A thermal compensation method and a thermal compensation device

Abstract

The present disclosure provides a thermal compensation method and a thermal compensation device, and belongs to the technical field of silicon wafer processing. The thermal compensation method comprises: monitoring a characteristic parameter of a thermal imbalance event, the thermal imbalance event representing an event in which, during the cutting process of a crystal bar, the temperature drop rate of the cutting interface of the crystal bar is greater than a preset temperature drop rate threshold; and based on the characteristic parameter, determining to heat the cutting interface when the thermal imbalance event occurs, so that the temperature difference between the heated cutting interface and the temperature of the cutting interface before the thermal imbalance event is less than a temperature difference threshold. The present disclosure can maintain the thermodynamic equilibrium of the cutting interface after the cutting is suddenly stopped due to an anomaly, and avoid the warping of the cutting interface caused by a sudden temperature drop.

Description

Technical Field

[0001] This disclosure relates to the field of silicon wafer processing technology, and in particular to a thermal compensation method and a thermal compensation device. Background Technology

[0002] In semiconductor wafer manufacturing processes, slicing single-crystal ingots using wire dicing equipment is a crucial front-end process. During normal dicing, the high-speed moving diamond wires experience intense friction with the single-crystal ingots, generating a significant amount of cutting heat. To prevent tool wear and overheating damage to the silicon wafers, wire dicing equipment is typically equipped with a cooling system that continuously sprays coolant at room temperature or low temperature onto the dicing area, thereby establishing a dynamic thermodynamic balance between heat generation and dissipation.

[0003] However, in actual cutting production, abnormal conditions such as wire breakage and abnormal shutdowns inevitably occur. When such abnormalities occur, the emergency stop mechanism of the wire EDM equipment is usually triggered immediately to stop the spindle rotation and table feed. Then, the operator intervenes to handle the situation and restarts the equipment.

[0004] However, at the moment of sudden interruption of the cutting process, due to the continuous spraying of the original cooling system or the presence of ambient air convection, the temperature at the cutting interface will drop drastically in a very short time, causing severe thermal shock at the silicon wafer cutting interface. This rapid temperature change will induce huge shrinkage stress at the cutting interface, which will then cause irreversible deformation at the microscale, i.e., warping, resulting in insufficient flatness of the silicon wafer after cutting. Summary of the Invention

[0005] This disclosure provides a thermal compensation device, method, and computer-readable storage medium; after a sudden stop of cutting due to an anomaly, it can maintain the thermodynamic balance of the cutting interface and prevent warping of the cutting interface due to a sudden drop in temperature.

[0006] The technical solution disclosed herein is implemented as follows: In a first aspect, this disclosure provides a thermal compensation method, which includes: Characterization parameters for monitoring thermal imbalance events, which are events that cause the temperature drop rate at the cutting interface of the crystal rod to exceed a preset cooling rate threshold during the cutting process of the crystal rod. When a thermal imbalance event is determined based on the characterization parameters, the cutting interface is heated so that the temperature difference between the heated cutting interface and the temperature of the cutting interface before the thermal imbalance event is less than the temperature difference threshold.

[0007] Secondly, this disclosure provides a thermal compensation device for use in wire cutting equipment. The thermal compensation device includes: a status monitoring unit, a thermal compensation unit, and a main control unit. The status monitoring unit is connected to the main control unit and is used to monitor the characterization parameters of thermal imbalance events and send the characterization parameters to the main control unit. The thermal imbalance event refers to an event that causes the temperature drop rate of the cutting interface of the crystal rod to exceed a preset cooling rate threshold during the crystal rod cutting process. The main control unit is used to send a drive signal to the thermal compensation unit when a thermal imbalance event occurs, based on the received characterization parameters. A thermal compensation unit, which is communicatively connected to the main control unit, is used to deliver a compensation heat medium to the cutting interface based on a drive signal, so that the temperature difference between the cutting interface after being heated by the compensation heat medium and the temperature of the cutting interface before the thermal imbalance event occurs is less than a temperature difference threshold, wherein the temperature of the compensation heat medium is greater than or equal to the temperature of the cutting interface before the thermal imbalance event occurs.

[0008] Thirdly, this disclosure provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the method described in the second aspect.

[0009] This disclosure provides a thermal compensation method and a thermal compensation device. After a thermal imbalance event occurs, the thermal compensation method heats the cutting interface so that the temperature of the heated cutting interface is approximately equal to the temperature before the thermal imbalance event, thereby reducing the thermal stress of the cutting interface, avoiding local warping of the silicon wafer during cutting, and improving the flatness of the cutting interface before and after the thermal imbalance event. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the composition of a wire cutting device provided in this disclosure.

[0011] Figure 2 This is a partially enlarged schematic diagram of the diced crystal rod provided in this disclosure.

[0012] Figure 3 This is a flowchart illustrating a thermal compensation method provided in this disclosure.

[0013] Figure 4 This is a schematic diagram illustrating the principle of dynamic heat regulation provided in this disclosure.

[0014] Figure 5 This is a schematic diagram of the structure of a thermal compensation device provided in this disclosure.

[0015] Figure 6 This is a schematic diagram of a condition monitoring unit including a mid-wave infrared optical sensor, as provided in this disclosure.

[0016] Figure 7 This is a schematic diagram of the structure of a thermal compensation unit including a jet nozzle with a flat cross-section, as provided in this disclosure.

[0017] Figure 8 This is a schematic diagram showing the comparison between the experimental group and the control group on the nanomorphology image provided in this disclosure. Detailed Implementation

[0018] The technical solutions in this disclosure will now be clearly and completely described with reference to the accompanying drawings.

[0019] To better understand the thermal compensation device and method provided in the embodiments of this disclosure, the application environment and underlying physical mechanism of the embodiments of this disclosure will be described in detail first.

[0020] See Figure 1 It shows a schematic diagram of the composition of a wire cutting device 10, which can be understood as follows: Figure 1 The structure shown is for illustrative purposes only and does not imply that those skilled in the art will not be able to apply it to specific implementations. Figure 1 The embodiments of the present invention do not impose specific limitations on the addition or removal of components in the illustrated composition structure. Figure 1 As shown, the wire cutting device 10 may include a wire cutting unit 101 and a carrier unit 102; the wire cutting unit 101 may be, in some examples, such as Figure 1 The support unit 102 is positioned below it in the vertical direction, but in some examples it may be positioned above it in the vertical direction. This disclosure does not limit this to the position.

[0021] Specifically, the wire cutting unit 101 may include a plurality of spools 1011 and cutting wires 1012, the cutting wires 1012 being wound around the spools 1011 to form an array of mutually parallel cutting wires 1012; Figure 1 In this example, two spools 1011 are used, and the reciprocating motion directions of the spools 1011 and the cutting wire 1012 toward and away from the bearing unit 102 are as follows: Figure 1 As shown by the solid arrow in the diagram, the reciprocating speed can be, for example, 10 m / s to 15 m / s. The support unit 102 is used to load and fix the crystal rod 11.

[0022] exist Figure 1 In the example shown, the carrier unit 102 may include a base 1021 and an intermediate component 1022. The intermediate component 1022 can fix the crystal rod 11 to the base 1021. For example, the crystal rod 11 can be fixed to the base 1021 by using resin to bond its circumferential surface to the lower surface of the base 1021.

[0023] for Figure 1The wire cutting device 10 shown can move the cutting wire 1012 and the crystal rod 11 in the vertical direction by moving the wire cutting unit 101 or the carrying unit 102. After the cutting wire 1012 and the crystal rod 11 come into contact with each other, the crystal rod 11 is cut by moving the cutting wire 1012 along its extension direction.

[0024] In such Figure 1 In the example shown, the wire cutting unit 101 can be moved along the direction indicated by the black arrow, and the support unit 12 can be moved along the direction indicated by the dashed white arrow to achieve vertical facing movement between the cutting wire 1012 and the crystal rod 11. It should be noted that this embodiment of the invention uses a lifting device (not shown in the figure) to move the wire cutting unit 101 or the support unit 102. It is understood that those skilled in the art can also achieve the movement of the wire cutting unit 101 or the support unit 102 in other ways according to actual needs and implementation scenarios; this embodiment of the invention will not elaborate on these methods.

[0025] In the manufacturing process of 300mm (12-inch) semiconductor wafers, the ingot 11 is typically grown using the Czochralski method. For example... Figure 2 The image shown is a partial enlarged view of an exemplary wire cutting a crystal rod 11. When the crystal rod is sliced ​​using the wire cutting equipment 10, the wire cutting 1012 operates at a high linear speed. The diamond abrasive grains bonded to the surface of the wire cutting 1012 undergo intense friction with the crystal rod 11, forming a cutting kerf 201 on the crystal rod 11. The cutting kerf 201 is related to the diameter of the wire cutting 1012, and is typically about 200 μm to 300 μm wide. During the cutting process, the temperature at the cutting interface 202 where the wire cutting 1012 contacts the crystal rod 11 rises rapidly due to friction. The cutting kerf 201, also known as a kerf or cutting groove, refers to the narrow, elongated kerf formed on the crystal rod 11 during the cutting process of the wire cutting 1012, which accommodates the wire cutting 1012 and the coolant. The cutting interface 202, also known as the cutting interface or cutting point, refers to the contact surface where the cutting line 1012 and the crystal rod 11 directly contact and undergo frictional cutting. It is the heat source in the cutting process.

[0026] Therefore, wire EDM equipment 10 is usually equipped with a cooling system, which sprays coolant (usually a mixture of deionized water and additives such as polyethylene glycol). Under normal steady-state cutting conditions, the frictional heat generation and the convective heat transfer of the coolant reach a dynamic thermodynamic equilibrium. Thermodynamic equilibrium means that the frictional heat generation and the convective heat loss of the coolant are approximately equal, so that the temperature of the cutting interface 202 is maintained at a stable value, such as around 80°C.

[0027] However, when mechanical overload or wear causes the cutting wire 1012 to break, or when there is an abnormal shutdown, the frictional heat source disappears within milliseconds. Under the combined effects of internal heat conduction, continuous external coolant spraying, or air convection, the temperature at the cutting interface 202 will drop sharply. According to the basic physical principle of thermal expansion and contraction of solids, the formula for calculating thermal stress σ is: Where E represents the elastic modulus of silicon. The coefficient of thermal expansion of silicon is... This represents the change in temperature. The sudden increase causes thermal stress σ at the cutting interface 202 to exceed the yield limit of silicon material, ultimately leading to irreversible microscale deformation, i.e., warping, at the cutting interface 202.

[0028] When the wire cutting equipment 10 resumes cutting, the newly generated cutting surface is spatially misaligned by about a few micrometers with the cutting interface before the wire breakage. When the surface quality is characterized by nano-morphology images in the future, this local warping will appear as a high-contrast line mark, resulting in insufficient flatness of the silicon wafer obtained by cutting.

[0029] Based on this, the present disclosure provides a thermal compensation device, see [link to relevant documentation]. Figure 3 The method includes the following steps S301 and S302.

[0030] In step S301, the characterization parameters of the thermal imbalance event are monitored.

[0031] Among them, a thermal imbalance event refers to an event that causes the temperature at the cutting interface of the crystal rod to decrease at a rate greater than a preset cooling rate threshold during the cutting process. Thermal imbalance events can be such as wire breakage events (e.g., the breakage of the cutting wire 1012), shutdown events (e.g., abnormal shutdown of the wire cutting equipment 10), or obstruction events (e.g., the wire cutting unit 101 being stuck). Thermal imbalance triggering events are used to characterize any event that may lead to a sudden loss of the frictional heat source at the cutting interface or excessive external cooling, resulting in a disruption of the original dynamic thermodynamic balance between heat generation and dissipation at the cutting interface.

[0032] Characterization parameters refer to parameters that can directly or indirectly reflect the occurrence of thermal imbalance events. These characterization parameters are the basis for determining thermal imbalance events and can include parameters such as temperature, tension, and equipment operating status.

[0033] In step S302, when a thermal imbalance event is determined to have occurred based on the characterization parameters, the cutting interface is heated so that the temperature difference between the heated cutting interface and the temperature of the cutting interface before the thermal imbalance event occurs is less than the temperature difference threshold.

[0034] It is understood that the cutting interface can be heated by a compensating heat medium. This compensating heat medium acts as a heat transfer medium, delivering heat to the cutting interface to offset the sudden temperature drop caused by the thermal imbalance event. The compensating heat medium can deliver heat to the cutting interface through any one or more heat transfer methods, including convection, contact conduction, and thermal radiation. The temperature of the compensating heat medium is a preset temperature, which is greater than or equal to the temperature of the cutting interface before the thermal imbalance event. By delivering the compensating heat medium to the cutting interface, the temperature difference caused by the thermal imbalance event is compensated, as described above. .

[0035] In this disclosure, since the compensating heat medium also experiences heat loss due to air convection during transmission, to avoid heat loss, the temperature of the compensating heat medium can be set higher than the reference cutting temperature of the cutting interface, i.e., the preset temperature is higher than the reference cutting temperature. Specifically, the reference cutting temperature refers to the dynamic thermodynamic equilibrium point established between the heat generated by cutting friction and the convective heat dissipation of the room-temperature coolant during normal steady-state cutting when no abnormalities occur in the wire cutting equipment 10. For example, this reference cutting temperature is usually stable at around 80°C. In some examples, during normal steady-state cutting, multiple temperatures can be collected at different cutting interfaces during the cutting process, and the average value of the collected multiple temperatures is determined as the reference cutting temperature. It should be noted that the temperature of the cutting interface before the thermal imbalance event can be the temperature actually collected at the cutting interface before the thermal imbalance event occurs, or the reference cutting temperature can be used as the temperature of the cutting interface before the thermal imbalance event.

[0036] For example, the preset temperature can be set to the temperature obtained by increasing the reference cutting temperature by 5°C to 15°C. For instance, if the reference cutting temperature is 80°C, the preset temperature can be any value within the range of 85°C to 95°C. Specifically, when the difference between the preset temperature of the compensating heat medium and the reference cutting temperature is less than 5°C, the compensating heat medium will not be able to compensate for the temperature difference caused by thermal imbalance events during its journey to the cutting interface due to heat loss, resulting in the cutting interface temperature being lower than the reference cutting temperature. However, when the difference between the preset temperature of the compensating heat medium and the reference cutting temperature is greater than 15°C, overcompensation will occur, leading to an excessively high cutting interface temperature, and the cutting interface will warp due to the large temperature difference before and after compensation by the compensating heat medium.

[0037] In one specific embodiment, because water has a high specific heat capacity and a high density of heat-carrying energy, it can not only quickly carry heat energy into the cutting interface within the kerf of the crystal rod 11, but also wash away the silicon powder generated during the cutting process. Therefore, the compensating heat medium can be a liquid with a high specific heat capacity at a preset temperature, such as high-temperature deionized water. Alternatively, the compensating heat medium can also be an inert gas at a preset temperature, such as nitrogen or argon. Since the kerf is narrow, the liquid will form a water film and an air cushion due to surface tension. The inert gas has a lower dynamic viscosity than the liquid and does not exhibit boiling cavitation or phase transition risks at temperatures exceeding 100°C. Furthermore, the inert gas can form an oxygen-barrier protective layer on the high-temperature cut surface to prevent oxidation of the silicon surface. Additionally, the compensating heat medium can also be thermal radiation generated by a thermal radiation source. In this disclosure, any heat transfer medium capable of compensating for the temperature difference at the cutting interface can be used as a compensating heat medium; the specific type of compensating heat medium is not elaborated in this disclosure.

[0038] Within the extremely short time difference (e.g., a total response lag of approximately 0.5 seconds) between the occurrence of a thermal imbalance trigger event and the completion of the determination and heating of the cutting interface, a slight physical cooling inevitably occurs at the cutting interface due to the high thermal diffusivity of silicon. At this time, a small amount of shrinkage stress has already begun to accumulate within the silicon lattice. If the target temperature is simply set back to the reference cutting temperature, these residual stresses will be frozen within the lattice, resulting in nanoscale deformation still existing on the final silicon wafer surface. Therefore, this embodiment releases a compensating heat medium at a temperature higher than the reference cutting temperature, inducing a very short period of lattice relaxation or mild annealing effect at the cutting interface. This overtemperature compensation provides additional thermal activation energy to the silicon atoms at the dislocation edges, causing the lattice to spontaneously rearrange and release the initial stress accumulated due to the time difference, thereby further reducing the risk of warping caused by stress concentration.

[0039] The temperature difference threshold refers to the maximum permissible deviation between the temperature of the cutting interface and the temperature of the cutting interface before the thermal imbalance event occurs during the thermal compensation process of the compensating heat medium. It is a non-negative absolute value. If the difference is less than the temperature difference threshold, it can ensure that the thermal stress generated by the temperature difference at the cutting interface is small and will not cause warping. For example, the temperature difference threshold is 2℃.

[0040] Furthermore, once a thermal imbalance event is confirmed, the supply of coolant to the cutting interface should be stopped. This prevents the coolant from further increasing the rate of temperature drop at the cutting interface after the thermal imbalance event has occurred. It also avoids the contradictory operation of simultaneously heating with compensating heat medium and cooling with coolant, which would require more compensating heat medium to maintain the temperature at the cutting interface until the thermal imbalance event occurs.

[0041] In this embodiment, after a thermal imbalance event occurs, the cutting interface is heated so that the temperature of the heated cutting interface is approximately equal to the temperature before the thermal imbalance event, thereby reducing the thermal stress on the cutting interface, avoiding local warping of the silicon wafer during cutting, and improving the flatness of the cutting interface before and after the thermal imbalance event.

[0042] In some specific implementations, the characterization parameters include the temperature of the cutting interface. In step S302, when a thermal imbalance event is determined to have occurred based on the characterization parameters, the cutting interface is heated. Specifically, the slope of a continuous temperature value sequence consisting of multiple temperature values ​​at the cutting interface is determined. When the slope is greater than a preset cooling rate threshold, a thermal imbalance event is determined to have occurred, and the cutting interface is heated.

[0043] Specifically, a continuous temperature sequence is obtained based on the continuously received temperatures at the cutting interface. The slope is obtained by calculating the derivative of the temperature sequence with respect to time. When a temperature decrease is detected (i.e., the slope is negative), and the absolute value of the slope is greater than a preset cooling rate threshold (e.g., the cooling rate threshold is set to 5℃ / s), a thermal imbalance event is determined to have occurred. Thus, the occurrence of a thermal imbalance event can be directly determined based on the measured temperature.

[0044] Furthermore, the narrow cutting kerf places high demands on hardware size when directly monitoring the temperature at the cutting interface. Therefore, in some embodiments, the characterization parameters for monitoring thermal imbalance events include: monitoring the surface radiation temperature at the opening of the cutting kerf; and determining the temperature at the cutting interface corresponding to the surface radiation temperature and the depth of the cutting interface based on a pre-established linear temperature-depth mapping model.

[0045] Due to the frictional cutting action between the cutting line 1012 and the crystal rod 11, the cutting interface is the heat source throughout the cutting process. Heat is transferred from the cutting interface to the opening of the cutting kerf. Simultaneously, the opening of the cutting kerf is continuously subjected to convective heat dissipation from the ambient coolant and surrounding air. Therefore, a steady-state heat conduction gradient is formed along the depth of the kerf, with the temperature gradually decreasing from the cutting interface to the cutting kerf opening. This heat conduction gradient is characterized by a monotonically decreasing temperature trend from the cutting interface to the cutting kerf opening with decreasing depth. Therefore, the surface radiation temperature at the cutting kerf opening collected by the mid-wave infrared optical sensor is necessarily lower than the temperature of the cutting interface. Based on this, the temperature at the cutting interface corresponding to the surface radiation temperature and the depth of the cutting interface can be determined using a pre-established linear temperature-depth mapping model.

[0046] In the stage of establishing the linear temperature depth mapping model, miniature temperature probes were pre-embedded at various depths of the crystal rod 11, such as 50mm, 100mm, and 150mm, to measure the temperature of the cutting interface at different depths and the surface radiation temperature at the corresponding cutting kerf opening. Based on the correspondence between multiple sets of surface radiation temperatures and the temperatures of the cutting interface at different depths, the mathematical expression of the linear temperature depth mapping model was obtained as follows: ,in, Let be the temperature of the cutting interface located at depth d. To balance the attenuation ratio of emissivity and transmittance, it is typically between 0.92 and 0.98. It is a depth correction factor that is positively correlated with the depth d of the cutting interface. As the depth of the cutting interface increases, the temperature difference between the cutting kerf opening and the cutting interface also increases. The higher the compensation value, the better.

[0047] When the online cutting equipment 10 is running, it acquires the surface radiation temperature and the depth d of the cutting interface in real time, substitutes them into the linear temperature depth mapping model, and outputs the temperature of the cutting interface, thus obtaining the temperature of the cutting interface without contact.

[0048] In some specific implementations, the characterization parameters include the tension of the cutting line. In step S302 above, when a thermal imbalance event is determined to have occurred based on the characterization parameters, the cutting interface is heated, which includes: when the tension is less than the tension threshold, a thermal imbalance event is determined to have occurred, and the cutting interface is heated.

[0049] During normal cutting, the tension of the cutting wire 1121 is maintained within the normal tension range, such as 25N to 30N. When the cutting wire 1121 breaks, the tension drops in a step-like manner, such as falling below 5N. At this time, it is determined whether the tension is less than the tension threshold. If 5N is less than the tension threshold of 10N, it is determined that a thermal imbalance event has occurred.

[0050] Since a wire breakage will inevitably stop cutting, the rate of temperature drop at the cutting interface after cutting stops will certainly exceed the preset cooling rate threshold. However, there is a time delay between the wire breakage and the detection of this temperature drop exceeding the preset threshold. Therefore, directly monitoring the tension can reduce this time delay. Upon detecting a wire breakage event, a compensating heat medium can be immediately supplied to the cutting interface, allowing intervention to begin as soon as the temperature at the cutting interface begins to show a downward trend, further reducing the risk of warping at the cutting interface.

[0051] Furthermore, in the extremely complex environment of a semiconductor cutting workshop, a single sensor is susceptible to fluctuations caused by electromagnetic interference, mechanical vibration, or coolant splashes. If a false trigger occurs, the delivery of compensation heat medium during normal cutting could actually cause the cutting interface to expand due to heat, jamming the cutting wire. Since wire breakage is the most common event during cutting, to avoid false detection of such events, the cutting interface can be heated only when a wire breakage event is detected and the rate of temperature drop exceeds a preset cooling rate threshold. That is, heating of the cutting interface only occurs when both the cutting wire breaks and the temperature drop slope exceeds a certain limit, thus avoiding false compensation caused by interference from a single sensor.

[0052] When the in-line cutting equipment 10 processes the crystal rod 11, the area of ​​the cutting interface changes dynamically as the cutting line 1121 feeds downward. If the compensation heat medium supplied to the cutting interface remains constant, heat accumulation may occur at the top or bottom of the crystal rod 11 (where the effective heat dissipation chord length is shorter and the heat dissipation area is smaller), while insufficient compensation may occur at the center of the crystal rod 11 (where the effective heat dissipation chord length is longer and the heat dissipation area is larger). Therefore, this embodiment introduces dynamic heat regulation.

[0053] Based on this, in some embodiments, the thermal compensation method further includes: obtaining the depth of the cutting interface; determining the effective heat dissipation chord length corresponding to the cutting interface based on the depth and the three-dimensional geometric model of the crystal rod; determining the release parameters of the compensation heat medium according to the effective heat dissipation chord length; the above-mentioned heating of the cutting interface includes: delivering the compensation heat medium to the cutting interface according to the release parameters to heat the cutting interface.

[0054] See Figure 4 This diagram illustrates the principle of dynamic heat regulation provided in this embodiment. Based on the depth d and the three-dimensional geometric model of the crystal rod 11, the effective heat dissipation chord length L corresponding to the cutting interface is determined. The cross-section of the crystal rod 11 perpendicular to the feed direction is a circle with radius R. According to analytical geometry principles, the effective heat dissipation chord length L of the current cutting interface exposed in three-dimensional space satisfies a nonlinear equation: .

[0055] Based on the effective heat dissipation chord length, determine the release parameters of the compensating heat medium; deliver the compensating heat medium to the cutting interface according to the release parameters. The release parameters refer to the dynamic quantitative control parameters of the compensating heat medium that needs to be directionally delivered to the cutting interface. For example, when the compensating heat medium is a liquid or inert gas, the release parameters can be injection pressure, preset temperature, flow rate, etc. When the compensating heat medium is a heat radiation source, the release parameters can be irradiation duration, focusing area range, radiation power, etc. Figure 4In the coordinate system, the horizontal axis represents the depth d of the cutting interface, and the vertical axis represents the heat generated per unit time by the compensating heat medium delivered to the cutting interface. As the depth increases, the effective heat dissipation chord length L increases, and the required heat also increases. When the depth d is R, the effective heat dissipation chord length is 2R, and the required heat is the maximum.

[0056] The heat release parameter can be adjusted by using the real-time effective heat dissipation chord length L as a dynamic gain coefficient through a PID algorithm. Thus, a longer effective heat dissipation chord length at the cutting interface results in more heat being replenished per unit time, while a shorter effective heat dissipation chord length results in less heat being replenished per unit time. This ensures that even if a thermal imbalance trigger event occurs at any stage of the cutting process, the cutting interface can maintain thermodynamic equilibrium.

[0057] In some embodiments, when the compensating heat medium is a liquid heated to a preset temperature, because the cutting kerf is typically small, the surface tension of a conventional circular spray pipe causes the liquid to form a dense liquid film at the kerf opening when spraying liquid into the extremely narrow kerf. This liquid film not only blocks the subsequent entry of the compensating heat medium but also seals in the air inside the cutting kerf, forming an insulating air cushion, leading to the failure of heat compensation.

[0058] Based on the same concept as the above-described thermal compensation method, this disclosure also provides a thermal compensation device, see [link to relevant documentation]. Figure 5 The diagram shows a schematic representation of the thermal compensation device 50 provided in an embodiment of this disclosure.

[0059] The thermal compensation device 50 includes: a status monitoring unit 501, a main control unit 502, and a thermal compensation unit 503. The status monitoring unit 501 and the thermal compensation unit 503 are respectively connected to the main control unit 502.

[0060] The status monitoring unit 501 is used to monitor the characterization parameters of thermal imbalance events and send the characterization parameters to the main control unit.

[0061] The main control unit 502 is used to send a drive signal to the thermal compensation unit 503 when a thermal imbalance event is determined based on the received characterization parameters.

[0062] Among them, the drive signal refers to the control command signal output by the main control unit 502 to the thermal compensation unit 503 after determining that a thermal imbalance event has occurred, which is used to start the thermal compensation action.

[0063] The thermal compensation unit 503 is used to deliver a heat compensation medium to the cutting interface based on a drive signal, so that the temperature difference between the cutting interface after being heated by the compensation medium and the temperature of the cutting interface before the thermal imbalance event occurs is less than a temperature difference threshold.

[0064] It is understood that the thermal compensation unit 503 includes a compensation thermal medium storage section and a compensation thermal medium release channel.

[0065] In some specific implementations, the characterization parameter can be the temperature of the cutting interface. The state monitoring unit 501 includes a temperature sensor disposed in the cutting gap for monitoring the temperature at the cutting interface.

[0066] Specifically, due to the narrow kerf, the temperature sensor is not implanted into the crystal rod 11, but is fixed at the entrance of the kerf by a bracket. Only the tip of the temperature sensor's probe is inserted into the kerf to measure the temperature at the cutting interface. To allow the probe to penetrate deep into the kerf, a miniature thermocouple probe is typically used as the temperature sensor.

[0067] The main control unit 502 determines that a thermal imbalance event has occurred and triggers a drive signal.

[0068] The cutting interface may be located inside the crystal rod 11, which is hundreds of millimeters in diameter. The contact-type temperature sensor cannot directly contact the cutting interface during the cutting process, resulting in uncertain accuracy of the temperature measurement results. Furthermore, due to the extremely narrow cutting gap, the size requirements for the temperature sensor are also relatively high.

[0069] If a conventional non-contact infrared sensor is used, the coolant sprayed by the wire cutting equipment contains a large amount of polyethylene glycol and water. According to spectroscopic analysis, water molecules have extremely strong characteristic absorption peaks in the infrared bands of 2.7μm to 3.0μm and above 6μm. Polyethylene glycol also produces spectral scattering in the near-infrared region. Most of the radiation energy that a conventional infrared sensor can receive is absorbed or blocked by the coolant, resulting in low accuracy of the temperature measurement results from the conventional infrared sensor.

[0070] Based on this, see Figure 6 The diagram shows a structural schematic of the status monitoring unit 501 provided in this embodiment, which includes a mid-wave infrared optical sensor 5011.

[0071] The six mid-wave infrared optical sensors 5011 shown in the figure are oriented towards and parallel to the cutting slit. They are used to monitor the surface radiation temperature at the opening of the cutting slit and transmit this surface radiation temperature to the main control unit 502 via sensor signal lines. In the figure, the diagonally filled portion of the crystal rod 11 represents the uncut portion, and the unfilled portion represents the cut portion.

[0072] In infrared spectroscopy, the 3μm to 5μm range is the transmission window for both atmosphere and liquid. Within this frequency band, the absorption coefficients of water and polyethylene glycol are at their lowest, while the thermal radiation energy of silicon materials at 80°C to 100°C still has a sufficiently detectable signal-to-noise ratio in this band. Therefore, in this embodiment, a mid-wave infrared optical sensor 5011 with an operating wavelength of 3μm to 5μm can be selected. Simultaneously, the mid-wave infrared optical sensor 5011 is equipped with a long focal depth lens at its front end. The field of view of this long focal depth lens is focused on the opening of the cut slit, thereby enabling the mid-wave infrared optical sensor 5011 to accurately capture the surface radiation temperature at the opening of the cut slit.

[0073] In some specific implementations, the characterization parameter is tension; the state monitoring unit 501 includes a tension sensor that is set on the tension wheel on the wire feeding side or the tension wheel on the wire taking-up side of the online cutting device 10, for monitoring the tension of the cutting wire 1121.

[0074] The main control unit 502 is used to determine that a thermal imbalance event has occurred when the tension is less than the tension threshold.

[0075] In some embodiments, such as Figure 7 As shown in the figure, the liquid output end of the thermal compensation unit 503 provided in this embodiment includes a jet nozzle 5031 with a flat cross-section. Eight jet nozzles 5031 are shown in the figure. The long axis of the jet nozzles 5031 is parallel and aligned with the direction of the cutting slit, i.e., parallel to the cutting line 1012. The liquid is high-pressure shaped into a flat fan-shaped jet through the jet nozzles 5031 with the flat cross-section. Figure 7 The image uses densely packed fan-shaped dashed lines to represent the fan-shaped jet ejected from a nozzle 5031. The nozzle 5031, with its flat cross-section, is located directly above or to the side of the cut slit of the crystal rod, at a distance of 50mm to 100mm from the surface of the crystal rod. The angle is adjustable to ensure that gravity and jetting force work together to deliver hot water into the cut slit.

[0076] The Weber number corresponding to the jet velocity of a flat fan-shaped jet satisfies a value greater than a preset critical Weber number. The Weber number is the ratio of the liquid's inertial force to its surface tension, and its expression is: ,in For the density of the liquid, The velocity of the liquid jet. For characteristic length, The surface tension coefficient of the liquid. It can be equal to the width of the cut.

[0077] When the main control unit 502 drives the high-pressure pump to continuously increase the jet velocity of the flat fan-shaped jet, making its actual Weber number greater than the preset critical Weber number, the downward dynamic inertial force of the liquid is greater than the surface tension at the opening of the cutting kerf, thus enabling the liquid at the preset temperature to smoothly reach the cutting interface for thermal compensation.

[0078] Furthermore, to address the issue of delayed hot water delivery caused by excessively long pipelines, this application embodiment optimizes the hardware flow channel structure.

[0079] The thermal compensation unit 503 integrates a three-way control valve at the liquid output end. The main control unit 502 controls the output of ambient temperature coolant or compensating heat medium at the liquid output end through the three-way control valve. The three-way control valve includes two inlets and one outlet. The two inlets are connected to the ambient temperature coolant circuit and the high temperature compensating heat medium circuit at atmospheric pressure, respectively. To further reduce the time interval between cutting interruption and heating of the cutting interface, a high-speed three-way control valve with higher sensitivity can be selected.

[0080] In a conventional wire EDM machine 10, there is usually only one set of spray pipes. If the room temperature coolant in the pipes is drained and then filled with compensating heat medium, it takes several seconds, which causes the critical time window for deformation of the cutting interface to be missed (after which the deformation cannot be changed), such as 2.5 seconds.

[0081] This embodiment integrates a high-speed three-way control valve with a short response time directly in situ at the liquid output end. During normal cutting, the three-way control valve is connected to the normal temperature coolant; when the main control unit 502 determines that a thermal imbalance trigger event has occurred, the solenoid valve of the three-way control valve instantly switches the flow path, directly switching the medium to the compensating heat medium at the nozzle end, making the total response time from detecting the abnormality to the heat energy contacting the cutting interface extremely short.

[0082] For example, as shown in Table 1, the final experimental results are compared between the control group without thermal compensation and the experimental group with thermal compensation according to this disclosure.

[0083] Table 1 Comparison of results between the control group and the experimental group

[0084] The results show that the control group experienced a very rapid temperature drop at the moment of wire breakage, with a temperature drop rate of 15.2℃ / s. In contrast, the experimental group, through hot water injection, controlled the temperature drop rate to within 1.8℃ / s, reducing the local warpage from 12.5μm in the control group to 3.2μm in the experimental group. This, in turn, reduced the wire trace depth from a minimum of 150nm to less than 30nm, and the total thickness change from 2.8μm to 1.1μm. Ultimately, the yield at the wire breakage location was 98% in the experimental group, compared to 45% in the control group, representing a 53% improvement in yield. This is reflected in the final morphology of the silicon wafer; the control group wafers exhibited a local warpage of up to 12.5μm at the wire breakage location. Figure 8The left image shows a transverse line mark with a depth of 175 nm in the nanostructure image. The local warpage of the experimental group is only 3.2 μm, close to the level of normal cutting. Figure 8 In the middle right image, the line marks on the nanostructure map are 18 nm deep and almost invisible. Furthermore, experimental records show that the average response time from signal triggering to temperature stabilization for the experimental group is approximately 0.85 seconds, far less than the critical time window of 2.5 seconds for irreversible deformation.

[0085] This disclosure also provides a computer-readable storage medium storing at least one instruction, which is executed by a processor to implement the thermal compensation methods described in the various embodiments above.

[0086] This disclosure also provides a computer program product including computer instructions stored in a computer-readable storage medium; a processor of a computing device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computing device to perform the thermal compensation method described in the above embodiments.

[0087] Those skilled in the art will recognize that the functions described in this disclosure in one or more of the examples above can be implemented using hardware, software, firmware, or any combination thereof. When implemented in software, these functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transfer of a computer program from one place to another. Storage media can be any available medium accessible to a general-purpose or special-purpose computer.

[0088] It should be noted that the technical solutions described in this disclosure can be combined arbitrarily as long as they do not conflict.

[0089] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A thermal compensation method, characterized in that, The method includes; Characterization parameters for monitoring thermal imbalance events, wherein the thermal imbalance event refers to an event that causes the temperature drop rate at the cutting interface of the crystal rod to exceed a preset cooling rate threshold during the cutting process of the crystal rod. When a thermal imbalance event is determined based on the characterization parameters, the cutting interface is heated so that the temperature difference between the heated cutting interface and the temperature of the cutting interface before the thermal imbalance event is less than a temperature difference threshold.

2. The thermal compensation method according to claim 1, characterized in that, The characterization parameters include the temperature of the cutting interface. When a thermal imbalance event is determined to have occurred based on the characterization parameters, heating the cutting interface includes: Determine the slope of a continuous temperature value sequence composed of multiple temperature values ​​at the cutting interface; When the slope is negative and the absolute value is greater than the preset cooling rate threshold, the thermal imbalance event is determined to have occurred, and the cutting interface is heated.

3. The thermal compensation method according to claim 2, characterized in that, The characterization parameters for monitoring thermal imbalance events include: Monitor the surface radiation temperature at the opening of the cut kerf; Based on a pre-established linear temperature-depth mapping model, the temperature at the cutting interface corresponding to the surface radiation temperature and the depth of the cutting interface is determined.

4. The thermal compensation method according to claim 1, characterized in that, The characterization parameters include the tension of the cutting line. When a thermal imbalance event is determined to have occurred based on the characterization parameters, heating the cutting interface includes: When the tension is less than the tension threshold, the thermal imbalance event is determined to have occurred, and the cutting interface is heated.

5. The thermal compensation method according to claim 1, characterized in that, The method further includes: When a thermal imbalance event is detected, the supply of coolant to the cutting interface is stopped.

6. The thermal compensation method according to claim 1, characterized in that, The method further includes: Obtain the depth of the cut interface; Based on the depth and the three-dimensional geometric model of the crystal rod, the effective heat dissipation chord length corresponding to the cutting interface is determined; Based on the effective heat dissipation chord length, determine the release parameters of the compensating heat medium; Heating the cut interface includes: The compensation heat medium is delivered to the cutting interface according to the release parameters to heat the cutting interface.

7. The thermal compensation method according to claim 6, characterized in that, The compensating heat medium is a liquid heated to a preset temperature.

8. A thermal compensation device, characterized in that, Applied to wire cutting equipment, the equipment includes: a status monitoring unit, a thermal compensation unit, and a main control unit; The status monitoring unit is communicatively connected to the main control unit and is used to monitor the characterization parameters of thermal imbalance events and send the characterization parameters to the main control unit. The thermal imbalance event refers to an event that causes the temperature drop rate of the cutting interface of the crystal rod to be greater than a preset cooling rate threshold during the cutting process of the crystal rod. The main control unit is used to send a drive signal to the thermal compensation unit when a thermal imbalance event is determined based on the received characterization parameters. The thermal compensation unit is communicatively connected to the main control unit and is used to deliver a compensation heat medium to the cutting interface based on the drive signal, so that the temperature difference between the cutting interface after being heated by the compensation heat medium and the temperature of the cutting interface before the thermal imbalance event is less than a temperature difference threshold, and the temperature of the compensation heat medium is greater than or equal to the temperature of the cutting interface before the thermal imbalance event.

9. The thermal compensation device according to claim 8, characterized in that, The thermal compensation unit integrates a three-way control valve at the liquid output end; When the main control unit determines that no thermal imbalance event has occurred based on the received characterization parameters, it controls the liquid output terminal to output room temperature coolant through the three-way control valve. When a thermal imbalance event is determined to have occurred based on the received characterization parameters, the compensation heat medium is output from the liquid output terminal through the three-way control valve.

10. The thermal compensation device according to claim 8, characterized in that, The liquid output end of the thermal compensation unit includes a jet nozzle with a flat cross-section, the long axis of which is aligned parallel to the cutting slit. The thermal compensation unit is used to inject the compensation heat medium into the cutting gap in the form of a flat fan-shaped jet, and the Weber number corresponding to the jet velocity of the flat fan-shaped jet satisfies a preset critical Weber number.

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