JPS61194381A - Apparatus for measuring electron beam - Google Patents

Abstract

PURPOSE:To make it possible to accurately measure the magnitude of electron beam, by forming a structure cyclically changed in its depth and applying the irradiation and scanning of electron beam to said cyclic structure to detect the cyclic change of a transmitted electron. CONSTITUTION:Electron beam to be measured emitted from an electron gun and shaped and condensed by an aperture and a condenser lens is controlled by a deflection control apparatus 4 and a deflection plate 5 to irradiate detectors 6, 7, 8. Each of the detectors to be used is prepared by a method wherein an oxide insulating film 7 of SiO2 is grown on a silicon substrate 8 to which conductivity was provided and PMMA is applied to said insulating film and image drawing is further applied to form a cyclic structure. Secondary electrons emitted from the detectors 6, 7, 8 by irradiating electron beam to be collected by a semiconductive electron detector 11 and amplified to a predetermined level by an amplifier 12 to be inputted to a recorder 13. Because this reflected secondary electrons and an absorbed current change corresponding to the diameter of the irradiated electron beam, the measurement of a beam diameter is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electron beam measuring device, and particularly in an electron beam device such as a scanning electron microscope or an electron beam lithography device that uses a finely focused electron beam. The present invention relates to an electron beam measuring device suitable for obtaining information on the size of an electron beam.

[Background of the invention]

Conventionally, this type of measurement has been carried out by measuring the electron beam current using a Faraday cup, by deflecting the electron beam irradiated onto a detector having a cross-sectional shape such as a knife shape, and by measuring the reflected/secondary electrons or absorbed current from the detector. Mourning is determined by measuring the rate of change. However, in conventional devices, the cross-sectional shape of the detector is not sharp, and the cut surface may have ridges, making accurate measurements impossible.

Furthermore, in a fine beam, transmitted electrons are scattered and spread within the detector. Since its expansion is equal to or larger than the fine beam diameter, it has a large influence on beam diameter measurement and has many disadvantages, such as making accurate measurements impossible.

[Purpose of the invention]

An object of the present invention is to provide an electron beam measuring device for measuring the size of an electron beam.

[Summary of the invention]

The detector has a periodic structure, and the period is made large enough to measure the desired beam diameter. The periodic structure corresponds to a ruler. The beam diameter is determined by determining whether or not periodicity is obtained as a clear signal when the periodic structure is irradiated and scanned with the beam, in relation to the beam diameter. This method is similar to the method used to test the resolution of high-resolution electron microscopy by testing whether the random fine structure of gold deposition images can be resolved.

[Embodiments of the invention]

The principle of the present invention will be explained below with reference to FIG. 1.2. 1st
The figure shows that a substance 1 is being irradiated with an electron beam 2, and that transmitted electrons 3 are spreading within the substance 1. Let the depth direction of the substance 1 be 2, and set the person B at the depth shown in Figure 1 as follows. FIG. 2 shows a Monte Carlo simulation of the scattering state of the irradiated electrons 2 in the substance 1, and the number of electrons arriving in the depth direction. In FIG. 2, NO is the number of incident electrons.几 is the range, experiment L2
6B-aO@84tn11c 弐几=0.412g and this simulation agreed well. Na is the number of transmitted electrons at a depth of 8, and Nu is the same.N is the number of electrons stationary within the material l excluding scattered and reflected electrons, and corresponds to the number of incident electrons that give the range. In the present invention, a structure whose depth changes periodically between A and B is created, and the periodic structure is irradiated and scanned with a beam to detect periodic changes in transmitted electrons. When the diameter of the beam is equal to or larger than this period, the amplitude of the detection signal is small. When the beam diameter becomes less than the period of the periodic structure, the amplitude of the detection signal changes in relation to the beam diameter, and the smaller the beam diameter, the larger the amplitude of the signal obtained.

Hereinafter, one embodiment of the present invention will be explained with reference to FIG. Third
The figure is a schematic configuration diagram of the apparatus, and the dotted line in the figure indicates the electron beam targeted for the side chamber. For example, it is emitted from an electron gun and shaped and focused using an aperture or condenser lens. A deflection control device 4 changes the electric field of a deflection plate 5 to control this electron beam.

The controlled electron beam is irradiated onto a detector consisting of 6,7.8. In the conventional device, a detector is made by combining seven Aradeck cups each with a metal wire, a mesh, or a knife. The device of the present invention uses the detector described below. The silicon substrate 8 is made conductive, an oxide insulating film 84 (h) is grown to a thickness of 80.1 μm, and then PMMAt-
Lines and spaces with a period of 0.1 .mu.m are drawn by coating and fine electron beam exposure, and then etching is performed to deposit A1.Finally, PMMA is removed to form a periodic structure 6, which serves as detectors 6, 7.8.

Ammeters 9 and 10 were connected to the detectors 6 and 7.8, and the absorbed current of the irradiated electron beam was measured. Also, this detector 6
, 7.8, a semiconductor electron detector 11 is arranged to capture and detect reflected secondary electrons from the detectors 6, 7.8. This detection signal is amplified to a predetermined level by the amplifier 12 and input to the recording tl-13. In this device, when the electron beam is deflected and irradiated in a direction that gradually changes the period of the detector 6, the reflected secondary electrons and absorption current will have the same period as the 60 periods of the detector, as shown in Figure 4. shows the change in ΔS in Fig. 4 is an amount that changes depending on the diameter of the irradiated electron beam. For example, ΔS for a given beam diameter is experimentally determined, and feedback is given to the condenser lens so that ΔS becomes . control to a constant value.

In FIG. 5, the W1 amplitude of the detector 6 is set at a cycle of 0.05 μm.

The signal obtained by the ammeter 9 when a periodic structure of 0.1 μm is made and the thickness is 0.4 μm is obtained by Monte Carlo simulation, and the horizontal axis is the beam diameter. This result shows that there is an approximately linear relationship between the beam diameter and the detection signal. Tsum ff.

According to this implementation sequence, the electron beam diameter can be measured. Utilizing this fact, it is also possible to accurately control the electron beam diameter to a desired value. Furthermore, as an application example, the detector 6,
7.8 as shown in Figure 6, the direction in which the period changes is 90
．． . It is also possible to correct astigmatism by changing the combination and scanning the electron beam in the direction of the solid arrow in FIG.

〔Effect of the invention〕

According to the present invention, since the shape of the electron beam is detected by the periodic body, a large number of beam diameter detectors are assembled. Therefore, a statistical signal is obtained, so
This is effective in avoiding detection errors caused by the shape of conventional devices.

In conventional methods, the spread of the irradiated electron beam inside the detector is a major cause of detection errors. In the present invention, this problem is not important because transmitted electrons are actively utilized and absorption current is measured below a certain depth without measuring lateral spread. By using a heavy metal such as gold or tungsten for the detector 6, reflection and secondary electron emission efficiency for the electron beam can be improved, and detection with a good S/N ratio can be performed.

The present invention has the advantage that the detector of the present invention can be manufactured using semiconductor process technology and the like.

[Brief explanation of drawings]

Fig. 1 is a diagram showing scattered electrons inside a substance, Fig. 2 is a diagram showing a transmission range, Fig. 3 is a schematic configuration diagram showing one implementation row of the device of the present invention, and Fig. 4 is a diagram showing measurement detection characteristics. The figure shown in Figure 5 is S.
FIG. 6 is a diagram showing the relationship between /N and the electron beam diameter, and is a diagram showing an example of application of the device of the present invention. 5... Deflection plate, 6, 7.8... Detector, 9.10.
...Current needle, 11...Semiconductor detector, 14.15...
・Detector, 16.17...Electron beam, 1...Inside of substance, 2...Irradiated electron beam, 3...Transmitted scattered electron.

Claims (1)

[Claims] 1. An electron beam detector and means for scanning the detector with an electron beam so that a signal is obtained from the detector; 1. An electron beam measuring device characterized in that a portion where the electron beam is generated and a portion where the beam is weakly generated are periodically formed, and information regarding the size of the electron beam is obtained based on the strength of the signal regarding these portions. 2. The electron beam measuring device according to claim 1, wherein the signal is a plurality of types of signals.