JP4038599B2 - Cleaning method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning method for a film forming apparatus for forming a film on a substrate such as a semiconductor wafer.
[0002]
[Prior art]
In general, in order to manufacture a semiconductor integrated circuit, a large number of desired elements are formed by repeatedly performing film formation and pattern etching on a substrate such as a semiconductor wafer.
By the way, as a wiring connecting each element, a contact metal for making an electrical contact with each element, or a barrier metal used as a countermeasure for suppressing the sucking up of Si of the substrate, the electric resistance is low. A highly corrosive material must be used.
Refractory metal materials such as Ti (titanium), W (tungsten), and Mo (molybdenum) tend to be used as materials that can meet such demands. Among them, there are characteristics such as electrical and corrosion resistance. In particular, Ti and TiN (titanium nitride), which is a nitride film, tend to be frequently used.
[0003]
The Ti film is generally formed by plasma CVD (Chemical Vapor Deposition) using TiCl ₄ (titanium tetrachloride) gas and hydrogen gas as source gases, and titanium chloride as a reaction by-product during the film forming process. Considerably adheres to the inside of the processing container.
Since this reaction by-product peels off during processing and causes particle problems, the reaction by-product is removed periodically or irregularly in order to avoid problems such as particles. Removal is performed.
[0004]
[Problems to be solved by the invention]
In order to remove titanium chloride adhering to the processing container, generally, an NF-based gas such as NF ₃ gas is used as a cleaning gas to generate plasma in the processing container, and the NF ₃ gas is decomposed by the plasma. The titanium chloride adhering to the active species is etched.
However, in such a cleaning method using plasma, for example, reaction by-products adhering to a mounting table on which a wafer is mounted can be removed to some extent, but reaction by-products in a part away from plasma are removed. Cannot be removed sufficiently, or it takes a long time to be removed.
In particular, there is a problem that a relatively large amount of reaction by-products tend to adhere, and that the adhesion generation part of the shower head part, which is likely to cause film peeling and is a major cause of particles, is difficult to remove.
[0005]
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 cleaning method capable of efficiently removing reaction by-products made of titanium chloride without using plasma.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a cleaning method for removing titanium chloride adhered in a processing container for forming a film on a substrate in a state where the processing container is heated to 130 ° C. or higher. The titanium chloride is removed using a ClF-based gas as a cleaning gas.
Specifically, in the invention according to claim 1, in the cleaning method for removing titanium chloride adhering to the shower head portion of the processing vessel for performing predetermined film forming process on a substrate, said process While the shower head in the container is heated to 130 ° C. or higher and 180 ° C. or lower, ClF gas, ClF _{3 is used} as a cleaning gas in the processing container. Gas, ClF ₅ By introducing any one of the gases , the titanium chloride adhering to the shower head portion is converted into TiF _4. And converted to TiF ₄ Is exhausted from the inside of the processing container .
[0007]
Thus, by using, for example, a ClF-based gas, which is a fluorine compound gas, as a cleaning gas, and heating a portion to be cleaned to 130 ° C. or higher, a reaction by-product made of titanium chloride can be obtained without using plasma. It can be removed.
In this case, the titanium chloride adhering to the shower head is efficiently removed by cleaning the shower head which is difficult to remove the adhering reaction by-product, particularly when heated to 130 ° C. or higher. can do.
The pressure during this cleaning is preferably in the range of 100 mTorr to 1 Torr, for example. As the ClF-based gas, for example, ClF gas, ClF ₃ gas, ClF ₅ gas, or the like can be used.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the cleaning method according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a configuration diagram showing a film forming apparatus to be cleaned.
The film forming apparatus 2 includes a processing container 4 as a chamber formed into a cylindrical shape with aluminum, for example, anodized inside, and the processing container 4 is grounded. A feed line insertion hole 8 is formed at the center of the bottom 6 of the processing vessel 4 and an exhaust port 10 is provided at the periphery, which is a vacuum provided with a vacuum pump (not shown). An exhaust system 12 is connected so that the inside of the container can be evacuated.
[0009]
In the processing container 4, a disk-shaped mounting table 14 made of a non-conductive material, for example, alumina, is provided, and a hollow cylindrical leg portion 16 extending downward is integrally formed at the center of the lower surface of the mounting table 14. The lower end of the leg portion 16 is attached and fixed in an airtight manner using a bolt 20 or the like with a seal member 18 such as an O-ring interposed in the periphery of the feed line insertion hole 8 of the container bottom portion 6.
For example, a carbon resistance heating element 22 coated with SiC is embedded in the mounting table 14, and the semiconductor wafer W as a substrate (object) placed on the upper surface side is brought to a desired temperature. It can be heated. An upper portion of the mounting table 14 is configured as a thin ceramic electrostatic chuck 26 in which a chucking electrode 24 made of a conductive plate such as copper is embedded, and by the Coulomb force generated by the electrostatic chuck 26. The wafer W is sucked and held on this upper surface.
[0010]
The resistance heating element 22 is connected to a power feeding section 30 through an insulated power feeding lead wire 28. The chucking electrode 24 of the electrostatic chuck 26 is connected to a high-voltage DC power supply 34 via an insulated power supply lead wire 32.
A plurality of lifter holes 36 are vertically penetrated at predetermined positions on the periphery of the mounting table 14, and wafer lifter pins 38 are accommodated in the lifter holes 36 so as to be vertically movable. When the wafer W is loaded / unloaded, the lifter pins 38 are lifted / lowered by a lifting / lowering mechanism (not shown) so that the wafer W is lifted or lowered.
[0011]
Further, a ceiling plate 42 integrally provided with a shower head portion 40 is attached to the ceiling portion of the processing container 4 through a sealing member 44 such as an O-ring, and the shower head portion 40 is mounted. A processing space S is formed between the mounting table 14 and the mounting table 14. The processing space S is formed between the mounting table 14 and the mounting table 14. The shower head unit 40 introduces a processing gas into the processing container 4 in a shower shape, and a plurality of injection holes 48 for ejecting the processing gas are formed on the injection surface 46 on the lower surface of the shower head unit 40. The An insulating material 50 is interposed in the mounting portion of the ceiling plate 42 and is insulated from the processing container 4.
[0012]
The ceiling plate 42 is provided with a gas introduction port 52 for introducing a processing gas into the shower head unit 40, and a supply passage 54 through which various gases flow is connected to the introduction port 52. And in this shower head part 40, the diffusion plate 58 which has many diffusion holes 56 is provided in order to diffuse the gas supplied from the supply channel | path 54. As shown in FIG. The head side wall is provided with a cooling jacket 60 for cooling the temperature of this portion during film formation and a heater 62 made of, for example, a resistance heating element for heating this portion to a predetermined temperature during cleaning.
[0013]
The supply passage 54, as a gas for film formation, such as H ₂ gas source 68 for storing the TiCl ₄ gas source 64, the H ₂ gas for storing the TiCl ₄ gas is connected via a branch pipe, the other, A ClF ₃ gas source 70 for storing a ClF-based gas, for example, ClF ₃ gas, as a cleaning gas used during cleaning is connected via a branch pipe. Further, for example, an Ar gas source 74 is connected to the supply passage 54 in order to supply an inert gas. The flow rate of each gas is controlled by a flow rate controller provided in each branch pipe, for example, the mass flow controller 72. Here, when forming a Ti film on the substrate surface, the film is formed by plasma CVD using TiCl ₄ gas, H ₂ gas and Ar gas.
[0014]
In order to form plasma during the Ti film formation, a matching circuit 77 and a high frequency power supply 78 for plasma of, for example, 13.56 MHz are connected to the ceiling plate 42 via lead wires 76.
In addition, a cooling jacket 80 for flowing a coolant, for example, is provided on the side wall of the processing container 4, and a gate valve 82 that is opened and closed at the time of loading / unloading the wafer is provided on a part of the side wall of the container 4. Provided.
[0015]
Next, the cleaning method of the present invention performed using the apparatus configured as described above will be described.
According to the cleaning method of the present invention, a chlorine compound as a reaction by-product adhering to the inside of a container when a Ti film is formed is removed using a ClF-based gas and maintaining the temperature in the container at 130 ° C. or higher.
First, film formation will be described.
For example, when a Ti film is formed on the surface of the substrate W, TiCl ₄ gas, H ₂ gas, and Ar gas are supplied from the shower head unit 40 into the processing container 4 at predetermined flow rates as film forming gases. At the same time, a high frequency is applied between the shower head unit 40 and the mounting table 14 from the high frequency power supply 78. As a result, plasma is generated in the processing space S, TiCl ₄ reacts with H ₂ and is reduced, and a Ti film is formed on the substrate. The film formation conditions at this time are, for example, a substrate temperature of about 550 ° C., a process pressure of about 1 Torr, and a plasma power of about 500 W.
[0016]
Such a film formation process simultaneously produces reaction by-products such as hydrochloric acid (HCl) and titanium chloride (TiClx: X = 2 to 3), and HCl is discharged as a gas. Since the vapor pressure is very low, it is difficult to be discharged and tends to adhere to the inner wall or the like of the processing vessel 4. In particular, a large amount of titanium chloride is applied to the injection surface 46, which is the lower surface of the shower head portion, depending on the number of processed sheets. Object M adheres.
[0017]
When the film forming process is performed on the plurality of wafers in this way, a cleaning process is performed to remove the attached titanium chloride.
At the time of this cleaning, a ClF-based gas, in this case, ClF ₃ gas, is supplied as a cleaning gas from the shower head unit 40 into the processing container 4 at a predetermined flow rate, for example, a flow rate of 100 sccm, and the container internal temperature is maintained at 130 ° C. or higher. To do. In order to increase the temperature of the shower head unit 40, the heater 62 incorporated therein may be energized. In this case, the mounting table 14 can be maintained at a high temperature of, for example, 500 ° C. or higher due to its structure, but the shower head unit 40 cannot be heated too high due to its structure. The value is set within a range up to about 180 ° C.
[0018]
If the structure of the shower head unit 40 can be improved to withstand a temperature higher than 180 ° C., it may be heated to the upper limit temperature value.
The pressure in the container at this time is 1 Torr, and cleaning is performed for about 60 minutes, for example. Further, at the time of this cleaning process, cleaning by heat is performed without using plasma.
By such a cleaning process using ClF ₃ gas, the titanium chloride adhering to the inside of the processing container 4 is changed to TiF ₄ (titanium tetrafluoride) having a higher vapor pressure, and evaporation or sublimation. Will be promoted and removed. In particular, since TiF ₄ starts to evaporate at about 130 ° C., it is relatively easy to heat it to about 130 ° C. or more during cleaning by a heater 62 built in the shower head unit 40. In addition, it is possible to remove the titanium chloride M that has adhered quickly.
[0019]
FIG. 2 is a graph showing the relationship between the temperature and the vapor pressure of TiCl ₄ (source gas), TiCl ₃ (reaction by-product), and TiF ₄ . As is apparent from the graph, TiCl ₃ that does not evaporate unless it is about 700 ° C., that is, difficult to remove by heating a portion to be cleaned to 130 ° C. or higher using a ClF-based gas as a cleaning gas as in the present invention. can be removed by this is converted to TiF ₄ (the reaction by-product) is evaporated at about 130 ° C. to initiate evaporated reduction.
FIG. 3 is a graph showing the cleaning state of the mounting table and the shower head when the cleaning process is performed using the method of the present invention, and various cleaning temperatures are changed. In the figure, black marks indicate that titanium chloride could not be removed, and white marks indicate that titanium chloride could be removed. The cleaning condition at this time is that the process pressure is 1000 mTorr, ClF ₃ The gas flow rate is 100 sccm, and the cleaning time is 30 minutes.
[0020]
As is apparent from the graph, the titanium chloride adhering to the mounting table became a white powder at room temperature (about 200 ° C.) and could not be sufficiently removed, but the mounting table temperature was reduced to 100 ° C. and 200 ° C. When raised, it was completely removed.
Moreover, the titanium oxide adhering to the shower head part could not be sufficiently removed as white powder even when the shower head part was heated to about 110 ° C. with a heater as well as at room temperature. As a result of cleaning by heating to 130 ° C., 150 ° C. and 180 ° C., titanium chloride could be almost completely removed.
[0021]
As described above, according to the present invention, titanium chloride adhering to the shower head part, which is the main cause of generation of particles, is almost completely removed by heating it to 130 ° C. or higher and using ClF ₃ gas. be able to.
Further, when the process pressure at the time of cleaning was examined, a graph showing the relationship between the temperature and the cleaning amount as shown in FIG. 4 was obtained. That is, it has been found that the cleaning efficiency with respect to the process pressure is most efficient at about 500 mTorr, and preferably within the range of 100 mTorr to 1 Torr.
[0022]
The reason for this is that when the process pressure is lower than 100 mTorr, the amount of ClF ₃ gas is too small to sufficiently convert to TiF _4, and when the process pressure is higher than 1 Torr, the ClF ₃ gas Although the amount increases, conversely, the vaporization of TiF ₄ is suppressed, and as a result, the cleaning efficiency is considered to decrease.
Here, the cooling jacket 60 and the heater 62 are provided in the shower head unit 40, but instead, for example, a temperature control mechanism capable of selectively flowing a high-temperature heat medium and a low-temperature refrigerant chiller is provided. The single temperature control mechanism may have two functions of cooling and heating.
[0023]
Here, the case where ClF ₃ gas is used as the ClF-based gas has been described as an example, but it is needless to say that ClF gas, ClF ₅ gas, or a mixed gas thereof exhibiting the same action may be used. .
Of course, the substrate is not limited to a semiconductor wafer, but can be applied to a glass substrate, an LCD substrate, or the like.
[0024]
【The invention's effect】
As described above, according to the cleaning method of the present invention, the following excellent operational effects can be exhibited.
ClF gas heated state of the treatment container on a 180 ° C. or less 130 ° C. or more, ClF ₃ Gas, ClF ₅ By cleaning with any one of the gases, titanium chloride can be removed efficiently, and since plasma is not used, cleaning is performed to every corner where plasma does not reach. Can be done.
In particular, by incorporating a heater in the shower head portion and heating it to 130 ° C. or higher, titanium chloride in the shower head portion, which is the main cause of particle generation, can be removed quickly and substantially completely.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a film forming apparatus to be cleaned.
FIG. 2 is a graph showing the relationship between the temperature and vapor pressure of TiCl ₄ (source gas), TiCl ₃ (reaction by-product), and TiF ₄ .
FIG. 3 is a graph showing the cleaning state of the mounting table and the shower head when the cleaning process is performed using the method of the present invention. FIG. 4 is a graph showing the relationship between the cleaning temperature and the cleaning efficiency.
[Explanation of symbols]
2 film formation apparatus 4 processing vessel 14 platforms 40 shower head 42 top plate 46 ejecting surface 48 injection hole 62 heater 64 TiCl ₄ gas source 66 NH ₃ gas source 70 ClF ₃ gas source 78 a high frequency power source M titanium chlorides W semiconductor Wafer (substrate)

Claims (2)

In a cleaning method for removing titanium chloride adhering to a shower head part in a processing container for performing a predetermined film forming process on a substrate ,
While the shower head in the processing container is heated to 130 ° C. or more and 180 ° C. or less, ClF gas, ClF _{3 is used} as a cleaning gas in the processing container. Gas, ClF ₅ By introducing any one of the gases , the titanium chloride adhering to the shower head portion is converted into TiF ₄ ,
TiF ₄ Is exhausted from the processing container . Wherein in a state where the pressure is in the range of 100mTorr~1Torr in the processing container, a cleaning method of請Motomeko 1, wherein said gas into the processing container inside is introduced.

Images