JP2004149892A - Method of forming titanium nitride film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a TiN film by which the uniformity of the film thickness or film quality in a TiN film can be improved. <P>SOLUTION: In the method of forming a TiN film, at first, a first TiN film 5 is formed on the film forming face (silicon oxide) 2 in a substrate 1 by a first film forming gas consisting of gaseous TiCl<SB>4</SB>and gaseous NH<SB>3</SB>controlled so that the the gaseous TiCl<SB>4</SB>lies in a feed rate-determining state. Next, a second TiN film 6 is formed on the first TiN film 5 by a second film forming gas consisting of gaseous TiCl<SB>4</SB>and gaseous NH<SB>3</SB>controlled so that the gaseous TiCl<SB>4</SB>lies in a reaction rate-determining state. Thus, the film thickness or film quality of the first and second TiN films 5 and 6 are made uniform on the whole. <P>COPYRIGHT: (C)2004,JPO

Description

表１には第１の実験により得られた評価結果がシート抵抗標準偏差の値として示されている。この表１から明らかなように、本発明の方法によって膜質ないしは膜厚の均一性の高いＴｉＮ膜が得られることが分かる。なお、第１のＴｉＮ膜のみであっても、２００オングストロームを越えると、シート抵抗の標準偏差は低くなるが、第１のＴｉＮ膜はステップカバレージが低いという別の問題があるため、近年の半導体デバイスの微細化、高集積化には不適当である。
【００２４】
なお、この第１の実験において本発明の方法でＴｉＮ膜を形成した後、厚さ４０００オングストローム（４００ｎｍ）のＷ膜を従来一般の方法で形成したが、良好な膜が得られた。
【００２５】
第２の実験では、試料として、表面に厚さ１０００オングストローム（１００ｎｍ）のＳｉＯ_２膜が形成された半導体ウェハを用意した。そして、下の表２に示すように、本発明の実施例に係る試料として、ＴｉＣｌ_４ガスの流量を１５ｍｇｍ、ＮＨ_３ガスの流量を５００ｓｃｃｍとして厚さ５０オングストローム（５ｎｍ）の第１のＴｉＮ膜をＳｉＯ_２膜上に形成し、その上に、ＴｉＣｌ_４ガスの流量を１７０ｍｇｍ、ＮＨ_３ガスの流量を１００ｓｃｃｍとして厚さ１５０オングストローム（１５ｎｍ）、２５０オングストローム（２５ｎｍ）、３５０オングストローム（３５ｎｍ）、４５０オングストローム（４５ｎｍ）の第２のＴｉＮ膜をそれぞれ形成した４種の試料を作成した。
【００２６】
また、比較例としては、第１のＴｉＮ膜は形成せずに、第２のＴｉＮ膜のみを形成した試料を４種用意した。それぞれの膜厚は、実施例の各試料の第１と第２のＴｉＮ膜の厚さの総計と同じとなるよう、２００オングストローム、３００オングストローム、４００オングストローム、５０オングストロームとした。
【００２７】
膜質ないしは膜厚の均一性の評価方法としては、第１の実験の場合と同様、シート抵抗の標準偏差を求める方法を採用した。
【００２８】
【表２】

表２には、この第２の実験による結果が示されており、図２はそれをグラフとしたものである。これらから、本発明の方法により膜質ないしは膜厚の均一性の高いＴｉＮ膜が得られることが理解されよう。また、本発明の方法によっても、膜厚の総計が５００オングストロームを越えると、第２のＴｉＮ膜のみからなるものと効果においては差がなくなるが、これは第２のＴｉＮ膜が厚くなるにつれ、第１のＴｉＮ膜の効力が低減されるためと考えられる。
【００２９】
この第２実験にて本発明の方法で形成されたＴｉＮ膜の上に、最上層として厚さ４０００オングストローム（４００ｎｍ）のＷ膜を従来一般の方法で形成したが、この場合も良好な結果が得られた。
【００３０】
【発明の効果】
以上述べたように、本発明によれば、Ｗ膜やＡｌ膜の下地層として形成されるＴｉＮ膜の膜質ないしは膜厚がより均一となり、ＷやＡｌの拡散防止効果等が半導体ウェハ等の基板の全域において均等に得られることとなる。従って、最終製品となる半導体デバイスの性能や歩留まりの向上にも寄与することとなる。
【図面の簡単な説明】
【図１】（ａ）〜（ｄ）は本発明の方法を用いてのＴｉＮ膜形成の手順を示す図である。
【図２】本発明による効果を示す実験結果を示すグラフである。
【符号の説明】
１…半導体ウェハ、２…ＳｉＯ_２膜、３…ＴｉＮ膜、４…Ｗ膜、５…第１のＴｉＮ膜、６…第２のＴｉＮ膜。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a film forming technique used in, for example, semiconductor manufacturing, and more particularly to a means for improving the film quality or uniformity of the film thickness of a titanium nitride (TiN) film formed by a CVD (chemical vapor deposition) method. .
[0002]
[Prior art]
2. Description of the Related Art In recent years, in semiconductor manufacturing, a method of forming a film of tungsten (W) or aluminum (Al) has been widely adopted for forming a wiring or filling a contact hole. Further, when a W film or an Al film is formed directly on a film forming surface (underlying layer) such as a silicon dioxide (SiO ₂ ) film, diffusion of W or Al occurs on the film forming surface, resulting in unstable film quality. Conventionally, a TiN film is formed on a film-forming surface, and a W film or an Al film is formed thereon (see Patent Document 1).
[0003]
As a method for forming a TiN film, a thermal CVD method using a titanium chloride (TiCl ₄ ) gas and an ammonia (NH ₃ ) gas is generally used. In addition, since it is necessary to obtain good step coverage with the recent increase in the degree of integration and miniaturization of semiconductor devices, the introduction flow rate of the TiCl ₄ gas is supplied in a thermochemical manner to the flow rate of the NH ₃ gas. It was general to set an excessive state, that is, a state in which the TiCl ₄ gas becomes the reaction rate-determining in the thermochemical reaction. For example, when NH ₃ gas is introduced into the processing chamber at a flow rate of 100 sccm, the flow rate of TiCl ₄ gas is about 170 mgm.
[0004]
[Patent Document 1]
JP-A-7-201779
[Problems to be solved by the invention]
Incidentally, it is desirable to form the TiN film so that the film thickness or film quality is as uniform as possible over the entire surface of the silicon oxide surface such as a SiO ₂ film or the silicon single crystal surface.
[0006]
Accordingly, an object of the present invention is to provide a novel TiN film forming method in which the film thickness or film quality uniformity of the TiN film is further improved as compared with the conventional method as described above.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a method of forming a TiN film according to the present invention includes a method of forming a first film forming gas containing TiCl ₄ gas and NH ₃ gas as main components in a processing chamber in which a substrate such as a semiconductor wafer is disposed. A first step of introducing and forming a first TiN film on a silicon oxide surface or a silicon surface of the substrate by a thermal CVD method, and after the first step, a TiCl ₄ gas and an NH ₃ gas are mainly contained in a processing chamber. A second film forming gas is introduced, and a second step of forming a second TiN film on the first TiN film by a thermal CVD method. The introduction amounts of the TiCl ₄ gas and the NH ₃ gas into the respective processing chambers are adjusted so that the supply rate of the _four gases is rate-limiting in the thermochemical reaction and the reaction rate of the NH ₃ gas is rate-limiting. ₄ gas is thermalized And NH ₃ gas becomes kinetically limited in the reaction is characterized in that to adjust the introduction amount of the respective processing chamber of TiCl ₄ gas and NH ₃ gas so that a supply rate-limiting. The silicon oxide may be SiOC or SiON having similar properties, in addition to SiO ₂ .
[0008]
According to the method of the present invention, when a film composed of the first TiN film and the second TiN film is viewed as a single-layer TiN film, the TiN film is a TiN film formed by a conventional method (referred to in the present invention). The film quality or the film thickness is more uniform than that of the second TiN film alone.
[0009]
The thickness of the first TiN film is 100 Å (10 nm) or less, preferably 30 to 100 Å (3 to 10 nm), and more preferably 50 to 70 (3 to 7 nm). It is preferable that the total thickness of the second TiN film is 150 to 500 angstroms (15 to 50 nm).
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a procedure for forming a TiN film 3 on a SiO ₂ film 2 on a semiconductor wafer (substrate) 1 and further forming a W film 4 thereon by the method of the present invention.
[0011]
First, the semiconductor wafer 1 (see FIG. 1A) on which the SiO ₂ film 2 is already formed is loaded into a processing chamber (not shown) of the thermal CVD apparatus, and the processing chamber is moved to about 10 Torr (1333.22 Pa). ). Next, the inside of the processing chamber is heated to raise the temperature of the semiconductor wafer 1 to about 600 to 750 ° C. (for example, 680 ° C.). Here, when a first film forming gas containing TiCl ₄ gas and NH ₃ gas as main components is introduced into the processing chamber and subjected to a thermochemical reaction, a thin first TiN film 5 is formed on the semiconductor wafer 1. (See FIG. 1B).
[0012]
In this process, the flow rate is set so that the NH ₃ gas controls the reaction of the thermochemical reaction. That is, for example, the flow rate of the TiCl ₄ gas is set to a small flow rate of 10 to 100 mgm, while the NH ₃ gas is set to a large flow rate of 500 sccm. By causing NH ₃ to control the reaction in this manner, step coverage is reduced, but sufficient NH ₃ gas is adsorbed on the entire surface of the wafer and reacts with NH ₃ adsorbed on the entire surface of the wafer when TiCl ₄ is introduced. Is formed on the film forming surface, that is, on the SiO ₂ film 2, a film to be a nucleus or seed effective for growing the second TiN film 6 to be subsequently formed. It is thought that.
[0013]
The thickness of the first TiN film 5 is not more than 100 angstroms (10 nm), preferably about 30 to 100 angstroms (3 to 10 nm), and more preferably about 50 to 70 angstroms (5 to 7 nm). If the thickness is less than 30 angstroms, the function as a nucleus for growing the TiN film will not be sufficiently exhibited, and if it exceeds 100 angstroms, the step coverage may be adversely affected.
[0014]
After the first TiN film 5 is formed, the first deposition gas is exhausted from the processing chamber. Then, while maintaining the degree of vacuum and the temperature in the processing chamber at the same level as when forming the first TiN film 5, a second film-forming gas is introduced, and the second TiN film 6 is formed by a thermochemical reaction. Is formed on the first TiN film 5. Like the first film-forming gas, the second film-forming gas is mainly composed of a TiCl ₄ gas and an NH ₃ gas, but is adjusted so that the reaction rate of the TiCl ₄ gas is controlled. Specifically, when the flow rate of the TiCl ₄ gas is, for example, 170 mgm, the flow rate of the NH ₃ gas is preferably set to about 100 sccm. Since the second film forming gas is the same as the film forming gas in the above-described conventional method, the step coverage is good, and the portion that cannot be covered by the first TiN film 5 can be filled. In addition, since the first TiN film 5 is formed first, the second TiN film 6 grows stably using the first TiN film 5 as a nucleus or a seed. As a result, the TiN film 3 composed of the first and second TiN films 5 and 6 is smaller than the conventional method in which only the second TiN film is directly formed on the SiO ₂ film with the second deposition gas. A more uniform film quality or thickness is obtained.
[0015]
When the total thickness of the first and second TiN films 5 and 6 reaches a predetermined value, the semiconductor wafer 1 is transferred to another thermal CVD apparatus (not shown), as is generally performed conventionally. Tungsten hexafluoride (WF ₆ ) and silane (SiH ₄ ) or H ₂ are introduced into the processing chamber, and a blanket W film 4 is formed on the second TiN film 6 by a thermochemical reaction. Of course, the film quality of the W film 4 formed on the second TiN film 6 having a uniform thickness and a uniform thickness is also improved. From the viewpoint of preventing diffusion of the W film 4 from the surface on which the film is formed, the total thickness of the first and second TiN films 5 and 6 is preferably about 150 to 500 angstroms (15 to 50 nm). The reason why the thickness is set to 500 angstroms is that if the value is exceeded, the effect of the first TiN film 5 is reduced, so that it is considered that the uniformity of the film quality and the like is reduced.
[0016]
The preferred embodiment of the present invention has been described above, but it goes without saying that the present invention is not limited to the above embodiment. For example, the first and second deposition gases may include other gases. Further, the film formed on the TiN film 3 may be an Al film or a film of another material. Further, the base of the TiN film is not limited to SiO ₂ , but may be another silicon oxide such as SiON, SiOC, or silicon.
[0017]
【Example】
Next, results of two experiments in which a TiN film is actually formed by the TiN film forming method of the present invention and the uniformity of the film quality is examined will be described. In the first experiment, the difference in uniformity such as film quality depending on the presence or absence of the first TiN film was examined. In the second experiment, the case where the first TiN film had a constant thickness and the thickness of the second TiN film was changed was examined.
[0018]
First, in a first experiment, a semiconductor wafer having a 1000 Å (100 nm) thick SiO ₂ film formed on the surface thereof was prepared. As an example of the present invention, a first TiN film was further formed on the SiO ₂ film. A sample in which a second TiN film was formed thereon, a sample in which only the first TiN film was formed, and a sample in which only the second TiN film was formed were prepared as comparative examples.
[0019]
Further, as samples according to the examples, 11 types were prepared as shown in Table 1 below. That is, the first film forming gas for forming the first TiN film has three flow rates of 15 mgm, 30 mgm, and 50 mgm of the TiCl ₄ gas, and the thickness of the first TiN film is 10 angstroms (for each). 1 angstrom), 30 angstrom (3 nm), 50 angstrom (5 nm), 70 angstrom (7 nm), and 100 angstrom (10 nm). Note that the flow rate of the NH ₃ gas in the first film formation gas was kept constant at 500 sccm. In addition, the second TiN film was formed such that the total thickness of the first and second TiN films in each sample according to the example was constant at 200 Å (20 nm). In the second film forming gas for forming the second TiN film, the flow rate of the TiCl ₄ gas was constant at 170 mgm, and the flow rate of the NH ₃ gas was constant at 100 sccm.
[0020]
On the other hand, a sample according to the comparative example in which only the first TiN film was formed was a sample according to the example in which the second TiN film was not formed, a flow rate of the TiCl ₄ gas was 15 mgm, and an NH ₃ gas was used. 9 flow rates of 500 sccm and only the first TiN film having a thickness of 200 angstroms (20 nm) were formed.
[0021]
In the sample according to the comparative example in which only the second TiN film was formed, the flow rate of the TiCl ₄ gas was constant at 170 mgm, and the flow rate of the NH ₃ gas was constant at 100 sccm, and the second TiN film was formed. The thickness of the second TiN film was set to 100 Å (10 nm), 130 Å (13 nm), 150 Å (15 nm), and 200 Å (20 nm).
[0022]
Although there are various methods for evaluating the film quality or the uniformity of the film thickness of the TiN film, in this experiment, the sheet resistance was measured at a plurality of locations on the semiconductor wafer to determine the standard deviation, and the film thickness or film quality was determined from the value. The method of judging the uniformity was adopted. The sheet resistance [Ω / □] refers to a resistance value per unit width and unit length. The smaller the value of the standard deviation, the smaller the width of the dispersion of the sheet resistance, indicating that the film quality or the film thickness is more uniform.
[0023]
[Table 1]

Table 1 shows the evaluation results obtained in the first experiment as sheet resistance standard deviation values. As is clear from Table 1, it can be seen that the method of the present invention can provide a TiN film having high film quality or uniform thickness. Even if only the first TiN film is used, if the thickness exceeds 200 angstroms, the standard deviation of the sheet resistance becomes low. However, the first TiN film has another problem that the step coverage is low. It is not suitable for miniaturization and high integration of devices.
[0024]
In the first experiment, after forming a TiN film by the method of the present invention, a W film having a thickness of 4000 Å (400 nm) was formed by a conventional method, but a good film was obtained.
[0025]
In the second experiment, a semiconductor wafer having a 1000 angstrom (100 nm) thick SiO ₂ film formed on the surface was prepared as a sample. As shown in Table 2 below, as a sample according to an example of the present invention, a first TiN film having a thickness of 50 angstroms (5 nm) with a TiCl ₄ gas flow rate of 15 mgm and an NH ₃ gas flow rate of 500 sccm. Is formed on a SiO ₂ film, and a thickness of 150 Å (15 nm), 250 Å (25 nm), 350 Å (35 nm), 450 Å with a TiCl ₄ gas flow rate of 170 mgm and an NH ₃ gas flow rate of 100 sccm is formed thereon. Four types of samples each having a second Angstrom (45 nm) TiN film were formed.
[0026]
As comparative examples, four kinds of samples were prepared in which only the second TiN film was formed without forming the first TiN film. Each film thickness was set to 200 Å, 300 Å, 400 Å, and 50 Å so as to be the same as the total thickness of the first and second TiN films of each sample of the example.
[0027]
As a method of evaluating the film quality or the uniformity of the film thickness, a method of obtaining the standard deviation of the sheet resistance was employed as in the case of the first experiment.
[0028]
[Table 2]

Table 2 shows the results of this second experiment, and FIG. 2 is a graph thereof. From these, it can be understood that the method of the present invention can provide a TiN film having a high film quality or a uniform film thickness. Also, according to the method of the present invention, when the total thickness exceeds 500 angstroms, there is no difference in the effect from the case where only the second TiN film is formed. However, as the second TiN film becomes thicker, It is considered that the effect of the first TiN film is reduced.
[0029]
In the second experiment, a 4000 W (400 nm) thick W film was formed as the uppermost layer on the TiN film formed by the method of the present invention by a conventional method. Obtained.
[0030]
【The invention's effect】
As described above, according to the present invention, the film quality or the film thickness of the TiN film formed as the underlayer of the W film or the Al film becomes more uniform, and the effect of preventing the diffusion of W and Al is reduced. Is obtained evenly over the entire area. Therefore, it also contributes to the improvement of the performance and yield of the semiconductor device as the final product.
[Brief description of the drawings]
FIGS. 1A to 1D are diagrams showing a procedure for forming a TiN film using the method of the present invention.
FIG. 2 is a graph showing experimental results showing the effects of the present invention.
[Explanation of symbols]
1 ... semiconductor wafer, 2 ... SiO ₂ film, 3 ... TiN film, 4 ... W film, 5 ... first TiN film, 6 ... second TiN film.

Claims (3)

In a method of forming a titanium nitride film on a silicon oxide surface or a silicon surface of a substrate,
A first film forming gas mainly composed of a titanium chloride gas and an ammonia gas is introduced into a processing chamber in which the substrate is disposed, and a first titanium nitride film is formed on the film forming surface of the substrate by a thermal CVD method. A first step of forming a film by
After the first step, a second film forming gas mainly composed of a titanium chloride gas and an ammonia gas is introduced into the processing chamber, and a second titanium nitride film is thermally formed on the first titanium nitride film. A second step of forming a film by a CVD method,
Adjusting the introduction amounts of the titanium chloride gas and the ammonia gas into the processing chamber such that the titanium chloride gas in the first film-forming gas becomes a supply-limiting rate in the thermochemical reaction and the ammonia gas becomes a reaction-limiting rate;
Adjusting the introduction amounts of the titanium chloride gas and the ammonia gas into the processing chamber such that the titanium chloride gas in the second film-forming gas becomes a reaction rate-determining reaction in the thermochemical reaction and the ammonia gas becomes a supply-limiting rate. A method for forming a titanium nitride film. 2. The method according to claim 1, wherein the thickness of the first titanium nitride film is 100 angstroms (10 nm) or less. 3. The method according to claim 2, wherein the total thickness of the first titanium nitride film and the second titanium nitride film is 150 to 500 Å (15 to 50 nm). 4.

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