JPH10321173A - Beam position correction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a beam position resulting from the change of beam conditions in a beam position correction device. SOLUTION: A beam position correction device 1 is provided with a beam deflection means 23 deflecting a beam position for the correction of a beam, and a correction means 10 adjusting the beam deflection amount of the beam deflection means 23 and correcting the beam position. Based on relationship between beam conditions and a beam position correction amount, the correction means 10 determines the beam deflection amount corresponding to the beam conditions so that the beam is deflected based on the previously obtained relationship between the beam conditions and the beam position correction amount so as to correct the beam position resulting from the change of the beam conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam position correcting apparatus for correcting an optical axis shift of a charged particle beam in an apparatus using a charged particle beam, such as an electron microscope and a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art In the field of semiconductors and the field of metals such as steel, an apparatus using a charged particle beam is used. For example, an electron microscope that detects X-rays and secondary electrons obtained by irradiating a charged particle beam onto a sample surface is used for surface analysis such as analysis of a sample surface and foreign material analysis. Also, a device using a charged particle beam is known.

In an apparatus using a charged particle beam, beam conditions such as an acceleration voltage supplied to a charged particle source and a beam current of the charged particle beam are adjusted in accordance with measurement conditions and processing conditions. Usually, when the beam condition is changed in this way, the beam position moves and a beam shift occurs.

FIG. 10 is a diagram for explaining movement of a beam position due to a change in beam conditions. In FIG.
The apparatus using the charged particle beam irradiates the sample 21 with the charged particle beam emitted from the charged particle source 24 through the converging lens 22, the objective aperture 26, the scanning lens 23, and the objective lens 25. FIG. 10 shows a schematic configuration, and other components are omitted. The beam condition is changed by adjusting the acceleration voltage applied to the charged particle source 24 and the power applied to the converging lens 22, and when these are changed, the beam moves as indicated by the broken line in FIG.

FIG. 11 is a diagram for explaining the movement of the scanning range due to a change in the beam condition. FIG. 11A shows a scanned image when there is no deviation of the beam position, and FIG.
Indicates a scanned image when the beam position is shifted.
In FIG. 11A, when there is no deviation of the beam position, an image 31 near the beam center (indicated by a solid circle) is displayed at the center of the scanned image. On the other hand, FIG.
When the beam position is displaced as shown in (1), an image 32 (indicated by a broken-line circle) near the beam center is displayed at a position displaced from the center of the scanned image.

When the beam position is shifted, the observation point or the processing position on the sample is shifted, a measurement error occurs or the processing accuracy is reduced, and when the shift amount is large, the beam position deviates from the observation area or the processing area. Will be. Conventionally, such a deviation of the beam position is not performed without correction.
Measurement or processing is performed while the beam position remains deviated, or the beam position is corrected by moving a support portion that supports a sample or a workpiece.

[0007]

If measurement or processing is performed without correcting the beam position as in the prior art, there is a problem in terms of measurement error and processing accuracy, and the sample and the workpiece are supported. When the beam position is corrected by moving the support unit, it is necessary to perform the correction of the beam position and the change of the beam position accompanying the movement of the observation point or the processing point by moving the common support unit, and The correction of the beam position and the change of the beam position may have significantly different levels of movement,
There is a problem that the operation of moving the support portion is complicated.

In the conventional correction of the beam position, it is necessary to set the beam position on the sample or the workpiece, and then move the support unit every time the beam condition is changed. Is complicated.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to provide a beam position correcting apparatus capable of correcting a beam position by changing a beam condition.

[0010]

SUMMARY OF THE INVENTION A beam position correcting apparatus according to the present invention deviates a beam based on a relationship between a previously obtained beam condition and a beam position correction amount, thereby changing a beam condition by changing the beam condition. The position is corrected.

In order to correct the beam, the beam position correcting apparatus of the present invention corrects the beam position by adjusting the beam deflection means for shifting the beam position and the beam deflection amount of the beam shifting means. And a correction means for performing
The correction unit determines a beam deviation amount corresponding to the beam condition based on a relationship between the beam condition and the beam position correction amount. Thus, the beam position is corrected by changing the beam condition.

The beam deflecting means is means for deflecting the beam emitted from the beam source between the beam source and the irradiation position, and can be constituted by a magnetic field generating means or an electric field generating means. The beam deviation is controlled by adjusting the power applied to the generating means or the electric field generating means.

The correcting means includes a relationship between the beam condition and the beam position correction amount of the beam deflecting means corresponding to the beam condition in the form of a map, a shift line, or a function. , A beam position correction amount is determined, and a deviation amount of the beam deviation means is determined.

According to the beam position correcting apparatus of the present invention, the relationship between the beam condition and the beam position deviation amount or the beam position correction amount based on the beam condition is determined in advance, and the relationship between the beam condition and the beam position correction amount is mapped. The data is stored in the correction means in the form of a shift line or a function. When the beam condition is changed, the correction means determines a beam position correction amount corresponding to the changed beam condition using the above relationship. The beam deviation means corrects the beam position using the beam position correction amount determined by the correction means. The setting of the beam position correction amount and the correction of the beam position based on the beam position correction amount are performed in conjunction with the change of the beam condition. Thereby, the interlocking correction of the beam position by changing the beam condition can be performed.

In an embodiment of the present invention, the beam conditions are an acceleration voltage for supplying a charged particle beam source and a beam current of the beam, and the beam current can be determined by the power supplied to the beam deflection means.

The correcting means according to the embodiment of the present invention uses a two-dimensional map in which the acceleration voltage and the beam current are used as variables, as to the relationship between the beam condition and the beam position correction amount of the beam deflecting means corresponding to the beam condition. The values between the beam position correction amounts determined and stored by the shift line or function are interpolated by the spline function, and the beam position can be corrected for any beam condition.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. A configuration example according to an embodiment of the present invention will be described with reference to the schematic configuration diagram of the beam position correction device of the present invention in FIG. The beam position correcting apparatus of the present invention is an apparatus that can be applied to an apparatus using a charged particle beam such as an electron microscope and a semiconductor manufacturing apparatus. In the electron microscope, the sample is irradiated with an electron beam emitted from an electron source. The surface of the sample is analyzed, and the semiconductor manufacturing apparatus performs processing by irradiating a workpiece with a charged particle beam such as an ion beam. FIG. 1 shows components necessary for the beam position correcting apparatus and a schematic configuration of an electron microscope.

In FIG. 1, an apparatus using a charged particle beam, such as an electron microscope, includes a charged particle beam source 24 for emitting a charged particle beam, a converging lens 22 and an objective aperture 26 for converging the emitted beam, A scanning lens 23 for scanning and an objective lens 25 for focusing a beam are provided, and X-rays and secondary electrons emitted from the sample 21 are detected by a detector (not shown).

The charged particle beam source 24 receives an acceleration voltage from the high voltage power supply 14 and emits a beam. Each lens disposed between the charged particle beam source 24 and the sample 21 can be constituted by a coil or an electrode. The converging lens 22 and the objective lens 25 are controlled by a current or a voltage supplied from the lens power supply 12. The scanning lens 23 scans a beam with a current or voltage supplied from the scanning power supply 13.

By controlling the acceleration voltage supplied from the high-voltage power supply 14, the beam intensity of the beam emitted from the charged particle beam source 24 is changed, and the current or voltage of the lens power supply 12 is adjusted to reduce the beam current. The control is performed to adjust the focal position of the beam. Normally, when the acceleration voltage or the beam current changes, the trajectory of the beam shifts, and the beam position on the sample 21 shifts.

The beam position corrector 1 (broken line in FIG. 1) includes a focus beam controller 2 for controlling a lens power supply 12, a scanning controller 3 for controlling a scanning power supply 13, and a high voltage controller for controlling a high voltage power supply 14. A high-voltage power supply control section 4, which is controlled by the focus beam control section 2. Further, the beam position correcting apparatus 1 of the present invention includes a correcting unit 10 for correcting a beam position, controls a beam deflecting unit via a correction power supply 11, and corrects a beam deflecting accompanying a change in a beam condition. Do. FIG. 1 shows a configuration in which the scanning lens 23 is used as the beam deflecting means. However, another coil is provided between the converging lens 22 and the sample 21, and the coil deflects the beam deflecting means. It can also be configured.

In the configuration shown in FIG. 1, the correction unit 10 receives beam conditions such as an acceleration voltage and a beam current from the focus beam control unit 2, and obtains a beam position correction amount corresponding to the beam conditions in advance. The level of the scanning signal supplied to the scanning lens 23 by the correction power supply 11 is changed according to the determined and determined beam position correction amount. By performing the adjustment of the scanning signal in the x direction and the y direction, the scanning range of the scanning lens 23 is deviated in the xy directions, and the beam deviation due to the beam condition is corrected.

When the beam deflecting means is constituted by a lens different from the scanning lens 23, a voltage or current corresponding to the beam position correction amount of the correction unit 10 is generated by the correction power supply 11, and this voltage or current is converted to the lens. And independently corrects the beam position.

The correction unit 10 receives the beam condition from the focus beam control unit 2, receives the beam condition from the scanning control unit, and stores the relationship between the beam condition and the beam deviation amount or the beam position correction amount. Or a configuration in which the beam condition is received from the focus beam control unit 2 and the beam deviation amount is received from the scanning control unit 3.

Measurement signals measured by the X-ray detector and the secondary electron detector, data from the data processing device, and the like are displayed on the display unit 7 via the signal selection display control unit 6. The control device 5 controls the focus beam control unit 2, the scanning control unit 3, the high-voltage power supply control unit 4, and the signal selection display control unit 6.

Next, the operation of the beam position correcting apparatus according to the present invention will be described with reference to FIGS. FIG. 2 is a schematic diagram showing the correction of the beam position by the correction signal from the correction means. The beam position correction shown in FIG. 2 shows a case where the beam is deflected by the scanning lens 23.
In FIG. 2, when the acceleration voltage of the charged particle beam source 24 is changed or the beam current is changed by changing the power supplied to the converging lens 22, the beam is displaced as shown. At this time, a correction signal such as a correction voltage or a correction current for correcting a beam position is output from a correction power supply in accordance with a command from the correction unit, and is applied to the scanning lens 23 while being superimposed on the scanning signal.

The scanning lens 23 deflects the beam in the x and y directions by a predetermined amount according to the correction signal. At this time, if the amount of deviation due to the correction signal is the same in the opposite direction as the amount of beam deviation caused by the change in the beam condition, the beam deviation caused by the change in the beam condition is corrected and the sample 21 is corrected.
Can be corrected to a predetermined position. In the correction unit, the relationship between the beam condition and the deviation amount of the beam position under the beam condition or the correction amount for correcting the deviation of the beam position is previously obtained and stored, and each time the beam condition is changed, the beam condition is changed. Is determined, and the beam position correction amount is applied to the scanning lens as a correction signal as a correction signal, whereby correction corresponding to each beam condition can be performed.

At this time, if the correction unit stores the relationship between the beam condition and the deviation amount of the beam position under the beam condition, the correction unit determines the beam position using the beam deviation amount determined by the relationship. A beam position correction amount to be corrected to a predetermined position is calculated.

The correction signal (Vx, Vy) shown in FIG.
Vx is added to the scanning signal in the direction to perform correction, and y
FIG. 3 shows a scan signal in the x direction, a correction signal, and a corrected scan signal at this time, and FIG. 4 shows a scan image. Is represented.

A tooth-like wave indicated by a broken line in FIG.
It is an example of the scanning signal of a direction. When the beam position is set at the coordinate center of the monitor, scanning with this scanning signal results in a scanned image 31 indicated by a solid line in FIG.
If the beam conditions are changed after the setting of the beam position, the beam position is deviated. This deviated beam position is a position deviated from the coordinate center on the monitor, and when a scanned image is obtained from the deviated beam using the scanning signal of FIG. One image becomes a deviated scan image 32 as shown, for example, by a dashed circle in FIG. This scanned image is displayed at a position shifted from the center coordinates of the monitor by the amount of beam deviation. Similarly, in the y-direction, the position is displayed at a position shifted by the beam deviation amount.

With respect to this beam deviation amount, a beam position correction amount Vx for deviating the beam by the same amount in the reverse direction is obtained.
A correction signal as shown in FIG. 3B is generated, and the correction signal shown in FIG.
Is superimposed on the scanning signal. FIG. 3B shows a scanning signal on which a correction signal is superimposed, which is a scanning signal to which a bias is applied by the beam position correction amount Vx. The beam is deviated by the beam position correction amount Vx, and when a scanning image is obtained using this scanning signal, the beam becomes a scanning image 31 in FIG. 4, and the beam deviation can be corrected. The y direction is the same as the x direction.

Next, the beam position correction amount stored in the correction unit will be described with reference to FIGS. The correction unit can store the beam position correction amount corresponding to the beam condition in the form of a map or a shift line, and can read the correction amount according to the beam condition. The chart shown in FIG. 5 is an example of a map showing the relationship between the beam condition and the beam position correction amount, and the beam position correction amount for the two beam conditions of the acceleration voltage applied to the beam source and the power ratio supplied to the converging lens. Vx and Vy are shown. The power ratio is
It shows the ratio when the maximum power applied to the converging lens is 100%.

The map shown in FIG. 5 shows that the acceleration voltage is 15 kV
Then, the beam position is set to a predetermined position based on the beam condition where the supplied power is 40%, and the beam position correction amounts Vx and Vy required to correct the beam deviation caused by a condition different from the beam condition are obtained and stored. FIG.
In the map, the acceleration voltages are 5 kV, 10 kV, and 15 kV.
V, 20 kV, and the supply power is 40
%, 30%, 20%, and 10% are shown. Therefore, the beam position correction amounts for the beam conditions are the beam position correction amounts Vx and Vy corresponding to the beam conditions of the acceleration voltage and the power ratio in the map of FIG.
Can be determined by reading.

FIG. 6 is an example of a shift line showing the relationship between the beam condition and the beam position correction amount. The beam position correction amount diagram shown in FIG. 6 shows the beam condition when the acceleration voltage is 15 kV and the supply power is 40%. The beam position is set to a predetermined position with reference to the above, and the beam position correction amounts Vx and Vy required to correct the beam deviation caused by a condition different from the beam condition are obtained and stored. In the map of FIG. 5, the acceleration voltages are 5 kV, 10 kV, 15 kV, and 20 kV.
2 shows shift lines of the beam position correction amounts Vx and Vy in the case of the above, and shift lines of the beam position correction amounts Vx and Vy in the case where the supply power is 40%, 30%, 20% and 10%. Therefore, the beam position correction amount for the beam condition can be determined by reading the beam position correction amounts Vx and Vy corresponding to the beam conditions of the acceleration voltage and the power ratio in the beam position correction amount diagram of FIG. Further, the relationship between the beam condition and the beam position correction amount can be determined by a function.

In the case of a beam condition not shown in the map of FIG. 5 or the beam position correction amount diagram of FIG. 6, neighboring beam position correction amounts Vx and Vy are used to interpolate between these beam position correction amounts. It can be obtained by doing. As an interpolation method, for example, interpolation using a spline function can be used.

Next, a method for obtaining the relationship between the beam condition and the beam position correction amount will be described. The first method is to adjust the scanning control unit 3 in the beam position correcting apparatus 1 shown in FIG. 1 while displaying the scanning image on the display device 7 so that the scanning image is at a predetermined position, and adjust the adjustment amount. It is obtained as a beam position correction amount and stored in the correction unit 10.

In the second method, in the beam position correcting apparatus 1 shown in FIG. 1, a scanning image is displayed on the display device 7, and the position of the scanning image deviated by the deviation of the beam position is designated on a monitor. The beam deviation amount is obtained, the beam position correction amount is obtained from the beam deviation amount, and stored in the correction unit 10.

FIGS. 7 and 8 are diagrams for explaining a second method for obtaining the relationship between the beam condition and the beam position correction amount. As shown in FIG. 7, a scanned image can be obtained by scanning a beam in the xy directions. When the beam position is deviated, the scanned image is shifted on the monitor by a beam deviation amount. Will be displayed. FIG. 8 shows scanning signals in the x and y directions. The signal value of the scanning signal corresponds to the position on the monitor, and the signal value of the scanning signal applied at that time can be obtained from the position on the monitor. Therefore, when the position of the scan image on the monitor is designated, the beam deviation amount can be obtained from the signal value of the scan signal at this time (VX in FIG. 8A, VY in FIG. 8B). . Beam position correction amount (V
x, Vy) can be obtained by calculating a value for correcting the beam position to a predetermined position based on the obtained beam deviation amount (VX, VY).

FIG. 9 is a diagram showing another example of the configuration of the beam position correcting apparatus of the present invention. The configuration example shown in FIG. 1 is a configuration in which both a scanning coil and a beam position correction coil are used as beam deflecting means, whereas the configuration example shown in FIG. Is provided. The beam position correction coil 27 receives a drive current from the correction power supply 11 and corrects the beam position.

[0040]

As described above, according to the beam position correcting apparatus of the present invention, the beam position can be corrected by changing the beam condition.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a beam position correction device of the present invention.

FIG. 2 is a schematic diagram showing correction of a beam position by a correction signal from a correction unit of the present invention.

FIG. 3 is a diagram illustrating a scanning signal in the x direction, a correction signal, and a corrected scanning signal according to the present invention.

FIG. 4 is a diagram for explaining a scan image by a correction unit of the present invention.

FIG. 5 is a table showing a relationship between a beam condition and a beam position correction amount according to the present invention.

FIG. 6 is a beam position correction amount diagram showing a relationship between a beam condition and a beam position correction amount according to the present invention.

FIG. 7 is a diagram for explaining a method of obtaining a relationship between a beam condition and a beam position correction amount according to the present invention.

FIG. 8 is a scanning signal diagram for explaining a method of obtaining a relationship between a beam condition and a beam position correction amount according to the present invention.

FIG. 9 is a diagram for explaining another configuration example of the beam position correction device of the present invention.

FIG. 10 is a diagram for explaining movement of a beam position due to a change in beam conditions.

FIG. 11 is a diagram for explaining movement of a scanning range due to a change in beam conditions.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Beam position correction apparatus, 2 ... Focus beam control part, 3 ... Scan control part, 4 ... High voltage power supply control part, 5 ... Control device, 6 ... Signal display control part, 7 ... Display part, 10 ... Correction part,
11 correction power supply, 12 lens power supply, 13 scanning power supply,
14 high voltage power supply, 21 sample, 22 convergent lens, 23
... scanning lens, 24 ... charged particle source, 25 ... objective lens,
26: Object aperture, 27: Beam position correction coil, 3
1, 32, 33 ... Scanned image.

Claims (1)

[Claims] 1. A system comprising: a beam deflecting means for deflecting a beam position; and a correcting means for adjusting a beam deflecting amount of the beam deflecting means to correct a beam position. A beam position correcting device for determining a beam deviation amount corresponding to a beam condition based on a relationship between the beam position correction amount and the beam position correction amount.