JPS60254741A - Voltage measuring device using electron beam - Google Patents

Abstract

PURPOSE:To perform effective analysis and to enhance arresting efficiency, when a draw-out electric field is intensified in order to reduce a local electric field effect, by dispersing secondary electrons in a broad angle range. CONSTITUTION:A draw-out electrode system of a speed-reducing electric-field type energy analyzer is composed of a plurality of electrodes 22a, 22b and 22c, and an electrostatic lens is formed. Voltages V1, V2...Vn are applied to the respective electrodes, and emitted secondary electrons 7 are converged. At this time, the voltages are adjusted so that an imaginary cross-over point A formed by the converged secondary electrons agrees with the centers of concentric spherical grids 21 and 23. To the drawing grid 23, the same voltage as that of an n-th drawing electrode 22n is applied. Therefore, the potential in the space surrounded by 22n and 23 becomes approximately the same. The secondary electrons are dispersed in the large angle range from the imaginary cross-over point to the entire secondary electron analyzer in this configuration. Therefore, the secondary electrons pass the broad part of the speed reducing electric field, which is formed between the grids 21-23. The secondary electrons are vertically inputted to the spherical surfaces having the equal potential between the grids 21-22. Therefore, energy can be analyzed accurately.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to a voltage measuring device using an electron beam (EB), and more specifically, to measuring the energy distribution of secondary electrons emitted from a sample by EB thermal irradiation. This invention relates to an improvement of a device for measuring the voltage of a sample by measuring it with a decelerating electric field type energy analyzer equipped with a decelerating electric field type energy analyzer.

(2) Background of the technology In order to check whether the IC is working as designed or to find the cause of failure in the case of failure of an IC that has been put on the market as a product, the potential of minute wiring inside the IC is measured. What is done is done. Conventionally, potential was measured by mechanical contact with a needle, but as IC wiring became minute, about 1 to 2 μm, the tip of such a needle became too thick to be used.

So I! for wiring! A method has been developed for irradiating B and analyzing the energy of secondary electrons emitted from the irradiation point. The apparatus used for this purpose is shown in FIG. 1, in which 1 is E
B lens barrel, 2 is sample chamber, 3 is EB pulse gate, 4 is deflection coil, 5 is EB, 6 is sample (test IC), 7 is secondary electron, 8 is sample driver, 9 is EB pulse gate driver , 10 is a deflection control circuit, 11 is a secondary electron detector, 12
indicates a signal processing circuit.

In the energy analysis of the secondary electrons described above, it was confirmed that there is a local electric field effect, which is a local electric field created by the fine wiring itself or between closely spaced wirings, which reduces measurement accuracy. Methods to reduce field effects are being investigated.

FIG. 2 shows a conventional voltage measuring device, in which the same parts as those already illustrated in this figure and the following figures are denoted by the same reference numerals, 21 is a deceleration grid, 22 is
is an extraction electrode, 23 is an extraction grid, ve is an extraction voltage, ν is a variable deceleration voltage, and deceleration grid 21. Extracting electrode 22. An energy analyzer is configured with the extraction grid 23 and the νAIV scale. The deceleration grid 21 and the drawer grid are arranged in concentric hemispherical shapes. The energy distribution of secondary electrons emitted by EB thermal irradiation shifts according to the magnitude of the potential at the emission point, so by detecting the magnitude of this shift, the potential at the point irradiated with EB can be determined. .

In order to reduce the local electric field effect, it is effective to increase the extraction electric field on the IC surface, so the larger the extraction voltage Vε is, the more the extraction electrode 22 and the surface of the sample 6 (IC surface)
The smaller the distance between the two, the better. However, in that case, the emitted secondary electrons 7 are transmitted to the deceleration grid 21 and the extraction grid 22.
Since the energy is concentrated near the grid aperture as shown by reference numeral 7' in the figure, effective energy analysis cannot be performed. In addition, the proportion of secondary electrons collected by the secondary electron detector 11 also decreases, and the signal sent to the signal processing circuit 13 becomes small, making effective analysis impossible.

(4) Object of the Invention In view of the above-mentioned conventional problems, an object of the present invention is to provide a voltage measuring device that has a high extraction electric field and that allows emitted secondary electrons to diverge over a wide angular range.

(5) Structure and purpose of the invention According to the present invention, the energy distribution of secondary electrons emitted from a sample by electron beam irradiation is measured using a deceleration electric field type energy analyzer equipped with hemispherical electrodes. In a voltage measuring device that measures the voltage of a sample by
Provided is a voltage measuring device characterized in that a secondary electron extraction electrode system is composed of a plurality of electrodes, a voltage is applied to each of the plurality of electrodes, and thereby emitted secondary electrons are diverged in a predetermined angular range. This is achieved by

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

The present invention consists of an extraction electrode system consisting of a plurality of electrodes and a single spherical grid in order to diffuse secondary electrons over a wide angular range when increasing the extraction electric field to reduce local field effects in JEB voltage measurement devices. By applying a voltage to each of them, the secondary electrons are focused and one virtual crossover point A is connected to the center of the concentric spherical grid.

FIG. 3 shows a deceleration electric field type energy analyzer which is a first embodiment of the present invention. The deceleration grid 21 and the extraction grid 23 are the same as the conventional example, but the extraction electrode system is composed of a plurality of electrodes 22a, 22b, and 22c to create an electrostatic lens, and voltages Vl, V2---Vn are applied to each electrode. The emitted secondary electrons 7 are focused by applying . At that time, the virtual crossover point A created by the focused secondary electrons is
The voltage etc. are adjusted so that the centers of the concentric spherical grids 21 and 23 coincide.

By applying the same voltage as the n-th extraction electrode 22n to the extraction grid 23, the space surrounded by 22n and 23 is made to have approximately equal potential.

As described above, the secondary electrons diverge from one virtual crossover point over a large angular range over the entire secondary electron analyzer, so the secondary electrons pass through a wide portion of the deceleration electric field formed between the grids 21 to 23.

Further, since the secondary electrons are perpendicularly incident on the spherical equipotential surface between the grids 21 and 22, energy analysis can be performed with high accuracy.

A second embodiment of the invention is shown in FIG. In this embodiment, the deceleration grid 21 and the extraction grid 23 are the same as in the conventional example, but the extraction electrode 22, the electrode 24, and the
The three electrodes No. 5 constitute an electrostatic lens. For example, V1=
By adjusting vl and v2 so that Vε, ν2=0, one virtual crossover point A is made to coincide with the center of the concentric hemispherical grid 21, 23, 26.

The concentric hemispherical grid 26 is a pants hybrid for canceling the influence of the voltage (supplementary electric field) generated within the secondary electron detection 911.

(7) Effects of the Invention As explained in detail above, according to the present invention, when the extraction electric field is strengthened to reduce the local field effect in a voltage measuring device using EB, secondary electrons are dispersed over a wide angular range. It is highly effective in increasing effective analysis and collection efficiency.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of an electron beam device, FIG. 2 is a layout diagram of a conventional voltage measuring device, and FIGS. 3 and 4 are layout diagrams of an embodiment of the present invention. 1-EB lens barrel, 2-sample chamber, 3-8B pulse gate, 4--deflection coil, 5--EB,
6-sample (test IC), 7-secondary electron, 8-sample driver, 9-EB pulse gate driver, 10-deflection control circuit,
11-Secondary electron detector, 12-Signal processing circuit, 21-Deceleration grid, 22.22a to 22n-Extraction electrode, 23-Extraction grid, 24-Second extraction electrode, 25-Third extraction electrode, 26-...Buffer Grisode

Claims (1)

[Claims] In a voltage measuring device that measures the voltage of a sample by measuring the energy distribution of secondary electrons emitted from the sample by electron beam irradiation using a deceleration electric field type energy analyzer equipped with a hemispherical electrode, A voltage measurement device characterized in that an extraction electrode system is composed of a plurality of electrodes, and a voltage is applied to each of the plurality of electrodes, thereby causing emitted secondary electrons to diverge in a predetermined angular range.