JP4558285B2 - Plasma cleaning method and substrate processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention generally relates to a method for manufacturing a semiconductor device, and more particularly to a cleaning method and a substrate processing method using plasma.
[0002]
Plasma generators are widely used in the manufacture of semiconductor devices and liquid crystal display devices. For example, by using a plasma generator, a film forming process or an etching process can be performed at a low temperature so that the concentration distribution of the impurity element formed in the semiconductor substrate does not change. The plasma generator is used to clean the inside of the processing container after the substrate processing.
[0003]
[Prior art]
FIG. 1 shows a configuration of a conventional typical single wafer CVD apparatus 10.
[0004]
Referring to FIG. 1, a single wafer type CVD apparatus 10 includes a susceptor 12 that includes a heating mechanism (not shown) and holds a substrate to be processed 12A, and is evacuated by a vacuum pump 13 through a shutoff valve 13A and a conductance valve 13B. In the processing container 11, a shower head 14 to which a source gas is supplied from a source gas supply system 15 via a line L 1 and a valve V 1 includes a substrate 12 A to be processed on the susceptor 12. It is provided to face.
[0005]
The raw material supply system 15 includes raw material gas sources 15A to 15C, the raw material gas in the raw material gas source 15A is connected to the line L1 via a valve 15VA, and the raw material gas in the raw material gas source 15B is connected to the line L1. The source gas in the source gas source 15C is supplied to the line L1 via the valve 15VC via 15VB.
[0006]
The source gas supplied through the line L1 is discharged into the process space in the processing vessel 11 through the shower head 14, and is decomposed on the surface of the substrate to be processed 12 by a decomposition reaction on the surface of the substrate to be processed 12A. Desired film formation occurs.
[0007]
In the single wafer CVD apparatus 10 of FIG. 1, the processing vessel 11 is provided with a gate valve structure (not shown) for taking in and out the substrate 12A to be processed, and the gate valve structure is provided in the substrate transfer chamber. Are combined. The single wafer type CVD apparatus 10 constitutes a single wafer type substrate processing system together with another processing apparatus coupled to the substrate transfer chamber.
[0008]
In the single wafer CVD apparatus 10 constituting such a single wafer processing system, the substrate temperature is controlled by a heating device formed in the susceptor 12 during the film forming process, and the wall surface of the processing container 10 is compared. It is kept at a low temperature, for example, room temperature to about 150 ° C. (cold wall).
[0009]
In such a cold wall type CVD apparatus, deposition of reaction products on the inner wall surface or the susceptor side wall surface of the processing vessel 11 is inevitable during film formation on the substrate 12A to be processed. Each time a film forming process for a plurality of substrates to be processed is completed, a cleaning process is performed in which an etching cleaning gas is supplied into the processing container 11 to remove deposits.
[0010]
Therefore, in the CVD apparatus of FIG. 1, a cleaning module 16 including an etching gas source 16A, a plasma gas (dilution gas) source 16B, and a remote plasma source 16C is provided outside the processing vessel 11, and the remote plasma source 16C is provided. The highly reactive etching gas formed by the line L2 and the valve 16V _C And is supplied to the process space inside the processing vessel 11. By providing the plasma source outside the processing container 11 in this manner, damage to the inner wall of the processing container 11 due to high-energy plasma can be avoided and stable cleaning can be performed. Further, since ions formed in the plasma recombine with electrons while being transported from the remote plasma source 16C to the processing container 11, only radicals that promote the reaction are supplied into the processing container 11 in the configuration of FIG. .
[0011]
In FIG. 1, the etching gas source 16A is NF. _Three Using a fluorine-based etching gas such as a cleaning gas, the remote plasma source 16C has a valve 16V. _A The plasma gas source 16B supplies a rare gas such as Ar to the remote plasma source 16C and a valve 16V. _B Supply through.
[0012]
The fluorine-based cleaning gas is NF _Three Halogen compounds such as _Three It is also possible to use non-halogen compounds such as COOH. In addition to Ar, He, Ne, Kr, Xe, or the like may be used as the dilution gas from the plasma gas source 16B. Further, as the dilution gas, H other than the rare gas may be used. ₂ O, O ₂ , H ₂ , N ₂ , C ₂ F ₆ It is also possible to use.
[0013]
As such a remote plasma source 16C, conventionally, an inductively coupled (ICP) type plasma generator 20 shown in FIG. 2A, an electron cyclotron resonance (ECR) type plasma generator 30 shown in FIG. A helicon wave excitation type plasma generator 40 shown in FIG. 2 (C), a microwave resonator type plasma generator 50 shown in FIG. 2 (D), a toroidal type plasma generator 60 shown in FIG. Yes. A parallel plate (CCP) type plasma generator 70 shown in FIG. 3 is used as a plasma source provided inside the processing vessel 11.
[0014]
In the ICP type plasma generator 20 of FIG. 2 (A), a high frequency coil 22 is wound around a plasma vessel 21 in which plasma is generated inside, and this is driven by a high frequency power source 23 so that the inside of the plasma vessel. A plasma is formed.
[0015]
Further, in the ECR type plasma generator 30 of FIG. 2B, a magnetic field is applied by disposing a magnet 32 around the plasma container 31 in a space inside the plasma container 31 in which plasma is generated. In this state, microwaves are supplied from a microwave power source 33 to the gas inside the container 31 to induce electron cyclotron resonance in the gas inside the container 31.
[0016]
In the helicon wave type plasma generating apparatus 40 of FIG. 2C, a magnet 44 is provided close to a plasma container 41 in which plasma is generated, and a loop antenna 42 is provided close to the plasma container 41. . The loop antenna is driven by high-frequency power from a high-frequency power source 43, and a helicon wave is propagated in the plasma vessel 41, thereby forming high-density plasma.
[0017]
In the microwave resonator type plasma generator 50 shown in FIG. 2D, a plasma container 51 in which plasma is formed forms a microwave resonator, and a microwave from a microwave power source 52 is formed in the microwave resonator. Is driven by an electric field to form plasma.
[0018]
In the toroidal type plasma generator 60 of FIG. 2 (E), a circulating gas passage 61 provided with a gas inlet 61A and a gas outlet 61B is provided, and a high-frequency coil 62 is provided outside the gas passage 61. Is wound.
[0019]
Therefore, a rare gas such as Ar introduced into the gas inlet 61A circulates in the circulating gas passage 61. At this time, the high-frequency coil 62 is driven by microwaves, thereby generating plasma in the rare gas. Induce. As the plasma induced in this manner circulates in the gas passage 61 at a high speed, a circular current path is formed in the gas passage 61, and the magnetic field lines formed by the high-frequency coil coincide with the current path. The route is narrowed down to Thus, when the magnetic lines of force are narrowed along the gas passage 61, electrons and ions in the plasma are narrowed down to a current path that matches the magnetic field lines, and the current density in the current path further increases. The increase in density results in further narrowing of the magnetic field lines into the magnetic field line path.
[0020]
In the toroidal type plasma generator 60 of FIG. 2 (E), since the high-density plasma is thus formed at a position away from the wall surface defining the circulating gas passage 61, the electrons accelerated particularly to high energy. This makes it possible to form plasma with less contamination and less contamination of the wall surface. Moreover, such a plasma with little contamination is maintained stably.
[0021]
Further, in the CCP type plasma generator 70 of FIG. 3, a pair of parallel plate electrodes 71A and 71B are arranged in a plasma container 71 in which plasma is generated, and this is driven by a high frequency power source 72, whereby Plasma is formed between the electrodes. That is, the plasma generator 70 in FIG. 2F itself constitutes a plasma processing apparatus, and the plasma vessel 71 is used as a processing vessel. In this case, the lower electrode 71B serves as a susceptor, and a substrate to be processed is placed thereon.
[0022]
[Patent Document 1]
US Pat. No. 6,374,831
[0023]
[Problems to be solved by the invention]
As described above, various plasma generators are conventionally used in the manufacturing process of semiconductor devices. Particularly in the plasma cleaning process and the plasma etching process, such as highly reactive F (fluorine) and Cl (chlorine), etc. Halogen-containing compounds are used as cleaning gas or etching gas, and therefore these gases must be introduced into the plasma and excited. At that time, the higher the concentration or partial pressure of the cleaning gas or etching gas introduced into the processing container, the more efficient the processing becomes possible.
[0024]
On the other hand, such halogens have a high electronegativity, and therefore halogen compounds used as plasma cleaning gas or plasma etching gas are difficult to excite plasma or require high power to excite and maintain plasma. Has general characteristics.
[0025]
In particular, in the toroidal type plasma generator shown in FIG. _Three Since even a slight amount of halogen-containing gas is introduced, plasma ignition does not occur. Therefore, when the plasma is ignited, the cleaning gas introduced into the gas passage 71 is purged, and the gas passage 71 has a low ionization voltage such as Ar. An atmosphere of 100% noble gas was formed. In this case, after the plasma is ignited, the composition of the gas supplied to the plasma generator is changed while maintaining the plasma, and the concentration of the cleaning gas is increased to a desired concentration.
[0026]
However, in such a plasma cleaning process or plasma etching process, particularly when using a single-wafer type substrate processing apparatus as shown in FIG. 1, it is necessary to frequently perform plasma ignition along with the single-wafer processing. When purging for a long time each time, there is a problem that the throughput of the substrate processing is lowered. In particular, in recent manufacturing processes of ultra-fine semiconductor devices, it is desirable to perform a plasma cleaning process in order to initialize the inside of the processing container every time a single substrate is processed. If the plasma cleaning process is performed each time, an ignition process is required for each substrate, and if the purge is performed each time, the substrate processing throughput is significantly reduced.
[0027]
Conventionally, when plasma is ignited in a state where a halogen-based cleaning gas is supplied to the plasma generator, since any type of plasma generator is difficult to ignite plasma as described above, it is high. The drive voltage must be applied, but when such a high drive voltage is applied, the impedance of the drive system including the coil and electrode changes greatly at the moment when the plasma ignites, and the overshoot drive voltage The drive system and the high frequency power supply may be damaged.
[0028]
Accordingly, it is a general object of the present invention to provide a new and useful plasma cleaning method that solves the above problems.
[0029]
A more specific object of the present invention is to provide a plasma cleaning method capable of igniting plasma at a low voltage and thereby avoiding damage to a power source, a coil, an electrode and the like due to the high voltage.
[0030]
[Means for Solving the Problems]
The present invention solves the above problems.
A plasma cleaning method for cleaning the inside of a processing container with a radical of a cleaning gas excited in a first pressure band,
Introducing a mixed gas of a dilution gas and a cleaning gas into the plasma generator;
Adjusting the pressure in the plasma generator to a second pressure zone that is lower than the first pressure zone and in the range of 6.65 Pa to 66.5 Pa;
After adjusting the pressure in the plasma generator to the second pressure zone, driving the plasma generator to ignite plasma in the mixed gas;
Increasing the pressure inside the processing vessel from the second pressure zone to the first pressure zone while maintaining the ignited plasma;
The cleaning gas is NF _Three Or F ₂ A halogen compound consisting of
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The dilution gas is Ar gas, which is solved by the plasma cleaning method.
The present invention also solves the above problems.
A substrate processing method for etching a surface of a substrate to be processed in a processing vessel in a first pressure zone by plasma-excited etching radicals,
Introducing a mixed gas of a dilution gas and an etching gas into the plasma generator;
Adjusting the pressure in the plasma generator to a second pressure zone that is lower than the first pressure zone and in the range of 6.65 Pa to 66.5 Pa;
Driving the plasma generator to ignite plasma in the mixed gas;
Increasing the pressure inside the processing vessel from the second pressure zone to the first pressure zone while maintaining the ignited plasma;
The etching gas is NF _Three Or F ₂ A halogen compound consisting of
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The dilution gas is Ar, which is solved by the substrate processing method.
The present invention also solves the above problems.
A plasma cleaning method for cleaning the inside of a processing container with a radical of a plasma-excited cleaning gas in a first flow rate zone,
Introducing a mixed gas of a dilution gas and a cleaning gas into the plasma generator;
Adjusting the flow rate of the cleaning gas to a second flow rate range that is lower than the first flow rate range and in the range of 3 sccm to 20 sccm;
After the step of adjusting the flow rate of the cleaning gas to the second flow rate zone, driving the plasma generator to ignite plasma;
Increasing the flow rate of the mixed gas from the second flow rate zone to the first flow rate zone while maintaining the ignited plasma;
The cleaning gas is NF _Three Or F ₂ A halogen compound consisting of
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The dilution gas is Ar, which is solved by a plasma cleaning method.
The present invention also solves the above problems.
A substrate processing method for etching a surface of a substrate to be processed in a processing vessel in a first flow rate zone by plasma-excited etching radicals,
Introducing a mixed gas of a dilution gas and an etching gas into the plasma generator;
The second flow rate zone is lower than the first flow rate zone and ranges from 3 sccm to 20 sccm. etching Adjusting the flow rate of the gas;
Driving the plasma generator to ignite plasma in the mixed gas;
Increasing the flow rate of the mixed gas from the second flow rate zone to the first flow rate zone while maintaining the ignited plasma;
The etching gas is NF _Three Or F ₂ A halogen compound consisting of
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The dilution gas is Ar, which is solved by the substrate processing method.
The present invention also solves the above problems.
A substrate processing apparatus for cleaning the inside of a processing container with a radical of a cleaning gas excited by a first pressure band,
A plasma generator connected to the processing vessel;
Gas supply means for supplying a mixed gas of a dilution gas and a cleaning gas to the plasma generator;
A plasma ignition device that is driven by high-frequency power or microwave power and ignites plasma in the mixed gas;
Plasma Ignition The apparatus ignites the plasma in a second pressure zone lower than the first pressure zone and in the range of 6.65 Pa to 66.5 Pa;
The gas supply means increases the pressure inside the processing vessel from the second pressure zone to the first pressure zone while maintaining the ignited plasma, and supplies the mixed gas into the processing vessel. And
The substrate processing apparatus is a toroidal plasma processing apparatus,
Said cleaning Gas is NF _Three Or F ₂ A halogen compound consisting of
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The dilution gas is Ar, which is solved by a substrate processing apparatus.
[0031]
According to the present invention, it is possible to perform plasma ignition at a low voltage by executing the plasma ignition step under a pressure lower than a normal process pressure. Accordingly, even if an impedance change occurs at the moment when the plasma is ignited, the occurrence of a large applied voltage overshoot that damages the plasma generator is avoided.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
As described above, in the conventional plasma generating apparatus, when a cleaning gas or an etching gas containing a halogen compound is supplied when the plasma is ignited, it becomes difficult to ignite the plasma, or a high voltage needs to be applied to the plasma ignition. Has occurred.
[0033]
In contrast, the inventor of the present invention pays attention to the fact that the mean free path of electrons becomes longer in a reduced pressure environment, and when a high frequency electric field is applied in a lower pressure reduced pressure environment than that used for normal cleaning and etching , That the electrons will be greatly accelerated by the electric field, so that they will gain large energy, and if the electrons thus have large energy, NF in Ar gas _Three Even when a gas containing a halogen compound having a high electronegativity is added, the inventors have come up with the idea that plasma may be ignited at a low driving voltage.
[0034]
Therefore, the inventor of the present invention uses a toroidal type plasma generator 60 (manufactured by ASTRONi, MKS, US Pat. No. 6,150,628) shown in FIG. 61 / Ar / NF _Three Supply mixed gas, Ar / NF _Three NF in mixed gas _Three Experiments were conducted to search for plasma ignition conditions while varying the concentration and further varying the total pressure.
FIG. 4 shows the result of such a search.
[0035]
Referring to FIG. 4, ● indicates that plasma ignition did not occur, and the NF _Three When the concentration was 2.5% or more, plasma ignition did not occur at any pressure tested, but NF _Three It has been found that when the concentration is 1.7%, plasma ignition occurs when the total pressure is reduced to 69 Pa (520 mTorr) as indicated by a circle in the figure. However, in the experiment of FIG. 3, the Ar / NF _Three The total flow rate of the mixed gas is 500 SCCM, and a high-frequency power of 1.7 kW is applied.
[0036]
Therefore, with respect to the toroidal plasma generator 60 of FIG. 2 (E), the above-mentioned Ar / NF is used starting from the ignition point thus discovered. _Three Total pressure, flow rate of mixed gas and NF in the mixed gas _Three When the plasma ignition point was searched by varying the concentration, the results shown in FIG. 5 were obtained. However, in the experiment of FIG. 5, a high frequency with a frequency of 400 kHz is supplied with a power of 1500 W.
[0037]
Referring to FIG. 5, the vertical axis represents the Ar / NF. _Three NF in mixed gas _Three Concentration (= NF _Three / (Ar + NF _Three )), The horizontal axis indicates the total pressure in the gas passage 21, and the shaded area indicates the conditions under which plasma ignition was possible.
[0038]
That is, NF capable of plasma ignition as the total pressure in the gas passage 21 decreases. _Three The concentration range increases and the Ar / NF _Three NF capable of plasma ignition as total gas flow decreases _Three It can be seen that the concentration range increases.
[0039]
On the other hand, if the total pressure in the gas passage 21 becomes too low, accelerated electrons are converted into Ar atoms or NF. _Three The probability of collision with molecules is reduced and plasma ignition becomes difficult.
[0040]
From FIG. 5, the total pressure in the gas passage 61 at the time of plasma ignition is 66.5 Pa (0.5 Torr) or less. so 6.65 Pa (0.05 Torr) more than By reducing to NF _Three Ar / NF containing 5% or more _Three Plasma ignition is possible in mixed gas, especially Ar / NF _Three NF in mixed gas _Three It can be seen that plasma ignition may be possible even when the concentration of the carbon reaches 45%.
[0041]
FIG. 5 shows Ar / NF supplied to the toroidal plasma generator during plasma ignition. _Three NF causing plasma ignition by reducing the flow rate of the mixed gas _Three The concentration range tends to increase. For example, Ar / NF _Three When the gas flow rate of the mixed gas is 80 SCCM, plasma ignition occurs but NF in which plasma ignition occurs _Three While the concentration range or pressure range is limited, plasma ignition occurs as the gas flow rate is reduced to 20 SCCM, 5 SCCM, or 3 SCCM. _Three It can be seen that the concentration range and pressure range expand. In addition, plasma ignition is the Ar / NF _Three If the gas flow rate of the mixed gas is 100 SCCM or less, the mixed gas is about 5% NF. _Three Even if it contains, it has been confirmed that it occurs.
[0042]
A similar relationship is Ar / F ₂ It has also been confirmed when mixed gas is used.
[0043]
FIG. 6 shows an Ar / F in the toroidal plasma generator 60 of FIG. ₂ The plasma ignition possible area | region at the time of supplying mixed gas is shown. However, in FIG. 6, the Ar / F ₂ The total gas flow rate of the mixed gas is set to 100 SCCM, and high-frequency plasma having a frequency of 400 kHz is supplied at a power of 1300 W.
[0044]
Referring to FIG. 6, when the total gas flow rate is set to 100 SCCM, the plasma is F ₂ In the case where no gas is added, ignition occurs in a pressure range of 6.65 to 79.8 Pa (0.05 to 0.6 Torr), whereas the Ar / F ₂ The mixed gas is F ₂ When 5% is included, it can be seen that the pressure range in which the plasma ignites decreases to 6.65 to 66.5 Pa (0.05 to 0.5 Torr).
[0045]
Ar / F ₂ F in mixed gas ₂ When the concentration is further increased, the pressure range that the plasma can ignite further decreases, but about 45% F ₂ It can be seen that the plasma can be ignited at a pressure of about 16.0 Pa (0.12 Torr) up to the concentration.
[0046]
FIG. 7 shows the relationship between the plasma ignition voltage and the total pressure in the toroidal plasma generator 60 of FIG. 2 (E) corresponding to the results of FIGS.
[0047]
Referring to FIG. 7, the example shown is the Ar / NF. _Three NF in mixed gas _Three However, the plasma ignition voltage decreases as the total pressure decreases and the mean free process of electrons increases, and the ignition point indicated by the circle in FIG. Minimizes at corresponding pressure. If the pressure is further reduced, the collision probability between electrons and atoms or gas molecules decreases, and as a result, the plasma ignition voltage rises rapidly.
[0048]
From the relationship of FIG. 7, even if the total pressure of the mixed gas is very high or very low, the plasma is ignited if a sufficient voltage exceeding the curve of FIG. 7 is applied to the mixed gas. However, when such a high voltage is applied, the impedance of the system suddenly decreases at the moment of plasma ignition as described above, and the large voltage overshoot accompanying this is high frequency power supply. There is a risk of damaging the coil, electrode, etc.
[0049]
The relationship shown in FIG. 7, that is, the plasma ignition voltage decreases on the low pressure side, and the tendency to rapidly increase when the pressure corresponding to a certain minimum value is exceeded is not limited to the toroidal type plasma generator, and is not limited to FIGS. Alternatively, in the plasma generators 20 to 70 shown in FIG. 3, it is considered that the tendency is universally established regardless of the type of rare gas and the type of halogen-containing etching gas or cleaning gas.
[0050]
Therefore, the present invention provides a rare gas and the halogen compound when plasma-cleaning the inside of a processing container using a gas containing a halogen compound or plasma etching the surface of a substrate to be processed using a gas containing a halogen compound. Plasma is ignited in the mixed gas containing the gas using the conditions that minimize the ignition voltage shown in FIG. In the present invention, plasma ignition occurs at a low voltage, so that a high voltage is not applied to the electrodes and coils of the plasma generator, and even if a large impedance changes instantaneously due to plasma ignition, The electrode, coil, etc. will not be damaged.
[0051]
On the other hand, as described above, in plasma cleaning or plasma etching, NF _Three Or F ₂ The higher the cleaning / etching gas concentration or partial pressure, the more efficient the process. Of course, if the plasma is ignited even in the ignition region of FIG. 5 or FIG. 6, since the cleaning / etching gas is included in the plasma, the cleaning process and the etching process are started. Insufficient efficiency cannot be achieved.
[0052]
Therefore, in the present invention, as described in the following embodiments, after the plasma is ignited, the total pressure of the mixed gas of the rare gas and the cleaning / etching gas is gradually increased to a desired process pressure.
[0053]
FIG. 8 shows a gas and RF power supply sequence used in a cleaning or etching process according to an embodiment of the present invention based on the above result.
[0054]
Referring to FIG. 8, in this embodiment, first, a small amount of Ar gas and NF are used. _Three Gas is supplied to the plasma generator shown in FIGS. 2A to 2E or FIG. 3, and RF power is supplied under the total pressure P1 substantially corresponding to the minimum ignition voltage shown in FIG. 7 to ignite the plasma. .
[0055]
After the plasma is ignited, the Ar gas and NF _Three The gas flow rate is gradually increased, and when a predetermined process pressure P2 is reached, a desired cleaning or etching process is performed, and then the RF power is shut off.
[0056]
9 shows a case where the toroidal type apparatus 60 of FIG. 2E is used as the remote plasma source 16C in the CVD apparatus 10 of FIG. 1 as the plasma generation apparatus from the pressure P1 to the pressure P2 of FIG. Ar / NF supplied to device 60 _Three An example in which the flow rate of the mixed gas and the conductance valve 13B in the CVD apparatus 10 in FIG. 1 are controlled to change the total pressure in the gas passage 61 and thus the internal pressure in the processing vessel 11 will be described.
[0057]
In the example of FIG. 9, from the ignition point (1) corresponding to the pressure P1 in FIG. 8 to the process point (2) corresponding to the pressure P2 in FIG. 8 where the actual cleaning process is performed, the Ar / NF _Three It has been verified whether the plasma is maintained from point (1) to point (2) by changing the total pressure and flow rate of the mixed gas through various paths. However, in this experiment, the valve 16Vc is fully opened in the CVD apparatus 10 of FIG. 1, and the pressure in the gas passage 61 of the toroidal plasma generator 60 of FIG. 2 (E) used as the remote plasma source 16C and the processing vessel. 11, the pressure is substantially equal.
[0058]
In the experiment of FIG. 9, the total pressure P1 at the ignition point (1) is about 11 Pa (0.08 Torr), and the Ar / NF _Three The total flow rate of the mixed gas is set to 3 SCCM, the total pressure P2 at the process point (2) is set to 1330 Pa (10 Torr), and the Ar / NF _Three The total flow rate of the mixed gas is set to 3 SLM.
[0059]
Referring to FIG. 9, in the path A, the gas flow rate is increased from the ignition point (1) while maintaining the pressure of about 11 Pa (0.08 Torr) to reach the point (4). That is, from point (1) to point (4), the pressure in the processing vessel 11 in the CVD apparatus 10 of FIG. _Three The conductance valve 13B of the exhaust system is gradually opened so as to be maintained constant even if the flow rate of the mixed gas increases, and at the point (4), the conductance valve 13B is fully opened. Thus, the point (4) is determined by the capability of the conductance valve 13B and the vacuum pump 13 cooperating therewith.
[0060]
In this state, the Ar / NF _Three When the flow rate of the mixed gas is gradually increased to a predetermined process flow rate corresponding to the process point (2), the pressure inside the processing vessel 11 and thus the total pressure in the gas passage 21 increases, and the point (5) is reached. To reach. From this point on, the Ar / NF _Three By gradually closing the conductance valve 13B while keeping the mixed gas flow rate constant, the pressure inside the processing vessel 11, and thus the pressure in the gas passage 21, gradually increases to the process point (2).
[0061]
On the other hand, in the route B of FIG. 9, the Ar / NF _Three By gradually closing the conductance valve 13B while keeping the mixed gas flow rate constant, the pressure inside the processing vessel 11, and thus the total pressure in the gas passage 21, gradually increases, and the point (6 ) Is reached. That is, the point (6) is determined by the amount of gas leak in the fully closed state of the conductance valve 13B and the capacity of the vacuum pump 13.
[0062]
In the path B, from the point (6), the Ar / NF is kept while the conductance valve 13B is kept in a fully closed state. _Three By increasing the flow rate of the mixed gas, the pressure inside the processing vessel 11, and thus the total pressure in the gas passage 21, gradually increases and reaches a point (7) corresponding to the process pressure of the process point (2). To reach. Furthermore, from the point (7), Ar / NF _Three The mixed gas flow rate is gradually increased to the process point (2). At this time, by gradually closing the conductance valve 13B, the pressure inside the processing vessel 11, and thus the total pressure in the gas passage 21, is maintained at the process pressure.
[0063]
Further, in the path C of FIG. 9, after the plasma is ignited at the ignition point (1), the Ar / NF is maintained while maintaining the opening degree of the conductance valve 13B. _Three By increasing the flow rate of the mixed gas to a point (3) corresponding to a predetermined process flow rate and then gradually reducing the conductance valve 13B, the pressure inside the processing vessel 11 and thus the process point (2) is increased. The total pressure in the gas passage 21 is increased.
[0064]
As described above, as a result of the experiment of changing the gas flow rate and the total pressure through various paths from the ignition point (1) to the process point (2), the points (1) to (7) in FIG. 9 are surrounded. In this region, it has been confirmed that the plasma once ignited does not disappear even if the total pressure and the gas flow rate are changed.
[0065]
As described above, the points (4) and (6), and therefore the route from point (4) to point (5) and the route from point (6) to point (7) are used. It is determined by the design of the conductance valve 13B of the CVD apparatus and the capacity of the vacuum pump 13, and when the maximum conductance of the conductance valve 13B is increased or the capacity of the vacuum pump 13 is increased, the point (4) is increased. The route to (5) shifts to the large flow rate side. When the minimum conductance of the conductance valve 13B is decreased or the capacity of the vacuum pump 13 is decreased, the path from the point (6) to the point (7) is shifted to the high pressure side.
[0066]
Further, the process point (2) can be set to any of known conditions that allow efficient plasma cleaning.
[0067]
That is, at the process point (2), for example, the Ar / NF _Three NF in mixed gas _Three By increasing the concentration to 80%, it is possible to achieve a cleaning rate of 2000 nm per minute for the thermal oxide film. In this case, the Ar / NF between the ignition point (1) and the process point (2). _Three NF in mixed gas _Three It is necessary to change the concentration. Even in such a case, it has been confirmed that once the plasma is ignited, the plasma is maintained.
[0068]
After reaching the process point (2) in this way, a normal cleaning process can be performed. In the CVD apparatus 10 of FIG. 1, it should be noted that the cleaning is started from the time when plasma ignition occurs in the toroidal type plasma generator 20 used as the remote plasma source 16C.
[0069]
In the case of shifting from the ignition point (1) to the process point (2) in FIG. 9, the Ar / NF _Three Ar gas and NF in mixed gas _Three The mixing ratio of gas may be fixed or changed. At that time, in the present invention, since the cleaning is started immediately after the plasma ignition occurs, the Ar / NF _Three NF in mixed gas _Three Not only can the concentration be increased during the transition from the ignition point (1) to the process point (2), but it can also be reduced if necessary.
[0070]
Further, in the CVD apparatus 10 of FIG. 1, the toroidal plasma generator 20 is used as a remote plasma source 16C, and plasma etching of an insulating film such as a thermal oxide film or a CVD oxide film or a W film or a Ti film in the processing vessel 11 is performed. Plasma etching of a metal film such as a film, plasma etching of a conductive nitride film such as a TiN film, and plasma etching of a polysilicon film can be performed.
[0071]
Further, in this embodiment, in the CVD apparatus 10 of FIG. 1, as shown in FIG. _Three It is also possible to provide a plurality of mass flow controllers 16a and 16b having different capacities in the gas source 16A, and switch these using valves. In FIG. 10, similarly, the Ar gas source 16B is also provided with a plurality of mass flow controllers 16c and 16d having different capacities, and these are switched and used by valves.
[0072]
Therefore, for example, from the ignition point (1) in FIG. _Three Considering the case where the mixed gas flow rate increases along the path C and the mass flow controller 16a is switched from the mass flow controller 16a to the larger mass flow controller 16b at the point (8) on the path C, the switching of the mass flow controller is performed. Accordingly, the flow rate and the total pressure may be temporarily reduced to the point (9). However, by driving the mass flow controller 16b having a larger capacity, it is possible to return to the point (10) on the path C. . At this time, according to this embodiment, as long as the point (9) is located in the plasma maintaining region shown in FIG. 9, the plasma ignited at the point (1) does not disappear.
[0073]
Further, the point (10) after the return is not limited to the path C, and can be selected at any point in the plasma maintenance region within a range where the flow rate is larger than the point (8).
[0074]
As described above, the present invention is applied to a toroidal plasma generator with Ar / NF. _Three Mixed gas or Ar / F ₂ The case where the mixed gas is supplied to form plasma has been described as an example. However, in the present invention, the plasma generator is not limited to the toroidal plasma generator, and the present invention is not limited to FIGS. 2 (A) to (E). Alternatively, the present invention can be applied to other plasma generators shown in FIG. Further, in the present invention, the dilution gas supplied for plasma formation is not limited to Ar, and the present invention is a rare gas such as He, Ne, Kr, Xe, or H ₂ O, O ₂ , H ₂ , N ₂ , C ₂ F ₆ Even if it is used. Further, the cleaning / etching gas used in the present invention is NF. _Three Or F ₂ It is not limited to other halogen compound gas, and further CH _Three COOH, CH _Three It is also possible to use compounds containing a COO group.
[0075]
Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the claims.
[0076]
【The invention's effect】
According to the present invention, by reducing the gas pressure during plasma ignition, it is possible to perform plasma ignition at a low voltage even for a gas containing a halogen compound. As a result, the occurrence of a large voltage overshoot caused by a large impedance change at the moment of plasma ignition and the damage of the drive power supply, electrode, coil or the like due to this are avoided. In the present invention, after the plasma is ignited in this way, it is possible to efficiently perform a desired cleaning process or etching process by increasing the gas pressure to a predetermined process condition while maintaining the plasma. .
[0077]
According to the present invention, since the plasma is ignited with respect to the gas containing the halogen compound, the halogen compound is added each time the plasma is ignited particularly in the process of frequently interrupting the plasma, such as the single wafer processing process. There is no need to purge the contained gas, and the throughput of cleaning or substrate processing is greatly improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a conventional CVD apparatus provided with a remote plasma generator.
FIGS. 2A to 2E are diagrams showing examples of various remote plasma sources. FIGS.
FIG. 3 is a view showing an example of a parallel plate type plasma source incorporated in a processing container of a substrate processing apparatus.
FIG. 4 is a diagram showing a search example of plasma ignition conditions in the present invention.
FIG. 5 shows NF discovered in the present invention. _Three It is a figure which shows the ignition area | region of the plasma containing gas.
FIG. 6 shows F found in the present invention. ₂ It is a figure which shows the ignition area | region of the plasma containing gas.
FIG. 7 is a diagram showing the principle of the present invention.
FIG. 8 shows a plasma cleaning process according to the present invention.
9 is a diagram showing an example of a transition path from an ignition process to a cleaning process in FIG.
FIG. 10 is a diagram showing a switching configuration of a mass flow control device in a gas source used in the plasma cleaning process of the present invention.
[Explanation of symbols]
10 CVD equipment
11 Processing container
12 Susceptor
13 Vacuum pump
13A shut-off valve
13B conductance valve
14 Shower head
15 Source gas supply system
15A-15C Source gas source
15V _A ~ 15V _C valve
16 Cleaning module
16A Cleaning gas source
16B Ar gas source
16a to 16d Mass flow controller
16C remote plasma source
16V _A ~ 16V _C valve
20 ICP type plasma generator
21 Plasma container
22 coils
23 High frequency power supply
30 ECR type plasma generator
31 Plasma container
32 magnets
33 Microwave power supply
40 Helicon wave type plasma generator
41 Plasma container
42 Loop antenna
43 High frequency power supply
44 Magnet
50 Microwave resonator type plasma generator
51 Microwave resonator
52 Microwave power supply
60 Toroidal plasma generator
61 Gas passage
61A Gas inlet
61B Gas outlet
62 High frequency coil
70 Parallel plate plasma generator
71 Plasma container
71A, 71B electrode
72 High frequency power supply
L1 raw material gas line
L2 cleaning gas line

Claims (13)

A plasma cleaning method for cleaning the inside of a processing container with a radical of a cleaning gas excited in a first pressure band,
Introducing a mixed gas of a dilution gas and a cleaning gas into the plasma generator;
Adjusting the pressure in the plasma generator to a second pressure zone that is lower than the first pressure zone and in the range of 6.65 Pa to 66.5 Pa;
After adjusting the pressure in the plasma generator to the second pressure zone, driving the plasma generator to ignite plasma in the mixed gas;
Increasing the pressure inside the processing vessel from the second pressure zone to the first pressure zone while maintaining the ignited plasma;
The cleaning gas contains a halogen compound composed of NF ₃ or F ₂ ,
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The plasma cleaning method, wherein the dilution gas is Ar gas.   The plasma cleaning method according to claim 1, wherein the plasma generator is a toroidal plasma generator.   The plasma generator is any one of a parallel plate plasma generator, an inductively coupled plasma generator, an ECR plasma generator, a helicon wave plasma generator, and a microwave resonator plasma generator. The plasma cleaning method according to claim 1 or 2. A substrate processing method for etching a surface of a substrate to be processed in a processing vessel in a first pressure zone by plasma-excited etching radicals,
Introducing a mixed gas of a dilution gas and an etching gas into the plasma generator;
Adjusting the pressure in the plasma generator to a second pressure zone that is lower than the first pressure zone and in the range of 6.65 Pa to 66.5 Pa;
Driving the plasma generator to ignite plasma in the mixed gas;
Increasing the pressure inside the processing vessel from the second pressure zone to the first pressure zone while maintaining the ignited plasma;
The etching gas contains a halogen compound composed of NF ₃ or F ₂ ,
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The substrate processing method, wherein the dilution gas is Ar.   5. The substrate processing method according to claim 4, wherein the plasma generator is a toroidal plasma generator.   The plasma generator is any one of a parallel plate plasma generator, an inductively coupled plasma generator, an ECR plasma generator, a helicon wave plasma generator, and a microwave resonator plasma generator. The substrate processing method according to claim 4 or 5. A plasma cleaning method for cleaning the inside of a processing container with a radical of a plasma-excited cleaning gas in a first flow rate zone,
Introducing a mixed gas of a dilution gas and a cleaning gas into the plasma generator;
Adjusting the flow rate of the cleaning gas to a second flow rate range that is lower than the first flow rate range and in the range of 3 sccm to 20 sccm;
After the step of adjusting the flow rate of the cleaning gas to the second flow rate zone, driving the plasma generator to ignite plasma;
Increasing the flow rate of the mixed gas from the second flow rate zone to the first flow rate zone while maintaining the ignited plasma;
The cleaning gas contains a halogen compound composed of NF ₃ or F ₂ ,
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The plasma cleaning method, wherein the dilution gas is Ar.   The plasma cleaning method according to claim 7, wherein the plasma generator is a toroidal plasma generator.   The plasma generator is any one of a parallel plate plasma generator, an inductively coupled plasma generator, an ECR plasma generator, a helicon wave plasma generator, and a microwave resonator plasma generator. The plasma cleaning method according to claim 7 or 8. A substrate processing method for etching a surface of a substrate to be processed in a processing vessel in a first flow rate zone by plasma-excited etching radicals,
Introducing a mixed gas of a dilution gas and an etching gas into the plasma generator;
Adjusting the flow rate of the etching gas to a second flow rate zone that is lower than the first flow rate zone and in the range of 3 sccm to 20 sccm;
Driving the plasma generator to ignite plasma in the mixed gas;
Increasing the flow rate of the mixed gas from the second flow rate zone to the first flow rate zone while maintaining the ignited plasma;
The etching gas contains a halogen compound composed of NF ₃ or F ₂ ,
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The substrate processing method, wherein the dilution gas is Ar.   The substrate processing method according to claim 10, wherein the plasma generator is a toroidal plasma generator.   The plasma generator is any one of a parallel plate plasma generator, an inductively coupled plasma generator, an ECR plasma generator, a helicon wave plasma generator, and a microwave resonator plasma generator. The substrate processing method according to claim 10 or 11. A substrate processing apparatus for cleaning the inside of a processing container with a radical of a cleaning gas excited by a first pressure band,
A plasma generator connected to the processing vessel;
Gas supply means for supplying a mixed gas of a dilution gas and a cleaning gas to the plasma generator;
A plasma ignition device that is driven by high-frequency power or microwave power and ignites plasma in the mixed gas;
The plasma ignition device ignites plasma in a second pressure band that is lower than the first pressure band and in a range of 6.65 Pa to 66.5 Pa,
The gas supply means increases the pressure inside the processing vessel from the second pressure zone to the first pressure zone while maintaining the ignited plasma, and supplies the mixed gas into the processing vessel. And
The substrate processing apparatus is a toroidal plasma processing apparatus,
The cleaning gas contains a halogen compound composed of NF ₃ or F ₂ ,
The mixed gas is a mixed gas of Ar gas containing a halogen compound gas of 5% or more and 45% or less and a gas of the halogen compound,
The substrate processing apparatus, wherein the dilution gas is Ar.

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