JPH06313756A - Foreign object inspection analysis device and method thereof - Google Patents

Abstract

PURPOSE:To solve the problems caused by coordinate transformation and the difference in resolution and then detect a small change in the size of a foreign object by providing a light reception system for receiving only elastic scattered light and that for receiving only a non-elastic scattered light in a single device and then inspecting and analyzing the foreign object under the same conditions. CONSTITUTION:A wafer 10 is fitted to a Q table 112 and then laser oscillation 121 is initiated to start inspection. Scattered light is generated at the application point of inspection light L due to the scratch on the surface of the wafer 10, a ground, etc. An image forming lens system 131 focuses one portion L1 of the scattered light on the image pick-up surface of a sensor 132 and then the sensor 132 outputs an inspection signal corresponding to the quantity of received light. The inspection signal is compared with a threshold 153. Then, excess of each peak over the threshold is judged to indicate the presence of a foreign object and then a detection signal is sent to a spectrum analysis circuit 162. On the other hand, an image-forming lens system 141 focuses one portion L2 of the scattered light, Raman spectral system 142 extracts only Stokes light, and then a sensor 143 receives it and then sends an inspection signal to the analysis circuit 162. An operation control part 170 identifies the constituent of the foreign object based on the information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter inspection analyzer and foreign matter inspection apparatus for inspecting defects such as foreign matter and scratches on the surface of a sample such as a semiconductor wafer or a liquid crystal substrate by receiving scattered light generated by laser irradiation. The present invention relates to an analysis method, and more particularly, to a foreign matter inspection / analysis apparatus and a foreign matter inspection / analysis method for detecting the size and existing position of a foreign matter or the like on the surface of a sample and also analyzing components of the foreign matter or the like.

[0002]

2. Description of the Related Art Defects such as adhered foreign substances and scratches existing on the surface of a sample such as a semiconductor wafer (hereinafter simply referred to as a wafer) and a liquid crystal substrate cause defects such as disconnection in the subsequent pattern formation. Therefore, before and during the manufacturing process, it is necessary to inspect in advance and perform appropriate processing such as cleaning or eliminating the sample in which a defect is detected.

FIG. 8 shows an example (hereinafter referred to as a first conventional example) of a conventional foreign matter inspection apparatus (200) for detecting foreign matter attached to the surface of a sample. The device (200) consists of a scanning part (210) that mounts the sample so that it can be scanned, a light projecting part (220) that obliquely irradiates the sample, and a sample surface that is installed almost vertically above the sample. It is roughly divided into a light receiving section (230) which receives the scattered light from and outputs a light receiving signal according to the amount of received light, and an electric circuit system (240) which processes the light receiving signal.

However, when adhering foreign matter appears at the irradiation point during sample scanning, strong scattered light is generated from the foreign matter, so that it can be captured by the light receiving section (230). By using the fact that the scattered light intensity changes depending on the size of foreign matter, etc., it was possible to detect the presence and size of foreign matter by comparing the received light signal with a predetermined threshold in the electric circuit system (240). . Also, by synchronizing the scanning signal to the scanning unit (210) and the light receiving signal, it was possible to know at which position in the sample the foreign matter existed.

Further, there is a case where it is desired to further know the component, shape, etc. of the foreign matter detected by the device (200). In such cases, the data of the inspected sample should be
Once stored in an auxiliary storage device such as a floppy disk, hard disk, or optical disk, or transferred via an input / output interface (for example, RS-232C standard), incorporated into a component analyzer or electron microscope to perform desired analysis and observation. Was there.

However, Rayleigh and Mie
According to the theory of light scattering, the absolute value of the light intensity of light scattered by a foreign substance is usually proportional to the square to the sixth power of the size (diameter) of the foreign substance. FIG. 9 shows the relationship between the size of the foreign matter and the scattered light intensity in the elastically scattered light. Therefore, if the size of the foreign matter to be detected becomes 10 times, for example, the absolute value of the light intensity of the scattered light due to this foreign matter will be approximately
It becomes 10 ^{2 to} 10 ⁶ times.

Therefore, in the first conventional example, the light receiving part (230) of the foreign matter inspection device (200) receives the electric circuit system (24).
When comparing the received light signal with a predetermined threshold in (0), if the electric circuit system (240) has only one built-in amplifier,
It is conceivable that the operating range of this electric circuit system (240) will be exceeded.

Then, first, as shown in FIG. 10, in the electric circuit system (241), a region (for example, 5
10 to 10 μm), the amplifier (242) (for example, the received light signal is amplified by A (constant) times), and the amplifier (243) (for example, 10 A times received light signal is detected) in the region where the diameter of the detection particle is medium (for example, 1 to 5 μm) In a region where the diameter of the detection particles is small (for example, 0.1 to 1 μm).
4) (for example, the light reception signal is amplified by 100 A times) is provided, and the light reception signal of the scattered light in each region is switched by the switching unit (245) according to the size of the amplifier (242), (24).
3), (244), and it is considered to measure by amplifying with a corresponding amplifier (hereinafter referred to as the second conventional example). Further, as a modified example of the second conventional example, instead of providing the switching unit (245), the amplifiers (242), (243), (2
It is also considered to provide a plurality of light receiving parts corresponding to each of 44).

In addition, an electric circuit system (2
46), the output Y for the input of the received light signal X is Y =
It has also been considered to measure a received light signal of scattered light using a Log amplifier (247) having KLog X (K: constant) (hereinafter, referred to as a third conventional example).

[0010]

As described above, since the foreign matter inspection apparatus of the first conventional example can detect only the presence (position of the foreign matter) and the size of the foreign matter adhering to the sample surface, the shape and composition of the foreign matter can be further improved. It was necessary to analyze with another device when it was desired to identify. Therefore, two or more devices must be provided, which is expensive and consumes the floor space of the device.

Further, in the above-mentioned method, the inspection process has a serial flow of "foreign substance inspection"->"datatransfer"->"foreign substance analysis", which requires a large amount of time.

Furthermore, since the coordinate system set for the mounted sample does not match between the foreign substance inspection apparatus, the analysis apparatus and the electron microscope, it is necessary to perform coordinate conversion after data transfer. However, the resolution of foreign matter inspection equipment is usually several hundred square μ
While the resolution is about m, the resolution of the analyzer and electron microscope is usually less than 1 μm 2. Therefore, even after the coordinate conversion, the desired foreign matter (sometimes fine particles of 1 μm or less) must be found out from the extracted scanning points of several hundred square μm with the analyzer / electron microscope. It was a difficult task.

In the second conventional foreign matter inspection device, the amplifiers (242), (243), (2
Since 44) is provided, the number of amplifiers increases and the signal processing circuit becomes very complicated.

In addition, in the foreign substance inspection apparatus of the third conventional example, since a signal of logarithm (Log) corresponding to the signal itself that receives the scattered light from the detection particles is output, it is possible to detect a weak change in the signal. Therefore, follow-up is impossible. Therefore, it is impossible to detect a minute change in the size of the foreign matter. That is, there is a problem that the resolution at the time of detection becomes insufficient.

Therefore, according to the present invention, the foreign matter inspection and analysis are performed on a single apparatus, so that the foreign matter inspection and analysis are performed under the same conditions, which causes problems due to coordinate conversion and difference in resolution. It is an object of the present invention to provide a foreign matter inspection / analysis apparatus and a foreign matter inspection / analysis method that solve the above problems, shorten the inspection time, and are small in size and inexpensive.

Further, the present invention reduces the number of light receiving parts,
An object of the present invention is to provide a high-resolution foreign matter inspection / analysis apparatus and a foreign matter inspection / analysis method that can simplify a signal processing circuit and detect a minute change in the size of a foreign matter.

[0017]

According to a first aspect of the present invention, the present invention has been made in consideration of the above problems, and scanning means for movably mounting an inspection target, and inspection light for the inspection target. A first projecting unit which is disposed above the scanning unit and in a direction other than the specular reflection direction of the inspection light, receives scattered light from the inspection object, and which corresponds to the received light amount. Of the scattered light having a wavelength component different from that of the inspection light, which is disposed above the scanning means and in a direction other than the specular reflection direction of the inspection light. Second light receiving means for outputting a second inspection signal according to the amount of received light, and first for detecting the presence position and size of the foreign matter by comparing the first inspection signal with a predetermined threshold value.
And a second signal processing means for spectrally analyzing the second inspection signal to identify a component of the foreign matter.

According to a second aspect of the present invention, the present invention provides a light projecting step of projecting the inspection light while scanning the inspection object, and a first step in which scattered light from the inspection object is received and the amount of the received light is adjusted. And a second light receiving step of outputting only a wavelength component of the scattered light different from the inspection light and outputting a second inspection signal according to the received light amount. A first signal processing step of detecting the presence position and size of the foreign matter based on the first inspection signal; and a second inspection at the foreign matter presence position detected in the first signal processing step. And a second signal processing step of spectrally analyzing the signal to identify the component of the foreign matter.

[0019]

In general, scattered light generated from a foreign object irradiated with light includes elastic scattered light (or Rayleigh scattered light and Mie scattered light) and inelastic scattered light (or Raman (R
aman) scattered light).

The elastically scattered light is a scattered light produced by optically reflecting or diffracting the incident light on the surface of the foreign matter and has no energy loss due to absorption, and therefore has the same wavelength component as the incident light. The absolute value of the light intensity of the elastically scattered light is usually proportional to the square of the size of the foreign matter to the sixth power.

On the other hand, the inelastically scattered light is the scattered light generated by the interaction between the incident light and the transverse wave mode during the thermal vibration of the molecule or atom on the surface of the foreign matter (that is, the inelastic scattering with the optical phonon). Is. A wavelength shift phenomenon occurs due to the transfer of energy during this interaction. It is known that the wavelength shift amount Δλ is unique to each substance (about several tens of nm). Here, the absolute value of the light intensity of the inelastically scattered light is about 10 ^{−4 to} 10 ⁻³ times weaker than that of the elastically scattered light, which is easily inferred from each factor. It is something. Here, FIG. 12 shows the wavelengths and the scattered light intensities of the elastically scattered light and the inelastically scattered light.

Therefore, in the present invention, by utilizing the above-mentioned property of light, only the elastically scattered light is received by the first light receiving means (or the first light receiving step), and the peak indicated by the first inspection signal is obtained. The presence of foreign matter can be detected by the method, and the size of the foreign matter can be measured by the magnitude of the peak value. In addition, the second light receiving means (or the second light receiving step) receives only the inelastically scattered light to obtain the second inspection signal. When a foreign substance is detected on the first inspection signal, the material component of the foreign substance can be identified by spectrally analyzing the second inspection signal in synchronization with this.

That is, by performing the foreign substance inspection and the component analysis under the same conditions, the problems caused by the coordinate conversion and the difference in resolution are solved, the inspection time is shortened, and the foreign substance inspection analysis is small and inexpensive. An apparatus and a foreign matter inspection / analysis method can be provided.

Further, in the present invention, the property of the light intensity distribution shown in FIG. 12 is utilized to simplify the signal processing circuit by the above-mentioned method and further detect a minute change in the size of the foreign matter. It is possible to provide a high resolution foreign matter inspection / analysis apparatus and a foreign matter inspection / analysis method that enable the above.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a general configuration of a foreign matter inspection / analysis device (100) according to a first embodiment of the present invention. This foreign matter inspection / analysis device (100) is provided with an R table (11
1), θ table (112), laser oscillator (121) as light projecting means, beam expander (122), objective lens system
(123) and a first imaging lens system as a first light receiving means
(131), the first sensor (132), the second image forming lens system (141) as the second light receiving means, the Raman spectroscopic system (142), the second sensor (143), and the first sensor (132) An amplification circuit (151) as a signal processing means, a noise removal circuit (152), a threshold comparison circuit (15
3) and an amplification circuit (161) as a second signal processing means,
A spectrum analysis circuit (162) and a calculation control section (170) are provided. Hereinafter, the specific configuration of each part will be described in detail.

The R table (111) is a pulse motor (111-
ball screw (111-b) connected to a) and ball screw (111-b)
It is composed of a straight advance table (111-c) into which b) is screwed, and a guide rail (111-d) through which the straight advance table (111-c) can be freely advanced and retracted in the R direction (one horizontal direction).

The θ table (112) is a pulse motor (112-a)
It is a rotary table (112-b) connected to
(111-c) It is rotatably supported on the upper column around the θ axis (vertical axis). Further, the upper surface of the rotary table (112-b) has a suction function, and the wafer (10) to be inspected is mounted and fixed at a predetermined position where the coordinate system is set. Then, the pulse motors (111-a) and (112-a) are synchronously driven so that the entire surface of the wafer (10) can be concentrically scanned. In addition, each pulse motor
By counting the pulse signals to (111-a) and (112-a), a position signal indicating the current scanning position (R, θ) can be output.

The laser oscillator (121) is a laser light source (for example, output: 300) that emits the inspection light L such as Ar ⁺ laser.
mw, wavelength: 488 nm) is used. Objective lens system (123)
Collects the inspection light L in a substantially elliptical shape of 10 μm × 1 μm and makes a predetermined scanning point on the wafer (10) substantially vertical with respect to the vertical direction.
It is designed to irradiate obliquely from the direction of 60 °. In addition,
In the objective lens system (123), if the incident light has a diameter larger than a certain value, it is easier to focus light geometrically. On the other hand, the light emitted from the laser oscillator (121) is usually 0.6 mm.
There is only a diameter. Therefore, the beam expander (122) arranged immediately in front of the objective lens system (123) converts the incident inspection light L into a parallel light obtained by enlarging the diameter of the inspection light L by about 10 to 20 times, and the objective lens system ( 123).

The first imaging lens system (131) is arranged in a direction perpendicular to the incident direction of the inspection light L and at an elevation angle of about 30 ° with respect to the scanning point, and foreign matter on the wafer (10). Part of the scattered light L ₁ generated when the light is irradiated is focused. This is because the specularly reflected light of the inspection light L is not detected. The first sensor (132) is a device configured by a combination of a photomultiplier tube, a light receiving element such as a photodiode, and a current / voltage conversion circuit, which receives scattered light L ₁ and responds to the light intensity thereof. A first inspection signal having a different signal level is output. The scattered light L
Strictly speaking, ₁ includes both Rayleigh scattered light and Raman scattered light, but the absolute value of the light intensity of the latter is about 10 ^-3 of the former.
Since it is only about twice, there is no problem in treating L ₁ as Rayleigh scattered light.

The second imaging lens system (141) is arranged substantially symmetrical to the first imaging lens system (131) with respect to the incident surface of the inspection light L, and the wafer (10) Part L _{2 of the} scattered light generated when the foreign matter above is irradiated is condensed.
This is because the intensity distribution of scattered light is approximately symmetrically biased symmetrically with respect to the incident surface of the inspection light L. The Raman spectroscope (142) is composed of a commonly known spectroscope such as a triple polychromator, a double polychromator, or a monochromator, and has a wavelength band of λ _{1 to} λ ₂ (where 488 nm <λ ₁ It is set in the range of <λ ₂ ) and blocks scattered light having the same wavelength as incident light (that is, Rayleigh scattered light), and Stokes light L _{2 ′} (where L _{2 'wavelength} lambda _2' of, λ _{2 '=} 488nm + Δλ and shall meet the [Delta] [lambda]> 0) is adapted to extract only. The second sensor (143) is a multi-channel photodetector,
The L _{2 ′} is received and a second inspection signal having a signal level corresponding to the intensity thereof is output.

The amplifier circuit (151) is composed of an ordinary amplifier element or the like, and is adapted to input the first inspection signal and amplify it at a predetermined magnification. Noise elimination circuit (152)
Is a circuit equipped with a filter function that blocks low-level fluctuation components in the input signal. In addition to the shot noise of the sensor (132), a weak peak due to inelastically scattered light in the first inspection signal Is designed to be removed. This is because, as described above, the absolute value of the intensity of inelastically scattered light is only about 10 ⁻³ times that of elastically scattered light. Threshold comparison circuit (15
3) compares the peak value of the input first inspection signal with a preset threshold value V _T, and if it is V _T or more, it is determined that a foreign substance is present, and the detection signal S is analyzed by a spectrum analysis described later. It is designed to output to the circuit (162) and the arithmetic control unit (170). The threshold value V _T can be generally obtained by computer simulation or various methods such as extracting reference data using standard particles. Since the signal level is almost proportional to the size of the foreign matter, when the size of the foreign matter is subdivided, these thresholds are V _T1 , V _T2 , V _T3 ... (However, V _T1 <V _T2 <V _T3 <...) And multiple will be set.

The amplifier circuit (161) amplifies the second inspection signal by a predetermined magnification. Spectrum analysis circuit
Reference numeral (162) is energized by the signal S from the threshold value comparison circuit (153) to spectrally analyze the second inspection signal, detect the wavelength shift amount Δλ of the Raman scattered light L _{2 ′} , and perform the calculation described later. It is designed to output to the control unit (170).

The arithmetic control unit (170) is normally a CPU (Centr).
al processing unit) and various hardware circuits, and the outputs of the threshold value comparison circuit (153) and the spectrum analysis circuit (162) are arithmetically processed based on a predetermined program. In addition, the arithmetic control unit (1
70) is electrically connected to each of the above-mentioned parts, and drives the R table (111) and the θ table (112) and each sensor (13
2) It controls the operation of the whole foreign matter inspection / analysis device (100) by synchronizing with the output of (143).

The arithmetic control unit (170) is equipped with an inspection /
CRT (Cathode Ray TRT) for displaying analysis results externally
ube) Display system (171) such as display or printer, input system (172) such as console for inputting and setting conditions such as inspection / analysis, disk device for storing arithmetic processing programs and inspection results Although the auxiliary storage device (173) is connected, it will not be described because it is not the gist of the present invention.

Next, the operation of the foreign matter inspection / analysis apparatus (100) and the operation of this embodiment will be described. Mount the wafer (10) to be inspected on the θ table (112) and
After the positioning work of (10), the operation control unit (170) issues a command to oscillate the laser oscillator (121) and simultaneously drive the R table (111) and the θ table (112) for inspection. To start.

At the irradiation point of the inspection light L, foreign matter and wafer (10)
Scattered light is generated due to surface defects / scratches or the base of the wafer (10). The first imaging lens system (131) focuses a part of the scattered light L ₁ on the image pickup surface of the first sensor (132). First
The sensor (132) outputs a first inspection signal according to the amount of received light, the amplifier circuit (151) amplifies this signal, and the noise removal circuit (152) blocks low-level components in the signal. here,
The scattered light L ₁ includes not only Rayleigh scattered light but also Raman scattered light. However, since the latter has a weak absolute value of the light intensity, the low-level signal component due to Raman scattered light has a noise removal circuit (15).
2) Strained by An example of the chart of the first inspection signal is shown in FIG. 2. The peaks due to the foreign substances 1, 2, 3 and 4 are respectively present at the inspection time t on the uniform signal due to the scattered light on the underlayer of the wafer (10). Suppose that they appear at ₁ , t ₂ , t ₃ , and t ₄ .

Next, the threshold value comparing circuit (153) compares the first inspection signal with a predetermined threshold value V _T to determine each peak point t.
_{At 1} , t ₂ , t ₃ , and t ₄ , the signal level exceeds V _T , so it is determined that a foreign substance is present, and the detection signal S is detected each time.
₍₁₎ , S ₍₂₎ , S ₍₃₎ and S ₍₄₎ are connected to the spectrum analysis circuit (1
62), and output to the arithmetic control unit (170). The position and size of the foreign matter can also be detected by these detection signals.

However, here, the signals due to the Rayleigh scattered light component of the scattered light from the wafer (10) are, for example, as shown in FIGS.
As shown in (c) (when the foreign matter A, B, C, D, E and the foreign matter 1, 2, 3, 4 are different objects), the measurement by the Rayleigh scattered light component becomes saturated. Can not. Therefore, the presence, position, size, etc. of the foreign matter are determined by referring to the signal of the Raman scattered light component. FIG. 4 shows the detection ranges of the Rayleigh scattered light component and the Raman scattered light component based on the relationship between the scattered light intensity and the diameter of the foreign matter.

The second imaging lens system (141) collects a part of the scattered light L ₂ and sends it to the Raman spectroscopic system (142). The Raman spectroscopic system (142) extracts only the Stokes light L _{2 ′ from the} Raman scattered light, and the second sensor (143) receives this and receives the second light.
The inspection signal of is output. The amplifier circuit (161) is the second
Amplify the inspection signal of.

Then, the spectrum analysis circuit (162) is energized by each of the detection signals S _{(1) to} S ₍₄₎ , and each of the inspection times t _{1 to} t corresponding to the first inspection signal shown in FIG. a second test signal by spectral analysis in _4, the half-value width ΔW of the scattered light intensity with each of the wavelength shift amount Δλ ₁ ~Δλ _{4 1}
~ ΔW ₄ is calculated. The results of each analysis are shown in Fig. 5 (b)
It is shown in (e). It should be noted that the scattered light signal originating from the base of the wafer (10) (t _{0 in} FIG. 2) is also the standard data (wavelength shift amount Δλ ₀ and full width at half maximum ΔW) for the base of the wafer (10).
₀ ) and spectral analysis. The results are shown in Fig. 5 (a). Then, the analyzed wavelength shift amounts Δλ _{1 to} Δλ ₄ and the half widths ΔW _{1 to} ΔW ₄ are output to the subsequent arithmetic control unit (170).

The arithmetic control unit (170) includes the threshold comparison circuit (1
53), the output of the spectrum analysis circuit (162) is subjected to arithmetic processing as described below based on the corresponding program.

That is, the detection signal S of the threshold value comparison circuit (153) is statistically processed to classify it according to the size of the foreign matter and create a histogram of the number thereof. In addition, each pulse motor (111-
Since the pulse signals to (a) and (112-a) are counted, the presence position of the foreign matter can be detected by comparing these count values with the detection time.

[0043] The wavelength shift amount obtained from the spectral analysis circuit (162) Δλ ₁ ~Δλ _4, the half-value width ΔW ₁ ~ΔW ₄
The components of the foreign matter are identified by comparing these with each other. For example, the following matters are derived from the charts of FIG. In addition, when performing the following work for identifying the component of the foreign matter, a triple polychromator, a double polychromator, or a plurality of monochromators is used as the Raman spectroscopic system (181).

(1) Δλ ₀ = Δλ ₄ and ΔW ₀ = ΔW ₄ . Therefore, the foreign matter 4 is composed of crystals or molecules of the same substance as the wafer 10, specifically, scratches or large roughness on the surface of the wafer 10.

(2) Δλ ₀ = Δλ ₂ , and the foreign matter 2 is the same substance as the wafer (10). However, ΔW ₀ <ΔW
_Since it is ₂ , it can be seen that the foreign material 2 is a defect in which an impure element or substance is mixed.

(3) Δλ ₀ ≠ Δλ ₁ , ΔW ₀ ≠ ΔW ₁ and Δλ ₀ ≠ Δλ ₃ , ΔW ₀ ≠ ΔW ₃ . Therefore,
The foreign matter 1 and the foreign matter 3 are different substances from the wafer (10). Further, the components of the foreign matter can be identified by comparing the respective wavelength shift amounts Δλ ₁ and Δλ ₃ with the values obtained in advance.

When the mounted wafer (10) is entirely scanned and the above processing is completed, the inspection of the wafer (10) is completed and the R table (111) and the θ table (112) are driven and the laser oscillator ( Oscillation of 121) stops. Then, the result of the above arithmetic processing is temporarily stored in the corresponding address on the memory built in the arithmetic control unit (170), and the display system (17
1) is output to the outside via an auxiliary storage device (173)
Stored in. If it is desired to inspect another wafer, the same operation is repeated after desorption / replacement.

Next, FIG. 6 shows the general construction of the foreign matter inspection / analysis apparatus (101) of the second embodiment of the present invention. Since the main structure is the same as that of the first embodiment, the same components will be designated by the same reference numerals.

The foreign matter inspection / analysis apparatus (101) includes an R table (111) and a θ table (112) as scanning means, a laser oscillator (121) as a light projecting means, and a beam expander (12).
2), objective lens system (123), imaging lens system (144) as light receiving means, Raman spectroscopic system (181), first sensor (132)
, A second sensor (143), an amplification circuit (151) as a first signal processing means, a noise removal circuit (152), a threshold comparison circuit (153), and an amplification circuit (second signal processing means 16
1), a spectrum analysis circuit (162) and an arithmetic control unit (170)
It has and.

In the second embodiment, as in the first embodiment, the first imaging lens system (1
31) is not used, and means for guiding light to the first sensor is provided inside the Raman spectroscopic system (181).
Hereinafter, the specific configuration of each part will be described in detail.

The R table (111) is a pulse motor (111-
ball screw (111-b) connected to a) and ball screw (111-b)
It is composed of a straight advance table (111-c) into which b) is screwed, and a guide rail (111-d) through which the straight advance table (111-c) can be freely advanced and retracted in the R direction (one horizontal direction).

The θ table (112) is the pulse motor (112-a)
It is a rotary table (112-b) connected to
(111-c) It is rotatably supported on the upper column around the θ axis (vertical axis). Further, the upper surface of the rotary table (112-b) has a suction function, and the wafer (10) to be inspected is mounted and fixed at a predetermined position where the coordinate system is set. Then, the pulse motors (111-a) and (112-a) are synchronously driven so that the entire surface of the wafer (10) can be concentrically scanned. In addition, each pulse motor
By counting the pulse signals to (111-a) and (112-a), a position signal indicating the current scanning position (R, θ) can be output.

The laser oscillator (121) is a laser light source (for example, an output of 300 m) that emits the inspection light L such as Ar ⁺ laser.
W, wavelength 488 nm) is used. The objective lens system (123) is
The inspection light L is condensed into a substantially elliptical shape of 10 μm × 1 μm, and a predetermined scanning point on the wafer (10) is obliquely irradiated from a direction of about 60 ° with respect to the vertical direction. In the objective lens system (123), if the incident light has a diameter larger than a certain value, it is easier to focus light geometrically. On the other hand, the light emitted from the laser oscillator (121) usually has a diameter of only about 0.6 mm. Therefore, the beam expander (122) arranged immediately in front of the objective lens system (123) converts the incident inspection light L into a parallel light obtained by enlarging the diameter of the inspection light L by about 10 to 20 times, and the objective lens system ( 123).

The imaging lens system (144) is arranged in a direction perpendicular to the incident direction of the inspection light L and at an elevation angle of about 30 ° with respect to the scanning point, and irradiates foreign matter on the wafer (10). A part L _{3 of the} scattered light generated at this time is condensed. The Raman spectroscope (181) is composed of a commonly known spectroscope such as a triple polychromator or a double polychromator and a monochromator, and has a wavelength band of λ _{1 to} λ ₂ (where 488 nm <λ ₁ <Λ ₂ ) and the scattered light (that is, Rayleigh scattered light) having the same wavelength as the incident light in a part L ₃ of the scattered light is shown in FIG. Half mirror
It is divided into two by (182) and one of them is directly detected by the first sensor (132) as Rayleigh scattering component L ₃ . The shutter (184) causes the Rayleigh scattered component L ₃
Is blocked so that it cannot reach the second sensor (143).

The first sensor (132) is a device constituted by a combination of a photomultiplier tube, a light receiving element such as a photodiode, a current / voltage conversion circuit, etc., and receives the scattered light L _3. A first inspection signal having a signal level according to the light intensity is output. Strictly speaking, the scattered light L ₃ includes both Rayleigh scattered light and Raman scattered light, but since the absolute value of the light intensity of the latter is only about 10 ⁻³ times that of the former, L _{3 is set} to Rayleigh. There is no problem in treating it as scattered light.

[0056] Additionally, other that bisected the scattered light by the half mirror (182) via a mirror (183) ..., Stokes of the Raman scattering component (Storks) light L _{3 '(where,} L _3' Has a wavelength λ _{3 ′} of λ _{3 ′} = 488 nm + Δλ and Δλ>
0) is to be extracted. The second sensor (143) is a multi-channel photodetector, which is adapted to receive L _{3 ′} and output a second inspection signal having a signal level according to its intensity.

The amplifier circuit (151) is composed of a normal amplifier element or the like, and is adapted to input the first inspection signal and amplify it at a predetermined magnification. Noise elimination circuit (152)
Is a circuit having a filter function for blocking low-level fluctuation components in the input signal, and is caused by the inelastically scattered light of the first inspection signal in addition to the shot noise of the first sensor (132). It is designed to remove weak peaks. This is because, as described above, the absolute value of the intensity of inelastically scattered light is only about 10 ⁻³ times that of elastically scattered light. The threshold value comparison circuit (153) compares the peak value of the input first inspection signal with a preset threshold value V _T, and if it is V _T or more, determines that foreign matter is present, and detects the detection signal S. It is designed to output to a spectrum analysis circuit (162) and a calculation control unit (170) described later. The threshold value V _T can be generally obtained by computer simulation or various methods such as extracting reference data using standard particles. Since the signal level is almost proportional to the size of the foreign matter, when subdividing the size of the foreign matter, this threshold value is set to V _T1 , V _T2 , V _T3 (where V _T1 <V _T2 <V _T3 <...) And multiple will be set.

The amplifier circuit (161) amplifies the second inspection signal by a predetermined magnification. Spectrum analysis circuit
Reference numeral (162) is energized by the signal S from the threshold value comparison circuit (153) to spectrally analyze the second inspection signal, detect the wavelength shift amount Δλ of the Raman scattered light L _{3 ′} , and perform the calculation described later. It is designed to output to the control unit (170).

The arithmetic control unit (170) is normally a CPU (Centr).
al processing unit) and various hardware circuits, and the outputs of the threshold value comparison circuit (153) and the spectrum analysis circuit (162) are arithmetically processed based on a predetermined program. In addition, the arithmetic control unit (1
70) is electrically connected to each of the above-mentioned parts, and drives the R table (111) and the θ table (112) and each sensor (13
2) It controls the operation of the whole foreign matter inspection / analysis device (101) by synchronizing with the outputs of (143).

The operation control unit (170) is equipped with an inspection /
CRT (Cathode Ray TRT) for displaying analysis results externally
ube) Display system (171) such as display or printer, input system (172) such as console for inputting and setting conditions such as inspection / analysis, disk device for storing arithmetic processing programs and inspection results Although the auxiliary storage device (173) is connected, it will not be described because it is not the gist of the present invention.

Next, the operation of the foreign matter inspection / analysis apparatus (101) and the operation of this embodiment will be described. Mount the wafer (10) to be inspected on the θ table (112) and
After the alignment work of (10), the arithmetic control unit (170) issues a command to oscillate the laser oscillator (121) and
The table (111) and the θ table (112) are driven synchronously to start the inspection.

At the irradiation point of the inspection light L, scattered light is generated by foreign matter on the wafer (10), defects / scratches on the surface of the wafer (10), the base of the wafer (10), and the like. The imaging lens system (144) collects a part of the scattered light L ₃ and sends it to the Raman spectroscopic system (142). The Raman spectroscopic system (181) splits scattered light (that is, Rayleigh scattered light) having the same wavelength as the incident light into two by a half mirror (182) as shown in FIG. The light is focused on the image pickup surface of the sensor (132). Then, the first sensor (132) outputs a first inspection signal according to the amount of received light, the amplification circuit (151) amplifies this, and the noise removal circuit (152) detects low-level components in the signal. Cut off. Here, the scattered light L ₃ includes not only Rayleigh scattered light but also Raman scattered light. However, since the latter has a weak absolute value of light intensity, a low-level signal component due to Raman scattered light causes noise removal circuit ( 152). An example of the chart of the first inspection signal is shown in FIG. 2. The foreign matter 1, 2 ,, on the uniform signal due to the scattered light of the underlayer of the wafer (10).
The peaks due to 3 and 4 are the inspection times t ₁ , t ₂ and t, respectively.
Suppose that it appears at ₃ , t ₄ .

Next, the threshold value comparison circuit (153) compares the first inspection signal with a predetermined threshold value V _T, and the peak points t
_{At 1} , t ₂ , t ₃ , and t ₄ , the signal level exceeds V _T , so it is determined that a foreign substance is present, and the detection signal S is detected each time.
₍₁₎ , S ₍₂₎ , S ₍₃₎ and S ₍₄₎ are connected to the spectrum analysis circuit (1
62), and output to the arithmetic control unit (170). The position and size of the foreign matter can also be detected by these detection signals.

However, here, the signals due to the Rayleigh scattered light component of the scattered light from the wafer (10) are, for example, as shown in FIGS.
As shown in (c) (when the foreign matter A, B, C, D, E and the foreign matter 1, 2, 3, 4 are different objects), the measurement by the Rayleigh scattered light component becomes saturated. Can not. Therefore, the presence, position, size, etc. of the foreign matter are determined by referring to the signal of the Raman scattered light component. FIG. 4 shows the detection ranges of the Rayleigh scattered light component and the Raman scattered light component based on the relationship between the scattered light intensity and the diameter of the foreign matter.

Therefore, in such a case, the Raman spectroscopic system (1
81), from the Raman scattered light through the half mirror (182) and the mirror (183), only the Stokes light L _{3 ′} is extracted, and the second sensor (143) receives this and receives the second Stokes light L _{3 ′} . Output inspection signal. Then, the amplifier circuit (161) amplifies the second inspection signal.

Then, the spectrum analysis circuit (162) is energized by each of the detection signals S _{(1) to} S ₍₄₎ , and each of the inspection times t _{1 to} t corresponding to the first inspection signal shown in FIG. a second test signal by spectral analysis in _4, the half-value width ΔW of the scattered light intensity with each of the wavelength shift amount Δλ ₁ ~Δλ _{4 1}
~ ΔW ₄ is calculated. The results of each analysis are shown in Fig. 5 (b)
It is shown in (e). It should be noted that the scattered light signal originating from the base of the wafer (10) (t _{0 in} FIG. 2) is also the standard data (wavelength shift amount Δλ ₀ and full width at half maximum ΔW) for the base of the wafer (10).
₀ ) and spectral analysis. The results are shown in Fig. 5 (a). Then, the analyzed wavelength shift amounts Δλ _{1 to} Δλ ₄ and the half widths ΔW _{1 to} ΔW ₄ are output to the subsequent arithmetic control unit (170).

The arithmetic control unit (170) includes the threshold comparison circuit (1
53), the output of the spectrum analysis circuit (162) is subjected to arithmetic processing as described below based on the corresponding program.

That is, the detection signal S of the threshold value comparison circuit (153) is statistically processed, classified according to the size of the foreign matter, and a histogram of the number thereof is created. In addition, each pulse motor (111-
Since the pulse signals to (a) and (112-a) are counted, the presence position of the foreign matter can be detected by comparing these count values with the detection time.

[0069] The wavelength shift amount obtained from the spectral analysis circuit (162) Δλ ₁ ~Δλ _4, the half-value width ΔW ₁ ~ΔW ₄
The components of the foreign matter are identified by comparing these with each other. For example, the following matters are derived from the charts of FIG. In addition, when performing the following work for identifying the component of the foreign matter, a triple polychromator, a double polychromator, or a plurality of monochromators is used as the Raman spectroscopic system (181).

(1) Δλ ₀ = Δλ ₄ and ΔW ₀ = ΔW ₄ . Therefore, the foreign matter 4 is composed of crystals or molecules of the same substance as the wafer 10, specifically, scratches or large roughness on the surface of the wafer 10.

(2) Δλ ₀ = Δλ ₂ , and the foreign matter 2 is also the same substance as the wafer (10). However, ΔW ₀ <ΔW
_Since it is ₂ , it can be seen that the foreign material 2 is a defect in which an impure element or substance is mixed.

(3) Δλ ₀ ≠ Δλ ₁ , ΔW ₀ ≠ ΔW ₁ and Δλ ₀ ≠ Δλ ₃ , ΔW ₀ ≠ ΔW ₃ . Therefore,
The foreign matter 1 and the foreign matter 3 are different substances from the wafer (10). Further, the components of the foreign matter can be identified by comparing the respective wavelength shift amounts Δλ ₁ and Δλ ₃ with the values obtained in advance.

When the mounted wafer (10) is entirely scanned and the above processing is completed, the inspection of the wafer (10) is completed, and the R table (111) and the θ table (112) are driven and the laser oscillator ( Oscillation of 121) stops. Then, the result of the above arithmetic processing is temporarily stored in the corresponding address on the memory built in the arithmetic control unit (170), and if necessary, the display system (17
1) is output to the outside via an auxiliary storage device (173)
Stored in. If it is desired to inspect another wafer, the same operation is repeated after desorption / replacement.

The structure of the present invention is not limited to the above-mentioned embodiments, but various modifications can be made. For example, the laser oscillator can use a monochromatic light source such as a He-Ne laser, a Kr laser, a semiconductor laser, and an infrared or ultraviolet pulse laser in addition to the Ar ⁺ laser. This is because it is only necessary to obtain a detectable Raman scattered light intensity.

The angle of incidence on the wafer (10) is 60 °, but vertical incidence or other oblique incidence is also possible. This is because the output of the inspection light and the area of the focused spot are not particularly limited as long as the intensity of the Raman scattered light that can be detected is obtained.

[0076]

As described above in detail, according to the foreign matter inspection / analysis apparatus and the foreign matter inspection / analysis method according to the present invention, the complexity of the apparatus is avoided, the apparatus cost is reduced, and the inspection time is shortened. Since the efficiency is improved, a great industrial effect can be obtained in the semiconductor manufacturing technical field.

[Brief description of drawings]

FIG. 1 (a) is a top view showing a general structure of a foreign matter inspection / analysis device according to a first embodiment of the present invention, and FIG. 1 (b) shows a general structure of this foreign matter inspection / analysis device. The front view, which is parallel to the incident direction, is the front view, which is orthogonal to the incident direction, showing the general configuration of this foreign matter inspection / analysis device.

FIG. 2 is a graph showing the relationship between the output signal of the first sensor and the inspection time for foreign matter 1 to foreign matter 4.

3 (a) is a schematic diagram showing the sizes of the foreign matters A to E, and FIG. 3 (b) is a relationship between the output signal of the first sensor for the foreign matters A to E and the inspection time. 2C is a graph showing the relationship between the output signal of the second sensor and the inspection time for the foreign matter A to foreign matter E.

FIG. 4 is a graph showing a detection range of a Rayleigh scattered light component and a Raman scattered light component based on the relationship between the scattered light intensity and the foreign substance diameter.

FIG. 5 is a graph showing a spectrum analysis result of Raman scattered light at each inspection time.

FIG. 6 (a) is a top view showing a general structure of a foreign matter inspection / analysis device according to a second embodiment of the present invention, and FIG. 6 (b) shows a general structure of this foreign matter inspection / analysis device. The front view, which is parallel to the incident direction, is the front view, which is orthogonal to the incident direction, showing the general configuration of this foreign matter inspection / analysis device.

FIG. 7 is a schematic configuration diagram of a monochromator, which is an example of a Raman spectroscope used in the present invention.

FIG. 8 is a schematic configuration diagram showing a foreign matter inspection apparatus of a first conventional example.

FIG. 9 is a graph showing the relationship between the size of a foreign matter and the intensity of scattered light in elastically scattered light.

FIG. 10 is a schematic configuration diagram showing an electric circuit system of a foreign matter inspection device of a second conventional example.

FIG. 11 is a schematic configuration diagram showing an electric circuit system of a foreign matter inspection apparatus of a third conventional example.

FIG. 12 is a graph showing the relationship between the intensity distribution of each scattered light of Rayleigh scattered light and Raman scattered light and the wavelength.

[Explanation of symbols]

111 ... R table, 112 ... θ table, 121 ... Laser oscillator, 122 ... Beam expander, 123 ... Objective lens system, 131 ... First imaging lens system, 132 ... First sensor,
141 ... Second imaging lens system, 142 ... Raman spectroscopic system, 143
... second sensor, 151,161 ... amplification circuit, 152 ... noise removal circuit, 153 ... threshold value comparison circuit, 162 ... spectrum analysis circuit, 170 ... calculation control unit, 171 ... display system, 172 ... input system,
173 ... Auxiliary storage device, 181 ... Raman spectroscopy system.

Claims (4)

[Claims] 1. A scanning unit for movably mounting an inspection target, and a light projecting unit for obliquely irradiating the inspection target with inspection light.
A first unit is provided above the scanning unit and in a direction other than the regular reflection direction of the inspection light to receive scattered light from the inspection target and output a first inspection signal according to the received light amount. A second inspection signal disposed above the light receiving means and above the scanning means and in a direction other than the regular reflection direction of the inspection light, the second inspection signal corresponding to the amount of received wavelength component of the scattered light different from the inspection light. The second inspection signal, the second light receiving means for outputting the first inspection signal, the first signal processing means for comparing the first inspection signal with a predetermined threshold value to detect the presence position and size of the foreign matter, and the second inspection signal. A foreign matter inspection / analysis apparatus comprising: a second signal processing means for spectrally analyzing and identifying a component of the foreign matter. 2. The first light receiving means and the second light receiving means are provided in directions substantially plane symmetrical to each other with respect to the incident surface of the inspection light. Foreign matter inspection and analysis device. 3. The foreign matter according to claim 1, wherein the first light receiving means and the second light receiving means are provided in substantially the same direction with respect to an incident surface of the inspection light. Inspection and analysis equipment. 4. A light projecting step of projecting inspection light while scanning the inspection object, and a first step of receiving scattered light from the inspection object and outputting a first inspection signal according to the received light amount. A light receiving step, a second light receiving step of receiving a wavelength component of the scattered light different from the inspection light and outputting a second inspection signal according to the amount of received light, and a second light receiving step based on the first inspection signal The first signal processing step for detecting the presence position and size of the foreign matter and the second inspection signal at the foreign matter presence position detected in the first signal processing step are spectrum-analyzed to perform the component of the foreign matter. And a second signal processing step for identifying.