Preparation method and processing device for extreme ultraviolet light source collector mirror

Abstract

The present invention relates to a preparation method and processing device for an extreme ultraviolet light source collector mirror. The method comprises the steps of: fabricating a mirror blank; performing preliminary processing on the surface of a substrate; preparing a silicon modified layer; polishing the surface of the silicon modified layer; measuring the surface figure precision and roughness of a collector mirror; photolithographically processing a grating structure on the surface of the collector mirror; measuring the processing precision of the grating structure; coating the surface of the grating structure with a film; and measuring parameters of the collector mirror. In the present invention, using a silicon carbide material to fabricate a substrate of a collector mirror reduces the thermal deformation of the substrate of the collector mirror during operation; and using silicon to modify the surface of the substrate improves the consistency of a linear expansion coefficient between the substrate of the collector mirror and a modified layer. Photolithographically processing a grating structure on the surface of a collector mirror reduces the requirements for ultra-precision processing devices, thereby solving the problem of insufficient precision in processing the grating structure on the silicon modified surface of the collector mirror using an ultra-precision lathe. The design uses a dedicated curved surface exposure device to solve the problems in curved surface exposure, thereby further improving the precision of grating structure processing.

Description

A preparation method and processing equipment for extreme ultraviolet light source collecting mirror Technical Field

[0001] The present invention relates to the technical field of extreme ultraviolet lithography, and in particular to a preparation method and processing equipment of an extreme ultraviolet light source collecting mirror. Background Art

[0002] Extreme ultraviolet lithography (EUVL) is an essential lithography technology for achieving large-scale mass production and industrialization of sub-7nm nodes in the semiconductor industry. EUV lithography machines are essential for the continued advancement of process technology. As the core subsystem of an EUV lithography machine, the EUV light source system must possess high output power and conversion efficiency to provide high-purity 13.5nm EUV light for the exposure system. The EUV light source collector is the most important optical component in the EUV light source system, playing a decisive role in the light source's collection efficiency and stability.

[0003] In EUV light source systems, the type of light source collector is determined by the method used to generate the EUV light source. Laser plasma (LPP) and discharge plasma (DPP) sources are the two most popular sources. DPP sources generate a large amount of debris along with the EUV light during emission. To prevent this debris from contaminating the mirrors of the EUV lithography illumination and projection systems, thereby reducing system life, DPP light source systems utilize grazing-incidence collectors and debris removal systems. However, this significantly limits the efficiency of EUV light collection.

[0004] Laser plasma light source systems use high-intensity lasers to bombard liquid droplets to produce extreme ultraviolet light, generating minimal debris. Furthermore, the LPP light source's collection mirror uses a single ellipsoidal reflector to achieve high EUV light collection efficiency, leading to the use of this type of light source in mainstream EUV lithography tools worldwide. However, because the EUV light is excited by an infrared-band driving light source, some of the infrared laser light is reflected by the collection mirror and enters the illumination system. This infrared light can cause severe thermal damage to critical optical components in the illumination and projection systems, necessitating the design of an infrared light filter.

[0005] The main infrared filtering methods currently used for EUV lithography include reflective grating filtering, transmissive grating thin film filtering, and EUV collecting mirror filtering with a grating structure. Since the 13.5nm wavelength of EUV light is extremely short and easily absorbed by matter, the use of reflective grating filtering devices and transmissive grating thin film filters will cause significant loss of EUV light. The loss of EUV light by collecting mirrors with grating structures mainly comes from the microstructure on the surface of the collecting mirror, and the loss is relatively small. It is necessary to focus on the research and development of reflective EUV light source collecting mirrors with grating structures that can filter out infrared radiation while reducing EUV light loss.

[0006] Currently, there are two relatively mature preparation methods. One technical solution is to use an aluminum alloy reflector substrate to prepare a collecting mirror that removes 10.6μm infrared radiation. The substrate surface is nickel-plated and polished. Then, a diamond turning tool is used on an ultra-precision lathe to machine the grating structure on the reflector surface. Finally, it is coated. The diameter of the collecting mirror is 400mm, and a phase grating with a period of 1mm is made on the surface. The other technical solution is a collecting mirror sample with a double-layer phase grating designed by IOF in Germany. The periods of the double-layer phase grating are 1mm and 100μm respectively. The reflector substrate is a silicon-aluminum alloy. The optical surface of the substrate is first diamond-turned and nickel-plated. The nickel layer is then diamond-turned to produce a grating with a period of 1mm and polished. Subsequently, ion beam etching is used to prepare a binary grating with a second period of 100μm directly on the Ni layer on the AlSi substrate.

[0007] The shortcomings of the existing technology are mainly in the collection mirror processing technology and equipment: there are two ways to use single-point diamond turning to turn the grating structure on the surface of the collection mirror. First, the grating structure is processed after the surface of the collection mirror is polished. This method can easily damage the original surface quality of the collection mirror and it is difficult to ensure the processing accuracy of the bottom of the grating. Second, the grating structure is processed first, and then the top and bottom of the grating are polished at the same time. This method is not easy to control the polishing time and it is difficult to ensure the size of the grating. In terms of equipment, the existing technical solutions have too high requirements on the precision of processing and polishing equipment, and it is difficult to process brittle and hard materials such as silicon and silicon carbide that are more suitable for collection mirror materials. Summary of the Invention

[0008] The present invention aims to solve the technical problems in the prior art and provides a preparation method and processing equipment for an extreme ultraviolet light source collecting mirror.

[0009] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0010] A method for preparing an extreme ultraviolet light source collecting mirror comprises the following steps:

[0011] Step 1: Mirror blank production;

[0012] Making a base for the collecting mirror;

[0013] Step 2: Preliminary processing of substrate surface;

[0014] The root mean square value of the surface accuracy error is λ / 10;

[0015] Step 3: preparing a silicon modified layer;

[0016] A silicon modified layer of a certain thickness is plated on the surface of the silicon carbide collecting mirror substrate;

[0017] Step 4: polishing the surface of the silicon modified layer;

[0018] Precision polishing of the silicon modified layer;

[0019] Step 5: Detect the surface accuracy and roughness of the collecting mirror;

[0020] Step 6: Photolithography to process the grating structure on the collecting mirror surface;

[0021] Step 7: Grating structure processing accuracy detection;

[0022] Step 8: Coating the grating structure surface;

[0023] Step 9: Check the parameters of the collecting mirror.

[0024] In the above technical solution, step 6 specifically includes:

[0025] Step 01: Cleaning and surface pretreatment of the collector mirror coating: Wet cleaning with deionized water is performed to remove contaminants and residual impurities adsorbed on the surface of the collector mirror's silicon modified layer; adhesion enhancement treatment is then performed to improve the adhesion between the coating and the photoresist.

[0026] Step 02: Apply and level the photoresist; evenly spread the photoresist that meets the requirements on the substrate to ensure that the thickness of the photoresist is uniform and stable;

[0027] Step 03: Pre-baking; reduce the solvent content in the photoresist, make the photoresist stronger and improve the corrosion resistance of the photoresist film;

[0028] Step 04: Exposure: Use curved surface exposure equipment to expose the collecting mirror;

[0029] Step 05: Post-baking: Bake the surface of the collector mirror after exposure to allow the photochemical reaction in the photoresist to be fully completed;

[0030] Step 06: Development and rinsing: First, wet the collecting mirror with deionized water, then evenly spray the developer on the photoresist surface of the collecting mirror or place the substrate in the developer to fully dissolve the exposed part in the photolithography, and then rinse with deionized water;

[0031] Step 07: Hard film baking; further reduce the solvent content in the photoresist to improve the etching resistance of the photoresist film;

[0032] Step 08: Etching: Use dry etching to rapidly erode the portion of the collecting mirror surface not covered by the photoresist under ion bombardment of chemical gas.

[0033] Step 09: Removal of adhesive and cleaning: Remove the remaining photoresist attached to the silicon modified layer of the collecting mirror and clean the entire collecting mirror surface to obtain the structure of the first layer of grating.

[0034] In the above technical solution, Step 04 is specifically as follows: positioning and clamping the collecting mirror on the exposure device, and controlling the laser of the exposure device to link with the axis of the clamping collecting mirror so that the laser focal spot is accurately scanned on the surface of the photoresist to obtain the grating pattern required by the design.

[0035] In the above technical solution, after Step 09, if a binary grating structure needs to be produced, repeat the steps: Step 02-Step 09.

[0036] In the above technical solution, step 7 specifically includes: using a white light interferometer to detect the dimensional accuracy of the grating of the collecting mirror, and using an atomic force microscope to detect the roughness of different positions of the grating, and the roughness value is less than 0.25nm rms.

[0037] In the above technical solution, step 8 specifically includes: depositing a Mo / Si multilayer film on the surface of the grating structure using a magnetron sputtering method.

[0038] In the above technical solution, step 9 specifically includes: evaluating the extreme ultraviolet collection rate and infrared radiation removal rate of the collection mirror.

[0039] A processing device for an extreme ultraviolet light source collecting mirror comprises: a base arranged at the bottom, a Z axis and an X axis arranged above the base; the X axis and the Z axis respectively perform linear reciprocating motion;

[0040] A B-axis is located above the Z-axis. A laser mounting bracket is connected to the B-axis, and a laser is connected above the laser mounting bracket. The B-axis controls the laser's rotation around the Y-axis. By adjusting the laser mounting bracket, the center of the laser's light is ensured to be at the required height and to provide a stable support for the laser's operation.

[0041] The C-axis is connected to the top of the X-axis, and the C-axis is connected to the pneumatic chuck, on which the collecting mirror is clamped; the C-axis drives the collecting mirror to rotate around the Z-axis;

[0042] The collecting mirror comprises a substrate, a silicon modified layer is provided on the surface of the substrate, and a light hole is provided in the center of the substrate; a grating structure is provided above the silicon modified layer, and the surface of the grating structure is coated with a multilayer film.

[0043] In the above technical solution, the material of the multilayer film is Mo / Si.

[0044] In the above technical solution, the number of periods of the multilayer film is 42 to 48, and the thickness of a single period is about 6 to 7 nm.

[0045] A processing device for an extreme ultraviolet light source collecting mirror, comprising: a laser direct writing optical path system and a precision motion platform;

[0046] The laser direct writing optical path system includes: a laser as a laser light source; an adjustment frame and a mounting plate as a laser shaping module; an industrial camera as a coaxial visual observation module; a focus sensor as a focus detection module; and an objective lens as a focusing objective lens;

[0047] The precision motion platform includes: a Z-axis and an X-axis set on the base, a B-axis set above the Z-axis, and a C-axis set above the X-axis; the X-axis and Z-axis are used to perform linear reciprocating motion in mutually perpendicular horizontal directions; the B-axis and C-axis are used to rotate in the horizontal and vertical directions respectively;

[0048] The B-axis is connected to the adjustment frame and the mounting plate above, and the laser, the industrial camera, the focus sensor and the objective lens are connected to the adjustment frame and the mounting plate in sequence; the B-axis is used to control the rotation of the adjustment frame and the mounting plate around the vertical direction; the adjustment frame and the mounting plate are used to ensure that the center of the light emitted by the laser is at the required height through adjustment, and to stably support the operation of the laser for exposure; the C-axis is connected to the X-axis above, and the C-axis is connected to the chuck, and the collecting mirror is clamped on the chuck; the C-axis is used to drive the collecting mirror to rotate around the Z-axis direction;

[0049] The collecting mirror comprises: a substrate, a silicon modified layer is provided on the surface of the substrate, and a light hole is provided in the center of the substrate; a grating structure is provided above the silicon modified layer, and the surface of the grating structure is plated with a multilayer film.

[0050] In the above technical solution, the material of the multilayer film is Mo / Si.

[0051] In the above technical solution, the number of periods of the multilayer film is 42 to 48, and the thickness of a single period is about 6 to 7 nm.

[0052] A method for preparing an extreme ultraviolet light source collecting mirror suitable for the above-mentioned extreme ultraviolet light source collecting mirror processing equipment comprises the following steps:

[0053] Step 1: Align and focus the laser direct writing optical system;

[0054] Step 2: Control the C-axis to rotate steadily at the calculated speed to ensure stable rotation of the C-axis;

[0055] Step 3: Control the light output of the laser direct writing optical system;

[0056] Step 4: After completing one circle of exposure, rotate the B axis to perform the next circle of exposure until a cycle of direct writing exposure is completed, and then turn off the light source of the laser direct writing optical system;

[0057] Step 5: Control the B axis to rotate a certain angle, and repeat steps 2 to 4 to perform direct writing exposure on the next period grating.

[0058] In the above technical solution, during the laser direct writing process, the focus detection module and the coaxial visual observation module monitor the light spot quality in real time. The present invention has the following beneficial effects:

[0059] The preparation method and processing equipment of the extreme ultraviolet light source collecting mirror of the present invention adopt silicon carbide material to make the collecting mirror substrate, which reduces the thermal deformation of the collecting mirror substrate during operation, and uses silicon to modify the surface of the substrate, thereby improving the consistency of the linear expansion coefficient of the collecting mirror substrate and the modified layer; adopts photolithography to process the grating structure on the surface of the collecting mirror, reduces the requirements for ultra-precision processing equipment, and solves the problem of insufficient precision of the grating structure on the surface of the collecting mirror modified by silicon when processed by ultra-precision lathe; designs and uses special curved surface exposure equipment to solve the problem of curved surface exposure and further improves the processing precision of the grating structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0061] FIG1 is a schematic diagram showing the steps of a method for preparing an EUV light source collecting mirror with a grating structure.

[0062] FIG2 is a schematic diagram showing the steps of a method for processing and coating a grating structure on the surface of a light source collecting mirror.

[0063] FIG3 is a schematic structural diagram of a specific embodiment of a processing device for preparing an EUV light source collecting mirror with a grating structure.

[0064] FIG4 is a schematic structural diagram of a collecting mirror.

[0065] FIG5 is another structural schematic diagram of the collecting mirror.

[0066] FIG6 is a schematic structural diagram of another specific embodiment of a processing device for preparing an EUV light source collecting mirror with a grating structure.

[0067] The reference numerals in the figures indicate:

[0068] 1-base; 2-Z-axis, 3-B-axis; 4-laser mounting frame; 5-laser; 6-collecting mirror; 7-pneumatic chuck; 8-C-axis; 9-X-axis; 10-substrate; 11-silicon modified layer; 12-light hole; 13-multilayer film; 14-grating structure.

[0069] 15-base; 16-Z-axis, 17-B-axis; 18-laser; 19-adjustment frame and mounting plate; 20-industrial camera; 21-focus sensor; 22-objective lens; 23-collecting mirror; 24-chuck; 25-C-axis; 26-X-axis. DETAILED DESCRIPTION

[0070] The inventive concept of the present invention is:

[0071] This paper proposes a method for fabricating an EUV light source collector mirror and develops an exposure device for curved surface lithography. The laser plasma light source collector mirror, with a microstructured surface, efficiently collects EUV light while effectively removing infrared radiation. It also reflects some infrared radiation back onto tin droplets to stimulate EUV light, improving energy efficiency. A phase grating structure fabricated on the surface primarily removes infrared radiation. When a Fresnel zone plate pattern is applied to the surface, it effectively refocuses IR light onto the tin droplets (recovery rate: 37%, with a maximum of 90%).

[0072] Regarding the selection of substrate materials, collector mirrors with the same structure using a silicon-aluminum alloy as the substrate experience greater thermal deformation than SiC substrates under the same operating conditions, which in turn affects the focusing performance of the collector mirror. Regarding the selection of surface modification materials, the linear expansion coefficient of AlSi alloy differs significantly from that of the modified materials Ni or NiP. In comparison, the linear expansion coefficients of SiC and Si are closer. Furthermore, mirrors with a silicon layer coated on a silicon carbide substrate are more suitable for coating with Mo / Si multilayers than mirrors with a nickel layer on the surface.

[0073] The present invention uses silicon carbide material to make a collecting mirror substrate to reduce the thermal deformation of the collecting mirror; silicon is used to modify the surface of the collecting mirror on the silicon carbide substrate to reduce the difference in linear expansion coefficient between the substrate material and the surface coating material; and then a higher surface quality is obtained by polishing the silicon layer on the surface of the collecting mirror. In order to process a grating structure that meets the use requirements on the surface of the collecting mirror, the present invention uses a photolithography process. First, photoresist is evenly coated on the polished collecting mirror surface, and after drying, it is exposed on an exposure device designed by the present invention. The exposed collecting mirror surface is developed and rinsed, and then etched on an etching device. Finally, the glue is removed and cleaned to complete the processing of a layer of grating structure of the collecting mirror. If a binary grating structure needs to be processed, the above processing steps are repeated. The curved surface photolithography process is used to process the grating structure on the surface of the collecting mirror, which solves the problem of insufficient precision in processing grating structures on the silicon-modified collecting mirror surface using an ultra-precision lathe, avoids damaging the surface quality of the polished collecting mirror, and can process high-precision grating sizes. At the same time, in order to solve the exposure problem of the microstructure on the surface of the curved reflector after the photolithography processing is carried out by gluing, an exposure device for the photolithography processing of the microstructure on the surface of the curved reflector is developed.

[0074] The present invention uses silicon carbide material to make the reflector substrate, which solves the problem of large thermal deformation of the AlSi substrate. Silicon is used on the silicon carbide substrate to modify the surface of the collecting mirror, avoiding the problem of a large difference in linear expansion coefficient between the silicon-aluminum alloy substrate and the nickel layer material, thereby achieving the purpose of improving the surface stability and focusing performance of the collecting mirror. In order to reduce the difficulty of processing the grating structure on the surface of the collecting mirror, a curved surface photolithography process is used to process the grating structure on the surface of the collecting mirror, which solves the problem of insufficient precision of the grating structure on the surface of the collecting mirror modified by silicon when processed by ultra-precision lathe, and avoids damaging the surface quality of the polished collecting mirror. In addition, an exposure device for photolithography processing of microstructures on the surface of curved reflectors has been developed, which solves the exposure problem after the microstructures on the surface of the curved reflector are coated with glue during photolithography processing.

[0075] The present invention will be described in detail below with reference to the accompanying drawings.

[0076] The method for preparing an extreme ultraviolet light source collecting mirror with a grating structure of the present invention adopts silicon carbide material to make a collecting mirror substrate with an ellipsoidal structure, firstly processes the surface of the silicon carbide substrate to improve the surface accuracy of the substrate surface, and adopts physical vapor deposition to prepare a silicon modified layer on the surface of the collecting mirror substrate, and then performs precision polishing on the silicon modified layer according to relevant processing indicators. The grating structure on the surface of the collecting mirror is manufactured by steps such as coating, exposure, development, and etching. The grating structure is shown in Figures 4 and 5. After the processing quality of the grating structure is completed, a multi-layer Mo / Si film is coated, and finally the focusing performance and infrared filtering performance of the reflector are tested. The flow chart of the preparation process is shown in Figure 1. During the preparation process, the collecting mirror after coating with glue needs to be exposed with high precision. This is a key step in determining the processing accuracy of the grating structure on the surface of the collecting mirror. The design of the present invention uses a dedicated exposure device, and Figure 3 is a schematic diagram of the equipment structure.

[0077] Focusing on the preparation of an EUV light source collecting mirror with a grating structure, the technical solutions of the preparation method and processing equipment of the present invention are divided into the following three parts:

[0078] Part 1: Substrate preparation, surface modification and polishing of laser plasma light source collecting mirror.

[0079] As shown in Figure 1, after obtaining the various design parameters of the collecting mirror, the first step is to complete the production of the mirror blank of the laser plasma light source collecting mirror of the corresponding size, and select silicon carbide (SiC) material with excellent physical, thermal, and mechanical properties to make the collecting mirror substrate.

[0080] After completing the substrate preparation, the second step is to perform preliminary processing on the surface of the silicon carbide substrate until the root mean square (RMS) value of the surface accuracy error is around λ / 10 (λ=632.8nm).

[0081] After completing the detection of the preliminary processing error of the substrate, the third step is to use physical vapor deposition to prepare a silicon modified layer, and to plate a silicon modified layer of a certain thickness on the surface of the silicon carbide collecting mirror. The specific thickness is determined by the design parameters, generally around 10μm.

[0082] The fourth step is to perform precision polishing on the silicon modified layer in the third step. The polishing method used here can be small grinding head polishing, ion beam polishing or magnetorheological polishing.

[0083] After polishing is completed, the surface error and surface roughness of the collecting mirror are tested by at least two detection methods. If the design requirements are met, the second part of the processing steps can be started.

[0084] The second part is the processing and coating of the grating structure on the surface of the laser plasma (LPP) light source collecting mirror. The processing flow chart is shown in Figure 2. The specific process is as follows:

[0085] Step 01: Cleaning and surface pretreatment of the collector mirror coating. First, wet cleaning with deionized water removes contaminants and impurities such as residues from the previous process adsorbed on the polished collector mirror silicon modified layer. Then, adhesion enhancement treatment is performed to improve the adhesion between the coating and the photoresist.

[0086] Step 02: Apply and level the photoresist. Spread the photoresist that meets the requirements evenly on the substrate that has completed the previous step, making the thickness of the photoresist uniform and stable.

[0087] Step 03: Pre-baking. This reduces the solvent content in the photoresist, making it stronger and improving the corrosion resistance of the photoresist film.

[0088] Step 4: Exposure. The collector mirror, which has completed the previous step, is exposed using the newly developed curved surface exposure equipment. Specifically, the collector mirror is first positioned and clamped to the exposure equipment. By controlling the exposure equipment's laser and the axis that holds the collector mirror, the laser spot is precisely scanned across the photoresist surface, resulting in the desired grating pattern.

[0089] Step 05: Post-baking. To compensate for the insufficient exposure intensity, the surface of the collector mirror is baked after exposure. Baking allows the photochemical reaction in the photoresist to be fully completed.

[0090] Step 06: Development and Rinse. First, wet the collector mirror obtained in the previous step with deionized water. Then, evenly spray the developer onto the photoresist surface of the collector mirror, or place the substrate in the developer to fully dissolve the exposed areas. Rinse with deionized water. This step preserves the unexposed areas, creating the designed grating pattern on the collector mirror surface.

[0091] Step 07: Hard film baking. Further reduce the solvent content in the photoresist to improve the etching resistance of the photoresist film, prevent it from affecting the next step of etching, and improve etching accuracy.

[0092] Step 08: Etching. Using dry etching, the portions of the collector mirror surface not covered by the photoresist are rapidly etched under ion bombardment from chemical gases. Etching methods include plasma etching, ion beam etching, and reactive ion etching. Wet etching can also be used, using an etchant to quantitatively etch the collector mirror after the previous step.

[0093] Step 09: Removal and Cleaning. Remove any remaining photoresist attached to the modified collector mirror layer and clean the entire collector mirror surface to obtain the first grating structure. Repeat the above steps if a binary grating structure is desired.

[0094] Step 10: Inspection and coating. Use a white light interferometer to inspect the dimensional accuracy of the grating of the collector mirror completed in the previous step. Use an atomic force microscope to inspect the roughness of different locations of the grating. The roughness value must be less than 0.25nm rms.

[0095] After testing, a Mo / Si multilayer film was deposited on the grating surface using magnetron sputtering. The Mo / Si periodic multilayer film has 42 to 48 periods, with a thickness of approximately 6 to 7 nm per period. The Mo layer accounts for approximately 43% of the total film thickness.

[0096] Finally, by evaluating the EUV collection rate and infrared radiation removal rate of the collecting mirror after completing the above steps, the collecting mirror can be used in the EUV lithography light source system after meeting the design requirements.

[0097] Step 01 to Step 09 in the above steps correspond to S01 to S09 in FIG. 2 .

[0098] Part 3, the structure and working principle of the curved surface lithography exposure system.

[0099] FIG3 shows a schematic diagram of the structure of the processing equipment, or exposure system, designed according to the present invention. The bottom portion comprises a base 1 for the exposure equipment, with a Z-axis 2 and an X-axis 9 positioned above the base 1. The X-axis 9 and Z-axis 2 each perform linear reciprocating motion. A B-axis 3 is positioned above the Z-axis 2, connected to a laser mounting frame 4. A laser 5 is attached to the laser mounting frame 4. The B-axis 3 controls the rotation of the laser 5 about the Y-axis. As shown in FIG3 , the Y-axis is a vertical direction perpendicular to the X-axis 9 and the Z-axis 2. Adjustment of the laser mounting frame 4 ensures that the center of the light emitted by the laser 5 is at the desired height and provides stable support for the operation of the laser 5 for exposure. A C-axis 8 is attached above the X-axis 9 and is connected to a pneumatic chuck 7, to which a collector mirror 6 is mounted. The C-axis 8 drives the collector mirror 6 to rotate about the Z-axis 2.

[0100] The structure of the collector mirror 6 is shown in Figures 4 and 5. A silicon-modified layer 11 is applied to the surface of a substrate 10, with a light-through hole 12 defined in the center. A grating structure 14 is positioned above the silicon-modified layer 11, and a multilayer film 13 made of Mo / Si is deposited on the surface of the grating structure 14. The multilayer film 13 has 42 to 48 periods, with a thickness of approximately 6 to 7 nm per period. The Mo layer accounts for approximately 43% of the total period.

[0101] During the collector mirror exposure process, the glue-coated collector mirror 6 is first clamped onto the pneumatic chuck 7. The rotation centerline of the laser 5 around the B-axis 3 is adjusted to the desired position. The specific position is determined by the design parameters of the collector mirror 6. The four-axis linkage of the exposure system is controlled to complete the exposure. Through the joint control of the C-axis 8 and the laser 5, after completing the exposure of one circle of circular grating, the B-axis 3 is rotated a certain angle, and the Z-axis 2 is adjusted at the same time to expose the next circle of grating structure. The above is a direct write exposure without a mask. The laser 5 can be replaced and a mask can be made to perform masked exposure.

[0102] Another specific embodiment of the extreme ultraviolet light source collecting mirror processing equipment of the present invention, that is, the exposure equipment for preparing the extreme ultraviolet lithography light source collecting mirror with a grating structure, is shown in Figure 6. The function of the equipment is to prepare the surface microstructure of the collecting mirror, and the equipment consists of a precision motion platform and a laser direct writing optical path system. The laser direct writing optical path system has the functions of laser spot shaping, focus detection and coaxial visual observation. The laser direct writing optical path system consists of a laser light source, a laser shaping module, a coaxial visual observation module (visual observation part), a focusing module and a focusing objective lens. The precision motion platform has four degrees of freedom, which are movement in the directions of the X-axis 26 and the Z-axis 16 and rotation in the directions of the C-axis 25 and the B-axis 17, and can realize four-axis linkage and communication with the laser direct writing optical path system.

[0103] The laser direct writing optical path system includes: a laser 18 as a laser light source; an adjustment frame and a mounting plate 19 as a laser shaping module; an industrial camera 20 as a coaxial visual observation module; a focus sensor 21 as a focus detection module; and an objective lens 22 as a focusing objective lens.

[0104] The precision motion platform includes a Z-axis 16 and an X-axis 26 mounted on a base 15, a B-axis 17 positioned above the Z-axis 16, and a C-axis 25 positioned above the X-axis 26. The X-axis 26 and Z-axis 16 are each designed to perform linear reciprocating motion in mutually perpendicular horizontal directions; the B-axis 17 and C-axis 25 are designed to rotate horizontally (toward the Z-axis 16) and vertically (toward the Y-axis), respectively.

[0105] As shown in Figure 6, the bottom of the exposure equipment is a base 15, above which are the Z-axis 16 and X-axis 26. Above the Z-axis 16 is a B-axis 17, to which is connected an adjustment frame and mounting plate 19. The adjustment frame and mounting plate 19 are connected in sequence to a laser 18, an industrial camera 20, a focus sensor 21, and an objective lens 22. The B-axis 17 controls the vertical rotation of the adjustment frame and mounting plate 19. Adjustment of the adjustment frame and mounting plate 19 ensures that the center of the light emitted by the laser 18 is at the required height and firmly supports the operation of the laser 18 for exposure. Above the X-axis 26 is a C-axis 25, which is connected to a chuck 24, to which a collector mirror 23 is clamped. The C-axis 25 drives the collector mirror 23 to rotate about the Z-axis 16. The chuck 24 can be either pneumatic or hydraulic. The collector mirror 23 comprises a substrate with a silicon-modified layer on its surface and a light-through hole in its center. A grating structure is located above the silicon-modified layer, and the surface of the grating structure is coated with a multilayer film. The multilayer film is made of Mo / Si, has a period number of 42 to 48, and a thickness of approximately 6 to 7 nm per period.

[0106] The steps of using the processing equipment of the extreme ultraviolet light source collecting mirror of the present invention to prepare and process the surface grating of the extreme ultraviolet lithography light source collecting mirror include:

[0107] The first step is to align and focus the laser direct writing optical system;

[0108] The second step is to control the C-axis 25 to rotate stably at the calculated required speed, so that the C-axis 25 rotates stably;

[0109] The third step is to control the light output of the laser direct writing optical system;

[0110] Step 4: After completing one round of exposure, rotate the B axis 17 to perform the next round of exposure until one cycle of direct writing exposure is completed, and then turn off the light source of the laser direct writing optical system;

[0111] In the fifth step, the B-axis 17 is controlled to rotate a certain angle, and the second to fourth steps are repeated to perform direct writing exposure on the next period grating.

[0112] During the laser direct writing process, the focus sensor 21 of the focus detection module and the industrial camera 20 of the coaxial visual observation module monitor the light spot quality in real time.

[0113] The preparation method and processing equipment of the extreme ultraviolet light source collecting mirror of the present invention adopt silicon carbide material to make the collecting mirror substrate, thereby reducing the thermal deformation of the collecting mirror substrate during operation, and using silicon to modify the surface of the substrate, thereby improving the consistency of the linear expansion coefficient of the collecting mirror substrate and the modified layer; adopting photolithography to process the grating structure on the surface of the collecting mirror, thereby reducing the requirements for ultra-precision processing equipment, and solving the problem of insufficient precision of the grating structure on the surface of the collecting mirror modified by silicon when processed by ultra-precision lathe; designing and using special curved surface exposure equipment, solves the problem of curved surface exposure and further improves the processing precision of the grating structure.

[0114] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing an extreme ultraviolet light source collector mirror, characterized in that, It includes the following steps: Step 1: Making the mirror blank; Making the substrate of the collecting mirror; Step 2: Preliminary processing of the substrate surface; Processing to a root mean square value of surface form accuracy error of λ / 10; Step 3: Preparing the silicon modified layer; Depositing a silicon modified layer with a certain thickness on the surface of the silicon carbide collecting mirror substrate; Step 4: Polishing the surface of the silicon modified layer; Performing precision polishing on the silicon modified layer; Step 5: Detecting the surface form accuracy and roughness of the collecting mirror; Step 6: Photolithographically processing the grating structure on the surface of the collecting mirror; Step 7: Detecting the processing accuracy of the grating structure; Step 8: Coating the surface of the grating structure; Step 9: Detecting the parameters of the collecting mirror.

2. The preparation method of the extreme ultraviolet light source collection mirror according to claim 1, wherein Step 6 specifically includes: Step01: Cleaning the coating of the collecting mirror and surface pretreatment; first, performing wet cleaning with deionized water to remove pollutants and residue impurities adsorbed on the surface of the silicon modified layer of the collecting mirror; then, performing an adhesion enhancement treatment to improve the adhesion between the coating and the photoresist; Step02: Coating and spin coating; spreading the photoresist that meets the usage requirements evenly on the substrate to make the thickness of the photoresist uniform and stable; Step03: Pre-baking; reducing the solvent content in the photoresist to make the photoresist firm and enhance the corrosion resistance of the photoresist film; Step04: Exposure; using a curved surface exposure device to expose the collecting mirror; Step05: Post-baking; baking the surface of the exposed collecting mirror to fully complete the photochemical reaction in the photoresist through baking; Step06: Development and rinsing; first, wetting the collecting mirror with deionized water, and then evenly spraying the developer on the surface of the photoresist of the collecting mirror or placing the substrate in the developer to fully dissolve the exposed part in the photolithography, and then rinsing with deionized water; Step07: Hard baking; further reducing the solvent content in the photoresist to enhance the etching resistance of the photoresist film; Step08: Etching; using dry etching to quickly corrode the part of the collecting mirror surface not covered by the photoresist under the ion bombardment of chemical gas; Step09: Removing the photoresist and cleaning; removing the remaining photoresist attached to the silicon modified layer of the collecting mirror and cleaning the entire surface of the collecting mirror to obtain the structure of the first layer of grating.

3. The preparation method of the extreme ultraviolet light source collector mirror according to claim 2, characterized in that, Step04 specifically is: Positioning and clamping the collecting mirror on the exposure device, and making the laser spot on the surface of the photoresist accurately scan by controlling the linkage of the laser of the exposure device and the axis clamping the collecting mirror to obtain the grating pattern required by the design.

4. The preparation method of the extreme ultraviolet light source collection mirror according to claim 2, characterized in that, After Step09, if a binary grating structure needs to be made, repeat the steps: Step02 - Step09.

5. The preparation method of the extreme ultraviolet light source collection mirror according to claim 1, characterized in that, Step 7 specifically includes: Using a white light interferometer to detect the dimensional accuracy of the grating of the collecting mirror, and using an atomic force microscope, etc. to detect the roughness of different positions of the grating, with the roughness value less than 0.25 nm rms.

6. The preparation method of the extreme ultraviolet light source collector mirror according to claim 1, wherein Step 8 specifically includes: Using magnetron sputtering to deposit a Mo / Si multilayer film on the surface of the grating structure.

7. The preparation method of the extreme ultraviolet light source collector mirror according to claim 1, characterized in that Step 9 specifically includes: Evaluating the extreme ultraviolet collection rate and infrared radiation removal rate of the collecting mirror.

8. A processing device for an extreme ultraviolet light source collector mirror, characterized in that, It includes: A base (1) arranged at the bottom, with a Z-axis (2) and an X-axis (9) arranged above the base (1); the X-axis (9) and the Z-axis (2) perform linear reciprocating motions respectively; Above the Z-axis (2), there is a B-axis (3). Connected to the B-axis (3) is a laser alignment bracket (4), and above the laser alignment bracket (4) is a laser (5) connected. The B-axis (3) controls the laser (5) to rotate around the Y-axis direction. By adjusting the laser alignment bracket (4), it is ensured that the center of the light emitted by the laser (5) is at the required height and firmly supports the operation of the laser (5). Above the X-axis (9), there is a C-axis (8) connected. The C-axis (8) is connected to a pneumatic chuck (7), and a collection mirror (6) is clamped on the pneumatic chuck (7). The C-axis (8) drives the collection mirror (6) to rotate around the Z-axis (2) direction. The collection mirror (6) includes: a substrate (10), on the surface of which there is a silicon modified layer (11), and in the center of the substrate (10) there is a light passing hole (12); above the silicon modified layer (11) there is a grating structure (14), and on the surface of the grating structure (14) there is a multilayer film (13).

9. The processing equipment for the extreme ultraviolet light source collector mirror according to claim 1, characterized in that, The material of the multilayer film (13) is Mo / Si.

10. The processing equipment for the extreme ultraviolet light source collector mirror according to claim 9, wherein The number of periods of the multilayer film (13) is 42 - 48, and the thickness of a single period is about 6 - 7 nm.

11. A processing device for an extreme ultraviolet light source collector mirror, characterized in that, Including: A laser direct writing optical path system and a precision motion platform; The laser direct writing optical path system includes: a laser (18) as a laser light source; an adjustment bracket and mounting plate (19) as a laser shaping module; an industrial camera (20) as a coaxial vision observation module; a focus sensor (21) as a focus detection module; and an objective lens (22) as a focusing objective lens; The precision motion platform includes: a Z-axis (16) and an X-axis (26) provided on a base (15), a B-axis (17) provided above the Z-axis (16), and a C-axis (25) provided above the X-axis (26); the X-axis (26) and the Z-axis (16) are respectively used to perform linear reciprocating motions in mutually perpendicular horizontal directions; the B-axis (17) and the C-axis (25) are respectively used to rotate around the horizontal direction and the vertical direction; Above the B-axis (17), it is connected to the adjustment bracket and mounting plate (19). On the adjustment bracket and mounting plate (19), the laser (18), the industrial camera (20), the focus sensor (21), and the objective lens (22) are successively connected. The B-axis (17) is used to control the adjustment bracket and mounting plate (19) to rotate around the vertical direction. The adjustment bracket and mounting plate (19) are used to ensure that the center of the light emitted by the laser (18) is at the required height through adjustment and firmly support the operation of the laser (18) for exposure. Above the X-axis (26), it is connected to the C-axis (25). The C-axis (25) is connected to a chuck (24), and a collection mirror (23) is clamped on the chuck (24). The C-axis (25) is used to drive the collection mirror (23) to rotate around the Z-axis (16) direction. The collection mirror (23) includes: a substrate, on the surface of which there is a silicon modified layer, and in the center of the substrate there is a light passing hole; above the silicon modified layer there is a grating structure, and on the surface of the grating structure there is a multilayer film.

12. The processing equipment for the extreme ultraviolet light source collector mirror according to claim 11, wherein The material of the multilayer film is Mo / Si.

13. The processing equipment for the extreme ultraviolet light source collection mirror according to claim 12, characterized in that, The number of periods of the multi-layer film is 42 to 48, and the thickness of a single period is about 6 to 7 nm.

14. A method for preparing an extreme ultraviolet light source collector for a processing device of an extreme ultraviolet light source collector according to any one of claims 11-13, characterized in that, It includes the following steps: The first step: Align and focus the laser direct writing optical path system. The second step: Control the C-axis (25) to rotate stably at the calculated required speed to make the rotation of the C-axis (25) stable. The third step: Control the laser direct writing optical path system to emit light. The fourth step: After completing one circle of exposure, rotate the B-axis (17) to perform the exposure of the next circle until the direct writing exposure of one period is completed, and turn off the light source of the laser direct writing optical path system. The fifth step: Control the B-axis (17) to rotate by a certain angle, and then repeat the second to fourth steps to perform the direct writing exposure on the grating of the next period.

15. The preparation method of the extreme ultraviolet light source collector mirror according to claim 14, characterized in that, During the laser direct writing process of the laser direct writing optical path system, the focus detection module and the coaxial vision observation module monitor the spot quality in real time.

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