Plasma ashing apparatus with adjustable wafer chuck height

Abstract

According to the present embodiment, a plasma ashing device may be provided comprising a wafer chuck, a lifting / lowering unit that supports and vertically moves the wafer chuck, a rotating part that rotates a plurality of screw threads to vertically move the lifting / lowering unit, and a power transmission part that receives power, converts electrical energy into rotational kinetic energy, and transmits the converted rotational kinetic energy to the rotating part.

Description

Technology Field

[0001] The present embodiment relates to a plasma ashing device capable of adjusting the height of a wafer chuck, and more specifically, to a plasma ashing device capable of finely adjusting the height of the wafer chuck by vertically moving a lifting / lowering unit using a servo motor. Background Technology

[0002] Plasma ashing devices play a crucial role in the semiconductor manufacturing process and are primarily used to remove organic materials from the wafer surface. By utilizing high-temperature plasma to chemically remove photoresist or other organic substances remaining on the wafer surface, plasma ashing devices can contribute to improving the efficiency and quality of subsequent processes.

[0003] In the semiconductor manufacturing process, the performance and reliability of semiconductor devices depend heavily on the precision of the micro-process. A wafer refers to a thin, flat disk used to manufacture semiconductor chips, and it creates semiconductor devices by integrating very small electronic components such as transistors, resistors, and capacitors. Recently, as technologies for reducing the size of semiconductor devices and implementing highly integrated circuits have advanced, there has been a need for advanced precision in the process.

[0004] In particular, for plasma ashing devices, it is necessary to ashing the photoresist uniformly to accurately form a pattern on the wafer surface and remove residues from the wafer surface.

[0005] However, conventional plasma ashing devices cannot adjust the height of the wafer chuck, so a problem may arise where the photoresist cannot be ashed uniformly when the stacking height of the die chips increases.

[0006] In addition, due to the uneven ashing of the photoresist, the stacking height of the die chips varies, which may lead to a degradation and loss of die chip functionality and cause failure. The problem to be solved

[0007] Against this backdrop, the objective of the present embodiment is, in one aspect, to provide a plasma ashing device capable of finely adjusting the height of a wafer chuck by vertically moving a lifting / lowering unit using a servo motor.

[0008] The objective of the present embodiment is, in another aspect, to provide a plasma ashing device capable of vertically moving the wafer chuck height in units of less than 10 μm by controlling the rotational angular frequency of the servo motor and the pitch value, which is the spacing of the screw threads of the rotating part. means of solving the problem

[0009] To achieve the aforementioned objective, the first embodiment may provide a plasma ashing device comprising a wafer chuck, a lifting / lowering unit that supports and vertically moves the wafer chuck, a rotating part that rotates a plurality of screw threads to vertically move the lifting / lowering unit, and a power transmission part that receives power, converts electrical energy into rotational kinetic energy, and transmits the converted rotational kinetic energy to the rotating part.

[0010] In a plasma ashing device, the plurality of screw threads can be arranged at regular intervals on the rotating part.

[0011] In a plasma ashing device, the power transmission unit includes a servo motor, and the servo motor may include a motor, a feedback system, and a control circuit.

[0012] In a plasma ashing device, the lifting and lowering unit may include a shaft supporting the wafer chuck and a fixed panel that fixes the shaft in a vertical direction and moves vertically through the rotation of the plurality of screw threads.

[0013] In a plasma ashing device, the shaft may include a bellows on its outer surface.

[0014] In the plasma ashing device, the lifting and lowering unit may further include a weight.

[0015] In a plasma ashing device, the fixed panel may include a first through hole formed to allow the weight to pass through, a second through hole formed to fix the shaft, and a third through hole formed to allow the rotating part to be inserted and rotate.

[0016] In a plasma ashing device, the shaft and the rotating part include a cylindrical structure, the diameter of the cross-section of the shaft cut in the xy plane is larger than the diameter of the cross-section of the rotating part cut in the xy plane, and the diameter of the second through hole may be larger than the diameter of the third through hole.

[0017] In a plasma ashing device, the fixed panel comprises a plurality of the second through holes and the third through holes, wherein the plurality of the second through holes are arranged on a first straight line parallel to the x-axis direction, and the plurality of the third through holes are arranged on a second straight line not parallel to the x-axis direction, and the intersection point of the first straight line and the second straight line may be located at the center of gravity of the fixed panel.

[0018] In a plasma ashing device, the fixed panel comprises a plurality of the second through holes and the third through holes, wherein the plurality of the second through holes are arranged on a first straight line parallel to the x-axis direction, and the plurality of the third through holes are arranged on a second straight line not parallel to the x-axis direction, and the intersection point of the first straight line and the second straight line may be located at the center of gravity of the fixed panel.

[0019] In a plasma ashing device, the rotating part may include a first rotating part that rotates by directly receiving rotational kinetic energy in conjunction with the power transmission part, and a second rotating part that rotates by indirectly receiving rotational kinetic energy connected to the first rotating part by a belt.

[0020] In a plasma ashing device, the vertical travel distance per unit time of the lifting and lowering unit can be directly proportional to the rotational angular frequency of the rotating part.

[0021] In a plasma ashing device, the vertical travel distance per unit time of the lifting / lowering unit can be directly proportional to tan(a) and the effective diameter value of the rotating part.

[0022] (Here, 'a' represents the acute angle formed by the screw thread meeting the cross-section obtained by cutting the rotating part in the xy-plane, and the effective diameter value represents the average of the maximum and minimum diameter values ​​of a circle on the surface of the rotating part, assuming the rotation axis of the rotating part is the center of the circle.)

[0023] In a plasma ashing device, the motor receives power and converts electrical energy into rotational kinetic energy, and the feedback system measures the output position of the motor and provides a feedback signal to the control circuit, and the control circuit can adjust at least one of the position, speed, or torque of the motor based on the feedback signal received from the feedback system.

[0024] In a plasma ashing device, the first rotating part, the second rotating part, and the belt can rotate in the same direction.

[0025] In a plasma ashing device, the rotating part may include a first rotating part coupled to the power transmission part and a second rotating part that rotates by receiving the rotational kinetic energy of the first rotating part, and the lifting / lowering unit may include a plurality of shafts that support the wafer chuck, and the plurality of shafts, the first rotating part, and the second rotating part may be characterized in that they are not arranged on the same plane with respect to their respective central axes.

[0026] In a plasma ashing device, the rotating part may be detachable.

[0027] In a plasma ashing device, the control circuit may include a controller that sets at least one of a height or a position and transmits a control signal to the servo motor, and software that controls the lifting and lowering unit according to parameters set through a user interface.

[0028] In the plasma ashing device, the servo motor may further include an encoder.

[0029] In a plasma ashing device, the vertical travel distance per unit time of the lifting and lowering unit may be directly proportional to the product of the rotational angular frequency of the rotating part and the pitch value, which is the spacing of the plurality of screw threads.

[0030] In a plasma ashing device, the lifting and lowering unit can be moved vertically in units of less than 10 μm. Effects of the invention

[0031] As described above, according to the present embodiment, by controlling the power of the servo motor, the height of the wafer chuck can be finely adjusted to a level corresponding to the stacking height of the die chip.

[0032] According to the present embodiment, the height of the wafer chuck can be controlled more finely by optimizing the pitch, which is the spacing of the screw threads of the rotating part.

[0033] According to the present embodiment, a plasma ashing device capable of uniformly ashing the photoresist by finely adjusting the height of the wafer chuck can be provided. Brief explanation of the drawing

[0034] FIG. 1 is a side view of a plasma ashing device according to one embodiment. FIG. 2 is a cross-sectional view showing the y-axis direction cross-section of a plasma ashing device according to one embodiment. FIG. 3 is a cross-sectional view illustrating the AA' cross section of a plasma ashing device according to one embodiment. FIG. 4 is an enlarged view showing B of a plasma ashing device according to one embodiment. Specific details for implementing the invention

[0035] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the present invention, detailed descriptions of related known components or functions are omitted if it is determined that such detailed descriptions may obscure the essence of the invention.

[0036] In addition, terms such as first, second, a, b, etc., may be used when describing the components of the present invention. These terms are intended merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by such terms. Where it is stated that a component is "connected," "combined," or "connected" to another component, it should be understood that while the component may be directly connected or connected to the other component, another component may also be "connected," "combined," or "connected" between the components.

[0037] FIG. 1 is a side view of a plasma ashing device (100) according to one embodiment.

[0038] Referring to FIG. 1, a plasma ashing device (100) may include a wafer chuck (200), a lifting / lowering unit (300) that supports and vertically moves the wafer chuck (200), a rotating part (400) that rotates a plurality of screw threads (410) to vertically move the lifting / lowering unit (300), and a power transmission part (500) that receives power, converts electrical energy into rotational kinetic energy, and transmits the converted rotational kinetic energy to the rotating part (400).

[0039] The plasma ashing device (100) includes a wafer chuck (200), a lifting / lowering unit (300), a rotating part (400), and a power transmission part (500), so as to not only stably fix the wafer but also finely adjust the height of the wafer chuck (200) to the level of the stacking height of the die chip.

[0040] A die chip can refer to a small semiconductor device individually cut from a semiconductor wafer. A die chip can represent the most basic unit of a semiconductor device, and it may house integrated electron components including transistors, diodes, and memory cells.

[0041] A wafer chuck (200) can refer to a structure that stably supports a wafer to prevent movement or shaking of the wafer during the plasma ashing process, and through such stable support of the wafer, it is possible to enable uniform ashing of the wafer surface.

[0042] The lifting / lowering unit (300) may refer to a structure that can adjust the position of the wafer chuck (200) according to various process conditions by moving the wafer chuck (200) vertically, and can make plasma ashing more uniform through precise vertical movement.

[0043] The rotating part (400) may refer to a structure that moves the lifting / lowering unit (300) vertically by rotating a plurality of screw threads (410), and by arranging the screw threads (410) at regular intervals, the vertical movement of the lifting / lowering unit (300) can be uniformly controlled, and by optimizing the pitch value, which is the spacing of the screw threads (410), it is possible to enable precise positioning of the fine wafer.

[0044] The power transmission unit (500) may represent a structure that converts electrical energy into rotational kinetic energy and transmits it to the rotation unit (400) to control the movement of the lifting / lowering unit (300), and through the efficient energy conversion of the power transmission unit (500), the overall efficiency of the ashing process of the plasma ashing device (100) can be improved.

[0045] In the plasma ashing device (100), the power transmission unit (500) includes a servo motor (510), and the servo motor (510) may include a motor, a feedback system, and a control circuit. However, it is not limited thereto, and may include various motors, configurations, or circuits within the scope of achieving the purpose of the present invention.

[0046] A servo motor (510) may refer to a motor having a structure that can be accurately controlled through feedback or error correction when moving a device to a specific position required by the system or operating it at a specific speed or torque.

[0047] A motor can refer to a device that converts electrical energy into kinetic energy to move in order to actually transmit power.

[0048] A feedback system refers to a system that detects the position, speed, or other status of a motor and returns this information to the control circuit for adjustment to achieve a desired goal. When the motor is operating, the feedback system can check the current position, compare it with the target position, and provide information to the control circuit.

[0049] For example, in a servo motor (510), the feedback system may include position feedback that detects the current position of the motor and compares it with a target position.

[0050] In a feedback system, position can include absolute position, relative position, angle, and position error.

[0051] Absolute position refers to a value measured from a reference point defined as the initial position or zero position, and, for example, can refer to the total angle rotated by the motor.

[0052] Relative position can refer to a value measuring the change from the current position rather than a reference point, and, for example, can mean a change of a specific angle from the current position.

[0053] Angle refers to the measured value of the angle of rotation of the motor's rotation axis, and the angle can be accurately measured through an encoder.

[0054] Position error can refer to the difference between the target position and the actual position, and for example, if the target position is 180 degrees and the actual position is 175 degrees, the error can be defined as 5 degrees.

[0055] In the plasma ashing device (100), the servo motor (510) may include at least one of an encoder, a resolver, or a Hall sensor.

[0056] Encoders can enable precise position control by providing position feedback. For example, incremental encoders can measure relative position by generating a pulse with every rotation, while absolute encoders can measure absolute position by assigning a unique code to each position.

[0057] Resolvers detect position using an analog method and can be used in high-temperature and high-vibration environments, while Hall sensors can detect rotational position using magnetic fields.

[0058] As another example, the feedback system in the servo motor (510) may include speed feedback that detects the rotational speed of the motor and transmits it to the control circuit.

[0059] In the plasma ashing device (100), the servo motor (510) may include a tachometer.

[0060] A tachometer refers to a device that measures the rotational speed of a device in real time, and it can enable accurate speed control by providing speed feedback.

[0061] As another example, in a servo motor (510), the feedback system may include torque feedback that detects the torque generated by the motor and returns it to the control circuit.

[0062] As another example, in a servo motor (510), the feedback system can reduce the error between the actual value and the target value through feedback information.

[0063] In the plasma ashing device (100), the servo motor (510) may include a feedback loop, and the feedback loop can correct the position error of the motor in real time.

[0064] A feedback loop may refer to a process of measuring the output of a feedback system and converting it into an input to adjust and control the operation of the feedback system, and may include at least one of an input, an output, a sensing device, a controller, or an actuator.

[0065] A control circuit may refer to a configuration that controls the position, speed, or torque of a motor based on information received from a feedback system.

[0066] The plasma ashing device (100) may have a power transmission unit (500) that includes a servo motor (510), thereby enabling fine vertical movement control of a lifting / lowering unit (300) for adjusting the height of a wafer chuck (200), and can correct errors that may occur during vertical movement of the wafer chuck (200) in real time.

[0067] In the plasma ashing device (100), the lifting and lowering unit (300) may include a shaft (310) that supports the wafer chuck (200) and a fixed panel (320) that fixes the shaft (310) in a vertical direction and moves vertically through the rotation of the plurality of screw threads (410).

[0068] A through hole may be formed in the fixed panel (320), and at least one of the shaft (310) or the rotating part (400) may be inserted into or penetrated through the through hole to fix its position. Additionally, the fixed panel (320) may move vertically through the rotational energy of the rotating part (400), and when moving vertically, force may be applied to the fixed shaft (310) in the upper or lower direction so that the shaft (310) can apply force to the lower part of the wafer chuck (200).

[0069] FIG. 2 is a cross-sectional view showing the y-axis direction cross-section of a plasma ashing device (100) according to one embodiment.

[0070] Referring to FIG. 2, in the plasma ashing device (100), the shaft (310) may include a bellows (330) on its outer surface.

[0071] The bellows (330) is made of a flexible structure and can have a structure that contracts or expands depending on changes in the external environment.

[0072] Plasma contains high-energy ions and electrons that can directly collide with equipment surfaces, causing physical damage. Such damage can accelerate device wear and shorten its lifespan. Furthermore, if contaminants generated during the plasma process are exposed to the equipment, they can cause contamination in subsequent processes, thereby degrading the quality and reliability of semiconductor devices.

[0073] In the plasma ashing device (100), the shaft (310) includes a bellows (330) on its outer surface to protect the device from high-energy ions and electrons leaking during the plasma ashing process, thereby preventing wear of the plasma ashing device (100) and preventing contamination, which minimizes contamination in subsequent processes, thereby ensuring the quality and reliability of the semiconductor device.

[0074] Additionally, the bellows (330) can expand or contract according to changes in internal or external pressure to precisely control the vertical movement of the shaft (310).

[0075] In the plasma ashing device (100), the lifting and lowering unit (300) may further include a weight (340).

[0076] In the case of the plasma ashing device (100), it is necessary to fix the wafer in an accurate position with a constant pressure so that the wafer surface is uniformly exposed to the plasma. The weight (340) can be fixed by setting the center of gravity (324) of the wafer chuck (200) so that the wafer does not move or shake during the ashing process, thereby providing uniform pressure to the contact surface of the wafer to accurately position the wafer on the wafer chuck (200) and uniformly expose the plasma to the wafer surface.

[0077] FIG. 3 is a cross-sectional view showing the AA' cross section of a plasma ashing device (100) according to one embodiment.

[0078] Referring to FIG. 1, a cross-section A-A' of a plasma ashing device (100) is shown, and referring to FIG. 3, a first through hole (321), a second through hole (322), and a third through hole (323) formed in a fixed panel (320) are shown.

[0079] In the plasma ashing device (100), the fixed panel (320) may include a first through hole (321) formed to allow the weight (340) to pass through, a second through hole (322) formed to allow the shaft (310) to be fixed, and a third through hole (323) formed to allow the rotating part (400) to be inserted and rotate.

[0080] A through hole refers to a hole drilled by penetrating a specific object, and can be used interchangeably with terms such as through hole, penetration hole, penetration opening, bore, piercing hole, and hole.

[0081] The fixed panel (320) may include a first through hole (321) so that the weight (340) does not come into contact with or collide with the fixed panel (320) when the lifting / lowering unit (300) moves vertically, thereby allowing the lifting / lowering unit (300) to move freely and preventing wear caused by friction or contact between the components of the plasma ashing device (100), and may include the first through hole (321) with a cross-sectional area larger than the cross-sectional area of ​​the weight (340).

[0082] In the plasma ashing device (100), the shaft (310) and the rotating part (400) include a cylindrical structure, and the diameter of the cross-section of the shaft (310) cut in the xy plane is larger than the diameter of the cross-section of the rotating part (400) cut in the xy plane, and the diameter of the second through hole (322) is larger than the diameter of the third through hole (323).

[0083] The shaft (310) and the rotating part (400) can be inserted and fixed in the vertical direction of the fixed panel (320), including a cylindrical structure, and by this fixing method, noise and vibration of the device can be minimized during the vertical movement of the lifting / lowering unit (300).

[0084] Additionally, referring to FIG. 3, a second through hole (322) is formed in the fixed panel (320) with a diameter larger than that of the third through hole (323), so that a shaft (310) having a diameter larger than that of the rotating part (400) and the rotating part (400) can be inserted into the third through hole (323) and the second through hole (322), respectively, and a wide cross-sectional area is secured so that the shaft (310) can stably support the wafer chuck (200) to adjust the horizontal balance of the wafer chuck (200), and a force greater than the pressure is applied to the wafer chuck (200) to efficiently perform support and vertical movement of the wafer chuck (200).

[0085] Additionally, referring to FIG. 3, the fixed panel (320) in the plasma ashing device (100) may include a plurality of the second through hole (322) and the third through hole (323).

[0086] A fixed panel (320) may include multiple second through holes (322) and third through holes (323), so that multiple shafts (310) and multiple rotating parts (400) can be inserted into each through hole. When multiple shafts (310) are fixed by the fixed panel (320) and move vertically, more force can be transmitted to the wafer chuck (200), and horizontal adjustment of the wafer chuck (200) may be possible. Additionally, multiple rotating parts (400) may rotate to induce the lifting / lowering unit (300) to move in the vertical direction, thereby transmitting a quantitatively greater rotational kinetic energy to the lifting / lowering unit (300), and the lifting / lowering unit (300) can easily perform vertical movement by receiving more vertical kinetic energy.

[0087] Additionally, referring to FIG. 3, a plurality of the second through holes (322) are arranged on a first straight line parallel to the x-axis direction, and a plurality of the third through holes (323) are arranged on a second straight line not parallel to the x-axis direction, and the intersection point of the first straight line and the second straight line can be located at the center of gravity (324) of the fixed panel (320).

[0088] As shown in FIG. 3, a plurality of second through holes (322) and a plurality of third through holes (323) are arranged on different straight lines as described above, and each through hole is arranged so that the intersection point where each straight line meets is located at the center of gravity (324) of the fixed panel (320), so that a plurality of shafts (310) and a plurality of rotating parts (400) can be inserted into the corresponding through holes, thereby improving the support force for the wafer chuck (200) in the x-axis direction and the y-axis direction, and thereby enabling fine horizontal adjustment of the wafer chuck (200).

[0089] In the plasma ashing device (100), the rotating part (400) may include a first rotating part (401) that rotates by directly receiving the rotational kinetic energy in conjunction with the power transmission part (500), and a second rotating part (402) that rotates by indirectly receiving the rotational kinetic energy connected to the first rotating part (401) by a belt (420).

[0090] Referring to FIG. 1, the first rotating part (401) can directly receive rotational kinetic energy transmitted from the power transmission part (500) and rotate through the received rotational kinetic energy, and the second rotating part (402) can be connected to the first rotating part (401) through a belt (420), and the first rotating part (401) can sequentially transmit rotational kinetic energy to the belt (420), and the belt (420) can transmit rotational kinetic energy to the second rotating part (402) to induce rotation of the second rotating part (402), and the first rotating part (401), the belt (420), and the second rotating part (402) can rotate in the same direction.

[0091] That is, the second rotating part (402) does not directly receive rotational kinetic energy from the power transmission part (500), but indirectly receives rotational kinetic energy through the first rotating part (401) and the belt (420), so that it can rotate clockwise when the first rotating part (401) rotates clockwise, and counterclockwise when the first rotating part (401) rotates counterclockwise.

[0092] Figure 4 shows part B of the first rotating part (401) shown in Figure 1.

[0093] Referring to FIG. 1 and FIG. 4, the vertical travel distance per unit time of the lifting / lowering unit (300) in the plasma ashing device (100) can be directly proportional to the rotational angular frequency of the rotating part (400), can be directly proportional to tan(a) and the effective diameter value of the rotating part (400), and can be directly proportional to the product of the rotational angular frequency of the rotating part (400) and the pitch value, which is the spacing of the plurality of screw threads (410).

[0094] (Here, a represents the acute angle formed by the screw thread (410) meeting the cross-section of the rotating part (400) cut in the xy plane, and the effective diameter value represents the average of the maximum and minimum diameter values ​​of a circle on the surface of the rotating part (400), assuming the rotation axis of the rotating part (400) is the center of the circle.)

[0095] The vertical travel distance per unit time of the lifting / lowering unit (300) can have the same value as the vertical travel speed of the wafer chuck (200).

[0096] Referring to FIG. 1, the first rotating part (401) can be coupled with the power transmission part (500), and the first rotating part (401) rotates by receiving rotational kinetic energy of the power transmission, so the rotational angular frequency of the first rotating part (401) can have the same value as the rotational angular frequency of the power transmission part (500).

[0097] The plasma ashing device (100) can control the movement distance finely by controlling variables that have a relationship directly proportional to the vertical movement distance per unit time of the lifting / lowering unit (300).

[0098] For example, the plasma ashing device (100) can finely adjust the rotational angular vibration frequency of the power transmission unit (500) through the servo motor (510), and can finely set the distance unit of the vertical movement of the lifting / lowering unit (300) by optimizing the pitch value, tan(a), and effective diameter value of the rotating unit (400), so that the lifting / lowering unit (300) can be vertically moved in a distance unit of less than 10 μm.

[0099] The plasma ashing device (100) can be vertically moved by the lifting and lowering unit (300) in units of less than 10 μm, so that the photoresist can be uniformly ashed even if the stacking height of the die chip increases.

[0100] In addition, the plasma ashing device (100) can uniformly perform ashing of the photoresist compared to the conventional plasma ashing device (100), so that the stacking height of the die chip can be formed uniformly, and the degradation and loss of the die chip function can be prevented, thereby solving the problem of failure of the die chip and the wafer equipment including it.

[0101] Referring to FIG. 3, in a plasma ashing device (100), the rotating part (400) includes a first rotating part (401) coupled to the power transmission part (500) and a second rotating part (402) that rotates by receiving rotational kinetic energy from the first rotating part (401), and the lifting / lowering unit (300) includes a plurality of shafts (310) that support the wafer chuck (200), and the plurality of shafts (310), the first rotating part (401), and the second rotating part (402) are not arranged on the same plane with respect to their respective center axes, thereby providing a structure that can stably support the wafer chuck (200) in the x-axis and y-axis directions.

[0102] In addition, the rotating part (400) in the plasma ashing device (100) may be detachable, and the user may control the setting values ​​such as the screw thread (410) pitch, tan (a), and effective diameter value of the rotating part (400) to match the control level intended by the user, such as the rotational resolution of the power transmission part (500) and the wafer height adjustment speed, thereby providing an optimized height adjustment function of the wafer chuck (200). Explanation of the symbols

[0103] 100: Plasma ashing device 200: Wafer Chuck 300: Lift / Lower Unit 310: Shaft 320: Fixed panel 321: 1st penetration hole 322: Second penetration hole 323: 3rd Penetrating Hole 324: Center of gravity 330: Bellows 340: Weight 400: Rotating part 401: 1st rotating part 402: Second rotating part 410: Screw thread 420: Belt 500: Power transmission unit 510: Servo motor

Claims

Claim 1 A plasma ashing device comprising: a wafer chuck; a lifting / lowering unit that supports the wafer chuck and moves it vertically; a rotating part that moves the lifting / lowering unit vertically by rotating a plurality of screw threads; and a power transmission part that receives power, converts electrical energy into rotational kinetic energy, and transmits the converted rotational kinetic energy to the rotating part; wherein the lifting / lowering unit comprises: a shaft that supports the wafer chuck; and a fixed panel that fixes the shaft in a vertical direction and moves it vertically through the rotation of the plurality of screw threads; and wherein the lifting / lowering unit further comprises a weight. Claim 2 A plasma ashing device according to claim 1, wherein the plurality of screw threads are arranged at regular intervals on the rotating part. Claim 3 A plasma ashing device according to claim 1 or claim 2, wherein the power transmission unit includes a servo motor, and the servo motor includes a motor, a feedback system, and a control circuit. Claim 4 delete Claim 5 A plasma ashing device according to claim 1, wherein the shaft includes a bellows on its outer surface. Claim 6 delete Claim 7 A plasma ashing device according to claim 1, wherein the fixed panel comprises: a first through hole formed to allow the weight to pass through; a second through hole formed to fix the shaft; and a third through hole formed to allow the rotating part to be inserted and rotate. Claim 8 A plasma ashing device according to claim 7, wherein the shaft and the rotating part include a cylindrical structure, the diameter of the cross-section of the shaft cut in the xy plane is greater than the diameter of the cross-section of the rotating part cut in the xy plane, and the diameter of the second through hole is greater than the diameter of the third through hole. Claim 9 A plasma ashing device according to claim 7, wherein the fixed panel comprises a plurality of the second through holes and the third through holes, wherein the plurality of the second through holes are arranged on a first straight line parallel to the x-axis direction, the plurality of the third through holes are arranged on a second straight line not parallel to the x-axis direction, and the intersection point of the first straight line and the second straight line is located at the center of gravity of the fixed panel. Claim 10 A plasma ashing device according to claim 1 or claim 2, wherein the rotating part comprises: a first rotating part that rotates by directly receiving the rotational kinetic energy in conjunction with the power transmission part; and a second rotating part that rotates by indirectly receiving the rotational kinetic energy connected together with the first rotating part by a belt.

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