Plasma processing apparatus and plasma processing method

Abstract

To facilitate plasma ignition to improve the generation efficiency of radicals.SOLUTION: Provided is a plasma processing device which includes: a chamber; a mounting table provided in the chamber; a microwave transmission window provided on the wall surface of the chamber; a microwave supply part for supplying a microwave into the chamber via the microwave transmission window; a shower plate which partitions the inside of the chamber into a plasma generating space which is a region where the microwave transmission window is arranged and a processing space which is a region where the mounting table is arranged; and a protruding part which protrudes from the shower plate into the plasma generating space and at least partially contains a conductor.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, the plasma processing apparatus of Patent Document 1 has a plurality of microwave radiation mechanisms arranged on the ceiling wall of a chamber, and a shower plate made of a conductive material set to ground potential below the plurality of microwave radiation mechanisms. When microwaves are radiated from the microwave radiation mechanism, the shower plate confines surface waves formed directly below the microwave radiation surface in a space surrounded by the microwave radiation surface and the shower plate, which is a high electric field region, and maintains high power absorption efficiency of plasma generated in the space.

[0003] It is important to use plasma to form films in order to obtain high-quality films at low temperatures. In recent years, the trend toward thinner films has progressed, and plasma ALD (Atomic Layer Deposition) film formation has been adopted. While the use of plasma allows high-quality thin films to be obtained at low temperatures, electrical and physical damage to the film can be an issue. To solve this problem, film formation using the ALD method using a remote source has been proposed. Such remote sources often use high-frequency waves (high-frequency waves with frequencies lower than the microwave band (300 MHz to 3 THz)) that are easy to operate using the ALD method during film formation, but it is known that the higher the frequency, such as in the microwave band, the higher the radical generation efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-33749 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can facilitate plasma ignition and improve the efficiency of radical generation. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a plasma processing apparatus having a chamber, a mounting table provided within the chamber, a microwave-transparent window provided on a wall of the chamber, a microwave supply unit that supplies microwaves into the chamber through the microwave-transparent window, a shower plate that divides the interior of the chamber into a plasma generation space which is an area where the microwave-transparent window is located, and a processing space which is an area where the mounting table is located, and a protrusion that protrudes from the shower plate into the plasma generation space and includes a conductor at least in part. Effect of the Invention

[0007] According to one aspect, plasma ignition can be facilitated and radical generation efficiency can be improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a plasma processing apparatus according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of the microwave plasma source shown in FIG. [Diagram 3] A plan view of the microwave transparent window and shower plate taken from the AA plane shown in Figure 1. [Figure 4] FIG. 4 is a cross-sectional view showing an example of a protrusion according to the embodiment. [Diagram 5] 11 is a graph showing an example of the relationship between a plasma potential and a floating potential. [Figure 6] 5A and 5B are diagrams for explaining the relationship between the arrangement of protrusions and plasma electron density. [Figure 7] FIG. 11 is a cross-sectional view showing a first modified example of a protrusion according to the embodiment. [Figure 8] FIG. 11 is a cross-sectional view showing a second modified example of the protrusion according to the embodiment. [Figure 9]3 is a flowchart showing a plasma processing method according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0010] [Plasma processing equipment] First, a plasma processing apparatus 100 according to an embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a cross-sectional view showing the plasma processing apparatus according to an embodiment. Fig. 2 is a block diagram showing the configuration of a microwave plasma source used in the plasma processing apparatus of Fig. 1. Fig. 3 is a plan view of a microwave transmission window and a shower plate viewed from the AA plane shown in Fig. 1.

[0011] The plasma processing apparatus 100 generates surface wave plasma using microwaves and performs a predetermined plasma processing on a wafer. The plasma processing is exemplified by a film forming processing or an etching processing.

[0012] The plasma processing apparatus 100 has an airtight, generally cylindrical, grounded chamber 1 made of a metal material such as aluminum or stainless steel, and a microwave plasma source 2 for forming a surface wave plasma by introducing microwaves into the chamber 1. An opening is formed in the upper part of the chamber 1, and the microwave plasma source 2 is provided from the opening toward the inside of the chamber 1 via a shower plate 151.

[0013] The plasma processing apparatus 100 has a control unit 3 equipped with a microprocessor. The control unit (control device) 3 may be a computer having a processor and a memory. The control unit 3 includes an arithmetic unit, a storage unit, an input device, a display device, a signal input / output interface, and the like. The control unit 3 controls each part of the plasma processing apparatus 100 including the microwave plasma source 2. In the control unit 3, an operator can use the input device to input commands and the like to manage the plasma processing apparatus 100. In addition, the control unit 3 can visualize and display the operating status of the plasma processing apparatus 100 using the display device. Furthermore, a control program and recipe data are stored in the memory. The control program is executed by the processor of the control unit 3 to execute various processes in the plasma processing apparatus 100. The processor executes the control program and controls each part of the plasma processing apparatus 100, so that various processes, for example, the plasma processing method of the present disclosure, are executed in the plasma processing apparatus 100 according to the recipe data.

[0014] A mounting table 11 is provided within the chamber 1. The mounting table 11 horizontally supports a semiconductor wafer (hereinafter, referred to as a wafer W), which is an example of a substrate. The mounting table 11 is supported by a cylindrical support member 12 that is erected via an insulating member 12a in the center of the bottom of the chamber 1. Examples of materials that may be used to form the mounting table 11 and the support member 12 include metals such as aluminum whose surfaces have been anodized (anodized), and insulating members (ceramics, etc.) having high-frequency electrodes inside.

[0015] Although not shown, the mounting table 11 is provided with an electrostatic chuck for electrostatically attracting the wafer W, a temperature control mechanism, a gas flow path for supplying a gas for heat transfer to the back surface of the wafer W, and lift pins for lifting and lowering to transport the wafer W. Furthermore, a high frequency bias power supply 14 is electrically connected to the mounting table 11 via a matching device 13. When high frequency power is supplied from the high frequency bias power supply 14 to the mounting table 11, ions in the plasma are attracted to the wafer W side. Note that the high frequency bias power supply 14 may not be provided depending on the characteristics of the plasma processing.

[0016] An exhaust pipe 15 is connected to the bottom of the chamber 1, and an exhaust device 16 including a vacuum pump is connected to the exhaust pipe 15. The inside of the chamber 1 is evacuated by operating the exhaust device 16, and thus the inside of the chamber 1 can be quickly depressurized to a predetermined vacuum level. A side wall of the chamber 1 is provided with a load / unload port 17 for loading and unloading the wafer W, and a gate valve 18 for opening and closing the load / unload port 17.

[0017] The microwave plasma source 2 has a microwave output unit 30, a microwave supply unit 40, and a microwave radiation plate 50. The microwave output unit 30 outputs microwaves by distributing them to multiple paths. The microwave supply unit 40 transmits the microwaves output from the microwave output unit 30 and radiates the microwaves into the chamber 1.

[0018] The microwave radiation plate 50 constitutes the ceiling wall of the chamber 1. The microwave radiation plate 50 has microwave transmission windows 44a to 44g (see FIG. 3) provided on the ceiling wall surface of the chamber 1, and the lower surfaces of the microwave transmission windows 44a to 44g serve as microwave radiation surfaces. The microwave transmission windows 44a to 44g are also collectively referred to as microwave transmission windows 44. Three of the seven microwave transmission windows 44, namely, microwave transmission windows 44a, 44b, and 44e, are shown in FIG. 1. The microwave supply unit 40 supplies microwaves into the chamber 1 through the microwave transmission windows 44.

[0019] The shower plate 151 is provided directly below the microwave transparent window 44 so as to face the microwave transparent window 44. The shower plate 151 is made of a conductive material and has a plurality of through holes 151a, and is supported by the side wall of the chamber 1 and is grounded. The shower plate 151 divides the inside of the chamber 1 into a plasma generation space U1, which is an area on the microwave transparent window 44 side, and a processing space U2, which is an area on the mounting table 11 side.

[0020] The microwave radiation plate 50 is provided with a first gas inlet 21 having a shower structure. A first gas supply source 22 is connected to the first gas inlet 21 via a gas supply pipe 111. A first gas, such as a gas for plasma generation, for example, Ar gas, or a gas to be decomposed with high energy, for example, O2 gas or N2 gas, is supplied from the first gas supply source 22 to the plasma generating space U1 via the first gas inlet 21.

[0021] A second gas inlet 23 having an annular shape is provided on the side wall of the chamber 1 below the shower plate 151 and above the mounting table 11. A second gas, such as a silane (SiH4) gas or a C5F8 gas, which is a process gas that is to be supplied without being decomposed as compared to the first gas during plasma processing such as film formation processing or etching processing, is supplied to the second gas inlet 23 from a second gas supply source 25. As the gas supplied from the first gas supply source 22 and the second gas supply source 25, various gases can be used according to the content of the plasma processing.

[0022] Next, a detailed structure of the microwave plasma source 2 will be described. As described above, the microwave plasma source 2 has the microwave output unit 30, the microwave supply unit 40, and the microwave radiation plate 50. As shown in Fig. 2, the microwave output unit 30 has a microwave power supply 31, a microwave oscillator 32, an amplifier 33 that amplifies the oscillated microwave, and a distributor 34 that distributes the amplified microwave into multiple parts.

[0023] The microwave oscillator 32 oscillates a microwave of a predetermined frequency, for example, using a PLL. The distributor 34 distributes the microwave amplified by the amplifier 33 while matching the impedance between the input side and the output side so as to minimize microwave loss. Various frequencies in the range from 700 MHz to 3 GHz can be used as the microwave frequency.

[0024] 1 and 2, the microwave supply unit 40 has a plurality of amplifier units 42 that mainly amplify the microwaves distributed by the distributor 34, and a plurality of microwave radiation mechanisms 43 provided corresponding to the amplifier units 42. The microwave supply unit 40 has seven amplifier units 42 and seven microwave radiation mechanisms 43. The seven microwave radiation mechanisms 43 are provided on a circular microwave radiation plate 50, with six arranged circumferentially on the outer periphery and one at the center. The microwaves propagated through the seven microwave radiation mechanisms 43 are radiated from seven microwave transparent windows 44 toward the inside of the chamber 1.

[0025] Fig. 3 is a plan view of the microwave-transmitting windows and the shower plate taken from the AA plane shown in Fig. 1, and does not show the main body 120. As shown in Fig. 3, microwave-transmitting windows 44 are provided at the center of the ceiling wall surface of chamber 1 and at the outer periphery surrounding this center, and consist of one central microwave-transmitting window 44a and six outer periphery microwave-transmitting windows 44b to 44g.

[0026] 2, the amplifier unit 42 of the microwave supply unit 40 amplifies the microwaves distributed by the distributor 34 and guides the amplified microwaves to each microwave radiation mechanism 43. The amplifier unit 42 has a phase shifter 46, a variable gain amplifier 47, a main amplifier 48, and an isolator 49.

[0027] The phase shifter 46 has a function of changing the phase of the microwave, and modulates the radiation characteristics by this phase control. For example, the directivity is controlled by adjusting the phase for each microwave radiation mechanism 43, and the plasma distribution is changed. Also, a circularly polarized wave can be obtained by shifting the phase by 90° between adjacent microwave radiation mechanisms 43. The phase shifter 46 can also be used to adjust the delay characteristics between components in the amplifier and for the purpose of spatial synthesis within the microwave radiation mechanism 43. However, if such modulation of the radiation characteristics or adjustment of the delay characteristics between components in the amplifier is not required, the phase shifter 46 does not have to be provided.

[0028] The variable gain amplifier 47 is an amplifier for adjusting the power level of the microwave input to the main amplifier 48 and adjusting the plasma intensity. By changing the variable gain amplifier 47 for each microwave radiation mechanism 43, it is possible to generate a distribution in the generated plasma.

[0029] The main amplifier 48 constitutes a solid-state amplifier, and includes, for example, an input matching circuit, a semiconductor amplifying element, an output matching circuit, and a high-Q resonant circuit.

[0030] 1 and 3 and travels toward the main amplifier 48, and includes a circulator and a dummy load (coaxial terminator). The circulator guides the reflected wave to the dummy load, and the dummy load converts the reflected wave guided by the circulator into heat.

[0031] 1, the microwave radiation mechanism 43 has a tuner 60. The tuner 60 has a function of transmitting the microwaves fed from the amplifier unit 42 and matching the impedance. The tuner 60 is attached to the upper surface of the microwave radiation plate 50.

[0032] The microwave radiation plate 50 has a main body 120 made of metal. The metal constituting the main body 120 is preferably a metal with high thermal conductivity such as aluminum or copper. A slow wave material 121 and a microwave transmitting window 44 constituting part of the microwave radiation mechanism 43 are fitted into the opening of the main body 120. The slow wave material 121 and the microwave transmitting window 44 are made of a dielectric material, have a disk shape, and are provided at positions corresponding to the tuners 60. A slot S (see FIG. 3) is formed in the portion between the slow wave material 121 and the microwave transmitting window 44 in the main body 120, forming a planar slot antenna.

[0033] The slow-wave material 121 has a dielectric constant greater than that of a vacuum, and is made of, for example, quartz, ceramics, fluorine-based resin such as polytetrafluoroethylene, or polyimide-based resin. Since the wavelength of microwaves becomes longer in a vacuum, the slow-wave material 121 has the function of shortening the wavelength of microwaves and making the antenna smaller.

[0034] The microwave-transmitting window 44 is made of a dielectric material that transmits microwaves, and has the function of forming a uniform surface wave plasma in the circumferential direction. The microwave-transmitting window 44 can be made of, for example, quartz, ceramics, fluorine-based resin such as polytetrafluoroethylene, or polyimide-based resin, similar to the slow-wave material 121. The radiation surface (lower surface) of the microwave-transmitting window 44 is exposed to the plasma generation space U1 of the chamber 1 at a position recessed inward from the lower surface of the main body 120.

[0035] The slot S penetrates from the upper surface position in contact with the slow-wave material 121 to the lower surface position in contact with the microwave-transmitting window 44, and has a shape, for example, an arc shape or a circumferential shape, that achieves desired microwave radiation characteristics. The periphery of the slot S between the main body 120 and the microwave-transmitting window 44 is sealed by a seal ring (not shown), and the microwave-transmitting window 44 covers and hermetically seals the slot S, functioning as a vacuum seal.

[0036] The slot S may be a vacuum, but is preferably filled with a dielectric. By filling the slot S with a dielectric, the effective wavelength of the microwave becomes shorter and the thickness of the slot can be made thinner. Examples of the dielectric that can be used to fill the slot S include quartz, ceramics, fluorine-based resins such as polytetrafluoroethylene, and polyimide-based resins.

[0037] The microwaves transmitted as TEM waves from the tuner 60 are introduced into the microwave radiation plate 50, and after passing through the slow-wave material 121, are transmitted to the slots S of the slot antenna and are mode-converted into TE waves. The microwaves are further radiated into the chamber 1 through the microwave-transmitting window 44, and a surface wave is formed on the surface of the microwave-transmitting window 44. The first gas introduced into the chamber 1 from the first gas introduction part 21 is turned into plasma by this surface wave, and a surface wave plasma is generated in the space of the chamber 1. Therefore, the lower surface of the microwave-transmitting window 44 becomes the microwave radiation surface.

[0038] The electric field strength in the chamber 1 when microwaves are radiated from the microwave radiating surface is greatest at the lower surface of the microwave transparent window 44, which is the microwave radiating surface, and decreases rapidly with increasing distance from the microwave radiating surface.

[0039] The shower plate 151 provided directly below the microwave radiation plate 50 is disposed in such a high electric field forming region. The microwave radiation plate 50 has an outer peripheral wall that forms part of the side wall of the chamber 1 extending downward around the periphery of the lower surface including the microwave radiation surface, and the shower plate 151 is attached between the outer peripheral wall of the microwave radiation plate 50 and the side wall of the chamber 1. The microwave radiation plate 50 and the shower plate 151 form a plasma generation space U1. When microwaves are radiated from the microwave radiation mechanism 43, the plasma generation space U1 becomes a high electric field region, and plasma is generated in the plasma generation space U1.

[0040] The shower plate 151 is set to a ground potential. The shower plate 151 has a function of confining a surface wave formed directly below the microwave radiation surface when microwaves are radiated from the microwave radiation surface of the microwave transmitting window 44 in a plasma generation space U1 that is a high electric field region, thereby maintaining high power absorption efficiency of the plasma.

[0041] In the present disclosure, the protrusion 24 is provided corresponding to the microwave transmission window 44a at the center. The protrusion 24 protrudes from the upper surface of the shower plate 151 toward approximately the center of the microwave transmission window 44a at the center into the plasma generation space U1, and at least a portion of the protrusion 24 includes a conductor. The protrusion 24 functions as a plasma ignition source. The configuration and function of the protrusion 24 will be described later.

[0042] This makes it easier for a stable discharge to occur in the plasma generating space U1, making it difficult for abnormal discharge to occur, and improving the ignition properties of the plasma. Metals with good electrical conductivity, such as aluminum and copper, can be suitably used as the conductive material constituting the shower plate 151. The thickness of the shower plate 151 is preferably about 10 to 30 mm, and the diameter of the through holes 151a of the shower plate 151 is preferably about 3 to 5 mm.

[0043] In order for the shower plate 151 to effectively exhibit the ion shielding function, the distance from the microwave emitting surface to the upper surface of the shower plate 151 is preferably 13 mm to 28 mm, and more preferably 18 mm to 28 mm.

[0044] The plasma generating space U1 is surrounded by the microwave radiation plate 50 and the shower plate 151, but there is a possibility that radicals in the plasma may disappear due to the metal parts on the side and bottom of the plasma generating space U1. In order to prevent the disappearance of radicals, it is preferable to cover the inner side of the outer peripheral wall of the microwave radiation plate 50 corresponding to the chamber side of the plasma generating space U1 with an insulating material, and to cover the upper surface of the shower plate 151 constituting the lower surface of the plasma generating space U1 with an insulating material.

[0045] [Protruding part (plasma ignition source)] In the plasma processing apparatus 100 having such a configuration, a microwave supply unit 40 having seven microwave transmission windows 44 of microwave radiation mechanisms 43 is mounted, and a shower plate 151 is disposed between the microwave transmission windows 44 and the mounting table 11. By providing a protrusion 24 at a position facing the microwave transmission window 44a in the center, the protrusion 24 is made to function as a plasma ignition source, and the plasma ignition performance can be improved.

[0046] The configuration and function of the protrusion 24 will be described with reference to Figs. 1 and 4. In plasma ignition using microwaves, the discharge electric field E bd The ignition performance is determined by the above.

[0047]

number

[0048] In contrast, in a parallel plate type plasma processing apparatus, the discharge voltage V V is calculated according to the formula (2) according to Paschen's law by discharging the electric current between the lower electrode and the upper electrode. bd The ignition performance is determined by the above.

[0049]

number

[0050] In formula (1), D and K are coefficients determined by the type of gas, p is the pressure in the chamber, and f is the frequency of the electromagnetic waves. m is a constant (approximately 0.5) determined by the type of gas. In formula (2), A and B are coefficients determined by the type of gas, p is the pressure in the chamber, d is the distance between the lower electrode and the upper electrode, and γ se is the secondary electron emission coefficient. The secondary electron emission coefficient is determined by the materials and surface conditions of the lower and upper electrodes.

[0051] In other words, Paschen's law does not hold for plasma ignition in the microwave plasma source 2. Therefore, in the microwave plasma source 2, the discharge voltage V bd In the microwave plasma source 2, the discharge electric field E shown in formula (1) is not determined by bd The stronger the pressure, the easier it will be to ignite.

[0052] Therefore, the protrusion 24 has a shape and arrangement that is easy to ignite specific to microwaves and VHF waves of 150 MHz or more, and makes it easy to ignite plasma in the plasma generating space U1. Specifically, the protrusion 24 protrudes from the shower plate 151 in the plasma generating space U1 and is provided away from the microwave transmitting window 44a. The protrusion 24 protrudes generally toward the center of the microwave transmitting window 44a.

[0053] When microwaves are radiated from the microwave radiation surface of the microwave transmission window 44 into the plasma generating space U1, the radiated microwaves are reflected by the conductor of the protruding portion 24 protruding from the opposing surface, and the microwaves (reflected waves) return to the microwave transmission window 44a side. Then, a standing wave is generated between the incident microwave wave output from the microwave transmission window 44 and the reflected wave reflected by the protruding portion 24. The electric field strength in the plasma generating space U1 when the microwaves are radiated is the highest at the lower surface position of the microwave transmission window 44, which is the microwave radiation surface. In addition, since the gap in the plasma generating space U1 is narrow, a high electric field is generated between the protruding portion 24 in the plasma generating space U1 and the microwave transmission window 44a, making it easy to ignite the plasma. On the other hand, after the plasma is ignited, the electric field between the protruding portion 24 in the plasma generating space U1 and the microwave transmission window 44a does not become high.

[0054] The protrusion 24 thus functioning as a plasma ignition source is a conductor or a dielectric with a conductor embedded therein. One example of the protrusion 24 may have a conductive rod-shaped member, for example, with a tip shaped like the tip of a mushroom (with a cross section of the tip being approximately trapezoidal). The entire protrusion 24 or the tip may be covered with a dielectric. For example, a portion of the protrusion 24 adjacent to the microwave-transmitting window 44 may be formed of a dielectric, and the conductor may be adjacent to the microwave-transmitting window 44 via the dielectric.

[0055] 4 is a cross-sectional view showing an example of the protrusion 24 according to the embodiment. In FIG. 4(a), the protrusion 24 has a conductive rod-shaped member 24b (including the tip 24a), and the surface thereof is coated with a dielectric material 24c such as ceramics. The internal rod-shaped member 24b has the same potential as the shower plate 151, and is at the ground potential. The dielectric material 24c may be omitted.

[0056] As shown in Fig. 4(b), only the tip 24a of the conductive rod-shaped member 24b of the protrusion 24 may be coated with a dielectric material 24c. In Fig. 4(b), an insulating member 24d is sandwiched between the shower plate 151 and the rod-shaped member 24b to set the rod-shaped member 24b to a floating potential.

[0057] In FIG. 4(c), a rod-shaped member 24b (including a tip portion 24a) itself is made of a dielectric material such as ceramics, and a conductive electrode 24e that functions as a passive ignition source is disposed inside the rod-shaped member 24b.

[0058] The protrusion 24 is a passive ignition source, and no voltage is applied to it. The protrusion 24 needs to have an electrode (conductor) for reflecting microwaves. Therefore, the protrusion 24 is not limited to the form shown in Figs. 4(a) to 4(c), and may have an electrode (conductor) for functioning as a passive ignition source provided near the microwave transmission window 44. The conductive portion of the protrusion 24 may be at ground potential or floating potential, but a floating potential is more preferable than a ground potential. Even if the conductive portion of the protrusion 24 is at ground potential, it functions as a passive ignition source. However, in consideration of contamination, particles, and damage, it is preferable that the tip 24a (electrode, conductive portion) of the protrusion 24 is at a floating potential. The reason for this will be described with reference to Fig. 5.

[0059] Fig. 5 is a graph showing an example of the relationship between plasma potential and floating potential. The horizontal axis Z of the graph in Fig. 5 indicates the distance (Z) from the surface of the microwave-transmitting window 44 to the tip of the electrode (conductor) of the protrusion 24, and the vertical axis indicates the plasma potential and the floating potential. Line P is the plasma potential according to the distance (Z), and line f is the floating potential according to the distance (Z). Line f shows the case where the protrusion 24 is configured to have a floating potential. In this experiment, the pressure in the plasma generation space U1 was controlled to 0.5 Torr (67 Pa), and Ar gas was supplied into the plasma generation space U1 to generate plasma of Ar gas.

[0060] According to this, when the rod-shaped member of the protrusion 24 is at ground potential, the plasma potential itself becomes the incident potential that indicates the force when ions are incident on the rod-shaped member. As a result, when Z is about 10 mm, a voltage of about 17 eV is applied to the rod-shaped member. In contrast, when the rod-shaped member is at floating potential, a voltage of about 10 eV is applied to the rod-shaped member when Z is about 10 mm, and the voltage applied to the rod-shaped member can be reduced by the potential difference between the plasma potential of line P and the floating potential of line f. If the rod-shaped member is coated with ceramics, a voltage of about 10 eV causes almost no damage to the surface of the protrusion 24.

[0061] From the above, the shortest distance from the conductor located at the tip of the protrusion 24 to the radiation surface (surface) of the microwave transparent window 44 may be about 3 mm to 10 mm. However, if this shortest distance is about 5 mm to 10 mm, contamination, particles, and damage can be further suppressed, which is more preferable. Therefore, it is even more preferable if this shortest distance is about 5 mm to 10 mm.

[0062] The protrusion 24 can shorten the time to turn on the plasma. The reason for this is as follows. In a normal matching box, first, the matching position in the matching box is adjusted to the plasma ignition position. After the plasma is ignited, the matching position is mechanically moved to the next matching position (the matching position after the plasma is ignited). This mechanical movement of the matching position takes time.

[0063] In contrast, the microwave plasma source 2 is configured to be set in advance to the matching position after plasma ignition. Normally, plasma does not ignite at the matching position after plasma ignition, but the microwave plasma source 2 is configured to easily ignite plasma even at the matching position after plasma ignition by providing the protrusion 24. Therefore, it is not necessary to move the matching position after plasma ignition.

[0064] Therefore, the protrusion 24 does not require the alignment position to be moved, and the time to turn on the plasma can be shortened. This allows the gas to be replaced and plasma to be ignited quickly, making the configuration more suitable for the ALD (atomic layer deposition) process and increasing productivity. However, it can also be applied to film formation by the CVD (Chemical Vapor Deposition) method.

[0065] For example, in FIG. 1, one protrusion 24 is provided at a position facing the microwave transmission window 44a at the center. In the film formation by the CVD method, unlike the ALD method, a process of repeating plasma on and off in a short time of about several seconds is not performed. Therefore, if microwave power is supplied to the microwave transmission window 44a at the center and plasma is ignited between the microwave transmission window 44a at the center and the protrusion 24, the electrons in the plasma ignited at the center reliably ignite plasma in the vicinity of the microwave transmission windows 44b to 44g at the outer periphery. At this time, the delay time from ignition on the microwave transmission window 44a at the center to ignition on the microwave transmission windows 44b to 44g at the outer periphery is on the order of milliseconds. For example, after supplying microwave power to the microwave transmission window 44a at the center, microwave power is supplied to the microwave transmission windows 44b to 44g at the outer periphery with a delay of 1 ms to 1 s. Even if plasma ignition on the outer peripheral microwave transmission windows 44b-44g side is delayed by 1 ms to 1 s from plasma ignition on the central microwave transmission window 44a side, there is no effect on the process on the wafer W. For this reason, only one protrusion 24 may be disposed at a position facing the central microwave transmission window 44a. Furthermore, the protrusion 24 may be provided so as to face at least one of the multiple microwave transmission windows 44 consisting of the central microwave transmission window 44a and the outer peripheral microwave transmission windows 44b-44g. However, by providing seven protrusions 24 facing each of the central and outer peripheral microwave transmission windows 44a-44g, the performance of plasma ignition can be further improved.

[0066] In the ALD film formation process, the plasma is repeatedly switched on and off in a short time. Therefore, the plasma ignition may be controlled on the order of milliseconds. Therefore, if the plasma ignition occurs on the microwave transmission window 44b to 44g side on the periphery with a delay on the order of milliseconds after the plasma ignition occurs on the microwave transmission window 44a side in the center, the film formation process may be affected.

[0067] 6(b), seven protrusions 24 in total are arranged to protrude from the shower plate 151 toward each of the microwave transmitting windows 44, one at a time facing each of the microwave transmitting windows 44a to 44g. This makes it possible to turn the plasma on and off in a short time below the seven microwave transmitting windows 44. This makes it suitable for a film formation process by the ALD method, and can also be used for a film formation process by the CVD method.

[0068] The relationship between the arrangement of the protrusions 24 and the plasma electron density will be described with reference to Figures 6(a) and (b). The reference example of Figure 6(a) shows a graph of the distribution of plasma electron density Ne when there are no protrusions 24 at any of the opposing positions of the microwave transmission window 44a at the center and the microwave transmission windows 44b to 44g at the periphery. The present embodiment of Figure 6(b) shows a graph of the distribution of plasma electron density Ne when protrusions 24 are provided at all of the opposing positions of the microwave transmission window 44a at the center and the microwave transmission windows 44b to 44g at the periphery.

[0069] 6(a), the plasma generated in the plasma generation space U1 by the microwaves radiated from the seven microwave transmission windows 44 has the highest peak of plasma electron density Ne below each microwave transmission window 44, and the plasma electron density Ne has a mountain-shaped distribution. Therefore, in the reference example, there is variation in the distribution of the plasma electron density Ne in the plasma generation space U1.

[0070] 6(b), the plasma generated in the plasma generation space U1 below the seven microwave transmitting windows 44 has a doughnut shape, and the peaks of the plasma electron density Ne below each microwave transmitting window 44 are flattened. This mitigates the peak-shaped distribution of the plasma electron density Ne at low pressure, and suppresses the variation in the distribution of the plasma electron density Ne.

[0071] In addition, not only when seven protrusions 24 are provided below the seven microwave-transparent windows 44, but also when one protrusion 24 is provided in the center opposite one microwave-transparent window 44a, the mountain-shaped distribution of plasma electron density Ne at low pressure can be alleviated compared to the reference example.

[0072] [Modification of protrusion] The above-described first and second modifications of the protrusion 24 functioning as a plasma ignition source will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a diagram showing the first modification of the protrusion. Fig. 8 is a diagram showing the second modification of the protrusion.

[0073] The protruding portion 24 according to the first and second modifications is partially embedded in the shower plate 151, protrudes from the shower plate 151 so as to be close to the microwave transmission window 44, and includes a conductor at least in part. The conductor functions as an electrode. Furthermore, the protruding portion 24 according to the first and second modifications is provided with a gas hole 24j that opens toward the microwave transmission window 44, and an end face of the gas hole 24j has an expanded diameter. The gas hole 24j of the protruding portion 24 is connected to the first gas supply source 22 instead of or together with the first gas introduction part 21, and supplies the first gas from the first gas supply source 22 to the plasma generation space U1.

[0074] The protruding portion 24 of the first modification of Fig. 7 is entirely cylindrical and made of a dielectric material 24g such as alumina, AlN, or quartz. A gas hole 24j penetrating the protruding portion 24 is formed inside the protruding portion 24 according to the first modification. The gas hole 24j has a fine hole 24j1 and an expanded diameter portion 24j2 expanded from the fine hole 24j1, and an opening 24h at the tip of the gas hole 24j opens from the expanded diameter portion 24j2 toward the microwave transmission window 44. A reducing gas is supplied from the gas hole 24j.

[0075] In the protrusion 24 of the first modification, a conductor 24i is embedded in a dielectric 24g. The conductor 24i is made of a metal such as aluminum and functions as an internal electrode. The conductor 24i is donut-shaped (annular) and is embedded in the outer periphery of the enlarged diameter portion 24j2 near the end face of the gas hole 24j. The conductor 24i is covered by the dielectric 24g that forms the protrusion 24 and is not exposed to the inner wall of the gas hole 24j.

[0076] The protrusion 24 according to the second modification is formed of a conductor 24k in its entirety, and the conductor 24k is covered with a dielectric 24f such as alumina. In this case, a gas hole 24j is formed inside the protrusion 24, and the gas hole 24j has a small hole 24j1 and an expanded diameter portion 24j2, and an opening 24h at the tip of the gas hole 24j opens from the expanded diameter portion 24j2 toward the microwave transmission window 44. The sizes of the small hole 24j1 and the expanded diameter portion 24j2 of the gas hole 24j are the same in the first and second modifications, and the depth (length) of the expanded diameter portion 24j2 from the tip of the gas hole 24j is 5 mm or more. The diameter of the small hole 24j1 of the gas hole 24j is smaller than 1 mm, for example, 0.3 mm. The diameter of the expanded diameter portion 24j2 and the opening 24h is 3 mm or more and 1 / 8 or less of the surface wave wavelength λ of the microwave in the plasma. In this manner, by providing the expanded diameter portion 24j2, abnormal discharge in the gas hole 24j can be suppressed.

[0077] 7 or 8, the electric field near the tip of the conductor 24i is sufficiently low, and the distance D may be about 3 mm to 10 mm. However, a distance D of about 5 mm to 10 mm is more preferable because it can further suppress contamination, particles, and damage.

[0078] By embedding the conductor 24i in the dielectric 24g and coating the conductor 24k with the dielectric 24f, the plasma resistance of the protrusion 24 can be increased and wear and deterioration due to plasma can be suppressed. The configurations of the first and second modifications of the protrusion 24 also facilitate plasma ignition and improve the efficiency of decomposing gas. The shape of the tip of the protrusion 24 shown in Figs. 7 and 8 may be rounded by chamfering the corners.

[0079] The gas holes 24j of the protrusion 24 eject gas toward the microwave transmission window 44. Therefore, by injecting gas into an area where the energy of the electromagnetic wave is concentrated, the first gas, which is a reducing gas such as N2 gas, can be sufficiently dissociated in the plasma generation space U1. This can further improve the efficiency of gas decomposition and the efficiency of radical generation. As a result, the protrusion 24 according to the first and second modifications functions as a gas nozzle in addition to the function as a plasma ignition source.

[0080] The higher the frequency, the higher the radical generation efficiency. Therefore, according to the plasma processing apparatus 100 of the present disclosure, the radical generation efficiency can be improved by the function of microwave remote plasma having a higher frequency than general radio frequency (a frequency lower than the microwave band).

[0081] According to the plasma processing apparatus 100 of the present disclosure, in order to realize the function of microwave remote plasma, the shower plate 151 is structured to have a protrusion 24 functioning as a plasma ignition source (passive ignition source). That is, the protrusion 24 having a conductor is installed at a distance of about 5 mm directly below the center of the radiation surface of the microwave transmission windows 44, and is made to act as a plasma ignition source. According to this, the electric field under the microwave transmission window 44 can be further strengthened by installing the protrusion 24 in the region where the ignition electric field is strongest under the radiation surface of the microwave transmission window 44 that emits microwaves. This strengthened electric field enables plasma ignition at the matching position during process execution, and the process can be executed without impedance matching time. This makes it possible to provide microwave remote plasma that can switch plasma ignition on and off at high speed.

[0082] In this manner, many of the ions in the plasma generated in the plasma generation space U1 are removed when passing through the shower plate 151. This makes it possible to provide microwave remote plasma that minimizes the ions in the plasma and supplies many radicals to the processing space U2.

[0083] [Plasma treatment method] When seven protrusions 24 are installed on seven microwave-transparent windows 44, microwave power is supplied simultaneously from the radiation surfaces of the microwave-transparent windows 44 via all of the microwave radiation mechanisms 43, and plasma is ignited below each microwave-transparent window 44.

[0084] When the protrusion 24 is installed only on the microwave transmitting window 44a in the center, the plasma ignition sequence is such that plasma ignition is first performed on the microwave transmitting window 44a in the center, followed by plasma ignition on the microwave transmitting windows 44b to 44g in the outer periphery with a delay, thereby plasma igniting the entire area. A plasma processing method for the latter plasma ignition sequence will be described with reference to FIG. 9. This plasma processing method is controlled by the control unit 3 and executed by the plasma processing device 100.

[0085] First, in step S1, the control unit 3 loads the wafer W into the chamber 1 and places it on the mounting table 11. Next, in step S3, the control unit 3 supplies a first gas, such as a reducing gas that is to be decomposed with high energy, from the first gas supply source 22 and discharges it from the first gas introduction part 21 into the plasma generating space U1. When the protruding part 24 according to the modified example is used, the control unit 3 supplies the first gas from the gas hole 24j to the vicinity of the microwave transmission window 44 in the plasma generating space U1. The first gas may be supplied from the gas hole 24j and / or the first gas introduction part 21. In addition, the control unit 3 supplies a second gas, such as a silane gas that is not to be decomposed, from the second gas supply source 25 and supplies it directly to the processing space U2 from the second gas introduction part 23.

[0086] Next, in step S5, the control unit 3 radiates microwaves from the microwave transmission window 44a in the center. Next, in step S7, the control unit 3 determines whether a predetermined time has elapsed. The predetermined time is, for example, 1 ms to 1 s.

[0087] In step S7, the control unit 3 waits until a predetermined time has elapsed, and if it determines that the predetermined time has elapsed, it determines that plasma has been ignited on the side of the microwave transmitting window 44a in the center. Then, in step S9, the control unit 3 radiates microwaves from the microwave transmitting windows 44b to 44g in the outer periphery. This ensures that plasma is ignited on the sides of the microwave transmitting windows 44b to 44g in the outer periphery as well.

[0088] Next, in step S11, the control unit 3 performs a film forming process such as a silicon-containing film on the wafer W, and ends this process.

[0089] In this embodiment, in the chamber 1, a shower plate 151 at ground potential is provided in a high electric field forming region immediately below the microwave radiation plate 50 to which the microwave transmission window 44 having a microwave radiation surface is exposed. As a result, when microwaves are radiated from the microwave transmission window 44, the plasma generation space U1 formed by the microwave radiation plate 50 and the shower plate 151 becomes a high electric field region, and plasma of the first gas supplied to the plasma generation space U1 is generated. At this time, the surface wave formed immediately below the microwave radiation surface is confined in the plasma generation space U1, which is a high electric field region. Therefore, the power absorption efficiency of the plasma can be maintained high in the plasma generation space U1. Furthermore, a protrusion 24 is provided near the microwave transmission window 44 to function as a plasma ignition source. As a result, stable discharge is easily generated in the plasma generation space U1, and abnormal discharge is less likely to occur. As a result, plasma ignition can be facilitated and the radical generation efficiency can be improved.

[0090] The protrusion 24 can be configured to detect the state of the plasma as an insulating probe. In this way, a signal obtained from the insulating probe can be transmitted to a computer connected to the protrusion 24 and analyzed by the computer, thereby making it possible to monitor the plasma electron density and plasma electron temperature in the chamber 1 and analyze the state of the plasma.

[0091] In this case, a measurement window may be opened in the chamber 1 and a plasma measurement monitor (OES (Optical Emission Spectrometer), insulating probe, etc.) may be attached to detect the state of the plasma.

[0092] The plasma processing apparatus and the plasma processing method according to the presently disclosed embodiments should be considered in all respects as illustrative and not restrictive, and various modifications and improvements can be made to the embodiments without departing from the spirit and scope of the appended claims. [Explanation of symbols]

[0093] 100 Plasma treatment device 1 Chamber 2. Microwave plasma source 3. Control Unit 11 Placement table 21 First gas inlet 23 Second gas inlet 24 Protrusion 30 Microwave output section 40 Microwave supply unit 43 Microwave Radiation Mechanism 44 Microwave transparent window 50 Microwave radiation plate 151 Shower Plate U1 Plasma generation space U2 Processing space

Claims

1. A chamber; a mounting table provided in the chamber; a microwave-transmitting window provided on a wall surface of the chamber; a microwave supply unit that supplies microwaves into the chamber through the microwave transparent window; a shower plate that divides the inside of the chamber into a plasma generation space, which is an area where the microwave transmission window is arranged, and a processing space, which is an area where the mounting table is arranged; a protruding portion protruding from the shower plate into the plasma generating space and including at least a portion of a conductor; A plasma processing apparatus comprising:

2. The protrusion functions as a plasma ignition source. The plasma processing apparatus according to claim 1 .

3. a portion of the protrusion adjacent to the microwave transmitting window is formed of a dielectric material; the conductor is adjacent to the microwave-transparent window via the dielectric; 3. The plasma processing apparatus according to claim 1 or 2.

4. The protruding portion is provided with a gas hole opening toward the microwave transmission window. The plasma processing apparatus according to any one of claims 1 to 3.

5. The end surface of the gas hole is expanded in diameter. The plasma processing apparatus according to claim 4 .

6. The shortest distance from the conductor to the surface of the microwave transparent window is 3 mm to 10 mm. The plasma processing apparatus according to any one of claims 1 to 5.

7. A plurality of through holes are formed in the shower plate. The plasma processing apparatus according to any one of claims 1 to 6.

8. the microwave-transmitting windows are provided in a central portion of a wall surface of the chamber and in an outer periphery surrounding the central portion, One or more of the protrusions are provided so as to face at least one of the microwave transparent windows consisting of the microwave transparent window in the center portion and the microwave transparent window in the outer circumferential portion. The plasma processing apparatus according to any one of claims 1 to 7.

9. The protrusion is provided so as to face the microwave-transparent window in the center. The plasma processing apparatus according to claim 8 .

10. The protrusions are provided in plurality so as to face the microwave-transmitting window in the center and the microwave-transmitting window in the outer periphery, The plasma processing apparatus according to claim 8 .

11. A plasma processing method performed by the plasma processing apparatus according to any one of claims 8 to 10, comprising: (a) providing a substrate; (b) providing a gas into the chamber; (c) supplying microwave power to at least one of the plurality of microwave transparent windows to ignite a plasma; (d) after a predetermined time has elapsed since step (c), supplying microwave power to the remaining plurality of microwave transmissive windows to which microwave power has not been supplied; (e) performing a predetermined process on the substrate using the generated plasma; A plasma processing method comprising:

12. The step (c) includes providing microwave power to the central microwave transparent window; The step (d) includes supplying microwave power to the microwave-transparent window of the outer periphery. The plasma processing method according to claim 11.

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