JPH01176932A - Fine foreign matter inspection device - Google Patents

Abstract

PURPOSE:To detect whether or not there is a fine foreign matter and whether or not there is an organic body by providing a 1st lighting means, an objective lens and, a photoelectric converting element, etc. CONSTITUTION:If there is a fine body 3 on the surface of a wafer 2, spot light from the 1st light source 4 is scattered and this scattered light is converged on a photometric stop 13 through the objective 7, a dichroic mirror 11, and an absorption filter 12. The stop 13 becomes conjugate to the surface of the wafer 2 at a reference position. Therefore, only the scattered light from an area on the wafer 2 conjugate to the hole of the stop 13 passes through the stop 13 and enters the incidence slit 14 of a spectroscope A. Then the incident light from the slit 14 is reflected by a total reflecting mirror 21 and a concave surface mirror 15 and then its light of (0)th order is reflected by a diffraction grating 16; and its reflected light is reflected by the concave surface mirror 15 and total reflecting mirror 22 and enters the projection slit 17. This scattered light is transmitted through the dichroic mirror 18 and converted photoelectrically by the photoelectric converting element 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a minute foreign matter inspection device that automatically inspects the presence or absence of minute foreign matter on the surface of a flat substrate, such as a wafer.

[Conventional technology]

As a micro foreign particle inspection device on the wafer surface, one or several light beams are irradiated on the wafer surface from an oblique direction.
There is a type that allows scattered light from minute foreign matter present in the irradiation to be incident on a photoelectric element, and automatically determines the presence or absence, size, etc. of the minute foreign matter by moving the beam and the wafer relative to each other. There is also a type that makes it possible to distinguish the scattered light from the pattern and the scattered light from the minute foreign matter by using polarized light, thereby making it possible to detect the minute foreign matter on the patterned wafer.

[Problem that the invention seeks to solve]

If minute foreign matter exists on the wafer surface during in-process, it will greatly affect the performance of the device, and there is a very high possibility that the device will be defective. Conventional micro foreign object inspection equipment can detect the presence or absence, size, and number of micro foreign objects, but cannot detect the true nature of the micro foreign objects.
Cannot be determined.

Therefore, an object of the present invention is to obtain a minute foreign matter inspection device that can detect the presence or absence of minute foreign matter and the presence or absence of organic matter.

(Means for Solving the Problems) Therefore, the present invention provides a first illumination means (4, 24) that projects a spot light onto a flat substrate from an oblique direction, and a first illumination means (4, 24) that projects a spot light onto a flat substrate from a direction perpendicular to the surface thereof. A second illumination unit (8,
9, 10, 11, 7), and a scanning means (la, 1.52.54) that places the flat substrate and moves it two-dimensionally, and scans the flat substrate two-dimensionally with the spot light.
．． 58), receives the scattered light from the flat substrate caused by the spot light and the fluorescent light from the flat substrate caused by the excitation light, separates the wavelengths of the scattered light and the fluorescent light, and performs photoelectric conversion of each. Light receiving means (7, 11,
12, 13, A, 18, 19, 20), and the presence or absence of minute foreign matter on the flat substrate from the photoelectric conversion signal of the scattered light,
Further, calculation and display means (
56, 57, 58, 60) The above object has been achieved by a micro foreign matter inspection device characterized by having the following.

(Function) According to the present invention, since the scattered light caused by the spot light of the first illumination means and the fluorescent light caused by the excitation light of the second illumination means are detected, it is possible to detect the presence or absence of not only minute foreign matter but also organic matter. You can know. Therefore, it is not only possible to identify whether the minute foreign matter is inorganic or organic, but also to detect the remaining resist on the flat substrate. Furthermore, in the case of patterned wafers, in the case of a configuration that uses scattered light to detect minute foreign objects, it is not possible to distinguish between the light scattered by the pattern and the light scattered by the minute foreign objects, so it is not possible to detect the minute foreign objects. According to fluorescence detection using excitation light, organic matter (organic dust, resist, etc.) on the wafer can be identified even if there is a pattern on the wafer.

(Example) Fig. 1 is a diagram showing the optical system of the first embodiment of the present invention, Fig. 2 is a perspective view of the vicinity of the irradiation position, Fig. 3 is a diagram explaining the principle, and Fig. 4 is an electrical block diagram. .

A wafer 2 as a flat substrate is placed on a mounting member 1a of the stage 1. The mounting member 1a is movable in the X direction, the two directions, and the φ direction (see FIG. 2) by a known mechanism.

Illumination light from a first illumination light source 4 composed of a laser, a laser diode, an LED, etc. is condensed by a condenser lens 24, and is projected obliquely onto the wafer 2 as a spot light. There is a condensing lens 23 in a direction with a reflection angle equal to the incident angle of this spot light, and this condensing lens 23 directs the light spot on the wafer 2 onto the vibration slit 6 when the wafer 2 is at the reference position in the Z direction. The light is focused on. The vibration slit 6 is formed in a direction perpendicular to the plane of the paper and vibrates in the direction of arrow P perpendicular to the optical axis. This vibration center position is a position where a light spot is generated by the condenser lens 23 when the wafer 2 is at the reference position.

The transmitted light of the vibrating slit 6 enters the detector 5 and is photoelectrically converted. After being appropriately processed, this photoelectric conversion signal is input to a calculation device and used to control the position of the mounting member 1a in the Z direction. That is, the first illumination light source 4, the condensing lens 24
．． 23, the vibrating slit 6, and the detector 5 constitute a well-known focus detection system.

The light emitted from the second illumination light source 8 composed of a mercury lamp, a laser, etc. is selected by a condensing lens 9, an excitation filter 10, and a gicroic mirror 11, and the light having an excitation wavelength is Focus the light on the focal point. Therefore,
The excitation light becomes a parallel light beam by the objective lens 7, and the light beam is condensed by the objective lens and enters the wafer 2. The optical axis of the objective lens 7 is set to pass through the intersection of the condenser lenses 23 and 24 that intersect with the surface of the wafer 2 at the reference position.

When there is a minute foreign object 3 such as dust on the surface of the wafer 2, scattered light of the spot light from the first illumination light source 4 is generated, and this scattered light passes through the objective lens 7, dichroic mirror 11, and absorption filter 12, and then reaches the photometric aperture 13. Focus the light upward. The photometric aperture 13 is conjugated with the surface of the wafer 2 and the objective lens 7 when the wafer 2 is at the reference position. Therefore, only scattered light from a region on the wafer 2 that is conjugate with the hole of the photometric aperture 13 passes through the photometric aperture 13 and enters the entrance slit 14 of the spectrometer A via a relay lens (not shown). The incident light from the input slit is reflected by the total reflection mirror 21 and the concave mirror 15, and then the 0th-order light is reflected by the diffraction grating 16. This reflected light is further reflected by the concave mirror 15 and the total reflection mirror 22, and then the output slit 1.
It is ejected from 7.

The scattered light emitted from the output slit 17 passes through the dichroic mirror 18, enters the photoelectric conversion element 20, and is photoelectrically converted.

On the other hand, if the minute foreign matter 3 is a substance that generates fluorescent light, the fluorescent light will be generated by irradiation with the excitation light, and this fluorescent light will pass through the objective lens 7, the glycoic mirror 11, and the absorption filter 12. The light is focused onto a photometric aperture 13. When the wafer 2 is at the reference position, only the fluorescent light from the area on the wafer 2 that is conjugate with the hole of the photometric aperture 13 passes through the photometric aperture 13, passes through the spectrometer A, is reflected by the dichroic mirror 18, and is photoelectrically converted. Element 1
9 and undergoes photoelectric conversion. The output signals of the photoelectric conversion elements 19 and 20 are input to the arithmetic display device 20, and are subjected to arithmetic processing and
Display is performed.

FIG. 3 shows the illumination light from the first illumination light source 4 mentioned above, the light scattered by the foreign matter, the excitation light, and the fluorescence generated from the foreign matter by the excitation light, focusing on their respective wavelengths.
The wavelength of the illumination light from the illumination light source 4 is λ1, the light scattered by foreign objects has the same wavelength, so it is also λ1, and the wavelength of the excitation light is λ.
2. The wavelength of fluorescent light is shown as λ. Note that, in FIG. 3, some of the members shown in FIG. 1 are omitted for simplification. As can be seen from FIG. 3, the dichroic mirror 11 has the characteristic of reflecting the wavelength λ2 of the excitation light and transmitting the wavelength λ1 of the scattered light and the wavelength λ of the fluorescent light. It has the characteristic of transmitting the wavelength λ1 of fluorescent light and reflecting the wavelength λ1 of fluorescent light.

FIG. 4 is an electrical block diagram used together with the optical system shown in FIG. control and set the wafer 2 at two-direction reference positions. Thereafter, the arithmetic unit 58 controls the X-direction drive device 53 and rotation drive device 55 of the stage 1 so that the spot light scans the wafer 2 in a spiral manner. At that time, the X direction position detector 52, the rotational position detector 5
Since the position signal from 4 is input to the calculation device 58, the calculation device can calculate the coordinate position on the wafer 2 that is irradiated with the spotlight. It goes without saying that this coordinate position may be based on curved coordinates or XY coordinates.

While the spot light spirally scans the wafer 2, when the spot light is scattered by the foreign object 3 on the wafer 2, this scattered light is transmitted to the objective lens 7 and the dichroic mirror 1.
1, absorption filter 12, photometric aperture 13, entrance slit 1
4. The light passes through the spectrometer A and the dichroic mirror 18 and enters the photoelectric conversion element 20. As a result, the photoelectric conversion element 20
A foreign object detection signal is input to the arithmetic unit 5 from the foreign object detector 56 including the foreign object detector 56 . The arithmetic device 58 stores the position signals from the X-direction position detector 52 and the one-rotation position detector 54 in the memory as foreign object presence coordinate values when the foreign object detection signal is input from the foreign object detector 58.

When the foreign matter 3 is an organic matter, the fluorescent light generated by the foreign matter 3 enters the photoelectric conversion element 19 through the objective lens 7, dichroic mirror 11, absorption filter 12, photometric aperture 13, and spectrometer A1 dichroic mirror 18. As a result, an organic substance detection signal is input to the arithmetic unit 58 from the organic substance detector 57 including the photoelectric conversion element 19 . When the organic matter detection signal is input from the organic matter detector 57, the arithmetic unit 58 labels the foreign matter recognized by the foreign matter detection signal from the foreign matter detector 58 as an organic substance.

Note that even if the organic motion detector 57 outputs an organic substance detection signal, the foreign substance detector 58 may not output a foreign substance detection signal, such as when there is a residual resist.

When the scanning of the wafer 2 by the spotlight 2 is completed by the movement of the mounting member 1a, the arithmetic device 5B (the arithmetic device 58, The X-direction drive device 53 and the rotation drive device 55 until the X-direction maximum movement position and maximum rotation speed are reached.
), the X-direction drive device 53 returns the mounting member 1a to the initial position, and the arithmetic device 58 causes the display 60 to display the coordinate value of the foreign object stored in the memory. At that time, those with organic labeling,
It is also indicated that the foreign matter is organic.

In addition, the arithmetic unit 58 operates to analyze organic substances in response to an operator's instructions from a keyboard (not shown) or the like. That is, the arithmetic unit 58 calculates the contents of the memory so that the mounting member 1a is located at the coordinate position where the organic matter is labeled (this position is the position where the minute foreign matter 3 approximately coincides with the optical axis of the objective lens 7). X-direction drive device 53 according to
The rotation drive device 55 is sequentially controlled. Specifically, the arithmetic unit 58 first searches the memory for a coordinate position where an organic substance is labeled sequentially from the initial coordinate position, moves the mounting member 1a to the coordinate position where the organic substance is labeled, and drives the grating of the spectrometer A. A control signal is output to the device 59 to cause the diffraction grating 16 to scan the wavelength. As a result, by synchronizing the output of the photoelectric conversion element 19 and the control signal of the grating drive device 59, the arithmetic device 58 can obtain the wavelength spectrum of the organic substance at the measurement coordinate position. This data is stored in memory.

When the wavelength spectra of all the organic substances are obtained in this way, the calculation device 58 compares each of the measured wavelength spectra with the wavelength spectra of various organic substances previously stored in the memory, and calculates the wavelength spectra of the substances. Identification is performed and the substance name is displayed on the display 60 along with the coordinate values.

FIG. 5 shows a second example of the present invention, and parts with the same functions as those in FIG. 1 are given the same reference numerals and their explanation will be omitted.

The light reflected by the total reflection mirror 21 is separated by a concave diffraction grating 27, and a fluorescence spectrum is imaged on the linear image sensor array. The concave diffraction grating 27 has a feature that it can separate light of a wide range of wavelengths at once without rotating the diffraction grating. The fluorescence spectrum imaged on 28 is photoelectrically converted at once by 28, and then sent to a data processing section 30.
Since the data is sent to , it is possible to increase the speed compared to the example shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, scattered light caused by oblique incidence of a light beam and fluorescent light caused by vertical incidence are treated as microscopic foreign objects from the same position and same range of illumination field, and the wavelengths of the scattered light and fluorescent light are Based on the difference, it becomes possible to perform photometry simultaneously, and it is possible to quickly determine whether the minute foreign matter is inorganic or organic over the entire area of a wafer or other object to be inspected.

In addition, substances can be identified by qualitatively analyzing the fluorescent light from organic substances using a spectrometer at high speed. By photometry using a device, it becomes possible to simultaneously detect the inorganic substance, the organic substance, and the qualitative analysis of the organic substance.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the optical system of the first embodiment of the present invention, Fig. 2 is a perspective view near the irradiation position, Fig. 3 is a diagram explaining the principle, Fig. 4 is an electrical block diagram of the first embodiment, FIG. 5 shows the second embodiment of the present invention.
It is a figure showing the optical system of an example. (Explanation of symbols of main parts) 1... Stage, 4... First illumination light source, 8...
2nd illumination light source, 11.1 day... Gikroic mirror 19.20...
・Photoelectric conversion element. Applicant Nippon Kogaku Kogyo Co., Ltd.

Claims (1)

[Scope of Claims] First illumination means for projecting a spot light onto a flat substrate from an oblique direction; and projecting excitation light onto the flat substrate from a direction perpendicular to the surface thereof so as to overlap the irradiation position of the spot light. a second illumination means; a scanning means that places the flat substrate and moves it two-dimensionally, and scans the flat substrate two-dimensionally with the spot light; light scattered from the flat substrate by the spot light; and a fluorescent light from the planar substrate caused by the excitation light, a light receiving means for wavelength-separating the scattered light and the fluorescent light, and outputting respective photoelectric conversion signals; and photoelectric conversion of the scattered light. It is characterized by comprising: calculation display means for determining and displaying the presence or absence of minute foreign matter on the flat substrate from a signal and the presence or absence of an organic matter on the flat substrate from the photoelectric conversion signal of the fluorescence, respectively. Micro foreign matter inspection device.