JPH0727930B2 - Wafer prober - Google Patents

Description

The present invention relates to a wafer prober for testing the characteristics of a large number of integrated circuits formed on a semiconductor wafer with a probe card.

<Prior Art> In general, a wafer prober sequentially tests the characteristics of each integrated circuit on a wafer through a probe card and attaches a mark by a marker on the chip of the integrated circuit determined to be defective. The above-mentioned probe card has a peripheral circuit for a characteristic test incorporated on a card substrate, and has a required number of probe needles capable of coming into contact with each terminal of an integrated circuit to be tested at the center of the lower surface. In the wafer prober, the probe needle is brought into contact with the terminals of each integrated circuit on the wafer by moving the wafer on the stage with respect to the probe card at regular intervals.

<Problems to be Solved by the Invention> By the way, in such a wafer prober, when the number of chips equal to or lower than the preset defective product rate is determined to be defective, the product of the marked chips is determined. A repeatability test is performed to see if the circuit is really bad.

Further, when the test program is changed, a characteristic test is performed by the new program on the chip marked by the old program in order to check whether the new test program produces the same test result as the old test program. .

In such a case, it is necessary to detect the marked chip from among the respective chips on the wafer while the wafer remains set at the predetermined position of the wafer prober. Conventionally, an operator visually detects and counts chips with a mark through a microscope equipped with a wafer prober.

However, when the wafer is still set at the predetermined position of the wafer prober, it is difficult to find the mark by visual observation, and it is easy to make an error in the detection, and it takes time to perform the reproducibility test and other tests. .

The present invention has been made in view of the above problems, and enables a chip with a mark to be automatically detected, so that a reproducibility test and a program check test can be performed accurately and quickly. The purpose is to

<Means for Solving the Problems> In order to achieve the above object, the present invention provides an optical system that transmits reflected light from a mark provided on any chip of a wafer set at a predetermined position, An optical filter having a photodetector for detecting transmitted light of the optical system and a display unit for displaying a detection state of the photodetector, and the optical system having the same color as the mark on the reflected light transmitting optical path. A wafer prober was constructed from the above.

<Operation> According to the above configuration, the reflected light of the mark provided on any chip of the wafer is incident on the photodetector through the optical system, so the mark is detected by the photodetector, and the detected state is detected. Is displayed on a display means such as a display lamp or a count display.

Further, since the optical system has an optical filter of the same color as the mark on the reflected light transmission optical path, only the reflected light from the mark will be detected by the photodetector after passing through the optical filter, False detection does not occur due to the reflected light from the adhered matter such as dust adhered on the wafer.

<Examples> Hereinafter, the present invention will be described in detail based on examples shown in the drawings. FIG. 1 is a configuration diagram of a wafer prober according to an embodiment of the present invention. The wafer prober has a probe card 1, a stage 3 for mounting and supporting a wafer 2, and a mark m on a chip of the wafer 2. In addition to having a marker 4 to be attached, a controller 5 for electrically controlling the above-mentioned parts, a microscope 6 for visually observing each chip of the wafer 2, a mark detecting part 7 and a display circuit part 8 are provided.

The probe card 1 has a peripheral circuit for a characteristic test incorporated on a card substrate 1a, and has a required number of probe needles 1b, ... Which can contact each terminal of the integrated circuit to be tested at the center of the lower surface. The probe card 1 is supported by a support member 10 below the opening 9a of the fixed base 9. The stage 3 moves the wafer 2 with respect to the probe card 1 with the wafer 2 placed thereon. The movement operation is performed by the controller 5 via the stage drive unit 11.
Controlled by. The marker 4 is provided on the base 9 so as to be able to swing and move back and forth, and is controlled by the controller 5 via the marker drive unit 12. When the result of the characteristic test of the integrated circuit by the probe card 1 is defective, The mark m is attached to the chip of the integrated circuit by projecting it toward the chip by red paint. The microscope 6 is installed directly above the center of the probe card 1. This microscope 6
In the middle part of the outer periphery of the, the open portion 9a of the base 9, the marker 4,
A sheet 13 that covers the entire mark detection unit 7 is attached. An annular illumination lamp 13 for irradiating the mark m on the wafer 2 is provided in the vicinity of the open portion 9a of the substrate 9. Reference numeral 14 is a probe card control unit.

The mark detection unit 7 is for optically detecting the mark m attached to the chip of the wafer 2 set at a predetermined position, and has a cylindrical body 15, a lens 16, and a red filter 17. , And a photodetector 18. The lens 16 and the red filter 17 constitute an optical system that transmits the reflected light from the mark m. The red filter 17 is provided in the optical system for the following reason. That is, the reflected light from the mark m made of red paint is red, and by providing the red filter 17, it is possible to transmit only the reflected light of the mark and exclude the light of other wavelengths. Therefore, even if dust or other attached matter is present on the wafer 2, the reflected light from the attached matter that becomes noise can be removed, and the detection accuracy of the mark m is correspondingly increased. The photodetector 18 receives the transmitted light of this optical system. The mark detecting unit 7 is installed on the base 9 by the supporting unit 19 and takes in the reflected light from the mark m of the chip at the test position. The detection signal from the mark detection unit 7 is input to the display circuit unit 8.

The display circuit section 8 is for displaying the detection state of the mark detection section 7, and a discrimination circuit 20 for discriminating whether or not the detection signal of the photodetector 18 is a signal indicating the detection of the mark m, and The display circuit 22 that lights the indicator lamp 21 in response to the discrimination output of the discrimination circuit 20, the counter 23 that introduces the discrimination output of the discrimination circuit 20 to count the number of detections of the mark m, and the count number of the counter 23 are It comprises a count display 24 for displaying. This display circuit section 8 is marked on the controller 5 by the mark m.
Is supplied (a discrimination output of the discrimination circuit 20 here) and the like, and the operation thereof is controlled by the controller 5.

In the above structure, the mark m among the chips on the wafer 2
When the chip with a mark faces the test position, the red reflected light is incident on the photodetector 18 through the lens 16 and the filter 17 of the mark detecting unit 7, so that the photodetector 18 detects the presence or absence of the mark m. .

The operation during various tests will be described below.

(A) Normal characteristic test The characteristic test of each integrated circuit of the wafer 2 is performed by the routine shown in the flowchart of FIG. First, the step
In S1, each chip is sequentially faced to the required position of the probe card 1 from the chip at the head position of the wafer 2, the probe needle 1b is brought into contact with the terminal of the integrated circuit of the chip, and the probe card 1 is used for the integrated circuit. Perform a characteristic test. In step S2, it is judged whether the characteristic test result is good or not. If the test result is not good, step
Moving to S3, the mark 4 is attached to the chip by the marker 4, and in step S4, the controller 5 counts up the number M of defective chips by “1”,
Proceed to S5. The total number M of defective chips is
It shall be stored in the memory in the controller 5.

If the result of the characteristic test is judged to be good in step S2, or if step S4 has been passed, step S5
Then, it is determined whether or not the characteristic test has been completed for all the chips. At the beginning, the judgment is No because all chips have not been characterized. In that case, the process proceeds to step S6, the stage 3 is shifted so that the next step comes to a predetermined position, and the process returns to step S1.

In this way, the routine from step S1 to step S6 is repeated for each of the second and subsequent chips, sequentially,
Perform a characteristic test.

When the characteristic test is completed for all the chips, the determination in step S5 becomes Yes, and the end is reached.

As a result, among the chips on the wafer 2, the defective chip is marked with the mark m, and the total number M of defective chips is stored in the memory.

(B) Automatic reproducibility test As a result of performing a characteristic test of an integrated circuit on a certain wafer 2, when it is determined that the number of chips is equal to or less than a preset defective product rate, the flowchart of FIG. A reproducibility test is performed by the routine shown in (1) to confirm whether the integrated circuit of the chip with the mark m is a defective circuit.

In step T1, the number of defective chips (the total number of defective chips already stored in the memory by the routine shown in FIG. 2) M obtained by the normal characteristic test is equal to or less than a preset defective product rate Mo. If it is not below, there is no problem. Therefore, the routine for the next step is performed without entering the routine for the original reproducibility test after step T2.

If the number of defective chips is less than or equal to the predetermined defective product rate, step T2
Then, it is judged whether the chip at the test position has the mark m or not. That is, the controller 5
The discrimination output of the discrimination circuit 20 is sampled to judge whether or not the mark detection unit 7 has detected the mark m. If there is no mark m on the chip, the process moves to step T3, and the stage 3 is shifted so that the next chip faces the test position. Thus, the loop of steps T2 and T3 is repeated until the chip with the mark m comes to the test position.

When it is determined in step T2 that the chip facing the test position has the mark m, the process proceeds to step T4, and the counter 23 of the display circuit unit 8 increments the number N of defective chips. Then, in step T5, a characteristic test is performed by the probe card 1, and in step T6, it is determined whether or not the result of the characteristic test is defective. That decision is Ye
If s, that is, the characteristic test result is defective, the same result as the previous characteristic test is obtained, so there is no problem. In this case, the process proceeds to step T7.

In step T7, it is judged whether or not the number of reproducibility tests has reached a fixed number, that is, whether or not a reproducibility test has been performed with respect to a fixed number of chips. If not, the process returns to step T3, and stage 3 After shifting by one chip, the process returns to step T2, and the routines after step T2 are repeated. As a result, the reproducibility test is performed on a fixed number of chips on each wafer.

If the judgment in step T6 is No, that is, if the result of the characteristic test is good, it means that the test result different from the result of the previous characteristic test has come out, so it is possible that the previous characteristic test was incomplete. is there. Therefore, in this case, the wafer 2 is taken out, the mark is removed, and cleaning is performed, and the characteristic test is performed again for each integrated circuit of the wafer 2.

(C) Manual reproducibility test As shown in the flow chart of FIG. 4, a reproducibility test can be performed manually for each chip of the wafer 2 by an operator.

Mark the chip facing the test position in step U1
If there is no mark m on the chip, the process moves to step U2 to shift the stage 3 so that the next chip faces the test position. The loop of steps U1 and U2 is repeated until the defective chip with the mark m comes to the test position.

When a defective chip faces the test position, the fact is displayed on the display lamp 21. Then, in step U4, the count number M of the defective chips in the counter 23 is counted up, and in step U5, the count number is displayed by the count indicator 24.
To display.

In step U6, it is determined whether or not the number of reproducibility tests has reached a certain number, and if the number has reached a certain number, the end is reached, but if the number of reproducibility tests has not reached the certain number,
Proceed to step U7.

In step U7, a characteristic test by the probe card 1 is performed according to an operator's manual instruction. Then, in step U8, it is determined whether or not the result of the characteristic test is defective. If the result of the characteristic test is bad as in the previous case, the stage 3 is shifted by a manual instruction of the operator in step U9 to move the next chip to the test position, and the process returns to step U1.

If the determination is No in step U8, that is, if a test result different from the previous characteristic test is obtained, the previous characteristic test may have been incomplete, so the wafer 2 is taken out and the mark m is removed and cleaned. Moving to the work, the characteristic test is performed again on all the chips of the wafer 2 from which the mark m is removed.

(D) Program check test Test items and values for each item, for example, probe card 1
If the energizing voltage value of is changed, the test program is changed. It is necessary to check the operation of the new test program. This operation check
A wafer 2 having a defective chip with a mark m tested by the old program is used as a standard wafer, and the standard wafer is subjected to a characteristic test again under the new program to confirm whether similar test results can be obtained. By doing.

Conventionally, when checking the operation of this new program,
The operator visually detected a defective chip with a mark m through a microscope.

In the embodiment of the present invention, a new program is automatically tested by the routine shown in the flowchart of FIG.

In step V1, the standard wafer, that is, the wafer 2 tested by the old program and having the mark m on the defective chip is set at a predetermined position. Then, in step V2, the characteristic test by the probe card 1 is performed on the integrated circuits of the respective chips in order from the chip at the head position. In step V3, it is determined whether or not the result of the characteristic test is good. If the integrated circuit of the chip is defective, the process proceeds to step V4 and the controller 5 counts up the number of defective chips M. Since the mark m has already been added to the defective chip, no new mark m is added in this routine.

If the chip is non-defective, step V3 to step V5
Then, the detection signal of the mark detecting section 7 is sampled to judge whether or not the mark m is attached to the chip. If there is no mark m, shift the stage 3 so that the next chip faces the test position, and step V2
Return to.

When it is determined that there is a mark m in step V5, the counter 23
At N, the count number N of chips with the mark m is counted up. Then, in the next step V8, the count number N is displayed on the count display 24. In Step V9, it is judged whether all chips have been tested,
If not 100% tested, return to step V6,
The characteristic test for the next chip and the detection of the mark m are performed.

In this way, by repeating steps V2 to V8, the characteristic test by the probe card 1 and the detection of the mark m are performed for all the chips, and the end is reached when the total test is completed.

<Effects of the Invention> As described above, according to the present invention, with respect to the wafer set at a predetermined position, the reflected light of the mark provided on any of the chips enters the photodetector through the optical system, While being detected by the photodetector, the detection state is
It is displayed by the display means. In this way, defective marks are automatically detected, so tests such as reproducibility tests and program check tests can be performed accurately and quickly without relying on visual observation by an operator as in the past. it can.

Further, since the optical system has an optical filter of the same color as the mark on the reflected light transmission optical path, only the reflected light from the mark will be detected by the photodetector passing through the optical filter. There is no erroneous detection due to reflected light from dust or other deposits on the wafer.
The mark can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIGS.
FIG. 2 is a flowchart showing the operation. FIG. 2 shows a normal characteristic test, FIG. 3 shows an automatic reproducibility test, FIG. 4 shows a manual reproducibility test, and FIG. 5 shows a program test. 1 ... Probe card, 2 ... Wafer, 3 ... Stage, 4 ... Marker, 7 ... Mark detection section, 8 ... Display circuit section, 16 ... Lens, 17 ... Filter, 18 ... Light detection Display device, 21, 24 ... display means (21 ... display lamp, 24 ... count display device).

Claims (1)

[Claims] 1. An optical system for transmitting reflected light from a mark provided on any chip of a wafer set at a predetermined position, a photodetector for detecting the transmitted light of the optical system, and this photodetection. Display means for displaying the detection state in the vessel,
Moreover, the wafer prober is characterized in that the optical system is provided with an optical filter of the same color as the mark on the reflected light transmission optical path.