Patent Publication Number: US-9892949-B2

Title: Imprint method, imprint apparatus, and article manufacturing method

Description:
This application is a continuation of copending U.S. patent application Ser. No. 14/887,472, filed Oct. 20, 2015, which is a continuation of U.S. patent application Ser. No. 13/647,667, filed Oct. 9, 2012, which matured into U.S. Pat. No. 9,201,298. 
     This application also claims the benefit of Japanese Patent Application No. 2011-226636, filed Oct. 14, 2011, and Japanese Patent Application No. 2012-220209, filed Oct. 2, 2012, which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an imprint method, an imprint apparatus, and an article manufacturing method. 
     Description of the Related Art 
     As the demand for microfabrication of semiconductor devices or MEMS increases, not only has conventional photolithography technology, but also, microfabrication technology, in which an uncured resin on a substrate is molded by a mold to thereby form a resin pattern on the substrate, has been receiving attention. This technology is also referred to as “imprint technology”, by which a fine structure with dimensions of a few nanometers can be formed on a substrate. One example of the imprint technology includes a photo-curing method. An imprint apparatus employing the photo-curing method first applies an ultraviolet curable resin (imprint material, photocurable resin) to a shot (imprint region) on a substrate (wafer). Next, the resin (uncured resin) is molded by a mold. After the ultraviolet curable resin is irradiated with ultraviolet light for curing, the cured resin is released from the mold, whereby a resin pattern is formed on the substrate. 
     Here, in a series of device manufacturing steps, heat processing in a film formation step, such as sputtering, is performed for a substrate to be subjected to imprint processing. Consequently, the entire substrate may be expanded or reduced, resulting in a change in the shape (size) of the pattern in the direction of two orthogonal in-plane axes. Thus, in an imprint apparatus, the shape of the substrate-side pattern formed on a substrate needs to be matched with the shape of the pattern section formed on a mold when the mold is pressed against the resin on the substrate. In a conventional exposure apparatus, such shape correction (magnification correction) can be ensured by changing the size of each shot during exposure processing by changing the reduction magnification of a projection optical system in accordance with the magnification of the substrate or by changing the scanning speed of a substrate stage. However, the imprint apparatus does not have a projection optical system and the mold is brought into direct contact with the resin on the substrate, and thus, it is difficult to perform such correction. Hence, the imprint apparatus employs a shape correction mechanism (magnification correction mechanism) that physically deforms a mold by imparting an external force to the sides of the mold or by expanding the mold by heating. 
     For example, assume a case wherein the imprint apparatus is applied to a manufacturing step of manufacturing a semiconductor device having a half-pitch of about 32 nm. At this time, according to ITRS (International Technology Roadmap for Semiconductors), the superposition accuracy is 6.4 nm. In order to accommodate this, shape correction also needs to be performed with an accuracy of a few nm or less. On the other hand, the mold (pattern section) used in the imprint apparatus may also be distorted by the following causes. For example, the pattern surface of a mold is directed upward when the mold is being prepared, whereas the pattern surface thereof is directed downward when the mold is used (during pressing). Thus, the pattern section may be deformed upon usage under the influence of gravity. Although the pattern section is typically formed by a drawing apparatus using an electron beam, or the like, the pattern section may also be distorted due to distortion aberration of the optical system of the drawing apparatus during formation thereof. Furthermore, even if the pattern section can be prepared without distortion, the occurrence of distortion in a substrate-side pattern may result in an adverse effect on the superposition accuracy. Accordingly, in order to suppress such distortion (deformation) of the mold and to improve superposition accuracy, Japanese Patent Laid-Open No. 2004-259985 discloses a pattern forming apparatus that controls the temperature of a mold and a substrate by means of a retention temperature control unit, and corrects the shape of the mold or the substrate by generating desired thermal deformation in the mold or the substrate. 
     In the conventional imprint apparatus, however, a substrate is held by a substrate holding unit, such as a wafer chuck, with the bottom surface of the substrate restricted thereto. Thus, even if thermal deformation is generated on the substrate under temperature control disclosed in Japanese Patent Laid-Open No. 2004-259985, it is still difficult to sufficiently change the shape of the substrate-side pattern relative to the shape of the pattern section. Accordingly, an imprint apparatus is desired that is capable of improving superposition accuracy between a mold and a resin on a substrate by readily implementing not only the correction of the shape of the mold, but also, the correction of the shape of the substrate (including the substrate-side pattern) relative to the shape of the mold. 
     SUMMARY OF THE INVENTION 
     The present invention provides an imprint apparatus that is advantageous for improving superposition accuracy between a mold and resin on a substrate. 
     According to one aspect, the present invention provides an imprint apparatus for forming a pattern of an imprint material on a substrate by using a mold that includes a substrate holding unit configured to hold the substrate by acting a suction force between the substrate and a holding surface, the substrate holding unit including a first suction unit for sucking a rear surface of a first region of the substrate with a first suction force and a second suction unit for sucking a rear surface of a second region of the substrate different from the first region of the substrate with a second suction force, a deformation mechanism configured to deform a shape of the first region in a direction along the holding surface when forming the pattern of the imprint material on the first region, and an adjusting unit configured to adjust the first suction force and the second suction force. The adjusting unit adjusts the first suction force to be less than the second force in at least a portion of a period during the deforming of the shape of the first region by the deformation mechanism. 
     According to another aspect, the present invention provides a method of manufacturing an article including the steps of (a) forming a pattern of an imprint material on a substrate using an imprint apparatus for forming the pattern on the substrate by using a mold, (b) processing the substrate on which the pattern is formed by the forming, and (c) manufacturing the article from the processed substrate. The imprint apparatus includes (i) a substrate holding unit configured to hold the substrate by acting as a suction force between the substrate and a holding surface, the substrate holding unit including a first suction unit for sucking a rear surface of a first region of the substrate with a first suction force and a second suction unit for sucking a rear surface of a second region of the substrate different from the first region of the substrate with a second suction force, (ii) a deformation mechanism configured to deform a shape of the first region in a direction along the holding surface when forming the pattern of the imprint material on the first region, and (iii) an adjusting unit configured to adjust the first suction force and the second suction force. The adjusting unit adjusts the first suction force to be less than the second force in at least a portion of a period during the deforming of the shape of the first region by the deformation mechanism. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating the configuration of an imprint apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a diagram illustrating the configuration of a wafer stage according to the first embodiment. 
         FIG. 3  is a flowchart illustrating the sequence of operations according to the first embodiment. 
         FIG. 4A  is a flowchart illustrating the sequence of operations according to a second embodiment. 
         FIG. 4B  is a flowchart illustrating a variant example of the sequence of operations shown in  FIG. 4A . 
         FIG. 5  is a diagram illustrating the configuration of a wafer stage according to a third embodiment. 
         FIG. 6  is a flowchart illustrating the sequence of operations according to a fourth embodiment. 
         FIG. 7  is a diagram illustrating the irradiation dose of light according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. 
     (First Embodiment) 
     First, a description will be given of the configuration of an imprint apparatus according to a first embodiment of the present invention.  FIG. 1  is a schematic diagram illustrating the configuration of an imprint apparatus  1  of the present embodiment. The imprint apparatus  1  is an apparatus that molds an uncured resin on a wafer (on a substrate), i.e., a substrate to be treated, using a mold, to thereby form a resin pattern on the wafer, which is used in the manufacture of devices, such as semiconductor devices, and the like, as articles. Note that the imprint apparatus of the present embodiment is an apparatus employing a photo-curing method. In the following drawings, a description will be given in which the Z axis is aligned parallel to the optical axis of an irradiation system that irradiates a resin on a wafer with ultraviolet light, and mutually orthogonal axes, X and Y, are aligned in a plane perpendicular to the Z axis. The imprint apparatus  1  includes a light irradiation unit  2 , a mold holding mechanism  3 , a wafer stage  4 , an application unit  5 , and a control unit  6 . 
     The light irradiation unit  2  irradiates a mold  7  with ultraviolet light  8  during imprint processing. The light irradiation unit  2  is constituted by a light source  9  and an optical element  10  that adjusts the ultraviolet light  8  emitted from the light source  9  to light suitable for imprinting. Note that, in the present embodiment, the light irradiation unit  2  is installed for employing a photo-curing method. If, however, a thermosetting method is employed, a heat source unit for curing a thermosetting resin may be installed, instead of the light irradiation unit  2 . Furthermore, the light irradiation unit  2  includes a heating light source  50  that functions as a heating mechanism (substrate deformation mechanism) for heating a wafer  11  by irradiating the wafer  11  with light in addition to light from the light source  9 . The light irradiated by the heating light source  50  is light near the wavelength range of infrared light, to which a photocurable resin is not sensitive. The heating mechanism also includes an adjuster that forms a predetermined irradiation dose distribution of light. In the present embodiment, a description will be given on the assumption that the heating light source  50  is integrated with the adjuster. Note that the adjuster may be provided separately from the heating light source  50 . For example, a liquid crystal device including a plurality of liquid crystal elements arranged in a region irradiated with light emitted from the heating light source  50  or a mirror device, including a plurality of mirrors arranged in a region irradiated with light, may also be used. Here, the mirror device may also be referred to as a “digital mirror device” or a “micro mirror device”. The liquid crystal device is capable of forming a predetermined irradiation dose distribution by independently adjusting voltages to be applied to a plurality of liquid crystal elements, whereas the mirror device is capable of forming a predetermined irradiation dose distribution by independently adjusting the surface directions of a plurality of mirrors. 
     The outer peripheral shape of the mold  7  is rectangular, and the mold  7  includes a pattern section (e.g., a circuit pattern, or the like)  71 , in which the concave and convex pattern is three-dimensionally formed on the surface of the facing wafer  11 . Also, the material of the mold  7  is a material such as quartz, or the like, through which the ultraviolet light  8  can pass. Furthermore, the mold  7  may be of a shape in which a cavity (concave portion)  7   b  for facilitating the deformation of the mold  7  is formed on the surface onto which the ultraviolet light  8  is irradiated. The cavity  7   b  has a circular planar shape, and the thickness (depth) of the cavity  7   b  is appropriately set, depending on the size or the material of the mold  7 . A light transmission member  13  may also be installed within an aperture region  17  in the mold holding mechanism  3 , to be described below, such that a space  12  enclosed by a part of the aperture region  17  and the cavity  7   b  is sealed, and the pressure in the space  12  may be adjusted by a pressure adjusting device (not shown). For example, the pressure adjusting device sets the pressure in the space  12  to be higher than the external pressure when the mold  17  is pressed against a resin  14  on the wafer  11 , so that the pattern section  7   a  is deflected into a convex shape toward the wafer  11 , and the pattern section  7   a  is brought into contact with the resin  14  from the central portion of the pattern section  7   a . With this arrangement, gas (air) is prevented from being entrapped between the pattern section  7   a  and the resin  14 , so that the resin  14  can be filled in every corner of the convex and concave portion of the pattern section  7   a.    
     The mold holding mechanism  3  has a mold chuck  15  that holds the mold  7  by suctioning/attracting the mold  7  using a vacuum suction force/and an electrostatic attraction force, and a mold drive mechanism  16  that holds the mold chuck  15  and moves the mold  7  (the mold chuck  15 ). Also, each of the mold chuck  15  and the mold drive mechanism  16  has the aperture region  17  at the central portion (the inside thereof), such that the ultraviolet light  8 , emitted from the light source  9  of the light irradiation unit  2 , is irradiated toward the wafer  11 . Furthermore, the mold holding mechanism  3  has a magnification correction mechanism (mold deformation mechanism)  18  that corrects the shape of the mold  7  (the pattern section  7   a ) by imparting an external force or a displacement to the side surface of the mold  7 . The magnification correction mechanism  18  is installed at the mold  7  holding side of the mold chuck  15 . The magnification correction mechanism  18  deforms the shape of the mold  7 , to thereby match the shape of the pattern section  7   a  formed on the mold  7  relative to the shape of the area on the substrate (substrate-side pattern area)  53  where the pre-existing pattern is formed. If it is difficult to match the shape of the pattern section  7   a  relative to the shape of the substrate-side pattern area  53 , the magnification correction mechanism  18  may also be adapted to make the shapes of both patterns close to each other (i.e., to reduce a shape differential between the two). While the one substrate-side pattern area  53  is shown in the figure, a plurality of substrate-side pattern areas are formed on the wafer  11 . 
     The mold drive mechanism  16  moves the mold  7  in the Z-axis direction so as to relatively bring the mold  7  into contact with the resin  14  on the wafer  11 , or to release the mold  7  from the resin  14 . Examples of an actuator employable for the mold drive mechanism  16  include a linear motor, an air cylinder, and the like. Also, the mold drive mechanism  16  may be constituted by a plurality of drive systems, such as a coarse movement drive system, a fine movement drive system, and the like, in order to accommodate position of the mold  7  with high accuracy. Furthermore, the mold drive mechanism  16  may have a position adjustment function for adjusting the position of the mold  7 , not only in the Z-axis direction, but also, in the X-axis direction, the Y-axis direction, or the θ (rotation about the Z axis) direction, a tilt function for correcting the tilt of the mold  7 , and the like. The contacting operation and the releasing operation performed by the imprint apparatus  1  may be realized by moving the mold  7  in the Z-axis direction, may be realized by moving the wafer stage  4  in the Z-axis direction, or may also be realized by moving both the mold  7  and the wafer stage  4  relative to each other. 
     The wafer  11  is, for example, a single crystal silicon substrate or an SOI (Silicon on Insulator) substrate, and an ultraviolet curable resin (hereafter referred to as “resin”)  14 , which is molded by the pattern section  7   a  formed in the mold  7 , is applied on the treatment surface of the wafer  11 . 
     The wafer stage  4  holds the wafer  11  and executes position matching between the mold  7  and the resin  14  before, or while the mold  7  is brought into contact with the resin  14  on the wafer  11 . The wafer stage  4  has a wafer chuck (substrate holding unit)  19 , on which a holding surface for holding the wafer  11  is formed, and a stage drive mechanism  20  that holds the wafer chuck  19  by a mechanical unit and is movable in the XY plane. 
       FIG. 2  is a schematic cross-sectional diagram illustrating the wafer chuck  19  of the present embodiment and the configuration of the peripheral portion thereof. The wafer chuck  19  includes a plurality of suction units  51  that holds the rear surface of the wafer  11  by suction. As shown in  FIG. 2 , the suction units  51  may be constituted by, for example, three suction units  51   a  to  51   c . These suction units  51   a  to  51   c  are connected to a pressure adjusting device  52  separate from the aforementioned pressure adjusting device, and function as a frictional force adjusting mechanism that adjusts the frictional force acting between the rear surface of the wafer  11  corresponding to a region including the substrate-side pattern area  53  and the surface of the wafer chuck  19 . The pressure adjusting device  52  adjusts the pressure to reduce the pressure between the wafer  11  and the suction units  51 , to thereby generate a suction force. Consequently, the pressure adjusting device  52  is capable of independently changing pressure values (suction forces) applied by the suction units  51   a  to  51   c , while holding the wafer  11  on the surface of the wafer chuck  19 . Note that the number of divided suction units  51  is not limited to three, but may be any number. Also, the wafer chuck  19  has a reference mark  21  that is used when the mold  7  is subjected to alignment on the surface thereof. 
     Examples of an actuator employable for the stage drive mechanism  20  include a linear motor. The stage drive mechanism  20  may also be constituted by a plurality of drive systems, such as a coarse movement drive system, a fine movement drive system, and the like, with respect to the X-axis and Y-axis directions. Furthermore, the stage drive mechanism  20  may have a drive system for adjusting the position of the wafer  11  in the Z-axis direction, a position adjustment function for adjusting the position of the wafer  11  in the  0  direction, a tilt function for correcting the tile of the wafer  11 , and the like. 
     The application unit  5  applies the resin (uncured resin)  14  to the wafer  11 . Here, the resin  14  is a photocurable resin (imprint material) having the property of being cured by receiving irradiation of the ultraviolet light  8 , and is appropriately selected depending on various conditions, such as the manufacturing process of semiconductor devices, or the like. The amount of the resin  14  to be ejected from the ejection nozzle of the application unit  5  is also appropriately determined by a desired thickness of the resin  14  to be formed on the wafer  11 , the density of the pattern to be formed, or the like. 
     The control unit  6  may control the operation, adjustment, and the like, of the components of the imprint apparatus  1 . The control unit  6  is constituted by a computer, or the like, and is connected to the components of the imprint apparatus  1  through a line so as to execute control of the components by a program, or the like. The control unit  6  of the present embodiment may control the operation of at least the light irradiation unit  2 , the wafer stage  4 , and the pressure adjusting device  52 . Note that the control unit  6  may be integrated with the rest of the imprint apparatus  1  (provided in a common housing) or may be provided separately from the rest of the imprint apparatus  1  (provided in a separate housing). 
     Also, the imprint apparatus  1  includes an alignment measurement system  22  that measures a positional shift between an alignment mark formed on the wafer  11  and an alignment mark formed on the mold  7  in each direction of the X-axis and the Y-axis as wafer alignment. Furthermore, the imprint apparatus  1  includes a base surface plate  24 , on which the wafer stage  4  is placed, a bridge surface plate  25  that fixes the mold holding mechanism  3 , and a strut  26  that is extended from the base surface plate  24 , and supports the bridge surface plate  25 . Furthermore, the imprint apparatus  1  includes a mold conveyance mechanism (not shown) that conveys the mold  7  from the exterior of the apparatus to the mold holding mechanism  3  and a substrate conveyance mechanism (not shown) that conveys the wafer  11  from the exterior of the apparatus to the wafer stage  4 . 
     Next, a description will be given of imprint processing performed by the imprint apparatus  1 . First, the control unit  6  places the wafer  11  on the wafer chuck  19  of the wafer stage  4  using the substrate conveyance mechanism, holds the wafer  11  on the holding surface of the wafer chuck  19  (holding step), and then moves the wafer stage  4  to the application position of the application unit  5 . Then, as an application step, the application unit  5  applies the resin  14  to the substrate-side pattern area (a shot area)  53 . Next, the control unit  6  moves the wafer stage  4  such that the substrate-side pattern area  53  on the wafer  11  is placed in a position directly below the pattern section  7   a  formed in the mold  7 . Next, the control unit  6  drives the mold drive mechanism  16  so as to press the mold  7  against the resin  14  on the wafer  11  (mold-pressing step) so that the mold  7  is brought into contact with the resin  14  (contacting step). During the contacting step, the resin  14  is filled in the convex and the concave pattern of the pattern section  7   a . Under this condition, as a curing step, the light irradiation unit  2  emits the ultraviolet light  8  from the rear surface (the top surface) of the mold  7 , and cures the resin  14  by the ultraviolet light  8  that has been transmitted through the mold  7 . Then, after the resin  14  is cured, the control unit  6  drives the mold drive mechanism  16  again, to thereby release the mold  7  from the resin  14  (mold-releasing step). By the aforementioned steps, a three-dimensionally shaped pattern (layer) of the resin  14  following the convex and concave pattern of the pattern section  7   a  is formed on the surface of the substrate-side pattern area  53  on the wafer  11 . Such a sequence of imprint operations is conducted two or more times, while the substrate-side pattern area  53  is changed under the drive of the wafer stage  4 , to thereby be able to form a plurality of patterns of the resin  14  on one wafer  11 . 
     Here, a description will be given of the suction control by means of the wafer chuck  19  when a pattern is formed on the wafer  11  for a predetermined shot.  FIG. 3  is a flowchart illustrating the sequence of operations from the mold-processing step to the curing step performed by the imprint apparatus  1 . At this time, a shot to be processed is located at the central portion of the wafer  11 , and, as shown in  FIG. 2 , the position is intended to correspond to the suction unit  51   b  provided in the wafer chuck  19 . In this case, the control unit  6  causes the pressure adjusting device  52  to reduce only the suction force generated by the suction unit  51   b , while maintaining the suction force generated by the suction units  51   a  and  51   c  prior to the correction of the shape of the pattern section  7   a  and the wafer  11  (step S  100 ). For example, the suction pressure of the suction unit  51   b  may be ambient pressure. If the suction pressure of the suction unit  51   b  is less than the suction force generated by the suction units  51   a  and  51   c , the suction pressure of the suction unit  51   b  may be ambient pressure or less. When the adjusting range of the irradiation dose of light emitted from the heating light source  50  is set in advance, the suction pressure of the suction unit  51   b  may be set such that the thermal deformation force W acting o the substrate-side pattern area  53  in a direction along the surface of the wafer  11  is greater than the maximum static frictional force F acting between the rear surface of the wafer  11  and the suction unit  51   b . When the temperature rise of the substrate-side pattern area  53  is give as “ΔT”, the thermal expansion coefficient thereof is given as “α”, and the modulus of elasticity thereof is given as “E”, all of which are determined depending on the irradiation dose, the thermal stress “σ” can be approximately expressed as the products of α, E, and ΔT. The thermal deformation force W, depending on the thermal stress “σ” and the cross-sectional area “S”, acts on the substrate-side pattern area  53 . When the maximum static frictional coefficient is given as “μ” and the vertical direction depending on the suction pressure is given as “N”, the maximum static frictional force F can be expressed as the product of μ and N. In other words, it is only necessary to satisfy the relationship of F&lt;W. Note that the region on the wafer  11  held by the suction unit  51   b  may be a region including at least the substrate-side pattern area  53  where the pattern is pre-formed on the wafer  11 . Next, the control unit  6  causes the alignment measurement system  22  to measure the positions of the mold  7  and the wafer  11  in the X-axis and the Y-axis directions (first alignment measurement, step S 101 ), and acquires information regarding differences between the shape of the pattern section  7   a  and the shape of the substrate-side pattern area  53  (acquiring step). However, when it is desired to correct only the shape of the substrate-side pattern area  53  formed on the wafer  11 , the control unit  6  may acquire only information regarding the shape of the substrate-side pattern area  53 . Then, the control unit  6  calculates the correction amount to a positional shift between the pattern section  7   a  and the substrate-side pattern area  53  based on the measurement result obtained in step S 101 . Next, the control unit  6  causes the heating light source  50  of the light irradiation unit  2  to heat the wafer  11  by irradiating the wafer  11  with light (deformation step: step S 102 ), and causes the magnification correction mechanism  18  to operate for inputting displacement (mold-deformation step: step S 103 ), and thus, the shapes of the pattern section  7   a  and the substrate side pattern area  53  are corrected. Since the maximum static frictional force acting between the rear surface of the wafer  11  corresponding to the substrate-side pattern area  53  and the holding surface is reduced, as described above, the thermal deformation force greater than the maximum static frictional force F can be applied to the wafer  11  in a direction along the surface thereof. Also, a temperature distribution is imparted to the substrate-side pattern area  53  by irradiating the substrate-side pattern area  53  with light having an irradiation dose distribution, whereby the shape of various components can be corrected. For example, among the calculated correction amount, a low-order component (e.g., a trapezoidal component) is corrected by heating the wafer  11  and a high-order component is corrected by displacement input, whereby the shape of the pattern section  7   a  can be preferably matched with the shape of the substrate-side pattern area  53 . When the shape of the pattern section  7   a  is matched with the shape of the substrate-side pattern area  53 , as a result of correction, the control unit  6  causes the pressure adjusting device  52  to reduce the suction pressure of the suction unit  51   b  again, so as to return the suction force generated by the suction unit  51   b  back to the level of the suction force generated by the suction units  51   a  and  51   c  (step S 104 ). Next, the control unit  6  causes the alignment measurement system  22  to measure the positions of the mold  7  and the wafer  11 , again, in the X-axis and the Y-axis directions (second alignment measurement: step S 105 ). Here, if it is determined that a positional shift is present between the mold  7  and the wafer  11 , the control unit  6  causes the mold drive mechanism  16  or the stage drive mechanism  20  to drive, to perform position adjustment between the mold  7  and the wafer  11  (step S 106 ). Then, the control unit  6  proceeds to the next process in the curing step. 
     The step of reducing the suction force generated by the suction unit  51   b  in step S 100  may be started, not only prior to the first alignment measurement in step S 101 , but also, after the first alignment measurement. It is preferable that the step of reducing the suction force generated by the suction unit  51   b  is performed prior to or during the deforming step of heating a substrate. In step S 102 , the correction of the shape of the substrate-side pattern area  53  on the wafer  11  is performed by heating due to the irradiation of light from the heating light source  50 , but the present invention is not limited thereto. For example, in a substrate deformation mechanism, instead of the heating light source  50 , a separately provided external force applying mechanism may impart an external force or input displacement in a planar direction directly to the wafer  11 , to thereby perform the correction of the shape of the substrate-side pattern area  53 . Furthermore, the shape of the substrate-side pattern area  53  may be matched with the shape of the pattern section  7   a  by performing shape correction only due to the heating of the wafer  11  in step S 102 , without performing the displacement input to the mold  7  in step S 103 . Note that steps S 102  and step S 103  may be performed inversely or in parallel. Also, it is preferable that the step of recovering the suction force generated by the suction unit  51   b  is performed after the deforming step, and prior to the mold-releasing step. 
     As described above, in the imprint apparatus  1 , the suction force generated by the suction unit  51   b  is reduced during a period from the mold-pressing step to the curing step, to thereby reduce a frictional force between the suction unit  51   b  and the rear surface of the wafer  11 , including at least the substrate-side pattern area  53 . Specifically, during the thermal deformation of the substrate-side pattern area  53  by the heating light source  50  of the light irradiation unit  2 , a frictional force acting between the wafer chuck  19  and the rear surface of the wafer  11 , corresponding to the substrate-side pattern area  53 , is reduced more than when the substrate-side pattern area  53  is not subjected to thermal deformation. Thus, the substrate-side pattern area  53  can be efficiently deformed by heating. In other words, the substrate-side pattern area  53  can be deformed by heating without an unnecessary increase in irradiation dose, and thus, an unnecessary rise in temperature of the peripheral members can be suppressed. Consequently, the adverse effect on superposition accuracy between the mold  7 , and the resin  14  on the wafer  11 , can be suppressed. Furthermore, at this time, the suction force generated by other suction units  51   a  and  51   c  remains maintained. Consequently, the wafer  11  is firmly fixed on the wafer chuck  19  by suction, even if the wafer  11  is subjected to thermal deformation, and thus, displacement of the entire wafer  11  is suppressed. There is no need to reduce a frictional force at all times during thermal deformation, but a frictional force may be reduced in at least a portion of the period during thermal deformation. 
     As described above, according to the present embodiment, the imprint apparatus  1 , which is advantageous for improving superposition accuracy between the mold  7  and the resin  14  on the wafer  11 , may be provided. 
     (Second Embodiment) 
     Next, a description will be given of an imprint apparatus according to a second embodiment of the present invention. The imprint apparatus of the present embodiment has the same configuration as that of the first embodiment, but the sequence of operations from the mold-pressing step to the curing step is changed.  FIGS. 4A and 4B  are flowcharts illustrating the sequence of operations from the mold-pressing step to the curing step performed by the imprint apparatus  1  according to the present embodiment. First, in the example shown in  FIG. 4A , after the mold-pressing step, the control unit  6  causes the magnification correction mechanism  18  to perform the displacement input to the mold  7  in step S  103 , in the sequence of operations of the first embodiment shown in  FIG. 3 , after the second alignment measurement in step S 105  (step S 205 ). Here, given that the alignment measurement in step S 201  is the first alignment measurement, a step corresponding to a step S 105 , shown in  FIG. 3 , is the second alignment measurement shown in  FIG. 4A  (step S 204 ). In this case, the control unit  6  causes the alignment measurement system  22  to perform the third alignment measurement the same as the second alignment measurement, again, after step S 205  (step S 206 ). Note that the third alignment measurement may be omitted by using the value obtained by the second alignment measurement. The processes in other steps are the same as those in the first embodiment. 
     On the other hand, in the example shown in  FIG. 4B , after the mold-pressing step, the control unit  6  causes the magnification correction mechanism  18  to perform the displacement input to the mold  7  in step S 103  in the sequence of operations of the first embodiment shown in  FIG. 3 , prior to the process of reducing the suction force generated by the suction unit  51   b  in step S 100  (step S 301 ). In this case, the control unit  6  causes the alignment measurement system  22  to perform the first alignment measurement, which is a process corresponding to step S 101  shown in  FIG. 3 , prior to step S 301  (step S 300 ). Also, the control unit  6  starts the process of reducing the suction force generated by the suction unit  51   b , which corresponds to step S 100  shown in  FIG. 3 , after step S 301  (step S 302 ). Then, after step S 304 , corresponding to step S 102  shown in  FIG. 3 , which is the correction of the shape of the substrate-side pattern area  53  on the wafer  11 , the control unit  6  raises the suction force generated by the suction unit  51   b  again (step S 305 ). The processes in the other steps are the same as those in the first embodiment. According to the present embodiment, as shown in  FIGS. 4A and 4B , the displacement input to the mold  7  by means of the magnification correction mechanism  18  is not performed while a frictional force is being reduced. Thus, the same effects as those in the first embodiment may be provided. In addition, unnecessary positional shift or unnecessary deformation of the wafer  11 , in association with deformation of the mold  7  upon inputting of displacement, can be further suppressed. 
     (Third Embodiment) 
     Next, a description will be given of an input apparatus according to a third embodiment of the present invention. In the imprint apparatus of the present embodiment, the configuration of the suction units  51  provided in the wafer chuck  19  according to the first embodiment is changed.  FIG. 5  is a schematic cross-sectional diagram illustrating an enlarged portion of the suction unit  51  ( 51   a ) provided in the wafer chuck  19  according to the present embodiment. The suction unit  51  has a plurality of suction pins  60  within the suction region, and a low-friction member  61  made of a low-friction material having a low friction coefficient against the wafer  11  is provided at the tip surface of each suction pin  60 , i.e., the surface in contact with the rear surface of the wafer  11 . Examples of such a low-friction material include DLC (diamond-like carbon). As described above, a frictional coefficient of the contact surface between the wafer chuck  19  and the wafer  11  is reduced, and thus, the wafer  11  (the substrate-side pattern area  53 ) can be efficiently deformed by heating with the heating light source  50  of the light irradiation unit  2 . 
     (Fourth Embodiment) 
     Next, a description will be given of an imprint apparatus according to a fourth embodiment of the present invention. In the imprint apparatus of the first embodiment, a description has been given by taking an example in which a frictional force, acting between the rear surface of the wafer  11  corresponding to the substrate-side pattern area  53  and the holding surface of the wafer chuck  19 , is adjusted. In the present embodiment, a description will be given taking an example in which a thermal deformation force acting on the substrate-side pattern area  53  is adjusted, without adjusting the friction force. Since the configuration of the imprint apparatus of the present embodiment is the same as that of the first embodiment, except that the control unit  6  is different in terms of function, a description of the configuration thereof will be omitted, while focusing on the function of the control unit  6 . 
       FIG. 6  is a flowchart illustrating the sequence of operations from the mold-pressing step to the curing step performed by the imprint apparatus  1  of the present embodiment. First, the control unit  6  reads the value of the suction pressure of the suction unit  51   b  provided in the wafer chuck  19  after the mold-pressing step (step S 400 ). Next, the control unit  6  orders to perform first alignment measurement corresponding to the process in step S 101  shown in  FIG. 3  (step S 401 ). The control unit  6  calculates the irradiation dose of light irradiated on a wafer, based on the value of the suction pressure of the suction unit  51   b  obtained in step S 400  (step S 402 ). Next, the shape of the substrate-side pattern area  543  is corrected by irradiating the wafer  11  with the calculated irradiation dose of light (step S 403 ). Then, the displacement input to the mold  7  (step S 404  corresponding to step S 103  shown in  FIG. 3 ) and the second alignment measurement (step S 405  corresponding to step S 105  shown in  FIG. 3 ) are executed. When a positional shift is present between the mold  7  and the wafer  11 , position adjustment between the mold  7  and the wafer  11  (step S 406 ) is performed. Then, the curing step is performed. 
     A description will be given of an irradiation dose to be calculated in step S 402 , with reference to  FIG. 7 . The heating mechanism irradiates the irradiation region on the wafer  11 , including at least the substrate-side pattern area  53  with light obtained as the sum of a uniform irradiation dose a and an irradiation dose b having a distribution. Here, the irradiation dose a is a uniform irradiation dose with respect to an irradiation region, in which a thermal deformation force applied to the irradiation region on the wafer  11  in a direction along the plane thereof is greater than the maximum static frictional force acting between the rear surface of the irradiation region on the wafer  11  and the suction unit  51 . The irradiation dose b is an irradiation dose having a distribution with respect to an irradiation region depending on the correction amount of the substrate-side pattern area  53  calculated by the control unit  6 , or depending on the value obtained by subtracting the amount of deformation of the wafer  11  caused by the irradiation dose a from the correction amount. 
     It is preferable that the irradiation dose a is determined depending on the suction pressure of the suction unit  51   b  (suction force). When the temperature rise of the substrate-side pattern area  53  is given as “ΔT”, the thermal expansion coefficient thereof is given as “α”, and the modulus of elasticity thereof is given as “E”, all of which are determined depending on the irradiation dose. The thermal stress “σ” can be approximately expressed as the product of α, E, and ΔT. The thermal deformation force W depending on the thermal stress “σ” and the cross-sectional area “S” acts on the substrate-side pattern area  53 . When the maximum static frictional coefficient is given as “μ” and the vertical directional force depending on the suction pressure is given as “N”, the maximum static frictional force F can be expressed as the product of μ and N. In other words, it is only necessary to satisfy the relationship F&lt;W. It is preferable that the irradiation dose b is determined on the basis of irradiation dose data prepared in advance, corresponding to the correction amount or the relationship in which the correction amount is associated with the irradiation dose. 
     In the present embodiment, although the suction pressure of the suction unit  51  is not adjusted for reducing a frictional force, the wafer  11  is heated by the irradiation of light at the irradiation dose a, such that thermal deformation force does not exceed the maximum static frictional force. Consequently, the shape of the substrate-side pattern area  53  can be efficiently corrected, as in the first embodiment. The present embodiment can be combined with pressure adjustment in the first embodiment. 
     (Article Manufacturing Method) 
     A method of manufacturing a device (e.g., a semiconductor integrated circuit element, a liquid display element, or the like), as an article, may include a step of forming a pattern on a substrate (e.g., a wafer, a glass plate, a film-like substrate, or the like) using the imprint apparatus described above. Furthermore, the manufacturing method may include a step of etching the substrate on which a pattern has been formed. When other articles, such as a patterned medium (storage medium), an optical element, or the like, is manufactured, the manufacturing method may include other steps of processing the substrate on which a pattern has been formed, instead of the etching step. The article manufacturing method of the present embodiment has an advantage, as compared with a conventional article manufacturing method, in at least one of performance, quality, productivity, and production cost of an article. 
     While the embodiments of the present invention have been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary 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.