Abstract:
A piezoelectric inkjet printhead capable of reducing a crosstalk and a method of manufacturing the same are provided. The inkjet printhead includes an upper substrate, an intermediate substrate, and a lower substrate that are sequentially stacked, wherein the upper substrate includes piezoelectric actuators on an upper surface of the upper substrate and pressure chambers and first restrictors on a lower surface of the upper substrate, the first restrictors extending from the pressure chambers and having a width smaller than a width of the pressure chambers, the intermediate substrate includes dampers passing therethrough, the dampers corresponding to the pressure chambers and second restrictors extending between the first restrictors and a manifold formed from a lower surface of the intermediate substrate and the lower substrate includes nozzles passing therethrough, the nozzles corresponding to the dampers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an inkjet printhead. More particularly, the present invention relates to a piezoelectric inkjet printhead capable of reducing a crosstalk and a method of manufacturing the same. 
     2. Description of the Related Art 
     An inkjet printhead is a device for ejecting fine ink droplets for use in printing. For example, it is used to print at a desired point on a paper and to print an image of a predetermined color. Inkjet printheads can be generally divided into two types according to the type of ink ejection employed. One type is a thermally-driven inkjet printhead that creates a bubble in ink using a heat source, to thereby eject the ink using the expansion force of the bubble. The other type is a piezoelectric inkjet printhead that uses a piezoelectric element to eject ink using a pressure applied to the ink, which is generated by deformation of the piezoelectric element. 
     The construction of a typical piezoelectric inkjet printhead is illustrated in  FIG. 1 . Referring to  FIG. 1 , a manifold  2 , a restrictor  3 , a pressure chamber  4  and a nozzle  5 , which together constitute an ink channel, are formed in the inside of a channel plate  1 . A piezoelectric actuator  6  is disposed on the channel plate  1 . The manifold  2  is a path through which ink flowing from an ink reservoir (not shown) is supplied to one or more pressure chambers  4 . The restrictor  3  is a path through which the ink flows from the manifold  2  to the pressure chamber  4 . The pressure chamber  4  is a space filled with ink to be ejected. A pressure change, for ejection or refill of ink, is generated in the pressure chamber  4  by changing its volume by driving the piezoelectric actuator  6 . The piezoelectric actuator  6  may deform an upper wall of the pressure chamber  4 , which may serve as a vibration plate  1   a.    
     In operation, when the piezoelectric actuator  6  is driven to inwardly deform the vibration plate  1   a , the volume of the pressure chamber  4  is reduced, resulting in a pressure change. Ink in the inside of the pressure chamber  4  is ejected to the outside through the nozzle  5  by the pressure change in the inside of the pressure chamber  4 . Subsequently, when the piezoelectric actuator  6  is driven to outwardly deform and restore the vibration plate  1   a  to its original shape, the volume of the pressure chamber  4  increases, resulting in a second pressure change. The second pressure change causes ink to flow into the the pressure chamber  4  from the manifold  2  through the restrictor  3  due to the increased volume. 
     A conventional piezoelectric inkjet printhead is illustrated in  FIG. 2 . Referring to  FIG. 2 , the conventional piezoelectric inkjet printhead is formed by stacking and bonding thin plates  11  through  16 . In particular, a first plate  11 , having nozzles  11   a  for ejecting ink, is disposed at the lowermost side of the printhead, a second plate  12 , having a manifold  12   a  and ink outlets  12   b , is stacked thereon and a third plate  13 , having ink inlets  13   a  and ink outlets  13   b , is stacked on the second plate  12 . The third plate  13  has an ink introducing port  17  for introducing ink to the manifold  12   a  from an ink reservoir (not shown). A fourth plate  14 , having ink inlets  14   a  and ink outlets  14   b , is stacked on the third plate  13  and a fifth plate  15  having pressure chambers  15   a , the ends of which communicate with the ink inlets  14   a  and the ink outlets  14   b , respectively, is stacked on the fourth plate  14 . The ink inlets  13   a  and  14   a  serve as paths through which ink flows from the manifold  12   a  to the pressure chambers  15   a , and the ink outlets  12   b ,  13   b , and  14   b  serve as paths through which ink is discharged from the pressure chambers  15   a  to the nozzles  11   a . A sixth plate  16  closing the upper portion of the pressure chambers  15   a  is stacked on the fifth plate  15 , and drive electrodes  20  and piezoelectric films  21  serving as piezoelectric actuators are formed on the sixth plate  16 . Thus, the sixth plate  16  serves as a vibration plate that is vibrated by the piezoelectric actuator and changes the volume of the pressure chamber  15   a  disposed beneath it using warp-deformation of the sixth plate  16 . 
       FIG. 3  illustrates a view of another example of a piezoelectric inkjet printhead and  FIG. 4  illustrates a vertical sectional view of the same. The inkjet printhead illustrated in  FIGS. 3 and 4  may have a structure in which three silicon substrates  30 ,  40  and  50  are stacked and bonded. Pressure chambers  32  of a predetermined depth may be formed on a backside of the upper substrate  30 . An ink inlet port  31 , connected to an ink reservoir (not shown), may pass through one side of the upper substrate  30 . The pressure chambers  32  may be arranged in two columns, one on each side of the printhead, in a lengthwise direction of a manifold  41  formed on the intermediate substrate  40 . Piezoelectric actuators  60 , for providing driving force to eject ink to the pressure chambers  32 , may be formed on an upper surface of the upper substrate  30 . The intermediate substrate  40  may have the manifold  41 , which may be connected with the ink inlet port  31  and restrictors  42 . The restrictors  42  may be connected with the respective pressure chambers  32  formed on both sides of the manifold  41 . Also, dampers  43  vertically passing through the intermediate substrate  40  may be formed on the intermediate substrate  40  in positions that correspond to the pressure chambers  32 . Also, nozzles  51  connected with the dampers  43  may be formed in a lower substrate  50 . 
     In operation, ink that has flowed into the manifold  41  through the ink inlet port  31  flows into the pressure chambers  32  by way of the restrictors  42 . Subsequently, when the piezoelectric actuators  60  operate to pressurize the pressure chambers  32 , the ink within the pressure chambers  32  passes through the dampers  43  and is ejected to the outside through the nozzles  51 . Here, the restrictors  42  not only serve as paths supplying the ink from the manifold  41  to the pressure chambers  32  but may also prevent the ink from flowing backward to the manifold  41  from the pressure chambers  32  when the ink is ejected. 
     However, when the piezoelectric actuators  60  pressurize the pressure chambers  32 , the pressure transferred to the pressure chambers  32  may also be transferred to the restrictors  42 . Such a situation may generate crosstalk between adjacent restrictors  42 . In this regard, crosstalk means mutual interference of pressures between adjacent restrictors  42 , generated when ink is ejected. Crosstalk may affect the size of an ink droplet ejected from the nozzles  51 , causing ink ejection to become non-uniform. That is, when crosstalk is generated, unintended ink may be ejected or an inaccurate amount of ink may be ejected, thus deteriorating print quality. 
     SUMMARY OF THE INVENTION 
     The present invention is therefore directed to a piezoelectric inkjet printhead capable of reducing a crosstalk and a method of manufacturing the same, which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art. 
     It is therefore a feature of an embodiment of the present invention to provide an inkjet printhead exhibiting reduced crosstalk between restrictors. 
     It is therefore a further feature of an embodiment of the present invention to provide an inkjet printhead formed of three substrates, wherein it is possible to increase the width of a manifold by processing the backside of an intermediate substrate so as to form the manifold and install the manifold in a lower portion of a pressure chamber formed in an upper substrate. 
     It is therefore also a feature of an embodiment of the present invention to provide an inkjet printhead having one or more partitions interposed between adjacent restrictors. 
     At least one of the above and other features and advantages of the present invention may be realized by providing a piezoelectric type inkjet printhead including an upper substrate, an intermediate substrate, and a lower substrate that are sequentially stacked, wherein the upper substrate may include piezoelectric actuators on an upper surface of the upper substrate and pressure chambers and first restrictors on a lower surface of the upper substrate, the first restrictors extending from the pressure chambers and having a width smaller than a width of the pressure chambers, the intermediate substrate may include dampers passing therethrough, the dampers corresponding to the pressure chambers and second restrictors extending between the first restrictors and a manifold formed from a lower surface of the intermediate substrate, and the lower substrate may include nozzles passing therethrough, the nozzles corresponding to the dampers. 
     A part of the intermediate substrate that defines an upper surface of the manifold may also define a lower surface of the pressure chambers. The second restrictors may pass through the part of the intermediate substrate. The upper substrate, the intermediate substrate and the lower substrate may each formed of a single-crystal silicon substrate The upper substrate may be formed from a silicon on isolator wafer that includes a first silicon substrate, an intermediate oxide film, and a second silicon substrate, sequentially stacked, and the pressure chambers and the first restrictors are formed out of the first silicon substrate, and the second silicon substrate serves as a vibration plate for the piezoelectric actuators. 
     The intermediate substrate may further include at least one support pillar that contacts the lower substrate, the support pillar extending from a surface of the intermediate substrate that defines an upper surface of the manifold. The intermediate substrate may further include a blocking wall disposed between adjacent restrictors and extending from a surface of the intermediate substrate that defines an upper surface of the manifold. A width of the first restrictors in a width direction of the pressure chambers may be less than, or greater than, a width of the second restrictors in the width direction of the pressure chambers. 
     The manifold may have a partition wall formed therein along the length direction of the manifold, the partition wall extending from a surface of the intermediate substrate that defines an upper surface of the manifold and the partition wall may contact the lower substrate. 
     At least one of the above and other features and advantages of the present invention may also be realized by providing a method of manufacturing a piezoelectric type inkjet printhead, including, in an upper substrate, forming an ink introducing port, pressure chambers, and first restrictors connected with the pressure chambers, in an intermediate substrate, forming a manifold to a predetermined depth from a lower surface of the intermediate substrate, second restrictors connected to the manifold, and dampers passing through the intermediate substrate, in a lower substrate, forming nozzles passing through the lower substrate, bonding the lower substrate, the intermediate substrate and the upper substrate to each other such that the manifold connects with the ink introducing port, the second restrictors connect with the first restrictors, the dampers connect with the pressure chambers, and the nozzles connect with the dampers, and forming piezoelectric actuators on the upper substrate. 
     The method may further include forming a base mask on each of the three substrates, the base mark serving as an alignment reference in the bonding of the substrates. The ink introducing port, the pressure chambers, and the first restrictors may be formed by etching a lower surface of the upper substrate. Each of the upper substrate, intermediate substrate and lower substrate may be formed from a single crystal silicon wafer, the upper substrate is an SOI wafer including a first silicon substrate, an intermediate oxide film, and a second silicon substrate sequentially stacked, and forming the ink introducing port, the pressure chambers, and the first restrictors may include etching using the intermediate oxide film as an etch stop layer. Forming a manifold to a predetermined depth from a lower surface of the intermediate substrate, second restrictors connected to the manifold, and dampers passing through the intermediate substrate may include forming a first etch mask having a predetermined pattern on a lower surface of the intermediate substrate, forming the manifold and a lower portion of the dampers by etching the lower surface of the intermediate substrate to a predetermined depth using the first etch mask, forming a second etch mask having a predetermined pattern on an upper surface of the intermediate substrate, and forming the second restrictors and an upper portion of the dampers that is connected with the lower portion of the dampers by etching the upper surface of the intermediate substrate to a predetermined depth using the second etch mask. 
     Forming nozzles passing through the lower substrate may include forming ink guide parts connected with the dampers by etching an upper surface of the lower substrate to a predetermined depth, and forming ink ejection ports connected with the ink guide parts by etching a lower surface of the lower substrate. The lower substrate may be formed from a single crystal silicon wafer having a major surface parallel to a ( 100 ) crystal plane, and the ink guide parts may be formed to have inclined side surfaces by using an anisotropic etch process. The bonding of the three substrates may be performed by silicon direct bonding. The method may further include forming a silicon oxide film on the upper substrate before forming the piezoelectric actuators. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  illustrates the construction of a typical piezoelectric inkjet printhead; 
         FIG. 2  illustrates a conventional piezoelectric inkjet printhead; 
         FIG. 3  illustrates a view of another example of a piezoelectric inkjet printhead; 
         FIG. 4  illustrates a vertical sectional view of the piezoelectric inkjet printhead illustrated in  FIG. 3 ; 
         FIG. 5  illustrates an exploded perspective view of a piezoelectric inkjet printhead according to an embodiment of the present invention; 
         FIG. 6  illustrates a partial sectional view of the printhead illustrated in  FIG. 5 , taken along the lengthwise direction of the pressure chambers; 
         FIG. 7  illustrates a partial perspective view taken along a line A-A of  FIG. 6 ; 
         FIG. 8  illustrates a plan view of the pressure chamber and the restrictor illustrated in  FIG. 7 ; 
         FIG. 9  illustrates a plan view of a pressure chamber and a restrictor of a printhead according to a second embodiment of the present invention; 
         FIG. 10  illustrates a plan view of a pressure chamber and a restrictor of a printhead according to a third embodiment of the present invention; 
         FIG. 11  illustrates a partial sectional view of an inkjet printhead, taken along the lengthwise direction of the pressure chamber, according to a fourth embodiment of the present invention; 
         FIG. 12  illustrates a perspective view of the back side of a manifold of the intermediate substrate illustrated in  FIG. 11 ; 
         FIG. 13  illustrates a plan view of a portion B illustrated in  FIG. 12 ; 
         FIGS. 14A through 14E  illustrate sectional views explaining operations of forming a base mark on an upper substrate in a method of manufacturing a piezoelectric type inject printhead according to the present invention; 
         FIGS. 15A through 15G  illustrate sectional views explaining operations of forming a pressure chamber and a first restrictor on an upper substrate according to the present invention; 
         FIGS. 16A through 16D  illustrate sectional views explaining operations of forming an ink introducing port on an upper substrate according to the present invention; 
         FIGS. 17A through 17H  illustrate sectional views explaining operations of forming the second restrictor on an intermediate substrate according to the present invention; 
         FIGS. 18A through 18H  illustrate sectional views explaining operations of forming a nozzle on a lower substrate according to the present invention; 
         FIG. 19  illustrates a sectional view of an operation of stacking a lower substrate, an intermediate substrate, and an upper substrate to bond the same according to the present invention; and 
         FIGS. 20A and 20B  illustrate sectional views explaining operations of forming piezoelectric actuators on an upper substrate to complete a piezoelectric inkjet printhead according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Korean Patent Application No. 10-2004-0079959, filed on Oct. 7, 2004, in the Korean Intellectual Property Office, and entitled: “Piezoelectric Type Inkjet Printhead and Method of Manufacturing the Same,” is incorporated by reference herein in its entirety. 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the figures, the dimensions of layers and regions are exaggerated for clarity of illustration. It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout. 
       FIG. 5  illustrates an exploded perspective view of a piezoelectric inkjet printhead according to an embodiment of the present invention,  FIG. 6  illustrates a partial sectional view of the printhead illustrated in  FIG. 5 , taken along the lengthwise direction of the pressure chambers, and  FIG. 7  illustrates a partial perspective view taken along a line A-A of  FIG. 6 . 
     Referring to  FIGS. 5 through 7 , the piezoelectric type inkjet printhead may include three substrates  100 ,  200  and  300  stacked and bonded together. Each of the three substrates may have elements constituting an ink channel thereon. Particularly, piezoelectric actuators  190 , for generating a driving force for use in ejecting ink, may be formed on the upper substrate  100 . Each of the three substrates  100 ,  200  and  300  may be formed of a single-crystal silicon wafer to allow the formation of elements constituting an ink channel more precisely and easily on each of the three substrates  100 ,  200  and  300 , e.g., by using micromachining technologies such as photolithography, etching, etc. 
     The ink channel may include an ink introducing port  110 , through which ink is introduced from an ink container (not shown), a manifold  210 , in which ink that has flowed through the ink introducing port  110  is stored, first and second restrictors  130 ,  220 , for supplying ink from the manifold  210  to a pressure chamber  120 , the pressure chamber  120  filled with ink to be ejected and generating a pressure change to eject the ink, and a nozzle  310  for ejecting the ink. A damper  230  for concentrating energy generated from the pressure chamber  120  by the piezoelectric actuator  190  toward the nozzle  310  and for buffering a drastic pressure change may be formed between the pressure chamber  120  and the nozzle  310 . The elements constituting the ink channel may be distributed on the three substrates  100 ,  200  and  300  as described above. 
     The pressure chambers  120 , which may have a predetermined depth, and the first restrictors  130  may be formed in the backside of the upper substrate  100  and the ink introducing port  110  may be formed on one side of the upper substrate  100 . The pressure chambers  120  may have a long, rectangular parallelepiped shape along a flow direction of ink and may be arranged in two columns, one on each side of a printhead chip along a lengthwise direction of the manifold  210 . The pressure chambers  120  may also be arranged in one column on one side of the printhead chip along the lengthwise direction of the manifold  210 . The first restrictor  130  provides a flow path that allows the ink from the manifold  210  to flow to the pressure chamber  120 . The first restrictor  130  may have a width smaller than that of the pressure chamber  120  and extends from the pressure chamber  120  to connect with the second restrictor  220 . 
     The upper substrate  100  may be formed of, e.g., a single-crystal silicon wafer of the type widely used in manufacturing integrated circuits (ICs), and more particularly, may be formed of a silicon on insulator (SOI) wafer. The SOI wafer has a structure in which a first silicon substrate  101 , an intermediate oxide film  102 , and a second silicon substrate  103  are sequentially stacked. The first silicon substrate  101  may be made of a single-crystal silicon and may have a thickness of about hundreds of μm. The intermediate oxide film  102  may be formed by oxidizing the surface of the first silicon substrate  101  and may have a thickness of about 1-2 μm. The second silicon substrate  103  may be made of a single-crystal silicon and may have a thickness of about tens of μm. 
     By using a SOI wafer for the upper substrate  100 , the height of the pressure chamber  120  may be accurately controlled. That is, since the intermediate oxide film  102 , which constitutes an intermediate layer of the SOI wafer, may serve as an etch stop layer, when the thickness of the first silicon substrate  101  is determined, the height of the pressure chamber  120  is determined accordingly. Also, a thickness of the vibration plate may be determined by the thickness of the second silicon substrate  103 . In particular, the second silicon substrate  103 , where it forms the upper wall of the pressure chamber  120 , may be warp-deformed by the piezoelectric actuator  190  during operation, thus serving as a vibration plate that changes the volume of the pressure chamber  120 . 
     The piezoelectric actuators  190  may be disposed on the upper substrate  100 . A silicon oxide layer  180  may be formed as an insulation layer between the upper substrate  100  and the piezoelectric actuators  190 . The piezoelectric actuator  190  may have lower electrodes  191  and  192  serving as a common electrode, a piezoelectric thin film  193  that deforms when a voltage is applied, and an upper electrode  194  serving as a drive electrode. The lower electrodes  191  and  192  may be formed on the entire surface of the silicon oxide layer  180  and may be formed of two metal thin film layers including, e.g., a Ti-layer  191  and a Pt-layer  192 . The Ti-layer  191  and the Pt-layer  192  may serve not only as a common electrode but may also serve as a diffusion barrier layer to prevent inter-diffusion between the piezoelectric thin film  193 , on the Ti-layer  191  and the Pt-layer  192 , and the upper substrate  100 , beneath the Ti-layer  191  and the Pt-layer  192 . The upper electrode  194  may be formed on the piezoelectric thin film  193  and serve as a drive electrode for applying a voltage to the piezoelectric thin film  193 . 
     The piezoelectric thin film  193  may be formed on the lower electrodes  191  and  192  and may be disposed on the upper portion of the pressure chamber  120 . In operation, the piezoelectric thin film  193  is deformed by application of a voltage. Such deformation of the piezoelectric thin film  193  warp-deforms a portion of the second silicon substrate  103 , i.e., it warp-deforms the vibration plate of the upper substrate  100  that constitutes the upper wall of the pressure chamber  120 . 
     The intermediate substrate  200  may include the manifold  210 , which is a common channel connected with the ink introducing port  110  to supply ink, which flows through the ink introducing port  110 , to the pressure chambers  120 . The manifold  210  may be formed to a predetermined depth from the backside of the intermediate substrate  200 , so that a ceiling wall  217  of a predetermined thickness remains on the upper portion of the manifold  210 . That is, the lower end of the manifold  210  may be limited by the lower substrate  300  and the upper end of the manifold  210  may be limited by the ceiling wall  217 , which is the remaining portion of the intermediate substrate  200 . 
     As described above, when the pressure chambers  120  are arranged in two columns on both sides of a printhead chip along a lengthwise direction of the manifold  210 , a partition wall  215  may formed in a lengthwise direction inside of the manifold  210 . Thus, the manifold  210  may be divided into two regions, e.g., right and left regions, which is desirable for a smooth flow of the a and for preventing a crosstalk between the divided left and right regions of the manifold  210  when piezoelectric actuators  190  on both sides of the manifold  210  are driven. 
     The intermediate substrate  200  may have the second restrictor  220 , which may be a separate channel connecting the manifold  210  with the first restrictor  130 . The second restrictor  220  may be spaced apart from the partition wall  215 , pass through the intermediate substrate  200 , e.g., in a vertical direction, and have an exit communicating with the first restrictor  130 . The second restrictor  220  may not only supply an appropriate amount of ink from the manifold  210  to the pressure chamber  120  in cooperation with the first restrictor  130 , but may also prevent ink from flowing backward to the manifold  210  from the pressure chamber  120  when the ink is ejected. 
     A damper  230  may pass through the intermediate substrate  200  and may be formed, e.g., in a vertical direction, in a position that corresponds to one end of the pressure chamber  120 , so as to connect the pressure chamber  120  with the nozzle  310 . 
     The first restrictor  130  may extend from the pressure chamber  120  and may be formed in the upper substrate  100  and the second restrictor  220  may be formed in the intermediate substrate  200  such that it corresponds to the first restrictor  130 . With the above-described structure, the first and second restrictors  130  and  220  may be formed in a central portion of the intermediate substrate  200 . This may allow a greater amount of space for formation of the manifold  210 . In other words, one portion of the manifold  210  may have its sides defined by the partition wall  215  and by a wall having a predetermined interval relative to the damper  230 . The thickness of the wall formed by the interval relative to the damper  230  may be reduced in comparison to conventional inkjet printheads. Therefore, the width of the manifold  210  may be increased in comparison to conventional inkjet printheads. 
     When the width of the manifold  210  increases as described above, the volume thereof increases and thus crosstalk between the adjacent restrictors  130  and  220  may be reduced. In detail, if a pressure is applied to ink accommodated inside the pressure chamber  120  by the piezoelectric actuator  190 , i.e., when the ink is ejected, the pressure is also transferred to ink inside the restrictors  130  and  220  connected with the pressure chamber  120 . Further, the pressure is transferred to the manifold  210  connected with the restrictors  130  and  220 , so that crosstalk between the adjacent restrictors  130  and  220  may occur. In inkjet printheads according to the present invention, the volume of the manifold  210  may be increased so that the amount of the ink that can be accommodated inside the manifold  210  may be increased. Accordingly, the intensity of the pressure transferred through the restrictors  130  and  220  per unit volume of ink inside the manifold  210  may be reduced, such that the pressure is dispersively absorbed. Since the pressure may be dispersively absorbed, the intensity of the pressure influencing the restrictors  130  and  220  may be reduced, so that crosstalk between the adjacent restrictors  130  and  220  may also be reduced. 
     Also, as described above, when the width of the manifold  210  is increased, the cross-sectional area increases, so that the ink ejection may operate stably at a high frequency. In detail, when the piezoelectric thin film  193  is restored after an ink droplet is ejected from the nozzle  310 , the pressure within the pressure chamber  120  is reduced and ink stored in an ink container (not shown) flows into the pressure chamber  120  through the manifold  210  and the restrictor  130  and  220 , to thereby replace the ink that was ejected. 
     By increasing the cross-sectional area of the manifold  210 , a flow resistance of ink in the manifold  210  due to wall shear stress may be reduced so that ink inflow supplied through the manifold  210  is increased. Accordingly, the supply of ink under high-frequency ejection may be quickly realized. Thus, even though a large number of ink ejections may be performed in rapid sequence, the ink ejection can be stably performed by increasing the width of the manifold  210 . 
     A nozzle  310  may be formed that pierces the lower substrate  300  in a position that corresponds to the damper  230 . In detail, the nozzle  310  may be formed at the lower portion of the lower substrate  300  and may include an ink-ejection port  312 , for ejecting ink, and an ink guide part  311  that is formed at the upper portion of the lower substrate  300 . The ink guide part may serve to connect the damper  230  with the ink-ejection port  312  as well as pressurizing and guiding ink from the damper  230  to the ink-ejection port  312 . The ink-ejection port  312  may have a shape of, e.g., a vertical hole having a predetermined diameter, and the ink guide part  311  may have, e.g., a quadrangular pyramid shape, circular pyramid shape, etc., the cross-section of which tapers toward the ink-ejection port  312 . As described below, according to the present invention, a quadrangular pyramid-shaped ink guide part  311  may be easily formed in a single-crystal silicon wafer-based lower substrate  300 . 
     As set forth above, the three substrates  100 ,  200  and  300 , formed as described above, may be stacked and bonded to each other to yield a piezoelectric inkjet printhead according to the present invention. Thus, an ink channel including the ink introducing port  110 , the manifold  210 , the restrictors  130  and  220 , the pressure chamber  120 , the damper  230  and the nozzle  310 , sequentially connected, may be formed from the three substrates  100 ,  200  and  300 . 
     In the operation of an inkjet printhead formed according to the present invention, ink may flow into the manifold  210  through the ink introducing port  110  from the ink container (not shown) and may be supplied to the inside of the pressure chamber  120  through the ink restrictors  130  and  220 . When a voltage is applied to the piezoelectric thin film  193  through the upper electrode  194  of the piezoelectric actuator  190  with the inside of the pressure chamber filled with the ink, the piezoelectric thin film  193  is deformed such that the second silicon substrate  103 , serving as a vibration plate, is warped downward. The volume of the pressure chamber  120  is reduced by the warp-deformation of the second silicon substrate  103 , which increases the pressure in the inside of the pressure chamber  120 , so that the ink in the inside of the pressure chamber  120  is ejected to the outside through the nozzle  310  by way of the damper  230 . 
     Subsequently, when the voltage applied to the piezoelectric thin film  193  of the piezoelectric actuator  190  is cut off, the piezoelectric thin film  193  is restored to its original state such that the second silicon substrate  103  serving as the vibration plate is restored to the original state and the volume of the pressure chamber  120  increases. The pressure within the pressure chamber  120  reduces and ink stored in the ink container (not shown) flows into of the pressure chamber  120  through the manifold  210  and the restrictor  130  and  220  to refill the ink in the pressure chamber  120  and thereby replace the ink that was ejected. 
       FIG. 8  illustrates a plan view of the pressure chamber and the restrictor illustrated in  FIG. 7 ,  FIG. 9  illustrates a plan view of a pressure chamber and a restrictor of a printhead according to a second embodiment of the present invention, and  FIG. 10  illustrates a plan view of a pressure chamber and a restrictor of a printhead according to a third embodiment of the present invention. As described above, for each of  FIGS. 8-10 , the upper substrate  100  has the pressure chamber  120  as well as the first restrictor  130  connected to the pressure chamber  120 . The intermediate substrate  200  has the second restrictor  220 , which corresponds to the first restrictor  130 . 
     In the embodiment illustrated in  FIG. 8 , a width of the second restrictor  220  in the width direction of the pressure chamber  120  is smaller than that of the first restrictor  130  (as illustrated, the width direction of the pressure chamber  120  is defined in a vertical direction in  FIG. 8 ). In this embodiment, even when an alignment error is generated between the upper substrate  100  and the intermediated substrate  200 , the exit of the second restrictor  220  can be completely open and unobscured where it interfaces with the first restrictor  130 . 
     In the embodiment illustrated in  FIG. 9 , the width of the second restrictor  220  in the width direction of the pressure chamber  120  is greater than that of the first restrictor  130 . In this embodiment, even when an alignment error is generated between the upper substrate  100  and the intermediated substrate  200 , the exit of the second restrictor  220  can be unaffected where it interfaces with the first restrictor  130 . That is, an alignment error may have little or no effect on the area of the interface, i.e., the size of the opening, at the interface between the first and second restrictors  120 ,  130 . 
     In the embodiment illustrated in  FIG. 9 , the width of the second restrictor  220  in the width direction of the pressure chamber  120  is smaller than that of the first restrictor  130 , but is increased relative to the embodiment illustratrated in  FIG. 8 . Also, the width of the first restrictor  130  is increased so as to remain greater than the increased width of the second restrictor  220 . The width of a portion of the first restrictor  130  where it interfaces with the second restrictor  220  may be less than, equal to, or greater than the width of the pressure chamber  120 . In this embodiment, even when an alignment error is generated between the upper substrate  100  and the intermediate substrate  200 , the exit of the second restrictor  220  can be completely open and unobscured where it interfaces with the first restrictor  130 . In addition to the embodiments just described, a variety of embodiments in which the exit of the second restrictor  220  can be open to the necessary degree in the direction of the first restrictor  130  are envisioned, and the present invention is not limited to the orientations and relative widths described above. 
       FIG. 11  illustrates a partial sectional view of an inkjet printhead, taken along the lengthwise direction of the pressure chamber, according to a fourth embodiment of the present invention,  FIG. 12  illustrates a perspective view of the back side of a manifold of the intermediate substrate illustrated in  FIG. 11  and  FIG. 13  illustrates a plan view of a portion B illustrated in  FIG. 12 . For the embodiment illustrated in  FIGS. 11-13 , the intermediate substrate  200  has both a support pillar  250  and a blocking wall  260  inside the manifold  210 , although these elements need not be used in conjunction. Thus, they are illustrated together merely for ease of description. 
     The support pillar  250  may support the ceiling wall  217  of the manifold  210 . That is, the support pillar  250  may extend from a surface of the intermediate substrate that defines an upper surface of the manifold. Detailing the operation of this embodiment, pressure transferred from the pressure chamber  120  may be sufficient to deform the manifold  210  inwardly. That is, the ceiling wall  217  of the manifold  210  may be deformed, resulting in a decrease in volume of the manifold  210  and possible concommitant undesired expulsion of ink. The support pillar  250  may support the ceiling wall  217  of the manifold  210  to prevent this deformation of the ceiling wall  217 . The support pillar  250  may protrude from the ceiling wall  217  of the manifold  210  and may contact a lower substrate  300  to support the ceiling wall  217  of the manifold  210 . A plurality of support pillars  250  may be provided as necessary to efficiently support the ceiling wall of the manifold  210 . Also, the support pillar  250  may have a shape and/or arrangement such that ink flowing in the inside of the manifold  210  is not hindered. 
     The blocking wall  260  may serve as a blocking object to reduce crosstalk between the second restrictors  230 . In detail, referring to  FIG. 13 , the blocking wall  260  is disposed between adjacent second restrictors  230  to reduce the influence of pressure transferred through the second restrictors  230 . Therefore, the crosstalk occurring between adjacent second restrictors  230  may be reduced. The blocking wall  260  may be formed of sufficient length as compared to the length of the second restrictor  230  so as to effectively reduce crosstalk interference between the second restrictors  230 . 
     Hereinafter, a method of manufacturing the a piezoelectric inkjet printhead according to the present invention will be described. As a general matter, the upper substrate, the intermediate substrate, and the lower substrate having the elements constituting the ink channel may be manufactured and subsequently stacked to be bonded to each other and one or more piezoelectric actuators may be formed on the upper substrate. Of course, the operations of manufacturing the upper substrate, the intermediate substrate, and the lower substrate can be performed in any order, such that the lower substrate or the intermediate substrate may be manufactured first, or two or three substrates can be simultaneously manufactured, etc. In the description that follows, the manufacturing method will be described in order of the upper substrate, the intermediate substrate, and the lower substrate, but this order is simply a matter of convenience in description. 
       FIGS. 14A through 14E  illustrate sectional views explaining operations of forming a base mark on an upper substrate in a method of manufacturing a piezoelectric type inject printhead according to the present invention. Referring to  FIG. 14A , the upper substrate  100  may be formed of a single-crystal silicon substrate. By using a single-crystal silicon substrate, widely used manufacturing techniques, e.g., those used to manufacture semiconductor devices, may be employed, thus allowing for efficient mass production. The thickness of the upper substrate  100  may be about 100-200 μm and may be determined to correspond to the height of the pressure chamber  120  that will be formed on the backside of the upper substrate  100 . When an SOI wafer is used for the upper substrate  100 , the height of the pressure chamber  120  may be accurately formed. As described above, the SOI wafer has a stacked structure including the first silicon substrate  101 , the intermediate oxide film  102  stacked or formed on the first silicon substrate  101 , and the second silicon substrate  103  bonded to or formed on the intermediate oxide film  102 . As illustrated in  FIG. 14A , silicon oxide films  151   a, b , may be formed on the upper and lower, i.e., backside, surfaces of upper substrate  100  by, e.g., using an oxidization furnace to wet-oxidize or dry-oxidize the upper substrate  100 . 
     Referring to  FIG. 14B , a photoresist (PR) may be spread on the surfaces of the silicon oxide films  151   a  and  151   b . Subsequently, the spread PR may be exposed and developed so as to form an opening  141  to be used in forming a base mark in an edge portion of the upper substrate  100 . Referring to  FIG. 14C , the portion of the silicon oxide films  151   a  and  151   b  exposed by the opening  141  may be removed through, e.g., a wet-etching process, using the PR for an etch-mask, so that the upper substrate  100  is partially exposed. Once completed, the remaining PR may be stripped. 
     Referring to  FIG. 14D , the exposed portion of upper substrate  100  may be removed by, e.g., a wet etch process, to a predetermined depth, wherein the silicon oxide films  151   a  and  151   b  serve as an etch-mask, to thereby form a base mark  140 . At this point, a Tetramethyl Ammonium Hydroxide (TMAH) can be used for etchant for silicon in wet-etching the upper substrate  100 . After the base mark  140  is formed, the remaining silicon oxide films  151   a  and  151   b  may be removed by, e.g., a wet etch process. In this way, any contamination formed during the above processes can be removed as well. 
     Referring to  FIG. 14E , process described above may be used to form the upper substrate  100  having the base mark  140  formed on the edge portion of the upper surface and the backside of the upper substrate  100 . The base mark  140  may be used in accurately aligning the upper substrate  100 , the intermediate substrate  200  and a lower substrate  300 , when stacking and bonding these substrates. It will be understood that the upper substrate  100  may have the base mark  140  on only the lower, or backside, thereof, or an alignment method or apparatus may be used in which the base mark  140  is not required. Accordingly, the above-described processes may be employed as the situation requires and the present invention is not limited thereby. 
       FIGS. 15A through 15G  illustrate sectional views explaining operations of forming a pressure chamber and a first restrictor on an upper substrate according to the present invention. Referring to  FIG. 15A , the upper substrate  100 , prepared by, e.g., the processes set forth above, may be oxidized to form silicon oxide films  152   a, b , on the upper and lower (backside) surfaces of the upper substrate  100  by, e.g., placing the upper substrate  100  in oxidation furnace, wet-etching, dry-etching, etc. Alternatively, the silicon oxide film  152   b  alone may be formed, i.e., the upper substrate  100  may be oxidized only on its backside. 
     Referring to  FIG. 15B , a second PR may be spread on the surface of the silicon oxide film  152   b . The spread PR may be exposed and developed so as to form an opening  121  for forming a pressure chamber and a first restrictor on the backside of the upper substrate  100 . Referring to  FIG. 15C , the backside of the upper substrate  100  may be partially exposed by removing the portion of the silicon oxide film  152   b  exposed by the opening  121  through, e.g., a dry etch process such as reactive-ion-etching (RIE), while using the PR for an etch mask. 
     Referring to  FIG. 15D , the exposed portion of the upper substrate  100  may be etched to a predetermined depth using a PR for an etch-mask to form the pressure chamber  120  and the first restrictor  130  and using the intermediate oxide film  102  as an etch stop layer. Etching of the upper substrate  100  may be performed by, e.g., dry etching using a process such as inductively coupled plasma (ICP). The depth of the features formed at this point may be determined by the thickness of the first silicon substrate  101 , allowing for a precise predetermination of their depth. 
     In detail, when an SOI wafer is used for the upper substrate  100  as illustrated, since the intermediate oxide film  102  of the SOI wafer serves as an etch-stop layer, only the first silicon substrate  101  is etched at this stage. Accordingly, when the thickness of the first silicon substrate  101  is controlled, the pressure chamber  120  and the first restrictor  130  may be accurately controlled to a desired height. The thickness of the first silicon substrate  101  may be easily controlled during a wafer polishing process. Further, the second silicon substrate  103  constituting the upper wall of the pressure chamber  120  serves as the vibration plate as described above and the thickness thereof can be also easily controlled during the wafer polishing process. 
       FIG. 15E  represents the upper substrate  100  after the PR is stripped after the pressure chamber  120  and the first restrictor  130  are formed. Note that, at this stage, contaminants such as a by-product or polymer produced during the above-described wet-etching or dry-etching using RIE, ICP, etc., may attach on the surface of the upper surface  100 . Therefore, the entire surface of the upper substrate  100  may be washed using, e.g., a tetramethyl ammonium hydroxide (TMAH) wash to remove the contaminants. The remaining silicon oxide films  152   a  and  152   b  may also be removed at this stage by, e.g., a wet etch process. 
     Referring to  FIG. 15F , the upper substrate  100  having a base mark  140  formed in the edge portions of the upper surface and the backside, the pressure chamber  120 , and the first restrictor  130  formed in the backside, have been prepared. After the pressure chamber  120  and the first restrictor  130  are formed by, e.g., dry etching the upper substrate  100  using the PR for the etch-mask, the PR is stripped. However, unlike the above process, the pressure chamber  120  and the first restrictor  130  may be formed by dry-etching the upper substrate  100  using the silicon oxide film  152   b  for the etch-mask after the PR is stripped first. That is, in the case where the silicon oxide film  152   b  formed on the backside of the upper substrate  100  is relatively thin, the etching process that forms the pressure chamber  120  and the first restrictor  130  may be performed with the PR in place. Otherwise, in the case where the silicon oxide film  152   b  is relatively thick, the etching may be performed using the silicon oxide film  152   b  for the etch-mask, after the PR has been stripped. 
     Referring to  FIG. 15G , silicon oxide films  153   a  and  153   b  may be further formed on the upper surface and the backside of the upper substrate  100  illustrated in  FIG. 15F  (note that, if the silicon oxide films  153   a  and  153   b  are formed, an operation, described below, of forming a silicon oxide layer  180  as an insulation film on the upper substrate  100  can be omitted). When the silicon oxide film  153   b  is formed on the inside of the pressure chamber  120  and the first restrictor  130 , the silicon oxide film  153   b  does not react to most kinds of ink due to the characteristic of the silicon oxide film  153   b , so that a variety of ink can be used. 
       FIGS. 16A through 16D  illustrate sectional views explaining operations of forming an ink introducing port on an upper substrate according to the present invention. Referring to  FIG. 16A , the ink introducing port  110  may be formed together with the pressure chamber  120  by the operations illustrated in  FIGS. 15A through 15G . Next, referring to  FIG. 16B , a PR may be spread on the surface of the silicon oxide film  152   a , exposed and developed, so as to form an opening  111  that may be used to piercing the ink introducing port  110  through the upper surface of the upper substrate  100 . 
     Referring to  FIG. 16C , the upper surface of the upper substrate  100  may be partially exposed by removing the portion of the silicon oxide film  152   a  exposed by the opening  111  through, e.g., a dry etching process such as a reactive-ion-etching (RIE), using the PR for an etch mask. Referring to  FIG. 16D , the exposed portion of the upper substrate  100  may be etched to a predetermined depth using the PR for an etch mask, after which the PR may be stripped. Etching of the upper substrate  100  may be performed by, e.g., a dry etch process such as ICP. Of course, the upper substrate  100  may be etched using the silicon oxide film  152   a  for an etch mask after having first removed the PR. 
     The intermediate oxide film  102  of the SOI wafer may serve as an etch-stop layer in the etching of the upper substrate  100 , such that only the second silicon substrate  103  is etched and the intermediate oxide film  102  remains in the ink introducing port  110 . The remaining intermediate oxide film  102  may be removed by processes such as those as described above to pierce the upper substrate and thereby complete the ink introducing port  110 . The upper substrate  100  may be completed by the operations illustrated in  FIGS. 15F and 15G , as described above. 
     It will be understood that the formation of the ink introducing port on the upper substrate  100  may be performed after forming the piezoelectric actuator. That is, part of the lower portion of the ink introducing port  110  may be formed together with the pressure chamber  120  by the operations illustrated in  FIGS. 15A through 15G . In the operation illustrated in  FIG. 15E , the pressure chamber  120  of a predetermined depth and part of the ink introducing port  110  of the same depth as the pressure chamber  120  may be formed on the backside of the upper substrate  100 . The ink introducing port  110  formed at a predetermined depth in the backside of the upper substrate  100  may be formed so as to connect with an ink storage (not shown) through a post processing of piercing the upper substrate  100  after processes of bonding the substrates and installing the piezoelectric actuator thereon are completed. That is, the piercing of the ink introducing port  100  may be performed after the operation of forming the piezoelectric actuator is completed. 
       FIGS. 17A through 17H  illustrate sectional views explaining operations of forming the second restrictor on an intermediate substrate according to the present invention. Referring to  FIG. 17A , the intermediate substrate  200  may be formed of a single-crystal silicon substrate and has a thickness of 200-300 μm. The thickness of the intermediate substrate  200  may be determined according to the dimensions of the manifold  210  and the damper  230 . 
     A base mark  240  may be formed on the edge portions of the upper and lower, i.e., backside, surfaces of the intermediate substrate  200 . Since operations of forming the base mark  240  on the intermediate substrate  200  may be the same as the operations illustrated in  FIGS. 14A through 14E , a detailed description thereof will be omitted. When the intermediate substrate  200  having the base mark  240  formed thereon is put into an oxidation furnace so as to wet-oxidize or dry-oxidize the intermediate substrate  200 , the upper surface and the backside of the intermediate substrate  200  may be oxidized as illustrated in  FIG. 17A  to form the silicon oxide films  251   a  and  251   b . Referring to  FIG. 17B , a PR may be spread on the surface of the silicon oxide film  251   b . Subsequently, the PR may be exposed and developed to form an opening  211  for forming the manifold  210  and an opening  231  for forming the damper  230  on the backside of the intermediate substrate  200 . 
     Referring to  FIG. 17C , the backside of the intermediate substrate  200  may be partially exposed by removing the portion of the silicon oxide film  251   b  exposed by the openings  211  and  231  through, e.g., a wet etch process, using a PR for an etch-mask, after which the PR may be stripped. Referring to  FIG. 17D , the exposed portion of the intermediate substrate  200  may be removed, e.g., through a wet etch process, to a predetermined depth using the silicon oxide films  251   b  for an etch-mask so as to form the lower portions of the manifold  210  and the damper  232 . TMAH may be used as an etchant for silicon in wet-etching the intermediate substrate  200 . 
     Referring to  FIG. 17E , a PR may be spread on the surface of the silicon oxide film  251   a . Subsequently, the PR may be exposed and developed to form an opening  221  for forming the second restrictor  220  and an opening  233  used in forming the upper portion of the damper  230  on the upper surface of the intermediate substrate  200 . Referring to  FIG. 17F , the upper surface of the intermediate substrate  200  may be partially exposed by removing the portion of the silicon oxide film  251   a  exposed by the openings  221  and  233  through, e.g., a wet etch process, to a predetermined depth using the PR for an etch-mask, after which the PR may be stripped. 
     Referring to  FIG. 17G , the exposed portion of the intermediate substrate  200  may be removed through, e.g., a wet etch process, to a predetermined depth using the silicon oxide films  251   a  for an etchmask to form the second restrictor  220  and the damper  230  that passes through the lower portion of the damper of  FIG. 17D . After removing the remaining silicon oxide films  251   a  and  251   b  by, e.g., a wet etch process, the intermediate substrate  200  having the base mark  240 , the second restrictor  220 , the manifold  210 , the partition wall  215 , and the damper  230 , may be produced as illustrated in  FIG. 17H . Though not shown, a silicon oxide film may again be formed on the entire backside of the upper surface of the intermediate substrate  200  illustrated in  FIG. 17H . 
       FIGS. 18A through 18H  illustrate sectional views explaining operations of forming a nozzle on a lower substrate according to the present invention. Referring to  FIG. 18A , the lower substrate  300  may be formed of a single-crystal silicon substrate and may have a thickness of 100-200 μm. A base mark  340  may be formed on the edge portions of the upper surface and the backside of the lower substrate  300 . Since operations of forming the base mark  340  on the lower substrate  300  may be the same as the operations illustrated in  FIGS. 14A through 14E , detailed description thereof will be omitted. The lower substrate  200 , having the base mark  340  formed thereon, may be put into an oxidation furnace to wet-oxidize or dry-oxidize the upper surface and the backside of the lower substrate  300 , as illustrated in  FIG. 18A , to form silicon oxide films  351   a  and  351   b.    
     Referring to  FIG. 18B , a PR may be spread on the surface of the silicon oxide film  351   a , exposed and developed to form an opening  315 , for an ink guide part  311  of the nozzle  310 , on the upper surface of the lower substrate  300 . The opening  315  may be formed at a position that corresponds the damper  230  formed in the intermediate substrate  200  illustrated in  FIG. 17H . Referring to  FIG. 18C , the upper surface of the lower substrate  300  may be partially exposed by removing the portion of the silicon oxide film  351   a  exposed by the opening  315  through, e.g., a wet etch process, to a predetermined depth using the PR for an etch-mask, after which the PR may be stripped. The silicon oxide film  351   a  may be removed by a dry etch process such as RIE. 
     Referring to  FIG. 18D , the exposed portion of the lower substrate  300  may be removed by, e.g., a wet etch process, to a predetermined depth using the silicon oxide films  351   a  for an etch-mask so as to form an ink guide part  311 . TMAH may be used for etchant in wet-etching the lower substrate  300 . When a silicon substrate having a ( 100 ) crystal face is used for the lower substrate  300 , the ink guide part  311  having a quadrangular pyramid shape may be formed using an anisotropic wet etch process. In detail, since the etch speed of the crystallize face ( 111 ) is considerably slow compared with that of the crystallize face ( 100 ), the lower substrate  300  may be effectively wet etched to yield inclined surfaces along the ( 111 ) crystal face, thereby forming the ink guide part  311  having the quadrangular pyramid shape. As illustrated, the ( 100 ) crystal face becomes the bottom of the ink guide part  311 . 
     Referring to  FIG. 18E , a PR may be spread on the surface of the silicon oxide film  351   b , exposed and developed to form an opening  316  for an ink ejection port  312  of the nozzle  310 . Referring to  FIG. 18F , the backside of the lower substrate  300  may be partially exposed by removing the portion of the silicon oxide film  351   b  exposed by the opening  316  through, e.g., a wet etch process, using the PR for an etch mask. The silicon oxide film  351   b  may be removed by a dry etch process such as RIE. 
     Referring to  FIG. 18G , the exposed portion of the lower substrate  300  may be etched to pierce the lower substrate  300  using the PR for an etchmask, so that the ink ejection port  312  connected with the ink guide part  311  may be formed. The etching of the lower substrate  300  may be performed by, e.g., a dry etch process using an ICP. Subsequently, when the PR is stripped, the lower substrate  300  having the base mark  340  on the edge portions of the upper surface and the backside of the lower substrate, and the nozzle  310  consisting of the ink guide part  311  and the ink ejection port  312  formed in the lower substrate  300  is produced as illustrated in  FIG. 18H . The nozzle  310  pierces the lower substrate  300 . 
     The silicon oxide films  351   a  and  351   b  formed on the upper surface and the backside of the lower substrate  300 , respectively, may be removed for washing, i.e., to rid the surfaces of contaminants, and, subsequently, a new silicon oxide film can be formed again on the entire surface of the lower substrate  300 . 
       FIG. 19  illustrates a sectional view of an operation of stacking a lower substrate, an intermediate substrate, and an upper substrate to bond the same according to the present invention. Referring to  FIG. 19 , the lower substrate  300 , the intermediate substrate  200 , and the upper substrate  100  prepared by, e.g., the above-described processes, may be sequentially stacked and bonded to each other. After the intermediate substrate  200  is bonded on the lower substrate  300 , the upper substrate  300  may bonded on the intermediate substrate  200 , although the bonding order can be changed. The three substrates  100 ,  200  and  300  may be aligned using a mask aligner. Since the base marks  140 ,  240  and  340  for alignment are formed in each of the three substrates  100 ,  200  and  300 , a highly accurate alignment may be achieved during the bonding process. 
     The bonding of the three substrates  100 ,  200  and  300  may be performed by, e.g., silicon direct bonding (SDB). In the SDB process, silicon-silicon oxide bonding is superior to silicon-silicon bonding. Therefore, referring to  FIG. 19 , the upper substrate  100  and the lower substrate  300  are used with the silicon oxide films  153   a ,  153   b ,  351   a  and  351   b  formed on the surfaces thereof, while the intermediate substrate  200  does not have a silicon oxide film on the surface thereof. 
       FIGS. 20A and 20B  illustrate sectional views explaining operations of forming piezoelectric actuators on an upper substrate to complete a piezoelectric inkjet printhead according to the present invention. Referring to  FIG. 20A , with the lower substrate  100 , the intermediate substrate  200 , and the upper substrate  300  sequentially stacked and bonded, a silicon oxide layer  180  as an insulation film may be formed on the upper surface of the upper substrate  100 , although this operation may be omitted. That is, in the case where the silicon oxide film  153   a  is already formed on the upper surface of the upper surface  100 , as illustrated in  FIG. 19 , or in the case where an oxide film of a sufficient thickness is already formed on the upper surface of the upper substrate  100 , e.g., in the operation of annealing during the above-described SDB process, the silicon oxide layer  180  illustrated in  FIG. 20A  doesn&#39;t need to be formed thereon. 
     Lower electrodes  191  and  192  of the piezoelectric actuator may be formed on the silicon oxide layer  180 . The lower electrodes may include two metal thin layers, e.g., a titanium (Ti) layer  191  and a platinum (Pt) layer  192 . The Ti-layer  191  and the Pt-layer  192  may be formed on the entire surface of the silicon oxide layer  180  by, e.g., sputtering to a predetermined thickness. The Ti-layer  191  and the Pt-layer  192  may serve not only as a common electrode of the piezoelectric actuator, but also serve as a diffusion barrier layer that prevents inter-diffusion between the piezoelectric thin film  193  on the Ti-layer  191  and the Pt-layer  192  and the upper substrates  100  beneath the Ti-layer  191  and the Pt-layer. Particularly, the Ti-layer  191  at the lower portion increases adhesiveness of the Pt-layer  192 . 
     Referring to  FIG. 20B , a piezoelectric thin film  193  and an upper electrode  194  may be formed on the lower electrode  191  and  192 . In detail, a piezoelectric material in a paste state may be spread to a predetermined thickness on the upper portion of the pressure chamber  120  using, e.g., screen printing, and then dried for a predetermined period of time. The piezoelectric material can be various materials, e.g., a general lead zirconate titanate (PZT) ceramic material. Subsequently, an electrode material, e.g., a gold-palladium (Ag—Pd) paste may be printed on the dried piezoelectric thin film  193 . The piezoelectric thin film  193  may then be sintered under a predetermined temperature, e.g., a temperature range of 900-1,000° C. The above-described Ti-layer  191  and Pt-layer  192  may act as diffusion barriers to prevent any inter-diffusion between the piezoelectric thin film  193  and the upper substrate  100  that might be generated during a high-temperature sintering process. Thus, the piezoelectric actuator  190  consisting of the lower electrodes  191  and  192 , the piezoelectric thin film  193  and the upper electrode  194  may be formed. 
     Since the sintering of the piezoelectric thin film  193  may performed in an open atmosphere, a silicon oxide film may be formed on the inside of the ink channel formed by the three substrates  100 ,  200  and  300  during sintering. Since the silicon oxide film formed in this manner does not react to most kinds of ink, a variety of ink may be used. Also, since the silicon oxide film has a hydrophilic property, inflow of air bubbles into the ink flow path when ink is initially filled in the ink channel may be prevented and air bubble generation may be suppressed when the ink is ejected. 
     A dicing process, cutting off the three bonded substrates  100 ,  200 , and  300  by chip unit, and a polling process of applying an electric field to the piezoelectric thin film  193  to generate a piezoelectric characteristic may be used in completing the piezoelectric inkjet printhead of the present invention. Of course, dicing may be performed before the sintering process of the piezoelectric thin film  193 . 
     While described above in detail in order to ensure a thorough understanding of the present invention, the method described herein for forming the respective elements of the printhead is merely exemplary and does not limit the present invention. For example, those skilled in the art will appreciate that various etching methods may be adopted and the order for the respective operations may be changed. 
     According to the piezoelectric inkjet printhead and the method of manufacturing the same of the present invention, it is possible to easily increase the width of the manifold by processing the backside of the intermediate substrate so as to form the manifold and install the manifold in the lower portion of the pressure chamber. Therefore, the volume of the manifold may be increase and the amount of ink accommodated therein similarly increased, so that pressure transferred to the inside of the manifold may be dispersively absorbed. Accordingly, when ink droplets are simultaneously ejected from the nozzles, crosstalk between adjacent restrictors may be reduced. Also, by increasing the width of the manifold, the cross-sectional area thereof is similarly increased and, thus, the flow resistance of the manifold is reduced. Accordingly, the amount of ink supply may be increased during the ink refill process that replaces the ejected ink and the printhead can stably operate even when ejecting ink at high-frequencies. 
     Further, according to the present invention, since the manifold may be formed below the lower portion of the pressure chamber and the first restrictor, with the manifold ceiling wall interposed therebetween, the substrate may save space to the extent that the width of the manifold in the arrangement of elements constituting an ink channel, and the chip size of printhead may be reduced. Therefore, the number of chips obtained per wafer may be increased, improving productivity. 
     Exemplary embodiments of the present invention have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.