Liquid ejection device, imprint device and control method

Abstract

To improve the efficiency of removal of foreign matter adhered to an ejection port.SOLUTION: A liquid ejection device is provided, comprising ejection means having an ejection surface with an ejection port opening through which liquid is ejected, a vibration element installed in the ejection port, and a holding member arranged opposite the ejection surface and capable of holding the liquid between the ejection surface and the holding member. The liquid ejection device further comprises detection means detecting vibration characteristics of the vibration element, and control means driving the vibration element at a drive cycle which is based on the detection result of the detection means while the liquid is held between the ejection surface and the holding member when cleaning the ejection port.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a liquid ejection technique. [Background technology]

[0002] In a liquid ejection device that ejects liquid, recovery processes such as clearing clogging of the ejection ports and removing foreign matter adhering to the periphery of the ejection ports are required. Patent Document 1 discloses a technology for cleaning the ejection ports by driving the vibration element of the ejection head while the liquid is in contact with the ejection surface. Driving the vibration element causes the liquid to flow inside and around the ejection ports, and foreign matter such as residue adhering to and around the ejection ports can be removed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-104094 A Summary of the Invention [Problem to be solved by the invention]

[0004] The technique of Patent Document 1 has room for improvement in terms of increasing the efficiency of removing foreign matter firmly attached to the ejection ports.

[0005] The present invention provides a technique for improving the efficiency of removing foreign matter adhering to a discharge port. [Means for solving the problem]

[0006] According to the present invention, A discharge means having a discharge surface with a discharge port for discharging a liquid; A vibration element provided at the ejection port; a holding member disposed opposite to the ejection surface and capable of holding liquid between the ejection surface and the holding member; A liquid ejection device comprising: A detection means for detecting a vibration characteristic of the vibration element; a control means for driving the vibration element at a drive cycle based on a detection result of the detection means in a state where liquid is held between the ejection surface and the holding member when the ejection port is cleaned, A liquid ejection device is provided. Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique for improving the efficiency of removing foreign matter adhering to a discharge port. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an imprint apparatus. [Diagram 2] FIG. 2 is a diagram showing the configuration of a liquid ejection unit and a recovery unit. [Diagram 3] FIG. [Figure 4] 4 is a flowchart showing an example of control by a control unit. [Diagram 5] 4 is a flowchart showing an example of control by a control unit. [Figure 6] 13A and 13B are diagrams showing examples of back electromotive force signal waveforms, and 13C is a diagram showing an example of an inspection signal. [Figure 7] FIG. 13 is a schematic diagram showing a state in which a cleaning liquid is filled between the ejection surface and the cap. [Figure 8] FIG. 4A is a diagram showing an example of a method for determining a natural period, and FIG. 4B is a diagram showing an example of a method for setting a drive period. [Figure 9] FIG. 4 is a diagram showing an example of a drive signal. [Figure 10] 1A is a diagram showing an example of another method for setting the drive period, and FIG. 1B is a diagram showing an example of a drive signal. [Figure 11] FIG. 4 is an explanatory diagram of a configuration for circulating a cleaning liquid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] First Embodiment <Imprint device overview> FIG. 1 is a schematic diagram showing the configuration of an imprinting apparatus 101 according to an embodiment of the present invention. In the figure, an arrow Z indicates the up-down direction, and arrows X and Y indicate horizontal directions perpendicular to each other. The imprinting apparatus 101 is used in the manufacture of various devices such as semiconductor devices. The imprinting apparatus 101 includes a liquid ejection apparatus 130. The liquid ejection apparatus 130 includes a liquid ejection section 10 and a recovery section 80. The liquid ejection section 10 ejects a liquid (here, resist) 114 onto an ejection target (substrate 111 in this embodiment). The liquid 114 is, for example, a photocurable resin that has a property of being cured by receiving ultraviolet (UV) light. The liquid 114 is appropriately selected according to various conditions such as a semiconductor device manufacturing process. In addition to photocurable liquid, for example, a thermosetting resist may be used, and the imprinting apparatus may be an apparatus that performs an imprinting process by curing the resist with heat. The liquid 114 may be called an ejection material or an imprinting material. The recovery section 80 is used in a recovery process for recovering the ejection performance of the liquid ejection section 10. In the case of this embodiment, the recovery process includes a cleaning process for cleaning the ejection ports of the liquid ejection unit 10.

[0011] The imprint apparatus 101 also includes a light irradiation unit 102 , a mold holding mechanism 103 , a substrate stage 104 , a control unit 106 , a measurement unit 122 , and a housing 123 .

[0012] The light irradiation unit 102 has a light source 109 and an optical element 110 for correcting ultraviolet light 108 irradiated from the light source 109. The light source 109 is, for example, a halogen lamp that generates i-rays or g-rays. The ultraviolet light 108 is irradiated onto the liquid 114 via a mold (shape) 107. The wavelength of the ultraviolet light 108 is a wavelength that corresponds to the liquid 114 to be cured. In the case of an imprint apparatus that uses a thermosetting resist as the resist, a heat source unit for curing the thermosetting resist is installed instead of the light irradiation unit 102.

[0013] The mold holding mechanism 103 has a mold chuck 115 and a mold driving mechanism 116. The mold 107 held by the mold holding mechanism 103 has a rectangular outer periphery, and has a pattern portion 107a on the surface facing the substrate 111, on which a three-dimensional concave-convex pattern such as a circuit pattern to be transferred is formed. In this embodiment, the mold 107 is made of a material that allows ultraviolet light 108 to pass through, such as quartz. The mold chuck 115 holds the mold 107 by vacuum suction or electrostatic force.

[0014] The mold driving mechanism 116 holds and moves the mold chuck 115 to move the mold 107. The mold driving mechanism 116 can move the mold 107 downward in the Z direction to press the mold 107 against the liquid 114. The mold driving mechanism 116 can also move the mold 107 upward in the Z direction to separate the mold 107 from the liquid 114. Examples of actuators that can be used for the mold driving mechanism 116 include a linear motor or an air cylinder.

[0015] Mold chuck 115 and mold driving mechanism 116 have an opening region 117 in the center. Furthermore, mold 107 has a concave cavity 107b on the surface irradiated with ultraviolet light 108. A light transmitting member 113 is installed in opening region 117 of mold driving mechanism 116, and a sealed space 112 surrounded by light transmitting member 113, cavity 107b, and opening region 117 is formed.

[0016] The pressure in space 112 is controlled by a pressure compensation device (not shown). The pressure compensation device sets the pressure in space 112 higher than the outside, causing pattern portion 107a to bend in a convex shape toward substrate 111. This causes the center of pattern portion 107a to come into contact with liquid 114. Therefore, when mold 107 is pressed against liquid 114, gas (air) is prevented from being trapped between pattern portion 107a and liquid 114, and liquid 114 can be filled into every corner of the uneven portions of pattern portion 107a. The depth of cavity 107b, which determines the size of space 112, is changed as appropriate depending on the size or material of mold 107.

[0017] The substrate stage 104 has a substrate chuck 119, a substrate stage housing 120, and a stage reference mark 121. A substrate 111 held by the substrate stage is a single crystal silicon substrate or an SOI (Silicon on Insulator) substrate, and a liquid 114 is discharged onto a processing surface of the substrate 111 to form a pattern.

[0018] The substrate chuck 119 holds the substrate 111 by vacuum suction. The substrate stage housing 120 moves the substrate 111 by moving the substrate chuck 119 in the X and Y directions while holding it by mechanical means. The stage reference mark 121 is used to set a reference position of the substrate 111 in alignment between the substrate 111 and the mold 107. For example, a linear motor is used as the actuator of the substrate stage housing 120. Alternatively, the actuator of the substrate stage housing 120 may be configured to include multiple drive systems, such as a coarse movement drive system or a fine movement drive system.

[0019] The measurement unit 122 has an alignment measurement instrument 127 and an observation measurement instrument 128. The alignment measurement instrument 127 measures the positional deviation in the X direction and the Y direction between an alignment mark formed on the substrate 111 and an alignment mark formed on the mold 107. The observation measurement instrument 128 is an imaging device such as a CCD camera, which captures an image of the pattern of the liquid 114 discharged onto the substrate 111 and outputs the image to the control unit 106 as image information.

[0020] The control unit 106 controls the entire imprint apparatus 101. The control unit 106a is provided in the liquid ejection apparatus 130, and controls the liquid ejection apparatus 130. When the imprint apparatus 101 operates, the control unit 106a controls the liquid ejection apparatus 130 based on commands from the control unit 106.

[0021] The control unit 106 is configured, for example, by a computer having a CPU, a ROM, and a RAM. The control unit 106 is connected to each component of the imprint apparatus 101 via a line, and the CPU controls each component according to a control program stored in the ROM. The control unit 106 also has a display unit and can perform various displays. The control unit 106 controls the operations of the mold holding mechanism 103 and the substrate stage 104 based on measurement information from the measurement unit 122.

[0022] The control unit 106a is configured, for example, by a computer having a CPU, a ROM, and a RAM. The CPU controls each component of the liquid ejection device 130 according to a control program stored in the ROM and instructions from the control unit 106. Note that the control unit 106 may also control the liquid ejection device 130 without providing the control unit 106a.

[0023] The housing 123 includes a base surface plate 124 on which the substrate stage 104 is placed, a bridge surface plate 125 to which the mold holding mechanism 103 is fixed, and supports 126 extending from the base surface plate 124 and supporting the bridge surface plate 125. The imprint apparatus 101 also includes a mold transport mechanism (not shown) that transports the mold 107 from outside the apparatus to the mold holding mechanism 103, and a substrate transport mechanism (not shown) that transports the substrate 111 from outside the apparatus to the substrate stage 104.

[0024] The imprint apparatus 101 performs an imprint process including the following series of steps. First, the imprint apparatus 101 causes the liquid discharge unit 10 to discharge liquid 114 onto the substrate 111. Then, a mold 107 having a molding pattern is pressed against the liquid 114 discharged onto the substrate, and in this state, the liquid 114 is cured by irradiation with light (ultraviolet rays). Thereafter, the mold 107 is separated from the cured liquid 114, thereby transferring the pattern of the mold 107 onto the substrate 111.

[0025] <Liquid ejection section and recovery section> FIG. 2 is a diagram showing the configuration of the liquid discharge unit 10 and the recovery unit 80. The liquid discharge unit 10 includes a discharge head 11, a storage container 12, and a pressure control unit 13. The storage container 12 stores a liquid 114. The internal space of the storage container 12 is divided into two spaces by a flexible separation membrane 14. One space 15 in the container stores the liquid 114, and the other space 16 stores a filling liquid. The thickness of the separation membrane 14 is, for example, 10 μm or more and 200 μm or less. The separation membrane 14 is formed of a material with low permeability to liquids and gases, and can be formed of, for example, a film of a fluororesin material such as PFA, or a composite multilayer film combining a fluororesin material and a plastic material.

[0026] The space 16 communicates with the pressure control unit 13 via a connecting pipe 17, and the space 15 communicates with the ejection head 11. The pressure control unit 13 includes a tank for storing the filling liquid, a pressure sensor, and a valve for opening and closing the connecting pipe 17, and is configured to be able to control the pressure in the space 16. By controlling the pressure of the filling liquid in the space 16 with the pressure control unit 13, the pressure of the liquid 114 in the space 15 can be controlled via the separation membrane 14. This stabilizes the shape of the gas-liquid interface in the ejection head 11, and allows the liquid 114 to be ejected with good reproducibility.

[0027] The recovery unit 80 includes a cap 81 through which waste liquid 114 is discharged from the discharge head 11. The cap 81 is a concave member having an opening larger than the discharge head 11, and is made of, for example, a machined part made of PTFE resin from which there is no risk of metal elution. The cap 81 may be subjected to acid cleaning, so that it is used in a physically and chemically clean state. It is disposed opposite the discharge surface 58 of the discharge head 11 during recovery processing. The cap 81 is also used as a holding member that holds a cleaning liquid when cleaning the discharge port of the discharge head 11. The cap 81 is provided so as to be displaceable in the Z direction by a drive mechanism (not shown), and the distance between the cap 81 and the discharge surface 58 is adjustable.

[0028] The recovery unit 80 also includes a waste liquid tube 85, a valve 83 for opening and closing the waste liquid tube 85, a waste liquid collection container 82, and a pump 84. The waste liquid tube 85 is in communication with the cap 81. The pump 84 is a tubing pump that pressure-feeds the waste liquid discharged into the cap 81 through the waste liquid tube 85 to the waste liquid collection container 82 for discharge.

[0029] FIG. 3 is a partially enlarged cross-sectional view of the ejection head 11. The ejection head 11 includes a common liquid chamber 56 and a module substrate 57. The module substrate 57 includes a plurality of nozzles 54. Each nozzle 54 includes a supply port 21 that opens to an upper surface 59 and takes in a liquid 114, and a discharge port 19 that opens to a discharge surface 58 and discharges the liquid 114. Inside each nozzle 54, a vibration element 18 that generates energy for discharging the liquid 114 is provided. A vibration element 18 is provided for each discharge port. The opening area of ​​the discharge port 19 is smaller than the opening area of ​​the supply port 21, and the cross-sectional area of ​​the flow path in the nozzle 54 is the smallest. In this embodiment, the vibration element 18 is a piezoelectric element represented by a piezo element, and hereinafter, the vibration element 18 may be referred to as a piezoelectric element 18.

[0030] The supply port 21 communicates with the ejection port 19 through the small liquid chamber 20 inside the module substrate 57. The drive of the piezoelectric element 18 is controlled by the control unit 106a through a drive circuit 90. By changing the volume of the small liquid chamber 20 by the piezoelectric element 18, the liquid 114 in the small liquid chamber 20 is ejected from the ejection port 19. The ejection head 11 may have a configuration similar to that of an ink ejection head used in an inkjet printer.

[0031] The discharge head 11 is open to the atmosphere through the discharge port 19, but the diameter of the discharge port 19 is several μm to several tens of μm, and the liquid 114 does not leak out by its own weight due to the capillary phenomenon. The liquid surface near the discharge port 19 is maintained in a concave, so-called meniscus state. The meniscus state can be stably maintained by maintaining the internal pressure of the discharge liquid 8 in the small liquid chamber 20 at a negative pressure of -0.1 to -1000 Pa by the pressure control unit 13. The discharge surface 58 is treated with a liquid repellent coating, which reliably prevents the liquid 114 from leaking out of the discharge port 19. For example, the liquid repellent coating may be performed by applying a fluorine-containing compound to the discharge surface 58 in the form of a film.

[0032] If the diameter of the discharge port 19 is small, ranging from a few μm to several tens of μm, the discharge performance will be reduced if particles adhere to the inside of the discharge port 19 or if some of the components contained in the liquid 114 dry and solidify around the discharge port 19. Examples of the reduction in discharge performance include non-discharge and fluctuations in the discharge amount and discharge direction. When such a reduction in discharge performance occurs, the recovery unit 80 performs a recovery process for the discharge performance.

[0033] <Control example> An example of recovery processing of the ejection head 11 executed by the control unit 106a will be described with reference to Fig. 4. Fig. 4 is a flow chart showing an example of processing executed by the control unit 106a. The illustrated processing is executed at a timing when the ejection operation of the liquid 114 onto the substrate 111 is not being performed. For example, the liquid ejection device 130 is moved to a standby position for performing maintenance, and then the following processing is executed.

[0034] In S1, the liquid ejection state of each ejection port 19 is inspected. In S2, ejection ports 19 with ejection defects are identified based on the inspection results of S1. As an example, the liquid ejection state is inspected by detecting the vibration characteristics of each piezoelectric element 18 and based on the detection results. In this embodiment, the back electromotive force of each piezoelectric element 18 is detected as the vibration characteristics and the inspection is performed based on the signal waveform. In other words, the piezoelectric elements 18 can also be used to detect the liquid ejection state of the ejection ports 19.

[0035] The piezoelectric element 18 is driven with a voltage that is 30% to 70% of the voltage applied when discharging the liquid 114, causing the volume of the small liquid chamber 20 to fluctuate (hereinafter referred to as test oscillation), and applying vibration to the liquid 114 in the small liquid chamber 20. For example, when a drive pulse of ±10 V is applied to the piezoelectric element 18 when discharging the liquid 114 from the discharge port 19, a drive pulse of ±6 V is applied to the piezoelectric element 18. In other words, the piezoelectric element 18 is driven to an extent that does not break the meniscus of the discharge port 19 and cause the liquid 114 to be discharged, and vibration is applied to the liquid 114 in the small liquid chamber 20.

[0036] Even if the driving of the piezoelectric element 18 is stopped, a counter electromotive force is generated in the piezoelectric element 18 due to the residual vibration of the liquid 114. The counter electromotive force is detected by a sensor 91 provided for each ejection port 19. The sensor 91 is, for example, a voltage sensor or a current sensor. If the ejection port 19 is blocked by a foreign object or if an air bubble has entered the small liquid chamber 20, the waveform of the counter electromotive force will differ from the standard state (the waveform when a meniscus is formed). In other words, the piezoelectric element 18 outputs a signal according to the liquid ejection state of the corresponding ejection port 19. This signal makes it possible to individually detect the liquid ejection state of each ejection port 19.

[0037] More specifically, the piezoelectric element 18 (piezo element) is deformed when a voltage is applied, and this deformation changes the pressure of the liquid 114 in the nozzle 54. When the piezoelectric element 18 is forcibly vibrated, residual vibration occurs, and a back electromotive force is generated due to the piezoelectric effect. The sensor 91 detects the back electromotive force generated by this residual vibration. Furthermore, since the back electromotive force is generated for each piezoelectric element 18, in other words, for each nozzle 54, the sensor 91 detects the back electromotive force for each nozzle 54.

[0038] 6(A) and 6(B) are diagrams showing an example of a back electromotive force signal waveform (change in current-time) when the signal shown in FIG. 6(C) is applied to the piezoelectric element 18 as an inspection signal for inspection oscillation.

[0039] 6C has a voltage waveform that changes at or below the natural period estimated for the piezoelectric element 18. As an example, if the natural period of the piezoelectric element 18 is estimated to be 4.5 μsec, a voltage with a waveform that changes over 4.5 μsec is applied.

[0040] Fig. 6(A) is an example of a signal waveform in a normal case where there is no degradation of the ejection performance of the ejection port 19. The dashed line in Fig. 6(B) is an example of a signal waveform in a normal case, and the solid line is an example of a signal waveform where there is degradation of the ejection performance. When a meniscus of the liquid 114 is no longer formed at the ejection port 19, the period of the signal becomes longer (the frequency becomes smaller) compared to when the ejection port 19 is normal. Also, the amplitude may become larger.

[0041] The difference in the signal waveforms makes it possible to determine whether the ejection performance of the ejection port 19 has deteriorated. The normal signal waveform to be compared can be stored in a storage device such as a ROM of the control unit 106. Instead of storing the normal signal waveform, a threshold value for determining whether ejection failure has occurred may be stored. The threshold value may be a threshold value related to the signal period of the back electromotive force or a threshold value related to the signal amplitude.

[0042] Using this method, the ejection port 19 having the ejection defect is identified in S2 of Fig. 4. If it is determined in S2 that none of the ejection ports 19 has an ejection defect, the process of Fig. 4 ends.

[0043] Note that, here, the liquid ejection state of the ejection port 19 was inspected by inspection oscillation, but an ejection port 19 (nozzle 54) having ejection problems may also be detected by measuring the presence or absence of landing and the landing position, speed, and amount using an impact inspection device (not shown).

[0044] In S3, the outlets 19 to be targeted for performance recovery are selected based on the identification results of S2. As one example, the outlets 19 identified in S2 are selected as the outlets 19 to be restored. As another example, the outlets 19 may be divided into groups according to their positions, and the outlets 19 for the recovery process may be selected on a group-by-group basis. As yet another selection method, the outlets 19 identified in S2 and the outlets 19 within a certain range surrounding it may be selected. As yet another example, if there is even one outlet 19 with a discharge defect in S2, all of the outlets 19 will be described as the outlets 19 to be restored.

[0045] In S4, recovery processing is performed for the outlet 19 selected in S3. Fig. 5 is a flow chart showing an example of the processing in S4.

[0046] In S11, the cap 81 is placed at a position facing the discharge surface 58. The cap 81 is capable of holding cleaning liquid between the discharge surface 58 and the inner wall surface of the cap 81. Thereafter, the small liquid chamber 20 corresponding to the discharge port 19 selected in S3 is pressurized by the pressure control unit 13. By pressurizing the small liquid chamber 20 from +10 kPa to +50 kPa, for example, it is possible to push out foreign matter and the like that is clogged in the discharge port 19. At this time, the liquid 114 and foreign matter and the like discharged from the discharge port 19 to the cap 81 are discharged by the pump 84 into the waste liquid recovery container 82. There are cases in which the clogged discharge port 19 is not cleared even after such pressurization recovery, so the process proceeds to the cleaning process next.

[0047] In S13, the bottom surface of the cap 81 and the ejection surface 58 are brought close to each other until the distance between them becomes 100 to 500 μm, and then a cleaning liquid is filled between the cap 81 and the ejection surface 58. In this embodiment, a liquid 114 is used as the cleaning liquid. The pressure control unit 13 pressurizes the filling liquid in the space 16 to about 10 kPa to 30 kPa, thereby making the pressure of the liquid 114 in the small liquid chamber 20 10 kPa or more. As a result, the liquid 14 is ejected from the ejection port 19 as the cleaning liquid. When the space between the cap 81 and the ejection surface 58 is filled with the liquid 114, the pressurization of the filling liquid in the space 16 is stopped.

[0048] Next, the pressure control unit 13 sets the pressure in the small liquid chamber 20 to a slightly positive pressure (several hundred Pa to several kPa), and then closes the valve of the pressure control unit 13 to close the pipe 17 connecting the pressure control unit 13 to the space 16. Since the liquid 114 on the cap 81 is open to the atmosphere, the pressure of the liquid 114 in the small liquid chamber 20 gradually decreases from the slightly positive pressure to atmospheric pressure. This prevents the liquid 114 from flowing out from the discharge head 11 into the cap 81, and prevents the liquid 114 from overflowing from the cap 81. In addition, the pressure of the liquid 114 in the small liquid chamber 20 is maintained at a slightly positive pressure from atmospheric pressure. This prevents the liquid 114 on the cap 81 from flowing back to the discharge head 11, and the liquid 114 is held between the cap 81 and the discharge surface 58 as shown in FIG. 7.

[0049] Next, in this embodiment, cleaning of the ejection port 19 selected as the recovery target is performed by physically vibrating the small liquid chamber 20 by driving the corresponding piezoelectric element 18. In S14 and S15 of Fig. 5, processing related to setting the drive cycle for driving each piezoelectric element 18 is performed. The cleaning effect is improved by resonating the piezoelectric element 18.

[0050] First, in S14, the natural period of the piezoelectric element 18 is identified. The natural period is identified for each piezoelectric element 18 (for each vibration element), and is identified based on the detection results by detecting the vibration characteristics of each piezoelectric element 18. In the inspection of the liquid ejection state in S1, a signal waveform of the back electromotive force has already been obtained as the vibration characteristic of each piezoelectric element 18. The natural period is calculated using this signal waveform. Note that in order to identify the natural period of the piezoelectric element 18 in S14, the vibration characteristics of each piezoelectric element 18 may be detected separately from the processing of S1. However, according to this embodiment, the detection of the vibration characteristics can be performed once for two purposes: inspecting the liquid ejection state and identifying the natural period.

[0051] In the determination in S14, the natural period T is calculated from the signal waveform of the back electromotive force of the piezoelectric element 18. An example is shown in Fig. 8(A). The signal waveform of the back electromotive force is a damped wave because it is a residual vibration that occurs after the vibration of the piezoelectric element 18. The natural period T is calculated by fitting the signal waveform with a function of the damped wave.

[0052] In S15, the drive period of the piezoelectric element 18 is set based on the natural period T calculated in S14. FIG. 8B shows a signal waveform (dotted line) when the piezoelectric element 18 is driven with a delay of the time of the natural period T from the signal waveform (solid line) of the back electromotive force generated in the piezoelectric element 18. The dotted line in FIG. 8B shows a case where the piezoelectric element 18 is vibrated with a period of one time of the natural period T. The second peak of the solid line waveform when the piezoelectric element 18 is driven for the first time overlaps with the first peak of the dotted line waveform when the piezoelectric element 18 is driven with a delay of one time of the natural period T. This causes the piezoelectric element 18 to resonate, increasing the vibration of the piezoelectric element 18 and increasing the fluidity of the liquid 114 in contact with the discharge surface 58. Foreign matter attached to the inside and periphery of the discharge port 19 is effectively removed.

[0053] Therefore, the cleaning effect can be improved by setting the drive period Td to the natural period T. However, the vibration period Td of the piezoelectric element 18 that has a cleaning effect does not need to be exactly the same as the natural period T, but may be within a certain range of the natural period T. If the minimum period of the drive period Td is Td_min and the maximum period is Td_max, then the drive period Td is given by Td_min≦ Td ≦Td_max (Equation 1) As an example, Td_min=T, Td_max=T+T×0.2. For example, if the natural period T of the piezoelectric element 18 is 4.5 μsec, the drive period Td is 4.5 μsec≦Td≦5.4 μsec. When the drive period Td is expressed in terms of the drive frequency fd, it is 185 KHz≦fd≦222 KHz.

[0054] In the ejection port 19 (nozzle 54) with ejection failure, the natural period T of the piezoelectric element 18 may be longer than the normal natural period T by several percent to 30%. In addition, the natural period T may differ depending on the amount of adhesion to the ejection port 19. In this embodiment, the natural period T is calculated for each piezoelectric element 18, and the drive period Td is set for each piezoelectric element 18. Therefore, a cleaning effect suitable for each ejection port 19 can be obtained. However, it is also possible to set the same drive period Td for all the piezoelectric elements 18. In this case, the drive period Td may be set based on the natural period T of any one piezoelectric element 18, or the drive period Td may be set based on the average value of the natural periods T of the multiple piezoelectric elements 18.

[0055] 5, the ejection port 19 is cleaned. Here, the piezoelectric element 18 is driven at the drive period Td set in S15, with the liquid 114 held between the ejection surface 58 and the cap 81. The ejection port 19 (nozzle 54) is cleaned by the physical vibration of the small liquid chamber 20 caused by the piezoelectric element 18 and the flow of the liquid 114 caused by the vibration.

[0056] 9 shows the waveform of a drive signal applied to the piezoelectric element 18. The horizontal axis represents time, and the vertical axis represents voltage. The drive signal shown is a trapezoidal wave, for example. The trapezoidal wave is made up of a pull-in component (rising edge) 201, a constant voltage component 202, and a push-out component (falling edge) 203. The drive period Td is the sum of the time of this trapezoidal wave and the standby time Tw at the initial value.

[0057] This trapezoidal wave has an initial pull component 201, which causes the liquid 114 in the cap 81 to flow into the discharge port 19. After the pull component 201, the voltage is kept constant by a constant voltage component 202. During this time, the liquid flowing from the cap 81 into the discharge port 19 decreases. The next push component 203 pushes the liquid 114 in the discharge port 19 into the cap 81. After that, during the waiting time Tw at the initial value, the liquid 114 pushed out from the discharge port 19 into the cap 81 decreases, and with the next trapezoidal wave, the liquid 114 in the cap 81 again flows into the discharge port 19.

[0058] Since the cleaning operation requires only that the liquid 114 flows in and out between the cap 81 and the inside of the discharge port 19, the waveform that drives the piezoelectric element 18 in the cleaning operation needs to have at least a pull-in component 201 that increases the voltage and a push-out component 203 that decreases the voltage. Although a trapezoidal wave is used in the explanation of Fig. 9, a similar cleaning effect can also be obtained by using a square wave, a sawtooth wave, a triangular wave, or a pulse wave.

[0059] For example, when the maximum driving frequency during imprint operation is 60 KHz, the driving signal can be realized by adding multiple driving signals during that period. In other words, the number of driving signals per unit time can be made different between when discharging liquid from the discharge port 19 to the substrate 111 and when cleaning the discharge port 19. This makes it possible to adjust the number of driving signals (trapezoidal waves) and the waiting time Tw to drive the piezoelectric element 18 with a vibration period Td of a desired driving waveform, as shown in FIG.

[0060] The voltage of the drive signal during cleaning may be about 20% to 40% higher than the voltage applied to the piezoelectric element 18 during ejection in the imprint operation, which can further improve the cleaning effect.

[0061] Driving the piezoelectric element 18 at the drive period Td during cleaning may increase the load on the drive circuit 90. Therefore, the drive period and drive stop period of the drive element 18 may be set alternately to perform cleaning repeatedly with short intervals.

[0062] For the outlets 19 that are not the object of the recovery process, the piezoelectric elements 18 are not driven, so that contaminants do not flow into the outlets 19, and secondary contamination can be prevented.

[0063] 5, the gap between the cap 81 and the ejection surface 58 is widened. Then, in order to replace the liquid 114 inside the ejection head 11, the liquid 114 is discharged from the ejection port 19 into the cap 81 in the same manner as the pressurized recovery process in S12. This makes it possible to prevent foreign matter from re-entering the ejection port 19. Thereafter, the pump 84 is driven to discharge the liquid 114 between the ejection surface 58 and the cap 81.

[0064] The discharge surface 58 of the discharge head 11 may be cleaned using a suction nozzle (not shown). Cleaning is performed by suctioning and removing the cleaning liquid (liquid 114) adhering to the discharge surface 58. A suction nozzle directly connected to a negative pressure source is brought close to the discharge surface 58 of the discharge head 11 to within 100 μm, and suction is started. While maintaining a distance from the discharge surface 58, the suction nozzle is scanned over the discharge surface 58 to suck up the droplets remaining on the surface of the discharge surface 58. The suction nozzle opening gap is set to 100 μm to 200 μm. There are cases where the surface of the discharge surface 58 and the tip of the suction nozzle are momentarily in a conductive state through the liquid 114 due to the remaining droplets. A suction nozzle made of PTFE resin may be used to prevent the risk of metal contamination.

[0065] In S18, a confirmation process is performed. Here, the same inspection as in S1 is performed again, and the inspection oscillation is executed again to check whether or not there is any ejection port 19 experiencing ejection defects. If there is an ejection port 19 experiencing ejection defects, the recovery process (S4) is performed again. If there is secondary contamination, this can be eliminated. If there is no ejection port 19 experiencing ejection defects, the process ends.

[0066] In this embodiment, the liquid ejection device 130 is mounted on the imprinting apparatus 101, and an inspection oscillation is performed on the ejection section 11. From the vibration characteristics obtained from the inspection oscillation, the natural period T of the piezoelectric element 18 is calculated, and the vibration period Td of the piezoelectric element 18 in the cleaning operation is set. However, before mounting the liquid ejection device 130 on the imprinting apparatus 101, an inspection oscillation may be performed, and the vibration period Td of the piezoelectric element 18 to be used during the cleaning operation may be set in advance. Second Embodiment If the drive period Td is short, the load on the drive circuit 90 becomes high. On the other hand, the longer the cleaning time by vibration of the piezoelectric element 18 is continuously performed, the more effective it becomes. By performing such cleaning for several hours to several days, even stubborn foreign matter can be removed. In this embodiment, cleaning is performed by driving the piezoelectric element 18 with a lower drive frequency than in the first embodiment.

[0067] During cleaning, if the piezoelectric element 18 is vibrated at a period that is a natural number multiple of the natural period T of the piezoelectric element 18, the piezoelectric element 18 resonates and increases the vibration of the piezoelectric element 18. The fluidity of the liquid 114 in contact with the ejection surface 58 increases, thereby improving the cleaning effect.

[0068] FIG. 10A shows a signal waveform (dotted line) when the piezoelectric element 18 is driven with a delay of twice the natural period T from the signal waveform (solid line) of the back electromotive force generated in the piezoelectric element 18. In other words, the dotted line in FIG. 10A shows a case where the piezoelectric element 18 is vibrated with a period twice the natural period T. The third peak of the solid line waveform when the piezoelectric element 18 is driven for the first time overlaps with the first peak of the dotted line waveform when the piezoelectric element 18 is driven with a delay of twice the natural period T. This causes the piezoelectric element 18 to resonate, increasing the vibration of the piezoelectric element 18 and increasing the fluidity of the liquid 114 in contact with the ejection surface 58. Foreign matter adhering to the inside and periphery of the ejection port 19 is effectively removed.

[0069] Therefore, the cleaning effect can be improved by setting the drive period Td to a period that is at least twice the natural period T. However, the vibration period Td of the piezoelectric element 18 that has a cleaning effect does not need to be exactly the same as a period that is at least twice the natural period T, but only needs to be within a certain range of the natural period T. If the multiple of the drive period Td of the piezoelectric element relative to the natural period T is n (a natural number of 2 or more), the minimum period of the drive period Tdn is Tdn_min, and the maximum period is Tdn_max, then the drive period Tdn is given by: Tdn_min≦Tdn≦Tdn_max (Formula 2) (n is a natural number greater than or equal to 2) As an example, Tdn_min=n×T-(T×0.2), Tdn_max=n×T+(T×0.2). Fig. 10(B) shows the waveform of the drive signal applied to the piezoelectric element 18. The horizontal axis indicates time, and the vertical axis indicates voltage. As with the example of Fig. 9, the illustrated drive signal is, for example, a trapezoidal wave.

[0070] In the case where the multiple n is 2, if the natural period T of the piezoelectric element 18 is 4.5 μsec, the drive period Td2 is 81 μsec≦Td2 ≦9.9 μsec. When the drive period Td2 is expressed in terms of the drive frequency f2, it is 101 KHz≦f2 ≦123 KHz.

[0071] When the value of the multiple n becomes large, the drive period Tdn becomes longer, and as a result, the flow of the liquid 114 between drives of the piezoelectric element 18 becomes weaker, which may result in a decrease in the cleaning effect. From this perspective, the multiple n may be a natural number of 7 or less.

[0072] <Third embodiment> During cleaning, the liquid 114 between the discharge head 10 and the cap 81 may be circulated while being filtered. FIG. 11 is a diagram showing an example of the configuration of this embodiment. The recovery unit 80' includes a cleaning device 60. The cleaning device 60 is a device for cleaning each discharge port 19 with a cleaning liquid, and includes a circulation device 61, a cap 81' replacing the cap 81, and a filter 66. The cleaning liquid is, for example, a liquid similar to the liquid 114, or a liquid using one of the materials contained in the liquid 114. A plurality of types of cleaning liquid may be used in one cleaning operation. For example, cleaning may be performed using a liquid different from the liquid 114 as a cleaning liquid, and then cleaning may be performed using the liquid 114 as a cleaning liquid.

[0073] The cap 81' is detachably attached to the discharge head 11. The circulation device 61 is a mechanism for circulating the cleaning liquid supplied to and discharged from the cap 81'. The filter 66 is provided midway along the circulation path of the cleaning liquid, and purifies the cleaning liquid. By circulating the cleaning liquid, the amount of cleaning liquid consumed can be reduced.

[0074] The circulation device 61 includes a container TK for storing the cleaning liquid, pipes 62 and 63, and a pump 65. The pipe 62 connects the container TK and the cap 81', and forms a flow path on the supply side of the cleaning liquid. The pipe 63 connects the container TK and the cap 81', and forms a flow path on the discharge side (recovery side) of the cleaning liquid. In this embodiment, the pump 65 is provided midway through the pipe 62, and pumps the cleaning liquid to the cap 81'. The filter 66 is provided midway through the pipe 62 and downstream of the pump 65, and purifies the cleaning liquid flowing through the pipe 62. Even if dust generated by the pump 65 gets mixed into the cleaning liquid, it is removed by the filter 66.

[0075] A tile 75 is provided on the bottom surface of the ejection head 11. The tile 75 holds an ejection surface 58 in which a plurality of ejection ports 19 are formed, a protective member 73 that protects the ejection surface 58, and a filler 74 that fills the gap between the ejection surface 58 and the protective member 73.

[0076] Cap 81' is a member that forms a space for holding a cleaning liquid inside so that the cleaning liquid comes into contact with discharge surface 58. Cap 81' is, for example, a machined part made of PTFE resin from which there is no concern of metal elution. Cap 81' after processing and molding can be used in a physically and chemically clean state by performing acid cleaning.

[0077] The cap 81' is formed with a supply port 81a and a plurality of discharge ports 81b. The supply port 81a is connected to a pipe 62, and the plurality of discharge ports 81b are connected to a pipe 63. The cleaning liquid pumped from the pump 65 is supplied into the cap 81' through the supply port 81a and discharged from the cap 81' through the plurality of discharge ports 81b.

[0078] The pressure (referred to as P1) of the cleaning liquid pumped into the cap 81′ can be measured by a pressure gauge (not shown) provided in the pump 65. By controlling the internal pressure (referred to as P2) of the discharge head 11 by the pressure control device 13, the magnitude relationship between the pressure P1 and the pressure P2 can be controlled.

[0079] In the present embodiment, the discharge port 19 can be cleaned by the process procedure shown in Fig. 4 and Fig. 5 in the first embodiment. When filling the space between the cap 81' and the discharge surface 58 with cleaning liquid in S13 in Fig. 5, the cleaning liquid stored in the container TK can be used. In this case, the pump 65 is driven to supply the cleaning liquid into the cap 81'.

[0080] During cleaning, the piezoelectric element 18 is driven at a drive period Td, while the pump 65 is driven to circulate the cleaning liquid between the cap 81' and the container TK. The circulation of the cleaning liquid can increase the flow of the cleaning liquid around the discharge port 19. Foreign matter separated from the periphery of the discharge port 19 by the drive of the piezoelectric element 18 reaches the filter 66 and is captured by the action of the circulation device 61. The cleaning liquid is purified by the filter 66, so it can be used repeatedly, and the amount of cleaning liquid consumed can be reduced even when cleaning is performed for a long period of time.

[0081] <Disclosure of the embodiment> The above embodiment discloses the following inventions.

[0082] Item.1 A discharge means having a discharge surface with a discharge port for discharging a liquid; A vibration element provided at the ejection port; a holding member disposed opposite to the ejection surface and capable of holding liquid between the ejection surface and the holding member; A liquid ejection device comprising: A detection means for detecting a vibration characteristic of the vibration element; a control means for driving the vibration element at a drive cycle based on a detection result of the detection means in a state where liquid is held between the ejection surface and the holding member when the ejection port is cleaned, A liquid ejection device comprising:

[0083] Item.2 The liquid ejection device according to item 1, The control means identifies a natural period of the vibration element based on the detection result, and drives the vibration element with a drive period based on the natural period. A liquid ejection device comprising:

[0084] Item.3 Item 2. The liquid ejection device according to item 2, If the natural period is T and the driving period is Td, then T ≤ Td ≤ T x 1.2 Satisfy the relationship A liquid ejection device comprising:

[0085] Item.4 Item 2. The liquid ejection device according to item 2, If the natural period is T and the driving period is Td, then (n×TT×0.2)≦Td≦(n×T+T×0.2) However, n is a natural number greater than or equal to 2. Satisfy the relationship A liquid ejection device comprising:

[0086] Item.5 The liquid ejection device according to any one of items 2 to 4, The liquid ejection device according to item 1, A plurality of the ejection ports are opened on the ejection surface, The vibration element is provided for each of the ejection ports, The control means specifies the natural period for each of the vibration elements and sets the drive period. A liquid ejection device comprising:

[0087] Item.6 The liquid ejection device according to item 1, the vibration element is a piezoelectric element that is driven by a drive signal and generates energy for ejecting liquid from the ejection port; The control means driving the piezoelectric element with drive signals having different numbers per unit time for discharging liquid from the discharge port to a discharge target and for cleaning the discharge port; A liquid ejection device comprising:

[0088] Item.7 Item 6. The liquid ejection device according to item 6, The waveform of the drive signal is a trapezoidal wave, a rectangular wave, a sawtooth wave, or a triangular wave. A liquid ejection device comprising:

[0089] Item.8 A liquid ejection device according to any one of items 1 to 7, a recovery container that recovers the liquid held between the ejection surface and the holding member; A liquid ejection device comprising:

[0090] Item.9 A liquid ejection device according to any one of items 1 to 7, a circulation means for circulating liquid through a filter between a container and a space between the ejection surface and the holding member; A liquid ejection device comprising:

[0091] Item.10 The liquid ejection device according to item 1, the vibration element is a piezoelectric element disposed in a liquid chamber communicating with the ejection port, the detection means detects a back electromotive force outputted from the piezoelectric element due to vibration of the liquid in the liquid chamber caused by driving the piezoelectric element. A liquid ejection device comprising:

[0092] Item.11 Item 11. The liquid ejection device according to item 10, The control means Inspecting the ejection state of the ejection port based on the signal waveform of the back electromotive force; setting the drive period based on the signal waveform of the back electromotive force; A liquid ejection device comprising:

[0093] Item.12 An imprint apparatus comprising a liquid ejection device, and ejecting liquid from the liquid ejection device to perform an imprint process on a substrate, The liquid ejection device includes: A discharge means having a discharge surface with a discharge port for discharging a liquid; A vibration element provided at the ejection port; a holding member disposed opposite to the ejection surface and capable of holding liquid between the ejection surface and the holding member; A detection means for detecting a vibration characteristic of the vibration element; a control means for driving the vibration element at a drive cycle based on a detection result of the detection means in a state where liquid is held between the ejection surface and the holding member when the ejection port is cleaned, 1. An imprint apparatus comprising:

[0094] Item.13 Item 13. An imprinting apparatus according to item 12, the control unit sets the drive cycle before the liquid ejection device is mounted on the imprint apparatus. 1. An imprint apparatus comprising:

[0095] Item.14 A discharge means having a discharge surface with a discharge port for discharging a liquid; A vibration element provided at the ejection port; a holding member disposed opposite to the ejection surface and capable of holding liquid between the ejection surface and the holding member; A method for controlling a liquid ejection device comprising: a detection step of detecting a vibration characteristic of the vibration element; a control step of driving the vibration element at a drive cycle based on a detection result of the detection step in a state where liquid is held between the ejection surface and the holding member when the ejection port is cleaned, A control method comprising:

[0096] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0097] 11 Discharge head, 18 Vibration element (piezoelectric element), 81 Cap, 106a Control unit, 130 Liquid discharge device

Claims

1. A discharge means having a discharge surface with a discharge port for discharging a liquid; A vibration element provided at the ejection port; a holding member disposed opposite to the ejection surface and capable of holding liquid between the ejection surface and the holding member; A liquid ejection device comprising: A detection means for detecting a vibration characteristic of the vibration element; a control means for driving the vibration element at a drive cycle based on a detection result of the detection means in a state where liquid is held between the ejection surface and the holding member when the ejection port is cleaned, A liquid ejection device comprising:

2. The liquid ejection device according to claim 1 , The control means identifies a natural period of the vibration element based on the detection result, and drives the vibration element with a drive period based on the natural period. A liquid ejection device comprising:

3. The liquid ejection device according to claim 2, If the natural period is T and the driving period is Td, then T≦Td≦T×1.2 Satisfy the relationship A liquid ejection device comprising:

4. The liquid ejection device according to claim 2, If the natural period is T and the driving period is Td, then (n×T−T×0.2)≦Td≦(n×T+T×0.2) However, n is a natural number greater than or equal to 2. Satisfy the relationship A liquid ejection device comprising:

5. The liquid ejection device according to claim 2, A plurality of the ejection ports are opened on the ejection surface, The vibration element is provided for each of the ejection ports, The control means specifies the natural period for each of the vibration elements and sets the drive period. A liquid ejection device comprising:

6. The liquid ejection device according to claim 1 , the vibration element is a piezoelectric element that is driven by a drive signal and generates energy for ejecting liquid from the ejection port; The control means driving the piezoelectric element with drive signals having different numbers per unit time for discharging liquid from the discharge port to a discharge target and for cleaning the discharge port; A liquid ejection device comprising:

7. The liquid ejection device according to claim 6, The waveform of the drive signal is a trapezoidal wave, a rectangular wave, a sawtooth wave, or a triangular wave. A liquid ejection device comprising:

8. The liquid ejection device according to claim 1 , a recovery container that recovers the liquid held between the ejection surface and the holding member; A liquid ejection device comprising:

9. The liquid ejection device according to claim 1 , a circulation means for circulating liquid through a filter between a container and a space between the ejection surface and the holding member; A liquid ejection device comprising:

10. The liquid ejection device according to claim 1 , the vibration element is a piezoelectric element disposed in a liquid chamber communicating with the ejection port, the detection means detects a back electromotive force outputted from the piezoelectric element due to vibration of the liquid in the liquid chamber caused by driving the piezoelectric element. A liquid ejection device comprising:

11. The liquid ejection device according to claim 10, The control means Inspecting the ejection state of the ejection port based on the signal waveform of the back electromotive force; setting the drive period based on the signal waveform of the back electromotive force; A liquid ejection device comprising:

12. An imprint apparatus comprising a liquid ejection device, and ejecting liquid from the liquid ejection device to perform an imprint process on a substrate, The liquid ejection device includes: A discharge means having a discharge surface with a discharge port for discharging a liquid; A vibration element provided at the ejection port; a holding member disposed opposite to the ejection surface and capable of holding liquid between the ejection surface and the holding member; A detection means for detecting a vibration characteristic of the vibration element; a control means for driving the vibration element at a drive cycle based on a detection result of the detection means in a state where liquid is held between the ejection surface and the holding member when the ejection port is cleaned, 1. An imprint apparatus comprising:

13. 13. The imprinting apparatus according to claim 12, the control unit sets the drive cycle before the liquid ejection device is mounted on the imprint apparatus.

1. An imprint apparatus comprising:

14. A discharge means having a discharge surface with a discharge port for discharging a liquid; A vibration element provided at the ejection port; a holding member disposed opposite to the ejection surface and capable of holding liquid between the ejection surface and the holding member; A method for controlling a liquid ejection device comprising: a detection step of detecting a vibration characteristic of the vibration element; a control step of driving the vibration element at a drive cycle based on a detection result of the detection step in a state where liquid is held between the ejection surface and the holding member when the ejection port is cleaned, A control method comprising:

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