JPH0794418A - Method for cleaning film forming chamber - Google Patents

Abstract

PURPOSE:To provide a cleaning method by which metallic films formed on parts other than a prescribed part can be selectively removed without deteriorating the selectivity of film formation at the time of selectively growing the metallic films by using the selective CVD method. CONSTITUTION:After forming a tungsten film on the surface of a substrate 7 to be treated by using the selective CVD method, the substrate 7 carrying the tungsten film is taken out from a reaction chamber 3 and tungsten films formed on a quartz susceptor 6, quartz-made fixing jig 10, etc., are selectively removed during the forming process of the tungsten film by introducing chlorine trifluoride (ClF3) gas to the reaction chamber 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a film forming chamber, and more particularly to an improvement in a method for cleaning a film forming chamber after selectively forming a metal film.

[0002]

2. Description of the Related Art In recent years, large-scale integrated circuits (LSIs) formed by integrating a large number of transistors, resistors and the like so as to achieve an electric circuit on a single chip have been formed in important parts of computers and communication devices. It is used a lot.

Since a thin film formation and its patterning are repeated many times in the manufacture of an LSI, the film forming technique occupies an important position in the semiconductor technique. The film formation can be roughly divided into two: modification of the substrate material and deposition on the substrate surface.
There are types.

A typical example of the former method is film formation of a silicon oxide film by direct oxidation of a silicon substrate. On the other hand, a typical example of the latter is, for example, CV.
There is film formation by the D method.

In recent years, the CVD method has been developed, and the selective CVD method using the difference in film quality (material) on the surface of the substrate has been studied and put into practical use. A specific example of the selective CVD method is to selectively grow and form a tungsten film in the contact hole. This is tungsten hexafluoride (W
By using F ₆ ) and silane (SiH ₄ ), the tungsten film does not grow on the oxide film forming the contact hole, and the underlayer A in the contact hole is formed.
A tungsten film can be selectively grown on the 1SiCu film.

However, even though the selective CVD method is used,
As the deposition time (processing time) of the tungsten film becomes longer, selective deposition is hindered as a result of the tungsten film inevitably being deposited on the inner wall of the chamber, the gas nozzle for introducing the raw material gas, and the substrate support. There is a problem that the generation of dust and particles is promoted. Such a problem is caused by the usual CVD method (blanket CVD
Method), it was not present as it was non-selective deposition.

In order to prevent the occurrence of the above problems, the tungsten film deposited on the inner wall of the chamber, the gas nozzle, the substrate support, etc. is usually removed before the film formation. Specifically, sulfur hexafluoride (SF ₆ ) gas and nitrogen trifluoride (N
The tungsten film is removed by plasma cleaning using F ₃ ) gas.

However, in the case of plasma cleaning, a jig such as a substrate support pedestal made of quartz contained in the chamber is etched by the charged particles in the plasma and the action of promoting light irradiation, and etching reaction products are produced. Or particles are generated. Since these become the nucleus of the growth of the tungsten film, there arises a problem that the film forming selectivity is deteriorated.

[0009]

As described above, in the conventional selective CVD method for the tungsten film, complete selective growth is impossible, so that the tungsten film deposited on the inner wall of the chamber during film formation. Had to be removed by plasma cleaning.

However, when the plasma cleaning is performed, the substrate supporting base made of quartz and the like contained in the chamber is consumed, and as a result, etching reaction products and particles are generated, and the selectivity of film formation is increased. There was a problem of lowering.

The present invention has been made in consideration of the above circumstances, and an object thereof is to form a metal film deposited on a portion other than a predetermined portion during the selective growth of the metal film by the selective CVD method. It is an object of the present invention to provide a method for cleaning a film forming chamber, which can selectively remove a metal film deposited on a portion other than the predetermined portion without deteriorating the selectivity of the film.

[0012]

The essence of the present invention is to generate a plasma in the reaction chamber by supplying a metal film deposited in the film formation chamber with a compound gas having a very high reactivity with the metal film. Without removing the metal film.

That is, in order to achieve the above object,
A method for cleaning a film forming chamber of the present invention introduces a substrate to be processed into a film forming chamber having a member formed of silicon oxide, and selectively forms a metal film on the substrate to be processed by a CVD method. And a step of removing the substrate to be processed from the film forming chamber, introducing an interhalogen compound gas containing a fluorine element and a halogen element other than the fluorine element into the film forming chamber, and in the step of forming the metal film, A step of selectively removing the metal film formed in the film forming chamber, wherein the member is, for example, an inner wall of the processing chamber or a substrate support provided in the processing chamber. It means a table (susceptor).

Further, as the interhalogen compound gas,
For example, ClF, ClF ₃ , BrF, BrF ₃ or B
It is preferable to use rF ₅ or the like. Furthermore, it is preferable that the interhalogen compound gas is excited by heating in the reaction chamber or excited by light, a charged particle beam or discharge in a region different from the reaction chamber.

[0015]

The interhalogen compound gas (interhalogen gas) exhibits extremely high reactivity with metals. On the other hand, the interhalogen compound gas does not react with silicon oxide at all.

Therefore, according to the present invention in which an interhalogen compound gas is used as a cleaning gas, a member formed of silicon oxide among the components of the reaction chamber is not etched and a predetermined amount is formed during film formation. The metal film formed on other than the portion can be selectively removed.

Therefore, it is possible to prevent the generation of etching reaction products and particles due to the etching of the member formed of silicon oxide, and it is possible to keep the selectivity of film formation high.

[0018]

Embodiments will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a single-wafer type thin film forming apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a container made of aluminum alloy, and a cooling pipe 2 and a heater 18 for heating are provided on the wall of the container 1. Further, the inside of the container 1 is a reaction chamber 3 for forming a thin film by the low pressure CVD method.

In the reaction chamber 3, a source gas supply pipe 4 and
The cleaning gas supply pipe 17 is connected. An exhaust port 5 connected to an exhaust system (not shown) is formed at the bottom of the reaction chamber 3 so that the inside of the reaction chamber 3 can be depressurized.

Further, a quartz susceptor 6 is arranged at the bottom of the reaction chamber 3, and a heater 8 for mounting and heating a substrate 7 to be treated is provided on the quartz susceptor 6.
A force pushing upward from the spring 9 acts on the heater 8, and the heater 8 is fixed by the spring 9. The quartz susceptor 6 and the heater 8 form a sample table.

The side walls of the heater 8 and the quartz susceptor 6 are covered with a quartz fixing jig 10 when the substrate to be treated is fixed. On the surface of the quartz fixing jig 10 on the heater 8 side, an aluminum film 11 is formed as a heat reflection means for reflecting the heat from the heater 8. Further, below the quartz fixing jig 10, there is provided a vertically moving mechanism 12 for fixing and releasing the substrate 7 to be processed on the heater 8.

Here, the substrate 7 to be processed is fixed and released as follows. That is, when the substrate 7 to be treated is fixed and heated on the heater 8, as shown in FIG. 1, the quartz fixing jig 10 is moved downward by the elevating mechanism 12, and the bottom surface of the quartz fixing jig 10 is moved. Is brought into close contact with the upper surface of the quartz susceptor 6. At this time, the outer peripheral part of the substrate 7 to be processed is pinched between the upper surface of the heater 8 and the upper end of the surface of the quartz fixing jig 10 on the heater 8 side by the force pushing upward from the spring 9, The substrate 7 to be processed is fixed. On the other hand, when releasing the substrate 7 to be processed, as shown in FIG. 2, the quartz fixing jig 10 is moved upward by the elevating mechanism 12.

The heater 8 has a structure in which the tungsten wire 13 is covered with alumina 14. The tungsten wire 13 becomes a heating body by applying a voltage and passing an electric current, whereby the substrate 7 to be processed is heated.

The tungsten wire 13 is connected to a stretchable nickel wire 15 spirally wound with silver solder, and the nickel wire 15 is connected to a copper wire 16. Furthermore, this copper wire 16 is connected to a power source (not shown),
The voltage of this power source is controlled so that the temperature of the substrate 7 to be processed is kept constant.

Next, a method for selectively growing a tungsten film and a cleaning method using the single-layer thin film forming apparatus having the above-described structure will be described. First, as the substrate 7 to be treated,
A semiconductor substrate provided with an AlSiCu wiring and an insulating film provided on the AlSiCu wiring and having a through hole (via hole) formed therein is prepared.

Next, the substrate 7 to be treated as described above is heated to 260 ° C. by using the heater 8, and then 10 SCCM of tungsten hexafluoride and 10 SCCM of silane gas are introduced into the reaction chamber 3 as raw material gases to carry out the reaction. The pressure in chamber 3 is 0.0
Hold at 05 Torr.

Under the above conditions, the AlSiCu of the substrate 7 to be processed is
A tungsten film can be selectively deposited on the wiring at a rate of 4000 A / min. However, if the deposition of the tungsten film is repeated several tens of times by this method, the quartz susceptor 6, the quartz fixing jig 10, and the gas nozzle 4 are used as in the conventional case.
Deposition of the tungsten film occurs in the above. Therefore, the following cleaning process is performed.

That is, first, the substrate 7 to be treated is placed in the reaction chamber 3
After taking it out from the reaction chamber 3 by the heater 18 for heating.
In addition to heating the entire interior, the radiant heat of the heater 8 is used to heat the tungsten adhesion portion to 100 ° C. or higher.

Then, chlorine trifluoride (ClF ₃ ) gas is supplied into the reaction chamber 3 through the cleaning gas supply pipe 17 in an amount of 10 times.
Supply 0SCCM, substrate temperature 200 ℃, pressure 1Torr
As described above, by holding for 5 minutes, the tungsten film attached to the quartz susceptor 6 and the quartz fixing jig 10 which are quartz jigs is selectively removed. It has been found that such a cleaning method can prevent the generation of etching reaction products and the generation of particles from these quartz jigs.

Here, the quartz susceptor 6 which is a jig made of quartz is used.
The reason why only the tungsten film is removed without etching the quartz fixing jig 10 is explained as follows. That is, an interhalogen compound gas such as ClF ₃ gas shows extremely high reactivity with a metal even at a low substrate temperature (less than 400 ° C.), and a tungsten film has a Cl
The W + 2ClF ₃ → WF ₆ + Cl ₂ WF ₆ , Cl ₂ that reacts with the F ₃ gas and is removed is vaporized and exhausted to the outside of the reaction chamber.

On the other hand, ClF ₃ gas has a low substrate temperature (4
At less than 00 ° C.), since it does not react with quartz (SiO ₂ ) at all, the quartz susceptor 6 and the quartz fixing jig 10, which are quartz jigs, are not etched. Therefore, only the tungsten film is removed.

FIG. 3 is a diagram showing the temperature dependence of the etching rate for the W film and the SiO ₂ film formed by the CVD method. As shown in FIG. 3, unlike the W film, the SiO ₂ film has an etching rate of substantially 0 at temperatures lower than 400 ° C.

Therefore, if the W film is etched at a substrate temperature lower than 400 ° C. as in this embodiment, the W film can be surely selectively etched. Although not shown in FIG. 3, the value of the etching rate of the SiO ₂ film at a substrate temperature of 700 ° C. is 100 at most.

Thus, according to this embodiment, consumption of the quartz jig and generation of etching reaction products and particles, which have been problems in the conventional plasma cleaning, are eliminated, and the tungsten film is selected at the time of film formation after cleaning. It becomes possible to greatly suppress the deterioration of sex. As a result, it is possible to reduce the production cost and the thin film deposition apparatus cost and improve the product yield.

Next, another embodiment of the present invention will be described. The present embodiment is different from the previous embodiments in that ClF ₃ gas excited in a region other than the reaction chamber (not in a plasma state) is used as a cleaning gas. That is, the cleaning gas supply pipe 1
ClF ₃ gas activated from 7 is introduced into the reaction chamber 3 for cleaning.

To activate the ClF ₃ gas, for example, a microwave power source is connected to the cleaning gas supply pipe 17 to cause discharge in the cleaning gas supply pipe 17 to excite the raw ClF ₃ gas. Further, it may be excited by light or a charged particle beam.

The present invention is not limited to the above embodiment. For example, in the above embodiment, ClF ₃ was used as the interhalogen compound gas of the fluorine element and the halogen element other than this, but instead of that, ClF 3 and Br were used.
F, BrF ₃ , BrF ₅ or the like may be used.

Further, although the selective CVD method for the tungsten film has been described in the above embodiment, the present invention can be applied to the selective CVD for other metal thin films such as molybdenum thin film and titanium thin film. Besides, various modifications can be made without departing from the scope of the present invention.

[0040]

As described in detail above, according to the present invention, since the metal film formed on a portion other than a predetermined portion can be selectively removed during film formation, the member formed of silicon oxide is etched. It is possible to prevent the generation of etching reaction products and particles due to the above, and it is possible to perform film formation with high selectivity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a sheet-type thin film forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a released state of the quartz fixing jig 10.

FIG. 3 is a characteristic diagram showing the temperature dependence of the etching rate for the W film and the SiO ₂ film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container 2 ... Cooling pipe 3 ... Reaction chamber 4 ... Raw material gas supply pipe 5 ... Exhaust port 6 ... Quartz susceptor 7 ... Substrate 8 ... Heater 9 ... Spring 10 ... Quartz fixing jig 11 ... Aluminum film 12 ... Mechanism 13 ... Tungsten wire 14 ... Alumina 15 ... Nickel wire 16 ... Copper wire 17 ... Cleaning gas supply pipe 18 ... Heating heater

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/304 341 M

Claims (1)

[Claims] 1. A step of introducing a substrate to be processed into a film forming chamber having a member formed of silicon oxide, and selectively forming a metal film on the substrate to be processed by a CVD method; Is taken out of the film forming chamber, an interhalogen compound gas containing a fluorine element and a halogen element other than the fluorine element is introduced into the film forming chamber, and is formed in the film forming chamber in the step of forming the metal film. And a step of selectively removing the metal film, the method for cleaning a film forming chamber.