JPS59127351A - Method and apparatus for stabilization of charged particle ray - Google Patents

Abstract

PURPOSE:To enable the vibration of the charged particle ray due to the stray magnetic field to be remarkably decreased without using a magnetic shielding member, by detecting the stray magnetic field at least at two places in X and Y directions in the vicinity of the body tube and supplying the detected signals to the deflecting means of the charged particle ray. CONSTITUTION:The correcting deflection system 8 is, for example, of an electrostatic arrangement having two sets of deflecting electrodes 8x, 8x, 8y, 8y. Each deflecting electrode set 8x, 8x, 8y, 8y of the correcting deflection system 8 is connected to the stabilaization circuit 20. The deflecting electrode set 8x, 8x is provided in the direction of the X axis of the rectangular (X-Y) coordinate and the deflecting electrode set 8y, 8y is provided in the direction of the Y axis. The stabilization circuit 20 calcultes the vibration amount of the charged particle ray 4 due to the stray magnetic field in accordance with the detected signals by the magnetic field detectors 10x, 10y, and generates and supplies the control signals to the deflecting electrodes 8x, 8x, 8y, 8y which are used by the correcting deflection system 8 for suppressing the vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to charged particle beam irradiation equipment used in so-called charged particle beam irradiation equipment that irradiates a sample with a charged particle beam, such as an electron beam exposure equipment, an electron microscope, an X-ray microanalyzer, and an ion microprobe. METHODS AND APPARATUS FOR STABILIZING LINES.

In conventional charged particle beam irradiation devices, the charged particle beam is often deflected and oscillated by a floating magnetic field existing around the device. When the charged particle beam oscillates in this way, the irradiation position of the charged particle beam on the sample fluctuates, and as a result, it is difficult to draw minute patterns, especially with devices that focus the charged particle beam narrowly, making it difficult to improve resolution. However, there are disadvantages such as not being able to analyze a single minute point.

The floating magnetic field is generated by electric cables, electric devices, electric lights, etc. placed inside a building.

It is extremely difficult to eliminate the causes of such stray magnetic fields.

For this reason, in the past, the lens barrel, sample chamber, etc. were covered with a material with high magnetic permeability, such as permalloy, for magnetic shielding.

However, it is theoretically difficult to increase the shielding rate (effectiveness) of magnetic shielding, and even if the lens barrel, sample, seedlings, etc. are magnetically shielded, there are electrical cables and vacuum in the lens barrel and sample chamber. piping, various operation knobs, etc., holes must be formed in the magnetic shielding member, and these holes also reduce the shielding rate, and in the end, conventional devices With this method, it was possible to reduce the amount of vibration of the charged particle beam due to the stray magnetic field to only a fraction of the amount.Furthermore, in conventional devices, the column and sample chamber are covered with magnetic shielding members, which requires a corresponding amount of space. However, the device becomes large, and the operating knobs and the like become complicated, reducing its operability.

Purpose of the Invention The present invention provides a floating device without using a magnetic shield member.
It is an object of the present invention to provide a charged particle beam stabilization method and apparatus that can significantly reduce the amount of vibration of a charged particle beam caused by an fi magnetic field.

Structure of the Invention According to the present invention, the above object is to detect a stray magnetic field in at least two locations in the X direction and Y direction near the lens barrel, and to supply the detection signal to a charged particle beam deflection means. achieved.

Embodiment In FIGS. 1 and 2, 1 is a main body of a charged particle beam irradiation apparatus, which has a lens barrel 2 and a sample chamber 3 continuing to the lower part of this lens barrel. The lens barrel 2 includes a particle beam m5 that generates a charged particle beam 4, a focusing lens 6 that focuses the charged particle beam 4 onto a sample 9, a main deflection device 7 that deflects the charged particle beam 4, and a particle beam m5 that generates a charged particle beam 4. A correction deflection device 8 is provided for correcting vibrations of the charged particle beam 4 caused by stray magnetic fields, and magnetic field detectors 10x for stray magnetic fields are provided at two locations near the lens barrel 2 in the X direction and the Y direction.
10y is provided.

The particle beam source 5, the focusing lens 6, and the main deflection device 7 are known devices, and are each connected to a power source (not shown).

The correction deflection device 8 is a known electric field type or magnetic field type deflection device like the main deflection device 7, and in the illustrated example, a second deflection device 8 is used.
As shown in the figure, two sets of deflection electrodes 8X, 8x, 8y, 8y
An electric field type device is used. Correction deflection device 8
each deflection electrode 8×.

8x, 8y, and 8y are each connected to a stabilizing circuit 20. The deflection electrodes 8x, 8x are provided in the X direction of orthogonal XY coordinates, and the deflection electrodes 8y, 8y are provided in the Y direction. The XY coordinates have their origin at the center of the charged particle beam 4, and do not necessarily have to match the XY coordinates of the main deflection device 7, but it is preferable that they match because it makes it easier to adjust the device. .

The sample chamber 2 is provided with a charged particle detector 11 that detects charged particles such as secondary electrons and backscattered electrons, and the detection signal of this charged particle detector 11 is transmitted to a display device 1 using a cathode ray tube.
2.

Each magnetic field detector 1Qx, 10V is a so-called Hall element or a multi-turn coil that utilizes the ball effect.
It is provided close to the lens barrel 2.

The magnetic field detector 10X detects the
The magnetic field detector 10V is located in the XY direction of the correction deflection device 8.
! It is located in the Y direction of the target and is provided to detect the magnetic field in the Y direction.

To provide the magnetic field detectors 10x, 10y in this manner, for example, if the magnetic field detectors 1QX, 101/ are coils with multiple turns, their central axes may be located in the X direction and the Y direction.

The stabilization circuit 20 calculates the amount of vibration of the charged particle beam 4 due to the floating magnetic field based on the detection signals of the magnetic field detectors 10X and 10V, and generates a control signal for suppressing this vibration with the correction deflection device 8. , the control signals are transmitted to the deflection electrodes 8x, 8x, 8y
, 8y.

In other words, since the stray magnetic field changes with time, the stray magnetic field in the X direction is By, and the stray magnetic field in the Y direction is By.
Then, j3x = fx(t)・・・・・・・・・・・・・・・
...(1) By =fy(t)...
It can be expressed as (2). In addition, the displacement of the charged particle beam 4 in the lens barrel 2 due to the floating magnetic field depends on the magnetic fields 3x and BV and is a composite of these, so if the displacement in the X direction is Δx and the displacement in the Y direction is Δy, then ΔX =A IFX (T+T O>+A 2FV
(T+T o) ・・・・・・・・・ (3) Eight V
-A 3 FX (T+T O)+A4FV
(T+To) ...... Represented by (4). Here, A1 to A4 are proportional constants of displacement with respect to the magnetic field, and TO is the delay time that occurs when the magnetic response speed of the material O' that makes up the lens barrel 2 is slow. Depending on the structure of the lens barrel, TO may be almost zero. There is also.

In order to make the above displacements Δx and Δy zero and stabilize the irradiation position of the charged particle beam, it is sufficient to add a displacement having the opposite polarity to the displacement expressed by equations 3 and 4 to the charged particle beam, Voltage Vx applied to correction deflection device 8.

Vy is Vx = -A ICIFX (T+T O>-A 2
G +Fy (T+T o)・・・・・・・・・(5
)vy =-A 302Fx (T+T O>-8
40 2FV (T+T o)...
... ... (6). Therefore, the stabilizing circuit 20 uses the detection signals of the magnetic field detectors 10x and 10y to
By calculating the formula and formula 6, the voltage VX is applied to the deflection electrode 3x,
8x, a voltage Vy is supplied to the deflection electrodes sy, sy, respectively.

Therefore, the stabilization circuit 20 includes two amplifiers 21 and 22 that amplify the detection signals of the magnetic field detector 10x, and two amplifiers 23 and 24 that amplify the detection signals of the magnetic field detector 10y.
, an adder circuit 25 that adds the outputs of amplifiers 21 and 23, and an adder circuit 26 that adds the outputs of amplifiers 22 and 24,
It has two delay circuits 27 and 28 that individually delay the outputs of the adder circuits 25 and 26. 8x, respectively.

In order to remove the influence of the floating magnetic field in this device, first, with the magnetic field detectors 10x and 1oy turned off, the charged particle beam 4 is two-dimensionally scanned over the sample 9 by the main deflection device 7, and the charged particle The output of the detector 11 is displayed on the display device 1
2 to display the scanned image on the display device 12. This J
In other words, a fluctuation in the scanned image is observed as the charged particle beam 4 vibrates due to the floating magnetic field.

Next, the magnetic field detectors 10X and 10y are turned on, and the amplifier 22 is set so that the vibration of the scanned image in the X direction is minimized.
．． The amplification factor of 24 and the delay time of delay circuit 28 are adjusted.

As a result, AlCl, A2Cl, and TO in equation 5 are set, the amplifier 22 outputs a signal corresponding to -A+C+Fx (T), and the amplifier 24 outputs -A2C
A signal corresponding to IFV (T) is output, and a signal corresponding to Vx of formula 5 is output from the delay circuit 28.

Next, the amplification factors of the amplifiers 21 and 23 and the delay time of the delay circuit 27 are adjusted so that the fluctuation of the scanned image in the Y direction is minimized. As a result, A3C2,A in formula 6
4C2,T O is set, the amplifier 21 outputs a signal corresponding to (nee △3C2FX (T), and the amplifier 24 outputs -AaC
A signal corresponding to 2Fy (T) is output, and a signal corresponding to Vy of equation 6 is output from the delay circuit 27.

Thereafter, the magnification of the scanned image is increased and the amplifier 22.2
The amplification factor of 4 and the delay time of the delay circuit 28 and the amplification factor of the amplifiers 21 and 23 and the delay time of the delay circuit 27 may be adjusted more precisely.

By doing this, the amplifier 21 will finally be
The signal corresponding to 302Fx (T) is sent to the amplifier 22
is the signal corresponding to -AICIFx(T> in equation 5, the amplifier 23 is the signal corresponding to -A 4C2Fy (T) in equation 6, and the amplifier 24 is the signal corresponding to -A2CIFV in equation 5.
(T), and the delay circuit 27
．． 28 delays the outputs of the adder circuits 25 and 26 in the preceding stage by the delay time TO, and outputs signals corresponding to Vx and Vy of equations 5 and 6.

In the above embodiment, the correction deflection device 8 is provided separately from the main deflection device 7, but the main deflection device 7 may also be used as the correction deflection device. In this case, the correction voltage is added to the main deflection voltage by an electric circuit and supplied to the main deflection device 7.

Effects of the Invention As described above, the present invention detects stray magnetic fields at at least two locations in the vicinity of the lens barrel in the force direction Yh, and uses the detected signals to minimize the displacement of the charged particle beam. Because of the correction, the displacement becomes practically zero, and the charged particle beam can be irradiated accurately and stably to a single point.As a result, in the case of an electron beam exposure device, fine patterns can be accurately drawn.
In the case of a scanning electron microscope, the resolution is significantly improved, and in the case of an X-ray microanalyzer, a single minute point can be analyzed. Further, since the present invention does not require covering the lens barrel etc. with a magnetic shielding member, not only does the charged particle beam irradiation device not need to be bulky, but the operating knobs etc. can be of simple configuration. There is no reduction in operability.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a charged particle beam irradiation device equipped with a stabilizing device according to the present invention, and FIG. 2 is a block diagram showing an embodiment of the electric circuit of the stabilizing device. 1: Charged particle beam irradiation device, 2: Lens barrel, 3: Sample chamber, 4:
Charged particle beam, 5: Particle beam source, 6: Focusing lens, 7: Main deflection device, 8: Correction deflection device, 9: Sample, 10: Magnetic field detector, 11: Particle beam detector, 12: Cathode ray tube display Device,
20: Stabilization circuit.

Claims (2)

[Claims] (1) At least X near the lens barrel of the charged particle beam irradiation device
A method for stabilizing a charged particle beam, comprising detecting a stray magnetic field as an electric signal at two locations in the direction and the Y direction, and supplying the detection signal to a charged particle beam deflection means to stabilize the irradiation position. (2) At least X near the lens barrel of the charged particle beam irradiation device
Magnetic field detectors are provided at two locations in the direction and the Y direction, and a control signal is generated to stabilize the irradiation position of the charged particle beam based on the output signal of the detector, and is supplied to the charged particle beam deflection means. A charged particle beam stabilization device equipped with a conversion circuit.