Substrate for liquid ejection head, liquid ejection head, and method for manufacturing substrate for liquid ejection head

Abstract

To improve cleaning-durability of a thermal action part to lengthen a service life of a substrate for a liquid discharge head, without deteriorating heat conduction efficiency.SOLUTION: A substrate for a liquid discharge head comprises: a base layer 101; a heating resistance element 108, provided above the base layer 101, which generates heat energy for discharging liquid; a first insulation layer 106 covering the heating resistance element 108; and a protection layer 107, provided above the first insulation layer 106, which has a first region 107a overlapping with the heating resistance element 108 through the first insulation layer 106 and a second region 107b not overlapping with the heating resistance element 108 and which is formed of materials including metal eluted off by electrochemical reaction, which further comprises second insulation layers 116 which are provided in a region where the protection layer 107 above the base layer 101 is not formed and in a region above the second region 107b of the protection layer 107.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a substrate for a liquid ejection head, a liquid ejection head, and a method for manufacturing a substrate for a liquid ejection head. [Background technology]

[0002] In a liquid ejection device such as an inkjet printer, a liquid ejection head that ejects liquid for recording onto a recording medium generally has an element substrate provided with a plurality of ejection ports and a heat generating resistor element connected to electrical wiring. A known method of recording involves using an element substrate as a liquid ejection head substrate to apply an electric current to the heat generating resistor element to generate heat, thereby causing film boiling in a liquid such as ink, and ejecting the liquid from the ejection ports using the generated bubbles.

[0003] One example of such an element substrate is one that protects the heating resistor element by providing a cavitation-resistant layer made of a highly hard, chemically stable material, such as Ir, on an insulating layer, such as a silicon nitride film. Meanwhile, heat generated by the heating resistor element causes colorants and additives contained in the ink or other liquid to heat up to high temperatures in the heat-sensitive area, decomposing them at the molecular level and turning them into hardly soluble substances that are physically adsorbed onto the cavitation-resistant layer. This phenomenon is called "burning," and can cause uneven heat conduction from the heat-sensitive area to the liquid, resulting in unstable bubbling of the liquid.

[0004] Patent Document 1 discloses a method for cleaning accumulated kogation during a series of recording processes. Specifically, the kogation accumulated on the cavitation-resistant layer is removed by elution due to an electrochemical reaction in which the cavitation-resistant layer acts as an electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-105364 Summary of the Invention [Problem to be solved by the invention]

[0006] When the above-described kogation cleaning method is adopted, the cavitation-resistant layer is scraped away and its thickness is reduced each time the removal process is performed, and therefore, from the viewpoint of extending the life of the element substrate and the liquid ejection head, it is desirable that the cavitation-resistant layer be thick. Also, it is desirable that the insulating layer located below the cavitation-resistant layer in the heat application portion be thin so that heat can be efficiently transferred from the heat-generating layer to the liquid through the insulating layer.

[0007] On the other hand, when etching the cavitation-resistant layer in areas other than the heat application area during the manufacture of the element substrate, if a physical etching process such as reactive ion etching is used, the insulating layer underneath the cavitation-resistant layer will also be etched at the same time. If the insulating layer is thinned, it will not function properly, resulting in a decrease in the electrical reliability and moisture resistance of the element substrate, and thus in a decrease in the reliability of the liquid ejection head. However, if the insulating layer is thickened to ensure that it remains sufficiently thick after etching, the insulating layer underneath the cavitation-resistant layer will also become thick, leading to a decrease in thermal conduction efficiency.

[0008] In view of the above problems, an object of the present invention is to extend the life of a liquid ejection head substrate while suppressing a decrease in heat conduction efficiency. [Means for solving the problem]

[0009] The liquid ejection head substrate of the present invention comprises: The base layer and a heat generating resistor element provided on the upper side of the base layer and configured to generate heat energy for discharging the liquid; a first insulating layer covering the heating resistor element; a protective layer provided on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; Equipped with a second insulating layer provided above an area above the base layer where the protective layer is not provided and above the second area of ​​the protective layer; The thickness of the first insulating layer in the region where the protective layer is not provided is smaller than the thickness of the region where the protective layer is provided. Ku, The thickness of the protective layer is 50% or more of the thickness of the first insulating layer located directly below the protective layer. It is characterized by: The liquid ejection head substrate of the present invention is The base layer and a heat generating resistor element provided on the upper side of the base layer and configured to generate heat energy for discharging the liquid; a first insulating layer covering the heating resistor element; a protective layer provided on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; Equipped with a second insulating layer provided above an area above the base layer where the protective layer is not provided and above the second area of ​​the protective layer; a thickness of the first insulating layer in a region where the protective layer is not provided is smaller than a thickness of the first insulating layer in a region where the protective layer is provided; The thickness of the first insulating layer in the region where the protective layer is not provided is half or less of the thickness of the region where the protective layer is provided. Further, the method for manufacturing a substrate for a liquid ejection head of the present invention comprises the steps of: A method for manufacturing a substrate for a liquid ejection head, the substrate comprising a base layer, a heat generating resistor element, an electrode wiring layer, a first insulating layer, a protective layer, and a second insulating layer, comprising: a first step of providing the heating resistor element, which generates thermal energy for discharging liquid, on an upper side of the base layer; a second step of laminating the first insulating layer on the heating resistor element; a third step of laminating the protective layer on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; a fourth step of partially removing the first insulating layer and the protective layer so that a layer thickness of a region where the protective layer is not provided is smaller than a layer thickness of a region where the protective layer is provided; a fifth step of laminating the second insulating layer on an area above the base layer where the protective layer is not provided and on at least the second area of ​​the protective layer; Including fruit, The protective layer is formed in the first step to a thickness of 50% or more of the thickness of the first insulating layer. It is characterized by: Further, the method for manufacturing a substrate for a liquid ejection head of the present invention comprises the steps of: A method for manufacturing a substrate for a liquid ejection head, the substrate comprising a base layer, a heat generating resistor element, an electrode wiring layer, a first insulating layer, a protective layer, and a second insulating layer, comprising: a first step of providing the heating resistor element, which generates thermal energy for discharging liquid, on an upper side of the base layer; a second step of laminating the first insulating layer on the heating resistor element; a third step of laminating the protective layer on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; a fourth step of partially removing the first insulating layer and the protective layer so that a layer thickness of a region where the protective layer is not provided is smaller than a layer thickness of a region where the protective layer is provided; a fifth step of laminating the second insulating layer on an area above the base layer where the protective layer is not provided and on at least the second area of ​​the protective layer; Including, In the fourth step, the first insulating layer and the protective layer are partially removed so that the layer thickness in the area where the protective layer is not provided is less than half the layer thickness in the area where the protective layer is provided. [Effects of the Invention]

[0010] According to the present invention, it is possible to extend the life of the liquid ejection head substrate while suppressing a decrease in heat conduction efficiency. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a plan view of a substrate for a liquid ejection head according to a first embodiment. [Figure 2] 1 is a cross-sectional view of a substrate for a liquid ejection head according to a first embodiment. [Figure 3] 3A to 3C are cross-sectional views illustrating a manufacturing process of the liquid ejection head substrate according to the first embodiment. [Figure 4] FIG. 1 is a perspective view of a liquid ejection head according to a first embodiment. [Figure 5] 10A and 10B are a plan view and a cross-sectional view of a substrate for a liquid ejection head according to a second embodiment. [Figure 6] 10A and 10B are a plan view and a cross-sectional view of a substrate for a liquid ejection head according to a third embodiment. [Figure 7] 10 is a table summarizing the etching conditions for the protective layer and the state of the liquid ejection head substrate. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes in detail exemplary embodiments of the present invention with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments may be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied. In other words, the scope of the present invention is not limited to the following embodiments.

[0013] The present invention relates to a liquid ejection head for ejecting liquid onto a recording medium to perform recording or the like, and a liquid ejection head The present invention relates to a substrate for a liquid ejection head provided on a head. The present invention is preferably applicable to, for example, an inkjet head for an inkjet recording method in which recording is performed by foaming a liquid such as ink using thermal energy. Below, the present invention will be described using an example in which it is applied to an inkjet head, but the liquid ejection head of the present invention is not limited to this, and can be applied to various liquid ejection heads and liquid ejection head substrates that eject liquid using thermal energy.

[0014] <1. First embodiment> (1.1 Configuration of liquid ejection head substrate) FIG. 1(a) is a plan view schematically illustrating a liquid ejection head substrate 11 according to a first embodiment, viewed from above. The liquid ejection head substrate 11, which serves as an element substrate, is provided with a plurality of ejection ports 129, and heat-generating resistor elements 108, which serve as heat-applying portions, are provided at positions corresponding to the ejection ports 129. FIG. 1(b) is an enlarged plan view of the vicinity of the heat-applying portion in FIG. 1(a). In order to show the positional relationship between the heat-generating resistor elements 108, the electrode wiring layer 105, and the protective layer 107, the flow path forming member 109 and the like are not shown, and the protective layer 107 is shown semi-transparently. FIG. 2 is a schematic diagram illustrating the AA cross section of FIG. 1(b) and illustrating the layer structure of the liquid ejection head substrate 11.

[0015] 2, the liquid ejection head substrate 11 has a plurality of layers made of metal or the like laminated on a base layer 101 made of silicon. In the liquid ejection head substrate 11 of this embodiment, a heat storage layer (not shown), a heat generating resistor element layer 104, an electrode wiring layer 105, a first insulating layer 106, a protective layer 107, a second insulating layer 116, and a flow path forming member 109 are formed in this order on the base layer 101.

[0016] The heat storage layer is formed of a thermal oxide film, a SiO film, a SiN film, etc. The heating resistor element layer 104 is formed of tantalum silicon nitride, etc., and is connected to the electrode wiring layer 105 for electrical connection to the outside. The electrode wiring layer 105, which functions as wiring, is formed of a metal material such as Al, Al-Si, or Al-Cu.

[0017] The heating resistor element 108, which serves as an electrothermal conversion element, is formed by partially removing the electrode wiring layer 105. In this embodiment, the heating resistor element layer 104 and the electrode wiring layer 105 are arranged in a stacked manner along the direction from the liquid supply port toward the liquid chamber so that their outlines have the same shape. By partially removing a portion of the electrode wiring layer 105, a gap is formed where the electrode wiring layer 105 is not present, and a portion where only the heating resistor element layer 104 is arranged is formed. This exposed portion of the heating resistor element layer 104 functions as the heating resistor element 108. The electrode wiring layer 105 is connected to a drive element circuit or an external power supply terminal (not shown) and is configured to receive a supply of power from an external source. Note that in the above embodiment, the electrode wiring layer 105 is arranged on the heating resistor element layer 104. However, the present invention is not limited to this configuration and may be configured to receive a supply of electrical energy from an external source. For example, the electrode wiring layer 105 may be embedded in a heat storage layer (not shown), and a metal plug such as tungsten may be used to supply power to a heat generating resistor element 108 formed as a single layer on the heat storage layer.

[0018] The first insulating layer 106 is provided on the electrode wiring layer 105 so as to cover the heating resistor element layer 104 and the electrode wiring layer 105. The first insulating layer 106 is formed of a SiO film, a SiN film, a SiC film, a SiCN film, or the like. Heat from the heating resistor element 108 is transferred to the liquid via the first insulating layer 106. The first insulating layer 106 needs to have a certain thickness to protect the electrical wiring and the heating resistor element and maintain insulation, but it is desirable for the layer thickness to be as thin as possible in order to efficiently transfer heat from the heating resistor element 108 to the liquid. In particular, the power consumption of liquid ejection heads has increased in recent years due to an increase in the number of ejection ports and faster ejection speeds. In order to suppress the force, it is becoming increasingly important to efficiently transfer the heat of the heating resistor element to the liquid.

[0019] The protective layer 107 is provided on the first insulating layer 106 and covers the heating resistor element 108 to protect the surface of the heating resistor element 108 from chemical and physical shocks caused by heat generation by the heating resistor element 108. That is, the protective layer 107 is positioned so as to include a position directly behind the heating resistor element 108 via the first insulating layer 106. In this embodiment, the protective layer 107 is formed of a platinum group metal such as iridium (Ir) or ruthenium (Ru) and is conductive. When liquid is ejected, the upper part of the protective layer 107 comes into contact with the liquid. The temperature of the liquid instantaneously rises above the protective layer 107, causing bubbles to form, and the bubbles then disappear, causing cavitation, exposing the protective layer 107 to a harsh environment. Therefore, in this embodiment, the protective layer 107 is formed of a highly corrosion-resistant and reliable material such as Ir or Ru, and functions as a cavitation-resistant layer to protect the heating resistor element 108. In this embodiment, the protective layer 107 includes a first region 107a that overlaps with the heating resistor element 108 via the first insulating layer 106, and a second region 107b that is located outside the first region 107a and does not overlap with the heating resistor element 108.

[0020] The thickness of the protective layer 107 decreases as the thermal application section is cleaned, as described below. Therefore, if the thickness decreases due to repeated cleaning, the protective layer loses its function as a cavitation-resistant layer, which may ultimately lead to disconnection of the heating resistor element and failure of the head. In other words, the cleaning durability of the liquid ejection head substrate and liquid ejection head depends on the initial thickness of the protective layer 107. Therefore, to extend the life of the liquid ejection head, it is desirable for the protective layer 107 to be as thick as possible.

[0021] The second insulating layer 116 is made of the same material as the first insulating layer 106 and is partially formed on the second region 107a of the protective layer 107. In this embodiment, the first insulating layer 106 and the second insulating layer 116 are made of the same material, but they may be made of different materials as long as they are configured to electrically insulate the liquid filling the liquid chamber from the electrode wiring layer 105.

[0022] If the second insulating layer 116 is present in the heat application portion on the first region 107a, the efficiency of heat conduction from the heating resistor element 108 to the liquid will decrease, resulting in increased energy loss. Therefore, in this embodiment, the second insulating layer 116 is formed so as not to cover the heating resistor element 108. Furthermore, in this embodiment, the portion from which the first insulating layer 106 has been removed is further covered with the second insulating layer 116, thereby ensuring the thickness of the insulating layer and ensuring reliable insulation. Therefore, it is preferable that the sum of the thicknesses of the first insulating layer 106 and the second insulating layer 116 in the region where the protective layer 107 is not provided be set larger than the thickness of the first insulating layer 106 in the region where the protective layer 107 is provided.

[0023] The flow path forming member 109 is formed on the second insulating layer. The flow path forming member 109 forms a flow path 119 for supplying liquid from a liquid supply port (not shown) and a discharge port 129 for discharging the liquid. In addition, an adhesion improving layer for connecting the flow path forming member 109 and the base layer 101 may be formed between the flow path forming member 109 and the second insulating layer 116. The adhesion improving layer is preferably made of a material such as SiO, SiCN, or SiOC, and functions as a surface protection layer. The provision of the adhesion improving layer also enables the flow path forming member 109 to adhere well to the second insulating layer 116.

[0024] In this embodiment, an electrochemical reaction between the protective layer 107 and ink is utilized for the cleaning operation to remove deposits on the heat application portion. Therefore, a through hole (not shown) is formed in the first insulating layer 106, and the protective layer 107 is electrically connected to the electrode wiring layer 105. The electrode wiring layer 105 is connected to an external electrode through a relay wiring portion, and the protective layer 107 is also electrically connected to the electrode wiring layer 105. It is electrically connected to an external electrode via the pole wiring layer 105 .

[0025] Furthermore, the protective layer 107 of this embodiment is divided into two regions: a region including a heat application portion formed on the heating resistor element 108, and a region on the opposing electrode side (not shown), and each region is electrically connected. These two regions are not electrically connected to each other when no solution is present on the substrate. However, when the substrate is filled with a liquid such as ink containing an electrolyte, a current flows through the solution, and an electrochemical reaction occurs at the interface between the protective layer 107 and the liquid. While ink used in inkjet printing contains an electrolyte, in this embodiment, Ir is used for the protective layer 107, so an electrochemical reaction or elution can occur when ink is present. Since metal elution occurs on the anode electrode side, kogation on the heating resistor element can be removed by applying a potential to the anode side and cathode side appropriately.

[0026] Although Ir is used for the protective layer 107 in this embodiment, other materials may be used as long as they contain a metal that dissolves due to an electrochemical reaction and do not form an oxide film that prevents dissolution upon heating. Note that the term "material that does not form an oxide film that prevents dissolution upon heating" does not refer to a material that does not form an oxide film at all, but rather to a material that, even if an oxide film is formed upon heating, only forms to the extent that it does not prevent dissolution. In the case of Ir alloys or Ru alloys, the extent to which an oxide film is formed tends to decrease as the Ir or Ru content increases. Therefore, the composition of the metal that constitutes the protective layer 107 can be selected depending on the tendency for an oxide film to form and the desired durability of the metal.

[0027] (1.2 Manufacturing Process of Liquid Ejection Head Substrate 11) The manufacturing process of the liquid ejection head substrate 11 according to the first embodiment will be described with reference to FIG. 3. FIGS. 3(a) to 3(f) are schematic cross-sectional views showing the manufacturing process of the liquid ejection head substrate 11 according to the first embodiment. In the manufacturing process of the liquid ejection head substrate 11, a base layer 101 made of Si has a drive circuit pre-built into it, and then each layer is laminated on the base layer 101. In this embodiment, too, semiconductor elements such as switching transistors for selectively driving the heat-generating resistor elements 108 are pre-built into the base layer 101 as drive circuits, and each layer is laminated on top of that to form the liquid ejection head substrate 11. For simplicity, the drive circuits and the like that have been pre-built are not shown in FIG. 3.

[0028] First, a heat storage layer (not shown) made of a thermally oxidized SiO2 film is formed on the base layer 101 by thermal oxidation, sputtering, CVD, or the like as a lower layer of the heat generating resistor element layer 104. For a substrate on which drive circuits are already built, it is also possible to form the heat storage layer during the manufacturing process of the drive circuits.

[0029] FIG. 3A shows the first step of forming a heating resistor element layer 104 and an electrode wiring layer 105 on the upper side of a base layer. The heating resistor element layer 104, such as TaSiN, is formed on the heat storage layer by reactive sputtering to a thickness of approximately 20 nm. The electrode wiring layer 105, an Al layer, is formed on the heating resistor element layer by sputtering to a thickness of approximately 300 nm. Then, photolithography is used to simultaneously dry-etch the heating resistor element layer 104 and the electrode wiring layer 105 to obtain a predetermined shape. In this embodiment, reactive ion etching (RIE) is used as the dry etching. Then, photolithography is used again to remove only the portion of the electrode wiring layer 105 that will become the heating resistor element 108 by wet etching using a mixed acid or the like. Through the above steps, the heating resistor element layer 104 and the electrode wiring layer 105 are formed in the shape shown in FIG. 6A, thereby obtaining the heating resistor element 108.

[0030] FIG. 3(b) shows the second step in which a SiN film that will become the first insulating layer 106 is formed on the electrode wiring layer. The SiN film is formed to a thickness of about 200 nm by plasma CVD. is formed.

[0031] 3(c) shows the third step in which a layer containing Ir that will become the protective layer 107 is formed on the first insulating layer so as to cover the heating resistor element 108. The layer made of Ir is formed by sputtering to a thickness of approximately 150 nm.

[0032] Figure 3(d) shows the fourth step, in which the first insulating layer 106 and the protective layer 107 are partially removed to obtain the desired shape. Materials such as Ir are generally known to be difficult to etch, and it is not easy to obtain the desired shape by dry etching alone. Therefore, reactive ion etching (RIE) using Ar ions or the like is used to utilize the physical etching action.

[0033] The method for removing the first insulating layer 106 and the protective layer 107 will now be described in detail. First, the layer formed of Ir is partially removed by dry etching using photolithography. Next, physical etching is performed using RIE. The etching conditions will be described in detail later, but the selectivity with respect to SiN is approximately 1.0. Therefore, 100% overetching is performed to ensure the pattern of the protective layer 107. Due to the overetching, the first insulating layer 106 is etched to a thickness of approximately 150 nm, which is approximately the same as the thickness of the protective layer 107. That is, in areas where the protective layer 107 is not provided, the first insulating layer 106 remains on the base layer with a thickness of approximately 50 nm. With physical etching methods, it is difficult to ensure a selectivity when an underlying insulating layer, such as a silicon nitride film, exists. In particular, if the thickness of the protective layer 107, which serves as a cavitation-resistant layer, is increased as in this embodiment, the thickness of the underlying first insulating layer 106 is reduced more than necessary, so appropriate etching conditions must be set.

[0034] The etching conditions used for the dry etching are as follows: The process gas used for etching was a mixture of Ar and chlorine at a flow ratio of approximately 2:1. In addition, to accelerate the physical etching of Ar atoms, the bias applied to the substrate was in the range of 300W to 400W.

[0035] 3(e) shows a fifth step in which a SiN film that will become the second insulating layer 116 is formed on the protective layer, and a sixth step in which the second insulating layer 116 is partially removed. First, a SiN film is formed to a thickness of about 200 nm as the second insulating layer 116 using a plasma CVD method. Next, photolithography and chemical dry etching are used to remove the second insulating layer 116 at a position directly behind the heating resistor element 108, with the first insulating layer 106 and protective layer 107 interposed therebetween, to open a thermal application portion.

[0036] FIG. 3(f) shows the process of forming the flow path forming member 109. A resist is applied by spin coating to the liquid ejection head substrate 11, which has the above-described layers formed on the base layer 101. The resist is a soluble solid layer that will ultimately form the liquid chambers. The resist material is, for example, polymethyl isopropenyl ketone, which acts as a negative resist. The resist layer is then patterned into the desired shape of the liquid chambers using photolithography. A coating resin layer is then formed to form the liquid flow path walls and ejection ports 129 that constitute the flow paths 119. Before forming this coating resin layer, a silane coupling treatment or other suitable process can be performed to improve adhesion. The coating resin layer can be formed by applying a resin to the base layer of the liquid ejection head substrate, on which the liquid chamber patterns for the liquid chambers have been formed, using a conventional coating method. Next, the coating resin layer is patterned into the desired shapes of the liquid flow path walls and ejection ports using photolithography.

[0037] After the flow path forming member 109 is formed, the back surface of the substrate (where the various layers of the base layer 101 are not provided) is A liquid supply port (not shown) is formed from the substrate (side) using anisotropic etching, sandblasting, anisotropic plasma etching, or the like. Most preferably, the liquid supply port can be formed by chemical silicon anisotropic etching using tetramethylhydroxyamine (TMAH), NaOH, KOH, or the like. Next, the entire surface is exposed to deep-UV light, and then developed and dried to remove the soluble solid layer. Through these steps, the liquid ejection head substrate 11 is manufactured.

[0038] According to the configuration of the above embodiment, even if a platinum group material such as Ir, which is difficult to etch, is used for the protective layer 107 and the thickness of the protective layer 107 is increased to improve durability, the thickness of the first insulating layer 106 disposed in the heat application portion can be kept to a necessary minimum. In other words, it is possible to manufacture a liquid ejection head substrate 11 with improved cleaning durability without reducing thermal efficiency.

[0039] (1.3 inkjet head) FIG. 4 shows an example of the configuration of an inkjet head 1 as a liquid ejection head on which the above-mentioned liquid ejection head substrate 11 is provided. The inkjet head 1 has the liquid ejection head substrate 11, an ink tank 12 as a housing, a TAB (Tape Automated Bonding) 13 as a relay wiring section, and a contact 14. The ink tank 12 stores ink to be ejected via the liquid ejection head substrate 11. The contact 14 comes into contact with an electrical output terminal of the liquid ejection device main body such as an inkjet printer to receive power. The power supplied to the contact 14 is transmitted to the liquid ejection head substrate 11 via the TAB 13.

[0040] The inkjet head is not limited to being integrated with the ink tank as described above. For example, the ink tank may be detachably attached, so that when the ink in the ink tank runs out, it can be removed and a new ink tank can be installed. The inkjet head may also be configured separately from the ink tank, with ink supplied via a tube or the like. Furthermore, the inkjet head may be applied to a serial recording system as described above, or may be applied to a line printer, having nozzles across the entire width of the recording medium.

[0041] (1.4 Cleaning durability rating) Using an inkjet head 1 equipped with a liquid ejection head substrate 11 of this embodiment, the heat application portion was repeatedly cleaned, and cleaning durability and the like were evaluated. In the cleaning evaluation, in order to confirm the effect of the present invention, multiple substrates were produced as comparative examples and evaluated in the same manner. The configuration of the comparative examples will be described later.

[0042] When cleaning was repeatedly performed using the inkjet head 1 equipped with the liquid ejection head substrate 11 of the first embodiment, it was confirmed that the protective layer 107 remained even after 90 cleaning operations.

[0043] As Comparative Example 1, a substrate was produced in a configuration in which the second insulating layer 116 was not provided, in contrast to the first embodiment. That is, Comparative Example 1 differs from the first embodiment only in that the second insulating layer 116 was not provided.

[0044] When a liquid ejection head equipped with the substrate of Comparative Example 1 was used, the inkjet head could not be driven. This is thought to be because a considerable amount of the first insulating layer 106 was removed by over-etching, which resulted in the electrode wiring layer 105, which should have been electrically insulated, losing its insulation and causing leakage.

[0045] As Comparative Example 2, a substrate was fabricated in which the thickness of protective layer 107 was 45% of that of first insulating layer 106, as compared to the substrate of Comparative Example 1. That is, Comparative Example 2 differs from the first embodiment in that it does not have a second insulating layer and the thickness of protective layer 107 is changed from 150 nm to 90 nm.

[0046] When a liquid ejection head equipped with the substrate of Comparative Example 2 was used, the liquid ejection head operated, unlike Comparative Example 1. This is thought to be because the thickness of the protective layer 107 in Comparative Example 2 was thinner than in the first embodiment and Comparative Example 1, so the thickness of the first insulating layer 106 removed by over-etching was also thinner, resulting in an increased thickness of the remaining first insulating layer 106. When cleaning operations were repeatedly performed using the substrate of Comparative Example 2, it was confirmed that the protective layer 107 had disappeared and part of the heating resistor element had been damaged after approximately 50 cleaning operations. In other words, it was confirmed that reducing the initial thickness of the protective layer 107 to reduce the thickness of the first insulating layer 106 removed by etching deteriorates durability against cleaning. From the viewpoint of cleaning durability, the thickness of the protective layer 107 is preferably at least 50% of the thickness of the first insulating layer 106, and more preferably at least 100 nm.

[0047] As described above, in a configuration in which only the first insulating layer 106 and the protective layer 107 are provided, if the initial thickness of the first insulating layer 106 is made thin and the initial thickness of the protective layer 107 is made thick, the thickness of the first insulating layer 106 will decrease. 6 does not remain, and insulation cannot be maintained. If both are made thin, the durability to cleaning becomes poor. If both the initial layer thicknesses of 07 and 08 are increased, the thermal conduction efficiency decreases. In other words, while in the conventional configuration there was a trade-off between the cleaning durability of the heat application part and the thermal conduction efficiency, by applying the present invention, it is possible to improve the cleaning durability without reducing the thermal conduction efficiency, thereby extending the life of the liquid ejection head substrate.

[0048] 2. Second embodiment As the second embodiment, a configuration in which the layer configuration is changed from that of the first embodiment will be described. In this embodiment, the electrode wiring layer is embedded in the heat storage layer 102. Other configurations similar to those of the first embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

[0049] (2.1 Configuration of the liquid ejection head substrate 11) Fig. 5(a) is an enlarged plan view of the vicinity of the heat application portion of the liquid ejection head substrate 11 according to the second embodiment of the present invention, and for simplification, the flow path forming member 109 is not shown, but the positional relationship between the heat generating resistor element 108 and the liquid supply port 130 is shown. Fig. 5(b) is a schematic view showing the BB cross section of Fig. 5(a).

[0050] The liquid ejection head substrate 11 of this embodiment is also formed by laminating multiple layers on a base layer 101 made of silicon. A heat storage layer 102 made of a thermal oxide film, SiO film, SiN film, or the like is disposed on the base layer 101, and a heating resistor element 108 is disposed on the heat storage layer 102. The heating resistor element 108 is electrically connected to the outside via an electrode wiring layer 105a serving as wiring made of a metal material such as Al, Al-Si, or Al-Cu, and a connection plug 105b. A first insulating layer 106 is disposed on the heating resistor element 108 and the heat storage layer 102.

[0051] In this embodiment, the electrode wiring layer 105a is connected to a drive element circuit or an external power supply terminal (not shown) and is configured to be able to receive power from the outside. In this embodiment, the electrode wiring layer 105a, which receives electrical energy from the outside, is embedded in the heat storage layer 102, and power is supplied to the heating resistor element 108 formed in a single layer on the heat storage layer 102 using a connection plug 105b made of a material such as tungsten. As described above, This embodiment differs from the first embodiment in the position where the electrode wiring layers are arranged.

[0052] Inside the liquid chamber, a first insulating layer 106 and a protective layer 107 are provided on the heat storage layer 102 so as to cover the heating resistor element 108, and a second insulating layer 116 is further provided on the second region 107b of the protective layer 107. The first insulating layer 106 and the second insulating layer 116 are preferably made of an insulating material such as an SiO film, an SiN film, an SiC film, or an SiCN film, and although the same material is used for each layer in this embodiment, different materials may also be used. The protective layer 107 is preferably made of a platinum group material such as iridium (Ir) or ruthenium (Ru).

[0053] In this embodiment, too, through-holes (not shown) are formed in the first insulating layer 106 to remove deposits on the heat application portion, and the protective layer 107 and the electrode wiring layer 105a are electrically connected, thereby enabling an electrochemical reaction between the protective layer 107 and the ink. The protective layer 107 may be made of any material other than those described above, as long as it contains a metal that dissolves due to an electrochemical reaction and does not form an oxide film that prevents dissolution by heating. The composition of the metal that constitutes the protective layer 107 can be selected depending on the degree of oxide film formation, the durability of the metal that is required, and the like.

[0054] (2.2 Manufacturing process of liquid ejection head substrate 11) The manufacturing process of the liquid ejection head substrate 11 according to the second embodiment will now be described. In general, in the manufacturing process of a liquid ejection head, a drive circuit is built into a base layer 101 made of Si beforehand, and then various layers are laminated on the base layer 101 to manufacture the inkjet head 1. In this embodiment as well, semiconductor elements such as switching transistors for selectively driving the heat generating resistor elements 108 are built into the base layer 101 beforehand as the drive circuit, and then various layers are laminated on top of that to form the liquid ejection head substrate 11.

[0055] First, a heat storage layer 102 made of a thermally oxidized SiO2 film is formed on a base layer by thermal oxidation, sputtering, CVD, or the like as a lower layer of the heating resistor element 108. For a base body on which a drive circuit is already built, the heat storage layer can be formed during the manufacturing process of the drive circuit. In this embodiment, when the heat storage layer is formed, an electrode wiring layer 105a is embedded in the heat storage layer 102, and a connection plug 105b is formed to connect the electrode wiring layer 105a to the heating resistor element 108.

[0056] Next, to form the first insulating layer 106, a SiN film is formed to a thickness of approximately 300 nm using a plasma CVD method. Furthermore, a layer of Ir is formed to a thickness of approximately 300 nm on the first insulating layer as the protective layer 107 using a sputtering method. The Ir layer is then partially removed by dry etching using a photolithography method. At this time, the protective layer 107 is formed, but because Ir is a chemically stable material, dry etching using a physical component such as RIE is required. The etching conditions will be described later. Since the selectivity with SiN is approximately 1.0, 90% over-etching is performed to ensure the pattern of the protective layer 107 is formed. During this process, the first insulating layer 106 is etched by approximately 270 nm due to the over-etching.

[0057] The etching conditions used for the dry etching are as follows: The process gas used for etching was a mixture of Ar and chlorine at a flow ratio of approximately 2:1. In addition, to accelerate the physical etching of Ar atoms, the bias applied to the substrate was in the range of 300W to 400W.

[0058] Next, a SiN film is formed to a thickness of about 200 nm by using the plasma CVD method as the second insulating layer 116. After that, a SiN film is formed on the first insulating layer 106 and the protective layer 107 at a position directly behind the heating resistor element 108 by using the photolithography method and the chemical dry etching method. The second insulating layer 116 of the device is removed to open the heat application portion.

[0059] Finally, in order to manufacture the liquid chamber and the liquid flow path, a flow path forming member 109 is formed, and anisotropic etching or the like is performed from the rear surface of the substrate to form a liquid supply port 130. Through the above steps, the liquid ejection head substrate 11 is manufactured.

[0060] According to the configuration of the above embodiment, even if a platinum group material such as Ir, which is difficult to etch, is used for the protective layer 107 and the thickness of the protective layer 107 is increased to improve durability, the thickness of the first insulating layer 106 disposed in the heat application portion can be kept to a necessary minimum. In other words, it is possible to manufacture a liquid ejection head substrate 11 with improved cleaning durability without reducing thermal efficiency.

[0061] (2.3 Cleaning durability evaluation) Using an inkjet head equipped with the liquid ejection head substrate 11 of this embodiment, a cleaning evaluation similar to that of the first embodiment was carried out. As a result, similar to the first embodiment, the protective layer 107 remained intact even after 90 cleaning cycles. It was confirmed that it remains.

[0062] 3. Third Embodiment As the third embodiment, a configuration in which the layer configuration is changed from that of the second embodiment will be described. In this embodiment, the first insulating layer 106 does not remain in the region where the protective layer 107 does not exist. Other components similar to those of the second embodiment are assigned the same reference numerals and will not be described again.

[0063] (3.1 Configuration of the liquid ejection head substrate 11) Fig. 6(a) is an enlarged plan view of the vicinity of the heat application portion of the liquid ejection head substrate 11 according to the second embodiment of the present invention, with the flow path forming member 109 removed to show the positional relationship between the heat generating resistor element 108 and the liquid supply port 130. Fig. 6(b) is a schematic view showing the CC cross section in Fig. 6(a).

[0064] In this embodiment, the substrate shown in the second embodiment has a configuration in which the first insulating layer 106 does not exist in the region where the protective layer 107 does not exist. When the configuration in which the electrode wiring layer 105a is embedded in the heat storage layer 102 and the electrode wiring layer 105a does not exist directly below the first insulating layer 106 is adopted as in this embodiment, there is no need to control the remaining layer thickness of the first insulating layer 106, which improves the freedom of selection of the manufacturing process.

[0065] (3.2 Manufacturing process of liquid ejection head substrate 11) In the manufacturing process of this embodiment, in order to remove the protective layer 107 more reliably, the overetching in the dry etching process when forming the protective layer 107 was increased to 120%. As a result, the first insulating layer 106, which has an initial thickness similar to that of the protective layer 107, was also removed by 120%. The remaining manufacturing steps are the same as those in the second embodiment.

[0066] According to the configuration of this embodiment, even if a platinum group material such as Ir, which is difficult to etch, is used for the protective layer 107 and the thickness of the protective layer 107 is increased to improve durability, the thickness of the first insulating layer 106 disposed in the heat application portion can be kept to a necessary minimum. In other words, it is possible to manufacture a liquid ejection head substrate 11 with improved cleaning durability without reducing thermal efficiency.

[0067] (3.3 Cleaning durability evaluation) Using an inkjet head equipped with the liquid ejection head substrate 11 of this embodiment, cleaning evaluation was carried out in the same manner as in the first and second embodiments. Therefore, the first insulating layer 106 does not remain in the area where the protective layer 107 is not provided, but the electrode wiring layer 105a is embedded in the heat storage layer 102 and is not removed by etching, so the inkjet head operated without any problems. When the heating portion was repeatedly cleaned, as in the first and second embodiments, the inkjet head did not operate even after 90 cleanings. It was confirmed that the protective layer 107 remained.

[0068] <4. Other comparative examples> In order to confirm the influence of the etching conditions of the protective layer 107 on whether or not the liquid ejection head can be driven, a comparative example was prepared in which the etching conditions were changed from those of the first embodiment or the second embodiment. It was produced.

[0069] (4.1 Comparative Examples 3 and 4) In comparison with the first embodiment, a liquid ejection head substrate and an inkjet head were fabricated by changing the etching conditions for the protective layer 107, and the state of the liquid ejection head substrate was confirmed. A list of the etching conditions used in this comparative example and the state of the fabricated liquid ejection head substrate 11 are shown in a table in FIG.

[0070] In Comparative Example 3, etching was performed by changing the Ar / chlorine flow rate ratio of the process gas to 4:1 (Condition 2). In Comparative Example 4, etching was performed by changing the range of the bias applied to the substrate to 500 W to 600 W (Condition 3). For each substrate, etching progressed to the electrode wiring layer and heat storage layer below the first insulating layer 106, and the liquid ejection head could not be driven, as in Comparative Example 1. In other words, it was confirmed that in a configuration in which the wiring layer is provided directly below the insulating layer, it is necessary for the liquid ejection head to be driven such that the insulating layer is not completely removed and remains so that the electrode wiring layer is not removed when the protective layer is etched.

[0071] (4.2 Comparative Examples 5 and 6) In comparison with the second embodiment, a liquid ejection head was manufactured by changing the etching conditions for the protective layer 107, and the state of the liquid ejection head substrate was confirmed. A list of the etching conditions used in this comparative example and the state of the manufactured liquid ejection head substrate 11 are shown in a table in FIG.

[0072] In Comparative Example 5, etching was performed by changing the Ar / chlorine flow rate ratio of the process gas to 1:1 (Condition 4). In Comparative Example 6, etching was performed by changing the range of the bias applied to the substrate to 100 W to 200 W (Condition 5). For each substrate, the protective layer 107 was not sufficiently etched, and the liquid ejection head could not be driven, as in Comparative Example 1. In other words, it was confirmed that in the process of removing the protective layer by etching, it is necessary to select conditions that ensure complete removal of the protective layer in order to drive the liquid ejection head. [Explanation of symbols]

[0073] 11...liquid ejection head substrate, 101...base layer, 106...first insulating layer, 107...protective layer, 107a...first region, 107b...second region, 108...heat generating resistor element, 116...second insulating layer

Claims

1. The base layer and a heat generating resistor element provided on the upper side of the base layer and configured to generate heat energy for discharging the liquid; a first insulating layer covering the heating resistor element; a protective layer provided on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; Equipped with a second insulating layer provided above an area above the base layer where the protective layer is not provided and above the second area of ​​the protective layer; a thickness of the first insulating layer in a region where the protective layer is not provided is smaller than a thickness of the first insulating layer in a region where the protective layer is provided; A liquid ejection head substrate, wherein the thickness of the protective layer is 50% or more of the thickness of the first insulating layer located directly below the protective layer.

2. A base layer, a heat generating resistor element provided on the upper side of the base layer and configured to generate heat energy for discharging the liquid; a first insulating layer covering the heating resistor element; a protective layer provided on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; Equipped with a second insulating layer provided above an area above the base layer where the protective layer is not provided and above the second area of ​​the protective layer; a thickness of the first insulating layer in a region where the protective layer is not provided is smaller than a thickness of the first insulating layer in a region where the protective layer is provided; The thickness of the first insulating layer in the region where the protective layer is not provided is a thickness of the liquid ejection head substrate being equal to or less than half of the thickness of the region where the liquid ejection head substrate is provided.

3. A substrate for a liquid ejection head as described in Claim 2, characterized in that the thickness of the protective layer is 50% or more of the thickness of the first insulating layer located directly below the protective layer.

4. 4. The liquid ejection head substrate according to claim 1, wherein the protective layer is made of a material that does not form an oxide film that prevents the elution due to heating.

5. 5. The liquid ejection head substrate according to claim 1, wherein the protective layer is made of a material containing iridium or ruthenium.

6. 6. The liquid ejection head substrate according to claim 1, wherein the protective layer has a thickness of 100 nm or more.

7. A substrate for a liquid ejection head described in any one of claims 1 to 6, characterized in that the sum of the layer thicknesses of the first insulating layer and the second insulating layer in the area not covered by the protective layer is greater than the layer thickness of the first insulating layer in the area where the first insulating layer is covered by the protective layer.

8. 8. The liquid ejection head substrate according to claim 1, wherein the second insulating layer is not provided above the first region of the protective layer.

9. 9. The liquid ejection head substrate according to claim 1, further comprising a surface protection layer provided on the second insulating layer and made of a material different from that of the second insulating layer.

10. 10. The liquid ejection head substrate according to claim 1, wherein the first insulating layer and the second insulating layer are made of the same material.

11. an element substrate; a relay wiring portion electrically connected to the element substrate; a housing that stores the liquid to be supplied to the element substrate; In a liquid ejection head having 11. A liquid ejection head, wherein the element substrate is a liquid ejection head substrate according to claim 1.

12. A method for manufacturing a substrate for a liquid ejection head, the substrate comprising a base layer, a heat generating resistor element, an electrode wiring layer, a first insulating layer, a protective layer, and a second insulating layer, a first step of providing the heating resistor element, which generates thermal energy for discharging liquid, on an upper side of the base layer; a second step of laminating the first insulating layer on the heating resistor element; a third step of laminating the protective layer on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; a fourth step of partially removing the first insulating layer and the protective layer so that a layer thickness of a region where the protective layer is not provided is smaller than a layer thickness of a region where the protective layer is provided; a fifth step of laminating the second insulating layer on an area above the base layer where the protective layer is not provided and on at least the second area of ​​the protective layer; Including, A method for manufacturing a substrate for a liquid discharge head, wherein the protective layer is formed in the first step to a thickness that is 50% or more of the thickness of the first insulating layer.

13. A method for manufacturing a substrate for a liquid ejection head, the substrate comprising a base layer, a heat generating resistor element, an electrode wiring layer, a first insulating layer, a protective layer, and a second insulating layer, a first step of providing the heating resistor element, which generates thermal energy for discharging liquid, on an upper side of the base layer; a second step of laminating the first insulating layer on the heating resistor element; a third step of laminating the protective layer on the first insulating layer, the protective layer having a first region overlapping the heating resistor element via the first insulating layer and a second region not overlapping the heating resistor element, the protective layer being made of a material containing a metal that dissolves by an electrochemical reaction; a fourth step of partially removing the first insulating layer and the protective layer so that a layer thickness of a region where the protective layer is not provided is smaller than a layer thickness of a region where the protective layer is provided; a fifth step of laminating the second insulating layer on an area above the base layer where the protective layer is not provided and on at least the second area of ​​the protective layer; Including, A method for manufacturing a substrate for a liquid ejection head, characterized in that in the fourth step, the first insulating layer and the protective layer are partially removed so that the layer thickness in the area where the protective layer is not provided is less than half the layer thickness in the area where the protective layer is provided.

14. A method for manufacturing a substrate for a liquid ejection head as described in Claim 13, characterized in that the protective layer is formed in the first step to a thickness of 50% or more of the thickness of the first insulating layer.

15. 15. The method for manufacturing a substrate for a liquid ejection head according to claim 12, wherein the protective layer is made of a material that does not form an oxide film that prevents the elution by heating.

16. 16. The method for manufacturing a substrate for a liquid ejection head according to claim 12, further comprising a sixth step of removing the second insulating layer located above the first region of the protective layer.

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