Electron beam recording apparatus

An electron beam recording apparatus provided with control means for forming a latent image in a resist layer on a disk substrate corresponding to a predetermined pattern by controlling the irradiation position of an electron beam irradiation unit on the surface of the resist layer in accordance with the rotation angle of the disk substrate by a rotational drive unit, the shift position by a shift drive unit and the recording data that represent the predetermined pattern, and beam-adjusting means for irradiating an electron beam so as to spread over a plurality of tracks in the direction of traversing the tracks in response to the irradiation position control due to the control means, and an electron beam recording method using the apparatus.

This application is a 371 of PCT/JP05/05650, filed Mar. 22, 2005.

1. Technical Field

This present invention relates to an electron beam recording apparatus which records patterns such as a servo pattern onto a disk substrate by exposure.

2. Background Art

In a hard disk drive (HDD), position information to detect the position of a magnetic head relative to a track of a magnetic disk is recorded in the magnetic disk as a servo pattern. In a magnetic disk, as shown inFIG. 1, a servo zone, in which servo patterns are recorded, and a data zone, in which data is recorded/reproduced, are arranged alternately at constant angular intervals along the track in the circumferential direction. The magnetic head can detect the recording or reproduction position at constant time intervals during data recording or reproduction.

However, in the conventional manufacture of a hard disk drive, it has been a common practice to record the servo pattern on each magnetic disk by means of a device called servo track writer, and thereafter to assemble the recorded disk into the hard disk drive. There has been a problem of low production efficiency for hard disk drives, since it takes approximately 10 min for the recording of the servo pattern in a 20 GB (gigabyte)/disk-class magnetic disk.

To cope with this problem, a method is known in which a master disk on which a magnetic film pattern corresponding to a servo pattern has been formed by lithography is magnetically transferred collectively in the whole area onto a magnetic disk (Fuji Electric Review, Vol. 75, No. 3, published on Mar. 10, 2002). By adopting this method, the time required for recording a servo pattern on a magnetic disk can be reduced. In the recording method for magnetic disks based on the magnetic transfer, there has been another problem that the process of recording on each magnetic disk becomes complicated.

Thus, highly precise formation of a servo pattern at the step of disk substrate recording is desired in order to enhance the production efficiency for hard disk drives. However, there is a problem that the conventional electron beam recording apparatus cannot be applied as it is, since the servo pattern of the magnetic disk for hard disk drives includes longitudinal patterns covering a plurality of tracks in the disk radial direction.

DISCLOSURE OF INVENTION

An object of the present invention is to provide an electron beam recording apparatus and an electron beam recording method which is capable of recording a servo pattern for magnetic disks on a disk substrate with high accuracy.

According to the invention, there is provided an electron beam recording apparatus comprising: a rotational drive unit for rotationally driving a disk substrate having a surface on which a resist layer is formed; an electron beam irradiation unit for irradiating an electron beam for exposure onto the surface of the resist layer in a freely deflectable manner; a shift drive unit for shifting the irradiation position of the electron beam by a predetermined distance in the radial direction of the disk substrate for each one rotation by the rotational drive unit to advance the irradiation position of the electron beam; and control means for forming a latent image corresponding to a predetermined pattern, in the resist layer by controlling the irradiation position caused by the electron beam irradiation unit on the surface of the resist layer in accordance with the rotation angle of the disk substrate caused by the rotational drive unit, the shift position caused by the shift drive unit and recording data that represents the predetermined pattern; wherein the electron beam irradiation unit includes beam-adjusting means for adjusting the irradiation of the electron beam in such a manner as to spread over a plurality of tracks in the direction of traversing the tracks on the surface of the resist layer in response to the irradiation position control by the control means.

According to the invention, there is provided an electron beam recording method comprising steps of: a rotational drive step for rotationally drives a disk substrate having a surface on which a resist layer is formed; an irradiation step for irradiating an electron beam for exposure onto the surface of the resist layer in a freely deflectable manner; a shift drive step for shifting the irradiation position of the electron beam by a predetermined distance in the radial direction of the disk substrate for each one rotation of the disk substrate to advance the irradiation position of the electron beam; and a control step for forming a latent image corresponding to a predetermined pattern, in the resist layer by controlling the irradiation position of the electron beam on the surface of the resist layer in accordance with the rotation angle of the disk substrate, the shift distance of the irradiation position of the electron beam in the radial direction of the disk substrate and recording data that represents the predetermined pattern; wherein the irradiation step irradiates the electron beam in such a manner as to spread over a plurality of tracks in the direction of traversing the tracks on the surface of the resist layer in response to the irradiation position control in the control step.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2shows an electron beam recording apparatus according to the present invention. This recording apparatus has an electron column1, a vacuum chamber2and a recording control system. InFIG. 2, the inner structures of the electron column1and the vacuum chamber2are shown.

The electron column1is a cylindrical member having therein an optical system which generates an electron beam and irradiates the beam onto a disk substrate4to be described later and placed in the vacuum chamber2. The optical system in the electron column1is provided with an electron emitter11, a condenser lens12, a blanking plate13, an aperture plate14, a deflection coil15, an alignment coil16, a high-speed deflector17, a focus lens18and an object lens19. These members11to19are arranged in the electron column1from the top in the described order.

The electron emitter11generates an electron beam when a high voltage is applied by means of an accelerating high voltage power source30to be described later. The condenser lens12condenses or converges the electron beam generated by the electron emitter11to form a crossover at the central area of the blanking plate13. The blanking plate13is, for example, an electrostatic deflector-type electrode to turn on or off the electron beam in response to the output signal of a beam modulator31to be described later. The aperture plate14is provided with a circular aperture to restrict the electron beam flux. The deflection coil15changes the advancing direction of the electron beam in response to the output signal of a deflection circuit not shown in the drawing. The alignment coil16deflects the electron beam in response to the output signal of a beam position corrector32to make the beam agree with the optical axis. The high-speed deflector17deflects the electron beam in an arbitrary direction in response to the output signal of a deflection controller37. The focus lens18makes the electron beam light in focus on the disk substrate4via the object lens19in response to the output signal of a focus controller33.

In the vacuum chamber2, a height detector21, a spindle motor22, a mirror23, a turntable24, a stage25and a stage-moving mechanism26are provided. The spindle motor22and the mirror23are arranged on the stage25. The spindle motor22rotates the turntable24. The disk substrate4is mounted and fixed on the turntable24. The disk substrate4is, for example, a silicon substrate on which an electron beam resist layer is formed. The stage25is configured so as to be movable in the radial direction of the disk substrate4(X-direction) by means of the stage-moving mechanism26. The stage-moving mechanism26moves the stage25by using a motor27attached to the outside of the vacuum chamber2as a driving power source. The mirror23is installed to measure the moving distance of the stage25in the disk radial direction. The height detector21is arranged at the upper part in the vacuum chamber2, and optically detects the height of a recording position on the disk substrate4.

The recording control system is provided with the accelerating high voltage power source30, the beam modulator31, the beam position corrector32, the focus controller33, a position controller34, a laser interferometer measuring system35, a rotation controller36, the deflection controller37and a main controller38.

The accelerating high voltage power source30applies high voltage to the electron emitter11in response to an instruction of the main controller38.

The beam modulator31supplies beam modulation signal to the blanking plate13in response to the recording data fed by the main controller38.

The focus controller33moves the focus position of the focus lens18in response to the height information of the recording position detected by the height detector21.

The laser interferometer measuring system35detects the position of the mirror23, i.e., shifting distance information r of the stage25by receiving the reflected light of a laser beam irradiated onto the mirror23. The shifting distance information r represents the recording position in the radial direction of the disk substrate4. The shifting distance information r measured with the laser interferometer measuring system35is fed to the position controller34. The position controller34compares the shifting distance information r with reference distance information REF and drives the motor27via motor driving means not shown in the diagram in response to the positional error signal resulting from the comparison. Further, this positional error signal is fed to the beam position corrector32. The beam position corrector32excites the alignment coil16in response to the positional error signal from the position controller34to deflect the electron beam.

The rotation controller36rotationally drives the spindle motor22in response to an instruction of the main controller38. The deflection controller37regulates the deflection of the electron beam by means of the high-speed deflector17in response to the recording data fed by the main controller38, rotation angle information θ for the spindle motor22obtained by the rotation controller36and the shift distance information r measured by the laser interferometer measuring system35. The rotation angle information θ represents the angle of the recording position on the disk substrate4.

The accelerating high voltage power source30, the beam modulator31, the focus controller33, the position controller34, the rotation controller36and the deflection controller37are controlled in response to each instruction of the main controller38, respectively.

Next, pattern recording on the disk substrate4with use of the electron beam recording apparatus of such configuration will be described.

In the recording of servo zone data and data zone data, the main controller38instructs to the position controller34to shift the stage by a predetermined track pitch as the aforementioned reference distance information REF, and instructs to the rotation controller36so that the spindle motor22rotates at a constant rotary linear velocity.

The position controller34compares the shifting distance information r for the stage25outputted from the laser interferometer measuring system35with the reference distance information REF, and drives the motor27via motor driving means not shown in the diagram in response to the positional error signal resulting from the comparison.

By virtue of these instructions and operations, the stage25is shifted by means of the stage shifting mechanism26by the track pitch in the radial direction of the disk substrate for each one rotation of the disk substrate4by means of the spindle motor22.

Moreover, the main controller38instructs to the accelerating high voltage power source30to apply high voltage to the electron emitter11, so that an electron beam is ejected from the electron emitter11, and further instructs to the focus controller33to focus the electron beam on the disk substrate4.

In response to the positional error signal from the position controller34, the beam position corrector32excites the alignment coil16to deflect the electron beam.

From the main controller38, recording data is fed to the beam modulator31in constant clock timing. This clock timing is in synchronism with the instructions to the position controller34and the rotation controller36. The recording data is data representing servo zone data as well as data zone data for one disk arranged in the order of recording. The beam modulator31generates a modulation signal in accordance with the recording data, and the blanking plate13deflects the electron beam ejected from the electron emitter11with the modulation signal. By such modulation, there occur two cases where the electron beam passes through the aperture in the aperture plate14, or does not. In the case of aperture passing, the passing electron beam is irradiated onto the recording plane of the disk substrate4in the form of spot through the deflection coil15, the alignment coil16, the high-speed deflector17, the focus lens18and the object lens19. By electron beam irradiation on the disk substrate4, the resist layer at the irradiated area is removed. The area where the resist layer has been removed forms a recessed portion, thus giving a pattern. On the other hand, in the case of no aperture passing, the electron beam cannot advance anymore after the aperture plate14, so that the beam is not irradiated onto the disk substrate4.

The main controller38supplies the aforementioned recording data to the deflection controller37. As shown inFIG. 3, when the deflection controller37acquires the current recording position in response to the rotation angle information θ obtained by the rotation controller36and the shift distance information r from the laser interferometer measuring system35(step S1), and detects from the recording data that the current recording position constitutes a recording portion covering two tracks or more in the disk radial direction (step S2), it supplies a predetermined deflection signal to the high-speed deflector17(step S3). The high-speed deflector17, when supplied with the predetermined deflection signal, deflects the electron beam by a two-track distance in the disk radial direction.

As a result, in the disk substrate4, patterns consisting of the servo zone and data zone as shown inFIG. 4are formed. In addition, in the servo zone, a servo clock area for generating clock signal, an address mark area for indicating the address information on tracks, and a position detection mark part for detecting the position on tracks are also formed as patterns. All of those servo clock, address mark and position detection mark areas need not always be formed in the servo zone, but a mark portion containing at least one of clock signal, address signal and position detection signal may be formed.

In the servo clock portion, a longitudinal mark extending so as to spread over all the tracks in the disk radial direction (the direction traversing the tracks) is formed for each predetermined unit angle Δθ. In the address mark area, the mark showing its address information is formed in the disk radial direction lengthwise. The mark length along the disk radial direction widely varies in the address mark area. In position detection mark area, a plurality of marks each having a length spreading over two tracks in the disk radial direction form a hound's-tooth-pattern. In the address mark area and the position detection mark area, the minimum mark-forming interval in the track direction is of a predetermined unit angle Δθ. The data zone is made in the form of patterned media. Namely, for each track, circular marks are formed in the track direction at predetermined unit angular intervals of Δθ. In a disk having the form of patterned media, a single circular mark is recorded as one bit during recording.

The longitudinal mark in the servo zone is formed sequentially from the inner periphery side of the disk substrate4, as shown inFIG. 5. InFIG. 5, six tracks n to n+5 are shown, in which a longitudinal mark41with a length spreading over the six tracks is formed by irradiating an electron beam under high-speed deflection by the two-track distance in the disk radial direction by means of the high-speed deflector17at the position of the same rotation angle θi for each of the five tracks n to n+4 so that the two-track deflected portions are continually connected at the overlapping region. Namely, in each of the tracks n+1 to n+4, a two-track deflection ending region overlaps the next two track-deflection starting region. A longitudinal mark42with a length spreading over four tracks is formed by irradiating an electron beam under high-speed deflection by the two-track distance in the disk radial direction by means of the high-speed deflector17at the position of the same rotation angle θi+1 for each of the three tracks n+1 to n+3 so that the two-track deflected portions are continually connected at the overlapping region. A longitudinal mark43with a length spreading over three tracks is formed by irradiating an electron beam under high-speed deflection by the two-track distance in the disk radial direction by means of the high-speed deflector17at the position of the same rotation angle θi+2 for each of the two tracks n and n+1 so that the two-track deflected portions are continually connected at the overlapping region. A longitudinal mark44with a length spreading over two tracks is formed by irradiating an electron beam under high-speed deflection by the two-track distance in the disk radial direction by means of the high-speed deflector17at the position of the rotation angle θi+2 for the track n+4. InFIG. 5, the direction shown by the arrow in a mark is the direction of a single deflection for the electron beam caused by the high-speed deflector17.

Each circular mark45in the data zone is formed by irradiating an electron beam, without deflection by the high-speed deflector17, in the track order of the tracks n to n+5 with a predetermined unit angle interval Δθ, as shown inFIG. 5.

FIG. 6illustrates another example of pattern formation on the disk substrate4with use of such an electron beam recording apparatus. Though the patterns in the servo zone ofFIG. 6are the same as those in the servo zone ofFIG. 4, the patterns in the data zone are of group recording type in which a mark continuing in the track direction is formed in each track.FIG. 7shows the method of forming each mark in the servo zone and data zone shown inFIG. 6wherein the servo zone is common to that ofFIG. 5. Each continuous mark46in the data zone is formed by continuously irradiating an electron beam, without any deflection by means of the high-speed deflector17, on tracks n to n+5 in the track order.

According to the foregoing embodiment, the patterns in the data zone and those in the servo zone can be formed in a single process, thus achieving a high accuracy of the recording position of each pattern.

In the case where the recording data corresponding to the rotation angle information θ and the shift distance information r at a current timing is supplied to the deflection controller37from the main controller38, direct supply of the rotation angle information θ and the shift distance information r to the deflection controller37is not necessary. Namely, it is enough for the deflection controller37to feed the deflection signal to the high-speed deflector17only in response to the recording data.

FIG. 8shows another example of the present invention. In the electron beam recording apparatus ofFIG. 8, the same parts as those shown inFIG. 2are given the same signs. Between the blanking plate13and the deflection coil15installed in the electron column1, an aperture plate51is arranged. The aperture plate51is provided with a plurality of apertures that restrict the luminous flux of an electron beam. The aperture plate51has, as the above apertures, a circular aperture51afor one track, longitudinal aperture51bfor two tracks and51cfor three tracks, as shown inFIG. 9. The aperture plate51is arranged so that the longitudinal direction of the apertures51band51cequals to the radial direction of the disk substrate4.

The beam modulator31receives recording data from the main controller38in synchronism with clock timing, and outputs modulation signal corresponding to the recording data to the blanking plate13. The modulation signal outputted by the beam modulator31indicates the selection of one of the apertures51ato51cof the aperture plate51or no selection of the aperture. The blanking plate13deflects the electron beam ejected from the electron ejection unit11in response to the modulation signal.

When the recording data indicates on (recording) (step S11) and the judgment in step S12indicates one-track recording as shown inFIG. 10, the beam modulator31supplies the blanking plate13with a modulation signal to select the aperture51a(step S14). The blanking plate13deflects the electron beam ejected from the electron ejection unit11in response to this modulation signal. By the deflection, the electron beam passes through the aperture51aof the aperture plate51.

When the judgment in step S13indicates two-track recording, the beam modulator31supplies the blanking plate13with a modulation signal to select the aperture51b(step S15). The blanking plate13deflects the electron beam ejected from the electron emitter11in response to this modulation signal. By the deflection, the electron beam passes through the aperture51bof the aperture plate51.

When the judgment in step S13indicates three-track recording, the beam modulator31supplies the blanking plate13with a modulation signal to select the aperture51c(step S16). The blanking plate13deflects the electron beam ejected from the electron emitter11in response to this modulation signal. By the deflection, the electron beam passes through the aperture51cof the aperture plate51.

When the recording data indicates off (non-recording) (step S11), the beam modulator31supplies the blanking plate13with a modulation signal to select none of the apertures51ato51c(step S17). Corresponding to this modulation signal, the blanking plate13deflects the electron beam ejected from the electron emitter11. By the deflection, the electron beam is blocked by the aperture plate51.

The electron beam, after passing one of the apertures51ato51c, advances to the deflection coil15, the alignment coil16, the focus lens18and the object lens19to be finally irradiated onto the recording plane of the disk substrate4in the form of a spot. By electron beam irradiation on the disk substrate4, the resist layer at the irradiated area is removed. The area where the resist layer has been removed forms a recessed portion, thus giving a pattern. On the other hand, in the case where the electron beam does not pass any of the apertures51ato51c, the electron beam cannot advance any more after the aperture plate51, so that the beam is not irradiated onto the disk substrate4.

As a result, as described above, patterns comprising the servo zone and data zone as shown inFIG. 4are formed on the disk substrate4.

The longitudinal mark in the servo zone is formed sequentially from the inner periphery side of the disk substrate4, as shown, for example, inFIG. 11. InFIG. 11similarly to the foregoingFIG. 5, six tracks n to n+5 are shown. A longitudinal mark61with a length spreading over six tracks is formed as follows; first of all, an electron beam passing through the aperture51cis irradiated over the three-track length in the disk radial direction at the position of the rotation angle θi for the track n, then, an electron beam passing the aperture51bis irradiated over the two-track length in the disk radial direction at the position of the rotation angle θi for the track n+2, and further an electron beam passing the aperture51cis irradiated over the three-track length in the disk radial direction at the position of the rotation angle θi for the track n+3, so that these irradiated areas are continuously connected at the overlapping areas. A longitudinal mark62with a length spreading over four tracks is formed as follows; first of all, an electron beam passing through the aperture51bis irradiated over the two-track length in the disk radial direction at the position of the rotation angle θi+1 for the track n+1, and then, an electron beam passing the aperture51cis irradiated over the three-track length in the disk radial direction at the position of the rotation angle θi+1 for the track n+2, so that these irradiated areas are continuously connected at the overlapping areas. A longitudinal mark63with a length spreading over three tracks is formed by irradiating an electron beam passing the aperture51cover the three-track length in the disk radial direction at the position of the rotation angle θi+2 for the track n. A longitudinal mark64with a length spreading over two tracks is formed by irradiating an electron beam passing the aperture51cover the two-track length in the disk radial direction at the position of the rotation angle θi+2 for the track n+4.

Circular marks65in the data zone are formed by irradiating the electron beam passing the aperture51ain the track order of the tracks n to n+5 with an interval of a predetermined unit angle Δθ as shown inFIG. 11.

FIG. 12shows the method of forming each mark in the case where the patterns consisting of the servo zone and data zone such as shown inFIG. 6are formed, wherein the servo zone is similar to that inFIG. 11. Continuous marks66in the data zone can be formed by continuously irradiating an electron beam passing through the aperture51ain the track order of the tracks n to n+5.

Meanwhile, in the foregoing example, the aperture plate51is provided with the three apertures51ato51c, but may be provided with at least the apertures for one track and two tracks.

FIG. 13further shows another example of the present invention. In the electron beam recording apparatus shown inFIG. 13, the same parts as those shown inFIG. 8are given the same signs.

Between the blanking plate13and the deflection coil15installed in the electron column1, a high-speed deflector50and the aperture plate51are sequentially arranged. The high-speed deflector50deflects an electron beam in response to the output signal of a deflection controller39. The aperture plate51is the same one as those shown inFIGS. 8 and 9.

The beam modulator31receives recording data in synchronism with clock timing from the main controller38and outputs beam modulation signal to the blanking plate13in response to the recording data. When the recording data indicates on (recording), the blanking plate13allows the electron beam to advance to the high-speed deflector50without deflection in response to the modulation signal. On the other hand, when the recording data indicates off (non-recording), the blanking plate13deflects the electron beam in response to the modulation signal.

The deflection controller39supplies the high-speed deflector50with deflection signal in response to the recording data fed by the main controller38. This deflection signal represents selecting one of the apertures51ato51cof the aperture plate51.

When the recording data represents one-track recording (step S22), the deflection controller39supplies the high-speed deflector50with a deflection signal to select the aperture51a(step S24) as shown inFIG. 14. The high-speed deflector50deflects the electron beam ejected from the electron emitter11in response to this deflection signal, so that the electron beam passes through the aperture51aof the aperture plate51.

When the recording data represents two-track recording (step S23), the deflection controller39supplies the high-speed deflector50with a deflection signal to select the aperture51b(step S25). The high-speed deflector50deflects the electron beam ejected from the electron emitter11in response to this deflection signal, so that the electron beam passes through the aperture51bof the aperture plate51.

When the recording data represents three-track recording (step S23), the deflection controller39supplies the high-speed deflector50with a deflection signal to select the aperture51c(step S26). The high-speed deflector50deflects the electron beam ejected from the electron emitter11in response to this deflection signal, so that the electron beam passes through the aperture51cof the aperture plate51.

Since the patterns formed on the disk substrate4by irradiation of the electron beam passing one of the apertures51ato51con the disk substrate4are similar to those obtained by the electron beam recording apparatus ofFIG. 8, their explanation is omitted here.

As shown inFIG. 15, a pattern containing the mark areas (the areas exposed to an electron beam) for each of the servo zone and the data zone formed by the electron beam irradiation on the disk substrate4in each of the examples described above is formed as a latent image7in a resist layer6of the disk substrate4(exposure step). After the disk substrate4thus treated is taken out of the electron beam recording apparatus, development treatment is carried out for the disk substrate4(development step). As a result, the mark areas exposed to the electron beam dissolve to form concavo-convex patterns in the servo zone and the data zone on the disk substrate4. Via a transfer step a stamper5is made by transferring from the disk substrate4in which the concavo-convex patterns are formed.

In each of the embodiments described heretofore, electron beam recording apparatuses based on an X-θ or θ-X stage are used, but with use of an electron beam recording apparatus of X-Y type, pattern formation in the disk substrate can be carried out in a similar manner.

Next, the method of producing a magnetic disk based on the stamper5is described.

First of all, as shown inFIG. 16, a transfer layer72such as a resist layer is formed on the surface of a substrate material71. The substrate material71is placed and fixed relative to the stamper5(substrate setting). The substrate material71is made of a non-magnetic material such as glass. Transfer is carried out by applying pressure to the transfer layer72by means of the stamper5(transfer step). Nano-in-printing method is applied for the transfer. For the substrate material71after the transfer step, etching is conducted (etching step). The transfer layer72remaining after the etching step is exfoliated off (exfoliation step). Through these steps, a substrate73having a surface on which the servo zones and the data zones are formed as concavo-convex patterns is made.

Then, a magnetic material film74is formed on the concavo-convex plane of the substrate73(step for magnetic material formation). The magnetic material film74is subjected to polishing treatment to leave the magnetic material film74only at the concaved areas in the surface of the substrate73(polishing step). Namely, each pattern in the servo zones and the data zones is formed with the magnetic material. Then, a lubricating layer75is formed on the surface of the substrate73(step for lubricating layer formation), resulting in a magnetic disk.

As has been described heretofore, according to the present invention, since the electron beam recording apparatus is provided with control means for forming a latent image in a resist layer corresponding to a predetermined pattern by controlling the irradiation position caused by the electron beam irradiation unit on the surface of the resist layer in accordance with the rotation angle of the disk substrate caused by a rotational drive unit, the shift distance caused by a shift drive unit and the recording data that represents the predetermined pattern, and beam-adjusting means that can irradiate an electron beam in such a manner as to spread over a plurality of tracks in the direction of traversing the tracks in response to the irradiation position control caused by the control means, a servo pattern can be formed on a disk substrate with a high accuracy. Further, the present invention has the advantage that magnetic transfer process using a servo track writer for a magnetic disk is unnecessary, because a servo pattern can be formed on a disk substrate in advance.