JPH09304289A - Method and apparatus for inspecting surface of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect adhered foreign matter and COP in the surface inspection of a wafer. SOLUTION: A low angle light detection system 38 of which the angle of elevation based on the surface of a wafer 1 is 30 deg. or less and a high angle light detection system 37 of which the angle of elevation is larger than 30 deg. are provided and the wafer 1 is scanned by laser beam and the low and high angle light detection systems 38, 37 detect the scattered beam of laser beam to perform the detection of foreign matter corresponding to scanning and the object detected at the same scanning position only by the high angle light detection system 38 is set to the flaw of the wafer 1 and the object detected by the low angle light detection system 38 or both of the low and high angle light detection systems is set to the adhered foreign matter of the wafer 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer surface inspecting method and an inspecting apparatus, and more particularly to an inspecting method capable of separating and detecting foreign substances adhering to the surface of a silicon wafer and crystal defects existing on the surface. A method and an inspection device.

[0002]

2. Description of the Related Art A silicon wafer as a material for a semiconductor IC is made of high-purity polycrystalline silicon. It is manufactured by making an ingot of single crystal silicon by a pulling method or the like, slicing this into a thin plate, polishing the surface of the ingot to finish it to a mirror surface, and further carefully cleaning foreign substances adhering to the surface. Despite this cleaning, some adherent foreign matter remains. If a large amount of this remains, it impairs the quality of the IC, so the presence or absence and the degree of foreign matter attached are inspected by a surface inspection device.

FIG. 10 shows the structure of a conventionally used wafer surface inspection apparatus. The surface inspection device is shown in Fig. 1.
As shown in 0 (a), it comprises a rotation / movement table 2, an inspection optical system 3, a data processing unit 4, and the like. A silicon wafer (hereinafter simply referred to as a wafer) 1 to be inspected is placed on a rotary / movable table 2. The inspection optical system 3 arranged above the wafer 1 is a laser light source 3 having a laser oscillation tube.
One. The laser beam LT that it outputs is
The vibrating mirror 3 is made parallel by the collimator lens 32.
3 sweeps in the X direction. Then, it is focused as a laser spot Sp (hereinafter referred to as spot Sp) by the focusing lens 34 and projected perpendicularly to the surface of the wafer 1, and the wafer is scanned according to the movement of the wafer 1.

The wafer 1 moves in the radial direction (X direction) while being rotated by the rotating / moving table 2.
As a result, the spot Sp scans the surface of the wafer 1 in a spiral manner, and as a result, the entire surface of the wafer 1 is scanned. The drive of the rotary / movable table 2 is controlled by the data processing unit 4 described later. When the foreign matter e is present on the surface of the wafer 1, the spot Sp generates scattered light Se in a random direction due to the foreign matter e, as shown in FIG. A part of the light is condensed by a condenser lens 35 having an optical axis of 45 °, and a photomultiplier tube (PMT) 36 which is a photoelectric converter.
Received. The light incident on the PMT 36 is converted into an electric signal here, and the converted received light signal is the foreign substance detection circuit 4
Input to 1. The foreign matter detection circuit 41 compares the predetermined threshold value VTH with the received light signal by a one-sided differential amplifier,
Amplifies components that exceed the threshold VTH. As a result, the detection signal (analog signal) from which the noise component has been removed is input to the data processing unit 4.

The detection signal is converted into a digital value by an A / D conversion circuit (A / D) 42b provided in the data processing device 42 and temporarily stored in the memory 42c by the MPU 42a, and the MPU 42a executes a predetermined program. As a result, the detection data is processed with the data of the scanning position (detection position). As a result, the size of the foreign matter e is determined according to the detected value. Further, the number of foreign matters is counted. Further, the MPU 42a executes a predetermined program to generate foreign substance data indicating the number, size, and position of the foreign substance e, which is output to the printer 43 or a display (not shown) or the like to display the state of the foreign substance on a map. To be done. The A / D 42b may be provided outside the data processing device 42. The spot S
p is a very strong light having a diameter of several μm, and the condensing lens 35 has a large diameter and a wide condensing angle. Further, the PMT 36 has characteristics of large amplification factor and low noise. As a result, it is possible to detect foreign matters or defects having a diameter of about 0.1 μm. The scanning of the spot Sp on the wafer 1 may be performed by the XY scanning method in addition to the rotary scanning method described above.

[0006]

[Problems to be Solved by the Invention]
Due to the improvement of the integration density of C and the thinning of wiring accompanying this, the allowable limit of the size of the foreign matter to be detected has become even smaller. Therefore, even defects due to the loss of silicon atoms in the wafer 1 have become a problem. This will be described with reference to FIGS. 11 and 12. The wafer is composed of a single crystal in which innumerable silicon atoms Si are bonded to each other in a lattice shape. As shown in FIG. 11, silicon atoms S
There is a case where i is oxidized to form a minute oxide on the surface, and the minute oxide is missing due to cleaning, resulting in a defect. This becomes a crystal defect. This crystal defect is caused by Cri.
stall-Originated-Particle
Since it is called (COP), this will be described below.

In FIG. 11, a plurality of consecutive (3 in FIG.
Silicon atoms Si are missing. When a large number of these are observed with a microscope, the cross section has a concave surface as shown in FIG. The diameter φ and the depth δz are of course varied, but the feature is that the depth δz is smaller than the diameter φ. For example, when the diameter φ is 1 to 2 μm, the depth δz is about 1/20 of 0.05 to 0.1 μm.
It is a degree. The size of the COP, which is a defect for the IC, is not a problem for a 16 Mbit IC memory (wiring width 0.7 μm) when the diameter φ is 2 μm.
It becomes harmful to IC memory of more than a bit. The number of COPs changes depending on the pulling rate and the number of times of cleaning when producing an ingot of single crystal silicon. On the other hand, the number of adhering foreign matters e is also reduced by cleaning, so it is necessary to appropriately determine the pulling rate and the number of times of cleaning. For that purpose, it is necessary to individually measure the number and size of the COP and the adhering foreign matter e.

Therefore, the COP is measured by the wafer surface inspection device.
There is a request to measure and obtain evaluation data. However, the inspection optical system 3 described above does not adhere to the foreign matter e
Since it is detected, the number of both, or the number of both and their sizes cannot be measured separately. Regarding the foreign matter detection device, US Pat. No. 5,245,403 discloses an invention of “glass foreign matter inspection device” by the present applicant, which has two light projection systems of high angle and low angle. It is an object of the present invention to provide a wafer surface inspection method capable of detecting adhered foreign matter and COP. An object of the present invention is to provide a wafer surface inspection device capable of detecting adhered foreign matter and COP.

[0009]

The features of the wafer surface inspecting method and the inspecting apparatus of the present invention for attaining the above-mentioned object are that the angle of elevation with respect to the surface of the wafer is 30 ° or less. It has a light receiving system and a high angle light receiving system with an elevation angle larger than this.The wafer is scanned with laser light, and the low angle light receiving system and the high angle light receiving device receive scattered light of the laser light and correspond to scanning. Foreign matter is detected by using the high angle light receiving system at the same scanning position to detect a wafer defect, and the foreign matter detected by the low angle light receiving system is detected as an adhering foreign matter. Further, regarding the adhering foreign matter, what is detected by both the low-angle light receiving system and the high-angle light receiving may be detected as the adhering foreign matter. further,
If necessary, the size of the adhering foreign matter or defect is determined, which is performed by the detected value of the foreign matter detected by the high-angle light receiving system. As the inspection device, a first photoelectric converter is provided in the low-angle light receiving system, a second photoelectric converter is provided in the high-angle light receiving system, and a first detection signal is output from the first photoelectric converter. When a second detection signal is received from the second photoelectric converter and the first detection signal having a predetermined value or more is received, or the first detection signal having a predetermined value or more and the first detection signal having a predetermined value or more are received. And a data processing device that detects the adhering foreign matter when both the second detection signal and the second detection signal are received, and detects the defect when only the second detection signal having the predetermined value or more is received.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Now, an experiment conducted by the inventor of the present invention on directivity characteristics of scattered light of adhering foreign matters and crystal defects will be described. Although scattered light of adhering foreign matters is almost omnidirectional, Since the crystal defects are very shallow in depth compared to the diameter, the scattered light has a directivity of about 30 ° or more with respect to the surface. Almost no scattering occurs in the direction below this. Due to such directional characteristics, the scattered light of the adhering foreign matter and the crystal defects are both received by the high-angle light receiving system provided in the angle direction of the elevation angle of 35 ° to 60 ° with respect to the wafer surface, and these are detected. To do. On the other hand, in a low-angle light receiving system provided in an angle direction with an elevation angle of 30 ° or less, almost no scattered light of crystal defects is incident, so that only scattered light of adhering foreign matter is received and detected. As can be understood from the description of the prior art, the angle at which scattered light such as crystal defects and adhering foreign matter can be strongly received is conventionally 35 ° to 60 °.
A range of degrees has been selected. And, in particular, the proper light receiving range is 40 ° to 50 °.

The low-angle light reception with the elevation angle of 30 ° or less is based on the experimental result shown in FIG. That is, in FIG. 7A, the CZOC when light is received at a high angle of elevation of 40 ° to 50 °
A map of foreign matter detection data for wafers manufactured by the HRALSKI method is shown in (b) with an elevation angle of 5 ° to
As an example, map degrees of foreign matter detection data for the same wafer when light is received at a low angle of 20 ° are shown. As can be seen by comparing these maps, the amount of foreign matter detected is large in FIG. 5A, which includes adhered foreign matter and crystal defects. On the other hand, in FIG. 6B, the foreign matter detection amount is small, and almost only the adhered foreign matter is detected.
Since it is difficult to completely remove the adhered foreign matter from the wafer for inspection, in order to verify this, foreign matter detection was performed on the wafer manufactured by the FLOATING ZONE method in which almost no COP defects occur. (C) shows the detected data when the light is received at a high angle of elevation of 40 ° to 50 °, and (d) shows the detected data when received at a low angle of 5 ° to 20 °. Are shown respectively. In the maps (c) and (d), unlike the previous maps (a) and (b), the foreign matter detected by the low-angle light reception and the foreign matter detected by the high-angle light reception are detected in substantially the same state. ing. These maps are typical examples, and there is little difference even if the above angles are moved back and forth. However, when the optical axis of the low-angle light receiving system is 30 ° or more, the state of (b) approaches the state of (a).

By the way, recently, as shown in FIG.
It has been found that P also exists inside the wafer. Further, an oxide layer (OSF; OxidationI) is further formed on the surface.
nducedStackingFolt), which produces scattered light when spotted, like adhering foreign matter. The scattered light from these acts as noise when the amplification factor of the PMT (photomultiplier tube) is increased. This noise becomes a problem in the detection of adhering foreign matter in a low-angle light receiving system whose detection level is relatively low. Therefore, the inventors paid attention to the Brewster angle θB at which the reflectance of the P-polarized component becomes almost zero. By applying this Brewster angle θB to the low-angle light receiving system, the noise component generated by the scattered light from the COP and the OSF can be reduced and the adhering foreign matter can be detected more accurately. The Brewster angle θB of the wafer 1 can be calculated from the refractive index n of silicon. However, in general, the refractive index n of silicon or glass changes depending on the wavelength λ. For example, the refractive index n of silicon with respect to a wavelength of 3 μm is disclosed as a value of 3.43 in an optical handbook or the like. However, this cannot be directly applied to the detection optical system.

FIG. 9 is a curve diagram showing experimental data on Brewster's angle, where the horizontal axis represents the incident angle θ1 and the vertical axis represents the reflectance r and the transmittance t in%. Argon laser tube is used as a laser light source, and it oscillates 488 nm
The angle of the linearly polarized wave of the wavelength is changed to generate the P polarized wave and the S polarized wave, which are projected on the surface of the wafer 1 and the incident angle θ
The reflectance r [P] for 1 (where [P] is the P-polarized component),
The transmittance t [P], the reflectance r [S] (where [S] is an S-polarized component), and the transmittance t [S] were measured. as a result,
The measured value indicated by x in the figure was obtained. The reflectance r [P] has a minimum value at θ1 = 76 °, where θ1 is the incident angle, and this is the Brewster angle θB. Therefore, when the refraction angle is θ2, θ2 is 14 °, which is 5 ° to
Enters the range of 20 °.

Here, if the P-polarized wave and the S-polarized wave are projected from the air side having the refractive index n1 = 1 onto the surface of the dielectric having the refractive index n2 at appropriate incident angles θ1, respectively. , N ₁ sin θ ₁ = n ₂ sin θ ₂ holds. Substituting θ1 = 76 ° and θ2 = 14 ° from this logical equation to obtain n2,
The refractive index n = 4.0 of the actual silicon wafer is obtained.
Therefore, based on this, r [P], t [P], r [S], t
When the theoretical value was calculated for [S], the calculated value indicated by "•" was obtained. The measured values of r [P] and t [P] have a difference of about 1% in the vicinity of Brewster's angle θB (76 °), but for the other measurement ranges, they almost agree with the calculated values. ing. However, the measured values of r [S] and t [S] do not match the calculated values. As a result, the angle of the low-angle light receiving system is set to around 14 °, and a light projecting system having a P-polarized light source having an irradiation angle equal to this angle is provided. The low-angle light receiving system is provided with an S polarization filter, and the scattered light is received through this. This makes it possible to more accurately detect only the adhered foreign matter. When the adhering foreign matter receives and scatters the P-polarized light, scattered light of the P component and the S component is generated, but the reflected light on the surface of the COP or OSF is mainly the P component. is there. This is cut by an S polarization filter to detect the adhering foreign matter. This allows COP and OSF
Since it is not necessary to receive scattered light from the S / N ratio, the sensitivity (amplification factor) of the PMT can be suppressed a little to suppress the influence on noise and accurately detect the adhered foreign matter. become.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an inspection optical system according to the present invention, and the same components as those in FIG. 8 are designated by the same reference numerals. The inspection optical system 3a of the wafer surface inspection apparatus 200 shown in FIG. 1 has substantially the same structure as the inspection optical system 3 of FIG. 8 described above, but this is that two high and low light receiving systems are arranged on the left and right. It differs from that of FIG. The first light receiving system is a high-angle light receiving system 37 whose elevation angle is 40 ° to 50 ° with respect to the surface of the wafer 1, and the second light receiving system is
The low-angle light receiving system 38 has an elevation angle of 5 ° to 20 °. The rotary / movable table 2 includes a rotary table 21 and a linear mechanism 22 for linearly moving the rotary table 21, and the position and rotation of the rotary table 21 are controlled by a data processing device 53 described later via a drive control circuit 55. The laser scanning system is a rotary scanning system as in FIG. 8, but it may be replaced with an XY scanning system.

The high-angle light receiving system 37 comprises focusing lenses 371 and PMT373, which are symmetrically provided on the left and right sides, and focusing lenses 372 and PMT374. The elevation angle θRH of the optical axis with respect to the surface of the wafer 1 is set within the range of 40 to 50 °. The low-angle light receiving system 38 includes focusing lenses 381, PMT383, and focusing lenses 382, PMT384, which are similarly provided symmetrically. The optical axis is the elevation angle θRL
Is set within the range of 15 to 25 °. FIG. 2 shows the structure of the wafer surface inspection apparatus 200 excluding the inspection optical system 3a. A foreign matter / defect detection circuit 51 and an adhering foreign matter detection circuit 52 are provided corresponding to the respective light receiving systems as corresponding to the foreign matter detection circuit 41 of FIG. The foreign matter / defect detection circuit 51 includes an adder circuit 51a for adding detection signals from the PMTs 373 and 374 for high-angle light reception, an amplifier 51b for amplifying and outputting the added detection signal, and this amplifier 51b.
Of the differential amplifier 51c for one-sided amplification for amplifying the signal portion exceeding the threshold value by comparing with the predetermined threshold value VTH1, the peak hold circuit 51d, and the A / D conversion circuit (A /
D) 51e. The adhering foreign matter detection circuit 52 adds a detection signal of the PMTs 383 and 384 for low-angle light reception, an amplifier 52b that amplifies and outputs the added detection signal, and a predetermined threshold value when receiving the output of the amplifier 52b. One-sided differential amplifier 52c that amplifies the signal portion exceeding the threshold value as compared with VTH2, and the peak hold circuit 5
1d, and an A / D conversion circuit (A / D) 52e. The thresholds VTH1 and VTH2 are adjustable and set to appropriate values according to the state of the detection signal of each light receiving system.

As a result, the detection signal of the foreign matter including the foreign matter and the defect detected in accordance with the spiral scan of the wafer is held by the peak hold circuit 51d, and at the same time, the detection signal of the foreign matter is held by the peak hold circuit 52d. It Each hold value is converted into a digital value by the A / Ds 51e and 52e according to the control signal of the data processing device 53, and is taken into the data processing device 53. The hold values of the peak hold circuits 51d and 52d are reset by the signals from the A / Ds 51e and 52e, respectively, and the peak values of the next detection signals are held by these, respectively.

The data processing unit 53 includes a microprocessor (MPU) 53a, a memory 53b, and a display 53.
c, a printer 53d, an interface 53e, etc., which are mutually connected via a bus 53f. Further, the memory 53b is provided with a foreign matter detection program 54a, a foreign matter / defect classification program 54b, a foreign matter size determination program 54c, a detected value counting program 54d, a table position control program 54e, and the like, and a foreign matter data area 54f, Defect data area 5
4g is provided. The MPU 53a executes the table position control program 54e to control the rotary / movable table 2 via the interface 53e to start scanning. Then, the control amount is stored in a predetermined area of the memory 53b as scanning position information.

The foreign matter detection program 54a uses the A / D 51
The data of e and 52e are fetched through the interface 53e at a predetermined timing and stored in the memory 53b together with the scanning position data. The particle / defect classification program 54b attaches the data obtained from the A / Ds 51e and 52e at the same detection position from the collected detection value data when the data values are equal to or more than the predetermined values set respectively. The data obtained from the A / D 52e is extracted as foreign matter detection data and stored in the foreign matter data area 54f, and the data obtained from the A / D 52e is less than or equal to a predetermined value. When it is equal to or larger than a predetermined value set for the defect data, it is extracted as defect data and stored in the defect data area 54g. It should be noted that the purpose of detecting data having a predetermined value or more is to remove noise data.

The foreign matter size determination program 54c reads the data in the foreign matter data area 54f, ranks the sizes according to the values, and adds size information (data indicating the size) to each data. Then, a process of storing the foreign matter data area 54f in the original storage position is performed. Further, the data in the defective data area 54g is read, and the sizes are similarly ranked according to the value, and the size information (data indicating the size) is added to each data to add the original data of the defective data area 54g. Is stored in the memory location. The detection value counting program 54d counts the number of adhered foreign matters according to the size by referring to the foreign matter data area 54f, and calculates the total amount of the adhered foreign matters. Further, referring to the defect data area 54g, each number and the total number of defects are counted and calculated in the same manner as described above according to the size. The foreign matter detection program 54a is a program that collects general measuring instrument data, and the foreign matter / defect classification program 54b is a program that simply refers to data values to determine the size of adhering foreign matter. The program 54c is also a general program that ranks a predetermined range. In addition, the detection value counting program 5
4d is also a program that simply counts only specific data. These are not special programs, so I will omit the details.

The process for detecting adhered foreign matters and defects will be described with reference to FIG. 3. First, an initial value is set (step 100) and scanning is started (step 101). As a result, when the spot Sp is projected perpendicularly to the surface of the wafer 1 to start scanning, the scattered light of the adhering foreign matter e and COP
The scattered light of
Collected by 1,372 respectively, and corresponding PMT
The light is received by 373 and 374. On the other hand, only the scattered light of the adhering foreign matter e is made incident and condensed on the condenser lenses 381 and 382 of the low-angle light receiving system 38, respectively, and the corresponding PMT 38.
The light is received at 3,384. The received light signals of the PMTs 373 and 374 are input to the foreign matter / defect detection circuit 51, compared with a threshold value VTH1 set therein to remove noise, and both the adhering foreign matter e and COP are detected, and the respective detection signals are detected. Is converted into a digital value by the A / D 51e and output to the interface 53e. In addition, PMT383,3
The received light signal 84 is input to the adhered foreign matter detection circuit 52, noise is similarly removed, only the adhered foreign matter e is detected, and the detection signal is converted into a digital value by the A / D 52e and output to the interface 53e.

The MPU 53a has a foreign matter detection program 54.
a is executed to collect detection data of low-angle light reception and high-angle light reception from the interface 53e (step 102),
The foreign matter / defect classification program 54b is executed to perform foreign matter / defect classification processing (step 103). Next, MPU
53a executes the foreign matter size determination program 54c to determine the size of the attached foreign matter (step 104), and then executes the detection value counting program 54d to count the number of the attached foreign matter according to the size. Then, the total amount of adhered foreign matters is calculated, the number of defects is also counted according to the size of the defect, the total amount of defects is calculated, and the size and the total amount are calculated (step 105). A process for outputting a defect or an adhering foreign substance to the display, or both of them, for example, by color coding and outputting as a map (step 106). of course,
Both may be displayed in a map without color coding. as a result,
A foreign matter map as shown in FIG. 7 is output.

FIG. 4 shows an inspection optical system 3b in which the S-polarization filter 385 is provided between the focusing lens 382 and the PMT 384 of the low-angle light receiving system 38 in FIG. The elevation angle is set to about 14 ° (the depression angle is about 76 °) based on 1, and a light receiving system 38a is provided by removing the focusing lenses 381 and PMT383 on the left side of the drawing. In addition, a light projecting system 330 for irradiating a P-polarized laser spot at a Brewster's angle and having an elevation angle of a light projecting optical axis of about 14 ° is provided. Then, the inspection optical system 3b is switched to the inspection optical system 3a by the optical system switching mechanism 39 and arranged on the wafer 1. This switching is performed by the data processing device 53 via the drive control circuit 55 after the inspection of the high-angle light receiving system by the inspection optical system 3a. d FIG. 4 shows the state after this switching. If both the inspection optical system 3a and the inspection optical system 3b can be arranged above the wafer 1, it is not necessary to provide the optical system switching mechanism 39 to switch the optical system.

The light projecting system 330 of the inspection optical system 3b is provided with an argon (Ar) laser light source 331 for irradiating P-polarized light, and a collimator lens 332 and two mirrors 33 are provided on this.
3, 334 and a focusing lens 335 are added to the positions shown in the figure. Amplifier 52 of foreign matter detection circuit 52
Here, the threshold value of b is VTH3 according to the relationship between the level of detected light and noise. Data processing device 53
Is the same as above. As the processing, the inspection data of the data processing device 53 is sampled by detecting the foreign matters and defects of the high-angle light receiving system 37 by scanning the entire surface of the wafer 1, and the inspection data is first sampled together with the inspection position data. The inspection optical system 3b is switched to, and the inspection position data sampled here by scanning the entire surface of the wafer 1 is stored at the same inspection position corresponding to the inspection position of the previously sampled data. In this regard, step 1 of FIG.
This is different from the process of collecting data at once in 01 and 102. The subsequent processing is the same as the processing after step 103 in the flowchart of FIG.

As a result, as shown in FIG.
The randomly polarized scattered light of the adhering foreign matter e on the surface of the wafer 1 is condensed by the condenser lens 382 of the light receiving system 38a, and the S polarized component is extracted by the S polarizing filter 385. On the other hand, COP and OSF existing on the surface and inside
Scatters the transmitted light T [P], and a part of this randomly polarized scattered light Sc is condensed by the condenser lens 382, and the S polarized component is extracted by the S polarizing filter 385. Since this is weaker than the S-polarized component of the scattered light Se of the adhered foreign matter, the scattered light Se of the adhered foreign matter e is received by the PMT 383 with almost no decrease in the S / N ratio. The foreign matter detection signal output from the PMT 383 is input to the adhered foreign matter detection circuit 52 and compared with the threshold value VTH3 to remove noise.
The adhering foreign matter e up to μm or less and their respective sizes are detected. In the figure, the output of the PMT 383 is input to the adhered foreign matter detection circuit 52 for convenience of explanation of the data processing, but originally, even if the output of the PMT 383 is input to the foreign matter / defect detection circuit 51 by the switching processing. Good. In this case, the threshold of the differential amplifier 51c is switched from VTH1 to TVH3. In this way, the adhered foreign matter detection circuit 52 becomes unnecessary.

FIG. 6 shows an example of the number data of the adhering foreign matter e and COP measured as described above. In FIG. 6, the horizontal axis represents the number of cleaning times n, and the vertical axis represents the number N, showing curves for the number Ne of adhering foreign matter e of 2 μm or more and the number Nc of COPs. The number Ne of the adhering foreign matter e naturally decreases in inverse proportion to the number of times of cleaning n. On the other hand, COP
The number NC of Nos. Increases with a considerable increase rate as the number of cleaning times n increases. However, the number Nc increases as the pulling speed of the ingot increases. The wafer manufacturer can determine the optimum cleaning number n and the like with reference to such measurement data. The present invention is not limited to blank wafers. For example, when a deposition film of aluminum Al or the like is formed on a wafer, the film thickness of the deposition film is 0. It has been confirmed that a defect and an adhering foreign matter can be detected if the thickness is about several μm. Further, as the processing for separating the data of the adhered foreign matter and the crystal defect in the data processing device, for example, the detection data of the scattered light from the spot received by the high angle light receiving system is simultaneously received by the low angle light receiving system. In that case, it can be done by setting a flag in the data.

[0027]

As described above, according to the present invention, a low-angle light receiving system having an elevation angle of 30 ° or less with respect to the surface of the wafer is provided, and the wafer is scanned with laser light to perform this scanning. According to the above-mentioned scanning, the adhered foreign matter is detected, and the high-angle light receiving with an elevation angle larger than this is provided to detect the adhered foreign matter and the defect in accordance with the above-mentioned scanning, and it is detected only by the high-angle light receiving system at the same scanning position. Is detected as a wafer defect, and the foreign matter detected by both the low-angle light receiving system and the high-angle light reception is detected as the adhering foreign matter, so that the adhering foreign matter and defects such as crystals can be distinguished and detected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an inspection optical system of a wafer surface inspection apparatus of the present invention.

FIG. 2 is an explanatory diagram of a data processing unit thereof.

FIG. 3 is a flowchart of a detection process of the adhering foreign matter and the defect.

FIG. 4 is an explanatory diagram of an embodiment in which a Brewster angle is further applied to the foreign matter detection system of the optical system in FIG.

FIG. 5 is an explanatory diagram of a scattered light state of an adhering foreign substance and COP, (a) is a case of the adhering foreign substance, and (b) is a diagram.
If there is a COP on the wafer surface, and (c)
This is the case where there is a COP inside the wafer.

FIG. 6 is an explanatory diagram of a correlation between the number of adhered foreign matters and the number of times of cleaning, showing an example of measurement data.

FIG. 7 is a diagram showing an adhering foreign substance and CO which are the basis of the present invention.
It is explanatory drawing of the directivity characteristic of the scattered light of P, (a) is CZ
It is a map figure of the foreign material detection data when the elevation angle about the wafer manufactured by the OCHRALSKI method is received at a high angle in the range of 40 ° to 50 °, and FIG. It is the same map figure when light is received at a low angle. Further, (c) is a map diagram of foreign matter detection data when a wafer manufactured by the FLOATING ZONE method is received at a high angle of elevation of 40 ° to 50 °, and (d) is the map above. It is the same map figure when light is received about the wafer at a low angle of 5 ° to 20 °.

FIG. 8 is a diagram showing crystal defects (CO
It is an explanatory view of P) and an oxide layer (OSF) on the surface.

FIG. 9 is a graph showing a relationship between experimental data and a logical value for Brewster's angle.

10A and 10B show a conventional wafer surface inspection apparatus, wherein FIG. 10A is a configuration diagram thereof, and FIG. 10B is an explanatory diagram of a scattered state of irradiation light for the foreign matter.

FIG. 11 is an explanatory diagram of crystal defects (COP).

FIG. 12 is an explanatory diagram of the shape of CO.

[Explanation of symbols]

1 ... Wafer, 2 ... Rotating / moving table, 3, 3a, 3b
... inspection optical system, 4 ... data processing unit, 37 ... high-angle light receiving system, 38 ... low-angle light receiving system, 373, 374, 383, 3
84 ... Photomultiplier tube (PMT), 51 ... Foreign matter / defect detection circuit, 51a, 52a ... Addition circuit, 51b, 52b ... Amplifier, 51c, 52c Differential amplifier, 51d, 52d ... Peak hold circuit, 51e, 52e ... A / D conversion circuit (A / D), 52 ... Adhesion foreign matter detection circuit, 53 ... Data processing device, 53a ... Microprocessor (MPU), 53
b ... memory, 53c ... display, 53d ... printer, 54a ... foreign matter detection program, 54b ... foreign matter / defect classification program, 54c ... foreign matter size determination program, 54d ... detection value counting program, 54e ... table position control program, 54f … Foreign matter data area, 5
4g ... Defect data area, 55 ... Drive control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeharu Iizuka 3-16-3 Higashi, Shibuya-ku, Tokyo Inside Hitachi Electronics Engineering Co., Ltd.

Claims (5)

[Claims] 1. A low-angle light receiving system having an elevation angle of 30 ° or less with respect to a surface of a wafer and a high-angle light receiving system having an elevation angle larger than this, and the wafer is scanned with laser light. Then, the low-angle light receiving system and the high-angle light receiving device receive scattered light of the laser light to detect foreign matter corresponding to the scanning, and those detected only by the high-angle light receiving system at the same scanning position. A method for inspecting a wafer surface, which comprises detecting defects in the wafer and detecting foreign matter adhering to the wafer detected by the low-angle light receiving system. 2. A low-angle light receiving system having an elevation angle of 30 ° or less with respect to the surface of the wafer and a high-angle light receiving system having an elevation angle larger than this, and the wafer is scanned with laser light. Then, the low-angle light receiving system and the high-angle light receiving device receive scattered light of the laser light to detect foreign matter corresponding to the scanning, and the high-angle light receiving system does not detect the foreign matter at the same scanning position. A wafer surface inspection method in which defects detected on only the angle light receiving system are detected as defects of the wafer, and those detected by both the low angle light receiving system and the high angle light receiving are detected as adhering foreign matters. 3. A projection optical system for irradiating a spot of the laser light in a vertical direction from above the wafer,
The wafer surface inspection method according to claim 1, wherein the angle of the low-angle light receiving system is in the range of 5 ° to 20 °, and the angle of the high-angle light receiving system is in the range of 35 ° to 60 °. 4. A projection optical system for irradiating the P-polarized laser spot from an oblique direction at an angle corresponding to the Brewster angle of the wafer, and the angle of the low-angle light receiving system corresponds to the Brewster angle. Is selected as the angle to
The wafer surface inspection method according to claim 2, wherein the scattered light of polarized light is received, and the angle of the high-angle light receiving system is in the range of 40 ° to 50 °. 5. A low-angle light receiving system having a first photoelectric converter and having an elevation angle of 30 ° or less with respect to a surface of a wafer, and a low-angle light receiving system having a second photoelectric converter. A high-angle light receiving system having a larger elevation angle, a scanning mechanism for scanning the wafer with a laser beam, and a first photoelectric converter to a first
When the second detection signal is received from the second photoelectric converter and the first detection signal having a predetermined value or more is received, or when the first detection signal having a predetermined value or more and the predetermined value or more is received. Foreign matter is detected when the second detection signal is received, and the first detection signal of a predetermined value or more is not received,
A wafer surface inspection apparatus comprising: a data processing apparatus which detects a defect when it receives only the second detection signal equal to or more than the predetermined value.