JP2011088107A - Method for manufacturing of filter, and filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily manufacture a high-performance filter at low cost. <P>SOLUTION: The filter 20 has a silicon single crystal with two or more holes 6 formed thereon, an opening of hole 6 is formed to the (110) plane of the silicon single crystal, and surfaces 6b1, 6b2, 6b3, and 6b4 forming a through-hole 6 are the (111) plane of the silicon single crystal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a filter for capturing a solid in a fluid and a method for manufacturing the filter.

  As a filter for capturing a solid in a fluid, such as fine foreign matter, or a method for manufacturing the filter, there are a twill method, a nonwoven fabric method, a press method, an etching method, a laser direct processing method, an electroforming method, etc. reference).

JP 2006-272631 A

However, it is difficult to form fine holes by the press method or the etching method. That is, the press method and the etching method have a low ability to capture fine foreign matters.
Further, in the twill method and the non-woven fabric method, the channel resistance is increased.
In addition, the electroforming method has a high manufacturing cost, and the laser method may generate scattered matters during filter manufacturing. For example, if scattered matter (debris from processing) adheres to the product filter, the quality of the product may deteriorate.

As described above, in the conventional technique, it is difficult to easily manufacture a high-performance filter at a low cost.
An object of the present invention is to easily manufacture a high-performance filter at low cost.

In order to solve the above problems, one embodiment of the present invention provides:
A filter manufacturing method for manufacturing a filter by forming a plurality of holes in a base material, wherein the base material is a material whose etching rate in a region altered by irradiation with laser light is larger than an etching rate in a region not altered The substrate is irradiated with a laser beam to form a modified portion obtained by modifying the material of the substrate to extend inside the substrate, and the modified portion that has been extended. A plurality of altered parts forming step in parallel in the substrate, an etching process for removing the altered part by etching from the surface of the base material, and forming a plurality of holes penetrating the base material, It is characterized by having.

With such a configuration, the hole formed by etching the altered portion can be made into a very fine hole. Moreover, a hole can be formed in a very thin base material with high density. Further, since the holes are formed through the etching process by irradiating with laser light, the holes are inexpensive and no scattered matter is generated.
Thus, a high performance filter can be easily manufactured at low cost.
Another aspect of the present invention is as follows:
The base is made of a material made of a single crystal, and further includes a patterning step of patterning an etching mask film having a pattern shape corresponding to the opening of the hole on the surface of the base, and forming the altered portion In the step, the altered portion is in a region surrounded by a range exposed from the pattern-shaped hole on the surface of the base material and a crystal lattice plane having the smallest etching rate that appears when etching proceeds in the range. The altered portion is formed so that the end portion of the present portion exists.

With such a configuration, the area exposed from the pattern-shaped hole on the surface of the base material and the crystal lattice plane with the smallest etching rate (less than other orientations) appearing by etching the area in the etching process By allowing the end portion of the altered portion to be present in the region surrounded by, etching can be reliably advanced along the altered portion.
Another aspect of the present invention is as follows:
The base material is composed of a silicon single crystal, and in the patterning step, the etching mask film is patterned on the (110) surface of the base material surface, and in the etching step, a hole penetrating the base material is formed. A plurality of layers are formed by wet etching.

With such a configuration, in the filter, the surface on which the hole is formed becomes the (111) surface, the surface on which the hole is formed becomes a highly smooth surface or a mirror surface, and the flow resistance of the hole is low.
Therefore, a high performance filter can be easily manufactured at low cost.
Another aspect of the present invention is as follows:
In the altered portion forming step, the laser light is transmitted through a diffractive optical element, branched into a plurality of beams, and irradiated onto the base material.

With such a configuration, a plurality of altered portions can be formed simultaneously.
Another aspect of the present invention is as follows:
In the altered portion forming step, the laser beam is transmitted through an axicon element that forms a long line image in the focal direction along the optical axis, thereby forming a condensing region of the laser beam extending in the thickness direction of the substrate. The modified portion extending in the thickness direction is formed by the condensing region of the laser beam.

With such a configuration, the altered portion extending in the thickness direction of the plate-like body can be formed in a short time.
Another aspect of the present invention is as follows:
A silicon single crystal having a plurality of through holes is formed, the opening of the through hole is formed in a (110) plane of the silicon single crystal, and the surface forming the through hole is formed of the silicon single crystal. It is a (111) plane.

With such a configuration, in the filter, the surface on which the hole is formed becomes the (111) surface, the surface on which the hole is formed becomes a highly smooth surface or a mirror surface, and the flow resistance of the hole is low.
Therefore, the filter is a high-performance filter and is easily manufactured at a low cost.
Another aspect of the present invention is as follows:
The through hole is formed by wet etching.

With such a configuration, the through hole can be easily formed by wet etching.
Another aspect of the present invention is as follows:
The hole has a width of 15 μm or more and 20 μm or less, a thickness of a wall separating adjacent holes is 5 μm or more and 10 μm or less, and the length of the hole is 200 μm or more. It is characterized by that.

With such a configuration, even when a relatively long hole such as 200 μm or more is required, the hole diameter can be reduced and the wall thickness of the hole can be reduced, that is, the hole pitch can be reduced.
Therefore, the filter is a high-performance filter and is easily manufactured at a low cost.

Another aspect of the present invention is as follows:
A filter having a plurality of holes, wherein the base material is made of a material whose etching rate in a region altered by laser light irradiation is larger than an etching rate in a region that is not altered, and the holes penetrating the base material are A plurality of isotropic etchings, the length of the hole is t, and the interval between adjacent holes is p,
p <t
It has the site | part where this relationship is materialized.

With such a configuration, the filter has a short pitch regardless of the length of the holes, and the holes are formed at a high density.
Therefore, the filter is a high-performance filter and is easily manufactured at a low cost.

It is a flowchart which shows each process of the manufacturing method of the filter of 1st Embodiment. It is a schematic sectional drawing of the board | substrate etc. in each process of the manufacturing method of a filter. It is sectional drawing which shows the detail of the A section of FIG.2 (d-1). It is sectional drawing which shows the process in which etching advances the inside of the board | substrate with which the modified part was formed. It is sectional drawing which shows the shape of the board | substrate which passed through the etching process. It is a figure which shows the shape of the filter manufactured by the manufacturing method of the filter of 1st Embodiment. It is a perspective view which shows the flow path of the rectangular cross section used for description of flow path resistance. It is a perspective view which shows the flow path of the circular pipe used for description of flow path resistance. It is the figure used for description of the structure which patterns an etching mask film | membrane by irradiation of a laser beam. It is the figure used for description of the structure which irradiates a laser beam to multiple places simultaneously by making the fundamental wavelength light of a laser branch into multiple points simultaneously with a diffractive optical element. It is the figure used for description of the structure which permeate | transmits the fundamental wavelength light of a laser to an axicon element. It is sectional drawing which shows the shape of the board | substrate which passed through the etching process in 2nd Embodiment. It is a figure which shows the shape of the filter manufactured by the manufacturing method of the filter of 2nd Embodiment. It is a figure which shows the comparative example with respect to this embodiment, and shows that the pitch p of the hole of an etching mask film is smaller than the board thickness t of a board | substrate (p <t). It is a figure which shows the comparative example with respect to this embodiment, and shows that the pitch p of the hole of an etching mask film | membrane is larger than the board thickness t of a board | substrate (p> t). It is sectional drawing which shows the shape of the board | substrate in the quality-change part formation process and etching process when a protective film is unnecessary. It is a figure which shows the shape of a board | substrate when patterning and etching an etching mask film | membrane only to one side of a board | substrate.

(First embodiment)
(Constitution)
The first embodiment is a method for manufacturing a filter to which the present invention is applied.
In the first embodiment, a filter is manufactured using a substrate having a plane orientation (110) made of a material made of silicon single crystal as a base material.

FIG. 1 shows each process of the manufacturing method of the filter of this embodiment. FIG. 2 is a schematic cross-sectional view of the substrate 10 and the like in each step.
As shown in FIG. 1, the manufacturing method of the filter of this embodiment includes a protective film forming step (Step S1), a patterning step (Step S2), an altered portion forming step (Step S3), an etching step (Step S4), and It has a protective film peeling process (step S5).

(Step S1: Protective film formation process)
In the filter manufacturing method of the present embodiment, first, the protective film 2 is formed on the substrate 10 (FIG. 2A) in the protective film forming step. In this protective film forming step, as shown in FIG. 2B, SiO ₂ films (silicon oxide films) are formed on the both surfaces 11 and 12 of the substrate 10 as the protective film 2. In this protective film forming step, a SiN film (silicon nitride film) can also be formed as the protective film 2.

(Step S2: Patterning process)
In the filter manufacturing method of this embodiment, the etching mask film 3 is patterned from the protective film 2 on both surfaces 11 and 12 of the substrate 10 in the subsequent patterning process (etching mask film forming process). In this patterning step, as shown in FIG. 2C, the etching mask film 3 is formed on both surfaces (surfaces) 11 and 12 which become the (110) surface by photolithography (resist film application, exposure and development) and protective film etching. Is patterned.

At this time, in the patterning step, the etching mask film 3 is patterned in accordance with the hole for forming the filter. That is, the etching mask film 3 is patterned according to the shape and size of the holes in the filter, the pitch between adjacent holes, the arrangement pattern of the holes, and the like. In the first embodiment, the hole arrangement pattern is a square arrangement pattern.
For example, the process of forming the etching mask film 3 by the protective film forming process and the patterning process is as follows.

In the protective film forming step, a SiO ₂ film is formed by a thermal oxidation method. In the subsequent patterning step, a resist is applied onto the SiO ₂ film by a spin coating method, and a resist pattern is formed using a photolithography technique. In the patterning step, the SiO ₂ film is removed according to the resist pattern shape using a hydrofluoric acid solution or the like, and the resist pattern that is no longer needed is peeled off to form the etching mask film 3.

(Step S3: Altered part forming step)
In the filter manufacturing method of the present embodiment, the substrate 10 is irradiated with an infrared laser in the subsequent altered portion forming step (laser light irradiation step) to form the altered portion of the material.
The infrared laser is a laser that is transparent to the substrate 10 made of a material made of silicon single crystal. The infrared laser used here is, for example, a YAG laser, a YVO ₄ laser, or a YLF laser.
In the altered portion forming step, the fundamental wavelength light 30 of the infrared laser is transmitted through the lens 31 and condensed in the substrate 10. In the altered part forming step, the condensing point is moved in the thickness direction of the substrate 10.

  At this time, the moving direction of the condensing point along the thickness direction of the substrate 10 is a direction from the surface 11 on the laser incident side toward the surface 12 opposite to the surface 11. That is, the moving direction of the condensing point along the thickness direction of the substrate 10 is the thickness direction starting from the surface 11 of the substrate 10. In addition, the moving direction of the condensing point along the thickness direction of the substrate 10 may be the opposite direction.

In the following description, out of the surface or both surfaces 11 and 12 of the substrate 10, the surface 11 on which the laser is incident is referred to as the first surface 11, and the surface 12 opposite to the first surface 11 is the second surface. It is called 12.
Thus, when the moving direction of a condensing point is made into the direction which goes to the 1st surface 11 side from the 2nd surface 12 side, as shown in FIG.2 (d-1), predetermined position P1 on the 2nd surface 12 side is shown. To the movement start position of the condensing point. In the altered portion forming step, as shown in FIG. 2D-2, the condensing point is moved from the second surface 12 side to the first surface 11 side in the thickness direction of the substrate 10. Then, in the altered part forming step, the movement and the irradiation of the laser beam are terminated when the condensing point reaches the predetermined position P2 on the first surface 11 side.

The predetermined position P2 on the first surface 11 side and the predetermined position P1 on the second surface 12 side of the substrate 10 will be described in detail later.
In the altered portion forming step, it is preferable to appropriately control the intensity of the laser beam and the degree of condensing (depth of focus) according to the movement of the condensing point. Specifically, in the altered portion forming step, it is preferable to control to increase the energy of the laser beam at the condensing point as the condensing point is closer to the second surface 12 side.

By the laser light irradiation as described above, the altered portion 4 of the material is formed in the substrate 10 along the moving path of the condensing point along the thickness direction of the substrate 10 (FIG. 2D-3). )).
Then, in the altered portion forming step, laser light is irradiated in correspondence with the arrangement of the pattern-shaped holes 3a and 3b of the etching mask film 3, and parallel to the substrate 10 as shown in FIG. A plurality of altered portions 4 are formed (in the width direction or the surface direction).

Therefore, in the altered part forming step, the substrate 10 is irradiated with laser light as described above while the substrate 10 and the laser are relatively moved in the width direction of the substrate 10. For example, in the altered part forming step, the workpiece is moved by moving the substrate 10 using an XY table, and the moving substrate 10 is irradiated with laser light.
In the altered part forming step, the laser beam can be moved by a galvano scanner.

(Step S4: Etching process)
In the filter manufacturing method of the present embodiment, a plurality of holes are formed in the substrate 10 in the subsequent etching process. In this etching process, anisotropic etching is performed by wet etching. Specifically, in the etching process, the substrate 10 is immersed in an aqueous solution 5 of potassium hydroxide (KOH). As a result, in the etching process, as shown in FIGS. 2E and 2F, the etching is advanced in correspondence with the pattern-shaped holes 3a and 3b of the etching mask film 3, and both surfaces 11 of the substrate 10 are formed. , 12 are formed in plural numbers.

Here, the reason why the positions of the condensing points at the start and end of the movement are set to the predetermined positions P1 and P2 as described above will be described.
FIG. 3 shows the details of part A of FIG. 2 (d-1).
When etching is performed, in an initial stage, as shown in FIG. 3, a surface exposed on the second surface 12 of the substrate 10 by the holes (pattern-shaped holes) 3b of the etching mask film 3 (hereinafter referred to as substrate exposed surface). 12a is etched. If the etching is continued as it is, the edges 13a and 13b of the pattern-shaped hole 3b on the second surface 12 of the substrate 10 have a predetermined angle with respect to the second surface 12 of the substrate 10 in the direction of the central axis of the hole 3b. The surfaces 14a and 14b extending in the direction appear.

Here, the surfaces 14a and 14b are (111) planes which are crystal lattice planes, and have extremely low etching rates or are difficult to be etched compared to other orientations. Therefore, the etching stops on the surfaces 14a and 14b.
For this reason, the predetermined position P1, which is the position of the condensing point at the start of movement, is an arbitrary position within a region surrounded by the substrate exposed surface 12a of the second surface 12 and the surfaces 14a and 14b where etching stops. Position. Therefore, the vertical depth of the second surface 12 from the substrate exposed surface 12a to the predetermined position P1 is shallower than the vertical depth from the substrate exposed surface 12a to the intersection of the surface 14a and the surface 14b.

Thus, in the altered portion forming step, one end portion 4b is present in a region surrounded by the substrate exposed surface 12a of the second surface 12 and the surfaces 14a and 14b on the second surface 12 side in the substrate 10. The denatured portion 4 is formed.
The same applies to the predetermined position (P2) that is the position of the condensing point at the end of the movement. That is, the predetermined position that is the position of the condensing point at the end of the movement is an arbitrary position within a region surrounded by the substrate exposed surface of the first surface 11 and the surface where etching stops on the first surface 11 side. .

FIG. 4 shows a process in which etching proceeds in the substrate 10 in which the altered portion 4 is formed.
As shown in FIG. 4A, in the initial stage of etching, the substrate exposed surfaces 11a and 12a of both surfaces 11 and 12 are etched. Then, the surfaces (a (111) surface) 14a, 14b, 15a, 15b having a slow etching rate appear from the initial stage of etching. As a result, the substrate exposed surfaces 11a and 12a surrounded by the surfaces 14a, 14b, 15a and 15b are subjected to etching. Further, when the etching of the substrate exposed surfaces 11a and 12a proceeds, the etching reaches the altered portion 4 (specifically, the end portions 4a and 4b).

  Here, the altered portion 4 is formed by irradiating a silicon single crystal with laser light, thereby breaking the bonds of atoms in the single crystal, generating microcracks, or destroying the crystallinity. It has been done. The etching rate of the altered portion 4 is much higher than that of the unmodified material region. That is, the altered portion 4 is more easily etched than a region of material that has not been altered.

For this reason, when the etching reaches the altered portion 4, the etching proceeds along the altered portion 4 as shown in FIG. As a result, a hole 6a is formed in advance in the substrate 10 along the altered portion 4 removed by etching.
And the hole 6a formed in advance in this way becomes a hole which induces etching, and etching advances. As shown in FIG. 4C, planes 16 and 17 parallel to the thickness direction of the substrate 10 appear as the etching progresses through the holes (hereinafter referred to as etching induction holes) 6a. The surfaces 16 and 17 are formed by (111) surfaces.

Then, as shown in FIG. 4D, the etching stops at the stage where the surfaces 16 and 17 are connected. As a result, a hole 6 penetrating both surfaces 11 and 12 is formed in the substrate 10.
As described above, in the etching process, the etching induction hole 6a is formed along the altered portion 4, and the etching induction hole 6a is enlarged by the etching, and the hole 6 penetrating the both surfaces 11 and 12 of the substrate 10 is finally formed. Formed.

  2 (f) and 5 show the shape of the substrate 10 after the etching process. Fig.5 (a) is a top view of the board | substrate 10, FIG.5 (b) (FIG.2 (f)) is sectional drawing of the board | substrate 10 of arrow AA shown to Fig.5 (a). As shown in FIGS. 2F and 5, a plurality of holes 6 corresponding to the etching mask film 3 are formed in the substrate 10. And the cross-sectional shape of the hole 6 becomes a rhombus.

  Here, as described above, in the etching process, the surfaces 16 and 17 are connected to each other, the etching is stopped, and the hole 6 is formed. At this time, the surface 16 and the surface 17 are constituted by (111) surfaces located in the same plane. Therefore, each surface 6b1, 6b2, 6b3, 6b4 forming the hole 6 is constituted by a (111) surface located in the same plane.

(Step S5: Protective film peeling step)
In the filter manufacturing method of this embodiment, the protective film (etching mask film 3) is peeled from the substrate 10 in the subsequent protective film peeling step. Here, when the protective film is an SiO ₂ film, the protective film is peeled off by wet etching using an HF-based protective film peeling solution. When the protective film is a SiN film, it is peeled off by dry etching.
In the filter manufacturing method of this embodiment, the filter 20 is manufactured through the above steps.

  FIG. 2G and FIG. 6 show the shape of the filter 20. Fig.6 (a) is a top view of the filter 20, FIG.6 (b) (FIG.2 (g)) is sectional drawing of the filter 20 of the arrow BB shown to Fig.6 (a). As shown in FIGS. 2 (g) and 6, the filter 20 has a plurality of holes 6 arranged in a square array. Here, the opening 6c of the hole 6 is formed in the (110) plane.

(Function and effect)
As described above, in the filter manufacturing method of the present embodiment, the surfaces 14a, 14b, 15a, and 15b ((111) surface) where the etching rate becomes small appear at the initial stage of the etching process.

In contrast, in the filter manufacturing method of the present embodiment, the altered portion 4 is formed in advance on the substrate 10 in the altered portion forming step that is a pre-process of the etching step. As a result, in the filter manufacturing method of the present embodiment, the surfaces 14a, 14b, 15a, 15b whose etching rate is reduced by etching are removed, and the holes 6 penetrating the both surfaces 11, 12 are formed.
And in the manufacturing method of the filter of this embodiment, the hole of the filter 20 can be made very fine by making the magnitude | size (diameter) of the quality change part 4 small. For example, the hole diameter (maximum diameter) of the filter 20 can be set to 20 μm or less, specifically about 15 μm.

  Furthermore, in the filter manufacturing method of the present embodiment, the wall separating the adjacent holes 6 by the filter 20 can be made extremely thin. Specifically, in the filter manufacturing method of the present embodiment, the thickness of the wall separating the adjacent holes 6 (the thickness w of the wall 18 shown in FIG. 2G) is set to 5 μm or more and 10 μm or less. be able to. Moreover, in the manufacturing method of the filter of this embodiment, the thickness of the wall which separates the adjacent hole 6 can also be made into less than 5 micrometers.

In the filter manufacturing method of this embodiment, the adjacent holes 6 are separated by the filter 20 by narrowing the pitch between adjacent holes (3a and 3a and 3b and 3b) in the etching mask film 3. The wall can be made extremely thin.
As described above, in the filter manufacturing method of the present embodiment, the filter 20 having a small diameter of the hole 6 and a thin wall separating the holes 6, that is, a filter 20 having a narrow pitch of the holes 6 can be manufactured. As a result, the filter has a very high density of holes 6.

Here, the pitch of the holes 6 is the distance between the centers of the openings 6 c of the adjacent holes 6.
In the filter manufacturing method of the present embodiment, the shape of the hole 6 formed in the filter 20 depends on the shape of the altered portion 4. Therefore, in the filter manufacturing method of the present embodiment, the accuracy of the shape of the hole 6 formed in the filter 20 can be increased by increasing the accuracy of forming the altered portion 4 (laser light irradiation accuracy, etc.). . As a result, in the filter manufacturing method of the present embodiment, variations in the shape of the holes 6 can be suppressed.

Further, in the filter manufacturing method of the present embodiment, since the holes 6 can be formed in the substrate 10 as long as the length of the altered portion 4 in the thickness direction of the substrate 10 can be ensured, the filter 20 is manufactured without limiting the thickness. it can. That is, in the filter manufacturing method of the present embodiment, the degree of freedom of the thickness of the filter 20 can be increased.
For example, as a method for forming holes in the filter, only dry etching is performed on a substrate having a plane orientation (110) of a silicon single crystal without irradiating the laser beam (forming an altered portion) as in this embodiment. A method of forming holes is also conceivable.

Here, the depth of the dry etching (digging amount) is normally about 200 μm at maximum if a relatively large large area is targeted.
For example, when the dry etching depth (digging depth) is 200 μm or more, the protective film is considered to be exhausted and the protective film is made extremely thick or disappears during the dry etching. It is necessary to form each time. Further, when it is attempted to ensure the depth of dry etching, it becomes difficult to form the holes themselves or to ensure the accuracy of the shape of the holes due to the occurrence of side etching or the receding of the protective film.

Thus, when the depth (digging amount) of dry etching is set to 200 μm or more, it becomes impractical. Therefore, the depth (digging amount) of dry etching is about 200 μm at the maximum as described above. That is, the maximum filter thickness or hole length that can be handled when holes are formed by dry etching is about 200 μm.
On the other hand, in the filter manufacturing method of the present embodiment, as described above, the filter 20 can be manufactured without limiting the thickness. That is, according to the filter manufacturing method of the present embodiment, a filter 20 having a thickness of 200 μm or more that has a limit thickness or the length of the hole 6 can be manufactured by dry etching.

Here, the length of the hole 6 is the distance between the center of the opening 6 c formed in the first surface 11 and the center of the opening 6 c formed in the second surface 12.
Moreover, according to the manufacturing method of the filter of this embodiment, the lower limit side of the thickness can be set to about 10 μm. Thus, according to the filter manufacturing method of the present embodiment, the degree of freedom of the thickness of the filter 20 is high. As a result, according to the filter manufacturing method of the present embodiment, the degree of freedom in designing the filter 20 can be increased.

Here, a general formula for calculating the channel resistance in the pipeline will be described. This will be described with reference to FIGS.
As shown in FIG. 7, in the case of a rectangular tube (rectangular hole) in which the long side of the rectangular cross section is a, the short side of the rectangular cross section is b, and the flow path length is L, the flow path resistance is Can be expressed as a value R obtained by the following equation.

R = (64 · η · L / (a · b ³ ) · (16 / 3-1024 · b / (π ⁵ · a) · (tanh (π · a / (2 · b)) + 1/3 ⁵ · tanh (3 · π · a / (2 · b)))
Further, in the case of a circular tube having a circular tube diameter d and a flow channel length L as shown in FIG. 8, when the viscosity is η, the flow channel resistance is shown as a value R obtained by the following equation. be able to.
R = 128 · η · L / (π · d ⁴ )
According to the above equation of channel resistance, the channel resistance increases when the tube diameter (a, b, or d) is small or the tube (L) is long. When this relationship is applied to the filter 20, if the diameter of the hole 6 of the filter 20 is small, the flow path resistance increases. Further, when the total length of the hole 6 of the filter 20 is long (when the filter 20 is thick), the flow path resistance increases. On the other hand, when the diameter of the hole 6 is small, the filter 20 has a high capability of capturing fine foreign matters and a function as a filter.

  For this reason, in order to increase the capture capability of fine foreign matters while suppressing the flow resistance, the filter 20 is formed with extremely fine and high-density holes 6 (the number of holes 6 per unit area). Many), and it is required to be extremely thin.

  On the other hand, according to the filter manufacturing method of this embodiment, the ultrafine holes 6 can be formed with high density as described above. Furthermore, according to the filter manufacturing method of the present embodiment, the thickness is flexible as described above, and the filter 20 can be made extremely thin. Therefore, according to the filter manufacturing method of the present embodiment, it is possible to provide a filter 20 having a high performance of capturing fine foreign matters while suppressing flow resistance. That is, the filter manufacturing method of the present embodiment can easily manufacture a high-performance filter at low cost.

In addition, as described above, each surface (four surfaces) forming the hole 6 is composed of (111) surfaces located in the same plane, so that the surface having high smoothness in the order of the crystal lattice or It becomes mirror-like. Thereby, the channel resistance of the hole 6 is reduced.
From the above, the characteristics of the filter 20 manufactured by the filter manufacturing method of the present embodiment are summarized as follows.

(1) The hole 6 is very fine. For this reason, fine foreign matter can be captured, and the ability to capture fine foreign matter is high.
(2) The holes 6 have a high density. Therefore, the channel resistance of the filter 20 as a whole is small. Thereby, even if it reduces in size, the capture capability is still high.
(3) Variation in the shape (diameter) of the holes 6 is small. Therefore, the capture selectivity of fine foreign matters is high.

(4) No debris is generated during the machining process. Therefore, there is no adhesion of waste and there is no contamination. Thereby, it is high quality.
(5) Since the material of the filter 20 is oxidized silicon, chemical resistance is high.

  For example, the filter 20 having such characteristics can be disposed in the ink flow path of the inkjet head. Moreover, it can arrange | position in the liquid flow path to which the technique of microTAS (Micro Total Analysis System) and MEMS (Micro Electro Mechanical Systems) was applied, for example, a chemical | medical solution flow path.

  Further, as described above, in the altered portion forming step, the condensing point is moved from the second surface 12 side to the first surface 11 side in the substrate 10. Thereby, in a quality change part formation process, it can prevent that the laser beam which forms a condensing point interferes with quality change part 4 which has already formed. As a result, the altered portion 4 can be formed with high accuracy in the altered portion forming step.

(Modification of the first embodiment)
(Modification 1)
In the patterning step, the etching mask film 3 can be patterned by removing unnecessary portions (hole forming portions of the substrate 10) of the protective film 2 by laser light irradiation, as shown in FIG. .

  Thereby, the photolithography process which is one process for manufacturing the filter 20 can be omitted. And if the irradiation equipment of the laser beam used at an altered part formation process is utilized, the filter 20 can be provided cheaply as a result. Needless to say, the protective film 2 can be processed by laser beam irradiation equipment dedicated to film processing.

(Modification 2)
In the altered portion forming step, as shown in FIG. 10, the laser fundamental wavelength light 30 can be simultaneously branched at multiple points by the diffractive optical element 32, and the laser light can be simultaneously irradiated to a plurality of target locations.
As a result, in the altered part forming step, a plurality of altered parts 4 can be formed in the substrate 10 by a single laser light irradiation scan. As a result, in the altered portion forming step, the number of scans of laser light irradiation can be reduced, and the manufacturing time of the filter 20 can be shortened.

(Modification 3)
In the altered part forming step, as shown in FIG. 11, the fundamental wavelength light 30 of the laser can be transmitted through the axicon element 33. Since the axicon element 33 is an optical element that creates a line image that is long in the focal direction along the optical axis, the laser light forms a condensing region (long focal point) extending in the thickness direction of the substrate 10. Become.
Thereby, in the altered part forming step, the altered part 4 extending in the thickness direction of the substrate 10 can be formed by one-time laser light irradiation, and the manufacturing time of the filter 20 can be shortened.

(Modification 4)
In the altered portion forming step, the altered portion 4 can also be formed by appropriately switching on and off of the fixedly arranged laser in synchronization with the rotation of the substrate 10 while rotating the substrate 10 at a high speed.
This eliminates the movement of accelerating / decelerating the substrate 10 as when the substrate 10 is moved by the XY table, thereby reducing the waste of manufacturing time.

(Modification 5)
The filter 20 can also be manufactured using the substrate 10 having a plane orientation (100) made of a material made of silicon single crystal as a base material.

(Second Embodiment)
(Constitution)
The second embodiment is a method for manufacturing a filter to which the present invention is applied.
In the second embodiment, a filter is manufactured using a substrate made of glass as a base material.
The steps of the filter manufacturing method of the second embodiment are the same as the steps of the filter manufacturing method of the first embodiment shown in FIG.

(Step S1: Protective film formation process)
In the filter manufacturing method of the present embodiment, first, the protective film 2 is formed on the substrate 10 (FIG. 2A) in the protective film forming step. In this protective film forming step, a Cr / Au film is formed as the protective film 2 on both surfaces 11 and 12 of the substrate 10 (FIG. 2B). In this protective film forming step, a Si film can be formed as the protective film 2.

(Step S2: Patterning process)
In the filter manufacturing method of the present embodiment, the etching mask film 3 is patterned in the subsequent patterning process (etching mask film forming process). In this patterning step, similarly to the first embodiment, the etching mask film 3 is patterned by photolithography (resist film application, exposure and development) and protective film etching (FIG. 2C).

  At this time, the etching mask film 3 is patterned according to the hole for forming the filter 20. That is, the etching mask film 3 is patterned according to the shape and size of the holes in the filter 20, the pitch between adjacent holes, the hole arrangement pattern, and the like. In the second embodiment, the hole arrangement pattern is a staggered arrangement pattern.

(Step S3: Altered part forming step)
In the method for manufacturing a filter according to the present embodiment, the altered portion 4 is formed by irradiating the substrate 10 with laser light in the subsequent altered portion forming step (laser beam irradiation step). In the second embodiment, an ultrashort pulse laser is used as the laser. The ultrashort pulse laser is a pulse laser of, for example, p seconds (picoseconds) or f seconds (femtoseconds).

As in the first embodiment, in the altered portion forming step, the fundamental wavelength light 30 of the laser is condensed in the substrate 10 by the lens 31, and the condensing point is the thickness direction of the substrate 10 (second In the direction from the surface 12 side toward the first surface 11 side).
Due to such laser light irradiation, an altered portion 4 of the material is formed in the substrate 10 along the moving path of the condensing point (thickness direction of the substrate 10) (FIG. 2 (d-3)).

  Here, in the said 1st Embodiment, the site | part ((111) plane) where an etching rate becomes slow existed in the board | substrate 10. FIG. On the other hand, in the second embodiment, since the substrate 10 is made of glass, there is no portion where the etching rate is slow. Therefore, in the second embodiment, the condensing point of the laser light can be moved in the thickness direction of the substrate 10 without considering the position of the condensing point at the start of movement and at the end of movement.

(Step S4: Etching process)
In the filter manufacturing method of the present embodiment, the plurality of holes 6 are formed in the substrate 10 in the subsequent etching process. In this etching process, isotropic etching is performed by wet etching. Specifically, in the etching process, the substrate 10 is immersed in an aqueous solution 5 such as HF (hydrofluoric acid) or BHF (buffered hydrofluoric acid). As a result, in the etching process, as shown in FIGS. 2E and 2F, the etching is advanced in correspondence with the pattern-shaped holes 3a and 3b of the etching mask film 3, and both surfaces 11 of the substrate 10 are formed. , 12 are formed in plural numbers. At this time, in the etching process, the etching progress is controlled by setting the etching time, and the target hole diameter is set.

  FIG. 12 shows the shape of the substrate 10 after the etching process. 12A is a plan view of the substrate 10, and FIG. 12B is a cross-sectional view of the substrate 10 taken along the line CC shown in FIG. 12A. As shown in FIG. 12, a plurality of holes 6 corresponding to the etching mask film 3 are formed in the substrate 10. And the cross-sectional shape of the hole 6 becomes circular. Specifically, the hole 6 has a substantially drum shape in which the diameter is large in the vicinity of both surfaces 11 and 12 and the diameter is small in the middle portion. For example, the minimum diameter of the intermediate portion of the hole 6 can be controlled by appropriately setting the etching time in the etching process.

(Step S5: Protective film peeling step)
In the filter manufacturing method of this embodiment, the protective film (etching mask film 3) is peeled from the substrate 10 in the subsequent protective film peeling step. Here, when the protective film is a Si film, it is peeled off using a protective film peeling solution of potassium hydroxide (KOH).
In the filter manufacturing method of this embodiment, the filter 20 is manufactured through the above steps.

  FIG. 13 and FIG. 2G show the shape of the filter 20. 13A is a plan view of the filter 20, and FIG. 13B (FIG. 2G) is a cross-sectional view of the filter 20 indicated by arrows DD shown in FIG. 13A. . As shown in FIGS. 13 and 2 (g), the filter 20 has a plurality of holes 6 in a staggered arrangement.

(Function and effect)
In the second embodiment, the same effect as in the first embodiment can be obtained.
That is, in the filter manufacturing method according to the second embodiment, as described above, the altered portion 4 is formed in the substrate 10 in the altered portion forming step, and then the holes 6 are formed in the substrate 10 by the etching step.

  At this time, since the etching rate of the altered portion 4 is much higher than that of the unmodified portion, the hole 6 is formed depending on the altered portion 4 and the etching induction hole 6a formed by the altered portion 4. Yes.

Thereby, in the manufacturing method of the filter of 2nd Embodiment, the hole 6 of the filter 20 can be made very fine by making the magnitude | size (diameter) of the quality change part 4 small. That is, for example, in the filter manufacturing method of the second embodiment, if the etching is completed when the etching induction hole 6a is formed by adjusting the etching time in the etching process, the ultrafine hole 6 can be formed. become.
Since the etching guide hole 6a is formed in advance, the hole 6 of the filter 20 has a substantially drum shape as shown in FIG.

As described above, the filter manufacturing method of the second embodiment can also manufacture the filter 20 having a small diameter of the hole 6 and a thin wall separating the holes 6, that is, the filter 20 having a narrow pitch of the holes 6. As a result, the filter has a very high density of holes 6.
Further, in the filter manufacturing method of the second embodiment, the hole 6 can be formed extremely finely without being affected by isotropic etching.

14 and 15 show a comparative example of this embodiment. The comparative example is an example in which holes are formed by isotropic etching without forming an altered portion (without irradiating a laser beam). That is, the comparative example is an example in which holes are formed by utilizing the characteristics of isotropic etching.
FIG. 14 shows a case where the pitch p of the holes 3a and 3b of the etching mask film 3 is smaller than the plate thickness t of the substrate 10 (p <t). FIG. 15 shows a case where the pitch p of the holes 3a and 3b of the etching mask film 3 is larger than the plate thickness t of the substrate 10 (p> t).

  As shown in FIG. 14, in the isotropic etching, the substrate exposed surfaces 11a and 12a exposed by the holes 3a and 3b of the etching mask film 3 on both surfaces 11 and 12 are cut into a spherical shape (FIG. 14). a) and FIG. 14 (b)). Therefore, as the etching progresses, the substrate 10 is turned to the back side of the etching mask film 3 (FIG. 14C). When the etching further proceeds, before the hole-shaped substrate exposed surfaces 11a and 12a proceeding from both surfaces 11 and 12 penetrate each other, adjacent substrate exposed surfaces (11a and 11a and 12a 12a) pass through each other (FIG. 14D).

As described above, when the pitch p is smaller than the plate thickness t, holes penetrating the both surfaces 11 and 12 cannot be formed by isotropic etching.
For this reason, as shown in FIG. 15, when utilizing the characteristics of isotropic etching, the pitch p needs to be larger than the plate thickness t (FIG. 15A). Even in this case, similarly to FIG. 14, the substrate exposed surfaces 11 a and 12 a of both surfaces 11 and 12 of the substrate 10 are cut into a spherical shape, and the substrate 10 is cut by going around the back side of the etching mask film 3. (FIG. 15 (a), FIG. 15 (b), FIG. 15 (c)). However, before the substrate exposed surfaces (11a and 11a and 12a and 12a) adjacent to each other on both surfaces 11 and 12 penetrate, the hole-shaped substrate exposed surfaces 11a and 12a that advance from both surfaces 11 and 12 penetrate each other. (FIG. 15D).

  Thus, when utilizing the characteristics of isotropic etching, the holes 6 penetrating the both surfaces 11 and 12 can be formed by making the pitch p larger than the plate thickness t. However, in this case, when the plate thickness t is increased, the pitch p of the holes 3a and 3b of the etching mask film 3, that is, the pitch p of the holes 6 of the filter 20 is increased, and the diameter of the holes 6 of the filter 20 is also increased. End up.

On the other hand, in the method for manufacturing a filter of the present embodiment, the etching guide hole 6a is formed in advance by forming the altered portion 4, so that the pitch p can be made small regardless of the plate thickness t. Holes 6 can be formed. That is, in the filter manufacturing method of the present embodiment, it is possible to manufacture the filter 20 in which the pitch p of the holes 6 is smaller than the plate thickness t of the substrate 10 (p <t), which is impossible with isotropic etching. .
As described above, the high-performance filter can be easily manufactured at low cost also by the filter manufacturing method of the second embodiment.

(Modification of the second embodiment)
(Modification 1)
The protective film 2 can be dispensed with.
FIG. 16A shows the substrate 10 on which the altered portion 4 is formed in the altered portion forming step, and FIG. 16B shows the substrate 10 etched in the etching step. As shown in FIG. 16, etching can be performed without forming the protective film 2. In this case, as shown as a change from FIG. 16A to FIG. 16B, the entire substrate 10 is etched to reduce the plate thickness.

By eliminating the need for the protective film 2 in this manner, the protective film forming step, the patterning step, and the protective film peeling step are omitted unless the thickness of the plate is reduced by etching or the shape accuracy of the hole 6 is not questioned. Can do.
Further, when the protective film 2 is not formed, the substrate 10 is thinned by etching. Therefore, in the filter manufacturing method of this embodiment, the same effect as that obtained by processing a thin plate on the filter can be obtained. For example, since the hole 6 is shortened by thinning, the flow path resistance of the entire filter can be reduced.

  Here, the hole 6 is formed without the protective film 2 or the etching mask film 3 because the etching of the altered portion 4 progresses more than the etching of the non-altered portion (laser non-irradiated portion) that has not been altered. This is because both surfaces 11 and 12 penetrate along the altered portion 4 as a result.

(Modification 2)
Rather than patterning the etching mask film 3 on both surfaces 11 and 12 of the substrate 10 (double-side patterning), patterning the etching mask film 3 on only one surface of the substrate 10 (one-side patterning of the other surface) You can also.

FIG. 17 shows the shape of the substrate 10 when the etching mask film 3 is patterned and etched only on one surface of the substrate 10. FIG. 17A is a plan view of the substrate 10, and FIG. 17B is a cross-sectional view of the substrate 10 taken along arrows EE shown in FIG. 17A. As shown in FIG. 17, the hole 6 has a substantially cone shape with a diameter decreasing toward the bottom.
Thereby, the minimum diameter part of the hole 6 becomes smaller, and the filter 20 becomes high in the capture capability of a fine foreign material.

(Modification 3)
Not only glass but also a filter can be manufactured using a substrate made of quartz, quartz, or sapphire as a base material. That is, the filter can be manufactured by the filter manufacturing method of the present embodiment as long as the etching rate of the deteriorated portion that has been deteriorated by laser light irradiation is higher than that of the non-modified portion.

  For example, the cross-sectional shape of the hole 6 of the filter 20 formed of such a material is substantially a drum shape or a cone shape as described above. In addition, the cross-sectional shape of the hole 6 of the filter 20 formed by the substrate 10 having a plane orientation (100) made of a material made of silicon single crystal is also substantially the drum shape or the cone shape as described above.

(Modification 4)
In the altered part forming step, the laser is not limited to the laser of the above example, and other lasers can be used as long as they are transparent to the material and can form the altered part of the substrate. For example, an ultraviolet laser can be used depending on the material of the substrate.

  2 protective film, 3 etching mask film, 4 altered portion, 6 holes, 10 substrate, 11 first surface, 12 second surface, 20 filter, 30 fundamental wavelength light (laser light), S1 protective film formation step, S2 patterning step , S3 Altered part forming step, S4 etching step, S5 protective film peeling step

Claims (9)

A filter manufacturing method for manufacturing a filter by forming a plurality of holes in a substrate,
The base material is made of a material having a higher etching rate in a region where the etching rate of the region altered by irradiation with laser light is not altered,
The base material is irradiated with a laser beam to form an altered portion obtained by altering the material of the base material so as to extend inside the base material, and the extended altered portion is arranged in parallel in the substrate. A modified part forming step of forming a plurality of
Etching process to remove the altered portion by proceeding etching from the surface of the base material, and to form a plurality of holes penetrating the base material;
A method for producing a filter characterized by comprising: The base material is composed of a material made of a single crystal,
A patterning step of patterning an etching mask film having a pattern shape corresponding to the opening of the hole on the surface of the substrate;
In the altered portion forming step, in a region surrounded by a range exposed from the pattern-shaped hole on the surface of the base material and a crystal lattice plane that appears when etching progresses in the range with the smallest etching rate. The method for producing a filter according to claim 1, wherein the altered portion is formed such that an end portion of the altered portion exists in the filter. The base material is composed of a silicon single crystal,
In the patterning step, the etching mask film is patterned on the (110) surface of the substrate surface,
The method for manufacturing a filter according to claim 2, wherein in the etching step, a plurality of holes penetrating the base material are formed by wet etching.   4. The method for manufacturing a filter according to claim 1, wherein, in the altered portion forming step, the laser light is transmitted through a diffractive optical element, is branched into a plurality of beams, and is irradiated onto the base material. 5.   In the altered portion forming step, the laser beam is transmitted through an axicon element that forms a long line image in the focal direction along the optical axis, thereby forming a condensing region of the laser beam extending in the thickness direction of the substrate. The method for producing a filter according to any one of claims 1 to 4, wherein an altered portion extending in the thickness direction is formed by a condensing region of the laser light. It has a silicon single crystal in which a plurality of through holes are formed,
The opening of the through hole is formed in the (110) plane of the silicon single crystal,
The surface on which the through hole is formed is a (111) plane of the silicon single crystal.   The filter according to claim 6, wherein the through hole is formed by wet etching. The width of the opening of the hole is 15 μm or more and 20 μm or less,
Having a site where the thickness of the wall separating adjacent holes is 5 μm or more and 10 μm or less;
The filter according to claim 6 or 7, wherein the hole has a length of 200 µm or more. A filter having a plurality of holes,
The base material is composed of a material whose etching rate in the region altered by the laser light irradiation is larger than the etching rate in the region not altered,
A plurality of holes penetrating the base material are formed by isotropic etching,
When the length of the hole is t and the interval between the adjacent holes is p,
p <t
A filter characterized by having a site where the above relationship is established.

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