Wafer levelness control method and wafer supporting device

Abstract

The invention provides a wafer levelness control method and a wafer supporting device.The wafer levelness control method comprises the steps that in the technological process, upward supporting force which is not in mechanical contact is applied to the supported face of a wafer, and the magnitude of the supporting force is regulated in real time according to the levelness of the wafer; the wafer supporting device comprises a wafer suction cup and a force applying assembly, the wafer suction cup is used for placing the sheet wafer and driving the sheet wafer to rotate, and the force applying assembly applies upward non-mechanical contact supporting force to the edge of the sheet wafer from the lower portion of the sheet wafer. The sheet wafer can be kept in a horizontal state in the gluing or developing process, the problems that edge gluing fails or developing liquid coverage is incomplete and the like are solved, the structure is simple, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor equipment technology, specifically relating to a method for controlling the levelness of a wafer and a wafer support device. Background Technology

[0002] RC-IGBT (Reverse Conducting Insulated Gate Bipolar Transistor) is a reverse-conducting insulated-gate transistor that combines the functions of an IGBT and a freewheeling diode. Traditionally, IGBTs and diodes are discrete components, resulting in bulky modules, high parasitic inductance, and increased packaging costs. RC-IGBT structures typically integrate the diode and IGBT onto the same chip, effectively improving functional density and switching efficiency. Currently, in RC-IGBT manufacturing, the industry practice is to thin the wafer to 80-150µm on the back side after the normal IGBT process. To prevent wafer fragmentation and facilitate transport during processing, a 2-3mm Taiko ring is usually added to the edge region to increase stress, resulting in a structure like... Figure 1 As shown, the thickness of the Taiko ring is 750 μm, and the thickness n of the middle part of the wafer is 80~150 μm. Then, ion implantation of the P / N junction on the back side is achieved through photolithography, ultimately realizing the conduction between the front and back sides.

[0003] Currently, the mainstream coating and developing machines in the semiconductor equipment market process 8-inch and 12-inch wafers with normal thickness (750um~800um). Coating and developing equipment for RC-IGBT processes are all modified machines. The modifications mainly involve the size of the rotary chuck and the vacuum adhesion between the chuck and the wafer during spin coating. Figure 2 , Figure 3 As shown, due to the presence of the Taiko ring and the extremely thin physical characteristics of the wafer during the coating and developing processes, the wafer edge is consistently positioned lower than the wafer center at low speeds. This makes it easy for the photoresist in the edge areas to be insufficiently covered during coating or developing, resulting in poor uniformity and incomplete developer coverage. Forcing the wafer to rotate at high speed before applying photoresist or developer can easily break the vacuum, leading to wafer breakage. Therefore, improving the uniformity of photoresist coating on thin wafers is a major challenge in the industry. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a method for controlling the levelness of a wafer and a wafer support device. This application enables thin wafers to maintain a level state during the coating or development process, avoiding problems such as edge coating failure or incomplete coverage by the developer.

[0005] This application provides a method for controlling the levelness of a wafer, comprising: applying a non-mechanical contact and upward supporting force to one side of the wafer during the process, wherein the magnitude of the supporting force is adjusted in real time according to the levelness of the wafer.

[0006] Furthermore, in the radial direction of the wafer, the supporting force gradually weakens from the edge of the wafer to the center of the wafer.

[0007] Furthermore, multiple layers of support are applied from the edge to the center of the wafer. All layers of support are distributed in concentric rings, and the same layer of support is applied on the wafer surface and on the same circle with the wafer center as the center.

[0008] Furthermore, the magnitude of the supporting force is adjusted in real time according to the levelness of the wafer, including: real-time acquisition of the vertical distance between the bottom surface of the wafer and the preset horizontal plane; increasing the supporting force when the vertical distance is less than the preset value; and decreasing the supporting force when the vertical distance is greater than the preset value.

[0009] Furthermore, the supporting force is the force generated by the airflow acting on the wafer. The magnitude of the supporting force is adjusted in real time according to the levelness of the wafer, including: real-time acquisition of the vertical distance between the bottom surface of the wafer and the preset horizontal plane; increasing the airflow rate when the vertical distance is less than the preset value; and decreasing the airflow rate when the vertical distance is greater than the preset value.

[0010] Furthermore, in the photoresist coating process, at least three layers of support force are applied from the edge of the wafer to the center of the wafer. All layers of support force are distributed in concentric rings, and the same layer of support force is applied to the wafer surface on the same circle with the wafer center as the center. The steps for controlling the magnitude of each layer of support force include: in the pre-wetting stage, applying multiple layers of support force to the wafer simultaneously, causing the wafer to rotate horizontally at a first speed; in the photoresist spraying stage, applying partial layers of support force to the wafer, at least the layers of support force near the wafer center do not apply force to the wafer, and at least the layers of support force near the wafer edge apply force to the wafer, causing the wafer to rotate horizontally at a second speed, wherein the second speed is greater than the first speed; in the film formation rotation stage and the finishing spin-drying stage, no support force is applied to the wafer; when removing the wafer, applying multiple layers of support force to the wafer simultaneously, so that the wafer remains horizontal.

[0011] This application also provides a wafer support device, including: a wafer chuck for placing a wafer and rotating the wafer; and a force application component for applying an upward non-mechanical contact lifting force to the bottom surface of the wafer from below.

[0012] Furthermore, the force application component includes an air source, at least one air supply pipe, at least one flow regulating valve, and at least one circular jet pipe. One end of each air supply pipe is connected to the air source, and the other end of each air supply pipe is connected to a jet pipe. Each air supply pipe is equipped with a flow regulating valve. The jet pipe is located below the wafer chuck and has an upward-spraying nozzle. When there are multiple jet pipes, each jet pipe has a different radius and is distributed in concentric rings, with the center of each ring being the rotation center of the wafer chuck.

[0013] Furthermore, the nozzle and other parts of the jet pipe are designed with an arc shape.

[0014] Furthermore, the wafer support device also includes a controller and at least one spacing sensor. The spacing sensor is connected to the controller and corresponds one-to-one with the jet pipe. The spacing sensor is used to measure the vertical spacing between the surface area of ​​the wafer corresponding to the jet pipe and the preset plane. The controller is linked with all flow regulating valves and is used to control the opening degree of the flow regulating valve connected to the corresponding jet pipe according to the vertical spacing measured by each spacing sensor.

[0015] The beneficial effects of this application are: The wafer level control method of this application applies a non-mechanical contact upward lifting force to the downward-facing side of the wafer. The magnitude of the lifting force is adjusted in real time according to the level of the wafer, so that the wafer remains level during the coating or development process. This avoids the wafer edge area bending downward due to gravity during spin coating or development because the wafer thickness is too thin, which would cause the edge coating to fail or the developer to fail to cover the wafer edge during development. Therefore, this application can achieve better coating or development effect, and has a simple structure and low cost. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0017] Figure 1 A state diagram of a wafer with a taiko ring during coating or development in the prior art; Figure 2 This is a diagram showing the state of a wafer with a taiko ring rotating at low speed in the prior art. Figure 3 This is a diagram showing the state of a wafer without a Taiko ring during low-speed rotation in the prior art. Figure 4 This is a state diagram of the wafer rotating at low speed in an embodiment of this disclosure; Figure 5 This is a schematic diagram of the wafer support device in an embodiment of the present disclosure; Figure 6 for Figure 5 Top view of the wafer chuck section; Figure 7 This is a schematic diagram of the wafer support device in another embodiment of the present disclosure; Figure 8 This is a diagram showing the state of the wafer support device when it does not apply a supporting force to the wafer in an embodiment of this disclosure. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0019] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” indicate that the element or object preceding “comprising” or “including” encompasses the element or object listed following “comprising” or “including” and its equivalents, and do not exclude other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0020] This disclosure provides a method for controlling the levelness of a wafer, comprising: applying a non-mechanical contact and upward supporting force to one side of the wafer during the process, wherein the magnitude of the supporting force is adjusted in real time according to the levelness of the wafer.

[0021] The wafer level control method of this application applies a non-mechanical contact upward lifting force to the downward-facing side of the wafer. The magnitude of the lifting force is adjusted in real time according to the level of the wafer, so that the wafer remains level during the coating or development process. This avoids the wafer edge area bending downward due to gravity during spin coating or development because the wafer thickness is too thin, which would cause the edge coating to fail or the developer to fail to cover the wafer edge during development. Therefore, this application can achieve better coating or development effect, and has a simple structure and low cost.

[0022] This disclosure also provides a wafer support device, including a wafer chuck and a force application assembly. The wafer chuck is used to place a thin wafer and rotate the thin wafer. The force application assembly applies an upward, non-mechanical contact lifting force to the edge of the thin wafer from below.

[0023] The wafer level control method and wafer support device of the present disclosure are described below with reference to the accompanying drawings.

[0024] This disclosure provides a method for controlling the levelness of a wafer. This method is primarily applicable to coating processes such as resist coating and development of thin wafers whose edges bend downwards under gravity. For example, it applies to the resist coating and development processes of thin wafers in the RC-IGBT process. The method includes applying a non-mechanical contact, upward supporting force to one side of the wafer during the process, with the magnitude of the supporting force adjusted in real time according to the levelness of the wafer.

[0025] Figure 4 This is a state diagram of the wafer rotating at low speed in an embodiment of this disclosure.

[0026] like Figure 4 As shown, when the wafer rotates at low speed, a non-mechanical contact and upward lifting force is applied to the supported side of the wafer to keep the wafer in a horizontal state.

[0027] In some embodiments, the lifting force gradually decreases from the edge of the wafer to the center in the radial direction of the wafer.

[0028] In some embodiments, multiple layers of support are applied from the edge to the center of the wafer, all layers of support are distributed in concentric rings, and the same layer of support is applied on the wafer surface and on the same circle centered on the wafer center.

[0029] For example, apply three layers of support from the edge of the wafer to the center of the wafer.

[0030] In some embodiments, the magnitude of the supporting force is adjusted in real time according to the levelness of the wafer, including: acquiring the vertical distance between the bottom surface of the wafer and a preset horizontal plane in real time. When the vertical distance is less than a preset value α, the supporting force is increased. When the vertical distance is greater than the preset value, the supporting force is decreased.

[0031] Specifically, the preset value is the vertical distance between the horizontal plane and the wafer when the wafer chuck is used to pick up a wafer of normal thickness (750um~800um).

[0032] In some embodiments, the supporting force is the force generated by airflow acting on the wafer, and the magnitude of the supporting force is adjusted in real time according to the levelness of the wafer. Specifically, this includes: real-time acquisition of the vertical distance between the bottom surface of the wafer and a preset horizontal plane; increasing the airflow rate when the vertical distance is less than a preset value; and decreasing the airflow rate when the vertical distance is greater than a preset value. Using airflow to generate the supporting force can prevent liquids on the front side of the wafer, such as developer and DI deionized water, from flowing back to the back side of the wafer.

[0033] Specifically, the Torr force is the force generated by high-purity nitrogen gas acting on the wafer. The Torr force can also be the force generated by other inert gases acting on the wafer.

[0034] In some embodiments, during the coating process, at least three layers of support are applied from the edge of the wafer to the center of the wafer, all layers of support are distributed in concentric rings, and the same layer of support is applied on the wafer surface and on the same circle centered on the wafer center.

[0035] The steps for adjusting the support force of each layer include: During the pre-wetting stage, multiple layers of support are applied to the wafer simultaneously, causing it to rotate horizontally at a low speed. Because the wafer chuck rotates at a low speed during pre-wetting, the wafer edges would sag due to gravity if no upward support is applied. Therefore, multiple layers of support are needed to maintain horizontal rotation. Even in the initial stage, although no solution is applied and the rotation speed is 2000 RPM, it is crucial to ensure the wafer's adhesion to the chuck is normal and that it rotates horizontally in subsequent steps. Therefore, an upward support is also required (this support may be very small or nonexistent).

[0036] During the photoresist coating stage, a partial layer support force is applied to the wafer. At least the layer support force near the wafer center does not apply force to the wafer, while at least the layer support force near the wafer edge applies force to the wafer, allowing the wafer to rotate horizontally at a relatively high speed. During the photoresist coating stage, since the wafer chuck rotates the wafer at a high speed, typically reaching 1200 RPM, the centrifugal force generated by the high-speed rotation ensures good overall wafer levelness. However, there is still some sagging at the wafer edges. To ensure uniform coating at the edges, at least the layer support force near the wafer edge applies force to the wafer, while the layer support force near the wafer center does not apply force. For example, when applying three layers of support force to the wafer, the two layers near the wafer edge apply force, while the layer support force near the wafer center is zero, thus keeping the wafer level.

[0037] During the film-forming spin stage and the final spin-drying stage, no upward force is applied to the wafer. In the film-forming spin stage, the coating is complete. This stage aims to ensure the uniformity of the coated film. The wafer rotation speed during this stage is generally greater than 2000 RPM. The centrifugal force generated by the high-speed rotation is sufficient to keep the wafer horizontal; therefore, no upward force is needed. In the final spin-drying stage, the film layer formed on the wafer surface has set. The wafer rotation speed at this stage is generally 1200 RPM. Slight sagging at the wafer edges does not significantly affect the uniformity of the film layer. At this point, the wafer rotation is mainly for drying the back-side rinsing solvent. No upward force is applied to the wafer to avoid backsplattering defects on the front side of the wafer caused by applying force to the back side rinsing solvent.

[0038] When removing the wafer, multiple layers of support are applied simultaneously to keep it horizontal. Since the wafer rotates at zero speed during removal, if no upward support is applied, the wafer's edges will sag due to gravity, making it difficult for the robotic arm to handle.

[0039] Figure 5 This is a schematic diagram of the wafer support device in an embodiment of this disclosure. Figure 6 for Figure 5 Top view of the wafer chuck section.

[0040] like Figure 5 , Figure 6 As shown in the embodiments of this disclosure, a wafer support device 100 is also provided. The wafer support device 100 includes a wafer chuck 10 and a force application component.

[0041] The wafer chuck 10 is used to place the wafer 200 and drive the wafer 200 to rotate.

[0042] The force-applying component applies an upward, non-mechanical contact lifting force to the bottom surface of the wafer from below.

[0043] In some embodiments, the force application component includes an air source (not shown), at least one air supply pipe, at least one flow regulating valve, and at least one circular jet pipe. One end of all the air supply pipes is connected to the air source, and the other end of each air supply pipe is connected to a jet pipe. Each air supply pipe is provided with a flow regulating valve, and the jet pipe is located below the wafer chuck 200 and has an upward-spraying nozzle.

[0044] When there are multiple jet tubes, each jet tube has a different radius and is distributed in concentric rings, with the center of each ring being the rotation center of the wafer chuck.

[0045] Specifically, the force application assembly includes an air source (not shown in the figure), three air supply pipes (221, 222, 223), three flow regulating valves (231, 232, 233), and three circular jet pipes (241, 242, 243). One end of air supply pipes 221, 222, and 223 is connected to the air source. The other end of air supply pipe 221 is connected to jet pipe 241, the other end of air supply pipe 222 is connected to jet pipe 242, and the other end of air supply pipe 223 is connected to jet pipe 243. The radii of jet pipes 241, 242, and 243 increase sequentially, and they are arranged in concentric rings, with the center of each ring being the rotation center of the wafer chuck 200. Jet pipe 241 is located below wafer chuck 200 and has an upward-spraying nozzle 2411; jet pipe 242 is located below wafer chuck 200 and has an upward-spraying nozzle 2421; jet pipe 243 is located below wafer chuck 200 and has an upward-spraying nozzle 2431. A flow regulating valve 231 is installed on air supply pipe 221; a flow regulating valve 232 is installed on air supply pipe 222; and a flow regulating valve 233 is installed on air supply pipe 223. The number of air supply pipes and jet pipes is not limited to these and can be set according to the wafer diameter and the required radial layer support force distribution.

[0046] Specifically, in a process, it can be controlled that the pressure of the airflow ejected from nozzle 2431 is greater than the pressure of the airflow ejected from nozzle 2421, and the pressure of the airflow ejected from nozzle 2421 is greater than the pressure of the airflow ejected from nozzle 2411. That is, among the concentrically distributed jet pipes 241, 242, and 243, the jet pipe 241 at the center generates the least layer support force, while the jet pipe 243 at the outer periphery generates the greatest layer support force.

[0047] In some embodiments, the nozzles on the jet pipes are provided with equal curvature. For example, the nozzle 2411 on jet pipe 241 is provided with equal curvature. The nozzle 2421 on jet pipe 242 is provided with equal curvature. The nozzle 2431 on jet pipe 243 is provided with equal curvature.

[0048] Specifically, air supply pipes 221, 222, and 223, jet pipes 241, 242, and 243 are all located inside the base platform 400, with only nozzles 2411, 2421, and 2431 communicating with the outside.

[0049] Specifically, the air source, air supply pipe, and jet pipe are connected by threaded sealing rings.

[0050] Specifically, a pressure gauge is installed downstream of each gas supply pipe to measure the gas pressure in each pipe after adjustment by the flow regulating valve. For example, each pipe is equipped with an electronic pressure display. For instance, gas supply pipe 221 has an electronic pressure display 251 downstream of flow regulating valve 231, gas supply pipe 222 has an electronic pressure display 252 downstream of flow regulating valve 232, and gas supply pipe 223 has an electronic pressure display 253 downstream of flow regulating valve 233.

[0051] In some embodiments, the wafer support device 100 further includes a controller (not shown) and at least one spacing sensor. The spacing sensor is connected to the controller, and each spacing sensor corresponds to a jet pipe. The spacing sensor is used to measure the vertical spacing between the surface area of ​​the wafer corresponding to the jet pipe and a preset plane. The controller is linked to all flow control valves and is used to control the opening degree of the flow control valve connected to the corresponding jet pipe according to the vertical spacing d measured by each spacing sensor.

[0052] Specifically, the preset plane is the plane where the measurement starting point is located in the spacing sensor.

[0053] Figure 7 This is a schematic diagram of the wafer support device in another embodiment of the present disclosure.

[0054] like Figure 7 As shown, for example, the wafer support device 100 also includes a controller (not shown) and three spacing sensors (261, 262, 263). Spacing sensor 261 is used to measure the vertical spacing between the surface area of ​​the wafer corresponding to the jet pipe 241 and a preset plane. Spacing sensor 262 is used to measure the vertical spacing between the surface area of ​​the wafer corresponding to the jet pipe 242 and the preset plane. Spacing sensor 263 is used to measure the vertical spacing between the surface area of ​​the wafer corresponding to the jet pipe 243 and the preset plane.

[0055] The specific control method of the controller is as follows: the standard distance α is the distance from the preset horizontal plane measured by the sensor to the bottom surface of the standard wafer (the edge of the wafer will not droop), and the spacing d is the distance between the preset horizontal plane measured by the spacing sensor and the bottom surface of the wafer. When the distance d between the spacing sensor and the bottom surface of the wafer is less than α, the controller controls the flow control valve corresponding to the spacing sensor to open to a certain degree, causing the corresponding nozzle to eject airflow with a certain pressure, thereby applying an upward force to the wafer. When the flow control valve is open and d is detected to be less than α, the controller controls the opening of the flow control valve corresponding to the spacing sensor to increase, increasing the gas pressure in the corresponding gas supply pipe, which in turn increases the pressure of the airflow ejected from the corresponding nozzle, thereby increasing the upward force applied to the wafer. When the flow control valve is open and d is detected to be equal to α ± error, the controller controls the flow control valve to maintain its current opening. When the flow control valve is open and d is detected to be greater than α, the controller controls the opening of the flow control valve corresponding to the spacing sensor to decrease, decreasing the gas pressure in the corresponding gas supply pipe, which in turn decreases the pressure of the airflow ejected from the corresponding nozzle, thereby decreasing the upward force applied to the wafer.

[0056] Specifically, the wafer support device 100 also includes an optical fiber amplifier 26, to which the spacing sensor is connected. The optical fiber amplifier is used to display the spacing measured by the spacing sensor digitally.

[0057] Specifically, the spacing sensor and fiber optic amplifier require a 12V DC power supply to operate.

[0058] Working principle and process: When using it for the first time, place a wafer of normal thickness (e.g., 750um) on the vacuum chuck. Each spacing sensor measures the distance α1, α2...αn... between itself and the wafer. The distances α1, α2...αn... measured by each spacing sensor are used as the standard distance.

[0059] Figure 8 This is a diagram showing the state of the wafer support device when it does not apply a supporting force to the wafer in an embodiment of this disclosure.

[0060] like Figure 8 As shown, after the wafer is adsorbed onto the rotating chuck, each spacing sensor measures the distance d1, d2...dn... from the wafer. Since the edge of the wafer droops, dn is less than αn. The controller controls the corresponding flow regulating valve to open, so that the airflow from the jet pipe applies an upward lifting force to the wafer. The controller also controls the opening of the corresponding flow regulating valve to gradually increase the upward lifting force applied to the wafer by the airflow from the jet pipe until d = α ± error. The controller then controls the corresponding flow regulating valve to maintain the current opening.

[0061] As the speed at which the rotating chuck drives the wafer to rotate increases, the distance the wafer edge droops will also decrease due to the centrifugal force, even when the wafer is not under any supporting force. Therefore, maintaining the opening of the previous flow regulating valve will make dn greater than αn. At this time, the controller controls the opening of the corresponding flow regulating valve to decrease, which reduces the upward supporting force exerted by the airflow from the jet pipe on the thin wafer, until dn = αn ± error.

[0062] After the rotating chuck drives the wafer to rotate at a certain speed, the wafer can remain horizontal even without any supporting force due to centrifugal force. At this time, the controller closes the flow regulating valve.

[0063] Specifically, in the coating process, three layers of support are applied from the edge of the wafer to the center (using three circular jet nozzles), and the specific control steps include: Step S1, the pre-wetting stage, involves opening flow control valves 231, 232, and 233, allowing the wafer to rotate horizontally at a low speed. Specifically, this step includes four stages: Step S1-1: Rotate the wafer at 2000 RPM for 1 minute. The purpose of opening the three flow control valves before coating is to ensure the wafer is properly attached to the wafer chuck and to ensure the wafer rotates horizontally during the following steps. Specifically, the wafer remains horizontal as the rotation speed decreases from 2000 RPM to 30 RPM. This prevents the wafer from being non-horizontal when the three flow control valves are opened after the rotation speed drops to 30 RPM, which would affect the uniformity of the RRC solvent coating.

[0064] In steps S1-2, after the wafer rotation speed is reduced to 30 RPM, RRC solvent (to reduce the solvent consumption of the photoresist process) is applied to the center of wafer 200, and the wafer is rotated at 30 RPM for 4 minutes.

[0065] In steps S1-3, after the wafer rotation speed drops to 0 RPM, it is left to stand for 1 minute.

[0066] In steps S1-4, after increasing the wafer rotation speed to 1200 RPM, rotate the wafer at 1200 RPM for 0.1 minutes. In steps S1-2, S1-3, and S1-4, all three flow control valves remain open to ensure the wafer is in a horizontal position, which guarantees that the RRC solvent can evenly cover the wafer surface, including the wafer edge area.

[0067] In step S2, during the photoresist spraying stage, while increasing the wafer rotation speed to 1200 RPM, flow control valves 232 and 233 remain open, and the opening of flow control valve 231 is gradually reduced to close. Once the wafer rotation speed reaches 1200 RPM, flow control valves 232 and 233 are open, and flow control valve 231 is closed. Photoresist 310 is sprayed onto the center of the wafer 200 using nozzle 300, and the wafer is rotated at 1200 RPM for 5 minutes. At this speed, the centrifugal force generated by the high-speed rotation ensures good overall wafer levelness, with only slight sagging at the wafer edges. Therefore, closing flow control valve 231 and opening flow control valves 232 and 233 keeps the wafer level.

[0068] Step S3, film formation rotation stage. Specifically, this step includes two stages: Step S3-1: Reduce the wafer rotation speed from 1200 RPM to 100 RPM, close the flow control valves 232 and 233, and rotate the wafer at 100 RPM for 1 minute.

[0069] Step S3-2: Increase the wafer rotation speed from 100 RPM to 2200 RPM and rotate it at 2200 RPM for 30 minutes.

[0070] The coating process is complete during the film-forming rotation stage. A brief reduction in rotation speed will not affect the uniformity of the film thickness. Furthermore, during this stage, the wafer rotation speed is approximately 2200 RPM. The centrifugal force generated by the high-speed rotation allows the wafer to remain horizontal without any upward force applied from below. Therefore, flow control valves 231, 232, and 233 are all in the closed state during this step.

[0071] Step S4, the final drying stage, involves reducing the wafer rotation speed to 1200 RPM and then rotating it at 1200 RPM for 5 minutes. During this step, flow control valves 231, 232, and 233 remain closed.

[0072] In the final spin-drying stage, since the film layer formed on the wafer surface has been shaped, although the wafer rotation speed is 1200 RPM, which is insufficient to keep the wafer horizontal, the slight drooping of the wafer edge will not have a significant impact on the uniformity of the film layer. At this time, the wafer rotation is mainly to spin-dry the back rinse solvent of the wafer back. No force is applied to the wafer to avoid the back rinse solvent of the wafer back being splashed back onto the front of the wafer, which would form splash defects.

[0073] Step S5: Remove the wafer, gradually reduce the wafer rotation speed to 0, and then open the flow control valves 231, 232, and 233 to keep the wafer horizontal, facilitating safe handling by the robotic arm.

[0074] The text and accompanying drawings in this disclosure are provided by way of example only to aid in understanding this disclosure. They should not be construed as limiting the scope of this disclosure in any way. Although certain embodiments and examples have been provided, it will be apparent to those skilled in the art, based on the content disclosed herein, that changes can be made to the illustrated embodiments and examples without departing from the scope of this disclosure.

[0075] Although this disclosure has been described with reference to exemplary embodiments, various changes and modifications may be suggested to those skilled in the art. This disclosure is intended to cover such changes and modifications that fall within the scope of the appended claims.

[0076] Nothing described in this disclosure should be construed as implying that any particular element, step, or function is an essential element that must be included within the scope of the claims. The scope of the patent subject matter is defined only by the claims.

Claims

1. A method for controlling the levelness of a wafer, characterized in that, include: During the process, a non-mechanical contact and upward supporting force is applied to the supported side of the wafer, and the magnitude of the supporting force is adjusted in real time according to the levelness of the wafer.

2. The wafer levelness control method according to claim 1, characterized in that, In the radial direction of the wafer, the supporting force gradually decreases from the edge of the wafer to the center of the wafer.

3. The wafer levelness control method according to claim 2, characterized in that, Multiple layers of support are applied from the edge of the wafer to the center of the wafer. All layers of support are distributed in concentric rings, and the same layer of support is applied on the wafer surface and on the same circle with the wafer center as the center.

4. The wafer levelness control method according to claim 1, characterized in that, The magnitude of the supporting force is adjusted in real time according to the levelness of the wafer, including: real-time acquisition of the vertical distance between the bottom surface of the wafer and the preset horizontal plane; When the vertical spacing is less than a preset value, the supporting force is increased; When the vertical spacing is greater than a preset value, the supporting force is reduced.

5. The wafer levelness control method according to claim 1, characterized in that, The supporting force is the force generated by airflow acting on the wafer, and the magnitude of the supporting force is adjusted in real time according to the levelness of the wafer, including: Real-time acquisition of the vertical distance between the bottom surface of the wafer and the preset horizontal plane; When the vertical spacing is less than a preset value, the airflow rate is increased; When the vertical spacing is greater than a preset value, the flow rate of the airflow is reduced.

6. The wafer levelness control method according to claim 1, characterized in that, In the coating process, at least three layers of support force are applied from the edge of the wafer to the center of the wafer. All layers of support force are distributed in concentric rings, and the same layer of support force is applied on the same circle centered on the wafer center. The steps for controlling the magnitude of each layer of support force include: During the pre-wetting stage, multiple layers of support forces are applied to the wafer simultaneously, causing the wafer to rotate horizontally at a first speed. During the photoresist spraying stage, a partial layer support force is applied to the wafer, wherein the layer support force near the center of the wafer does not apply force to the wafer and the layer support force near the edge of the wafer applies force to the wafer, causing the wafer to rotate horizontally at a second speed, wherein the second speed is greater than the first speed. No supporting force is applied to the wafer during the film-forming rotation stage and the final spin-drying stage; When the wafer is removed, multiple layers of support are applied to the wafer simultaneously to keep it horizontal.

7. A wafer support device, characterized in that, include: A wafer chuck is used to place a wafer and rotate it. as well as A force-applying component applies an upward, non-mechanical contact lifting force to the bottom surface of the wafer from below.

8. The wafer support device according to claim 7, characterized in that, The force application assembly includes an air source, at least one air supply pipe, at least one flow regulating valve, and at least one circular jet pipe. One end of all the air supply pipes is connected to the air source, and the other end of each of the different air supply pipes is connected to one of the jet pipes. Each air supply pipe is provided with one of the flow regulating valves. The jet pipe is located below the wafer chuck and has an upward-spraying nozzle. When there are multiple jet tubes, each jet tube has a different radius and is distributed in concentric rings, with the center of each ring being the rotation center of the wafer chuck.

9. The wafer support device according to claim 8, characterized in that, The nozzle on the jet pipe is set with an arc shape.

10. The wafer support device according to claim 8, characterized in that, It also includes a controller and at least one spacing sensor, the spacing sensor being connected to the controller, the spacing sensor corresponding to each jet pipe, and the spacing sensor being used to measure the vertical spacing between the surface area of ​​the wafer corresponding to the jet pipe and a preset plane, the controller being linked to all the flow regulating valves, and the controller being used to control the opening degree of the flow regulating valve connected to the corresponding jet pipe according to the vertical spacing measured by each of the spacing sensors.

Images