Cleaning method and plasma processing apparatus

Abstract

The objective of this invention is to properly remove reaction products adhering to the beveled and back surfaces of a substrate during plasma etching. This invention provides a substrate cleaning method comprising: providing a substrate having a silicon-containing Low-k layer to a substrate support; etching the Low-k layer using plasma generated from a first gas; removing the etched substrate from the substrate support; and removing the reaction products adhering to the substrate during etching using plasma generated from a second gas; wherein the second gas contains a first carbon-containing gas denoted as CxHyFz (y ≧ 0, x / z > 1 / 4).

Description

[Technical Field]

[0001] This invention relates to a cleaning method and a plasma treatment apparatus. [Previous Technology]

[0002] According to Patent Document 1, a traveling shock wave can be generated within the cavity, and this shock wave causes foreign objects attached to the back of the substrate to detach. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2005-317782 [Summary of the Invention]

[0004] [The problem the invention aims to solve]

[0005] The technology of the present invention can appropriately remove reaction products adhering to the beveled and back surfaces of the substrate during plasma etching. [Technical Means for Solving the Problem]

[0006] One embodiment of the present invention is a method for cleaning a substrate, comprising: providing a substrate having a silicon-containing Low-k layer to a substrate support; etching the Low-k layer using plasma generated from a first gas; removing the etched substrate from the substrate support; and removing reaction products adhering to the substrate during etching using plasma generated from a second gas; wherein the second gas contains a first carbon-containing gas denoted as CxHyFz (y≧0, x / z>1 / 4). [Effects of the Invention]

[0007] According to the present invention, reaction products adhering to the beveled and back surfaces of the substrate during plasma etching can be appropriately removed.

Implementation Method

[0009] In the manufacturing process of semiconductor devices, an etching process is performed on the etch target film formed by depositing it on the front side of a semiconductor substrate (hereinafter referred to as "substrate") to form a patterned mask layer as a mask. This etching process is usually performed in a plasma processing apparatus. Furthermore, in recent years, low-k materials such as SiOC film or SiOCH film have sometimes been used as the etch target film.

[0010] In plasma processing apparatus, there is a concern that during the above-mentioned etching process, reaction products of, for example, fluorocarbon (CF) based polymers may adhere to the beveled or back surface of the substrate to be etched. The reaction products adhering to the substrate may detach during substrate processing or transport and contaminate the interior of the apparatus, thereby causing apparatus malfunction or affecting the substrate processing results.

[0011] Here, as a method for removing such reaction products, examples may include: a method of introducing gas into the chamber to remove the reaction products as disclosed in Patent Document 1 (gas cleaning), or a method of generating plasma in the chamber to remove the reaction products (plasma cleaning), etc.

[0012] However, for example, when the etching target film has a Low-k film, there is a risk of deterioration or damage to the Low-k film when the plasma cleaning is performed using a CF-based gas (e.g., CF4 gas) with a low carbon ratio, expressed as CxHyFz (x / z≦1 / 4).

[0013] The technology of the present invention was made in view of the above-described circumstances, and can appropriately remove reaction products adhering to the beveled surface and back surface of the substrate during plasma etching. Hereinafter, with reference to the drawings, the plasma processing apparatus as the substrate processing apparatus of this embodiment and the plasma processing method including the cleaning method of this embodiment will be described. Furthermore, in this specification and drawings, elements having substantially the same functional configuration are omitted from repeated description by using the same symbols.

[0014] <Plasma Processing Apparatus> Figure 1 is a schematic longitudinal sectional view showing the general structure of a plasma processing system. Furthermore, in the following description, the side of the substrate W to be etched, 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 "front side", and the side opposite to the front side is referred to as the "back side".

[0015] 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 housing a substrate W, a substrate support 11 including a lower electrode, an upper electrode 20, a gas supply unit 30, and an exhaust system 40.

[0016] The processing container 10 is, for example, made of aluminum alloy and electrically grounded. The inner wall of the processing container 10 is covered with an aluminum oxide film or a yttrium oxide film (Y2O3). Furthermore, the processing container 10 has an inlet / outlet (not shown) for a substrate (wafer) W on its side, and is externally connected to the plasma processing apparatus 1 via this inlet / outlet. The inlet / outlet is configured to be freely openable and closed by a gate valve (not shown).

[0017] A substrate support 11 for holding a substrate W is disposed inside the processing container 10. The substrate support 11 includes a body portion 111 and a focusing ring 112. The focusing ring 112 is configured to surround the electrostatic chuck 115 described below on the body portion 111.

[0018] 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 sequence stacked from the bottom side of the processing container 10.

[0019] The support platform 113 has a generally cylindrical shape, and an insulating plate (not shown) is disposed approximately at the center of the bottom surface of the processing container 10. Furthermore, a flow path C is formed inside the support platform 113. A heat transfer medium from a cooling unit (not shown) is circulated through 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 the desired temperature.

[0020] The base 114 is supported on the support platform 113. The base 114 includes conductive components such as aluminum alloy. The conductive components of the base 114 function as lower electrodes. A high-frequency power supply 114b is electrically connected to the base 114 via a matching adapter 114a. The high-frequency power supply 114b can output a first high-frequency voltage in the range of 2 MHz to 20 MHz, for example, 2 MHz. The matching adapter 114a can match the internal impedance of the high-frequency power supply 114b with the load impedance. Furthermore, the high frequency from the high-frequency power supply 114b can be pulsed.

[0021] The electrostatic chuck 115 is supported on the base 114. The electrostatic chuck 115 has an adsorption electrode 115a inside. 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, and the electrostatic force causes the substrate W to be adsorbed and held on the upper surface (substrate mounting surface) of the electrostatic chuck 115.

[0022] Furthermore, a cylindrical inner wall member 116 containing quartz is installed on the outer periphery of the support platform 113 and the base 114.

[0023] Furthermore, the main body 111 of the substrate support 11 is provided with a gas supply pipe 120 and a lifter 130.

[0024] The gas supply pipe 120 is configured to pass through the body portion 111 in the thickness direction and is connected to a gas supply source (not shown). In this way, the gas supply pipe 120 supplies heat transfer gas such as He gas (back gas) between the back side of the substrate W and the electrostatic chuck 115, and can control the substrate W adsorbed and held on the upper surface of the electrostatic chuck 115 to the required temperature.

[0025] 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. The lifting device 130 lifts and lowers the substrate W on the base 114 (more specifically, on the electrostatic chuck 115) and adjusts the height of the front end of the lifting pin 131 so that the back side of the substrate W reaches the desired position.

[0026] The lifting pin 131 is a columnar member that moves up and down by protruding from and being inserted into the substrate mounting surface of the electrostatic chuck 115 at its upper end, and is configured to insert into the interior of a pin-through hole formed along the thickness direction of the body portion 111 of the substrate support 11. A plurality of lifting pins 131 are arranged at intervals along the circumference of the electrostatic chuck 115 (substrate mounting surface), for example, three or more. The lifting pins 131 are arranged at equal intervals along the aforementioned circumferential direction. The actuator 132 generates a driving force to move the lifting pins 131 up and down, thereby causing the plurality of lifting pins 131 to move up and down.

[0027] The lifting device 130 is configured to raise and lower the lifting pin 131 by the action of the actuator 132, thereby allowing the lifting pin 131 to move freely between the junction position (the position where the upper end protrudes from the substrate mounting surface), the standby position (the position where the upper end does not protrude from the substrate mounting surface), and the cleaning position (the position where the upper end protrudes from the substrate mounting surface and the upper end position is lower than the junction position) of the substrate W. In other words, it is configured to allow the substrate W held on the lifting pin 131 to move freely between the junction position (the position where the junction with the substrate transport robot takes place), the processing position (the position where the substrate is placed on the substrate mounting surface), and the cleaning position (the position where the reaction products attached to the substrate W are removed) by the action of the actuator 132.

[0028] Furthermore, a high-pass filter 140 is electrically connected to the base 114 that constitutes the lower electrode. The high-pass filter 140 is used to block the high frequency from the high-frequency power supply 114b connected to the lower electrode and to ground the high frequency from the high-frequency power supply 20b connected to the upper electrode 20 described below.

[0029] An upper electrode 20 is provided above the substrate support 11, parallel to the base 114 constituting the lower electrode. A plasma generation space S is formed between the base 114 and the upper electrode 20.

[0030] The upper electrode 20 includes an outer annular upper electrode 21 and an inner circular 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 with a frequency of 40 MHz or higher (e.g., 60 MHz). The matching device 20a can match the internal impedance of the high-frequency power supply 20b with the load impedance. Furthermore, the high frequency from the high-frequency power supply 20b can be pulsed.

[0031] The outer upper electrode 21 is configured to surround the inner upper electrode 22. An annular dielectric (not shown) is disposed between the outer upper electrode 21 and the inner upper electrode 22. Furthermore, an annular insulating shielding member (not shown) containing alumina is disposed, for example, hermetically sealed 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. The lower end of the upper electrode rod 24 is electrically connected to the center of the upper surface of the power supply cylinder 211 via the connector 23. The upper end of the upper electrode rod 24 is connected to the output side of the matching device 20a.

[0032] The inner upper electrode 22 constitutes a cluster nozzle that ejects the required gas into the plasma generation space S on the substrate W supported by the substrate support 11. The inner upper electrode 22 includes a circular plate-shaped electrode plate 221 having a plurality of gas inlet holes 221a (refer to FIG. 2), and an electrode support 222 that can be detachably supported on the upper surface side of the electrode plate 221. The electrode support 222 is formed into a circular plate with a diameter approximately the same as that of the electrode plate 221.

[0033] As shown in FIG. 1, 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 provided in the middle of the lower electrode rod 25. By adjusting the electrostatic capacitance of the variable capacitor 26, when a second high-frequency voltage is applied from the high-frequency power supply 20b, the relative ratio between the electric field strength formed directly below the outer upper electrode 21 and the electric field strength formed directly below the inner upper electrode 22 can be adjusted.

[0034] In one embodiment, the inner upper electrode 22 has a plurality of first gas inlet portions, and in this embodiment, it has two first gas inlet portions. The first gas inlet portions introduce gas into different regions within the substrate W surface supported on 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"). Hereinafter, these two first gas inlet portions will be referred to as the first gas inlet portion 230 for introducing gas into the central region and the second gas inlet portion 240 for introducing gas into the edge region, respectively.

[0035] The first gas inlet section 230, which is the first supply section, includes a buffer chamber 222a formed inside the electrode support 222 and a plurality of gas inlet holes 221a formed on its lower surface. The buffer chamber 222a and the electrode support 222 are formed correspondingly inside the central region, that is, in the central region of the substrate W adsorbed and held on the substrate support 11.

[0036] 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 mechanism 31 described below, and 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 mechanism 33 described below. The processing gas inlet 240a is arranged around the first gas inlet 230. The auxiliary gas inlet 240b is also arranged around 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.

[0037] The processing gas introduction section 240a, serving as the second supply section, includes a buffer chamber 222b formed inside the electrode support 222 and a plurality of gas introduction holes 221a formed on its lower surface. Furthermore, the additional gas introduction section 240b, serving as the third supply section, includes a buffer chamber 222c formed inside the electrode support 222 and a plurality of gas introduction holes 221a formed on its lower surface. The buffer chambers 222b and 222c are formed correspondingly within the peripheral region of the electrode support 222, i.e., at the edge region of the substrate W adsorbed and held on the substrate support 11.

[0038] Furthermore, buffer chambers 222a, 222b and 222c may be formed independently inside the electrode support 222, for example. Alternatively, an integral buffer chamber may be formed inside the electrode support 222, and this integral buffer chamber may be formed by dividing it, for example, by using O-rings or the like.

[0039] Furthermore, in each buffer chamber 222a, 222b and 222c, gas that meets the purpose is supplied from the gas supply unit 30. For the central region of the substrate W, gas is ejected through the buffer chamber 222a of the first gas inlet unit 230, and for the edge region of the substrate W, gas is ejected through the buffer chamber 222b or 222c of the second gas inlet unit 240.

[0040] A cylindrical grounding conductor 250 is provided on the outer side of the power supply cylinder 211 connected to the outer upper electrode 21. This conductor has a sidewall with a diameter approximately the same as that of the processing container 10. 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 penetrates the central portion of the upper surface of the grounding conductor 250. An insulating member (not shown) is interposed at the contact portion between the grounding conductor 250 and the upper electrode rod 24.

[0041] Furthermore, the low-pass filter 260 is electrically connected to the inner side of the upper electrode 22 of the upper electrode 20. The low-pass filter 260 is used to block the high frequency from the high-frequency power supply 20b connected to the upper electrode 20 and to ground the high frequency from the high-frequency power supply 114b connected to the lower electrode.

[0042] Furthermore, although this embodiment describes the case where 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, the configuration of the inner upper electrode 22 is not limited to this. In other words, although this embodiment divides the surface of the substrate W into two regions, a central region and an edge region, the number of divisions of the region formed within the surface of the substrate W is not limited to two. 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 a plurality of different regions, or the edge region (and the second gas inlet portion 240 of the inner upper electrode 22) can be further divided into a plurality of different regions.

[0043] Refer back to the description of Figure 1. The gas supply unit 30 includes: a processing gas supply mechanism 31, which supplies processing gas for etching the substrate W; a flow rate adjustment mechanism 32, which adjusts the flow rate of the processing gas from the processing gas supply mechanism 31; and an auxiliary gas supply mechanism 33, which supplies the required auxiliary gas.

[0044] The processing gas supply mechanism 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 of the inner upper electrode 22 via a flow rate adjustment mechanism 32 (e.g., a flow divider). The flow rate adjustment mechanism 32 adjusts the flow rate of the processing gas 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 mechanism 31 to the buffer chambers 222a and 222b respectively).

[0045] As shown in FIG3, in one embodiment, the processing gas supply mechanism 31 includes a gas tank housing a plurality of (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 distribution adjustment mechanism 32 via its 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.

[0046] In gas supply source 310a, for example, gases such as CF4, C4F8, CHF3, and CH2F2, represented by CxHyFz (y≧0), are sealed as etching gases. In gas supply source 310b, for example, O2 gas is sealed as a gas to control the CF-based reaction products. In gas supply source 310c, inert gases such as Ar, or N2, COS, etc., are sealed as carrier gases.

[0047] Furthermore, the number of gas supply sources for the processing gas supply mechanism 31 is not limited to the example shown in the figure. For example, one, two, or four or more sources may be provided. Also, the types of gas supplied from the processing gas supply mechanism 31 are not limited to the examples described above. It may be configured to supply gases such as CO, CO2, and H2 as alternatives to the aforementioned gases, or to supply gases such as CO, CO2, and H2 in addition to the aforementioned gases.

[0048] The flow rate adjustment mechanism 32 includes: a pressure adjustment unit 320, which adjusts the pressure in the connecting pipe 34 between the processing gas supply mechanism 31 and the buffer chamber 222a; and a pressure adjustment unit 321, which adjusts the pressure in the connecting pipe 35 between the processing gas supply mechanism 31 and the buffer chamber 222b. Specifically, the pressure adjustment unit 320 includes a pressure sensor 320a for detecting the pressure in the connecting pipe 34 and a valve 320b for adjusting the opening and closing degree of the connecting pipe 34. Furthermore, the pressure adjustment unit 321 includes a pressure sensor 321a for detecting the pressure in the connecting pipe 35 and a valve 321b for adjusting the opening and closing degree of the connecting pipe 35.

[0049] Pressure adjustment 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 pressure detected from pressure sensors 320a and 321a. Pressure controller 322 is controlled by control unit 2, for example.

[0050] Furthermore, the connecting pipes 34 and 35 that connect the processing gas supply mechanism 31 and the buffer chambers 222a and 222b respectively can be branched inside the flow rate adjustment mechanism 32 as shown in Figures 1 and 3, or they can be branched outside the flow rate adjustment mechanism 32.

[0051] The additional gas supply mechanism 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.

[0052] As shown in FIG3, in one embodiment, the additional gas supply mechanism 33 includes a plurality of gas tanks (three in the illustrated example) housing gas supply sources 330a, 330b, and 330c. Each gas supply source 330a, 330b, and 330c is connected to the buffer chamber 222c via its corresponding flow controller 331a, 331b, and 331c. Each flow controller 331a, 331b, and 331c may include, for example, a mass flow controller or a pressure-controlled flow controller.

[0053] A CF-based gas that promotes etching, such as C4F8 or other CxFy gases, is sealed in the gas supply source 330a. O2 gas, for example, is sealed in the gas supply source 330b as a gas to control the CF-based reaction products. Furthermore, as shown in FIG3, a second carbon-containing gas (e.g., CO2 gas) may be sealed in the gas supply source 330b as a gas to improve the efficiency of the plasma cleaning process described below. A plasma cleaning gas (hereinafter simply referred to as "cleaning gas") used to remove reaction products adhering to the beveled or back surface of the etched substrate W, or the surface of the substrate support 11, is sealed in the gas supply source 330c. For example, CF-based gases represented by CxHyFz (y≧0, x / z>1 / 4), such as C3F8, C4F6, C4F8, CHF3, and CH2F2, are sealed in as the first carbon-containing gas.

[0054] Furthermore, the number of gas supply sources for the additional gas supply mechanism 33 is not limited to the example shown in the figure. For example, one, two, or more than four sources may be provided. Also, for example, the gas supply source 330c may be omitted, and clean gas may be supplied from the gas supply source 330a.

[0055] Refer back to the description of Figure 1. The exhaust system 40 may, for example, be connected 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 allows adjustment of the internal pressure of the processing container 10. The vacuum pump may include a turbomolecular pump, a dry vacuum pump, or a combination thereof.

[0056] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to execute the various steps described herein. The control unit 2 may be configured to control the various elements of the plasma processing apparatus 1 to execute the various steps described herein. In one embodiment, 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 (Central Processing Unit)) 2a1, a memory unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control actions based on a program stored in the memory unit 2a2. The memory unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or combinations thereof. The communication interface 2a3 can communicate with the plasma processing device 1 via a communication line such as a LAN (Local Area Network).

[0057] Various exemplary embodiments have been described above, but various additions, omissions, substitutions, and modifications can be made, and the embodiments are not limited to those described above. Furthermore, elements from different embodiments can be combined to form other embodiments.

[0058] For example, although this embodiment describes the case where the plasma processing system has a parallel plate-type plasma processing device 1 as an example, the configuration of the plasma processing system is not limited to this. For example, the plasma processing system may have a processing device that includes a plasma generation unit such as capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR), helicon wave plasma (HWP), or surface wave plasma (SWP). Furthermore, processing devices that include various types of plasma generation units, including AC (alternating current) plasma generation units and DC (direct current) plasma generation units, may also be used.

[0059] <Plasma Processing Method> Next, a plasma processing method for a substrate W implemented using a plasma processing system configured as described above will be described. Figure 4 shows a timing diagram of plasma processing according to one embodiment. In Figure 4, the horizontal axis represents time, and the vertical axis represents (a) the internal pressure of the processing container 10, (b) the DC voltage applied to the adsorption electrode 115a, (c) the application of a high-frequency voltage (RF), and (d) the height position of the front end of the lifting pin 131.

[0060] Furthermore, in this embodiment, as shown in FIG5, the case of etching a substrate W having an etch target layer E comprising a low-k material and a mask layer M on the front area layer is described as an example. Furthermore, in this embodiment, the low-k material refers to a material having a dielectric constant at least less 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. Also, the etch target layer E (low-k material) may be porous.

[0061] First, the substrate W, on which the aforementioned etching target layer E and masking layer M are formed on the front side, is transported into the processing container 10 by a substrate transport robot (not shown) located outside the plasma processing apparatus 1. After the substrate W is transported into the processing container 10, the lifting pin 131 is raised from the standby position to the handover position by the action of the actuator 132, and the substrate W is handed over to the lifting pin 131 by the substrate transport robot (T1 in FIG4). Furthermore, at the handover position, the substrate W is separated from the substrate mounting surface of the substrate support 11 (electrostatic chuck 115) and does not contact it, while the back side is held at the upper end of the lifting pin 131.

[0062] After the substrate is delivered to the upper end of the lifting pin 131, the actuator 132 causes the lifting pin 131 to descend from the handover position to the standby position, and the substrate W is delivered from the lifting pin 131 to the substrate mounting surface of the electrostatic chuck 115 (T2 in FIG. 4). In other words, the actuator 132 causes the substrate W to move from the handover position to the processing position. Subsequently, by applying a DC voltage to the adsorption electrode 115a of the electrostatic chuck 115, the substrate W is adsorbed and held on the substrate mounting surface of the electrostatic chuck 115 by electrostatic force.

[0063] Subsequently, after sealing the interior of the processing container 10, a first gas is supplied to the plasma generation space S from the gas supply section 30 to generate plasma from the first gas. Then, etching begins on the substrate W adsorbed and held on the substrate mounting surface (T4 in FIG4). Furthermore, the aforementioned "first gas" used for etching includes processing gas from the processing gas supply mechanism 31 and supplementary gas from the supplementary gas supply mechanism 33.

[0064] Specifically, firstly, etching processing gas (e.g., CxHyFz gas, O2 gas, and Ar gas) is supplied by the processing gas supply mechanism 31, and additional gas (e.g., CxFy gas and O2 gas) is supplied by the additional gas supply mechanism 33. Furthermore, 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 plasma generation space S.

[0065] Subsequently, after obtaining the desired etching result for the etched layer E, the etching in the plasma processing apparatus 1 is terminated. Here, due to the etching performed in the plasma processing apparatus 1, as described above, the reaction products may adhere as foreign matter to the inclined or back surface of the substrate W to be processed, or to the surface of the substrate support 11. The reaction products adhering to the substrate W or the substrate support 11 may cause malfunctions in the apparatus or malfunctions in the processing result of the substrate W.

[0066] In this respect, in the plasma processing apparatus 1 of this embodiment, after the etching of the substrate W is completed, a plasma cleaning process (hereinafter sometimes simply referred to as "cleaning process") is performed inside the same processing container 10 to remove the reaction products attached to the substrate W, etc.

[0067] When the cleaning process of the substrate W begins, the generation of electrostatic force between the electrostatic chuck 115 and the substrate W is stopped by stopping the supply of DC voltage to the adsorption electrode 115a of the electrostatic chuck 115.

[0068] Here, the cleaning process for the substrate W described below is performed while the substrate W is detached from the substrate mounting surface by the lifting pin 131. However, as mentioned above, if only the DC voltage supplied to the adsorption electrode 115a is stopped, the substrate W may remain adsorbed and held on the substrate mounting surface due to residual charges, etc., and may not be able to be properly lifted by the lifting pin 131. In this embodiment, before the substrate W is lifted by the lifting pin 131, a high-frequency voltage (T6 in FIG. 4) is applied momentarily to the substrate support 11. This removes the influence of residual charges between the substrate W and the substrate mounting surface, and properly stops the adsorption and holding of the substrate W by the electrostatic chuck 115.

[0069] Furthermore, from the viewpoint of properly separating the substrate W from the electrostatic chuck 115 in this manner, it is preferable to supply an inert gas (e.g., Ar gas) from the gas supply section 30 to the plasma generation space S instead of the first gas during the period from the end of etching in the plasma processing apparatus 1 to the start of the cleaning process described below.

[0070] After a high-frequency voltage is applied to the substrate support 11, the actuator 132 causes the lifting pin 131 to rise from the standby position to the cleaning position, and the substrate W is handed over to the lifting pin 131 from the electrostatic chuck 115 (substrate mounting surface) (T7 in FIG4). In the cleaning position, the substrate W is separated from the substrate mounting surface of the electrostatic chuck 115 without contact, and the back side is held at the upper end of the lifting pin 131. 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 more than 2.0 mm and less than 4.0 mm, preferably more than 2.5 mm and less than 3.8 mm, and more preferably more than 3.0 mm and less than 3.5 mm.

[0071] After the substrate W is held at the upper end of the lifting pin 131, a second gas is then supplied to the plasma generation space S from the gas supply section 30. Plasma is generated by the second gas, and the cleaning process of the substrate W begins (T8 in FIG4). Furthermore, the "second gas" used for the cleaning process includes at least the cleaning gas from the auxiliary gas supply mechanism 33. Also, in this embodiment, in addition to the CxHyFz gas supplied from the gas supply source 330c, CO2 gas supplied from the gas supply source 330b is also included in the cleaning gas.

[0072] Specifically, firstly, a clean gas (e.g., CxHyFz gas and CO2 gas) is supplied by the auxiliary gas supply mechanism 33. Then, a high-frequency voltage is supplied to the base 114 (lower electrode) or upper electrode 20 of the substrate support 11, thereby generating plasma from the second gas supplied to the plasma generation space S.

[0073] Here, after careful research, the inventors discovered that when the etched target layer E contains a Si-containing material as a low-k dielectric material, as described above, the reaction products adhering to the substrate W during etching contain either a CF-based polymer or Si. Furthermore, after careful research, the inventors discovered that when the generated reaction products are subjected to plasma cleaning treatment using CO2 gas as described above, only Si components are detected as residue after the plasma cleaning treatment. In other words, it was found that although the reaction products containing CF-based polymers can be removed by plasma cleaning treatment using CO2 gas, the reaction products containing Si cannot be removed and residue is formed.

[0074] Here, when removing Si-containing reaction products by plasma cleaning, a CF-based gas is added to the cleaning gas, for example. However, if a CF-based gas with a low carbon (C) ratio is added as the cleaning gas, there are concerns about its impact on the surface of the substrate W, such as the consumption of the mask layer M, the substrate film, the 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, it is necessary to adjust the gas type, flow rate, or other parameters to minimize the impact on the surface of the substrate W.

[0075] In this embodiment, to properly remove the reaction products adhering to the substrate W, as an example, plasma cleaning of the substrate W is performed under the following conditions. Furthermore, the processing conditions shown below are examples, and etching processing conditions can be appropriately selected. • Flow rate of the second gas (cleaning gas): CxHyFz gas (y≧0, x / z>1 / 4): 1~5 sccm • Flow rate of CO2 gas: 500~1200 sccm • Pressure of the plasma generation space S: 300~800 mTorr • Temperature of the substrate W: 10~60℃ • High-frequency power: 500~600 W • Frequency of the high-frequency power: 10~100 MHz • Front height of the lifting pin 131: 2.0~4.0 mm

[0076] Specifically, in the cleaning process of this embodiment, plasma generated from CO2 gas is used to remove the CF-based polymer as a reaction product, and plasma generated from CxHyFz gas (CF-based gas) with a flow rate sufficiently low relative to the CO2 gas flow rate (e.g., a flow rate ratio of 1% or less relative to the CO2 gas flow rate) is used to remove the Si component as a reaction product. In other words, since both the CF-based polymer and the Si component as reaction products can be removed simultaneously, the cleaning efficiency can be improved.

[0077] Furthermore, by using a gas denoted as CxHyFz (y≧0, x / z>1 / 4), more specifically a gas richer in carbon (C) than CF4 gas, as the CF-based gas included in the cleaning gas, it is possible to protect the Low-k film formed on the front side of the substrate W and to appropriately remove the Si component of the reaction products. Here, it has been found that if a CF-based gas with a lower carbon (C) ratio (e.g., CF4 gas) denoted as CxHyFz (x / z≦1 / 4) is used, the etch target layer E may be etched during the cleaning process. In this case, for example, the pattern (hole) formed on the etch target layer E may become darker, potentially damaging the substrate wiring formed on the layer below the etch target layer E. Therefore, it is more ideal to use a gas denoted as CxHyFz (y≧0, x / z>1 / 4) as the CF-based gas included in the cleaning gas.

[0078] 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. This allows plasma to be appropriately introduced into the space between the back surface of the substrate W and the substrate mounting surface, thereby appropriately removing reaction products adhering to the beveled or back surface of the substrate W and the surface of the electrostatic chuck 115. Furthermore, by setting the height of the tip of the lifting pin 131 (the separation 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, preferably 3.0 mm or more and 3.5 mm or less, excessive plasma penetration between the back surface of the substrate W and the surface of the electrostatic chuck can be suppressed, thus preventing damage to the back surface of the substrate W or the surface of the electrostatic chuck. Moreover, if the height of the tip 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, reaction products cannot be appropriately removed from the edge region (beveled surface) of the substrate W. On the other hand, if 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) is greater than 4.0 mm, the etching (cleaning) will proceed to the vicinity of the center of the back side of the substrate W.

[0079] Furthermore, in this embodiment, as shown in the above-described apparatus configuration (refer to FIG. 1), a cleaning gas for cleaning the substrate W can be supplied from the additional gas inlet 240b of the inner upper electrode 22 corresponding to the edge region of the substrate W. Here, the reaction products generated during etching tend to adhere to the beveled portion (edge ​​region) of the substrate W or the surface of the substrate support 11 along the beveled portion. Regarding this point, as shown in this embodiment, since the gas is supplied from the additional gas inlet 240b corresponding to the beveled portion (edge ​​region), the reaction products adhering to the beveled portion can be removed, and for example, the influence on the central region of the substrate W can be suppressed.

[0080] Furthermore, in this embodiment, the pressure of the plasma generation space S during the cleaning process can be a pressure that allows the plasma to be stably maintained; for example, it is set to 300 mTorr or higher. By using a pressure area of ​​300 mTorr or higher for cleaning, it is possible to ensure the uniformity of the cleaning process on the substrate W in the circumferential direction, i.e., the uniformity of concentric circles, and to improve the removal rate of reaction products on the beveled surface.

[0081] Subsequently, after the removal of the reaction products attached to the substrate W is completed, the supply of high-frequency voltage to the base 114 (lower electrode) or upper electrode 20 of the substrate support 11 is stopped, and the cleaning process of the substrate W is ended (T9 in FIG4). At this time, the second gas remaining inside the processing container 10 is discharged to the outside of the processing container 10 by means of the exhaust system 40.

[0082] Subsequently, by the action of actuator 132, lifting pin 131 is raised from the cleaning position to the handover position, and substrate W is handed over to substrate transport robot (not shown) (T10 in FIG4) from lifting pin 131. Afterwards, substrate W is transported to the outside of processing container 10 by substrate transport robot (not shown), and one series of plasma processes (etching and cleaning processes) in plasma processing apparatus 1 is completed.

[0083] <Effects of the Technology of the Invention> As an example of the experimental results showing the effects of the technology of the present invention, FIG6 is an explanatory diagram showing the front view of the substrate W after etching without cleaning treatment (Reference Example 1), the front view of the substrate W after etching with only CO2 gas cleaning treatment (Reference Example 2), and the front view of the substrate W after etching with CO2 gas and C4F8 gas cleaning treatment (Example).

[0084] As shown in Figure 6, it can be seen that by using a cleaning gas containing CO2 and C4F8 gases in the plasma cleaning process, the CF-based polymer and Si components, which are reaction products, can be removed from Reference Example 1 or Reference Example 2 without causing significant process changes. More specifically, as shown in Figure 6, the BARC Remain (Bottom Anti-Reflection Coating Remain), CD value, or Recess value, although a slight process change is visible due to the addition of C4F8 gas, it can be seen that this change value is within the allowable range that can be adjusted by the processing conditions. Furthermore, according to this embodiment, the added C4F8 and CO2 gases can be used to remove the reaction products adhering to the substrate W during etching without affecting the process results of the substrate W.

[0085] Figures 7 and 8 are graphs illustrating an example of the simulation experiment results, showing the relationship between the amount of plasma etching of the etched target layer E formed on the back of the dummy substrate and the front height of the lifting pin 131 (the separation distance between the substrate W and the electrostatic chuck 115). In Figures 7 and 8, the upper graph focuses on the distribution of the amount of reaction products at the periphery of the back of the substrate W, while the lower graph focuses on the distribution of the amount of reaction products in the diameter direction of the back of the substrate W. In Figures 7 and 8, the vertical axis of the upper graph represents the amount of reaction products attached to the periphery of the back of the substrate W, and the horizontal axis represents the azimuth angle of the back of the substrate W when the notch portion viewed from the center of the back of the substrate W is 180°. Also, in Figures 7 and 8, the vertical axis of the lower graph represents the amount of reaction products attached to the back of the substrate W, and the horizontal axis represents the position of the back of the substrate W in the diameter direction when the center of the back of the substrate W is 0 mm.

[0086] As can be seen from the simulation results shown in Figures 7 and 8, by making the height of the lifting pin 131 at least 2.0 mm (Figure 7 shows the height of the lifting pin 131 at 2.5 mm or more), the reaction products attached to the beveled surface (edge ​​region) of the substrate W can be removed. Furthermore, by making the height of the lifting pin 131 at least 4.0 mm or less (Figure 7 shows the height of the lifting pin 131 at 3.5 mm or less), etching on the central side (central region) of the back surface of the substrate W can be suppressed.

[0087] Furthermore, as shown in Figures 7 and 8, it can be seen that by making the height of the lifting pin 131 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 of the edge area of ​​the substrate W can be uniformly distributed throughout the entire perimeter.

[0088] In summary, as can be seen from the results shown in Figures 6 to 8, according to the plasma processing method of the substrate W in this embodiment, by adding a small amount of CxHyFz (y≧0, x / z>1 / 4), such as C4F8 gas, to a large flow of CO2 gas as a cleaning gas to remove the reaction products generated during etching, even when the etching target layer E formed on the front side of the substrate W contains a low dielectric constant (Low-k) material, both the CF-based polymer and the Si component generated as reaction products can be removed.

[0089] Furthermore, in particular, according to this embodiment, by using a gas that is relatively rich in carbon (C) and expressed as x / z > 1 / 4 as the CxHyFz gas added to the cleaning gas, the Low-k film formed on the front side of the substrate W can be properly protected, and the Si component of the reaction product can be removed.

[0090] Furthermore, according to this embodiment, cleaning is performed when the substrate W is detached from the substrate mounting surface of the electrostatic chuck 115 by the lifting pin 131, and in particular, 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 more than 2 mm and less than 4 mm. In this way, reaction products adhering to the inclined surface or back surface of the substrate W, or the surface of the electrostatic chuck 115, can be appropriately removed by the plasma generated in the plasma generation space S.

[0091] Furthermore, according to this embodiment, a cleaning gas can be introduced into the plasma generation space S during the cleaning process of the additional gas introduction portion 240b corresponding to the main adhesion area, i.e., the edge area, of the substrate W with the reaction products. More specifically, the cleaning gas can be introduced into the corresponding edge area of ​​the substrate W from the outermost peripheral portion of the upper inner electrode 22 where the gas introduction hole 221a is formed. In this way, the reaction products adhering to the edge area of ​​the substrate W can be removed, and the influence on the central area of ​​the substrate W can be suppressed.

[0092] Furthermore, according to the above embodiment, cleaning gas is supplied only from the additional gas inlet portion 240b located at the outermost periphery of the inner upper electrode 22. However, the supply position of the cleaning gas can be appropriately changed, for example, depending on the adhesion position of the reaction products to the substrate W. In other words, the additional gas supply mechanism 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 a substitute for or supplement to the buffer chamber 222c formed inside the electrode support 222.

[0093] 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 may be appropriately changed depending on the attachment position of the reaction products to the substrate W.

[0094] It should be considered that all the embodiments disclosed herein are illustrative and not limiting. The above embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended patent application. [Simplified Explanation of the Diagram]

[0008] Figure 1 is a longitudinal sectional view showing the configuration of a plasma processing system according to one embodiment. Figure 2 is a bottom view showing the configuration of the inner upper electrode according to one embodiment. Figure 3 is a system diagram showing the configuration of a gas supply unit according to one embodiment. Figure 4 is a timing diagram of plasma processing according to one embodiment. Figure 5 is an explanatory diagram of the etching target layer and mask layer formed on the substrate. Figure 6 is an explanatory diagram showing an example of the plasma processing result of the embodiment. Figure 7 is an explanatory diagram showing an example of the plasma processing result of an experimental example. Figure 8 is an explanatory diagram showing an example of the plasma processing result of an experimental example.

Claims

1. A cleaning method, which is a method for cleaning a substrate, and includes: The step of providing a substrate having a silicon-containing Low-k layer to a substrate support; The process includes: etching the Low-k layer using plasma generated from a first gas; removing the etched substrate from the substrate support; removing reaction products adhering to the substrate during etching using plasma generated from a second gas; wherein the second gas contains a first carbon-containing gas denoted as CxHyFz (y≧0, x / z>1 / 4), and the second gas further contains a second carbon-containing gas different from the first carbon-containing gas, wherein the flow rate ratio of the first carbon-containing gas to the second carbon-containing gas in the second gas is 1% or less.

2. The cleaning method as requested in item 1, wherein the second carbon-containing gas is CO2 gas.

3. The cleaning method of claim 1 or 2, wherein the separation distance between the substrate and the substrate support when removing the reaction products is within the range of 2.0 mm to 4.0 mm.

4. The cleaning method of claim 1 or 2, wherein 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-k layer.

5. The cleaning method as described in claim 4, wherein the internal pressure of the processing container is 300 mTorr or higher when removing the above-mentioned reaction products.

6. The cleaning method of claim 1 or 2, wherein the substrate to be treated has a central region and an annular peripheral region surrounding the central region in plane, and the second gas is supplied only to the peripheral region when removing the reaction products.

7. A plasma processing apparatus comprising: a processing container; a substrate support disposed inside the processing container; an actuator for lifting and lowering a substrate relative to the substrate support; a gas supply unit for supplying gas to the interior of the processing container; a high-frequency power supply connected to the substrate support; and a control unit; wherein the control unit sequentially performs the following steps: a step of supplying a substrate having a silicon-containing Low-k layer to the substrate support; a step of etching the Low-k layer using plasma generated from a first gas; a step of removing the etched substrate from the substrate support; a step of removing reaction products adhering to the substrate during etching using plasma generated from a second gas containing at least a first carbon-containing gas denoted as CxHyFz (y≧0, x / z>1 / 4); wherein the control unit controls the gas supply unit to further include a second carbon-containing gas different from 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 less than 1%.

8. The plasma processing apparatus of claim 7, wherein the control unit performs control of the actuator so that the separation distance between the substrate and the substrate support when removing the reaction products is within the range of 2.0 mm to 4.0 mm.

9. The plasma processing apparatus of claim 7 or 8, wherein the gas supply unit comprises: 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 surrounding the central region; and a third supply unit that supplies the second gas to the peripheral region.

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