Particle detection device and particle detection method

Abstract

The invention discloses a particle detection device and a particle detection method, and belongs to the technical field of semiconductors. The laser beam generated by the light source is amplified through the light beam expanding device; a switch array is arranged on the light emitting side of the light beam expanding device, and the part, incident to each switch, of the laser beam is independently controlled through each switch, so that editing of the laser beam is achieved; according to the invention, the laser beam is edited, then the edited laser beam is shrunk through the beam expanding device, and the finally output laser beam can form a local light-spot-free region, so that precise control of micron-sized light spots is realized, and the area of a scanning region influenced by switching off of a switch can be greatly reduced, thereby improving the particle detection sensitivity.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a particle detection device and a particle detection method. Background Technology

[0002] As semiconductor design rules become increasingly stringent, the size of particulate defects on wafer surfaces is shrinking, placing ever higher demands on the sensitivity of particle inspection tools. Existing solutions improve sensitivity by increasing laser power intensity, but this approach lowers the size threshold at which particles undergo ablation, making them prone to explosion and causing contamination.

[0003] Currently, to prevent laser ablation, a pre-scan is performed to locate large particles (i.e., areas prone to explosion). During the final scan, the electronic shutter is closed at these locations to skip these areas, thus preventing particle ablation. However, closing the shutter creates a scanning blind zone, leading to decreased sensitivity in this area and a risk of missing small particle defects. The more times the shutter is closed, the higher the risk of missed detection. Therefore, how to reduce the impact of decreased particle detection sensitivity caused by closing the electronic shutter is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this application is to provide a particle detection device and a particle detection method, thereby reducing the impact of decreased particle detection sensitivity caused by the closing of the electronic shutter.

[0005] To achieve the above objectives, this application provides a particle detection device, comprising: a scanning device and a detection device; the scanning device includes a light source, a beam expander, a switch array, and a beam confinement device arranged sequentially along the laser beam transmission direction;

[0006] The light source is used to generate a first laser beam;

[0007] The beam expander is used to enlarge the size of the spot of the first laser beam to obtain a second laser beam;

[0008] The switch array includes at least two switches disposed on a first plane; the first plane forms an angle with the transmission direction of the laser beam; each switch is used to control the passage or cut-off of the second laser beam incident on the switch to obtain a third laser beam;

[0009] The beam confinement device is used to reduce the size of the spot of the third laser beam to obtain a fourth laser beam; the fourth laser beam irradiates the wafer surface to scan the wafer surface and generate signal light.

[0010] The detection device is used to detect the signal light.

[0011] Optionally, the size of the spot of the fourth laser beam is equal to the size of the spot of the first laser beam.

[0012] Optionally, a reflector is provided on the light-emitting side of the beam confinement device along the laser beam transmission direction; the reflector is used to reflect the fourth laser beam onto the wafer surface.

[0013] Optionally, the detection device includes an optical filter and a photoelectronic detection system arranged sequentially along the signal light transmission direction;

[0014] The optical filter is used to filter the signal light;

[0015] The optoelectronic detection system is used to detect the filtered signal light.

[0016] Optionally, the beam expanding device includes a Galilean beam expander; the Galilean beam expander includes a first concave lens and a first convex lens arranged sequentially along the transmission direction of the laser beam, used to magnify the size of the spot of the first laser beam and convert the resulting second laser beam into collimated light.

[0017] Optionally, the third laser beam is collimated light;

[0018] The beam confinement device includes a reverse Galilean beam expander; the reverse Galilean beam expander includes a second convex lens and a second concave lens arranged sequentially along the laser beam transmission direction, used to reduce the size of the spot of the third laser beam to obtain a fourth laser beam.

[0019] Optionally, the beam expansion ratio of the second laser beam and the first laser beam is equal to the absolute value of the ratio of the focal length of the first convex lens to the focal length of the first concave lens.

[0020] The distance between the first concave lens and the first convex lens is equal to the absolute value of the difference between the focal length of the first convex lens and the focal length of the first concave lens.

[0021] The beam-contraction ratio of the fourth laser beam and the third laser beam is equal to the absolute value of the ratio of the focal length of the second concave lens to the focal length of the second convex lens.

[0022] The distance between the second convex lens and the second concave lens is equal to the absolute value of the difference between the focal length of the second convex lens and the focal length of the second concave lens.

[0023] Optionally, the first plane is perpendicular to the laser beam transmission direction; the switches are sequentially arranged on the first plane along the direction perpendicular to the laser beam transmission direction;

[0024] And / or, the switch includes an electronic shutter.

[0025] To achieve the above objectives, this application also provides a particle detection method applied to the particle detection device described above, comprising:

[0026] The particle detection device is used to pre-scan the surface of the wafer to be tested, determine the position of large particles on the surface of the wafer to be tested and the laser beam irradiating the large particles, and determine the switch corresponding to the laser beam.

[0027] The particle detection device is used to perform a final scan on the surface of the wafer under test. When the large particle is detected, the corresponding switch is turned off to skip the large particle, and the signal light generated during the final scan is detected.

[0028] Optionally, the speed of the fourth laser beam output by the particle detection device during the final scan is less than the speed of the fourth laser beam output by the particle detection device during the pre-scan.

[0029] The power of the fourth laser beam output by the particle detection device during the final scan is greater than the power of the fourth laser beam output by the particle detection device during the pre-scan.

[0030] Obviously, the particle detection device provided in this application amplifies the laser beam generated by the light source through a beam expander; and a switch array is set on the output side of the beam expander, with each switch independently controlling the portion of the laser beam incident on each switch, thus editing the laser beam; subsequently, the beam expander reduces the edited laser beam, and the final output laser beam can form a local spotless area, achieving precise control of micron-level spots, which can significantly reduce the area of ​​the scanning region affected by the switch being closed, thereby improving the particle detection sensitivity. This application also provides a particle detection method using the above-mentioned particle detection device, which pre-scans the position of large particles to locate the corresponding switches; during the final scan, the corresponding switches are closed to skip large particles, which can significantly reduce the area of ​​the scanning region affected by the switch being closed, thereby improving the particle detection sensitivity. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the distribution of particles on a wafer surface;

[0033] Figure 2 This is a schematic diagram illustrating the formation of a scanning blind zone;

[0034] Figure 3 This is a schematic diagram of the structure of a particle detection device provided in an embodiment of this application;

[0035] Figure 4 This is a partial structural diagram of a scanning device provided in an embodiment of this application;

[0036] Figure 5 This is a flowchart of a particle detection method provided in an embodiment of this application.

[0037] The annotations in the attached figures are explained as follows:

[0038] 1-Wafer; 2-Particle; 21-Large particle; 3-Light spot; 41-Scanning device; 411-Light source; 412-Beam expander; 4121-First concave lens; 4122-First convex lens; 413-Switch array; 4131-Switch; 414-Beam confinement device; 4141-Second convex lens; 4142-Second concave lens; 415-Mirror; 42-Detection device; 421-Optical filter; 422-Optoelectronic detection system;

[0039] 51 - Spot of the first laser beam; 52 - Spot of the second laser beam; 53 - Spot of the third laser beam; 54 - Spot of the fourth laser beam. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] As semiconductor design rules tighten, the size of defects on wafer surfaces (such as particulate defects) is shrinking accordingly. Particulate defects are typically detected using particle inspection tools. As particle size decreases, the sensitivity requirements for these tools increase. To ensure the detection of increasingly smaller particles, current solutions involve continuously increasing laser power intensity. However, increasing laser power intensity lowers the size threshold for particle ablation, potentially leading to particle explosion. Figure 1 As shown, a large particle is broken down into hundreds of smaller particles 2 in the surrounding area of ​​the surface of wafer 1 (see Figure 2). Figure 1 (The area within the dashed box in the image), thus leading to particulate pollution.

[0042] Currently, to prevent laser ablation, a pre-scan is performed first. Based on a set size threshold of the LPM (Laser Particle Monitor), the location of large particles (i.e., areas prone to explosion) is identified. Then, a final scan is performed. When the scan reaches the location of large particles identified in the previous steps, the high-speed electronic shutter is closed (i.e., the laser spot is closed) to skip these areas, thus preventing explosion. Specifically:

[0043] In the scanning direction, the electronic shutter closing length = electronic shutter closing time × scan line speed;

[0044] Electronic shutter closing area = spot width × electronic shutter closing length in the scanning direction;

[0045] In the formula, the electronic shutter closing time includes the response time and the scanning time of the large particle. The product of the scanning time of the large particle and the scanning line speed represents the width of the large particle. Taking a spot width of 10mm as an example, the scanning line speed of the spot is 80mm / s, the response time of the electronic shutter closing is 0.03s, and the electronic shutter closing area of ​​a single large particle on the wafer surface accounts for approximately 0.03%.

[0046] like Figure 2 As shown, closing the electronic shutter at the position of large particle 21 (i.e., closing spot 3) creates a scanning blind zone, leading to decreased sensitivity in this area and a risk of missing small particle defects. Closing the electronic shutter too frequently increases the risk of missing small particle defects in this area. Therefore, this application provides a particle detection device that uses a beam expander, a switch array, and a beam constraint device to amplify, edit, and reduce the laser beam, achieving precise control of the micron-level spot, thereby reducing the impact of decreased particle detection sensitivity caused by closing the electronic shutter.

[0047] Please refer to Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of the structure of a particle detection device provided in an embodiment of this application; Figure 4 This is a partial structural diagram of a scanning device 41 provided in an embodiment of this application. The particle detection device may include a scanning device 41 and a detection device 42. The scanning device 41 includes a light source 411, a beam expander 412, a switch array 413 and a beam confinement device 414 arranged sequentially along the laser beam transmission direction.

[0048] Light source 411 is used to generate the first laser beam;

[0049] The beam expander 412 is used to enlarge the size of the spot 51 of the first laser beam to obtain the second laser beam;

[0050] The switch array 413 includes at least two switches 4131 disposed on a first plane; the first plane has an angle with the laser beam transmission direction; each switch 4131 is used to control the passage or cut-off of a second laser beam incident on the switch 4131 to obtain a third laser beam;

[0051] The beam confinement device 414 is used to reduce the size of the spot 53 of the third laser beam to obtain a fourth laser beam; the fourth laser beam irradiates the surface of the wafer 1 to scan the surface of the wafer 1 to generate signal light.

[0052] The detection device 42 is used to detect the signal light.

[0053] It should be noted that in this embodiment, the size of the spot 52 of the second laser beam is larger than the size of the spot 51 of the first laser beam; the size of the spot 54 of the fourth laser beam is equal to the size of the spot 53 of the third laser beam.

[0054] This embodiment does not limit the specific type of beam expander 412, as long as it can amplify the size of the spot 51 of the first laser beam. For example, the beam expander 412 may include a Galilean beam expander; the Galilean beam expander includes a first concave lens 4121 and a first convex lens 4122 arranged sequentially along the laser beam transmission direction, used to amplify the size of the spot 51 of the first laser beam and convert the resulting second laser beam into collimated light. It should be noted that the laser beam output by the Galilean beam expander in this embodiment is collimated light, and this collimated light is still output as collimated light after being transmitted through the switch array 413.

[0055] This embodiment does not limit the specific beam expansion ratio of the second laser beam and the first laser beam. It can be determined according to the specific type of beam expansion device 412. For example, the beam expansion ratio of the second laser beam and the first laser beam can be equal to the absolute value of the ratio of the focal length of the first convex lens 4122 to the focal length of the first concave lens 4121.

[0056] This embodiment does not limit the specific distance between the first concave lens 4121 and the first convex lens 4122. It can be determined based on the specific focal length of the first convex lens 4122 and the specific focal length of the first concave lens 4121. For example, the distance between the first concave lens 4121 and the first convex lens 4122 can be equal to the absolute value of the difference between the focal length of the first convex lens 4122 and the focal length of the first concave lens 4121.

[0057] This embodiment does not limit the specific type of switch 4131, as long as it can control the passage or cut-off of the second laser beam incident on the switch 4131. For example, switch 4131 may include an electronic shutter.

[0058] This embodiment does not limit the specific arrangement of the switches 4131. As long as it can ensure that the second laser beam can be divided into multiple small sub-beams on a plane that is not parallel to the laser beam transmission direction, and the passage or closing of the sub-beams can be controlled respectively, for example, the first plane can be perpendicular to the laser beam transmission direction; the switches 4131 are arranged sequentially on the first plane along the direction perpendicular to the laser beam transmission direction.

[0059] This embodiment does not limit the specific type of beam confinement device 414, as long as it can reduce the size of the spot 53 of the third laser beam. For example, when the third laser beam is collimated, the beam confinement device 414 may include an inverse Galilean beam expander. The inverse Galilean beam expander includes a second convex lens 4141 and a second concave lens 4142 arranged sequentially along the laser beam transmission direction, which are used to reduce the size of the spot 53 of the third laser beam to obtain a fourth laser beam.

[0060] This embodiment does not limit the specific beam reduction ratio of the fourth laser beam and the third laser beam. It can be determined according to the specific type of beam confinement device 414. For example, the beam reduction ratio of the fourth laser beam and the third laser beam can be equal to the absolute value of the ratio of the focal length of the second concave lens 4142 to the focal length of the second convex lens 4141.

[0061] This embodiment does not limit the specific distance between the second convex lens 4141 and the second concave lens 4142. It can be determined based on the specific focal length of the second convex lens 4141 and the second concave lens 4142. For example, the distance between the second convex lens 4141 and the second concave lens 4142 can be equal to the absolute value of the difference between the focal length of the second convex lens 4141 and the focal length of the second concave lens 4142.

[0062] It should be noted that, in this embodiment, to ensure precise control of the micron-level light spot through the switch array 413, a beam expander 412 is provided on the light-incident side of the switch array 413 to expand the laser beam. Although the area of ​​the scanning region affected by the closure of the switch 4131 can be reduced by closing the switch 4131 corresponding to the large particle, the beam expander 412 increases the size of the laser beam spot. To avoid the spot size becoming too large, a beam constraint device 414 is provided on the light-outceasing side of the switch array 413 to reduce the size of the laser beam. Preferably, the size of the spot 54 of the fourth laser beam can be equal to the size of the spot 51 of the first laser beam. It should be noted that, in this embodiment, the beam constraint device 414 restores the laser beam, reducing the emitted laser beam to its normal size, which avoids the negative effects of beam expansion and maximizes the effect of the switch array 413 in reducing the area of ​​the scanning region affected by the closure of the switch 4131.

[0063] This embodiment does not limit the specific method of transmitting the fourth laser beam to the surface of wafer 1, as long as it can ensure that the fourth laser beam can irradiate the surface of wafer 1. For example, a reflector 415 can be provided on the light-emitting side of the beam confinement device 414 along the laser beam transmission direction; the reflector 415 is used to reflect the fourth laser beam to the surface of wafer 1.

[0064] It should be noted that in this embodiment, the fourth laser beam will generate signal light after irradiating the surface of wafer 1. After receiving the signal light, the detection device 42 can identify particles by detecting the signal light. This embodiment does not limit the specific type of signal light, as long as it can be received by the detection device 42 and particles can be identified based on the signal light. For example, the signal light can be scattered light.

[0065] This embodiment does not limit the specific type of detection device 42, as long as it can receive signal light and determine particles based on the signal light. For example, the detection device 42 may include an optical filter 421 and a photoelectronic detection system 422 arranged sequentially along the signal light transmission direction; the optical filter 421 is used to filter the signal light; and the photoelectronic detection system 422 is used to detect the filtered signal light.

[0066] Based on the above embodiments, this application amplifies the laser beam generated by the light source using a beam expander; and sets a switch array on the light-emitting side of the beam expander, so that the portion of the laser beam incident on each switch can be independently controlled by each switch, thereby achieving editing of the laser beam; then the edited laser beam is reduced by the beam expander, and the final output laser beam can form a local spotless area, realizing precise control of micron-level spots, which can significantly reduce the area of ​​the scanning region affected by the switch being closed, thereby improving the particle detection sensitivity.

[0067] Please refer to Figure 5 , Figure 5 A flowchart of a particle detection method provided in this application embodiment, which can be applied to the particle detection device described above, includes:

[0068] S101: A particle detection device is used to pre-scan the surface of the wafer to be tested, determine the position of large particles on the surface of the wafer to be tested and the laser beam irradiating the large particles, and determine the switch corresponding to the laser beam.

[0069] S102: A particle detection device is used to perform a final scan of the surface of the wafer under test. When a large particle is detected, the corresponding switch is turned off to skip the large particle, and the signal light generated during the final scan is detected.

[0070] This embodiment does not limit the specific process conditions for pre-scanning and final scanning. To avoid particle explosion, in this embodiment, the speed of the fourth laser beam output by the particle detection device during the final scan can be less than the speed of the fourth laser beam output by the particle detection device during the pre-scan.

[0071] The power of the fourth laser beam output by the particle detection device during the final scan can be greater than the power of the fourth laser beam output by the particle detection device during the pre-scan.

[0072] Based on the above embodiments, this application uses the above-described particle detection device to locate the corresponding switch by pre-scanning the position of large particles; during the final scan, the corresponding switch is turned off to skip large particles, which can significantly reduce the area of ​​the scanning region affected by the switch being turned off, thereby improving the particle detection sensitivity.

[0073] The particle detection process described above is illustrated below with specific examples. This embodiment uses... Figure 3 The particle detection device shown employs... Figure 4 The scanning device 41 shown contains a beam expander 412, which employs a Galilean beam expander to amplify and convert the laser beam generated by the light source 411 into collimated light. Figure 4 It can be seen that the size of the spot 52 of the second laser beam on the output side of the Galilean beam expander is larger than the size of the spot 51 of the first laser beam on the input side; the switch 4131 uses an electronic shutter, and a row of small electronic shutters is arranged along the path of the output collimated light perpendicular to the light transmission direction; the beam confinement device 414 uses a reverse Galilean beam expander, which reduces the laser beam to its normal size. Figure 4 It can be seen that the size of the spot 54 of the fourth laser beam on the output side of the inverse Galilean beam expander is smaller than the size of the spot 53 of the third laser beam on the input side.

[0074] The specific process of particle detection using this particle detection device is as follows:

[0075] 1. A particle detection device outputs a high-speed, low-power laser beam to pre-scan the surface of the wafer to be tested, and locates the electronic shutter corresponding to the large particle.

[0076] 2. A particle detection device outputs a low-speed, high-power laser beam to perform a final scan of the surface of the wafer 1 to be tested. When a large particle is detected, the corresponding switch 4131 is turned off to skip the large particle, forming a local area without light spots, which greatly reduces the area of ​​the scanned region affected by the shutdown of switch 4131. The signal light generated during the final scan is detected with high sensitivity.

[0077] This document uses specific examples to illustrate the principles and implementation methods of this application. The various embodiments are progressive, with each embodiment focusing on its differences from others. Similar or identical parts between embodiments can be referred to interchangeably. The descriptions of the embodiments above are merely illustrative of the method and core ideas of this application. For those skilled in the art, various improvements and modifications can be made to this application without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this application.

[0078] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

Claims

1. A particle detection device, characterized in that, include: A scanning device and a detection device; the scanning device includes a light source, a beam expander, a switch array, and a beam confinement device arranged sequentially along the laser beam transmission direction; The light source is used to generate a first laser beam; The beam expander is used to enlarge the size of the spot of the first laser beam to obtain a second laser beam; The switch array includes at least two switches disposed on a first plane; the first plane forms an angle with the transmission direction of the laser beam; each switch is used to control the passage or cut-off of the second laser beam incident on the switch to obtain a third laser beam; The beam confinement device is used to reduce the size of the spot of the third laser beam to obtain a fourth laser beam; the fourth laser beam irradiates the wafer surface to scan the wafer surface and generate signal light. The detection device is used to detect the signal light.

2. The particle detection device according to claim 1, characterized in that, The size of the spot of the fourth laser beam is equal to the size of the spot of the first laser beam.

3. The particle detection device according to claim 1, characterized in that, A reflector is provided on the light-emitting side of the beam confinement device along the laser beam transmission direction; the reflector is used to reflect the fourth laser beam onto the wafer surface.

4. The particle detection device according to claim 1, characterized in that, The detection device includes an optical filter and an optoelectronic detection system arranged sequentially along the signal light transmission direction; The optical filter is used to filter the signal light; The optoelectronic detection system is used to detect the filtered signal light.

5. The particle detection device according to any one of claims 1 to 4, characterized in that, The beam expanding device includes a Galilean beam expander; the Galilean beam expander includes a first concave lens and a first convex lens arranged sequentially along the transmission direction of the laser beam, used to magnify the size of the spot of the first laser beam and convert the resulting second laser beam into collimated light.

6. The particle detection device according to claim 5, characterized in that, The third laser beam is collimated light; The beam confinement device includes a reverse Galilean beam expander; the reverse Galilean beam expander includes a second convex lens and a second concave lens arranged sequentially along the laser beam transmission direction, used to reduce the size of the spot of the third laser beam to obtain a fourth laser beam.

7. The particle detection device according to claim 6, characterized in that, The beam expansion ratio of the second laser beam and the first laser beam is equal to the absolute value of the ratio of the focal length of the first convex lens to the focal length of the first concave lens. The distance between the first concave lens and the first convex lens is equal to the absolute value of the difference between the focal length of the first convex lens and the focal length of the first concave lens. The beam-contraction ratio of the fourth laser beam and the third laser beam is equal to the absolute value of the ratio of the focal length of the second concave lens to the focal length of the second convex lens. The distance between the second convex lens and the second concave lens is equal to the absolute value of the difference between the focal length of the second convex lens and the focal length of the second concave lens.

8. The particle detection device according to claim 5, characterized in that, The first plane is perpendicular to the laser beam transmission direction; the switches are arranged sequentially on the first plane along the direction perpendicular to the laser beam transmission direction; And / or, the switch includes an electronic shutter.

9. A method for particle detection, characterized in that, The particle detection device according to any one of claims 1 to 8 comprises: The particle detection device is used to pre-scan the surface of the wafer to be tested, determine the position of large particles on the surface of the wafer to be tested and the laser beam irradiating the large particles, and determine the switch corresponding to the laser beam. The particle detection device is used to perform a final scan on the surface of the wafer under test. When the large particle is detected, the corresponding switch is turned off to skip the large particle, and the signal light generated during the final scan is detected.

10. The particle detection method according to claim 9, characterized in that, The speed of the fourth laser beam output by the particle detection device during the final scan is less than the speed of the fourth laser beam output by the particle detection device during the pre-scan. The power of the fourth laser beam output by the particle detection device during the final scan is greater than the power of the fourth laser beam output by the particle detection device during the pre-scan.

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