Device, equipment and method for fixing long-strip mirror of double-frequency laser interferometer

Abstract

The invention provides a dual-frequency laser interferometer long-strip mirror fixing device, equipment and a method, and aims to solve the problem of dynamic deformation caused by fixation of two ends of a long-strip mirror in ultra-precision motion platform equipment, a rigid container is arranged, and dynamic compensation is realized by using air film rigidity and air pressure difference; the bending trend of the long-strip mirror raises the air pressure in the container to generate a reverse force to inhibit deformation; when the device is static or at a constant speed, air pressure is reduced, and external atmospheric pressure provides supporting force. According to the method, an intermediate mechanical fixing point is not needed, the over-constraint problem is avoided, high precision and installation convenience are achieved, and the method is suitable for an ultra-precision platform in the fields of semiconductor manufacturing, precision detection and the like.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor manufacturing equipment, and particularly relates to a fixing method, device and equipment for a long mirror of a dual-frequency laser interferometer. Background Art

[0002] In the field of semiconductor manufacturing, the positioning accuracy of the wafer stage of a lithography machine directly determines the limit of the chip feature size. As two core positioning technologies, laser interferometers and grating interferometers have significant differences in their technical routes, which significantly affect the performance of the equipment. Among them, the laser interferometer uses the wavelength of helium-neon laser (about 633 nm) as a reference, and realizes nanoscale positioning by measuring the phase difference of the dual-frequency laser. It has the advantage of being traceable to the International System of Units (SI) and is widely used in ultra-precision equipment such as extreme ultraviolet (EUV) and deep ultraviolet (DUV) lithography machines. However, the fixing method of the core component of this technical route - the long mirror, still faces the dual challenges of dynamic stability and installation accuracy.

[0003] Currently, the long mirrors of dual-frequency laser interferometers (usually with a length of more than 300 mm) generally adopt a three-point support structure with rigid compression at both ends and suspension in the middle. When the moving stage accelerates and decelerates (the acceleration can reach more than 5 m / s²), this design will cause the following problems: uneven bending moment distribution: the fixed points at both ends of the long mirror bear the main load, and the middle area generates bending moment concentration due to suspension, resulting in micron-level flexural deformation of the mirror surface; dynamic response lag: the traditional fixing method cannot compensate for the deformation in real time, resulting in a phase difference between the displacement signal measured by the interferometer and the actual movement, which is ultimately converted into a positioning error.

[0004] However, the traditional solutions still have great limitations: 1. Using adhesives such as epoxy resin to completely bond the bottom surface of the long mirror to the base, but about 1-3% volume shrinkage will occur during the curing process of the adhesive, resulting in residual stress on the mirror surface and affecting the initial installation accuracy. In addition, the Young's modulus of the adhesive (E ≈ 2-4 GPa) is much lower than that of glass (E ≈ 70 GPa), and creep deformation is likely to occur under long-term thermal cycling. 2. Adding mechanical fulcrums (such as ball head plungers) in the middle of the long mirror can reduce the flexural deformation, but it will introduce overconstraint problems: freedom conflict: the length change caused by thermal expansion of the long mirror is restricted by the mechanical fulcrum, resulting in thermal stress. 3. Nonlinear contact stiffness: The contact stiffness of the mechanical fulcrum does not match the stiffness of the long mirror itself, which is likely to cause the amplification effect of high-frequency vibration. Summary of the Invention

[0005] Based on this, it is necessary to provide a fixing device, equipment and method for a long mirror of a dual-frequency laser interferometer in view of the above technical problems.

[0006] In the first aspect, the present application provides a fixing device for a long mirror of a dual-frequency laser interferometer, which is characterized by comprising: A long strip mirror, the two ends of which are supported by sliding tables; At least one rigid container, fixed on the sliding table and located on one or both sides of the middle suspended area of the long strip mirror; An air pressure damping cavity is formed between the long strip mirror and the rigid container; the distance of the air pressure damping cavity is 5-10 microns.

[0007] In one embodiment, the surface of the rigid container is distributed with communicating micropores, and the internal pores communicate with each other.

[0008] In one embodiment, the rigid container includes a horizontally oriented container and a vertically oriented container, which are respectively located in the horizontal and vertical suspended areas of the long strip mirror.

[0009] In one embodiment, the rigid container is made of ceramic, metal or composite material.

[0010] In one embodiment, the ceramic is alumina, silicon nitride or zirconia; In one embodiment, the metal is sintered stainless steel or aluminum alloy; In one embodiment, the composite material is carbon fiber reinforced silicon carbide.

[0011] In one embodiment, the micropore diameter of the rigid container is 20-100 microns, and the porosity is 30%-60%.

[0012] In one embodiment, the air film stiffness of the air pressure damping cavity is .

[0013] In one embodiment, the rigid container is fixed on the sliding table by gluing, welding or mechanical fastening.

[0014] In a second aspect, the present application further provides an ultra-precision motion platform device, which is characterized by including: An XY motion sliding table; A dual-frequency laser interferometer system; The long strip mirror fixing device described in the above embodiment, and the long strip mirror reflects laser to determine the position of the sliding table.

[0015] In a third aspect, the present application further provides a method for fixing a dual-frequency laser interferometer long strip mirror, which is characterized by including the following steps: Fix the two ends of the long strip mirror on the sliding table; Set a rigid container in the middle suspended area of the long strip mirror to form an air pressure damping cavity with a distance of 5-10 microns; Use the air pressure difference of the air pressure damping cavity to dynamically suppress the deformation of the long strip mirror during the acceleration and deceleration of the sliding table.

[0016] The fixing device, equipment and method for the long mirror of the dual-frequency laser interferometer add an elastic damping device in the middle of the long mirror. The device is jointly composed of the long mirror and a rigid container, and realizes dynamic compensation by using the air film stiffness and air pressure difference: when the sliding table accelerates, the bending trend of the long mirror causes the air pressure in the container to rise, generating a reverse force to inhibit deformation; when it is stationary or moving at a constant speed, the air pressure decreases, and the external atmospheric pressure provides a supporting force. Through the double-container structure in the horizontal and vertical directions, bidirectional dynamic stability is achieved. This method does not require intermediate mechanical fixing points, avoids overconstraint problems, has both high precision and simplicity of installation, and is applicable to ultra-precision motion platforms in fields such as semiconductor manufacturing and precision detection. The core innovation lies in the integrated design of the air pressure damping device and the long mirror, effectively solving the contradiction between dynamic deformation and installation complexity of traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 Schematic diagram of the structure of the fixing device for the long mirror of the dual-frequency laser interferometer in an embodiment of the present invention; Figure 2 Schematic diagram of the structure of the fixing device for the long mirror of the dual-frequency laser interferometer in an embodiment of the present invention; Figure 3 Layout diagram of the air pressure damping cavity in the suspended area in the middle of the fixing structure in an embodiment of the present invention; Figure 4 Schematic diagram of the deformation and air pressure compensation principle of the long mirror during the acceleration of the sliding table in an embodiment of the present invention; Figure 5 Enlarged schematic diagram of the microporous structure in an embodiment of the present invention.

[0019] In Figures 1 to 5 , 1: Sliding table; 2: Long mirror; 3: Rigid container in the horizontal direction; 4: Rigid container in the vertical direction; 5, 6: Fixed seat; 7: Laser DETAILED DESCRIPTION OF THE EMBODIMENTS Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] A long mirror fixing device for a dual-frequency laser interferometer provided by an embodiment of the present application is as Figures 1-2 shown. The device includes: A long mirror 2, supported at both ends by a sliding table 1; At least one rigid container 3, 4, fixed on the sliding table 1 and located on one side or both sides of the suspended area in the middle of the long mirror 2; An air pressure damping cavity is formed between the long mirror 2 and the rigid containers 3, 4, and the distance is 5-10 micrometers; The surfaces of the rigid containers 3, 4 are distributed with connected micropores, the pore diameter is 20-100 micrometers, and the internal pores communicate with each other.

[0021] Referring to Figure 4 shown, the dynamic compensation mechanism of the fixing device is as follows. Since there is no support in the middle, the forces at both ends of the long mirror are greater than those in the middle part, and the middle part has a bending tendency as shown in the figure. When there is this tendency, the long mirror is equivalent to pressurizing the alumina ceramic container, and at the same time, the pressure inside the pressure vessel increases and gives a reaction force to the long mirror to inhibit this deformation tendency. Similarly, when the acceleration is in the opposite direction to the direction shown in the figure, the deformation tendency is also opposite to that shown in the figure. The long mirror has a tendency to move away from the pressure vessel in the horizontal direction, and the pressure inside the pressure vessel will be less than the atmospheric pressure. At this time, the external atmospheric pressure will give a force to the long mirror to inhibit the tendency of the long mirror to move away from the pressure vessel. The principle of action in the height direction is similar, and the two directions act together to ensure the stable position of the middle part of the long mirror on the sliding table.

[0022] The long mirror 2 can be made of glass, quartz or sapphire, and its surface roughness Ra≤10nm to ensure high reflection accuracy and low scattering loss. Both ends of the long mirror are fixed to the XY sliding table 1 through fixing seats 5, 6. This fixing method not only ensures the stability of the long mirror but also avoids excessive restraint on the long mirror body, preventing stress from deteriorating the optical performance.

[0023] In one embodiment, the rigid containers 3, 4 can be selected as alumina ceramic containers (Al 2 O 3Purity 99.6%): One alumina ceramic container is set in the horizontal direction and one in the vertical direction respectively. The micropores on its surface have a pore diameter of 20 - 100 microns and a porosity of 30% - 60%. These micropores form an array communication structure through laser micro - machining, enabling the internal pores of the container to communicate with each other, forming an air - pressure damping cavity, which can store part of the air and also ensure the sensitivity of the whole system to air - pressure changes. For example, Figure 5 As shown. Such a micropore design and processing technology enable the air - pressure damping cavity to dynamically suppress the deformation of the long - strip mirror through the real - time change of the air - pressure difference during the acceleration and deceleration of the sliding table.

[0024] For the air - pressure damping cavity, the distance between the long - strip mirror and the container is 5 - 10 μm, forming an approximately sealed air film, and the stiffness of the air film is . The stiffness value is achieved by precisely controlling the distance and micropore parameters, which can provide sufficient support force while ensuring the movement flexibility of the long - strip mirror. When the sliding table is moving at a constant speed or with a relatively small acceleration or deceleration, the long - strip mirror is suspended without deforming to affect the system accuracy. Among them, preferably, the distance between the long - strip mirror and the container is set to 6 μm.

[0025] Optionally, as Figure 3 shown, the rigid containers 3 and 4 include a horizontal - direction container 3 and a vertical - direction container 4, which are respectively located in the horizontal and vertical suspended areas of the long - strip mirror 2, forming air - pressure damping cavities in the horizontal and vertical directions.

[0026] Optionally, the rigid container is made of ceramic, metal or composite material.

[0027] Furthermore, the ceramic is alumina, silicon nitride or zirconia; The metal is sintered stainless steel or aluminum alloy; The composite material is carbon - fiber - reinforced silicon carbide.

[0028] Those skilled in the art can understand that the above - listed are only the materials or structures of conventional rigid containers. The core function of the rigid container is to realize dynamic compensation of air - pressure difference through the micropore structure. As Figure 5 shown, those skilled in the art can, by reasonably selecting replacement materials, take into account performance, cost and environmental adaptability.

[0029] The rigid containers 3 and 4 are fixed to the sliding table 1 by gluing, welding or mechanical fastening methods.

[0030] Those skilled in the art can understand that the structure shown in the figure is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the equipment to which the solution of this application is applied. The specific equipment may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0031] In one embodiment, a super-precision motion platform device is further provided, including: An XY motion stage; A dual-frequency laser interferometer system; The long mirror fixing device described in the above embodiment, where the long mirror reflects laser to determine the position of the stage.

[0032] In one embodiment, a method for fixing a long mirror of a dual-frequency laser interferometer is further provided, including the following steps: Fix both ends of the long mirror to the stage; Set a rigid container in the suspended area in the middle of the long mirror to form a pneumatic damping cavity with a spacing of 5-10 micrometers; Dynamically suppress the deformation of the long mirror when the stage accelerates and decelerates by using the air pressure difference in the pneumatic damping cavity.

[0033] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0034] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present application. It can be understood that the present invention is described through some embodiments. Those skilled in the art know that, without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and embodiments. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application belong to the scope protected by the present invention.

Claims

1. A dual-frequency laser interferometer strip mirror fixing device, characterized in that: include: A long mirror, supported at both ends by slides; At least one rigid container, fixed on the slide and located on one side or both sides of the suspended area in the middle of the long mirror; An air pressure damping cavity is formed between the strip mirror and the rigid container; the spacing between the air pressure damping cavities is 5-10 microns; The rigid container has interconnected micropores distributed on the surface, and the internal pores are interconnected, so that some air can be stored.

2. The device according to claim 1, characterized in that: The rigid container comprises a horizontal container and a vertical container, which are respectively located in the horizontal and vertical suspended areas of the long mirror.

3. The device according to claim 1, characterized in that: The rigid container is made of ceramic, metal or composite material.

4. The device according to claim 3, characterized in that: The ceramic is aluminum oxide, silicon nitride or zirconium oxide, silicon carbide; The metal is sintered stainless steel or aluminum alloy; The composite material is carbon fiber reinforced silicon carbide.

5. The device according to claim 1, characterized in that: The micropore diameter of the rigid container is 50 micrometers and the porosity is 30%-60%.

6. The device according to claim 1, characterized in that: The air film stiffness of the air pressure damping cavity is .

7. The device according to claim 1, characterized in that: The rigid container is fixed to the slide table by gluing, welding or mechanical fastening.

8. An ultra-precision motion platform device, characterized in that: include: XY motion slide; Dual-frequency laser interferometer system; The strip mirror fixing device according to any one of claims 1 to 7, wherein the strip mirror reflects laser light to determine the position of the slide.

9. A method for fixing a long mirror of a dual-frequency laser interferometer, characterized in that: The following steps are involved: Fix both ends of the long mirror on the slide; A rigid container is arranged in the suspended area in the middle of the long mirror to form an air pressure damping cavity with a spacing of 5-10 microns; Using the air pressure difference of the air pressure damping cavity to dynamically suppress the deformation of the long mirror when the slide table is accelerated or decelerated; The rigid container has interconnected micropores distributed on the surface, and the internal pores are interconnected, so that some air can be stored.

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