JPH1167854A - Wafer prober - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fully cope with severe requirements on space and operability which will be brought about by switchover to a 12-inch wafer in the near future, on testing electrical performances in a semiconductor element area of a wafer. SOLUTION: A probe head assembly 20 is connected electrically to a multimeter for determining the electrical characteristics of a semiconductor element area, while the probe head assembly 20 is provided with probe needles which point to the semiconductor element area of a wafer WF. A chuck 5 for loading and holding the wafer WF is made of a fixed type, and the probe head assembly 20 is moved horizontally, at least from the end of connection to the tester, as a basic point, by a drive mechanism (multi-axis robot or X-Y direction drive linear motor). The probe head assembly 20 driven by the drive mechanism is moved horizontally and sequentially makes tests of the semiconductor element area of the wafer loaded and held on the chuck 5 of the fixed type, through the probe needles thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer prober and, more particularly, to a space plane in a system for testing the electrical characteristics of a semiconductor device area partitioned in parallel on a wafer by a probe needle connected to a tester. This is a proposal with a view to a shift to a larger wafer diameter in the not-so-distant future.

[0002] In this specification, the term "semiconductor element region" refers to a circuit unit having the same circuit configuration which is partitioned by scribe lines on a wafer and arranged in a matrix, and is used for testing electrical characteristics. It is later cut along a scribe line to become a semiconductor element such as an IC chip.

[0003] In this specification, the "X, Y, Z directions" refer to three-dimensional directions orthogonal to each other, and in the following description, the XY directions are horizontal directions, and the Z directions are vertical directions.

[0004]

2. Description of the Related Art There are a serial method and a parallel method for testing the electrical characteristics of a plurality of semiconductor element areas formed in a matrix on a wafer. In any case, a probe needle connected to a tester and a wafer are tested. It is necessary to sequentially move the semiconductor element area relative to the semiconductor element area so that the probe needle contacts a large number of pads formed in each semiconductor element area. Conventionally, a system as shown in FIGS. 5 and 6 is generally employed for this test. This test system includes a tester 11, a probe card 7 electrically connected to the tester 11, and a prober 1 attached to the probe card 7 (downward in the example in the figure).

[0005] The tester 11 has a timing required for a test,
Outputs electrical signals including levels and logic elements. Further, the electric signal output from the semiconductor element area is input to the comparison unit of the tester 11, and the level and the logic are determined.

The probe card 7 is electrically connected to a tester 11 by a cable 10 for signal transmission, and the number of probe needles 9 pointing to the semiconductor element area of the wafer, the number required for one test, usually each semiconductor The same number of bonding pads as the number of bonding pads formed in the element area are provided. Each probe needle 9 contacts a bonding pad formed on a corresponding semiconductor element area on the wafer to transfer an electric signal. The electric signal output from the tester 11 is transmitted to the semiconductor element area of the wafer via the probe needle 9 of the probe card 7. The output electric signal from the semiconductor element area is transmitted to the tester 11 through the reverse route.

An X, Y stage 3 is provided on the prober 1 in a horizontal direction, and a chuck 5 is mounted on the X, Y stage 3.
And is driven by an appropriate drive mechanism (not shown) to move at least in the XY directions. The upper surface of the chuck 5 is configured to be able to place and hold the wafer WF by vacuum suction or the like. When working, chuck 5 each time
Is moved by a required distance in the X and Y directions, the number of semiconductor element areas covered by the movement is tested, and this movement is repeated as many times as necessary until all the semiconductor element areas on the wafer are tested. .

[0008]

However, in the case of the test system using the conventional movable chuck, it is necessary to secure a very large area for moving the chuck. A major problem arises in terms of gender. In particular, the current wafer size is 8
12 inches (3 cm) in the future not far from inches (20 cm)
0 cm), and these problems become more serious as the wafer size increases. Hereinafter, the securing of the movement area when the movable chuck is used will be described in detail with reference to examples.

In examining the movement area of the chuck, it is necessary to take into consideration the assumptions inherent in the test using the wafer prober. In other words, in the test of the same contents, it is necessary to avoid repeating the same semiconductor element region twice or more in order to improve the working efficiency.
In addition, if one test is performed for a semiconductor element area and two tests are performed for another semiconductor element area, there will be a difference in the statistical accuracy of the test results. That is, the same semiconductor element area must not contact the probe needle of the probe card more than once.

Consider the most severe movement condition expected under this premise, that is, the case where the movement distance of the wafer becomes the largest. FIG. 7 shows the probe card 7 and the wafer W
F is modeled and shown. It is assumed that the probe card has four channels (Nos. 1 to 4) and a size T in the relative movement direction. Wafer has six semiconductor device areas (NO. 1 to 6)
Are arranged side by side in the relative movement direction, and the size in the movement direction is W. The size of the semiconductor element area in the relative movement direction is C. Although several tens of semiconductor element regions are formed on the actual wafer in the moving direction, in order to facilitate understanding in the drawings, as described above, six semiconductor element regions are formed in the relative moving direction. Is formed.

In FIG. 8, the semiconductor device areas 1 to 4 are tested first, and then the wafer is moved to the left.
Suppose you want to test. The moving distance D1 in this case is (2W
-C).

Similarly, in FIG.
6, the semiconductor device area 1 is tested after the wafer is moved to the right. The moving distance D2 in this case is equal to (2WC).

If the above-mentioned left and right movements are summarized as shown in FIG. 10, the required total movement distances are D1 and D
By subtracting the overlap W of D1 and D2 from the value obtained by adding 2, the following equation is obtained.

[0014]

(Equation 1)

However, in addition to the chuck, there are various auxiliary parts (not shown) on the prober, and it is necessary to take into consideration the space for these parts. It is necessary to secure in both the X and Y directions, and the state is as shown in FIG. For example, for an 8 inch (20 cm) wafer, 60 cm ×
The moving area of 60 cm is 9 for a 12-inch wafer.
It is necessary to secure a moving area of 0 cm × 90 cm.

Since the moving area of the chuck usually occupies a considerable portion on the prober, the large moving area means that the occupied space of the prober becomes large. The floor cost in a semiconductor product manufacturing plant accounts for a relatively large proportion of the manufacturing cost and cannot be ignored. Accordingly, the need to secure a large chuck moving area as described above is a significant negative factor in terms of manufacturing cost when the wafer is 12 inches.

Further, the enlargement of the wafer has a problem in workability. Worker M at the time of test by wafer prober
Are located on the side opposite to the test main frame 13 with respect to the prober 1 as shown in FIG. The distance from the worker to the tester head 15 across the prober 1 is about 100 cm even in the case of an 8-inch wafer in consideration of the necessity of securing the moving area of the chuck as described above. This intervening distance is large enough for the small-sized worker M to reach the tester head 15. Therefore, when the wafer has a size of 12 inches, it is almost impossible for the operator to reach the tester head 15, that is, to perform an appropriate operation.

In view of the state of the prior art, an object of the present invention is to test the electrical performance of a semiconductor device area of a wafer, and to provide space and workability caused by a shift to a larger wafer in the near future. An object of the present invention is to provide a wafer prober which can sufficiently cope with the strict requirements on the above.

[0019]

According to the present invention, there is provided a tester for measuring electrical characteristics of a semiconductor device area, a fixed chuck for mounting and holding a wafer, and a tester electrically connected to the tester. The probe head assembly is provided with a probe needle which is oriented so as to be able to contact a pad formed on the semiconductor element area, and a drive mechanism for moving the probe head assembly at least in a horizontal direction is provided.

[0020]

The probe head assembly driven by the driving mechanism moves in the horizontal direction, and sequentially tests the semiconductor element area of the wafer mounted and held on the fixed chuck through the probe needle.

[0021]

FIG. 1 shows a basic configuration of a wafer prober according to the present invention. Probe head assembly 20
Has a set of a plurality of probe heads 21 arranged in parallel and a cable 25 for electrically connecting each probe head 21 to a tester (not shown) via a connector 23.
In the present embodiment, the probe head assembly 20 faces the fixed chuck 5 capable of mounting and holding the wafer WF on the upper surface thereof from above, and is driven by a drive mechanism (not shown). By moving in the Y direction, the electrical performance of the semiconductor device area of the wafer WF held on the fixed chuck 5 is sequentially tested.

It is desirable to use a coaxial cable, and more preferably a flexible flat cable, as the cable 25, so that a cable that is small and easy to bend can be obtained, and radiation loss and external disturbance can be effectively avoided. . As the connector 23 used in combination with the cable 25, it is preferable to use a coaxial connector, and further, a standardized connector that facilitates connection with the flat cable described above. The coaxial connector has an unified standard, which is advantageous for replacement maintenance.

Next, an example in which a module type probe head, that is, a probe head modularized by mounting a circuit element of a noise filter circuit on the probe head assembly 20 will be described with reference to FIGS. FIG.
3 and 3, the probe head 21 has a base holder 211, and a predetermined wiring 220 is formed on the surface of the base holder 211 (only one part is shown in FIG. 3). This wiring has a connector side end 220a connected to the above-described connector 23 and a needle side end 220b connected to the probe needle, and transmits a signal from the tester to the probe needle 215 via the connector 23. It is configured as follows. Further, circuit elements such as a bus line, a capacitor, and a relay, which will be described later, are also connected to the wiring 220 at a portion (not shown). This base holder 2
A filter relay base 219 is attached to the surface on which the eleventh wiring 220 is formed.
3, a ground-side bus line 214, a relay 217, and a bypass capacitor 218 are mounted. The power probe needle 215a and the ground probe needle 215b are connected to the power bus line 213 and the ground bus line 214, respectively. A plurality of power probe needles 215a and ground probe needles 215b are provided in one corresponding semiconductor element area, that is, one bus line, and these power supply side bus line 213 and ground side bus line 21 are provided.
4 is the plurality of probe needles 215a and 215a
15b serves as a bus connecting them to each other.
In the drawings, the probe needle 2 is used for easy understanding.
15a and 215b are shown only once in one semiconductor element area. Further, the relay 21 is placed on the filter relay base 219 at a position above the bypass capacitor 218.
7 is directly mounted. In the present embodiment, 1
Power supply side bus line 21 for each probe head 21
3, four units are arranged side by side with the ground-side bus line 214, the bypass capacitor 218 and the relay 217 as one unit, and this one probe head 21 enables testing of four semiconductor element areas.

As shown in FIG. 4, eight probe heads 21 shown in FIG. 3 are held side by side on a support 221 which is shown with one part cut away. On the upper surface of the support 221, the number of connectors 23 corresponding to the probe head 21, that is, eight, is provided. Have been. Each connector 23 has a flat cable 25 for connection to a tester.
(Note that only one cable 25 is shown, and the other seven are omitted.) The modularized probe head assembly 20 is constituted by these structures shown in FIG. Although eight probe heads 21 are mounted in the illustrated example, the number of mounted probe heads is not limited to this. The number is appropriately and freely set according to the specification of the test to be performed.

By using the modular probe head assembly as described above, if the probe needle is damaged or worn out during use and needs to be replaced, only the probe head to which the probe needle belongs needs to be replaced. There is no need to replace the entire probe head assembly. For this reason, the maintainability is greatly improved.

Further, since the operation of attaching the probe can be divided, the operation of replacing the probe with a new probe can be sped up. For example, in order to attach 64 probe needles, if they are not modularized, they must be attached one by one one by one. However, when modularized, for example, the probe heads can be divided into eight probe head groups and the mounting of the probe needles in each group can be performed in parallel.

For example, even if the number of simultaneous tests in the parallel test is changed, the number of probe heads 21 can be increased or decreased to flexibly cope with the change. That is, the degree of freedom in changing the test specifications increases.

By the way, as described above, the most severe moving condition, that is, the case where the moving distance is the longest, when the fixed type chuck and the movable type probe head assembly are combined will be examined. FIG. 12 shows a model of the probe head 21 and the wafer WF. As in the case of the above-described prior art, it is assumed that the size of the probe head in the relative movement direction is T, the size of the wafer in the movement direction is W, and the size of the semiconductor element region in the relative movement direction is C. .

In FIG. 13, it is assumed that the test is performed with the leftmost movement, and then the test is performed with the most rightward movement. The total moving distance D 'in this case is given by the following equation.

[0030]

(Equation 2)

That is, as shown in FIG. 15, it is necessary to secure a movement area of only D 'in the X and Y directions. For example, an 8 inch (20 cm) wafer is converted into 4 channels (4c).
28cm x when testing with the probe head of m)
It is sufficient to secure a moving area slightly larger than 28 cm (taking into account the additional components). 60c of the conventional case described above
It may be much smaller than the value of mx 60 cm. By the way, when testing a 12-inch (30 cm) wafer with a 4-channel (4 cm) probe head, it is sufficient to secure a movement area slightly larger than 38 cm × 38 cm. Similarly, since the moving area to be secured in the case of the prior art is 90 cm × 90 cm, the size of the moving area to be secured is significantly reduced in the case of the present invention.

The probe head assembly 20 moves by being driven by a driving mechanism. The movement by the driving mechanism is performed at least in the horizontal direction.

Although various types of drive mechanisms are conceivable, FIGS. 16 to 18 show an embodiment using a multi-axis robot. By using the multi-axis robot, the probe head assembly can be positioned with respect to the wafer with high accuracy.

In the figure, a multi-axis robot 30 (in this case, two axes) has two arms 31 and 33 pin-connected to each other at the ends, and a probe head 21 is provided at the tip of the arm 33. Supported. In this embodiment, the probe head 21 is driven by the multi-axis robot 30 to move in the X and Y directions.

The turning range of the multi-axis robot 30 shown in FIG. 18 is 300 mm and the wafer size is 8 inches (200 mm).
In the case of, 500 mm in the X direction and 300 mm in the Y direction
The probe head 21 can test all the semiconductor device areas on the wafer WF by the movement of.

FIG. 19 shows an example of the configuration of a test system when a multi-axis robot is used. The loader 40 takes out the wafer in the wafer storage cassette 41 after the completion of the wafer test, and places the wafer on the chuck 5 after detecting the notch. The wafer after the predetermined test is sent to the cassette 41 by the loader 40 and then stored in the storage section 43.

Next, as another embodiment, FIG. 20 shows an example of a configuration in which a linear motor is used as a driving mechanism. When using the above-described multi-axis robot, a relatively expensive robot is required to drive a heavy head assembly with high positioning accuracy,
In the case of a linear motor, a high overload can be driven by nature, so that it can be configured relatively easily.

In the figure, the probe head 21 is attached to the surface of the X-direction block 51 by a magnet block 50. The X-direction block 51 is connected to an output shaft of an X-direction drive linear motor (not shown) via an X-direction beam 52. In order to make this connection freely connectable and detachable, X
It is desirable to use an electromagnet for the directional beam 52. The X-direction block 51 is attached to the lower surface of the Y-direction block 53 so as to be relatively movable. This Y-direction block 53
Is connected to an output shaft of a Y-direction drive linear motor (not shown) via a Y-direction beam 54. It is desirable to use an electromagnet also for the Y-direction beam 54 so that the connection can be freely moved.

Driven by the X-direction drive linear motor, the probe head 21 moves in the X-direction along the Y-direction block 53 together with the X-direction block 51. The probe head 21 is driven by the Y-direction drive linear motor to move in the Y direction together with the Y block 53 and the X direction block 51. The position of the chuck 5 on which the wafer is placed is measured by, for example, a known laser interference method. The relative movement between the head assembly and the wafer WF in the X and Y directions is made possible by using the above-described multi-axis robot or linear motor as a driving mechanism. It is preferable to move the wafer WF up and down by moving the wafer WF up and down. It is not preferable to configure the driving in the Z direction as one mechanism in addition to the driving mechanism in the XY directions as described above, since the driving mechanism becomes large when the head assembly becomes relatively heavy.

[0040]

According to the present invention, the probe head side is movable with respect to the movement in the X and Y directions while the wafer held by the chuck is fixed. The moving area to be secured can be greatly reduced. Therefore, the floor space can be efficiently used, and the burden on the worker is greatly reduced. Due to these excellent effects, it is possible to avoid various problems in terms of space, workability, and manufacturing cost even when migrating to a 12-inch wafer, and to deal with it smoothly.

The maximum number of pins of the current tester is 1400 pins,
The maximum number of simultaneous tests calculated from the number of pins of the memory device is 32. If this is realized by the wafer prober of the present invention using a movable probe head assembly, the size will be 100 mm × 100 mm. When realized with a probe card using a conventional movable chuck, a circular shape of 250 mm or 300 mm is standard, and therefore, according to the present invention, space utilization is very efficient and movement is easy. .

By using a coaxial connector for the connection cable to the tester and the connection to the probe head, the tester head can be easily replaced and stored. When a coaxial cable is used, since a fine coaxial cable having high flexibility is used, it can withstand a stress caused by moving the probe head more than one million times.

In the case of the wafer prober using the movable probe head of the present invention, the moving space can be reduced by 50% or more as compared with the case where the conventional movable chuck is used. This can reduce the prober body size by about 40%.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an overall configuration of a wafer prober of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of an embodiment M of a probe head used for the wafer prober.

FIG. 3 is a perspective view of the same.

FIG. 4 is a perspective view showing a configuration of an embodiment of a probe head assembly including a set of the above-described probe heads.

FIG. 5 is a perspective view showing an overall configuration of a conventional wafer prober.

FIG. 6 is a side view of the same.

FIG. 7 is an explanatory diagram showing a dimensional relationship between a wafer and a probe card in the case of a conventional technique.

FIG. 8 is an explanatory diagram showing a movement distance in one movement mode of the wafer.

FIG. 9 is an explanatory diagram showing a movement distance in another movement mode of the wafer.

FIG. 10 is an explanatory diagram showing the total movement distance of a wafer under the most severe conditions in the prior art.

FIG. 11 is a plan view showing an arrangement relationship between a tester main frame and a wafer prober in the case of an 8-inch wafer according to the related art.

FIG. 12 is an explanatory diagram showing a dimensional relationship between a wafer and a probe card in the case of the present invention.

FIG. 13 is an explanatory diagram showing the total movement distance of a wafer under the strictest conditions in the present invention.

FIG. 14 is a plan view showing the size of a moving area to be secured in the case of the related art.

FIG. 15 is a plan view showing the size of a moving area to be secured in the case of the present invention.

FIG. 16 is a perspective view showing an example of a configuration in a case where a multi-axis robot is used as a drive mechanism of a probe head assembly.

FIG. 17 is a side view of the same.

FIG. 18 is a plan view of the same.

FIG. 19 is a perspective view showing an example of a configuration of a test system when a multi-axis robot is used.

FIG. 20 is a perspective view showing an example of a configuration in which a linear motor is used as a drive mechanism of the probe head assembly.

[Explanation of symbols]

 1: Prober 3: XY stage 5: Chuck 7: Probe card 9: Probe needle 10: Cable 11: Tester 15: Tester head 20: Probe head assembly 21: Probe head 23: Connector 25: Cable 27: Driving mechanism 30: Many Axis robot 40: Loader 51: X direction block 52: X direction beam 53: Y direction block 54: Y direction beam 211: Base holder 213: Power supply side bus line 214: Ground side bus line 215: Probe needle 217: Relay 218: Bypass capacitor

Claims (4)

[Claims] A tester for measuring electrical characteristics of a semiconductor device area; a fixed chuck for mounting and holding a wafer;
A probe head assembly having a probe needle electrically connected to the tester and pointing to be able to contact a pad formed on the semiconductor element area of the wafer; and a drive mechanism for moving the probe head assembly at least in a horizontal direction. A wafer prober. 2. A probe head assembly comprising: a module type probe block having at least two probe modules having a large number of probes arranged side by side; a cable group connected to a tester; and a probe head interposed between the probes. The wafer prober according to claim 1, further comprising a connector group. 3. The wafer prober according to claim 1, wherein the driving mechanism is a multi-axis robot. 4. The wafer prober according to claim 1, wherein the drive mechanism is an X, Y direction drive linear motor.