Patent Grant
11912028
The present disclosure relates to a substrate for liquid ejection head and a liquid ejection head.
One of the recording methods using a typical inkjet head as a liquid ejection head is a method in which ink is heated and foamed by a heating element and ink is ejected by utilizing the bubbles.
Japanese Patent Application Laid-Open No. 2016-137705 discloses the use of an insulator such as SiO as an interlayer insulating film for electrically insulating multiple electric wiring layers or between an electric wiring layer and a heating resistance element.
In an inkjet head disclosed in Japanese Patent Application Laid-Open No. 2016-137705 in which SiO is applied to an interlayer insulating film, when the inkjet head is used for a long period of time in a state in which ink has intruded into a substrate for liquid ejection head due to accidental disconnection or the like, the interlayer insulating film may be dissolved by the ink. When ink reaches an electric wiring layer common to multiple elements due to dissolution of the interlayer insulating film, ink cannot be ejected even from adjacent elements.
As described above, it is a disadvantage that the reliability of the inkjet head is lowered by dissolution of the interlayer insulating film. It should be noted that the interlayer insulating film of the substrate for liquid ejection head is required to satisfy performance such as electrical insulation and low stress in addition to dissolution resistance to ink.
It is therefore an aspect of the present disclosure to provide a liquid ejection head substrate having a longer life by suppressing the deterioration of reliability of a liquid ejection head due to the dissolution of an interlayer insulating film while satisfying the performance required as an interlayer insulating film such as electrical insulation and low stress.
A liquid ejection head substrate of the present disclosure is a substrate for liquid ejection head having a base material, a heating element including a heating resistor layer for generating thermal energy for discharging a liquid, a wiring layer for supplying electric power to the heating element, and an interlayer insulating film for insulating the heating resistor layer and the wiring layer.
A part of a first interlayer insulating film for insulating the heating resistor layer and a first wiring layer adjacent to the heating resistor layer, and a second interlayer insulating film for insulating the first wiring layer and a second wiring layer adjacent to the second interlayer insulating film includes a material layer represented by SiwOxCyNz (w+x+y+z=100 (at. %), 37≤w≤60 (at. %), 30≤x≤53 (at. %), 6≤y≤29 (at. %), 4≤z≤9 (at. %)).
According to the present disclosure, it is possible to provide a substrate for liquid ejection head having a longer service life by suppressing deterioration in reliability of the liquid ejection head due to dissolution of an interlayer insulating film caused by a liquid such as ink while satisfying performance required as an interlayer insulating film such as electrical insulation and low stress.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
A liquid ejection head can be mounted on a printer, a copying machine, a facsimile having a communication system, a word processor having a printer section, or an industrial recording apparatus combined with various processing apparatuses. By using the liquid ejection head, recording can be performed on various recording media such as paper, yarn, fiber, fabric, metal, plastic, glass, wood and ceramics.
As used herein. “record(ing)” means not only imparting an image having a meaning such as a character or a figure to the recording medium, but also imparting an image having no meaning such as a pattern.
Furthermore, the term “liquid” should be broadly interpreted and refers not only to the ink used for the recording operation, but also to the liquid used for formation of images, designs, patterns, etc. by imparting to the medium being recorded, for processing of the recording medium or for treatment of ink or recording medium. Here, the treatment of ink or recording medium refers to, for example, treatment for improving fixability due to solidification or insolubilization of the color material in the ink applied to the medium to be recorded, improving recording quality or color development, and improving image durability. Further, the “liquid” used in the liquid ejection apparatus of the present disclosure generally contains a large amount of electrolyte and has conductivity.
In the present disclosure, the description given to the members such as “first” and “second” formally indicates the order and does not specify the members themselves.
Embodiments of the present disclosure will be described below with reference to the drawings. In the following description, components having the same functions are given the same numbers in the drawings.
The liquid ejection head substrate 100 (
Here, at least one of the first interlayer insulating film 104f, the second interlayer insulating film 104e, and the third interlayer insulating film 104d is formed of an insulator including the following SiOCN film (silicon oxynitride film). That is, at least one of the films includes a material layer represented by SiwOxCyN (w+x+y+z=100 (at. %), 37≤w≤60 (at. %), 30≤x≤53 (at. %), 6≤y≤29 (at. %), 4≤z≤9 (at. %)). The first interlayer insulating film 104f, the second interlayer insulating film 104e, and the third interlayer insulating film 104d may include not only a SiwOxCyNz film but also an insulating film such as SiO formed by high-density plasma CVD in a part thereof in order to improve the adhesion property to the wiring layer. By forming a part or all of these interlayer insulating films into a SiwOxCyNz film, it is possible to improve the resistant to dissolution against ink. Further, it is preferable that apart or all of the interlayer insulating films in the region close to the heating resistor layer 101A, such as the first interlayer insulating film 104f and the second interlayer insulating film 104e, be formed of a SiwOxCyNz film. This is because the SiwOxCyNT film has a lower thermal conductivity than the SiO film, and the energy required for driving the heating element 101 can be reduced. Since the temperature detecting element 116 is optional, when the temperature detecting element 116 is not provided, the first interlayer insulating film 104f and the second interlayer insulating film 104e are regarded as a single first interlayer insulating film, and other configurations are as described above.
Here, each of the insulating films may have a planarized upper surface in which each of the wiring layers is embedded. That is, when the interlayer insulating films are formed by laminating multiple films, the upper surface of the film in which the wiring layer is embedded may be planarized. For example, in
Referring back to
As shown in
As shown in
The heating resistor layer 101A is covered with a protective film 105. The protective film 105 is formed of SiN, for example, and has a film thickness of about 0.15 to 0.3 μm. The protective film 105 may be formed of SiO or SiC. The protective film 105 is covered with a cavitation resistant film 106. The cavitation resistant film 106 is made of Ta or the like and has a film thickness of about 0.2 to 0.3 μm. As the cavitation resistant film 106, Ir or Ta and Ir may be laminated.
Multiple connecting members 102 for connecting the wiring layers 103 and the heating resistor layer 101A are provided in the interlayer insulating films 104. Multiple connecting members 102 extending in the film thickness direction (Z direction) arranged at intervals along the second direction Y. Some connecting members 102 are covered with the heating resistor layer 101A when viewed from a direction orthogonal to a surface on which the heating element 101 is provided. Some connecting members 102 connect the wiring layers 103 and the heating resistor layer 101A in the vicinity of both side ends in the X direction of the heating element 101. Thus, current flows along the heating resistor layer 101A in the first direction X. Multiple connecting members 102 are provided in the vicinity of both side ends of the heating element 101 in the X direction. The heating resistor layer 101A has a connection region 110 to which multiple connecting members 102 are connected on one end side and the other end side, respectively. Connecting members 102 are plugs extending in the Z direction from near the end of wiring layers 103. Although the connecting member 102 has substantially square cross sections in the present embodiment, a connecting member may have rounded corners, may not be limited to have a quadrate shape, and may have other shapes such as a rectangular shape, a circular shape, an elliptical shape, or the like. The connecting member 102 is metal plug, and typically formed of tungsten, but may be formed of any of titanium, platinum, cobalt, nickel, molybdenum, tantalum, silicon (polysilicon), or a compound containing any of these. The connecting member 102 may be integrally formed with the wiring layer 103. That is, a part of the wiring layer 103 may be cut off in the thickness direction to form the connecting member 102 integrated with the wiring layer 103.
The connection region 110 is a minimum rectangular region including all connecting members 102 and whose four sides circumscribe any of connecting members 102. The connection region 110 extends along a second direction Y orthogonal to the first direction X, but the second direction may not be orthogonal to the first direction X. That is, the connection region 110 may extend along a second direction that intersects the first direction X at an angle. The region actually contributing to the foaming of the ink in the heating element 101, that is, the region where the ink foams is called the foaming region 111. The foaming region 111 is located inside the outer periphery of the heating element 101, and a region between the foaming region 111 and the outer periphery of the heating element 101 is a region (hereinafter referred to as frame region 112) not contributing to foaming of ink. Even in the frame region 112, heat is generated by energization, but the amount of heat radiation to the surroundings is large, and ink does not foam. The X and Y dimensions of the foamed region 111 are determined by the structure around the heating resistor layer 101A and the thermal conductivity of the heating resistor layer 101A. The connection region 110 is adjacent to the foaming region 111 in the first direction X across the frame region 112, and extends a range including the entire length of the foaming region 111 in the second direction Y. That is, when viewed in the first direction X, both side edges 110a, 110b of the connection region 110 with respect to the Y direction are closer to both side peripheral edges 101a, 101b with respect to the Y direction of the heating resistor layer 101A than both side peripheral edges 111a, 111b with respect to the Y direction of the foaming region 111. Therefore, the current density is made uniform in the whole area of the foaming region 111.
The underlying portion of each of the wiring layers 103 and the heating resistor layer 101A are planarized by a process such as chemical mechanical polishing (CMP: Chemical Mechanical Polishing). Therefore, as shown in
In
In the present embodiment, 4 layers of wiring layers 103 are disposed in the interlayer insulating films 104. Specifically, the first and the second electric wiring layers 103d and 103c for passing a current to the heating element 101, and the third and the fourth electric wiring layers 103b and 103a for signal wiring and logic power wiring for driving the heating element are disposed. The first and the second electric wiring layers 103d, 103c are arranged on the side close to the heating element 101 with respect to the third and the fourth electric wiring layers 103b, 103a, and the film thickness of each of the first and the second electric wiring layers 103d, 103c is preferably relatively thick in view of efficiency. Conversely, the third and the fourth electric wiring layers 103b, 103a are disposed closer to the driving circuit 203 with respect to the first and the second electric wiring layers 103d, 103c, and the film thickness each thereof is preferably relatively small.
As shown in
The SiwOxCyNz film according to the present disclosure can be formed by using a plasma CVD method.
First, the distance (gap) between the showerhead 303 functioning as an upper electrode in plasma discharge and the sample stage 302 functioning as a lower electrode is determined by adjusting the height of the sample stage 302. The temperature of the sample stage 302 is adjusted by heating by a heater 304.
Next, various gases to be used flow into the film forming chamber 310 through the showerhead 303. In this case, the flow rate of the various gases is controlled by a mass flow controller 301 attached to each corresponding pipe 300. Thereafter, by opening the introduction valve 307 of the gas to be used, the gas is mixed in the piping and supplied to the showerhead 303. Subsequently, the exhaust valve 307b attached to the exhaust orifice 305 connected to the vacuum pump (not shown) is adjusted to control the exhaust amount, thereby keeping the pressure in the film forming chamber 310 constant. Plasma is then discharged between showerhead 303 and sample stage 302 by 2 frequency RF power supplies 308a and 308b. The atoms dissociated in the plasma are deposited on the wafer 306 to form a film.
As the process gas, a Si source gas for supplying silicon, an N source gas for supplying nitrogen, a C source gas for supplying carbon, an O source gas for supplying oxygen, and a carrier gas for carrying these gases as necessary are used. As the Si source gas, silane gas (SiH4), dichlorosilane (SiH2Cl2) or the like can be used. As the N source gas, nitrous oxide (N2O) serving also as ammonia gas or the O source gas can be used. Lower alkanes (methane (CH4) and ethane (C2H)) can be used as the C source gas. As the O source gas, oxygen (O2), ozone (O3), nitrogen monoxide (NO), carbon monoxide (CO), water (H2O) or the like can be used. As the carrier gas, inert rare gas, nitrogen gas or hydrogen gas can be used.
Hereinafter, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to these examples.
The conditions for the formation of the SiwOxCyNz film according to the present disclosure are appropriately selected from the following.
By adjusting these conditions and changing the flow rates of the process gases SiH4, N2O and CH4, SiwOxCyNz films having different composition ratios can be obtained. As a result, SiwOxCyNz films of the standards A to K shown in Table 1 were obtained. In this specification, the content ratio of each element in the SiwOxCyNz film is expressed by an atomic percentage (at. %). The SiwOxCyNz films formed in the present disclosure contain hydrogen derived from the source gas of the CVD method described above, but the hydrogen content is not considered. The film formed by using the process gas described above generally contains about 15 to 30 (at. %) of hydrogen, and may contain hydrogen as long as it does not greatly deviate from the range. The SiwOxCyNz film with w≤36 and the SiwOxCyNT film with z≥10 could not be formed by varying the flow rates of the process gases SiH4, N2O and CH4.
Experimental examples for determining the performance of the SiwOxCyNz films from A to K in Table 1 will be shown below. In the following experimental examples, a SiO film was added as the standard L, and similar experiments were performed for all films.
The following experiments were carried out to confirm the erosion resistance of each SiwOxCyNz film to ink. First, each SiwOxCyNz film was formed on a silicon substrate. Thereafter, the substrate on which the SiwOxCyNz film was formed was cut to a size of 20 mm×20 mm. The cut piece was immersed in 30 ml of pigment ink having a pH of about 9, heated at 60° C. and left for 72 hours to examine the amount of dissolution. In the above experiment, the back surface and the side surface of the substrate were protected with an ink-insoluble resin in order to eliminate the influence of Si exposed to the end surface and the back surface of the substrate being dissolved. The film thickness was measured by using a spectroscopic ellipsometer in this experimental example.
In this experiment, the erosion resistance of the SiwOxCyNz film against the ink was confirmed by examining the change of the film thickness. The results are shown in Table 2. As the criterion in this experiment, a case in which the amount of dissolution was less than 1 nm was determined as A, a case in which the amount of dissolution was 1 nm or more and less than 10 nm was determined as B, a case in which the amount of dissolution was 10 nm or more and less than 30 nm was determined as C, and a case in which the amount of dissolution was 30 nm or more was determined as D.
In the above criteria, A is very effective, B is effective, C is less effective, and D is almost ineffective. The same judgement was also applied to the results of the following experimental examples.
From the results shown in Table 2, it can be seen that the composition range of the SiwOxCN, film satisfying the erosion resistance to the ink is 6≤y (at. %). In particular, it is effective to use a SiwOxCyNz film within this composition range when a pigment ink is used. Similar results were obtained for the pigment ink and the dye ink having a pH of about 5 to 11.
The following experiment was carried out to confirm the electrical insulation of each of the above SiwOxCyNz films. First, on a silicon substrate on which a silicon thermal oxide film having a film thickness of 1 μm was formed, a metal layer made mainly of aluminum was formed to have a thickness of 200 nm and processed to have a size of 2.5 mm 2.5 mm for use as a first electrode. A SiwOxCyNz film having a thickness of 300 nm was formed on the first electrode, and a metal layer containing aluminum as a main material was formed thereon as a second electrode. The metal film had a thickness of 200 nm and a shape of 2 mm×2 mm, and was formed so as not to protrude from the area directly above the first electrode. Then, a through hole for making electrical contact with the first electrode was opened in the SiwOxCyNz film. Using such a sample, a current amount was measured when a voltage of 32 V was applied between the first electrode and the second electrode.
In this experiment, the electrical insulation of the SiwOxCyNz film was confirmed by measuring the current. The results are shown in Table 3. The criterion in this experiment was as follows. A current amount of less than 0.1 mA was defined as A, a current amount of 0.1 mA or more and less than 10 mA was defined as B, a current amount of 10 mA or more and less than 100 mA was defined as C, and a current amount of 100 mA or more was defined as D.
From the results shown in Table 3, it can be seen that the composition range of the SiwOxCyNz film satisfying practical electrical insulating properties is 30≤x (at. %).
The following experiment was carried out to measure the stress of each of the SiwOxCyNz films of the present disclosure. A SiwOxCyNz film was formed on a silicon substrate, and the stress was measured by a stress measuring instrument. The results are shown in Table 4. The value of the stress 0 or more indicates tensile stress, and the value less than 0 indicates compressive stress. The criteria for this experiment is as follows. An absolute value of stress of less than 150 MPa was defined as A, an absolute value of stress of 150 MPa or more but less than 400 MPa was defined as B, an absolute value of stress of 400 MPa or more but less than 500 MPa was defined as C, and an absolute value of stress of 500 MPa or more was defined as D.
From the results shown in Table 4, it can be seen that the composition range of the SiwOxCyNz film satisfying the low stress is 4≤z (at. %).
The results of the experimental examples 1 to 3 are summarized in Table 5. The lowest evaluation among the results of each experiment was used for the overall judgement. The standards for which the overall judgement was B or C were the standards B, D, E, F, G, H, I and J.
The interlayer insulating film 104 of the element substrate 114 of the liquid discharge head is required to have the performance mentioned in the above experimental examples 1 to 3. Considering the results of the experimental examples and the fact that the SiwOxCyNz film with w≤36 and the SiwOxCyNz film with z≥10 could not be formed, the composition of the SiwOxCyNz film satisfying each performance is as follows. First, it is required to satisfy w+x+y+z=100 (at %), 37≤w (at. %), 30≤x (at. %), 6≤y (at. %), 4≤z≤9 (at. %). Since w+x+v+z=100 (at %), the upper limit for w, y, or y is w≤60 (at. %), x≤53 (at. %), y≤29 (at. %) respectively. Therefore, the composition of the SiwOxCyNz film capable of exhibiting the desired performance is w+x+y+z=100 (at. %), 37≤w≤60 (at. %), 30≤x≤53 (at. %), 6≤y≤29 (at. %), 4≤z≤9 (at. %).
Further, since the standards for which the overall judgement was B were the standards D, F, G and H, it is more preferable that 37≤w≤39 (at. %), 33≤x≤41 (at. %), 12≤y≤22 (at. %), 7≤z≤8 (at. %) are satisfied in the SiwOxCyNz film.
In this example, liquid ejection was actually performed using the various liquid ejection heads that were prepared. In this example, SiwOxCyNz films were used for the interlayer insulating films 104d, 104e, and 105f As a result, with respect to the liquid ejection head using each of the standards of B, D to J shown in Table 5 as the interlayer insulating film, even when an accidental disconnection occurred, the adjacent element was not affected, the warpage of the substrate was small, and no electrical failure occurred.
On the other hand, with respect to the liquid ejection head using the standard K as the interlayer insulating films 104d, 104e, and 105f, the ejection performance remarkably deteriorated because a leakage current was generated between the wiring layers. With respect to the liquid ejection head using the standard C as the interlayer insulating films, no defect occurred, but the substrate warped greatly, and a transport error and a suction error occurred in part of the head manufacturing process.
With respect to each of the liquid ejection heads using the standards A and L (SiO film) as the interlayer insulating films, although no defect usually occurred, when ejection was continued after an accidental disconnection had occurred, elements adjacent to the disconnection element also failed ejection. As the ejection continued, the range of elements that failed to eject increased. Thereafter, when ejection was continued, electrical failure occurred, and driving of the head became impossible. After the ejection durability test, the liquid ejection head was disassembled, and the cross section of the substrate for liquid ejection head was observed using a focused ion beam device and a scanning electron microscope. In a wide range of the region where the ejection failure occurred, there was a trace that ink had penetrated into the inside, the interlayer insulating film 104f and the interlayer insulating film 104e were dissolved, and the electric wiring layer 103d was also dissolved. In some regions, the interlayer insulating film 104d and the electric wiring layer 103c were also dissolved.
in this example, the liquid ejection head was prepared using a SiwOxCyNz film of each of the standards B, D to J for the interlayer insulating film 104d and SiO films for the other interlayer insulating films. There was no defect during normal operation. However, when ejection was continued after the occurrence of accidental disconnection, in case that the wiring layer 103d was a solid wiring, the elements adjacent to the disconnected element failed to eject, and as the ejection continued, the range of elements that failed to eject increased. Further ejection was continued thereafter, but the failure of driving of the head due to the occurrence of an electrical failure did not occur. In case that an individual wiring was used as the wiring layer 103c, the disconnection did not spread widely even after the occurrence of accidental disconnection of the head.
After the ejection durability test, the liquid ejection head was disassembled, and the cross section of the substrate for liquid ejection head was observed using a focused ion beam device and a scanning electron microscope. In a wide range of the region where the ejection failure occurred, there was a trace that ink had penetrated into the inside, the interlayer insulating film 104f and the interlayer insulating film 104e were dissolved, and the electric wiring layer 103d was also dissolved. However, the dissolution of the interlayer insulation film 104d (SiwOxCyNz film) was not found.
In this example, the liquid ejection head was prepared using a SiwOxCyNz film of each of the standards B, D to J for the interlayer insulating film 104e and SiO films for the other interlayer insulating films. The disconnection did not spread widely even after the occurrence of accidental disconnection of the head.
Further, when each of B, D to J was used, the energy required for driving the heating element was reduced as compared with the case of using the SiO film. When the thermal conductivity was measured, the thermal conductivity of the SiwOxCyNz film was lower than that of the SiO film. Therefore, the reduction of the required energy was considered to be caused by the high heat storage property.
In this example, the liquid ejection head was prepared using a SiwOxCyNz film of each of the standards B, D to J for the interlayer insulating film 104f and SiO films for the other interlayer insulating films. The disconnection did not spread widely even after the occurrence of accidental disconnection of the head.
The energy required for driving each heating element was reduced as compared with the case where the SiO film was used also in this example. In this example, since the SiwOxCyNz film is closer to the heating resistance element than in the example 3, the energy required for driving was even smaller than in example 3.
This example was performed in the same manner as Example 3, except that the interlayer insulating film 104e was formed as having the second SiO film 104z, the SiwOxCyNz film 104x, and the first SiO film 10y, as shown in
Further, in the present example, since the first SiO film 104y is the only film to be planarized in manufacturing process, the complication of the step could be avoided.
This example was performed in the same manner as example 5, except that the interlayer insulating film 104e was formed to include a planarized second SiO film 104z and a SiwOxCyNz film 104x formed thereon as shown in
This example was performed in the same manner as Example 3, except that the interlayer insulating film 104e was formed to include, the SiwOxCyNz film 104x formed on the ground wiring 103d and the first SiO film 104y formed thereon, as shown in
In this example, since the number of times of film formation is smaller than that in Examples 5 and 6, it is possible to avoid the complication of the process.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2020-189845, filed Nov. 13, 2020, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-189845 | Nov 2020 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 10906305 | Teshima | Feb 2021 | B2 |
| 11001062 | Teranishi | May 2021 | B2 |
| 20220153026 | Minami | May 2022 | A1 |
| Number | Date | Country |
|---|---|---|
| 1341514 | Mar 2002 | CN |
| 108973332 | Dec 2018 | CN |
| H05-198865 | Aug 1993 | JP |
| H11-10882 | Jan 1999 | JP |
| 2009-113302 | May 2009 | JP |
| 2016137705 | Aug 2016 | JP |
| 506905 | Oct 2002 | TW |
| Number | Date | Country | |
|---|---|---|---|
| 20220153023 A1 | May 2022 | US |
