Silicon wafer thinning equipment with double-grinding-wheel structure

Abstract

The invention discloses silicon wafer thinning equipment with a double-grinding-wheel structure, and belongs to the technical field of semiconductor processing. The device comprises a grinding head, a motor is installed in the grinding head, and the output end of the motor is in driving connection with a fine grinding wheel seat and a rough grinding wheel seat which are coaxially arranged in a nested mode; a fine grinding wheel is detachably fixed to the bottom of the fine grinding wheel seat, the coarse grinding wheel seat is axially and slidably arranged on the peripheral side of the fine grinding wheel seat in a sleeving mode through a spline structure, and a coarse grinding wheel is detachably fixed to the bottom of the coarse grinding wheel seat. The grinding head is further provided with at least one driving mechanism, the output end of the driving mechanism is connected with the coarse grinding wheel base, and the driving mechanism is used for driving the coarse grinding wheel base to slide relative to the fine grinding wheel base in the axial direction so as to adjust the relative positions of the coarse grinding wheel and the fine grinding wheel in the axial direction. According to the invention, rough grinding and accurate grinding procedures can be completed in sequence through the single main shaft, the grinding wheel switching time is eliminated, the processing efficiency is greatly improved, the equipment cost and the placing space are saved, and the dual purposes of high precision and high efficiency are realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing equipment technology, and more specifically, to a grinding device for back-side thinning of silicon wafers, particularly a silicon wafer thinning device with a dual-grinding-wheel structure. Background Technology

[0002] Silicon wafers are the fundamental material for manufacturing semiconductor devices. In the integrated circuit manufacturing process, after front-end processes (such as photolithography, etching, and ion implantation), the back side of the silicon wafer typically needs to be thinned to reduce the chip's package size, lower thermal resistance, improve heat dissipation, and prepare for subsequent processes such as dicing and packaging. Silicon wafer thinning technology is a crucial step in semiconductor back-end processes.

[0003] Currently, the mainstream silicon wafer thinning technology employs mechanical grinding, which uses a high-precision rotary grinder with diamond grinding wheels to remove material from the back side of the wafer. To balance processing efficiency and surface quality, traditional thinning processes are typically divided into two stages: rough grinding and fine grinding. The rough grinding stage uses coarser-grained grinding wheels to quickly thin the wafer to near the target thickness with a high removal rate; the fine grinding stage uses finer-grained grinding wheels to eliminate the subsurface damage (SSD) layer caused by rough grinding with a lower removal rate, and to obtain the required surface roughness and flatness.

[0004] To achieve the aforementioned rough grinding and fine grinding processes, the existing mainstream equipment configuration schemes mainly include the following two types: Dual-axis / dual-station grinding machines: These machines are equipped with two independent grinding spindles, one with a coarse grinding wheel and the other with a fine grinding wheel. The machine also includes one or more workpiece supports (tables). The wafer is first moved under the coarse grinding spindle for rough grinding, and then moved under the fine grinding spindle for fine grinding. The advantage of this approach is that rough and fine grinding can be completed sequentially within the same machine, eliminating the need to transfer the wafer between different machines. However, its disadvantages are obvious: the machine structure is complex, requiring two complete spindle systems, drive systems, cooling systems, and control systems, resulting in high manufacturing costs and a large footprint. Furthermore, the alignment calibration between the two spindles is complex, and the movement and repositioning of the wafer between the two stations introduces additional auxiliary time and may introduce positioning errors.

[0005] Single-axis, single-wheel grinders with automatic wheel changers: These machines have only one grinding spindle, but are equipped with a grinding wheel magazine and an automatic tool changer. During machining, the spindle first loads a coarse grinding wheel for rough grinding. After completion, the spindle moves to the tool change position, automatically unloads the coarse grinding wheel, grabs a fine grinding wheel from the magazine, loads it, and then returns to the machining position for fine grinding. Compared to dual-axis machines, this approach is more compact and less expensive. However, its core drawback is the long wheel switching time, typically tens of seconds or even minutes. For semiconductor mass production lines aiming for high throughput, this is a critical bottleneck affecting overall efficiency. Frequent tool changes also place high demands on the automation reliability of the equipment, and the interface between the grinding wheel and the spindle is susceptible to wear under high-precision repeated disassembly and assembly, potentially affecting long-term machining accuracy.

[0006] Single-axis, single-wheel grinding machines with manual wheel changing: This is the most traditional solution, with the simplest equipment cost and structure, but the lowest efficiency. Manual intervention is required between rough and fine grinding, which is not only extremely time-consuming and cannot meet the requirements of automated production, but also poses potential pollution and safety risks due to manual operation.

[0007] In summary, existing technologies either face problems such as high equipment costs and large footprints, or processing efficiency is constrained by grinding wheel changeover time. How to achieve seamless integration of rough and fine grinding on a single machine and a single spindle, while simultaneously considering efficiency, cost, and space utilization, is a pressing technical challenge in the field of semiconductor wafer thinning technology. Although the market has an urgent need for improved efficiency and cost savings, there is currently no mature solution in China that can integrate rough and fine grinding wheels onto a single grinding head mechanism. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a silicon wafer thinning device with a dual-grinding wheel structure, thereby solving the problem that existing technologies cannot simultaneously achieve high efficiency, low cost, and compact space to realize integrated rough grinding and fine grinding processing on a single device.

[0009] The above-mentioned objective of this invention is achieved through the following technical solutions: This invention provides a silicon wafer thinning device with a dual-grinding-wheel structure, comprising: a grinding head, wherein a motor is installed inside the grinding head; a fine grinding wheel holder, detachably fixed to the output end of the motor and driven to rotate by the motor; a fine grinding wheel, detachably fixed to the bottom of the fine grinding wheel holder; a coarse grinding wheel holder, axially slidably coaxially sleeved on the outer periphery of the fine grinding wheel holder and circumferentially fixedly connected to the fine grinding wheel holder so as to be synchronously driven to rotate by the motor; a coarse grinding wheel, detachably fixed to the bottom of the coarse grinding wheel holder; and at least one driving mechanism, mounted on the grinding head, the output end of which is connected to the coarse grinding wheel holder for driving the coarse grinding wheel holder to slide relative to the fine grinding wheel holder along its axial direction, so as to adjust the relative position of the coarse grinding wheel and the fine grinding wheel in the axial direction.

[0010] According to one embodiment of the present invention, the outer wall of the fine grinding wheel holder is provided with a spline structure extending along the axial direction, and the inner wall of the coarse grinding wheel holder is provided with a spline groove that mates with the spline structure, so as to realize the circumferential fixed and axial sliding connection between the coarse grinding wheel holder and the fine grinding wheel holder.

[0011] According to one embodiment of the present invention, the driving mechanism includes: a cylinder fixed on the grinding head; a transmission assembly connected to the output end of the cylinder; a bearing cap connected to the output end of the transmission assembly; and a bearing, the inner ring of which is mounted on the coarse grinding wheel seat, and the outer ring of which is fixedly connected to the bearing cap; the cylinder drives the bearing cap to move axially through the transmission assembly, thereby driving the coarse grinding wheel seat to slide through the bearing.

[0012] According to one embodiment of the present invention, the driving mechanism further includes a fixed ring, which is fixed to the bottom of the grinding head; the transmission assembly includes a first swing angle and a second swing angle; one end of the first swing angle is hinged to the fixed ring, and the other end is hinged to the output end of the cylinder; one end of the second swing angle is hinged to the middle of the first swing angle, and the other end of the second swing angle is hinged to the bearing cap.

[0013] According to one embodiment of the present invention, the output shaft of the motor is a hollow structure; the device further includes a flushing mechanism, the flushing mechanism comprising: a water inlet pipe, one end of which is connected to an external water source, and the other end of which is sealed and inserted into the interior of the output shaft of the motor; a water delivery pipe, the top end of which is connected to the interior of the output shaft of the motor and is driven to rotate by the output shaft; a sprinkler plate base, fixed to the bottom end of the water delivery pipe, having a cavity inside; and a sprinkler plate, fixed to the bottom of the sprinkler plate base, and together with the sprinkler plate base forming a spray nozzle communicating with the cavity.

[0014] According to one embodiment of the present invention, the bottom edge of the sprinkler plate base extends downward to form a first conical surface; a second conical surface opposite to the first conical surface is provided on the sprinkler plate; the gap between the first conical surface and the second conical surface forms the spray nozzle, and the spray nozzle is an annular gap surrounding the central axis of the equipment.

[0015] According to one embodiment of the present invention, the sprinkler plate is provided with a plurality of circumferentially spaced mounting columns inside the cavity, the sprinkler plate is fixed to the bottom of the mounting columns, and a water passage is formed between adjacent mounting columns to connect the cavity and the water supply pipe.

[0016] According to one embodiment of the present invention, the driving mechanism is configured as a plurality of such mechanisms and is evenly distributed along the circumference of the grinding head.

[0017] According to one embodiment of the present invention, the outer diameter of the coarse grinding wheel is larger than the outer diameter of the fine grinding wheel.

[0018] According to one embodiment of the present invention, the output end of the motor is connected to the fine grinding wheel seat via an air bearing.

[0019] In summary, compared with the prior art, the present invention has at least one of the following beneficial technical effects: Highly integrated, dual-purpose: By integrating coaxially arranged coarse and fine grinding wheels on the same grinding head spindle, and utilizing a spline structure and drive mechanism to achieve independent axial movement of the coarse grinding wheel, one machine and one spindle can sequentially complete the coarse and fine grinding processes. This not only replaces the work that traditionally requires two machines or dual spindle machines, but also greatly saves equipment costs and valuable cleanroom space.

[0020] Significantly Improved Processing Efficiency: Compared to traditional single-axis automatic wheel-changing equipment, this invention completely eliminates the time required to change between rough and fine grinding wheels. During processing, seamless switching between processes can be achieved simply by quickly adjusting the axial height of the rough grinding wheel via the drive mechanism, reducing wheel switching time from minutes to seconds or even milliseconds, thereby significantly improving the throughput of a single machine. In a vertical comparison, integrating the two processes into the same workstation avoids the time required for wafer transfer and repositioning between different workstations, further enhancing the overall process efficiency.

[0021] Labor cost savings: Because the fully automated rough and fine grinding process is integrated, the entire process does not require manual intervention to change tools or move wafers, which improves the automation level of the production line, reduces reliance on operators, and lowers labor costs.

[0022] Improved machining accuracy and quality: Rough grinding and fine grinding are completed on the same spindle, and the wafer is always held on the same worktable, avoiding repeated positioning errors caused by changing spindles or workstations. The fine grinding wheel can immediately dress the surface after rough grinding, which helps to obtain better surface quality and more accurate total thickness deviation (TTV).

[0023] Flexible processing modes: Through precise control of the height of the coarse grinding wheel by the drive mechanism, this equipment can not only achieve sequential coarse grinding and fine grinding, but also achieve a composite grinding mode in which coarse grinding and fine grinding are performed simultaneously (for example, by controlling the coarse and fine grinding wheels to be at the same height, both can process the wafer surface at the same time, further improving the removal rate of a specific stage), providing greater flexibility for process development.

[0024] Integrated flushing and heat dissipation: The unique central water outlet flushing mechanism uses centrifugal force to evenly spray coolant / flushing fluid onto the grinding wheel and wafer surface through a conical nozzle. This not only effectively cleans grinding waste and prevents grinding wheel clogging and wafer scratches, but also provides efficient heat dissipation for the motor by the water flow through the hollow motor shaft, extending the service life of the equipment.

[0025] Although the high precision requirements of this invention during assembly result in a slightly higher initial manufacturing cost than ordinary single-axis equipment, its significant advantages in production efficiency, cost savings, and space utilization make its overall economic benefits far exceed those of existing products on the market, giving it extremely high practical value and broad market prospects. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0027] Figure 2 This is a top view of the present invention.

[0028] Figure 3 A cross-sectional view of the present invention.

[0029] Figure 4 An exploded front view of the sprinkler tray base and sprinkler tray is shown for the present invention.

[0030] Figure 5 This is an exploded reverse view of the sprinkler tray base and sprinkler tray for the present invention.

[0031] Reference numerals: 100, grinding head; 110, grinding head housing; 120, motor; 121, output shaft; 122, flange; 130, air bearing; 140, fine grinding wheel holder; 141, spline structure; 150, fine grinding wheel; 160, coarse grinding wheel holder; 161, spline groove; 170, coarse grinding wheel; 200, drive mechanism; 210, cylinder; 220, connector; 230, first swing angle; 240, second swing angle. Two swing angles; 250, fixing ring; 260, bearing cover; 270, bearing; 280, bearing ring; 300, flushing mechanism; 310, first flange; 320, water inlet pipe; 330, water delivery pipe; 340, sprinkler plate seat; 341, cavity; 342, first conical surface; 343, mounting column; 344, water passage; 350, sprinkler plate; 351, second conical surface; 360, spray nozzle; 400, mounting plate. Detailed Implementation

[0032] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0033] In the description of this application, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] This invention discloses a silicon wafer thinning device with a dual-grinding-wheel structure, including a grinding head 100. A motor 120 is installed inside the grinding head 100. An air bearing 130 is mounted on the output shaft 121 of the motor 120 via a flange. A fine grinding wheel holder 140 is detachably fixed to the bottom of the air bearing 130. A fine grinding wheel 150 is detachably fixed to the bottom of the fine grinding wheel holder 140. A spline structure 141 is provided on the outer wall of the fine grinding wheel holder 140. A coarse grinding wheel holder 160 can be moved up and down via the spline structure 141. A coarse grinding wheel 170 is slidably disposed on the periphery of the fine grinding wheel holder 140 and detachably fixed to the bottom of the coarse grinding wheel holder 160; the motor 120 drives the coarse grinding wheel 170 and the fine grinding wheel 150 to rotate synchronously through the air bearing 130; it also includes at least one drive mechanism 200 disposed on the outside of the grinding head 100, the drive mechanism 200 is used to drive the coarse grinding wheel holder 160 to move axially up and down on the outside of the fine grinding wheel holder 140 to adjust the axial height position of the coarse grinding wheel 170 relative to the fine grinding wheel 150.

[0036] Furthermore, multiple drive mechanisms 200 are configured, and the multiple drive mechanisms 200 are evenly distributed along the circumference of the grinding head 100.

[0037] Furthermore, the drive mechanism 200 includes a cylinder 210, a connector 220, a first swing angle 230, a second swing angle 240, a retaining ring 250, a bearing cap 260, a bearing 270, and a bearing ring 280; the cylinder 210 is fixed to the outer wall of the grinding head 100, and the end of the piston rod of the cylinder 210 is hinged to one end of the first swing angle 230 through the connector 220; the retaining ring 250 is detachably fixed to the bottom of the grinding head 100 and sleeved on the outside of the air bearing 130; the other end of the first swing angle 230 is hinged to the retaining ring 250; the first swing angle 240... The middle part of the first swing angle 230 is hinged to one end of the second swing angle 240; the other end of the second swing angle 240 is hinged to the bearing cover 260; the bearing 270 is mounted on the outer circumferential surface of the coarse grinding wheel seat 160, the bearing ring 280 is mounted on the outer side of the bearing 270, and the bearing 270 and the bearing ring 280 are fixed by the bearing cover 260; when the piston rod of the cylinder 210 extends or retracts, the bearing cover 260 is driven by the connecting rod of the first swing angle 230 and the second swing angle 240 to drive the bearing 270 and the coarse grinding wheel seat 160 to move up and down along the spline structure 141.

[0038] Furthermore, the silicon wafer thinning equipment also includes a rinsing mechanism 300, the outlet of which is located at the center of the fine grinding wheel 150 and the coarse grinding wheel 170, for rinsing the grinding waste on the wafer surface during the thinning process.

[0039] Furthermore, the flushing mechanism 300 includes a first flange 310, a water inlet pipe 320, a water delivery pipe 330, a sprinkler plate seat 340, and a sprinkler plate 350; the first flange 310 is detachably fixed to the top of the motor 120, one end of the water inlet pipe 320 is installed on the first flange 310 and communicates with an external water source, and the other end is sealed and inserted into the hollow output shaft 121 of the motor 120; the top end of the water delivery pipe 330 is fixed to the output shaft 121 of the motor 120 and communicates with the hollow interior of the output shaft 121, and the bottom end of the water delivery pipe 330 is fixedly connected to the sprinkler plate seat 340; the sprinkler plate 350 is fixed to the bottom of the sprinkler plate seat 340.

[0040] Furthermore, the sprinkler plate base 340 has a cavity 341 inside, and the bottom edge of the cavity 341 extends downward to form a first conical surface 342; the sprinkler plate 350 is provided with a second conical surface 351 that is in clearance fit with the first conical surface 342, and an annular conical spray nozzle 360 ​​that communicates with the cavity 341 is formed between the first conical surface 342 and the second conical surface 351.

[0041] Furthermore, the sprinkler disc base 340 has multiple mounting posts 343 evenly spaced around the inside of the cavity 341, and the mounting posts 343 are integrally formed with the sprinkler disc base 340; the sprinkler disc 350 is fixed to the bottom of the mounting posts 343 by multiple screws, and a water passage 344 is formed between adjacent mounting posts 343 to connect the cavity 341 and the water pipe 330.

[0042] Furthermore, a mounting plate 400 is detachably fixed to one side of the outer wall of the grinding head 100 for mounting the entire grinding head 100 mechanism onto the Z-axis slide of the thinning equipment.

[0043] Furthermore, the outer diameter of the coarse grinding wheel 170 is larger than that of the fine grinding wheel 150.

[0044] Furthermore, the spline structure 141 is a straight-tooth spline provided on the outer wall of the fine grinding wheel holder 140, which matches the straight-tooth spline groove 161 provided on the inner wall of the coarse grinding wheel holder 160, for transmitting torque and allowing axial sliding. Example

[0045] Please refer to the following: Figures 1 to 5 This invention provides a silicon wafer thinning device with a dual-grinding wheel structure. This device is mainly used for back-side thinning of semiconductor silicon wafers and can sequentially complete rough grinding and fine grinding processes on a single spindle.

[0046] like Figure 1 and Figure 2As shown, the device mainly includes a core grinding head assembly 100. The grinding head assembly 100 includes a grinding head housing 110. The grinding head housing 110 is typically made of high-strength, high-rigidity metal materials (such as cast iron or steel) to ensure structural stability under high-speed rotation and grinding forces. The interior of the grinding head housing 110 forms a receiving space for mounting a drive motor 120. The motor 120 is the core cylinder that realizes the rotation of the grinding wheel, and typically employs a high-precision, high-speed electric spindle motor. The output shaft 121 of the motor 120 has a hollow structure and extends downwards. An air bearing 130 is mounted at the end of the output shaft 121 via a flange structure (which can be an integrally formed flange 122 or a separate connection to the output shaft).

[0047] Air bearing 130 is a high-precision bearing that uses gas (usually air) as a lubricant. It features low friction, high speed, and high rotational accuracy, making it ideal for high-precision grinding applications. In this embodiment, the stator portion (not shown) of air bearing 130 is fixed to the grinding head housing 110 or a related support structure, while its rotor portion is fixedly connected to flange 122 and rotates synchronously with the motor output shaft 121. The bottom of air bearing 130, i.e., the lower end of its rotating portion, is designed with a precision mounting interface for detachably fixing the fine grinding wheel holder 140. This detachable fixing method can be a high-precision threaded connection with end face key positioning, or it can be secured with multiple high-strength bolts to ensure connection reliability and repeatability.

[0048] The fine grinding wheel holder 140 is generally cylindrical in shape. Its bottom has a precision mounting surface for detachably securing the fine grinding wheel 150 with bolts or other fasteners. The fine grinding wheel 150 is a fine-grained diamond wheel used for fine machining of wafer surfaces to obtain a final surface with low roughness and a low-damage layer.

[0049] One of the core improvements of this invention lies in the outer wall structure of the precision grinding wheel holder 140. For example... Figure 3 As shown, the outer wall of the fine grinding wheel holder 140 is provided with a spline structure 141 along the axial direction. In a preferred embodiment, the spline structure 141 is a straight involute spline, with its tooth profile extending along the axial direction. A coarse grinding wheel holder 160 is sleeve-shaped, and its inner wall is provided with a spline groove 161 that matches the spline structure 141 on the outer wall of the fine grinding wheel holder 140. Through the cooperation of the spline structure 141 and the spline groove 161, the coarse grinding wheel holder 160 can be coaxially sleeved on the periphery of the fine grinding wheel holder 140 and can slide freely along the axial direction (i.e., the up and down direction). At the same time, this cooperation can effectively transmit the rotational torque output by the motor 120 to the coarse grinding wheel holder 160, so that it can rotate synchronously with the fine grinding wheel 150.

[0050] The bottom of the coarse grinding wheel holder 160 is provided with a coarse grinding wheel mounting surface for detachably fixing the coarse grinding wheel 170. The coarse grinding wheel 170 is a coarse-grained diamond grinding wheel, and its diameter is usually larger than that of the fine grinding wheel 150 to achieve a higher material removal rate. This coaxial nested, relatively axially sliding dual-grinding wheel structure design ingeniously integrates two grinding wheels with different functions on a single spindle and a single rotation center, laying the foundation for subsequent process switching.

[0051] To achieve height adjustment of the coarse grinding wheel 170 relative to the fine grinding wheel 150, the equipment is also equipped with at least one drive mechanism 200. For example... Figure 1 , Figure 2 As shown, in this embodiment, in order to provide a uniform and stable driving force and avoid the coarse grinding wheel holder 160 from tilting during movement, three drive mechanisms 200 are provided, which are evenly distributed (at 120-degree intervals) along the circumference of the grinding head housing 110. Of course, depending on different load and accuracy requirements, one, two or more drive mechanisms can also be provided.

[0052] The specific structure of the drive mechanism 200 is as follows: Figure 3 As shown. It includes a cylinder 210, a connector 220, a first swing angle 230, a second swing angle 240, a retaining ring 250, a bearing cap 260, a bearing 270, and a bearing ring 280.

[0053] Cylinder 210 serves as the power source, and its cylinder body is fixedly mounted on the outer wall of the grinding head housing 110 via a cylinder mounting bracket. The end of the piston rod of cylinder 210 is hinged to one end of the first swing angle 230 via connector 220. Connector 220 can be a connector with a fisheye bearing or a spherical bearing to accommodate rotation of the hinge point.

[0054] The retaining ring 250 is a ring-shaped component that is detachably fixed to the bottom of the grinding head housing 110 by bolts and surrounds the outside of the air bearing 130, providing a stable mounting base for the moving parts below it. The first swing angle 230 is a lever structure, one end of which is hinged to the retaining ring 250 via a first hinge axis. Thus, the first swing angle 230 can swing about the first hinge axis. The other end (drive end) of the first swing angle 230 is hinged to the connector 220, and the middle part (transmission end) is hinged to one end of the second swing angle 240. The other end of the second swing angle 240 is hinged to the bearing cap 260.

[0055] The bearing cap 260 is an annular component that secures the bearing 270 and bearing ring 280 and connects them to the drive mechanism 200. The bearing 270 can be a high-precision deep groove ball bearing or angular contact ball bearing, with its inner ring mounted on the outer circumferential surface of the coarse grinding wheel seat 160. The bearing ring 280 is mounted on the outer ring of the bearing 270, providing axial positioning and protection for the bearing. The bearing 270 and bearing ring 280 are then fixed and housed as a single unit at the bottom of the bearing cap 260. Specifically, the bearing cap 260 can be designed as an annular cap with a stepped bore, within which the bearing 270 and bearing ring 280 are mounted and axially secured by a clamping ring or end cap.

[0056] During operation, the drive mechanism 200 drives a set of linkage mechanisms (first swing angle 230 and second swing angle 240) through the extension and retraction of the cylinder 210 to convert the motion into the vertical movement of the bearing cover 260, which in turn drives the coarse grinding wheel seat 160 to slide up and down through the bearing 270.

[0057] like Figure 3 As shown, when the coarse grinding wheel 170 needs to be in a low position for coarse grinding, the piston rod of the cylinder 210 extends, pushing the driving end of the first swing angle 230 downward. The first swing angle 230 rotates around the first hinge axis, and its transmission end lifts upward, pushing the second swing angle 240 to swing upward. The other end of the second swing angle 240 presses down on the bearing cap 260. The bearing cap 260 transmits the downward pressure to the coarse grinding wheel seat 160 through the bearing 270, forcing the coarse grinding wheel seat 160 to overcome any possible friction and slide downward along the spline structure 141 of the fine grinding wheel seat 140 until the bottom surface of the coarse grinding wheel 170 is lower than the bottom surface of the fine grinding wheel 150. At this time, the coarse grinding wheel 170 contacts the wafer for processing.

[0058] like Figure 3 As shown, when the rough grinding stage ends and it is time to switch to fine grinding, the piston rod of cylinder 210 retracts, pulling the drive end of the first swing angle 230 upward. The first swing angle 230 rotates in the opposite direction, pulling its transmission end downward, which in turn pulls the bearing cap 260 upward through the second swing angle 240. The bearing cap 260 lifts the rough grinding wheel seat 160 upward through the bearing 270, causing it to slide upward along the spline until the bottom surface of the rough grinding wheel 170 is higher than the bottom surface of the fine grinding wheel 150. At this time, the rough grinding wheel 170 leaves the wafer surface, and only the fine grinding wheel 150 contacts the wafer for finishing.

[0059] Furthermore, by precisely controlling the stroke of cylinder 210, the coarse grinding wheel 170 can be adjusted to be completely flush with the fine grinding wheel 150, thereby achieving a composite processing mode in which both participate in grinding simultaneously. This may have application value in some intermediate stages that require extremely high removal rates.

[0060] To effectively remove grinding waste (silicon powder, diamond chips, etc.) from the wafer surface during grinding and to cool and lubricate the grinding zone, this invention also includes a unique flushing mechanism 300. For example... Figures 3-5 As shown, the rinsing mechanism 300 cleverly utilizes the structure of a hollow motor shaft.

[0061] The flushing mechanism 300 includes a first flange 310, a water inlet pipe 320, a water delivery pipe 330, a sprinkler plate seat 340, and a sprinkler plate 350. The first flange 310 is detachably fixed to the top of the motor 120 by bolts and seals the top opening of the motor 120. One end of the water inlet pipe 320 is mounted on the first flange 310 via a rotary joint (not shown) and communicates with an external high-pressure coolant / water source. The other end of the water inlet pipe 320 is sealed inside the hollow motor output shaft 121. Since the motor output shaft 121 rotates at high speed while the water inlet pipe 320 is fixed, a dynamic sealing structure, such as a mechanical seal or a labyrinth seal, is required between the two.

[0062] The water supply pipe 330 is a slender tube whose top end is fixed to the inner wall or bottom of the motor output shaft 121 via a connector, and communicates with the hollow interior of the motor output shaft 121. Thus, when the motor output shaft 121 rotates, it drives the water supply pipe 330 to rotate as well. The bottom end of the water supply pipe 330 extends downwards and is fixedly connected to the sprinkler disc holder 340. The sprinkler disc holder 340 is hollow inside, forming a cavity 341. The sprinkler disc 350 is fixed to the bottom of the sprinkler disc holder 340.

[0063] A key design optimization lies in the structure of the sprinkler disc holder 340 and the sprinkler disc 350. For example... Figure 3 , Figure 4 and Figure 5 As shown, the bottom edge of the cavity 341 of the sprinkler disc holder 340 extends downward to form a conical surface, referred to as the first conical surface 342. The sprinkler disc 350 has a corresponding conical surface, referred to as the second conical surface 351. When the sprinkler disc 350 is installed at the bottom of the sprinkler disc holder 340, a small and uniform gap is maintained between the first conical surface 342 and the second conical surface 351. This gap forms an annular conical spray nozzle 360 ​​surrounding the central axis. This spray nozzle 360 ​​communicates with the cavity 341.

[0064] To support the sprinkler disc 350 and allow water flow, the sprinkler disc base 340 has multiple circumferentially evenly spaced mounting posts 343 inside the cavity 341. The mounting posts 343 are integrally formed with the sprinkler disc base 340, for example, by casting or machining. The sprinkler disc 350 is secured to the bottom of the mounting posts 343 by multiple screws 352 passing through threaded holes in the mounting posts 343. Because the mounting posts 343 are spaced apart, a water passage 344 naturally forms between adjacent mounting posts 343, connecting the cavity 341 and the water pipe 330.

[0065] During operation, external high-pressure water enters the hollow motor output shaft 121 through the inlet pipe 320. As the water flows through the output shaft 121, it carries away the heat generated by the motor 120 during operation, providing internal cooling. Then, the water flows into the rotating water supply pipe 330, where it flows downwards along the inner wall under centrifugal force. After entering the sprinkler disc seat 340, the water first enters the cavity 341 through the water passage 344. Because the sprinkler disc seat 340 and sprinkler disc 350 rotate at high speed with the main shaft, the water entering the cavity 341 is subjected to strong centrifugal force and thrown against the outer wall of the cavity 341. Subsequently, this high-pressure water flows through the conical nozzle 360 ​​formed by the first conical surface 342 and the second conical surface 351, and is ejected at extremely high speed and an ideal spray angle. Because the water nozzle is annular, the sprayed water curtain evenly covers the fine grinding wheel 150, the coarse grinding wheel 170, and the wafer surface below, achieving efficient and uniform cleaning and cooling.

[0066] To facilitate the installation of the entire grinding head assembly 100 onto the Z-axis slide of the thinning device (a mechanism for controlling the up and down feed of the grinding head), a mounting plate 400 is detachably fixed to one side of the outer wall of the grinding head housing 110. The mounting plate 400 is provided with precision mounting holes and positioning keyways for docking with the Z-axis slide.

[0067] Based on the above structure, the working process of the dual-grinding-wheel structure silicon wafer thinning equipment of the present invention is as follows: Initial state: The equipment is in standby state. The cylinder 210 of the drive mechanism 200 can be in the retracted state, so that the coarse grinding wheel 170 is in a high position (higher than the fine grinding wheel 150), or in the extended state, so that the coarse grinding wheel 170 is in a low position. Normally, for safety or to prepare for coarse grinding, the coarse grinding wheel can be preset to the low position.

[0068] Rough Grinding Stage: The wafer is held in place on a rotating worktable (not shown in the figure). The grinding head assembly 100 descends rapidly under the drive of the Z-axis slide until it reaches the rough grinding position. At this time, the rough grinding wheel 170 is in a low position, contacting the wafer surface. The motor 120 starts, driving the fine grinding wheel 150 and the rough grinding wheel 170 to rotate at the same speed simultaneously via the air bearing 130. At the same time, the rinsing mechanism 300 starts working to rinse and cool the processing area. In this stage, the rough grinding wheel 170 mainly relies on high-speed, high-feed grinding to quickly remove most of the material on the back side of the wafer, reducing the wafer thickness to near the target thickness. The fine grinding wheel 150 is above the wafer surface at this time and does not participate in the processing.

[0069] Switching Phase: Once the preset thickness or time has been reached during coarse grinding, the control system issues a switching command. The cylinder 210 of the drive mechanism 200 actuates (e.g., if previously extended, now retracts), rapidly lifting the coarse grinding wheel holder 160 upwards via a linkage mechanism, raising the coarse grinding wheel 170 to a position higher than the fine grinding wheel 150. This process is very rapid, typically completed within a few seconds.

[0070] Fine grinding stage: The grinding head assembly 100 descends slightly again under the drive of the Z-axis slide (or maintains its original height, depending on the initial height setting of the fine grinding wheel), bringing the fine grinding wheel 150 into contact with the wafer surface. At this time, the fine grinding wheel 150 performs fine grinding on the wafer surface after rough grinding, removing the damaged layer left by rough grinding and improving surface roughness and TTV. The rough grinding wheel 170 is above the wafer surface at this time and does not participate in processing. The rinsing mechanism 300 continues to operate.

[0071] Processing complete: After the fine grinding meets the final requirements, the grinding head assembly is raised 100 degrees, the spindle stops rotating, and rinsing stops. The worktable removes the processed wafer, completing one processing cycle.

[0072] Through the above technical solutions, the present invention has achieved significant technical progress and solved a technical problem that has long plagued the field.

[0073] First, in terms of integration and space utilization, this invention integrates coarse and fine grinding wheels onto a single grinding head, enabling one machine to perform integrated coarse and fine grinding processes that previously required two single-axis machines or one dual-axis machine. For semiconductor cleanrooms where space is extremely limited, this translates to a significant increase in output per unit area, and can substantially reduce the construction and operating costs of the facility.

[0074] Secondly, from the perspective of processing efficiency, this is the core advantage of this invention. Compared horizontally with the traditional "single-axis + automatic tool changer" solution, this invention completely eliminates the time-consuming step of changing the grinding wheel. In the traditional solution, the tool change time (from the end of rough grinding to the start of fine grinding) typically takes 30 seconds or even longer, which is a serious bottleneck in large-scale mass production. However, this invention adjusts the height of the rough grinding wheel through a drive mechanism, and the switching time is only 1-2 seconds, which is almost negligible. Compared vertically with the "dual-axis / dual-station" solution, this invention not only saves the cost of a spindle, but more importantly, it saves the time spent moving and aligning the wafer between the two stations, further improving efficiency. Taking a typical processing cycle as an example, the traditional process may require 60 seconds for rough grinding, 30 seconds for tool / station change, and 60 seconds for fine grinding, totaling 150 seconds. With this invention, rough grinding takes 60 seconds, switching takes 2 seconds, and fine grinding takes 60 seconds, totaling 122 seconds, an efficiency improvement of approximately 18.7%. Considering more complex processes or slower tool change speeds, the efficiency improvement will be even more significant.

[0075] Secondly, from the perspective of processing accuracy, since rough grinding and fine grinding are performed at the same station and on the same spindle, the wafer does not need to be repositioned during the entire processing, avoiding positioning errors caused by table movement and secondary adsorption. This helps to obtain a smaller TTV (Total Thickness Deviation) value and better surface microstructure consistency. At the same time, the fine grinding wheel follows the rough grinding wheel in processing, which can promptly correct edge warping or stress caused by rough grinding, further improving yield.

[0076] From an economic perspective, although the initial purchase cost of the equipment of this invention is slightly higher than that of ordinary single-axis equipment due to its complex structure and high assembly precision requirements, the comprehensive economic benefits brought about by the efficiency improvement, labor saving, and space saving far outweigh the increase in initial cost. According to preliminary calculations, under the same production capacity requirements, using the equipment of this invention can reduce the number of equipment purchased, reduce the number of operators and maintenance personnel, and significantly shorten the overall investment payback period.

[0077] Furthermore, the integrated flushing and heat dissipation system of this invention also has unique advantages. Traditional external spraying methods often fail to accurately and evenly spray coolant onto the grinding arc area and are prone to splashing. The central water outlet structure of this invention utilizes the centrifugal force generated by rotation to evenly spray coolant at a certain speed and angle through the annular conical surface, forming a cooling and cleaning curtain covering the entire grinding area. This not only provides better cooling but also more effectively flushes away silicon powder generated during grinding from the grinding wheel surface, preventing wheel clogging and extending wheel life. Simultaneously, the water flow effectively cools the internal structure of the hollow motor shaft, solving the heat dissipation problem of high-power electric spindles under long-term high-speed operation, which is beneficial for maintaining the stability of machining accuracy and extending motor life.

[0078] Based on the above embodiments, those skilled in the art can make various modifications and variations, all of which fall within the protection scope of this invention.

[0079] Variations in the drive mechanism: The cylinder driving the coarse grinding wheel holder is not limited to air cylinders; hydraulic cylinders, linear motors, servo motors, and precision transmission mechanisms such as ball screws or racks and pinions can also be used. For example, a servo motor can drive a synchronous pulley, which in turn rotates a nut threaded to the coarse grinding wheel holder, thus converting rotational motion into linear motion. This approach allows for more precise closed-loop position control. The arrangement of the drive mechanism is not limited to three; it can be two, four, or more, as long as uniform force is ensured. The linkage mechanism can also take many forms, such as using linear guides with levers, or using a cam mechanism to achieve rapid lifting and lowering.

[0080] Variations of spline structures: Besides spur splines, splines can also be helical splines. While helical splines can theoretically generate an axial force component while transmitting torque, with appropriate drive, spur splines are a better choice considering the need for precise axial position control because they decouple motion and power transmission. The tooth profile of a spline can also be trapezoidal, rectangular, etc., as long as sliding and torque transmission are achieved.

[0081] Variations in the flushing mechanism: The gap between the conical spray nozzles can be fixed or adjustable. For example, a shim can be placed between the spray disc base and the spray disc, or a threaded structure can be designed to adjust the axial position of the spray disc, thereby changing the gap between the first and second conical surfaces to adjust the water curtain flow rate and spray angle. Other types of rotary joints can also be used to connect the water inlet pipe. If the motor shaft is not hollow, water can be introduced from the side, but a hollow structure is the most compact and efficient solution.

[0082] Variations in the grinding wheel holder connection method: Besides bolt fixing, the connection between the precision grinding wheel holder and the bottom of the air bearing, as well as the connection between the grinding wheel and the grinding wheel holder, can also utilize other quick-change interfaces, such as HSK and KM tool holder interfaces, to meet the needs of automated changing of different grit grinding wheels. Although this invention aims to eliminate tool changing, this interface design remains compatible in situations where special grinding wheels need to be replaced.

[0083] Variations in application scope: Although this invention primarily targets silicon wafer thinning, its principles are equally applicable to the thinning or grinding of other hard and brittle materials (such as silicon carbide, sapphire, and glass), as long as these materials require two steps: rough grinding and fine grinding. Therefore, any grinding equipment employing the coaxial nested, axially movable double grinding wheel structure of this invention should fall within the protection scope of this invention.

[0084] In summary, the silicon wafer thinning equipment with a dual-grinding wheel structure provided by this invention successfully resolves the contradiction between efficiency and cost in existing technologies through innovative structural design. It achieves seamless integration of rough grinding and fine grinding processes on a single spindle, and has outstanding advantages such as high efficiency, high precision, low cost, and high integration. It provides a brand-new and highly competitive solution for semiconductor wafer thinning processes, meeting the market's urgent need for improved efficiency and cost savings.

[0085] The implementation principle of this invention is as follows: This invention discloses a silicon wafer thinning device with a dual-grinding-wheel structure, belonging to the field of semiconductor processing technology. This invention includes a grinding head 100, inside which a motor 120 is installed. The output end of the motor 120 drives a fine grinding wheel holder 140 and a coarse grinding wheel holder 160, which are coaxially nested. A fine grinding wheel 150 is detachably fixed to the bottom of the fine grinding wheel holder 140. The coarse grinding wheel holder 160 is axially slidably fitted onto the outer periphery of the fine grinding wheel holder 140 via a spline structure 141, and a coarse grinding wheel 170 is detachably fixed to its bottom. At least one driving mechanism 200 is also installed on the grinding head 100. The output end of the driving mechanism 200 is connected to the coarse grinding wheel holder 160 and is used to drive the coarse grinding wheel holder 160 to slide axially relative to the fine grinding wheel holder 140, thereby adjusting the relative axial positions of the coarse grinding wheel 170 and the fine grinding wheel 150. This invention allows for the sequential completion of rough grinding and fine grinding processes using a single spindle, eliminating grinding wheel switching time, significantly improving processing efficiency, saving equipment costs and space, and achieving high precision and high efficiency with a single machine.

[0086] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A silicon wafer thinning device with a dual-grinding wheel structure, characterized in that, include: A grinding head (100) with a motor (120) installed inside the grinding head (100); A fine grinding wheel holder (140) is detachably fixed to the output end of the motor (120) and driven to rotate by the motor (120); A fine grinding wheel (150) is detachably fixed to the bottom of the fine grinding wheel holder (140); A coarse grinding wheel seat (160) is axially slidably coaxially sleeved on the outer periphery of the fine grinding wheel seat (140) and circumferentially fixedly connected to the fine grinding wheel seat (140) so as to be synchronously driven to rotate by the motor (120); A coarse grinding wheel (170) is detachably fixed to the bottom of the coarse grinding wheel seat (160); as well as At least one drive mechanism (200) is mounted on the grinding head (100), and its output end is connected to the coarse grinding wheel holder (160) for driving the coarse grinding wheel holder (160) to slide relative to the fine grinding wheel holder (140) along its axial direction to adjust the relative position of the coarse grinding wheel (170) and the fine grinding wheel (150) in the axial direction.

2. The silicon wafer thinning equipment with a dual grinding wheel structure according to claim 1, characterized in that, The outer wall of the fine grinding wheel holder (140) is provided with a spline structure (141) extending along the axial direction, and the inner wall of the coarse grinding wheel holder (160) is provided with a spline groove (161) that cooperates with the spline structure (141) to realize the circumferential fixed and axial sliding connection between the coarse grinding wheel holder (160) and the fine grinding wheel holder (140).

3. The silicon wafer thinning equipment with a dual grinding wheel structure according to claim 1, characterized in that, The drive mechanism (200) includes: A cylinder (210) is fixed on the grinding head (100); A transmission assembly is connected to the output end of the cylinder (210); A bearing cap (260) is connected to the output end of the transmission assembly; and A bearing (270) has its inner ring mounted on the coarse grinding wheel seat (160) and its outer ring fixedly connected to the bearing cap (260); The cylinder (210) drives the bearing cap (260) to move axially through the transmission assembly, and then drives the coarse grinding wheel seat (160) to slide through the bearing (270).

4. The silicon wafer thinning equipment with a dual grinding wheel structure according to claim 3, characterized in that, The drive mechanism (200) further includes a fixing ring (250) fixed to the bottom of the grinding head (100); the transmission assembly includes a first swing angle (230) and a second swing angle (240); one end of the first swing angle (230) is hinged to the fixing ring (250), and the other end is hinged to the output end of the cylinder (210); one end of the second swing angle (240) is hinged to the middle of the first swing angle (230), and the other end of the second swing angle (240) is hinged to the bearing cap (260).

5. The silicon wafer thinning equipment with a dual grinding wheel structure according to claim 1, characterized in that, The output shaft (121) of the motor (120) has a hollow structure; the device also includes a rinsing mechanism (300), which includes: A water inlet pipe (320) has one end connected to an external water source and the other end sealed and inserted into the inside of the output shaft (121) of the motor (120); A water pipe (330) has its top end connected to the interior of the output shaft (121) of the motor (120) and is driven to rotate by the output shaft (121); A sprinkler plate base (340) is fixed to the bottom end of the water pipe (330), and its interior is provided with a cavity (341); and A water spray plate (350) is fixed to the bottom of the water spray plate base (340) and together with the water spray plate base (340) forms a water spray nozzle (360) that communicates with the cavity (341).

6. The silicon wafer thinning equipment with a dual grinding wheel structure according to claim 5, characterized in that, The bottom edge of the sprinkler plate base (340) extends downward to form a first conical surface (342); a second conical surface (351) opposite to the first conical surface (342) is provided on the sprinkler plate (350); the gap between the first conical surface (342) and the second conical surface (351) forms the spray nozzle (360), and the spray nozzle (360) is an annular gap surrounding the central axis of the equipment.

7. A silicon wafer thinning device with a dual grinding wheel structure according to claim 5, characterized in that, The sprinkler plate base (340) is provided with a plurality of circumferentially spaced mounting columns (343) inside the cavity (341). The sprinkler plate (350) is fixed to the bottom of the mounting columns (343). A water passage (344) is formed between adjacent mounting columns (343) to connect the cavity (341) and the water supply pipe (330).

8. The silicon wafer thinning equipment with a dual grinding wheel structure according to claim 1, characterized in that, The drive mechanism (200) is configured as a plurality of such mechanisms and is evenly distributed along the circumference of the grinding head (100).

9. A silicon wafer thinning device with a dual grinding wheel structure according to claim 1, characterized in that, The outer diameter of the coarse grinding wheel (170) is larger than the outer diameter of the fine grinding wheel (150).

10. A silicon wafer thinning device with a dual grinding wheel structure according to claim 1, characterized in that, The output end of the motor (120) is connected to the fine grinding wheel seat (140) via an air bearing (130).

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