JP6435629B2 - Substrate dry etching method - Google Patents

Description

  The present invention relates to a dry etching method for a substrate such as a crystal or a semiconductor.

  For example, in the processing of a substrate such as a crystal or a semiconductor, a dry etching method is used as a method for forming a shape without being affected by the crystal axis of the substrate (see, for example, Patent Document 1). In the dry etching method for a substrate disclosed in Patent Document 1, a nickel chrome (NiCr) film and a gold (Au) film are formed on the substrate from the substrate side, and a resist corresponding to the etching position of the substrate is formed on the gold film. A nickel (Ni) film is formed at a position other than the film and the resist film. Then, after the resist film is peeled off, dry etching is performed using the nickel film as a mask. In this method, the etching rate between the substrate to be etched and the nickel film constituting the mask is improved by increasing the adhesion between the nickel chrome film and the nickel film by using a nickel chromium film. The etching selectivity which is the ratio of the above becomes high. Thereby, dry etching of a thick substrate can be easily performed.

JP 2007-234912 A

  However, in the above-described dry etching method of the substrate, the side surface of the resist film on the side wall shape on the substrate side of the resist film is affected by, for example, fine irregularities on the substrate surface or the difference in thermal expansion between the resist film and the substrate. May cause unevenness. If there is unevenness on the side wall shape of the resist film on the substrate side, the unevenness in the side wall shape of the resist film is transferred to the nickel film formed along the side wall of the resist film, and the unevenness is formed on the side wall on the substrate side. . When the unevenness is formed on the side wall of the nickel film, there is a problem that when the substrate is dry-etched, a dimensional error occurs in the etched shape of the substrate due to the protrusion on the side wall of the nickel film.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  [Application Example 1] A substrate dry etching method according to this application example includes a step of preparing a substrate, and a protruding portion that protrudes on the substrate side from the side opposite to the substrate in a sectional view on the substrate. A step of forming a resist layer, a step of forming a plating layer on the substrate, and a step of dry etching the substrate using the plating layer as a mask.

  According to this application example, in the cross-sectional view, the protruding portion provided in the resist layer on the substrate side forms a concave portion in which the side wall on the substrate side is recessed in the plating layer. By making the substrate side of the plating layer positively concave, even if there are fine irregularities on the surface of the substrate or differences in thermal expansion between the resist film and the substrate, convex portions that protrude from the side walls of the plating layer are formed. This eliminates the occurrence of dimensional errors in the etching shape of the substrate due to the influence of the convex portions on the side walls. This makes it possible to accurately form a desired outer shape in dry etching of the substrate.

  Application Example 2 The substrate dry etching method according to the application example described above preferably includes a step of forming a seed layer between the substrate and the plating layer.

  According to this application example, since the adhesion between the substrate and the plating layer and the seed layer is high, the seed layer is provided between the substrate and the plating layer, thereby increasing the adhesion between the substrate and the plating layer. be able to. Thereby, the etching selectivity which is the ratio of the etching rate between the substrate and the plating layer constituting the mask can be increased.

  Application Example 3 In the substrate dry etching method according to the application example described above, in the step of forming the resist layer, it is preferable that the protrusion is formed by heating the resist after pattern formation.

  According to this application example, since the protrusion is formed by heating the resist, the protrusion can be easily formed.

  Application Example 4 In the substrate dry etching method according to the application example described above, in the step of forming the resist layer, a step of forming a first resist having a first interval on the substrate; Forming a second resist having a second spacing wider than the first spacing and a portion of the first resist overlapping, wherein the step of forming the plating layer includes: Preferably, the method includes a step of forming the plating layer.

  According to this application example, the concave portion can be easily formed on the substrate side of the plating layer by the first resist partially overlapping the second resist.

  Application Example 5 In the substrate dry etching method according to the application example, when the processing ratio r = the processing amount of the substrate / the processing amount of the plating layer, the height t3 of the protruding portion is t3 < It is preferable that the plating layer thickness t2− (the substrate thickness t1 / the processing ratio r).

  According to this application example, when the height t3 of the protrusion is set to t3 <thickness t2 of the plating layer (the thickness t1 / the processing ratio r of the substrate), the plating layer is etched when the substrate is etched. Even if the etching is performed, the etching does not reach the concave portion, and the concave portion can be reliably formed in the lower portion (substrate side) of the plating layer.

The perspective view which shows schematic structure of a tuning fork type crystal vibrating piece. The perspective view which shows schematic structure of a tuning fork type crystal vibrating piece. The schematic perspective view which shows the external shape patterning of the external shape process of a tuning fork type crystal vibrating piece. Process drawing which shows the outline of the external shape process based on 1st Embodiment in the manufacturing process of a tuning fork type crystal vibrating piece. It is sectional drawing explaining the protrusion part of a resist layer, (a) is a protrusion part of 1st Embodiment, (b) is a figure which shows the protrusion part of 2nd Embodiment. Process drawing which shows the outline of the external shape process based on 2nd Embodiment among the manufacturing processes of a tuning fork type crystal vibrating piece.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.

<First Embodiment>
The dry etching method according to the present invention will be described with reference to FIGS. 1 to 5 using an example in which the tuning fork type crystal vibrating piece is applied to the outer shape. 1 and 2 are perspective views showing a schematic configuration of a tuning fork type crystal vibrating piece. FIG. 3 is a schematic perspective view showing external patterning for external processing of a tuning fork type crystal vibrating piece. FIG. 4A to FIG. 4G are process diagrams showing an outline of the process related to the outer shape processing in the manufacturing process of the tuning-fork type crystal vibrating piece. 5A and 5B are cross-sectional views for explaining the protrusions of the resist layer. FIG. 5A shows the first embodiment, and FIG. 5B shows the second embodiment.

(Configuration of tuning-fork type crystal vibrating piece)
First, the configuration of a tuning fork type crystal vibrating piece to which the dry etching method according to the first embodiment of the present invention is applied will be described. As shown in FIG. 1, the tuning-fork type crystal vibrating piece 100 is cut out from, for example, a single crystal of quartz and processed into a tuning-fork type outer shape using a dry etching method. The tuning-fork type crystal vibrating piece 100 is cut out from a single crystal of crystal so that the X axis is an electric axis, the Y axis is a mechanical axis, and the Z axis is an optical axis. By arranging the electric shaft in the X-axis direction in this way, the tuning-fork type crystal vibrating piece 100 suitable for all electronic devices such as mobile phone devices that require high accuracy is obtained. In addition, when cutting from a single crystal of quartz, in the orthogonal coordinate system composed of the X-axis, Y-axis, and Z-axis described above, the XY plane composed of the X-axis and the Y-axis is about 1 degree counterclockwise around the X-axis. In addition, a tuning fork type crystal vibrating piece 100 is formed as a so-called crystal Z plate tilted by 5 degrees.

  The tuning-fork type crystal vibrating piece 100 includes a base portion 130 and arm portions 120 and 121 that are, for example, two vibrating arms formed so as to protrude from the base portion 130 in the Y-axis direction. A groove part 120a is provided on the surface side of the arm part 120, and a groove part 121a is provided on the surface side of the arm part 121 as a vibrating arm. A groove 120 a is also provided on the back side of the arm 120 as a vibrating arm, and a groove 121 a is also provided on the back side of the arm 121.

  In the tuning fork type crystal vibrating piece 100 shown in FIG. 1, the thickness in the Z-axis direction is, for example, about 0.1 mm, and the arm width (width in the X-axis direction) of the arm portions 120, 121 is about It is about 0.1 mm. The interval between the arm part 120 and the arm part 121 is about 0.06 mm. The groove widths (width in the X-axis direction) of the groove portions 120a and 121a are, for example, about 0.07 mm, and the groove depth (depth in the Z-axis direction) is, for example, about 0.02 to 0.045 mm. ing.

  In the tuning-fork type crystal vibrating piece 100 formed in this way, electrodes 140 and 141 are formed in the portions indicated by hatching in FIG. That is, the electrodes 140 and 141 are disposed from the base portion 130 to the two arm portions 120 and 121, and the electrodes 140 and 141 are also disposed on the side surfaces of the arm portions 120 and 121 and the groove portions 120a and 121a. The electrodes 140 and 141 arranged in this way generate an electric field when a voltage is applied from the outside, and vibrate the crystal arm portions 120 and 121 which are piezoelectric bodies.

  The tuning-fork type crystal vibrating piece 100 formed as described above can vibrate, for example, at a resonance frequency of 32.768 kHz. In the above-described configuration, for example, an outer shape having a configuration in which the interval between the arm portion 120 and the arm portion 121 is narrow with respect to the thickness of the tuning fork type crystal vibrating piece 100 is required. A dry etching method is used to form the outer shape of the tuning fork type crystal vibrating piece 100 having such a configuration. In the dry etching method, for example, as shown in FIG. 3, a mask pattern 53 is formed on the substrate 50, and the exposed portion 51 of the substrate 50 where the mask pattern 53 is not formed is plasma-etched using a reactive gas. Etching with an apparatus. Hereinafter, an outer shape forming method of the tuning fork type crystal vibrating piece 100 including this dry etching method will be described with reference to FIG.

(Outline forming method of tuning-fork type crystal vibrating piece)
With reference to FIG. 4A and FIG. 4B, the step of forming the first resist 102 and the step of forming the second resist 104 will be described.
First, in the step of preparing the substrate 110 prior to the formation of the first resist 102, as shown in FIG. 4A, a substrate 110 obtained by processing a so-called quartz Z plate into a plate shape is prepared. Then, the process proceeds to the step of forming the seed layer 105 on the upper surface 111 of the substrate 110. As an example, the seed layer 105 has a structure in which chromium (Cr) is formed on a base layer and copper (Cu), gold (Au), or the like is formed thereon. In forming the seed layer 105, a vacuum deposition method, a vacuum sputtering method, or the like can be used. By forming the seed layer 105 in this manner, the adhesion between the substrate 110 and the plating layer 103 can be increased. As a result, the etching selectivity, which is the ratio of the etching rate between the substrate 110 and the plating layer 103 constituting the mask, can be increased.

  Then, as shown in FIG. 4A, a first resist 102 that becomes a protrusion is formed on the upper surface 105 f of the seed layer 105. The first resist 102 is disposed with a first interval W1 on both sides of a non-etched region where the substrate 110 is not etched, that is, a metal plating layer 103 (see FIG. 4C) described later. For example, after the resist is applied to the upper surface 105f of the seed layer 105, the first resist 102 is patterned using a photolithography technique and an etching technique.

  Next, as shown in FIG. 4B, the second resist having the wall surface 106 having the second interval W <b> 2 on both sides of the non-etched region and disposed so as to overlap a part of the first resist 102. 104 is formed. That is, the second resist 104 is provided across the first resist 102 located outside the non-etched region and the upper surface 105 f of the seed layer 105 exposed outside the first resist 102. At this time, the second interval W2 is arranged to be wider than the first interval W1, which is the interval inside the first resist 102. By disposing the second resist 104 in this way, a part of the first resist 102 located on the substrate 110 side in a sectional view protrudes from the wall surface 106 of the second resist 104 located on the opposite side to the substrate 110. It becomes a protruding part. Also in the second resist 104, the shape of the second resist 104 is formed by patterning using, for example, a photolithography technique and an etching technique. The first resist 102 and the second resist 104 described above constitute a resist layer.

  As described above, by providing a resist layer composed of the second resist 104 and the first resist 102 partially overlapping with the second resist 104, a substrate of a plating layer 103 (see FIG. 4D) described later is provided. The concave portion 108 (see FIG. 4D) can be easily formed on the 110 side (lower portion).

  The first resist 102 and the second resist 104 can be either a negative type resist or a positive type resist based on a resin material, but in this embodiment, a negative type resist is used. When one side of the second resist 104 is a non-etched region, the first resist 102 protruding from the second resist 104 may be disposed on one side of the second resist 104 on the non-etched region side.

  Next, the process of forming the plating layer 103 that functions as a mask pattern will be described. As shown in FIG. 4C, the plating layer 103 is formed inside (non-etched region) the second interval W2 formed by the second resist 104. Specifically, the plating layer 103 has a second interval extending from the protruding portion (first resist 102) protruding from the wall surface 106 of the second resist 104 to the substrate 110 side and the upper surface 105f of the seed layer 105 exposed in the non-etched region. Provided inside W2. The plating layer 103 is configured by metal plating. The plated layer 103 in this embodiment is formed by nickel (Ni) plating. In addition, as another metal which comprises the plating layer 103, copper (Cu), gold | metal | money (Au), titanium (Ti), titanium tungsten (TiW) etc. can be mentioned as an example.

  Next, a process of removing the first resist 102 and the second resist 104 will be described. As shown in FIG. 4D, the first resist 102 and the second resist 104 are stripped leaving the plating layer 103. The first resist 102 and the second resist 104 are peeled by being immersed in a resist stripping solution. By peeling off the first resist 102 and the second resist 104, the plating layer 103 has side surfaces 107 formed on both sides opposite to the substrate 110 (upper surface side), and a recess recessed from the side surfaces 107 on both sides. 108 remains on the seed layer 105 as a structure formed on the substrate 110 side. That is, the plating layer 103 has a so-called T-shaped cross-sectional shape in which a connection portion with the seed layer 105 is recessed when viewed in cross-section.

  Next, the step of etching the seed layer 105 will be described. As shown in FIG. 4E, the seed layer 105 is removed by etching the exposed portion 105b (the portion to be etched) by, for example, a wet etching method using the plating layer 103 as a mask. Then, the substrate 110 is exposed in the portion where the seed layer 105 is removed, and the lower portion of the plating layer 103 becomes a base layer of the plating layer 103 as the remaining portion 105a.

  Next, a process of dry etching the substrate 110 will be described. As shown in FIG. 4F, in the step of dry etching the substrate 110, the etching is started on the exposed surface of the substrate 110 using the plating layer 103 as a mask, and the etched portion 110b is etched, thereby tuning fork type quartz crystal. The component 110a of the vibrating piece 100 is made to appear and the outer shape of the tuning fork type quartz vibrating piece 100 is formed. At this time, the plating layer 103 is also etched at a slower etching rate than the etching progress rate of the substrate 110. The etched portion of the plating layer 103 is indicated by a two-dot chain line as an etching portion 103b in the drawing, and the remaining portion is indicated as a remaining plating layer 103a.

In the dry etching, the substrate 110 is etched using a reaction gas such as carbon tetrafluoride (CF ₄ ) gas. In this embodiment, reactive ion etching in which carbon tetrafluoride (CF ₄ ) gas is ionized and radicalized by plasma to perform etching is used. In such dry etching, the etching proceeds in a direction perpendicular to the plane of the mask with the outer shape of the mask as a boundary, and therefore, in the plating layer 103, the wall surface 107a protruding on the side surfaces on both sides functions as the mask boundary. Therefore, even if the recess 108 is provided on the substrate 110 side of the plating layer 103, the etching shape is not affected. In this dry etching process, so-called deposition of forming an insulating layer on the etched exposed surface can be performed simultaneously with the progress of etching or alternately. As a reactive gas, for example, sulfur hexafluoride (SF _6), trifluoromethane (CHF ₃₎ it is possible to use a gas, such as.

  By performing dry etching using the plating layer 103 having such a recess 108 as a mask, the unevenness on the side wall of the plating layer 103 caused by fine unevenness on the surface of the substrate 110 is not formed. Thereby, it is possible to prevent the occurrence of a dimensional error in the etching shape of the substrate 110 caused by the unevenness of the side wall of the plating layer 103.

  Next, the process of peeling the plating layer 103 and the seed layer 105 will be described. The plating layer 103 and the seed layer 105 are peeled off from the substrate 110 on which the outer shape has been formed by the above-described dry etching, using respective stripping solutions. As a result, as shown in FIG. 4G, the outer shape of the tuning-fork type crystal vibrating piece 100, for example, two arms 120 and 121 are formed.

In the dry etching process described above, as shown in FIG. 5A, the height t3 of the concave portion 108 of the plated layer 103 (in other words, the first protrusion serving as a resist protrusion for forming the concave portion 108). The height of the resist 102 is preferably in the range determined by the following formula (2) from the relationship with the processing ratio r (formula (1)).
Processing ratio r = processing amount of substrate 110 / processing amount L of plating layer 103 (1)
When
The height t3 of the recess 108 (protrusion) <the thickness t2- of the plating layer 103 (the thickness t1 / the processing ratio r of the substrate 110) (2)
In addition, it is desirable to set the processing ratio r in the present embodiment to be in the range of 10 to 20, and when forming the outer shape of the tuning fork type crystal vibrating piece 100 of the present embodiment, the processing ratio r is set to It is set to about 15.

  By setting the height t3 of the recess 108 (projection) within the above range, even when the plating layer 103 is etched (processing amount L) when dry etching the substrate 110, the recess 108 is etched. The recess 108 can be reliably formed without reaching.

According to the outer shape forming method of the tuning fork type crystal vibrating piece 100 using the dry etching method as described above, the protrusion formed by the second resist 104 and the first resist 102 partially overlapping with the second resist 104. Depending on the portion, the concave portion 108 can be easily formed on the substrate 110 side (lower portion) of the plating layer 103.
The concave portion 108 formed on the side surface 107 of the plating layer 103 on the side of the substrate 110 causes the plating layer 103 even if there are fine irregularities on the upper surface 111 of the substrate 110 or a difference in thermal expansion between the resist and the substrate 110. The protrusion protruding from the side surface 107 is not formed, and the occurrence of dimensional variation in the etching shape of the substrate 110 due to the influence of the protrusion can be prevented. Thereby, in dry etching of the substrate 110, a desired outer shape can be formed with high accuracy, and the vibration characteristics of the tuning-fork type crystal vibrating piece 100 can be improved.

Second Embodiment
A second embodiment of the dry etching method according to the present invention will be described with reference to FIG. 6 using an example of applying to the outer shape processing of a tuning fork type crystal vibrating piece. FIG. 6A to FIG. 6G are schematic process diagrams showing the outer shape machining process according to the second embodiment in the manufacturing process of the tuning-fork type crystal vibrating piece. In the second embodiment, since the same tuning fork type crystal vibrating piece as in the first embodiment is used, the same components are denoted by the same reference numerals and description of the components is omitted.

(Outline forming method of tuning-fork type crystal vibrating piece)
The method for forming the outer shape of the tuning-fork type crystal vibrating piece of the second embodiment is different from the method of forming the concave portion provided on the substrate side of the plating layer in the first embodiment. Therefore, in the following description, different steps will be described, and description of similar steps will be omitted.

  First, as shown in FIG. 6A, a substrate 110 is prepared by processing a so-called quartz Z plate into a plate shape. Then, a seed layer 105 is formed on the upper surface 111 of the substrate 110. Since the seed layer 105 is the same as that of the first embodiment, the description thereof is omitted.

  Then, as illustrated in FIG. 6A, a resist layer 204 is formed on the upper surface 105 f of the seed layer 105. The resist layer 204 is formed at a site that later becomes an etching region. For example, after the resist is applied to the upper surface 105f of the seed layer 105, the resist layer 204 is patterned using a photolithography technique and an etching technique. As the resist layer 204, either a negative type resist or a positive type resist based on a resin material can be used, but in this embodiment, a negative type resist is used.

  Next, as shown in FIG. 6B, a process of forming the protrusions 202 on both sides of the resist layer 204 on the substrate 110 side (lower part) in the cross-sectional view will be described. In this step, the patterned resist layer 204 is heated to about 100 ° C. to form the protrusions 202 on both sides of the resist layer 204. Note that this heat treatment can be performed in a photolithography process for forming the resist layer 204. Specifically, in a baking process performed after applying a resist layer and patterning (exposure and development processes), the temperature can be set as appropriate. Therefore, it is not necessary to add a new process for the heat treatment.

  When the resist layer 204 is heated to a predetermined temperature, for example, about 100 ° C., the viscosity is lowered and the fluidity is improved. In the resist layer 204 that is heated and has increased fluidity, a skirt-like (fillet-like) protruding portion 202 appears on the side wall 206 on the substrate 110 side (below the resist layer 204) due to the influence of surface tension or gravity. . Thereafter, the protrusion 202 is formed by stopping the heating. As described above, the protrusion 202 can be easily formed by heating the resist layer 204.

  Next, a process for forming the plating layer 203 as a mask pattern will be described. As shown in FIG. 6C, the plating layer 203 is provided in a region where the resist layer 204 is not provided, that is, a region corresponding to a non-etched region. The plating layer 203 is configured by metal plating. The plated layer 203 in this embodiment is formed by nickel (Ni) plating. In addition, as another metal which comprises the plating layer 203, copper (Cu), gold | metal | money (Au), titanium (Ti), titanium tungsten (TiW) etc. can be mentioned as an example.

  Next, a process for removing the resist layer 204 will be described. As shown in FIG. 6D, the resist layer 204 is removed leaving the plating layer 203. The resist layer 204 is peeled by being immersed in a resist stripping solution. By peeling off the resist layer 204, the plating layer 203 has side surfaces 207 formed on both sides opposite to the substrate 110 (upper surface side), and has a skirt shape (fillet shape) from the side surfaces 207 on both sides. The concave portion 208 remains on the seed layer 105 as a structure formed on the substrate 110 side. That is, the plating layer 203 has a cross-sectional shape in which a connection portion with the seed layer 105 is recessed in a skirt shape when viewed in cross-section.

Next, as in the first embodiment, using the plating layer 203 as a mask, the seed layer 105 is etched as shown in FIG. 6E, and the substrate 110 is dry-etched as shown in FIG. 6F. By doing so, the outer shape of the tuning-fork type crystal vibrating piece 100 is formed.
As shown in FIG. 6E, the seed layer 205 is removed by etching the exposed portion 205b (etched portion) by, for example, wet etching using the plating layer 103 as a mask. Then, the substrate 110 is exposed in the portion from which the seed layer 205 has been removed, and the lower portion of the plating layer 203 serves as a base layer for the plating layer 203 as a remaining portion 205a.
As shown in FIG. 6 (f), in the step of dry etching the substrate 110, etching is started on the exposed surface of the substrate 110 using the plating layer 203 as a mask, and the etched portion 110b is etched, thereby tuning the quartz crystal. The component 110a of the vibrating piece 100 is made to appear and the outer shape of the tuning fork type quartz vibrating piece 100 is formed. At this time, the plating layer 203 is also etched at a slower etching rate than the etching progress rate of the substrate 110. The etched portion of the plating layer 103 is indicated by a two-dot chain line as an etching portion 203b in the drawing, and the remaining portion is indicated as a remaining plating layer 203a. Since dry etching is the same as that in the first embodiment, description thereof is omitted.

  By performing dry etching using the plating layer 203 having such a recess 208 as a mask, unevenness on the side wall of the plating layer 203 caused by fine unevenness on the surface of the substrate 110 is not formed. Thereby, it is possible to prevent the occurrence of a dimensional error in the etching shape of the substrate 110 caused by the unevenness of the side wall of the plating layer 203.

  Next, as in the first embodiment, the plating layer 203 and the seed layer 105 are peeled from the substrate 110 having the outer shape formed by dry etching. As a result, as shown in FIG. 6G, the outer shape of the tuning-fork type crystal vibrating piece 100, for example, two arms 120 and 121 are formed.

In the dry etching process described above, as shown in FIG. 5B, the height t3 of the recess 208 of the plating layer 203 is equal to the processing ratio r (formula (1)), as in the first embodiment. From this relationship, it is preferable to be within the range determined by the following formula (2). Note that the height of the recess 208 in the second embodiment is the height of the bottom shape that forms the protrusion 202 of the resist, that is, the distance between the recess 208 and the upper surface 111 of the substrate 110. In the second embodiment, the height of the recess 208 is a dimension from the upper surface 111 of the substrate 110 to a position where the side surface 207 of the plating layer 203 intersects the recess 208.
Processing ratio r = processing amount of substrate 110 / processing amount L of plating layer 203 (1)
When
The height t3 of the recess 208 (protrusion) <the thickness t2 of the plating layer 203 (the thickness t1 / the processing ratio r of the substrate 110) (2)

  By setting the height t3 of the recess 208 (projection) within the above range, even when the plating layer 203 is etched (processing amount L) when dry etching the substrate 110, the recess 208 is etched. The recess 208 can be reliably formed without reaching.

According to the outer shape forming method of the tuning-fork type crystal vibrating piece 100 using the dry etching method according to the second embodiment as described above, the substrate 110 of the plating layer 203 is formed by the protrusion 202 formed on the resist layer 204. A skirt-shaped concave portion 208 can be easily formed on the side (lower portion).
The concave portion 208 formed on the side surface 207 of the plated layer 203 on the substrate 110 side allows the plated layer 203 to be formed even if there are fine irregularities on the upper surface 111 of the substrate 110 or a difference in thermal expansion between the resist and the substrate 110. The protrusions protruding from the side surfaces 207 are not formed, and the occurrence of dimensional variations in the etching shape of the substrate 110 due to the influence of the protrusions can be prevented. Thereby, in dry etching of the substrate 110, a desired outer shape can be formed with high accuracy, and the vibration characteristics of the tuning-fork type crystal vibrating piece 100 can be improved.

  Although the example in which the seed layer 105 is provided between the substrate 110 and the plating layer 103 has been described above, the present invention can also be applied to a configuration in which the seed layer 105 is not provided. Specifically, the first resist 102, the second resist 104, and the plating layer 103 can be provided on the upper surface 111 of the substrate 110.

  In the above description, the method for forming the outer shape of the tuning-fork type crystal vibrating piece 100 using a quartz substrate has been described as an example. However, the dry etching method for a substrate according to the present invention is not limited to this. The substrate dry etching method according to the present invention can also be applied to, for example, a semiconductor substrate, a glass substrate, etc., and examples of using a quartz substrate include timing elements such as an AT-cut quartz vibrating piece and sensor elements such as a gyro sensor element. An example using a semiconductor substrate can be applied to a semiconductor element, or an example using a glass substrate to a glass package substrate.

  DESCRIPTION OF SYMBOLS 50 ... Board | substrate, 51 ... Exposed part, 53 ... Mask pattern, 100 ... Tuning fork type crystal vibrating piece, 102 ... First resist, 103, 203 ... Plating layer, 103a, 203a ... Remaining plating layer, 103b, 203b ... Plating layer 104 ... second resist, 105 ... seed layer, 105a ... residual portion of seed layer, 105b ... exposed portion of seed layer, 105f ... upper surface, 106 ... wall surface of second resist, 107,207 ... side surface, 107a , 207a ... wall surface, 108,208 ... concave, 110 ... substrate, 110a ... constituent part, 110b ... etched part, 111 ... upper surface, 120,121 ... arm part, 120a, 121a ... groove part, 130 ... base part, 140,141 ... Electrode, 202 ... Projection, 204 ... Resist layer, 206 ... Wall surface of resist layer.

Claims (5)

Preparing a substrate;
On the substrate, a step of forming a resist layer having a protruding portion protruding from the opposite side to the substrate on the substrate side in a sectional view;
Forming a plating layer on the substrate;
Look including the the steps of dry-etching the substrate with the plating layer as a mask,
In the step of forming the resist layer,
A method of dry etching a substrate, wherein the protrusion is formed by heating the resist after pattern formation .   Forming a first resist having a first portion and a second portion spaced apart from each other across a first opening having a first interval on one side of the substrate;
  The surfaces of the first resist opposite to the substrate are spaced apart from each other across a second opening having a second interval wider than the first interval and overlapping the first opening in plan view. Forming a second resist having a third portion and a fourth portion,
  Forming a plating layer on the first opening and the second opening;
  Using the plating layer as a mask, dry etching the substrate;
Including
  The step of forming the plating layer is a step of forming the plating layer having side surfaces in contact with the third portion and the fourth portion,
  The method for dry etching a substrate, wherein the step of dry etching is a step of performing the dry etching so that the etching proceeds perpendicularly to the substrate with the side surface as the boundary of the mask. Dry etching method of a substrate according to claim 1 or 2, characterized in that it comprises a step of forming a seed layer between the substrate and the plating layer. When processing ratio r = processing amount of the substrate / processing amount of the plating layer,
The height t3 of the protrusion is
t3 <thickness t2- of the plating layer (thickness t1 / thickness ratio r of the substrate)
The method for dry etching a substrate according to claim 1, wherein:   When processing ratio r = processing amount of the substrate / processing amount of the plating layer,
  The height t3 of the first part and the second part is:
  t3 <thickness t2- of the plating layer (thickness t1 / thickness ratio r of the substrate)
  The method for dry etching a substrate according to claim 2, wherein:

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