JPH0524669B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a pellet visual inspection device.

[Conventional technology]

Generally, as a measure to improve the reliability of semiconductor devices, semiconductor pellets that have some cracks or chips are removed by visual inspection.

For example, diode pellet inspection equipment uses a pattern matching method to perform inspection.

That is, the reference pattern signal of the pellet is stored in advance inside the inspection device, the difference between the measurement pattern signal and the reference pattern signal is calculated, the coordinates of the reference pattern area and the inspection pattern area are corrected, and then both patterns are overlapped.

Judgment is made by counting the size of the area of the mismatched portion of both patterns and comparing it with a predetermined value to determine pass/fail.

FIG. 4 is a block diagram of an example of a conventional pellet appearance inspection device, and FIG. 5 is a diagram of a diode pellet to be measured corresponding to the state of electrode part chipping and peripheral part chipping to explain the operation of the circuit shown in FIG. FIG. 3 is a diagram of a comparator input image.

The pellet appearance inspection apparatus includes a TV camera 1 that images a diode pellet _P3 to be measured placed on an inspection stage D, and a binary signal S of 1 or 0 that converts an image signal Si of the imaged pellet. ₂ , an image memory unit 11 that stores the binary signal S ₂ as a measurement pattern, and a reference pattern memory unit 13 that stores the reference pattern signal S ₅ that becomes the inspection reference image. Detects feature points of the reference pattern and measurement pattern and calculates the amount of coordinate deviation
It is configured to include a CPU 6, an address controller 12 to which the amount of coordinate deviation is input, a comparator 15 to which both output signals S _M and S _S of both the memory units 11 and 13 are input, and a counter 16.

The address controller 12 simultaneously addresses the image memory section 11 and the reference pattern memory section 13 in accordance with the data given by the CPU 6 so that the comparison coordinate points of the inspection pattern and the reference pattern match.

The pattern signals S _M and S _S outputted from both the memory sections 11 and 13 in this way are input to the comparator 15, where the exclusive OR is calculated and the counter 16
is input.

Therefore, the counter 16 counts the number of differences between the reference pattern signal S _S and the measurement pattern signal S _M.

After completing one screen scan, the CPU 6 reads the counted value of the counter 16, compares it with a predetermined tolerance value, and supplies a pass/fail determination output signal S _OCL to the output terminal 8.

As shown in Fig. 5, in the case of a defective diode pellet _P3 , the reference pattern signal S _S and the inspection pattern signal S _M are overlapped with their coordinate centers C, and the white electrode part E and the stage part corresponding to 1 are overlapped. The peripheral edge portions _R3 corresponding to D and O are compared by a comparator 15, and the area of the peripheral edge portion chipping P _D of the pellet and the electrode portion chipping E _D is counted as the chipping portion.

[Problem that the invention seeks to solve]

The above-mentioned conventional pellet appearance inspection equipment uses a pattern matching method for inspection, so if there is an angular error between the coordinate axes of the reference pellet and the coordinate axes of the measurement pellet, the pellet may be defective even if it is a good pellet. There were many cases where the judgment was made as follows, and the problem was that the angle tolerance was small.

Furthermore, there was a problem that the reliability of the pass/fail judgment was low because the error in calculating the amount of deviation of the overlapping position directly affected the judgment.

Furthermore, since the device must have a reference pattern signal, a large amount of image memory is required.
There was a problem in that the reference pattern signal had to be changed every time the product type was changed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pellet appearance inspection apparatus that is free from errors due to angles or positional deviations in the placement coordinates of pellets to be inspected, and does not require changes in reference pattern signals due to changes in product types.

[Means for solving problems]

The pellet appearance inspection apparatus of the present invention includes: (A) an imager that outputs image signals of a plurality of regions of a semiconductor pellet to be measured; (B) an input end that inputs the image signals, and an output end that outputs two of the image signals. a binarization circuit that outputs a digitized signal; (C) an inverter whose input terminal receives the digitized signal and whose output terminal outputs an inverted digitized signal corresponding to the binarized signal; (D ) An input end inputs the binarized signal to measure the center of gravity coordinates of one region of the binarized signal, and further inputs the inverted binarized signal to measure the barycentric coordinates of the other region of the binarized signal. A center of gravity measuring device that measures the coordinates of the center of gravity and supplies the respective outputs to the output end; It is configured to include an arithmetic circuit that supplies a defect determination output signal to the output end when the value is equal to or greater than a predetermined value.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the invention.

An image signal Si output from the TV camera 1 is input to a binarization circuit 2.

The binarized signal S ₂ of the binarization circuit 2 is the center of gravity measuring circuit 4
and is input to the inverter 3.

The inverted binary signal ₂ of the inverter 3 is input to the center of gravity measuring circuit 5.

The center of gravity coordinate signals S _G1 and S _G2 of the center of gravity measurement circuit 4 and the center of gravity measurement circuit 5 are sent to the CPU 6 via the data bus 7.
is read into.

The CPU 6 operates on the read data and outputs a judgment output signal _S0 to the judgment output terminal 8.

The image signal Si of the diode pellet Pi from the TV camera 1 is processed by the binarization circuit 2 so that the peripheral edge R of the pellet is black, and the electrode part E and the stage part D are
and are binarized into 0 and 1, respectively, corresponding to white.

The binarized signal _S2 thus binarized is used to measure the barycenter coordinate G _R of the black portion, that is, the barycenter coordinate G _R of the peripheral edge R of the pellet, by the barycenter measuring circuit 4.

Further, the binary signal S ₂ is inverted in black and white by the inverter 3, and converted into an inverted binary signal ₂ in which the electrode portion E and the stage portion D are black, and then by the center of gravity measuring circuit 5,
The black part, that is, the barycentric coordinates G _R of the electrode section E and the stage section D is measured.

The centroid coordinates G _R of the pellet periphery and the centroid coordinates G _R of the stage part D and the electrode measured in this way are as follows:
Read by CPU6, distance l between each center of gravity coordinates
is calculated, and if it is greater than or equal to a predetermined range, a defective determination output signal S ₀ is output to the determination output terminal 8.

Figures 2 a to c are two diagrams of diode pellets under test corresponding to normal, chipped electrode, and chipped peripheral states, respectively, to explain the operation of the circuit shown in Figure 1.
FIG. 3 is an image diagram of a valued signal.

As shown in Figure 2a, in the case of a good diode pellet P, the barycentric coordinates G _R of the peripheral edge R of the pellet P and the barycentric coordinates G _R of the stage part D and the electrode part E.
are in agreement, and the distance l between the center of gravity coordinates is zero.

As shown in Figure 2b, if the electrode part _E1 is chipped, the periphery centroid coordinate G _R1 is in the direction of the periphery chip, and the stage part and electrode barycenter coordinate G _R1 are opposite to the chip in the electrode part. move in each direction.

In this case, the distance between the center of gravity coordinates G _R1 and G _R1 is l ₁ .

As shown in FIG. 2c, when a chip occurs in the peripheral edge _R2 of the pellet, only the coordinate G _R2 of the center of gravity of the peripheral edge moves in the opposite direction to the chipped coordinate.

Therefore, the CPU 6 calculates the distance _l2 between the center of gravity coordinates G _R2 of the peripheral edge part and the coordinates G _R2 of the center of gravity of the stage part D and the electrode part, and compares it with a predetermined value L, thereby making it possible to detect the chipped state of each pellet Pi.

FIG. 3 is a block diagram of a second embodiment of the present invention.

The changeover switch 9 is controlled by a switch control signal S ₀ from the CPU 6, and is switched between the binarization circuits 2 and 2.
Input the value signal S ₂ and store the barycenter coordinate signal in memory section 1
After storing it as 0, the inverted binary signal ₂ of the inverter 3
is switched and input to the center of gravity measuring circuit 4.

This embodiment is more economical than the first embodiment because only one center of gravity measuring circuit is required.

In the above embodiment, the center of gravity measuring circuit uses the black part corresponding to 0 as the measurement target area, but the white part corresponding to 1 may also be used as the target area.

〔Effect of the invention〕

As explained above, the present invention measures the barycentric coordinates of the peripheral edge of the pellet and the barycentric coordinates of the electrode part from the white area and black area of the inspection screen of the semiconductor pellet, and measures the distance between each barycentric coordinate. As a result, the appearance of the pellets is judged to be good or bad, so that the judgment can be made accurately regardless of the positional and angular deviations of the pellets, and there is no need for a reference pattern.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the present invention;
2A to 2C are image diagrams of binary signals of the diode pellet under test corresponding to normal, electrode part chipped, and peripheral part chipped states, respectively, for explaining the operation of the circuit shown in FIG. 1. The figure is a block diagram of a second embodiment of the present invention, FIG. 4 is a block diagram of an example of a conventional pellet appearance inspection device, and FIG. FIG. 4 is a comparator input image diagram of a diode pellet to be measured corresponding to a chipped peripheral edge state. 1...TV camera, 2...binarization circuit, 3...
Inverter, 4... Center of gravity measuring circuit, 5... Second center of gravity measuring circuit, 6... CPU, S ₂ ... Binarized signal, ₂
...Inverted binary signal, Si...Image signal, _S0 ...Judgment output signal, _l1 , _l2 ...Distance between barycentric coordinates.

Claims (1)

[Scope of Claims] 1. (A) An imager that outputs image signals of a plurality of regions of a semiconductor pellet to be measured; (B) An input end for inputting the image signals, and an output end for binarizing the image signals. a binarization circuit that outputs a signal; (C) an inverter whose input terminal receives the binarized signal and whose output terminal outputs an inverted binarized signal corresponding to the binarized signal; (D) an input One end inputs the binarized signal to measure the barycenter coordinates of one region of the binarized signal, and further inputs the inverted binarized signal to measure the barycenter coordinates of the other region of the binarized signal. (E) A center of gravity measuring device that measures the center of gravity and supplies the respective outputs to the output terminal; 1. A pellet appearance inspection device comprising: an arithmetic circuit that supplies an output signal for determining defectiveness to an output terminal when the value is greater than or equal to a value.