JP2011232267A - Surface inspection method and surface inspection device for semiconductor wafer, and method for producing semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means capable of easily inspecting a surface defect of a semiconductor wafer with high reliability.SOLUTION: A surface inspection method for a semiconductor wafer is provided, including: irradiating the surface of a semiconductor wafer as an inspection object with inspection light from a light source unit; detecting scattered light from an irradiation region irradiated with the inspection light of the wafer surface; and evaluating the presence or absence of a defect and/or a degree of the defect on the wafer surface based on the detected scattered light. The inspection light is made to be incident in an oblique direction to the wafer surface, the light having a width equal to or larger than the radius of the wafer, so as to form an irradiation region having a width equal to or larger than the radius of the wafer and including the wafer center on the wafer surface; and the entire surface of the wafer is scanned with the inspection light by moving at least one of the wafer and the light source unit.

Description

The present invention relates to a semiconductor wafer surface inspection method and a surface inspection apparatus, and more specifically, a method and apparatus for inspecting the presence or extent of foreign matter, crystal defects, scratches, etc. on the surface of a semiconductor wafer using scattered light. It is about.
Furthermore, the present invention relates to a method for producing a semiconductor wafer using the method.

  With the miniaturization and high integration of semiconductor devices, various defects (foreign matter, crystal defects, scratches, slips, etc.) on the surface of a semiconductor wafer such as a silicon wafer have increased the influence on product yield and reliability. Therefore, along with improvement of the manufacturing process for providing a wafer with reduced defects, establishment of an inspection method for accurately evaluating the surface defects of the wafer before shipment is also required.

  Conventionally, inspection of relatively large surface defects called so-called macro defects has been performed by visual inspection under a condenser lamp. However, visual inspection is overlooked when the wafer diameter is large, detection sensitivity is high but often depends on individual differences, data cannot be quantified and stored, and objective quality standards and defective standards are created and automated There were problems such as being difficult.

  On the other hand, in recent years, particle counters are widely used as inspection devices for wafer surface dust and defects. The particle counter scans the wafer surface with laser light, and recognizes the number, size and position of the particles by measuring the light scattering intensity from the adhered particles, but the introduction and maintenance costs are high. This is disadvantageous in terms of cost because measurement time is long. In addition, there are two types of particle counter laser beam incidence methods, the normal incidence method and the oblique incidence method. The normal incidence method has high detection sensitivity for crystal defects, scratches, slips, etc., but it depends on the surface roughness. Since the detection sensitivity changes, a constant sensitivity cannot be maintained. On the other hand, the oblique incidence method has high sensitivity to attached particles, but low sensitivity to crystal defects and scratches. There are also commercially available devices that provide multiple detectors with an oblique incidence method and improve the sensitivity to detection of crystal defects, scratches, slips, etc., and have achieved a certain level of sensitivity improvement, but there is a concern that the detection reliability is lacking There is. Furthermore, as a particle counter, an apparatus incorporating both a normal incidence method and an oblique incidence method is commercially available, but it has not yet been solved that the detection sensitivity changes due to the roughness of the surface. In addition, the particle counter also has a problem that it takes time to scan the entire wafer surface due to the measurement principle of the apparatus.

  In addition to the above, various methods for inspecting wafer surface defects by using scattered light have been proposed (see, for example, Patent Documents 1 to 6), but none of them is sufficient in terms of reliability and simplicity. There wasn't.

JP 2009-236519 A JP 2000-252334 A JP 2003-177104 A JP 2001-83100 A JP 2001-33395 A JP 2008-241716 A

  Accordingly, an object of the present invention is to provide a means capable of simply and reliably inspecting a surface defect of a semiconductor wafer.

  As a result of intensive studies in order to achieve the above object, the present inventor makes the inspection light irradiated on the wafer surface incident to the wafer surface with a width greater than the wafer radius from the oblique direction to obtain the scattered light. Thus, it has been found that the entire surface of the wafer can be easily inspected without omission, and the present invention has been completed.

That is, the above object has been achieved by the following means.
[1] irradiating inspection light from the light source unit toward the surface of the semiconductor wafer to be inspected;
Detecting scattered light from the irradiated area irradiated with the inspection light on the wafer surface; and
Evaluating the presence and / or extent of defects on the wafer surface based on the detected scattered light;
A method for inspecting a surface of a semiconductor wafer including:
By making the inspection light incident on the wafer surface with a width equal to or greater than the wafer radius from an oblique direction, forming an irradiation region having a width equal to or greater than the wafer radius and including the wafer center on the wafer surface;
A method for inspecting a surface of a semiconductor wafer, wherein the inspection light is scanned over the entire surface of the wafer by moving at least one of the wafer and the light source section.
[2] The semiconductor wafer surface inspection method according to [1], wherein the scattered light is detected by a detector disposed vertically above the irradiation region.
[3] The semiconductor according to [2], wherein a detector having a condensing part larger than the irradiation area is used as the detector, and the scattered light from the irradiation area is condensed by the condensing part. Wafer surface inspection method.
[4] The semiconductor wafer surface inspection method according to any one of [1] to [3], wherein the inspection light is scanned over the entire surface of the wafer by rotating the wafer around the center thereof.
[5] By making the inspection light incident with a width equal to or greater than the wafer diameter, an irradiation region having a width equal to or greater than the wafer diameter and including the wafer center is formed on the wafer surface;
The surface inspection method for a semiconductor wafer according to any one of [1] to [3], wherein inspection light is scanned over the entire surface of the wafer by moving the wafer in a direction perpendicular to the width direction of the irradiation region.
[6] A light source unit for injecting inspection light to the surface of the semiconductor wafer to be inspected with a width equal to or larger than the wafer radius from an oblique direction relative to the wafer surface;
A detector for detecting scattered light from the wafer surface;
A moving mechanism for moving at least one of the light source unit and the wafer;
A surface inspection apparatus for a semiconductor wafer used in the method according to any one of [1] to [5].
[7] A method for manufacturing a semiconductor wafer, comprising evaluating a semiconductor wafer, selecting a semiconductor wafer having a quality higher than a target, and shipping the selected semiconductor wafer as a product wafer,
The said evaluation is performed by the method in any one of [1]-[5], The manufacturing method of the semiconductor wafer characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to evaluate macro defects, such as a foreign material, a crystal defect, a crack | wound, and a slip, which exist on the semiconductor wafer surface with high sensitivity simply and inexpensively. Thereby, a high-quality semiconductor wafer can be shipped as a product.

It is explanatory drawing which shows the outline | summary of the test | inspection method concerning one Embodiment of this invention. It is explanatory drawing which shows the outline | summary of the test | inspection method concerning one Embodiment of this invention. It is a schematic diagram which shows the evaluation result obtained by the Example and the comparative example.

The present invention irradiates inspection light from a light source unit toward the surface of a semiconductor wafer to be inspected, detects scattered light from an irradiation region irradiated with inspection light on the wafer surface, and is detected The present invention relates to a method for inspecting a surface of a semiconductor wafer, including evaluating the presence and / or extent of defects on the wafer surface based on scattered light. In the surface inspection method according to the present invention, the inspection light is incident on the wafer surface from an oblique direction with a width equal to or larger than the wafer radius, whereby an irradiation region having a width equal to or larger than the wafer radius and including the wafer center is formed on the wafer surface. And at least one of the wafer and the light source unit is moved to scan the entire surface of the wafer with the inspection light.
Furthermore, the present invention provides a light source unit for injecting inspection light to the surface of a semiconductor wafer to be inspected with a width greater than or equal to the wafer radius from the oblique direction with respect to the wafer surface, a detector for detecting scattered light from the wafer surface, And a moving mechanism for moving at least one of the light source section and the wafer. The present invention relates to a semiconductor wafer surface inspection apparatus used in the semiconductor wafer surface inspection method of the present invention.
Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing an overview of an inspection method according to an embodiment of the present invention. In the embodiment shown in FIG. 1, the inspection light is incident on the surface of the semiconductor wafer to be inspected from the oblique direction with a width equal to or larger than the wafer radius, so that the wafer has a width equal to or larger than the wafer radius. An irradiation region including the center (× in FIG. 1) is formed. 1 is a top view of a semiconductor wafer irradiated with inspection light in the above state, and FIG. 1 is a cross-sectional view thereof.
Conventionally, a method in which inspection light is incident in a spot shape from an oblique direction has been proposed (see, for example, Patent Documents 1 and 3, etc.), but it is extremely difficult to scan the entire surface of the wafer without leakage by such a method. is there. On the other hand, it is conceivable to irradiate the wafer surface with inspection light that covers the entire surface of the wafer from vertically above. However, with such an irradiation method, it is difficult to obtain scattered light from the edge portion. Hard to get.
In contrast, in the method of the present invention, as described above, the inspection light is incident on the wafer surface with a width equal to or larger than the wafer radius from an oblique direction. Thus, as will be described later, if at least one of the wafer and the light source is moved (for example, the wafer is rotated), the inspection light can be irradiated onto the entire surface of the wafer without leaking, so that scattered light information can be easily obtained from the entire surface of the wafer. it can. Here, the reason why the inspection light is incident from an oblique direction is to obtain high-intensity scattered light. The light source unit may be installed at a position where the inspection light can be incident from an oblique direction with respect to the wafer surface. From the viewpoint of the scattered light intensity obtained, the light source unit is 65 when the direction perpendicular to the wafer surface is 90 °. It is preferable to set it at a position of ° to 85 °. One or more light sources (for example, laser light sources) are incorporated in the light source unit. From the standpoint of the obtained scattered light intensity, it is preferable to use a light emitting source capable of irradiating the inspection light with an illuminance of about 10,000 to 1,000,000 lux. The desired illuminance may be realized by one light source, or the desired illuminance may be realized by two or more light sources. In the light source unit, in order to make the inspection light intensity in the irradiation region uniform, it is possible to arrange two or more light emitting sources at an appropriate interval.

  In the method of the present invention, the inspection light is incident as described above, and the scattered light from the irradiation region is detected. Since the intensity of scattered light from each part in the surface varies depending on the presence / absence of surface defects and the degree thereof, the presence / absence and degree of defects on the wafer surface can be evaluated based on the scattered light image and intensity distribution information. As a detector used for detecting scattered light, an apparatus having a condensing unit capable of condensing (receiving) scattered light and a detecting unit capable of converting the collected scattered light into image information or numerical information is used. it can. An image sensor such as a CCD is suitable as the detection unit. The distance between the detector and the wafer surface may be set as appropriate in consideration of the detection sensitivity of the detector, and is not particularly limited.

  The detector may be placed at an angle with respect to the wafer surface or vertically above, but in order to efficiently collect the scattered light from the irradiated area, the detector is set vertically above the irradiated area. It is preferable. One or a plurality of detectors may be installed. In an embodiment in which one detector is used, in order to detect scattered light from the irradiation region with high sensitivity, as shown in FIG. It is preferable to collect scattered light from the region. On the other hand, when a plurality of detectors are used, it is preferable to install the detectors at a predetermined interval in a direction parallel to the width direction of the irradiation region so that scattered light can be detected without omission. For example, it is preferable to install two sub-detectors opposite to each other at a position of about ± 15 °, where the direction from the wafer surface toward the main detector is 0 °, in order to detect scattered light without omission. Further, it is possible to collect scattered light by moving the detector during the inspection, but it is preferable to perform the inspection with the detector fixed from the viewpoint of detection accuracy.

  In the method of the present invention, in order to scan the entire surface of the wafer with the inspection light irradiated as described above, at least one of the wafer and the light source unit is moved. From the viewpoint of simplicity, it is preferable to move the wafer. By providing a known rotation or movement mechanism on the wafer support, the wafer can be moved. As a mode of movement of the wafer, there are a mode in which the wafer is rotated and a mode in which the wafer is moved back and forth and / or left and right in the horizontal direction. As shown in FIG. 1, when inspection light having a width not less than the radius of the wafer and less than the diameter is incident, rotating the wafer around its center can easily scan the entire surface of the wafer without leakage. This is preferable because it is possible. The rotational speed at this time is not particularly limited, but is preferably about 5 to 60 ° / sec from the viewpoint of detection time.

  On the other hand, when the inspection light is incident on the wafer surface with a width greater than the wafer diameter, the wafer is moved in a direction perpendicular to the width direction of the irradiation area, rotated around the center, or a combination thereof. It is preferable to scan the entire surface of the wafer with the inspection light in order to easily scan the entire surface of the inspection light without omission. Such an embodiment will be described with reference to FIG.

  FIG. 2 is an explanatory diagram showing an outline of the inspection method according to the embodiment of the present invention. In the embodiment shown in FIG. 2, the inspection light is incident on the surface of the semiconductor wafer to be inspected with a width equal to or larger than the wafer diameter from an oblique direction with respect to the surface, so that the wafer has a width equal to or larger than the wafer diameter. An irradiation region including the center (× in FIG. 2) is formed. 2 is a top view of the semiconductor wafer irradiated with the inspection light in the above state, and the lower view of FIG. 2 is a cross-sectional view thereof. In the aspect shown in FIG. 1 described above, it is preferable to rotate the wafer because the entire area in the diameter direction of the wafer cannot be irradiated with the inspection light before the movement. On the other hand, in the embodiment shown in FIG. 2, the entire region in the diameter direction can be irradiated with the inspection light already in the state before the movement. Therefore, if the wafer is moved in a state perpendicular to the width direction of the irradiation region in this state, the entire surface of the inspection light can be scanned. The moving speed of the wafer in this case can be set to, for example, about 5 to 50 mm / sec, but is not particularly limited as long as it is a speed at which scattered light can be detected with high sensitivity.

As described above, according to the present invention, scattered light can be easily and easily detected from the entire surface of the wafer, so that a high-sensitivity inspection of surface defects based on scattered light information can be performed. In addition, since the device used for the inspection is less expensive than the particle counter, the cost for the inspection can be reduced.
The entire scanning of the detection light may be performed at least once, but it is possible to perform evaluation by synthesizing or averaging the obtained scattered light information two or more times. Highly sensitive inspection is possible. In addition, the width of the irradiation region formed on the wafer surface is as described above, but the shape is not particularly limited. 1 and 2, the irradiation area is shown as a rectangle, but the irradiation area may be a circle, an ellipse, a square, or the like. The larger the maximum length in the direction perpendicular to the width direction (hereinafter also referred to as “thickness”), the wider the irradiation area, so that the entire surface can be scanned in a short time. The intensity of scattered light that can be obtained by reducing the intensity of light decreases. Therefore, it is preferable to determine the thickness so that an irradiation area of an appropriate size is formed in consideration of the illuminance of the irradiation light. Considering the power of a light source that is usually used, the thickness of the irradiation region is preferably about 1 to 30 mm.

  Examples of wafers to be inspected for surface defects according to the present invention include various semiconductor wafers such as silicon wafers used as device substrates. The wafer may be a wafer having any diameter such as φ200 mm, φ300 mm, and φ450 mm. According to the present invention, even a large-diameter wafer having a diameter of 300 mm or more can be inspected without omission and a highly reliable inspection result can be obtained. Further, the surface defects to be evaluated are those that can be detected by scattered light, such as crystal defects including pits, foreign matters attached to the wafer surface in the manufacturing process, scratches generated during the process, slips, and the like. it can. Since the method of the present invention can be used as a method replacing the visual inspection, it is suitable as a surface defect inspection method called a so-called macro defect having a size of 0.2 μm or more generally evaluated by visual inspection.

  Furthermore, the present invention relates to a method for manufacturing a semiconductor wafer, including evaluating a semiconductor wafer, selecting a semiconductor wafer having a quality exceeding a target, and shipping the selected semiconductor wafer as a product wafer. Here, the evaluation is performed by the inspection method of the present invention.

  It is possible to provide a high-quality wafer with high reliability by evaluating the wafer before shipping the product and shipping the wafer determined to be non-defective as a product. However, if the evaluation before shipment is poor in convenience, it takes a long time for the evaluation, leading to a decrease in productivity. If the reliability is poor, it is difficult to provide a high-quality product wafer. On the other hand, as described above, according to the inspection method of the present invention, it is possible to evaluate the presence or absence and degree of surface defects without leakage over the entire wafer surface by a simple operation of light irradiation and movement of the wafer and / or the light source unit. it can. Therefore, by using such a method, a product wafer can be selected in a short time, and both productivity and reliability can be achieved. The target quality can be set in consideration of physical properties required for the wafer according to the use of the wafer. Further, the semiconductor wafer to be evaluated is as described above, and they can be manufactured by a known method.

  Hereinafter, the present invention will be further described based on examples. However, this invention is not limited to the aspect shown in the Example.

1. Production of Inspection Wafers A plurality of silicon wafers with a diameter of 300 mm in which the same surface defects (crystal defects, scratches, slips and particles) were intentionally generated on the mirror-polished surface were produced.

2. Examples and comparative examples of surface defect inspection

[Example 1]
Above 1. The surface defects of the silicon wafer produced in the above were inspected by the inspection method of the aspect shown in FIG. A specific inspection method will be described below.
(1) The direction perpendicular to the wafer surface is set so that an irradiation region having a width of 310 mm larger than the wafer diameter and a thickness of 5 mm is formed on the silicon surface to be inspected. Inspection light of 50000 lux was irradiated from a light source unit arranged at a position of 75 °. By this irradiation, the irradiation intensity in the irradiation region became 50,000 ± 500 lux. In this embodiment, the light source unit incorporating one light source (laser light source) is used. As described above, in order to make the irradiation intensity uniform in the irradiation region, a plurality of light source sources are provided in the light source unit. It is also possible to provide individual pieces.
(2) As a detector, a line CCD capable of photographing the wafer diameter (301 mm) was installed coaxially with the condenser lens at a position 200 mm above the wafer surface in the vertical direction. The focal point was fixed on the wafer surface. Note that although one detector is used in this embodiment, a plurality of detectors can be arranged in a direction parallel to the width direction of the irradiation region, and the same field of view can be observed by these detectors. By detecting one defect at the same position by a plurality of detectors and detecting one defect detected on one side, it is possible to reduce variations in detectors and suppress fluctuations in the number of detections due to light source unevenness. Can do.
(3) Under the above installation conditions, the wafer was moved at a speed of 30 mm / sec in a direction perpendicular to the width direction of the irradiation area, and a scattered light image of the entire wafer surface was acquired by the CCD.
(4) Next, the wafer was rotated 90 degrees, and the entire surface of the wafer was scanned in the same manner as in (3) above, and a scattered light image of the entire surface of the wafer was acquired by the CCD.
(5) Next, the images acquired in the above (3) and (4) were synthesized and displayed as measurement data.

[Example 2]
Above 1. The surface defects of the silicon wafer produced in the above were inspected by the inspection method of the aspect shown in FIG. A specific inspection method will be described below.
(1) The direction perpendicular to the wafer surface is set so that an irradiation area having a width of 160 mm larger than the wafer radius and a thickness of 5 mm is formed on the wafer surface to be inspected. Inspection light of 50000 lux was irradiated from a light source unit arranged at a position of 75 ° as the angle.
(2) As a detector, a line CCD capable of photographing the wafer radius (155 mm) was installed coaxially with the condenser lens at a position 200 mm away above the wafer surface in the vertical direction. The focal point was fixed on the wafer surface.
(3) Under the above installation conditions, the wafer was rotated at an angle of 15 ° / sec with the center of the wafer as a fulcrum, and a scattered light image of the entire wafer surface was acquired by the CCD.

[Comparative Example 1]
(1) A laser particle counter capable of switching between two lines of laser light at a laser wavelength of 488 nm was prepared. The breakdown of the two lines is normal incidence and two directions of incidence from an angle inclined by 70 degrees from the perpendicular.
(2) 1. The silicon wafer produced in (1) was measured with the above-mentioned apparatus, and scattered light data was acquired.
(3) The scattering data from the two directions were combined to obtain one detection result.

Evaluation Results FIG. 3 shows a schematic diagram of the scattered light images obtained in Examples 1 and 2 and Comparative Example 1. The leftmost figure in FIG. 3 is a basic image produced by visual observation and observation with a differential interference microscope. As shown in FIG. 3, the surface defects could be detected without omission over the entire wafer surface in Examples 1 and 2.
On the other hand, in the comparative example, it can be seen that there are omissions in detection near the edge portion and omissions in detection of flaws.
From the above results, it can be confirmed that surface defects can be detected without omission according to the present invention.

  The inspection method of the present invention is suitable as a quality control method for a semiconductor wafer manufacturing process.

Claims (7)

Irradiating inspection light from the light source part toward the surface of the semiconductor wafer to be inspected,
Detecting scattered light from the irradiated area irradiated with the inspection light on the wafer surface; and
Evaluating the presence and / or extent of defects on the wafer surface based on the detected scattered light;
A method for inspecting a surface of a semiconductor wafer including:
By making the inspection light incident on the wafer surface with a width equal to or greater than the wafer radius from an oblique direction, forming an irradiation region having a width equal to or greater than the wafer radius and including the wafer center on the wafer surface;
Scanning the entire surface of the wafer with the inspection light by moving at least one of the wafer and the light source unit;
A method for inspecting a surface of a semiconductor wafer. The semiconductor wafer surface inspection method according to claim 1, wherein the scattered light is detected by a detector arranged vertically above the irradiation region. The surface of the semiconductor wafer according to claim 2, wherein a detector having a condensing part larger than the irradiation area is used as the detector, and the scattered light from the irradiation area is condensed by the condensing part. Inspection method. The surface inspection method for a semiconductor wafer according to claim 1, wherein the inspection light is scanned over the entire surface of the wafer by rotating the wafer around its center as a fulcrum. By making the inspection light incident with a width equal to or greater than the wafer diameter, an irradiation region having a width equal to or greater than the wafer diameter and including the wafer center is formed on the wafer surface; and
The surface inspection method for a semiconductor wafer according to claim 1, wherein inspection light is scanned over the entire surface of the wafer by moving the wafer in a direction perpendicular to the width direction of the irradiation region. A light source unit for injecting inspection light to the surface of the semiconductor wafer to be inspected with a width equal to or larger than the wafer radius from an oblique direction with respect to the wafer surface;
A detector for detecting scattered light from the wafer surface;
A moving mechanism for moving at least one of the light source unit and the wafer;
The surface inspection apparatus of the semiconductor wafer used for the method of any one of Claims 1-5 which has these. A method for manufacturing a semiconductor wafer, comprising evaluating a semiconductor wafer, selecting a semiconductor wafer having a quality higher than a target, and shipping the selected semiconductor wafer as a product wafer,
The said evaluation is performed by the method of any one of Claims 1-5, The manufacturing method of the semiconductor wafer characterized by the above-mentioned.