JPS58132671A - Measuring device for voltage wherein electron beam is used - Google Patents

Abstract

PURPOSE:To improve S/N of a detection signal and thereby to enable the accurate detection of the potential of a sample by a constitution wherein an electrode grid for accelerating a secondary electron from a material to be irradiated and an electrode grid for decelerating the same are provided in the foregoing part of a detector to increase the efficiency of focusing the secondary electron. CONSTITUTION:When a primary electron beam 21 is applied on a material 11 to be measured, a secondary electron 22 is emitted from the vicinity of the point of application and accelerated in the direction of an electrode grid 12 by an electric field generated by the grid. The electron 22 passing through the grid 12 is subjected to the action of an electric field generated by an electrode grid 13, and the potential gradient of an electric field formed between the grids 12 and 13 turns negative. Accordingly, the electron 22 which is accelerated and focused forcedly by the grid 12 is decelerated. At the tip of a detector 15 a deflection electrode 14 whereon a positive voltage is impressed is located, and the electron 22 is focused on the surface of the detector 15 by this deflection electrode.

Description

Detailed Description of the Invention [Technical Field of the Invention] This invention relates to an improvement in a voltage measuring device that uses an electron beam to detect the voltage of a sample by touching it instead of using a conventional gold wire stylus. .

[Technical background of the invention and its problems]

Recently, a voltage measuring device has been developed that measures the voltage of the sample by irradiating the measured part of the sample with 111t electrons and detecting the secondary electrons emitted from the sample to perform failure diagnosis and characteristic evaluation of semiconductor devices. I'm here. This device is based on the principle that the amount of emitted secondary electrons and the binerase change as the potential of the sample surface changes, and has the following features (1) to (4).

(1) There is no risk of mechanical damage because the measurement is performed without contacting the sample.

(2) Unlike a probe, it has zero stray capacitance and lead inductance, so it is capable of high-speed response.

(3) - Electrically deflect child #S at high speed! Can be rowed.

(4) It becomes possible to measure minute areas that cannot be measured with a probe.

By the way, when measuring the potential of the sample by detecting the secondary single signal emitted when the sample surface is irradiated with electrons 4I,
Two properties are used: the potential dependence of the amount of secondary electrons and the potential dependence of the emission structure. In the case of elderly people, the electric field formed just above the sample surface by the sample potential acts as a potential barrier, and the emitted secondary electrons are pulled back or repelled by 1, increasing the number of secondary electrons that reach the detector position. changes. Without the action of the local electric field created by the potential region around the sample, the change in the detected secondary electron direct current would be 1=1
Correspond with this. In the latter case, the 4-tensional energy of the secondary electrons ejected from below the surface of the sample by the primary electrons increases or decreases depending on the potential of the surface, so the power Louis distribution of the emitted secondary electrons is affected. Move in parallel by the amount of change in potential of the measurement sample. Therefore, the sample potential can be determined by measuring this amount of movement with a detection system using a spectrometer or an energy analyzer. To perform all measurements using these methods, conventional scintillators and spectrometers require several hundred to several thousand CVs at the tip.
2 emitted from the sample surface by the focusing electrode to which a positive voltage of J was applied.
The next electronic signal was captured. 8 of the captured secondary electron signal
In order to improve the N ratio, it is sufficient to increase the voltage applied to the focusing electrode to increase the efficiency of capturing secondary electrons, but if the electric field strength is too large, the primary electrons will be forced out.
A fear 7L that deflects will appear.

FIG. 1 is a four-dimensional schematic diagram showing a conventional voltage measuring device.
An example is shown in which the primary electron beam is bent toward the detector by the focusing electrode electric field (indicated by a broken line in the figure). In the figure, 2 is the IFi sample, 2 is the primary electron beam, S is the secondary electron, and 4 is the Detector, 5 is the focusing electrode of the detector 4, 5 is the focusing electrode with several hundred to several tens of
This is a power supply that applies a voltage of 00 (vJ).In addition, in the conventional device with the groove bottom, the emission efficiency of the secondary electrons 3 is lower than that of the primary electrons.
Since the maximum is in the incident direction of 2, the detection 64 is the primary electron -2
It is often placed near the 0-incidence path. Therefore, the voltage applied to the focusing electrode 5 attached to the tip of the detector 4 is:
There is a restriction that the electric field is set within a range that does not affect the primary electrons @2, and the focusing efficiency of the secondary electrons 3 is eventually sacrificed. The incident path of primary electron a2, detector 4 and f!
:4! This can be done by tilting the #1 leg of the sample 1, but in this case, a new problem arises in that topographical information on the surface of the sample 1 is mixed into the detected secondary electron signal. Furthermore, if the focusing electrode electric field is small, the secondary electron signal reaching the detector 4 will be affected by the local electric field created by the potential region around one sample, making it difficult to accurately measure the sample surface potential. It becomes difficult.

[Object of the Invention] The object of the present invention is to improve the efficiency of secondary electron signals emitted from the sample surface, improve the signal-to-noise ratio of the detection signal, and reduce the local electric field created by the potential region around the sample. An object of the present invention is to provide a voltage measuring device using an electron beam that can reduce the influence and accurately detect the potential of a sample.

[Invention O1! Summary The present invention provides a voltage measuring device using electrons S that measures the voltage of the sample by irradiating a sample to be measured with electrons m and detecting the secondary electrons emitted from the sample with an electron detector. A first electrode grid for accelerating the secondary electrons is provided on the incident side of the adult edge of the sample, and a first electrode grid for decelerating the accelerated secondary electrons is provided between the first electrode grid and the electron detector. Two electrode grids are provided.

〔Effect of the invention〕

According to the present invention, secondary electrons emitted from the sample surface by primary electron irradiation are detected by the electric field created by the first electrode grid against the local electric field formed by the sample and the potential region around the sample. The sensor is accelerated in the direction of the detector, and is further decelerated by the electric field created by the second electrode grid at a position in front of the detector. Therefore, the secondary electrons can be efficiently deflected toward the detector by the electric field of Kuwa TEPCO et al. attached to the tip of the detector.

By doing so, it is possible to increase the efficiency of collecting secondary electrons and to further reduce the influence of the local electric field on the secondary electrons. Therefore, it is possible to significantly improve the S/N ratio of the secondary Sushi detection signal and to improve the accuracy of sample potential detection.

Then, the sample is in a moving state, and an electron beam is placed at one point? When irradiating the sample while it is still above the ground and inputting the detected secondary electron signal into a synchroscope or V coder to observe the temporal change in sample motion as a waveform, the voltage accuracy of the graph shown is much better than before. In addition, if the sample surface is scanned while chipping the electron beam in synchronization with Sample!Ii1, the contrast changes depending on the position of Sample1!
However, conventionally, the r
It was only a matter of determining the logic Ii of OJ and rlJ. On the other hand, in the present invention, since voltage measurement can be performed accurately, detailed one-element analysis is possible even in logic transition states. From the above, the present invention provides measurement and
It has the effect of greatly increasing the precision of pressing.

[Embodiments of the invention]

FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention. In FIG.
First and second electrode gratings 12813 are disposed above the sample 1 (Seriko 1-Incidence 1Illil) in parallel with the upper surface of the sample. And these electrode gratings 12. J
Above the electron detector 3, an electron detector 15 is provided, which is made up of seven antitilators and has a deflection electrode 14 at its tip. In the figure, reference numerals 16, 17, and 18 indicate power sources that apply a full predetermined voltage to the electrode grids 12, 13 and the deflection electrodes 14, respectively. The first electrode grid 12 located at the position closest to the sample 1 has several tens to several i o o (v)
When a positive voltage of 0 to several [
The positive voltage of [v] is marked J)0, and the deflection electrode 14 has a10
A voltage of 0 to several thousand volts is applied.

With such a configuration, when the sample to be measured 11 is irradiated with the primary electron beam 21, secondary electrons 22 are emitted from the vicinity of the irradiation point. Is this secondary electron 22 at most several tens of electrons? They are charged particles with a certain amount of energy. The amount of emission and the distributed energy band change with the surface potential of the sample 11.

This two forceps 22V'i first electrode grid 12 is closed'
It is accelerated in the direction of the electrode grid 12 by the electric field. When potential regions exist around the 41 measurement points on the sample 1, each potential region serves as an electrode and forms a complex electric field directly above the sample surface. The low-energy secondary electrons 22 are easily affected by this local electric field, which makes it difficult to accurately measure the sample voltage using the secondary electron signal. 1st
The electrode grid 12 overcomes this local electric field and directs the secondary electrons 22t-7 in the detection azs direction, which are emitted from the surface of the sample to be measured.
He has the intuition to speed up to 111. Also, the primary electron 1ili1
Since the secondary electrons 22 emitted from the vicinity of the irradiation point 21 are forcibly accelerated in the detection aZS direction, it also has the function of improving the detection efficiency and the 8N ratio of the total secondary electron signal. Note that although some electrons are generated due to field emission, since the contribution of these electrons to the measured value is constant, there is no problem in voltage measurement. The secondary electrons 22 that are accelerated in the direction of the electrode grid 12 and pass through the n electrode grid 12 are now transferred to the second electrode grid 13 (f).
is affected by the electric field created by

A low voltage of 0 to several [V] is applied to the electrode grid 13, and the potential gradient of the electric field formed between the first electrode grid 12 and the second electrode grid 13 becomes negative. Therefore, the secondary electrons 22 that have been accelerated and forcibly focused by the first electrode grid 12 are decelerated here. At the tip of the detector 15 there is a deflection electrode I4 to which a positive charge is applied, and the secondary electrons 22 are focused on the detector surface by this deflection electric field. The secondary electrons 22 are already on the electrode grid I
Since it is decelerated by J, the deflection electrode voltage is 100 [V]
Low voltages before and after are sufficient, so primary electrons 1II2
There is no risk of bending or defocusing the route of No. 1. In this way, the voltage of the sample 11 can be accurately measured.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof.For example, the first and second electrode gratings 12 of e 1 j does not necessarily have to be a flat plate, but may be a hemispherical 1/4b as shown in FIG. Alternatively, it may be a yarn using energy analysis. Furthermore, the voltages applied to the first and second electrode grids and the deflection electrodes may be determined according to specifications.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a conventional voltage measuring device, FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. I@3 is a schematic configuration diagram showing a modified example. DESCRIPTION OF SYMBOLS 11... Sample, 12... First electrode grid, 13...
- Second electrode grid, 14... Deflection electrode, 16... Electron detection 4.16.17.18... Power supply, 21... 1
Secondary electron 1-122... Secondary electron.

Claims (3)

[Claims] (1) In a voltage measuring device using an electron beam, the voltage tS of the sample is determined by irradiating the sample to be measured with electrons and detecting the secondary electrons emitted from the sample with an electron detector. A first electrode grid arranged on the electron beam incident side of the sample to accelerate the secondary electrons; and a first electrode grid arranged between the first electrode grid and the electron detector to decelerate the accelerated secondary electrons. A voltage measuring device using an electron beam with 1g2 electrode grid. (2) The first electrode grid applies a positive pressure of several 10 to several 100 (V), and the electrode grid @2 applies a positive pressure of several tens to several hundreds (V).
2. The electron beam voltage measuring device according to claim 1, wherein a positive voltage is applied. (3) The electron detector is constructed by applying a positive voltage of several hundred to several io o o (v) to the tip of a scintillator or spectrometer and disposing nine focusing electrodes. A voltage measuring device using an electronic AT according to claim 1. )