JPS591978B2 - Object condition inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting the condition of an object, and particularly to a method for inspecting the appearance of wiring boards for electronic devices, semiconductor elements, and the like.

In order to automatically inspect the 'turn' of wiring or electrodes formed on the surface of a wiring board or a semiconductor element, first, an electrical signal corresponding to the wiring or electrode pattern is formed by photoelectric conversion means.

The electrical signal is converted into a binary pulse signal so as to enable digital arithmetic processing. The above signal corresponds to the reference pattern of the above wiring or electrode.
By comparing with the pulse signal, undesired substances remaining on the surface of the substrate or semiconductor element and defects in wiring or electrodes are detected. In the above-mentioned inspection, it is necessary that the pulse signals accurately correspond to the no-turns of the wiring or electrodes.

However, as shown in FIG.
The electrical signal obtained by scanning the substrate 2 where T2 remains is as shown in the figure b, and therefore, it is possible to binarize this electrical signal using one threshold voltage Vth. It has become clear that no response signal is obtained, as shown in c in the same figure, which does not respond to relatively small defects or unnecessary objects.

Therefore, one object of the present invention is to provide an inspection method that can accurately inspect the surface condition of an object.Another object of the present invention is to provide an inspection method that can accurately inspect the surface condition of an object, and another object is to detect objects that should be present on the surface, the presence or absence of scratches, and unnecessary objects that should not be present on the surface. The object of the present invention is to provide a testing method that can simultaneously test for the presence or absence of. According to the present invention, an electrical signal outputted from a photoelectric conversion device according to a no-turn on the surface of an object to be inspected is supplied to a detection circuit for a low threshold voltage and a detection circuit for a high threshold voltage. A pulse signal output from the circuit is determined by a determination circuit. The present invention will be explained below with reference to Examples.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 1 is a light emitting lamp, 2 is a wiring board made of glass, 8 is a wiring film made of Cr, 4 is a magnifying optical lens, and 5 is a photoelectric conversion element.

Light from the light emitting lamp 1 is irradiated onto the photoelectric conversion element 1 through the wiring board 2. The entire surface of the substrate 2 is scanned by this light beam in a certain period of time. The photoelectric conversion element 5 linearly converts the intensity of light into a change in voltage.

The electrical signal output from the photoelectric conversion element 5 is applied to two detection circuits Al and A2. The detection circuit A1 and the detection circuit A2 are set to have different threshold voltages Vlh. That is, the threshold voltage Vlhl of the detection circuit A1 is set low, and the threshold voltage Vth2 of the detection circuit A2 is set high. The respective outputs of the detection circuits Al and A2 are applied to determination circuits B1 and B2, respectively. This judgment circuit Bl
, B2, a signal of the reference pattern is stored in memory. Then, in each determination circuit Bl, B2, the output signal of the detection circuit is compared with a signal indicating the memorized reference pattern, and the output of the determination circuit is displayed on the display section Cl, C2.
send to FIG. 2 shows signals generated in each part when light is scanned over a part of the wiring board.

For example, if there is a defect 6 in the wiring part of the wiring board to be inspected and unnecessary wiring material 7 is present in a part where no wiring should be formed, as shown in FIG. The result is as shown in Figure b. And detection circuit A
Since the Vlh of the circuit is low, the output waveform of No. 1 is a pulse generated in a portion where defect 6 and wiring do not exist, as shown in FIG. On the other hand, since the Vth of the circuit is high, the output waveform of the detection circuit A2 is a pulse generated in a portion where there is no wiring or unnecessary wiring material 7, as shown in FIG. Then, in each of the determination circuits B, B2, the output signal of the detection circuit is compared with the signal stored in the determination circuit, and the output thereof is sent to the display section.

The output of the determination circuit C1 appears as a pulse indicating the existence of a defect 6 occurring in the wiring 3, as shown in FIG. On the other hand, the output of the determination circuit C2 appears as a pulse indicating the presence of the unnecessary substance 7, as shown in h of the figure. In this way, 1h1 of the detection circuit A1 is set to be slightly higher than the output signal level of the photoelectric conversion element 5 when receiving light from a part of the board where wiring with no defects exists, and Vlh2 of the detection circuit A2 is set to a level of the wiring material. By keeping the output signal level slightly lower than the output signal level of the photoelectric conversion element 5 when receiving light from a part of the board where no trace exists, it is possible to determine whether there are defects in the wiring, unnecessary wiring materials, or other unnecessary materials. be able to. That is,
According to the present invention, a photoelectrically converted electrical signal is simultaneously applied to two detection circuits with different threshold values, and the output is compared with a signal obtained from a reference pattern in separate judgment circuits. , produces an output indicating the presence or absence of wiring defects on the one hand and the presence or absence of unnecessary wiring material on the other hand.

Therefore, it is possible to determine the size of a defect or an unnecessary object from the width of the pulse obtained as an output, and to determine whether or not it is acceptable. In this case, even if the unwanted item is of an unacceptable size, it can generally be corrected. On the other hand, when an inspection device is configured with a single circuit system, as shown in Figure 4, unless there is a signal change that exceeds one preset threshold, the presence of defects or unnecessary objects is detected. There is no output indicating this.

Therefore, measurement results indicating the existence of minute defects and unnecessary objects cannot be obtained. However, as in the present invention,
By applying the output signal of the photoelectric conversion element 5 to detection circuits A and A2 with different threshold values, and detecting the presence or absence of a low-level signal and the presence or absence of a high-level signal separately, minute defects can be detected.
Don't overlook the existence of unnecessary items.

In addition to the embodiments described above, the present invention can also be implemented in the following embodiments.

In other words, a pulse with a width slightly narrower than the pulse width corresponding to the minimum width between interconnections existing in the reference pattern is stored in the judgment circuit B1 that receives the output of the low Vlh detection circuit A1, and the inspection light is scanned. do.

Then, the width determining circuit B1 detects whether there is a pulse whose width is narrower than the stored pulse. In this case, if there is a pulse narrower in width than the stored pulse, there is a recess or defect in the wiring that should not be present in the reference pattern. Similarly, a judgment circuit B receives the output of the detection circuit A2 of a height of 1h for a noggle whose width is slightly narrower than the normal width corresponding to the minimum width of the wiring existing in the reference pattern.
Let me remember it in 2. Then, it is detected whether there is a pulse whose width is narrower than the memorized pulse. In this case, if there is a pulse with a narrower width than the stored pulse, this means that there is a convex portion, that is, an unnecessary object that is not in the reference pattern. According to the above-described embodiment, if there is a slight difference in dimensions between the reference gauge and the wiring board to be inspected, the mismatch will generate a pulse output indicating the presence of a defect or an unnecessary object, resulting in an error. However, according to this embodiment, there is no such risk. In this case, after completing the entire surface scan in the X direction, further scan the entire surface in the Y direction,
Perform a more complete inspection. As described above, the present invention can be implemented in various ways. FIG. 3 shows an embodiment using a photodiode array as a photoelectric conversion element, and a switching circuit that operates in sequence with this photodiode array is used to detect a wiring board of a certain length in an extremely short time.

The inspection apparatus according to the present invention can inspect not only the presence or absence of defects or unnecessary materials, but also whether the wiring width and the width between wirings match the standard.

Further, these embodiments detect the transmitted light of the object to be inspected, and the reflected light can also be used as the inspection light beam by utilizing the difference in reflectance between the wiring on the surface and the substrate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. Figure 2a is a cross-sectional view of the portion of the wiring to be inspected;
h is a diagram of each signal waveform in each block in FIG.
FIG. 3 is a circuit diagram showing another embodiment of the present invention. Fourth
Figure a is a cross-sectional view of a portion of the wiring to be inspected showing problems in the conventional case, and figures B and c are corresponding signal waveform diagrams. 1... Luminous lamp, 2...
...Substrate, 3...Wiring, 4...Magnifying lens, 5...Photoelectric conversion element, 6...Defect, 7... Unwanted material, Al, A2...detection circuit, Bl, B2...determination circuit, Cl, C2
...Display section, d...Scanning line.

Claims (1)

[Claims] 1 A method for inspecting the pattern of a substrate having a predetermined pattern of film made of a desired material formed on the surface, the method comprising: forming an electrical signal corresponding to the pattern based on light scanning the substrate; The signal has a first threshold voltage set to a level to detect defects in the film and a second threshold voltage set to a level to detect unwanted matter on a surface portion of the substrate where the film is not to be formed. converting the film into first and second binary signals using a value voltage, and inspecting the pattern of the film based on the first and second binary signals and a signal indicating a pre-stored pattern. An object condition inspection method characterized by: