JPH0237740A - Device for visual comparison and check of wafer - Google Patents

Abstract

PURPOSE:To perform correctly the visual comparing check of a wafer by putting marks on the wafer by means of signal output for errors in a comparator which outputs differential signals out of image signals. CONSTITUTION:A comparator 10 which compares image output signals given by video cameras 6 and 7 leaves a differential mode as it is and a control device 12 observes the whole region of chips by moving wafer chucks 1 and 2 in parallel on a pedestal 3 by means of control signals 13. When visually defective places are detected, the control device 12 gives control signals 15 to a laser marker 1 6 to put marks on a chip. If no defective places are found after checking the whole surface of its chip, the other chip is checked. In this case, this device makes the wafer chuck 1 move to return to the initial position of such a superior chip and then, the wafer chuck 2 operates independently of the chuck 1 to move to the same position that another superior chip holds. The visual check of a wafer is thus carried out correctly at great speed as well.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the visual inspection of wafers that have completed diffusion in the manufacture of semiconductor integrated circuits, and in particular to the visual inspection of wafers that automatically performs visual inspection by comparing with non-defective chips. This invention relates to a comparative inspection device.

[Conventional technology]

A semiconductor integrated circuit may become a product, be shipped to the market, and break down while being used (hereinafter, this will be referred to as a market defect). Analysis of products that caused market defects shows 3~
Approximately 40% of the time, defects in appearance are found on the surface of the integrated circuit.

- For example, in a photoresist process, a part of the insulation 11'J is not formed properly due to dust, foreign matter, etc. There will be a step in this part, so
The metal wiring above it becomes thinner at the step.

At the time of manufacture, this metal wiring is electrically connected, so it passes inspection, but while it is being used on the market, it breaks due to mechanical stress caused by temperature changes, leading to failure. Conventional appearance inspections were performed visually.

[Problem to be solved by the invention]

The conventional visual inspection described above is good for rough inspections during the photoresist process (to determine whether rework is necessary), but
Fine inspection of completed wafers is not possible. If this were to be done, it would require a large amount of man-hours and would be unrealistic.

An object of the present invention is to provide a wafer appearance comparison inspection apparatus that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, the wafer appearance comparison inspection apparatus according to the present invention mounts a wafer on which a semiconductor integrated circuit is formed, and uses a wafer mounting device having a movement and rotation function to image a pattern on the surface of the wafer. The apparatus includes a device for converting into a signal, a comparison device for outputting a difference signal between image signals, and means for marking a wafer by outputting an error signal from the comparison device.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example 1) Figure 1 (a) is a block diagram of Example 1 of the present invention, (b)
is a plan view showing the pedestal. In Figure 1(a), 1
and 2 are wafer chucks on which wafers are mounted, and 3 is a pedestal on which the wafer chucks 1 and 2 are placed and moved and rotated.

4 is a good wafer for comparison reference, and 5 is a wafer to be inspected. 6 and 7 are video cameras that enlarge and photograph the wafer surface, and 8 and 9 are respective image signals. 10 is a comparator which compares the image output signals from the video cameras 6 and 7, and 11 is a differential output signal after comparison. 12 is a control device, 13 is a pedestal 3
This control signal is used to control the rotation and movement of the wafer chucks 1 and 2. 14 is a control signal to the comparator, which controls the 13 operations of the comparator. Based on this signal, the comparator 1o outputs the difference between the middle image signals 8 and 9, and masks the image signal 8 of (). Select one of the following three modes: (, 3) a mode in which both image signals 9 are masked and the image signal 8 is output. It is a laser marker that marks the chip that has been removed.】5
is a control signal sent from the control device 612 to the laser marker 16.

Next, I will explain the 4'l+ work.

(1) Align the direction of the wafer with the Y-axis and Y-axis of the pedestal (see FIG. 1). The control device 12 uses the control signal 14 to select the mode in which the comparator 10 outputs an image (No. 3 and 8 only) to view the image of the wafer 4. The control device 12 rotates the wafer chuck 1 based on the control signal 13 to detect the chip boundary line on the wafer 4. Align it so that it is parallel to the Y axis and the Y axis.Next, control signal 14
The mode for outputting the image signal 9 is selected, and the axis alignment of the wafer 5 is performed in the same manner as for the wafer 4.

(2) Alignment The non-defective chip in the comparison reference wafer 4, which is selected by p, is aligned with the chip in the wafer to be inspected 5. First, the control device 2 is set to a mode in which the image signal 8 (image of the wafer 4) is output to the comparator 10 by the control signal 14, and the wafer chunk 1 is moved to search for the corner of the above-mentioned good chip. Next, the mode is switched to output the image signal 9 (image of the wafer 5), and the wafer chuck 2 is moved to match the corner of the chip of the wafer to be inspected (the same corner as the good chip).

Further, the comparator is switched to a mode for taking a difference, and the wafer chuck 2 is finely adjusted so that the difference output force becomes O'.

(3) Comparison Inspection The presence or absence of a mismatch (defect in appearance) is inspected based on the difference between the images of the non-defective chip of the comparison standard and the chip to be inspected.

The comparator remains in the differential mode and the controller 61
2 is a wafer chuck 1 on a pedestal 3 by a control signal 13.
and 2 in parallel to view the entire chip area.

The situation along the way is shown in Figure 2. In FIG. 2, 4 is a wafer for comparison reference, and 4a is a good chip among the wafers. 5 is a wafer to be inspected, and 5a is a chip therein. 4b and 5b are video cameras 6 and 7 (
(See Figure 1). 5c is an appearance defect in the chip to be inspected. 12 is the same comparator as in FIG. 1, 1b is a difference image between images 4b and 5b, and only the defective appearance portion 16a is detected. Upon discovering such a defect, the controller 12 issues a control signal 15 to the laser marker 16 to mark the chip. The entire surface of the chip is inspected, and if nothing is found, move on to the next chip. At this time, wafer chuck 1 is moved and returned to the initial position of the good chip (the corner position described above), and wafer chuck 2 is moved independently of wafer chuck 1 to the same position as the next good chip. . From then on, perform the same steps starting from (2).

By repeating (2) and (3) above, all chips on the wafer 5 to be inspected are inspected.

(Example 2) FIG. 3 is a block diagram of a second embodiment of the present invention.

In FIG. 3, 17 is a wafer chuck, and 3 is a pedestal for rotating and moving the wafer chuck I7. 18 is a wafer. 19 is a video camera, and 23 is its image signal output. 20 is an image storage device that stores image signals. 2I is its output signal. 10 is a comparator, 1
1 is its output. , 12 is a control device, 24 is a pedestal;
3, 22 is a control signal to the image storage device 20, 14 is a control signal to the comparator IO (No. M. 1
G is a laser marker, and 15 is a control signal sent from the control device 12 to the laser marker 16. In this second embodiment, image memory'! It is characterized by the installation of Ai + ¥20, one video camera and one wafer chuck. The operation is as follows.

(1) Image memory of comparison reference chip First, a wafer for comparison is placed on the wafer chuck 17.

Axis alignment is performed in the same manner as in the first embodiment. Next, the control device 12
While moving the wafer chuck 17 according to the control signals 24 and 22, an image is stored in the image storage device 20 over the entire surface of the good chip.

(2) Comparative Inspection Place the wafer to be inspected on the wafer chuck 17 instead of the wafer for comparison reference. Perform axis alignment in the same way as in (1).

1 (the alignment is the same as in the first embodiment except that the image stored in the image storage device 20 is used instead of the direct image of the good chip. Next, control signals 24 and 22 are used to While moving the chuck 17, an external appearance inspection is performed by comparing the image of the chip on the wafer to be inspected with the image of a good chip as a comparison standard stored in the image storage device 20.Second.
If a defect as shown in the figure is detected, the control device 12 issues a control signal 5, marks the chip with the laser marker 16, and moves on to the first chip. If there are no defects, the entire surface of the chip is inspected and then the next chip is moved on.

〔Effect of the invention〕

As explained above, by adopting the above-described configuration, the present invention can accurately and quickly perform visual inspection of wafers. Therefore, market defects due to poor appearance will not occur, and there is an effect that market defects can be reduced by 30 to 50%. Moreover, by monitoring the yield of this visual inspection, it is possible to know the extent of diffusion dust and the state of the photoresist process, which has the effect of being useful for controlling diffusion.

[Brief explanation of the drawing]

1f4(a) is a block diagram showing Embodiment 1 of the present invention,
(b) is a plan view showing the pedestal, FIG. 2 is a diagram explaining the inspection process, and FIG. 33 is a block diagram showing Embodiment 2 of the present invention. 1.2... Wafer chuck 3... Pedestal 4,
5 =, Wafer 6,7.19...Video camera 10...Comparator J2...Control device 16...Laser marker 13,14.15
...Control signal 20...Image storage device

Claims (1)

[Claims] (1) A wafer mounting device that mounts a wafer on which a semiconductor integrated circuit is formed and has a movement and rotation function, a device that converts the pattern on the surface of the wafer into an image signal, and a comparison device that outputs a difference signal between the image signals. 1. A wafer external appearance comparison inspection apparatus comprising: and a means for marking a wafer on the basis of an error signal output from the comparison apparatus.