Lifting and slow descending device and method for inscribing workpiece table

Abstract

The invention discloses a hoisting and slow descending device and method for an inscribing workpiece table, and belongs to the technical field of semiconductor photoetching equipment. The device comprises an air floatation assembly and a jacking assembly, the air floating assembly comprises an air floating block of which the bottom surface is provided with a small hole throttling structure and the upper supporting surface is provided with a conical groove; the jacking assembly comprises a jacking cover supported on the air floating block through an elastic piece in a floating mode and a jacking screw connected with the jacking cover in a threaded mode, and the lower end of the jacking screw is provided with a ball head matched with the conical groove in a universal tangent mode. The method comprises the following steps: a preparation stage: separating the ball head from the conical groove; in the buffering contact stage, the workpiece table falls to compress the elastic piece to achieve impact-free supporting; in the rigid conversion stage, the screw-in ball head converts the load into rigid support; air is supplied to form an air film to push the workpiece table to move horizontally in the air floatation translation stage; and in the precise slow descending stage, the jacking screw is reversely adjusted to make the workpiece table fall in parallel. The device is simple in structure, convenient to operate and high in cleanliness adaptability, impact-free contact, horizontal movement and precise slow descending of the workpiece table can be achieved, and the mounting precision and safety are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor lithography equipment technology, specifically to a hoisting and slow-descent device and method for a workpiece writing stage. Background Technology

[0002] The writing stage is the core component of a lithography machine, and its stability and precision directly determine the accuracy and efficiency of wafer or chip manufacturing. Due to the requirements of the writing process, the structure of the writing stage includes ultra-precision components such as air-floating / magnetic-floating micro-stages, interferometer assemblies, and grating detection systems. Once a bump or impact occurs, it can affect the overlay accuracy at best, and cause direct equipment failure at worst, resulting in extremely high repair costs.

[0003] Currently, most writing stages use natural granite as the base material to ensure structural stability, thermal expansion coefficient matching, and grindability. However, granite is brittle and has poor impact resistance. During hoisting and descent, it is prone to chipping, cracking, or even shattering due to uneven contact or localized stress, leading to particulate matter contamination of the clean environment or affecting the normal operation of the micro-motion stage.

[0004] In existing technologies, commonly used heavy equipment descent devices include screw jacks, hydraulic jacks, and air cushion transport devices. However, these devices have significant limitations in the application of semiconductor lithography: screw jacks and hydraulic devices are bulky, have limited operating space, and are prone to oil evaporation, failing to meet the requirements of cleanroom use; while air cushion lifting devices can achieve contactless transport, they require high precision in air pressure control, are prone to vibration during start-up and shutdown, and require preload pressure adjustment, making operation complex, training costs high, and difficult to achieve precise and stable descent control in confined spaces. Therefore, in response to the multiple requirements of stability, cleanliness, ease of operation and spatial adaptability of the writing workpiece stage during hoisting and installation, there is an urgent need for a slow-descent device and method that is simple in structure, safe in operation, adaptable to clean environments, and can precisely control the descent process. Summary of the Invention

[0005] This invention aims to overcome the problems of impact risk, complex operation, and poor cleanliness adaptability in the existing technology during the hoisting and installation of writing workpiece stages, and provides a hoisting and slow-descent device and method for writing workpiece stages. It employs a small-orifice throttling air-float block, combined with a lifting assembly and elastic buffer, enabling the workpiece stage to move horizontally and descend slowly without impact contact, achieving safe, efficient, stable, and high-precision installation.

[0006] This invention is achieved through the following technical solution: A hoisting and descent device for a writing workpiece table, characterized in that it includes an air flotation component and a lifting component whose height can be adjusted relative to the air flotation component; The air flotation assembly includes an air flotation block and an elastic buffer. The bottom surface of the air flotation block is provided with an air film generating structure for suspending the device when gas is introduced. The top surface of the air flotation block is provided with an adaptive support part at its center. The lifting assembly includes a lifting cover, an anti-slip pad disposed on the top of the lifting cover, and a lifting screw penetrating the lifting cover; One end of the elastic buffer is fixedly installed on the top surface of the air flotation block, and the other end abuts against the lifting cover to provide initial buffer stroke; The lower end of the lifting screw is provided with a universal joint that cooperates with the adaptive receiving part. The universal joint can deflect at multiple angles relative to the adaptive receiving part. The device has three working states: buffer support state, rigid locking state, and air-float translation state. In the buffer support state, the universal joint of the lifting screw is either disengaged or in a virtual contact with the adaptive receiving part, and the workpiece table load is borne by the elastic buffer. In the rigid locking state, the lifting screw is rotated so that its universal joint head presses against the adaptive receiving part, transferring the workpiece table load to the air float block and locking the height of the lifting cover relative to the air float block; In the air-float translation state, the device is in a rigid locking state and an air film is formed on the bottom surface of the air-float block, realizing horizontal movement with load.

[0007] Furthermore, the adaptive receiving part is a conical groove formed on the top surface of the air-bearing block, and the universal joint is a ball head set at the lower end of the lifting screw; the ball head is embedded in the conical groove to form a ball-and-socket joint structure. When there is an inclination angle at the bottom of the workpiece table, the lifting screw can automatically deflect in the conical groove according to the posture of the workpiece table, maintain the stress concentration transmission of point contact or line contact, and avoid lateral shear force damaging the threads.

[0008] Furthermore, the elastic buffer includes multiple compression springs evenly distributed along the circumference; the bottom of the inner cavity of the lifting cover is provided with a spring limiting groove, the upper end of the compression spring is embedded in the groove, and the lower end is fixed to the top surface of the air float block to prevent the spring from radially instability or slippage during the buffer compression process.

[0009] Furthermore, the lifting screw is provided with a tool interface in the middle, which is a polygonal cylindrical structure, and has an axial through hole on each side. The axis of the through hole is perpendicular to the axis of the lifting screw, and is configured to allow a slender lever tool to be inserted and apply rotational torque, so as to meet the needs of one-handed or two-person collaborative operation in the narrow installation space under the writing worktable.

[0010] Furthermore, the air film generating structure includes a plurality of microporous throttling arrays uniformly distributed on the bottom surface of the air flotation block; the pore size of the microporous throttling array ranges from 5μm to 15μm, and the air flotation block is provided with a concealed airflow channel to uniformly distribute the airflow from the external air inlet to each micropore, so as to form a micron-scale air film with uniform thickness and moderate stiffness on the bottom surface.

[0011] Furthermore, the anti-slip mat is made of a non-metallic material with a high coefficient of friction and low volatility, and its surface is provided with anti-slip texture; the main structure of the air flotation block and the lifting assembly are made of non-magnetic, corrosion-resistant and low-emission metal materials to meet the environmental requirements of ISO Class 5 and above for semiconductor cleanrooms.

[0012] Second, the present invention also provides a method for hoisting and lowering a writing workpiece stage using the above-mentioned device, characterized by comprising the following steps: S1. Preset and initial adjustment: Place at least three of the aforementioned slow-descent devices on the workpiece table's falling path, and adjust the lifting screw to make the device in a buffer support state, i.e., a safety gap h1 is reserved between the universal joint head and the adaptive receiving part; S2. Flexible landing: Control the workpiece stage to descend until it contacts the anti-slip pad, and use the compression deformation of the elastic buffer to absorb the remaining kinetic energy of the workpiece stage to achieve primary buffering. At this time, the compression amount of the elastic buffer is h2. S3. Adaptive locking: After the workpiece table is stationary on the elastic buffer, the lifting screws of each device are rotated synchronously to drive the universal joint head into the adaptive receiving part and gradually bear the load. During this process, the adaptability of the universal joint head is used to compensate for the initial horizontal error at the bottom of the workpiece table until the device is completely converted to a rigid locking state. At this time, the elastic buffer is in a pre-compressed state but no longer bears the main gravity load. S4. Air-float precision transfer: Air is introduced into the air-float block to put the device into an air-float translation state. Utilizing the low friction characteristics of the air film, the device position is finely adjusted to drive the workpiece stage to perform micron-level precise positioning in the horizontal plane, so that it is aligned with the final mounting base. S5. Synchronous spiral descent: After shutting off the air supply, the operator coordinates to fine-tune each lifting screw in the reverse direction, so that the workpiece table descends slowly and synchronously in a spiral feed manner under rigid support; during the descent, the levelness of the workpiece table is monitored in real time, and the posture is dynamically corrected by adjusting the rotation amount of each lifting screw in a differentiated manner to ensure that the workpiece table is parallel and fits the mounting base. S6. Unloading and Removal: After the workpiece table is fully in place, continue to unscrew the lifting screw until it is disengaged from the adaptive receiving part, return to the buffer support state or the completely separated state, and remove all slow-descent devices.

[0013] Furthermore, in step S2, the total supporting force of the elastic elements in each device must not be less than the weight G of the workpiece table, that is, the relationship must be satisfied: G≤n×j×k×h2, where n is the number of devices, j is the number of elastic elements in each device, and k is the stiffness coefficient of the elastic element; at the same time, h2>h1 must be satisfied to ensure that the ball end of the lifting screw in the buffer stage does not interfere with the conical groove.

[0014] Furthermore, in step S3, after the rigid support conversion is completed, the following relationship must be satisfied: d1 > d2, where d1 is the adjustable distance between the lower end of the lifting screw and the inner surface of the lifting cover, and d2 is the current distance between the lower plane of the workpiece table and the target mounting surface, so as to ensure that there is enough adjustment stroke to completely lower the workpiece table.

[0015] Furthermore, in step S5, the descent speed of the synchronous spiral descent is controlled between 0.1 mm / s and 0.5 mm / s, and the levelness correction accuracy is controlled within ±2 μm / m, so as to eliminate the risk of workpiece stage distortion caused by asynchronous multi-point support.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention employs a dual protection mechanism of "initial buffering with elastic springs and final slow descent with screw fine-tuning". At the moment of contact with the workpiece stage, the deformation of the springs absorbs most of the impact energy; in the final landing stage, the descent speed is controlled by a high-precision screw pair (up to 0.1mm / s level), which completely avoids rigid impact and effectively protects the precision optical components and guide rail surface at the bottom of the workpiece stage.

[0017] 2) The universal joint formed by the ball head and conical groove can automatically adapt to slight tilts and unevenness at the bottom of the workpiece table. Even in the case of multiple points and multiple supports, it can ensure that each support point is evenly stressed, avoiding single-point overload or suspension caused by the principle of "three points determine one surface", which significantly improves the success rate and safety of installation.

[0018] 3) By introducing the principle of air flotation, the sliding friction between the device and the ground is transformed into fluid friction (friction coefficient <0.001). Under heavy load conditions, the operator only needs a very small force to push the workpiece table to move smoothly and without vibration, solving the industry problem of high-precision alignment of heavy workpiece tables in confined spaces, and eliminating the risk of scratches caused by mechanical prying.

[0019] 4) The device adopts an oil-free lubrication design (air flotation drive) and low outgassing materials (such as stainless steel and PEEK), eliminating the need for a hydraulic oil station and removing the risk of oil pollution from the source. It fully meets the ISO Class 5 and above cleanroom environmental standards required for the installation of semiconductor lithography machines.

[0020] 5) Through a dedicated through-hole design and a clear "three-state" operating procedure, the complex precision installation process is standardized and simplified. Tasks that previously required a large professional team can now be completed by one or two people, significantly reducing installation costs and lowering the operational threshold. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the hoisting and slow-descent device for the workpiece writing table of the present invention; Figure 2 An exploded view of the workpiece table hoisting and slow-descent device of this invention is shown below; Figure 3 This is a schematic diagram of the air flotation component in the present invention, wherein (a) is a perspective view and (b) is a cross-sectional view.

[0022] Figure 4 This is a schematic diagram of the internal structure of the lifting assembly in this invention; Figure 5 This is a diagram illustrating the usage status of the workpiece lifting and lowering device for the engraving table according to the present invention. In the picture: Air flotation component 1: Air flotation block 3, elastic buffer 4 Lifting assembly 2: anti-slip pad 5, lifting cover 6, and lifting screw 7. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are only for explaining the invention and do not constitute any limitation on the scope of protection of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0024] like Figure 1-4 As shown, this embodiment provides a hoisting and slow-descent device for a writing workpiece stage, which is applied to the installation process of the writing workpiece stage, a core component of a semiconductor lithography machine. It aims to solve the problem of localized contact and collision caused by the uneven bottom of the workpiece stage in existing hoisting methods, as well as the shortcomings of traditional hydraulic or screw lifting devices that cannot meet the requirements of high cleanliness and small space operation.

[0025] This device consists of two main parts: an air-float assembly 1 and a lifting assembly 2. The air-float assembly 1 is installed at the bottom of the device and provides air-float support and cushioning. The lifting assembly 2 is installed above the air-float assembly 1 and is used to directly contact the writing workpiece stage for fine-tuning of its height. Employing a small-orifice throttling air-float block, in conjunction with the lifting assembly and elastic buffer, the workpiece stage can move horizontally and descend slowly without impact, achieving safe, efficient, stable, and high-precision installation.

[0026] In this embodiment, the entire device is made of 304 stainless steel with a passivated surface treatment to meet the requirements of semiconductor cleanrooms for materials that are non-volatile, particle-free, and corrosion-resistant. The device has external dimensions of Φ120mm×80mm, and the rated load capacity of a single unit is 500kg. Three to four units can be combined to meet the hoisting needs of workpiece tables of different specifications.

[0027] like Figure 3 As shown, the air flotation assembly 1 includes a small-hole throttling air flotation block 3 and an elastic buffer 4.

[0028] The air flotation block 3 is made of a high-strength material with a low coefficient of thermal expansion, preferably martensitic stainless steel or surface-hardened aluminum alloy, to meet the requirements of cleanrooms for non-volatile and corrosion-resistant properties. The bottom surface of the air flotation block 3 is ground to a flatness control within 0.002 mm to ensure stability when in contact with the mounting base (such as a granite platform or floor). The bottom surface is evenly distributed with several small, throttling air holes, with a diameter within 10 μm (preferably 5-8 μm). These holes are connected to the threaded air inlet on the end face via internal flow channels. When compressed gas (usually clean nitrogen or multi-stage filtered compressed air, pressure range 0.4-0.6 MPa) is introduced, the gas is ejected from the holes to form a micron-sized gas film, enabling the device to float.

[0029] The upper support surface of the air flotation block 3 has a protrusion at its center, and a conical groove is machined on the top of the protrusion. The cone angle of the conical groove is preferably 60°-90°, and the surface roughness Ra≤0.4μm. It is used to form a universal support pair with the ball head of the lifting screw to form point contact or line contact, allowing for slight angle self-adjustment.

[0030] Several elastic buffer elements 4 are evenly distributed around the circumference of the upper support surface of the air float 3. The lower end of the elastic buffer element 4 is fixed to the upper support surface of the air float 1, and the upper end abuts against the inner end face of the lifting cover 6. Spring stiffness coefficient. k Select the appropriate buffer based on the total weight G of the workpiece stage and the required buffer stroke to ensure that the impact energy can be effectively absorbed at the moment of contact between the workpiece stage and the workpiece stage.

[0031] like Figure 3 As shown, in this embodiment, the lifting assembly 2 includes an anti-slip pad 5, a lifting cover 6, and a lifting screw 7. The lifting cover 6 has a shell-like structure and is hollow inside. It has an internally threaded through hole in its center for screwing the lifting screw 7 in. The lower inner end face of the lifting cover 6 has a countersunk hole or positioning groove for fixing the upper end of the elastic buffer 4 and preventing the spring from being misaligned.

[0032] Anti-slip pad 5 is fixedly installed on the upper surface of the lifting cover 6. It is made of a material with a high coefficient of friction that does not damage the workpiece table surface, such as polyetheretherketone (PEEK), special rubber, or a composite material coated with Teflon. The upper surface of the anti-slip pad 5 may be designed with a fine mesh pattern to increase friction with the bottom of the workpiece table support groove and prevent slippage during horizontal movement.

[0033] One end of the lifting screw 7 is a smooth ball end, the radius of which is tangentially fitted to the conical groove on the air float 3, allowing for omnidirectional rotation without slippage. This allows the lifting screw to be finely tilted under load, automatically adapting to unevenness at the bottom of the workpiece table. The other end of the lifting screw 7 is an externally threaded end, which engages with the internal thread of the lifting cover 6 to achieve high-resolution vertical displacement adjustment. The middle of the lifting screw 7 has a polygonal step, with through holes on each step surface, allowing for rotational lifting of the lifting screw 7 using a rod-shaped tool.

[0034] The specific operational procedure for hoisting and lowering the workpiece stage using the aforementioned device is described. This method combines three mechanisms: mechanical buffering, air-float translation, and screw fine-tuning, to ensure the safe placement of the workpiece stage.

[0035] Step 1. Before the workpiece table hoisting begins, place 3-4 of these devices around the workpiece table installation area. Rotate each lifting screw 7 using the rod-shaped tool to move its ball head upwards, completely disengaging it from the conical groove on the upper surface of the air-float block 3 by a distance h1. At this point, the lifting assembly 2 is supported only above the air-float block 3 by the elastic buffer 4, and the lifting cover 6 is in a free state.

[0036] Step 2. Start the hoisting equipment and slowly lower the workpiece platform. When the workpiece platform is about a few centimeters away from the upper surface of the anti-slip mat 5, stop the descent. Move 3-4 of these devices to the corresponding positions of the preset support grooves at the bottom of the workpiece platform, ensuring that the devices are evenly distributed and that the central axis of the lifting cover 6 is aligned with the center of the support groove.

[0037] Step 3. Continue lowering the workpiece stage until its bottom contacts the anti-slip pad 5 of this device, at which point the elastic buffer 4 begins to compress. As the workpiece stage continues to fall, the compression of the elastic buffer 4 gradually increases until the workpiece stage is completely supported by the elastic buffers 4 of the four devices. At this point, the total compression h2 of the elastic buffer 4 should satisfy Hooke's Law: In the formula, G is the weight of the workpiece stage, n is the number of devices, j is the number of elastic buffers in each device, and k is the stiffness coefficient of the elastic buffer. In this embodiment, the weight of the workpiece stage G = 8000N, n = 4, j = 4, k = 50N / mm, and the calculated h2 = 10mm, which meets the design requirement of h2 > h1.

[0038] Step 4. After the workpiece stage is fully supported by this device, the operator uses a rod-shaped tool to rotate each lifting screw 7 in sequence, causing its ball head to move downwards and enter the conical groove on the upper surface of the air float 3. Continue fine-tuning until the ball head and the conical groove are tightly fitted, and further apply preload to gradually transfer the gravity load of the workpiece stage from simple spring support to the rigid support link of "lifting screw-air float". The criterion for judging the adjustment endpoint is: all lifting screws 7 are uniformly stressed, and the lifting cover 6 no longer continues to press down on the spring under the weight of the workpiece stage (or the spring is in a preset pre-compression state). During this process, it is necessary to ensure that the geometric relationship satisfies: the distance d1 between the lower end of the lifting screw 7 and the inner surface of the lifting cover 6 is greater than the distance d2 between the lower plane of the workpiece stage and the final mounting surface (i.e., d1>d2), to ensure that there is sufficient adjustment stroke to completely lower the workpiece stage.

[0039] Step 5. Turn on the air source and supply air into the air float 3 through the air inlet on the side of the air float 3. The gas is ejected through a 10μm hole at the bottom, forming an air film of approximately 5μm thickness between the bottom surface of the air float 3 and the ground (or mounting base). At this time, the entire device, along with the workpiece stage above it, is in a "floating" state, and the coefficient of friction is reduced to an extremely low level (<0.001). The operator only needs to apply a very small horizontal thrust to push the heavy workpiece stage to slide freely in the horizontal plane. Utilizing this characteristic, the workpiece stage can be precisely moved to the final installation position. This process avoids the scratches or vibrations that may occur with traditional dragging methods.

[0040] Step 6. After the workpiece stage is moved to the target installation position, the air source is turned off, the air film disappears, and the device slowly falls back to the installation base. At this time, the workpiece stage is still supported on the device by the lifting assembly 2, maintaining a gap of d2=12mm between it and the target installation surface. The operator uses a rod-shaped tool to gradually adjust each lifting screw 7 in diagonal sequence, so that the lifting screw 7 slowly screws into the lifting cover 6, thereby lowering the height of the lifting cover 6. During the adjustment process, the rotation angle does not exceed 15° each time, and the adjustment amount of each lifting screw 7 remains consistent. At the same time, the level on the workpiece stage is observed in real time. If the level deviation is found to exceed 0.01mm / m, the adjustment should be stopped immediately, and the lifting screw 7 in the direction of the deviation should be adjusted in the opposite direction to compensate until the level is restored before continuing to lower. Repeat the above fine-tuning process until the lower plane of the workpiece stage is in complete contact with the target installation surface. There should be no obvious impact at the moment of contact, and each lifting screw 7 should still have a slight preload to ensure that the workpiece stage is tightly attached to the installation surface.

[0041] Step 7. After the workpiece table is fully in place, continue to rotate each lifting screw 7 in the opposite direction to disengage its ball head from the conical groove of the air float 3, thus releasing the connection between the device and the workpiece table. Pull the four devices out from the bottom of the workpiece table to complete the entire hoisting and descent process.

[0042] For workpiece stages of different specifications, the number of devices can be adjusted according to the actual weight and size. For small workpiece stages (weight < 2000 kg), three devices can be arranged in a triangle; for extra-large workpiece stages (weight > 5000 kg), six or more devices can be evenly distributed for support. The adjustment of the number of devices should meet the total load-bearing capacity requirements and ensure the uniform distribution of support points.

[0043] In addition to compression springs, the elastic buffer 4 can also be in the form of disc springs, rubber springs, or air springs. Disc springs are suitable for space-constrained applications and can provide greater stiffness; rubber springs have good shock absorption performance and can further reduce impact; air springs can change stiffness by adjusting air pressure to adapt to workpiece stages of different weights.

[0044] Besides the orifice throttling type, the air flotation block 3 can also adopt a porous material throttling type or a surface throttling type structure. The porous material throttling type uses graphite or ceramic porous materials, which has better pressure equalization effect and higher load-bearing capacity; the surface throttling type achieves throttling by processing micro-grooves on the air flotation surface, and has a simple structure and is easy to process. Different throttling methods can be selected according to the actual application requirements.

[0045] The polygonal step in the middle of the lifting screw 7 can be in various forms, such as internal hexagon, external hexagon, or star-shaped, to facilitate operation with standard tools. The ball joint and conical groove can also be fitted with a ball joint and a ball socket, providing a wider range of angle adaptability.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the claims.

Claims

1. A hoisting and slow-descent device for an inscription workpiece table, characterized in that, It includes an air flotation assembly and a lifting assembly that can be height-adjusted relative to the air flotation assembly; The air flotation assembly includes an air flotation block and an elastic buffer. The bottom surface of the air flotation block is provided with an air film generating structure for suspending the device when gas is introduced. The top surface of the air flotation block is provided with an adaptive support part at its center. The lifting assembly includes a lifting cover, an anti-slip pad disposed on the top of the lifting cover, and a lifting screw penetrating the lifting cover; One end of the elastic buffer is fixedly installed on the top surface of the air flotation block, and the other end abuts against the lifting cover to provide initial buffer stroke; The lower end of the lifting screw is provided with a universal joint that cooperates with the adaptive receiving part. The universal joint can deflect at multiple angles relative to the adaptive receiving part. The device has three working states: buffer support state, rigid locking state, and air-float translation state. In the buffer support state, the universal joint of the lifting screw is either disengaged or in a virtual contact with the adaptive receiving part, and the workpiece table load is borne by the elastic buffer. In the rigid locking state, the lifting screw is rotated so that its universal joint head presses against the adaptive receiving part, transferring the workpiece table load to the air float block and locking the height of the lifting cover relative to the air float block; In the air-float translation state, the device is in a rigid locking state and an air film is formed on the bottom surface of the air-float block, realizing horizontal movement with load.

2. The hoisting and slow-descent device for the writing workpiece table according to claim 1, characterized in that, The adaptive receiving part is a conical groove opened on the top surface of the air-floating block (3), and the universal mating head is a ball head set at the lower end of the lifting screw; the ball head is embedded in the conical groove to form a ball-and-socket joint structure. When there is an inclination angle at the bottom of the workpiece table, the lifting screw can automatically deflect in the conical groove according to the posture of the workpiece table, maintain the stress concentration transmission of point contact or line contact, and avoid lateral shear force damaging the thread.

3. The hoisting and slow-descent device for the workpiece writing table according to claim 1, characterized in that, The elastic buffer includes multiple compression springs evenly distributed along the circumference; the bottom of the inner cavity of the lifting cover is provided with a spring limiting groove, the upper end of the compression spring is embedded in the groove, and the lower end is fixed to the top surface of the air float block to prevent the spring from radially instability or slippage during the buffer compression process.

4. The hoisting and slow-descent device for the workpiece writing table according to claim 1, characterized in that, The lifting screw has a tool interface in the middle, which is a polygonal cylindrical structure with a through hole axially through each side. The axis of the through hole is perpendicular to the axis of the lifting screw and is configured to allow a slender lever tool to be inserted and apply rotational torque, so as to meet the needs of one-handed or two-person collaborative operation in the narrow installation space under the writing worktable.

5. The hoisting and slow-descent device for the workpiece writing table according to claim 1, characterized in that, The air film generating structure includes a number of micropore throttling arrays uniformly distributed on the bottom surface of the air flotation block (3); the pore diameter of the micropore throttling array ranges from 5μm to 15μm, and the air flotation block is provided with a concealed airflow channel to uniformly distribute the airflow from the external air inlet to each micropore, so as to form a micron-level air film with uniform thickness and moderate stiffness on the bottom surface.

6. The hoisting and slow-descent device for the writing workpiece table according to claim 1, characterized in that, The anti-slip mat is made of a non-metallic material with a high coefficient of friction and low volatility, and its surface is textured with anti-slip material; the main structure of the air flotation block and the lifting assembly is made of non-magnetic, corrosion-resistant and low-emission metal material to meet the environmental requirements of ISO Class 5 and above for semiconductor cleanrooms.

7. A method for hoisting and slowly lowering a workpiece stage using the apparatus described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Preset and initial adjustment: Place at least three of the aforementioned slow-descent devices on the workpiece table's falling path, and adjust the lifting screw to make the device in a buffer support state, i.e., a safety gap h1 is reserved between the universal joint head and the adaptive receiving part; S2. Flexible landing: Control the workpiece stage to descend until it contacts the anti-slip pad, and use the compression deformation of the elastic buffer to absorb the remaining kinetic energy of the workpiece stage to achieve primary buffering. At this time, the compression amount of the elastic buffer is h2. S3. Adaptive locking: After the workpiece table is stationary on the elastic buffer, the lifting screws of each device are rotated synchronously to drive the universal joint head into the adaptive receiving part and gradually bear the load. During this process, the adaptability of the universal joint head is used to compensate for the initial horizontal error at the bottom of the workpiece table until the device is completely converted to a rigid locking state. At this time, the elastic buffer is in a pre-compressed state but no longer bears the main gravity load. S4. Air-float precision transfer: Air is introduced into the air-float block to put the device into an air-float translation state. Utilizing the low friction characteristics of the air film, the device position is finely adjusted to drive the workpiece stage to perform micron-level precise positioning in the horizontal plane, so that it is aligned with the final mounting base. S5. Synchronous spiral descent: After shutting off the air supply, the operator coordinates to fine-tune each lifting screw in the reverse direction, so that the workpiece table descends slowly and synchronously in a spiral feed manner under rigid support; during the descent, the levelness of the workpiece table is monitored in real time, and the posture is dynamically corrected by adjusting the rotation amount of each lifting screw in a differentiated manner to ensure that the workpiece table is parallel and fits the mounting base. S6. Unloading and Removal: After the workpiece table is fully in place, continue to unscrew the lifting screw until it is disengaged from the adaptive receiving part, return to the buffer support state or the completely separated state, and remove all slow-descent devices.

8. The method for slow descent of the writing stage according to claim 7, characterized in that, In step S2, the total supporting force of the elastic elements in each device must not be less than the weight G of the workpiece table, that is, the relationship must be satisfied: G≤n×j×k×h2, where n is the number of devices, j is the number of elastic elements in each device, and k is the stiffness coefficient of the elastic element; at the same time, h2>h1 must be satisfied to ensure that the ball end of the lifting screw in the buffer stage does not interfere with the conical groove.

9. The method for slow descent of the writing stage according to claim 7, characterized in that, In step S3, after the rigid support conversion is completed, the following relationship must be satisfied: d1 > d2, where d1 is the adjustable distance between the lower end of the lifting screw and the inner surface of the lifting cover, and d2 is the current distance between the lower plane of the workpiece table and the target mounting surface, so as to ensure that there is enough adjustment stroke to completely lower the workpiece table.

10. The method for slow descent of the writing stage according to claim 7, characterized in that, In step S5, the descent speed of the synchronous spiral descent is controlled between 0.1 mm / s and 0.5 mm / s, and the levelness correction accuracy is controlled within ±2 μm / m, so as to eliminate the risk of workpiece stage distortion caused by asynchronous multi-point support.

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