JPS6243053A - Strobe electron beam device - Google Patents

Abstract

PURPOSE:To enable high-speed scanning free from phase shift by dividing the frequency of a high frequency clock by a first and a second frequency-dividing circuit and varying the frequencies of two clock signals supplied to an IC driver and a strobe SEM. CONSTITUTION:A high frequency clock 101 from a high-frequency-basic-clock- generating circuit 1 is supplied to a first frequency-dividing circuit 2 for dividing in M portions and a second frequency-dividing circuit 3 for dividing in (M+L) portions and the outputs of the circuits 2 and 3 are delivered to an IC driver 5 and a strobe-SEM-controlling circuit 11. The phase of the basic clock applied to the strobe-SEM-controlling circuit 11 is adjusted to be slightly ahead of the phase of a clock applied to an IC driver 5 for each period. The phase shift caused during performing frequency scanning is prevented by synchronously producing the clock signal. Due to the above structure, it is possible to measure the waveform of the IC internal signal with high resolution by achieving high speed without using any delay line.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a strobe electron beam device that can detect wiring voltage without contact and without removing a protective film. The phase scanning operation is performed by shifting the cycle of the supplied clock, and the IC and strobe STE
The present invention provides a strobe electron beam device characterized in that the clock signal supplied to M is a signal generated by dividing the frequency of the same basic clock signal using counter circuit means.

For example, an IMHz clock signal generated by dividing a 1GHz basic clock by 1000 into a non-test IC.
The signal is given to the driver and used as the basic clock signal of the IC.

Further, a clock signal of 10/1001 Hz outputted from the basic clock of the same IGHz through a 1001 frequency dividing circuit is used as the basic clock of the strobe SEM circuit.

Then, the transient response of the IC wiring voltage will be detected in synchronization with the basic clock of the strobe SEM circuit. The basic clock of the strobe SEM circuit has a phase lead of 2π/1000 radians per cycle with respect to the IMtlz clock supplied to the IC driver. Therefore, the signal waveform inside the IC is
Since it is cycled by the IMIIz clock given to
If the strobe SEM is operated, the IC internal signal waveform can be measured with 1000 samplings per cycle.The present invention thus allows one phase scan operation to be performed at high speed without using a delay line. This has the advantage of being able to measure waveforms with high accuracy, in a short time, and with high resolution.

[Industrial application field]

The present invention relates to an electron beam device that applies an electron beam to wiring inside an integrated circuit and detects wiring voltage from the intensity of secondary electrons generated therefrom, and particularly relates to an electron beam device that detects wiring voltage from the intensity of secondary electrons generated therefrom, and in particular supplies it to a 1C driver and a robot SEM. The present invention relates to a strobe electron beam device that performs a phase scanning operation by shifting the period of a clock signal.

[Traditional technique]

BACKGROUND OF THE INVENTION With the development of large-scale integrated circuits, it has become increasingly important to establish advanced fault detection and diagnostic techniques for diagnosing whether the internal logical operations of large-scale integrated circuits are normal. In order to know the logical state of an integrated circuit or the change in gate output in response to a change in input, it is necessary to know the voltage state or voltage change of the wiring connected to the output of each gate.

In this case, the wiring voltage can be determined by touching the probe of the voltage needle to the wiring, but in large-scale integrated circuits, the width of the internal wiring is very narrow and it is difficult to contact the wiring with the probe. Further, wiring problems may occur due to contact. Furthermore, such a probe method has the disadvantage that each wiring is examined sequentially, so that the measurement time is extremely long. Therefore,! & Recently, an electron beam device that is attracting attention is an electron beam device that detects wiring voltage without contact and without removing the protective film. This electron beam device mounts an integrated circuit as a sample on a stage.

An electron beam is applied to the IC from the top of the stage.

The wiring voltage is detected by measuring the energy of the secondary electron beam emitted from the wiring inside the IC. It is possible to observe not only the voltage change of each wire with the input voltage, that is, the temporal change, but also the voltage state of all wires within the field where the beam is applied, that is, the spatial voltage distribution. It is something.

Conventionally, in this type of electron beam device, the phase scanning method has been used as a means of measuring the time response of each wiring under the insulator, that is, the voltage waveform. In this case, the clocks of the IC driver and strobe SEM operate aperiodically. I went there.

However, this type of conventional method has the disadvantage that when phase scanning operations are performed multiple times, phase drift cannot be ignored and voltage waveforms cannot be measured with high precision.

[Problem that the invention seeks to solve]

The present invention eliminates the conventional drawbacks and performs a high-speed and highly accurate phase scan operation by dividing a high-frequency basic clock and using clock signals with slightly different frequencies as clocks for the IC driver and strobe SEM, respectively. The basic clock that is supplied to the strobe SF and M circuits is the IC.
The phase is slightly 1 per period for the black and ri applied to
By performing a 9-phase scan operation while stopping,
Provided is a strobe electron beam device that enables measurement of IC internal signal waveforms with high resolution.

(Means for Solving the Problems) The present invention provides a strobe electron beam device capable of detecting wiring voltage without contact and without removing a protective film, including a clock generating means for generating a high-frequency basic clock, and a clock generating means for generating a high-frequency basic clock; a first M frequency dividing circuit that divides the high frequency clock outputted from the means by M;
A second frequency dividing circuit that divides the frequency by
Provided is a strobe electron beam device, characterized in that the output of a frequency dividing circuit is supplied to a strobe SEM, and a phase scanning operation is performed by shifting the periods of the two clock signals supplied to an IC driver and a strobe SEM. Furthermore, the present invention provides a strobe electron beam device characterized in that the frequency of the basic clock signal is IGHz or higher.

[For production]

Generates a high-speed basic clock of 1 GHz and converts it to 100
IMllz and 1 are sent to the Ic driver and strobe SEM through a frequency dividing circuit that divides the frequency by 0 and by 1001, respectively.
By applying the clock signals of 09/100111z, the clock signal of the strobe SEM circuit can be adjusted per cycle to the IMIIz clock given to the IC.
The phase is set to advance by 2π/1000 radians.

Since the signal waveform inside the IC is output in synchronization with the basic clock of this SEM circuit, the signal waveform inside the IC can be measured with 1000 samplings per cycle.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

The configuration of the strobe electronic device of the present invention is shown in FIG. 1st
In the figure, an electron beam pulse projected from an electron gun 7 through a pulse gate in an electron beam column, that is, an SEM main body 6, is deflected in an appropriate direction by a deflection coil and then is inside a detection IC 9 in a sample chamber. Applied to the surface of internal wiring. When an electron beam (EB) pulse is projected,
When secondary electrons are emitted from the surface of the internal wiring and detected by the secondary electron detector 10, an analog secondary electron signal 107 is output. The strobe SEM control circuit 11 is
This analog secondary electron signal 107 is amplified and sampled,
At the same time as further quantizing and converting to a digital signal,
Transfer the digital data to the internal control computer. The computer includes a function of averaging digital signals near each sample point in order to increase the S/N ratio. The IC 9 to be tested is supplied with a power supply voltage and an input voltage by the IC driver 5, and is also supplied with a clock signal. The output of each gate changes according to the input logic or input change given to each clock cycle of the clock signal, and the state of the change or steady logic state is propagated to the wiring connected to the gate output. become.

A driver drive for the EB pulse gate (No. 4, that is, a blanking pulse 106, which is formed by an appropriate method in the strobe SEM control circuit 11, is given to the blanker 8, and with this blanking pulse as a trigger, the electron beam is sent to the electron gun 7. is projected as an EB pulse from
This pulse projection is based on the basic clock 1 given to the IC.
Since it is released with a slight delay with respect to the rise of 05, I
The secondary electron signals emitted from each wiring of C9 are input to the detection 310 without interference. Inside the strobe SEM control circuit 11, an analog secondary electronic signal input via the detector 10 is input to an A/D conversion circuit via an amplifier. The frequency.

Gives the resolution of the wiring signal waveform. In this case, it is necessary to form a clock signal 103 for specifying the timing of sampling the analog signal. In the present invention,
In order to perform a high-speed, high-precision phase scan operation, a high-frequency basic clock is generated by a high-frequency clock generation circuit 1, and this high-frequency clock is divided by frequency dividing circuits 2 and 3, respectively, to generate different frequencies. Clock signals 102 and 103 are sent to Ic driver 5 and strobe SEX, respectively.
By using this as a clock, high-resolution sampling is possible.

Next, this frequency division method will be explained using the timing chart of FIG.

The high frequency basic clock generation circuit 1 has a high frequency N Il
It generates a clock signal of z. now.

Assume that this N is 1 GHz, that is, 10 tlz. Said N
The llz clock signal is input to frequency divider circuits 2 and 3. Frequency divider circuit 2 is a 1M frequency divider circuit.

A clock signal of M/Nllz is outputted to the output line 102.

It is applied to the IC driver 5 and the AND gate 4. M to 10
00, the frequency of the basic clock given to the Ic driver is IMIIz, that is, 1011z.

On the other hand, the 1 frequency divider circuit 3 is a (M+1) frequency divider circuit,
Its output, the basic clock 103, is applied to the strobe output control circuit 11 and other inputs of the AND gate 4. Here, L is an integer, but is a divisor of 1M. If L=1, the M+L frequency divider circuit 3 divides the input basic clock of ICl1z by (1000+1) (10
/1001) Output line 1 of the basic clock of llz
It will be generated on 03. That is, when N=10, that is, lG11z, M is 1000, and L is 1, the clock of N/M, that is, IMIIz, becomes the basic clock signal of the IC driver by the 2M frequency divider circuit 2, and M
The +L frequency divider circuit 3 divides N/(M+L), that is, (10
/1001) Strobe SE with llz clock signal
It is input to the M circuit.

The basic clock signal 102 given to the IC driver 5 is a clock signal whose period is M/N as shown in FIG. This is a clock signal with a period of (M+L)/N.

Now, in the repetition period of the signal line 104, the signal ℃-102 has τ and one riser in one cycle, while the signal 103 has τ and one riser in one cycle. It turns out. When M = 1000, the signal 102 has one period from 0 to 2π.

The signal 103 has 1001 rising edges.

Has 1000 standers and ji. As a result, the number of pulses in one period of signal 103 is one less than that of signal 102. Therefore, the phase of the first pulse of signal 103 with respect to signal 102 is (2πL/M)
It will have a phase of XI radians. Similarly, the phase of the second pulse is (2πL/M)x2, and the phase of the third pulse is (2πL/M)x3. The phase will be . The rising edge of these pulses has no phase shift with respect to the rising edge of No. 18 102 in the first pulse.

The first rising edge is the signal λcL with respect to the signal 102.
The rising edge of the +103 pulse has a phase difference of (-2-) Fujian. For the n-th (λ
This means that there is a phase shift of radians of TDL, )×n. Therefore, the signal 103 leads the phase of the signal 102 by 2πL/M per period, that is, 2π radians. A signal 102 is given to the IC driver 5. The signal waveform inside I'C works with ri to 2 as a clock, so it is synchronized with signal 102, and as shown in the last waveform in Figure 2, the voltage of a certain wire is output in synchronization with signal 102. Become.

On the other hand, the signal 103 is given to the strobe output control circuit 103 and serves as a sampling clock, so the IC signal waveform is measured with M samplings per period. This is N= , I G11z, M =
1000. If L=1, the basic clock of 102 is IMIIz, and the IC is driven by this clock. Since IMHz is 10' times/second, 1
00IX During a time interval of 10-' seconds, signal 103 will be sampled 1000 times, so 1
0 The signal waveform will be observed with a time resolution of 1 nsec. In this case, the time required for one phase scan operation is l m5ec.

Note that the signal 104 is a signal obtained by ANDing the signals 102 and 103, and indicates the origin of the phase scanning operation as shown in the third waveform in FIG. 2. In other words, it is a signal that has rising edges of pulses only at the beginning and end of one period 2π, and is a clock signal of -outer spring 11-llll. This clock signal is a signal indicating the operating cycle of the entire system. In this way, the present invention uses an IC driver and a scan S.
One-phase scanning operation is performed by slightly shifting the period of the clock signal supplied to the EM, and the clock signal 10 is supplied to the IC driver and strobe SEM.
2 and 13 are made from the same basic clock signal section, ie, the basic clock generation circuit 1.

The feature is that this high frequency basic clock is generated by dividing the frequency using counter circuits 2 and 3, respectively. That is, the clock signal 102 of the IC driver and strobe SEM
and 103 are made by a synchronous operation using a counter.

(Effects of the Invention) As described above, the present invention provides clock signals to be applied to the IC driver and the strobe SEM that are generated synchronously, so that there is no one phase shift even when scanning operations are performed many times, and a line extension can be reduced. Since it is not used, there is no need for the time required for switching.Furthermore, by setting N to IC; Hz or more, 1 nse
This has the effect that waveforms can be measured with a time resolution of c or more.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a strobe electronic device according to the present invention. FIG. 2 is a timing chart showing the clock frequency division method of the strobe electronic device of the present invention. 1...Ntlz basic clock. 2...M frequency divider circuit. 3...M+L frequency dividing circuit. 4 ・ ・ ・AND gate. 5...IC driver. 6...SEM body. 7...Electron gun. 8... Blanker 1 9... IC1 10... Detector. 11... Strobe SEM control circuit. 101...N11z basic clock signal. 102...N/M fiz clock (No. 8. 103...N/(M+L) fiz clock signal. 105...IC drive signal. 106...Blanking pulse. 107...Secondary electronic signal (v) Part - ~ Circle - +T■ψ 2nd drawing of the moving lower roof varnish in May

Claims (2)

[Claims] (1) In an electron beam device equipped with a strobe function,
Clock generation means for generating a high-frequency basic clock; a first M-divider circuit for dividing the high-frequency clock outputted from the clock generating means by M; and a second frequency-dividing circuit for dividing the high-frequency clock by M+L. and supplying the output of the first frequency dividing circuit as a clock signal of the IC to be tested, and supplying the output of the second frequency dividing circuit to a strobe SEM,
A strobe electron beam device characterized in that a phase scanning operation is performed by shifting the periods of the two clock signals supplied to an IC driver and a strobe SEM. (2) The strobe electron beam device according to claim 1, wherein the frequency of the basic clock signal is 1 GHz or more.