Method for manufacturing ink jet recording heads

A method for manufacturing ink jet recording heads includes the steps of forming a film of a first inorganic material in the form of ink flow path pattern using a soluble first inorganic material on the substrate having ink-discharge, pressure-generating elements formed thereon, forming a film of a second inorganic material becoming ink flow walls on the film of the first inorganic material using the second inorganic material, forming ink-discharge openings on the film of the second inorganic material above the ink-discharge, pressure-generating elements, and eluting the film of the first inorganic material. With this method, it becomes possible to set the ink-discharge, pressure-generating elements and the ink-discharge openings (ports) of each head with extremely high precision in a shorter distance with a good reproducibility to record images with higher quality and without any deformation of the head due to the applied heat, while providing a good resistance to ink and erosion, as well as a higher dimensional precision and reliability that may be affected otherwise by swelling or the like.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a method for manufacturing ink jet
 recording heads. More particularly, the invention relates to a method for
 manufacturing ink jet recording heads, that is capable of setting the
 ink-discharge, pressure-generating elements and the ink-discharge openings
 (ports) of each head with extremely high precision in a shorter distance
 with a good reproducibility to record images in higher quality without any
 deformation of the head due to the applied heat, while providing a good
 resistance to ink and erosion, as well as a higher dimensional precision
 and reliability that may be affected otherwise by swelling or the like.
 2. Related Background Art
 An ink jet recording head applicable to the ink jet recording method
 (liquid jet recording method) is generally provided with fine
 recording-liquid discharge openings (ports), liquid-flow paths, and
 liquid-discharge, energy-generating portions, each arranged on a part of
 each liquid-flow path. Then, to obtain high quality images using an ink
 jet recording head of this kind, it is desirable to discharge small
 droplets of the recording liquid from the respective discharge openings
 (ports) each in an equal volume always at the same discharge speed. In
 this respect, there has been disclosed in the specifications of Japanese
 Patent Application Laid-Open Nos. 4-10940 to 4-10942, a method for
 discharging ink droplets in such a manner that driving signals are applied
 to the ink-discharge pressure-generating elements (electrothermal
 transducing elements) in accordance with recording information to cause
 the electrothermal transducing elements to generate thermal energy, which
 provided a rapid temperature rise to ink beyond its nuclear boiling point,
 thus forming bubbles in the ink to discharge ink droplets by communicating
 these bubbles with the air outside.
 As an ink jet recording head that may implement such method, it is
 preferable to make the distance between each of the electrothermal
 transducing elements and discharge openings (ports) (hereinafter referred
 to as the "OH distance") as small as possible. Also, for this method, the
 discharge volume is determined almost only by the OH distance. Therefore,
 it is necessary to set the OH distance exactly together with a good
 reproducibility.
 Conventionally, as a method for manufacturing ink jet recording heads,
 there is a method such as disclosed in the specifications of Japanese
 Patent Application Laid-Open Nos. 57-208255, and 57-208256, wherein the
 nozzles formed by ink-flow paths and discharge openings (ports) are
 patterned by the use of photosensitive resin material on the substrate
 having ink-discharge, pressure-generating elements formed on it, and then,
 a glass plate or the like is bonded to cover the substrate, or a method
 such as disclosed in the specifications of Japanese Patent Application
 Laid-Open No. 61-154947, wherein the ink flow path pattern is formed by
 soluble resin, and this pattern is covered with epoxy resin or the like to
 harden it, and then, after the substrate is cut off, the pattern formed by
 the soluble resin is removed by elution. However, any one of these methods
 is arranged to be adoptable for manufacturing only an ink jet recording
 head whose discharge direction is different from (almost perpendicular to)
 the development direction of bubbles. Then, for a head of this type, it is
 arranged to set the distance between the ink-discharge, pressure
 generating elements and the discharge openings (ports) by cutting off each
 of the substrates. As a result, the cutting precision becomes an extremely
 important factor for controlling the distance between them. Since,
 however, the cutting is executed by the use of a dicing saw or some other
 mechanical means in general, it is difficult to carry out the setting
 performance with an extremely high precision.
 Also, as a method for manufacturing an ink jet recording head whose type is
 such that the development direction of bubbles is almost the same as that
 of the discharges, there is a method disclosed in the specification of
 Japanese Patent Application Laid-Open No. 58-8658, wherein the substrate
 and the dry film that becomes the orifice plate are bonded through the
 other patterned dry film, and then, the discharge openings (ports) are
 formed by means of photolithography, or a method disclosed in the
 specification of Japanese Patent Application Laid-Open No. 62-264975,
 wherein the substrate having the ink-discharge, pressure-generating
 elements formed on it and the orifice plate processed by electrolytic
 casting are bonded through dry film, among some others. Nevertheless, with
 any one of these methods, it is difficult to form the orifice plate thin
 uniformly (in a thickness of 20 .mu.m or less, for example), and even if
 such thin orifice plates can be produced, it becomes extremely difficult
 to execute the bonding process between the substrate having the
 ink-discharge, pressure-generating elements on it with the thin orifice
 plate due to its brittleness.
 In order to solve these problems, there is disclosed in Japanese Patent
 Application Laid-Open No. 6-286149 a method for manufacturing ink jet
 recording heads that is capable of setting the ink-discharge,
 pressure-generating elements and the discharge openings (ports) with a
 short distance in an extremely high precision and with a good
 reproducibility to record images in higher quality with such a manner that
 (1) after ink-flow paths are formed by the patterning by use of soluble
 resin on the substrate having ink-discharge, pressure-generating elements
 on it, (2) the solid epoxy resin containing coating resin in it is
 dissolved in a solvent at room temperature, which is coated on the soluble
 resin layer by the application of solvent coating to form the covering
 resin layer that may become ink-flow path walls on the soluble resin
 layer, and then, (3) after the ink-discharge openings (ports) are formed
 on the covering resin layer above the ink-discharge, pressure-generating
 elements, (4) the soluble resin layer is eluted for the provision of the
 aforesaid ink jet recording head. With this method, it is possible to
 shorten the processes of manufacture and obtain an inexpensive but
 reliable ink jet recording head.
 Nevertheless, there are still problems given below for the method disclosed
 in the specification of Japanese Patent Application Laid-Open No.
 6-286149.
 (1) Since the ink-flow-path walls are usually formed with resin on the
 silicon substrate, deformation tends to take place due to the difference
 in linear expansion factors of the inorganic material and resin. As a
 result, a problem is encountered with respect to the mechanical
 characteristics of the walls thus formed.
 (2) The edge portion of resin formation is often rounded. Then, the
 sharpness of the resultant edge thereof is often insufficient. In some
 cases, therefore, the dimensional precision obtained is not necessarily
 good enough.
 (3) Resin is subjected to swelling and easy peeling off. In some cases,
 therefore, its reliability is not necessarily good enough.
 SUMMARY OF THE INVENTION
 The present invention is designed with a view to solving these problems
 encountered in the conventional art. It is an object of the invention to
 provide a method for manufacturing ink jet recording heads that is capable
 of setting the ink-discharge, pressure-generating elements and the
 ink-discharge openings (ports) of each head with extremely high precision
 in a shorter distance with a good reproducibility to record images with
 higher quality and without any deformation of the head due to the applied
 heat, while providing a good resistance to ink and erosion, as well as a
 higher dimensional precision and reliability that may be affected
 otherwise by swelling or the like.
 Also, with this method, it is possible to shorten the processes of
 manufacture as in the method disclosed in the specification of Japanese
 Patent Application Laid-Open No. 6-286149, and to obtain a highly reliable
 ink jet recording head at lower costs of manufacture.
 In order to achieve the objects of the present invention, the method for
 manufacturing ink jet recording heads comprises the steps of forming a
 film of a first inorganic material in the form of an ink-flow-path pattern
 using the soluble first inorganic material on the substrate having
 ink-discharge, pressure-generating elements formed thereon; forming a film
 of a second inorganic material becoming ink-flow walls on the film of the
 first inorganic material using the second inorganic material; forming
 ink-discharge openings on the film of the second inorganic material above
 the ink-discharge, pressure-generating elements; and eluting the film of
 the first inorganic material.
 Also, the method of the present invention for manufacturing an ink jet
 recording head, which is provided with ink-discharge openings for
 discharging ink, ink-flow paths communicating with the ink-discharge
 openings for supplying ink to the ink-discharge openings, heat-generating
 elements arranged in the ink-flow paths for creating bubbles in liquid
 distributed in the ink-flow paths, and supply openings for supplying
 liquid to the ink-flow paths, comprises the steps of forming silicon oxide
 film on the surface of an elemental substrate having Si as the base
 thereof with at least the heat-generating elements formed on the surface
 thereof; forming on the surface of the elemental substrate the portions
 covered with the silicon oxide film, and the portions having the surface
 of the elemental substrate exposed by selectively removing the silicon
 oxide film on the surface of the elemental substrate; forming a
 polycrystal Si layer on the portions covered by the silicon oxide film, at
 the same time, forming a monocrystal Si layer on the portions having the
 surface of the elemental substrate exposed by developing Si epitaxially in
 a desired thickness all over the surface of the elemental substrate
 including the portions covered by the silicon oxide film; forming SiN film
 all over the surface of the monocrystal Si layer and the polycrystal Si
 layer in a desired thickness; forming the ink-discharge openings on the
 SiN film on the polycrystal Si layer; removing the portions covered with
 the silicon oxide film formed on the surface of the elemental substrate by
 forming the through holes becoming the supply openings from the reverse
 side of the elemental substrate; and forming the ink-flow paths by
 removing only the polycrystal Si layer.
 Also, the method of the present invention for manufacturing an ink jet
 recording head, which is provided with ink-discharge openings for
 discharging ink, ink-flow paths communicating with the ink-discharge
 openings for supplying ink to the ink-discharge openings, heat-generating
 elements arranged in the ink-flow paths for creating bubbles in liquid
 distributed in the ink flow paths, and supply openings for supplying
 liquid to the ink flow paths, comprises the steps of forming silicon oxide
 film on the surface of an elemental substrate having Si as the base
 thereof with at least the heat-generating elements formed on the surface
 thereof; forming on the surface of side portions of the elemental
 substrate the portions covered with the silicon oxide film, at the same
 time, exposing the surface of the elemental substrate other than the side
 portions by selectively removing the silicon oxide film on the surface of
 the elemental substrate; forming a polycrystal Si layer on the portions
 covered by the silicon oxide film, at the same time, forming a monocrystal
 Si layer on the portions having the surface of the elemental substrate
 exposed by developing Si epitaxially in a desired thickness all over the
 surface of the elemental substrate including the portions covered by the
 silicon oxide film; forming SiN film all over the surface of the
 monocrystal Si layer and the polycrystal Si layer in a desired thickness;
 forming the ink-discharge openings on the SiN film on the polycrystal Si
 layer; removing the portions covered with the silicon oxide film formed on
 the side portions of the elemental substrate; and forming the ink-flow
 paths and the supply openings by removing only the polycrystal Si layer.
 Other objectives and advantages besides those discussed above will be
 apparent to those skilled in the art from the description of a preferred
 embodiment of the invention which follows. In the description, reference
 is made to accompanying drawings, which form a part hereof, and which
 illustrate an example of the invention. Such example, however, is not
 exhaustive of the various embodiments of the invention, and therefore
 reference is made to the claims which follow the description for
 determining the scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 In accordance with the present invention, it is preferable to use a first
 inorganic material that is easier to be dissolved than a second inorganic
 material by the solvent (etching solution) used at the time of elution,
 and that is capable of being eluted later, and eluted by the injection of
 alkaline ink even when there is the residue of elution (etching residue).
 For such material, it is preferable to use PSG (Phospho-Silicate Glass),
 BPSG (Boron Phospho-Silicate Glass), silicon oxide, or the like, for
 example. For a material of the kind, it is possible to remove it by
 elution using hydrofluoric acid in the later process. For the first
 inorganic material, it is particularly preferable to use the PSG as the
 first inorganic material, because it has a higher etching rate against the
 buffered hydrofluoric acid. Also, with attention given to the damage that
 may be brought to the inorganic material because of the solvent used for
 elution, it is preferable to use Al as the first inorganic material, and
 as the solvent, it is preferable to use the phosphric acid or hydrochloric
 acid, which is used at the room temperature.
 Also, for the second inorganic material in accordance with the present
 invention, it is usual to adopt the material that is not easily soluble by
 the solvent (etching solution) used for elution as compared with the first
 inorganic material, while having a good chemical stability, such as
 resistance to ink, as well as a good physical property, such as a
 mechanical strength sufficiently good to satisfy its use as the
 discharge-opening surface. For such material, it is preferable to adopt
 the silicon oxide that is used for the general semiconductor manufacture.
 In accordance with the present invention, it is possible to obtain the
 following effects if PSG (Phospho-Silicate Glass), BPSG (Boron
 Phospho-Silicate Glass), or silicon oxide is used for the first inorganic
 material, and silicon oxide is used for the second inorganic material:
 (1) Resistance to erosion, such as to ink, becomes excellent.
 (2) Difference in thermal expansion becomes smaller, and the problem of
 thermal deformation is eliminated, because silicon substrate is usually
 used as the one that is adopted for the present invention.
 (3) The dimensional precision and positional precision are excellent,
 because it becomes possible to execute the photolithographic process to
 form discharge openings (ports) on the silicon nitride film.
 (4) Reliability becomes higher because there is no swelling taking place
 due to ink.
 (5) It becomes possible to execute all the formation processes by means of
 photolithography, and the mechanical assembling is possible under a
 cleaner environment. As a result, the problem of dust particles is
 eliminated.
 (6) There is no possibility that the surface of ink discharge pressure
 element, such as electrothermal converting means, is contaminated, because
 no resin is used, nor is any organic solvent used here.
 (7) It becomes possible to form the discharge openings (ports)
 perpendicular or in the reversely tapered configuration.
 (8) Heat treatment is possible at a temperature of 300.degree. C. to
 400.degree. C. after the formation of discharge openings (ports). As a
 result, the water-repellent treatment is given uniformly to the surface of
 discharge openings (ports) by means of plasmic polymerization.
 (9) The resistance to abrasion becomes higher against wiping at the time of
 head recovery to make the durability of the head higher, because the
 silicon nitride film is hard.
 Also, when Al is used as the first inorganic material in accordance with
 the present invention, the following effects are further obtainable:
 (1) In a case where the silicon nitride is used as the second inorganic
 material, which is not easily soluble against the etching solution, while
 having a high chemical stability, such as resistance to ink, as well as
 having a good physical property, such as the mechanical strength that may
 satisfy its use as the discharge-opening surface, the etching selection
 ratio is as large as 20:1 if CF.sub.4, C.sub.2 F.sub.6, C.sub.3 F.sub.8,
 SF.sub.6, or some other gas is used for etching the orifice portion. As a
 result, it becomes possible to produce the etching-stopper effect (the
 prevention of any possible damage to the base material).
 (2) Also, in the formation of the orifice portion, there is no under cut
 configuration brought about by the base-material etching.
 Also, if the structure is arranged so that the main component of the
 material of the liquid-flow-path member, which is provided with the
 discharge openings (ports) and liquid-flow paths, is Si as the elemental
 substrate whose basic material is also Si, there is no difference that may
 take place in the thermal expansion factors of the elemental substrate and
 the liquid-flow path member. As a result, the close contact between the
 elemental substrate and the liquid-flow-path member or the relative
 positional precision between them is not degraded by the thermal influence
 exerted by the heat accumulation in the head at the time of higher speed
 printing. Also, with the liquid-flow-path member that can be produced by
 the application of the semiconductor process, the distance between the
 heat-generating elements and discharge openings (ports) is set with an
 extremely high precision with a good reproducibility. Further, since the
 main component of the liquid-flow-path member is Si, this member is made
 excellent in resistance to ink or resistance to erosion. With these
 advantages described above, it becomes possible to perform highly reliable
 recording with higher quality.
 (First Embodiment)
 FIGS. 1A and 1B are views illustrating a side-shooter-type ink jet
 recording head manufactured in accordance with a first embodiment of the
 present invention; FIG. 1A is a plan view; and FIG. 1B is a
 cross-sectional view taken along line 1B--1B in FIG. 1A. Here, discharge
 openings (ports) 14 are formed on the discharge-opening surface 15 formed
 by silicon nitride. FIGS. 2A to 2H are views that illustrate the process
 of manufacture in accordance with the present embodiment, that correspond
 to the section taken along lines 2A--2A to 2H--2H in FIG. 1A.
 As shown in FIG. 2A, the electrothermal converting means 7 (heaters formed
 by HfB.sub.2) are, at first, formed as the discharge energy-generating
 devices. Then, on the bottom end of a silicon substrate 1 an SiO.sub.2
 film 2 is formed in a thickness of approximately 2 .mu.m at a temperature
 of 400.degree. C. by the application of the CVD method. On the silicon
 substrate, there are formed the transducing devices and the wiring that
 arranges the electric connection therefor, and also, a cavitation-proof
 film as the protection film that protects them.
 As shown in FIG. 2B, resist is coated on the SiO.sub.2 film 2. Then, after
 exposure and development, the opening 11 is formed by means of dry or wet
 etching. The SiO.sub.2 film 2 serves as a mask when a through hole 13 is
 made later. The through hole 13 is formed from the opening 11. For the
 etching of the SiO.sub.2 film 2, the reactive ion etching or the plasma
 etching is performed with CF.sub.4 as the etching gas if the dry etching
 is adopted. If wet etching is adopted, buffered hydrofluoric acid is used.
 Then, as shown in FIG. 2C, by the application of the CVD method, PSG
 (Phospho-Silicate Glass) film 3 is formed in a thickness of approximately
 20 .mu.m on the upper end side of the substrate at a temperature of
 350.degree. C.
 Subsequently, as shown in FIG. 2D, the PSG film 3 is processed to form the
 specific pattern of flow paths. Here, it is preferable to adopt the dry
 etching using resist for the PSG film processing, because with this
 etching, the SiO.sub.2 film on the bottom end is not subjected to any
 damage that may be caused otherwise.
 Then, as shown in FIG. 2E, the silicon nitride film 3 is formed in a
 thickness of approximately 5 .mu.m on the PSG film 3, which is configured
 in the form of flow-path pattern, by the application of the CVD method at
 a temperature of 400.degree. C. At this juncture, the opening 12 is also
 buried with the silicon nitride film.
 The thickness of the silicon nitride film, which is formed here, regulates
 the thickness of the discharge openings (ports), and the thickness of the
 PSG film that is formed earlier regulates each gap of ink flow paths.
 Therefore, these thicknesses may exert a great influence on the
 ink-discharge characteristics of the ink-jet performance. Each of them
 should be determined appropriately depending on the characteristics as
 required.
 Then, as shown in FIG. 2F, the SiO.sub.2 film 2 the contour of that has
 been formed is used as a mask. Then, with this mask, the through hole 13
 is formed on the silicon substrate 1 as the ink-supply opening. Here, any
 method may be adoptable for the formation of the through hole, but it is
 preferable to use the ICP (inductive coupling plasma) etching with
 CF.sub.4 and oxygen as the etching gas, because with this etching, the
 substrate is not subjected to any electrical damages, and also, formation
 is possible at a lower temperature.
 Now, as shown in FIG. 2G, using resist, the discharge openings (ports) 14
 are formed on the silicon nitride film 4 by the application of dry
 etching. Here, by the use of the highly anisotropic reactive ion etching,
 the additional effect is produced as given below.
 In other words, with the conventional structure of the side-shooter-type
 ink jet head, the edge portion thereof tends to be rounded because the
 discharge-opening portion is formed by resin, and the discharge
 characteristics may be affected in some cases. In order to avoid this
 possibility, an orifice plate, which is formed by means of electrocasting,
 is bonded to such an opening portion. In accordance with the present
 embodiment, however, the discharge openings (ports) 14 are formed on the
 silicon nitride film 4 formed by the application of the reactive ion
 etching, hence making it possible to form the edges of the discharge
 openings (ports) sharp.
 Further, with the silicon nitride film that has been multi-layered, the
 etching rate is made higher on the lower part or the composition may be
 changed gradually. In this manner, it becomes possible to provide the
 reversed taper configuration to make the exit of each of the discharge
 openings (ports) narrower, while the interior thereof is made wider. With
 the reversely tapered discharge openings (ports), printing accuracy is
 further enhanced.
 Also, with good edge configuration of each of the discharge openings
 (ports), it becomes possible to form a water-repellent film only on the
 surface thereof when the water-repellent film should be formed by the
 application of plasmic polymerization. Also, when water-repellency should
 be produced by implanting ion on the surface of the silicon nitride film,
 there is no possibility that the water-repellency is provided for the
 interior of each discharge opening (port). As a result, the flight
 direction of ink is not caused to be deviated, thus making it possible to
 print with higher precision.
 Then, as shown in FIG. 2H, using buffered hydrofluoric acid, the PSG film 3
 is removed by elution from the discharge openings (ports) and the through
 holes as well.
 After that, the water-repellent film that contains Si is formed on the
 discharge opening surface by the application of the plasmic
 polymerization. Then, on the bottom end of the Si substrate 1, an ink
 supply member (not shown) is bonded to complete an ink jet recording head.
 (Second Embodiment)
 In accordance with the first embodiment, the PSG base is formed in order to
 eliminate steps on the discharge-opening surface. As shown in FIGS. 3A and
 3B, however, grooves 16 are arranged between discharge openings (ports) to
 enable ink to escape in accordance with the present embodiment. FIGS. 3A
 and 3B are views that illustrate the discharge-opening surface of an ink
 jet recording head in accordance with a second embodiment of the present
 invention; FIG. 3A is a plan view and FIG. 3B is a cross-sectional view
 taken along line 3B--3B in FIG. 3A. FIGS. 4A to 4H are cross-sectional
 views taken along lines 4A--4A to 4H--4H, that illustrate the process for
 manufacturing the ink jet recording head of the second embodiment of the
 present invention.
 This manufacturing process is the same as that of the first embodiment
 except for the difference in pattern upon forming the flow path by
 processing the PSG film 3. FIGS. 4A to 4H correspond to FIGS. 2A to 2H.
 As shown in FIGS. 4A to 4C, the electrothermal converting means 7 (the
 heaters formed by HfB.sub.2 which are not shown in FIGS. 4A to 4C), that
 serve as the discharge-energy-generating devices are formed on the silicon
 substrate 1 in the same manner as the first embodiment, and then, after
 the SiO.sub.2 film 2 is formed on the bottom end thereof in a thickness of
 approximately 2 .mu.m, the opening 11 is formed. Further, on the upper end
 side of the substrate, the PSG film 3 is formed.
 Then, as shown in FIG. 4D, the specific flow-path pattern is formed. In
 accordance with the present embodiment, each of the openings 12 is formed
 larger.
 Subsequently, as shown in FIG. 4E, the silicon nitride film 4 is formed on
 the PSG film 3, which is configured in the form of flow-path pattern,
 hence the grooves of silicon nitride film being formed on each portion of
 the openings 12.
 After that, exactly in the same manner as the first embodiment, the through
 hole 13 is formed as the ink-supply opening as shown in FIGS. 4F to 4H.
 Then, after the discharge openings (ports) 14 are formed by the
 application of dry etching using resist, the PSG film 3 is removed by
 elution from the discharge openings (ports) 14 and the through hole 13
 using buffered hydrofluoric acid.
 Subsequently, an ink jet recording head is completed in the same manner as
 the first embodiment.
 (Third Embodiment)
 FIGS. 5A and 5B are views that illustrate the side-shooter-type ink jet
 recording head manufactured in accordance with the present embodiment of
 the present invention; FIG. 5A is a plan view and FIG. 5B is a
 cross-sectional view taken along line 5B--5B in FIG. 5A. Here, the
 discharge openings (ports) 14 are formed on the discharge-opening surface
 15 formed by silicon nitride. FIGS. 6A to 6H are views which illustrate
 the method for manufacturing the ink jet recording head of the present
 embodiment corresponding to the section taken along line 6A--6A to 6H--6H
 in FIG. 5A.
 As shown in FIG. 6A, the electrothermal converting means 7 (heaters formed
 by TaN.sub.2) are, at first, formed as the discharge-energy-generating
 devices. Then, on the bottom end of a silicon substrate 1 an SiO.sub.2
 film 2 is formed in a thickness of approximately 2 .mu.m at a temperature
 of 400.degree. C. by the application of the CVD method. On the silicon
 substrate, there are formed the transducing devices and the wiring that
 arranges the electric connection therefor, as well as a cavitation proof
 film as the protection film that protects them.
 As shown in FIG. 6B, resist is coated on the SiO.sub.2 film 2. Then, after
 exposure and development, the opening 11 is formed by means of dry or wet
 etching. The SiO.sub.2 film 2 serves as a mask when a through hole 13 is
 made later. The through hole 13 is formed from the opening 11. For the
 etching of the SiO.sub.2 film 2, the reactive ion etching or the plasma
 etching is performed with CF.sub.4 as the etching gas if the dry etching
 is adopted. If the wet etching is adopted, buffered hydrofluoric acid is
 used.
 Then, as shown in FIG. 6C, Al film 23 is formed on the upper end side of
 the substrate 1 by the sputtering or vapor deposition in a thickness of
 approximately 10 .mu.m.
 After that, as shown in FIG. 6D, the Al film 23 is processed to form the
 specific flow-path pattern. Here, it is preferable to process the Al film
 by the wet etching using resist, because then the lower end of the
 SiO.sub.2 film 2 is not damaged.
 Subsequently, as shown in FIG. 6E, the silicon nitride film 4 is formed in
 a thickness of approximately 10 .mu.m on the Al film 23, which is
 configured in the form of flow-path pattern, by the application of the CVD
 method at a temperature of 400.degree. C. At this juncture, the opening 12
 is also buried with the silicon nitride film 4.
 The thickness of the silicon nitride film 4 that is formed here regulates
 the thickness of the discharge openings (ports), and the thickness of the
 Al film 3 that is formed earlier regulates each gap of ink flow paths.
 Therefore, these thicknesses may exert a great influence on the
 ink-discharge characteristics of the ink jet performance. Each of them
 should be determined appropriately depending on the characteristics as
 required.
 Then, as shown in FIG. 6F, the SiO.sub.2 film 2 the contour of which has
 been formed is used as a mask. Then, with this mask, the through hole 13
 is formed on the silicon substrate 1 as the ink-supply opening. Here, any
 method may be adoptable for the formation of the through hole 13, but it
 is preferable to use the ICP (inductive coupling plasma) etching with
 CF.sub.4, C.sub.2 F.sub.6, C.sub.3 F.sub.8, SF.sub.6, or some other gas
 and oxygen as the etching gas, because with this etching, the substrate is
 not subjected to any electrical damages, and also, the formation is
 possible at a lower temperature.
 Now, as shown in FIG. 6G, using resist, the discharge openings (ports) 14
 are formed on the silicon nitride film 4 by the application of dry
 etching. Here, by the use of the highly anisotropic reactive ion etching,
 such as ICP etching, the additional effect is produced as given below.
 In other words, with the conventional structure of the side-shooter-type
 ink jet head, the edge portion thereof tends to be rounded because the
 discharge-opening portion is formed by resin, and the discharge
 characteristics may be affected in some cases. In order to avoid this
 possibility, an orifice plate, which is formed by means of electrocasting,
 is bonded to such opening portion. In accordance with the present
 embodiment, however, the discharge openings (ports) 14 are formed on the.
 silicon nitride film 4 formed by the application of the reactive ion
 etching, hence making it possible to form the edges of the discharge
 openings (ports) sharp.
 Further, with the silicon nitride film that has been multi-layered, the
 etching rate is made higher on the lower part or the composition may be
 changed gradually. In this manner, it becomes possible to provide the
 reversed taper configuration to make the exit of each of the discharge
 openings (ports) narrower, while the interior thereof is made wider. With
 the reversely tapered discharge openings (ports), the printing accuracy is
 enhanced still more.
 Also, with the good edge configuration of each of the discharge openings
 (ports), it becomes possible to form the water-repellent film only on the
 surface thereof when the water-repellent film should be formed by the
 application of plasmic polymerization. Also, when the water-repellency
 should be produced by implanting ion on the surface of the silicon nitride
 film, there is no possibility that the water-repellency is provided for
 the interior of each of the discharge openings (ports). As a result, the
 flight direction of ink is not caused to be deviated, thus making it
 possible to print with higher precision.
 Then, as shown in FIG. 6H, using phosphoric acid or hydrochloric acid at
 the room temperature, the Al film 23 is removed by elution from the
 discharge openings (ports) and the through holes as well.
 After that, the water-repellent film that contains Si is formed on the
 discharge-opening surface by the application of the plasmic
 polymerization. Then, on the bottom end of the Si substrate 1, an
 ink-supply member (not shown) is bonded to complete an ink jet recording
 head.
 Also, when the discharge openings (ports) are formed, Al is used for the
 basic layer after the silicon nitride film has been etched. Etching comes
 to a stop here. This etching layer is rarely affected by etching gas. As a
 result, there is no influence exerted on the basic layer.
 (Fourth Embodiment)
 In accordance with the third embodiment, the Al base is formed in order to
 eliminate steps on the discharge-opening surface. As shown in FIGS. 7A and
 7B, however, grooves 16 are arranged between discharge openings (ports) to
 enable ink to escape in accordance with the present embodiment. Here, FIG.
 7A is a plan view and FIG. 7B is a cross-sectional view taken along line
 7B--7B in FIG. 7A. FIGS. 8A to 8H are views that illustrate the process
 for manufacturing the ink jet recording head of the fourth embodiment of
 the present invention, which correspond to the section taken along line
 8A--8A to 8H--8H in FIG. 7A.
 The process of manufacture in accordance with the present embodiment is the
 same as that of the third embodiment with the exception of the pattern
 that is different from the one used for the flow-path pattern by
 processing the Al film 23. FIGS. 8A to 8H correspond to FIGS. 6A to 6H.
 As shown in FIGS. 8A to 8C, the electrothermal converting means 7 (the
 heaters formed by TaN.sub.2, but not shown in FIGS. 8A to 8C), which serve
 as the discharge-energy-generating-devices, are formed on the silicon
 substrate 1 in the same manner as the third embodiment, and then, after
 the SiO.sub.2 film 2 is formed on the bottom end thereof in a thickness of
 approximately 2 .mu.m, the opening 11 is formed. Further, on the upper end
 side of the substrate 1, the Al film 23 is formed.
 Then, as shown in FIG. 8D, the specific flow-path pattern is formed. In
 accordance with the present embodiment, each of the openings 12 is formed
 larger.
 Subsequently, as shown in FIG. 8E, the silicon nitride film 4 is formed on
 the Al film 23, which is configured in the form of a flow-path-pattern,
 and hence the grooves of silicon nitride film are formed on each portion
 of the openings 12.
 After that, exactly in the same manner as the third embodiment, the through
 hole 13 is formed as the ink-supply opening as shown in FIGS. 8F to 8H.
 Then, after the discharge openings (ports) 14 are formed by the
 application of dry etching using resist, the Al film 23 is removed by
 elution from the discharge openings (ports) 14, as well as the through
 hole 13, using phosphoric acid or hydrochloric acid at the room
 temperature.
 Subsequently, an ink jet recording head is completed in the same manner as
 the third embodiment.
 As has been described above, in accordance with the first to fourth
 embodiments, it is generally practiced to form the through hole 13 as
 shown in FIG. 10 in plan view. However, in a case where the through hole
 is formed by means of ICP etching as adopted for the first to fourth
 embodiments, it becomes possible to configure the through hole freely.
 Therefore, with the formation of the through hole that surrounds each of
 the discharge openings (ports) as shown in FIG. 9, the ink refilling
 condition is improved with the resultant enhancement of the discharge
 speeds.
 (Fifth Embodiment)
 FIG. 11 is a perspective view that shows most suitably a liquid jet head in
 accordance with a fifth embodiment of the present invention. FIG. 12 is a
 cross-sectional view taken along line 12--12 in FIG. 11. The ink jet
 recording head shown in FIGS. 11 and 12 comprises an elemental substrate
 201 having two lines of plural heat-generating elements 202 on the central
 portion of the surface of the Si substrate; liquid-flow paths (ink flow
 paths) 204 that distribute liquid onto each of the heat-generating
 elements 202; the monocrystal Si 203 that forms side walls of the
 liquid-flow paths 204 formed on the elemental substrate 201; the SiN film
 205 formed on the monocrystal Si 203, which becomes the ceiling of the
 liquid-flow paths 204; a plurality of ink-discharge openings (ports) 206
 drilled on the SiN film 205, which face each of the plural heat-generating
 elements 202, respectively; and supply opening 207 that penetrates the
 elemental substrate 201 for supplying liquid to the liquid-flow paths 205.
 In this manner, the monocrystal Si 203 and the SiN film 205 serve as the
 liquid-flow-path members that constitute the liquid-flow paths 204 on the
 elemental substrate 201. Also, the monocrystal Si 203 does not cover both
 side portions of the elemental substrate 201 where the electric pads 210
 are formed to supply electric signals from the outside to the
 heat-generating elements 202.
 Now, the above-mentioned elemental substrate 201 will be described. FIG. 13
 is a cross-sectional view that shows the portion corresponding to the
 heat-generating member (bubble generating area) of the elemental substrate
 201. In FIG. 13, a reference numeral 101 designates the Si substrate and
 102, the thermal oxide film (SiO.sub.2 film) which serves as the heat
 accumulation layer. A reference numeral 103 designates the Si.sub.2
 N.sub.4 film that serves as the interlayer film that functions dually as
 the heat accumulation layer; 104 designates a resistive layer; 105
 designates the Al alloy wiring such as Al, Al-Si, Al-Cu; 106 denotes
 SiO.sub.2 film or Si.sub.2 N.sub.4 film that serves as the protection
 film; and 107 denotes the cavitation proof film that protects the
 protection film 106 from the chemical and physical shocks that follow the
 heat generation of the resistive layer 104. Also, a reference numeral 108
 designates the heat-activation unit of the resistive layer 104 in the area
 where no electrode wiring 105 is arranged. These constituents are formed
 by the application of semiconductor process technologies and techniques.
 FIG. 14 is a cross-sectional view that shows schematically the main element
 when it is cut vertically.
 On the Si substrate of P-type conductor, there are structured the P-MOS 450
 on the N-type well region 402 and the N-MOS 451 on the P-type well region
 403 by means of impurities induction and diffusion or some other ion
 plantation using the general MOS process. The P-MOS 450 and the N-MOS 451
 comprise the gate wiring 415 formed by poly-Si deposited by the
 application of CVD method in a thickness of 4,000 .ANG. or more and 5,000
 .ANG. or less through the gate-insulation film 408 in a thickness of
 several hundreds of n, respectively; and the source region 405, the drain
 region 406, and the like formed by the induction of N-type or P-type
 impurities. Then, the C-MOS logic is constructed by these P-MOS and N-MOS.
 Here, the N-MOS transistor for use of element driving is constructed by the
 drain region 411, the source region 412, and the gate wiring 413, among
 some others, on the P-well substrate also by the processes of impurity
 induction and diffusion or the like.
 In this respect, a description has been provided of the structure that uses
 N-MOS transistors, but this invention is not necessarily limited to the
 use of the N-MOS transistors. It may be possible to use any type of
 transistors if only the transistors are capable of driving a plurality of
 heat-generating elements individually, while having the function to
 achieve the fine structure as described above.
 Also, the device separation is executed by the formation of the oxide-film
 separation areas 453 by means of the filed oxide film in a thickness of
 5,000 .ANG. or more and 10,000 .ANG. or less. This filed oxide film is
 arranged to function as the first layer of the heat-accumulation layer 414
 under the heat-activation unit 108.
 After each of the elements is formed, the interlayer insulation film 416 is
 accumulated in a thickness of approximately 7,000 .ANG. by PSG, BPSG film,
 or the like by the application of CVD method. Then, smoothing treatment or
 the like is given by means of heat treatment. After that, wiring is
 conducted through the contact hole by the Al electrode 417 that becomes
 the first wiring layer. Subsequently, by the application of plasma CVD
 method, the interlayer insulation film 418, such as the SiO.sub.2 film, is
 accumulated in a thickness of 10,000 .ANG. or more and 15,000 .ANG. or
 less. Then, by way of the through hole, the TaN.sub.0.8,hex film is formed
 as the resistive layer 104 in a thickness of approximately 1,000 .ANG. by
 the application of the DC sputtering method. After that, the second wiring
 layer Al electrode is formed to serve as the wiring to each of the
 heat-generating elements.
 As the protection film 106, the Si.sub.2 N.sub.4 film is formed in a
 thickness of approximately 10,000 .ANG. by the application of plasma CVD.
 On the uppermost layer, the cavitation proof layer 107 is formed with Ta
 or the like in a thickness of approximately 2,500 .ANG..
 As described above, in accordance with the present embodiment, the
 materials that form the liquid-flow path member and the elemental
 substrate are all Si as its main component.
 Now, with reference to FIGS. 15A and 15B and FIGS. 16G to 16J, a
 description will be provided of a method for manufacturing a substrate
 used for the ink jet recording head of the present embodiment.
 At first, in FIG. 15A, the elemental substrate 201 is formed in the manner
 as described in conjunction with FIGS. 3A and 3B and FIGS. 4A to 4H. To
 briefly describe, the driving element is formed on the Si [100] substrate
 by the application of the thermal diffusion and ion implantation or some
 other semiconductor process. Further, the wiring and heat-generating
 elements, which are connected to the driving element, are formed. Then, as
 shown in FIG. 15B, the surface and the reverse side of the elemental
 substrate 201 are all covered by the oxide film 302 to form the portion
 covered by the oxide film (SiO.sub.2 film) 302 and the portion where the
 elemental substrate 201 is exposed on the surface of the elemental
 substrate 201 by means of photolithographic method as shown in FIG. 15C.
 After that, by means of epitaxial development, such as the low-temperature
 epitaxial development, Si is developed in a thickness of approximately 20
 .mu.m all over the surface of the elemental substrate 201 as shown in FIG.
 15D. At this juncture, the monocrystal Si 203 is formed on the portion
 where the elemental substrate 201 is exposed, and the polycrystal Si 304
 is formed on the portion covered by the oxide film 302.
 Then, as shown in FIG. 15E, the SiN film 205 is formed in a thickness of
 approximately 5 .mu.m by the application of the CVD method or the like all
 over the surfaces of the monocrystal Si 203 and the polycrystal Si 304.
 Subsequently, as shown in FIG. 15F, by means of the photolithographic
 method, the orifice holes (discharge openings) 206 are formed on the SiN
 film 205 on the polycrystal Si 304 for ink discharges. Then, part of the
 oxide film 302 on the reversed side of the elemental substrate 201 is
 exposed by means of the photolithographic method. After that, the film is
 removed by use of buffered hydrofluoric acid. In this manner, as shown in
 FIG. 15G, the window 307 is used for use of anisotropic etching. Then, the
 through hole (supply opening) 207 for use of ink supply is formed on the
 elemental substrate 201 by means of the anisotropic etching using
 tetramethyl ammonium hydroxide as shown in FIG. 15H, and the SiO.sub.2
 film 302 formed on the surface of the elemental substrate 201 is exposed
 in order to develop the polycrystal Si 304. Subsequent to having formed
 the through hole 207, the SiO.sub.2 film 302 on the surface and the
 reverse side of the elemental substrate 201 is removed using buffered
 hydrofluoric acid as shown in FIG. 15I. Lastly, using tetramethyl ammonium
 hydroxide again only the polycrystal Si film 304 is removed by etching as
 shown in FIG. 15J to form the liquid-flow paths. In other words, since the
 etching rate is largely different between the monocrystal Si 203, the SiN
 film 205, and the polycrystal Si 304, the monocrystal Si 203 and the SiN
 film 205 are left intact if the etching is suspended at the completion of
 the polycrystal Si etching, hence forming the liquid-flow paths. With the
 processes described above, it is possible to form the liquid-flow paths
 204 structured with the side walls of the monocrystal Si 203 on the
 elemental substrate 201 whose main component is Si, and also, with the
 ceiling of the SiN film 205. Then, the substrate thus formed in the above
 processes is cut off per chip to provide each of the ink jet recording
 heads as shown in FIG. 11.
 (Sixth Embodiment)
 In place of the head structure described in accordance with the fifth
 embodiment, it is conceivable to structure a head for which liquid is
 supplied from the side end of the substrate, not from the substrate side.
 FIG. 17 is a perspective view that shows most suitably an ink jet
 recording head of the present embodiment. FIG. 18 is a cross-sectional
 view taken along line 18--18 in FIG. 17. The ink jet recording head of the
 present embodiment shown in FIGS. 17 and 18 comprises the elemental
 substrate 501, which is provided with a plurality of heat-generating
 elements 502 in line on both side portions on the surface of the Si
 substrate; a plurality of liquid-flow paths 504 that distribute liquid to
 each of the heat-generating elements 502; the monocrystal Si 503 that
 forms side walls of the liquid-flow paths on the elemental substrate 501,
 the SiN film 505 formed on the monocrystal Si 503 to produce the ceiling
 of the liquid-flow paths 504; a plurality of discharge openings (ports)
 506 that face each of the heat-generating elements; and supply openings
 507 to supply liquid to each of the liquid-flow paths on both sides of the
 elemental substrate 501. In this way, the monocrystal Si 503 and the SiN
 film 505 become the liquid-flow-path member that forms the liquid-flow
 paths 504 on the elemental substrate 501. Here, the monocrystal Si 503
 does not cover the surface of both side ends of the elemental substrate
 201 where no heat-generating elements and liquid-flow paths are arranged,
 but the electric pads 510 are formed to supply electric signals to each of
 the heat-generating elements 502 from the outside.
 A structure of this kind can be produced by forming the polycrystal Si on
 both sides of one substrate in the processes described in accordance with
 the fifth embodiment. Now, in conjunction with FIGS. 19A to 19F and FIGS.
 20F and 20H, a description will be provided of the method for
 manufacturing the ink jet recording head of the present embodiment.
 At first, in FIG. 19A, the elemental substrate 501 is formed in the same
 manner as described in accordance with the fifth embodiment shown in FIGS.
 13 and 14. To briefly describe it, the driving element is formed on the Si
 [100] substrate by the application of thermal diffusion and ion
 implantation or some other semiconductor process. Further, the wiring and
 heat-generating elements, which are connected to the driving element, are
 formed. Then, as shown in FIG. 19B, the surface and the reverse side of
 the elemental substrate 501 are all covered by the oxide film 602 to form
 the portion covered by the oxide film (SiO.sub.2 film) 602 and the portion
 where the elemental substrate 501 is exposed on the surface of the
 elemental substrate 501 by means of photolithographic method as shown in
 FIG. 19C. In this case, different from the fifth embodiment, the surface
 of the side ends of the substrate 501 are covered by the oxide film 602.
 Then, the portions thus covered by the oxide film 602 are formed in
 accordance with the desired flow-path pattern. After that, by means of
 epitaxial development, such as the low-temperature epitaxial development,
 Si is developed in a thickness of approximately 20 .mu.m all over the
 surface of the elemental substrate 501 as shown in FIG. 19D. At this
 juncture, the monocrystal Si 503 is formed on the portion where the
 elemental substrate 201 is exposed, and the polycrystal Si 604 is formed
 on the portion covered by the oxide film 602.
 Then, as shown in FIG. 19E, the SiN film 505 is formed in a thickness of
 approximately 5 .mu.m by the application of the CVD method or the like all
 over the surfaces of the monocrystal Si 503 and the polycrystal Si 504.
 Subsequently, as shown in FIG. 19F, by means of the photolithographic
 method, the orifice holes (discharge ports) 506 are formed on the SiN film
 505 on the polycrystal Si 504 for ink discharges. After that, the oxide
 film 602 formed on the surface of the side ends and the reverse side of
 the substrate 501 are removed by use of buffered hydrofluoric acid as
 shown in FIG. 20G. Lastly, using tetramethyl ammonium hydroxide, the
 polycrystal Si film 504 is removed by etching as shown in FIG. 20H to form
 the liquid-flow paths. In other words, since the etching rate is largely
 different between the monocrystal Si 503, the SiN film 505, and the
 polycrystal Si, the monocrystal Si 503 and the SiN film 505 are left
 intact if the etching is suspended at the completion of the polycrystal Si
 etching, hence forming the liquid-flow paths. With the processes described
 above, it is possible to form the liquid-flow paths 504 structured with
 the side walls of the monocrystal Si 503 on the elemental substrate 501
 whose main component is Si, and also, with the ceiling of the SiN film
 505. Then, the substrate thus formed in the above processes is cut off per
 chip to provide each of the ink jet recording heads as shown in FIG. 17.
 (The Other Embodiment)
 FIG. 21 is a perspective view which schematically shows one example of the
 image recording apparatus to which the ink jet recording head of the above
 embodiments is applicable for use when being mounted on it. In FIG. 21, a
 reference numeral 701 designates a head cartridge that is integrally
 formed with the ink jet recording head of the above embodiments and a
 liquid containing tank. The head cartridge 701 is mounted on the carriage
 707, which engages with the spiral groove 706 of the lead screw 705
 rotative by being interlocked with the regular and reverse rotation of a
 driving motor 702 through the driving power transmission gears 703 and
 704. Then, by means of the driving power of the driving motor 702, the
 head cartridge reciprocates together with the carriage 707 in the
 directions indicated by arrows a and b. With the use of a
 recording-medium-supply device (not shown), a printing sheet (recording
 medium) P is carried on a platen roller 709 in cooperation with a sheet
 pressure plate 710 that presses the printing sheet P to the platen roller
 709 all over in the traveling direction of the carriage.
 In the vicinity of one end of the lead screw 705, photocouplers 711 and 712
 are arranged. The photocouplers serve as home-position sensing means that
 detects and confirms the presence of the lever 707a of the carriage 707 in
 this region in order to switch over the rotational directions of the
 driving motor 702 and the like. In FIG. 21, a reference numeral 713
 designates a supporting member of a cap 714 that covers the front end of
 the head cartridge 701 where the discharge openings (ports) of ink jet
 recording head are present. Also, a reference numeral 715 designates the
 ink suction means that sucks the ink that has been retained in the
 interior of the cap 714 due to the idle discharges of the liquid jet head
 or the like. The suction recovery of the liquid jet head is performed by
 this suction means 715 through the aperture arranged in the cap. A
 reference numeral 717 designates a cleaning blade; 718 denotes a member
 that makes the blade 717 movable in the forward and backward directions
 (in the direction orthogonal to the traveling direction of the carriage
 707). The blade 717 and this member 718 are supported by the main-body
 supporting member 719. The blade 717 is not necessarily limited to this
 mode, but it should be good enough to adopt any one of known cleaning
 blades. A reference numeral 720 designates the lever that effectuates
 suction for the suction recovery operation. This lever moves along the
 movement of the cam 721 that engages with the carriage 707. The movement
 thereof is controlled by known transmission means, such as the clutch that
 switches over the transmission of the driving power from the driving motor
 702. Here, the recording-control unit (which is not shown here) is
 arranged on the main body of the apparatus in order to control the
 provision of signals to the heat-generating elements on the liquid jet
 head mounted on the head cartridge 701, and also, to control the driving
 of each of the mechanisms described above.
 The image recording apparatus 700 thus structured performs its recording on
 the printing sheet (recording medium) P with the head cartridge 701 that
 reciprocates over the entire width of the printing sheet P that is carried
 on the platen 709 by means of a recording material supply device (not
 shown).