JP3520728B2 - Ink jet recording head and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head and a method of manufacturing the same, and more particularly, to an ink cavity containing ink by vibrating or fluctuating a vibrating plate by applying electric energy to a piezoelectric element. The present invention relates to an ink jet recording head that ejects and ejects ink by applying pressure to the ink, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, an element made of lead zirconate titanate (hereinafter referred to as "PZT") has been used as a drive source for ejecting ink, that is, an element for converting electrical energy into mechanical energy. There is an ink jet type recording head.

This ink jet recording head is generally a substrate having a large number of individual ink passages (ink cavities, ink pools, etc.), and a diaphragm attached to the substrate so as to cover all the individual ink passages. A piezoelectric element including a lower electrode, a PZT film, and an upper electrode is formed in each portion of the vibration plate corresponding to the individual ink passage.

In this ink jet type recording head, the ink contained in the individual ink passage is ejected by the pressure generated by vibrating or displacing the diaphragm by applying an electric field to the piezoelectric element. It is configured so that it can be pushed out or ejected from the hole (ink ejection port) of the nozzle plate provided on the side.

In this ink jet recording head, a silicon wafer (hereinafter referred to as "wafer") is used as a substrate.
Is used, first, after patterning is performed to form a plurality of piezoelectric elements on the wafer, the wafer is divided into chips.

In this ink jet recording head, the piezoelectric element is usually formed by the following steps. That is, a lower electrode forming film, a PZT film and an upper electrode forming film made of platinum or the like are formed on a wafer which is a substrate through a silicon oxide film (thermal oxide film).

Next, a photoresist is coated on the upper electrode forming region on the upper electrode forming film and patterned, and the upper electrode forming film and the PZT film are etched using this as a mask. Then, a photoresist is formed in the lower electrode formation region of this substrate and patterned, and the lower electrode formation film is etched using this as a mask.

When a metal having low reactivity such as platinum is used as a material for forming the lower electrode forming film, the upper electrode forming film and the PZT film are once over-etched. There is a problem that the electrode material is redeposited (remains as a residue), which causes a leak between electrodes or causes a short circuit. Therefore,
In order to prevent this redeposition, this photoresist is formed in a trapezoidal shape whose side wall is tapered.

In the structure of the ink jet type recording head,
If the partition wall of the ink cavity does not have sufficient rigidity, when the ink cavity is pressed, the partition wall is bent and a problem arises in that sufficient pressure for ejecting ink cannot be obtained. In addition, as a result of the pressure being easily propagated to the adjacent ink cavities, there is a problem that the characteristics of ejecting ink are changed depending on ON / OFF of the adjacent element.

Therefore, in order to increase the rigidity of the partition walls of the ink cavity, the thickness of the wafer is reduced.

[0011]

However, as a result of diligent study by the present inventor, when the thickness of the wafer is reduced,
When the lower electrode forming film is formed on the wafer, the wafer is likely to be warped or distorted due to the difference between the thermal expansion coefficient of the wafer and the thermal expansion coefficient of the lower electrode forming film. Thus, when the wafer is warped or distorted, the patterning mask (photoresist or the like) for forming the upper electrode, the PZT film, and the lower electrode cannot be formed in a uniform shape, and each piezoelectric body is not formed. There is a problem that the reproducibility of the element shape or the accuracy is reduced. Further, as described above, there is a problem that it is difficult to prevent redeposition (occurrence of residue) due to the shape of the photoresist.

On the other hand, residual stress exists in the layers laminated on the substrate, and the residual stress may cause warping or distortion of the wafer. Therefore, it is further necessary to perform patterning of elements with high accuracy. There is room for improvement.

Therefore, according to the present invention, the warp and distortion of the wafer are prevented, the patterning of the element is performed with good reproducibility, and
It is an object of the present invention to provide an ink jet recording head which is performed with high accuracy.

Another object of the present invention is to provide an ink jet recording head in which desired elements are formed and which is easy to fit a chip separated from a wafer onto a substrate. Still another object is to provide an ink jet recording head having improved adhesion between a nozzle plate and a substrate having an ink cavity formed therein. Still another object of the present invention is to provide a method for manufacturing these ink jet recording heads.

[0015]

In order to achieve this object, the present invention provides a substrate having individual ink passages formed therein, and piezoelectric elements formed at respective portions corresponding to the individual ink passages. In an ink jet recording head provided with an ink ejecting unit for ejecting ink in the individual ink passage, an intermediate film having a thermal expansion characteristic similar to that of a lower electrode forming the piezoelectric element is provided on the ink ejecting unit side. It is characterized in that it is provided in.

[0016]

In the ink jet recording head having such a structure, since the films having the same thermal expansion characteristics are formed on both surfaces of the substrate, the lower electrode forming material and the substrate have different thermal expansion characteristics. However, the warp and distortion of the substrate caused by this are canceled by the intermediate film and the lower electrode.

That is, the thermal expansion characteristics of the films formed on the first surface side and the second surface side of the substrate are determined by the physical deformation of the substrate such as warpage, distortion, or twist on the substrate. It is set within the same range until the pattern error of the element configuration and the pattern accuracy are not substantially affected.

In the present invention, having the same degree of thermal expansion property means that the difference in the coefficient of thermal expansion between the films or layers to be compared is within ± 10%.

Here, one aspect of the thermal expansion characteristic is the thermal expansion coefficient. In particular, when the film thickness of the intermediate film described above is approximately the same as the film thickness of the lower electrode, the intermediate film may be made of a material having substantially the same thermal expansion coefficient as that of the lower electrode. on the other hand,
Another aspect of thermal expansion properties is the product of the coefficient of thermal expansion times the thickness of the film of interest. That is, the product of the film thickness of the lower electrode and its coefficient of thermal expansion should be approximately the same as that of the lower electrode. In short, in the present invention, the thermal expansion property is a means or element for balancing the compressive stress of the film or layer to be compared. Therefore, it is not limited to the above-mentioned two aspects. The elements and means of the thermal expansion characteristics suitable for the composition and form of the film or layer may be selected or designed appropriately.

More preferably, the intermediate film is made of a lower electrode forming material. By doing so, in addition to the above advantages, the adhesiveness between the substrate and the nozzle plate is also improved.
Further, it is preferable that the lower electrode and the intermediate film are formed to have the same film thickness.

According to the present invention, the piezoelectric element formed on the first surface of the substrate, the ink cavity formed on the substrate at a position corresponding to the piezoelectric element, and the first surface of the substrate. An ink jet recording head comprising: a nozzle means formed on a second surface opposite to the first surface, the nozzle means having an ejection port for ejecting the ink contained in the ink cavity; The present invention provides an inkjet recording head in which the substrate is exposed on the outer periphery of the surface.

A step may be formed on the outer peripheral portion of the chip. With such a structure, the exposed portion or the stepped portion of the substrate can be engaged with the predetermined position of the base body on which the substrate is fitted, and the base substrate can be easily fitted on the base body.

Further, the present invention provides an ink jet recording line head in which a plurality of chips constituting the ink jet recording head are arranged side by side. By doing so, high resolution is achieved, and it is possible to easily deal with dynamic printing.

Further, according to the present invention, a piezoelectric element composed of a lower electrode, a piezoelectric film and an upper electrode formed on the first surface of the substrate and a position corresponding to the piezoelectric element on the substrate are formed. An ink cavity; and a nozzle means having a discharge port formed on the second surface of the substrate opposite to the first surface, for discharging the ink contained in the ink cavity,
A method for manufacturing an ink jet recording head, comprising: an intermediate film having a lower electrode forming film on a first surface of a substrate and a thermal expansion characteristic similar to that of the lower electrode forming film on a second surface. Forming a film, forming a piezoelectric film and an upper electrode on the lower electrode forming film, and then patterning the lower electrode forming film to form a piezoelectric element, and forming the intermediate layer. A method for manufacturing an ink jet recording head, comprising the steps of forming an ink cavity in the formed substrate and providing a nozzle means on the substrate in which the ink cavity is formed through the intermediate film. Is.

According to this method, the flatness of the substrate is improved after the films having the same thermal expansion characteristics are formed on both surfaces of the substrate, that is, the films cancel each other out the warp and the strain of the substrate. After that, patterning for forming a piezoelectric element is performed. Therefore, uniform and highly accurate patterning can be performed.

Further, according to the present invention, the piezoelectric element composed of the lower electrode, the piezoelectric film and the upper electrode formed on the first surface of the substrate, and the piezoelectric element formed on the substrate at a position corresponding to the piezoelectric element. Ink jet recording comprising an ink cavity and a nozzle means having a second surface opposite to the first surface of the substrate and having an ejection port for ejecting the contained ink in the ink cavity. A method for manufacturing a pad, comprising the steps of sequentially forming a lower electrode forming film, a piezoelectric film forming film and an upper electrode forming film on a substrate, and the upper electrode forming film and the piezoelectric film forming film. And a step of dividing the lower electrode forming film into chips, and patterning the divided upper electrode forming film, piezoelectric film forming film and lower electrode forming film into chip units to form piezoelectric elements. An ink jet comprising a step of There is provided a manufacturing method of the recording head.

In the present invention, the "chip" means
A unit in which a plurality of piezoelectric elements and ink cavities are formed and which functions as an ink jet recording head.

According to this method, the film for forming the upper electrode, the film for forming the piezoelectric film, and the film for forming the lower electrode are divided into chip units to reduce the warpage and distortion generated on the substrate, and then the piezoelectric element. Patterning is performed to form the. Therefore, uniform and highly accurate patterning can be performed.

Further, according to the present invention, since the warp and strain of the substrate are largely due to the residual stress of the piezoelectric element, a film for canceling or balancing the stress is formed on the piezoelectric element side of the ink jet recording head. Characterize. Since the warp and strain of the substrate largely depend on the tensile stress due to the lower electrode in the piezoelectric element, particularly platinum, the ink jet recording head of the present invention is particularly suitable for a film having a compressive stress on the piezoelectric element side of the substrate. Is formed to cancel this tensile stress.

One embodiment of the present invention is characterized in that a metal oxide film having a compressive stress commensurate with the tensile stress of the piezoelectric element is provided on the piezoelectric element side of the ink jet recording head. It is a thing.

Another embodiment of the present invention is characterized in that the tensile stress and the compressive stress are balanced to such an extent that no warp or strain is generated in the substrate.

In still another embodiment of the present invention, in an ink jet recording head, a film having a compressive stress is formed on the piezoelectric element side so as to exert the compressive stress as a whole, and also on the ink ejecting side. It is characterized in that a film exhibiting a compressive stress is formed to generate a compressive stress having a value which is balanced on both surfaces of the substrate, that is, which does not cause warping or distortion of the substrate. This configuration is achieved by forming the film thickness of the metal oxide film on the piezoelectric element side to a value larger than the film thickness of the metal oxide film on the ink cavity side. In a typical example, the former film thickness is approximately twice the latter film thickness.

The balance of the compressive force on both sides of the substrate can be achieved by forming a metal oxide film on each of the piezoelectric element side and the ink cavity side and adjusting the film thickness and material of both sides appropriately. When the same metal oxide film is formed on both surface sides of the substrate, as described above, the thickness of the metal oxide on the side where the lower electrode having the tensile stress is formed is the same as that of the metal oxide on the ink cavity side. It becomes larger than the film thickness.

The preferable range (ratio) of film thickness is as follows.

Lower electrode: 0.3-0.9 PZT: 0.5-3.0 Upper electrode: 0.05-0.2 Silicon oxide film (lower electrode side): 1.0-2.0 Silicon oxide Film (ink cavity side): 0.5-1.
5 (The above unit is μm.) The oxide film is preferably a silicon oxide film (silicon dioxide). In particular, the silicon oxide film formed by the thermal oxidation method is effective because it becomes a dense crystal.
Alternatively, zirconium dioxide, tantalum oxide, or iridium oxide may be used. Further, it is possible to provide these zirconium dioxides and the like on the piezoelectric element side and stack them on the silicon oxide film to appropriately adjust the compressive stress.

A more specific form of the present invention is the first substrate.
A piezoelectric element formed on the surface of the substrate, and an ink cavity formed on the substrate at a position corresponding to the piezoelectric element;
An ink jet recording head, comprising: a nozzle unit having a discharge port for discharging ink contained in the ink cavity, the nozzle unit being formed on a second surface of the substrate opposite to the first surface. The thickness of the first oxide film between the piezoelectric element and the substrate is larger than the thickness of the second oxide film between the nozzle means and the substrate. It is characterized by.

The ink jet recording head according to the present invention is characterized in that the compressive stress on the piezoelectric element side and the compressive stress on the ink ejecting side are balanced so that the substrate does not warp or distort. Therefore, the patterning of the device can be performed with high accuracy.

In the present invention, the nozzle means means
For example, it is realized by a member forming an ink ejection port.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view showing an example of an ink jet recording head. FIG. 1 shows a part of the ink jet recording head. In this ink jet recording head, the piezoelectric element 20 formed on the first surface of the silicon substrate 11 via the silicon oxide film 12 and the ink formed on the silicon substrate 11 at a position corresponding to the piezoelectric element 20. The cavity 18, the intermediate film 17 formed on the second surface of the silicon substrate 11 opposite to the first surface via the silicon oxide film 13, and the intermediate film 17 formed on the intermediate film 17 and inside the ink cavity 18. And a nozzle plate 26 having an ejection port 25 for ejecting the ink accommodated therein.

The piezoelectric element 20 has a structure in which a lower electrode 14, a PZT film 15 and an upper electrode 16 are sequentially laminated from the silicon substrate 11 side. In this embodiment, platinum is used as the lower electrode forming material and the upper electrode forming material. The intermediate film 17 was made of the same material as the lower electrode forming material, that is, platinum. This intermediate film 17
Has the same film thickness as the lower electrode 14. The nozzle plate 26 is made of stainless steel.

In the ink jet type recording head having this structure, the lower electrode 14 is provided on the first surface of the silicon substrate 11.
On the second surface, the intermediate film 1 made of the same material as the lower electrode 14 is formed.
7, the lower electrode 14 and the silicon substrate 1 are formed.
Even if the coefficient of thermal expansion is different from that of No. 1, the warp and strain of the silicon substrate 11 caused thereby can be canceled by the intermediate film 17 and the lower electrode 14. Therefore, the piezoelectric element 20 having a uniform shape can be formed, redeposition (residual) does not occur, and an inkjet recording head with high accuracy and high reliability can be provided.

Further, the presence of the intermediate film 17 can improve the adhesiveness between the silicon substrate 11 on which the silicon oxide film 13 is formed and the nozzle plate 26.

Next, a method of manufacturing an ink jet recording head having this structure will be described with reference to FIG. First, in the step shown in FIG. 2A, the silicon oxide film 1 is formed on the first surface of the silicon substrate 11 by the thermal oxidation method.
2, a silicon oxide film 13 is formed on the second surface opposite to the first surface. Next, an intermediate film 17 made of platinum is formed on the silicon oxide film 13 by a thin film forming method such as a sputtering film forming method.

Next, in the step shown in FIG. 2B, the lower electrode forming film 1 made of platinum is formed on the silicon oxide film 12.
4A is formed. The lower electrode forming film 14A was formed to have the same film thickness as the intermediate film 17. By this step, platinum films are formed on both surfaces of the silicon substrate 11, so that even if the platinum and the silicon substrate have different thermal expansion coefficients, the silicon substrate 11 is prevented from being warped or strained. be able to.

Next, a PZT film 15A is formed on the lower electrode forming film 14A by a film forming method such as a sol-gel method, a high frequency sputtering film forming method and a CVD method. Then, the silicon substrate 11 on which these films are formed is heat-treated.

Next, in the step shown in FIG. 2C, PZ
The upper electrode forming film 16A is formed on the T film 15A by a thin film forming method such as a sputtering film forming method. Next, FIG.
In the step shown in (4), the photoresist film 21 is formed in the upper electrode formation region on the upper electrode formation film 16A.

On the other hand, a photoresist pattern 22 is formed on a region other than the ink cavity forming region on the intermediate film 17. The photoresist 21 prevents the material once etched from being redeposited when the lower electrode forming film 14A is patterned in a later step.
The side surface was tapered so as to spread toward the silicon substrate side.

Next, in the step shown in FIG. 2 (5), the upper electrode forming film 16A is formed using the photoresist 21 as a mask.
And the PZT film 15A is etched to form the upper electrode 16 and the PZT film 15. Then photoresist 2
Remove 1.

The photolithography (patterning) process performed in FIGS. 2 (4) and 2 (5) is performed by the silicon substrate 1
It can be performed without warping or distortion. Therefore, the photoresists 21 and 22 can be formed on the wafer surface with good reproducibility and in a uniform shape, and good etching can be performed while preventing redeposition.

Next, in the step shown in FIG. 2 (6), the lower electrode forming film 1 on which the upper electrode 16 and the PZT film 15 are formed.
In the lower electrode formation region on 4A, a photoresist 23 having a uniform shape is formed as described above.

Next, in the step shown in FIG. 2 (7), the lower electrode forming film 14A is etched by using the photoresist 23 as a mask to form the lower electrode 14. In this way
The piezoelectric element 20 including the lower electrode 14, the PZT film 15 and the upper electrode 16 was formed on the silicon substrate 11 via the silicon oxide film 12.

Next, in the step shown in FIG. 2 (8), the intermediate film 17 is etched using the photoresist 22 as a mask. Next, in the step shown in FIG.
The silicon oxide film 13 and the silicon substrate 11 are etched using the intermediate film 17 patterned in the step shown in FIG. 3 as a mask to form an ink cavity 18.

After that, the nozzle plate 26 is inserted through the intermediate film 17.
By carrying out a desired process such as provision of the above, an ink jet type recording head is completed. Although platinum is used as the lower electrode forming material and the intermediate film forming material here, the material is not limited to this, and iridium, platinum iridium alloy, platinum palladium alloy, or the like may be used.

Although the case where the lower electrode 14 and the intermediate film 17 are made of the same material has been described, the present invention is not limited to this, and the intermediate film 17 has a thermal expansion coefficient similar to that of the lower electrode forming material. Other materials, the material may be different from that of the lower electrode forming material.

(Second Embodiment) Next, a second embodiment according to the present invention will be described with reference to the drawings. In this embodiment, the same members as those of the ink jet recording head described in the first embodiment are designated by the same reference numerals, and detailed description thereof may be omitted.

FIG. 3 is a sectional view showing a part of the ink jet recording head according to the second embodiment, FIG. 4 is a sectional view showing a manufacturing process of the ink jet recording head shown in FIG. 3, and FIG. 3 is an exploded view of the ink jet recording head according to Embodiment 2. FIG.

In the ink jet recording head shown in FIG. 3, the silicon oxide film 1 is formed on the first surface of the silicon substrate 11.
2, the ink cavity 18 formed in the silicon substrate 11 at a position corresponding to the piezoelectric element 20, and the second surface of the silicon substrate 11 opposite to the first surface. A nozzle plate 26 formed through the silicon oxide film 13 and having an ejection port 25 for ejecting the ink contained in the ink cavity 18,
It is configured with.

The chip outer peripheral portion on the first surface of the silicon substrate 11 is exposed without being covered with the silicon oxide film 12, and a step portion 19 is formed in this portion. As shown in FIG. 5, the step portion 19 is formed by attaching the nozzle plate 26 to the silicon substrate 11 on which the above-mentioned elements are formed, and then when fitting the nozzle plate 26 to the base body 90, the engaging portion 91 of the base body 90. Engage with. By the step portion 19, the silicon substrate 11 is simply and surely fixed to the base body 90. Reference numeral 98 is a wiring board for giving a signal to the piezoelectric element 20.

Next, a method of manufacturing an ink jet recording head having this structure will be described with reference to FIG. First, in the step shown in FIG. 4A, the silicon oxide film 12 is formed on the first surface and the silicon oxide film 13 is formed on the second surface of the wafer-shaped silicon substrate 11 by the same method as in the first embodiment. Formed, and further on the silicon oxide film 12,
The lower electrode forming film 14A and the PZT film 15A are formed.

Next, in the step shown in FIG.
An upper electrode forming film 16A is formed on the PZT film 15A obtained in the step shown in (1). Next, in a step shown in FIG. 4C, a photoresist 41 for dividing the silicon substrate 11 on which the above-described film is formed into chips is formed on the upper electrode forming film 16A.

Next, in the step shown in FIG. 4D, the upper electrode forming film 16 is formed using the photoresist 41 as a mask.
A, the PZT film 15A and the lower electrode forming film 14A are etched and divided into chip units. In this way, the lower electrode forming films 14B and P divided into chip units are formed.
The ZT film 15B and the upper electrode forming film 16B are obtained.

By this step, since the lower electrode forming film 14A which causes the warp or strain in the silicon substrate 11 is divided into chips, it is possible to suppress the warp or strain in the silicon substrate 11. Further, since the photolithography process performed at the time of dividing this chip unit does not require accuracy as compared with the above-described patterning, even if the silicon substrate 11 has some warp or distortion, it does not cause a particular problem. .

FIG. 4 (5) and subsequent drawings are enlarged sectional views of one chip obtained in the step shown in FIG. 4 (4). In the step shown in FIG. 4 (6), a photoresist 42 is formed in the upper electrode formation region on the upper electrode formation film 16B.

On the other hand, a photoresist 43 is formed on a region other than the ink cavity forming region on the silicon oxide film 13. The photoresist 42 prevents the material that has been once etched from being redeposited when the lower electrode forming film 14B is patterned in a later step.
The side surface was tapered so as to spread toward the silicon substrate side.

Next, in the step shown in FIG. 4 (7), the upper electrode forming film 16B is formed using the photoresist 42 as a mask.
The PZT film 15B and the PZT film 15B are etched by ion milling to form the pattern of the upper electrode 16 and the PZT film 15. At this time, the silicon oxide film 12 exposed on the outer periphery of the chip is also etched at the same time, and the silicon substrate 11 thereunder is also etched.
1 is exposed and a step 19 is formed.

Then, the photoresist 42 is removed.
Thus, the lower electrode 14, the PZT film 15, and the upper electrode 1 are formed on the silicon substrate 11 with the silicon oxide film 12 interposed therebetween.
A piezoelectric element 20 composed of 6 was formed.

The photolithography process performed in this step can be performed in a state where the silicon substrate 11 is not warped or distorted by dividing the chip unit. Therefore, the photoresists 42 and 43 can be formed in a uniform shape with good reproducibility, and good etching can be performed while preventing redeposition.

Next, in the step shown in FIG. 4 (8), after the silicon oxide film 13 is patterned using the photoresist 43 as a mask, the silicon substrate 11 is etched using the patterned silicon oxide film 13 as a mask to form an ink cavity. 18 is formed.

Thereafter, desired steps such as providing the nozzle plate 26 at a predetermined position are performed to complete the ink jet recording head. Although the first and second embodiments have described the case where the PZT-based material is used as the piezoelectric film,
You may use what added other metal oxides, such as niobic acid, nickel oxide, and magnesium oxide, to this system, and materials other than PZT system.

FIG. 9 shows an example of a nozzle unit which replaces the nozzle plate 26 for the substrate 11 (the pressure chamber substrate forming the ink cavity 18 which becomes the pressure chamber) of FIG. More specifically, FIG. 9 shows a layered structure of the pressure chamber substrate 100 and the nozzle unit. Here, a type in which the common flow path of ink is formed on the reservoir chamber forming substrate instead of the pressure chamber substrate is shown.

The nozzle unit 2 includes a communication passage substrate 260 having a communication passage 270 formed therein, an ink supply passage forming substrate 240 having a plurality of ink supply holes 250, a reservoir chamber forming substrate 220 having an ink reservoir chamber 230, and a plurality of reservoir chamber forming substrates 220. The nozzle forming substrate 200 having the nozzles 210 is used. The pressure chamber substrate 100 and the nozzle unit 2 are joined by an adhesive. The ink reservoir chamber 230 has a function similar to that of the common flow channel 112 in FIG.

For the sake of simplification, FIG. 2 shows a structural diagram in which the nozzles are arranged in 4 rows and 4 columns, but in reality,
The number of nozzles and the number of rows are not limited, and any combination may be used. In FIG. 5, the substrate 11 is provided with pressure chambers (ink cavities) in a plurality of strips, and a common channel 112 for supplying ink to all the pressure chambers is provided. Each ink cavity is separated by a side wall 18A.

(Third Embodiment) Next, a third embodiment according to the present invention will be described with reference to the drawings. In the third embodiment, a line head in which a plurality of chips obtained in the second embodiment are installed on a line will be described. Since this chip has the same structure as that obtained in the second embodiment, the same reference numerals are given and detailed description thereof will be omitted.

This line head, as shown in FIG.
The base 91 has a structure in which four chips are arranged. That is, it has a structure in which four inkjet recording heads shown in FIG. 5 are arranged on a line.

Black ink, cyan ink, magenta ink, and yellow ink are contained in the ink cavities 18 of the line head, respectively. This supports force printing.

In the third embodiment, the case where the chip obtained in the second embodiment is used has been described, but the present invention is not limited to this, and the ink jet recording according to the present invention such as the chip obtained in the first embodiment is used. Needless to say, chips having other structures may be used as long as they are chips constituting the head. Further, the number of chips to be installed is not limited to four and can be set arbitrarily.

(Embodiment 4) FIG. 7 is a sectional view of an ink jet recording head provided with a film having a compressive stress for relaxing, relieving or compensating the tensile stress generated by the lower electrode of the piezoelectric element. is there. In this embodiment,
It is manufactured by the process described in FIG. 2 described above. In this embodiment, the same components as those of the embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted.

This ink jet recording head is shown in FIG.
Similar to that of the above, the silicon oxide films 12 and 13 are formed on the piezoelectric element 20 side and the ink cavity 18 side of the substrate 11, respectively.
Is equipped with. The nozzle plate 26 and the silicon oxide film 1
The intermediate film 17 between 3 and 3 is omitted.

The piezoelectric element 20 composed of the upper electrode 16, the PZT film 15 and the lower electrode film 14 has a tensile stress as a whole. Each of these films shows a tendency to have a tensile stress, and since the shrinkage ratio of the lower electrode is large during the high temperature annealing during the heat treatment of PZT, and the upper electrode is not formed during the annealing, it is close. The influence of the tensile stress of the lower electrode largely affects the flatness of the substrate.

On the other hand, the silicon oxide film 12 between the lower electrode 14 and the silicon substrate 11 and the silicon oxide film 13 between the substrate, the silicon substrate 11 and the nozzle plate 26.
Has a compressive stress. The following relations are set to show the relation of stress of these films.

A + B = C A: Tensile stress of piezoelectric element (+) B: Compressive stress of silicon oxide film 12 (-) C: Compressive stress of silicon oxide film 13 (-) By setting this relationship, Since the tensile stress on the piezoelectric element side is canceled by the compressive stress of the silicon oxide film 12 and the compressive stress on the piezoelectric element side and the ink cavity side of the silicon wafer are balanced, PZ
The wafer does not warp even after the heat treatment of T, and the patterning after (5) in FIG. 2 can be performed with high accuracy.

The silicon oxide film is formed by the thermal oxidation method as in the case of FIG. The stress relationship is realized by appropriately adjusting the film thickness of the silicon oxide film. The piezoelectric element side of the substrate overcomes the tensile stress of the piezoelectric element to generate compressive stress, and the piezoelectric element side of the substrate and the ink cavity side compressive stress are balanced. The thickness of the silicon oxide film 12 is larger than the thickness of the silicon oxide film 13 on the ink cavity side, and the silicon oxide film on the piezoelectric element side generates a larger value of compressive stress. Is formed in.

The film thickness of these silicon oxide films is appropriately determined in consideration of the film thickness of the piezoelectric element and the like.

FIG. 8 is a diagram corresponding to (3) in FIG. 2. In this embodiment, the silicon oxide film 12 on the piezoelectric element side has a value almost twice that of the silicon oxide film 13 on the ink cavity side. It is formed with a film thickness. The silicon oxide films 12 and 13 are formed by separate steps,
By making the thermal oxidation time for forming the silicon oxide film of reference numeral 12 longer than that of the silicon oxide film of reference numeral 13, the silicon oxide film of reference numeral 12 can be formed thicker than that of reference numeral 13. In the case of FIG. 8, since compressive stresses that are balanced are formed on the upper and lower surfaces of the silicon substrate, it is difficult for the substrate to undergo physical deformation such as warpage, distortion, or twisting.

If the silicon oxide film 12 on the piezoelectric element side is approximately balanced with the tensile stress of the piezoelectric element,
The silicon oxide film 13 on the ink cavity side can be omitted. Further, instead of or in addition to the silicon oxide film, another metal oxide film such as ZrO ₂ , Ta is used.
₂ O ₅ and IrO _x are formed on the silicon oxide film 12,
The compressive stress may be adjusted.

As in the embodiment of FIG. 1, the intermediate film 17
Warp of the substrate by combining two or more of providing the substrate 11 and dividing into chips as in the embodiment of FIG. 4 and forming a film for stress relaxation as shown in FIG. Highly accurate patterning can be achieved by effectively preventing or mitigating physical deformation such as. As a result, it is possible to obtain an ink jet recording head in which leakage between electrodes and short circuit are prevented.

The ink ejecting means and the nozzle means are not particularly limited, and may be those using a nozzle plate or nozzle units as shown in FIG.

[0090]

As described above, according to the present invention, a photolithography process for forming a piezoelectric element can be performed on a flat substrate. As a result, it is possible to perform patterning of the element with high accuracy, prevent leakage or short circuit between the electrodes, and provide a highly reliable inkjet recording head.

Further, it is easy to fit the chip on which the desired element is formed on the substrate, and it is also possible to improve the adhesiveness between the substrate on which the ink cavity is formed and the nozzle plate.

If a plurality of chips according to the present invention are arranged side by side, they can be used as a line head. As a result, higher resolution is achieved, and color printing can be easily supported.

[Brief description of drawings]

FIG. 1 is a sectional view showing a part of an ink jet recording head according to a first embodiment of the invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the ink jet recording head shown in FIG.

FIG. 3 is a sectional view showing a part of an ink jet recording head according to a second embodiment of the invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of the ink jet recording head shown in FIG.

FIG. 5 is an exploded assembly view of the ink jet recording head according to the second embodiment of the present invention.

FIG. 6 is a plan view of an ink jet recording line head according to a third embodiment of the invention.

FIG. 7 is a sectional view of an ink jet recording line head according to a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view showing one of the steps on the way.

FIG. 9 is an exploded perspective view of a nozzle unit.

[Explanation of symbols]

11 Silicon substrate 12, 13 Silicon oxide film 14 Lower electrode 15 PZT film 16 Upper electrode 17 Intermediate film 18 ink cavities 19 step 20 Piezoelectric element

Claims (9)

(57) [Claims] 1. A piezoelectric element formed on a first surface of a substrate, an ink cavity formed at a position corresponding to the piezoelectric element on the substrate, and an ink cavity on a side opposite to the first surface of the substrate. Nozzle means formed on the second surface and having an ejection port for ejecting the ink contained in the ink cavity;
An ink jet recording head comprising: an intermediate film having a thermal expansion characteristic similar to that of a lower electrode constituting the piezoelectric element, between the second surface of the substrate and the nozzle means. Inkjet recording head. 2. The ink jet recording head according to claim 1, wherein the intermediate film is made of a lower electrode forming material. 3. The ink jet recording head according to claim 1, wherein the film thickness of the lower electrode is equal to the film thickness of the intermediate film. 4. The ink jet recording head according to claim 1, wherein a film for canceling stress of the piezoelectric element is formed between the substrate and the lower electrode. 5. The film for canceling the stress is made of a metal oxide, and the film thickness of this metal oxide film on the piezoelectric element side is formed to be larger than the film thickness of this metal oxide film on the ink ejection side. The ink jet recording head according to claim 4. 6. The ink jet recording head according to claim 1, wherein the substrate is exposed at the outer peripheral portion of the chip on the first surface side of the substrate. 7. An ink jet recording line head in which a plurality of chips constituting the ink jet recording head according to any one of claims 1 to 6 are arranged side by side. 8. A piezoelectric element composed of a lower electrode, a piezoelectric film and an upper electrode formed on a first surface of a substrate, and an ink cavity formed at a position of the substrate corresponding to the piezoelectric element. Manufacturing of an ink jet recording head, comprising: a nozzle means formed on a second surface of the substrate opposite to the first surface and having an ejection port for ejecting ink contained in the ink cavity. A method of sequentially forming a lower electrode forming film, a piezoelectric film forming film and an upper electrode forming film on a substrate, and the upper electrode forming film, the piezoelectric film forming film and the lower electrode forming method. Dividing the working film into chips, patterning the upper electrode forming film, the piezoelectric film forming film and the lower electrode forming film, which are divided into the chip units, to form a piezoelectric element, Inkjet recording head equipped with Manufacturing method. 9. A piezoelectric element formed on a first surface of a substrate, an ink cavity formed at a position corresponding to the piezoelectric element on the substrate, and an ink cavity on a side opposite to the first surface of the substrate. Nozzle means formed on the second surface and having an ejection port for ejecting the ink contained in the ink cavity;
An ink jet recording head comprising: a first oxide film between the piezoelectric element and the substrate, the thickness of the first oxide film being greater than the thickness of the second oxide film between the nozzle means and the substrate. An ink jet recording head characterized by being formed so as to have a large film thickness.