JP5286710B2 - Fine structure forming method and fluid ejecting head manufacturing method - Google Patents

Description

  The present invention relates to a fine structure forming method and a fluid ejecting head manufacturing method.

As one of the methods capable of processing a fine structure with high accuracy, there is a Bosch process method described in Patent Document 1. The Bosch process method repeats a dry etching process using a sulfur fluoride-based gas such as SF ₆ and a step of forming a sidewall protective film (passivation) using a fluorocarbon-based gas such as CHF ₃ and C ₄ F _8. This method is characterized in that etching with high anisotropy can be performed.

  3 and 4 are process cross-sectional views showing a process of forming a recess in the substrate by the Bosch process method. First, as shown in FIG. 3A, a mask 31 is formed on the substrate 30. A through hole 32 is formed in the mask 31.

  Next, as shown in FIG. 3B, when the substrate 30 is dry-etched through a mask 31, an opening 33 is formed on the substrate. The opening 33 is formed with excellent anisotropy, and the side wall of the opening 33 along the side wall of the first through hole 32 is formed substantially perpendicular to the substrate 30. The bottom surface of the opening 33 is parallel to the surface of the substrate 30. Strictly speaking, the side wall of the opening 33 has a slightly curved shape rather than a planar shape, but in order to make the drawing easier to see, the cross-sectional structure is represented by a straight line and shown as a shape perpendicular to the surface of the substrate 30.

  Next, as shown in FIG. 3C, when the substrate 30 is passivated through the mask 31, a protective film 34 is formed on the surfaces of the mask 31 and the opening 33.

  Next, as shown in FIG. 3D, when dry etching is performed again in the same manner, the protective film 34 formed on the upper surface of the mask 31 and the bottom surface of the opening 33 that are parallel to the surface of the substrate 30 disappears. Etching proceeds. The protective film 34 formed on the side walls of the mask 31 and the opening 33 remains.

  Further, the steps shown in FIGS. 3C and 3D are alternately repeated as many times as necessary, and the formation of the recesses by the Bosch process method is completed by digging down to the required depth.

  Further, for example, as shown in FIG. 4A, it is assumed that a mask 41 having a through hole 42 having a stepped step structure is attached to a substrate 40 and etching is performed by a Bosch process method through the mask 41.

  In that case, as shown in FIG. 4B, first, the low step of the through hole disappears, and etching proceeds until the substrate 40 is exposed. At that time, the substrate 40 exposed in the through hole is also etched to form a first opening 43 having a vertical side wall portion and a horizontal bottom surface. The protective film formed by passivation is formed on the mask 41, the first opening 43, and the newly exposed surface of the substrate 40.

  Next, as shown in FIG. 4C, the first opening 43 is dug further vertically along the side wall. In addition, since the substrate 40 is dug vertically along the shape of the remaining side wall of the mask 41, the substrate 40 reflects the stepped step structure provided in the through hole 42 and the side wall of the first opening. A stepped step structure in which vertical surfaces formed along the mask 41 are connected is formed.

  As described above, when etching is performed by the Bosch process method, the protective film and the mask are removed and the etching proceeds in a plane portion where ions are incident by dry etching. Further, the formed protective film remains on the side wall portion, and the substrate is protected from the incidence of ions generated slightly in the horizontal direction. As a result, etching with high anisotropy in the direction perpendicular to the substrate is possible.

  By the way, the shape of precision parts used in electronic devices is not limited to a vertical shape and a horizontal plane. For example, a specific shape of a part is configured by combining shapes having a certain inclination with respect to a horizontal plane (taper shape).

As methods for forming various tapered shapes, there are methods described in Patent Documents 2 to 4. In the method of Patent Document 2, a multi-stage tapered shape with different depths is manufactured by performing wet etching in two stages through an etching mask having a level difference. In the methods of Patent Documents 3 and 4, an appropriate amount of gas that generates a reaction product is added to the etching gas, and dry etching is performed while depositing reactive organisms on the side wall of the groove as a protective film. It has been proposed to protect from etching and produce a tapered shape.
US Pat. No. 5,501,893 JP 2005-183419 A JP-A-10-70104 Japanese Patent Laid-Open No. 6-5565

  However, the above method has the following problems. That is, in any method, the configuration is intended only for forming a tapered shape. Therefore, using the above method to form a shape combining a tapered shape with another shape still requires a complicated process.

  For example, a shape in which a tapered shape and a vertical shape communicate with each other is very useful because it can be applied to a nozzle hole of a fluid ejecting apparatus or wiring for three-dimensional mounting. However, in order to form such a shape using the method proposed in the above-mentioned patent document, it is necessary to perform the process of forming each shape in a separate process.

  FIG. 5 is a process cross-sectional view for forming the communicating shape by a conventional method. First, as shown in FIG. 5A, a first mask 51 having a through hole is attached to a substrate 50, and an opening 52 having a tapered shape is formed by a conventional method. Next, as shown in FIG. 5B, the side wall portion of the first mask 51 and the side wall portion and the tapered portion of the opening 52 are protected by the second mask 53. Next, as shown in FIG. 5C, a vertical shape is formed by performing dry etching on the substrate 50 via the first mask 51 and the second mask 53, and the intended communication shape is formed. It is necessary to take Therefore, a plurality of processes are complicated.

  The present invention has been made in view of such circumstances, and includes a first opening having a side wall perpendicular to the substrate, and a second opening having a tapered side wall communicating with the first opening. And a manufacturing method of a fluid jet head using this method.

In order to solve the above-described problems, the fine structure forming method of the present invention includes a first opening having a side wall perpendicular to the substrate, a large opening area communicating with the first opening and toward the substrate surface. A second opening portion having a tapered side wall portion, and a first step of forming a mask having a through hole having a stepped step structure on the substrate, The first opening and the second opening are formed by alternately repeating a passivation process for forming a protective film and a dry etching process for etching the substrate through the mask. A second step, wherein in the second step, the amount of etching in the dry etching process is larger than the amount of the protective film formed in the passivation process, Etching the bottom surface of the first opening while etching a part of the substrate that becomes the side wall of the second opening forms the side wall of the second opening in a tapered shape. .
According to this method, it is not necessary to create the vertical shape and the tapered shape in independent processes, and it is possible to form a shape in which these shapes communicate with each other at a time. Therefore, it is possible to simplify the process by omitting the labor of processing.

In the present invention, in the second step, it is desirable to control the etching amount in the dry etching process and the amount of the protective film formed in the passivation process by controlling the temperature of the substrate.
In general, when the temperature of the substrate is raised, the film formation rate decreases and the etching rate increases. Conversely, when the substrate temperature is lowered, the deposition rate increases and the etching rate decreases. Therefore, by controlling the temperature of the substrate, it is possible to easily control the amount of the protective film formed by the passivation process and the etching amount by the dry etching process.

In the present invention, it is preferable that the second step is performed on a support base capable of controlling the temperature of the substrate.
According to this method, a desired shape can be formed easily and with good reproducibility by processing the substrate at a desired temperature.

In the present invention, in the second step, the etching amount in the dry etching process and the formation time in the passivation process are controlled by controlling the etching time in the dry etching process and the formation time of the protective film in the passivation process. It is desirable to control the amount of protective film applied.
According to this method, the amount of the protective film formed by the passivation process and the amount of etching by the dry etching process are arbitrarily controlled by individually controlling the process time of the dry etching process and the process time of the passivation process. be able to. Therefore, the balance between the amount of the protective film formed by the passivation process and the etching amount by the dry etching process can be accurately controlled, and as a result, a desired shape can be easily formed.

In the present invention, in the second step, the temperature of the substrate, the etching time in the dry etching process, and the formation time of the protective film in the passivation process are constant from the start to the end of the second step. It is desirable to be.
According to this method, the taper shape and the vertical shape can be simultaneously formed only by performing etching while maintaining the substrate temperature and each processing time at predetermined constant conditions. Therefore, a desired shape can be formed very easily. Moreover, since it is not necessary to change the conditions during the process, the process can be simplified.

The substrate is preferably a silicon substrate.
The processed silicon substrate can be used for a MEMS device such as a fluid ejecting head or a substrate for three-dimensional mounting.

According to another aspect of the invention, there is provided a fluid ejection head manufacturing method including: a first opening having a side wall perpendicular to the substrate; and a second opening having a tapered side wall communicating with the first opening. A method of manufacturing a fluid ejecting head provided with a nozzle hole including a structure, wherein the shape of the nozzle hole is formed by the fine structure forming method of the present invention described above.
According to this manufacturing method, a shape in which the tapered shape and the vertical shape communicate with each other can be easily formed as the nozzle hole of the fluid ejecting head. Therefore, it is possible to easily manufacture a fluid ejecting head capable of reducing the ejection resistance during fluid ejection and ejecting with a weak driving force.

  Hereinafter, a method for forming a microstructure according to an embodiment of the present invention will be described with reference to FIG. In all the drawings below, the film thicknesses and dimensional ratios of the constituent elements are appropriately changed in order to make the drawings easy to see. Strictly speaking, the surface etched by the dry etching process to be described later has a slightly curved shape instead of a planar shape, but the cross-sectional structure is represented by a straight line for easy viewing of the drawing.

  FIG. 1 is a process cross-sectional view illustrating a fine structure forming method according to an embodiment of the present invention. First, as shown in FIG. 1A, a substrate 1 is prepared and a mask 2 is formed on the substrate 1 (first step). The mask 2 includes a first mask portion 3 having a thin film thickness and a second mask portion 4 having a thick film thickness, and has a step structure having different steps in height. The mask 2 is provided with a first opening H1 having a small opening area and a second opening H2 having a large opening area in order from the substrate 1 side, and the two communicate with each other to form one through hole 5. ing. The second opening H2 has a bottom surface that is horizontal to the substrate 1, and the first opening H1 is disposed on the bottom surface. The side walls of the first opening H1 and the second opening H2 are formed perpendicular to the substrate.

  In the present embodiment, a silicon substrate is used as the substrate 1. A silicon oxide film is used as the mask 2. The thickness of the mask 2 is 1 μm, for example, and the depth of the first opening H1 is 0.6 μm to 0.7 μm, for example. The planar shape of the first opening H1 and the second opening H2 is, for example, a circle, and the diameter of the first opening H1 is, for example, 20 μm, and the diameter of the second opening H2 is 35 μm. The type of the mask 2 is not particularly limited as long as a desired mask 2 can be formed. As a method for forming the step of the mask 2, for example, a method of separately processing the first opening H1 and the second opening H2 using a photolithography method, or a resist formed on the mask 2 using a gradation mask. It can be formed by employing a conventionally known method such as controlling the thickness of the film.

Next, as shown in FIGS. 1B to 1F, a passivation process and a dry etching process are alternately performed (second step). In this embodiment, for example, dry etching is performed using SF ₆ at a gas flow rate of 450 sccm to 600 sccm for 8 seconds to 10 seconds, and C ₄ F ₈ is used for a passivation process from 160 sccm. Passivation is performed between 200 sccm for 5 to 7 seconds, and these processes are performed alternately and continuously. Further, the processing of the substrate 1 is performed on the support base 6 capable of controlling the temperature of the substrate, and the temperature of the substrate 1 is controlled between 35 ° C. and 40 ° C., for example. Furthermore, the above conditions are kept constant during etching.

  Note that these processing conditions of the present embodiment are partly common with the conditions for forming the shape of FIG. The difference is that the substrate temperature is controlled between 0 ° C. and 10 ° C. under the conditions for forming the shape of FIG. In general, when the temperature condition is raised, the amount of etching by the dry etching process increases and the protective film formed by the passivation process tends to decrease. As the gas used in the dry etching process, other sulfur fluoride-based gases can also be used. In addition, as the gas used in the passivation process, other fluorocarbon gases can be used. The gas used in the passivation process can be used by mixing with argon, or can be used without mixing with argon.

  FIG. 1 (b) shows a state after the passivation process among the two processes which are alternately repeated. As the etching proceeds, the substrate 1 is anisotropically etched into a shape corresponding to the first through hole, and a first opening 7 having a vertical side wall and a horizontal bottom surface is formed. The first mask portion disappears by etching, the surface of the substrate 1 is exposed, and the remaining second mask portion 4 forms the second through hole 9. Further, the protective film 8 generated by the passivation process is formed on the entire surface of the substrate 1 so as to cover the bottom surface and the side surface of the first opening 7 exposed at the bottom surface of the through hole 9.

  Next, as shown in FIG. 1C, when a subsequent dry etching process is performed, each of the second mask portion 4, the substrate 1 exposed in the second through hole 9, and the bottom surface of the first opening portion 7. The protective film 8 formed on the horizontal plane disappears by dry etching. The protective film 8 formed on the side walls of the first opening 7 and the second mask part 4 where there is almost no incident of ions by the dry etching process remains without disappearing.

  Next, as shown in FIG. 1D, etching is further performed. Then, anisotropic etching proceeds in the vertical direction along the shape of the second mask portion 4 on the surface of the substrate 1 exposed in the second through hole 9 and in the vicinity of the side wall of the second mask portion 4. The molding surface is formed. In addition, anisotropic etching also proceeds on the bottom surface of the first opening 7 in the vertical direction along the side wall of the first opening 7. On the other hand, the protective film 8 remaining on the side wall of the first opening 7 is also gradually etched from above, thereby exposing the substrate above the side wall of the first opening 7 to the outside. As a result, in the upper portion of the side wall of the first opening 7 exposed by the dry etching process, etching proceeds from the corner of the joint between the side wall of the first opening 7 and the surface of the substrate 1, and the second tapered shape is gradually formed. Opening 10 is formed.

  Next, as shown in FIG. 1E, when a passivation process is performed, the generated protective film 8 is exposed to the bottom surface of the through hole 9, the bottom surface of the first opening 7, the side wall portion, and the side wall of the second opening portion 10. It is formed on the entire surface of the substrate 1 so as to cover the part.

  Next, as shown in FIG. 1 (f), when further etching is performed, a vertical molding surface is formed along the side wall of the first opening 7 and the side wall of the second mask portion 4. Forms a multistage structure in which the second openings 10 having a tapered shape communicate with each other. Etching further proceeds on the bottom surface of the first opening 7. Thereafter, if necessary, the steps shown in FIGS. 1E and 1F are repeated to dig the opening to a desired depth. As described above, the formation of the fine structure according to the present embodiment is completed.

  According to the fine structure forming method having the above-described structure, anisotropic etching proceeds along the mask 2 and the side wall of the first opening 7 formed by the dry etching process in the vertical direction, and the vertical shape is It is formed. At the same time, a second opening 10 having a tapered shape is formed on the substrate 1 corresponding to a location where a difference in the thickness of the mask 2 occurs. Therefore, it is not necessary to create the vertical shape and the tapered shape by independent processes, and it is possible to form a shape in which these shapes communicate with each other at a time. Therefore, it is possible to simplify the process by omitting the labor of processing.

  In the present embodiment, by controlling the temperature of the substrate 1, the etching amount in the dry etching process and the amount of the protective film 8 formed in the passivation process are controlled. Therefore, the amount of the protective film 8 formed by the passivation process and the etching amount by the dry etching process can be accurately controlled, and as a result, a desired shape can be easily formed.

  Moreover, in this embodiment, it is supposed to carry out on the support stand 6 which can control the temperature of the board | substrate 1. FIG. Therefore, the temperature of the substrate 1 can be easily controlled by the function of the support base 6. Therefore, the substrate 1 can be processed while maintaining a desired temperature with high reproducibility, and a desired shape can be formed easily and with high reproducibility.

  In the present embodiment, the temperature of the substrate 1, the etching time in the dry etching process, and the formation time of the protective film 8 in the passivation process are constant from the start to the end of the opening forming process. . Therefore, the taper shape and the vertical shape can be simultaneously formed only by performing etching while maintaining the temperature of the substrate 1 and each processing time at predetermined constant conditions. Therefore, a desired shape can be formed very easily. Moreover, since it is not necessary to change the conditions during the process, the process can be simplified.

  In this embodiment, in the second step, the etching amount in the dry etching process and the amount of the protective film 8 formed in the passivation process are controlled by changing the control temperature of the substrate 1. It is also possible to control the etching amount in the dry etching process and the amount of the protective film 8 formed in the passivation process by controlling the etching time in step 1 and the formation time of the protective film 8 in the passivation process. In that case, for example, the time of the passivation process is between 2 seconds and 4 seconds, and the temperature of the support base 6 of the substrate 1 is between 0 ° C. and 10 ° C. Other conditions are common to the present embodiment. This is partly in common with the conditions for forming the shape of FIG. 4B described above, and the difference is that the time of the passivation process in the processing conditions of FIG. 4B is between 5 seconds and 7 seconds. However, the point is changed between 2 seconds and 4 seconds.

  According to this method, the etching time in the dry etching process and the amount of the protective film 8 formed in the passivation process can be arbitrarily controlled by individually controlling the process time of the dry etching process and the process time of the passivation process. Can be controlled. Therefore, the balance between the amount of the protective film 8 formed by the passivation process and the etching amount by the dry etching process can be accurately controlled, and as a result, a desired shape can be easily formed.

  In the present embodiment, the processing conditions from the start to the end of the opening forming process are made constant, but some conditions may be changed during the processing.

  In the present embodiment, the formed opening does not penetrate the substrate, but the opening may penetrate the substrate.

  Next, a fluid ejecting head manufactured by using the microstructure forming method of the present invention will be described with reference to FIG. 2A and 2B are diagrams illustrating a droplet discharge head which is an embodiment of the fluid ejecting head. FIG. 2A is a perspective view of a main part, and FIG. 2B is a cross-sectional view of the main part.

  As shown in FIG. 2A, the droplet discharge head 20 includes, for example, a nozzle plate 21 and a vibration plate 22, which are joined via a partition member (reservoir plate) 23. A plurality of spaces 24 and a liquid reservoir 25 are formed between the nozzle plate 21 and the diaphragm 22 by the partition member 23. Each space 24 and the liquid reservoir 25 are filled with a liquid material, and each space 24 and the liquid reservoir 25 communicate with each other via a supply port 26. In addition, a plurality of nozzle holes 27 are formed in the nozzle plate 21 in a state where the nozzle holes 27 are aligned vertically and horizontally in order to eject the liquid material from the space 24. On the other hand, a hole 28 for supplying a liquid material to the liquid reservoir 25 is formed in the diaphragm 22.

  As shown in FIG. 2B, a piezoelectric element (piezo element) 29 is bonded to the surface of the diaphragm 22 opposite to the surface facing the space 24. The piezoelectric element 29 is positioned between a pair of electrodes 30 and is configured to bend so that when energized, it projects outward. The diaphragm 22 to which the piezoelectric element 29 is bonded in such a configuration is integrally bent with the piezoelectric element 29 and bends outward at the same time, whereby the volume of the space 24 is increased. It is going to increase. Accordingly, the liquid corresponding to the increased volume in the space 24 flows from the liquid reservoir 25 through the supply port 26. Further, when the energization to the piezoelectric element 29 is released from such a state, both the piezoelectric element 29 and the diaphragm 22 return to their original shapes. Accordingly, since the space 24 also returns to its original volume, the pressure of the liquid material inside the space 24 rises, and the liquid droplet 31 is discharged from the nozzle hole 27 toward the substrate.

  Here, the nozzle hole 27 is formed by using the fine structure forming method described above. The nozzle hole 27 has a shape in which a tapered shape and a vertical shape communicate with each other, and is provided so that the tapered shape faces the inside of the space 24. Therefore, when the liquid droplet 31 is ejected from the nozzle hole 27, the pressure of the liquid material is reduced to abrupt change from the pressure inside the space 24 to the pressure inside the nozzle hole 27. Therefore, the resistance caused by the pressure change can be lowered. As a result, discharge is possible with a weak driving force.

  In FIG. 2, the liquid droplet ejection head 20 that ejects (discharges) liquid droplets as a fluid has been described. However, the fine structure forming method of the present invention is applicable to other fluid ejection heads that eject powder or the like as a fluid. It can also be applied to a method for forming nozzle holes. Furthermore, the present invention can be applied to a method for forming a through-hole in a substrate that is required for three-dimensional mounting, and can be widely applied to a general method for forming an opening.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

It is process drawing which shows the formation method of the microstructure of this invention. It is explanatory drawing which shows the droplet discharge head manufactured using the formation method of this invention. It is process drawing which shows the formation method of the board | substrate by the Bosch process method. It is process drawing which shows the formation method of the board | substrate by the Bosch process method. It is process drawing which shows the formation method of the multistage structure by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Mask, 6 ... Support stand, 8 ... Protective film, 20 ... Droplet discharge head (fluid ejection head), 27 ... Nozzle hole

Claims (6)

A first opening having a side wall perpendicular to the substrate and a second opening having a tapered side wall that communicates with the first opening and increases in opening area toward the substrate surface. A method of forming a structure,
A first step of forming a mask having a through hole having a stepped step structure on the substrate;
The first opening and the second opening are formed by alternately and alternately repeating a passivation process for forming a protective film and a dry etching process for etching the substrate through the mask. A second step,
In the second step, the depth etched per unit time in the dry etching process is larger than the thickness of the protective film formed per unit time in the passivation process, and the side wall portion of the second opening A method for forming a fine structure, wherein the side wall of the second opening is tapered by etching the bottom of the first opening while etching a part of the substrate.   In the second step, by controlling the temperature of the substrate, the depth etched per unit time in the dry etching process and the thickness of the protective film formed per unit time in the passivation process are controlled. The method for forming a fine structure according to claim 1.   3. The method for forming a microstructure according to claim 2, wherein the second step is performed on a support base capable of controlling the temperature of the substrate. In the second step, the temperature of the substrate, the etching time in the dry etching process, and the protective film forming time in the passivation process are constant from the start to the end of the second step. The method for forming a microstructure according to any one of claims 1 to 3 . The method for forming a microstructure according to any one of claims 1 to 4 , wherein the substrate is a silicon substrate. Fluid ejection provided with a nozzle hole including a fine structure including a first opening having a side wall perpendicular to the substrate and a second opening having a tapered side wall communicating with the first opening. A method of manufacturing a head,
The method of manufacturing a fluid ejecting head, wherein the shape of the nozzle hole is formed by the fine structure forming method according to claim 1.

Images