JPH0513518A - Wafer prober - Google Patents

Abstract

PURPOSE:To efficiently adjust the position of a semiconductor chip with high accuracy by processing the output video signal of an image pickup device and calculating the positional coordinates of the images of a probe needle and the semiconductor chip in the output video signals, and then, converting the difference between both positional coordinates into the moving amount of a stage in an orthogonal coordinate system. CONSTITUTION:A stage 2 is moved to a position below a probe card 1 after a wafer 8 has been placed on and fixed to the stage 2. Then a reflecting mirror section 5 is moved to a position between a probe needle 11 and the electrode pad 81 of the wafer 8 and their images are taken with a camera 4. The coordinates of the tip of the needle 11 in the video is calculated by means of the picture processing section 71 of an electronic circuit section 7 which processes the output video signal of the camera 4. Then the lower-side video is folded upward at the center line and, when the center coordinates of the pad 81 do not coincide with those of the tip of the needle 11, distance information of the position error is sent to a control section 74. The section 74 moves the stage until the positional error becomes zero by outputting a command to a stage driving section 72.

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 wafer prober having automatic probe needle positioning means.

[0002]

2. Description of the Related Art A conventional wafer prober has a probe needle 11 fixed to a probe card 1 as shown in FIG.
The image of the microscope 9 illuminated by the operator with the light 6 as shown in FIG. 5 by the operator in order to align the position of the tip of the with the electrode pad 81 on the wafer 8 which is the wafer under test placed on the stage 2. While observing, the position was adjusted as follows.

First, the stage 2 is raised to bring the probe needle 11 into contact with the electrode pad 81. At this time, it is confirmed whether or not the tips of all the probe needles 11 are aligned with the center of the electrode pad 81. The position was adjusted repeatedly until it was obtained. The amount of movement of the stage 2 at the time of position adjustment at this time is recorded as a correction value, and at the time of the next test of the wafer under test, the correction value is used so that the operator does not have to perform position adjustment one by one. It's ready to go.

Further, in another example of the conventional wafer prober, the probe needle 11 is once brought into contact with the electrode pad 81 as described above, and the stage is placed under a television camera (not shown) installed at a different position. Move into the field of view.
At this time, the moving position of the stage is adjusted so that the center of the visual field of the microscope 9 and the center of the visual field of the television camera coincide with each other, that is, the positional relationship between the optical axes of both optical systems is maintained. On the screen of the monitor displaying the image picked up by the television camera, the probe needle 1 is attached to the electrode pad 81.
The same as in the case of the direct observation described above so that the scratches caused by the contact of 1, i.e., the probe needle contact mark, and the marker indicating the coordinates of the setting position of the tip of the probe needle 11 input in advance are matched Adjust the position as described in. In this way, the position of the probe needle contact mark in the field of view of the microscope 9 and the position of the probe needle contact mark in the field of view of the television camera can be matched.

[0005]

In the conventional wafer prober described above, the operator manually adjusts the position of the probe needle and the electrode pad by directly observing the probe needle contact mark with a microscope or the display image on the television monitor. However, there is a drawback in that the positional adjustment accuracy varies greatly depending on the skill of the operator. In addition, there is a drawback that the probe needle is worn or bent and the electrode pad is damaged due to the stress caused by the contact between the probe needle and the electrode pad.

[0006]

A wafer prober of the present invention is provided with a probe card having a probe needle that comes into contact with an electrode pad of a semiconductor chip formed on a semiconductor wafer, and the electrical conductivity of the semiconductor chip is obtained through the probe needle. In a wafer prober for testing static characteristics, a first stage on which the semiconductor wafer is mounted and fixed, a second stage that can move on the same orthogonal coordinate system as the first stage and can move up and down, An imaging device installed on a second stage, and a first mirror surface that is installed on the second stage and reflects a first image, which is an image of the probe needle of the probe card, in the optical axis direction of the imaging device. And a reflecting mirror device having a second mirror surface that reflects a second image, which is an image of the semiconductor chip on the first stage, in the optical axis direction of the imaging device, Processing the output video signal of the imaging device to calculate the first and second position coordinates, which are the respective position coordinates on the output video of the first and second images, and calculate the first and second position coordinates. And an image processing device for converting the difference into a movement amount of the first stage on the orthogonal coordinate system.

[0007]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the wafer prober of the present invention.

As shown in FIG. 1, the wafer prober of this embodiment has a probe card 1 having probe needles 11.
A stage 2 for mounting and fixing a wafer under test, a stage 3 that can move on the same orthogonal coordinate system as the stage 2 and can move up and down, and a camera 4 installed on the stage 3.
The reflecting mirror unit 5, the light 6 installed on the stage 3 for illuminating the optical axis direction of the camera 4, the electronic circuit unit 7, and the wafer 8 as the wafer under test having the electrode pad 81 are configured. ..

The reflecting mirror section 5 is installed on the stage 3,
It has a mirror surface 51 that reflects the image of the probe needle 11 in the optical axis direction of the camera 4, and a mirror surface 52 that reflects the image of the semiconductor chip of the wafer on the stage 2 in the optical axis direction of the camera 4.

FIG. 2 is a block diagram showing an example of the configuration of the electronic circuit section 7.

As shown in FIG. 2, the electronic circuit section 7 comprises an image processing section 71, stage driving sections 72 and 73 for driving the stages 2 and 3, respectively, and a control section 74.

Next, the operation of this embodiment will be described.

First, after mounting and fixing the wafer 8 on the stage 2, the stage 2 is moved below the probe card 1 by the drive of the stage driving unit 72 according to a command from the control unit 74 of the electronic circuit unit 7. Next, the stage 3 is driven by the stage drive unit 73 in response to a command from the control unit 74, so that the reflecting mirror unit 5 is located at an intermediate position between the probe needle 11 and the electrode pad 81 of the wafer 8 as shown in FIG. Move to position. At this time, the vertical position is adjusted so that the tip of the probe needle 11 and the electrode pad 81 have a symmetrical positional relationship with the optical axis ab of the camera 4, that is, the distance from the optical axis ab is equal. To do. At this time, the stop position H3 of the stage 3 with respect to the reference plane R shown in FIG. 1 is set in advance so as to satisfy the relationship of the following equation.

H3 = {(H1-t1-t2) + (H2 +
t3 + t4)} / 2 where H1 and H2 are the distances from the reference plane R to the upper surface of the probe card 1 and the upper surface of the stage 2, respectively, and t
1 is the thickness of the probe card 1, t2 is the probe card 1
From the lower surface to the tip of the probe needle 11, t3 is the thickness of the wafer 8, and t4 is the thickness of the electrode pad.

FIG. 3 shows an example of an image of the reflector section 5 illuminated by the light 6 and imaged by the camera 4 at the above positions. The image above the center line cd is the image of the probe needle 11 by the mirror surface 51 of the reflecting mirror portion 5, and the image below the center line cd is the image of the electrode pad 81 by the mirror surface 52. The subjects on both mirror surfaces 51 and 52 are, as described above,
Since it is at the same distance from the optical axis ab of the camera 4, naturally, when the lower image is folded back upward along the center line cd with the same magnification, the image of the field of view of the microscope 9 shown in FIG. Become.

In the present embodiment, the coordinates l, m, n of the tip of the probe needle 11 in the image are calculated by the image processing section 71 of the electronic circuit section 7 which processes the output image signal from the camera 4. Next, the lower image is folded back up along the center line cd, and it is checked whether the center of the electrode pad 81 and the calculated coordinates l, m, n of the tip of the probe needle 11 match. if,
If they do not match, the distance information of the position error is calculated by the control unit 74.
And outputs a command to the stage drive unit 72 to move the stage 2 so that the position error becomes zero. By the above processing, the position adjustment of the tip of the probe needle 11 and the center of the electrode pad 81 can be automatically performed without contact. Next, the movement amount at this time is stored in the control unit 74 as a correction value. During the next test of the wafer under test, this correction value is used to adjust the position.

In order to adjust the position by the above method, it is necessary to determine the relative position between the probe card 1 and the stage 3 on which the camera 4 and the reflector 5 are installed before starting the test. .. As an example of the method, it is performed as follows. On the lower surface of the head plate on which the probe card 1 is installed, the drive coordinate axes orthogonal to the stage 3, for example,
Markers corresponding to the X and Y axes are attached, and these markers and a reference line preset by the image processing unit 71 are made to coincide on the respective axes on the image, so that the relative position of the two can be determined. ..

[0019]

As described above, the wafer prober of the present invention comprises an image pickup device installed on a stage that can move up and down on the same orthogonal coordinate system as the stage on which the semiconductor wafer is mounted and fixed, The image of the probe needle and the image of the semiconductor chip are respectively reflected in the optical axis direction of the image pickup device.
A mirror device with two mirror surfaces and the image signal output from the imaging device are processed to calculate the position coordinates of the probe needle and the image of the semiconductor chip on the output image, and the difference between the two is calculated as the amount of movement of the stage on the orthogonal coordinate system. By providing the image processing device for converting into, the position adjustment of the probe needle and the electrode pad is performed by the image signal processing, so that highly accurate position adjustment can be efficiently performed regardless of the skill of the operator. effective. Further, since it is a non-contact position adjusting method, there is an effect that it is possible to prevent wear and bending of the probe needle and damage to the electrode pad.

[Brief description of drawings]

FIG. 1 is a conceptual block diagram showing a part of an embodiment of a wafer prober of the present invention in blocks.

FIG. 2 is a block diagram showing an example of an electronic circuit unit of the wafer prober of the present embodiment.

FIG. 3 is a diagram showing an example of an image of a reflecting mirror section imaged by the camera of this embodiment.

FIG. 4 is a structural conceptual diagram showing an example of a conventional wafer prober.

FIG. 5 is a diagram showing an example of an image directly observed with a microscope in a conventional wafer prober.

[Explanation of symbols]

 1 Probe Card 2, 3 Stage 4 Camera 5 Reflecting Mirror 6 Light 7 Electronic Circuit 8 Wafer 9 Microscope 11 Probe Needle 51, 52 Mirror Surface 71 Image Processing 72, 73 Stage Drive 74 Controller 81 Electrode Pad

Claims (1)

Claim: What is claimed is: 1. A probe card having a probe needle that contacts an electrode pad of a semiconductor chip formed on a semiconductor wafer, the electrical characteristic of the semiconductor chip being tested through the probe needle. In the wafer prober, a first stage on which the semiconductor wafer is mounted and fixed, a second stage that can move up and down on the same orthogonal coordinate system as the first stage, and a second stage that can move up and down. An imaging device installed, a first mirror surface that reflects a first image, which is an image of the probe needle of the probe card installed on the second stage, in the optical axis direction of the imaging device, and the first A reflecting mirror device having a second mirror surface that reflects a second image, which is an image of the semiconductor chip on a stage, in the optical axis direction of the imaging device, and an output image of the imaging device The signal is processed to calculate first and second position coordinates, which are respective position coordinates on the output image of the first and second images, and the difference between the first and second position coordinates is calculated as the first An image processing device for converting the amount of movement of the stage on the orthogonal coordinate system.