JPH08264605A - Method for inspecting laminated board, soi wafer using the same, semiconductor integrated circuit using the wafer and apparatus for inspecting the laminated board - Google Patents

Abstract

PURPOSE: To provide an inspecting technology of a laminated board in which the particles, the fine unevenness of the surface of an SOI wafer in which the thickness of the silicon thin film of a surface layer is 1μm or less and the thickness irregularity of the laminated film can be separately inspected. CONSTITUTION: The inspecting apparatus for a thin film SOI wafer 1 comprises a semiconductor laser 2 for irradiating the wafer 1 with a light beam from above in such a manner that the incident angle of the light can be adjusted, a photodetector 4 for detecting the side scattered reflected light of the reflected light by the irradiation light via a condenser lens 3 in such a manner that the detecting angle can be adjusted, and a wafer table 5 for drivably installing the wafer 1. The particles, the processing residue and the fine unevenness of the surface are separately inspected by the combination of the incident angle of the laser beam from the laser 2 and the disposing angle of the photodetector 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for inspecting a laminated substrate composed of a silicon substrate, an insulating film such as a silicon oxide film and a silicon thin film, and more particularly to an SO for a semiconductor integrated circuit device.
In I (Silicon On Insulator) wafers, the so-called thin film S in which the film thickness of the silicon thin film on the laminated surface is 1 μm or less
The present invention relates to a method for inspecting a laminated substrate suitable for inspecting an OI wafer, an SOI wafer using the same, a semiconductor integrated circuit device using this SOI wafer, and a technique effectively applied to an inspection device for a laminated substrate.

[0002]

2. Description of the Related Art For example, as a technique studied by the inventor, a method for inspecting particles on the surface of a silicon wafer for semiconductor integrated circuit devices is disclosed in Press Journal Co., Ltd., “Monthly Semiconductor W” issued on July 20, 1994.
orld August, 1994, "P78-P83, there is a method in which scattered light generated by vertical or oblique irradiation of laser light is used for detection.

Further, when the thickness of the surface silicon thin film of the SOI wafer is 1 μm or more, the inspection can be performed by the same technique as the particle inspection method on the surface of the silicon wafer.
Further, as a technique for inspecting particles and roughness on the surface of an SOI wafer, “Monthly Semiconductor World December 1992 issue” P, which is also issued on November 20, 1992, P
90 to P96, the X-ray topography method, the infrared interference method, and the ultrasonic flaw detection method are listed as the main inspection methods.

[0004]

By the way, according to the study by the present inventors, a particle inspection of the surface of an SOI wafer having a surface layer silicon thin film having a film thickness of 1 μm or less is conducted by using the inspection technique as described above. In that case, there may be a problem that an accurate inspection cannot be performed because minute unevenness on the surface or variation in the film thickness of the laminated film in a relatively wide area scatters or interferes with incident light.

Therefore, an object of the present invention is to make it possible to separately inspect particles on the surface of an SOI wafer in which the thickness of the silicon thin film of the surface layer is 1 μm or less, and minute irregularities and variations in the film thickness of the laminated film. (EN) Provided are a substrate inspection method, an SOI wafer using the same, a semiconductor integrated circuit device using the SOI wafer, and a laminated substrate inspection device.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0007]

Of the inventions disclosed in the present application, a representative one will be briefly described below.
It is as follows.

That is, the laminated substrate inspecting method of the present invention irradiates light from an optimum angle above the laminated film and detects the scattered reflected light at the optimum angle. This is achieved by separating the scattered reflected light due to the minute irregularities and the interference due to the variation in the film thickness of the laminated film.

In another method of inspecting a laminated substrate of the present invention, light is irradiated from an optimum angle above the laminated film, and a signal obtained by removing the pulse wave intensity signal from the intensity signal of the forward scattered reflected light is detected. By using this, it is achieved by separating scattered and reflected light due to minute irregularities on the surface and interface from scattered and reflected light due to particles and interference due to variation in film thickness of the laminated film.

Further, according to another method of inspecting a laminated substrate of the present invention, a film thickness variation of the laminated film is detected by detecting a sudden change of scattered reflected light or specular reflected light of light which enters the laminated film substantially vertically. It is achieved by separating scattered reflection light from particles and scattered reflection light from minute surface irregularities.

Further, the SOI wafer of the present invention is manufactured or guaranteed in quality by inspecting and selecting the manufactured SOI wafer by using the above-mentioned laminated substrate inspection method, and in particular, the silicon in the upper layer of the laminated film of the SOI wafer is guaranteed. The thin film has a thickness of 1 μm or less.

Further, the semiconductor integrated circuit device of the present invention is
A predetermined integrated circuit is formed on the SOI wafer.

Further, the laminated substrate inspection apparatus of the present invention includes a light source which allows light to be incident on the laminated substrate from at least one upper direction, and the incident angle of the light can be adjusted.
The side scattered reflected light of the reflected light by the incident light, the signal obtained by removing the pulse wave intensity signal from the intensity signal of the forward scattered reflected light in a predetermined area, or the reflected light intensity locally due to the interference of the forward specular reflected light And a detection means capable of detecting any of these sudden changes and adjusting the detection angle.

[0014]

According to the above-described laminated substrate inspection method, SOI wafer using the same, semiconductor integrated circuit device using this SOI wafer, and laminated substrate inspection device, the particles on the laminated film are irradiated with laser light. Then, the reflected light is specularly reflected light that travels toward the reflection side at the same angle as the incident angle,
Two types of scattered and reflected light that travel in various directions are generated depending on the minute irregularities on the surface of the particles and the surface of the laminated film. These scattered and reflected light are forward scattered light and side scattered light depending on the state of the surface opposite to the incident angle. Can be separated into

That is, by utilizing this method, light is irradiated from an optimum angle obliquely above the laminated film, and the scattered and reflected light of the particles has the side scattered light whose intensity is the side scattered light due to the minute unevenness of the surface and interface. Since the reflected light is sufficiently larger than the reflected light, the scattered reflected light from the particles can be detected by detecting the side scattered reflected light.

Further, the forward scattered reflected light reflected by the laminated film includes particles, and reflection components of minute irregularities on the surface and interface, but from the intensity signal of the forward scattered reflected light from an appropriate area to the pulse wave intensity signal. When the signal except is detected,
Only the forward scattered reflected light due to the minute irregularities on the surface and interface can be detected.

Further, light is made to enter the laminated film almost vertically, and interference occurs in the specularly reflected light due to variations in the film thickness of the laminated film. This interference becomes bright and dark when the wavelength width of the incident light is narrow,
By detecting this abrupt change in the reflected light intensity, it is possible to inspect the film thickness variation of the laminated film.

As a result, in the inspection of an SOI wafer in which the thickness of the silicon thin film of the surface layer is 1 μm or less, it is possible to highly accurately inspect the particles on the surface, the fine irregularities on the surface or the interface, and the variation in the film thickness of the laminated film. Therefore, it is possible to increase the number of non-defective thin film SOI wafers, increase the number of non-defective thin film SOI wafers per semiconductor integrated circuit using the thin film SOI wafer, and further reduce the manufacturing cost of each.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic configuration diagram showing a main part of an inspection apparatus for a laminated substrate which is Embodiment 1 of the present invention.

First, the construction of the essential parts of the laminated substrate inspection apparatus of this embodiment will be described with reference to FIG.

The laminated substrate inspecting apparatus of this embodiment is an SOI wafer inspecting apparatus composed of, for example, a silicon substrate, a silicon oxide film, and a silicon thin film, and is viewed from one direction above the thin film SOI wafer 1 (laminated substrate). A semiconductor laser 2 (light source) that irradiates light and the incident angle of this light is adjustable, and side scattered reflected light of reflected light by this irradiated light is detected via a condenser lens 3, And the photodetector 4 (detection means) whose detection angle is adjustable
And a wafer table 5 on which the thin film SOI wafer 1 is drivably installed.

This thin film SOI wafer 1 has a silicon oxide film 7 having a film thickness of 0.2 to 0.5 μm on a lower silicon substrate 6 and a silicon thin film 8 having a film thickness of 1 μm or less on the uppermost layer.
It has a three-layer structure.

Next, regarding the operation of this embodiment, the thin film SO
A method of inspecting the I wafer 1 will be described with reference to FIG.

First, a laser beam having a wavelength of 780 nm is emitted from the semiconductor laser 2 onto the thin film SOI wafer 1 and is incident on the surface of the thin film SOI wafer 1 at an incident angle of 57 degrees.
Irradiate along. Then, the side scattered reflected light along the reflected light optical path 10 due to this irradiation is detected by the photodetector 4 via the condenser lens 3 directly above the thin film SOI wafer 1.

The thin film SOI wafer 1 is placed on the wafer table 5, and the drive of the wafer table 5 and the output signal from the photodetector 4 are synchronized.

In the inspection result of this experiment, the generation position of the scattered reflected light obtained by the combination of the incident angle of the laser light from the semiconductor laser 2 and the arrangement angle of the photodetector 4 is set as the position of the wafer table 5. Can be reproduced. Therefore, by observing this place with an electron microscope, it was possible to confirm particles or processing residues at the time of forming the laminated film at the positions where the scattered reflected light was generated.

On the other hand, in a comparative experiment, when the incident angle was changed to 10 degrees, it was not possible to separate the particles from the fine irregularities on the surface. When the incident angle was set to 88 degrees, the irradiation area of the laser beam was large, and the laser beam intensity per unit irradiation area was small, so that a sufficient signal could not be obtained. Further, when the incident angle was 1 degree and the angle of the photodetector 4 was 30 degrees, the particles and the minute irregularities on the surface could not be separated.

Therefore, according to the laminated substrate inspection apparatus of the present embodiment, the combination of the incident angle of the laser light from the semiconductor laser 2 and the arrangement angle of the photodetector 4 causes particles, processing residues, and minute irregularities on the surface. It was found that the method is separable, and the thin film SOI wafer 1 is manufactured by using this inspection method to obtain a good product of the thin film SOI wafer 1 and a good product per wafer of a semiconductor integrated circuit using the thin film SOI wafer 1. Can be increased.

Then, when inspecting four commercially available thin film SOI wafers 1 that have been shipped and inspected by the wafer manufacturer, 0.5 is found on the surface of the 5-inch thin film SOI wafer 1.
Particles with a size of μm or more are 790 and 21
It was found that 40,000, and 2057 pieces were attached. These particles cannot be detected by the conventional inspection method.

(Embodiment 2) FIG. 2 is a schematic configuration diagram showing a main part of an inspection apparatus for a laminated substrate which is Embodiment 2 of the present invention. FIG. 3 shows a forward scattered reflected light intensity signal as a pulse wave in this embodiment. FIG. 4 is an explanatory diagram showing an example in which a component and a low frequency component are separated, and FIG. 4 is a schematic configuration diagram showing a main part of a laminated substrate inspection apparatus which is a modified example of the present embodiment.

As in the first embodiment, the laminated substrate inspecting apparatus of this embodiment is a thin film SOI wafer 1a (laminated substrate) inspecting apparatus, and as shown in FIG. 2, a semiconductor laser 2a (light source) and a condenser lens 3a. , The photodetector 4a (detection means), and the wafer table 5a. The difference from the first embodiment is that the pulse wave intensity signal is removed from the intensity signal of the forward scattered reflected light in a predetermined area by the photodetector 4a. The point is that the signal is detected.

That is, the thin film SOI wafer 1 of this embodiment
In the inspection method of a, first, the thin film SOI wafer 1a is irradiated with laser light having a wavelength of 780 nm from the semiconductor laser 2a on the surface of the thin film SOI wafer 1a at an incident angle of 57 degrees along the incident light optical path 9a. Then, the photodetector 4 is placed at a position forming an angle of 10 degrees with respect to the specularly reflected light optical path 10a of the forward scattered reflected light by this irradiation, via the condenser lens 3a.
Detect with a.

In the inspection result of this experiment, the signal shown in FIG. 3 is obtained from the photodetector 4a, and this is separated into the low frequency component and the pulse wave component by the electric filter, and the low frequency component is larger than the reference value. The area showing the value was specified. A detailed inspection of this region confirmed minute irregularities on the surface or interface of the laminated film.

On the other hand, in a region having a value smaller than the reference value, the minute unevenness was such that it did not become a defect when manufacturing a semiconductor integrated circuit device. Further, detailed inspection of the place where the pulse wave component was generated revealed particles. However, it was found that, out of all the particles confirmed in Example 1, the particles were limited to those having a high intensity of reflected scattered light.

Further, in a modified example as shown in FIG.
Even when the incident angle was 1 degree and the position of the photodetector 4a was 30 degrees, minute irregularities could be confirmed on the surface of the laminated film or at the interface in the same manner as described above.

Therefore, according to the laminated substrate inspection apparatus of the present embodiment, the combination of the incident angle of the laser beam from the semiconductor laser 2a and the arrangement angle of the photodetector 4a is such that minute irregularities on the surface, particles and processing residues are generated. Of the thin film SOI wafer 1a by manufacturing the thin film SOI wafer 1a using this inspection method.
It is possible to increase the number of non-defective products of “a” and non-defective products per wafer of the semiconductor integrated circuit using the thin film SOI wafer 1a.

Then, when 10 pieces of commercially available thin film SOI wafers 1a which had been shipped and inspected by the wafer manufacturer were actually inspected, 10 to 30 nm was formed at the interface between the surface silicon thin film and the silicon oxide film of the 5-inch thin film SOI wafer 1a.
It was found that there is a region where a large number of minute unevennesses exist.
These minute irregularities on the interface cannot be detected by the conventional inspection method.

(Embodiment 3) FIG. 5 is a schematic configuration diagram showing a main part of an inspection apparatus for a laminated substrate which is Embodiment 3 of the present invention. FIG. 6 shows the specular reflection optical signal intensity on an SOI wafer in this embodiment. It is explanatory drawing shown corresponding to.

The laminated substrate inspection apparatus according to the present embodiment is similar to the first and second embodiments in that the thin film SOI wafer 1b (laminated substrate) is used.
As an inspection device for the semiconductor laser 2 as shown in FIG.
b (light source), a condenser lens 3b, a photodetector 4b (detection means), and a wafer table 5b. The difference from the first and second embodiments is that the photodetector 4b is reflected by interference of forward specular light. The point is that a local rapid change in light intensity is detected.

That is, the thin film SOI wafer 1 of this embodiment
In the inspection method of b, first, the thin-film SOI wafer 1b is irradiated with laser light having a wavelength of 488 nm from the semiconductor laser 2b on the surface of the thin-film SOI wafer 1b at an incident angle of 1 degree along the incident light optical path 9b. Then, the specularly reflected light along the reflected light optical path 10b due to this irradiation is detected by the photodetector 4b via the condenser lens 3b.

In the inspection result of this experiment, the reflected light intensity signal corresponding to the thin film SOI wafer 1b as shown in FIG. 6 is obtained, and the striped pattern is the interference caused by the interference of the incident light with the thin film SOI wafer 1b. The stripes indicate that the film thickness differs by Δd = λ / 4n at one dark line.

When the wavelength λ is 488 nm, it is known that the refractive index n of the silicon thin film is 4.37, so that it is possible to detect that the thickness is different by about 28 nm with one dark line as a boundary, It was possible to inspect the film thickness variation of the laminated film.

Therefore, according to the laminated substrate inspection apparatus of the present embodiment, it has been found that this is a method capable of inspecting the film thickness variation of the laminated film, and the thin film SOI wafer 1b is manufactured by using this inspection method. It is possible to increase the number of non-defective thin film SOI wafers 1b and the number of non-defective thin film SOI wafers 1b per semiconductor integrated circuit using the thin film SOI wafer 1b.

Therefore, when inspecting 10 commercially available thin film SOI wafers 1b which have been shipped and inspected by the wafer manufacturer, the film thickness variation between the surface silicon thin film and the silicon oxide film of the 5-inch thin film SOI wafer 1b is large, A maximum variation of 300 nm is recognized, and FIG. 6 is an example thereof. These variations in film thickness cannot be detected by the conventional inspection method.

Although the invention made by the present inventor has been specifically described based on the first to third embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

For example, in the inspection apparatus for a laminated substrate of the above-mentioned embodiment, a silicon oxide film having a thickness of 0.2 to 0.5 μm on a silicon substrate and a silicon thin film having a thickness of 1 μm or less at the uppermost layer are used. The case of inspecting an SOI wafer having a layered structure has been described, but the present invention is not limited to the above-described embodiment, and for example, for a silicon oxide film,
The present invention can be applied to the case of forming another film thickness of 0.2 to 0.5 μm, and also to the case of forming another insulating film. Good.

[0048]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1). By detecting the side-scattered / reflected light due to the light incident on the laminated substrate, particles on the surface and interface of the laminated substrate, processing residues, minute irregularities, and variation in film thickness of the laminated film are used to generate particles. Since only the processing residue can be separated and detected, it is possible to inspect particles on the surface and interface of the laminated substrate with high accuracy.

(2). Particles on the surface and interface of the laminated substrate are detected by detecting a signal obtained by removing the pulse-wave intensity signal from the intensity signal of the forward scattered reflected light in a predetermined area due to the light incident on the laminated substrate. Since only the fine irregularities can be detected separately from the processing residue, the fine irregularities, and the variation in the film thickness of the laminated film, the fine irregularities on the surface and the interface of the laminated substrate can be inspected with high accuracy.

(3) Detecting a film thickness variation of the laminated film of the laminated substrate by detecting a local rapid change in the reflected light intensity due to the interference of the forward specularly reflected light caused by the light incident on the laminated substrate. Therefore, it becomes possible to inspect the film thickness variation of the laminated film with high accuracy.

(4) Because of the above (1) to (3), in the inspection of the SOI wafer in which the film thickness of the silicon thin film of the surface layer is 1 μm or less, the inspection accuracy of particles, minute irregularities and film thickness variation is improved. , The number of non-defective SOI wafers can be increased, and the manufacturing cost of this SOI wafer and the semiconductor integrated circuit device using this SOI wafer can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a laminated substrate inspection apparatus that is Embodiment 1 of the present invention.

FIG. 2 is a schematic configuration diagram showing a main part of a laminated board inspection apparatus that is Embodiment 2 of the present invention.

FIG. 3 is an explanatory diagram showing an example in which a forward scattered reflected light intensity signal is separated into a pulse wave component and a low frequency component in the second embodiment.

FIG. 4 is a schematic configuration diagram showing a main part of a laminated board inspection apparatus that is a modification of the second embodiment.

FIG. 5 is a schematic configuration diagram showing a main part of a laminated board inspection apparatus that is Embodiment 3 of the present invention.

FIG. 6 is a graph showing the intensity of a specular reflection light signal as SOI in Example 3.
It is explanatory drawing shown correspondingly on a wafer.

[Explanation of symbols]

 1, 1a, 1b Thin film SOI wafer (laminated substrate) 2, 2a, 2b Semiconductor laser (light source) 3, 3a, 3b Condensing lens 4, 4a, 4b Photodetector (detecting means) 5, 5a, 5b Wafer table 6 Silicon substrate 7 Silicon oxide film 8 Silicon thin film 9, 9a, 9b Incident light optical path 10, 10a, 10b Reflected light optical path

Claims (11)

[Claims] 1. A method for inspecting a laminated substrate composed of a silicon substrate, an insulating film such as a silicon oxide film, and a silicon thin film, wherein light is incident on the laminated substrate from one direction above, and the incident light is incident. Among the forward specular reflected light, the forward scattered reflected light, and the side scattered reflected light of the reflected light by, the side scattered reflected light is detected, and particles, processing residues, minute irregularities, and a laminated film on the surface and interface of the laminated substrate are detected. The method for inspecting a laminated substrate is characterized in that only particles and processing residues are separately detected and inspected based on the variation in the film thickness. 2. The method for inspecting a laminated substrate according to claim 1, wherein an incident angle of light with respect to a surface of the laminated substrate is 10 degrees or more, preferably 30 degrees or more with respect to a vertical direction, and the side scattering. A method for inspecting a laminated substrate, wherein a detecting means for detecting reflected light is located almost directly above the surface of the laminated substrate. 3. A method for inspecting a laminated substrate composed of a silicon substrate, an insulating film such as a silicon oxide film, and a silicon thin film, wherein light is incident on the laminated substrate from one direction above and the incident light is incident. Among the forward specular reflected light, the forward scattered reflected light and the side scattered reflected light of the reflected light by detecting the signal excluding the pulse wave intensity signal from the intensity signal of the forward scattered reflected light in a predetermined region, the laminated substrate A method for inspecting a laminated substrate, characterized in that only minute irregularities are separately detected and inspected from particles on the surface and interface, processing residues, minute irregularities, and variations in film thickness of the laminated film. 4. The method for inspecting a laminated substrate according to claim 3, wherein an incident angle of light with respect to a surface of the laminated substrate is 10 degrees or less, preferably 5 degrees or less with respect to a vertical direction. A method for inspecting a laminated substrate, wherein a detecting means for detecting light is located at a position inclined by 20 to 70 degrees with respect to a position directly above the surface of the laminated substrate. 5. A method of inspecting a laminated substrate composed of a silicon substrate, an insulating film such as a silicon oxide film, and a silicon thin film, wherein light is incident on the laminated substrate from one direction above, and the incident light is incident. Among the forward specular reflected light, the forward scattered reflected light, and the side scattered reflected light of the reflected light, a local rapid change in the reflected light intensity due to the interference of the forward specular reflected light is detected,
A method for inspecting a laminated substrate, which comprises inspecting a variation in film thickness of a laminated film of the laminated substrate. 6. The method for inspecting a laminated substrate according to claim 5, wherein an incident angle of light with respect to a surface of the laminated substrate is 10 degrees or less, preferably 5 degrees or less with respect to a vertical direction, and the forward regular reflection is performed. A method for inspecting a laminated substrate, wherein a detecting means for detecting light is located at a position on the regular reflection light path corresponding to the incident angle. 7. The laminated substrate inspection method according to claim 1, 2, 3, 4, 5 or 6, wherein the light incident on the surface of the laminated substrate is a laser beam. Inspection method. 8. The method of claim 1, 2, 3, 4, 5, 6, or 7.
An SOI wafer using the method for inspecting a laminated substrate as described above, characterized in that fabrication or quality is guaranteed by using the inspection method. 9. The SOI wafer according to claim 8, wherein:
An SOI wafer, wherein the film thickness of the silicon thin film above the laminated film of the SOI wafer is 1 μm or less. 10. A semiconductor integrated circuit device using the SOI wafer according to claim 8 or 9, wherein a predetermined integrated circuit is formed on the SOI wafer. 11. A device for inspecting a laminated substrate composed of a silicon substrate, an insulating film such as a silicon oxide film, and a silicon thin film, wherein light is incident on at least one direction above the laminated substrate and The incident light of which the angle of incidence is adjustable, the side scattered reflected light of the reflected light by this incident light, the signal excluding the pulse wave intensity signal from the intensity signal of the forward scattered reflected light of a predetermined area, or the forward direction An apparatus for inspecting a laminated substrate, comprising: a detecting unit that detects any of local abrupt changes in reflected light intensity due to interference of specularly reflected light, and that has a detection angle adjustable.