JPH03227034A - Wafer foreign substance inspecting device - Google Patents

Abstract

PURPOSE:To make it possible to identify reliably the presence or absence of adhesion of foreign substances by a method wherein one scanning waveform pattern converted by a photodetector is stored and thereafter, an irregular pulse waveform and a pulse waveform, has a regularity, but has a high peak level, which exist in the pattern, are decided as pulse waveforms due to the foreign substances. CONSTITUTION:A laser oscillator 1 is slanted at a proper angle and is fixed, a wafer 3 and the oscillator 1 are moved relatively to each other and the oscillator 1 is moved to scan the surface of the wafer. At this time, reflected light complemented by a photodetector 4 is converted into a current and the current is outputted as a current waveform. This output signal is temporarily stored in a signal storage circuit 5 in every one scanning and is sent to a signal decision circuit 6. Here, in the case foreign substances adhere on a chip 7 and there are foreign substances 9 existing except foreign substances existing t pattern edges, the foreign substances 9 appear as signals 12 due to the foreign substances 9 existing except those existing at the pattern edges. As the waveforms of these signals 12 have not a regular period, the circuit 6 decides the signals 12 as signals due to the foreign substances 9. When the foreign substances are adhered on the pattern edge parts, signals due to the foreign substances overlap with signals 11 due to the pattern edges and appear as signals 13 due to the foreign substances existing at the pattern edge parts. As the peak level of the waveforms of these signals 13 is higher than that of the waveforms of the signals 11, the signals 13 are decided as signals due to the foreign substances.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides: - A wafer foreign matter inspection device for inspecting the presence or absence of foreign matter on the surface of a wafer on which a pattern such as a circuit element or a resist film is formed on the main surface. Regarding.

[Conventional technology]

Conventionally, although not shown in the drawings, this type of wafer foreign object inspection equipment has a laser beam that irradiates a wafer surface on which a pattern is formed and scans the wafer surface by moving relative to the wafer. and a light-receiving element that captures reflected and scattered light from the wafer surface and converts the reflected and scattered light into photocurrent.

When inspecting a wafer on which a circuit pattern is formed using this wafer foreign object inspection device, first, the inclination of the laser oscillator with respect to the wafer surface is adjusted so that the scattered light is more easily reflected at the stepped portion of the circuit pattern, and then First, the wafer surface is scanned with a laser beam, the reflected and scattered light is captured by a photodetector, and this photocurrent waveform is projected onto an oscilloscope.
[Problem to be solved by the invention] However, the above-mentioned conventional wafer foreign object detection apparatus simply identifies regularly appearing pulse waveforms as pattern steps. Since the pulse waveform that appears irregularly is determined to be a foreign object, when the sensitivity of the light receiving element is lowered and the inspection is performed to clarify the difference between the step and the foreign object, only the waveform due to the step is piled up. However, it has the disadvantage that accurate inspection cannot be performed because waveforms due to foreign objects may not appear. In addition, when inspecting a wafer with increased sensitivity and there is a foreign object on a stepped portion, the waveform caused by the foreign object overlaps the regular waveform, making it difficult to determine whether there is a foreign object.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer foreign matter inspection device that eliminates the drawback of smearing and can reliably identify the presence or absence of foreign matter.

[Means to solve the problem]

The wafer foreign matter inspection apparatus of the present invention includes a laser oscillator that irradiates a patterned wafer surface with a laser beam and scans the wafer surface by moving relative to the wafer, and a laser oscillator that scans the wafer surface by moving relative to the wafer, and a laser oscillator that scans the wafer surface by scanning the wafer surface with a laser beam, and In a wafer foreign matter inspection apparatus having a light receiving element that supplements the reflected and scattered light and converts the reflected and scattered light into a photocurrent, a signal storage circuit that stores a photocurrent waveform pattern generated when scanning a laser beam, and a signal storage circuit that stores the photocurrent waveform pattern generated when scanning a laser beam, and The apparatus includes a signal determination circuit that determines that a photocurrent pulse waveform that appears due to an irregular period and a difference in level intensity in a photocurrent waveform pattern is caused by a foreign object.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of the wafer foreign matter inspection apparatus of the present invention. As shown in Fig. 1, this wafer foreign object inspection device reflects a laser beam with a mirror 2, irradiates it onto a 3 surface of a process fer on which a circuit pattern is formed, and moves the laser beam relative to the wafer 3. A laser oscillator 1 that scans the surface of the upstream wafer 3, a light receiving element 4 that captures reflected and scattered light from the wafer 3 surface and converts the reflected and scattered light into a photocurrent, and a photocurrent that is generated when scanning the laser light. It includes a signal storage circuit 5 that stores waveform patterns, and a signal determination circuit 6 that determines that a photocurrent pulse waveform that appears due to irregular periods and differences in level intensity in the obtained photocurrent waveform pattern is caused by a foreign object. There is.

FIG. 2 is a pattern on a wafer and a waveform diagram when scanning this pattern to explain the operation of the wafer foreign matter inspection apparatus shown in FIG. Next, the operation of this wafer foreign matter inspection apparatus will be explained. Here, an example will be described in which whether or not there is a gift on the chip 7, which is a partial area on the wafer shown in FIG. 2, is inspected. First, the laser oscillator 1 is fixed at an appropriate angle, and the wafer 3 and the laser oscillator 1 are moved relatively to scan the wafer surface. As a result, the reflected light captured by the light receiving element 4 is converted into a current and output as a current waveform. This output signal is temporarily stored in the signal storage circuit 5 for each scan, and when the next signal is input, the waveform signal from the previous scan is sent to the signal determination circuit 6. When scanning is performed sequentially in this manner, as shown in FIG. 2, the signal 11 due to the pattern edges appears as a pulse-like waveform in the stepped portion of the pattern 8 at regular intervals.

In this way, the surface of the wafer 3 is sequentially scanned to complete the inspection.

Here, if there is a foreign substance attached to the chip 7, when the laser beam is scanned on the chip of the tool C, if there is a foreign substance 9 other than the pattern edge, a signal 12 due to the foreign substance other than the pattern edge will be detected. appear. Since this waveform does not have a regular period, the signal determination circuit 6 determines that it is a foreign object. Further, when a gift adheres to the pattern edge, it overlaps with the signal 11 due to the pattern edge and appears as a signal 13 due to the foreign object present at the pattern edge.

This waveform becomes a signal that overlaps with the signal 11 due to the pattern edge, but since the peak level is higher than the signal due to the pattern edge, the signal determination circuit 6 determines that it is a foreign object.

FIG. 3 is a block diagram of a wafer foreign matter inspection apparatus showing another embodiment of the present invention. This wafer foreign matter inspection equipment is
A pattern signal storage circuit 14 is provided in advance to store a waveform pattern obtained when a chip to which no foreign matter is attached is scanned. The rest is the same as the previous embodiment.

When inspecting the presence or absence of foreign matter on the wafer surface with this wafer foreign matter inspection device, the signal judgment circuit compares the waveform pattern obtained for each scan with the laser beam with the waveform pattern stored in the pattern signal storage circuit 14. 6, the presence or absence of foreign matter is determined.

Since the wafer foreign matter inspection apparatus of this embodiment stores the signal waveform from the pattern edge in advance, it has the advantage that when inspecting a plurality of wafers, it can be inspected continuously in a short time.

〔Effect of the invention〕

As explained above, the present invention scans the wafer surface with laser light, provides a light receiving element that captures the scattered light reflected from steps or foreign objects on the wafer surface, and stores the one-scan waveform pattern converted by this light receiving element. By providing a signal storage circuit that detects foreign objects, and providing a signal determination circuit that determines irregular pulse waveforms and regular but high peak level pulse waveforms in one scanning waveform pattern of this signal storage circuit as foreign objects. This has the effect of providing a wafer foreign matter inspection device that can reliably identify the presence or absence of foreign matter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the wafer foreign matter inspection apparatus of the present invention, and FIG. 2 shows a pattern on a wafer and a time when this pattern is scanned to explain the operation of the wafer foreign matter inspection apparatus of FIG. 1. FIG. 3 is a block diagram of a wafer foreign matter inspection apparatus showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Laser oscillator, 2...-Mirror 3... Wafer 4... Light receiving element, 5... Signal storage circuit, 6...
・Signal judgment circuit, 7...chip, 8...pattern,
9--Foreign object other than the pattern edge, 10-Foreign object at the pattern edge, 11--Signal due to pattern edge, 12--Signal due to foreign object other than the pattern edge, 13-- Foreign object at pattern edge Signal due to foreign matter, 14... Pattern signal storage circuit.

Claims (1)

[Claims] a laser oscillator that irradiates a patterned wafer surface with laser light and scans the wafer surface by moving relative to the wafer; and a laser oscillator that captures reflected and scattered light from the wafer surface and removes the reflected and scattered light In a wafer foreign matter inspection apparatus having a light receiving element that converts into a photocurrent, there is provided a signal storage circuit that stores a photocurrent waveform pattern generated when scanning a laser beam, and an irregular period in the obtained photocurrent waveform pattern. and a signal determination circuit that determines that a photocurrent pulse waveform that appears due to a difference in level intensity is caused by a foreign substance.