JPH09145630A - Method and device for detecting foreign matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform foreign matter detection on a large to-be-inspected material with sure, by irradiating a material to-be-inspected with the light of S polarization component at a specified incident angle, and selecting only the S polarization component out of light scattered by the material to-be-inspected, for detecting a foreign matter based on the photodetected intensity from a specified angle direction. SOLUTION: The laser beam outputted from a laser oscillator 6 is made into the laser beam of only S polarization component, passing through a polarizer 7. The laser beam is converged with a converging lens 9, and made to fall onto a semiconductor wafer as a small laser sport 10. Relating to the wafer 4, when a foreign matter is in the scanned spot 10, the scattered light is produced. A polarizer 12 makes only the S polarization component, out of the scattered light, pass it through to guide it to a fiber plate 13. The fiber plate 13 selectively converges the light based on a diverging angle of a specified part of the scattered light produced on the surface of wafer 4, and directs the light to a photomultiplier tube 14. The multiplier tube 14 outputs the scattered light signal Q corresponding to the light intensity of S polarization component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates an object to be inspected, such as a semiconductor wafer, with light, and from the intensity of scattered light generated on the object to be inspected at this time, minute foreign matter on the order of submicron adhered to the semiconductor wafer TECHNICAL FIELD The present invention relates to a foreign matter inspection method and apparatus for inspecting.

[0002]

2. Description of the Related Art In such a foreign matter inspection method, for example, the surface of a semiconductor wafer is irradiated with a laser beam, and this laser beam is scanned over the entire surface of the semiconductor wafer. When the surface of the semiconductor wafer is irradiated with the laser beam in this manner, scattered light is generated on the surface of the semiconductor wafer at this time, and the scattered light is detected by the photodetector.

Then, the foreign matter adhering to the surface of the semiconductor wafer is detected from the intensity of the scattered light detected by the photodetector. In such a foreign matter detecting method, a foreign matter having a size of up to 0.2 μm can be detected with respect to the foreign matter adhering to the metal film on the surface of the semiconductor wafer.

Further, in consideration of the polarization direction of the laser beam incident on the semiconductor wafer and the arrangement of the photodetector for receiving the scattered light generated on the semiconductor wafer, finer particles (size 0.
(About 07 μm) can be detected.

Such a foreign matter detecting method is applied to a semiconductor wafer such as a bare wafer having a very small surface roughness,
That is, it is suitable for detecting foreign matter on the surface of a mirror-like semiconductor wafer.

However, a semiconductor wafer having a large surface roughness such as a metal film is also used in an actual semiconductor manufacturing line, for example, a manufacturing process of 256M DRAM currently under development, and a semiconductor wafer having a large surface roughness is used. In this case as well, it is necessary to detect foreign matter having a size of 0.2 μm or less.

However, the above-described foreign matter inspection method cannot deal with detection of foreign matter having a size of 0.2 μm or less on a semiconductor wafer having a large surface roughness. That is, the detection sensitivity of a foreign substance is generally S / N ≧ 3, where S is the intensity of scattered light from the foreign substance and N is the intensity of scattered light from the surface of the semiconductor wafer.

In the case of a semiconductor wafer having a large surface roughness, the scattered light intensity N from the surface of the semiconductor wafer becomes large, so that the detection limit is lowered and it is not possible to detect a foreign matter of 0.2 μm or less.

Further, in JP-A-64-3545, S-polarized light beams having different wavelengths are irradiated from two light sources, respectively, and the light amount of the P-polarized component and the light amount of the S-polarized component in the reflected light are detected, and the ratio thereof is detected. A technique for detecting a foreign substance based on the value of is disclosed. A similar technique is disclosed in Japanese Patent Laid-Open No. 2-2840447.
This is also disclosed in the official gazette.

These are intended for a semiconductor wafer on which a pattern is formed, and the surface of the semiconductor wafer on which a pattern having a predetermined regular unevenness is formed is irradiated with S-polarized light. The polarization state is conserved in a regular pattern, and P is used for a foreign substance having a random shape.
It is used to change to polarized light. Therefore, the ratio of S-polarized light and P-polarized light is taken.

However, when a semiconductor wafer with a metal film having a large surface roughness, which is the object of the present invention, is targeted, a large amount of P-polarized light component is detected in the above method, that is, the surface roughness and The state becomes indistinguishable from the foreign matter (state with low S / N), and it becomes extremely difficult to detect the foreign matter.

In addition to the fact that a plurality of detectors must be provided, a process for obtaining the ratio of the detection intensities of the P-polarized component and the S-polarized component is required, which complicates the configuration and the signal processing method.

[0013]

As described above, when detecting a foreign substance having a size of 0.2 μm or less on a semiconductor wafer having a large surface roughness, the scattered light intensity N from the surface of the semiconductor wafer is detected.
Becomes large, the detection limit is lowered, and it is not possible to detect minute foreign matter.

Therefore, an object of the present invention is to provide a foreign matter detecting method capable of surely detecting a minute foreign matter even on an object to be inspected having a large surface roughness. It is another object of the present invention to provide a foreign matter detection device that can reliably detect minute foreign matter even on an object to be inspected having a large surface roughness.

[0015]

According to a first aspect of the present invention, light having an S-polarized component is irradiated onto an object to be inspected at a predetermined incident angle,
This is a foreign matter inspection method in which only the S-polarized component of the scattered light generated on the object to be inspected is selected and received from a predetermined angle direction, and the foreign matter on the surface of the object to be inspected is detected based on the intensity of the received light.

According to a second aspect of the present invention, there is provided a foreign matter inspection method for inspecting a foreign matter and the like on the surface of the object to be inspected by scanning the surface of the object to be inspected with light and detecting scattered light generated on the object to be inspected. This is a foreign matter inspection method in which a spot shape of light scanning on a body surface is formed long in a direction coinciding with the scanning direction on the surface of the body to be inspected.

According to the third aspect of the present invention, the S-polarized component light is applied to the object under inspection at a predetermined incident angle, and the spot shape of the S-polarized component light coincides with the scanning direction on the surface of the object under inspection. Scan the surface of the object to be inspected by forming it in the direction of
In addition, it is a foreign matter inspection method that selects only the S-polarized component of the scattered light generated on the inspected object, receives it from a predetermined angle direction, and detects foreign matter and the like on the surface of the inspected object based on the received light intensity.

According to a fourth aspect, in the foreign matter inspection method according to the first or third aspect, the irradiation angle of the S-polarized component light with which the inspection object is irradiated is 20 ° or less with respect to the surface of the inspection object, and Of the scattered light generated on the inspection object, only the S-polarized component is 10 ° to 40 ° with respect to the surface of the inspection object and 110 ° with respect to the incident plane of the light of the S-polarized component with which the inspection object is irradiated.
Light is received in the angle range of up to 150 °.

According to the fifth aspect, a light irradiation optical system for irradiating the light to be inspected with only the S-polarized component at a predetermined incident angle, and the light to be inspected by the light irradiation optical system. A light receiving optical system that selects only the S-polarized component of the scattered light that sometimes occurs on the inspection object and receives it from a predetermined angle direction, and a light receiving intensity on the surface of the inspection object based on the received light intensity detected by this light receiving optical system. A foreign matter inspection apparatus including: a foreign matter detecting unit that detects a foreign matter and the like.

With such a foreign matter inspection apparatus, light having only the S-polarized component is irradiated onto the inspection object at a predetermined incident angle, and only the S-polarized component of the scattered light generated at the inspection object at this time. Is selected to receive light from a predetermined angle direction, and at least the presence or absence of foreign matter on the surface of the object to be inspected is detected based on the received light intensity. As a result, the detection limit, which is the ratio of the intensity of scattered light from foreign matter to the intensity of scattered light from the object to be inspected, does not decrease, and it is possible to reliably detect minute foreign matter even on an object to be inspected with large surface roughness. .

According to a sixth aspect of the present invention, a laser oscillator for outputting a laser beam, a polarizer for making the laser beam output from the laser oscillator only light of S-polarized component, and the light from the polarizer are inspected. A converging irradiation optical system that condenses light by forming it in a spot shape at a predetermined incident angle with respect to the body,
Scanning means for relatively moving the laser beam and the object to be inspected to scan the surface of the object to be inspected, and scattering generated on the object to be inspected when the laser beam is applied to the object to be inspected by the converging irradiation optical system. A light-receiving optical system that selects only the S-polarized component of the light and receives it from a predetermined angle direction, and a foreign matter detection unit that detects a foreign matter or the like on the surface of the object to be inspected based on the received light intensity detected by the light-receiving optical system. And a foreign matter inspection device.

According to such a foreign matter inspection apparatus, the laser beam output from the laser oscillator is passed through the polarizer and S
The light having only the polarization component is formed, and the light having only the S polarization component is formed into a spot shape to irradiate the inspection object at a predetermined incident angle, and the laser beam and the inspection object are relatively moved. The surface of the object to be inspected is scanned with a laser beam. Then, only the S-polarized component is selected from the scattered light generated on the inspection object when the inspection object is irradiated with the laser beam, and the S-polarized component is received from a predetermined angle direction. Detect foreign objects.

According to a seventh aspect of the present invention, there is provided a foreign matter inspection apparatus for inspecting a foreign matter or the like on the surface of an object to be inspected by scanning a laser beam on the surface of the object to be inspected and detecting scattered light generated on the object to be inspected. A laser oscillator that outputs a beam and a laser beam that is output from this laser oscillator are formed into a spot shape that is elongated in a direction that matches the scanning direction on the surface of the inspection object, and the laser beam spot is irradiated to the inspection object. Based on a light irradiation optical system, a light receiving optical system that receives scattered light generated in the inspection object when the inspection object is irradiated with a laser beam by the light irradiation optical system, and a light reception intensity detected by the light reception optical system. And a foreign matter detecting means for detecting at least foreign matter on the surface of the object to be inspected.

In such a foreign matter inspection apparatus, the laser beam output from the laser oscillator is formed into a spot shape elongated on the surface of the inspection object in a direction corresponding to the scanning direction, and the inspection object is irradiated with the spot beam. At this time, the scattered light generated on the inspection object is received, and at least a foreign substance on the surface of the inspection object is detected based on the received light intensity.

According to the present invention, the S-polarized component light is applied to the object under inspection at a predetermined incident angle, and the spot shape of the S-polarized component light coincides with the scanning direction on the surface of the object under inspection. A light irradiation optical system that is formed long in the direction of scanning and scans the surface of the object to be inspected, and only the S-polarized component of the scattered light generated in the object to be inspected when light is irradiated to the object to be inspected by the light irradiation optical system. Foreign matter including a light receiving optical system for selecting and receiving light from a predetermined angle direction, and foreign matter detecting means for detecting at least foreign matter on the surface of the object to be inspected based on the light receiving intensity detected by the light receiving optical system. It is an inspection device.

With such a foreign matter inspection apparatus, the S-polarized component light is applied to the inspection object at a predetermined incident angle, and the spot shape of the S-polarized light component is scanned on the surface of the inspection object. It is formed long in a direction coinciding with the direction and is scanned on the surface of the object to be inspected, and only the S-polarized component is selected from the scattered light generated on the object to be inspected at this time and received from a predetermined angle direction. Based on the above, at least the presence or absence of foreign matter on the surface of the inspection object is detected.

According to a ninth aspect, in the foreign matter inspection apparatus according to the fifth, sixth or eighth aspect, the incident angle of the S-polarized component light with which the object to be inspected is irradiated is 20 ° or less with respect to the surface of the object to be inspected. In addition, only the S-polarized light component of the scattered light generated in the inspection object is 10 ° to 40 ° with respect to the surface of the inspection object, and 110 is incident on the incident plane of the light of the S-polarization component that irradiates the inspection object.
Light is received in the angle range of ° to 150 °.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The foreign matter inspection method of the present invention irradiates an object to be inspected (hereinafter referred to as a semiconductor wafer) such as a semiconductor wafer having a large surface roughness such as a metal film with light of S polarization component at a predetermined incident angle. Of the scattered light generated on the semiconductor wafer at this time, only the S-polarized component is selected and received from a predetermined angle direction, and the foreign matter on the surface of the semiconductor wafer is detected based on the received light intensity.

When such a method is adopted, the magnitude of the S-polarized component in the noise component (N) due to the surface roughness of scattered light and
Since the magnitude of the S-polarized component in the signal component (S) due to the foreign matter is greatly different, this can be utilized to accurately detect the foreign matter of 0.2 μm or less even in a semiconductor wafer having a large surface roughness.

In this case, the irradiation angle ρ of the light of the S-polarized component with which the semiconductor wafer is irradiated is 20 with respect to the surface of the semiconductor wafer.
The incident plane of the S-polarized component light that irradiates the semiconductor wafer with an elevation angle θ of 10 ° to 40 ° with respect to the semiconductor wafer surface. With respect to the horizontal angle φ of 110 ° to 1
It is set to receive light in the range of 50 °.

Here, the irradiation angle ρ is set to an angle that reduces the influence of the surface roughness of the semiconductor wafer, and the elevation angle θ is set to an angle at which scattered light due to foreign matter can be better received. It is apparent from Japanese Patent Laid-Open No. 3-128445.

FIG. 1 is a block diagram of a foreign matter inspection apparatus to which such a foreign matter inspection method is applied. The uniaxial stage 1 has a function of being movable in the direction of the arrow (a) which is the uniaxial direction, and the rotary stage 2 is provided on the uniaxial stage 1.

The rotary stage 2 is provided with a wafer chuck 3, and the semiconductor wafer 4 is fixed on the rotary stage 2 by the wafer chuck 3. The surface of the semiconductor wafer 4 has a large surface roughness like a metal film.

The uniaxial stage 1 and the rotary stage 2 constitute a scanning means for scanning the entire surface of the semiconductor wafer 4 with a laser beam. On the other hand, the turntable 2
A light irradiation optical system 5 for irradiating the semiconductor wafer 4 with a laser beam of only the S-polarized component at a predetermined irradiation angle of 20 ° or less is disposed obliquely above.

This light irradiation optical system 5 is an argon laser oscillator (hereinafter, referred to as an “laser beam”) which outputs a laser beam having a wavelength of 488 nm.
A laser oscillator 6 is abbreviated), and a polarizer 7, a reflection mirror 8 and a condenser lens 9 which form a condenser irradiation optical system are arranged on the optical path of a laser beam output from the laser oscillator 6. There is.

Of these, the polarizer 7 has the property of converting the laser beam output from the laser oscillator 6 into light having only the S-polarized component. The reflection mirror 8 is arranged so that the laser beam having only the S-polarized component transmitted through the polarizer 7 has a predetermined incident angle with respect to the semiconductor wafer 4, for example, an incident angle of 20 ° with respect to the surface of the semiconductor wafer 4. Has been done.

The condenser lens 9 is arranged on the reflection optical path of the reflection mirror 8 and condenses the laser beam of only the S-polarized component to form a small laser spot 10 on the surface of the semiconductor wafer 4.
Has the function of forming

Further, above the rotary stage 2, when the semiconductor wafer 4 is irradiated with the laser beam, the semiconductor wafer 4
A light receiving optical system 11 that selects only the S-polarized light component of the scattered light generated in 1) and receives it from a predetermined angle direction is arranged.

As shown in FIG. 2, the light receiving optical system 11 has an elevation angle of 10 ° to 40 ° with respect to the surface of the semiconductor wafer 4 with the irradiation position of the laser spot 10 as the center, and an S-polarized component for irradiating the semiconductor wafer 4. The light is set to be received within a horizontal angle range of 110 ° to 150 ° with respect to the incident plane.

Here, it is set so that the surface of the semiconductor wafer 4 has an elevation angle of 25 ° and the light of the S-polarized component with which the semiconductor wafer 4 is irradiated is received at a horizontal angle of 130 °. .

The light receiving optical system 11 comprises a polarizer 12, a fiber plate 13 and a photomultiplier tube 14. Of these, the polarizer 12 has a function of receiving scattered light having a divergence angle of ± 20 ° around the laser irradiation position and guiding it to the photomultiplier tube 14 through the fiber plate 13.

The polarizer 12 has a property of passing only the S-polarized component of the scattered light generated on the semiconductor wafer 4. The photomultiplier tube 14 has a function of photoelectrically converting incident scattered light and outputting it as a scattered light signal Q corresponding to the light intensity of the scattered light.

The output terminal of the photomultiplier tube 14 is connected to a computer 17 via an amplifier circuit 15 and an interface circuit 16. The interface circuit 16 is
The scattered light signal Q output from the photomultiplier tube 14 and amplified by the amplifier circuit 15 is A / D converted and computer 17
Control signals s1 and s2 for the uniaxial stage 1 and the rotary stage 2 sent from the computer 17
To the uniaxial stage 1 and the rotary stage 2.

The computer 17 controls the control signals s1 and s for operating the uniaxial stage 1 and the rotary stage 2, respectively.
It has the function of sending 2. Also, the computer 17
Receives the scattered light signal Q output from the photomultiplier tube 14 through the interface circuit 16, and detects the presence or absence of foreign matter on the surface of the semiconductor wafer 4 and the size thereof based on the received light intensity obtained from the scattered light signal Q. In addition, it has a function as foreign matter detecting means for detecting the position of the foreign matter from the control signals s1 and s2 for the uniaxial stage 1 and the rotary stage 2.

Next, the operation of the device configured as described above will be described. The semiconductor wafer 4 is fixed on the rotary stage 2 by the wafer chuck 3 on the rotary stage 2.

The computer 17 sends a control signal s2 for rotating the rotary stage 2 at a predetermined rotation speed and controls the uniaxial stage 1 to move in the uniaxial direction by a predetermined pitch each time the rotary stage 2 makes one rotation. The signal s1 is transmitted.

These control signals s1 and s2 are sent to the rotary stage 2 and the uniaxial stage 1 through the interface circuit 16, respectively. As a result, the rotary stage 2 rotates at a predetermined rotation speed, and the uniaxial stage 1 repeats the operation of moving by a predetermined pitch in the uniaxial direction each time the rotary stage 2 makes one rotation.

On the other hand, the wavelength from the laser oscillator 6 is 488 nm.
When the laser beam of is output, this laser beam
By passing through the polarizer 7, a laser beam having only S-polarized components is obtained.

The laser beam having only the S-polarized component is reflected by the reflection mirror 8, condensed by the condenser lens 9, and irradiated as a small laser spot 10 on the surface of the semiconductor wafer 4.

The laser spot 10 is incident on the surface of the semiconductor wafer 4 at an irradiation angle of 20 °. Therefore,
Since the semiconductor wafer 4 rotates at a predetermined rotation speed, and the semiconductor wafer 4 moves by a predetermined pitch in one axis direction each time the semiconductor wafer 4 makes one rotation, the laser spot 10 is spirally scanned on the surface of the semiconductor wafer 4. .

If there is a foreign substance in the laser spot 10 scanned on the semiconductor wafer 4, the foreign substance causes scattered light. The polarizer 12 passes only the S-polarized component of the scattered light and guides it to the fiber plate 13. The fiber plate 13 selectively collects a specific portion of the scattered light generated on the surface of the semiconductor wafer 4 with a spread angle of ± 20 ° and guides it to the photomultiplier tube 14.

The photomultiplier tube 14 photoelectrically converts the scattered light of the S-polarized component passing through the fiber plate 13 and outputs it as a scattered light signal Q corresponding to the light intensity of the scattered light. The scattered light signal Q is amplified by the amplifier circuit 15,
The interface circuit 16 performs A / D conversion and sends to the computer 17.

This computer 17 takes in the digital scattered light signal Q, detects the presence or absence of foreign matter on the surface of the semiconductor wafer 4 and the size thereof based on the received light intensity obtained from this scattered light signal Q, and also the uniaxial stage. 1. The position of the foreign matter is detected from the control signals s1 and s2 for the rotary stage 2.

By the way, in a semiconductor process, a film of aluminum (Al) and tungsten (W) is formed on a semiconductor wafer by a CVD process. In this process, the surface of the film is formed on the surface of a bare silicon semiconductor wafer. It has a large roughness in comparison.

When detecting such a foreign substance on the surface of the semiconductor wafer 4, scattered light is generated due to the uneven shape of the surface of the semiconductor wafer 4 even when there is no foreign substance in the laser spot 10, and this scattered light is a noise component. (N).

In the foreign matter detection, the scattered light due to the foreign matter is used as the signal component (S). Therefore, when the surface roughness of the semiconductor wafer 4 increases and the scattered light of the noise component (N) increases, the S / N ratio is relatively increased. Will decrease and the detection sensitivity will decrease.

Here, FIG. 3 shows characteristics of scattered light by the Al film. The irradiation angle θ of the laser beam is 20 ° with respect to the surface of the semiconductor wafer 4, and the incident polarized light is S polarized light. Here, the irradiation angle θ is set to 20 ° or less in order to suppress the generation of the noise component (N) due to the surface roughness.

The characteristics of this scattered light are h ₁ , S when the fiber plate 13 is not attached on the detection side (prior art).
Three cases are shown: h ₂ when only polarized light is detected and h ₃ when only P polarized light is detected.

As can be seen from the characteristics of the scattered light, the smallest condition of the scattered light (N) is h ₂ when only S-polarized light is detected.
Side scattered light (horizontal angle φ around 130 °) is detected.
In this way, the condition that the scattered light (N) becomes the smallest is h ₂ when only S-polarized light is detected, even if the film thickness of the Al film is changed or the material is changed to tungsten. I know that.

On the other hand, in FIG. 4, as an example, 0.
The characteristics of scattered light due to a foreign substance having a diameter of 2 μm are shown. The characteristics of this scattered light are similar to those shown in FIG.
The irradiation angle ρ of the laser beam with respect to the surface of the
It shows the results of experiments conducted with incident polarized light of S-polarized light, ie, h ₁ when the fiber plate 13 is not attached on the detection side, h ₂ when only S-polarized light is detected, and only when P-polarized light is detected. The _three cases of h ₃ are shown.

The conditions under which the scattered light (S) becomes maximum from the characteristics of the scattered light are the case where there is no fiber plate 13 and the case where only the S-polarized light is detected and the side scattered light of h ₂ is detected. FIG. 5 shows S / N characteristics obtained from FIGS. 3 and 4.

As shown in this S / N characteristic, the condition of h ₂ which is the case of only S-polarized light is generally high, and the condition in which the horizontal angle φ is 130 ° shows the best result. .
Therefore, by irradiating the semiconductor wafer 4 with the S-polarized laser beam and detecting only the S-polarized light of the scattered light generated on the semiconductor wafer 4, even a film having a higher S / N and a larger surface roughness than that of the prior art can be obtained. It is possible to detect foreign matter of 2 μm or less.

FIG. 6 shows a summary of the evaluation of the detection sensitivity with respect to foreign matter of 0.2 μm dust when the incident polarization and the detection polarization are changed. In this evaluation of detection sensitivity, the parameters that affect the scattering of the film include the incident angle of the laser beam, the type of polarization, the type of film, and the film thickness. The conditions for reducing the light were found, and the detection sensitivity of dust having a particle size of 0.2 μm was evaluated under the condition that the scattered light intensity of this film was reduced.

As shown in this evaluation result, when the irradiation angle φ of the laser beam is 20 °, the scattered light intensity (that is, scattered light (N)) of the film becomes the weakest when the incident polarization S and the detection polarization S are obtained. , S / N is improved.

Further, it is known that the spatial distribution of scattered light of the film does not change even if the type and thickness of the film change.
Approximately similar results are obtained even when the type and thickness of the film are changed. As a result of detection of dust of 0.2 μm under the condition that the scattered light intensity of the film is the weakest, it can be seen that the S / N is doubled as compared with the conventional case (incident polarization S, detection polarization is unpolarized).

As described above, in the first embodiment, the semiconductor wafer 4 is irradiated with the S-polarized component laser beam at a predetermined incident angle, and only the S-polarized component of the scattered light generated on the semiconductor wafer 4 is irradiated. Is selected and light is received from a predetermined angle direction, and foreign matter on the surface of the semiconductor wafer 4 is detected based on the received light intensity. Therefore, in an actual semiconductor manufacturing line, for example, in the manufacturing process of 256MDRAM currently under development. Although a semiconductor wafer having a large surface roughness such as a metal film is used, a foreign substance having a size of 0.2 μm or less can be detected even on a semiconductor wafer having a large surface roughness.

The first embodiment may be modified as follows. For example, in order to make the incident polarization of the laser beam incident on the semiconductor wafer 4 S-polarized, a linearly polarized output laser beam may be used without using the fiber plate 13 and the polarization planes may be aligned.

Further, as the scanning stage, an XY orthogonal system stage may be used instead of the uniaxial stage 1.
An optical lens system may be used instead of the polarizer 13 to collect scattered light generated on the semiconductor wafer 4.

The object to be inspected is not limited to the semiconductor wafer 4 and can be any plate-shaped object. (2) Next, a second embodiment of the present invention will be described with reference to the drawings. The foreign matter inspection method of the present invention is applied to an inspected object such as a semiconductor wafer having a large surface roughness such as a metal film (hereinafter,
In the foreign matter inspection method of inspecting foreign matter on the surface of the semiconductor wafer by scanning a laser beam with respect to a semiconductor wafer) and detecting scattered light generated on the semiconductor wafer at this time, The spot shape is formed so that the direction that coincides with the scanning direction on the surface of the semiconductor wafer is long.

FIG. 7 is a block diagram of a foreign matter inspection apparatus to which such a foreign matter inspection method is applied. A wafer chuck 23 is provided on the X stage 20 and the Y stage 21, and the semiconductor wafer 4 is fixed by the wafer chuck 3.

The semiconductor wafer 4 has a large surface roughness like a metal film. The XY-axis stages 20 and 21 constitute a scanning unit that scans the entire surface of the semiconductor wafer 4 with a laser beam.

On the other hand, diagonally above the rotary table 22,
A laser oscillator 24 that outputs a laser beam and a light irradiation optical system 25 are arranged. Of these, the light irradiation optical system 2
Reference numeral 5 forms a laser beam output from the laser oscillator 24 into a spot shape, for example, an elliptical laser beam spot, which is elongated in a direction coinciding with the scanning direction on the surface of the semiconductor wafer 4, and the laser beam spot is formed. It has a function of irradiating the laser beam 4 and is composed of an anamorphic expander 26, a reflection mirror 27 and a condenser lens 28.

Of these, anamorphic expander 2
Reference numeral 6 has a function of transforming the laser beam output from the laser oscillator 24 into an elliptical laser beam.
The reflection mirror 27 is an anamorphic expander 26.
The elliptical laser beam that has passed through is arranged so that the semiconductor wafer 4 has a predetermined incident angle.

The condenser lens 28 is arranged on the reflection optical path of the reflection mirror 27 and has a function of condensing the elliptical laser beam to form a small laser spot 29 on the surface of the semiconductor wafer 4. .

Further, above the X stage 20 and the Y stage 21, there is arranged a light receiving optical system 30 for receiving scattered light generated in the semiconductor wafer 4 when the laser beam is applied to the semiconductor wafer 4 from a predetermined angle direction. ing.

The light receiving optical system 30 is composed of an optical fiber 31 and a photomultiplier tube 32. Among them, the photomultiplier tube 32 photoelectrically converts and amplifies the scattered light received through the optical fiber 31, and its electric signal (scattered light signal Q).
Has the function of outputting.

A computer 34 is connected to an output terminal of the photomultiplier tube 32 via an amplifier circuit 33. This computer 34 is provided with XY stages 20, 21.
Has a function of controlling the operation of each.

Further, the computer 34 uses the photoelectron image multiplier 3
The scattered light signal Q output from 2 is taken in through the amplifier circuit 33, the presence or absence and size of foreign matter on the surface of the semiconductor wafer 4 is detected based on the received light intensity obtained from this scattered light signal Q, and the XY stage 20 is used. , 21 and the rotary stage 22 have a function as foreign matter detecting means for detecting the position of the foreign matter from the control position.

Next, the operation of the device configured as described above will be described. Wafer chuck 2 on the rotary stage 22
The semiconductor wafer 4 is fixed on the rotary stage 2 by 3.

The computer 34 controls the X stage 20 to move at a constant speed by a distance corresponding to both ends of the semiconductor wafer 4, and the Y stage 21 moves to the elliptical laser beam spot every time the X stage 20 moves at a constant speed. Two
The step movement control for the predetermined distance of 9 is repeated.

On the other hand, when a laser beam is output from the laser oscillator 24, this laser beam is transformed into an elliptical laser beam by the anamorphic expander 26.

This elliptical laser beam is reflected by the reflection mirror 27, condensed by the condenser lens 28, and irradiated as a small laser spot 29 on the surface of the semiconductor wafer 4.

Therefore, the laser spot 29 is scanned on the semiconductor wafer 4 at a constant speed in the X-axis direction, and every time the constant speed scanning in the X-axis direction is performed, the laser spot 29 is stepped by a predetermined distance in the Y-axis direction. The semiconductor wafer 4 is moved, and this scanning, that is, vector scanning is repeated to scan the entire surface of the semiconductor wafer 4.

If there is a foreign substance in the laser spot 29 scanned on the semiconductor wafer 4, the foreign substance causes scattered light. The optical fiber 31 guides the scattered light generated on the surface of the semiconductor wafer 4 to the photoelectron multiplier 32.

The photomultiplier tube 32 includes an optical fiber 31.
The scattered light guided by is received, photoelectrically converted and amplified, and output as the scattered light signal Q. This scattered light signal Q is
It is sent to the computer 34 through the amplifier circuit 33.

Here, FIG. 8 shows a signal waveform of the scattered light signal Q when the semiconductor wafer 4 has a foreign substance on a bare wafer having a very small surface roughness, for example. In this case, the noise component N _A is the photoelectron multiplier 3 used as the detector.
Due to shot noise of 2. The value of this noise component N _A is defined as follows, where P is the power of the laser beam to be applied.

[0087]

(Equation 1) There is a relationship. ΔB is the frequency band of the electrical system.

On the other hand, FIG. 9 shows a signal waveform when a foreign substance is present on the semiconductor wafer 4 having a film having a large surface roughness such as Al. In this case, the noise component N _B is generated because the surface roughness varies depending on the location of the semiconductor wafer 4.

When the surface of the semiconductor wafer 4 is irradiated with the laser beam, scattered light proportional to the surface roughness of the semiconductor wafer 4 is generated. When the laser spot 29 scans the surface of the semiconductor wafer 4 in that state, the surface roughness of the semiconductor wafer 4 varies, so that the intensity of scattered light varies. The variation of the intensity of this scattered light is N _B.

Here, the fluctuation N _B of the scattered light intensity is shown in FIG.
Calculate using the model shown in. It is assumed that a laser spot 29 of power P, for example, a spot-shaped laser spot 29 in the X-axis direction D ₁ and the Y-axis direction D ₂ moves from the A state to the B state on the surface of the semiconductor wafer 4.

It is assumed that the surface of the semiconductor wafer 4 is divided into parameters R ₁ and R ₂ which represent the magnitude of roughness per unit area. In the state A, the intensity I _A of scattered light by the surface of the semiconductor wafer 4 is

[0092]

(Equation 2) Becomes Further, in the B state, the intensity I _B of the scattered light by the surface of the semiconductor wafer 4 is

[0093]

(Equation 3) Becomes

The fluctuation N _B of the scattered light intensity is N _B = I _A −I _B (4)

[0095]

(Equation 4) Becomes This indicates that the noise component N _{B of} Al is proportional to (laser power P) / (laser spot diameter D _{1 in the} scanning direction). That is,

[0096]

(Equation 5)

Although Al also contains a shot noise component, it can be ignored when compared with the noise component N _B. By the way, the intensity I _s of the scattered light due to the foreign matter is

[0098]

(Equation 6) Is represented by That is, it is proportional to the power density of the laser spot 29. When the S / N is obtained by using the intensity I _s of the scattered light due to the foreign matter as a signal component, in the case of a bare wafer,

[0099]

(Equation 7) Becomes

Therefore, in order to improve the S / N, it is understood that the power of the laser beam should be increased and the laser spot 29 should be decreased. On the other hand, in the case of Al, S
/ N is

[0101]

(Equation 8) And the spot diameter D perpendicular to the scanning direction of the laser beam
It can be seen that the S / N is improved by making ₂ small.

Further, it can be seen that the spot diameter D ₁ parallel to the laser power P and the scanning direction is independent of S / N.
By the way, in the foreign matter inspection, it is necessary that the S / N is good (the detection sensitivity is high) and the inspection time is short. If the spot diameter D ₂ is reduced from the above equation (9) in order to improve the S / N, the inspection time becomes long.

Therefore, since the S / N is irrelevant to the laser power P and the spot diameter D ₁ parallel to the scanning direction,
If the spot diameter D ₁ is increased and the scanning speed is increased, the inspection time is shortened and the S / N is improved.

When the scanning speed of the laser beam is increased, a high frequency band is required. From the above equation (9), S
Since / N has nothing to do with the frequency band, there is no problem. Therefore, the computer 34 fetches the scattered light signal Q output from the photomultiplier tube 32 through the amplifier circuit 33,
The presence / absence and size of foreign matter on the surface of the semiconductor wafer 4 are detected based on the received light intensity obtained from the scattered light signal Q, and the position of the foreign matter is detected from the control position for the XY stages 20, 21 and the rotary stage 22. .

As described above, in the second embodiment, the surface of the semiconductor wafer 4 is scanned with the laser beam, and the scattered light generated on the semiconductor wafer 4 at this time is detected to detect the foreign matter on the surface of the semiconductor wafer 4. In the case of inspecting, since the spot shape of the laser beam for scanning on the surface of the semiconductor wafer 4 is formed long in the direction coinciding with the scanning direction on the surface of the semiconductor wafer 4, the scattered light from the surface of the semiconductor wafer 4 The strength N becomes smaller, the S / N becomes higher, the detection limit is improved, and like the first embodiment, an actual semiconductor manufacturing line, for example, 256MDRAM currently under development.
It is possible to detect a foreign substance having a size of 0.2 μm or less even on a semiconductor wafer having a large surface roughness such as a metal film in the manufacturing process.

The second embodiment may be modified as follows. For example, in order to make the spot shape of the laser beam elliptical, not only the anamorphic expander 26 but also a cylindrical lens may be used.

The scanning of the laser spot 29 is a vector scanning using the XY stages 20 and 21, but it may be a spiral scanning using a rotary stage and a uniaxial stage. In this case, the major axis of the laser spot 29 is in the rotation axis direction.

The laser spot 29 may be scanned by raster scanning using a polygon scanner and a uniaxial stage. In this case, the major axis is the scanning direction of the polygon scanner.

The scattered light generated on the semiconductor wafer 4 may be guided to the photomultiplier tube 32 by using a condenser lens instead of the optical fiber 31. (3) Next, a third embodiment of the present invention will be described with reference to the drawings.

According to the foreign matter inspection method of the present invention, the semiconductor wafer 4 is irradiated with the laser beam of the S-polarized component at a predetermined incident angle, and the spot shape of the light of the S-polarized component is scanned on the surface of the semiconductor wafer 4. Formed in a direction coinciding with the direction, scan on the surface of the semiconductor wafer 4, and select only the S-polarized component of the scattered light generated on the semiconductor wafer 4 at this time and receive it from a predetermined angle direction, A foreign substance on the surface of the semiconductor wafer 4 is detected based on the received light intensity.

In this case, the incident angle of the laser beam of the S-polarized component with which the semiconductor wafer 4 is irradiated is set to 20 ° or less with respect to the surface of the semiconductor wafer 4, and the S-polarized light of the scattered light generated on the semiconductor wafer 4 under the conditions is set. Only the component is received at an elevation angle of 10 ° to 40 ° with respect to the surface of the semiconductor wafer 4 and within a horizontal angle range of 110 ° to 150 ° with respect to the incident plane of the S-polarized component light with which the semiconductor wafer 4 is irradiated. Has become.

FIG. 11 is a block diagram of a foreign matter inspection apparatus to which such a foreign matter inspection method is applied. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. Wavelength 48
An anamorphic expander 26, a polarizer 7, a reflection mirror 8 and a condenser lens 9 are arranged on the laser beam optical path of an argon laser oscillator (hereinafter, abbreviated as laser oscillator) 6 that outputs a laser beam of 8 nm. ing.

These optical elements irradiate the semiconductor wafer 4 with the laser beam of the S-polarized component at a predetermined incident angle, and the spot shape of the laser beam of the S-polarized component is set in the scanning direction on the surface of the semiconductor wafer 4. It is formed to be long in the same direction.

Next, the operation of the apparatus configured as described above will be described. The semiconductor wafer 4 is fixed to the wafer chuck 3 on the rotary stage 2. The computer 17
A control signal s2 for rotating the rotary stage 2 at a predetermined rotation speed is sent, and a control signal s1 for moving the uniaxial stage 1 in the uniaxial direction by a predetermined pitch is sent every time the rotary stage 2 makes one rotation.

As a result, the rotary stage 2 rotates at a predetermined rotational speed, and the uniaxial stage 1 repeats the operation of moving by a predetermined pitch in the uniaxial direction each time the rotary stage 2 makes one rotation.

On the other hand, the wavelength from the laser oscillator 6 is 488 nm.
When the laser beam of is output, this laser beam
The anamorphic expander 26 transforms the laser beam into an elliptical laser beam.

Next, the laser beam passes through the polarizer 7 and becomes a laser beam having only the S-polarized component. The laser beam having the elliptical shape and only the S-polarized component is reflected by the reflection mirror 8, condensed by the condenser lens 9, and irradiated as a small laser spot 10 on the surface of the semiconductor wafer 4.

Therefore, the semiconductor wafer 4 rotates at a predetermined rotation speed, and each time the semiconductor wafer 4 makes one rotation, it moves by a predetermined pitch in the uniaxial direction, so that the laser spot 10 spirals on the surface of the semiconductor wafer 4. Are scanned in a circular pattern.

If there is a foreign substance in the laser spot 10 scanned on the semiconductor wafer 4, the foreign substance causes scattered light. The polarizer 12 passes only the S-polarized component of the scattered light and guides it to the fiber plate 13. The fiber plate 13 spreads a specific portion of scattered light at an angle of ± 20.
The light is selectively collected at an angle of ° and guided to the photomultiplier tube 14.

The photomultiplier tube 14 photoelectrically converts the scattered light of the S-polarized component that has passed through the fiber plate 13 and outputs it as a scattered light signal Q corresponding to the light intensity of the scattered light. The computer 17 takes in the digital scattered light signal Q amplified by the amplifier circuit 15 and digitally converted by the interface circuit 16, and based on the received light intensity obtained from this scattered light signal Q, the presence or absence of foreign matter on the surface of the semiconductor wafer 4 is detected. , The size is detected and the uniaxial stage 1,
The position of the foreign matter is detected from the control signals s1 and s2 for the rotary stage 2.

As described above, in the third embodiment, the semiconductor wafer 4 is irradiated with the laser beam of the S-polarized component at a predetermined incident angle, and the spot shape of the light of the S-polarized component is changed. Is formed long in a direction corresponding to the scanning direction on the surface of the semiconductor wafer 4 and is scanned on the surface of the semiconductor wafer 4, and only the S-polarized component of the scattered light generated on the semiconductor wafer 4 at this time is selected to have a predetermined angle. This is a combination of the first and second embodiments in which light is received from the direction and foreign matter on the surface of the semiconductor wafer 4 is detected based on the received light intensity. Similarly, even on a semiconductor wafer having a large surface roughness such as a metal film used in an actual semiconductor manufacturing line, for example, a manufacturing process of 256M DRAM currently under development, the size of 0.2 is obtained. m can be detected following foreign matter. Further, in each of the above-described embodiments, the object detected by the scattered light is not limited to the foreign matter, but may be any object that can obtain the scattered light such as scratches.

[0122]

As described in detail above, claims 1 to 5 of the present invention.
According to 4, it is possible to provide a foreign matter detection method capable of reliably detecting a minute foreign matter even on an object to be inspected having a large surface roughness. or,
According to the fifth to tenth aspects of the present invention, it is possible to provide a foreign matter detection device capable of reliably detecting a minute foreign matter even on an object to be inspected having a large surface roughness.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a foreign matter inspection apparatus according to the present invention.

FIG. 2 is a diagram showing an arrangement angle of a light receiving optical system in the device.

FIG. 3 is a diagram showing characteristics of scattered light by an Al film.

FIG. 4 is a diagram showing characteristics of scattered light due to a foreign substance having a diameter of 0.2 μm on an Al film.

FIG. 5 is a diagram showing S / N characteristics of scattered light detection.

FIG. 6 is a diagram showing evaluation of detection sensitivity for foreign matter of 0.2 μm dust.

FIG. 7 is a configuration diagram showing a second embodiment of a foreign matter inspection device according to the present invention.

FIG. 8 is a diagram showing a scattered light signal waveform due to a foreign substance on a bare wafer having a very small surface roughness.

FIG. 9 is a diagram showing a signal waveform due to a foreign substance on a semiconductor wafer on which a film having a large surface roughness such as Al is attached.

FIG. 10 is a diagram showing a model for calculating a variation N _B of scattered light intensity.

FIG. 11 is a configuration diagram showing a third embodiment of a foreign matter inspection device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Uniaxial stage, 2 ... Rotating stage, 4 ... Semiconductor wafer, 5 ... Light irradiation optical system, 6 ... Laser oscillator, 7 ... Polarizer, 8 ... Reflecting mirror, 9 ... Condensing lens, 11 ... Light receiving optical system, 12 ... Polarizer, 13 ... Fiber plate, 14 ... Photomultiplier tube, 17 ... Computer, 20 ... X stage,
21 ... Y stage, 22 ... Rotation stage, 24 ... Laser oscillator, 25 ... Light irradiation optical system, 26 ... Anamorphic expander, 27 ... Reflecting mirror, 28 ... Condensing lens,
30 ... Receiving optical system, 31 ... Optical fiber, 32 ... Photomultiplier tube, 34 ... Computer.

Claims (9)

[Claims] 1. An object to be inspected is irradiated with light of S-polarized component at a predetermined incident angle, and only S-polarized component of scattered light generated in the object to be inspected is selected and received from a predetermined angle direction. ,
A foreign matter inspection method characterized by detecting a foreign matter or the like on the surface of the object to be inspected based on the received light intensity. 2. A foreign matter inspection method for inspecting a foreign matter and the like on the surface of the object to be inspected by scanning light on the surface of the object to be inspected and detecting scattered light generated on the object to be inspected. A foreign matter inspection method, wherein a spot shape of the light for scanning upward is formed long in a direction coinciding with a scanning direction on the surface of the inspection object. 3. The light of S polarization component is irradiated onto the inspection object at a predetermined incident angle, and the spot shape of the light of the S polarization component is elongated in a direction coinciding with the scanning direction on the surface of the inspection object. After being formed and scanned on the surface of the object to be inspected, only the S-polarized component of the scattered light generated on the object to be inspected is selected and received from a predetermined angle direction, and the object to be inspected is based on the received light intensity. A foreign matter inspection method characterized by detecting foreign matter on the surface. 4. The irradiation angle of the S-polarized component light with which the inspection object is irradiated is 20 ° or less with respect to the surface of the inspection object, and only the S-polarized component of the scattered light generated on the inspection object is The light is received in a range of an angle of 10 ° to 40 ° with respect to the surface of the object to be inspected and an angle of 110 ° to 150 ° with respect to an incident plane of the light of the S-polarized component with which the object to be inspected is irradiated. The foreign matter inspection method according to claim 1. 5. A light irradiation optical system for irradiating an object to be inspected with light of only S-polarized component at a predetermined incident angle, and the object to be inspected when the light to be inspected is irradiated by the light irradiation optical system. A light receiving optical system that selects only the S-polarized component of the scattered light generated in the inspection object and receives it from a predetermined angle direction, and a foreign substance or the like on the surface of the inspection object based on the light reception intensity detected by this light receiving optical system A foreign matter inspection device comprising: a foreign matter detecting means for detecting the presence or absence of the foreign matter. 6. A laser oscillator that outputs a laser beam, a polarizer that uses the laser beam output from this laser oscillator as light having only an S-polarized component, and light from this polarizer that is predetermined for an object to be inspected. Converging irradiation optical system for forming and condensing in a spot shape at an incident angle of, and scanning means for relatively moving the laser beam and the inspection object to scan the surface of the inspection object with the laser beam. And S out of scattered light generated in the inspected object when the inspected object is irradiated with a laser beam by the converging irradiation optical system.
A light receiving optical system for selecting only a polarized component and receiving light from a predetermined angle direction, and a foreign matter detecting means for detecting foreign matter on the surface of the object to be inspected based on the light receiving intensity detected by the light receiving optical system. A foreign matter inspection device characterized by being provided. 7. A foreign matter inspecting apparatus for inspecting a foreign matter or the like on the surface of the object to be inspected by scanning a laser beam on the surface of the object to be inspected and detecting scattered light generated on the object to be inspected. An output laser oscillator and a laser beam output from the laser oscillator are formed into a spot shape elongated on a surface of the object to be inspected in a direction coinciding with a scanning direction, and the laser beam spot is irradiated to the object to be inspected. A light irradiation optical system, a light receiving optical system for receiving scattered light generated in the object to be inspected when the laser beam is irradiated to the object to be inspected by the light irradiation optical system, and a light reception intensity detected by the light receiving optical system. A foreign matter detecting device for detecting at least a foreign matter on the surface of the object to be inspected based on the above. 8. The S-polarized component light is irradiated onto the inspection object at a predetermined incident angle, and the spot shape of the S-polarized component light is elongated in a direction coinciding with the scanning direction on the surface of the inspection object. A light irradiation optical system for forming and scanning on the surface of the inspection object, and only the S-polarized component of the scattered light generated in the inspection object when the light irradiation optical system irradiates the inspection object with light. A light receiving optical system that selectively receives light from a predetermined angle direction, and a foreign matter detection unit that detects at least a foreign matter on the surface of the object to be inspected based on the light receiving intensity detected by the light receiving optical system. Foreign matter inspection device characterized by: 9. The incident angle of the S-polarized component light with which the inspection object is irradiated is 20 ° or less with respect to the surface of the inspection object, and only the S-polarized component of the scattered light generated on the inspection object is detected. The light is received in a range of an angle of 10 ° to 40 ° with respect to the surface of the object to be inspected and an angle of 110 ° to 150 ° with respect to an incident plane of the light of the S-polarized component with which the object to be inspected is irradiated. The foreign matter inspection device according to claim 5, 6, or 8.