JPS6010550A - Strobe electron beam system - Google Patents

Abstract

PURPOSE:To observe the voltage waveform of LSI having long period with high time resolution, by delaying specific time interval from the long period clock timing synchronous with the clock and controlling the timing for producing the electron beam pulse. CONSTITUTION:Clock 2 is provided from a pulse generator 1 to pulse counters 7, 27. The counter 27 will receive a frequency division specifying signal 28 from a control computer 8 and provide as LSI clock 4 to LSI driver 3. The counter 7 will count the pulses of clock 2 from the timing of synchronous signal 6 of driver 3 to produce an original delay point signal 10 from the number of clocks set by a clock number specifying signal 9. A high accuracy delay circuit 11 will produce a strobe signal 13 which is formed by delaying the signal 10 through a delay time specifying signal 12 provided from the computor 8 to control a pulse gate deflector 18 through an electron beam pulse width specifying signal 15 provided from the computor 8 and the signal 13. Consequently, the voltage waveform of LSI 5 can be observed with high time resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to control of an electron beam device using a strobe method.

(2) Background of the technology As a method of observing the voltage waveform inside an LSI that operates at high speed, a pulse-shaped secondary waveform is generated by irradiating an observation point on the LSI with an electron beam pulse in synchronization with the LSI that operates for five cycles. There is a strobed EB prober that detects electrons as a voltage signal. The stroboscopic EB prober is a non-contact, high-speed observation method that is useful for testing LSIs, etc., and observes time changes in voltage, that is, voltage waveforms, by shifting the timing of irradiation of electron beam pulses by a minute time every cycle. In order to improve observation accuracy, it is necessary to vary the electron beam pulse irradiation timing with high precision.Furthermore, in order to observe the voltage waveform of one cycle of LSI with a long operating cycle, it is necessary to change the variable range of the electron beam pulse irradiation timing. It is requested that it be expanded.

(3) Prior Art and Problems An example of controlling the electron beam pulse irradiation timing using the conventional method is shown in FIG.

Figure 1 (al is LSI black 7ri, all LS
The operation of I is performed in synchronization with this clock.

In this embodiment, the frequency of the LSI clock is 2 MHz. FIG. 1 Tb) is an LSI internal voltage waveform and shows a certain voltage inside the LSI that changes in synchronization with the LSI clock. FIG. 1(C) is a repeating period synchronization signal, and L
A pulse waveform having the same cycle as the repetition cycle of the SI internal voltage waveform is shown.

FIG. 1 (dl indicates a strobe signal that outputs an electron beam pulse).

Conventionally, in order to observe the LSI internal voltage waveform synchronized with the LSI clock, a repetition period synchronization signal having the same period as the repetition period (hereinafter referred to as repetition period) of the internal voltage waveform of the LSR is used as a delayed origin signal, and this delayed origin is The electron beam pulse is output after being delayed by a specified time (n·Δt, (n+1)Δt) from the signal. When observing voltage waveforms, the delay time is extended by a small amount of time △t for each repetition period and the electron beam pulse is output at -, so the delay time can be changed with high precision over a wide time range for LSIs with long repetition periods. A delay time creation circuit is required. It is not easy to realize such a delay time creation circuit, and the delay time jitter t1, which becomes more pronounced as the specified delay time is longer, may reduce the time resolution or cause the delay time variable range to be insufficient. There is a drawback that an impossible time region t2 may occur.

(4) Purpose of the Invention In view of the above drawbacks of the prior art, the present invention makes it possible to observe voltage waveforms of long-period LSIs with high time resolution by controlling the irradiation timing of electron beam pulses over a wide time range with high precision. The purpose is to

(5) Structure of the Invention The present invention comprises a pulse generating means for generating a first clock, a long-period second clock synchronized with the first clock,
pulse counting means for counting the first clock from the timing of the second clock and generating a third clock synchronized with the first clock at a designated count value;
Provided is an electron beam device characterized in that it has a delay circuit that delays a clock generation timing by a specified time width, and controls timing for generating an electron beam pulse by the output of the delay circuit.

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

FIG. 2 is a block diagram of the present invention.

A high frequency output from the pulse generator 1 (for example, input to the counter 7 and pulse counter 27).

The pulse counter 7 and the pulse counter 27 each receive a clock number designation signal 9 and a frequency division designation signal 28 from the control calculator 8, and set a pulse output timing and a pulse frequency division ratio. The output signal of the pulse counter 27 is input to the LSI driver 3 as an LSI clock 4 synchronized with the local clock 2. The output of the LSI driver 3 is input to the pulse counter 7 as an LSI to be tested and a repetition period synchronization signal 6. The pulse counter 7 counts the pulses of the local tally clock 2 from the timing of the repetition period synchronization signal 6, and generates a delayed origin signal synchronized with the local tally clock 2 by inputting the clock number set in advance by the clock number designation signal 9. Outputs 10. The high-precision delay circuit 11 outputs a strobe signal 13 obtained by delaying the delayed origin signal 10 by a time specified by a delay time designation signal 12 from the control calculator 8. The pulse gate drino 14 receives the strobe signal 13 and the electron beam pulse width designation signal 15 from the control calculator 8 to generate the deflection voltage 16.
is output and applied to the pulse gate deflector 18 in the electron beam column 17 to create an electron beam pulse 19. Secondary electrons 2o obtained by irradiating the LSI 5 to be tested with the electron beam pulse 19 are input to the signal processing circuit 23 as a secondary electron signal 22 via the secondary electron detector 21. The signal processing circuit 23 receives the strobe signal 13. According to the sampling timing specification 24, the secondary electronic signal 22 is subjected to digital data processing, averaging processing, etc., and its output is inputted to the control calculator 8 as a digital signal 25, and is input to the control calculator 8 as a digital signal 25.
The internal voltage waveform of the LSI and the like are displayed on the display device 26.

At this time, it is necessary that the LSI internal voltage waveform (FIG. 3(C)) and the repetition period synchronization signal (FIG. 3(d)) are synchronized.

FIG. 3 shows a method of controlling the electron beam pulse irradiation timing according to the present invention in the form of a timing chart.

FIG. 3 (al is local clock 2, which is a pulse waveform having a frequency of 10 MHz in this embodiment.
Figure (bl, (cl, (dl) are each 2MHz L
SI Croc 4. The LSI internal voltage waveform and the repetition period synchronization signal 6 are shown. These waveforms are the same as those described in the prior art example, but each waveform is synchronized with the local tally clock 2.

FIG. 3 (el indicates the clock number n. The clock number n is the number expressing the delay time from the repetition period synchronization signal 6 in terms of the period of the local clock 2. The clock number of the delay is N, and becomes zero after 10 more clocks have elapsed.

FIG. 3ff) shows the delayed origin signal 10. In the conventional example, the delay origin was equal to the repetition period synchronization signal 6, but according to the present invention, when an arbitrary integer n of O-H is given, the delay origin signal 10 is given when the clock number 2 n is generated. Fig. 3 (gl is a minute time Δt than the delayed origin signal 10
, 2·Δ is the strobe signal 13 that outputs an electron beam pulse delayed by 2·Δ. A sample value of the LSI internal voltage waveform can be obtained by irradiating an electron beam pulse and detecting secondary electrons. The LSI internal voltage waveform can be observed over one period by continuously changing and observing the delay time of the electron beam pulse in a minute time width equal to the repetition period of the LSI internal voltage waveform.

The delay τ of the output timing of the strobe signal 13 with respect to the repetition period synchronization signal 6 synchronized with the repetition period of the internal voltage waveform of the LSI is determined by the clock number n and the delay time k.
It is expressed as △t.

τ=n-T+k・△t becomes. Here, T represents the period of the local tarok.

If m・△t='l', the delay τ' when = m+β is r'=n-T+ (m+g)-Δt= (n+1)T+
1・△t, and by changing the clock number, an arbitrary delay can be calculated by changing the clock number n and the delay time k・in a limited variable range.
It can be obtained by Δ1 <0≦k<m). In the present invention, by specifying the clock number n when specifying the delay time τ, the delayed origin signal 1 is synchronized with the local clock 2.
Obtain o and specify the delay time k·Δt from there. Third
In the timing chart shown in the figure, n=8. ni=1 and n=8
．． = 2.

When n=13 is specified, the pulse counter 7 outputs a delayed origin signal 10 synchronized with local tarlock No. 8. The high-precision delay circuit 11 is a strobe signal 1 delayed by Δt and 2・Δ from the delayed origin signal 10 when = l and k = 2, respectively.
Outputs 3. As a result, the delays from the repetition cycle synchronization signal 6 are 8T+t and BT+2·Δt, respectively, as shown in FIG. 3(g).

In the embodiment, the strobe is applied at each repetition period, but the present invention is not limited to this, and a configuration in which the strobe is applied at a period that is an integral multiple of the repetition period is also possible. Furthermore, the cycles of the local clock 2 and the LSI clock 4 are not limited to those of the embodiment.

(6) As described in detail, according to the present invention, in a strobe electron beam device, the delay time from the strobe synchronization signal can be changed with high precision over a wide time range, and it is possible to change the delay time from the strobe synchronization signal over a wide time range with high precision. It becomes possible to observe the voltage waveform of a periodic LSI with high time resolution. Furthermore, according to the present invention, the delay circuit only needs to vary the delay within the range of the local clock cycle, so
) It becomes easy to realize a highly accurate delay circuit.

[Brief explanation of drawings]

Figure 1 is a timing chart showing a conventional method of controlling electron beam pulse irradiation timing in the strobe method.
FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a timing chart showing a method of controlling electron beam pulse irradiation timing according to the present invention. 1...Pulse Q stopper, 2...-local tarlock, 3...LSI driver. 4...LSI clock, 7...Pulse counter,
8...Control calculator. 9... Clock number designation signal, 10... Delay origin signal, 11... High precision delay circuit, 12... Delay time designation signal. 13... Strobe signal, 27... Pulse callan 7. 28... Frequency division designation signal patent applicant Fujitsu Limited

Claims (3)

[Claims] (1) a pulse generating means for generating a first clock; and a long-period second clock synchronized with the first clock;
pulse counting means for counting the first clock from the timing of the second clock and generating a third clock synchronized with the first clock at a designated count value;
What is claimed is: 1. An electron beam device comprising: a delay circuit that delays a clock generation timing by a specified time width; and the timing of generating an electron beam pulse is controlled by the output of the delay circuit. (2) Controlling the count value of the pulse counting means and the delay time of the delay circuit, and continuously changing the time from the generation timing of the second clock to the generation of the electron beam pulse in a minute width. The strobe electron beam device according to claim 1, further comprising control means for controlling the strobe electron beam device. (3) It is characterized by having an observation means for observing a phenomenon synchronized with the second clock by continuously changing the timing of irradiating the electron beam pulse over a plurality of cycles within the second clock. A strobe electron beam device according to claim 2.