inner mask layer. In the state masked by the mask layer, the piezoelectric diaphragm is etched by a wet etching method so that the etching amount of each part of the piezoelectric diaphragm is made different according to the etching rate of each mask layer. Etch the mask layer in the area adjacent to the outer periphery of the piezoelectric vibration area. While completely melted in the middle of the process with etching the piezoelectric vibration plate in a predetermined shape, it was processed to the thinMold the part as a through holeI am doing so.
[0028]
  According to this, due to the etching rate difference of the mask layerPiezoelectric diaphragmIt is possible to form not only irregularities on the surface, but also to form a through hole at a specific location as the etching operation proceeds.
[0031]
  Also,When a piezoelectric diaphragm having a predetermined shape is extracted from a base plate of the piezoelectric diaphragm by etching, the piezoelectric diaphragm is formed with a part of the outer edge of the piezoelectric diaphragm being connected to the base plate of the piezoelectric diaphragm by a connecting piece. For the etching methodThe portion of the base plate of the piezoelectric diaphragm that is not masked by the mask layer on the surface of the connecting piece and is adjacent to the connecting piece and requires a large etching amount Is masked by the first mask layer, and other regions where the etching amount may be small are masked by the second mask layer whose etching rate is lower than the etching rate of the first mask layer. Then, by etching the base plate of the piezoelectric diaphragm by a wet etching method, the etching amount of each part of the piezoelectric diaphragm is made different from each other according to the magnitude of the etching rate of each mask layer. While completely melting the mask layer in the area adjacent toTo make the connecting piece thinner than other partsis doing.
  In addition, when the piezoelectric diaphragm having a predetermined shape is extracted from the base plate of the piezoelectric diaphragm by etching, the piezoelectric diaphragm is connected with a part of the outer edge of the piezoelectric diaphragm being connected to the base plate of the piezoelectric diaphragm by a connecting piece. In this etching method, a process for thinning only a part of the piezoelectric vibration plate is performed, and then the surface of the part that becomes a piezoelectric vibration region in the piezoelectric vibration plate, the thinning process is performed. The portion that has been performed and the surface of the portion to be the connecting piece are not masked by the mask layer, and are adjacent to the piezoelectric vibration region on the outer peripheral side thereof and require a large amount of etching, and The first mask layer masks a portion that is adjacent to the portion to be the connecting piece and requires a large amount of etching with the first mask layer, and etches in the other region. The base plate of the piezoelectric diaphragm is etched by the wet etching method in a state where the portion where the etching amount may be small is masked by the second mask layer whose etching rate is lower than the etching rate of the first mask layer. Accordingly, the etching amount of each part of the piezoelectric diaphragm is made different from each other in accordance with the etching rate of each mask layer, and the mask layer in the area adjacent to the piezoelectric vibration area on the outer peripheral side thereof is being etched. The piezoelectric diaphragm is etched into a predetermined shape while being completely melted, and the thinned portion is formed as a through hole, and the mask layer in the region adjacent to the connecting piece is etched. The connecting piece is formed to be thinner than the other parts while being completely melted on the way.
[0032]
  This technique can be applied to, for example, a case where a large number of crystal wafers of a tuning fork type crystal resonator are formed simultaneously from one crystal base plate (so-called multi-cavity). That is, when each crystal wafer is formed into a predetermined shape in a state where each crystal wafer is connected to the crystal base plate by the connection portion, and then the crystal wafer is separated from the crystal base plate by breaking the connection portion. Applied. At this time, the connecting portion is formed by etching so that the connecting piece is thinner than the other portions, so that it can be easily broken, and it is not broken at any portion other than this connecting portion. A quartz wafer is obtained. In addition, there is a low possibility that crystal fragments will be generated at the time of breakage, and it is possible to avoid adversely affecting the vibration characteristics due to the presence of the crystal fragments.
  The mask layer for masking a portion that requires a large amount of etching in the piezoelectric diaphragm is composed of only one layer of Cr, while the mask layer for masking a portion that requires a small amount of etching in the piezoelectric diaphragm is formed of Cr as a lower layer. And two layers with Au as an upper layer.
  Furthermore, the mask layers for masking the portions on the outer peripheral side of the portion that becomes the piezoelectric vibration region in the piezoelectric diaphragm are made of the same material, and the thickness dimension of the mask layer in the piezoelectric diaphragm where the etching amount is large is set. The thickness is set smaller than the thickness dimension of the mask layer in the portion where the etching amount may be small in the piezoelectric diaphragm.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, a case will be described in which the present invention is applied to a crystal wafer constituting an AT-cut crystal resonator as an etching molded product.
[0034]
(First embodiment)
First, the first embodiment will be described. FIG. 1 is a perspective view of a crystal wafer 1 molded in this embodiment, and FIG. 2 is a diagram showing an etching molding process of the crystal wafer 1.
[0035]
As shown in FIG. 1, a concave portion 2 for forming an electrode 22 is formed in the central portion of the crystal wafer 1. The central portion of the concave portion 2 is formed as an ultrathin piezoelectric vibration region 21, and an excitation electrode 22 (the back surface is not shown) is formed on the front and back surfaces thereof. The excitation electrode 22 is externally connected by an extraction electrode (not shown). Connected with. Further, the outer edge portion of the crystal wafer 1 is formed as a reinforcing portion 3 having a thickness dimension several times that of the piezoelectric vibration region 21. Further, a stepped portion 4 is formed between the piezoelectric vibration region 21 and the reinforcing portion 3 (this embodiment includes two stepped portions 41 and 42 on the inside and the outside). This step 4 is for ensuring sufficient mechanical strength of the piezoelectric vibration region 21 and for mitigating the influence of external force.
[0036]
As an example of the thickness of each part, when obtaining a fundamental vibration frequency of 600 MHz, the thickness of the piezoelectric vibration region 21 is 3 μm, the thickness of the reinforcing portion 3 is about 10 μm, and the area of the piezoelectric vibration region 21 is about 0.5 mm.²The area of the excitation electrode 22 is about 0.2 mm²It is such a fine structure. Such formation of the piezoelectric vibration region 21 of the recess 2 is performed by a wet etching method described later. The electrode 22 is formed by a vacuum deposition method or the like, and aluminum, silver, or the like is used as each electrode material.
[0037]
Although not shown, such a piezoelectric vibration device is housed in a package made of ceramics such as alumina, and electrical connection is made to lead out each extraction electrode to the outside. By bonding, a surface-mount type crystal resonator can be obtained.
[0038]
<Molding operation of crystal wafer 1>
Next, the shaping | molding operation | movement of the said crystal wafer 1 which is the characteristics of this form is demonstrated. As shown in FIG. 2 (a), the crystal wafer 1 before processing as a molding is mirror-finished on the upper and lower surfaces, and on the upper and lower surfaces, a mask layer R1, having a predetermined shape that is characteristic of the present embodiment. R2 and R3 are formed. The operation for forming the mask layers R1, R2, R3 will be described later. Then, using the mask layers R1, R2, and R3 formed on the upper and lower surfaces of the crystal wafer 1 as a mask, the crystal wafer 1 is immersed in an etching solution such as hydrofluoric acid + ammonium fluoride solution to perform wet etching. . Hereinafter, this wet etching process will be described in detail.
[0039]
First, the crystal wafer 1 before wet etching will be described. The entire lower surface of the crystal wafer 1 is covered with a lower mask layer R1 having a two-layer structure of a lower Cr layer and an upper Au layer. On the other hand, on the upper surface of the crystal wafer 1, no mask layer is formed in a portion where the piezoelectric vibration region 21 is formed, and only a Cr layer is formed in a portion corresponding to the upper surface of the inner step portion 41 on the outer peripheral side. An inner mask layer R2 made of layers is formed. Further, an outer mask having a two-layer structure in which the Cr layer is the lower layer and the Au layer is the upper layer on the outer side of the Cr layer and corresponding to the upper surface of the outer step 42 (the upper surface of the outer edge portion of the crystal wafer 1). Layer R3 is formed. Each Cr layer of the inner mask layer R2 and the outer mask layer R3 is formed as a continuous layer. In this way, a Cr layer having an etching rate is formed on a portion corresponding to the upper surface of the inner step portion 41, and an Au layer having no etching rate (a Cr layer on the lower layer) is formed on a portion corresponding to the upper surface of the outer step portion 42. In other words, the etching amount at various points on the upper surface of the quartz wafer 1 is set to be different from each other.
[0040]
In this manner, the quartz wafer 1 is immersed in an etching solution such as a hydrofluoric acid + ammonium fluoride solution with the mask layers R1, R2, and R3 formed on the quartz wafer 1. Thereby, the etching of the crystal wafer 1 is immediately started in the region where the mask layer is not formed (the portion where the piezoelectric vibration region 21 is formed). On the other hand, in the inner mask layer R2 on the outer peripheral side, the melting of the Cr layer is started, and the etching of the crystal wafer 1 is started after the inner mask layer R2 is completely melted. That is, in the portion corresponding to the upper surface of the inner step portion 41, the etching start time is delayed by the time required for melting the Cr layer, compared to the portion where the piezoelectric vibration region 21 is formed. FIG. 2B shows a cross-sectional shape of the crystal wafer 1 when the Cr layer of the inner mask layer R2 is completely melted. At this time, etching of the upper surface of the inner step portion 41 is started. In the outer mask layer R3, an Au layer exists above the Cr layer, and since this Au layer does not have an etching rate, etching is not performed in this portion.
[0041]
Such an etching operation is continuously performed until the piezoelectric vibration region 21 has a predetermined thickness dimension. FIG. 2C shows the cross-sectional shape of the quartz crystal wafer 1 when the piezoelectric vibration region 21 has a predetermined thickness dimension. In this way, when the portion where the piezoelectric vibration region 21 is formed has a predetermined thickness dimension, the quartz wafer 1 is taken out of the etching solution, washed and dried, and the masks remaining on the upper and lower surfaces of the quartz wafer 1 Layers R1, R3 are removed. Thereby, as shown in a cross section in FIG. 2D, the crystal wafer 1 in which stepped steps 41 and 42 are formed between the piezoelectric vibration region 21 and the reinforcing portion 3 is formed.
[0042]
Note that the matching of the fundamental frequency of the quartz crystal wafer 1 formed into a predetermined shape in this way is performed by dry etching or the like after the completion of the etching operation. If the fundamental frequency can be adjusted only by the etching operation, the crystal wafer 1 is completed simultaneously with the completion of the etching operation.
[0043]
As described above, according to the etching method of the present embodiment, the crystal wafer 1 having the stepped portion 4 is formed by one etching process by changing the etching rate of the mask layer formed on each surface of the crystal wafer 1. Accordingly, it is possible to prevent surface roughness of the crystal wafer 1, avoid etching defects, and prevent damage to the thin-walled portion and its peripheral portion, and to provide a stable and high-quality crystal wafer 1. Is possible. It is also possible to mold the crystal wafer 1 having an arbitrary shape by setting the location of each mask layer and the etching rate.
[0044]
In the present embodiment, the outer mask layer R3 has a two-layer structure including a Cr layer and an Au layer, but may have a single-layer structure including only an Au layer.
[0045]
(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the first embodiment, the Cr layer and the Au layer are used as the mask layer. However, in this embodiment, the crystal wafer 1 having the same step 4 as the above is formed once while the mask layer is formed only by the Cr layer. It can be formed by this etching process.
[0046]
First, the crystal wafer 1 before wet etching will be described. The entire lower surface of the crystal wafer 1 has a lower mask layer made of a relatively thick layer of Cr (a layer that does not melt completely in the time required to form the piezoelectric vibration region 21 of the crystal wafer 1). Covered by R1. On the other hand, the upper surface of the quartz wafer 1 is not formed with a mask layer in the portion where the piezoelectric vibration region 21 is formed, and the portion corresponding to the upper surface of the inner step portion 41 on the outer peripheral side is relatively thin of Cr. An inner mask layer R2 made of layers is formed. Further, an outer mask layer R3 made of a relatively thick Cr layer similar to the lower surface side of the crystal wafer 1 is formed outside the inner mask layer R2 and corresponding to the upper surface of the outer stepped portion 42. . The inner mask layer R2 and the outer mask layer R3 are formed as an integrated layer. In this way, by forming a thin Cr layer on the portion corresponding to the upper surface of the inner step portion 41 and forming a thick Cr layer on the portion corresponding to the upper surface of the outer step portion 42, various portions on the upper surface of the crystal wafer 1 are formed. The etching start timing is set to be different from each other.
[0047]
In this way, with the mask layers R1, R2, and R3 formed on the crystal wafer 1, the crystal wafer 1 is immersed in the etching solution. Thereby, the etching of the crystal wafer 1 is immediately started in the region where the mask layer is not formed (the portion where the piezoelectric vibration region 21 is formed). On the other hand, melting of the Cr layer is started in both the inner mask layer R2 and the outer mask layer R3 on the outer peripheral side. In this case, since the inner mask layer R2 is thinner than the outer mask layer R3, the Cr layer of the inner mask layer R2 is completely melted first, and the Cr wafer is completely melted in this portion after the Cr layer is completely melted. Etching is started. That is, in the portion corresponding to the inner step portion 41, the etching start time is delayed by the time required for melting the thin Cr layer, compared to the portion where the piezoelectric vibration region 21 is formed. At this point, the outer mask layer R3 is still left, so that this portion is not etched. FIG. 3B shows a cross-sectional shape of the quartz crystal wafer 1 when the Cr layer of the inner mask layer R2 is completely melted. That is, etching from the upper surface of the inner step portion 41 is started from this point.
[0048]
Such an etching operation is continuously performed until the piezoelectric vibration region 21 has a predetermined thickness dimension. FIG. 3C shows a cross-sectional shape of the quartz crystal wafer 1 when the piezoelectric vibration region 21 has a predetermined thickness dimension. In this way, when the portion where the piezoelectric vibration region 21 is formed has a predetermined thickness dimension, the crystal wafer 1 is taken out, cleaned and dried, and the mask layers R1, L1 remaining on the upper and lower surfaces of the crystal wafer 1 are removed. R3 is removed. As a result, as shown in FIG. 3D, the crystal wafer 1 in which stepped step portions 41 and 42 are formed between the piezoelectric vibration region 21 and the reinforcing portion 3 is formed.
[0049]
As described above, according to the etching method of the present embodiment, the mask layer at each surface portion of the crystal wafer 1 is formed of the same material (Cr), but the etching rate is changed by making the thicknesses of the mask layers different from each other. The crystal wafer 1 having the stepped portion 4 can be formed by a single etching process. This also makes it possible to prevent surface roughness of the crystal wafer 1, avoid etching defects, and prevent damage to the thin-walled portion and its peripheral portion.
[0050]
In this embodiment, even when the piezoelectric vibration region 21 has a predetermined thickness dimension, the mask layers R1 and R3 still remain, that is, the crystal wafer 1 is etched on the outer edge and the lower surface of the crystal wafer 1. The thickness dimensions of the mask layers R1 and R3 are set so as not to be performed. The present invention is not limited to this, and each mask layer R1, R2, R3 is set so that the time point when the piezoelectric vibration region 21 reaches a predetermined thickness dimension substantially coincides with the time point when the mask layers R1, R3 are completely melted. If the thickness dimension is set, the operation of removing the remaining mask layer becomes unnecessary.
[0051]
Further, the thickness dimensions of the mask layers R1 and R3 are set so that the mask layers R1 and R3 are completely melted before the piezoelectric vibration region 21 reaches a predetermined thickness dimension. It is also possible to reduce the thickness of the entire crystal wafer 1 by performing some etching on the lower surface. According to this, it becomes possible to make the thickness further thinner than the critical dimension when the quartz wafer 1 is made thin by polishing.
[0052]
(Third embodiment)
Next, a third embodiment will be described. The present embodiment relates to a case where the flat crystal wafer 1 is formed into a predetermined thickness by etching, and etching is performed from both the upper and lower surfaces of the crystal wafer 1.
[0053]
For example, when the crystal wafer 1 before being etched is polished, a certain degree of processing strain layer exists on the upper and lower surfaces thereof. If the processing strained layer on one of the upper and lower surfaces is thick, if the same etching is performed from both sides of the upper and lower surfaces, the processing strained layer on one surface may not be completely removed. The present embodiment has been made in view of this point. This will be specifically described below.
[0054]
Now, let us consider a case where the processed strain layer on the upper surface of the polished quartz wafer 1 is thicker than the processed strain layer on the lower surface. In FIG. 4, the processing strain layer portion is hatched. In this case, it is preferable that the etching amount on the upper surface is larger than the etching amount on the lower surface so that the processing strain layer on the upper surface can be completely removed.
[0055]
In this embodiment, as shown in FIG. 4, the mask layers R4 and R5 at the time of etching the quartz crystal wafer 1 are formed of only a Cr layer, and the mask layer R4 on the surface (upper surface) on which the etching amount is desired to be increased It is made thinner than the mask layer R5 on the surface (lower surface).
[0056]
With the mask layers R4 and R5 thus formed on the quartz wafer 1, the quartz wafer 1 is immersed in an etching solution. As a result, as shown in FIG. 4B, when the mask layer R4 is thin, the mask layer R4 is completely melted before the bottom surface, and after the Cr layer is completely melted, Etching of the wafer 1 is started.
[0057]
Then, after the etching of the upper surface of the crystal wafer 1 and the etching of the Cr layer on the lower surface are performed in parallel, the etching of the crystal wafer 1 is started on the lower surface when the Cr layer on the lower surface is completely melted. (See FIG. 4 (c)).
[0058]
Such an etching operation is continuously performed for a predetermined time, and when the crystal wafer 1 reaches a predetermined thickness as shown in FIG. 4D, the crystal wafer 1 is taken out, cleaned, and dried. A quartz wafer 1 having a predetermined shape is obtained. As a result, the processing strain layer that is relatively thick on the upper surface side can be removed more than the processing strain layer on the lower surface side, and the crystal wafer 1 from which each processing strain layer is completely removed can be obtained.
[0059]
As an effect of etching both the upper and lower surfaces, each etching depth can be reduced, so that an etching remaining portion (an obliquely engraved portion) due to anisotropy of crystal is less likely to occur, so that it is difficult to reduce the effective vibration region (flat surface).
[0060]
Note that if a method of making the thicknesses of the upper and lower mask layers different from each other as in the present embodiment is used, the complicated-shaped quartz wafer 1 as shown in FIGS. It can be formed by an etching operation. 5 (a) and 5 (b) show the piezoelectric vibration region 21 formed without a stepped portion at the center of the quartz wafer 1, and FIGS. 5 (c) and 5 (d) show the quartz wafer. The step portion 4 is formed on both the upper and lower surfaces of the central portion of 1, and the piezoelectric vibration region 21 is formed inside the step portion 4.
[0061]
In this embodiment, the mask layers R4 and R5 are formed on the upper and lower surfaces. However, the mask layer is not necessarily required on the surface (upper surface in the above case) where the etching amount is desired to be increased. In this embodiment, a quartz wafer 1 having only one surface polished can also be applied.
[0062]
(Fourth embodiment)
Next, a fourth embodiment will be described. In this embodiment, a Cr layer and a Cr oxide layer (hereinafter referred to as a CrO layer) are used as mask layers. In general, the etching rate of the CrO layer is lower than that of the Cr layer (it is difficult to dissolve in the etching solution), and the crystal wafer 1 having a predetermined shape is obtained by utilizing the difference between these etching rates. . Hereinafter, the formation operation of each layer will be specifically described.
[0063]
6A and 6B show a process example in the case where a Cr layer and a CrO layer are formed adjacent to each other on the crystal wafer 1. First, as shown in FIG. 6A, Cr is deposited on a predetermined region of the crystal wafer 1 to form a Cr layer. Then, by excimer UV irradiation only on the region where the etching rate is desired to be lowered, this portion of Cr is oxidized and changed to a CrO layer (see FIG. 6B). Thereby, the etching rate of only this part becomes low, and it functions as a layer replacing the Au layer of the first embodiment described above. That is, the crystal wafer 1 is not etched in the portion covered with the CrO layer, or the etching start timing of the crystal wafer 1 is delayed.
[0064]
As a means for changing the Cr layer to a CrO layer, UV-O_ThreeDry cleaning machine and O₂Means such as plasma can also be employed. Further, after the entire CrO layer is oxidized to make the entire mask layer a CrO layer, a reduction process may be performed only on the region where the etching rate is desired to be partially returned to the Cr layer. . Further, when Cr is sputter deposited on the quartz wafer 1 to form a Cr layer, oxygen is supplied into the chamber, and the CrO layer is also deposited on the quartz wafer 1 while oxidizing Cr. Is possible. Specifically, Ar—O during sputtering deposition.₂This can be realized by introducing a gas into the chamber.
[0065]
As described above, in this embodiment, it is possible to form two types of mask layers having different etching rates using only Cr without using Au. This eliminates the need for Au as a film forming material and eliminates the Au removal step after etching. For this reason, the manufacturing cost of the crystal wafer 1 and the film-forming process can be reduced. In particular, when an attempt is made to form a mask layer equivalent to the Au layer by using only a Cr layer, a film thickness of several thousand mm (for example, 4000 mm) is required. On the other hand, according to the present embodiment, the performance as a mask layer having a sufficiently low etching rate can be ensured even if the film thickness is about the same as that of the Au layer (thickness of several hundred mm: for example, 300 mm). Thus, a small amount of film forming material can be achieved. With the thinning of the mask layer, the dimensional accuracy for forming the shape of the mask layer is improved, and when the external shape of the crystal wafer 1 is formed by etching, the external accuracy can be improved.
[0066]
In addition, when the CrO layer is formed and the etching start timing of this portion is delayed, the timing at which this CrO layer is completely dissolved and the point at which the piezoelectric vibration region 21 reaches a predetermined thickness dimension are substantially the same. If the thickness dimension of each mask layer is set as described above, the operation of removing the remaining mask layer is not necessary.
[0067]
In this embodiment, the case where the Cr layer and the CrO layer are formed adjacent to each other has been described. However, as shown in FIGS. 6C, 6D, and 6E, a part of the mask layer is made of the Cr layer and the CrO layer. You may make it comprise by the two-layer structure with a layer.
[0068]
Further, the material is not limited to Cr as long as the etching rate is changed by the oxidation treatment, and the same can be applied to the case where the mask layer is formed of Ni or other various materials.
[0069]
In addition, the process for changing the etching rate is not limited to the above-described oxidation treatment, and a method of forming a part of the mask layer (the part for which the etching rate is to be changed) with an alloy layer made of a plurality of metals can be adopted. It is.
[0070]
(Fifth embodiment)
Next, a fifth embodiment will be described. In the above-described fourth embodiment, the Cr layer and the CrO layer obtained by oxidizing the Cr layer allow the mask layer to have an etching rate difference while eliminating the Au layer. In this embodiment, materials having different etching rates are used as the mask layer, and the Au layer is discarded.
[0071]
A specific combination of materials is Cr and Ni (nickel). When the Ni layer is formed on the surface of the quartz wafer 1, the etching rate is lower than that of the Cr layer. That is, it becomes difficult to dissolve in the etching solution. This makes it possible to give the mask layer a difference in etching rate while using different materials other than Au. Three or more kinds of materials may be combined. For example, Cr, CrO and Ni.
[0072]
The film forming material for the mask layer is not limited to these, and various materials can be applied.
[0073]
Further, even when the mask layer is formed using different materials as described above, the method of the fourth embodiment described above can be applied. That is, the etching rate is changed by selectively performing a treatment such as oxidation on the mask layers made of different materials.
[0074]
(Mask layer forming method)
Next, a specific example of a method for forming the mask layer R formed as in each of the above-described embodiments will be described. Examples of film forming methods applicable in the present invention include the following. In the following description, the case where the mask layer is formed of only the Cr layer will be described, but the present invention can be similarly applied to the case where the mask layer is formed of other materials or a plurality of materials.
[0075]
<Laser irradiation>
One method for forming the mask layer R is to selectively remove the mask layer by laser irradiation and leave the mask layer only in a predetermined region. For example, as shown in FIG. 7A, in a state where Cr is vapor deposited over the entire upper and lower surfaces of the crystal wafer 1, this Cr layer has a predetermined region (region where etching of the crystal wafer 1 is desired to be promoted). In this method, laser light is irradiated to selectively remove only Cr in this region. As a result, as shown in FIG. 7 (b), it is possible to easily form a portion where the Cr layer is removed or the Cr layer is thinned in a partial region.
[0076]
<Milling>
Milling is also listed as a method for forming the mask layer R. For example, as shown in FIG. 8, the milling apparatus is provided with a movable mask M, and as shown in FIG. 8A, Cr is vapor deposited over the entire upper and lower surfaces of the crystal wafer 1. In this method, the movable mask M is intermittently moved to the outside, and the Cr layer is milled to selectively remove only a predetermined region (a region where etching of the crystal wafer 1 is desired to be promoted). In the steps shown in FIGS. 8B to 8E, stepwise Cr layers (see FIG. 8E) are formed by milling while moving the pair of upper and lower movable masks M intermittently outward. Shows when to do.
[0077]
<Deposition>
Next, the case where a mask layer is formed by a vapor deposition method will be described. As shown in FIG. 9A, a masking material M is disposed in a predetermined region of the crystal wafer 1, and Cr is deposited in this state. As a result, a first layer of Cr having a predetermined thickness is formed (see FIG. 9B). Further, thereafter, as shown in FIG. 9C, a masking material M is disposed on a part of the first Cr layer, and further Cr is deposited in this state. As a result, the second layer of Cr is deposited only on the unmasked portion. That is, only this portion is formed as a Cr layer having a large thickness. Thereafter, by removing the masking material M, a step-like Cr layer is formed by the first layer made of only Cr and the first layer and the second layer made of Cr (FIG. 9). (See (d)).
[0078]
<Metal etching>
As a method for forming a mask layer by metal etching, for example, as shown in FIG. 10A, a resist material is applied to a part of the Cr layer in a state where Cr is deposited over the entire upper and lower surfaces of the crystal wafer 1. R is arranged and metal etching is performed in this state. As a result, a part of the Cr layer (the central portion in the figure) is removed by a predetermined thickness (see FIG. 10B). Further, after that, a resist material R is disposed on another part of the Cr layer, and metal etching is performed in this state. As a result, a part of the Cr layer is removed by a predetermined thickness. Thereafter, by removing the resist material R, a stepped Cr layer is formed by a plurality of layers having different removed thicknesses.
[0079]
<Lift off>
As a method for forming a mask layer by lift-off, for example, as shown in FIG. 11A, a resist material R for lift-off is disposed in a predetermined region of the crystal wafer 1, and Cr is deposited in this state ( (Refer FIG.11 (b)). As a result, a Cr layer having a predetermined thickness is formed over the crystal wafer 1 and the resist material R. Thereafter, a part of the Cr layer together with the resist material R is removed from the crystal wafer 1 by a lift-off method (see FIG. 11C). Further, after that, a resist material R for lift-off is disposed on a part of the remaining Cr layer (see FIG. 11D), and Cr is deposited again in this state (see FIG. 11E). ). As a result, a Cr layer having a predetermined thickness is formed over the crystal wafer 1 and the resist material R. Thereafter, a part of the Cr layer together with the resist material R is removed from the crystal wafer 1 by the lift-off method similar to the above (see FIG. 11F). As a result, a step-like Cr layer is formed by the first layer made of only Cr and the first layer and the second layer made of Cr.
[0080]
(Sixth embodiment)
Next, a sixth embodiment will be described. The crystal wafer 1 of each embodiment described above was a flat plate. The crystal wafer 1 according to the present embodiment is configured by connecting a vibrating portion and a frame portion surrounding the vibrating portion by a plurality of bridges. The structure and etching method will be described below.
[0081]
12 is a plan view of the crystal wafer 1 according to the present embodiment, and FIG. 13 is a cross-sectional view taken along the line AA in FIG. As shown in these drawings, the vibrating section 5 is configured with an inverted mesa structure that is substantially the same as that of the quartz crystal wafer 1 according to the above-described embodiment. Specifically, the upper and lower surfaces have stepped portions 54, and excitation electrodes 52 are attached to a piezoelectric vibration region 51 formed at the center thereof.
[0082]
On the other hand, the frame portion 6 is formed so as to surround the outer periphery of the vibration portion 5 and is connected to the vibration portion 5 via four bridges 7, 7. With this configuration, the piezoelectric vibration region 51 located at the center of the vibration part 5 is not only supported by the reinforcing part 53 which is the outer edge part of the vibration part 5 but also the frame part 6 via the bridges 7, 7. Therefore, high mechanical strength is ensured. Further, the frame portion 6 is a portion that is supported by an adhesive on the quartz resonator package, but since this portion and the vibrating portion 53 are connected only by the bridges 7, 7,. Even if deformation such as warpage occurs in the frame portion 6 due to the influence of contraction or the like, the influence of the deformation hardly reaches the vibration portion 5. Further, the connection position between the vibrating part 5 and the frame part 6 by the bridges 7, 7,... Is a stress sensitivity with an angle of 30 ° with respect to the Z axis of the vibrating part 5 (axis extending in the left-right direction in FIG. 12). Is set to a position of “0”. For this reason, even if an external force acts on the frame portion 6 and is transmitted to the vibration portion 5, the vibration characteristics are hardly affected.
[0083]
Next, a processing method of the crystal wafer 1 according to this embodiment will be described. 14 to 19 show the processing steps of the crystal wafer 1. The processing steps of the crystal wafer 1 include a resist film formation step (FIG. 14), a preliminary etching step (FIG. 15), an Au removal step (FIG. 16), a lift-off step (FIG. 17), a main etching step (FIG. 18), It consists of an electrode formation process (FIG. 19). Each step will be described below.
[0084]
<Resist film formation process>
In this step, first, a resist film R having a two-layer structure of Cr and Au is deposited on the entire upper and lower surfaces of the crystal wafer 1 (FIG. 14A). Thereafter, in order to form the bridges 7 and 7, a positive type resist film PR (hereinafter referred to as a positive resist film) is formed on the entire surface except only a portion where the through hole 71 is formed therebetween (FIG. 14). (B)). In this state, etching is performed with an Au etching solution and a Cr etching solution, respectively, and the Au layer and the Cr layer where the positive resist film PR does not exist are removed (FIG. 14C). Thereafter, the positive resist film Pr is removed (FIG. 14D), and this mask layer forming step is completed.
[0085]
<Preliminary etching process>
In this step, the portion from which Au and Cr are removed in the resist film forming step (the portion where the through hole 71 between the bridges 7 and 7 is formed) and the central portion of the crystal wafer 1 (the portion that becomes the piezoelectric vibration region 21) A positive resist film PR is formed on the entire upper and lower surfaces excluding (). Thereafter, the quartz wafer 1 is etched by being immersed in a quartz etching solution. As a result, as shown in FIG. 15B, only a predetermined amount is etched only at a portion where the through hole 71 between the bridges 7 and 7 is formed. Next, etching is performed with an Au etching solution and a Cr etching solution, respectively, to remove Au and Cr in portions where the positive resist film PR does not exist (FIG. 15C). Thereafter, the positive resist film PR is removed (FIG. 15D), and this preliminary etching step is finished.
[0086]
<Au removal process>
In this step, a negative type resist film NR (hereinafter referred to as a negative resist film) is formed on the entire upper and lower surfaces of the portion where the frame portion 6 is to be formed (FIG. 16A). Thereafter, etching is performed with an Au etching solution to remove Au in a portion where the negative resist film NR does not exist (FIG. 16B). Thereafter, the negative resist film NR is removed (FIG. 16C), and this Au removal process is completed.
[0087]
<Lift-off process>
This step is a step for forming a stepped Cr layer so as to form a stepped recess in the center of the vibration part 5. That is, a stepped Cr layer is formed by depositing Cr on a portion of the Cr layer remaining on the quartz wafer 1 at the end of the Au removal step. For this reason, first, a negative resist film NR is formed over the entire region except for the region where it is necessary to deposit additional Cr (FIG. 17A). In this state, Cr is vapor-deposited on the upper and lower surfaces of the crystal wafer 1, and only the Cr layer where there is no negative resist film NR is made thick (FIG. 17B). Thereafter, the negative resist film NR is removed by a lift-off method (FIG. 17C), and this lift-off process Au is completed. Thus, a mask layer for performing the etching process according to the present invention is formed.
[0088]
<Main etching process>
This step is performed in the same manner as the concave forming step described in the second embodiment. That is, the etching is started at an early stage in the upper and lower surfaces of the crystal wafer 1 without the Cr layer, and the etching is started with a slight delay in the thin and thick portion of the Cr layer. Further, the etching is hardly performed in the thin and thick portion of the Cr layer. For this reason, in the state where the piezoelectric vibration region 51 is etched until it has a predetermined thickness, as shown in FIG. 18B, the bridges 7, 7,... As a result, a stepped step portion 54 is formed in the vibration portion 5.
[0089]
<Electrode formation process>
In this step, the electrodes are formed by the same operation as before. That is, as shown in FIG. 19A, after the electrode material (Al or Ag) is deposited on the entire upper and lower surfaces of the crystal wafer 1, the electrode forming portion and the extraction electrode portion (illustrated) in the piezoelectric vibration region 51 are shown. (Omitted) is covered with a negative resist film NR (FIG. 19B). Thereafter, the electrode material is removed by etching or the like as shown in FIG. 19C, and further, the negative resist film NR is removed as shown in FIG. The material remains, whereby the excitation electrode 52 having a predetermined shape is formed.
[0090]
As shown in FIGS. 12 and 13, the crystal wafer 1 having the vibrating portion 5 and the frame portion 6 disposed so as to surround it and connected to the vibrating portion 5 by the bridges 7, 7,. It is formed.
[0091]
(Seventh embodiment)
Next, a seventh embodiment will be described. This embodiment is an application example of a technique in which the thickness dimension of each part of the crystal wafer 1 can be arbitrarily set by using the etching rate difference of the mask layer as in the above embodiments.
[0092]
Here, a case where the technical idea of the present invention is applied to the production technology of a tuning fork type crystal resonator will be described.
[0093]
As shown in FIG. 20, a large number of crystal wafers of the tuning fork type crystal resonator are formed simultaneously from one crystal base plate 8. In this case, when the individual tuning fork type crystal wafers 1, 1,... Are separated from the crystal base plate 8, the base portion of the crystal wafer 1 which is a connecting portion between them is broken. At this time, as shown in FIGS. 21 (a) and 21 (b), when the fracture position is shifted, the crystal wafer 1 cannot be accommodated in the package or can be mounted at a predetermined position even if it can be accommodated. The problem of disappearing occurs. Further, in the conventional device, crystal fragments are likely to be generated at the time of breakage, and there is a possibility that the crystal fragments adhere to the surface of the crystal wafer 1 and adversely affect the vibration characteristics. In this embodiment, when the base portion of the crystal wafer 1 is broken, the technique of the present invention is applied in order to prevent generation of fragments at an appropriate position. This will be described in detail below.
[0094]
FIG. 22A is a cross-sectional view of the previous stage of manufacturing the tuning fork type crystal wafer 1 by etching the crystal base plate 8, and shows the base of the tuning fork type crystal wafer 1 (on the line BB in FIG. 20). A sectional view taken along the line). As shown in FIG. 22 (a), a portion where the mask layer R does not exist and a portion where the mask layer R formed by the stepped Cr layer exists are formed in advance on the base of the tuning fork crystal wafer 1. Keep it. In other portions, a mask layer (resist film) composed of two layers of Cr and Au is formed in an area where a predetermined tuning fork shape can be formed by etching.
[0095]
Thereby, at the time of etching processing of the crystal base plate 8, as shown in FIG. 22B, the etching progresses in a portion where the mask layer R does not exist, and the thickness dimension of the crystal wafer 1 becomes extremely thin, while a stepped shape is obtained. In the portion of the mask layer R made of the Cr layer, the thickness dimension of the crystal wafer 1 is increased stepwise. Therefore, when the individual tuning fork type crystal wafers 1, 1,... Are separated from the crystal base plate 8 after the mask layer R is removed as shown in FIG. And no debris is generated. For this reason, it is possible to satisfactorily mount the crystal wafer 1 in the package and to avoid adversely affecting the vibration characteristics due to the presence of crystal fragments.
[0096]
FIG. 23 shows a stepwise Cr layer formed on the base of the tuning-fork type crystal wafer 1 on the upper and lower surfaces of the crystal base plate 8, thereby etching the base from the upper and lower sides to form a locally thin portion. It is what you do. Also by this, the thin part of a base part is fractured | ruptured favorably and a fragment | piece will not generate | occur | produce.
[0097]
In this embodiment, the case where the present invention is applied to the technique for separating the tuning fork type crystal wafer 1 from the crystal base plate 8 has been described. When this technical idea is applied to the production of the quartz wafer 1 according to the sixth embodiment, for example, as shown in FIG. 24, the connecting portion 11 for coupling the quartz wafer 1 to the quartz base plate 8 is the tuning fork type quartz wafer described above. Molding is performed in the same manner as the base portion of 1. That is, the crystal base plate 8 around the outer periphery of the crystal wafer 1 is removed by etching, leaving the connecting portion 11 formed thin so that it can be easily separated. In this case, at the same time that the connecting portion 11 is formed thin, the thickness dimensions of the piezoelectric vibration region 51, the reinforcing portion 53, the bridge 7, the frame portion 6 and the like can be arbitrarily determined by the processing method of the sixth embodiment described above. Can be molded to dimensions.
[0099]
    -Other embodiments-
  Each of the above-described embodiments has been described for the case where the present invention is applied to the processing of a reverse mesa crystal wafer, but the present invention is also applicable to the processing of a mesa crystal wafer.
[0101]
In addition, in the case where a large number of crystal wafers 1, 1,... Are formed simultaneously from a single crystal base plate 8 as in the seventh embodiment, so-called a large number of crystal wafers 1, 1,. If the etching rate is changed individually by changing the material and film thickness of the mask layer for the molded part, it is possible to simultaneously mold many types of quartz wafers 1, 1,... With different fundamental vibration frequencies. Become.
[0102]
【The invention's effect】
  As described above, in the present invention, a quartz wafer or the likeWet etching of piezoelectric diaphragmWhen forming into a predetermined shape by using a plurality of mask layers having different etching rates, a difference is caused in the etching amount in each place, therebyPiezoelectric diaphragmCan be formed into an arbitrary shape. For this reason, the trouble of the conventional method of repeating the immersion step and the drying step in the etching solution a plurality of times can be solved at once. In other words, it is possible to avoid the rough surface of the etched molded product, to prevent the etching failure due to poor wraparound of the etching solution, and to prevent the etched molded product from being damaged by reducing the processing steps when the etched molded product is thin. it can.
[0103]
In addition, when a difference in the etching rate of each mask layer is caused by changing the thickness dimension of the mask layer or by performing processing on the mask layer, the selection of the material constituting the mask layer is restricted. Any etching rate can be set without this. For this reason, it is not necessary to use an expensive layer such as Au, and the manufacturing cost of the etched molded product can be reduced.
[0104]
  Furthermore,Piezoelectric diaphragmWhen the etching process is performed in a state where each of the front and back surfaces is masked by mask layers having different etching rates,Piezoelectric diaphragmThe etching amount from the front surface side and the etching amount from the back surface side can be made different from each other. For this reason,Piezoelectric diaphragmIt is possible to selectively remove the front side or the back side including many parts to be removed by etching such as a processing strain layer ofPiezoelectric diaphragmWhile minimizing the etching amount as a whole, it is possible to completely remove the processing strain layer etc. on each side of the front and back surfaces, thereby reducing processing costs and improving the quality of the etched molded product. it can.
[0105]
  In addition, prior to the etching operation,Piezoelectric diaphragmIf the thinned portion is processed as a through hole by performing the above etching operation without masking the thinned portion with a mask layer. Can more freely set the shape of the molded product that can be molded by the etching operation.
[Brief description of the drawings]
FIG. 1 is a perspective view of a crystal wafer according to an embodiment.
FIG. 2 is a view showing a crystal wafer etching molding process according to the first embodiment.
FIG. 3 is a diagram showing an etching molding process of a crystal wafer according to a second embodiment.
FIG. 4 is a diagram showing an etching molding process of a crystal wafer according to a third embodiment.
FIG. 5 is a diagram showing a modification of the third embodiment.
FIG. 6 is a diagram for explaining a CrO layer forming operation according to a fourth embodiment.
FIG. 7 is a diagram showing a process for forming a mask layer by laser irradiation.
FIG. 8 is a diagram showing a process for forming a mask layer by milling.
FIG. 9 is a diagram showing a process when forming a mask layer by vapor deposition of Cr.
FIG. 10 is a diagram showing a process for forming a mask layer by metal etching.
FIG. 11 is a diagram showing a process for forming a mask layer by lift-off.
FIG. 12 is a plan view of a crystal wafer according to a sixth embodiment.
13 is a cross-sectional view taken along line AA in FIG.
FIG. 14 is a process diagram showing a mask layer forming process in the sixth embodiment.
FIG. 15 is a process diagram showing a preliminary etching process in the sixth embodiment.
FIG. 16 is a process diagram showing an Au removal process in the sixth embodiment.
FIG. 17 is a process diagram showing a lift-off process in the sixth embodiment.
FIG. 18 is a process diagram showing a main etching process in the sixth embodiment.
FIG. 19 is a process diagram showing an electrode forming process in the sixth embodiment.
FIG. 20 is a plan view of a quartz base plate according to a seventh embodiment.
FIG. 21 is a diagram showing an example of a fractured state of a crystal wafer of a tuning fork type crystal resonator in a conventional example.
FIG. 22 is a diagram showing a crystal wafer processing step in the seventh embodiment.
FIG. 23 is a diagram showing a crystal wafer processing step in a modification of the seventh embodiment.
FIG. 24 is a view corresponding to FIG. 20 when the processing technique of the seventh embodiment is applied to manufacture of a crystal wafer according to the sixth embodiment.
FIG. 25 is a perspective view of a crystal wafer according to a conventional example.
FIG. 26 is a diagram showing a processing step of a conventional inverted mesa type quartz wafer.
FIG. 27 is a diagram showing a conventional mesa crystal wafer processing step.
[Explanation of symbols]
1 Crystal wafer
71 Through hole
R mask layer
Cr chrome layer
CrO chromium oxide layer
Au gold layer

Claims (10)

An etching method for etching a piezoelectric diaphragm for a piezoelectric vibrating device into a predetermined shape,
In the piezoelectric diaphragm, the surface of the portion that becomes the piezoelectric vibration region is not masked by the mask layer, and the portions on the outer peripheral side of the portion that becomes the piezoelectric vibration region are masked by the same material. After each masking, the etching rate is reduced only for the constituent material of the mask layer in the region other than the region adjacent to the outer periphery of the piezoelectric vibration region where the etching amount may be small. Then, the piezoelectric diaphragm is etched by a wet etching method, so that the portion of the piezoelectric diaphragm that is not masked, the portion that is masked by the mask layer that is not subjected to the treatment, and the mask layer that is subjected to the treatment described above. The amount of etching at each location masked by the The etching method of the piezoelectric diaphragm piezoelectric vibrating device, wherein the etching the while completely melt the mask layer adjacent regions in the middle of an etching process piezoelectric vibrating plate in a predetermined shape at the outer circumferential side of the area. The method for etching a piezoelectric diaphragm for a piezoelectric vibrating device according to claim 1,
A method for etching a piezoelectric vibration plate for a piezoelectric vibration device, characterized in that the treatment for the constituent material of the mask layer in a portion where the etching amount may be small in the piezoelectric vibration plate is an oxidation treatment. An etching method for etching a piezoelectric diaphragm for a piezoelectric vibrating device into a predetermined shape,
In the piezoelectric diaphragm, the surface of the portion that becomes the piezoelectric vibration region is not masked by the mask layer, and the portions on the outer peripheral side of the portion that becomes the piezoelectric vibration region are masked by the same material. After masking each surface and oxidizing the entire surface of the mask layer, the material of the mask layer in the area that is adjacent to the piezoelectric vibration region on the outer periphery side and requires a large amount of etching. Then, the piezoelectric diaphragm is etched by a wet etching method, and the piezoelectric diaphragm is masked by a portion where the masking is not performed and a mask layer subjected to both the oxidation treatment and the reduction treatment. Etching of each part masked by the mask layer subjected to only the above oxidation treatment Piezoelectric vibration device characterized in that the piezoelectric vibration plate is etched into a predetermined shape while different amounts are used and the mask layer in the region adjacent to the outer periphery of the piezoelectric vibration region is completely melted during the etching process. Etching method for piezoelectric diaphragm for use. An etching method for etching a piezoelectric diaphragm for a piezoelectric vibrating device into a predetermined shape,
In the piezoelectric vibration plate, the surface of the portion that becomes the piezoelectric vibration region is not masked by the mask layer, and is a region that is adjacent to the piezoelectric vibration region on the outer peripheral side and requires a large amount of etching. This piezoelectric diaphragm is masked with an outer mask layer having an etching rate lower than the etching rate of the inner mask layer in a region other than that where the etching amount may be small. Is etched by a wet etching method, the etching amount of each part of the piezoelectric diaphragm is made different according to the magnitude of the etching rate of each mask layer, and is adjacent to the piezoelectric vibration region on the outer peripheral side thereof. Piezoelectric diaphragm while completely melting the mask layer in the middle of the etching process A piezoelectric vibration device characterized in that, after etching into a predetermined shape, in a state where each of the mask layers does not exist, a process of thinning the entire piezoelectric diaphragm is performed by uniformly etching the entire piezoelectric diaphragm. Etching method for piezoelectric diaphragm for use. An etching method for etching a piezoelectric diaphragm for a piezoelectric vibrating device into a predetermined shape,
In the state where the front and back surfaces of the piezoelectric diaphragm are masked by mask layers having different etching rates, the piezoelectric diaphragm is etched from both the front and back surfaces by a wet etching method, so that the etching rate of each mask layer is adjusted. After performing processing that makes the etching amount from the front surface side and the etching amount from the back surface side different from each other according to the size, the surface of the portion that becomes the piezoelectric vibration region in the piezoelectric vibration plate The mask layer is not masked, and the area adjacent to the piezoelectric vibration area on the outer peripheral side, which requires a large etching amount, is masked by the inner mask layer, and the other areas are etched. Etching of the inner mask layer with an etching rate where the amount may be small The piezoelectric diaphragm is etched by the wet etching method in a state masked by the outer mask layer lower than the mask, and the etching amount of each part of the piezoelectric diaphragm according to the etching rate of each mask layer And the piezoelectric vibration plate is etched into a predetermined shape while the mask layer in the region adjacent to the outer periphery of the piezoelectric vibration region is completely melted during the etching process. Etching method of piezoelectric diaphragm. An etching method for etching a piezoelectric diaphragm for a piezoelectric vibrating device into a predetermined shape,
Masking is performed with a mask layer on the surface of the piezoelectric vibration region and the thinned portion of the piezoelectric vibration plate after the thinning of only a part of the piezoelectric vibration plate. The area adjacent to the piezoelectric vibration region on the outer periphery side and requiring a large etching amount is masked by the inner mask layer, and the etching amount is small in other regions. In a state where the good portion is masked by the outer mask layer whose etching rate is lower than the etching rate of the inner mask layer, this piezoelectric diaphragm is etched by the wet etching method, so that the etching rate of each mask layer is large. Depending on the piezoelectric vibration plate, the etching amount of each part of the piezoelectric diaphragm is made different from each other. Etching the piezoelectric diaphragm into a predetermined shape while completely melting the mask layer in the region adjacent to the outer periphery of the region in the middle of the etching process, and forming the thinned portion as a through hole A method of etching a piezoelectric diaphragm for a piezoelectric vibrating device. When a piezoelectric diaphragm having a predetermined shape is extracted from a base plate of the piezoelectric diaphragm by etching, the piezoelectric diaphragm is formed with a part of the outer edge of the piezoelectric diaphragm being connected to the base plate of the piezoelectric diaphragm by a connecting piece. An etching method,
The portion of the base plate of the piezoelectric diaphragm that is not masked by the mask layer on the surface of the connecting piece and is adjacent to the connecting piece and requires a large etching amount Is masked by the first mask layer, and other regions where the etching amount may be small are masked by the second mask layer whose etching rate is lower than the etching rate of the first mask layer. Then, by etching the base plate of the piezoelectric diaphragm by a wet etching method, the etching amount of each part of the piezoelectric diaphragm is made different from each other according to the magnitude of the etching rate of each mask layer. While the mask layer in the area adjacent to the part to be completely melted during the etching process, the connecting piece is moved to the other part. The etching method of the piezoelectric diaphragm piezoelectric vibrating device, which comprises forming thinner than. When a piezoelectric diaphragm having a predetermined shape is extracted from a base plate of the piezoelectric diaphragm by etching, the piezoelectric diaphragm is formed with a part of the outer edge of the piezoelectric diaphragm being connected to the base plate of the piezoelectric diaphragm by a connecting piece. An etching method,
A process for thinning only a part of the piezoelectric diaphragm is performed, and then the surface of the piezoelectric vibration region in the piezoelectric diaphragm, the part subjected to the thinning process, and the part to be the connecting piece are processed. The surface is not masked by the mask layer and is adjacent to the piezoelectric vibration region on the outer peripheral side thereof, and the region adjacent to the portion that requires a large amount of etching and the portion that becomes the connecting piece In addition, the first mask layer masks a portion that requires a large etching amount, and the etching rate is higher than the etching rate of the first mask layer in other regions where the etching amount may be small. The base plate of this piezoelectric diaphragm is etched by a wet etching method while masked by a lower second mask layer. Accordingly, the etching amount of each part of the piezoelectric diaphragm is made different from each other according to the magnitude of the etching rate of each mask layer, and the mask layer in the area adjacent to the piezoelectric vibration area on the outer peripheral side thereof is being etched. The piezoelectric diaphragm is etched into a predetermined shape while being completely melted, and the thinned portion is formed as a through hole, and the mask layer in the region adjacent to the connecting piece is etched. A method for etching a piezoelectric vibration plate for a piezoelectric vibration device, characterized in that the connecting piece is formed thinner than other portions while being completely melted in the middle. In the etching method of the piezoelectric diaphragm for a piezoelectric vibrating device according to any one of claims 4 to 8,
A mask layer for masking a portion that requires a large amount of etching in the piezoelectric diaphragm is composed of only one layer of Cr, while a mask layer for masking a portion that requires a small amount of etching in the piezoelectric diaphragm is composed of Cr as a lower layer and Au. An etching method for a piezoelectric diaphragm for a piezoelectric vibrating device, comprising two layers as an upper layer. In the etching method of the piezoelectric diaphragm for a piezoelectric vibrating device according to any one of claims 4 to 8,
The mask layers for masking each part on the outer peripheral side of the portion that becomes the piezoelectric vibration region in the piezoelectric diaphragm are made of the same material.
The thickness dimension of the mask layer at a location where a large amount of etching is required in the piezoelectric diaphragm is set smaller than the thickness dimension of the mask layer at a location where the etching amount may be small in the piezoelectric diaphragm. Etching method of piezoelectric diaphragm for piezoelectric vibrating device.

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