Planarization device, planarization method, and article manufacturing method

Abstract

To provide a method of real time leveling control between a superstrate and a substrate.SOLUTION: A contact force model is identified which indicates a relationship between total contact force for planarization of a formable material between a superstrate and a substrate and a force component of the total contact force along each of a plurality peripheral axes. A set point force required for performing the planarization is determined. Each force component is calculated on the basis of the contact force model. The planarization is executed by applying each force component along a corresponding axis of the plurality of peripheral axes. The contact force model is identified on the basis of a parallel condition between two contact surfaces of a superstrate chuck for retaining the superstrate and a stack of the superstrate, the substrate, and the formable material between the superstrate and the substrate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to substrate processing, and more particularly, to surface planarization processing in semiconductor manufacturing.

Background Art

[0002] Planarization techniques are useful in manufacturing semiconductor devices. For example, the processes for fabricating semiconductor devices include repeating the addition of materials to the substrate and the removal of materials from the substrate. This process can generate a layered substrate with irregular height variations (i.e., topography), and as more layers are added, the height variations of the substrate can increase. The height variations have a negative impact on the ability to add further layers to the layered substrate. Separately, a semiconductor substrate (e.g., a silicon wafer) itself is not always perfectly flat and can include initial surface height variations (i.e., topography). One way to address this problem is to planarize the substrate between deposition steps. Various lithography patterning methods benefit from patterning on a planar surface. In ArF laser-based lithography, planarization improves the depth of focus (DOF), critical dimension (CD), and critical dimension uniformity. In extreme ultraviolet lithography (EUV), planarization improves the placement of features and the DOF. In nanoimprint lithography (NIL), planarization improves feature filling and CD control after pattern transfer.

[0003] A planarization technique, sometimes called inkjet-based adaptive planarization (IAP), involves dispensing a variable drop pattern of a polymeric material between the substrate and a superstrate, and the drop pattern varies depending on the substrate topography. The superstrate then contacts the polymeric material, and thereafter, the material is polymerized on the substrate and the superstrate is removed. Improvements to planarization techniques, including IAP technology, are desired, for example, to improve all wafer processes and semiconductor device manufacturing.

Summary of the Invention

[0004] A method for real-time leveling control of a superstrate and a substrate is provided. A contact force model is identified that shows the relationship between the total contact force for planarization of a formable material between the superstrate and the substrate and the force components of the total contact force along each of a plurality of peripheral axes. A setpoint force required to perform the planarization is determined. Each force component is calculated based on the contact force model. Planarization is performed by applying each force component along a corresponding axis among the plurality of peripheral axes. The contact force model is identified based on the parallel state between two contact surfaces, namely, a superstrate chuck for holding the superstrate and a stack of the superstrate, the substrate, and the formable material between the superstrate and the substrate. Each of the plurality of peripheral axes may extend in a direction parallel to an axis along which a planarization head moves orthogonally to a reference plane. Each of the plurality of peripheral axes may be equidistant from the center of the superstrate chuck and may be uniformly distributed in the azimuthal direction around the superstrate, the substrate, and the stack of the formable material. The reference plane may have a parallelism with the upper surface of the substrate chuck within 100 milliradians.

[0005] The above method may further include a step of estimating the force component of the total contact force by measuring, at each of a plurality of positions along a first axis among the plurality of peripheral axes, the force generated by the actuator along each of the plurality of peripheral axes, and adjusting the measured force so as to obtain an estimated contact force based on the mechanical compliance force and the calibration spring force generated by the parallel state. Also, the calibration spring force may be estimated before performing planarization. For example, the planarization head including the super straight chuck is moved to a first position where the stack is disposed upward when planarization is being performed. After the planarization head is settled at the first position, information on the position and the applied control force of the planarization head is collected. The planarization head is moved to a second position where the stack is disposed downward when planarization is being performed. After the planarization head is settled at the second position, information on the position and the applied force of the planarization head is collected. Then, the spring force is calibrated based on the information on the position and the applied force collected from the upward and downward movements of the planarization head. The spring force may be calibrated by moving the planarization head and a substrate chuck for holding the substrate away from each other before moving the planarization head. The calibration spring force of the plurality of peripheral axes may be reset by collecting and averaging a plurality of measurements of the estimated contact force over a predetermined period.

[0006] An apparatus is provided for leveling a superstrate together with a substrate during a planarization process. The apparatus includes a force controller, a position controller, and a force estimator. The force controller adjusts a setpoint force based on a specific contact model and adjusts a setpoint position of the position controller based on a feedback law and a difference between the setpoint force and an estimated force required to perform the planarization process. The position controller is configured to adjust an applied force to a planarization head based on a difference between a measured position and the setpoint position that depends on an output of the force controller and a feedback control law regarding a parallel state between two contact surfaces. The position controller receives information from an encoder for measuring positions along a plurality of peripheral axes and transmits control information to a plurality of actuators for applying forces along the plurality of peripheral axes to process the parallel state. The force estimator receives control effort information from the position controller and is configured to provide a calibration spring force for estimating a contact force using the setpoint position as an input, a total contact force for the planarization process, and a contact force model configured to provide information indicating a relationship between force components of the total contact force along each of a plurality of peripheral axes of coordinates based on a contact point position adjusted to specify the contact force model. The contact force model is specified based on a parallel state between two contact surfaces of a superstrate chuck for holding the superstrate and a stack of the superstrate, the substrate, and a moldable material between the superstrate and the substrate.

[0007] The apparatus may further include an amplifier configured to rotate a contact curve smoothed by a digital filter having an amplified position scale configured to detect a plurality of initial contact positions for measuring the parallel state. The position controller may be further configured to measure the parallel state based on rotation of the stack.

[0008] A method of manufacturing an article is provided. In the method, a formable material is supplied onto a substrate. A flattening head is moved so as to approach the vicinity of a contact surface between a superstrate and a contact surface between the superstrate and a stack of the substrate. A force offset is reset before contact between the superstrate and the substrate. A contact force model indicating a relationship between a total contact force for flattening the formable material between the superstrate and the substrate and force components of the total contact force along each of a plurality of peripheral axes is specified. A setpoint force required to perform the flattening is determined. Each force component is calculated based on the contact force model. Flattening is performed by adding each force component along a corresponding axis among the plurality of peripheral axes. The contact force model is specified based on a parallel state between two contact surfaces, namely, a superstrate chuck for holding the superstrate and a stack of the superstrate and the substrate. Each of the plurality of peripheral axes may extend in a direction parallel to an axis along which the flattening head moves orthogonally to a reference plane. Each of the plurality of peripheral axes may be equidistant from the center of the superstrate chuck and may be uniformly distributed in an azimuthal direction around the stack of the superstrate, the substrate, and the formable material. The reference plane may have a parallelism within 100 milliradians with respect to the upper surface of the substrate chuck.

[0009] The total contact force may be estimated by measuring, at each of a plurality of positions along a first axis among the plurality of peripheral axes, the forces generated by the actuator along each of the plurality of peripheral axes, and adjusting the measured forces so as to obtain an estimated contact force based on a mechanical compliance force and a calibration spring force generated by the parallel state. The mechanical compliance force may include a spring force. Further, the spring force may be calibrated by the following steps before performing planarization. The planarization head including the super straight chuck is moved to a first position where the stack is disposed upward when planarization is being performed. After the planarization head is settled at the first position, information on the position and the applied force of the planarization head is collected. The planarization head is moved to a second position where the stack is disposed downward when planarization is being performed. After the planarization head is settled at the second position, information on the position and the applied force of the planarization head is collected. The spring force is calibrated based on the information on the position and the applied force collected from the upward and downward movements of the planarization head. By collecting and averaging a plurality of measurements of the estimated contact force over a predetermined period, the force offset for calibrating the plurality of peripheral axes may be reset. The parallel state between the two contact surfaces may be measured based on the rotation of the stack around an axis perpendicular to the displacement axis of the planarization head.

[0010] These and other objects, features, and advantages of the present disclosure will become apparent by reading the following detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings and the provided claims.

Brief Description of the Drawings

[0011] To enable a detailed understanding of the features and advantages of the present invention, a more specific description of embodiments of the present invention can be made by referring to the embodiments shown in the accompanying drawings. However, it should be noted that the accompanying drawings only show typical embodiments of the present invention, and thus, the present invention can recognize other equally effective embodiments, and should not be regarded as limiting the scope of the present invention.

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[0025] Throughout the drawings, unless otherwise specified, the same reference numerals and letters are used to denote similar features, elements, components, or parts of the illustrated embodiments. Further, although the present disclosure is described in detail with reference to the drawings, it is made in connection with exemplary embodiments that are useful for explanation. It is intended that changes and modifications can be made to the described exemplary embodiments without departing from the true scope and spirit of the disclosure of the subject matter defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Planarization system FIG. 1 shows an apparatus 100 that can be used, inter alia, to planarize or shape a film on a substrate 102, such as a wafer. The substrate 102 may be coupled to a substrate chuck 104. The substrate chuck 104 may be a vacuum chuck, a pin type chuck, a groove type chuck, an electrostatic chuck, an electromagnetic chuck, etc., but is not limited thereto.

[0027] The substrate 102 and the substrate chuck 104 may be further supported by a substrate positioning stage 106. The substrate positioning stage 106 can provide translational and / or rotational movement along one or more of the x, y, z, θ, ψ, and φ axes. Also, the substrate positioning stage 106, the substrate 102, and the substrate chuck 104 may be positioned on a base (not shown). The substrate positioning stage may be part of a positioning system.

[0028] Spaced apart from the substrate 102 is a superstrate 108 having a working surface 112 facing the substrate 102. The superstrate 108 may be formed of materials including, but not limited to, fused silica, quartz, silicon, organic polymers, siloxane polymers, borosilicate glass, fluorocarbon polymers, metals, hardened sapphire, etc. In one embodiment, the superstrate is readily transparent to UV light. The surface 112 generally has the same area size as or is slightly smaller than the surface of the substrate 102. The surface 112 of the superstrate 108 can include a flat contact surface. In another embodiment, the contact surface 112 can include features that define any original pattern that forms the basis of a pattern formed on the substrate 102. In another embodiment, the superstrate 108 may be smaller than the substrate 102, and the planarization process may be performed in a step-and-repeat manner.

[0029] The super straight 108 may be connected to or held by the super straight chuck 118. The super straight chuck 118 may be a vacuum chuck, a pin type chuck, a groove type chuck, an electrostatic chuck, an electromagnetic chuck, and / or other similar chuck types, but is not limited thereto. The super straight chuck 118 may be configured to apply stress, pressure, and / or strain that varies across the super straight 108 to the super straight 108. In one embodiment, the super straight chuck may be easily transparent to UV light. The super straight chuck 118 may include a system such as a zone-based (partition-based) vacuum chuck, an actuator array, a pressure bladder, etc., which can apply a pressure difference to the back surface of the super straight 108 to bend and deform the super straight. In one embodiment, the super straight chuck 118 includes a zone-based vacuum chuck that can apply a pressure difference to the back surface of the super straight, and bends and deforms the super straight as further detailed herein.

[0030] The super straight chuck 118 can be connected to a head 120 (also known as a flattening head, an imprint head, or a shaping head) that is part of a positioning system. The head 120 may be movably connected to a bridge (not shown). The head 120 may include one or more actuators such as a voice coil motor, a piezoelectric motor, a linear motor, a nut and screw motor, etc., which are configured to move the super straight chuck 118 relative to the substrate 102 at least in the z-axis direction and potentially other directions (e.g., x, y, θ, ψ, and φ axes). For example, the head 120 can include a first actuator that moves along a first z-axis z1, a second actuator that moves along a second z-axis z2, and a third actuator that moves along a third z-axis z3. When all the actuators displace the super straight by the same distance along a plurality of axes, the super straight does not tilt or incline. If the actuators produce non-uniform amounts of displacement along each axis, the tilt and inclination of the super straight can be adjusted. There is a moving body plane that intersects each end point of the actuators, and this tilt and inclination change according to the positions of the actuators along a plurality of peripheral axes. The plurality of peripheral axes may be equidistant from the center of the super straight chuck 118. The plurality of peripheral axes can be uniformly distributed azimuthally around the head 120 and around the stack (laminate) of the super straight 108, the substrate 102, and the formable material 124. The moving body plane may be parallel to the chucking surface of the super straight chuck 118. The working surface 112 is also parallel to the moving body plane. Each of the plurality of peripheral axes may extend parallel or azimuthally with respect to an axis orthogonal to the reference plane.

[0031] Apparatus 100 may further comprise a fluid dispenser 122. The fluid dispenser 122 may also be movably coupled to the bridge. In one embodiment, the fluid dispenser 122 and the head 120 share one or more of all the positioning components. In an alternative embodiment, the fluid dispenser 122 and the head move independently of each other. The fluid dispenser 122 may be used to deposit droplets of a liquid formable material 124 (e.g., a photocurable polymerizable material) onto the substrate 102, and the volume of the deposited material varies across the region of the substrate 102 based at least in part on its topographic profile. Different fluid dispensers 122 may use different techniques for dispensing the formable material 124. If the formable material 124 is jetable, an inkjet-type dispenser may be used to dispense the formable material. For example, thermal inkjetting, microelectromechanical system (MEMS)-based inkjetting, valve jet, and piezoelectric inkjetting are common techniques for dispensing jetable liquids.

[0032] Apparatus 100 further comprises a curing system including a radiation source 126 that directs actinic energy, such as UV radiation, along an exposure path 128. The head 120 and the substrate positioning state 106 may be configured to position the superstrate 108 and the substrate 102 in overlay with the exposure path 128. The radiation source 126 sends actinic energy along the exposure path 128 after the superstrate 108 contacts the formable material 128. FIG. 1 shows the exposure path 128 when the superstrate 108 is not in contact with the formable material 124. This is done for illustrative purposes so that the relative positions of the individual components can be easily identified. One skilled in the art will understand that the exposure path 128 does not substantially change when the superstrate 108 contacts the formable material 124.

[0033] The apparatus 100 further comprises a camera 136 arranged to view the spread of the formable material 124 when the superstrate 108 contacts the formable material 124 during the planarization process. FIG. 1 shows the optical axis 138 of the image field of the field camera. As shown in FIG. 1, the apparatus 100 can include one or more optical components (dichroic mirrors, beam combiners, prisms, lenses, mirrors, etc.) that couple actinic radiation to the light detected by the camera 136. The camera 136 can include one or more of a CCD, sensor array, line camera, and photodetector configured to collect light at wavelengths that exhibit contrast between the area under the superstrate 108 and in contact with the formable material 124 and the area under the superstrate 108 but not in contact with the formable material 124. The camera 136 may be configured to provide an image of the spread of the formable material 124 under the superstrate 108 and / or the separation of the superstrate 108 from the cured formable material 124. Additionally, the camera 136 may be configured to measure interference fringes that change as the formable material 124 spreads into the gap between the surface 112 and the substrate surface.

[0034] The apparatus 100 can be adjusted, controlled, and / or directed by one or more processors 140 (controllers) that communicate with one or more components and / or subsystems such as the substrate chuck 104, the substrate positioning stage 106, the super straight chuck 118, the head 120, the fluid dispenser 122, the radiation source 126, and / or the camera 136. The processor 140 can operate based on instructions in a computer-readable program stored in the non-transitory computer memory 142. The processor 140 can be or include one or more of a CPU, MPU, GPU, ASIC, FPGA, DSP, and a general-purpose computer. The processor 140 can be a dedicated controller or a general-purpose computing device applied to a controller. Examples of non-transitory computer-readable memory include, but are not limited to, RAM, ROM, CD, DVD, Blu-Ray, hard drive, network-attached storage (NAS), an intranet-connected non-transitory computer-readable storage device, and an internet-connected non-transitory computer-readable storage device.

[0035] During operation, the flattening head 120, the substrate positioning stage 106, or both vary the distance between the super straight 108 and the substrate 102 to define a desired space (a three-dimensional bounded physical extent) filled with the formable material 124. For example, the head 120 can be moved towards the substrate and apply a force to the super straight 108 such that, as further detailed herein, the super straight contacts a droplet of the formable material 124 and spreads the droplet.

[0036] Planarization process The planarization process includes the steps schematically shown in FIGS. 2A - 2C. As shown in FIG. 2A, the formable material 124 is dispensed onto the substrate 102 in the shape of droplets. As previously described, the substrate surface has some topography, which may be known based on previous processing operations or may be measured using a profilometer based on optical interference effects such as a Zygo NewView 8200, AFM, SEM, or optical surface profiler. The local volume density of the deposited formable material 124 varies according to the substrate topography. Next, the superstrate 108 is placed in contact with the formable material 124. In another embodiment, the superstrate 108 also has topography and the planarization process also includes forming features within the formable material.

[0037] FIG. 2B shows the post - contact step after the superstrate 108 is in full contact with the formable material 124 but before the polymerization process begins. When the superstrate 108 contacts the formable material 124, the droplets combine to form a film 144 of the formable material that fills the space between the superstrate 108 and the substrate 102. Preferably, the filling process is performed in a uniform manner such that no air or bubbles are trapped between the superstrate 108 and the substrate 102 in order to minimize unfilled defects. The polymerization process or curing of the formable material 124 may be initiated by actinic radiation (e.g., UV radiation). For example, the radiation source 126 of FIG. 1 may provide actinic radiation that cures, solidifies, and / or cross - links the film 144 of the formable material to define a cured planarization layer 146 on the substrate 102. Alternatively, the curing of the film 144 of the formable material may also be initiated by using heat, pressure, chemical reactions, other types of radiation, or any combination thereof. Once cured, the planarization layer 146 is formed and the superstrate 108 may be separated therefrom. FIG. 2C shows the cured planarization layer 146 on the substrate 102 after separation of the superstrate 108.

[0038] In an alternative embodiment where the contact surface of the superstrate 108 includes pattern features, a process similar to that described above can be performed to form a patterned layer on the substrate 102 (e.g., "whole wafer" patterning). Whole wafer processing is useful in semiconductor device manufacturing as well as in biological or optical device manufacturing. Such whole wafer processing can further be adapted such that the local film thickness can be adjusted as a function of the desired local film thickness.

[0039] During the planarization spread, the bending curvature of the superstrate can affect the planarization throughput, and the contact line movement speed of the formable material can affect the uniformity of the residual film thickness (RLT). The planarization spread is the period during which the formable material 124 spreads due to capillary action and the curvature of the superstrate 108 to form an uncured planarization film. Before the superstrate 108 contacts the formable material 124 on the substrate 102, pressure is applied in the intermediate zone 118M to bend the superstrate 108, and then the working surface 112 can be moved towards the substrate 102. The superstrate starts to contact the formable material 124 on the substrate 102 from the center of the substrate, and then, by using multivariable control such as controlling the contact force and the pressure applied to the intermediate zone 118M, the contact line can move smoothly to the edge of the substrate. At the end of the planarization spread, the superstrate 108 contacts the formable material 124 across the entire substrate, and the superstrate conforms to the shape of the substrate.

[0040] While the superstrate is being chucked and re-chucked on the substrate, the leveling between the superstrate and the substrate is one of the important requirements for the planarization process. The parallel state often affects the diffusion throughput. While re-chucking the superstrate, the substrate, and the stack (laminate) of the cured moldable material sandwiched between the superstrate and the substrate, the vacuum pressure can bend the superstrate so as to generate separation cracks along the edge of the superstrate or propagate the initial cracks generated by the push pins to the edge of the superstrate. The bending moment can be significantly reduced by the leakage caused by the gap between the stack and the superstrate chuck, which is sensitive to the parallel state between the contact surfaces of the superstrate and the substrate. Therefore, the chucking contact conditions mainly depend on the gap (spacing) between the chucking surface of the stack and the superstrate chuck, which can be determined by the relative position and direction between the chucking surfaces, i.e., the leveling offset, especially at the edge of the chucking surface.

[0041] Super straight substrate leveling system Figure 3 shows a system for measuring and controlling the leveling offset. This system can calculate and adjust the leveling offset based on the measurement results of the inclination of the contact surface between the template (superstrate) and the substrate using upward and downward non-contact sensors, and align the surface inclination so as to adjust the leveling offset. However, the leveling accuracy can still be limited by the flatness of the surfaces of the template and the substrate, the stage vertical error operation, the sampling points, the sensor accuracy, and other characteristics. Furthermore, the measurement time increases rapidly as the number of sampling points and the surface area increase, which can have a significant impact on the throughput. As shown in FIG. 3, the real-time leveling measurement control system includes a flattening head that includes a fixed body 1 and a moving body 3. The fixed body 1 and the moving body 3 are connected to each other by a weight compensation spring flexure 16. The movement of the moving body 3 of the flattening head is detected and measured by a position sensor 2, and the movement of the moving body 3 is controlled via an actuator that moves a super straight along a plurality of z-axes (z1, z2, and z3) and the weight compensation spring flexure 16 based on the measurement result of the position sensor 2. The flattening head further includes a super straight chuck 17 for holding the super straight 5, and the super straight chuck may be planar or may include a pattern that is transferred to a formable material formed on the substrate of the substrate 14. The substrate 14 is held by a substrate chuck 7 that can be mounted on an XYθ stage. The XYθ stage includes a θ stage 9 that supports and controls the substrate 14 via a mechanical compliant member 8, a Y stage 13 connected to the θ stage 9 via both the mechanical compliant member 8 and an air bearing member 10, and a Y stage 13 connected to the X stage 11 via the air bearing member 10. Both the X stage 11 and the Y stage 13 are disposed on a granite table 12 via the air bearing member 10. The body of the super straight 5 can have a thickness in the range of 30 microns to 2000 microns. In one embodiment, the substrate 14 and the super straight 5 can have a diameter of 300 mm. Each of the substrate 14 and the super straight 5 can have a diameter of 300 mm to 600 mm. Alternatively, the diameter of the substrate 14 and the super straight 5 may be between 300 mm and 450 mm. In another embodiment, the diameter of the substrate 14 and the super straight 5 may be between 450 mm and 600 mm.

[0042] During chucking and unchucking, the super straight chuck 17 may be moved up and down and swung about a reference plane, for example, a plane defined by the X-axis and the Y-axis. The movement of the super straight chuck 17 can be detected and measured by a downward displacement sensor 4 attached to the contact surface of the moving body 3 of the flattening head and an upward displacement sensor 6 attached to the concave peripheral region of the substrate chuck 7. FIG. 4 is an exploded view of the real-time leveling measurement control system shown in FIG. 3. A plurality of encoders 15 for detecting the position of the moving body 3 of the flattening head along a plurality of parallel axes are installed around the flattening head. Each of the encoders 15 may include an encoder scale 18 attached around the moving body 3 and an encoder sensor head 19 provided around the fixed body 1. This system includes a plurality of actuators for generating forces along a plurality of parallel axes for performing planarization. Each of the actuators may include a magnet 20 and a voice coil 21. The contact force generated by the actuator can be measured based on the flow of current flowing through the voice coil 21 or determined based on the control effort information sent to the actuator by the processor 140 or the position controller. The flexure 16 can be installed on the surfaces of the fixed body 1 and the moving body 3 to guide the operation and provide compliance between the fixed body 1 and the moving body 3. The plurality of peripheral axes may extend in a direction parallel to the axis along which the flattening head moves orthogonally to the reference plane. The reference plane may be defined by each bearing point of the flexure 16 associated with each of the actuators. The reference plane may be substantially parallel to the upper surface of the substrate chuck. Substantially parallel may be a parallelism within 100 milliradians.

[0043] Estimation of contact force Since the compliance of the entire stack including at least the superstrate and the substrate includes mechanical compliance and an air bearing, the estimated contact force between the superstrate 5 and the substrate 14 depends on the compliance and the leveling (parallel state) between the superstrate 5 and the substrate 14. A leveling control system based on a force for measuring and controlling a leveling offset based on a force estimated using a hybrid force-position control method is shown in FIG. 5. The hybrid control system includes a force controller 41 and a position controller 42. As shown in FIG. 5, the setpoint force F sept (s) is input to the force controller 41. Here, s is a complex variable, and F sept (s) represents the Laplace transform of the time series of the values of the setpoint force. The setpoint force F sept (s) may be a function (linear function, non-linear function, or via a calibration table) of the current flowing through the voice coil 21, as shown in FIG. 4. F FB (s) generates an output to the position controller 42 based on a feedback control law and the difference between the setpoint force and the estimated contact force which is the setpoint position input of the position controller 42. The feedback control law is a mathematical equation or look-up table used by the position controller to determine an output based on one or more inputs. The control law may take into account the current input, past inputs, and predicted future inputs. P FB (s) generates a force applied to the flattening head based on a feedback control law and the difference between the position measured by the encoder and the setpoint position P sept (s) obtained from the force controller 41. Also, the setpoint position P sept(s) can be adjusted by a position offset that restores and / or maintains the parallelism between two contact surfaces (e.g., between a super straight chuck and a stack of super straight and substrate) fed back from an encoder 44, which includes an encoder scale 18 and an encoder sensor head 19 as shown in FIG. 4. During re-chucking, the two contact surfaces can include the chucking surface of the super straight chuck that contacts the back surface of the super straight, and the back surface of the super straight that faces the working surface on the stack including the super straight 108, the cured planarization layer 146, and the substrate 102. Before curing the formable material, the two contact surfaces can include the working surface 112 of the super straight 108 and the surface of the substrate 102 on which the formable material 124 is deposited. Also, the output of the force estimator 43 is used to identify the contact model 46 and enables real-time adjustment of the contact force along each axis to perform real-time leveling control and measurement. The setpoint force F FB (s) is adjusted based on information from both feedback from the contact model 46 and the force estimator 43.

[0044] To estimate the offset method of the contact force and the reset force, the contact force at a given height position Z of the planarization head along a plurality of peripheral axes (z i ) can be estimated as follows. JPEG0007699506000001.jpg9162Here, Z is the height of the planarization head along the displacement direction or displacement axis (Z-axis) of the planarization head relative to the stack of super straight, cured formable material, and substrate; z i is an axis that extends substantially parallel to the Z-axis and intersects the peripheral position of the stack; i indicates the index (indicator) of each peripheral z-axis; F m (z i ) indicates the estimated force at a given position z i and the height Z of the planarization head; F I (z irepresents the force generated from each voice coil and is a function (proportional thereto) of the current flowing through one of the voice coils at a given position of each z-axis subject to disturbance; F cal (z i ) represents the spring force at a given position z of each z-axis i . F offset (z i ) represents the force offset of each z-axis to compensate for the disturbance in the steady state. The spring force F cal (z i ) and the offset force F offset (z i ) are calibrated and reset based on the definition of the contact force that becomes zero when there is no contact between the super straight and the substrate. The force offset is stored in the computer memory to handle the quasi-static disturbance that is set to zero at the start of the tool control system. Each force is a set having one element for each z-axis. For example, if there are three peripheral z-axes, there are three elements associated with each force, one for each of the three peripheral z-axes.

[0045] The spring force F cal (z i ) can be calibrated statically or dynamically. To calibrate the spring force statically, the flattening head, i.e., the flattening head can be moved to a position, for example, about 0.3 mm above the flattening rising plane. The flattening rising plane is a position 0.1 to 10 mm above the flattening plane and is, for example, the position where the working surface 112 is held before flattening for the safety of other operations during dispensing or substrate loading. The position information and control information (information on the force applied for control) along the three peripheral axes are collected until the flattening head is set. The control information is F I (z irepresents. The control information can be equal to, proportional to, or a function of the current (measured or commanded) supplied to each voice coil. Depending on the motion damping state of the flattening head, the settling time until the flattening head settles can be from 0.001 to 10 seconds, provided that there is no longer any acceleration or deceleration of the working surface. Next, the flattening head is moved downward to the measurement position in configured steps, for example, 0.025 mm. Then, after the flattening head is set to a parallel state at the measurement position as indicated by the encoder 44, the control information is collected. The movement and collection of the control information are repeated until a position about 0.3 mm below the flattening plane is reached. Spring force F cal (z i ) The calibration sample results are illustrated as shown in FIG. 7. To dynamically calibrate the spring force, the flattening head is moved to a position 0.3 mm above the flattening up plane, and then moved at a constant low speed, for example, 0.1 mm / second, to a position about 0.3 mm below the flattening plane to minimize the influence of acceleration on the measurement. The position information and control information of the flattening head along the three peripheral axes are collected during the movement and used to dynamically calibrate the spring force. Spring force F cal (z i ) is calibrated in such a way that the working surface 112 never contacts another surface. Contact may be prevented, for example, by lowering the substrate chuck 104 relative to the working surface 112 or by translating the substrate chuck 104 away from the working surface 112.

[0046] When there are dynamic or quasi-static disturbances and the super straight and the substrate are not in contact with each other, the repulsive force F m (Z i ) is no longer zero. The force offset is updated so that the force Fm(zi) is equal to zero. JPEG0007699506000002.jpg9162 Here, the updated force offset F offset_update (z i ) is the previous force offset F offset (z iUpdate (0). To smooth the measurement noise, about 100 measured force values Fm(zi) can be collected over several milliseconds to smooth the measurement noise.

[0047] To determine the leveling state (parallel state) between the super straight and the substrate, as shown in FIG. 4, R x and R y It is also beneficial to understand that the tip inclination of the moving body 3 and the working surface 112 described by are used by the position controller 42, and that, as shown in FIG. 6, the respective tip inclinations Rx and Ry of the moving body 3 and the working surface 112 at the Z position are measured and controlled by three peripheral Z-axis position control systems. Referring to both FIGS. 4 and 6, three actuators near the sensor positions z1, z2, and z3 apply forces F1, F2, and F3 to the working surface 112 during planarization and to the moving body transferred to the stack of the super straight, formable material, and wafer (substrate) during rechecking. The contact force can be detected after subtracting the spring force and resetting the quasi-static disturbance generated from the planarization module environment. The Z position of the center of the super straight chuck in the xy plane, and the relative rotation R of the moving body 3 and the fixed body 1 x and R y can be expressed as follows. JPEG0007699506000003.jpg22162x Si =r S cosθ i ,y Si =r S sinθ i , i = 1, 2, 3, where z i indicates the position along the z-axis measured by the position sensor, r S indicates the radial distance from the sensor to the center of the substrate. Theoretically, when the two contact surfaces of the superstrate and the substrate are perfectly parallel to each other, the three contact forces estimated from the forces generated by each of the actuators should be the same. The measurement sensitivity for the parallel state based on the difference in contact forces is proportional to the substrate radius. Therefore, the sensitivity can be increased by reducing the radial distance from the substrate edge to the center of each actuator to, for example, about 70 mm due to space limitations. In the planarization tool, even when the two contact surfaces are exactly parallel, the three forces are different as shown in FIG. 7. The contact force depends on the position of the actuator, the position of the position sensor or encoder, the flatness of the two contact surfaces, and the compliance of the entire planarization module. An accurate contact force model can improve the leveling control accuracy based on force control. The upper surface of the superstrate chuck and the stack of the superstrate and the substrate chucked on the substrate chuck can be used to identify the contact model for minimizing the influence caused by the flatness of the superstrate and the substrate, as well as the shapes of the substrate and the superstrate in their free states. The superstrate and the substrate both come into contact with the formable material 124 sandwiched between them to minimize the influence from the flatness of the contact surfaces between the superstrate and the substrate under the same conditions for the planarization process.

[0048] FIG. 8 shows the process of identifying the contact model using the hybrid control system as shown in FIG. 4. In step S801, the planarization head is moved so as to approach the vicinity of the contact surface between the superstrate chuck and the stack of the superstrate 108, the formable material 124, and the substrate 102 without making contact. In step S802, the superstrate chuck is smoothly moved at a speed of about 0.01 to 0.1 mm / sec so as to contact the stack. During the movement in step S802, F i (z i)(i = 1, 2, 3) The contact force curves are measured (step S803). In step S804, the parallel state between the two contact surfaces of the super straight and the substrate is measured based on the initial contact positions of each of the three axes. The contact force curve F i (z i ) According to, for example, the curve as shown in FIG. 9, the contact force Fi(zi) along each axis is zero when there is no contact between the contact surfaces. When the flattening head is continuously moved toward the stack, the contact force gradually increases. The contact force distribution depends on the parallel state between the contact surfaces and the compliance after contact. When the two contact surfaces are parallel to each other, the initial contact positions along the three axes should be the same, and there is no influence from the compliance difference. Therefore, the initial contact position can be used, for example, as shown in FIG. 4, by the position controller 42 to measure the parallel state. The measurement accuracy depends on the accuracy of the detection of the initial contact position, which can be specified by the steps as shown in FIG. 10 described later. When the measured parallel condition is such that the difference in contact positions is within a predetermined level, for example, less than 0.0001 mm to 0.001 mm, step S805 is executed. Otherwise, steps S806 and S807 are executed. In step S806, the leveling offsets R x and R y are adjusted based on the difference in contact point positions using the above formula (3). Then, in step S807, the flattening head is moved back to the proximity surface, and the process returns to step S801.

[0049] In step S804, when the difference in contact positions deviates from a predetermined level (height), step S805 is executed after making the two contact surfaces parallel, using the contact force curves obtained in steps S802 and S803, and the piecewise cubic polynomial coefficients a i,j 、b i,j 、c i,j 、d i,j solved by the least squares method to minimize the influence from the measurement noise for each contact force related to each peripheral z-axis are used to model the contact force. The piecewise cubic polynomial needs to be continuous across the first derivative and the second derivative with respect to the z coordinate axis. JPEG0007699506000004.jpg22162This satisfies the following. JPEG0007699506000005.jpg24162Here, the position z i,j indicates the j-th position along the i-th z-axis where the fragments of the piecewise function are connected. Then, the contact force curve F i (z), for example, a curve as shown in FIG. 10, is used to model the force distribution along each axis as an input by compliance having a desired total contact force, i.e., the sum of the forces along each axis.

[0050] FIG. 11 shows a process for measuring the initial contact position in step S804 as shown in FIG. 8. In step S1101, the contact force curve is smoothed by a digital filter. In one embodiment, the filter coefficient can be obtained by fitting successive subsets of adjacent data points with a low-order polynomial by the linear least squares method. In S1102, the position scale is enlarged or amplified by the coefficient S c and the contact force curve is rotated counterclockwise by an angle θ by a coordinate transformation as in the following equation. JPEG0007699506000006.jpg17162In step S1103, the initial position can be determined by the position of the maximum force in the transformed contact force curve as shown in FIG. 12. Then, the initial contact position can be determined by reversing the coordinate transformation in step S1104.

[0051] The contact force model shown in FIG. 10 is the setpoint force F septprovides information on how it is distributed along the three axes. By adjusting the forces distributed along each axis, real-time leveling control during the diffusion of the formable material can be achieved. FIG. 13 shows the processing of a method for real-time leveling control during diffusion. In step S1301, the flattening head 120 is moved so as to approach the vicinity of the contact surface between the super straight chuck and the stack of the super straight and the substrate. In step S1302, when there is no contact between the super straight and the substrate, the force offset is reset. In S1303, the set point force F sept is dynamically adjusted. More specifically, based on the required total set point force, the set point forces along each of the three axes can be calculated by spline interpolation. In step S1304, the super straight is smoothly brought into contact with the substrate under force tracking feedback control. After the working surface 122 is brought into contact with the formable material 124, the deviation of the working surface 122 from the parallel state with respect to the substrate 102 can be determined based on the contact model. Then, this information can be used to improve the parallel state of the working surface 122 with respect to the substrate 102 while the formable material spreads under the super straight 108 so that a parallel state is achieved when the formable material is cured.

[0052] Further modifications and alternative embodiments in various aspects will be apparent to those skilled in the art in view of this description. Accordingly, this description should be construed as illustrative only. It should be understood that the forms shown and described herein should be construed as examples of embodiments. It will be apparent to those skilled in the art after receiving the benefit of this description that elements and materials can be replaced with those illustrated and described herein, parts and processes can be reversed, and specific features can be utilized independently.

Claims

1. A method for leveling control between a super straight and a substrate, comprising: identifying a contact force model showing the relationship between the total contact force for flattening a formable material between the super straight and the substrate and the force components of the total contact force along each of a plurality of peripheral axes; determining a setpoint force required to perform the flattening; calculating each force component based on the contact force model; performing flattening by adding each force component along a corresponding axis among the plurality of peripheral axes; including wherein the contact force model a super straight chuck for holding the super straight; a stack of the super straight, the substrate, and a formable material between the super straight and the substrate; is identified based on the parallel state between two contact surfaces of, and is characterized by the method.

2. The method according to claim 1, wherein each of the plurality of peripheral axes extends in a direction parallel to an axis along which a flattening head moves orthogonally to a reference plane.

3. The method according to claim 2, wherein each of the plurality of peripheral axes is equidistant from the center of the super straight chuck and is uniformly distributed in the azimuthal direction around the super straight, the substrate, and the stack of the formable material.

4. The method according to claim 2, wherein the parallelism of the reference plane with the upper surface of the substrate chuck is within 100 milliradians.

5. estimating the force components of the total contact force by measuring, at each of a plurality of positions along a first axis among the plurality of peripheral axes, the forces generated by actuators along each of the plurality of peripheral axes; adjusting the measured forces so as to obtain an estimated contact force based on a mechanical compliance force and a calibration spring force generated by the parallel state; further including the step of estimating by, and is characterized by the method according to claim 1.

6. The method according to claim 5, wherein the mechanical compliance force includes a spring force.

7. Before performing flattening, the calibration spring force is moving a flattening head including the super straight chuck to a first position where the stack is disposed upward when flattening is being performed; after the flattening head is settled at the first position, collecting information on the position of the flattening head and the applied control force. Move the flattening head to a second position where the stack is disposed below when flattening is being performed, After the flattening head has settled at the second position, collect information on the position and applied force of the flattening head, Calibrate the spring force based on the information on the position and applied force collected from the upward and downward movements of the flattening head, The method according to claim 6, further comprising the step of estimating by doing so.

8. Calibrating the spring force further includes moving the flattening head and a substrate chuck for holding the substrate away from each other before moving the flattening head, The method according to claim 7, characterized in that

9. The method according to claim 5, further comprising the step of resetting the calibration spring force of the plurality of peripheral axes by collecting and averaging a plurality of measurements of the estimated contact force over a predetermined period.

10. An apparatus for leveling a super straight together with a substrate during a flattening process, A force controller that adjusts a set point force based on a specific contact model and adjusts a set point position of a position controller based on a feedback law and a difference between the set point force and a required estimated force for performing the flattening process, A position controller that adjusts the applied force to the flattening head based on the difference between the measured position and the set point position depending on the output of the force controller and a feedback control law regarding the parallel state between two contact surfaces, wherein the position controller receives information from an encoder for measuring positions along a plurality of peripheral axes and transmits control information to a plurality of actuators for applying forces along the plurality of peripheral axes to process the parallel state. A position controller, A force estimator that receives control effort information from the position controller, The force estimator uses a set point position as an input to estimate a contact force with a calibration spring force, A contact force model configured to provide information indicating the relationship between the total contact force for the flattening process and the force components of the total contact force along each of the plurality of peripheral axes of the coordinates based on the contact point position adjusted to identify the contact force model, A force estimator configured to provide Comprising The contact force model is A super straight chuck for holding the super straight, the superstrate, the substrate, and a stack of formable material between the superstrate and the substrate, characterized by being specified based on the parallel state between two contact surfaces thereof. **Claim 11** The apparatus according to claim 10, further comprising an amplifier that rotates a contact curve smoothed by a digital filter having an amplified position scale configured to detect a plurality of initial contact positions for measuring the parallel state. **Claim 12** The apparatus according to claim 10, wherein the position controller is configured to measure the parallel state based on the rotation of the stack. **Claim 13** An article manufacturing method, comprising: supplying a formable material onto a substrate; moving a flattening head so as to approach the vicinity of a contact surface between a superstrate and a stack of the superstrate and the substrate; resetting a force offset before contact between the superstrate and the substrate; specifying a contact force model showing the relationship between a total contact force for flattening the formable material between the superstrate and the substrate and force components of the total contact force along each of a plurality of peripheral axes; determining a setpoint force required to perform the flattening; calculating each force component based on the contact force model; performing flattening by adding each force component along a corresponding axis among the plurality of peripheral axes; including: wherein the contact force model is specified based on the parallel state between two contact surfaces of a superstrate chuck for holding the superstrate and a stack of the superstrate and the substrate. **Claim 14** Each of the plurality of peripheral axes extends parallel to a displacement axis along which the flattening head moves, according to the article manufacturing method of claim 13. **Claim 15** estimating the total contact force by further including: measuring, at each of a plurality of positions along a first axis among the plurality of peripheral axes, a force generated by an actuator along each of the plurality of peripheral axes; adjusting the measured force so as to obtain an estimated contact force based on a mechanical compliance force and a calibration spring force generated by the parallel state. **Claim 16** ​ ​ ​ The method for manufacturing an article according to claim 15, characterized in that the mechanical compliance force includes a spring force.

17. Before performing planarization, Move the planarization head including the super straight chuck to a first position where the stack is disposed above when planarization is being performed, After the planarization head settles at the first position, collect information on the position and applied force of the planarization head, Move the planarization head to a second position where the stack is disposed below when planarization is being performed, After the planarization head settles at the second position, collect information on the position and applied force of the planarization head, Calibrate the spring force based on the information on the position and applied force collected from the upward and downward movements of the planarization head, The method for manufacturing an article according to claim 16, further comprising a step of calibrating by doing so.

18. The method for manufacturing an article according to claim 15, further comprising a step of resetting the force offset for calibrating the plurality of peripheral axes by collecting and averaging a plurality of measurements of the estimated contact force over a predetermined period.

19. The method for manufacturing an article according to claim 15, further comprising a step of measuring the parallel state between two contact surfaces based on the rotation of the stack around an axis perpendicular to the displacement axis of the planarization head.

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