JP2863558B2 - Charge neutralizer for focused ion beam equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge neutralization device of a focused ion beam device, and keeps a constant distribution of electrons to be irradiated to neutralize the charge of an ion beam. In addition, the present invention relates to a charge neutralizing device of a focused ion beam device suitable for eliminating a displacement of an irradiation position of an ion beam.

[Prior Art] FIG. 8 is a view showing a schematic configuration of a focused ion beam processing apparatus which is a focused ion beam apparatus, FIG. 9 is an explanatory view showing an ion beam irradiation position shift due to charge-up, and FIG.
FIGS. 10A and 10B are longitudinal sectional views each showing a schematic configuration of an electron shower as an electron generator for neutralizing the charge of the ion beam.

In a focused ion beam processing apparatus, as shown in FIG. 8, an ion beam 2 is extracted from a high-intensity ion source 1 such as a liquid metal ion source, and a workpiece to be irradiated is placed on a stage 5. 6 is focused by the electrostatic lens 3. Processing positioning as the irradiation position of the ion beam 2 is performed by deflecting the ion beam 2 by the deflector 4.

However, since the ions of the ion beam 2 have a positive charge 7, the surface of the workpiece 6 is positively charged up. Therefore, as shown in FIG. 9, the ion beam 2 is repelled and bent near the surface of the workpiece 6. In this state, it is impossible to process LSIs, masks, and the like that require positioning accuracy of 1 μm or less.

Therefore, in order to neutralize the positive charges 7 on the surface of the workpiece 6, a method of irradiating electrons is generally used.

There are several types of electron showers, which are electron generators for neutralizing the charge of ions.

The electron shower 8 shown in FIG. 10 (a) is of a type that simply irradiates the surface of the workpiece 6 with the electrons 9 generated by the electron source 11. In this type, only the electron source 11 is provided in the electron shower 8, and the electrons 9 reach the surface of the workpiece 6 while spreading at the emission angle from the electron source 11. In this case, when the current of the ion beam 2 increases, a situation occurs in which the charge cannot be completely neutralized.

The electron shower 8 shown in FIG. 10 (b) has a lens 12 for focusing the electrons 9 in order to increase the current density of the electrons 9. The electron shower 8 of this type is provided with a deflector 13 for deflecting the electrons 9 so that the irradiation position of the electrons 9 can be adjusted to the irradiation position of the ion beam 2 on the surface of the workpiece 6.

[Problems to be Solved by the Invention] FIGS. 11 (a), (b) and (c) are explanatory views showing the relationship between the center position of the electron distribution and the position of the axis of the ion beam.

The electron distribution 18 on the surface of the workpiece 6 of the electrons 9 emitted from the electron shower 8 usually extends from 1 mmφ to several mmφ.

When the center of the electron distribution 18 is coincident with the axis of the ion beam 2 as shown in FIG. 11 (a), the irradiation position of the ion beam 2 does not shift.

However, the electron distribution 18 may be shifted for the following reasons.

Negative charge with a Faraday cup (e ^-) but be preset irradiation point of the electron beam is considered, the actual workpiece 6 FIB (F ocus I on B ea
m) When brought to the irradiation position, the electrolysis near the irradiation point changes, and the irradiation point of the e ^- beam may deviate from the initially set position.

During machining start, the correct point e ^- even if the beam is irradiated, the drift of the thermal drift and electrical circuits, e ^- have the irradiation point of the beam is shifted.

In any case, as shown in FIGS. 11 (b) and 11 (c), when the center of the electron distribution 18 is shifted from the axis of the ion beam 2, the negative charge of the electron 9 and the positive There is a problem that the charge 7 becomes non-uniform, a potential gradient appears on the surface of the workpiece 6, and the irradiation position of the ion beam 2 is shifted from a desired processing position.

An object of the present invention is to provide a charge neutralizing device of a focused ion beam device capable of maintaining a constant electron distribution and eliminating a deviation in irradiation position of an ion beam.

[Means for Solving the Problems] The object is to provide a detecting means for detecting an electron supply situation near an irradiation position of an ion beam on a surface of an irradiation object, and a center of an electron distribution according to information detected by the detecting means. This is achieved by providing the electron generating device with a controller that performs feedback control so that the portion is aligned with the axis of the ion beam.

Further, the above object is achieved by disposing a plurality of Faraday cups around the irradiation position of the ion beam on the surface of the irradiation object as the detection means.

Further, the above object is achieved by disposing a plurality of electrodes for current detection around the irradiation position of the ion beam on the surface of the irradiation object as the detection means.

Still further, the above object is achieved by disposing a plurality of electrodes for detecting a current of emitted electrons around the electron emission hole of the electron generator as the detection means.

In addition, the object is that as the detection means, an imaging means for observing the surface of the irradiation object constituted by a change in the amount of secondary particles generated when the ion beam is scanned on the surface of the irradiation object, and this imaging means Process the image observed by
This is achieved by providing an image processing means for detecting an electron supply state and sending the detection result to a controller of the electron generating device.

Further, the object is achieved more accurately by configuring the controller to control the voltage of the electrode for deflecting the electron trajectory.

[Operation] In the present invention, the surface of the irradiation object is irradiated with the ion beam, and electrons for neutralizing the charge of the ion beam are supplied to the irradiation position of the ion beam by the electron generator.

Then, the electron supply state near the irradiation position of the ion beam on the surface of the irradiation object is detected by the detection means for detecting the electron supply state, and the detection result is sent to the controller of the electron generator.

The controller performs feedback control on the electron generator in accordance with information on the state of electron supply to the surface of the irradiation target detected by the detection means so that the center of the electron distribution coincides with the axis of the ion beam. This makes it possible to always keep the electron distribution constant and to eliminate the deviation of the irradiation position of the ion beam due to the deviation of the electron distribution.

Further, in the present invention, the detection means is configured by arranging a plurality of Faraday cups around the irradiation position of the ion beam on the surface of the irradiation object. Then, the current values in the X and Y directions of the electron distribution are detected by the plurality of Faraday cups, and the detection results are sent to the controller of the electron generator. In this controller, the current value detected by the Faraday cup is X Feedback control is applied to the electron generator so that the directions are equal in both directions. This makes it possible to always keep the electron distribution constant and to eliminate the deviation of the irradiation position of the ion beam due to the deviation of the electron distribution.

Further, in the present invention, the detection means is configured by arranging a plurality of electrodes for current detection around the irradiation position of the ion beam on the surface of the irradiation object. Thus, the current values in the X and Y directions of the electron distribution are detected by the plurality of electrodes, and the detection results are sent to the controller of the electron generator. In this controller, the current value detected by the electrodes is X Feedback control is applied to the electron generator so that the directions are equal in both directions.
This makes it possible to keep the electron distribution constant and to eliminate the deviation of the irradiation position of the ion beam due to the deviation of the electron distribution.

Furthermore, in the present invention, the detection means is configured by arranging a plurality of electrodes for detecting the current of emitted electrons around the electron emission hole of the electron generation device. With the plurality of electrodes, the current value of the electron distribution is detected by the electron generating device itself, and the detection result is sent to a controller of the electron generating device, where the current value of the electron distribution detected by the electrodes is kept constant. Thus, feedback control is applied to the electron generator. Therefore, it is possible to always keep the electron distribution constant by using a simple detection means, and to eliminate the deviation of the irradiation position of the ion beam caused by the deviation of the electron distribution.

Further, in the present invention, the detection means is constituted by an imaging means of the surface of the irradiation object and an image processing means. The imaging means observes the surface of the irradiation object constituted by a change in the amount of secondary particles generated when the ion beam is scanned on the surface of the irradiation object, and sends the image to the image processing means. The image processing means processes the image sent by the imaging means, detects an electron supply state, and sends the detection result to a controller of the electron generating device. The controller performs feedback control on the electron generator based on the detection result of the electron supply state by the image processing means so that the center of the electron distribution coincides with the axis of the ion beam. This makes it possible to always keep the electron distribution constant and to eliminate the deviation of the irradiation position of the ion beam due to the deviation of the electron distribution.

Further, in the present invention, the controller is configured to control the voltage of the electrode for deflecting the electron trajectory. The displacement of the irradiation position of the beam can be eliminated.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

 FIG. 1 is a perspective view showing a first embodiment of the present invention.

In the first embodiment, the focused ion beam device is a focused ion beam processing device, and the object to be irradiated with the ion beam is a workpiece.

In the first embodiment, the charge neutralizing device is provided in an ion source (not shown) for extracting the ion beam 2, a chamber having vacuum means (none is shown), and installed in the chamber. A stage 5 on which the workpiece 6 is placed, a Faraday cup 14 which is a detecting means for detecting an electron supply state near the irradiation position of the ion beam on the surface of the workpiece 6, and The electronic shower 8 includes an electronic shower 8 that is an electron generator that supplies the electrons 9 to be added, and a controller 16 of the electronic shower 8.

The Faraday cup 14 is provided at the tip of the supporter 15. Further, four Faraday cups 14 are provided, and two Faraday cups 14 are arranged in the plane parallel to the surface of the workpiece 6 so as to face each other in the X direction and the Y direction. A current value as an electron supply situation near the irradiation position is detected, and the detected current value is sent to the controller 16.

The electron shower 8 has an electron source 11, a lens 12 for focusing a beam of electrons 9 emitted from the electron source 11, and a deflector 13 for deflecting the beam of electrons 9 focused by the lens 12. In this embodiment, the electrons 9 are irradiated with the negative charges (e ⁻ ) with respect to the positive charges of the ions.

The controller 16 inputs a current value, which is information detected from the four Faraday cups 14, and performs electronic control in the controller 16 or a higher-level controller (not shown) that controls the controller 16 according to a predetermined algorithm. The voltage applied to the upper and lower electrodes of the deflector 13 of the electronic shower 8 is feedback-controlled so as to keep the supply state constant.

Next, the operation of the focused ion beam processing apparatus of the first embodiment and the operation of the charge neutralizing apparatus will be described.

The workpiece 6 is placed on the stage 5 installed in a vacuum chamber. The workpiece 6 is, for example, an LSI chip or a mask.

The ion beam 2 is focused on the surface of the workpiece 6 placed on the stage 5 into a spot of 1 μmφ or less.
At this time, electrons 9 are irradiated from the electron shower 8 to neutralize the positive charges of the ions in order to prevent the irradiation position of the ion beam 2 from shifting due to charge-up due to the positive charges of the ions.

In the electron shower 8, electrons 9 are generated from an electron source 11, the electrons 9 are focused by a lens 12, and a deflector 13
This deflects the electron beam, and irradiates the electron 9 of negative charge to the vicinity of the irradiation position of the ion beam 2 on the surface of the workpiece 6. Since the electron shower 8 aims at the irradiation point of the ion beam 2, its center axis is
It is installed so as to pass through the irradiation point.

The supply state of the electrons 9 is detected by four Faraday cups 14. Each Faraday cup 14, for example, 1mmφ
And four supporters 15 extending from the X direction and the Y direction to the irradiation position of the ion beam 2.
Each Faraday cup 14 is not mounted on the stage 5 and has four axes of the ion beam 2.
It is fixed to pass through the center of 14.

The current value of the electrons 9 detected by the Faraday cup 14 is sent to the controller 16 of the electronic shower 8. Within this controller 16 or this controller 16
In the upper controller, feedback control is applied to the electronic shower 8 according to a certain algorithm so that the current value detected by the Faraday cup 14 keeps a certain interval.

FIGS. 2A and 2B show an example of control by the controller.

Now, it is assumed that the axis of the ion beam 2 and the electron distribution 18 are displaced in the X direction as shown in FIG. At this time, the current values detected by the two Faraday cups 14 arranged in the X direction have different values. Therefore, the controller 16 shown in FIG. 1 instructs to apply + δV to the upper electrode of the teflector 13 of the electronic shower 8 and −δV to the lower electrode.

As the magnitude of the voltage δV applied to the upper and lower electrodes of the deflector 13 of the electronic shower 8 changes, the current value detected by the Faraday cup 14 changes. As shown, the value of δV is set where the current values detected by both Faraday cups 14 are equal. However, the electron distribution 18 may not always be symmetric. In this case, it is necessary to input the relationship between the electron distribution and the detected current value into the controller 16 of the electronic shower 8 or a higher-level controller in advance.

In the first embodiment, the electron source of the electronic shower 8 is
The current of electrons 9 emitted from 11 and the Faraday cup 14
Is controlled so that the absolute value of the current of the electrons 9 can be kept constant based on the relationship with the current value detected in step (1). In other words, while the current of the emitted electrons 9 remains constant, the Faraday cup
If all of the current values detected at 14 increase, electrons 9
It is determined that the focusing state has deteriorated and the electron distribution 18 on the workpiece 6 has widened, and the voltage applied to the lens 12 of the electronic shower 8 is changed. Conversely, the current of the emitted electrons 9 and
If the current value detected by the Faraday cup 14 simultaneously increases while maintaining a constant relationship, the current flowing to the electron source 11 is reduced so as to reduce the emission of the electrons 9 itself. As described above, by controlling each part of the electronic shower 8 based on information from the current value detected by the farada cup 14 according to a constant algorithm, the electrons 9 are quantitatively determined so that the constant electron distribution 18 is always obtained. The irradiation position of the ion beam 2 can be avoided.

FIG. 3 is a perspective view showing a second embodiment of the present invention.

In the second embodiment, a current detection plate 17 having a shape obtained by dividing a circular electrode into four equal parts is used as a means for detecting an electron supply state.

A hole 17 'through which the ion beam 2 passes is formed in the center of the electrode where the four current detection plates 17 are arranged in a circle.

In the second embodiment, since the configuration of the electrodes is almost the same as the axis of the ion beam 2, the influence of the electric field from the stage 5 and the like can be avoided.

Further, in the second embodiment, the current detection plate 17 can be formed by simply dividing one disk into equal parts, so that the current detection plate 17 can be easily manufactured and assembled as compared with the first embodiment. is there.

The other configurations and operations of the second embodiment are the same as those of the first embodiment.

Next, FIG. 4 shows a third embodiment of the present invention, and is a vertical front view of the electronic shower, and FIG. 5 is a left side view of FIG.

In the third embodiment, an electrode 19 for detecting an electron distribution 18 is provided near an electron emission hole of an electron shower 8 as an electron generator.
Is provided.

The electrodes 19 are formed in a shape obtained by dividing a circle into four. The four electrodes 19 are attached to the electron emission port side of the electron shower 8.

In the third embodiment, a current value detected by each electrode 19 is sent to a controller (omitted in FIGS. 4 and 5) of the electronic shower 8, and the controller controls the current value according to the first and second embodiments. Similarly, the electronic shower 8 is subjected to feedback control so as to keep the supply state of the electrons 9 constant.

Although the third embodiment does not directly detect the electron distribution 18 on the workpiece 6 as in the first and second embodiments, the state of the electron distribution 18 has a simple structure. The first and second
Can be detected almost in the same manner as in the embodiment.

Next, FIG. 6 is a block diagram showing a fourth embodiment of the present invention, and FIG. 7 is an explanatory diagram of image processing in this embodiment.

In the fourth embodiment, includes an imaging unit 20 for detecting means of the electronic supply situation get up surface of the SIM of the workpiece 6 (S canning I on M icroscop ), and an image processing unit 21 of the SIM image It is configured.

The imaging means 20 detects secondary particles generated by the irradiation of the ion beam 2, here, secondary ions, and detects a SIM image 22 of the surface of the workpiece 6 by the same principle as that of a scanning electron microscope.
Get. At this time, the region irradiated with the electrons 9 from the electron shower 8 has a different secondary ion emission ability from the region not irradiated with the electrons 9. Therefore, the region irradiated with the electrons 9 usually looks bright. However, since it differs depending on the workpiece 6, it may appear dark on the contrary. The light / dark reversal is dealt with by processing the image each time.

Assuming that the region irradiated with the electrons 9 looks bright, when a region wider than the spread of the electron distribution 18 is scanned by the ion beam 2 and the SIM image 22 is viewed, as shown in FIG. The spread area 23 of the distribution looks bright.

The image processing means 21 binarizes the image as shown in FIG. 7 and obtains the center 27 of the spread region 23 of the electron distribution in the X and Y directions. At this time, in this embodiment, in both the X direction and the Y direction, as shown in FIG. 7, the luminance signals 24 and 25 are projected and then binarized to obtain the center 27 of the spread region 23 of the electron distribution. Has adopted.

Next, the image processing means 21 calculates the distance and direction between the center 26 of the SIM image 22 and the center 27 of the spread region 23 of the electron distribution, and sends the calculation result to the controller 16.

In the controller 16, based on the distance and direction of the centers 26 and 27 calculated by the image processing means 21, the center 27 of the spread region 23 of the electron distribution is calculated according to the same algorithm as in the first and second embodiments. SIM image 22
The electronic shower 8 is subjected to feedback control so that it coincides with the axis of the ion beam 2 which is the center 26 of the ion shower 2.

Thereby, the center of the electron distribution 18 is always set to the ion beam 2
Can be made to coincide with the axis.

[Effect of the Invention] According to the invention described in claim 1 of the present invention described above,
While irradiating the surface of the irradiation object with the ion beam, the electron generating device supplies electrons for neutralizing the charge of the ion beam to the irradiation position of the ion beam, and a detecting unit for detecting an electron supply state, An electron supply state near the irradiation position of the ion beam on the surface of the irradiation object is detected, and the detection result is sent to a controller of the electron generator, and the controller supplies the electrons to the surface of the irradiation object detected by the detection means. According to the information on the situation, feedback control is performed on the electron generator so that the center of the electron distribution coincides with the axis of the ion beam. There is an effect that the irradiation position deviation of the ion beam can be eliminated.

According to the invention described in claim 2 of the present invention, the detection means is configured by arranging a plurality of Faraday cups around the irradiation position of the ion beam on the surface of the irradiation object, The current values in the X and Y directions of the electron distribution are detected by a plurality of Faraday cups, and the detection results are sent to the controller of the electron generating device. In this controller, the current values detected by the Faraday cup are detected in the X and Y directions. Since the feedback control is applied to the electron generator so that the directions are equal, the electron distribution is always kept constant, and there is an effect that the irradiation position deviation of the ion beam caused by the deviation of the electron distribution can be eliminated. .

Further, according to the invention described in claim 3 of the present invention, the detecting means is configured by arranging a plurality of electrodes for current detection around the irradiation position of the ion beam on the surface of the irradiation object. And the plurality of electrodes allow the electron distribution X
Direction, the current value in the Y direction is detected, and the detection result is sent to the controller of the electron generation device. In this controller, the current value detected by the Faraday cup is set to be uniform in both the X direction and the Y direction. In this case, the electron distribution is always kept constant, and there is an effect that the irradiation position deviation of the ion beam caused by the deviation of the electron distribution can be eliminated.

Furthermore, according to the invention described in claim 4 of the present invention,
The detection means, around the electron emission hole of the electron generator,
A plurality of electrodes for detecting the current of the emitted electrons are arranged, and the plurality of electrodes detect the current value of the electron distribution by the electron generator itself, and use the detection result to control the electron generator. In this controller, the feedback control is applied to the electron generator so that the current value of the electron distribution detected by the electrode becomes constant, so that the electron distribution is always kept constant using simple detection means. In addition, there is an effect that the irradiation position shift of the ion beam caused by the shift of the electron distribution can be eliminated.

Further, according to the invention of claim 5 of the present invention, the detecting means is constituted by an imaging means for imaging the surface of the object to be irradiated and an image processing means, wherein the imaging means emits an ion beam to the object to be irradiated. Observes the surface of the irradiation target constituted by the change in the amount of secondary particles generated when scanning on the surface of the object, sends the image to the image processing means, and the image processing means sends the image sent by the imaging means To detect the state of electron supply, send the detection result to the controller of the electron generator, the controller based on the detection result of the state of electron supply in the image processing means, the center of the electron distribution to the axis of the ion beam Since the feedback control is applied to the electron generating device so as to make them coincide with each other, the present invention also keeps the electron distribution constant, and the ion beam caused by the deviation of the electron distribution. An effect capable of eliminating the irradiation position shift of.

Further, according to the invention of claim 6 of the present invention, the controller is configured to control the voltage of the electrode for deflecting the electron trajectory, and as a result, the electron distribution is more accurately fixed. And it is possible to eliminate the deviation of the irradiation position of the ion beam caused by the deviation of the electron distribution.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention, FIGS. 2 (a) and 2 (b) are views showing an example of control of a controller,
FIG. 3 is a perspective view showing a second embodiment of the present invention, FIG. 4 shows a third embodiment of the present invention, and a vertical front view of an electronic shower, and FIG. 5 is a left side of FIG. FIG. 6 is a block diagram showing a fourth embodiment of the present invention, and FIG. 7 is an explanatory diagram of image processing in this embodiment. FIG. 8 is a diagram showing a schematic configuration of a focused ion beam processing apparatus which is a focused ion beam apparatus, FIG. 9 is an explanatory view showing an ion beam irradiation position shift due to charge-up, and FIGS. 11 is a longitudinal sectional view showing a schematic configuration of an electron shower which is an electron generator for neutralizing the charge of the ion beam. FIGS. 11 (a), (b) and (c) show the center position of the electron distribution and the ion FIG. 4 is an explanatory diagram showing a relationship with a position of a beam axis. DESCRIPTION OF SYMBOLS 1 ... Ion source, 2 ... Ion beam, 5 ... Stage for work, 6 ... Work which is an irradiation object of an ion beam, 7 ... Positive charge, 8 ... Electron generator A certain electronic shower, 9 ... electron, 11 ... electron source, 12 ... lens, 13 ... deflector, 14 ... Faraday cup, 15 ...
... Faraday cup supporter, 16 ... Electronic shower controller, 17 ... Electrode for detecting current value of electron distribution, 18
…… electron distribution, 19 …… electrode for current value detection of electron distribution,
20 SIM image pickup means, 21 image processing means, 22 S
IM image, 23: Spread area of electron distribution, 24, 25 ... Luminance signal in X and Y directions, 26: Center of SIM image, 27 ... Center of spread area of electron distribution.

Claims (6)

(57) [Claims] An ion beam is extracted from an ion source, and the ion beam is focused and deflected to irradiate the surface of an object to be irradiated. In a charge neutralizing device of a focused ion beam device configured to supply electrons for neutralizing charges, a detecting means for detecting an electron supply situation near an irradiation position of an ion beam on a surface of the irradiation object, and the detecting means A controller that performs feedback control on the electron generator so that the center of the electron distribution coincides with the axis of the ion beam according to the information detected by the controller. Sum equipment. 2. A charged ion beam apparatus according to claim 1, wherein a plurality of Faraday cups are arranged around the irradiation position of the ion beam on the surface of the object to be irradiated as said detection means. Sum equipment. 3. A focused ion beam apparatus according to claim 1, wherein a plurality of electrodes for current detection are arranged around the irradiation position of the ion beam on the surface of the object to be irradiated as said detection means. Charge neutralization device. 4. The focused ion beam according to claim 1, wherein a plurality of electrodes for detecting a current of emitted electrons are arranged around the electron emission holes of the electron generator as the detection means. Device charge neutralization device. 5. An image pickup means for observing the surface of an irradiation object constituted by a change in the amount of secondary particles generated when an ion beam is scanned on the surface of the irradiation object as said detection means, and said imaging means 2. The focused ion beam apparatus according to claim 1, further comprising image processing means for processing an image observed by the method, detecting an electron supply state, and sending a result of the detection to a controller of the electron generator. Charge neutralizer. 6. A charge neutralizing device for a focused ion beam apparatus according to claim 1, wherein said controller controls the voltage of an electrode for deflecting an electron trajectory.