JPH03280340A - Beam dia measuring device for charged particle rays - Google Patents

Abstract

PURPOSE:To remove influence of noise and enhance the accuracy by superposing minor amplitude circular oscillation over a beam, measuring beam dias. for a plurality of circular oscillation amplitudes, and determining beam dias. from the results of measurements. CONSTITUTION:To measure beam dias., No.2 deflector 18 is driven by No.2 deflection amplifier 19, and the process shall proceed by the same means as conventional in the condition that the high-speed, minor amplitude circular oscillation is superposed over an electron beam 2. That is, the circular oscillation amplitude is enlarged for the noise, and a substantially straight line is obtained when the results from the measurements are plotted in a diagram. An accurate beam dia. can be determined from the intersection of this substantially straight line with a straight line when the circular oscillation amplitude is zero.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in a measuring device for measuring the beam diameter of a charged particle beam such as an electron beam in an electron beam exposure device that exposes an IC mask pattern, for example. be.

[Conventional technology]

FIG. 3 is a schematic diagram showing the configuration of a conventional measuring device for measuring the probe diameter of an electron beam, which is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-133655. In this figure, (1) is the electron lens barrel, and the device N (2) that generates the electron beam (2) is
(not shown) and a deflector B) that deflects and scans the converging part of the electron beam one-dimensionally or two-dimensionally. (4) is a sample chamber provided at the bottom of the electron lens barrel, (4 is a movable sample stage installed in the sample chamber, and sample (6)
A mounting part (7) on which the machine is placed, a knife blade (9) that is attached to a vertical fine movement device (5) provided on the side thereof and is movable in the vertical direction in the figure, and a A Faraday cup is provided.
(11) is a controller that controls each device mentioned above; (12)
(13) is a vertical fine movement control device that controls the vertical position of the vertical fine movement device; (14) is a sample table controller that controls the position of the sample table (5) based on a command signal from the controller;
is a signal amplifier that amplifies the signal detected by the Faraday cup, and (15) is a differentiator that differentiates the output of the signal amplifier.
The differential output is sent to the XY recorder (16) via the controller (11).
Enter it in Y. A deflection signal, which will be described later, is input to X. (17) is a deflector (3) based on the command from the controller.
) is a deflection amplifier that provides a deflection signal to the

In such a configuration, a method of measuring the beam diameter of the electron beam focused on the surface of the sample (6) will be explained.

First, the tip of the knife (9) is exposed to the electron beam (2).
Move the sample stage (51) to the controller (11) so that it is at the focusing position.
and moved by the sample stage controller (12).

Next, the deflection signal from the deflection amplifier (17) is adjusted to scan the electron beam (2) across the knife (9), and the transmitted beam current is synchronized with the deflection signal and detected by a Faraday cup (lO). . This signal becomes as shown by the solid line in FIG. 4(A).

The signal detected by the Faraday cup is processed by a signal amplifier (1
4) and the XY recorder (I6) via the differentiator (15)
Since the deflection signal is input to the Y of the XY recorder and the deflection signal is input to the X of the XY recorder, the output of the xY recorder becomes as shown by the solid line in FIG. 4(B). In Figure 4 (A) and (B), the horizontal axis represents the scanning position of the electron beam focusing section, the vertical axis in (A) represents the intensity of the Faraday cup detection signal, and the vertical axis in (B) represents the differential detection signal. The strength is shown respectively. The beam diameter can be determined as the dimension between the two intersections of the differential detection signal and the straight line of 1/e of its peak value, ie, d in FIG. 4(B).

However, the beam diameter determined in this way includes errors due to noise, so as a means to reduce the influence of noise, several vertical positions of the knife beam were selected and the same operations as above were performed for each. Find the beam diameter d for each beam, and derive the correct beam diameter from multiple data (
In other words, as shown in Figure 5, the vertical axis is the beam diameter, and the horizontal axis is the vertical position Z of the knife (the downward dimension of the electron beam axis with respect to the surface of the sample). Display each of the above-mentioned data (dL, dz...) on the diagram, find the optimal straight line as shown in the figure using the method of least squares, etc., and at the intersection of this straight line and the straight line of Z=O, Recognize a certain dO as the correct beam diameter.

[Problem to be solved by the invention]

Since the conventional electron beam diameter measuring device is configured as described above, the output of the signal amplifier (14) is affected by noise in the control system of the deflector, as shown by the dotted line in FIG. 4(A). It changes more gently than when there is no noise (solid line), and the output of the differentiator (15) also spreads out compared to when there is no noise (solid line), as shown by the dotted line in Figure 4 ([1)]. Because of this tendency, there was a problem in that the measured beam diameter was larger than the actual beam diameter.

The present invention was made to solve these problems, and aims to provide a highly accurate beam diameter measuring device by eliminating the influence of noise.

[Means to solve the problem]

The beam diameter measuring device according to the present invention has a small amplitude (
For example, circular oscillations (for example, 10μ brittle) are superimposed, beam diameters for a plurality of circular oscillation amplitudes are measured, and highly accurate beam diameters are obtained from each measurement result.

[For production]

According to this invention, when the circular oscillation amplitude is increased with respect to noise, each measurement result becomes close to a straight line when expressed in the above chart, so that the relationship between this straight line and the straight line where the circular oscillation amplitude is 0 is An accurate beam diameter can be determined from the intersection point.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

In this figure, (18) is the second
The deflector is driven by a second deflection amplifier (19) connected to the controller (11), and superimposes a high-speed (e.g. 5 MHz) and small amplitude (e.g. 10 μm) circular oscillation on the electron beam (21). It is for.

Since the other configurations are the same as those of the conventional device, corresponding parts will be given the same reference numerals and explanations will be omitted.

When measuring the beam diameter, the second deflector (18) is driven by the second deflection amplifier (19), and the electron beam (2
) with a high-speed, small-amplitude circular oscillation superimposed, the procedure is similar to that of the conventional device.

FIG. 2 is a chart similar to FIG. 5, but the horizontal axis represents the circular oscillation amplitude. In other words, while adjusting the amplitude of the circular oscillation, the actual measured values of the beam diameters (
(black circle in the figure).

Now, assuming that there is a high frequency noise of 1 μm, the value measured without superimposing circular oscillation is 11 μm.

Here, if we superimpose high frequency (for example 5 MHz) circular oscillation on the electronic beam rotor, the noise and oscillation are not synchronized, so (measured value) = (true beam diameter) + oscillation 〒"? 1Ft
K7, and the measured value becomes like the black circle in FIG.

When the circular oscillation amplitude increases relative to the noise,
It can be understood from the above equation that the black circles are arranged linearly. The intersection point dO between the approximate straight line and the straight line of circular oscillation amplitude O can be recognized as the true beam diameter.

In the above explanation, an example was shown in which high-speed, small-amplitude oscillation is superimposed on the electron beam (2) using the second deflection H (18) and the second deflection amplifier (19). The electron beam is scanned by the deflector (3) by superimposing a high-speed, small-amplitude oscillation signal on the input signal of the deflection amplifier (17) without using the deflector (18) and the second deflection amplifier (19). You can do it like this.

Further, similar effects can be expected even if an ion beam is generated instead of an electron beam. Furthermore,
Although the deflector (31) and the second deflector (18) are shown as coil-shaped, they may be of any type as long as they can provide a deflection function, for example, they may be parallel plate electrodes. .

In the above embodiments, the case where the beam diameter is 10 μm was illustrated, but this invention can be applied to beam diameters ranging from the microscopic level to the welding machine level, that is, from the submicron level to the 100 μm beam diameter.
[Effects of the Invention] As described above, according to the present invention, small amplitude oscillations can be superimposed on a beam, and a beam with multiple circular oscillation amplitudes can be applied. Since each diameter is measured and the beam diameter is determined from each measurement result, an accurate beam diameter can be determined without being affected by noise.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of the present invention, Fig. 2 is a chart showing the relationship between circular oscillation amplitude and beam diameter, and Fig. 3 is a schematic diagram showing a conventional electron beam diameter measuring device. 4
The figure is a characteristic diagram qualitatively showing the relationship between the detection signal and the differential detection signal with respect to the scanning position, and FIG. 5 is a graph showing the relationship between the knife height and the beam diameter. In the figure, the mouth is the electron beam, (3) is the deflector, ((5)
is the test U unit, (6) is the sample, (9) is the knife, (!
l) is a controller, (14) is a signal amplifier, (15) is a differentiator, (17) is a deflection amplifier, (18) is a second deflector,
(19) is a second deflection amplifier. Note that the same reference numerals in the figures indicate corresponding parts. Agent Patent Attorney Masuo Ohatsu Figure 1 Figure 2 0 2 4 k 8 H. -m-Yen large shilling 1 shi is υ(su--(threat 5← Yo surprise)

Claims (1)

[Claims] A charged particle beam is focused on a sample, and the diameter of the beam is measured at a plurality of scanning positions while scanning the focused part of the beam, and the beam diameter is determined from each measurement result. 1. A beam diameter measuring device for a charged particle beam, characterized in that a small-amplitude intra-oscillation is superimposed on the beam, the beam diameter is measured for each of a plurality of circular oscillation amplitudes, and the beam diameter is determined from each measurement result.