Semiconductor process chamber and lower electrode potential control method

Abstract

The application provides a semiconductor process chamber, which comprises a cavity, an upper electrode assembly, a susceptor and a lower electrode assembly. The susceptor is arranged in the cavity and used for carrying a wafer. The upper electrode assembly is used for providing a radio frequency signal to a process gas in the cavity to excite the process gas in the cavity to form a plasma. The susceptor has a lower electrode inside. The lower electrode assembly is connected between the lower electrode and a ground terminal and used for adjusting an impedance connected between the lower electrode and the ground terminal to keep the lower electrode at a preset potential. In the application, the lower electrode assembly can adjust a radio frequency voltage division ratio between upper and lower impedances of the lower electrode by adjusting the impedance connected between the lower electrode and the ground terminal, so that the potential of the lower electrode can be kept at a required preset potential without introducing new radio frequency power. The radio frequency power has a reduced influence on plasma damage to the wafer and on plasma distribution above the wafer. The application also provides a method for controlling a lower electrode potential.

Description

[0001] This application is a divisional application of patent application No. 2021114207479, filed on November 26, 2021, entitled "Semiconductor Process Chamber and Lower Electrode Potential Control Method". Technical Field

[0002] This invention relates to the field of semiconductor process equipment, and more specifically, to a semiconductor process chamber and a method for controlling the lower electrode potential implemented by the semiconductor process equipment. Background Technology

[0003] In the field of semiconductor manufacturing, as the geometric dimensions of electronic devices continue to shrink and the density of devices continues to increase, the feature sizes in semiconductor processes are becoming increasingly smaller (such as 7nm, 5nm and lower technology bands), and the aspect ratios of film patterns are becoming increasingly larger (such as 10:1, 20:1 or higher). Ordinary deposition methods can no longer meet the needs of next-generation products. Atomic layer deposition (ALD) has become a widely adopted new thin film deposition method.

[0004] The self-limited surface reaction mechanism of atomic layer deposition (ALD) technology determines that ALD has advantages such as excellent three-dimensional conformality (i.e., the morphology of the newly deposited film is the same as the initial morphology of the substrate), large-area uniformity, and precise film thickness control, making it a leader in the field of microelectronics and nanodevice manufacturing and a very important coating technology in the integrated circuit industry.

[0005] Atomic layer deposition (ALD) typically requires the reaction of two gases to generate the desired film. First, a first reactive gas is introduced into the process chamber, allowing a sufficient amount of the first reactive gas to be adsorbed onto the wafer surface. Then, a purge gas is introduced into the process chamber to remove any excess first reactive gas. Subsequently, a second reactive gas is introduced into the reaction chamber, and radio frequency pulses are used to generate plasma from the second reactive gas, which then reacts with the first reactive gas adsorbed on the wafer surface to form the deposited material film.

[0006] In atomic layer deposition (ALD) processes, two gas activity enhancement methods are generally used to improve the activity of reactant gases: heating (the process is called thermal ALD) and plasma enhancement (the process is called plasma enhanced atomic layer deposition (PEALD)). Among them, plasma enhanced atomic layer deposition is widely used because it has a lower process temperature and higher atomic activity.

[0007] However, when using existing plasma-enhanced atomic layer deposition (ALD) chambers for ALD processes, uneven film thickness on the wafer surface often occurs, affecting product yield.

[0008] Therefore, how to provide a semiconductor process chamber that can improve the uniformity of film thickness on the wafer surface has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The present invention aims to provide a semiconductor process chamber that can improve the uniformity of film thickness on the wafer surface and a method for controlling the lower electrode potential through the semiconductor process chamber. The semiconductor process chamber can reduce the plasma damage to the wafer caused by radio frequency power and the influence on the plasma distribution above the wafer, and improve the uniformity of the film thickness deposited on the wafer surface.

[0010] To achieve the above objectives, as one aspect of the present invention, a semiconductor process chamber is provided, comprising a cavity, an upper electrode assembly, a base, and a lower electrode assembly. The base is disposed in the cavity for supporting a wafer. The upper electrode assembly is used to provide a radio frequency signal to the process gas in the cavity to excite the process gas in the cavity to form plasma. The base has a lower electrode inside. The lower electrode assembly is connected between the lower electrode and a ground terminal and is used to adjust its own impedance connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode at a preset potential.

[0011] Optionally, the lower electrode assembly includes a potential adjustment device and a potential determination device. The potential determination device is used to determine the current preset potential based on the number of film deposition cycles of the wafer. The potential adjustment device is used to adjust its own impedance connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode at the preset potential determined by the potential determination device.

[0012] Optionally, the potential determining device is used to determine the preset potential as a first preset potential when the number of film deposition cycles is less than or equal to 25, to determine the preset potential as a second preset potential when the number of film deposition cycles is greater than 25 and less than or equal to 50, to determine the preset potential as a third preset potential when the number of film deposition cycles is greater than 50 and less than or equal to 80, and to determine the preset potential as a fourth preset potential when the number of film deposition cycles is greater than 80, wherein the first preset potential is less than the second preset potential, less than the third preset potential, and less than the fourth preset potential.

[0013] Optionally, the potential adjustment device includes a control unit, a potential detection unit, and an impedance adjustment unit. The first end of the impedance adjustment unit is connected to the lower electrode, and the second end of the impedance adjustment unit is grounded. The potential detection unit is used to detect the potential at the first end of the impedance adjustment unit to obtain a potential feedback signal. The control unit is used to control the impedance adjustment unit to adjust its own impedance according to the potential feedback signal and the preset potential determined by the potential determination device, so as to maintain the potential of the lower electrode at the preset potential.

[0014] Optionally, the control unit is specifically used to control the impedance of the impedance adjustment unit to change by a preset adjustment amount towards a first trend, and to determine whether the potential difference between the potential of the lower electrode and the preset potential decreases based on the potential feedback signal. If the potential difference decreases, the control unit continues to control the impedance of the impedance adjustment unit to change towards the first trend until the potential difference is zero; if the potential difference does not decrease, the control unit changes the impedance of the impedance adjustment unit towards a second trend until the potential difference is zero; the first trend is opposite to the second trend.

[0015] Optionally, the impedance adjustment unit includes at least one adjustable component and at least one adjustment drive unit corresponding to the adjustable component. The adjustable component is connected between the first end and the second end of the impedance adjustment unit, and the impedance of the adjustable component is adjustable. The control unit is used to control the adjustment drive unit to adjust the impedance of the adjustable component.

[0016] Optionally, the impedance adjustment unit includes a fixed inductor, an adjustable capacitor, and a capacitor adjustment drive unit. The fixed inductor and the adjustable capacitor are connected in series between the first and second ends of the impedance adjustment unit. The control unit is used to control the capacitor adjustment drive unit to adjust the capacitance value of the adjustable capacitor.

[0017] Optionally, the potential detection unit includes a first voltage divider element, a second voltage divider element, and a signal processor. The first end of the first voltage divider element is connected to the first end of the impedance adjustment unit, the second end of the first voltage divider element is connected to the first end of the second voltage divider element, the second end of the second voltage divider element is grounded, and the signal processor is used to detect the potential signal at the first end of the second voltage divider element and send the potential feedback signal that reflects the amplitude of the potential signal to the control unit.

[0018] The control unit is used to control the impedance adjustment unit to adjust its own impedance according to the potential feedback signal, the impedance of the first voltage divider element and the impedance of the second voltage divider element, so as to maintain the potential of the lower electrode at the preset potential.

[0019] Optionally, the first voltage divider element includes a first fixed capacitor, and the second voltage divider element includes a second fixed capacitor.

[0020] Optionally, the control unit is a digital signal processor or a microcontroller.

[0021] As a second aspect of the present invention, a method for controlling the lower electrode potential is provided, applied to the aforementioned semiconductor process chamber, the method comprising:

[0022] Adjust the impedance of the lower electrode assembly connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode at a preset potential.

[0023] Optionally, adjusting the impedance of the lower electrode assembly connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode above a preset potential further includes:

[0024] The current preset potential is determined based on the number of film deposition cycles of the wafer.

[0025] Optionally, adjusting the impedance of the lower electrode assembly connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode at the preset potential specifically includes:

[0026] A potential feedback signal is obtained by detecting the potential at the first terminal of the impedance adjustment unit;

[0027] The impedance adjustment unit adjusts its own impedance according to the potential feedback signal and the preset potential, so as to maintain the potential of the lower electrode at the preset potential.

[0028] Optionally, the impedance adjustment unit adjusts its own impedance according to the potential feedback signal and the preset potential to maintain the potential of the lower electrode at the preset potential, specifically including:

[0029] The impedance of the impedance adjustment unit is controlled to change by a preset adjustment amount towards a first trend, and the potential difference between the potential of the lower electrode and the preset potential is determined based on the potential feedback signal.

[0030] If the potential difference decreases, the impedance of the impedance adjustment unit is controlled to continue changing towards the first trend until the potential difference is zero; if the potential difference does not decrease, the impedance of the impedance adjustment unit is controlled to change towards the second trend until the potential difference is zero.

[0031] The first trend is the opposite of the second trend.

[0032] In the semiconductor process chamber provided by this invention, the lower electrode assembly of the semiconductor process chamber can adjust the ratio between the impedance between the upper and lower electrodes and its own impedance by adjusting the impedance connected between the lower electrode and the ground terminal. This adjusts the RF voltage division ratio between the upper and lower impedances of the lower electrode, thereby regulating the potential on the lower electrode. This maintains the potential of the lower electrode at the required preset potential without introducing new RF power, thereby reducing the plasma damage to the wafer caused by RF power and the impact on the plasma distribution above the wafer, and improving the uniformity of the film thickness deposited on the wafer surface. Attached Figure Description

[0033] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0034] Figure 1 This is a schematic diagram of the structure of a semiconductor process chamber provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the potential adjustment device in the semiconductor process chamber provided in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the potential adjustment device in a semiconductor process chamber according to another embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the potential detection unit in the semiconductor process chamber provided in an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of the structure of a potential detection unit in a semiconductor process chamber according to another embodiment of the present invention;

[0039] Figure 6 This is a flowchart illustrating the lower electrode potential control method provided in an embodiment of the present invention;

[0040] Figure 7 This is a flowchart illustrating a lower electrode potential control method provided in another embodiment of the present invention;

[0041] Figure 8 This is a flowchart illustrating a lower electrode potential control method provided in another embodiment of the present invention;

[0042] Figure 9 This is a flowchart illustrating some steps of the lower electrode potential control method provided in this embodiment of the invention. Detailed Implementation

[0043] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0044] In existing plasma-enhanced atomic layer deposition (PALD) process chambers, power supplies on the upper and lower sides of the chamber typically provide radio frequency (RF) signals to the electrodes on the upper and lower sides of the process gas, respectively. This generates an electromagnetic field at the location of the process gas, exciting it to form plasma. Specifically, one RF power supply transmits RF power to the upper electrode via a matching adapter, while another RF power supply is connected to the lower electrode in the substrate (used to support the wafer) via a matching adapter to control the potential on the lower electrode. This creates an electric field between the upper and lower electrodes, thereby exciting the process gas above the wafer to form plasma.

[0045] However, the inventors of this invention discovered in their research that the radio frequency power supplied to the upper electrode by a radio frequency power source itself can cause plasma damage to the wafer surface. Connecting another radio frequency power source to control the lower electrode potential further aggravates the plasma damage to the wafer. Moreover, excessive radio frequency power can affect the distribution of plasma in the chamber, thereby affecting the uniformity of film formation.

[0046] To address the aforementioned technical problems, as one aspect of the present invention, a semiconductor process chamber is provided, such as... Figure 1 As shown, the semiconductor process chamber includes a cavity 100, an upper electrode assembly, a base 300, and a lower electrode assembly 400. The base 300 is disposed in the cavity 100 and is used to support the wafer. The upper electrode assembly is used to provide radio frequency signals to the process gas in the cavity 100 to excite the process gas in the cavity 100 to form plasma. The base 300 has a lower electrode 310 inside. The lower electrode assembly 400 is connected between the lower electrode 310 and the ground terminal and is used to adjust its impedance between the lower electrode 310 and the ground terminal to maintain the potential of the lower electrode 310 at a preset potential.

[0047] In the semiconductor process chamber provided by the present invention, the objects between the upper and lower electrodes (e.g., plasma, coatings accumulated in the chamber during the process), the lower electrode 310, and the lower electrode assembly 400 are connected in series between the upper electrode assembly and the ground terminal. The lower electrode assembly 400 of the semiconductor process chamber can adjust the ratio between the impedance between the upper and lower electrodes and its own impedance by adjusting the impedance of itself connected between the lower electrode 310 and the ground terminal, so as to adjust the radio frequency voltage division ratio between the upper and lower impedances of the lower electrode, thereby adjusting the potential on the lower electrode 310. In this way, without introducing new radio frequency power (the lower electrode assembly 400 is a passive device, and only the upper electrode assembly provides radio frequency power to the cavity 100), the potential of the lower electrode 310 is maintained at the required preset potential, thereby reducing the plasma damage to the wafer caused by radio frequency power and the impact on the plasma distribution above the wafer, and improving the uniformity of the thickness of the film deposited on the wafer surface.

[0048] As an optional embodiment of the present invention, such as Figure 1 As shown, the semiconductor process chamber may further include a shield 500. The upper electrode assembly includes a radio frequency (RF) power supply 210, a matching device 220, an RF feeder 240, and an upper electrode connected in sequence. The upper electrode is located at the top opening of the chamber 100 and is positioned opposite the lower electrode 300. The shield 500 is located on top of the chamber 100 and the upper electrode to prevent RF energy leakage within the chamber 100. The RF power supply 210 and the matching device 220 are located outside the chamber 100 and the shield 500. The matching device 220 is connected to the lower electrode via the RF feeder 240. The RF power supply 210 transmits RF power to the upper electrode through the matching device 220 and the RF feeder 240, thereby forming plasma between the upper and lower electrodes 310 to process the wafer surface.

[0049] Optionally, such as Figure 1 As shown, the semiconductor process chamber also includes an air intake assembly (not shown) and a screen 230 (showerhead). The screen 230 is disposed at the top opening of the chamber 100, and the air intake assembly is used to uniformly release process gas into the chamber 100 through the screen 230.

[0050] Preferably, such as Figure 1 As shown, the screen 230 can be reused as the upper electrode of the upper electrode assembly; that is, the RF power supply 210 is used to transfer RF power to the screen 230 through the matching unit 220 and the RF feeder 240, so that plasma is formed between the screen 230 and the lower electrode 310. Optionally, as Figure 1 As shown, a heating plate 250 is provided on the top of the screen 230 to heat the screen 230 and increase the temperature of the process gas flowing through the screen 230.

[0051] Optionally, such as Figure 1 As shown, the semiconductor process chamber may further include a confinement ring 600, an insulating ring 700, and a remote plasma source 900 (RPS). The confinement ring 600 is disposed around the base 300 to confine the plasma above the base 300 so that the plasma can effectively act on the wafer. The insulating ring 700 is disposed at the top opening edge of the chamber 100 to ensure insulation between the screen 230 (upper electrode) and the grounded chamber 100, thereby ensuring the potential accuracy of the upper electrode. The remote plasma source 900 is used to provide plasma to the chamber 100 to clean the chamber 100 and remove residual process gases or reaction products in the chamber 100.

[0052] Optionally, such as Figure 1 As shown, the bottom of the cavity 100 has a vacuum pump port 800. The vacuum pump draws gas from the process chamber through the vacuum pump port 800 to control the gas pressure in the cavity 100 within the required range, so as to ensure the normal operation of the semiconductor process.

[0053] The material of the base 300 is not specifically limited in this embodiment of the invention. For example, the base 300 can be made of metal or ceramic. Optionally, the base 300 is also used to heat the wafer supported on it.

[0054] The present invention does not specifically limit the application scenarios of the semiconductor process chamber. For example, the semiconductor process chamber can be used in iontophoresis enhanced atomic layer deposition (PEALD) process, iontophoresis enhanced chemical vapor deposition (PECVD) process, or other semiconductor processes that use radio frequency power to excite process gas to form plasma.

[0055] The inventors of this invention also discovered in their research that during the processing of some wafers in a semiconductor process chamber, as the number of film deposition cycles increases (in some cases, the film layer on the wafer surface needs to undergo multiple cycles of reaction between process gases to form a deposition layer, eventually accumulating into a film layer of the required thickness), the thickness of the film layer deposited on the wafer also increases, causing the impedance of the film layer to change, which in turn causes the total radio frequency voltage of the object above the wafer to change, thereby affecting the film deposition quality on the wafer surface.

[0056] To solve the above-mentioned technical problems, as a preferred embodiment of the present invention, the lower electrode assembly 400 can automatically adjust the preset potential according to the number of film deposition cycles, so that the preset potential corresponds to the film thickness on the wafer surface in real time.

[0057] Specifically, such as Figure 1As shown, the lower electrode assembly 400 includes a potential adjustment device 410 and a potential determination device 420. The potential determination device 420 is used to determine the current preset potential based on the number of film deposition cycles of the wafer. The potential adjustment device 410 is used to adjust its impedance connected between the lower electrode 310 and the ground terminal to maintain the potential of the lower electrode 310 at the preset potential determined by the potential determination device 420.

[0058] In this embodiment of the invention, the lower electrode assembly 400 includes a potential adjustment device 410 and a potential determination device 420. The potential determination device 420 can determine the current preset potential based on the number of film deposition cycles of the wafer and send the preset potential to the potential adjustment device 410. This allows the passive potential adjustment device 410 to maintain the potential of the lower electrode 310 at the preset potential determined in real time by adjusting its own impedance. As a result, the potential on the lower electrode 310 is matched with the thickness of the film deposited on the wafer surface in real time, thereby ensuring the film deposition quality on the wafer surface and improving product yield.

[0059] As an optional embodiment of the present invention, the potential determination device 420 can be a device integrated into the control station of the semiconductor process equipment. For example, the potential determination device 420 can be an execution device in a recipe control station (used to control the semiconductor process in the semiconductor process chamber according to the menu). That is, when the recipe control station controls the semiconductor process chamber to perform multiple film deposition cycles on a single wafer according to the menu, the potential determination device 420 in the recipe control station determines in real time the potential of the lower electrode 310 (i.e., the preset potential) corresponding to the film thickness on the wafer surface according to the number of film deposition cycles, and sends the preset potential to the potential adjustment device 410.

[0060] In one optional embodiment of the present invention, the preset potential increases with the increase of the number of film deposition cycles (film thickness on the wafer surface). Specifically, the potential determining device 420 is used to determine the preset potential as a first preset potential when the number of film deposition cycles is less than or equal to 25, to determine the preset potential as a second preset potential when the number of film deposition cycles is greater than 25 and less than or equal to 50, to determine the preset potential as a third preset potential when the number of film deposition cycles is greater than 50 and less than or equal to 80, and to determine the preset potential as a fourth preset potential when the number of film deposition cycles is greater than 80. The first preset potential is less than the second preset potential, less than the third preset potential, and less than the fourth preset potential.

[0061] As an optional embodiment of the present invention, the first preset potential is 0V, the second preset potential is 50V, the third preset potential is 100V, and the fourth preset potential is 150V or greater. That is, in the initial stage of film deposition (the first 25 cycles), the film thickness on the wafer surface is small, and the potential of the lower electrode 310 needs to be kept at 0V to reduce the damage of radio frequency power to the wafer; during the 25 to 50 cycles, a film layer of a certain thickness is deposited on the wafer surface, and the lower electrode voltage can be slightly increased to improve the film quality, for example, the potential of the lower electrode 310 can be increased to 50V (this value cannot be too large, otherwise it will damage the wafer); during the 50 to 80 cycles, the lower electrode voltage can be increased again to 100V; after 80 cycles, a higher voltage is needed to improve the film quality, and the voltage can be increased to 150V or higher.

[0062] In other embodiments of the present invention, the lower electrode assembly 400 may also directly determine the current preset potential based on the thickness of the wafer surface film. For example, when the wafer surface film thickness is less than or equal to 25 Å, the preset potential is determined as the first preset potential; when the wafer surface film thickness is greater than 25 Å and less than or equal to 50 Å, the preset potential is determined as the second preset potential; when the wafer surface film thickness is greater than 50 Å and less than or equal to 80 Å, the preset potential is determined as the third preset potential; and when the wafer surface film thickness is greater than 80 Å, the preset potential is determined as the fourth preset potential. The first preset potential is less than the second preset potential, less than the third preset potential, and less than the fourth preset potential.

[0063] The embodiments of the present invention do not specifically limit the trend of the preset potential. For example, in some cases, the preset potential may always be a fixed value, or it may decrease as the number of film deposition cycles (film thickness on the wafer surface) increases.

[0064] As an optional embodiment of the present invention, such as Figure 2 As shown, the potential adjustment device 410 includes a control unit 421, a potential detection unit 422, and an impedance adjustment unit 423. The first end of the impedance adjustment unit 423 is connected to the lower electrode 310, and the second end of the impedance adjustment unit 423 is grounded. The potential detection unit 422 is used to detect the potential of the first end of the impedance adjustment unit 423 to obtain a potential feedback signal. The control unit 421 is used to control the impedance adjustment unit 423 to adjust its own impedance according to the potential feedback signal and the preset potential determined by the potential determination device 420, so as to maintain the potential of the lower electrode 310 at the preset potential.

[0065] It should be noted that the potential signal on the lower electrode 310 is an AC voltage signal. The potential feedback signal is used for the corresponding logic circuit in the control unit 421 to analyze the potential of the lower electrode 310. Therefore, the potential feedback signal must be a DC signal, and the magnitude of the DC potential feedback signal can reflect the amplitude of the potential signal on the lower electrode 310, so that the control unit 421 can compare the potential signal on the lower electrode 310 with the preset potential magnitude.

[0066] Optionally, such as Figure 2 As shown, the potential adjustment device 410 also includes a grounded housing (i.e., the structure shown in the box outside the control unit 421, potential detection unit 422 and impedance adjustment unit 423 in the figure). The control unit 421, potential detection unit 422 and impedance adjustment unit 423 are all disposed in the housing. The lower electrode 310 is connected to the port on the housing through a cable. The first end of the impedance adjustment unit 423 (i.e. the left end of the impedance adjustment unit 423 in the figure) is connected to the port, and the second end of the impedance adjustment unit 423 (i.e. the right end of the impedance adjustment unit 423 in the figure) is connected to the housing to achieve grounding.

[0067] To improve the efficiency of the potential adjustment device 410 in adjusting the potential of the lower electrode 310 to the target potential, in a preferred embodiment of the present invention, the control unit 421 is specifically used to control the impedance of the impedance adjustment unit 423 to change by a preset adjustment amount towards a first trend, and to determine whether the potential difference between the potential of the lower electrode 310 and the preset potential decreases based on the potential feedback signal. If the potential difference decreases, the control unit 423 continues to change its impedance towards the first trend until the potential difference is zero; if the potential difference does not decrease, the control unit 423 changes its impedance towards a second trend until the potential difference is zero. The first trend and the second trend are opposite; for example, the first trend can be increasing and the second trend can be decreasing, or the first trend can be decreasing and the second trend can be increasing.

[0068] In this embodiment of the invention, the control unit 421 directly analyzes the change in the potential difference between the potential of the lower electrode 310 and the preset potential based on the potential feedback signal to determine whether the impedance change direction of the impedance adjustment unit 423 is correct. This saves the calculation time for the specific adjustment amount and adjustment direction, and improves the efficiency of the potential adjustment device 410 in adjusting the potential of the lower electrode 310 to the target potential.

[0069] As an optional embodiment of the present invention, such as Figure 3As shown, the impedance adjustment unit 423 includes at least one adjustable component and at least one adjustment drive unit corresponding to the adjustable component. The adjustable component is connected between the first end and the second end of the impedance adjustment unit 423, and the impedance of the adjustable component is adjustable. The control unit 421 is used to control the adjustment drive unit to adjust the impedance of the adjustable component, thereby realizing the adjustment of the total impedance between the first end and the second end of the impedance adjustment unit 423.

[0070] As an optional embodiment of the present invention, such as Figure 2 , Figure 3 As shown, the adjustment drive unit can be a motor M (e.g., a stepper motor). The output shaft of the motor M is connected to an adjustable component. The control unit 421 adjusts the feed amount of the motor M by sending a control signal to the motor M, thereby adjusting the impedance of the adjustable component.

[0071] Optionally, the impedance adjustment unit 423 may also include a component with fixed impedance connected between the first end and the second end of the impedance adjustment unit 423.

[0072] This invention does not specifically limit the type and number of components connected between the first and second terminals of the impedance adjustment unit 423. For example, as an optional implementation of this invention, such as Figure 3 As shown, the impedance adjustment unit 423 includes a fixed inductor L1, an adjustable capacitor C1, and a capacitor adjustment drive unit. The fixed inductor L1 and the adjustable capacitor C1 are connected in series between the first and second ends of the impedance adjustment unit 423. The control unit 421 is used to control the capacitor adjustment drive unit to adjust the capacitance value of the adjustable capacitor C1.

[0073] When the first trend is increasing and the second trend is decreasing, when the control unit 421 adjusts the impedance of the impedance adjustment unit 423, it first controls the capacitor adjustment drive unit (motor M) to increase the capacitance value of the adjustable capacitor C1, and judges whether the potential difference between the potential of the lower electrode 310 and the preset potential decreases according to the potential feedback signal. If the potential difference decreases, the control unit continues to increase the capacitance value of the adjustable capacitor C1 until the potential difference is zero; if the potential difference does not decrease, the control unit decreases the capacitance value of the adjustable capacitor C1 until the potential difference is zero.

[0074] In other embodiments of the present invention, the impedance adjustment unit 423 may also include an adjustable inductor (and a fixed capacitor), or different types of adjustable components may be connected between the first end and the second end of the impedance adjustment unit 423. For example, it may include one or more variable inductors, one or more variable capacitors, or one or more components with fixed impedance (fixed inductors or fixed capacitors).

[0075] Furthermore, the connection relationship between these components is not specifically limited in the embodiments of the present invention. As long as the total impedance between the first and second ends of the impedance adjustment unit 423 can change regularly when the adjustable component is driven by the adjustment drive to change the impedance, multiple components can be connected in series or in parallel between the first and second ends of the impedance adjustment unit 423. Alternatively, the first end of the impedance adjustment unit 423 can be connected to the second end of the impedance adjustment unit 423 in various forms such as series-to-parallel or parallel-to-series.

[0076] As an optional embodiment of the present invention, the control unit 421 is a digital signal processor (DSP) or a microcontroller.

[0077] To facilitate the measurement of the potential of the lower electrode 310, as a preferred embodiment of the present invention, such as... Figure 4 As shown, the potential detection unit 422 includes a first voltage divider element a, a second voltage divider element b, and a signal processor c. The first end of the first voltage divider element a is connected to the first end of the impedance adjustment unit 423, the second end of the first voltage divider element a is connected to the first end of the second voltage divider element b, the second end of the second voltage divider element b is grounded, and the signal processor c is used to detect the potential signal at the first end of the second voltage divider element b and send a potential feedback signal that can reflect the amplitude of the potential signal to the control unit 421.

[0078] The control unit 421 is used to control the impedance adjustment unit 423 to adjust its own impedance according to the potential feedback signal, the impedance of the first voltage divider element a and the impedance of the second voltage divider element b, so as to maintain the potential of the lower electrode 310 at a preset potential.

[0079] In this embodiment of the invention, the potential detection unit 422 includes a signal processor c and a radio frequency voltage divider circuit composed of a first voltage divider element a and a second voltage divider element b. The signal processor c performs potential detection on the node between the first voltage divider element a and the second voltage divider element b to obtain a potential feedback signal. That is, the potential difference between the potential of the lower electrode 310 and the ground terminal (potential is zero) (i.e., the potential of the lower electrode 310) is distributed to the first voltage divider element a and the second voltage divider element b according to the impedance ratio of the first voltage divider element a and the second voltage divider element b, thereby reducing the range of the signal processor c and reducing the material cost of the potential detection unit 422.

[0080] Specifically, the impedance ratio between the first voltage divider element a and the second voltage divider element b is a / b, and the potential of the lower electrode 310 is represented by U. Then, the potential at the node between the first voltage divider element a and the second voltage divider element b is b / (a+b). U, the signal processor c performs a full-wave integration of the AC potential at the node to obtain a DC signal (i.e., the potential feedback signal). After receiving the potential feedback signal, the control unit 421 can calculate the potential at the node between the first voltage divider element a and the second voltage divider element b based on the potential feedback signal. Multiplying this potential by (a+b) / b and then reversing the calculation, the potential at the first end of the impedance adjustment unit 423, i.e. the potential of the lower electrode 310, can be obtained. Then, the impedance adjustment unit 423 can be controlled to adjust its own impedance based on the potential of the lower electrode 310.

[0081] To improve the efficiency of the control unit 421 in determining the potential of the lower electrode 310 based on the potential feedback signal, the impedance of the first voltage divider a, and the impedance of the second voltage divider b, as a preferred embodiment of the present invention, the above calculation can be directly fitted into a fitting curve of the potential of the lower electrode 310 changing with the potential feedback signal, and pre-stored in the control unit 421. The control unit 421 can directly calculate the potential of the lower electrode 310 based on the potential feedback signal and the pre-stored fitting curve.

[0082] It should be noted that the impedance of the first voltage divider element a and the second voltage divider element b is much greater than the maximum impedance between the first and second terminals of the impedance adjustment unit 423, so as to avoid affecting the effect of the impedance change of the impedance adjustment unit 423 on the potential of the lower electrode 310.

[0083] As an optional embodiment of the present invention, such as Figure 5 As shown, the first voltage divider element a includes a first fixed capacitor C2, and the second voltage divider element b includes a second fixed capacitor C3. In other embodiments of the present invention, the first voltage divider element a and the second voltage divider element b may both be capacitors or both be resistors.

[0084] As a second aspect of the present invention, a method for controlling the lower electrode potential is provided, the method being implemented by a lower electrode assembly 400 in a semiconductor process chamber provided in an embodiment of the present invention, the method comprising:

[0085] Adjust the impedance between the lower electrode 310 and the ground terminal to maintain the potential of the lower electrode 310 at a preset potential.

[0086] In the lower electrode potential control method provided by the present invention, the object between the upper and lower electrodes, the lower electrode 310, and the lower electrode assembly 400 are connected in series between the upper electrode assembly and the ground terminal. The lower electrode assembly 400 of the semiconductor process chamber can adjust the ratio between the impedance between the upper and lower electrodes and its own impedance by adjusting the impedance of itself connected between the lower electrode 310 and the ground terminal, so as to adjust the radio frequency voltage division ratio between the upper and lower impedances of the lower electrode, thereby adjusting the potential on the lower electrode 310. In this way, the potential of the lower electrode 310 is maintained at the required preset potential without introducing new radio frequency power, thereby reducing the plasma damage of radio frequency power to the wafer and the impact on the plasma distribution above the wafer, and improving the uniformity of the thickness of the film layer deposited on the wafer surface.

[0087] To solve the above-mentioned technical problems, as a preferred embodiment of the present invention, the lower electrode assembly 400 can automatically adjust the preset potential according to the number of film deposition cycles, so that the preset potential corresponds to the film thickness on the wafer surface in real time.

[0088] Specifically, such as Figure 1 , Figure 6 As shown, the lower electrode assembly 400 includes a potential adjustment device 410 and a potential determination device 420. The method specifically includes:

[0089] Step S1: The potential determination device 420 determines the current preset potential based on the number of film deposition cycles of the wafer;

[0090] Step S2: The potential adjustment device 410 adjusts its impedance connected between the lower electrode 310 and the ground terminal to maintain the potential of the lower electrode 310 at the preset potential determined by the potential determination device.

[0091] As an optional embodiment of the present invention, the preset potential increases with the increase of the number of film deposition cycles (film thickness on the wafer surface). Specifically, step S1 may include:

[0092] When the number of film deposition cycles is less than or equal to 25, the preset potential is determined as the first preset potential; when the number of film deposition cycles is greater than 25 and less than or equal to 50, the preset potential is determined as the second preset potential; when the number of film deposition cycles is greater than 50 and less than or equal to 80, the preset potential is determined as the third preset potential; and when the number of film deposition cycles is greater than 80, the preset potential is determined as the fourth preset potential. The first preset potential is less than the second preset potential, less than the third preset potential, and less than the fourth preset potential.

[0093] As an optional embodiment of the present invention, the first preset potential is 0V, the second preset potential is 50V, the third preset potential is 100V, and the fourth preset potential is 150V or greater than 150V. That is, as shown... Figure 7As shown, in the initial stage of coating (the first 25 cycles), the film thickness on the wafer surface is relatively small, and the potential of the lower electrode 310 needs to be kept at 0V to reduce the damage of RF power to the wafer. From 25 to 50 cycles, a film of a certain thickness is deposited on the wafer surface, and the lower electrode voltage can be slightly increased to improve the film quality, such as increasing the potential of the lower electrode 310 to 50V (this value should not be too large, otherwise it will damage the wafer). From 50 to 80 cycles, the lower electrode voltage can be increased again to 100V. After 80 cycles, a higher voltage is needed to improve the film quality, and the voltage can be increased to 150V or higher.

[0094] The embodiments of the present invention do not specifically limit the trend of the preset potential. For example, in some cases, the preset potential may always be a fixed value, or it may decrease as the number of film deposition cycles (film thickness on the wafer surface) increases.

[0095] As an optional embodiment of the present invention, such as Figure 2 , Figure 8 As shown, the potential adjustment device 410 includes a control unit 421, a potential detection unit 422, and an impedance adjustment unit 423. The first end of the impedance adjustment unit 423 is connected to the lower electrode 310, and the second end of the impedance adjustment unit 423 is grounded. Step S2 may specifically include:

[0096] Step S21: The potential detection unit 422 detects the potential at the first end of the impedance adjustment unit 423 and obtains a potential feedback signal;

[0097] In step S22, the control unit 421 maintains the potential of the lower electrode 310 at a preset potential based on the potential feedback signal and the impedance of the preset potential control impedance adjustment unit 423 determined by the potential determination device 420.

[0098] To improve the efficiency of the potential adjustment device 410 in adjusting the potential of the lower electrode 310 to the target potential, as a preferred embodiment of the present invention, such as... Figure 9 As shown, step S22 may specifically include:

[0099] The impedance of the control impedance adjustment unit 423 is adjusted by a preset amount to change towards the first trend, and the potential difference between the potential of the lower electrode 310 and the preset potential is determined based on the potential feedback signal.

[0100] If the potential difference decreases, the impedance of the control impedance adjustment unit 423 continues to change towards the first trend until the potential difference is zero; if the potential difference does not decrease, the impedance of the control impedance adjustment unit 423 changes towards the second trend until the potential difference is zero.

[0101] In this case, the first trend is opposite to the second trend. For example, the first trend can be increasing and the second trend can be decreasing, or the first trend can be decreasing and the second trend can be increasing.

[0102] In this embodiment of the invention, the control unit 421 directly analyzes the change in the potential difference between the potential of the lower electrode 310 and the preset potential based on the potential feedback signal to determine whether the impedance change direction of the impedance adjustment unit 423 is correct. This saves the calculation time for the specific adjustment amount and adjustment direction, and improves the efficiency of the potential adjustment device 410 in adjusting the potential of the lower electrode 310 to the target potential.

[0103] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A semiconductor process chamber, characterized in that, The device includes a cavity, an upper electrode assembly, a base, and a lower electrode assembly. The base is disposed in the cavity and is used to support the wafer. The upper electrode assembly is used to provide a radio frequency signal to the process gas in the cavity to excite the process gas in the cavity to form plasma. The base has a lower electrode inside. The lower electrode assembly is connected between the lower electrode and a ground terminal and is used to adjust its own impedance between the lower electrode and the ground terminal to maintain the potential of the lower electrode at a preset potential. The lower electrode assembly includes a potential adjustment device and a potential determination device. The potential determination device is used to determine the current preset potential based on the number of film deposition cycles of the wafer. The potential adjustment device is used to adjust its own impedance connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode at the preset potential determined by the potential determination device. The potential adjustment device includes a control unit, a potential detection unit, and an impedance adjustment unit. The first end of the impedance adjustment unit is connected to the lower electrode, and the second end of the impedance adjustment unit is grounded. The potential detection unit is used to detect the potential of the first end of the impedance adjustment unit to obtain a potential feedback signal. The control unit is used to control the impedance adjustment unit to adjust its own impedance according to the potential feedback signal and the preset potential determined by the potential determination device, so as to maintain the potential of the lower electrode at the preset potential.

2. The semiconductor process chamber according to claim 1, characterized in that, The potential determination device is used to determine the preset potential as a first preset potential when the number of film deposition cycles is less than or equal to 25, to determine the preset potential as a second preset potential when the number of film deposition cycles is greater than 25 and less than or equal to 50, to determine the preset potential as a third preset potential when the number of film deposition cycles is greater than 50 and less than or equal to 80, and to determine the preset potential as a fourth preset potential when the number of film deposition cycles is greater than 80, wherein the first preset potential is less than the second preset potential, less than the third preset potential, and less than the fourth preset potential.

3. The semiconductor process chamber according to claim 2, characterized in that, The control unit is specifically used to control the impedance of the impedance adjustment unit to change by a preset adjustment amount towards a first trend, and to determine whether the potential difference between the potential of the lower electrode and the preset potential decreases based on the potential feedback signal. If the potential difference decreases, the control unit continues to control the impedance of the impedance adjustment unit to change towards the first trend; if the potential difference does not decrease, the control unit changes the impedance of the impedance adjustment unit towards a second trend; the first trend is opposite to the second trend.

4. The semiconductor process chamber according to claim 1, characterized in that, The impedance adjustment unit includes at least one adjustable component and at least one adjustment drive unit corresponding to the adjustable component. The adjustable component is connected between the first end and the second end of the impedance adjustment unit, and the impedance of the adjustable component is adjustable. The control unit is used to control the adjustment drive unit to adjust the impedance of the adjustable component.

5. The semiconductor process chamber according to claim 4, characterized in that, The impedance adjustment unit includes a fixed inductor, an adjustable capacitor, and a capacitor adjustment drive unit. The fixed inductor and the adjustable capacitor are connected in series between the first and second ends of the impedance adjustment unit. The control unit is used to control the capacitor adjustment drive unit to adjust the capacitance value of the adjustable capacitor.

6. The semiconductor process chamber according to claim 1, characterized in that, The potential detection unit includes a first voltage divider element, a second voltage divider element, and a signal processor. The first end of the first voltage divider element is connected to the first end of the impedance adjustment unit, the second end of the first voltage divider element is connected to the first end of the second voltage divider element, and the second end of the second voltage divider element is grounded. The signal processor is used to detect the potential signal at the first end of the second voltage divider element and send the potential feedback signal that reflects the amplitude of the potential signal to the control unit. The control unit is used to control the impedance adjustment unit to adjust its own impedance according to the potential feedback signal, the impedance of the first voltage divider element and the impedance of the second voltage divider element, so as to maintain the potential of the lower electrode at the preset potential.

7. The semiconductor process chamber according to claim 6, characterized in that, The first voltage divider element includes a first fixed capacitor, and the second voltage divider element includes a second fixed capacitor.

8. The semiconductor process chamber according to claim 1, characterized in that, The control unit is a digital signal processor or a microcontroller.

9. A method for controlling the lower electrode potential, applied to the semiconductor process chamber according to any one of claims 1-8, characterized in that, The method includes: Adjust the impedance of the lower electrode assembly connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode at a preset potential.

10. The method for controlling the lower electrode potential according to claim 9, characterized in that, Adjusting the impedance of the lower electrode assembly connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode above a preset potential also includes: The current preset potential is determined based on the number of film deposition cycles of the wafer.

11. The method for controlling the lower electrode potential according to claim 9 or 10, characterized in that, Adjusting the impedance of the lower electrode assembly connected between the lower electrode and the ground terminal to maintain the potential of the lower electrode at the preset potential specifically includes: A potential feedback signal is obtained by detecting the potential at the first terminal of the impedance adjustment unit; The impedance adjustment unit adjusts its own impedance according to the potential feedback signal and the preset potential, so as to maintain the potential of the lower electrode at the preset potential.

12. The lower electrode potential control method according to claim 11, characterized in that, The impedance adjustment unit adjusts its own impedance according to the potential feedback signal and the preset potential to maintain the potential of the lower electrode at the preset potential, specifically including: The impedance of the impedance adjustment unit is controlled to change by a preset adjustment amount towards a first trend, and the potential difference between the potential of the lower electrode and the preset potential is determined based on the potential feedback signal. If the potential difference decreases, the impedance of the impedance adjustment unit is controlled to continue changing towards the first trend; if the potential difference does not decrease, the impedance of the impedance adjustment unit is controlled to change towards the second trend. The first trend is the opposite of the second trend.

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