JPH0268844A - Instrument for measuring position and shape of charged particle beam - Google Patents

Abstract

PURPOSE:To make it excellent in space resolution by seeking the position and shape of charged particle beams based on the current flow in each position being amplified. CONSTITUTION:A semiconductor position detector 8, being arranged in the direction that it crosses the direction of irradiation of beam B at right angles, detects emission intensity on a fluorescent screen 7 corresponding to the position of a picture element with light receiving elements 8a as picture elements so as to take it out as an output signal related to the emission intensity at each position. The output signal of this semiconductor position detector 8 is sent to a signal treatment circuit 9, and in this signal treatment circuit 9 the position and shape of the beam B is calculated based on the output signal. Since the electron flux E is magnified by an electrostatic lens 5, the measurement of the position and the shape of the beam B with a fine diameter also becomes possible, and it becomes excellent in space resolution.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention relates to charged particle beams used in equipment such as analytical instruments (electron microscopes, S[MS], semiconductor manufacturing equipment, and ion implantation equipment). This invention relates to a charged particle beam position/shape measuring device that measures position/shape.

(Prior art and its problems) When applying charged particle beams such as electron beams and ion beams, it is very important to know the position and shape of the beam. For this reason, many measuring devices have been provided in the past in order to accurately measure the position and shape of the beam.

In general, these devices are broadly classified into methods that directly measure the beam current and methods that measure using signals caused by the beam. As an example of the former, Naifetsu-style applied physics Vol. 52, No. 4 (1983), P348
-353). In this method, the flow of the beam is interrupted by a sharp knife, and the position and shape of the beam is determined from the amount of change in current caused by changes in the relative positional relationship between the knife and the beam. Another example of the former is the multi-wire type radiation VO1, 9, fio, 3.
, (19g3), P56-61). This involves stretching thin metal wires with a diameter of several tens of microns in parallel at equal intervals, capturing the charged particles that collide with each wire as an electrical signal, and determining the beam position and location based on the magnitude of the electrical signal obtained for each wire.
I'm trying to find the shape.

However, since these methods involve measurement in contact with the beam itself, that is, destructive measurement, there is a problem in that it cannot be used at all for purposes such as monitoring while using the beam. Moreover, since the beam was directly irradiated onto the sensor itself, there was a problem that the sensor was severely damaged and its lifespan was shortened.

On the other hand, the latter method, that is, a method of measuring using a signal caused by a beam, includes a method using electrostatic induction and a method using secondary electrons generated by irradiating the residual gas with the beam. Method using electrostatic induction (Tnst,
Phys, Conf, Ser, N (138, 1978
, Chapter 3. In P125-130), a pair of electrodes are installed across the beam passage path, and the center of gravity of the beam current is determined from the amount of charge induced in each electrode.

However, this method merely determines the position of the center of gravity, and has a problem in that it is not suitable for measuring the position and shape of the beam.

Mata, method of using secondary electrons (IEEE Tran
sa-ctions on Nuclear 5cie
nce, Vol, N5-26. k3 (1979
)) collects secondary electrons using parallel electrode plates arranged at regular intervals parallel to the beam axis, and determines the position and shape of the beam based on the value of the current flowing through each electrode.

However, since very few secondary electrons are generated by irradiating the residual gas with the beam, this method has a problem of low sensitivity. In order to obtain sufficient sensitivity,
Although it is possible to widen the electrode width for collecting secondary electrons, another problem arises in that the spatial resolution decreases.

(Objective of the Invention) An object of the present invention is to solve the problems of the prior art described above and to provide a charged particle beam position/shape measuring device that is non-destructive and has excellent sensitivity and spatial resolution.

(Means for Achieving the Object) The present invention is a charged particle beam position/shape measuring device for measuring the beam position/shape of a charged particle beam. an accelerating electrode that accelerates secondary electrons generated by irradiation of the electron beam, an electron lens that magnifies the accelerated electron flux, and an electron current amplification means that amplifies the electron flow at each incident point of the expanded electron flux; and detection means for determining the position and shape of the charged particle beam based on the amplified electron flow at each position.

(Embodiment) FIG. 1 is a cross-sectional view showing a charged particle beam position/shape measuring device which is an embodiment of the present invention, and FIG. 2 is an enlarged perspective view of the main part thereof. As shown in the figure, a grounded vacuum duct 2 is provided in the upper part of the main body 1, and a charged particle beam B (hereinafter simply referred to as "beam B") is placed approximately in the center of the vacuum duct 2.

) is configured to pass in a direction perpendicular to the plane of the paper in FIG. The inside of the vacuum duct 2 is evacuated by an evacuation pump, and residual gas remains that is not evacuated even by the evacuation pump. The components of the residual gas include the same components as the beam B (for example, H2 in the case of a hydrogen ion beam) and H2O, Co, H2, etc. released from the surface of the vacuum duct 2. When the beam B is irradiated into this vacuum duct 2,
A part of beam B collides with the residual gas, causing 2
Next electron is generated. Since the distribution of the secondary electrons generated at this time has a correlation with the charged particle density of the beam B, it is theoretically possible to determine the position and shape of the beam B by measuring the distribution of the secondary electrons.

Therefore, by applying this principle, this device expands the electron flux of secondary electrons generated by irradiating the residual gas with beam B, and multiplies the number of electrons at each position. It is configured to determine the position and shape of beam B based on the flow.

Specifically, an aperture 3 is provided between the main body 1 and the vacuum duct 2, which functions as a diaphragm for electron flux. Further, at the lower position of the aperture 3, an accelerating electric current source 11 is provided.
A positive high voltage (1 to several KV) is applied to the accelerating electrode 4 which accelerates the secondary electrons generated in the vacuum duct 2 towards the main body 1 side, and an electrostatic lens power supply 12 supplies power to accelerate the secondary electrons. An electron lens 5 is provided to magnify the electron flux E accelerated by the electrode 4.

A microchannel plate 6 serving as an electron flow amplification means is arranged at a position where the electron flux E is imaged by the electron lens 5. This microchannel plate 6 is composed of a large number of secondary electron multiplier tubes 6a each having a tube diameter of about 10 μm, and the number of electrons incident on each secondary electron multiplier tube 6a increases. 1 at the time of exiting the multiplier tube 6a
It is multiplied to about 0.07 times.

A fluorescent screen 7 is arranged on the output side of the microchannel plate 6. Microchannel plate 6 is attached to this fluorescent screen 7.
By applying a positive potential of approximately 4 KV to Light is emitted with an intensity corresponding to the number of electrons e.

A semiconductor device detector 8 is arranged in correspondence with this fluorescent screen 7 . The semiconductor device detectors 8 are arranged in a line in a direction perpendicular to the irradiation direction of the beam B, and detect the light emission intensity on the fluorescent screen 7 corresponding to each pixel position using each light receiving element 8a as a pixel unit. and is configured to be extracted as an output signal related to the emission intensity for each position. The output signal of the semiconductor device detector 8 is sent to a signal processing circuit 9, and the signal processing circuit 9 calculates the position and shape of the beam 8 based on the output signal.

Fluorescent screen 7 above. The semiconductor device detector 8 and the signal processing circuit 9 constitute a detection means.

Note that power is supplied to the microchannel plate 6, the fluorescent screen 7, and the semiconductor device detector 8 by a detector power supply 10 external to the main body 1.

Next, the operation of the charged particle beam position/shape device will be explained. When the vacuum duct 2 is irradiated with the beam B, the beam B collides with the residual gas in the vacuum duct 2, and secondary electrons are generated by ionization. The generated secondary electrons pass through the aperture 3, are accelerated by the accelerating electrode 4, and the electron flux E is expanded by the electrostatic lens 5 and guided to the microchannel plate 6. At this time, the number of electrons incident on each secondary electron multiplier 6a of the microchannel plate 6 is proportional to the charged particle density of the beam B corresponding to each position. The electron flux E incident on the microchannel plate 6 is amplified by about 107 times by each secondary electron multiplier 6a, and is emitted toward the fluorescent screen 7 as an electron current e. The electron flow e is accelerated to enough energy to cause the fluorescent screen 7 to emit light, and at the incident position of each electron ie on the fluorescent screen 7, light emission occurs with an intensity corresponding to the number of electrons in the corresponding electron flow e. It will be done. The light emission intensity at each position on the fluorescent screen 7 is detected by the semiconductor device detector 8 and taken out as an output signal related to the light emission intensity at each position.The signal processing circuit 9 emits a beam based on the output signal. The position and shape of B are calculated.

According to this charged particle beam position/shape measuring device, since the electron flux E is expanded by the electrostatic lens 5, it is possible to measure the position and shape of the beam B with a fine diameter, and the device has excellent spatial resolution. For example, the diameter of the secondary electron multiplier tube 6a is 10μ.
If a microchannel plate 6 of about m is used and the magnification ratio of the electrostatic lens 5 is M, the resolution of beam diameter measurement is very small (10/M (μm). Therefore,
Even if the beam B has a diameter of several tens of micrometers or less, its position and shape can be measured with a resolution accuracy of several (-10/M) micrometers. In addition, using the microchannel plate 6,
Since the secondary electrons are amplified and detected, the measurement sensitivity is improved even though the electron flux E is expanded. For example, if the beam B has a minute current of several hundred nA,
The position and shape of the beam B can be accurately measured by amplifying the generated secondary electrons by about 107 times using the microchannel plate 6. In addition, since it is a non-destructive method, while using beam B for its original purpose,
The position and shape of beam B can be measured and can be used as an online control sensor.

In the above embodiment, the electron flow e amplified by the microchannel plate 6 is guided to the fluorescent plate 7 while being accelerated and converted into light, and the semiconductor device detector 8 converts the electron flow e to the fluorescent plate 7. The position and shape of the beam B are determined by detecting the emission intensity at each position in F, but instead of the fluorescent screen 7 and the semiconductor device detector 8, the fluorescent plate 7 and the semiconductor device detector 8 are arranged parallel to the beam axis at equal intervals. The parallel electrode plates collect the electron flow e at each position amplified by the microchannel plate 6, and the position and shape of the beam B are determined based on the current value flowing through each electrode. You can also make it look like this. Furthermore, a magnetic field lens may be used as the electron lens instead of the electrostatic lens 5. Furthermore, when the beam B current is small, instead of the semiconductor device detector 8 that outputs a signal corresponding to the emission intensity distribution as in the above embodiment, a type of detection called PSD that detects the center of gravity position of the emission intensity is used. A container may also be used.

(Effects of the Invention) As described above, according to the charged particle beam position/shape measuring device of the present invention, the electron flux of secondary electrons generated by irradiating the residual gas with the beam is enlarged by an electron lens. Since the position and shape of the beam is measured based on the electron flow amplified by the current amplification means, the position and shape of the charged particle beam can be measured with extremely high spatial resolution and sensitivity without affecting the beam or sensor.・The effect of being able to measure the shape can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a charged particle beam position/shape measuring device which is an embodiment of the present invention, and FIG. 2 is a perspective view of the main parts thereof. 4... Accelerating electrode, 5... Electrostatic lens, 6...
・Microchannel plate,

Claims (2)

[Claims] (1) A charged particle beam position/shape measuring device for measuring the beam position/shape of a charged particle beam, which comprises: an accelerating electrode that accelerates secondary electrons generated by irradiating residual gas with the charged particle beam; an electron lens that magnifies the electron flux; an electron flow amplification means that amplifies the electron flow at each incident point of the expanded electron flux; A charged particle beam position/shape measuring device equipped with a detection means for determining the position/shape. (2) The detection means includes a fluorescent screen disposed on the emission side of the electron current amplification means, a semiconductor position detector that outputs a signal related to the emission intensity distribution on the fluorescent screen, and a semiconductor position detector that outputs a signal related to the emission intensity distribution on the fluorescent screen. 2. The charged particle beam position/shape measuring device according to claim 1, further comprising a signal processing circuit for determining the position/shape of said charged particle beam based on an output signal.