JP6000203B2 - Power supply device and electron beam drawing apparatus for electron beam generator - Google Patents

Description

  The present invention relates to a power supply device and an electron beam drawing apparatus for an electron beam generator that generates an electron beam from an electron gun.

  For example, there is an electron beam drawing apparatus as an electron beam generating apparatus that generates an electron beam from an electron gun. The electron beam drawing apparatus performs drawing by irradiating an object with an electron beam from an electron gun. The electron beam is accelerated by a voltage from a high-voltage power supply device and irradiated from an electron gun (see, for example, Patent Document 1). The power supply device of the electron beam drawing apparatus is composed of a high voltage unit that generates a high DC voltage and a control unit for controlling the output voltage of the high voltage unit to be constant. The output voltage of the high voltage unit is the load of the electron gun that is a load. Output as acceleration voltage.

  In such an electron beam drawing apparatus power supply device, when the acceleration voltage, which is the output voltage of the high voltage unit, is several tens kV of direct current, the stability standard is strict, for example, 2.0 ppm / hour. In order to maintain the stability standard, the voltage fluctuation range of the acceleration voltage is preferably less than 2.0 ppm / hour.

  The high-voltage unit of the power supply device of the electron beam lithography system boosts the AC voltage from the inverter circuit of the control unit with a transformer, converts it into a DC voltage boosted with a high-voltage generator, and uses it as an acceleration voltage for the electron gun. Output.

  In this case, in order to approximate the voltage waveform on the primary side of the transformer to a sine wave, the secondary open inductance of the transformer (inductance converted to the primary side when the secondary winding of the transformer is opened) and The parallel resonance is performed by the equivalent input capacitance of the high voltage generator (primary conversion value of the stray capacitance on the secondary side). That is, the drive frequency of the main element of the inverter circuit of the control unit is adjusted to coincide with this resonance frequency. Thereby, the voltage fluctuation width of the electron beam from the electron gun is reduced, and the acceleration stability is stabilized.

JP-A-5-144404

  However, in the conventional device, when the output current of the electron gun that is a load changes, the resonance frequency changes. As a result, the drive frequency deviates from the resonance frequency, and the acceleration stability may become unstable. The reason why the resonance frequency changes when the output current changes is that the impedance on the output side viewed from the input side changes due to the change in the output current.

  Therefore, when the output current is constant or the output current range is narrow, the drive frequency of the main element of the inverter circuit of the control unit can be handled at a constant frequency (resonance frequency), but the load of the electron gun When the operating width of the output current is increased, the driving frequency is deviated from the resonance frequency, and the acceleration stability is not stabilized.

  Until now, the operating range of the output current of the electron beam drawing apparatus has been narrow, but recently, an electron beam drawing apparatus having a large output current has been developed, and the operating range of the output current has been increased.

  An object of the present invention is to provide a power supply device and an electron beam drawing apparatus for an electron beam generator that can be adjusted to an optimum driving frequency in accordance with the operating range of the output current of the electron beam generator.

A power supply device for an electron beam generator according to the present invention includes a high voltage unit that generates a DC high voltage as an acceleration voltage of an electron gun of the electron beam generator, a constant output voltage of the high voltage unit, and the electron gun. A control unit for controlling the output current of the current setter to be a current set value set in the current setter, and a digital potentiometer linked to the current set value of the current setter, and based on the set position of the digital potentiometer And a frequency setting unit for setting the drive frequency so that the drive frequency of the control unit becomes a predetermined frequency.

  An electron beam drawing apparatus according to the present invention comprises the power supply device for an electron beam generator according to claim 1 or 2.

  According to the present invention, it is possible to adjust to an optimum driving frequency corresponding to the operating width of the output current of the electron beam generator, and thus a stable acceleration voltage can be obtained. In addition, the frequency setting unit has a digital potentiometer that is linked to the current setting value, so fine adjustment of the frequency setting is possible, and the frequency setting can be performed accurately even when the operating range of the output current is widened. Is obtained.

The block diagram of the power supply device of the electron beam generator which concerns on embodiment of this invention. The graph which shows the relationship between the output current of an electron gun and acceleration voltage stability which made the parameter the drive frequency of the control unit in embodiment of this invention. The wave form diagram of the acceleration voltage of the drive frequency f1 of the control unit in the embodiment of the present invention. The wave form diagram of the acceleration voltage of the drive frequency f2 of the control unit in the embodiment of the present invention.

  Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram of a power supply device of an electron beam generator according to an embodiment of the present invention. In the following description, a case where the power supply device for the electron beam generator is a power supply device for an electron beam lithography apparatus will be described. The power supply device of the electron beam drawing apparatus includes a high voltage unit 11 that generates a high DC voltage, a control unit 12 that controls the output voltage and output current of the high voltage unit 11, and a frequency for setting the drive frequency of the control unit 12. The setting unit 13 includes a current setting unit 15 for setting a current setting value of an output current of the high voltage unit 11 (an output current of the electron gun 14).

  The high voltage unit 11 includes a transformer 17 that receives and boosts the AC voltage from the inverter circuit 16 of the control unit 12, and a high voltage generator 20 that further boosts the AC voltage boosted by the transformer 17 and converts it into a DC voltage. Have

  The transformer 17 of the high voltage unit 11 boosts the AC voltage obtained by the inverter circuit 16 of the control unit 12. The inverter circuit 16 of the control unit 12 drives and controls the main element of the inverter circuit 16 at the drive frequency set by the frequency setting unit 13 by the frequency circuit 18 of the control unit, and the DC voltage of the DC power source 19 is changed to an alternating current of a predetermined frequency. Convert to voltage.

  Here, the predetermined frequency is a frequency at which the voltage fluctuation width of the electron beam from the electron gun 14 satisfies the stability standard. For example, the resonance frequency of the parallel resonance circuit formed by the inductance L2 when the secondary winding of the transformer 17 of the high-voltage unit 11 is opened and the stray capacitance C2 on the secondary side of the transformer 17 is used. In the present invention, the inductance L2 when the secondary winding of the transformer 17 is opened and the stray capacitance C2 on the secondary side of the transformer 17 are externally connected to the inductance and stray capacitance. This also includes the case where capacity is added.

  By making the drive frequency of the main element of the inverter circuit 16 (hereinafter referred to as the drive frequency of the control unit) the resonance frequency of the parallel resonance circuit, the voltage waveform on the primary side of the transformer 17 is made close to a sine wave, and the electron gun 14 To reduce the voltage fluctuation range of the electron beam from and stabilize the acceleration stability.

  Next, the high pressure generator 20 of the high voltage unit 11 is formed by a Cockcroft-Walton circuit. The Cockcroft-Walton circuit is formed by connecting half-wave voltage doubler rectifier circuits in multiple stages, and has a function of boosting an AC voltage and converting it to a DC voltage. The output voltage of the high voltage generator 20 is output as the acceleration voltage of the electron gun 14 that is a load.

  The output voltage of the high voltage generator 20 is detected by the voltage detector 21, and the output current of the high voltage generator 20 is detected by the current detector 22 and input to the control circuit 23 of the control unit 12. The control circuit 23 of the control unit 12 ensures that the output current of the high voltage generator 20 becomes the current set value set by the current setter 15, and the output voltage of the high voltage generator 20 becomes a predetermined voltage. Thus, the inverter circuit 16 is controlled. As a result, the applied voltage of the electron gun 14 becomes a predetermined voltage, and the output current of the electron gun 14 becomes a current setting value set in the current setting device 15.

  The frequency setting unit 13 sets the driving frequency of the control unit 12 based on the current setting value set in the current setting unit 15 so that the driving frequency of the control unit 12 becomes a predetermined frequency (resonance frequency of the resonance circuit). To do. As described above, when the output current of the electron gun 14 that is a load changes, the resonance frequency of the resonance circuit changes. As a result, the drive frequency of the control unit 12 deviates from the resonance frequency, and the voltage fluctuation range of the electron beam increases. Acceleration stability may not be stable.

  Therefore, in order to reduce the voltage fluctuation range of the electron beam from the electron gun 14 and stabilize the acceleration voltage stability, the drive frequency of the control unit 12 is adjusted to be a predetermined frequency (resonance frequency of the resonance circuit). That is, the drive frequency of the control unit 12 is changed so that the drive frequency of the control unit 12 becomes a predetermined frequency (resonance frequency of the resonance circuit) in accordance with the current setting value set in the current setting device 15.

  The frequency setting unit 13 includes a digital potentiometer 24 that is linked to the current set value of the current setter 15, and the pulse generator 25 is configured so that the drive frequency of the control unit 12 is set to a predetermined frequency based on the set position of the digital potentiometer 24. Thus, the drive frequency of the control unit 12 is set in the frequency circuit 18. For example, the pulse generator 25 is formed by a timer IC, a digital potentiometer 24 is provided instead of the variable resistor, and the frequency is adjusted by changing the wiper of the setting position of the digital potentiometer 24.

  FIG. 2 is a graph showing the relationship between the output current of the electron gun 14 and the acceleration voltage stability with the drive frequency of the control unit 12 in the embodiment of the present invention as a parameter. FIG. 2 shows the acceleration voltage stability when the output voltage (acceleration voltage) of the high voltage generator 20 is about E0 kV of direct current. Moreover, the drive frequency f of the control unit 12 shows a case where it is changed between f1 <f <f2. As described above, when the acceleration voltage is E0 kV, the stability standard is 2.0 ppm / hour, so that the voltage fluctuation range of the acceleration voltage is preferably less than 2.0 ppm / hour. A function of this graph is stored in the pulse generation circuit 25 in advance.

  As shown in FIG. 2, when the drive frequency f of the control unit 12 is f1, the voltage fluctuation range of the acceleration voltage satisfies less than 2.0 ppm / hour because the output current of the electron gun 14 is in the range ΔI1 between I11 and I12. It is. When the drive frequency f of the control unit 12 is f2, the voltage fluctuation width of the acceleration voltage satisfies less than 2.0 ppm / hour is in the range ΔI2 where the output current of the electron gun 14 is I22 or less.

  Similarly, for the drive frequencies fa, fb, fc, and fd that satisfy f1 <fa <fb <fc <fd <f2, the output current of the electron gun 14 is the same at the drive frequency fa (f1 <fa <fb). When the driving frequency fb (fa <fb <fc) is within the range ΔIa between Ia1 and Ia2, when the output current of the electron gun 14 is within the range ΔIb between Ib1 and Ib2, and when the driving frequency fc (fb <fc <fd) Is the voltage of the acceleration voltage when the output current of the electron gun 14 is in the range ΔIc below Ic2, and at the drive frequency fd (fc <fd <f2), the output current of the electron gun 14 is in the range ΔId below Id2. Satisfies fluctuation range of less than 2.0 ppm / hour. Therefore, the drive frequency f of the control unit 12 can be set to satisfy the voltage fluctuation range of less than 2.0 ppm / hour of the acceleration voltage in the entire range where the output current of the electron gun 14 is equal to or less than I12 (about I0 + 4Iα).

  For example, when the output current value of the electron gun 14 set in the current setting unit 15 is I0 + 3Iα, the pulse generation circuit 25 sets f1 as the drive frequency f of the control unit 12. When the output current value of the electron gun 14 is I0 + 3Iα, the range that satisfies the voltage fluctuation range of less than 2.0 ppm / hour of the accelerating voltage satisfies not only the drive frequency f1 but also the drive frequencies fa and fb. . As described above, the range satisfying the voltage fluctuation range of less than 2.0 ppm / hour of the acceleration voltage overlaps with the respective drive frequencies f1, fa, fb, fc, fd, and f2. When the output current value of the electron gun 14 is in the overlapping range, it is desirable to select the drive frequency f whose output current value is close to the minimum value (minimum value). Alternatively, a function in which the output current value of the electron gun 14 set in the current setting unit 15 becomes a minimum value (minimum value) may be calculated, and the drive frequency fx determined by the function may be calculated and output.

  FIG. 3 is a waveform diagram of the acceleration voltage at the drive frequency f1 of the control unit. FIG. 3A is a waveform of the acceleration voltage at the drive frequency f1 of the control unit when the output current of the electron gun of FIG. 2 is I0 (point A). FIG. 3 and FIG. 3B are waveform diagrams of the acceleration voltage at the drive frequency f1 of the control unit when the output current of the electron gun of FIG. 2 is I0 + 3Iα (point B). FIGS. 3A and 3B show the waveform of the acceleration voltage per hour.

  As shown in FIG. 3A, the acceleration voltage of the drive frequency f1 of the control unit 12 when the output current of the electron gun 14 of FIG. 2 is I0 (point A) has a large voltage fluctuation range ΔEa with respect to the acceleration voltage E0kV. It can be seen that the stability standard of 2.0 ppm / hour is not satisfied. This is because, as shown in FIG. 2, the point A is outside the range where the acceleration voltage at the drive frequency f1 of the control unit 12 satisfies the voltage fluctuation range of less than 2.0 ppm / hour.

  On the other hand, as shown in FIG. 3B, the acceleration voltage at the drive frequency f1 of the control unit 12 when the output current of the electron gun 14 of FIG. 2 is I0 + 400 (point B) is a voltage fluctuation range with respect to the acceleration voltage E0kV. It can be seen that ΔEb is small and satisfies the stability standard of 2.0 ppm / hour. This is because, as shown in FIG. 2, the point B is within a range where the acceleration voltage at the drive frequency f <b> 1 of the control unit 12 satisfies a voltage fluctuation range of less than 2.0 ppm / hour.

  4 is a waveform diagram of the acceleration voltage at the drive frequency f2 of the control unit. FIG. 4A is a waveform diagram of the acceleration voltage at the drive frequency f2 of the control unit when the output current of the electron gun of FIG. 2 is I0. FIG. 4B is a waveform diagram of the acceleration voltage at the drive frequency f2 of the control unit when the output current of the electron gun of FIG. 2 is I0 + 1.2Iα, and FIG. It is a wave form diagram of drive frequency f2 acceleration voltage of a control unit. 4 (a), 4 (b), and 4 (c) show waveforms of acceleration voltage per hour.

  As shown in FIG. 4A, the acceleration voltage at the drive frequency f2 of the control unit 12 when the output current of the electron gun 14 of FIG. 2 is I0 (point C) has a small voltage fluctuation range ΔEc with respect to the acceleration voltage E0kV. It can be seen that the stability standard satisfies 2.0 ppm / hour. This is because, as shown in FIG. 2, the point A is within a range in which the acceleration voltage at the drive frequency f <b> 2 of the control unit 12 satisfies a voltage fluctuation range of less than 2.0 ppm / hour.

  Further, as shown in FIG. 4 (b), the acceleration voltage of the drive frequency f2 of the control unit 12 when the output current of the electron gun 14 of FIG. 2 is I0 + 1.2Iα (point D) is compared with FIG. 4 (a). It can be seen that the voltage fluctuation range ΔEd is larger than the acceleration voltage E0 kV and does not satisfy the stability standard of 2.0 ppm / hour. This is because the point D is out of the range where the acceleration voltage at the drive frequency f2 of the control unit 12 satisfies the voltage fluctuation range of less than 2.0 ppm / hour, as compared with the case of the point C.

  Further, as shown in FIG. 4C, the acceleration voltage of the drive frequency f2 of the control unit 12 when the output current of the electron gun 14 of FIG. 2 is I0 + 3Iα (point E) is compared with FIG. It can be seen that the voltage fluctuation range ΔEe is further increased with respect to the acceleration voltage E0 kV and does not satisfy the stability standard of 2.0 ppm / hour. This is because the point E is further away from the range where the acceleration voltage at the drive frequency f2 of the control unit 12 satisfies the voltage fluctuation range of less than 2.0 ppm / hour, and is outside the range.

  As described above, in the present invention, as shown in FIG. 2, it is found that the drive frequency f of the control unit 12 and the output current value have a certain relationship, and the electron gun 14 set in the current setting unit 15. The drive frequency f is changed in accordance with the current set value of the output current so that the voltage fluctuation range of the electron beam from the electron gun 14 satisfies the stability standard.

  That is, the frequency is adjusted by changing the set position of the digital potentiometer 24 connected to the pulse generator 25 that generates the frequency in conjunction with the current set value of the current setter 15. As a result, the drive frequency f can be automatically determined based on the current set value set in the current setter 15.

  In this case, the relationship between the drive frequency f and the output current value shown in FIG. 2 is stored in the pulse generator 25 in advance, and the drive frequency f is automatically set using a function of the drive frequency f and the output current value. To decide.

  As a result, the driving frequency f of the control unit 12 automatically becomes an optimum frequency depending on the output current of the electron gun 14, so that a stable acceleration voltage satisfying the stability standard can be obtained. Further, by digitizing the frequency setting unit 13, the drive frequency f can be finely adjusted, and a stable acceleration voltage can be obtained even when the current width is widened.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 ... High voltage unit, 12 ... Control unit, 13 ... Frequency setting unit, 14 ... Electron gun, 15 ... Current setting device, 16 ... Inverter circuit, 17 ... Transformer, 18 ... Frequency circuit, 19 ... DC power supply, 20 ... High voltage Generating device, 21 ... voltage detector, 22 ... current detector, 23 ... control circuit, 24 ... digital potentiometer, 25 ... pulse generator

Claims (4)

A high-voltage unit that generates a DC high voltage as the acceleration voltage of the electron gun of the electron beam generator;
A control unit for controlling so that the output voltage of the high voltage unit to the output current current setting value of the electron gun to control constant,
Based on the previous SL current setting value, so that the driving frequency of the control unit is a frequency of the voltage fluctuation range of the electron beam satisfies the stability standards, and a frequency setting unit for setting the driving frequency A power supply device for an electron beam generator, comprising:   The control unit has an inverter circuit that converts a DC voltage into an AC voltage, and the high-voltage unit has a transformer that boosts the AC voltage obtained by the inverter circuit, and the drive frequency of the control unit is The drive frequency of the main element of the inverter circuit of the control unit, and the predetermined frequency is an inductance when the secondary winding of the transformer of the high-voltage unit is opened and a floating of the secondary side of the transformer 2. The power supply device for an electron beam generator according to claim 1, wherein the power supply device has a resonance frequency of a parallel resonance circuit formed by a capacitor. The frequency setting unit stores a relationship between the output current of the electron gun and the stability of the acceleration voltage of the electron gun using the drive frequency of the control unit as a parameter. Item 3. A power supply device for an electron beam generator according to Item 1 or 2. An electron beam drawing apparatus comprising the power supply device for an electron beam generator according to any one of claims 1 to 3 .

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