JP2003347188A - Electron beam lithography device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam lithography device which is capable of reducing a change of the image magnification or rotation of an image caused by a focal correction to a minimum and also decreasing deflection aberration to a minimum when an astigmatic correction and a focal correction are superimposed on a deflector and carrying out a lithography operation with high accuracy. <P>SOLUTION: The electron beam lithography device is equipped with an operation device that digitally adds up astigmatic correction signals and focal correction signals and superimposes the summed signals on the eight-pole electrostatic deflector. The deflector is arranged at the most suitable position for a focal correction, and then the deflector is optimized in shape as a deflection aberration is taken into consideration, whereby the deflector having an optimal focal correction function and an optimal deflection function at the same time can be obtained. <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 writing apparatus used for manufacturing a semiconductor integrated circuit and the like.
The present invention relates to an electron beam writing apparatus that performs high-speed and high-accuracy writing.

[0002]

2. Description of the Related Art High density and high integration of semiconductor integrated circuits typified by LSIs are rapidly progressing, and accordingly, miniaturization of circuit patterns to be formed is rapidly progressing. Especially 100
Pattern formation at the nm node and below is extremely difficult with the extension of conventional photolithography technology. On the other hand, electron beam lithography is an effective means for forming a fine pattern, but in order to apply it to a production site, a higher lithography speed is required while maintaining high lithography accuracy. .

One of the factors that lowers the drawing speed is an eddy current generated in a surrounding metal material by a magnetic field generated by a coil constituting a deflector or a focus corrector. Focus correction in an electron beam lithography apparatus is important because it is used for correcting a height variation of a sample to be written and a field curvature component due to deflection. In other words, the magnetic field generated by the deflector and focus corrector due to the magnetic field acts on the surrounding metal material having a small electric resistance, so that the eddy current generated on the surface generates a magnetic field, and unnecessary deflection action on the electron beam Will be generated. Since the time until the influence of the eddy current disappears is longer than the drawing cycle, the waiting time is increased, and as a result, the drawing speed is reduced. If the deflector and the focus compensator are of an electrostatic type, there is no problem of eddy current, and high-speed operation is possible. For example, Japanese Patent Publication No. 4-47944 and Patent
Japanese Patent No. 38005 discloses a high-speed electrostatic lens focus corrector in which a cylindrical deflection plate is disposed in a magnetic field lens. In these examples, the focus is to be corrected at a low voltage, that is, to increase the sensitivity.

When an electrostatic deflector and an electrostatic lens are used at the same time, it is necessary to arrange different electrodes so as not to interfere with each other, and the optical path of the electron optical system becomes longer.
In addition, installing a deflector and a focus compensator independently,
It is not preferable because each mechanical error causes an increase in electro-optical aberration. For this reason, JP-A-20
In Japanese Patent Application Publication No. 00-173522, the deflector driving power supply is floated to a high voltage for the electrostatic lens and is superimposed, so that the deflector simultaneously has the function of converging the electrostatic lens.

FIG. 1 is a sectional view showing a conventional example in which a cylindrical deflection plate is disposed in a magnetic lens and a high-speed electrostatic lens focus corrector is used.

The electron beam 2 emitted from the electron gun 201
Numeral 02 is irradiated on the first mask 203 having a rectangular opening, and further imaged on the second mask 205. The image on the second mask 205 is projected by the two reduction lenses 206, the first objective lens 207, and the second objective lens 208, deflected by the main deflector 214 and the sub deflector 216, and is coated with a photosensitive agent. Irradiate on the top to draw. further,
Focus correction is performed by the focus corrector 218.

At this time, a plurality of pattern-shaped openings provided in advance in the second mask 205 are connected to the selective deflector 20.
4, it is also possible to draw with an aperture-shaped beam.

A predetermined area is drawn by the main deflector 214 in the objective deflecting lens, and a wider area is drawn while shifting this area by the sub deflector 216. The XY stage control device 212 moves the sample (object to be drawn) 209 placed on the XY stage 210 to perform drawing, except for the area that can be deflected by the control of the sub deflector 216.

The entire drawing is performed according to the drawing pattern data.
The beam position is controlled by the main deflection control device 213 and the sub deflection control device 215 deflecting the beam according to the pattern data. The sample height measuring device 220 is XY
It is provided above the stage 210 and acquires height data of the sample 209 by optical means. The height signal H of the sample 209 is supplied to the drawing control device 211, and a correction control signal is supplied to the focus corrector 218 via the focus correction control device 217.

Here, the main deflector 214 and the sub deflector 216
The focus corrector 218 has an eight-pole deflecting plate, which is shown in FIG. Eight-pole deflecting plates consisting of deflecting plates X1 to X4 and Y1 to Y4 are arranged on the same circumference at equal intervals. Therefore, in FIG. 1, the main deflector 214, the sub deflector 216, and the focus corrector 218 are represented as two opposing deflector plates, which are representative.

Here, the signal voltage applied to the 8-pole deflection plate is defined. The signal voltage applied to the eight-pole deflecting plate shown in FIG. 2 is as shown in equation (1).

[0012]

(Equation 1) Here, X is a deflection signal indicating an X coordinate, Y is a deflection signal indicating a Y coordinate, r is a constant, and Xs and Ys are astigmatism points in two directions which are functions of the deflection signal X and the deflection signal Y. Df indicates a focus correction signal which is a function of the deflection signal X, the deflection signal Y and the height signal H.

Next, the configuration of the main deflection control device 213 is shown in FIG.
This will be described with reference to FIG.

The deflection signals X and Y output from the drawing control unit 212 are subjected to predetermined arithmetic processing so as to satisfy the above-mentioned equation (1), and as shown in FIG.
4 and the deflection plates X1 to X4 constituting the sub deflector 216
And Y1 to Y4. Also, the deflection signal X,
The Y and the height signal H are subjected to predetermined arithmetic processing, and as shown in FIG.
1 to X4 and Y1 to Y4.

Next, a description will be given of a specific example of a configuration for performing arithmetic processing corresponding to the equation (1). First, the calculation processing of the signal voltages of the deflection plates X1 to X4 will be described.

The deflection signals X and Y are output from the drawing control unit 212 as, for example, 20-bit digital data. The deflection signals X and Y are converted into analog signals by DA converters 701X and 702Y. The signal output from the DA converter 702Y is multiplied by r by a constant multiplying circuit and rY
Is made. This constant r is, for example, (√2-1). The outputs X and rY of the DA converter 701X and the constant multiplying circuit are added by adders 707X1 to 707X4 with the polarity corresponding to the expression (1). The outputs of these adders serve as a basic part of the deflection voltages of the deflection plates X1 to X4 among the signal voltages applied to the 8-pole deflection plates.

Numerals 703X and 704Y denote arithmetic circuits, which calculate the X and Y astigmatism correction signals with the deflection signals X and Y as inputs and output them as 12-bit digital data. This digital data is stored in the DA converters 704X and 704.
It is converted to an analog signal by Y. The signals output from the respective DA converters are amplified by amplifier circuits 705X and 705.
It is amplified to a value determined from the required sensitivity by Y, and output as astigmatism correction signals Xs, Ys. These astigmatism correction signals Xs and Ys have polarities corresponding to the equation (1), and
The outputs of 07X1 to 707X4 are added to an adder circuit 708X1.
To 708X4.

The output signals of the adders 708X1 to 708X4 are amplified by the amplifiers 709X1 to 709X4 and applied to the deflecting plates X1 to X4 constituting the main deflector 214 and the sub deflector 216.

Next, the main deflector 214 and the sub deflector 21
The voltage applied to the deflecting plates Y1 to Y4 that constitutes No. 6 is
Deflection signals X and Y output from drawing controller 212
Is replaced by the same process as described above. That is,
The deflection signals Y and X are converted into analog signals by the DA converters 701Y and 702X. The signal output from the DA converter 702X is multiplied by r by a constant multiplying circuit to be rY. This constant r is, for example, (√2-1). D
A converter 701Y and outputs Y and rX of constant multiplying circuit
Are added by adders 707Y1 to 707Y4 with the polarity corresponding to the expression (1). The output of these addition circuits is the deflection plate Y1 of the signal voltages applied to the eight-pole deflection plate.
To Y4 as a basic part of the deflection voltage.

These adders 707Y1 to 707Y4
The above-mentioned astigmatism correction signals Xs and Ys are
With the polarity corresponding to equation (1), the addition circuits 708Y1 to 7
08Y4. The output signals of the adders 708Y1 to 708Y4 are
9Y4, and is added to the deflection plates Y1 to Y4 constituting the main deflector 214 and the sub deflector 216.

Reference numeral 706 denotes an arithmetic circuit, which comprises deflection signals X and Y.
The X and Y focus correction signals are calculated using the input signal and the height signal H as inputs. Here, the height signal H is given as 9-bit digital data. The arithmetic circuit 706 outputs 10-bit digital data. This digital data is converted into an analog signal by the DA converter 707. DA converter 7
The signal output from 07 is amplified by the amplifier circuit 708 and output as a focus correction signal Df. This focus correction signal Df is applied to the focus corrector 218.

As described above, the configuration of the main deflection control device 213 mainly includes an analog circuit. In addition, the focus corrector 218 and the focus correction control device 217 are provided independently.

[0023]

As described above, applying the same voltage to each pole of the electrostatic deflector to provide a lens function and perform focus correction reduces the number of electron optical elements.
This is an effective means from the viewpoint of reducing aberrations due to mechanical errors.
Further, if the deflector has eight or more poles, astigmatism can be corrected by controlling the voltage applied to each pole.
Therefore, it is useful to simultaneously realize the deflecting action, the astigmatism correcting action, and the focus correcting action with one deflector having eight or more poles.

Usually, however, the necessary deflection amount, astigmatism correction amount determined from the characteristics of the electron optical system and the drawing system configuration, the deflection sensitivity determined from the focus correction amount and the shape of the deflection plate, the astigmatism correction sensitivity, and the focus correction sensitivity. Does not match. For this reason, the maximum voltage and voltage resolution required for electron beam deflection and the maximum voltage and voltage resolution (minimum unit) required for astigmatism correction and focus correction are different. Conventionally, in order to resolve this difference, a DA (digital-analog) converter for deflection signals, a DA converter for astigmatism correction, and a DA converter for focus correction have been provided, each of which has a value determined by the required sensitivity. After adjustment, the voltage was output to the deflector by analog calculation such as voltage addition.

[0025] However, in recent years deflection resolution for determining the drawing position accuracy with miniaturization of semiconductor elements 20 to 21 bits (1 × 10 ⁶ or higher) and very high accuracy has become necessary. Achieving this accuracy with the DA converter for deflection signal, the DA converter for astigmatism correction, and the DA converter for focus correction, and maintaining the same even after addition by analog arithmetic are problems of measurement, adjustment, and DA. It is very difficult considering the large number of converters.

Using a focus corrector for an electrostatic lens by disposing a cylindrical electrode in an electromagnetic lens is disclosed in Japanese Patent Publication No. 4-47.
No. 944. This aims at performing high-speed focus correction at a low voltage, that is, increasing sensitivity. Further, Japanese Patent No. 3138005 discloses that when performing electrostatic focus correction in a magnetic lens, it is possible to reduce the change in magnification due to focus correction by using a two-stage electromagnetic lens. . Also, Japanese Patent Laid-Open No. 2000-
In Japanese Patent Publication No. 173522, the deflector driving power supply is floated to a high voltage for an electrostatic lens so that the power is superimposed and the deflector has the function of converging the electrostatic lens at the same time. However,
No mention is made of dynamically controlling according to the drawing area, such as focus correction.

The main problems in designing an objective deflecting lens of a high-accuracy and high-speed electron beam lithography system are reduction of lens aberrations, particularly deflection aberrations, and magnification change and rotation change at the time of focus correction due to height fluctuation and deflection of a drawing sample. Is to make the reduction of both compatible. When the electrostatic focus correction function and the deflection function are realized by a single deflector in the magnetic lens, the optimal position of the deflector on the optical axis in the electromagnetic lens determined by the deflection aberration and the focus correction The position of the focus corrector that minimizes the change in image magnification and the image rotation due to the difference is different. For this reason, if the deflector and the focus corrector are the same electrode, they will deviate from their optimal positions, and there has been a problem that high-precision drawing cannot be realized. SUMMARY OF THE INVENTION It is an object of the present invention to reduce deflection aberration at an optimum position for focus correction. This is a new problem not found in the above three examples.

[0028]

According to the present invention, a deflection signal, an astigmatism correction signal, and a focus correction signal are supplied to one deflector in a superimposed manner. For this purpose, an arithmetic unit for digitally calculating each signal data is provided. Furthermore, conditions for an optimally designed deflector that reduces the deflection aberration that occurs when a single deflector has both a deflection action and a focus correction action will be specifically proposed.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.

FIG. 4 specifically shows an example of an electron beam writing apparatus to which the present invention is applied in the form of a sectional view. Items having the same functions or the same functions as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG. As can be seen by comparing FIG. 4 with FIG. 1, in the present invention, the focus correction control device 217 and the focus corrector 218 to which the correction control signal is supplied via the focus correction control device 217 are eliminated. Other configurations are the same.

As described above, applying the same voltage to each pole of the electrostatic deflector to provide a lens function and perform focus correction reduces the number of electron optical elements and causes aberrations due to mechanical errors. This is an effective means from the viewpoint of reduction. Furthermore, if the deflector has eight or more poles, it is possible to correct astigmatism by controlling the voltage applied to each pole. Strict analysis of the optimal position of the deflector on the optical axis determined by aberrations and the position of the focus corrector that minimizes image magnification change and image rotation due to focus correction make the deflector and focus corrector the same deflector. I realized that.

A feature of the electron beam writing apparatus of the present invention is that the focus correction and the astigmatism correction function are superimposed on the main deflector. The change of the focal position and the deflection astigmatism due to the height fluctuation of the sample 209 and the field curvature due to the deflection are corrected only by the main deflector 214 in accordance with the deflection position. The focus and astigmatism correction signal is superimposed by digital operation in the main deflection control device 213 based on the deflection signal output from the drawing control device 211, and is sent to the main deflector 214 via DA conversion and an amplifier. .

Next, the configuration of the main deflection control device 213 is shown in FIG.
This will be described with reference to FIG. Also in this embodiment, the main deflector 21
Reference numeral 4 denotes an 8-pole deflector shown in FIG. 2, and the voltage applied to each deflector is the same as in the above-described equation (1). In FIG. 5, the number on the line indicating the data flow indicates the number of bits.

The deflection signal X output from the drawing control device 212 is applied to the deflection plates X1 to X4 as an added 20-bit digital signal as an addition circuit 406.
X1 to 406X4. Drawing control device 212
A 20-bit digital signal is input to the constant multiplication circuit 401Y for the deflection plates X1 to X4, and the deflection signal Y output from X1 to X4 is calculated by a constant r. The data rY of the deflection signal Y multiplied by the constant is applied to the adders 406X1 to 406X4. Here, calculation is performed in accordance with the signs + and-assigned to the input positions of the signals of the respective adders.

Reference numerals 402X and 402Y denote astigmatism correction amount operation circuits, which take the deflection signals X and Y as inputs, digitally operate the X and Y astigmatism correction signals, and output them as 12-bit data. This is to calculate the amount of astigmatism correction in two directions according to the deflection signal (beam deflection position). This digital data is supplied to the astigmatism correction operation circuits 403X and 403Y.
Performs a constant multiplication operation on data Xs and Ys of the astigmatism correction signal.
Is output. The output data Xs and Ys are 20-bit digital data. This constant magnification value will be described later. The output data Xs and Ys of the astigmatism correction signal are also input to the four adders 406X1 to X4 with the polarities shown in FIG.

Reference numeral 404 denotes a focus correction amount calculation circuit to which data of the deflection signal X, the deflection signal Y and the height signal H are inputted. The focus correction amount calculation circuit 404 outputs a focus correction amount according to the deflection signal (beam deflection position) and the sample height. The data of the focus correction amount is subjected to a constant multiplication operation by the focus sensitivity correction operation circuit 405 to obtain a focus correction signal Df
Is output. This constant magnification value will be described later. The data Df of the outputted focus correction signal Df is also added to the four adders 406.
X1 to X4 are input with the polarities shown in the figure.

Each of the four adders 406X1 to 406X receives each signal as 20-bit digital data and outputs a calculation result maintaining high accuracy. Four adders 406
The output data of X1 to X4 are input to independent DA converters 407X1 to X4, respectively, and are converted into analog signals. This analog signal is output from the amplifiers 408X1 to X4
And supplied to the deflection plates X1, X2, X3 and X4. With this configuration, the operation of Expression (1) is realized.

For the deflecting plates Y1, Y2, Y3 and Y4, an operation of a constant r times is performed by replacing the deflecting signal X with the deflecting signal Y and the deflecting signal Y with the deflecting signal X. Calculations of the correction signal data Xs and Ys and the focus correction signal Df are performed by the adders 406Y1 to Y4, and the output data of the four adders 406Y1 to Y4 is
The signals are input to independent DA converters 407Y1 to Y4, respectively, and are converted into analog signals. This analog signal is amplified by the amplifiers 408Y1 to Y4, and the deflection plates Y1, Y4
2, Y3 and Y4. Even in this configuration, the operation of Expression (1) is realized.

As described above, in this embodiment, one deflector 2
14, the deflection signals X and Y, the astigmatism correction signals Xs and Ys, and the focus correction signal Df are superimposed. Usually, in this case, the necessary deflection amount, astigmatism correction amount, focus correction amount and the deflection sensitivity, astigmatism correction sensitivity, and focus correction sensitivity determined from the shape of the deflection plate do not match. Also, the resolution required for deflection, astigmatism correction, and focus correction is different. Therefore, it is necessary to adjust the sensitivity required for astigmatism correction and focus correction to the resolution of the deflection signal.

In the electron optical system of this embodiment, 20 bits are required as the resolution of the deflection signal from the deflection width (1 mm at the maximum) and the minimum drawing unit (1 nm). The astigmatism correction and the focus correction determined by the drawing accuracy are each 12 bits,
A resolution of 0 bits is required. In this embodiment, from the calculation of the electron optical system, the maximum voltage required for a deflection width of 1 mm is ± 3.
The maximum voltage required for astigmatism correction was ± 10 V, and the maximum voltage required for focus correction was ± 80 V. From the maximum voltage and the resolution, the minimum unit voltage (per bit) of deflection, astigmatism correction, and focus correction, that is, a unit voltage, is calculated. The ratio between the unit voltage of the astigmatism correction signal and the unit voltage of the deflection signal is the constant magnification of the astigmatism correction. This constant magnification is the constant magnification value of the astigmatism sensitivity correction calculation circuits 403X and 403Y described above. The ratio between the unit voltage of the focus correction signal and the unit voltage of the deflection signal is a constant magnification of the focus correction. This constant magnification is the constant magnification value of the focus sensitivity correction operation circuit 405 described above.

FIG. 6 shows a specific example for adjusting the sensitivity required for astigmatism correction and focus correction to the resolution of the deflection signal. FIG. 6A shows the relationship between these values by numerical values.
FIG. 6B shows an example in which the constant magnification of astigmatism correction is 8 and the constant magnification of focus correction is 256 in this embodiment by digital processing.
This shows that it is possible with a simple operation of bit shift. That is, in the astigmatism sensitivity correction operation circuits 403X and 403Y, the input 12 bits are shifted by 3 bits, and 0 is added to the upper bits.
Is added to make a 20-bit output. Further, the focus sensitivity correction operation circuit 405 shifts the input 10 bits by 8 bits and adds 0 to the higher order to output 20 bits.

In the present invention, arithmetic processing of all signals is performed by digital data, and the deflection plates X1 to X4 and Y1 to Y
At the stage of applying a voltage to the D / A converter 4
07X1 to X4 and 407Y1 to Y4 are input and converted to analog signals. This analog signal is output to the amplifier 4
08X1 to X4 and amplified by Y1 to Y4, and deflection plates X1, X2, X3, X4 and Y1, Y2, Y3, X4
Supplied to Therefore, the arithmetic processing is performed while the required accuracy is sufficiently maintained, and there is no problem of variation in characteristics that is common in analog adders.

In the present embodiment, the bit shift operation is performed, but a normal multiplication operation can also be performed. Further, in this embodiment, the adders 406X and 406Y use dedicated hardware, but software means such as a general-purpose CPU, DSP, and FPGA may be used as long as the calculation speed is higher than the deflection speed. Of course, the constant multiplication circuits 401X, 401
The same applies to the Y, astigmatism correction amount calculation circuits 402X and 402Y, the astigmatism correction calculation circuits 403X and 403Y, the focus correction amount calculation circuit 404, and the focus sensitivity correction calculation circuit 405. It may be calculated.

As described above, the optimum position of the deflector determined by the deflection aberration is usually different from the position of the focus corrector which minimizes the change in image magnification and the image rotation due to the focus correction. For this reason, a more specific explanation will be given of arranging the deflector at a point on the optical axis where the image magnification change and image rotation due to focus correction are minimized, and optimizing the deflection aberration at this position to be minimized. .

FIG. 7 is a view focusing on the first objective lens 207, the second objective lens 208 and the main deflector 214 in FIG. 4 showing an embodiment of the present invention. Therefore, the sub deflector 216 is not shown. The electron beam 802 from the object surface 801 is
It is converged by the objective lens 208 and forms an image on the image plane 805 (on the sample plane). The first objective lens 207 and the second objective lens 208 are excited in mutually opposite directions to reduce aberration. The position of the beam is determined by the deflector 214. The distance from the center of the length of the deflector plate of the deflector 214 to the object surface is defined as the position of the deflector. In the objective lens of the present embodiment,
The distance between the object surface and the image surface was 300 mm, the inner diameter of the deflector 214 was 32 mm, and the length was 44 mm.

FIG. 8 shows the voltages (indicated by black circles, left scale) necessary for performing focus correction when the same voltage is applied to each pole of the deflector 214 and used as a focus corrector, and the focus correction time. The result of measuring the relationship between the change in the image magnification (displayed with a black square, the right scale) and the distance from the object surface of the deflector is shown. As can be seen, in the objective lenses 207 and 208, the point at which the focus correction sensitivity is high (the required voltage is low) almost coincides with the point at which the magnification does not change even when the focus correction is performed. Was. If the change in magnification does not match the point where the focus correction sensitivity is high, the change in magnification may be prioritized. Although not illustrated, a deflector may be provided at a point where image rotation during focus correction is minimized. In this way, the position of the focus corrector (the distance from the object surface) is determined to be one point,
It cannot be placed elsewhere.

In the present invention, as shown in FIG. 7, a two-stage electromagnetic lens of a first objective lens 207 and a second objective lens 208 is used. This is because, in a single-stage electromagnetic lens, a position where the change in magnification is small as described above and a position where practical deflection aberration can be obtained are incompatible. FIG. 9 shows the deflection aberration at the corner of the 1 mm square deflection area (displayed as a white circle, left scale) and the change in image magnification at the time of focus correction (displayed as a black square, right scale) when a single-stage electromagnetic lens is used. 4 shows a relationship between a deflector and an object surface. Here, the distance between the object surface and the image surface, the shape of the deflector, and the magnification as the objective lens are all the same as those shown in FIG. As shown in FIG. 9, the position where the change in image magnification is small (substantially zero) is about 70 mm from the image plane.
It is. However, when the deflector used as the focus corrector is installed at a position 70 mm from the image plane, the deflection aberration is 4
It exceeds 00 nm. Most of these deflection aberrations are deflection coma and chromatic aberration that cannot be corrected. Even if the aberration is reduced by the shape of the deflector, it cannot be applied to the electron beam lithography system of the present invention, which is the object of 100 nm node and beyond.

On the other hand, by using a two-stage electromagnetic lens and installing a focus corrector closer to the object surface than the lens main surface (between the two lenses) in which the two-stage lens is combined, There are methods for increasing the sensitivity and reducing the change in magnification. In the present invention, as shown in FIG. 8, it has been found that the optimum position (150 mm from the object plane) of focus correction by the two-stage electromagnetic lens can be made the same as the position where the deflection aberration is small.
FIG. 8 also shows the relationship between the deflection aberration (indicated by a white circle, left scale) and the distance from the object surface of the deflector. The deflection aberration could be reduced to almost the minimum value. This is 2
By adjusting the strength of the two electromagnetic lenses and optimizing the shape of the deflector, the optimal position of focus correction and the optimal position of deflection aberration can be adjusted in a well-balanced manner. Specifically, it is substantially at the center of the first objective lens 207, and is closer to the object surface than the lens main surface in which the two-stage lens is combined. As a result, it was possible to install a deflector for performing focus correction at a position where the change in magnification is almost 0 and the focus correction sensitivity is high.

Also, a deflector is installed inside the reduction lens 206 upstream (closer to the electron gun) of the objective lens composed of the first objective lens 207 and the second objective lens 208 shown in FIG. It is also possible to do. However, the magnification of the reduction lens 206 is usually set lower than that of the objective lens, and the focal length is short. Therefore, a large voltage is required to obtain the same focus correction effect. In addition, the deflection sensitivity is lowered for the same reason, and practical optical design is difficult.

As described above, according to the present invention, the deflector is installed at the optimum position for the focus correction, and the deflection aberration can be minimized. Can be simultaneously realized. With this configuration, it is possible to maximize the features of the control device of the present invention in which the focus correction signal and the astigmatism correction signal are superimposed on the deflection signal and supplied to the deflector.

[0051]

According to the present invention, the number of optical elements in the electron optical system is reduced by superimposing astigmatism correction and focus correction signals on an octupole electrostatic deflector by digital operation in an electron beam writing apparatus. This makes it possible to reduce mechanical error factors and perform highly accurate drawing with a simple circuit configuration.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a conventional example in which a cylindrical deflection plate is disposed in a magnetic lens and a high-speed electrostatic lens focus corrector is used.

FIG. 2 is a diagram showing an example of an arrangement of an 8-pole deflecting plate constituting a main deflector 214, a sub deflector 216, and a focus corrector 218.

FIG. 3 is a diagram showing a configuration of a conventional main deflection control device 213.

FIG. 4 is a diagram specifically showing an example of an electron beam writing apparatus to which the present invention is applied in the form of a cross-sectional view.

FIG. 5 is a diagram showing a configuration of a main deflection control device 213 of the present invention.

6A and 6B show specific examples for adjusting the sensitivity required for astigmatism correction and focus correction to the resolution of a deflection signal, wherein FIG. 6A shows the relationship between these values by numerical values, and FIG. As an example in which the constant magnification of astigmatism correction is 8 and the constant magnification of focus correction is 256 in digital processing, the constant multiplication operation can be performed by a simple operation of 3-bit shift and 8-bit shift. FIG.

7 is a diagram illustrating a configuration focusing on a first objective lens 207, a second objective lens 208, and a main deflector 214 in FIG. 4;

FIG. 8 shows a voltage necessary for performing focus correction when the same voltage is applied to each pole of the deflector 214 and used as a focus corrector, changes in image magnification during focus correction, deflection aberrations, The figure which shows the relationship of the distance from an object surface.

FIG. 9 is a diagram illustrating a relationship between a deflection aberration (a value at a corner of a 1 mm deflection area), a change in image magnification during focus correction, and a distance from an object surface of a deflector when the number of electromagnetic lenses is one.

[Explanation of symbols]

101: 8-pole deflection calculation circuit, 102: Astigmatism correction calculation circuit, 103: Focus correction calculation circuit, 104: Digital addition circuit, 105: DA converter, 106: Amplifier, 10
7: 8-pole deflector, 201: electron gun, 202: electron beam, 203: first mask, 204: selective deflector, 20
5: second mask, 206: reduction lens, 207: first objective lens, 208: second objective lens, 209: sample, 2
10: XY stage, 211: drawing control device, 212:
XY stage controller, 213: main deflection controller, 21
4: Main deflector, 215: Sub-deflection control device, 216: Sub-deflection device, 217: Focus correction control device, 218: Focus correction device, 220: Sample height measurement device, 401: Constant multiplication circuit, 402: Non-constant Point correction amount calculation circuit, 403: Astigmatism correction calculation circuit, 404: Focus correction amount calculation circuit, 405: Focus sensitivity correction calculation circuit, 406: Adder, 407: DA converter, 408: Amplifier, 701: DA conversion Vessel, 702:
DA converter, 703: astigmatism correction amount calculation circuit, 704: D
A converter, 705: DA converter, 706: sensitivity correction amplifier, 707: analog adder, 708: analog adder, 709: amplifier, 801: object plane, 802: electron beam, 805: image plane.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kimiaki Ando             Ibaraki Prefecture Hitachinaka City Oaza Ichimo 882 shares             Design and manufacture of Hitachi High-Technologies Corporation             In the headquarters Naka office F-term (reference) 2H097 CA16 LA10                 5C033 GG02 GG05                 5C034 BB04 BB08                 5F056 CB16 CB29 CB34 EA06

Claims (3)

[Claims] An electron which performs drawing using a means for generating an electron beam, one or more electromagnetic lenses for projecting the electron beam onto a sample, and an electrostatic deflector having eight or more poles for deflecting the electron beam. In the beam writing apparatus, the deflector shares the functions of astigmatism correction and focus correction, and corrects the astigmatism correction signal for correcting the astigmatism of the electron beam to the deflection signal for deflecting the electron beam and the focus of the electron beam. A focus correction signal to be superimposed is supplied to the deflector to perform drawing, and each signal is processed by a digital signal, converted to an analog signal, amplified, and provided to the deflector. Electron beam drawing equipment. 2. Prior to adding the deflection signal, the astigmatism correction signal, and the focus correction signal, the astigmatism correction signal and the focus correction signal, which are determined from the required astigmatism correction sensitivity and the required focus correction sensitivity, respectively. 2. An electron beam writing apparatus according to claim 1, further comprising an independent constant multiplication unit for matching the minimum unit of the deflection signal with the minimum unit of the deflection signal, and processing the digital signal. 3. An electron beam drawing device using a means for generating an electron beam, two or more electromagnetic lenses for projecting the electron beam onto a sample, and an electrostatic deflector having eight or more poles for deflecting the electron beam. In the beam writing apparatus, the deflector shares the function of a focus corrector, and the position where the sensitivity of the focus corrector is maximized or the position where the change in magnification of the electromagnetic lens is minimized by the focus correction action, or 2. The electron beam writing apparatus according to claim 1, wherein the deflector is arranged at a position where a change in the amount of rotation of the electromagnetic lens is minimized by a focus correction operation.