JP2008143068A - Pattern forming method and manufacturing method of droplet discharge head - Google Patents

Abstract

When forming a structure having recesses with different depths, such as a step structure, highly accurate pattern formation is performed without increasing the number of steps.
A resist film 12 on a substrate 10 is patterned to form a first opening 13a and a plurality of second openings 13b having an opening width narrower than the first opening 13a. Next, vertical anisotropic etching is performed to form a first recess 14a in the first opening 13a and a plurality of recesses 14b corresponding to each of the second openings 13b. Next, isotropic etching is performed to remove the side walls of the plurality of recesses 14b formed in the plurality of second openings 13b, and the second recesses 17 are formed. The opening width of the first opening portion 13a and the opening width of the second opening portion 13b are such that the plurality of second opening portions 13b are arranged while the first opening portion 13a reaches the depth of the first recess 14a. The etching rate difference reaching the depth of the second concave portion 17 is set.
[Selection] Figure 1

Description

  The present invention relates to a pattern forming method by dry etching and a method for manufacturing a droplet discharge head.

  Microdevices such as droplet discharge heads, micro electro mechanical systems (MEMS), and semiconductors are configured by bonding together multiple substrates with components such as wiring and electrodes, recesses, and through holes. There are many that are.

  For example, as disclosed in Patent Document 1, when a recess is formed in a substrate, not only a cylindrical recess is provided in accordance with the opening of one mask, but also various cavities, positioning reference holes, and a substrate are provided. It may be necessary to form a recess having a step on the inner wall for adhesive escape when the two are bonded together. The concave portion having a step on the inner wall is formed by first forming a deep concave portion having the smallest diameter and then forming a shallow concave portion by using a mask having a diameter larger than the opening of the concave portion by an etching method. Can be obtained by:

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. Patent Document 2 discloses an example in which an inkjet head is formed using a dry etching method.
JP 2005-153369 A JP-A-9-248914

  The dry etching method has an advantage that high-precision processing can be performed in a desired direction regardless of the crystal plane, and is suitable for forming a recess having a step on the inner wall of the substrate. However, there is a problem in that a step of forming a resist film for forming a step shape for each step and an etching step for processing the substrate are required, which increases the number of steps and accordingly increases the manufacturing cost.

  An object of the present invention is to provide a pattern forming method capable of forming a highly accurate pattern without increasing the number of steps when forming a structure having recesses having different depths such as a step structure.

  A pattern forming method according to the present invention is a pattern forming method for forming a first recess and a second recess having a depth smaller than that of the first recess on a substrate, wherein the substrate surface is formed of a resist film. A first step of covering and patterning the resist film to form a first opening corresponding to the first recess, and in a region corresponding to the second recess from the first opening A second step of forming a plurality of second openings with a narrow opening width and vertical anisotropic etching are performed to form the first recesses in the first openings, and the plurality of second openings A third step of forming a plurality of recesses corresponding to each of the openings, and isotropic etching to remove sidewalls between the plurality of recesses formed in the plurality of second openings , A fourth step of forming the second recess, and the remaining resist film And the opening width of the first opening and the opening width of the second opening are set such that the first opening is the first recess in the third step. In this case, the plurality of second openings are set so as to have an etching rate difference reaching the depth of the second recess while the depth is reached.

According to the present invention, by utilizing the fact that the etching rate varies depending on the opening width of the resist film, recesses having different depths are formed by one vertical anisotropic etching. Further, for the recess having a shallow depth, a portion where the resist film is not opened remains as a side wall, and therefore, these walls are removed by isotropic etching in a later step. This makes it possible to form recesses having different depths by reducing the number of times of etching. Further, the resist film may be formed only once.
As described above, since the recesses having different depths can be formed without increasing the number of times in both the etching process and the resist film forming process, the manufacturing process is simplified, the manufacturing cost is reduced, and high-precision processing is performed. be able to.
Further, with the reduction of the resist film forming process, the possibility of contamination is reduced and the quality can be improved.

  The plurality of second openings are preferably formed at equal intervals. As a result, the sidewalls between the plurality of recesses formed corresponding to the second opening are also formed with the same thickness, and therefore when removing these sidewalls by isotropic etching in the fourth step. It can be done efficiently.

The pattern forming method according to the present invention can be particularly suitably used when a step shape is formed by the first recess and the second recess.
For example, in the second step, each second opening is arranged concentrically around the first opening, and the second depression is arranged around the first depression. When forming a shape, it can be used in various fields.

A method for manufacturing a droplet discharge head according to the present invention is a method for manufacturing a droplet discharge head having a structure including a step shape, and includes a first step of covering a substrate surface with a resist film, and patterning the resist film. And forming a first opening corresponding to the first recess, and a plurality of second openings having a narrower opening width than the first opening in a concentric manner with the first opening as a center. A second step of forming and performing vertical anisotropic etching to form the first recess in the first opening, and a plurality of recesses corresponding to each of the plurality of second openings. And isotropic etching to remove the sidewalls of the plurality of recesses formed in the plurality of second openings, and the first step around the first recesses. A step shape in which a second recess having a shallower depth than the recess is arranged. And a fifth step of removing the remaining resist film, wherein the opening width of the first opening and the opening width of the second opening are the third step. In this step, an etching rate difference is set so that the plurality of second openings reach the depth of the second recess while the first opening reaches the depth of the first recess. It is characterized by that.
According to the present invention, a structure including a step shape is formed by vertical anisotropic etching once by utilizing the difference in etching rate caused by the opening width of the resist film. Further, for the recess having a shallow depth, a portion where the resist film is not opened remains as a side wall, and therefore, these walls are removed by isotropic etching in a later step. This makes it possible to form a structure including a step shape by reducing the number of times of etching. Further, the resist film may be formed only once.
Thus, according to the present invention, a structure including a step shape can be formed without increasing the number of times in both the etching step and the resist film forming step, thereby simplifying the manufacturing process and reducing the manufacturing cost. High-precision processing can be performed.
Further, with the reduction of the resist film forming process, the possibility of contamination is reduced and the quality can be improved.
In the droplet discharge head, for example, it is necessary to provide a step structure for escape of the adhesive in the positioning reference hole for bonding the flow path forming substrate and the nozzle plate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process diagram showing a fine structure forming method according to the present invention.
First, the surface of the substrate 10 is covered with a resist film 12. Next, as shown in FIG. 1A, an opening is formed in the resist film 12 and patterned. A plan view at this time is shown in FIG.
As shown in FIGS. 1A and 2, the resist film 12 has a circular opening (first opening) 13a and an outer side of the circular opening 13a, and is substantially concentric with the circular opening 13a as a center. A plurality of arranged annular openings (second openings) 13b are provided. At the same time, the opening 13c may be provided in the resist film 12. The diameter of the circular opening 13a is, for example, 100 μm to 500 μm, and the width of the ring of the annular opening 13b is much smaller than the diameter of the circular opening 13a, for example, 0.1 μm to 5 μm. The size of the opening 13c is set so that a necessary effect can be obtained in the subsequent etching. The material of the substrate 10 is not particularly limited as long as it can be suitably processed by an etching method such as a silicon substrate.

  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, etc. through a photomask corresponding to the shape of the opening. Can do. The resist material can be applied to the surface of the substrate 10 using a known method such as a spin coating method, a scan coating method, a spray coating method, or a squeegee coating method.

  Subsequently, as shown in FIG. 1B, a first recess 14a and a plurality of recesses 14b are formed in the substrate 10 by etching using the resist film 12 as a mask. The etching method uses dry etching with a reactive gas that can be processed with high accuracy.

  The first recess 14a corresponds to the circular opening 13a, and the recess 14b is formed to correspond to the annular opening 13b. Here, the depths of the first recess 14a and the recess 14b are determined by the opening width of the circular opening 13a and the opening width of the ring-shaped opening 13b. This is because the etching rate is determined by the opening width due to the microloading effect.

  The microloading effect is the effect that the etchant becomes difficult to enter the opening as the etching mask opening size becomes smaller, resulting in a slower etching rate and a difference in the etching rate between the wide opening and the narrow opening. Say.

  Therefore, as shown in FIG. 1B, the opening width (ring width) of the ring-shaped opening 13b is extremely smaller than the opening width (diameter) of the circular opening 13a as in this embodiment. In addition, the depth Hb of the recess 14b can be made shallower than the depth Ha of the first recess 14a. For the recess 14c formed corresponding to the opening 13c of the resist film 12, the depth of the recess 14c is set to the depth of the first recess 14a if the area of the opening 13c is approximately the same as that of the circular opening 13a. It can be formed to the same extent.

Vertical anisotropic etching with a reactive gas is performed by introducing the reactive gas into a chamber in which the substrate 10 is installed. Examples of the reactive gas include a fluorine-based gas, a halogen-based gas containing at least one of chlorine and bromine. When the substrate 10 is composed of a silicon single crystal, 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 In particular, it is preferable to use any one of SF ₆ and C ₄ F ₈ gases alone or a mixed gas thereof, thereby enabling efficient processing.

  Next, the reactive gas is turned into plasma and dry etching is performed again. Isotropic etching can be performed by converting the reactive gas into plasma. By performing isotropic etching, the side wall 16 of the recess 14b is removed by etching, and as shown in FIG. 1C, a second recess 17 is formed to form a recess 15 having a step shape. it can. At this time, as shown in FIG. 1A, the side walls 16 can be efficiently removed by forming the annular openings 13b at equal intervals. Moreover, since the thinner side wall 16 is easier to remove, it is better to provide the ring-shaped openings 13b densely.

  In the isotropic dry etching performed by converting the reactive gas into plasma, the chamber, the first introduction valve for introducing the reactive gas into the chamber, and the first cooling medium gas for cooling the substrate 10 are introduced. 2, a pair of electrodes provided so as to face each other in the chamber, 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 the substrate 10 This can be performed using a dry etching apparatus provided with an installation base for fixing. 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, and the plasma generating gas is interposed between the pair of electrodes. A high frequency voltage is applied between the electrodes in a filled state. As a result, plasma is generated between the electrodes, and the generated ions and electrons collide with the substrate 10 through the openings of the resist film 12 so that the side walls 16 of the recesses 14b are formed by this isotropic plasma etching. Can be removed. An ICP dry etching apparatus may be used for this isotropic plasma etching.

  In this embodiment, the same reactive gas is used for vertical anisotropic etching and isotropic plasma etching, but the present invention is not limited to the case where the same reactive gas is used. May be used.

  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. 1D, the resist film 12 is removed, so that a recess 15 having a step shape can be formed in the substrate 10. The resist film 12 is stripped by, for example, exposing it to oxygen plasma or ozone vapor under atmospheric pressure or reduced pressure, or immersing the resist film 12 in a resist stripping solution such as acetone or alkylbenzenesulfonic acid that can dissolve the resist film 12. The film 12 can be liquefied.

In addition, the level | step difference of the recessed part 15 which has a level | step difference shape can be multistage not only in 1 step | paragraph.
For example, as shown in FIG. 3A, a circular opening 23a and a plurality of first annular openings 23b concentrically arranged around the circular opening 23a in the resist film 22 and concentric circles on the outer side. A plurality of second ring-shaped openings 23c arranged at the same position are formed. Here, the width of the first annular opening 23b is narrower than the width of the circular opening 23a, and the width of the second annular opening 23c is narrower than the width of the first annular opening 23b.

  Next, as shown in FIG. 3B, vertical anisotropic etching is performed. As described above, the circular opening recess 24a and the first annular opening recess 24b shallower than the circular opening recess 24a can be formed on the substrate by utilizing the microloading effect. Furthermore, since the width of the second ring-shaped opening 23c is made narrower than the width of the first ring-shaped opening 23b by the resist film 22, the second ring-shaped opening 23c is more detailed than the first ring-shaped opening 23b. In addition, the microloading effect becomes remarkable, and the second annular opening recess 24c, which is shallower than the first annular opening recess 24b, can be simultaneously formed on the substrate.

  Next, the reactive gas is turned into plasma and isotropic plasma etching is performed. By removing the side walls of the first annular opening recess 24b and the second annular opening recess 24c using isotropic plasma etching, the inner wall has two steps as shown in FIG. A recess 25 can be formed. In this way, a recess having two or more steps can be formed on the inner wall by a simple method.

  In this embodiment, a structure having a step shape of one step or two or more steps is formed. However, if a plurality of recesses having different depths are formed on one substrate, the step shape is formed. The present invention is not limited to this.

As described above, according to the present invention, when a plurality of recesses having different depths are formed on one substrate, particularly when a fine structure including one or more steps is formed, high processing accuracy is achieved. By using dry etching and determining the opening size of the resist film using the microloading effect, concave portions having different depths are formed by one vertical anisotropic etching. Further, with respect to the concave portions other than the deepest concave portion, a portion where the resist film is not opened is left as a thin wall, and these walls are removed by isotropic etching in a subsequent process. As a result, it is possible to form a structure including a plurality of recesses and step shapes having different depths by a minimum number of etchings. Further, the resist film may be formed only once.
Thus, according to the present invention, it is possible to form a structure including a plurality of recesses and step shapes having different depths without increasing the number of steps in both the etching step and the resist step, thereby simplifying the manufacturing process. The manufacturing cost can be reduced.
Further, with the reduction of the resist process, the possibility of contamination is reduced and quality can be improved.

(Droplet ejection head)
Next, a method for manufacturing a droplet discharge head according to the present invention will be described with reference to the drawings.
The droplet discharge head manufactured in this embodiment is the inkjet head 1 of the inkjet printer shown in FIG. 4, and as shown in FIGS. 5 and 6, the nozzle plate 320, the flow path forming substrate 100, 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 The driving IC 120 is provided.

  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 thermal oxidation, and then an insulator film 55 and a lower electrode film are formed 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 method according to the present invention is used here.

  First, as shown in FIG. 7B, 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. 7C, a resist film 422 is provided on the surface of the silicon substrate 100 '. The resist film 422 has a first opening for forming a positioning reference hole 105 (see FIG. 8A) and a second opening for forming a cavity 102 (see FIG. 8A) serving as an ink chamber. . The first and second openings include a circular opening at the center (first opening) and a plurality of ring-shaped openings (second opening) arranged concentrically around the circular opening. Consists of

  The ink flow path 102 and the positioning reference hole 105 are simultaneously formed by the first vertical anisotropic dry etching. Although the ink flow path 102 and the positioning reference hole 105 have the same etching rate, a plurality of ring-shaped openings arranged concentrically are formed to be extremely smaller than the circular openings, so that the microloading effect is achieved. This reduces the etching rate. Therefore, when the etching reaches a predetermined bottom portion at the center of the ink flow path 102 and the positioning reference hole 105, the annular portion is formed shallow (FIG. 7A).

  Subsequently, as shown in FIG. 8B, the second recess 426 is formed by removing the side wall of the annular opening by the second isotropic dry etching method, and shown in FIG. 8C. As described above, the remaining resist film 424, adhesive resin 400, and 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 positioning reference hole 105.

  Next, as shown in FIG. 6, 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. Further, the connection wiring is formed by wire bonding between the drive IC 120 and the connection portions 60 a and 90 a of the lower electrode film 60 and the lead electrode 90, thereby completing the inkjet head 1.

  With such a configuration, when the nozzle plate 320 is bonded to the flow path forming substrate 100, the second recess 426 can function as an adhesive escape.

  The pattern forming method of the present invention is not limited to the droplet discharge head, and can be used in various microdevice manufacturing processes.

It is process drawing which shows the pattern formation method which concerns on this invention. It is a top view which shows the pattern formation method which concerns on this invention. It is process drawing which shows the other example of the pattern formation method which concerns on this invention. It is a schematic perspective view of an inkjet printer. It is a figure for demonstrating the manufacturing method of an inkjet head. It is a figure for demonstrating the manufacturing method of an inkjet head. It is a figure for demonstrating the manufacturing method of an inkjet head. It is a figure for demonstrating the manufacturing method of an inkjet head.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 12, 22, 422 ... Resist film, 13a, 13b, 13c, 23a, 23b, 23c ... Opening of resist film, 14a, 24a ... Circular opening recessed part of board | substrate, 14b, 24b, 24c ... Ring-shaped opening of board | substrate Concave part, 14c ... Opening concave part of substrate, 15, 25 ... Concave part having step shape, 17, 426 ... Second concave part, 100 ... Passage forming substrate, 102 ... Ink chamber, 105 ... Positioning reference hole

Claims (5)

A pattern forming method for forming a first recess and a second recess having a depth smaller than that of the first recess on a substrate,
A first step of coating the substrate surface with a resist film;
The resist film is patterned to form a first opening corresponding to the first recess, and a plurality of second openings having an opening width narrower than the first opening in a region corresponding to the second recess. A second step of forming the opening of
A third step of performing vertical anisotropic etching to form the first recess in the first opening and to form a plurality of recesses corresponding to each of the plurality of second openings; ,
A fourth step of performing isotropic etching, removing sidewalls of the plurality of recesses formed in the plurality of second openings, and forming the second recesses;
A fifth step of removing the remaining resist film,
The opening width of the first opening and the opening width of the second opening are determined while the first opening reaches the depth of the first recess in the third step. A pattern forming method, wherein the second opening is set so as to produce an etching rate difference that reaches the depth of the second recess.   The pattern forming method according to claim 1, wherein the plurality of second openings are formed at equal intervals.   The pattern forming method according to claim 1, wherein the first concave portion and the second concave portion form a step shape. In the second step, each second opening is arranged concentrically around the first opening,
The pattern forming method according to claim 3, wherein a step shape in which the second concave portion is disposed is formed around the first concave portion. A method of manufacturing a droplet discharge head having a structure including a step shape,
A first step of coating the substrate surface with a resist film;
The resist film is patterned to form a first opening corresponding to the first recess, and a plurality of second openings that are concentrically centered on the first opening and narrower than the first opening. A second step of forming two openings;
A third step of performing vertical anisotropic etching to form the first recess in the first opening and to form a plurality of recesses corresponding to each of the plurality of second openings; ,
Isotropic etching is performed to remove sidewalls of the plurality of recesses formed in the plurality of second openings, and a second shallower depth than the first recess is formed around the first recesses. A fourth step of forming a step shape in which the concave portion is disposed;
A fifth step of removing the remaining resist film,
The opening width of the first opening and the opening width of the second opening are determined while the first opening reaches the depth of the first recess in the third step. A method for manufacturing a droplet discharge head, characterized in that the second opening is set to have an etching rate difference that reaches the depth of the second recess.

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