Patent Publication Number: US-2020290346-A1

Title: Ejection apparatus, ejection method, article manufacturing apparatus, and storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/JP2018/043561, filed Nov. 27, 2018, which claims the benefit of Japanese Patent Application No. 2017-242784, filed Dec. 19, 2017, both of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an ejection apparatus that ejects a fluid in a liquid state, an ejection method, an article manufacturing apparatus, and a storage medium. 
     Background Art 
     Recently, ejection apparatuses that eject an ejection material such as a fluid in a liquid state from a plurality of nozzles to perform microfabrication have been used to manufacture semiconductor devices, MEMS, and so on. As such an ejection apparatus, an imprint apparatus has been known which, for example, ejects a fluid in a liquid state such as an uncured resin  114  having relatively high viscosity from nozzles onto a substrate and presses a mold processed to have concavities and convexities against the ejected resin  114  to thereby form a predetermined pattern in the resin  114 . The imprint apparatus is capable of forming an article having a fine structure on the order of several nanometers on a substrate. 
     The ejection apparatus used in an apparatus that performs microfabrication, such as the imprint apparatus, is required to have high accuracy in, for example, ejection speed and ejection volume of the ejection material to be ejected from its nozzles. In a case where the ejection speed of the ejection material from the nozzles deviates from a target value, the ejection material is displaced from the positions on the ejection target object, such as a substrate, to which the ejection material is supposed to adhere. Also, if the ejection volume from the nozzles deviates from a target ejection volume, there is a possibility that the thickness of the applied ejection material will be uneven and the pattern to be formed will not have the desired shape. 
     Then, in a case where the ejection speed and the ejection volume deviate from the respective target values, it is conceivable to correct the waveform of a drive signal to be inputted into each of ejection energy generation elements (piezoelectric elements) included in the nozzles. Patent Literature 1 discloses a technique in which the waveform of a drive signal to be inputted into each nozzle is corrected based on the ejection speed and the ejection volume of an ejection material ejected from the nozzle as a result of inputting a drive signal with a reference waveform into an ejection energy generation element in the nozzle. 
     In the technique disclosed in Patent Literature 1, a table indicating a relationship between parameters that determine the waveform of the drive signal and the ejection volume and ejection speed is generated for one representative nozzle selected from among the plurality of nozzles. Then, the ejection speed and the ejection volume of all nozzles are adjusted based on this table. For this reason, in a case where the degree of change in ejection volume and ejection speed (ejection tendency) in response to a change in the parameters greatly varies among nozzles, not all of the nozzle&#39;s ejection can be appropriately adjusted. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Laid-Open No. 2012-45780 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an ejection apparatus, an ejection method, and an article manufacturing apparatus capable of ejecting a fluid appropriately from all nozzles. 
     The present invention provides an ejection apparatus comprising: ejection unit having a plurality of nozzles for ejecting a fluid in a liquid state; control unit configured to control ejection of the fluid from each of the plurality of nozzles by applying a drive signal to an ejection energy generation element included in the nozzle; obtaining unit configured to obtaining an ejection result of the fluid ejected from the nozzle; and storage unit for storing an adjustment table for adjustment of the drive signal for each of the plurality of nozzles, the adjustment table indicating a relationship between waveform information on the drive signal for each of the nozzles and an ejection volume and ejection speed of the fluid ejected from the nozzle, in which the control unit adjusts ejection from each of the nozzles based on the corresponding adjustment table and the corresponding ejection result obtained by the obtaining unit. 
     Also, the present invention provides an ejection method of ejecting a fluid in a liquid state from each of a plurality of nozzles for ejecting the fluid by applying a drive signal to an ejection energy generation element included in the nozzle, characterized in that the ejection method comprises: preparing an adjustment table for adjustment of the drive signal for each of the nozzles; obtaining an ejection result of the fluid ejected from the nozzle; storing the adjustment table for adjustment of the drive signal for each of the plurality of nozzles, the adjustment table indicating a relationship between waveform information on the drive signal for each of the nozzles and an ejection volume and ejection speed of the fluid ejected from the nozzle; and adjusting ejection from each of the nozzles based on the corresponding adjustment table and the corresponding ejection result obtained by the obtaining. 
     Also, the present invention provides an article manufacturing apparatus that ejects a fluid in a liquid state onto a predetermined ejection target object from a plurality of nozzles provided in ejection unit, and pressing a mold against the fluid ejected onto the ejection target object to thereby form a pattern in the fluid, characterized in that the article manufacturing apparatus comprises: control unit configured to control ejection of the fluid from each of the plurality of nozzles by applying a drive signal to an ejection energy generation element included in the nozzle; obtaining unit configured to obtain an ejection result of the fluid ejected from the nozzle; and storage unit configured to store an adjustment table for adjustment of the drive signal for each of the plurality of nozzles, the adjustment table indicating a relationship between waveform information on the drive signal for each of the nozzles and an ejection volume and ejection speed of the fluid ejected from the nozzle, in which the control unit adjusts ejection from each of the nozzles based on the corresponding adjustment table and the corresponding ejection result obtained by the obtaining unit. 
     Further features of the present invention will become apparent from the following description of an exemplary embodiment to be given with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view schematically showing an entire configuration of an article manufacturing apparatus in an embodiment; 
         FIG. 2A  is a conceptual diagram showing a process of ejection of a droplet from a nozzle, and shows a state before a piezoelectric element in the nozzle is driven; 
         FIG. 2B  is a conceptual diagram showing the process of ejection of a droplet from the nozzle, and shows a state where a resin is pulled in inside the nozzle as a result of driving the piezoelectric element; 
         FIG. 2C  is a conceptual diagram showing the process of ejection of a droplet from the nozzle, and shows a state immediately after a droplet is ejected from the nozzle as a result of driving the piezoelectric element; 
         FIG. 3  is a diagram showing the waveform of a drive signal to be applied to a nozzle, and the surface position of a fluid inside the nozzle; 
         FIG. 4A  is a diagram showing a first parameter of the drive signal; 
         FIG. 4B  is a diagram showing a second parameter of the drive signal; 
         FIG. 5  is a diagram showing a first adjustment table for the drive signal; 
         FIG. 6  is a diagram showing the first adjustment table and a second adjustment table obtained by correcting the first adjustment table; and 
         FIG. 7  is a flowchart showing a process of adjusting the ejection volume from each nozzle. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present invention will be described below in detail with reference to the drawings.  FIG. 1  is a front view schematically showing an entire configuration of an imprint apparatus as an article manufacturing apparatus. 
     An imprint apparatus  101  mainly performs an imprint process as below. Firstly, an uncured resin (a fluid in a liquid state)  114  is ejected onto a surface (upper surface in the view) of a substrate  111 , which is an ejection target object. Then, a mold on which is formed a pattern having a concavo-convex shape is pressed against the uncured resin  114  ejected onto the surface of the substrate  111 . Then, after the resin  114  reaches a cured state, the mold is separated (released) from the resin. By the imprint process including the above steps, an article is obtained which has a three-dimensional pattern following the pattern on the mold. 
     Such an imprint process is capable of forming an article having an extremely fine pattern on the order of nanometers, and is preferably used in manufacturing of semiconductor devices and the like. Note that in the present embodiment, an imprint apparatus employing a photo-curing method, in which the resin  114  with a pattern formed therein is cured by being irradiated with light, is presented as an example. However, the present invention is also applicable to imprint apparatuses using other techniques, e.g., an imprint apparatus using a thermosetting method, in which the resin is cured by heat. 
     The imprint apparatus  101  includes a light application unit  102 , a mold holding mechanism  103  holding the mold  107 , a substrate stage  104 , an ejection unit  105 , obtaining unit  122 , a control unit  106 , a housing  123 , and so on. Also, in the apparatus shown, a Z axis is set in parallel to an optical axis  108   a  of an ultraviolet ray  108  to be applied to the resin  114  ejected onto the substrate  111 , and an X axis and a Y axis perpendicular to each other are set in a plane perpendicular to the Z axis. 
     The housing  123  includes a base surface plate  124  holding the later-described substrate stage  104 , a bridge surface plate  125  holding the mold holding mechanism  103  and the light application unit  102 , and columns  126  supporting the bridge surface plate  125 . The columns  126  are provided upright on the base surface plate  124 . 
     The substrate stage  104  has the function of a movement mechanism that holds the substrate  111  to which the resin  114  to be subjected to an imprint process is to be applied and moves the substrate  111  along the plane defined by the X axis and the Y axis (XY plane). By moving the substrate  111  along the XY plane by unit of this substrate stage  104 , the substrate  111  and the ejection unit  105  are positioned relative to each other in the XY plane and the resin  114  ejected onto the surface of the substrate  111  and the mold  107  are positioned relative to each other in the XY plane. 
     The substrate stage  104  has a substrate chuck  119  that holds the substrate  111  by vacuum suction, and a substrate stage housing  120  that holds the substrate chuck  119  and moves it in the XY plane with mechanical unit. Further, the substrate stage  104  is provided with a stage reference mark  121  to be utilized to determine the positions of the surface of the substrate chuck  119  and the mold  107 , which is located above the substrate chuck  119 , relative to each other in the XY plane. 
     The substrate stage housing  120  is provided with an actuator for moving the substrate chuck  119 . A linear motor that moves the substrate chuck  119  in the X axis direction and the Y axis direction, for example, can be employed as the actuator. Also, the substrate stage housing  120  may include a plurality of drive systems such as an X- and Y-axis coarse movement drive system and an X- and Y-axis fine movement drive system. Further, the substrate stage housing  120  may be provided with a drive system for correcting the position of the substrate chuck  119  in the Z axis direction, and a configuration having a function to correct the position of the substrate chuck  119  in a direction θ, a tilt function to correct the inclination of the substrate chuck  119 , and so on. 
     The substrate  111  is, for example, a monocrystalline silicon substrate or an SOI (Silicon On Insulator) substrate, onto a surface of which the curable resin  114  to be shaped by a pattern portion  107   a  formed on the above-mentioned mold  107  is ejected from the later-described ejection unit  105 . Note that an ultraviolet curable resin  114 , which cures by being irradiated with an ultraviolet ray, is used as the curable resin  114  in the present embodiment. 
     The light application unit  102  is held on the bridge surface plate  125  and, in an imprint process, applies light with a predetermined wavelength, e.g., the ultraviolet ray  108 , to the mold  107 . This light application unit  102  includes a light source  109  and an optical element  110  that corrects the direction and position of the ultraviolet ray  108  emitted from this light source  109  to an appropriate direction and position relative to the resin  114  ejected onto the substrate  111 . Note that the light application unit  102  is installed since a photo-curing method is employed in the present embodiment. In a case where a thermosetting method is employed, for example, a heat source unit that cures a thermosetting resin  114  may be installed in place of the light application unit  102 . 
     The mold  107  includes the pattern portion  107   a,  which, in an example, has a rectangular outer periphery and a three-dimensional shape for transferring a concavo-convex pattern such as a circuit pattern into the resin  114  ejected onto the substrate  111 . Meanwhile, the mold  107  is made of a material capable of transmitting the ultraviolet ray  108 , such as quartz. Further, the mold  107  may be shaped such that its surface to be irradiated with the ultraviolet ray  108  has a cavity  107   b  formed in a recessed shape in order to facilitate deformation of the mold  107 . This cavity  107   b  has a circular and planar shape, and its depth is set as appropriate according to the size and material of the mold  107 . 
     The mold holding mechanism  103  has a mold chuck  115  that holds the mold  107  by attracting it with vacuum suction force or electrostatic force, and a mold drive mechanism  116  that moves the mold chuck  115  in the Z axis direction. The mold drive mechanism  116  moves the mold chuck  115  holding the mold  107  in the Z axis direction so as to selectively perform pressing or separation (release) of the mold  107  against or from the resin  114  on the substrate  111 . Examples of actuators employable for this mold drive mechanism  116  include a linear motor, an air cylinder, and so on. Also, for accurate positioning of the mold  107 , the mold drive mechanism  116  may include a plurality of drive systems such as a coarse movement drive system and a fine movement drive system. Further, a configuration may be employed which has a function to correct not only the position in the Z axis direction but also the positions in the X axis direction and the Y axis direction or the position in the direction θ, which represents rotation about the Z axis, a tilt function to correct the inclination of the mold  107 , and the like. Note that the operation of pressing and separating the mold  107  against and from the resin  114  ejected onto the substrate  111  may be implemented by moving the mold chuck  115  in the Z axis direction, as described above, but may be implemented by moving the substrate stage  104  in the Z axis direction or by moving both the mold chuck  115  and the substrate stage  104  relative to each other. 
     An opening region  117  is formed through center portions of the mold chuck  115  and the mold drive mechanism  116  so that the ultraviolet ray  108  emitted from the light source  109  of the light application unit  102  can be applied to the substrate  111  via the optical element  110 . 
     Also, the configuration can be such that in the opening region  117 , which is formed in the above-mentioned mold holding mechanism  103 , an optically transmissive member  113  that forms a closed space  112  is installed and the pressure inside the space  112  is controlled by a pressure correction apparatus. With this configuration, in an example, the pressure correction apparatus raises the pressure inside the space  112  to above the pressure of the outside space in a case where the mold  107  is pressed against the resin  114  ejected onto the substrate  111 , for example. By raising the pressure inside the space  112 , the pattern portion  107   a  bends to arch toward the substrate  111  and comes into contact with the resin  114  from a center portion of the pattern portion  107   a . In this manner, it is possible to prevent entrapment of a gas (air) between the pattern portion  107   a  and the resin  114  and thus fill the resin  114  thoroughly in and on the concavities and convexities of the pattern portion  107   a.    
     The ejection unit  105  has a plurality of nozzles that eject the uncured resin  114  into the form of droplets and apply them onto the substrate  111 . In the present invention, each nozzle includes a portion forming a region in which an ink is present, and an ejection energy generation element that generates ejection energy for ejecting the ink in the region from an opening portion (ejection opening). The present embodiment employs a method in which a piezoelectric element, which converts electrical energy into mechanical energy, is used as the ejection energy generation element and its piezoelectric effect is utilized to eject the resin  114  from the nozzle. Specifically, the later-described control unit  106  generates a drive signal having a predetermined waveform, and the piezoelectric element is controlled to deform into a shape suitable for ejection by receiving the drive signal. The plurality of nozzles are controlled independently of each other by the control unit  106 . 
     The resin  114  to be ejected from the ejection unit  105  is a photo-curable resin  114  having such properties that it cures by receiving the ultraviolet ray  108 , and its material is selected as appropriate according to various conditions in a semiconductor device manufacturing process or the like. Also, the amount of the resin  114  to be ejected into the form of a droplet (hereinafter also referred to as droplet) from each ejection nozzle of the ejection unit  105  is determined as appropriate according to the desired thickness of the resin  114  to be formed on the substrate  111 , the density of the pattern to be formed, and so on. This ejection unit  105 , the mold drive mechanism  116 , and the control unit  106  constitute an ejection apparatus. 
     The obtaining unit  122  includes an alignment measurement instrument  127  and an observation measurement instrument  128  as representative measurement instruments. The alignment measurement instrument  127  measures misalignment between an alignment mark formed on the substrate  111  and an alignment mark formed on the mold  107  in the X axis direction and the Y axis direction. The observation measurement instrument  128  is an image capturing apparatus such as a CCD camera, for example, and obtains image information of the pattern formed in the resin  114  ejected onto the substrate  111 . 
     The control unit (control unit)  106  is capable of controlling the operations of constituent components of the imprint apparatus  101 , correction, and so on. In an example, the control unit  106  is a computer or the like including a CPU, a ROM, and a RAM (storage unit), and the CPU performs various arithmetic processes. The control unit  106  is connected to constituent components of the imprint apparatus  101  through lines and controls the constituent components in accordance with a program stored in the ROM or the like. In an example, the control unit  106  controls the operations of the mold holding mechanism  103 , the substrate stage  104 , and the ejection unit  105  based on measurement information from the obtaining unit  122 . Note that the control unit  106  may be configured integrally with other parts of the imprint apparatus  101  or may be configured as a separate part from the other parts of the imprint apparatus  101 . Also, a configuration including a plurality of computers, instead of a single computer, an ASIC, and so on may be employed. 
     The imprint apparatus  101  further includes a mold conveyance mechanism not shown that conveys the mold  107  from outside the apparatus to the mold holding mechanism  103 , and a substrate conveyance mechanism not shown that conveys the substrate  111  from outside the apparatus to the substrate stage  104 . The operations of the mold conveyance mechanism and the substrate conveyance mechanism are controlled by the control unit  106 . 
     Next, an imprint process by the imprint apparatus  101  will be described. The control unit  106  controls the substrate conveyance mechanism to place and fix the substrate  111  onto the substrate chuck  119  on the substrate stage  104  and then moves the substrate chuck  119  to an application position for the ejection unit  105 . Thereafter, the control unit  106  controls the ejection unit  105  and the substrate stage  104  so as to execute an application step of applying the resin  114  onto the substrate  111 . 
     In the application step, the control unit  106  applies drive signals with waveforms generated according to the ejection tendencies of the plurality of nozzles provided in the ejection unit  105 , to the piezoelectric elements provided in the nozzles, respectively. As a result, a droplet of the resin  114  is ejected in the same ejected state from each nozzle. Note that the ejection tendency of a nozzle refers to the degree of change in ejection volume and ejection speed in response to a change in parameters being waveform information that determines the waveform of the drive signal to be applied to the ejection energy generation element provided in the nozzle. 
     Also, during the ejection operation, the control unit  106  moves the substrate chuck  119  along the XY plane in a direction crossing (usually the direction perpendicular to) the array direction of the nozzles. As a result, the resin  114  is applied onto a pattern formation region being a predetermined processing target region on the substrate  111 . 
     Thereafter, the control unit  106  moves the substrate chuck  119  such that the pattern formation region on the substrate  111  with the resin  114  applied thereto is located directly below the pattern portion  107   a  formed on the mold  107 . The control unit  106  then performs a pressing step of pressing the mold  107  against the resin  114  on the substrate  111  by driving the mold drive mechanism  116 . By this pressing step, the resin  114  comes into tight contact with the concavities and convexities of the pattern portion  107   a.    
     In this state, the control unit  106  performs a curing step by driving the light application unit  102 . The ultraviolet ray  108  emitted from the light application unit  102  is applied to the upper surface of the mold  107  via the optical element  110  and the optically transmissive member  113 . The ultraviolet ray applied to the mold  107  travels through the mold  107 , which is optically transmissive, and is applied to the resin  114 . As a result, the resin  114  cures. 
     After the resin  114  cures, the control unit  106  performs a separation step of raising the mold chuck and separating the mold  107  from the resin  114  by driving the mold drive mechanism  116 . As a result, on the surface of the pattern formation region on the substrate  111 , a pattern of the resin  114  is formed which has a three-dimensional shape following the concavities and convexities of the pattern portion  107   a.    
     By performing a series of imprint operations as above a plurality of times while changing the pattern formation region by driving the substrate stage  104 , a plurality of the patterns of the resin  114  can be formed on a single substrate  111 . 
     Next, with reference to  FIGS. 2 and 3 , a process of ejection of a resin droplet  203  from a nozzle  201  will be described along with a drive signal  220  to be applied to the piezoelectric element (ejection energy generation element) included in the nozzle and the liquid surface position of the liquid resin  114  in the nozzle. 
       FIGS. 2A, 2B, and 2C  show a XZ-plane cross section of one nozzle  201  among the plurality of nozzles provided in the ejection unit  105 .  FIG. 2A  shows a state before the piezoelectric element of the nozzle  201  is driven,  FIG. 2B  shows a state where the resin  114  is pulled in inside the nozzle  201  as a result of driving the piezoelectric element, and  FIG. 2C  shows a state immediately after a droplet  203  is ejected from the nozzle  201  as a result of driving the piezoelectric element. Note that the X, Y, and Z directions in the diagrams correspond to those in  FIG. 1 . Also, the interface between the resin  114  in the nozzle  201  and the ambient air is shown as a liquid surface  202 , and the ejected resin  114  is shown as the droplet  203 . 
     Part (a) of  FIG. 3  shows the waveform of the drive signal  220  to be applied to a piezoelectric element provided in the ejection unit  105 . Here, the horizontal axis represents time while the vertical axis represents voltage. The waveform of the drive signal  220  in the present embodiment is trapezoidal, which is the most basic waveform. The drive signal  220  with this trapezoidal waveform is a voltage signal to be applied to the piezoelectric element to eject the resin  114  in the nozzle  201  into the form of the droplet  203 , and includes the following five components. Specifically, the drive signal  220  includes five components of a pull component  204 , a first hold component  205 , a push component  206 , and a second hold component  207  and a return component  207  for returning the voltage value to the initial value. 
     These components of the drive signal  220  correspond to five time sections divided from a time period from T 0  to T 5 . The voltage waveform in the time section from T 0  to T 1  represents the pull component  204 , the voltage waveform in the time section from T 1  to T 2  represents the first hold component  205 , and the voltage waveform in the time section from T 2  to T 3  represents the push component  206 . Further, the voltage waveform in the time section from T 3  to T 4  represents the second hold component  207 , and the voltage waveform in the time section from T 4  to T 5  represents the return component  208 . Note that the time section from T 5  to T 6  represents the time taken by the liquid surface  202  of the resin  114  in the nozzle  201  to return to the position in the initial state shown in  FIG. 2A  (a reference position  209  in part (b) of  FIG. 3 ) after the droplet  203  is ejected from the nozzle  201 . 
     Part (b) of  FIG. 3  is a diagram showing the liquid surface position in the nozzle  201 , and shows the position of the liquid surface  202  in the Z direction. In the initial state before the piezoelectric element included in the nozzle  201  is driven, the liquid surface  202  is at the reference position  209 . Then, as the piezoelectric element is driven, the liquid surface  202  is firstly pulled in in the +Z direction to a pulled position  210  and then pushed in the −Z direction to a pushed position  211 . The droplet  203  is formed before this pushed position  211  is reached. Thus, the actual position of the liquid surface is on the −Z direction side relative to the position shown in part (b) of  FIG. 3 . However, for a simple illustration, part (b) of  FIG. 3  does not show the position at which the droplet  203  is formed and shows a representative position of the liquid surface  202 . Technically, the liquid surface  202  moves after a delay from the time at which voltage is applied to the piezoelectric element. Note, however, that the present embodiment will be described while ignoring this delay component. 
     In the drive signal with the trapezoidal waveform, the voltage of the pull component  204  is applied to the piezoelectric element to thereby cause the piezoelectric element to pull in the liquid surface  202  at the reference position  209  in the +Z direction (see  FIG. 2B ). This is done in order to perform ejection by efficiently utilizing force attempting to bring the pulled liquid surface  202  back to the original position. After the voltage of the pull component  204  is applied, the voltage of the first hold component  205  is held constant. Here, the liquid surface  202  starts moving in the −Z direction after reaching the pulled position  210 , which is the farthest position to which the liquid surface  202  is pulled in in the +Z direction. Then, the voltage of the push component  206  is applied, so that the piezoelectric element pushes the liquid surface  202  all the way in the −Z direction. By the pushing force from the piezoelectric element, the resin  114  is pushed outward from the nozzle  201  and forms a liquid column. Then, the resin  114  gets separated from the liquid column by its own surface tension into the droplet  203 , and lands on a region on the substrate  111 . 
     hereafter, the voltage of the second hold component  207  is applied to the piezoelectric element. While this voltage is applied, the movement direction of the liquid surface  202  switches from the −Z direction to the +Z direction. Subsequently, the voltage of the return component  208  is applied to the piezoelectric element. This voltage serves to bring the liquid surface position back to the initial position in order to maintain continuity for repetition of the waveform, but its impact on the liquid surface  202  is small since the amount of change in voltage is small as compared to those by the other components. Thereafter, the liquid surface  202  restores itself toward its original state while repetitively vibrating in the Z direction, and returns to the reference position  209  at T 6 . After the droplet  203  is ejected through a series of processes as described above, similar processes are repeated again to form droplets  203  successively. 
     Note that the time taken by the liquid surface position to be restored to the reference position after the application of a single drive signal (the time period from T 5  to T 6 ) is determined by a composite component containing the short-lasting component shown (return component  208 ) and a long-lasting component not shown. For this reason, if the next drive signal is inputted in the time period from T 5  to T 6 , a phenomenon called crosstalk occurs in which the liquid surface  202  is brought into the next ejection operation before returning to the reference position  209 . In a case where the interval at which the droplets  203  are ejected is long, the occurrence of the crosstalk does not have an impact on the liquid surface return time or may have an impact but the level of the impact is negligibly low. However, in a case where the ejection interval is short, ejection has to be performed in a state where the change in the liquid surface position by the operation of ejecting the last droplet  203  still has an impact. Thus, the impact from the ejection of the last droplet changes the ejection speed and the ejection volume of the next droplet  203 . The change in the ejection speed and the ejection volume appears as the difference to be handled in the later-described drive signal waveform adjustment. 
     Next, an adjustment table used in the present embodiment will be described by using  FIG. 4 . An adjustment table  313  is obtained by recording and grouping measured values of the ejection volume and the ejection speed of the resin  114  ejected from each nozzle after at least one of the time component and the voltage component forming the waveform of the corresponding drive signal  220  is changed. This adjustment table  313  is a first table serving as a reference and generated at an initial stage before the shipment of the ejection unit. In this section, an adjustment table to be used for driving one nozzle  201  among the plurality of nozzles provided in the ejection unit  105  will be described as an example. 
     In this example, the above-mentioned drive signal  220  with a trapezoidal waveform is used, and two parameters to be used for the adjustment are selected. One of the parameters is a voltage component being the pull component  204  for pulling in the resin  114  in the nozzle in the +Z direction as shown in part (b) of  FIG. 3 , and this will be referred to as a first parameter  301 . The other one of the parameters is a voltage component being the push component  206  for pushing the resin  114  in the nozzle  201  in the −Z direction as shown in part (b) of  FIG. 3 , and this will be referred to as a second parameter  302 . 
       FIG. 4A  is a diagram showing states where the first parameter  301  of the drive signal  220  to be used to drive the nozzle  201  (drive the piezoelectric element) is changed, and the horizontal axis represents time while the vertical axis represents voltage. The solid line in the diagram indicates the voltage waveform of a reference drive signal for the voltage to be adjusted. Assume that the value of the first parameter  301  of this reference drive signal is A. Also, a long-dashed line in the diagram indicates the voltage waveform of a drive signal obtained by making the value of the first parameter larger than A by a (A+a), and a short-dashed line indicates the voltage waveform of a drive signal obtained by making the value of the first parameter smaller than A by a (A−a). 
       FIG. 4B  is a diagram showing states where the second parameter  302  of the drive signal  220  to be used to drive the nozzle  201  is changed, and the horizontal axis represents time while the vertical axis represents voltage. The solid line in the diagram indicates the voltage waveform of the reference drive signal, and the value of its second parameter  302  is set at B. A long-dashed line in the diagram indicates the waveform of a drive signal obtained by making the value of the second parameter larger than B by b (B+b), and a short-dashed line indicates the waveform of a drive signal obtained by making the value of the second parameter smaller than B by b (B−b). 
       FIG. 5  is a diagram showing the ejection speeds and the ejection volumes of droplets  203  ejected from the nozzle  201  after the first parameter  301  and the second parameter  302  of the drive signal  220  are changed. In the diagram, the horizontal axis represents the ejection speed while the vertical axis represents the ejection volume. 
     The nozzle  201  is required to have such ejection performance as to eject a droplet  203  with a target value  303  including a target ejection speed S g  and a target ejection volume V g . For this target value  303 , a predetermined range of errors is allowed in each the ejection volume and the ejection speed in view of product specifications. These allowable error ranges are shown as a target range  315  in the diagram. Here, in a case where the allowable range of the ejection speed is ±s, for example, the product specifications are met if the ejection speed is in the range of S g −s to S g +s. Also, in a case where the allowable range of the ejection volume is V±v, the specifications are met if the ejection volume is in the range of V g −v to V g +v. 
     Thus, the waveform of the drive signal  220  to be applied to the piezoelectric element of the nozzle  201  is adjusted such that the ejection volume and the ejection speed fall within the respective allowable error ranges mentioned above. In the present embodiment, a measured value  304  of the ejection volume and the ejection speed of the nozzle  201  falls within the target range  315  in a case where a drive signal  220  having a waveform with the first parameter  301  set at A and the second parameter  302  set at B is applied to the piezoelectric element of the nozzle. Note that the same applies to the nozzles other than the nozzle  201 . The measured values  304  of the ejection volumes and the ejection speeds of the plurality of nozzles provided in the ejection unit  105  are all adjusted to fall within the target range  315 . 
     The dots shown in  FIG. 5  represent the measured values of the ejection volume and the ejection speed of droplets  203  ejected from the nozzle  201  after the first parameter  301  and the second parameter  302  are changed. In the present embodiment, for the first parameter, the reference value is A and the adjustment range is ±a, and three values of A, A−a, and A+a are used as the first parameter for measurement. Likewise, for the second parameter, the reference value is B and the adjustment range is ±b, and three values of B, B−b, and B+b are used for measurement. Thus, in measurement of the ejection volume and the ejection speed of the nozzle  201 , nine types of drive signals  220  in total are generated by combining the three first parameters and the three second parameters, and each drive signal is applied to the nozzle  201  to measure the resultant ejection speed and ejection volume. 
     A measured value  305  shown in  FIG. 5  is the measured value in a case where the first parameter is set at A−a and the second parameter is set at B. A measured value  306  is the measured value in a case where the first parameter is set at A+a and the second parameter is set at B. A measured value  307  is the measured value in a case where the first parameter is set at A and the second parameter is set at B−b. A measured value  308  is the measured value in a case where the first parameter is set at A−a and the second parameter is set at B−b. A measured value  309  is the measured value in a case where the first parameter is set at A+a and the second parameter is set at B−b. A measured value  310  is the measured value in a case where the first parameter is set at A and the second parameter is set at B+b. A measured value  311  is the measured value in a case where the first parameter is set at A−a and the second parameter is set at B+b. A measured value  312  is the measured value in a case where the first parameter is set at A+a and the second parameter is set at B+b. 
     Decreasing the first parameter  301  and the second parameter  302  decreases the ejection speed and the ejection volume of the droplet  203  from the nozzle. Increasing the first parameter  301  and the second parameter  302  increases the ejection speed and ejection volume of the droplet  203  from the nozzle. By providing a graph showing the ejection speeds and ejection volumes in  FIG. 5  with an axis  601  of the first parameter  301  and an axis  602  of the second parameter  302 , it is possible to visualize how the ejection speed and ejection volume changes in response to a change in the later-described adjustment table for adjusting the waveform of the drive signal. The amount of change in each of ejection speed and ejection volume in response to a change in a parameter varies by how much the parameter is changed. Thus, by changing the combination of the value of the first parameter and the value of the second parameter, each of the ejection speed and the ejection volume can be changed by a desired amount. The adjustment table  313  is a group of amounts of change in the parameters and measured values of the ejection speed and the ejection volume corresponding to these with the waveform of the drive signal  220  with the measure value  304  as an origin. 
     The tendency of this adjustment table  313  varies by the selected parameters. Thus, in the selection of parameters, it is important to figure out in advance how the ejection speed and ejection volume change after a change is made and to select parameters with which it is easy to make an adjustment. Note that in the selection of the parameters to be used for the waveform adjustment, it is preferable to select such parameters that the ejection speed and the ejection volume change linearly in response to changes in the values of the parameters. This is because the adjustment uses an approximation of measured values, and thus using parameters that cause a linear change can improve the prediction accuracy. 
     Note that, in the present embodiment, amounts of change in the parameters and measured values corresponding to them are recorded individually to generate the adjustment table  313 . However, the amount of change in each of ejection speed and ejection volume for the amount of change in each parameter can be defined as sensitivity, and this sensitivity can be used as an adjustment parameter. Also, various parameters may be prepared to enable various changes in ejection speed or ejection volume for the amount of change in each parameter. In the present embodiment, an example using two parameters is shown for a simple description. Increasing the types of parameters improves the ease of adjustment of the drive signal  220 . Also, in a case where the ejection speed and the ejection volume can be adjusted with only one parameter, it is preferable not to use a plurality of parameters but to use only one parameter and change it since this can minimize the change in shape of the drive signal  220 . 
     In general, the adjustment table  313  is generated before the shipment of the ejection unit  105 . In the generation of the adjustment table  313 , the ejection speed and the ejection volume are measured using a dedicated adjustment device provided as a separate part from the body part of the imprint apparatus  101 . Note that the adjustment table generation step can be executed as long as the ejection speed and the ejection volume can be measured. Thus, the adjustment table may be generated after the ejection unit  105  is mounted in the imprint apparatus  101  by measuring the ejection speed and the ejection volume with the obtaining unit  122 . This adjustment table is generated for each of the plurality of nozzles provided in the ejection unit  105  and stored in the RAM of the control unit  106 . 
     Next, a method of adjusting the waveform of the drive signal  220  by using the adjustment table  313  will be described with reference to  FIG. 5 . The adjustment table  313  is a record of measured values of the ejection speed and the ejection volume after the adjustment parameters are changed. In this section, assume that the waveform of the drive signal  220  has been adjusted in the last adjustment such that the measured value is  304 . 
     Let a measured ejection speed S m  and a measured ejection volume V m  be the ejection speed and the ejection volume, respectively, in an ejection result  404  obtained by the obtaining unit  122  in obtaining step S 501  to be described later shown in a flowchart of  FIG. 7 . Then, the ejection result  404  can be expressed as (S m , V m ) in a coordinate system shown in  FIG. 6 . Also, let S 0  and V 0  be the ejection speed and the ejection volume in the measure value  304 , respectively. Then, the ejection result  304  can be expressed as (S 0 , V 0 ) in the same coordinate system. Here, in a case where the ejection results are measured under the same condition, the measured value  304  and the ejection result  404  are supposed to match. However, even in a case where the same parameters are set, the imprint apparatus  101  may have a difference between the measured values (ejection speed and ejection volume) depending on conditions such as the distribution of heat around the ejection unit  105  and the inclination of the ejection unit  105  and the substrate  111  relative to each other. For example, even in the case where the same parameters are set, there is a possibility that the measured value  304  is offset to the measured value  404 , as shown in  FIG. 6 . In a case where such a difference between the ejection results is defined as an ejection speed difference S a  and an ejection volume difference V a , these differences S a  and V a  can be expressed as S a =S m −S 0  and V a =V m −V 0 , respectively. 
     The above ejection speed difference S a  and ejection volume difference V a  are used as a shift amount (correction amount)  402  for correcting the adjustment table  313 , and the correction amount  402  is used to generate a corrected adjustment table  403 . Specifically, the ejection speed difference S a  and the ejection volume difference V a  are added to the ejection speed and the ejection volume, respectively, in each of the above-mentioned nine measured values, or the measured values  304 ,  305 ,  306 ,  307 ,  308 ,  309 ,  310 ,  311 , and  312 . As a result, the measured value  304  is corrected to the measured value  404 , the measured value  305  is corrected to a measured value  405 , the measured value  306  is corrected to a measured value  406 , the measured value  307  is corrected to a measured value  407 , and the measured value  308  is corrected to a measured value  408 . Likewise, the measured value  309  is corrected to a measured value  409 , the measured value  310  is corrected to a measured value  410 , the measured value  311  is corrected to a measured value  411 , and the measured value  312  is corrected to a measured value  412 . 
     As described above, in the present embodiment, an error that occurs due to the imprint apparatus  101  similarly affects an ejection result (measured value) obtained after the drive signal  220  is changed. For this reason, the adjustment table  313 , which is generated before the shipment, is corrected to generate a new corrected table  403 . Note that this corrected table  403 , like the table  313  before the correction, is generated for each of the plurality of nozzles provided in the ejection unit  105  and then stored in the RAM of the control unit  106 . 
     As shown in  FIG. 6 , the positional relationship between the corrected adjustment table  403  and the target value  303  in the coordinate system is such that the target value  303  is surrounded by the ejection result  404  and the corrected measured values  406 ,  410 , and  412 . This indicates that a drive signal  220  with which the ejection result  404  falls inside the target range  315  can be set by changing the first parameter  301  within a section from A to A+a and changing the second parameter  302  within a section from B to B+b. 
     Among the measurement results, the corrected measured value  412  is the closest to the target value  303 . Coordinates (SC 0 , VC 0 ) are set as the origin for the adjustment, where SC 0  and VC 0  are the ejection speed and the ejection volume in the corrected measured value  412 , respectively. The reason for selecting the closest measurement result is to reduce the later-described correction amount as much as possible. Reducing the correction amount to a small value can reduce the correction errors. 
     Thereafter, since the first parameter is to be changed within the section from A to A+a and the second parameter is to be changed within the section from B+b to B, the corrected measured value  410  and the corrected measured value  406  are used for the adjustment of the waveform of the drive signal. In a case of expressing the ejection speed and the ejection volume in each of the measured value  410  and the measured value  406  as coordinates, the corrected measured value  410  and the corrected measured value  406  are expressed as (SC 1 , VC 1 ) and (SC 2 , VC 2 ), respectively. 
     The amount of adjustment from the corrected measured value  412  to the target value  303  is S g −SC 0  for the ejection speed and V g −VC 0  for the ejection volume, and this amount of adjustment may be adjusted from the corrected measured value  412 . 
     The amount of change in the first parameter  301  from the corrected measured value  412  to the corrected measured value  410  is −a. Thus, the amount of change in the ejection speed is (SC 1 −SC 0 )/−a, and the amount of change in the ejection volume is (VC 1 −Vc0)/−a. Further, the amount of change in the second parameter  302  from the corrected measured value  412  to the corrected measured value  406  is −b. Thus, the amount of change in the ejection speed is (SC 2 −SC 0 )/−b, and the amount of change in the ejection volume is (VC 2 −VC 0 )/−b. 
     Let a1 be the amount of change in the first parameter  301  from the corrected measured value  412 , and let b1 be the amount of change in the second parameter  302  from the corrected measured value  412 . Then, the following holds. 
     
       
         
           
             
               
                 
                   
                     
                       
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     the above are obtained. 
     Since the first parameter  301  of the drive signal  220  with the corrected measured value  412  is A+a, A+a+a1 is the result of the adjustment of the first parameter  301 . Likewise, since the second parameter  302  of the drive signal  220  with the corrected measured value  412  is B+b, B+b+b1 is the result of the adjustment of the second parameter  302 . The waveform of the drive signal  220  is updated based on these adjustment results. The present embodiment has been described for the one nozzle  201  as an example. In practice, the adjustment table  313  generated for each nozzle is used to adjust the waveform of the corresponding drive signal  220  mentioned above. Also, in the present embodiment, the amount of change in the first parameter  301  is ±a. In addition to ±a as an amount of change, another amount of change (e.g., ±2a or the like) may be set to increase the number of measured values. The larger the number of measured values, the higher the accuracy of the above-mentioned adjustment method. Thus, it is preferable to increase the number of measured values. For the amount of change in the second parameter  301  too, it is preferable to increase the number of measured values, as with the first parameter  301 . 
     Note that the above-described method of adjusting the parameters of the drive signal  220  is merely an example. The ejection speed and the ejection volume can be adjusted by another drive signal parameter adjustment method. Specifically, the present invention can be carried out by using another adjustment method of adjusting the ejection result  404  to the target value  303 . Also, even in a case where the ejection result  404  is present in the target range  315 , the waveform of the drive signal may still be adjusted to bring the ejection result  404  closer to the target value  303 . 
     Next, an ejection adjustment method executed in the present embodiment will be described.  FIG. 7  is a flowchart showing steps in the ejection adjustment in the present embodiment, and the description will be given through four separate steps S 501  to S 504 . Note that, before entering these steps, the waveform of the drive signal to be applied to the piezoelectric element of each nozzle  201  are adjusted, and the adjustment table  313  is obtained for each nozzle and stored in the RAM of the control unit  106 . 
     In S 501 , the ejection results  404  of all nozzles provided in the ejection unit  105  are obtained by using the obtaining unit  122 . Specifically, the resin  114  is ejected onto the substrate  111  from each of the plurality of nozzles provided in the ejection unit  105 , and the position and shape of the resin  114  ejected onto the substrate  111  are observed using the observation measurement instrument  128  to thereby obtain each ejection result  404  of the resin  114 . In S 502 , the amount of adjustment of the ejection waveform is calculated based on this ejection result  404 , and the ejection is adjusted. The CPU included in the control unit or the like is used to perform the ejection of the resin  114 , the obtaining of the ejection result with the observation measurement instrument  128 , and so on in S 501 . 
     Note that the obtaining unit for obtaining the ejection result  404  of the resin  114  is not limited to the one that observes the position and shape of the resin  114  ejected onto the substrate  111 . In an example, a measurement device that directly measures the ejection volume and the ejection speed of a droplet  203  can be installed as obtaining unit in the imprint apparatus  101 , and the result of that measurement can be used as an ejection result. 
     Also, in the present embodiment, an example in which the obtaining unit  122  is provided in the body of the imprint apparatus  101  has been presented. However, a measurement device provided outside the body of the apparatus can be used to measure the resin  114  applied onto the substrate  111  and obtain its ejection result. In an example, after the resin  114  applied from each nozzle onto the substrate  111  is cured, the outside measurement device may be used to measure the thickness of the resin  114  or to measure the applied position and shape of the resin  114 . 
     Then, in S 502 , the waveform of each drive signal is adjusted based on the corresponding adjustment table  313  pre-stored in the RAM of the control unit  106  and the corresponding ejection result  404  obtained in S 501 . This adjustment is performed as follows. 
     First, the amount of offset between the applied position of the resin  114  ejected onto the substrate  111  in S 501  and a target applied position is calculated, and the amount of adjustment in the ejection speed is calculated based on the amount of the offset. Also, the surface area of the applied resin  114  is read from the shape of that resin  114 , the amount of adjustment in the ejection volume is calculated from the difference between the read surface area and a target surface area. 
     The first parameter  301  and the second parameter  302  of each drive signal  220  are adjusted by using the amount of adjustment in the ejection speed and the amount of adjustment in the ejection volume obtained as described above from the corresponding ejection result  404  and the corresponding adjustment table  313  stored in the RAM of the control unit  106 . The adjustment method is as described above, and description thereof is omitted here. 
     In S 503 , the adjusted drive signal  220  is stored in the RAM of the control unit  106 . Specifically, waveform information on the drive signal  220  recorded in the control unit  106  is updated to waveform information on the drive signal  220  obtained in S 502 . This change is made for all nozzles mounted in the ejection unit  105 . Note that the waveform information on the drive signal  220  before the update is saved in the RAM of the control unit  106  as a record. 
     In S 504 , each ejection adjustment result is checked. As for the content to be checked, the ejection result  404  of the resin  114  ejected onto the substrate  111  from the nozzle based on the updated signal  220  is obtained, and whether the ejection result  404  is within the target range  315  is checked. The adjustment process is terminated for those nozzles  201  whose ejection results  404  are within the target range  315 . For those nozzles  201  whose ejection results  404  are not within the target range  315 , the ejection adjustment process is performed again in S 501  to S 503  to perform a re-adjustment. Then, the ejection adjustment process is completed if the waveform information on the drive signals  220  for all nozzles is updated. 
     As described above, in the present embodiment, each nozzle of the ejection unit  105  is provided with an adjustment table (first adjustment table)  313  for adjusting the waveform of its drive signal. Then, in a case where the ejection volume and the ejection speed of any nozzle have errors, the ejection volume and the ejection speed are corrected by determining the amount of adjustment of the drive signal waveform based on the amounts of the errors between the ejection volume and the ejection speed of the nozzle and the adjustment table  313  dedicated for the nozzle. In this manner, all nozzles provided in the ejection unit  105  can undergo accurate correction based on their respective ejection tendencies. Hence, a droplet can be ejected appropriately from each nozzle. 
     Also, according to the present embodiment, it is possible to handle not only ejection errors that occur due to a structural variation of the ejection unit but also ejection errors that occur after the mounting of the shipped ejection unit  105  into an imprint apparatus or the like. Examples of the ejection errors that occur with the shipped ejection unit  105  include ejection errors due to a difference between apparatuses (e.g., imprint apparatuses) in which the ejection unit is designed to be mounted, inclination of the ejection unit  105  and the substrate  111  relative to each other, and a difference in distribution of heat around the ejection unit. In a case where such an ejection error occurs, a new adjustment table (second adjustment table) is generated for each nozzle by correcting its first adjustment table, which serves as a reference, as mentioned above, and the ejection error of each nozzle is adjusted based on its second adjustment table. In this manner, it is possible to accurately maintain the ejection accuracy of each nozzle in the ejection unit  105 . 
     Other Embodiments 
     The present invention is not limited to the above embodiment, but various modifications and changes can be made without departing from the gist of the present invention. 
     For instance, the waveform of the drive signal  220  shown in the present embodiment is a mere example. Even with a waveform different from this waveform, an adjustment table can still be generated as long as the ejection volume and the ejection speed after a change in the parameters are figured out. Thus, the present invention can be implemented by providing a table other than the above-described adjustment table for each nozzle. 
     Also, in the above embodiment, an example has been presented in which two parameters (first parameter and second parameter) are used to determine the waveform of the drive signal to be applied to the ejection energy generation element. However, the number of parameters that determine the waveform of the drive signal may be one or three or more, and an adjustment table may be generated for each nozzle based on such a parameter(s) used. In this manner, it is possible to accurately adjust the ejection speed and the ejection volume of a droplet to be ejected from each nozzle based on a plurality of adjustment parameters. 
     Further, the timing of application of the drive signal to the piezoelectric element (ejection energy generation element) can be included as a parameter that determines the waveform of the drive signal. In this way, it is also possible to change the timing of ejection of a droplet from each nozzle. In the imprint apparatus  101 , the resin  114  (droplets  203 ) ejected from the ejection unit  105  toward the substrate  111  on the substrate stage  104  moving relative to the ejection unit  105  to apply the resin onto the substrate  111 . For this reason, by changing the timing of ejection of a droplet from each nozzle with a parameter, it is possible to change the applied position in the movement direction of the substrate stage  104 . In this way, it is possible to change the ejection speed of the droplet to be ejected from each nozzle without changing its ejection volume. A time T by which to change the ejection timing can be calculated by T=X/Ss, where X is the amount of adjustment in the movement direction of the substrate stage  104 , and Ss is the movement speed of the substrate stage  104 . 
     The present invention can be implemented with a process involving: supplying a program that implements one or more of the functions in the above embodiments to a system or an apparatus through a network or a storage medium; and causing one or more processors in a computer in the system or the apparatus to read out and execute the program. Also, the present invention can be implemented with a circuit that implements one or more of the functions (e.g., ASIC). 
     While the present invention has been described with reference to embodiments, it is needless to say that the present invention is not limited to the above embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.