A special fixture for cutting grooves of silicon carbide crystal boat

Abstract

This invention relates to the field of semiconductor wafer processing technology and discloses a special fixture for grooving silicon carbide wafer boats. The fixture includes a base plate, two sets of side plates, and two sets of support plates, all interconnected by fasteners to form a top-opening, enclosed support frame. The inner sides of the base plate, side plates, and support plates are respectively provided with corresponding groove structures for conformal fitting with different parts of the wafer boat. Micro-gaps are reserved between the inner walls of each groove and the mating surfaces of the wafer boat to accommodate self-adaptive permeation filling of liquid paraffin, forming a stress-free rigid hold after the paraffin solidifies. Furthermore, the relative positions of the side plates and support plates are adjustable to accommodate wafer boats of different sizes. Small perforated structures are provided at the bottom of the support plates as drainage channels. Through the guidance of the three-dimensional grooves and the solidification of the paraffin, localized compressive stress deformation is eliminated. This high-rigidity support frame effectively resists cutting vibration, thereby improving the precision grooving quality of the wafer boat.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer processing technology, specifically to a special fixture for slotting silicon carbide wafer boats. Background Technology

[0002] Silicon carbide wafer boats are crucial support structures in semiconductor wafer thermal processing. Their manufacturing requires high-precision grooving of the support rods on the raw material to ensure the wafer can be accurately inserted into the slots during subsequent use. Due to the extremely high hardness of silicon carbide, the industry typically uses ceramic diamond grinding wheels in conjunction with machining centers for high-speed cutting. This specific machining condition places extremely high demands on stress control during workpiece clamping and the structural rigidity of the fixture.

[0003] In existing grooving processes, traditional fixtures typically use mechanical grippers or bolts to clamp the raw material of the crystal boat. This clamping method, based on purely mechanical external force, inevitably applies localized and non-uniform compressive forces to the workpiece surface. After the crystal boat is processed and the clamping mechanism is released, the clamping stress accumulated inside the workpiece is released, causing microscopic deformation of the entire crystal boat. This stress deformation directly changes the relative spatial position of the cut grooves, making it difficult for the final product to meet the stringent micron-level tolerance requirements of the semiconductor industry.

[0004] Considering the dynamic working conditions of machining centers, traditional fixtures often employ open structures or simple single-sided support frames, resulting in relatively weak overall bending moment of inertia and torsional stiffness. When subjected to complex cutting loads from the high-speed rotation of diamond grinding wheels, such insufficiently rigid fixtures are prone to high-frequency vibration resonance with the machine tool, which can affect the surface finish of the cut grooves and even cause chipping defects in brittle silicon carbide boats.

[0005] In the specific processing steps, high-intensity grooving operations require continuous spraying of large amounts of cutting fluid for cooling and chip removal. Existing fixtures are mostly solid structures, making it easy for cutting fluid to accumulate inside the fixture and between the fixture and the bearing surface. This results in the expensive cutting tools being immersed in waste fluid containing grinding debris for extended periods, accelerating spindle tool wear. Furthermore, semiconductor manufacturing frequently requires processing wafer boats of varying lengths, but existing fixed fixtures are often designed for a single size, lacking flexibility and adjustability. When processing tasks change, manufacturers must customize and replace the entire set of dedicated fixtures, increasing downtime for line changes and leading to high tooling manufacturing costs. These combined defects severely restrict the final yield rate of silicon carbide wafer boat grooving, making expensive raw materials highly susceptible to scrap, reducing production line efficiency, and necessitating a breakthrough in overcoming these bottlenecks. Summary of the Invention

[0006] The technical problem solved by this invention is that in the existing precision grooving of silicon carbide crystal boats, traditional mechanical clamping easily generates local extrusion stress on the workpiece, resulting in deformation of the crystal boat and limited positioning accuracy. In addition, traditional fixtures are not rigid enough under high-speed cutting conditions with diamond grinding wheels, which easily generates micro-vibrations that affect the quality of the grooving. Furthermore, the cutting waste fluid accumulated during processing can easily cause damage to the tool due to prolonged immersion. Moreover, fixtures with a single fixed structure cannot flexibly adapt to crystal boats of different sizes and specifications, resulting in high tooling costs.

[0007] To address the above problems, the present invention provides the following technical solution: The present invention provides a special fixture for grooving silicon carbide boats, comprising a base plate, two sets of side plates and two sets of support plates. The two sets of side plates are symmetrically arranged at both ends of the base plate, and the two sets of support plates are vertically installed on the top two sides of the base plate.

[0008] The base plate, the side plate, and the support plate are interconnected to form a load-bearing frame. The base plate has an upward-opening base plate groove structure, the side plate has a side plate groove on its inner side, and the support plate has a support plate groove structure on its inner side.

[0009] The bottom plate groove structure, the side plate groove structure, and the support plate groove structure are respectively used to conform to different parts of the crystal boat.

[0010] Furthermore, the specific positioning and mating structures of the side plate groove, the support plate groove structure, and the bottom plate groove structure are as follows: The side plate groove is used to fit and cooperate with the top plate and bottom plate of the crystal boat. The support plate groove structure is located on the upper inner side of the support plate and is used to limit the left and right support rods of the crystal boat. The bottom plate groove structure is located in the middle of the bottom plate and is used to conformally cooperate with the lower support rod of the crystal boat.

[0011] Through this three-dimensional, all-around contouring and fitting, the fixture can effectively restrict the spatial degrees of freedom of the crystal boat, forming a stable geometric constraint system, ensuring that the crystal boat obtains high initial positioning accuracy before cutting, and reducing the dependence on external mechanical clamping force.

[0012] Preferably, a fitting gap is reserved between the inner wall surfaces of the side plate groove, the support plate groove structure, and the bottom plate groove structure and the corresponding mating surfaces of the crystal boat. The gap is used to accommodate the liquid paraffin that self-permeates after being heated and melted, so as to form a stress-free rigid fixation after the paraffin solidifies. As a phase change medium, paraffin melts into a low-viscosity fluid after being heated. Driven by surface tension, it generates a capillary effect, spontaneously permeating and filling the tiny gaps between the crystal boat and the fixture. As the temperature drops and solidifies, the paraffin forms a dense and tightly bonded layer, firmly adhering the workpiece to the fixture and evenly distributing the cutting force to the surface of the crystal boat, effectively eliminating the stress concentration phenomenon caused by traditional point or line fixtures.

[0013] In a preferred embodiment of the present invention, fastening structures four are provided at both ends of the inner surfaces of the two sets of side plates, and fastening structures six are provided at both ends of the two sets of support plates. The connection between the side plates and the support plates has a fitting allowance for position adjustment. Fastening structures four and six are used to lock the side plates and support plates relative to each other within the fitting allowance, so that the relative position of the side plates and support plates can be adjusted along the length direction, thereby adapting to crystal boats of different lengths. The adjustable design breaks the limitation of fixed fixture dimensions. Operators only need to loosen the corresponding fasteners to stretch or shorten the longitudinal length of the support frame, so that the same set of fixtures can be compatible with various semiconductor crystal boat raw materials of different specifications and sizes, improving the versatility of the fixtures, and can compensate for the slight deformation error of the crystal boat material itself through fine adjustment.

[0014] Furthermore, the support plate has several square hollow structures in its center, which are used to reduce the overall weight of the fixture. This weight reduction not only facilitates manual loading and unloading but also optimizes the dynamic characteristics of the machining system. During high-speed feed, weight reduction lowers the load on the machine tool motor and reduces motion inertia, minimizing wear on the lead screw and guide rails. The square hollow structures eliminate redundant material that does not bear the main stress, while retaining the critical force paths, achieving a balance between lightweight and rigidity.

[0015] Preferably, the lower part of the support plate near the base plate has several small perforated structures, which serve as channels for cutting fluid drainage. During high-speed cutting, the high-pressure cutting fluid needs to quickly remove cutting heat and debris. The small perforated structures form a low-resistance drainage network at the bottom of the fixture, allowing the cutting fluid to drain smoothly, preventing the formation of fluid accumulation zones, and preventing tool damage from soaking. Simultaneously, it avoids excessive accumulation of cutting fluid that could cause thermal expansion and affect positioning accuracy.

[0016] Furthermore, the base plate, the two sets of side plates, and the two sets of support plates collectively constitute a top-opening, enclosed load-bearing frame. The two ends of the two sets of side plates overlap and fit with the two ends of the two sets of support plates, and are locked together by fasteners. This top-opening, enclosed frame structure increases the contact area between components through overlapping surfaces, and, together with the fasteners, forms a rigid, integrated structure. This closed-loop, annular load-bearing structure possesses an extremely high torsional section modulus, effectively absorbing and dissipating alternating cutting loads in multiple directions, ensuring high stability during dynamic machining.

[0017] Furthermore, the base plate, serving as an integral rigid base, is equipped with a precision, detachable rigid fastening structure. The base plate is securely connected to the machine tool table of an external vertical machining center via this fastening structure. This precision, detachable rigid fastening structure ensures a high-precision fit between the fixture and the machine tool table, allowing the fixture to maintain good repeatability even after multiple disassemblies and reassemblies, thus laying the foundation for continuous grooving machining of the crystal boat.

[0018] Preferably, the grooved structure of the support plate ensures that the crystal boat maintains stable, high-precision guiding support when subjected to dynamic cutting loads. The high-standard contour machining accuracy allows the support plate to provide extremely precise line-surface contact, ensuring that the fixture accuracy far exceeds product tolerance requirements, thus providing a reliable guarantee for the finished crystal boat to meet dimensional standards.

[0019] This invention provides a dedicated fixture for grooving silicon carbide crystal boats. It offers the following advantages: 1. This invention abandons the traditional mechanical clamping method and uses the groove structure of the bottom plate, the groove of the side plate and the groove structure of the support plate to achieve three-dimensional contouring guidance of the crystal boat. By leaving a gap between the mating surfaces and introducing liquid paraffin at high temperature, the high fluidity and capillary phenomenon of the paraffin after melting when heated allow it to adaptively penetrate and fill the mating gap. After cooling and solidifying, the flexible liquid contact surface is transformed into a fully bonded high-strength rigid holding layer. This mechanism evenly distributes the holding force on the surface of the crystal boat, eliminating the stress deformation caused by local mechanical extrusion from the source and improving the processing accuracy of the crystal boat groove.

[0020] 2. The base plate, side plate and support plate of the present invention are locked together by staggered fasteners to form a box-shaped load-bearing frame with a top machining opening. This high-rigidity three-dimensional mechanical structure improves the overall torsional section modulus and bending moment of inertia of the fixture, thereby effectively transmitting and resisting multi-dimensional dynamic cutting loads when the diamond grinding wheel is performing high-speed cutting operations, so that the crystal boat can maintain a highly stable state with zero displacement and zero vibration.

[0021] 3. The present invention features a small hollow structure at the bottom edge of the support plate, which avoids the reduction of the service life of expensive tools due to prolonged immersion. At the same time, the design of fastening structure four and fastening structure six with position adjustment allowance gives the fixture adjustable freedom of position on the assembly axis, overcoming the interference problem of fixed dimensions of conventional integrated fixed frames. This allows operators to make precise adjustments according to the actual size and shape of the material, achieving multiple uses in one fixture and effectively reducing the cost of production tooling. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall three-dimensional structure of the present invention; Figure 2 This is a schematic diagram of the special fixture for slotting silicon carbide crystal boats proposed in this invention in conjunction with the crystal boat; Figure 3 This is an exploded view of the components of a special fixture for grooving silicon carbide crystal boats proposed in this invention; Figure 4 This is a schematic diagram of the support plate structure of a special fixture for grooving silicon carbide crystal boats proposed in this invention; Figure 5 This is a schematic diagram of the base plate structure of a special fixture for grooving silicon carbide crystal boats proposed in this invention. Figure 6 This is a schematic diagram of the crystal boat structure of a special fixture for grooving silicon carbide crystal boats proposed in this invention.

[0023] The components are as follows: 1. Side plate; 2. Support plate; 3. Base plate; 4. Fastening hole; 5. Crystal boat; 6. Square hollow structure; 7. Small hollow structure; 8. Left and right support rods; 9. Fastening structure one; 10. Fastening structure two; 11. Fastening structure three; 12. Fastening structure four; 13. Fastening structure five; 14. Side plate groove; 15. Fastening structure six; 16. Support plate groove structure; 17. Fastening structure seven; 18. Crystal boat top plate; 19. Crystal boat bottom plate; 20. Base plate groove structure; 21. Lower support rod. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see the appendix Figure 1 - Appendix Figure 6This invention provides a special fixture for grooving silicon carbide crystal boats, including a base plate 3, side plates 1, and support plates 2. The base plate 3 serves as a basic bearing platform, providing a stable mounting base for the entire fixture. Two sets of side plates 1 are symmetrically arranged at both ends of the base plate 3 to define the position of the workpiece in the horizontal direction. Two sets of support plates 2 are vertically installed on the front and rear sides of the top of the base plate 3, mainly undertaking the function of supporting and supporting the workpiece.

[0026] The base plate 3 serves as an integral rigid base and is firmly connected to the machine tool table of the vertical machining center through a precise detachable rigid fastening structure 9. The base plate 3 has an upward-opening base plate groove structure 20 in the middle, which conforms to the support rod 21 below the crystal boat 5, thereby increasing the radial positioning of the crystal boat 5 in the circumferential direction.

[0027] Two sets of side plates 1 are vertically fixed to the base plate 3 through fastening structure three 11 and fastening structure five 13 and fastening hole 4. Two sets of support plates 2 are symmetrically arranged above the edge of the base plate 3 and are connected to the base plate 3 through high-precision linear fastening structure two 10 and fastening structure seven 17.

[0028] Meanwhile, the two sets of side plates 1 are fastened to both ends of the support plate 2 by fastening structure four 12 and fastening structure six 15, thus forming a sturdy, high-rigidity load-bearing frame with a sturdy four-sided covering and an open top. This design, which uses rigid fasteners for connection in all directions, ensures that the fixture maintains zero displacement and zero vibration under the high-speed cutting conditions of diamond grinding wheels.

[0029] To protect the cutting tool and facilitate operation, the support plate 2 has several square hollow structures 6 in the middle, which not only meet the load-bearing requirements, but also effectively reduce the overall weight of the fixture. Several small hollow structures 7 are opened at the bottom near the base plate 3, so that when the product is sprayed with cutting fluid, the accumulated waste liquid can be smoothly discharged through the small hollow structures 7, avoiding the bottom of the cutting tool from being immersed in the cutting fluid for a long time.

[0030] To achieve micron-level positioning, the inner side of the side plate 1 is designed with a side plate groove 14, which is used to precisely fit and cooperate with the crystal boat top plate 18 and the crystal boat bottom plate 19 of the crystal boat 5.

[0031] The upper inner side of the support plate 2 is designed with a support plate groove structure 16 to limit the left and right support rods 8 of the crystal boat 5. The support plate groove structure enables the crystal boat 5 to achieve highly stable support without micro-vibration under dynamic cutting loads.

[0032] In addition, fastening structures 12 are provided at both ends of the inner surfaces of the two sets of side plates 1, and fastening structures 15 are provided at both ends of the two sets of support plates 2. The side plates 1 and the support plates 2 form a position adjustment margin through slidable mating surfaces or reserved adjustment holes. Fastening structures 12 and 15 are locked relative to each other within this position adjustment margin, so that the relative position of the side plates 1 and the support plates 2 can be adjusted along the length direction to flexibly adapt to raw materials of different lengths of crystal boats 5 and achieve multiple uses in one piece.

[0033] Working principle: First, the base and the workpiece are initially assembled. The base plate 3 is placed on the assembly table, and the one-piece molded silicon carbide crystal boat 5 raw material is placed on the base plate 3, so that the lower support rod 21 of the crystal boat 5 falls steadily into the bottom plate groove structure 20 of the base plate 3.

[0034] Next, the frame is assembled by wrapping it, and the two sets of side plates 1 are attached to the two sides of the crystal boat 5 respectively, so that the crystal boat top plate 18 and the crystal boat bottom plate 19 are respectively embedded in the side plate grooves 14 of the two side plates 1, and are initially connected to the bottom plate 3 through fastening structure three 11 and fastening structure five 13. Subsequently, the two sets of support plates 2 are fastened to the top two sides, so that the left and right support rods 8 of the crystal boat 5 are inserted into the support plate groove structure 16 of the support plate 2, and the support plate 2 is initially connected to the side plate 1 and the bottom plate 3 through the corresponding fastening structure. At this time, the entire frame is in a slightly loose state.

[0035] Then, flexible fine-tuning and mechanical locking are performed to adjust all the above-mentioned fastening structures. The three-dimensional grooves of the fixture are used to guide the crystal boat 5 to naturally fit with each groove of the fixture, and the overall frame is locked within the reserved fitting allowance.

[0036] In order to completely eliminate the extrusion stress deformation caused by traditional mechanical grippers, the fixture containing the crystal boat 5 is pushed into the oven for preheating. After the fixture and the crystal boat are heated to a set temperature higher than the melting point of paraffin wax, they are removed from the oven or, under the heat preservation condition, since the sides and bottom of the crystal boat 5 are covered by the frame, the operator directly drips or pours liquid paraffin wax from the exposed joint edge at the top of the fixture.

[0037] By utilizing the high fluidity of liquid paraffin at high temperatures and the capillary effect generated by the micron-level gaps, the liquid paraffin automatically penetrates downwards and inwards to fill the entire gap. After natural cooling, the paraffin solidifies, forming a stress-free rigid fixation.

[0038] Finally, the assembly fixture with the crystal boat 5 is placed on the worktable of the machining center and locked to the machine tool by the fastening structure 9 on the base plate 3. The ceramic diamond grinding wheel of the machining center extends into the top opening of the fixture and begins high-precision grooving operation under the condition of continuous spraying of cutting fluid for cooling.

[0039] The cutting fluid is not only used for chip removal, but its cooling effect, which removes cutting heat, ensures that the temperature of the fixture and the crystal boat is always far below the melting point of the paraffin wax throughout the entire machining process, thereby maintaining the high strength of the paraffin wax and ensuring that the holding force does not fail.

Claims

1. A special fixture for grooving of silicon carbide boat, characterized in that, It includes a base plate (3), two sets of side plates (1) and two sets of support plates (2). The two sets of side plates (1) are symmetrically arranged at both ends of the base plate (3), and the two sets of support plates (2) are vertically installed on the top two sides of the base plate (3). The base plate (3), the side plate (1) and the support plate (2) are connected to each other to form a load-bearing frame. The base plate (3) is provided with an upward-opening base plate groove structure (20). The inner side of the side plate (1) is provided with a side plate groove (14). The inner side of the support plate (2) is provided with a support plate groove structure (16). The bottom plate groove structure (20), the side plate groove (14), and the support plate groove structure (16) are respectively used to conform to different parts of the crystal boat (5).

2. The special purpose tool for dicing of silicon carbide crystal boats as claimed in claim 1, wherein, The specific positioning and fitting structures of the side plate groove (14), the support plate groove structure (16), and the bottom plate groove structure (20) are as follows: The side plate groove (14) is used to fit and cooperate with the crystal boat top plate (18) and crystal boat bottom plate (19) of the crystal boat (5). The support plate groove structure (16) is located on the upper inner side of the support plate (2) and is used to limit the left and right support rods (8) of the crystal boat (5). The bottom plate groove structure (20) is located in the middle of the bottom plate (3) and is used to conformally cooperate with the lower support rod (21) of the crystal boat (5).

3. The special purpose tool for dicing of silicon carbide crystal boats as claimed in claim 2, wherein, The inner wall surfaces of the side plate groove (14), the support plate groove structure (16) and the bottom plate groove structure (20) are reserved with the corresponding mating surfaces of the crystal boat (5). The mating gaps are used to accommodate the liquid paraffin that has been heated and melted and has self-adaptively penetrated into the liquid.

4. The special purpose tool for dicing of silicon carbide crystal boats according to claim 1, wherein, Both sides of the inner surfaces of the two sets of side plates (1) are provided with fastening structures four (12) at both ends, and both sides of the two sets of support plates (2) are provided with fastening structures six (15). The connection between the side plate (1) and the support plate (2) has a fit allowance for position adjustment. The fastening structures four (12) and six (15) are used to lock the side plate (1) and the support plate (2) relative to each other within the fit allowance, so that the relative position of the side plate (1) and the support plate (2) can be adjusted along the length direction.

5. The special fixture for grooving silicon carbide boats according to claim 1, characterized in that, The support plate (2) has several square hollow structures (6) in the middle, which are used to reduce the overall weight of the fixture.

6. The special fixture for grooving silicon carbide boats according to claim 5, characterized in that, The lower part of the support plate (2) near the bottom plate (3) has several small hollow structures (7), which are used as channels for draining cutting fluid.

7. The special fixture for grooving silicon carbide boats according to claim 1, characterized in that, The base plate (3), the two sets of side plates (1) and the two sets of support plates (2) together form a top-opening enclosed load-bearing frame, wherein the two ends of the two sets of side plates (1) respectively form overlapping and fitting surfaces with the two ends of the two sets of support plates (2), and are vertically fixed by fasteners.

8. The special fixture for grooving silicon carbide boats according to claim 1, characterized in that, The base plate (3) serves as an integral rigid base. A precision detachable rigid fastening structure (9) is provided on the base plate (3). The base plate (3) is firmly connected to the machine tool worktable of the external vertical machining center through the fastening structure (9).

9. The special fixture for grooving silicon carbide boats according to claim 2, characterized in that, The contour machining accuracy error of the groove structure (16) of the support plate is within ±2μm, so that the crystal boat (5) maintains stable high-precision guiding support when subjected to dynamic cutting load.

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