JPS6010636A - Strobe electron beam device - Google Patents

Abstract

PURPOSE:To enable to observe the internal voltage waveform of a sample even if the time stability of a clock pulse is insufficient except an accurate delay unit by providing an arbitrary clock pulse in a repetition period of the observing time origin. CONSTITUTION:An electron optical barrel 1 emits an electron beam to the observing point of a sample 3 placed in a sample chamber 2. The production of an electron beam is controlled by a pulse driver 6. A pulse generator 7 responses to signals on lines 8-11. The counted output of a counter 20 is connected to one input of a comparator 21, and the set output of a register 22 is connected to the other input. The output of the comparator 21 is connected to a variable delay unit 23. A control counter 14 outputs a clock pulse number designation signal and a time designation signal. The output of the secondary electron detector 13 is connected through a signal processor 16 for addition-averaging it to the counter 14. An electron beam emitting timing pulse is supplied through a line 17 from the generator 7.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a strobe electron beam device, and in particular, a voltage waveform is observed using an arbitrary clock pulse within a period consisting of a plurality of clock pulses as the time origin. This invention relates to a strobe electron beam device.

(b) Background of the technology As a diagnostic technology for semiconductor integrated circuits (LSI, etc.), it is possible to
Observe the internal voltage waveform of a high-speed operation LSI using the signal obtained by irradiating an electron beam synchronized with the S I repetitive operation cycle and detecting the secondary electrons emitted from the electron beam that reflect the observation point potential. There is a technique (stroboscopic method) that is seen as promising and is being actively developed.

The strobe electron beam device must have an electron beam irradiation means that can irradiate the electron beam in synchronization with the high-speed operation of the LSI and with minute time lags, but the electron beam irradiation standards for the electron beam irradiation means must be met. Since the time point setting is fixed, various problems are caused, and there is a strong desire for the development of technical means that can eliminate these problems.

(c) Prior Art and Problems The time origin for electron beam irradiation in a conventional strobe electron beam device is the r, sr operation cycle signal (see FIG. 1). Therefore, if one attempts to observe any time within the operation cycle from this time origin, a delay unit that can perform highly accurate delay over a wide range is essential. Also, since the time stability of the clock pulse of the LSI itself is not sufficient, 1. Even if the SI operation period signal is used as the time origin, it is not always possible to emit the electron beam at the desired observation time.

Object of the Invention The present invention was devised in view of the drawbacks of conventional devices such as dual-unit systems. An object of the present invention is to provide a strobe electron beam device capable of observing voltage waveforms.

(E) Structure of the Invention The object of the invention is to provide a strobe electronic device having an electron optical column and an electron beam irradiation control means for irradiating an electron beam from the electron optical column to an observation point of a sample operating at a predetermined operation cycle. In a beam device, circuit means for specifying a clock pulse number within a repetition period of the sample, a circuit for generating a signal indicating a time origin in response to a synchronization signal of the sample, its clock pulse, and the clock pulse number; In response to the signal indicating the time origin, the drive pulse is applied to the electron beam within the time period before the next clock pulse in successive cycles, and at a timing having a shift amount that increases by a predetermined time in each successive cycle. This is achieved by comprising circuit means for supplying the radiation control means.

(F) Embodiments of the Invention The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 2 shows an embodiment of the invention. In this figure, 1
is an electron optical column, which irradiates an observation point of a sample 3 placed in a sample chamber 2 with an electron beam. Sample 3 is, for example, an LSI that operates with an operation cycle consisting of one or more clocks, and the cycle is becoming longer.

Generation of the electron beam in the electron optical column 1 is under the control of a pulse driver 6 which receives a strobe pulse (drive pulse) on line 4 and a pulse width designation signal on line 5.

Line 4 is the output line of pulse generator 7;
generates a pulse on line 4 in response to signals on lines 8, 9, 10, and 11, and this circuit portion constitutes the essential part of the present invention. The details are shown in FIG.

In FIG. 3, 20 is a counter, a line 8 is connected to its count input, and a line 9 is connected to its reset input.

The count output of this counter 20 is connected to one input of a comparison circuit 21, and the other input is connected to a register 2.
2 cent outputs are connected. Line 10 is connected to the cent input of register 22. The output of the comparison circuit 21 is connected to a variable delay device 23, the output of which is connected to line 4. Line 1 is connected to the delay amount determination input of the variable delay device 23.
1 is connected.

Lines 8 and 9 are a line for transmitting a repetitive periodic synchronization signal and a line for transmitting a clock pulse, respectively, from the sample driver 12 (see FIG. 1), and line 9 is also connected to the sample 3 as a line 13. Lines 10 and 11 are lines for transmitting a clock pulse number designation signal and a time designation signal from the control calculator 14, respectively.

15 is a secondary electron detector, the output of which is connected to the control calculator 14 via a signal processing circuit 16 that performs averaging processing. The electron beam emission timing pulse to be processed by the signal processing circuit 16 is supplied from the pulse generator 7 via a line 17.

Next, the operation of the apparatus of the present invention configured as described above will be explained.

An observation point of the sample 3 is irradiated with an electron beam from the electron optical column l, and secondary electrons emitted from the observation point are detected by a secondary electron detector 15. After the secondary electronic signal is processed by the signal processing circuit 16, it is taken into the control computer 14 and provided for visual display.

The electron beam irradiation on the sample 3 that enables such observation is generated by a gate pulse (sampling pulse) from a pulse driver 6, and the output pulse of the pulse driver 6 is supplied from a control calculator 14 via a line 5. is generated in response to a pulse width designation signal and a strobe pulse supplied via line 4 from pulse generator 7.

The strobe pulse is generated as follows. That is, the clock pulse driving the specimen 3 is also supplied to the counter 20 via line 8, and the synchronization signal indicating the repetition period of the specimen 3 is supplied to the counter 20 via line 9. Here, for convenience of explanation, as shown in FIG. 4, the synchronization signal ((1) in FIG.
It is assumed that the counter 20 has been reset by the counter 20 (see 2)), and that the clock pulse number designation signal supplied from the control calculator 4 via the line 10 has been sent to the register 22. It is assumed that the designated clock pulse number is the third clock pulse number counting from the synchronization signal.

When the value of the counter 20 that counts clock pulses (see (4-1) in FIG. 4) reaches 3, a pulse is generated from the comparison circuit 21 that compares this value with the value of the register 22. However, this output pulse becomes the time origin in the present invention (see (4-3) in FIG. 4). When the output pulse is passed through the variable delay device 23, a predetermined delay is caused.

In the first case, the signal on line 11 is a signal indicating no delay, so the output pulse is sent out on line 4 as is. Therefore, the electron beam controlled by the pulse driver 6 is also generated at the time origin (((
(See 4-4).

In the next period T, the same operation as described above is caused, but the delay amount of the variable delay device 23 is reduced to, for example, 1 nsec.
There is a difference in that. Therefore, the electron beam is generated at a time delayed by △ from the time origin ((4-
4)).

Hereinafter, as the subsequent period advances by one, the amount of deviation from the time origin increases by (n-1)△, where n is the number of periods counted from the period in which the amount of deviation is zero, and the electron beam The secondary electron signal is generated at a corresponding delay time, and the above-mentioned secondary electron signal is acquired and used for observing the voltage waveform at that observation point.

If it is desired to select another clock pulse within the repetition period as the time origin, the clock number set in the register 22 via the line 10 may be set to a value corresponding to the clock number.

As described above, according to the present invention, the time origin can be set at any clock pulse within the repetition period.

Therefore, especially when observing the voltage waveform of an LSI using the strobe method, a high-precision delay unit is not required to observe the voltage waveform at any clock within the long-period operation of the LSI. Furthermore, even when the time stability of the clock pulse is not sufficient, it becomes possible to observe the internal voltage waveform of L'SI.

Note that the generation of the pulse indicating the time origin is not limited to the circuit described above, and may be replaced by a circuit that counts down a set clock number and generates an output pulse when the value reaches the reference value. Of course.

(G) Effects of the Invention As described above, according to the present invention, (1) the time origin can be set to any clock pulse within the repetition period; (2) the need for a high-precision delay device can therefore be eliminated; (2) Even when the time stability of the clock pulse is not sufficient, effects such as being able to observe the internal voltage waveform of the sample can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a timing chart for explaining the parts related to the present invention of a conventional device, Fig. 2 is a diagram showing an embodiment of the present invention, and Fig. 3 is a detail of the main parts of the present invention in the device shown in Fig. 2. 4 are diagrams showing timing charts for explaining the operation of the apparatus of the present invention. In the figure, 1 is an electron optical lens barrel, 3 is a sample, 6 is a pulse driver, 7 is a pulse generator, 12 is a sample driver, 14 is a control calculator, 15 is a secondary electron detector, and 6 is a signal processing circuit. , 20 is a counter, 21 is a comparison circuit, 22 is a register,
23 is a variable delay device. ! M+iH,'ii 1

Claims (1)

[Claims] In a strobe electron beam apparatus having an electron optical column and an electron beam pulse irradiation control means for irradiating an electron beam pulse from the electron optical column to an observation point of a sample operating at a predetermined operation cycle, circuit means for specifying a clock pulse number within the sample, a circuit for generating a signal indicating a time origin in response to the synchronization signal of the sample, its clock pulse, and the clock pulse number; circuit means for supplying drive pulses to the electron beam pulse irradiation control means within the time before the next clock pulse in successive cycles, and at a timing having a shift amount that increases by a predetermined time in each successive cycle; A strobe electron beam device comprising: