JP2002008991A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method for efficiently removing a needless film, without damaging a process vessel of quartz and the like. SOLUTION: A cleaning method is provided wherein a cleaning gas is fed into a process vessel 8, in which a film is deposited on a work piece W such as a semiconductor wafer to remove the needless film. Here, the cleaning gas is heated, for activation as an example, with a gas heating mechanism 52 in advance, which is fed into the process vessel. Thus, a needless film is removed efficiently, without damaging the process vessel of quartz and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method for removing an unnecessary film adhered in a processing container.

[0002]

2. Description of the Related Art In general, in order to manufacture a semiconductor device, a film forming process and a pattern etching process are repeatedly performed on a semiconductor wafer to produce a desired device. The specifications, that is, the design rules, are becoming stricter year by year as the degree of integration increases.For example, even thinner oxide films such as the insulating film and gate insulating film of a capacitor in a device need to be made thinner. And at the same time higher insulation is required. Under these circumstances,
Metal oxide films, such as tantalum oxide films (Ta ₂ O ₅ ) and tantalum oxide films, may be used as materials having better electric characteristics such as insulating properties and dielectric constants in place of the conventionally used silicon oxide films and silicon nitride films. A composite metal oxide film having a larger dielectric constant than an oxide film, for example, SrTiO ₃ (hereinafter, referred to as SrTiO ₃ )
STO) or Ba _x Sr _1-x TiO ₃ (hereinafter referred to as B
STO) is being studied. In addition, various metal films, metal oxide films, and the like have been studied as dielectric layers.

Meanwhile, in a heat treatment apparatus such as a film formation apparatus, for example, a so-called batch type heat treatment apparatus having a vertical or horizontal cylindrical processing vessel made of quartz, from the viewpoint of preventing generation of particles, In order to remove an unnecessary film adhered to the inner wall of the processing container, the wafer boat, or the like, a cleaning process for removing the unnecessary film periodically or irregularly is performed. In this cleaning process, a large-scale wet cleaning for removing an unnecessary film by removing the processing container itself and immersing it in a cleaning solution, and ClF ₃ , HCl, and the like in a state where the processing container is assembled without removing the processing container. Cl ₂ , NF ₃ , F ₂
Dry cleaning is performed, which is simple and requires a short time to remove unnecessary films by flowing a cleaning gas such as this.

[0004]

From the viewpoint of improving the productivity (throughput) of the whole semiconductor device, it is required to remove unnecessary films more efficiently by using dry cleaning. However, there is a case where the unnecessary film cannot be sufficiently removed from a composite metal oxide film such as the above-mentioned STO or BSTO, which is being studied recently, or a new metal oxide film.
For example, in general, the higher the temperature of the processing container at the time of cleaning, the higher the reactivity of the cleaning gas. As a result, new film types that could not be removed until now can be removed, and cleaning efficiency increases, but at the same time, a quartz processing vessel itself and a quartz wafer boat holding semiconductor wafers The cleaning gas itself is easily damaged, and the temperature of the processing container cannot be excessively increased.

Further, even if it is desired to remove unnecessary films such as a silicon oxide film and a silicon nitride film which are conventionally used more efficiently and in a shorter time, as described above, If the temperature is increased, the processing container itself will be seriously damaged. Therefore, this temperature cannot be increased to, for example, 800 ° C. or more, depending on the type of the cleaning gas, and the cleaning efficiency is further improved. Could not. Further, in the vicinity of the introduction portion of the cleaning gas, since this gas is introduced at a temperature of about room temperature, the temperature partially drops, so that an unnecessary film in the vicinity of the gas introduction portion cannot be sufficiently removed. There is also a problem that a case may occur. The present invention has been devised in view of the above problems and effectively solving them. An object of the present invention is to provide a cleaning method capable of efficiently removing an unnecessary film without damaging a quartz processing container or the like.

[0006]

The invention according to claim 1 is
In a cleaning method for removing an unnecessary film by flowing a cleaning gas into a vacuum-treatable processing container, the cleaning gas is preheated to a predetermined temperature in advance, and the preheated cleaning gas is introduced into the processing container. I do. According to the second aspect of the present invention, an unnecessary film is removed by flowing a cleaning gas into a vacuum-evacuable processing vessel for performing a predetermined process on a plurality of workpieces held by the workpiece holder. In the cleaning method, the cleaning gas is pre-heated to a predetermined temperature in advance, and the pre-heated cleaning gas is introduced into the processing container in a state in which the object holder is stored in the processing container. I do. This makes it possible to improve the removal rate of unnecessary films without damaging the processing container or the processing container and the holder for the object to be processed, or to efficiently remove unnecessary films that cannot be removed by the conventional method. It is possible to do.

In this case, for example, the predetermined temperature is a temperature for activating the cleaning gas, or as defined in claim 4, for example, the predetermined temperature is And the temperature at which the cleaning gas is thermally decomposed.

Further, as defined in claim 5, for example, the film is of the same type as the film deposited on the surface of the object to be processed. Furthermore, as defined in claim 6, for example, the processing container is formed of quartz or SiC.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the cleaning method according to the present invention will be described below in detail with reference to the accompanying drawings. Figure 1
FIG. 1 is a configuration diagram illustrating a film forming apparatus for performing a cleaning method according to the present invention. Here, LP is used as a film forming apparatus.
-A vertical type film forming apparatus by CVD will be described as an example.
As shown in the figure, this film forming apparatus has a double-tube structure including a cylindrical quartz inner cylinder 2 and a quartz outer cylinder 6 concentrically disposed outside the inner cylinder 2 with a predetermined gap 4 interposed therebetween. A processing container 8 is provided, and the outside thereof is provided with a heating means 10 such as a heater.
And a heating unit 14 having a heat insulating material 12.
The heating means 10 is provided on the entire inner surface of the heat insulating material 12.

The lower end of the processing vessel 8 is supported by a cylindrical manifold 16 made of, for example, stainless steel, and the lower end of the inner cylinder 2 has a ring-shaped support plate 16A projecting inward from the inner wall of the manifold 16. , And a quartz wafer boat 18 as a workpiece holder holding a large number of semiconductor wafers W as workpieces from below the manifold 16 can be vertically inserted and removed. The wafer boat 18 is mounted on a turntable 22 via a heat insulating tube 20 made of quartz.
The rotary table 22 is supported on a rotary shaft 26 that penetrates a lid 24 that opens and closes a lower end opening of the manifold 16. For example, a magnetic fluid seal 28 is interposed in the penetrating portion of the rotating shaft 26, and the rotating shaft 26 is rotatably supported while hermetically sealing. Also, the lid 24
A seal member 30 made of, for example, an O-ring or the like is interposed between the peripheral portion of the container and the lower end portion of the manifold 16 to maintain the sealing property in the container.

The rotating shaft 26 is attached to the tip of an arm 34 supported by an elevating mechanism 32 such as a boat elevator.
Etc. can be moved up and down integrally. A gas introduction nozzle 3 for introducing a film forming gas or an inert gas, for example, N ₂ gas, into the inner cylinder 2 is provided on a side portion of the manifold 16.
6. A cleaning gas introduction nozzle 3 for introducing a cleaning gas during dry cleaning in the processing container 8.
8 and an exhaust port 40 for exhausting the atmosphere in the container from the bottom of the gap 4 between the inner cylinder 2 and the outer cylinder 6, respectively.
The exhaust port 40 is connected to a vacuum exhaust system provided with a vacuum pump or the like (not shown). Further, a cleaning gas supply unit 42 is connected to the cleaning gas introduction nozzle 38. The cleaning gas supply means 42 includes a gas passage 46 connected to a cleaning gas source 44.
In the gas passage 46, an on-off valve 48, a flow controller 50 such as a mass flow controller for controlling the flow rate of the cleaning gas, and a cleaning gas flowing through the downstream side of the flow controller 50. A gas heating mechanism 52 for pre-heating the cleaning gas to a predetermined temperature is interposed so that the cleaning gas whose flow rate is controlled to a desired value can be heated to a predetermined temperature and flow into the processing vessel 8. The gas heating mechanism 52 has a gas heater 54 whose temperature can be controlled. The inside of the gas heating mechanism 52 is not limited as long as it can heat the cleaning gas.
Here, ClF ₃ gas which is, for example, chlorine trifluoride is used as the cleaning gas. Note that chlorine fluoride (ClF) can also be used as a cleaning gas. In the figure, reference numeral 56 denotes the lower end of the outer cylinder 6 and the manifold 1.
6 is a seal member such as an O-ring interposed between the upper end of O.

Next, a film forming process using the apparatus configured as described above will be described. First, when the wafer boat (workpiece holder) 18 for holding a semiconductor wafer (workpiece) W is in an unloaded state and the film forming apparatus is in a standby state, the processing chamber 8 is kept at a film forming process temperature, for example, 60 ° C.
It is maintained at 0 ° C. or lower. Then, the wafer boat 18 is moved from a wafer carrier (not shown).
The unprocessed wafers W are transferred to the wafer boat 18, and the wafer boat 18 holding a large number of wafers W at room temperature is loaded into the processing container 8 by being lifted from below, and the lid 24 is loaded.
The inside of the container is closed by closing the lower end opening of the manifold 16 with. Then, while maintaining the inside of the processing container 8 at a predetermined film forming process pressure, the process waits until the wafer temperature rises and stabilizes at the predetermined film forming process temperature.
A predetermined film forming gas or the like is introduced into the processing vessel 8 from the processing gas introduction nozzle 36. The deposition gas is a processing gas introduction nozzle 3
After being introduced into the bottom of the inner tube 2 from the inner tube 2, the film W rises due to a film forming reaction while being in contact with the wafer W being rotated therethrough. The gas flows down the gap 4 and is discharged from the exhaust port 40 to the outside of the container. As a result, a predetermined film is formed on the wafer W.

The above is the flow of the film forming process. When such a film forming process is repeatedly performed, an unnecessary film is formed on the wall surface of the quartz member which comes into contact with the film forming gas in the flowing direction. It is unavoidable that they are formed little by little. Unnecessary films adhere to the wafer boat 18, the inner and outer surfaces of the inner tube 2, the inner surface of the outer tube 6, the surface of the heat retaining tube 20, and the like. Therefore, after the film forming process is performed a certain number of times, a cleaning operation for removing an unnecessary adhered film that causes particles is performed. This cleaning operation is performed, for example, in a state where an empty wafer boat 18 that does not hold a wafer is introduced into the processing container 8. That is, first, after the film forming process is finally performed through the above-described steps, the wafer boat 18 is unloaded from the inside of the processing container 8 by driving the elevating mechanism 32. Thereafter, all of the processed wafers W stored in the wafer boat 18 are transferred to a wafer carrier (not shown) by using a transfer mechanism (not shown) to empty the wafer boat 18. As described above, when the transfer of the processed wafer W is completed, the lifting mechanism 3
2 to drive the empty wafer boat 18
Is loaded into the processing container 8, and the lower end opening of the manifold 16 is closed with the lid 24. And heating means 10
The processing container 8 at a predetermined temperature, for example, 200 to 100
While maintaining the temperature within the range of 0 ° C., ClF ₃ gas as a cleaning gas whose flow rate is controlled is supplied from the cleaning gas introduction nozzle 38 to the bottom of the inner cylinder 2 and, if necessary, an inert gas such as an inert gas, for example, as a diluting gas. N ₂ gas is supplied from the processing gas introduction nozzle 36. In this case, the cleaning gas is heated to a predetermined temperature by the gas heating mechanism 52 immediately before being introduced into the processing container 8,
Preheated.

The inert gas and the cleaning gas preheated to a predetermined temperature in advance are mixed in a processing vessel 8, and this mixed gas flows through the inner cylinder 2 in the same manner as the film forming gas. It rises to reach the ceiling, and then turns back, flows down in the gap 4 between the inner cylinder 2 and the outer cylinder 6, and is discharged out of the container through the exhaust port 40. This Cl
Unnecessary film adhering to the wall surface in the flow path of the F ₃ gas reacts with the ClF ₃ gas, is etched, and is gradually removed. At this time, since the cleaning gas is heated to a predetermined temperature immediately before being introduced into the processing container 8 as described above, the cleaning gas is in a state of high reactivity, and is efficiently and quickly. Unnecessary films can be removed, and cleaning can be performed efficiently, for example, in a short time.

Specifically, the heating temperature of the cleaning gas in the gas heating mechanism 52 may be simply a temperature at which the kinetic energy of the gas molecules increases, or the gas molecules are excited to a high energy state. A temperature at which a chemical reaction is very easily activated, for example, in the case of ClF ₃ gas, it may be heated to about 200 to 400 ° C., or a temperature at which gas molecules are decomposed into elements. For example, in the case of ClF ₃ gas, 300 to 100
You may heat to about 0 degreeC. As described above, since the cleaning gas is preheated to a predetermined temperature immediately before the cleaning gas is introduced into the processing container 8, first, when the cleaning gas is introduced to a temperature of about room temperature as in the conventional method, The temperature in the vicinity of the gas introduction part was partially reduced, and there was a case where unnecessary film in this part could not be completely removed.
In the case of the method of the present invention, there is no decrease in temperature near the gas introduction part, and therefore, unnecessary films in this part can be almost completely removed.

Further, if cleaning is performed by setting the cleaning process conditions such as the temperature of the processing container 8 to the same as the conventional method, the cleaning rate (film removal rate) is increased by preheating the cleaning gas, and the cleaning rate is accordingly increased. , Cleaning time can be reduced, and
No major damage to quartz components. In addition, in the conventional method, even if the quartz component is greatly damaged, an unnecessary film that cannot be removed without increasing the cleaning temperature is reduced according to the method of the present invention. Even if the cleaning gas temperature is set low, the temperature of the cleaning gas is raised to a temperature at which the unnecessary film reacts with the unnecessary film by preheating. It is possible to efficiently remove only the unnecessary film for cleaning.

Further, in the case where the upper limit temperature of the heating unit 14 at which the heating unit 14 can be heated is about 800 to 1000 ° C. due to the configuration of the power equipment or the like, an unnecessary film cannot be removed at such a temperature. However, in the case of the method of the present invention, the cleaning process temperature (the temperature of the processing container 8 and the like) is maintained at about 800 to 1000 ° C. as described above, and the cleaning gas is heated to a higher temperature, for example, about 1200 ° C. By preheating up to this point, it is possible to remove unnecessary films that could not be removed by the conventional method without damaging the quartz components. In addition, the pressure inside the processing container in the conventional cleaning method is expressed by the following equation.
It was about 100 Pa (several Torr).
By setting the pressure to kPa (several hundred Torr), unnecessary films can be removed more efficiently, and the cleaning efficiency can be further improved.

Here, the unnecessary film to be cleaned includes, for example, a Si film, a SiO ₂ film, and a Si ₃ N ₄ film.
Film, BSTO (Ba _x Sr _1-x TiO ₃ ) film, STO
(SrTiO ₃ ) film, TiN film, Ru film, RuO ₂ film,
For example, MO such as Ta ₂ O ₅ film, W film, WSi film, etc.
Many films, such as those used in SFETs, are of interest.
In the above embodiment, the structure of the vertical processing container 8 is
The case of a double tube structure composed of the outer tube 6 and the outer tube 6 has been described as an example, but the present invention is not limited to this, and the processing vessel 8 as shown in FIG. The present invention can also be applied to a film forming apparatus having a structure. In FIG. 2, the same components as those in the apparatus shown in FIG. Here, as described above, the processing container 8 is constituted by only one outer cylinder 6 made of quartz, for example. A large-diameter exhaust port 40 is provided at the upper end of the outer cylinder 6, and vacuum exhaust is performed from here.

In this case, at the time of cleaning, the cleaning gas preliminarily heated from the cleaning gas introduction nozzle 36 provided in the manifold 16 adheres to the surface of the quartz component while rising inside the processing vessel 8. The unnecessary film is removed, and the gas is discharged out of the container through the exhaust port 40 at the upper end. Further, in the case of the example of the apparatus having a single pipe structure shown in FIG.
As shown in FIG. 1, the exhaust port 40 is provided in the manifold 16 similarly to the case shown in FIG. 1, and the gas inlet nozzle 36 and the cleaning gas inlet nozzle 38
Are installed along the inner wall of the processing vessel 8 (outer cylinder 6), both of which have a single-tube structure, and their nozzle ports are located on the ceiling of the processing vessel 8. According to this, the cleaning gas introduced in advance from the cleaning gas introduction nozzle 36 removes an unnecessary film adhering to the surface of the quartz component while descending inside the processing container 8, and This gas is discharged out of the container through the exhaust port 40 provided in the manifold 16.

In the case of the apparatus shown in FIGS. 2 and 3, the same operation and effect as those shown in FIG. 1 are exhibited, and unnecessary films can be efficiently produced without damaging the surface of, for example, a quartz member. It becomes possible to remove it. Further, here, the method of the present invention has been described by taking, as an example, a batch-type film forming apparatus capable of processing a plurality of semiconductor wafers at a time, but the present invention is not limited to this, and the method of the present invention may use one semiconductor wafer. It is needless to say that the present invention can be applied to a single-wafer type film forming apparatus that performs processing one by one. Further, the object to be processed is not limited to a semiconductor wafer, and an LCD substrate and a glass substrate can of course be used. Further, the processing vessel 8 having a double pipe structure or a single pipe structure may be made of SiC.

[0021]

As described above, according to the cleaning method of the present invention, the following excellent functions and effects can be exhibited. Since the cleaning gas is preheated and introduced into the processing container in advance, without damaging the processing container or the processing container and the workpiece holder.
The removal rate of the unnecessary film can be improved, or the unnecessary film that cannot be removed by the conventional method can be efficiently removed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a film forming apparatus for performing a cleaning method according to the present invention.

FIG. 2 is a view showing a film forming apparatus having a single-tube structure in which a processing container includes only one quartz outer cylinder.

FIG. 3 is a diagram showing another film forming apparatus having a single tube structure.

[Explanation of symbols]

 Reference Signs List 8 processing container 18 wafer boat 20 heat retaining cylinder 36 gas introduction nozzle 38 cleaning gas introduction nozzle 42 cleaning gas supply means 44 cleaning gas source 52 gas heating mechanism W semiconductor wafer (object to be processed)

Continuation of the front page (72) Inventor Kazuaki Nishimura 1-2-4, Shiroyamacho, Tsukui-gun, Kanagawa Prefecture Inside the Sagami Office of Tokyo Electron Tohoku Co., Ltd. (72) Inventor Sport Philip 1-2-cho, Shiroyamacho, Tsukui-gun, Kanagawa Prefecture No. 41 Tokyo Electron Tohoku Co., Ltd. Sagami Office F-term (reference) 4K030 CA04 CA12 DA06 KA04 KA25 KA41 5F004 AA15 BB19 BB29 5F045 AA06 AD06 AD07 DP19 EB03 EB06 EC02 EE06 EK21 EM10

Claims (6)

[Claims] In a cleaning method for removing an unnecessary film by flowing a cleaning gas into a processing vessel capable of being evacuated, said cleaning gas is preheated to a predetermined temperature in advance, and said preheated cleaning gas is supplied to said cleaning gas. A cleaning method, wherein the cleaning method is introduced into a processing container. 2. A cleaning method for removing unnecessary films by flowing a cleaning gas into a vacuum-evacuable processing vessel for performing a predetermined process on a plurality of workpieces held by a workpiece holder. In the method, the cleaning gas is preliminarily heated to a predetermined temperature, and the preheated cleaning gas is introduced into the processing container in a state in which the workpiece holder is accommodated in the processing container. A cleaning method characterized in that: 3. The method according to claim 1, wherein the predetermined temperature is a temperature for activating the cleaning gas.
Or the cleaning method according to 2. 4. The apparatus according to claim 1, wherein the predetermined temperature is a temperature at which the cleaning gas is thermally decomposed.
Or the cleaning method according to 2. 5. The cleaning method according to claim 1, wherein the film is of the same type as a film deposited on the surface of the object. 6. The cleaning method according to claim 1, wherein the processing container is formed of quartz or SiC.