JP2003193237A - Method of depositing metallic nitride film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of depositing a uniform metallic nitride film by uniformizing the formation of the nuclei of metallic nitride on the surface of a substrate. <P>SOLUTION: A substrate set in a vacuum reaction tank is exposed to plasma of nitrogen atom-containing gas selected from nitrogen, an ammonia derivative, a hydrazine derivative, an azide derivative, and a nitrous oxide, or the substrate is treated with gaseous ammonia. After that, reaction gas containing gaseous metallic halide and gaseous ammonia is introduced therein, and a metallic nitride film is deposited on the substrate by a thermal CVD (chemical vapor deposition) method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a metal nitride film, and more particularly to a method for forming a metal nitride film by a thermal CVD method. The formed metal nitride film is, for example, a barrier film provided between the copper wiring and the insulating film, S
It is used as a barrier film such as a silicidation prevention barrier film provided between a film containing i or GaAs and a metal wiring, a barrier film provided between a high dielectric or ferroelectric film and an electrode. obtain.

[0002]

2. Description of the Related Art In recent years, low-resistance copper wiring has been proposed in place of aluminum wiring because of the demand for high-speed operation in semiconductor devices. In this case, since copper has a large diffusion coefficient in silicon crystals or silicon oxide, a barrier film made of metal nitride is formed on the surface of a silicon substrate or a silicon oxide thin film, and then copper wiring is formed thereon. ing.

Conventionally, in order to form such a barrier film, a sputtering method, a thermal CVD method or a PE-CV method is used.
Method D is used. For example, a tungsten nitride film that can be used as a barrier film is often formed by a chemical reaction between tungsten fluoride gas and ammonia gas by a thermal CVD method. As an example of this thermal CVD method, Japanese Patent Application Laid-Open No. 2001-23930 discloses a method of forming a tungsten nitride film by a reduction reaction using tungsten fluoride gas, ammonia gas, monosilane gas and oxygen gas as raw materials. According to this method for forming a tungsten nitride film, a substrate such as a silicon wafer installed in a reaction chamber whose pressure is reduced to about 1 to 100 Pa is generally used for about 35
The tungsten nitride film is obtained by heating the substrate to a temperature of 0 to 450 ° C., blowing the above raw material gas onto the heated substrate and causing the reaction.

Further, in the case of manufacturing a semiconductor device having a multi-layered wiring, the wirings are laminated with an interlayer insulating film sandwiched between them. In addition, it is necessary to reduce the capacitance value of the interlayer insulating film and the resistance value of the barrier film. The barrier film is required to have a low resistance value such as 400 μΩcm or less.

[0005]

In the film formation by the above-mentioned method of the prior art, the raw material gas reaches the wafer rather than the tungsten nitride film starts to grow on the wafer at the moment the raw material gas reaches the wafer. For a while, the tungsten nitride nuclei are generated and the film does not grow. Then, after a certain period of time has passed and a large number of nuclei have been formed, the tungsten nitride film starts to grow. At that time, since the number of nuclei generated is influenced by the surface condition of the wafer, a large number of nuclei are not simultaneously formed on the entire surface of the wafer. Even if film growth starts at a location where a large number of nuclei are formed on the wafer, it may still be in the middle of nucleation at another location. Therefore, even if an attempt is made to form a film having a predetermined film thickness, a film having a desired thickness is formed at a certain location, but a film having a thickness less than the desired thickness is formed at another location. Occur. Such a difference in film thickness depending on the location becomes remarkable especially when a thin film is formed, and therefore, it is inconvenient when industrially manufacturing a semiconductor device using a tungsten nitride film.

An object of the present invention is to solve the above-mentioned problems of the prior art. A uniform metal nitride film is formed by homogenizing nucleation of a metal nitride such as tungsten nitride on the surface of a substrate. To provide a way to do.

[0007]

In order to make the initial nucleation and the subsequent film growth uniform, the inventors of the present invention have proposed various gases and their mixing ratios, and the timing of introducing the reaction gas into the reaction tank. The research on such conditions was earnestly studied. As a result, homogenization of nucleus growth and subsequent uniform film growth can be obtained by introducing ammonia gas at a specific time to process the substrate or by exposing the substrate to plasma of a specific gas. Moreover, they have found that the formed film has excellent adhesion to the lower layer, and have completed the present invention.
The method for forming a metal nitride film of the present invention is a method for forming a metal nitride film on a substrate placed in a reaction tank by a thermal CVD method, in which the heated substrate is exposed to plasma of a nitrogen atom-containing gas. Or after introducing ammonia gas into the reaction vessel in advance and treating the heated substrate,
A reaction gas containing a metal halide gas and an ammonia gas is introduced to form a metal nitride film on the substrate.

The nitrogen atom-containing gas is nitrogen, formula: NH
_{3-n (C m H 2m} + 1) n ( where, n = 0,1~ 3,
m = 1-6. ) An ammonia derivative having the formula:
_{N 2 H 4 -n (C m} H 2m + 1) n ( where, n = 0,1~
4, m = 1-6. ) A hydrazine derivative having
A gas selected from an azide derivative having the formula: N ₃ (C _m H _{2m + 1} ) (in the formula, m = 0 and _{1 to 6} ) and nitrous oxide is preferable. Of these gases,
More preferred is a gas selected from nitrogen, ammonia, hydrazine, and nitrous oxide. In the above formula, when m exceeds 6, it is difficult to use as a gas. The metal halide gas may be appropriately selected and used depending on the type of the intended barrier film, for example, tungsten, tantalum, titanium, and fluoride gas of a metal selected from vanadium, chloride gas, It is preferably iodide gas or bromide gas.

As described above, according to the present invention, after the heated substrate surface is exposed to the plasma of the nitrogen atom-containing gas, or the ammonia gas is introduced into the reaction tank in advance,
Since the reaction gas is supplied to form the metal nitride film after treating the substrate surface, it is possible to form a thin film having excellent adhesion to the underlying insulating film and the like with high accuracy in a short induction time. . The adhesion between the metal nitride film and the lower layer is because the surface of the substrate is nitrided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION According to an embodiment of the present invention, 1
A substrate such as a silicon wafer installed in a reaction tank depressurized to about 100 Pa is heated to about 300 to 400 ° C., and a nitrogen atom-containing gas (nitrogen gas, ammonia derivative gas, hydrazine derivative, etc.) is introduced into the reaction tank. Gas, azide derivative gas, nitrous oxide gas, etc.), metal halide gas, silane gas such as monosilane or disilane, and oxygen gas are introduced, and metal nitridation is performed on the heated substrate by thermochemical reaction (CVD method). A method for forming a physical film, in which the substrate is treated with ammonia gas or exposed to plasma of nitrogen atom-containing gas before introducing these reaction gases, and then the film forming step is performed. . At this time, for example, Ar gas: 35 sccm, RF: 450 /
After performing the ICP plasma pretreatment under the condition of 300 W for 15 seconds, the treatment with ammonia gas or the treatment with the nitrogen atom-containing gas plasma may be performed, or the treatment with the ammonia gas may be further performed with the nitrogen atom-containing gas. Plasma treatment may be performed, or ammonia treatment may be further performed after the plasma treatment.

The above ammonia treatment is generally carried out, for example, by
NH ₃ gas: 250 sccm, RF: 450/300
It can be performed under conditions such as W and 15 seconds. The plasma treatment is generally performed, for example, with N ₂ gas: 100 scc.
m, RF: 450/300 W, 15 seconds. The formation of the metal nitride film is performed under known thermal CVD process conditions, for example, the reaction gas flow rate:
100 to 300 sccm, film forming temperature: 300 to 400
C., deposition pressure: 5 to 200 Pa, film formation time: 5 to 60 seconds.

Among the nitrogen atom-containing gases used in the present invention,
As an ammonia derivative, for example, NH_Three, NH_Two(C
H_Three), NH_Two(C_TwoH₅), NH_Two(C_ThreeH₇), NH (C
H_Three) _Two, NH (C_TwoH₅)_Two, NH (C_ThreeH₇)_Two, N (C
H_Three)_Three, N (C_TwoH₅)_Three, N (C_ThreeH₇)_ThreeEtc., hydra
Examples of the gin derivative include N_TwoH_Four, N_TwoH_Three(CH
_Three), N_TwoH_Three(C_TwoH₅), N_TwoH_Three(C_ThreeH₇), N_Two
H_Two(CH_Three)_Two, N_TwoH _Two(C_TwoH₅)_Two, N_TwoH_Two(C
_ThreeH₇)_Two, N_TwoH (CH_Three)_Three, N_TwoH (C_TwoH₅) _Three,
N_TwoH (C₃H₇)_Three, And as an azide derivative
If N_ThreeH, N_Three(CH_Three), N_Three(C_TwoH₅), N_Three(C
_ThreeH₇) Etc. can be used.

According to the present invention, the metal halide gas which is one of the reaction gases can be appropriately selected according to the metal nitride film to be formed. For example, when forming a tungsten nitride film, a tungsten fluoride gas (WF ₆ ) or the like, and when forming a tantalum nitride film, tantalum fluoride gas (TaF ₅ ) or tantalum chloride gas (Ta).
Cl ₄ ), etc., when forming a titanium nitride film, titanium fluoride gas (TiF ₄ ) or titanium chloride gas (TiCl ₄ ).
When forming a silicon nitride film, silicon dichloride or the like can be used. Further, when forming a molybdenum nitride film or a niobium nitride film, a halide gas of Mo or Nb can be used.

[0014] Silane gas monosilane gas such as SiH ₄ gas, disilane gas, such as SiH ₄ gas, trisilane, tetrasilane, be used two silicon chloride or the like. As the substrate to be processed, a substrate in which a thermal oxide film of silicon (SiO ₂ film) or an insulating film made of an inorganic / organic low-k material is provided on the substrate can be used. Examples of organic low-k materials include FSG, HSQ,
MSQ, HOSP, Black Diamond, Co
ral, Aurora, SiLK, Flare, BCB
Etc. can be used.

As described above, when the metal nitride film is formed after the surface of the substrate having the insulating film is exposed to the plasma of the nitrogen atom-containing gas or after the surface of the substrate is treated with the ammonia gas, a short induction time is obtained. Can form a desired thin film with high accuracy. The metal nitride film thus obtained had good adhesion to the surface of the pretreated substrate and did not peel off in the Scotch tape test. However, when the metal nitride film was formed without plasma pretreatment or ammonia pretreatment, the metal nitride film was easily peeled off from the substrate by the Scotch tape test. The surface of the substrate that has been subjected to such pretreatment is FT
When analyzed by -IR (Fourier transform infrared spectroscopy), the surface was nitrided.

In the above Scotch tape test, as will be described in detail in the examples below, a diamond pen is used to scratch and scratch any part of the surface of the obtained metal nitride film. Adhere a scotch tape to the location where you want to remove this scotch tape suddenly, check if the film peels from the substrate and adheres to the tape at that time, and evaluate the adhesion by scoring the peeled state Is.

As described above, after the metal nitride film is formed according to the present invention, in the semiconductor device manufacturing process, for example, the following processes are performed. On the metal nitride film, for example, by a plating method or a sputtering method, for example, A
LTS under conditions of r: 9 sccm, DC: 8 kW, 32 seconds
Forming a Cu seed and then growing a copper film; After the copper film is formed, the surface is polished by the CMP method, and the copper film and the metal nitride film on the insulating film are removed by polishing, so that the wiring film made of the copper film is formed in the holes and the premises. Since the metal nitride film is arranged between the wiring film and the semiconductor substrate or between the wiring film and the insulating film, copper is prevented from diffusing into the insulating film.

Next, after a base film and an insulating film are alternately laminated (for example, four layers) on the wiring film, the surface of the wiring film is opened to form a hole or a groove. The wiring film is exposed on the bottom surface of the hole or groove. The CV is applied to the substrate processed in this way.
The metal nitride film is loaded into the D apparatus and the metal nitride film is formed under the same conditions as above. Thus, the inner wall of the hole or groove and the surfaces of the insulating film and the copper wiring film are covered with the metal nitride film. After that, when a copper film is grown by a plating method or a sputtering method, the inside of the hole or groove is filled with the copper film. Finally, when the surface is polished by the CMP method, a copper wiring film is formed by the copper film filled in the holes or the grooves. Since the barrier film is arranged between the wiring film and the insulating film, copper is prevented from diffusing into the insulating film.

[0019]

EXAMPLES The present invention will be described in detail below based on examples and comparative examples. Example 1 A tungsten nitride film (film thickness: 10 nm) was formed on a silicon wafer under the conditions shown in Table 1. As shown in Table 1, before the film formation, a specific gas is introduced into the reaction tank, plasma of the specific gas is generated to pretreat the wafer, and in the film formation step, the source gas is used. The type and the flow rate were the same in all the examples, and the tungsten nitride film was formed by changing the film formation time and the film formation rate. Table 1 shows the uniformity and sheet resistance (specific resistance) of the obtained film.

(Table 1)

As is clear from Table 1, when a wafer is processed by introducing ammonia gas in advance as a pretreatment step (Examples 2 to 3 (Example)), initial nuclei growth is carried out over the entire surface of the wafer. Since it occurs rapidly and uniformly, although it depends on the flow rate of the introduced ammonia gas, the film formation starts with a short induction time, the film thickness after film formation is uniform, and the specific resistance of the film is small. Was sufficiently usable as a barrier film. In addition, when the wafer is exposed to the plasma of ammonia gas prior to film formation (Example 4)
In (Example), a film having a uniform film thickness and a small specific resistance was obtained with an induction time shorter than that obtained by simply introducing ammonia gas in advance. Further, when the wafer was exposed to nitrogen gas plasma prior to film formation (Example 5 (Example)), a film having a uniform film thickness and a small specific resistance was obtained. The films obtained in Examples 4 and 5 were also sufficiently practical as a barrier film.

On the other hand, prior to film formation, a specific gas other than ammonia gas (WF ₆ , SiH ₄ , H
₂ ) is introduced to perform pretreatment (Examples 6 to 10 (comparative example)) or a pretreatment process is not performed prior to film formation (example 1 (comparative example)). Although the film started to adhere after an induction time of 1 minute or more, the film formed was not suitable as a barrier film because it remained nonuniform and had a high specific resistance. As described above, when a gas other than ammonia gas is introduced into the reaction tank in advance and pretreatment is performed, it can be said that it has the property of alienating the initial nucleation and film growth.

As a result of FT-IR analysis of the surface of the wafer which has been subjected to the ammonia plasma pretreatment as described above, it is clear from FIG. 1 which shows the ammonia plasma time dependence of Si—CH ₃ and Si—N. Since the Si-N / Si-O (%) increased with the ammonia plasma treatment time, it was confirmed that the wafer surface was nitrided. In FIG. 1, the horizontal axis shows the ammonia plasma treatment time (sec), and the vertical axis shows the Si—CH ₃ peak vs. initial comparison (%) and Si—N / Si—O (%). Si-
The CH ₃ data is the ratio of the peak reduction when the ammonia plasma treatment time of 0 seconds is 100%, and the Si—N data is the Si—O peak vs. Si peak.
-N peak increase rate. The state of the wafer surface was the same when the ammonia gas pretreatment and the nitrogen plasma pretreatment were performed as when the ammonia plasma pretreatment was performed. In addition, sputter cleaning with argon gas was tried, but the effect as much as the pretreatment with ammonia gas was not obtained. Note that, regardless of which pretreatment is performed, in a tungsten nitride film having a certain thickness (for example, 50 nm), there is almost no difference in specific resistance. Therefore,
It can be said that the above-mentioned pretreatment has an effect of modifying the surface of the wafer at the initial stage of film formation.

From the above results, prior to the introduction of all the reaction gases into the reaction vessel, ammonia gas is introduced to pretreat the wafer surface for several tens of seconds, or the wafer is treated with nitrogen gas, ammonia gas, etc. It can be seen that the thin metal nitride film can be uniformly formed by performing any one of the pretreatments of exposing to the plasma of the nitrogen atom-containing gas.
However, when the wafer surface treatment by the introduction of ammonia gas in advance or the wafer surface treatment by the plasma of nitrogen atom-containing gas is not performed, the formed film becomes non-uniform and a long induction time exists, so that the thin film It was difficult to reproducibly produce. Next, according to the above method, a tungsten nitride film is formed under the conditions shown in Table 2 below, and the adhesion between the silicon wafer surface and the tungsten nitride film when a copper film is formed thereon by a known plating method is shown. It investigated by the Scotch tape test.

First, a thermal oxide film (SiO ₂ film) or a Low-k insulating film was formed as a base insulating film on a silicon wafer. Next, plasma pretreatment (N
H ₃ gas flow rate, Ar gas flow rate, H ₂ gas flow rate: 250, 35, 200 sccm, RF: 450/3, respectively
00W, 60 seconds), and then a tungsten nitride film having a thickness of 15 nm is formed by a thermal CVD method (film forming condition: W
_{F 6: 6.6 / SiH 4:} 112 / NH 3: 11 /
O ₂ : 1.6 / Ar: 100 sccm). An LTS-Cu seed is formed on the tungsten nitride film (A
r: 9 sccm, DC: 8 kW, 32 seconds), and a Cu film having a thickness of 200 nm was formed by a plating method.

The surface of the thus obtained tungsten nitride film was scratched on the surface of the arbitrary 9 spots with a diamond pen, and the scotch tape was attached to the scratched spots.
Then, the Scotch tape was suddenly peeled off, and it was examined whether the film was peeled off from the wafer and adhered to the tape at that time. 4 points if the film is not peeled at all, 3 points if the scratched part is slightly peeled off, 2 points if the corners of the square "Ta" are slightly peeled off, and the square of the square "Ta" is The adhesiveness of the tungsten nitride film was evaluated by setting 1 point when one was peeled and 0 point when all the masses were peeled, and Table 2 shows the score of each sample.

(Table 2)

When the underlying insulating film is a thermal oxide film, peeling occurs between this oxide film and the tungsten nitride film, and when the underlying insulating film is a low-k film, peeling occurs between the tungsten nitride film and the copper film. Occurred in between. As is clear from Table 2, when the surfaces of the thermal oxide film as the underlayer and the organic low-k insulating film were treated with ammonia plasma, the adhesion with the tungsten nitride film was extremely good. But,
When the ammonia plasma treatment was not performed, the tungsten nitride film formed on the thermal oxide film and the organic low-k insulating film was easily peeled off by the Scotch tape test, resulting in poor adhesion. The tendency of adhesion as described above is the same when a plasma treatment of a gas other than ammonia plasma such as nitrogen, hydrazine, or nitrous oxide is performed, or when an ammonia gas treatment is performed prior to the reaction. It was

[0029]

EFFECTS OF THE INVENTION According to the present invention, since the film formation step is performed after the substrate is treated by introducing ammonia gas into the reaction vessel in advance or after the substrate is exposed to the plasma of the nitrogen atom-containing gas, the metal The nucleus growth in the initial stage of the growth of the nitride film can be made uniform on the substrate, and then the uniform film can be grown. In this case, with a short induction time and high accuracy,
It is possible to form a thin film having excellent adhesion to the lower insulating film.

[Brief description of drawings]

FIG. 1 FT-IR of the surface of a wafer treated with ammonia plasma.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mikio Watanabe             1220-1 Suyama, Susono City, Shizuoka Al             Back Semiconductor Technology Laboratory F-term (reference) 4K030 AA04 AA06 AA13 AA17 BA38                       CA04 DA02 DA03 FA10 LA15                 4M104 BB29 BB30 BB32 BB33 DD45                       FF18

Claims (4)

[Claims] 1. A method for forming a metal nitride film by a thermal CVD method on a substrate placed in a vacuum reaction chamber,
After exposing the heated substrate to the plasma of the nitrogen atom-containing gas, or after introducing the ammonia gas into the reaction vessel in advance and treating the heated substrate, the reaction containing the metal halide gas and the ammonia gas. A method for forming a metal nitride film, which comprises introducing a gas to form a metal nitride film on a substrate. 2. The nitrogen atom-containing gas is nitrogen, formula: N
H _3-n (C _m H _{2m +1} ) _n (wherein n = 0, 1-3,
m = 1-6. ) An ammonia derivative having the formula:
_{N 2 H 4-n (C} m H 2m + 1) n ( where, n = 0,1~
4, m = 1-6. ) A hydrazine derivative having
A gas selected from an azide derivative having the formula: N ₃ (C _m H _{2m + 1} ) (where m = 0 and _{1 to 6} ) and nitrous oxide. Of forming a metal nitride film of. 3. The method for forming a metal nitride film according to claim 1, wherein the nitrogen atom-containing gas is a gas selected from nitrogen, ammonia, hydrazine, and nitrous oxide. 4. The metal halide gas is a fluoride gas, a chloride gas, an iodide gas, or a bromide gas of a metal selected from tungsten, tantalum, titanium, and vanadium. 4. The method for forming a metal nitride film according to any one of 1 to 3.