JP2019166658A - Method for production of base plate for liquid discharge head - Google Patents

Abstract

An object of the present invention is to prevent seepage of an etching solution and an etching gas when forming a through hole in a semiconductor substrate. A substrate on which a recording element is formed, a flow path passing over the recording element formed on the substrate and communicating with the discharge port, a nozzle plate forming the discharge port, A liquid supply head formed through the first surface and the second surface on which the recording elements are formed, and having a liquid supply port communicating with the flow path, wherein the first surface of the substrate is provided. A sacrificial layer is formed, the liquid supply port is formed by anisotropic etching using alkali from the second surface of the substrate toward the sacrificial layer, and when the liquid supply port is formed, An etching stop layer covering the sacrificial layer is formed on the first surface, and the etching stop layer is formed of a metal film having alkali resistance. [Selection] Figure 2

Description

  The present invention relates to a method for manufacturing a substrate for a liquid discharge head.

2. Description of the Related Art In recent years, research has been actively conducted in which through holes are formed in a semiconductor substrate such as a silicon wafer by isotropic or anisotropic etching and applied to a device such as a liquid discharge head.
As a method for providing a liquid discharge head having a high production yield and a high printing speed in Patent Document 1, a protective layer is formed on an etching stop layer, and an adhesion layer disposed under the discharge port forming member and the column is provided as a protective layer. There is a method of forming it away from the substrate.
Patent Document 1 discloses a processing procedure of a through hole for a silicon substrate on which such a sacrificial layer is formed.

A sacrificial layer made of polycrystalline silicon (hereinafter referred to as AL-Si) is formed at a through-hole forming position of the single crystal silicon substrate, and an etching stop layer is formed thereon. In this case, the through hole etched by the etching mask layer on the back surface of the single crystal silicon substrate is designed to be formed inside the sacrificial layer when it reaches the sacrificial layer.
When the through hole reaches the sacrificial layer, the sacrificial layer is immediately dissolved by the etching solution. Anisotropic etching on the surface side of the single crystal silicon substrate is started from the edge portion of the sacrificial layer, and finally a through hole with a constricted portion is formed.

JP2012-240208A

In the method of forming a through-hole using a sacrificial layer, the opening shape and position of the through-hole can be set according to the position of the sacrificial layer, so that processing with higher accuracy is possible.
However, since the etching stop layer is formed on the sacrificial layer, the thickness of the etching stop layer may be reduced at the corner of the sacrificial layer. May occur.
When the film stress of the etching stop layer is high, cracks may not be prevented even if a protective layer is formed on the corner as in the conventional configuration.

As an etching solution used for a single crystal silicon substrate, a strong alkaline solution such as an aqueous solution of tetramethylammonium hydroxide (hereinafter referred to as TMAH) or a potassium hydroxide aqueous solution at a temperature of 80 ° C. or higher is used. Used.
Therefore, when a crack is generated in the etching stop layer, if the etching solution flows around the surface of the single crystal silicon substrate through the crack, the single crystal silicon substrate is seriously damaged.
Further, also in the step of removing the etching stop layer, the etching gas penetrates from the cracks and causes serious damage to the single crystal silicon substrate.
As a result, a defective substrate that cannot eject liquid is produced, and the manufacturing yield is greatly reduced.

  An object of the present invention is to manufacture a liquid discharge head that can suppress the occurrence of cracks in an etching stop layer and the penetration of an etchant and an etching gas when a through hole is formed in a semiconductor substrate. It is to provide a method.

The present invention includes a substrate on which a recording element that generates energy for discharging liquid from an ejection port is formed;
A flow path that communicates with the discharge port through the recording element formed on the substrate, a nozzle plate that forms the discharge port,
A liquid supply port formed through the first surface of the substrate on which the recording element is formed and a second surface facing the first surface, and communicated with the flow path;
A method of manufacturing a liquid discharge head having
Forming a sacrificial layer on the first surface of the substrate forming the liquid supply port, and forming the liquid supply port by anisotropic etching using alkali from the second surface of the substrate toward the sacrificial layer; Have
In the step of forming the liquid supply port, an etching stop layer covering the sacrificial layer is formed on the first surface of the substrate, and the etching stop layer is formed of a metal film having alkali resistance. The present invention relates to a method for manufacturing a liquid discharge head.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress the penetration | invasion of the etching liquid and etching gas resulting from the fracture | rupture of an etching stop layer, and can provide the manufacturing method of the liquid discharge head which improved the manufacture yield.

FIG. 3 is a perspective view of a liquid discharge head 6 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a process of manufacturing the liquid ejection head 6 according to an embodiment of the present invention, and shows a cross section taken along line A-A ′ of FIG. It is a schematic diagram which shows an example of the manufacturing method of the liquid discharge head of this invention. It is a figure which shows the cross section of a liquid discharge head.

<Liquid discharge head>
A perspective view of a liquid discharge head 6 according to the present invention is shown in FIG. A part of the nozzle plate 2 is omitted so that the internal structure can be seen. The liquid discharge head 6 according to the present invention includes a liquid discharge head substrate 1 having a recording element 7 for generating energy for discharging a liquid such as ink from the discharge port 3 on the first surface. Also, a nozzle plate 2 formed on the liquid discharge head substrate 1 and a chip plate 4 which is a flow path constituting member that forms a flow path that communicates with the discharge port through the recording element formed on the substrate, Are bonded by an adhesive 5. The nozzle plate 2 has a plurality of through holes provided so as to penetrate through a facing portion facing the surface of the liquid discharge head substrate 1 on which the recording elements 7 are provided. Such a nozzle plate 2 is made of a resin material, and the plurality of through holes are collectively provided using, for example, a photolithography technique or an etching technique. Here, the through-hole provided in the nozzle plate 2 is provided on the first opening that opens at a position facing the surface of the liquid discharge head substrate 1 on which the recording element 7 is provided, and on the liquid discharge side. The second opening is provided in communication with the second opening. The plurality of through holes are used as the ejection ports 3 that eject the liquid using the energy generated by the recording elements 7, and these are arranged in a line at a predetermined pitch to constitute the ejection port array.

A recording element 7 is provided on the first surface of the liquid discharge head substrate 1. As the recording element 7, an electrothermal conversion element (heater), a piezoelectric element (piezo element), or the like can be used. A plurality of recording elements 7 are provided at a position facing the ejection port array, and an element array is formed by arranging a plurality of recording elements 7. A liquid supply port 8 for supplying a liquid to the recording element 7 is formed at a position between the element rows so as to penetrate the first surface of the liquid discharge head substrate 1 and the second surface opposite to the first surface. Is provided.
Further, when the nozzle plate 2 and the liquid discharge head substrate 1 are in contact with each other, the space between them becomes the ink flow path 9. The liquid discharge head substrate 1 has a contact pad 10 for supplying electricity to the recording element 7.
A chip plate 4 is adhered to the surface of the liquid discharge head substrate 1 facing the nozzle plate 2 by an adhesive 5 to make an electrical connection to the contact pad 10 of the recording element substrate 1, and electricity is supplied to the recording element 7. Then, the liquid discharge operation is performed.

FIG. 2 is a cross-sectional view in the process of manufacturing the liquid discharge head according to the present invention.
A first heat storage layer 11, a second heat storage layer 12, and a recording element 7 are stacked on the liquid discharge head substrate 1, and electrode layers 13 for supplying power from both ends thereof are disposed. As an upper layer, an electrically insulating layer 14 having ink resistance and insulating properties, and an anti-cavitation layer 15 for preventing destruction due to cavitation are disposed. A sacrificial layer 16 is provided between the first heat storage layer 11 and the second heat storage layer 12 for controlling the opening when the liquid supply port 8 is formed. An etching stop layer 17 is provided on the upper layer (upper part). In the present invention, a metal film having alkali resistance is used as the etching stop layer 17. The reason for this is that the metal film having alkali resistance not only has resistance to an alkali liquid as an etching liquid, but also has sufficient spreadability against the stress applied to the opening when the liquid supply port is opened. . For example, Au, Pt, Ag, Fe, Ti, W, Ta, or the like can be used as the metal constituting the metal film having alkali resistance. In the present invention, as the metal film, a metal film used when the element on the substrate 1 or the contact pad 10 is manufactured, for example, Au, Ta, or the like can be used as the etching stop layer. That is, Au and Ta used as contact pads can be formed in the same layer together with the etching stop layer. This can suppress the occurrence of film breakage without increasing the number of steps. Note that the metal film of the etching stop layer 17 may be a laminate of a gold diffusion prevention film and Au (gold).
Moreover, it is preferable that the metal film which is the etching stop layer 17 is formed with a film thickness of 0.05 μm to 20 μm. If the thickness of the metal film is 0.05 μm or more, it is possible to prevent breakage against stress at the time of opening the liquid supply port. Moreover, it is preferable from a viewpoint of the discharge performance determined by the structure of the nozzle plate 2 that the film thickness of the metal film is 20 μm or less.
In other words, the liquid ejection head according to the present invention having the above-described configuration prevents the occurrence of film breakage due to stress when the alkali-resistant metal film as the etching stop layer 17 is opened at the liquid supply port, thereby improving the manufacturing yield. It can be greatly improved.

Hereinafter, embodiments of the present invention will be described including a specific manufacturing method.
Example 1
An example of a method for manufacturing a liquid discharge head according to the present invention will be described with reference to FIGS.
As shown in FIG. 3A, a SiO ₂ film having a thickness of 0.6 μm was formed as a first heat storage layer 11 on the Si substrate 1 having a Si crystal orientation of <100> plane by thermal oxidation. An SiO film is formed as the second heat storage layer 12 to a thickness of 0.5 μm by CVD, a resist (not shown) is used as an etching mask by photolithography, and then reactive ion etching is performed using CF _4. Thus, an opening for exposing the surface of the substrate 1 was formed.
Subsequently, AL-Si is deposited on the first surface of the substrate 1 with a thickness of 0.4 μm by the CVD method as a layer that becomes the sacrificial layer 16 when the liquid supply port 8 is opened, and the recording element is formed by the sputtering method. As a layer (not shown) 7, TaSiN was formed to a thickness of 0.01 μm.

Next, Al was formed to a thickness of 0.6 μm as a layer to be the electrode layer 13. The obtained Al film was etched into a predetermined shape by reactive ion etching in which BCl ₃ and Cl ₂ gases were mixed, using the resist as an etching mask by a photoresist method. Thereafter, the resist was removed by O ₂ plasma ashing and stripping solution. An etching mask was formed again by photolithography, Al on TaSiN was removed by wet etching, and the resist was removed again by O ₂ plasma ashing and a stripping solution, whereby the recording element 7 and the electrode layer 13 were formed. Next, SiN is formed to a thickness of 0.3 μm by a CVD method as a layer to be an electrical insulating layer 14, and Ta is formed to a thickness of 0.2 μm by a sputtering method as a layer to be an anti-cavitation layer 15. did.

Next, as shown in FIG. 3B, the sacrificial layer 16 is exposed. First, an etching mask is formed by photolithography, the Ta film and the SiN film are etched into a predetermined shape by reactive ion etching using CF ₄ , the resist is removed by O ₂ plasma ashing and a stripping solution, and electrical insulation is performed. Layer 14 was formed. Further, an etching mask is formed by photolithography, etched into a predetermined shape by reactive ion etching using CF ₄ , and the resist is removed by O ₂ plasma ashing and a stripping solution. Thereby, the electrical insulating layer 14 and the anti-cavitation layer 15 were formed. At this time, the sacrificial layer 16 serving as the opening of the liquid supply port 8 and the electrical insulating layer 14 and the anti-cavitation layer 15 between the heat storage layer 11 were formed to be removed.

Subsequently, as shown in FIG. 3C, as a diffusion preventing film 18 of the gold plating layer formed as the etching stop layer 17, titanium tungsten, which is a refractory metal material, is formed with a thickness of 0.2 μm by a vacuum film forming apparatus. Filmed. At this time, considering that titanium tungsten will be removed later by wet etching, a target of 10 mass% Ti and 90 mass% Ti was used. Note that the metal film of the etching stop layer 17 may be a laminate of a gold diffusion prevention film and gold.
Thereafter, Au (gold) having a role of a cathode electrode for receiving an electric current in an electrolytic plating process and a role of a plating seed layer (not shown) serving as a nucleus of plating growth was formed on the entire surface with a thickness of 0.05 μm.
Next, the photoresist was removed by photolithography so as to expose the plating seed layer where the etching stop layer 17 was to be formed, and a resist mask was formed. Next, by electrolytic plating, a predetermined current is passed through the plating seed layer in the gold sulfite electrolytic bath to deposit gold in a predetermined area not covered with the resist mask to a thickness of 5.0 μm. Thus, an etching stop layer 17 was formed. Next, the resist is removed with a stripping solution to expose the plating seed layer. Next, the plating seed layer that became unnecessary was immersed and removed in a gold etching solution containing a nitrogen-based organic compound and potassium iodide for a predetermined time, thereby exposing the entire surface of the gold diffusion preventing film 18. Thereafter, the gold diffusion preventing film 18 was removed by being immersed in an H ₂ O ₂ -based etching solution for a predetermined time. Next, an annealing treatment was performed at about 250 ° C. for 30 to 120 minutes so that the gold plating layer as the etching stop layer 17 became soft gold having a gold hardness of 70 Hv or less.

  Next, as shown in FIG. 3D, a positive photosensitive resin layer is formed on the formed substrate, and the positive photosensitive resin layer is patterned by a photolithography process to form a pattern 19 of the liquid flow path 9. Form. Next, a negative photosensitive resin layer 20 serving as a member of the nozzle plate 2 was formed in a thickness of 70 μm on the upper layer on which the pattern 19 was formed, and the pattern 21 of the discharge port 3 was formed by patterning. Here, the negative photosensitive resin 20 serving as a member of the nozzle plate 2 is formed so as to have a columnar portion in contact with the etching stop layer.

  Next, as shown in FIG. 3E, a liquid supply port 8 is formed from the back surface opening on the second surface of the Si substrate 1 to the sacrificial layer 16 on the first surface (step of forming a liquid supply port). . The liquid supply port was formed by immersing the Si substrate 1 in a 83 ° C. TMAH aqueous solution (concentration 22 wt%) for a predetermined time and performing anisotropic etching. In the anisotropic etching, a mask layer (not shown) that defines the opening on the back surface of the substrate is formed, and the resin resist (not shown) The first surface side of the substrate 1 was protected by the illustration.

Further, as shown in FIG. 3 (f), from the second surface (back surface) side of the substrate 1, it is immersed in an H ₂ O ₂ -based etching solution for a predetermined time, and the gold diffusion prevention film 18 under the etching stop layer is formed. Was removed. Next, the etching stop layer 17 was removed by immersing and removing in a gold etching solution containing a nitrogen-based organic compound and potassium iodide. By removing the etching stop layer, the columnar portion is separated from the first surface of the substrate 1. Thereafter, the positive photosensitive resin layer forming the pattern 19 of the ink flow path 9 is removed, and the pattern 21 of the discharge port 3 is removed, whereby the ink flow path 9 and the discharge port 3 are formed in the nozzle plate 2. Formed.

  The above steps are manufactured so that a large number of chips are formed on the Si wafer as the substrate 1. After the substrate thus formed is cut into chips by dicing, each chip is connected to a chip plate 4 for supplying liquid such as ink and used as a liquid discharge head. The liquid discharge head of the present invention is completed by the above-described liquid discharge head manufacturing method.

(Example 2)
FIG. 4 shows a cross-sectional view in the manufacturing process of the second embodiment of the liquid ejection head according to the present invention. In Example 1, after forming SiN as the electrical insulating layer 14 and Ta as the anti-cavitation layer 15, the space between the heat storage layers 11 serving as the openings of the ink supply ports 8 was removed. In this example, after forming and patterning SiN as a layer to be the electrical insulating layer 14, Ta was formed as a layer to be the anti-cavitation layer 15. Next, by patterning so that the cavitation-resistant layer 15 remains between the heat storage layers 11 serving as openings of the ink supply ports 8, the Ta layer that is the cavitation-resistant layer also serves as an etching stop layer. In other words, the metal film Ta is formed in the same layer as the anti-cavitation layer. Since Ta is a metal film that has alkali resistance and has a spread product, even in the above configuration, the occurrence of film breakage due to stress at the opening of the ink supply port is suppressed, and the manufacturing yield is greatly improved. I was able to.

<Comparative example>
In contrast to the configurations described in Examples 1 and ₂ , SiO ₂ , SiN, Al ₂ O ₃ , and TiO _2, which are inorganic films having no alkali resistance and poor spreadability, are used as the etching stop layer 17. Used as an example. As a result, in any inorganic film, the coverage property was low at the 16 corners of the underlying sacrificial layer, and film breakage occurred in the etching stop layer when the ink supply port 8 was formed from the thin film part.
In addition, when Al, Zn, and Pb, which are amphoteric metals having no alkali resistance, were used as the etching stop layer 17, it was confirmed that the etching solution at the opening of the ink supply port 8 wraps around the substrate 1.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Nozzle plate 3 Discharge port 4 Chip plate 5 Adhesive 6 Liquid discharge head 7 Recording element 8 Liquid supply port 9 Liquid flow path 10 Contact pad 11 First heat storage layer 12 Second heat storage layer 13 Electrode layer 14 Electrical insulation Layer 15 Anti-cavitation layer 16 Sacrificial layer 17 Etching stop layer 18 Gold diffusion prevention film 19 Pattern 20 of liquid flow path 9 Negative photosensitive resin composition layer 21 Pattern of discharge port 3

Claims (10)

A substrate on which a recording element that generates energy for discharging liquid from the discharge port is formed;
A flow path that communicates with the discharge port through the recording element formed on the substrate, a nozzle plate that forms the discharge port,
A liquid supply port formed through the first surface of the substrate on which the recording element is formed and a second surface facing the first surface, and communicated with the flow path;
A method of manufacturing a liquid discharge head having
Forming a sacrificial layer on the first surface of the substrate forming the liquid supply port, and forming the liquid supply port by anisotropic etching using alkali from the second surface of the substrate toward the sacrificial layer; Have
In the step of forming the liquid supply port, an etching stop layer covering the sacrificial layer is formed on the first surface of the substrate, and the etching stop layer is formed of a metal film having alkali resistance. A method for manufacturing a liquid discharge head.   The method of manufacturing a liquid discharge head according to claim 1, wherein the metal film is formed to a thickness of 0.05 μm to 20 μm.   The method of manufacturing a liquid ejection head according to claim 1, wherein the metal film is a laminate of a gold diffusion prevention film and gold.   The method for manufacturing a liquid discharge head according to claim 3, wherein the gold is formed in the same layer as a contact pad of the liquid discharge head.   The method for manufacturing a liquid discharge head according to claim 1, wherein the metal film is Ta.   6. The method of manufacturing a liquid ejection head according to claim 5, wherein the Ta is formed in the same layer as the anti-cavitation layer covering the recording element.   The method of manufacturing a liquid ejection head according to claim 1, further comprising a step of removing the etching stop layer.   The nozzle plate is formed to have a columnar portion in contact with the etching stop layer, and the columnar portion is separated from the first surface by the step of removing the etching stop layer. A method for manufacturing the liquid discharge head described above.   The method for manufacturing a liquid discharge head according to claim 1, wherein the anisotropic etching using the alkali is etching with a TMAH aqueous solution.   The method for manufacturing a liquid ejection head according to claim 1, wherein the substrate is a Si substrate.

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