JPH0479252A - Integrated circuit testing device - Google Patents

Abstract

PURPOSE:To allow highly accurate voltage measurement without analysis characteric difference lay mounting a substrate to be mounted with a testing LSI on a movable stage and shifting the movable stage so as to permit the gravity center of a measuring pad to nearly coincide with the deflection center coordinate. CONSTITUTION:While operating a movable stage manual operating part 31 and observing an SEM image, a movable stage 26 is shifted so as to permit a measuring pad 4A to be positioned within the area which allows an electric beam 15 to be deflected. The stage coordinate of the deflection center position at such time is supplied to one of the input terminal of an adding machine. Then, the electron beam 15 is used to scan and the gravity center coordinate of the measuring pad 4A is calculated. The gravity center coordinate is converted into a scale for a stage coordinate system by a scale converting circuit 34 and a coordinate where the deflection center axis of the electronic beam 15 is to be positioned is obtained by the adding machine 35. The coordinate is supplied to a movable stage shift control circuit 30 and a movable stage 26 is controlled by a movable stage shifting mechanism 29 so as to permit the gravity center position of a measuring pad 4a to almost coincide with the electronic beam deflection center axis.

Description

[Detailed Description of the Invention] [Summary] An integrated circuit testing device, more specifically, an integrated circuit testing device, in particular,
For example, regarding an integrated circuit testing device that uses an electron beam and is suitable for testing the characteristics of a multi-pin integrated circuit packaged using a PGA container, A simple board with a wiring structure consisting of external pins of the integrated circuit under test and time-pitch measurement pads can be used as the mounting board, and high-precision voltage measurement with no difference in analysis characteristics can be used. A movable stage is provided, the substrate is mounted on the movable stage, and the coordinates of the center of gravity of the measurement pad that is the object of voltage measurement among the measurement pads are aligned with the central axis of deflection of the electron beam. After the movable stage is moved so as to substantially coincide with each other, the voltage measurement can be performed on the measurement pad that is the target of the voltage measurement.

[Industrial Application Field] The present invention relates to an integrated circuit testing device, more specifically, an integrated circuit (hereinafter referred to as LSI), particularly, for example, a PGA test device.
The present invention relates to an integrated circuit testing device using an electron beam, which is suitable for testing the characteristics of an LSI with a multi-pin structure packaged using a (pin grid array) container.

[Prior Art] Conventionally, an integrated circuit testing device, the main part of which is shown in FIG. 4, has been proposed.

In the figure, 1 is a lens barrel, 2 is an opening formed in the lens barrel 1, 3 is a substrate made of ceramic that is immovably mounted on the lens barrel 1 so as to close the opening 2, and 4 is a base plate of the substrate 3. A measurement pad formed on the lower surface, 5 a socket fixed to the upper surface of the board 3, and 6 an LSI to be tested mounted on the socket 5.
This LSI 6 is packaged in a PGA container. In addition, 7 is an LSI drive circuit that drives the LSI 6, and 8 is a control circuit that controls the entire system.

Here, the input/output pin 9 of the LSI 6 is connected to the measurement pad 4 via a wiring 10 in the socket and a wiring 11 in the board 3. Further, all or part of the wiring 11 within the substrate 3 is branched within the substrate 3 and connected to the LSI drive circuit 7 via an external wiring 8112. This is intended to drive the LSI 6 via the external wiring 12.

In addition, since the substrate 3 is mounted in a fixed position relative to the lens barrel 1, the measurement pads 4 are arranged in a matrix or in a range within which the electron beam (described later) can be deflected and scanned, for example, within a range of 2 to 3 mm. They are concentrated in a staggered pattern. Therefore, the substrate 3 has a complicated multilayer wiring structure.

Note that reference phase voltage data, strobe signals, etc. are supplied from the LSI drive circuit 7 to the control circuit 8, and voltage data of the measurement pad 4, etc. are supplied from the control circuit 8 to the LSI drive circuit 7.

Further, 13 is an exhaust pump for exhausting the inside of the lens barrel 1;
4 is an electron gun that generates an electron beam, 15 is an electron beam generated from the electron gun 14, and 16.17 is an electron beam 15.
18 is an electron beam pulse gate that chops the electron beam 15 and forms it into a pulse, a so-called EB pulse gate; 19 is an EB pulse gate driver that drives the EB pulse gate 18, a so-called gate driver. , this gate driver 19 is configured to drive the EB pulse gate 18 based on the EB pulse generation phase control signal supplied from the control circuit 8.

Further, 20 is a deflection coil that deflects the electron beam 15;
1 is a deflection driver that drives this deflection coil 2o, and this deflection driver 21 is configured to drive the deflection coil 20 based on a deflection position control signal supplied from a control circuit 8.

In addition, 22 is a measuring pad 4 which is irradiated with an electron beam 15.
23 is an energy analyzer that controls the passage of the secondary electrons 22 based on the analysis voltage and makes it possible to measure the voltage of the measurement pad; 24 supplies the analysis voltage to the energy analyzer 23; The analysis voltage generator 24 is configured to generate an analysis voltage based on an analysis voltage control signal supplied from the control circuit 8 .

Further, 25 is a secondary electron detector that detects the secondary electrons 22 that have passed through the energy analyzer 23 and outputs an electric signal with an intensity corresponding to the energy of the secondary electrons 22, a so-called secondary electron signal. The secondary electronic signal is configured to be supplied to the control circuit 8.

In such an integrated circuit testing apparatus, the LSI 6 is driven by the LSI driving circuit 7 during testing.

On the other hand, an electron beam 15 is generated from the electron gun 14, pulsed by the EB pulse gate 18, deflected and scanned by the deflection coil 20, and irradiated onto each measurement pad 4. Here, secondary electrons 2 from measurement pad 4
2 is extracted, passes through an energy analyzer 23 and is detected by a secondary electron detector 25 to obtain a secondary electron signal, and the voltage of the measurement pad 4 is measured from the magnitude of this secondary electron signal. (See Japanese Patent Application No. 01-1271).

An integrated circuit testing device using such an electron beam has the advantage of being able to easily perform characteristic tests on multi-pin structured LSIs packaged in PGA containers, for which it is difficult to use so-called probes. ing.

[Problems to be Solved by the Invention] However, in the conventional integrated circuit testing apparatus shown in FIG. Since the electron beam 15 is attached to a
It is necessary to form the required number of measurement pads 4 within a 3 mm opening. For example, in order to test an LSI having a 20×20 pin structure with a total of 400 pins, it is necessary to form a 20×20 measurement pad 4 in a 2 to 3 mm opening.

In order to cope with this, it is necessary to make the board 3 a complex and fine multilayer wiring structure, and this board 3 also has a
It must be able to sufficiently withstand atmospheric pressure when the inside of the lens barrel 1 is evacuated, and for this purpose, it is necessary to be made of ceramic. As a result, in the conventional integrated circuit testing apparatus shown in FIG. 4, a large amount of cost is required to prepare the substrate 3, which has been a problem.

Furthermore, the number of pins in LSIs with a multi-pin structure packaged in a PGA container is increasing.
Figure: A board like the one used in the conventional example, in which measurement pads are concentrated in the electron beam deflection and scannable area, requires complicated wiring and miniaturization, making the wiring even more complicated than the current one. , it is technologically almost impossible to achieve miniaturization.

Therefore, for the board on which the LSI to be tested is mounted, a board with a simple structure is used to reduce the cost of manufacturing the board, and the integrated circuit is configured so that it can support the further increase in the number of pins of the LSI. There was a request to develop a test device.

If it is possible to use a substrate with a simple wiring structure, which has external pins of the LSI to be tested and time-pitch measurement pads formed thereon, this requirement can be met.

However, in this case, the area where the measurement pad is formed on the lower surface of the substrate becomes much wider than the area where the electron beam can be deflected and scanned.

Therefore, the inventor provided a movable stage in the lens barrel, mounted the board on which the LSI to be tested is mounted on this movable stage, divided the measurement pad forming area into several regions, and moved the movable stage. We developed an integrated circuit testing device that can measure the voltage of a measurement pad by scanning an electron beam in each divided measurement pad formation area.

However, in such integrated circuit testing equipment, there is a difference in analysis characteristics between measurement pads that coincide with or near the central axis of electron beam deflection and measurement pads that are distant from the central axis of electron beam deflection. We have newly discovered that there is a problem in that it is not possible to perform highly accurate voltage measurements.

In view of this point, the present invention makes it possible to use a board with a simple wiring structure in which external pins of the LSI to be tested and time-pitch measurement pads are formed as a board on which the LSI to be tested is mounted. Moreover, it is an object of the present invention to provide an integrated circuit testing device that can perform highly accurate voltage measurements without any difference in analytical characteristics.

[Means for Solving the Problems] The integrated circuit testing apparatus according to the present invention has an electron beam irradiation mechanism 14, 16, 17 inside thereof, for example, to explain its components in accordance with FIG. 1 of the embodiment drawings. .18.2
0 and an opening 2 formed in the electron beam irradiation direction, and a lens barrel 1 that surrounds the opening 2 on the outside of the lens barrel 1 and is two-dimensional in a direction perpendicular to the central axis of deflection of the electron beam 15. A movable stage 26 is mounted on the movable stage 26 to close the opening 2 and close the lens barrel 1.
The LSI 6 to be tested is attached to the outer part of the lens barrel via the socket 5, and the measurement pad 4, which is electrically connected to the external pin 9 of the LSI 6, is attached to the inner part of the lens barrel. A substrate 28 formed by the pitch of the external pins 9 and a pitch of time -, an energy analyzer 23 that analyzes the energy of the secondary electrons 22 emitted from the measurement pad 4 by irradiation with the electron beam 15, and this energy analyzer 23. a secondary electron detector 25 that detects the secondary electrons 22 that have passed through the device 23 as a secondary electron signal; and a movable stage positioning means 27 that positions the movable stage 26.
The movable stage positioning means 27 moves the movable stage 26 so that the measurement pad that is the object of voltage measurement among the measurement pads 4 is located within the deflectable region of the electron beam 15, and then moves the electron beam. Through processing of the secondary electron signal obtained by scanning the electron beam 15, the barycenter coordinates in the stage coordinate system of the measurement pad that is the object of voltage measurement are calculated, and the deflection center coordinates of the electron beam 15 are made to approximately match the barycenter coordinates. The structure is such that the movable stage 26 can be moved at any time.

[Function] In the present invention, the movable stage 26 is provided, the board 28 to which the LSI 6 to be tested is mounted is mounted on the movable stage 26, and the center of gravity of the measurement pad to be measured for voltage among the measurement pads 4 is set. Since the movable stage 26 can be moved so that the coordinates substantially coincide with the deflection center coordinates of the electron beam 15, it is possible to move the movable stage 26 so that the measurement pads 4 are concentrated in the area where the electron beam 15 can be deflected. Even if it is not used, a substrate 28 with a simple structure in which the measurement pads 4 are formed at a pitch equal to the pitch of the external pins 9 of the LSI 6 can be used.

Moreover, according to the present invention, since the electron beam 15 can be irradiated with the same polarization to all the measurement pads that are the targets of voltage measurement, it is possible to perform highly accurate voltage measurement without any difference in analytical characteristics. can.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3. In FIG. 1, parts corresponding to those in FIG. 4 are denoted by the same reference numerals, and redundant explanation thereof will be omitted.

FIG. 1 is a conceptual diagram showing the main parts of an embodiment of the present invention,
This embodiment is different from the conventional example shown in FIG.
A movable stage 26 is provided which is arranged to be two-dimensionally movable in a direction perpendicular to the central axis of deflection. (2) A movable stage positioning means 27 for moving and positioning the movable stage 26 is provided. (1) As a board on which the LSI 6 is mounted, a board 28 with a simple wiring structure consisting of external pins 9 formed on the LSI 6 and time-pitch measurement pads 4 is prepared, and this board 28 is used as a movable stage. 26, and the other features are the same as the conventional example shown in FIG.

Here, the movable stage positioning means 27 includes a movable stage moving mechanism 29 that moves the movable stage 26, a movable stage movement control circuit 30 that controls the movement of the movable stage 26 by the movable stage moving mechanism 29, and a movable stage movement control circuit 30 that controls the movement of the movable stage 26. a movable stage manual operation unit 31 that can manually operate the movement of the movable stage 26 via the control circuit 30;
The coordinates of the center of gravity of the measurement pad to be measured in the stage coordinate system are calculated, and this is calculated by the movable stage movement control circuit 30.
A measuring pad/stage coordinate system barycenter coordinate calculation circuit 32 is provided for supplying the electron beam 15 to the center of gravity of the measurement pad and aligning the center axis of deflection of the electron beam 15 with the coordinates of the center of gravity of the measurement pad. Note that the movable stage movement control circuit 30 controls the current electron beam 15.
Adder 3 stores the deflection center coordinates of
5 is configured to be supplied to one input terminal of 5.

This measurement pad/stage coordinate system gravity center coordinate calculation circuit 32
a measurement pad/electron beam deflection coordinate system barycenter coordinate calculation circuit 33 that calculates the barycenter coordinate in the electron beam deflection coordinate system of the measurement pad that is the object of voltage measurement from the secondary electron signal and the deflection position control signal; A scale conversion circuit 34 converts the χ and Y components of the barycenter coordinate of the measurement pad, which is the object of voltage measurement, obtained by the measurement pad/electron beam deflection coordinate system barycenter coordinate calculation circuit 33 to the scale of the stage coordinate system, and It is configured by providing a container 35. This adder 35 adds the deflection center coordinates of the electron beam 15 supplied from the movable stage movement control circuit 30 and the gravity center coordinates of the measurement pad that is the subject of scale-converted voltage measurement. This is to calculate the stage coordinates where the coordinate axes should be located.

2 and 3 are diagrams used to explain the positioning method of the movable stage 26, and FIG. 2 shows an SEM (scanning electron microscope) image of a portion of the lower surface of the substrate 28. The size of this SEM image corresponds to the deflectable region of the electron beam 15.

Further, FIG. 3 is a diagram showing the relationship between the stage coordinate system and the electron beam deflection area. In addition, 4A is the measurement pad 4,
In particular, it shows the measurement pad that is the object of voltage measurement.

In this embodiment, first, the movable stage manual operation section 3
1 and while observing the SEM image, as shown in FIG.
The stage coordinates (Xs, Ys) of the deflection center position of the electron beam 15 at this time when the movable stage 26 is moved so as to be located within the deflectable region are supplied to one input terminal of the adder 35. Furthermore, this movable stage 2
Movement 6 can also be performed automatically. In this case, a voltage different from that of the other measurement pads, for example, a voltage several times lower than that of the other measurement pads, is applied to the measurement pad 4A to obtain a stage scanning image. Calculate and use the measurement pad 4A from this result.
The movable stage 26 may be automatically moved so that the electron beam is located within the electron beam deflectable region.

Next, the electron beam 15 is scanned, and the barycenter coordinate (XB
, Ya). In this way, this measurement pad/electron beam deflection coordinate system barycenter coordinate calculation time Ft
Center of gravity coordinates obtained at @33 (XB, YB)
In the scale conversion circuit 34, the X component and Y component of
Converted to scale in stage coordinate system. Here, if α and β are coefficients in the X direction and Y direction that correspond to the stage coordinate system and the electron beam deflection coordinate system, respectively, then the output of the scale conversion circuit 34 is (aXB, βYB)
becomes.

Therefore, in the adder 35, (XS, Ys)
+ (aXB, βYa) is performed, and (XS +
The following result can be obtained: (ZXB, Y5+βYa). These coordinates (Xs+αXB, Ys+βYB) are the coordinates where the deflection center axis of the electron beam 15 should be located, so these coordinates are supplied to the movable stage movement control circuit 30, and the movable stage movement control circuit 30
The deflection center coordinates of 5 are the coordinates (X s + αX B , Y
The movable stage moving mechanism 29 is controlled so that the movable stage 26 is moved so as to be s+βYll), that is, as shown by a vector 37 in FIG. Here, measuring pad 4
Since the barycenter coordinates of A and the deflection center coordinates of the electron beam 15 substantially match, the measurement pad 4A can then be irradiated with the electron beam 15 and the voltage of the measurement pad 4A can be measured. Thereafter, for other measurement pads to be measured, the movable stage 29 can be moved and positioned in the same manner, and the voltage can be measured.

According to this embodiment, the movable stage 26 is provided, the substrate 28 is mounted on the movable stage 26, and the inside of the measurement pad 4 is
The movable stage 26 is moved so that the center of gravity of the measurement pad 4A, which is the object of voltage measurement, approximately coincides with the central axis of electron beam deflection.
By having a configuration that allows the fourth
Figure 3: A substrate 3 with a complicated wiring structure in which the measurement pads 4 are concentrated in the area where the electron beam 15 can be deflected, as in the conventional example.
It is possible to use a substrate 28 with a simple wiring structure in which the measurement pads 4 are formed at a pitch equal to the pitch of the external pins 9 of the LSI 6 and the pitch of the external pins 9 of the LSI 6. Since all of the pads 4A can be irradiated with the electron beam 15 with the same polarization, highly accurate voltage measurements with no difference in analytical characteristics can be performed.

[Effects of the Invention] As described above, according to the present invention, a movable stage is provided,
LSIt - the board to be tested is mounted on the movable stage, and the movable stage is moved so that the center of gravity coordinates of the measurement pad that is the target of voltage measurement among the measurement pads approximately coincides with the electron beam deflection center coordinates. By adopting a configuration that allows measurement pads to be placed in a concentrated area within the area where the electron beam can be deflected, it is not necessary to use a board with a complicated wiring structure, and the measurement pads can be placed at the same pitch as the external pins of the LSI. It is possible to use a substrate with a simple wiring structure made of It is possible to perform high-precision voltage measurements without any noise.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the main parts of an embodiment of the present invention, FIG. 2 is a diagram showing a SEM image of the bottom surface of the substrate, and FIG. 3 is a diagram showing the relationship between the stage coordinate system and the electron beam deflectable area. , FIG. 4 is a conceptual diagram showing the main parts of a conventional integrated circuit testing device. 26...Movable stage 27...Movable stage positioning means 28...Substrate

Claims (4)

[Claims] (1) A lens barrel in which an electron beam irradiation mechanism is provided and an opening is formed in the electron beam irradiation direction, and the opening is surrounded on the outside of the lens barrel and is perpendicular to the central axis of deflection of the electron beam. a movable stage disposed so as to be two-dimensionally movable in a direction of
The integrated circuit to be tested is attached to the outer part of the lens barrel via a socket, and the measurement pad electrically connected to the external pins of the integrated circuit is attached to the inner part of the lens barrel. A substrate formed with substantially the same pitch; an energy analyzer that analyzes the energy of secondary electrons emitted from the measurement pad by irradiation with the electron beam; A secondary electron detection means for detecting as a secondary electron signal and a movable stage positioning means for positioning the movable stage are provided, and the movable stage positioning means is configured to detect a measurement pad to be subjected to voltage measurement among the measurement pads. After moving the movable stage to be located within the deflectable region of the electron beam, the measurement pad that is the object of the voltage measurement is processed through the processing of the secondary electron signal obtained by scanning the electron beam. An integrated circuit test characterized in that the movable stage is configured to calculate barycenter coordinates in a stage coordinate system and move the movable stage so that the deflection center coordinates of the electron beam substantially match the barycenter coordinates. Device. (2) The movement of the movable stage to position the measurement pad, which is the object of the voltage measurement, within the deflectable region of the electron beam can be performed through manual operation while observing a scanning electron microscope image. 2. The integrated circuit testing apparatus according to claim 1, wherein the integrated circuit testing apparatus is configured as follows. (3) Move the movable stage to position the measurement pad, which is the object of the voltage measurement, within the deflectable region of the electron beam, with respect to the measurement pad, which is the object of the voltage measurement, with respect to other measurement pads. The method is configured to obtain approximate stage coordinates of the measurement pad from a stage scanning image obtained by performing stage scanning while applying different voltages, and to automatically perform the process based on this result. The integrated circuit testing device according to claim 1, characterized in that: (4) Calculation of the barycentric coordinates in the stage coordinate system of the measurement pad that is the target of the voltage measurement is performed after calculating the barycentric coordinates in the electron beam deflection coordinate system with the deflection center axis of the electron beam as the origin. This can be done by converting the X and Y components of the center of gravity coordinates to the scale of the stage coordinate system, and then adding the scale-converted center of gravity coordinates to the coordinates of the electron beam deflection center axis expressed in the stage coordinate system. Claim 1 characterized in that:
Integrated circuit test equipment as described.