JP2836567B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a barrier metal layer by a chemical vapor deposition method.

[0002]

2. Description of the Related Art Generally, a contact structure of a semiconductor device is formed as shown in FIG. That is, first, referring to FIG. 3A, the P ⁻ type silicon substrate 1
An interlayer insulating layer 2 is formed thereon, and a contact hole CONT is formed on the interlayer insulating layer 2 by using a photolithography technique.
To form Next, an N ⁺ -type impurity diffusion layer 3 is formed in the P ⁻ -type silicon substrate 1 in a self-aligned manner. Next, referring to FIG. 3B, a barrier metal layer 4 made of titanium nitride (TiN) is formed on the entire surface. Finally, referring to FIG. 3C, a metal layer 5 made of aluminum or the like is formed on the barrier metal layer 4. In this case, the metal layer 5
Is embedded in the contact hole CONT. Next, the metal layer 5 and the barrier metal layer 4 are patterned to complete a contact structure.

The barrier metal layer 4 in FIG. 3 has good contact with the N ⁺ type impurity diffusion layer 3 (P ⁻ type silicon substrate 1), good contact with the metal layer 5, and low electric resistance. Is required. At the same time, the barrier metal layer 4 is required to have a barrier performance in which the metal layer 5 and the N ⁺ -type impurity diffusion layer 3 (P ⁻ -type silicon substrate 1) do not react via the barrier metal layer 4. Conventionally, the above-described barrier metal layer 4 in the contact hole CONT or the via hole has been formed by a sputtering method. A vapor phase growth method (CVD method) is employed.

A first method for forming a barrier metal layer using a CVD method is a film formation from an inorganic material. For example, T
Low pressure CVD (LPC) using iCl ₄ and NH ₃ as source gases
VD) is introduced into a film formation chamber, and TiN is formed at a high temperature of 500 to 700 ° C. As a result, a barrier metal layer 4-A shown in FIG. This barrier metal layer 4-A is mainly used as a contact hole barrier metal layer because the film formation temperature is high.

[0005] A second method for forming a barrier metal layer using a CVD method is film formation from an organic material. For example, an organic Ti compound and NH ₃ are introduced as raw material gases into a LPCVD film forming chamber, and a TiN film is formed at a low temperature of about 400 ° C. (see “Gurtej S. Sandhu et al.,“ CHARACTERI ”).
ZATION OF TiN FILMS DEPOSITED USING METAL-ORANICCH
EMICAL VAPOR DEPOSITION ", Conference Proceedings U
LSI-VII, Materials Research Society, pp. 323-328, 1
992, and JP-A-63-230877). As a result, the barrier metal layer 4-A shown in FIG.
Is obtained.

A third method of forming a barrier metal using the CVD method is a film formation by thermal decomposition of an organic raw material. For example, an azide compound Ti [N (CH
₃ ) ₂ ] ₄ is thermally decomposed and introduced into an LPCVD deposition chamber,
Deposit TiN at a low temperature of 00 to 400 ° C. (see:
Kozoh Sugiyama et al., "Low Temperature Deposition
of Metal Nitrides by Thermal Decomposition of Org
anometallic Compounds ", J. Electrochem. Soc., VoL.
122, No. 11, pp. 1545-1549, November, 1975). Thereby, a barrier metal layer 4-B shown in FIG. 4B is obtained.

[0007]

However, in the first and second forming methods described above, the barrier metal layer 4-A of FIG. It has a columnar structure. That is, the crystal grain boundary exists continuously from the upper interface to the lower interface. Therefore, this becomes a diffusion path of atoms, and deteriorates barrier performance. For example, a metal layer 5 made of W is formed on a barrier metal layer 4-A made of TiN having a thickness of 100 ° by a CVD method using WF ₆ and H ₂ as source gases, and this is heat-treated at 600 ° C. or more. In this case, W of the metal layer 5 and unreacted WF ₆ and F reach the N ⁺ -type impurity diffusion layer 3 (P ⁻ -type silicon substrate 1) through the crystal grain boundaries of the barrier metal layer 4-A.
As a result, the junction leakage current characteristics deteriorate. In particular, when the metal layer 5 is formed of Cu, the junction leakage current characteristics are significantly deteriorated due to the downward diffusion of Cu. Therefore, the barrier metal layer 4-A is not suitable as a fine barrier metal layer. Although the barrier performance can be improved by increasing the thickness of the barrier metal layer 4-A, this goes against the trend of miniaturization. Further, it has been proposed to reduce the number of crystal grain boundaries per 1 μm to one or less to avoid the problems caused by the grain boundaries of the columnar structure (see JP-A-63-230877). It is practically impossible to reduce the number of grain boundaries per 1 μm to zero, and the size of the crystal grains increases, so that the distance over which one grain boundary extends increases, and the adverse effect is widespread. Will span. In general, unless a material having a structure sufficiently small in view of the size of the contact structure is used, the material is not regarded as an average material, and the method of reducing the crystal grain boundaries cannot secure the yield stability.

[0008] In the above-mentioned third forming method,
Since the barrier metal layer 4-B shown in FIG. 4B contains a large amount of impurities such as C and O, crystallization is suppressed, and as a result, the barrier metal layer 4-B becomes amorphous. Are not present and therefore exhibit good barrier performance. However, due to this amorphous state, the electric resistance value is, for example, several m.
Ω · cm (specific resistance) also becomes very large. Further, FIG.
As shown in the figure, the specific resistance also has a temporal change such that it increases by several 100% in one day. Therefore,
The barrier metal layer 4-B is not suitable as a fine barrier metal layer.

Accordingly, it is an object of the present invention to provide a method for forming a barrier metal layer having a good barrier performance without a low resistance value or a rise in electric resistance value over time.

[0010]

In order to solve the above-mentioned problems, the first means is to mix a compound containing titanium as a constituent element with a nitrogen source and to mix a fluoride with a source gas.
It is introduced into a film formation chamber at a temperature lower than 50 ° C., thereby forming a barrier metal layer made of titanium nitride on a semiconductor substrate. According to the first means, in the first and second conventional methods for forming a barrier metal layer, a fluoride is added to a source gas in order to amorphize crystal grains having a columnar structure.
Further, a second means for solving the above-mentioned problem is to mix a fluoride into a raw material gas obtained by heating and evaporating a compound containing titanium and nitrogen as components, and introduce the mixed gas into a film formation chamber;
Thus, a barrier metal layer made of titanium nitride is formed on the semiconductor substrate. According to the second means,
In the third conventional method for forming a barrier metal layer, a fluoride is added to a source gas in order to increase the oxidation resistance of the amorphous barrier metal layer and suppress the increase in electric resistance over time. That is, it is considered that the time-dependent increase in the electric resistance value of the barrier metal layer is caused by the substitution of O atoms for the Ti—H bonds remaining in the barrier metal layer. Therefore, the fluoride acts to reduce the number of Ti—H bonds in the barrier metal layer in advance by extracting H atoms from the Ti—H bonds in the barrier metal layer in the form of HF. As a result, the resistance of the barrier metal layer is stabilized.

[0011]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. That is, TiCl ₄ is used as a raw material compound containing titanium, and NH ₃ is used as a nitrogen source.
And / or silicon fluoride as a fluoride is mixed into a raw material gas in which hydrazines are mixed and introduced into a CVD film formation chamber. The film forming conditions in this case are as follows: TiCl ₄ flow rate: 5 to 15 sccm 5% monomeric hydrazine / 95% NH ₃ mixed gas:
100-250 sccm Silicon fluoride flow rate: 10-20 sccm Deposition chamber pressure: 0.1-10 Torr Deposition chamber temperature (substrate temperature): 350-450 ° C. As a result, F atoms of silicon fluoride suppress crystallization, and as shown in FIG.
An i-N-Si barrier metal layer 4-A 'is obtained. Note that F is introduced to introduce silicon into the barrier metal layer 4-A ′.
When silanes containing no atoms (such as SiH ₄ ) are used, crystallization is not suppressed. The substrate temperature is set to 550 °
When the temperature is higher than C, crystallization is not suppressed. Further, instead of silicon fluoride, silicon hydride may be used. A similar amorphous Ti—N—Ge barrier metal layer can be obtained using germanium fluoride and germanium hydride.

A second embodiment of the present invention is shown in FIG.
This will be described with reference to FIG. That is, tetrakis-diethylamino-titanium (T
DEAT) is heated and led into a vaporizer, where it is mixed with nitrogen gas and led to a CVD film formation chamber. Furthermore, it is mixed fluoride molybdenum (M o F ₆₎ in the film forming chamber of the CVD. Film forming conditions in this case, TDEAT flow: 0.01μl / min nitrogen gas: 700 sccm M o F ₆ flow rate: 5～20Sccm deposition chamber pressure: 0.1～5Torr deposition chamber temperature (substrate temperature): 350 500 ° C. As a result, a barrier metal layer 4-B ′ shown in FIG. 1B is obtained. That is, TDEAT is thermally decomposed into TiN. In parallel with this, Ti in the barrier metal layer
The —H bond reacts with MoF ₆ based on the following reaction formula (coefficient omitted) to extract H. _{Ti-H + M o F 6} → TiF 4 ↑ + M o + HF ↑ Consequently, oxidation resistance of the barrier metal layer is improved. Further, by raising the deposition chamber temperature, the electrical resistance decreases so TiF ₄ is liable to decompose leaving further further electrical resistance is reduced by the incorporation into the barrier metal layer of M o itself. Finally, a specific resistance of 2000 μmΩ · cm or less was obtained. Instead of the metal M o, Dangusuten, rhenium, germanium metal similar low resistance barrier metal layer 4-B be used 'is obtained. Also, when germanium metal is used, the formation of Ge-Ti-N-based amorphous material is promoted, and the electric resistance value is not reduced much, but the oxidation resistance is improved and the stable amorphous barrier material is used. A metal layer is obtained.

Further, TD is used as a starting compound containing titanium.
The EAT is heated and led into a vaporizer, where it is mixed with nitrogen gas and led to a CVD film formation chamber. Further, boron fluoride (BF ₃ ) is mixed in a CVD film forming chamber. The film forming conditions in this case are: TDEAT: 0.01 μl / min Nitrogen gas: 700 sccm BF ₃ Flow rate: 5 to 20 sccm Film forming chamber pressure: 0.1 to 5 Torr Film forming chamber temperature (substrate temperature): 350 to 500 ° C. It is. As a result, a barrier metal layer 4-B ′ also shown in FIG. 1B is obtained. That is, TDEAT is thermally decomposed into TiN. In parallel with this, the Ti—H bond in the barrier metal layer and MoF ₆ form the following reaction formula (coefficient omitted):
H is extracted in response to the reaction. _{Ti-H + BF 3 → TiB} X + HF ↑ As a result, the titanium boride is conductive, indicating a very high barrier performance. It should be noted that a similar low-resistance barrier metal layer 4-B ′ can be obtained by using nonmetallic silicon instead of nonmetallic boron. In this case, the film formation is performed at a temperature of 400 ° C. and a flow rate of SiF ₄ , SiHF ₄ , and SiH ₂ F ₂ of 5 to 20 sccm. In the case where carbon, nitrogen or arsenic is used as a nonmetallic element, hydrogen is extracted and amorphousization is promoted. Therefore, although the electric resistance value does not decrease so much, the oxidation resistance is improved and a stable amorphous barrier metal layer can be obtained.

Further, as a raw material compound containing titanium, T
The DAT is heated and led into a vaporizer, where it is mixed with nitrogen gas and led to a CVD film formation chamber. Further, nitrogen fluoride (NF ₃ ) is mixed in a CVD film formation chamber. The deposition conditions in this case are as follows: TDEAT flow rate: 0.01 μl / min Nitrogen gas: 700 sccm NF ₃ flow rate: 50 to 100 sccm Deposition chamber pressure: 0.1 to 5 Torr Deposition chamber temperature (substrate temperature): 350 to 500 ° C. As a result, a barrier metal layer 4-B ′ also shown in FIG. 1B is obtained. That is, TDEAT is thermally decomposed into TiN. In parallel with this, the Ti—H bond in the barrier metal layer reacts with NF ₃ to extract H. As a result, the oxidation resistance of the barrier metal layer is improved, and a stable amorphous barrier metal layer is obtained. However, although the electric resistance does not decrease so much, as shown in FIG. 2, the increase with time in the electric resistance is improved to + 5% / 24 hours. Note that a similar barrier metal layer 4-B 'can be obtained by using an inert element of argon, krypton, or xenon instead of the inert element nitrogen.

In the above-described second embodiment,
A similar barrier metal layer can be obtained by using tetrakis dimethylamino titanium (TDMAT) instead of TDEAT.

[0016]

As described above, according to the present invention, the electric resistance value is low or a rise with time is suppressed, and
An amorphous barrier metal layer having good barrier performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of a method for forming a barrier metal layer according to the present invention.

FIG. 2 is a graph showing a change over time in an electric resistance value of a barrier metal layer according to the present invention.

FIG. 3 is a cross-sectional view illustrating a general method of manufacturing a contact structure.

FIG. 4 is a cross-sectional view illustrating a conventional method for forming a barrier metal layer.

FIG. 5 is a graph showing a change over time of an electric resistance value of a conventional barrier metal layer.

[Explanation of symbols]

1─P ^- -type silicon substrate 2─ interlayer insulating layer 3─N ⁺ -type impurity diffusion layer 4,4-A, 4-B, 4-A ', 4-B'─ barrier metal layer 5─ metal layer CONT─ Contacts hole

Claims (9)

(57) [Claims] 1. A fluoride is mixed with a raw material gas obtained by mixing a nitrogen source with a compound containing titanium as a constituent element.
The substrate is introduced into a film formation chamber at a temperature lower than 0 ° C., thereby forming a barrier metal layer (4) made of titanium nitride on the semiconductor substrate (1, 3).
-A ′) A method for manufacturing a semiconductor device for forming (A ′). Wherein a said compound TiC l _4, a method of manufacturing a semiconductor device according to claim 1 wherein the fluoride is any one of hydrogen fluoride compound of fluoride and silicon silicon. Wherein a said compound TiC l _4, a method of manufacturing a semiconductor device according to claim 1 wherein the fluoride is any one of hydrogen fluoride compound of fluoride and germanium germanium. 4. The method according to claim 1, wherein the nitriding source is at least one of nitrogen gas, NH ₃ and hydrazines. 5. A raw material gas obtained by heating a compound containing titanium and nitrogen as components, mixing with a nitrogen gas, and evaporating the raw material gas.
A method of manufacturing a semiconductor device in which a fluoride is mixed and introduced into a film formation chamber, whereby a barrier metal layer (4-B ′) made of titanium nitride is formed on a semiconductor substrate (1, 3). 6. The method according to claim 5, wherein the compound is any one of tetrakis-diethylamino-titanium and tetrakis-dimethylamino-titanium. 7. The method according to claim 5, wherein the fluoride is a fluoride of a metal element, and the metal element is any of tungsten, molybdenum, rhenium, and germanium. 8. The method according to claim 5, wherein the fluoride is a nonmetallic element fluoride, and the nonmetallic element is any of boron, silicon, carbon, nitrogen and arsenic. 9. The method according to claim 5, wherein the fluoride is a fluoride of an inert gas, and the inert gas is any of argon, krypton, xenon, and nitrogen.