Substrate processing method and substrate processing apparatus

Abstract

The present invention provides a substrate processing method and a substrate processing apparatus capable of suppressing the occurrence of arc discharge during an etching process. The present invention is a substrate processing method in a chamber, wherein the chamber includes: a stage for placing a substrate; an upper electrode opposed to the stage; and a gas supply port for supplying a processing gas into the chamber, and the substrate processing method includes the following a) to d). a) is a step of providing a substrate to the stage. b) is a step of supplying a first processing gas into the chamber. c) is a step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode while continuously supplying an RF signal. d) is a step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode while supplying a pulsed RF signal. c) and d) are alternately and repeatedly executed. In addition, the period of each execution of c) is 30 seconds or less.

Description

Technical Field

[0001] Aspects and embodiments of the present invention relate to a substrate processing method and a substrate processing apparatus. Background Art

[0002] There is known a technique for preparing a substrate having a plurality of base layers located at different heights and an object film formed on the plurality of base layers, using a mask having a plurality of openings above each base layer, and forming holes having different depths in the object film by etching (for example, refer to Patent Document 1 below).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-9259 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] The present invention provides a substrate processing method and a substrate processing apparatus capable of suppressing the occurrence of arc discharge during etching.

[0008] Technical Solution for Solving the Technical Problem

[0009] One aspect of the present invention is a substrate processing method in a chamber, wherein the chamber includes: a mounting table for mounting a substrate; an upper electrode opposed to the mounting table; and a gas supply port for supplying a processing gas into the chamber, and the substrate processing method includes the following steps a) to d). a) is a step of providing a substrate to the mounting table. b) is a step of supplying a first processing gas into the chamber. c) is a step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode and continuously supplying an RF signal. d) is a step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode and supplying a pulsed RF signal. Steps c) and d) are alternately repeated. In addition, the period of each execution of c) is 30 seconds or less.

[0010] Advantageous Effects of the Invention

[0011] According to aspects and embodiments of the present invention, generation of arc discharge during etching can be suppressed. Brief Description of the Drawings

[0012] Figure 1 It is a schematic cross-sectional view showing an example of an etching apparatus in an embodiment of the present invention.

[0013] Figure 2 It is a view showing an example of a cross-section of a substrate before etching.

[0014] Figure 3 This is a diagram showing an example of a cross section of a substrate after etching.

[0015] Figure 4 This is a schematic diagram showing an example of the behavior of electrons in a chamber during plasma etching.

[0016] Figure 5 This is a schematic diagram showing an example of the behavior of electrons in the chamber when the supply of the RF signal is stopped.

[0017] Figure 6 This is a diagram showing an example of control of an RF signal and a DC voltage.

[0018] Figure 7 This is a diagram showing an example of the execution time of the first etching step and the second etching step.

[0019] Figure 8 It means V pp This is a graph showing an example of how the size of a sample changes with respect to etching time.

[0020] Figure 9 This is a diagram showing an example of the etching amount of a conductive film with respect to etching time.

[0021] Figure 10 This is a schematic diagram showing an example of the state of the hole immediately after etching is completed.

[0022] Figure 11 This is a diagram showing an example of a state in which a conductive film is corroded.

[0023] Figure 12 This is a diagram showing an example of the state of the hole formed according to this embodiment.

[0024] Figure 13 This is a flowchart showing an example of an etching method.

[0025] Description of Reference Numerals

[0026] ER marginal ring

[0027] H hole

[0028] P pattern

[0029] S Processing Space

[0030] W substrate

[0031] 1 Etching device

[0032] 10 Device body

[0033] 11 Control device

[0034] 12 chambers

[0035] 12a conductors

[0036] 12e exhaust ports

[0037] 12g openings

[0038] 14 support parts

[0039] 16 bases

[0040] 18 electrostatic chucks

[0041] 20 electrodes

[0042] 22 DC power supplies

[0043] 24 flow paths

[0044] 26 pipes

[0045] 28 pipes

[0046] 30 upper electrodes

[0047] 32 insulating shielding parts

[0048] 34 electrode plates

[0049] 34a gas release holes

[0050] 36 electrode supports

[0051] 36a diffusion chambers

[0052] 36b gas flow holes

[0053] 36c gas inlets

[0054] 38 pipes

[0055] 40 gas supply sources

[0056] 42 valves

[0057] 43 separators

[0058] 44 flow controllers

[0059] 46 sediment shields

[0060] 48 baffles

[0061] 50 exhaust devices

[0062] 52 exhaust pipes

[0063] 54 gate valves

[0064] 56 conductive parts

[0065] 58 Power supply rod

[0066] 58a Rod-shaped conductive member

[0067] 58b Cylindrical conductive member

[0068] 58c Insulating member

[0069] 60 Matcher

[0070] 61 Matcher

[0071] 62 First RF power supply

[0072] 63 Second RF power supply

[0073] 64 Switch

[0074] 65 Variable DC power supply

[0075] 66 LPF

[0076] 67 Switch

[0077] 100 Mask film

[0078] 102 Insulating film

[0079] 104 Conductive film

[0080] 106 Polymer

[0081] 108 Oxide film

[0082] 200 Ion

[0083] 201 Sheath

[0084] 202 Electron

[0085] 203 Sheath. Detailed implementation manners

[0086] Hereinafter, based on the drawings, the implementation manners of the substrate processing method and the substrate processing apparatus will be described in detail. In addition, the disclosed substrate processing method and substrate processing apparatus are not limited by the following implementation manners.

[0087] With the miniaturization of semiconductor devices in recent years, the aspect ratio of holes formed in the substrate for semiconductor devices has a tendency to increase. When forming holes with a large aspect ratio in the substrate by plasma etching, the etching time becomes longer, and thus the charge amount of the substrate sometimes becomes larger. When the charge amount of the substrate becomes larger, there are cases where discharges (arcing) occur in parts of the substrate having a structure with a small gap. When arcing occurs, there are cases where the substrate is damaged or materials scattered due to the arcing become particles and adhere to other areas of the substrate to become defects.

[0088] Then, the present invention provides a technique capable of suppressing the occurrence of arcing during etching.

[0089] [Structure of Etching Apparatus 1]

[0090] Figure 1 It is a schematic cross-sectional view showing an example of an etching apparatus 1 in an embodiment of the present invention. The etching apparatus 1 includes an apparatus main body 10 and a control device 11 for controlling the apparatus main body 10. The apparatus main body 10 is a capacitively coupled parallel plate plasma etching apparatus and has a substantially cylindrical chamber 12 formed of aluminum or the like whose surface has been anodized. The chamber 12 is safely grounded. The etching apparatus 1 is an example of a substrate processing apparatus.

[0091] The chamber 12 has an electrostatic chuck 18 and an upper electrode 30. A substantially cylindrical support portion 14 formed of an insulating material is disposed at the bottom inside the chamber 12. The support portion 14 supports a base 16 formed of a metal such as aluminum. The base 16 is provided inside the chamber 12. In the present embodiment, the base 16 also functions as a lower electrode.

[0092] An electrostatic chuck 18 is provided on the upper surface of the base 16. The electrostatic chuck 18 is an example of a mounting table. The electrostatic chuck 18 has a structure in which an electrode 20 as a conductive film is disposed between a pair of insulating films or insulating sheets. The electrode 20 is electrically connected to a DC power supply 22. The electrostatic chuck 18 adsorbs and holds the substrate W on the upper surface thereof by static power such as Coulomb force generated by the DC voltage supplied from the DC power supply 22.

[0093] An edge ring ER is disposed around the electrostatic chuck 18 on the upper surface of the base 16. The edge ring ER is provided to improve the uniformity of etching. The edge ring ER is formed of a material appropriately selected according to the material of the film to be etched. In the present embodiment, the edge ring ER is formed of, for example, silicon or quartz.

[0094] A flow path 24 is formed inside the base 16. A refrigerant controlled to a predetermined temperature is circulated and supplied to the flow path 24 from a cooling unit provided outside via pipes 26a and 26b. The refrigerant is, for example, cooling water. By controlling the temperature of the refrigerant circulating in the flow path 24, the temperature of the substrate W placed on the electrostatic chuck 18 can be controlled.

[0095] A pipe 28 is provided between the electrostatic chuck 18 and the base 16. The pipe 28 is connected to a supply source of a heat transfer gas such as He gas, for example. The heat transfer gas supplied from the supply source of the heat transfer gas is supplied to the space between the electrostatic chuck 18 and the substrate W via the pipe 28.

[0096] The upper electrode 30 is disposed above the base 16 that functions as a lower electrode in a manner such that the base 16 and the upper electrode 30 are substantially parallel to each other. The upper electrode 30 faces the electrostatic chuck 18. A processing space S for generating plasma is defined between the upper electrode 30 and the base 16.

[0097] The upper electrode 30 is supported at the upper part of the chamber 12 via an insulating shielding member 32. The upper electrode 30 includes an electrode plate 34 and an electrode support 36. The lower surface of the electrode plate 34 faces the processing space S. A plurality of gas release holes 34a penetrating in the thickness direction of the electrode plate 34 are formed in the electrode plate 34. The gas release holes 34a are an example of gas supply ports for supplying a processing gas into the chamber 12.

[0098] The electrode support 36 is formed of a conductive material such as aluminum, for example, and detachably supports the electrode plate 34. The electrode support 36 may have a water-cooling structure. A diffusion chamber 36a is provided inside the electrode support 36. The diffusion chamber 36a communicates with the gas release holes 34a via a plurality of gas flow holes 36b. In addition, a gas introduction port 36c for introducing the processing gas into the diffusion chamber 36a is provided in the electrode support 36. The gas introduction port 36c is connected to a pipe 38.

[0099] The electrode support 36 is connected to a variable DC power supply 65 via a switch 67 and an LPF (Low Pass Filter) 66. The variable DC power supply 65 supplies a negative DC voltage to the electrode support 36. The magnitude of the absolute value of the negative DC voltage supplied from the variable DC power supply 65 to the electrode support 36 is controlled by the control device 11. The LPF 66 removes the high-frequency components of the negative DC voltage supplied to the electrode support 36. The switch 67 switches between the supply and cut-off of the negative DC voltage from the variable DC power supply 65 to the electrode support 36. The switch 67 is controlled by the control device 11. The variable DC power supply 65 is an example of a voltage supply unit.

[0100] The pipe 38 is connected to the gas supply sources 40a to 40e via the separator 43, the valves 42a to 42e, and the flow controllers 44a to 44e. The flow controllers 44a to 44e are, for example, MFC (Mass Flow Controller) or FCS (Flow Control System). The gas supply source 40a and the flow controller 44b are, for example, sources for supplying gases containing carbon and fluorine. In the present embodiment, the gas supply source 40a supplies, for example, C4F8 gas, and the gas supply source 40b supplies, for example, C4F6 gas. The gas supply source 40c is, for example, a source for supplying an oxygen-containing gas. In the present embodiment, the oxygen-containing gas is, for example, O2 gas. In addition, the oxygen-containing gas may be CO gas or the like. The gas supply source 40d is, for example, a source for supplying a noble gas. In the present embodiment, the noble gas is, for example, Ar gas. The gas supply source 40e is a source for supplying a nitrogen-containing gas. In the present embodiment, the nitrogen-containing gas is, for example, N2 gas.

[0101] The gases supplied from the gas supply sources 40a to 40e are supplied into the diffusion chamber 36a via the flow controllers 44a to 44e, the valves 42a to 42e, the separator 43, and the pipe 38. The gases supplied into the diffusion chamber 36a diffuse in the diffusion chamber 36a and are supplied into the processing space S in a spray form via the gas flow holes 36b and the gas release holes 34a.

[0102] In addition, a conductor 12a is provided above the chamber 12 so as to extend upward from the side wall of the chamber 12 to a position above the height of the upper electrode 30. The conductor 12a is grounded via the chamber 12.

[0103] In addition, a deposit shield 46 is detachably provided along the inner wall of the chamber 12 of the apparatus main body 10. The deposit shield 46 is also provided on the outer periphery of the support portion 14. The deposit shield 46 prevents by-products of etching (so-called deposits) from adhering to the chamber 12. The deposit shield 46 is formed of, for example, aluminum, and its surface is covered with a ceramic such as Y2O3.

[0104] On the bottom side of the chamber 12, a baffle 48 is provided between the support portion 14 and the inner wall of the chamber 12. The baffle 48 is formed of, for example, aluminum or the like, and its surface is covered with a ceramic such as Y2O3. Inside the chamber 12, an exhaust port 12e is provided below the baffle 48. The exhaust port 12e is connected to an exhaust device 50 via an exhaust pipe 52. The exhaust device 50 has a vacuum pump such as a turbo molecular pump and can reduce the pressure inside the chamber 12 to a predetermined vacuum level. The exhaust device 50 maintains the pressure inside the chamber 12 at a vacuum level of, for example, 15 to 40 mTorr. In addition, an opening 12g for feeding in and out the substrate W is formed in the side wall of the chamber 12, and the opening 12g can be opened and closed by a gate valve 54.

[0105] A conductive member 56 grounded in a DC manner is provided on the inner wall of the chamber 12. The conductive member 56 is provided at a position substantially the same height as the substrate W in the height direction. By using the conductive member 56, abnormal discharge can be prevented. In addition, the conductive member 56 only needs to be provided within the region where plasma is generated, and its installation position is not limited to Figure 1 the position shown. For example, the conductive member 56 can also be provided near the susceptor 16 such as around the susceptor 16. In addition, the conductive member 56 can also be provided in a ring shape near the upper electrode 30 outside the upper electrode 30.

[0106] The susceptor 16 constituting the lower electrode is connected to a power supply rod 58 for supplying an RF (Radio Frequency) signal to the susceptor 16. The power supply rod 58 has a coaxial two-layer tube structure and includes a rod-shaped conductive member 58a and a tubular conductive member 58b. The rod-shaped conductive member 58a extends from outside the chamber 12 through the bottom of the chamber 12 in a substantially vertical direction into the chamber 12. The upper end of the rod-shaped conductive member 58a is connected to the susceptor 16. The tubular conductive member 58b is coaxially provided around the rod-shaped conductive member 58a so as to surround the rod-shaped conductive member 58a. The tubular conductive member 58b is supported by the bottom of the chamber 12. A substantially annular insulating member 58c is disposed between the rod-shaped conductive member 58a and the tubular conductive member 58b. By means of the insulating member 58c, the rod-shaped conductive member 58a and the tubular conductive member 58b can be electrically insulated.

[0107] The rod-shaped conductive member 58a and the tubular conductive member 58b are connected to a matcher 60 and a matcher 61 via a switch 64. The matcher 60 is connected to a first RF power supply 62, and the matcher 61 is connected to a second RF power supply 63. The first RF power supply 62 and the second RF power supply 63 are an example of an RF signal supply unit.

[0108] The first RF power supply 62 is a power supply that generates a first RF signal for plasma generation, generating an RF signal with a frequency of 27 to 100 MHz, and in one example, a frequency of 40 MHz. In addition, the power of the first RF signal is 100 to 2000 W in one example.

[0109] The second RF power supply 63 supplies a high-frequency bias voltage to the susceptor 16 and generates a second RF signal for introducing ions into the substrate W. The frequency of the second RF signal is in the range of 400 kHz to 13.56 MHz, and in one example, it is 3 MHz. In addition, the power of the second RF signal is 100 to 5000 W in one example.

[0110] The switch 64 switches the supply and cut-off supply of the first RF signal and the second RF signal to the rod-shaped conductive member 58a and the cylindrical conductive member 58b. Thereby, the first RF signal and the second RF signal are supplied to the susceptor 16 in a pulsed manner. The switch 64 is controlled by the control device 11. Additionally, hereinafter, when the first RF signal and the second RF signal are collectively referred to without distinction, they are described as RF signals.

[0111] The control device 11 includes a memory, a processor, and an input / output interface. Data and programs such as recipes are stored in the memory. The memory is, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), or an SSD (Solid State Drive). The processor controls each part of the device main body 10 via the input / output interface based on the data such as recipes stored in the memory by executing the program read from the memory. The processor is a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), etc.

[0112] When performing plasma etching using the etching device 1, the gate valve 54 is opened, and the substrate W is placed on the electrostatic chuck 18 by a transfer robot (not shown). Then, the gas in the chamber 12 is exhausted by the exhaust device 50, and gases from the gas supply sources 40a to 40d are supplied to the chamber 12 at predetermined flow rates, and the pressure in the chamber 12 is adjusted to a predetermined pressure.

[0113] Then, a first RF signal from the first RF power supply 62 and a second RF signal from the second RF power supply 63 are supplied to the susceptor 16, and a negative DC voltage from the variable DC power supply 65 is supplied to the upper electrode 30. As a result, an RF electric field is formed between the upper electrode 30 and the susceptor 16, and plasma is generated from the gas supplied to the processing space S. Then, the substrate W is etched with ions, radicals, etc. contained in the plasma generated in the processing space S.

[0114] [Structure of Substrate W]

[0115] Next, the structure of the substrate W etched by the etching apparatus 1 described in Figure 1 will be described. The substrate W in the present embodiment is used, for example, for the structure of a NAND type flash memory for forming a multilayer film having a three-dimensional structure. Figure 2 is a diagram showing an example of a cross section of the substrate W before etching.

[0116] A plurality of conductive films 104a to 104c having different lengths in a direction intersecting the thickness direction of the insulating film 102 are formed in the insulating film 102. In the present embodiment, the insulating film 102 is, for example, an oxide film (silicon oxide film), and each of the conductive films 104a to 104c is, for example, silicon or tungsten. A mask film 100 is provided on the insulating film 102, and patterns Pa to Pc corresponding to predetermined holes are formed in the mask film 100. In Figure 2 the example, in the thickness direction of the insulating film 102, the conductive film 104a is disposed below the pattern Pa, the conductive film 104b is disposed below the pattern Pb, and the conductive film 104c is disposed below the pattern Pc. The conductive films 104a to 104c each function as an etching stopper layer when etching the insulating film 102. In addition, hereinafter, when collectively referring to the respective conductive films 104a to 104c without distinction, they are described as the conductive film 104.

[0117] By etching the insulating film 102 using the mask film 100 as a mask, for example, as shown in Figure 3 , holes Ha to Hc are formed in the insulating film 102. Figure 3 is a diagram showing an example of a cross section of the substrate W after etching. By burying metal in the holes Ha to Hc, wirings are formed that are individually connected to each of the conductive films 104a to 104c.

[0118] [Behavior of Electrons in Plasma]

[0119] Figure 4It is a schematic diagram showing an example of the activity of electrons in chamber 12 during plasma etching. By supplying a first RF signal from a first RF power source 62 and a second RF signal from a second RF power source 63 to susceptor 16, a plasma is generated from the gas supplied into chamber 12. The plasma contains ions 200, radicals, etc. By generating a plasma in chamber 12, a sheath layer 203 is generated near susceptor 16. Through sheath layer 203, the ions 200 contained in the plasma are introduced to substrate W, and substrate W is etched.

[0120] In addition, when ions 200 are introduced into substrate W in excess, sometimes substrate W is damaged. Therefore, a negative DC voltage is supplied to upper electrode 30. Thereby, a sheath layer 201 is generated near upper electrode 30, and a part of the ions 200 in the plasma is introduced into upper electrode 30. Thereby, the ions 200 hitting substrate W can be reduced, and the damage to substrate W can be alleviated. In addition, electrons 202 are released from upper electrode 30 due to the ions 200 introduced into upper electrode 30.

[0121] Here, when plasma etching is performed, substrate W is charged due to the ions 200 introduced into substrate W. Electrons 202 are released from upper electrode 30 due to the ions 200 introduced into upper electrode 30, and the released electrons 202 are blocked from reaching substrate W by sheath layer 203 as shown, for example, as Figure 4 shown. Therefore, the charging of substrate W cannot be neutralized by electrons 202. Thus, when the plasma etching time becomes long, sometimes arc discharge occurs on substrate W. In the experiment, when the plasma etching continued for more than 30 seconds, arc discharge occurred on substrate W.

[0122] Here, for example, as Figure 5 shown, when the supply of the RF signal to susceptor 16 is cut off, the sheath layer 203 near susceptor 16 disappears. Therefore, the electrons 202 released from upper electrode 30 due to the ions 200 introduced into upper electrode 30 become easy to reach substrate W. Thereby, the charge amount of substrate W is reduced. Figure 5 It is a schematic diagram showing an example of the activity of electrons 202 in chamber 12 when the supply of the RF signal is stopped.

[0123] At this time, when the absolute value of the negative DC voltage supplied to upper electrode 30 is increased, the sheath layer 201 near upper electrode 30 becomes thicker, and the amount of ions 200 introduced into upper electrode 30 increases. Thereby, the amount of electrons 202 released from upper electrode 30 due to the ions 200 introduced into upper electrode 30 also increases. Thereby, the amount of electrons 202 reaching substrate W becomes larger, and the charge amount of substrate W rapidly decreases.

[0124] Then, consider, for example, as Figure 6The control shown controls the RF signal and the negative DC voltage. Figure 6 FIG. is an example showing the control of the RF signal and the DC voltage.

[0125] The RF signal is supplied (ON) and cut off (OFF) at each predetermined cycle as shown in, for example, Figure 6 (a). Thereby, in the first period ΔT1 during which the RF signal is supplied, etching progresses, and in the second period ΔT2 during which the supply of the RF signal is cut off, the charging of the substrate W is neutralized.

[0126] In the present embodiment, it is preferable that the length of one cycle ΔT0 including the supply and cut-off of the RF signal is, for example, 50 milliseconds or less. That is, it is preferable that the frequency of the supply and cut-off of the RF signal is, for example, 20 Hz or more.

[0127] Further, in the present embodiment, it is preferable that the duty ratio of the RF signal is 90% or more. The duty ratio of the RF signal refers to the ratio of the first period ΔT1 during which the RF signal is supplied to one cycle ΔT0 including the supply and cut-off of the RF signal.

[0128] Further, for example, as shown in Figure 6 (b), in the second period ΔT2 during which the supply of the RF signal is cut off, a negative DC voltage V2 (|V1| < |V2|) whose absolute value is larger than the absolute value of the negative DC voltage V1 supplied in the first period ΔT1 during which the RF signal is supplied is supplied. Specifically, the negative DC voltage V2 in the second period ΔT2 is, for example, -1000 V, and the negative DC voltage V1 in the first period ΔT1 is, for example, -200 V. Thereby, a sufficient amount of electrons can be supplied to the substrate W in the second period ΔT2, and the charged amount of the substrate W can be rapidly reduced.

[0129] Here, as long as the control of the RF signal and the negative DC voltage as shown in Figure 6 is performed, the arc discharge of the substrate W can be reduced. However, in the control of the RF signal shown in Figure 6 , in the second period ΔT2 during which the supply of the RF signal is cut off, no polymer is formed on the conductive film 104. Therefore, the selectivity of the conductive film 104 with respect to the insulating film 102 is reduced, and the conductive film 104 becomes easily etched. Therefore, in the control of the RF signal shown in Figure 6 , the function of the etching stopper layer of the conductive film 104 is reduced, and sometimes holes are formed through the conductive film 104. As a result, it is difficult to form holes in the substrate W according to the design.

[0130] Then, in the present embodiment, for example, as shown in Figure 7 , the first etching process and the second etching process are alternately and repeatedly executed. In the first etching process, etching is performed in a state where the RF signal and the negative DC voltage are continuously supplied. In the second etching process, byFigure 6 Etching is performed by controlling the illustrated RF signal and negative DC voltage. Thereby, arcing of the substrate W can be suppressed, and the etching amount of the conductive film 104 can be reduced.

[0131] [V of the RF signal pp

[0132] In addition, the peak-to-peak value (V pp ) of the voltage of the RF signal varies according to the state inside the chamber 12. For example, when the execution time of plasma etching becomes longer, due to the influence of deposits adhering to the inner wall of the chamber 12 and the consumption of components inside the chamber 12, etc., the impedance between the chamber 12 and the plasma changes. Thereby, sometimes the control amounts of the matchers 60 and 61 change, and the magnitude of V of the RF signal pp changes. When the magnitude of V of the RF signal pp changes, the amount of polymer formed on the conductive film 104 changes.

[0133] For example, when V of the RF signal pp becomes smaller, the amount of polymer formed on the conductive film 104 becomes less. When the amount of polymer formed on the conductive film 104 becomes less, the selectivity of the conductive film 104 with respect to the insulating film 102 decreases. Thereby, the conductive film 104 becomes more easily etched.

[0134] To avoid this situation, in the present embodiment, in the first etching step and the second etching step, V of the RF signal pp is controlled to a magnitude within a predetermined range. Thereby, a sufficient amount of polymer can be formed on the conductive film 104, the selectivity of the conductive film 104 with respect to the insulating film 102 can be increased, and the etching amount of the conductive film 104 can be reduced.

[0135] Figure 8 is a diagram showing an example of the change of the magnitude of V pp with respect to the etching time. In the case where the adjustment of V of the RF signal pp is not performed, as shown in the comparative example of Figure 8 , as the etching time elapses, V of the RF signal pp becomes smaller.

[0136] In contrast, in the present embodiment, V of the RF signal pp is controlled to a magnitude within a predetermined range. Thereby, for example, as shown in Figure 8 , even when the etching time exceeds 350 hr, the variation in the magnitude of V of the RF signal pp is suppressed within approximately 8 V.

[0137] Figure 9 ​It is a diagram showing an example of the etching amount of the conductive film 104 with respect to the etching time. Without adjusting the V of the RF signal, as shown in the comparative example of pp , as the etching time elapses, the etching amount of the conductive film 104 increases. The state where the etching amount of the conductive film 104 reaches 100% means the state where the hole has penetrated the conductive film 104. Figure 9

[0138] In contrast, in the present embodiment, by controlling the V of the RF signal pp to a size within a predetermined range, for example, as shown in Figure 9 , an increase in the etching amount of the conductive film 104 is suppressed. In the example of Figure 9 , even when the etching time exceeds 300 hr, the etching amount of the conductive film 104 is suppressed to less than 30%. Thus, in the present embodiment, by controlling the V of the RF signal pp to a size within a predetermined range, a sufficient amount of polymer can be formed on the conductive film 104. Therefore, the selectivity of the conductive film 104 with respect to the insulating film 102 can be increased, and the etching amount of the conductive film 104 can be reduced.

[0139] [Removal of Polymer]

[0140] Figure 10 It is a schematic diagram showing an example of the state of the hole H immediately after etching. Immediately after etching, for example, as shown in Figure 10 , a polymer 106 is formed at the bottom of the hole H. An oxide film 108 is formed between the polymer 106 and the conductive film 104 by reaction with an oxygen-containing gas.

[0141] Here, when the substrate W in the state shown in Figure 10 is exposed to the atmosphere, moisture contained in the atmosphere reacts with the polymer 106, and hydrofluoric acid is generated at the bottom of the hole H. As a result, the bottom of the hole H is further eroded, for example, as shown in Figure 11 . Figure 11 It is a diagram showing an example of the state where the conductive film 104 is eroded. As a result, the conductive film 104 is etched excessively compared to the design value.

[0142] Therefore, in the present embodiment, the substrate W in the state of Figure 10 after the etching of the substrate W is exposed to a plasma of a nitrogen-containing gas. As a result, for example, as shown in Figure 12 , the polymer 106 remaining at the bottom of the hole H is removed. Figure 12 It is a diagram showing an example of the state of the hole H formed by the present embodiment. After that, the oxide film 108 is removed by ashing, and the processing of the next step is performed. Thus, a hole H having a shape close to the design value can be formed on the substrate W. ​

[0143] [Etching Method]

[0144] Figure 13 is a flowchart showing an example of an etching method. Figure 13 The etching method exemplified in is implemented, for example, by a processor of the control device 11 reading and executing a program stored in a memory of the control device 11 and controlling each part of the device main body 10 via an input / output interface of the control device 11. Figure 13 The etching method exemplified in is an example of a substrate processing method.

[0145] First, a substrate W is introduced into the chamber 12 (S10). In step S10, the gate valve 54 is opened, and the substrate W is introduced into the chamber 12 by a transfer robot (not shown) and placed on the electrostatic chuck 18. Then, the gate valve 54 is closed. Step S10 is an example of the a) process.

[0146] Next, a processing gas is supplied into the chamber 12 (S11). In step S11, the gas in the chamber 12 is exhausted by the exhaust device 50. Then, C4F8 gas from the gas supply source 40a, C4F6 gas from the gas supply source 40b, O2 gas from the gas supply source 40c, and Ar gas from the gas supply source 40d are supplied into the chamber 12 at predetermined flow rates, respectively. Then, the pressure in the chamber 12 is adjusted to a predetermined pressure. Hereinafter, the gas containing C4F8 gas, C4F6 gas, O2 gas, and Ar gas is referred to as the first processing gas. Step S11 is an example of the b) process.

[0147] Next, a first etching process is performed (S12). In the first etching process, a negative DC voltage is continuously supplied from the upper electrode 30, and an RF signal is continuously supplied into the chamber 12. Thereby, plasma is generated from the first processing gas supplied into the chamber 12, and the substrate W placed on the electrostatic chuck 18 is etched with the plasma of the first processing gas. Step S12 is an example of the c) process.

[0148] The main processing conditions in the first etching process are as follows.

[0149] Pressure: 10 - 30 mTorr

[0150] Power of the first RF signal: 1000 - 2000 W

[0151] Power of the second RF signal: 3000 - 6000 W

[0152] Negative DC voltage: -300 - -100 V

[0153] C4F8 gas: 20 - 40 sccm

[0154] C4F6 gas: 5 - 20 sccm

[0155] O2 gas: 10 - 30 sccm

[0156] Ar gas: 300 - 600 sccm

[0157] Next, it is determined whether a predetermined time t1 has elapsed since the start of the first etching process (S13). In the present embodiment, the time t1 is, for example, 30 seconds. If the time t1 has not elapsed (S13: No), it is determined whether a predetermined time t0 has elapsed since the start of etching (S14). If the time t0 has not elapsed (S14: No), the process shown in step S12 is executed again. On the other hand, if the time t0 has elapsed (S14: Yes), the process of step S18 described later is executed. The time t0 is the total etching time and is the time required to form the deepest hole.

[0158] On the other hand, if the time t1 has elapsed (S13: Yes), the second etching process is executed (S15). In the second etching process, the substrate W placed on the electrostatic chuck 18 is etched by continuously supplying a negative DC voltage to the upper electrode 30 while repeatedly supplying and cutting off the RF signal at a predetermined cycle. Further, in the second etching process, during the first period ΔT1 when the RF signal is supplied, a negative DC voltage V1 with a small absolute value is supplied to the upper electrode 30, and during the second period ΔT2 when the supply of the RF signal is cut off, a negative DC voltage V2 with a large absolute value is supplied to the upper electrode 30. In the first period ΔT1, for example, a negative DC voltage V1 of -200 V is supplied to the upper electrode 30, and in the second period ΔT2, for example, a negative DC voltage V2 of -1000 V is supplied to the upper electrode 30. In the second etching process, the main processing conditions are the same as those in the first etching process except for the intermittent supply of the RF signal and the switching of the absolute value of the negative DC voltage. Step S15 is an example of the d) process.

[0159] Next, it is determined whether a predetermined time t2 has elapsed since the start of the second etching process (S16). In the present embodiment, the time t2 is, for example, 60 seconds. If the time t2 has not elapsed (S16: No), it is determined whether a predetermined time t0 has elapsed since the start of etching (S17). If the time t0 has not elapsed (S17: No), the process shown in step S14 is executed again.

[0160] On the other hand, when the time t0 has elapsed (S17: Yes), a second processing gas is supplied into the chamber 12 (S18). In step S18, the gas in the chamber 12 is exhausted by the exhaust device 50. Then, an Ar gas from the gas supply source 40d and an N2 gas from the gas supply source 40e are supplied into the chamber 12 at predetermined flow rates, and the pressure in the chamber 12 is adjusted to a predetermined pressure. Hereinafter, the gas containing the Ar gas and the N2 gas is referred to as the second processing gas. Step S18 is an example of the e) process.

[0161] Next, a removal process is performed (S19). In the removal process, an RF signal is continuously supplied into the chamber 12. Thereby, a plasma is generated from the second processing gas supplied into the chamber 12, and the polymer in the holes is removed by the plasma of the second processing gas. Step S19 is an example of the f) process.

[0162] The main processing conditions of the removal process are as follows.

[0163] Pressure: 10 - 30 mTorr

[0164] Power of the first RF signal: 200 - 2000 W

[0165] Power of the second RF signal: 100 - 1000 W

[0166] N2 gas: 50 - 200 sccm

[0167] Ar gas: 100 - 500 sccm

[0168] Processing time: 5 - 20 seconds

[0169] Then, the gas in the chamber 12 is exhausted by the exhaust device 50, the gate valve 54 is opened, and the substrate W is taken out of the chamber 12 by a transfer robot (not shown) (S18). Then, the etching method shown in this flowchart ends.

[0170] The above describes one embodiment. As described above, the substrate processing method in this embodiment is a substrate processing method in chamber 12, where chamber 12 includes: an electrostatic chuck 18 for placing substrate W; an upper electrode 30 opposite to the electrostatic chuck 18; and a gas release hole 34a for supplying a processing gas into chamber 12. This substrate processing method includes the following steps a) to d). a) is the step of providing the substrate to the electrostatic chuck 18. b) is the step of supplying a first processing gas into chamber 12. c) is the step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode 30 while continuously supplying an RF signal. d) is the step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode 30 while supplying a pulsed RF signal. Steps c) and d) are alternately repeated. In addition, the duration of each execution of c) is 30 seconds or less. Thereby, the occurrence of arc discharge during the etching process can be suppressed.

[0171] In addition, in the above embodiment, the duration of each execution of step d) is 60 seconds or less. Thereby, excessive etching can be suppressed.

[0172] In addition, in step d) of the above embodiment, the ratio of the duration of the supply of the RF signal to one pulse period of the pulsed RF signal is 90% or more. Thereby, in step d), the occurrence of arc discharge can also be suppressed and etching can proceed.

[0173] In addition, in step d) of the above embodiment, the duration of one pulse period of the pulsed RF signal is 50 milliseconds or less. Thereby, in step d), the occurrence of arc discharge can also be suppressed.

[0174] In addition, in step d) of the above embodiment, the absolute value of the negative DC voltage V2 supplied to the upper electrode 30 during the second period ΔT2 when the supply of the RF signal is cut off is greater than the absolute value of the negative DC voltage V1 supplied to the upper electrode 30 during the first period ΔT1 when the RF signal is supplied. Thereby, the substrate W can be discharged in a short time and efficiently.

[0175] In addition, in the above embodiment, substrate W has: a conductive film 104; an insulating film 102 provided on the conductive film 104; and a pattern PR film provided on the insulating film 102 and having a predetermined pattern P formed thereon. In addition, the insulating film 102 is, for example, an oxide film (silicon oxide film), and the conductive film 104 is a film of silicon or tungsten. In the etching of substrate W having such a structure, the occurrence of arc discharge can be suppressed.

[0176] In addition, in the above-described embodiment, the first processing gas includes a carbon- and fluorine-containing gas, an oxygen-containing gas, and a noble gas. The carbon- and fluorine-containing gas is C4F8 gas or C4F6 gas, the oxygen-containing gas is O2 gas or CO gas, and the noble gas is Ar gas. Thereby, plasma can be generated from the first processing gas, and the substrate W is etched with the generated plasma.

[0177] In addition, the substrate processing method in the above-described embodiment further includes steps e) and f). Step e) is performed after repeatedly performing c) and d), and is a step of supplying a second processing gas containing a nitrogen-containing gas and a noble gas into the chamber 12. Step f) generates plasma from the second processing gas by supplying an RF signal into the chamber 12, and removes the polymer remaining in the hole H formed in the substrate W by steps c) and d) with the generated plasma. The nitrogen-containing gas is N2 gas, and the noble gas is Ar gas. Thereby, a hole H having a shape close to the design value can be formed in the substrate W.

[0178] In addition, in steps c) and d) of the above-described embodiment, the magnitude of the voltage V of the pulsed RF signal is controlled within a predetermined range. Thereby, a sufficient amount of polymer can be formed on the conductive film 104, the selectivity of the conductive film 104 with respect to the insulating film 102 can be increased, and the etching amount of the conductive film 104 can be reduced. pp

[0179] In addition, the etching apparatus 1 in the above-described embodiment includes: a chamber 12; an upper electrode 30 provided in the chamber 12; an electrostatic chuck 18 for placing the substrate W opposite to the upper electrode 30; a first RF power supply 62 and a second RF power supply 63 for supplying RF signals; a variable DC power supply 65 for supplying a negative DC voltage to the upper electrode 30; and a control device 11. The control device 11 performs the following steps a) to d). Step a) is a step of providing the substrate W to the electrostatic chuck 18. Step b) is a step of supplying the first processing gas into the chamber 12. Step c) is a step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode 30 while continuously supplying an RF signal into the chamber 12. Step d) is a step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode 30 while supplying a pulsed RF signal. Steps c) and d) are alternately repeated. The period of each time of step c) is 30 seconds or less. Thereby, the occurrence of arc discharge during the etching process can be suppressed.

[0180] [Other]

[0181] In addition, the technology disclosed in the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of its gist.

[0182] ​For example, in each of the above-described embodiments, the etching apparatus 1 using a capacitively coupled plasma (CCP) as a plasma source has been described as an example, but the plasma source is not limited thereto. As plasma sources other than capacitively coupled plasmas, for example, inductively coupled plasmas (ICP), microwave-excited surface wave plasmas (SWP), electron cyclotron resonance plasmas (ECP), and helicon wave-excited plasmas (HWP) can be cited.

[0183] In addition, it should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. In fact, the above-described embodiments can be implemented in various ways. In addition, the above-described embodiments can be omitted, replaced, and changed in various ways without departing from the appended claims and their spirit.

Claims

1. A method for substrate processing in a chamber, characterized in that: The chamber includes: a stage for placing a substrate; an upper electrode opposite to the stage; and a gas supply port for supplying a processing gas into the chamber. This substrate processing method includes: a) A step of providing a substrate to the stage; b) A step of supplying a first processing gas into the chamber; c) A step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode while continuously supplying a continuous RF signal; and d) A step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode while supplying a pulsed RF signal. Steps c) and d) are alternately and repeatedly executed. The duration of each execution of step c) is 30 seconds or less.

2. The substrate processing method according to claim 1, characterized in that: The duration of each execution of step d) is 60 seconds or less.

3. The substrate processing method according to claim 1 or 2, characterized in that: In step d), The duty ratio of the pulsed RF signal is 90% or more.

4. The substrate processing method according to claim 1 or 2, characterized in that: In step d), The duration of one pulse period of the pulsed RF signal is 50 milliseconds or less.

5. The substrate processing method according to claim 1 or 2, characterized in that: In step d), The pulse frequency of the pulsed RF signal is 20 Hz or more.

6. The substrate processing method according to claim 1 or 2, characterized in that: In step d), The absolute value of the negative DC voltage supplied to the upper electrode during the period when the supply of the pulsed RF signal is cut off is greater than the absolute value of the negative DC voltage supplied to the upper electrode during the period when the pulsed RF signal is supplied.

7. The substrate processing method according to claim 1 or 2, characterized in that: The substrate has: a conductive film; an insulating film provided on the conductive film; and a mask film provided on the insulating film and having a predetermined pattern formed thereon.

8. The substrate processing method according to claim 7, characterized in that: The insulating film is an oxide film. The conductive film is a film of silicon or tungsten.

9. The substrate processing method according to claim 1 or 2, characterized in that: The first processing gas contains a gas containing carbon and fluorine, an oxygen-containing gas, and a noble gas.

10. The substrate processing method according to claim 9, characterized in that: The gas containing carbon and fluorine is C4F8 gas or C4F6 gas.

11. The substrate processing method according to claim 9, characterized in that: The oxygen-containing gas is O2 gas or CO gas.

12. The substrate processing method according to claim 9, characterized in that: The noble gas is Ar gas.

13. The substrate processing method according to claim 9, wherein It further includes: e) A step of supplying a second processing gas containing a nitrogen-containing gas and a noble gas into the chamber, which is executed after repeatedly performing steps c) and d); and f) A step of generating plasma from the second processing gas by supplying the continuous RF signal into the chamber to remove the polymer remaining in the holes formed in the substrate in the steps c) and d).

14. The substrate processing method according to claim 13, wherein: The nitrogen-containing gas is N2 gas, The noble gas is Ar gas.

15. The substrate processing method according to claim 1 or 2, wherein: In the steps c) and d), The peak-to-peak voltage of the continuous RF signal and the pulsed RF signal is controlled within 8V.

16. A substrate processing apparatus, characterized in that, Comprising: A chamber; An upper electrode disposed in the chamber; A stage for placing the substrate opposite to the upper electrode; An RF signal supply unit for supplying an RF signal; A voltage supply unit for supplying a negative DC voltage to the upper electrode; and A control device, The control device performs the following steps: a) A step of providing the substrate to the stage; b) A step of supplying a first processing gas into the chamber; c) A step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode and continuously supplying a continuous RF signal into the chamber; And d) A step of generating plasma from the first processing gas by continuously supplying a negative DC voltage to the upper electrode and supplying a pulsed RF signal, The steps c) and d) are alternately repeated, The period of each time of the step c) is 30 seconds or less.

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