JPS6176963A - Voltage measuring device by electron beam - Google Patents

Abstract

PURPOSE:To reduce the number of times of measurement, and to execute the measurement at a high speed by deriving a ratio of a secondary electronic signal in plural specified analysis voltages, converting its ratio by a table derived in advance, and deriving a wiring voltage. CONSTITUTION:An electron beam is irradiated on an IC1-1 placed on an X-Y stage 1-2 through a pulse gate 1-0. By its irradiation, a secondary electron is emitted from the IC1-1 and its quantity is detected by an analyzer 1-3. Its output is amplified by a detector 2, provided as a secondary electronic signal to an A/D converter 3 and converted to digital data. Also, the IC1-1 is driven by a driver 4, and applied as a repeat signal to a delaying circuit 5. This circuit 5 outputs a delay pulse, for instance, proportional to a delay quantity applied from a controlling circuit 6 and applies it to a pulse generator 7. On the other hand, an output of the generator 7 is provided to a gate circuit 8. Also, a ratio of an output of the analyzer in a specified analysis voltage is derived, and a wiring voltage is derived from its ratio.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a strobe electron beam device, and in particular to high precision voltage measurement and high speed voltage measurement using an electron beam.
, 11, regarding a fixed device.

[Conventional technology]

A strobe electron beam device is used as a device to indirectly measure the voltage of an IC or the like. This device can measure the voltage of ICs, etc. without connecting a probe, and can also measure wiring voltage waveforms during operation, making it possible to perform many effective measurements such as testing the operation of these ICs.

In general, a strobe electron beam device irradiates an IC to be measured with an electron beam in synchronization with the operating cycle, detects the secondary electrons, and measures the voltage at the irradiated point, as shown in Figure 2 (al). The secondary electrons are detected by a hemispherical analyzer, and are further converted into digital data and processed by an A/D converter, etc., but the output from one analyzer is minute and is processed multiple times. For example, the detection voltage is obtained by measuring 100 times and calculating the average.The detection voltage is not in a simple proportional relationship with the voltage at the point to be measured (the point irradiated with the electron beam). For this reason, as shown in Figure 2 (bl), the relationship between one analysis voltage and the detection voltage of one analyzer (measurement analysis curve) is determined by changing the analysis voltage applied to the analyzer during measurement. The voltage at the measured point is determined by comparing it with the reference analysis curve provided.

With this measurement method, at one point of one analysis voltage, 1
Since the measurement is carried out 00 times and the measurement is repeated every time the analysis voltage is changed, the voltage measurement at one point to be measured requires measurements in FIG. 2 (n cycles cn times as shown in C1). For example, approximately 212 to 2 measurements are required. Therefore, there was a problem in that the measurement required a lot of time.

On the other hand, as a method to solve this problem, as shown in Figure 2 (d+), there is a method of changing the 1 analysis voltage corresponding to the detection voltage so that the detection voltage is at a specific slice level, and then focusing and measuring. However, this method also requires changing the analysis voltage about eight times, and although the measurement time has been shortened, it still has the problem of requiring time.

[Problem that the invention seeks to solve]

As mentioned above, the conventional voltage measuring device using an electron beam
There were problems in that the measurement time was long and the accuracy was not sufficient. The present invention seeks to solve this problem.

[Structure of the invention]

The present invention is characterized in that a strobe electron beam device includes a detection means for detecting secondary electron signals based on at least two types of analysis voltages, and a voltage ratio of the secondary electron signals based on the at least two types of analysis voltages. It has a ratio calculation means and a storage means for storing in advance the relationship between the wiring voltage and the voltage ratio of the secondary electron signal due to the two types of analysis voltages, and the output of the ratio calculation means is stored in the storage means. An object of the present invention is to provide a voltage measuring device using an electron beam, which is characterized in that the voltage is determined by converting it into a wiring voltage using the electron beam.

[Embodiments of the invention]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

The electron beam emitted from the electron gun (not shown) in the strobe electron beam device 1 passes through the pulse gate 1-0 to
The light is irradiated onto an object to be measured, that is, an IC, which is placed on an X-Y stage 1-2 that is movable in the axial direction and the Y-axis direction. Due to the irradiation, secondary electrons are emitted from the rc, and the amount thereof is detected by the analyzer 1-3. The output is amplified by the detector and applied as a secondary electronic signal to the A/D converter 3, where it is converted into digital data. In the present invention, the above-mentioned operation is repeated multiple times within one cycle. This control is performed by the control circuit 6 described below.
etc.

ICl-1 is driven by a driver 4, and the operating period is determined by the driver 4 and applied to the delay circuit 5 as a repetitive signal. In the embodiment of the present invention, since the analysis is performed multiple times, for example, 100 times at the same analysis voltage, in synchronization with the operating cycle, the delay circuit 5 outputs a delay pulse proportional to the amount of delay applied by the control circuit 6, for example. Note that the delay pulses outputted here correspond one-to-one to the repetitive signals applied from the driver 4.

The delayed pulse is then applied to the pulse generator 7. The pulse generator 7 generates n clocks starting from delay pulses from the gate circuit 8 based on frequency data inputted from the control circuit 6, for example, data indicating 1/n cycle of the operating cycle, etc.
Output to. Fig. 3(a) is a repetitive signal, Fig. 3(b)
l indicates the output of the pulse generator 7. For example, 1/
When the pulse generator 7 generates pulses in units of 10 periods and measures 100 points of the waveform within one period (dividing one period into 100), the delay circuit 5 is supplied with signals from the control circuit 6 from 0 to 100. A delay amount varying in units of T/100 of 9T/100 (T is repetition operation time) is added.

Of course, since measurements are performed 100 times, for example, as will be described later, to measure one point of the signal under test, the amount of delay described above changes in units of 100 cycles.

The output of the pulse generator 7 mentioned above is applied to a gate circuit 8. (■ in the figure indicates that it is connected) This gate circuit 8 outputs a pulse applied from the pulse generator 7 to the pulse gate driver 10 in response to a control signal applied from the averaging processing circuit 9.

This gate circuit 8 is a circuit for preventing the IC from being irradiated with a strobe electron beam when the averaging process or the like is completed. If measurement is in progress, this input pulse is applied to the pulse gate via the pulse gate driver 10, and turns on the pulse gate 1-0 that irradiates the electron beam.
Turn off. As a result, the strobe electron beam is
As shown in C1, the object to be measured is irradiated.

On the other hand, the 1-pulse gate driver 10 outputs a sampling signal to the A/D converter 3 in one-to-one correspondence with the strobe pulses applied to the pulse gates 1-0. A/
The D converter 3 starts sampling based on this (i %), and the 2 output from the detector 2 shown in FIG.
Convert the next electronic signal to digital data.

The averaging processing circuit 9 is a circuit that performs addition processing on the digital signals applied from the A/D converter 3 in correspondence with pulses within the operating cycle, and has a register for storing the addition results. For example, as mentioned above, 10
10 if the clock is output from the pulse generator 7.
It has 2 registers.

The averaging processing circuit 9 clears the contents of the register and starts the addition process in response to the start signal from the control circuit 6, and then outputs an end signal to the control circuit 6 when the control circuit 6 performs the addition process for the number of averages added. At the same time, the average result is output to the memory M1 via the switch SW.

The above-mentioned addition process is a process in which addition is performed corresponding to the position of each clock within one cycle, and in the case of FIG. 3(d), al+22+33"-, b++b2, . . .

etc. The memory M1 stores the average value of the secondary electron signal at analysis voltage 1, that is, the detection voltage.

The memory M2 stores the detected voltage at the analysis voltage V2. Note that the switch SW is connected to the analysis voltage (Vl) applied from the control circuit 6.
, V2) changes.

By changing the delay of the operation described above, the memory M1. M2
Each data as shown in FIG. 4 is stored in .

5 and 6 show the ratio calculation circuit 11 and the ratio table circuit 12.
A characteristic diagram showing the relationship between the analysis voltage and the analyzer output and the relationship between the wiring voltage (voltage to be measured) and the analyzer output ratio (S=/S1) to explain the operation of the verification circuit 13 to which these outputs are added. be. As shown in FIG. 5, one analyzer output also depends on the wiring voltage. Conventionally, as mentioned above, the wiring voltage was determined by the amount by which the curve that changes depending on the wiring voltage moves in the X-axis direction, but in the present invention, the ratio of the analyzer outputs Sl and S2 at specific analysis voltages Vl and V2 is calculated, and the wiring voltage is calculated from the ratio. In other words, as shown in Figure 6, the wiring voltage and the analyzer output ratio (S2/S port) are determined in advance, and the 2 analyzer output ratio S
2/S + Find the wiring voltage.

The memories Ml and M2 contain the analyzer outputs 31 of Vl and V2 of each measurement point for each delay. Since S2 is stored, the ratio calculation circuit 11 to which the outputs of the memories M1 and M2 are added calculates S2/S1 using this data.

The ratio table circuit 12 is a circuit having a table in which the relationship between the wiring voltage and the analyzer output ratio (S2/S+) shown in FIG. 6 is given. Since these outputs are added to the collation circuit 13, the S2/St added by the ratio calculation circuit 11 is converted into a wiring voltage based on the table data output from the ratio table circuit, and outputted to the control section 6. The control circuit 6 then outputs the measurement results to a display device (not shown) or the like.

Although the inputs and outputs of the memories M1 and M2 are not shown, addresses are designated under the control of the control circuit 6.

In the embodiment of the present invention described above, the outputs of the ratio calculation circuit 11 and the ratio table circuit 12 are added to the collation circuit 13, but the ratio table circuit is configured with a memory and the outputs of the ratio calculation circuit 11 and the ratio table circuit 12 are added to the comparison circuit 13. By storing the relationship between the analyzer output ratio and the wiring voltage, it is also possible to add the output of the ratio calculation circuit to the address of the memory so that the corresponding wiring voltage is output from the memory.

Furthermore, in one embodiment of the present invention, a plurality of points are measured in one cycle, but it is also possible to measure one point.

〔Effect of the invention〕

As described above, the present invention does not determine the characteristic curve between the analysis voltage and the secondary electron signal, that is, the detection voltage, but rather determines the ratio of the secondary electron signal at a plurality of specific analysis voltages, and calculates the ratio in advance from that ratio. According to the present invention, the number of measurements is extremely small, and a voltage measuring device using an electron beam that can perform high-speed measurements can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the prior art, FIG. 3 is a timing chart of the embodiment of the present invention, and FIG. 4 is a memory M1. A memory configuration diagram explaining the contents of M2, FIG. 5 is a characteristic curve diagram representing the relationship between analysis voltage and analyzer output, and FIG. 6 is a characteristic curve diagram representing the relationship between wiring voltage and analyzer output ratio. DESCRIPTION OF SYMBOLS 1... Strobe electron beam device, 2... Detector, 3... A/D computer. 4...Driver', 5...Delay circuit. 6... Control circuit, 7... Pulse generator. 8...Gate circuit, 9...Additional averaging processing circuit, 10...Pulse gate driver. 11...Ratio calculation circuit, 12...Ratio table circuit, 13...Verification circuit. ↑ (Q) (C) 4th @

Claims (1)

[Claims] In the strobe electron beam device, a detection means for detecting secondary electron signals based on at least two types of analysis voltages;
ratio calculation means for calculating the voltage ratio of the secondary electron signal due to the at least two types of analysis voltages; and storage means for storing in advance the relationship between the wiring voltage and the voltage ratio of the secondary electron signal due to the at least two types of analysis voltages; A voltage measuring device using an electron beam, characterized in that the voltage is determined by converting the output of the ratio calculation means into a wiring voltage using the storage means.