Cleaning method and plasma processing apparatus

Abstract

To properly remove a reaction product adhering to a bevel part and a rear surface of a substrate in plasma etching.SOLUTION: A cleaning method of a substrate comprises the steps of: providing a substrate having a Low-k layer containing silicon to a substrate support; etching the Low-k layer with plasma generated from first gas; separating the substrate from the substrate support after the etching; and removing a reaction product adhering to the substrate in the etching with plasma generated from second gas. The second gas contains first carbon-containing gas expressed by CxHyFz(y≥0, x / z>1 / 4).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a cleaning method and a plasma processing apparatus. [Background technology]

[0002] According to Patent Document 1, this generates a traveling shock wave in the chamber, and the foreign matter adhering to the rear surface of the substrate is detached by the shock wave. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-317782 A Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed herein appropriately removes reaction products adhering to the bevel portion and back surface of a substrate during plasma etching. [Means for solving the problem]

[0005] One aspect of the present disclosure is a method for cleaning a substrate, the method comprising the steps of: providing a substrate having a silicon-containing low-k layer on a substrate support; etching the low-k layer with plasma generated from a first gas; separating the substrate after etching from the substrate support; and removing a reaction product attached to the substrate during etching with plasma generated from a second gas, the second gas including a first carbon-containing gas represented by CxFz(x / z>1 / 4). and the distance between the substrate and the substrate support during removal of the reaction product is 2.0 mm or more. . Effect of the Invention

[0006] According to the present disclosure, reaction products adhering to the bevel portion and back surface of a substrate can be appropriately removed during plasma etching. [Brief description of the drawings]

[0007] [Figure 1] 1 is a vertical cross-sectional view showing a configuration of a plasma processing system in accordance with an embodiment; [Diagram 2] FIG. 4 is a bottom view showing a configuration of an inner upper electrode according to one embodiment. [Diagram 3] FIG. 2 is a system diagram showing a configuration of a gas supply unit according to one embodiment. [Figure 4] 1 is a timing chart of a plasma process according to an embodiment. [Diagram 5] 2 is an explanatory diagram of an etching target layer and a mask layer formed on a substrate. FIG. [Figure 6] FIG. 13 is an explanatory diagram showing an example of a plasma processing result according to an embodiment of the present invention. [Figure 7] FIG. 11 is an explanatory diagram showing an example of a plasma processing result according to an experimental example. [Figure 8] FIG. 11 is an explanatory diagram showing an example of a plasma processing result according to an experimental example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In a manufacturing process of a semiconductor device, an etching process is performed on an etching target film formed by stacking on the surface of a semiconductor substrate (hereinafter simply referred to as "substrate") using a mask layer on which a pattern is formed as a mask. This etching process is generally performed in a plasma processing device. In recent years, low dielectric constant (Low-k) materials such as SiOC film and SiOCH film are sometimes used as the etching target film.

[0009] In the plasma processing apparatus, there is a concern that reaction products of, for example, fluorocarbon (CF)-based polymers may adhere to the bevel portion or back surface of the substrate to be etched during the above-mentioned etching process. The reaction products adhered to the substrate may be detached during processing or transportation of the substrate, thereby contaminating the inside of the apparatus, which may cause malfunctions in the apparatus or affect the processing results of the substrate.

[0010] Here, methods for removing these reaction products include, for example, a method of introducing a gas into the chamber to desorb the reaction products (gas cleaning) as disclosed in Patent Document 1, and a method of generating plasma inside the chamber to remove the reaction products (plasma cleaning).

[0011] However, for example, when the above-mentioned etching target film includes a low-k film, if the above-mentioned plasma cleaning is performed using a CF-based gas (e.g., CF gas) having a low carbon ratio represented by CxHyFz (x / z≦1 / 4), the low-k film may be deteriorated or damaged.

[0012] The technology according to the present disclosure has been made in consideration of the above circumstances, and appropriately removes reaction products adhering to the bevel portion and back surface of a substrate during plasma etching. Hereinafter, a plasma processing apparatus as a substrate processing apparatus according to the present embodiment, and a plasma processing method including a cleaning method according to the present embodiment will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and duplicated description will be omitted.

[0013] <Plasma processing equipment> 1 is a vertical cross-sectional view showing a schematic configuration of a plasma processing system. In the following description, the surface of a substrate W to be etched, i.e., the surface on which a low-k film as a film to be etched is formed, may be referred to as the "front surface" and the surface opposite to the front surface as the "back surface."

[0014] In one embodiment, the plasma processing system includes a parallel plate type plasma etching apparatus (hereinafter referred to as a "plasma processing apparatus 1") and a controller 2. The plasma processing apparatus 1 includes a substantially cylindrical processing vessel 10 that accommodates a substrate W, a substrate support 11 including a lower electrode described below, an upper electrode 20, a gas supply unit 30, and an exhaust system 40.

[0015] The processing vessel 10 is made of, for example, an aluminum alloy and is electrically grounded. The inner wall surface of the processing vessel 10 is covered with an alumina film or an yttrium oxide film (Y2O3). A loading / unloading port (not shown) for a substrate (wafer) W is provided on the side of the processing vessel 10, and the processing vessel 10 is connected to the outside of the plasma processing apparatus 1 through the loading / unloading port. The loading / unloading port is configured to be freely opened and closed by a gate valve (not shown).

[0016] A substrate support 11 on which a substrate W is placed is disposed inside the processing vessel 10. The substrate support 11 includes a main body 111 and a focus ring 112. The focus ring 112 is disposed to surround the periphery of an electrostatic chuck 115 (described later) of the main body 111.

[0017] In one embodiment, the main body 111 includes a support table 113, a susceptor 114, and an electrostatic chuck 115. The support table 113, the susceptor 114, and the electrostatic chuck 115 are stacked in this order from the bottom side of the processing vessel 10.

[0018] The support table 113 has a substantially cylindrical shape and is disposed at substantially the center of the bottom surface of the processing vessel 10 via an insulating plate (not shown). A flow path C is formed inside the support table 113. A heat transfer medium is circulated and supplied to the flow path C from a chiller unit (not shown). This allows the temperature of the substrate W on the susceptor 114 (more specifically, on the electrostatic chuck 115) to be controlled to a desired temperature.

[0019] The susceptor 114 is supported on a support table 113. The susceptor 114 is made of a conductive member such as an aluminum alloy. The conductive member of the susceptor 114 functions as a lower electrode. A high frequency power supply 114b is electrically connected to the susceptor 114 via a matching device 114a. The high frequency power supply 114b can output a first high frequency voltage having a frequency in the range of 2 MHz to 20 MHz, for example, at a frequency of 2 MHz. The matching device 114a can match the internal impedance of the high frequency power supply 114b with the load impedance. The high frequency from the high frequency power supply 114b may be pulsed.

[0020] The electrostatic chuck 115 is supported on the susceptor 114. An adsorption electrode 115a is provided inside the electrostatic chuck 115. The adsorption electrode 115a is connected to a DC power supply, and by applying a voltage from the DC power supply to the adsorption electrode 115a, an electrostatic force such as Coulomb force is generated, and the substrate W is adsorbed and held on the upper surface (substrate mounting surface) of the electrostatic chuck 115 by the electrostatic force.

[0021] A cylindrical inner wall member 116 made of, for example, quartz is attached to the outer circumferential surfaces of the support table 113 and the susceptor 114 .

[0022] Inside the main body 111 of the substrate support 11, a gas supply pipe 120 and a lifter 130 are provided.

[0023] The gas supply pipe 120 is disposed so as to penetrate the main body 111 in the thickness direction, and is connected to a gas supply source (not shown). In this manner, the gas supply pipe 120 supplies a heat transfer gas (backside gas) such as He gas between the back surface of the substrate W and the electrostatic chuck 115, and the substrate W attracted and held on the upper surface of the electrostatic chuck 115 can be controlled to a desired temperature.

[0024] The lifter 130 includes a lifter pin 131 and an actuator 132. Examples of the actuator include an electric actuator, an air cylinder, a motor, etc. The lifter 130 raises and lowers the substrate W on the susceptor 114 (more specifically, on the electrostatic chuck 115), and adjusts the tip height of the lifter pin 131 so that the rear surface of the substrate W is positioned at a desired position.

[0025] The lifter pins 131 are columnar members that rise and fall so that their upper ends protrude and sink from the substrate mounting surface of the electrostatic chuck 115, and are arranged to be inserted into pin through holes formed by penetrating the main body 111 of the substrate support 11 in the thickness direction. A plurality of lifter pins 131, for example, three or more lifter pins 131 are provided at intervals from each other along the circumferential direction of the electrostatic chuck 115 (substrate mounting surface). The lifter pins 131 are provided at equal intervals along the circumferential direction. The actuator 132 generates a driving force that raises and lowers the lifter pins 131, thereby raising and lowering the plurality of lifter pins 131.

[0026] The lifter 130 raises and lowers the lifter pins 131 by the operation of the actuator 132, and is configured to freely move the lifter pins 131 between a transfer position for the substrate W (a position where the upper end protrudes from the substrate mounting surface), a standby position (a position where the upper end does not protrude from the substrate mounting surface), and a cleaning position (a position where the upper end protrudes from the substrate mounting surface and the upper end position is lower than the transfer position). In other words, the substrate W held by the lifter pins 131 by the operation of the actuator 132 is freely moved between a transfer position (a position where the substrate W is transferred to and from a substrate transport robot), a processing position (a position where the substrate W is placed on the substrate mounting surface), and a cleaning position (a position where reaction products attached to the substrate W are removed).

[0027] A high-pass filter 140 is electrically connected to the susceptor 114 constituting the lower electrode. The high-pass filter 140 blocks high-frequency waves from a high-frequency power supply 114b connected to the lower electrode and passes high-frequency waves from a high-frequency power supply 20b connected to the upper electrode 20 (described later) to the ground.

[0028] An upper electrode 20 is provided above the substrate support 11 so as to face in parallel with a susceptor 114 constituting a lower electrode. A plasma generation space S is formed between the susceptor 114 and the upper electrode 20.

[0029] The upper electrode 20 includes a ring-shaped outer upper electrode 21 and a disk-shaped inner upper electrode 22. A high-frequency power supply 20b is electrically connected to the upper electrode 20 via a matching device 20a. The high-frequency power supply 20b can output a second high-frequency voltage having a frequency of 40 MHz or more (e.g., 60 MHz). The matching device 20a can match the internal impedance of the high-frequency power supply 20b with the load impedance. The high-frequency power from the high-frequency power supply 20b may be pulsed.

[0030] The outer upper electrode 21 is disposed so as to surround the inner upper electrode 22. A ring-shaped dielectric (not shown) is interposed between the outer upper electrode 21 and the inner upper electrode 22. A ring-shaped insulating shielding member (not shown) made of, for example, alumina is airtightly interposed between the outer upper electrode 21 and the inner peripheral wall of the processing vessel 10. The outer upper electrode 21 is connected to the matching box 20a and the high frequency power supply 20b via the power supply tube 211, the connector 23, and the upper electrode bar 24. The power supply tube 211 is formed, for example, in a substantially cylindrical shape with an open lower surface, and the lower end is connected to the outer upper electrode 21. The lower end of the upper electrode bar 24 is electrically connected to the center of the upper surface of the power supply tube 211 by the connector 23. The upper end of the upper electrode bar 24 is connected to the output side of the matching box 20a.

[0031] The inner upper electrode 22 constitutes a shower head that ejects a desired gas toward a plasma generation space S on the substrate W supported by the substrate support 11. The inner upper electrode 22 includes a disk-shaped electrode plate 221 having a large number of gas introduction holes 221a (see FIG. 2), and an electrode support 222 that detachably supports the upper surface side of the electrode plate 221. The electrode support 222 is formed in a disk shape having approximately the same diameter as the electrode plate 221.

[0032] 1, the matching box 20a and the high frequency power supply 20b are connected to the upper surface of the electrode support 222 via the lower electrode bar 25, the connector 23, and the upper electrode bar 24. A variable capacitor 26 is provided in the middle of the lower electrode bar 25. By adjusting the capacitance of this variable capacitor 26, it is possible to adjust the relative ratio between the electric field intensity formed directly below the outer upper electrode 21 and the electric field intensity formed directly below the inner upper electrode 22 when the second high frequency voltage is applied from the high frequency power supply 20b.

[0033] In one embodiment, the inner upper electrode 22 has a plurality of first gas introduction parts, two in this embodiment, that introduce gas toward different regions in the plane of the substrate W supported by the substrate support 11, for example, toward a central region (hereinafter, "center region") of the substrate W and a peripheral region (hereinafter, "edge region") of the substrate W. Hereinafter, these two first gas introduction parts are referred to as a first gas introduction part 230 that introduces gas into the center region and a second gas introduction part 240 that introduces gas into the edge region, respectively.

[0034] The first gas introduction part 230 as a first supply part is composed of a buffer chamber 222a formed inside the electrode support 222 and a large number of gas introduction holes 221a formed on the lower surface thereof. The buffer chamber 222a is formed in the inside of the central region of the electrode support 222, that is, corresponding to the central region of the substrate W held by suction on the substrate support 11.

[0035] The second gas introduction part 240 is further divided into a processing gas introduction part 240a for introducing a processing gas from a processing gas supply means 31 described later into the processing vessel 10, and an additional gas introduction part 240b for introducing an additional gas to be added to the processing gas introduced from the processing gas introduction part 240a from an additional gas supply means 33 described later into the processing vessel 10. The processing gas introduction part 240a is disposed so as to surround the periphery of the first gas introduction part 230. Moreover, the additional gas introduction part 240b is disposed so as to surround the periphery of the processing gas introduction part 240a. In other words, the first gas introduction part 230, the processing gas introduction part 240a, and the additional gas introduction part 240b are disposed in this order from the radial inside of the inner upper electrode 22.

[0036] The process gas introduction section 240a as the second supply section is composed of a buffer chamber 222b formed inside the electrode support 222 and a number of gas introduction holes 221a formed on the lower surface thereof. The additional gas introduction section 240b as the third supply section is composed of a buffer chamber 222c formed inside the electrode support 222 and a number of gas introduction holes 221a formed on the lower surface thereof. The buffer chambers 222b and 222c are formed in the inside of the peripheral region of the electrode support 222, that is, corresponding to the edge region of the substrate W held by suction on the substrate support 11.

[0037] The buffer chambers 222a, 222b, and 222c may be formed independently, for example, inside the electrode support 222. Alternatively, for example, an integrated buffer chamber may be formed inside the electrode support 222, and the integrated buffer chamber may be partitioned by, for example, an O-ring or the like.

[0038] Gas according to the purpose is supplied to each buffer chamber 222a, 222b, and 222c from the gas supply section 30, and gas is ejected to the center region of the substrate W through the buffer chamber 222a of the first gas introduction section 230, and gas is ejected to the edge region of the substrate W through the buffer chamber 222b or 222c of the second gas introduction section 240.

[0039] A cylindrical ground conductor 250 having a sidewall with approximately the same diameter as the processing vessel 10 is provided on the outside of the power feed tube 211 connected to the outer upper electrode 21. In other words, the power feed tube 211 is covered with the ground conductor 250. A lower end of the ground conductor 250 is connected to an upper part of the sidewall of the processing vessel 10. The above-mentioned upper electrode bar 24 penetrates the center of the upper surface of the ground conductor 250. An insulating member (not shown) is interposed at the contact portion between the ground conductor 250 and the upper electrode bar 24.

[0040] A low-pass filter 260 is electrically connected to the inner upper electrode 22 of the upper electrode 20. The low-pass filter 260 is for blocking high frequency waves from a high frequency power supply 20b connected to the upper electrode 20 and for passing high frequency waves from a high frequency power supply 114b connected to the lower electrode to the ground.

[0041] In this embodiment, the inner upper electrode 22 is provided with the first and second gas introduction parts 230, 240 in order to introduce gas toward the center region and edge region, respectively, in the plane of the substrate W, but the configuration of the inner upper electrode 22 is not limited to this. In other words, in this embodiment, the plane of the substrate W is divided into two regions, the center region and the edge region, but the number of divisions of the regions formed in the plane of the substrate W is not limited to two. That is, for example, the center region of the substrate W (and the first gas introduction section 230 of the inner upper electrode 22) may be further divided into a plurality of different regions, or the edge region (and the second gas introduction section 240 of the inner upper electrode 22) may be further divided into a plurality of different regions.

[0042] Returning to the explanation of Figure 1. The gas supply section 30 includes a processing gas supply means 31 that supplies processing gas for etching the substrate W, a branch flow rate adjustment means 32 that adjusts the branch flow rate of the processing gas from the processing gas supply means 31, and an additional gas supply means 33 that supplies a desired additional gas.

[0043] The process gas supply means 31 is connected to the buffer chamber 222a of the first gas introduction part 230 and the buffer chamber 222b of the second gas introduction part 240 in the inner upper electrode 22 via a branch flow rate adjustment means 32 (e.g., a flow splitter). The branch flow rate adjustment means 32 adjusts the branch flow rate of the process gas to the buffer chambers 222a and 222b based on the pressures in the buffer chambers 222a and 222b (more specifically, the pressures in the connection pipes 34 and 35 that connect the process gas supply means 31 to the buffer chambers 222a and 222b, respectively).

[0044] 3, in one embodiment, the process gas supply means 31 is configured by a gas box accommodating a plurality of (three in the illustrated example) gas supply sources 310a, 310b, and 310c. Each of the gas supply sources 310a, 310b, and 310c is connected to the branch flow rate adjustment means 32 via a corresponding flow rate controller 311a, 311b, and 311c. Each of the flow rate controllers 311a, 311b, and 311c may include, for example, a mass flow controller or a pressure-controlled flow rate controller.

[0045] The gas supply source 310a supplies, as an etching gas, C4F8, CHF3, CH2F2, etc. x H y F z A gas represented by (y≧0) is enclosed. In the gas supply source 310b, for example, O2 gas is enclosed as a gas for controlling the reaction products of the CF system. The gas supply source 310c contains an inert gas such as Ar, or N2, COS, or the like as a carrier gas.

[0046] The number of gas supply sources of the process gas supply means 31 is not limited to the example shown in the figure, and may be, for example, one, two, or four or more. The types of gas supplied from the process gas supply means 31 are also not limited to the above example, and instead of or in addition to the above gases, gases such as CO, CO2, and H2 may be supplied.

[0047] The branch flow rate adjustment means 32 includes a pressure adjustment unit 320 that adjusts the pressure in a connection pipe 34 that connects the process gas supply means 31 and the buffer chamber 222a, and a pressure adjustment unit 321 that adjusts the pressure in a connection pipe 35 that connects the process gas supply means 31 and the buffer chamber 222b. Specifically, the pressure adjustment unit 320 includes a pressure sensor 320a that detects the pressure in the connection pipe 34, and a valve 320b that adjusts the opening and closing degree of the connection pipe 34. In addition, the pressure adjustment unit 321 includes a pressure sensor 321a that detects the pressure in the connection pipe 35, and a valve 321b that adjusts the opening and closing degree of the connection pipe 35.

[0048] The pressure adjustment units 320 and 321 are connected to a pressure controller 322. The pressure controller 322 adjusts the opening and closing degree of the corresponding valves 320b and 321b based on the pressures detected by the pressure sensors 320a and 321a. The operation of the pressure controller 322 is controlled by the control unit 2, for example.

[0049] The connection pipes 34, 35 connecting the process gas supply means 31 and the buffer chambers 222a, 222b, respectively, may branch inside the branch flow rate control means 32 as shown in Figures 1 and 3, or may branch outside the branch flow rate control means 32.

[0050] The additional gas supply means 33 is connected to the buffer chamber 222c of the second gas introduction part 240 in the inner upper electrode 22 via a connection pipe .

[0051] 3, in one embodiment, the additional gas supply means 33 is configured by a gas box accommodating multiple (three in the illustrated example) gas supply sources 330a, 330b, and 330c. Each of the gas supply sources 330a, 330b, and 330c is connected to the buffer chamber 222c via a corresponding flow rate controller 331a, 331b, and 331c. Each of the flow rate controllers 331a, 331b, and 331c may include, for example, a mass flow controller or a pressure-controlled flow rate controller.

[0052] The gas supply source 330a is a CF-based gas capable of promoting etching, such as C4F8. x F y Gas is sealed in. In the gas supply source 330b, for example, O2 gas is enclosed as a gas for controlling CF-based reaction products. In addition, in the gas supply source 330b, for example, as shown in FIG. 3, a second carbon-containing gas (for example, CO2 gas) may be enclosed as a gas for improving the efficiency of a plasma cleaning process described later. The gas supply source 330c is supplied with a plasma cleaning gas (hereinafter simply referred to as a "cleaning gas") for removing reaction products adhering to the bevel portion or rear surface of the substrate W after etching, or the surface of the substrate support 11, and a first carbon-containing gas such as C3F8, C4F6, C4F8, CHF3, or CH2F2. x H y F z CF gas represented by (y≧0, x / z>1 / 4) is enclosed.

[0053] The number of gas supply sources of the additional gas supply means 33 is not limited to the example shown in the figure, and may be, for example, one, two, or four or more. Also, for example, the gas supply source 330c may be omitted, and the cleaning gas may be supplied from the gas supply source 330a.

[0054] Returning to the explanation of Figure 1. The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the processing vessel 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure regulating valve regulates the internal pressure of the processing vessel 10. The vacuum pump may include a turbo molecular pump, a dry pump, or a combination thereof.

[0055] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various steps described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform various steps described herein. In one embodiment, a part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processing unit (CPU) 2a1, a storage unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control operations based on a program stored in the storage unit 2a2. The storage unit 2a2 may include a RAM, a ROM, an HDD, an SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a LAN.

[0056] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and modifications may be made. In addition, elements in different embodiments can be combined to form other embodiments.

[0057] For example, in the present embodiment, the plasma processing system is described as having a parallel plate type plasma processing apparatus 1, but the configuration of the plasma processing system is not limited to this. For example, the plasma processing system may have a processing apparatus including a plasma generating unit such as a capacitively coupled plasma (CCP), an inductively coupled plasma (ICP), an electron-cyclotron-resonance plasma (ECR plasma), a helicon wave plasma (HWP), or a surface wave plasma (SWP). In addition, processing apparatuses including various types of plasma generating units including an alternating current (AC) plasma generating unit and a direct current (DC) plasma generating unit may be used.

[0058] <Plasma treatment method> Next, a plasma processing method for a substrate W performed using the plasma processing system configured as above will be described. Fig. 4 shows a timing chart of the plasma processing according to one embodiment. In Fig. 4, the horizontal axis represents time, and the vertical axis represents (a) the internal pressure of the processing vessel 10, (b) the application of a DC voltage to the attraction electrode 115a, (c) the application of a radio frequency (RF) voltage, and (d) the height position of the tip of the lifter pin 131.

[0059] In this embodiment, as shown in Fig. 5, a case where etching is performed on a substrate W having an etching target layer E made of a low dielectric constant (Low-k) material and a mask layer M laminated on the surface is described. In the embodiment, the low dielectric constant (Low-k) material refers to a material having a dielectric constant at least smaller than SiO2 (dielectric constant: approximately 4.0), and in one example, the low dielectric constant (Low-k) material may be a Si-containing material such as SiOC or SiOCH. The etching target layer E (Low-k material) may be porous.

[0060] First, the substrate W to be processed, on whose surface the above-mentioned etching target layer E and mask layer M are formed, is carried into the processing vessel 10 by a substrate transport robot (not shown) provided outside the plasma processing apparatus 1. When the substrate W is carried into the processing vessel 10, the lifter pins 131 are raised from the standby position to the transfer position by the operation of the actuator 132, and the substrate W is transferred from the substrate transport robot to the lifter pins 131 (T1 in FIG. 4). At the transfer position, the back side of the substrate W is held by the upper end of the lifter pins 131 in a state separated from but not in contact with the substrate placement surface of the substrate support 11 (electrostatic chuck 115).

[0061] When the substrate W is delivered to the upper ends of the lifter pins 131, the actuator 132 operates to lower the lifter pins 131 from the delivery position to the standby position, and the substrate W is delivered from the lifter pins 131 to the substrate mounting surface of the electrostatic chuck 115 (T2 in FIG. 4). In other words, the actuator 132 operates to move the substrate W from the delivery position to the processing position. Thereafter, a DC voltage is applied to the adsorption electrode 115a of the electrostatic chuck 115, whereby the substrate W is attracted and held on the substrate mounting surface of the electrostatic chuck 115 by electrostatic force.

[0062] Next, after the inside of the processing vessel 10 is sealed, a first gas is supplied from the gas supply unit 30 to the plasma generation space S, and plasma derived from the first gas is generated. Then, etching is started for the substrate W adsorbed and held on the substrate mounting surface (T4 in FIG. 4). The above-mentioned "first gas" used for etching includes the processing gas from the processing gas supply means 31 and the additional gas from the additional gas supply means 33.

[0063] Specifically, first, a processing gas for etching (e.g., C x H y F z The supply of the additional gas (e.g., C gas, O gas, and Ar gas) is started, and the additional gas supply means 33 supplies the additional gas (e.g., C x F y Start supplying O2 gas and O2 gas. Moreover, a high frequency voltage is supplied to the susceptor 114 (lower electrode) and the upper electrode 20 of the substrate support 11, whereby the first gas supplied into the plasma generating space S generates plasma.

[0064] Thereafter, when a desired etching result is obtained for the etching target layer E, the etching in the plasma processing apparatus 1 is terminated. Here, as described above, the etching performed in the plasma processing apparatus 1 causes reaction products to adhere as foreign matter to the bevel portion or back surface of the substrate W to be processed, or to the front surface of the substrate support 11. The reaction products adhered to the substrate W or the substrate support 11 may cause, for example, malfunctions of the apparatus or malfunctions in the processing results for the substrate W.

[0065] Therefore, in the plasma processing apparatus 1 according to the present embodiment, after the etching of the substrate W described above is completed, a plasma cleaning process (hereinafter, sometimes simply referred to as a "cleaning process") is performed inside the same processing vessel 10 to remove reaction products adhering to the substrate W, etc.

[0066] When starting the cleaning process for the substrate W, the supply of DC voltage to the attraction 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.

[0067] Here, a cleaning process for the substrate W, which will be described later, is performed in a state in which the substrate W has been detached from the substrate mounting surface by the lifter pins 131. However, as described above, simply stopping the supply of DC voltage to the attraction electrode 115a may result in the substrate W remaining attracted and held on the substrate mounting surface due to the influence of, for example, residual charges, and the substrate W may not be lifted appropriately by the lifter pins 131. Therefore, in this embodiment, a high-frequency voltage is instantaneously applied to the substrate support 11 (T6 in FIG. 4) before the substrate W is raised by the lifter pins 131. This removes the influence of residual charges between the substrate W and the substrate mounting surface, and appropriately stops the electrostatic chuck 115 from attracting and holding the substrate W.

[0068] In order to properly detach the substrate W from the electrostatic chuck 115, it is desirable to supply an inert gas (e.g., Ar gas) instead of the first gas described above from the gas supply unit 30 to the plasma generation space S after the etching in the plasma processing device 1 is completed and before the start of the cleaning process described below.

[0069] When the high frequency voltage is applied to the substrate support 11, the actuator 132 operates to raise the lifter pins 131 from the standby position to the cleaning position, and the substrate W is transferred from the electrostatic chuck 115 (substrate mounting surface) to the lifter pins 131 (T7 in FIG. 4). At the cleaning position, the back side of the substrate W is held by the upper end of the lifter pins 131 while being separated from the substrate mounting surface of the electrostatic chuck 115 without contacting it. In addition, the height position of the tip of the lifter pin 131 during cleaning (the distance between the back surface of the substrate W and the substrate supporting 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.

[0070] After the substrate W is held on the upper end of the lifter pin 131, the second gas is supplied from the gas supply unit 30 to the plasma generation space S, plasma is generated from the second gas, and the cleaning process of the substrate W is started (T8 in FIG. 4). The above-mentioned "second gas" used in the cleaning process includes at least the cleaning gas from the additional gas supply means 33. In this embodiment, the C gas supplied from the above-mentioned gas supply source 330c is x H y F zIn addition to the gas, the cleaning gas includes CO2 gas supplied from gas source 330b.

[0071] Specifically, first, a cleaning gas (e.g., C x H y F z The company will start supplying gas and CO2 gas. Moreover, a high frequency voltage is supplied to the susceptor 114 (lower electrode) or the upper electrode 20 of the substrate support 11, whereby the second gas supplied into the plasma generating space S generates plasma.

[0072] Here, the inventors have conducted intensive research and found that, as described above, when the etching target layer E contains a Si-containing material as a low dielectric constant (Low-k) material, the reaction products adhering to the substrate W during etching include CF-based polymers and Si. Furthermore, the inventors conducted extensive research and found that when a plasma cleaning process using CO2 gas was performed on the reaction products generated as described above, only the Si component was detected as a residue after the plasma cleaning process. In other words, the inventors found that while the reaction products, which are CF-based polymer components, could be removed by the plasma cleaning process using CO2 gas, the reaction products, which are Si components, could not be removed and remained as residues.

[0073] Here, when the reaction product containing Si is removed by plasma cleaning, for example, 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 is a concern about the influence on the surface of the substrate W, such as the consumption of the mask layer M, the liner film, and the low-k film, or the expansion of the CD (Critical Dimension). For this reason, when a CF-based gas is added to the cleaning gas to remove the reaction product containing Si, it is necessary to adjust the gas type, flow rate, and other parameters that have a small influence on the surface of the substrate W.

[0074] In this embodiment, therefore, in order to properly remove the reaction products adhering to the substrate W, as an example, a plasma cleaning process is performed on the substrate W under the following conditions. Note that the process conditions shown below are all examples, and the etching process conditions can be appropriately selected. Second gas (cleaning gas) C x H y F z Gas (y≧0, x / z>1 / 4) flow rate: 1~5sccm CO2 gas flow rate: 500~1200sccm Pressure in plasma generation space S: 300~800mTorr Substrate W temperature: 10 to 60°C High frequency power: 500~600W High frequency power frequency: 10~100MHz Lifter pin 131 tip height: 2.0~4.0mm

[0075] Specifically, in the cleaning process according to the present embodiment, CF-based polymers as reaction products are removed by plasma generated from CO2 gas, and C2 gas having a flow rate sufficiently small relative to the flow rate of CO2 gas (for example, a flow rate ratio of 1% or less relative to CO2 gas) is also used. x H y F z The plasma generated from the gas (CF-based gas) removes the Si component as a reaction product. In other words, the CF-based polymer and the Si component as reaction products can be removed simultaneously, improving the cleaning efficiency.

[0076] At this time, the CF gas contained in the cleaning gas is C x H y F z By using a gas represented by (y≧0, x / z>1 / 4), more specifically, a gas richer in carbon (C) than CF4 gas, it is possible to adequately remove the Si component of the reaction product while protecting the low-k film formed on the surface of the substrate W. Here, C x H y F zIt has been found that if a CF gas (e.g., CF4 gas) with a small carbon (C) ratio represented by (x / z≦1 / 4) is used, the etching target layer E may be etched during the cleaning process. In this case, for example, the pattern (hole) formed in the etching target layer E may become deep, which may damage the substrate wiring formed under the etching target layer E. For this reason, the CF gas contained in the cleaning gas is preferably C x H y F z It is preferable to use a gas represented by (y≧0, x / z>1 / 4).

[0077] In this embodiment, the cleaning process is performed in a state where the substrate W is separated from the substrate mounting surface of the electrostatic chuck 115 by the lifter pins 131. This makes it possible to appropriately introduce plasma into the space generated between the back surface of the substrate W and the substrate mounting surface, and as a result, it is possible to appropriately remove reaction products attached to the bevel portion and back surface of the substrate W and the surface of the electrostatic chuck 115. Furthermore, at this time, by setting the height position of the tip of the lifter pin 131 (the distance between the back surface of the substrate W and the substrate mounting surface) to 2.0 mm or more and 4 mm or less, more preferably 3.0 mm or more and 3.5 mm or less, excessive penetration of plasma into the gap between the back surface of the substrate W and the electrostatic chuck surface is suppressed, thereby suppressing damage to the back surface of the substrate W or the electrostatic chuck surface. If the height position of the tip of the lifter pin 131 (the distance between the back surface of the substrate W and the substrate mounting surface) is set to less than 2.0 mm, it is not possible to properly remove reaction products from the edge region (bevel portion) of the substrate W. On the other hand, if the height position of the tip of the lifter pin 131 (the distance between the back surface of the substrate W and the substrate mounting surface) is set to more than 4.0 mm, etching (cleaning) progresses up to near the center of the back surface of the substrate W.

[0078] In this embodiment, as shown in the above-mentioned apparatus configuration (see FIG. 1), a cleaning gas for performing a cleaning process on the substrate W may be supplied from the additional gas inlet 240b in the inner upper electrode 22 corresponding to the edge region of the substrate W. Here, reaction products generated during etching tend to easily adhere to the bevel portion (edge ​​region) of the substrate W and to the surface of the substrate support 11 along the bevel portion. In this regard, as shown in the present embodiment, the additional gas is supplied from the additional gas introduction section 240b corresponding to the bevel portion (edge ​​region), so that the reaction products adhering to the bevel portion can be removed and, for example, the effect on the center region of the substrate W is suppressed.

[0079] In this embodiment, the pressure in the plasma generating space S during the cleaning process may be any pressure at which the plasma is stably maintained, and is set to 300 mTorr or more, for example. By performing the cleaning process using a pressure region of 300 mTorr or more in this manner, the removal rate of reaction products in the bevel portion can be improved while ensuring uniformity in the circumferential direction of the cleaning process for the substrate W, in other words, uniformity in the concentric circle.

[0080] Thereafter, when the removal of the reaction products attached to the substrate W is completed, the supply of the high frequency voltage to the susceptor 114 (lower electrode) or the upper electrode 20 of the substrate support 11 is stopped, and the cleaning process for the substrate W is terminated (T9 in FIG. 4). At this time, the second gas remaining inside the processing vessel 10 is exhausted to the outside of the processing vessel 10 by the exhaust system 40.

[0081] Subsequently, the lifter pins 131 are raised from the cleaning position to the delivery position by the operation of the actuator 132, and the substrate W is delivered from the lifter pins 131 to a substrate transport robot (not shown) (T10 in FIG. 4). Thereafter, the substrate W is transferred to the outside of the processing chamber 10 by a substrate transfer robot (not shown), and a series of plasma processes (etching and cleaning processes) in the plasma processing apparatus 1 is completed.

[0082] <Effects of the technology disclosed herein> FIG. 6 is an explanatory diagram showing, as an example of experimental results illustrating the effect of the technology of the present disclosure, the surface state of a substrate W after etching without a cleaning process (Reference Example 1), the surface state of a substrate W after etching which has been subjected to a cleaning process using only CO2 gas (Reference Example 2), and the surface state of a substrate W after etching which has been subjected to a cleaning process using CO2 gas and C4F8 gas (Example).

[0083] As shown in Fig. 6, by using a cleaning gas containing CO2 gas and C4F8 gas in the plasma cleaning process, it is possible to remove CF-based polymers and Si components as reaction products without causing large process fluctuations from Reference Examples 1 and 2. More specifically, as shown by the BARC Remain value, CD value, and Recess value in Fig. 6, it was found that although some process fluctuations were observed by adding C4F8 gas, such fluctuations were within the allowable range that could be adjusted by the process conditions. According to this embodiment, the reaction products adhering to the substrate W during etching can be removed by the added C4F8 gas and CO2 gas without affecting the process results of the substrate W in this way.

[0084] 7 and 8 are graphs showing an example of a simulation result showing the relationship between the plasma etching amount of the etching target layer E formed on the back surface of the dummy substrate and the tip height of the lifter pin 131 (the separation distance between the substrate W and the electrostatic chuck 115). The upper graphs in FIGS. 7 and 8 are graphs focusing on the distribution of the amount of reaction products on the peripheral portion of the back surface of the substrate W, and the lower graphs in FIGS. 7 and 8 are graphs focusing on the distribution of the amount of reaction products in the diameter direction of the back surface of the substrate W. The vertical axis of the upper graphs in FIGS. 7 and 8 indicates the amount of reaction products attached to the peripheral portion of the back surface of the substrate W, and the horizontal axis indicates the azimuth angle of the back surface of the substrate W when the notch portion viewed from the center of the back surface of the substrate W is set to 180°. The vertical axis of the lower graphs in FIGS. 7 and 8 indicates the amount of reaction products attached to the back surface of the substrate W, and the horizontal axis indicates the position in the diameter direction of the back surface of the substrate W when the center of the back surface of the substrate W is set to 0 mm.

[0085] As can be seen from the simulation experiment results shown in Figures 7 and 8, by making the height of the lifter pins 131 at least 2.0 mm or more (Figure 7 shows the height of the lifter pins 131 as being 2.5 mm or more), reaction products adhering to the bevel portion (edge ​​region) of the substrate W can be removed. Furthermore, by setting the height of the lifter pins 131 to at least 4.0 mm or less (lifter pins 131 having a height of 3.5 mm or less are illustrated in FIG. 7), etching can be prevented from progressing in the center side of the rear surface of the substrate W (center region).

[0086] Furthermore, as shown in Figures 7 and 8, it has been found that by setting the height of the lifter pins 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, the etching amount distribution around the entire circumference, especially in the edge region of the substrate W, can be made uniform.

[0087] As can be seen from the results shown in FIGS. 6 to 8, according to the plasma processing method for the substrate W according to the present embodiment, a large flow rate of CO gas as a cleaning gas and a small flow rate of C x H y F z (y≧0, x / z>1 / 4), for example, by adding C4F8 gas to remove the reaction products generated during etching, it is possible to remove both the CF-based polymer and the Si component as the reaction products generated thereby, even when the etching target layer E formed on the surface of the substrate W contains a low dielectric constant (Low-k) material.

[0088] In particular, according to this embodiment, C is added to the cleaning gas. x H y F z By using a gas that is relatively carbon (C) rich, expressed as x / z>1 / 4, it is possible to remove the Si component of the reaction product while adequately protecting the low-k film formed on the surface of the substrate W.

[0089] Furthermore, according to this embodiment, the cleaning process is performed in a state in which the substrate W is detached from the substrate mounting surface of the electrostatic chuck 115 by the lifter pins 131, particularly in a state in which the separation distance between the back surface of the substrate W and the substrate mounting surface of the electrostatic chuck 115 is controlled to be 2 mm or more and 4 mm or less. This makes it possible to appropriately remove reaction products attached to the bevel portion and back surface of the substrate W or the surface of the electrostatic chuck 115 by the plasma generated in the plasma generation space S.

[0090] Furthermore, according to this embodiment, the cleaning gas may be introduced into the plasma generation space S during the cleaning process from the additional gas inlet 240b, which corresponds to the edge region, which is the main adhesion region of the reaction products on the substrate W. More specifically, the cleaning gas may be introduced from the outermost periphery of the inner upper electrode 22 in which the gas inlet holes 221a are formed, toward the corresponding edge region of the substrate W. This makes it possible to remove the reaction products adhering to the edge region of the substrate W and to suppress the influence on the center region of the substrate W.

[0091] According to the above embodiment, the cleaning gas is supplied only from the additional gas inlet 240b located at the outermost periphery of the inner upper electrode 22, but the supply position of the cleaning gas may be changed as appropriate, for example, depending on the adhesion position of the reaction product on the substrate W. In other words, the additional gas supply means 33 for supplying the cleaning gas may be connected to the buffer chamber 222a corresponding to the center region of the substrate W and the buffer chamber 222b corresponding to the edge region of the substrate W, instead of or in addition to the buffer chamber 222c formed inside the electrode support 222.

[0092] As described above, the arrangement, shape and number of the buffer chambers formed inside the electrode support 222 are not limited to those in the above embodiment, and can be changed as appropriate, for example, depending on the adhesion position of the reaction product on the substrate W.

[0093] The embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0094] 1. Plasma processing equipment 2. Control section 10 Processing vessel 11 Substrate support 20b high frequency power supply 30 Gas supply section 114b high frequency power supply 130 Lifter E Layer to be etched W substrate

Claims

1. 1. A method for cleaning a substrate, comprising: Providing a substrate with a silicon-containing low-k layer on a substrate support; Etching the low-k layer with a plasma generated from a first gas; separating the etched substrate from the substrate support; removing reaction products attached to the substrate during etching by plasma generated from a second gas; the second gas includes a first carbon-containing gas represented by CxFz (x / z>1 / 4); A cleaning method, wherein the separation distance between the substrate and the substrate support during removal of the reaction product is 2.0 mm or more.

2. 2. The method of claim 1, wherein the second gas further comprises a second carbon-containing gas different from the first carbon-containing gas.

3. The second carbon-containing gas is CO ２ The cleaning method according to claim 2 , wherein the gas is a gas.

4. 4. The cleaning method according to claim 2, wherein a flow rate ratio of the first carbon-containing gas to the second carbon-containing gas in the second gas is 1% or less.

5. 5. The cleaning method according to claim 1, wherein a distance between the substrate and the substrate support during removal of the reaction product is within a range of 2.0 mm to 4.0 mm.

6. 6. The cleaning method according to claim 1, wherein an internal pressure of the processing container during removal of the reaction products is set higher than an internal pressure of the processing container during etching of at least the low-k layer.

7. 7. The cleaning method according to claim 6, wherein the internal pressure of the processing vessel during removal of the reaction product is 300 mTorr or more.

8. The substrate to be processed has a central region and an annular peripheral region surrounding the central region within a plane thereof, 8. The cleaning method according to claim 1, wherein the second gas is supplied only toward the peripheral region during removal of the reaction products.

9. A processing vessel; a substrate support disposed within the processing vessel; an actuator for raising and lowering the substrate relative to the substrate support; a gas supply unit that supplies a gas into the processing chamber; a radio frequency power source connected to the substrate support; A plasma processing apparatus comprising: The control unit is providing a substrate comprising a silicon-containing low-k layer on the substrate support; Etching the low-k layer with a plasma generated from a first gas; separating the etched substrate from the substrate support; removing reaction products adhered to the substrate during etching by plasma generated from a second gas containing at least a first carbon-containing gas represented by CxFz (x / z>1 / 4); The plasma processing apparatus, wherein a distance between the substrate and the substrate support during removal of the reaction product is 2.0 mm or more.

10. The plasma processing apparatus of claim 9 , wherein the control unit controls the gas supply unit so that the second gas further contains a second carbon-containing gas different from the first carbon-containing gas.

11. The plasma processing apparatus according to claim 10 , wherein the control unit controls a flow rate ratio of the first carbon-containing gas to the second carbon-containing gas in the second gas to 1% or less.

12. The plasma processing apparatus according to any one of claims 9 to 11, wherein the control unit controls the actuator so that a separation distance between the substrate and the substrate support during removal of the reaction product is within a range of 2.0 mm or more and 4.0 mm or less.

13. The gas supply unit includes: a first supply unit that supplies the first gas to a central region of the substrate to be processed; a second supply unit that supplies the first gas to an annular peripheral region that surrounds the central region; 13. The plasma processing apparatus according to claim 9, further comprising: a third supply unit that supplies the second gas to the peripheral region.

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