JP2003332217A - Electron beam lithography system and information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably draw snaking continuous grooves or a pit column with small pitches by compensating a proximity effect caused by adjoining pattern exposure with a simple constitution, when the snaking continuous grooves or the pit column are formed at a constant period, with one electron beam in a continuous exposure mode of only one time. <P>SOLUTION: An aperture 13 that performs beam shaping for an electron beam comprises: an mechanism part 14 with variable aperture that continuously varies an area of an aperture part 22 through which the electron beam passes; and a part 15 for varying the area of aperture that controls the degree of opening of the mechanism part 14. A pattern generator 31 sends an aperture area control signal, corresponding to a pattern to be drawn, to the part 15, to vary the degree of opening of the mechanism part 14. Thereby a diameter of the electron beam is controlled. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing apparatus and an information recording medium used in the field of micromachining various media for recording information such as semiconductors, encoders, optical elements or mastering steps of masters for optical disks, and more particularly,
Rather than the overpainting drawing mode, a continuous exposure mode is performed only once with one electron beam, for example, a continuous groove or pit row meandering with a regular cycle is formed along a virtual spiral locus with a constant pitch. The present invention relates to the correction of the proximity effect caused by the adjacent pattern exposure at the time.

[0002]

2. Description of the Related Art For example, in a mastering process of a master for an optical disk, a resist film is usually exposed to a laser beam to form a bit and a guide groove. The limit of exposure of this laser beam is determined by the diffraction limit of light determined by the wavelength of light and the numerical aperture of the objective lens, and in order to cope with the recent increase in the amount of information surrounding information devices such as computers, it is the limit. There is. In order to form minute pits and grooves that exceed the exposure limit of the laser beam, an electron beam drawing method used in a semiconductor process is being studied.

An electron beam drawing apparatus employs a stepper exposure method as represented by a semiconductor process. As an electron beam scanning method, a rectangular pattern or a circle or an ellipse arranged on a semiconductor chip is used. As shown in FIG. 11 (a), raster scanning or vector scanning, which is a drawing mode in which these areas 50 are overwritten and filled, is adopted. Further, a continuous movement method using an X-θ table is adopted as the stage movement method. This continuous movement method is a method of holding a wafer or a glass plate on a stage and continuously moving it at a predetermined speed to perform drawing, and feed back the position change and control error of the stage to an electron beam deflector to The electron beam irradiation point does not move when viewed from the gun. That is, the pattern shape accuracy and the position accuracy are governed by the interaction between the X-θ table and the electron gun. When a rectangular pattern such as a semiconductor chip is drawn using this overpainting method, overexposure is allowed in almost all parts except the area boundary line, and only the positional accuracy of the start and end points of the area is a problem. .

[0004]

When the master for an optical disc is exposed by this electron beam drawing apparatus, the electron beam scanning method is as shown in FIG. It is necessary to adopt a one-stroke drawing method in which only the line 51, which is approximately exposed to the beam size, is continuously exposed and drawn with one stroke. 3m when drawing with this one-stroke method
High-speed drawing of / s or more and position control in nm unit are required. Further, when the pattern shape accuracy is 40 GB / square inch, only variations of 10 nm or less are allowed.
In order to satisfy such high-speed drawing performance, an X-θ table that has a high-speed rotation and nm feed accuracy is arranged, and the blanking rising time 1
nm, electron beam deflection of 40 MHz, etc. are required. All pit lengths and widths and groove widths and phases formed by drawing with the one-stroke method are the time and address information itself, and are used to determine various signal values and jitter in the final recording medium. It is necessary to improve the exposure quality by performing fine control in.

As fine control in this exposure process, (a) high density recording in which the size of pits is modulated,
(B) Fine adjustment of the pit width and groove width in the pre-formatting of the RAM disk, and (c) Correction of exposure interference, that is, proximity effect, which becomes a problem when the meandering grooves periodically approach each other.

The proximity effect is a phenomenon in which incident electrons are reflected and scattered backward inside the substrate, and a portion other than a predetermined area is also exposed. This proximity effect becomes more remarkable as the pit width or groove width and pitch amount of the actual pattern become smaller, and adjacent pits or groove boundary areas are crushed and become indistinguishable. For example, the results of plotting the pit diameter and groove width against the dose time, which is the irradiation time of the electron beam per unit length, when the electron beam diameter, exposure time, and pitch level were experimentally combined and exposed. Is shown in FIG. As shown in FIG. 7, as the pitch becomes smaller, the dot diameter becomes larger due to the proximity effect. In the master disk for a disc, pattern density such as track pitch is narrowed due to high density of recorded information, and it is necessary to reduce the influence of proximity effect.

As a method of reducing the proximity effect, according to Monte Carlo simulation, if the acceleration voltage of incident electrons is increased to 100 KeV, the scattering term becomes small and the proximity effect can be avoided. However, the exposure efficiency is extremely reduced and the processing throughput time becomes enormous, which is not practical. In reality, an electron beam of about 20 KeV must be used, and the exposure energy must be adjusted to correct the proximity effect. There is. The exposure energy is determined by the acceleration voltage or current value of the electron beam and the beam diameter. Since the current electron beam drawing apparatus is premised on that the acceleration voltage and the current value are constant, it is necessary to adjust the beam diameter on the drawing surface in order to adjust the exposure energy.

How the line width drawn on the resist of the disk by the one-stroke drawing method changes by adjusting the beam diameter will be described. As in the case of laser beam exposure, the electron beam used for drawing has a two-dimensional Gaussian distribution on the XY plane, and the standard deviation of the Gaussian distribution is σ,
When the beam current is I, the current density distribution J (X, Y) of the electron beam to be drawn can be expressed by the following equation (1).

[0009]

[Equation 1]

When the electron beam scans the disk surface in the Y direction at a speed v, the exposure dose crosses the X direction.
The distribution of can be expressed by the following equation (2).

[0011]

[Equation 2]

Assuming an initial γ value of the resist sensitivity S and neglecting electron scattering in the resist and the substrate, ± X
The width line is developed. At this time, the line width w at the half-value width of the beam diameter d can be expressed by the following equation (3).

[0013]

[Equation 3]

From the equation (3), the line width w is determined by the line dose I / v, the beam diameter d and the resist sensitivity S. That is, by changing the line dose,
You can measure the line width drawn with an electron beam,
The beam diameter d and the resist sensitivity S can be evaluated from the equation (3). Further, for simplification, the following equation (4) can be derived by rearranging the equation (3) by the least squares method.

[0015]

[Equation 4]

As shown in equation (4), W ² and ln (I / v)
There is a linear relationship between the two, and the line width w can be controlled by adjusting the beam diameter d.

As a method of adjusting the beam diameter d, a variable shaped beam system utilizing overlapping and beam deflection of apertures for on / off modulation of an electron beam and beam shaping, selection of an aperture and beam deflection are used. There are two methods, one is a pattern transfer beam method which is used, and the other is a Gaussian beam method by switching a zoom lens or a lens. The variable shaped beam method and the figure batch transfer beam method are originally used for high-speed painting of a predetermined specific pattern, such as a rectangle or a circle, and are used in the mastering process of optical disks. It is not suitable for the one-stroke drawing method. In addition, the Gaussian beam type zoom lens system controls the combination of the intensities of the first and second converging lenses, and the lens switching system selects either the first or second converging lens to select each beam. Although the diameter is controlled, it takes 5 minutes or more to stabilize each of them, and it is difficult to control the beam diameter d so that the rod follows the speed when performing high-speed drawing by the one-stroke drawing method.

The present invention has been made to solve the above-mentioned disadvantages, and a continuous groove or pit train that meanders at a regular cycle is formed in a continuous exposure mode of only one electron beam. An electron beam drawing apparatus and an information recording medium capable of stably writing a meandering continuous groove or a pit row by correcting a proximity effect due to adjacent pattern exposure when forming, by a simple configuration. It is intended to be provided.

[0019]

An electron beam drawing apparatus according to the present invention performs beam shaping of an electron beam in an electron beam drawing apparatus which draws only one electron beam in a continuous exposure mode. The aperture has an aperture variable mechanism that continuously changes the area of the aperture through which the electron beam passes, and an aperture area variable that controls the aperture of the aperture variable mechanism.
The drawing control unit is characterized in that it sends an opening area control signal according to a pattern to be drawn to the opening area changing unit.

When exposing the resist film of the master for the information recording medium, the drawing control unit determines that the distance between adjacent tracks or adjacent pits in the radial direction is constant depending on the exposure conditions, the thickness of the resist film and the resist material. At a position below the value, an aperture area control signal that reduces the aperture of the aperture variable mechanism section is sent to the aperture area variable section to change the electron beam diameter that exposes the resist film and change the exposure energy to achieve the proximity effect. to correct.

Further, the aperture area varying portion continuously varies the opening degree of the aperture varying mechanism portion by the expansion / contraction action of the electrostrictive element.

Further, the drawing control section calculates and determines the control amount and timing of the opening degree of the opening variable mechanism section based on the pattern generation signal and the actual exposure position information, and enhances the accuracy of exposure correction.

Furthermore, the drawing control unit introduces the reciprocal value of the inter-pattern distance to achieve the target shape with higher accuracy when calculating the control amount and timing of the opening degree of the opening variable mechanism unit.

The information recording medium according to the present invention is manufactured by the master disk manufactured by the electron beam drawing apparatus, and records high quality information with reduced jitter and reading error rate.

[0025]

1 is a block diagram of an electron beam drawing apparatus of the present invention. The electron beam drawing apparatus 1 used in the mastering process of an optical disk has an electron beam unit 2 and a table driving unit 5 that horizontally moves horizontally while rotating a turntable 4 holding a resist plate 3 for drawing in a vacuum chamber 6. It is provided. A load lock chamber 7 is provided in the vacuum chamber 6 as a spare chamber.
It is arranged on an extension of the turntable 4 inside.

The electron beam unit 2 has an electron beam generating system 8 and an electron beam lens system 9 for focusing the generated electron beam. The electron beam generation system 8 has an electron gun 10, a condenser lens 11, an electron beam modulator 12 having a pair of electrodes, and an aperture 13. Electron gun 10
Emits an electron beam. The condenser lens 11 emits an electron beam emitted from the electron gun 10 to an electron beam modulator 12
Focus on. The electron beam modulator 12 deflects the electron beam by the electromagnetic field generated by the pair of electrodes and irradiates the aperture 13 with the electron beam. The aperture 13 is shown in FIG.
As shown in the block diagram of FIG. 1, the aperture changing mechanism unit 14 for changing the area of the aperture through which the electron beam passes and the aperture changing mechanism unit 1
The opening area variable unit 15 variably controls the opening degree of No.
As shown in the plan view of FIG. 3, for example, the variable aperture mechanism unit 14 uses a diaphragm mechanism of a camera, is formed in an annular shape, and has a rotating plate 17 having a protrusion 16 on the outer peripheral portion and, for example, a thickness of 10 μm. It has a plurality of movable blades 18 formed of a metal plate such as stainless steel. Each movable blade 18 has an inner peripheral surface formed of a parabolic curved surface, and has a guide pin 20 that fits into a guide groove 19 provided in the rotating plate 17, and the fixed pin 2
1 is rotatably attached to the movable blade 18, the opening 22 is formed on the inner peripheral surface of the movable blade 18, and the rotary plate 17 is rotated by the protrusion 16 so that the movable blade 18 is guided by the guide groove 1.
The area of the opening 22 is changed by rotating in accordance with 9. The opening area varying unit 15 has an electrostrictor 24 provided so as to face a case 23 formed in a U shape with the protrusion 16 of the rotating plate 17 interposed therebetween. As the material of the electrostrictive element 24, for example, Pb (MgxNby) O ₃ -PbTiO ₃ -based ceramics can be used to easily obtain the electric field induced strain of 0.2%. The electron beam lens system 9 includes an electron beam deflector 25 having a pair of electrodes, a first focus lens 26 and a second focus lens 27.

The table driving section 5 includes a rotating mechanism section 28 having a motor for rotating the turntable 4, and a rotating mechanism section 2.
It has a feed mechanism section 29 for moving 8 in the horizontal direction. The table driving unit 5 and the vacuum chamber 6 are installed on the stone surface plate 30 to prevent the influence of disturbance vibration.

As shown in FIG. 2, the electron beam modulator 12 of the electron beam unit 2, the aperture area variable unit 15 of the aperture 13, and the electron beam deflector 25 are modulated according to a graphic pattern drawn from the pattern generator 31. A signal, an aperture area control signal and a deflection control signal are sent respectively. Further, a driver 32 for driving and controlling each motor of the rotation mechanism section 28 and the feed mechanism section 29 of the table drive section 5,
A rotation control signal and a feed control signal are sent to the pattern generator 33 from the pattern generator 31, respectively.

On the resist plate 3 in the electron beam drawing apparatus 1,
When writing an information track in the CLV format (constant linear velocity), the table driving unit 5 rotates the turntable 4 holding the resist plate 3 and sends it at a constant pitch, while the electron gun 10 of the electron beam generation system 8 emits electrons. Emit the beam. The emitted electron beam is condensed by the condenser lens 11 and deflected when passing through the electromagnetic field generated by the electron beam modulator 12 composed of a pair of electrodes. The deflected electron beam is applied to the aperture 13. When the deflection of the electron beam is large, it is blocked by the aperture 13 and does not reach the resist plate 3, and when it is not deflected, it passes through the opening 22 of the aperture 13 and reaches the resist plate 3, which is similar to the light modulation. / Off modulation can be performed. Further, when the electron beam passes through the opening 22 of the aperture 13, beam shaping is simultaneously performed and is introduced into the electron beam lens system 9. In the electron beam lens system 9, when forming a wobbled groove, the electron beam deflector 25 gives a deflection angle to the electron beam. After that, the electron beam is focused on the resist plate 3 by the first focus lens 26 and the second focus lens 27, and as shown in FIG. 4, spiral tracks 34 of equal pitch are drawn.

As shown in FIG. 5, the grooves 35 formed in the resist plate 3 by this drawing meander (wobble) based on the rule that the adjacent grooves 35 are present. The meandering amplitude (fluctuation width) and cycle mean address and time. Proximity parts and distant parts are intricately mixed and mixed, and approach and disperse are repeated with a fixed period. This meandering state is schematically shown in FIG. FIG. 5A shows, for example, N in FIG.
The track portion and the (N + 1) track portion are enlarged, and the distance between the tracks 34 changes as time t1 to tn to t (n + m) elapses. When drawing the meandering track 34, if the resist plate 3 is exposed until the electron beam diameter is constant, at the time tn when the track 34 approaches, a groove thicker than a predetermined value is formed due to the proximity effect and the amplitude value becomes large. I will end up.

Therefore, as shown in FIG. 5B, an aperture area control signal is sent from the pattern generator 31 to the electrostrictor 24 of the aperture area variable section 15 of the aperture 13 in accordance with the pattern of the meandering track 34, and electrostriction is performed. Inflate child 24,
The electron beam passing through the aperture 13 is contracted to move the protrusion 16 to rotate the rotary plate 17 to rotate the movable blade 18 to change the area of the opening 22 formed in the inner peripheral portion of the movable blade 18 The proximity effect is corrected by changing the bundle and changing the electron beam diameter for writing on the resist plate 3. In this way, a meandering groove having a constant width can be formed in the resist plate 3.

As shown in FIGS. 7 (a) and 7 (b), the aperture area control signal output from the pattern generator 31 according to the pattern of the meandering track 34 includes electron beam diameter, exposure time, and pitch level. When various combinations are experimentally used for exposure, an appropriate correction amount of the electron beam diameter is obtained from the experimental results obtained by plotting the pit diameter and the groove width, and is applied, or the groove width calculation formula (4) is used. The appropriate correction amount of the electron beam diameter may be obtained and applied from the calculation result shown in FIG. 8 which is calculated by changing the parameter d indicating the electron beam diameter at. For example, in FIG. 8, if the opening diameter is reduced by 5 μm under the condition of the probe current of 1.00E-09, the diameter reduction rate of about 10% can be obtained. Controlling the diameter reduction rate to about 0.5% is practically sufficient. A frequency response of about 20 MHz is required for forming the meandering groove, but a frequency response of about 200 KHz at maximum can be secured for the correction of the proximity effect.

For example, as shown in FIG. 7B, a parameter as an SQRT proximity effect index was developed based on the experimental result of the dose time which is the irradiation time of the electron beam per unit length and the groove width. FIG. 9 shows the result of examining the correlation with the actual groove width with the value on the horizontal axis. The parameter of this SQRT is defined by the square root of the product of the reciprocal of the dose time and the distance between adjacent patterns. As shown in FIG. 9, the correlation between the SQRT parameter and the actual groove width is good, and by combining the SQRT parameter with the groove width calculation formula (4), the required electron beam diameter can be increased. Can be accurately determined.

That is, the dose time is constant in the CLV exposure mode. If the meandering amount of the groove is ± 0.1 pitch with respect to the reference pitch of the spiral track 34, the pitch becomes 0.2 pitch at the closest position. The effect of this on the groove width can be obtained by substituting X ± ΔX into the curve relational expression in FIG. 7. By using the obtained groove width change ΔW in the equation (4) which is the theoretical expression of the groove width, the required electron beam diameter change Δd can be obtained, and the aperture of the aperture 13 is made to achieve this change. The opening area of the portion 22 may be controlled.

Further, when writing a pit row, pit groups having different lengths have different integrated energies of the electron beam traveling direction component, and the longer the length, the thicker the pit width. Also in this case, the pits having a uniform width can be formed by changing the opening area of the opening 22 of the aperture 13 according to the pattern of the pit group having different lengths.

In the above description, the case in which the aperture changing mechanism portion 14 of the aperture 13 has the same mechanism as the aperture of the camera has been described. However, as shown in FIG. 10, the opposing surfaces are formed by a quadratic curve such as an ellipse. The two movable blades 40 are overlapped to form the opening 22, and the electrostrictor 24 fixed to the fixed member 41 is attached to each of the two movable blades 40.
A tension spring 42 is attached between the fixed member 41 and the movable blade 40, and the two movable blades 40 are moved according to a pattern drawn by the electrostrictor 24 and the tension spring 42 to change the opening area of the opening 22. You may do it.

[0037]

As described above, the present invention has a variable aperture area mechanism provided in an aperture for beam shaping of an electron beam when writing is performed in a continuous exposure mode of only one electron beam. Since the area of the opening through which the electron beam passes is continuously changed in the part, the exposure energy of the electron beam can be adjusted with high accuracy, and the desired pattern can be drawn with high accuracy while avoiding excessive decrease in exposure. be able to.

Further, when the resist film of the master for the information recording medium is exposed, the distance between adjacent tracks or adjacent pits in the radial direction becomes less than a constant value determined by the exposure condition, the thickness of the resist film and the resist material. By changing the exposure energy by changing the electron beam diameter that exposes the resist film by decreasing the opening of the opening area variable mechanism at the position, it is possible to correct the proximity effect and draw a stable pattern. it can.

In addition, the opening area varying unit changes the opening degree of the opening area varying mechanism section by the expansion and contraction action of the electrostrictive element, so that the opening degree of the opening area varying mechanism section can be continuously and stabilized with a simple structure. You can change it.

Further, the irradiation position information of the electron beam is reflected in real time by calculating and determining the control amount and timing of the opening of the opening area variable mechanism section based on the pattern generation signal and the actual exposure position information. The exposure correction accuracy can be stably maintained.

Further, by introducing the reciprocal value of the inter-pattern distance when calculating the control amount and timing of the opening degree of the opening area variable mechanism section, the target shape can be achieved more accurately and stable. The drawn pattern can be drawn.

By producing the information recording medium from the master produced by this electron beam drawing apparatus, it is possible to provide an information recording medium such as a high-quality optical disc with reduced jitter and read error rate.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electron beam drawing apparatus of the present invention.

FIG. 2 is a block diagram showing a configuration of an electron beam drawing apparatus.

FIG. 3 is a configuration diagram of an aperture.

FIG. 4 is a plan view showing a spiral track drawn on a resist plate.

FIG. 5 is a schematic view showing a meandering groove.

FIG. 6 is a schematic diagram showing a meandering track and an electron beam diameter with respect to the meandering track.

FIG. 7 is a characteristic diagram showing experimental results of changes in dot diameter and groove width with respect to dose time.

FIG. 8 is a change characteristic diagram of the probe current and the probe diameter when the aperture diameter of the aperture is changed.

FIG. 9 is a characteristic diagram showing an index of SQRT proximity effect.

FIG. 10 is a configuration diagram of another aperture.

FIG. 11 is a schematic diagram showing a pattern to be drawn.

[Explanation of symbols]

1; electron beam drawing apparatus, 2; electron beam unit, 3; resist plate, 4; turntable, 5; table drive unit,
6; vacuum chamber, 7; load lock chamber, 8; electron beam generation system, 9; electron beam lens system, 10; electron gun, 1
1; condenser lens, 12; electron beam modulator, 1
3; Aperture, 14; Aperture changing mechanism part, 15; Aperture area changing part, 16; Protrusion, 17; Rotating plate, 18; Movable blade, 22; Opening part, 24; Electrostrictor, 25; Electron beam deflecting part, 26; 1st focus lens, 27; 2nd focus lens, 28; rotation mechanism part, 29; feed mechanism part, 30; stone surface plate, 31; pattern generator.

Claims (6)

[Claims] 1. In an electron beam drawing apparatus for drawing with a single electron beam in a continuous exposure mode only once, the aperture for forming the beam of the electron beam has a continuous aperture area through which the electron beam passes. It has an opening variable mechanism part for changing and an opening area variable part for controlling the opening degree of the opening variable mechanism part, and the drawing controller sends an opening area control signal according to the pattern to be drawn to the opening area variable part. An electron beam drawing apparatus characterized by: 2. When the resist film of a master for an information recording medium is exposed, the drawing controller determines the distance between adjacent tracks or adjacent pits in the radial direction depending on the exposure condition, the thickness of the resist film and the resist material. An exposure area control signal for reducing the opening degree of the aperture variable mechanism section is sent to the aperture area variable section at a position where the value becomes a certain value or less, and the exposure energy is varied by changing the electron beam diameter for exposing the resist film. The electron beam drawing apparatus according to claim 1. 3. The opening area varying portion varies the opening degree of the opening varying mechanism portion by the expansion and contraction action of an electrostrictive element.
Alternatively, the electron beam drawing apparatus according to item 2. 4. The drawing control unit calculates and determines the control amount and timing of the opening degree of the opening variable mechanism section based on the pattern generation signal and the actual exposure position information to determine.
The electron beam drawing apparatus described. 5. The electron beam drawing apparatus according to claim 4, wherein the drawing control unit introduces a reciprocal value of the inter-pattern distance when calculating the control amount and timing of the opening degree of the opening variable mechanism unit. 6. An information recording medium produced by using a master produced by the electron beam drawing apparatus according to claim 2.