Crystal surface processing equipment

Abstract

The invention discloses crystal surface processing equipment. The equipment comprises a bearing module and a processing module, the processing module comprises a diamond wire unit, a cutting fluid pumping unit and an ultrasonic unit; the diamond wire unit can drive a diamond wire to move in the axial direction. The cutting fluid pumping unit can pump cutting fluid to the surface of the diamond wire, and the cutting fluid flows on the surface in an attached mode to form a flow beam. The ultrasonic unit is in contact with the cutting fluid and applies ultrasonic waves to the flow beam. Machining of the side surface and the datum plane of the hard crystal ingot is completed in a diamond wire cutting mode, in the wire cutting process, cutting fluid is pumped to form a flow beam, ultrasonic waves are directly applied to the flow beam through the ultrasonic unit, the focusing degree of ultrasonic energy is remarkably improved, cutting machining is assisted, and the machining efficiency is improved. The problems of machining errors and surface quality caused by direct application of ultrasound to the diamond wire are avoided, the problems of pollution and waste of hard material powder formed by grinding are also avoided, and the material utilization rate is remarkably increased.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor material preparation, and in particular to a crystal surface processing device. Background Art

[0002] Most semiconductor materials are hard materials. For example, silicon carbide single crystal materials are widely used in electric vehicles, photovoltaics, radio frequency communications and other fields due to their wide bandgap, high thermal conductivity and high breakdown field strength. They are the most important third-generation semiconductor materials and devices.

[0003] Silicon carbide devices must go through a very complex growth process including crystal growth, side surface processing, reference surface processing, slicing, polishing, epitaxy, ion implantation, and etching to be completed. At present, physical vapor transport or liquid phase methods are generally used to grow silicon carbide ingots at home and abroad. The original silicon carbide ingot after growth is subjected to side surface processing to form a silicon carbide crystal rod with a regular circular geometry. The above-mentioned silicon carbide crystal rod is then processed to produce a reference surface that meets semiconductor standards. Subsequently, the processed silicon carbide crystal rod with the reference surface is cut into silicon carbide wafers of a certain thickness. After grinding and polishing, qualified silicon carbide substrate products are manufactured. Silicon carbide devices are made through processes such as epitaxial etching and are used in electric vehicles, 5G radio frequency communications, consumer electronics and other fields.

[0004] The side surface processing and reference surface processing of silicon carbide ingots are one of the essential processes for manufacturing silicon carbide substrates. At present, high-precision mechanical grinders are widely used in the industry to grind the outer circle of the side surface of silicon carbide ingots using diamond grinding wheels with a Mohs hardness of ten. Due to the high hardness of silicon carbide, Mohs hardness of 9.5, close to the hardness of diamond, the consumption of diamond grinding wheels is huge and the processing efficiency is low. The rounding processing time of the side surface of a 6-inch silicon carbide ingot is about 8-9 hours. High-quality ultra-fine diamond grinding wheels need to be imported, which is very expensive.

[0005] In addition, during the silicon carbide grinding wheel rolling process, the diamond grinding wheel exerts a large vertical mechanical extrusion force on the silicon carbide ingot, which can easily cause the silicon carbide ingot, a brittle material, to crack and become scrapped.

[0006] The reference surface processing of silicon carbide is generally processed on a high-precision surface grinder using a diamond grinding wheel. The reference surface length of a 6-inch standard crystal ingot is 47.5mm, and the processing time is about 3 hours, which is costly and inefficient. During the grinding process between the diamond grinding wheel and the silicon carbide crystal ingot, all the silicon carbide materials that need to be removed are ground into powder. The silicon carbide powder is not only useless but also pollutes the environment. The subsequent processing cost of the silicon carbide powder is very high.

[0007] It can be seen that the current processing of the side surfaces and reference surfaces of hard crystal ingots such as silicon carbide has problems such as inability to process continuously, low processing efficiency, and pollution and waste of removed materials. A more advanced side surface and reference surface processing equipment and process are urgently needed. Summary of the invention

[0008] In view of the deficiencies in the prior art, an object of the present invention is to provide a crystal surface processing device.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: The present invention provides a crystal surface processing device, comprising a bearing module and a processing module, wherein the bearing module is used to bear a hard crystal ingot, and the processing module can move relative to the bearing module to process the hard crystal ingot; The processing module includes a diamond wire unit, a cutting fluid pump unit and an ultrasonic unit; The diamond wire unit can drive the diamond wire to move along the axial direction to process the hard crystal ingot; the cutting fluid pump unit can continuously pump cutting fluid to the surface of the diamond wire, and make the cutting fluid adhere to the surface of the diamond wire and flow to form a flow beam; the ultrasonic unit is in contact with the cutting fluid and is used to apply ultrasonic waves to the flow beam.

[0010] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention at least include: The processing equipment provided by the present invention utilizes diamond wire cutting to complete the processing of the side surface and reference surface of the hard crystal ingot. During the wire cutting process, the cutting fluid is pumped to form a flow beam, and an ultrasonic unit is used to directly apply ultrasound to the flow beam, which significantly improves the focusing degree of the ultrasonic energy, assists in completing the cutting process, and avoids the processing errors and surface quality problems caused by directly applying ultrasound to the diamond wire.

[0011] In addition, the technical solution provided by the present invention can avoid the pollution and waste of hard material powder formed by grinding, and significantly improve the material utilization rate.

[0012] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them according to the contents of the specification, the following is a description of the preferred embodiments of the present invention in conjunction with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the state of a processing device provided by a typical implementation case of the present invention before cutting begins; Figure 2 It is a schematic diagram of the state of a processing device provided by a typical implementation case of the present invention at the beginning of cutting; Figure 3 It is a schematic diagram of the state of a processing device provided by a typical implementation case of the present invention when cutting a reference surface; Figure 4 It is a schematic diagram of the state of a processing device provided by a typical implementation case of the present invention when cutting a side surface; Figure 5 It is a schematic diagram of the structure of a cut crystal ingot provided by a typical implementation case of the present invention; Figure 6 It is a schematic structural diagram of a crystal ingot residue obtained by cutting provided in a typical implementation case of the present invention.

[0014] Explanation of the accompanying reference numerals: 1. Silicon carbide ingot; 2. Diamond wire; 3. First ultrasonic generator; 4. Second ultrasonic generator; 5. First liquid outlet channel; 6. Second liquid outlet channel; 7. Cutting fluid; 8. Cutting fluid; 9. Cutting fluid recoverer; 10. Circulation drive mechanism; 11. Precision moving platform; 12. Finished ingot; 12-1. Side surface; 12-2. Reference plane; 13. Residue. DETAILED DESCRIPTION

[0015] The existing technology generally uses a diamond grinding wheel to process the side surface of the original silicon carbide ingot, and the reference surface is processed on the external cylindrical processing equipment and the surface grinder equipment in turn. The first step is to process the side surface of the original silicon carbide ingot, and round the irregular side surface (generally 20-35mm thick) of the grown original silicon carbide ingot into a circular side surface. The second step is to process the required reference surface on the surface grinder. The length and direction of the reference surface must comply with the corresponding semiconductor industry standards. The rounding time of the side surface of a 6-inch silicon carbide ingot is about 8-9 hours, and the reference surface takes 3 hours.

[0016] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0017] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0018] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0019] An embodiment of the present invention first provides a crystal surface processing device, including a carrying module and a processing module, wherein the carrying module is used to carry a hard crystal ingot, and the processing module can move relative to the carrying module for processing the hard crystal ingot; the processing module includes a diamond wire unit, a cutting fluid pumping unit and an ultrasonic unit; the diamond wire unit can drive the diamond wire to move along an axial direction to process the hard crystal ingot; the cutting fluid pumping unit can continuously pump cutting fluid to the surface of the diamond wire, and make the cutting fluid adhere to the surface of the diamond wire and flow to form a flow beam; the ultrasonic unit is in contact with the cutting fluid, and is used to apply ultrasonic waves to the flow beam.

[0020] The hard crystal ingot processed by the present invention is typically represented by silicon carbide crystal ingot, but it does not mean that it is limited to this. Crystal ingots of other materials with similar hardness can also use the technical solution provided by the present invention to process the side surface and reference surface. For example, in some implementation cases, the time for processing the side surface and reference surface of a 6-inch silicon carbide crystal ingot using the equipment of the present invention is about 2.6 hours, and the time for processing the side surface and reference surface of an 8-inch silicon carbide crystal ingot is about 3.5-4.5 hours, and the production efficiency is improved by more than 50%. The residual silicon carbide edge material can also be recycled to improve the economic benefits of the industry.

[0021] The diamond single wire is used to cut out the side surface and reference surface required by the standard silicon carbide ingot at one time, replacing the traditional diamond grinding wheel to round the side surface of the original silicon carbide ingot and the surface grinding of the reference surface of the original silicon carbide ingot, saving equipment investment, saving processing time, and improving production efficiency. During the processing, high-precision processing of the side surface and reference surface can be completed in one clamping, ensuring the geometric dimensional accuracy of the processed crystal rod and improving the product yield.

[0022] In some typical examples, the original silicon carbide ingot described in the present invention refers to an unprocessed silicon carbide ingot blank material grown by physical vapor transport method, liquid phase method or flux method. In some typical examples, when the original silicon carbide ingot described in the present invention is fixed on the processing platform, the bonding surface of the silicon carbide seed crystal must be firmly in contact with the processing platform, and the natural growth surface (non-plane) of the original silicon carbide ingot is facing upward.

[0023] In addition, the technical effects of other aspects of the present invention are that the side surface and reference surface of the silicon carbide ingot can be processed at one time, and the high-precision processing of the side surface and the reference surface can be completed by clamping once during the processing process, ensuring the geometric dimensional accuracy of the processed crystal rod, improving the product yield, saving processing time, saving equipment investment, and improving production efficiency by more than 50%. For example, the method provided by the present invention takes about 3-3.5 hours to process the side surface and reference surface of a 6-inch silicon carbide ingot, and about 4.5-6 hours to process the side surface and reference surface of an 8-inch silicon carbide ingot, and the production efficiency is improved by more than 50%.

[0024] The silicon carbide ingot side surface and reference plane processing equipment and the method for using the same proposed in the present invention have the following principles: using a single diamond wire to cut the outer circle and reference plane of the silicon carbide ingot, and using ultrasonic vibration to assist the diamond wire cutting to achieve higher efficiency, faster speed, higher surface finish of the cut surface, and no dust or noise pollution during the cutting process. Moreover, the silicon carbide residue after cutting can be reused as artificial moissanite, which has certain economic value.

[0025] The principle of ultrasonic vibration-assisted machining is to utilize the high frequency and small amplitude of ultrasonic waves, convert mechanical vibrations into ultrasonic vibrations through ultrasonic oscillators, and transmit ultrasonic waves to the surface of the workpiece or the surface of the machining tool through coupling parts. Ultrasonic waves can produce a violent cavitation effect during the transmission process, that is, bubbles are generated during the vibration cycle. When the bubbles collapse during the cycle, the shock waves generated can generate high-frequency and high-energy forces. This force can change physical phenomena such as friction, deformation and cutting force in traditional machining processes, thereby improving machining efficiency and cutting quality.

[0026] Although the processing method of cutting with ultrasonic wave to assist diamond wire has a long history in the field of hard material processing, many different matching methods have been proposed in the prior art. For example, in some prior art, ultrasonic waves are directly applied to the diamond wire body by some designed equipment, and the characteristics of the diamond wire conducting ultrasonic waves are used to enable ultrasonic waves to assist the cutting of the diamond wire, thereby improving the cutting efficiency and quality. However, the inventors of the present invention have found through practice that this method is not suitable for processing high-hardness ingots, especially silicon carbide ingots. This is because the hardness of such ingots is close to the hardness of the diamond particles on the surface of the diamond wire. In this case, directly applying ultrasound to the diamond wire body will cause the position of the diamond wire to shift, resulting in problems such as excessive processing size or reduced surface quality. In most cases, among many different ultrasonic-assisted cutting methods, the inventors have tried several times and often found that a diamond wire has broken or lost its sharpness before the ingot processing is completed. This is also one of the difficulties in realizing wire cutting processing of hard ingots such as silicon carbide.

[0027] Some existing technologies have proposed using an immersion method to perform ultrasonic-assisted diamond wire cutting. The cutting process occurs in a container that contains cutting fluid. Ultrasound is applied to the cutting fluid in the container to indirectly act on the cutting position, thereby assisting in chip removal and increasing the cutting rate. However, the above method may produce better results for ingots with slightly lower hardness, but for super-hard ingots such as silicon carbide, since the ultrasound is dispersed in the entire liquid phase, the energy of the ultrasound is not focused on the cutting position, so it is difficult to obtain a higher ultrasonic power density, thereby failing to effectively improve the cutting efficiency and cut surface quality for such super-hard ingots.

[0028] The basic technical concept adopted by the present invention is different from the above-mentioned existing technology. It adopts a flow beam ultrasound mode. By pumping cutting fluid to the diamond wire, a flow beam is formed along the diamond wire. On the one hand, it plays a role of cooling and lubrication. On the other hand, ultrasound is directly applied to the flow beam, so that the energy of the ultrasound is limited by the flow beam without divergence, and is concentrated on the cutting interface, effectively playing a role of increasing efficiency and improving quality. In addition, since ultrasound is not directly applied to the diamond wire body, but is transmitted to the cutting interface through liquid phase focusing, it will not interfere with the translational movement of the diamond wire, thereby meeting the high-precision dimensional requirements and higher section quality requirements. These effects cannot be achieved by the above two methods.

[0029] As for other implementation details, in some embodiments, the diamond wire moves along the direction of gravity, and the liquid outlet channel of the cutting fluid pump unit and the ultrasonic unit are arranged above the cutting position of the diamond wire, and the liquid outlet channel and the ultrasonic unit are arranged in multiple groups and are distributed in rotational symmetry with the diamond wire as the axis.

[0030] In some embodiments, the cutting fluid pump unit includes a first liquid outlet channel and a second liquid outlet channel, and the ultrasonic unit includes a first ultrasonic generator and a second ultrasonic generator, the first ultrasonic generator is arranged in cooperation with the first liquid outlet channel, and the second ultrasonic generator is arranged in cooperation with the second liquid outlet channel, the first liquid outlet channel and the second liquid outlet channel are arranged relative to each other with the diamond wire as the axis, and the liquid outlet directions are both pointing to the diamond wire.

[0031] In the present invention, it is preferred to use a plurality of groups of liquid outlets and ultrasonic units in combination to form symmetrical flow beams and ultrasonic waves around the diamond wire, thereby avoiding the influence of the diamond wire being deviated in one direction, thereby improving the cutting accuracy and the quality of the cut surface.

[0032] It is not limited to two groups of symmetrically arranged liquid outlets and ultrasonic units, and multiple groups can be symmetrically distributed along the diamond wire; in addition, different liquid outlets can pump out the same liquid, such as a mixed liquid with auxiliary cutting and cooling functions, or they can pump out different liquids separately, for example, some liquids are for auxiliary cutting, and some liquids only have a cooling function. After multiple liquids are mixed on the surface of the diamond wire, they play a corresponding role together and synchronously transmit ultrasound.

[0033] In some embodiments, the distance between the outlet of the liquid outlet channel and the hard crystal ingot is 3-5 mm. One of the key parameters in the present invention is the distance between the outlet of the liquid outlet channel and the hard crystal ingot. This distance is an important parameter for balancing the transmission efficiency of ultrasonic energy and cutting accuracy. If the distance is too small, it will cause physical collision between the surface of the crystal ingot and the liquid outlet channel, damaging the crystal ingot (reason: the surface of the crystal ingot after growth is a slightly convex interface, not a strict plane). If the distance is too large, the transmission of ultrasound will be affected, resulting in power loss, which significantly reduces the auxiliary effect.

[0034] In some embodiments, the cutting fluid pump unit further includes a cutting fluid recoverer, which is disposed below the diamond wire and is used to collect the cutting fluid in the flow stream and pump the collected cutting fluid to the liquid outlet channel.

[0035] In some embodiments, diamond particles are embedded on the surface of the diamond wire, and the particle size of the diamond particles is 3-12 μm; and the diameter change rate of the diamond wire is less than 2%.

[0036] As a typical example, in the present invention, the diamond wire used can attach artificial diamond particles to the steel wire busbar by sintering or electroplating, and the diameter of the diamond particles is in the range of 3-12um, and the optimal diameter is 6-9um. The diameter of the diamond wire is 0.45-0.90mm. The cutting efficiency of the diamond wire with a diameter less than 0.45mm is low, the tension resistance is small, and the wire is easy to break. The surface roughness of the rear side surface and the reference surface of the diamond wire with a diameter greater than 0.90mm is high, the finish is poor, and it does not meet the quality standards. The optimal value of the diamond wire diameter is 0.60-0.80mm, and the tensile fracture strength is greater than 260 Newtons.

[0037] In some embodiments, the diamond wire unit includes a circulating driving mechanism, and the diamond wire cooperates with the circulating driving mechanism to move along its own axial direction under the drive of the circulating driving mechanism.

[0038] In some embodiments, the supporting module includes a precision mobile platform having at least two degrees of freedom of movement, the precision mobile platform includes a fixed part and a moving part, the hard crystal ingot can be fixed on the moving part, and at least two of the degrees of freedom are arranged perpendicularly to the geometric axis of the hard crystal ingot; and the geometric axis of the crystal ingot is parallel to the diamond wire in the cutting position.

[0039] In some embodiments, the precision mobile platform includes a first track and a second track, the first track is fixedly arranged, the second track is perpendicularly intersected with the first track, and is slidably matched with the first track, and can be driven to translate along the extension direction of the first track; the hard crystal ingot is fixed on the second track, and can be driven to translate along the extension direction of the second track.

[0040] In addition, regarding the driving method of the diamond wire, in some embodiments, the diamond wire is a ring-shaped wire connected end to end, and either unidirectional drive or reciprocating drive is possible; or in some embodiments, the diamond wire is a linear wire that is not connected end to end, and the diamond wire unit can drive the diamond wire to perform linear reciprocating motion.

[0041] As a typical example, the routing speed range of the diamond wire described in the present invention is generally 40-65m / s. If the routing speed is lower than 40m / s, the cutting efficiency is low and the service life of the cutting coolant is shortened. If the routing speed is higher than 65m / s, the wire is prone to breakage during the cutting process. The optimal routing speed is 45-55m / s.

[0042] Ultrasonic waves act on the diamond wire, causing it to vibrate horizontally with high frequency and small amplitude to increase the contact area. The ultrasonic frequency is 20-160KHZ, the amplitude is 3-10um, and the power is 100-800W. The power is continuously adjustable. If the amplitude is less than 3um, the ultrasonic assisted cutting effect is not obvious. If the amplitude is greater than 10um, the wire is easily broken during the cutting process. The optimal ultrasonic amplitude is 5-8um, and the optimal ultrasonic frequency is 20-60KHz.

[0043] In addition, exemplarily, the cutting fluid includes 40-65% by mass of water, 25-35% by mass of a surfactant, and 10-35% by mass of a corrosion inhibitor; wherein the corrosion inhibitor is an alkaline suspended substance.

[0044] The cutting coolant has three functions. The first is to assist the diamond wire in lubricating the cutting of silicon carbide materials. The second is to take away the silicon carbide powder after cutting. The third is to act as a propagation medium for ultrasonic waves and transmit ultrasonic energy to the diamond wire. The cutting coolant can be recycled and used many times.

[0045] As some typical examples of the above technical solutions, the processes of the processing equipment and the processing method provided by the present invention can be seen in Figure 1-Figure 4 As shown, it is used to process the silicon carbide ingot 1 for processing, wherein the diamond wire 2 can attach fine diamonds to the steel wire busbar by sintering or electroplating. The diameter of the diamond particles is in the range of 3-12um, the optimal diameter is 6-9um, and the tensile strength of the diamond wire is greater than 260 Newtons. The first ultrasonic generator 3 and the second ultrasonic generator 4 can emit ultrasonic waves within a certain frequency range to assist the cutting ability of the diamond wire. The first liquid outlet channel 5 and the second liquid outlet channel 6 are pipes for outputting cutting fluid.

[0046] The cutting fluids 7 and 8 output from different outlet channels merge to form a flow beam, which flows downward along the diamond wire 2. An exemplary cutting fluid may include components such as pure water, a surfactant, and a corrosion inhibitor, wherein pure water accounts for 40-65%, and the surfactant polyethylene glycol accounts for 25-35%. The surfactant has an excellent lubricating effect, which can effectively prevent brittle cracking or scratches during the cutting process and reduce the roughness of the silicon carbide side surface and reference surface. The corrosion inhibitor is mainly composed of alkaline suspended matter, accounting for 10-35%, and has a unique suspension property, which prevents the silicon carbide cutting powder from depositing and clogging the machine pipeline. All raw materials are environmentally friendly materials, and the wastewater after cutting is easy to handle; it has excellent lubrication, cooling, corrosion prevention, rust prevention and other functions, the roughness of the silicon carbide side surface reference surface after cutting is low, there are no wireless scratches, and it can extend the service life of the diamond wire.

[0047] The cutting fluid recovery device 9 refers to a power device that can collect and recycle the cutting fluid, such as a container and a water pump. The flowing cutting fluid is collected by the container and then transported to the liquid outlet channel by the pump. The circulation drive mechanism 10 refers to a mechanical device that can make the diamond wire circulate to cut the crystal ingot. The optional driving modes include unidirectional circulation drive (the ring-shaped diamond wire rotates in one direction) or reciprocating circulation. The precision moving platform 11 refers to a mechanical platform that loads the silicon carbide crystal ingot and can move precisely in the XY direction perpendicular to gravity.

[0048] Through the above equipment, using appropriate cutting processes, the finished ingot 12 and the residual material 13 can be obtained. The finished ingot 12 has a side surface 12-1 and a reference surface 12-2. The residual material 13 is a block material with excellent quality and can be used for gem processing.

[0049] Specific exemplary cutting process flow is as follows: Step 1: Use a high-precision X-ray crystallography instrument to orient the reference plane crystal orientation [10-10] of the grown original silicon carbide ingot 1, and mark it on the original silicon carbide ingot, such as Figure 1The original grown silicon carbide ingot (with a diameter greater than 6 or 8 inches) that needs to be processed on the side surface and reference surface is fixed on the precision moving platform 11 of the single-wire cutting equipment. The platform has the function of two-axis precision movement in the X direction and the Y direction, and has the function of rotation. The fixing method can use vacuum adsorption, high-viscosity glue or mechanical clamps to ensure that the original silicon carbide ingot and the processing platform do not move relative to each other during the cutting process, the growth surface of the original silicon carbide ingot is facing up, and the bottom surface of the original silicon carbide ingot bonded with the seed crystal is in contact with the processing platform.

[0050] Step 2: Install a diamond wire 2 with a diameter of 0.45-0.90mm on the cutting equipment. The non-uniformity of the diamond wire diameter is less than 2%, and the maximum tensile strength is greater than 260 Newtons. The diamond wire can be made by electroplating or sintering. The diamond particle diameter is in the range of 3-12um, and the optimal diameter is 6-9um. If the diamond particle diameter is less than 3um, the cutting efficiency is low. If the diamond particle diameter is greater than 12um, the wire is easy to break during the cutting process, and the cutting surface is rough, which is easy to produce defects such as edge collapse and fragmentation. Adjust the position of the processing platform loaded with the silicon carbide ingot so that the diamond wire is 2-5mm away from the crystal edge position A in the direction of the reference plane [10-10] of the original silicon carbide ingot, ensuring that the diamond wire does not contact the silicon carbide ingot when starting high-speed movement, that is, the diamond wire is in a no-load running state, and the diamond wire has a circular routing speed of 40-65m / s in the up and down directions.

[0051] Step 3: Adjust the relative positions of the first ultrasonic generator 3 and the first liquid outlet channel 5, the second ultrasonic generator 4 and the first liquid outlet channel 6 on the equipment and the silicon carbide ingot on the platform. The appropriate static spacing is 3-5mm. Start the diamond wire routing function on the equipment. The diamond wire performs high-speed up and down circular motion. The diamond wire only moves in the longitudinal Z-axis direction and does not move in the XY direction.

[0052] Step 4: Start the power supply of the ultrasonic generator to generate a power ultrasonic wave with a frequency of 20-160KHZ, turn on the cutting fluid circulation power supply for cooling the diamond wire, and the cutting fluid 7 and the cutting fluid 8 flow out at high speed through the first liquid outlet channel 5 and the second liquid outlet channel 6 respectively to cool the diamond wire 2. The ultrasonic wave acts on the diamond wire after being transmitted through the medium of the cutting fluid 7 and 8, so that the diamond wire moves with a high frequency micro-amplitude (3-10um), which can improve the cutting efficiency by more than 30%.

[0053] Step 5: According to the standard size of the finished ingot 12, the motion trajectory of the processing platform is programmed, and the processing platform is moved by the computer of the equipment. The platform is slowly moved according to the designed motion trajectory, and the moving rate is 0.03-0.05mm / s. When the edge of the reference surface of the silicon carbide ingot on the platform contacts the high-speed moving diamond wire [10-10], the cutting begins. Figure 2 shown.

[0054] Step 6: After the cutting starts, the platform moves slowly in the X direction. When the diamond wire cuts to the edge A of the original ingot reference surface ( Figure 2 ) point, the cutting of the reference surface 12-2 begins. When the diamond wire cuts to the edge B of the original ingot reference surface ( Figure 2 ) point, the cutting of the reference surface 12-2 is completed, and when the platform starts to make a combined movement in the X direction and the Y direction, the diamond wire cuts the side surface of the original crystal ingot until the diamond wire cuts to the C point of the original crystal ingot, the processing of the side surface 12-1 of the crystal ingot is completed, and the processed crystal ingot product 12 is physically separated from the silicon carbide residual material 13.

[0055] Step 7: Turn off the power of ultrasonic generators 3 and 4 and the power of the cutting fluid supply system, turn off the power of the diamond wire routing movement, move the platform in the X direction under computer control, move the platform and the ingot away from the diamond wire, remove the cut silicon carbide ingot and the silicon carbide scraps after cutting and separation, measure the processing quality of the silicon carbide side surface and the reference surface, the surface finish is 0.3-0.6um, which meets the quality standards.

[0056] Step 8: Figure 5 As shown in the figure, after the quality of the silicon carbide ingot is tested and qualified, it will be put into the next normal production process, such as Figure 6 As shown, the leftover silicon carbide scraps can be recycled and reused as artificial moissanite and processed into artificial moissanite jewelry.

[0057] Based on the above process flow, the technical solution provided by the present invention is suitable for the side surface and reference surface processing of original silicon carbide ingots of any diameter size, and can also process materials of any outer contour shape. It is not affected by the conductive properties of silicon carbide and is suitable for conductive and semi-insulating silicon carbide ingots. It can also be suitable for processing the side surfaces and reference surfaces of gallium nitride and aluminum nitride original ingots, and is not affected or limited by the crystal diameter size.

[0058] The original silicon carbide has a diameter of more than 6 inches or more than 8 inches. After the method is used, it is cut into a standard ingot with a diameter of 6 inches or 8 inches. The thickness of the ingot is not restricted, and the general thickness is 15-30 mm, which is suitable for original silicon carbide ingots of any thickness. The thicker the silicon carbide ingot, the more cost and production efficiency advantages the method of the present invention has.

[0059] The processed side surface and reference surface have high surface finish, with a roughness value Ra of 0.3-0.6um, which meets the quality standards; compared with traditional diamond grinding wheel processing, the production efficiency is increased by more than 50%; the silicon carbide residue after diamond wire cutting has recycling value and can be made into artificial moissanite jewelry, which has certain economic value.

[0060] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention, and do not limit the scope of the present invention.

[0061] Example 1 Step 1: Use a high-precision X-ray crystallography instrument to orient the base plane crystal orientation of the grown original silicon carbide ingot [10-10], and mark it on the original silicon carbide ingot. Fix the original grown silicon carbide ingot (diameter 160mm, thickness 25mm) that needs to be processed on the side surface and base surface on the processing platform of the single-wire cutting equipment. The platform has two-axis precision movement functions in the X and Y directions and has a rotation function. The fixing method can use vacuum adsorption, high-viscosity glue or mechanical clamps to ensure that the original silicon carbide ingot and the processing platform do not move relative to each other during the cutting process. The growth surface of the original silicon carbide ingot is facing up, and the bottom surface of the original silicon carbide ingot bonded with the seed crystal is in contact with the processing platform.

[0062] Step 2: Install a diamond wire with a diameter of 0.45mm on the cutting equipment. The unevenness of the diamond wire diameter is 1.5%, and the maximum tensile strength is 280 Newtons. The diamond wire can be made by electroplating, and the diamond particle size diameter is 3um. Adjust the position of the processing platform loaded with the silicon carbide ingot so that the diamond wire is 4mm away from the crystal edge position A in the direction of the reference plane [10-10] of the original silicon carbide ingot, ensuring that the diamond wire does not contact the silicon carbide ingot when starting high-speed movement, that is, the diamond wire is in a no-load running state, and the diamond wire has a circular routing speed of 40m / s in the up and down directions.

[0063] Step 3: Adjust the relative positions of the two sets of ultrasonic generators and the liquid outlet channels on the equipment and the silicon carbide ingot on the platform. The appropriate static spacing is 3mm. Start the diamond wire routing function on the equipment. The diamond wire performs high-speed up and down circular motion. The diamond wire only moves in the longitudinal Z-axis direction and does not move in the XY direction.

[0064] Step 4: Start the power supply of the ultrasonic generator to generate a power ultrasonic wave with a frequency of 20KHZ, turn on the cutting coolant circulation power supply used to cool the diamond wire, and two streams of cutting fluid flow out at high speed through different channels to cool the diamond wire. The ultrasonic wave acts on the diamond wire after being transmitted through the cutting coolant medium, causing the diamond wire to move with high frequency micro-amplitude (amplitude 10um).

[0065] Step 5: According to the standard size of the target SiC ingot, program the motion trajectory of the processing platform. The equipment computer controls the moving processing platform. The platform moves slowly according to the designed motion trajectory at a speed of 0.05 mm / s. When the edge of the SiC ingot reference surface [10-10] on the platform contacts the high-speed moving diamond wire, cutting begins.

[0066] Step 6: After the cutting starts, the platform moves slowly in the X direction. When the diamond wire cuts to the edge A of the original ingot reference surface ( Figure 2 ) point, the cutting of the reference surface begins. When the diamond wire cuts to the edge B of the original ingot reference surface ( Figure 2 ) point, the cutting of the reference surface is completed. When the platform starts to make a combined movement in the X and Y directions, the diamond wire cuts the side surface of the original crystal ingot until the diamond wire cuts to point C of the original crystal ingot. The side surface processing of the crystal ingot is completed. The processed silicon carbide ingot is physically separated from the silicon carbide residual material. The total cutting process takes 2.63 hours, which improves the cutting efficiency by 50%.

[0067] Step 7: Turn off the power of the ultrasonic generator and the cutting fluid supply system, turn off the power of the diamond wire routing movement, move the platform in the X direction under computer control, move the platform and the ingot away from the diamond wire, remove the cut silicon carbide ingot and the silicon carbide scraps after cutting and separation, measure the geometric dimensions and surface processing quality of the silicon carbide side surface and reference surface, the silicon carbide ingot has a diameter of 150mm, a thickness of 25mm, a side surface roughness of 0.3um, and a reference surface roughness of 0.3um, which meets the quality standards.

[0068] Step 8: After the quality of the silicon carbide ingot is inspected and qualified, it will be put into the next normal production process. The silicon carbide scraps can be recycled and reused as artificial moissanite and processed into artificial moissanite jewelry.

[0069] Comparative Example 1 This comparative example adopts the same diamond wire cutting method as Example 1, but the difference is that the ultrasonic unit is moved elsewhere and directly applied to the roller in contact with the diamond wire, directly generating ultrasonic vibration to the diamond wire, and the cutting fluid is still pumped to the surface of the diamond wire according to the original structure.

[0070] The rest of the conditions such as ultrasonic frequency, power, routing speed, etc. remain unchanged.

[0071] The ultrasonic wave acts directly on the roller in contact with the diamond. However, the roller itself has a large weight and is usually tightly fixed on the mechanical spindle. Therefore, it is difficult for the roller to make a relatively large high-frequency vibration under the action of ultrasonic waves. Naturally, it is difficult for the diamond wire on the roller to obtain a large proportion of the high-frequency vibration energy. Therefore, on the one hand, this vibration mode has no vibration efficiency and extremely low energy utilization. On the other hand, since the diamond wire itself is vibrated, the roller that fixes it will also be vibrated. Therefore, the geometric positioning of the diamond wire will be greatly affected. Not only is it difficult to improve the cutting efficiency, but it is also easy to produce dimensional errors and wavy cut surfaces. Problems such as shape are not suitable for cutting such hard crystal ingots.

[0072] Comparative Example 2 This comparative example adopts the same diamond wire cutting method as Example 1, but the difference is that an immersion method is adopted. The mobile platform is inverted so that the ingot is immersed in a container filled with cutting fluid. The diamond wire is cut below the liquid surface through multiple guide wheels. At the same time, two high-power ultrasonic generators with the same frequency as Example 1 are placed in the cutting fluid.

[0073] The consequence is that, on the one hand, the mobile platform will be corroded by the immersed cutting fluid, seriously affecting the movement accuracy of the platform, or the platform will soon fail to work normally; on the other hand, in the immersion ultrasonic application method, the ultrasonic energy is dispersed in the entire container and is not concentrated at the cutting interface. Therefore, applying ultrasound in this way has almost no effect on improving cutting efficiency and section quality.

[0074] Comparative Example 3 This comparative example adopts the same diamond wire cutting method as Example 1, but the difference is that the distance between the liquid outlet and the crystal ingot is adjusted to 1 cm. As a result, the ultrasonic energy decays quickly in the air, which is basically no different from when no ultrasound is applied at all. The cutting rate is very slow and the section quality is also poor.

[0075] Based on the above embodiments and comparative examples, it can be clearly seen that the processing equipment and the corresponding processing method provided in the embodiments of the present invention use diamond wire cutting to complete the processing of the side surface and reference surface of the hard crystal ingot. During the wire cutting process, the cutting fluid is pumped to form a flow beam, and an ultrasonic unit is used to directly apply ultrasound to the flow beam, which significantly improves the focusing degree of ultrasonic energy, assists in completing the cutting process, and avoids the processing errors and surface quality problems caused by directly applying ultrasound to the diamond wire.

[0076] In addition, the technical solution provided by the embodiment of the present invention can avoid the pollution and waste of hard material powder formed by grinding, and significantly improve the material utilization rate.

[0077] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A crystal surface processing device, comprising a bearing module and a processing module, wherein the bearing module is used to bear a hard crystal ingot, and the processing module can move relative to the bearing module to process the hard crystal ingot; It is characterized in that The processing module includes a diamond wire unit, a cutting fluid pump unit and an ultrasonic unit; The diamond wire unit can drive the diamond wire to move along the axial direction to process the hard crystal ingot; the cutting fluid pump unit can continuously pump cutting fluid to the surface of the diamond wire, and make the cutting fluid adhere to the surface of the diamond wire and flow to form a flow beam; the ultrasonic unit is in contact with the cutting fluid and is used to directly apply ultrasonic waves to the flow beam.

2. The surface processing equipment according to claim 1, characterized in that: The diamond wire moves along the direction of gravity, and the liquid outlet channel of the cutting fluid pump unit and the ultrasonic unit are arranged above the cutting position of the diamond wire. The liquid outlet channels and ultrasonic units are arranged in multiple groups and are distributed in rotational symmetry with the diamond wire as the axis.

3. The surface processing equipment according to claim 2, characterized in that: The cutting fluid pump unit includes a first liquid outlet channel and a second liquid outlet channel, and the ultrasonic unit includes a first ultrasonic generator and a second ultrasonic generator. The first ultrasonic generator is arranged in cooperation with the first liquid outlet channel, and the second ultrasonic generator is arranged in cooperation with the second liquid outlet channel. The first liquid outlet channel and the second liquid outlet channel are arranged relative to each other with the diamond wire as the axis, and the liquid outlet directions both point to the diamond wire.

4. The surface processing equipment according to claim 2 or 3, characterized in that: The distance between the outlet of the liquid outlet channel and the hard crystal ingot is 3-5 mm.

5. The surface processing equipment according to claim 2, characterized in that: The cutting fluid pump unit further includes a cutting fluid recovery device, which is disposed below the diamond wire and is used to collect the cutting fluid in the flow beam and pump the collected cutting fluid to the liquid outlet channel.

6. The surface processing equipment according to claim 1, characterized in that: The surface of the diamond wire is embedded with diamond particles, and the particle size of the diamond particles is 3-12 μm; The diameter change rate of the diamond wire is below 2%.

7. The surface processing equipment according to claim 6, characterized in that: The diameter of the diamond wire is 0.45-0.90 mm.

8. The surface processing equipment according to claim 1, characterized in that: The bearing module comprises a precision mobile platform with at least two degrees of freedom of movement, the precision mobile platform comprises a fixed part and a mobile part, the hard crystal ingot can be fixed on the mobile part, and at least two of the degrees of freedom are arranged perpendicularly and crosswise with the geometric axis of the hard crystal ingot; And, the geometric axis of the ingot is parallel to the diamond wire at the cutting position.

9. The surface processing equipment according to claim 8, characterized in that: The precision mobile platform includes a first track and a second track. The first track is fixedly arranged, and the second track is perpendicularly intersected with the first track and slidably cooperates with the first track, and can be driven to translate along the extension direction of the first track; the hard crystal ingot is fixed on the second track and can be driven to translate along the extension direction of the second track.

10. The surface processing equipment according to claim 1, characterized in that: The diamond wire is a ring-shaped wire connected end to end; Or the diamond wire is a line type with its ends not connected, and the diamond wire unit can drive the diamond wire to perform linear reciprocating motion.

Images