JP5374749B2 - Insulating film forming method, computer-readable storage medium, and processing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an insulating film which forms an insulating film having a thickness equivalent to that in conventional CVD and good film quality under low temperature. <P>SOLUTION: A CVD step (step S2) for depositing a silicon oxide film as an insulating film on a silicon layer by CVD, and a plasma modification step (step S4) for modifying the silicon oxide film by plasma generated under pressure conditions in the range of 6.7-267 Pa using processing gas containing rare gas and oxygen are carried out until the silicon oxide film reaches a desired film thickness. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an insulating film forming method for forming an insulating film by a CVD (Chemical Vapor Deposition) method, a computer-readable storage medium, and a processing system.

  The CVD method is widely used for the purpose of forming an insulating film such as a silicon oxide film or a high dielectric constant insulating film in the manufacturing process of various semiconductor devices. In the CVD method, a gas phase reaction is caused in a film forming raw material using energy such as heat to form an insulating film on a target object.

  When forming an insulating film by the CVD method, there are many dangling bonds in the formed insulating film (for example, silicon oxide film), and moisture and impurities derived from the film forming raw material remain. The film quality is not so good. Therefore, it is necessary to improve the film quality by annealing the insulating film formed by the CVD method at a high temperature of, for example, 700 ° C. or higher. However, since it is impossible to recombine Si—O bonds by supplying energy by heat, it is difficult to improve the basic film quality by annealing after film formation. Further, in order to enhance the modification effect by the annealing treatment, a treatment at a high temperature is required, but the annealing treatment at a high temperature leads to an increase in the thermal budget. When the thermal budget increases, it becomes difficult to control the distribution of impurities diffused in the silicon layer, which may cause an undesirable effect on the quality of the semiconductor device.

  In addition, when a glass substrate or a synthetic resin substrate is used as in a liquid crystal display or an organic EL display, for example, it is impossible to perform an annealing process at a high temperature for the modification process of the insulating film.

  For this reason, a technique for modifying the film quality at a relatively low temperature by plasma treatment of the silicon oxide film has been proposed (for example, Patent Documents 1 and 2).

WO2002 / 059956 WO2001 / 69665

  The modification process of the silicon oxide film by the plasma process described in Patent Document 1 and Patent Document 2 is an excellent technique in that a high-quality silicon oxide film can be manufactured while reducing the thermal budget. However, there is a limit to the depth at which oxygen radicals in the plasma generated by the RLSA plasma processing apparatus diffuse into the silicon oxide film. For this reason, there is a limit to the thickness of the silicon oxide film that can be modified by the methods described in Patent Document 1 and Patent Document 2, and for example, only a silicon oxide film having a thickness of 10 nm or less can be modified. For these reasons, it has been difficult to improve the film quality by plasma reforming treatment for a relatively thick insulating film exceeding the above-mentioned film thickness.

  In addition, as described above, the conventional thermal CVD method and plasma CVD method can form the insulating film with a large film thickness, but have a drawback that the film quality is poor.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for forming an insulating film that can form an insulating film having a high film quality and a high film thickness at a low temperature equivalent to that of a conventional CVD method. It is.

In order to solve the above problems, an insulating film forming method of the present invention is a CVD method in which an insulating film is formed on a silicon exposed on the surface of an object to be processed with a film thickness within a range of 2 nm to 10 nm by a CVD method. Process,
In the plasma processing apparatus that introduces microwaves into the processing chamber with a planar antenna having a plurality of holes for the insulating film, a plasma reforming process for performing a reforming process using plasma of a processing gas containing oxygen;
And an insulating film is formed by repeating the CVD step and the plasma modification treatment step.

  In the method for forming an insulating film of the present invention, the plasma reforming treatment step has a treatment pressure in a range of 6.7 Pa to 267 Pa, and a flow rate ratio of oxygen to a total flow rate of the treatment gas is 0.1%. It is preferable to be performed within the range of 30% or less.

  In the method for forming an insulating film of the present invention, it is preferable that the processing pressure in the plasma reforming process is in a range of 6.7 Pa to 67 Pa.

  In the method for forming an insulating film of the present invention, it is preferable that the processing time in one plasma reforming process is in the range of 5 seconds to 600 seconds.

  In the method for forming an insulating film of the present invention, it is preferable that the CVD process and the plasma reforming process are repeated until the total film thickness of the insulating film falls within a range of 4 nm to 1000 nm.

  In the method for forming an insulating film of the present invention, it is preferable that the CVD process and the plasma modification treatment process are repeated in a vacuum state.

  In the method for forming an insulating film of the present invention, it is preferable that a processing temperature in the plasma reforming process is in a range of 200 ° C. or more and 600 ° C. or less.

  In the insulating film forming method of the present invention, the insulating film is preferably formed by a plasma CVD method or a thermal CVD method.

In the method for forming an insulating film of the present invention, the insulating film is preferably a silicon oxide film deposited by a CVD method using dichlorosilane and N ₂ O as source gases.

The computer-readable storage medium of the present invention is a computer-readable storage medium storing a control program that runs on a computer,
In the processing system having a plurality of processing chambers for performing predetermined processing on the object to be processed at the time of execution, the control program has a thickness of 2 nm or more and 10 nm or less by a CVD method on silicon exposed on the surface of the object to be processed. In a plasma process for forming an insulating film with a film thickness within the range of and a plasma processing apparatus for introducing microwaves into the processing chamber by a planar antenna having a plurality of holes for the insulating film, plasma of a processing gas containing oxygen The processing system is controlled by a computer so that a method for forming an insulating film is repeatedly performed by performing a plasma reforming process step in which a reforming process is performed using.

The processing system of the present invention is a processing system having a plurality of processing chambers for performing different processing on an object to be processed,
A CVD process for forming an insulating film with a film thickness within a range of 2 nm or more and 10 nm or less by a CVD method on silicon exposed on the surface of an object to be processed in the first processing chamber, and the first processing chamber In a different second processing chamber, a plasma of a processing gas containing oxygen is formed by introducing microwaves into the second processing chamber by a planar antenna having a plurality of holes with respect to the insulating film. And a controller for controlling the first processing chamber and the second processing chamber so as to repeatedly perform a plasma reforming process using the plasma reforming process.

  According to the method for forming an insulating film of the present invention, a high-quality insulating film having a dense film quality and less impurities and dangling bonds is obtained by repeatedly depositing the insulating film by CVD and improving the film quality by plasma modification treatment. Can be formed in a desired thickness. Therefore, the insulating film forming method of the present invention is applied to an application that requires a relatively thick film having excellent film quality, such as a gate insulating film of a thin film transistor (TFT) element, a tunnel oxide film of a flash memory element, By applying it to an interphase insulating film or the like of a semiconductor device, a highly reliable device having excellent electrical characteristics can be manufactured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a substrate processing system in which an insulating film forming method according to an embodiment of the present invention is performed will be described with reference to FIG. FIG. 1 shows a substrate processing system 200 configured to perform various processes such as a film forming process and a reforming process on a semiconductor wafer (hereinafter simply referred to as “wafer”) W as a substrate, for example. It is a schematic block diagram. The substrate processing system 200 is configured as a cluster tool having a multi-chamber structure.

  The substrate processing system 200 has four process modules 101a, 101b, 101c, and 101d that perform various processes on the wafer W as main components, and a gate valve G1 for these process modules 101a to 101d. The connected vacuum side transfer chamber 103, the two load lock chambers 105a and 105b connected to the vacuum side transfer chamber 103 via the gate valve G2, and the gate valve for these two load lock chambers 105a and 105b And a loader unit 107 connected via G3.

  The four process modules 101a to 101d are processing apparatuses that perform processing such as CVD processing and plasma modification processing on the wafer W, for example. In the present embodiment, at least in the process modules 101a and 101c, a film forming process is performed on the wafer W by the CVD method, and the silicon oxide films formed by the film forming process are processed in the process modules 101b and 101d. It is configured to be able to perform a plasma modification process in which modification is performed by applying plasma. The combination of processing contents in the process modules 101a to 101d can be adjusted as appropriate in consideration of throughput.

  The vacuum-side transfer chamber 103 configured to be evacuated is provided with a transfer device 109 as a first substrate transfer device that transfers the wafer W to the process modules 101a to 101d and the load lock chambers 105a and 105b. ing. The transfer device 109 has a pair of transfer arm portions 111a and 111b arranged to face each other. Each of the transfer arm portions 111a and 111b is configured to bend and stretch and turn about the same rotation axis. Further, forks 113a and 113b for mounting and holding the wafer W are provided at the tips of the transfer arm portions 111a and 111b, respectively. The transfer device 109 transfers the wafer W between the process modules 101a to 101d or between the process modules 101a to 101d and the load lock chambers 105a and 105b with the wafer W placed on the forks 113a and 113b. I do.

  In the load lock chambers 105a and 105b, mounting tables 106a and 106b for mounting the wafer W are provided, respectively. The load lock chambers 105a and 105b are configured to be switched between a vacuum state and an air release state. The wafer W is transferred between the vacuum-side transfer chamber 103 and the atmosphere-side transfer chamber 119 (described later) via the loading tables 106a and 106b of the load lock chambers 105a and 105b.

  The loader unit 107 includes an atmosphere-side transfer chamber 119 provided with a transfer device 117 as a second substrate transfer device for transferring the wafer W, and three load ports LP disposed adjacent to the atmosphere-side transfer chamber 119. And an orienter 121 as a position measuring device for measuring the position of the wafer W, which is disposed adjacent to the other side surface of the atmosphere-side transfer chamber 119.

  The atmosphere-side transfer chamber 119 includes, for example, a circulation facility (not shown) that forms a clean environment by flowing down nitrogen gas or clean air, and the clean environment is maintained. The atmosphere-side transfer chamber 119 has a rectangular shape in plan view, and a guide rail 123 is provided along the longitudinal direction thereof. A conveying device 117 is supported on the guide rail 123 so as to be slidable. That is, the transport device 117 is configured to be movable in the X direction along the guide rail 123 by a drive mechanism (not shown). The transfer device 117 has a pair of transfer arm portions 125a and 125b arranged in two upper and lower stages. Each of the transfer arm portions 125a and 125b is configured to be able to bend and stretch and turn. Forks 127a and 127b as holding members for mounting and holding the wafer W are provided at the tips of the transfer arm portions 125a and 125b, respectively. The transfer device 117 transfers the wafer W between the wafer cassette CR of the load port LP, the load lock chambers 105a and 105b, and the orienter 121 in a state where the wafer W is placed on the forks 127a and 127b. Do.

  The load port LP can mount the wafer cassette CR. The wafer cassette CR is configured so that a plurality of wafers W can be placed and accommodated in multiple stages at the same interval.

  The orienter 121 includes a rotating plate 133 that is rotated by a drive motor (not shown) and an optical sensor 135 that is provided at the outer peripheral position of the rotating plate 133 and detects the peripheral edge of the wafer W.

  In the substrate processing system 200 having the above configuration, the CVD process and the plasma modification process are performed on the wafer W in the following procedure. First, using the fork 127 of the transfer device 117 in the atmosphere-side transfer chamber 119, one wafer W is taken out from the wafer cassette CR of the load port LP, aligned with the orienter 121, and then loaded into the load lock chamber 105 a (or 105 b). ). The gate valve G3 is closed while the wafer W is placed on the placement table 106a (or 106b), and the inside of the load lock chamber 105a (or 105b) is evacuated to a vacuum state. Thereafter, the gate valve G2 is opened, and the wafer W is carried out of the load lock chamber 105a (or 105b) by the fork 113 of the transfer device 109 in the vacuum side transfer chamber 103, and is transferred into any of the process modules 101a to 101d. .

  In the present embodiment, for example, the process modules 101a and 101c are configured such that a CVD process for forming an insulating film such as a silicon oxide film on the wafer W can be performed. Further, the process modules 101b and 101d are configured such that after the insulating film is formed, a plasma reforming process for modifying the insulating film can be performed. Accordingly, the wafer W carried out of the load lock chamber 105a (or 105b) by the transfer device 109 is first loaded into one of the process modules 101a and 101c. Then, after the gate valve G1 is closed, the CVD process is performed on the wafer W. An insulating film is deposited on the silicon of the wafer W by the CVD process.

  Next, the gate valve G1 is opened, and the wafer W on which the insulating film is formed by the CVD method is transferred from the process module 101a (or 101c) to the process module 101b (or 101d) by the transfer device 109 while being in a vacuum state. Then, after the gate valve G1 is closed, a plasma reforming process is performed on the insulating film. Next, the gate valve G1 of the process module 101b (or 101d) is opened, and the plasma-modified wafer W is taken out by the transfer device 109 and loaded into the load lock chamber 105a (or 105b). Then, the processed wafer W is stored in the wafer cassette CR of the load port LP in the reverse procedure to the above, and the processing for one wafer W in the substrate processing system 200 is completed. In addition, as long as the arrangement | positioning of each processing apparatus in the substrate processing system 200 is an arrangement | positioning which can process efficiently, what kind of arrangement | positioning structure may be sufficient as it. Furthermore, the number of process modules in the substrate processing system 200 is not limited to four, and may be five or more.

  FIG. 2 is a cross-sectional view schematically showing a schematic configuration of the plasma processing apparatus 100 that can be used for the plasma reforming process performed in the substrate processing system 200. FIG. 3 is a plan view showing a planar antenna of the plasma processing apparatus 100 of FIG.

The plasma processing apparatus 100 constituting the process modules 101b and 101d is configured by introducing microwaves into a processing chamber using a planar antenna having a plurality of slot-shaped holes, in particular, an RLSA (Radial Line Slot Antenna). It is configured as an RLSA microwave plasma processing apparatus that can generate microwave-excited plasma with high density and low electron temperature. In the plasma processing apparatus 100, processing with plasma having a plasma density of 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ and a low electron temperature of 0.7 to 2 eV is possible. Therefore, the plasma processing apparatus 100 can be suitably used for the purpose of modifying a silicon oxide film (for example, SiO ₂ film) formed by a CVD method in the manufacturing process of various semiconductor devices.

  The plasma processing apparatus 100 includes, as main components, an airtight chamber (processing chamber) 1, a gas supply mechanism 18 for supplying gas into the chamber 1, and an exhaust mechanism for evacuating the chamber 1 under reduced pressure. An exhaust device 24, a microwave introduction mechanism 27 for introducing a microwave into the chamber 1, and a control unit 50 for controlling each component of the plasma processing apparatus 100. Yes.

  The chamber 1 is formed of a substantially cylindrical container that is grounded. The chamber 1 may be formed by a rectangular tube-shaped container. The chamber 1 has a bottom wall 1a and a side wall 1b made of a material such as aluminum.

  Inside the chamber 1 is provided a mounting table 2 for horizontally supporting a wafer W as an object to be processed. The mounting table 2 is made of a material having high thermal conductivity, such as ceramics such as AlN. The mounting table 2 is supported by a cylindrical support member 3 extending upward from the center of the bottom of the exhaust chamber 11. The support member 3 is made of ceramics such as AlN, for example.

Further, the mounting table 2 is provided with a cover ring 4 that covers the outer edge portion thereof and guides the wafer W. The cover ring 4 is an annular member made of a material such as quartz, AlN, Al ₂ O ₃ , or SiN.

  In addition, a resistance heating type heater 5 as a temperature adjusting mechanism is embedded in the mounting table 2. The heater 5 is heated by the heater power supply 5a to heat the mounting table 2 and uniformly heats the wafer W, which is a substrate to be processed, with the heat.

  The mounting table 2 is provided with a thermocouple (TC) 6. By measuring the temperature with the thermocouple 6, the heating temperature of the wafer W can be controlled in a range from room temperature to 900 ° C., for example.

  The mounting table 2 is provided with wafer support pins (not shown) for supporting the wafer W and raising and lowering it. Each wafer support pin is provided so as to protrude and retract with respect to the surface of the mounting table 2.

  A cylindrical liner 7 made of quartz is provided on the inner periphery of the chamber 1. In addition, a quartz baffle plate 8 having a large number of exhaust holes 8 a is annularly provided on the outer peripheral side of the mounting table 2 in order to uniformly exhaust the inside of the chamber 1. The baffle plate 8 is supported by a plurality of support columns 9.

  A circular opening 10 is formed at a substantially central portion of the bottom wall 1 a of the chamber 1. An exhaust chamber 11 that communicates with the opening 10 and protrudes downward is provided on the bottom wall 1a. An exhaust pipe 12 is connected to the exhaust chamber 11 and is connected to an exhaust device 24 via the exhaust pipe 12.

  An annular upper plate 13 is joined to the upper portion of the chamber 1. The inner periphery of the upper plate 13 protrudes toward the inner side (chamber inner space) to form an annular support portion 13a.

  An annular gas inlet 15 is provided on the side wall 1 b of the chamber 1. The gas introduction unit 15 is connected to a gas supply mechanism 18 that supplies an oxygen-containing gas and a plasma excitation gas. The gas introduction part 15 may be provided in a nozzle shape or a shower shape.

  Further, on the side wall 1b of the chamber 1, a loading / unloading port 16 for loading / unloading the wafer W between the plasma processing apparatus 100 and the transfer chamber 103 (see FIG. 1) adjacent thereto is provided, and this loading / unloading port. A gate valve G1 for opening and closing 16 is provided.

  The gas supply mechanism 18 includes, for example, an inert gas supply source 19a, an oxygen-containing gas supply source 19b, and a hydrogen gas supply source 19c. The gas supply mechanism 18 includes, as gas supply sources (not shown) other than the above, for example, a purge gas supply source used when replacing the atmosphere in the chamber 1, a cleaning gas supply source used when cleaning the inside of the chamber 1, and the like. It may be.

As the inert gas, for example, N ₂ gas or rare gas can be used. As the rare gas, for example, Ar gas, Kr gas, Xe gas, He gas, or the like can be used. Among these, it is particularly preferable to use Ar gas because it is economical. As the oxygen-containing gas, for example, oxygen gas (O ₂ ), water vapor (H ₂ O), nitrogen monoxide (NO), dinitrogen monoxide (N ₂ O), or the like can be used.

  The inert gas, oxygen-containing gas, and hydrogen gas reach the gas introduction unit 15 through the gas line 20 from the inert gas supply source 19a, the oxygen-containing gas supply source 19b, and the hydrogen gas supply source 19c of the gas supply mechanism 18. The gas is introduced into the chamber 1 from the gas introduction part 15. Each gas line 20 connected to each gas supply source is provided with a mass flow controller 21 and front and rear opening / closing valves 22. With such a configuration of the gas supply mechanism 18, the supplied gas can be switched and the flow rate can be controlled.

  The exhaust device 24 as an exhaust mechanism includes a high-speed vacuum pump such as a turbo molecular pump. As described above, the exhaust device 24 is connected to the exhaust chamber 11 of the chamber 1 through the exhaust pipe 12. The gas in the chamber 1 flows uniformly into the space 11a of the exhaust chamber 11, and is further exhausted to the outside through the exhaust pipe 12 by operating the exhaust device 24 from the space 11a. Thereby, the inside of the chamber 1 can be depressurized at a high speed to a predetermined degree of vacuum, for example, 0.133 Pa.

  Next, the configuration of the microwave introduction mechanism 27 will be described. The microwave introduction mechanism 27 includes a transmission plate 28, a planar antenna 31, a slow wave material 33, a cover 34, a waveguide 37, a matching circuit 38, and a microwave generator 39 as main components.

The transmission plate 28 that transmits microwaves is disposed on a support portion 13 a that protrudes to the inner peripheral side of the upper plate 13. The transmission plate 28 is made of a dielectric, for example, ceramics such as quartz, Al ₂ O ₃ , and AlN. A gap between the transmission plate 28 and the support portion 13a is hermetically sealed through a seal member 29. Therefore, the inside of the chamber 1 is kept airtight.

  The planar antenna 31 is provided above the transmission plate 28 so as to face the mounting table 2. The planar antenna 31 has a disk shape. The shape of the planar antenna 31 is not limited to a disk shape, and may be a square plate shape, for example. The planar antenna 31 is locked to the upper end of the upper plate 13.

  The planar antenna 31 is made of, for example, a copper plate or an aluminum plate having a surface plated with gold or silver. The planar antenna 31 has a number of slot-shaped microwave radiation holes 32 that radiate microwaves. The microwave radiation holes 32 are formed through the planar antenna 31 in a predetermined pattern.

  Each microwave radiation hole 32 has an elongated rectangular shape (slot shape), for example, as shown in FIG. And typically, the adjacent microwave radiation holes 32 are arranged in a “T” shape. Further, the microwave radiation holes 32 arranged in combination in a predetermined shape (for example, T shape) are further arranged concentrically as a whole.

  The length and arrangement interval of the microwave radiation holes 32 are determined according to the wavelength (λg) of the microwave. For example, the interval between the microwave radiation holes 32 is arranged to be λg / 4, λg / 2, or λg. In FIG. 3, the interval between adjacent microwave radiation holes 32 formed concentrically is indicated by Δr. Note that the microwave radiation hole 32 may have another shape such as a circular shape or an arc shape. Furthermore, the arrangement form of the microwave radiation holes 32 is not particularly limited, and may be arranged in a spiral shape, a radial shape, or the like in addition to a concentric shape.

  A slow wave material 33 having a dielectric constant larger than that of a vacuum is provided on the upper surface of the planar antenna 31. The slow wave material 33 has a function of adjusting the plasma by shortening the wavelength of the microwave because the wavelength of the microwave becomes longer in vacuum. As the material of the slow wave material 33, for example, quartz, polytetrafluoroethylene resin, polyimide resin or the like can be used.

  The planar antenna 31 and the transmission plate 28 and the slow wave member 33 and the planar antenna 31 may be brought into contact with or separated from each other, but they are preferably brought into contact with each other.

  A cover 34 is provided on the upper portion of the chamber 1 so as to cover the planar antenna 31 and the slow wave material 33. The cover 34 is made of a metal material such as aluminum or stainless steel. The upper end of the upper plate 13 and the cover 34 are sealed by a seal member 35. A cooling water channel 34 a is formed inside the cover 34. By allowing the cooling water to flow through the cooling water flow path 34a, the cover 34, the slow wave material 33, the planar antenna 31 and the transmission plate 28 can be cooled. The cover 34 is grounded.

  An opening 36 is formed at the center of the upper wall (ceiling) of the cover 34, and a waveguide 37 is connected to the opening 36. A microwave generator 39 that generates microwaves is connected to the other end of the waveguide 37 via a matching circuit 38.

  The waveguide 37 is connected to a coaxial waveguide 37a having a circular cross section extending upward from the opening 36 of the cover 34, and an upper end portion of the coaxial waveguide 37a via a mode converter 40. And a rectangular waveguide 37b extending in the horizontal direction. The mode converter 40 has a function of converting the microwave propagating in the TE mode in the rectangular waveguide 37b into the TEM mode.

  An inner conductor 41 extends at the center of the coaxial waveguide 37a. The inner conductor 41 is connected and fixed to the center of the planar antenna 31 at its lower end. With such a structure, the microwave is efficiently and uniformly propagated radially and uniformly to the planar antenna 31 via the inner conductor 41 of the coaxial waveguide 37a.

  With the microwave introduction mechanism 27 configured as described above, the microwave generated by the microwave generator 39 is propagated to the planar antenna 31 via the waveguide 37 and further introduced into the chamber 1 via the transmission plate 28. It has come to be. For example, 2.45 GHz is preferably used as the frequency of the microwave, and 8.35 GHz, 1.98 GHz, or the like can also be used.

  Each component of the plasma processing apparatus 100 is connected to and controlled by the controller 50. The control unit 50 includes a computer, and includes a process controller 51 having a CPU, a user interface 52 connected to the process controller 51, and a storage unit 53, as shown in FIG. In the plasma processing apparatus 100, the process controller 51 is a component related to process conditions such as temperature, pressure, gas flow rate, and microwave output (for example, the heater power supply 5a, the gas supply mechanism 18, the exhaust device 24, the microwave). This is a control means for controlling the generator 39 and the like in an integrated manner.

  The user interface 52 includes a keyboard on which a process manager manages command input to manage the plasma processing apparatus 100, a display that visualizes and displays the operating status of the plasma processing apparatus 100, and the like. The storage unit 53 stores a recipe in which a control program (software) for realizing various processes executed by the plasma processing apparatus 100 under the control of the process controller 51 and processing condition data are recorded. Yes.

  If necessary, an arbitrary recipe is called from the storage unit 53 according to an instruction from the user interface 52 and is executed by the process controller 51, so that the process controller 51 controls the inside of the chamber 1 of the plasma processing apparatus 100. The desired process is performed. The recipes such as the control program and processing condition data may be stored in a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a flash memory, a DVD, or a Blu-ray disk. Alternatively, it may be transmitted from other devices as needed via, for example, a dedicated line and used online.

  In the plasma processing apparatus 100 configured as described above, it is possible to perform damage-free plasma processing on the base film or the like at a low temperature of 800 ° C. or lower. In addition, since the plasma processing apparatus 100 is excellent in plasma uniformity, it is possible to achieve processing uniformity within the surface of the wafer W.

  FIG. 5 shows a schematic configuration example of a single wafer CVD film forming apparatus 300 applicable as the process modules 101a and 101c. The single wafer CVD film forming apparatus 300 includes a substantially cylindrical processing container 301 that is airtight. In the processing container 301, a susceptor 303 for horizontally supporting a wafer W as an object to be processed is provided. The susceptor 303 is supported by a cylindrical support member 305. A heater 307 is embedded in the susceptor 303. The heater 307 is supplied with power from the heater power source 309 to heat the wafer W to a predetermined temperature.

A shower head 311 is provided on the open / close top wall 301 a of the processing container 301. The shower head 311 has a gas diffusion space 311a inside. In addition, a large number of gas discharge holes 313 communicating with the gas diffusion space 311 a are formed on the lower surface of the shower head 311. A gas supply pipe 315 communicating with the gas diffusion space 311a is connected to the center of the shower head 311. This gas supply pipe 315 is provided with a film forming source gas such as dichlorosilane, dinitrogen monoxide (N ₂ O), or a processing container via a mass flow controller (MFC) 317 and valves 318a and 318b arranged before and after the mass flow controller (MFC) 317. It is connected to a gas supply source 319 for supplying a purge gas for replacing the atmosphere in 301. Then, the film forming source gas and the like are supplied from the gas supply source 319 to the shower head 311 via the gas supply pipe 315 and the mass flow controller 317.

  An exhaust hole 331 is formed in the bottom wall 301 b of the processing container 301, and an exhaust device 335 is connected to the exhaust hole 331 through an exhaust pipe 333. The exhaust device 335 is operated so that the inside of the processing vessel 301 can be depressurized to a predetermined vacuum level. Note that, by supplying high frequency power from a high frequency power source (not shown) to the shower head 311, the source gas supplied into the processing container 301 through the shower head 311 can be converted into plasma to form a film.

  Further, a loading / unloading port 337 for loading / unloading the wafer W is provided on the side wall 301 c of the processing container 301, and the wafer W is loaded / unloaded through the loading / unloading port 337. The loading / unloading port 337 is opened and closed by the gate valve G1.

In the single wafer CVD film forming apparatus 300 configured as described above, the source gas is supplied from the shower head 311 toward the wafer W while the wafer W is heated by the heater 307 while the wafer W is placed on the susceptor 303. As a result, a thin film of, for example, a SiO ₂ film can be formed on the surface of the wafer W by the CVD method.

  The single wafer CVD film forming apparatus 300 having the above configuration is also controlled by the control unit 50 (see FIG. 4). The CVD film forming apparatus is not limited to a single wafer type, and a batch type film forming apparatus can also be used.

  Next, a method for forming an insulating film including a plasma modification process performed in the substrate processing system 200 will be described with reference to FIGS. FIG. 6 is a flowchart showing a flow of a silicon oxide film forming method including a film forming process of a silicon oxide film as an insulating film and a reforming process thereof, and FIG. 7 is a drawing for explaining the main process. It is.

  The silicon oxide film forming method of the present embodiment is performed, for example, by the procedure from step S1 to step S5 shown in FIG. First, in step S <b> 1 of FIG. 6, the wafer W to be processed is loaded into the CVD film forming apparatus (process module 101 a or 101 c) by the transfer device 109 in the vacuum side transfer chamber 103.

  Next, in step S2, as shown in FIG. 7A, a film forming process by a CVD method is performed on the silicon layer 201 exposed on the surface of the wafer W. As a result, as shown in FIG. 7B, a silicon oxide film 202 as an insulating film is formed on the silicon layer 201. As this CVD method, a thermal CVD method is used in the present embodiment using the substrate processing system 200, but it is possible to form a film by a method such as a plasma CVD method, a low pressure CVD method, or an atmospheric pressure CVD method. .

Thickness T ₁ of the silicon oxide film 202 is formed on the silicon layer 201 of the wafer W by a film forming process by the CVD method, from the viewpoint of obtaining sufficient modification effect by the plasma modification treatment step to be performed later, 2 nm or more It is preferably within the range of 10 nm or less, and more preferably within the range of 4 nm or more and 8 nm or less. Thickness T ₁ of the silicon oxide film 202 as a target of modification treatment is less than 2 nm, becomes large number of iterations until the thickening to the desired thickness, which is inefficient. On the other hand, the thickness T ₁ of the silicon oxide film 202 is, in the case of 10nm greater, it is difficult to sufficiently modify the entire thickness direction as described later.

  Next, in step S3, the wafer W on which the silicon oxide film 202 is formed is transferred to a plasma processing apparatus 100 (process module 101b or 101d) as a plasma modification processing apparatus. This transfer is performed in a vacuum state by the transfer device 109 in the vacuum side transfer chamber 103. Next, in step S4, as shown in FIG. 7C, a plasma reforming process is performed on the silicon oxide film 202. The procedure and conditions of the plasma modification process performed using the plasma processing apparatus 100 are as follows.

[Plasma reforming procedure]
First, while evacuating the chamber 1 of the plasma processing apparatus 100 under reduced pressure, the inert gas and the oxygen-containing gas are respectively supplied from the inert gas supply source 19a and the oxygen-containing gas supply source 19b of the gas supply mechanism 18 at a predetermined flow rate. It introduces into the chamber 1 through the introduction part 15. In this way, the inside of the chamber 1 is adjusted to a predetermined pressure.

  Next, a microwave having a predetermined frequency, for example, 2.45 GHz, generated by the microwave generator 39 is guided to the waveguide 37 via the matching circuit 38. The microwave guided to the waveguide 37 sequentially passes through the rectangular waveguide 37 b and the coaxial waveguide 37 a and is supplied to the planar antenna 31 through the inner conductor 41. That is, the microwave propagates in the TE mode in the rectangular waveguide 37b, and the TE mode microwave is converted into the TEM mode by the mode converter 40, and the inside of the coaxial waveguide 37a is directed to the planar antenna 31. Will be propagated. Then, the microwave is radiated from the slot-shaped microwave radiation hole 32 formed through the planar antenna 31 to the space above the wafer W in the chamber 1 through the transmission plate 28. The microwave output at this time can be selected according to the purpose within the range of 2000 W or more and 4000 W or less, for example, when processing a wafer W having a diameter of 200 mm or more.

An electromagnetic field is formed in the chamber 1 by the microwave radiated from the planar antenna 31 through the transmission plate 28 to the chamber 1, and the inert gas and the oxygen-containing gas are turned into plasma, respectively. The microwave-excited plasma has a high density of about 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ and a vicinity of the wafer W when microwaves are radiated from a large number of microwave radiation holes 32 of the planar antenna 31. Then, it becomes a low electron temperature plasma of about 1.2 eV or less. The plasma formed in this way has little plasma damage due to ions or the like on the underlying film. Then, plasma modification is performed by the action of O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals, which are the main active species in the plasma, and dangling bonds and weak bonds are terminated to form Si—O bonds. Thus, a dense and defect-free silicon oxide film is formed.

[Plasma reforming treatment conditions]
As a processing gas for the plasma reforming treatment, it is preferable to use a gas containing a rare gas and an oxygen-containing gas. It is preferable to use Ar gas as the rare gas and O ₂ gas as the oxygen-containing gas. In this case, the volumetric flow ratio of O ₂ gas to the total process gas (O ₂ gas flow rate / total process gas flow rate percentage of) is, O ₂ ⁺ ions and O (1 ^D ₂₎ radicals and predominantly as the active species in the plasma In view of the above, it is preferable to be in the range of 0.1% to 30%, and more preferable to be in the range of 0.1% to 5%. For example, the flow rate of Ar gas is in the range of 500 mL / min (sccm) to 5000 mL / min (sccm), and the flow rate of O ₂ gas is in the range of 0.5 mL / min (sccm) to 1000 mL / min (sccm). The flow rate ratio can be set.

The treatment pressure is preferably in the range of 6.7 Pa to 267 Pa, and preferably 6.7 Pa to 67 Pa from the viewpoint of predominating O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals as active species in the plasma. Within the range is more preferable.

Moreover, the power density of the microwave is 0.51 W / cm ² or more and 2.56 W / cm ² or less from the viewpoint of efficiently generating active species O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals in plasma. It is preferable to be within the range. The microwave power density means the microwave power supplied per 1 cm ² area of the transmission plate 28 (the same applies hereinafter). For example, when processing a wafer W having a diameter of 200 mm or more, it is preferable that the microwave power is in the range of 1000 W to 5000 W.

  Further, the heating temperature of the wafer W is preferably set, for example, in the range of 200 ° C. or more and 600 ° C. or less, and more preferably in the range of 400 ° C. or more and 600 ° C. or less as the temperature of the mounting table 2.

By performing plasma modification treatment on the silicon oxide film 202 formed by the CVD method under the above conditions using the plasma processing apparatus 100, the silicon oxide film 202 has a depth within the range of 2 nm to 10 nm from the surface of the silicon oxide film 202. The film quality can be improved in practical use. Accordingly, the thickness T ₁ of the silicon oxide film 202 formed in one CVD process is preferably in the range of 2 nm to 10 nm as described above, and the plasma modification processing time in this case is 5 seconds or more. It is preferable to be within the range of 600 seconds or less. Even if the silicon oxide film 202 having the above thickness is subjected to plasma reforming treatment under the above conditions for a time of less than 5 seconds, the modification may be insufficient. Even if the quality treatment is performed, the improvement effect cannot be expected and it is not efficient.

  The above conditions are stored as a recipe in the storage unit 53 of the control unit 50. The process controller 51 reads the recipe and sends a control signal to each component of the plasma processing apparatus 100, such as the gas supply mechanism 18, the exhaust device 24, the microwave generator 39, the heater power supply 5a, etc. Plasma reforming treatment is performed under conditions.

After the plasma reforming process in step S4 is completed, in the present embodiment, the processes in steps S2 and S4 are repeated a plurality of times as necessary. That is, after the process of step S4 is completed, the wafer W is transferred to the CVD film forming apparatus (process module 101a or 101c) (see step S1). Then, as shown in FIG. 7D, an insulating film is deposited again on the modified silicon oxide film 202a by the CVD method (see step S2). Thus, as shown in FIG. 7 (e), on the silicon oxide film 202a of the reforming already, the silicon oxide film 203 with a thickness T ₁ is laminated.

Next, the wafer W is transferred to the plasma processing apparatus 100 (process module 101b or 101d) (see step S3), and as shown in FIG. 7F, the uppermost silicon oxide film 203 is subjected to plasma modification processing. (See step S4). As shown in FIG. 7 (g), the processes in step S2 and step S4 are performed in the total film thickness T ₂ (stacked insulating film 210 (modified silicon oxide films 202a, 203a, 204a, 205a, 206a...)). = Film thickness T ₁ × number of times of film formation) is repeated until a predetermined thickness is reached. The total thickness _{T 2} of the this case is preferably a 4nm than 1000nm or less, and more preferably to 4nm than 100nm or less.

  As described above, after the processes of step S2 and step S4 are repeated to form the laminated insulating film 210 having a predetermined thickness, the wafer W that has been processed by the transfer apparatus 109 in the vacuum transfer chamber 103 is processed in the plasma processing apparatus in step S5. 100 (process module 101b or 101d) is taken out and stored in the wafer cassette CR of the load port LP in the above procedure.

Formed by the method for forming the insulating film of the present embodiment, by repeating the processing of steps S2 and S4, dense without defects high-quality insulating film (silicon oxide film 202 and 203 ...) with the desired thickness T ₂ can do. Even if a silicon oxide film having a thick film thickness of 10 nm to 1000 nm can be formed by a single CVD method, it is difficult to reform the entire film into a dense and high-quality film by plasma modification treatment. . As will be described later, since O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals, which are important active species in the plasma modification process, have a low ability to permeate the silicon oxide film that is the object of the modification process, This is because there is a limit to the thickness (depth from the surface) of the silicon oxide film that can be modified. In the method for forming an insulating film of this embodiment, the deposition of a silicon oxide film by an CVD method as an insulating film and the plasma modification treatment are repeatedly performed, so that the film is arbitrarily limited without being limited by the modification limit film thickness. of a thickness T _2, the dense good quality film quality of the insulating film in comparison with the conventional CVD film can be formed with a film thickness equivalent to a conventional CVD film.

  Further, in the substrate processing system 200, the film forming process of the silicon oxide film by the CVD method and the reforming process can be continuously repeated under vacuum, so that the throughput necessary for practical use (for example, 30 to 60 sheets per hour). In this way, it is possible to form an insulating film having a thick film thickness equivalent to that of the conventional CVD method and a quality better than that of the conventional CVD film.

[Action]
Next, an operation mechanism of the silicon oxide film forming method performed in the substrate processing system 200 will be described with reference to FIG. When plasma of a processing gas containing oxygen is generated using the plasma processing apparatus 100, the oxidation active species in the plasma changes depending on the processing pressure. Specifically, O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals in plasma increase under low pressure conditions (267 Pa or less, preferably 6.7 Pa to 267 Pa, more preferably 6.7 Pa to 67 Pa). To do.

FIG. 8 schematically shows a chemical change caused in the silicon oxide film by the plasma modification process. O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals have low ability to permeate the silicon oxide film that is the target of the modification treatment. For this reason, when the plasma reforming process is performed under the plasma generation condition in which these active species are dominant in the plasma, as shown in FIG. 8, O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals are converted into silicon oxide. It enters into the film 203 and forms a bond with Si. At this time, impurities such as Cl, H, and OH derived from film-forming raw materials in the CVD method, which are included in the silicon oxide film 203 in an unstable form, are replaced with O ₂ ⁺ ions or O ( ¹ D ₂ ) radicals. It is discharged out of the membrane. By such a mechanism, by performing the plasma reforming process under a low pressure condition of 267 Pa or less, the silicon oxide film is thicker than the conventional CVD film with a thickness equivalent to the film thickness formed by the conventional CVD method. The film quality becomes dense, and the film is modified to a high quality film with few defects such as impurities and dangling bonds.

On the other hand, under high pressure conditions (for example, 333 Pa or more), O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals decrease as active species in the plasma, and O ( ³ P ₂ ) radicals are mainly used instead. Since this O ( ³ P ₂ ) radical has a property of passing through the silicon oxide film, under the plasma generation conditions in which the O ( ³ P ₂ ) radical is dominant, O ₂ ⁺ ions and O ( ¹ D ₂ ) An excellent modification effect such as radicals cannot be obtained.

In the method for forming an insulating film according to this embodiment, attention is paid to the change of active species in plasma due to the above processing pressure, and low pressure conditions in which O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals are dominant. By selecting (267 Pa or less) and performing a plasma modification process on the silicon oxide film, a high modification effect can be obtained on the silicon oxide film. Then, the problem of the reforming limit film thickness, which is a problem in the reforming process under a low pressure condition (267 Pa or less) in which O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals are dominant in plasma, is formed by CVD. This is solved by repeating the plasma reforming process. In addition, in the substrate processing system 200, the silicon oxide film forming process by the CVD method and the silicon oxide film modifying process can be continuously performed under vacuum, so that a practically necessary throughput can be obtained.

  The insulating films (silicon oxide films 202, 203...) Formed in this way are modified into a dense and high-quality insulating film with few impurities and dangling bonds by plasma reforming treatment at a low temperature. It can be advantageously used as an insulating film of a semiconductor device. In particular, in the method for forming an insulating film of the present embodiment, a high-quality insulating film can be formed with a desired thickness. Therefore, for example, a relatively thick film within a range of 4 nm to 1000 nm, preferably 4 nm to 100 nm. It is most suitable for use as a gate insulating film of a thin film transistor (TFT) element used in thickness, a gate insulating film of a CCD (Charge Coupled Device) element, a gate insulating film of a high power transistor, and the like.

FIG. 9 is a cross-sectional view showing a schematic configuration of a TFT element 400 to which the insulating film forming method according to the present embodiment can be applied. On the glass substrate 401, a gate electrode 402 made of a metal material such as Mo or Al is partially formed. A gate insulating film 403 made of silicon dioxide (SiO ₂ ) is formed so as to cover the surfaces of the gate electrode 402 and the glass substrate 401. The gate insulating film 403 is integrally formed by laminating a first silicon oxide film 403a, a second silicon oxide film 403b, and a third silicon oxide film 403c in order from the bottom. An a-Si (amorphous silicon) film 404 is formed on the gate insulating film 403 as an Si-based film for forming a transistor, and a channel portion 405 is formed on the gate electrode 402. A source electrode 406 and a drain electrode 407 containing a refractory metal material such as molybdenum or tungsten are formed on the a-Si film 404. A passivation film 408 made of silicon nitride (Si ₃ N ₄ ) is formed on the source electrode 406 and the drain electrode 407 to protect the surface of the TFT element 400.

  In the case of applying the insulating film forming method of the present embodiment to the TFT element 400 having the configuration as shown in FIG. 9, a metal material to be the gate electrode 402 is formed on the glass substrate 401 to form a pattern. Next, a gate insulating film 403 is formed by a CVD method so as to cover the surfaces of the gate electrode 402 and the glass substrate 401. In forming the gate insulating film 403, the CVD process and the plasma modification process are repeated a predetermined number of times as described above. That is, first, a first silicon oxide film 403 a is formed by a CVD method, and subsequently, the first silicon oxide film 403 a is subjected to plasma modification processing using the plasma processing apparatus 100. Next, a second silicon oxide film 403b is formed on the first silicon oxide film 403a by a CVD method. Next, the second silicon oxide film 403b is plasma-reformed using the plasma processing apparatus 100. To do. Further, a third silicon oxide film 403c is formed on the second silicon oxide film 403b by a CVD method, and then the third silicon oxide film 403c is subjected to plasma modification using the plasma processing apparatus 100. . In this manner, a dense gate insulating film 403 with few defects such as impurities and dangling bonds can be formed by low-temperature treatment. Note that the silicon oxide film included in the gate insulating film 403 is not limited to three layers, and may be two layers or four or more layers depending on the thickness of the gate insulating film 403. The above processing can be performed according to the procedure of step S1 to step S5 in FIG.

  Thereafter, the film formation and etching are repeated in accordance with a conventional method, and the film formation and pattern formation of the a-Si film 404, the film formation and pattern formation of the source electrode 406 and the drain electrode 407, the film formation of the passivation film 408, and the ITO electrode (illustrated). The TFT element 400 can be formed by forming (omitted).

  In the TFT element 400 illustrated in FIG. 9, the gate insulating film 403 can be formed with a desired thickness by repeating the CVD process and the plasma modification process. In addition, the plasma modification process enables the film quality of the entire gate insulating film 403 to be a dense and high-quality film with few defects such as impurities and dangling bonds by low-temperature processing. Electrical performance can be improved.

  Next, experimental data on which the present invention is based will be described. Plasma modification processing was performed on the silicon oxide film formed by the thermal CVD method under the following conditions 1 to 4 using the plasma processing apparatus 100 shown in FIG. With respect to the silicon oxide film after modification, the amount of increase in film thickness, the amount of increase in refractive index, and the wet etching rate by 0.125% dilute hydrofluoric acid treatment (30 seconds) were examined. Further, a MOS capacitor is manufactured using the modified silicon oxide film as a gate insulating film, and its electrical characteristics include leakage current density (Jg; −10 MV / cm), insulating film breakdown over time (TDDB; 63%) The amount of change of the electron trap (Δvge; 11 seconds) was examined. For comparison, the same measurement as described above was performed for the case where the modification was not performed, the case where the modification was performed by annealing, and the thermal oxide film. The results are shown in Table 1.

[Reforming condition 1]
Ar gas flow rate: 1000 mL / min (sccm)
O ₂ gas flow rate; 300 mL / min (sccm)
Flow rate ratio (O ₂ / Ar + O ₂ ); 0.23
Processing pressure: 6.7 Pa
Temperature of mounting table 2; 500 ° C
Microwave power: 4000W
Microwave power density: 2.05 W / cm ² (per 1 cm ² area of transmission plate)

[Reforming condition 2]
Ar gas flow rate: 1980 mL / min (sccm)
O ₂ gas flow rate: 20 mL / min (sccm)
Flow rate ratio (O ₂ / Ar + O ₂ ); 0.01
Processing pressure: 200 Pa
Temperature of mounting table 2; 500 ° C
Microwave power: 4000W
Microwave power density: 2.05 W / cm ² (per 1 cm ² area of transmission plate)

[Reforming condition 3]
Ar gas flow rate: 1200 mL / min (sccm)
O ₂ gas flow rate: 400 mL / min (sccm)
Flow rate ratio (O ₂ / Ar + O ₂ ); 0.25
Processing pressure: 667 Pa
Temperature of mounting table 2; 500 ° C
Microwave power: 4000W
Microwave power density: 2.05 W / cm ² (per 1 cm ² area of transmission plate)

[Reforming condition 4]
Ar gas flow rate: 1200 mL / min (sccm)
O ₂ gas flow rate: 370 mL / min (sccm)
H ₂ gas flow rate: 30 mL / min (sccm)
Flow rate ratio (O ₂ / Ar + O ₂ + H ₂ ); 0.23
Flow rate ratio (H ₂ / Ar + O ₂ + H ₂ ); 0.019
Processing pressure: 667 Pa
Temperature of mounting table 2; 500 ° C
Microwave power: 4000W
Microwave power density: 2.05 W / cm ² (per 1 cm ² area of transmission plate)

[Annealing treatment conditions]
Atmosphere; N ₂ / O ₂ = 10 / 0.1 L / min
Temperature: 900 ° C
Pressure: 133Pa

[Thermal oxide film formation conditions]
Atmosphere; H ₂ / O ₂ = 450/900 mL / min (sccm)
Temperature: 950 ° C
Pressure: 15000Pa

[Thermal CVD deposition conditions]
SiH ₂ Cl ₂ gas flow rate; 75 mL / min (sccm)
N ₂ O gas flow rate; 150 mL / min (sccm)
Processing pressure: 48Pa
Processing temperature: 780 ° C

  From the results of physical analysis shown in Table 1, when the plasma modification treatment is performed under conditions 1 and 2 at a low pressure of 200 Pa or less, the refractive index increases and the wet etching rate decreases. These data indicate that the film quality of the silicon oxide film is improved by the plasma modification treatment, and the film density is increased. In addition, when the wet etching rates of conditions 1 and 2 are compared with the modification treatment by annealing, it is shown that conditions 1 and 2 have a lower etching rate and higher modification effect than thermal annealing modification. It was done.

In addition, when the plasma modification treatment was performed under condition 4, no change in refractive index was observed, and the wet etching rate was almost the same as the modification treatment by annealing. In other words, with respect to the effect of improving the film quality, the plasma modification treatment under condition 4 was the same result as the modification treatment by annealing. However, when the plasma modification treatment was performed under condition 4, the increase in the thickness of the silicon oxide film was noticeable. This was thought to be because the interface between the silicon oxide film formed by the CVD method and the underlying silicon was oxidized by O ( ³ P ₂ ) radicals in the plasma to increase the film thickness.

  From the above results, in the plasma reforming process at a processing pressure of 267 Pa or less, for example, 6.7 Pa or more and 267 Pa or less, the effect of improving the quality of the silicon oxide film formed by the CVD method is higher than the reforming process by annealing. Indicated. On the other hand, in the case of the plasma reforming process under a high pressure condition of 667 Pa, the effect of improving the quality of the silicon oxide film formed by the CVD method is equivalent to the reforming process by annealing. It was found to have an effect.

  According to the results of the electrical characteristic evaluation shown in Table 2, when the plasma reforming process is performed under conditions 1 and 2 where the processing pressure is as low as 200 Pa or less, the leakage current density (Jg) is as high as 667 Pa. Compared to Condition 3 and the modification process by annealing, the process was greatly improved.

FIG. 10 shows the relationship between the processing pressure and the leakage current of the plasma reforming process under conditions 1 to 3. Here, the annealing modification treatment and the leakage current of the thermal oxide film are also shown. From FIG. 10, it can be seen that when the processing pressure is 267 Pa or less, for example, 6.7 Pa or more and 267 Pa, the leakage current can be suppressed to 2.1 × 10 ⁻⁴ [A / cm ² ] or less. Therefore, when the purpose is to improve the leakage current characteristics, it is preferable to set the processing pressure of the plasma reforming process to 267 Pa or less.

  The dielectric breakdown over time (TDDB) was significantly improved when the plasma modification treatment was performed under conditions 1 to 3 as compared to the modification treatment by annealing. In particular, in the case of the plasma reforming treatment under condition 2, very excellent reliability exceeding the thermal oxide film was shown.

FIG. 11 shows the relationship between the processing pressure of the plasma reforming treatment under conditions 1 to 3 and TDDB. Here, the annealing modification treatment and the leakage current of the thermal oxide film are also shown. From FIG. 11, it can be seen that if the processing pressure is 533 Pa or less, the TDDB can be 33 [C / cm ² ] or more. Therefore, when the purpose is to improve the TDDB characteristics, it is preferable to set the processing pressure of the plasma reforming treatment to 533 Pa or less, such as 6.7 Pa to 533 Pa, more preferably 400 Pa or less, such as 6.7 Pa to 400 Pa, 267 Pa or less, for example, 6.7 Pa or more and 267 Pa or less is desirable.

FIG. 12 shows the relationship between the O ₂ / (Ar + O ₂ ) ratio and TDDB under conditions 1 to 3. In the plasma reforming treatment, as shown in FIG. 12, the TDDB characteristic can be effectively improved by setting the O ₂ / (Ar + O ₂ ) ratio to 0.23 or less, and in particular, the O ₂ / (Ar + O ₂ ) ratio. It was found that by setting the ratio to 0.1 or less, high TDDB characteristics exceeding the thermal oxide film can be obtained.

Regarding the amount of change (Δvge) of the electron trap, when the plasma reforming process was performed under conditions 1 and 2, it was almost halved compared to the reforming process by annealing, which was greatly improved. Even when the plasma reforming process was performed under condition 3, the amount of change in the electron trap was slightly reduced compared with the reforming process by annealing. Further, in the plasma reforming treatment, as shown in Table 2, it was found that the Δvge characteristic can be effectively improved by setting the O ₂ / (Ar + O ₂ ) ratio to 0.23 or less.

From the above results, the silicon oxide film is brought to a level equivalent to that of the thermal oxide film by performing the plasma reforming process at a low processing pressure of 267 Pa or less and an O ₂ / Ar + O ₂ ratio of 0.23 or less. It has been shown that the film quality can be improved to a dense and high-quality film with few defects. It was also confirmed that the electrical characteristics of the device can be improved by using the silicon oxide film thus modified.

Next, it was examined how the amount of chlorine (derived from the raw material SiH ₂ Cl ₂ ) remaining in the silicon oxide film formed by the CVD method changes due to the plasma modification treatment. The amount of residual chlorine in the silicon oxide film was measured by TXRF (total reflection X-ray Fluorescence) analysis. The results are shown in Table 3.

Table 3 shows that when the plasma reforming process is performed, the amount of residual chlorine is smaller than when the reforming process is not performed, and impurities in the silicon oxide film can be removed. Note that a thermal annealing process may be performed after the plasma modification process. By combining the plasma reforming treatment with the thermal annealing treatment, the amount of residual chlorine could be reduced to 9.60 × 10 ¹¹ [atoms / cm ² ].

  As described above, in the method for forming an insulating film according to the present embodiment, deposition and modification of a silicon oxide film are repeated, so that impurities and dangling are formed with a film thickness equivalent to that formed by the conventional CVD method. It can be preferably used for applications requiring a dense and high-quality insulating film with few defects such as bonds (for example, forming a gate insulating film of a TFT element, a gate insulating film of a CCD element, and a gate insulating film of a high power transistor).

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the silicon oxide film (SiO film ₂ ) formed by the thermal CVD method is cited as the insulating film to be subjected to the plasma modification process. However, the insulating film is not limited to the silicon oxide film by the thermal CVD method, It is possible to target a silicon oxide film formed by another CVD method such as a plasma CVD method. In this case, a higher reforming effect can be obtained for a silicon oxide film having a poor film quality (for example, a poor film quality).

  Further, the insulating film to be subjected to the plasma reforming treatment is not limited to the silicon oxide film, but a high dielectric constant metal oxide film containing an oxide of metal such as zirconium, tantalum, titanium, barium, strontium, aluminum, hafnium, etc. The plasma modification process can also be applied to the (Hi-k film).

It is a top view which shows schematic structure of a substrate processing system. It is a schematic sectional drawing which shows an example of the plasma processing apparatus suitable for implementation of the formation method of the insulating film of this invention. It is drawing which shows the structure of a planar antenna. It is explanatory drawing which shows the structure of a control part. It is a schematic sectional drawing which shows an example of the single wafer CVD film-forming processing apparatus suitable for implementation of the formation method of the insulating film of this invention. It is explanatory drawing which shows the outline of the procedure of the formation method of the insulating film which concerns on embodiment of this invention. It is explanatory drawing explaining the main processes of the formation method of the insulating film which concerns on embodiment of this invention. It is explanatory drawing which illustrates typically the modification | reformation mechanism in a plasma modification process. It is sectional drawing which shows schematic structure of the TFT element which can apply the formation method of the insulating film which concerns on embodiment of this invention. It is a graph which shows the relationship between the pressure of a plasma modification process, and the leakage current characteristic of a MOS capacitor. It is a graph which shows the relationship between the pressure of a plasma modification process, and the TDDB characteristic of a MOS capacitor. Is a graph showing the relationship between the _{O 2 / (Ar + O 2} ) ratio and TDDB in plasma modification process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Chamber (processing chamber), 2 ... Mounting stand, 3 ... Support member, 5 ... Heater, 12 ... Exhaust pipe, 15 ... Gas introduction part, 16 ... Carry-in / out port, 18 ... Gas supply mechanism, 19a ... Inert gas supply 19b ... oxygen-containing gas supply source, 19c ... hydrogen gas supply source, 24 ... exhaust device, 28 ... transmission plate, 29 ... sealing member, 31 ... planar antenna, 32 ... microwave radiation hole, 37 ... waveguide, 37 ... Coaxial waveguide, 37b ... Rectangular waveguide, 39 ... Microwave generator, 50 ... Control unit, 51 ... Process controller, 52 ... User interface, 53 ... Storage unit, 100 ... Plasma processing device, 200 ... Substrate Processing system, 300 ... Single wafer CVD film forming apparatus, W ... Semiconductor wafer (substrate)

Claims (10)

A CVD step of forming an insulating film with a film thickness in the range of 2 nm or more and 10 nm or less on the silicon exposed on the surface of the object by CVD;
A plasma reforming process for performing a reforming process on the insulating film using a plasma of a processing gas containing a rare gas and an oxygen gas in a plasma processing apparatus that introduces microwaves into a processing chamber using a planar antenna having a plurality of holes. Process,
And repeating the CVD process and the plasma modification treatment process to form an insulating film,
In the plasma reforming process, a processing pressure is in a range of 6.7 Pa to 67 Pa, and a flow rate ratio of the oxygen gas to a total flow rate of the processing gas is in a range of 0.1% to 30%. And the power density of the microwave is within the range of 0.51 W / cm ² or more and 2.56 W / cm ² or less, and the active species in the plasma is O ₂ ⁺ as compared with the O ( ³ P ₂ ) radical. A method for forming an insulating film, characterized by using plasma with relatively high concentrations of ions and O ( ¹ D ₂ ) radicals.   2. The method for forming an insulating film according to claim 1, wherein a flow rate ratio of the oxygen gas to a total flow rate of the processing gas in the plasma reforming process is in a range of 0.1% to 5%. . The method for forming an insulating film according to claim 2 , wherein a processing time in one plasma reforming process is in a range of 5 seconds to 600 seconds. The method for forming an insulating film according to claim 3 , wherein the CVD process and the plasma modification process are repeated until the total film thickness of the insulating film falls within a range of 4 nm to 1000 nm. Method of forming a dielectric film according to any one of claims 1 to 4, characterized in that repeating said CVD step and the plasma modification process in a vacuum. The plasma modification process treatment in step temperature, method of forming a dielectric film according to any one of claims 1 to 5, characterized in that in the range of 200 ° C. or higher 600 ° C. or less. Wherein an insulating film, insulating film forming method according to any one of claims 1 to claim 6, characterized in that formed by a plasma CVD method or a thermal CVD method. The method for forming an insulating film according to claim 7 , wherein the insulating film is a silicon oxide film deposited by a CVD method using dichlorosilane and N ₂ O as source gases. A computer-readable storage medium storing a control program that runs on a computer,
In the processing system having a plurality of processing chambers for performing predetermined processing on the object to be processed at the time of execution, the control program has a thickness of 2 nm or more and 10 nm by silicon on the silicon exposed on the surface of the object to be processed. In a CVD process for forming an insulating film with a film thickness within the following range, and a plasma processing apparatus for introducing microwaves into the processing chamber by a planar antenna having a plurality of holes for the insulating film, a rare gas and an oxygen gas are used. And a plasma reforming process step of performing a reforming process using plasma of a processing gas containing, and causing the computer to control the processing system so that an insulating film forming method is repeatedly performed.
In the plasma reforming process, a processing pressure is in a range of 6.7 Pa to 67 Pa, and a flow rate ratio of the oxygen gas to a total flow rate of the processing gas is in a range of 0.1% to 30%. And the microwave power density is in the range of 0.51 W / cm ² or more and 2.56 W / cm ² or less, and the active species in the plasma is O ₂ as compared with O ( ³ P ₂ ) radicals. A computer-readable storage medium, characterized in that it is performed using a plasma with a relatively high concentration of ⁺ ions and O ( ¹ D ₂ ) radicals. A processing system having a plurality of processing chambers for performing different processing on an object to be processed,
A CVD process for forming an insulating film with a film thickness within a range of 2 nm or more and 10 nm or less by a CVD method on silicon exposed on the surface of an object to be processed in the first processing chamber, and the first processing chamber In a different second processing chamber, a plasma of a processing gas containing a rare gas and an oxygen gas is formed by introducing a microwave into the second processing chamber with respect to the insulating film by a planar antenna having a plurality of holes. A control unit that controls the first processing chamber and the second processing chamber so as to repeatedly perform a plasma reforming process step of performing a plasma reforming process using the plasma, and the control unit further includes: , the plasma processing pressure of the reforming process is in the range of less 67Pa above 6.7 Pa, the flow rate ratio of the oxygen gas to the total flow rate of the process gas In the range of 30% or less 0.1% or more, and, the power density of the microwave is performed in the range of 0.51W / cm ² or more 2.56 W / cm ² or less, the plasma used is a plasma It is characterized by controlling the plasma so that the concentration of O ₂ ⁺ ions and O ( ¹ D ₂ ) radicals is relatively high compared to O ( ³ P ₂ ) radicals as the active species in them. Processing system.

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