CN112447160A - Silencing structure, silencing device, equipment comprising motion table and photoetching equipment - Google Patents

Silencing structure, silencing device, equipment comprising motion table and photoetching equipment Download PDF

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CN112447160A
CN112447160A CN201910816608.4A CN201910816608A CN112447160A CN 112447160 A CN112447160 A CN 112447160A CN 201910816608 A CN201910816608 A CN 201910816608A CN 112447160 A CN112447160 A CN 112447160A
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sound
silencing
cavity
micro
layer
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CN112447160B (en
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杜碧
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Shanghai Micro Electronics Equipment Co Ltd
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Shanghai Micro Electronics Equipment Co Ltd
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/161—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general in systems with fluid flow
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form
    • B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
    • B32B3/266—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70691—Handling of masks or workpieces
    • G03F7/70716—Stages
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/70858—Environment aspects, e.g. pressure of beam-path gas, temperature
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
    • G10K11/04—Acoustic filters ; Acoustic resonators
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/162—Selection of materials
    • G10K11/168—Plural layers of different materials, e.g. sandwiches
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/10—Properties of the layers or laminate having particular acoustical properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Abstract

The invention relates to a silencing structure, a silencing device, equipment comprising a motion platform and photoetching equipment. The silencing structure comprises a frame, an airflow channel is formed inside the frame, and a resistive silencing unit, a shunt silencing unit and a micro-perforated silencing unit are arranged inside the airflow channel; the resistive silencing unit comprises at least one metal layer and at least one layer of sound absorption material, the sound absorption material is arranged between the inner wall of the airflow channel and the metal layer, and the sound absorption material covers all the inner walls of the airflow channel; the flow dividing and silencing unit comprises a flow dividing column and a flow dividing cavity formed in the airflow channel, and the flow dividing column is transversely arranged in the flow dividing cavity to divide the flow dividing cavity into at least two channels with different lengths; the micro-perforated silencing unit comprises at least one layer of micro-perforated plate and an accommodating cavity formed in the airflow channel, wherein the at least one layer of micro-perforated plate is transversely arranged in the accommodating cavity, and a cavity is reserved behind the micro-perforated plate; the purpose of this is to improve the sound damping effect and to reduce the disturbance of the gas flow.

Description

Silencing structure, silencing device, equipment comprising motion table and photoetching equipment
Technical Field
The present invention relates to the field of noise control technologies, and in particular, to a noise reduction structure, a noise reduction apparatus, an apparatus including a motion stage, and a lithographic apparatus.
Background
Lithographic apparatus is commonly used in the manufacture of Integrated Circuits (ICs). A lithographic apparatus is a machine that applies a desired pattern onto a silicon wafer, which can be imaged onto a target portion (e.g., comprising part of, one or more dies) on a substrate (e.g., a silicon wafer). With the ever-increasing demand for high precision and high resolution, positioning between components of a lithographic apparatus, such as a mask table to hold a patterning device (e.g., a mask), a projection system, and a workpiece table to carry a silicon wafer, needs to be very precise.
In general, in a lithographic apparatus, since a short-term image error is caused by a structural vibration, the overall dynamic performance is reduced and controlled, and therefore, the error is reduced to a lower level, which requires a better dynamic stability of the apparatus frame. One of the main factors causing the structure to vibrate is the acoustic noise loading. The acoustic noise Load (Acoustics Load) is defined as the effect of the pressure of air as a function of time. According to the test of the photoetching machine at the client side, the disturbance of sound and noise transmitted in a clean air environment to the internal world accounts for about 40 percent of the total vibration disturbance, and particularly, the disturbance to the interior of the photoetching machine is increased when the workpiece table moves at a high speed. Thus, noise and air flow disturbances can have a significant impact on the internal environment of the lithographic apparatus.
More specifically, the noise mainly includes environmental noise, electrical noise, and movement noise of the mask stage and the workpiece stage. Taking the noise of the motion table as an example, three kinds of noise can be generated, including (1) rigid motion noise, which is caused by rigid motion acceleration, and the frequency is far lower than 150Hz, which can affect overlay alignment accuracy (overlay); (2) structural vibration noise, with frequencies higher than 150Hz, can affect overlay alignment accuracy and attenuation (fading); (3) the aerodynamic noise, which is generated by air resistance, is mostly higher than 500 Hz. Therefore, in order to improve the lithographic accuracy and resolution of the lithographic apparatus, the noise loading and gas flow disturbances must be reduced or even eliminated.
However, the noise reduction method provided in the prior art includes active noise reduction and passive noise reduction, and does not have the problem of better solution for eliminating noise in each frequency band, for example, passive noise reduction is poor in control effect on low-frequency band noise, and active noise reduction only can eliminate noise in a fixed frequency band, and cannot meet the complex working condition of noise.
Disclosure of Invention
The invention aims to provide a silencing structure, a silencing device, equipment comprising a motion table and photoetching equipment, which have better silencing effects on low, medium and high-frequency noises, can reduce airflow disturbance and improve the dynamic stability of equipment operation, and simultaneously, the size of a cavity of an airflow channel can meet the use requirement in a compact space.
In order to achieve the purpose, the invention provides a silencing structure, which comprises a frame, wherein an airflow channel is formed inside the frame, and a resistive silencing unit, a shunt silencing unit and a micro-perforated silencing unit are arranged inside the airflow channel;
the resistive noise elimination unit comprises at least one metal layer and at least one layer of sound absorption material, wherein the at least one layer of sound absorption material is arranged between the inner wall of the airflow channel and the at least one metal layer, and covers all the inner walls of the airflow channel;
the flow dividing and silencing unit comprises at least one flow dividing column and a flow dividing cavity formed in the airflow channel, the at least one flow dividing column is transversely arranged in the flow dividing cavity to divide the flow dividing cavity into at least two channels, and the lengths of the at least two channels are unequal;
the micro-perforated silencing unit comprises at least one layer of micro-perforated plate and an accommodating cavity formed in the airflow channel, wherein the at least one layer of micro-perforated plate is transversely arranged in the accommodating cavity, and a cavity is reserved behind the micro-perforated plate.
Optionally, the resistive sound attenuation unit comprises a metal layer and a sound absorbing material, and the metal layer is a composite metal plate.
Optionally, the resistive noise elimination unit includes two metal layers and a layer of sound absorption material, and the frame directly constitutes one of the metal layers, one layer of sound absorption material is disposed between the two metal layers, and the two metal layers are all composite metal plates.
Optionally, the calculation formula of the muffling volume of the resistive muffling unit is as follows:
Figure BDA0002186521700000031
wherein: TL1 is noise elimination volume; f is the perimeter of the cross section of the airflow channel; s is the cross-sectional area of the airflow channel; l is the effective length of the airflow channel; and alpha is sound absorption coefficient.
Optionally, the flow dividing silencing unit comprises a flow dividing column, and the flow dividing column is made of sound absorption materials.
Optionally, the cross-sectional shape of the splitter column is circular, diamond, or oval.
Optionally, the flow dividing column divides the flow dividing cavity into a first channel and a second channel, the second channel is longer than the first channel, and the lengths of the second channel and the first channel meet the following requirements:
Figure BDA0002186521700000032
wherein: l1 is the length of the first channel; l2 is the length of the second channel; n is any natural number; λ is the incident acoustic wavelength.
Optionally, the cross-sectional shape of the second channel is trapezoidal or V-shaped, and/or the cross-sectional shape of the first channel is rectangular.
Optionally, the micro-perforated sound attenuation unit includes two layers of micro-perforated plates, the two layers of micro-perforated plates are arranged at intervals in the accommodating cavity, and the cavities are reserved between the adjacent micro-perforated plates and the frame and the nearest micro-perforated plate.
Optionally, sound absorbing material is provided in the cavity between adjacent microperforated panels and/or sound absorbing material is provided in the cavity between the frame and the nearest microperforated panel.
Optionally, the cross-sectional shape of the accommodating cavity is rectangular.
Optionally, the formula for the noise reduction of the single-layer micro-perforated plate is:
Figure BDA0002186521700000033
Figure BDA0002186521700000034
Figure BDA0002186521700000035
Figure BDA0002186521700000041
wherein: TL3 is noise elimination volume; f. ofrIs the resonance frequency of the microperforated panel; g is the air conductivity; v is the volume of the cavity behind the plate; t is the thickness of the micro-perforated plate; s is the cross-sectional area of the cavity; d is the equivalent diameter of the hole on the micro-perforated plate; f is the frequency of the incident sound wave; and c is medium sound velocity.
Optionally, the effective length of the air flow channel from the inlet to the outlet is between 20 and 50 mm.
Optionally, the thickness of the micro-perforated plate is less than or equal to 1.0mm, and the aperture of an opening on the micro-perforated plate is 0.5-1.0 mm.
In order to achieve the above object, the present invention further provides a silencing apparatus, including a metal base plate, wherein a plurality of silencing structures as described in any one of the above are formed on the metal base plate, and an airflow channel of each silencing structure penetrates through the metal base plate in a thickness direction.
Optionally, a plurality of the sound attenuating structures are uniformly distributed on the metal bottom plate.
To achieve the above object, the present invention also provides an apparatus comprising a moving table, the apparatus further comprising a sound-deadening device according to any one of the preceding claims, one or more of the sound-deadening devices being installed around the moving table.
To achieve the above object, the present invention further provides a lithographic apparatus comprising a motion stage and a noise reduction device according to any of the previous claims, one or more of the noise reduction devices being mounted around the motion stage.
Optionally, the motion stage is a workpiece stage for carrying a silicon wafer.
Optionally, the motion stage is a mask stage for carrying a reticle.
The silencing structure adopts the principle of throttling decompression and resistive and resistant composite silencing to solve the problems of airflow disturbance and sound noise load in the equipment comprising the moving table, this arrangement can achieve a high noise reduction amount, particularly, low, medium, and high frequency noise reduction characteristics, and therefore, has better noise reduction effect on low, medium and high frequency noise, reduces the vibration influence of noise load on the structure, furthermore, the throttling effect of the microperforated plate is used to reduce the pressure of gas flow disturbances due to moving stages (e.g., a workpiece stage in a lithographic apparatus), consume some of the acoustic energy, thereby reducing the influence caused by the disturbance of the air flow, improving the stability of the structure near the high-speed moving part, finally improving the dynamic stability of the equipment comprising the moving table, such as dynamic stability of the lithographic apparatus, to improve the accuracy of the operation of the apparatus and to improve product quality.
Drawings
The drawings are included to provide a better understanding of the invention and are not to be construed as unduly limiting the invention. Wherein:
FIG. 1 is a longitudinal cross-sectional view of a sound attenuating structure provided in accordance with one embodiment of the present invention;
fig. 2 is a schematic diagram of a three-layer structure of a resistive muffler unit according to an embodiment of the present invention;
FIG. 3 is a top view of the sound attenuating structure shown in FIG. 1;
FIG. 4 is a schematic structural diagram of a muffler device according to an embodiment of the present invention;
fig. 5 is a view of a sound-damping device used in an apparatus including a motion stage according to an embodiment of the present invention.
In the figure:
10-a sound-deadening structure;
10' -a frame;
11-an air flow channel;
111-an inlet;
112-an outlet;
12-a resistive muffler unit;
121-an outer layer;
122-an intermediate layer;
123-inner layer;
13-a shunt silencing unit;
131-a split-flow column;
132-a distribution chamber;
132 a-a first channel;
132 b-a second channel;
14-a micro-perforated sound attenuation unit;
141-a microperforated plate;
142-a housing chamber;
20-a silencer;
21-a metal base plate;
30-equipment;
31-a box body;
32-a motion stage;
33-inner space.
Detailed Description
As background, in order to improve the lithographic accuracy and resolution of a lithographic apparatus, the noise loading and gas flow disturbances must be reduced or even eliminated.
In order to solve the noise problem, a noise reduction method using a resonator (or called resonator) is provided in the prior art. A single resonator can be seen to be made up of several acoustic elements that differ in their acoustic action. The specific principle is that air in the opening pipe and near the pipe orifice vibrates along with sound waves, so that the pressure in the cavity changes along with the air, and a compliant element is formed. The air in the cavity vibrates with the sound waves to a certain extent and also has a certain sound quality. The air vibrates and rubs on the wall surface of the opening, and the acoustic effect of the air is acoustic resistance. When the frequency of the incident sound wave approaches the natural frequency of the resonator, the air column of the throat produces strong vibrations, during which the sound energy is dissipated by overcoming the frictional resistance. Conversely, when the frequency of the incident sound wave is far from the natural frequency of the resonator, the resonator vibrates very weakly, so that the sound absorption effect is very small, the sound absorption coefficient of the visible resonator varies with the frequency, and the highest sound absorption coefficient occurs at the resonant frequency. For example, three resonators have been designed at present, and the pipe orifice has a plurality of different volumes, so that the sound absorption frequency can be expanded, and the volume of the cavity can be adjusted through an active device, so that the sound absorption frequency of the resonators can be dynamically adjusted. However, the sound-absorbing material used in the acoustic resistance at the opening has a small control effect on low-frequency noise, and if the low-frequency noise needs to be controlled well, a very long wavelength must be involved, at this time, the sound-absorbing material with sufficient thickness needs to be provided, and the volume of the muffler is very large, so that the cost is obviously very high, and particularly, after the thickness of the sound-absorbing material reaches a certain degree, the sound-absorbing effect cannot be enhanced by increasing the thickness, and the sound-absorbing frequency is limited. In more detail, if a sound of a certain frequency is to resonate, its wavelength cannot exceed 4 times the length of the resonance cavity, and if a low-frequency noise is to be controlled, the wavelength needs to be long, which inevitably requires the volume of the resonance cavity to be large, but the compactness of the internal structure of the lithographic apparatus does not provide such a practical condition.
In addition, in order to solve the Noise problem, the prior art provides another Noise reduction method, i.e. an Active Noise Control (ANC) technique, which is implemented based on the young's interference theory. Generally, the conventional noise control method is effective for controlling high frequency noise, but is not effective for controlling low frequency noise. In the early 20 th century and 30 s, the concept of active control was developed, and the principle of active control was mainly to use transducers to emit noise with equal sound pressure and opposite direction to offset the original noise, so as to achieve the purpose of noise reduction, and the control noise was obtained from the original noise measurement by electronic means. The secondary noise source uses electronic circuit and loudspeaker, and the noise power emitted by the secondary noise source must be greater than that of the original noise source to realize control. As before, various types of active mufflers (or loudspeakers) have been designed to reduce the effect of noise on the lithographic apparatus. The projection system may be affected by acoustic, air flow and other disturbances due to movement of the workpiece and mask stages, and the effect of these disturbances on the lithographic apparatus may be reduced by arranging a series of loudspeakers. Specifically, the noise in the gas bath pipeline is detected through a sensor, the loudspeaker is driven through a control system, secondary noise is generated, original noise is offset, and the influence caused by the gas bath noise is reduced. The plurality of sensors and the plurality of speakers are controlled by a control system to reduce the influence of noise on the projection objective. In addition, external structures such as a base frame radiate noise under excitation, and the active muffler is arranged near the mainboard to absorb the noise so as to reduce the influence of the noise on the mainboard. By arranging microphones in the vicinity of the horizontal calibrator (PSE) as well as the vertical calibrator, the influence of noise on the measuring instrument can be reduced under control of the control system. However, the active noise elimination technology only eliminates noise for a single frequency, and the noise elimination is limited, so that the active noise elimination technology is not suitable for being applied to a noise-complicated environment.
Aiming at one or more of the problems, the invention provides a silencing structure, which aims to reduce the problems of low, medium and high frequency noise and airflow disturbance by combining the principles of throttling depressurization, resistive silencing and resistive silencing, thereby reducing the structural vibration caused by noise load, improving the dynamic stability of the whole machine, simultaneously reducing the influence caused by airflow disturbance, improving the stability of the structure near a high-speed moving part, finally improving the working precision of equipment and improving the product quality.
The invention is described in further detail below with reference to the figures and the detailed description. Advantages and features of the present invention will become more apparent from the following description, which is given to enable those skilled in the art to fully and effectively understand the nature of the present invention and to repeatedly implement the technical solution described above, while understanding the content of the present invention. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise. The term "plurality" is generally used in a sense that it includes two or more.
Fig. 1 is a longitudinal sectional view of a sound-deadening structure according to an embodiment of the present invention. As shown in fig. 1, the sound deadening structure 10 of the present embodiment includes a frame 10 '(preferably, a metal frame), and a gas flow passage 11 is formed inside the frame 10', the gas flow passage 11 having an inlet 111 and an outlet 112. Preferably, the effective length L of the gas flow channel 11 is between 20mm and 50mm, and in this range, a gas flow channel with a shorter length can be provided, which is beneficial to reducing the volume of the noise reduction structure 10, so as to form a microstructure, and further facilitate the use in an environment with a compact space, such as the use inside a lithography machine.
The silencing structure 10 further comprises a resistive silencing unit 12, a shunt silencing unit 13 and a micro-perforated silencing unit 14 which are all arranged in the airflow channel 11. The resistive noise elimination unit 12 is disposed on the inner wall of the airflow channel 11 and covers all the inner walls of the airflow channel 11, that is, the inner wall of the airflow channel 11 is completely covered by the resistive noise elimination unit 12, so that the resistive noise elimination unit 12 extends from the inlet 111 to the outlet 112 of the airflow channel, and the noise transmitted along the airflow channel 11 is completely attenuated in impedance, thereby achieving the purpose of noise elimination. Here, the resistive noise elimination unit 12 eliminates noise by using the combined action of the resistive sound absorption material and the metal structure, and the noise elimination effect of the middle-high frequency band noise is good.
The resistive noise elimination unit 12 comprises at least one metal layer and at least one layer of sound absorption material, wherein the at least one metal layer is arranged far away from the inner wall of the airflow channel 11, and the at least one layer of sound absorption material is arranged close to the inner wall of the airflow channel 11. For example, the resistive muffler unit 12 includes a metal layer and a layer of sound absorbing material, the layer of sound absorbing material being adhered to the inner wall of the airflow passage 11, and the metal layer being wrapped around the outside of the sound absorbing material. In other embodiments, the resistive muffler unit 12 includes two metal layers and a sound absorbing material, the sound absorbing material is disposed between the two metal layers, and the frame 10 'preferably directly forms a metal layer, i.e., a sound absorbing material is disposed between the frame 10' and another metal layer, which is convenient to manufacture. Furthermore, the metal layer is a composite metal plate, and the noise reduction effect is good. The sound absorption material is a porous sound absorption material, and the porous sound absorption material comprises but is not limited to glass fiber, low-carbon steel wire mesh, felt or foamed plastic and the like. However, the resistive muffler unit 12 may also have a structure with more than three layers, and the metal layer and the sound-absorbing material are sequentially staggered, such as the metal layer, the sound-absorbing material, the metal layer, and the sound-absorbing material are sequentially arranged.
In more detail, fig. 2 is a schematic structural diagram of the resistive muffler unit 12 according to an embodiment of the present invention, wherein the resistive muffler unit 12 has a three-layer structure, namely an outer layer 121, an intermediate layer 122 and an inner layer 123, the outer layer 121 and the inner layer 123 are both made of composite metal plates, the intermediate layer 122 is made of porous sound-absorbing material, and preferably, the frame 10' is directly configured as the inner layer 123, and the outer layer 121 directly contacts with the airflow.
In practice, since the sound absorption coefficient of the porous sound absorption material is relatively easy to measure, the sound absorption coefficient is used to approximate the sound attenuation amount of the resistive sound attenuation. Further, the noise elimination volume of the resistive noise elimination can be calculated according to the race formula, specifically as follows:
Figure BDA0002186521700000091
in formula (1): TL1 is noise elimination volume; f is the perimeter of the cross section of the airflow channel; s is the cross section area of the airflow channel, namely the cross section perpendicular to the length direction of the airflow channel; l is the effective length of the airflow channel; and alpha is sound absorption coefficient.
The flow dividing silencing unit 13 comprises a flow dividing column 131 and a flow dividing cavity 132, the flow dividing cavity 132 is formed in the airflow channel 11 and is optionally arranged close to the inlet 111, and at least one flow dividing column 131 is arranged in the flow dividing cavity 132 in a transverse mode. At least one of the flow dividing columns 131 divides the flow dividing cavity 132 into at least two channels, so that the airflow is divided into at least two paths to flow out after entering the flow dividing cavity 132, and the divided sound waves meet at the outlet of the flow dividing cavity 132 due to the change of the phase and then mutually offset to achieve the purpose of reactive sound attenuation. That is, the shunt noise elimination unit 13 utilizes the impedance change caused by the resonant cavity in the process of sound wave transmission to generate the interference of sound waves, so as to achieve the purpose of noise elimination. Preferably, the number of the flow dividing column 131 is one, so that the flow dividing chamber 132 is divided into two passages, i.e., a first passage 132a and a second passage 132b, and the length of the first passage 132a is shorter than that of the second passage 132b, in this case, the noise reduction requirement can be basically satisfied, and the structure is simple.
Taking two channels as an example, referring to fig. 1, the requirements to be met by interferometric muffling are as follows:
Figure BDA0002186521700000092
in formula (2): l1 is the length of the first channel; l2 is the length of the second channel; n is any natural number, such as 0, 1, 2, or (1); λ is the incident acoustic wavelength.
That is, if the divided sound waves need to interfere with each other and cancel each other, the condition of equation (2) needs to be satisfied, for example:
when the value of n is 0, the reaction solution is,
Figure BDA0002186521700000101
when the value of n is 1, the reaction solution is,
Figure BDA0002186521700000102
the cross-sectional shape of the splitter 131 is not limited, and may be, for example, circular, diamond, oval, or the like, preferably a shape that helps to guide the airflow. Further, the splitter 131 is made of a porous sound absorbing material, such as the aforementioned glass fiber or foam plastic, and is used for absorbing sound at a high frequency and a middle frequency of 360 degrees, so as to further improve the sound attenuation effect.
The cross-sectional shapes of the two channels of the distribution chamber 132 are not limited, for example, the cross-sectional shape of the first channel 132a is rectangular, the cross-sectional shape of the second channel 132b is V-shaped or trapezoidal, and the inner wall of the second channel 132b may or may not be smooth. Furthermore, the present invention does not require the cross-sectional shape and relative size of the two channels.
The micro-perforated sound attenuation unit 14 includes at least one micro-perforated plate 141 and a housing chamber 142, the housing chamber 142 is formed in the airflow channel 11, and optionally, the housing chamber 142 is disposed adjacent to the outlet 112. At least one layer of micro-perforated plate 141 is transversely arranged in the accommodating cavity 142, and two opposite sides along the length or width direction are fixedly connected with the accommodating cavity 142, but the fixed connection mode is not required. And at least one layer of microperforated panels 142 leaves a cavity behind the panel. Namely, the micro-perforated plate sound absorption structure is utilized by the micro-perforated plate sound absorption unit 14 to achieve the purpose of noise reduction and elimination.
More specifically, the thickness of the micro-perforated plate 141 is less than or equal to 1.0mm, and the micro-perforated plate 141 is provided with a proper amount of openings with the diameter of less than 1mm (preferably between 0.5 mm and 1.0 mm), and the perforation rate p meets the requirement (generally 1% to 3%), and a certain cavity is reserved behind each layer of micro-perforated plate 141. The material of the micro-perforated plate 141 is a metal material, and may be, for example, a steel plate, a stainless steel plate, or an alloy plate. The micro-perforated plate sound absorption structure is a sound absorption element with high sound resistance and low sound quality. The micro-perforated sound-absorbing unit 14 may be a single-layer micro-perforated plate structure, or may be a two-layer or more micro-perforated plate structure. In order to ensure high sound absorption in a wide frequency band, the micro-perforated sound attenuation unit 14 is preferably of a two-layer or more micro-perforated plate structure, that is, the micro-perforated sound attenuation unit 14 includes two or more layers of micro-perforated plates 141, and the multiple layers of micro-perforated plates 141 are arranged in the accommodating cavity 142 at intervals.
And the size of the cavity between the micro-perforated plate 141 and the frame 10' and between the adjacent micro-perforated plates 141 is different according to the frequency band to be absorbed, for example, when absorbing low frequency, medium frequency and high frequency, the size of the cavity is 150-200 mm, 80-120 mm and 30-50 mm in sequence. In addition, the depth of the front cavity of the double-layer structure is generally smaller than that of the rear cavity, the ratio of the depths of the front cavity to the rear cavity is not more than 1:3, and the perforation rate of a layer of the micro-perforated plate at the front part close to the airflow is higher than that of the rear layer. It should be understood that the microperforated plate that makes up the gas flow channels is referred to as the first layer. Between the first microperforated plate layer and its frame 10', an additional microperforated plate layer is provided, called the second layer. The space occupied between the first and second layers is called the front cavity, and the vertical distance between the two is called the front cavity depth. The space occupied between the second layer of microperforated panels and the frame is called the back cavity, and the vertical distance between the two is called the back cavity depth. The cavity depth of the front cavity and the cavity depth of the rear cavity are determined according to the resonance frequency of the noise reduction required. Furthermore, the end surface of the accommodating cavity 142 is rectangular, so that the processing is convenient. Furthermore, a porous sound-absorbing material is arranged in a cavity (namely a front cavity) between the adjacent layers of the micro-perforated plates, or a porous sound-absorbing material is arranged in a cavity (namely a rear cavity) between the frame 10' and the nearest micro-perforated plate, or a porous sound-absorbing material (such as a porous rock wool material) is arranged in both the front cavity and the rear cavity, so that the silencing effect of the medium-high frequency noise is further improved.
With reference to fig. 1, in the present embodiment, the accommodating cavities 142 are symmetrically distributed on two sides of the airflow channel 11, and two layers of micro-perforated plates are disposed in the upper and lower chambers of the accommodating cavity 142. The specific noise elimination principle is that when sound waves are incident to the micro-perforated plate 141, air rubs in the small holes to generate enough sound resistance, so that the purpose of noise elimination is achieved. The advantages are high sound absorption coefficient, wide sound absorption frequency band, low air flow regeneration noise and easy control.
For porous sound attenuation, the main measures of sound absorption performance are: acoustic impedance and acoustic absorption coefficient.
(1) Acoustic impedance Z
Figure BDA0002186521700000111
Wherein: r is the acoustic resistivity:
Figure BDA0002186521700000112
ω m is the acoustic reactance rate:
Figure BDA0002186521700000113
Figure BDA0002186521700000114
wherein: omega is the angular frequency of the incident wave, c is the medium sound velocity (such as the sound velocity in air), n is the air viscosity coefficient, rho is the air density, p is the aperture ratio on the micro-perforated plate, t is the thickness of the micro-perforated plate, d is the equivalent diameter of the aperture on the micro-perforated plate, and H is the depth of the cavity behind the plate.
(2) Sound absorption coefficient α N:
Figure BDA0002186521700000121
the sound absorption coefficient alpha N is a function of the structural parameters and the frequency, when the system resonates, the acoustic reactance is zero, the sound absorption coefficient reaches the maximum, and the corresponding frequency is the resonant frequency fr。
(3) The formula for calculating the noise elimination amount of the single-layer micro-perforated plate is as follows:
Figure BDA0002186521700000122
Figure BDA0002186521700000123
Figure BDA0002186521700000124
Figure BDA0002186521700000125
wherein: f. ofrFor micro-punctureThe resonant frequency of the orifice plate; g is the air conductivity; v is the volume of the cavity behind the plate; s is the cross section area of the cavity (namely the cross section area of the containing cavity), and d is the equivalent diameter of the opening on the micro-perforated plate; f is the frequency of the incident sound wave; and c is medium sound velocity.
From the above calculation, it can be seen that the diameter d of the small hole on the microperforated panel mainly affects the acoustic resistivity, and has little effect on the resonant frequency, and the depth H of the resonant cavity behind the panel has the greatest effect on the resonant frequency, and the larger H, the lower the resonant frequency. Therefore, the resonance frequency can be increased by increasing the perforation rate, the maximum sound absorption coefficient is also slightly increased, and the influence on the sound absorption characteristic is not large when the thickness t of the microperforated plate is more than 1.0 mm.
Fig. 3 is a top view of the sound attenuating structure shown in fig. 1. As shown in FIG. 3, the width L3 of the frame 10 'is determined according to the actual noise reduction requirement, the sound wave flow can be adjusted by increasing the width L3 of the frame 10', and the larger the width L3 is, the larger the sound cavity is, the frequency of the control noise can be further covered by the low-frequency noise.
Fig. 4 is a schematic structural diagram of a silencer according to an embodiment of the present invention. As shown in fig. 4, the present embodiment further provides a silencing apparatus 20, which includes a metal base plate 21, and a plurality of silencing structures 10 are formed on the metal base plate 21, the number of the silencing structures 10 is set as required, so that after the gas passes through the silencing apparatus 20, the gas pressure is reduced to a critical value to the maximum extent, so that the silencing apparatus obtains a better silencing effect, and better reduces the disturbance of the gas flow, and meanwhile, the thickness of the metal base plate 21 can be reduced, thereby reducing the processing difficulty and the processing cost. It should be understood that the metal bottom plate 21 directly forms the frame of the sound-deadening structure 10, so that a plurality of sound-deadening structures 10 are directly prepared on the metal bottom plate 21, and a plurality of air flow passages 11 penetrating through the bottom plate in the thickness direction are formed on the metal bottom plate 21, and each air flow passage 11 is provided with the resistive sound-deadening unit 12, the shunt sound-deadening unit 13, and the micro-perforated sound-deadening unit 14.
Obviously, the noise reduction structure 10 is distributed on the metal bottom plate with a certain thickness, which is equivalent to that a plurality of slits are formed on the orifice plate, so that the throttling function is achieved, the impact pressure of the airflow is reduced, and the purposes of throttling, pressure reduction and noise reduction are achieved. In practical application, the silencer 20 is also conveniently installed in the equipment needing noise reduction through the metal bottom plate 21. In more detail, the silencer 20 is manufactured using the throttle pressure reduction principle. The flow cross section is properly designed according to the magnitude of the air flow, so that the pressure can be reduced to the critical value to the maximum extent when high-pressure air passes through the metal bottom plate 21. Because the airflow noise power is in direct proportion to the high order of the pressure drop, if the pressure abrupt change evacuation is changed into the pressure gradual reduction and then evacuation in the silencer, the flow speed in the silencer can be controlled under the critical flow speed, the shock wave noise cannot be generated, the pressure is reduced to the critical value to the maximum extent, the silencer obtains better silencing effect, and meanwhile, the wall thickness of the metal base plate required by design is greatly reduced, so the processing difficulty is reduced, and the processing cost is reduced.
Furthermore, the pressure at the inlet of each silencing structure is generally given, so that when the pressure is higher, in order to obtain the desired silencing value, the pressure before the gas enters the small hole is designed to be proportionally reduced by the pressure P1 at the inlet of the silencer; assuming a critical pressure ratio of q (q < 1), we can obtain:
P2＝P1*q (12)
in formula (12): p2 is the pressure at the muffler outlet; p1 is the pressure at the muffler inlet; q is the critical pressure ratio.
According to the gas state equation, the continuity equation and the critical flow velocity formula, the through-flow section of the throttling device can be known and can be calculated according to the following formula:
Figure BDA0002186521700000131
in the formula (13), S1-represents the throttle area (cm 2);
g-is the mass flow (t/h) of the exhaust gas;
v1-is the specific volume of the gas before throttling (m 3/kg);
p1-is the absolute pressure of the gas before throttling (kg/cm 2);
mu-to ensure the correction coefficient of the cross section, 1.2-2.0 is usually adopted.
Further, the noise elimination amount of throttling and pressure reduction is calculated according to the following formula:
Figure BDA0002186521700000141
in formula (14): k is an empirical correction coefficient, and 0.9 plus or minus 0.2 is taken;
p1-exhaust pressure before the inlet of the silencing structure, kg/cm 2;
p2-exhaust pressure at the outlet of the silencing structure, kg/cm 2;
p0-absolute pressure of ambient atmosphere kg/cm2, 1.033kg/cm 2;
n-the number of the silencing structures, namely the number of the silencers on the metal bottom plate.
Furthermore, according to the structural characteristics of the metal base plate, the sound-deadening structures 10 are preferably uniformly distributed, for example, a circumferential array or a linear array is arranged on the metal base plate with a certain thickness, so that a certain sound-deadening amount can be achieved. The total noise elimination calculation can be estimated by algebraically adding the noise elimination:
Figure BDA0002186521700000142
wherein: VL is the total silencing volume of the silencing device; VLiThe value of i is 1 to M for the ith silencing structure.
Fig. 5 is a schematic structural diagram of an apparatus including a motion stage according to an embodiment of the present invention. As shown in fig. 5, the embodiment of the present invention further provides an apparatus 30, which includes a box 31, wherein a plurality of motion stages 32 are installed in the box 31, and the motion stages 32 can rotate and/or move. Since noise and airflow disturbance are generated during movement, muffling devices 20 are installed around the moving tables 32, such as the upper, left, right, and other areas, to reduce or eliminate noise and airflow disturbance by one or more muffling devices 20, so as to improve the stability of the operation of the apparatus, especially the stability of the structure near the high-speed moving parts, improve the working accuracy of the apparatus, and improve the product quality.
The box 31 may form an outer space for mounting the motion stage 32, and the apparatus 30 further includes an inner space 33, in which a precision machining process, such as photolithography, is performed in the inner space 33, thereby isolating the inner space from the outer space and ensuring cleanliness of the inner space.
Further, the apparatus 30 may be a lithographic apparatus, which further includes a mask stage for loading a mask and a workpiece stage for loading a silicon wafer. Furthermore, one or more silencing devices 20 are arranged near the workpiece table, and/or one or more silencing devices 20 are arranged near the mask table, so that structural vibration caused by noise to the photoetching equipment is reduced, the dynamic stability in the photoetching equipment is improved, meanwhile, the influence caused by airflow disturbance is reduced, pressure pulsation is reduced, the stability of structures near high-speed moving parts is improved, the photoetching precision is improved, and the photoetching quality is improved.
It should be noted that the sound-absorbing materials are selected from pollution-free sound-absorbing materials, and are safe to use and environment-friendly.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (20)

1. A silencing structure is characterized by comprising a frame, wherein an airflow channel is formed inside the frame, and a resistive silencing unit, a shunt silencing unit and a micro-perforated silencing unit are arranged inside the airflow channel;
the resistive noise elimination unit comprises at least one metal layer and at least one layer of sound absorption material, wherein the at least one layer of sound absorption material is arranged between the inner wall of the airflow channel and the at least one metal layer, and covers all the inner walls of the airflow channel;
the flow dividing and silencing unit comprises at least one flow dividing column and a flow dividing cavity formed in the airflow channel, the at least one flow dividing column is transversely arranged in the flow dividing cavity to divide the flow dividing cavity into at least two channels, and the lengths of the at least two channels are unequal;
the micro-perforated silencing unit comprises at least one layer of micro-perforated plate and an accommodating cavity formed in the airflow channel, wherein the at least one layer of micro-perforated plate is transversely arranged in the accommodating cavity, and a cavity is reserved behind the micro-perforated plate.
2. The sound attenuating structure of claim 1, wherein the resistive sound attenuating unit comprises a metal layer and a layer of sound absorbing material, and the metal layer is a composite metal plate.
3. The sound attenuating structure of claim 1, wherein the resistive sound attenuating unit comprises two metal layers and a layer of sound absorbing material, and the frame directly forms one of the metal layers, the layer of sound absorbing material being disposed between the two metal layers, both metal layers being a composite metal sheet.
4. The silencing structure of claim 1, wherein the calculation formula of the silencing amount of the resistive silencing unit is as follows:
Figure FDA0002186521690000011
wherein: TL1 is noise elimination volume; f is the perimeter of the cross section of the airflow channel; s is the cross-sectional area of the airflow channel; l is the effective length of the airflow channel; and alpha is sound absorption coefficient.
5. The sound attenuating structure according to claim 1, wherein the flow dividing sound attenuating unit includes a flow dividing pillar, and the flow dividing pillar is made of a sound absorbing material.
6. The sound-deadening structure according to claim 5, wherein the cross-sectional shape of the branching column is circular, rhombic, or elliptical.
7. The sound attenuating structure as claimed in claim 5, wherein the flow dividing pillar divides the flow dividing chamber into a first passage and a second passage, the second passage being longer than the first passage, and the lengths of the second passage and the first passage satisfy the following requirements:
Figure FDA0002186521690000021
wherein: l1 is the length of the first channel; l2 is the length of the second channel; n is any natural number; λ is the incident acoustic wavelength.
8. The sound-attenuating structure as claimed in claim 7, wherein the cross-sectional shape of the second passage is trapezoidal or V-shaped, and/or the cross-sectional shape of the first passage is rectangular.
9. The silencing structure of claim 1, wherein the microperforated silencing unit comprises two layers of microperforated plates, the two layers of microperforated plates are arranged in the accommodating cavity at intervals, and a cavity is reserved between each of the microperforated plates in adjacent layers and the frame and the nearest microperforated plate.
10. The sound-attenuating structure according to claim 9, characterized in that the cavity between the microperforated panels of adjacent layers is provided with sound-absorbing material and/or the cavity between the frame and the nearest microperforated panel is provided with sound-absorbing material.
11. The sound-deadening structure according to claim 9, wherein the sectional shape of the housing chamber is a rectangle.
12. The sound-deadening structure according to claim 1, wherein the sound-deadening amount of the single-layer micro-perforated plate is calculated by the formula:
Figure FDA0002186521690000022
Figure FDA0002186521690000023
Figure FDA0002186521690000024
Figure FDA0002186521690000025
wherein: TL3 is noise elimination volume; f. ofrIs the resonance frequency of the microperforated panel; g is the air conductivity; v is the volume of the cavity behind the plate; t is the thickness of the micro-perforated plate; s is the cross-sectional area of the cavity; d is the equivalent diameter of the hole on the micro-perforated plate; f is the frequency of the incident sound wave; and c is medium sound velocity.
13. The sound-deadening structure according to any one of claims 1 to 12, wherein an effective length of the gas flow passage from the inlet to the outlet is between 20 and 50 mm.
14. The sound-deadening structure according to any one of claims 1 to 12, wherein the microperforated sheet has a thickness of 1.0mm or less and the diameter of the opening in the microperforated sheet is 0.5 to 1.0 mm.
15. A noise-reducing device comprising a metal base plate having a plurality of noise-reducing structures according to any one of claims 1 to 14 formed thereon, wherein a gas flow passage of each of the noise-reducing structures penetrates the metal base plate in a thickness direction.
16. The acoustic abatement apparatus of claim 15, wherein a plurality of the acoustic abatement structures are uniformly distributed on the metal base plate.
17. An apparatus comprising a motion stage, comprising a silencing device according to claim 15 or 16, one or more of said silencing devices being mounted around said motion stage.
18. A lithographic apparatus comprising a motion stage and a silencing device according to claim 15 or 16, one or more of said silencing devices being mounted around said motion stage.
19. The lithographic apparatus of claim 18, wherein the motion stage is a workpiece stage for carrying a silicon wafer.
20. The lithographic apparatus of claim 18, wherein the motion stage is a mask stage for carrying a reticle.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB495576A (en) * 1937-05-22 1938-11-16 Fernand Jiles Joseph Servais Improvements in and relating to silencers for gaseous currents
GB1420356A (en) * 1973-02-27 1976-01-07 Steel Grip Mfg Co Inc Flugger Silencers
GB2017211A (en) * 1978-01-05 1979-10-03 Glynwed Screws & Fastenings Lt Engine Exhaust Silencer
CN101520600A (en) * 2008-02-27 2009-09-02 中国科学院微电子研究所 Method for preparing transparent nano imprinting template based on X-ray exposure technology
CN104575482A (en) * 2014-12-29 2015-04-29 浙江天晨胶业股份有限公司 Air silencer

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB495576A (en) * 1937-05-22 1938-11-16 Fernand Jiles Joseph Servais Improvements in and relating to silencers for gaseous currents
GB1420356A (en) * 1973-02-27 1976-01-07 Steel Grip Mfg Co Inc Flugger Silencers
GB2017211A (en) * 1978-01-05 1979-10-03 Glynwed Screws & Fastenings Lt Engine Exhaust Silencer
CN101520600A (en) * 2008-02-27 2009-09-02 中国科学院微电子研究所 Method for preparing transparent nano imprinting template based on X-ray exposure technology
CN104575482A (en) * 2014-12-29 2015-04-29 浙江天晨胶业股份有限公司 Air silencer

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