CN112140375A - Multi-wire cutting system and method for silicon carbide wafer - Google Patents
Multi-wire cutting system and method for silicon carbide wafer Download PDFInfo
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- CN112140375A CN112140375A CN202011043570.0A CN202011043570A CN112140375A CN 112140375 A CN112140375 A CN 112140375A CN 202011043570 A CN202011043570 A CN 202011043570A CN 112140375 A CN112140375 A CN 112140375A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28D—WORKING STONE OR STONE-LIKE MATERIALS
- B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
- B28D5/04—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor by tools other than rotary type, e.g. reciprocating tools
- B28D5/045—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor by tools other than rotary type, e.g. reciprocating tools by cutting with wires or closed-loop blades
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28D—WORKING STONE OR STONE-LIKE MATERIALS
- B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
- B28D5/0058—Accessories specially adapted for use with machines for fine working of gems, jewels, crystals, e.g. of semiconductor material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28D—WORKING STONE OR STONE-LIKE MATERIALS
- B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
- B28D5/0058—Accessories specially adapted for use with machines for fine working of gems, jewels, crystals, e.g. of semiconductor material
- B28D5/0076—Accessories specially adapted for use with machines for fine working of gems, jewels, crystals, e.g. of semiconductor material for removing dust, e.g. by spraying liquids; for lubricating, cooling or cleaning tool or work
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Abstract
The invention discloses a multi-line cutting system and a multi-line cutting method for a silicon carbide wafer, wherein the multi-line cutting system for the silicon carbide wafer comprises: a fixed platform; the cutting platform is connected with the fixed platform and is used for cutting the silicon carbide crystal into the silicon carbide wafer; the tension regulating and controlling mechanism is connected with the cutting platform through a steel wire net and is used for regulating the tension of the steel wire net; the cutting fluid nozzle is connected to the fixed platform and used for spraying cutting fluid onto the cutting platform; the circulating monitoring pool is connected with the cutting platform; and the cooling system is connected with the cutting platform and the circulating monitoring pool. The invention can improve the quality of the wafer and is beneficial to unifying the surface type of the silicon carbide wafer.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a multi-wire cutting system and a multi-wire cutting method for a silicon carbide wafer.
Background
At present, silicon carbide single crystal materials mainly include a conductive substrate and a semi-insulating substrate. The problem of the silicon carbide single crystal material with high quality and large size is the first problem to be solved in the development of the silicon carbide technology. With the increase of the size of the silicon carbide single crystal piece, the processing difficulty is gradually increased from four inches to six inches. In the actual production process, the production yield and the control of the product surface type directly affect the cost and the product quality (quantum efficiency, light extraction efficiency, product power and the like) of the silicon carbide wafer. Therefore, control in the material processing process is particularly important, when a substrate is produced, linear cutting is critical to wafer production, specific requirements are provided for the thickness, total thickness change, curvature, warping degree and other numerical values of a cut product, and meanwhile, the control of the surface shape of the cut product can also influence the control of the curvature and warping degree of the product by grinding and polishing and the unified control of the surface shape. In addition, many of the conventional cutting devices cannot control the tension of the wire mesh well and cannot cut the wire mesh sufficiently with the cutting fluid.
Disclosure of Invention
In view of the defects of the prior art, the invention provides a multi-wire cutting system and a multi-wire cutting method for a silicon carbide wafer, which can obviously improve the quality of the wafer, can make the tension of a steel wire net uniform during cutting, and is beneficial to unifying the surface type of the silicon carbide wafer.
To achieve the above and other objects, the present invention provides a multi-wire saw system for silicon carbide wafers, comprising:
a fixed platform;
the cutting platform is connected with the fixed platform and is used for cutting the silicon carbide crystal into the silicon carbide wafer;
the tension regulating and controlling mechanism is connected with the cutting platform through a steel wire net and is used for regulating the tension of the steel wire net;
the cutting fluid nozzle is connected to the fixed platform and used for spraying cutting fluid onto the cutting platform;
the circulating monitoring pool is connected with the cutting platform;
the cooling system is connected with the cutting platform and the circulating monitoring pool;
the tension regulating mechanism comprises a tension wheel and at least two wire guide wheels arranged side by side, wherein the vertical center line of the tension wheel is vertical to the horizontal center connecting line of the at least two wire guide wheels arranged side by side;
the tension wheel is connected with the fixed platform through a tension arm, and the tension arm can drive the tension wheel to swing in a pendulum manner in the vertical direction.
In one embodiment, the fixed platform is in the shape of a vertically placed disk.
In one embodiment, the loop monitor pool comprises:
the sedimentation tank is connected with the cutting platform;
the filtering device is positioned at the top end of the sedimentation tank and is provided with a liquid inlet;
the stirring monitoring pool is connected with the sedimentation pool in parallel and is used for storing the cutting fluid flowing from the sedimentation pool;
and the liquid guide channel is communicated with the top end of the sedimentation tank and the top end of the stirring monitoring tank.
In one embodiment, a stirring paddle is arranged in the stirring monitoring pool.
In one embodiment, the cutting platform comprises:
the first grooved wheel is transversely fixed on the fixed platform;
the second grooved wheel is arranged in parallel with the first grooved wheel and is fixed on the fixed platform;
and the steel wire net is wound on the first sheave, the second sheave and the tension regulating and controlling mechanism.
In one embodiment, the cutting fluid nozzle includes a first nozzle and a second nozzle, the first nozzle and the second nozzle being parallel to each other.
The invention also aims to provide a method for cutting a silicon carbide wafer, which at least comprises the following steps:
providing a multi-wire cutting system for the silicon carbide wafer;
the tension of the steel wire net is adjusted through the tension adjusting mechanism;
spraying cutting fluid onto the cutting platform through the cutting fluid nozzle;
controlling the cutting parameters of the steel wire mesh in real time according to the cutting position of the steel wire mesh on the longitudinal section of the silicon carbide crystal;
and cutting the silicon carbide crystal into the silicon carbide wafer through the cutting platform and the cutting liquid.
In one embodiment, the step of controlling the cutting parameters of the steel wire mesh in real time according to the cutting position of the steel wire mesh on the longitudinal section of the silicon carbide crystal comprises 3-5 stages of cutting processes.
In an embodiment, the silicon carbide crystal includes a plurality of silicon carbide boules having a carbon facing layer and a silicon facing layer.
In one embodiment, the cutting parameters include a feed speed, a swing angle, a feed speed, a constant speed time and/or an acceleration and deceleration time.
In one embodiment, the silicon carbide wafer has a saddle-shaped profile.
In one embodiment, the incoming wire speed, rocking angle and constant speed time for the silicon carbide wafer is greater than 6 inches and is greater than the incoming wire speed, rocking angle and constant speed time for the silicon carbide wafer is less than 6 inches.
In one embodiment, the cutting parameters of the wire mesh change in a parabolic manner during the cutting process.
In one embodiment, the average value of warp of the silicon carbide wafer is less than 40 microns, and the bow value is less than 20 microns.
In one embodiment, the silicon carbide wafer has a total thickness variation of less than 10 microns and a total surface flatness of less than 10 microns.
In one embodiment, the silicon carbide crystal ingots are bonded together by a ring-filling resin.
In one embodiment, the central axes of the plurality of silicon carbide crystal ingots are positioned on the same horizontal line, and the carbon surface layer and the silicon surface layer of different silicon carbide crystal ingots are parallel to each other.
In one embodiment, the cutting fluid is a diamond cutting fluid.
In one embodiment, when the silicon carbide wafer is 6 inches in size, the cutting position includes a feed amount of 0% -10% of the total length of the silicon carbide crystal, a feed amount of 10% -30% of the total length of the silicon carbide crystal, a feed amount of 30% -70% of the total length of the silicon carbide crystal, a feed amount of 70% -90% of the total length of the silicon carbide crystal, and a feed amount of 90% -100% of the total length of the silicon carbide crystal.
The invention provides a multi-wire cutting system and a multi-wire cutting method for a silicon carbide wafer, wherein the multi-wire cutting system for the silicon carbide wafer can enable the steel wire net to have uniform cutting tension. The circulating monitoring pool can filter large particles, and liquid in the circulating monitoring pool can be directly used as cutting fluid to be introduced into the cutting platform to cut the silicon carbide crystals. According to the cutting method, for example, five-stage cutting process parameters, specific process parameters and process parameter ranges are designed mainly according to the cutting position of the silicon carbide crystal, so that the WARP (WARP), Bow (Bow), Total Thickness Variation (TTV), Linear Thickness Variation (LTV) and total surface flatness (TIR) parameters of the silicon carbide crystal are obviously reduced, the consistency of the WTW (wafer to wafer) thicknesses among different wafers is obviously improved, and the quality of a final product is improved. The invention can obtain the silicon carbide wafer with high quality and low cost, the quality of the silicon carbide wafer obtained by cutting is effectively improved, and the silicon carbide wafer is totally in a saddle-shaped surface shape, namely the saddle-shaped percentage of the cut product is 100%. The invention reduces the processing difficulty of the subsequent polishing process and epitaxial growth. The silicon carbide device is low in cost, is easy to popularize in a marketization mode, and can effectively promote the development of the silicon carbide device industrial chain. The invention can fully utilize the cutting fluid and greatly reduce the production cost.
Drawings
FIG. 1 is a schematic structural diagram of a multi-wire saw system for cutting silicon carbide wafers according to an embodiment of the present invention;
FIG. 2 is a schematic view of the cutting platform and the tension modulating mechanism without cutting the silicon carbide crystal according to one embodiment of the present invention;
FIG. 3 is a front view of the loop monitor pool in accordance with an embodiment of the present invention;
FIG. 4 is a schematic view of the agitation monitoring tank in an embodiment of the present invention;
FIG. 5 is a schematic view of the settling tank in an embodiment of the present invention;
FIG. 6 is a schematic representation of the structure of a silicon carbide crystal according to one embodiment of the present invention;
FIG. 7 is a schematic view of the structure of the silicon carbide ingot in an embodiment of the present invention;
FIG. 8 is a schematic structural view of the resin of the present invention;
fig. 9 is a flow chart illustrating a method for cutting a silicon carbide wafer according to an embodiment of the present invention.
Description of the symbols
101. A fixed platform; 1021. a first sheave; 1022. a second sheave; 1023. a steel wire mesh; 1031. a tension pulley; 1032. a wire guide wheel; 1033. a tension arm; 1041. a first nozzle; 1042. a second nozzle; 1051. a sedimentation tank; 1052. a filtration device; 1053. a stirring monitoring pool; 10531. a stirring paddle; 10532. a stirrer; 1054. a drainage channel; 106. a cooling system; A. a silicon carbide crystal; B. a silicon carbide ingot; C. and (5) ring-packaging resin.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
In the present invention, it should be noted that, as the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, their indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, and are only for convenience of describing the present application and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first" and "second," if any, are used for descriptive and distinguishing purposes only and are not to be construed as indicating or implying relative importance.
The multi-wire cutting system for the silicon carbide wafer can enable the steel wire net to have uniform cutting tension. The circulating monitoring pool can filter large particles, and liquid in the circulating monitoring pool can be directly used as cutting fluid to be introduced into the cutting platform to cut the silicon carbide crystals. The cutting method provided by the invention is mainly characterized in that cutting technological parameters, specific technological parameters and technological parameter ranges of five stages are designed according to the cutting position of the silicon carbide crystal, so that warping degree (WARP), bending degree (Bow), Total Thickness Variation (TTV), Linear Thickness Variation (LTV) and total surface flatness (TIR) parameters are obviously reduced, the thickness consistency of different wafers is obviously improved, and the quality of a final product is improved.
Referring to fig. 1-5, in one embodiment, the multi-wire saw system for silicon carbide wafers includes, but is not limited to, a fixed platen 101, a cutting platen, a tension adjusting mechanism, a cutting fluid nozzle, a circulation monitoring tank, and a cooling system 106. The multi-wire cutting system for the silicon carbide wafer can enable the steel wire net to have uniform cutting tension.
Referring to fig. 1 to 2, in an embodiment, the fixed platform 101 is, for example, a vertically disposed disc. The cutting platform is connected with the fixed platform 101, and the cutting platform is used for cutting the silicon carbide crystal A into the silicon carbide crystal. Specifically, the cutting platform comprises a first sheave 1021, a second sheave 1022 and a steel wire mesh 1023, wherein the first sheave 1021 is transversely fixed on the fixed platform 101, the second sheave 1022 is arranged side by side with the first sheave 1021, the second sheave 1022 is fixed on the fixed platform 101, and the steel wire mesh 1023 is wound on the first sheave 1021, the second sheave 1022 and the tension regulation mechanism. The steel wire mesh 1023 is formed by coiling a diamond wire.
Referring to fig. 1 to 2, in an embodiment, the tension adjusting mechanism includes a tension wheel 1031 and at least two side-by-side wire guide wheels 1032, and a vertical center line of the tension wheel 1031 is perpendicular to a horizontal center line of the at least two side-by-side wire guide wheels 1032. Tension regulation and control mechanism passes through copper wire net 1023 with cutting platform connects, tension regulation and control mechanism is used for adjusting the tension of copper wire net 1023, and is concrete, tension wheel 1031 pass through tension arm 1033 with fixed platform 101 is connected, tension arm 1033 can drive tension wheel 1031 is pendulum type swing in vertical direction, works as on cutting platform steel wire net 1023 when having the lax state, can sway to vertical direction position relatively, works as on cutting platform steel wire net 1023 is when too tight, can sway to vertical direction position relatively, tension regulation and control mechanism can make the tension of copper wire net 1023 is even.
Referring to fig. 1, in an embodiment, the cutting fluid nozzle 104 includes a first nozzle 1041 and a second nozzle 1042, and the first nozzle 1041 and the second nozzle 1042 are parallel to each other. Specifically, the first nozzle 1041 is arranged in parallel with the first sheave 1021, the second nozzle 1042 is arranged in parallel with the second sheave 1022, one end of the cutting fluid nozzle 104 is connected to the fixed platform 101, the cutting fluid nozzle 104 is configured to spray the cutting fluid onto the cutting platform, and the other end of the cutting fluid nozzle 104 is configured to spray the cutting fluid.
Referring to fig. 1, 3, 4 and 5, in one embodiment, the circulation monitoring tank is connected to the cutting platform, the circulation monitoring tank includes, but is not limited to, a sedimentation tank 1051, a filtering device 1052, a stirring monitoring tank 1053 and a liquid guiding channel 1054, the sedimentation tank 1051 is connected to the cutting platform, the filtering device 1052 is located at the top end of the sedimentation tank 1051, and a liquid inlet 1055 is disposed on the filtering device 1052. A conduit 10511 is arranged in the sedimentation tank 1051. The agitation monitoring tank 1053 is connected side by side with the sedimentation tank 1051. As shown in fig. 4, the left side of the stirring monitoring tank 1053 is used as a reference, a stirring paddle 10531 is disposed in the stirring monitoring tank 1053, a stirrer 10532 is disposed at the top end of the stirring monitoring tank 1053, and the stirrer 10532 is connected to the stirring paddle 10531. The stirring monitoring tank 1053 is used for storing the cutting fluid flowing from the sedimentation tank 1051, and the fluid guide channel 1054 is communicated with the top end of the sedimentation tank 1051 and the top end of the stirring monitoring tank 1053. The liquid flowing out of the cutting platform firstly enters the filtering device 1052 from the liquid inlet 1055, large particles are filtered, and then the liquid flows to the sedimentation tank 1051, the flow rate is relatively flat, silicon carbide powder generated after cutting is precipitated at the bottom of the sedimentation tank 1051, the liquid at the upper part of the sedimentation tank 1051 slowly flows to the circulation monitoring tank 1053, and the liquid in the circulation monitoring tank 1053 can be directly introduced into a processed product in the cutting platform as cutting liquid. The liquid composition fluctuation in the circulating tank 1053 is monitored through a viscometer, and when the viscosity exceeds a specified value, newly-configured diamond liquid is added through replacement, so that the cost is reduced to the maximum extent while the normal cutting effect is ensured.
Referring to fig. 1, in an embodiment, the cooling system 106 is connected to the cutting platform and the circulation monitoring pool, and the cooling system 106 mainly cools the whole system, so that the temperature of the whole system can be stabilized within a normal range during continuous operation.
Referring to fig. 9, in an embodiment, the method for cutting a silicon carbide wafer at least includes the following steps:
s1, providing a multi-wire cutting system of the silicon carbide wafer;
s2, adjusting the tension of the steel wire net through the tension adjusting mechanism;
s3, spraying cutting fluid onto the cutting platform through the cutting fluid nozzle;
s4, controlling cutting parameters of the steel wire mesh in real time according to the cutting position of the steel wire mesh on the longitudinal section of the silicon carbide crystal;
and S5, cutting the silicon carbide crystal into the silicon carbide wafer through the cutting platform and the cutting liquid.
Specifically, in step S3, the cutting fluid is, for example, a diamond cutting fluid, and the present invention performs cutting by using a combination of diamond wires and diamond cutting fluid, so as to effectively increase yield, reduce thickness of the damaged layer, improve surface shape, and improve product quality.
Specifically, in step S4, a cutting process including 3 to 5 stages, for example, is performed according to the size of the silicon carbide wafer. The cutting parameters include, for example, feed speed, swing angle, feed speed, constant speed time and/or acceleration and deceleration time.
Specifically, in step S4, referring to fig. 6 to 8, the silicon carbide crystal a includes a plurality of silicon carbide crystal ingots, for example, bonded by a plurality of silicon carbide crystal ingots, and specifically, the silicon carbide crystal a is bonded by a hoop resin C therebetween. The silicon carbide crystal ingot is provided with a carbon surface layer and a silicon surface layer, when the silicon carbide crystal ingot and the silicon carbide crystal ingot are sequenced, the crystal planes are ensured to be in the same orientation, the carbon surface layer (hereinafter referred to as C surface) and the silicon surface layer (hereinafter referred to as Si surface), namely C/Si surfaces, of different silicon carbide crystal ingots are kept parallel, and the central axes of the silicon carbide crystal ingots are positioned on the same horizontal line. Before real-time control of cutting parameters of the steel wire mesh according to the cutting position of the steel wire mesh on the longitudinal section of the silicon carbide crystal A, detection, orientation and rod sticking processes of crystal ingots are included, wherein the detection of the crystal ingots comprises but is not limited to appearance detection, dimension specification detection and crystal phase/crystal plane detection. The appearance detection refers to visual observation to determine whether the crystal ingot has edge breakage and cracks, and a strong light is used for detecting whether large bubbles exist in the crystal ingot. The dimension specification detection means that a vernier caliper, a micrometer and a thickness gauge are used for detecting whether the diameter, the roundness and the thickness range of the silicon carbide crystal ingot B meet the specification requirements or not. And the crystal phase/crystal face detection means that an X-ray diffractometer is used for detecting whether the carbon surface layer, the silicon surface layer and the positioning edge of the silicon carbide crystal ingot B meet the requirements or not, and the next procedure is carried out after all the silicon carbide crystal ingots are detected to be qualified. The orientation is used for determining the crystal face orientation of the crystal, preparing for subsequent ingot stick sticking, using an X-ray diffractometer, irradiating the crystal surface through X-rays, measuring the diffraction angle of the silicon face of the ingot, finding the needed ingot direction, and marking. The stick is that a plurality of silicon carbide crystal ingots are bonded into a whole and are fixed on a material sticking plate through a graphite support, the silicon carbide crystal ingots and the silicon carbide crystal ingots are filled and fixed through a ring-mounted resin ring, the same crystal plane orientation is ensured when the silicon carbide crystal ingots and the silicon carbide crystal ingots are sequenced, C/Si planes of different silicon carbide crystal ingots are kept parallel, and central axes of different silicon carbide crystal ingots are positioned on the same horizontal line.
Specifically, in step S4, the step of controlling the cutting parameters of the wire mesh in real time according to the cutting position of the wire mesh on the longitudinal section of the silicon carbide crystal a specifically includes: carrying out first-stage cutting, wherein the cutting position is 0% -10% of the longitudinal section of the silicon carbide crystal A of the steel wire mesh; carrying out second-stage cutting, wherein the cutting position is that the steel wire mesh is 10% -30% of the longitudinal section of the silicon carbide crystal A; carrying out third-stage cutting, wherein the cutting position is that the steel wire net is 30% -70% of the longitudinal section of the silicon carbide crystal A; cutting at a fourth stage, wherein the cutting position is 70% -90% of the longitudinal section of the silicon carbide crystal A of the steel wire mesh; and performing fifth-stage cutting, wherein the cutting position is that the steel wire net is 90% -100% of the longitudinal section of the silicon carbide crystal A. In the 5 stages, the variation trend of some cutting parameters of the steel wire net is changed in a parabolic manner, such as the wire feeding speed, for example, in the third stage cutting process, the parameter value of the wire feeding speed is the largest, the parameter value of the first stage cutting process is the same as that of the fifth stage cutting process, and the parameter value of the second stage cutting process is the same as that of the fourth stage cutting process. In the invention, the position of the steel wire mesh on the longitudinal section of the silicon carbide crystal A is based on the diameter of the longitudinal section of the silicon carbide crystal A, for example, the cutting position is 0% -10% of the position of the steel wire mesh on the longitudinal section of the silicon carbide crystal A, specifically 0% -10% of the position of the steel wire mesh on the diameter of the longitudinal section of the silicon carbide crystal A. The cutting method can ensure that the surface flatness and the surface shape of a cut product are better, and can further reduce surface line marks.
Specifically, in step S4, for the cutting parameters, for example, processing a silicon carbide wafer of 6 inches or more, the feeding speed can be increased, the feeding speed can be decreased, the swing angle can be increased, and the constant speed time can be increased. Namely, the incoming line speed, the swing angle and the constant speed time of the silicon carbide wafer are greater than 6 inches and are greater than the incoming line speed, the swing angle and the constant speed time of the silicon carbide wafer which is less than 6 inches.
Specifically, in step S5, the silicon carbide wafer has a saddle-shaped surface. According to the cutting parameters in the cutting method, the warping degree (WARP), the Bow degree (Bow), the Total Thickness Variation (TTV), the Linear Thickness Variation (LTV) and the total surface flatness (TIR) parameters are obviously reduced, the consistency of the thickness WTW (wafer to wafer) among different silicon carbide wafers is obviously improved, and finally the silicon carbide wafers with high quality and low cost can be obtained.
Referring to fig. 1 to 5, in an embodiment, the silicon carbide crystal a includes a plurality of six-inch N-type silicon carbide ingots, and the main process flows of the processing scheme are detailed by taking five steps of ingot detection, orientation, rod sticking, multi-line cutting, wax removal and cleaning as examples.
Specifically, the detection of the silicon carbide crystal ingot B comprises appearance detection, dimension specification detection and crystalline phase/crystal face detection, wherein the appearance detection refers to visual observation to determine whether the silicon carbide crystal ingot B has edge breakage and cracks, a strong light is used for detecting whether large bubbles exist in the silicon carbide crystal ingot B, and if yes, the silicon carbide crystal ingot B is unqualified. The dimension specification detection means that a vernier caliper, a micrometer and a thickness gauge are used for detecting whether the diameter, the roundness and the thickness range of the silicon carbide crystal ingot B meet the specification requirements or not. The diameter of the silicon carbide crystal ingot B is 150 +/-0.2 mm, the roundness is less than or equal to 0.05 mm, the cylindricity is less than or equal to 0.05 mm, and the thickness range is less than or equal to 0.05. In the process of detecting the crystal phase/crystal face, for example, an X-ray orientation instrument is used for detecting the crystal direction of the end face of the silicon carbide crystal ingot B, the crystal direction of the end face of the crystal direction is determined to be within a standard range (the crystal direction of the C face is 20 degrees, 50 '+/-6'), a laser pen or a highlight lamp is used for detecting whether the crystal bar has defects, and the next process is carried out after all the defects are detected to be qualified. Using an X-ray diffractometer, measuring the diffraction angle of the silicon surface of the crystal ingot by X-ray irradiation on the crystal surface, finding the diffraction angle of 17 degrees 49' of the Si surface, and marking each silicon carbide crystal ingot B to prepare for the subsequent stick bonding of the silicon carbide crystal ingot B into the silicon carbide crystal A. The shape of the silicon carbide crystal ingots B is shown in figure 2, each silicon carbide crystal ingot B is provided with a carbon surface layer and a silicon surface layer, each silicon carbide crystal ingot B is provided with a positioning edge, and after the required direction of the silicon carbide crystal ingot B is found, a marking process is carried out.
Specifically, for example, a plurality of silicon carbide crystal ingots B are bonded and fixed into the silicon carbide crystal A through hot-melt glue, then the silicon carbide crystal A is bonded with a graphite support and a material bonding plate, and an X-ray diffractometer is used for assisting the bonding process, so that the silicon carbide crystal ingots and the silicon carbide crystal ingots are ensured to have the same crystal plane orientation when being sequenced, the C/Si surfaces of different silicon carbide crystal ingots are kept parallel, and the central axes are positioned on the same horizontal line. The silicon carbide ingot and the silicon carbide ingot are fixed by, for example, a 6 mm thick hoop resin plate C having a shape as shown in fig. 4, and the entire bonding is completed as shown in fig. 6. And checking whether the silicon carbide crystal ingot B and the graphite support are firmly adhered, whether impurities, residual glue and the like are not on the surface of the silicon carbide crystal ingot B, and fixing the material adhering plate on a discharging platform of the silicon carbide multi-wire cutting system after the qualification is determined.
Specifically, the cutting parameters of the steel wire mesh 1023 are controlled in real time according to the cutting position of the steel wire mesh on the longitudinal section of the silicon carbide crystal a. For example, the cutting device is divided into five cutting stages, in the first cutting stage, for example, 15-16 mm of feed amount, 2.3-2.4 mm/h of feed speed, 1.8-2 DEG of swing angle, 480-. In the second cutting stage, for example, a feed amount of 44-45 mm, a feed speed of 2.0-2.1 mm/h, a swing angle of 1.8-2 °, a feed speed of 690-700 m/min, an acceleration/deceleration time of 2.8-3 s, a constant speed of 25-26 s, and a swing speed of 280-300 °/min are set. In the third cutting stage, for example, the feed amount of 60-61 mm is set, the feed speed of 1.7-1.8 mm/h is set, and the swing angle is 1.8-2 degrees; the incoming line speed is 950-1000 m/min, the acceleration and deceleration time is 4.8-5 s, the constant speed time is 29-30 s, and the swing speed is 280-300 DEG/min. In the fourth cutting stage, for example, a feed amount of 44-45 mm, a feed speed of 2.0-2.1 mm/h, a swing angle of 1.8-2 °, a feed speed of 690-700 m/min, an acceleration/deceleration time of 2.8-3 s, a constant speed of 25-26 s, and a swing speed of 280-300 °/min are set. In the fifth cutting stage, for example, a feed amount of 15-16 mm, a feed speed of 2.3-2.4 mm/h, a swing angle of 1.8-2 °, a feed speed of 480-.
Specifically, after the cutting parameters of the steel wire mesh are controlled in real time according to the cutting position of the steel wire mesh on the longitudinal section of the silicon carbide crystal A, the silicon carbide crystal A is cut by using a multi-wire cutting system of the silicon carbide crystal. In the cutting process, the flashlight is used for checking once every half hour to check whether the wire bow is uniform or not and whether a jumper wire exists or not. And controlling the steel wire mesh to move out slowly, and taking down the adhesive plate and the wafer. And separating the wafer from the adhesive plate and the graphite support. And heating by using a heating table, wherein the glue adhered inside is hot-melt glue, taking down the wafers after heating and melting, putting all the wafers into a blocking box, and determining the crystal face orientation. And (3) putting the card plug box with the wafer into an ultrasonic cleaning machine, cleaning for 10 minutes by using an alcohol solution, taking out, drying by using a blower after taking out the residual cutting fluid and particles on the surface of the silicon carbide wafer, and putting into a wafer box. At this stage, the multi-line slicing preparation process from the silicon carbide ingot B to the wafer is completed, and the processing effect of the processed wafer is described later. Through face type check out test set, face type and thickness parameter that detect out: the mean value of WARP WARP parameters is within 40 micrometers, BOW value parameters are within 20 micrometers, total thickness variation TTV value parameters are within 10 micrometers, and total surface flatness TIR value parameters are within 10 micrometers. Referring to fig. 5, the silicon carbide wafer is all saddle-shaped, and the shape of the saddle-shaped surface can effectively improve the quality of the subsequent polishing process and epitaxial growth, and the cutting method according to the present invention can effectively improve the quality of the silicon carbide wafer according to the parameter data of the saddle-shaped surface.
In particular, the cutting process is, for example, less than 5 cutting stages, including, for example, 2-5 cutting stages, for silicon carbide wafers of 6 inches or less. The parameter value range change trend of each stage is changed in a parabolic manner.
In summary, the present invention provides a multi-wire cutting system and a multi-wire cutting method for silicon carbide wafers, wherein the multi-wire cutting system for silicon carbide wafers can make the steel wire mesh have uniform cutting tension. The circulating monitoring pool can filter large particles, and liquid in the circulating monitoring pool can be directly used as cutting fluid to be introduced into the cutting platform to cut the silicon carbide crystals. According to the cutting method, for example, five-stage cutting process parameters, specific process parameters and process parameter ranges are designed mainly according to the cutting position of the silicon carbide crystal, so that the WARP (WARP), Bow (Bow), Total Thickness Variation (TTV), Linear Thickness Variation (LTV) and total surface flatness (TIR) parameters of the silicon carbide crystal are obviously reduced, the consistency of the WTW (wafer to wafer) thicknesses among different wafers is obviously improved, and the quality of a final product is improved. The invention can obtain the silicon carbide wafer with high quality and low cost, the quality of the silicon carbide wafer obtained by cutting is effectively improved, and the silicon carbide wafer is totally in a saddle-shaped surface shape, namely the saddle-shaped percentage of the cut product is 100%. The invention reduces the processing difficulty of the subsequent polishing process and epitaxial growth. The silicon carbide device is low in cost, is easy to popularize in a marketization mode, and can effectively promote the development of the silicon carbide device industrial chain. The invention can fully utilize the cutting fluid and greatly reduce the production cost.
The above description is only a preferred embodiment of the present application and a description of the applied technical principle, and it should be understood by those skilled in the art that the scope of the present invention related to the present application is not limited to the technical solution of the specific combination of the above technical features, and also covers other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, for example, the technical solutions formed by mutually replacing the above features with (but not limited to) technical features having similar functions disclosed in the present application.
Other technical features than those described in the specification are known to those skilled in the art, and are not described herein in detail in order to highlight the innovative features of the present invention.
Claims (10)
1. A multi-wire saw system for silicon carbide wafers, comprising:
a fixed platform;
the cutting platform is connected with the fixed platform and is used for cutting the silicon carbide crystal into the silicon carbide wafer;
the tension regulating and controlling mechanism is connected with the cutting platform through a steel wire net and is used for regulating the tension of the steel wire net;
the cutting fluid nozzle is connected to the fixed platform and used for spraying cutting fluid onto the cutting platform;
the circulating monitoring pool is connected with the cutting platform;
the cooling system is connected with the cutting platform and the circulating monitoring pool;
the tension regulating mechanism comprises a tension wheel and at least two wire guide wheels arranged side by side, wherein the vertical center line of the tension wheel is vertical to the horizontal center connecting line of the at least two wire guide wheels arranged side by side;
the tension wheel is connected with the fixed platform through a tension arm, and the tension arm can drive the tension wheel to swing in a pendulum manner in the vertical direction.
2. The multi-wire sawing system of claim 1, wherein the stationary platform is in the form of a vertically disposed disk.
3. The multi-wire sawing system of claim 1, wherein the circulation monitoring tank comprises:
the sedimentation tank is connected with the cutting platform;
the filtering device is positioned at the top end of the sedimentation tank and is provided with a liquid inlet;
the stirring monitoring pool is connected with the sedimentation pool in parallel and is used for storing the cutting fluid flowing from the sedimentation pool;
and the liquid guide channel is communicated with the top end of the sedimentation tank and the top end of the stirring monitoring tank.
4. The multi-wire sawing system of claim 3, wherein a stirring paddle is disposed within the stirring monitoring basin.
5. The multi-wire sawing system of claim 1, wherein the sawing platform comprises:
the first grooved wheel is transversely fixed on the fixed platform;
the second grooved wheel is arranged in parallel with the first grooved wheel and is fixed on the fixed platform;
and the steel wire net is wound on the first sheave, the second sheave and the tension regulating and controlling mechanism.
6. A method for cutting a silicon carbide wafer is characterized by comprising at least the following steps:
providing a multi-wire saw system of a silicon carbide wafer according to any one of claims 1 to 5;
the tension of the steel wire net is adjusted through the tension adjusting mechanism;
spraying cutting fluid onto the cutting platform through the cutting fluid nozzle;
controlling the cutting parameters of the steel wire mesh in real time according to the cutting position of the steel wire mesh on the longitudinal section of the silicon carbide crystal;
and cutting the silicon carbide crystal into the silicon carbide wafer through the cutting platform and the cutting liquid.
7. The method according to claim 6, wherein the step of controlling the cutting parameters of the wire mesh in real time according to the cutting position of the wire mesh on the longitudinal section of the silicon carbide crystal comprises 3 to 5 stages of cutting processes.
8. The cutting method as set forth in claim 6 wherein the silicon carbide crystal comprises a plurality of silicon carbide ingots having a carbon facing layer and a silicon facing layer.
9. The cutting method according to claim 6, wherein the cutting parameters comprise feed speed, swing angle, feed speed, constant speed time and/or acceleration and deceleration time.
10. The dicing method according to claim 1, wherein the silicon carbide wafer has a saddle-shaped profile.
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Application publication date: 20201229 |