Method for preventing arc discharge from occurring in lower electrode assembly and plasma processing equipment

Abstract

The present invention provides a method for preventing arc discharge from occurring in a lower electrode assembly and a plasma processing device, the method comprising: measuring a DC self-bias voltage of a substrate to obtain a corresponding self-bias voltage measurement value; calculating a self-bias voltage compensation value based on the self-bias voltage measurement value; applying a first DC voltage to the lower electrode assembly, the voltage value of the first DC voltage being the self-bias voltage compensation value, so as to achieve a voltage difference between the lower electrode assembly and the substrate being less than a preset first threshold value. The advantage is that by applying a first DC voltage having a voltage value of the self-bias voltage compensation value to the lower electrode assembly, the voltage difference between the substrate and the lower electrode assembly is effectively reduced, the probability of arc discharge occurring in the lower electrode assembly during high aspect ratio etching is greatly reduced, and the safety of substrate processing is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preventing arc discharge from occurring in a lower electrode assembly and plasma processing equipment. Background Art

[0002] In the field of semiconductor manufacturing technology, it is often necessary to perform plasma treatment on a substrate in a plasma processing device. The plasma processing device has a vacuum reaction chamber, in which an electrostatic chuck for placing the substrate is provided. The electrostatic chuck includes a base and a dielectric layer disposed on top of the base, and the base serves as the lower electrode of the reaction chamber.

[0003] The reaction gas is input into the reaction chamber, and one or more RF power supplies can be applied separately to the lower electrode to deliver RF power to the lower electrode, thereby generating an RF electric field inside the reaction chamber. Most of the electric field is contained in the processing area above the substrate. This electric field accelerates a small amount of electrons present inside the reaction chamber, causing them to collide with the gas molecules of the input reaction gas. These collisions lead to the ionization of the reaction gas and the excitation of the plasma, thereby generating plasma (including active particles such as electrons, cations, and electrically neutral free radicals) in the reaction chamber. Finally, chemical reactions and / or physical actions (such as etching, deposition, etc.) occur between the plasma and the substrate to form various characteristic structures.

[0004] During the process, electrons have a smaller mass than cations and are more easily accelerated by the electric field, so they have a greater movement speed than cations. Electrons gradually accumulate on the surface of the substrate and the focusing ring, causing the substrate and the focusing ring to be gradually biased to a negative voltage, generating a DC self-bias on the substrate and the focusing ring. The DC self-bias is proportional to the RF power supplied to the electrostatic chuck. The RF power in high aspect ratio etching is usually high, so the DC self-bias of the substrate and the focusing ring is also high, resulting in a large voltage difference between the substrate and the base, and between the focusing ring and the base, thereby greatly increasing the risk of arcing in the helium hole of the electrostatic chuck and between the focusing ring and the base. Once an arc discharge occurs, the substrate will be scrapped and even the electrostatic chuck will be damaged.

[0005] How to avoid excessive voltage difference between the substrate and the base, and between the focusing ring and the base caused by the DC self-bias of the substrate and the focusing ring is a problem that needs to be solved urgently in the industry. Summary of the invention

[0006] The purpose of the present invention is to provide a method and plasma processing equipment for preventing arc discharge in a lower electrode assembly. The present invention calculates a corresponding self-bias compensation value based on the measured value of the DC self-bias voltage of the substrate, and effectively reduces the voltage difference between the substrate and the lower electrode assembly by applying a first DC voltage with a voltage value equal to the self-bias compensation value to the lower electrode assembly, thereby greatly reducing the risk of arc discharge in the lower electrode assembly during high aspect ratio etching.

[0007] In order to achieve the above object, the present invention provides a method for preventing arc discharge from occurring in a lower electrode assembly, wherein the lower electrode assembly is placed in a vacuum reaction chamber of a plasma processing device, and a substrate is supported by the lower electrode assembly, and the method comprises:

[0008] measuring a direct current self-bias voltage of the substrate to obtain a corresponding self-bias voltage measurement value;

[0009] Calculating a self-bias voltage compensation value based on the self-bias voltage measurement value;

[0010] A first DC voltage is applied to the lower electrode assembly, wherein the voltage value of the first DC voltage is the self-bias compensation value, so that the voltage difference between the lower electrode assembly and the substrate is less than a preset first threshold value.

[0011] Optionally, during the process, low-frequency RF power is provided to the lower electrode assembly by a first RF power supply; the DC self-bias voltage of the substrate is measured during the entire working cycle of the first RF power supply, and the self-bias voltage measurement value is a time average value of the DC self-bias voltage.

[0012] Optionally, the operating mode of the first RF power supply includes a pulse mode; in the pulse mode, the operating cycle of the first RF power supply includes at least a first stage and a second stage; in the first stage, the first RF power supply outputs high RF power; in the second stage, the first RF power supply outputs low RF power.

[0013] Optionally, the operating mode of the first RF power supply includes a continuous wave mode; in the continuous wave mode, the first RF power supply outputs constant RF power to the lower electrode assembly, and the self-bias voltage compensation value is equal to the self-bias voltage measurement value.

[0014] Optionally, the duration of the first stage is shorter than the duration of the second stage; the self-bias voltage measurement value and the self-bias voltage compensation value are both negative values, and the absolute value of the self-bias voltage compensation value is greater than the absolute value of the self-bias voltage measurement value.

[0015] Optional, let represents the self-bias voltage measurement value, V1 represents the self-bias voltage compensation value, ; α is the proportional coefficient, 1<α<1 / x; x is the duty cycle of the high RF power.

[0016] Optionally, the lower electrode assembly includes an electrostatic chuck, which includes a dielectric layer and a metal base located below the dielectric layer, and an electrostatic electrode is disposed in the dielectric layer; and the first DC voltage is applied to the base.

[0017] Optionally, the method for preventing arc discharge from occurring in the lower electrode assembly further comprises:

[0018] Calculate the voltage value of the DC voltage that needs to be applied to the electrostatic electrode to make the electrostatic chuck generate a preset electrostatic suction force when the reaction chamber is idle ;

[0019] make represents the self-bias voltage measurement value; in the process, a second DC voltage is applied to the electrostatic electrode, and the voltage value of the second DC voltage is .

[0020] Optionally, the first RF power supply generates a first coupling voltage at the electrostatic electrode; during the process, the DC self-bias voltage of the substrate is measured by measuring the amplitude of the first coupling voltage.

[0021] Optionally, within the working cycle of the first RF power source, the amplitude of the first coupling voltage is measured to obtain a corresponding first amplitude measurement value; the first amplitude measurement value is a time average value of the amplitude of the first coupling voltage;

[0022] make represents the self-bias voltage measurement value, represents the first amplitude measurement value, ; β is a proportionality coefficient associated with the process parameters of the process, Indicates taking the absolute value.

[0023] Optionally, before the process starts, the proportionality coefficient β is obtained by the following steps:

[0024] Make the process parameters associated with the proportionality coefficient β meet the process requirements;

[0025] Providing a test substrate; setting the working mode of the first radio frequency power supply to a continuous wave mode, wherein the first radio frequency power supply outputs a constant radio frequency power to the lower electrode assembly in the continuous wave mode;

[0026] The DC self-bias voltage of the test substrate is measured by a probe to obtain the corresponding measurement value V pin ;

[0027] Measuring the amplitude of the second coupling voltage generated by the first radio frequency power supply at the electrostatic electrode ;

[0028] .

[0029] Optionally, the process parameters include: the gas pressure value in the reaction chamber during the process.

[0030] Optionally, the proportional coefficient β and the process parameters associated therewith are stored in a table, and the proportional coefficient β is obtained by querying the table.

[0031] Optionally, the lower electrode assembly further comprises a focus ring and an edge electrode;

[0032] The focusing ring surrounds the periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode;

[0033] The first DC voltage is applied to the edge electrode.

[0034] Optionally, the lower electrode assembly further comprises a focus ring and an edge electrode;

[0035] The focusing ring surrounds the periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode;

[0036] In the process, a third DC voltage is applied to the edge electrode, and the third DC voltage is a negative voltage;

[0037] Let V3 represent the voltage value of the third DC voltage, represents the radio frequency power value of the first radio frequency power source, ; is the preset scaling factor.

[0038] The present invention also provides a plasma processing device for implementing the method according to the present invention, comprising:

[0039] A vacuum reaction chamber, wherein a lower electrode assembly is provided in the reaction chamber; and a substrate is carried by the lower electrode assembly;

[0040] A self-bias voltage measurement module, used to measure the DC self-bias voltage of the substrate and obtain a corresponding self-bias voltage measurement value;

[0041] A first high-voltage output module, whose signal is connected to the self-bias voltage measurement module to obtain the self-bias voltage measurement value; the first high-voltage output module also calculates a self-bias voltage compensation value based on the self-bias voltage measurement value; during the process, a first DC voltage is applied to the lower electrode assembly through the first high-voltage output module, and the voltage value of the first DC voltage is the self-bias voltage compensation value, so that the voltage difference between the lower electrode assembly and the substrate is less than a preset first threshold value.

[0042] Optionally, the plasma processing equipment also includes: a first RF power supply, whose working cycle includes at least a first stage and a second stage; during the process, the first RF power supply outputs high RF power and low RF power to the lower electrode assembly in the first stage and the second stage respectively; the self-bias voltage measurement value is the time average value of the DC self-bias voltage measured in the entire working cycle of the first RF power supply.

[0043] Optionally, the duration of the first stage is shorter than the duration of the second stage; represents the self-bias voltage measurement value, V1 represents the self-bias voltage compensation value, ; α is the proportional coefficient, 1<α<1 / x; x is the duty cycle of the high RF power.

[0044] Optionally, the lower electrode assembly includes an electrostatic chuck, which includes a dielectric layer and a metal base located below the dielectric layer, and an electrostatic electrode is disposed in the dielectric layer; and the first DC voltage is applied to the base.

[0045] Optionally, the plasma processing device further comprises: a second high-voltage output module, which is communicatively connected to the self-bias voltage measurement module to obtain the self-bias voltage measurement value;

[0046] In the process, a second DC voltage is applied to the electrostatic electrode through the second high voltage output module, and the voltage value of the second DC voltage is ;

[0047] is the self-bias voltage measurement value; When the reaction chamber is idle, in order for the electrostatic chuck to generate a preset electrostatic suction force, a voltage value of a DC voltage needs to be applied to the electrostatic electrode.

[0048] Optionally, the self-bias voltage measurement module is electrically connected to the electrostatic electrode; the first RF power supply generates a first coupling voltage at the electrostatic electrode; during the process, the self-bias voltage measurement module measures the DC self-bias voltage of the substrate by measuring the amplitude of the first coupling voltage.

[0049] Optionally, the plasma processing equipment further includes a filter, which suppresses the radio frequency energy transmitted from the electrostatic electrode to the self-bias measurement module and the second high-voltage output module, and suppresses the radio frequency energy transmitted from the base to the first high-voltage output module.

[0050] Optionally, the lower electrode assembly comprises a focus ring and an edge electrode;

[0051] The focusing ring surrounds the periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode;

[0052] The first DC voltage is applied to the edge electrode.

[0053] Optionally, the plasma processing equipment further comprises a third high voltage output module electrically connected to the first RF power supply;

[0054] The lower electrode assembly includes a focus ring and an edge electrode;

[0055] The focusing ring surrounds the periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode;

[0056] The third high-voltage output module applies a third DC voltage to the edge electrode based on the RF power of the first RF power supply; the third DC voltage is a negative voltage;

[0057] Let V3 represent the voltage value of the third DC voltage, represents the radio frequency power value of the first radio frequency power source, ; is the preset scaling factor.

[0058] Optionally, the plasma processing equipment further includes an isolation circuit for preventing the radio frequency power applied to the edge electrode from interfering with the third high-voltage output module.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] 1) The method for preventing arc discharge in the lower electrode assembly and the plasma processing equipment of the present invention calculate the corresponding self-bias compensation value based on the measurement result of the DC self-bias voltage of the substrate, and apply a first DC voltage with a voltage value of the self-bias compensation value to the lower electrode assembly, thereby effectively reducing the voltage difference between the substrate and the lower electrode assembly, greatly reducing the probability of arc discharge in the lower electrode assembly, and improving the safety of substrate processing.

[0061] 2) In the process of the present invention, the substrate is biased by the first RF power supply, and the first RF power supply alternately outputs high and low RF power to the lower electrode assembly, so the DC self-bias voltage of the substrate also periodically changes between high and low. Since the duty cycle of the first RF power supply outputting high RF power is usually less than 50%, and the self-bias voltage measurement value is the time average value of the DC self-bias voltage (sufficient time accuracy cannot be achieved when measuring the DC self-bias voltage), the self-bias voltage measurement value approaches the DC self-bias voltage value when the first RF power supply outputs low RF power. When the voltage of the lower electrode assembly is compensated based on the self-bias measurement value to reduce the voltage difference between the substrate and the lower electrode assembly, it is easy to have insufficient voltage compensation for the lower electrode assembly, and arc discharge is still easy to occur between the lower electrode assembly and the substrate. The present invention makes the self-bias voltage compensation value approach the intermediate value of the DC self-bias voltage value when the first RF power supply outputs high RF power and low RF power. The magnitude of the first DC voltage compensated on the lower electrode assembly is determined according to the self-bias compensation value, and when the first RF power supply outputs high RF power, the risk of arc discharge in the lower electrode assembly can be greatly reduced.

[0062] 3) In the present invention, the range of the self-bias compensation value is controlled based on the duty cycle of the first RF power supply outputting high RF power, which can effectively avoid under-compensation and over-compensation of the voltage of the lower electrode assembly by the first DC voltage, and greatly reduce the risk of arc discharge in the lower electrode assembly during the entire working cycle of the first RF power supply.

[0063] 4) When the reaction chamber is idle, in order for the electrostatic chuck to generate a preset electrostatic suction force, the DC voltage value to be applied to the electrostatic electrode is In the present invention, a second DC voltage is applied to the electrostatic electrode, and the difference between the voltage value of the second DC voltage and the measured value of the self-bias voltage is , in order to compensate for the insufficient electrostatic attraction caused by the DC self-bias of the substrate, and ensure that during the entire working cycle of the first RF power supply, the difference between the actual electrostatic attraction generated by the electrostatic chuck and the preset electrostatic attraction falls within a reasonable range, ensuring stable adsorption of the substrate while making it easy to desorb the substrate.

[0064] 5) The present invention does not need to use a probe to measure the DC self-bias voltage of the substrate during the process, which can greatly reduce the contamination caused to the substrate.

[0065] 6) The first DC voltage of the present invention can be applied to the base and the edge electrode to reduce the voltage difference between the substrate and the base, and between the substrate and the focusing ring. The present invention can also apply a third DC voltage to the edge electrode according to the output power of the first RF power supply (which is positively correlated with the DC self-bias voltage on the surface of the focusing ring) to reduce the voltage difference between the substrate and the focusing ring. The safety of the lower electrode assembly is improved in various ways. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for the description. Obviously, the drawings described below are an embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0067] Figure 1 is a schematic diagram of a plasma processing device;

[0068] Figure 2 for Figure 1 Schematic diagram of voltage waveform of RF power supply;

[0069] Figure 3 is a schematic diagram of voltage waveforms of the substrate and the base when the base voltage is not compensated;

[0070] Figure 4 To apply a voltage value to the base Schematic diagram of voltage waveform between substrate and base when DC voltage is ;

[0071] Figure 5 It is a schematic diagram of a plasma processing device in Embodiment 1 of the present invention;

[0072] Figure 6 It is a flow chart of a method for preventing arc discharge from occurring in a lower electrode assembly in Embodiment 1 of the present invention;

[0073] Figure 7 To apply a voltage value to the base Schematic diagram of voltage waveform between substrate and base when DC voltage is ;

[0074] Figure 8 This is a schematic diagram of voltage waveforms between the substrate and the base when a DC voltage with a voltage value of V1 is applied to the base in the first embodiment of the present invention;

[0075] Fig. 9 A schematic diagram of the voltage waveform between the substrate and the base when the base voltage is over-compensated;

[0076] Fig.10 A flow chart of a method for preventing arc discharge from occurring in a lower electrode assembly in another embodiment of the present invention;

[0077] Fig.11 A schematic diagram of a DC voltage difference between a substrate and an electrostatic electrode for generating an electrostatic attraction in another embodiment of the present invention;

[0078] Fig.12 This is a schematic diagram of applying a first DC voltage to an edge electrode in Embodiment 2 of the present invention;

[0079] Fig.13 is a comparison diagram of the DC bias voltage difference before and after the first DC voltage is applied to the edge electrode in the second embodiment of the present invention;

[0080] Fig.14 is a schematic diagram of applying a third DC voltage to an edge electrode in Embodiment 3 of the present invention;

[0081] Fig.15 is a comparison diagram of the DC bias voltage difference before and after the third DC voltage is applied to the edge electrode in the third embodiment of the present invention;

[0082] Fig.16 FIG. 4 is a schematic diagram of a plasma processing device in another embodiment of the present invention. DETAILED DESCRIPTION

[0083] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0084] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0085] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0086] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0087] As used in this specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0088] In addition, in the description of the present application, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0089] Figure 1 1 is a schematic diagram of the structure of a plasma processing device 1. The plasma processing device 1 is a capacitively coupled plasma (CCP) processing device, which includes a vacuum reaction chamber 10.

[0090] A lower electrode assembly is provided at the bottom of the reaction chamber 10, and the lower electrode assembly includes an electrostatic chuck 102, and the electrostatic chuck 102 includes a dielectric layer 1021 and a metal base 1022 located below the dielectric layer 1021, and the substrate W to be processed is placed on the dielectric layer 1021. An electrostatic electrode 1023 is provided in the dielectric layer 1021, and a DC voltage is applied to the electrostatic electrode 1023 through a DC power supply 160 to generate an electrostatic adsorption force to fix the substrate W. A cooling gas channel (not shown in the figure) is provided inside the electrostatic chuck 102, which is used to pass cooling gas (usually helium) to the back of the substrate to adjust the temperature of the substrate W.

[0091] The focusing ring 105 surrounds the periphery of the substrate W and is used to control the RF electric field distribution at the edge of the substrate W to be processed, so that the plasma is focused on the substrate W and the plasma characteristics and ion directionality at the center and edge of the substrate are uniform.

[0092] The reaction chamber 10 also includes a gas shower head 103 arranged opposite to the lower electrode assembly, and the space between the gas shower head 103 and the lower electrode assembly is a processing area for processing the surface of the substrate W. The gas shower head 103 is connected to an external gas supply device 120 through a gas path, and is used to transport reaction gas into the reaction chamber 10. An exhaust port 130 is provided at a suitable position of the reaction chamber 10, and the exhaust port 130 is connected to an external vacuum device (such as a vacuum pump, not shown in the figure) to discharge reaction by-products out of the reaction chamber 10.

[0093] The gas shower head 103 serves as the upper electrode of the reaction chamber 10, and the source RF power supply 140 applies RF signals to the upper electrode and / or the lower electrode assembly ( Figure 1 The source RF power supply 140 in the reactor applies a radio frequency signal to the lower electrode assembly, and the upper electrode is grounded) to generate an electric field between the upper electrode and the lower electrode assembly, which accelerates a small amount of electrons present inside the reaction chamber 10 and causes them to collide with gas molecules of the input reaction gas. These collisions lead to ionization of the reaction gas and excitation of the plasma, thereby generating plasma in the reaction chamber 10. The plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules, and electrically neutral free radicals. The source RF power supply 140 usually has a relatively high frequency, such as 10MHz-200Mhz. In practical applications, the plasma concentration in the reaction chamber 10 can be effectively adjusted by adjusting the RF power of the source RF power supply 140.

[0094] The RF impedance matcher 141 is electrically connected between the source RF power supply 140 and the lower electrode assembly. The RF impedance matcher 141 makes the source RF power supply 140 and the reaction chamber 10 in an impedance matching state, so that the RF power of the source RF power supply 140 is coupled to the lower electrode assembly as much as possible.

[0095] Since electrons have a smaller mass than ions, they are more easily accelerated by the electric field, so they move faster than ions. In this way, between the plasma and the substrate W, since the electrons move faster, more electrons will collide with the substrate in the same time at the beginning of the RF electric field, thereby generating an electric field near the substrate W, which will prevent more electrons from reaching the substrate W and accelerate the movement of ions toward the substrate W. After the electrons and ions are finally stabilized, a plasma sheath is formed on the surface of the substrate W. Similarly, a plasma sheath will also be formed on the cavity wall.

[0096] The voltage of the plasma sheath on the surface of substrate W is referred to as substrate sheath voltage, which is the voltage difference between substrate W and plasma. The larger the substrate sheath voltage, the greater the energy of ion bombardment of substrate W, and the higher the etching rate of substrate W. Under the action of substrate sheath voltage, ions accelerate downward and bombard the area to be etched of substrate W, thereby weakening the binding force between molecules in the area to be etched. The area to be etched with weakened molecular binding force is captured by free radicals, converted into volatile gas compounds and released, thereby forming an etching pattern in the area to be etched, that is, completing the etching process.

[0097] like Figure 1 As shown, a low-frequency RF power source 150 (e.g., 1kHz-20MHz) is applied to the base 1022 through the RF impedance matcher 151 to generate a larger DC self-bias voltage (meaning that its absolute value is larger) on the substrate W, thereby obtaining a larger substrate sheath voltage. represents the substrate voltage, represents the coupling voltage generated by the RF power source 150 on the substrate W, represents the DC self-bias voltage of substrate W, then .make represents the plasma voltage, represents the substrate sheath voltage, then .because The absolute value of is proportional to the voltage amplitude of the RF power supply 150. By controlling the output power of the RF power supply 150, the DC self-bias voltage can be controlled. , thereby controlling the substrate sheath voltage , to adjust the energy of ions bombarding the substrate W.

[0098] In the high aspect ratio etching process, the RF power supply 150 usually outputs high and low RF power alternately to the susceptor 1022, such as Figure 2 As shown, the voltage waveform of the RF power supply 150 can be regarded as the superposition of two sine waves with different amplitudes. When the RF power supply 150 outputs high RF power, the ion energy is high, and the etching performed by the ions has strong anisotropy. When the RF power supply 150 outputs low RF power, the plasma sheath on the surface of the substrate W is very thin, and the plasma sheath cannot completely fill the etching pattern, making it easy for electrons to enter the bottom of the etching pattern to neutralize the residual ions. Avoid etching problems such as bowing and tilting during the etching process due to the accumulated ions at the bottom of the etching pattern repelling the ions in the plasma.

[0099] Figure 3 FIG. 1 is a schematic diagram of voltage waveforms of the substrate W and the pedestal 1022 when the pedestal voltage is not compensated. Figure 3 In the figure, the first stage and the second stage each show a sine wave cycle, which is only for example. Since the absolute value of the DC self-bias voltage is proportional to the voltage amplitude of the RF power supply 150, when the RF power supply 150 alternately outputs high and low RF power to the lower electrode, the DC self-bias voltage of the substrate W also periodically changes between high and low. Figure 3 As shown, when the RF power supply 150 outputs high RF power, the DC self-bias voltage of the substrate W is When the RF power supply 150 outputs low RF power, the DC self-bias voltage of the substrate W is . and are all negative values, and , Indicates taking the absolute value.

[0100] The voltage of the RF power supply 150 is , Figure 3 The voltage difference between the substrate W and the base 1022 .like Figure 3As shown, at time T0 (in the first stage), the RF power supply 150 outputs the maximum positive voltage. At this time, the voltage difference . The maximum voltage difference between the pedestal 1022 and the substrate W during the entire working cycle of the RF power supply 150. In high aspect ratio etching, the voltage difference It is easy to exceed the preset first threshold value (which can be understood as the maximum voltage difference that prevents arc discharge from occurring between the substrate W and the lower electrode assembly), resulting in arc discharge in the cooling gas channel, between the base 1022 and the substrate W, and between the base 1022 and the focusing ring 105, thereby causing the substrate W to be scrapped or even damaging the electrostatic chuck 102.

[0101] like Figure 1 As shown, a DC voltage (negative voltage) can be applied to the pedestal 1022 by the DC power supply 160 to reduce the pedestal voltage, thereby reducing the voltage difference between the substrate W and the pedestal 1022 at time T0, and reducing the risk of arc discharge in the lower electrode assembly. The voltage value of the DC voltage can be a measured value of the DC self-bias voltage of the substrate (referred to as the self-bias voltage measured value).

[0102] In the prior art, the time accuracy of the DC self-bias voltage measurement is not high, and the measured value of the self-bias voltage is the time average value of the DC self-bias voltage, which is recorded as . , a is the duty cycle of the RF power supply 150 outputting high RF power. Since the duty cycle a is usually less than 50%, the self-bias voltage measurement value Approaching the DC self-bias voltage value when the RF power source 150 outputs low RF power (i.e. ).

[0103] Figure 4 As shown in FIG. 1 , the DC power supply 160 applies a voltage value to the base 1022. Schematic diagram of the voltage waveform between the substrate W and the base 1022 when the DC voltage is . The voltage difference between the substrate W and the base 1022 .like Figure 4 As shown, at time T0 (in the first stage), the RF power supply 150 outputs the maximum positive voltage. At this time, the voltage difference . is the maximum voltage difference between the base 1022 and the substrate W during the entire working cycle of the RF power supply 150. (which is a negative value) approaches , and Although slightly smaller than This indicates that the pedestal voltage compensation is insufficient and the risk of arc discharge between the pedestal 1022 and the substrate W is still very high.

[0104] The purpose of the present invention is to provide a method and plasma processing equipment for preventing arc discharge in a lower electrode assembly, by calculating a corresponding self-bias compensation value based on the measured value of the DC self-bias voltage of the substrate, and by applying a first DC voltage having a voltage value equal to the self-bias compensation value to the lower electrode assembly, the voltage difference between the substrate W and the lower electrode assembly is effectively reduced, thereby greatly reducing the risk of arc discharge in the lower electrode assembly during high aspect ratio etching.

[0105] Embodiment 1

[0106] Figure 5 A plasma processing device 2 is shown in FIG. Figure 5 As shown, it includes: a vacuum reaction chamber 20, a source RF power supply 240, and a first RF power supply 250.

[0107] A lower electrode assembly is disposed in the reaction chamber 20 , and the substrate W is supported by the lower electrode assembly. An upper electrode is disposed above the reaction chamber 20 and is opposite to the lower electrode assembly.

[0108] In this embodiment, the lower electrode assembly includes an electrostatic chuck 202, and the electrostatic chuck 202 includes a dielectric layer 2021 and a metal base 2022 located below the dielectric layer 2021. The substrate W is placed on the dielectric layer 2021, and an electrostatic electrode 2023 for generating electrostatic attraction is provided in the dielectric layer 2021, and the substrate W is fixed by the electrostatic attraction. A cooling gas channel (not shown in the figure) is provided inside the electrostatic chuck 202, which is used to pass cooling gas (usually helium) to the back of the substrate to adjust the temperature of the substrate W.

[0109] The upper electrode includes a gas shower head 203 , a gas path of which is connected to an external gas supply device 220 , and a reaction gas is transported into the reaction chamber 20 through the gas shower head 203 .

[0110] The source RF power source 240 (whose frequency is usually 10 MHz-200 MHz) is applied to the upper electrode and / or the lower electrode assembly to generate plasma in the reaction chamber 20. In this embodiment, Figure 5 As shown, the source RF power 240 is applied to the base 2022 through the matcher 241. In other embodiments, the source RF power 240 may also be applied to the gas shower head 203, which is not limited in the present invention.

[0111] During the process, RF power is provided to the lower electrode assembly by the first RF power supply 250. The working modes of the first RF power supply 250 include a pulse mode and a continuous-wave mode. In the pulse mode, the working cycle of the first RF power supply 250 includes multiple stages, and the RF power and duration of at least two stages are different. In the continuous-wave mode, the first RF power supply 250 outputs a constant RF power.

[0112] In this embodiment, the first RF power source 250 is applied to the base 2022. The working mode of the first RF power source 250 in the process is a pulse mode, and its working cycle includes a first stage and a second stage, and the duration of the first stage is less than the duration of the second stage. The first RF power source 250 outputs high RF power in the first stage and outputs low RF power in the second stage.

[0113] The DC self-bias voltage value of the substrate W is proportional to the voltage amplitude of the first RF power source 250. When the first RF power source 250 outputs high RF power, the DC self-bias voltage value of the substrate W is recorded as When the first RF power source 250 outputs low RF power, the DC self-bias voltage value of the substrate W is recorded as . and are all negative values, and , Indicates taking the absolute value.

[0114] This embodiment provides a method for preventing arc discharge from occurring in the lower electrode assembly, such as Figure 6 As shown, the steps include:

[0115] S100, measuring the DC self-bias voltage of the substrate W to obtain a corresponding self-bias voltage measurement value;

[0116] Currently, a probe is commonly used to measure the DC self-bias voltage of the substrate W. A probe channel (not shown in the figure) is provided inside the electrostatic chuck 202 for accommodating the probe. When measuring the DC self-bias voltage of the substrate W, the probe extends from the corresponding probe channel and contacts the back of the substrate. However, during the process, contaminants from the probe channel can easily cause particle contamination to the substrate W, affecting the yield of the substrate W processing.

[0117] The electrostatic electrode 2023 and the base 2022 are equivalent to two plates of a capacitor, and the first RF power supply 250 applied to the base 2022 generates a first coupling voltage at the electrostatic electrode 2023. Since there is a proportional relationship between the DC self-bias value of the substrate W and the voltage amplitude of the first RF power supply 250, there is also a proportional relationship between the DC self-bias value of the substrate W and the amplitude of the first coupling voltage. Therefore, in the process of the present invention, the self-bias voltage measurement module 260 (such as Figure 5As shown and described in detail later), the amplitude of the first coupling voltage is measured to measure the DC self-bias value of the substrate W (which is a negative value).

[0118] The waveform of the first coupling voltage can also be regarded as the superposition of two sine waves with different amplitudes. The sine waveform of the first coupling voltage in the first stage has a larger amplitude (denoted as V ohH ), the sine wave in the second stage has a smaller amplitude (denoted as V ohL ). At present, when measuring the amplitude of the first coupling voltage, sufficient time accuracy cannot be guaranteed. That is, it is impossible to accurately measure the amplitude of the first coupling voltage in the first stage and the second stage respectively. Therefore, in this embodiment, the amplitude of the first coupling voltage is measured during the entire working cycle of the first RF power source 250 to obtain the corresponding first amplitude measurement value (recorded as ). The first amplitude measurement value is the time average value of the amplitude of the first coupling voltage. , x is the duty cycle of the first RF power supply 250 outputting high RF power, and x is less than 50%.

[0119] First amplitude measurement The time average of the DC self-bias voltage of the substrate (denoted as , is a negative value). Therefore, in this embodiment, the time average value As the self-bias voltage measurement value of the substrate W in the process, the first amplitude measurement value can be Calculate the self-bias voltage measurement value of substrate W .

[0120] make , β is the proportionality coefficient. When the first RF power source 250 outputs the same RF power, different process conditions (for example, the gas pressure in the reaction chamber 10) will result in the first amplitude measurement value Therefore, β is a proportionality coefficient associated with the process parameters of the process (including the gas pressure value in the reaction chamber 10 ).

[0121] In this embodiment, before the process starts, the proportionality coefficient β is obtained by the following steps:

[0122] H100, make the process parameters associated with the proportional coefficient β meet the process requirements;

[0123] The purpose of this step is to ensure that the proportionality factor β is suitable for calculating the self-bias voltage measurement value in the process.

[0124] H200, providing a test substrate; setting the working mode of the first radio frequency power supply to a continuous wave mode;

[0125] In the process of obtaining the proportional coefficient β, the first RF power source 250 outputs a constant RF power P0. In another embodiment, the first RF power source 250 is also in a continuous wave mode during the process and outputs a constant RF power P1. P0 and P1 may be the same or different, and are not limited in the present invention.

[0126] H300, measure the DC self-bias voltage of the test substrate through a probe (not shown in the figure) to obtain the corresponding measurement value V pin ;

[0127] H400, measure the amplitude of the second coupling voltage generated by the first RF power supply on the electrostatic electrode ; .

[0128] Since the second RF power source outputs a constant RF power, the waveform of the second coupling voltage is a single sine wave, and the DC self-bias voltage of the substrate W will not change with time. Therefore, the amplitude measured is is the actual amplitude of the second coupling voltage, the measured value V pin is the actual self-bias value of the substrate W, ensuring the accuracy of the proportionality coefficient β.

[0129] In one embodiment, the obtained proportional coefficient β and the process parameters associated therewith are stored in a table, and the proportional coefficient β applicable to the current process is obtained by querying the table to perform self-bias voltage measurement. Since there is no need to measure the DC self-bias voltage of the substrate W by a probe in the actual process (an electrostatic chuck 202 without a probe channel can be used), the particle contamination caused to the substrate W is greatly reduced.

[0130] S200, calculating a self-bias voltage compensation value based on the self-bias voltage measurement value;

[0131] S300, applying a first DC voltage to the lower electrode assembly, wherein the voltage value of the first DC voltage is the self-bias compensation value, so that the voltage difference between the lower electrode assembly and the substrate is less than a preset first threshold value.

[0132] The voltage output by the first RF power source 250 is recorded as , the substrate voltage is recorded as If the voltage applied to the base 2022 is The DC voltage is used to reduce the voltage difference between the base 2022 and the substrate W. , then .like Figure 7 As shown, at time T1 (in the first stage), the first RF power source 250 outputs the maximum positive voltage. At this time, the voltage difference between the substrate W and the base 2022 is . is the maximum voltage difference between the base 2022 and the substrate W during the entire working cycle of the first RF power source 250. is the time average value of the DC self-bias voltage of the substrate during the process, , so the self-bias voltage measurement value Approaching the DC self-bias voltage value when the first RF power source 250 outputs low RF power (i.e. ). Voltage difference It still exceeds the first threshold, indicating that the base voltage compensation is insufficient and arc discharge is still prone to occur between the base 2022 and the substrate W.

[0133] The self-bias compensation value (denoted as V1) in the present invention is a negative value, and .like Figure 5 As shown, in this embodiment, the first DC voltage with a voltage value of V1 is applied to the base 2022 by the first high voltage output module 261 to reduce the voltage difference between the base 2022 and the substrate W. Figure 8 FIG. 2 shows a schematic diagram of voltage waveforms between the substrate W and the base 2022 after a DC voltage with a voltage value of V1 is applied to the base 2022. Figure 8 As shown, at time T1 (in the first stage), the first RF power source 250 outputs the maximum positive voltage. At this time, the voltage difference between the base 2022 and the substrate W is . It is the maximum voltage difference between the base 2022 and the substrate W during the entire working cycle of the first RF power source 250. ,and is smaller than the first threshold.

[0134] The present invention calculates the corresponding self-bias compensation value based on the measurement result of the DC self-bias voltage of the substrate, and by applying a first DC voltage having a voltage value of the self-bias compensation value to the lower electrode assembly, the self-bias compensation value can be made close to the DC self-bias value (i.e., the DC self-bias voltage) when the first RF power source 250 outputs high RF power. ). This effectively solves the problem that arc discharge is easily generated between the lower electrode assembly and the substrate W due to insufficient voltage compensation of the lower electrode assembly when the first RF power source 250 outputs high RF power, thereby greatly improving the safety of substrate W processing.

[0135] In a preferred embodiment, , α is the proportional coefficient, 1<α<1 / x. Fig. 9 The figure shows the compensation for the base voltage ( Too large). Fig. 9 As shown, at time T2 (in the second stage), the first RF power source 250 outputs the minimum negative voltage. At this time, the voltage difference between the base 2022 and the substrate W is . It is the maximum voltage difference between the base 2022 and the substrate W during the entire working cycle of the first RF power source 250. At time T2, it is negative. The maximum refers to Maximum. When the power consumption of the lower electrode assembly is greater than the first threshold, arc discharge is likely to occur in the lower electrode assembly when the first RF power source 250 outputs low RF power.

[0136] In the present invention, the self-bias compensation value V1 is made to fall within a suitable range through the proportional coefficient α, which can effectively avoid under-compensation and over-compensation of the voltage of the lower electrode assembly by the first DC voltage, and greatly reduce the risk of arc discharge in the lower electrode assembly during the entire working cycle of the first RF power supply 250.

[0137] In one embodiment, the working mode of the first RF power source 250 in the process is a continuous wave mode, and the self-bias voltage compensation value is equal to the self-bias voltage measurement value. The first DC voltage is applied to the base 2022, so as to reduce the voltage difference between the base 2022 and the substrate W.

[0138] In another embodiment, the working mode of the first RF power source 250 in the process is a continuous wave mode, and the working stages of the first RF power source 250 include a first stage, a second stage, and a third stage (the number of working stages is only an example, and there may be more than three stages), and the first stage has the shortest duration. The first RF power source outputs high RF power in the first stage, and outputs low RF power in both the second stage and the third stage, and the RF power in the second stage is the lowest. A better one can be determined through experiments , making V1 close to the average value of the substrate self-bias voltage in the first and second stages.

[0139] In another embodiment, Fig.10 As shown, the method for preventing arc discharge from occurring in the lower electrode assembly also includes the steps of:

[0140] S400, calculating the voltage value of the DC voltage that needs to be applied to the electrostatic electrode when the reaction chamber is idle in order to make the electrostatic chuck generate a preset electrostatic suction force ;

[0141] S500, in the process, applying a second DC voltage to the electrostatic electrode, wherein the voltage value of the second DC voltage is .

[0142] like Figure 5 As shown, the second high voltage output module 262 applies a voltage value of The DC voltage is such that the voltage difference used to generate the electrostatic attraction in the first stage is , the voltage difference used to generate electrostatic attraction in the second stage (like Fig.11 As shown in FIG. 1 ). Although the electrostatic attraction in the first stage is slightly smaller than the preset electrostatic attraction, it can still stably adsorb the substrate W. Although the electrostatic attraction in the second stage is slightly larger than the preset electrostatic attraction, it will not make it difficult to desorb the substrate W. Therefore, the electrostatic attraction generated by the electrostatic chuck 202 in the first stage and the second stage meets the process standards.

[0143] Embodiment 2

[0144] like Fig.12 As shown, the lower electrode assembly further includes a focusing ring 230 and an edge electrode 231. The focusing ring 230 surrounds the periphery of the substrate W and is used to control the RF electric field distribution at the edge of the substrate W to be processed, so that the plasma is concentrated on the substrate W, and the plasma characteristics and ion directionality at the center area and the edge area of ​​the substrate are uniform.

[0145] However, as the plasma treatment process is repeated, the erosion of the focusing ring 230 caused by ion bombardment deepens, the thickness of the focusing ring 230 decreases, and the plasma sheath on the surface of the focusing ring 230 moves downward with the erosion of the focusing ring 230, causing the plasma sheath in the edge area of ​​the substrate to be distorted. The ion incident direction in the edge area of ​​the substrate tends to tilt toward the center of the substrate, resulting in a skew phenomenon.

[0146] like Fig.12 As shown, the edge electrode 231 is arranged inside the focusing ring 230 or below the focusing ring 230, and the edge electrode 231 is electrically insulated from the electrostatic electrode 2023. Low-frequency RF power is provided to the edge electrode 231 by an independent second RF power supply 270. The second RF power supply 270 has the same working mode as the first RF power supply 250, and the output power of the second RF power supply 270 is positively correlated with the output power of the first RF power supply 250. In this embodiment, the second RF power supply 270 is in pulse mode during the process, and the working cycle of the second RF power supply 270 includes a first stage (outputting high RF power) and a second stage (outputting low RF power). In other embodiments, a certain amount of RF power can also be allocated to the edge electrode 231 by the first RF power supply 250.

[0147] The edge impedance adjustment unit 271 is electrically connected between the edge electrode 231 and the second RF power supply 270, and is used to adjust the potential of the edge electrode 231 (denoted as ), thereby adjusting the voltage of the plasma sheath on the surface of the focusing ring 230, and then adjusting the distribution of the plasma sheath at the focusing ring sheath and the edge area of ​​the substrate, thereby improving the verticality of the ion incident direction in the edge area of ​​the substrate.

[0148] During the process, a DC self-bias voltage (denoted as ), due to the different RF powers distributed to the substrate W and the focusing ring 230, this causes the DC self-bias voltage of the focusing ring 230 to The DC self-bias voltage of the substrate W Not equal.

[0149] The coupling voltage generated by the first RF power source 250 on the substrate W is expressed as , substrate voltage The focusing ring voltage is recorded as , The voltage difference between the focusing ring 230 and the substrate W is In the high aspect ratio etching process, the voltage difference between the substrate W and the focus ring 230 is relatively large, which causes arc discharge to easily occur between the substrate W and the focus ring 230 .

[0150] The voltage difference between the focus ring 230 and the substrate W is determined by the RF voltage difference and DC bias difference ( In this embodiment, the voltage difference between the focusing ring 230 and the substrate W is reduced by reducing the DC bias voltage difference.

[0151] The difference from the first embodiment is that Fig.12 As shown, in this embodiment, the first DC voltage is applied to the edge electrode 231 through the first high voltage output module 261. The voltage value of the first DC voltage is .make , Respectively represent the DC self-bias value of substrate W in the first stage and the second stage. It can make V1 close to and The average value of .

[0152] make They represent the DC self-bias voltage of the focusing ring 230 in the first stage and the second stage respectively. Fig.13 As shown, after the first DC voltage is applied to the edge electrode 231, the DC bias voltage difference is reduced to , which is reduced to The possibility of arc discharge between the substrate W and the focus ring 230 is greatly reduced. Embodiment 3

[0153] make represents the RF power value of the first RF power source 250, Represents the absolute value of the substrate DC self-bias voltage. and is positively correlated, and the RF power value Ability to obtain in real time, such as Fig.14 As shown, this embodiment is based on the radio frequency power value The third DC voltage (the voltage value of which is recorded as V3, V3<0) is applied to the edge electrode 231 through the third high-voltage output module 263, so that the voltage value V3 of the third DC voltage follows the DC self-bias voltage changes with the changes of.

[0154] In this embodiment, , is the preset proportional coefficient. The proportional coefficient can be calibrated by experiment , so that satisfy . Calibration scale factor The steps include:

[0155] F100, making the first RF power source 250 operate in a continuous wave mode;

[0156] F200, provide a test substrate W, and measure the DC self-bias voltage of the substrate W through a probe. Obtain the corresponding measurement value ;

[0157] F300, measure the RF power value of the first RF power supply ; .

[0158] In the first stage, In the second stage .like Fig.15 As shown, after the third DC voltage is applied to the edge electrode 231, the DC bias voltage difference between the focus ring 230 and the substrate W is reduced to , which is reduced to When the first RF power source 250 outputs high or low RF power, the voltage difference between the focus ring 230 and the substrate W can be greatly reduced, thereby reducing the possibility of arc discharge between the substrate W and the focus ring 230 .

[0159] The present invention also provides a plasma processing device 2 for implementing the method according to the present invention, such as Figure 5 As shown, it includes: a vacuum reaction chamber 20 , a self-bias voltage measurement module 260 , a first high voltage output module 261 , a first RF power source 250 , and a source RF power source 240 .

[0160] The reaction chamber 20 is provided with a lower electrode assembly, through which the substrate W is supported. Figure 5As shown, the lower electrode assembly includes an electrostatic chuck 202. The electrostatic chuck 202 includes a dielectric layer 2021 and a metal base 2022 located below the dielectric layer 2021, and an electrostatic electrode 2023 is disposed in the dielectric layer 2021.

[0161] The gas shower head 203 is disposed above the lower electrode assembly and is used to deliver reaction gas into the reaction chamber 20. The gas shower head 203 serves as the upper electrode of the reaction chamber 20.

[0162] The first RF power source 250 is used to bias the substrate W, and its working cycle includes a first stage and a second stage. In the process, the first RF power source 250 outputs high RF power and low RF power to the lower electrode assembly in the first stage and the second stage respectively, and the duration of the first stage is shorter than the duration of the second stage. Figure 5 As shown, the first RF power source 250 outputs RF power to the base 2022 .

[0163] The source RF power source 240 is applied to the upper electrode and / or the lower electrode assembly to generate plasma in the reaction chamber 20 .

[0164] The self-bias voltage measurement module 260 is used to measure the DC self-bias voltage of the substrate W to obtain a corresponding self-bias voltage measurement value. The self-bias voltage measurement value is the time average value of the DC self-bias voltage measured during the entire working cycle of the first RF power source 250. Figure 5 As shown, the self-bias voltage measurement module 260 is electrically connected to the electrostatic electrode 2023. The first RF power supply 250 generates a first coupling voltage at the electrostatic electrode 2023. The self-bias voltage measurement module 260 measures the DC self-bias voltage of the substrate W by measuring the amplitude of the first coupling voltage during the process.

[0165] The first high-voltage output module 261 is connected to the self-bias voltage measurement module 260 by signal to obtain the self-bias voltage measurement value. The first high-voltage output module 261 also calculates the self-bias voltage compensation value based on the self-bias voltage measurement value. In the process, the first high-voltage output module 261 applies a first DC voltage to the lower electrode assembly (in this embodiment, the first DC voltage is applied to the base 2022), and the voltage value of the first DC voltage is the self-bias voltage compensation value, so that the voltage difference between the lower electrode assembly and the substrate W is less than a preset first threshold value.

[0166] make represents the self-bias voltage measurement value, and V1 represents the self-bias voltage compensation value. In a preferred embodiment, α is a proportionality coefficient, 1<α<1 / x, and x is a duty cycle of the high RF power output by the first RF power source 250. By making the self-bias compensation value V1 fall within a suitable range through the proportionality coefficient α, under-compensation and over-compensation of the voltage of the lower electrode assembly by the first DC voltage can be effectively avoided, and the risk of arc discharge in the lower electrode assembly is greatly reduced during the entire working cycle of the first RF power source 250.

[0167] Further, such as Figure 5 As shown, the plasma processing device 2 further includes: a second high voltage output module 262, which is communicatively connected to the self-bias voltage measurement module 260 to obtain a self-bias voltage measurement value.

[0168] In the process, the second DC voltage is applied to the electrostatic electrode 2023 through the second high voltage output module 262, and the voltage value of the second DC voltage is . When the reaction chamber 20 is idle, in order to make the electrostatic chuck 202 generate a preset electrostatic suction force, a voltage value of a DC voltage needs to be applied to the electrostatic electrode 2023. By applying a second DC voltage to the electrostatic electrode 2023, the difference between the electrostatic suction force generated by the electrostatic chuck 202 in the first stage and the second stage and the preset electrostatic suction force falls within a reasonable range, which can stably adsorb the substrate W and will not cause the substrate W to be difficult to desorb, meeting the process standards.

[0169] Further, such as Figure 5 As shown, the plasma processing equipment 2 also includes a filter 264, which suppresses the radio frequency energy transmitted from the electrostatic electrode 2023 to the self-bias measurement module 260 and the second high-voltage output module 262, and suppresses the radio frequency energy transmitted from the base 2022 to the first high-voltage output module 261, thereby effectively ensuring the safety of substrate W processing.

[0170] In another embodiment, Fig.12 As shown, the plasma processing device 2 also includes a focusing ring 230, an edge electrode 231, a second RF power supply 270, an edge impedance adjustment unit 271 and an isolation circuit 290. The focusing ring 230 surrounds the outer periphery of the substrate W, and the edge electrode 231 is arranged inside the focusing ring 230 or below the focusing ring 230. The second RF power supply 270 provides low-frequency RF power to the edge electrode 231 through the edge impedance adjustment unit 271 to control the RF electric field distribution at the edge of the substrate to be processed. A first DC voltage is applied to the edge electrode 231 through the first high-voltage output module 261 to reduce the voltage difference between the focusing ring 230 and the substrate W. The isolation circuit 290 is used to prevent the RF power of the second RF power supply 270 from interfering with the first high-voltage output module 261.

[0171] In another embodiment, Fig.14 As shown, the plasma processing device 2 further includes a third high voltage output module 263, which applies a third DC voltage to the edge electrode 231 based on the RF power of the first RF power supply 250 to reduce the voltage difference between the focus ring 230 and the substrate W. The isolation circuit 290 is used to prevent the RF power of the second RF power supply 270 from interfering with the third high voltage output module 263.

[0172] like Fig.16 As shown, the technical solution of the present invention can also be used in inductively coupled plasma (ICP) processing equipment. Fig.16 The plasma processing device 3 includes: a reaction chamber 30, a liner 320, an insulating window 317, a plurality of inductively coupled coils 315, a lower electrode assembly, a first RF power supply 350, a self-bias voltage measurement module 360 ​​and a first high voltage output module 361.

[0173] The reaction chamber 30 includes a reaction chamber side wall 301 made of metal material and having a substantially cylindrical shape. The liner 320 is disposed inside the reaction chamber 30 to protect the inner wall of the reaction chamber 30 from being corroded by plasma. The insulating window 317 is disposed at the top of the reaction chamber 30, and a reaction gas injection port 303 is disposed at one end of the reaction chamber side wall 301 close to the insulating window 317. The inductive coupling coil 315 is disposed above the insulating window 317 and is connected to the RF source 340 through the RF matching network 316. The inductive coupling coil 315 generates an induced magnetic field under the excitation of the RF source 340, and the reaction gas in the reaction chamber 30 generates plasma under the action of the induced magnetic field.

[0174] The lower electrode assembly is arranged at the bottom of the reaction chamber 30, and the lower electrode assembly includes an electrostatic chuck 302 for carrying the substrate W. The electrostatic chuck 302 includes a base 3022 and a dielectric layer 3021. The dielectric layer 3021 is arranged on the base 3022, and an electrostatic electrode 3023 for generating electrostatic attraction is arranged inside the dielectric layer 3021 to adsorb the substrate W carried on the dielectric layer 3021. The first RF power supply 350 applies RF power to the base 3022 to control the bombardment energy of ions.

[0175] The self-bias voltage measurement module 360 ​​is electrically connected to the electrostatic electrode 3023. In the process, the self-bias voltage measurement module 360 ​​measures the amplitude of the first coupling voltage generated by the first RF power supply 350 at the electrostatic electrode 3023 to measure the DC self-bias voltage of the substrate W and obtain the corresponding self-bias voltage measurement value.

[0176] The first high-voltage output module 361 is connected to the self-bias voltage measurement module 360 ​​by signal to obtain the self-bias voltage measurement value. The first high-voltage output module 361 also calculates the self-bias voltage compensation value based on the self-bias voltage measurement value. In the process, the first high-voltage output module 361 applies a first DC voltage to the lower electrode assembly, and the voltage value of the first DC voltage is the self-bias voltage compensation value, so that the voltage difference between the lower electrode assembly and the substrate W is less than a preset first threshold value.

[0177] Further, such as Fig.16 As shown, the plasma processing device 3 further includes: a second high voltage output module 362, which is communicatively connected to the self-bias voltage measurement module 360 ​​to obtain a self-bias voltage measurement value.

[0178] In the process, the second DC voltage is applied to the electrostatic electrode 3023 through the second high voltage output module 362, and the voltage value of the second DC voltage is .

[0179] Further, such as Fig.16 As shown, the plasma processing equipment 3 also includes a filter 364, which suppresses the radio frequency energy transmitted from the electrostatic electrode 3023 to the bias measurement module 360 ​​and the second high-voltage output module 362, and suppresses the radio frequency energy transmitted from the base 3022 to the first high-voltage output module 361.

[0180] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0181] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preventing arc discharge from occurring in a lower electrode assembly, wherein the lower electrode assembly is placed in a vacuum reaction chamber of a plasma processing device and a substrate is supported by the lower electrode assembly, characterized in that: The method comprises: In the process, a low-frequency radio frequency power is provided to the lower electrode assembly through a first radio frequency power supply; a DC self-bias voltage of the substrate is measured during the entire working cycle of the first radio frequency power supply to obtain a corresponding self-bias voltage measurement value; the self-bias voltage measurement value is a time average value of the DC self-bias voltage; Calculating a self-bias voltage compensation value based on the self-bias voltage measurement value; A first DC voltage is applied to the lower electrode assembly, wherein the voltage value of the first DC voltage is the self-bias compensation value, so that the voltage difference between the lower electrode assembly and the substrate is less than a preset first threshold value.

2. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 1, characterized in that: The working mode of the first RF power supply includes a pulse mode; in the pulse mode, the working cycle of the first RF power supply includes at least a first stage and a second stage; in the first stage, the first RF power supply outputs high RF power; In the second stage, the first RF power source outputs low RF power.

3. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 1, characterized in that: The working mode of the first RF power supply includes a continuous wave mode; in the continuous wave mode, the first RF power supply outputs a constant RF power to the lower electrode assembly, and the self-bias voltage compensation value is equal to the self-bias voltage measurement value.

4. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 2, characterized in that: The duration of the first stage is shorter than that of the second stage; the self-bias voltage measurement value and the self-bias voltage compensation value are both negative values, and the absolute value of the self-bias voltage compensation value is greater than the absolute value of the self-bias voltage measurement value.

5. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 4, characterized in that: make represents the self-bias voltage measurement value, V1 represents the self-bias voltage compensation value, ; α is the proportional coefficient, 1<α<1 / x; x is the duty cycle of the high RF power.

6. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 1, wherein: The lower electrode assembly comprises an electrostatic chuck, and the electrostatic chuck comprises a dielectric layer and a metal base located below the dielectric layer, and an electrostatic electrode is arranged in the dielectric layer; the first DC voltage is applied to the base.

7. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 6, characterized in that: Also includes: Calculate the voltage value of the DC voltage that needs to be applied to the electrostatic electrode to make the electrostatic chuck generate a preset electrostatic suction force when the reaction chamber is idle ; make represents the self-bias voltage measurement value; in the process, a second DC voltage is applied to the electrostatic electrode, and the voltage value of the second DC voltage is .

8. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 6, wherein: The first radio frequency power source generates a first coupling voltage at the electrostatic electrode; during the process, the DC self-bias voltage of the substrate is measured by measuring the amplitude of the first coupling voltage.

9. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 8, characterized in that: During the working cycle of the first RF power source, the amplitude of the first coupling voltage is measured to obtain a corresponding first amplitude measurement value; the first amplitude measurement value is a time average value of the amplitude of the first coupling voltage; make represents the self-bias voltage measurement value, represents the first amplitude measurement value, ; β is a proportionality coefficient associated with the process parameters of the process, Indicates taking the absolute value.

10. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 9, characterized in that: Before the process starts, the proportionality coefficient β is obtained by the following steps: Make the process parameters associated with the proportionality coefficient β meet the process requirements; Providing a test substrate; setting the working mode of the first radio frequency power supply to a continuous wave mode, wherein the first radio frequency power supply outputs a constant radio frequency power to the lower electrode assembly in the continuous wave mode; The DC self-bias voltage of the test substrate is measured by a probe to obtain the corresponding measurement value V pin ; Measuring the amplitude of the second coupling voltage generated by the first radio frequency power supply at the electrostatic electrode ; 。 11. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 9, characterized in that: The process parameters include: the gas pressure value in the reaction chamber during the process.

12. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 9, wherein: The proportionality coefficient β and the process parameters associated therewith are stored in a table, and the proportionality coefficient β is obtained by querying the table.

13. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 1, wherein: The lower electrode assembly also includes a focus ring and an edge electrode; The focusing ring surrounds the outer periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode; The first DC voltage is applied to the edge electrode.

14. The method for preventing arc discharge from occurring in the lower electrode assembly according to claim 1, wherein: The lower electrode assembly also includes a focus ring and an edge electrode; The focusing ring surrounds the outer periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode; In the process, a third DC voltage is applied to the edge electrode, and the third DC voltage is a negative voltage; Let V3 represent the voltage value of the third DC voltage, represents the radio frequency power value of the first radio frequency power source, ; is the preset scaling factor.

15. A plasma processing device for implementing the method according to any one of claims 1 to 14, characterized in that: include: A vacuum reaction chamber, wherein a lower electrode assembly is provided in the reaction chamber; and a substrate is carried by the lower electrode assembly; A self-bias voltage measurement module is used to measure the DC self-bias voltage of the substrate and obtain a corresponding self-bias voltage measurement value; in the process, a low-frequency RF power is provided to the lower electrode assembly through a first RF power supply; the self-bias voltage measurement value is a time average value of the DC self-bias voltage measured during the entire working cycle of the first RF power supply; A first high-voltage output module, whose signal is connected to the self-bias voltage measurement module to obtain the self-bias voltage measurement value; the first high-voltage output module also calculates a self-bias voltage compensation value based on the self-bias voltage measurement value; during the process, a first DC voltage is applied to the lower electrode assembly through the first high-voltage output module, and the voltage value of the first DC voltage is the self-bias voltage compensation value, so that the voltage difference between the lower electrode assembly and the substrate is less than a preset first threshold value.

16. The plasma processing apparatus according to claim 15, wherein: The working cycle of the first RF power supply includes at least a first stage and a second stage. During the process, the first RF power supply outputs high RF power and low RF power to the lower electrode assembly in the first stage and the second stage respectively.

17. The plasma processing apparatus according to claim 16, wherein: The duration of the first stage is shorter than the duration of the second stage; represents the self-bias voltage measurement value, V1 represents the self-bias voltage compensation value, ; α is the proportional coefficient, 1<α<1 / x; x is the duty cycle of the high RF power.

18. The plasma processing apparatus according to claim 16, wherein: The lower electrode assembly comprises an electrostatic chuck, and the electrostatic chuck comprises a dielectric layer and a metal base located below the dielectric layer, and an electrostatic electrode is arranged in the dielectric layer; the first DC voltage is applied to the base.

19. The plasma processing apparatus according to claim 18, wherein: Also includes: A second high-voltage output module, which is communicatively connected to the self-bias voltage measurement module to obtain the self-bias voltage measurement value; In the process, a second DC voltage is applied to the electrostatic electrode through the second high voltage output module, and the voltage value of the second DC voltage is ; is the self-bias voltage measurement value; When the reaction chamber is idle, in order for the electrostatic chuck to generate a preset electrostatic suction force, a voltage value of a DC voltage needs to be applied to the electrostatic electrode.

20. The plasma processing apparatus according to claim 18, wherein: The self-bias voltage measurement module is electrically connected to the electrostatic electrode; the first RF power supply generates a first coupling voltage at the electrostatic electrode; during the process, the self-bias voltage measurement module measures the DC self-bias voltage of the substrate by measuring the amplitude of the first coupling voltage.

21. The plasma processing apparatus according to claim 19, wherein: It also includes a filter, through which the radio frequency energy transmitted from the electrostatic electrode to the self-bias voltage measurement module and the second high-voltage output module is suppressed, and the radio frequency energy transmitted from the base to the first high-voltage output module is suppressed.

22. The plasma processing apparatus according to claim 16, wherein: The lower electrode assembly includes a focus ring and an edge electrode; The focusing ring surrounds the outer periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode; The first DC voltage is applied to the edge electrode.

23. The plasma processing apparatus according to claim 16, wherein: It also includes a third high-voltage output module, which is electrically connected to the first radio frequency power supply; The lower electrode assembly includes a focus ring and an edge electrode; The focusing ring surrounds the periphery of the substrate, and the edge electrode is arranged inside the focusing ring or below the focusing ring; the RF electric field distribution at the edge of the substrate to be processed is controlled by providing low-frequency RF power to the edge electrode; The third high-voltage output module applies a third DC voltage to the edge electrode based on the RF power of the first RF power supply; the third DC voltage is a negative voltage; Let V3 represent the voltage value of the third DC voltage, represents the radio frequency power value of the first radio frequency power source, ; is the preset scaling factor.

24. The plasma processing apparatus according to claim 23, wherein: It also includes an isolation circuit for preventing the radio frequency power applied to the edge electrode from interfering with the third high-voltage output module.

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