JP3473611B2 - Manufacturing method of liquid jet head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid jet head which is suitable for use in a liquid jet recording apparatus.

Generally, a liquid jet recording apparatus is provided with a liquid chamber, a nozzle, a liquid jet head having a liquid flow path, and an ink supply system, and by applying energy to the ink filled in the liquid chamber, Ink is pushed out into the liquid flow path, and as a result ink droplets are ejected from the nozzle,
As a result, the character / image information is recorded.

As means for applying energy to ink, means for pressurizing the liquid chamber using a piezoelectric element or means for heating ink in the liquid chamber using a heater are widely used.

The present invention particularly relates to a method for manufacturing a liquid jet head having means for pressurizing the liquid chamber by using a piezoelectric element.

[0005]

2. Description of the Related Art As a conventional technique of the liquid jet head as described above and the constituent elements related to the present invention, Japanese Patent Publication No.
No. 22790, JP-A-2-219654, US Pat. No. 4
No. 312008, Torii, etc. (Japanese Journal of Applied Physics, Vo1.30, No. 12)
B, December 1991, pp. 3562-3566),
There are those disclosed in JP-B-4-43435 and JP-A-3-124450.

In JP-B-62-22790, an electrode is formed on a substrate having a thin portion corresponding to the liquid chamber, and PZT is formed at the portion corresponding to the liquid chamber by a thin film forming method such as sputtering or printing. A method of manufacturing a liquid jet head, which forms a thin film, is disclosed.

In Japanese Patent Laid-Open No. 219654/1990, a liquid chamber and a liquid flow path are formed in a thin plate laminated on a semiconductor substrate provided with a nozzle, and a vibration plate laminated above the liquid chamber, and the above-mentioned diaphragm. A liquid jet head including a piezoelectric vibrator provided on the upper portion, and a nozzle are formed on a semiconductor substrate, a dry film is adhered on the semiconductor substrate, and a diaphragm, a lower electrode, a piezoelectric film, and an upper portion on the dry film. A method of manufacturing a liquid ejecting head is disclosed, which is formed by laminating an electrode and removing the dry film.

[0008] In US Pat. No. 4,311,008, a liquid jet head comprising a liquid channel formed on the surface of a substrate and a liquid chamber penetrating the substrate, the substrates being bonded to both surfaces of the substrate, and a piezoelectric body. Is disclosed.

Torii et al. (Japanese Journal of Applied Physics, Vo 1.30, No. 12B, 1
In December 991, pages 3562-3566), it is disclosed that platinum is used for the lower electrode of the PZT thin film.

In Japanese Patent Publication No. 4-43435, for a piezoelectric thin film, a base metal thin film and a platinum film are formed on an insulating thin film, and heat treatment is performed at a temperature at which the surface of the platinum film becomes uneven due to crystal grain growth. The method for forming an electrode is disclosed.

Further, Japanese Patent Laid-Open No. 3-124450, by the present inventors, discloses that a nozzle is formed from one surface of a single crystal silicon substrate and p-type single crystal silicon is formed on the other surface of the single crystal silicon substrate. A method of manufacturing a liquid jet head is disclosed in which a piezoelectric element is epitaxially grown, a p-type silicon layer and a single crystal silicon substrate are then etched, and a liquid chamber, a cantilever, and a double-sided vibrating plate are formed.

However, the above-mentioned conventional liquid jet head, its constituent elements, and their manufacturing method have the following problems to be solved.

In Japanese Patent Publication No. 62-22790, although the thickness of the constituent elements is not set in the claim, the PZT thickness tp in the embodiment is 50 μm and the diaphragm thickness tv is 50-.
It is set to about 100 μm, and tp + tv is 10 μm.
It is clear that no attention has been paid to areas below m. If tp + tv is about 100 μm, since this is still too thick, the amount of deformation of the vibrating plate when the voltage is applied to the PZT is small, and in order to deform the volume of the liquid chamber so that the liquid can be ejected, the same embodiment is used. As described above, a circular liquid chamber having a diameter of about 2 mm is required. At this time, if an attempt is made to improve the resolution, as shown in the same embodiment, a planar configuration of liquid chamber pitch> nozzle pitch is obtained, resulting in poor area efficiency. That is, the plane size of the liquid jet head having seven nozzles is 20 mm × 15.
It also becomes mm. If the number of nozzles is further increased, not only will the plane size dramatically increase, but the liquid flow path connecting the liquid chamber and the nozzle will also become longer, the flow path resistance will increase, and the speed of the liquid ejection operation will be extremely high. descend.

Furthermore, in the conventional example, a thin diaphragm is formed at a location corresponding to the liquid chamber, and PZT is formed on the thin diaphragm. According to the experiments conducted by the present inventors, the liquid chamber,
In the method of forming PZT after forming the diaphragm,
When the tp + tv is further reduced, for example, tp is 3 μ
When m and tv were set to 1 μm, phenomena such as sagging, wrinkling, and breakage of the diaphragm occurred during the manufacturing process, and the manufacturing yield of the liquid jet head was extremely reduced.

In Japanese Unexamined Patent Publication No. 2-219654, the nozzle is formed by processing a biaxial (100) Si substrate. For example, if the thickness is about 300 μm (10
0) When forming a nozzle by anisotropically etching a Si substrate, due to the angular relationship with the (111) plane with a slow etching rate, even if the nozzle size is 30 μm square, the opening on the opposite substrate surface is inevitable. Therefore, it becomes about 400 μm square. Therefore, the nozzle pitch does not become 400 μm or less, and the resolution is at most about 60 dpi (dot per inch). That is, it is impossible to increase the density of the nozzles of the liquid jet head.

Further, in the embodiment of the prior art, both the piezoelectric film and the upper and lower electrodes are formed larger than the liquid chamber. With such a structure, the piezoelectric film is efficiently vibrated when a voltage is applied to the piezoelectric film. It is impossible to deform the plate and eject the liquid. Further, it does not mention the size relationship and the thickness relationship of the piezoelectric film, the upper and lower electrodes, and the liquid chamber for efficiently ejecting the liquid.

[0017]

Further, in the embodiment of the prior art,
The Sio ₂ 1 layer is used for the diaphragm. SiO ₂ has a small Young's modulus of the order of 10 ¹⁰ N / m ² , and when a piezoelectric thin film is formed on top of it and the piezoelectric thin film is laterally deformed by applying a voltage, at the same time, it greatly expands laterally, and The deformation in the direction does not become so large. That is, S on the diaphragm
Even when the iO ₂ 1 layer is used, it is impossible to efficiently deform the vibrating plate and eject the liquid when a voltage is applied to the piezoelectric film. Further, it does not mention the characteristics of the diaphragm or the material for efficiently ejecting the liquid.

In US Pat. No. 4,312,008 it is stated in the claim that the piezoelectric crystal is mounted on a diaphragm. Further, in the examples, there is a description of mounting with indium-based solder, and it is obvious that a piezoelectric body having a thickness larger than that shown in JP-B-62-22790 is targeted. Therefore, as in the above Japanese Patent Publication No. 62-22790, the nozzle density cannot be increased substantially. Further, in this US Pat. No. 4,312,008, when the liquid flow path is formed by using anisotropic etching, the flow path shape is determined by both positions of the Si substrate, and it is impossible to freely select the shape. Met. For example, when (100) Si is used, the cross-sectional shape of the liquid channel is an inverted triangle, while when (110) Si is used, it is rectangular. If the liquid flow path is an inverted triangle, bubbles tend to accumulate, causing troubles. In addition, (11
0) When forming a rectangular liquid flow path in Si, it is difficult to control the depth, and the finished depth becomes non-uniform, so that the liquid ejection characteristics vary.

Further, undercut etching is inevitably generated at the contact point between the liquid flow path and the liquid chamber, which causes the contact shape to be varied, and the liquid ejection characteristic is not constant. In addition, in the conventional example, two substrates for Si substrate encapsulation are required, and two bonding processes are required, which complicates the manufacturing process and disadvantages in manufacturing cost.

[0020]

2. Description of the Related Art Torii et al. (Japanese Journal of Applied Physics, Vo1.30, No. 12B,
In December 1991, pp. 3562-3566, a platinum film is directly formed on SiO ₂ as a lower electrode of a PZT film. However, it is a well known fact that such a structure has a problem in the adhesion between silicon oxide and platinum, and even in the experiment of the present inventor, PZT
Peeling occurred between the silicon oxide and platinum during film formation or subsequent heat treatment, or during operation after completion. Further, in order to solve the above problems and improve the adhesion between an insulating material such as silicon oxide and platinum, it is necessary to insert titanium between the platinum and the insulating material as shown in JP-B-4-43435. Although it is known that the PZT film is formed and projections are formed on the platinum surface during the subsequent heat treatment, which lowers the withstand voltage of the PZT film.

In Japanese Patent Laid-Open No. 3-124450, the etching liquid is automatically introduced to the surface of the piezoelectric element side when anisotropically etching the single crystal silicon substrate. The phenomenon that the piezoelectric element is side-etched by a conductive etching solution, for example, an aqueous solution of potassium hydroxide, reduces the yield of the liquid ejecting head.

[0022]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and manufactures a liquid jet head which can achieve a high manufacturing yield rate even if a thin diaphragm or a piezoelectric element is formed. The purpose is to provide a method.

[0023]

A method of manufacturing a liquid jet head according to the present invention comprises a step of forming a vibration plate on a substrate and a piezoelectric element in which a lower electrode, a piezoelectric film and an upper electrode are sequentially laminated on the vibration plate. And a step of protecting the surface of the substrate on the piezoelectric element side with a jig so that the etching liquid does not flow into the surface, and etching a predetermined portion of the surface of the substrate opposite to the surface on the piezoelectric element side. And a step of forming a liquid chamber with a liquid. As a result, the liquid jet head can be formed with good yield even if a very thin diaphragm or piezoelectric element is used.

Further, the manufacturing process has a step of forming a silicon oxide layer on the substrate and a step of forming the liquid chamber or the step of removing the silicon oxide layer formed in contact with the liquid chamber by etching. The diaphragm can be prevented from cracking or peeling during the process, and the manufacturing yield can be improved.

Further, there is a first heating step of heating the piezoelectric film in the step of forming the piezoelectric element on the vibration plate, and a second heating step of reheating the piezoelectric film after forming the liquid chamber in the substrate. You may do it. As a result, the piezoelectric strain constant of the PZT film is increased and the piezoelectric characteristics can be improved.

Further, a step of joining the second substrate having the liquid channel formed therein to the liquid chamber opening of the first substrate having the liquid chamber formed therein may be added. This simplifies the process because the bonding process is performed only once, and the cost of the liquid jet head can be reduced.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view of a liquid jet head in an embodiment of the present invention.

In the figure, a vibrating plate 103 formed on a liquid chamber 102, a first substrate 101 on which a piezoelectric element composed of a lower electrode 104, a piezoelectric film 105 and an upper electrode 106 is formed, and a liquid flow path. Second substrate 10 on which 108 is formed
It is configured by joining 7 together. Reference numeral 109 is a nozzle formed in the opening of the cross section where the first substrate 101 and the second substrate 107 are joined. Here, a plurality of liquid chambers 102 and nozzles 109 are arranged at the same pitch.

The operation of this liquid jet head will be briefly described. A voltage is applied between the lower electrode 104 and the upper electrode 106 to form a piezoelectric element including the lower electrode 104, the piezoelectric film 105, and the upper electrode 106, and the vibrating plate 103. The liquid chamber 102
Is reduced, the ink filled in the liquid chamber 102 is pushed out to the liquid flow path 108, and the ink is ejected from the nozzle 109.

The liquid jet head and the manufacturing method thereof according to the present invention will be described in detail below according to the manufacturing process.

2A, 2B, and 2C are cross-sectional views showing a manufacturing process until the piezoelectric element and the liquid chamber are formed on the first substrate 101 in the embodiment of the present invention. In addition,
In this sectional view, the direction perpendicular to the paper surface is the depth direction of the liquid chamber.

First by the bicrystalline (110) single crystal silicon
Substrate 101 is thermally oxidized at 1200 ° C. to form silicon oxide layers 201 on both sides of substrate 101 with a thickness of 5000Å. Then, the vibration plate 103 is formed on one surface of the substrate 101. The diaphragm 103 is formed, for example, by forming silicon nitride to a thickness of 1 μm by PECVD (plasma chemical vapor deposition) and performing heat treatment at 800 ° C. in a nitrogen atmosphere. Further, the substrate 10
1. A photoresist is formed on both surfaces of No. 1 and an opening is provided on the surface opposite to the side where the vibration plate 103 is provided.
Is patterned with an aqueous solution of hydrofluoric acid and ammonium fluoride,
The opening 202 is formed, and the cross-sectional view shown in FIG. At this time, the depth direction of the opening 202, that is, the direction perpendicular to the paper surface is defined as <1-1 2> or <-1 12> direction.

Then, the lower electrode 104 is placed on the vibrating plate 103.
Are formed in this order by sputtering with a thickness of 50 Å of titanium and a thickness of 2000 Å of platinum, and the patterning is performed with an aqua regia solution. Next, PZT is formed as the piezoelectric film 105 by sputtering to have a thickness of 3 μm, and is patterned with an aqueous solution of hydrochloric acid. Although various methods have been attempted in recent years as a method for forming a PZT film, the present inventors have used a sintered body target in which lead oxide is excessively added to modified PZT mixed with niobium to obtain a substrate in an argon atmosphere. High frequency sputtering was performed without heating. After patterning the PZT, heat treatment is performed at 700 ° C. in an oxygen atmosphere, and the upper electrode 106 is made to have a titanium thickness of 50 by a sputtering method.
Å, gold was formed in this order with a thickness of 2000Å, and patterned with an aqueous solution of iodine and potassium iodide, and then, as shown in FIG.
The sectional view shown in FIG.

After that, a protective film 203 is formed with a photosensitive polyimide to a thickness of 2 μm, the protective film in the electrode extraction portion (not shown) is removed by development, and heat treatment is performed at 400 ° C.
Next, the surface on the piezoelectric element side where the protective film 203 is formed is shown in FIG.
Protected by a jig shown in FIG. 1 (details will be described later) and dipped in a potassium hydroxide aqueous solution to open the opening 2 of the silicon oxide layer 201.
From 02, the single crystal silicon substrate 101 is anisotropically etched to form the liquid chamber 102. At this time, the single crystal silicon substrate 10
Since the position of 1 is (110) and the depth direction of the opening 202 is the <1-1 2> or <-1 12> direction, the side wall forming the side of the liquid chamber 102 in the depth direction is defined. The plane can be a (111) plane. When an aqueous solution of potassium hydroxide is used, the ratio of the etching rates of the (110) plane and the (111) plane of single crystal silicon is about 300: 1, and a groove having a depth of 300 μm is side-etched by
The liquid chamber 102 can be formed by suppressing the thickness to about m. Then, with the substrate 101 fixed to the jig, the silicon oxide in contact with the vibrating plate 103 is removed by etching with an aqueous solution of hydrofluoric acid and ammonium fluoride to obtain a cross-sectional view shown in FIG. 2 (c).

In this embodiment, after the liquid chamber 102 is formed without the protective film 203, the heat treatment may be performed again at 700 ° C. in an oxygen atmosphere to further form the protective film. . This is a piezoelectric film (PZT film) 1
This is because the piezoelectric characteristics can be further improved by performing heat treatment twice on 05. Although the detailed reason for this effect is not clear, the PZ that constitutes the piezoelectric film is
It is estimated that the sintering of T progresses and the crystal grain size increases, resulting in an increase in the piezoelectric strain constant.

3A and 3B are views showing a jig for protecting the surface on the piezoelectric element side during anisotropic etching of the substrate 101 in the embodiment of the present invention, as described above. Yes, the figure (a) is a block diagram of the jig, the figure (b) is the substrate 10
It is sectional drawing of the state which fixed 1 to the jig.

An O-ring 302 is attached to a cylindrical fixed frame 301 having an opening on one side and an inner wall surface of which a thread is cut.
The substrate 101 and the O-ring 302 are fitted in this order, and a fixing ring 303 having a thread cut on the outer wall surface thereof is attached to the fixing frame 3
The inner wall of 01 is screwed and fixed. At this time, the surface of the substrate 101 to be etched is fixed to the fixing frame 3
01 on the opening side. It is immersed in an etching solution such as an aqueous solution of potassium hydroxide in the state shown in FIG. 3B, but at this time, it is sealed by the fixing ring 303, the O-ring 302, and the surface of the substrate 101 to be etched. Therefore, the etching liquid can be prevented from flowing around to the piezoelectric element side of the substrate 101. The present inventors used polypropylene as the material for the jig.

FIG. 4 is a conceptual view of the mounting structure of the liquid jet head in the embodiment of the present invention.

In the figure, a first substrate 101 in which a piezoelectric element and a liquid chamber are formed and a second substrate in which a liquid flow path 108 is formed
The substrate 107 is bonded to the nozzle 109 and the liquid introduction hole 40.
4 is formed. The liquid chamber 403 is formed by surrounding the liquid introduction hole 404 side with the base material 401. Liquid is supplied to the liquid chamber 403 from the outside (not shown). The base material 401 is attached to the mounting substrate 402.
The second substrate 107 was formed integrally with the liquid flow path 108 by injection-molding plastic.

The above is the outline of the liquid jet head of the present invention.

Next, the dimensions of the liquid chamber / electrode, the thickness of the piezoelectric film,
The relationship between the dimensions and the thickness of the diaphragm will be described. The inventors of the present invention have obtained various findings when conducting a liquid ejecting experiment using the liquid ejecting head described above.

The present inventors first of all, the liquid chamber 102, the lower electrode 1
04, the planar positional relationship between the piezoelectric film 105 and the upper electrode 106 by PZT was set.

First, the lower electrode 104, the piezoelectric film 105, and the upper electrode 106 were evaluated according to the manufacturing process up to the upper electrode forming step.

Comparing the case where the upper electrode is larger than the lower electrode and the case where the lower electrode is larger than the upper electrode on the contrary, the former shows that the leak current between the upper and lower electrodes is about two digits larger than the latter. I understood. This is P at the end of the lower electrode.
It is considered that this is due to the large leak current of the ZT film.

Further, in the case where the lower electrode is larger than the upper electrode, the PZT film is larger than the lower electrode, and the PZT film is smaller than the lower electrode, in the former, the end of the PZT film is turned up from the underlying silicon nitride. However, the latter could be formed without film peeling. This is PZT
It was considered that the adhesion between the film and the silicon nitride layer was insufficient. Therefore, from the above results, the relation of upper electrode ≦ PZT film <lower electrode is established, that is, the upper electrode length in the arrangement direction of the liquid chambers is Lu, and the PZT in the arrangement direction of the liquid chambers is Lu.
Lp is the length and L1 is the length of the lower electrode in the arrangement direction of the liquid chamber.
In such a case, the relationship of Lu ≦ Lp <L1 is established, the upper electrode length in the depth direction of the liquid chamber is Wu, and the PZ in the depth direction of the liquid chamber is
When the T length is Wp and the lower electrode length in the depth direction of the liquid chamber is W1, by setting Wu ≦ Wp <W1, the manufacturing process has no problem and the leak current is suppressed. A piezoelectric element could be constructed.

Further, in order to take out the electrode from the upper electrode 106, after forming the liquid chamber 102 according to the above manufacturing process, wire bonding was tried to the upper electrode 106.
Then, when wire bonding was performed on the upper electrode 106 just above the liquid chamber 102, the vibration plate 103 was broken by the pressure. On the other hand, when the upper electrode 106 is extended in the depth direction of the liquid chamber, that is, the length of the liquid chamber in the depth direction is W, and the length of the upper electrode in the depth direction of the liquid chamber is Wu.
Then, the magnitude relation W <Wu is established. Then, wire bonding was performed on a portion where the substrate 101 exists below the upper electrode 106 (a portion where the liquid chamber 102 does not exist). Therefore, from the above results, it was found that the electrode extraction from the upper electrode 106 was facilitated by setting W <Wu.

Next, under the condition of Lu ≦ Lp <L1, the relationship with the length L of the liquid chamber 102 in the arrangement direction is optimized by examining the amount of deformation of the vibration plate 103 in the central portion of the liquid chamber. An experiment was conducted. The materials and thicknesses of the diaphragm, the lower electrode, the PZT, and the upper electrode are as described above.
Then, the center of the piezoelectric element is arranged at the center of the side in the liquid chamber arranging direction so as to be symmetrical. The applied voltage between the upper and lower electrodes was 30V. L = 100μm fixed, L
The results when u, Lp, and L1 were changed are shown in Table 1 below.

[0049]

[Table 1]

As shown in Table 1 above, the magnitude relationship between the liquid chamber 102 and the PZT film 105 or the lower electrode 104 in the arrangement direction has little influence on the vibration plate deformation amount.
However, the size relationship between the liquid chamber 102 and the upper electrode 106 affects the deformation amount of the diaphragm, and if the upper electrode 106 is larger than the liquid chamber 102, the deformation amount of the diaphragm decreases. From this result, it is considered that the diaphragm can be efficiently deformed if the deformed portion of the piezoelectric element is contained within the liquid chamber. The planar positional relationship that makes such a state is
In the liquid chamber array direction, the length L of the liquid chamber in the array direction> the upper electrode length Lu of the array direction of the liquid chamber.

Based on the plane size relationship described above,
Next, a liquid jet experiment was conducted. Aqueous ink was used as the liquid. From the nozzle 109, the length L (unit: μm) of the liquid chambers in the array direction, the length W (unit: μm) in the depth direction of the liquid chambers, the thickness tp (unit: μm) of the PZT film, and the thickness tv (unit: μm) of the diaphragm are used as parameters. The liquid jetting speed (unit: m / sec) was measured at a portion separated by 5 mm. The electric field applied to the PZT film was 5 V / μm. The diaphragm material, the lower electrode material and thickness, the upper electrode material and thickness, the protective film material and thickness are as described above. The results are shown in Table 2 below.

[0052]

[Table 2]

Consider the following results.

First, L = 100 μm and W = 15000 μ
m and tv = 0.4 μm, tp = 0.8
The liquid is ejected in the case of μm, and the liquid is not ejected in the case of tp = 0.7 μm. It is considered that this is because the pressure applied to the liquid in the liquid chamber is insufficient at tp = 0.7 μm. According to the teaching of material mechanics, the pressure applied to the liquid in the liquid chamber is generally proportional to the cube of tp + tv and inversely proportional to the cube of L. Therefore, if the above experimental results are applied to this condition, (tp + tv) ³ / L ³ ≧ 1.7 × 10 ⁻⁶ , that is, if (tp + tv) /L≧0.012 The applied pressure is
It is possible to give something that only ejects a liquid. Further, if the left side of the inequality becomes large, it is expected that the liquid ejection characteristics will be improved. In fact, when tp = tv = 3 μm, the liquid ejection speed of 17 m / sec is recorded.

However, when tp = 3 μm and tv = 5 μm, the liquid was not ejected. This is because the vibration plate 103 becomes thicker and its rigidity is increased, so that the vibration plate 103 is not deformed by an amount enough to eject the liquid. Therefore, the diaphragm 103
Is not desired to be too thick, and applying numerical conditions to the above inequality requires (tp + tv) ³ / L ³ <5.12 × 10 ⁻⁴ , that is, (tp + tv) / L <0.08. Becomes This inequality means that the sum of the PZT thickness tp and the diaphragm thickness tv should be reduced in order to shorten the length L of the liquid chamber in the arrangement direction and to increase the density of the nozzles of the liquid jet head. It is necessary. Conversely, by reducing tp + tv, L can be reduced and nozzle density can be increased.

Now, in this state (tp = 3 μm, tv = 5)
As a means for ejecting the liquid in the (μm state), it is conceivable to further increase the depth direction length W of the liquid chamber. However, with such a configuration, the liquid ejecting head becomes extremely large in plan view, which is outside the practical range. Further, when W becomes large, the flow path resistance in the liquid chamber becomes large, and the operating speed of the liquid jet head decreases. Therefore, from the above experimental results, it is desirable that tp ≧ tv and W / L ≦ 150 for the planar miniaturization and high-speed operation of the liquid ejecting head.

Further, L = 200 μm, tp = 4 μm, t
When v = 2 μm, the liquid is ejected when W = 2000 μm and is not ejected when W = 1000 μm. This is W
This is because the depth length of the liquid chamber for ejecting the liquid is too short when = 1000 μm. Therefore, L = 200 μm
As described below, it has been found that it is necessary to satisfy W / L ≧ 10 when arranging the liquid chambers with high density and densifying the nozzles.

The features of the liquid jet head described above are summarized as follows.

By using PZT for the piezoelectric curtain 105, liquid ejection efficiency is good. PZT has a large piezoelectric strain constant among the piezoelectric materials, and d ₃₁ = 150 pC / N is achieved also in PZT in the present embodiment. The PZT in the present invention is not limited to the composition, the kind and amount of the additive added in the above-described examples, and the kind and amount of the compound that can be further solid-dissolved in the above practical example. . Further, the forming method thereof does not have to be limited to the above method.

The arrangement pitch of the liquid chambers 102 is set to the nozzle 109.
Since the arrangement pitch is the same, the space for drawing around the liquid flow path 108 connecting the liquid chamber and the nozzle is unnecessary, the liquid jet head can be downsized, and even if the number of nozzles is increased, There is no increase in size.

By setting 10 ≦ W / L ≦ 150, tp ≧ tv and 0.012 ≦ (tp + tv) / L <0.08, a thin diaphragm 103 and a PZT film 105 are used to form a liquid chamber having a narrow width. Even if formed, the liquid can be ejected, and the liquid ejecting head can be downsized and the nozzle density can be increased.

The substrate 101 is made of single crystal silicon having a plane orientation (110), and the depth direction of the liquid chamber 102 is set to the <1-1 2> or <-1 12> direction. Since the surface of the side wall forming the side can be the (111) plane, it is possible to form the liquid chamber having a depth of 300 μm while suppressing the side etching in the arrangement direction to about 1 μm, and the precision of the liquid chamber is improved. Is possible.

By setting Lu.ltoreq.Lp <L1, it becomes possible to construct a piezoelectric element in which there is no problem in the manufacturing process and the leak current is suppressed.

By setting L> Lu, the vibration plate can be efficiently deformed, and as a result, efficient liquid ejection can be performed.

By setting W <Wu <Wp <W1,
There is no problem in the manufacturing process, it is possible to configure a piezoelectric element with suppressed leakage current, and it is easy to take out the electrode from the upper electrode.

First with piezoelectric element and liquid chamber 102 formed
The substrate 101 and the second substrate 107 in which the liquid channel 108 is formed are integrally joined so that the liquid chamber and the liquid channel communicate with each other, thereby controlling the shape and depth of the liquid channel. In addition, it is possible to make the contact shape between the liquid flow path and the liquid chamber constant, and it is possible to improve the degree of freedom in designing the liquid flow path and the liquid ejection characteristics. It is possible to eliminate the cause of variation.

By using the opening of the cross section where the first substrate 101 and the second substrate 107 are joined as a nozzle, an expensive nozzle plate which is required as a separate component is not required.

After forming the piezoelectric element, a means for protecting the surface on this side is provided, and the liquid chamber is formed from the surface on the opposite side. Therefore, the yield can be obtained even when a thin diaphragm and PZT are used. A liquid jet head can be formed well. In the present embodiment, the means for protecting the surface on the piezoelectric element side is a jig, but the means is not limited to this, and other means such as thick coating of photoresist may be used. good.

By using the manufacturing method in which the second substrate 107 in which the liquid flow path is formed is bonded to the liquid chamber opening side of the first substrate 101 in which the liquid chamber is formed, the substrate 101 is sealed. Since one substrate (second substrate) can be used for one bonding step, it is possible to reduce the price of the liquid ejecting head.

The silicon oxide layer 201 is formed on the substrate 101 and the silicon oxide layer 201 formed in contact with the liquid chamber 102 is removed in the same step as the step of forming the liquid chamber 102 or after that. It becomes possible to prevent the diaphragm 103 from cracking or peeling during the process, and the manufacturing yield of the liquid jet head is improved. Furthermore, it becomes possible to remove the influence of the silicon oxide layer 201 remaining when the diaphragm vibrates, and it is possible to improve the liquid ejection characteristics.

Example 2 In order to obtain information on the material of the diaphragm 103, the diaphragm material was changed in the structure of FIG. 2C, and the amount of deformation of the diaphragm in the center of the liquid chamber was examined. The lower electrode 104 was not patterned at all, and was formed on the entire surface of the substrate 101. As a condition, L =
100 μm, Lp = 94 μm, Lu = 88 mμm, W =
The applied voltage between the upper and lower electrodes was 30 V at 15 mm, tp = 3 μm, and tv = 1 μm.

As the material of the vibrating plate 103, in addition to the nitrogen silicon used in the first embodiment, silicon oxide formed by a thermal oxidation method, silicon in which boron is thermally diffused at 10 ²¹ cm ⁻³ ,
Five kinds of zirconium oxide and aluminum oxide formed by the sputtering method were used. The results are shown in Table 3 below.

[0073]

[Table 3]

From the following results, the larger the Young's modulus of the diaphragm 103, the larger the amount of deformation of the diaphragm. This shows that when the Young's modulus of the vibration plate 103 is small, when the piezoelectric thin film is deformed in the lateral direction, the piezoelectric film is greatly expanded in the lateral direction at the same time, and the deformation in the longitudinal direction is not so large. In order to efficiently deform the diaphragm and eject the liquid, it is necessary to use a diaphragm having a large Young's modulus.

Approximately estimating the excluded volume of the liquid chamber by the vibrating plate 103 from the above result, it becomes 1.5 × 10 ⁻¹³ m ³ when silicon oxide is used, and the liquid jet is performed using the water-based ink. It is at the limit of the excluded volume necessary for the case. Therefore, the Young's modulus of the diaphragm is 1 × 10
^{If it is 11} N / m ² or more, it is possible to eject the liquid with a margin, and if it is 2 × 10 ¹¹ N / m ² or more, the vibration plate deformation amount is remarkably increased and the liquid chamber The length W in the depth direction can be reduced, and the liquid jet head can be downsized and the operation speed can be increased.

According to the above results, as the diaphragm material,
It can be seen that zirconium oxide, silicon nitride, and aluminum oxide having a large Young's modulus are desirable. In addition to this, titanium nitride, aluminum nitride, boron nitride, tantalum nitride,
Tungsten nitride, zirconium nitride, titanium nitride, silicon carbide, titanium carbide, tungsten carbide, and tantalum carbide have a Young's modulus of 2 × 10 ¹¹ N / m ² or more and can be said to be desirable diaphragm materials.

Further, other components may be added with the above-mentioned material as the main component, or a material containing two or more of the above-mentioned materials. For example, tungsten carbide is the main component,
Cemented carbide containing trace amounts of titanium carbide, tartar carbide, cobalt, titanium carbide and titanium carbonitride
The cermet may be used for the diaphragm by adding a small amount of impurities.

(Embodiment 3) FIG. 5 is a cross-sectional view of a substrate in which a piezoelectric element and a liquid chamber are formed in a liquid jet head having a vibrating plate of a laminated structure according to an embodiment of the present invention.

In the figure, 501 has a Young's modulus of 1 × 1.
The material layer is 0 ¹¹ N / m ² or more, preferably 2 × 10 ¹¹ N / m ² or more, and silicon nitride was used as in the above (Example 1). Reference numeral 502 denotes a silicon oxide layer, which was continuously formed after the nitrogen silicon layer 501 was formed in the PECVD apparatus in which the nitrogen silicon layer 501 was formed. The other elements are the same as those in the first embodiment.

By providing the silicon oxide layer 502, the adhesion between the lower electrode 104 and the vibration plate is strengthened. In addition, the PZT film 105 that occurs during heat treatment during the manufacturing process
Since it is possible to relieve the stress applied to, it is possible to improve the manufacturing yield. Silicon nitride layer 501 to 1
The liquid jetting characteristics when the silicon oxide layer 502 has a thickness of 1000 .mu.m and a thickness of 1000 .mu.m are the same as those shown in Table 2 in Example 1,
The provision of the silicon oxide layer 502 did not deteriorate the liquid ejection characteristics.

In this embodiment, it is desirable to apply the processing temperature at or after the PZT film formation is 710 ° C. or less. This is because lead in the PZT film diffuses into the silicon oxide layer 502 of the diaphragm through the lower electrode 104. Normally, silicon oxide is in a solid state in this temperature range, but silicon oxide in which lead is diffused becomes a liquid at 714 ° C. or higher, and this is jetted to the outside to destroy the liquid jet head. .

(Embodiment 4) FIG. 6 is a cross-sectional view of a substrate in which a piezoelectric element and a liquid chamber are formed in a liquid jet head in which an aluminum oxide layer is inserted between a diaphragm and a lower electrode.

In the figure, an aluminum oxide layer 60 is formed on a diaphragm composed of a silicon nitride layer 501 and a silicon oxide layer 502.
1 was formed with a thickness of 1000Å by the sputtering method,
The lower electrode 104 is formed from the upper part. Other than that is the same as the third embodiment.

By forming the aluminum oxide layer 601, the diffusion of lead in the PZT into the diaphragm as described in the third embodiment can be suppressed. This makes 710
Even if the high temperature heat treatment of not less than 0 ° C. is performed, it is possible to prevent the liquid jet head from being destroyed due to the jetting of the silicon oxide layer 502 to the outside, and it is possible to improve the manufacturing yield of the liquid jet head. Furthermore, since it is possible to perform heat treatment efficiently at a high temperature of 710 ° C. or higher, it is possible to further improve the piezoelectric characteristics of the PZT film and improve the liquid ejection characteristics.

It has been found that the effect of providing the aluminum oxide layer 601 can be obtained by using other materials. As a result of the experiment, the effect was similarly confirmed even when zirconium oxide, tin oxide, zinc oxide, or titanium oxide was used other than the above-mentioned aluminum oxide. Further, a material containing these as main components and an additive, or a material containing as a main component two or more kinds of these materials is also applicable.
Further, this effect was confirmed not only in the diaphragm configuration in which the silicon oxide layer was provided on the surface but also in the single crystal silicon diaphragm mixed with boron.

(Fifth Embodiment) The present inventors have made the lower electrode 104
The following experiment was conducted to determine the composition of the.

On a single crystal silicon substrate provided with a silicon oxide layer,
As the lower electrode 104, titanium and platinum were continuously formed in this order by a sputtering method. The platinum thickness was changed to 2000Å and the titanium thickness was changed from 50Å to 1000Å. Titanium is necessary to improve the adhesion between the electrode material platinum and the diaphragm material silicon oxide layer.

From above, PZ was carried out by the method shown in Example 1.
T is formed to a film thickness of 1 μm, heat treatment is performed at 600 ° C. for 4 hours in an oxygen atmosphere, and aluminum is used as an upper electrode for 3 hours.
It was formed by mask vapor deposition in the size of mm square.

In this sample, a voltage was applied between the upper and lower electrodes and the withstand voltage characteristics of the PZT film were evaluated. here,
The PZT film withstand voltage is defined as a leak current of 100.
The applied voltage when flowing nA was used. The results are shown in Table 4.

[0090]

[Table 4]

The above results show that there is a correlation between the titanium film thickness and the withstand voltage of the PZT film, and the withstand voltage increases as the titanium film thickness becomes thinner. In addition, according to the observation by the present inventors, delicate projections were formed on the platinum surface, and the density of the projections increased as the titanium film thickness increased. For example, for titanium 50Å, 20000 pieces / m
What was about m ² is 21 for titanium 200Å
It was observed that the number was about 0000 pieces / mm ² . From this, it is considered that the minute projections on the platinum surface formed by the heat treatment reduce the withstand voltage of the PZT film.

By lowering the titanium film thickness from 100Å to 80Å, the withstand voltage of the PZT film was greatly improved from 18V to 30V. If the withstand voltage of the PZT film is improved, the applied voltage can be increased and the liquid ejecting characteristics of the liquid ejecting head can be improved. In addition, the liquid can be ejected even when the PZT film is thinned, and the productivity in manufacturing can be improved.

With respect to this withstand voltage value, if it is 10 V or less, it cannot withstand practical use, and about 20 V is still insufficient, but if it exceeds 20 V, it can be regarded as a practical region. From the above experimental results, it can be seen that the withstand voltage of the PZT film is remarkably improved when the titanium film layer is 80 Å or less. Therefore, it is desirable to set the titanium film thickness to 80 Å or less, and the present inventors set the titanium film thickness to 50 Å even in the above-mentioned embodiments.

In the above-mentioned embodiment, platinum is used as the electrode material provided on titanium having a thickness of 80 Å or less, but this may be an alloy containing platinum. The inventors of the present invention continuously form 50 liters of titanium on a single crystal silicon substrate provided with a silicon oxide layer, and further continuously form an alloy of 70 at% of platinum and 30 at% of iridium by a sputtering method, and perform heat treatment at 600 ° C. for 4 hours in an oxygen atmosphere. The surface of this alloy after heat treatment was 8
When microscopically observed at 00 times, no fine protrusions on the surface were observed. PZT as in the previous embodiment
When a film was formed and the withstand voltage was measured, a result of 70 V was obtained, and further improvement in characteristics was observed.

Further, the material of the diaphragm is not limited to the single crystal silicon provided with the silicon oxide layer, and the materials mentioned in the above-mentioned embodiments can be applied.

(Embodiment 6) FIG. 7 shows a piezoelectric element in a liquid jet head in which a hydrophilic material layer is formed on the inner surface of a liquid chamber.
It is sectional drawing of the board | substrate which formed the liquid chamber.

In the figure, 701 is a hydrophilic material layer. The manufacturing method in this embodiment is almost the same as that in Embodiment 1, except that the single crystal silicon substrate 101 is anisotropically etched before forming the protective film 203, and then 800 ° C.
By thermally oxidizing the surface of the substrate 101 at a temperature of about
The difference from Example 1 is that silicon oxide is formed as the hydrophilic material layer 701. After that, the protective film 203 is formed on the surface of the piezoelectric element side.

As a method of forming the hydrophilic material layer 701,
Silicon oxide may be formed by SOG (Spin On Glass) method or the like so as to cover under the vibrating plate 103. Furthermore, after the liquid jet head is assembled, a liquid mixed with hydrophilic material particles is used to form a liquid flow path or a liquid chamber. Alternatively, the hydrophilic material particles may be left on the surface of the liquid channel or the liquid chamber by passing through.

With such a structure, when a water-based material such as a water-based ink is used as the liquid, the wettability of the liquid with the liquid chamber or the liquid flow path is improved and the generation of bubbles is reduced. Become. At the same time, if a hydrophilic material such as glass is used for the second substrate 107, this effect is further improved.

(Embodiment 7) FIG. 8A and FIG.
3A and 3B are a plan view and a cross-sectional view of a liquid jet head in which nozzles are formed on a substrate 107 of FIG.

In the figure, a nozzle 801 is formed on a second substrate 107 having a liquid flow path 108 formed thereon, and is joined to the first substrate 101. The nozzle 801 is
It may be formed by irradiating an excimer laser.

By adopting such a configuration, as shown in FIG.
As shown in (a), it is possible to arrange the liquid chambers 102 in a zigzag manner and further to arrange the nozzles 801 in a straight line. Therefore, the arrangement pitch of the nozzles 801 can be set to half the arrangement pitch of the liquid chambers 102, and when the liquid chamber size is 100 μm as in the first embodiment described above, the nozzles 80
It is possible to further increase the density. Further, since they can be arranged on a straight line, when recording a liquid such as ink on a medium such as paper, dot deviation does not occur and high-quality printing is possible.

(Embodiment 8) FIG. 9 is a conceptual diagram of a liquid jet recording apparatus using the liquid jet head of the present invention.

In the figure, a liquid jet head 901 having a plurality of nozzles is connected to a control circuit (not shown) so that the liquid jet head 901 is appropriately driven by this control circuit and ink is selectively jetted. Has become. Then, information such as characters and images is recorded as a set of dots formed by ink droplets on a recording sheet 909 located at a position facing the liquid ejecting head 901.

A cartridge 902 storing ink is connected to the liquid jet head 901, and a guide rail 903 and a feed belt 904 are connected to the cartridge 902. Feed roller 905
When is rotated, the feed belt 904 is driven, and the liquid jet head 901 and the cartridge 902 are moved along the guide rail 903.

On the other hand, the recording paper 909 is held by the nip roller 90.
7 and the paper feed roller 908 are in close contact with the platen 906. The liquid ejecting head 901 is scanned in the main scanning direction (the direction in which the liquid ejecting head 901 moves by the guide rail 903), and when recording is completed, the paper feed roller 908 is rotated stepwise, and the liquid ejecting head 901 is again rotated.
Ink is ejected from and the next recording is started.

This recording apparatus has the characteristics and effects of the liquid jet head described above as they are.

In the present embodiment, the recording paper is used as the medium on which the ink is ejected, but it is not limited to this and may be cloth or the like. Also, a three-dimensional object such as metal, resin or wood may be used.

[0109]

As described above, according to the method of manufacturing a liquid jet head of the present invention, a step of forming a vibration plate on a substrate, and a lower electrode, a piezoelectric film and an upper electrode are sequentially laminated on the vibration plate. A step of forming a piezoelectric element, a step of protecting the surface of the substrate on the piezoelectric element side so that an etching liquid does not flow, and an etching on a predetermined portion of the surface of the substrate opposite to the surface on the piezoelectric element side. The step of forming a liquid chamber with a liquid has an effect that a high manufacturing yield rate can be achieved even if a thin diaphragm or a piezoelectric element is formed.

[Brief description of drawings]

FIG. 1 is a perspective view of a liquid jet head according to an embodiment of the present invention.

FIGS. 2A to 2C are cross-sectional views showing a manufacturing process until a piezoelectric element and a liquid chamber are formed on the first substrate 101. FIGS.

3A is a configuration diagram of a jig for protecting the surface of the substrate 101 on the piezoelectric element side during anisotropic etching of the substrate 101, and FIG. 3B is a cross-sectional view of the substrate 101 fixed to the jig. It is a figure.

FIG. 4 is a conceptual diagram of a mounting structure of a liquid jet head of the present invention.

FIG. 5 is a cross-sectional view of a substrate on which a piezoelectric element and a liquid chamber are formed in a liquid jet head having a vibration plate having a laminated structure.

FIG. 6 is a cross-sectional view of a substrate in which a piezoelectric element and a liquid chamber are formed in a liquid jet head in which an aluminum oxide layer is inserted between a diaphragm and a lower electrode.

FIG. 7 is a cross-sectional view of a piezoelectric element and a substrate on which a liquid chamber is formed in a liquid jet head in which a hydrophilic material layer is formed on the surface of the liquid chamber.

8A is a plan view of a liquid jet head in which nozzles are formed on a second substrate 107 of the present invention, and FIG. 8B is a sectional view thereof.

FIG. 9 is a conceptual diagram of a liquid jet recording apparatus using the liquid jet head of the present invention.

[Explanation of symbols]

101 first substrate 102 Liquid chamber 103 diaphragm 104 Lower electrode 105 Piezoelectric film 106 upper electrode 107 second substrate 108 liquid flow path 109 nozzles 203 protective film

─────────────────────────────────────────────────── ─── Continuation of front page (31) Priority claim number Japanese Patent Application No. 5-57430 (32) Priority date March 17, 1993 (1993. 3.17) (33) Country of priority claim Japan (JP) (31) Priority claim number Japanese Patent Application No. 5-72426 (32) Priority date March 30, 1993 (March 30, 1993) (33) Country of priority claim Japan (JP) (31) Priority claim number Japanese Patent Application No. 5-10226 (32) Priority date January 25, 1993 (January 25, 1993) (33) Priority claiming country Japan (JP) (56) Reference JP-A-2-289352 (JP, A) JP-A-3-151248 (JP, A) JP-A-2-297445 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/16 B41J 2/045 B41J 2 / 055

Claims (6)

(57) [Claims] 1. A step of forming a vibration plate on a substrate, a step of sequentially laminating a lower electrode, a piezoelectric film, and an upper electrode on the vibration plate to form a piezoelectric element, and a surface of the substrate on the piezoelectric element side. A step of protecting the substrate with a jig so that the etching liquid does not flow into the substrate, and a step of forming a liquid chamber with the etching liquid in a predetermined portion of the surface of the substrate opposite to the surface on the piezoelectric element side. And a method for manufacturing a liquid jet head. 2. The substrate is made of single crystal silicon having a plane orientation (110), and the depth direction of the liquid chamber is <1-1 2> or <-1 12> direction. 2. The method for manufacturing a liquid jet head according to 1. 3. A step of forming a silicon oxide layer on the substrate, the same step as the step of forming the liquid chamber, or a step of etching and removing the silicon oxide layer formed in contact with the liquid chamber after that. The method of manufacturing a liquid jet head according to claim 1, wherein the liquid jet head is manufactured. 4. A first heating step of heating the piezoelectric film in a step of forming the piezoelectric element on the diaphragm, and a step of reheating the piezoelectric film after forming the substrate and the liquid chamber. The second heating step, and the method for manufacturing a liquid jet head according to claim 1, wherein the second heating step is included. 5. A step of joining a second substrate having a liquid flow path formed therein to a liquid chamber opening of a first substrate having the liquid chamber formed therein is added. 5. The method for manufacturing a liquid jet head according to any one of 4 above. 6. A step of forming a vibration plate on a substrate, a step of sequentially laminating a lower electrode, a piezoelectric film and an upper electrode on the vibration plate to form a piezoelectric element, and a surface of the substrate on the piezoelectric element side. A step of providing a member for forming a protective space for preventing the piezoelectric element formed on the substrate from being exposed to an etching solution; and an etching solution on a predetermined portion of the surface of the substrate opposite to the surface on the piezoelectric element side. A method of manufacturing a liquid ejecting head, comprising: a step of forming a liquid chamber.