JP2008235611A - Plasma processing equipment and method for processing plasma - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for processing plasma capable of preventing occurrence of abnormal discharge on a gas guiding path formed at a shower head having the function of a top plate. <P>SOLUTION: The plasma processing equipment comprises a gas guiding path 84 for guiding the gas containing at least plasma exciting gas into a process vessel 32 that can be depressurized, and a shower head 60 which, comprising a plurality of gas discharging openings 86, is communicated with the gas guiding path, for discharging gas into the process vessel. In the method for processing plasma, the electromagnetic waves is guided into the process vessel through the shower head so that a processed body W is applied with plasma processing. The gas pressure in the gas guiding path 84 is set to be 4,000 Pa (30 Torr) or higher. Thus, an abnormal discharge is prevented from occurring at the gas guiding path 84 formed to the shower head having the function of a top plate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for performing plasma processing on an object to be processed such as a semiconductor wafer.

In recent years, with the increase in density and miniaturization of semiconductor products, plasma processing apparatuses are frequently used for processes such as film formation, etching, and ashing in the manufacturing process of semiconductor products, and in particular, 0.1 mTorr (13. Since a plasma can be stably generated even in a high vacuum state where the pressure is relatively low, such as 3 mPa) to several tens of mTorr (several Pa), a plasma processing apparatus that generates high-density plasma using a microwave or high frequency is used. Tend to.
Such plasma processing apparatuses are disclosed in Patent Documents 1 to 7 and the like. Here, for example, a general plasma processing apparatus using a microwave will be schematically described with reference to FIG. FIG. 9 is a schematic configuration diagram showing a conventional general plasma processing apparatus using a microwave.

  In FIG. 9, the plasma processing apparatus 2 includes a mounting table 6 on which a semiconductor wafer W is mounted in a processing container 4 that can be evacuated, and microwaves are applied to a ceiling portion facing the mounting table 6. A transparent top plate 8 made of discoidal aluminum nitride, quartz or the like is provided in an airtight manner. A gas nozzle 9 is provided on the side wall of the processing vessel 4 as a gas introduction means for introducing a predetermined gas into the vessel.

  Then, a disc-shaped planar antenna member 10 having a thickness of several millimeters on the top surface of the top plate 8 and a slow wave made of, for example, a dielectric for shortening the wavelength of the microwave in the radial direction of the planar antenna member 10 The material 12 is installed. The planar antenna member 10 is formed with a large number of slots 14 formed of, for example, long groove-like through holes. The slots 14 are generally arranged concentrically or spirally. Then, the central conductor 18 of the coaxial waveguide 16 is connected to the central portion of the planar antenna member 10 and a 2.45 GHz microwave generated by the microwave generator 20 is generated by the mode converter 22 in a predetermined vibration mode. It comes to guide after converting to.

  Then, while the microwaves are propagated radially in the radial direction of the antenna member 10, the microwaves are emitted from the slots 14 provided in the planar antenna member 10 and are transmitted through the top plate 8 to enter the processing container 4 below. A microwave is introduced, and a plasma is generated in the processing space S in the processing container 4 by the microwave so that the semiconductor wafer W is subjected to predetermined plasma processing such as etching or film formation.

  Recently, as the wafer size increases, a shower head having a large number of gas discharge holes has been used as a gas introduction means because it is necessary to supply gas uniformly into the processing vessel (Patent Document). 5-7), gas is uniformly discharged into the processing space from each gas discharge port provided on the lower surface of the shower head. In this case, since the plasma generated in the processing space may flow backward from the gas discharge port and abnormal discharge or film deposition may occur, the gas discharge port or the like has air permeability to prevent this. Measures such as reducing the conductance by using a porous ceramic material (Patent Documents 5 and 6), or setting the diameter of the gas discharge port to a very small value of about 0.1 to 0.3 mm, etc. (Patent Document 7).

Japanese Patent Laid-Open No. 3-191073 JP-A-5-343334 Japanese Patent Laid-Open No. 9-181052 JP 2003-332326 A JP 2004-39972 A JP 2005-33167 A WO2006 / 112392

  By the way, as described above, when a porous ceramic material is used on the gas discharge port side, or when the conductance is lowered by reducing the diameter of the gas discharge port, the back flow of the plasma to the gas discharge port side is to some extent. Can be prevented.

However, in the case of the structure as described above, the top plate to be the shower head is exposed to a strong electromagnetic field, so that the gas flowing in the gas introduction path formed on the top plate to be the shower head is dissociated, There has been a problem that abnormal discharge occurs here.
The present invention has been devised to pay attention to the above problems and to effectively solve them. An object of the present invention is to provide a plasma processing method and a plasma processing apparatus capable of preventing abnormal discharge from occurring in a gas introduction path formed in a shower head having a function of a top plate.

  As a result of diligent research on measures for preventing abnormal discharge in the gas introduction path of the shower head, the present inventors have prevented the abnormal discharge by setting the pressure in the gas introduction path to 30 Torr or more, preferably 300 Torr or more. The present invention has been achieved by obtaining the knowledge that it can be performed.

  According to the first aspect of the present invention, there is provided a gas introduction path for introducing a gas containing at least a plasma excitation gas into a processing container that can be depressurized, and the gas being discharged into the processing container connected to the gas introduction path. And a shower head having a plurality of gas discharge ports. The electromagnetic wave is introduced into the processing container through the shower head to excite the gas to generate plasma, and the plasma is used to treat the object to be processed. In the plasma processing method, the pressure of the gas in the gas introduction path is set to be 4000 Pa (30 Torr) or more.

  Thus, since the pressure in the gas introduction path is set to be 4000 Pa (30 Torr) or more, it is possible to prevent abnormal discharge from occurring in the gas introduction path.

In this case, for example, as described in claim 2, the pressure in the gas introduction path is 40 kPa (300 Torr) or more.
For example, as described in claim 3, at least a part of the gas introduction path is provided inside the shower head.
Further, for example, as described in claim 4, the pressure in the gas introduction path is measured by a pressure measuring device, and the pressure in the gas introduction path is determined by the flow rate of gas flowing into the gas introduction path and the processing container. The predetermined pressure value is maintained by adjusting at least one of the displacement from the exhaust gas.
Further, for example, as described in claim 5, the plasma processing is started when the pressure in the gas introduction path is stabilized at a predetermined pressure value.
For example, as described in claim 6, when the pressure in the gas introduction path is out of the range of ± 10% of the set pressure during the processing, the processing is interrupted.

Further, for example, as described in claim 7, when the pressure in the gas introduction path becomes an abnormal discharge occurrence region during the processing, the processing is interrupted.
For example, as described in claim 8, when the supply of the gas into the processing container is started, the supply is started at a larger flow rate than the gas supply amount at the time of the processing.

For example, as described in claim 9, when switching the type of gas supplied into the processing container, the gas remaining in the gas introduction path is moved in a direction opposite to the gas introduction direction. Force exhaust.
As described above, when the type of gas supplied into the processing container is switched, the gas remaining in the gas introduction path is forcibly exhausted in a direction opposite to the gas introduction direction. The discharge of the residual gas in the gas introduction path can be promoted, and the throughput can be improved correspondingly.

Further, for example, as described in claim 10, a carrying-in process for carrying the object to be processed into the processing container, a plasma processing process for performing a plasma treatment on the object to be processed, and the processing that has been processed from within the processing container A gas-exciting gas over at least two processes selected from the above-mentioned processes, including a carrying-out process for carrying out the object to be processed and a cleaning process for cleaning the processing container by flowing a cleaning gas. To flow continuously.
In addition, for example, as described in claim 11, the plasma treatment is a film formation process for forming a thin film on a surface of the object to be processed.

  According to a twelfth aspect of the present invention, there is provided a plasma processing apparatus for performing plasma processing on an object to be processed, wherein a processing container whose ceiling is opened and the inside of which can be depressurized, A mounting table provided in the processing container; a top plate functioning airtightly attached to the opening of the ceiling portion; a gas introduction path for introducing a gas containing at least a plasma excitation gas; and the gas introduction path A shower head which is a gas introduction means having a plurality of gas discharge ports that are communicated to discharge the gas into the processing container, and an electromagnetic wave for introducing an electromagnetic wave for generating plasma into the processing container through the shower head A plasma processing apparatus comprising: introduction means; and means for supplying the gas to the gas introduction path so that a gas pressure in the gas introduction path is 4000 Pa or higher.

In this case, for example, as described in claim 13, an introduction path pressure measuring device for measuring the gas pressure of the gas introduction path is provided.
Further, for example, as described in claim 14, an introduction path vacuum exhaust system for exhausting the atmosphere in the gas introduction path is provided.
For example, as described in claim 15, the introduction path evacuation system is also used as an evacuation system for evacuating the atmosphere in the processing container.
For example, as described in claim 16, a second gas introduction means for introducing gas into the processing container is provided.

  The invention according to claim 17 is a processing container in which a ceiling part is opened and the inside is made depressurizable, a mounting table provided in the processing container for mounting the object to be processed, A gas introduction path for introducing a gas containing at least a plasma excitation gas, and a plurality of the gas introduction paths communicating with the gas introduction path and discharging the gas into the processing container. A shower head which is a gas introduction means having a gas discharge port, an electromagnetic wave introduction means for introducing an electromagnetic wave for generating plasma into the processing container via the shower head, and a pressure in the gas introduction path is measured. The plasma processing method according to any one of claims 1 to 11, when performing plasma processing using a plasma processing apparatus comprising an introduction path pressure measuring device and control means for controlling the operation of the entire apparatus. A storage medium characterized by storing a computer readable program for controlling the plasma processing apparatus as rows.

According to the plasma processing apparatus and the plasma processing method of the present invention, the following excellent operational effects can be exhibited.
Since the pressure in the gas introduction path is set to 4000 Pa (30 Torr) or more, abnormal discharge can be prevented from occurring in the gas introduction path.
In particular, according to the ninth aspect of the invention, when switching the type of gas supplied into the processing container, the gas remaining in the gas introduction path is evacuated in a direction opposite to the gas introduction direction. As a result, the exhaust gas is forcibly exhausted, so that the exhaust of the residual gas in the gas introduction path can be promoted, and the throughput can be improved accordingly.

Hereinafter, a preferred embodiment of a plasma processing apparatus and a plasma processing method according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a configuration diagram showing an example of a plasma processing apparatus according to the present invention, and FIG. 2 is a plan view showing a positional relationship between an arrangement of gas introduction passages and gas discharge ports provided in a shower head having the function of a top plate. 3 is an enlarged cross-sectional view showing the structure of the gas discharge port.

  As shown in the figure, the plasma processing apparatus 30 has a cylindrical processing container 32 made of an aluminum alloy or the like. The processing vessel 32 is grounded, and the central portion of the bottom thereof is formed in a convex shape downward. In the processing container 32, a mounting table 36 is provided which is erected from a central portion at the bottom by a support 34. A semiconductor wafer W as a processing object is mounted and held on the upper surface of the mounting table 36. The The mounting table 36 is made of a ceramic material such as alumina or aluminum nitride. An electrostatic chuck 38 and a resistance heater 40 are embedded in the mounting table 36, and the electrostatic chuck 38 electrostatically charges the wafer W. The wafer W can be held by suction with an attractive force, or the wafer W can be heated and maintained at a predetermined temperature by the resistance heater 40.

  The mounting table 36 functions as a lower electrode, and the electrostatic chuck 38 is connected to a chuck power source 44 and a bias high frequency power source 46 of 13.56 MHz, for example, via a power supply line 42. The mounting table 36 is also provided with lifter pins (not shown) for raising and lowering the wafer when the wafer W is loaded and unloaded.

  An exhaust port 46 is provided on the concave bottom side wall of the processing container 32, and a vacuum exhaust system 48 is connected to the exhaust port 46. The vacuum exhaust system 48 has an exhaust passage 50 connected to the exhaust port 46, and a pressure adjusting valve 52 and a vacuum pump 54 are interposed in the middle of the exhaust passage 50. A vacuum can be drawn to a predetermined pressure while detecting the pressure in the processing container 32 by a meter.

  Further, a loading / unloading port 56 for loading / unloading the wafer W is provided on the side wall of the processing container 32, and a gate valve 58 that is opened and closed when the wafer is loaded / unloaded is provided at the loading / unloading port 56. And the ceiling part of the processing container 32 is opened, The shower head 60 which is a gas introduction means which serves also as a top plate is airtightly attached to the opening part through a sealing member 62 such as an O-ring. ing. The shower head 60 is made of a dielectric material such as quartz or alumina so as to be able to transmit electromagnetic waves, that is, microwaves, and is set to a thickness that can withstand atmospheric pressure.

  A ring-shaped space 64 is formed in the side wall portion of the processing container 32 corresponding to the side surface of the shower head 60, and the inner side is opened and formed along the circumferential direction. Between the side wall of the shower head 60 and the side wall of the processing container 32, two seal members 66 made of an O-ring or the like are interposed so as to be sealed. A part of the ring-shaped space 64 is communicated with a gas introduction port 68 through which a gas containing at least a plasma excitation gas flows, and a gas passage 70 through which a gas flows from the outside as needed. Is connected.

The gas passage 70 is provided with a flow rate controller (not shown) such as an on-off valve 72 or a mass flow controller, so that at least plasma excitation gas can be supplied while controlling the flow rate as required. ing. As this plasma excitation gas, a rare gas such as Ar gas, He gas or Ne gas can be used, and other gases such as N ₂ or O ₂ can be flowed depending on the processing mode. Yes.

  The gas introduction port 68 is provided with an introduction path pressure measuring device 74 for measuring the pressure in the gas introduction path, which will be described later, via the ring-shaped space 64, and the gas passage 70 is provided with this gas. An introduction path evacuation system 76 for evacuating and exhausting the atmosphere in the introduction path 70 is connected. The introduction passage vacuum exhaust system 76 has an exhaust passage 78 connected to the gas passage 70, and an open / close valve 80 and a vacuum pump 82 are interposed in the exhaust passage 78, and a vacuum is provided as necessary. Can be pulled. Depending on the processing mode, the introduction path evacuation system 76 may not be provided, and the evacuation path of the evacuation system 48 for evacuating the inside of the processing vessel without providing the vacuum pump 82. It may be connected to the upstream side of the 50 vacuum pumps 54 so that the vacuum exhaust system 76 is also used.

  As shown in FIG. 2, a plurality of gas introduction paths 84 that are long and short from the outer peripheral surface of the shower head 60 toward the center of the shower head 60 are formed in the shower head 60. A plurality of gas discharge ports 86 whose lower ends are opened toward the processing space S in the processing container 32 are communicated with 84.

  Specifically, as shown in FIG. 2, a large number of gas introduction paths 84 are provided so as to cover substantially the entire area of the shower head 60, and branch downward from a predetermined portion of the gas introduction path 84. A gas introduction path 84 a is provided, and the lower end of the branch gas introduction path 84 a is communicated with the gas discharge port 86. The gas discharge ports 86 are arranged so as to be substantially evenly distributed in the surface of the shower head 60. As a result, the gas introduced from the outside flows through the ring-shaped space 64 to the gas introduction passages 84 and the branch gas introduction passages 84 a and is led to the gas discharge ports 86. Here, the diameter of the gas introduction path 84 is about φ1 to φ3 mm, and the diameter of the branch gas introduction path 84a is about φ1 to φ3 mm, both of which are relatively fine and affect the electromagnetic field in the shower head 60. It is made small so that abnormal discharge does not occur in the introduction path as much as possible.

  The gas discharge port 86 is set to have a diameter of about 10 mm and a depth (height) of about 10 mm, and a gas-permeable ceramic material 88 is mounted in the gas discharge port 86. Specifically, a breathable porous (porous) ceramic sintered body 88a having pores communicating in the gas flow direction is accommodated in the back (upper part) of the gas discharge port 86, and below (processed). In the space S side), a ceramic molded body 88b in which a plurality of gas injection holes 90 having a diameter of about 50 μm are formed in the vertical direction is accommodated to form the whole.

  As a result, the overall conductance is very low as described above, and the ceramic molded body having the porous ceramic sintered body 88a and the fine gas injection holes 90 for the gas flowing into the branch gas introduction path 84a. It can be introduced little by little into the processing space S through a ceramic material 88 made of 88b. 3A shows a state before the ceramic material 88 is mounted, and FIG. 3B shows a state after the ceramic material 88 is mounted. In addition to the plasma excitation gas, oxygen or ammonia may be introduced from the shower head 60 as a gas that actively generates radicals.

  Here, the length of the gas injection hole 90 formed in the ceramic molded body 88b is set to be longer than the average free path which is the average distance until the electrons are scattered, thereby greatly reducing the back flow of the plasma. Is possible. This mean free path is inversely proportional to the pressure, and is about 4 mm at 0.1 Torr, for example.

  Actually, since the pressure on the gas introduction side (upper side in FIG. 3) of the gas injection hole 90 is high, the mean free path is shorter than 4 mm, but in this embodiment, the length of the gas injection hole 90 is reduced. It is set to about 5 mm and is longer than the mean free path. However, since the mean free path is only an average distance, there are electrons that travel without being scattered over a longer distance when viewed statistically. Therefore, here, a porous ceramic sintered body 88a having pores communicating in the gas flow direction is installed on the gas introduction side (upper side) of the gas injection hole 90 to prevent the entry of electrons.

  An electromagnetic wave introducing means 92 for introducing an electromagnetic wave for generating plasma into the processing space S of the processing container 32 is provided on the upper surface of the shower head 60 in order to generate plasma in the processing container 32. Here, microwaves are used as the electromagnetic waves. Specifically, the electromagnetic wave introducing means 92 has a disk-shaped planar antenna member 94 provided on the upper surface of the shower head 60, and a slow wave material 96 is provided on the planar antenna member 94. . The slow wave material 96 has a high dielectric constant characteristic in order to shorten the wavelength of the microwave, and is made of, for example, aluminum nitride. The planar antenna member 94 is configured as a bottom plate of a waveguide box 98 made of a conductive hollow cylindrical container covering the entire upper surface of the slow wave member 96. A cooling jacket 100 through which a coolant flows to cool the waveguide box 98 is provided at the top of the waveguide box 98.

  The waveguide box 98 and the peripheral portion of the planar antenna member 94 are both electrically connected to the processing container 32, and an outer tube 102a of the coaxial waveguide 102 is connected to the center of the upper portion of the waveguide box 98. The inner conductor 102 b on the inner side is connected to the central portion of the planar antenna member 94 through the central through hole of the slow wave member 96. The coaxial waveguide 102 is connected to a rectangular waveguide 106 via a mode converter 104, and the rectangular waveguide 106 is connected to a microwave generator 108 of 2.45 GHz, for example. Microwaves are propagated to the planar antenna member 94. Therefore, the microwave generator 108 and the planar antenna member 94 are connected by the rectangular waveguide 106 and the coaxial waveguide 102 so as to propagate microwaves. Here, the frequency of the microwave is not limited to 2.45 GHz, and other frequencies such as 8.35 GHz may be used.

  The planar antenna member 94 is made of a conductive material having a diameter of 400 to 500 mm and a thickness of 1 to several mm, for example, for a wafer having a size of 300 mm, for example, a copper plate or aluminum having a surface plated with silver. The disk is formed with a large number of slots 94a made of, for example, long groove-like through holes. The arrangement form of the slots 94a is not particularly limited. For example, the slots 94a may be arranged concentrically, spirally, or radially, or may be distributed uniformly over the entire surface of the antenna member. The planar antenna member 94 has a so-called RLSA (Radial Line Slot Antenna) type antenna structure, whereby plasma having features of high density and low electron temperature is obtained.

  The lower stage shower plate 110 made of a conductor such as aluminum alloy or stainless steel is provided as a second gas introduction means at the middle part of the processing container 32 in the upper and lower parts, and a sealing member such as an O-ring. 112 is provided in an airtight state. The lower shower plate 110 has a gas supply port 114, and a plurality of gas flow paths 116 for introducing the gas supplied therefrom into the processing space S are formed in the gas supply port 114.

  A large number of gas holes 118 are formed in the lower surface of the gas flow path 116 so that the gas can be discharged into the processing space S. The lower shower plate 110 has a plurality of large openings 120 for allowing the plasma generated in the upper processing space to pass through the lower processing space efficiently by diffusion between the adjacent gas flow paths 116. Is formed.

  An opening / closing valve 124 is interposed in the gas passage 122 connected to the gas supply port 114 so that a gas necessary for processing can be supplied while controlling the flow rate as necessary. For example, when a film forming process is performed by plasma CVD, a film forming gas is supplied from the lower shower plate 110, and an etching gas can be flowed when etching is performed. In a plasma etching apparatus that is often performed at a low pressure, the electron temperature of the plasma is high, so that the lower shower plate 110 is greatly damaged by ions, which causes problems such as metal contamination and particles. Therefore, the lower shower plate 110 is not provided, and the etching gas may be supplied from the shower head 60 together with the plasma excitation gas. In many cases, the etching gas is actively dissociated to increase the reactivity, and it is better to supply the etching gas from the shower head 60 even in such a case. In any case, there are various apparatus configurations for the type of gas to be introduced and the gas introduction means to be used depending on the mode of the plasma treatment.

  Returning to FIG. 1, the overall operation of the plasma processing apparatus 30 configured as described above is controlled by the control means 126 including, for example, a computer, and a computer program for performing this operation. Is stored in a storage medium 128 such as a floppy, a CD (Compact Disc), a hard disk, or a flash memory. Specifically, in accordance with commands from the control means 126, the start, stop and flow control of each gas, the supply and power control of microwaves and high frequencies, the control of process temperature and process pressure, and the inside of the gas introduction path 84 Pressure control or the like is performed.

Next, for example, a plasma film forming method performed using the plasma processing apparatus 30 configured as described above will be described.
First, the overall flow will be briefly described. The semiconductor wafer W is accommodated in the processing chamber 32 by the transfer arm (not shown) via the gate valve 58, and the lifting pins (not shown) are moved up and down. The wafer W is mounted on the mounting surface on the upper surface of the mounting table 36, and the wafer W is electrostatically attracted by the electrostatic chuck 38. The wafer W is maintained at a predetermined process temperature by the resistance heater 40, and, for example, Ar gas is introduced as a plasma excitation gas from the shower head 60 having the function of a top plate into the processing space S while controlling the flow rate of the wafer W. A film forming gas is introduced into the processing space S from the gas hole 118 of the plate 110 while controlling the flow rate.

  Specifically, the Ar gas spreads from the gas introduction port 68 to the entire circumference along the ring-shaped space 64, flows into each gas introduction path 84 provided radially toward the center of the shower head 60, and It is introduced into the processing space S through the porous ceramic sintered body 88a provided at each gas discharge port 86 and the gas injection holes 90 of the ceramic molded body 88b. In this case, since the conductance of the gas path in the shower head 60 is very low, the pressure in the gas introduction path 84 is considerably higher than in the processing space S, and this pressure does not cause abnormal discharge as will be described later. The pressure range is set to such a range. The inside of the processing vessel 32 is maintained at a predetermined process pressure by the pressure adjustment valve 52 of the vacuum exhaust system 48.

  At the same time, the microwave generator 108 of the electromagnetic wave introducing means 92 is turned on, so that the microwave generated by the microwave generator 108 is transmitted to the planar antenna member 94 via the rectangular waveguide 106 and the coaxial waveguide 102. To the processing space S, the microwave whose wavelength is shortened by the slow wave material 96 is introduced through the shower head 60 having the function of a top plate, thereby generating plasma in the processing space S to obtain a predetermined value. The film forming process using the plasma is performed.

Here, the plasma film forming method will be described in detail with reference to FIGS. FIG. 4 is a process diagram showing an example of a plasma film forming method, and FIG. 5 is a graph showing the pressure dependence of the discharge start voltage in an Ar gas atmosphere.
First, the inside of the processing container 32 is continuously evacuated, and the unprocessed wafer W is loaded into the processing container 32 via the gate valve 58 (loading step) as described above, and this is placed on the mounting table 36. The processing container 32 is placed in an airtight state by placing it on the top (S1).

  Next, supply of, for example, Ar gas, which is a plasma excitation gas, is started (S2). The Ar gas flows through the gas passage 70 while being controlled in flow rate, reaches the ring-shaped space 64 from the gas introduction port 68, and flows from the ring-shaped space 64 into the gas introduction passages 84 as described above to flow into the gas discharge ports 86. Thus, the air is introduced into the processing space S through the air-permeable ceramic material 88. In this case, as described above, since the conductance of the gas path in the shower head 60 is very low, the pressure in the gas introduction path 84 is considerably higher than in the processing space S, and the gas discharge port 86 performs processing. In order to stabilize the flow rate of the gas introduced into the space S, it is necessary to stabilize the pressure in the gas introduction path 84.

  Therefore, here, the pressure in the gas introduction path 84 is constantly measured by the introduction path pressure measuring device 74 provided in the gas introduction port 68, and the system waits until the measured value becomes a predetermined pressure and stabilizes. When the predetermined pressure is stabilized, the operation proceeds to the next operation (S3). The relationship among the pressure in the processing space S, the pressure in the gas introduction path 84, and the gas flow rate actually introduced into the processing space S from the gas discharge port 86 is determined in advance. The pressure in the gas introduction path 84 is determined.

  As described above, when the pressure in the gas introduction path 84 is stabilized at a predetermined pressure, the process proceeds to a plasma processing step in which actual processing is performed. Here, the supply of the raw material gas for film formation from the lower shower plate 110 is started while controlling the flow rate, the pressure in the processing container 32 is maintained at a predetermined pressure (process pressure), and the electromagnetic wave introducing means 92 The microwave generator 108 is turned on to introduce a microwave into the processing container 32 to generate plasma (S4). As a result, plasma processing is actually performed, and film formation processing is performed on the wafer surface here. Then, the plasma processing is executed for a predetermined time (S5).

  Here, the relationship between the said processing space S and the pressure in the gas introduction path 84 of the shower head 60 is demonstrated with reference to FIG. FIG. 5 is a graph showing the pressure dependence of the discharge start voltage in an Ar gas atmosphere. The horizontal axis represents pressure and the vertical axis represents the discharge start voltage.

  As is apparent from FIG. 5, in the case of Ar gas, the discharge start voltage becomes the lowest when the pressure is around 1 Torr, and the discharge start voltage gradually increases as the pressure is increased or decreased. The characteristic curve is convex downward.

  Here, in order to prevent discharge from occurring in the gas introduction path 84 of the shower head 60 in which discharge is generated only in the processing space S and the electromagnetic field is particularly strong, the discharge start voltage in the gas introduction path 84 is It can be seen that it is preferable that the voltage is always higher than the discharge start voltage in the processing space S.

  Therefore, in the present invention, the pressure in the processing space S, that is, the process pressure, is set so as to be a constant value within a pressure range of 0.04 to 10 Torr, for example, as performed in a film formation or surface modification process. is doing. In the gas introduction path 84, for example, a constant value of 30 Torr or more is set so that the discharge start voltage is higher than the discharge start voltage at the process pressure determined by a constant value within the pressure range of 0.04 to 10 Torr. To do.

  In another example, the pressure in the processing space S, that is, the process pressure, is set to be a constant value within a pressure range of 0.005 to 0.2 Torr as performed, for example, in an etching process. . In the gas introduction path 84, for example, a constant value of 300 Torr or higher so that the discharge start voltage is higher than the discharge start voltage at the process pressure determined by a constant value within the pressure range of 0.005 to 0.2 Torr. Set to.

  The maximum value of the pressure in the gas introduction path 84 is, for example, about 600 Torr considering the allowable conductance of the gas path in the shower head 60. Further, if necessary, the conductance of the gas path in the shower head 60 is adjusted so as to satisfy each pressure range as described in FIG.

  As described above, when plasma is generated in the processing space S in S4 and S5 in FIG. 4, the pressure in the gas introduction path 84 is measured by the introduction path pressure measuring device 74 as described above. The pressure in the gas introduction path 84 is constantly kept at a constant value of 30 Torr or higher, preferably 300 Torr or higher by controlling the flow rate of gas flowing into the gas passage 70 and the exhaust amount of the processing container 32. It is controlled. Of course, this control is performed by the control means 126.

When the plasma processing is completed as described above, for example, the supply of all gases is stopped, the microwave generator 108 is turned off to stop the supply of microwaves (S6), and then the processed wafer W is processed. Is carried out from the inside of the processing container 32 (S7).
In the case of single wafer cleaning in which cleaning is performed each time one wafer is processed, the shower head 60 or the lower shower plate 110 is used to supply the cleaning gas into the processing container 32 and at the same time, the shower. An Ar gas is supplied from the head 60 to generate plasma, and a plasma cleaning process is performed to remove unnecessary films and the like attached to the processing container 32 (S8). Even when plasma is generated during the cleaning process, as described in S3 and S4, the pressure in the gas introduction path 84 is controlled so that abnormal discharge does not occur in the gas introduction path 84.

When the cleaning process is completed and there is a waiting wafer waiting for further processing (YES in S9), the process returns to S1 and the steps S1 to S8 are repeatedly executed as described above. If there is no wafer (NO in S9), the entire process is terminated.
As described above, in the present invention, the pressure in the gas introduction path 84 is set to be 4000 Pa (30 Torr) or higher, so that abnormal discharge can be prevented from occurring in the gas introduction path 84. it can.

In addition, a breathable ceramic material 88 made of a porous ceramic sintered body 88a and a ceramic molded body 88b in which extremely fine gas injection holes 90 are formed is mounted in the gas discharge port 86 of the shower head 60. Therefore, it is possible to prevent the plasma from flowing back into the gas discharge port 86 or the gas introduction path 84 to cause abnormal discharge or the like.
In the above embodiment, as an example of the film forming gas, when a silicon-based film is formed, a silane-based gas such as monosilane or disilane can be used, and a low dielectric constant film such as a CF-based film is formed. In this case, a CF-based gas such as C ₅ F ₈ gas can be used, and an organic metal gas can also be used.

In the flowchart shown in FIG. 4, the cleaning process is performed every time one wafer W is processed. However, the present invention is not limited to this, and the cleaning process may be performed every time a plurality of wafers W are processed. Good.
Further, in the flowchart shown in FIG. 4, the supply of Ar gas, which is a plasma excitation gas, is stopped every time one wafer W is processed, but the plasma excitation gas is divided into a plurality of steps without stopping the supply. You may make it flow continuously over. For example, Ar gas is allowed to flow continuously throughout all the steps, that is, the wafer loading step (S1), the plasma processing step (S4, S5), the wafer unloading step (S7), and the cleaning step (S8). You may do it. Furthermore, you may flow Ar gas continuously over one or more processes selected from a plasma processing process and each other three processes.

  According to this, as will be described later, since the gas remaining in the gas introduction path 84 of the shower head 60 does not escape rapidly, the gas pressure in the gas introduction path 84 of the shower head 60 is increased to stabilize the Ar gas. 4 can be omitted or shortened, that is, the throughput can be improved accordingly.

  Normally, when Ar gas, which is a plasma excitation gas, is supplied at a constant flow rate at the time of the process (plasma treatment) at the same time as the gas supply starts, in order to improve throughput At the start of supply, Ar gas may be flowed at a flow rate larger than the gas supply amount (flow rate) during the process, and the gas supply amount may be gradually reduced to a set flow rate. In this case, for example, Ar gas may be caused to flow by PID control in accordance with a differential pressure with respect to the target pressure of the gas introduction path 84, for example.

  FIG. 6 is a graph showing the relationship between the supply amount of Ar gas and the pressure in the gas introduction path in the method of the present invention and the conventional method, and FIG. 6A shows the gas flow rate of Ar gas in the method of the present invention and the conventional method. An example is shown and FIG. 6 (B) is a graph which shows the pressure change in the gas introduction path of the method of this invention and a conventional method. In the conventional method, as shown by a straight line A1 in FIG. 6 (A), Ar gas is supplied at a constant process flow rate from the start of gas supply, and therefore, as shown by a curve A2 shown in FIG. It takes a long time T1 to stabilize to the set pressure in the introduction path 84.

  On the other hand, if, for example, PID control is performed in which the pressure is measured by the introduction path internal pressure measuring device 74 and the gas flow rate is controlled in accordance with the differential pressure between the measured value and the target pressure, the pressure in FIG. As indicated by a curve B1, Ar gas is supplied at a flow rate considerably higher than the process flow rate for a while immediately after the start of gas supply. As a result, as shown by a curve B2 in FIG. 6B, the pressure in the gas introduction path 84 rapidly increases, reaches the set pressure in a time T2 much shorter than the time T1, and stabilizes early. Can be made. Therefore, the throughput can be improved by the time difference (T1-T2).

In addition, during the plasma processing shown in S5 in FIG. 4, the pressure value in the gas introduction path 84 measured by the introduction path pressure measuring device 74 fluctuates more than the set pressure (target pressure) for some reason. In this case, for example, when the pressure is outside the range of ± 10% of the set pressure, the film quality as designed may not be obtained.
Similarly, when the pressure value measured by the pressure measuring device 74 in the introduction path becomes an abnormal discharge generation region in the gas introduction path 84 for some reason, for example, it is smaller than 30 Torr in FIG. In this case, the plasma processing may be interrupted immediately because there is a risk that the designed film quality may not be obtained.

  Further, when the gas type introduced from the shower head 60 introduces another gas, for example, A gas in addition to Ar gas, another gas, for example, B gas is introduced instead of this A gas. When switching in this way, the conductance of the gas path in the shower head 60 is very small as described above. Therefore, if the inside of the processing container 32 is evacuated, it remains in the gas introduction path 84 of the shower head 60 and the like. Gas does not escape quickly, and it takes a long time to fully escape.

  Therefore, in the present invention, the evacuation system 48 is continuously operated, the on-off valve 72 of the gas passage 70 is closed to stop the gas supply to the shower head 60, and at the same time, the introduction passage evacuation system 76 is driven. The on-off valve 80 interposed therein is opened, and the A gas remaining in the gas introduction path 84, the branch gas introduction path 84a and the gas discharge port 86 of the shower head 60 is reversed (to the introduction side). ) Forcibly evacuate to quickly exhaust the remaining A gas.

  According to this, the throughput can be improved by the amount that the remaining A gas can be exhausted quickly. In this case, when the introduction path evacuation system 76 is not used, the residual gas in the gas introduction path 84 and the like can be evacuated in about 10 minutes, for example, but when the introduction path evacuation system 76 is used. It was confirmed that the residual gas could be exhausted in only about 1 minute, and the processing efficiency could be greatly improved.

  Further, here, the gas discharge port 86 is provided with a breathable ceramic material 88, and the conductance is designed to be low by reducing the inner diameter of the gas introduction path 84 or the branch gas introduction path 84a. If another member having a finer gas injection hole 90 that can prevent the backflow of plasma without providing the air-permeable ceramic material 88 can be mounted, the other member is replaced with the ceramic material 88. What is necessary is just to provide.

Here, the lower shower plate 110 is provided as the second gas introduction means. At this time, the film forming gas released from the gas holes 118 of the lower shower plate 110 may diffuse to the lower surface of the shower head 60. In particular, when a heavy gas such as C ₅ F ₈ is used as a film forming gas, the temperature of the lower surface of the shower head 60 is lower than that of the surrounding area, so that the concentration of relatively heavy molecules (atoms) increases on the low temperature side. The concentration of C ₅ F ₈ gas on the lower surface of the shower head 60 becomes considerably high and an insulating film or the like is formed, which is not preferable. Therefore, Ar gas was flown from the shower head 60 and C ₅ F ₈ gas was flown from the lower shower plate 110 by simulation, and the respective flow rates were varied to obtain the results of FIG.

In FIG. 7, the vertical axis represents the reverse diffusion ratio, and the horizontal axis represents the Ar gas flow rate from the shower head 60. The reverse diffusion ratio is the concentration ratio (%) of C ₅ F ₈ gas 20 mm below and 20 mm above the lower shower plate 110, and the pressure in the processing vessel is a viscous flow region of 20 mm Torr or more. In the figure, ◆ indicates the case where the Ar gas flow rate and the C ₅ F ₈ gas flow rate are 1: 1, and ■ indicates that the Ar gas flow rate is varied from 200 to 2000 sccm, and the C ₅ F ₈ gas flow rate is constant at 200 sccm. Is one point of data when the Ar gas flow rate and the C5F8 gas flow rate are 100: 1.

As is apparent from FIG. 7, the Ar diffusion flow rate: C ₅ F ₈ gas flow rate is 1: 1, and even when the gas flow rate is changed from 1: 1 to 10: 1, the reverse diffusion ratio is almost similar. It can be seen that a curve is shown, which simply depends on the flow rate of Ar gas. Accordingly, the flow rate of Ar gas flowing from the shower head 60 is 600 sccm (reverse diffusion ratio 70%) or more, more preferably 1000 sccm (reverse diffusion ratio 50%) or more, more preferably 2000 sccm (reverse diffusion ratio 20%) or more. It can be seen that a diffusion preventing effect can be obtained. The Ar gas flow rate in the above, each divided by the open area of the lower shower plate ^{110, 0.4sccm / cm 2, 0.7sccm} / cm 2, was 1.4sccm / cm ^2, the lower shower plate 110 Even if the size and the opening area are changed, it is considered that the same reverse diffusion ratio can be obtained by flowing Ar gas at a flow rate per unit area.

Furthermore, here, the lower shower plate 110 is provided as the second gas introduction means in the middle part of the processing vessel 32. However, the present invention is not limited to this, and the lower shower plate is not limited to this, as in the modification of the plasma processing apparatus shown in FIG. Instead of providing the plate 110, only the shower head 60 may be provided as the gas introduction means.
Also in this case, except for the case where the shower plate 110 is used, the same function and effect as those described with reference to FIGS.

  Further, the plasma processing apparatus as shown in FIG. 8 is preferably applied to an etching processing apparatus in which members located in the processing space S are easily etched. In this case, by omitting the installation of the shower plate 110, It is possible to prevent unnecessary particles from being generated by etching.

In particular, in such a plasma etching processing apparatus, for example, a multilayer insulating layer having different film types may be continuously etched in a plurality of stages while switching the etching gas type. For example, it is necessary to sequentially switch the etching gas added to the Ar gas to N ₂ , O ₂ , H _2, or the like according to the type of film to be etched. In this case, as described above, the introduction path evacuation system is used when the gas is switched. By driving 76, the gas remaining in the gas introduction path 84 of the shower head 60 and the like can be evacuated in the reverse direction, and this residual gas can be quickly eliminated.

As described above, the plasma processing is described as an example of the plasma processing here, but the present invention is not limited to this, and the present invention is also applicable to other plasma processing apparatuses such as a plasma ashing apparatus. Can do.
Furthermore, although the microwave is used as the electromagnetic wave introducing means 92, the present invention is not limited to this, and a high frequency with a frequency of 13.56 MHz, for example, can also be used. The present invention can be applied to various plasma processing apparatuses such as a coupled plasma processing apparatus.
Although the semiconductor wafer is described as an example of the object to be processed here, the present invention is not limited thereto, and the present invention can be applied to a glass substrate, an LCD substrate, a ceramic substrate, and the like.

It is a block diagram which shows an example of the plasma processing apparatus which concerns on this invention. It is a top view which shows the positional relationship of the arrangement | sequence of the gas introduction path provided in the shower head which has a function of a top plate, and a gas discharge port. It is an expanded sectional view which shows the structure of a gas discharge port. It is process drawing which shows an example of the plasma film-forming method. It is a graph which shows the pressure dependence of the discharge start voltage in Ar gas atmosphere. It is a graph which shows the relationship between the supply amount of Ar gas in the method of this invention, and the conventional method, and the pressure in a gas introduction path. It is a graph which shows the relationship between the flow volume of the gas from a shower head, and a back diffusion ratio. It is a block diagram which shows the modification of a plasma processing apparatus. It is a schematic block diagram which shows the conventional general plasma processing apparatus using a microwave.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 Plasma processing apparatus 32 Processing container 36 Mounting stand 40 Resistance heating heater 48 Vacuum exhaust system 60 Shower head (gas introduction means)
64 ring-shaped space 68 gas introduction port 74 pressure measuring device in introduction passage 76 introduction passage evacuation system 82 vacuum pump 84 gas introduction passage 84a branch gas introduction passage 86 gas discharge port 88 porous ceramic material 88a porous ceramic sintered body 88b Alumina sintered body 90 Gas injection hole 92 Electromagnetic wave introduction means 94 Planar antenna member 108 Microwave generator 110 Lower shower plate (second gas introduction means)
126 Control means 128 Storage medium W Semiconductor wafer (object to be processed)

Claims (17)

A gas introduction path for introducing a gas containing at least a plasma excitation gas into the processing container that can be depressurized, and a plurality of gas discharge ports that communicate with the gas introduction path and discharge the gas into the processing container. A shower head, electromagnetic waves are introduced into the processing container through the shower head to excite the gas to generate plasma, and the target object is processed using the plasma. In the plasma processing method,
A plasma processing method, wherein the pressure of the gas in the gas introduction path is set to 4000 Pa (30 Torr) or more. 2. The plasma processing method according to claim 1, wherein the pressure in the gas introduction path is 40 kPa (300 Torr) or more. The plasma processing method according to claim 1, wherein at least a part of the gas introduction path is provided inside the shower head.

The pressure in the gas introduction path is measured by a pressure measuring device, and the pressure in the gas introduction path adjusts at least one of the gas flow rate flowing into the gas introduction path and the exhaust amount from the processing container. 4. The plasma processing method according to claim 1, wherein the plasma processing method is maintained at a predetermined pressure value. The plasma processing method according to any one of claims 1 to 4, wherein the plasma processing is started when the pressure in the gas introduction path is stabilized at a predetermined pressure value. 6. The process according to claim 1, wherein, during the plasma process, the process is interrupted when the pressure in the gas introduction path is out of a range of ± 10% of a set pressure. The plasma processing method as described. The plasma processing method according to claim 1, wherein the processing is interrupted when the pressure in the gas introduction path becomes an abnormal discharge generation region during the processing. The plasma processing according to any one of claims 1 to 7, wherein when the supply of the gas into the processing container is started, the supply is started at a flow rate larger than a gas supply amount during the processing. Method. When switching the type of gas supplied into the processing container, the gas remaining in the gas introduction path is forcibly exhausted in a direction opposite to the gas introduction direction. The plasma processing method according to claim 1. A loading step of loading the object to be processed into the processing container;
A plasma processing step of performing plasma processing on the object to be processed;
An unloading step of unloading the object to be processed from the processing container;
A cleaning step of flowing a cleaning gas into the processing container to perform cleaning, and the plasma excitation gas is allowed to flow continuously over at least two steps selected from the steps. The plasma processing method according to any one of claims 1 to 9, wherein The plasma processing method according to claim 1, wherein the treatment is a film formation treatment for forming a thin film on a surface of the object to be processed. In a plasma processing apparatus for performing plasma processing on an object to be processed,
A processing container whose ceiling is opened and the inside of which can be decompressed;
A mounting table provided in the processing container for mounting the object to be processed;
A gas introduction path that has a function of a top plate that is airtightly attached to the opening of the ceiling portion, introduces a gas containing at least a plasma excitation gas, and communicates with the gas introduction path to enter the gas into the processing container. A shower head which is a gas introduction means having a plurality of gas discharge ports for discharging gas;
Electromagnetic wave introducing means for introducing electromagnetic waves for plasma generation into the processing container through the shower head;
Means for supplying the gas to the gas introduction path so that the gas pressure in the gas introduction path is 4000 Pa or more;
A plasma processing apparatus comprising: 13. The plasma processing apparatus according to claim 12, further comprising an in-introduction pressure measuring device for measuring a gas pressure in the gas introduction path. 14. The plasma processing apparatus according to claim 12, further comprising an introduction path vacuum exhaust system for exhausting an atmosphere in the gas introduction path. 15. The plasma processing apparatus according to claim 14, wherein the introduction path evacuation system is also used as an evacuation system for evacuating the atmosphere in the processing vessel. 16. The plasma processing apparatus according to claim 12, further comprising second gas introduction means for introducing a gas into the processing container. A processing container whose ceiling is opened and the inside of which can be decompressed;
A mounting table provided in the processing container for mounting the object to be processed;
A gas introduction path that has a function of a top plate that is airtightly attached to the opening of the ceiling portion, introduces a gas containing at least a plasma excitation gas, and communicates with the gas introduction path to enter the gas into the processing container. A shower head which is a gas introduction means having a plurality of gas discharge ports for discharging gas;
Electromagnetic wave introducing means for introducing electromagnetic waves for plasma generation into the processing container through the shower head;
An introduction path pressure measuring device for measuring the pressure in the gas introduction path;
Control means for controlling the operation of the entire apparatus;
When performing plasma processing using a plasma processing apparatus equipped with
A storage medium storing a computer-readable program for controlling the plasma processing apparatus so as to execute the plasma processing method according to claim 1.

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