JPH0883591A - Charged beam radiating device and radiating method - Google Patents

Abstract

PURPOSE: To enhance accuracy of exposure, and simplify device constitution by performing feedback to a deflecting system through a correcting circuit so as to correct a moving distance of a charged beam radiating position on the basis of the size of a change in a measured magnetic field. CONSTITUTION: A uniaxial magnetic field measuring probe contained in a magnetic field measuring unit 1 is arranged after the largest place and the largest direction in the correlation between a change in a magnetic field and a change in a beam position are judged by an evaluating circuit 5. A magnetic field changing signal from an output circuit of the measuring unit 1 is inputted to a correcting circuit 2, and is converted into a correction signal branched off into two systems to correct the (x) axis and the (y) axis, and is supplied to a beam position deflecting system 3 arranged in an exposure device. A signal and a stage position from the measuring unit 1 and a detecting signal from a beam position detector 112 are inputted to the evaluating circuit 5, and a correction quantity is determined from measurement of the correlation between both. A correction quantity of a change in the beam position and the correcting direction are determined by the correcting circuit 2 on the basis of this evaluated result, and are outputted to the deflecting system 3 in an electric current or voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged beam irradiation apparatus and an irradiation method applicable to an exposure apparatus, an electron microscope and the like.

[0002]

2. Description of the Related Art In recent years, the progress of high density and miniaturization of semiconductor integrated circuits has been remarkable, and a minimum line width of 0.15 has been reached in this century.
It is expected that μm 1G bit DRAM and ULSI with a minimum line width of 0.1 μm or less will be developed in the 21st century. At present, there is an exposure method using an electron beam as one of the influential techniques for forming such a fine ULSI pattern.

FIG. 4 is a schematic diagram showing a conventionally used electron beam exposure apparatus. The electron beam emitted from the electron gun 101 is applied to the beam shaping first aperture 103 by the condenser lens 102. This first
The image of the aperture 103 is formed on the beam forming second aperture 105 by the projection lens 104. The beam size can be changed by controlling the degree of overlap between the two apertures 103 and 105 by the beam shaping deflector 106. The image resulting from the overlapping of the apertures 103 and 105 is the reduction lens 107 and the objective lens 1
The image is reduced by 08 and imaged on the sample 109. The beam position on the sample surface is controlled by the main deflector 110 with a resolution of about 0.01 μm (for example, J.
Vac.Sci.Technol.B11 (1994) 2309).

When forming an extremely fine pattern with such an apparatus, the precision and stability of various control systems are indispensable, but as the resolution of the exposure apparatus improves and the minimum line width for exposure becomes smaller. A change in the installation environment of the device, such as an external magnetic field, room temperature, or the temperature of the device cooling water, can greatly affect the performance of the device.

Particularly, the fluctuation of the external magnetic field has a great influence on the irradiation position of the beam. For example, in the case of a 50 keV electron beam, when a magnetic field of 10 ⁻⁷ T is present in the direction perpendicular to the optical axis, while traveling 5 cm in space, About 0.02μm in the direction perpendicular to the magnetic field
Will result in a deviation. In everyday space without magnetic shields, there are magnetic fields that fluctuate due to geomagnetic fluctuations and urban traffic such as trains, and magnetic fields that leak from transmission and distribution lines. The magnitude of fluctuations is 10 ^-7 to 10 ^-6. T.
For an electron beam exposure apparatus having a resolution of 0.01 μm, such a variation (disturbance) causes a variation in the irradiation position of the beam, which causes deterioration in accuracy.

In order to prevent the influence of magnetic field fluctuations in the exposure apparatus, there are roughly three means. The first means is a method of preventing an external magnetic field from entering the exposure apparatus by using a magnetic shield made of a high magnetic permeability material (for example,
J.Vac.Sci.Technol.B11 (6) 2309 and JP-A-4-2643.
39 publication). In this case, a high shielding effect can be obtained by using multiple shields, but the thickness and weight increase correspondingly, and there are many structural restrictions such as workability and exhaust / air conditioning equipment. Further, there is a problem that the influence of magnetic field fluctuations generated inside the shield cannot be avoided.

A second means is a method of installing a large Helmholtz coil so as to surround the entire exposure apparatus to cancel the external magnetic field (for example, Japanese Patent Laid-Open No. 4-370638). In this case, since a large coil is used, it is difficult to install it with high accuracy, and it is considered that it is difficult to follow up when the frequency of fluctuation is high. The above-mentioned two means are large facilities and are expensive.

As a third means, there is a method of correcting the beam position, which has been changed due to the magnetic field change, by using the deflector by the changed amount (for example, Japanese Patent Laid-Open No. 62-216324). This method detects magnetic field fluctuations near the exposure apparatus with two coils (for the x-axis and y-axis), inputs the current generated in the coil by electromagnetic induction to the deflector via an amplifier, and changes the beam. The position is corrected. It can be realized more easily than the above two methods, but in the actual installation environment, there is a problem that the magnetic field is not uniform in the structure of the building or the device, so that a sufficient effect cannot be obtained.

[0009]

As described above, in the conventional electron beam exposure apparatus, when aiming at the miniaturization of the minimum size, there is a problem that the irradiation position of the beam changes due to the change of the magnetic field. I have dealt with the problem by the means mentioned above. However, in order to erase the external magnetic field using a magnetic shield, there is a problem that the structure of the device is complicated and workability deteriorates. It was found that there was a problem that the orientations of the two were different, and a sufficient effect could not be obtained.

The present invention has been made in consideration of the above circumstances, and an object thereof is to change the irradiation position of the charged beam due to the magnetic field change, which is simple and corresponds to the actual structure of the building / apparatus. SUMMARY OF THE INVENTION It is an object of the present invention to provide a charged beam irradiation apparatus and an irradiation method which can correct the exposure error and can improve the accuracy of exposure and simplify the apparatus configuration.

[0011]

In order to solve the above problems, the present invention employs the following configurations. That is, the present invention (Claim 1) is a charged particle beam irradiation apparatus for irradiating a sample with a charged particle beam, and a magnetic field measuring means for measuring the magnitude and direction of a magnetic field fluctuation due to an external magnetic field, and the magnetic field measuring means. Correction means for outputting a correction amount corresponding to the magnetic field fluctuation amount, and beam deflection means for deflecting the charged beam in accordance with the correction amount output by the correction means,
Beam position measuring means for measuring the beam position on the sample,
It is characterized by comprising an evaluation means for determining a correction amount by the correction means on the basis of the magnetic field fluctuation amount measured by each measuring means and the beam position, and for giving the optimum correction amount to the correction means.

Further, the present invention (claim 5) is a charged beam irradiation method for irradiating a predetermined position on a sample with a charged beam, comprising a magnetic field measuring probe for measuring the magnitude and direction of a magnetic field fluctuation due to an external magnetic field. Installed in a position where the correlation between the magnetic field fluctuation and the beam position fluctuation measured at is the largest and in the direction where the correlation between the magnetic field fluctuation and the beam fluctuation is the largest, and the charged beam is deflected according to the magnetic field fluctuation amount measured by the probe. Then, the deflected beam position is measured, and the optimum beam deflection correction amount for the magnetic field fluctuation amount is determined from the relationship between the measured beam position and the magnetic field fluctuation amount.

The preferred embodiments of the present invention are as follows. (1) The magnetic field measuring means is a magnetic field measuring probe capable of measuring the magnitude and direction of the magnetic field, and is placed at the position where the correlation between the magnetic field fluctuation and the beam fluctuation is maximized and in the direction where the correlation between the magnetic field fluctuation and the beam fluctuation is maximized. It is installed in. (2) The magnetic field measuring means comprises a magnetic field measuring probe capable of measuring the magnitude and direction of the magnetic field, which is installed outside the magnetic shield surrounding the main body of the charged beam irradiation apparatus. (3) The magnetic field measuring means is a magnetic field measuring probe capable of uniaxial magnetic field measurement or a magnetic field measuring probe capable of triaxial magnetic field measurement. (4) The evaluation means obtains the correlation between each measured magnetic field fluctuation amount and the beam position, and determines the optimum beam correction direction and correction amount for the magnetic field fluctuation amount based on this correlation. is there. (5) The amount of variation of the magnetic field is input, and a correction signal corresponding to the amount of variation is supplied to at least one pair of orthogonal two-axis (X-direction, Y-direction) deflection means. The deflecting means may be a deflector provided in advance in the lens barrel, or a dedicated correcting deflector may be newly provided. (6) The phase of the correction signal should be output at an arbitrary angle with respect to the phase of the fluctuation component. (7) Discriminate the frequency of magnetic field fluctuation and select and output the correction signal of any frequency. (8) The beam position is deflected using an electromagnetic coil or an electrostatic deflector with respect to the correction signal output by the correction circuit. (9) Install a deflector that deflects the beam position at a position that is easily affected by magnetic field fluctuations. (10) Appropriate detection direction and detection position of the magnetic field can be evaluated and judged corresponding to the correlation measurement of the magnetic field fluctuation and the beam position. (11) Supplying a signal for detecting the magnetic field fluctuation and for correcting the influence of the detected magnetic field fluctuation to the deflector attached to the charged beam apparatus. (12) Measure the amount of change in the magnetic field and the beam position, find the correlation between the two, and determine the correction amount and correction direction so that the correlation disappears.

[0014]

According to the present invention, the irradiation position of the charged beam which fluctuates due to the magnetic field fluctuation is measured via the correction circuit so as to measure the magnitude of the magnetic field fluctuation and correct the movement amount of the irradiation position based on the result. It feeds back to the deflection system. This makes it possible to prevent fluctuations in the irradiation position when performing exposure using a charged beam, improving performance such as minimum line width and resolution during exposure that was limited by magnetic field fluctuations. Manufacturing of a semiconductor integrated circuit using the device becomes extremely easy.

In particular, in the present invention, it has been found that the fluctuations of the beam position in the X and Y directions are both proportional to the fluctuations of the external magnetic field, and the magnetic field fluctuation direction that is most correlated with the beam position fluctuation is detected and corrected. Therefore, the process of correcting the beam position due to the magnetic field fluctuation becomes easy, and there is an advantage of great practicality. Further, by using the uniaxial magnetic field measurement probe as a means for measuring the magnetic field fluctuation, the process of correcting the beam position due to the magnetic field fluctuation is further facilitated. Further, the present invention can be realized more easily than in the case of using the prior art, and moreover, corresponds to the actual structure of the building / apparatus, and the operability and the reliability of correction are improved.

[0016]

The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 relates to an embodiment of the present invention and is a device in which a beam irradiation position correction mechanism is incorporated in an electron beam exposure apparatus. The same parts as those in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

The magnetic field measuring device 1 is composed of a magnetic field measuring probe capable of detecting a magnetic field in the uniaxial direction utilizing the Hall effect, and an output circuit for outputting a measurement result by using a signal of the probe as an input. As will be described later, the magnetic field measurement probe is installed at a location where the correlation between the magnetic field variation and the beam position variation is the largest and in the direction in which the correlation is largest. This allows
The correction can be performed even when the direction of the spatial magnetic field and the direction of the magnetic field in the exposure apparatus are different.

The magnetic field fluctuation signal output from the measuring device 1 is input to the correction circuit 2 and the evaluation circuit 5. Correction circuit 2
The magnetic field fluctuation signal input to is converted into a correction signal for controlling the deflector by branching into two systems for x-axis correction and y-axis correction, and the converted signal is output. It is supplied to the deflector 3. The deflector 3 is an electromagnetic coil or an electrostatic deflector, and can control the beam position two-dimensionally in the x-axis direction and the y-axis direction. The deflector 3 does not necessarily have to be newly provided for correction, and various deflectors already installed in the lens barrel may be used.

A movable stage 111 is movable in x and y directions, and is used as a beam position measuring means 4 on which a mark stand for beam position measurement, a sample 109 and the like are installed. The detection signals of the stage position and beam position detector 112 are
It is input to the evaluation circuit 5 together with the magnetic field fluctuation signal, and the correlation between the two is measured and the correction amount is determined.

FIG. 2 is a diagram showing the correlation between the magnetic field fluctuation and the beam position fluctuation, which is a conventional example in which the correction function is not used. In this figure, it can be seen that the phases in the x and y directions are 180 ° opposite. FIG. 3 is a diagram showing the correlation between the magnetic field fluctuation and the beam irradiation position when the beam position is corrected using the correction mechanism according to the present embodiment. 2 and 3 have the same scale. In each figure, (a) is a magnetic field variation, (b) is a beam position variation in the x direction, and (c) is y.
The beam position variation in the direction is shown. In FIG. 3, the magnitude of the magnetic field fluctuation is substantially the same as that in FIG. 2, but the correlation with the beam position disappears, and it can be seen that the correction effect is obtained.

As described above, the direction of the magnetic field on the beam axis, which generally affects the electron beam, changes the magnetic path due to the presence of various structures that make up the exposure apparatus, and the direction of the location where the magnetic field measurement probe is installed is changed. The direction of the magnetic field is different.
However, it is considered that the magnitude of the magnetic field fluctuation is proportional to the positions of the two. Therefore, the evaluation circuit 5 determines the direction in which the beam positions of both the x-axis and the y-axis have a strong correlation, and determines the orientation of the magnetic field measurement probe. More simply, the magnetic field measurement probe may be installed at a position where the measurement magnetic field by the probe becomes maximum and in a direction where the measurement magnetic field becomes maximum.

Regarding the installation position of the magnetic field measurement probe,
In order to improve the magnetic field detection accuracy, the evaluation circuit 5 determines a location where the magnitude of the magnetic field fluctuation is large, and the probe is installed at that location. In particular, when a magnetic shield is present, if a probe is installed outside the magnetic shield and measurement is performed, the detection signal becomes large, which is effective in improving the correction accuracy.

When the orientation of the magnetic field measuring probe is selected, the orientation of the spatial magnetic field can be easily determined by simultaneously performing measurement on three axes. By this means, the direction of the spatial magnetic field can be determined and then the correction can be performed by the method using the above-mentioned uniaxial probe. Further, it is possible to simultaneously measure the three axes and use the vector sum of the measured values of the three axes as the magnitude of the spatial magnetic field as an input signal to the correction circuit 2 and the evaluation circuit 5.

When there are a plurality of causes of the magnetic field fluctuation which influences the beam position, at least one or more probes are installed and each probe position and direction correlated with the beam position fluctuation are judged by the evaluation circuit 5, The correction can be performed by superimposing a plurality of magnetic field fluctuation signals so that the beam position fluctuation finally disappears.

The correction amount and the correction direction of the beam position fluctuation are determined by the correction circuit 2 based on the correlation measurement evaluation result of the magnetic field fluctuation and the beam position fluctuation by the evaluation circuit 5. The correction signal provided to the deflector 3 can be obtained with an appropriate correction amount by changing the amplification degree of the amplifier in the correction circuit 2. Since the beam position can be measured independently in x and y in the correction direction
It can be done independently for each direction. The output of the correction circuit 2 can be output as a current when the deflector 3 is an electromagnetic coil, and as a voltage when the deflector 3 is an electrostatic deflector.

The correction circuit 2 may be provided with a frequency discriminating function to selectively correct the magnetic field fluctuation component having an arbitrary frequency. Furthermore, the output phase of the correction signal is
In addition to 180 ° inversion, it can be output in any phase. In this case, the selection of the frequency and phase of the correction circuit 2 is
This is performed based on the evaluation result of the evaluation circuit 5.

In the embodiment shown in FIG. 1, the aperture 10
The image due to the optical overlap of 3,105 is the reduction lens 10
The beam position deflector 3 is attached near the objective lens 108 between the reduction lens 107 and the sample surface 109, which is reduced by 7 and is easily affected by the magnetic field fluctuation. Further, the deflector 3 is not limited to the above-mentioned position, but is incorporated in a position where a high correction sensitivity can be obtained and used. Further, when there are a plurality of causes of the magnetic field variation, at least one deflector can be installed for each cause to perform the correction.

As described above, according to this embodiment, by using the uniaxial magnetic field measuring probe and feeding back the output to the deflector 3, the irradiation position of the electron beam which fluctuates due to the fluctuation of the magnetic field can be corrected. Further, it is possible to prevent the irradiation position from varying when the electron beam exposure is performed. For this reason, performances such as the minimum line width and resolution at the time of exposure which are limited by the magnetic field fluctuation are improved, and the manufacture of a semiconductor integrated circuit using the exposure apparatus becomes extremely easy. In particular, since it is possible to correct the x-direction and the y-direction from the output of the uniaxial magnetic field measurement probe in a proportional relationship, there is a great advantage that the process of correcting the beam position due to the magnetic field variation becomes easy.

The present invention is not limited to the above embodiment. In the embodiment, the electron beam exposure apparatus has been described, but the present invention is not limited to this and can be applied to an ion beam exposure apparatus. Further, the invention can be applied not only to the exposure device but also to an electron microscope, and in short, any device that irradiates a sample with a charged beam can be applied. In addition, various modifications can be made without departing from the scope of the present invention.

[0030]

As described in detail above, according to the present invention, the magnitude and direction of the external magnetic field fluctuation are measured by the magnetic field measuring probe, and a correction signal corresponding to the magnetic field fluctuation amount is supplied to the deflector to deflect the beam position. By doing so, it is possible to correct the position of the charged beam that has changed due to the magnetic field fluctuation to the same position as when there was no magnetic field fluctuation. As a result, it is possible to make the exposure highly accurate and simplify the device configuration in a simple and corresponding manner to the actual structure of the building / device.

[Brief description of drawings]

FIG. 1 is a view for explaining an embodiment of the present invention, showing an example in which a beam irradiation position correction mechanism is incorporated in an electron beam exposure apparatus.

FIG. 2 is a diagram showing a correlation between a magnetic field fluctuation and a beam position fluctuation before correction.

FIG. 3 is a diagram showing a correlation between a magnetic field fluctuation and a beam irradiation position when correction is performed.

FIG. 4 is a schematic configuration diagram showing an optical system of a conventional electron beam exposure apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic field measuring device 2 ... Correction circuit 3 ... Deflector 4 ... Beam position measuring means 5 ... Evaluation circuit 101 ... Electron gun 102 ... Condenser lens 103 ... Beam shaping first aperture 104 ... Projection lens 105 ... Beam shaping second aperture 106 Beam shaping deflector 107 Reduction lens 108 Objective lens 109 Sample surface 110 Main deflector 111 Movable stage 112 Beam position detector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/027

Claims (5)

[Claims] 1. A charged beam irradiation apparatus for irradiating a sample with a charged beam, which corresponds to magnetic field measuring means for measuring the magnitude and direction of magnetic field fluctuation due to an external magnetic field, and magnetic field fluctuation amount measured by the magnetic field measuring means. Correction means for outputting a correction amount, beam deflection means for deflecting the charged beam corresponding to the correction amount output by the correction means, beam position measurement means for measuring the beam position on the sample, and each of the measurements Charged beam irradiation, characterized in that it comprises an evaluation means for determining the correction amount by the correction means on the basis of the magnetic field fluctuation amount measured by the means and the beam position, and for giving the optimum correction amount to the correction means. apparatus. 2. The magnetic field measuring means uses a magnetic field measuring probe capable of measuring the magnitude and direction of a magnetic field at a position where the correlation between the magnetic field fluctuation and the beam position fluctuation is maximized, and the correlation between the magnetic field fluctuation and the beam position fluctuation. The charged particle beam irradiation apparatus according to claim 1, wherein the charged beam irradiation apparatus is installed in a direction that maximizes 3. The magnetic field measuring means comprises a magnetic field measuring probe capable of measuring the magnitude and direction of the magnetic field, which is installed outside a magnetic shield surrounding the main body of the charged beam irradiation apparatus. Or the charged beam irradiation apparatus as described in 2. 4. The evaluation means obtains a correlation between each measured magnetic field fluctuation amount and the beam position, and determines an optimum beam correction direction and correction amount for the magnetic field fluctuation amount based on this correlation. The charged particle beam irradiation apparatus according to claim 1, wherein: 5. In a charged beam irradiation method for irradiating a predetermined position on a sample with a charged beam, a magnetic field measuring probe for measuring a magnitude and a direction of a magnetic field fluctuation due to an external magnetic field is provided, and the magnetic field fluctuation and the beam position measured by the probe. It is installed at the position where the correlation of fluctuations is the largest and in the direction where the magnetic field fluctuation is the largest, the charged beam is deflected according to the magnetic field fluctuation measured by the probe, and the deflected beam position is measured and measured. A charged beam irradiation method, characterized in that an optimum beam deflection correction amount for a magnetic field fluctuation amount is determined from the relationship between the beam position and the magnetic field fluctuation amount.