JPH03230544A - Apparatus for inspecting appearance of wafer - Google Patents

Abstract

PURPOSE:To simply detect a position of a different substance existing in a short time by radiating laser light of a single wavelength having a spot diameter of approximately 5 to 10mum to a wafer surface formed with a multi-layer film and observing an interference fringe generated by the light reflected from the different substance and by the light reflected on the film. CONSTITUTION:An apparatus for inspecting appearance of a wafer comprises an optical system and a laser oscillator 1 for radiating laser light having a spot size of 5 to 10mum on a wafer 5 surface with a multi-layer film formed on one principal face and an optical system and an image-pickup camera 11 for acquiring reflected light by the laser light. If a different substance 15 exists in an upper film 7 or on a lower film 6, an interference fringe 16 due to difference in light paths for the light reflected from the film and the light reflected from the different substance is picked up on a pattern 14 in a region of a laser light spot 13 in addition to the different substance 15. When the different substance is on the upper film 7, no interference fringe is observed. Thus a precise position of the different substance can be known.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for: - detecting the presence or absence of foreign matter in a wafer having a multilayer film formed on its main surface, and determining where in the multilayer film this foreign matter is present; The present invention relates to a wafer appearance inspection device for inspecting wafers.

[Conventional technology]

Conventionally, this type of wafer appearance inspection equipment did not have any special equipment, and when inspecting the presence or absence of foreign substances attached to a wafer, the wafer surface was observed with a general-purpose microscope and monitor, and a standard I was inspecting it while comparing it with the pattern with foreign matter.

In addition, when inspecting where a foreign substance is present in a multilayer film, the wafer surface is irradiated with white light, the focus position is changed, and the position is observed using a microscope or a monitor. I was doing it.

[Problem to be solved by the invention]

However, the conventional wafer visual inspection equipment described above requires repeated focusing of the microscope several times in order to inspect the position of foreign objects, which not only takes many man-hours but also requires skill. There are drawbacks.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer visual inspection apparatus that eliminates these drawbacks and is easier to operate and can be inspected in a shorter time.

[Means to solve the problem]

The wafer appearance inspection apparatus of the present invention is a wafer appearance inspection apparatus that detects the presence or absence of foreign matter on a wafer having a multilayer film formed on its main surface and inspects the position of the foreign material on the multilayer film, comprising: 5 to 1 on the surface of the wafer
It is equipped with an optical system and a laser oscillator that irradiate a laser beam with a spot diameter of 0/l m, and an optical system and an imaging camera that take in the reflected light from this laser beam, and observes interference fringes generated within the multilayer film. The present invention is characterized in that the location of the foreign object is known by this.

〔Example〕

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

FIG. 1 is a bronch diagram of a wafer visual inspection apparatus showing an embodiment of the present invention. As shown in the figure, this wafer appearance inspection apparatus includes a white lamp 4 that irradiates white light onto a wafer 5 on which a multilayer film is formed, a single wavelength laser beam oscillator 1 that emits laser light, and a laser beam oscillator 1 that emits a laser beam. A beam expander 3 that expands the spot diameter of light to about 5 to 10 μm, a switching mirror 3 that switches the light irradiated onto the wafer 5 to the white light or laser light, and receives the white light and laser light reflected from the wafer 5. It has a prism 9, a half mirror 10, and an imaging camera 11 that captures images via a mirror 8.

FIGS. 2(a) and 2(b) are diagrams showing patterns in the field of view of an imaging camera for explaining the operation of the wafer visual inspection apparatus shown in FIG. Next, the operation of this wafer visual inspection apparatus will be explained.

First, in a normal inspection for the presence of foreign matter, as shown in FIG. 1, the white lamp 4 is turned on to generate white light. After the zero-order irradiation of the surface, this reflected white light is reflected by the mirror 8, transmitted through the half mirror 10, enters the imaging camera 11, and images the surface of the wafer 5.

Further, when observing the location of a foreign object, the switching mirror 3 in FIG. 1 is switched as shown by the solid line. Next, a single wavelength laser beam oscillator 1 generates a laser beam, a beam expander 2 expands the laser beam spot to a diameter of about 8 μm, and a switching mirror 3 irradiates the surface of the wafer 5 with the laser beam.

A part of the laser beam is reflected by the upper layer film 7, and the other part is transmitted. Further, part of the light transmitted through the upper layer film 7 is reflected on the surface of the lower layer film 6, and the rest is transmitted and reflected on the underlying surface. All of these reflected lights are captured by an imaging camera 11 through a light receiving prism 9 and a half mirror 10, and a pattern is captured.

Of course, since reflected light is also generated from the foreign matter 15 in the film, the foreign matter 15 is also photographed.

Here, if the foreign matter 15 is in the upper layer film 7 or on the lower layer film 6, as shown in FIG. 2(a), the laser beam is In addition to the foreign matter 15, interference fringes 16 are imaged in the pattern 14 in the area of the light spot 13.

By this, conversely, it becomes clear whether or not foreign matter is present in the film, depending on whether or not these interference fringes are present. Further, when foreign matter is on the upper layer film 7, no interference fringes are observed as shown in FIG. 2(b).

FIG. 3 is a block diagram of a wafer visual inspection apparatus showing another embodiment of the present invention. This wafer visual inspection equipment is
As shown in the figure, the wafer visual inspection apparatus of the above embodiment is provided with an incident angle adjustment prism 17 that changes the incident angle in the projection light path. This wafer appearance inspection apparatus has the advantage that the incident angle can be varied depending on the refractive index of the film, so that the position of foreign particles can be determined more precisely.

〔Effect of the invention〕

As explained above, the present invention irradiates a single wavelength laser beam with a spot diameter of about 5 to 10 μm onto the wafer surface on which a multilayer film is formed, and the reflected light from the foreign matter and the reflected light from the film are emitted. By observing the interference fringes generated by this method, there is an effect that a wafer appearance inspection apparatus can be obtained that can easily and quickly determine the location of foreign matter.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a wafer visual inspection apparatus showing an embodiment of the present invention, and FIGS. 2(a) and (b) are views of an imaging camera for explaining the operation of the wafer visual inspection apparatus shown in FIG. FIG. 3 is a block diagram of a wafer visual inspection apparatus showing another embodiment of the present invention. ■...Single wavelength laser beam oscillator, 2...Beam expander, 3...-Switching mirror, 4...White lamp, 5...
・・Wafer, 6・・Layer film, 7−・Upper layer film, 8・
・Mirra 9--Light receiving prism, 10-・Half mirror-1
11... Imaging camera, 12... Missing number, 13... Laser light spot, 14... Pattern, 15... Foreign object, 1
6... Interference fringes, 17... Incident angle adjustment prism.

Claims (1)

[Claims] In a wafer appearance inspection device that detects the presence or absence of foreign matter on a wafer having a multilayer film formed on one principal surface and inspects the position of the foreign matter on the multilayer film, a spot of 5 to 10 μm is placed on the wafer surface. An optical system and a laser oscillator that emit a laser beam having a diameter, an optical system and an imaging camera that capture reflected light from the laser beam,
A wafer appearance inspection apparatus characterized in that the location of the foreign matter is known by observing interference fringes generated within the multilayer film.