Wafer discarding method

Abstract

The application provides a wafer disc removing method, and belongs to the technical field of semiconductor manufacturing. The method comprises the following steps: completing main plasma etching on a wafer; releasing active adsorption of the wafer by an electrostatic chuck, closing a bias power supply, keeping a plasma source power supply open, and keeping normal exhaust pressure; introducing process gas into a chamber, controlling a throttle valve to be in a conductive state, lifting a needle to a middle position, making a plasma sheath gathered in a central area of the chamber expand to the periphery of the chamber, forming a chip removal path in the chamber, and using the process gas to inhibit etching reaction; lifting the needle to a target position, closing the plasma source power supply, and transferring the wafer. In the sheath expansion process, free electrons and charged ions in the plasma fully penetrate into a fitting gap between the wafer and the electrostatic chuck, so that residual charges between the wafer and the electrostatic chuck are neutralized, and then adsorption force caused by the residual charges is eliminated. The wafer damage is reduced.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more particularly to a wafer stripping method. Background Technology

[0002] During wafer etching, an electrostatic chuck (ESC) is typically used to hold the wafer in place. After etching, the wafer needs to be removed from the ESC, i.e., detached from the chuck, for subsequent processes. However, during the etching operation, the source power, bias power, ESC voltage, helium cooling pressure on the back of the wafer, and plasma charging effect all interact, resulting in a strong electrostatic attraction between the wafer and the ESC.

[0003] In existing technologies, the plasma is typically turned off and the voltage to the chuck is cut off after etching, and then the wafer is lifted by a lifting pin to remove it from the chuck. However, even after the plasma is turned off, there is still a residual charge between the wafer and the electrostatic chuck, causing the electrostatic chuck to still have an attraction force on the wafer; lifting the lifting pin at this time can easily lead to wafer breakage. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a wafer removal method that can reduce the adhesion between the chuck and the wafer during the removal process, thereby reducing the likelihood of wafer breakage.

[0005] To achieve the above objectives, the technical solution adopted in the embodiments of this application is as follows:

[0006] This application provides a wafer detachment method, including:

[0007] Complete the plasma main etching of the wafer;

[0008] Release the electrostatic chuck from actively adsorbing the wafer, turn off the bias power supply and keep the plasma source power supply on, and maintain normal exhaust pressure;

[0009] Process gas is introduced into the chamber, the throttle valve is controlled to be in the open state, and the ejector pin is raised to the middle position, so that the plasma sheath layer accumulated in the central region of the chamber expands to the periphery of the chamber and forms a chip removal path in the chamber. The process gas is used to suppress the etching reaction.

[0010] Raise the ejector pin to the target position, turn off the plasma source power, and transfer the wafer.

[0011] In some embodiments, the process gas is introduced into the chamber, the throttle valve is controlled to be in the open state, and the ejector pin is raised to the middle position, including:

[0012] Process gas is introduced into the chamber until the pressure range within the chamber is sufficient to sustain plasma ignition.

[0013] The throttle valve is controlled to be fully open to generate a pressure transient effect and a directional exhaust airflow in the chamber. The pressure transient effect causes the plasma sheath to expand to the periphery of the chamber, and the directional exhaust airflow forms the chip removal path.

[0014] Raise the ejector pin to the middle position, where the raising height of the middle position is less than the raising height of the target position.

[0015] In some embodiments, the pressure range for maintaining plasma ignition is from 50 mTorr to 200 mTorr.

[0016] In some embodiments, controlling the throttle valve to be adjusted to a fully open conducting state includes:

[0017] The throttle valve is directly adjusted to the fully open conducting state; or,

[0018] The throttle valve is gradually adjusted to the fully open state according to a gradual curve aimed at full opening.

[0019] In some embodiments, the chip removal path sequentially includes the upper region of the wafer, the edge region of the wafer, the side region of the electrostatic chuck, the inner wall region of the chamber, and the bottom exhaust region of the chamber.

[0020] In some embodiments, raising the ejector pin to the target position, turning off the plasma source power supply, and transferring the wafer includes:

[0021] Raise the ejector pin to the target position;

[0022] Acquire monitoring signals;

[0023] The wafer's detachment status is determined based on the monitoring signals;

[0024] If the monitoring signal indicates that the wafer has been removed from the disk, the plasma source power supply is turned off, and the wafer is transferred from the target location.

[0025] In some embodiments, the monitoring signal includes at least one of the following: the optical emission spectrum of the plasma, the impedance of the plasma, the pressure inside the cavity, the leakage current of the electrostatic chuck, the gas pressure on the back of the wafer, and the drive motor current of the ejector pin.

[0026] In some embodiments, determining that the wafer has been removed from the disk includes at least one of the following:

[0027] The optical emission spectrum exhibits characteristic peaks in spectral intensity;

[0028] The rate of change of the impedance of the plasma within a preset time is greater than or equal to a first threshold.

[0029] The rate of change of pressure within the chamber is greater than or equal to a second threshold within the preset time.

[0030] The rate of change of the gas pressure on the back of the wafer within the preset time is greater than or equal to a third threshold.

[0031] The leakage current of the electrostatic chuck is less than or equal to the fourth threshold.

[0032] The current of the drive motor of the ejector pin is less than or equal to the fifth threshold.

[0033] In some embodiments, the process gas includes a first gas and a second gas, wherein the flow rate of the first gas is greater than the flow rate of the second gas, the first gas includes argon or nitrogen, and the second gas includes at least one of helium, neon, and oxygen.

[0034] In some embodiments, the volume ratio between the first gas and the second gas ranges from 2.5 to 7.

[0035] In this embodiment, after the main plasma etching of the wafer is completed, the power supply to the electrostatic chuck is disconnected to release the active electrostatic adsorption of the wafer; the bias power supply is turned off to remove the process bias voltage applied to the wafer surface, stop the etching process, and reduce the continued accumulation of charge on the wafer; while the plasma source power supply is kept on to maintain the normal plasma state in the chamber. With the plasma source power supply on, a process gas with an anti-etching effect is introduced into the chamber to reduce the secondary etching damage to the wafer caused by residual etching gas; and the throttle valve is controlled to be in the conducting state, thereby regulating the chamber pressure to form a pressure transient effect and directional exhaust airflow. In this way, under the action of chamber pressure transient, the plasma sheath layer originally concentrated in the central region of the chamber and located on the wafer surface expands to the periphery of the chamber and the outer region of the wafer. During the expansion of the sheath layer, the free electrons and charged ions in the plasma fully penetrate into the bonding gap between the wafer and the electrostatic chuck, thereby neutralizing the residual charge between the wafer and the electrostatic chuck, and thus eliminating the adsorption force caused by the residual charge. Simultaneously, under the directional exhaust airflow formed by the throttle valve, a chip removal path is created within the chamber. Suspended particles and etching reaction byproducts within the chamber can be discharged along this path, reducing contaminant adhesion to the wafer surface. Finally, the ejector pin is raised to the target position, the plasma source power is turned off, and the wafer is transferred, improving the reliability of the wafer removal process and reducing wafer breakage. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of one of the wafer removal methods in the embodiments of this application;

[0037] Figure 2 This is the second schematic diagram illustrating the wafer removal method in the embodiments of this application;

[0038] Figure 3 This is the third flowchart illustrating the wafer removal method in this application.

[0039] Figure 4 This diagram illustrates the plasma sheath expansion and suspended matter discharge process in an embodiment of this application.

[0040] Figure 5 This diagram illustrates the wafer removal process in an embodiment of this application.

[0041] Figure 6 This is a schematic diagram of the overall process in the embodiments of this application;

[0042] Figure 7 This is the fourth flowchart illustrating the wafer removal method in the embodiments of this application. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application 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 application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application are within the scope of protection of this application.

[0044] In existing technologies, after etching, residual charge remains between the wafer and the electrostatic chuck during wafer removal, causing the chuck to maintain its attraction to the wafer. This can lead to wafer breakage when the ejector pin is lifted. This application provides a wafer removal method that eliminates residual charge, reduces the attraction between the chuck and the wafer, and thus minimizes wafer breakage.

[0045] This application provides a wafer removal method that can be applied to semiconductor process equipment. The semiconductor process equipment includes a chamber, an electrostatic chuck, a ejector pin, a throttle valve, a plasma source power supply for exciting gas in the chamber to form plasma, and a bias power supply for providing bias voltage to the wafer. The electrostatic chuck and ejector pin are disposed in the chamber, and the throttle valve is disposed at the bottom of the chamber. The throttle valve is used to regulate the pressure in the chamber.

[0046] like Figure 1 As shown, the wafer removal method includes the following steps:

[0047] Step 10: Complete the plasma main etching of the wafer.

[0048] In this step, etching gas, such as fluorine- or chlorine-containing active etching gas, can be introduced into the chamber; and the plasma source power supply is turned on to excite the etching gas in the chamber and form plasma; at the same time, the bias power supply is turned on to apply a bias voltage to the wafer, so as to drive the charged particles in the plasma to bombard the wafer surface in a directional manner, thereby realizing the main etching process of the wafer with a predetermined structure; during the entire main etching process, the electrostatic chuck is continuously powered, so that the electrostatic chuck can stably adsorb the wafer by actively generating electrostatic force, thereby improving the etching accuracy.

[0049] Step 20: Release the electrostatic chuck from actively adsorbing the wafer, turn off the bias power supply and keep the plasma source power supply on, and maintain normal exhaust pressure.

[0050] In this step, after the main plasma etching of the wafer, the power supply to the electrostatic chuck is disconnected to release the active electrostatic adsorption of the wafer; the bias power supply is turned off to remove the process bias voltage applied to the wafer surface, stop the etching process, and reduce the continued accumulation of charge on the wafer; and the plasma source power supply is kept on and the normal exhaust pressure is maintained to maintain the normal plasma state in the chamber and provide a stable plasma environment for subsequent removal of residual charge.

[0051] Step 30: Introduce process gas into the chamber, control the throttle valve to be in the open state, raise the ejector pin to the middle position, so that the plasma sheath layer accumulated in the central area of ​​the chamber expands to the periphery of the chamber and forms a chip removal path in the chamber. The process gas is used to suppress the etching reaction.

[0052] In this step, considering that even after the etching process is completed, and the electrostatic chuck releases its active grip on the wafer, residual charge remains between the wafer and the chuck, causing the chuck to still exert an adhesive force on the wafer, a process gas with anti-etching properties is introduced into the chamber while keeping the plasma source power on. This reduces the risk of secondary etching damage to the wafer caused by residual etching gas. Furthermore, the throttle valve is kept in the conducting state, regulating the chamber pressure to create a pressure transient effect and directional exhaust airflow. Under the effect of the chamber pressure transient, the plasma sheath, originally concentrated in the central region of the chamber and located on the wafer surface, expands to the periphery of the chamber and the outer edge of the wafer. During this expansion, free electrons and charged ions from the plasma fully penetrate the gap between the wafer and the electrostatic chuck, neutralizing the residual charge and eliminating the adhesive force caused by the residual charge. This reduces the likelihood of wafer breakage during subsequent ejector pin lifting. At the same time, under the action of the directional exhaust airflow formed by the throttle valve, a chip removal path is formed in the chamber. Suspended particles and etching reaction byproducts in the chamber can be discharged from the chamber along the chip removal path, reducing the adhesion of contaminants on the wafer surface and improving wafer quality.

[0053] In some embodiments, such as Figure 2 As shown, step 30, introducing process gas into the chamber, controlling the throttle valve to be in the open state, and raising the ejector pin to the middle position, includes the following steps:

[0054] Step 301: Introduce process gas into the chamber until the pressure range sufficient to sustain plasma ignition is reached within the chamber.

[0055] In this step, the plasma source power supply is kept on to maintain the normal existence of the plasma in the chamber, and process gas is introduced into the chamber until the pressure range that can maintain plasma ignition is reached, reducing the possibility of plasma extinction during subsequent pressure regulation.

[0056] In some embodiments, the process gas includes a first gas and a second gas, with the flow rate of the first gas being greater than that of the second gas. The first gas includes argon or nitrogen, and the second gas includes at least one of helium, neon, and oxygen. A non-etching process gas, primarily composed of argon or nitrogen, is introduced into the chamber, optionally mixed with one or more of helium, neon, and oxygen, to maintain stable chamber pressure. This provides a basis for the pressure transient effect formed by the subsequent full opening of the throttle valve, and assists in driving sheath expansion and directional discharge of particulate matter.

[0057] Argon and nitrogen do not cause additional etching reactions and can protect the wafer and chamber; in addition, argon has a high atomic mass, which can increase the collision of ions and neutral particles, resulting in a thicker sheath for the plasma.

[0058] Helium and neon ions, with their small mass and rapid diffusion rate, can improve the overall uniformity of the plasma, supplementing areas such as wafer edges and electrostatic chuck sidewalls that are difficult for argon ions to cover, and enhancing the comprehensiveness of residual charge neutralization. Oxygen can moderately alter the plasma ionization characteristics, regulate the electric field gradient of the sheath, and, in conjunction with the pressure transient effect, make the sheath expansion process more stable.

[0059] In some embodiments, the volume ratio between the first gas and the second gas can be in the range of 2.5 to 7. For example, the flow rate of the first gas can be 500 slm-700 slm, and the flow rate of the second gas can be 100 slm-200 slm, in order to stably maintain the normal ignition and morphology of the plasma, so that the plasma sheath can expand smoothly and the residual charge between the wafer and the electrostatic chuck can be continuously neutralized.

[0060] In some embodiments, the pressure range for maintaining plasma ignition can be from 50 mTorr to 200 mTorr to improve the stable ionization of process gases and maintain a uniform and controllable plasma state, providing a reliable plasma environment for subsequent residual charge neutralization and plasma sheath expansion. Preferably, the pressure range for maintaining plasma ignition is from 80 mTorr to 120 mTorr. This pressure range avoids the problems of difficult plasma ignition and low charge neutralization efficiency due to insufficient particle density at excessively low pressures, while also reducing the defects of excessively violent particle collisions and suppressed sheath expansion at excessively high pressures. This effectively drives the plasma sheath to expand uniformly towards the chamber walls and wafer periphery, eliminating electrostatic adsorption forces, and, in conjunction with directional exhaust airflow, achieving efficient removal of particulate matter from the chamber.

[0061] Step 302: Control the throttle valve to the fully open state to form a pressure transient effect and directional exhaust airflow in the chamber. The pressure transient effect causes the plasma sheath to expand to the periphery of the chamber, and the directional exhaust airflow forms a chip removal path.

[0062] In this step, the throttle valve is adjusted to its full open state. The throttle valve regulates the chamber pressure, creating a pressure transient effect and a directional exhaust airflow. Under this pressure transient, the plasma sheath, originally concentrated in the central region of the chamber and located on the wafer surface, expands to the periphery of the chamber and the wafer. During sheath expansion, free electrons and charged ions within the plasma fully penetrate the gap between the wafer and the electrostatic chuck, neutralizing the residual charge between them and eliminating the adhesion force caused by the residual charge. This reduces the likelihood of wafer breakage during subsequent ejector pin lifting. Simultaneously, the directional exhaust airflow created by the throttle valve forms a chip removal path within the chamber. Suspended particles and etching reaction byproducts can be discharged along this path, reducing contaminant adhesion to the wafer surface and improving wafer quality.

[0063] In some embodiments, such as Figure 3 As shown, step 302, adjusting the throttle valve to the fully open conducting state, can be achieved in one of the following two ways:

[0064] Step 3021: Control the throttle valve to be directly adjusted to the fully open conducting state.

[0065] In one example, the throttle valve can be controlled to be directly adjusted to the fully open state, which can quickly form a high-intensity pressure transient effect and establish a chamber pressure gradient instantly. This accelerates the expansion of the plasma sheath layer that was originally concentrated on the wafer surface to the periphery of the chamber, thereby increasing the neutralization speed of residual charge. This is suitable for working conditions that require rapid dust removal.

[0066] Step 3022: Control the throttle valve to gradually adjust it to the fully open state according to the gradual curve with the goal of full opening.

[0067] In another example, the throttle valve can be gradually adjusted to its full opening state using a gradual curve aimed at full opening, such as a linear ramp curve or an S-curve. This allows the throttle valve opening to increase continuously and smoothly over time, eventually reaching full opening after a transition adjustment process. The rate of change of the gradual curve can be pre-programmed according to process requirements, making the adjustment process controllable. This allows the plasma sheath to expand outward at a uniform and stable speed, reducing turbulence caused by sudden changes in flow field and pressure, minimizing impact on the wafer, and making it suitable for removing thin and large wafers from their trays.

[0068] In some embodiments, the chip removal path may sequentially include the upper region of the wafer, the edge region of the wafer, the side region of the electrostatic chuck, the inner wall region of the chamber, and the bottom exhaust region of the chamber.

[0069] For example, plasma sheath expansion and suspended matter discharge can be seen in... Figure 4The initial sources of suspended matter mainly include reaction byproducts generated during the preceding etching process and detached etching film debris, which adhere to the SiC wafer surface or float in the area above the wafer (i.e., position shown in number 1). By controlling the throttle valve to its full opening state, the chamber pressure rapidly decreases, creating a pressure transient effect and directional exhaust airflow. The plasma sheath, originally concentrated in the central region of the chamber, expands to the surrounding area. Under the combined action of plasma expansion and directional exhaust airflow, the suspended matter is guided towards the edge region of the wafer (i.e., position shown in number 2), detaching from the wafer surface and preventing it from falling back and contaminating the wafer during subsequent lifting. Simultaneously, free electrons and charged ions in the plasma fully penetrate the bonding gap between the wafer and the electrostatic chuck (i.e., the side region of the electrostatic chuck, not shown in the figure at position 3), neutralizing the residual charge between the wafer and the electrostatic chuck, eliminating the adsorption force caused by the residual charge, and achieving natural de-adhesion. Furthermore, the suspended matter continues to move from the wafer edge towards the inner wall region of the chamber (i.e., location shown in number 4). The suspended matter flows upwards and downwards along the chamber wall, guided to the bottom exhaust region of the chamber (i.e., location shown in number 5), and is finally extracted from the chamber by the vacuum pump. Thus, under the action of the directional exhaust airflow, a chip removal path is formed within the chamber, namely the upper region of the wafer (location shown in number 1), the edge region of the wafer (location shown in number 2), the side region of the electrostatic chuck (location shown in number 3, not shown in the figure), the inner wall region of the chamber (location shown in number 4), and the bottom exhaust region of the chamber (location shown in number 5). Suspended particles and etching reaction byproducts within the chamber can be discharged along the chip removal path, reducing contaminant adhesion to the wafer surface.

[0070] Step 303: Raise the pin to the middle position. The lifting height at the middle position is less than the lifting height at the target position.

[0071] In this step, the ejector pin is raised to the middle position. The middle position is a safe range for raising the ejector pin, avoiding the situation where the ejector pin is raised directly to the maximum height, but the residual adsorption force is still large, which may cause wafer damage.

[0072] In some embodiments, such as Figure 5 As shown, the wafer removal process can include a first stage, a second stage, a third stage, and a fourth stage.

[0073] The first stage can be during or immediately after the main etching process. At this time, the plasma is concentrated in the central region of the chamber, and there is still a strong adsorption force between the wafer and the electrostatic chuck.

[0074] The second stage can be achieved after the main etching, by keeping the plasma source power on to maintain the normal plasma state within the chamber and introducing process gas into the chamber to make the plasma density more uniform, facilitating subsequent sheath expansion; and maintaining the plasma ignition pressure range to reduce the possibility of plasma extinction during subsequent pressure regulation. The process gas is used to suppress the etching reaction, thereby reducing the risk of residual etching gas causing secondary etching damage to the wafer.

[0075] The third stage can be the pressure regulation stage, where the throttle valve is adjusted to the fully open state, causing the chamber pressure to drop rapidly, forming a pressure transient effect and a directional exhaust airflow. The pressure transient effect causes the plasma sheath to expand to the periphery of the chamber, and the directional exhaust airflow forms a chip removal path.

[0076] The fourth stage can be the sheath expansion stage. Under the influence of pressure transient effects, a pressure gradient is formed from the central region of the chamber to the interior, causing the plasma sheath, originally concentrated in the central region, to expand to the surrounding areas. Furthermore, under the action of directional exhaust airflow, a chip removal path is formed within the chamber, allowing suspended particles and etching reaction byproducts to be discharged along this path, reducing contaminant adhesion to the wafer surface. During sheath expansion, free electrons and charged ions within the plasma fully penetrate the bonding gap between the wafer and the electrostatic chuck, neutralizing the residual charge between them and eliminating the adhesion force caused by the residual charge, thus achieving natural de-adhesion.

[0077] After completing the plasma sheath expansion and suspended matter removal, the ejector pin can be raised to the middle position. The middle position is a safe stroke for lifting the ejector pin, avoiding the situation where the ejector pin is directly raised to the maximum height, but the residual adsorption force is still large, which may cause wafer damage.

[0078] In some embodiments, such as Figure 6 As shown, in the plasma etching process, etching gas, such as fluorine- or chlorine-containing active etching gas, can be introduced into the chamber; and the plasma source power supply is turned on to excite the etching gas in the chamber, forming plasma that accumulates in the central region of the chamber; at the same time, the bias power supply is turned on to apply a bias voltage to the wafer, so as to drive the charged particles in the plasma to bombard the wafer surface in a directional manner, thereby achieving the etching process of the wafer with a predetermined structure; and throughout the etching process, the electrostatic chuck is continuously powered, so that the electrostatic chuck can stably adsorb the wafer by actively generating electrostatic force, thereby improving the etching accuracy.

[0079] During the wafer removal process, the bias power supply is turned off, while the plasma source power supply remains on. A process gas with anti-etching properties is introduced into the chamber to reduce secondary etching damage to the wafer caused by residual etching gas. Simultaneously, the throttle valve is kept on, regulating the chamber pressure to create a pressure transient effect. This pressure transient causes the plasma sheath, initially concentrated in the center of the chamber, to expand outwards. During this expansion, free electrons and charged ions from the plasma fully penetrate the gap between the wafer and the electrostatic chuck, neutralizing the residual charge and eliminating the adhesion force caused by the residual charge. Simultaneously, the directional exhaust airflow created by the throttle valve forms a chip removal path within the chamber. Suspended particles and etching byproducts can be discharged along this path, reducing contaminant adhesion to the wafer surface.

[0080] After completing plasma sheath expansion and suspended matter removal, the ejector pin is further controlled to rise to the intermediate position. The intermediate position represents a safe range for ejector pin rise, avoiding wafer damage caused by raising the ejector pin directly to its maximum height while still having significant residual adsorption force. Once the intermediate position is reached, the ejector pin can be left to stand for a period of time to allow any remaining residual charge to be fully neutralized, thereby further eliminating the adsorption force caused by residual charge.

[0081] In the wafer transfer process, the ejector pin is raised to the target position, which can be the maximum raised position of the ejector pin. The plasma source power is then turned off, and the wafer is transferred. See the following description for details:

[0082] Step 40: Raise the ejector pin to the target position, turn off the plasma source power, and transfer the wafer.

[0083] In this step, after achieving smooth wafer removal through charge neutralization, the ejector pin is raised. Once the ejector pin smoothly lifts the wafer to the target position, the plasma source power is shut off to terminate the plasma excitation state within the chamber. This reduces the likelihood of residual charge buildup and electrostatic adsorption rebound caused by premature power cutoff, improving the reliability of the wafer removal process and reducing wafer breakage. Furthermore, a robotic arm or other conveying mechanism can be used to remove the fully removed wafer from the chamber and transport it to the next semiconductor process.

[0084] The enabling conditions for starting the ejector pin include: the electrostatic chuck is de-energized, the bias power supply is turned off, the plasma source power supply remains on, and the throttle valve is in the conducting state.

[0085] It should be understood that in this embodiment, the ejector pin is used to assist in wafer removal. It relies on charge neutralization to reduce the electrostatic attraction caused by residual charge, rather than mechanical brute force. Compared to existing wafer removal methods, this reduces the risk of wafer chipping, warping, cracking, and film damage caused by the ejector pin.

[0086] In some embodiments, such as Figure 7 As shown, step 40, raising the ejector pin to the target position, turning off the plasma source power, and transferring the wafer, includes the following steps:

[0087] Step 401: Raise the pin to the target position.

[0088] In this step, the target position can be the maximum lifting position of the ejector pin, so as to facilitate the subsequent transfer of the wafer.

[0089] Step 402: Acquire monitoring signals.

[0090] In this step, the monitoring signals may include at least one of the following: the optical emission spectrum of the plasma, the impedance of the plasma, the pressure inside the chamber, the leakage current of the electrostatic chuck, the gas pressure on the back of the wafer, and the drive motor current of the ejector pin.

[0091] Step 403: Determine the wafer detachment status based on the monitoring signal.

[0092] In this step, different monitoring signals can reflect the separation status of the wafer and ESC from different dimensions, improving the accuracy of judging the wafer detachment status.

[0093] In some embodiments, determining that the wafer has been unloaded from the disk includes at least one of the following:

[0094] The optical emission spectrum exhibits characteristic peaks in spectral intensity;

[0095] The rate of change of plasma impedance within a preset time is greater than or equal to a first threshold.

[0096] The rate of change of pressure within the chamber is greater than or equal to the second threshold within a preset time.

[0097] The rate of change of gas pressure on the back of the wafer is greater than or equal to the third threshold within a preset time.

[0098] The leakage current of the electrostatic chuck is less than or equal to the fourth threshold.

[0099] The current of the drive motor for the ejector pin is less than or equal to the fifth threshold.

[0100] For example, at the moment the wafer separates from the ESC, the plasma load state changes abruptly, and a characteristic peak appears in the spectral intensity of a specific wavelength in the chamber. Based on this, when a characteristic peak appears in the spectral intensity of the optical emission spectrum, it can be determined that the wafer has been removed from the disk.

[0101] For example, after the wafer is removed from the ESC, the impedance of the plasma will change significantly in a short period of time. When the impedance change rate within a preset time reaches a preset first threshold, it can be determined that the wafer has been removed from the disk.

[0102] For example, when the wafer is tightly attached to the ESC, the space behind the wafer is isolated from the chamber, and the overall pressure in the chamber remains stable. When the wafer separates from the ESC, the sealed gas cavity on the back suddenly connects with the chamber, and the gas volume and flow field inside the chamber change instantaneously, causing characteristic fluctuations in the overall pressure. When the rate of change of pressure inside the chamber reaches a preset second threshold within a preset time, it can be determined that the wafer has been successfully detached from the disk.

[0103] For example, under normal adsorption conditions, the back-blown gas on the back side of the wafer is sealed between the wafer and the ESC bonding surface, and the back pressure is stable; when the wafer separates from the ESC, the sealing structure of the bonding surface fails. When the rate of change of the gas pressure on the back side of the wafer reaches a preset third threshold within a preset time, it can be determined that the wafer has been successfully detached from the disk.

[0104] For example, after the residual charge is neutralized and the wafer is detached, the leakage current of the ESC will drop below a preset fourth threshold. Thus, when the leakage current of the electrostatic chuck is less than or equal to the fourth threshold, it can also be determined that the wafer has been detached.

[0105] For example, after the wafer is separated from the ESC, the residual adsorption resistance of the ejector pin disappears, and the motor drive current will drop significantly to the no-load level. At this time, the drive motor current of the ejector pin can be a preset fifth threshold. Thus, when the drive motor current of the ejector pin is less than or equal to the fifth threshold, it can also be determined that the wafer has been unloaded.

[0106] This multi-signal synchronous monitoring avoids misjudgments caused by interference from the chamber environment with a single signal. When at least one of the conditions for wafer removal is met, the wafer is determined to have been successfully removed from the disk, improving the reliability of the removal determination. Furthermore, controlling the plasma source power supply to shut down terminates the plasma excitation state within the chamber, reducing the risk of residual charge buildup and electrostatic adsorption rebound due to premature power cutoff. Finally, the wafer is transferred from the target location via a conveyor mechanism, minimizing the possibility of wafer breakage.

[0107] Step 404: If the monitoring signal indicates that the wafer has been removed from the disk, turn off the plasma source power supply and transfer the wafer from the target location.

[0108] In this step, if the monitoring signal indicates that the wafer has been removed from the disk, the plasma source power is turned off to terminate the plasma excitation state in the chamber, reducing the possibility of residual charge accumulation and electrostatic adsorption rebound caused by premature power cut-off. Finally, the wafer is transferred from the target position by the conveying mechanism, which improves the reliability of the wafer removal process and reduces the possibility of wafer breakage.

[0109] In this embodiment, after the main plasma etching of the wafer is completed, the power supply to the electrostatic chuck is disconnected to release the active electrostatic adsorption of the wafer; the bias power supply is turned off to remove the process bias voltage applied to the wafer surface, stop the etching process, and reduce the continued accumulation of charge on the wafer; while the plasma source power supply is kept on to maintain the normal plasma state in the chamber. With the plasma source power supply on, a process gas with an anti-etching effect is introduced into the chamber to reduce the secondary etching damage to the wafer caused by residual etching gas; and the throttle valve is controlled to be in the conducting state, thereby regulating the chamber pressure to form a pressure transient effect and directional exhaust airflow. In this way, under the action of chamber pressure transient, the plasma sheath layer originally concentrated in the central region of the chamber and located on the wafer surface expands to the periphery of the chamber and the outer region of the wafer. During the expansion of the sheath layer, the free electrons and charged ions in the plasma fully penetrate into the bonding gap between the wafer and the electrostatic chuck, thereby neutralizing the residual charge between the wafer and the electrostatic chuck, and thus eliminating the adsorption force caused by the residual charge. Simultaneously, under the directional exhaust airflow formed by the throttle valve, a chip removal path is created within the chamber. Suspended particles and etching reaction byproducts within the chamber can be discharged along this path, reducing contaminant adhesion to the wafer surface. Finally, the ejector pin is raised to the target position, the plasma source power is turned off, and the wafer is transferred, improving the reliability of the wafer removal process and reducing wafer breakage.

[0110] In the various method embodiments of this disclosure, the sequence number of each step is not intended to limit the order of the steps. For those skilled in the art, any changes in the order of the steps are within the scope of protection of this disclosure without any creative effort.

[0111] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, since the embodiments are basically similar to the product embodiments, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions of the product embodiments.

[0112] The above are preferred embodiments of this disclosure. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of this disclosure, and these improvements and modifications should also be considered within the scope of protection of this disclosure.

Claims

1. A wafer removal method, characterized in that, include: Complete the plasma main etching of the wafer; Release the electrostatic chuck from actively adsorbing the wafer, turn off the bias power supply and keep the plasma source power supply on, and maintain normal exhaust pressure; Process gas is introduced into the chamber, the throttle valve is controlled to be in the open state, and the ejector pin is raised to the middle position, so that the plasma sheath layer accumulated in the central region of the chamber expands to the periphery of the chamber and forms a chip removal path in the chamber. The process gas is used to suppress the etching reaction. Raise the ejector pin to the target position, turn off the plasma source power, and transfer the wafer.

2. The method according to claim 1, characterized in that, The process of introducing process gas into the chamber, controlling the throttle valve to be in the open state, and raising the ejector pin to the middle position includes: Process gas is introduced into the chamber until the pressure range within the chamber is sufficient to sustain plasma ignition. The throttle valve is controlled to be fully open to generate a pressure transient effect and a directional exhaust airflow in the chamber. The pressure transient effect causes the plasma sheath to expand to the periphery of the chamber, and the directional exhaust airflow forms the chip removal path. Raise the ejector pin to the middle position, where the raising height of the middle position is less than the raising height of the target position.

3. The method according to claim 2, characterized in that, The pressure range that can sustain plasma ignition is 50 mTorr to 200 mTorr.

4. The method according to claim 2, characterized in that, The control of adjusting the throttle valve to the fully open conducting state includes: The throttle valve is directly adjusted to the fully open conducting state; or, The throttle valve is gradually adjusted to the fully open state according to a gradual curve aimed at full opening.

5. The method according to any one of claims 1 to 4, characterized in that, The chip removal path sequentially includes the upper region of the wafer, the edge region of the wafer, the side region of the electrostatic chuck, the inner wall region of the chamber, and the bottom exhaust region of the chamber.

6. The method according to any one of claims 1 to 4, characterized in that, The steps of raising the ejector pin to the target position, turning off the plasma source power, and transferring the wafer include: Raise the ejector pin to the target position; Acquire monitoring signals; The wafer's detachment status is determined based on the monitoring signals; If the monitoring signal indicates that the wafer has been removed from the disk, the plasma source power supply is turned off, and the wafer is transferred from the target location.

7. The method according to claim 6, characterized in that, The monitoring signals include at least one of the following: the optical emission spectrum of the plasma, the impedance of the plasma, the pressure inside the cavity, the leakage current of the electrostatic chuck, the gas pressure on the back of the wafer, and the current of the drive motor of the ejector pin.

8. The method according to claim 7, characterized in that, Determining that the wafer has been unloaded from the disk includes at least one of the following: The optical emission spectrum exhibits characteristic peaks in spectral intensity; The rate of change of the impedance of the plasma within a preset time is greater than or equal to a first threshold. The rate of change of pressure within the chamber is greater than or equal to a second threshold within the preset time. The rate of change of the gas pressure on the back of the wafer within the preset time is greater than or equal to a third threshold. The leakage current of the electrostatic chuck is less than or equal to the fourth threshold. The current of the drive motor of the ejector pin is less than or equal to the fifth threshold.

9. The method according to any one of claims 1 to 4, characterized in that, The process gas includes a first gas and a second gas, wherein the flow rate of the first gas is greater than the flow rate of the second gas, the first gas includes argon or nitrogen, and the second gas includes at least one of helium, neon and oxygen.

10. The method according to claim 9, characterized in that, The volume ratio between the first gas and the second gas ranges from 2.5 to 7.

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