JP2007165651A - Recess formation method and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recess formation method for forming an inner multistage wall without giving a damage to the inner wall of a recess. <P>SOLUTION: The recess formation method comprises a first process for forming a first recess 13; a second process for forming a resist film 14 which covers the bottom and the inner wall of the first recess as well as the surface of solid phase 10; a third process for removing the resist film 14 formed in the inner wall of the first recess from the solid phase surface to a predetermined depth, while providing a bigger opening which contains the opening of the first recess to the resist film 14 formed in the surface of the solid phase; and a fourth process for removing the remaining film while forming a second recess 15, where the horizontal cross section is larger than that of the first recess and the depth is equal to that of the removed resist film by using a etching method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of forming a recess having an inner wall on a solid surface such as a substrate.

  Many micro devices such as a droplet discharge head are configured by bonding together a plurality of substrates on which components such as wiring and electrodes, concave portions, through holes, and the like are formed.

  As disclosed in Japanese Patent Application Laid-Open No. 2005-153369 (Patent Document 1) and the like, when forming a recess in a substrate, not only a cylindrical recess is provided in accordance with the opening of one mask but also various cavities. In some cases, it is necessary to form a recess having a multi-stage inner wall for positioning reference holes, escape of adhesive when the substrates are bonded together, and the like. For the recesses whose inner walls are multi-stepped, first, the deepest recesses with the smallest diameter are formed by etching, and then shallower recesses are formed using a mask having a diameter larger than the opening of the recesses. Can be obtained by repeating.

  Various fine processing techniques are used as a method for providing a recess in a substrate, but in recent years, a dry etching method has been widely used for processing with higher dimensional accuracy.

  The processing by the dry etching method has an advantage that high-precision processing can be performed in a desired direction regardless of the crystal plane, but there is a tendency that crystal defects and contamination are likely to occur. Therefore, when dry etching must be performed a plurality of times as in the case where the inner wall forms a multi-stage recess, the inner wall of the recess is damaged and it is difficult to maintain dimensional accuracy.

  Accordingly, an object of the present invention is to provide a method for forming a recess having a multi-stage inner wall without damaging the inner wall of the recess.

  In order to solve the above-mentioned problems, a recess forming method according to the present invention is a method of forming a recess having a multistage structure inside, and includes a first step of forming a first recess on a solid surface. A second step of forming a resist film covering the bottom and inner walls of the first recess and the solid phase surface, and an opening of the first recess in the resist film formed on the solid phase surface. And a third step of removing the resist film formed on the inner wall of the first recess from the solid phase surface to a predetermined depth, and an etching method to provide the first opening. And a fourth step of forming a second recess having a depth equal to the depth obtained by removing the resist film and removing the remaining resist film.

  According to such a configuration, when the second recess is formed, the resist film is formed on portions of the bottom and inner walls of the first recess that need not be further processed. Therefore, the bottom and inner walls of the first recess are damaged by the etching for forming the second recess and the shape does not change, and the dimensional accuracy can be ensured. The removal of the resist film formed on the solid surface can be easily performed by exposure using a suitable photomask and development, and the resist film formed on the inner wall of the first recess can also be exposed. At this time, since the energy can be adjusted so that the resist film is removed to a desired depth, the process can be performed at the same time.

  In the second step, it is desirable to form a resist film by a spray coating method. According to the spray method, a uniform thin resist film can be formed on the solid surface, the bottom of the first recess, and the inner wall, so that the resist film can be easily removed in the third step and the fourth step. .

  In the second step, it is also preferable that the resist film is formed by a spin coating method, a scan coating method, or a squeegee coating method, and after the resist film is formed, the resist film is formed to have a substantially uniform thickness. . According to these coating methods, since the inside of the first recess is filled with the resist film, it is difficult to remove the resist film in the first recess in the third step and the fourth step. However, even when coating is performed by these methods, such a problem does not occur if the resist film is formed to have a substantially uniform thickness after the resist film is formed. The resist film can be removed by exposure and development using a photomask as appropriate as described above.

  The etching method used in the method for forming a recess according to the present invention is preferably dry etching using an ICP dry etching apparatus. According to the ICP dry etching apparatus, it is possible to increase the etching rate ratio (selection ratio) between the material to be etched and the resist. Therefore, when the resist film is removed in the third step or the fourth step. Processing to the solid surface and the inner wall of the recess can be prevented.

  It is also preferable that after the second recess is formed, the second to fourth steps are repeated as many times as necessary with the second recess as the first recess. With such a configuration, the concave portion in which the inner wall has three or more steps can be formed by repeating simple steps.

  Or this invention also provides an electronic device provided with the solid-phase surface which has a recessed part formed by the recessed part formation method concerning this invention. Such an electronic apparatus has a high quality because it includes a substrate processed by the above-described recess forming method. Here, the electronic device includes a video camera, a television, a large screen, a mobile phone, a personal computer, a portable information device (so-called PDA), and other various devices.

Hereinafter, a substrate processing method according to the present invention will be described in detail with reference to the drawings.
(Recess formation method)
FIG. 1 is a process diagram showing an outline of one embodiment of a recess forming method according to the present invention.

  First, as shown in FIG. 1A, a resist film 12 is formed on the surface of a substrate (solid phase) 10 and an opening is provided in a region where a first recess is formed. A plan view at this time is shown in FIG. As illustrated, in the present embodiment, the opening has a circular shape. The material of the substrate 10 is not particularly limited as long as it can be suitably processed by an etching method, but in the present embodiment, it is a silicon substrate.

  Here, the resist film 12 can be obtained by, for example, a photolithography method. Specifically, after applying a resist material on the substrate 10, the resist material is formed by exposing and developing the resist material with i-line, ultraviolet light, electron beam or the like through a photomask corresponding to the shape of the opening. Can do. The resist material may be negative or positive. The negative resist materials include rosin-bichromate, polyvinyl alcohol (PVA) -bichromate, shellac-dichromate. Water-soluble photoresists such as casein-dichromate, PVA-diazo, acrylic photoresist, etc., polyvinyl cinnamate, cyclized rubber-azide, polyvinyl cinnamylidene acetate, polycinnamic acid β-vinyloxy Examples include oil-soluble photoresists such as ethyl ester. Examples of positive resist materials include oil-soluble photoresists such as o-naphthoquinonediazide.

  As the resist material, an inorganic solvent, various organic solvents, or a mixed solvent thereof is appropriately selected and dissolved or dispersed therein, and a known method substrate 10 such as a spin coating method, a scan coating method, a spray coating method, or a squeegee coating method is used. Can be applied to the surface.

  Subsequently, first recesses 13a and 13b are formed by an etching method using the resist film 12 as a mask. The etching method is preferably dry etching capable of processing with high accuracy. In the present embodiment, for comparison, the second recess is formed only in the first recess 13b.

  Next, the resist film 12 is removed from the substrate 10 as shown in FIG. Although this step is optional, once the resist film 12 is removed, a new resist film for forming the second recess is formed, whereby the resist film can be easily formed to have a uniform thickness.

  After removing the resist film 12, a resist film 14 is formed to cover the bottom and inner walls of the first recesses 13a and 13b and the surface of the substrate 10 as shown in FIG. As described above, the resist film 14 can be formed by applying a liquid resist material to the surface of the substrate 10 by a known method such as spin coating, scan coating, spray coating, or squeegee coating. In particular, when the spray coating method is used, the resist film 12 having a uniform thickness can be formed on the surface of the substrate 10 and the bottom and inner walls of the first recess by a single coating process. When a spin coating method, a scan coating method, a squeegee coating method, or the like is used, the recess is filled with a resist film 14 'as shown in FIG. 3 after the coating process. In such a case, a mask having an opening having a diameter smaller than the diameter of the first concave portion is provided on the upper portion of the first concave portion, irradiated with light, and developed, whereby the resist film 14 ′ is formed as shown in FIG. It can be molded as shown in D). By setting the resist film 14 to have a uniform thickness in this way, it becomes easy to peel off the resist film 14 later. A schematic plan view in the state shown in FIG. 1D is shown in FIG.

  Subsequently, as shown in FIG. 1E, the resist film 14 is appropriately exposed and developed through a photomask to provide a larger opening including the opening of the first recess 13b. A schematic plan view at this time is shown in FIG. Since the second recess is provided through the opening provided here, the shape of the opening becomes the shape of the horizontal section of the second recess. Further, as shown in FIG. 1E, the resist film formed on the inner wall of the first recess 13b is also removed from the surface of the substrate 10 to a predetermined depth. The depth at which the resist film 14 is removed is the depth of the second recess. The resist film 14 is removed by adjusting the amount of energy of light to be irradiated so that the resist film 14 is removed to a desired depth.

  Next, as shown in FIG. 1F, the substrate 10 is processed through the resist film 14 to form the second recess 15. The second recess 15 has a larger horizontal cross-sectional diameter and a smaller depth than the first recess 13b. By providing such a second recess 15, a step structure can be formed inside the recess. The formation of the second recess 15 can be performed by an etching method through the resist film 14. As the etching method, dry etching is preferable, and it is particularly desirable to perform the etching method using an ICP dry etching apparatus that can take a large etching rate ratio (selection ratio) between the silicon substrate 10 and the resist film 14.

  The dry etching method includes a chamber, a first introduction valve for introducing a plasma generating gas into the chamber, a second introduction valve for introducing a cooling medium gas for cooling the substrate 10, and a chamber. A pair of electrodes provided to face each other, a cooling plate for cooling the substrate 10 installed on one electrode side through a communication hole through which a cooling medium gas can pass, and an installation table for fixing the substrate 10 This is performed using the dry etching apparatus provided. First, the substrate 10 is fixed to the installation table, and the pressure in the chamber is reduced. Then, the cooling medium gas introduced from the second introduction valve is sprayed from the side opposite to the processing side of the substrate 10 to transmit the temperature of the cooling plate and the cooling medium gas to cool, and the plasma introduced from the first introduction valve In a state where the generating gas is supplied between the pair of electrodes, a high frequency voltage is applied between the electrodes. As a result, plasma is generated between the electrodes, and a second recess is formed by colliding with the substrate 10 through the opening of the resist film 14 where the generated ions and electrons are formed.

Examples of the plasma generating gas include a fluorine-based gas, a halogen-based gas containing at least one of chlorine and bromine, and the substrate 10 is composed of a silicon single crystal as in this embodiment. In this case, it is preferable to use SF ₆ , C ₄ F ₈ , CBrF ₃ , CF ₄ / O ₂ , Cl ₂ , SF ₆ / N ₂ / Ar, BCl ₂ / Cl ₂ / Ar gas, particularly SF _6. In addition, it is preferable to use any one of C ₄ F ₈ gas alone or a mixed gas thereof, thereby enabling efficient processing.

  The cooling medium gas is not particularly limited as long as it is excellent in cooling efficiency and does not affect the generation of plasma, and examples thereof include inert gases such as helium, argon, and nitrogen. Among these, helium is preferred as the main component. Helium is preferably used as a cooling medium gas because it has a particularly excellent cooling effect.

  Further, the temperature of the cooling plate, that is, the temperature of the cooling medium gas is preferably about −20 to 60 ° C., and more preferably about −10 to 10 ° C. Thereby, it becomes possible to cool the substrate 10 and maintain an appropriate temperature.

  Finally, as shown in FIG. 1G, by removing the resist film 14, a concave portion having a single step is obtained. For example, the resist film 14 is stripped by exposing it to oxygen plasma or ozone vapor under atmospheric pressure or reduced pressure, or by immersing it in a resist stripping solution such as acetone or alkylbenzene sulfonic acid that can dissolve the resist film 14. The film 14 can be liquefied.

  According to the method of the present invention, as described above, the resist film 14 is also formed in the first recesses 13a and 13b, and the resist film 14 is removed only in a region necessary for forming the second recess. Therefore, the periphery is protected by the resist film 14 even in the dry etching process. Therefore, it is possible to ensure dimensional accuracy even when dry etching is repeatedly performed to form a multistage structure.

  In addition, when the dry etching method is used, there is a problem that the resist film 14 exposed to plasma is generally cured and it is difficult to remove the resist film 14 in the recess. However, according to the method according to the present embodiment, as described above, since the resist film 14 is uniformly and thinly formed, the resist film 14 can be easily removed.

  Next, FIG. 4 is a schematic process diagram of a method of forming the third recess by performing the recess forming method according to the present invention again after FIG. 1 (G), and forming two steps in the recess. Show. First, as shown in FIG. 4B, a resist film 16 that covers the bottoms and inner walls of the first recesses 13 a and 13 b and the second recess 15 and the surface of the substrate 10 is formed. As described above, depending on the coating method of the resist film 16, the resist film 16 is formed so as to fill the first recesses 13a and 13b and the second recess 15; The resist film 16 is formed so as to have a uniform thickness by irradiating and developing light.

  Subsequently, as shown in FIG. 3C, a larger opening including the opening of the second recess 15 is provided in the resist film 16, and the resist film 16 formed on the inner wall of the second recess 15 is provided. Then, the substrate 10 is removed from the surface to a predetermined depth. The shape of the opening is the shape of the horizontal section of the third recess, and the depth is the depth of the third recess.

  Next, as shown in FIG. 4D, the substrate 10 is processed by an etching method through the resist film 16 to form a third recess 17. The third recess 17 has a cylindrical shape that is larger in diameter and shallower than the second recess 15.

Finally, when the resist film 16 is removed, a recess having a two-step structure formed therein can be obtained.
(Electronics)
Next, as an example of an electronic apparatus including a substrate having a recess provided by the recess forming method according to the present invention, an inkjet head of an inkjet printer will be described as an example.

  The ink jet head 1 manufactured in the present embodiment is the ink jet head 1 of the ink jet printer 2 shown in FIG. 5. As shown in FIGS. 6 and 7, the nozzle plate 320, the flow path forming substrate 100, and the like. On the elastic film 50, the piezoelectric element 300 provided on the elastic film 50, the reservoir forming substrate 30, the piezoelectric element 300 provided on the reservoir forming substrate 30, the reservoir forming substrate 30, and the reservoir forming substrate 30 And a driving IC 120 provided. The ink jet head 1 constitutes a piezo jet head.

  Such an inkjet head 1 can be manufactured as follows, for example. First, an elastic film 50 made of a silicon dioxide film is formed by subjecting a silicon substrate 100 ′ to be a flow path forming substrate 100 to a thermal oxidation process, and then an insulator film 55 and a lower electrode film on the elastic film 50. 60 is formed. Next, after forming the piezoelectric element 300 and the lead electrode 90 on the lower electrode film 60, the through hole 110 is completed. Then, the surface of the silicon substrate 100 ′ on which the piezoelectric element 300 is provided and the reservoir forming substrate 30 are bonded to each other with the adhesive layer 35. A cross-sectional view at this stage is illustrated in FIG. Thus, at this stage, the elastic film 50, the insulator film 55, and the reservoir forming substrate 30 are provided on one surface side of the silicon substrate 100 '.

  Thereafter, the ink chamber 102 and the concave portion constituted by the ink supply path 104, the communication portion 103, and the positioning reference hole 105 are formed in the silicon substrate 100 ′ to obtain the flow path forming substrate 100, and then the flow path forming substrate. The nozzle plate 320 is bonded to 100. Therefore, it is necessary to provide a step structure for escape of the adhesive for attaching the nozzle plate 320 inside the recess of the flow path forming substrate 100, and the recess forming method according to the present invention is used here.

  First, as shown in FIG. 8B, a protective substrate 420 is bonded to the side of the silicon substrate 100 ′ on which the reservoir forming substrate 30 is bonded via an adhesive resin 400. The protective substrate 420 is used to stably continue the processing of the silicon substrate 100 ′ even when the strength is partially insufficient due to the processing.

  Next, as shown in FIG. 8C, a resist film 422 is provided on the surface of the silicon substrate 100 '. The material and application method of the resist film 422 are as described above.

  Subsequently, as shown in FIG. 4D, a first recess that becomes the ink chamber 102 and the positioning reference hole 105 is formed in the silicon substrate 100 ′ by using a dry etching method. The dry etching method is performed while cooling by a method such as spraying an inert gas cooled from the lower side of the substrate 100 ′ in the drawing. Then, by removing the resist film 422 by the above-described method, the flow path forming substrate 100 provided with the ink chamber 102 and the positioning reference hole 105 is formed as shown in FIG.

  Next, as shown in FIG. 9A, a resist film 424 that covers the ink chamber 102, which is the first recess, the bottom and inner walls of the positioning reference hole 105, and the surface of the flow path forming substrate 100 is formed. The resist film 424 is formed with a uniform thickness as shown in the drawing by applying a resist material by spray coating as described above. When the resist film 424 is formed so as to fill the ink chamber 102 and the positioning reference hole 105 by applying by a spin coating method, a scan coating method, a squeegee coating method, etc., exposure and development are performed through a photomask. It is desirable that the resist film 424 in the ink chamber 102 and the positioning reference hole 105 is made uniform by removing unnecessary resist films.

  Next, as shown in FIG. 9B, a larger opening including the openings of the ink chamber 102 and the positioning reference hole 105 which are the first recesses is provided in the resist film 424. Further, the resist film 424 formed on the inner walls of the ink chamber 102 and the positioning reference hole 105 is also removed to a predetermined depth. The resist film 424 can be removed by exposure and development through a photomask having a predetermined shape as described above. The resist film 424 formed on the inner walls of the ink chamber 102 and the positioning reference hole 105 It can be removed to a desired depth by adjusting the energy of light during exposure.

  Subsequently, as shown in FIG. 9C, the flow path forming substrate 100 is processed by a dry etching method to form a second recess 246, and the remaining portion is left as shown in FIG. The resist film 424, the adhesive resin 400, and the protective substrate 420 are removed from the flow path forming substrate 100. Thus, a recess having a step structure is formed on the inner wall of the ink chamber 102.

  Next, after the nozzle plate 320 is bonded to the flow path forming substrate 100, the drive IC 120 is mounted, and the compliance substrate 40 is bonded. Furthermore, the connection wiring is formed by wire bonding between the drive IC 120 and the connection portions 60a and 90a of the lower electrode film 60 and the lead electrode 90, and the inkjet head 1 is completed.

  With this configuration, when the nozzle plate 320 is bonded to the flow path forming substrate 100, the second recess 246 can function as an adhesive escape.

  As described above, the method for forming a recess according to the present invention has been described by taking the method for manufacturing an inkjet head as an example. However, the present invention is not limited to these, and can be used in various microdevice manufacturing processes. Moreover, the recess forming method according to the present invention can be applied not only to a substrate-like substance but also to any solid phase surface. The electronic device manufactured by applying the recess forming method according to the present invention is not limited to an ink jet printer. In addition, in the method for forming a recess according to the present invention, one or two or more optional steps may be added.

It is a schematic sectional drawing explaining the process of the recessed part formation method which concerns on this invention. It is a schematic plan view explaining the process of the recessed part formation method which concerns on this invention. It is a schematic sectional drawing explaining 1 process of the recessed part formation method which concerns on this invention. It is a schematic sectional drawing explaining the process of the recessed part formation method which concerns on this invention. 1 is a schematic perspective view of an ink jet printer that is an example of an electronic apparatus according to the invention. It is a figure for demonstrating the manufacturing method of an inkjet recording-type head. It is a figure for demonstrating the manufacturing method of an inkjet recording-type head. It is a figure for demonstrating the manufacturing method of an inkjet recording-type head. It is a figure for demonstrating the manufacturing method of an inkjet recording-type head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 12, 14, 16, 422, 424 ... Resist film | membrane, 13 ... 1st recessed part, 15 ... 2nd recessed part, 17 ... 3rd recessed part, 100 ... Channel formation substrate, 102 ... Ink chamber ( (First recess), 105 ... positioning reference hole (first recess), 426 ... second recess

Claims (6)

A method of forming a recess having an inner multi-stage structure,
A first step of forming a first recess in the solid phase surface;
A second step of forming a resist film covering the bottom and inner walls of the first recess and the solid phase surface;
The resist film formed on the solid phase surface is provided with a larger opening including the opening of the first recess, and the resist film formed on the inner wall of the first recess is formed on the solid phase. A third step of removing from the surface to a predetermined depth;
Forming a second recess having a horizontal section larger than the first recess and having a depth equal to the depth from which the resist film has been removed by etching, and removing the remaining resist film. Recess formation method.   The recess forming method according to claim 1, wherein in the second step, the resist film is formed by a spray coating method.   In the second step, the resist film is formed by a spin coating method, a scan coating method, or a squeegee coating method, and after the resist film is formed, the resist film is formed to have a substantially uniform thickness. The recessed part formation method as described in any one of.   The method of forming a recess according to claim 1, wherein the etching method is performed using an ICP dry etching apparatus.   5. The recess forming method according to claim 1, wherein the second to fourth steps are repeated as many times as necessary with the second recess as the first recess. An electronic device comprising a solid phase surface having a recess formed by the recess forming method according to claim 1.

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