1. Field of the Invention
The present invention relates to an optical surface defect inspection apparatus and an optical surface defect inspection method, and specifically to the optical surface defect inspection apparatus and the optical surface defect inspection method suitable for adaptation to change and segmentation of defect types.
2. Description of the Related Art
Both a high-speed inspection applicable to 100% full inspection and a highly sensitive inspection (to detect a microdefect a few tens of nm wide and a few nm deep) are required for an optical surface defect inspection apparatus that inspects for a microdefect on a surface of a subject such as a magnetic disk, an IC wafer, and the like.
One such conventional technique is described in Patent Document 1(Japanese Patent Laid-Open 2012-042375). In the method described in Patent Document 1, as shown in
However, there is lately a demand for classifying new defects or inspecting more finely classified defects.
The method described in Patent Document 1 inspects for a microdefect on a surface of a subject setting thresholds based on a predetermined algorithm for discriminating each type of defect. Although the method described in Patent Document 1 is capable of the 100% full inspection and suitable for performing a high-speed and high-sensitive inspection, the inspection method itself is not allowed for much freedom and cannot cope with the demand for classifying new defects or inspecting more finely classified defects.
Accordingly, the present invention aims to provide an optical surface defect inspection apparatus or an optical surface defect inspection method capable of classifying new defects or inspecting more finely classified defects.
In order to achieve the above object, the present invention includes at least the following features.
The present invention provides an optical surface defect inspection apparatus including: an irradiation means irradiating a subject with an inspection light; a plurality of detecting optical systems detecting a scattered light from a surface of the subject; a processing unit processing an output from each optical receiver in the plurality of detecting optical systems and inspecting for a defect on the surface of the subject based on the processing result; and a storage unit storing therein data processed by the processing unit,
wherein the storage unit stores therein a reference matrix recipe provided with a plurality of feature items indicative of features of the defect on one axis of the matrix and optical items including a range of detected value levels of the plurality of detecting optical systems with respect to the feature items on the other axis, the reference matrix recipe having information defining the defect at a plurality of points in the matrix, and the reference matrix recipe being generated in advance with respect to each of the defects, and
the processing unit determines a type of the defect by creating a work matrix recipe corresponding to the reference matrix recipe based on the output from the plurality of detecting optical systems and comparing the work matrix recipe with the reference matrix recipe.
The present invention also provides an optical surface defect inspection method including the steps of: irradiating a subject with an inspection light; focusing a scattered light from a surface of the subject onto a plurality of optical receivers; and inspecting for a defect on the surface of the subject based on outputs from the optical receivers, the method further including the steps of:
creating in advance and storing therein a reference matrix recipe with respect to each defect, the reference matrix recipe being provided with a plurality of feature items indicative of features of the defect on one axis of the matrix and optical items including a range of detected value levels of the plurality of detecting optical systems with respect to the feature items on the other axis, and the reference matrix recipe having information defining the defect at a plurality of points in the matrix, and
determining a type of the defect by creating a work matrix recipe corresponding to the reference matrix recipe based on the output from the plurality of detectors and comparing the work matrix recipe with the reference matrix recipe.
The present invention can thus provide the optical surface defect inspection apparatus or the optical surface defect inspection method capable of classifying new defects or inspecting more finely classified defects.
Hereinbelow, configurations of the inspection optical system 1, the preprocessing unit 4, the data processing device 11, and the scanning unit 10 according to the present embodiment and an inspection method using these configurations will be described in the order with reference to drawings.
First, the configuration of the inspection optical system 1 as a feature of the embodiment of the present invention will be described with reference to
The first inspection optical system 600 shown in
The first illumination optical system 610 includes a laser light source 611, a beam expanding lens 612 expanding a laser light emitted from the laser light source 611, a collimator lens 613 converting the laser light expanded by the beam expanding lens 612 into a parallel light, and a converging lens 614 converging the parallel laser light with the expanded diameter onto a surface of the work 2.
The first regular reflection light detecting optical system 620 is arranged along an optical axis of a regular reflection light from the work 2 irradiated with the laser light converged by the illumination optical system 610, and includes a condenser lens 621, a beam splitter 625, an imaging lens 623, a slit 622, and a first detector 624. The condenser lens 621 condenses the reflection lights including the regular reflection light and the scattered light from the work 2. The beam splitter 625 distributes the condensed reflection light to the bright-field detecting optical system 640 at a predetermined rate. The imaging lens 623 focuses the reflection light from the condenser lens 621 at a predetermined magnification. The slit 622 shields the scattered light from the work 2 among the reflection light focused by the imaging lens. The first detector 624 detects only the regular reflection light, and two detectors 624a and 624b are included to improve the resolution.
The first regular reflection light detecting optical system 620 detects a defect that hardly causes scattering or diffraction. For example, because an irradiation of a laser light onto a pit defect causes an axis misalignment and a lens effect due to the defect and changes an intensity distribution of the regular reflection light, the first regular reflection light detecting optical system 620 detects a change in the amount of the light passing through the slit 622, thereby detecting the pit defect.
The dark-field detecting optical system 630 includes a condenser lens 631 condensing the laterally scattered light from the work 2 irradiated with the laser light, and a second detector 632 detecting the scattered light condensed by the condenser lens 631.
When the laser light is irradiated onto the foreign object on the work 2, an intense scattered light (diffracted light) is generated from the subject surface and a scattered light is generated from the foreign object, and therefore the dark-field detecting optical system 630 detects a deposited foreign object by capturing the scattered light. Such an intense scattered light from the subject surface like a disk becomes a random diffracted light due to an influence from a polishing trace. A light receiving angle is set low so that the scattered light from the foreign object may hardly be influenced by the diffracted light and that the scattering intensity may easily be received.
The bright-field detecting optical system 640 includes the beam splitter 625 mainly reflecting the scattered light of the reflections light, an imaging lens 641 focusing the scattered light reflected by the beam splitter, and a third detector 642 receiving the focused scattered light.
When the laser light is irradiated onto a flaw such as a scratch or contamination on the subject 2, a scattered diffraction pattern with directivity different from that of a diffraction pattern from a normal surface of the subject is generated, and therefore the bright-field detecting optical system 640 detects the flaw such as the scratch or the contamination by capturing the scattering diffracted light.
On the other hand, the second inspection optical system 700 shown in
The second regular reflection light detecting optical system 720 is arranged along an optical axis of a regular reflection light from the work 2 irradiated with the laser light converged by the illumination optical system 710, and includes a condenser lens 721, an imaging lens 723, and a fourth detector 724. The condenser lens 721 condenses the reflections including the regular reflection light and the scattered light from the subject 2. The imaging lens 723 focuses the reflection light from the condenser lens 621 at a predetermined magnification.
Like the first regular reflection light detecting optical system 620, the second regular reflection light detecting optical system 720 detects a defect that hardly causes scattering or diffraction. When a laser light conforming to the size (width) of the defect is irradiated onto the defect such as a bump and a dimple, the first regular reflection light detecting optical system 620 detects a light/dark pattern of the regular reflection light from the defect, thereby detecting the corresponding defect.
Next, an explanation is given about a mechanism and an operation of a full scanning of the subject surface by spirally scanning the subject 2 in a doughnut shape like a magnetic disk. A work table 3 is, as shown in
Such a mechanism enables spiral scanning of the subject according to a constant-speed spiral scanning program 13b stored in a storage unit 13. Specifically, the subject 2 is placed so that the center of the subject 2 coincides with the center of rotation of the θ-rotation table 6, and an inspection light 21 is set to an inner edge of the doughnut. Subsequently, while rotating the work table 3 using the θ-rotation table 6 at a constant speed, the work table 3 is moved by the linearly moving table 5 in the direction of the radius (R) of the subject 2, i.e., in a horizontal direction in
The scanning is not limited to the spiral form, but scanning in a rectangular shape or moving the inspection optical system 1 for scanning is also conceivable.
The measured data of the scattered light at each measuring point in the case of full-surface scanning is converted into a digital value via the preprocessing unit 4 and transferred to the data processing device 11, and each measuring point (scanning) position specified by each encoder 5a, 6a and the measured value at the point are stored in a measurement result storage area 13c of the storage unit 13. A defect analysis program 13a stored in the storage unit 13 makes it possible to analyze the data on each measuring point of which position is recognized, inspect for the foreign object such as a scratch S, and display the result on a display device 15. Note that denoted by 16 in
Explained hereinbelow is a defect detection method that characterizes the present invention.
In this embodiment, the matrix recipe is generated for each defect, and then the subject 2 is inspected using the matrix.
Next, for each defect, a plurality of data pieces that can be obtained using a simulation or a simulated defect are sorted on the matrix shown in
The matrix recipe shown in
If, for example, many particles are found and they are characterized by their positions of generation, the positions are entered as a radial position. By doing so, it is possible to grasp a problem in the production process of the subject 2. Furthermore, for example, different matrix recipes by the size level such as large, medium, and small may be prepared depending on the detected value level D of the dark-field detecting optical system 630 or the D/B of the both. Thus, the fine classification can be facilitated depending on the purpose and the problem in the production process can be grasped.
The matrix recipe shown in
The matrix recipe shown in
As described above, the reference matrix recipe for comparison with each defect is prepared in advance.
First, the measured data is obtained at each point while moving the subject 2 (S5). The work matrix recipe corresponding to the reference matrix recipe is obtained by processing the data (S6).
It should be noted that not all the feature items must be processed because some feature items may not include any data and some feature items are less necessary.
Next, the defect is determined by comparing the obtained work matrix recipe with the reference matrix recipe (S7), and the work matrix recipe is displayed on the display device 15 (S8).
When the inspection is performed by the lot unit, the feature items are narrow down the items by which that the feature of a defect comes out, the other items may be deleted.
In
Furthermore, as explained with reference to
Moreover, instead of obtaining data on many feature items from the beginning as shown in
In this manner, the inspection using the matrix recipe allows for easy addition, deletion, or fine classification of a feature item, enabling an inspection with high degree of freedom.
Number | Date | Country | Kind |
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2012-199593 | Sep 2012 | JP | national |