Method for determining particle size

Abstract

This provides a method for determining the size of a particle. [Solution] The method includes the steps of: (a) providing a substrate having particles on a nonmetallic surface; (b) having a gap between a metal layer on the particles and a metal layer on the nonmetallic surface; (c) causing at least a portion of the irradiated electromagnetic wave to be absorbed by the metal layer on the particles and another portion of the electromagnetic wave to be reflected by the metal layer on the nonmetallic surface of the substrate, thereby generating reflected electromagnetic waves; (d) receiving the scattered or reflected electromagnetic waves with an array of photodiodes; forming an image including pixels, wherein each pixel in the image corresponds to each photodiode in the array, and the color of each pixel in the image corresponds to the intensity and / or frequency of the electromagnetic wave received by the photodiode corresponding to that pixel; and processing the image to determine the size of the particles.

Description

Technical Field

[0001] The present invention relates to a method for determining the size of particles, particularly a method for determining the size of particles on a non-metallic surface (such as a silicon wafer), and this method comprises providing a metal layer on the particles and the non-metallic surface, irradiating the metal layer on the particles and the metal surface of the substrate with electromagnetic waves, forming an image using the scattered electromagnetic waves or the reflected electromagnetic waves, and processing the image to determine the size of the particles. It is thus included.

Background Art

[0002] It has been found that existing techniques for determining the size of particles are insufficient. The existing techniques involve providing a metal surface on a substrate, then providing particles on the metal surface. Next, a metal layer is provided on the particles and the metal surface of the substrate, the metal layer on the particles and the substrate is irradiated with electromagnetic waves, an image is formed using the scattered electromagnetic waves or the reflected electromagnetic waves, and then the image is processed to determine the size of the particles.

[0003] The drawback in these existing techniques is that in order to determine the size of the particles, a metal surface has to be provided on the substrate and then the particles have to be provided on the metal surface of the substrate (i.e., these existing techniques only function when the particles are provided on a metal surface).

[0004] The existing techniques do not function when adapted to provide a metal layer on particles on a non-metallic surface. This is because the metal layer becomes discontinuous and the gaps in the metal layer cause noise in the image, making it impossible to accurately determine the size of the particles.

[0005] Furthermore, if the thickness of the metal layer is increased to make it more continuous (with fewer gaps), many smaller particles (i.e., particles smaller than the thickness of the metal layer) will be completely embedded within the metal layer. Particles completely embedded within the metal layer do not scatter electromagnetic waves or reflected electromagnetic waves, and therefore do not appear in the image. In other words, a drawback is that only the size of very large particles can be determined. [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to mitigate or eliminate the drawbacks associated with the aforementioned existing technologies. [Means for solving the problem]

[0007] According to the present invention, these objectives are achieved by a method having the steps described in independent claim 1 of this application, and dependent claims describe any features of preferred embodiments.

[0008] Advantageously, the method of the present invention determines the size of particles on a non-metallic surface. This is particularly useful for determining the size of particles on the surface of a substrate such as a silicon wafer.

[0009] Exemplary embodiments of the present invention are disclosed in this description and illustrated in the drawings. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows a flowchart of the process when implementing the method according to the present invention. [Modes for carrying out the invention]

[0011] According to the present invention, a method for determining particle size is provided, which involves the following steps: (a) A step of providing a substrate having a nonmetallic surface having particles on the nonmetallic surface, (b) A process in which a metal layer is deposited on a nonmetallic surface of a substrate and on particles present on a nonmetallic surface of a substrate, such that each particle has a single metal layer and the areas on the nonmetallic surface where there are no particles have a metal layer, wherein for each particle, there is a gap between the metal layer on the particle and the metal layer on the nonmetallic surface. (c) A step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, wherein the electromagnetic waves are scattered by the metal layer on the particle, and scattered electromagnetic waves are generated, or a step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, wherein at least a portion of the electromagnetic waves is absorbed by the metal layer on the particle and another portion of the electromagnetic waves is reflected by the metal layer on the non-metallic surface of the substrate, and reflected electromagnetic waves are generated. (d) A step of receiving scattered electromagnetic waves with an array of photodiodes, or a step of receiving reflected electromagnetic waves with an array of photodiodes, (e) A step of forming an image including pixels, wherein each pixel in the image corresponds to each photodiode in the array, and the color of each pixel in the image corresponds to the intensity and / or frequency of electromagnetic waves received by the photodiode corresponding to that pixel. (f) A step of processing the image in order to determine the size of the particles, Includes.

[0012] For example, in one embodiment, the formed image is a black and white image. In this embodiment, the "color" of a pixel in the formed image is defined by the "intensity" of the electromagnetic waves received by the photodiode corresponding to that pixel (the intensity of the pixel is directly proportional to the number of photons incident on the photodiode corresponding to that pixel). In another embodiment, the formed image is a color image. In this embodiment, the "color" of a pixel in the formed image is defined by the "frequency" and "intensity" of the electromagnetic waves received by the photodiode corresponding to that pixel (for example, a "red" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the range of 430 to 480 THz, and the "intensity" of a "red" pixel is proportional to the number of photons in the frequency range of 430 to 480 THz received by the photodiode corresponding to that pixel; an "orange" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the range of 480 to 510 THz, and the "intensity" of an "orange" pixel is proportional to the number of photons in the frequency range of 430 to 480 THz received by the photodiode corresponding to that pixel The intensity of a pixel is proportional to the number of photons in the 480-510 THz frequency range received by the photodiode. A "yellow" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the 510-540 THz range, and the "intensity" of a "yellow" pixel is proportional to the number of photons in the 510-540 THz frequency range received by the photodiode corresponding to that pixel. A "green" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the 540-580 THz range, and the "intensity" of a "green" pixel is proportional to the number of photons in the 540-580 THz frequency range received by the photodiode corresponding to that pixel.

[0013] For example, the color of a pixel in a formed image can be numerically represented as the number of photons received by the photodiode corresponding to that pixel when only one frequency band is present in the scattered electromagnetic wave (the image can be represented as a two-dimensional matrix). In another example, the color of a pixel in a formed image can be numerically represented as the number of photons received by the photodiode corresponding to that pixel, along with each of the frequency bands, when multiple frequency bands are present in the scattered electromagnetic wave (the image can be represented by a 3-d matrix). In yet another example, when only a single frequency band exists in the scattered electromagnetic wave, or when the scattered electromagnetic wave has different frequency bands but is combined into a single frequency band (for example, by summing the different intensities of different frequency bands), the color of a pixel in the formed image can be simplified to brightness.

[0014] In a preferred embodiment, the method comprises the following steps: (a) A step of providing a substrate having a nonmetallic surface having particles on the nonmetallic surface, (b) A process in which a metal layer is deposited on the non-metallic surface of a substrate and on particles present on the non-metallic surface of a substrate, wherein each particle has a single metal layer, and areas on the non-metallic surface where there are no particles have a metal layer, and for each particle, there exists a gap between the metal layer on that particle and the metal layer on the non-metallic surface. (c) A step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, wherein the electromagnetic waves are scattered by the metal layer on the particle, and scattered electromagnetic waves are generated in each case. (d) A process of receiving scattered electromagnetic waves with an array of photodiodes, (e) A step of forming a dark-field image including pixels, wherein each pixel in the image corresponds to each photodiode in the array, and the color of each pixel in the image corresponds to the intensity and / or frequency of scattered light received by the photodiode corresponding to that pixel, (f) A step of processing the dark-field image to determine the size of the particles, Includes.

[0015] Step (a) Step (a) includes providing a substrate having a non-metallic surface with particles on the non-metallic surface.

[0016] Step (a) preferably includes providing a substrate having a non-metallic surface, and the non-metallic surface preferably includes at least one or more of silicon, SiO2 (glass), quartz, gallium arsenide, Si3N4, TiO2, HfO2, ZnSe, ZnS, ZrO2, Nb2O5, LaTiO3, To2O5, LiF, MgF2, Na3AlF6, photoresist, corrosion inhibitor layer, or adhesion promoter layer. Examples of photoresist include, but are not limited to, polyhydroxystyrene (PHS), acrylic polymer, and phenolic resin. Examples of corrosion inhibitor include, but are not limited to, benzotriazole. Examples of adhesion promoter layer include, but are not limited to, hexamethyldisilazane (HMDS). In the present invention, it should be understood that the non-metallic surface is not limited to requiring at least one or more of silicon, SiO2 (glass), quartz, gallium arsenide, Si3N4, TiO2, HfO2, ZnSe, ZnS, ZrO2, Nb2O5, LaTiO3, To2O5, LiF, MgF2, Na3AlF6, photoresist, corrosion inhibitor layer, or adhesion promoter layer. Rather, the non-metallic surface can include any other suitable non-metallic material / compound.

[0017] The non-metallic surface preferably has a roughness of less than 100 angstroms. Most preferably, the non-metallic surface has a roughness of less than 50 angstroms. Any suitable known means for measuring roughness can be used to determine the roughness of the non-metallic surface. For example, the roughness measurement may be the root mean square measured by an atomic force microscope measured over a certain distance.

[0018] Step (b) Step (b) is a step in which each of the particles has a single metal layer, and a region on the non-metallic surface of the substrate that has no particles is provided with a metal layer, such that a metal layer is deposited on the non-metallic surface of the substrate and on the particles present on the non-metallic surface of the substrate, and for each particle, there is a gap between the metal layer on the particle and the metal layer on the non-metallic surface.

[0019] Step (b) is not limited to requiring the deposition of a metal layer on the entire non-metallic surface of the substrate and / or on all of the particles on the entire non-metallic surface of the substrate. Rather, in alternative embodiments, it should be understood that the layer or metal is deposited only on a selected portion of the non-metallic surface of the substrate and only on the particles on the selected portion of the non-metallic surface of the substrate. For example, the selected portion may be a strip-shaped portion that crosses the non-metallic surface.

[0020] In a preferred embodiment, the metal layer deposited on the non-metallic surface of the substrate and the metal layer deposited on the particles on the non-metallic surface of the substrate contain particles of a plurality of different sizes. In other words, the deposited metal layer is multi-granular. Most preferably, the average size of all the particles in the deposited metal layer is in the range of 10 nm to 100 nm. Some of the particles in the deposited metal layer may have a size larger than 100 nm, and some of the particles in the deposited metal layer may have a size smaller than 10 nm, but the average size of all the particles in the deposited metal layer is preferably in the approximate range of 10 nm to 100 nm. In one embodiment, at least 85% of the particles in the deposited metal layer have a size in the range of 10 nm to 100 nm.

[0021] In one embodiment, the average size of all the particles in the deposited metal layer is in the range of 10 nm to 70 nm. In one embodiment, the average size of all the particles in the deposited metal layer is in the range of 10 nm to 35 nm.

[0022] The average particle size is in the following manner The deposition rate of the metal layer The temperature of the substrate when the metal layer is being deposited It may be affected by one or more of the following. In one embodiment, the substrate temperature when the metal layer is deposited may be in the range of -100°C to 80°C. In one embodiment, the substrate temperature when the metal layer is deposited may be in the range of 0°C to 40°C. In one embodiment, the substrate temperature when the metal layer is deposited may be 20°C. In one embodiment, the substrate temperature is controlled by controlling the temperature of the chuck (the chuck is a component that holds the substrate when the metal layer is deposited). The chuck temperature may be controlled using methods known in the art, such as solid-phase (thermoelectric) heating / cooling or fluid-assisted heating / cooling. Preferably, closed-loop control is used to maintain the substrate temperature within a predetermined temperature range (or maintain the chuck temperature, thereby indirectly maintaining the substrate temperature).

[0023] In this application, the “size” of a particle may be defined by any measurable dimension (including, but not limited to, diameter, length, width, height, etc.). In the most preferred embodiment, each particle is assumed to be spherical, and the “size” is defined by the “diameter,” i.e., the diameter of a spherical particle. Some of the particles whose size is measured may not be spherical, but for non-spherical particles, the size measurement obtained in the present invention is preferably the diameter of a corresponding spherical particle that would produce an equivalent level of scattered electromagnetic radiation upon irradiation.

[0024] In a preferred embodiment, each of the metal layers deposited on the particles is continuous or substantially continuous; in other words, the layers provided on each particle are gapless or substantially gapless. For example, in one embodiment, the layers provided on each particle are gapless (e.g., gaps with a diameter greater than 10 nm). This ensures that each particle has a single mass of metal layer. Preferably, a gap exists between the single mass of metal layer on each particle and the metal layer provided on the non-metallic surface of the substrate, so that the substantially isolated single mass of metal layer on each particle can form an electric dipole that vibrates when excited by a light source, and the gap advantageously functions to produce amplified light scattering and / or amplified light absorption.

[0025] The metal layer deposited on the non-metallic surface of the substrate and the metal layer deposited on the particles contain at least one of W, Co, Ag, Au, Al, and Cu. In one embodiment, the metal layer deposited on the non-metallic surface of the substrate and the metal layer deposited on the particles contain an alloy containing at least 75% by weight of at least one of W, Co, Ag, Au, Al, and Cu. In another embodiment, the metal layer deposited on the non-metallic surface of the substrate and the metal layer deposited on the particles contain an alloy containing at least 90% by weight of at least one of Ag, Au, and Al.

[0026] The metal layers deposited on the non-metallic surface of the substrate and the metal layers deposited on the particles may alternatively include at least one alloy of Au, Ag, Al, Cu, Co, W, Ir, Pt, Pd, Ti, Fe, Cr, Sb, Ce, Dy, Er, Eu, Gd, Ge, Hf, In, Lu, Mg, Mn, Mo, Ni, Nb, Re, Ru, Ta, Zn, Y, V, Sn, Tm, and / or any other suitable metal in an amount of 10% or less.

[0027] In one embodiment, the method further includes defining a minimum size of particles whose size should be determined, wherein the thickness of the metal layer deposited on the non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are greater than the defined minimum size.

[0028] In one embodiment, the non-metallic surface of the substrate is inorganic, and the thickness of the metal layer deposited on the non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 10 nm to 150 nm. Preferably, the thickness of the metal layer deposited on the inorganic non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 20 nm to 80 nm. More preferably, the thickness of the metal layer deposited on the inorganic non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 40 nm to 70 nm. Most preferably, the thickness of the metal layer deposited on the inorganic non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are 50 nm.

[0029] In another embodiment, the nonmetallic surface of the substrate is organic, and the thickness of the metal layer deposited on the organic nonmetallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 20 nm to 160 nm. Preferably, the thickness of the metal layer deposited on the organic nonmetallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 40 nm to 100 nm. More preferably, the thickness of the metal layer deposited on the organic nonmetallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 40 nm to 70 nm. Most preferably, the thickness of the metal layer deposited on the organic nonmetallic surface of the substrate and the thickness of the metal layer deposited on the particles are 50 nm.

[0030] In one embodiment, step (b) includes depositing a metal layer on a non-metallic surface of a substrate and depositing a metal layer on particles at a deposition rate in the range of 0.2 angstroms / second to 50 angstroms / second. Preferably, the deposition rate is in the range of 0.8 angstroms / second to 5 angstroms / second. Most preferably, the deposition rate is 1.2 angstroms / second.

[0031] For example, in the most preferred embodiment, the nonmetallic surface contains silicon, the metal layer deposited on the nonmetallic surface of the substrate and the metal layer deposited on the particles contain silver (Ag), the thickness of the metal layer deposited on the nonmetallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 40 nm to 70 nm (most preferably the thickness is 50 nm), and step (b) includes the steps of depositing a metal layer on the nonmetallic surface of the substrate and depositing a metal layer on particles at a deposition rate in the range of 0.8 angstroms / second to 5 angstroms / second (most preferably the deposition rate is 1.2 angstroms / second).

[0032] Physical vapor deposition (PVD) is preferably used to deposit metal layers on non-metallic surfaces of a substrate and metal layers on particles, such that each particle comprises a metal layer and areas of non-metallic surface without particles also comprises a metal layer. Alternatively, pulsed laser deposition, electron beam deposition, or thermal deposition can be used. In a preferred embodiment, sputtering is used to deposit metal layers on non-metallic surfaces of a substrate and on particles, such that each particle comprises a metal layer and areas of non-metallic surface without particles also comprise a metal layer.

[0033] In one embodiment, sputtering (such as magnetron sputtering), which is a type of physical vapor deposition method, is used to deposit a metal layer on a non-metallic surface of a substrate and on particles, so that each particle is provided with a metal layer and areas of non-metallic layer where there are no particles are provided with a metal layer. In this embodiment in which sputtering is used, the substrate is preferably placed in a chamber. Before starting PVD in the sputtering manner, the pressure in the chamber is lowered to a level below 7E-5mbar (preferably below 5E-5mbar, most preferably below 3E-5mbar). The chamber is then filled with an inert gas / noble gas to a predetermined operating pressure. The inert gas / noble gas is preferably argon (Ar). Next, the pressure inside the chamber is set to a pressure level in the range of 1E-3mbar to 1E-1mbar (preferably, the pressure inside the chamber is set to a pressure level in the range of 1E-2mbar to 8E-2mbar; most preferably, the pressure inside the chamber is set to a pressure level in the range of 2E-2mbar to 7E-2mbar). At this point, sputtering can be started, and the metal is deposited on the non-metallic surface of the substrate, forming a metal layer on the non-metallic surface of the substrate and on each particle. In this embodiment, the metal is ejected from the target into the chamber and onto the non-metallic surface of the substrate.

[0034] Any suitable method known in the art can be used to make the metal layer deposited on the non-metallic surface of the substrate more uniform and the metal layer deposited on each particle more uniform. For example, to make the metal layer deposited on the non-metallic surface of the substrate more uniform and the metal layer deposited on each particle more uniform, the method may further include rotating the substrate as the metal layer is deposited. The substrate may rotate about the center of its geometric shape, or about a point offset from the center of its geometric shape. The axis of rotation may or may not coincide with the center of the target geometric shape. Alternatively or additionally, multiple metal sources may be provided at each source supplying the metal to be deposited during the PVD process. Alternatively or additionally, magnetic field modulation can be used for sputtering. Alternatively or additionally, the substrate may be oriented so as to be offset from parallel orientation during the PVD process.

[0035] Process (c)-(e) Step (c) includes a step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves such that the electromagnetic waves are scattered by the metal layer on the particle, resulting in scattered electromagnetic waves, or a step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves such that at least a portion of the electromagnetic waves are absorbed by the metal layer on the particle and another portion of the electromagnetic waves are reflected by the metal layer on the non-metallic surface of the substrate, resulting in reflected electromagnetic waves. In the most preferred embodiment, step (c) includes a step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves such that the electromagnetic waves are scattered by the metal layer on the particle, resulting in scattered electromagnetic waves.

[0036] In a preferred embodiment, the metal layer is partially irradiated until the entire metal layer (including the metal layer over all particles) is irradiated. However, step (c) is not limited to requiring the irradiation of the entire metal layer over the entire non-metallic surface of the substrate and / or the entire metal layer over all particles on the entire non-metallic surface of the substrate. Rather, in an alternative embodiment, only a portion of the entire metal layer over the non-metallic surface is irradiated, and only a portion of the metal layer over the particles is irradiated. In such embodiments, it should be understood that the metal layer is partially irradiated, but only selected portions (or selected portions) of the entire metal layer are irradiated.

[0037] Step (d) includes receiving scattered electromagnetic waves with an array of photodiodes, or receiving reflected electromagnetic waves with an array of photodiodes. In the most preferred embodiment, step (d) includes receiving scattered electromagnetic waves with an array of photodiodes.

[0038] Step (e) includes the step of forming an image including pixels, where each pixel in the image corresponds to a photodiode in an array, and the color of each pixel in the image corresponds to the intensity and / or frequency of electromagnetic waves received by the photodiode corresponding to that pixel. In the most preferred embodiment, step (e) is the step of forming a dark-field image including pixels, where each pixel in the image corresponds to a photodiode in an array, and the color of each pixel in the image corresponds to the intensity and / or frequency of scattered light received by the photodiode corresponding to that pixel.

[0039] In one embodiment, the formed image is a black and white image. In this embodiment, the "color" of a pixel in the formed image is defined by the "intensity" of the electromagnetic waves received by the photodiode corresponding to that pixel (the intensity of the pixel is directly proportional to the number of photons incident on the photodiode corresponding to that pixel). In another embodiment, the formed image is a color image. In this embodiment, the "color" of a pixel in the formed image is defined by the "frequency" of the electromagnetic waves received by the photodiode corresponding to that pixel (for example, a "red" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the range of 430 to 480 THz, an "orange" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the range of 480 to 510 THz, a "yellow" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the range of 510 to 540 THz, and a "green" pixel means that the frequency of the electromagnetic waves received by the photodiode corresponding to that pixel is in the range of 540 to 580 THz).

[0040] In one embodiment, the electromagnetic wave incident on the photodiode array has a wavelength in the range of 120 nm to 750 nm. In the most preferred embodiment, the electromagnetic wave incident on the photodiode array has a wavelength in the range of 280 nm to 500 nm.

[0041] In one embodiment, the scattered electromagnetic waves include Rayleigh scattered electromagnetic waves.

[0042] In one embodiment, the metal layer on each particle and the metal layer on the non-metallic surface of the substrate are irradiated with electromagnetic waves in a dark-field setting, and at least a portion of the electromagnetic waves are scattered by the metal layer on each particle, resulting in scattered electromagnetic waves (e.g., Rayleigh scattering). The scattered electromagnetic waves are received by an array of photodiodes, and a dark-field image containing pixels is formed, where each pixel in the dark-field image corresponds to each photodiode in the array. The color of each pixel in the dark-field image corresponds to the intensity and / or frequency of the scattered electromagnetic waves received by the photodiode corresponding to that pixel. Photodiodes that receive more scattered electromagnetic waves appear brighter than pixels corresponding to photodiodes that receive less scattered electromagnetic waves. In other words, each pixel in the dark-field image has a color corresponding to the intensity and / or frequency of the scattered electromagnetic waves received by the corresponding photodiode in the array. Electromagnetic waves scattered by the metal layer on each particle generate brightly colored pixels in the dark-field image.

[0043] In the aforementioned embodiment using dark-field imaging, electromagnetic waves are preferably incident on the metal layer on each particle and on the metal layer on the non-metallic surface of the substrate at an angle offset by 90 degrees with respect to the surface plane of the metal layer on the non-metallic surface of the substrate. Preferably, electromagnetic waves are generated by irradiating the metal layer on the particle and on the metal surface with broadband illumination (e.g., white light).

[0044] In each of the embodiments described above, preferably, the metal layer on each particle and the metal layer on the nonmetallic surface of the substrate are irradiated with electromagnetic waves by irradiating the particles and the metal layer on the nonmetallic surface with broadband illumination (e.g., white light).

[0045] In one embodiment, in order to acquire a dark-field or bright-field image, the metal layer on each particle and the metal layer on the non-metallic surface of the substrate are irradiated with electromagnetic waves emitted from multiple different light sources. In other words, the electromagnetic waves irradiating the metal layer on each particle and the metal layer on the non-metallic surface of the substrate are generated by multiple different light sources. In one embodiment, the multiple different light sources include multiple different light sources, each having a different frequency band.

[0046] In one embodiment, the method may further include a pixel binning step, which involves combining multiple pixels into a single pixel. This step is feasible when some predetermined types of photodiodes are used in step (d) and reduces noise in the image formed in step (e).

[0047] Process (f) Step (f) includes processing the formed image to determine the size of the particles. In a preferred embodiment, since the formed image is a dark-field image, step (f) includes processing the dark-field image to determine the size of the particles.

[0048] In this application, it should be understood that the “size” of a particle can be defined by any measurable dimension (including, but not limited to, diameter, length, width, height, etc.). In the most preferred embodiment, it is assumed that each particle is spherical, and the “size” is defined by the “diameter,” i.e., the diameter of a spherical particle. Some of the particles whose size is measured may not be spherical, but the size measurement obtained for non-spherical particles in this invention is preferably the diameter of the corresponding spherical particle that would produce an equivalent level of scattered electromagnetic radiation upon irradiation. Thus, in the preferred embodiment, even if some of the particles whose size is measured are non-spherical, the “size” of these particles is still defined by their “diameter.” Therefore, determining the “size” of a particle in step (f) of this invention preferably means determining the diameter of each particle.

[0049] In a preferred embodiment, the formed image is first processed to reduce noise in the image before performing step (f) of processing the formed image in order to determine the size of the particles. For example, to process the formed image and reduce noise, image smoothing or appropriate noise filtering techniques may be performed on the image.

[0050] In one embodiment, a step of removing the background from the formed image is performed before performing step (f) of processing the formed image to determine the particle size. In this embodiment, first the background of the formed image is estimated using any suitable means, and then the estimated background is subtracted from the formed image. For example, the background of the formed image may be estimated by determining the median color of all pixels in the formed image, or the background of the formed image may be estimated by determining the median color of one or more clusters of pixels in the formed image (each cluster may have any suitable number of pixels - for example, a cluster may have 1000 pixels). In another embodiment, the background of the formed image may be determined in advance in a calibration step, which is A process for providing a substrate having a nonmetallic surface free of particles on the nonmetallic surface, A process of depositing a metal layer on a non-metallic surface of a substrate. A process of irradiating a metal layer on a non-metallic surface of a substrate with electromagnetic waves. The process of receiving arbitrary scattered electromagnetic waves with an array of photodiodes. A process for forming an image containing pixels, wherein each pixel in the image corresponds to a photodiode in an array, the color of each pixel in the image corresponds to the intensity and / or frequency of electromagnetic waves received by the photodiode corresponding to that pixel, and since no particles are present on the non-metallic surface, the formed image defines an estimate of the background. This includes. In another example, the background of the formed image may be estimated by fitting a multidimensional plane (2D for monochromatic (black and white) images, 3D for multicolor (multiple frequency bands of electromagnetic waves) images) to the formed image, preferably using an optimization algorithm such as constrained least squares with constraints on higher derivatives. It should be noted that the derivative is the change in color of a pixel and therefore represents the change in the number of photons from scattered light rays incident on the photodiode corresponding to that pixel. Furthermore, it should be noted that particles usually result in higher derivatives in color. Therefore, particles are retained by fitting a design with a sufficiently small derivative and using this design as the background. Preferably, a small derivative means a derivative smaller than half the derivative from the smallest particle to be detected. The derivative from the smallest particle to be detected is preferably obtained by the following steps: A step of depositing such particles onto a metal surface free of other particles, and a step of depositing a metal layer on the particles and on the non-metallic surface of the substrate, A process of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, The process involves receiving arbitrary scattered electromagnetic waves with an array of photodiodes, A step of forming an image containing pixels, wherein each pixel in the image corresponds to a photodiode in an array, the color of each pixel in the image corresponds to the intensity and / or frequency of electromagnetic waves received by the photodiode corresponding to that pixel, and the mean derivative of the particles in the image is calculated. It should be noted that this is estimated by [the relevant factor].

[0051] The process of processing the image formed to determine the size of the particles is, Preferably, the following steps, (i) A step of inputting an image into a predetermined model, wherein the predetermined model defines different combinations of predetermined image features and defines a predetermined particle size associated with each of the different combinations of predetermined image features, (ii) A step of extracting features from an image, and a step of identifying a predetermined combination of image features that matches the extracted features, (iii) A step of outputting a predetermined particle size associated with an identified combination of predetermined image features that match the extracted features, wherein the output predetermined particle size corresponds to the size of the particles shown in the image. Includes.

[0052] For example, in one embodiment, a color threshold is defined, and clusters of pixels in the image formed in step (e) are defined. Here, each pixel in a cluster has a color above the color threshold, and for each cluster, the number of pixels constituting that cluster is counted. A predetermined calibration curve is provided that relates the number of pixels to the size of the particles (in other words, the curve is a graph of the number of pixels against the size of the particles). (It should be noted that this predetermined calibration curve is preferably determined in a calibration step in which an image of particles of known size is taken up, thereby producing an image with clusters of pixels, where each pixel in a cluster has a color above the color threshold. Since the number of pixels in the cluster for each particle is recorded, a calibration curve showing the relationship between the number of pixels and the size of the particles can be formed.) The particle size on the calibration curve is associated with the counted number of pixels and corresponds to the size of the particle represented by the cluster of pixels. In this way, the size of each particle can be determined. The color threshold may be selected based on the smallest particle size for which the size is determined. This embodiment is preferably used for large-sized particles (typically, large-sized particles are particles with a size (e.g., diameter) larger than 50 nm; however, it should be understood that the size of large-sized particles depends on variable factors such as irradiation intensity, optical system efficiency, photodiode efficiency, and photodiode size). This is because large particles cause multiple pixels to exceed the threshold in a cluster (and in some cases even the photodiode may become saturated, and thus information may be lost). The number of pixels exceeding the threshold in a cluster is related to the particle size.

[0053] Larger particles (e.g., particles larger than 50 nm) scatter more electromagnetic waves. Therefore, larger particles result in brighter pixels (colors represented by a higher number of photons) in the formed image. Smaller particles (for example, typically small particles are those smaller than 50 nm in size (e.g., diameter). However, it should be understood that what constitutes a small particle depends on variable factors such as illumination intensity, optical system efficiency, photodiode efficiency, and photodiode size) scatter less, resulting in less scattered electromagnetic waves and consequently fewer pixels in the formed image with colors exceeding the color threshold. Therefore, in one embodiment, the color of pixels in the formed image is used to estimate the particle size. For example, in one embodiment, a lookup table is provided with particle sizes associated with pixel colors as entries. This lookup can be determined in a calibration step, in which images of particles of known sizes are formed and the intensity of pixels in those images is recorded so that different pixel color values ​​corresponding to each different particle size in the lookup table are associated. Embodiments of the present invention proceed through the following steps: A step of defining the minimum particle size for which the size should be determined, The process involves retrieving the pixel color value associated with the particle size corresponding to the defined minimum particle size from a predetermined lookup table, Furthermore, the extracted pixel color values ​​correspond to the grain size.

[0054] High background signals appearing on the formed image may resemble the shapes of particles within the image. Therefore, this can be a source of noise that impairs the results of the method. Thus, it is preferable to adapt particle detection when high background signals are expected in the image. For example, this can be done by raising the threshold for the smallest particle size to be detected.

[0055] In one embodiment, the formed image is processed to estimate the background signal. Preferably, this processing is carried out in the following steps: (i) A step of inputting an image into a predetermined model, wherein the predetermined model defines different combinations of predetermined image features and defines a predetermined background signal associated with each of the different combinations of predetermined image features, (ii) A step of extracting features from an image, and a step of identifying a predetermined combination of image features that matches the extracted features, (iii) A step of outputting a background signal associated with an identified combination of predetermined image features that match the extracted features, wherein the output background signal corresponds to background signal characteristics shown in the image, This includes, preferably, characteristics presumed to be due to background signals are ignored in particle detection and size estimation.

[0056] For example, the median color of an image is calculated and used to estimate the background signal. One embodiment of the present invention may further include the step of retrieving from a predetermined lookup table the smallest particle that is associated with the estimated background signal and whose size can be reliably detected.

[0057] Larger particles scatter more electromagnetic waves, and this increased scattering can introduce noise (sometimes called an "interference pattern") into nearby pixels in the resulting image, which can be mistaken for other particles. Therefore, in one embodiment, the method further includes the following steps: A step of defining a threshold particle size, wherein this threshold particle size defines the minimum particle size that a particle must have in order to constitute a large particle. A process of identifying clusters of pixels in the formed image that represent large-sized particles, A step of removing pixels from the formed image that are within a predetermined threshold distance from the identified cluster, Includes.

[0058] In other embodiments, the color derivative between adjacent pixels is used to determine whether a pixel represents an image of a particle or noise. For example, if a pixel is identified as having a color significantly above a color threshold, and all pixels adjacent to that identified pixel have colors significantly below the color threshold, it can be assumed that the color of the identified pixel is due to noise and not to the presence of a particle (i.e., not to electromagnetic waves scattered by a particle). Preferably, if the difference between the color of the identified pixel and the colors of the pixels adjacent to the identified pixel exceeds a predetermined threshold, it is assumed that the color of the identified pixel is due to noise and not to the presence of a particle. On the other hand, if the difference between the color of the identified pixel and the colors of the pixels adjacent to the identified pixel is below a predetermined threshold, the identified pixel and its surrounding adjacent pixels are considered to represent a particle (i.e., due to electromagnetic waves scattered by a particle), and in this case, the pixels adjacent to the identified pixel are considered when determining the size of the particle. For example, a predetermined calibration curve is provided that correlates the color of a pixel with the size of a particle. Therefore, the intensities of the identified pixel and its surrounding and adjacent pixels are summed, and then the size of the corresponding particle is determined from the pixel color using a predetermined calibration curve related to the particle size. It should be noted that this predetermined calibration curve is preferably determined in a calibration curve step in which an image of particles of known size is taken up, and for each particle, the intensities of the pixels representing each particle in the image are summed, and the sum of the pixel intensities provides a calibration curve related to the particle size.

[0059] In one embodiment, the image formed in step (e) corresponds to only a portion of the entire surface area of ​​the substrate; therefore, in this embodiment, steps (i) to (iii) are repeated for each of the multiple images until an image of the entire surface area of ​​the substrate has been processed. For example, in one embodiment, when the metallic layer on the particles and the metallic layer on the non-metallic surface are irradiated, the array of photodiodes is moved to different positions on the substrate. This allows the array of photodiodes to receive electromagnetic waves scattered in different areas of the substrate, and images of different areas of the substrate are captured. These steps are repeated until an image covering the entire surface area of ​​the substrate is captured. In another embodiment, the image formed in step (e) is a single image corresponding to the entire surface area of ​​the substrate; therefore, steps (i) to (iii) only need to be performed once for the single image.

[0060] In another embodiment, the method further includes the step of using the determined particle sizes to determine the particle size distribution. This can be done after the sizes of multiple particles have been determined. The distribution can then be expressed as the number of particles present within a given size range (for example, determining that there are "X" particles within a given size range of 8 nm and 12 nm, and "Y" particles within a given size range of 13 nm to 20 nm).

[0061] In another embodiment, the method further includes estimating the location of particles on a non-metallic surface of a substrate using the image formed in step (e). In this embodiment, the relative position of the array of photodiodes to the substrate is known (for example, by having an array of photodiodes maintained at a predetermined physical position when performing step "d") while the array of photodiodes is receiving scattered electromagnetic waves. Knowing the relative position of the array of photodiodes to the substrate and parameters of the array of photodiodes, such as focal length, the physical location of the depicted particles on the substrate in the formed image can be determined from the position of the pixels depicting the particles in the formed image. In yet another embodiment, the method includes identifying pixels in the formed image that indicate reference markers having known physical locations on the substrate. By using these reference marker pixels as references, the physical location of the depicted particles on the substrate can be determined from the position of the pixels in the formed image relative to the pixels indicating the reference markers.

[0062] If the image formed in step (e) is used to estimate the position of particles on the non-metallic surface of the substrate, the size distribution on the substrate surface may be determined.

[0063] In one embodiment, the image formed in step (e) is used to estimate the position of particles on a non-metallic surface, and the method is as follows: The process involves moving the Raman laser source above the position of the particle, A step comprising irradiating a metal layer at the location where particles are present with a Raman laser emitted from a Raman laser source, wherein the Raman laser is scattered by the metal layer in such a way that scattered light is produced, and the scattered light includes both Raman scattered light and Rayleigh scattered light. The process involves receiving scattered light with an objective lens, A step of filtering out Rayleigh scattered light from the received scattered light, and a step of allowing only Raman scattered light to pass through the objective lens, A process of using an optical dispersion grating to disperse Raman scattered light at different frequencies, A process in which dispersed Raman scattered light is received by a linear photodiode having multiple pixels, wherein each pixel is associated with a predetermined different optical frequency, and A step of determining the number of photons per pixel, wherein the number of photons per pixel corresponds to the light intensity for a specific frequency, A step of plotting the number of acquired photons per frequency to form a Raman spectrum, The method may further include the step of using Raman spectra to characterize the material of the particles. This characterization may be performed using a reference spectral library. The reference spectral library may be constructed based on previous experiments in which reference spectra based on known particles coated on a surface were established.

[0064] According to a further aspect of the present invention, an assembly is provided that is operable to perform any one of the embodiments of the method described above. This assembly comprises at least, A station comprising means for depositing metal layers on a non-metallic surface and on particles present on a non-metallic surface of a substrate, such that each particle has a metal layer and regions of the non-metallic surface without particles also have a metal layer, wherein for each particle, a gap exists between the metal layer on the particle and the metal layer on the non-metallic surface. A station comprising means for irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, thereby scattering the electromagnetic waves by the metal layer on the particle and generating scattered electromagnetic waves, or a station comprising means for irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, thereby absorbing at least a portion of the electromagnetic waves by the metal layer on the particle and reflecting another portion of the electromagnetic waves by the metal layer on the non-metallic surface of the substrate and generating reflected electromagnetic waves, A station equipped with an array of photodiodes that can receive scattered electromagnetic waves or reflected electromagnetic waves. A station comprising means for forming an image including pixels, wherein each pixel in the image corresponds to each photodiode in the array, and the color of each pixel in the image corresponds to the intensity and / or frequency of electromagnetic waves received by the photodiode corresponding to that pixel, A station equipped with means for processing the formed image in order to determine the size of the particles, It is equipped with.

[0065] Various modifications and variations of the described embodiments of the present invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. For example, in one embodiment, the method comprises providing a substrate having a nonmetallic surface having particles on the nonmetallic surface, in other words, particles already present on the nonmetallic surface. This may be, for example, a silicon wafer being provided, with particles (or fragments) present on the surface of the wafer. In another embodiment, a substrate having a clean nonmetallic surface is provided, and particles are coated onto the clean nonmetallic surface. Such an embodiment may comprise the steps of bringing a fluid sample containing particles into contact with the nonmetallic surface of the substrate, and removing the fluid that has been in contact with the nonmetallic surface from the nonmetallic surface so that only the particles present in the fluid sample remain on the nonmetallic surface of the substrate, thereby providing a substrate having a nonmetallic surface having particles on the nonmetallic surface. This embodiment may further comprise the step of rotating the substrate as the fluid sample is brought into contact with the nonmetallic surface of the substrate. This embodiment may further comprise the step of evaporating the fluid sample from the nonmetallic surface.

[0066] While the present invention is described in relation to certain preferred embodiments, it should be understood that the claimed invention should not be excessively limited to such specific embodiments.

Claims

1. In a method for determining particle size, The method involves the following steps: (a) A step of providing a substrate having a nonmetallic surface having particles on the nonmetallic surface, (b) A process in which a metal layer is deposited on a non-metallic surface of a substrate and on particles present on the non-metallic surface of a substrate, wherein each particle has a single metal layer, and areas on the non-metallic surface that do not have particles have a metal layer, and for each particle, a gap exists between the metal layer on that particle and the metal layer on the non-metallic surface. (c) A step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, wherein the electromagnetic waves are scattered by the metal layer on the particle, and scattered electromagnetic waves are generated in each case, or a step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, wherein at least a portion of the electromagnetic waves is absorbed by the metal layer on the particle and another portion of the electromagnetic waves is reflected by the metal layer on the non-metallic surface of the substrate, and reflected electromagnetic waves are generated. (d) A step of receiving scattered electromagnetic waves with an array of photodiodes, or a step of receiving reflected electromagnetic waves with an array of photodiodes, (e) A step of forming an image including pixels, wherein each pixel in the image corresponds to each photodiode in the array, and the color of each pixel in the image corresponds to the intensity and / or frequency of electromagnetic waves received by the photodiode corresponding to that pixel. (f) A step of processing the image in order to determine the size of the particles, Methods that include...

2. The above method involves the following steps: (a) A step of providing a substrate having a nonmetallic surface having particles on the nonmetallic surface, (b) A process in which a metal layer is deposited on the non-metallic surface of a substrate and on particles present on the non-metallic surface of a substrate, wherein each particle has a single metal layer, and areas on the non-metallic surface where there are no particles have a metal layer, and for each particle, there exists a gap between the metal layer on that particle and the metal layer on the non-metallic surface. (c) A step of irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, wherein the electromagnetic waves are scattered by the metal layer on the particle, and scattered electromagnetic waves are generated in each case. (d) The process of receiving scattered electromagnetic waves with an array of photodiodes. (e) A step of forming a dark-field image including pixels, wherein each pixel in the image corresponds to each photodiode in the array, and the color of each pixel in the image corresponds to the intensity and / or frequency of scattered light received by the photodiode corresponding to that pixel. (f) A step of processing the dark-field image to determine the size of the particles, The method according to claim 1, including the method described in claim 1.

3. Step (a) includes providing a substrate having a non-metallic surface, The non-metallic surface is silicon, SiO ２ (glass), quartz, gallium arsenide, Si ３ N ４ , TiO ２ , HfO ２ , ZnSe, ZnS, ZrO ２ , Nb ２ O ５ , LaTiO ３ , To ２ O ５ , LiF, MgF ２ , Na ３ AlF ６ including at least one or more of a photoresist, a corrosion inhibitor layer, or an adhesion promoter layer The method according to claim 1 or 2.

4. Metal layers deposited on the non-metallic surface of the substrate and metal layers deposited on particles, W, Co, Ag, Au, Al, Cu Including at least one of the following: The method according to any one of claims 1 to 3.

5. The method includes a step of defining the minimum size of the particle whose size should be determined, The thickness of the metal layer deposited on the non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are greater than the defined minimum size. The method according to any one of claims 1 to 4.

6. The non-metallic surface of the substrate is inorganic, and the thickness of the metal layer deposited on the non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 10 nm to 150 nm. The method according to any one of claims 1 to 5.

7. The non-metallic surface of the substrate is organic, and the thickness of the metal layer deposited on the non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 20 nm to 160 nm. The method according to any one of claims 1 to 6.

8. Step (b) includes depositing a metal layer on a non-metallic surface of a substrate and depositing a metal layer on particles at a deposition rate in the range of 0.2 angstroms / second to 50 angstroms / second. The method according to any one of claims 1 to 7.

9. The metal layer deposited on the non-metallic surface of the substrate and the metal layer deposited on the particles contain silver (Ag). The thickness of the metal layer deposited on the non-metallic surface of the substrate and the thickness of the metal layer deposited on the particles are in the range of 40 nm to 70 nm. Step (b) includes depositing a metal layer on a non-metallic surface of a substrate and depositing a metal layer on particles at a deposition rate in the range of 0.8 angstroms / second to 5 angstroms / second. The method according to any one of claims 1 to 8.

10. Electromagnetic waves have wavelengths in the range of 180 nm to 750 nm. The method according to any one of claims 1 to 9.

11. The process of processing the image formed to determine the size of the particles is, (i) A step of inputting an image into a predetermined model, wherein the predetermined model defines different combinations of predetermined image features and defines a predetermined particle size associated with each of the different combinations of predetermined image features, (ii) A step of extracting features from an image, and a step of identifying a predetermined combination of image features that matches the extracted features, (iii) A step of outputting a predetermined particle size associated with an identified combination of predetermined image features that match the extracted features, wherein the output predetermined particle size corresponds to the size of the particles shown in the image. including, The method according to any one of claims 1 to 10.

12. The image formed in step (e) corresponds to only a portion of the entire surface area of ​​the substrate, and steps (i) to (iii) are repeated for each of the multiple images until the image of the entire surface area of ​​the substrate is processed or until the image of a selected portion of the surface area of ​​the substrate is processed, or The image formed in step (e) is a single image corresponding to the entire surface area of ​​the substrate, and steps (i) to (iii) are performed once for a single image, or the image formed in step (e) is a single image corresponding to a selected portion of the surface area of ​​the substrate, and steps (i) to (iii) are performed once for a single image. The method according to claim 11.

13. This includes using the formed image to estimate the position of particles on a non-metallic surface. The method according to any one of claims 1 to 12.

14. The above method involves the following steps: The process involves moving the Raman laser source above the position of the particle, A step comprising irradiating a metal layer at the location where particles are present with a Raman laser emitted from a Raman laser source, wherein the Raman laser is scattered by the metal layer in such a way that scattered light is produced, and the scattered light includes both Raman scattered light and Rayleigh scattered light. The process involves receiving scattered light with an objective lens, A step of filtering out Rayleigh scattered light from the received scattered light, and a step of allowing only Raman scattered light to pass through the objective lens, A process of using an optical dispersion grating to disperse Raman scattered light at different frequencies, A process in which dispersed Raman scattered light is received by a linear photodiode having multiple pixels, wherein each pixel is associated with a predetermined different optical frequency, and A step of determining the number of photons per pixel, wherein the number of photons per pixel corresponds to the light intensity for a specific frequency, A step of plotting the number of acquired photons per frequency to form a Raman spectrum, The method according to claim 13, further comprising:

15. The method according to claim 14, further comprising the step of using a Raman spectrum to characterize the material of the particles.

16. The deposited metal layer contains particles of multiple different sizes. The average size of all particles in the metal layer is in the range of 10 nm to 100 nm. The method according to any one of claims 1 to 15.

17. Using physical vapor deposition, a metal layer is deposited on the non-metallic surface of the substrate and on the particles, such that each particle has a metal layer, and the non-metallic surface regions where no particles are present also have a metal layer. For each particle, a gap exists between the metal layer on the particle and the metal layer on the metal surface. The method according to any one of claims 1 to 16.

18. An assembly operable to perform the method described in any one of claims 1 to 17, The assembly in question is, A station comprising means for depositing metal layers on a non-metallic surface and on particles present on a non-metallic surface of a substrate, such that each particle has a metal layer and regions of the non-metallic surface without particles also have a metal layer, wherein for each particle, a gap exists between the metal layer on the particle and the metal layer on the non-metallic surface. A station comprising means for irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, thereby scattering the electromagnetic waves by the metal layer on the particle and generating scattered electromagnetic waves, or a station comprising means for irradiating a metal layer on a particle and a metal layer on a non-metallic surface of a substrate with electromagnetic waves, thereby absorbing at least a portion of the electromagnetic waves by the metal layer on the particle and reflecting another portion of the electromagnetic waves by the metal layer on the non-metallic surface of the substrate and generating reflected electromagnetic waves, A station equipped with an array of photodiodes that can receive scattered electromagnetic waves or reflected electromagnetic waves. A station comprising means for forming an image including pixels, wherein each pixel in the image corresponds to each photodiode in the array, and the color of each pixel in the image corresponds to the intensity and / or frequency of electromagnetic waves received by the photodiode corresponding to that pixel, A station equipped with means for processing the formed image in order to determine the size of the particles, An assembly comprising:

Images