JP2009061668A - Processing method of silicon substrate, and manufacturing method of liquid discharge head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a perforation efficiently while forming a small opening of the perforation at the rear surface of a silicon substrate. <P>SOLUTION: This processing method of a silicon substrate includes a process for forming an etching mask layer 6 with an opening 7 at the rear surface of the silicon substrate 1, a process for forming a deterioration layer 8 in the silicon substrate 1 by irradiating the opening 7 of the etching mask layer 6 with a laser beam from the rear surface of the silicon substrate 1, a process for forming a plurality of guidance holes 9 which are not penetrated from the rear surface of the silicon substrate 1 to the surface of the silicon substrate 1 by irradiating the opening 7 of the etching mask layer 6 with the laser beam from the rear surface of the silicon substrate 1, and a process for forming an ink supply port 11 used as the perforation penetrated to the surface of the silicon substrate 1 by applying anisotropic etching to the silicon substrate 1 wherein the guidance hole 9 and the deterioration layer 8 have been formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for processing a silicon substrate for forming a through hole in a silicon substrate, and a method for manufacturing a liquid ejection head that ejects a liquid such as ink onto a recording material such as recording paper.

  As an ink jet head that discharges ink that is liquid, an ink jet head that discharges ink upward of a heater that generates discharge energy (hereinafter referred to as a side shooter type head) is known. In this side shooter type head, a through hole is provided in a silicon substrate on which a heater is formed, and ink is supplied from the back side of the surface on which the heater is formed through a long ink supply port that is a through hole. The method is adopted.

  In this side shooter type head, as a method of forming an ink supply port penetrating the silicon substrate, for example, there is a method disclosed in Patent Document 1. In Patent Document 1, an ink supply port is formed in a silicon substrate having a <100> plane crystal plane orientation by anisotropic etching with a strong alkaline solution. In this anisotropic etching of the silicon substrate, the ink supply port is formed by utilizing the difference in solubility between the <100> plane and the <111> plane forming the crystal plane orientation of the silicon substrate with respect to the strong alkaline solution.

  By the way, the process of forming the ink supply port on the silicon substrate by anisotropic etching using a strong alkaline solution is one of the factors that reduce the production efficiency of the inkjet head because the etching time is relatively long.

  Also, as shown in FIG. 10, the cross-sectional shape of the ink supply port 106 formed by anisotropic etching is such that the opening cross-sectional area varies from the back side to the front side along the angle 54.7 ° formed by the <111> plane. It will be formed in the taper shape which becomes small gradually toward. That is, the opening width of the ink supply port 106 on the back surface side of the silicon substrate 101 is wider than the opening width of the ink supply port 106 on the front surface side of the silicon substrate 101 on which the heater 103 is formed. As a result, the lateral width (dimension in the short side direction of the long ink supply port) of the element substrate (inkjet head substrate) constituting the ink jet head having the heater and the nozzle for discharging ink is the back surface of the silicon substrate. It depends on the opening width of the ink supply port on the side. That is, the large width of the ink jet chip causes an increase in the manufacturing cost of the ink jet head. Therefore, in order to reduce the manufacturing cost, it is necessary to reduce the lateral width of the inkjet chip by reducing the opening width of the ink supply port on the back surface side of the inkjet chip.

As a countermeasure against this, a method of forming an ink supply port with a wall surface perpendicular to the front and back surfaces (main surface) of the silicon substrate using dry etching has been proposed. Also disclosed is a method in which dry etching and anisotropic etching are combined to form the wall surface of the ink supply port in a vertical shape on the front and back surfaces of the silicon substrate (see Patent Document 2).
JP-A-9-011479 JP 2004-148824 A

  However, when dry etching is used in the ink supply port formation process as described above, the etching process requires a relatively long etching time, thereby reducing the etching time and improving the production efficiency. Is required.

  Therefore, the present invention provides a silicon substrate processing method, a liquid discharge head manufacturing method, and a liquid discharge head that can form a through hole on the back surface of the silicon substrate to be small and can efficiently form the through hole. For the purpose.

  In order to achieve the above-described object, a silicon substrate processing method according to the present invention includes a step of forming an etching mask layer having an opening on the back surface of the silicon substrate, and a laser from the back surface of the silicon substrate to the opening of the etching mask layer. A step of forming a deteriorated layer inside the silicon substrate by irradiating light, and a plurality of laser beams that do not penetrate from the back surface of the silicon substrate to the surface of the silicon substrate by irradiating the opening of the etching mask layer from the back surface of the silicon substrate. A step of forming a non-through hole, and a step of forming a through hole penetrating to the surface of the silicon substrate by performing anisotropic etching on the silicon substrate on which the non-through hole and the altered layer are formed.

  According to the present invention, the opening of the through hole on the back surface of the silicon substrate can be formed small and the through hole can be formed efficiently. Therefore, according to the present invention, the processing speed of the through hole can be improved and the manufacturing cost can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  The silicon substrate processing method according to the present invention provides a through hole such as an ink supply port (liquid supply port) of an inkjet head in a manufacturing process of a structure including a silicon substrate, particularly a device such as an inkjet head. It is preferably used when forming on a silicon substrate. A feature of the present invention is that, prior to the etching process of the silicon substrate, the silicon substrate forming the ink supply port is irradiated with laser light to make the altered layer amorphous in the silicon substrate, and the non-through hole And leading holes are formed respectively.

(First embodiment)
The silicon substrate processing method of the present embodiment includes a step of forming an etching mask layer having an opening on the back surface of the silicon substrate, a step of irradiating a laser beam to form a deteriorated layer inside the silicon substrate, and a laser beam. And forming a plurality of leading holes as non-through holes. Further, this processing method includes a step of forming a through hole penetrating to the surface of the silicon substrate by performing anisotropic etching on the silicon substrate on which the leading hole and the altered layer are formed.

  FIG. 1 shows a perspective view of a part of an inkjet head substrate. As shown in FIG. 1, an electrothermal conversion element (TaN) 2 serving as a heater serving as a discharge energy generating element that generates energy for discharging ink is disposed on the surface of a silicon substrate 1 having a crystal axis (100). Yes. Further, a SiN layer 4 and a Ta layer 5 are laminated on the surface of the silicon substrate 1 as a protective layer of the electrothermal conversion element 2.

  The electrothermal conversion element 2 is electrically connected to a control signal input electrode (not shown) for driving the element. The thickness of the silicon substrate 1 is about 625 μm. In the present embodiment, a single silicon substrate 1 that forms a part of the substrate for an ink jet head will be described. However, in reality, the same processing is performed in units of wafers.

FIG. 2 shows an AA cross section in FIG. As shown in FIG. 2, on the back surface of the silicon substrate 1, a polyether amide resin is laminated on the SiO ₂ layer 1a of the silicon substrate 1, and an etching mask layer 6 having an opening 7 is formed. The inside of the part 7 becomes an etching part.

  First, as shown in FIG. 3, an altered layer formed into an amorphous state in the silicon substrate 1 by irradiating laser light into the opening 7 of the etching mask layer 6 from the back surface to the front surface of the silicon substrate 1. 8 is formed. At this time, the laser beam is focused on a position at a depth of about 500 μm from the back surface of the silicon substrate 1, and the altered layer 8 is formed on the silicon substrate (inkjet head substrate) 1 by laser processing using multiphoton absorption. They are arranged in rows along the long side direction. That is, the silicon substrate 1 is formed in a row parallel to the long side direction of the ink supply port as a long through hole formed in the silicon substrate 1. The altered layer 8 is made amorphous so that the etching rate is relatively fast.

  In the present embodiment, the altered layers 8 are formed in six rows along the long side direction of the silicon substrate 1 on a plane parallel to the front surface (back surface) of the silicon substrate 1. The altered layer 8 was formed with a pitch distance of 36 μm with respect to the short side direction of the silicon substrate 1 and with a length of about 8.6 mm with respect to the long side direction of the silicon substrate 1. The altered layer 8 was formed using a laser beam of a fundamental wave (wavelength 1060 nm) of a YAG laser, and the output and frequency of the laser beam were set to appropriate values.

  In the present embodiment, the deteriorated layer 8 is processed using laser light having a fundamental wave (wavelength 1060 nm) of a YAG laser. However, the laser beam used for processing is not limited to this laser beam as long as multiphoton absorption by the laser beam can be used for silicon which is a material for forming the silicon substrate 1. For example, the femtosecond laser can similarly perform multiphoton absorption processing on silicon, and the altered layer may be formed using such laser light.

  In the step of forming the deteriorated layer 8, it is preferable that the deteriorated layer 8 is formed at a position in the range of 10% to 50% of the thickness of the silicon substrate 1 from the surface of the silicon substrate 1. When the altered layer is formed at a position less than 10% of the thickness of the silicon substrate 1 from the surface of the silicon substrate 1, heat transfer on the surface of the silicon substrate is caused by variations in the laser processing depth when the altered layer is formed. It is difficult to control damage to the conversion element or the like due to laser light. Further, when the altered layer is formed at a position less than 50% of the thickness of the silicon substrate 1 from the surface of the silicon substrate 1, the processing time of wet etching for forming the ink supply port becomes longer, and the formation is performed. In some cases, the width in the short side direction of the ink supply port on the back side of the silicon substrate is increased.

  Next, as shown in FIG. 4, a plurality of non-through holes that do not penetrate from the back surface to the front surface of the silicon substrate 1 from the back surface to the front surface of the silicon substrate 1 by irradiating laser light from the back surface of the silicon substrate 1. A plurality of leading holes 9 are formed. In the step of forming the leading hole 9, the leading hole 9 was formed by using a third harmonic wave (THG: wavelength 355 nm) laser beam of a YAG laser, and the output and frequency of the laser beam were set to appropriate values. In the present embodiment, the diameter of the leading hole 9 is formed to about φ40 μm. The diameter of the leading hole 9 is desirably about φ5 μm to 100 μm. If the diameter of the leading hole is too small, it is not preferable because the etchant hardly enters the leading hole during anisotropic etching performed in the subsequent process. Further, when the diameter of the leading hole is too large, it is not preferable because it takes a relatively long time to form the leading hole having a desired depth. As the depth of the leading hole 9, it was formed from the back surface of the silicon substrate 1 to a depth of about 500 μm to 575 μm.

  Further, the plurality of leading holes 9 have a rectangular frame shape surrounding the altered layer 8 along the outer periphery of a region parallel to the surface of the silicon substrate 1 in the altered layer 8 formed inside the silicon substrate 1. Arranged to form. That is, the plurality of leading holes 9 were arranged at a pitch distance of 33 μm with respect to the long side direction of the silicon substrate 1 and formed in two rows parallel to the long side direction. At both ends in the longitudinal direction of the leading holes 9 arranged in two rows, a plurality of leading holes 9 are also arranged at the same pitch in the short side direction of the silicon substrate 1, and the width is 150 μm in the short side direction. It was formed to make. In FIG. 5, the perspective view from the back surface of the silicon substrate 1 in which the leading hole 9 was formed is shown. This silicon substrate constitutes a part of the ink jet head.

  In the present embodiment, the leading hole 9 is processed using a laser beam of a third harmonic (THG: wavelength 355 nm) of a YAG laser. However, the wavelength may be any wavelength that allows holes to be drilled in silicon, which is the material of the silicon substrate 1, and the laser beam used for processing the leading holes 9 is not limited to this laser beam. For example, even a second harmonic wave (SHG: wavelength 532 nm) of a YAG laser has a relatively high absorption rate with respect to silicon like THG, and a leading hole is formed using such laser light. May be. The leading hole may be formed by laser beam ablation, so-called laser ablation.

  The leading hole 9 is preferably formed such that the leading end of the leading hole is positioned at the same depth as the altered layer 8 in the thickness direction of the silicon substrate 1. That is, it is desirable to process the leading hole 9 to a depth at which the tip of the leading hole 9 reaches the deteriorated layer 8. If the leading end of the leading hole 9 does not reach the deteriorated layer 8, it is not preferable because rapid etching may not be performed when performing wet etching in a later step.

  Next, anisotropic etching was performed on the silicon substrate 1 on which the altered layer 8 and the leading hole 9 were formed by laser processing. As this anisotropic etching, for example, wet etching using an alkaline aqueous solution such as TMAH (tetramethylammonium hydroxide) was performed. Wet etching is preferable from the viewpoint of throughput because several tens of silicon substrates can be processed at once.

  By wet etching the silicon substrate 1 that has been subjected to laser processing, first, the etching solution penetrates into each of the leading holes 9, and the etching inside the leading holes 9 proceeds as shown in FIG. Subsequently, when the etching solution reaches the altered layer 8, the altered layer 8 is subjected to multiphoton absorption processing, and its crystal structure is broken, so that the etching rate becomes faster than other portions. Therefore, as shown in FIG. 7, the etching of the altered layer 8 proceeds preferentially. As a result, as shown in FIG. 8, the region surrounded by the altered layer 8 and the leading hole 9 is removed as a piece-like silicon portion 10. Accordingly, wet etching for forming a through hole (ink supply port) in the silicon substrate 1 can be performed in a relatively short time.

  After removing the silicon portion 10, wet etching was performed until an ink supply port 11 penetrating to the surface of the silicon substrate 1 was formed. Further, the SiN layer 4 formed at the opening portion of the ink supply port 11 on the surface of the silicon substrate 1 was removed by dry etching to obtain the ink supply port 11 opening on the surface side of the silicon substrate 1 (FIG. 9). ).

  In the embodiment described above, 25 silicon substrates 1 are wet-etched at once, and the time required for the etching process is 5 hours. The processing time per silicon substrate including laser processing was about 20 minutes.

  Conventionally, when a silicon substrate is processed by dry etching, the processing time is 40 minutes to 60 minutes per silicon substrate, and when dry etching and wet etching are combined, processing time is 30 minutes to 50 minutes per silicon substrate. Needed. Therefore, the silicon substrate processing method of the present embodiment can efficiently form an ink supply port having a relatively narrow opening width on the back surface of the silicon substrate, as compared with the conventional processing method.

  As described above, the silicon substrate processing method of the present embodiment includes the step of forming the altered layer 8 inside the silicon substrate 1, the step of forming the plurality of leading holes 9, the leading hole 9 and the altered layer 8. And forming the ink supply port 11 which is a through hole by performing anisotropic etching on the formed silicon substrate 1. As a result, the ink supply port 11 can be formed with a small opening on the back surface of the silicon substrate 1 and the ink supply port 11 can be efficiently formed. Therefore, according to this embodiment, the processing speed of the ink supply port 11 can be improved, and the manufacturing cost of the inkjet head can be reduced.

  In the above-described embodiment, the processing example in which the ink supply port 11 is formed on the silicon substrate 1 has been described. However, when manufacturing the ink jet head, it is preferable that a step of forming an ink flow path forming member on the surface of the silicon substrate 1 is performed before the step of forming the ink supply port 11 performed in the present embodiment. Although not shown, in the case of this configuration, an ink flow path forming member having, on the surface of the silicon substrate 1, a discharge port that discharges ink that is a liquid and an ink flow path as a liquid flow path that communicates with the discharge port. Is formed.

(Second Embodiment)
In the present embodiment, each step is performed in the same manner as in the first embodiment, except that the step of forming the leading hole 9 is performed before the step of forming the deteriorated layer 8 in the first embodiment. Then, an ink supply port is formed in the silicon substrate.

  In the present embodiment, in the step of forming the leading holes, a plurality of leading holes are arranged in a frame shape as described above on a plane parallel to the surface of the silicon substrate. Subsequently, in the step of forming the deteriorated layer, the deteriorated layer is formed in a frame formed by a plurality of leading holes formed in the silicon substrate. Then, wet etching is performed on the silicon substrate on which the leading hole and the altered layer are formed to form an ink supply port penetrating to the surface of the silicon substrate.

  In addition, the wet etching processing time in this embodiment is 5 hours as in the first embodiment. Therefore, the time required for forming the ink supply port can be shortened regardless of the order of the step of forming the altered layer 8 and the step of forming the leading hole 9 first.

It is a perspective view which shows a part of inkjet head typically. It is sectional drawing which shows a silicon substrate typically. It is sectional drawing which shows typically the process of forming a deteriorated layer in the inside of a silicon substrate. It is sectional drawing which shows typically the process of forming a leading hole from the back surface of a silicon substrate. It is a perspective view showing typically a silicon substrate in which a plurality of leading holes were formed. It is sectional drawing which shows typically the process of etching to the silicon substrate in which the deteriorated layer and the leading hole were formed. It is sectional drawing which shows typically the state which the etching of the silicon substrate advanced. It is sectional drawing which shows typically the state which the etching of the silicon substrate advanced. It is sectional drawing which shows typically the state in which the ink supply port which penetrates a silicon substrate was formed. It is sectional drawing which shows typically the ink supply port which penetrates the conventional silicon substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Electrothermal conversion element 6 Etching mask layer 7 Opening part 8 Altered layer 9 Leading hole 10 Silicon part 11 Ink supply port (through hole)

Claims (9)

Forming an etching mask layer having an opening on the back surface of the silicon substrate;
Irradiating the opening of the etching mask layer with a laser beam from the back surface of the silicon substrate to form an altered layer inside the silicon substrate;
Irradiating the opening of the etching mask layer with a laser beam from the back surface of the silicon substrate to form a plurality of non-through holes that do not penetrate from the back surface of the silicon substrate to the surface of the silicon substrate;
Forming a through hole penetrating to the surface of the silicon substrate by performing anisotropic etching on the silicon substrate on which the non-through hole and the altered layer are formed;
A method for processing a silicon substrate.   In the step of forming the non-through hole, the tip of the non-through hole is positioned so that the depth of the non-through hole with respect to the thickness direction of the silicon substrate is the same as the altered layer formed in the silicon substrate. The method for processing a silicon substrate according to claim 1, formed as described above.   In the step of forming the non-through holes, the plurality of non-through holes are arranged in a frame shape along the outer periphery of a region parallel to the surface of the silicon substrate in the altered layer formed in the silicon substrate. A method for processing a silicon substrate according to claim 1 or 2. In the step of forming the non-through holes, the plurality of non-through holes are arranged in a frame shape on a plane parallel to the surface of the silicon substrate,
The method for processing a silicon substrate according to claim 1, wherein in the step of forming the deteriorated layer, the deteriorated layer is formed in a frame formed by the plurality of non-through holes.   5. The method for processing a silicon substrate according to claim 1, wherein, in the step of forming the deteriorated layer, the deteriorated layer is formed using multiphoton absorption by laser light.   6. The method for processing a silicon substrate according to claim 1, wherein in the step of forming the non-through hole, the non-through hole is formed by ablation of laser light.   7. The silicon substrate according to claim 1, wherein in the step of forming the deteriorated layer, the deteriorated layer is formed in a plurality of rows in a plane parallel to the surface of the silicon substrate. Processing method.   8. The process according to claim 1, wherein in the step of forming the deteriorated layer, the deteriorated layer is formed at a depth in a range of 10% to 50% of the thickness of the silicon substrate from the surface of the silicon substrate. 2. A method for processing a silicon substrate according to item 1. 9. A silicon substrate processing method according to claim 1, wherein a discharge port for discharging a liquid, a liquid channel communicating with the discharge port, and energy for discharging a liquid from the discharge port. A liquid discharge head manufacturing method for forming a liquid supply port for supplying a liquid to the liquid flow path on a silicon substrate provided with a discharge energy generating element for generating a liquid on the surface side,
A method of manufacturing a liquid ejection head, wherein the liquid supply port communicating with the liquid flow path is formed by forming the through hole from the back surface of the silicon substrate.

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