JP2011091127A - Si SUBSTRATE WORKING METHOD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Si substrate working method for accurately working an Si substrate using Si anisotropic dry etching. <P>SOLUTION: In the Si substrate working method of forming a recess on an Si substrate where an etching mask is formed by an Si anisotropic dry etching method of alternately repeating an etching step and a protective film forming step of forming a protective film, the etching step includes a first etching step and a second etching step to be performed after the first etching step. First bias power is applied to the Si substrate so as to remove the protective film formed on the bottom surface of the recess in the protective film forming step in the first etching step, and second bias power smaller than the first bias power is applied to the Si substrate in the second etching step. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a Si substrate processing method.

  In recent years, semiconductor microfabrication technology has come to be used not only for the production of integrated circuits but also for the production of mechanical structures and the integration of mechanical structures and electronic circuits. A device constituted by integration of these mechanical structures and mechanical structures and electronic circuits is called a micromachine or MEMS (Micro Electro Mechanical System).

  As one of the above-mentioned semiconductor microfabrication techniques, there is a demand for an etching technique that can form a structure such as a groove, particularly a trench (deep groove or deep hole) with high accuracy on a silicon (Si) substrate.

In Patent Document 1, an etching method for trench etching is disclosed. In this etching method, a deep groove or a deep hole (hereinafter referred to as a deep groove or the like) is formed by alternately repeating an etching process and a polymerization process. In the etching process, an etching mask having a desired shape is formed on the surface of the silicon substrate, and then the substrate surface is dry-etched using a plasma gas mixture of SF ₆ and Ar to form grooves or holes (hereinafter referred to as grooves). . In the polymerization process (protective film forming process), a protective film is formed on the side wall of the groove or the like using plasma mixed gas of CHF ₃ and Ar. In the etching process and the polymerization process, a substrate bias is generated on the substrate electrode for ion acceleration.

  By the above etching method, the wall surface of the groove or the like formed by dry etching is then covered with a protective film, and the protective film protects the wall surface during the next dry etching. Is described, and it is described that a groove or the like having an apparently vertical wall surface is formed.

  In Japanese Patent Laid-Open No. 2004-260260, a process of continuously performing dry etching on an etching ground while applying a bias potential by constantly applying electric power to a silicon substrate and a process of forming a protective film on a vertical structure surface are sequentially repeated. An etching method is shown. In this etching method, an optimal mixing ratio of a mixed gas is disclosed so that the vertical structure surface to be formed is sufficiently smooth, has an excellent squareness, and has a high etching rate.

JP 7-503815 A JP 2004-296474 A

  In Patent Documents 1 and 2, an etching method in which an etching process and a protective film forming process are alternately performed on a Si substrate is also referred to as Si anisotropic dry etching, and the etching mask becomes thinner with the etching.

  In the above etching method, it is conceivable to determine the initial thickness of the etching mask in consideration of the mask selectivity shown in the following formula (1).

Mask selection ratio = Si etching amount / etching mask etching amount (1)
The mask selection ratio of the formula (1) indicates a ratio obtained from respective etching amounts when Si and etching mask are etched under the same conditions and the same time by Si anisotropic dry etching. The mask selection ratio is determined mainly by the material for forming the etching mask, but also depends on the shape formed by etching. For example, when a minute hole having a diameter of about 5 μm is formed, the etching rate becomes smaller as the hole becomes deeper, which is called a microloading effect, and the mask selection ratio becomes smaller due to the microloading effect.

  When a trench (deep groove or deep hole) is formed in a Si substrate by using Si anisotropic dry etching, as can be seen from Equation (1), the value of the mask selectivity is determined by the material of the etching mask, When deeper, the etching mask needs to be thicker. Furthermore, the etching mask may be made thicker due to the microloading effect.

  However, when forming a thick etching mask, for example, the side wall surface of the opening provided in the etching mask is inclined, and the pattern on the surface of the etching mask differs from the pattern on the surface in contact with the Si substrate. The accuracy is lowered, and as a result, the processing accuracy of the Si substrate is lowered.

  In addition, it is necessary to perform a photolithography process a plurality of times to form a step corresponding to the step in an etching mask used when forming a groove having a different depth, for example, a groove having a step in the Si substrate. When performing the second and subsequent photolithography processes, it becomes difficult to form a photoresist film uniformly depending on the pattern of the etching mask formed first, and the accuracy of the etching mask is lowered. This decrease in accuracy increases as the thickness of the etching mask increases, and as a result, the processing accuracy of the Si substrate decreases.

  In Patent Documents 1 and 2, there is no specific description regarding an etching mask when forming a trench with high accuracy.

  The present invention has been made in view of the above problems, and an object thereof is to provide a Si substrate processing method for processing a Si substrate with high accuracy using Si anisotropic dry etching. .

  Said subject is solved by the following structures.

1. In a Si substrate processing method for forming a recess by an Si anisotropic dry etching method in which an etching process and a protective film forming process for forming a protective film are alternately repeated on an Si substrate on which an etching mask is formed.
The etching step includes a first etching step and a second etching step performed after the first etching step,
In the first etching step, a first bias power is applied to the Si substrate so that the protective film formed on the bottom surface of the depression in the protective film forming step can be removed,
In the second etching process, a second bias power smaller than the first bias power is applied to the Si substrate.

  2. 2. The Si substrate processing method according to 1, wherein the second bias power is substantially zero.

3. 3. The Si substrate processing method according to 1 or 2, wherein the etching mask is formed of a SiO ₂ film.

  4). 4. The Si substrate processing method according to any one of 1 to 3, wherein the etching mask has a step.

  According to the present invention, since the etching mask for performing Si anisotropic dry etching can be thinned, the Si substrate can be processed with high accuracy.

It is a figure which shows the example of an inkjet recording head. 2 is a cross-sectional view of an ink jet recording head. FIG. It is sectional drawing of the nozzle periphery formed in the nozzle plate. It is a figure which shows the process of forming a small diameter part, a 1st large diameter part, and a 2nd large diameter part. It is a figure which shows the relationship between bias electric power and a protective film etching rate. It is a diagram showing a relationship between bias power and the Si etching rate and the SiO ₂ film etching rate. It is a figure which shows the relationship between the bias electric power at the time of using the conventional Si anisotropic dry etching method, and a mask selection ratio. It is a figure which shows the process of forming the etching mask with a level | step difference.

  Although the present invention will be described based on an embodiment, the present invention is not limited to the embodiment. The present invention relates to a method of accurately forming minute holes and grooves on an Si substrate by an etching method (Si anisotropic dry etching) in which an etching process and a protective film forming process are alternately repeated. A nozzle plate formed using a Si substrate of a recording head will be described as an example.

  FIG. 1 schematically shows a nozzle plate 1, a body plate 2, and a piezoelectric element 3 constituting an ink jet recording head (hereinafter referred to as a recording head 100) which is an example of a liquid discharge head.

  In the nozzle plate 1, a plurality of nozzles 11 having ejection openings (openings in the ejection surface 12) for ink ejection are arranged. Further, the nozzle plate 1 is bonded to the body plate 2 so that the pressure chamber groove 24 serving as a pressure chamber, the ink supply path groove 23 serving as an ink supply path, the common ink chamber groove 22 serving as a common ink chamber, and the ink. A channel groove such as the supply port 21 is formed.

  And the flow path unit M is formed by bonding the nozzle plate 1 and the body plate 2 so that the nozzle 11 of the nozzle plate 1 and the pressure chamber groove 24 of the body plate 2 correspond one-to-one. Hereafter, the reference numerals of the pressure chamber groove, the supply path groove, and the common ink chamber groove used in the above description are also used for the pressure chamber, the supply path, and the common ink chamber, respectively.

  FIG. 2 schematically shows a cross section at the position of Y-Y ′ of the nozzle plate 1 and the position of X-X ′ of the body plate 2 shown in FIG. 1. As shown in FIG. 2, the piezoelectric element 3 is bonded to the flow path unit M to the surface of the bottom 25 of each pressure chamber 24 opposite to the surface to which the nozzle plate 1 of the body plate 2 is bonded. Thus, the recording head 100 is completed. A driving pulse voltage is applied to each piezoelectric element 3 of the recording head 100, and vibration generated from the piezoelectric element 3 is transmitted to the bottom 25 of the pressure chamber 24, and the pressure in the pressure chamber 24 is changed by the vibration of the bottom 25. Ink droplets are ejected from the nozzle 11.

  FIG. 3 shows a view focusing on the periphery of one nozzle 11 of the nozzle plate 1. For the sake of explanation, the liquid repellent layer 45 provided on the ejection surface 12 shown in FIG. 2 is omitted in FIG. The nozzle 11 has a small-diameter portion 13 having an opening as an opening, and a first large-diameter portion 15 and a small-diameter portion 13 that are opened in the pressure chamber as an inlet to the nozzle 11 for liquid discharged from the discharge port. The second large-diameter portion 14 communicates with the large-diameter portion 15.

The substrate C forming the nozzle plate 1 is a Si substrate having an etching stop layer 16 which is a layer having an etching rate slower than Si between the small diameter portion 13 and the second large diameter portion 14, for example, a SiO ₂ layer. There is an SOI (Silicon On Insulator) substrate provided with. By using the SOI substrate, the length (nozzle length) of the small-diameter portion 13 can be processed with high accuracy using the etching rate difference between Si and SiO ₂ .

Examples of the material constituting the etching stop layer 16 include, but are not limited to, SiO ₂ , an insulating material such as Al ₂ O _3, and a metal such as Ni and Cr. Further, a Si substrate that does not have the etching stop layer 16 may be used as the base material of the nozzle plate 1. Note that the thickness of the SiO ₂ layer that is the etching stopper layer 16 of the present embodiment is 0.2 μm.

  FIG. 4 shows a process of manufacturing the nozzle 11 composed of the small diameter portion 13, the second large diameter portion 14, and the first large diameter portion 15 using the SOI substrate (substrate C).

  FIG. 4A shows a cross-sectional view of the substrate C on which etching masks 61b and 62a are formed on both sides. The substrate C includes an etching stop layer 16, a first Si layer 17 that forms the first large diameter portion 15 and the second large diameter portion 14, and a second Si layer 18 that forms the small diameter portion 13. . An etching mask 61b for forming the first large diameter portion 15 and the second large diameter portion 14 is formed on the surface of the first Si layer 17, and a small diameter portion 13 is formed on the surface of the second Si layer 18. Etching masks 62a are formed respectively.

The etching masks 61b and 62a can be formed by a known photolithography process (resist application, exposure, development) and an etching process. The material for forming the etching masks 61b and 62a is not particularly limited as long as the first Si layer 17 and the second Si layer 18 of the substrate C can be used as etching masks in the Si substrate processing method of the present invention described later. Examples thereof include a photoresist and SiO ₂ , and SiO ₂ is preferable.

The reason why SiO ₂ is preferable as an etching mask is that microfabrication is easy, a uniform film can be easily formed on the surface of the Si substrate as a thermal oxide film, and there is no concern about contamination of the device / Si processed surface. The material of the etching mask in this embodiment is SiO ₂ . As shown in FIG. 4A, the etching mask 61b has a level difference corresponding to the depth of the second large diameter portion 14 and the first large diameter portion 15 formed in the first Si layer 17 of the substrate C. Is provided.

A hole to be the second large-diameter portion 14 is formed at a predetermined depth in the first Si layer 17 using the Si substrate processing method of the present invention (FIG. 4B). The etching apparatus for performing the Si substrate processing method of the present invention is preferably an ICP RIE apparatus. For example, sulfur hexafluoride (SF ₆ ) is used as an etching gas in the etching process, and a deposition gas is formed in the protective film formation (deposition) process. Fluorocarbon (C ₄ F ₈ ) is used alternately.

Here, an example of conventional conditions when performing etching by the Si substrate processing method of the present invention using an ICP type RIE apparatus is shown below.
(Etching process)
SF ₆ flow rate: 130 sccm
Pressure: 2.66 Pa
High frequency power: 600W
Bias power: 25W
Cycle time: 13 seconds (protective film formation process)
C ₄ F ₈ flow rate: 85 sccm
Pressure: 2.66 Pa
High frequency power: 600W
Bias power: 0W
Cycle time: 5 seconds In the etching process, Si is etched by RIE (Reactive Ion Etching) reaction with F radicals and F ions in SF ₆ plasma. In the protective film formation process, a polymer film having a composition close to Teflon (registered trademark) is deposited on the inner wall surface of the hole by a polymerization reaction of CFx radicals in C ₄ F ₈ plasma and their ions, and this film is etched by the etching process. Acts as a protective film.

  At the beginning of each etching step, the protective film on the bottom surface of the hole is removed before the side wall surface due to the etching anisotropy of RIE. After that, the side wall surface is protected from the lateral etching while the protective film remains, and the vertical Si etching proceeds.

  FIG. 7 shows the mask selection ratio when the bias power is changed under the above-described etching process conditions. From FIG. 7, the mask selection ratio is about 400 at most.

On the other hand, in the Si substrate processing method according to the present invention, the conventional Si anisotropic dry etching etching process includes a first etching process and a second etching process performed subsequently thereto. Specific examples of etching conditions are shown below. Note that the conditions for the protective film forming step may be the same as those in the prior art, and in the present embodiment, they are the same as described above, so the description below is omitted.
(First etching process)
SF ₆ flow rate: 130 sccm
Pressure: 2.66 Pa
High frequency power: 600W
First bias power: 50W
Cycle time: 1.5 seconds (second etching process)
SF ₆ flow rate: 130 sccm
Pressure: 2.66 Pa
High frequency power: 600W
Second bias power: 0W
Cycle time: 11.5 seconds In the first etching step, bias power (first bias) is applied to the substrate C so that the protective film formed on the bottom surface of the hole that becomes the second large diameter portion 14 in the protective film forming step can be removed. Power). In the next second etching step, a second bias power smaller than the first bias power is applied to the substrate C, and the second bias power is more preferably substantially zero. In the present embodiment, the second bias power is zero. It is said. Substantially zero means that the value of the second bias power is from 0 (zero) to less than 3 W.

  Here, the relationship between the bias power and the protective film etching rate is shown in FIG. FIG. 5 shows that the etching rate of the protective film increases in proportion to the bias power.

FIG. 6 shows the relationship between the bias power, the Si etching rate, and the etching rate of the SiO ₂ film that is the etching mask 61b. From FIG. 6, the Si etching rate is less dependent on the bias power, and even if the bias power is decreased, the etching rate is slightly decreased. This is presumably because the etching of Si is isotropic etching mainly by radical molecules. On the other hand, the SiO ₂ film etching rate largely depends on the bias power, and it can be seen that the SiO ₂ film etching rate decreases when the bias power is decreased. This is considered because the etching of the SiO ₂ film is mainly an anisotropic etching by ions. Such a decrease in the etching rate due to the decrease in the bias power is SiO 2 if it is a material to be the etching mask 61b. _It is not limited to _two films.

  The inventors have invented the conventional etching process into a first etching process and a second etching process from FIGS. 5 and 6 obtained as a result of the examination.

  The first etching step aims to remove the protective film formed on the bottom surface of the hole so as to correspond to the initial stage of the conventional etching step. By removing the protective film formed on the bottom surface of the hole, the Si surface at the bottom surface is exposed, and Si etching for digging up the bottom surface can be facilitated. At this time, the protective film removal time can be adjusted by adjusting the bias power (first bias power) shown in FIG. 5, and the protective film can be removed earlier by increasing the bias power. For example, when the bias power is 50 W, the protective film having a thickness of 75 mm formed per cycle can be removed in less than 1.5 seconds.

  The second etching step is a step performed after the first etching step, and aims to dig down the bottom surface of the hole. As shown in FIG. 6, the Si etching rate is less dependent on the bias power (second bias power), and even when the bias power is zero, the Si etching rate is only about 15% lower than the Si etching rate with a bias power of 50 W.

On the other hand, the SiO ₂ film etching rate greatly depends on the bias power. As shown in FIG. 6, when the bias power is zero, the SiO ₂ film etching rate is remarkably reduced to about 10% as compared with the SiO ₂ film etching rate with the bias power of 50 W.

In the second etching process, by applying a second bias power smaller than the first bias power to the substrate C, the SiO ₂ film is compared with the decrease in the etching rate of Si compared to the conditions of the first etching process. The etching rate can be greatly reduced. For this reason, the mask selection ratio can be increased as compared with the case of the first bias power.

In the condition examples shown in the first etching step and the second etching step, the Si etching rate is 4.3 μm / min, the SiO ₂ film etching rate is 30 Å / min, and the mask selectivity is about 1400. Compared to 400, it can be significantly increased.

Therefore, in the Si substrate processing method of the present invention, the SiO ₂ film etching rate can be drastically reduced without greatly reducing the Si etching rate, and the etching mask 61b is greatly reduced in etching amount. The first Si layer 17 can be processed with high accuracy. Further, even if the same etching mask material is used, the mask selection ratio is increased. Therefore, for example, an etching mask material that has been used for a while because the mask selection ratio is low, such as a photoresist, can be added as an option.

  Furthermore, the protective film formed on the bottom surface of the hole that becomes the second large diameter portion 14 in the first etching step can be removed quickly, and the Si etching rate is not greatly reduced in the second etching step. The processing efficiency of the first Si layer 17 does not significantly decrease and falls within the practical range.

Next, an unnecessary mask portion B of the etching mask 61b in FIG. 4B is removed by dry etching using, for example, CHF ₃ , and the etching mask 61b is used to form the first large diameter portion 15. 61c (FIG. 4C). Thereafter, etching is performed on the first Si layer 17 until the etching stop layer 16 is exposed by the same Si substrate processing method of the present invention as described above. Etching is stopped in a state where the etching stop layer 16 is exposed over the entire bottom surface of the second large-diameter portion 14, thereby completing the formation of the second large-diameter portion 14 and the first large-diameter portion 15 ( FIG. 4 (d)).

Here, the production of the etching mask 61b having a step will be described with reference to FIGS. An oxide film 61 (SiO ₂ film) serving as an etching mask 61b is provided on the surface of the first Si layer 17 of the substrate C, and further, a first photoresist film 71 is provided on the oxide film 61 (FIG. 8A). )). Thereafter, a desired pattern is exposed and developed to form a first photoresist pattern 71a (FIG. 8B).

  The oxide film 61a is etched using the first photoresist pattern 71a to form the oxide film 61a (FIG. 8C). The oxide film 61a has an opening through which the Si surface for forming the second large diameter portion 14 is exposed. Thereafter, the first photoresist pattern 71a is removed.

  After the first photoresist pattern 71a is removed, a second photoresist film 72 is provided on the oxide film 61a having an opening (FIG. 8D). Thereafter, exposure and development are performed in the same manner as described above to form a second photoresist pattern 72a (FIG. 8E).

  By etching the oxide film 61a to a predetermined depth using the second photoresist pattern 72a, an etching mask 61b having a step for forming the first large diameter portion 15 is formed (FIG. 8 ( f)). Thereafter, the second photoresist pattern 72a is removed (FIG. 8G).

  As described above, the etching mask 61b for forming the first large diameter portion 15 and the second large diameter portion 14 in the first Si layer is completed.

  By using the Si substrate processing method of the present invention, the oxide film 61 can be made thinner than the conventional method, so that the oxide film 61a having an accurate opening can be formed.

  Further, since the second photoresist film 72 shown in FIG. 8D has a thin oxide film 61a, the second photoresist film 72a can be provided uniformly without being affected by the opening, and a highly accurate second photoresist pattern 72a is formed. can do. Therefore, the etching mask 61b formed on the oxide film 61a using the second photoresist pattern 72a can be made with high accuracy.

  Although the second photoresist film 72 provided on the oxide film 61a depends on the size of the hole formed in the oxide film 61a, it is difficult to provide the second photoresist film 72 uniformly when the thickness of the oxide film 61a exceeds 3 μm. Become. For this reason, the ability to form the etching mask 61b from the thin oxide film 61 not only enables the Si substrate to be processed with high accuracy, but also makes it very difficult to produce a complicated shape having a larger number of steps. It is an advantage.

  After the formation of the second large diameter portion 14 and the first large diameter portion 15 in FIG. 4D is completed, an etching stop layer is formed using the etching mask 62a formed on the surface of the second Si layer 18 of the substrate C. Etching is performed on the second Si layer 18 using the Si substrate processing method according to the present invention until 16 is exposed to form the small diameter portion 13 (FIG. 4E). Thereafter, the substrate C is immersed in a diluted hydrofluoric acid solution, and the etching masks 61c and 60a and the etching stop layer 16 are removed. By removing the etching stop layer 16, the small diameter portion 13, the second large diameter portion 14, and the first large diameter portion 15 communicate with each other to form a nozzle, thereby completing the nozzle plate 1 (FIG. 4F).

  The depth of the first large-diameter portion and the second large-diameter portion and the length of the small-diameter portion (nozzle length) by the SOI substrate in which the thickness of each of the first Si layer 17 and the second Si layer 18 is determined. Of course, the first large-diameter portion, the second large-diameter portion, and the small-diameter portion 13 are faithfully formed in a desired shape by the Si substrate processing method of the present invention. can do.

  Thereafter, a liquid repellent layer 45 described later is preferably provided on the ejection surface 12 from which the etching mask 62a has been removed.

  The liquid repellent layer 45 will be described. It is preferable to provide the liquid repellent layer 45 on the ejection surface 12 where the ejection holes of the nozzle plate 1 shown in FIG. By providing the liquid repellent layer 45, it is possible to suppress the seepage and spread due to the liquid getting into the discharge surface 12 from the discharge hole. Specifically, for example, a material having water repellency is used if the liquid is aqueous, and a material having oil repellency is used if the liquid is oily. Generally, FEP (ethylene tetrafluoride, propylene hexafluoride) is used. ), PTFE (polytetrafluoroethylene), fluorosiloxane such as fluorosiloxane, fluoroalkylsilane, amorphous perfluororesin, and the like are often used, and the film is formed on the discharge surface 12 by a method such as coating or vapor deposition. The thickness of the film is not particularly limited, but is preferably about 0.1 μm to 3 μm.

  The liquid repellent layer 45 may be formed directly on the ejection surface 12 of the nozzle plate 1 or may be formed via an intermediate layer in order to improve the adhesion of the liquid repellent layer 45. .

  Next, a body plate 2 as shown in FIG. 1 is manufactured. For example, a pressure chamber groove 24 serving as a plurality of pressure chambers respectively communicating with the nozzle 11 using a known photolithography process (resist application, exposure, development) and a Si anisotropic dry etching method using a Si substrate, A plurality of ink supply grooves 23 serving as a plurality of ink supply paths communicating with the pressure chambers, a common ink chamber groove 22 serving as a common ink chamber communicating with the ink supply, and a flow path groove such as an ink supply port 21 are formed. This Si anisotropic dry etching method can be made more accurate by using the Si substrate processing method of the present invention. Thereafter, the prepared nozzle plate 1 and the body plate 2 are bonded together using an adhesive or the like, and the piezoelectric element 3 as pressure generating means is attached to the back surface of each pressure chamber 24 of the body plate 2 so that the recording head 100 can be used. Complete.

Example 1
The nozzle plate 1 was manufactured according to FIGS. The Si substrate processing method of the present invention uses an ICP type RIE apparatus, and the processing conditions are the same as the contents shown in the above (first etching step), (second etching step) and (protective film forming step). .

  The substrate C is an SOI silicon (Si) wafer / diameter of φ100 mm and a thickness of 350 μm, and details will be described below.

First Si layer 17 Thickness: 350 μm
Etching stop layer 16 (SiO ₂ ) thickness: 0.2 μm
Second Si layer 18 Thickness: 5 μm
Oxide films (SiO ₂ ) 61, 62 on both sides Thickness: 7000 mm
As shown in FIG. 8, an etching mask 61b was obtained by photolithography and etching. The etching mask pattern was such that the first large diameter portion 15 had a diameter φ100 μm and the second large diameter portion 14 had a diameter φ60 μm.

  The thickness of the etching mask 61b in FIG. 8 (g) and FIG. 4 (a) was 7000 mm for the A portion and 2500 mm for the B portion.

  As shown in FIG. 4B, the first Si layer 17 was etched by a diameter φ of 60 μm and a depth of 168 μm using the Si substrate processing method of the present invention. The etching cycle was 230 times. The thickness of the etching mask 61b at the end of this etching was 5600 mm for the A portion and 1100 mm for the B portion.

As shown in FIG. 4C, etching was performed using CHF ₃ until the oxide film in the B portion shown in FIG. The thickness of part A of the etching mask 61c at the end of this etching was 4100 mm.

  As shown in FIG. 4D, etching is performed using the Si substrate processing method of the present invention until the bottom surface reaches the etching stop layer 16 to form a hole having a diameter of 100 μm. The etching cycle was 370 times. The thickness of part A of the etching mask 61c at the end of this etching was 1800 mm.

  The total etching cycle so far is 600 times and the required time is 180 minutes.

  As shown in FIG. 4E, the Si substrate processing method of the present invention is used to form a hole with a diameter of 5 μm in the first Si layer 17 using the etching mask 62 a and etch until the bottom surface reaches the etching stop layer 16. The small diameter part 13 was formed.

  As shown in FIG. 4E, the remaining etching masks 62a and 61c and the etching stop layer 16 were removed by immersing them in diluted hydrofluoric acid, whereby the nozzle plate 1 was obtained.

When the surface of the substrate C is observed, the shapes of the first large-diameter portion 15 and the second large-diameter portion 14 are in a state close to the original shape without any particular expansion of the opening end, and the etching mask 61c is not masked. It functioned sufficiently and the flat surface was the original smooth state of the Si wafer, and good results were obtained.
(Comparative Example 1)
The nozzle plate 1 was manufactured according to FIGS. In the conventional Si anisotropic dry etching, an ICP type RIE apparatus is used, and the processing conditions are the same as the contents shown in the above (etching process) and (protective film forming process).

  The substrate C is an SOI silicon (Si) wafer / diameter of φ100 mm and a thickness of 350 μm, and details will be described below.

First Si layer 17 Thickness: 350 μm
Etching stop layer 16 (SiO ₂ ) thickness: 0.2 μm
Second Si layer 18 Thickness: 5 μm
Oxide films 61, 62 on both sides (SiO ₂ ) Thickness: 18000 mm
As shown in FIG. 8, an etching mask 61b was obtained by photolithography and etching. The etching mask pattern was such that the first large diameter portion 15 had a diameter φ100 μm and the second large diameter portion 14 had a diameter φ60 μm.

  The thickness of the etching mask 61b in FIG. 8 (g) and FIG. 4 (a) was 18000 mm for the A portion and 7500 mm for the B portion.

  As shown in FIG. 4B, the first Si layer 17 was etched by a diameter of 60 μm and a depth of 168 μm using conventional Si anisotropic dry etching. The etching cycle was 210 times. The thickness of the etching mask 61b at the end of this etching was 11490 mm for the A portion and 990 mm for the B portion.

As shown in FIG. 4C, etching was performed using CHF ₃ until the oxide film in the B portion shown in FIG. The thickness of part A of the etching mask 61c at the end of this etching was 10,000 mm.

  As shown in FIG. 4D, etching is performed using conventional Si anisotropic dry etching until the bottom surface reaches the etching stop layer 16 to form a hole having a diameter of 100 μm. The etching cycle was 315 times. The thickness of part A of the etching mask 61c at the end of this etching was 225 mm.

  The total etching cycle so far is 525 times and the required time is 157.5 minutes.

  As shown in FIG. 4 (e), a hole having a diameter of 5 μm is formed in the first Si layer 17 using the etching mask 62 a by conventional Si anisotropic dry etching, and etching is performed until the bottom surface reaches the etching stop layer 16. And the small diameter part 13 was formed.

  As shown in FIG. 4E, the remaining etching masks 62a and 61c and the etching stopper layer 16 were removed by immersion in diluted hydrofluoric acid to obtain a nozzle plate.

When the surface of the substrate C is observed, the shape of the first large diameter portion 15 and the second large diameter portion 14 is found to be spread about several μm at the opening end, and the masking of the etching mask 61c is insufficient. Therefore, fine irregularities were recognized on the flat surface unlike the original smooth state of the Si wafer, and good results were not obtained.
(result)
The thickness (A part) of the initial etching mask 61b is 7000 mm in Example 1 and 18000 mm in Comparative Example 1, which is thicker in Comparative Example 1. However, when the etching of the first Si layer 17 in FIG. 4D is completed, the remaining thickness of the etching mask 61c is reversed to 1800 mm in Example 1 and 225 mm in Comparative Example 1, and There was a big difference, and there was also a difference in the quality of the manufactured nozzle plate. The required time for forming the first large-diameter portion 15 and the second large-diameter portion 14 is 180 minutes for Example 1, 157.5 minutes for Comparative Example 1, and about 15 for Example 1. % Long but well within the practical range. From this, it was confirmed that the present invention has a great effect.

DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Body plate 3 Piezoelectric element 11 Nozzle 12 Discharge surface 13 Small diameter part 14 2nd large diameter part 15 1st large diameter part 16 Etching stop layer 17 1st Si layer 18 2nd Si layer 21 Ink supply口 22 Common ink chamber (groove)
23 Ink supply path (groove)
24 Pressure chamber (groove)
45 Liquid repellent layer 61, 61a Oxide film 61b, 61c, 62a Etching mask 100 Recording head C Substrate

Claims (4)

In a Si substrate processing method for forming a recess by an Si anisotropic dry etching method in which an etching process and a protective film forming process for forming a protective film are alternately repeated on an Si substrate on which an etching mask is formed.
The etching step includes a first etching step and a second etching step performed after the first etching step,
In the first etching step, a first bias power is applied to the Si substrate so that the protective film formed on the bottom surface of the depression in the protective film forming step can be removed,
In the second etching process, a second bias power smaller than the first bias power is applied to the Si substrate.   The Si substrate processing method according to claim 1, wherein the second bias power is substantially zero. The Si substrate processing method according to claim 1, wherein the etching mask is formed of a SiO ₂ film.   The Si substrate processing method according to claim 1, wherein the etching mask has a step.

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