JPS647498B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that automatically measures the internal potential of an IC during operation.

FIG. 1 shows an example of a conventional IC automatic measuring device. In the figure, 1 is a pattern generator, 2 is a power supply, 3 is a test IC, 4 is a control computer, and 5 is a comparator. With such conventional IC automatic measuring instruments,
The pattern generator 1 adds a test pattern to the IC under test 3 according to the signal from the control computer 4, and
The quality of the IC is determined by comparing the output signal appearing at the output terminal of the IC 3 with an expected value programmed in advance in the control computer 4 using a comparator 5. However, when an IC is defective, it is difficult to determine the location of the defect just by determining the input/output.Therefore, when investigating and analyzing abnormalities in the manufacturing process and products complained of by users, various measuring instruments have traditionally been used. The location of the failure was investigated using internal probes and other equipment obtained. However, it is extremely difficult to probe the pattern of an even smaller LSI, and it is no longer possible to clearly identify the location of a failure even through failure analysis using a computer or the like.

The purpose of the present invention is to provide a new automatic measuring device to replace such conventional measuring devices.According to the measuring device of the present invention, it is possible to automatically measure the potential and operating speed at any point inside an IC. Therefore, it is possible to judge the quality of the IC with high precision, and it is also possible to investigate even submicron fine patterns by using an electron beam to investigate the potential on the LSI pattern.

FIG. 2 shows an example of the configuration of an automatic measuring device according to the present invention. 1 is the pattern generator, 2 is the power supply, 3 is the test object
IC, 4 is a control computer, 5 is a comparator, 6
1 is an E-gun for generating an electron beam, 62 is a beam chopper, 63 is a deflector, 7 is a secondary electron detector,
8 is an amplifier. In this configuration, the power supply 2 applies a voltage to the device under test 3 in response to a signal from the control computer 4, and the pattern generator 1 applies a test pattern to the IC under test 3. Up to this point, it is the same as the conventional automatic measuring instrument, but in the present invention, the electron beam generated by the electron beam generating E-gun 61 of the electron beam device 6 is converted into a pulse beam by the beam chopper 62, and the electron beam is converted into a pulse beam by the computer 4. Deflector 63
The measured point on the IC 3 under test is irradiated by the control voltage. That is, the control computer 4 controls the timing of chopping the beam at the beam chopper 62 and the amount of beam deflection at the deflector 63 according to a program. The secondary electrons that come out from the point to be measured by the electron beam irradiation in an amount corresponding to the potential of that point are detected by the secondary electron detector 7, and the electrical signal amplified by the amplifier 8 is controlled. The comparator 5 compares it with the expected reference voltage generated by the power supply 2 under the control of the control computer 4, and if the magnitude relationship is as programmed in the control computer 4, the measured point is determined by the control computer 4. It is determined that there is no electrical abnormality. At this time, the timing of chopping the beam at the beam chopper 63 is continuously changed by the control computer 4, and by repeatedly measuring, the temporal potential change at the measured point is known, and the operating speed at that point is determined. It can also be measured. For example, when a chopped beam is continuously irradiated onto a measurement point along the time axis as shown in Fig. 3, the secondary electron detector 7 outputs an output at each timing according to potential changes at the measurement point. is taken out. According to this output, the waveform at the measured point can be measured. If the measured point is irradiated with direct current without chopping the beam, only the average output of secondary electrons will be obtained, so it will not be possible to grasp the correct signal waveform. As shown in the figure, the signal waveform at the measured point can be accurately measured. Therefore, as shown in Fig. 4a, the input point P1 of a certain circuit is irradiated with a chopped beam, the waveform at that point P1 is detected, and the waveform at the output point P2 is detected.
When the waveforms at each point are measured and the waveforms at each point are combined based on the reference timings A1 and A2 of the chopped beam, the difference becomes the delay time in the circuit, and the operating speed between the input and output of the circuit can be determined. I can do it. Also, at this time, by measuring in advance the power supply wiring section and each input terminal section to which a potential can be applied from the outside, the signal level due to secondary electrons from a certain set potential section is sent to the control computer 4 or pattern generator 1. By storing the memorized value and comparing the signal generated by secondary electrons from other measured points,
It becomes possible to measure the potentials of other measured points with higher accuracy. Similarly, by including a clock pulse input terminal externally applied at arbitrary timing in the measured point and repeatedly measuring the clock pulse input terminal, the change in the secondary electron signal due to the temporal change in the input potential at this measured terminal By storing the time in the pattern generator 1 or the control computer 4, and knowing the time difference between the stored time and the change time of the secondary electron signal due to the potential change at any other point to be measured, The accuracy of measuring the operating speed can be improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a conventional automatic measuring device, Fig. 2 is a block diagram showing the configuration of an automatic measuring device according to the present invention, Fig. 3 is a timing diagram of waveform measurement at the measured point, and Fig. 4 4a is a circuit diagram to be measured, and FIG. 4b is a measurement timing diagram thereof. 1... Pattern generator, 3... Test IC, 4...
...Computer, 5...Comparator, 6...Electron beam equipment, 7...Secondary electron detection device.

Claims (1)

[Claims] 1 An electron beam device that generates an electron beam to irradiate the IC under test, a beam chopper that converts the generated electron beam into a pulsed beam, and an irradiation position of the pulsed beam on the IC under test according to a predetermined program. an irradiation position control device for moving the pulsed beam, a means for continuously changing the timing of chopping the beam at the beam chopper, a detection device for detecting secondary electrons generated by irradiation with the pulsed beam, and an output of the detection device. and a device for comparing the expected value corresponding to the irradiation position, and irradiates the measured point of the test IC with a pulse beam whose tip timing is continuously changed. An automatic IC internal potential measuring device characterized by repeatedly measuring the potential change over time.