JPH1019791A - Method and device for inspecting semiconductor material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the inspecting method for a semiconductor material which can easily detect a slip and a foreign matter without making the inspection time of the semiconductor material substantially long and the device which is used to implement the method. SOLUTION: An optical filter 7 which attenuate reflected light to a specific quantity is arranged in the optical path of the Ar laser light L reflected by the semiconductor material S, and the transmitted light of the optical filter 7 is made incident on an image pickup device 8 to form an image of the area irradiated with the Ar laser light L on a CCD that the image pickup device 8 is equipped. The image pickup device 8 converts the image on the CCD photoelectrically into an image signal, and an image processor 9 binarizes the given image signal on the basis of a threshold to generate a binarized image, which is outputted to an output device such as a display device and a printer. Then when an island-shaped image is formed in the binarized image, it is decided that there is a foreign matter at the position and when a linear image is formed, it is decided that a slip is present.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inspecting a semiconductor material such as a semiconductor wafer and a semiconductor element material for defects or a foreign substance adhering to the semiconductor material, and an apparatus used for implementing the method.

[0002]

2. Description of the Related Art When a semiconductor material is irradiated with excitation light having an energy larger than the energy gap of the semiconductor material, intrinsic luminescence is emitted from the semiconductor material. It is known that the intensity of the luminescence depends on the crystallinity of the semiconductor material. Therefore, an apparatus for measuring the generated luminescence and inspecting the semiconductor material has been put to practical use.

FIG. 5 is a block diagram showing the configuration of a conventional semiconductor material inspection apparatus. In the figure, reference numeral 21 denotes a laser light source which emits Ar laser light (wavelength 514.5 nm) L as excitation light having required energy. . On the optical path of the Ar laser light L, a reflecting mirror 22, a first lens 23, and a stage 32 are provided in this order. The stage 32 is xy by a support member (not shown).
A flat surface is slidably supported, and a semiconductor material S is mounted on the stage 32. The Ar laser light L emitted from the laser light source 21 is reflected by the reflecting mirror 22 and is reflected by the first lens
23, and the first lens 23 has a required spot diameter (1
(About 2 mm) and irradiate the semiconductor material S mounted on the stage 32 at a predetermined incident angle. Semiconductor material S
Immediately above the irradiation area of the Ar laser light L
Lens 24 is installed. The light containing luminescence emitted from the semiconductor material S is condensed by the second lens 24 and is incident on the spectroscope 25. The spectroscope 25 has a wavelength of 1.14.
Luminescence of μm is split. The split luminescence is incident on the optical sensor 26, and the optical sensor 26 converts the incident luminescence into an electric signal having an intensity corresponding to the amount of light, and outputs the electric signal as a luminescence signal.

[0004] In order to inspect the semiconductor material S with such an apparatus, the above-described stage 32 is moved by one in the x-axis direction or the y-axis direction.
The luminescence signal is obtained by moving the luminescence signal by about 2 mm, and the signal intensity of the luminescence signal obtained at each position is mapped. If there is a portion lower than a predetermined signal intensity, it is determined that the portion has a crystal defect, and the semiconductor material S is evaluated as a defective product.

[0005]

However, the conventional semiconductor material inspection apparatus has the following problems.

FIG. 6 is a schematic diagram showing the result of mapping the signal intensity of a luminescence signal by a conventional semiconductor material inspection apparatus. As a semiconductor material, a 6-inch wafer was heated in a nitrogen atmosphere at 800 ° C. for 16 hours.
Further, the substrate was heated at 1100 ° C. for 16 hours in an oxygen atmosphere, and the signal intensity of the luminescence signal was mapped for a quarter region of the wafer. As is clear from FIG. 6, the signal intensity of the luminescence signal is low at the center of the wafer, and defects such as stacking faults or oxygen precipitates have occurred. This result had a high correlation with the result of detecting a defect such as a stacking fault or an oxygen precipitate by an etching method which is a destructive inspection method.

By the way, there is also a portion where the signal intensity of the luminescence signal is low, such as a portion surrounded by a circle, also at the peripheral portion of the wafer where the signal intensity is higher than the central portion. It is known that, in addition to stacking faults and oxygen precipitates, a defect called a slip, in which a linear concave portion is formed on the wafer surface, occurs at the periphery of the wafer. When the occurrence of the slip is detected, it is determined that the process apparatus for manufacturing the wafer or device manufacturing using the wafer is abnormal, and the wafer on which the slip has occurred is damaged in another process apparatus. It is important to determine whether or not there is a slip, in addition to the presence or absence of the slip. However, the conventional apparatus that maps the signal intensity of the luminescence signal has a problem that it is difficult to determine whether or not a portion of the peripheral portion of the wafer where the signal intensity of the luminescence signal is low is slip. This slip can be detected by the X-ray topography method. However, when this is introduced into the apparatus shown in FIG. 5, there is a problem that the cost of the apparatus increases and the time required for inspection of the semiconductor material increases. Was.

On the other hand, when foreign matter is present on the surface of the wafer, no luminescence is emitted from the foreign matter, and the signal intensity of the luminescence signal in that portion is reduced. Can be detected, but the defect cannot be distinguished from the foreign matter. If the size of the foreign matter is smaller than the spot diameter of the laser beam and the signal intensity of the luminescence signal is not lower than a predetermined value, it is determined that there is no abnormality, and the foreign matter cannot be detected. For a defect such as a stacking fault or an oxygen precipitate, when the degree of the defect is low, that is, when the signal intensity of the luminescence signal is lower than a predetermined value, the wafer can be used as a substrate of the LSI, but foreign substances are present. In such a case, it is not possible to form an LSI in that portion, and therefore, there is a problem that the presence of a foreign substance cannot be detected.

The present invention has been made in view of the above circumstances, and has as its object to detect luminescence emitted from a semiconductor material by irradiating excitation light and to irradiate the semiconductor material with excitation light. By taking an image of the portion, binarizing the obtained image based on a preset threshold value, and determining the type of defect on the surface of the semiconductor material based on the binarized image, the inspection time of the semiconductor material is reduced. It is an object of the present invention to provide a semiconductor material inspection method capable of easily detecting slip and foreign matter without substantially increasing the length of the semiconductor material, and an apparatus used for implementing the method.

[0010]

According to a first aspect of the present invention, there is provided a method for inspecting a semiconductor material, comprising irradiating an excitation light having an energy larger than a band gap of the semiconductor material, detecting luminescence emitted from the semiconductor material, and detecting the luminescence emitted from the semiconductor material. In the method of inspecting, a portion of the semiconductor material irradiated with the excitation light is imaged, the obtained image is binarized based on a preset threshold, and based on the binarized image, the surface of the semiconductor material is It is characterized in that the type of a certain defect is determined.

[0011] A semiconductor material inspection apparatus according to a second aspect of the present invention comprises:
In an apparatus for irradiating excitation light having energy greater than the band gap of the semiconductor material and inspecting the semiconductor material by detecting luminescence emitted from the semiconductor material,
An image pickup device for picking up an image of a portion of the semiconductor material irradiated with the excitation light, and obtaining the obtained image based on a preset threshold value.
And an image processing device for generating a binarized image by converting the value.

A semiconductor material inspection apparatus according to a third aspect of the present invention comprises:
A second invention is characterized in that a filter for attenuating the amount of excitation light incident on the imaging device is provided.

The semiconductor material is irradiated with excitation light having energy larger than the band gap of the semiconductor material, luminescence emitted from the semiconductor material is detected, and a portion of the semiconductor material irradiated with the excitation light is imaged. 0.1 for semiconductor materials
To irradiate strong excitation light of about 0.6 W / cm ² ,
Interference occurs due to slight unevenness existing on the surface of the semiconductor material, and interference fringes appear in the obtained image. Since the interference fringes become sharper as the size of the irregularities increases, an image clearer than the interference fringes appearing as the background of the image is generated when slips and foreign matter are present. Therefore, when the image is binarized using a predetermined threshold value for eliminating the background interference fringes, only the image due to slip and foreign matter remains in the obtained binarized image. In the binarized image, if the image is linear, it is determined to be a slip, and if it is island, it is determined to be a foreign object. Further, the presence or absence of a defect such as a stacking fault or an oxygen precipitate is inspected by detecting luminescence.

On the other hand, since the amount of excitation light incident on the imaging device is usually larger than the allowable incident light amount of the imaging device, a filter is provided in the optical path of the excitation light to the imaging device to reduce the amount of excitation light incident on the imaging device. The light is attenuated to the allowable incident light amount.

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a semiconductor inspection apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes an Ar laser beam (wavelength) which is excitation light having a required energy.
514.5 nm) A laser light source that emits L. In the optical path of the Ar laser light L, a reflecting mirror 2, a first lens 3 and a stage 12
Are installed in this order. The stage 12 is slidably supported on the xy plane by a support member (not shown),
On the stage 12, a semiconductor material S is mounted. The Ar laser light L emitted from the laser light source 1 is reflected by the reflecting mirror 2 and enters the first lens 3, where it is condensed to a required spot diameter (1-2 mm) and the stage 12 Is irradiated at a predetermined incident angle onto the semiconductor material S placed on the substrate. The second lens 4 is provided right above the irradiation region of the Ar laser beam L irradiated on the semiconductor material S. Light containing luminescence emitted from the semiconductor material S is condensed by the second lens 4 and is incident on the spectroscope 5, where the luminescence having a wavelength of 1.14 μm is split. The separated luminescence is incident on the optical sensor 6, and the optical sensor 6 converts the incident luminescence into an electric signal having an intensity corresponding to the amount of light, and outputs the electric signal as a luminescence signal.

The stage 12 is moved by 1 mm in the x-axis direction or the y-axis direction to obtain luminescence signals, and the signal intensity of the luminescence signal obtained at each position is mapped. As a result of this mapping, if there is a portion smaller than the predetermined signal intensity, it is determined that the portion has a crystal defect, and the semiconductor material S is evaluated as a defective product.

On the other hand, A reflected by the semiconductor material S
An optical filter 7 for attenuating the amount of reflected light to a predetermined amount is disposed in the optical path of the r laser light L, and the transmitted light of the optical filter 7 is incident on the imaging device 8 and provided to the imaging device 8. An image of each irradiation region of the Ar laser light L obtained at the time of the above-described mapping is formed on a CCD (two-dimensional imaging device).

FIG. 2 is an explanatory view for explaining the relationship between the irradiation area of the Ar laser beam L and the imaging area. In the figure, S denotes a wafer which is a semiconductor material. An irradiation region 15 of Ar laser light having a spot diameter of 1 to 2 mm is formed on the semiconductor material S,
An image of the rectangular imaging region 16 including the irradiation region 15 and the periphery thereof is formed on a CCD provided in the imaging device.

The image pickup device 8 photoelectrically converts an image on the CCD to generate an image signal, and supplies the image signal to the image processing device 9.
A threshold value is set in the image processing device 9 in advance, and based on the threshold value, the image processing device 9 generates a binarized image by binarizing a given image signal and outputs the binarized image to a display device or a printer. Output to output device. If an island-shaped image is formed in the binarized image, it is determined that a foreign substance exists at that position, and if a linear image is formed, it is determined that a slip has occurred.

FIG. 3 is an explanatory view for explaining an example of an image picked up by the image pickup device 8 shown in FIG. 1. FIG. 3 (a) shows a case where the amount of Ar laser light L incident on the image pickup device 8 is appropriate. 3B illustrates a case where the light amount of the Ar laser light L incident on the imaging device 8 is inappropriate. In addition, a 6-inch wafer is used as a semiconductor material at 1100 ° C. at 30 ° C./min.
And then cooled to room temperature at 30 ° C./min, and irradiated with Ar laser light having a power of about 20 mW so that the spot diameter became 2 mm. The light transmitted through the optical filter was incident on an image pickup apparatus equipped with a 1/2 inch CCD having 510 × 492 pixels. As the optical filter, a filter having a Cr metal film formed on the surface of quartz glass and transmitting 8% of light having a wavelength of 0.5 to 1.1 μm is used. Three filters are used and two filters are used in (b).

As shown in FIG. 3B, when two filters transmitting 8% of light having a wavelength of 0.5 to 1.1 μm are used,
The amount of Ar laser light having a power of about 20 mW cannot be attenuated to the allowable input amount of the CCD, and no image is formed. On the other hand, as shown in FIG.
When two sheets are used, a lattice-shaped image is formed. This is presumably because the laser beam having a high energy of about 0.6 W / cm ² was irradiated and interference was caused by slight irregularities on the wafer surface.

FIG. 4 is an explanatory diagram for explaining an image obtained by imaging a portion where a slip has occurred. As shown in FIG. 4, due to the slip generated on the wafer surface, the Ar laser light strongly interferes, and one linear image is formed more clearly at the position indicated by the arrow than the other images. As a result of analyzing this portion by the X-ray topography method, it was found that the portion was slip. on the other hand,
When a foreign substance exists on the surface of the semiconductor material, the foreign substance strongly interferes with the Ar laser light, and an image corresponding to the size of the foreign substance is formed. Therefore, when such an image is binarized to generate a binarized screen, only an image of a slip or a foreign substance is generated, and it is determined whether the image is a slip or a foreign substance based on the shape of the image. be able to.

[0023]

As described above in detail, according to the present invention, it is possible to detect luminescence emitted from a semiconductor material by irradiating excitation light, and to image a portion of the semiconductor material irradiated with the excitation light. The inspection time of the semiconductor material is substantially increased by binarizing the obtained image based on a preset threshold value and determining the type of a defect generated on the surface of the semiconductor material based on the binarized image. Slip and foreign matter detection can be performed with high reliability without
The present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a semiconductor inspection device according to the present invention.

FIG. 2 is an explanatory diagram illustrating a relationship between an irradiation region of Ar laser light and an imaging region.

FIG. 3 is an explanatory diagram illustrating an example of an image captured by the imaging device illustrated in FIG. 1;

FIG. 4 is an explanatory diagram illustrating an image obtained by imaging a portion where a slip has occurred.

FIG. 5 is a block diagram showing a configuration of a conventional semiconductor material inspection apparatus.

FIG. 6 is a schematic diagram showing a result of mapping a signal intensity of a luminescence signal by a conventional semiconductor material inspection apparatus.

[Explanation of symbols]

 Reference Signs List 1 laser light source 3 first lens 4 second lens 7 optical filter 8 imaging device 9 image processing device S semiconductor material

Claims (3)

[Claims] 1. A method of inspecting a semiconductor material by irradiating excitation light having energy larger than the band gap of the semiconductor material and detecting luminescence radiated from the semiconductor material, wherein the semiconductor material is irradiated with the excitation light. And inspecting the obtained image to binarize the image based on a preset threshold value, and determining the type of a defect on the surface of the semiconductor material based on the binarized image. Method. 2. An apparatus for inspecting a semiconductor material by irradiating excitation light having energy larger than the band gap of the semiconductor material and detecting luminescence radiated from the semiconductor material, wherein the semiconductor material is irradiated with the excitation light. And an imaging device that captures an image of the image based on a threshold value set in advance.
An image processing apparatus for generating a binarized image by binarizing the semiconductor material. 3. The semiconductor material inspection apparatus according to claim 2, further comprising a filter for attenuating the amount of excitation light incident on the imaging device.