JPH06174655A - Detecting method of foreign substance of filmed wafer and inspection apparatus of foreign substance - Google Patents

Abstract

PURPOSE:To furnish a method which is applied to a filmed wafer having an aluminum thin film evaporated and wherein grains of the thin film are removed as much as possible and a sticking foreign substance is detected, and an inspection apparatus of the foreign substance to which this method is applied. CONSTITUTION:This apparatus comprises a rotating-moving mechanism 3 for a filmed wafer 1', a light-projecting system 4 which projects a laser beam onto the surface of the filmed wafer 1' at a small angle of 15 deg. to 20 deg. and bundles 511 and 512 of optical fibers and photomultiplier tubes 521 and 522 being in a plurality respectively. The apparatus is equipped with a large-angle light sensing system 5A and a small-angle light sensing system 5B which sense scattered lights from an aluminum thin film and a foreign substance sticking thereto, in the range of a large angle of about 45 deg. or above and in the range of a small angle of about 45 deg. or below and in radial directions in a plurality, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting foreign matter adhered to a film-coated wafer and an inspection apparatus for the adhered foreign matter.

[0002]

2. Description of the Related Art The quality of a silicon wafer used as a material for semiconductor ICs deteriorates when foreign matter adheres during each processing step and during transportation, and therefore the surface inspection of the foreign matter is performed in a timely manner. In FIG. 5, the wafer 1 is inspected for defects and adhering foreign substances at the stage of a mirror surface (substrate) having a smooth surface, and then an aluminum thin film 2 is deposited on the entire surface of the wafer 1 having a good inspection result. A film-coated wafer 1'is formed, and a foreign matter inspection is performed on it.
FIG. 6 shows a basic configuration of an inspection apparatus for the wafer 1 on the substrate. The wafer 1 to be inspected has a rotational movement mechanism 3
It is chucked by the spindle 32 and is rotated by the motor 31, and is moved in the radial direction by the moving unit 33. On the other hand, the light projecting system 4 is provided, and the laser beam from the laser light source 41 is converted into a parallel beam having an appropriate diameter by the light projecting lens 42.
The wafer 1 is focused by the focusing lens 44 via the mirror 43.
A laser spot is projected perpendicularly to the surface of the. Since the wafer 1 is moving in the radial direction while being rotated by the rotation moving mechanism 3, the laser spot scans the surface in a spiral shape. When there are defects or foreign substances on the surface, the laser spot scatters the scattered light by these, and the scattered light is received by the optical fiber bundle (bundle) 51 of the light receiving system 5 and is input to the photomultiplier tube 52. A light receiving signal is output. The signal processing unit 6 removes noise with an appropriate threshold value to detect defects or adhering foreign matter, and the data processing unit 7 edits the detection signal into map display data to map the defect and adhering foreign matter to the printer 8. Is displayed.
There are various defects on the wafer 1, such as scratches, pits, unevenness, and haze called haze.
In order to detect each of these defects as distinctively as possible, an apparatus in which the light projecting system 4 and the light receiving system 5 of the basic configuration of FIG. 6 described above are improved is used.

[0003]

Now, when the foreign matter inspection on the aluminum thin film 2 deposited on the entire surface of the wafer 1 is inspected by the above-mentioned inspection apparatus, the surface of the thin film 2 has a nodule of minute aluminum molecules. Due to the presence of grains (hereinafter referred to as “G”), the laser spot is scattered and detected together with the adhered foreign matter. FIG. 7 shows an example of an experimental result for detecting the grain G of the aluminum thin film 2. In the experiment, as shown in (a), a film-coated wafer 1'having an aluminum thin film 2 deposited on the entire surface is taken,
The left half is left as it is, and standard particles P _T having an appropriate particle size (0.5 μm in this case) are sprayed onto the surface of the right half to obtain a test wafer. (b) shows a map display obtained by inspection of the test wafer, in which a large number of detected grains G are displayed in the left half, and in the right half, the grains G with respect to the detected standard particles P _T are displayed. Has been added to increase the total number. (c) is the standard particle P _T for the map display of (b)
And the number distribution curve of the grain G is shown, and if the grain G is not detected, it should be a dotted line having a peak at the particle size of the standard particles P _T of 0.5 μm, but in reality, as shown by the solid line, 0. A peak for grain G appears at a particle size smaller than 5 μm. The solid line shows that the number is distributed to the larger particle size d, which is the standard particle P _T superposed with the large particle G. In order to inspect the adhered foreign matter, it is naturally necessary to remove the grain G and display only the adhered foreign matter on the map. In this case, since the respective devices obtained by improving the inspection device of FIG. 6 for the purpose of distinguishing defects are ineffective in distinguishing the adhered foreign matter from the grains G. Therefore, in order to remove the grain G, it is necessary to separately improve the light projecting system 4 and the light receiving system 5, and to add required processing means to the data processing unit 6. The present invention has been made in view of the above, and is directed to a film-coated wafer on which an aluminum thin film is vapor-deposited. An object is to provide a foreign matter inspection device.

[0004]

The present invention is a foreign matter detection method and foreign matter inspection apparatus for a film-coated wafer. The foreign matter detection method is such that a laser beam is projected at a low angle of 15 ° to 20 ° on the surface of a film-coated wafer on which an aluminum thin film is vapor-deposited to perform a spiral scan, and the aluminum thin film and foreign matter attached to the thin film are detected. The scattered light is received in a plurality of radial directions in a high angle range of approximately 45 ° or more and a low angle range of approximately 45 ° or less, and each received light signal received in the high angle range and the low angle range is appropriately received. Noise is removed by a threshold value to detect a high angle detection signal and a low angle detection signal. The high angle detection signal and the low angle detection signal detected at the same time are compared, and when the high angle detection signal is smaller than the low angle detection signal,
It is determined that both detection signals are due to the aluminum thin film, and when the high angle detection signal is larger than the low angle detection signal,
The both detection signals are determined to be due to the adhered foreign matter, and the foreign matter data is output. The foreign matter inspection apparatus mounts a film-coated wafer, rotates, and rotates a radial movement mechanism, and projects a laser beam at a low angle of 15 ° to 20 ° to the surface of the aluminum thin film of the film-coated wafer. And a scanning light projection system, a plurality of optical fiber bundles, and a photomultiplier tube, respectively, for scattering the scattered light of the aluminum thin film and its adhered foreign matter in a high angle range of approximately 45 ° or more,
It has a high-angle light receiving system and a low-angle light receiving system that receive light in a plurality of radial directions in a low angle range of approximately 45 ° or less. By the above scanning, noise is removed from each photodetection signal output from each photomultiplier tube of the high-angle photodetection system and the low-angle photodetection system with an appropriate threshold value, and the high-angle detection signal and the low-angle detection signal are detected. The signal processing unit and the high angle detection signal and the low angle detection signal detected at the same time by the signal processing unit are compared, and when the former is smaller than the latter, it is determined that both detection signals are due to the aluminum thin film. When the data is cut and the former is larger than the latter, both detection signals are determined to be due to adhered foreign matter, and a data processing unit that outputs map data of the adhered foreign matter and a printer that displays the map data as a map are configured. . In the above, a hollow metal hemisphere with an appropriate diameter is provided, and a projection hole through which a laser beam at a low angle from the light projecting system passes is punched in the metal hemisphere. In the center direction of the metal hemisphere, the insertion holes for the optical fiber bundle are drilled at equal intervals in the radial direction, and multiple optical fiber bundles of the high-angle light receiving system and the low-angle light receiving system are inserted and held in each insertion hole. To do.

[0005]

In general, when the laser beam is projected at a low angle, the directivity of the scattered light of the adhering foreign matter is stronger in the high angle direction than in the low angle direction, while the directivity of the scattered light by the rough surface such as aluminum is On the contrary, there is a characteristic that the high angle direction is weaker than the low angle direction. That is, since the grain size of the grain G of the aluminum molecule is considerably small and the irregularities thereof are gentle, the laser beam projected at a low angle mainly scatters in the direction of regular reflection at a low angle. This can be known by visually observing the reflected light on the aluminum surface.
On the other hand, since the adhered foreign matter is projected from the surface of the thin film, the laser beam is scattered in each direction, and its directional characteristics are variously changed depending on the shape of the foreign matter p. However, the forward scattered light on the side opposite to the laser beam projection side of the adhering foreign matter is considerably weak, and the side scattered light (in this case, the high angle direction) is quite strong.
It has been found by theoretical analysis of the scattering characteristics of fine particles. The foreign matter detection method utilizes the above-mentioned directional characteristics, and a laser beam is projected onto the surface of the aluminum thin film of the film-coated wafer at a low angle of 15 ° to 20 ° and spirally scanned to form an aluminum thin film. The scattered light of the foreign matter attached to the thin film is efficiently received in a plurality of radial directions in a high angle range of approximately 45 ° or more and a low angle range of approximately 45 ° or less. Noise is removed from each received light signal by an appropriate threshold value, and a high angle detection signal and a low angle detection signal are detected. Both detection signals detected at the same time are compared, and when the high angle detection signal (including 0) is smaller than the low angle detection signal, it is determined that these detection signals are due to the aluminum thin film, and the data is cut. To be done. On the other hand, when the high angle detection signal is larger than the low angle detection signal (including the case of 0), it is determined that these detection signals are due to the adhered foreign matter, and the foreign matter data is output. The foreign matter inspection apparatus embodies the above-mentioned detection method. A laser beam is projected from the projection system at a low angle of 15 ° to 20 ° onto the surface of the aluminum thin film of the film-coated wafer to rotate the wafer. The movement causes a spiral scan. Due to this spiral scanning, the scattered light scattered by the aluminum thin film and the adhered foreign matter is generated by a plurality of light beams of a high angle light receiving system for a high angle range of approximately 45 ° or more and a low angle light receiving system for a low angle range of approximately 45 ° or less. By the optical fiber bundle of, the light is efficiently received in a plurality of radial directions, and the light receiving signal is output from the photomultiplier tube of each light receiving system,
Furthermore, the signal processing unit removes noise from each received light signal by an appropriate threshold value, and a high angle detection signal and a low angle detection signal are detected. The data processing unit compares the high angle detection signal and the low angle detection signal detected at the same time by the signal processing unit, and when the former (including 0) is smaller than the latter, these detection signals are Cut the data by judging that it is due to the thin film. On the other hand, when the former is larger than the latter (including the case of 0), it is determined that this detection signal is caused by the adhered foreign matter, map data of the adhered foreign matter is output, and this map data is input to the printer and displayed on the map. In the above, the laser beam at a low angle from the light projecting system passes through the projection hole formed in the metal hemisphere and is projected on the surface of the film-coated wafer. Also, on each of the high-angle and low-angle circumferences of the metal hemisphere, a plurality of high-angle light-receiving systems and low-angle light-receiving systems are provided for each insertion hole formed in the center direction and drilled at equal intervals in the radial direction. An optical fiber bundle is inserted and held accurately to stabilize the reception of scattered light.

[0006]

EXAMPLE The directional characteristics of scattered light due to the adhered foreign matter p and the grain G of the aluminum thin film 2 will be described with reference to FIG.
In FIG. 1, a laser beam L _T is projected at a low angle θ _T of 15 ° to 20 ° onto a film-coated wafer 1 ′ on which an aluminum thin film 2 is vapor-deposited. For the reason described above, of the scattered light due to the grains G of the thin film 2, L _{RL in the} low angle direction has stronger directivity than L _{RH in the} high angle direction. on the other hand,
It is understood that among scattered light of the adhered foreign matter p, L _{RH in the} high angle direction is generally stronger than L _{RL in the} low angle direction.

FIG. 2 shows an embodiment of the foreign matter inspection apparatus of the present invention. The film-coated wafer 1'to be inspected is chucked by the spindle 32 of the rotary moving mechanism 3 and rotated by the motor 31.
The moving unit 33 moves in the radial direction. On the other hand, the light projecting system 4 is provided, and the laser beam from the laser light source 41 is converted into a parallel beam having an appropriate diameter by the light projecting lens 42.
After passing through the mirror 43, the light is focused by the focusing lens 44, further reflected by the mirror 45, and an elliptical laser spot is projected onto the surface of the aluminum thin film 2 at a low angle θ _T of 15 ° to 20 °. The laser spot scans the surface in a spiral shape by the rotation and the radial movement of the wafer 1 ′, and the grains G of the thin film 2 and the adhering foreign matter p scatter the scattered light. On the other hand, a plurality of optical fiber bundles 511 arranged in a high angle range, a high angle light receiving system 5A including a photomultiplier tube 521 in which these are collectively connected, and a low angle range are arranged. A low-angle light receiving system 5B including a plurality of optical fiber pandas 512 and a photomultiplier tube 522 connected together is provided. The plurality of bundles 511 and 512 receive the scattered light L _RH with a high angle and the scattered light L _RL with a low angle, respectively, and the photodetection signals are output from both photomultiplier tubes 521 and 522. The received light signals output from the photomultiplier tubes 521 and 522 are output to the signal processing unit 6
Noise is removed by an appropriate threshold value, the high angle detection signal and the low angle detection signal are respectively detected, and both detection signals are input to the data processing unit 7. In the data processing unit 7, the high angle detection signal and the low angle detection signal detected at the same time are compared, and when the latter is larger than the former (including the case of 0), these detection signals are due to the grain G. And cut the data. On the other hand, when the former is larger than the latter (including the case of 0), it is determined that this detection signal is due to the adhered foreign matter p, and the map data thereof is created. The map data is input to the printer 8 and a map display of the adhered foreign matter p is printed. Note that the comparison processing method of both detection signals is easily performed by a normal data processing technique, and the map display method is already known, so detailed description will be omitted.

FIG. 3 shows an example of the number distribution curve with respect to the particle diameter d of the standard particles P _T and the grains G obtained by the above-mentioned inspection apparatus for the test wafer of FIG. The standard particles P _T are clearly detected with a peak at 0.5 μm, the particles G having a small particle size d are almost removed, and the particles having particle sizes close to 0.5 μm are detected, and the total number thereof is greatly reduced. Is understood. In this way, although the grains G are not completely removed, the surface state of the thin film 2 can be controlled by judging the size of the detected grains G, so that it is considered to have a sufficient utility value.

FIG. 4 shows a metal hemisphere 9 for holding the above-mentioned plurality of optical fiber bundles 511 and 512, in which (a) is an external view and (b) and (c) are sectional views at the center. Metal hemisphere 9
Passage holes 911 and 912 for the low-angle laser beam L _T and its specularly reflected light L _T ′ are drilled at symmetrical positions on both lower surfaces of the laser beam. Further, the directions of the center O of the metal hemisphere 9 are formed on the circumferences of the high angle and the low angle, and the two angles φ ₁ and φ are respectively formed.
₂ and φ ₃ and φ _{4 form} a plurality of insertion holes 92 at equal intervals in the circumferential (radial) direction, and a plurality of bundles 511 and 512 of a high-angle light receiving system and a low-angle light receiving system are provided in each insertion hole 92, respectively. Insert and hold. The angles φ ₁ , φ ₂ , φ ₃ , and φ ₄ are, for example, 65 °, 50 °, 35 °, and 20 °, and each bundle has a light receiving range of about 15 °, so that the high-angle light receiving system is almost the same. The range of 45 ° to 72 ° is 45
It is possible to stably receive light in the range of 12 ° to 12 ° without leakage.

[0010]

As described above, in the foreign matter detecting method according to the present invention, the wafer with a film on which the aluminum thin film is vapor-deposited is targeted, and when the laser beam is projected on the surface at a low angle, The directivity of scattered light from adhering foreign matter is stronger in the high-angle direction than in the low-angle direction, while the directivity of scattered light in the aluminum thin film is conversely weaker in the high-angle direction than in the low-angle direction. The foreign matter inspecting device embodies this foreign matter detecting method, and the low-angle light-projecting system, the high-angle light-receiving system, and the low-angle light-receiving system are removed. , And a data processing means are provided to efficiently detect the adhering foreign matter, and there is a great contribution to the foreign matter inspection of the film-coated wafer on which the aluminum thin film is vapor-deposited.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a directivity characteristic of scattered light due to a deposited foreign matter p and a grain G of an aluminum thin film 2, which is a basis of the present invention.

FIG. 2 is a configuration diagram of a foreign matter inspection device according to an embodiment of the present invention.

3 shows an example of inspection data of a test wafer by the inspection device of FIG.

4 shows a metal hemisphere 9 holding bundles 511, 512 of optical fibers in the embodiment of FIG. 2, (a) is an external view and (b), (c) are sectional views.

FIG. 5 is an explanatory diagram of a film-coated wafer 1 ′.

FIG. 6 is a block diagram of an inspection apparatus for inspecting defects and adhering foreign matter on the wafer 1 of the substrate.

FIG. 7 is an explanatory diagram for an inspection result of a test wafer by the inspection device of FIG.

[Explanation of symbols]

1 ... Substrate wafer, 1 '... Film-coated wafer, 2
... Aluminum thin film, 3 ... Rotary movement mechanism, 4 ... Emitting system, 41 ... Laser light source, 42 ... Emitting lens, 43 ... Mirror, 44
Focusing lens 45 ... Mirror, 5 ... Light receiving system, 5A ... High angle receiving system, 5B ... Low angle receiving system, 51,511, 512 ... Optical fiber bundle, 52, 521, 522 ... Photomultiplier tube, 6 ... Signal processing unit, 7 ... Data processing unit , 8 ... printer, 9 ... metal hemisphere,
911 ... passage hole, 92 ... insertion holes, L _T ... projected laser beam,
L _T ′ ... Regular reflection laser beam, L _RH ... High angle scattered light, L
_RL ... Low angle scattered light, P _T ... Standard particles, p ... Adhering foreign matter, G
… Aluminum grain, θ _T … Laser beam projection angle, θ _{R1 to} θ _R4 … Bundle insertion angle.

Claims (3)

[Claims] 1. A surface of a film-coated wafer on which an aluminum thin film has been vapor-deposited is projected by a laser beam at a low angle of 15 ° to 20 ° to perform spiral scanning, and the aluminum thin film and foreign matter attached to the thin film. Scattered light is received in a plurality of radial directions in a high angle range of approximately 45 ° or more and a low angle range of approximately 45 ° or less, and each received light signal received in the high angle range and the low angle range is received. , The high angle detection signal and the low angle detection signal are detected by removing noise with an appropriate threshold value, the high angle detection signal and the low angle detection signal are compared at the same time point, and the high angle detection signal is the low angle detection signal. When it is smaller, it is determined that both detection signals are due to the aluminum thin film, and when the high angle detection signal is larger than the low angle detection signal, both detection signals are determined as due to the adhering foreign matter and the foreign matter data is detected. And outputting a
Foreign matter detection method for film-coated wafer. 2. A rotation moving mechanism for mounting and rotating a film-coated wafer to move in a radial direction, and a laser beam at a low angle of 15 ° to 20 ° with respect to the surface of an aluminum thin film of the film-coated wafer. A projecting system that projects and scans, each consisting of multiple optical fiber bundles and photomultiplier tubes,
A high-angle light-receiving system and a low-angle light-receiving system that receive scattered light of the aluminum thin film and foreign matter attached to the thin film in a plurality of radial directions in a high angle range of approximately 45 ° or more and a low angle range of approximately 45 ° or less, respectively. A photoreception system is provided, and noise is removed from each photoreception signal output from each photomultiplier tube of the high-angle photoreception system and the low-angle photoreception system by an appropriate threshold by scanning, and a high-angle detection signal and a low-angle detection signal are detected. A signal processing unit that detects an angle detection signal and a high angle detection signal and a low angle detection signal detected at the same time by the signal processing unit are compared, and when the high angle detection signal is smaller than the low angle detection signal, When both the detection signals are determined to be due to the aluminum thin film and the data is cut, and when the high angle detection signal is larger than the low angle detection signal, it is determined that the detection signals are due to the adhered foreign matter and the adhered foreign matter is detected. Foreign matter inspection apparatus for a film-coated wafer, comprising: a data processing unit that outputs the map data of 1. and a printer that displays the map data as a map. 3. A hollow metal hemisphere having an appropriate diameter is provided, and a projection hole through which a laser beam at a low angle from the light projecting system passes is provided in the metal hemisphere, and the metal hemisphere has a high angle and a low angle. On the circumference of an angle, the center direction of the metal hemisphere is formed, and insertion holes for the bundle of optical fibers are bored at equal intervals in the radial direction, and a plurality of the high-angle light receiving system and the low-angle light receiving system are formed in each insertion hole. The foreign matter inspection apparatus for a film-coated wafer according to claim 2, wherein a bundle of optical fibers is inserted and held.