JPS5819041B2 - How to measure electron beam diameter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring an electron beam diameter with high accuracy.

Conventionally, the most commonly used method for measuring the electron beam diameter is to coat a dielectric or semiconductor substrate, such as a Si substrate, with a metal film, such as an Au film, by vapor deposition, sputtering, etc., as shown in Figure 1. When the electron beam 4 is scanned across the edge 2a of the substrate 1 and the metal film 2, the amount of electrons reflected by the electron beam 4 differs between the substrate 1 and the metal film 2. When reflected electrons (including secondary electrons) are received and their current values are measured, the current characteristics near the boundary between the substrate 1 and the metal 2 are shown in FIG. 2 with respect to the scanning distance of the electron beam.

In this case, the beam diameter is determined by the effective interval between the slopes when the beam passes through the boundary.

Although this method is simple, if the edge 2a of the metal film 2 is sloping, the electron reflection direction will be different, and the electron detection efficiency will change, so the effective interval A between the slopes will change. As a result, the measurement error of the beam diameter increases.

Another measurement method is to set up a knife in the middle of the electron beam input to the electron detector, scan this knife with the electron beam, and enlarge (or reduce) the part of the electron beam that is blocked by the knife. There is a method of obtaining current characteristics similar to those shown in FIG. 2 and determining the beam diameter.

However, in this case, since there are fine irregularities on the end face of the knife, there is a drawback that unstable parts are generated at the rising part and the upper limit part of the inclined curve, and the precision of the beam diameter is deteriorated.

An object of the present invention is to provide a highly accurate method for measuring the diameter of an electron beam.

In order to achieve the above object, the method for measuring the diameter of an electron beam according to the present invention includes a method for measuring an electron beam diameter, in which a second material is placed on a first material substrate and has a different amount of electrons reflected from the electron beam than the first material substrate. The electron beam diameter is measured by scanning the boundary of the cleaved cross section of an element having a cleaved cross section formed by forming a layer and dividing the same with the electron beam and detecting the electrons reflected from the cleaved cross section. That is.

The present invention will be described in detail below with reference to examples.

FIG. 3 is an explanatory diagram showing the configuration of an embodiment of the present invention.

In the same figure, as in FIG. 1, an Au film 2 is placed on a Si substrate 1.
This Si substrate is split along the crystal cleavage plane, and the vicinity of the boundary 13 between the Si substrate portion 11 and the Au film portion 12 in the cleaved cross section is used as a scanning area for measuring the electron beam diameter. This is what I did.

That is, if the electron beam 4 is scanned across this boundary 13 and the reflected electrons 4' are detected by the electron detector 3, a current characteristic similar to that shown in FIG. 2 is obtained, but in this case, the boundary 13 is Si. Since it appears on the cleaved cross section of the substrate 11, it becomes a surface with uniform properties in terms of crystal structure, and Au
Since the film surface 12 follows, the boundary 13 is sharply formed, and unlike the conventional method, there is no room for uncertain or unstable parts to occur, and therefore the effective current characteristics are A highly accurate beam diameter can be obtained from the tilt interval.

If the electron beam diameter is a perfect circle, it is sufficient to measure only one scanning direction as described above, but if the electron beam diameter is elliptical or distorted circular, highly accurate detection in only one scanning direction is sufficient. The overall beam shape is not determined.

Figure 4 shows that in order to measure the beam diameter in each direction with high precision, a plurality of elements (three in this case) are made with the cleaved cross section obtained in Figure 3 as the surface, and these elements are As shown at 211, 212, and 213 in Figure A, the diameters of the beam shape in three directions can be determined with high precision by arranging them radially on separate substrates and scanning each with an electron beam in a direction perpendicular to the boundary surface. The overall shape can be almost determined.

In the figure, the electron beam is scanned in the X direction 20X and the Y direction 20y, and the boundaries of the cleavage cross sections of the elements 22□ and 22° are perpendicular to each other. The diameter corresponding to the long axis and short axis can be measured with high precision.

Here, the beam diameter is measured in a direction perpendicular to the cleaved cross section.

FIG. 5 shows the output of an electron detector using the element shown in FIG. 4, and corresponds to FIG. 2.

The electron beam moves from another substrate to the level of the Si substrate, then follows a slope as it passes through the boundary and reaches the level of the Au film.

The effective interval B between the inclined parts is the beam width, and the center thereof indicates the boundary between the Si substrate and the Au film.

If the above-mentioned substrate material and the material layer deposited thereon exhibit a difference in the amount of reflected electrons when irradiated with an electron beam and exhibit a slope as shown in FIG. 2 or FIG. can be used.

Therefore, for example, insulators, dielectrics, semiconductors, etc. are used as substrate materials, and Au, Ag, etc. are used as material layers to be deposited.
A conductive material such as , Cu, or AI is used.

As explained above, according to the present invention, a layer of material such as metal is deposited on a substrate, the layer is split to create a cleaved cross section, and the boundary of the cross section is scanned with an electron beam to collect the reflected electrons. By detecting this, the diameter of the electron beam can be measured with high precision, and by using multiple elements with cleaved cross sections, the diameter in each direction can be detected with high precision even for beams that are not perfectly circular. It is possible to
It is believed that this method is extremely useful for improving pattern accuracy using electron beams.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of a conventional example; FIG. 3 is an explanatory diagram showing the configuration of an embodiment of the present invention; FIG. 4 is an explanatory diagram showing the configuration of another embodiment of the present invention; The figure is an explanatory diagram of the operation of the embodiment shown in FIG. 4, and in the figure, 1 is a substrate, 2 is a metal film, 3 is an electron detector, 4 is an electron beam, 11 is a cleaved cross section of the substrate, 12 is a cross section of a metal film, 13 is a boundary, 20x and 22y are electron beam scanning directions, and 21, to 213, 220, and 22□ are cleavage cross-section elements.

Claims (1)

[Claims] 1. Formed by forming a second material layer on a first material substrate, which differs in the amount of electrons reflected from the electron beam from the first material substrate, and dividing the second material layer. A method for measuring an electron beam diameter, characterized in that the electron beam diameter is measured by scanning a boundary of the cleaved cross section of an element having a cleaved cross section with the electron beam and detecting electrons reflected from the cleaved cross section. 2. The device is characterized in that the elements are arranged so that the directions of the boundaries of the cleavage cross sections are different, and the change in the electron beam diameter (direction) is measured from the measurement results of reflected electrons generated when each boundary is scanned. Claim 1
Method for measuring electron beam diameter as described in section.