JPS62128422A - Electron beam device - Google Patents

Abstract

PURPOSE:To remove the influence of charge accumulating on a protective film by changing, at random, a position on the surface of a semiconductor to be irradiated by an electron beam by a control means and the timing to be delayed relatively to a repeated operation of a semiconductor element. CONSTITUTION:A reflection driver 4 operates so that an electron-beam may be radiated on the position to be indicated by the position data given by a random pattern memory 3. After fixing a deflection position by said deflection driver 4, a delayed pulse corresponding to a measuring time read out from each random EB deflection position array of a random pattern memory is outputted from the control circuit of a random pattern memory 3. A strobo- driver 5 puts an EB pulse gate 8 inside an electron beam device ON synchronizing with the delayed pulse. An electron gun is arranged on the upper part of the EB pulse gate 8, while ON, OFF of the EB pulse gate 8 performs control whether or not allowing the electron beam emitted from said electron gun to pass the gate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] When measuring the wiring voltage of a semiconductor element in which an insulating protective film is provided on the semiconductor surface, an error occurs due to charge accumulation on the above-mentioned insulating protective film. In order to solve this problem, the present invention measures at random phases in synchronization with the repetition period, and also randomly changes the position of the strobe electron beam irradiated onto the semiconductor surface, thereby reducing the amount of charge accumulated on the insulating protective film. Measurements are made with less influence.

[Industrial application field]

The present invention relates to a strobe electron beam device, and more particularly to a strobe electron beam device that measures the voltage at an irradiation point by controlling the timing and position of irradiation with a strobe electron beam.

[Traditional technique]

A strobe electronic beat device is a device that irradiates a measurement point with an electron beam and measures the voltage at the measurement point based on the amount of secondary electrons generated in response to the irradiation. Since this strobe electron beam device can measure the voltage at a point to be measured without contact, it is widely used as a device for measuring the wiring voltage of semiconductors, especially LSIs.

For example, when measuring the wiring voltage in an LSI,
I is repeatedly driven with a specific test pattern operation, and the phase (delay time) is sequentially changed with respect to the repetition period. This phase change corresponds to the time axis of the LSI operating waveform, and by sequentially changing the phase, the LSI
The voltage waveform during repeated operation of I is determined.

On the other hand, when a problem occurs such as when the LSI does not operate as intended, the voltage of the entire area of the LSI chip is determined in units of specific phases, and the voltage of the entire area is adjusted by changing the specific phase. We are measuring how things are changing. Then, the point where the desired action is not achieved, that is, L
They were looking to find out where SI obstacles, etc. existed.

[Problem that the invention sought to solve]

Since a strobe electron beam device irradiates an electron beam onto a point to be measured, the object to be measured must be such that the irradiated electrons flow out through a conductor or the like.

However, for example, an LSI or the like is provided with a protective film that protects the surface of the LSI depth, and in such a case, there is a problem that a desired voltage waveform cannot be obtained. For example, when attempting to measure the voltage of a wiring having a wiring voltage waveform as shown in Figure 5, the charge due to the electron beam accumulates in the protective film, and as shown in Figure 7, the secondary electron The problem is that the signal waveform becomes a waveform obtained by differentiating the wiring voltage waveform.

This problem occurs not only when voltage is constantly being measured at a specific position, but also when the voltage waveform is measured over the entire area of an LSI chip as described above.

[Means for solving problems]

The present invention solves the above-mentioned problem by IW, and its features include repeatedly operating a semiconductor element, and irradiating the surface of the semiconductor with a one-shot electron beam in synchronization with the repeated operation of the semiconductor element. , in a strobe electron beam device that measures the voltage at a point irradiated with the strobe electron beam on the surface of the semiconductor element by means of secondary electron emission by the strobe electron beam; While randomly delaying the repetitive operation of the semiconductor element, the strobe electronic beano is applied to the semiconductor! The present invention is directed to an electron beam apparatus characterized in that it is provided with a control means for randomly determining the position at which the j6 rays are emitted.

[For production]

A semiconductor element is operated repeatedly, and a strobe electron beam is irradiated onto the surface of the semiconductor in synchronization with the repetitive operation of the semiconductor element, and the strobe electron beam on the surface of the semiconductor is irradiated with the amount of secondary electrons emitted by the strobe electron beam. In a strobe electron beam device that measures the voltage at an irradiated point, a control means changes the position on the semiconductor surface where the electron beam is irradiated and the timing of delaying the repetitive operation of the semiconductor element to rung J. Eliminate A-effect due to accumulated charge.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of an electron beam device according to an embodiment of the present invention. LSI test 1 is a circuit that drives LSI 2, which is a one-dimensional object. The LSI tester 1 repeatedly performs a specific operation on this LSI. The LSI tester 1 adds a test trigger to the random pattern memory in synchronization with the repetition of this specific operation. The random pattern memory 3 has a control circuit which reads position data and measurement time data of the LSI 2 to be sequentially measured in synchronization with the tester trigger, and outputs position information to the deflection driver 4. Then, a strobe pulse having a delay corresponding to the measurement time data further read from the tester/register is applied to the strobe driver 5. Note that the delay of the measurement time by the amount of data is made by the number of tester clocks added from the LSI tester 1. For example, when delaying by 10 clocks, the strobe pulse is applied to the strobe driver 5 after 10 tester clocks after the tester trigger is applied. FIG. 2 is a random test pattern number arrangement diagram, and FIG. 3 is a random BB deflection position arrangement diagram. The random EB deflection position array stores measured position data and measurement time data in the order of measurement. The random test pattern number array stores the numbers of the random EB deflection position array shown in FIG. The control circuit of the random pattern memory reads out the random EB deflection position array according to the random test pattern number array shown in FIG.
Measure the time-delayed voltage at each indicated point of I2 in turn. That is, first, the random EB deflection position array of the first test pattern number of the random test pattern number array is sequentially read out to measure the voltage. And then the second
Similarly, the voltage measurement is performed by sequentially reading out the random EB deflection position array of the numbers stored in the eggplant 1 pattern number array. Similarly, measurements are performed according to the random EB deflection position arrangement in the order of the random pattern number arrangement. FIG. 4 is a random pattern memory configuration diagram showing the relationship between the random EB deflection position array and the random test pattern array.

The random EB deflection position array has two-dimensional data indicating the position of the LSI 2 on the plane and its time data,
The two-dimensional data is run vertically in the order of random test pattern numbers.

On the other hand, the deflection driver 4 is a circuit that drives an EB deflector (two-dimensional deflection in x and y directions) 7 that deflects electrons emitted by an electron gun provided in the electron beam device 6, and is a circuit that drives a random pattern. It operates so that the electron beam is irradiated to the position indicated by the position data added from the memory 3. After the deflection position is determined by the deflection driver 4, the control circuit of the random pattern memory 3 outputs a pulse delayed in accordance with the measurement time read out from each random EB deflection position array of the random pattern memory mentioned above. be done. The strobe driver 5 turned on the EB pulse gate 8 in the electron beam device in synchronization with this delayed pulse. The electron gun is placed above the EB pulse gate 8, and turning the EB pulse gate 8 on and off means controlling whether or not to allow the electron beam emitted from the electron gun to pass through. be.

When the light is allowed to pass, a voltage sufficient to pass the light is applied by the strobe driver 5. Since the strobe driver 5 drives the EI3 pulse gate 8 with a very short pulse in synchronization with the measurement pulse applied from the random pattern memory, during this time the electron beam passes through the CI3 deflector 7 and
SI2 is irradiated.

The electron beam irradiated LSI2 causes secondary electrons to
Occurs from SI2. Since the time during which the electron beam is irradiated is very short and constant, the amount of time that secondary electrons are generated is related to the voltage at the irradiated point.

The detector 9 detects this secondary electron beam, and the detector 9 outputs a voltage proportional to the amount of secondary electrons to the A/D converter 10. Note that the generation of secondary electrons changes depending on the voltage at the point where the LSI 2 is irradiated with the electron beam, so
A voltage related to the voltage applied to the LSI 2 is applied to the A/D converter 10.

The A/D converter 10 is a circuit that converts an analog voltage into a digital value, and this circuit stores data representing the voltage value at a point further delayed by a specific time with respect to the operation clock, that is, the test trigger 3, to the voltage image memory 11 at the target position. Output.

The voltage image memory 11 is a memory provided in a three-dimensional array, and the delay time and x, y coordinates, that is, the electron beam
Since the irradiated position data on SI2 has been added to the voltage image memory 11, the digital data of the A/D converter described above is stored in order in the positions corresponding to these data.

Since the position data and measurement time data stored in the random pattern memory 3 are stored in random numbers, L
Measurements in SI2 are similarly performed randomly. However, as described above, data corresponding to the accessed position and measurement time is added to the voltage image memory 11, and a specific memory position is determined by this data. The output data is sorted by position and time and stored.

That is, the data is stored three-dimensionally along the X-axis and y-axis of the LSI 2, and also in chronological order.

The data stored in the voltage image memory is, for example, modulated in brightness in proportion to the voltage value, and the voltage pattern in the x and y axes of the LSI 2 at the same time is displayed on the display device 12. This display is performed by a control circuit (not shown), and it is also possible to use a display different from the above-mentioned display, for example, by setting the horizontal axis of the display to time,
It is also possible to display the vertical axis as a voltage value at a specific point on the LSI 2.

FIG. 6 is a waveform diagram showing data obtained when the wiring voltage waveform at a specific point of the LSI 2 shown in FIG. 5 is measured. Similar to FIG. 5, in FIG. 6, the horizontal axis is time t, and the vertical axis is the secondary electron signal. As is clear from FIG. 6, a waveform similar to the wiring voltage waveform is obtained, and the differential waveform error shown in FIG. 7 unlike the conventional device is eliminated. This is because the influence of accumulation of electrons due to the protective film etc. provided on the surfaces of t and s+2, for example, is almost eliminated by measuring the random number positions and times stored in the random pattern memory.

The present invention has been described above in detail using the embodiments of the present invention. However, the measurement in the present invention is performed using a single point at the same position and the same time, but instead of jumping to that point, the above-mentioned operations are performed multiple times, and, for example, by calculating the average ring. It is also possible to further increase the accuracy. Furthermore, since the voltage at the measurement point generally varies greatly, an analysis voltage is applied to an analyzer (not shown), and a slice level is provided at which the secondary electron signal becomes a specific output. Then, the wiring voltage is determined from the analysis voltage that becomes the slice level, but in this case, by repeating the above-mentioned operations in sequence until the analysis voltage converges,
It is possible to obtain a voltage waveform with high precision and which is further prevented from being distorted by a protective film or the like.

〔Effect of the invention〕

As described above, the present invention performs measurement using an electron beam device. For example, even if a protective film is provided on the surface of an LSI,
Since the electronic beano measures the voltage sequentially by randomly changing the position and time to prevent electrons from being emitted and accumulating, the present invention allows for accurate non-contact voltage measurement of LSIs, etc. that have a protective film over the entire surface of the LSI. You can get the electronic beano and equipment to do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electron beam device according to an embodiment of the present invention, FIG. 2 is a random test pattern number arrangement diagram, FIG. 3 is a random EB deflection position arrangement diagram, FIG. 4 is a random pattern memory configuration diagram, and FIG. 5 is a wiring voltage waveform diagram, FIG. 6 is a secondary electronic signal waveform diagram of the device according to the embodiment of the present invention, and FIG. 7 is a secondary electronic signal waveform diagram of the conventional device. ■... LSI tester, 3... Random pattern memory, 11... Voltage image memory. Fig. 2 Fig. 3 ``F]J-Kuno de turnme 7ri prologue sword figure Fig. 4 Fig. 6 Fig. 7

Claims (1)

[Claims] 1) A sample is moved repeatedly, a strobe electron beam is irradiated onto the surface of the sample in synchronization with the repetitive movement of the sample, and the amount of secondary electrons emitted by the strobe electron beam is determined by the amount of secondary electrons emitted from the sample. In a strobe electron beam device that measures the voltage at a point irradiated with a strobe electron beam on the surface of An electron beam device characterized in that it is provided with a control means that randomly determines a position where the electron beam is moved. 2) The control means has a storage means for storing a time for randomly delaying the irradiation timing of the strobe electron beam with respect to the repetitive motion of the sample, and a random position at which the strobe electron beam is irradiated to the sample. An electron beam device according to claim 1, characterized in that: