JP2002075911A - Method for continuously forming titanium film and titanium nitride film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously forming a titanium film and a titanium nitride film that have small contact resistance, and can prevent contamination due to byproducts. SOLUTION: This method for continuously forming the titanium and titanium nitride films 10 and 12 on the surface of a body 2 to be treated includes a titanium film formation process that forms the titanium film on the surface of the body to be treated, a titanium nitriding process that allows the surface of the titanium film to be subjected to plasma treatment under the atmosphere of reduction and ammonia gases for nitriding, and a titanium nitride film formation process that forms the titanium nitride film on the titanium film where the surface is nitrided, thus reducing the contact resistance and contamination due to byproducts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously forming a titanium film and a titanium nitride film formed in a contact hole, a via hole and the like in a semiconductor device.

[0002]

2. Description of the Related Art In general, a semiconductor device tends to have a multilayer wiring structure in response to recent demands for higher density and higher integration. In this case, a lower device and an upper aluminum wiring are required. Embedding technology such as a contact hole that is a connection portion between the wiring and a via hole that is a connection portion between the lower aluminum wiring and the upper aluminum wiring is important for establishing an electrical connection between the two.

[0003] Aluminum alloys and tungsten alloys are generally used for filling contact holes and via holes. When these alloys come into direct contact with the underlying silicon substrate or aluminum wiring, aluminum is bound at the boundary between these. Since a diffusion layer formed in silicon is destroyed due to a suction effect or the like, it is not preferable in a current semiconductor device that requires power saving and high-speed operation. Further, when a tungsten alloy is used for embedding, the WF ₆ gas, which is one of the processing gases used in this process, tends to enter the Si substrate side and deteriorate the electrical characteristics and the like. Absent.

Therefore, in order to prevent the above phenomenon, a barrier metal layer is formed thinly over the entire area of the hole before the contact hole or through hole is filled with an aluminum alloy or a tungsten alloy. Embedding is being done. As a material of the barrier metal layer, TiN (titanium nitride) is generally used.

The barrier metal layer formed in the contact hole will be described with reference to FIG. 5. In FIG. 5, reference numeral 2 denotes an object to be processed.
It consists of a mold substrate. For example, n
⁺ Diffusion layer 4 and a portion corresponding to this diffusion layer 4 has S
A contact hole 8 is formed by etching the insulating layer 6 made of iO ₂ or the like. Then, a titanium film 10 is first formed on the bottom of the contact hole 8 in order to achieve electrical conduction with the diffusion layer 4 by PVD (Physical Va) in order to achieve ohmic contact.
por Deposition) and CVD (Chemi)
Then, a titanium nitride film 12 is formed thereon as a barrier metal layer including the side wall of the hole. After that, the contact hole 8 is buried using tungsten or aluminum.

[0006]

In the case where a titanium film and a titanium nitride film are continuously formed as described above, if these films are simply formed continuously, the interface between the two films is not sufficiently bonded. Since the contact resistance increases due to peeling, the surface is nitrided after forming the titanium film to form a nitrided film 13 to prevent this, and the titanium nitride film is formed thereon. It is supposed to. This nitriding treatment is conventionally performed by N
Under the atmospheric pressure of ₂ atmospheres, the substrate 2 is heated to, for example, 800 ° C., and lamp annealing is performed.
In this case, after the titanium film is formed, the substrate is exposed to the atmosphere when the substrate is transferred to the annealing process chamber. At this time, the titanium film surface has a high resistance TiO ₂
Are formed, which is not desirable in today's strict design rules.

Therefore, in order to perform the titanium film formation and the nitriding treatment in the same processing chamber, the titanium film is formed by CVD using TiCl ₄ (titanium tetrachloride), H ₂ gas and Ar gas as the processing gas. Then, a method of nitriding the surface of the titanium film by performing plasma processing in an N ₂ gas atmosphere or an NH ₃ gas atmosphere in the same processing chamber has been developed. In this case, since the formation of the titanium film and the nitridation of the surface can be performed in the same processing chamber, the formation of the TiO ₂ film as described above can be prevented, but a new problem occurs. That is, when a titanium film is formed by CVD, Ti
White or black complex containing (titanium), such as Ti
Clx (X = 2 to 3) adheres to the inner wall of the chamber and the like, and peels off from the chamber wall at the time of the next plasma nitriding treatment, thus contaminating the substrate.

Further, in an atmosphere containing only N ₂ gas,
It has been found that when plasma nitriding is performed in an atmosphere containing only H ₃ gas, the contact resistance may not be sufficiently reduced. The present invention has been devised in view of the above problems and effectively solving them. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for continuously forming a titanium film and a titanium nitride film, which has a low contact resistance and can suppress contamination by a by-product.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies on the continuous formation of a titanium film and a titanium nitride film. As a result, the plasma nitriding treatment in an N ₂ gas or NH ₃ gas atmosphere caused a nitriding force. High N (nitrogen) radicals are generated and bi-products (by-products) are nitrided, causing the peeling,
The present invention has been made based on the finding that reducing gas, for example, H ₂ gas may be supplied together to suppress this.

According to the present invention, there is provided a method for continuously forming a titanium film and a titanium nitride film on a surface of an object to be processed, comprising: a titanium film forming step of forming a titanium film on the surface of the object to be processed; A titanium nitriding step of nitriding the surface of the titanium film by performing a plasma treatment in an atmosphere containing a reducing gas and an ammonia gas, and a titanium nitride film forming a titanium nitride film on the titanium film having a nitrided surface. And a step of forming a ride film.

Such a titanium film forming step and a titanium nitriding step are performed in the same processing chamber while maintaining a vacuum atmosphere. As described above, the nitriding treatment of the titanium film is performed by plasma-treating the object to be treated in an atmosphere containing a reducing gas and an ammonia gas. As a result, the yield can be maintained high, and the contact resistance can be reduced. Further, both the titanium film forming step and the titanium nitride film forming step can be performed by CVD. The titanium nitride film can be used as a barrier metal such as a contact hole and a through hole formed in a semiconductor wafer.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for continuously forming a titanium film and a titanium nitride film according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing a cluster tool device for performing the method of the present invention, and FIG.
FIG. 2 is a configuration diagram showing a film forming plasma apparatus for performing titanium film formation and nitriding. First, a cluster tool apparatus and a film forming plasma processing apparatus that carry out the method of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the cluster tool device 14 comprises a film forming plasma device 16 for continuously performing a titanium film forming process on a semiconductor substrate 2 and a nitriding process on the surface thereof, and thereafter a cluster tool device 14. The apparatus has a film forming apparatus 18 for performing a titanium nitride film forming process.
Is a transfer arm 20 that can be bent and extended and pivoted inside.
Are connected in common via gate valves G1 and G2. In the transfer chamber 22,
The first and second cassette chambers 24 and 26 are connected via gate valves G3 and G4. First cassette chamber 24
Accommodates a cassette C1 for accommodating unprocessed substrates 2, and accommodates a processed substrate 2 in a second cassette chamber 26.
Is accommodated in the cassette C2. The transfer of the substrate 2 between the respective devices and in the space is all performed by bending and extending and turning the transfer arm 20.

Next, the configuration of the film forming plasma apparatus 16 for performing the main steps of the present invention will be described with reference to FIG. As shown in the drawing, the film forming plasma apparatus 16 has a processing chamber 28 formed in a cylindrical shape from, for example, aluminum, and a mounting table 30 for mounting the substrate 2 therein is installed therein. I have. In the mounting table 30, for example, a resistance heater 32 is provided as a heating unit so that the substrate 2 can be heated to a predetermined temperature.

Also, on the ceiling of the processing chamber 28,
A shower head 36 insulated from the chamber wall via an insulating material 34 is provided, and a processing gas introduced from a gas inlet 38 is supplied to a processing chamber in the chamber through a number of gas outlets 40 provided on the lower surface. It is designed to supply space. A gas supply system 42 is connected to the gas inlet 38. The gas supply system 42 includes a processing gas such as Ar gas or H ₂ gas required when performing titanium film formation by plasma CVD.
A gas and a TiCl ₄ gas flowing system, and a processing gas required when performing a plasma nitriding process on the titanium film, ie, N 2
_Two gas and H ₂ gas flowing systems are connected respectively. Each gas is supplied while the flow rate is individually controlled by mass flow controllers 44 and 46 which are described as representatives of the respective systems. Here, in order to easily understand the treatment process, the gas is described as being separated into two systems. However, in practice, one system is used as the H ₂ gas common to both systems. Of course.

The showerhead 36 functions as an upper electrode during the plasma nitridation of the Ti film. For this purpose, the showerhead 36 is supplied with a 13.56 MHz plasma through a matching circuit 48. A high frequency source 50 for outputting a high frequency for generation is connected. An exhaust port 52 is provided around the bottom of the processing chamber 28. A vacuum pump (not shown) is connected to the exhaust port 52 to evacuate the inside.

Next, the method of the present invention performed using the example of the apparatus configured as described above will be described with reference to FIG. FIG. 3A shows a state in which a contact hole 8 is formed in the insulating layer 6 on the substrate 2 in the previous step and the diffusion layer 4 is formed therein. 1
A large number of cassettes are accommodated in the cassette C1 in the cassette chamber 24. Such an unprocessed substrate 6 is taken into the transfer chamber 22 in an inert atmosphere such as N ₂ gas by the transfer arm 20 in the transfer chamber 22, and after closing the gate valve G3, the inside of the transfer chamber 22 is removed. Vacuum. Next, the gate valve G1 is opened, and the substrate 2 is carried into the film forming plasma apparatus 16 which has been vacuumed in advance, and is mounted on the mounting table 30 to complete the transfer.

Next, the process proceeds to a titanium film forming step. That is, the substrate 2 is heated to a predetermined process temperature, for example, about 580 ° C. by the resistance heater 32 in the mounting table 30, and Ar gas, H ₂ gas, and TiCl ₄ gas, for example, are used as a film forming process gas in the shower head. A predetermined amount of each is introduced into the chamber 28 from 36, and a titanium film is formed by plasma CVD. The process pressure at this time is approximately 10
A titanium film 10 is selectively deposited on the bottom of the contact hole 8 where the conductor is exposed at about 00 mTorr (see FIG. 3B). The thickness of the titanium film 10 is, for example, about 20 nm. During this titanium deposition,
A high-frequency voltage is applied to the shower head 36, and undecomposed products, for example, TiClx (x = 2 to 3) adhere to the inner wall of the chamber and the lower surface of the shower head 36 as biproducts 54. Since the environment does not change during film formation, the film hardly peels off.

After the titanium film forming step is completed, a titanium nitriding step is performed in the same processing chamber 28 without unloading the substrate 2. That is,
The supply of the processing gas for titanium film formation was stopped, and chamber 2 was stopped.
Then, a mixed gas of N ₂ gas and H ₂ gas is supplied into the chamber 28 from the shower head 36 as a processing gas for plasma nitriding, and at the same time, the high frequency source 50 A high frequency voltage of 13.56 MHz is applied to the shower head 36 as an upper electrode to generate plasma. As a result, the surface of the titanium film 10 is subjected to a nitriding treatment, and a nitriding film 13 is formed as shown in FIG. The processing conditions at this time were N ₂ gas and H ₂ gas.
The gas supply amounts to 500 sccm and 1500 respectively.
sccm, process pressure is about 1 Torr,
The process temperature is about 580 ° C. The flow rates of the N ₂ gas and the H ₂ gas may be appropriately selected, and are not limited to the above flow rates.

When the titanium nitriding process is completed in this manner, the substrate 2 is taken into the transfer chamber 22 maintained in a vacuum state by using the transfer arm 20 in the transfer chamber 22, and is further preliminarily stored. The wafer is transferred into the film forming apparatus 18 maintained in a vacuum state. Then, in this film forming apparatus 18,
As shown in FIG. 3D, a film forming process for forming a titanium nitride film is performed using a conventionally known processing method. Thus, a titanium nitride film 12 is formed as a barrier metal layer on the inner wall surface of the contact hole 8 and the entire upper surface of the insulating layer 6 by CVD. At this time, as the processing gas, for example, TiCl ₄ , NH ₃ , and N ₂ can be used. The process temperature is about 500 ° C.
The process pressure is about 350 mTorr. As described above, when the titanium nitride film forming step is completed, the processed substrate 2 may be unloaded from the film forming apparatus 18 and stored in the cassette C2 for storing the processed wafer. Then, as shown in FIG. 3E, a conductive material 56 such as tungsten or aluminum is buried in the contact hole 8.

As described above, in the method of the present invention, when the surface of the titanium film 10 is nitrided, plasma is generated in a mixed atmosphere of N ₂ gas and H ₂ gas. It can be greatly suppressed that the biproduct 54 adhered to the inside of the chamber during the titanium film formation in the step is peeled off. The reason is that in the conventional method using only N ₂ gas or only NH ₃ gas, a large amount of nitrogen radical having high nitriding power is generated, and the by-product remains as a heterogeneous mixture of materials having different hardnesses. However, this was peeled off. Here, as a result of performing a plasma treatment using a mixed gas of N ₂ gas and H ₂ gas, active hydrogen atoms react with the biproduct 54 to form a uniform substance which is hard to peel off. It is considered to be. That is, for example, in a conventional plasma nitriding process using only N ₂ gas, a reaction occurs as shown in the following formula 1, and in a plasma nitriding process of the present invention using N ₂ gas and H ₂ gas, the reaction is expressed in the following formula 2. It is believed that a reaction occurs. 3TiCl ₃ + N ₂ → 2TiN + TiCl ₂ + 7/2 · Cl ₂ {Formula 1 2TiCl ₃ + N ₂ + 3H ₂ → 2TiN + 6HCl} Formula 2 Here, TiCl ₂ in Formula 1 is a deliquescent substance, TiN
Is a solid, and as a by-product, the undecomposed product becomes a non-uniform mixture of substances having different hardness, and thus is easily peeled off. On the other hand, in the case of Formula 2, since the biproduct is almost hard TiN, it is difficult to peel off.

Actually, an experiment was conducted to determine how many substrates can be processed before the biproduct is peeled off by repeatedly performing the titanium film forming process and the nitriding process of the conventional method and the method of the present invention. This result indicates that in the case of the conventional method using N ₂ gas at the time of nitriding, the peeling of the by-product was confirmed visually when five substrates were processed, but in the case of the method of the present invention, 50 or more substrates were removed. No peeling of the by-product was observed even when the substrate was processed. At this time, the conditions of both plasma nitriding treatments are as follows: process pressure is 1 Torr, RF power is 500 W (13.56 MHz), and process temperature is 5
At 80 ° C., the processing time is 2 minutes. Regarding the processing gas, the conventional method uses N ₂ gas at 1000 sccm, and the method of the present invention uses N ₂ gas at 500 sccm and H ₂ gas at 1500 sccm.
cm each.

Further, as a result of performing the plasma nitridation process using the N ₂ gas and the H ₂ gas as described above, the contact resistance can be significantly reduced. The reason for this is that the H ₂ gas strongly reduces the TiCl ₄ raw material remaining in the titanium film to extract Cl, and even if Cl ₂ is generated by degassing from the biproduct, the H ₂ gas is added to this. This is considered to be because chlorine, which acts and is reduced to cause an increase in resistance, does not remain on the substrate surface. Actually, as a result of performing the plasma nitriding treatment of the conventional method and the method of the present invention, the method of the present invention was able to obtain good results as shown in FIG. In this experiment, a number of contact holes (chips) were formed on the surface of the substrate, and the distribution of contact resistance was examined by performing plasma nitridation of the titanium film. The hole diameter at this time is 0.5 μm, and the vertical axis represents the cumulative frequency of the number of chips.

As is clear from this graph, in the conventional method using only N ₂ gas, the contact resistance itself is 10%.
It is as high as 00 Ω or more, and the characteristics are very poor.
The H ₃ gas only conventional method using, there is also what the contact resistance is small and 0～200Omu, also larger or more 1000 [Omega], since it is fairly distributed spreads, there is a problem in uniformity of properties. On the other hand, in the case of the method of the present invention using N ₂ gas and H ₂ gas, it is found that the contact resistance is considerably small as 0 to 200 Ω, and there is almost no distribution, showing good results. .
Further, according to the present invention, the processing can be performed without exposing the substrate to the air during the continuous formation of the titanium film and the titanium nitride film, so that inconvenience such as oxidation of the surface can be avoided. In the above embodiment, the titanium film is
Although formed by VD, the present invention is not limited to this, and the titanium film may be formed by PVD. Also, here, the description has been given of the embedding of the contact hole as an example, but the present invention can of course be applied to the embedding of the through hole.

[0025]

As described above, according to the method for continuously forming a titanium film and a titanium nitride film of the present invention, the following excellent functions and effects can be exhibited. Since the nitriding of the surface of the titanium film is performed by performing a plasma treatment in an atmosphere containing a reducing gas and an ammonia gas, not only can the contact resistance be significantly reduced, but also a problem occurs during the titanium film formation. Biproduct contamination can also be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a cluster tool device for implementing a method of the present invention.

FIG. 2 is a configuration diagram showing a film forming plasma apparatus for performing titanium film formation and nitriding.

FIG. 3 is a process chart for explaining the process of the method of the present invention.

FIG. 4 is a graph showing a distribution of contact resistance for comparing the method of the present invention with a conventional method.

FIG. 5 is a view for explaining a conventional method for continuously forming a titanium film and a titanium nitride film.

[Explanation of symbols]

 2 Substrate (workpiece) 6 Insulating layer 8 Contact hole 10 Titanium film 12 Titanium nitride film 13 Nitriding film 14 Cluster tool device 16 Deposition plasma device 18 Deposition device 28 Processing chamber 30 Mounting table (lower electrode) 36 Shower Head (upper electrode) 50 High frequency source 54 Bi-product

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Yoshikawa 5-3-6 Akasaka, Minato-ku, Tokyo TBS Transmission Center Tokyo Electron Limited F term (reference) 4K030 AA03 AA13 AA16 AA17 AA18 BA18 BA38 CA04 FA01 LA15 4M104 BB14 CC01 DD43 DD46 DD86 FF18 FF22 HH15 5F033 JJ08 JJ18 JJ19 JJ33 KK01 NN03 NN06 NN07 PP01 PP04 PP06 PP07 QQ90 QQ98 XX09

Claims (5)

[Claims] In a method for continuously forming a titanium film and a titanium nitride film on a surface of an object, a titanium film forming step of forming a titanium film on the surface of the object is provided. A titanium nitriding step of nitriding the surface of the titanium film by plasma treatment in an atmosphere containing a reducing gas and an ammonia gas, and a titanium nitride forming step of forming a titanium nitride film on the titanium film having a nitrided surface. A method for continuously forming a titanium film and a titanium nitride film. 2. The method for continuously forming a titanium film and a titanium nitride film according to claim 1, wherein the titanium film forming step and the titanium nitriding step are performed in the same processing chamber. 3. The method according to claim 1, wherein the titanium film forming step and the titanium nitride film forming step are performed by chemical vapor deposition (CVD).
3. The method for continuously forming a titanium film and a titanium nitride film according to claim 1 or 2, wherein the method is carried out by or deposition. 4. The continuous titanium film and titanium nitride film according to claim 1, wherein the titanium nitride film is a barrier metal formed in a contact hole or a through hole. Film formation method. 5. The method for continuously forming a titanium film and a titanium nitride film according to claim 1, wherein said reducing gas is hydrogen gas.