Abstract:
A method for manufacturing a silicon substrate comprises: forming a silicon nitride film on a patterning area on a surface of a silicon base material; forming a silicon oxide film on an area excluding the patterning area on the surface of the silicon base material after forming the silicon nitride film; removing the silicon nitride film to expose the silicon base material of the patterning area; and etching the silicon base material of the patterning area.

Description:
BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     The present invention relates to a method for manufacturing a silicon substrate, a method for manufacturing a droplet discharging head, and a method for manufacturing a droplet discharging apparatus.  
         [0003]     2. Related Art  
         [0004]     A droplet discharging head driven by electrostatic force is required to be compact, low cost, densely fabricated, and have stable discharging characteristics. In order to satisfy these requirements, some droplet discharging heads have a four-layer structure composed of an electrode substrate, a cavity substrate, a reservoir substrate, and a nozzle substrate. Among these heads, there are a few cases in which a silicon base material is used as a reservoir substrate. Hence, process stability and yield improvement are required in manufacturing such a few droplet discharging heads in which the above reservoir substrate is used.  
         [0005]     Some documents disclosed a droplet discharging head having a four-layer structure, provided with an electrode substrate, a cavity substrate, a reservoir substrate, and a nozzle substrate, and a method for manufacturing the head. For example, JP-A-2006-103167 (in pages 9 and 10, in FIGS. 8 and 9) indicated a method for manufacturing a reservoir substrate in which the reservoir substrate made of a silicon base material is manufactured by etching the silicon base material from the both sides.  
         [0006]     The method for manufacturing a droplet discharging head disclosed in the above document, however, in which a reservoir (common droplet chamber) and a nozzle communicating hole are dry etched, has a problem in that a large etching area yields a wide variation in an etched depth and it&#39;s shape collapses easily. In addition, a nozzle communicating hole is formed through a silicon base material by etching the both sides of the material. This process easily forms a step inside the nozzle communicating hole due to misalignment. Further, the step sometimes yields a flight curve during a droplet discharging.  
         [0007]     There are other examples of methods for manufacturing a droplet discharging head including a reservoir substrate made of a silicon base material. Among them, in a method in which a laser is not used for forming a nozzle communicating hole, a reservoir and the like is patterned after forming the nozzle communicating hole.  
         [0008]     The above method needs to protect the nozzle communicating hole with resist to prevent a silicon oxide film formed inside the nozzle communicating hole from being etched. The process of covering the nozzle communicating hole with resist is, however, cumbersome and sometimes lowers a yield. Further, in a method in which a nozzle communicating hole is formed by using a laser, it takes a long time in processing.  
       SUMMARY  
       [0009]     An advantage of the invention is to provide a method for manufacturing a silicon substrate that can pattern a silicon base material without using resist, a method for manufacturing a droplet discharging head, and a method for manufacturing a droplet discharging apparatus, and especially, to provide a method for manufacturing a silicon substrate that can pattern a reservoir and an individual electrode terminal part without using resist after forming a nozzle communicating hole and prevent incomplete resist coverage of the nozzle communicating hole, a method for manufacturing a droplet discharging head having the substrate, and a method for manufacturing a droplet discharging apparatus having the head.  
         [0010]     A method for manufacturing a silicon substrate according to a first aspect of the invention includes forming a silicon nitride (SiN) film on a patterning area on a surface of a silicon base material, forming a silicon oxide (SiO 2 ) film on an area excluding the patterning area on the surface of the silicon base material after forming the silicon nitride film, removing the silicon nitride film to expose the silicon base material of the patterning area, and etching the silicon base material of the patterning area.  
         [0011]     The method enables the patterning area, on which the silicon nitride film is formed, to be patterned without using resist.  
         [0012]     A method for manufacturing a silicon substrate according to a second aspect of the invention includes forming a first silicon oxide film on a surface of a silicon base material, forming a silicon nitride film on the first silicon oxide film corresponding to a patterning area on the surface of the silicon base material, forming a second silicon oxide film on the first silicon oxide film excluding the silicon nitride film after forming the silicon nitride film, removing the silicon nitride film, exposing the silicon base material of the patterning area, and etching the silicon base material of the patterning area.  
         [0013]     The method enables the patterning area, on which the silicon nitride film is formed, to be patterned without using resist. In addition, the method can prevent the silicon base material from being roughed during a patterning when resist patterning is carried out on the silicon nitride film since the first silicon oxide film is formed under the silicon nitride film.  
         [0014]     In this case, the silicon nitride film may be subjected to a resist patterning and etched so as to be formed in a shape of the patterning area.  
         [0015]     The method can prevent the silicon base material from being roughed during the patterning since the resist patterning is carried out on the silicon nitride film with the first silicon oxide film formed under the silicon nitride film.  
         [0016]     A method for manufacturing a droplet discharging head according to a third aspect of the invention includes a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes forming a silicon nitride film on a patterning area on a surface of a silicon base material, forming a silicon oxide film on an area excluding the patterning area on the surface of the silicon base material after forming the silicon nitride film, removing the silicon nitride film to expose the silicon base material of the patterning area, and etching the silicon base material of the patterning area.  
         [0017]     The method can provide the droplet discharging head including the silicon substrate manufactured by the method in which the patterning area, on which the silicon nitride film is formed, is patterned without using resist.  
         [0018]     A method for manufacturing a droplet discharging head according to a fourth aspect of the invention includes a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes forming a first silicon oxide film on a surface of a silicon base material, forming a silicon nitride film on the first silicon oxide film corresponding to a patterning area on the surface of the silicon base material, forming a second silicon oxide film on the first silicon oxide film excluding the silicon nitride film after forming the silicon nitride film, removing the silicon nitride film, exposing the silicon base material of the patterning area, and etching the silicon base material of the patterning area.  
         [0019]     The method can provide the droplet discharging head including the silicon substrate manufactured by the method in which the patterning area, above which the silicon nitride film is formed, is patterned without using resist, and the surface of which can be prevented from being roughed during the patterning.  
         [0020]     According to a fifth aspect of the invention, a method for manufacturing a droplet discharging head that is provided with a nozzle substrate having a nozzle hole, a cavity substrate having a nozzle communicating hole communicating with the nozzle hole and a discharge chamber discharging a droplet from the nozzle hole by pressure produced inside the discharge chamber, and a reservoir communicating with the discharge chamber includes a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes forming a silicon nitride film on a patterning area on a surface of a silicon base material, forming a silicon oxide film on an area excluding the patterning area on the surface of the silicon base material after forming the silicon nitride film, removing the silicon nitride film to expose the silicon base material of the patterning area, and etching the silicon base material of the patterning area. The reservoir substrate is made of the silicon base material.  
         [0021]     The method can provide the droplet discharging head including the reservoir substrate that is made of the silicon base material and manufactured by the method in which the patterning area, on which the silicon nitride film is formed, is patterned without using resist.  
         [0022]     According to a sixth aspect of the invention, a method for manufacturing a droplet discharging head that is provided with a nozzle substrate having a nozzle hole, a cavity substrate having a nozzle communicating hole communicating with the nozzle hole and a discharge chamber discharging a droplet from the nozzle hole by pressure produced inside the discharge chamber, and a reservoir communicating with the discharge chamber includes a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes forming a first silicon oxide film on a surface of a silicon base material, forming a silicon nitride film on the first silicon oxide film corresponding to a patterning area on the surface of the silicon base material, forming a second silicon oxide film on the first silicon oxide film excluding the silicon nitride film after forming the silicon nitride film, removing the silicon nitride film, exposing the silicon base material of the patterning area, and etching the silicon base material of the patterning area. The reservoir substrate is made of the silicon base material.  
         [0023]     The method can provide the droplet discharging head including the reservoir substrate that is made of the silicon base material and is manufactured by the method in which the patterning area, on which the silicon nitride film is formed, is patterned without using resist and roughing the surface of the silicon base material.  
         [0024]     In the fifth aspect of the invention, the patterning area may serve to form the reservoir and an individual electrode terminal part, and in the etching step, the silicon base material of the patterning area may be etched to form the reservoir and individual electrode terminal part.  
         [0025]     The method can provide the droplet discharging head including the silicon substrate manufactured by the method in which the patterning area, on which the silicon nitride film is formed, is patterned without using resist and etched to form the reservoir and the individual electrode terminal part.  
         [0026]     According to a seventh aspect of the invention, a method for manufacturing a droplet discharging head that is provided with a nozzle substrate having a nozzle hole, a cavity substrate having a nozzle communicating hole communicating with the nozzle hole and a discharge chamber discharging a droplet from the nozzle hole by pressure produced inside the discharge chamber, and a reservoir communicating with the discharge chamber includes a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes: forming a silicon nitride film on a patterning area on a first surface of the silicon base material, the patterning area serving to form the reservoir and an individual electrode terminal part; forming a silicon oxide film on an area excluding the patterning area on the first surface of the silicon base material after forming the silicon nitride film; etching the silicon base material from a second surface opposite to the first surface to form the nozzle communicating hole; removing the silicon nitride film to expose the silicon base material of the patterning area after forming the nozzle communicating hole; and etching the silicon base material of the patterning area to form the reservoir and individual electrode terminal part. The reservoir substrate is made of the silicon base material.  
         [0027]     This method allows the patterning area serving to form the reservoir and the individual electrode terminal part on the reservoir base material to be patterned without using resist, and also the nozzle communicating hole to be prevented from incomplete resist coverage.  
         [0028]     According to an eighth aspect of the invention, a method for manufacturing a droplet discharging head that is provided with a nozzle substrate having a nozzle hole, a cavity substrate having a nozzle communicating hole communicating with the nozzle hole and a discharge chamber discharging a droplet from the nozzle hole by pressure produced inside the discharge chamber, and a reservoir communicating with the discharge chamber includes a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes: forming a first silicon oxide film on a first surface of a silicon base material, forming a silicon nitride film on the first silicon oxide film corresponding to a patterning area on the first surface of the silicon base material, the patterning area serving to form the reservoir and an individual electrode terminal part; forming a second silicon oxide film on the first silicon oxide film excluding the silicon nitride film after forming the silicon nitride film; etching the silicon base material from a second surface opposite to the first surface to form the nozzle communicating hole; removing the silicon nitride film to expose the silicon base material of the patterning area after forming the nozzle communicating hole; and etching the silicon base material of the patterning area to form the reservoir and individual electrode terminal part. The reservoir substrate is made of the silicon base material.  
         [0029]     This method allows the patterning area serving to form the reservoir and the individual electrode terminal part on the reservoir base material to be patterned without using resist, and also the nozzle communicating hole to be prevented from incomplete resist coverage. In addition, the first silicon oxide film formed under the silicon nitride film can prevent the surface of the reservoir base material from being roughed when the silicon nitride film is patterned. The first silicon oxide film also can prevent cooling gas from being leaked when the nozzle communicating hole is formed by dry etching.  
         [0030]     A method for manufacturing a ninth aspect of the invention includes a method for manufacturing a droplet discharging apparatus including a method for manufacturing a droplet discharging head including a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes forming a silicon nitride film on a patterning area on a surface of a silicon base material, forming a silicon oxide film on an area excluding the patterning area on the surface of the silicon base material after forming the silicon nitride film, removing the silicon nitride film to expose the silicon base material of the patterning area, and etching the silicon base material of the patterning area.  
         [0031]     The method can provide the droplet discharging apparatus including the droplet discharging head having the silicon substrate manufactured by the method in which the patterning area, on which the silicon nitride film is formed, is patterned without using resist.  
         [0032]     A method for manufacturing a tenth aspect of the invention includes a method for manufacturing a droplet discharging apparatus including a method for manufacturing a droplet discharging head including a method for manufacturing a silicon substrate. The method for manufacturing a silicon substrate includes forming a first silicon oxide film on a surface of a silicon base material, forming a silicon nitride film on the first silicon oxide film corresponding to a patterning area on the surface of the silicon base material, forming a second silicon oxide film on the first silicon oxide film excluding the silicon nitride film after forming the silicon nitride film, removing the silicon nitride film, exposing the silicon base material of the patterning area, and etching the silicon base material of the patterning area.  
         [0033]     The method can provide the droplet discharging apparatus including the droplet discharging head having the silicon substrate manufactured by the method in which the patterning area, on which the silicon nitride film is formed, is patterned and etched without using resist and roughing the surface of the silicon base material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]     The invention will be described with reference to the accompanying drawings, wherein like number reference like elements.  
         [0035]      FIG. 1  is an exploded perspective view of a droplet discharging head according to a first embodiment of the invention.  
         [0036]      FIG. 2  is a vertical cross-sectional view of a state in which the droplet discharging head shown in  FIG. 1  is assembled.  
         [0037]      FIGS. 3A  to  3 D are sectional views illustrating manufacturing steps of a reservoir substrate of the first embodiment.  
         [0038]      FIGS. 4A  to  4 D are sectional views illustrating manufacturing steps following the steps shown in  FIGS. 3A  to  3 D.  
         [0039]      FIGS. 5A  to  5 D are sectional views illustrating manufacturing steps following the steps shown in  FIGS. 4A  to  4 D.  
         [0040]      FIGS. 6A  to  6 D are sectional views illustrating manufacturing steps following the steps shown in  FIGS. 5A  to  5 D.  
         [0041]      FIGS. 7A and 7B  are sectional views illustrating manufacturing steps following the steps shown in  FIGS. 6A  to  6 D.  
         [0042]      FIG. 8  is an explanatory diagram of a dry etching apparatus according to the first embodiment.  
         [0043]      FIG. 9A  is a sectional view illustrating a manufacturing step of the droplet discharging head of the first embodiment.  
         [0044]      FIGS. 10A  to  10 D are sectional views illustrating manufacturing steps following the step shown in  FIG. 9A .  
         [0045]      FIGS. 11A and 11B  are sectional views illustrating manufacturing steps following the steps shown in  FIGS. 10A  to  10 D.  
         [0046]      FIG. 12  is a sectional view illustrating manufacturing steps following the steps shown in  FIGS. 11A and 11B .  
         [0047]      FIG. 13  is a perspective view illustrating a droplet discharging apparatus using the droplet discharging head.  
         [0048]      FIG. 14  is a perspective view illustrating major structural means of the droplet discharging apparatus. 
     
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS  
     First Embodiment  
       [0049]      FIG. 1  is an exploded perspective view of a droplet discharging head according to a first embodiment of the invention.  FIG. 2  is a vertical cross-sectional view of a state in which the droplet discharging head of the first embodiment is assembled. The droplet discharging head shown in  FIGS. 1 and 2  is a face-eject type in which a droplet is discharged from a nozzle hole prepared in the surface of a nozzle substrate, and employs the electrostatic drive method driven by an electrostatic force.  
         [0050]     Although it will be described that the nozzle substrate having the nozzle hole is located on an electrode substrate, the nozzle substrate is mostly located under the electrode substrate in actual use.  
         [0051]     As shown in  FIGS. 1 and 2 , a droplet discharging head  1  is composed of an electrode substrate  2 , a cavity substrate  3 , a reservoir substrate  4  and a nozzle substrate  5 . On one surface of the reservoir substrate  4 , the nozzle substrate  5  is bonded while on the other surface of the reservoir substrate  4 , the cavity substrate  3  is bonded. On one surface of the cavity substrate  3 , the electrode substrate  2  is bonded. On the other surface opposite to the one surface, the reservoir substrate  4  is bonded. Inside the droplet discharging head  1 , a driver IC  60  supplying a driving signal to an individual electrode (described later) is disposed.  
         [0052]     The electrode substrate  2  has a thickness of about 1 mm and is made of heat resistance hard glass such as borosilicate glass having an approximate linear expansion coefficient to that of silicon, for example. In addition, a plurality of concave parts (electrode groove)  20 , serving as an electrode chamber and having a depth of about 0.2 μm, for example, is formed by etching corresponding to respective discharge chambers (described later) formed in the cavity substrate  3 . The concave parts  20  are formed in facing two lines, in each of which they are arranged with a constant interval. Inside each concave part  20 , an individual electrode  22  and a terminal part  23  continuously formed from the individual electrode  22  are formed by sputtering indium tin oxide (ITO), for example. The individual electrodes  22  and the terminal parts  23  form electrode lines E 1  and E 2 , in each of which, each long side of the individual electrodes  22  and the terminal parts  23  is in parallel each other. Each individual electrode  22  also arranged so as to face respective vibration plates (described later) prepared in the cavity substrate  3 . Here, the pattern shape of the concave part  20  disposed in the electrode substrate  2  is made slightly larger than the shape of an electrode (the individual electrode  22  and the terminal part  23 ) since the electrode is prepared inside the concave part  20 .  
         [0053]     In the first embodiment, ITO, which is transparent and includes tin oxides doped as an impurity, is used for the material of the electrode prepared inside the concave part  20 . ITO is deposited inside the concave part  20  as a film with a thickness of 0.1 μm by sputtering, for example. Therefore, a gap G formed between a vibration plate (described later) and the electrode depends on the depth of the concave part  20 , the thickness of the electrode, and the vibration plate (TEOS film). The gap G greatly influences on discharge characteristics. The material for the electrode is not limited to ITO, but metal such as chromium may be used. The reason why ITO is used in the first embodiment is that the inside of the gap G is easily observed, discharge is easily checked due to its transparency and the like. The electrode substrate  2  also has a liquid supply hole  70   a  communicating with a reservoir (described later).  
         [0054]     Between the electrode lines E 1  and E 2 , an IC mount concave part (mount groove)  21  is formed orthogonally with respect to the long side direction of the individual electrode  22  so as to have a depth similar to that of the concave part  20  serving as the electrode chamber. In the IC mount concave part  21 , three mount lead wires  26  are formed parallel reach other in the groove direction of the IC mount concave part  21  by sputtering ITO.  
         [0055]     The driver IC  60  is mounted to the IC mount concave part  21  and connected to the terminal part  23  of the individual electrode  22  included in the electrode lines E 1  and E 2 , allowing a driving signal to be supplied to the electrode lines E 1  and E 2  to control an actuator. While the droplet discharging head  1  has two driver ICs  60 , the number of driver ICs  60  may be one or more than two.  
         [0056]     The cavity substrate  3  is made of monocrystalline silicon having a (110) plane direction with a thickness of about 50 μm. In the cavity substrate  3 , a concave part  32   a  is formed that serves as a discharge chamber  32  having a vibration plate  30  as the bottom wall thereof. The concave parts  32   a  are formed in two lines corresponding to individual electrodes  22  (in the electrode lines E 1  and E 2 ) of the electrode substrate  2 . The cavity substrate  3  also has a first hole  33  passing through the cavity substrate  3  between two lines composed of the concave part  32   a , and a common electrode  34  for applying voltage to the vibration plate  30 . The common electrode  34  connects to an FPC  35   a.    
         [0057]     The vibration plate  30 , prepared as the bottom wall of the concave part  32   a  serving as the discharge chamber, is a highly boron-doped layer. In order to form the vibration plate  30  having a desired thickness, boron-doped layer having the same thickness is formed. The thickness of the vibration plate  30  and the volume of the concave part  32   a  serving as the discharge chamber  32  are formed with high accuracy by using a called etching stop technique. The etching stop technique utilizes that an etching rate is enormously decreased in a highly doped region (about 5×10 19  atoms·cm −3  or more) of boron serving as a dopant when silicon is subjected to an anisotropic wet etching with an alkaline aqueous solution.  
         [0058]     The cavity substrate  3  has an insulation film  31  made of tetra-ethyl-ortho-silicate or tetra-ethoxy-silane (TEOS) with a thickness of 0.1 μm on the lower surface (the surface facing the electrode substrate  2 ). The insulation film  31  is formed by plasma chemical vapor deposition (CVD). The insulation film  31  prevents insulation breakdown and short circuits when the vibration plate  30  is driven. The cavity substrate  3  also has a liquid supply hole  70   b , corresponding to the liquid supply hole  70   a  of the electrode substrate  2 , passing through the cavity substrate  3 . In addition, between the first hole  33  of the cavity substrate  3  and the concave parts  20  of the electrode substrate  2 , a sealing member  71  is disposed to prevent the gap G from penetration of moisture or the like. The sealing member  71  can prevent the vibration plate  30  from adhering to the individual electrode  22 .  
         [0059]     The reservoir substrate  4  is made of monocrystalline silicon having a thickness of 180 μm, for example. The reservoir substrate  4  has two concave parts  40   a , located at both sides thereof in the width direction so as to face each other. Each of the concave parts  40   a  serves as a reservoir  40  that supplies, for example, liquid like ink (hereinafter, referred to as ink) to the discharge chamber  32  of the cavity substrate  3 . The concave part  40   a  has a supply inlet  41  on the bottom surface thereof to transfer ink from the reservoir  40  to each discharge chamber  32 . The concave part  40   a  has a liquid supply hole  70   c  on the bottom surface thereof. The liquid supply hole  70   c  passes through the bottom surface of the concave part  40   a . The liquid supply hole  70   c  formed in the reservoir substrate  4 , the liquid supply hole  70   b  formed in the cavity substrate  3 , and the liquid supply hole  70   a  formed in the electrode substrate  2  communicate each other to form a liquid supply hole  70  that supplies ink from an external source to the reservoir  40  when the reservoir substrate  4 , the cavity substrate  3 , and the electrode substrate  2  are bonded. In addition, between the reservoirs  40  facing each other in the reservoir substrate  4 , a second hole  42  passing through the reservoir substrate  4  is formed.  
         [0060]     The first hole  33  prepared in the cavity substrate  3  communicates with the second hole  42  prepared in the reservoir substrate  4  and further the resulting holes connect the IC mount concave part  21  prepared on the electrode substrate  2  to form an individual electrode terminal part  72 . Inside the individual electrode terminal part  72 , the driver IC  60  is housed while it is fixed to the IC mount concave part  21 .  
         [0061]     In addition, between the concave part  40   a  and the second hole  42  of the reservoir substrate  4 , a nozzle communicating hole  35  communicating with the discharge chamber  32  is disposed to transfer ink from the discharge chamber  32  to a nozzle hole (described later) of the nozzle substrate  5 .  
         [0062]     The reservoir substrate  4  has a second concave part  39   b  on the surface thereof facing the concave part  32   a  of the cavity substrate  3  (on the bottom surface of the reservoir substrate  4 ). The second concave part  39   b  serves as a second discharge chamber  39  and form the discharge chamber  32  together with the concave part  32   a  of the cavity substrate  3  when the reservoir substrate  4  and the cavity substrate  3  are bonded.  
         [0063]     The nozzle substrate  5  is made of a silicon base material having a thickness of about 50 μm, for example. The nozzle substrate  5  has a plurality of nozzle holes  43 , each communicating with the respective nozzle communicating holes  35  of the reservoir substrate  4 . Each of the nozzle holes  43  has a large-diameter part and a small-diameter part as two steps to improve straight flying property when a droplet is discharged.  
         [0064]     In the droplet discharging head  1  structured as described above, the driver IC  60  fixed to the IC mount concave part  21  prepared in the electrode substrate  2  is housed in the individual electrode terminal part  72 , which is closed by the nozzle substrate  5 , the cavity substrate  3 , the reservoir substrate  4  and the electrode substrate  2 . That is, the individual electrode terminal part  72  is closed by the nozzle substrate  5  covering the upper surface of the individual electrode terminal part  72 , the electrode substrate  2  covering the lower surface of the individual electrode terminal part  72 , and the cavity substrate  3  and the reservoir substrate  4  both of which cover respective side surfaces of the individual electrode terminal part  72 .  
         [0065]     Next, the operation of the droplet discharging head  1  will be described with reference to  FIG. 2 . Ink is supplied from an external source to the reservoir  40  through the liquid supply hole  70 , supplied from the reservoir  40  to the discharge chamber  32  through the supply inlet  41 . The driver IC  60  received a driving signal (pulse voltage) from a controller (not shown) of the droplet discharge device  1  through an IC wiring line  36  of the FPC  35   a  and the lead wires  26  prepared on the electrode substrate  2 .  
         [0066]     For example, the driver IC  60  oscillates at 24 kHz and applies a pulse voltage of 30V between the electrodes to supply electric charges. When the individual electrode  22  is charged positive by supplying electric charges, the vibration plate  30  is charged negative and thereby is attracted to the individual electrode  22  to bend. This bending increases the volume of the discharge chamber  32 . When electric charge supply to the individual electrode is stopped, the vibration plate  30  returns to the original shape. At the same time, the volume of the discharge chamber  32  also returns to the original one, resulting pressure discharging a droplet equivalent to the difference in the volume of the discharge chamber  32 . The discharged droplet is landed on, for example, a recording paper as a recoding object to perform a recoding. Here, such method is a called drawing shot. There is also a called pushing shot discharging a droplet by using a spring or the like. Again, electric charges are supplied to the individual electrode  22  by applying a pulse voltage, so that the vibration plate  30  bends toward the individual electrode  22 . As a result, ink is resupplied from the reservoir  40  into the discharge chamber  32  through the supply inlet  41 .  
         [0067]     In the droplet discharging head  1 , ink is supplied to the reservoir  40  through a droplet supply tube (not shown) connected to the liquid supply hole  70 , for example.  
         [0068]     Also, in the first embodiment, the FPC  35   a  is connected to the driver IC  60  so that the longitudinal direction of the FPC  35   a  is in parallel with the short side direction of the individual electrode  22  included in the electrode lines. This structure allows the droplet discharging head  1  including the electrode lines E 1  and E 2 , and the FPC  35   a  to be compactly connected.  
         [0069]     Next, manufacturing steps of the droplet discharging head  1  will be described with reference to  FIGS. 3A  to  12 . While the component of droplet discharging head  1  is simultaneously formed in a plurality of numbers from a silicon wafer in practice, only a part of them is shown in  FIGS. 3A  to  12 .  
         [0070]     First, the manufacturing steps of a reservoir base plate  4  made of a silicon base material will be described with reference to  FIGS. 3A  to  8 . (a) The both surfaces of a silicon base material  400  (reservoir base material) having a (100) plane direction are mirror polished to achieve a base material having a thickness of 180 μm. As for the both surfaces, hereinafter, on surface to which the nozzle substrate  5  is connected is referred to as a surface A while the other surface to which the cavity substrate  3  is connected is referred to as a surface B. Then, as shown in  FIG. 3A , silicon oxide (SiO 2 ) films  401   a  and  401   b  having a thickness of about 0.1 μm are formed on both surfaces A and B of the silicon base material  400  respectively by oxidizing it at 1000° C. for three hours in an oxygen atmosphere.  
         [0071]     (b) As shown in  FIG. 3B , a silicon nitride (SiN) film  402  is formed on the surface A of the silicon base material  400  by plasma CVD. The film is formed with a thickness of 0.1 μm by the following conditions: the processing temperature is 500° C. or less, the pressure is 1.3 kPa or less (10 Torr or less), and the gas flow ratio (NH 3 /SiH 4 ) is 15 or more.  
         [0072]     In the above steps, the silicon nitride film  402  is formed in step (b) after step (a). Here, in step (a), the silicon oxide films  401   a  and  401   b  are formed on the surfaces A and B of the silicon base material  400 , respectively, while in step (b), the silicon nitride film  402  is formed on the surface A of the silicon base material  400  by plasma CVD. However, the silicon nitride film  402  can be formed on the surface A of the silicon base material  400  by plasma CVD after mirror polishing the surfaces A and B of the silicon base material  400  without forming the silicon oxide films  401   a  and  401   b  on the surfaces A and B, respectively.  
         [0073]     (c) A resist is coated on the silicon nitride film formed on the surface A. Then, as shown in  FIG. 3C , resist patterning is carried out for a part  400   a  in which the concave part  40   a  of the reservoir  40  will be formed and for a part (not shown) in which the second hole  42  included in the individual electrode terminal part  72  will be formed. Next, the resist is removed by etching the silicon nitride film  402  with a reactive ion etching (RIE) apparatus under the following conditions: the pressure is 26.6 Pa (0.2 Torr), the RF power is 200 W, and the gas flow rate is 30 cc/minute.  
         [0074]     In the process, in which the silicon nitride film  402  is formed after forming the silicon oxide films  401   a  and  401   b  on the silicon base material  400  and then resist patterning is carried out on the silicon nitride film  402 , the surface of the silicon base material  400  is prevented from being etched by etching gas since the silicon oxide film  401   a , the layer under the silicon nitride film  402 , functions as a mask.  
         [0075]     (d) Then, as shown in  FIG. 3D , silicon oxide films  401   a  and  401   b  having a thickness of about 1.2 μm are grown and formed on both surfaces A and B of the silicon base material  400  respectively by oxidizing it at 1075° C. for four hours in an oxygen and moisture atmosphere. The silicon oxide films  401   a  and  401   b  are not grown on a part on which the silicon nitride film  402  has been formed.  
         [0076]     (e) A resist is coated above the surfaces A and B of the silicon base material  400 . Then, resist patterning is carried out for a part  350 , in which the nozzle communicating hole  35  will be formed, on the surface B. Next, the silicon oxide film  401   b  is patterned by etching with a fluoric acid aqueous solution as shown in  FIG. 4E . Then, the resist is removed.  
         [0077]     (f) A resist is coated above the surfaces A and B of the silicon base material  400 . Then, resist patterning is carried out for a part  410  in which the supply outlet  41  through which the reservoir  40  communicates with the discharge chamber  32  will be formed, a part  700   c  in which the liquid supply hole  70   c  to supply ink from the cavity substrate  3  will be formed, and a part (not shown) in which the hole  42  included in the individual electrode terminal part  72  will be formed, above the surface B in which the part  350  serving to form the nozzle communicating hole  35  is formed. Next, the silicon oxide film  401   b  is patterned by etching with a fluoric acid aqueous solution by about 0.8 μm deep so as to leave the silicon oxide film having a thickness of about 0.4 μm, as shown in  FIG. 4F . Then, the resist is removed.  
         [0078]     (g) A resist is coated above the surfaces A and B of the silicon base material  400 . Then, resist patterning is carried out for a part  391   b , in which a second concave part  390   b  will be formed, above the surface B in which the part  350  serving to form the nozzle communicating hole  35  is formed. Next, the silicon oxide film  401   b  is patterned by etching with a fluoric acid aqueous solution by about 0.5 μm deep so as to leave the silicon oxide film  401   b  having a thickness of about 0.7 μm, as shown in  FIG. 4C . Then, the resist is removed.  
         [0079]     (h) The part  350  serving to form the nozzle communicating hole  35  is etched by about 150 μm deep as shown in  FIG. 4D  by using an ICP dry etching apparatus (described later). The etching is carried out by the following conditions. The etching process is as follows: the SF 6  flow rate is 400 cm 3 /minute (400 sccm), the etching time is 3.5 seconds, the chamber pressure is 8 Pa, the coil power is 2200 W, the platen power is 55 W, and the platen temperature is 20° C. The deposition process is as follows: C 4 F 8  flow rate is 200 cm 3 /minute (200 sccm), the etching time is 2.5 seconds, the chamber pressure is 2.7 Pa, the coil power is 1800 W, and the platen temperature is 20° C. The etching process and deposition process equals one cycle. About 380 cycles are carried out.  
         [0080]     (i) A resist is coated above the surface A. The silicon oxide film  401   b  that remains at the part  410 , in which the supply inlet  41  will be formed, and the like is etched as shown in  FIG. 5I  by soaking the silicon base material  400  in a fluoric acid aqueous solution. Then, the resist is removed.  
         [0081]     (j) The part  410  serving to form the supply inlet  41  is etched by about 20 μm deep (the part  350  serving to form the nozzle communicating hole  35  is etched by about 170 μm deep) as shown in  FIG. 5B  by using an ICP dry etching apparatus. The etching is carried out by the following conditions. The etching process is as follows: the SF 6  flow rate is 400 cm 3 /minute (400 sccm), the etching time is 3.5 seconds, the chamber pressure is 8 Pa, the coil power is 2200 W, the platen power is 55 W, and the platen temperature is 20° C. The deposition process is as follows: C 4 F 8  flow rate is 200 cm 3 /minute (200 sccm), the etching time is 2.5 seconds, the chamber pressure is 2.7 Pa, the coil power is 1800 W, and the platen temperature is 20° C. The etching process and deposition process equals one cycle. About 50 cycles are carried out.  
         [0082]     (k) A resist is coated above the surface A. The silicon oxide film  401   b  that remains at the part  391   b , in which the second concave part  390   b  will be formed, and the like is etched as shown in  FIG. 5C  by soaking the silicon base material  400  in a fluoric acid aqueous solution. Then, the resist is removed.  
         [0083]     (l) The part  391   b , in which the second concave part  390   b  will be formed, is etched by about 10 μm deep (the part  350  corresponding to the nozzle communicating hole  35  is etched by about 180 μm deep and the part  410  serving to form the supply inlet  41  and the like are etched by about 30 μm deep) as shown in  FIG. 5D  by using an ICP dry etching apparatus. The etching is carried out by the following conditions. The etching process is as follows: the SF 6  flow rate is 400 cm 3 /minute (400 sccm), the etching time is 3.5 seconds, the chamber pressure is 8 Pa, the coil power is 2200 W, the platen power is 55 W, and the platen temperature is 20° C. The deposition process is as follows: C 4 F 8  flow rate is 200 cm 3 /minute (200 sccm), the etching time is 2.5 seconds, the chamber pressure is 2.7 Pa, the coil power is 1800 W, and the platen temperature is 20° C. The etching process and deposition process equals one cycle. About 25 cycles are carried out. In the step, the part  350  serving to form the nozzle communicating hole  35  passes through the silicon substrate  400 , but the silicon oxide film  401   a  remains at the bottom of the part  350  (on the same plane of the surface A). The silicon oxide film  401   a  can prevent cooling gas of the etching apparatus from being leaked.  
         [0084]     (m) The silicon oxide films  401   a  and  401   b  are etched as shown in  FIG. 6A  by soaking the silicon base material  400  in a fluoric acid aqueous solution.  
         [0085]     (n) As shown in  FIG. 6B , silicon oxide films  401   a  and  401   b  having a thickness of about 1.7 μm are formed on both surfaces of the silicon base material  400  respectively by oxidizing it at 1075° C. for eight hours in an oxygen and moisture atmosphere. In this step, in the same manner of the step shown in  FIG. 3D , the silicon oxide film  401   a  is not grown on a part on which the silicon nitride film  402  has been formed.  
         [0086]     (o) Silicon oxide film slightly formed on the surface of the silicon nitride film  402  is removed by soaking the silicon base material  400  in a fluoric acid aqueous solution (not shown). Then, the silicon base material  400  is soaked in a heated phosphoric acid aqueous solution (180° C.) to remove the silicon nitride film  402  that remains on the part  400   a  in which the reservoir  40  will be formed and a part (not shown) in which the second hole  42  included in the individual electrode terminal part  72  will be formed, as shown in  FIG. 6C .  
         [0087]     (p) The silicon base material  400  is soaked in a fluoric acid aqueous solution to etch the silicon oxide film  401   a  that covers the part  400   a  in which the concave part  40   a  of the reservoir  40  will be formed and a part (not shown) in which the second hole  42  included in the individual electrode terminal part  72  will be formed so that the surface of the silicon base material  400  is exposed as shown in  FIG. 6D .  
         [0088]     (q) The silicon base material  400  is soaked in a potassium hydrate aqueous solution of a concentration of 25 wt % to etch the part  440   a  in which the concave part  40   a  of the reservoir  40  will be formed and the part (not shown) in which the second hole  42  included in the individual electrode terminal part  72  as shown in  FIG. 7Q . The part  440   a  in which the concave part  40   a  of the reservoir  40  will be formed and the part in which the second hole  42  included in the individual electrode terminal part  72  are etched until the silicon oxide film  401   b  formed on a surface adjacent to the surface B is disposed as shown in  FIG. 7Q .  
         [0089]     (r) The silicon oxide films  401   a  and  401   b  are removed as shown in  FIG. 7B  by soaking the silicon base material  400  in a fluoric acid aqueous solution.  
         [0090]     Through the above manufacturing steps from (a) to (r), the reservoir substrate  4  is achieved as shown in  FIG. 7B .  
         [0091]     In the manufacturing steps, the concave part  40   a  of the reservoir  40  is formed by etching the part  440   a  serving to form the concave part  40   a  of the reservoir  40  while the second hole  42  included in the individual electrode terminal part  72  is formed by etching the part serving to form the second hole  42  included in the individual electrode terminal part  72 . The etching process is carried out after the nozzle communicating hole  35  is passed through ( FIG. 5D ). The penetration of the nozzle communicating hole  35  is carried out by using an ICP dry etching apparatus from a side adjacent to the part  350  serving to form the nozzle communicating hole  35 .  
         [0092]      FIG. 8  is a schematic view illustrating a dry etching apparatus. A dry etching apparatus  50  has a cathode  52  in a chamber  51  as shown in  FIG. 8 . The cathode  52  serves as a support table to place and fix the silicon base material  400  with a chucking mechanism, and also functions as an electrode upon receiving power from a power supply means  58 . Facing to the cathode  52  an anode  53  is disposed as a counter electrode. Process gas to carry out etching is supplied from a supply tube  54  to the inside of the chamber  51  and exhausted by a pump (not shown) through an exhausted tube  55  to maintain the inside of the chamber  51  at a predetermined pressure.  
         [0093]     The cathode  52  has a concave part  56 , which is filled with base material cooling gas such as helium to prevent the silicon base material  400  from being over heated. Overheating the silicon base material  400  may affect an etching speed and the oxidization process of the silicon base material  400 . If a resist is used as a mask, the resist may get burned. Thus, the temperature of the silicon base material  400  is maintained with base material cooling gas. In this regard, the silicon base material  400  functions as a called lid to prevent base material cooling gas from leaking in the inside of the chamber  51 .  
         [0094]     For dry etching the silicon base material  400 , the silicon base material  400  is placed inside the chamber  51  of the dry etching apparatus  50  as shown in  FIG. 8 . The silicon base material  400  is placed so that the surface A thereof faces the cathode  52 . Here, the surface A is connected to the nozzle substrate  5 . While the silicon base material  400  is kept in this state, the part  350  serving to form the nozzle communicating hole  35  and the like are dry etched to form a hole having a predetermined depth from a side adjacent to the surface B by utilizing inductively coupled plasma (ICP) or the like. Here, dry etching and process gas are not limited to any kind, as long as they can etch the silicon base material  400 . For example, sulfur hexafluoride (SF 6 ) can be used.  
         [0095]     Next, steps to manufacture the droplet discharging head  1  by using the reservoir substrate  4  manufactured as described above will be described.  FIGS. 9A  to  12  are schematic views illustrating the manufacturing step of the droplet discharging head  1 .  
         [0096]     While the component of droplet discharging head  1  is simultaneously formed in a plurality of numbers from a silicon wafer in practice, only a part of them is shown in  FIG. 9A  through  FIG. 12 .  
         [0097]     (a) As shown in  FIG. 9A , the concave part  20  serving as an electrode groove having a depth of 0.2 μm is formed to a glass base material  200  of having a thickness of about 1 mm by aligning with the shape pattern of the electrode. After the concave part  20  is formed, the electrode  22  is formed with a thickness of 0.1 μm by sputtering. Then, the liquid supply hole  70   a  is formed by sandblasting or cutting work.  
         [0098]     (b) A cavity base material  300  is prepared. The cavity base material  300  is formed to have a thickness of 220 μm by mirror polishing one surface of a silicon base material having a (110) plane direction and low oxygen concentration. To the mirror polished surface of the cavity base material  300 , a highly boron doped layer (not shown) is formed with a thickness equal to that of the vibration plate. In addition, on the surface of the boron doped layer, a TEOS insulation film (not shown) is formed with a thickness of 0.1 μm.  
         [0099]     Next, the cavity base material  300  and the electrode substrate  2  on which a pattern has been formed are heated at 360° C. Then, the cavity base material  300  and the electrode substrate  2  are anodic bonded by applying a voltage of 800 V after the electrode substrate  2  is connected to a negative pole while the cavity base material  300  is connected to a positive pole, as shown in  FIG. 10A .  
         [0100]     (c) After the anodic bonding, the surface of the cavity base material  300  is grinded to a thickness of about 60 μm. Then, the cavity base material  300  is etched by about 10 μm with a potassium hydrate aqueous solution of a concentration of 32 wt % to remove a work-affected layer. As a result, the cavity base material having a thickness of about 50 μm is achieved as shown in  FIG. 10B .  
         [0101]     (d) The cavity base material  300 , which has been subjected to the anodic bonding, is etched by using a potassium hydrate aqueous solution to form the concave part  32   a  serving to form the discharge chamber  32 . In this silicon etching process, etching is stopped at the boron doped layer due to decreasing of the etching rate. This process suppresses the surface of the vibration plate  30  from being roughed to increase the thickness accuracy, allowing the discharge performance of the droplet head  1  to be stabilized. In this regard, silicon thin film remains in the through holes such as the first hole  33  included in the individual electrode terminal part  72 . In order to remove the film, plasma is applied only to the through hole for RIE dry etching after fixing a silicon mask on the surface of the cavity base material  300 . As a result, the film is removed to form an opening whereby the cavity substrate  3  is achieved as shown in  FIG. 10C .  
         [0102]     (e) The bonded base materials shown in  FIG. 10C  are dried to remove moisture inside the gap G. As shown in  FIG. 10D , the gap G is sealed with a sealing member  71  of an epoxy resin by pouring the epoxy resin into a though hole  38  for sealing the gap G. As a result, the gap G is sealed up.  
         [0103]     (f) The reservoir substrate  4 , which has been manufactured in steps shown in  FIGS. 3A  to  7 B, is bonded to the cavity substrate  3  with an epoxy resin adhesive as shown in  FIG. 11A .  
         [0104]     (g) As shown in  FIG. 11B , the driver IC  60  is mounted to the terminal part  23  of the electrode substrate  2 .  
         [0105]     (h) As shown in  FIG. 12 , the nozzle substrate  5  is bonded to the reservoir substrate  4  with an epoxy resin adhesive. Then, an individual head is achieved after a cutting by dicing.  
         [0106]     The droplet discharging head  1  according to the invention can be easily handled since parts such as the concave part  32   a  serving to form the discharge chamber  32  are formed in the cavity base material  300  after the cavity base material  300  and the electrode substrate  2  are bonded. The easy handling can reduce the breakage of the base material and achieve a larger size base material. The larger size base material allows the larger number of droplet discharging heads  1  to be manufactured from a single base material, enabling the productivity to be increased. In addition, stacking the reservoir substrate  4  thicker than the cavity substrate  3  on the cavity substrate  3  reduces the flow path resistance of the reservoir  40 , allowing discharge capacity to be improved and a head to be downsized.  
         [0107]     The reservoir substrate  4  of the droplet discharging head  1  is processed as follows: the silicon nitride film  402  is formed on the patterning areas for the concave part  40   a  of the reservoir  40  and the second hole  42  of the individual electrode terminal part  72 ; the silicon oxide film  401   a  is formed as a mask in silicon etching; the silicon nitride film  402  is removed; and the concave part  40   a  of the reservoir  40  and the second hole  42  of the individual electrode terminal part  72  are patterned. Using such manufacturing method allows the concave part  40   a  of the reservoir  40  and the second hole  42  of the individual electrode terminal part  72  to be patterned without resist after forming the nozzle communicating hole  35 . As a result, incomplete resist coverage of the nozzle communicating hole  35  can be prevented.  
         [0108]     Also, in manufacturing the reservoir substrate  4  of the droplet discharging head  1 , the silicon oxide film  401   a  can be formed thin as an underlayer prior to forming the silicon nitride film  402 . The underlayer can prevent the surface of the reservoir base material  400  from being roughed in patterning the silicon nitride film  402 , and also prevent cooling gas from being leaked when the nozzle communicating hole  35  is passed through during the dry etching.  
       Second Embodiment  
       [0109]      FIG. 13  is a perspective view illustrating a droplet discharging apparatus using the droplet discharging head  1  manufactured in the first embodiment.  FIG. 14  is a perspective view illustrating major structural means of the droplet discharging apparatus shown in  FIG. 13 . A droplet discharging apparatus  100  in  FIG. 13  performs printing by a droplet discharge method (inkjet method) and belongs to a called serial type.  
         [0110]     As shown in  FIG. 14 , the droplet discharging apparatus  100  mainly includes a drum  601  and the droplet discharging head  1  as major structural means. The drum  601  supports a printing paper  610 . The droplet discharging head  1  discharges ink to the printing paper  610  for performing a record. In addition, ink supply means (not shown) is provided for supplying ink to the droplet discharging head  1 . The printing paper  610  is pressed and held to the drum  601  by a paper pressing-holding roller  603  disposed in parallel with the axial direction of the drum  601 . In parallel with the axial direction of the drum  601 , a lead screw  604  is disposed to hold the droplet discharging head  1 . By rotating the lead screw  604 , the droplet discharging head  1  moves in the axial direction of the drum  601 .  
         [0111]     On the other hand, the drum  601  is rotary driven by a motor  606  with a belt  605  and the like. In addition, printing control means  607  drives the lead screw  604  and the motor  606  based on printing image data and a control signal, and an oscillation circuit (not shown) to vibrate the vibration plate  30 . As a result, a printing is carried out on the printing paper  610  under the control of the printing control means  607 .  
         [0112]     While liquid is discharged to the printing paper  610  as ink in this case, liquid discharged from the droplet discharging head  1  is not limited to ink. A variety of liquid may be discharged from a droplet discharging head provided in respective apparatuses used in the following exemplary cases. In an application where liquid is discharged to a substrate serving as a color filter, liquid containing a pigment may be used. In another application where liquid is discharged to a substrate serving as a display panel (such as OLED) using an electroluminescent element such as an organic compound, liquid containing a compound serving as an light-emitting element may be used. In another application where liquid is discharged on a substrate for forming electrical wire lines, liquid containing conductive metal may be used. When liquid is discharged to a substrate serving as a biomolecule micro array by using the droplet discharging head as a dispenser, liquid may be discharged that contains a probe such as deoxyribo nucleic acids (DNA), other nucleic acids such as ribo nucleic acids and peptide nucleic acids, and other proteins. The apparatus also can be used to discharge a dye for clothes or the like.