JPS62191Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the quality of a semiconductor element by measuring the potential of any part of the semiconductor element using an electron beam.

With the development of semiconductor manufacturing technology, integrated circuits (hereinafter referred to as
As the degree of integration of integrated circuits (ICs) increases, the number of semiconductor elements mounted on a single chip gradually increases, reaching several thousand or more at present. However, on the other hand, the number of external terminals on an IC is limited to about a few dozen to a hundred at most. Therefore, when trying to measure the electrical characteristics of an IC, the characteristics of semiconductor elements that can be directly measured using external terminals are extremely limited. There is no suitable method for measuring the characteristics other than a mechanical method using a microprober or the like. This mechanical measurement method using a microprober uses a contact made of an extremely thin tungsten wire, which is pressed against a measurement point on a semiconductor device and measures the potential at that point. etc. is detected. However, such a mechanical method does not have a very high positioning accuracy and has problems such as a large contact area with the semiconductor element due to the limit of the diameter of the contact. For example, in current ICs, the size of the semiconductor element is about 4 to 5 mm square, and the width of the aluminum wiring pattern is about 5 microns, but if the diameter of the tungsten contact was made as thin as this wiring pattern, the mechanical strength would be insufficient. It becomes fragile and difficult to handle. Further, the aluminum of the wiring pattern is extremely easily oxidized in the air, and the surface of the wiring pattern is usually covered with an oxide film. To measure potential, it is necessary to break the oxide film and bring the contact directly into contact with the internal wiring pattern, but this is impossible if the contact is fragile, so it is necessary to press the contact onto an insulator. This means that the potential of the internal wiring pattern is measured, which is subject to many errors. Furthermore, if the contactor is strong, there is a risk that the device to be measured may be destroyed by mechanical contact.

The present invention aims to improve this problem by irradiating an arbitrary part of the device to be measured with an electron beam and detecting the amount of secondary electrons emitted from the irradiated part. The potential of the relevant part is measured, and the quality is judged based on this.
According to this method, it is possible to easily measure the potential of any minute part inside the IC, and since there is no mechanical contact, by appropriately selecting the beam current and acceleration voltage, it is possible to easily measure the potential of any minute part inside the IC. neither will it destroy it.

The measuring device using an electron beam of the present invention includes a device that applies an input signal based on measurement conditions to irradiate an arbitrarily selected portion of a semiconductor device in an operating state with an electron beam, and a device that irradiates an arbitrarily selected portion of a semiconductor device with an electron beam to the electron beam irradiation device. a control means for outputting a signal for deflecting the electron beam to an arbitrarily selected portion and outputting a predetermined potential at the portion; and a control means for collecting secondary electrons emitted from the arbitrarily selected portion. A circuit that measures the potential of the part from the amount of secondary electrons compares the output potential of the potential measuring circuit with the planned potential from the control means, and depending on whether these potentials match or do not match, determines the potential of the part of the semiconductor element. The present invention will be described in detail below with reference to embodiments of the drawings.

FIG. 1 shows a measuring device according to the present invention, in which 1 is an electron gun, 2 is a focusing lens, 3 is an electron beam deflector,
4 is an integrated circuit to be measured, 5 is a beam deflection circuit, 6 is a secondary electron detection circuit, 7 is an input signal generation circuit, 8 is a signal conversion circuit, 9 is a coincidence circuit, and 10 is a control circuit.

Next, the measurement method will be described. The control circuit 10 inputs measurement conditions for the integrated circuit under test 4 prepared in advance to the input signal generation circuit 7. Input signal generation circuit 7
generates an input signal based on this measurement condition, which is input to the integrated circuit under test 4 to put this circuit into a normal operating state. For example, as shown in FIG. 3, the integrated circuit 4 has AND gates _G1 , _G2 , input terminals _t1 to
t ₃ and an output terminal t ₄ , _the circuit 7 inputs, for example, " ₁ ", " ₁ ",
Input a binary signal such as "1". As a result, the integrated circuit 4 has two AND gates G ₁ and G ₂ in the normal state.
One input and one output are all at high level, that is, "1". Next, the control circuit 10
outputs a signal instructing the X-axis and Y-axis deflection voltages necessary to project the electron beam to a measurement location, for example, point P in the integrated circuit 4, and inputs this signal to the beam deflection circuit 5. Further, the control circuit 10 outputs a predetermined potential at the measurement point, which has been determined in advance by a method such as simulation, which is "1" in this example, and inputs this to the reference value terminal of the matching circuit 9. The predetermined potential signal input to the matching circuit 9 may be taken from an electronic computer, which is appropriate when the integrated circuit 4 has a complicated circuit configuration because it does not increase the size of the control circuit 10.

When an electron beam 11 is emitted from an electron gun 1, the electron beam 11 is adjusted by a focusing lens 2 so that it is properly focused on an integrated circuit 4, and then is focused in a predetermined X-axis direction and Y-axis direction by an electron beam deflector 3. The beam is deflected by the beam and is correctly incident on the part to be measured on the integrated circuit 4. When the electron beam 11 is incident, reflected electrons, mainly secondary electrons, are emitted from the portion to be measured. Since this amount of secondary electrons has a strong correlation with the potential of the part to be measured, by setting this amount, the potential of the part to be measured can be determined conversely. The emitted secondary electrons are collected by a secondary electron detection circuit 6 and converted into a potential by a signal conversion circuit 8. This measured potential is input to the matching circuit 9, and the control circuit 9
It is compared with the predetermined potential value of the part to be measured input from , and a match or mismatch is determined. The matching circuit 9 outputs a signal indicating that the part to be measured of the integrated circuit 4 is normal when the two potentials match, and outputs an abnormal signal when they do not match. The control circuit 10 is normal,
After receiving the abnormal signal, it performs appropriate display or recording, then outputs the signals necessary to measure the next part of the integrated circuit 4 to be measured, and sends these to the input signal generation circuit 7 and the beam deflection circuit 5. Let them input.

Measure the potential of the next measured point in the same manner.
Judgment is made by a matching circuit. In this way, in this apparatus, the control circuit 10 can automatically measure a large number of integrated circuit parts one after another.

The accelerating voltage and beam current of the electron beam 11 are appropriately set so that each semiconductor element of the integrated circuit to be measured is not destroyed by the electron beam 11.
Since the electron beam 11 can be deflected freely and the beam diameter can be narrowed down to about 1 μm, the electron beam can be projected onto any minute part, such as a desired position on a narrow aluminum wiring pattern, and the measurement can be carried out. I can do it.

Measurements or inspections using electron beams have already been carried out, for example with electron microscopes. However, in the case of an electron microscope, a desired part of the object to be examined is scanned, so when this is used for inspecting integrated circuits, the semiconductor elements 4 of the integrated circuit 4 are scanned as shown in FIG.
A, 4b, and 4c, for example, 4b, are scanned by the electron beam, and a detector receives the secondary electrons emitted at this time.The output of this detector is input to the cathode ray tube via an amplifier, etc. It is necessary to display the secondary electron image of 4b and compare it with a planned secondary electron image simulated in advance to determine whether it is normal or abnormal. However, such a method involves a complicated operation of comparing images, and is not practical. In this respect, according to the present invention, since the potentials are compared, normality and abnormality can be easily determined using the matching circuit 9 having a simple circuit configuration.

As explained in detail above, the present invention focuses on the correlation between the amount of secondary electrons emitted when irradiated with an electron beam and the electric potential.
An electron beam is irradiated onto an arbitrary measurement location in the IC, and the potential is measured based on the amount of secondary electrons emitted from that location. Therefore, unlike mechanical measurement methods such as microprobers, potential can be measured without contact.
This method has the advantage that it is possible to easily detect the quality of the semiconductor element inside the IC, as well as disconnections and short circuits in the metal wiring portion, and that the measurement can be performed automatically.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a measuring device according to the present invention, and FIGS. 2 and 3 are explanatory diagrams of an integrated circuit to be measured. In the figure, 1, 2, 3, 5 are electron beam irradiation devices, 6, 8 are measurement circuits, 4 is an integrated circuit, 4a, 4
b, 4c are semiconductor elements, 9 is a coincidence circuit, and 10 is a control circuit.

Claims (1)

[Claims for Utility Model Registration] A device for irradiating an arbitrarily selected portion of a semiconductor device into an operating state with an electron beam by applying an input signal based on measurement conditions; outputs a signal to deflect the electron beam to the
and a control means for outputting a predetermined potential in the portion; a circuit that collects secondary electrons emitted from the arbitrarily selected portion and measures the potential of the portion from the amount of secondary electrons; and the potential measurement. A matching circuit that compares the output potential of the circuit with a predetermined potential from the control means and determines the quality of the corresponding part of the semiconductor element based on the match or mismatch of these potentials. Measuring device.