JP3905726B2 - Cleaning method for cold wall forming film processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning method for a cold wall forming film processing apparatus.
[0002]
[Prior art]
The CVD apparatus used for the film formation process of the semiconductor integrated circuit is a hot wall type in which the entire processing vessel is placed in an electric furnace to heat the semiconductor wafer, and the semiconductor wafer is heated without affecting the temperature of the processing vessel. It can be divided into cold wall type. In general, the hot wall type is used for batch processing for forming a large number of semiconductor wafers at a time, whereas the cold wall type is used for single wafer processing for forming semiconductor wafers one by one.
[0003]
In a cold wall type CVD apparatus, a semiconductor wafer is set on a susceptor (substrate mounting table), and the semiconductor wafer is heated through an appropriate heater through the susceptor, or directly exposed to light from outside without passing through the susceptor. Meanwhile, a predetermined gas is supplied to the surface of the semiconductor wafer, and a decomposition product or a reaction product of the gas is deposited on the wafer. When a film is formed on the semiconductor wafer in this way, the reaction gas decomposition products or reaction products are deposited on the surfaces of the susceptor, wafer holding means and the like around the semiconductor wafer, and the film adheres. Moreover, such a film may adhere to the inner wall surface of the processing container.
[0004]
Conventionally, as a method of cleaning the inside of a cold wall type CVD apparatus, a cleaning gas containing NF3 is supplied into the apparatus, and the coating film adhering to the susceptor, wafer holding means, etc. as described above is removed by etching with this cleaning gas. How to do is known. In this cleaning method, since NF3 itself is not degradable, plasma is used. That is, an electrode plate is disposed at a position facing the susceptor in the processing container, a high frequency voltage is applied between the susceptor and the electrode plate, plasma is generated there, and NF3 is excited to an active state by the plasma. I am doing so.
[0005]
The NF3 plasma cleaning method as described above can effectively remove the film on the susceptor surface side and wafer holding means surface side in contact with the plasma , but removes the film on the susceptor back side where the plasma does not reach. could not. In addition, since plasma is used, there is a restriction that it cannot be implemented in a cold wall forming film processing apparatus that cannot generate plasma in a processing container.
[0006]
Also, from the viewpoint of exhaust gas regulation, it is customary to attach an expensive removal device for decomposing and removing harmful and dangerous gas components from exhaust gas in the CVD apparatus, but NF3 is a gas that is difficult to decompose. Therefore, a common removal device cannot be used with other exhaust gases such as a reaction gas, and a separate removal device is required separately. For this reason, two removal devices have to be installed.
[0007]
The present invention, this problem has been made in view of the point, undesired skin layer adhering to the substrate holding base and the inner wall of the container in the processing apparatus can be effectively cleaned, and require special removal apparatus It is an object of the present invention to provide a cleaning method for a cold wall forming film processing apparatus.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a cleaning method of the present invention is a method for cleaning the inside of a processing container of a cold wall forming film processing apparatus, wherein a substrate mounting table on which a substrate to be processed is mounted by the film forming processing apparatus The substrate is heated by a mounting table heating means, a reactive gas is supplied into the processing container through a porous plate to perform film formation on the substrate to be processed, and then purging is performed in the processing container through the porous plate. Gas is removed, the reaction gas remaining in the processing container is removed, then the inside of the processing container is depressurized to a predetermined degree of vacuum, and the substrate mounting table is configured by the mounting table heating means. The substrate mounting base is heated to a first temperature within the range of the corrosion resistance temperature of the material against ClF 3 , and the wall of the processing vessel is within the range of the corrosion resistance temperature against the material ClF 3 constituting the wall by wall heating means. To the second temperature A cleaning gas containing ClF3 is supplied from the ClF3 gas supply source into the processing container through the perforated plate while heating, and the substrate mounting table in the processing container and the walls of the processing container are formed during the film forming process. unwanted skin film deposited is removed by a plasma-free atmosphere in the cleaning gas containing the ClF3 on.
[0009]
In the cleaning method of the present invention, when the substrate mounting table and the wall of the processing container are heated, the upper limit of the corrosion resistance temperature of the material constituting the substrate mounting table to ClF 3 and the corrosion resistance temperature of the material constituting the wall to ClF 3 are set to 400. It may be ℃ . Further, it is preferable to reduce the pressure in the processing container to a pressure of 1 to 50 Torr. Further, when supplying the cleaning gas containing ClF3 into the processing container, it is preferable that N2 is also included in the cleaning gas and supplied at a flow rate at which the ratio of the flow rate of ClF3 to the flow rate of N2 is 0.2 or more.
[0010]
In the present invention, a single-wafer type film forming process in a processing container of a cold wall forming film processing apparatus ( a substrate mounting table on which a substrate to be processed is mounted in a processing container is heated by a mounting table heating means, After the reaction gas is introduced from the perforated plate into the film and the film is formed on the substrate to be processed, purging gas is supplied from the perforated plate into the processing container and remains in the processing container. Then, the reaction gas is removed, and then the inside of the processing container is cleaned under reduced pressure . In this cleaning, the substrate mounting table and the wall are heated by the substrate mounting table and the wall heating unit through the perforated plate while heating the substrate mounting table and the wall to the first and second temperatures, respectively, within the range of the corrosion resistance to ClF 3 of each constituent material. A cleaning gas containing ClF3 is supplied into the processing container. At that time, plasma is not used. Since ClF3 gas is very active, it reacts easily with the coating at temperatures within the range of corrosion resistance temperature. That is, when a part of ClF3 gas reacts to generate reaction heat, the reaction heat activates nearby ClF3 gas and reacts, and the reaction heat activates more ClF3 gas to react. The etching is developed spontaneously .
[0011]
According to the cleaning method of the present invention, the substrate mounting table and the wall in the processing container are individually heated by each individual heating means within the range of the corrosion resistance against ClF 3 of each constituent material under reduced pressure , since supplies ClF 3 gas deploying the spontaneous etching to ClF 3 gas without plasma, suitably undesired skin film attached to each site to every corner of the substrate holding base and wall during the film formation process It can be efficiently removed at a high etching rate , and corrosion (causing particles) of the substrate mounting table and walls can be prevented. Further, since ClF3 gas has good decomposability, the exhaust gas can be treated with a common removal device with the reaction gas exhaust gas.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a cold-wall type single-wafer CVD apparatus will be described with reference to the accompanying drawings.
[0013]
In FIG. 1, a processing container 10 of this CVD apparatus is a cylindrical chamber made of, for example, aluminum, and a susceptor (substrate mounting table) 12 is disposed at the center thereof. When the film forming process is performed, the semiconductor wafer 14 is placed on the susceptor 12 as indicated by a dotted line. A gate valve 16 is provided on one side wall of the processing container 10, and the semiconductor wafer 14 is taken in and out through the gate valve 16.
[0014]
A perforated plate 18 for uniformly supplying gas is attached above the susceptor 12, and a gas discharge portion 20 a of the gas introduction pipe 20 is vertically placed in the container from the back (upper part) of the perforated plate 18. . A reaction gas supply system 22 and a cleaning gas supply system 24 are connected to the gas introduction pipe 20, and these are switched by valves 26 and 28.
[0015]
The cleaning gas supply system 24 includes a ClF3 gas supply unit 30 for supplying ClF3 as an etching gas and an N2 gas supply unit 32 for supplying N2 gas as a dilution carrier gas. Are connected to the gas introduction pipe 20 via gas flow regulators (MFC) 34, 36 and valves 38, 40, respectively. The supply flow rates of ClF3 gas and N2 gas are adjusted by the gas flow rate regulators 34 and 36, whereby the cleaning gas in which ClF3 is diluted to a predetermined concentration is supplied to the gas introduction pipe 20.
[0016]
In the lower part of the processing container 10, a plurality of exhaust ports 42 are provided in the container bottom surface 10 a. The reaction product gas generated in the processing vessel 10 and the surplus reaction gas or cleaning gas are discharged from the exhaust port 42 through the exhaust pipe 44 to the vacuum pump 46 side. As the vacuum pump 46, an oil-free dry pump is preferably used. This is because if ClF3 is used as the cleaning gas, the use of a wet pump may cause deterioration of the pump oil or deterioration of the pump itself due to chlorine or fluorine mixed in the oil.
[0017]
The discharge system downstream of the vacuum pump 46 is provided with a removal device 48 for removing harmful and dangerous gas components from the exhaust gas of the reaction gas or cleaning gas discharged from the pump. The removal device 48 accommodates a cylinder 50 containing a chemical for adsorbing or decomposing harmful and dangerous gas components.
[0018]
A quartz window 52 is attached to the bottom of the container below the susceptor 12, and a halogen lamp 54 for heating is disposed below the quartz window 52. During the film forming process, the light from the halogen lamp 54 irradiates the back surface of the susceptor 12 through the quartz window 52, and the susceptor 12 is heated to, for example, 650 to 700 ° C. by the light energy. The semiconductor wafer 14 is heated to about 500 ° C. to 550 ° C., for example.
[0019]
Next, a tungsten film forming process in the CVD apparatus and a cleaning process of the CVD apparatus will be described.
[0020]
First, the tungsten film-forming process will be described. The semiconductor wafer 14 subjected to the film forming process is loaded onto the susceptor 12 through a gate valve 16 by a wafer transfer mechanism (not shown) such as a hand arm. Next, as reaction gases, for example, WF6 (tungsten hexafluoride) and Si H2 C12 (dichlorosilane) are introduced into the processing vessel 10 from the reaction gas supply system 22 through the gas introduction pipe 20 at a predetermined flow rate. The introduced reaction gas is blown onto the semiconductor wafer 14 through the perforated plate 18 to form a WSi (tungsten silicide) film on the surface of the semiconductor wafer 14. When WF6 and H2 are used as different reaction gases, a W (tungsten) film is formed on the surface of the semiconductor wafer 14.
[0021]
In this film forming process, the semiconductor wafer 14 is heated by the heating lamp 54 via the susceptor 12, but the processing container 10 itself is kept at a normal temperature (room temperature). The reaction gas decomposition products or most of the reaction products are deposited on the surface of the semiconductor wafer 14, but a part of the reaction gas adheres to the outer peripheral edge of the susceptor 12 and a wafer holding member (not shown). It adheres to the inner wall surface of 10 slightly. When the film forming process is completed, the semiconductor wafer 14 is unloaded from the susceptor 12 by the wafer transfer mechanism. During the unloading or loading, the film may be peeled off from the semiconductor wafer 14 or the susceptor 12, the wafer holding member, etc., and the peeled film piece adheres to the bottom surface 10 a of the processing container 10.
[0022]
When the film formation process as described above is performed a predetermined number of times, the film formation process is temporarily interrupted, the reaction gas supply system 22 and the heating lamp 54 are switched off, and the semiconductor wafer 14 is not contained in the processing vessel 10. In this state, the cleaning according to the present embodiment is performed at room temperature. Prior to this cleaning, purging with H2 gas or N2 gas or the like is performed, and the reaction gas is removed from the processing vessel 10.
[0023]
In the cleaning according to this embodiment, a cleaning gas obtained by diluting ClF3 gas with N2 gas to a predetermined concentration from the cleaning gas supply system 24 as described above is introduced into the processing vessel 10 through the gas introduction pipe 20, and the introduction thereof. The cleaned cleaning gas is supplied from the perforated plate 18 to the susceptor 12 and other parts of the apparatus.
[0024]
ClF3 gas is a chemically active gas and reacts well with a film, particularly a tungsten-based film, even without plasma. Therefore, the supply flow rate is controlled so that the cleaning gas is filled in the processing container 10, whereby ClF3 gas spreads to every corner in the processing container 10, and the WSi film or W film adhering to each part is ClF3. Etching is effectively performed only by receiving the supply of gas.
[0025]
Thus, the coating on the bottom 10a of the container, which is difficult to remove by the conventional NF3 plasma cleaning method, can be easily removed by the cleaning method of this embodiment. Therefore, manual cleaning that bothers workers is unnecessary. When the ClF3 gas passes through the exhaust port 42 and the exhaust pipe 44, the film adhering thereto is also etched away.
[0026]
Further, since ClF3 gas has a good decomposability and is easily dissolved in an alkali solution or the like, the exhaust gas can be treated by the common removal device 48 in the same manner as the reaction gas exhaust gas. Therefore, a special removing device for cleaning is unnecessary.
[0027]
2-5 is a graph which shows the etching effect by the cleaning method of a present Example. The data shown in the figure shows that when a semiconductor wafer having a W film formed on the surface is placed on the susceptor 12 as a test material and the cleaning gas containing the ClF3 gas is supplied under various conditions, the W film of the semiconductor wafer is supplied. This was obtained in an experimental example in which the etching rate was measured.
[0028]
First, the graph of FIG. 2 shows the characteristics of the etching rate when the flow rate of ClF3 gas and N2 gas in the cleaning gas is kept constant at 500 sccm and the gas pressure is changed at room temperature. As shown in FIG. 2, as the gas pressure is increased, the reaction between the ClF3 gas and the W film is promoted to increase the etching rate, and the etching rate is about 2000 to 4000 angstroms / min with respect to the pressure of 10 to 50 Toor. It can be seen that the rate is obtained.
[0029]
The graph of FIG. 3 shows the characteristics of the etching rate when the flow rate of N2 gas is kept constant at 1500 sccm, the pressure is kept constant at 10 Torr, and the flow rate of ClF3 gas is changed at room temperature. From FIG. 3, as the flow rate of ClF3 gas is increased, the supply amount of ClF3 gas is increased and the etching rate is increased, and an etching rate of about 3000 to 6000 angstroms / min is obtained for a ClF3 gas flow rate of 400 to 1000 sccm. I understand that.
[0030]
The graph of FIG. 4 shows the characteristics of the etching rate when the flow rate of ClF3 gas is kept constant at 500 sccm, the pressure is kept constant at 10 Torr, and the flow rate of N2 gas is changed at room temperature. From FIG. 4, it can be seen that as the N2 gas flow rate is increased, the ClF3 gas is diluted to lower the etching rate, and an etching rate of about 4500 to 2500 angstroms / min is obtained with respect to the N2 gas flow rate of 500 to 5000 sccm. .
[0031]
The graph of FIG. 5 shows the characteristics of the etching rate when the total flow rate is changed with the pressure maintained at 10 Torr and the flow rate ratio of ClF3 gas and N2 gas constant (1: 3) at room temperature. From this figure, as the flow rate of the cleaning gas is increased, the supply amount of ClF3 gas is increased and the etching rate is increased, and about 3600 to 4800 angstroms / min with respect to the flow rate of ClF3 / N2 gas of 400/1200 to 1000/3000. It can be seen that the etching rate can be obtained.
[0032]
As described above, according to the cleaning method using ClF3 gas, an etching rate of 3000 angstroms / min or more can be easily obtained by appropriately selecting conditions such as gas flow rate, pressure, and ClF3 gas concentration even at room temperature. Can do. It has been confirmed by experiments that the same etching rate can be obtained with the WSi film. In this respect, since the etching rate obtained by the conventional plasma type cleaning method using NF3 gas is at most about 2000 angstrom / min, the cleaning efficiency is not inferior to the conventional method.
[0033]
Next, an embodiment of the present invention will be described. In one embodiment of the present invention, in a cold wall type processing apparatus, for example, a processing apparatus as shown in FIG. 1, a heatable portion such as a susceptor 14, a wafer holding member (not shown), an inner wall of the processing container 10, etc. A cleaning gas containing ClF3 is supplied to ClF3 while maintaining a high temperature within the range of the corrosion resistance temperature to clean each part of the container 10 and the like, in particular, a heatable part.
[0034]
FIG. 6 shows preferred materials that can be used for the heatable part in the cold wall type processing apparatus of the present invention, that is, SUS430, SUS304, SUS316, aluminum (Al), nickel (Ni), inconel, quartz, alumina (Al2). The respective corrosion resistance temperatures of silicon carbide (SiC), zirconium oxide (ZrO2) and aluminum nitride (AlN) with respect to ClF3 are shown. When these materials are used for heatable parts such as susceptors, wafer holding members, processing containers, etc., the cleaning speed increases as the temperature increases. However, if the corrosion resistance range is exceeded, particles are generated from the member itself, which is not good. Therefore, it is desirable to keep it below the corrosion resistance temperature of each part even if it is high temperature.
[0035]
FIG. 7 shows that the heatable part in the cold wall type processing apparatus is made of silicon carbide (SiC), the degree of vacuum in the container (10 Torr), the flow rate of the cleaning gas (ClF3 / N2) (100/2000 sccm), and the cleaning gas. The characteristics of the etching rate when changing the cleaning temperature while fixing various conditions of the supply method (simultaneous delivery of ClF3 / N2) and the cleaning time (20 seconds) are shown. As shown in FIG. 7, it is understood that the etching rate increases as the cleaning temperature is increased, and an etching rate of about 3200 angstroms / min is obtained at a high temperature around 200 ° C.
[0036]
As the heating means, a heating means for heat treatment such as the halogen lamp 54 in FIG. 1 may be used. Further, a heating means such as nichrome wire is provided inside the wall of the processing vessel 10 for cleaning. It may be buried.
[0037]
In the above-described embodiment, cleaning is performed by removing the W film or WSi film. However, the cleaning method of the present invention is not limited to a tungsten-based film but also for an undesired film of another film forming material. Can be used. Further, although the cold wall type processing apparatus in the above-described embodiment is a single wafer type CVD apparatus, the cleaning method of the present invention is not limited to such a film forming processing apparatus, It can also be used for a cold wall forming film processing apparatus.
[0038]
【The invention's effect】
As described above, according to the cleaning method of the present invention, the substrate placed in the processing chamber under a reduced pressure to remove the reaction gas by performing the purging after film forming process in the process vessel cold wall forming film processor the base and walls by supplying a cleaning gas containing ClF3 while heating separately by each individual heating means within the corrosion temperature for ClF 3 of the constituent material, adhered to the substrate holding base and wall during the film formation process since so as to remove at spontaneous etching effect of C l F 3 gas unwanted skin layer without using plasma, it is possible to achieve effective cleaning of the inside of the processing container. Furthermore, the cleaning exhaust gas can be processed by a common removal device with other exhaust gases such as reaction gas, and no special removal device is required, so that the installation cost of the removal device can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an overall configuration of a cold wall type single wafer CVD apparatus for carrying out a cleaning method according to an embodiment of the present invention.
FIG. 2 is a graph showing characteristics of an etching rate with respect to pressure in the cleaning method of the embodiment.
FIG. 3 is a graph showing characteristics of an etching rate with respect to a flow rate of ClF 3 gas in the cleaning method of the embodiment.
FIG. 4 is a graph showing the characteristics of the etching rate with respect to the flow rate of N 2 gas in the cleaning method of the embodiment.
FIG. 5 is a graph showing the etching rate characteristics with respect to the total flow rate of the cleaning gas in the cleaning method of the embodiment.
FIG. 6 is a table showing various corrosion resistance temperatures for various materials of ClF 3 that can be used for a heatable portion in the cold wall forming film processing apparatus according to the embodiment.
FIG. 7 is a graph showing a characteristic of an etching rate with respect to temperature in the cleaning method of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Processing container 12 Susceptor 14 Semiconductor wafer 22 Reaction gas supply system 24 Cleaning gas supply system 30 ClF3 gas supply part 32 N2 gas supply part 48 Removal apparatus

Claims (5)

A method of cleaning the inside of a processing container of a cold wall forming film processing apparatus,
A substrate mounting table on which a substrate to be processed is placed by the film forming apparatus is heated by a mounting table heating means, and a reactive gas is supplied into the processing container via a porous plate to perform a film forming process on the substrate to be processed. After purging, a purging gas is supplied into the processing vessel through the perforated plate to remove the reaction gas remaining in the processing vessel, and then the inside of the processing vessel is set to a predetermined degree of vacuum. under reduced pressure by heating the substrate holding stage in the range of corrosion temperature for ClF 3 of the material of the substrate holding table by the installation stand heating unit to a first temperature, by a wall heating means the wall of the processing chamber a cleaning gas containing ClF3 than ClF3 gas supply source into the processing chamber while heating to a second temperature in the range of corrosion temperature for ClF 3 of the material constituting the wall is supplied through the perforated plate, wherein the processing at the time of the film formation process The cleaning method for removing a substrate holding base and unwanted skin layer adhering to the walls of the processing chamber in an atmosphere free from plasma by a cleaning gas containing ClF3 in the container.   2. The cleaning method according to claim 1, wherein the purging gas comprises H2 gas or N2 gas. 3. The upper limit of the corrosion resistance temperature of the material constituting the substrate mounting base with respect to ClF 3 and the upper limit of the corrosion resistance temperature of the material constituting the processing vessel with respect to ClF 3 are 400 ° C. 3 . Cleaning method.   The cleaning method according to any one of claims 1 to 3, wherein a degree of vacuum in the processing container is set to 1 to 50 Torr.   5. The N 2 for dilution is mixed with the cleaning gas containing ClF 3, and is supplied into the processing container at a flow rate at which the ratio of the flow rate of ClF 3 to the flow rate of N 2 is 0.2 or more. The cleaning method as described in.

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