JPS60103634A - Automatic wafer prober device - Google Patents

Abstract

PURPOSE:To enable rapid scanning with a simple construction by driving the titled device so as to take a fixed relative position against a CCD element by a method wherein two CCD elements are arranged, and scribe lines are detected by analyzing wafer image signals by a computer. CONSTITUTION:If the direction of the scribe line 4 on the wafer is not coincident with the direction of the CCD elements 1 and 2 (of scanning), the superposition of signals by the shift registers 7a and 7b of a cut-out circuit 7 is not carried out, but the signals are inputted from the cut-out circuit to a frequency distribution circuit 8 at high frequency. A microcomputer 9 adjusts the direction of an X-Y-Z-theta stage 11 via stage drive circuit 12 until the frequency of signal output from the cut-out circuit becomes lower as prescribed, thus making the direction of the scribe line on the wafer coincident with the direction of the CCD element. The microcomputer further drives the stage via stage drive circuit in such a manner that each point of intersection of the scribe lines comes to the fixed relative position against the CCD element successively.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is an automatic method that sequentially automatically connects a large number of chips on a wafer separated by a number of orthogonal scribe lines to a testing machine to measure their characteristics. The present invention relates to a wafer prober device.

[Background of the invention]

There have been automatic wafer prober devices that sequentially connect a large number of chips on a wafer to a test machine to measure their characteristics, but usually the wafer is irradiated with a laser beam from above to measure the characteristics of the chips. The reflected light signal, which differs depending on the area or scribe line, is photoelectrically converted using a photomultiplier tube, and after A/D conversion, is input to a computer. It was used for analyzing and recognizing shapes.

Although photomultiplier tubes have high sensitivity, they are expensive and do not necessarily have a long lifespan. Therefore, conventional automatic wafer prober devices tend to be expensive and require time and effort to maintain.

[Purpose of the invention]

An object of the present invention is to provide an automatic wafer prober device that is relatively inexpensive and has stable performance.

[Summary of the invention]

In order to achieve the above object, in the present invention, as a -dimensional image sensor for X and Y directions orthogonal to each other,
Two CCD elements each having a large number of pixels are arranged, and the wafer image signals obtained from these two elements are analyzed by a computer to detect the scribe line. First, scribe lines in two orthogonal directions on the wafer were arranged for the X and Y directions (11. Drive so that they were parallel to the cD element, and then the scribe lines were aligned with the CCD element.
In a state parallel to the element, each intersection of the scribe lines is driven to take a predetermined relative position relative to the CCD element, starting from a predetermined position near the wafer periphery. Each time the device reaches a predetermined relative position, the probe of the device is brought into contact with the bonding pad of the chip at a predetermined position relative to the intersection of the scribe lines, and the tester measures the characteristics of the chip. I made it.

Since the scribe lines on the wafer are parallel to the CCD elements for the X and Y directions, their direction is constant, so when the intersection of the scribe lines comes to a specific relative position with respect to the placement position of the CCD elements, In this case, each bonding band placed at a predetermined position on the chip separated by a scribe line will be present at a corresponding position under a specific probe attached to a probe card. Therefore, if the probe card is lowered in this state, each probe will come into contact with its corresponding bonding band.

When a photomultiplier tube is used as a photoelectric conversion element as in a conventional device, it is difficult to configure the device so that signals from each part of the target wafer are separated and handled as signals from each pixel.
This cannot be done with just a photomultiplier tube. (Normally, mechanical scanning is performed in cooperation with a stage.) On the other hand, when a CCD element is used as a photoelectric conversion element (as a -dimensional image sensor), the pixel naturally moves due to its charge transfer electrode. By dividing, a CCD element of about 2048 pixels can be obtained relatively easily. Therefore, in the device according to the present invention, it is relatively easy to electrically scan with the photoelectric conversion section, and rapid scanning is possible with a simple configuration, and subsequent processing can be performed easily.

Scribe lines and chips are manufactured to have exactly the same dimensions as possible, and are repeatedly and regularly arranged on a wafer in large numbers, so from the technical standpoint of image analysis and recognition, scribe lines and their intersection points are is extremely easy to detect, and can be detected by applying known techniques that have already been developed.

[Embodiments of the invention]

FIG. 1 shows a wafer 10 of interest. In the figure, many vertical and horizontal lines dividing the surface of the wafer indicate scribe lines. FIG. 2 shows an enlarged view of the portion indicated as A in FIG. 1. In FIG. 2, 1 is an X-direction CCD element, 2 is a Y-direction CCD element, 3 is a chip, and 4 is a scribe line. FIG. 3 is a block diagram of an embodiment of the present invention, in which 1.2 are CCD elements for X and Y directions, and 5
6 is an A/D conversion circuit, 6 is a multi-value circuit to prevent false detection due to strong local reflections (noise) that appear irregularly due to etching, etc., 7 is a cutting circuit, and 7a is a chip width. (for example, 5000 μm), 7b is a shift register with a number of stages equal to 000 pixels corresponding to the scribe line width (for example, 70 to 150 μm), 8 is a frequency distribution (addition) circuit, 9 is a microcomputer that controls each part of this device; 10 is a wafer to be inspected; 11 is an x, y, z, and θ stage; 12 is a stage drive (control) circuit using pulse smoke, etc.; and 13 is a changeover switch. It is.

Fig. 4(a) is a side view showing the scribe line carved on the wafer surface, and Fig. 4(b) shows the reflected light signal generated there (at the stepped part of the scribe line) and how this signal is binarized. FIG. 10C is a diagram showing the threshold voltage V 1 at that time, and (c) is a diagram showing a binarized reflected light signal. If the direction of the scribe line on the wafer does not match the (scanning) direction of the CCD element, the shift registers 7a, 7 of the cutting circuit 7
The signals are not superimposed by b, and the cutout circuit 7
A signal is inputted to the frequency distribution circuit 8 at a high frequency. The microcomputer 9 adjusts the directions of the x, y, z, and θ stages 11 via the stage drive circuit 12 until the signal output frequency from the cutting circuit 7 reaches a predetermined low frequency, and changes the direction of the scribe line on the wafer. Match the direction of the CCD element. After this state is established, the microcomputer 9 further drives the stage 11 via the stage drive circuit 12 so that each intersection of the scribe lines is sequentially located at a predetermined relative position with respect to the CCD element.

Noise caused by roughness on the wafer surface due to etching is irregular (no characteristics in frequency components, etc.) and is like salt and pepper, so the signal value at a certain point in the image and the average of the signals at surrounding points When the difference from the value exceeds a certain level, the multivalue conversion circuit 8 performs preprocessing using a known method of replacing the value with an average value, thereby preventing false detection due to noise.

The shift register of the cutting circuit is actually installed in RAM, and if the number of stages needs to be changed depending on the type of wafer or chip, it can be changed using a microcomputer program, increasing the versatility of the device. increases. Furthermore, it is advantageous to improve the processing speed by converting microprograms for portions that do not need to be changed depending on the type of chip (for example, a multilevel circuit) into firmware as much as possible.

As described above, with the device of the present invention, when changing the size of the wafer to be measured (for example, 4", 5", 6") or the type of chip, it is only necessary to replace the probe card with the probe attached. , is otherwise highly versatile.

〔Effect of the invention〕

As described above, according to the present invention, an automatic wafer prober device that is inexpensive, has stable performance, and is versatile can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a wafer, FIG. 2 is an enlarged view of the vicinity of point A in FIG. 1, FIG. 3 is a block diagram of an embodiment of the present invention, and FIG.
Figure (a) is a side view showing a scribe line carved on a wafer, and Figure 4 (b) is a reflected light signal generated at the stepped portion of the scribe line and the threshold voltage V when this signal is binarized. FIG. 4(c) is a diagram showing a binarized reflected light signal. 1 - CCD element for X direction, 2 - CCD element for Y direction, 3
-chip, 4-scribe line, 5-A/D conversion circuit, 6-multilevel circuit for preventing false detection, 7-cutting circuit, 7a
- - Shift register with the number of stages corresponding to the chip width, 7b - - Shift register with the number of stages corresponding to the scribe line width, 8 - Frequency distribution circuit, 9 - Microcomputer, 10 - Wafer to be measured for chip characteristics, 11 - X, Y, Z, θ stage, 1
2- Stage drive circuit, 13- Changeover switch. Agent Patent Attorney Takeo Agata 0 Figure 4 (Phantom) Yu 1

Claims (1)

[Claims] Each probe is equipped with a number of probes connected to a testing machine, and each specific probe is placed on a number of bonding pads provided for each chip on a wafer separated by a number of orthogonal scribe lines. In an automatic wafer prober mounting device that automatically sequentially measures the characteristics of all chips on a wafer by bringing them into contact with corresponding specific bonding pads,
Two CCD elements each having a large number of pixels are arranged as a -dimensional image sensor for the Y direction, and these two CCD elements each have a large number of pixels.
A computer analyzes the wafer image signal obtained from the device to detect the scribe lines, and the ,X,
Then, with the scribe line parallel to the CCD element, each intersection of the scribe line is sequentially moved to the CCD from a predetermined position near the wafer periphery. An automatic wafer plowing device, characterized in that it is driven to take a predetermined relative position with respect to an element, and causes a tester to measure chip characteristics each time it takes a predetermined relative position.