Patent Application
20120181445
The present invention relates to an electron beam recording apparatus, particularly relates to an electron beam recording apparatus that uses electron beams to manufacture a master of high-speed rotational recording media such as magnetic discs or the like.
Beam recording apparatuses that use exposure beams such as electron beams, laser beams, or the like to perform lithography are widely applied to master manufacturing apparatuses of high-capacity disks such as digital versatile discs (DVDs), optical discs such as Blu-ray discs, hard disks for magnetic recording, or the like.
The beam recording apparatuses control to form a resist layer on a recording surface of a substrate that is to become a master to manufacture the above discs/disks, rotate, and translate the substrate so as to appropriately send a beam spot to the recording surface of the substrate comparatively in a radius direction and a contact line direction such that a spiral track or concentric track is drawn on the substrate recording surface, thereby forming a latent image on the resist.
According to the beam recording apparatus, rotational runout is caused by mechanical precision or the like of a feeding motor, spindle motor, or the like to rotate and translate the substrate so as to reduce the precision of forming the track. Accordingly, it is necessary to correct the rotational runout by some methods so as to perform beam exposure.
As it is known, the rotational runout of the disc substrate is classified into synchronous runout (synchronous rotational runout) that is a deflectionary component synchronous to a rotational frequency of a turntable (substrate) and irregular asynchronous runout (asynchronous rotational runout) that does not depend on a rotational frequency of a turntable (substrate).
With reference to the asynchronous rotational runout, a correction method of an optical disc master exposing apparatus is disclosed (for example, refer to Patent Literature 1). The Patent Literature 1 discloses a technique to correct the asynchronous rotational runout such that the track pitch precision (comparative positional precision to an adjacent track) of the optical disc master exposing apparatus is improved.
In contrast, the synchronous rotational runout deteriorates the roundness precision of a track (absolute precision), however, it does not affect the precision of a track pitch. Since a roundness error caused by the synchronous rotational runout can be followed by a tracking servo of a reproducer in the case of an optical disc, attention has not been paid to the synchronous rotational runout as much as to the asynchronous rotational runout. However, in recent years, as hard disks that are magnetic recording media have had higher recording density, there has been an increasing demand for using an electron beam exposing apparatus to manufacture magnetic recording media that are called discrete track media or patterned media. Because the hard disk rotates at a high speed to record/reproduce and a controlling range of a swing arm type controlling mechanism to control tracks of a recording/reproducing head is small, the disc/disk medium is required to have highly precise track roundness. Because of this, the master exposing apparatus to manufacture the disc/disk media needs to correct the asynchronous rotational runout as well as the synchronous rotational runout precisely.
For example, controlling (correcting) an irradiating position of a recording beam according to a result of computation is disclosed, wherein displacement in a radial direction of a turntable measured by the prescribed number of rotations or smaller (hereafter, also referred to as radial displacement) is set as reference displacement and a difference from the reference displacement of the radial displacement measured real-time at the time of beam exposure is computed (for example, refer to Patent Literature 2).
However, according to this method, it is assumed that a synchronous component of rotational runout is small at the time of low speed rotation, and the rotational synchronous component increases proportionately as the number of rotations increases, wherein the displacement at the time of low speed rotation is set as a reference. However, the rotational synchronous component cannot be disregarded even at the time of low speed rotation, and moreover, the rotational synchronous component does not always increase proportionately as the number of rotations increases. Therefore, according to the method, the component of synchronous rotational runout included at the time of rotation to capture a reference displacement wave shape is unknown, hence it cannot be corrected.
As a problem to be solved by the present invention, the above problem is included as one example. An object of the present invention as one example is to provide a high precision electron beam recording apparatus that is capable of correcting rotational runout in an order of sub-nanometer to nanometer.
The electron beam recording apparatus according to the present invention is an electron beam recording apparatus to rotate a turntable, wherein a substrate is placed and irradiate an electron beam to a resist layer formed on the substrate according to a recording signal, thereby forming a latent image on the resist layer, wherein it comprises: a displacement detector comprising at least three displacement sensors that are arranged at a different angle to each other in a radial direction of the turntable so as to detect displacement in the radial direction of a rotational side surface of the turntable; a shape calculator to calculate shape data according to a roundness error of the turntable and an eccentricity component of the turntable; a memory to store the above shape data; a rotational runout computing part to calculate rotational runout of the turntable that does not include an eccentricity component according to detected displacement from the displacement sensor when the turntable rotates and the above shape data; and a beam irradiating position adjuster to adjust an irradiating position of the electron beam according to the above rotational runout.
The electron beam recording apparatus according to the present invention is an electron beam recording apparatus to record by rotating a turntable, wherein a substrate is placed and irradiating an electron beam to the substrate according to a recording signal, wherein it comprises: a displacement sensor to detect displacement information in a radial direction of the turntable; eccentricity component obtaining means for obtaining an eccentricity component attributed to eccentricity of the turntable according to the above displacement information; rotational runout information generating means for generating rotational runout information by subtracting the above eccentricity component from the above displacement information; and a beam irradiating position adjuster to adjust an irradiating position of the electron beam according to the above rotational runout information.
The electron beam recording apparatus according to the present invention is an electron beam recording apparatus to record by rotating a turntable, wherein a substrate is placed and irradiating an electron beam to the substrate according to a recording signal, wherein it comprises: displacement data obtaining means for obtaining displacement data that is displacement in a radial direction of the turntable; eccentricity component obtaining means for obtaining an eccentricity component attributed to eccentricity of the turntable; rotational runout information obtaining means for obtaining rotational runout information, wherein the above eccentricity component is removed from the above displacement data; and a beam irradiating position adjuster to adjust an irradiating position of the electron beam according to the above rotational runout information.
Below, the embodiments of the present invention will be described in detail by referencing to the drawings. In the following embodiments, equivalent component elements are given the same referential marks.
The electron beam recording apparatus 10 is provided with a vacuum chamber 11, a drive mechanism to set, rotate, translate, and drive a substrate 15 arranged in the vacuum chamber 11, an electron beam column 20 installed in the vacuum chamber 11 and various circuits and controls to drive and control the substrate and control an electron beam, or the like.
More specifically, the surface of the substrate 15 for a disc master is coated with resist and set on a turntable 16. The turntable 16 is rotated and driven around a vertical axis of a primary surface of the disc substrate by a spindle motor 17 that is a rotational driving apparatus to rotate and drive the substrate 15. The spindle motor 17 is provided on a feeding stage (hereafter, also referred to as an X stage) 18. The X stage 18 is joined to a feeding motor 19 that is a transporting (translating and driving) apparatus so as to move the spindle motor 17 and turntable 16 in a prescribed direction (X direction) in a plane parallel to the primary surface of the substrate 15. Accordingly, an Xθ stage comprises an X stage 18, spindle motor 17, and turntable 16.
The spindle motor 17 and X stage 18 are driven by a stage driving part 37 and a feeding amount of the X stage 18 that is a driving amount thereof and a rotational angle of the turntable 16 (that is to say, substrate 15) are controlled by a controller 30.
The turntable 16 is made of a dielectric body, for example, ceramic, comprising a chucking mechanism such as a static chucking mechanism (not illustrated) to hold the substrate 15. The chucking mechanism secures the substrate 15 set on the turntable 16 to the turntable 16.
A reflective mirror 35A that is a part of a laser interferometer 35 is arranged on the X stage 18.
A vacuum chamber 11 is mounted via a vibration isolation table (not illustrated) such as an air dumper or the like so as to control external vibrations from being transmitted. A vacuum pump (not illustrated) is connected to the vacuum chamber 11 to exhaust the chamber such that the inner part of the vacuum chamber 11 is set to be a vacuum atmosphere having a prescribed pressure.
An electron gun (emitter) 21 to emit an electron beam, converging lens 22, blanking electrode 23, aperture 24, beam deflection electrode 25, focus lens 27, and object lens 28 are arranged in the electron beam column 20 in this order.
The electron gun 21 emits an electron beam (EB) accelerated to several dozen KeV, for example, by a negative electrode (not illustrated) wherein high voltage supplied from an accelerating voltage power source (not illustrated) is applied. Emitted electron beams are converged by the converging lens 22. The blanking electrode 23 turns on and off the electron beam according to a modulation signal from a blanking controlling part 31. That is to say, a passing electron beam is deflected considerably by applying voltage between the blanking electrodes 23, thereby the electron beam is prevented from passing the aperture 24 so as to turn off the electron beam.
The beam deflection electrode 25 is capable of deflection controlling the electron beam at high speed according to a control signal from the beam deflection part 33. By the deflection control, a spot position of the electron beam is controlled on the substrate 15. The focus lens 28 is driven according to a drive signal from the focus controlling part 34, thereby controlling a focus of the electron beam.
The vacuum chamber 11 is provided with a height detecting part 36 to detect a height of a surface of the substrate 15. An optical detector 36B that includes a position sensor, a charge coupled device (CCD), or the like, for example, receives an optical beam that is emitted from a light source 36A and reflected by the surface of the substrate 15, and supplies the received optical signal to the height detecting part 36. The height detecting part 36 detects the height of the surface of the substrate 15 according to the received optical signal so as to generate a detection signal. The detection signal indicating the height of the surface of the substrate 15 is supplied to the focus controlling part 34, and the focus controlling part 34 controls the focus of the electron beam according to the detection signal.
The laser interferometer 35 uses laser light irradiated from a light source in the laser interferometer 35 to measure a length of displacement of the X stage 18, and then feeds the measured length data, that is to say, the feeding position data of the X stage 18 (X direction) to the stage driving part 37.
Furthermore, a rotation signal of the spindle motor 17 is also supplied to the stage driving part 37. More specifically, the rotation signal includes an origin point signal indicating a reference rotational position of the substrate 15 and a pulse signal (rotary encoder signal) for every prescribed rotational angle from the reference rotational position. The stage driving part 37 obtains a rotational angle, a rotation speed, or the like of the turntable 16 (substrate 15) from the rotation signal.
The stage driving part 37 generates position data indicating the position of an electron beam spot on the substrate according to feeding position data from the X stage 18 and a rotation signal from the spindle motor 17 so as to supply them to the controller 30. The stage driving part 37 drives the spindle motor 17 and feeding motor 19 according to a control signal from the controller 30, thereby rotating and feed driving them.
Track pattern data used for discrete track media, patterned media, or the like, or data (recording data) RD to record (expose) is supplied to the controller 30.
The controller 30 sends a blanking control signal CB, deflection control signal CD, and focus control signal CF to a blanking controlling part 31, beam deflection part 33, and focus controlling part 34 respectively, thereby controlling the recording data (exposing or drawing) according to the recording data RD. That is to say, an electron beam (EB) is irradiated to the resist on the substrate 15 according to the recording data RD, wherein a latent image is formed only at a spot exposed by irradiating the electron beam so as to be recorded (exposed).
Furthermore, an electron beam recording apparatus 10 is provided with a displacement detecting apparatus 41 to detect displacement in the radius direction (hereafter, referred to as a radial direction) when the turntable 16 rotates. More specifically, the turntable 16 is in a cylindrical shape and the substrate is set on the primary surface thereof (primary flat surface). The turntable 16 is rotated and driven around the central axis thereof, and the displacement detecting apparatus 41 detects displacement in the radius direction (radial direction) of the side surface of the turntable 16. As described below, the displacement detecting apparatus 41 comprises at least three displacement sensors.
The displacement (detected displacement) detected by the displacement detecting apparatus 41 is supplied to a rotational runout computing part 43. It is acceptable to constitute such that an amplifying apparatus 42 to amplify the detection signal is provided and the amplified detection signal is supplied from the amplifying apparatus 42 to the rotational runout computing part 43.
The rotational runout computing part 43 performs a prescribed computation of the detected displacement so as to calculate rotational runout. The calculated rotational runout is supplied to the controller 30. The controller 30 controls the beam deflection part 33 according to the calculated rotational runout, thereby adjusting (correcting) an irradiating position of an electron beam.
The recording control is performed according to the above feeding position data and rotating position data. A primary signal line has been described in relation to the blanking controlling part 31, beam deflection part 33, focus controlling part 34, and stage driving part 37. Each of these constituent parts is constituted to be connected to the controller 30 bilaterally so as to transmit or receive a required signal.
Then, the constitution and operation of the electron beam recording apparatus 10 will be described in detail by referencing drawings, wherein the rotational runout is detected and computed so as to adjust the irradiating position of a beam according to the rotational runout.
The substrate 15 (not illustrated) is set on the primary surface (xy flat surface) of the turntable 16 and, as illustrated in
Rotations of the spindle motor 17 to rotate the turntable 16 is controlled by a motor controlling circuit 45. The motor controlling circuit 45 operates according to a reference signal from a reference signal generating apparatus 44 and a rotary encoder signal from a rotary encoder 46. The rotary encoder signal from the rotary encoder 46 is supplied to a rotational runout computing part 43.
The rotational runout computing part 43 operates with the rotary encoder signal as a reference clock. That is to say, the rotational runout computing part 43 operates at a timing of a rotational angle reference of the turntable 16 based on the rotary encoder signal.
First, the rotational runout computing part 43 calculates a roundness error indicating an error from a true circle in a side shape of the turntable 16 that is a cylindrical surface measured in advance. As a method to calculate the roundness error, a computation method based on the principle of three-point method of measuring a true circle is available. Below, the displacement sensor to measure a roundness error r(θ) and a rotational runout computation will be described.
As illustrated in
The displacement sensors 41A, 41B, 41C detect the radial displacement of the side surface of the turntable 16A by an optical method, electric method, or the like. For example, the displacement sensors 41A, 41B, 41C are constituted to be a laser interferometer, having adequate detecting precision (for example, detecting precision in sub-nanometer (that is to say, 1 nm or smaller)) compared to the precision of a beam exposure. Detection of displacement is not limited by an optical method such as a laser interferometer and displacement may be detected by other methods. For example, it is possible to use a static capacity type displacement meter or the like to detect radial displacement according to a change in an electrostatic capacity.
The displacement sensor 41A is arranged in the X direction, while the displacement sensors 41B, 41C are arranged to be at an angle φ, (2π−τ) to the displacement sensor 41A (φ, τ>0). If a rotational angle θ is made with reference to the direction of the displacement sensor 41A (X direction), a roundness error of the cylindrical surface 16A to be measured can be written as r(θ) in the polar coordinate system. The roundness error (hereafter, also referred to as roundness error data) r(θ) can be written as an error from a true circle with a reference radius r0.
The spindle motor 17 is caused to rotate so as to measure the radial displacement of the cylindrical surface measured (turntable side surface) 16A. The radial displacement data SA(θ), SB(θ), SC(θ) (the direction that becomes distant from the sensor is positive) from each of the displacement sensors 41A, 41B, 41C are sent to the rotational runout computing part 43, wherein they are sampled to be triggered by a pulse from the rotary encoder 46 and then subjected to digital/analog (D/A) conversion. In this case, if necessary, it is acceptable to perform a process such as filtering, averaging, or the like. By using the roundness error data r(θ) obtained in this manner and the radial displacement data SA(θ), SB(θ), SC(θ) measured by the displacement sensors 41A, 41B, 41C, rotational runout data x(θ), y(θ) in the X and Y directions are obtained by the following computation.
x(θ)=[{SB(θ)+r(θ−φ)} cos τ−{SC(θ)+r(θ+τ)} cos φ]/sin(θ+τ)y(θ)=−r(θ)−SA(θ)
The principle of three-point method of roundness measurement is described in detail, for example, in Non-Patent Literature “Transactions of the Japan Society of Mechanical Engineers, C, Volume 48, No. 425, p. 115 (Sho 57-1)” or the like.
However, in principle, the above roundness error data r(θ) does not include a first degree Fourier component, that is to say, an eccentricity component of the turntable side surface 16A. Whereas, each radial displacement data to be measured includes an eccentricity component of the turntable side surface, hence computed rotational runout x(θ), y(θ) include the eccentricity component of the turntable side surface 16A.
However, the eccentricity of the turntable side surface 16A does not correspond to the eccentricity of the substrate to be drawn, and it is merely the eccentricity of the cylindrical surface measured. If recording position correction is performed accordingly, it results in only recording a deflected concentric circle to the rotation center of the substrate that is set thereon.
The level of the rotational runout of the electron beam recording apparatus to which the present invention is applied is in sub-nanometer to nanometer, whereas the level of the eccentricity of the turntable side surface is normally in sub-micrometer to micrometer even if it is installed and adjusted precisely. Because of this, if the above rotational runout x(θ), y(θ) are used to perform recording position correction, an exposure beam is caused to deflect more than necessary because recording position correction of an eccentricity component of the turntable side surface is performed, which is not originally required. If an electron beam is deflected large as described above, aberration of an electron beam is caused to increase, which is disadvantageous to form a minute pattern.
Furthermore, it is not preferred that the beam irradiating position adjustment apparatus has a wide range of beam deflection in micrometer so as to correct rotational runout in nanometer, which is the original objective, from a viewpoint of an S/N ratio of a beam deflection signal.
The correction system of rotational runout of the present invention is constituted to reduce the amplitude of the rotational runout correction by using rotational runout data that does not include an eccentricity component.
First, radial displacement data SA(θ), SB(θ), SC(θ) of the turntable side surface 16A are captured by each of the displacement sensors 41A, 41B, 41C. The rotational runout computing part 43 calculates the true roundness from the radial displacement data SA(θ), SB(θ), SC(θ) by the three-point method of roundness measurement so as to set it as roundness error data r(θ) (Step S22). As described above, the roundness error data r(θ) obtained by the three-point method of roundness measurement does not include the first degree Fourier component, that is to say, the eccentricity component.
The eccentricity data e(θ) is calculated (Step S22). The eccentricity data e(θ) can be obtained by analyzing the radial runout data of the displacement sensor by Fourier transform, for example. Specifically, the radial runout data SA(θ) sampled is subjected to Fourier transform so as to extract only the first degree component, wherein reverse Fourier transform is performed, thereby obtaining the eccentricity data e(θ).
The eccentricity data e(θ) is added to the roundness error data r(θ) calculated so as to calculate shape data f(θ) (Step S23).
By referencing
The shape data f(θ) is stored in a memory (RAM) 48. The rotational runout computing part 43 reads the shape data f(θ) (=r(θ)+e(θ)) stored in the memory (RAM) 48 according to the data (rotary encoder signal) of a rotational angle (angle position θ) from the rotary encoder 46 (
The rotational runout computing part 43 executes the above computation such as a subtraction or the like by high-speed processing means such as a digital signal processor (DSP) or the like. Accordingly, two-dimensional rotational runout components xf(θ), yf(θ) are calculated in the X and Y direction real-time.
Herein, the rotational runout component data xf(θ), yf(θ) are expressed as follows:
x
f(θ)=[{SB(θ)+f(θ−φ)} cos τ−{SC(θ)+f(θ+τ)} cos φ]/sin(θ+τ) (1)
y
f(θ)=−f(θ)−SA(θ) (2)
The wave shape data xf(θ), yf(θ) obtained in this manner are supplied to the controller 30. The controller 30 controls the beam deflection part 33 according to the rotational runout data xf(θ), yf(θ) calculated, thereby adjusting (correcting) the irradiating position of the electron beam (EB) real-time. That is to say, the irradiating position of the exposure beam (electron beam) is displaced according to a rotational runout signal, thereby performing recording position correction.
As described above, the rotational runout data xf(θ), yf(θ) do not include the eccentricity component. Because of this, it becomes possible to reduce the deflection range of the beam irradiating position adjustment apparatus. As a result, it is possible to control the effect of the rotational runout and record a precise concentric circle and a spiral pattern without deteriorating a drawing pattern caused by a beam deflection aberration or deflection noise.
Herein, it is preferred to match a setting angle of one of the displacement sensors (sensor A) with a feeding direction of the feeding stage (X stage) (refer to
y
f(θ)=f(θ)−SA(θ) (3)
As described above, according to the present invention, the shape data f(θ) is obtained by adding the eccentricity data e(θ) to the roundness error data r(θ) calculated according to the principle of three-point method of roundness measurement. Each radial displacement data measured real-time and the shape data f(θ) are computed, thereby calculating the rotational runout data. Since the beam irradiating position adjustment is performed according to the rotational runout data that does not include the eccentricity component, it is possible to reduce the deflection range of the position adjustment correction and record a precise concentric circle and a spiral pattern.
There is a method to calculate and subtract the eccentricity data from the radial runout data measured real-time at the time of the position adjustment and then the roundness error data is used to compute the rotational runout data, however, the computation becomes complex. Moreover, there is a method to calculate and subtract the eccentricity component from the rotational runout data computed by using the roundness error data, however, the computation is complex and this is disadvantageous to the real-time computation process at the time of the position adjustment.
In this embodiment, the displacement sensors 41A to 41C that had measurement sensitivity in sub-nanometer were used, however, it is acceptable to add an adjustment mechanism to adjust the position (height) of the displacement sensors 41A to 41C such that an error is not made in the height when the sensor is installed (measurement height of radial displacement). The height adjustment mechanism adjusts the position (height) of the displacement sensors 41A to 41C such that an error of the shape data f(θ) remains in a prescribed range when the shape data f(θ) is obtained by the controller 30, for example.
The direction to arrange the displacement sensor is not limited to the one illustrated in
Moreover, it is predominantly the rotational runout component in the X direction of the stage feeding direction, which is the radial direction of the turntable 16 (substrate 15), that actually affects the track roundness error at the time of exposure of a disc master. Accordingly, as described above, it is preferred to set one of the three displacement sensors 41A to 41C in the X direction (feeding direction). In this case, the X direction is a simple subtraction, which has advantage in that the computation process at the time of correction becomes streamlined.
Furthermore, as illustrated in
Moreover, in the above embodiment, the adjustment of the irradiating position of the exposure beam was described by using the shape data f(θ) that was obtained in advance and stored in the memory (RAM) 48, thereby obtaining the rotational runout data Xf(θ), yf(θ). However, it is acceptable to calculate the shape data real-time and then adjust the irradiating position real-time. That is to say, the shape data f(θ) at the time of recording (at the time of exposure) the electron beam irradiated to the substrate may be calculated, wherein the wave shape data r(θ) thereof is used to calculate the real-time rotational runout data Xf(θ), yf(θ), thereby adjusting the irradiating position of the electron beam.
Furthermore, it is acceptable to calculate the real-time shape data and then update the shape data f(θ). That is to say, for example, as illustrated in
As illustrated in
As described above, if the measurement height position is changed by thermal expansion of the turntable or spindle, and even if the measurement cross-sectional wave shape of the turntable is changed, by constituting to update the shape data f(θ) real-time, the result of computing the rotational runout does not produce an error, hence a long time exposure is possible.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/066791 | 9/28/2009 | WO | 00 | 3/27/2012 |
