JP2000318155A - Electrostatic actuator and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a high-density ink-jet head capable of changing an ink ejection amount without causing an increase in drive voltage. SOLUTION: As a driving method of an electrostatic actuator,
The insulating film 14 for ensuring insulation between the diaphragm 15 and the individual electrode 13 is formed on the individual electrode 13 when performing a contact drive in which the diaphragm 15 and the insulating film 14 are in direct contact with each other. A step-like step is formed so that the interval (gap length) between the diaphragm 15 and the individual electrode 13 is at least two or more. If the gap length is two or more, the effect of reducing the drive voltage of the actuator can be seen, but the effect becomes more pronounced as the number of steps increases. In this case, by forming the individual electrodes 13 and the insulating film 14 up to the n-step position, the area where the electrostatic attraction of the vibration plate 15 and the electrode substrate acts can be increased, so that efficient operation is possible. Become.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator and a method for manufacturing the same, and more particularly, to an ink jet head using the electrostatic actuator. More specifically, the present invention relates to an electrostatic ink jet head for an on-demand type ink jet printer and an ink jet head. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Various heads for an ink jet printer using an electrostatic actuator for recording by ejecting ink droplets directly from a nozzle onto a recording medium and a method for driving the same have been conventionally proposed. In general, there are two types, a non-contact driving method in which the diaphragm and the individual electrode are driven so as not to directly contact each other, and a contact driving method in which the individual electrode directly contacts the diaphragm.
For example, it is disclosed in JP-A-7-214770. However, each of the driving methods has advantages and disadvantages. In particular, the contact driving method can obtain a stable and constant ink ejection amount with little variation between bits (digital), but on the other hand, the ink ejection weight It is difficult to control the ejection characteristics such as the above variously so as to correspond to multiple gradations.
To solve the problem, see, for example, Japanese Patent Application Laid-Open No. 9-392.
No. 35 discloses that a gap in the longitudinal direction between a diaphragm of an electrostatic inkjet head and an individual electrode is formed in multiple stages.

The applicant of the present invention has proposed that the gap between the diaphragm of the electrostatic ink jet head and the individual electrode in the lateral direction is 2.
An ink jet head having a step and having a thick region and a thin region of the diaphragm has been proposed. However, the driving method of the ink jet head is a non-contact driving method, which is an essential method related to this driving method. The problem is that the amount of ink ejected from each nozzle is uneven due to the uneven spring constant due to the distribution of the diaphragm thickness. It is also difficult to make the dot diameter in a recorded image uniform.
In addition, the individual electrodes are in the gap formed in two steps, and
Since it is arranged only in the region where the gap length is long, the area of action of the electrostatic attraction acting on the diaphragm and the individual electrodes is reduced, and the driving voltage is increased.

[0004]

There is an on-demand type ink jet head as an application product of the electrostatic type actuator, and the driving method of the electrostatic type ink jet head includes:
As described above, there are roughly two types, a non-contact driving method in which the diaphragm and the individual electrode are driven so as not to directly contact each other, and a contact driving method in which the individual electrode directly contacts the diaphragm.
In the case of non-contact drive, the electric and
Although the mechanical stress is small, there is an advantage that the service life of the head is relatively long, but ink discharged from each nozzle due to unevenness of the spring constant of each diaphragm due to differences in shape such as thickness of the diaphragm. It was difficult to make the amount constant. On the other hand, the contact drive method in which the individual electrode directly contacts the diaphragm is different from the non-contact drive, and the diaphragm is always driven at a voltage higher than the voltage at which the diaphragm comes into contact with the individual electrode. Since the amount is uniquely determined by the gap length, the ink ejection amount is stabilized (Japanese Patent Application Laid-Open No. 7-214770). However, when such contact driving is performed, a stable and constant ink ejection amount with small variation between bits can be obtained (digitally). On the other hand, ejection characteristics such as ink ejection weight are more variously controlled.
It was difficult to support multiple gradations. In order to solve the problem, Japanese Patent Application Laid-Open No. 9-39235 discloses that a gap in the longitudinal direction between a diaphragm of an electrostatic ink jet head and an individual electrode is formed in multiple stages. However, in the trend of high density, the driving voltage increases for the following reasons, which causes the cost of the driving circuit to increase.

In an ink jet head, it is essential to increase the density of nozzles in order to perform high-speed, high-quality printing. However, in an ink jet head that drives a diaphragm by electrostatic attraction, the nozzle pitch is reduced. In order to increase the density, it is necessary to shorten the short side length in the nozzle pitch direction of each diaphragm. From equation (1), the amount of displacement of the diaphragm due to electrostatic attraction is proportional to the fourth power of the shorter side of the diaphragm. Therefore, if the shorter side of the diaphragm is shortened for the purpose of higher density, the amount of displacement becomes smaller. It becomes significantly smaller. Therefore, in order to increase the displacement and secure the required amount of ink droplets to be ejected, the thickness of the diaphragm is reduced by using the equations (1) and (2) or the distance between the diaphragm and the individual electrode is reduced. It is necessary to reduce the gap length or increase the driving voltage.

[0006]

(Equation 1)

Here, reducing the thickness of the diaphragm is as follows.
This means that the rigidity of the diaphragm is reduced, which causes a reduction in the ink ejection force, which is not preferable. On the other hand, shortening the gap length between the diaphragm and the individual electrodes means that the amount of ink ejection decreases as the amount of displacement of the diaphragm decreases, and this is not preferable because it causes ink blurring. Therefore, an attempt was made to cope with higher density by increasing the drive voltage, but there was a problem that the cost of the power supply and the drive circuit was increased.

An object of the present invention is to solve the above-mentioned problems and to provide an electrostatic actuator capable of coping with an ink jet head corresponding to high density. In other words, without causing the drive voltage to increase,
It is an object of the present invention to provide an electrostatic actuator that realizes a high-density inkjet head that can vary the ink ejection amount.

[0009]

The present invention comprises a diaphragm and an individual electrode provided on an electrode substrate joined to the diaphragm via a gap, the individual electrode being provided so as to face the diaphragm. A driving voltage is applied between the common electrode and the individual electrodes attached to the actuator and the electrostatic actuator deforms the diaphragm by electrostatic force, wherein the diaphragm is configured by rectangles having short sides and long sides. And a gap forming a gap between the individual electrodes, the short side of the gap is concave,
And, at least, it is formed in a step shape having a gap length of two or more, furthermore, the long side of the gap is concave, and in a step shape having a gap length of at least two or more Being formed, further, that the individual electrode is formed so as to cover the step, in the concave shape, and in the step-shaped gap, furthermore, an insulator is provided on the individual electrode. Being formed, furthermore,
The insulator formed on the individual electrode is a silicon oxide film or a silicon nitride film, and the electrode substrate on which the individual electrode is formed is a silicon wafer or borosilicate glass. It is.

The present invention also relates to a method of manufacturing the above-mentioned electrostatic actuator, wherein the method comprises the steps of: forming a gap between a diaphragm constituted by rectangles having short and long sides and an individual electrode; , A first gap forming step, further at least a second gap forming step of forming a second gap wider than the first gap width formed in the first gap forming step, further gaps And a method for manufacturing an electrostatic actuator having a stepwise gap that forms two or more gap lengths.

Further, the present invention relates to an ink jet head using the above-mentioned electrostatic actuator, wherein the ink jet head uses a part of a vibration plate to form a liquid chamber for discharging ink. It features a head.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a part of a top view of an electrostatic actuator according to the present invention, and FIG. 2 is a diagram showing a main part of the electrostatic actuator according to the present invention.
FIG. 2 is an enlarged view of a single bit of the electrostatic actuator of the present invention shown in FIG. 1, showing a cross section taken along line AA in a short side direction of a pad portion for applying a drive voltage;
FIG. 2B is a view showing a cross section taken along line BB which is a short side direction of the diaphragm region of the single-bit electrostatic actuator shown in FIG. 1, and FIG. 2C is a view showing the electrostatic actuator shown in FIG. It is a figure which shows the CC cross section which is a long side direction of an actuator.

1 and 2, reference numeral 11 denotes a silicon substrate or a glass substrate which is a support of the electrostatic actuator according to the present invention. Reference numeral 12 denotes a silicon oxide film formed at least stepwise in a cross section taken along the line AA in FIG. 1 to perform insulation separation between the silicon substrate 11 and the individual electrodes or between the individual electrodes when a silicon substrate is used as the support. It is. On the other hand, when a glass substrate is used for the support 11, the glass substrate is formed in a step shape and is used as it is, so that 11 and 12 are the same, and both are glass substrates. Reference numeral 13 denotes an individual electrode of the electrostatic actuator, which is composed of n + or P + polycrystalline silicon, a high melting point metal such as TiN, or Al,
It is a metal such as Au. As a driving method of the electrostatic actuator, an insulating film such as silicon oxide or silicon nitride for ensuring insulation between the vibration plate 15 and the individual electrodes 13 when performing a contact drive in which the vibration plate 15 and the insulating film 14 are in direct contact with each other. 1
4 are formed on the individual electrodes 13.

As shown in the cross-sections of FIGS. 2A and 2B, step-like steps are formed so that the distance (gap length) between the diaphragm 15 and the individual electrode 13 is at least two or more. Have been. If the gap length formed by the step-like steps is two or more, the effect of lowering the drive voltage of the actuator can be obtained. However, the n gap length shown in FIG. 2B: G1 to Gn (n steps) As the number of steps increases,
The effect is remarkable. In this case, the individual electrode 13 and the insulating film 14 are formed up to the n-step position, so that the diaphragm 1
Since the area where the electrostatic attraction of the electrode substrate 5 and the electrode substrate 13 act can be increased, efficient operation is possible.

As shown in FIGS. 1 and 2, the effect of lowering the drive voltage of the actuator has a step-like shape in the cross section taken along the line BB of FIG. 1 (FIG. 2B), which is the short side direction of the actuator. It is obtained by forming a step and forming two or more gap lengths, and further by forming two or more gap lengths in the long side CC line direction in addition to the short side direction of the actuator, The effect can be enhanced.

FIG. 3 and FIG. 4 show the configuration of a main part for explaining an embodiment in which two or more gap lengths are formed also in the long side direction (CC line direction) of the actuator as described above. FIG. 3 is a top view and FIG.
(A) is an enlarged view of a single bit of the electrostatic actuator shown in FIG. 3, and shows a cross section taken along line AA of FIG. 3, which is a short side direction of a pad portion for applying a drive voltage; FIG.
3B is a cross-sectional view taken along the line BB in FIG. 3, which is a short side direction of the diaphragm region of the single-bit electrostatic actuator.
FIG. 3C shows a cross section taken along the line CC of FIG. 3, which is a long side direction of the electrostatic actuator shown in FIG.

3 and 4, reference numeral 21 denotes a silicon substrate or a glass substrate which is a support of the electrostatic actuator according to the present invention. Reference numeral 22 denotes at least a section taken along the line AA in FIG. 3 (FIG. 4A) for performing insulation separation between the silicon substrate 21 and the individual electrodes or between the individual electrodes when a silicon substrate is used as the support. This is a silicon oxide film formed in a step shape. On the other hand, when a glass substrate is used as the support, the glass substrate is formed in steps and used as it is, so that both 21 and 22 are the same glass substrate. 23 is an individual electrode of the electrostatic actuator, n + or P +
Polycrystalline silicon, high melting point metal such as TiN, or A
1 and metals such as Au. As a driving method of the electrostatic actuator, when performing contact driving in which the diaphragm 25 and the insulating film 24 are in direct contact with each other, an insulating film such as silicon oxide or silicon nitride for ensuring insulation between the diaphragm 25 and the individual electrodes 23. 24 are formed on the individual electrodes 23.

The steps (gap lengths) between the diaphragm 25 and the individual electrodes 23 are at least two or more, and the step-like steps are formed as shown in FIGS. 4A and 4B. 3
Are formed at the AA line cross section and the BB line cross section.
If the gap length formed by the step-like steps is two or more, the effect of lowering the drive voltage of the actuator can be obtained, but the number n of the actuators shown in FIG.
), The effect becomes remarkable as the number of steps increases, as in G1 to Gn (n steps). In this case, by forming the individual electrode 23 and the insulating film 24 up to the n-step position, the area where the electrostatic attraction of the vibration plate 25 and the electrode substrate 23 acts can be increased, so that efficient operation is possible. Become.

In order to further reduce the driving voltage, a cross section taken along line AA of FIG. 3 (FIG. 4A) and a cross section taken along line BB of FIG.
In addition to (B)), as shown in FIG. 4 (C), steps G5 to Gn (in the illustrated example, G5 to G8 in the example shown in FIG. Formed. If at least two or more types of gap lengths are formed,
Although the effect is seen, n gap lengths: G1 to Gn
By forming (n stages), the driving voltage is significantly reduced.

Next, with reference to FIG. 5, the reason why the drive voltage is reduced in the electrostatic actuator having two or more gaps formed by the step-like steps as described above will be described. FIG. 5 is a sectional view taken along the line BB of FIGS. 1 and 3 (corresponding to FIGS. 2 (B) and 4 (B)).
A driving voltage is applied to the individual electrode 33, the diaphragm 35 is bent by the electrostatic attraction F, and comes into contact with the insulator 34. , A state in which the contact driving is performed. At this time, the angle between the surface of the silicon substrate 31 and the step-like step was defined as θ ° (: gap taper angle), and the relationship of the attraction force F due to the electrostatic force was shown in FIG. As shown in FIG. 6, since the electrostatic attraction F increases rapidly as the gap taper angle (θ °) decreases, the voltage required to generate the same electrostatic attraction decreases as the gap taper angle decreases. Become
The drive voltage drops. In order to reduce the gap taper angle, the etching amount for forming the gap may be reduced, and the number of steps may be increased.

Next, a manufacturing process of the electrostatic actuator of the present invention will be described with reference to FIGS. 7 and 8 (note that in FIGS. 7 and 8, the left-hand drawing is taken along the line II-II of the right-hand drawing). The cross-sectional view and the right-hand drawing are cross-sectional views taken along line II of the left-hand drawing.) FIG. 7 shows a process of processing a silicon oxide film to form a step-like step. In this case, a step flow can be similarly formed by processing using a glass substrate as a support instead of processing a silicon oxide film formed on a silicon substrate as a support. FIG. 8 shows a manufacturing flow in which a silicon substrate as a support is processed and a step-like step is formed in advance, and then a silicon oxide film is formed on the silicon surface to form a step-like step. The electrostatic actuator of the present invention may be formed by any method.

First, the example of FIG. 7 will be described. A silicon oxide film 41 'is formed in a thickness of 1 to 5 [mu] m on a silicon substrate 41 which is a support, and an individual electrode region of the electrostatic actuator is patterned with a resist 42 for forming a first gap (FIG. 7A). Using the resist 42 as a mask, the silicon oxide film 41 'is etched by anisotropic or isotropic dry etching or wet etching to form a first gap pattern (FIG. 7B).

Next, the resist 43 is patterned to form a second gap having a width larger than the first gap pattern width in the short side direction. At this time, when the second gap formation patterning is performed in the long side direction with the same length as the first gap pattern, the electrostatic actuator having the configuration shown in FIGS. When the second gap formation patterning is performed with a shorter length, an electrostatic actuator having the configuration shown in FIGS. 3 and 4 is obtained (FIG. 7C). Using the second gap pattern 43 as a mask, the silicon oxide film is dry-etched or wet-etched to form a step-like step having a first gap pattern and a second gap pattern (FIG. 7D )). Further, desirably, the third, fourth,...
(D ′)) and etching (FIG. 7D ″) are repeated in the same manner as described above. By repeating the patterning and etching of the gap, a gap having many steps is formed in the silicon oxide film or the glass substrate. Formed.

Next, polycrystalline silicon containing a large amount of phosphorus or boron, which is an individual electrode, or a refractory metal such as TiN, or a metal 44 such as Al or Au is formed on the entire surface. Insulator 4 such as silicon oxide film and silicon nitride film
5 is formed (FIG. 7E). The thickness of the insulator 45 is a thickness that does not cause dielectric breakdown even when a drive voltage for driving the electrostatic actuator is applied to the individual electrodes.

The insulator 45 is etched in the pattern of the individual electrode 44, the individual electrode 44 is etched in a self-aligned manner, and the individual electrode 44 ′ and the patterned insulator 4 are etched.
5 'is formed in a gap having a step-like step (FIG. 7F). A conductive plate 46 made of silicon or the like is anodic-bonded or directly bonded or eutectic-bonded to the electrode substrate as described above to complete the electrostatic actuator of the present invention (FIG. 7 (G)).

Next, the fabrication flow of processing the silicon substrate as a support shown in FIG. 8 and forming a step in the form of a thread step in advance and then forming a silicon oxide film on the silicon surface to form the step in the step will be described. explain. First, an individual electrode region of an electrostatic actuator is first patterned to form a gap on a silicon substrate 51 as a support with a resist 52 (FIG. 8A). Using the resist 52 as a mask, the silicon substrate is etched by anisotropic or isotropic dry etching or wet etching to form a first gap pattern (FIG. 8B).

Next, a resist 53 is patterned for forming a second gap having a width larger than the first gap pattern width in the short side direction. At this time, when the second gap forming patterning is performed in the long side direction with the same length as the first gap pattern, the electrostatic actuator having the configuration shown in FIGS. 1 and 2 is obtained. When the second gap formation patterning is performed with a short length, an electrostatic actuator having the configuration shown in FIGS. 3 and 4 is obtained (FIG. 8C). Using the second gap pattern 53 as a mask, the silicon substrate is dry-etched or wet-etched to form a step-like step having a first gap pattern and a second gap pattern on the silicon substrate (FIG. 8D )). More preferably, the third, fourth, and n-th gap patterning (FIG. 8 (D ')) and etching (FIG. 8 (D ")) are similarly repeated. Is repeated, a gap having many steps is formed on the silicon substrate (FIG. 8).
(D ″)).

Next, a silicon oxide film 54 having a thickness of 100 nm to 3 μm is formed on the entire surface of the silicon substrate on which many steps are formed (FIG. 8E). Next, polycrystalline silicon containing a large amount of phosphorus or boron, which is an individual electrode, or a refractory metal such as TiN, or a metal 55 such as Al or Au is formed on the entire surface, and a silicon oxide film is further formed thereon. Then, an insulator 56 such as a silicon nitride film is formed (FIG. 8F).
The thickness of the insulator 56 is a thickness that does not cause dielectric breakdown even when a drive voltage for driving the electrostatic actuator is applied to the individual electrodes.

The insulator 56 is etched in the pattern of the individual electrode 55, and the individual electrode 55 is etched in a self-aligned manner.
Is formed in a gap having a step-like step (FIG. 8).
(G)). The conductive plate 57 made of silicon or the like is connected to the electrode substrate as described above by anodic bonding, direct bonding, or eutectic bonding to complete the electrostatic actuator of the present invention (FIG. 8).
(H)).

Next, an example in which the electrostatic actuator of the present invention is used in an ink jet head will be described as an application example with reference to FIG. Conduction type is P type or N type, plane orientation (11
1) One side of the single-crystal Si substrate 61 is doped with an impurity exhibiting a P-type or N-type conductivity to a depth equal to the thickness of the diaphragm.
A diffusion region 62 diffused by not less than E19 / cm ^3, and a single-crystal Si etching mask pattern such as a silicon oxide film, a silicon nitride film, and a tantalum pentoxide for defining an ink liquid chamber and an ink nozzle on a surface opposite to the diffusion region 62. The ink liquid chamber substrate 60 on which the 63 is formed is joined to the electrode substrate 40 or 50 (FIGS. 7F and 8G) shown in FIGS. Or,
A single-crystal thin film (corresponding to 62) having a thickness equal to the thickness of the diaphragm is formed on a (110) plane-oriented single-crystal Si substrate 61 via a Si oxide film: SOI (silicon silicon)
n Insulator) substrate and the electrode substrate may be joined. The bonding is performed by a direct bonding method of bonding in an oxygen or nitrogen atmosphere at a reduced pressure or a normal pressure at a temperature of 800 ° C. or higher, Na ion,
After an insulating film containing mobile ions such as H ions is entirely formed on the diffusion region 62 of the (110) single crystal Si substrate 61 by a sputtering method, 200 ° C. to 500 ° C., preferably 350 ° C. to 450 ° C. while applying an electric field. (FIG. 9 (A)).

The electrode substrate 40 (or 5) shown in FIG.
0) and the ink liquid chamber substrate 60 are bonded to a single crystal S
i from the side where the etching mask pattern 63 is formed.
(110) single crystal Si substrate 6 by OH, TMAH, etc.
1 is anisotropically etched. At this time, the etching is spontaneously stopped in the diffusion region 62 containing the impurity at a high concentration, and the vibration plate 62 is formed (FIG. 9B). When the SOI substrate is anisotropically etched, the etching stops on the Si oxide film. At this time, there is no problem even if the Si oxide film is removed. An ink liquid chamber cover 64 made of a glass plate or a metal plate having an ink supply channel 65 formed by sandblasting or laser processing is attached to the upper portion of the anisotropically etched (110) single crystal silicon substrate. Only in pad area A, Si thin film diaphragm 62 and individual electrode 1
The insulator 14 (24) on 3 (23) is removed by etching to expose the surface of the individual electrode, thereby completing the ink jet head of the present invention (FIG. 9C).

At this point, on the ink liquid chamber side, an individual liquid chamber 68 corresponding to each nozzle formed by anisotropic etching and a common liquid chamber 66 for supplying ink thereto are formed. The structure is such that they are connected by a flow path 57 formed by anisotropic etching. When a voltage is applied to the individual electrode 44 '(55') in the pad area of the ink jet head, the single crystal Si diaphragm 63 and the individual electrode 44 '
(55 '), an electrostatic force acts, the diaphragm 62 flexes in the direction of the individual electrode 44' (55 '), the liquid chamber 68 becomes negative pressure, and flows from the common liquid chamber 66 through a flow path 67 for ink supply. The ink is supplied to the individual liquid chamber 68. When the voltage is turned off, the single crystal Si vibration plate 62 returns to the original position due to the rigidity of Si. At this time, the individual liquid chamber 68 is pressurized, the ink is ejected through the nozzle 69 in the direction of the arrow, and lands on the recording paper.

Although the ink discharge direction is shown as an example in the horizontal direction with respect to the substrate, ink can be discharged in the normal direction of the substrate by changing the direction of the ink nozzle. Also, in the present ink jet head manufacturing flow, an example is shown in which the vibration plate, the ink liquid chamber, and the nozzle portion are formed by joining the single crystal silicon substrate and the electrode substrate that form the vibration plate and the ink liquid chamber and then performing anisotropic etching. However, the nozzle portion may be formed after the single crystal silicon substrate on which the ink liquid chamber and the vibration plate are formed by anisotropic etching and the electrode substrate are joined.

(Embodiment 1) FIG. 10 is a sectional view of an essential part for explaining an embodiment of an electrostatic actuator according to the present invention. In this embodiment, the electrostatic actuator according to the present invention is applied to an ink jet head. It was done. FIG.
1A shows a cross section taken along the line AA (corresponding to FIG. 2A), which is a short side direction of the pad portion for applying the driving voltage of FIG. 1, and FIG. 10B shows the vibration of FIG. A cross section taken along line BB (corresponding to FIG. 2B), which is a short side direction of the plate region, is shown. Further, FIG. 10C shows a cross section taken along the line CC (corresponding to FIG. 2C), which is the long side direction of FIG. The inkjet head of this example was manufactured according to the manufacturing flow shown in FIG. In FIG. 10, 81 is a plane orientation (100),
It is an n-type single crystal Si substrate having a resistivity of 10 to 20 Ω-cm. Reference numeral 81 'denotes a gap spacer between the vibration plate 92 and the individual electrode 86, which is a Si oxide film formed by a pyro-oxidation furnace in an atmosphere of H2 gas and O2 gas, and formed by repeating lithography and etching, for example, a four-stage structure. It is a silicon oxide film having a step-like step. At this time, the Si oxide film thickness between the individual electrode 86 and the single crystal silicon substrate 81 is 2 μm at the maximum.
m and at least 400 nm. There are four types of gap lengths between the diaphragm 92 and the individual electrodes 86, as shown in FIG.
Using the expression of FIG. 4B, G1 = 1.6 μm, G2
= 1.2 µm, G3 = 0.8 µm, and G4 = 0.4 µm. The individual electrode 86 is a 200-nm-thick TiN individual electrode. On the individual electrode 86, a 200-nm-thick silicon oxide film 87 formed by a plasma CVD method is formed.

The silicon oxide film 87 secures insulation between the vibration plate 92 and the individual electrode 86 when the diaphragm 92 and the silicon oxide film 87 are brought into direct contact with each other to perform driving. The one used as an etching mask for patterning was used as it was. Reference numeral 86 'denotes an electrode pad region where the silicon oxide film 87 is not formed for applying a drive voltage to the individual electrode 86. Boron impurity atoms formed by anisotropically etching a single crystal Si substrate 91 having a plane orientation of (110) with KOH are removed by 1E.
A 3 μm-thick diaphragm 92 containing 20 / cm ³ or more is joined to the Si oxide film 81 ′ of the gap spacer. An ink liquid chamber 98 formed by anisotropic etching of KOH and a common liquid chamber 96 for supplying ink thereto are formed on the (110) single-crystal Si substrate 91 in plane orientation, and both are communicated by a flow path 97. ing.

Further, the glass plate 9 on which the ink supply channels 95 and the ink nozzles 99 are formed by sandblasting.
4 is stuck on the ink liquid chamber 98. At this time, the width of the ink liquid chamber 98 is smaller than the width of the step-shaped gap spacer in which the individual electrode 86 is formed. In such an ink jet head, the diaphragm 92 was electrically grounded, a positive drive voltage was applied to the individual electrode 86 via the electrode pad 86 ', and the ink jet head was driven at a constant frequency. When a voltage was applied, an electrostatic attraction was exerted between the diaphragm 92 and the individual electrode 86, and the diaphragm 92 was pulled in the direction of the individual electrode 86.
At this time, the ink liquid chamber 98 became negative pressure, and the ink was supplied from the common liquid chamber 96 to the individual liquid chamber 98 via the flow path 97 for supplying ink. Diaphragm 9 corresponding to the frequency of the drive voltage
2 returned to the original position due to the rigidity of Si, at this time, the individual liquid chamber 98 was pressurized, ink was ejected in the direction of the arrow via the nozzle 99, landed on the recording paper, and was recorded.

(Embodiment 2) FIG. 11 is a cross-sectional view of a principal part for explaining another embodiment of the electrostatic actuator according to the present invention. It is a case when applied to. FIG. 11A is a cross-sectional view (corresponding to FIG. 2A) taken along the line AA in the short side direction of the pad portion for applying the driving voltage of FIG. 1, and FIG. 1 shows a cross section taken along the line BB (corresponding to FIG. 2B), which is a short side direction of the diaphragm region. Further, FIG. 11 (C) shows C-
The cross section taken along the line C (corresponding to FIG. 2C) is shown. The ink jet head according to the present embodiment was manufactured according to the manufacturing flow shown in FIG. Reference numeral 101 denotes a support on which a gap spacer between the vibration plate 112 and the individual electrode 106 is formed, and is a glass substrate having four steps formed by repeating lithography and etching. At this time, there are four types of gap lengths between the diaphragm 112 and the individual electrodes 106, and using the expressions in FIGS. 2B and 4B, G1 =
2.0 μm, G2 = 1.5 μm, G3 = 1.0 μm, G4
= 0.5 μm. Reference numeral 106 denotes an Al individual electrode having a thickness of 500 nm. On this individual electrode 106, plasma C
A 150-nm-thick silicon nitride film 107 formed by the VD method is formed.

The silicon nitride film 107 has a diaphragm 112
Is used as an etching mask for patterning the Al individual electrode when the contact driving is performed in which the silicon nitride film 107 and the silicon nitride film 107 are brought into direct contact with each other to perform insulation. Was used as is. Reference numeral 106 'denotes an electrode pad region where the silicon nitride film 107 is not formed for applying a drive voltage to the individual electrode 106. Single crystal Si with plane orientation (110)
A 3 μm diaphragm 112 containing 1E20 / cm ³ or more of boron impurity atoms formed by anodically bonding a substrate and the electrode substrate at a substrate temperature of 400 ° C. while applying a voltage at a substrate temperature of 400 ° C. and then forming an anisotropic etching with KOH forms a gap spacer. Glass substrate 101 to be bonded. An ink liquid chamber 118 formed by anisotropic etching of KOH and a common liquid chamber 116 for supplying ink thereto are formed on the (110) plane orientation single crystal Si substrate 111, and both are communicated by a channel 117. ing.

Further, a glass plate 114 on which an ink supply channel 115 and an ink nozzle 119 are formed by sandblasting is adhered on the ink liquid chamber. At this time, the width of the ink liquid chamber 118 is smaller than the width of the step-shaped gap spacer in which the individual electrode is formed. In such an ink jet head, the diaphragm 112 is electrically grounded, and the individual electrodes 1 are connected via the electrode pads 106 '.
06 was applied with a positive drive voltage to drive at a constant frequency.
When a voltage was applied, an electrostatic attraction acted between the diaphragm 112 and the individual electrode 106, and the diaphragm 112 was pulled in the direction of the individual electrode 106. At this time, the ink liquid chamber 118 has a negative pressure and passes through the flow path 117 for supplying ink to the common liquid chamber 11.
6 to the individual liquid chamber 118. In accordance with the frequency of the drive voltage, the diaphragm 112 returns to the original position due to the rigidity of Si. At this time, the individual liquid chamber 118 is pressurized,
Ink was ejected through the nozzle 119 in the direction of the arrow, landed on the recording paper, and was recorded.

(Embodiment 3) FIG. 12 is a cross-sectional view of a principal part for explaining still another embodiment of the electrostatic actuator according to the present invention. This is applied to the head. FIG. 12A is a cross-sectional view (corresponding to FIG. 2A) taken along the line AA in the short side direction of the pad portion for applying the driving voltage of FIG. 1, and FIG. A cross section taken along the line BB (corresponding to FIG. 2B), which is a short side direction of the diaphragm region of FIG. Further, FIG. 12C shows C- direction which is the long side direction of FIG.
The cross section taken along the line C (corresponding to FIG. 2C) is shown. The inkjet head of this example was manufactured according to the manufacturing flow shown in FIG. Reference numeral 121 denotes a p-type single crystal Si substrate having a plane orientation (100) and a resistivity of 10 to 20 Ω-cm.
Reference numeral 121 'denotes a gap spacer between the vibration plate 132 and the individual electrode 126. The gap spacer is formed by repeating lithography and etching with respect to the single crystal silicon substrate 121 to form a step-like step. It is a silicon oxide film formed in a pyro-oxidation furnace, and is a silicon oxide film in which eight steps are formed. At this time, the individual electrode 1
The Si oxide film thickness between 26 and single crystal silicon substrate 121 is 1 μm. There are eight types of gap lengths between the diaphragm 132 and the individual electrodes 126. According to the expressions shown in FIGS. 4B and 4C, G1 = 2.0 μm, G2 = 1.8 μm, G
3 = 1.6 μm, G4 = 1.4 μm, G5 = 1.2 μm,
G6 = 1.0 μm, G7 = 0.8 μm, G8 = 0.6 μm
It is. 126 is a phosphor atom having a thickness of 300 nm
/ Cm ³ or more. On the individual electrode 126, a thickness of 20
A 0 nm silicon oxide film 127 is formed.

The silicon oxide film 127 is formed on the diaphragm 132
When the contact drive is performed in which the silicon oxide film 127 and the silicon oxide film 127 are brought into direct contact with each other, the insulation between the diaphragm 132 and the individual electrodes 126 is ensured. Reference numeral 126 'denotes a drive voltage applied to the individual electrode 1.
This is an electrode pad region where the silicon oxide film 127 is not formed for application to the electrode pad 26. Plane orientation (11
0) A 3 μm diaphragm 132 containing boron impurity atoms of 1E20 / cm ³ or more formed by anisotropically etching a single crystal Si substrate 131 with KOH is used as a gap spacer Si.
It is bonded to the oxide film 121 '. An ink liquid chamber 138 formed by KOH anisotropic etching and a common liquid chamber 136 for supplying ink thereto are formed on the (110) plane orientation single crystal Si substrate 131, and both are communicated by a flow path 137. ing.

Further, a glass plate 134 in which an ink supply channel 135 and an ink nozzle 139 are formed by sandblasting is stuck on the ink liquid chamber 138. At this time, the width of the ink liquid chamber 138 is smaller than the width of the step-shaped gap spacer in which the individual electrode is formed. In such an ink jet head, the diaphragm 132 was electrically grounded, a positive drive voltage was applied to the individual electrode 126 via the electrode pad 126 ', and the ink jet head was driven at a constant frequency. When a voltage is applied, the diaphragm 132 and the individual electrode 1
26, the diaphragm 132 was pulled in the direction of the individual electrode 126. At this time, the ink liquid chamber 138 became negative pressure, and the ink was supplied from the common liquid chamber 136 to the individual liquid chamber 138 via the flow path 137 for supplying ink. In accordance with the frequency of the drive voltage, the diaphragm 132 returns to its original position due to the rigidity of Si. At this time, the individual liquid chamber 138 is pressurized, and ink is ejected in the direction of the arrow via the nozzle 139, onto the recording paper. Landed and recorded.

[0043]

According to the first aspect of the present invention, the short side of the gap is concave and is formed in a step shape having at least two gap lengths. Low voltage driving becomes possible, and the cost of the driver can be reduced. Further, the rigidity of the diaphragm is increased, and an actuator having strong driving force and repulsive force can be formed.

In the electrostatic actuator according to the second aspect, the short side and the long side of the gap are concave, and the gap is formed in a step shape having at least two or more gap lengths. Further, the actuator can be driven at a lower voltage than in the first aspect of the present invention.

In the electrostatic actuator according to the third aspect, since the individual electrodes are formed in the concave and step-shaped gaps so as to cover the steps, the individual electrodes, the diaphragm and The area on which the electrostatic attraction acts increases, and the actuator can be driven efficiently.

In the electrostatic actuator according to the fourth aspect, since the insulator is formed on the individual electrode,
Contact driving in which the diaphragm and the individual electrode are in contact with each other is enabled, and variation in the amount of vibration displacement between the actuators can be reduced.

In the electrostatic actuator according to the fifth, sixth, and seventh aspects, the insulator formed on the individual electrode is a silicon oxide film or a silicon nitride film, and the individual electrode is formed. Since the electrode substrate is a silicon wafer, it can be manufactured using a normal silicon semiconductor process, so that a significant cost reduction is possible.

In the electrostatic actuator according to the eighth aspect, since the electrode substrate on which the individual electrodes are formed is made of borosilicate glass, the bonding temperature is relatively low when the vibration plate and the electrode substrate are bonded, and the process margin is reduced. Since wide anodic bonding can be performed, process costs including yield can be significantly reduced.

In the method of manufacturing an electrostatic actuator according to the ninth aspect, in forming the gap, the first gap forming step may be further performed at least by the first gap width formed in the first gap forming step. Step of forming a wide second gap, further, since a step-shaped gap having two or more gap lengths is formed in the step of forming a larger gap, the step-shaped gap is well controlled,
Furthermore, since it can be formed with good reproducibility, the variation in the gap shape can be reduced.

In an ink jet head using the electrostatic actuator according to the present invention,
Since the liquid chamber is formed using a part of the diaphragm in order to eject ink, not only can an ink jet head with low power consumption be manufactured, but also an ink jet head having high-density nozzles can be easily realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a part of an upper surface showing an example of an electrostatic actuator according to the present invention.

FIG. 2 is a cross-sectional configuration diagram of a main part of the electrostatic actuator illustrated in FIG. 1;

FIG. 3 is a diagram showing a part of the upper surface showing another example of the electrostatic actuator according to the present invention.

FIG. 4 is a sectional view showing a principal part of the electrostatic actuator shown in FIG. 3;

FIG. 5 is a cross-sectional view of a main part for describing an operation of the electrostatic actuator according to the present invention.

FIG. 6 is a diagram showing a relationship between an attractive force F by an electrostatic force and a gap taper angle.

FIG. 7 is a diagram for explaining an example of a manufacturing process of the electrostatic actuator according to the present invention.

FIG. 8 is a diagram for explaining another manufacturing process of the electrostatic actuator according to the present invention.

FIG. 9 is a sectional view of an essential part for explaining an example in which the electrostatic actuator according to the present invention is used for an ink jet head.

FIG. 10 is a sectional view of an essential part for explaining an embodiment in which the electrostatic actuator according to the present invention is applied to an ink jet head.

FIG. 11 is a sectional view of a principal part for explaining another embodiment in which the electrostatic actuator according to the present invention is applied to an ink jet head.

FIG. 12 is a sectional view of a principal part for explaining still another embodiment in which the electrostatic actuator according to the present invention is applied to an ink jet head.

[Explanation of symbols]

11, 21, 31 ... substrate, 12, 22, 32 ... insulating member, 13, 23, 33 ... individual electrode, 14, 24, 34,
55 ': insulating film; 15, 25, 35, 46 ... diaphragm.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Goichi Otaka 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Eiichi Ota 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (72) Inventor Makoto Tanaka 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2C057 AF24 AF39 AF52 AF55 AF93 AG12 AG53 AG54 AG93 AP02 AP24 AQ02 BA04 BA15 CA01

Claims (10)

[Claims] 1. A vibration plate and an individual electrode provided on an electrode substrate joined to the diaphragm with a gap interposed therebetween, wherein a driving voltage is applied between the diaphragm and the individual electrode. And an electrostatic actuator that deforms the vibrating plate by electrostatic force, wherein a gap that forms a gap between the vibrating plate and the individual electrodes, each of which has a rectangular shape with short sides and long sides, is formed. An electrostatic actuator having a gap, wherein a short side of the gap is concave, and is formed in a step shape having at least two or more gap lengths. 2. The electrostatic actuator according to claim 1, wherein a long side of the gap has a concave shape, and
An electrostatic actuator characterized by being formed in a step shape having at least two gap lengths. 3. The electrostatic actuator according to claim 1, wherein the individual electrode is formed in the concave and step-shaped gap so as to cover a step. Electric actuator. 4. The electrostatic actuator according to claim 3, wherein an insulator is formed on the individual electrode. 5. The electrostatic actuator according to claim 4, wherein the insulator formed on the individual electrode is a silicon oxide film. 6. The electrostatic actuator according to claim 4, wherein the insulating film formed on the individual electrode is a silicon nitride film. 7. The electrostatic actuator according to claim 1, wherein the electrode substrate on which the individual electrodes are formed is a silicon wafer. 8. The electrostatic actuator according to claim 1, wherein the electrode substrate on which the individual electrodes are formed is made of borosilicate glass. 9. The method for manufacturing an electrostatic actuator according to claim 1, wherein a gap between the diaphragm formed of the rectangle having the short side and the long side and the individual electrode is formed. In the method for forming a gap being formed, a first gap forming step, and further, at least a second gap forming a second gap wider than the first gap width formed in the first gap forming step Forming a gap length of two or more steps in a step-like manner. 10. An ink jet head using the electrostatic actuator according to claim 1, wherein a liquid chamber is formed using a part of the vibration plate in order to discharge ink. An ink jet head, characterized in that: