JPH03112042A - pulse ion gun - Google Patents

Abstract

PURPOSE:To measure the pulse wave-form and current value concurrently with the radiation of an ion beam by providing a conducting member around an aperture plate (AP), connecting an ion beam monitor to the AP plate, and providing a magnetic field generating member around the AP plate. CONSTITUTION:An ion beam extracted from an ion generating section 7 by an extracting electrode 8 is bent by applying the potential difference to two deflecting plates 1. When this potential difference is changed, the beam is swept, and the ion pulse beam going out through a chopping aperture 3 is radiated to a sample. The beam extracted as the ion pulse beam hits an AP 2, and the ion beam current is measured by a ion beam monitor 6 to measure the beam current and pulse width. When positive charges hit the AP 2, the current value is apparently increased by the emission of secondary electrons, and it is decreased for the ion beam with negative charges. The secondary electrons going out through the AP 2 are driven to a cylinder 4 by the magnetic field of a permanent magnet 5 to suppress it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ion gun, and particularly to a pulse ion gun used in semiconductor manufacturing, analysis, and the like.

[Prior Art] Methods for generating pulsed ion beams can be roughly divided into three types: methods in which the ion gun is directly pulse modulated, and methods in which the beam is deflected or concentrated. Among these, the ion gun using the beam deflection method will be explained using Fig. 5.
The ion beam extracted from the ion generator 7 by the extraction electrode 8 passes through the deflection plate 1 and reaches the aperture plate 2, and by applying a potential difference between the two deflection plates 1, the ion beam is bent. By changing this potential difference, the beam can be swung, and the sample is irradiated with a pulsed ion beam from the chopping aperture 3. This situation can be seen in Figure 6, a detailed diagram of the deflection plate and aperture part, and Figure 7.
This will be explained using the waveform diagram in the figure. When a sinusoidal voltage as shown in FIG. 7(a) is applied to the deflection plate 1, the sample is irradiated with a pulsed ion beam as shown in FIG. 7(b) from the chopping aperture 3. When the beam diameter of the ion beam is d and the aperture diameter is D, the pulse width of the ion pulse beam is A, sin (2πf/2) = d+
This is the value obtained from D. Note that Ao is the deflection amplitude on the aperture plane, and f is the deflection frequency. Therefore 1,
Deflection voltage swing of deflection plate 1 @A.

By increasing , the pulse width of the pulse beam can be reduced. At this time, only the ion beam passing through the aperture is taken out as a pulsed beam, and the rest hits the aperture plate 2 and the charge falls to the ground. In this pulsed beam generation method using the beam deflection method, the amount of current of the ion beam is conventionally measured using a Faraday cup or the like when the sample is not irradiated with the ion beam. Also,
The pulse width of the pulse beam is measured by various methods such as indirectly evaluating the deflection voltage of the deflection plate 1 or directly observing the waveform of the pulse beam.

[Problems to be Solved by the Invention] In conventional ion beam measurements, the Faraday cup is placed outside the ion gun, but for this reason, for example, when performing sputtering with the ion gun, the sample may have to be removed. Ta.

In addition, it is difficult to simultaneously observe the beam current amount or pulse width when the ion beam is actually irradiating the sample, so in order to change the beam current amount or pulse width, it is necessary to measure Based on this data, we use an unstable method of changing parameters such as the ion beam acceleration voltage, gas pressure, and deflector deflection voltage.

The present invention was devised to eliminate the drawbacks of the conventional techniques as described above, and it is possible to simultaneously measure the pulse waveform and current value of the ion beam while irradiating the sample with the ion beam. The purpose is to provide a pulsed ion gun.

[Means for Solving the Problems] In order to achieve the above object, the pulse ion gun of the present invention includes a conductive member provided around an aperture plate,
It has an ion beam monitor connected to the aperture plate and a magnetic field generating member around the aperture plate.

[Operation] The ion gun configured as described above deflects the ion beam with a deflection plate, irradiates the sample with the ion pulse beam emitted from the chopping aperture of the aperture plate, and monitors the amount of beam current hitting the aperture plate. Detected by. At this time, secondary electrons emitted when the ion beam hits the aperture plate are confined by a magnetic field such as that generated by the magnetic field generating member and captured by the conductive member around the aperture plate.

[Example] An example will be described with reference to FIGS. 1, 2(a), and (b).
Since the aperture plate 2 is surrounded by a cylinder 4 electrically connected to the ion beam monitor 6 and the ion beam monitor 6 is connected to the cylinder 4, the aperture plate 2 is electrically connected to the ion beam monitor 6. Further, a permanent magnet 5 is provided around the aperture plate 2. Note that FIG. 2(a) is an enlarged view of the aperture portion, and FIG. 2(b) is a sectional view of the aperture portion.

The ion beam extracted from the ion generating section 7 by the extraction electrode 8 is bent by applying a potential difference between the two deflection plates 1. By changing this potential difference, the beam is swung, and the ion pulse beam emerging from the chopping aperture 3 is irradiated onto the sample. On the other hand, the beam that is not extracted as a pulsed ion beam is
Therefore, by measuring the ion beam current hitting this aperture plate 2 with the ion beam monitor 6, the beam current and pulse width can be measured.

At this time, the problem is that when the positively charged ion beam hits the aperture plate 2, secondary electrons are emitted, and the apparent increase in the current value due to the secondary electron emission is above. Note that in the case of a negatively charged ion beam, the current value apparently decreases. In order to suppress this, a uniform magnetic field is created by the permanent magnet 5, and the secondary electrons ejected from the aperture plate 2 are bent and applied to the cylinder 4 electrically connected to the aperture plate 2, thereby preventing the influence of the secondary electrons. I'm here. The strength of the magnetic field is only a few tens of Gauss to bend the secondary electrons, and the trajectory of the ion beam is hardly affected by this.

At this time, the current waveform of the ion beam monitored by the ion beam monitor 6 is as shown in FIG. The peak value of the current in FIG. 3 is the amount of current drawn from the ion generating section, and the valley portion is the current waveform of the pulsed ion beam.

Therefore, if the ion beam current amount detected by the ion beam monitor 6 or the pulse width of its pulse waveform is used to control the ion beam acceleration voltage, gas pressure, amplitude value of the deflection signal of the deflector, etc., the ion beam At the same time as the beam is irradiated onto the sample, the current value and pulse width of the beam can be controlled to desired values.

FIG. 4 is a block diagram for automating the control of the ion pulse beam, in which the aperture plate 2 is connected to a peak current value monitor 9 and a pulse waveform monitor 10. The peak current value monitor 9 and pulse waveform monitor 10 operate in synchronization with the deflection plate pulse voltage generator 12, and the detected peak current value and pulse width are input to the CPU11. Based on the input peak current value and pulse width, the CPU II controls the deflection plate voltage generator 12, the ion generation amount controller 13, and the ion acceleration voltage controller 1.
4, etc., the current value and pulse width of the ion pulse beam are controlled to desired values.

In the embodiment shown in Figure 1, a permanent magnet was used as the magnetic field generating member, but a coil can also be used to generate a DC magnetic field, and the conductive member is not limited to a cylinder, but can also be used for secondary electron An arc-shaped conductive member may be provided only in the portion where the light is incident.

[Effects of the Invention] As explained above, in the present invention, the secondary electrons emitted when the ion beam hits the aperture plate can be captured by the conductive member around the aperture plate. can be detected accurately,
Furthermore, since the beam current value and pulse width can be detected at the same time as the sample is irradiated with the ion beam, the beam current value and pulse width can be easily controlled to desired values.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a pulse ion gun embodying the present invention, FIGS. 4 is a block diagram showing an example of an automatic control circuit used in the pulse ion gun of the present invention, and FIG. 5 is a waveform diagram showing the beam current detected by the pulse ion gun of the present invention. FIG. 6 is a detailed view of the deflection plate and aperture part of the pulse ion gun shown in FIG. 5, and FIGS.
FIG. 3 is a waveform chart showing the operation of the pulse ion gun shown in FIG. 1. Deflection plate, 2. Aperture plate, 3. Chopping aperture, 4. Cylinder, 5. Permanent magnet, 6. Ion beam detector, 7. Ion generator, 8. Extraction electrode, 9・Peak current value monitor, 10... Pulse waveform monitor, 11... CPU, 12... Deflection plate voltage generator, 1
3. Ion generation amount controller, 14. Ion accelerating voltage controller Figure 3

Claims (1)

[Claims] (1) In a pulse ion gun that has an ion beam generating section, a deflection plate that deflects the ion beam, and an aperture plate provided with a chopping aperture, a conductive member is provided around the aperture plate, and the ion beam is placed on the aperture plate. A pulse ion gun connected to a monitor and further comprising a magnetic field generating member provided around the aperture plate.