JP2005068559A - Method and apparatus for film formation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film formation method free of heavy metal contamination by forming a precoat-metal-containing thin film on an installation table. <P>SOLUTION: In the method for forming a metal-containing film 74 on a treatment object W placed on a placing table 16 in a treatment vessel 4, a precoat-metal-containing thin film 72 having a two-layer structure consisting of a first thin film 68 and a second thin film 70 formed one after another, both containing a metal same as that contained in the metal-containing film 74, is formed; then, the metal-containing film 74 is formed on the surface of the treatment object W placed on the placing table. The precoat-metal-containing thin film prevents metallic atoms of the placing table from going outside and therefore from causing heavy metal contamination. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a film forming method and a film forming apparatus for forming a metal-containing film such as a titanium film on an object to be processed such as a semiconductor wafer.

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.

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 the TiN film is similarly formed by using TiCl ₄ and N as source gases. _The film is formed by plasmaless CVD using _two gases or by plasma film formation in the presence of nitrogen.

  By the way, as a mounting table for the film forming apparatus used for the film formation, a ceramic mounting table such as AlN (aluminum nitride) which is generally excellent in heat resistance and corrosion resistance is used. Is quite expensive. In addition, since the ceramic itself has low conductivity, a potential difference occurs in the mounting surface of the ceramic mounting table or between the mounting table and, for example, the side wall of the processing vessel during the plasma CVD process, which is generated in the processing space. In some cases, the plasma is not stably generated, and the plasma density is uneven.

  For this reason, it is conceivable to stabilize the plasma by forming the mounting table itself from a metal material having good conductivity and suppressing the occurrence of a potential difference in the mounting surface or between this and the container side wall. In this case, since the semiconductor wafer itself placed on the placement surface is contaminated by the metal constituting the placement table, so-called heavy metal contamination occurs, it cannot be adopted as it is.

  It is also conceivable to prevent heavy metal contamination by firmly attaching a coating layer made of ceramic or the like to the surface of the metal mounting table in advance. In this case, the metal mounting table and the ceramic mounting table may be used. Due to the difference in coefficient of thermal expansion with the coating layer, there is a problem that the coating layer is peeled off or cracked due to repeated film formation, and thus cannot be employed.

Furthermore, in the case of a ceramic material, since the thermal conductivity is low, there is also a problem that the heating efficiency for the wafer is not so good.
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 film forming method and a film forming apparatus free from heavy metal contamination by forming a precoat metal-containing thin film on a mounting table.

  In order to solve the above-described problems, the present invention provides a film forming method for forming a metal-containing film on an object to be processed placed on a placing table in a processing container, wherein the metal is formed on the surface of the placing table. Forming a pre-coated metal-containing thin film having a two-layer structure in which a first thin film and a second thin film, which are films containing the same metal as the containing film, are sequentially stacked, and then placing the object on the mounting table Then, the metal-containing film is formed on the surface of the object to be processed.

Thus, prior to the actual metal-containing film formation on the object to be processed, a thin film containing the same metal as the metal contained in the metal-containing film is formed on the surface of the mounting table as a pre-coated metal-containing thin film. Therefore, even if the metal in the precoat metal-containing thin film penetrates into the metal-containing film of the object to be processed, heavy metal contamination does not occur because these are the same kind of metal.
Such a metal-containing film formed on the object to be processed is, for example, a titanium (Ti) film or a titanium nitride (TiN) film. At this time, as the precoat metal-containing thin film, a titanium thin film or a titanium nitride thin film or These two-layer structures are used. In order to form a titanium nitride thin film, the titanium nitride thin film may be deposited and laminated on the lower titanium thin film, or the surface portion of the lower titanium thin film may be nitrided to form an upper layer. A titanium nitride thin film may be formed. By forming the two-layer structure in this way, it becomes possible to improve the adhesion of the titanium thin film to the mounting table.

According to the film forming method and the film forming apparatus of the present invention, the following excellent operational effects can be exhibited.
Since the precoat metal-containing thin film containing the same metal as the metal-containing thin film to be processed is attached to the surface of the mounting table and covered, the metal atoms constituting the mounting table are confined to this thin film on the outside. It can be prevented from coming out and heavy metal contamination to the object to be treated can be prevented.
As a result, the mounting table can be formed of a metal material having good conductivity without worrying about heavy metal contamination, so that it is possible to prevent potential differences that adversely affect the plasma distribution, and the plasma can be stably and uniformly distributed. Can be formed.
In addition, when a titanium film or a titanium nitride film is formed on an object to be processed, the adhesion of the titanium thin film to the mounting table is achieved by adopting a laminated structure of a titanium thin film and a titanium nitride thin film as the precoat metal-containing thin film. Can be improved, and it can be prevented from peeling off.

Hereinafter, an embodiment of a film forming method and a film forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an embodiment of a film forming apparatus of the present invention. In this embodiment, a case where a Ti (titanium) film is formed as a metal film by a film forming apparatus will be described as an example.
As shown in the figure, the film forming apparatus 2 has a processing container 4 formed in a cylindrical shape, and the processing container 4 is grounded. An exhaust port 8 for exhausting the atmosphere in the container is provided at the bottom 6 of the processing container 4, and an exhaust system 12 having a vacuum pump 10 is connected to the exhaust port 8. The inside of the processing container 4 can be evacuated uniformly from the bottom periphery.

  In the processing container 4, a disk-like mounting table 16 made of metallic material, for example, Hastelloy (trademark) is provided via a support 14 made of a conductive material. A wafer W can be placed thereon. The mounting table 16 also serves as a lower electrode. The mounting table 16 includes a lower table 16A that is directly supported by the support column 14 and an upper table 16B that is bonded to the upper surface, and a resistance heater 18 is sandwiched between them. Yes. The lower base 16A and the upper base 16B are joined together by welding, for example, at the joint surface. The mounting table 16 is not limited to the Hastelloy described above, and may be any metal as long as it has corrosion resistance and conductivity. For example, stainless steel, nickel, Inconel (trademark) or the like can be used.

A ceiling plate 22 integrally provided with a shower head 20 that also serves as an upper electrode is attached to the ceiling portion of the processing vessel 4 in an airtight manner with respect to the side wall of the vessel via an insulating material 24. The shower head 20 is provided so as to face almost the entire upper surface of the mounting table 16, and a processing space S is formed between the shower head 20 and the mounting table 16. The shower head 20 introduces various gases into the processing space S in a shower shape, and a plurality of injection holes 28 for injecting gas are formed on the injection surface 26 on the lower surface of the shower head 20. In addition, a diffusion plate 32 having a large number of diffusion holes 30 is provided inside the shower head 20 so that gas can be diffused.
A gas introduction port 34 for introducing gas into the head is provided at the upper portion of the shower head 20. A plurality of, for example, two supply passages 36 and 38 for flowing gas are provided in the gas introduction port 34. It is connected.

A plurality of branch pipes 40 are connected to one supply passage 36, and each branch pipe 40 stores, for example, a TiCl ₄ gas source 42 that stores TiCl ₄ gas as a film forming gas, and H ₂ gas. An H ₂ gas source 44, an Ar gas source 46 for storing, for example, Ar gas as a plasma gas, and a ClF ₃ gas source 48 for storing a ClF-based gas, for example, ClF ₃ gas, are used as cleaning gases for cleaning. The other supply passage 38 is connected to an N ₂ gas source 50 that stores N ₂ gas as a film forming gas. The flow rate of each gas is controlled by a flow rate controller such as a mass flow controller 52 provided in each branch pipe 40 and the supply passage 80. Here, TiCl ₄ gas and N ₂ gas are separately conveyed to the shower head 20 and mixed in the shower head, but the present invention is not limited to this, and both gases are conveyed in a mixed state. Alternatively, the inside of the shower head 20 may be separated, and mixed when sprayed into the processing space S. The same applies to other gases such as TiCl ₄ , H ₂ , and Ar.

In addition, a matching circuit 56 and a high frequency power source 58 for plasma of, for example, 13.56 MHz are connected to the ceiling plate 22 through lead wires 54 in order to mainly form plasma during Ti film formation.
Further, in order to adjust the temperature of the wall surface, for example, a temperature control jacket 60 for the container for selectively flowing a cooled or heated heat medium is provided on the side wall of the processing container 4 as necessary. The jacket 60 is connected to a temperature controller (not shown). On the side wall of the container, a gate valve 62 is provided that can be opened and closed in an airtight manner when a wafer is loaded into and unloaded from the load lock chamber 64.
Further, the shower head 20 is also provided with a head temperature control jacket 66 for selectively flowing, for example, a cooled or heated heat medium as necessary in order to adjust the surface temperature. The jacket 66 is connected to a temperature controller (not shown). For example, a chiller can be used as the temperature control heat medium.

Next, a film forming method performed based on the apparatus configured as described above will be described with reference to FIG.
In the method of the present invention, before the film is actually formed on the semiconductor wafer W, the pre-coated metal-containing thin film is formed on the surface of the metal mounting table using a gas substantially the same as that used for the wafer film formation. To cover the mounting table. In this case, since the purpose is to form a Ti film on the wafer, a thin film containing Ti metal, for example, a Ti thin film, a TiN thin film, or both of these thin films is formed as the precoat metal-containing thin film. become. Here, a case where both the thin films are laminated will be described as an example.

First, without introducing the semiconductor wafer W into the processing container 4, for example, the load is kept in the load lock chamber 64. In this state, as shown in FIG. 2 (A), no film is formed on the surface of the metal mounting table 16, and the metal constituting the mounting table 16 is exposed.
Thus, in a state where nothing is placed on the mounting table 16, TiCl ₄ gas and H ₂ gas are used as the film forming gas, and Ar gas is used as the plasma gas from the shower head 20 at a predetermined flow rate. And the inside of the processing container 4 is evacuated by the vacuum pump 10 and maintained at a predetermined pressure.

At the same time, a high frequency of 13.56 MHz is applied from the high frequency power source 58 to the shower head 20 as the upper electrode, and a high frequency electric field is applied between the shower head 20 and the mounting table 16 as the lower electrode. As a result, the Ar gas is turned into plasma to promote the reduction reaction between the TiCl ₄ gas and the H ₂ gas, and the Ti thin film 68 is covered over the entire surface of the mounting table 16 as shown in FIG. 2B. Will be formed. The Ti thin film 68 is set to have a thickness of about 200 to 300 mm, for example. The Ti thin film 68 is a first thin film of a precoat metal-containing thin film 72 described later.

The temperature of the mounting table 16 is heated to a predetermined temperature by a resistance heater 18 embedded in the mounting table 16.
Further, the side wall of the processing vessel 4 and the shower head 20 that tend to be heated by the plasma flow the refrigerant through the container temperature control jacket 60 and the head temperature control jacket 66 respectively provided to the predetermined temperature. Cooling.
The process conditions at this time are a mounting table temperature of, for example, about 700 ° C., a container side wall of about 130 ° C., a shower head 20 of about 130 ° C., a process pressure of about 1 Torr, and a high-frequency power of about 700 W.
The gas flow rates are, for example, about 200 to 300 sccm for TiCl ₄ gas, 1.5 to 2 liter / min for H ₂ gas, and about 1 liter / min for Ar gas.

In this way, when the first thin film of the precoat metal-containing thin film 72, that is, the Ti thin film 68 is formed, the inside of the processing container 4 is evacuated to form the second thin film of the precoat metal-containing thin film 72. Embark on.
First, TiCl ₄ gas and N ₂ gas are introduced from the shower head 20 into the processing container 4 at a predetermined flow rate as film forming gases, respectively, and the inside of the processing container 4 is maintained at a predetermined pressure by the vacuum pump 10. . In this case, the TiN thin film 70 is formed by thermal CVD without using a high frequency, that is, without plasma, as shown in FIG. 2C.

The TiN thin film 70 is set to have a thickness of about 200 to 300 mm, for example. The TiN thin film 70 is a second thin film of a precoat metal-containing thin film 72 described later. The process conditions at this time are a mounting table temperature of about 700 ° C., a container side wall of about 130 ° C., a shower head 20 of about 130 ° C., and a process pressure of about 1 Torr. The gas flow rate at this time is, for example, about 10 sccm for TiCl ₄ gas and about 50 sccm for N ₂ gas.
Thus, by making the precoat metal-containing thin film 72 into a two-layer structure of the Ti thin film 68 and the TiN thin film 70, the adhesion between the Ti thin film 68 and the mounting surface of the mounting table 16 is greatly improved, and this peeling is performed. Can be prevented.

When the formation of the precoat metal-containing thin film 72 for preventing heavy metal contamination having a two-layer structure is completed in this way, the process proceeds to an actual film forming operation on the wafer surface.
First, the wafer W is loaded into the processing container 4 from the load lock chamber 64 via the opened gate valve 62 (see FIG. 1) (FIG. 2C) and placed on the mounting table 16 (see FIG. 2C). FIG. 2 (E)).
Then, the film forming process is started in a state where the inside of the processing container 4 is airtight.
First, here, a Ti film is formed on the wafer surface. This Ti film is formed, for example, under the same film forming gas and process conditions as those for forming the Ti thin film 68 of the precoat metal-containing thin film 72. That is, TiCl ₄ gas and H ₂ gas as film forming gases and Ar gas as plasma gases are introduced into the processing vessel 4 at a predetermined flow rate, respectively, and the inside of the processing vessel 4 is maintained at a predetermined pressure by evacuation. To do. Then, a Ti film 74 having a predetermined thickness is formed on the wafer surface as a metal-containing film by a plasma-assisted reduction reaction as shown in FIG. 2 (F).

If necessary, a TiN film 76 is formed as a metal-containing film on the Ti film 74 as shown in FIG. 2G, for example, to form a barrier metal or a wiring structure. The deposition gas and process conditions for the TiN film 76 are also the same as the deposition gas and process conditions used when the TiN thin film 70 of the precoat metal-containing thin film 72 is formed. That is, film formation is performed by plasmaless CVD using TiCl ₄ gas and N ₂ gas as film formation gases.
As described above, once the precoat metal-containing thin film 72 is formed, a predetermined number of wafers, for example, about 20 to 25 wafers, are continuously formed. During this time, reaction byproducts such as titanium compounds are processed. Since it adheres to the inside of the container 4 and the internal structure, as described above, the cleaning process inside the container is performed when the film forming process for a predetermined number of wafers is completed.

In this cleaning process, a ClF-based gas, for example, ClF ₃ gas, is flowed into the processing container 4 as a cleaning gas, and the mounting table 16, the shower head 20, the container side wall and the like are maintained at a constant temperature, and titanium adhered to the inside. This is done by evaporating and removing the chloride. During this cleaning process, the precoat metal-containing thin film 72 previously formed on the mounting table 16 is also removed. Therefore, before performing the next wafer film formation, the precoat metal-containing thin film 72 is again formed by the above-described process. A film is formed, and then an actual film forming process is performed on the wafer.
Thus, before the wafer film formation, a thin film containing the same metal as the metal included in the wafer film formation is formed on the metal mounting table 16 as the precoat metal-containing thin film 72 so as to cover the surface of the mounting table. It is possible to suppress the metal atoms of the mounting table 16 from going outside, and it is possible to prevent heavy metal contamination due to the constituent metal of the mounting table 16 from occurring on the wafer.

In addition, even when the Ti metal contained in the precoat metal-containing thin film 72 is moved to the wafer W side during the film formation of the wafer, it is the same metal as that contained in the film formation of the wafer W. Does not occur.
Further, since the mounting table 16 is made of a metal material such as Hastelloy, for example, it has good conductivity. Therefore, a potential difference is generated in the surface of the mounting table 16 during plasma film formation. There is no potential difference between them. For this reason, it is possible to suppress the deviation of the plasma density due to the potential difference, to make the plasma density uniform, and to maintain the formation in a stable state.
Moreover, since the mounting table 16 is made of a metal having good thermal conductivity, the heat conduction efficiency can be improved as compared with the case where it is made of a ceramic material.

In the step shown in FIG. 2, when the precoat metal-containing thin film 72 is formed, the second TiN thin film 70 is deposited and laminated after the first Ti thin film 68 is formed. However, the present invention is not limited to this, and may be configured as shown in FIG. 3, for example. That is, as shown in FIG. 3A, a slightly thick Ti thin film 80 is formed on the surface of the mounting table 16 by using the same film forming method as that for forming the first thin Ti film 68 of the first layer. Form. Then, as shown in FIG. 3B, plasma is generated while N ₂ gas is allowed to flow into the processing container 4, and the surface portion of the slightly thick Ti thin film 80 is nitrided. As a result, as shown in FIG. 3C, the surface portion of the Ti thin film 80 or the upper half of the original Ti thin film 80 is subjected to nitriding treatment to form a second TiN thin film 82. A precoated metal-containing thin film 72 having a structure may be formed.

Further, the precoat metal-containing thin film 72 has been described by taking the case of a two-layer structure as an example. However, the present invention is not limited to this. For example, as the precoat metal-containing thin film 72, as shown in FIG. Or it is good also as a 1 layer structure of only the TiN thin film 70. In any case, as long as the surface of the metal mounting table 16 is covered with a thin film containing the same metal as that contained during film formation of the wafer, the structure and the type of metal are not limited.
In the above embodiment, titanium has been described as an example of the metal contained in the film formation. However, the present invention is not limited to this and can be applied to other metals such as tungsten, molybdenum, and aluminum. is there.
Furthermore, the object to be processed is not limited to a semiconductor wafer, and can be applied to a glass substrate, an LCD substrate, and the like.

It is a block diagram which shows one Example of the film-forming apparatus of this invention. It is process drawing for demonstrating this invention method. It is process drawing which shows the modification of this invention method. It is process drawing which shows the other modification of this invention method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Film-forming apparatus 4 Processing container 16 Mounting stand 18 Resistance heater 20 Shower head 58 High frequency power supply 68 Ti thin film 70 TiN thin film 72 Precoat metal containing thin film 74 Ti film (metal containing film)
76 TiN film (metal-containing film)
80 Ti thin film 82 TiN thin film W Semiconductor wafer (object to be processed)

Claims (8)

In the film forming method for forming a metal-containing film on an object to be processed mounted on a mounting table in a processing container, the first film is a film containing the same metal as the metal-containing film on the surface of the mounting table. A pre-coated metal-containing thin film having a two-layer structure in which a thin film and a second thin film are sequentially laminated is formed, and then the metal is placed on the surface of the object to be processed in a state where the object to be processed is placed on the mounting table. A film forming method characterized in that a containing film is formed. The metal-containing film is a titanium (Ti) film or a titanium nitride (TiN) film, the first thin film is a titanium thin film, and the second thin film is a titanium nitride thin film. The film forming method according to claim 1. 3. The film forming method according to claim 1, wherein the mounting table is made of metal. 4. The film forming method according to claim 2, wherein the titanium nitride thin film is formed by nitriding a surface portion of the titanium thin film. 4. The film forming method according to claim 2, wherein the titanium nitride thin film is formed by forming the titanium thin film and laminating the titanium nitride thin film thereon. In a film forming apparatus for forming a metal-containing film on an object to be processed placed on a placing table in a processing container,
A pre-coated metal-containing thin film having a two-layer structure in which a first thin film and a second thin film, which are films containing the same metal as the metal contained in the metal-containing film, are sequentially stacked is formed on the surface of the mounting table. A film forming apparatus. The film forming apparatus according to claim 6, wherein the mounting table is made of metal. The metal-containing film is a titanium (Ti) film or a titanium nitride (TiN) film, the first thin film is a titanium thin film, and the second thin film is a titanium nitride thin film. The film forming apparatus according to claim 6 or 7.

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