A method and apparatus for cleaning gain laser plasma filaments

Abstract

The present application relates to a kind of gain laser plasma light filaments cleaning method, for cleaning substrate, the method includes the following steps: the direction of parallel substrate surface exports laser beam;Gain gas is transported to closed cleaning chamber and pressurized, the laser beam passes through the gain gas in the closed cleaning chamber, to form the gain light filament that the substrate surface is cleaned to the substrate surface. By passing through the closed cleaning chamber filled with gain gas and pressurized, the gain light filament with longer length and wider spectral width is formed, and acts on the substrate surface to be cleaned, to realize more efficient cleaning.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser cleaning, in particular to a gain laser plasma light filament cleaning method and device. BACKGROUND

[0002] Laser cleaning technology is a product of the combination of laser material processing technology and material surface cleaning technology, which has the advantages of laser processing and can meet the requirements of the development of material surface cleaning technology. It is a new cleaning technology. Laser plasma light filament cleaning is a new technology derived from plasma shock wave cleaning. When a strong femtosecond laser is transmitted in air, plasma filaments are generated due to the combined action of Kerr self-focusing effect and plasma defocusing effect. The light filaments are parallelly injected into the surface of the substrate, and the light intensity and mechanical effect of the light filaments are used to remove the particles on the surface of the substrate. Compared with the one-time effective cleaning area of the plasma shock wave cleaning, the cleaning technology has larger effective cleaning area and higher efficiency.

[0003] The existing light filament cleaning method, such as the applicant's prior application "Laser plasma light filament cleaning method", announcement number: CN 111992543B, is based on the plasma filaments formed by the breakdown of air medium when the ultrafast laser is transmitted in air as the cleaning means. However, since air has multiple gas components, the ionization threshold of each gas component is inconsistent, which affects the brightness and length of the plasma filaments, and further affects the cleaning power and efficiency of the light filaments. Therefore, it is necessary to provide a gain laser plasma light filament cleaning method and device with long distance and high intensity. SUMMARY

[0004] The purpose of the present application is to provide a gain laser plasma light filament cleaning method and device with long distance and high intensity.

[0005] According to one aspect of the present application, a gain laser plasma light filament cleaning method is provided for cleaning a substrate, the method comprising the steps of:

[0006] outputting a laser beam in a direction parallel to the surface of the substrate;

[0007] delivering a gain gas into a closed cleaning chamber and pressurizing, and the laser beam passes through the gain gas in the closed cleaning chamber, thereby forming a gain light filament for cleaning the surface of the substrate.

[0008] More preferably, the step of outputting a laser beam in a direction parallel to the surface of the substrate further comprises the step of:

[0009] placing the substrate to be cleaned in a closed cleaning chamber, the surface of the substrate being the surface to be cleaned, and the closed cleaning chamber is configured to allow laser to pass through the area above the surface of the substrate.

[0010] More preferably, the step of delivering gain gas into the closed cleaning chamber and pressurizing further comprises the steps of:

[0011] The laser beam output in the direction parallel to the substrate surface passes through the air medium in the closed cleaning chamber, and the original light filament formed acts on the substrate surface;

[0012] The first spectral width of the original light filament is measured by a spectrometer.

[0013] More preferably, the step of delivering gain gas into the closed cleaning chamber and pressurizing further comprises the steps of:

[0014] The laser beam output in the direction parallel to the substrate surface passes through the gain gas in the closed cleaning chamber, and the gain light filament formed acts on the substrate surface;

[0015] The second spectral width of the gain light filament is measured by a spectrometer.

[0016] The substrate surface is photographed by a CCD camera, and the cleaning effect of the gain light filament on the substrate surface is observed by a super-depth microscope.

[0017] More preferably, the first spectral width is denoted as a, and the second spectral width is denoted as b;

[0018] When b≥2a, it is determined that the original light filament forms a gain light filament under the action of the gain gas;

[0019] When b<2a, it is determined that the original light filament does not form a gain light filament under the action of the gain gas, at which time the gas pressure in the closed cleaning chamber is increased by continuously inputting gain gas until a gain light filament is formed.

[0020] More preferably, the area of the region cleaned by the gain light filament on the substrate surface is denoted as M, and the area of the region in which stains remain after the substrate surface is cleaned by the gain light filament is denoted as N;

[0021] When M≥10N, it is determined that the cleaning effect of the gain light filament meets the standard;

[0022] When M<10N, it is determined that the cleaning effect of the gain light filament does not meet the standard, and the power of the laser beam is increased until the cleaning effect meets the standard.

[0023] More preferably, the gain gas is any one or a combination of nitrogen, xenon, krypton, and argon.

[0024] More preferably, the gas pressure in the closed cleaning chamber is denoted as H, and satisfies the relationship:

[0025] 0.5×10 5Pa < H < 2 x 10 5 Pa.

[0026] A gain laser plasma optical filament cleaning device for implementing the method, the device comprising:

[0027] A strong femtosecond laser outputs a laser beam in a direction parallel to the substrate surface;

[0028] A closed cleaning chamber is filled with gain gas and pressurized, and the laser beam passes through the gain gas in the closed cleaning chamber, thereby forming a gain optical filament for cleaning the substrate surface.

[0029] More preferably, the device further comprises:

[0030] A first lens assembly is arranged between the strong femtosecond laser and the closed cleaning chamber, and the laser beam enters the closed cleaning chamber after passing through the first lens assembly;

[0031] A CCD camera is located on the side of the closed cleaning chamber facing the substrate surface and is used to take pictures of the substrate surface;

[0032] An ultra-depth-of-field microscope is used in combination with the CCD camera to observe the cleaning effect of the gain optical filament on the substrate surface;

[0033] A spectrometer is located on the side of the closed cleaning chamber facing away from the strong femtosecond laser and is located on the light path of the laser beam, and is used to measure the spectral width of the gain optical filament;

[0034] The first lens assembly comprises:

[0035] A polarization beam splitter prism is arranged between the strong femtosecond laser and the closed cleaning chamber;

[0036] A half-wave plate is arranged between the polarization beam splitter prism and the strong femtosecond laser for adjusting the power of the laser beam;

[0037] A first focusing lens is arranged between the polarization beam splitter prism and the closed cleaning chamber;

[0038] The closed cleaning chamber is made of transparent material;

[0039] A second focusing lens is further arranged between the spectrometer and the closed cleaning chamber, and a first ND filter is further arranged between the spectrometer and the second focusing lens;

[0040] A second ND filter is further arranged between the CCD camera and the closed cleaning chamber.

[0041] The present application has the following beneficial effects:

[0042] By passing the laser beam through the sealed cleaning cabin filled with gain gas and pressurized, a gain optical filament with longer length and wider spectral width is formed, and acts on the surface of the substrate to be cleaned, thereby achieving more efficient cleaning. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0044] Figure 1 The principle diagram of the gain laser plasma optical filament cleaning device according to an embodiment of the present application;

[0045] Figure 2 The scene diagram of the gain laser plasma optical filament cleaning device according to an embodiment of the present application;

[0046] The figure number explanation: 100, device; 10, strong femtosecond laser; 20, sealed cleaning cabin; 21, gain gas; 30, first lens assembly; 41, CCD camera; 42, super-depth microscope; 51, spectrometer; 31, polarization beam splitter prism; 32, half-wave plate; 33, first focusing lens; 52, second focusing lens; 53, first ND filter; 43, second ND filter; 90, substrate; 91, substrate surface; DETAILED DESCRIPTION

[0047] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0048] It should be noted that when an element is referred to as being “fixed” to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being “connected” to another element, it can be directly connected to the other element or there can be an intervening element. The terms “vertical”, “horizontal”, “left”, “right” and similar expressions used herein are for illustrative purposes only.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0050] Reference should be made to Figure 1 Figure 2 An embodiment of the application provides a gain laser plasma filament cleaning method for cleaning a substrate 90, the method comprising the steps of:

[0051] Step S10: placing the substrate 90 to be cleaned in a closed cleaning chamber 20, the substrate surface 91 being the surface to be cleaned, the closed cleaning chamber 20 being configured to allow laser to pass through the area above the substrate surface 91.

[0052] Specifically, referring to Figure 1 The substrate 90 to be cleaned is placed in the closed cleaning chamber 20. The substrate 90 can be a metal, a semiconductor wafer, a ceramic, a magnetic material, a plastic, and an optical component, etc. The substrate surface 91 is the surface to be cleaned. The closed cleaning chamber 20 is configured to allow laser to pass through the area above the substrate surface 91, i.e. the inside of the cleaning chamber has a light-transmitting window, so that the laser can irradiate the substrate surface 91. In the embodiment, the closed cleaning chamber 20 is made of glass, so that the closed cleaning chamber 20 has light-transmitting properties in any direction, facilitating the observation of the environment in the closed cleaning chamber 20 by the spectrometer 51, the CCD camera 41, and the ultra-deep microscope 42.

[0053] Step S20: outputting a laser beam in a direction parallel to the substrate surface 91;

[0054] Specifically, referring to Figure 2 The substrate 90 is placed flat on a table, the substrate surface 91 is a plane, and a strong femtosecond laser 10 is used to output a laser beam in a direction parallel to the substrate surface 91.

[0055] Step S30: the laser beam output in a direction parallel to the substrate surface 91 passes through the air medium in the closed cleaning chamber 20, and the original filament formed acts on the substrate surface 91;

[0056] ​Specifically, the intense femtosecond laser is parallelly incident in the air medium in the air chamber, and a plasma filament is generated under the joint action of the Kerr self-focusing effect and the plasma defocusing effect, which is recorded as an original filament to distinguish from the gain filament formed by passing through the gain gas 21. The original filament is a nonlinear optical effect generated by the laser beam in the air, which can oxidize, decompose and volatilize the pollutants on the substrate surface 91, thereby playing a role in cleaning the substrate surface 91.

[0057] Step S40: The first spectral width of the original filament is measured by the spectrometer 51.

[0058] Specifically, the spectrometer 51 can be a Fourier transform spectrometer 51, a spectrophotometer, etc. In the embodiment, the spectrometer 51 is a Fourier transform spectrometer 51, which measures the radiation intensity of the original filament acting on the substrate surface 91 at each wavelength to obtain the spectral width thereof.

[0059] Step S50: The gain gas 21 is delivered into the sealed cleaning chamber 20 and pressurized, and the laser beam passes through the gain gas 21 in the sealed cleaning chamber 20, thereby forming a gain filament for cleaning the substrate surface 91.

[0060] Specifically, in the embodiment, referring to Figure 2 , the gain gas 21 is stored in a compressed gas tank and delivered into the sealed cleaning chamber 20 through a spray head. The opening degree of the electromagnetic valve of the spray head is controlled by observing the pressure gauge of the transparent chamber, so as to control the pressure of the gain medium in the cleaning chamber. When the pressure and concentration of the gain medium in the chamber are stable, the brightness and spectral width of the plasma filament tend to be stable. The femtosecond laser plasma filament in the gain medium is measured and analyzed by using the super-depth-of-field microscopic system and the spectrometer 51, so as to determine the formation position, spatial structure, light intensity distribution and other dynamic characteristic information parameters of the filament.

[0061] Specifically, the gain gas 21 is any one or a combination of nitrogen, xenon, krypton and argon. In the embodiment, the gain gas 21 is nitrogen.

[0062] More preferably, the air pressure in the sealed cleaning chamber 20 is recorded as H, and when the relationship 0.5×105Pa<H<2×105Pa is satisfied, the concentration of the gain gas 21 reaches a threshold value. The gain gas 21 at this concentration is more likely to produce a circuit, and the laser beam passing through the gain gas 21 at this concentration is more likely to form a filament with a longer length and a higher energy intensity. The filament generated under this condition is recorded as a gain filament. Since it has a longer filament length, it can act on a larger range of substrate surface 91, and has a higher energy intensity, which can effectively improve the ability to remove stains and greatly improve the effect of laser cleaning.

[0063] Step S60: The laser beam output in the direction parallel to the substrate surface 91 passes through the gain gas 21 in the sealed cleaning chamber 20, and the gain light filament formed thereby acts on the substrate surface 91.

[0064] Specifically, the gain light filament has higher brightness, longer light filament length, and wider spectral width than the original light filament, i.e., a stronger plasma light filament can be obtained with smaller laser energy after the gain gas 21 is blown, the gain plasma light filament has stronger energy, and the generated shock wave is stronger, which can greatly increase the area of the cleaning region and improve the cleaning efficiency.

[0065] Step S70: The second spectral width of the gain light filament is measured by the spectrometer 51.

[0066] Specifically, the first spectral width is denoted as a, and the second spectral width is denoted as b.

[0067] When b≥2a, the intensity of the light filament reaches the expectation, and it is determined that the original light filament forms a gain light filament under the action of the gain gas 21.

[0068] When b<2a, the intensity of the light filament does not reach the expectation, and it is determined that the original light filament does not form a gain light filament under the action of the gain gas 21. At this time, the gain gas 21 is continuously input to increase the gas pressure in the sealed cleaning chamber 20 until a gain light filament is formed.

[0069] Step S80: The substrate surface 91 is photographed by the CCD camera 41, and the cleaning effect of the gain light filament on the substrate surface 91 is observed by the super-depth-of-field microscope 42.

[0070] Specifically, the area of the region cleaned by the gain light filament on the substrate surface 91 is denoted as M, and the area of the region in which stains remain after the substrate surface 91 is cleaned by the gain light filament is denoted as N.

[0071] When M≥10N, the removal rate of the stain particles on the substrate surface 91 is not less than 90%, and it is determined that the cleaning effect of the gain light filament meets the standard.

[0072] When M<10N, the removal rate of the stain particles on the substrate surface 91 is less than 90%, and it is determined that the cleaning effect of the gain light filament does not meet the standard. The power of the gain light filament is then increased to improve the ability of the gain light filament to remove the stain particles on the substrate surface 91, until the cleaning effect meets the standard.

[0073] Further, the power of the optical filament can be adjusted by adjusting the output power of the strong femtosecond laser 10, or by adjusting the power of the laser beam passing through the lens assembly, thereby adjusting the power of the gain optical filament. In this embodiment, the control of the power of the laser beam is realized by adjusting the half-wave plate 32. Specifically, the laser beam is output from the strong femtosecond laser 10, first passes through the half-wave plate 32 to adjust the power, then passes through the polarization beam splitter prism 31, and then passes through the first focusing lens 33, and then enters the transparent sealed cleaning chamber 20.

[0074] Further, the distance between the plasma optical filament and the substrate surface 91 can also be adjusted by mounting the emission end of the strong femtosecond laser 10 on a three-dimensional high-precision linear moving platform.

[0075] On the one hand, the distance between the plasma optical filament and the substrate surface 91 can be reduced, so that the plasma optical filament directly acts on the microparticles, and the microparticles are removed by the light intensity and mechanical action generated by the plasma optical filament, thereby improving the cleaning effect.

[0076] On the other hand, in the case of avoiding damage to the substrate surface 91, the distance between the plasma optical filament and the substrate surface 91 can be increased, so that the plasma optical filament only removes the stain particles, thereby avoiding damage to the substrate of the substrate surface 91.

[0077] As to how to accurately adjust the distance between the plasma optical filament and the substrate surface 91, the following method can be referred to:

[0078] Step A1: Place an aluminum foil on the cleaning platform perpendicular to the direction of the optical filament;

[0079] Step A2: When the plasma optical filament is transmitted, it penetrates the aluminum foil and makes a small hole on the aluminum foil, then the lower edge position of the optical filament is intercepted through the small hole, and finally the distance between the lower edge position of the optical filament and the surface of the silicon wafer is determined as the action distance of the optical filament;

[0080] Step A3: By fine-tuning the three-dimensional high-precision linear moving platform, different action distances between the plasma optical filament and the substrate surface 91 are realized.

[0081] Embodiment 2

[0082] This embodiment 2 provides a gain laser plasma optical filament cleaning device 100 for realizing the method of embodiment 1, and the device 100 comprises a strong femtosecond laser 10, a sealed cleaning chamber 20, a first lens assembly 30, a CCD camera 41, an ultra-depth-of-field microscope 42, a spectrometer 51, a second focusing lens 52, a first ND filter 53, and a second ND filter 43.

[0083] The strong femtosecond laser 10 outputs a laser beam along the direction parallel to the substrate surface 91. The closed cleaning chamber 20 is filled with gain gas 21 and pressurized, and the pressure in the closed cleaning chamber 20 is denoted as H, satisfying the relationship:

[0084] 0.5×105Pa<H<2×105Pa.

[0085] The laser beam passes through the gain gas 21 in the closed cleaning chamber 20, thereby forming a gain optical filament for cleaning the substrate surface 91.

[0086] The first lens assembly 30 is arranged between the strong femtosecond laser 10 and the closed cleaning chamber 20, and the laser beam passes through the first lens assembly 30 and enters the closed cleaning chamber 20, and the closed cleaning chamber 20 is made of a transparent material.

[0087] The CCD camera 41 is arranged on the side of the closed cleaning chamber 20 facing the substrate surface 91 and is used to take pictures of the substrate surface 91. The super-depth-of-field microscope 42 is used in combination with the CCD camera 41 to observe the cleaning effect of the gain optical filament on the substrate surface 91. The spectrometer 51 is arranged on the side of the closed cleaning chamber 20 away from the strong femtosecond laser 10 and is located on the light path of the laser beam, and is used to measure the spectral width of the gain optical filament.

[0088] The first lens assembly 30 includes a polarization beam splitter prism 31, a half-wave plate 32, and a first focusing lens 33.

[0089] Specifically, the polarization beam splitter prism 31 is arranged between the strong femtosecond laser 10 and the closed cleaning chamber 20. The half-wave plate 32 is arranged between the polarization beam splitter prism 31 and the strong femtosecond laser 10 and is used to adjust the power of the laser beam. The first focusing lens 33 is arranged between the polarization beam splitter prism 31 and the closed cleaning chamber 20. The second focusing lens 52 is arranged between the spectrometer 51 and the closed cleaning chamber 20. The first ND filter 53 is arranged between the spectrometer 51 and the second focusing lens 52, and the second ND filter 43 is arranged between the CCD camera 41 and the closed cleaning chamber 20.

[0090] In this way, by passing the laser beam through the closed cleaning chamber 20 filled with gain gas 21 and pressurized, a gain optical filament with a longer length and a wider spectral width is formed, and acts on the substrate surface 91 to be cleaned, thereby achieving more efficient cleaning.

[0091] The above described embodiments only express several embodiments of the present application, which are described in more detail and in more detail, but cannot be understood as limiting the scope of the application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application patent should be subject to the appended claims.

Claims

1. A method of gain laser plasma optical filament cleaning for cleaning a substrate, characterized in that, The method comprises the steps of: placing the substrate to be cleaned in a closed cleaning chamber, the surface of the substrate being the surface to be cleaned, the closed cleaning chamber being configured to allow the laser to pass through the area above the surface of the substrate; outputting a laser beam in a direction parallel to the surface of the substrate; the laser beam passes through the air medium in the closed cleaning chamber to form an original light filament acting on the surface of the substrate; a spectrometer is used to measure the first spectral width of the original light filament; delivering gain gas into the closed cleaning chamber and pressurizing, the laser beam passing through the gain gas in the closed cleaning chamber to form a gain light filament for cleaning the surface of the substrate; a spectrometer is used to measure the second spectral width of the gain light filament; the first spectral width is denoted as a, and the second spectral width is denoted as b; when b≥2a, it is determined that the original light filament forms a gain light filament under the action of the gain gas; when b<2a, it is determined that the original light filament does not form a gain light filament under the action of the gain gas, at which time the gas pressure in the closed cleaning chamber is increased by continuously inputting gain gas until a gain light filament is formed; a CCD camera is used to take a picture of the surface of the substrate, and an ultra-deep microscope is used to observe the cleaning effect of the gain light filament on the surface of the substrate; the area of the surface of the substrate cleaned by the gain light filament is denoted as M, and the area of the surface of the substrate cleaned by the gain light filament and having residual stains is denoted as N; when M≥10N, it is determined that the cleaning effect of the gain light filament meets the standard; when M<10N, it is determined that the cleaning effect of the gain light filament does not meet the standard, and the power of the laser beam is then increased until the cleaning effect meets the standard.

2. The gain laser plasma wire cleaning method of claim 1, wherein, The gain gas is any one or a combination of nitrogen, xenon, krypton, and argon.

3. The gain laser plasma thread cleaning method of claim 1, wherein, The gas pressure in the closed cleaning chamber is denoted as H, and the following relationship is satisfied: 0.5 x 10 5 Pa < H < 2 x 10 5 Pa.

4. A gain laser plasma filament cleaning device for implementing the method of any one of claims 1 to 3, characterized in that, The device comprises: a strong femtosecond laser for outputting a laser beam in a direction parallel to the surface of the substrate; a closed cleaning chamber filled with gain gas and pressurized, the laser beam passing through the gain gas in the closed cleaning chamber to form a gain light filament for cleaning the surface of the substrate.

5. The gain laser plasma thread cleaning device of claim 4, wherein, The device further comprises: a first lens assembly arranged between the strong femtosecond laser and the closed cleaning chamber, the laser beam entering the closed cleaning chamber after passing through the first lens assembly; a CCD camera located on the side of the closed cleaning chamber facing the surface of the substrate and used to take a picture of the surface of the substrate; an ultra-deep microscope used in combination with the CCD camera to observe the cleaning effect of the gain light filament on the surface of the substrate; a spectrometer located on the side of the closed cleaning chamber away from the strong femtosecond laser and on the light path of the laser beam, and used to measure the spectral width of the gain light filament; The first lens assembly comprises: a polarization beam splitter prism arranged between the strong femtosecond laser and the closed cleaning chamber; a half-wave plate arranged between the polarization beam splitter prism and the strong femtosecond laser and used to adjust the power of the laser beam; a first focusing lens arranged between the polarization beam splitter prism and the closed cleaning chamber; The closed cleaning chamber is made of a transparent material. The spectrometer is further provided with a second focusing lens between the second focusing lens and the closed cleaning bin. The CCD camera is further provided with a second ND filter between the CCD camera and the closed cleaning bin.

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