Method and device for controlling positive and negative bow values by wafer dicing process and dicing apparatus

Abstract

The application discloses a method, device and wire cutting equipment for controlling positive and negative BOW values in a wafer wire cutting process, and the method comprises the following steps: obtaining a correlation model among temperature changes of a main roller shaft, axial displacement amounts of the main roller shaft and silicon wafer bending degrees BOW values; determining a target temperature curve of the main roller shaft and a target axial displacement amount generated by the main roller shaft in a wafer cutting process according to a desired BOW value direction and the correlation model; and controlling the temperature of the main roller shaft according to the target temperature curve in the wafer cutting process, controlling the main roller shaft to generate the target axial displacement amount due to thermal expansion through the temperature changes of the main roller shaft, and driving the wire net on the main roller shaft to generate axial displacement based on the target axial displacement amount, so that the BOW value direction of the silicon wafer formed by cutting is consistent with the desired BOW value direction. Thus, the application improves the control precision of the positive and negative directions of the BOW values of the processed silicon wafer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method, apparatus, and wire cutting equipment for controlling the positive and negative values ​​of BOW values ​​through a wafer wire cutting process. Background Technology

[0002] In semiconductor manufacturing, wafer warpage (BOW) directly affects not only the precision of photolithography but also subsequent packaging yield. For example, during photolithography, non-uniform warpage on the wafer surface leads to uneven exposure dose distribution, reducing the accuracy of pattern transfer and ultimately impacting the electrical performance of integrated circuits. Furthermore, excessive warpage can cause soldering defects and chip cracking during packaging, thereby reducing product reliability and lifespan. Therefore, effectively controlling the BOW value is crucial for improving the overall performance of semiconductor devices.

[0003] In some applications, semiconductor materials are processed using wire cutting technology. During wire cutting, the Box-of-War (BOW) value of the silicon wafer is controlled primarily by adjusting process parameters such as wire speed, tension, slurry flow rate, slurry temperature, and feed rate. However, limitations in equipment precision make it difficult to achieve symmetrical stress distribution during the cutting process, resulting in a large dispersion of the BOW value in the processed silicon wafer. It typically exhibits a positive and negative dispersion around 0µm, making it impossible to effectively control the BOW value to be entirely positive or entirely negative. Furthermore, fluctuations in process parameters such as cutting speed and coolant ratio further exacerbate the uncertainty of the BOW value. Thus, the wire cutting technology results in low precision in controlling the positive and negative directions of the BOW value of the processed silicon wafer, further affecting the consistency of the silicon wafer morphology and consequently impacting the yield of subsequent epitaxial growth, photolithography, and other processes. Summary of the Invention

[0004] This invention discloses a method, apparatus, and wire cutting equipment for controlling the positive and negative BOW values ​​of wafers through a wire cutting process, in order to solve the problem of low control accuracy of the positive and negative directions of the BOW values ​​of processed silicon wafers.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0006] In a first aspect, this application discloses a method for controlling the positive and negative BOW value through a wafer wire dicing process, applied to a wire dicing equipment. The wire dicing equipment includes a main roller and a wire mesh wound around the main roller. The wire dicing method includes: acquiring a correlation model among the temperature change of the main roller, the axial displacement of the main roller, and the BOW value of the silicon wafer; determining the target temperature curve of the main roller and the target axial displacement of the main roller during the wafer dicing process based on the desired BOW value direction and the correlation model, wherein the target temperature curve includes the target temperature of the main roller at different dicing depth nodes; controlling the temperature of the main roller according to the target temperature curve during the wafer dicing process, controlling the target axial displacement of the main roller due to thermal expansion by the temperature change of the main roller, and driving the wire mesh on the main roller to generate axial displacement based on the target axial displacement, so that the BOW value direction of the diced silicon wafer is consistent with the desired BOW value direction.

[0007] Secondly, this application discloses a device for controlling the positive and negative values ​​of BOW values ​​through a wafer wire cutting process, applied to a wire cutting equipment. The wire cutting equipment includes a main roller and a wire mesh wound around the main roller, used to execute the method mentioned in the first aspect for controlling the positive and negative values ​​of BOW values ​​through a wafer wire cutting process. The wire cutting device includes: a temperature control component disposed inside the main roller for adjusting the temperature of the main roller; a displacement detection component fixed on the frame of the wire cutting equipment and facing the end face of the main roller for detecting the axial displacement of the main roller caused by temperature changes; and a controller connected to the temperature control component and the displacement detection component respectively, the controller being used to execute the method mentioned in the first aspect.

[0008] Thirdly, this application also discloses a wire cutting device, including the device mentioned in the second aspect for controlling the positive and negative values ​​of the BOW value through the wire cutting process of the wafer.

[0009] The technical solution adopted in this invention achieves the following technical effects: By constructing a correlation model among the main roller temperature change, axial displacement, and silicon wafer BOW value, the embodiment of this invention achieves directional control of the BOW value direction. Based on the desired BOW value direction, the target temperature curve and target axial displacement of the main roller at different cutting depth nodes are determined. Then, temperature control drives the axial displacement generated by the thermal expansion of the main roller, which in turn drives the wire mesh to generate a corresponding axial displacement. This effectively counteracts the influence of asymmetric stress during cutting, ensuring that the BOW value direction of the cut silicon wafer is completely consistent with the desired direction. This improves the control accuracy of the positive and negative directions of the BOW value, ensuring that the silicon wafer BOW value remains stable within the target range of all positive or all negative values, and significantly reducing the fluctuation range of the BOW value. Furthermore, the target temperature curve clearly defines the target temperature of the main roller at different cutting depth nodes. Temperature control ensures the stability of the main roller's thermal expansion, thereby guaranteeing the accuracy of the axial displacement. The axial displacement of the main roller directly drives the wire mesh displacement, achieving precise compensation for cutting stress. This reduces the impact of fluctuations in parameters such as steel wire speed and slurry flow rate on the BOW value, ensuring that the silicon wafer BOW value remains stable within the target range. This significantly improves the consistency and stability of silicon wafer processing and reduces the scrap rate caused by BOW value fluctuations. Thus, by controlling the positive and negative directions of the BOW value, this embodiment of the invention ensures that the BOW value direction of batch-processed silicon wafers is uniform and the fluctuations are minimal, significantly improving the morphological consistency of the silicon wafers and ensuring that the surface flatness and curvature of the silicon wafers meet the requirements of subsequent processes. Simultaneously, the precise control of the main roller temperature and axial displacement reduces residual internal stress in the silicon wafers during cutting, further optimizing the mechanical properties and surface quality of the silicon wafers, effectively improving the yield of the entire semiconductor processing flow and reducing production costs. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of a wire cutting device disclosed in an embodiment of the present invention.

[0011] Figure 2 This is a flowchart illustrating a method for controlling the positive and negative values ​​of BOW values ​​through a wafer wire cutting process, as disclosed in an embodiment of the present invention.

[0012] Figure 3 This is a schematic diagram of a wafer cutting process disclosed in an embodiment of the present invention. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0014] Please refer to Figures 1 to 3 , Figure 1 This is a schematic diagram of the structure of a wire cutting device disclosed in an embodiment of the present invention. Figure 2 This is a flowchart illustrating a method for controlling the positive and negative values ​​of the BOW value through a wafer wire-cutting process, as disclosed in an embodiment of the present invention. Figure 3 This is a schematic diagram of wafer cutting provided in an embodiment of the present invention.

[0015] like Figure 1 As shown, Figure 1 The wire cutting equipment comprises a semiconductor processing chamber and a clamping and feeding device 11. The semiconductor processing chamber mainly consists of a main roller 101 and steel wires 102 wound around the main roller at a certain tension and spacing. The clamping and feeding device 11 is used to clamp the wafer 12. During processing, the clamping and feeding device 11 clamps the wafer 12 and feeds it to the steel wire. The steel wire runs at high speed carrying slurry. The clamping and feeding device 11 descends to transport the wafer to the steel wire 102. As the wafer 12 descends, it is cut by the steel wire, thereby obtaining multiple silicon wafers. Existing methods for controlling the BOW value of silicon wafers mainly involve changing the steel wire speed, tension, slurry flow rate, slurry temperature, and feed speed. However, the BOW value of the processed silicon wafers is generally widely distributed, with the BOW value around 0µm, making it impossible to effectively control the BOW value to be all positive or all negative.

[0016] like Figure 2 As shown in the embodiment of the present invention, a method for controlling the positive and negative values ​​of BOW values ​​through a wafer wire-cutting process includes the following steps:

[0017] Step S201: Obtain the correlation model between the temperature change of the main roller shaft, the axial displacement of the main roller shaft, and the BOW value of the silicon wafer bending.

[0018] Specifically, the embodiments of the present invention are as follows: Figure 1In the semiconductor processing chamber shown, the main roller shaft has an independent water pipe system and a temperature control component, which includes temperature sensors (such as thermocouples or thermistors), heaters, coolant flow regulating valves, and a PID controller. Temperature sensors are installed at the center of the main roller shaft to collect temperature data from different parts of the shaft in real time. Simultaneously, displacement sensors (such as laser displacement gauges or eddy current displacement sensors) are installed at the ends of the main roller shaft to monitor the axial displacement caused by thermal expansion or contraction during the cutting process. Displacement data and temperature data are collected synchronously at a sampling frequency of no less than 10 Hz. Furthermore, after the wire-cutting process, the BOW value of each silicon wafer is obtained using a laser warpage measuring instrument (e.g., using a non-contact optical interferometry principle), and the corresponding cutting depth percentage (0%, 30%, 70%, 100%) and the wafer's position in the ingot (e.g., MC side or OP side) are recorded.

[0019] Furthermore, the embodiments of the present invention employ a multi-factor, multi-level experimental design. As an optional embodiment of the present invention, obtaining the correlation model among the temperature change of the main roller shaft, the axial displacement of the main roller shaft, and the BOW value of the silicon wafer bending includes: performing a DOE experiment, changing the temperature of the main roller shaft, measuring the axial displacement of the main roller shaft at the corresponding temperature and the BOW value of the cut silicon wafer; and establishing a correlation model based on the temperature change of the main roller shaft, the axial displacement of the main roller shaft at the corresponding temperature, and the BOW value of the cut silicon wafer.

[0020] Specifically, embodiments of the present invention set multiple curve patterns for the temperature variation of the main roller shaft along the cutting depth, including but not limited to:

[0021] Mode A: The temperature first decreases and then increases with the cutting depth (e.g., 23℃ → 22.5℃ → 22.5℃ → 22.8℃).

[0022] Mode B: The temperature first increases and then decreases with the cutting depth (e.g., 23℃ → 24.5℃ → 24.5℃ → 23℃).

[0023] Mode C: Constant temperature (e.g., 23℃ → 23℃ → 23℃ → 23℃), serving as a control group.

[0024] Furthermore, for each temperature mode, the following data was recorded:

[0025] Temperature values ​​at both ends and the center of the main roller shaft corresponding to each cutting depth node (0%, 30%, 70%, 100%).

[0026] Axial displacement of the main roller shaft corresponding to each node (unit: μm).

[0027] The BOW value (unit: μm) of each silicon wafer in the corresponding cutting batch was calculated, and its mean, standard deviation and positive and negative distribution ratio were statistically analyzed.

[0028] Furthermore, using the experimental data above, multiple regression analysis or neural network fitting methods were employed, and the correlation model was represented by linear regression or quadratic regression models:

[0029]

[0030] In the above formula, This indicates the temperature of the core of the main roller shaft. This indicates the percentage of the wafer's cutting depth. This refers to the axial displacement of the main roller shaft. , , as well as These represent the coefficients obtained by fitting experimental data.

[0031] Furthermore, in this embodiment of the invention, several sets of experimental data that were not involved in the modeling are input into the above-mentioned correlation model. The BOW value predicted by the correlation model is compared with the actual measured BOW value. If the root mean square error of the prediction is greater than the threshold, the above-mentioned correlation model is corrected by introducing a nonlinear term or adding an interaction term.

[0032] Finally, the validated correlation model is embedded into the control system of the wire cutting equipment, serving as the basis for real-time adjustment of the main roller temperature setpoint and prediction of the direction and magnitude of the BOW value. Based on the current cutting depth and the desired BOW direction (positive or negative), the control system reverse-engineers the required main roller temperature change curve and dynamically adjusts the heating and cooling power through a PID controller, achieving unidirectional closed-loop control of the BOW value.

[0033] Step S202: Based on the desired BOW value direction and the correlation model, determine the target temperature curve of the main roller and the target axial displacement generated by the main roller during the wafer dicing process.

[0034] The target temperature profile includes the target temperature of the main roller at different cutting depth nodes.

[0035] Specifically, after obtaining the correlation model between the temperature change of the main roller shaft, the axial displacement, and the BOW value of the silicon wafer, the present invention uses the correlation model to calculate the target temperature curve that the main roller shaft should follow during the cutting process, as well as the target axial displacement of the main roller shaft corresponding to the target temperature curve, based on the actual process requirements for the bending direction of the silicon wafer (e.g., requiring all silicon wafers to have all negative or all positive BOW values).

[0036] Furthermore, in this embodiment of the invention, if the desired BOW value direction is negative (BOW value is negative), for example, the desired BOW value is set to -0.5µm; if the desired BOW value direction is positive (BOW value is positive), for example, the desired BOW value is set to +0.5µm. Simultaneously, a set of cutting depth nodes is defined. In a specific embodiment of the invention, the cutting depth nodes are set as four key points: 0% (cutting start point), 30%, 70%, and 100% (cutting end point). These nodes correspond to the moments when the main roller temperature needs to be independently controlled.

[0037] Furthermore, through the correlation model in step S101, due to the axial displacement... It is itself a function of the main roller shaft temperature (caused by thermal expansion), and a sub-model can be further established:

[0038]

[0039] In the above formula, This indicates the amount of axial displacement. This represents the coefficient of thermal expansion. This indicates the effective length of the main roller shaft. It can be set as a reference temperature, which can be set according to actual conditions, such as 23 degrees Celsius. This indicates the temperature of the core of the main roller shaft.

[0040] Furthermore, by substituting the aforementioned sub-models into the association model, we obtain only... And a prediction model with D as the independent variable.

[0041] Furthermore, in this embodiment of the invention, a desired BOW value is input for different cutting depths. To prevent excessive thermal stress or temperature runaway on the main roller, a temperature constraint range is set. For example... Greater than or equal to 22 degrees Celsius and less than or equal to 25 degrees Celsius.

[0042] Furthermore, at different cutting depths, D and the desired BOW value are input into the above prediction model to obtain the results containing... The equation. Solving for each cutting depth. Target temperature value .

[0043] Furthermore, the target temperature values ​​at each cutting depth are connected sequentially according to the cutting depth, and linear interpolation or cubic spline interpolation is used between adjacent cutting depths to form a continuous target temperature curve. .

[0044] Furthermore, the cutting depths of the aforementioned target temperature curve are... Target temperature value Substituting the above thermal expansion sub-model, the target axial displacement corresponding to each cutting depth can be calculated using the following formula:

[0045]

[0046] In the above formula, This represents the target axial displacement corresponding to the cutting depth. This indicates the coefficient of thermal expansion determined by the material used for the main roller shaft, such as... The value is 11.7 × 10−6 / ℃ (steel). The effective length of the main roller shaft. The reference temperature is 23 degrees Celsius.

[0047] Furthermore, during the actual cutting process, the control system collects the actual temperature and axial displacement of the main roller in real time and compares them with the target temperature curve and target displacement. If the deviation exceeds the preset threshold (e.g., temperature deviation > 0.1℃ or displacement deviation > 0.5 μm), the heating power and coolant flow rate are dynamically adjusted by the PID controller to make the actual temperature curve approach the target temperature curve, thereby ensuring that the BOW value always develops in the desired direction.

[0048] Furthermore, in this embodiment of the invention, a desired BOW value direction is set according to product requirements. As an optional embodiment of the invention, determining the target temperature curve and target axial displacement of the main roller during wafer dicing based on the desired BOW value direction and the correlation model includes: when the desired BOW value direction is negative, determining the target axial displacement of the main roller in a first direction, and determining the target temperature curve as a curve that first decreases and then increases with the wafer dicing depth; when the desired BOW value direction is positive, determining the target axial displacement of the main roller in a second direction, and determining the target temperature curve as a curve that first increases and then decreases with the dicing depth, the second direction being opposite to the first direction.

[0049] Specifically, in this embodiment of the invention, the main roller shaft is controlled to generate a target axial displacement that expands in a first direction. The first direction is defined as the direction towards the ingot feed direction (i.e., towards the front of the cutting wire mesh, or "positive direction"). As the cutting depth increases, the main roller shaft first expands positively, then gradually contracts in the middle and later sections, and finally returns to a position close to the initial position at the cutting endpoint. In one specific embodiment, through inverse solving using an associative model, it is found that: at the 0% cutting depth node, the positive expansion displacement of the main roller shaft is +4.5 μm to +5.0 μm; at the 30% to 70% nodes, the displacement gradually decreases and turns negative (contraction), approximately -1.5 μm to -2.0 μm; at the 100% node, the displacement recovers to +2.5 μm to +3.0 μm. The overall displacement curve exhibits a fluctuating pattern of "first positive expansion, then contraction, and then a small positive expansion," the net effect of which is to subject the silicon wafer to stress bending in the first direction during the cutting process, resulting in a negative BOW value.

[0050] Furthermore, in this embodiment of the invention, the target temperature curve is determined to be a curve that first decreases and then increases with the wafer dicing depth. That is, a higher main roller temperature is set at the beginning of the dicing stage, the temperature is gradually reduced as the dicing depth increases, a lower temperature is maintained in the middle and later stages of dicing, and the temperature is moderately increased again near the end of the dicing.

[0051] Furthermore, when it is desired that all silicon wafers have positive BOW values ​​(i.e., the silicon wafers warp to the opposite side, BOW > 0 μm), the target parameters determined by this method are opposite to those in the negative case. In this embodiment of the invention, the main roller shaft is controlled to generate a target axial displacement that expands in a second direction. The second direction is opposite to the first direction, i.e., away from the ingot feed direction (towards the rear of the cutting wire mesh, or "reverse"). As the cutting depth increases, the main roller shaft first undergoes reverse expansion, then gradually contracts in the middle and later sections, and finally recovers at the cutting endpoint. In a specific embodiment, the following is obtained through the correlation model: at the 0% cutting depth node, the reverse expansion displacement of the main roller shaft is -4.0 μm to -4.5 μm (if the first direction is positive, then the second direction is negative); at the 30% to 70% nodes, the displacement gradually decreases and turns into positive contraction (approximately +1.5 μm to +2.0 μm); at the 100% node, the displacement recovers to -2.0 μm to -2.5 μm. This displacement curve subjects the silicon wafer to stress that bends in the second direction, resulting in a positive BOW value.

[0052] Furthermore, in this embodiment of the invention, the target temperature curve is determined to be a curve that first rises and then falls with the cutting depth. That is, a lower main roller temperature is set at the beginning of the cutting stage, the temperature is gradually increased as the cutting depth increases, a higher temperature is maintained in the middle and later stages of the cutting, and the temperature is appropriately reduced when approaching the end of the cutting.

[0053] It is worth noting that in this invention, the "first direction" and the "second direction" are two spatially opposite axial directions. In one specific embodiment, such as... Figure 3 As shown, the main roller 101 is installed horizontally, with a first direction toward the wafer 12 feed side (i.e., the direction from the MC side to the OP side) and a second direction away from the wafer 12 feed side (i.e., the direction from the OP side to the MC side). When the main roller 101 expands in the first direction due to temperature control, the steel wire 102 undergoes a slight displacement in that direction, resulting in a negative BOW (Bottom-of-War) silicon wafer; when it expands in the second direction, the silicon wafer exhibits a positive BOW.

[0054] Thus, the above embodiments of the present invention achieve precise and reliable control of the positive and negative unidirectional BOW value, significantly improving the consistency of silicon wafer morphology in the wire cutting process.

[0055] Furthermore, as an optional embodiment of the present invention, the cutting depth nodes include a cutting start point, a cutting depth 30% point, a cutting depth 70% point, and a cutting end point; the curve of the wafer cutting depth first decreasing and then increasing includes: the temperature of the main roller at the cutting start point is a first temperature, it decreases to a second temperature at the cutting depth 30% point, it remains at the second temperature at the cutting depth 70% point, and it rises to a third temperature at the cutting end point; wherein, the first temperature is greater than the second temperature, the third temperature is greater than the second temperature and the third temperature is lower than the first temperature.

[0056] Specifically, the first temperature is 23.5℃, the second temperature is 22.8℃, and the third temperature is 23.3℃; or the first temperature is 23℃, the second temperature is 22.5℃, and the third temperature is 22.8℃.

[0057] Furthermore, in one embodiment of the present invention, the cutting start point (0%) is: the main roller temperature is 23.5°C.

[0058] At 30% cutting depth: the main roller temperature drops to 22.8℃. At 70% cutting depth: the main roller temperature remains at 22.8℃. At the cutting endpoint (100%): the main roller temperature rises to 23.3℃. Under the above temperature control, the wafers are wire-cut. After processing, the BOW value of all silicon wafers is measured using a laser warpage meter. Statistical results show that the mean BOW value is -2.39 μm, and the BOW values ​​of all silicon wafers are distributed below 0 μm (i.e., all negative), with a standard deviation of 0.41 μm, indicating excellent unidirectional negative control.

[0059] Furthermore, in another optional embodiment, the cutting start point (0%): the main roller temperature is 23.0°C. At 30% cutting depth: the main roller temperature drops to 22.5°C. At 70% cutting depth: the main roller temperature remains at 22.5°C. At the cutting end point (100%): the main roller temperature rises to 22.8°C. After wire cutting under these conditions, the following was observed: the average BOW value is -1.82 μm, and the BOW values ​​of all silicon wafers are also distributed below 0 μm, with a standard deviation of 0.35 μm, indicating good unidirectional negative control.

[0060] It is worth noting that the specific values ​​of the first, second, and third temperatures mentioned above are not the only limitations. Under the condition that "first temperature > second temperature, third temperature > second temperature, third temperature < first temperature", appropriate adjustments can be made based on actual equipment thermal response characteristics, ingot size, wire tension, and other process parameters. Typically, the first temperature ranges from 23.0℃ to 24.0℃, the second temperature from 22.0℃ to 23.0℃, and the third temperature from 22.5℃ to 23.5℃, with the difference between the first and second temperatures not less than 0.5℃ and the difference between the third and second temperatures not less than 0.3℃. As long as the overall trend of the temperature curve conforms to a pattern of first decreasing and then increasing, and a low-temperature plateau region exists in the middle and later stages, unidirectional negative control of the silicon wafer BOW value can be achieved.

[0061] Furthermore, as an optional embodiment of the present invention, the cutting depth nodes include a cutting start point, a cutting depth 30% point, a cutting depth 70% point, and a cutting end point. The curve that rises and then falls with the cutting depth includes: the temperature of the main roller at the cutting start point is the fourth temperature, it rises to the fifth temperature at the cutting depth 30% point, it remains at the fifth temperature at the cutting depth 70% point, and it falls to the sixth temperature at the cutting end point; wherein, the fifth temperature is greater than the fourth temperature, the sixth temperature is lower than the fifth temperature and equal to the fourth temperature.

[0062] Specifically, in one embodiment of the present invention, the cutting start point (0%) is: the main roller temperature is 23.0°C.

[0063] At 30% cutting depth: the main roller temperature rises to 24.5℃. At 70% cutting depth: the main roller temperature remains at 24.5℃. At the cutting endpoint (100%): the main roller temperature drops to 23.0℃. Under the above temperature control, the wafers are wire-cut. After processing, the BOW value of all silicon wafers is measured using a laser warpage meter. Statistical results show that the mean BOW value is +1.17 μm, and the BOW value of all silicon wafers is positive (i.e., all greater than 0 μm), with a standard deviation of 0.52 μm, indicating excellent unidirectional positive control.

[0064] It is worth noting that the specific values ​​of the fourth, fifth, and sixth temperatures mentioned above are not the only limitations. Under the condition that "fifth temperature > fourth temperature, sixth temperature = fourth temperature < fifth temperature", appropriate adjustments can be made based on factors such as the actual thermal response characteristics of the equipment, ingot size, and the desired absolute value of the BOW (Boiler Wave). Typically, the fourth temperature (i.e., the initial temperature) ranges from 22.5℃ to 23.5℃, the fifth temperature (i.e., the mid-high temperature range) ranges from 24.0℃ to 25.0℃, and the sixth temperature (i.e., the final temperature) is equal to or substantially equal to the fourth temperature (with an allowable deviation of ±0.1℃). As long as the overall trend of the temperature curve conforms to an initial rise followed by a fall, and a high-temperature plateau exists in the mid-to-late stages, unidirectional positive control of the silicon wafer's BOW value can be achieved.

[0065] Step S203: During the wafer dicing process, the temperature of the main roller is controlled according to the target temperature curve. The temperature change of the main roller controls the target axial displacement of the main roller due to thermal expansion. Based on the target axial displacement, the wire mesh on the main roller is driven to generate axial displacement so that the BOW value direction of the diced silicon wafer is consistent with the desired BOW value direction.

[0066] Specifically, in this embodiment of the invention, the temperature of the main roller shaft is detected by a thermocouple or platinum resistance temperature sensor at the shaft center. The temperature of the main roller shaft is regulated by an electric heater and a coolant flow proportional regulating valve installed in the water pipes inside the main roller shaft. The actual axial displacement of the main roller shaft is monitored in real time by a laser displacement sensor or eddy current displacement sensor installed at the end of the main roller shaft. A programmable logic controller (PLC) or industrial computer with a built-in PID control algorithm communicates with the main control system of the wire cutting equipment.

[0067] Furthermore, after the wire cutting process begins, taking a negative BOW value as an example, temperature control is performed according to the following steps: Before the cutting start point (0% depth), the control unit adjusts the heater and coolant flow rate through a PID algorithm to stabilize the main roller temperature at the initial value of the target temperature curve (e.g., 23.5℃ for a negative BOW), with a stabilization time of no less than 30 seconds to ensure a uniform temperature field on the main roller. As the cutting depth increases (provided in real-time feedback by the position encoder of the feed system), the control unit reads the corresponding target temperature value from the target temperature curve based on the current cutting depth percentage. The PID controller compares the deviation between the measured temperature and the target temperature value and outputs a control signal to adjust the heating power or coolant flow rate.

[0068] When the measured temperature is lower than the target temperature, increase the heating power or decrease the cooling flow rate. When the measured temperature is higher than the target temperature, decrease the heating power or increase the cooling flow rate.

[0069] Furthermore, near the 30% cutting depth point, the temperature needs to decrease from the initial value to the second temperature (e.g., 22.8℃), with the control unit setting the cooling rate to no more than 0.5℃ / min to avoid excessive thermal stress. In the holding section (30%~70% depth), temperature fluctuations are controlled within ±0.1℃. Before the end point, the temperature is increased to the third temperature (e.g., 23.3℃) at a set rate. Simultaneously with temperature control, the displacement sensor collects the actual axial displacement of the main roller in real time, comparing it with the target axial displacement calculated based on the thermal expansion model. If the deviation exceeds 0.5 μm, the system issues a warning signal, prompting the operator to check the temperature sensor or heater status and make fine adjustments if necessary.

[0070] Furthermore, the main roller is typically made of steel or other metallic materials with a definite coefficient of thermal expansion. When the temperature of the main roller rises, the shaft expands and elongates axially; when the temperature decreases, the shaft contracts and shortens. Because the steel wire is tightly wound into the groove of the main roller with a certain tension, the axial displacement of the main roller will cause the wire mesh to produce an almost perfectly uniform axial displacement through friction.

[0071] Furthermore, specifically, taking the desired negative BOW as an example: at the beginning of the cutting process, the main roller temperature is 23.5℃, and the roller is in a relatively expanded state, generating a positive (first direction) axial displacement of approximately +4.7 μm, causing the wire mesh to move slightly in the ingot feeding direction. As the cutting depth increases, the temperature drops to 22.8℃, the roller contracts, and the axial displacement changes from positive to negative (contraction), causing the wire mesh to move slightly in the opposite direction. Before the cutting endpoint, the temperature rises back to 23.3℃, ​​the roller expands positively again, and the wire mesh moves positively again. This dynamic wire mesh displacement changes the relative position of the steel wire and the ingot and the cutting stress distribution, causing controllable bending stress to form on the silicon wafer in the thickness direction, ultimately resulting in a full negative BOW value. Conversely, when a positive BOW is desired, the temperature first rises and then falls, and the wire mesh displacement direction is reversed, resulting in a full positive BOW value.

[0072] For example, in the wire cutting of a batch of 12-inch silicon ingots, a target temperature curve with a desired negative BOW (23.5℃→22.8℃→22.8℃→23.3℃) was adopted, and real-time temperature control was performed according to the method described above. After processing, 10 silicon wafers each from the head, middle, and tail sections were randomly selected for BOW testing. The results showed that the BOW values ​​of all 30 silicon wafers were negative, with a mean of -2.31 μm and a standard deviation of 0.38 μm, completely consistent with the target direction. Simultaneously, the actual axial displacement curve recorded by the displacement sensor matched the theoretically calculated curve well, with a maximum deviation of no more than 0.3 μm, verifying the effectiveness of the temperature control.

[0073] Based on the same inventive concept as the above-described method for controlling the positive and negative BOW value through the wire dicing process of a wafer, this embodiment of the invention also provides a device for controlling the positive and negative BOW value through the wire dicing process of a wafer, applied to a wire dicing equipment. The wire dicing equipment includes a main roller and a wire mesh wound around the main roller, used to execute the method for controlling the positive and negative BOW value through the wire dicing process of a wafer mentioned in the above embodiments. The wire dicing device includes: a temperature control component disposed inside the main roller for adjusting the temperature of the main roller; a displacement detection component fixed on the frame of the wire dicing equipment and facing the end face of the main roller for detecting the axial displacement of the main roller caused by temperature changes; and a controller connected to the temperature control component and the displacement detection component respectively, the controller being used to execute the method for controlling the positive and negative BOW value through the wire dicing process of a wafer mentioned in the above embodiments.

[0074] Specifically, the wire cutting equipment has a closed or semi-closed semiconductor processing chamber, within which at least a pair of parallel main rollers are installed. Steel wire is wound onto the grooves of the main rollers according to a set tension and spacing, forming a wire mesh. The ingot is mounted above the wire mesh via a clamping and feeding device, and can be vertically fed to achieve cutting. The wire cutting device of this invention improves upon the existing equipment described above, with a temperature control component located inside the main rollers for regulating their temperature. The main rollers have at least one internal water passage along their axial direction, which is connected to an external coolant circulation system.

[0075] Furthermore, as an optional embodiment of the present invention, the temperature control component includes: a water pipe, a water temperature control unit, and a temperature sensor; the water pipe is located inside the center of the main roller shaft, and has an inlet on the MC side of the main roller shaft and an outlet on the OP side; the water temperature control unit is located inside the water pipe and is used to control the temperature of the medium flowing into the water pipe; the controller controls the power of the water temperature control unit to adjust the temperature of the medium in the water pipe by controlling the monitored temperature in the water pipe detected by the temperature sensor.

[0076] Specifically, the main roller shaft has at least one internal water passage along its axial direction. This water passage is connected to an external coolant circulation system. The water passage has an inlet on the MC side (i.e., the ingot feed side) and an outlet on the OP side (i.e., the opposite side). Cooling medium (e.g., deionized water or coolant) flows in through the inlet, passes through the entire interior of the main roller shaft, and exits through the outlet, thus regulating the temperature of the main roller shaft. The water temperature control unit can use an electric heating rod or heating sleeve and a cooling flow regulating valve. The electric heating rod is installed around the internal water passage of the main roller shaft or embedded in the shaft material to actively heat the main roller shaft. It directly contacts the flowing medium and controls the temperature of the medium flowing into the water passage. The cooling flow regulating valve, located on the coolant inlet pipe, is a proportional regulating valve or an electric ball valve, used to control the flow rate of coolant passing through the interior of the main roller shaft. At least three temperature sensors are installed on the surface of the main roller shaft at the left end, the shaft center, and the right end, or embedded inside the shaft shaft, respectively, to collect the temperature of different parts of the main roller shaft in real time. The temperature sensors are preferably PT100 platinum resistance thermometers or K-type thermocouples, with an accuracy of not less than ±0.1℃.

[0077] Furthermore, the heating element, cooling flow regulating valve, and temperature sensor are all electrically connected to the controller. The temperature sensor transmits the detected temperature signal to the controller, which sends control commands to the heating element and cooling flow regulating valve according to a preset target temperature curve. A PID algorithm is used to dynamically adjust the output power of the water temperature control unit. When the monitored temperature is lower than the target temperature, the controller increases the heating power; conversely, it decreases the power, thereby precisely regulating the temperature of the medium in the water pipes and controlling the thermal expansion behavior of the main roller shaft. Through this structure, rapid, closed-loop control of the main roller shaft temperature is achieved.

[0078] Furthermore, the displacement detection component is fixed to the frame of the wire cutting equipment, facing the end face of the main roller, and is used to detect the axial displacement of the main roller caused by temperature changes. The displacement detection component uses a non-contact laser displacement sensor, with its emitter vertically aligned with the center point of one end face of the main roller. The sensor is fixed to the stationary frame of the wire cutting equipment by a bracket, with an initial distance of 10 mm between it and the end face of the main roller, a measurement range of ±5 mm, and a resolution better than 0.1 μm. To ensure measurement reliability, a displacement detection component can be installed at each end of the main roller to monitor the difference in displacement between the two ends. The displacement detection component is electrically connected to the controller, sending the real-time acquired axial displacement signal to the controller for closed-loop verification and early warning.

[0079] Furthermore, the controller is electrically connected to the temperature control components (including heating elements, cooling flow regulating valves, and temperature sensors) and the displacement detection components. The controller can be a stand-alone programmable logic controller or an industrial control computer, or it can be integrated into the main control system of the in-line cutting equipment.

[0080] Furthermore, the operator inputs the desired BOW (Browser Overhead) value direction (all negative or all positive) through the human-machine interface. The controller retrieves the corresponding target temperature curve from the storage module based on this direction. Before cutting begins, the controller controls the heating element and cooling flow regulating valve to ensure the main roller temperature reaches the initial temperature of the target temperature curve (e.g., 23.5℃ for negative BOW) and maintains it for at least 30 seconds to ensure a uniform temperature field. The displacement detection component records the initial axial displacement at this time as the zero point. After cutting begins, the controller calculates the required target temperature in real-time from the target temperature curve based on the current cutting depth percentage fed back by the feed system. The controller reads the actual temperature measured by the temperature sensor and outputs a control signal through PID calculation: if the measured temperature is lower than the target temperature, the heating element power is increased or the cooling flow is decreased; if the measured temperature is higher than the target temperature, the heating power is decreased or the cooling flow is increased. The control cycle is 0.5 seconds, and the temperature control accuracy reaches ±0.1℃.

[0081] Furthermore, changes in the temperature of the main roller cause it to expand or contract thermally, resulting in a corresponding axial displacement of the wire mesh wound around it. This displacement alters the relative position of the steel wire and the ingot, as well as the distribution of cutting stress, ultimately aligning the BOW (Browser Overhead) direction of the cut silicon wafer with the desired direction. After cutting, the controller slowly restores the temperature of the main roller to room temperature (cooling rate not exceeding 0.3℃ / min) to avoid thermal shock.

[0082] For example, the aforementioned wire cutting device was used to cut a batch of 12-inch silicon ingots, with the desired BOW direction set to all negative. The controller executed the target temperature curves: 0% depth 23.5℃, 30% depth 22.8℃, 70% depth 22.8℃, and 100% depth 23.3℃. During the cutting process, the maximum deviation between the actual temperature measured by the temperature sensor and the target temperature was 0.08℃, and the actual axial displacement curve recorded by the displacement detection component closely matched the theoretical curve (maximum deviation 0.2 μm). After cutting, the BOW values ​​of all silicon wafers were measured, and all results were negative, with a mean of -2.35 μm and a standard deviation of 0.40 μm, verifying the effectiveness of the device.

[0083] Furthermore, as an optional embodiment of the present invention, the displacement detection component includes a laser displacement sensor or a grating ruler, which is fixedly mounted on the frame of the wire cutting equipment and faces the end face of the main roller shaft, for monitoring and feeding back the axial displacement of the main roller shaft to the controller.

[0084] Based on the same inventive concept as the above-described method for controlling the positive and negative values ​​of BOW through the wire dicing process of wafers, this embodiment of the invention also provides a wire dicing apparatus, including a wire dicing apparatus body and the device mentioned in the above embodiments for controlling the positive and negative values ​​of BOW through the wire dicing process of wafers.

[0085] The above embodiments of the present invention focus on describing the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be described in detail here.

[0086] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A method for controlling the positive and negative values ​​of BOW (Browser Overhead) values ​​through a wafer wire-cutting process, characterized in that, Applied to a wire cutting equipment, the wire cutting equipment including a main roller and a wire mesh wound on the main roller, the wire cutting method including: Obtain a correlation model among the temperature change of the main roller shaft, the axial displacement of the main roller shaft, and the BOW value of the silicon wafer curvature; Based on the desired BOW value direction and the correlation model, the target temperature curve of the main roller and the target axial displacement generated by the main roller during the wafer dicing process are determined. The target temperature curve includes the target temperature of the main roller at different dicing depth nodes. During the wafer dicing process, the temperature of the main roller is controlled according to the target temperature curve. The temperature change of the main roller controls the target axial displacement caused by thermal expansion of the main roller. Based on the target axial displacement, the wire mesh on the main roller is driven to generate axial displacement so that the BOW value direction of the diced silicon wafer is consistent with the desired BOW value direction.

2. The method for controlling the positive and negative values ​​of the BOW value through the wire dicing process of a wafer according to claim 1, characterized in that, The determination of the target temperature curve of the main roller and the target axial displacement generated by the main roller during the wafer dicing process, based on the desired BOW value direction and the correlation model, includes: When the desired BOW value is negative, the target axial displacement of the main roller shaft expanding in the first direction is determined, and the target temperature curve is determined to be a curve that first decreases and then increases with the cutting depth of the wafer. When the desired BOW value direction is positive, the target axial displacement of the main roller shaft expanding in the second direction is determined, and the target temperature curve is determined to be a curve that first rises and then falls with the cutting depth, with the second direction being opposite to the first direction.

3. The method for controlling the positive and negative values ​​of the BOW value through the wire dicing process of a wafer according to claim 2, characterized in that, The cutting depth nodes include the cutting start point, the 30% cutting depth point, the 70% cutting depth point, and the cutting end point; The curve that decreases and then increases with the cutting depth of the wafer includes: the temperature of the main roller at the starting point of the cutting is a first temperature, it decreases to a second temperature at 30% of the cutting depth, it maintains the second temperature at 70% of the cutting depth, and it increases to a third temperature at the end point of the cutting. Wherein, the first temperature is greater than the second temperature, and the third temperature is greater than the second temperature and lower than the first temperature.

4. The method for controlling the positive and negative values ​​of the BOW value through the wire cutting process of a wafer according to claim 3, characterized in that, The first temperature is 23.5℃, the second temperature is 22.8℃, and the third temperature is 23.3℃; or, the first temperature is 23℃, the second temperature is 22.5℃, and the third temperature is 22.8℃.

5. The method for controlling the positive and negative BOW value through the wire dicing process of a wafer according to claim 2, characterized in that, The cutting depth nodes include the cutting start point, the 30% cutting depth point, the 70% cutting depth point, and the cutting end point. The curve that rises and then falls with the cutting depth includes: the temperature of the main roller at the cutting start point is the fourth temperature, it rises to the fifth temperature at the 30% cutting depth point, it maintains the fifth temperature at the 70% cutting depth point, and it falls to the sixth temperature at the cutting end point. Wherein, the fifth temperature is greater than the fourth temperature, the sixth temperature is lower than the fifth temperature and equal to the fourth temperature.

6. The method for controlling the positive and negative BOW value through the wire dicing process of a wafer according to claim 1, characterized in that, The correlation model for obtaining the temperature change of the main roller, the axial displacement of the main roller, and the BOW value of the silicon wafer includes: Perform a DOE experiment, change the temperature of the main roller, and measure the axial displacement of the main roller at the corresponding temperature and the BOW value of the cut silicon wafer; The correlation model is established based on the temperature change of the main roller, the axial displacement of the main roller at the corresponding temperature, and the BOW value of the cut silicon wafer.

7. A device for controlling the positive or negative BOW value through a wafer wire-cutting process, characterized in that, An apparatus for use in wire cutting equipment, the wire cutting equipment comprising a main roller and a wire mesh wound around the main roller, for performing the method for controlling the positive or negative BOW value through a wafer wire cutting process as described in any one of claims 1-6, the wire cutting apparatus comprising: A temperature control component, located inside the main roller shaft, is used to regulate the temperature of the main roller shaft; The displacement detection component is fixed on the frame of the wire cutting equipment and faces the end face of the main roller shaft, and is used to detect the axial displacement of the main roller shaft caused by temperature changes. A controller is connected to the temperature control component and the displacement detection component respectively, and the controller is used to execute the method according to any one of claims 1 to 6.

8. The apparatus for controlling the positive and negative values ​​of the BOW value through a wafer wire-cutting process according to claim 7, characterized in that, The temperature control components include: water pipes, a water temperature control unit, and a temperature sensor; The water pipe is located inside the center of the main roller shaft, and the water pipe has an inlet located on the MC side of the main roller shaft and an outlet located on the OP side. The water temperature control unit is located inside the water pipe and is used to control the temperature of the medium flowing into the water pipe; The controller adjusts the temperature of the medium in the water pipe by controlling the power of the water temperature control unit based on the monitored temperature in the water pipe detected by the temperature sensor.

9. The apparatus for controlling the positive and negative values ​​of the BOW value through a wafer wire-cutting process according to claim 7, characterized in that, The displacement detection component includes a laser displacement sensor or a grating ruler, which is fixedly mounted on the frame of the wire cutting equipment and faces the end face of the main roller shaft. It is used to monitor and feed back the axial displacement of the main roller shaft to the controller.

10. A wire cutting device, characterized in that, Includes the apparatus for controlling the positive or negative value of the BOW value through the wire dicing process of the wafer as described in any one of claims 7 to 9.

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