A high electrical insulating, high temperature resistant film, such as Al2O3, AlN, Si3N4, SiO2, MgO, Ta2O5, SiC, YSZ, ZrO2, HfAlO or HfO2, is employed for the insulating layer 106. Note that the dielectric constant of the insulating layer 106 should be higher than that of the piezoelectric layer 107, so that a strong, intense field will be applied to the piezoelectric layer 107 when laminated with the insulating layer 106. Also, since the insulating layer 106 is employed as an etching stop layer, an etching speed for the insulating layer 106 should be higher than the etching speed for the piezoelectric layer 107. In addition, while a thin insulating layer 106 is desirable because only a low voltage is to be applied, the film thickness of the insulating layer 106 should be sufficient to prevent damage should a strong field be applied. Specifically, a film thickness of 20 to 200 nm is appropriate, while a film thickness of 40 to 200 nm is even more appropriate.
A piezoelectric member having a perovskite structure containing lead zirconate titanate, relaxor or barium titanate as the primary element is employed as the piezoelectric layer 107.
Using etching, holes are formed in the substrate 101, under the vibration plate 103, for use as ink pressure chambers 111. Furthermore, ink orifices 112 that are consonant with the ink pressure chambers 111 are formed in an Si substrate 113 that is adhered to the substrate 101.
So long as the ink pressure chambers 111 are produced through etching and adhesion, and a discharge force can be effectively exerted on ink, the manufacturing method that can be used is not limited to the method described above.
The vibration plate 103 is formed over the ink pressure chambers 111 and on partition walls that separate the ink pressure chambers 111. The insulating layer 106 is also extended to a partition wall for an adjacent piezoelectric device.
Further, as shown in
An example process for manufacturing the ink jet recording head according to the invention will now be described while referring to
(A) Through thermal oxidization, the thermal oxide film (the SiO2 layer) 104 is deposited on the silicon substrate 101 on which the SOI layer 103 is formed.
(B) The lower electrode 105, made of Pt/Ti, is deposited on the thermal oxide film 104 using sputtering, and further, the insulating film 106 is overlaid using the LPCVD method or the sputtering method. The thickness of the lower electrode 105 is about 300 to 1000 Å, and the thickness of the insulating layer 106 is about 1000 Å to 1 μm.
(C) A thin film containing lead zirconate titanate or barium titanate as the primary element is deposited on the insulating film 106 using sputtering or CVD, and the entire structure is sintered at 600° C. to 800° C. The thus obtained layer is used as a material layer for the piezoelectric layer 107. Then, a metal, such as Pt/Ti, is formed on the piezoelectric layer 107 and patterned, and in this manner, the upper electrodes 108 are formed.
(D) The piezoelectric layer 107 is etched to obtain the piezoelectric elements 109. At this time, the dry etching method is performed by using the insulating layer 106 as an etching stop layer. Since the insulating layer 106 is used as an etching stop layer, over-etching of the PT/Ti of the lower electrode 105 is prevented, and the attachment of Pt/Ti to the end face of the piezoelectric elements 109 does not occur.
In addition, the portion of the insulating layer 106 that is exposed during dry etching should be thinner than the portion of the insulating layer 106 located under the piezoelectric layer 107. This is because as the exposed portion of the insulating layer 106 becomes thinner, the constraint placed on the entire vibration plate 103 is reduced.
(E) After resist patterning has been completed, the ink pressure chambers 111 are formed below the piezoelectric elements 109 using the ICP (Inductively Coupled Plasma) etching method.
(F) Using this ICP method, the ink orifices 112 are formed in another silicon substrate, and the resultant substrate serves as an orifice plate 113.
(G) The orifice plate 113 is adhered to the above described substrate 101, and an ink discharge head 114 is completed.
Using etching, holes were formed in the substrate 101 to form ink pressure chambers 111 under the vibration plate 103. Then, a silicon substrate 113, 200 μm thick, used for orifices, was adhered to the substrate 101, and ink orifices 112, each having a diameter of 40 μmσ, were formed in correspondence with the ink pressure chambers 111.
In this case, the width of an ink pressure chamber 111 was 100 μm, the depth was 3 mm, and the pitch between the devices 109 was 120 μm.
A printing test was conducted, using this head and water ink having a viscosity of 2 cp, at 30 kHz, with ink droplets of 3 pl that had a width of 12.5 mm. High quality printed matter could be obtained up to 2×1010 times, before a portion was generated in which no ink was discharged.
As shown in
The process for manufacturing an ink jet recording head for this invention will be described while again referring to
(A) Using thermal oxidization, a thermal oxide film (an SiO2 layer) 104, 3000 Å thick, was deposited on a silicon substrate 101, 200 μm thick, on which were formed a box layer 102, 1 μm thick, and an SOI layer 103, 5 μm thick.
(B) Thereafter, a lower electrode of 105 Pt/Ti=3000/300 Å was overlaid using sputtering, and then an insulating film 106 of Ta2O5, which was 3000 Å thick, was deposited using sputtering.
(C) PZT, 3 μm thick, was deposited on the insulating film 106 using sputtering, and the entire structure was sintered at 700° C. for five hours. In this manner, a piezoelectric layer 107 was obtained. Furthermore, Pt/Ti−3000/300 Å was deposited on the piezoelectric layer 107 using sputtering and was patterned, and upper electrodes 108 were obtained.
(D) Dry etching was performed for the piezoelectric layer 107 employing C4F8 and Cl2, and piezoelectric elements 109 were formed. During this process, a Ta2O5 layer served as an etching stop layer.
(E) After resist patterning was completed, SF6 and C4F8 were alternatively introduced, and using the ICP (Inductively Coupled Plasma) etching method, Si was etched until the box layer was reached. As a result, ink pressure chambers 111 were obtained below the piezoelectric elements 109.
(F) Also using the ICP method, ink orifices 112, each having a diameter of 40 μm, were formed in another silicon substrate that was 150 μm thick, and the resultant silicon substrate was employed as an orifice plate 113.
(G) Au/Ti=1000/300 Å was deposited on the orifice plate 113 using sputtering, and thereafter, the two substrates 101 and 113 were adhered to each other by a vacuum bonding machine under a pressure of 3 MPa at 300° C. As a result, an ink jet recording head was completed.
The sizes of the individual portions of the head were the same as those for example 1-1. A printing test was conducted, using this head and water ink having a viscosity of 2 cp, at 30 kHz, with ink droplets of 3 pl that had a width of 12.5 mm. High quality printed matter could be obtained up to 3×1010 times, before a portion was generated in which no ink was discharged.
According to the first embodiment, the insulating layer deposited between the piezoelectric film and the lower electrode prevented a fault caused by electricity leaking from the end face of a piezoelectric device, which was formed after the piezoelectric device was etched. Furthermore, since the insulating layer having a different etching speed from that of the piezoelectric material was formed on the lower electrode, over-etching of the lower electrode could be avoided, and the piezoelectric device could be protected from being contaminated by the dispersing of the material of the low electrode.
The insulating layer 106 is the same as that for the first embodiment
A liquid discharge head according to the present invention includes: plural pressure chambers for applying pressure to liquid, which communicate with liquid discharge openings for discharging liquid respectively; and plural piezoelectric elements, arranged corresponding to the plural pressure chambers respectively, include, lower electrodes, piezoelectric layers and upper electrodes layered in order from the pressure chambers, the lower electrodes being extended to areas corresponding to areas between the plural pressure chambers wherein an insulating layer is provided so as to cover at least all the lower electrodes located in the areas corresponding to areas between the plural pressure chambers. Piezoelectric member having a perovskite structure that contains, as the primary element, lead zirconate titanate, relaxor or barium titanate is employed as the piezoelectric layer 107.
Using etching, holes are formed in the substrate 101 to form ink pressure chambers 111 under the vibration plate 103. Furthermore, an orifice plate 113, in which ink communication ports 115 and ink orifices 112 are formed, is adhered to the substrate 101. As a result, the ink jet recording head is completed. An SUS substrate or an Si substrate can be employed as the orifice plate 113.
So long as a discharge force can be effectively exerted on ink, the structure, the material and the manufacturing method for the ink pressure chambers are not limited to those described above. Further, for an electrode material, an insulating film and a piezoelectric member, an appropriate formation method can also be employed.
The vibration plate 103 is formed on partition walls that separate the ink pressure chambers 111, and the insulating layer 106 is also formed on the partition walls for adjacent piezoelectric device.
Further, as shown in the structure in
According to either structure in
An example process for the manufacture of the ink jet recording head according to this invention will be described, while referring to
(A) The lower electrode, of Pt/Ti, is formed on the silicon substrate 101 on which the vibration plate layer 103, which is an SOI layer, and the oxide film 102, which is a box layer, are deposited. In addition, the insulating layer 106 is overlaid. Al2O3, AlN, Si3N4, SiO2, MgO, Ta2O5 or SiC can be applied for the insulating layer 106.
(B) The non-film formation areas 106d are formed by patterning the insulating layer 106.
(C) A thin film that contains lead zirconate titanate or barium titanate as the primary element is deposited on the patterned insulating layer 106, and the entire structure is sintered at 600° C. to 800° C. to obtain the piezoelectric layer 107. A metallic material such as Pt/Ti, for the upper electrodes 108, is deposited on the piezoelectric layer 107.
(D) The upper electrodes 108 are obtained by patterning.
(E) Device separation is performed by etching the piezoelectric layer 107, and the piezoelectric elements 109 are obtained. For this process, the dry etching method is employed, using the insulating layer 106 as an etching stop layer. When the insulating layer 106 is employed as an etching stop layer, the occurrence of a phenomenon where Pt/Ti, of the lower electrode 105, is sputtered and is attached to the end face of the piezoelectric elements can be prevented.
The portions of the insulating layer 106 that are exposed by dry etching should be thinner than the insulating layer 106c located under the piezoelectric layer 107. This is because, as the exposed portions of the insulating layer become thinner, the constraint imposed on the entire vibration plate is relaxed.
(F) After resist patterning has been completed, the silicon substrate 101 is etched from the side opposite the face at which the piezoelectric elements 109 are formed. In this manner, the ink pressure chambers 111 are formed below the piezoelectric elements 109.
(G) The ink communication portions 115 and the ink orifices 112 are formed in another silicon substrate, and the resultant silicon substrate is employed as the orifice plate 113.
(H) The silicon substrate 101 and the orifice plate 113 are adhered to each other, and the ink jet recording head 114 is completed.
In the substrate 101, holes were formed using etching in order to prepare ink pressure chambers 111. Further, the substrate 101 was adhered to a silicon substrate 113, used for orifices of 200 μm, in which ink communication portions 115 and ink orifices 112 were formed. In this manner, an ink jet recording head was completed. The width of the ink pressure chambers 111 was 100 μm, the depth was 3 mm, and the pitch between the piezoelectric elements 109 was 220 μm.
A printing test was conducted, using this head and water ink having a viscosity of 2 cp, at 30 kHz, with ink droplets of 3 pl that had a width of 12.5 mm. High quality printed matter could be obtained up to 2×1010 times, before a portion appeared in which no ink was discharged.
The same process as in example 2-1 was performed to manufacture piezoelectric elements, except that an insulating layer 106 was not formed. A printing test was conducted, using this ink jet recording head and water ink having a viscosity of 2 cp, at 30 kHz, with ink droplets of 3 pl that had a width of 12.5 mm. As a result, when printing had been performed 5×109 times, a short occurred between the upper and lower electrodes, and a portion appeared in which no ink was discharged.
As shown in
A method for manufacturing an ink jet recording head according to the present invention will be described, while referring to
(A) A lower electrode 105, made of Pt/Ti=300/30 nm, was deposited, using sputtering, on a silicon substrate 101 of 200 μm on which a box layer 102, 1 μm thick, which serves as an SiO2 layer, and an SOI layer 103, 5 μm thick, were deposited. Furthermore, an insulating layer 106 made of Ta2O5, 300 nm thick, was overlaid using sputtering.
(B) Then, the insulating layer 106 was partially removed, using etching, to obtain non-film formation areas 106d.
(C) PZT, 3 μm thick, was deposited, using sputtering, on the insulating layer 106 where the non-film formation areas 106d were formed, and the entire structure was sintered at 700° C. for five hours under an oxygen atmosphere. As a result, a piezoelectric layer 107 was formed. In addition, using sputtering, Pt/Ti=300/30 nm thick was deposited as an electrode layer on the piezoelectric layer 107.
(D) The Pt/Ti layer=300/30 nm was patterned to form upper electrodes 108.
(E) Dry etching was performed for the piezoelectric layer 107 using an etching gas that contained C4F8 and Cl2, and piezoelectric elements 109 were obtained. At this time, the Ta2O5 layer served as an etching stop layer.
(F) After resist pattering was completed, while the box layer 102 was used as a stop etching layer, etching was performed from the face opposite the face at which the piezoelectric elements 109 were formed. A method that enables vertical deep etching is an appropriate etching method. The etching in this example was performed using a so-called Bosch process that employs, as a plasma source, an ICP (Inductively Coupled Plasma) source that can generate a high density plasma, and uses SF6 and C4F8 as an etching gas. The etching was performed until the box layer 102 was exposed, and the exposed portion of the box layer 102 was removed using buffered hydrofluoric acid. In this manner, ink pressure chambers 111 were obtained.
(G) Also using the ICP method, ink communication portions 115 and ink orifices 112 having a diameter of 30 μm were formed in another silicon substrate 150 μm thick, and the resultant substrate was employed as an orifice plate 113.
(H) Au/Ti=100/30 nm was deposited on the orifice plate 113 using sputtering, and the orifice plate 113 and the silicon substrate 101 were adhered to each other by a vacuum bonding machine under a 3 MPa pressure at 300° C. As a result, an ink jet recording head was completed.
The sizes of the individual portions of the head were the same as those in example 2-1. A printing test was conducted, using this head and water ink having a viscosity of 2 cp, at 30 kHz, with ink droplets of 3 pl that had a width of 12.5 mm. High quality printed matter could be obtained up to 3×1010 times, before a portion occurred in which no ink was discharged.
According to the above described second embodiment, since the insulating layer is formed on the lower electrode so that part of the insulating layer extends below the piezoelectric layer, the lower electrode will not be exposed and sputtered during the etching process, and contamination of the device portion can be prevented by dispersing the material of the lower electrode. Furthermore, since the insulating member having a lower dielectric constant than the piezoelectric member is located between the piezoelectric member and the lower electrode, the electrostatic capacity of the piezoelectric device can be reduced, and quicker response to a drive wave is enabled. Therefore accurate discharge control can be performed.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2006-244150, filed Sep. 8, 2006, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2006-244150 | Sep 2006 | JP | national |