Cleaning method and plasma processing apparatus

Abstract

The present disclosure relates to a cleaning method and a plasma processing apparatus which appropriately remove reaction products attached to a bevel portion and a back surface of a substrate in plasma etching. The cleaning method of a substrate includes the following steps: providing a substrate support body with a substrate having a Low-k layer containing silicon; etching the Low-k layer by plasma generated from a first gas; separating the substrate after etching from the substrate support body; and removing reaction products attached to the substrate in etching by plasma generated from a second gas, wherein the second gas contains C x H y F z a first carbon-containing gas represented by CxHyFz (y ≥ 0, x / z > 1 / 4).

Description

Technical Field

[0001] This disclosure relates to a cleaning method and a plasma treatment apparatus. Background Technology

[0002] According to Patent Document 1, this generates a traveling shock wave within the cavity, which is used to detach foreign objects attached to the back of the substrate.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-317782 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The techniques disclosed herein appropriately remove reaction products that adhere to the beveled and back surfaces of a substrate during plasma etching.

[0008] Solution for solving the problem

[0009] One aspect of this disclosure is a substrate cleaning method comprising the following steps: providing a substrate having a Low-k layer containing silicon to a substrate support; etching the Low-k layer using plasma generated by a first gas; separating the etched substrate from the substrate support; and removing reaction products adhering to the substrate during etching using plasma generated by a second gas, wherein the second gas contains C x H y F z (y≥0, x / z>1 / 4) represents the first carbon-containing gas.

[0010] The effects of the invention

[0011] According to this disclosure, it is possible to properly remove reaction products that adhere to the bevel and back surfaces of a substrate during plasma etching. Attached Figure Description

[0012] Figure 1 This is a longitudinal cross-sectional view showing the structure of a plasma processing system according to one embodiment.

[0013] Figure 2 This is a bottom view showing the structure of the inner upper electrode according to one embodiment.

[0014] Figure 3 This is a system diagram showing the structure of a gas supply unit according to one embodiment.

[0015] Figure 4This is a timing diagram of plasma processing involved in one implementation method.

[0016] Figure 5 This is an illustration of the etching target layer and mask layer formed on the substrate.

[0017] Figure 6 This is an explanatory diagram illustrating an example of the plasma processing results involved in the embodiment.

[0018] Figure 7 This is an explanatory diagram showing an example of the plasma treatment results involved in the experimental case.

[0019] Figure 8 This is an explanatory diagram showing an example of the plasma treatment results involved in the experimental case. Detailed Implementation

[0020] In the manufacturing process of semiconductor devices, an etching process is performed on the etching target film, which is stacked on the surface of a semiconductor substrate (hereinafter referred to as "substrate"), using a patterned mask layer as a mask. This etching process is usually performed using a plasma processing apparatus. In recent years, low-k materials such as SiOC film and SiOCH film have sometimes been used as the etching target film.

[0021] There is a concern that during the etching process described above in a plasma processing apparatus, reaction products, such as those from fluorocarbon (CF) based polymers, may adhere to the beveled surface or back side of the substrate to be etched. There is a risk that these reaction products adhering to the substrate may detach during substrate processing or transport, contaminating the interior of the apparatus and potentially causing adverse conditions or affecting the substrate processing results.

[0022] Here, as methods for removing these reaction products, examples include, for example, the method disclosed in Patent Document 1, which involves introducing gas into the interior of a chamber to remove the reaction products (gas cleaning), and the method of generating plasma inside the chamber to remove the reaction products (plasma cleaning), etc.

[0023] However, for example, in the case where the etched object film described above has a Low-k film, when using C x H y F z When plasma cleaning is performed with CF-based gases (e.g., CF4 gas) that have a low carbon ratio (x / z≤1 / 4), the Low-k film may be degraded or damaged.

[0024] The technology disclosed herein was developed in view of the above circumstances, effectively removing reaction products adhering to the beveled and back surfaces of the substrate during plasma etching. Hereinafter, a plasma processing apparatus, which is a substrate processing apparatus according to this embodiment, and a plasma processing method including the cleaning method according to this embodiment will be described with reference to the accompanying drawings. Furthermore, in this specification and the accompanying drawings, elements having substantially the same functional structure are labeled with the same reference numerals, thereby omitting repeated descriptions.

[0025] <Plasma Processing Device>

[0026] Figure 1 This is a schematic longitudinal cross-sectional view showing the outline of the structure of the plasma processing system. Furthermore, in the following description, the side of the substrate W on which etching is performed, i.e., the surface on which the Low-k film, which is the film to be etched, is formed, is sometimes referred to as the "surface," and the side opposite to the surface is referred to as the "back side."

[0027] In one embodiment, the plasma processing system includes a parallel-plate type plasma etching apparatus (hereinafter referred to as "plasma processing apparatus 1") and a control unit 2. The plasma processing apparatus 1 includes a generally cylindrical processing container 10 for accommodating a substrate W, a substrate support 11 including a lower electrode (described later), an upper electrode 20, a gas supply unit 30, and an exhaust system 40.

[0028] The processing container 10 is made of, for example, aluminum alloy and is electrically grounded. The inner wall of the processing container 10 is covered with an alumina film or a yttrium oxide film (Y₂O₃). Additionally, a substrate (wafer) W inlet / outlet (not shown) is provided on the side of the processing container 10, through which it connects to the outside of the plasma processing apparatus 1. The inlet / outlet is configured to open and close freely via a gate valve (not shown).

[0029] A substrate support 11 for mounting a substrate W is disposed inside the processing container 10. The substrate support 11 includes a main body 111 and a focusing ring 112. The focusing ring 112 is configured to surround the electrostatic chuck 115, which will be described later, around the main body 111.

[0030] In one embodiment, the main body 111 includes a support platform 113, a base 114, and an electrostatic chuck 115. The support platform 113, the base 114, and the electrostatic chuck 115 are arranged in a stacked manner from the bottom side of the processing container 10.

[0031] The support platform 113 has a generally cylindrical shape and is disposed approximately at the center of the bottom surface of the processing container 10, separated by an insulating plate (not shown). Furthermore, a flow path C is formed inside the support platform 113. A heat transfer medium from a cooling device (not shown) is circulated and supplied to the flow path C. This allows the temperature of the substrate W on the base 114 (more specifically, on the electrostatic chuck 115) to be controlled to a desired temperature.

[0032] The base 114 is supported on the support platform 113. The base 114 is constructed of conductive components such as aluminum alloy. The conductive components of the base 114 function as lower electrodes. The base 114 is electrically connected to the high-frequency power supply 114b via a matching adapter 114a. The high-frequency power supply 114b is capable of outputting a first high-frequency voltage in the range of, for example, 2MHz to 20MHz, with a frequency of, for example, 2MHz. The matching adapter 114a enables the internal impedance of the high-frequency power supply 114b to be matched with the load impedance. Furthermore, the high-frequency voltage from the high-frequency power supply 114b can also be pulsed.

[0033] An electrostatic chuck 115 is supported on a base 114. An adsorption electrode 115a is disposed inside the electrostatic chuck 115. The adsorption electrode 115a is connected to a DC power supply. By applying a voltage from the DC power supply to the adsorption electrode 115a, an electrostatic force such as Coulomb force is generated. The substrate W is adsorbed and held on the upper surface (substrate mounting surface) of the electrostatic chuck 115 by the electrostatic force.

[0034] In addition, cylindrical inner wall members 116, for example made of quartz, are installed on the outer peripheral surfaces of the support platform 113 and the base 114.

[0035] In addition, a gas supply pipe 120 and a lifter 130 are provided inside the main body 111 of the substrate support 11.

[0036] The gas supply pipe 120 is configured to penetrate the main body 111 along the thickness direction, and the gas supply pipe 120 is connected to a gas supply source (not shown). As a result, the gas supply pipe 120 supplies a heat transfer gas (back-side gas) such as He gas between the back side of the substrate W and the electrostatic chuck 115, so as to control the substrate W adsorbed and held on the upper surface of the electrostatic chuck 115 to a desired temperature.

[0037] The lifting device 130 includes a lifting pin 131 and an actuator 132. An example of the actuator includes an electric actuator, a cylinder, a motor, etc. For the lifting device 130, the height of the front end of the lifting pin 131 is adjusted to lift the substrate W on the base 114 (more specifically on the electrostatic chuck 115) so that the back side of the substrate W reaches the desired position.

[0038] The lifting pin 131 is a columnar component that moves up and down by protruding and retracting its upper end relative to the substrate mounting surface of the electrostatic chuck 115. The lifting pin 131 is configured to insert into a pin-through hole formed along the thickness direction of the main body 111 of the substrate support 11. Multiple, for example, three or more lifting pins 131 are arranged at intervals along the circumference of the electrostatic chuck 115 (substrate mounting surface). The lifting pins 131 are evenly spaced along the aforementioned circumferential direction. An actuator 132 generates a driving force to move the lifting pins 131 up and down, thereby causing the multiple lifting pins 131 to move.

[0039] The lifting device 130 is configured such that the lifting pin 131 is raised and lowered by the action of the actuator 132, thereby allowing the lifting pin 131 to move freely between the following positions on the substrate W: a junction position (where the upper end protrudes from the substrate mounting surface), a standby position (where the upper end does not protrude from the substrate mounting surface), and a cleaning position (where the upper end protrudes from the substrate mounting surface and its upper end is lower than the junction position). In other words, the actuator 132 is configured to allow the substrate W held on the lifting pin 131 to move freely between the junction position (where it is junctioned with the substrate transport robot), the processing position (where it is placed on the substrate mounting surface), and the cleaning position (where reaction products adhering to the substrate W are removed).

[0040] Additionally, a high-pass filter 140 is electrically connected to the base 114 that forms the lower electrode. The high-pass filter 140 is used to cut off the high frequency from the high-frequency power supply 114b connected to the lower electrode and to pass the high frequency from the high-frequency power supply 20b connected to the upper electrode 20 (described later) to the ground line.

[0041] An upper electrode 20 is disposed above the substrate support 11 and faces the base 114, which constitutes the lower electrode, in parallel with it. A plasma generation space S is formed between the base 114 and the upper electrode 20.

[0042] The upper electrode 20 includes an annular outer upper electrode 21 and a circular inner upper electrode 22. The upper electrode 20 is electrically connected to the high-frequency power supply 20b via a matching adapter 20a. The high-frequency power supply 20b is capable of outputting a second high-frequency voltage with a frequency of 40MHz or higher (e.g., 60MHz). The matching adapter 20a enables the internal impedance of the high-frequency power supply 20b to be matched with the load impedance. Furthermore, the high-frequency voltage from the high-frequency power supply 20b can also be pulsed.

[0043] The outer upper electrode 21 is configured to surround the inner upper electrode 22. An annular dielectric (not shown) is provided between the outer upper electrode 21 and the inner upper electrode 22. Additionally, an annular insulating shielding member (not shown), for example made of alumina, is hermetically provided between the outer upper electrode 21 and the inner peripheral wall of the processing container 10. The outer upper electrode 21 is connected to the matching device 20a and the high-frequency power supply 20b via a power supply cylinder 211, a connector 23, and an upper electrode rod 24. The power supply cylinder 211 is, for example, formed as a generally cylindrical shape with an open lower surface, and its lower end is connected to the outer upper electrode 21. At the center of the upper surface of the power supply cylinder 211, it is electrically connected to the lower end of the upper electrode rod 24 via the connector 23. The upper end of the upper electrode rod 24 is connected to the output side of the matching device 20a.

[0044] The inner upper electrode 22 constitutes a spray head that ejects a desired gas into the plasma generation space S supported on the substrate W by the substrate support 11. The inner upper electrode 22 includes a number of gas inlet holes 221a (see reference). Figure 2 The electrode plate 221 is a circular plate and the electrode support 222 supports the upper surface of the electrode plate 221 in a detachable manner. The electrode support 222 is formed into a circular plate with a diameter approximately the same as that of the electrode plate 221.

[0045] like Figure 1 As shown, a matching device 20a and a high-frequency power supply 20b are connected to the upper surface of the electrode support 222 via a lower electrode rod 25, a connector 23, and an upper electrode rod 24. A variable capacitor 26 is disposed in the middle of the lower electrode rod 25. The ratio of the electric field strength formed directly below the outer upper electrode 21 to the electric field strength formed directly below the inner upper electrode 22 when a second high-frequency voltage is applied from the high-frequency power supply 20b can be adjusted by adjusting the capacitance of the variable capacitor 26.

[0046] In one embodiment, the inner upper electrode 22 has multiple first gas introduction sections for introducing gas into different regions within the substrate W surface supported by the substrate support 11, such as the central region of the substrate W (hereinafter referred to as the "central region") and the peripheral region of the substrate W (hereinafter referred to as the "edge region"). In this embodiment, these are two first gas introduction sections. Hereinafter, these two first gas introduction sections will be referred to as the first gas introduction section 230 for introducing gas into the central region and the second gas introduction section 240 for introducing gas into the edge region, respectively.

[0047] The first gas inlet section 230, which serves as the first supply section, includes a buffer chamber 222a formed inside the electrode support 222 and a number of gas inlet holes 221a formed on the lower surface of the buffer chamber 222a. The buffer chamber 222a is formed corresponding to the interior of the central region of the electrode support 222, that is, the central region of the substrate W adsorbed and held on the substrate support 11.

[0048] The second gas inlet 240 is further divided into a processing gas inlet 240a and an auxiliary gas inlet 240b. The processing gas inlet 240a is used to introduce processing gas into the processing container 10 from the processing gas supply unit 31 (described later). The auxiliary gas inlet 240b is used to introduce auxiliary gas, which is added to the processing gas introduced from the processing gas inlet 240a, into the processing container 10 from the auxiliary gas supply unit 33 (described later). The processing gas inlet 240a is configured to surround the first gas inlet 230. The auxiliary gas inlet 240b is configured to surround the processing gas inlet 240a. In other words, the first gas inlet 230, the processing gas inlet 240a, and the auxiliary gas inlet 240b are arranged sequentially from the radially inner side of the inner upper electrode 22.

[0049] The processing gas inlet section 240a, serving as the second supply section, includes a buffer chamber 222b formed inside the electrode support 222 and a plurality of gas inlet holes 221a formed on the lower surface of the buffer chamber 222b. Additionally, the supplementary gas inlet section 240b, serving as the third supply section, includes a buffer chamber 222c formed inside the electrode support 222 and a plurality of gas inlet holes 221a formed on the lower surface of the buffer chamber 222c. The buffer chambers 222b and 222c are formed corresponding to the interior of the peripheral region of the electrode support 222, i.e., the edge region of the substrate W held and adsorbed on the substrate support 11.

[0050] Furthermore, buffer chambers 222a, 222b, and 222c may be formed independently, for example, inside the electrode support 222. Alternatively, for example, a single buffer chamber may be formed inside the electrode support 222, and this single buffer chamber may be divided by, for example, an O-ring.

[0051] Furthermore, the gas supply unit 30 supplies the gas corresponding to the purpose to each buffer chamber 222a, 222b and 222c, and the gas is sprayed into the central region of the substrate W through the buffer chamber 222a of the first gas inlet unit 230, and the gas is sprayed into the edge region of the substrate W through the buffer chamber 222b or 222c of the second gas inlet unit 240.

[0052] A cylindrical grounding conductor 250 with a sidewall having a diameter approximately the same as that of the processing container 10 is provided on the outside of the power supply cylinder 211, which is connected to the outer upper electrode 21. In other words, the power supply cylinder 211 is covered by the grounding conductor 250. The lower end of the grounding conductor 250 is connected to the upper part of the sidewall of the processing container 10. The aforementioned upper electrode rod 24 extends through the center of the upper surface of the grounding conductor 250. An insulating member (not shown) is provided at the contact portion between the grounding conductor 250 and the upper electrode rod 24.

[0053] Additionally, a low-pass filter 260 is electrically connected to the upper electrode 22 on the inner side of the upper electrode 20. The low-pass filter 260 is used to cut off the high frequency from the high-frequency power supply 20b connected to the upper electrode 20, and to pass the high frequency from the high-frequency power supply 114b connected to the lower electrode to the ground line.

[0054] Furthermore, in this embodiment, the example described is that the inner upper electrode 22 has a first gas inlet portion 230 and a second gas inlet portion 240 to introduce gas into the central region and the edge region within the surface of the substrate W, respectively. However, the structure of the inner upper electrode 22 is not limited to this. In other words, in this embodiment, the surface of the substrate W is divided into two regions: a central region and an edge region. However, the number of divisions of the region formed within the surface of the substrate W is not limited to two.

[0055] That is, for example, the central region of the substrate W (and the first gas inlet portion 230 of the inner upper electrode 22) can be further divided into multiple different regions, or the edge region (and the second gas inlet portion 240 of the inner upper electrode 22) can be further divided into multiple different regions.

[0056] return Figure 1 Explanation.

[0057] The gas supply unit 30 includes a processing gas supply unit 31 that supplies processing gas for etching to the substrate W, a flow rate adjustment unit 32 that adjusts the flow rate of the processing gas from the processing gas supply unit 31, and an additional gas supply unit 33 that supplies desired additional gas.

[0058] The processing gas supply unit 31 is connected to the buffer chamber 222a of the first gas inlet 230 and the buffer chamber 222b of the second gas inlet 240 in the inner upper electrode 22 via a flow rate adjustment unit 32 (e.g., a flow divider). The flow rate adjustment unit 32 adjusts the flow rate of the processing gas diverted to the buffer chambers 222a and 222b based on the pressure in the buffer chambers 222a and 222b (more specifically, the pressure in the connecting pipes 34 and 35 that connect the processing gas supply unit 31 to the buffer chambers 222a and 222b, respectively).

[0059] like Figure 3 As shown, in one embodiment, the processing gas supply unit 31 includes a gas tank housing multiple (three in the illustrated example) gas supply sources 310a, 310b, and 310c. Each gas supply source 310a, 310b, and 310c is connected to the flow rate adjustment unit 32 via a corresponding flow controller 311a, 311b, and 311c. Each flow controller 311a, 311b, and 311c may, for example, include a mass flow controller or a pressure-controlled flow controller.

[0060] In the gas supply source 310a, for example, CF4, C4F8, CHF3, CH2F2, etc. are sealed in using C x H y F z (y≥0) represents the gas used as the etching gas.

[0061] For example, O2 gas is sealed into the gas supply source 310b to control the reaction products of the CF system.

[0062] Inactive gases such as Ar, or N2, COS, etc., are sealed into the gas supply source 310c as carrier gases.

[0063] Furthermore, the number of gas supply sources for the processing gas supply unit 31 is not limited to the example shown in the figure; for example, it could be one, two, or even four or more. Additionally, the types of gas supplied from the processing gas supply unit 31 are not limited to the examples described above; it could also be configured to supply gases such as CO, CO2, and H2 as substitutes or supplements for the aforementioned gases.

[0064] The flow rate adjustment unit 32 includes a pressure adjustment section 320 and a pressure adjustment section 321. The pressure adjustment section 320 adjusts the pressure in the connecting pipe 34 that connects the processed gas supply unit 31 to the buffer chamber 222a, and the pressure adjustment section 321 adjusts the pressure in the connecting pipe 35 that connects the processed gas supply unit 31 to the buffer chamber 222b. Specifically, the pressure adjustment section 320 includes a pressure sensor 320a that detects the pressure in the connecting pipe 34 and a valve 320b that adjusts the opening and closing degree of the connecting pipe 34. Additionally, the pressure adjustment section 321 includes a pressure sensor 321a that detects the pressure in the connecting pipe 35 and a valve 321b that adjusts the opening and closing degree of the connecting pipe 35.

[0065] Pressure regulating units 320 and 321 are connected to pressure controller 322. Pressure controller 322 adjusts the opening and closing degree of corresponding valves 320b and 321b based on the detected pressure from pressure sensors 320a and 321a. For example, the operation of pressure controller 322 is controlled by control unit 2.

[0066] Furthermore, the connecting pipes 34 and 35 that connect the processing gas supply unit 31 to the buffer chambers 222a and 222b respectively can be as follows: Figure 1 and Figure 3 As shown, the branching can be done inside the flow rate adjustment unit 32, or it can be done outside the flow rate adjustment unit 32.

[0067] The auxiliary gas supply unit 33 is connected to the buffer chamber 222c of the second gas inlet section 240 in the inner upper electrode 22 via the connecting pipe 36.

[0068] like Figure 3 As shown, in one embodiment, the auxiliary gas supply unit 33 includes a gas tank housing multiple (three in the illustrated example) gas supply sources 330a, 330b, and 330c. Each gas supply source 330a, 330b, and 330c is connected to the buffer chamber 222c via its respective flow controller 331a, 331b, and 331c. Each flow controller 331a, 331b, and 331c may, for example, include a mass flow controller or a pressure-controlled flow controller.

[0069] A CF-based gas, such as C4F8, that promotes etching is sealed in the gas supply source 330a. x F y gas.

[0070] For example, O2 gas is sealed into the gas supply source 330b to control the reaction products of the CF system. Additionally, for example... Figure 3 As shown, a second carbon-containing gas (e.g., CO2 gas) can also be sealed in the gas supply source 330b as a gas to improve the efficiency of the plasma cleaning process described later.

[0071] In the gas supply source 330c, for example, C3F8, C4F6, C4F8, CHF3, CH2F2, etc. are sealed as the first carbon-containing gas. x H y F z (y≥0,x / z>1) / 4) represents a CF-based gas, which is used as a plasma cleaning gas (hereinafter simply referred to as "cleaning gas") to remove reaction products adhering to the beveled surface, back surface, or surface of the substrate support 11 of the etched substrate W.

[0072] Furthermore, the number of gas supply sources for the auxiliary gas supply unit 33 is not limited to the example shown in the figure; for example, it can be one, two, or even four or more. Additionally, it can be configured such that gas supply source 330c is omitted and clean gas is supplied from gas supply source 330a.

[0073] return Figure 1 Explanation.

[0074] The exhaust system 40 can be connected, for example, to a gas outlet 10e located at the bottom of the processing container 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure regulating valve adjusts the internal pressure of the processing container 10. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0075] The control unit 2 processes computer-executable commands for causing the plasma processing apparatus 1 to perform the various processes described herein. The control unit 2 can be configured to control the various elements of the plasma processing apparatus 1 to perform the various processes described herein. In one embodiment, the plasma processing apparatus 1 may include part or all of the control unit 2. The control unit 2 may, for example, include a computer 2a. The computer 2a may, for example, include a processing unit (CPU) 2a1, a storage unit 2a2, and a communication interface 2a3. The processing unit 2a1 can be configured to perform various control actions based on a program stored in the storage unit 2a2. The storage unit 2a2 may include RAM, ROM, HDD, SSD (Solid State Drive), or combinations thereof. The communication interface 2a3 can communicate with the plasma processing apparatus 1 via a communication line such as a LAN.

[0076] The above descriptions have illustrated various exemplary embodiments, but the embodiments are not limited to these exemplary embodiments. Various additions, omissions, substitutions, and modifications can be made. Furthermore, elements from different embodiments can be combined to form other embodiments.

[0077] For example, in this embodiment, the plasma processing system is described using a parallel-plate type plasma processing device 1 as an example, but the structure of the plasma processing system is not limited to this. For example, the plasma processing system may also have a processing device that includes a plasma generation unit such as capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR plasma (Electron-Cyclotron-resonance plasma), Helicon Wave Plasma (HWP), or surface wave plasma (SWP). In addition, processing devices including various types of plasma generation units may be used, such as AC (Alternating Current) plasma generation units and DC (Direct Current) plasma generation units.

[0078] <Plasma Treatment Methods>

[0079] Next, the plasma processing method for substrate W using the plasma processing system configured as described above will be explained. Figure 4 This is a timing diagram illustrating a plasma processing method according to one embodiment. Figure 4 In the figure, the horizontal axis represents time, and the vertical axis represents: (a) the internal pressure of the processing container 10; (b) the application of DC voltage to the adsorption electrode 115a; (c) the application of high frequency voltage (RF); and (d) the height position of the front end of the lifting pin 131.

[0080] Furthermore, in this embodiment, such as Figure 5 As shown, the example described is the etching of a substrate W on which a mask layer M and an etching target layer E made of a low-k material are stacked on the surface. Furthermore, in this embodiment, a low-k material refers to a material having a dielectric constant at least smaller than that of SiO2 (dielectric constant: approximately 4.0). In one example, the low-k material may be a Si-containing material such as SiOC or SiOCH. Additionally, the etching target layer E (low-k material) may be porous.

[0081] First, a substrate transport robot (not shown) located outside the plasma processing apparatus 1 transports a substrate W, which is the processing target having the aforementioned etching target layer E and mask layer M formed on its surface, into the processing container 10. When the substrate W is transported into the processing container 10, the actuator 132 actuates the lifting pin 131 from the standby position to the transfer position, thus transferring the substrate W from the substrate transport robot to the lifting pin 131. Figure 4 (T1). Furthermore, at the junction position, the back side of the substrate W is held at the upper end of the lifting pin 131 in a state where it is separated from the substrate mounting surface of the substrate support 11 (electrostatic chuck 115).

[0082] When the substrate W is handed over to the upper end of the lifting pin 131, the actuator 132 is used to lower the lifting pin 131 from the handover position to the standby position, so that the substrate W can be handed over from the lifting pin 131 to the substrate mounting surface of the electrostatic chuck 115. Figure 4 (T2). In other words, the substrate W is moved from the handover position to the processing position by the action of the actuator 132. Then, a DC voltage is applied to the adsorption electrode 115a of the electrostatic chuck 115, thereby the substrate W is adsorbed and held on the substrate mounting surface of the electrostatic chuck 115 by electrostatic force.

[0083] Next, after sealing the interior of the processing container 10, a first gas is supplied to the plasma generation space S by the gas supply unit 30, and plasma originating from the first gas is generated. Then, etching is performed on the substrate W, which is adsorbed and held on the substrate mounting surface. Figure 4 (T4). In addition, the aforementioned "first gas" used for etching includes processing gas from processing gas supply unit 31 and additional gas from additional gas supply unit 33.

[0084] Specifically, firstly, the processing gas for etching (e.g., C) is supplied by the processing gas supply unit 31. x H y F z (Gas, O2 gas and Ar gas), and begins to supply additional gas (e.g. C gas) by the additional gas supply unit 33. x F y (Gas and O2).

[0085] In addition, a high-frequency voltage is supplied to the base 114 (lower electrode) and upper electrode 20 of the substrate support 11, thereby generating plasma from the first gas supplied to the interior of the plasma generation space S.

[0086] Then, when the desired etching result is obtained on the etched target layer E, the etching in the plasma processing apparatus 1 is terminated.

[0087] Here, due to the etching performed in the plasma processing apparatus 1, as described above, reaction products adhere as foreign matter to the beveled or back surface of the substrate W, or the surface of the substrate support 11, etc., which are the substrates to be processed. The reaction products adhering to the substrate W and the substrate support 11 may, for example, cause malfunctions in the apparatus or adverse processing results of the substrate W.

[0088] Therefore, in the plasma processing apparatus 1 according to this embodiment, after the etching of the substrate W is completed as described above, a plasma cleaning process (hereinafter sometimes simply referred to as "cleaning process") for removing reaction products adhering to the substrate W is performed inside the same processing container 10.

[0089] When the cleaning process of the substrate W begins, the supply of DC voltage to the adsorption electrode 115a of the electrostatic chuck 115 is stopped, thereby stopping the generation of electrostatic force between the electrostatic chuck 115 and the substrate W.

[0090] Here, the cleaning process for the substrate W, which will be described later, is performed while the substrate W is detached from the substrate mounting surface by the lifting pin 131. However, if the DC voltage supply to the adsorption electrode 115a is simply stopped as described above, the substrate W may remain adsorbed and held on the substrate mounting surface due to residual charge, and the lifting pin 131 may not be able to properly lift the substrate W.

[0091] Therefore, in this embodiment, a high-frequency voltage is instantaneously applied to the substrate support 11 before the substrate W is raised by the lifting pin 131. Figure 4 (T6). Thus, the effects of residual charge and the like between the substrate W and the substrate mounting surface are removed, and the adsorption and holding of the substrate W by the electrostatic chuck 115 is appropriately stopped.

[0092] Furthermore, from the viewpoint of properly separating the substrate W from the electrostatic chuck 115 in this way, it is desirable that, after the etching in the plasma processing apparatus 1 is completed, during the period until the cleaning process described later begins, an inactive gas (e.g., Ar gas) is supplied from the gas supply unit 30 to the plasma generation space S in place of the first gas.

[0093] When a high-frequency voltage is applied to the substrate support 11, the actuator 132 then moves the lifting pin 131 from the standby position to the cleaning position, performing a transfer of the substrate W from the electrostatic chuck 115 (substrate mounting surface) to the lifting pin 131. Figure 4 (T7). In the clean position, the back side of the substrate W is held at the upper end of the lifting pin 131 in a state where it is separated from the substrate mounting surface of the electrostatic chuck 115 without contacting it.

[0094] Furthermore, the height position of the front end of the lifting pin 131 during cleaning (the separation distance between the back side of the substrate W and the substrate mounting surface of the electrostatic chuck 115) is controlled to be 2.0 mm or more and 4.0 mm or less, preferably 2.5 mm or more and 3.8 mm or less, and more preferably 3.0 mm or more and 3.5 mm or less.

[0095] When the substrate W is held at the upper end of the lifting pin 131, a second gas is then supplied from the gas supply section 30 to the plasma generation space S, and plasma is generated by the second gas to begin the cleaning process of the substrate W. Figure 4 (T8). Furthermore, the aforementioned "second gas" used in the cleaning process includes at least the cleaning gas from the auxiliary gas supply unit 33. Additionally, in this embodiment, the cleaning gas includes C supplied from the aforementioned gas supply source 330c. x H y F z In addition to the gas, it also includes CO2 gas supplied from gas supply source 330b.

[0096] Specifically, firstly, clean gas (e.g., C) is supplied by the auxiliary gas supply unit 33. x H y F z (Gas and CO2 gas).

[0097] In addition, a high-frequency voltage is supplied to the base 114 (lower electrode) or the upper electrode 20 of the substrate support 11. As a result, plasma is generated by the second gas supplied to the interior of the plasma generation space S.

[0098] Here, the inventors of the present invention have conducted careful research and found that when the etch target layer E contains a Si-containing material as a low-k material, as described above, the reaction product that adheres to the substrate W during etching contains a CF-based polymer and Si.

[0099] Furthermore, the inventors of this invention conducted careful research and found that after performing plasma cleaning treatment with CO2 gas on the reaction products generated as described above, only the Si component was detected as residue. In other words, it was found that while plasma cleaning treatment with CO2 gas can remove the reaction products containing CF-based polymer components, the reaction products containing Si components cannot be removed, resulting in residue.

[0100] Here, when removing Si-containing reaction products through plasma cleaning, a CF-based gas is added to the cleaning gas. However, when a CF-based gas with a low carbon (C) ratio is added as the cleaning gas, there are concerns about potential impacts on the surface of the substrate W, such as the consumption of the mask layer M, liner film, or low-k film, or the expansion of the critical dimension (CD). Therefore, when adding a CF-based gas to the cleaning gas to remove Si-containing reaction products, adjustments need to be made to the gas type, flow rate, and other parameters to minimize the impact on the surface of the substrate W.

[0101] Therefore, in this embodiment, in order to properly remove the reaction products adhering to the substrate W, plasma cleaning of the substrate W is performed under the following conditions, for example. Furthermore, all the processing conditions shown below are illustrative, and etching processing conditions can be appropriately selected.

[0102] • Second gas (cleaning gas)

[0103] C x H y F z Gas flow rate (y≥0, x / z>1 / 4): 1~5 sccm

[0104] CO2 gas flow rate: 500~1200sccm

[0105] • Pressure in plasma generation space S: 300–800 mTorr

[0106] • Temperature of substrate W: 10~60℃

[0107] High-frequency power: 500-600W

[0108] • Frequency of high-frequency power: 10–100 MHz

[0109] • Height of the front end of lifting pin 131: 2.0~4.0mm

[0110] Specifically, in the cleaning process involved in this embodiment, the CF-based polymer, which is a reaction product, is removed by plasma generated from CO2 gas, and by a sufficiently small flow rate of C plasma relative to the flow rate of CO2 gas (e.g., less than 1% relative to the flow rate of CO2 gas). x H y F z Plasma generated by a gas (CF-based gas) is used to remove the Si component, which is a reaction product. In other words, it can simultaneously remove both the CF-based polymer and the Si component, which are reaction products, thus improving cleaning efficiency.

[0111] Additionally, at this time, by using C x H y F z The gas represented by (y≥0, x / z>1 / 4), more specifically the CF-based gas containing more carbon (C) than CF4 gas as the cleaning gas, can appropriately remove the Si component of the reaction products while protecting the Low-k film formed on the surface of the substrate W.

[0112] Here, it was found that when using C... x H y F z When using CF-based gases (e.g., CF4 gas) with a low carbon (C) ratio (x / z ≤ 1 / 4), the target layer E may be etched during cleaning. In this case, for example, the patterns (holes) formed in the target layer E may become deeper, potentially damaging the substrate wiring and other components formed beneath the target layer E. Therefore, it is desirable to use gases with a low carbon (C) ratio (x / z ≤ 1 / 4). x H y F z The gas represented by (y≥0, x / z>1 / 4) is used as the CF series gas contained in the clean gas.

[0113] Furthermore, in this embodiment, the cleaning process is performed while the substrate W is separated from the substrate mounting surface of the electrostatic chuck 115 by the lifting pin 131. As a result, plasma can be appropriately introduced into the space generated between the back surface of the substrate W and the substrate mounting surface, and consequently, reaction products adhering to the inclined surface, back surface, and surface of the electrostatic chuck 115 of the substrate W can be appropriately removed.

[0114] Furthermore, by setting the height position of the front end of the lifting pin 131 (the separation distance between the back side of the substrate W and the substrate mounting surface) to 2.0 mm or more and 4 mm or less, and more preferably 3.0 mm or more and 3.5 mm or less, it is possible to suppress excessive plasma intrusion between the back side of the substrate W and the surface of the electrostatic chuck, thereby suppressing damage to the back side of the substrate W or the surface of the electrostatic chuck.

[0115] Furthermore, when the height position of the front end of the lifting pin 131 (the separation distance between the back surface of the substrate W and the substrate mounting surface) is less than 2.0 mm, it is not possible to properly remove the reaction products in the edge region (beveled portion) of the substrate W. On the other hand, when the height position of the front end of the lifting pin 131 (the separation distance between the back surface of the substrate W and the substrate mounting surface) is greater than 4.0 mm, the etching (cleaning) progresses to near the center of the back surface of the substrate W.

[0116] Furthermore, in this embodiment, as described above in the device structure (refer to...) Figure 1As shown in the figure, cleaning gas for cleaning the substrate W can be supplied from the additional gas inlet 240b in the inner upper electrode 22 corresponding to the edge region of the substrate W.

[0117] Here, the reaction products generated during etching tend to adhere to the beveled portion (edge ​​region) of the substrate W and the surface of the substrate support 11 along the beveled portion.

[0118] In this regard, as shown in this embodiment, the gas is supplied from the additional gas inlet 240b corresponding to the beveled portion (edge ​​region), so that the reaction products attached to the beveled portion can be removed and the influence on, for example, the central region of the substrate W can be suppressed.

[0119] Furthermore, in this embodiment, the pressure of the plasma generation space S during the cleaning process is sufficient to maintain a stable plasma pressure, and for example, it is set to 300 mTorr or higher. By using a pressure region of 300 mTorr or higher for cleaning, it is possible to ensure the circumferential uniformity of the cleaning process on the substrate W, in other words, the concentric circular uniformity, while improving the removal rate of reaction products at the beveled surface.

[0120] Subsequently, when the removal of reaction products adhering to the substrate W is complete, the supply of high-frequency voltage to the base 114 (lower electrode) or upper electrode 20 of the substrate support 11 is stopped, thus ending the cleaning process of the substrate W. Figure 4 (T9). In addition, at this time, the second gas remaining inside the processing container 10 is discharged to the outside of the processing container 10 by the exhaust system 40.

[0121] Next, the actuator 132 causes the lifting pin 131 to rise from the cleaning position to the handover position, thus transferring the substrate W from the lifting pin 131 to the substrate transfer robot (not shown). Figure 4 (T10).

[0122] Subsequently, when the substrate W is moved to the outside of the processing container 10 by the substrate transport robot (not shown), a series of plasma treatments (etching and cleaning processes) in the plasma processing apparatus 1 are completed.

[0123] <The effects of the technology disclosed herein>

[0124] Figure 6These are explanatory diagrams showing the surface state of the substrate W after etching without cleaning (Reference Example 1), the surface state of the substrate W after cleaning with CO2 gas only after etching (Reference Example 2), and the surface state of the substrate W after cleaning with CO2 gas and C4F8 gas after etching (Examples) as examples of experimental results illustrating the effects of the technology disclosed herein.

[0125] like Figure 6 As shown, by using a cleaning gas containing both CO2 and C4F8 in the plasma cleaning process, the CF-based polymer and Si components, which are reaction products, can be removed without causing significant process changes compared to Reference Example 1 and Reference Example 2. More specifically, as Figure 6 As shown by the BARC Remain value, CD value, or Recess value of the bottom anti-reflective coating, it can be seen that although there are slight process variations due to the addition of C4F8 gas, these variations are within the allowable range that can be adjusted by processing conditions.

[0126] Furthermore, according to this embodiment, the reaction products adhering to the substrate W during etching can be removed without affecting the process results of the substrate W by using the added C4F8 gas and CO2 gas.

[0127] Figure 7 and Figure 8 This is a graph illustrating an example of the results of a simulation experiment, showing the relationship between the plasma etching amount of the etch target layer E formed on the back side of the dummy wafer and the tip height of the lifting pin 131 (the separation distance between the substrate W and the electrostatic chuck 115). Figure 7 and Figure 8 The upper graph shows the distribution of reaction products on the periphery of the back side of substrate W. Figure 7 and Figure 8 The lower curve in the graph is a curve showing the distribution of the amount of reaction products along the diameter of the back side of the substrate W. Figure 7 and Figure 8 The vertical axis of the curve at the top represents the amount of reaction products attached to the periphery of the back surface of substrate W, and the horizontal axis represents the azimuth angle of the back surface of substrate W when the cut portion observed from the center of the back surface of substrate W is set to 180°. Additionally, in Figure 7 and Figure 8 In the middle, the vertical axis of the curve on the lower side represents the amount of reaction products attached to the back side of the substrate W, and the horizontal axis represents the position of the back side of the substrate W in the diameter direction when the center of the back side of the substrate W is set to 0mm.

[0128] According to Figure 7 and Figure 8As the simulation results show, by setting the height of the lifting pin 131 to at least 2.0 mm (in... Figure 7 The middle figure shows that the height of the lifting pin 131 is 2.5 mm or more, which can remove reaction products attached to the beveled part (edge ​​area) of the substrate W.

[0129] Additionally, by setting the height of the lifting pin 131 to at least 4.0 mm (in... Figure 7 The figure shows that the height of the lifting pin 131 is less than 3.5 mm, which can suppress the etching progress on the central side (central region) of the back side of the substrate W.

[0130] In addition, such as Figure 7 and Figure 8 As shown, by specifically setting the height of the lifting pin 131 to 2.5 mm or more and 3.8 mm or less, and more preferably 3.0 mm or more and 3.5 mm or less, it is possible to make the etch amount distribution uniform throughout the entire perimeter of the edge region of the substrate W.

[0131] The above, as per Figures 6-8 As can be seen from the results, according to the plasma treatment method for substrate W according to this embodiment, by adding a small flow rate of C to a large flow rate of CO2 gas as a cleaning gas... x H y F z (y≥0, x / z>1 / 4), such as C4F8 gas, is used to remove the reaction products generated during etching. Even if the etch target layer E formed on the surface of the substrate W includes a low dielectric constant (Low-k) material, it is possible to remove both the CF-based polymer and the Si component generated as reaction products.

[0132] Furthermore, in particular, according to this embodiment, by adding C to the clean gas x H y F z Using a gas with a high carbon (C) content (x / z>1 / 4) can effectively protect the Low-k film formed on the surface of the substrate W while removing the Si component of the reaction products.

[0133] Furthermore, according to this embodiment, cleaning is performed with the substrate W detached from the substrate mounting surface of the electrostatic chuck 115 by the lifting pin 131, and especially with the separation distance between the back surface of the substrate W and the substrate mounting surface of the electrostatic chuck 115 controlled to be 2 mm or more and 4 mm or less. Therefore, reaction products adhering to the inclined surface, back surface, or surface of the electrostatic chuck 115 of the substrate W can be appropriately removed using plasma generated in the plasma generation space S.

[0134] Furthermore, according to this embodiment, cleaning gas can also be introduced into the plasma generation space S during cleaning processing from the additional gas introduction section 240b corresponding to the main adhesion area of ​​the reaction products to the substrate W, i.e., the edge region. More specifically, cleaning gas can also be introduced into the corresponding edge region of the substrate W from the outermost peripheral portion of the inner upper electrode 22 where the gas introduction hole 221a is formed. This allows the removal of reaction products adhering to the edge region of the substrate W and suppresses the impact on the central region of the substrate W.

[0135] Furthermore, according to the above embodiment, cleaning gas is supplied only from the additional gas inlet 240b located at the outermost periphery of the inner upper electrode 22. However, the supply position of the cleaning gas can be appropriately changed according to the adhesion position of the reaction products to the substrate W. In other words, the additional gas supply unit 33 for supplying cleaning gas can be connected to the buffer chamber 222a corresponding to the central region of the substrate W and the buffer chamber 222b corresponding to the edge region of the substrate W, as an addition or alternative to the buffer chamber 222c formed inside the electrode support 222.

[0136] Furthermore, as described above, the arrangement, shape, and number of buffer chambers formed inside the electrode support 222 are not limited to the examples of the above embodiments, and can be appropriately changed according to the attachment position of the reaction product to the substrate W.

[0137] It should be understood that all points in the embodiments disclosed herein are illustrative rather than restrictive. The above embodiments may be omitted, substituted, or modified in various ways without departing from the appended claims and their spirit.

[0138] Explanation of reference numerals in the attached figures

[0139] 1: Plasma processing apparatus; 2: Control unit; 10: Processing container; 11: Substrate support; 20b: High-frequency power supply; 30: Gas supply unit; 114b: High-frequency power supply; 130: Lifter; E: Etching target layer; W: Substrate.

Claims

1. A cleaning method for a substrate, comprising the following steps: A substrate having a low dielectric constant layer containing silicon is provided to the substrate support; The low dielectric constant layer is etched by plasma generated by a first gas. Separate the etched substrate from the substrate support; as well as Reaction products adhering to the substrate during etching are removed by plasma generated from a first carbon-containing gas contained in a second gas and plasma generated from a second carbon-containing gas contained in the second gas. Wherein, the first carbon-containing gas is C x H y F z This means that y ≥ 0 and x / z > 1 / 4. The composition of the second carbon-containing gas is different from that of the first carbon-containing gas. The flow rate ratio of the first carbon-containing gas to the second carbon-containing gas in the second gas is less than 1%. The separation distance between the substrate and the substrate support during the removal of the reaction products is within the range of 2.0 mm or more and 4.0 mm or less.

2. The cleaning method according to claim 1, characterized in that, The second carbon-containing gas is CO2 gas.

3. The cleaning method according to claim 1 or 2, characterized in that, The internal pressure of the processing container when removing the reaction products is set to be at least higher than the internal pressure of the processing container when etching the low dielectric constant layer.

4. The cleaning method according to claim 3, characterized in that, The internal pressure of the processing vessel for removing the reaction products is above 300 mTorr.

5. The cleaning method according to claim 1 or 2, characterized in that, The substrate to be processed has a central region and an annular peripheral region surrounding the central region in its surface. When removing the reaction products, the second gas is supplied only toward the peripheral region.

6. A plasma processing apparatus, comprising: Handling containers; A substrate support is disposed inside the processing container; An actuator that causes the substrate to move up and down relative to the substrate support; A gas supply unit for supplying gas into the interior of the processing container; A high-frequency power supply, which is connected to the substrate support; and Control Department The control unit sequentially performs the following procedures: A substrate having a low dielectric constant layer containing silicon is provided to the substrate support; The low dielectric constant layer is etched by plasma generated by a first gas. Separate the etched substrate from the substrate support; and Reaction products adhering to the substrate during etching are removed by plasma generated from a first carbon-containing gas contained in a second gas and plasma generated from a second carbon-containing gas contained in the second gas. The first carbon-containing gas is C x H y F z This means that y ≥ 0 and x / z > 1 / 4. The composition of the second carbon-containing gas is different from that of the first carbon-containing gas. The control unit controls the flow rate ratio of the first carbon-containing gas to the second carbon-containing gas in the second gas to be below 1%. The control unit executes the control of the actuator so that the separation distance between the substrate and the substrate support when removing the reaction product is within the range of 2.0 mm or more and 4.0 mm or less.

7. The plasma processing apparatus according to claim 6, characterized in that, The gas supply unit includes: A first supply unit supplies the first gas to the central region of the substrate to be processed. The second supply unit supplies the first gas to the annular peripheral region surrounding the central region; as well as The third supply unit supplies the second gas to the peripheral region.

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