JP2005159049A - Plasma deposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma deposition method in which a plasma forming area and a deposition area are divided, wherein the quality of a film is enhanced. <P>SOLUTION: In the plasma deposition method, an inside of a process envelope is reduced in a pressure and microwaves are supplied to a radial line slot antenna in a pulse-like form. The inside of the process envelope is reduced in a pressure down to, for example, about 4.0 Pa, and a pulse of the microwaves is set such that a duty ratio is about 50% and a repetition period is 10 to 100 kHz, for example. By doing so, an energy of a plasma to be generated is suppressed, and damages or a deterioration of a film on a substrate due to a collision of electric charge particles is suppressed. As this result, the film having the good quality is formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a plasma on a substrate.

  For example, in a manufacturing process of a semiconductor device or a liquid crystal display device, for example, a film forming process for forming a conductive film or an insulating film on the surface of a substrate is performed. For this film forming process, a plasma film forming process for forming a film on a substrate using plasma is employed.

  The plasma film forming process is usually performed by a plasma film forming apparatus, and a plasma film forming apparatus for forming a film by generating plasma by a microwave electric field is often used for the plasma processing apparatus. According to this plasma film forming apparatus, the film forming process on the substrate can be efficiently performed in a short time by the high density plasma.

  The plasma film forming apparatus includes a mounting table on which a substrate is mounted in a processing container, and a radial line slot antenna that generates microwaves in an upper part of the processing container. The processing vessel is provided with a plasma excitation gas supply unit for supplying a plasma excitation gas and a source gas supply unit for supplying a film source gas.

  When the film is formed on the substrate, the plasma excitation gas is converted into plasma by microwaves immediately below the radial line slot antenna, and the source gas is dissociated by the generated plasma. A predetermined film was deposited on the substrate by radicals or the like.

  By the way, in recent years, the above-described plasma film forming apparatus has been proposed in which a lattice-shaped shower plate for supplying a processing gas downward is provided between the radial line slot antenna and the mounting table. . In this plasma film forming apparatus, the inside of a processing vessel is divided into an upper plasma generation region where plasma is generated and a lower film formation region where a source gas is dissociated and a substrate is formed. In this way, by dividing the inside of the processing vessel into a plasma generation region and a film formation region, for example, it is possible to suppress dissociated radicals from adhering to a radial antenna and the like to attenuate microwaves, and to reduce the density of generated plasma. (For example, refer to Patent Document 1).

  However, in the above-described plasma deposition apparatus, high-density and high-energy plasma is generated in the plasma generation region, so that high-energy charged particles directly collide with the substrate on the mounting table and grow on the substrate, for example. In some cases, bonds between atoms in the film are broken or the bonds become unstable. For this reason, a damaged and deteriorated film is formed on the substrate, and the film quality may be deteriorated. In order to prevent such deterioration of the film quality on the substrate, it is conceivable to reduce the energy of charged particles colliding with the substrate by lowering the output of the microwave for plasma generation. Since the plasma density is suppressed and a film having a predetermined thickness is not formed on the substrate.

  On the other hand, in the above microwave film forming apparatus, the plasma generation region and the film formation region are separated, so that the charged particles in the plasma generation region are sufficiently diffused into the film formation region and the charged particles and the source gas are sufficiently reacted. It is necessary to let For this reason, it is conceivable to reduce the pressure in the processing vessel. However, if the diffusion of charged particles is promoted simply by lowering the pressure in the processing vessel, not only will the plasma itself be generated, but high-energy charged particles will not be generated. It will be urged to collide with the substrate, and deterioration of the film quality is inevitable.

JP 2002-299330 A

  The present invention has been made in view of the above points, and a plasma film forming method capable of forming a high-quality film in the plasma film forming apparatus in which the plasma generation region and the film formation region are separated as described above. The purpose is to provide.

  In order to achieve the above object, according to the present invention, a mounting table on which a substrate is mounted and a high-frequency supply unit that supplies a high frequency for plasma generation are arranged opposite to each other. Plasma is generated by the high frequency supplied from the high frequency supply unit in a processing vessel in which a space between the supply unit and the high frequency supply unit is separated into a plasma generation region on the high frequency supply unit side and a film formation region on the mounting table side. In the method of forming a film on the substrate on the mounting table, the plasma is generated by supplying a high frequency from the high frequency supply unit in a pulse shape with a predetermined repetition period in a state where the inside of the processing container is decompressed. It is characterized by generating.

  According to the inventor's knowledge, when a high frequency is supplied in a pulse form, a strong high frequency is intermittently supplied, so that plasma can be generated appropriately in the plasma generation region. On the other hand, since the electron temperature of the generated charged particles can be kept lower than before, when the charged particles collide with the substrate, for example, the structure in the film on the substrate is adversely affected and the film is damaged or deteriorated. Can be suppressed. Further, since the inside of the processing container is depressurized, the generated charged particles are diffused, for example, the source gas is sufficiently dissociated by the charged particles, and a desired film is efficiently formed on the substrate. At this time, even if the charged particles directly collide with the substrate, the electron temperature of the charged particles is kept low, so that damage to the film can be suppressed. Therefore, according to the present invention, a high quality film can be formed on the substrate.

  The repetition frequency of the high frequency supplied in the form of pulses is preferably in the range of 10 to 100 kHz, and the duty ratio of the high frequency is preferably in the range of 40 to 60%. Further, the inside of the processing container is preferably decompressed to 7.0 Pa or less. Note that the film formed on the substrate may be a fluorine-added carbon film.

  According to the present invention, damage and deterioration in the film on the substrate due to collision of charged particles are prevented, so that film quality can be improved.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 schematically shows a longitudinal section of a plasma film forming apparatus 1 in which a plasma film forming method according to an embodiment of the present invention is performed. The plasma film forming apparatus 1 is a CVD (chemical vapor deposition) apparatus that generates plasma using a radial line slot antenna.

  The plasma film forming apparatus 1 includes, for example, a bottomed cylindrical processing container 2 having an upper surface opened. The processing container 2 is made of, for example, an aluminum alloy. The processing container 2 is grounded. A mounting table 3 as a mounting unit for mounting the substrate W, for example, is provided at a substantially central portion of the bottom of the processing container 2.

  For example, an electrode plate 4 is built in the mounting table 3, and the electrode plate 4 is connected to a DC power source 5 provided outside the processing container 2. The DC power supply 5 can generate an electrostatic force on the surface of the mounting table 3 to electrostatically attract the substrate W onto the mounting table 3. The electrode plate 4 may be connected to a high frequency power source for bias (not shown), for example.

A dielectric window 11 made of alumina (Al ₂ O ₃ ) or quartz glass is provided in the upper opening of the processing container 2 via a sealing material 10 such as an O-ring for ensuring airtightness, for example. . The inside of the processing container 2 is closed by the dielectric window 11. A radial line slot antenna 12 as a high-frequency supply unit that supplies microwaves for plasma generation is provided on the top of the dielectric window 11.

  The radial line slot antenna 12 includes a substantially cylindrical antenna body 20 having an open bottom surface. A disc-shaped slot plate 21 in which a large number of slots are formed is provided in the opening on the lower surface of the antenna body 20. A slow phase plate 22 made of a low loss dielectric material is provided on the upper portion of the slot plate 21 in the antenna body 20. A coaxial waveguide 23 is connected to the upper surface of the antenna body 20 and communicates with a microwave oscillation device 24 that oscillates microwaves. The microwave oscillation device 24 is provided with a microwave oscillation control unit 25 that controls the oscillation of the microwave. The microwave oscillation control unit 25 can oscillate the microwave in a pulse shape with a predetermined output to the radial line slot antenna 12 with a predetermined output. Therefore, from the radial line slot antenna 12 leading to the microwave oscillator 24, a pulsed microwave of a predetermined period is compressed by the slow phase plate 22 to reduce the wavelength, and the circular polarization is generated by the slot plate 21. Thereafter, it can be supplied into the processing container 2 through the dielectric window 11.

  Between the mounting table 3 in the processing container 2 and the radial line slot antenna 12, for example, a raw material gas supply structure 30 as a substantially flat partition member is provided. The source gas supply structure 30 is formed in a circular shape whose outer shape is larger than at least the diameter of the substrate W when viewed from the plane. By this source gas supply structure 30, the inside of the processing vessel 2 is divided into a plasma generation region R1 on the radial line slot antenna 12 side and a film formation region R2 on the mounting table 3 side.

  As shown in FIG. 2, the source gas supply structure 30 is constituted by a continuous source gas supply pipe 31 arranged in a substantially lattice pattern on the same plane. The source gas supply pipe 31 has a rectangular longitudinal section when viewed from the axial direction. A large number of openings 32 are formed in the gaps between the source gas supply pipes 31. The charged particles generated in the plasma generation region R1 on the upper side of the source gas supply structure 30 can pass through the opening 32 and enter the film formation region R2 on the mounting table 3 side.

A large number of source gas supply ports 33 are formed on the lower surface of the source gas supply pipe 31 of the source gas supply structure 30 as shown in FIG. These source gas supply ports 33 are evenly arranged in the surface of the source gas supply structure 30. A gas pipe 35 communicating with a source gas supply source 34 installed outside the processing container 2 is connected to the source gas supply pipe 31. The source gas supply source 34 is filled with, for example, a fluorine-added carbon-based gas, for example, a C ₅ F ₈ gas as a source gas. The source gas introduced into the source gas supply pipe 31 from the source gas supply source 34 through the gas pipe 35 is supplied from each source gas supply port 33 toward the lower film formation region R2.

  A plasma excitation gas supply port 40 is formed on the inner peripheral surface of the processing vessel 2 located on the outer peripheral surface of the plasma generation region R1 to supply a plasma excitation gas serving as a plasma raw material. The plasma excitation gas supply ports 40 are formed at a plurality of locations along the inner peripheral surface of the processing container 2, for example. Connected to the plasma excitation gas supply port 40 is, for example, a plasma excitation gas supply pipe 42 that penetrates the side wall of the processing container 2 and communicates with a plasma excitation gas supply source 41 installed outside the processing container 2. Yes. The plasma excitation gas supply pipe 42 is provided with a valve 43 and a mass flow controller 44. With this configuration, a plasma excitation gas having a predetermined flow rate can be supplied from the side into the plasma generation region R1 in the processing chamber 2. In the present embodiment, a plasma excitation gas supply source 41 is filled with, for example, an argon (Ar) gas, which is a rare gas as a plasma excitation gas.

  Exhaust ports 50 for exhausting the atmosphere in the processing container 2 are provided on both sides of the mounting table 3 at the bottom of the processing container 2. An exhaust pipe 52 communicating with an exhaust device 51 such as a turbo molecular pump is connected to the exhaust port 50. By exhausting from the exhaust port 60, the inside of the processing container 2 can be reduced to a predetermined pressure.

  Next, a film forming method on the substrate W performed by the plasma film forming apparatus 1 configured as described above will be described. In this embodiment, a CF film used as an insulating film having a low relative dielectric constant is formed on the substrate W.

  First, the substrate W is carried into the processing container 2 and sucked and held on the mounting table 3. Subsequently, the exhaust device 51 starts exhausting the processing container 2 and the pressure in the processing container 2 is reduced to a predetermined pressure, for example, 7.0 Pa or less, preferably 4.0 Pa (30 mTorr).

When the inside of the processing chamber 2 is depressurized, argon gas, which is a plasma excitation gas, is supplied from the plasma excitation gas supply port 40 into the plasma generation region R1, and the raw material gas supply structure 30 supplies the raw material into the film formation region R2. C ₅ F ₈ gas, which is a gas, is supplied. A microwave is supplied from the radial line slot antenna 12 toward the plasma generation region R1 directly below. The supply of the microwave is intermittently performed in the form of a rectangular wave pulse as shown in FIG. 3, for example, under the control of the microwave transmission control unit 25. The pulsed microwave is supplied so that, for example, the output is 1.5 kW, the repetition period is 10 to 100 kHz, and the duty ratio is about 40 to 60%. By this microwave supply, the plasma excitation gas in the plasma generation region R1 is ionized to generate plasma.

  FIG. 4 shows, for example, the electron temperature (Te) and plasma density (Ne: charged particles) of charged particles generated in the plasma generation region R1 when a microwave is supplied in a pulse shape with a duty ratio of 50% and a repetition period of 10 kHz. It is a graph which shows the fluctuation | variation of (density). FIG. 5 is a graph showing fluctuations in the electron temperature (Te) and plasma density (Ne) of charged particles when microwaves are continuously supplied as in the prior art. As shown in FIGS. 4 and 5, the plasma density when the microwave pulse is supplied is maintained at the same level as that when the microwave is supplied continuously. In addition, when the microwave pulse supply is OFF, the electron temperature of the charged particles is temporarily reduced. Thus, when the supply of microwaves is performed in the form of pulses, the plasma density is maintained and the total electron temperature, which is the sum of the electron temperatures of all charged particles, is reduced compared to the case of continuous supply. Therefore, when microwaves are supplied in pulses, plasma with a low total electron temperature and high density can be generated in the plasma generation region R1.

The charged particles in the plasma generated in the plasma generation region R1 pass through the source gas supply structure 30 and diffuse into the film formation region R2 due to the cathode of the mounting table 3 and the low pressure in the processing vessel 2. In the film formation region R2, the C ₅ F ₈ gas supplied from the source gas supply structure 30 is dissociated by charged particles, and a fluorine-added carbon film (CF film) is formed on the substrate W by the dissociated radicals. Deposit and grow.

  Thereafter, when the CF film grows and a CF film having a predetermined thickness is formed on the substrate W, the microwave emission, the supply of the source gas, and the plasma excitation gas are stopped. A series of plasma film-forming processes are completed after being unloaded from the processing container 2.

  Next, the characteristics of the CF film formed by using the plasma film forming method described above will be verified. 6 to 8 are graphs showing the desorption intensity (degassing amount) of fluorine gas at each temperature of the CF film formed by supplying microwaves in pulses. FIG. 9 is a graph showing the desorption strength (degassing amount) of fluorine gas at each temperature of a CF film formed by continuously supplying a microwave with a constant output as in the prior art. FIG. 6 shows a case where the film is formed under the conditions that the duty ratio D of the microwave pulse is 50%, the repetition period T is 100 kHz, and the pressure P in the processing container 2 is 6.67 Pa (50 mToor). Is a case where the film is formed under the conditions that the duty ratio D is 50%, the repetition period T is 10 kHz, and the pressure P is 6.67 Pa. FIG. 8 shows a case where the film is formed with a duty ratio D of 50%, a repetition period T of 100 kHz, and a pressure P in the processing container 2 of 4.0 Pa.

  FIG. 9 shows a case where a pulsed microwave having a duty ratio D of 50% and a repetition period T of 100 kHz shown in FIG. 6 is supplied and the pressure P in the processing container 2 is reduced to 6.67 Pa. It can be confirmed that the degassing amount of fluorine gas is reduced compared to the case of continuous microwave supply. The decrease in the degassing amount means that the bonds between atoms in the CF film, for example, C—F bonding is sufficiently performed, and at this time, the increase in the relative dielectric constant of the film due to degassing is suppressed. . Further, the gas in the CF film is released during the heat treatment in the manufacturing process of the substrate W, and the CF film is suppressed from shrinking and peeling. Therefore, in the example of FIG. 6, it can be seen that a high-quality CF film having a low relative dielectric constant and suppressing shrinkage and peeling of the film is formed.

  According to FIG. 7, it can be confirmed that the degassing amount of the fluorine gas is decreased even when a microwave having a pulse repetition period T of 10 kHz is supplied. Therefore, it is considered that the same tendency can be seen over the repetition period T of the pulse from 100 kHz to 10 kHz. In these cases, a high-quality CF film is formed as compared with the case where the microwave of FIG. 9 is continuously supplied. I understand that. Further, according to FIG. 8, it can be confirmed that the degassing amount is further reduced by reducing the pressure P in the processing container 2 to 4.0 Pa. Therefore, in this case, it can be seen that a higher quality CF film is formed.

  From the above verification, it is understood that the film quality of the CF film is improved when the microwave is supplied in a pulse form from the radial line slot antenna 12 as in the film forming method described above. This is because a strong microwave is intermittently supplied, so that a sufficient amount of plasma is generated in the plasma generation region R1, and in addition, the total electron temperature in the generated plasma is low. It can be inferred that the adverse effect on the CF film due to is suppressed. According to another experiment by the inventor, it has been confirmed that the generation of plasma becomes unstable when the pulse repetition period is less than 10 kHz or the duty ratio is less than 40%. Further, it has been confirmed that when the pulse duty ratio exceeds 60%, the film quality of the CF film finally formed approaches that in the case of continuous supply of microwaves. Therefore, when the pulse repetition period is about 10 to 100 kHz and the duty ratio is about 50%, for example, 40 to 60%, an optimum CF film with a small degassing amount is formed.

  It can also be seen that the film quality of the CF film is improved by reducing the pressure inside the processing vessel 2 as in the above embodiment. It can be inferred that this is because the plasma in the plasma generation region R1 was appropriately diffused toward the film formation region R2 and the source gas in the film formation region R2 was sufficiently dissociated. In particular, when the pressure is reduced to about 4.0 Pa, the amount of degassing when the CF film is heated can be significantly reduced.

  The example of the embodiment of the present invention has been described above, but the present invention is not limited to this example and can take various forms. For example, in the above embodiment, the CF film, which is an insulating film, is formed on the substrate W. However, the present invention is also applicable to the case where other films such as other types of insulating films and electrode films are formed. it can.

  The present invention is useful when forming a high-quality film in a film forming method using plasma.

It is explanatory drawing of the longitudinal cross-section which shows the outline of a structure of the plasma film-forming apparatus concerning this Embodiment. It is a top view of a source gas supply structure. It is explanatory drawing which shows the supply waveform of a microwave. It is a graph which shows the fluctuation | variation of the electron temperature at the time of supplying a pulse-shaped microwave and a plasma density. It is a graph which shows the fluctuation | variation of the electron temperature at the time of supplying continuously the microwave of a fixed output, and a plasma density. It is the graph which showed the desorption intensity | strength of the fluorine gas in each temperature of CF film at the time of supplying a microwave with the pulse shape of 50% of duty ratios, and a repetition period of 100 kHz. It is the graph which showed the desorption intensity | strength of the fluorine gas in each temperature of CF film at the time of supplying a microwave with the pulse shape of 50% of duty ratio, and a repetition period of 10 kHz. It is the graph which showed the desorption intensity | strength of the fluorine gas in each temperature of the CF film | membrane formed on 4.0 Pa decompression conditions. It is the graph which showed the detachment | leave of the fluorine gas in each temperature of CF film | membrane at the time of supplying the microwave of a fixed output continuously.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma film-forming apparatus 2 Processing container 3 Mounting stand 12 Radial line slot antenna 30 Source gas supply structure R1 Plasma generation area | region R2 Film-forming area | region W board | substrate

Claims (5)

A mounting table on which the substrate is placed and a high-frequency supply unit that supplies a high frequency for plasma generation are arranged to face each other, and a space between the mounting table and the high-frequency supply unit is defined by the partition member through which plasma can pass. Plasma is generated by a high frequency supplied from a high frequency supply unit in a processing chamber divided into a plasma generation region on the side and a film formation region on the mounting table, and is formed on the substrate on the mounting table A method,
The plasma deposition method, wherein the plasma is generated by supplying a high frequency from the high frequency supply unit in a pulse shape with a predetermined repetition period in a state where the inside of the processing vessel is decompressed. The plasma film forming method according to claim 1, wherein a repetition period of the high frequency supplied in a pulse form is 10 to 100 kHz. 3. The plasma film forming method according to claim 1, wherein a duty ratio of the high frequency supplied in a pulse form is 40 to 60%. 4. The plasma film forming method according to claim 1, wherein the pressure in the processing container is reduced to 7.0 Pa or less. The plasma film-forming method according to claim 1, wherein the film formed on the substrate is a fluorine-added carbon film.

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