JP2002050084A - Aligner for master disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner for master disk capable of correcting a pit position highly precisely at a low cost by narrowing a measurement range for the deflection correction of an exposure beam. SOLUTION: The output Δtp of a phase comparator 31 is given to a loop filter and a voltage-controlled oscillator(VCO) 32, and is simultaneously given to a deflection correction circuit 22. The output of the loop filter and the VCO 32 is given to a formatter 34 as the output of a write clock PLL circuit. That is, it is given to the formatter 34 as a write clock signal WCLK which is a reference for pit formation. Pit formation timing is also fluctuated so as to follow the fluctuation of the rotation of a spindle motor 14, and thereby, the pit position accuracy in the circumferential direction is improved. Furthermore, the Δtp which is a jitter component which the write clock PLL circuit can not follow is given to a deflection correction circuit 22, and then the fine adjustment of the deflection angle in the circumferential direction of an electron beam is performed through a deflector 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master disc exposure apparatus for producing a master disc of an information storage medium such as an optical disc by irradiating a rotating master disc with an exposure beam such as a laser beam or an electron beam. In particular, the present invention
The present invention relates to a master exposure apparatus that improves the positional accuracy of information pits formed in a circumferential direction.

[0002]

2. Description of the Related Art In this type of master exposure apparatus, a glass master coated with a resist is rotated by a spindle motor, and is moved in the radial direction of the master while irradiating the resist with an exposure beam. Thereby, a row of information pits is formed spirally or concentrically. As the exposure beam, a laser beam of visible light or ultraviolet light is often used, but an apparatus using an electron beam for realizing high-density recording with a finer beam is also being developed.

A master exposure apparatus using an electron beam emits an electron gun for generating an electron beam, an electron optical system for enlarging or reducing the diameter of the electron beam, a blanker for controlling the on / off of the electron beam, and an irradiation on the master. A deflection system for changing the spot position of the electron beam, a spindle motor for rotating the master, and an X stage for moving the spindle motor in the radial direction of the master. The master, its rotary stage and X stage are housed in a sample chamber maintained in a high vacuum.

The spindle motor is supported by air bearings (air bearings) in both the radial and thrust directions in order to minimize jitter. In order to control the rotation of the spindle motor with high accuracy, a rotary encoder capable of generating an electric signal of several thousands to tens of thousands of pulses per rotation is attached, and based on the electric signal, a PLL (phase locked loop) is provided. ) Control is performed.

FIG. 1 shows a PLL of a conventional spindle motor.
4 shows an example of a control circuit. The output signal S of the rotary encoder 15 attached to the spindle motor 14
P. en and the reference clock signal SP. ref is compared with the phase error detector 12.
FIG. 2 shows the output signal SP. e
n and the reference clock signal SP. The waveform of ref is shown.

As shown in FIGS. 1 and 2, the output signal SP. en and the reference clock signal SP. The difference Ts in the rise time from ref is output from the phase error detector 12 and supplied to the motor driver circuit 13 including the phase compensation circuit. Motor driver circuit 13
Drives the spindle motor 14 to keep the time difference Ts constant.

However, in practice, it is difficult to control the time difference Ts to be completely constant.
P. ref as a trigger, the output signal SP. When the oscilloscope observes the output signal SP.en, as shown in FIG. The rise of en is Δ
It appears to fluctuate within the range of ts. This fluctuation Δts is called jitter. This jitter Δts is, as shown in FIG.
This is caused by the time difference Ts fluctuating at a constant cycle (rotation cycle).

The jitter Δts decreases as the control frequency of the PLL control circuit increases, but when a mechanical structure such as the spindle motor 14 exists in the control loop, the control frequency of the PLL control circuit depends on the mechanical resonance frequency. Is limited. This frequency is usually around 10 Hz, which is one of the causes of deteriorating the pit position accuracy in the circumferential direction.

FIG. 4 is a schematic view showing a state in which circumferential positions of pits formed on the master by the master exposure apparatus are shifted between adjacent tracks. The master disc exposure apparatus is required to reduce such displacement to the order of nanometers.

FIG. 5 shows a configuration for correcting the above-described circumferential displacement of pits by controlling the deflection of the electron beam in a conventional master exposure apparatus using an electron beam. P of the spindle motor shown in FIG.
In addition to the LL control circuit, a phase error detection circuit 21, a deflection correction circuit 22, and a deflector 23 are provided. The phase error detection circuit 21 measures the jitter Δts, and supplies the output signal to the deflection correction circuit 22. The deflection correction circuit 22 adjusts the deflection angle of the electron beam in the circumferential direction according to the amount of the jitter Δts.

For example, the deflection correction circuit 22 has a jitter Δts
Is subjected to A / D conversion, and an average value for one round is stored as a steady component. Then, only the deviation (non-stationary component) from the average value (stationary component) is corrected by deflection. In this way, the circumferential displacement of the pits between adjacent tracks due to the jitter Δts is reduced.

[0012]

However, in the conventional configuration shown in FIG. 5, in order to control the circumferential position accuracy of the pits between adjacent tracks on the order of nanometers, the jitter by the phase error detection circuit 21 must be controlled. Extremely high precision (resolution) is required for the measurement of Δts. Moreover, a dynamic range (measurement range) that can cover the entire jitter Δts as shown in FIG. 3 is required. Therefore, not only is a multi-bit A / D converter necessary, but the voltage per step is on the order of millivolts or less, and it is necessary to reduce the noise of the entire circuit system. As a result, there is a problem that the cost of the entire circuit cannot be avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has a narrow measurement range for correcting the deflection of an exposure beam, thereby enabling low-cost and highly accurate pit position correction. It is an object to provide a master exposure apparatus.

[0014]

A master disc exposure apparatus according to the present invention intermittently irradiates an exposure beam onto a storage medium master that is rotationally driven by a rotary drive mechanism including a spindle motor, thereby providing a predetermined pit. A master exposure apparatus for performing exposure corresponding to a row, comprising: a write clock PLL for synchronizing a write clock signal serving as a reference for exposure timing with an output signal of a rotation position detection means for detecting a rotation position of the rotation drive mechanism. And a deflecting means for deflecting the exposure beam in the rotation direction based on the phase error signal of the write clock PLL circuit.

Preferably, there is further provided an arithmetic circuit for calculating a rotation fluctuation component of the rotary drive mechanism from a phase error signal of the write clock PLL circuit, and an output of the arithmetic circuit is provided to the deflection means.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 is a block diagram showing the configuration of the master exposure apparatus according to the first embodiment of the present invention. The same components as those in FIGS. 1 and 5 referred to in the description of the conventional example are denoted by the same reference numerals, and redundant description will be omitted.

The master exposure apparatus of the present embodiment includes a rotary encoder 15 mounted on a spindle motor 14.
(Hereinafter referred to as a write clock PLL circuit) using the output signal of the second clock as a reference clock.
The write clock PLL circuit has a general configuration, and includes a phase comparator 31, a loop filter VCO (voltage controlled oscillator)
32 and a frequency divider 33. Rotary encoder 1
The output signal 5 becomes one input (reference clock) of the phase comparator 31. The other input of the phase comparator 31 receives the output of the loop filter and the VCO 32 via the frequency divider 33 (signal CMP).

The output Δtp of the phase comparator 31 is supplied to the loop filter and the VCO 32 and also to the deflection correction circuit 22. Also, a loop filter and VCO3
2 is given to the formatter 34 as the output of the write clock PLL circuit. That is, the write clock signal WCLK serving as a reference for pit formation is given to the formatter 34.

Phase comparator 31, loop filter and VC
The write clock PLL circuit including the O32 and the frequency divider 33 has basically the same configuration as the PLL circuit including the phase error detector 12, the motor driver circuit 13, the spindle motor 14, and the rotary encoder 15 illustrated in FIG. . However, the write clock PLL circuit does not have a mechanical part such as the spindle motor 14 and the rotary encoder 15, and the loop filter and the VCO 32 replace it. For this reason, the write clock PLL circuit can secure a control frequency band that is about two orders of magnitude higher than the PLL circuit of the spindle motor 14.

FIG. 7 shows a reference clock signal SP.D in the master exposure apparatus of FIG. ref, rotary encoder 15
Output signal SP. en and the output signal CM of the frequency divider 33
It is a figure showing the phase relation of P. FIG. 8 shows the jitter Δ
FIG. 4 is a diagram illustrating a relationship between ts and an output Δtp of a phase comparator 31. As can be seen from these figures, the write clock P
The LL circuit is considerably (about 2 digits) compared to the jitter Δts
With the small phase comparison output signal Δtp, the spindle motor 14
Speed fluctuation can be followed. This tracking signal CM
A write clock signal WCLK that is higher than P by the frequency division ratio of the frequency divider 33 is used to generate a pit formation blanking signal. That is, the write clock signal WCLK is supplied to the formatter 34 and supplied to the blanker 36 via the output blanking driver 35.

Therefore, when the rotation of the spindle motor 14 is slow, the pit formation timing is late, and when it is fast, the pit formation timing is fast. In other words, the pit formation timing also changes so as to follow the change in the rotation of the spindle motor 14, and the pit position accuracy in the circumferential direction is improved. Further, Δtp, which is a jitter component that could not be followed by the write clock PLL circuit, is given to the deflection correction circuit 22, and fine adjustment of the deflection angle of the electron beam in the circumferential direction is performed via the deflector 23. Deflector 23
Can change the deflection angle of the electron beam in the circumferential direction by electrostatic deflection or electromagnetic deflection. Thus, the pit position accuracy in the circumferential direction is further improved.

Phase comparator 31 constituting clock PLL
May cover at least Δtp.
In contrast to the conventional configuration shown in FIG. 5 in which the phase error detection circuit 21 requires a measurement range that covers the jitter Δts, the phase comparator 31 of the configuration of the present embodiment can be used with a much narrower measurement range. This is advantageous in terms of design, and enables cost reduction and high reliability.

FIG. 9 is a block diagram showing a configuration of a master exposure apparatus according to a second embodiment of the present invention. The same components as those in FIG. 6 referred to in the description of the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

Although the conventional master exposure apparatus shown in FIG. 5 does not include a formatter unit, the master exposure apparatus of the first embodiment shown in FIG.
This makes the formatter unit independent so that it can handle multiple types of formats in a normal master disk exposure device,
This is because the master exposure apparatus of the first embodiment generates a write clock that is used as a reference by the formatter unit 34 on the master exposure apparatus (mechanism control unit) side. For this reason, the master exposure apparatus of the first embodiment has a drawback that it is difficult to separate the formatter unit and the mechanism control unit, and lacks versatility.

The second embodiment solves the above-mentioned disadvantages of the first embodiment. In the master exposure apparatus according to the second embodiment, the output Δtp of the phase comparator 31 is not supplied to the deflection correction circuit 22 as it is, but is supplied to the deflection correction circuit 22 via the Δts back calculation circuit 41. That is, when the jitter Δts of the spindle motor 14 is corrected by the deflection of the electron beam, the deflection correction amount is not directly obtained from Δtp, but the deflection is determined based on Δts obtained by reversely calculating the Δts back calculation circuit 41 from Δtp. A correction amount is obtained.

The Δts back calculation circuit 41 generates a clock PL which is a result of the clock PLL not following the jitter Δts.
L phase error (ie, output of phase comparator 31) Δtp
And the jitter Δts is calculated back using the transfer function of the clock PLL. That is, if the loop transfer function of the clock PLL is G (s), Δts can be obtained from the following equation.

Δts = (G (s) −1) Δtp If a recent high-speed processor is used, the phase error of the clock PLL can be digitized, and the control operation can be performed by software. Therefore, from the above equation, Δt
It is also easy to reversely calculate s, extract a non-stationary component, and execute deflection correction limited to the non-stationary component. In this embodiment, similarly to the first embodiment, the measurement range of the phase error Δtp of the clock PLL may be narrower than the measurement range of the jitter Δts. Therefore, the superiority with respect to the circuit noise is ensured, and the effect that cost reduction and high reliability can be obtained is also obtained.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, but can be implemented in various forms. For example, the master exposure apparatus of the above embodiment uses an electron beam as an exposure beam, and uses an electrostatic deflector or an electromagnetic deflector as a deflecting apparatus for the exposure beam in the circumferential direction, but the present invention is not limited to this. is not. The present invention can also be applied to a master exposure apparatus using a laser beam as an exposure beam and an EOD deflector using a photoelectric effect of a crystal as a device for deflecting the exposure beam in the circumferential direction.

[0029]

As described above, according to the master exposure apparatus of the present invention, the measurement range of the circuit for detecting the circumferential pit position shift caused by the jitter of the rotary drive system including the spindle motor is narrowed. Therefore, it is possible to use an A / D converter having a low resolution and to raise the allowable value of the electrical noise level. as a result,
Improvement of the pit position accuracy in the circumferential direction can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a PLL control circuit of a conventional spindle motor.

FIG. 2 is a diagram showing waveforms of an output signal of a rotary encoder and a reference clock signal in the configuration of FIG. 1;

FIG. 3 is a diagram showing how the time difference Ts fluctuates at a constant cycle in the configuration of FIG. 1;

FIG. 4 is a schematic diagram showing a state in which circumferential positions of pits formed on a master by a master exposure apparatus are shifted between adjacent tracks.

FIG. 5 is a diagram showing a configuration for correcting a circumferential pit position shift by controlling deflection of an electron beam in a conventional master exposure apparatus using an electron beam.

FIG. 6 is a block diagram showing a configuration of a master exposure apparatus according to the first embodiment of the present invention.

7 is a diagram showing a phase relationship among a reference clock signal, an output signal of a rotary encoder, and an output signal of a frequency divider in the master exposure apparatus of FIG. 6;

FIG. 8 is a diagram illustrating a relationship between a jitter Δts and an output Δtp of a phase comparator.

FIG. 9 is a block diagram illustrating a configuration of a master exposure apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 14 spindle motor 15 rotation position detection means 22, 23 deflection means 31, 32, 33 write clock PLL circuit 41 arithmetic circuit WCLK write clock signal Δtp phase error signal Δts rotation fluctuation component of rotation drive mechanism

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 19/06 501 G11B 19/06 501E F-term (Reference) 2H097 AA03 AB07 BB03 CA16 CA17 LA20 5D066 FA02 GA03 GA04 GA06 5D090 AA01 BB01 CC01 DD03 EE02 FF07 FF50 5D118 AA27 BA01 BB09 BF03 CD05 CD17 5D121 AA02 BB21 BB38 BB40

Claims (2)

[Claims] 1. A master disc exposure apparatus for performing exposure corresponding to a predetermined pit row by intermittently irradiating an exposure beam to a storage medium master that is rotationally driven by a rotary drive mechanism including a spindle motor. A write clock PLL circuit for synchronizing a write clock signal serving as a reference for exposure timing with an output signal of a rotational position detecting means for detecting a rotational position of the rotary drive mechanism; and a phase error signal of the write clock PLL circuit. And a deflecting means for deflecting the exposure beam in the rotation direction based on the original. 2. An apparatus according to claim 1, further comprising an arithmetic circuit for calculating a rotation fluctuation component of said rotary drive mechanism from a phase error signal of said write clock PLL circuit, wherein an output of said arithmetic circuit is provided to said deflection means. Item 3. A master exposure apparatus according to Item 1.