WO2013146627A1

WO2013146627A1 - Process for producing filter for filtration

Info

Publication number: WO2013146627A1
Application number: PCT/JP2013/058474
Authority: WO
Inventors: 剛守屋; 憲ー片岡; 加川　健一; 大麻　隆彦
Original assignee: 東京エレクトロン株式会社
Priority date: 2012-03-29
Filing date: 2013-03-18
Publication date: 2013-10-03
Also published as: TW201350194A; JP2013202559A

Abstract

A process for producing a filter for filtration is provided in which grooves precisely controlled with respect to not only the width but also the depth can be formed. The upper surface of a silicon-on-insulator (SOI) substrate (25) that comprises a lower silicon layer (23), an upper silicon layer (23), and an intermediate oxide layer (24) sandwiched between the two silicon layers (23) is subjected to a thermal oxidation treatment in which the treatment time is regulated, thereby forming an upper oxide layer (26) that has a thickness regulated to a given value. On the upper oxide layer (26) having a regulated thickness is formed a mask film (27) which has openings (28) for channel formation that correspond to raw-liquid channels (13) and filtrate channels (15) and which further has openings (29) for slit formation that correspond to filtration slits (14). This SOI substrate (25) is subjected to wet etching with an ultrahigh-purity buffered hydrofluoric acid to etch the upper oxide layer (26) that is exposed in the openings (28) for channel formation and the openings (29) for slit formation, thereby forming grooves (30) and grooves (31) that extend to the upper silicon layer (23).

Description

Filtration filter manufacturing method

The present invention relates to a method for manufacturing a filter for filtration using an etching process.

Filtration filters are frequently used when purifying clean water by removing pollutants and impurities from wastewater (sewage) from factories and households, or when purifying fresh water by removing salt from seawater. As a filter for filtration, a reverse osmosis membrane using a polymer material, for example, a methyl acetate polymer membrane is known.

However, the reverse osmosis membrane has a polymer membrane as its main component, so it is low in strength, and will be broken if the pressure (primary side pressure) applied to sewage or seawater is increased to increase the purification efficiency and a load is applied. There is a problem. Therefore, in recent years, a reverse osmosis membrane made of a highly rigid porous ceramic body has been developed (see, for example, Patent Document 1).

When a reverse osmosis membrane made of a porous ceramic body is used, the efficiency of filtration can be increased by increasing the primary pressure, while the diameter of the through-hole cannot be directly controlled in the manufacturing process. Further, even when it is necessary to configure the through-hole of the reverse osmosis membrane with a through-hole having a diameter of several nm or less, the reverse osmosis membrane has a through-hole having a diameter larger than several nm, for example, a diameter of several tens of nm. In some cases, there may be several through holes with a diameter of several hundreds of nanometers. As such, there are still concerns regarding the removal of contaminants and salt. Furthermore, when a reverse osmosis membrane is used for sorting a plurality of pharmaceutical components having different sizes contained in a liquid, there is a possibility that a pharmaceutical component that is not a desired size may pass through the through-hole, and the pharmaceutical components cannot be sorted. There is a problem. That is, when forming a through-hole of a reverse osmosis membrane, it is an important subject to accurately control the size and shape of the through-hole.

Corresponding to this, the present inventors have proposed using an etching process, such as a plasma etching process, which has many achievements in fine groove processing and fine through hole processing in the field of semiconductor device manufacturing (for example, , See Patent Document 2). Specifically, a mask film in which the width of the opening is controlled by a lithography technique is used to obtain a large number of grooves whose widths are uniformly adjusted by etching in a silicon substrate, and the grooves are used as slits for a filter for filtration. It is advocated to use.

In the etching process using lithography technology, the groove width can be uniformly controlled in units of several nanometers, so that spherical foreign substances having a diameter larger than a desired diameter can be reliably prevented from passing through the filter for filtration. Can do.

Special table 2007-526819 Japanese Patent Application No. 2010-253080

However, when grooves are formed by etching, the cross-sectional shape of the grooves tends to be a tapered shape or a reverse spindle shape. For example, when a groove shape is a reverse spindle shape, as shown in FIG. When the slit 81 having a width R is formed by etching to select the shaped foreign matter 80 (indicated by a broken line in the figure), the depth of the slit 81 becomes R or more, for example, an elliptical cross-sectional shape having a major axis of R or more There is a possibility that the foreign matter 82 passes through the slit 81. Further, the formed groove has an unintended depth, and there arises a problem that the flow rate of the liquid to be passed through the groove cannot be accurately controlled. That is, in order to perform filtration more accurately, it is necessary to form slits in which not only the width but also the depth are controlled with high accuracy.

An object of the present invention is to provide a method of manufacturing a filter for filtration that can form a groove in which not only the width but also the depth are controlled with high precision.

In order to achieve the above object, according to the present invention, there is provided a method for producing a filter for filtration, wherein a filter for filtration is produced from a substrate having a first layer adjusted to a first predetermined thickness in advance. Forming an upper layer on the first layer by adjusting the second layer to a second predetermined thickness as an upper layer; and on the second layer having the adjusted thickness, A mask film forming step for forming a mask film having an opening of a predetermined width, and an upper portion for forming a groove reaching the first layer by etching the second layer exposed in the opening of the mask film There is provided a method for manufacturing a filter for filtration comprising a layer etching step, wherein the first layer is made of a material that is not etched when the second layer is etched.

In the present invention, it is preferable that the etching of the second layer is continued for a predetermined time even after the groove reaches the first layer.

In the present invention, it is preferable that the second layer is formed by oxidation of the first layer, and in the upper layer forming step, the thickness of the second layer is adjusted by an oxidation time.

In the present invention, it is preferable that the first layer is made of silicon and the second layer is made of silicon oxide.

In the present invention, it is preferable that the second layer is formed by an atomic layer deposition method, and in the upper layer formation step, the thickness of the second layer is adjusted by a deposition time.

In the present invention, the substrate further includes a third layer formed as a lower layer below the first layer, and the third layer is made of a material that is not etched when the first layer is etched. Preferably, the method further includes a first layer etching step of etching the first layer exposed in the upper layer etching step to form another groove reaching the third layer.

In order to achieve the above object, according to the present invention, a first layer adjusted to a first predetermined thickness in advance and a lower layer formed under the first layer are provided, The lower layer is a method for manufacturing a filter for filtration, wherein the filter is manufactured from a substrate made of a material that is not etched when the first layer is etched, and the lower layer is formed on the first layer whose thickness is adjusted. In addition, a mask film forming step for forming a mask film having an opening with a predetermined width, and a groove reaching the lower layer by etching the first layer exposed in the opening of the mask film are formed. A method of manufacturing a filter for filtration having one layer etching step is provided.

In the present invention, after the first layer etching step, an upper portion of the first layer that was not etched in the first layer etching step is etched to form a plurality of shallow grooves in the upper portion of the first layer. It is preferable to do.

In the present invention, the etching of the first layer is preferably continued for a predetermined time after the groove reaches the lower layer.

In the present invention, the substrate further includes a fourth layer formed below the lower layer, and the fourth layer is made of a material that is not etched when the lower layer is etched. The lower layer exposed in the etching step is preferably etched in a portion different from the groove to form another groove etching step for forming another groove reaching the fourth layer.

In the present invention, it is preferable that the first layer is polished by chemical mechanical polishing to be adjusted to the first predetermined thickness.

In the present invention, it is preferable that the first layer and the fourth layer are made of silicon, and the lower layer is made of silicon oxide.

According to the method for manufacturing a filter for filtration according to the present embodiment, the mask is formed by etching using a mask film having an opening with a predetermined width formed on the second layer adjusted to a predetermined thickness. The second layer exposed in the opening of the film is etched to form a groove reaching the first layer. Since the first layer is made of a material that is not etched when the second layer is etched, the first layer is not etched even when the groove reaches the first layer. That is, the width of the groove formed by penetrating the second layer is regulated by the opening in the mask film, and the depth of the groove is regulated by the first layer. As a result, it is possible to form a groove in which not only the width but also the depth are accurately controlled.

It is a side view of a filtration unit constituted by laminating filtration filters in a diagram schematically showing a configuration of a filtration filter produced by a method for producing a filtration filter according to an embodiment of the present invention. It is sectional drawing which follows the line BB in the filter for filtration of FIG. 1A, Comprising: It is a top view of the filter for filtration. It is sectional drawing which follows the line CC in FIG. 1B. It is sectional drawing which follows the line DD in FIG. 1B. It is sectional drawing which follows the line EE in FIG. 1B. It is process drawing of the manufacturing method of the SOI substrate used in the manufacturing method of the filter for filtration concerning this Embodiment. It is process drawing of the manufacturing method of the filter for filtration concerning this Embodiment. It is process drawing of the manufacturing method of the filter for filtration concerning this Embodiment. It is process drawing of the 1st modification of the manufacturing method of the filter for filtration concerning this Embodiment. It is process drawing of the 2nd modification of the manufacturing method of the filter for filtration concerning this Embodiment. It is process drawing of the 3rd modification of the manufacturing method of the filter for filtration concerning this Embodiment. It is an expanded partial sectional view of the filter for filtration manufactured using the conventional etching process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1A to 1E are diagrams schematically showing a configuration of a filter for filtration manufactured by the method for manufacturing a filter for filtration according to the present embodiment, and FIG. 1A is configured by laminating filters for filtration. 1B is a cross-sectional view taken along line BB in FIG. 1A, is a plan view of the filter for filtration, and FIG. 1C is a cross-sectional view taken along line CC in FIG. 1B. FIG. 1D is a sectional view taken along line DD in FIG. 1B, and FIG. 1E is a sectional view taken along line EE in FIG. 1B.

In FIG. 1A, a filtration unit 10 includes three filtration filters 11 stacked, a transparent material covering the upper surface of the uppermost filtration filter 11, for example, an observation plate 12 made of glass, and a liquid before filtration. An introduction pipe 19 for introduction and a discharge pipe 20 for discharging the liquid after filtration are provided. All of the three filtration filters 11 have the same structure, and the inside is communicated with each other through an introduction hole 17 and a discharge hole 18 described later.

In FIG. 1B to FIG. 1E, the filter 11 for filtration is formed by groove processing by etching on a main body made of a substrate formed by laminating two layers of materials having different etching characteristics, for example, an SOI (Silicon On Insulator) substrate. The pre-filtration flow path 13, the filtration slit 14, and the post-filtration flow path 15 are formed.

The pre-filtration flow path 13 and the post-filtration flow path 15 are formed in a comb shape in plan view, and each pre-filtration branch flow path 13a corresponding to the comb teeth of the pre-filtration flow path 13 and the comb teeth of the post-filtration flow path 15 The corresponding post-filter separation flow paths 15a are arranged face to face so as to be nested with each other. A wall portion 16 is interposed between each pre-filtration branch flow path 13a and each post-filtration branch flow path 15a. Are arranged to communicate with each other.

In the filter 11 for filtration, the liquid containing the foreign material flows from the pre-filtration flow path 13 to the post-filtration flow path 15 via the pre-filtration flow paths 13a, the filtration slits 14, and the post-filtration flow paths 15a (FIG. 1B). The width and depth of each filtration slit 14 is set to a predetermined value, for example, 100 nm, so that the diameter included in the liquid flowing in the pre-filtration flow path 13a is a predetermined value, for example, Foreign matter of 100 nm or more cannot pass through each filtration slit 14 and does not flow into the post-filtration branch channel 15a. That is, each filtration slit 14 removes foreign matters having a diameter equal to or larger than a predetermined value and filters the liquid. The number of the filtration slits 14 formed on the upper surface of the wall portion 16 is preferably large from the viewpoint of improving the filtration efficiency. For example, 1,000,000 or more are preferably formed.

An introduction hole 17 penetrating the bottom surface is provided on the bottom surface of the pre-filtration flow path 13, and the pre-filtration flow path 13 of the filter for filtration 11 passes through the introduction hole 17 before the pre-filtration flow of the other filtration filters 11. It communicates with the road 13. Further, the bottom surface of the post-filtration flow path 15 is provided with a discharge hole 18 penetrating the bottom surface, and the post-filtration flow path 15 of the filter for filtration 11 is filtered through the discharge hole 18 by another filter for filtration 11. It communicates with the rear channel 15. Therefore, in the filtration unit 10, the pre-filtration liquid introduced from the introduction pipe 19 to the pre-filtration flow path 13 of the uppermost filtration filter 11 is distributed to the pre-filtration flow paths 13 of the filtration filters 11 by the introduction holes 17. After being filtered by the filtration slit 14 of each filtration filter 11, the filtered liquid existing in the post-filtration flow path 15 of each filtration filter 11 is filtered by the uppermost filtration filter 11 through each discharge hole 18. Collects in the rear flow path 15 and is discharged through the discharge pipe 20.

FIG. 2 is a process diagram of a method for manufacturing an SOI substrate used in the method for manufacturing a filter for filtration according to the present embodiment.

First, a substrate 21 made of only silicon (Si) is prepared (FIG. 2A), and the upper surface of the substrate 21 is subjected to thermal oxidation treatment to transform the upper portion into silicon oxide (SiO 2) to form an oxide layer 22 (FIG. 2). 2B). Since the amount of silicon oxide formed from silicon is substantially proportional to the time during which the thermal oxidation treatment is performed, the thickness of the oxide layer 22 is adjusted by adjusting the thermal oxidation treatment time. Although only one substrate 21 is shown in FIGS. 2A and 2B, since the SOI is manufactured by bonding two substrates 21 as will be described later, at least two substrates 21 are prepared. The substrate 21 is subjected to a thermal oxidation process.

Next, the two substrates 21 are bonded together so that the oxide layers 22 come into contact with each other (FIG. 2C), and further heated for a predetermined time. At this time, the respective oxide layers 22 are joined to each other so that the two substrates 21 are in close contact with each other, and an SOI substrate 25 having two silicon layers 23 and one intermediate oxide layer 24 sandwiched between the two silicon layers 23 is obtained. Formed (FIG. 2D). Thereafter, this process is terminated.

As described above, the SOI substrate 25 can be manufactured very simply and inexpensively because it can be obtained simply by bonding and heating the two substrates 21 after subjecting the two substrates 21 to thermal oxidation. it can. In addition, since the intermediate oxide layer 24 includes the two oxide layers 22 whose thicknesses are adjusted, the thickness of the intermediate oxide layer 24 is also adjusted.

3 and 4 are process diagrams of a method for manufacturing a filter for filtration according to the present embodiment.

First, an SOI substrate 25 is prepared (FIG. 3A), and the upper surface of the SOI substrate 25 is subjected to a thermal oxidation process to transform the upper portion into silicon oxide to form an upper oxide layer 26 (second layer) as an upper layer. (FIG. 3B). At this time, the thermal oxidation treatment time is adjusted, and the thickness of the upper oxide layer 26 is adjusted to a predetermined value (second predetermined thickness), for example, 10 nm (upper layer forming step).

Here, the thickness of the substrate 21 before the SOI substrate 25 is adjusted in advance by a chemical polishing process (CMP, Chemical Mechanical Polishing), and the oxide layer 22 and the upper oxide layer 26 formed on the substrate 21 are also included. Since the thickness is adjusted, as a result, the thickness of the silicon layer 23 (first layer) on the intermediate oxide layer 24 (third layer) as the lower layer is also a predetermined value (first predetermined thickness). ) In advance.

Next, a mask film 27 made of, for example, a photoresist is formed on the upper oxide layer 26 (mask film forming step). The mask film 27 is provided with a flow passage opening 28 corresponding to the pre-filtration flow path 13 and the post-filtration flow path 15 and a slit opening 29 corresponding to each filtration slit 14. The portion 28 and the slit opening 29 expose the upper oxide layer 26 (FIG. 3C). In particular, the width (predetermined width) of the slit opening 29 is strictly adjusted, for example, 10 nm, which is the same as the thickness of the upper oxide layer 26.

Next, by using an oxide layer etching process in which ultra-high purity buffered hydrofluoric acid (a mixture of BHF: NH ₄ F and HF) is used as an etchant and wet etching is performed on the SOI substrate 25, the channel openings 28 and the slit openings are formed. The upper oxide layer 26 exposed in the portion 29 is etched to form grooves 30 and grooves 31 reaching the upper silicon layer 23 (FIG. 3D) (upper layer etching step).

At this time, since silicon alone is not dissolved by BHF, the upper silicon layer 23 is not etched by BHF. Therefore, the

grooves

30 and 31 formed by etching the upper oxide layer 26 do not become deeper when reaching the upper silicon layer 23, and as a result, the depth is accurately controlled. On the other hand, when the

groove

30 or 31 reaches the upper silicon layer 23, the

groove

30 or 31 has a tapered shape, for example, a downwardly convex spindle shape. It is not constant in the depth direction. Correspondingly, in the present embodiment, after the

groove

30 or 31 reaches the upper silicon layer 23, the wet etching process is performed for a predetermined time, for example, the

groove

30 or 31 reaches the upper silicon layer 23. Continue for a time corresponding to 30% of the time. Accordingly, the growth in the width direction of the

grooves

30 and 31 can be promoted while the growth in the depth direction of the

grooves

30 and 31 is restricted by the upper silicon layer 23, and thus the flow to the

grooves

30 and 31 can be promoted. The widths of the road openings 28 and the slit openings 29 can be accurately reflected, and as a result, the widths of the

grooves

30 and 31 are accurately controlled.

Next, ashing with oxygen plasma or organic cleaning liquid is performed on the SOI substrate 25 to remove the mask film 27 (FIG. 3E).

Next, a mask film 32 made of, for example, a photoresist is formed on the upper oxide layer 26 again. The mask film 32 is provided with a channel opening 33 corresponding to the groove 30. The channel opening 33 exposes the upper silicon layer 23, while the mask film 32 covers each groove 31. The upper silicon layer 23 is not exposed (FIG. 4A).

Next, a deposition process performed with an etching process on the SOI substrate 25 by a plasma generated from a carbon fluoride gas (for example, C ₄ F ₈ ) for a predetermined time, for example, 5 seconds, and a sulfur fluoride gas (for example, SF) ₆ ) and a flow path opening 33 by a silicon layer etching process in which a plasma etching process is alternately performed on the SOI substrate 25 for another predetermined time, for example, 10 seconds, by plasma generated from a processing gas comprising oxygen gas. The upper silicon layer 23 exposed in step 1 is etched to form a groove 34 reaching the intermediate oxide layer 24 (FIG. 4B) (first layer etching step).

At this time, since the silicon oxide is not etched by the plasma generated in the silicon layer etching process, the intermediate oxide layer 24 is not etched in the plasma etching process. Therefore, the groove 34 formed by etching the upper silicon layer 23 does not become deeper when it reaches the intermediate oxide layer 24, and as a result, the depth is accurately controlled. On the other hand, when the groove 34 reaches the intermediate oxide layer 24, the groove 34 has a tapered shape, for example, a downwardly convex spindle shape, and therefore the width of each groove 34 is not constant in the depth direction. Correspondingly, in the present embodiment, the plasma etching process is continued for another predetermined time, for example, 5 seconds after the groove 34 reaches the intermediate oxide layer 24. Accordingly, the growth in the width direction of the groove 34 can be promoted while the growth in the depth direction of the groove 34 is regulated by the intermediate oxide layer 24, so that the width of the opening 33 for the flow path is accurately set in the groove 34. As a result, the width of the groove 34 is accurately controlled.

Next, an ashing process using oxygen plasma or an organic cleaning liquid is applied to the SOI substrate 25 to remove the mask film 32 (FIG. 4C). At this time, the groove 34 whose depth and width are accurately controlled constitutes the pre-filtration flow path 13 and the post-filtration flow path 15, and the groove 31 whose depth and width is precisely controlled constitutes the filtration slit 14. .

Thereafter, the observation plate 12 is stuck on the uppermost filter 11 for filtration in the filtration unit 10 (FIG. 4D), and the manufacturing method is completed.

According to the method for manufacturing a filter for filtration according to the present embodiment, a channel opening 28 or a slit aperture having a predetermined width formed on the upper oxide layer 26 having a thickness adjusted to a predetermined value. The upper oxide layer 26 exposed to the flow path opening 28 and the slit opening 29 of the mask film 27 is etched by the BHF wet etching process using the mask film 27 having the portion 29 to the upper silicon layer 23. Reaching grooves 30 and grooves 31 are formed. Since the upper silicon layer 23 is made of silicon alone that is not dissolved by BHF, the upper silicon layer 23 is not etched even if the

grooves

30 and 31 reach the upper silicon layer 23. That is, the depth of the

grooves

30 and 31 is regulated by the upper silicon layer 23. Thereby, the groove | channel 31 and the filtration slit 14 by which the depth was controlled accurately can be formed.

Further, in the method for manufacturing a filter for filtration according to the present embodiment, the groove 34 is formed by plasma etching using the mask film 32 formed on the upper silicon layer 23 whose thickness is adjusted to a predetermined value as a mask. Reaches the intermediate oxide layer 24. Since the intermediate oxide layer 24 is made of silicon oxide that is not etched by the plasma generated from the processing gas, even if the groove 34 reaches the intermediate oxide layer 24, the intermediate oxide layer 24 is not etched. That is, the depth of the groove 34 formed through the upper silicon layer 23 is regulated by the intermediate oxide layer 24. Thereby, the pre-filtration flow path 13 and the post-filtration flow path 15 whose depths are accurately controlled can be formed.

In the above-described method for manufacturing a filter for filtration according to the present embodiment, etching with BHF is continued for a predetermined time after the groove 31 reaches the upper silicon layer 23, and the groove 34 is formed in the intermediate oxide layer 24. Since the etching by plasma is continued for another predetermined time even after reaching, the width of the slit opening 29 and the channel opening 33 can be accurately reflected in the groove 31 and the groove 34. As a result, the pre-filtration flow path 13, the filtration slit 14 and the post-filtration flow path 15 whose widths are accurately controlled can be formed.

In the filter 11 for filtration manufactured by the method for manufacturing a filter for filtration according to the above-described embodiment, the width and depth of each filtration slit 14 are accurately controlled, so that the filtration can be performed more accurately. .

Moreover, the filter 11 manufactured by the method for manufacturing a filter according to this embodiment described above is manufactured from an SOI substrate 25 based on silicon having high rigidity, and the filter slit 14 is formed from hard silicon oxide. Since the oxide layer 22 is formed, it is possible to apply a high pressure to the liquid containing foreign matter in each filtration filter 11 and pass each filtration slit 14, thereby increasing the amount of filtration per unit time. And the filtration efficiency can be improved.

Furthermore, in the method for manufacturing a filter for filtration according to the above-described embodiment, the number of filtration slits 14 is determined by the number of slit openings 29 in the mask film 27, so that each slit opening is formed in the mask film 27. By increasing the number of openings 29 for each slit within a range in which the accuracy of the width of the portion 29 is not deteriorated, the number of filtration slits 14 can be increased, thereby further increasing the amount of filtration per unit time and filtering efficiency. Can be further improved.

In the method for manufacturing the filter for filtration according to the present embodiment described above, each filtration slit 14 is formed in the upper oxide layer 26, and the pre-filtration flow path 13 and the post-filtration flow path 15 are formed in the upper silicon layer 23. However, each filtration slit 14 may be formed in the upper silicon layer 23, and the pre-filtration flow path 13 and the post-filtration flow path 15 may be formed in the intermediate oxide layer 24.

FIG. 5 is a process diagram of a first modification of the method for manufacturing a filter for filtration according to the present embodiment.

In this modification, for example, first, an SOI substrate 25 is prepared (FIG. 5A), the upper silicon layer 23 is polished by chemical polishing, and the thickness of the upper silicon layer 23 is set to a predetermined value, for example, 10 nm. (FIG. 5B).

Next, the upper silicon layer 23 that is made of a photoresist and is exposed in the opening using a mask film (not shown) having openings corresponding to the pre-filtration flow path 13, the filtration slit 14, and the post-filtration flow path 15.

Grooves

30 and 31 that reach the intermediate oxide layer 24 by etching by the silicon layer etching process are formed in the upper silicon layer 23 (FIG. 5C), and after the mask film is removed, openings corresponding to the grooves 30 are formed. The intermediate oxide layer 24 exposed in the opening is etched by BHF using another mask film (not shown) having a groove 34 to reach the lower silicon layer 23 (fourth layer), and the like. The manufacturing method is finished by removing the mask film (FIG. 5D) (lower layer etching step).

Also in this modification, since the intermediate oxide layer 24 is not etched by the plasma generated from the processing gas, the growth in the depth direction of the groove 31 is regulated by the intermediate oxide layer 24 and formed under the intermediate oxide layer 24 by BHF. Since the lower silicon layer 23 is not etched, growth of the groove 34 in the depth direction is restricted by the lower silicon layer 23. As a result, it is possible to form the pre-filtration flow path 13, the post-filtration flow path 15 and the filtration slit 14 whose depth is accurately controlled.

In this modification, the etching by plasma is continued for a predetermined time after the groove 31 reaches the intermediate oxide layer 24, and the etching by BHF is performed after the groove 34 reaches the lower silicon layer 23. Since it continues for a predetermined time, the width of the opening of the mask film or other mask film can be accurately reflected in the

grooves

31 and 34, and as a result, the pre-filtration flow path 13 whose width is accurately controlled. The filtration slit 14 and the post-filtration flow path 15 can be formed.

Further, each filtration slit 14, pre-filtration flow path 13 and post-filtration flow path 15 may be formed in the upper silicon layer 23.

FIG. 6 is a process diagram of a second modification of the method for manufacturing a filter for filtration according to the present embodiment.

In this modification, for example, first, an SOI substrate 25 is prepared, the upper silicon layer 23 is polished by chemical polishing, and the thickness of the upper silicon layer 23 is adjusted to a predetermined value, for example, 100 nm ( FIG. 6A).

Next, the above silicon layer etching process is applied to the upper silicon layer 23 made of photoresist and exposed at the opening using a mask film (not shown) having openings corresponding to the pre-filtration flow path 13 and the post-filtration flow path 15. A groove 30 reaching the intermediate oxide layer 24 by etching is formed in the upper silicon layer 23 (FIG. 6B), and further, after removing the mask film, the groove 30 is covered and an opening corresponding to each filtration slit 14 The upper silicon layer 23 exposed at the opening is etched by the above silicon layer etching process using another mask film (not shown) having a thickness to form each filtration slit 14 having a predetermined depth. And the present manufacturing method is finished (FIG. 6C).

Also in this modification, the intermediate oxide layer 24 is not etched by the silicon layer etching process, so that the growth in the depth direction of the groove 30 is restricted by the intermediate oxide layer 24. As a result, the pre-filtration flow path 13 and the post-filtration flow path 15 whose depth is accurately controlled can be formed.

Even in this modification, the etching by plasma is continued for a predetermined time after the groove 30 reaches the intermediate oxide layer 24, so that the width of the opening of the mask film can be accurately reflected in the groove 30. As a result, the pre-filtration flow path 13 and the post-filtration flow path 15 can be formed from the groove 30 whose width is accurately controlled.

Further, the filtration filter 11 may be manufactured using one substrate 21 instead of the SOI substrate 25.

FIG. 7 is a process diagram of a third modification of the method for manufacturing a filter for filtration according to the present embodiment.

In this modification, for example, first, the substrate 21 is prepared, and the upper surface of the substrate 21 is subjected to a thermal oxidation process to form the oxide layer 22. At this time, the thickness of the oxide layer 22 is adjusted to a predetermined value, for example, 2000 nm by adjusting the thermal oxidation treatment time (FIG. 7A).

Next, the oxide layer 22 made of photoresist and exposed at the opening is etched with BHF using a mask film (not shown) having openings corresponding to the pre-filtration flow path 13, the filtration slit 14, and the post-filtration flow path 15. Then, grooves 30 and each groove 31 reaching the silicon layer 23 are formed in the oxide layer 22 (FIG. 7B), and after removing the mask film, each groove 31 is covered and an opening corresponding to the groove 30 is provided. The silicon layer 23 exposed in the opening using another mask film (not shown) is etched by the above-mentioned silicon layer etching process to form a groove 34 having a predetermined depth, and the other mask film is removed and this manufacturing is performed. The method ends (FIG. 7C).

Also in this modification, since the silicon layer 23 is not etched by BHF, the growth in the depth direction of the groove 31 is regulated by the silicon layer 23. As a result, the filtration slit 14 whose depth is accurately controlled can be formed.

Even in this modification, since the etching with BHF is continued for a predetermined time after the groove 31 reaches the silicon layer 23, the width of the opening of the mask film can be accurately reflected in the groove 31. As a result, each filtration slit 14 whose width is accurately controlled can be formed.

The substrate 21 described above has been subjected to a thermal oxidation process to form an oxide layer 22, but the substrate 21 may be exposed to a predetermined gas in a high temperature atmosphere to form another altered layer on the surface. When 21 is exposed to nitrogen gas in a high temperature atmosphere, a nitride layer made of silicon nitride is formed on the surface of the substrate 21. In this case as well, the thickness of the nitride layer can be adjusted by adjusting the time of exposure to nitrogen gas in a high temperature atmosphere. The other deteriorated layer is preferably composed of a stable silicon compound such as silicon carbide, silicate (MgSiO ₃ or the like) or silicon resin.

Alternatively, without forming the oxide layer 22 on the substrate 21, silicon oxide may be stacked by ALD (Atomic Layer Deposition) to form a heterogeneous layer on the surface of the substrate 21. In ALD, since radicals of silicon oxide are stacked on a layer-by-layer basis, the thickness can be adjusted in nm units. In the substrate 21, the thickness of the heterogeneous layer can be adjusted by adjusting the processing time of ALD.

It is preferable that the above-mentioned other deteriorated layer or heterogeneous layer is made of a material that is not etched when the silicon layer 23 is etched, and the silicon layer 23 is formed when other deteriorated layer or heterogeneous layer is etched. Preferably it is not etched. Thereby, the growth in the depth direction of the groove 34 (the pre-filtration flow path 13 and the post-filtration flow path 15) or the groove 31 (the filtration slit 14) formed in the silicon layer 23, another altered layer, or a heterogeneous layer, The layer can be regulated by a layer different from the layer in which the

grooves

34 and 31 are formed.

Also, the substrate 21 does not need to be made of silicon, and may be made of a material that undergoes oxidation or nitridation to significantly change the etching rate or change to a material that is not etched, such as aluminum.

As mentioned above, although this invention was demonstrated using said each embodiment, this invention is not limited to said each embodiment.

For example, in each of the above embodiments, the silicon layer etching process is performed by treatment with plasma of C ₄ F ₈ as a carbon fluoride gas, and treatment with plasma of a mixed gas of SF ₆ as sulfur fluoride gas and oxygen gas. However, the processing gas that can be used in the silicon layer etching process is not limited to these processing gases as long as the gas can be anisotropically etched with high accuracy. C ₅ F ₈ , CF _4, or the like may be used as the silicon layer etching process, and the silicon layer etching process is not an alternating process in which a different gas plasma is alternately repeated. For example, a mixture of sulfur hexafluoride gas and oxygen gas is used. Gas plasma, single gas such as chlorine gas, bromine gas, CCl ₄ , CF ₂ Cl ₂ , SiCl ₄ , or HBr It may be a single treatment with plasma.

In each of the above embodiments, wet etching is used as the oxide layer etching process. However, the oxide layer etching process is not limited to this, and dry etching may be used.

This application claims priority based on Japanese Application No. 2012-076349 filed on March 29, 2012, the entire contents of which are incorporated into this application.

DESCRIPTION OF SYMBOLS 10 Filtration unit 11 Filtration filter 13 Flow path before filtration 14 Filtration slit 15 Flow path after filtration 21 Substrate 22 Oxide layer 23 Silicon layer 24 Middle surface oxidation layer 25 SOI substrate 26 Upper oxide layers 27 and 32

Mask films

28 and 33 Opening 29 slit opening 30, 34 groove 31 slit

Claims

A method for producing a filtration filter for producing a filtration filter from a substrate having a first layer adjusted to a first predetermined thickness in advance,
Forming an upper layer on the first layer by adjusting the second layer to a second predetermined thickness as an upper layer;
A mask film forming step of forming a mask film having an opening of a predetermined width on the second layer having the adjusted thickness;
An upper layer etching step of etching the second layer exposed in the opening of the mask film to form a groove reaching the first layer;
The method for manufacturing a filter for filtration, wherein the first layer is made of a material that is not etched when the second layer is etched.
The method for producing a filter for filtration according to claim 1, wherein the etching of the second layer is continued for a predetermined time after the groove reaches the first layer.
The second layer is formed by oxidation of the first layer;
2. The method for manufacturing a filter for filtration according to claim 1, wherein, in the upper layer forming step, the thickness of the second layer is adjusted by an oxidation time.
The method for manufacturing a filter for filtration according to claim 1, wherein the first layer is made of silicon, and the second layer is made of silicon oxide.
The second layer is formed by an atomic layer deposition method;
The method for manufacturing a filter for filtration according to claim 1, wherein, in the upper layer forming step, the thickness of the second layer is adjusted by a deposition time.
The substrate further includes a third layer formed as a lower layer under the first layer, and the third layer is made of a material that is not etched when the first layer is etched,
2. The first layer etching step according to claim 1, further comprising a first layer etching step of etching the first layer exposed in the upper layer etching step to form another groove reaching the third layer. A method for producing a filter for filtration.
A first layer adjusted to a first predetermined thickness in advance, and a lower layer formed under the first layer, wherein the lower layer is etched when the first layer is etched. A method for producing a filter for filtration, comprising producing a filter for filtration from a substrate made of a material that is not etched,
A mask film forming step of forming a mask film having an opening with a predetermined width on the first layer having the adjusted thickness;
And a first layer etching step of etching the first layer exposed in the opening of the mask film to form a groove reaching the lower layer.
After the first layer etching step, an upper portion of the first layer that has not been etched in the first layer etching step is etched to form a plurality of shallow grooves in the upper portion of the first layer. The manufacturing method of the filter for filtration of Claim 7.
The method for manufacturing a filter for filtration according to claim 7, wherein the etching of the first layer is continued for a predetermined time after the groove reaches the lower layer.
The substrate further includes a fourth layer formed below the lower layer, and the fourth layer is made of a material that is not etched when the lower layer is etched,
The method further comprises a lower layer etching step of forming another groove reaching the fourth layer by etching the lower layer exposed in the first layer etching step at a portion different from the groove. The manufacturing method of the filter for filtration of Claim 7.
The method for manufacturing a filter for filtration according to claim 7, wherein the first layer is polished by chemical mechanical polishing to be adjusted to the first predetermined thickness.
The method for manufacturing a filter for filtration according to claim 10, wherein the first layer and the fourth layer are made of silicon, and the lower layer is made of silicon oxide.