Plasma processing device and plasma processing method

Abstract

The present invention provides a plasma processing device and a plasma processing method capable of suppressing ion impact on a substrate while efficiently generating plasma for plasma processing. The plasma processing device performs plasma processing on a substrate, and comprises: a processing container; a substrate mounting table disposed in the processing container and capable of mounting the substrate; a grounded lower electrode included in the substrate mounting table; an upper electrode disposed opposite to the lower electrode; a gas supply unit for supplying a processing gas between the upper electrode and the substrate mounting table; a high-frequency power supply for applying high-frequency electric power to the upper electrode to generate plasma of the processing gas; and a voltage waveform shaping unit disposed between the high-frequency power supply and the upper electrode, which shapes the voltage waveform of the high-frequency power supply to suppress the positive voltage in the high-frequency voltage applied to the upper electrode.

Description

Technical Field

[0001] The present invention relates to a plasma processing device and a plasma processing method. Background Art

[0002] Plasma processing is often used as a treatment for substrates such as semiconductor wafers. Patent document 1 discloses a plasma processing device, which includes: a vacuum container; a substrate electrode in which a substrate is placed and connected to a high-frequency power supply; and a ground electrode provided in the vacuum container, and plasma is generated between the substrate electrode and the ground electrode. In addition, Patent document 1 describes a structure in which a potential adjustment mechanism including a diode is connected to the substrate electrode.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-306891 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The present invention provides a plasma processing apparatus and a plasma processing method capable of efficiently generating plasma for plasma processing while suppressing ion impact on a substrate.

[0008] Technical solutions to the problem

[0009] A plasma processing device in one embodiment of the present invention is a plasma processing device for performing plasma processing on a substrate, and includes: a processing container; a substrate mounting table arranged in the processing container and capable of mounting a substrate; a grounded lower electrode contained in the substrate mounting table; an upper electrode arranged opposite to the lower electrode; a gas supply unit for supplying a processing gas between the upper electrode and the substrate mounting table; a high-frequency power supply for applying high-frequency electric power to the upper electrode to generate plasma of the processing gas; and a voltage waveform shaping unit, which is arranged between the high-frequency power supply and the upper electrode and shapes the voltage waveform of the high-frequency power supply to suppress the positive voltage in the high-frequency voltage applied to the upper electrode.

[0010] Effects of the Invention

[0011] According to the present invention, a plasma processing apparatus and a plasma processing method are provided which can efficiently generate plasma to perform plasma processing while suppressing ion impact on a substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 FIG. 1 is a cross-sectional view schematically showing the plasma processing apparatus according to the first embodiment.

[0013] Figure 2 This is a diagram showing the plasma potential at the moment when the upper electrode is 0 V in a general capacitively coupled plasma processing apparatus.

[0014] Figure 3 This is a diagram showing the instantaneous plasma potential when the upper electrode is 100 V in a general capacitively coupled plasma processing apparatus.

[0015] Figure 4 This is a diagram showing a voltage waveform applied to an upper electrode in a general capacitively coupled plasma processing apparatus.

[0016] Figure 5 This is a diagram showing an estimated sheath voltage in a general capacitively coupled plasma processing apparatus.

[0017] Figure 6 Yes means Figure 1 Graphs showing voltage waveforms of upper electrodes of a plasma processing apparatus and a general capacitively coupled plasma processing apparatus.

[0018] Figure 7 Yes Figure 1 A diagram showing the estimated sheath voltage for accelerating ions of a plasma processing apparatus and a general capacitively coupled plasma processing apparatus.

[0019] Figure 8 Yes means Figure 1 Graph showing energy distribution of ions when the output power of the high frequency power source is 100 W in a plasma processing apparatus and a general capacitively coupled plasma processing apparatus.

[0020] Fig. 9 Yes means Figure 1 Graph showing energy distribution of ions when the output power of the high frequency power source is 500 W in a plasma processing apparatus and a general capacitively coupled plasma processing apparatus.

[0021] Fig.10 Yes means Figure 1 A diagram showing the flow of plasma and gas generated when plasma is ignited in a plasma processing apparatus.

[0022] Fig.11 This is a diagram showing plasma generated when plasma is ignited in a general capacitively coupled plasma processing apparatus and the flow of gas.

[0023] Fig.12 This is a diagram showing the flow of plasma and gas generated when plasma is excited in a plasma processing apparatus in which a high-frequency power supply is connected to a lower electrode and a voltage waveform shaping unit is provided on the lower electrode side.

[0024] Fig.13 It is a cross-sectional view schematically showing a plasma processing apparatus according to a second embodiment.

[0025] Fig.14 The diagram shows a voltage waveform of an upper electrode of a general capacitively coupled plasma processing apparatus and a voltage waveform of the upper electrode when a switching element of a voltage waveform shaping unit is appropriately opened and closed.

[0026] Fig.15 It is a cross-sectional view schematically showing a plasma processing apparatus according to a third embodiment.

[0027] Fig.16 Yes means Fig.15 FIG. 1 is a diagram of a voltage waveform of an upper electrode in a plasma processing apparatus.

[0028] Fig.17 Yes means Fig.15 Diagram of the sheath voltage in a plasma processing device.

[0029] Fig.18 It is a diagram showing another example of a voltage waveform shaping unit of the plasma processing apparatus according to the third embodiment.

[0030] Fig.19 FIG. 1 is a cross-sectional view schematically showing a plasma processing apparatus according to a fourth embodiment.

[0031] Fig. 20 It is a diagram showing another example of a voltage waveform shaping unit of the plasma processing apparatus according to the fourth embodiment.

[0032] Fig.21 It is a cross-sectional view schematically showing a plasma processing apparatus according to a fifth embodiment.

[0033] Fig. 22 It is a diagram showing another example of a voltage waveform shaping unit of the plasma processing apparatus according to the fifth embodiment.

[0034] Fig.23 It is a cross-sectional view showing a plasma processing apparatus according to a sixth embodiment.

[0035] Fig.24 This indicates that the voltage waveform shaping unit is used. Fig.23 A graph showing the relationship between film formation time and film thickness when a Ti film is formed on Si in a plasma processing apparatus using a voltage waveform shaping unit and a plasma processing apparatus not using a voltage waveform shaping unit.

[0036] Fig.25 This indicates that the voltage waveform shaping unit is used. Fig.23A graph showing the relationship between film formation time and film thickness when a Ti film is formed on SiN in a plasma processing apparatus using a voltage waveform shaping unit and a plasma processing apparatus not using a voltage waveform shaping unit.

[0037] Fig.26 This shows the use of the voltage waveform shaping unit Fig.23 A graph showing the average value of the selectivity ratio of the film thickness of the Ti film on Si and on SiN (Si / SiN selectivity ratio) for a plasma processing apparatus using a voltage waveform shaping unit and a plasma processing apparatus not using a voltage waveform shaping unit.

[0038] Fig. 27 It is a cross-sectional view showing a plasma processing apparatus according to a seventh embodiment.

[0039] Fig.28 This is a diagram showing an upper voltage waveform when continuous wave high frequency electric power is applied.

[0040] Fig.29 The figures show the waveforms of the upper electrode when pulsed high-frequency electric power is applied, wherein (a) is the case where the duty cycle is 30%, (b) is the case where the duty cycle is 50%, and (c) is the case where the duty cycle is 80%.

[0041] Fig.30 It is a cross-sectional view showing a plasma processing apparatus according to an eighth embodiment.

[0042] Fig.31 This indicates that the voltage waveform shaping unit is used. Fig.30 Graph showing a voltage waveform of an upper electrode in a plasma processing apparatus using a voltage waveform shaping unit and a plasma processing apparatus not using a voltage waveform shaping unit.

[0043] Fig.32 This indicates that the voltage waveform shaping unit is used. Fig.30 Graph of the etching rate at each wafer position (X direction and Y direction) in a plasma processing apparatus using a voltage waveform shaping unit and a plasma processing apparatus not using a voltage waveform shaping unit.

[0044] Fig.33 This indicates that the voltage waveform shaping unit is used. Fig.30 A graph showing the relationship between high frequency power and electron density (average value) in a plasma processing apparatus using a voltage waveform shaping unit and a plasma processing apparatus not using a voltage waveform shaping unit.

[0045] Description of Reference Numerals

[0046] 1, 111, 201: Processing container

[0047] 2.216: substrate mounting table (lower electrode)

[0048] 10, 120, 234: Shower head (upper electrode)

[0049] 20, 130, 250: Gas supply unit

[0050] 30: High frequency power supply

[0051] 33, 331, 332, 333, 334, 335, 336, 337: Voltage waveform shaping unit

[0052] 34: Capacitor

[0053] 35: Diode

[0054] 36, 361, 362, 363, 364, 365, 366, 367: Grounding circuit

[0055] 37: Switching element

[0056] 60: High frequency pulse power supply

[0057] 100, 101, 102, 103, 104, 105, 105a, 106: plasma processing device 112: substrate mounting table

[0058] 114: Lower electrode

[0059] 381, 381a, 381b, 381c: Zener diodes

[0060] 383: Resistance

[0061] 384: Variable resistor

[0062] 385: Power Supply

[0063] 386: Variable Power Supply

[0064] W: substrate DETAILED DESCRIPTION

[0065] Hereinafter, embodiments will be described with reference to the drawings.

[0066] <First embodiment>

[0067] First, a first embodiment will be described as a basic embodiment.

[0068] Figure 1 FIG. 1 is a cross-sectional view schematically showing the plasma processing apparatus according to the first embodiment.

[0069] The plasma processing apparatus 100 is an apparatus that performs plasma processing on a substrate W, and is configured as a capacitively coupled plasma processing apparatus. The substrate W may be, for example, a semiconductor wafer, but is not limited thereto.

[0070] The plasma processing apparatus 100 has a substantially cylindrical metal processing container 1. The processing container 1 is grounded. A substrate mounting table 2 for horizontally mounting a substrate W is provided inside the processing container 1. The substrate mounting table 2 includes a grounded lower electrode. In the example shown in the figure, the substrate mounting table 2 is made of metal, and the substrate mounting table 2 functions as a lower electrode, and the substrate mounting table 2 is grounded. The substrate mounting table 2 may also be made of an insulator, in which case the substrate mounting table 2 may have a structure in which a metal grounded lower electrode is embedded.

[0071] The substrate mounting table 2 may also have a heating mechanism or a cooling mechanism corresponding to the plasma processing. In addition, a plurality of lifting pins (not shown) that can protrude and retract relative to the upper surface of the substrate mounting table 2 are inserted, and the substrate W is delivered relative to the substrate mounting table 2 by lifting and lowering the plurality of lifting pins by a lifting mechanism (not shown).

[0072] An opening is formed at the top of the processing container 1, and a shower head 10 is embedded in the opening via an insulating member 9 in a manner opposite to the substrate mounting table 2. The shower head 10 is made of metal, has an overall cylindrical shape, and includes an upper electrode. In the example shown in the figure, the shower head 10 itself functions as the upper electrode, but a part of the shower head 10 may also be the upper electrode. The shower head 10 includes a main body 11 having an opening at the bottom and a shower tray 12 arranged in a manner to close the opening of the main body 11, and the internal space therebetween functions as a gas diffusion space. A plurality of gas release holes 13 are formed in the shower tray 12.

[0073] The shower head 10 is formed with a gas introduction hole 14, and the processing gas for plasma processing supplied from the gas supply unit 20 is introduced into the shower head 10 through the gas introduction hole 14. Then, the processing gas introduced into the shower head 10 is released into the processing container 1 from the gas release hole 13, and the processing gas is supplied to the space between the shower head 10 as the upper electrode and the substrate mounting table 2 as the lower electrode.

[0074] The gas supply unit 20 supplies a variety of gases such as processing gas, plasma generation gas, and purge gas required for plasma processing. As the processing gas, an appropriate gas can be selected according to the plasma processing to be performed. The gas supply unit 20 has a plurality of gas supply sources and gas supply piping, and a flow controller such as a valve and a mass flow controller is provided on the gas supply piping.

[0075] A high frequency power source 30 is connected to the approximate center of the shower head 10 as the upper electrode via a power supply line 31. A power source with a frequency of 10 kHz to 60 MHz can be used as the high frequency power source 30. By supplying high frequency electric power from the high frequency power source 30 to the shower head 10 as the upper electrode, capacitively coupled plasma is generated between the shower head 10 as the upper electrode and the substrate mounting table 2 as the lower electrode.

[0076] A matching device 32 is connected to the downstream side of the high frequency power source 30 of the power supply line 31. The matching device 32 is a device for matching the load impedance with the internal (or output) impedance of the high frequency power source 30.

[0077] Between the high-frequency power source 30 and the upper electrode, more specifically, at the downstream side of the matching device 32 of the power supply line 31, a voltage waveform shaping unit 33 is provided, which shapes the voltage waveform of the high-frequency power source so as to suppress the positive voltage in the high-frequency voltage applied to the upper electrode. In the present embodiment, the voltage waveform shaping unit 33 includes a capacitor 34 provided on the downstream side of the matching device 32 and a grounding circuit 36 ​​branched from the downstream side of the capacitor 34 and grounded via a diode 35. As the capacitor 34, a capacitor having a sufficient capacity to reduce the impedance as viewed from the high-frequency power source 30 is used. Instead of the capacitor 34, a blocking capacitor of the matching device 32 may be used.

[0078] The voltage waveform shaping section 33 is configured to utilize the function of accumulating electric charge realized by the capacitor 34 and the rectifying function of the diode 35 in the ground circuit 36, so that when the high-frequency power supply 30 outputs a positive voltage, the current flows to the ground side through the diode 35. At this time, the power output by the high-frequency power supply 30 is accumulated in the capacitor 34. As a result, the phenomenon that the upper electrode voltage fluctuates greatly to the positive side can be eliminated, and the rise of the plasma potential is suppressed. That is, by providing the voltage waveform shaping section 33, the plasma potential can be made lower than when the voltage waveform shaping section 33 does not exist. On the other hand, when the high-frequency power supply 30 outputs a negative voltage, the power output by the high-frequency power supply 30 and the power accumulated in the capacitor 34 are input into the plasma. At this time, the power is input into the sheath of the upper electrode, so it has almost no effect on the ion impact on the substrate W.

[0079] Furthermore, when plasma is excited in a state where the voltage waveform shaping unit 33 having the diode 35 is provided, high-density plasma is generated biased toward the vicinity of the shower head 10 as the upper electrode. Therefore, the gas released from the gas release hole 13 of the shower head 10 reliably passes through the high-density plasma region, and the supplied gas is efficiently converted into plasma or radicals and supplied to the processing region.

[0080] An exhaust port 41 is provided on the bottom wall of the processing container 1, and an exhaust device 43 is connected to the exhaust port 41 via an exhaust pipe 42. The exhaust device 43 has an automatic pressure control valve and a vacuum pump, and the processing container 1 can be exhausted through the exhaust device 43, and the processing container 1 can be maintained at a desired vacuum level.

[0081] Although not shown, a carry-in / carry-out port for carrying the substrate W in and out of the processing container 1 is provided on the side wall of the processing container 1 , and the carry-in / carry-out port is configured to be openable and closable by a gate valve.

[0082] The valves, flow controller, high frequency power supply, etc. of the gas supply unit 20, which are components of the plasma processing apparatus 100, are controlled by the control unit 50. The control unit 50 includes a main control unit, an input device, an output device, a display device, and a storage device. The main control unit includes a CPU. The plasma processing apparatus 100 is controlled based on the processing recipe stored in the storage medium of the storage device.

[0083] Next, the operation of the plasma processing apparatus 100 configured as described above will be described.

[0084] First, the gate valve is opened, and the substrate W is brought into the processing container 1 through the delivery port by a conveying device (not shown) and placed on the substrate mounting table 2. After the conveying device is moved away, the gate valve is closed.

[0085] Next, after the pressure of the processing container 1 is adjusted, a processing gas is introduced into the processing container 1, and high-frequency electric power is supplied to the shower head 10 as the upper electrode from the high-frequency power supply 30. As a result, a high-frequency electric field is formed between the shower head 10 as the upper electrode and the substrate mounting table 2 as the lower electrode, and a capacitively coupled plasma is generated therebetween.

[0086] At this time, in a general capacitively coupled plasma processing device, when the lower electrode is grounded, the plasma potential is highly dependent on the upper electrode potential. Figure 2 As shown in Figure 2, at the moment when the upper electrode is 0 V, the plasma potential is α V. However, Figure 3 As shown, at the moment when the upper electrode is at 100 V, the plasma potential becomes approximately 100+αV.

[0087] The ions in the plasma are accelerated by the sheath voltage (the difference between the plasma potential and the substrate potential) on the upper surface of the substrate and flow into the substrate W. Figure 4 When the power applied from the high frequency power supply 30 is increased to increase the intensity of the generated plasma, a high voltage is also applied to the positive side. Figure 5As shown, in the positive side portion, the plasma potential is raised and the sheath voltage becomes higher, the acceleration of the ions becomes larger, and the ion impact on the substrate W becomes stronger.

[0088] Therefore, in this embodiment, a voltage waveform shaping unit 33 is provided at the downstream side of the matching unit 32 to shape the voltage waveform of the high-frequency power source so as to suppress the positive voltage in the high-frequency voltage applied to the upper electrode.

[0089] In the present embodiment, the voltage waveform shaping unit 33 specifically utilizes the function of accumulating charge realized by the capacitor 34 and the rectification function of the diode 35 in the ground circuit 36, and operates as follows. First, when the high-frequency power supply 30 outputs a positive voltage, the current flows to the ground side through the diode 35. At this time, the power output by the high-frequency power supply 30 is accumulated in the capacitor 34. As a result, the phenomenon that the upper electrode voltage fluctuates greatly to the positive side can be eliminated, and the rise in the plasma potential is suppressed. Therefore, the impact of ions on the substrate W can be reduced. On the other hand, when the high-frequency power supply 30 outputs a negative voltage, the power output by the high-frequency power supply 30 and the power accumulated in the capacitor 34 are input into the plasma. At this time, the power is input into the sheath of the upper electrode, so it has almost no effect on the ion impact on the substrate W.

[0090] Figure 6 This means that a voltage waveform shaping unit 33 is provided. Figure 1 FIG. 3 is a diagram showing the upper electrode voltage waveform of a plasma processing apparatus with a capacitor coupled plasma processing apparatus and a general capacitor coupled plasma processing apparatus without a voltage waveform shaping unit 33. As shown in the figure, by providing the voltage waveform shaping unit 33, the phenomenon that the upper electrode voltage fluctuates greatly toward the positive side, which occurs when the voltage waveform shaping unit 33 is not provided, can be eliminated, and the rise of the plasma potential can be suppressed. As a result, the impact of ions on the substrate W can be suppressed. That is, the control of the plasma intensity and the suppression of the impact of ions on the substrate W can be performed independently.

[0091] Figure 7 This is a diagram showing the voltage waveform shaping unit 33 provided with the voltage waveform shaping unit 33, which is derived by simple calculation. Figure 1 3 and a general capacitively coupled plasma processing apparatus without the voltage waveform shaping unit 33. As shown in the figure, by providing the voltage waveform shaping unit 33, the sheath voltage is reduced to near 0V, and the impact of ions on the substrate W can be reduced.

[0092] Next, the following describes the operation of the device provided with the voltage waveform shaping unit 33. Figure 1 The ion energy of the plasma processing apparatus and the general capacitively coupled plasma processing apparatus without the voltage waveform shaping unit 33 are measured. Figure 8The energy distribution of ions when the output power of the high frequency power supply 30 is 100 W is shown. Fig. 9 The diagram shows the energy distribution of ions when the output power of the high frequency power source 30 is 500 W. As shown in these figures, by providing the voltage waveform shaping unit 33, a decrease in ion energy was also confirmed in actual evaluation.

[0093] Furthermore, when the plasma is excited in a state where the voltage waveform shaping unit 33 having the diode 35 is provided, the upper electrode does not fluctuate toward the forward side, and therefore, Fig.10 As shown, the high-density plasma region P is generated in a manner biased toward the vicinity of the shower head 10 as the upper electrode. Therefore, the gas released from the gas release hole 13 of the shower head 10 reliably passes through the high-density plasma region P, and the supplied gas is efficiently converted into plasma or radicals and supplied to the processing region. In addition, since the power from the high-frequency power supply 30 is input into the high-density plasma region P generated in a manner biased toward the vicinity of the shower head 10, the power is also highly efficient.

[0094] In contrast, when the voltage waveform shaping unit 33 is not provided, Fig.11 As shown in the figure, in addition to the high-density plasma region P near the upper electrode, a high-density plasma region P' is also generated on the substrate mounting table 2 side as the lower electrode, and the input power is dispersed to the high-density plasma region P and the high-density plasma region P'. Therefore, the density of the high-density plasma region P near the upper electrode through which the gas released from the gas release hole 13 of the shower head 10 reliably passes is lower than when the voltage waveform shaping unit 33 is provided. Therefore, the efficiency of radical generation is reduced.

[0095] Further, if Fig.12 As shown in the figure, similarly to Patent Document 1, when a high frequency power source 30' is connected to the substrate mounting table 2 as the lower electrode, and a voltage waveform shaping section 33' having a grounding circuit 36' grounded via a capacitor 34' and a diode 35' is provided on the downstream side of a matching device 32' on the lower electrode side, plasma P' is generated only on the side of the substrate mounting table 2. Therefore, a part of the gas is exhausted from the processing space without contacting the high density plasma region P', and the efficiency of radical generation is reduced.

[0096] As described above, in this embodiment, it is possible to suppress ion impact on the substrate W and to efficiently generate plasma and perform plasma processing.

[0097] <Second embodiment>

[0098] Next, a second embodiment will be described.

[0099] Fig.13It is a cross-sectional view schematically showing a plasma processing apparatus according to a second embodiment.

[0100] The plasma processing device 101 of the second embodiment is the same as the plasma processing device 100 of the first embodiment, and is a basic embodiment. The plasma processing device 101 of this embodiment is different from the plasma processing device 100 only in that a voltage waveform shaping unit 331 having a different structure is provided instead of the voltage waveform shaping unit 33 of the first embodiment. Therefore, Fig.13 In, with Figure 1 The same parts are denoted by the same reference numerals, and description thereof will be omitted.

[0101] The voltage waveform shaping unit 331 is provided at the downstream side of the matching device 32 of the power supply line 31, and has a function of shaping the voltage waveform of the high-frequency power supply to suppress the positive voltage in the high-frequency voltage applied to the upper electrode. In the present embodiment, the voltage waveform shaping unit 331 has a capacitor 34 provided at the downstream side of the matching device 32 and a grounding circuit 361 branched from the downstream side of the capacitor 34 and grounded via a switching element 37. That is, in the present embodiment, instead of the diode 35 of the first embodiment, a switching element 37 is provided as an element having a function of selectively flowing a current to the ground side when a positive voltage is applied to the upper electrode. As the capacitor 34, a blocking capacitor of the matching device 32 may also be used. In addition, the switching element 37 may be either a mechanical relay or a semiconductor switch such as a transistor.

[0102] The voltage waveform shaping section 331 can utilize the function of accumulating electric charge realized by the capacitor 34 and the opening and closing function of the switch element 37 in the grounding circuit 361 to make the current flow to the ground side when the high-frequency power supply 30 outputs a positive voltage. That is, by opening and closing the switch element 37, for example, at the moment when the voltage waveform is close to 0V, the current flows to the ground side when the high-frequency power supply 30 outputs a positive voltage, and it can have the same function as the diode 35 in the first embodiment. At this time, the power output by the high-frequency power supply 30 is accumulated in the capacitor 34. As a result, the phenomenon that the upper electrode voltage fluctuates greatly to the positive side can be eliminated, and the rise of the plasma potential is suppressed. On the other hand, when the high-frequency power supply 30 outputs a negative voltage, the power output by the high-frequency power supply 30 and the power accumulated in the capacitor 34 are input into the plasma. At this time, the power is input into the sheath of the upper electrode, so there is almost no effect on the ion impact on the substrate W.

[0103] Fig.141 is a diagram showing (a) a voltage waveform of the upper electrode of a general capacitively coupled plasma processing apparatus without a voltage waveform shaping unit 331, and (b) a voltage waveform of the upper electrode when the switch element 37 of the voltage waveform shaping unit 331 is properly turned on and off. As shown in the figure, by properly turning on and off the switch element 37 of the voltage waveform shaping unit 331, it is possible to eliminate the phenomenon that the upper electrode voltage fluctuates greatly to the positive side, and the increase in the plasma potential is suppressed. As a result, the impact of ions on the substrate W can be suppressed.

[0104] In addition, in this embodiment as well, similarly to the first embodiment, the supplied gas is efficiently converted into plasma or radicals and supplied to the processing region.

[0105] <Third Embodiment>

[0106] Next, a third embodiment will be described.

[0107] Fig.15 It is a cross-sectional view schematically showing a plasma processing apparatus according to a third embodiment.

[0108] The plasma processing apparatus 102 of the third embodiment is different from the plasma processing apparatus 100 of the first embodiment in that a voltage waveform shaping unit 332 having a Zener diode 381 is provided as a voltage regulating unit for regulating the voltage applied to the upper electrode instead of the voltage waveform shaping unit 33 of the first embodiment. Therefore, Fig.15 In, with Figure 1 The same parts are denoted by the same reference numerals, and the description thereof will be omitted.

[0109] The voltage waveform shaping unit 332 is provided at the downstream side of the matching device 32 of the power supply line 31, and has a function of suppressing the positive voltage in the high frequency voltage applied to the upper electrode, and shaping the voltage waveform so that the upper limit of the positive voltage of the upper electrode is arbitrarily determined. In this embodiment, the voltage waveform shaping unit 332 includes a capacitor 34 provided on the downstream side of the matching device 32 and a grounding circuit 362 branched from the downstream side of the capacitor 34. The grounding circuit 362 includes a diode 35 and a Zener diode 381 as a voltage adjustment unit provided in series with the diode 35, and is grounded via them.

[0110] The Zener diode 381 has a function of starting to flow current when the voltage reaches a certain value (Zener voltage Vz) without applying a voltage above this value. This function can relax the function of the diode 35 and arbitrarily determine the upper limit of the positive side (forward side) voltage of the upper electrode (shower head 10). That is, by adjusting the Zener voltage Vz, the positive voltage applied to the upper electrode can be arbitrarily changed, the plasma potential can be adjusted, and the ion energy supplied to the substrate W can be appropriately adjusted.

[0111] Fig.16 Yes means Fig.15 1 is a diagram showing a voltage waveform of an upper electrode when a Zener diode having a Zener voltage Vz of 39 V is used as the Zener diode 381 in a plasma processing apparatus having a grounding circuit 362 provided with a diode 35 and a Zener diode 381. As shown in the figure, by using the grounding circuit 362 having the diode 35 and the Zener diode 381, the maximum voltage on the positive side (forward direction side) of the upper electrode can be set to the level of the Zener voltage Vz.

[0112] Fig.17 Yes means Fig.15 In the plasma processing apparatus of FIG. 1 , the sheath voltage for accelerating ions is derived by simple calculation. As shown in the figure, by providing a voltage waveform shaping unit 332 having a grounding circuit 362 provided with a diode 35 and a Zener diode 381 so that the sheath voltage takes a value near the Zener voltage Vz, the ion energy for the substrate W can be adjusted.

[0113] Furthermore, in the present embodiment, there is also an effect of suppressing the voltage on the forward side of the upper electrode, and thus it is possible to maintain the effect of efficiently converting the supplied gas into plasma or radicals.

[0114] In the present embodiment, the voltage waveform shaping section 333 can be adopted which can switch between different Zener voltages and can switch the upper limit value of the positive voltage of the upper electrode. Fig.18 3 is a diagram showing such a voltage waveform shaping unit 333. The voltage waveform shaping unit 333 has a grounding circuit 363 having a plurality of grounded lines with different Zener voltages, which can be switched by a switch 39, on the downstream side of the diode 35. In this example, as the plurality of lines, there are a first line 382a without a Zener diode (Vz=0), a second line 382b with a first Zener diode 381a (Vz=40), a third line 382c with a second Zener diode 381b (Vz=80), and a third line 382d with a third Zener diode 381c (Vz=120). In addition, the Zener voltage Vz of each line here is only an example and is not limited to this.

[0115] By providing Zener diodes with different Zener voltages Vz in each line and switching them with switches, the upper limit of the positive voltage of the upper electrode (shower head 10) can be switched to multiple levels. Thus, the ion energy supplied to the substrate W can be controlled simply by switching the switch.

[0116] In addition, in this embodiment, the switching element of the second embodiment may be used instead of the diode 35 .

[0117] <Fourth embodiment>

[0118] Next, a fourth embodiment will be described.

[0119] Fig.19 FIG. 1 is a cross-sectional view schematically showing a plasma processing apparatus according to a fourth embodiment.

[0120] The plasma processing apparatus 103 of the fourth embodiment is different from the plasma processing apparatus 100 of the first embodiment only in that a voltage waveform shaping unit 334 having a resistor 383 is provided as a voltage adjustment unit. Fig.19 In, with Figure 1 The same parts are denoted by the same reference numerals, and the description thereof will be omitted.

[0121] The voltage waveform shaping unit 334 is provided at the downstream side of the matching device 32 of the power supply line 31, and has a function of suppressing the positive voltage in the high frequency voltage applied to the upper electrode, and shaping the voltage waveform so that the upper limit of the positive voltage of the upper electrode is arbitrarily determined. In this embodiment, the voltage waveform shaping unit 334 includes a capacitor 34 provided on the downstream side of the matching device 32 and a grounding circuit 364 branched from the downstream side of the capacitor 34. The grounding circuit 364 includes a diode 35 and a resistor 383 as a voltage adjustment unit provided in series with the diode 35, and is grounded via these.

[0122] The upper limit of the positive side (forward side) voltage of the upper electrode (shower head 10) can be arbitrarily determined by the resistor 383. That is, by adjusting the resistance value of the resistor 383, the positive voltage applied to the upper electrode can be arbitrarily changed, the plasma potential can be adjusted, and the ion energy supplied to the substrate W can be appropriately adjusted. In this way, an appropriate amount of ions can be supplied to the substrate W according to the plasma treatment.

[0123] Furthermore, in the present embodiment, there is also an effect of suppressing the voltage on the forward side of the upper electrode, and thus it is possible to maintain the effect of efficiently converting the supplied gas into plasma or radicals.

[0124] In this embodiment, the resistor may be a variable resistor. Fig. 20 3 is a diagram showing a voltage waveform shaping unit 335 having a grounding circuit 365 provided with a variable resistor 384 instead of the resistor 383. By providing the variable resistor 384 in this way, the ion energy supplied to the substrate W can be controlled by simply switching the resistance value thereof.

[0125] In addition, in this embodiment, the switching element of the second embodiment may be used instead of the diode 35 .

[0126] <Fifth embodiment>

[0127] Next, a fifth embodiment will be described.

[0128] Fig.21 It is a cross-sectional view schematically showing a plasma processing apparatus according to a fifth embodiment.

[0129] The plasma processing apparatus 104 of the fifth embodiment is different from the plasma processing apparatus 100 of the first embodiment only in that a voltage waveform shaping unit 336 having a power supply 385 is provided as a voltage adjustment unit. Fig.21 In, with Figure 1 The same parts are denoted by the same reference numerals, and the description thereof will be omitted.

[0130] The voltage waveform shaping unit 336 is provided at the downstream side of the matching device 32 of the power supply line 31, and has a function of suppressing the positive voltage in the high frequency voltage applied to the upper electrode, and shaping the voltage waveform so that the upper limit of the positive voltage of the upper electrode is arbitrarily determined. In this embodiment, the voltage waveform shaping unit 336 includes a capacitor 34 provided on the downstream side of the matching device 32 and a grounding circuit 366 branched from the downstream side of the capacitor 34. The grounding circuit 366 includes a diode 35 and a power supply 385 as a voltage adjustment unit provided in series with the diode 35, and is grounded via them. In this example, a DC power supply is provided as the power supply 385.

[0131] The upper limit of the positive side (forward side) voltage of the upper electrode (shower head 10) can be arbitrarily determined by the power supply 385. That is, by adjusting the voltage of the power supply 385, the positive voltage applied to the upper electrode can be arbitrarily changed, the plasma potential can be adjusted, and the ion energy supplied to the substrate W can be appropriately adjusted.

[0132] Furthermore, in the present embodiment, there is also an effect of suppressing the voltage on the forward side of the upper electrode, and thus it is possible to maintain the effect of efficiently converting the supplied gas into plasma or radicals.

[0133] In this embodiment, the power supply may be a variable power supply. Fig. 22 3 is a diagram showing a voltage waveform shaping unit 337 having a grounding circuit 367 provided with a variable power supply 386 instead of the power supply 385. By providing the variable power supply 386 in this way, the ion energy supplied to the substrate W can be controlled by simply switching the resistance value thereof.

[0134] In addition, in this embodiment, the switching element of the second embodiment may be used instead of the diode 35 .

[0135] <Sixth embodiment>

[0136] Next, a sixth embodiment will be described as a specific embodiment.

[0137] In this embodiment, an example in which the plasma processing apparatus having the basic structure described in the first embodiment is applied to a film forming apparatus is described.

[0138] Fig.23 It is a cross-sectional view showing a plasma processing apparatus according to a sixth embodiment.

[0139] The plasma processing apparatus 105 is a plasma CVD apparatus for forming a Ti film on a substrate W by plasma CVD, and is configured as a capacitively coupled plasma processing apparatus. The substrate W may be, for example, a semiconductor wafer, but is not limited thereto.

[0140] The plasma processing apparatus 105 includes a cylindrical metal processing container 111. The processing container 111 includes an exhaust chamber 151 that protrudes downward so as to cover a circular hole 150 formed in the center of a bottom wall 111b of the main body. An exhaust pipe 152 is connected to the side of the exhaust chamber 151, and an exhaust device 153 including an automatic pressure control valve and a vacuum pump is provided in the exhaust pipe 152. The exhaust device 153 can exhaust the processing container 111 and maintain the processing container 111 at a desired vacuum level.

[0141] A carry-in / carry-out port 157 for carrying the substrate W into and out of the processing container 111 is provided on the side wall of the processing container 111 . The carry-in / carry-out port 157 can be opened and closed by a gate valve 158 .

[0142] A substrate stage 112 for horizontally placing a substrate W is provided inside the processing container 111. The substrate stage 112 includes a main body 113 made of a metal such as Ni, and a lower electrode 114 and a heater 115 provided therein. The lower electrode 114 is grounded. The heater 115 generates heat by receiving power from a heater power supply 116, and heats the placed substrate W to a desired temperature. The substrate stage 112 is supported by a cylindrical support member 117 extending downward from the lower center of the main body 113, and the support member 117 is mounted on the bottom wall of the exhaust chamber 151 via an insulating member 118.

[0143] An opening is formed in the top wall 111a of the processing container 111, and a shower head 120 is embedded in the opening in a manner opposite to the substrate mounting table 112 via an insulating member 119. The shower head 120 is made of metal, has an overall cylindrical shape, and includes an upper electrode. In the example shown in the figure, the shower head 120 itself functions as the upper electrode, or a part of the shower head 120 may be the upper electrode. The shower head 120 includes a base member 121 and a shower tray 122, the shower tray 122 is formed in a disc shape, and a flange portion 122a is formed on its outer periphery, and the flange portion 122a is screwed to the base member 121 via an intermediate member 123 formed in a circular ring shape. In addition, a gas diffusion space 124 is formed between the base member 121 and the shower tray 122. The base member 121 has a flange portion 121a formed on its outer periphery, and the flange portion 121a is supported by the insulating member 119. A plurality of gas release holes 125 are formed in the shower plate 122. A gas introduction hole 126 is formed near the center of the upper portion of the base member 121. A gas pipe 130a connected to a gas supply unit 130 described later is connected to the gas introduction hole 126, and a process gas supplied from the gas supply unit 130 is introduced into the process container 111 in a spraying manner via the shower head 120. That is, the process gas is supplied to the space between the shower head 120 as the upper electrode and the substrate mounting table 112 including the lower electrode 114.

[0144] In addition, a heater 147 for heating the shower head 120 is provided on the base member 121 of the shower head 120. The heater 147 is powered from a heater power source (not shown) to heat the shower head 120 to a desired temperature. A heat insulating member 149 is provided in a recess formed on the upper portion of the base member 121.

[0145] The gas supply unit 130 includes: a plurality of gas supply sources for separately supplying TiCl4 gas, Ar gas, and H2 gas; and a plurality of gas supply pipes for supplying each gas from the plurality of gas supply sources. A flow controller such as an on-off valve and a mass flow controller (not shown) is provided in each gas supply pipe, through which the supply / stop of the above-mentioned gas and the flow rate control of each gas can be performed. In addition to these gases, other gases such as N2 gas and NH3 gas may also be included.

[0146] The shower head 120 as the upper electrode is connected to a high frequency power supply 30 via a power supply line 31 as in the first embodiment. As the high frequency power supply 30, a power supply with a frequency of 10 kHz to 60 MHz can be used. By supplying high frequency electric power from the high frequency power supply 30 to the shower head 120 as the upper electrode, capacitively coupled plasma is generated between the shower head 120 as the upper electrode and the lower electrode 114 included in the substrate mounting table 112. A matching device 32 is connected to the downstream side of the high frequency power supply 30 of the power supply line 31.

[0147] As in the first embodiment, a voltage waveform shaping unit 33 is provided at the downstream side of the matching device 32 of the power supply line 31, and the voltage waveform of the high-frequency power source is shaped so as to suppress the positive voltage in the high-frequency voltage applied to the upper electrode. The voltage waveform shaping unit 33 includes a capacitor 34 provided at the downstream side of the matching device 32 and a grounding circuit 36 ​​branched from the downstream side of the capacitor 34 and grounded via a diode 35. As the capacitor 34, a capacitor having a sufficient capacity to reduce the impedance as viewed from the high-frequency power source 30 is used. Instead of the capacitor 34, a blocking capacitor of the matching device 32 may be used.

[0148] The voltage waveform shaping unit 33 is similar to the first embodiment, and is configured to utilize the charge accumulation function of the capacitor 34 and the rectification function of the diode 35 of the ground circuit 36, so that when the high-frequency power source 30 outputs a positive voltage, the current flows to the ground side through the diode 35. This suppresses the increase in plasma potential and the impact of ions on the substrate W.

[0149] Valves, flow rate controllers, high frequency power supplies, and the like of the gas supply unit 130, which are components of the plasma processing apparatus 105, are controlled by a control unit 160. The control unit 160 is configured similarly to the control unit 50 of the first embodiment.

[0150] Next, the operation of the plasma processing apparatus 105 configured as described above will be described.

[0151] First, the gate valve 158 is opened, and the substrate W is introduced into the processing container 111 through the introduction and delivery port 157, and placed on the substrate mounting table 112 maintained at a predetermined temperature. Then, the pressure in the processing container 111 is adjusted, and the Ar gas as the plasma generation gas, the H2 gas as the reduction gas, and the TiCl4 gas as the Ti raw material gas are made to flow to the pre-flow line (not shown) for pre-flow. Next, while keeping the gas flow rate and pressure the same, the line for film formation is switched, and these gases are introduced into the processing container 111 through the shower head 120.

[0152] Then, while Ar gas, H2 gas and TiCl4 gas are introduced into the processing container 111, the high-frequency power supply 30 is turned on to generate plasma, and a Ti film is formed on the surface of the substrate W by using plasma CVD.

[0153] As the conditions at this time, the temperature of the substrate mounting table 112 can be set to 300 to 700° C., and the pressure in the processing container 111 can be set to a range of 13.3 to 1333 Pa (0.1 to 10 Torr).

[0154] The formation of Ti film using plasma CVD is accomplished by utilizing the ion impact caused by plasma to destroy the surface of the base film, form dangling bonds, and adsorb the dissociated products of TiCl4, which is the film-forming raw material (precursor), namely TiCl3 or TiCl2, onto the dangling bond forming part.

[0155] When a Ti film is formed on a substrate with low bond energy such as Si or SiGe, it is preferable to reduce the ion impact and make the ion energy of plasma as low as possible.

[0156] In addition, in a substrate having Si or SiGe and other materials (such as SiN or SiO2) on the surface, it is necessary to selectively form a Ti film on Si or SiGe. In such a case, it is also effective to lower the ion energy.

[0157] That is, the bond energies of Si and SiGe are as small as 327 kJ / mol and 301 kJ / mol, respectively, while the bond energies of SiN and SiO2 are 798 kJ / mol and 439 kJ / mol, respectively, which are larger than Si and SiGe. Therefore, it is believed that by reducing the ion energy to a level that can only dissociate Si or SiGe, selective film formation on Si or SiGe can be achieved.

[0158] In addition, the selective film formation of the Ti film is not limited to Si and SiGe. As long as the surface has a first material portion with relatively small bonding energy and a second material portion with relatively large bonding energy, the Ti film can be selectively formed on the first material portion.

[0159] As a way to reduce ion energy, it is generally considered to increase the pressure in the processing container to high pressure, reduce the high-frequency power, etc. In plasma processing using TiCl4 gas, it is difficult to maintain high-voltage / low-power discharge because of the power consumed in its decomposition.

[0160] In contrast, in this embodiment, as in the first embodiment, the voltage waveform of the high-frequency power source 30 is shaped by the voltage waveform shaping unit 33 to suppress the positive voltage in the high-frequency voltage applied to the upper electrode. Specifically, the capacitor 34 generates a bias voltage to maintain Vpp, and the rectifying function of the diode 35 of the grounding circuit 36 ​​is used to eliminate the phenomenon that the upper electrode voltage fluctuates greatly to the positive side, thereby suppressing the increase in the plasma potential. As a result, the ion energy for the substrate W can be reduced without changing the plasma generation conditions, and the desired film formation process can be achieved.

[0161] When the frequency of the high-frequency power source 30 is high, the electron temperature is low and the discharge margin is reduced. Therefore, the frequency of the high-frequency power source 30 is preferably about 10 kHz to 60 MHz, for example, 450 kHz.

[0162] Next, the experimental results of forming a Ti film on Si and SiN on the surface of a substrate by using a device using the voltage waveform shaping unit 33 and a device not using the voltage waveform shaping unit 33 are described. Here, the Ti film is formed after the natural oxide film on the surface of Si and SiN is removed by dry treatment.

[0163] The conditions at this time are as follows.

[0164] High frequency electric power frequency: 450kHz

[0165] High frequency power: 40W

[0166] Pressure: 2.0 Torr

[0167] Electrode gap: 13.5mm

[0168] Substrate stage temperature: 450°C

[0169] Gas: TiCl4 / Ar / H2=25 / 2400 / 1000sccm

[0170] Fig.24 This indicates that the voltage waveform shaping unit 33 is used. Fig.23 33 and a plasma processing apparatus without using the voltage waveform shaping unit 33, when a Ti film is formed on Si. As shown in the figure, the film thickness on Si is almost the same regardless of whether the voltage waveform shaping unit 33 is used or not.

[0171] on the other hand, Fig.25 This indicates that the voltage waveform shaping unit 33 is used. Fig.23 33 and a plasma processing apparatus without using the voltage waveform shaping unit 33, when a Ti film is formed on SiN. As shown in the figure, it is confirmed that the film thickness is reduced by about 60% on SiN by using the voltage waveform shaping unit 33.

[0172] Fig.26 This is a graph showing the average value of the selectivity ratio of the film thickness of the Ti film on Si and on SiN (Si / SiN selectivity ratio) based on the above results. As shown in this figure, it is confirmed that the Si / SiN selectivity ratio is about 1.5 to 1.6 when the voltage waveform shaping unit 33 is not used, and it is greatly improved to 3.3 to 3.6 by using the voltage waveform shaping unit 33. In addition, although not shown in the figure, it is confirmed that the Si / SiN selectivity ratio is improved from 1.6 to 4.9 with respect to the center of the substrate, and the improvement range is further expanded.

[0173] In this embodiment, plasma is generated near the shower head 120 as the upper electrode by igniting plasma with the voltage waveform shaping unit 33. Therefore, the released gas reliably passes through the high-density plasma region, and thus can be efficiently converted into plasma or radicals.

[0174] In this embodiment, as an element that selectively flows current to the ground side when a positive voltage is applied, a switch element may be used instead of a diode as in the second embodiment. In addition, as a grounding circuit, not only elements that selectively flow current to the ground side when a positive voltage is applied, such as a diode and a switch element, but also a voltage adjustment unit such as a Zener diode, a resistor, and a power supply may be provided as in the third to fifth embodiments. Thus, the ion energy can be appropriately controlled using the substrate, and the film forming property can be controlled, especially the selective film forming property.

[0175] <Seventh embodiment>

[0176] Next, a seventh embodiment will be described as a specific embodiment.

[0177] Fig. 27 It is a cross-sectional view showing a plasma processing apparatus according to a seventh embodiment.

[0178] The plasma processing apparatus 105a of this embodiment is different from the plasma processing apparatus 105a in that a high-frequency pulse power supply 60 is used instead of the high-frequency power supply 30. Fig.23 The plasma processing apparatus 105 of the sixth embodiment is different from Fig.23 Since the structure is the same as that of the plasma processing device, the same figure marks are given and the description is omitted.

[0179] In this embodiment, by Fig. 27 The plasma processing apparatus 105a not only realizes the selective film formation of the Ti film as in the sixth embodiment, but also suppresses the corrosion of the Ti film using pulsed high-frequency electric power.

[0180] In the sixth embodiment, the voltage waveform shaping unit 33 is used to suppress the rise of the plasma potential, and the ion energy to the substrate W is reduced without changing the plasma generation conditions, so that only the first material portion with a small bond energy can be dissociated, thereby achieving selective film formation. A specific example is that the ion energy is reduced so that SiN or SiO2 with a relatively large bond energy does not dissociate, and only Si or SiGe with a relatively small bond energy dissociates, thereby achieving selective film formation.

[0181] In this way, when the Ti film is to be thickened by selective film formation of the Ti film using the voltage waveform shaping unit 33, it is considered to increase the high-frequency electric power or to extend the film formation time. However, it is found that in either case, the residual concentration of Cl in the film becomes high and the corrosion of the film becomes serious. In the case of a non-corroded Ti film, O, N, and Cl are detected on the surface side of the Ti film, and an oxide layer is generated on the surface of the Ti film. In the case of a corroded Ti film, O, N, and Cl are detected from the film, and an oxide layer is generated between the Ti film and the underlying Si film.

[0182] Therefore, in this embodiment, a high-frequency pulse power source 60 is used to apply pulsed high-frequency electric power to the shower head 120 as the upper electrode to generate plasma. The pulsed high-frequency electric power is typically applied periodically so that the high-frequency electric power is repeatedly turned on and off.

[0183] By supplying pulsed high-frequency electric power in this manner, even if the power is increased or the film formation time is prolonged in order to thicken the Ti film in the selective film formation of the Ti film, the corrosion of the film can be suppressed.

[0184] The mechanism by which the corrosion of the Ti film is suppressed by supplying pulsed high-frequency electric power is assumed to be as follows.

[0185] When the pulse is off, TiCl4 does not form a film, which helps to etch the weak Cl bonds on the film surface. In addition, the film formation rate is also slowed down, so the time for de-Cl can be ensured.

[0186] Furthermore, the afterglow sheath disappears after the pulse is turned off, and the electrons are absorbed by the ions to generate ion-ion plasma. In addition, the substrate is negatively charged at the moment the pulse is turned off, so the H 3+ ions toward the substrate. It is believed that as a result, H 3+ The Cl in the Ti film is reduced, and the corrosion suppression effect is enhanced.

[0187] The high frequency of the high frequency pulse power supply 60 is the same as the frequency of the high frequency power supply 30 of the sixth embodiment, preferably about 10kHz to 60MHz, for example, 450kHz. In addition, the frequency of the pulse is preferably 0.1 to 500kHz, for example, 10kHz. In addition, the duty ratio of the pulse can be in the range of 1 to 99%, preferably 10 to 90%.

[0188] When high-frequency electric power is applied, the upper voltage waveform becomes Fig.28 In contrast, when a pulsed high frequency electric power is applied, Fig.29 Like that. Fig.29 (a) is the case where the duty ratio is 30%, (b) is the case where the duty ratio is 50%, and (c) is the case where the duty ratio is 80%. The frequency of the high-frequency electric power is 450 kHz, and the pulse frequency is 10 kHz.

[0189] In addition, the pulsed high-frequency electric power may not be completely turned on / off as described above, but may be repeatedly in a state of high power and a state of low power.

[0190] Next, the application of continuous wave high frequency electric power is described. Fig.23 Device and from applying pulsed high frequency electric power Fig. 27 The experimental results of forming a Ti film on Si and SiN on the surface of a substrate by removing the voltage waveform shaping section 33 from the device of FIG. Here, the Ti film is formed after removing the natural oxide film on the surface of Si and SiN by dry treatment.

[0191] Here, when applying pulsed high-frequency electric power, the duty ratio is set to 80% and 50%. The film forming time is 360 seconds in the case of continuous wave, and in the case of pulsed high-frequency electric power, in order to make the time of applying high-frequency electric power the same, the duty ratio is set to 450 seconds when the duty ratio is 80%, and the duty ratio is set to 720 seconds when the duty ratio is 50%.

[0192] Other conditions are as follows.

[0193] High frequency electric power frequency: 450kHz

[0194] High frequency power: 100W

[0195] Pressure: 4.0 Torr

[0196] Electrode gap: 13.5mm

[0197] Substrate stage temperature: 450°C

[0198] Gas: TiCl4 / Ar / H2=25 / 2400 / 1000sccm

[0199] Pulse frequency: 10kHz

[0200] After film formation, the substrate was sent out from the processing container, the presence or absence of corrosion of the Ti film was confirmed, and the sheet resistance was measured. As a result, the corrosion of the Ti film became serious in the case of the continuous wave, and the sheet resistance of the film was 510.1Ω / sq. In contrast, in the case of the pulse with a duty cycle of 80%, although the corrosion of the Ti film was observed, it was suppressed compared with the case of the continuous wave, and the sheet resistance was 276.4Ω / sq. In addition, no corrosion of the Ti film was observed in the case of the pulse with a duty cycle of 50%.

[0201] That is, while corrosion becomes serious when continuous wave high frequency power is used, corrosion of the Ti film can be suppressed by pulsed high frequency power, and it was confirmed that corrosion of the Ti film is further suppressed by reducing the duty ratio of the pulse.

[0202] In the above experiment, a device without a voltage waveform shaping unit was used, so a Ti film having the same thickness was formed on the Si film and the SiN film, and no selectivity was observed.

[0203] Next, the method of applying a continuous wave high frequency electric power through the voltage waveform shaping unit 33 is described. Fig.23 A device having a voltage waveform shaping unit 33 and applying a pulsed high-frequency electric power Fig. 27 The experimental results of forming a Ti film on Si and SiN on the surface of a substrate using a device. Here, the Ti film is formed after the natural oxide film on the surface of Si and SiN is removed by dry treatment.

[0204] Here, as conditions A and B, 40W continuous wave high frequency power was applied for 900 seconds and 1200 seconds respectively. In addition, as condition C, 60W pulsed high frequency power was applied with a duty cycle of 20% for 1500 seconds.

[0205] Other conditions are as follows.

[0206] High frequency electric power frequency: 450kHz

[0207] Pressure: 6.0 Torr

[0208] Electrode gap: 13.5mm

[0209] Substrate stage temperature: 450°C

[0210] Gas: TiCl4 / Ar / H2=25 / 2400 / 1000sccm

[0211] Pulse frequency: 10kHz

[0212] After the film formation, the substrate was taken out from the processing container, and the film thickness of the Ti film on the Si film and the film thickness of the Ti film on the SiN film under each condition were measured.

[0213] As a result, under condition A, the average thickness of the Ti film on the Si film and the Ti film on the SiN film were 5.7 nm and 0.8 nm, respectively, and the average value of the Si / SiN selectivity ratio was 7.2. Under condition B, the average thickness of the Ti film on the Si film and the Ti film on the SiN film were 6.2 nm and 0.8 nm, respectively, and the average value of the Si / SiN selectivity ratio was 7.8. Under condition C, the average thickness of the Ti film on the Si film and the Ti film on the SiN film were 8.15 nm and 1.07 nm, respectively, and the average value of the Si / SiN selectivity ratio was 7.63. Thus, in either case, the Si / SiN selectivity ratio was high due to the use of the voltage waveform shaping unit 33.

[0214] Next, corrosion of the Ti film was checked. No corrosion was found under condition A, but corrosion was found under condition B where the treatment time was prolonged. Under condition C where pulsed high-frequency electric power was applied, corrosion of the Ti film was not found even though the film thickness was thicker than under condition B. In addition, sheet resistance was checked. The result was 336.2Ω / sq. under condition A and 259.1Ω / sq. under condition C. As a result of applying pulsed high-frequency electric power to suppress corrosion of the film, a decrease in sheet resistance was found.

[0215] The above results confirm that by using the voltage waveform shaping unit 33 and the pulsed high-frequency electric power together, the effect of forming a Ti film on a Si film with a high selectivity is maintained, and corrosion can be suppressed and the thickness of the Ti film on the Si film can be increased.

[0216] <Eighth Embodiment>

[0217] Next, an eighth embodiment will be described as a specific embodiment.

[0218] In this embodiment, an example in which the plasma processing apparatus having the basic structure described in the first embodiment is applied to an etching apparatus is described.

[0219] Fig.30 It is a cross-sectional view showing a plasma processing apparatus according to an eighth embodiment.

[0220] The plasma processing apparatus 106 of the present embodiment is an etching apparatus that etches a film present on a substrate W, and is configured as a capacitively coupled plasma processing apparatus. The substrate W may be, for example, a semiconductor wafer, but is not limited thereto.

[0221] The plasma processing apparatus 106 includes a cylindrical metal processing container 201. The processing container 201 is safely grounded.

[0222] A cylindrical metal support table 214 is disposed at the bottom of the processing container 201 via an insulating plate 212 made of ceramic or the like, and a cylindrical substrate mounting table 216 made of, for example, aluminum is disposed on the support table 214. The substrate mounting table 216 constitutes a lower electrode and is grounded. The substrate mounting table 216 has an electrostatic chuck 218 on the upper surface that holds the substrate W by electrostatic force. The electrostatic chuck 218 is a component having a structure in which an electrode 220 is disposed inside an insulator, and by applying a DC voltage from a DC power supply 222 to the electrode 220, the substrate W is held by electrostatic force such as the Lorentz force.

[0223] A conductive focus ring 224 made of, for example, silicon is disposed around the electrostatic chuck 218 on the upper surface of the substrate stage 216 to improve etching uniformity. A cylindrical inner wall member 226 made of, for example, quartz is disposed on the side surfaces of the substrate stage 216 and the support table 214.

[0224] A refrigerant chamber 228 is provided inside the support table 214. A refrigerant, such as cooling water, is circulated in the refrigerant chamber through pipes 230a and 230b by a refrigeration unit (not shown) provided externally, and the processing temperature of the substrate W on the substrate mounting table 216 is controlled by the temperature of the refrigerant.

[0225] Furthermore, a heat transfer gas such as He gas is supplied from a heat transfer gas supply mechanism (not shown) between the upper surface of the electrostatic chuck 218 and the back surface of the substrate W through the gas supply line 232 .

[0226] A shower head 234 as an upper electrode is provided above the substrate mounting table 216 as a lower electrode so as to face the substrate mounting table 216. Thus, a space between the shower head 234 as an upper electrode and the substrate mounting table 216 as a lower electrode serves as a plasma generation space.

[0227] The shower head 234 as the upper electrode is supported on the upper part of the processing container 201 via an insulating shielding member 243. The shower head 234 is composed of an electrode plate 236 which forms a surface opposite to the substrate mounting table 216 and has a plurality of gas release holes 237, and an electrode support body 238 of a water-cooling structure which detachably supports the electrode plate 236. A gas diffusion chamber 240 is provided inside the electrode support body 238, and a plurality of gas flow holes 241 which are connected to the gas release holes 237 extend downward from the gas diffusion chamber 240. A gas introduction hole 242 for introducing a processing gas into the gas diffusion chamber 240 is formed in the electrode support body 238, and a gas pipe 251 connected to a gas supply unit 250 described later is connected to the gas introduction hole 242, and the processing gas supplied from the gas supply unit 250 is released in a spray shape into the processing container 201 via the shower head 234. That is, the processing gas is supplied between the shower head 234 as the upper electrode and the substrate mounting table 216 as the lower electrode.

[0228] The gas supply unit 250 has a gas supply source that separately supplies multiple gases including Ar gas and O2 gas, and multiple gas supply pipes for supplying each gas from the multiple gas supply sources. In addition, in the figure, only Ar and O2 are depicted in the gas supply unit 250, but in addition to Ar gas and O2 gas, other gases required for etching can also be contained. As other gases, for example, halogen-containing gases such as CF4, C4F8, CHF3, HBr, and Cl2 can be listed. A flow controller such as an on-off valve and a mass flow controller (not shown) is provided in each gas supply pipe, thereby enabling the supply / stop of the above-mentioned gas and the flow control of each gas.

[0229] An exhaust port 260 is provided at the bottom of the processing container 201, and an exhaust device 264 is connected to the exhaust port 260 via an exhaust pipe 262. The exhaust device 264 has an automatic pressure control valve and a vacuum pump, and the processing container 201 can be exhausted through the exhaust device 264, and the processing container 201 can be maintained at a desired vacuum level.

[0230] A carry-in / carry-out port 265 for carrying the substrate W in and out of the processing container 201 is provided on the side wall of the processing container 201 . The carry-in / carry-out port 265 can be opened and closed by a gate valve 266 .

[0231] The shower head 234 as the upper electrode is connected to a high frequency power supply 30 via a power supply line 31 as in the first embodiment. As the high frequency power supply 30, a power supply with a frequency of 10 kHz to 60 MHz can be used. By supplying high frequency electric power from the high frequency power supply 30 to the shower head 234 as the upper electrode, capacitively coupled plasma is generated between the shower head 234 as the upper electrode and the substrate mounting table 216 as the lower electrode. A matching device 32 is connected to the downstream side of the high frequency power supply 30 of the power supply line 31.

[0232] As in the first embodiment, a voltage waveform shaping unit 33 is provided at the downstream side of the matching device 32 of the power supply line 31, and the voltage waveform of the high-frequency power supply is shaped so as to suppress the positive voltage in the high-frequency voltage applied to the upper electrode. The voltage waveform shaping unit 33 includes a capacitor 34 provided at the downstream side of the matching device 32 and a grounding circuit 36 ​​branched from the downstream side of the capacitor 34 and grounded via a diode 35. As the capacitor 34, a capacitor having a sufficient capacity to reduce the impedance as viewed from the high-frequency power supply 30 is used. Instead of the capacitor 34, a blocking capacitor of the matching device 32 may be used.

[0233] The voltage waveform shaping unit 33 is similar to the first embodiment, and is configured to utilize the charge accumulation function of the capacitor 34 and the rectification function of the diode 35 of the ground circuit 36, and when the high frequency power source 30 outputs a positive voltage, the current flows to the ground side through the diode 35. This suppresses the increase in plasma potential and reduces the ion energy to the substrate W.

[0234] The valves, flow controller, high frequency power supply, etc. of the gas supply unit 250 as components of the plasma processing apparatus 106 are controlled by the control unit 270. The control unit 270 is configured similarly to the control unit 50 of the first embodiment.

[0235] Next, the operation of the plasma processing apparatus 106 configured as described above will be described.

[0236] First, the gate valve 266 is opened, and the substrate W having the etching target film is introduced into the processing container 201 through the introduction and delivery port 265 and placed on the substrate mounting table 216. Then, the processing container 201 is exhausted by the exhaust device 264, the pressure is adjusted, and the gas containing Ar gas and O2 gas is supplied from the gas supply unit 250 to the shower head 234 as the processing gas for etching, and supplied into the processing container 201 through the gas release hole 237. At the same time, the high frequency power supply 30 is turned on to generate plasma to perform plasma etching on the etching target film of the substrate W.

[0237] As conditions at this time, the temperature of the substrate mounting table 216 (electrostatic chuck 218) can be set to 30°C or less, and the pressure in the processing container 201 can be set to 0.133-133 Pa (1-1000 mTorr), for example, 67 Pa (500 mTorr).

[0238] Ar / O2 mixed plasma is often used for plasma etching or plasma ashing, and improving its controllability is technically important. In particular, the reaction at the interface between plasma and substrate is very important, and the difference in ion energy at the interface has a great influence on the surface reaction and processing results.

[0239] In this embodiment, as in the first embodiment, the voltage waveform shaping unit 33 is used to shape the voltage waveform of the high-frequency power supply 30 so as to suppress the positive voltage in the high-frequency voltage applied to the upper electrode. Specifically, the electrochemical storage function of the capacitor 34 is used to generate a bias, and the rectification function of the diode 35 of the ground circuit 36 ​​is used to eliminate the phenomenon that the upper electrode voltage fluctuates greatly to the positive side, thereby suppressing the increase in the plasma potential. In this way, the ion energy for the substrate W can be reduced without changing the plasma state, and the etching property can be controlled. When the temperature of the substrate mounting table 216 (electrostatic chuck 218) is a low temperature of 30°C or less, etching caused by ion energy is dominant, so the etching controllability can be improved by reducing the ion energy.

[0240] Next, the experimental results of plasma etching of photoresist using Ar / O 2 plasma by using a device using the voltage waveform shaping unit 33 and a device not using the voltage waveform shaping unit 33 are described.

[0241] The conditions at this time are as follows.

[0242] Substrate: 300mmSi wafer

[0243] High frequency electric power frequency: 450kHz

[0244] High frequency power: 300W

[0245] Pressure: 800mTorr

[0246] Gas: Ar / O2=1000 / 500sccm

[0247] Electrode gap: 15mm

[0248] Electrostatic chuck temperature: 23℃~

[0249] Focus ring: Si (floating)

[0250] Fig.31 This indicates that the voltage waveform shaping unit 33 is used. Fig.303 and a plasma processing apparatus without using the voltage waveform shaping unit 33, and a voltage waveform of the upper electrode. As shown in the figure, by using the voltage waveform shaping unit 33, the voltage on the positive side of the upper electrode is reduced.

[0251] Fig.32 This indicates that the voltage waveform shaping unit 33 is used. Fig.30 The etching rate at each wafer position (X direction and Y direction) in the plasma processing apparatus using the voltage waveform shaping unit 33 and the plasma processing apparatus not using the voltage waveform shaping unit 33 is shown in the figure. As shown in the figure, it is confirmed that the etching rate becomes 0.44 times that of the case where the voltage waveform shaping unit 33 is not used by using the voltage waveform shaping unit 33. Since the temperature of the electrostatic chuck in this experiment is very low, which is below 30°C, the etching of ion energy is dominant compared to O radicals, and the reduction in etching rate caused by using the voltage waveform shaping unit 33 is an effect caused by the reduction in ion energy.

[0252] Next, in the case where the voltage waveform shaping unit 33 is used Fig.30 In a plasma processing apparatus using the voltage waveform shaping unit 33 and a plasma processing apparatus not using the voltage waveform shaping unit 33, the high frequency power was changed to 100 W, 300 W, 500 W, and 800 W, and the electron density in the X direction and the Y direction at the middle height position between the shower head 234 as the upper electrode and the substrate mounting table 216 as the lower electrode was obtained. Fig.33 Indicates the result. Fig.33 1 is a graph showing the relationship between the high frequency power at this time and the average value of the electron density at each position in the X direction and the Y direction. As shown in this graph, it is confirmed that the electron density (plasma density) does not change significantly regardless of whether the voltage waveform shaping unit 33 is used or not.

[0253] From the above results, it was confirmed that by using the voltage waveform shaping unit 33, it is possible to utilize Ar / O 2 mixed plasma to reduce only the ion energy without greatly changing the electron density, thereby enabling plasma etching with good controllability.

[0254] In this embodiment, plasma is also generated near the shower head 234 as the upper electrode by exciting plasma with the voltage waveform shaping unit 33. Therefore, the released gas reliably passes through the high-density plasma region, so that plasma or radicalization can be achieved efficiently.

[0255] In this embodiment, as an element that selectively flows current to the ground side when a positive voltage is applied, a switch element may be used instead of a diode as in the second embodiment. In addition, as a grounding circuit, not only elements that selectively flow current to the ground side when a positive voltage is applied, such as a diode and a switch element, may be provided, but also a voltage adjustment unit such as a Zener diode, a resistor, and a power supply may be provided as in the third to fifth embodiments. Thus, the ion energy can be controlled, the film forming property can be controlled, and in particular, the selective film forming property can be controlled, and the controllability of plasma etching can be further improved.

[0256] <Other applications>

[0257] Although the embodiments have been described above, the embodiments disclosed herein are illustrative in all aspects and are not restrictive. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0258] For example, in the above embodiment, an example of using a shower head that introduces gas between the upper electrode and the lower electrode as the upper electrode is cited, but the gas introduction part and the upper electrode may be provided separately. In addition, the device of the above embodiment is only an example, and any capacitively coupled plasma processing device that applies high-frequency electric power to the upper electrode and grounds the lower electrode can be applied. In addition, a semiconductor wafer is exemplified as a substrate, but it is not limited to a semiconductor wafer, and may also be a FPD (flat panel display) substrate represented by a LCD (liquid crystal display) substrate, a ceramic substrate, or other substrates.

Claims

1. A plasma processing device for performing plasma processing on a substrate, characterized in that: include: Handling containers; A substrate mounting table disposed in the processing container and capable of mounting a substrate; A grounded lower electrode included in the substrate mounting table; an upper electrode disposed opposite to the lower electrode; a gas supply unit for supplying a processing gas between the upper electrode and the substrate mounting table; a high-frequency power source for applying high-frequency electric power to the upper electrode to generate plasma of the processing gas; and a voltage waveform shaping unit disposed between the high-frequency power source and the upper electrode, and shaping the voltage waveform of the high-frequency power source so as to suppress a positive voltage in the high-frequency voltage applied to the upper electrode; The voltage waveform shaping unit includes a capacitor provided on a power supply line of the high-frequency power source.

2. The plasma processing device according to claim 1, wherein: The voltage waveform shaping unit further includes a grounding circuit that branches from the downstream side of the capacitor of the power supply line and is grounded via a diode.

3. The plasma processing apparatus according to claim 1, wherein: The voltage waveform shaping unit further includes a grounding circuit branched from the downstream side of the capacitor of the power supply line and grounded via a switching element, wherein the switching element is turned on / off to selectively allow current to flow to the ground side when a positive voltage is applied to the upper electrode.

4. The plasma processing device according to claim 2 or 3, characterized in that: The ground circuit further includes a voltage adjustment unit that adjusts a voltage applied to the upper electrode.

5. The plasma processing device according to claim 4, characterized in that: The voltage adjustment unit includes a Zener diode.

6. The plasma processing apparatus according to claim 5, wherein: The grounding circuit includes: a plurality of grounding lines having different Zener voltages; and a switch capable of switching to any of the plurality of lines.

7. The plasma processing apparatus according to claim 4, wherein: The voltage adjustment unit includes a resistor.

8. The plasma processing apparatus according to claim 7, wherein: The resistor is a variable resistor.

9. The plasma processing apparatus according to claim 4, wherein: The voltage regulating unit includes a power supply.

10. The plasma processing apparatus according to claim 9, wherein: The power supply is a variable power supply.

11. The plasma processing apparatus according to any one of claims 1 to 3, characterized in that: The gas supply unit includes a shower head that releases the processing gas toward the substrate, and the shower head includes the upper electrode.

12. The plasma processing apparatus according to any one of claims 1 to 3, characterized in that: The process gas contains TiCl4, H2 and Ar, The plasma treatment is a treatment for forming a Ti film on the surface of the substrate.

13. The plasma processing apparatus according to claim 12, wherein: The substrate has a first material portion with relatively small bonding energy and a second material portion with relatively large bonding energy on the surface, and a Ti film is selectively formed on the first material portion.

14. The plasma processing apparatus according to claim 13, wherein: The first material portion is Si or SiGe.

15. The plasma processing apparatus according to claim 13, wherein: The second material portion is SiN or SiO2.

16. The plasma processing apparatus according to claim 12, wherein: The high-frequency power source is a high-frequency pulse power source that supplies pulsed high-frequency electric power.

17. The plasma processing apparatus according to any one of claims 1 to 3, characterized in that: The processing gas contains Ar and O2, The plasma treatment is an etching treatment for performing plasma etching on a surface portion of the substrate.

18. A plasma processing method, using the plasma processing apparatus according to any one of claims 1 to 17 to perform plasma processing on a substrate, the plasma processing method comprising: A step of placing a substrate on the substrate placing table; A step of supplying a processing gas between the upper electrode and the substrate mounting table; A step of supplying high-frequency electric power from the high-frequency power supply to the upper electrode to generate plasma; and The step of plasma treating the substrate with the plasma.

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