JPS5990034A - Apparatus for inspecting material state - Google Patents

Abstract

PURPOSE:To inspect exactly a surface state of a material by supplying an electric signal outputted from a photoelectric converter corresponding to a pattern of a surface of a material to be inspected to two detection circuits having different threshold voltages to discriminate a pulse signal outputted from each detection circuit by a discriminating circuit. CONSTITUTION:If a defect 6 exists at wiring part of a printed board to be inspected and an unnecessary wiring material 7 exists at the part where the wiring should not be formed, the output signal of a photoelectric converting element 5 is shown as a figure (b). The output waveform of a detecting circuit A1 is shown as a figure (c) where pulse is generated at the part in which there are no defect 6 and no wiring due to low circuit Vth. Inversely the output waveform of the detecting circuit A2 is shown as a figure (e) where pulse is generated at the part in which there are no wiring and no wiring material 7 due to high Vth of the circuit. The output signal of the detecting circuit and the signal stored in the discriminating circuit are compared in each discriminating circuit B1, B2, and the output is sent to the display part. The output of a discriminating circuit C1 appears as the pulse indicating the existence of the defect 6 caused in the wiring 3 as shown in a figure (g).

Description

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

When a wiring or electrode pattern formed on the surface of a wiring board or a semiconductor element is automatically inspected, an electric signal corresponding to the wiring or electrode pattern is first generated by photoelectric conversion means. The electrical signal is converted into a binary pulse signal to enable digital arithmetic processing. By comparing the pulse signal with a pulse signal corresponding to the reference pattern of the wiring or electrode, undesirable remaining objects on the surface of the substrate or semiconductor element and defects in the wiring or electrode are detected. It turns out.

In the above-mentioned inspection, it is necessary that the pulse signal corresponds accurately to the pattern of the wiring or electrode.

However, for example, the 41st! on the surface as in XI(a).

The electrical signal obtained by scanning the wiring 6 containing defects such as scratches 61, 62 and the board 2 where unnecessary wiring material 71, 72 remains is as shown in the same figure (b). It has become clear that if the signal is binarized using one threshold voltage V1h, only a pulse signal that does not respond to relatively small defects or unnecessary objects can be obtained, as shown in FIG. 3(C).

Therefore, one object of the present invention is to provide an inspection device that can accurately inspect the surface condition of an object, and another object of the present invention is to provide an inspection device that can accurately inspect the surface condition of an object. An object of the present invention is to provide an inspection device that can simultaneously inspect the presence or absence of an object.

According to the present invention, an electrical signal from a photoelectric conversion device output according to a pattern on the surface of an object to be inspected is supplied to a low threshold voltage detection circuit and a high threshold voltage detection circuit, and from each detection circuit. The output pulse signal 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, 3 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 A, , A2. This detection circuit AI
The threshold voltage t11 is set to be different between the detection circuit A2 and the detection circuit A2. That is, the threshold voltage ■thl of the detection circuit A1 is low, and the threshold voltage ■th of the detection circuit A1 is low.
2 is set high. The respective outputs of the detection circuits A, . . . A2 are applied to determination circuits B1 and B, respectively. In the judgment circuits B, B2, the reference pattern is converted into a signal and one signal is stored in memory. And each judgment circuit B
, , B2 compares the output signal of the detection circuit with the signal indicating the memorized reference pattern, and sends the output of the determination circuit to the display sections C, , C2.

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 as shown in FIG. The signal becomes as shown in the same figure (bl).Then, the detection circuit A
The output waveform of , in the same figure (cl
As shown in FIG. 2, a pulse is generated in a portion where there is no defect 6 and no wiring. On the contrary, since the vth of the circuit is high, the output waveform of the detection circuit A2 is such that a pulse is generated in a portion where there is no wiring or unnecessary wiring material 7, as shown in FIG. 2(e).

Then, each determination circuit 1131. At B2, the output signal of the detection circuit is compared with the signal stored in the determination circuit, and the output is sent to the display section. The output of the determination circuit C appears as a pulse indicating the existence of a defect 6 occurring in the wiring 3, as shown in FIG. 3(g).

On the other hand, the output of the determination circuit C7 appears as a pulse indicating the presence of the unnecessary substance 7, as shown in FIG.

In this way, the Vtbl of the detection circuit A is set to be slightly higher than the output signal level of the photoelectric conversion element 5 when receiving light from the part of the board where wiring with no defects exists, and the Vth2 of the detection circuit A2 is set to By keeping the output signal level of the photoelectric conversion element 5 slightly lower than when receiving light from a part of the substrate where no material is present, it is possible to determine whether or not there are defects in the wiring.
It is possible to determine the presence or absence of unnecessary wiring materials and other unnecessary materials.

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. Therefore, outputs are produced that indicate 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 judge the harshness of defects or unnecessary objects from the width of the pulse obtained as the output, and to judge whether or not it is acceptable. In this case, even if the unnecessary items are of an unacceptable size, they 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, the output signal of the photoelectric conversion element 5 is applied to detection circuits A and A2 with different threshold values, and the presence or absence of a low-level signal and the presence or absence of a high-level signal are detected separately. Due to slight defects.

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 B that receives the output of the low ■th detection circuit A1, and the pulse is used as the inspection light. scan. Then, the determination circuit B 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 pulse having a width slightly wider than the pulse corresponding to the minimum width of the wiring existing in the reference pattern is stored in the determination circuit B2 that receives the output of the high Vtb detection circuit A. 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 present in the reference pattern. According to the above-described embodiment, if there is a slight difference in dimensions between the reference pattern and the wiring board to be inspected, the mismatch will generate a pulse output indicating the presence of defects or unnecessary items, resulting in a false display. However, according to this embodiment, there is no such fear. In this case, after completing the entire surface scan in the X direction, a further full surface scan is performed in the X direction to 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 operating in sequence with this photodiode array is used to detect a wiring board over a certain length in an extremely short time.

It should be noted that the inspection apparatus according to the present invention can inspect not only the presence or absence of defects or unnecessary materials, but also whether or not the width of the wiring and the width between the wires match the standards. These embodiments detect transmitted light of an object to be inspected. The reflected light can also be used as an inspection light beam by utilizing the difference in reflectance between the surface wiring and the substrate.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2(a) is a cross-sectional view of a portion of the wiring to be inspected, and FIG. 2(h) is a diagram of each signal waveform in each block of FIG. 1. FIG. 4 is a circuit diagram showing an embodiment. FIG. 4(a) is a cross-sectional view of the inspected portion of the wiring showing problems in the conventional case, and FIG. 4(b) and (c) are corresponding results. 1 is a signal waveform diagram shown in FIG. 1. 1... Light emitting lamp, 2... Board, 3... Wiring, 4
... Magnifying lens, 5... Photoelectric conversion element, 6... Defect, 7... Unnecessary matter, A, , A,... Detection circuit, B,
, B...judgment circuit, C,, C2... display section, d.
...Scanning line.

Claims (1)

[Claims] 1. A device for inspecting the pattern of a substrate having a predetermined pattern of film made of a desired material formed on the surface thereof, and a photoelectric conversion device for forming an electrical signal corresponding to the pattern based on light scanning the substrate. means, and the electrical signal,
A first threshold voltage is set to a level to detect defects in the film, and a second threshold voltage is set to a level to detect waste on a surface portion of the substrate where the film should not be formed. The first threshold voltage is determined by the threshold voltage. a detection circuit for converting into a second binary signal; and the first detection circuit. An object state inspection device comprising: a determination circuit that detects a pulse width narrower than the minimum pulse width determined by the predetermined pattern among the respective pulse widths of the second binary signal.