Recording element substrate

Abstract

To secure flatness under a heating resistor by suppressing a slight recess of an insulating film in a configuration having a heat sink of the same layer as a wiring layer under the heating resistor.SOLUTION: A wiring board includes a heating resistor layer in which a heating resistor is provided, an electrical wiring connected to the heating resistor, a wiring layer in which a heat sink disposed below the heating resistor is provided in the same layer, an insulating film that insulates the heating resistor and the electrical wiring, and a plug that penetrates the insulating film provided to electrically connect the heating resistor and the electrical wiring. The insulating film includes a lower insulating film provided on a side close to the wiring layer and planarized and an upper insulating film provided on the lower insulating film, the upper insulating film is provided on the lower insulating film at least in a region below the heating resistor in a stacking direction, and a ratio of a distance between the electric wiring and the heat sink to a film thickness of the wiring layer is 2 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a recording element substrate. [Background technology]

[0002] A recording device using a liquid ejection method (inkjet recording method) performs recording by depositing a liquid (e.g., ink) ejected from ejection ports provided in a liquid ejection head onto a recording material such as paper. For example, a recording device that ejects a liquid by utilizing the bubbling of the liquid caused by the thermal energy generated by an electrothermal conversion element is capable of high-quality and high-speed recording.

[0003] A liquid ejection head generally includes a recording element substrate, wiring for supplying power and control signals, and a storage section for storing liquid. The recording element substrate has multiple ejection ports, flow paths communicating with the ejection ports, and multiple electrothermal conversion elements that generate thermal energy for ejecting liquid. The electrothermal conversion elements are composed of a heating resistor and electrodes for supplying power to the resistor. The electrothermal conversion elements are covered with an insulating protective layer, such as silicon nitride, to ensure insulation between the liquid and the electrothermal conversion elements.

[0004] In liquid ejection heads with electrothermal conversion elements, it is important to balance heat storage and heat dissipation. Excessive heat storage can cause the liquid to re-bubble after ejection (reboiling), while excessive heat dissipation can slow the ejection frequency because it takes too long to supply enough heat for the bubbling. In recent years, there has been a trend toward multilayer wiring structures to increase the density and functionality of printing element substrates, and the thickness of the insulating film that contributes to heat storage has also been increasing. This has led to an increased need to properly dissipate the thermal energy generated by electrothermal conversion elements.

[0005] Patent Document 1 discloses a configuration in which a material with high thermal conductivity is placed as a heat sink under an electrothermal conversion element in the same layer as the wiring layer in order to improve heat dissipation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-137705 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to improve the heat dissipation effect, it is necessary to increase the area of ​​the heat sink. However, as shown in Patent Document 1, if the heat sink and wiring layer are formed on the same layer, increasing the size of the heat sink will shorten the distance between the electrical wiring and the heat sink, and the coverage of the insulating film formed on the space between the heat sink and wiring will deteriorate. As a result, voids may form in the insulating layer between the heat sink and wiring, and the film quality may deteriorate.

[0008] For stable foaming, it is preferable that the area under the heating resistor is flat, so in a recording element substrate with a multilayer wiring structure, the heating resistor is formed on an insulating film that has been flattened by CMP (Chemical Mechanical Polishing) etc. At this time, in areas where voids have formed in the insulating film or the film quality has deteriorated, slight depressions of about a few nanometers may occur during the flattening process.

[0009] The wiring layer of a typical semiconductor is formed with a film thickness of about 100 nm to 1000 nm, so even if there is a recess of a few nm, there is almost no reduction in the functionality or reliability of the wiring. However, in order to save power, there is a trend to make the film thickness of the heating resistor on the print element substrate thinner, for example, to about 10 to 50 nm. Therefore, even if the depression in the insulating film is only a few nm, the thickness of the heating resistor becomes thinner in some places, which can lead to concerns such as a decrease in the uniformity of heat generation and a locally high current density, shortening the lifespan.

[0010] The present invention has been made in view of the above-mentioned problems, and its object is to suppress minor depressions in the insulating film and ensure flatness below the heating resistor in a configuration in which a heat sink in the same layer as the wiring layer is provided below the heating resistor, and to provide a liquid ejection head recording element substrate that is highly functional and reliable. [Means for solving the problem]

[0011] The present disclosure employs the following configuration: A recording element substrate in which a plurality of layers are stacked in a stacking direction on a base material, a heat generating resistor layer provided with a heat generating resistor for ejecting the liquid contained in the liquid chamber; a wiring layer including electrical wiring for supplying a voltage to the heating resistor from an external source, and a heat sink formed in the same layer as the electrical wiring and disposed below the heating resistor in the stacking direction; an insulating film provided between the heating resistor layer and the wiring layer, for insulating the heating resistor from the electrical wiring; a plug penetrating the insulating film for electrically connecting the heating resistor and the electrical wiring; and the insulating film includes a lower-layer insulating film that is provided on a side closer to the wiring layer in a stacking direction and has a flattened upper portion, and an upper-layer insulating film that is provided on the flattened lower-layer insulating film, the upper-layer insulating film is provided on the lower-layer insulating film at least in a region below the heating resistor in the stacking direction, The ratio of the distance between the electrical wiring and the heat sink to the thickness of the wiring layer is 2 or less. The recording element substrate is characterized by the above. [Effects of the Invention]

[0012] According to the present invention, in a configuration in which a heat sink in the same layer as the wiring layer is provided below the heating resistor, slight depressions in the insulating film can be suppressed and flatness below the heating resistor can be ensured. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing the configuration of a recording device. [Figure 2] A perspective view of a recording head [Figure 3] Configuration diagram of the recording element board [Figure 4] Cross-sectional view of a recording element substrate [Figure 5] FIG. 1 is an enlarged cross-sectional view of a heat generating resistor portion of a recording element substrate according to a first embodiment; [Figure 6] 5A and 5B are diagrams showing a method for manufacturing the heat generating resistor portion of the recording element substrate according to the first embodiment; [Figure 7] An enlarged cross-sectional view of a heat generating resistor portion of a conventional recording element substrate. [Figure 8] Cross-sectional view of a conventional print element board (narrow space between electrical wiring and heat sink) [Figure 9] Cross-sectional view of a conventional print element board (wide space between electrical wiring and heat sink) [Figure 10] Cross-sectional view of the wiring layer being deposited (comparison example) [Figure 11] FIG. 10 is an enlarged cross-sectional view of a heat generating resistor portion of a recording element substrate according to a second embodiment; [Figure 12] 10A and 10B are diagrams showing a method for manufacturing a heat generating resistor portion of a recording element substrate according to a second embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in these embodiments are not intended to limit the scope of the present invention to those. Furthermore, the materials, shapes, etc. of components described once in the following description will remain the same in subsequent descriptions unless otherwise specified. Well-known or publicly known technologies in the relevant technical field can be applied to configurations and processes not specifically illustrated or described. Furthermore, the present invention is not limited to these embodiments, and not all of the combinations of features described in the embodiments are necessarily essential to the solutions of the present invention.

[0015] First Embodiment (Configuration of recording device) First, a recording apparatus (liquid ejection apparatus) equipped with a recording head (liquid ejection head) according to a first embodiment will be described with reference to FIGS. 1 and 2. In this specification, an inkjet recording apparatus that records by ejecting liquid such as ink onto a recording medium will be described as an example. In this recording apparatus, the recording head that ejects liquid to record corresponds to the liquid ejection head that ejects liquid. FIG. 1 is a schematic diagram of a recording apparatus equipped with a recording head, with a portion cut away. FIG. 2 is a perspective view of the head unit.

[0016] The recording device 500 includes a carriage 505 to which the head unit 410 can be detachably attached. The carriage 505 is attached to a belt 501 that is endlessly stretched between a drive pulley 503A and a driven pulley 503B. The carriage 505 is also slidably mounted on a guide shaft 502 that is arranged parallel to the extension direction of the belt 501. When the drive pulley 503A, driven by a carriage motor 504, rotates, the belt 501 rotates, and the carriage 505 moves in the direction of arrow A while being supported by the guide shaft 502. Therefore, the carriage 505 is configured to be able to move back and forth in the direction of arrow A depending on the rotation direction of the drive pulley 503A.

[0017] The recording device 10 is equipped with an encoder sensor 508. The encoder sensor 508 detects the slits of a linear scale 507 extending in the A direction. The control unit of the recording device 500 detects the position of the carriage 505 in the A direction based on the detection result of the linear scale 507 by the encoder sensor 508. The linear scale 507 and the encoder sensor 508 can be collectively considered to be position detection means 506.

[0018] The recording apparatus 500 includes a first pair of conveying rollers 509 and 510 and a second pair of conveying rollers 511 and 512. The first and second conveying roller pairs 511 and 512 are rotated by a conveying motor to convey the recording medium P in the direction of arrow B. The first conveying roller pair 509 and 5 10 is located on the upstream side in the Y direction, which is the conveying direction of the recording medium P, and the second conveying roller pair 51 The first pair of conveying rollers 509 and 510 and the second pair of conveying rollers 511 and 512 are located downstream in the Y direction. The first and second conveying roller pairs are positioned so as to sandwich the area onto which the liquid is ejected. The first and second conveying roller pairs nip and convey the recording medium P, thereby maintaining smoothness at the position facing the recording head in the head unit 410.

[0019] The control unit of the recording device 500 then drives the carriage motor 504 to perform a recording operation in which liquid is ejected from the recording head of the head unit 410 onto the recording medium P in accordance with the recording data. At this time, the control unit drives the carriage motor 504 based on the detection result of the encoder sensor 508. As a result, one band's worth of image is recorded on the recording medium P. Thereafter, the control unit drives the transport motor to perform a transport operation in which the recording medium P is transported in the direction of arrow B by a distance equivalent to one band. The recording device 500 forms a recorded image on the recording medium P by repeatedly alternately performing the recording operation and the transport operation in this manner.

[0020] The recording device 500 also has a recovery unit 513 for performing maintenance on the recording head of the head unit 410 at a home position located at one end in direction A. The recovery unit 513 includes a cap member for protecting the recording head, and a pump for suctioning to generate negative pressure inside the cap member.

[0021] In this embodiment, four head units 410 can be arranged on the carriage 505. Each head unit 410 is capable of ejecting cyan, magenta, yellow, and black liquids (inks). As shown in FIG. 2, each head unit 410 includes a tank 404 that contains liquid therein and a print head 1 for ejecting the liquid contained in the tank 404. The head unit 410 also includes a wiring tape 402 for supplying print data, power, and the like to the print head 1. The wiring tape 402 has contact points 403 formed thereon for electrically connecting the head unit 410 to the printing device 500 when the head unit 410 is attached to the carriage 505.

[0022] While the present embodiment uses a head unit 410 in which the tank 404 and the print head 1 are integrated, this is not limiting. That is, the tank 404 and the print head 1 may be separate. Specifically, the print head 1 is mounted on the carriage 505, and liquid is supplied to the print head 1 via a tube or the like from a tank 404 detachably mounted within the printing device 500. In this case, a print head 1 may be provided for each color, or only one print head capable of ejecting four liquids may be provided. The number of liquids used in the printing device 500 and the types of liquids ejected are not limited to those described above. That is, the number of liquids may be one color, two, three, or five or more colors. Furthermore, the type of liquid may be a processing liquid other than ink that performs a predetermined process on the printing medium P or the like.

[0023] (Explanation of the recording element substrate) Next, the configuration of a recording element substrate 100 for a recording head will be described. Fig. 3 is a schematic perspective view of the recording element substrate 100 according to this embodiment. The recording element substrate 100 includes a substrate 110 as a base material, on which are formed a liquid supply path 176 that supplies liquid to a liquid chamber 172 and a liquid recovery path 174 that recovers liquid from the liquid chamber 172. On one surface of this substrate 110, a nozzle member 170 is provided, on which is formed an ejection port array consisting of a plurality of ejection ports 171 for ejecting liquid. In addition, on the other surface of the substrate 110 opposite to the one surface, a cover plate 180 is formed.

[0024] The liquid supply channel 176 and the liquid recovery channel 174 extend in the direction in which the ejection port array in the nozzle member 170 extends. Furthermore, on one surface of the substrate 110, a plurality of supply ports 173 that communicate with the liquid supply channel 176 are arranged in the direction in which the ejection port array extends. Furthermore, on one surface of the substrate 110, a plurality of recovery ports 177 that communicate with the liquid recovery channel 174 are arranged in the direction in which the ejection port array extends.

[0025] A thermal application section for foaming the liquid with thermal energy is formed on one surface of the substrate 110 at a position corresponding to the ejection port 171. This thermal application section includes a heating resistor 101 (also called a "printing element," "electrothermal conversion element," or "heating resistor element") for ejecting the liquid to perform printing, and an electrode 301 that also serves as an anti-cavitation layer to protect the heating resistor 101. The thermal application section is located inside a liquid chamber 172 formed in the nozzle member.

[0026] Furthermore, on one surface of the substrate 110, a terminal 190 is formed which is electrically connected to the heating resistor 101 by an electrical wiring (not shown) provided on the substrate 110. Therefore, the heating resistor 101 generates heat based on a pulse signal input via an external wiring substrate (not shown). This causes the liquid in the liquid chamber 172 to boil. The liquid is ejected from the ejection port 171 by the force of bubbles generated by this boiling.

[0027] The cover plate 180 is provided with an opening 175 that communicates with the liquid supply path 176 and an opening (not shown) that communicates with the liquid recovery path 174. Liquid is supplied to the recording head from this opening 175, and the liquid is recovered from the recording head via an opening that communicates with the liquid recovery path 174. Therefore, in the recording element substrate 100, liquid is supplied to the liquid chamber 172 through the opening 175, the liquid supply path 176, and the supply port 173. Furthermore, the liquid supplied to the liquid chamber 172 is recovered through the recovery port 177, the liquid recovery path 174, and an opening that communicates with the liquid recovery path 174.

[0028] FIG. 4 is a schematic cross-sectional view of the recording element substrate 100. FIG. 5 is an enlarged schematic view of the peripheral area of ​​the heating resistor 101. The recording element substrate 100 has a structure including a plurality of electrical wirings 103, plugs 102 for electrically connecting the electrical wirings 103 to each other, and insulating films 104 for electrically isolating the electrical wirings 103, stacked on a substrate 110. Note that terms indicating the top and bottom in the stacking direction of multiple layers, such as "upper / lower" and "upper layer / lower layer," in the description of this disclosure correspond to the top-bottom relationship in the drawings. However, such expressions are for convenience and do not define the actual vertical arrangement of the recording element substrate 100. In this disclosure, the upper layer refers to the upper layer when the stacking direction is the direction in which multiple layers are stacked, with the substrate 110 as the base material being the lowest layer.

[0029] As shown in FIG. 5, the heating resistor 101 is electrically connected to electrical wiring 103a and 103b via a plug 102, and converts heat when a desired voltage is supplied. The electrical wiring 103a and 103b are provided on a wiring layer. A heat sink 123 (described later) is also provided on the wiring layer in the same layer as the electrical wiring 103a and 103b. The heating resistor 101 applies heat to the liquid above it, causing film boiling, thereby ejecting the liquid from an ejection port 171 formed by a nozzle member 108. The heat generated during ejection is radiated to the heat sink 123. The heat accumulated in the heat sink 123 is conducted by the electrical wiring 103 and the plug 102 and is ultimately absorbed by the substrate 110, which is a silicon base material.

[0030] If this heat dissipation is insufficient, heat will accumulate with each ejection. To avoid the effects of this heat during the next ejection, it is necessary to wait until the temperature around the heating resistor reaches the same level as before the ejection. Insufficient heat dissipation will result in a decrease in the ejection frequency. Therefore, it is effective to use a material with a high thermoelectric coefficient for the heat sink 123, such as the material used for the electrical wiring 103, such as AlCu or AlSi. Furthermore, the larger the heat sink, the greater the heat dissipation effect. Therefore, the electrical wiring 103 and the heat sink 123 can be formed in the same layer during film formation, making them the same layer. This simplifies the manufacturing process compared to providing the electrical wiring 103 and the heat sink 123 separately.

[0031] (Method of manufacturing a recording element substrate) A manufacturing method for the recording element substrate 100 of the present invention will be described with reference to FIG. 4. First, a driving circuit 107 including transistors and the like and a field oxide film 109 are formed on a substrate 110, which serves as a base material. These can be formed using common semiconductor manufacturing methods, so details are omitted. An insulating film 104 made of an SiO film approximately 300 nm to 1000 nm thick is then formed on top of this, which serves as the insulating layer. At this time, precision is required to control variations in foaming and resistance value to obtain more uniform liquid ejection characteristics, so it is preferable that the base (lower region) of the heating resistor layer (described below) be flat. Therefore, in this configuration, the electrical wiring of each layer and the layer below the heating resistor layer are flattened. For example, chemical mechanical polishing (CMP) can be used for flattening. The thickness of the insulating film polished by CMP is approximately 150 nm to 500 nm.

[0032] Next, to connect the drive circuit 107 and the electrical wiring 103, through-holes are formed through the planarized insulating film 104 and plugs 102 are embedded therein. W (tungsten), for example, can be used as the material for the plugs. Electrical wiring 103 is then formed thereon using AlCu, AlSi, or the like, with a thickness of approximately 400 nm to 1000 nm, and patterned. A multilayer wiring structure is formed by repeating the process of forming the insulating film 104, forming the through-holes, embedding the plugs 102, forming the electrical wiring 103, and patterning the electrical wiring 103. At this time, it is preferable that the thickness of the insulating film 104 in each layer included in the multilayer structure be increased in accordance with the thickness of the underlying electrical wiring 103. For example, if the underlying electrical wiring 103 is formed to a thickness of 1000 nm, the thickness of the upper insulating film 104 after planarization is preferably 1000 nm or more.

[0033] Next, an insulating film 104 is formed on the topmost electrical wiring 103, i.e., above the wiring layer, and through-holes are formed and plugs 102 are embedded therein, followed by forming and patterning a layer of the heating resistor 101. The heating resistor is preferably made of a material with high resistivity, such as TaSiN, and can be formed to a thickness of, for example, about 10 nm to 50 nm. A protective film 126 and an anti-cavitation film 128 may also be formed on the heating resistor 101. The protective film 126 can be made of SiN with a thickness of about 200 nm to 300 nm, and the anti-cavitation film 128 can be made of a material such as Ta or Ir with a thickness of about 200 nm to 300 nm.

[0034] (Issues with conventional methods for manufacturing recording element substrates) 8 and 9, the problems associated with the conventional method for manufacturing the recording element substrate 100 will be described. Here, the explanation will focus particularly on the processes of film formation / patterning of the electrical wiring 103, film formation of the insulating film 104, formation of the through-holes, embedding of the plugs 102, and film formation / patterning of the heating resistors 101.

[0035] FIG. 9 shows a case where the size of the heat sink 123 is small and there is a sufficient distance between the electrical wiring 103b and the heat sink 123. FIG. 9(a) shows the initial stage of forming the insulating film 104 on the layer on which the electrical wiring 103b and the heat sink 123 are provided. Since the insulating film 104 is deposited on the bottom surface and the side surfaces of the electrical wiring 103 and the heat sink 123, voids 185 exist in the initial stage. As the deposition of the insulating film 104 progresses, as shown in FIGS. 9(b) and 9(c), the voids 185 gradually become smaller. Finally, in FIG. 9(d), the voids 185 have disappeared. Then, in FIG. 9(e), through holes are formed, plugs 102 are embedded, and the heating resistors 101 are formed.

[0036] In this way, the insulating film 104 formed on the electrical wiring 103 is deposited from below on the flat portion between the electrical wiring 103 and the heat sink 123, and is deposited along the sidewalls of the electrical wiring 103 and the heat sink 123. If the distance between the electrical wiring 103 and the heat sink 123 is sufficient, deposition from below will be dominant in the center between the electrical wiring 103 and the heat sink 123. The insulating film 104 is deposited to a thickness approximately twice the required thickness, and then planarized by CMP or the like, thereby making the upper surface of the insulating film 104 flat. For example, if the thickness of the electrical wiring 103 is 1000 nm, the insulating film 104 is deposited to a thickness of approximately 2000 nm to 3000 nm, and then polished and planarized by CMP to a thickness of approximately 1000 nm to 1500 nm. This allows the layer of the heating resistor 101 to be deposited flat on the planarized insulating film 104.

[0037] Figure 8 shows a case where the size of the heat sink 123 is large, resulting in a narrow gap between the electrical wiring 103b and the heat sink 123. Figure 8(a) shows the initial stage of forming the insulating film 104 on the layer on which the electrical wiring 103b and the heat sink 123 are provided. As the insulating film 104 is deposited on the bottom surface and the side surfaces of the electrical wiring 103 and the heat sink 123, voids 185 exist. Then, in Figure 8(b), the voids 185 become smaller as the deposition of the insulating film 104 progresses.

[0038] 8, unlike FIG. 9, deposition from the sidewalls of the electrical wiring 103 and the heat sink 123 is dominant in the central portion between the electrical wiring 103 and the heat sink 123. When deposition from the sides (sidewalls) progresses in this manner, a void 188 may form between the electrical wiring 103b and the heat sink 123, as shown in FIG. 8(c). Furthermore, there is a tendency for film quality to deteriorate in areas where the void 188 occurs. In particular, when the ratio of the distance between the electrical wiring 103b and the heat sink 123 to the film thickness of the wiring layer is 2 or less, there is a growing concern that the void 188 may occur. In the present disclosure, the void 188 is a minor void that occurs during the formation process of the insulating film 104, and is an area where the insulating material is not well filled.

[0039] In FIG. 8(c), the insulating film 104 is formed to a thickness approximately twice the required thickness. Then, as shown in FIG. 8(d), the insulating film 104 is polished and flattened by CMP. However, a slight depression 189 occurs locally in the area of ​​the cavity 188 during polishing. As shown in FIG. 8(e), the heating resistor 101 formed on the insulating film 104 with the depression 189 is a very thin film, typically 10 nm or more but 50 nm or less, and is affected even by a slight depression in the underlying layer. As a result, the layer of the heating resistor 101 is not formed flat and is partially thin. FIG. 8(f) is an enlarged view of region R in FIG. 8(e). In the circled region X, the heating resistor 101 formed along the slight depression is thin.

[0040] When current is passed through a heating resistor 101 having thin regions in this way, there are concerns that the uniformity of heat generation may decrease, or that the current density may become locally high, shortening the lifespan. Figure 10 shows an example in which a typical wiring layer 104' is formed on an insulating film 104. If the thickness of this wiring layer 104' is 400 nm or more, there is almost no effect from the slight depression. As the wiring layer 104' is formed on top, the slight depression is gradually smoothed out and becomes flat, and the upper side of the wiring layer 104' becomes almost flat.

[0041] (Manufacturing method of this embodiment) The print element substrate 100 of this embodiment will be described with reference to FIG. 6. The insulating film 104 in FIG. 6 includes a lower insulating film 104a provided in a layer closer to the electrical wiring 103 in the stacking direction, and an upper insulating film 104b provided in a layer farther from the wiring layer and closer to the heating resistor 101 in the stacking direction. The films shown in FIGS. 6(a) to 6(c) are formed using the same process as those shown in FIGS. 8(a) to 8(b). In the planarization process for the lower insulating film 104a in FIG. 6(d), the film thickness of the lower insulating film 104a is made thinner than in the planarization process for the insulating film 104 in FIG. 8(d) of the prior art. For example, the film thickness of the lower insulating film 104a may be made thinner during film formation before CMP, or the CMP process time may be extended to make the lower insulating film 104a thinner. The lower insulating film 104a can be formed using a SiO film with a thickness of approximately 1000 nm. At the time of FIG. 6(d), a slight depression 189 formed during CMP is present in the lower insulating film 104a.

[0042] In FIG. 6(e), an upper insulating film 104b is formed on the lower insulating film 104a to cap the slight recess 189. The upper insulating film 104b can be formed of an SiO film having a thickness of about 100 to 1000 nm. At this time, the insulating film 104 in FIG. 8(d) is formed so that the film thickness of the insulating film 104 is approximately the same as the combined film thickness of the lower insulating film 104a and the upper insulating film 104b in FIG. 6(e). Note that by using the same material for the lower insulating film 104a and the upper insulating film 104b, it is possible to ensure functionality equivalent to that of a conventional insulating film 104.

[0043] To eliminate the influence of the recess 189, it is preferable that the thickness of the upper insulating film 104b be approximately 100 to 1000 nm when formed. However, this is not limiting as long as the upper insulating film 104b can be planarized. For example, the upper insulating film 104b may be formed to a thickness of 300 nm, and then processed by CMP to reduce the film thickness to 100 nm or less.

[0044] Furthermore, by providing the upper insulating film 104b, the influence of the recess 189 can be reduced, and the performance of the recording head can be improved more than with the conventional configuration.

[0045] It is also possible to change the thickness of upper insulating film 104b depending on the size of the recess. For example, suppose an insulating film with a thickness of 400 nm is required, and lower insulating film 104a is deposited to a thickness of 350 nm and upper insulating film 104b to a thickness of 50 nm, but the effect of recess 189 cannot be completely eliminated. In this case, the effect of recess 189 can be eliminated by depositing lower insulating film 104a to a thickness of 200 nm and upper insulating film 104b to a thickness of 200 nm.

[0046] According to this manufacturing method, the slight depressions 189 in the lower insulating film 104a are leveled and gradually flattened in the process of forming the upper insulating film 104b. The upper insulating film 104b is preferably formed to be thicker than the heating resistor 101 formed thereon. The upper insulating film 104b may be flattened, but its functionality can be ensured even if it is not flattened.

[0047] (Method for verifying flatness) Whether the lower insulating film 104a is planarized or not can be verified by a cross-sectional analysis of the recording element substrate 100. For example, a method can be adopted in which the recording element substrate 100 is processed using a focused ion beam (FIB) and then detected using a transmission electron microscope (TEM). In this embodiment, the lower insulating film 104a and the upper insulating film 104b are formed separately, and the film interface of such separately formed films can be suitably analyzed using a transmission electron microscope.

[0048] As described above, in the past, when the in-plane width between the electrical wiring 103 and the heat sink 123 on the same layer was relatively narrow and a void formed in the insulating film 104, the heating resistor 101 could become partially thin due to the influence of a slight depression 189 in the insulating film. As a result, there was a risk of the heating resistor 101 becoming less uniform or the current density becoming locally high, resulting in a shorter lifespan. Therefore, in the recording element substrate 100 obtained by this embodiment, the upper insulating film 104b is provided on the lower insulating film 104a, thereby ensuring flatness below the heating resistor 101. As a result, it has become possible to provide a recording head with high functionality and reliability.

[0049] <Second embodiment> The second embodiment will be described below with reference to the drawings. Fig. 11 is a schematic cross-sectional view showing an enlarged view of the peripheral area of ​​the heating resistor 101 of the recording element substrate 100 in the second embodiment. A lower insulating film 104a is provided below the upper insulating film 104b, and a base insulating film 104c formed by high-density plasma CVD is provided between the lower insulating film 104a and the electrical wiring 103.

[0050] The insulating base film 104c is used to improve the embedding ability of the interlayer insulating film. In other words, the presence of the insulating base film 104c improves the ease of film formation in stepped portions such as grooves. In high-density plasma CVD, film formation is slower on protrusions and corners than on other portions, resulting in the shape of the protrusions and corners being less pronounced. As a result, voids are less likely to occur when the lower insulating film 104a is formed on the insulating base film 104c.

[0051] An example of a material that can be used for the base insulating film 104c is a SiO film. An SiO film formed by high-density plasma CVD is called HDP-SiO. The presence of the HDP-SiO film below the lower insulating film 104a tends to improve coverage in the narrow area between the electrical wiring 103b and the heat sink 123. Even in a configuration in which the narrow area between the electrical wiring 103b and the heat sink 123 makes it easy for a slight depression 189 to occur when the lower insulating film 104a is formed and planarized, the condition of the slight depression 189 tends to improve.

[0052] FIG. 12 shows a manufacturing method for the recording element substrate 100 according to the second embodiment. For example, if the electrical wiring 103b and the heat sink 123 are formed of 1000 nm AlCu on the same layer, as shown in FIGS. 12(a) and 12(b), a base insulating film 104c of approximately 1000 nm is formed on the electrical wiring 103 using HDP-SiO. Then, as shown in FIG. 12(c), a 1000-3000 nm thick SiO film is formed on the base insulating film 104c by plasma CVD as a lower insulating film 104a. Then, as shown in FIG. 12(d), the lower insulating film 104a is polished and planarized by CMP or the like. At this time, a recess 189 is present in the lower insulating film 104a.

[0053] Next, as shown in FIG. 12(e), an upper insulating film 104b of SiO is formed by plasma CVD to a thickness of approximately 100 nm to 1000 nm on the planarized lower insulating film 104a. Next, as shown in FIG. 12(f), through holes are formed and plugs 102 are embedded. Furthermore, the heating resistor 101 is formed and patterned. The heating resistor 101 is formed to a thickness of approximately 10 nm to 50 nm using a material with high resistivity, such as TaSiN (tantalum silicon nitride). Furthermore, a protective film 126 and an anti-cavitation film 128 may be formed on the heating resistor 101, as shown in FIG. 11. The protective film can be formed to a thickness of approximately 200 nm to 300 nm using SiN, and the anti-cavitation film can be formed to a thickness of approximately 200 nm to 300 nm using a material such as Ta or Ir.

[0054] As described above, the recording element substrate 100 obtained by this embodiment also ensures flatness under the heating resistor 101, as in the first embodiment, making it possible to provide a recording head with high functionality and reliability.

[0055] [Configuration 1] A recording element substrate in which a plurality of layers are stacked in a stacking direction on a base material, a heat generating resistor layer provided with a heat generating resistor for ejecting the liquid contained in the liquid chamber; a wiring layer including electrical wiring for supplying a voltage to the heating resistor from an external source, and a heat sink formed in the same layer as the electrical wiring and disposed below the heating resistor in the stacking direction; an insulating film provided between the heating resistor layer and the wiring layer, for insulating the heating resistor from the electrical wiring; a plug penetrating the insulating film for electrically connecting the heating resistor and the electrical wiring; and the insulating film includes a lower-layer insulating film that is provided on a side closer to the wiring layer in a stacking direction and has a flattened upper portion, and an upper-layer insulating film that is provided on the flattened lower-layer insulating film, the upper-layer insulating film is provided on the lower-layer insulating film at least in a region below the heating resistor in the stacking direction, The ratio of the distance between the electrical wiring and the heat sink to the thickness of the wiring layer is 2 or less. A recording element substrate comprising: [Configuration 2] The heating resistor is formed to a film thickness of 50 nm or less. 2. The recording element substrate according to configuration 1. [Configuration 3] The material of the heating resistor is TaSiN. 3. The recording element substrate according to configuration 1 or 2. [Configuration 4] The insulating film is made of SiO 3. The recording element substrate according to configuration 1 or 2. [Configuration 5] Between the lower insulating film and the wiring layer, there is an underlying insulating film formed by high density plasma CVD. 5. The recording element substrate according to any one of configurations 1 to 4. [Configuration 6] The upper insulating film is planarized. 5. The recording element substrate according to any one of configurations 1 to 4. [Configuration 7] The upper insulating film is not planarized. 5. The recording element substrate according to any one of configurations 1 to 4. [Configuration 8] The upper insulating film has a thickness greater than that of the heating resistor layer. 8. The recording element substrate according to any one of configurations 1 to 7. [Explanation of symbols]

[0056] 100: recording element substrate, 110: base material, 101: heating resistor, 103: electrical wiring, 123: heat sink, 104: insulating film, 104a: lower insulating film, 104b: upper insulating film

Claims

1. A recording element substrate in which a plurality of layers are stacked in a stacking direction on a base material, a heat generating resistor layer provided with a heat generating resistor for ejecting the liquid contained in the liquid chamber; a wiring layer including electrical wiring for supplying a voltage to the heating resistor from an external source, and a heat sink formed in the same layer as the electrical wiring and disposed below the heating resistor in the stacking direction; an insulating film provided between the heating resistor layer and the wiring layer, for insulating the heating resistor from the electrical wiring; a plug penetrating the insulating film for electrically connecting the heating resistor and the electrical wiring; and the insulating film includes a lower-layer insulating film that is provided on a side closer to the wiring layer in a stacking direction and has a flattened upper portion, and an upper-layer insulating film that is provided on the flattened lower-layer insulating film, the upper-layer insulating film is provided on the lower-layer insulating film at least in a region below the heating resistor in the stacking direction, The ratio of the distance between the electrical wiring and the heat sink to the film thickness of the wiring layer is 2 or less. A recording element substrate comprising:

2. The heating resistor is formed to a film thickness of 50 nm or less.

2. The recording element substrate according to claim 1.

3. The material of the heating resistor is TaSiN.

3. The recording element substrate according to claim 1, wherein the recording element substrate is a recording element substrate.

4. The insulating film is made of SiO 3. The recording element substrate according to claim 1, wherein the recording element substrate is a recording element substrate.

5. Between the lower insulating film and the wiring layer, there is an underlying insulating film formed by high density plasma CVD.

3. The recording element substrate according to claim 1, wherein the recording element substrate is a recording element substrate.

6. The upper insulating film is planarized.

3. The recording element substrate according to claim 1, wherein the recording element substrate is a recording element substrate.

7. The upper insulating film is not planarized.

3. The recording element substrate according to claim 1, wherein the recording element substrate is a recording element substrate.

8. The upper insulating film has a thickness greater than that of the heating resistor layer.

3. The recording element substrate according to claim 1, wherein the recording element substrate is a recording element substrate.

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