WO2020038360A1

WO2020038360A1 - Detection system

Info

Publication number: WO2020038360A1
Application number: PCT/CN2019/101587
Authority: WO
Inventors: 陈鲁; 黄有为; 崔高增; 王天民
Original assignee: 深圳中科飞测科技有限公司
Priority date: 2018-08-21
Filing date: 2019-08-20
Publication date: 2020-02-27
Also published as: TWM592964U; CN110849899A

Abstract

A detection system. The detection system comprises: a detection assembly (102) configured to generate detection light spots based on detection beams, wherein each of the detection light spots comprises a detection area, and the detection area is linear; a signal collection assembly (103) configured to collect signal light formed after the detection light spots are scattered by an object under detection and then generate detection information corresponding to the detection light spots; and a processor assembly (104) configured to determine, on the basis of the detection information acquired in the detection area, defect feature information on the object under detection. By using the detection system, the movement time of a wafer is saved on, and the detection speed and accuracy can be distinctly improved.

Description

Detection Systems

Technical field

The present application belongs to the field of detection, and particularly relates to a detection system.

Background technique

Wafer defect inspection refers to detecting the presence of defects such as grooves, particles, scratches, and defect locations in the wafer. Wafer defect detection is widely used: On the one hand, as a chip substrate, the presence of defects on the wafer may cause the expensive processes made above to fail. Wafer manufacturers often perform defect inspection to ensure product qualification rates, and wafer users also need to Determining the cleanliness of the wafer before use can ensure the product pass rate. On the other hand, because semiconductor processing is very strict in controlling additional pollution during processing, and it is difficult to directly monitor additional pollution during processing, people often pass wafer bare chips. Defect comparison before and after processing to determine the degree of additional pollution of the process. Therefore, people have explored various wafer defect detection methods.

At present, the commonly used wafer defect detection methods mainly include electron beam detection and optical detection. Thanks to the extreme wavelength of the electron wave, the electron beam detection can directly image and the resolution can reach 1 to 2 nanometers. However, it takes a long time to detect and requires a high vacuum environment. It is usually used to sample a few key circuit links an examination. Optical inspection is a general term for a method that uses light to interact with a chip to achieve inspection. Its basic principle is to scan for the presence and intensity of incident light and scattered light from defects, and determine the presence and size of defects.

Utility model content

In view of the shortcomings of long time consumption and low accuracy of the current optical measurement methods, the present application proposes a system capable of implementing multiple incident angle detection on a wafer.

The present application proposes a detection system including: a detection component configured to generate a detection spot based on a detection beam; and a signal collection component configured to linearly collect a test object formed under the action of the detection light spot. Signal light to generate detection information corresponding to the detection light spot; and a processor component configured to determine defect feature information on the object to be tested based on the detection information.

By adopting the technical solution of the present application, the area of each scanning area can be increased, the moving time of the wafer can be saved, and the detection speed can be significantly increased. In addition, bright and dark field detection can be performed at the same time to improve the efficiency. By using the technical solution of the present application, different light sources can be used to detect different particles.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments are shown and explained with reference to the drawings. These drawings serve to clarify the basic principles and thus show only the aspects necessary for understanding the basic principles. These drawings are not to scale. In the drawings, the same reference numerals denote similar features.

FIG. 1 is a structural diagram of a detection system according to an embodiment of the present application; FIG.

2a is an optical architecture diagram of a detection system according to an embodiment of the present application;

2b is a schematic diagram of the imaging-like collection principle according to an embodiment of the present application;

3 is a schematic diagram of a scanning trajectory according to an embodiment of the present application;

FIG. 4 is a structural diagram of a detection system according to another embodiment of the present application.

detailed description

In the following detailed description of the preferred embodiments, reference will be made to the accompanying drawings, which form a part hereof. The accompanying drawings show, by way of example, specific embodiments that can implement the present application. The exemplary embodiments are not intended to be exhaustive of all embodiments according to the present application. It can be understood that other embodiments may be used and structural or logical modifications may be made without departing from the scope of the present application. Therefore, the following detailed description is not restrictive, and the scope of the present application is defined by the appended claims.

Techniques, methods, and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but where appropriate, the techniques, methods, and equipment should be considered as part of the description.

First, the terms involved in this application will be explained. The detection beam refers to a beam generated by the light source assembly to finally form a detection spot. The angle of incidence refers to the angle between the detection beam and the normal direction of the surface of the object (such as a wafer). The detection area is the illumination area corresponding to the signal light received by the detector. For example, the part with relatively strong light intensity in the detection spot illumination area is received by the detector to analyze the measured object.

The inventors have found through a large number of studies that in the process of light scattering detection of wafers, if a point light source is used (that is, the detection spot is converged as small as possible, and the spot diameter is in the order of tens to hundreds of microns) for point scanning Detection, because only point areas can be detected at the same time, in order to increase the detection speed of the wafer, it is often necessary to speed up the wafer's rotational movement speed and increase the photodetector sampling rate. However, the movement trajectory of the electric rotary moving platform carrying the wafer needs to be accurately controlled, and its rotation speed is often restricted.

In addition, the existing dark field detection methods for wafer defect detection are generally easy to process using a reflector to collect scattered light. The signal collected by the reflector contains scattered light from the wafer and noise on the wafer surface. Based on the principle of the reflector, it can be known that it is designed to collect as much scattered light as possible. Therefore, there is more noise mixed in the signal collected by the reflector.

Furthermore, because the spot spot size is relatively small, the areas illuminated by the spot spot need to be overlapped or the actual detection area will be partially overlapped during the detection, thus causing the same area to be illuminated twice by the spot spot. Accordingly, the area The signal light is also collected twice, resulting in complex signal processing methods.

Because the reflector collects scattered light in a way that makes it difficult for the scattered light at different points to converge at different points, the existing detection methods can only use the point scanning method for detection.

In view of the above problems, this application proposes a line scan solution for wafer defect detection. Compared to point scans, the area of each inspection is increased. Line scans are detected as line regions at the same time, which can significantly increase the detection speed and reduce the instrument cost.

According to the incident light angle (for example, normal or oblique incidence, and the corresponding oblique incidence angle), the range of signal light collection angle (normal collection or illegal collection), the light scattering method has multiple implementations, including: (1) Normal collection of normal incidence lighting; (2) illegal collection of normal incidence lighting; (3) normal collection of oblique incidence lighting; (4) and illegal collection of oblique incidence lighting.

In addition, depending on the angle of the incident light and the type of defect, the scattered light will exhibit different distribution characteristics. Specifically, for convex defects (such as particles) distributed on the wafer, when light is incident normally, the scattered light of the defects is more evenly distributed in the normal and illegal collection channels; for pits distributed on the wafer Defects. When light is incident normally, the scattered light of the defects is mainly distributed in the normal collection channel, and the scattered light collected by the illegal collection channel is relatively weak. Similarly, for convex defects distributed on the wafer, when light is incident obliquely, the scattered light of the defects is mainly distributed in the illegal collection channel; for pit defects distributed on the wafer, when the light is incident obliquely, the light is illegally transmitted. The scattered light collected by the collecting channel is weak. It can be understood that, for oblique incidence, when the light incident angle changes, the corresponding scattered light distribution also changes accordingly. It can be understood that the collection channel corresponds to the exit angle of the scattered light.

It can be seen from the above that, for convex defects, oblique incidence detection sensitivity is higher; for concave defects, normal incidence has higher detection sensitivity. Therefore, based on the detection method and corresponding signal distribution, defect type analysis can be performed.

FIG. 1 is a structural diagram of a detection system according to an embodiment of the present application.

As shown in the figure, the detection system includes a light source component 101, a detection component 102, a signal collection component 103, and a processor component 104. The light source component 101 provides a detection beam through a light generator (such as one or more lasers).

The detection component 102 is configured to generate a detection spot corresponding to a specified incident angle based on the received detection beam. In one embodiment, the detection component 102 may generate a plurality of detection spots. When the wafer is under inspection (that is, the detection spot is illuminated on the wafer), the wafer will generate (for example, by scattering or reflection) corresponding signal light under the effect of the detection spot. It can be understood that when the detection spot is irradiated to the defect, the signal light generated will change according to the type of the defect or other parameters. The inspection component 102 also includes a machine for carrying wafers, and the machine is moved under the control of the processor component 104, so that the wafer can be moved according to a specified trajectory, and the relative position of the wafer and the inspection light spot can be adjusted to realize scanning inspection .

The signal collection component 103 includes a detection branch corresponding to a plurality of scattered light collection channels, and can collect signal light generated by the line detection spot at different angles, thereby generating corresponding detection information.

The processor component 104 determines defect characteristic information on the wafer based on the detection information from the signal collection component 103, such as the type, location, and other parameters of the defect.

FIG. 2a is an optical architecture diagram of a detection system according to an embodiment of the present application.

As shown in the figure, the light source 201 generates a detection light beam, and the detection light beam reaches the wafer surface through the shaping lens group 2021 in the detection component to form a linear detection light spot. It can be understood that the width and length of the linear detection spot can be controlled by the shaping lens group 2021.

In one embodiment, the detection component further includes a polarizer 2022 (for example, a quarter or half wave plate) to change the polarization state of the detection beam. For example, different polarization states are achieved for different detection beams, such as p-light, s-light, and circularly-polarized light.

When the detection spot irradiates the wafer surface, most of the incident light will be reflected from the other side at the same angle as the incident light. When there is a defect in the illumination position, the defect will cause part of the light to go upward at various angles in the form of scattered light issue. Therefore, by setting multiple scattered light collection channels at different positions to achieve detection of scattered light intensity at different angles, it is possible to judge the defect information at the position of the linear detection spot. It is understandable that collecting signal light through multiple signal collection channels can improve detection accuracy.

In this embodiment, the signal light collection channel is divided into a normal collection channel P1 and an illegal collection channel P2 and P3 according to the collection angle range. The collection angle range corresponding to the normal collection channel P1 is 0 ° to 20 °, which is illegal. The collection angle range corresponding to the collection channel P2 and P3 is 20 ° to 90 °. For example, the collection angle range corresponding to the illegal collection channel P2 is 35 ± 10 °, and the collection angle range corresponding to the illegal collection channel P3 is 55 ± 10. °. In this embodiment, the detection branch corresponding to each collection channel includes a detection lens group and a detector to realize imaging-type collection of signal light. When a line detector is used, the detection area is linear. In one embodiment, the center of the detection area coincides with the center of the detection detection spot, and the length of the detection area is smaller than the length of the detection spot of the detection spot. In practical applications, the light intensity at the center of the detection spot is strong, the light intensity at both ends is weak, and the signal light at both ends is easily flooded by noise. Therefore, the detection accuracy can be improved by setting the length of the detection area to be shorter than the length of the detection spot.

FIG. 2b is a schematic diagram of an imaging collection principle according to an embodiment of the present application.

As shown in the figure, the detection beam is irradiated on the wafer surface to form a detection spot. When there is a defect at the position A, the scattered light generated by the defect under the action of the detection spot travels in all directions above the wafer. In this embodiment, a plurality of collection channels are provided in a normal direction and an illegal direction, and each collection channel collects scattered light that is spatially distributed at a nearby angle with a scattering angle as a center.

The defect at the position A emits scattered light within a specific angle range and is projected to the designated position of the detector TCa via the detection lens group 21; similarly, when there is a defect at the position B, the defect is scattered by the detection spot B The light is projected to a designated position of the detector TCb via the detection lens group 22. The scattered light of the defect at the position A is projected to the position next to the detector TCb via the detection lens group 22, similarly, the scattered light of the defect at the position B is projected to the position next to the detector TCa via the detection lens group 21. Therefore, the detectors TCa and TCb independently collect the scattered light generated by the defects at the A and B positions, and do not interfere with each other.

By making each collection channel independent of each other, when it is necessary to collect normal and oblique incident light spots respectively in normal and illegal directions, multi-channel collection of signal light can be realized.

Please refer to FIG. 2a again, the signal collection component includes first to third detection branches, wherein the first detection branch includes a line detector TC1 and a first detection lens group TJ1 to collect wafers under the action of the detection light spot. The signal light generated on the normal collection channel P1; the second detection branch includes the line detector TC2 and the second detection lens group TJ2 to collect the light generated by the wafer on the illegal collection channel P2 under the effect of the detection spot Signal light; the third detection branch includes a line detector TC3 and a third detection lens group TJ to collect the signal light generated by the wafer at the detection spot on the illegal collection channel P3.

In one embodiment, the detection area corresponding to each detection spot (that is, the portion received by the line detector) may be set as a portion (line shape) with the strongest light intensity in each detection spot. In other words, the detector can collect signal light linearly. The center of the detection area coincides with the center of the detection spot, and the length of the detection area is less than or equal to the length of the detection spot.

In one embodiment, the detection spot is linear, and the length of the detection area is 90% -95% of the length of the detection spot. In one embodiment, the detection spot has a length of 5 mm to 10 mm and a width of 5 μm to 100 μm.

Although three detection branches are shown in FIG. 2a, in other embodiments, other numbers of detection branches can also be set according to the defect characteristics of the wafer, where each detection branch corresponds to one and other detection branches. Different incident angles of branches.

It can be known from the above that through imaging collection, the signal light corresponding to each point in the detection area can be collected by the detection lens group to a designated position on the line detector, so that each point on the line detector collects light independently from each other and detects The scattered light at the spot position is directly related. In this way, through the detection lens group and the line detector, a relatively strong light intensity portion in the spot irradiation area can be obtained as a linear detection area.

FIG. 3 is a schematic diagram of a scanning trace according to an embodiment of the present application.

As shown in the figure, the detection spot extends in the radial direction of the wafer, so that the concentric circle can be scanned from the outer circle to the inner circle.

In the initial state of detection, the detection spot is located at the outermost position of the wafer by the movement of the machine. It can be understood that in this embodiment, the entire wafer is tested. If the area to be tested is part of the wafer, the detection spot needs to be moved to the outermost side of the area to be tested. Then, the machine drives the wafer to rotate, and the signal light scattered by the wafer is collected in the normal direction and the illegal direction at the same time by the signal collection component. After completing one revolution along the first concentric circle, the machine drives the wafer to move, so that the detection spot moves a distance d in the first radial direction (that is, the distance between the centers of adjacent concentric circles is d) for the next scan. And so on, until the detection along the Nth concentric circle is completed (at this time, the light spot is irradiated to the center of the wafer), so that scanning of the wafer is completed, and a set of detection information corresponding to the detection light spot is obtained. It is understandable that, after each revolution, a ring-shaped area can be scanned. In one embodiment, the moving distance d is greater than or equal to 80% of the length of the detection spot, and less than or equal to the length of the detection spot.

In this embodiment, the detection area of the detection light spot extends in the radial direction, and the scanning direction of the detection light spot is perpendicular to the extending direction of the detection light spot. It can be understood that, in another embodiment, the included angle between the scanning direction of the detection light spot and the extension direction of the detection light spot is greater than 0 and less than 90 °.

Although the above embodiment detects from the outer ring to the inner ring of the wafer, it can be understood that in another embodiment, the scanning can also be performed by moving from the inner ring to the outer ring. In addition, the detection spot may extend in the radial direction of the wafer or in other directions. The scanning path of the wafer may also be spiral, Z, S, rectangular, or the like. For example, when a spiral trajectory scan is used, the scanning mode moves the platform while rotating and slowly translates in one direction to complete the entire area scan.

Therefore, when the detection areas do not overlap with each other, a plurality of detection light spots may be set to detect the wafer, and the plurality of detection light spots may partially overlap or not overlap.

From the foregoing, it can be known that, for a pit-like defect, a normal incidence method can be used to achieve better detection accuracy, and an oblique incident light source detection can achieve a high-precision detection of a convex-type defect. Therefore, the detection system can adopt not only separate vertical and oblique incidence, but also a scheme for detecting both vertical and oblique incidence light. In order to distinguish between vertically incident scattered light and oblique incident scattered light, a wavelength division method can be adopted, that is, light sources with different wavelengths are used for the detection of normal incidence and oblique incidence.

FIG. 4 is a structural diagram of a detection system according to another embodiment of the present application. Through the detection system, bright field and dark field synchronous detection can be implemented.

As shown in the figure, the first light source component 410 generates a first detection light beam, reaches the wafer surface through the diaphragm 431, the polarizing plate 432, and the beam splitter 433 to form a first detection light spot S1. The second light source component 420 generates a second detection light beam and reaches the wafer surface through the shaping lens group 434 to form a detection light spot S2 that at least partially overlaps the detection light spot S1. In one embodiment, the detection spot S2 is a linear spot, so that the light intensity can be concentrated as much as possible in the dark field.

For bright field, the wafer generates the corresponding reflected light under the action of the first detection spot S1, and then passes through the signal light collector 435 (such as a detection lens group or other elements with an imaging collection function), a beam splitter in order. 433 reaches the beam splitter 436. In the normal direction, the first filter 437 selectively receives the light beam from the beam splitter 436 so that the polarization line detector 440 receives the reflected light generated based on the first detection spot S1 to implement bright-field detection.

For the dark field, the wafer will generate scattered light in the normal and illegal directions under the effect of the detection spot S2. The scattered light generated in the normal direction reaches the beam splitter 436 through the signal light collector 435 and the beam splitter 433 in turn. The second filter 438 selectively receives the light beam from the beam splitter 436, thereby making the line detector 441 receives the normal scattered light based on the second detection spot S2. The scattered light generated in the illegal direction passes through the signal light collection device 439 and reaches the line detector 442.

It can be understood that the beam splitter 436 may be removed when the scattered light generated by the detection spot S2 in the normal direction does not need to be analyzed.

It can be seen from the above that by splitting and selectively receiving the reflected light and scattered light in the normal direction, the detection system 400 can simultaneously realize the light path for simultaneous bright and dark field detection. In this method, bright field detection and dark field detection are implemented simultaneously. Line scan detection, and the same detection position at the same time, by using different wavelength light sources in the light and dark fields, independent detection of different schemes is achieved.

Although the above content is based on the simultaneous generation of detection spots corresponding to two wavelengths and partially overlapping, for example, those skilled in the art can understand that in other embodiments, it is also possible to generate multiple wavelengths that partially overlap. To detect the light spot, only the corresponding beam splitter and filter are required to selectively receive the light beam. For example, the detection system 400 may further include a third light source component (not shown), which may generate a third detection light beam having a different wavelength from the first and second detection light beams, and generate a detection light spot S3. By setting a corresponding beam splitter and filter, the scattered light or reflected light generated by the detection spot S3 can be selectively received.

The present application proposes a detection method, including: generating a detection spot based on a detection beam; collecting signal light formed by a test object under the action of the detection spot in a linear manner, and then generating detection information corresponding to the detection spot. ; Determining defect feature information of the measured object based on the detection information.

This application also proposes a detection method, which includes the following steps: generating a detection spot based on the detection beam, the detection spot including a linear detection area; collecting signal light formed by the detection spot by scattering of the test object, and then generating and detecting Detection information corresponding to the light spot; based on the detection information formed by the detection area, the defect characteristic information of the measured object is determined.

The step of collecting signal light formed by scattering of the detection light spot by the test object includes: scanning the area to be measured of the test object by moving the detection light spot relative to the test object, and In the process, the signal light is collected.

When the measured area of the measured object is circular, the scanning step includes: rotating the measured object around the center of the measured area; after rotating the measured object around the center of the measured area, making the measured object along the measured area relative to the detection spot. The diameter direction of the measurement area is translated by a specific step; the above steps are repeated until the area to be measured is covered by the detection spot and the center of the detection area. In this way, rotation and translation are not performed at the same time, which can improve the stability of the system, improve the imaging quality, and further improve the detection accuracy.

In one embodiment, the specific step size is equal to or smaller than the size of the detection area in the translation direction.

The detection method can also be performed by the aforementioned detection system. Specifically, the detection component generates a detection light spot based on the detection light beam. Under the control of the processor component, the signal collection component collects signal light formed by the test object after the detection light spot is scattered by the test object, and then generates a phase corresponding to the detection light spot. Corresponding detection information; and determining defect feature information of the measured object through the detection information acquired by the processor component based on the detection area.

Although the above embodiments use linear light spots for detection, the detection method of the present application may also use spot light spots or surface light spots. Understandably, when a spot / area spot is used to detect a wafer, the shaping lens group needs to be adjusted to form a spot / area spot. For example, a spot can be used to inspect a wafer by a spiral method.

Compared with the traditional detection method, the detection method of the present application uses line scanning, each scanning area is large, and the signal received by the line detector is relatively uniform, which not only saves the wafer moving time, but also significantly increases the detection. Speed and accuracy.

Therefore, although the present application is described with reference to specific examples, which are intended to be illustrative only, and not to limit the present application, it will be apparent to those skilled in the art that Based on the spirit and scope of the application, changes, additions or deletions to the disclosed embodiments may be made.

Claims

A detection system, comprising:

A detection component configured to generate a detection spot based on a detection beam, the detection spot including a detection area, the detection area being linear;

A signal collection component configured to collect signal light formed by the detection light spot after being scattered by a test object, thereby generating detection information corresponding to the detection light spot; and

A processor component configured to determine defect feature information on the measured object based on detection information obtained by the detection area.
The detection system according to claim 1, wherein the signal collection component comprises:

At least one detection branch, each of which includes a signal light collector and a line detector, wherein the signal light collector is used to project the collected signal light to the line detector.
The detection system according to claim 1, wherein the signal collection component comprises:

A first scattered light detection branch configured to collect scattered light having a first exit angle;

The second scattered light detection branch is configured to collect scattered light having a second exit angle, which is not equal to the first exit angle.
The detection system of claim 1, wherein the detection component is configured to:

Generating a first detection light spot based on the first detection light beam, wherein the first detection light spot is a linear light spot;

A second detection light spot is generated based on a second detection light beam, wherein the first detection light spot and the second detection light spot partially overlap, and a wavelength of the first detection light beam is different from a wavelength of the second detection light beam .
The detection system according to claim 3, wherein

The first scattered light detection branch includes a first signal collector and a first line detector, wherein the first signal light collector is configured to project the collected signal light onto the first line. detector;

The second scattered light detection branch includes a second signal light collector, a first beam splitter, a first filter, and a second line detector, wherein the second signal light collector is configured to collect the collected signal light. The signal light is projected onto the second line detector in an imaging manner, the first filter receives the signal light via the first beam splitter, and selectively receives the received signal light based on a wavelength.
The detection system according to claim 5, wherein the signal collection component is further configured to collect signal light formed after the detection spot is reflected by the measured object, and the signal collection component further comprises:

A third detection branch including a first filter and a third line detector, wherein the second filter receives the signal light via the first beam splitter, and the received signal is based on a wavelength. Signal light is selectively received.
The detection system according to claim 1, wherein the processor component is configured to cause the detection component to detect the measured object with a specified detection trajectory,

The specified detection trajectory is a scanning trajectory of a center of a detection area corresponding to the detection spot with respect to the surface of the measured object, and the specified detection trajectory includes a plurality of concentric circles arranged in a radial direction.
The detection system according to claim 7, wherein:

The difference between the radii of the concentric circles adjacent to each other is less than or equal to the size of the detection area along the concentric circle radius direction.
The detection system according to claim 5, wherein the first signal light collector and / or the second signal light collector is a detection lens group.
The detection system according to claim 1, wherein the detection area of the detection light spot extends in a radial direction, and the scanning direction of the detection light spot is perpendicular to the extending direction of the detection area, or the detection light spot The included angle between the scanning direction and the extending direction of the detection area is an acute angle or an obtuse angle.
The detection system according to claim 1, wherein the detection light spot is linear, and an extension direction of the detection light spot is the same as an extension direction of the detection area.
The detection system according to claim 11, wherein a center of the detection area coincides with a center of the detection light spot, and a length of the detection area is shorter than a length of the detection light spot.
The detection system according to claim 1, wherein a length of the detection area is 90% to 95% of a length of the detection spot.
The detection system according to claim 1, wherein a length of the detection light spot is 5 mm to 10 mm, and a width of the detection light spot is 5 micrometers to 100 micrometers.