JPH0513036A - Ion beam irradiation and device therefor - Google Patents

Abstract

PURPOSE:To observe change in a sample during ion beam irradiation by maintaining a stable level of the value difference in acceleration voltage applied to a transport and drawing voltage so as to adjust the value of acceleration voltage and whereby facilitating adjustment of power source voltage following change in the acceleration voltage. CONSTITUTION:A differential voltage of 10kV is kept between acceleration voltage and drawing voltage, and when acceleration voltage generated by an acceleration power source 21 is set to 0.5kV, output voltage of a drawing power source 22 is xkV. An expression 0.5kV-xkV=10kV is formed, while output voltage of the power source 22 is determined -9.5kV. When the acceleration voltage is to be changed to 0.6kV, the power source 22 is adjusted for the output voltage to be -9.4V. By carrying out this adjustment, adjustment of output voltage of the other sources i.e., an upstream lens power source 23, a right auxiliary deflection power source 24, a left auxiliary deflection power source 25, a magnet power source 26 for analysis, a downstream lens power source 27, electrostatic prism power sources 28, 29 is no more necessary, while appropriate level of ion beam diameter and ion beam direction are maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam irradiation method and apparatus for irradiating a sample made of a metal material, a ceramic material, a semiconductor material, or another material with an ion beam.

[0002]

2. Description of the Related Art When observing a sample for ion irradiation damage,
Ions generated by the ion source are accelerated by an accelerating tube, given the required energy, focused by a lens, mass-analyzed by a magnet, then focused again by the lens and deflected by an electrostatic prism inside the electron microscope. Then, the sample of the electron microscope is irradiated with the ions and observed. The ion source and the acceleration tube form an ion beam generator.

When irradiating a sample such as a metal material with an ion beam, generally, a DC high voltage of several tens of kV or more is applied between the ion beam generating section and the sample, and ions sufficiently accelerated by this are applied. The sample is irradiated. However, there are cases where it is desired to irradiate the sample with a low acceleration ion beam. In this case, for example, the final acceleration voltage is 1 k.
A voltage of about 30 kV is applied to the ion accelerating portion and 29 kV is applied to the sample portion so that the voltage becomes about V.

On the other hand, when the sample is located in the electron microscope, the voltage applied to the sample cannot be set so high because of problems such as electrical insulation. Therefore, a large ion beam current is generated from the ion beam generator. It is necessary to be able to set the applied voltage to the sample portion low while pulling it out.

In order to meet this demand, the invention described in JP-A-2-24946 has been proposed.
As shown in FIG. 4, the present invention, from the ion source section 1 to a predetermined sample S via an acceleration tube section 2 and a transport T,
The sample S is irradiated with a low-acceleration ion beam to maintain the sample S at a substantially ground potential, the extraction voltage applied to the transport T is set to a negative value, and the acceleration voltage applied to the ion source unit 1 is set low. It is a thing. The transport T is a conductive portion that covers the upstream lens unit 3, the analysis magnet 7, the downstream lens unit 8 and the like. Also, the acceleration power source E
1, an upstream lens power source E2, an analyzing magnet power source E3, a downstream lens power source E4, and a drawing power source E5 are provided.

In such an invention, the ion source section 1
Since a sufficiently high voltage can be applied between the extraction voltage and the extraction voltage, a large amount of ions can be extracted from the ion source unit 1 and the ion beam can move the space in the high potential transport at the extraction potential to the vicinity of the sample. Since the ion beam extracted from the ion source unit 1 does not diverge so much and a desired low-acceleration ion beam can be applied to the sample S at the ground potential, the relationship between the sample of ceramics, living things, or the device can be improved. Therefore, it is possible to irradiate a sample to which a voltage cannot be applied with a low acceleration ion beam.

[0007]

However, in the above-mentioned conventional example, when the sample S is to be irradiated with the ion beam while changing the acceleration voltage, first, the acceleration power source E1 is adjusted to a desired voltage, and then, The voltage of the upstream lens power supply E2, the analysis magnet power supply E3, and the downstream lens power supply E4 are adjusted to adjust the beam diameter to a predetermined size and to adjust the center of the beam to the center of the sample. They need to be controlled individually and the effects of other power sources need to be corrected repeatedly. Therefore, the control is very delicate.

For example, in the above-mentioned conventional example, when the voltage of the acceleration power source E1 is set to 0.5 kV, each voltage of the upstream lens power source E2, the analyzing magnet power source E3, the downstream lens power source E4, the extraction power source E5, and the electrostatic prism power source. Is set as shown in FIG. In this state, when the voltage of the acceleration power source E1 is changed from 0.5 kV to 1.0 kV, the upstream lens power source E2, the analysis magnet power source E3,
Each voltage of the downstream lens power source E4 and the electrostatic prism power source needs to be changed as shown in FIG. It should be noted that FIG. 5 shows a representative example of the power source to be changed, and in addition to these, it is actually necessary to change the voltages of the two left and right auxiliary deflection power sources and the like. Is extremely complicated.

Therefore, in the above-mentioned conventional example, there is a problem that the work of adjusting the voltage of each of the power supplies is complicated due to the change of the acceleration voltage, and when the acceleration voltage is changed once. In addition, if adjustment of the voltage of each power supply is also included, it actually takes about 30 minutes to adjust, and the change of the sample when the ion beam is irradiated while changing the energy is changed in real time. There is a problem that it is not possible to observe it in.

According to the present invention, a large amount of ions can be extracted from the ion beam generator, and a target such as ceramics, living things, etc. to which a voltage cannot be applied, or a target including the sample S depending on the condition of the device structure such as an electron microscope. When irradiating a sample that cannot be applied with a deceleration voltage with the ion beam, it is easy to adjust the power supply voltage when changing the acceleration voltage, and the sample changes when the ion beam is irradiated while changing the energy. It is an object of the present invention to provide an ion beam irradiation method and an apparatus therefor capable of observing in time.

[0011]

According to the present invention, the sample is held at approximately the ground potential, and the extraction voltage applied to the transport is set to a value having a polarity opposite to that of the acceleration voltage. The value of the accelerating voltage is adjusted while keeping the difference from the value of (4) almost constant. Further, the present invention is provided with voltage adjusting means for adjusting the value of the accelerating voltage while keeping the difference between the value of the accelerating voltage and the value of the extraction voltage constant.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of an embodiment of the present invention.

This embodiment is roughly divided into an ion beam generator 10, a transport T, an electron microscope barrel 40, and power supplies.

The ion beam generator 10 is composed of an ion source for generating ions and an accelerating tube for accelerating the generated ions. The ionizing gas is supplied to the ion source through the adjusting valve V and the introduction hole G. be introduced. Ion beam generator 1
Specifically, 0 has a filament F, an ion source magnet IM, and an arc portion, and an acceleration voltage is applied from an acceleration power supply 21.

In the transport T, the upstream lens L
1, the auxiliary deflection electrodes D1 and D2, and the downstream lens L2 are provided, and an extraction voltage is applied from the extraction power supply 22 between the transport T and the ground potential. This extraction voltage causes an action of extracting ions between the accelerating tube and the extraction electrode 22a of the transport T, and keeps the space around the ion beam at a constant voltage. Since the diameter of the ion beam generated by the ion source and accelerated by the accelerating tube increases with the beam travel distance, the upstream lens L1 and the downstream lens L2 converge the ion beam to reduce its diameter, This is to prevent divergence.

The analysis magnet AM removes unnecessary ions contained in the ion beam. The mass analysis magnet AM analyzes the energy and mass of the ions to analyze only the necessary ions. It is sent to the sample S existing downstream of the transport T.

In the lens barrel portion 40 of the electron microscope 41, a part of the shield tube ST connected to the ground potential,
An electrostatic prism P inside the shield tube ST and a sample S are provided. A predetermined voltage is applied to the electrostatic prism P by the electrostatic prism power supplies 28 and 29 (when the difference voltage between the acceleration voltage and the extraction voltage is, for example, 10 kV, the electrostatic prism voltage is, for example, 0.9 kV). Is being applied. The upper end of the shield tube ST covers the downstream end of the transport T, and the downstream end of the transport T is downstream of the prism P.
It extends to the vicinity of the sample S.

The acceleration power source 21 is provided between the ion generating section 10 and the ground potential, applies a positive voltage to the ion generating section 10, and the extraction power source 22 is provided between the transport T and the ground potential. Therefore, a negative voltage is applied to the transport T. In this case, the value of the acceleration voltage is adjusted while maintaining the difference between the value of the acceleration voltage by the acceleration power supply 21 and the value of the extraction voltage by the extraction power supply 22 to be substantially constant. When the difference between the acceleration voltage value and the extraction voltage value is kept substantially constant in this way, the acceleration power source 21 is manually adjusted and the extraction power source 22 is manually adjusted.

In addition to this, the upstream lens power supply 23, the right auxiliary deflection power supply 24, the left auxiliary deflection power supply 25, the analysis magnet power supply 26, the downstream lens power supply 27, and the electrostatic prism power supply 2
8, 29, a filament power source 31, an arc power source 32, and an ion source magnet power source 33 are provided.

Next, the operation of the above embodiment will be described.

Here, the difference voltage between the acceleration voltage and the extraction voltage is maintained at 10 kV, and when the acceleration voltage by the acceleration power supply 21 is set to 0.5 kV, the output voltage of the extraction power supply 22 is set to xkV. In this case, 0.5kV
−xkV = 10 kV and xkV = 0.5 kV−10
Since kV = −9.5 kV, therefore, the output voltage of the extraction power source 22 is set to −9.5 kV.

At this time, if it is desired to change the accelerating voltage to 0.6 kV, the accelerating power source 21 is adjusted to set its output voltage to 0.6 kV, and the extraction power source 22 is set.
Is adjusted to set its output voltage to -9.4 kV (that is, 0.6 kV-10 kV = -9.4 kV). If such adjustment is performed, other power supplies, that is, the upstream lens power supply 23, the right auxiliary deflection power supply 24, the left auxiliary deflection power supply 25, the analysis magnet power supply 26, the downstream lens power supply 27, and the electrostatic prism power supplies 28 and 29 are used. The ion beam diameter and the ion beam direction are appropriately maintained without adjusting the output voltage, and the ion density with which the sample S is irradiated is maintained at a predetermined value. Of course, it is not necessary to adjust the output voltage of the filament power supply 31, the arc power supply 32, and the ion source magnet power supply 33.

When the accelerating voltage is changed from 0.5 kV to a voltage other than 0.6 kV, the accelerating voltage is also changed to 0.5 kV.
When changing from a voltage other than V to another voltage, similarly to the above, it is only necessary to adjust the output voltage of the extraction power source 22, and it is not necessary to adjust any other power source such as the upstream lens power source 23.

In the above embodiment, when changing the accelerating voltage, it is sufficient to adjust the output voltage of the accelerating power supply 21 and the output voltage of the extracting power supply 22, so that the accelerating voltage is changed. The work of adjusting the power supply voltage is easy, and therefore the change of the sample S can be observed in real time when the ion beam is irradiated while changing the acceleration voltage.

Further, in the above-described embodiment, since the electrostatic prism P is provided in the electron microscope and a predetermined potential is applied to the electrostatic prism P, the ions passing through the electrostatic prism P will be described. There is an advantage that the scattering of the beam is small. There is a strong magnetic field in the electron microscope,
Since this magnetic field is shielded by the shield tube ST, the magnetic field does not disturb the ion beam. Further, since the electric field generated by the electrostatic prism P is shielded by the shield tube ST, the electric field does not affect the operation of the microscope.

FIG. 2 is a circuit diagram showing a main part of another embodiment of the present invention.

The embodiment shown in FIG. 2 is basically the same as the embodiment shown in FIG. 1. Instead of the acceleration power supply 21 and the extraction power supply 22 in the embodiment shown in FIG. It is provided. That is, in the embodiment of FIG. 1, the configuration other than the acceleration power supply 21 and the extraction power supply 22 is common to the embodiment shown in FIG. 1 and the embodiment shown in FIG.

The voltage adjusting means 20 is a voltage adjusting circuit 20a.
, Acceleration power supply 51, extraction power supply 52, voltmeter Va, Vb
Have and. Further, the voltage adjusting means 20 maintains the difference between the value of the acceleration voltage and the value of the extraction voltage to be substantially constant,
It is an example of a voltage adjusting unit that simultaneously adjusts the values of the acceleration voltage and the extraction voltage.

The voltage adjusting circuit 20a has one reference power source 20b and a potentiometer 20r connected in parallel to the reference power source 20b and having its movable contact 20c connected to the ground potential. The positive side of the reference power source 20b is
It is connected to the reference voltage terminal 51a of the acceleration power supply 51 to generate the reference voltage for the acceleration power supply 51, and the negative side of the reference power supply 20b is connected to the reference voltage terminal 52a of the extraction power supply 52 to supply the reference voltage for the extraction power supply 52. It has occurred.

The acceleration power supply 51 is an ordinary power supply having a function of obtaining an error signal between the acceleration voltage detection signal proportional to the acceleration voltage and the reference voltage for the acceleration power supply 51, and controlling so that the error signal becomes zero. is there. The extraction power supply 22 is a normal power supply having a function of obtaining an error signal between the extraction voltage detection signal proportional to the extraction voltage and the reference voltage for the extraction power supply 52 and controlling the error signal to be zero.

The acceleration voltage, which is the output voltage of the acceleration power supply 51, is displayed by the voltmeter Va, and the extraction voltage, which is the output voltage of the extraction power supply 52, is displayed by the voltmeter Vb.

Moving contact 20c of potentiometer 20r
Is moved to the left in the figure, the reference voltage for the acceleration power supply 51 becomes low and the reference voltage for the extraction power supply 52 also becomes low. In other words, since the reference voltage has a negative polarity, the absolute value becomes large. Therefore, in order to decrease the acceleration voltage and increase the absolute value of the extraction voltage at the same time, the movable contact 20c of the potentiometer 20r is moved to the left in the figure, and the display value of the voltmeter Va or Vb becomes the desired voltage value. The movable contact 20c may be stopped at the open position.

On the contrary, when the acceleration voltage is increased and the absolute value of the negative extraction voltage is decreased at the same time, the movable contact 20c may be moved to the right in the figure contrary to the above.

Also in this case, if the potential difference between the acceleration voltage and the extraction voltage is maintained at 10 kV and the acceleration voltage is set at 0.5 kV, the voltmeter Va shows 0.5 kV and the voltmeter Vb shows -9. It shows 0.5 kV. At this time, when it is desired to change the acceleration voltage to 0.6 kV, the potentiometer 20r is adjusted so that the voltmeter Va indicates 0.6 kV. If this adjustment is performed, the upstream lens power supply 23, the right auxiliary deflection power supply 24, the left auxiliary deflection power supply 25,
The ion beam diameter and the ion beam direction are appropriately maintained without the need to adjust the output voltage of other power sources such as the analysis magnet power source 26, the downstream lens power source 27, and the electrostatic prism power sources 28 and 29.

The acceleration voltage is changed from 0.5 kV to 0.6
Even when the voltage is changed to a voltage other than kV, or when the acceleration voltage is changed from a voltage other than 0.5 kV to another voltage, just by adjusting the potentiometer 20r, the upstream lens power supply 23, etc. can be adjusted. No need to adjust any other power supply.

Therefore, the voltage adjusting means 20 shown in FIG.
By using, the power supply adjustment work accompanying the change of the accelerating voltage is completed quickly, the work of adjusting the power supply voltage is easier, and when changing the accelerating voltage and irradiating the ion beam, it is possible to change the sample. It is extremely easy to observe in time. In this case, the voltmeter Vb may be omitted.

FIG. 3 is a diagram showing the characteristics when 10 kV, 8 kV, 6 kV, and 4 kV are adopted as the voltage of the power supply 20b (that is, the potential difference between the acceleration voltage and the extraction voltage) in the embodiment shown in FIG. is there. In this way, the power supply 2
If the output voltage itself of 0b is also changed, the power source 20
It is preferable to provide voltmeters at both ends of b.

In the above embodiment, the case of positive ions was described, but in the case of negative ions, the polarities of the applied voltages may all be set opposite to those shown in the figure. Although not shown, the ion beam generator 10 and the transport T are covered with a cover kept at a low potential. Furthermore, in the above embodiment, the case where the accelerating voltage is sufficiently low has been described, but the accelerating voltage is reduced to, for example, about half the voltage (several kV to several tens of kV) of the conventional one, and the transport T has the accelerating voltage May be applied in consideration of the reduction of

[0039]

According to the present invention, a deceleration voltage cannot be applied to a target due to a large amount of ions extracted from the ion beam generator, a sample such as ceramics and living things to which no voltage can be applied, or the structure of the device and the like. When irradiating the sample or the sample to which the reduced accelerating voltage is applied with the ion beam, it is easy to adjust the power supply voltage due to the change of the accelerating voltage, and the sample changes when the ion beam is irradiated. There is an effect that it can be observed in real time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main part of another embodiment of the present invention.

FIG. 3 is a diagram showing characteristics when the output voltage of the power supply 20b is changed in the embodiment shown in FIG.

FIG. 4 is a diagram showing an example of a conventional example.

FIG. 5 is an operation explanatory diagram of the conventional example.

[Explanation of symbols]

10 ... Ion beam generator, 20 ... Voltage adjusting means, 20b ... power supply, 20r ... Potentiometer, 21, 51 ... Acceleration power supply, 22, 52 ... Drawer power supply, 23 ... upstream lens power supply, 24, 25 ... Auxiliary deflection power supply, 26 ... Analysis magnet power supply, 27 ... Downstream lens power supply, 28, 29 ... Electrostatic prism power supply, 40 ... Electron microscope lens barrel, T ... transport, L1 ... upstream lens, AM ... analysis magnet, L2 ... Downstream lens, D1, D2 ... Auxiliary deflection electrode, P ... electrostatic prism, S ... sample.

Claims (2)

[Claims] 1. A predetermined sample is held substantially at ground potential, and the extraction voltage applied between the transport and the ground potential is set to a value having a polarity opposite to the acceleration voltage,
An ion beam irradiation method of irradiating an ion beam to the sample from the ion beam generator via the transport, characterized in that the difference between the value of the acceleration voltage and the value of the extraction voltage is maintained substantially constant. Ion beam irradiation method. 2. A predetermined sample is held substantially at the ground potential, and the extraction voltage applied between the transport and the ground potential is set to a value having a polarity opposite to the acceleration voltage,
In an ion beam irradiation method of irradiating an ion beam from the ion beam generator to the sample via the transport, the acceleration is performed while maintaining a difference between the acceleration voltage value and the extraction voltage value substantially constant. An ion beam irradiation apparatus comprising a voltage adjusting means for adjusting the voltage and the value of the extraction voltage at the same time.