JP2004223959A - Method for manufacturing liquid ejection head and method for adjusting film thickness of thin film structure - Google Patents

Abstract

An object of the present invention is to provide a method of manufacturing a liquid discharge head which can efficiently manufacture a diaphragm with high precision at a low cost and a method of adjusting the thickness of a thin film structure which requires a high degree of thickness precision.
In a method for manufacturing a liquid discharge head in which a boron-doped layer is formed on a Si substrate and the boron-doped layer is formed as a vibration plate, after forming a vibration plate, the Si substrate is thermally oxidized by thermal oxidation. The method includes a step of forming the oxide film 106 and a step of removing the thermal oxide film 106 by etching.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a liquid discharge head represented by an ink jet head, and more particularly, to a method for manufacturing a diaphragm acting as a diaphragm pump of a liquid discharge head, and a method for adjusting the thickness of a small and precise thin film structure. .
[0002]
[Prior art]
The liquid discharge head is generally used as an ink jet head of an ink jet recording apparatus, and is also widely used in a microarray manufacturing apparatus such as a DNA chip and a color filter manufacturing apparatus. A typical ink jet head generally has a structure in which three substrates are stacked, a discharge chamber including a concave portion is formed in an intermediate first substrate (Si substrate), and a bottom wall portion of the discharge chamber is formed. Is a diaphragm. A second substrate provided with an actuator electrode so as to face the diaphragm is bonded to one surface of the first substrate, and a third substrate is provided on the other surface of the first substrate so as to cover the discharge chamber. Substrates are bonded. Then, there are a method of providing a nozzle hole for discharging ink droplets on the surface of the third substrate (face inkjet type) and a method of providing a nozzle hole at an end of the first substrate (edge inkjet type). As a discharge drive method, for example, an electrostatic drive method is known, and by turning on and off an electrostatic attraction between a diaphragm and an actuator electrode, the diaphragm is operated like a diaphragm pump, and ink is discharged. Discharge droplets.
Methods for manufacturing such an ink jet head are disclosed in, for example, Patent Documents 1 to 3.
[0003]
[Patent Document 1]
JP-A-9-288037 (paragraphs [0021] to [0028], FIG. 4)
[Patent Document 2]
JP-A-2002-86734 (paragraphs [0025] to [0039], FIGS. 2, 3, and 6)
[Patent Document 3]
JP-A-2002-240299 (paragraphs [0007] to [0014, FIG. 1)
[0004]
[Problems to be solved by the invention]
In the manufacture of the liquid discharge head, a particular problem is the thickness of the diaphragm which affects the discharge performance of the liquid droplet. In each of the above Patent Documents, a Si substrate is used as a substrate material for forming the diaphragm. In Patent Document 1, boron is diffused on one side of the Si substrate, and the etching rate of the high-concentration boron-doped layer is extremely high. The diaphragm is formed by utilizing the phenomenon of dropping (etching stop). That is, the thickness of the diaphragm is adjusted by the thickness of the boron-doped layer when the etching is stopped. However, according to this method, SiO 2 which becomes an etching protection film by thermal oxidation treated at a high temperature of 1000 ° C. or more₂Since a film (thermal oxide film) is formed, there is a problem that boron diffused in a Si substrate at a high concentration further diffuses heat inside the Si substrate, thereby lowering the boron concentration. As a result, the etching stop did not work sufficiently, and a diaphragm with a submicron thickness could not be manufactured.
Therefore, in order to solve this problem, Patent Documents 2 and 3 disclose a SiO 2 film serving as an etching protection film.₂By forming the film by CVD capable of forming a film at a low temperature, thermal diffusion of boron is suppressed, and a diaphragm having a submicron thickness is realized. However, in this method, an expensive apparatus and a material gas are used, and the etching protective film is formed by CVD, which is a single wafer processing, so that there is a great disadvantage in terms of cost and mass productivity. there were.
[0005]
The present invention has been made in order to solve the above-described problems, and provides a method of manufacturing a liquid discharge head that can efficiently manufacture a diaphragm with high accuracy at a low cost. This is the first purpose.
A second object of the present invention is to provide a method for adjusting the thickness of a thin film structure requiring a high degree of thickness accuracy by utilizing the technology of the present invention.
[0006]
[Means for Solving the Problems]
A first method for manufacturing a liquid discharge head according to the present invention is a method for manufacturing a liquid discharge head, wherein a boron-doped layer is formed on a Si substrate, and the boron-doped layer is formed as a diaphragm.
(1) after forming the diaphragm, forming a thermal oxide film on the Si substrate by thermal oxidation;
(2) removing the thermal oxide film by etching;
It is characterized by having.
[0007]
A second method for manufacturing a liquid ejection head according to the present invention is a method for manufacturing a liquid ejection head in which an active layer of an SOI substrate is formed as a diaphragm.
(1) after forming the diaphragm, forming a thermal oxide film on the SOI substrate by thermal oxidation;
(2) removing the thermal oxide film by etching;
It is characterized by having.
[0008]
That is, in the first manufacturing method of the present invention, a Si substrate is used as a substrate material, and in the second manufacturing method, an SOI (Silicon On Insulator) substrate is used. The SOI substrate is formed by implanting oxygen ions into a Si substrate by a high-concentration ion beam and annealing the Si substrate to obtain a SiO.sub.₂A film is formed and its surface layer is formed as an active layer of Si single crystal.It is considered to be the optimal substrate material for microdevices or thin film structures that achieve high precision, high integration, high speed, etc. I have. Note that, in addition to the above-described method of implanting oxygen ions, an SOI substrate is formed by bonding an Si substrate on which an oxide film is formed and another Si substrate (this is called direct bonding, and the surface is cleaned). There is also a method in which Si substrates are overlapped and bonded by processing at a temperature close to 1000 ° C.), and an Si layer on one side is ground and polished to form an active layer. An SOI substrate manufactured by such direct bonding May be used.
[0009]
In a first manufacturing method using a Si substrate, a diaphragm of a liquid discharge head is made of a boron-doped layer. However, the boron-doped layer is formed on the surface of the Si substrate by thermal oxidation to form an SiO.₂If the film is exposed to a high temperature of 1000 ° C. or more to form a film (thermal oxide film), the boron concentration may decrease, and the etching stop may not function as desired.
On the other hand, when the Si substrate is thermally oxidized, Si equivalent to 45% of the thickness of the formed (grown) thermal oxide film is changed to an oxide film. In other words, the surface of the Si substrate is eroded by an amount corresponding to 45% of the thickness of the thermal oxide film.
The present invention utilizes this phenomenon to adjust the diaphragm to a target thickness. The thickness of the diaphragm can be adjusted by performing thermal oxidation as described in (1) and peeling (removing the thermal oxide film by etching) as in (2).
Also in the second manufacturing method using the SOI substrate, the thickness of the diaphragm made of the active layer can be adjusted by similarly performing the thermal oxidation and the thermal oxide film peeling.
Therefore, according to the present invention, it is possible to reduce the thickness of the diaphragm to a submicron level, and it is possible to manufacture the diaphragm with extremely high accuracy with little variation in thickness accuracy. Furthermore, since batch processing can be performed using a thermal oxidation apparatus, mass productivity is excellent and manufacturing costs are low.
[0010]
In the first and second manufacturing methods of the present invention, a thermal oxide film is formed by wet oxidation or dry oxidation.
A thermal oxide film can be formed in a short time by using Wet oxidation that performs heat treatment in a thermal oxidation furnace in an oxygen and water vapor atmosphere, and a diaphragm can be formed by using Dry oxidation that performs heat treatment in a thermal oxidation furnace in an oxygen atmosphere. Can be further fine-tuned. Further, wet oxidation and dry oxidation may be used in combination. In this case, wet oxidation is performed first, and dry oxidation is performed later. However, after the Wet oxidation and the Dry oxidation, the step (2) of removing the thermal oxide film is performed.
[0011]
Further, by repeating the steps (1) and (2) a plurality of times, it is possible to further finely adjust the submicron thickness of the diaphragm.
Therefore, it is possible to obtain a liquid discharge head which has high reliability and has an extremely fine droplet discharge performance. This also contributes to downsizing and improvement of image quality in the case of an ink jet head, and to downsizing and high density and improvement of quality in the case of a liquid ejection head used for manufacturing a microarray, a color filter and the like.
[0012]
In the case where the liquid ejection head is of an electrostatic drive system using electrostatic attraction, it is preferable to form an insulating film on the diaphragm after the step (2) in order to prevent a short circuit between the diaphragm and the actuator electrode. .
[0013]
In the step (1), after forming the diaphragm, the thickness of the diaphragm is measured, and the thermal oxidation conditions are determined based on the measurement result.
In the thermal oxidation conditions, the growth rate of the oxide film varies depending on the oxidation temperature and the oxidation time. Therefore, in order to accurately adjust the diaphragm to the target thickness, the thickness of the diaphragm before oxidation is accurately measured, and based on the measurement result, the thickness of the oxide film to be formed, and thus the oxidation time, It is necessary to determine the oxidation temperature.
[0014]
Further, by using the above-described film thickness adjusting method of the present invention, it is possible to adjust the film thickness of a thin film structure used as a micro device or a MEMS device with extremely high precision.
Therefore, the first method for adjusting the film thickness of the thin film structure according to the present invention includes: (1) a step of forming a boron-doped layer on a Si substrate;
(2) etching from the surface of the Si substrate opposite to the boron-doped layer until reaching the boron-doped layer;
(3) forming a thermal oxide film by thermal oxidation on the boron-doped layer after the etching;
(4) removing the thermal oxide film by etching;
It is characterized by having.
[0015]
The second method for adjusting the thickness of a thin film structure according to the present invention includes: (1) etching from the surface of the SOI substrate on the side opposite to the active layer until reaching the active layer of the SOI substrate;
(2) forming a thermal oxide film on the active layer after the etching by thermal oxidation;
(3) removing the thermal oxide film by etching;
It is characterized by having.
[0016]
That is, the first film thickness adjusting method of the present invention is a method of using a Si substrate and adjusting the film thickness of a boron-doped layer formed on the Si substrate. In this method, a substrate is used and the thickness of the active layer of the SOI substrate is adjusted. As described above, the film thickness can be adjusted by performing thermal oxidation and peeling of the thermal oxide film (removal of the thermal oxide film by etching) on the target boron-doped layer or active layer.
[0017]
In the present invention, when adjusting the film thickness, as described above, a thermal oxide film is formed by wet oxidation or dry oxidation.
In the case of the first film thickness adjusting method, the steps (3) and (4) are repeated a plurality of times.
In the case of the second film thickness adjusting method, the steps (2) and (3) are repeated a plurality of times.
In the case of the first film thickness adjusting method, in the step (3), the thickness of the boron-doped layer is measured, and the condition of the thermal oxidation is determined based on the measurement result.
In the case of the second film thickness adjusting method, in the step (2), the thickness of the active layer is measured, and the thermal oxidation conditions are determined based on the measurement result.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the configuration of a liquid ejection head to which the present invention is applied will be described by taking an inkjet head as an example.
FIG. 3 is a cross-sectional view showing a configuration of a face ink jet type, for example. In this example, the intermediate first substrate 1 is formed using a Si substrate, and a diaphragm 11 made of a boron-doped layer is formed on the lower surface of the Si substrate. The thickness of the diaphragm 11 is formed to a desired thickness within a range of, for example, 0.5 to 1 μm. Further, a discharge chamber 12 having a recess formed so that a bottom wall portion becomes a vibration plate 11 and a reservoir 13 for storing ink are formed on the Si substrate by etching, and a through hole 14 for wiring is further etched. Formed by
[0019]
The second substrate 2 bonded to the lower surface of the first substrate 1 is formed of a glass substrate, and a concave portion 22 for mounting the actuator electrode 21 is formed on the second substrate 2 by etching. The actuator electrode 21 is, for example, an indium oxide film doped with tin oxide as an impurity, that is, ITO (Indium Tin Oxide: Indium oxide A tin) film is formed in the recess 22. However, the electrode 21 is not limited to this. Reference numeral 15 denotes an insulating film provided to prevent a short circuit between the vibration plate 11 and the actuator electrode 21, and an insulating film 15 formed by thermal oxidation of the first substrate 1.₂It is a membrane.
[0020]
The third substrate 3 joined to the upper surface of the first substrate 1 is made of a Si substrate, and supplies a nozzle hole 31 for discharging ink droplets, a backflow of ink, and ink from the reservoir 13 to the discharge chamber 12. And a narrow groove 32 are provided.
After the three substrates 1, 2, and 3 on which the respective elements are formed are joined to each other, the oscillation circuit 4 for driving the vibration plate 11 through the through-hole 14 includes the first substrate 1 and the actuator electrode 21. Is wired between
[0021]
The ink droplet ejection operation is performed as follows. In the electrostatic drive type ink jet head as shown in this embodiment, a predetermined pulse voltage is applied to the actuator electrode 21 by the oscillation circuit 4 to charge the actuator electrode 21 positively and to charge the diaphragm 11 negatively. Let it. Therefore, the diaphragm 11 is attracted to the electrode 21 side by the electrostatic attraction and flexes, and the volume of the discharge chamber 12 increases. When the supply of electric charge to the actuator electrode 21 is stopped by the oscillation circuit 4 in this state, the diaphragm 11 returns to its original state, and a constant amount of ink droplets corresponding to the difference in volume change is generated from the nozzle 31 by the pressure at that time. Discharged. Next, when the vibration plate 11 bends downward again, ink is supplied from the reservoir 13 into the ejection chamber 12 through the narrow groove 32. By repeating the above operations, characters, images, and the like can be recorded on any recording medium such as paper, film, sheet, metal plate, and cloth.
[0022]
Next, a manufacturing method for manufacturing the above-described diaphragm 11 of the inkjet head to a predetermined thickness with high precision will be described.
In the first embodiment, a Si substrate is used as a material, and in the second embodiment, an SOI substrate is used.
[0023]
Embodiment 1 FIG.
1 and 2 are manufacturing process diagrams of an ink-jet head according to Embodiment 1 of the present invention.
In the first embodiment, a silicon oxide substrate is used, a boron-doped layer is formed on a surface of the substrate on which a diaphragm is formed, and then a thermal oxide film (SiO 2) serving as an etching protection film is formed on both surfaces.₂Film), patterning the thermal oxide film, forming a cavity-shaped discharge chamber, a diaphragm composed of a bottom wall portion of the discharge chamber, and other components by etching stop technology, and then further heating. Oxidation and thermal oxide film peeling (removal of thermal oxide film by etching) are performed to adjust the diaphragm to a predetermined thickness with high accuracy.
[0024]
Hereinafter, each step will be described in detail with reference to the step diagrams shown in FIGS. Referring to FIG.
(A) First, both surfaces of the Si substrate 1, that is, the Cav surface 101 and the Dope surface 102 are each mirror-polished to produce a substrate having a thickness of, for example, 180 μm.
(B) Next, a boron diffusion plate (not shown) is made to face the Dope surface 102 of the Si substrate 1, and a heat treatment is performed at a temperature of, for example, 1100 ° C. for 6 hours to diffuse boron (B) to the Dope surface 102. Then, a boron doped layer 103 is formed.
(C) The Si substrate 1 having the boron doped layer 103 formed on the Dope surface is set in a thermal oxidation furnace to be in an atmosphere of oxygen and water vapor, subjected to a thermal oxidation treatment at a temperature of, for example, 1075 ° C. for 4 hours, and etched on the surface of the Si substrate 1 1.2 μm SiO serving as protective film₂A film (thermal oxide film) 104 is formed.
(D) Next, the SiO 2 on both surfaces of the Si substrate 1₂A resist 105 is coated on the film 104, and resist patterning is performed on the Cav surface 101 side to form components such as the discharge chamber 12, the reservoir 13, and the through hole 14.
(E) Then, the Cav surface 101 on which the resist patterning has been performed is etched with a hydrofluoric acid aqueous solution to remove the Cav surface SiO₂The film 104 is patterned, and the resists 105 on both sides of the Si substrate 1 are peeled off.
(F) Next, the Si substrate 1 is immersed in a 35 wt% aqueous solution of potassium hydroxide at a high concentration, and Si etching is performed. At this time, the substrate is etched from the Si exposed on the Cav surface of the Si substrate 1. Then, the etching is continued until the residual thickness of Si by the etching becomes, for example, 10 μm. Next, the Si substrate 1 is immersed in a 3 wt% aqueous solution of potassium hydroxide having a low concentration to perform Si etching. When the Si substrate 1 reaches the boron-doped layer 103, the etching is stopped to leave the boron-doped layer 103, and the diaphragm 11a is moved. Form. At this time, the thickness of the diaphragm 11a is, for example, 2 μm.
(G) SiO remaining on Si substrate 1₂The film 104 is removed by etching with a hydrofluoric acid aqueous solution.
[0025]
In this embodiment, as described above, the boron-doped layer 103 forming the diaphragm 11a is exposed to a high temperature of 1000 ° C. or more by thermal oxidation for forming an etching protection film, so that the boron concentration is reduced, Stops may not work well. Therefore, the thickness of the diaphragm 11a tends to vary greatly. Therefore, in order to adjust the thickness of the diaphragm 11a to a target thickness with high accuracy, a process shown in FIG. 2 is further performed.
[0026]
Before performing the following steps, the primary thickness T of the diaphragm 11a manufactured by the steps shown in FIG.₁Is desirably measured accurately. Based on the measurement results, appropriate thermal oxidation conditions are determined as described later. The measurement is performed using, for example, an infrared spectrometer (FT-IR).
(H) First, the Si substrate 1 on which the vibration plate 11a is formed is set in a thermal oxidation furnace to be in an atmosphere of oxygen and water vapor, and under a condition of thermal oxidation (wet oxidation) as shown in FIG. The substrate is subjected to a thermal oxidation treatment at a temperature of₂A film 106 is formed.
(I) Next, the SiO formed on the Si substrate 1₂The film 106 is removed by etching with a hydrofluoric acid aqueous solution.
(J) Finally, in order to prevent a short circuit between the diaphragm 11 and the actuator electrode 21, SiO 2 serving as an insulating film is used.₂A film 15 is formed on the surface of the Si substrate 1 by thermal oxidation. Note that this step may be performed as needed, and may be omitted if there is no risk of short circuit.
[0027]
By the way, in the step (h), when an oxide film is formed by thermal oxidation, Si having a thickness of 45% of the oxide film thickness is changed to an oxide film. Therefore, the thickness of the diaphragm that changes due to thermal oxidation is set to dT_SiAnd the primary thickness of the vibration plate 11a before oxidation is T₁The secondary thickness of the vibration plate 11b after the oxide film is stripped is T₂Assuming that the thickness of the oxide film is t, oxidation occurs on both sides of the diaphragm, and the following relationship is established.
dT_Si= T₁−T₂
= 2 × t × 0.45 Equation 1
Therefore, the thickness of the diaphragm is set to dT by wet oxidation._SiWhen the thickness of the oxide film to be formed is t,
t = dT_Si/0.9 ・ ・ ・ Equation 2
Becomes
[0028]
FIG. 4 shows the conditions of wet oxidation in relation to oxidation temperature, oxidation time, and oxide film thickness. For example, when the diaphragm 11a having the primary thickness is formed and the Si substrate 1 is thermally oxidized at a temperature of 1000 ° C. in an atmosphere of oxygen and water vapor, as described above, once the thickness T of 2 μm is obtained.₁The vibration plate 11a formed by the above method has a thickness T of 1 μm.₂According to the equation (2), the thickness t of the oxide film to be formed is 1.1 μm, and the oxidation time required to form the thickness t of the oxide film may be 320 minutes from FIG. Understand.
Also, as can be seen from FIG. 4, at the same temperature, as the oxide film becomes thicker, the growth rate of the oxide film becomes slower, and the oxide film does not become so thick even if the oxidation time is made longer. When the temperature is increased, the oxidation time required to obtain an oxide film having the same thickness is shortened. Therefore, the oxidation time may be shortened at a temperature as high as possible, and the oxidation of (h) and the peeling of the oxide film of (i) may be repeated a plurality of times, whereby the thickness of the diaphragm at a level of several μm can be adjusted. .
[0029]
On the other hand, the oxidation of the Si substrate 1 on which the diaphragm is formed may be performed by dry oxidation in which heat treatment is performed in an oxygen atmosphere.
FIG. 5 shows the conditions of Dry oxidation in relation to the oxidation temperature, oxidation time, and oxide film thickness. In this case, since the growth rate of the oxide film is much lower than in the case of wet oxidation, fine adjustment of the diaphragm thickness on the order of several tens of nm is possible. It is also possible to use the above-mentioned wet oxidation and dry oxidation in combination. In this case, wet oxidation is performed first, the oxide film is stripped, dry oxidation is performed, and the oxide film is further stripped. .
[0030]
In this embodiment, a diaphragm is manufactured from a boron-doped layer formed on a Si substrate by the above-described method, and the thickness of the diaphragm is adjusted by performing thermal oxidation and thermal oxide film peeling on the Si substrate. Therefore, the diaphragm can be manufactured with high accuracy of 1 ± 0.1 μm for a target thickness of 1 μm, for example. In addition, since the thermal oxide film has high film thickness uniformity, the thermal oxidation and thermal oxide film peeling are performed as described above, thereby maintaining the accuracy of the diaphragm thickness at the end of etching of the diaphragm. Can be reduced to a submicron level. In addition, since the apparatus can be manufactured using a thermal oxidation apparatus that is inexpensive and can perform batch processing, it is advantageous in terms of mass productivity and cost.
On the other hand, when the diaphragm becomes thicker than a desired thickness due to a process variation in manufacturing the diaphragm, the diaphragm can be thinned by performing the above-described thermal oxidation and thermal oxide film peeling. It is also possible to readjust the thickness of the plate (repair). Further, it is also possible to finely adjust the thickness of the diaphragm by preparing the diaphragm in advance and selecting the conditions of thermal oxidation appropriately.
[0031]
Embodiment 2 FIG.
The second embodiment is a method for manufacturing a diaphragm using an SOI substrate. The SOI substrate is formed by implanting oxygen ions into a Si substrate with a high-concentration ion beam, and then subjecting the Si substrate to a heat treatment so that SiO₂A film is formed, and an active layer of Si single crystal is formed on the surface thereof. Alternatively, the SOI substrate may be formed by direct bonding between Si substrates as described above, and may be used. A diaphragm is manufactured for the active layer thus obtained.
[0032]
Hereinafter, the manufacturing method will be described with reference to FIGS. First, in FIG. 6, (a) both surfaces of the SOI substrate 10, that is, the Cav surface 101 and the active layer 108 of the Si substrate 1 are mirror-polished, respectively, to produce a substrate having a thickness of, for example, 180 μm. The thickness of the active layer 108 is, for example, 2 μm. In the figure, reference numeral 109 denotes SiO 2 formed by implantation of high-concentration oxygen ions.₂It is a membrane.
The steps (b) to (f) are the same as the steps (c) to (g) in FIG. That is, the SOI substrate 10 is set in a thermal oxidation furnace to be in an atmosphere of oxygen and water vapor, and subjected to a thermal oxidation treatment at a temperature of, for example, 1075 ° C. for 4 hours, so that a 1.2 μm SiO 2 serving as an etching protection film is formed on the surface of the SOI substrate 10.₂A film (thermal oxide film) 104 is formed.
(C) Next, the SiOI on both sides of the SOI substrate 10₂A resist 105 is coated on the film 104, and resist patterning is performed on the Cav surface 101 side to form components such as the discharge chamber 12, the reservoir 13, and the through hole 14.
(D) Then, the Cav surface 101 on which the resist patterning has been performed is etched with a hydrofluoric acid aqueous solution to remove the SiO on the Cav surface.₂The film 104 is patterned, and the resists 105 on both sides of the SOI substrate 10 are removed.
(E) Next, the SOI substrate 10 is immersed in an aqueous solution of potassium hydroxide having a high concentration of 35 wt%, and Si etching is performed. At this time, the substrate is etched from the Si exposed on the Cav surface of the SOI substrate 10. Then, the etching is continued until the residual thickness of Si by the etching becomes, for example, 10 μm. Next, the SOI substrate 10 is immersed in an aqueous solution of potassium hydroxide having a low concentration of 3 wt% to perform Si etching. Form. At this time, the thickness of the diaphragm 11a is, for example, 2 μm.
(F) SiO remaining on SOI substrate 10₂The film 104 is removed by etching with a hydrofluoric acid aqueous solution.
[0033]
The process of adjusting the thickness of the diaphragm 11a manufactured by the above process (see FIG. 7) is basically the same as the process of FIG. Therefore, in the above (f), the primary thickness T of the diaphragm 11a is obtained.₁Is formed, the diaphragm 11a is moved to the target thickness T.₂In order to adjust the SOI substrate 10, thermal oxidation (FIG. 7 (g)) is applied to the SOI substrate 10 by applying the wet oxidation conditions shown in Equation 2 and FIG. 4 or the dry oxidation conditions shown in FIG. 5. And thermal oxide film (SiO₂(FIG. 7 (h)). Finally, if necessary, an insulating film (SiO 2) is formed on the diaphragm 11b having the target thickness.₂(Film) 15 is applied.
[0034]
In this embodiment, since a target diaphragm is manufactured from an active layer already formed using an SOI substrate, at least one step can be omitted as compared with the first embodiment, and cost reduction can be achieved. Can be planned. Further, since the thickness of the active layer can be freely controlled, the diaphragm can be manufactured to have an arbitrary thickness. The thickness accuracy of the diaphragm is the same as in the first embodiment. Similar effects can be obtained in terms of mass productivity and cost.
[0035]
Embodiment 3 FIG.
In the above embodiment, the case of the inkjet head has been described, but it goes without saying that the manufacturing method of the present invention is not limited to the inkjet head. As a liquid discharge head, in addition to an ink jet head, it can be used for producing a microarray such as a DNA chip and a color filter. It can also be used for micropumps, microactuators, and the like for medical use, and its uses are wide.
Further, if the above-described diaphragm thickness adjusting technology is used, it is possible to adjust the thickness of the thin film structure requiring a high degree of thickness accuracy. As is already clear, in this film thickness adjusting method, a Si substrate or an SOI substrate is used as a substrate material.
When a Si substrate is used, a boron-doped layer is formed on one surface of the Si substrate, and etching is performed from the surface opposite to the boron-doped layer so that the boron-doped layer becomes an element portion (element wafer). Thereafter, the thickness of the boron-doped layer is adjusted by performing thermal oxidation and peeling of the thermal oxide film (removal of the thermal oxide film by etching) as described above (one or more appropriate times). I will do it. At this time, appropriate conditions for the thermal oxidation are selected in accordance with the conditions of the wet oxidation (FIG. 4) or the dry oxidation (FIG. 5).
In this way, a target element portion (element wafer) can be manufactured with a high-precision thickness.
When an SOI substrate is used, the above boron-doped layer may be replaced with the active layer of the SOI substrate.
Therefore, according to this embodiment, it is possible to manufacture a MEMS device (optical mirror, micro heater, micro motor, micro actuator, etc.) using the thin film structure with high accuracy.
[Brief description of the drawings]
FIG. 1 is a manufacturing process diagram of an inkjet head according to a first embodiment of the present invention.
FIG. 2 is a manufacturing process diagram following FIG. 1;
FIG. 3 is a cross-sectional view illustrating a configuration of an inkjet head.
FIG. 4 is a correlation diagram showing temperature-oxidation time-oxide film thickness showing wet oxidation conditions.
FIG. 5 is a correlation diagram of temperature-oxidation time-oxide film thickness showing Dry oxidation conditions.
FIG. 6 is a manufacturing process diagram of the inkjet head according to the second embodiment of the present invention.
FIG. 7 is a manufacturing process diagram following FIG. 6;
[Explanation of symbols]
REFERENCE SIGNS LIST 1 first substrate (Si substrate), 2 second substrate (glass substrate), 3rd substrate (Si substrate), 4 oscillation circuit, 10 SOI substrate, 11, 11a, 11b diaphragm, 12 discharge chamber, Reference Signs List 13 reservoir, 14 through hole, 15 insulating film, 21 actuator electrode, 22 recess, 31 nozzle hole, 32 narrow groove, 101 Cav plane, 102 Dope plane, 103 boron doped layer, 104 SiO₂Film (thermal oxide film), 105 resist, 106 SiO₂Film (thermal oxide film), 108 active layer, 109 SiO₂film

Claims (13)

In a method for manufacturing a liquid discharge head in which a boron-doped layer is formed on a Si substrate and the boron-doped layer is formed as a diaphragm,
(1) after forming the diaphragm, forming a thermal oxide film on the Si substrate by thermal oxidation;
(2) removing the thermal oxide film by etching;
A method for manufacturing a liquid discharge head, comprising: In a method for manufacturing a liquid ejection head in which an active layer of an SOI substrate is formed as a diaphragm,
(1) after forming the diaphragm, forming a thermal oxide film on the SOI substrate by thermal oxidation;
(2) removing the thermal oxide film by etching;
A method for manufacturing a liquid discharge head, comprising: 3. The method according to claim 1, wherein the thermal oxide film is formed by wet oxidation or dry oxidation. 4. The method according to claim 1, wherein the steps (1) and (2) are repeated a plurality of times. The method according to claim 1, further comprising, after the step (2), forming an insulating film on the diaphragm. 6. The method according to claim 1, wherein in the step (1), after forming the diaphragm, a thickness of the diaphragm is measured, and the thermal oxidation condition is determined based on the measurement result. 5. The method for manufacturing a liquid ejection head according to item 1. (1) forming a boron doped layer on a Si substrate;
(2) etching from the surface of the Si substrate opposite to the boron-doped layer until reaching the boron-doped layer;
(3) forming a thermal oxide film by thermal oxidation on the boron-doped layer after the etching;
(4) removing the thermal oxide film by etching;
A method for adjusting the thickness of a thin film structure, comprising: (1) etching from the surface of the SOI substrate opposite to the active layer until reaching the active layer of the SOI substrate;
(2) forming a thermal oxide film on the active layer after the etching by thermal oxidation;
(3) removing the thermal oxide film by etching;
A method for adjusting the thickness of a thin film structure, comprising: 9. The method according to claim 7, wherein the thermal oxide film is formed by wet oxidation or dry oxidation. 10. The method according to claim 7, wherein the steps (3) and (4) are repeated a plurality of times. The method according to claim 8, wherein the steps (2) and (3) are repeated a plurality of times. 11. The thin film structure according to claim 7, wherein in the step (3), the thickness of the boron-doped layer is measured, and the thermal oxidation condition is determined based on the measurement result. How to adjust body thickness. 12. The thin film structure according to claim 8, wherein, in the step (2), the thickness of the active layer is measured, and the condition of the thermal oxidation is determined based on the measurement result. How to adjust body thickness.

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