JPH0531297B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a testing device or a scanning electron microscope device that evaluates the characteristics or detects failures of electronic devices such as VLSI using a charged beam in a non-contact manner.

[Conventional technology]

In order to realize high quality and low cost electronic devices, especially VLSI, in the future, it is essential to develop microfabrication technology in the submicron region, as well as test equipment and test methods for electronic devices during each manufacturing stage. . Contact-type mechanical probe methods have been used to conventionally test the electrical characteristics of electronic devices, but their application to the submicron region is impossible, especially in terms of spatial resolution. To address this problem, high-resolution non-contact electron beam testers have recently come into use. For example, the above electron beam tester is used for "VLSI testing using an electronic probe" (VLSI TESTING USING).
ELECTRON PROBE, Scanning Electron
Microscopy, 1979, vol.1, p.285).

However, this type of conventional equipment inputs a test signal from the outside and uses an electron beam only to detect the output signal, so it is used for functional inspection of finished products, etc., and is used for testing during manufacturing. was not used. Additionally, conventional devices of this type use an electron beam as a probe to display voltage contrast as an image or to observe the voltage waveform (time change) at a predetermined point; Not talked about. When using a charged beam as a probe for voltage supply, it is important to measure the beam current in addition to measuring the potential of the area irradiated with the charged beam in order to control the supplied voltage.

As a method for measuring potential, for example, "Secondary electron detection system for quantitative potential measurement"
(Secondary Electron Detection Systems for
Quantitative Voltage Measurements,
Scanning, 1983, vol. 5, p. 151) uses an energy analyzer. In addition, as a method for measuring beam current, a method is used in which a deep groove (Faraday groove) that prevents secondary electrons from jumping out is provided on the sample stage, etc., and the current is measured by irradiating the groove with a charged beam. ing.

[Problem that the invention seeks to solve]

However, this Faraday groove is usually provided in a portion of the sample stage where no electronic device is attached. Therefore, if you want to measure the beam current while measuring an electronic device, move the sample stage to match the position of the Faraday groove, measure the beam current, and then move it again to the specified position of the electronic device. It is necessary to move the sample stage and adjust the position of the beam so that the charged beam is irradiated onto the position, which is time consuming and inconvenient.

The secondary electron emission ratio also depends on the material of the measuring device,
It varies depending on the degree of surface contamination, adhesion of foreign substances, etc. Therefore, the above properties can be tested by measuring the secondary electron emission ratio. However, when observing voltage contrast or the voltage waveform (time change) at a predetermined point, a relative value rather than an absolute value of this secondary electron emission ratio is required, and usually the secondary electron emission ratio with respect to the energy analysis voltage is Although the change in emission amount (so-called S curve) is measured, the secondary electron emission ratio itself is not measured.

[Means for solving problems]

In order to solve these problems, the present invention
A secondary electron detection electrode with a mesh in a part in the direction of the secondary electron detector, and a secondary electron suppression provided outside the secondary electron detection electrode with a mesh in a part in the direction of the secondary electron detector. A secondary electron detection electrode, a secondary electron suppression electrode, and a means for measuring the sum of currents flowing through the sample stage are provided.

In addition, a secondary electron detection electrode with a mesh part in the direction of the secondary electron detector, and a secondary electron detection electrode with a mesh part in the direction of the secondary electron detector provided outside the secondary electron detection electrode and a mesh part in the direction of the secondary electron detector. An electron suppression electrode, means for measuring the sum of the currents flowing through the secondary electron detection electrode and the secondary electron suppression electrode, and means for measuring only the current flowing through the sample stage are provided.

[Effect]

In the present invention, potential, beam current, and secondary electron emission ratio can be measured without moving the sample stage.

〔Example〕

An embodiment of an electronic device testing apparatus according to the present invention is shown in FIG. In FIG. 1, 1 is an electron beam focused in an optical column (not shown);
2 is a deflected electron beam, 2 is an electronic device, and 3 is a sample stage on which the electronic device 2 is loaded. Around the electronic device 2, there are a secondary electron detection electrode 5 and a secondary electron suppression electrode 6, each of which is partially meshed in the direction of the secondary electron detector 7. At this time, the changeover switch 8 is connected to a positive voltage source 9 and switched so that the secondary electrons are incident on the secondary electron detector 7. To measure the beam current, the changeover switch 8 is connected to the negative voltage source 10, and a negative voltage is applied to the secondary electron suppression electrode 6 to confine the secondary electrons inside the secondary electron detection electrode 5. Make it. In this case, the secondary electrons or reflected electrons are transmitted through the secondary electron suppression electrode 6, the secondary electron detection electrode 5,
It is caught on one of the sample stands 3. Therefore, the beam current is determined by measuring the current with the ammeter 13 as the sum of the currents flowing through the secondary electron suppressing electrode 6, the secondary electron detecting electrode 5, and the sample stage 3. In addition, when observing a secondary electron image or measuring the potential, a positive voltage is applied to the secondary electron suppressing electrode 6, the secondary electrons are made to enter the secondary electron detector 7, and the secondary electron image is can be observed or measured using an energy analyzer.

Second part of the electronic device testing apparatus according to the present invention
An example of this is shown in FIG. In FIG. 1, a hemispherical secondary electron detection electrode was used, but here a parallel plate type secondary electron detection electrode 5 is used. Reference numeral 4 denotes an energy analysis electrode for analyzing the energy of secondary electrons generated from the electronic device to determine the potential. Outside this energy analysis electrode 4, there are a secondary electron detection electrode 5 and a secondary electron suppression electrode 6, which are partially meshed in the direction of the secondary electron detector 7. An energy analysis power source (not shown) is connected to the energy analysis electrode 4, and as is well known, the potential can be measured from the change in the amount of secondary electrons with respect to this voltage. In this case, if the gap between the sample stage 3 and the energy analysis electrode 4 is wide, the secondary electrons will escape through the gap, making it impossible to perform accurate measurements. The same applies to the case where there is an extraction electrode (not shown) between the energy analysis electrode 4 and the sample stage 3. In these cases, either narrow the gap between the energy analysis electrode 4 or extraction electrode and the sample stage 3, or provide a conductive structure surrounding the electronic device 2 on the sample stage 3 as shown in FIG. It is necessary to prevent secondary electrons from leaking outside the energy analyzer.
In addition, when an energy analysis electrode 4 is provided, the beam current is measured by an ammeter (not shown) as the sum of currents flowing through the secondary electron suppression electrode 6, secondary electron detection electrode 5, sample stage 3, and energy analysis electrode 4. You can ask for it. Note that if there is an extraction electrode between the energy analysis electrode 4 and the sample stage 3, the beam current may be determined by including the current flowing through the extraction electrode.

Third aspect of the electronic device testing apparatus according to the present invention
An example of this is shown in FIG. This third embodiment relates to the invention set forth in claim 2. In the figure, the same or corresponding parts as in FIG. 1 are given the same reference numerals. Secondary electron suppression electrode 6,
The current due to the emission of secondary electrons can be measured by the ammeter 31 as the sum of the currents flowing through the secondary electron detection electrode 5 and the energy analysis electrode 4. Also, ammeter 32
The current flowing through the sample stage 3 is measured. The total current of the current flowing through the ammeter 31 and the current flowing through the sample stage 3, that is, the beam current can be measured by the ammeter 13. Therefore, the secondary electron emission ratio can be determined from the ratio of the current values of the ammeter 31 and the ammeter 13. When the primary charged beam is an electron beam, here,
The ratio of the current based on the amount of emission including secondary electrons and reflected electrons to the total current is determined as the secondary electron emission ratio. The secondary electron emission ratio changes depending on the material, potential, and surface conditions such as contamination of the charged beam irradiated portion of the electronic device. Therefore, by measuring the secondary electron emission ratio, it is possible to detect contamination on the surface of an electronic device, adhesion of foreign matter, difference in material, and presence of a thin film. Furthermore, the values of gate leakage and juncture leakage of MOS capacitors can be determined from the current flowing through the sample stage, and the electrical characteristics and failures of electronic devices can be detected.

Note that when the primary charged beam is an electron beam, strictly speaking, the secondary electron emission ratio measured by this method also includes a component of reflected electrons. Since reflected electrons have high energy and secondary electrons have low energy, secondary electrons are more suitable for obtaining information such as the potential on the surface of an electronic device. The amount of reflected electrons is
In the range where the accelerating voltage of the charged beam is several hundred to several kilovolts, it is about one order of magnitude smaller than the amount of secondary electrons, and has almost no effect. If it is necessary to distinguish between backscattered electrons and secondary electrons, the voltage applied to the energy analysis electrode 4 should be set to about 10 to 20 volts to allow only high-energy backscattered electrons to pass. If the current flowing through the beam 5 is separately measured, the emission ratio of reflected electrons can be measured from the ratio between this current and the beam current. The true secondary electron emission ratio is the amount obtained by subtracting the emission ratio of reflected electrons from the ratio of the current values of the ammeter 31 and the ammeter 13.

Fourth aspect of the electronic device testing apparatus according to the present invention
An example of this is shown in FIG. This fourth embodiment relates to the invention set forth in claim 3. In the figure, the same or corresponding parts as in FIG. 1 are given the same reference numerals. Although the changeover switch, power supply, etc. are omitted in the figure, the wiring is the same as in FIG. 1. 44 is an extraction electrode to which a positive voltage is applied in order to extract secondary electrons, and is connected to the ammeter 13 shown in FIG.
45 is an electrode kept at the same potential as the sample stage 3;
It is insulated from the secondary electron detection electrode 5, energy analysis electrode 4, etc. by an insulator 46. This electrode 45 is provided in a cylindrical shape along the incident path of the charged beam 1 . The purpose of providing this electrode 45 is to deflect the charged beam by changing the voltage applied to the energy analysis electrode 4 when measuring potential, or by changing the voltage applied to the secondary electron detection electrode 5 by switching the changeover switch 8. This is to prevent the irradiation position of the charged beam from shifting from a predetermined position due to a change in the amount. Note that the extraction electrode, which is not shown in FIG. 3, is necessary to improve the accuracy of potential measurement, but is not necessarily necessary to measure the beam current.

〔Effect of the invention〕

As explained above, the present invention includes a secondary electron detection electrode that is partially meshed in the direction of the secondary electron detector, and a secondary electron detection electrode that is provided outside the secondary electron detection electrode and that is arranged in the direction of the secondary electron detector. The potential and beam current can be measured by providing an electrode for suppressing secondary electrons with a mesh part, and a means for measuring the sum of the current flowing through the secondary electron detection electrode, the secondary electron suppression electrode, and the sample stage. This can be done without moving the sample stage, and has the advantage of being able to measure the potential and beam current at a predetermined point on an electronic device in a non-contact manner.

In addition, by providing a means for measuring the sum of the currents flowing through the secondary electron detection electrode and the secondary electron suppression electrode, and a means for measuring only the current flowing through the sample stage, it is possible to increase the potential, beam current, and secondary electron emission ratio. can be measured without moving the sample stage, the potential and beam current at a predetermined point on an electronic device can be measured without contact, and gate leakage, juncture leakage, and their potential dependence can be measured quickly. Moreover, it has the advantage that it can be applied to minute electronic devices. Furthermore, by measuring the secondary electron emission ratio, it is possible to detect differences in materials, degree of surface contamination, adhesion of foreign substances, and thin films.

Furthermore, this test device has the advantage that it can be applied to cases such as measuring beam current while observing a secondary electron image with a scanning electron microscope.

[Brief explanation of drawings]

FIG. 1 is a schematic layout diagram showing a first embodiment of an electronic device testing apparatus according to the present invention, FIG. 2 is a schematic layout diagram showing a second embodiment, and FIG. 3 is a schematic layout diagram showing a third embodiment. FIG. 4 is a schematic layout diagram showing the fourth embodiment. 1...electron beam, 2...electronic device, 3...
...Sample stage, 4...Energy analysis electrode, 5...Secondary electron detection electrode, 6...Secondary electron suppression electrode, 7...
... Secondary electron detector, 8 ... Changeover switch, 9
... Positive voltage source, 10... Negative voltage source, 11... Energy analysis power supply, 12... Power supply, 13, 31,
32...Ammeter, 44...Extraction electrode, 45...
...electrode, 46...insulator.

Claims (1)

[Scope of Claims] 1. A secondary electron detection electrode that is partially meshed in the direction in which the secondary electron detector is arranged, and a secondary electron detection electrode that is provided outside the secondary electron detection electrode and in which the secondary electron detector is arranged. a secondary electron suppression electrode with a mesh formed in a part of the direction in which the An electronic device testing device characterized by measuring beam current. 2. A secondary electron detection electrode with a mesh in a part in the direction in which the secondary electron detector is arranged, and a part in the direction in which the secondary electron detector is arranged outside the secondary electron detection electrode. A secondary electron suppression electrode having a mesh of A testing device for an electronic device, characterized in that the value of the secondary electron emission ratio or the backscattered electron emission ratio of the electronic device is measured from the ratio of the two. 3. Claims 1 or 2, characterized in that the secondary electron detection electrode has an electrode maintained at the same potential as the sample stage along the incident path of the charged beam.
Test equipment for electronic devices as described in Section 1.