JP4308867B2 - Method of forming refractory metal nitride film - Google Patents

Description

  The present invention relates to a method for forming a refractory metal nitride film, and more particularly, to a refractory metal nitride film having a growth process of a refractory metal nitride serving as a barrier metal material interposed between a semiconductor layer and a wiring. It relates to a forming method.

  In recent years, there has been a demand for higher density in semiconductor devices. In a semiconductor substrate, a diffusion layer is thinned and wirings are multilayered. Therefore, in order to prevent the electrode metal from entering the diffusion layer, improve the adhesion of the electrode, and prevent the hillock of the electrode, the refractory metal nitride is used as the electrode underlayer or the electrode surface layer. Barrier metal is used.

  In the case of forming a barrier metal serving as a base of a wiring layer, a thermal chemical vapor deposition (CVD) method using a refractory metal halide gas and ammonia gas has been widely studied.

For example, when TiN 4 serving as a barrier metal is formed by thermal CVD using TiCl ₄ and NH ₃ as reaction gases, the growth temperature at which good step coverage is obtained is 650 ° C. or higher.

  In this case, chlorine remains in the barrier metal and causes high resistance, so that a growth temperature higher than 600 ° C. is required to remove chlorine. The details are described in, for example, the following three documents.

(1) MJ Buiting, AF Otterloo, and AH Montree, J. Electrochem. Soc., VOL.138, No.2, Feb. 1991, (2) IJ Raaijmakers and A. Sherman, Proc. VMIC, Santa Clara, June 1990, (3) E. 0. Travis, WM Paulson, F. Pintchovski, B. Boeck, LC Parillo, ML Kottke, KY Yu, MJ Rice, JB Price, and EC Eichman, IEEE IEDM Tech. Dig., 47 ( 1990)
TiCl ₄ and NH ₃ undergo the following reaction even at room temperature.

TiCl ₄ + NH ₃ → TiCl ₄ · n NH ₃
In addition, the following reaction occurs in the high temperature region where TiN can grow, and NH ₄ Cl precipitates in the cold place of the reaction chamber.

TiCl ₄ + NH ₃ → TiN + HCl + N ₂ , NH ₃ + HCl → NH ₄ Cl
TiCl ₄ · n NH ₃ and NH ₄ Cl are solid at room temperature, and if they adhere to the inner wall of the chamber, they cause particles. In order to sublimate this, the inner wall of the chamber of the CVD apparatus must be heated to 120 ° C. or higher. However, if a mechanism for heating the chamber is provided, the CVD apparatus becomes larger and the amount of electricity used increases.

On the other hand, there is a method of growing TiN by ECR (Electron Cyclotron Resonance) -CVD method using TiCl ₄ and N ₂ as the reaction gas, but the growth temperature becomes very high, and μ wave and ECR are increased. The equipment to be generated is complex, large, and expensive. The growth method is reported in the following literature.

(4) T. Akahori and A. Tanihara, Extended Abstracts Solid State Devices and Materials, 180 (1991)
MJ Buiting, AF Otterloo, and AH Montree, J. Electrochem. Soc., VOL.138, No.2, Feb. 1991 IJ Raaijmakers and A. Sherman, Proc. VMIC, Santa Clara, June 1990 E. 0. Travis, WM Paulson, F. Pintchovski, B. Boeck, LC Parillo, ML Kottke, KY Yu, MJ Rice, JB Price, and EC Eichman, IEEE IEDM Tech.Dig., 47 (1990) T. Akahori and A. Tanihara, Extended Abstracts Solid State Devices and Materials, 180 (1991) IJ Raaijmakers, RN Vrtis, GS Sandhu, J. Yang, EKBroadbent, DA Toberts, and A. Lagendijk, June 9-10, 1992 VMIC Conf. KazuyaISHIHARA et al., JAPANESE JOURNAL OF APPLIED PHYSICS VOL.29, No.10, Oct.1990 KOICHI IKEDA et al., 1990 Symposium on VLSI Technology CY TiNG AND M. WITTMER, Thin Solid Films, 96 (1982) 327-345, ELECTRONICS AND OPTICS

  However, when the TiN barrier metal is grown at such a high temperature as described above, the multilayer wiring structure after the aluminum wiring has a problem that aluminum melts or causes hillocks in the aluminum wiring.

  On the other hand, TiN can be grown at a growth temperature of 450 ° C. or less by thermal CVD or photo CVD using an organic titanium source. However, TiN obtained by this method has poor step coverage and high It is a resistive film. This is described in the following documents.

(5) IJ Raaijmakers, RN Vrtis, GS Sandhu, J. Yang, EKBroadbent, DA Toberts, and A. Lagendijk, June 9-10, 1992 VMIC Conf., (6) KazuyaISHIHARA et al., JAPANESE JOURNAL OF APPLIED PHYSICS VOL .29, No.10, Oct.1990, (7) KOICHI IKEDA et al., 1990 Symposium on VLSI Technology
On the other hand, it is known that when a barrier metal made of a refractory metal nitride is formed directly on a semiconductor substrate, they do not contact well, and it is necessary to interpose a contact metal between them. This is described in the following document.

(8) CY TiNG AND M. WITTMER, Thin Solid Films, 96 (1982) 327-345, ELECTRONICS AND OPTICS
When the contact metal is formed, the natural oxide film must be removed without growing. However, at present, after removing the natural oxide film with a mixed solution of hydrofluoric acid and pure water, a contact metal is formed using a sputtering apparatus, and then a barrier metal is formed using a CVD apparatus. The semiconductor wafer is moved out in the air for each different process.

  However, since there is no technique for performing such a series of processes without releasing the reduced pressure state, the natural oxide film is not completely removed when the contact metal is formed, and contact failure is likely to occur.

  The present invention has been made in view of such a problem, and forms a refractory metal nitride serving as a barrier metal of a wiring at a low temperature and a low resistance, and in the reaction product chamber during film growth. An object of the present invention is to provide a method for forming a refractory metal nitride film capable of preventing adhesion and performing a process from removal of a natural oxide film to growth of contact metal and barrier metal under reduced pressure.

The above-mentioned problem is to form a refractory metal nitride film on a semiconductor substrate by chemical vapor deposition using a source gas containing an alkylamino compound of a refractory metal and a reducing gas containing hydrazine or a hydrazine alkyl compound. This is achieved by a method for forming a refractory metal nitride film comprising the step of activating the reducing gas.

In addition, the above-described problem is solved by chemical vapor deposition on a semiconductor substrate using a source gas containing an alkylamino compound of a refractory metal and a reducing gas containing an alkylamino compound or an alkyl azide compound. A method of forming a refractory metal nitride film for forming a nitride film, comprising the step of activating the reducing gas, is achieved.

  Alternatively, in the step of activating the reducing gas, the reducing gas is activated by bringing the semiconductor substrate to a temperature of 300 ° C. or more and 500 ° C. or less. To achieve.

  Alternatively, the step of activating the reducing gas is achieved by a method for forming a refractory metal nitride film, wherein the reducing gas is activated by plasma. Alternatively, the step of activating the reducing gas is achieved by a method for forming a refractory metal nitride film, wherein the reducing gas is activated by ultraviolet rays.

  Alternatively, before forming the refractory metal nitride film on the semiconductor substrate, the semiconductor substrate is exposed to hydrazine or a hydrazine alkyl compound gas to remove a natural oxide film on the surface of the semiconductor substrate. This is achieved by a method for forming a melting point metal nitride film.

  An embodiment of the present invention will be described below with reference to the drawings.

  (A) Description of First Embodiment of the Invention FIG. 1 is a schematic configuration diagram showing a thermal chemical vapor deposition (thermal CVD) apparatus used for growth of a barrier metal according to the first embodiment of the present invention.

  This thermal CVD apparatus includes a chamber 1 for growing a film, a mounting table 2 for mounting a semiconductor substrate with a built-in heater, and a first gas inlet 3 for introducing a source gas into the chamber 1. And a second gas inlet 4 for introducing a reducing gas into the chamber 1 and an exhaust port 5 connected to an exhaust mechanism (not shown) for exhausting the gas in the chamber 1.

  Next, a process of forming TiN as a barrier metal on a semiconductor substrate using the above-described thermal CVD apparatus is shown in FIGS. 2 (A) to 2 (D) and FIGS. 3 (A) to 3 (C). The description will be given with reference.

  Prior to the description of the growth of the barrier metal, the semiconductor substrate before the barrier metal is formed and the laminated structure thereon will be described.

  FIG. 2A is a cross-sectional view showing a state where a contact hole is formed in the interlayer insulating film covering the MOSFET.

On the upper surface of the semiconductor substrate 11 made of p-type silicon, a field oxide film 12 made of SiO ₂ is formed to a thickness of 6000 mm by selective thermal oxidation. A MOSFET is formed in a region surrounded by the field oxide film 12. The MOSFET comprises a gate insulating film 13 made of SiO ₂ having a thickness of about 100 Å formed on the surface of the semiconductor substrate 11 by thermal oxidation, and a polysilicon film having a thickness of about 2000 さ れ grown thereon by a CVD method. It has a gate electrode 14 and n + -type S / D region layers 15a and 15b formed on the semiconductor substrate 11 on both sides of the gate electrode 14 by ion implantation.

The S / D region layers 15a and 15b are formed by, for example, implanting arsenic (As) into the semiconductor substrate 11 at a dose of 4 × 10 ¹⁵ / cm ² and an acceleration energy of 30 KeV, and activating the regions at 850 ° C. is there.

  Further, the gate electrode 14, the S / D region layers 15a and 15b, and the field oxide film 12 are covered with an inter-layer insulating film 16 made of a silicon oxide film having a thickness of 5000 mm, and are formed on the S / D region layers 15a and 15b. Contact holes 17a and 17b are formed.

  The semiconductor substrate 11 on which such a MOSFET is formed is mounted on the mounting table 2 of the CVD apparatus, and the temperature of the semiconductor substrate 11 is 600 ° C. or less, preferably 300 ° C. to 500 ° C. by the heater inside the mounting table 2. And heat to maintain the state. Further, the gas in the chamber 1 is exhausted through the exhaust port 5 and the inside thereof is decompressed.

Then, N ₂ gas as a carrier gas is bubbled through the Ti (N (CH ₃ ) ₂ ) ₄ liquid, which is an alkylamination product of Ti, at a flow rate of 10 sccm, and Ti (N (CH ₃ )) obtained thereby is passed through. ₂ ) A mixed gas of ₄ and N ₂ is introduced into the chamber 1 from the first gas inlet 3 as a source gas. At this time, the partial pressure of the source gas is about 40 mTorr, of which about 10 mTorr is the partial pressure of Ti (N (CH ₃ ) ₂ ) ₄ .

Further, dimethylhydrazine ((CH ₃ ) ₂ NNH ₂ ) gas as a reducing agent and a nitriding source is introduced into the chamber 1 from the second gas inlet 4 at a flow rate of 10 to 100 sccm. Since (CH ₃ ) ₂ NNH ₂ has a vapor pressure of about 150 Torr at room temperature (25 ° C.), it is directly supplied using an MFC (Mass Flow Controller).

  When such gas is introduced, the gas exhaust amount is adjusted to maintain the internal pressure of the chamber 1 at several tens mTorr to 1 Torr.

A carrier gas such as H ₂ may be introduced at a flow rate of about 10 to 1000 sccm, and this serves to assist reduction, but is not indispensable.

Under such conditions, in the chamber 1, (CH ₃ ) ₂ NNH ₂ is activated by the heating temperature and reacts with Ti (N (CH ₃ ) ₂ ) _4, and TiN, CH ₄ (gas) and H ₂ (gas) is generated. Thereby, TiN as a reaction product is deposited along the upper surfaces of the S / D region layers 15a and 15b, the inner peripheral surfaces of the contact holes 17a and 17b, and the upper surface of the interlayer insulating film 16, and the remaining CH ₄ and H ₂ becomes a gas at normal temperature and is exhausted from the exhaust port 25.

  This state is maintained for a predetermined time, and as shown in FIG. 2B, a TiN film 18 that is a refractory metal nitride is formed on the semiconductor substrate 11 to a thickness of about 400 mm.

  Next, as shown in FIG. 2C, an Al film 19 is deposited on the TiN film 18 by a PVD method such as sputtering to a thickness of about 5000 mm. Subsequently, the two-layer film of the TiN film 18 and the Al film 19 is patterned using the same mask to form S / D electrodes 20a and 20b drawn from the S / D region layers 15a and 15b.

  Subsequently, as shown in FIG. 2D, after forming an interlayer insulating film 21 such as PSG, via holes 21a and 21b are formed on the S / D electrodes 20a and 20b.

  Next, as shown in FIGS. 3A and 3B, a TiN film 22 having a film thickness of about 400 mm and an Al film having a film thickness of about 5000 mm are formed by the same formation method as the TiN film 18 and Al film 19 described above. 23 bilayer films are formed.

  Subsequently, as shown in FIG. 3C, the TiN film 22 and the Al film 23 are patterned by lithography to form Al wiring layers 24a and 24b connected to the S / D electrodes 20a and 20b. Thereafter, although not particularly illustrated, a wiring pad, a protective insulating film, and the like are formed to complete the semiconductor device.

As described above, in the first embodiment of the present invention, Ti (N (CH ₃ ) ₂ ) ₄ which is an alkylaminated product of Ti is used as a source gas containing a refractory metal element. A TiN film 18 is formed on the substrate by a CVD method using a gas containing (CH ₃ ) ₂ NNH ₂ gas, which is an alkylamino compound, as the reducing and nitriding gas.

At this time, in addition to TiN as a reaction product, it only generates an alkyl compound, nitrogen and hydrogen gas that are in a gaseous state at room temperature. Like the conventional technique using TiCl ₄ and NH ₃ gas, Nothing like NH ₄ Cl, which becomes solid at room temperature, is produced. Since CH ₄ gas and H ₂ gas are exhausted from the exhaust port 5 of the chamber 1, unnecessary reaction products are not deposited on the inner wall of the chamber 1, and a heater for sublimating the reaction products is added to the CVD apparatus. There is no need to add.

  In addition, by using the source gas and the reducing gas as described above, activation can be performed both thermally and at about 300 ° C., and the film forming temperature can be greatly lowered from the conventional 600 ° C. or higher. As a result, the thermal strain generated between the TiN film 22 and the Al films 19 and 23 formed above and below it is suppressed, and it is difficult for the S / D electrodes 20a and 20b and the Al wirings 24a and 24b to melt or hillock. Become.

In the above description, Ti (N (CH ₃ ) ₂ ) ₄ which is an alkyl aminated product of Ti is used as the source gas, but Ti (N (C ₂ H ₅ ) ₂ ) ₄ Also good. Other source gases containing Ti include alkoxides such as Ti (i-OC ₃ H ₇ ) ₄ and Ti (t-OC ₄ H ₉ ) ₄ or halogens such as TiCl ₄ , TiCl ₃ , TiCl ₂ and TiF _4. gas containing compound, or _{Cp 2 Ti (N 3) 2} , Cp may be used a gas containing ₂ cyclopentadienyl compound such as Ti.

However, since Cp ₂ Ti (N ₃ ) ₂ , Cp ₂ Ti, etc., which are cyclopentadienyl compounds, are usually solid at normal temperature, they are sublimated at a temperature of about 200 ° C. and used after gasification.

Of these chemical formulas, i represents iso and t represents tarsal. Cp represents a cyclopentadienyl group and is abbreviated C ₅ H ₅ .

Further, as the reducing gas, in addition to (CH ₃ ) ₂ NNH ₂ , (CH ₃ ) HNNH ₂ , CH ₃ NH ₂ , (CH ₃ ) ₂ NH, (CH ₃ ) ₃ N, (C ₂ H ₅ ) Alkylamino compounds such as ₂ NH, (C ₂ H ₅ ) ₃ N, CH ₃ NHNH ₂ , and C ₆ H ₅ NHNH ₂ may also be used. In addition, a gas containing hydrazine N2H4 or a gas containing an alkyl compound of hydrazine may be used. Examples of the hydrazine alkyl compound include (CH ₃ ) HNNH ₂ and (CH ₃ ) ₂ NNH ₂ as described above. Furthermore, it can be an alkyl azide compound, such as (CH ₃ ) N ₃ or (C ₂ H ₅ ) N ₃ . These reducing gases also act as a nitriding source.

  In this embodiment, TiN is used as the barrier metal, but tungsten (W) or molybdenum (Mo) nitride may be used as the other refractory metal nitride. The source gas in this case is an alkyl amination product, alkoxide compound, halide, or cyclopentadienylation product of these refractory metals.

Next, the film formation rate, specific resistance, chlorine concentration, and step coverage when TiCl ₄ is used as the source gas and methyl hydrazine ((CH ₃ ) HNNH ₂ , hereinafter referred to as MH) is used as the reducing and nitriding gas will be described. To do. As a test, the pressure in the chamber was 100 mTorr, and TiN was grown in a temperature range of 400 to 700 ° C. FIG. 4 shows the growth rate when MH is used as the reducing agent and when NH ₃ is used.

The growth rate of TiN by MH reduction was an order of magnitude higher than that of NH ₃ reduction, and a growth rate of 800 Å / min was obtained when the growth temperature was 400 ° C. with an MH flow rate of 10 sccm. This shows that the reactivity of MH reduction is extremely higher than NH ₃ reduction.

Further, when the crystal structure of TiN grown by MH reduction was examined by X-ray diffraction, a typical NaCl type TiN crystal grew and preferentially oriented in the (200) plane, and the grain size of the crystal was 200. It was found to be ~ 260cm. TiN grew on the SiO ₂ film and preferentially oriented in the (200) plane. In addition, when forming on the Ti film by PVD method, it preferentially orients to the (111) plane.

FIG. 5 shows the relationship between the specific resistance and the growth temperature. The specific resistance decreased as the growth temperature increased, and TiN grown by MH reduction became 90 μΩ · cm at 500 ° C. In order to obtain an equivalent specific resistance by NH ₃ reduction, a high temperature of 700 ° C. or higher is required.

FIG. 6 shows the relationship between the chlorine concentration in the TiN film and the growth temperature. The chlorine concentration in TiN grown by NH ₃ reduction is 3.3 atomic% at a growth temperature of 500 ° C., whereas MH. In TiN grown by reduction, it became 0.18 atomic% at the same growth temperature.

This shows that MH gas can sufficiently reduce TiCl ₄ and reduce the residual chlorine concentration. The chlorine concentration decreases with the upper layer of the growth temperature, and considering the results shown in FIG. 5, the specific resistance is considered to decrease as the residual chlorine concentration decreases.

When the chlorine concentration is lowered, the corrosion of aluminum formed thereon is reduced. The corrosion is observed after washing with water. Therefore, TiN was formed by MH reduction, an aluminum film was laminated thereon, and after microscopic observation after washing with water, no corrosion of the aluminum surface was observed. On the other hand, according to NH ₃ reduction, it is necessary to increase the growth temperature to 550 ° C. or more and reduce the chlorine content in order to eliminate corrosion.

Incidentally, when the source gas is reduced by NH ₃ to form TiN, corrosion of aluminum occurs at the interface between the interlayer insulating film and the aluminum film. This is thought to be because chlorine in the TiN film diffuses into the water that permeates into the interface during washing.

  With regard to step coverage, when TiN produced by MH reduction was grown to a thickness of 1700 mm, it was found that a contact hole of 0.2 μmφ and an aspect ratio of about 2.6 was completely embedded, and the coverage was also good. . It has also been confirmed that the leakage current is as large as before.

  The above-described refractory metal nitride is similarly applied to the case where a hole formed in the insulating film is buried.

  (B) Description of Second Embodiment of the Invention FIG. 7 is a block diagram of a CVD apparatus for forming a refractory metal nitride according to the second embodiment of the present invention.

  FIG. 7 differs from FIG. 1 in that there is means for applying a high-frequency voltage to the parallel plate electrodes as means for activating the reducing gas.

  In the reaction chamber 31 of the CVD apparatus, a mounting table 32 for mounting a semiconductor substrate, a gas introduction port 33 for introducing a source gas into the reaction chamber 31, and an exhaust port 35 connected to an exhaust device (not shown) are provided. Have.

  A plasma chamber 36 is connected on the reaction chamber 31, and these spaces are partitioned by a mesh-like ion trap portion 37 that prevents the plasma from entering the reaction chamber 31.

  Further, a gas introduction port 34 for introducing a reducing gas is provided inside the plasma chamber 36, and a pair of electrodes 38a and 38b are arranged around the outside thereof, and an electric field is applied between the electrodes. When applied, the reducing gas in the plasma chamber 36 is activated. One electrode 38b is connected to a high-frequency power source 39 for supplying a high-frequency voltage having a frequency of 13.46 MHz, and the other electrode 38a is grounded.

  Then, a reducing gas introduced into the plasma chamber 36 is activated by applying a high frequency voltage between the two electrodes 38a and 38b. In this case, since the reducing gas is activated by the plasma, the substrate can be sufficiently grown even when the substrate heating temperature by the heater built in the mounting table 31 is 500 ° C. or less.

  Also in such a CVD apparatus, as in the first embodiment of the present invention, as a source gas containing a refractory metal element, an alkylaminated product, alkoxide product, halide or cyclopentadienylated product of a refractory metal is used. A gas containing an alkylamino compound or an alkyl azide compound, or a gas containing hydrazine or an alkyl compound thereof is used as a reducing agent for reducing the source gas.

By such a reaction between the source gas and the reducing gas, a refractory metal nitride such as TiN and an alkyl compound that becomes gaseous at normal temperature, N ₂ and H _2, are generated. These gases are exhausted from the exhaust port 35 of the reaction chamber 31 and do not remain on the inner wall of the reaction chamber 31. The TiN is formed on the semiconductor substrate as in the first embodiment, and is used as a barrier metal for wiring.

  In this embodiment, the source gas and the reducing gas are used, and the reducing gas is activated by the electric field of the high frequency voltage. Therefore, the substrate heating temperature for obtaining TiN is in the range of 300 ° C. to 500 ° C. When the wiring layer is under the electrode, the thermal influence on the lower wiring layer is further reduced, and the occurrence of melt and hillocks in the aluminum wiring is suppressed.

Further, when NH ₃ is used as the reducing agent for the source gas and when the reducing agent of this example is used, the film forming rate is higher, the specific resistance is lower, and the chlorine concentration is higher. Is low and the step coverage is good.

  (C) Description of Third Embodiment of the Invention FIG. 8 is a block diagram of a CVD apparatus for forming a TiN film according to the third embodiment of the present invention.

  8 is different from FIG. 1 in that a mercury lamp that irradiates ultraviolet rays is used as means for activating the reducing gas.

  In the chamber 41 of the CVD apparatus, a mounting table 42 with a built-in heater for mounting a semiconductor substrate on which a film is grown, a gas inlet 43 for introducing a source gas into the chamber 41, and a reducing property in the chamber 41. A gas introduction port 44 for introducing gas, an exhaust port 45 for exhausting the gas in the chamber 41 connected to an exhaust device (not shown), and for irradiating the chamber 41 with ultraviolet rays to activate the reducing gas It has a mercury lamp 46 and a transmission window 47 that is formed in a part of the wall of the chamber 41 and transmits ultraviolet rays from the mercury lamp 45.

  In this CVD apparatus, the reducing gas and the source gas in the chamber 41 are activated by high energy ultraviolet rays generated when the mercury lamp 45 is turned on. By this ultraviolet irradiation, the substrate heating temperature is sufficient to be 500 ° C. or less.

  Further, as a source gas containing a refractory metal element introduced into the chamber 41, a gas containing an aluminide, alkoxide, halide or cyclopentadienylate of a refractory metal as in the first embodiment. In addition, as the reducing gas of the source gas, as in the first embodiment, an alkyl azide compound, a gas containing an alkylamino compound, a gas containing hydrazine or an alkyl compound thereof, etc. are used. A refractory metal nitride film to be a barrier metal is formed. This reducing gas also acts as a nitriding gas.

In this case, in addition to the refractory metal nitride as the reaction product, only an alkyl compound, N ₂ and H ₂ , which are gaseous at normal temperature, are generated, and these are formed on the inner wall of the chamber 41. Does not remain.

  Further, since the source gas and the reducing gas are activated by the high-energy ultraviolet rays using the reaction gas and the reducing gas described above, the substrate heating temperature for forming the barrier metal made of TiN is 300 ° C. to 500 ° C. When the temperature range is sufficient, and there is a wiring layer under the barrier metal, the thermal influence on the lower wiring layer is further reduced, and the occurrence of hillocks in the aluminum wiring is suppressed.

  The film formation rate, specific resistance, chlorine concentration, and coverage are similar to those of the first embodiment, and are optimal as a wiring barrier metal material for semiconductor devices.

  (D) Description of Fourth Embodiment of the Invention FIG. 9 is a cross-sectional view showing a process for manufacturing a semiconductor device of the fourth embodiment of the invention. In this embodiment, since the CVD apparatus shown in FIG. 1 used in the first embodiment is used, description of the CVD apparatus is omitted.

  A part of the cross section of the semiconductor substrate before TiN is formed as the barrier metal is in a state as shown in FIG. A field oxide film 12 is formed by a selective oxidation method in a portion surrounding the element formation region on the upper surface of the semiconductor substrate 11 made of p-type silicon, and a gate insulating film 13 and a gate electrode 14 of the MOSFET are formed in the element formation region. S / D region layers 15a and 15b are formed, and contact holes 17a and 17b for exposing the S / D region layers 15a and 15b are formed in the interlayer insulating film 16 covering them.

A natural oxide film (SiO ₂ ) 50 is grown on the surfaces of the S / D region layers 15a and 15b exposed from the contact holes 17a and 17b.

  In such a state, the semiconductor substrate 11 is put into the chamber 1 of the CVD apparatus as shown in FIG. 1 and the semiconductor substrate 11 is placed on the mounting table 2. This is followed by a pretreatment process for contact metal formation.

First, after reducing the pressure in the chamber 1 to 1 × 10 ⁻⁴ Torr or less, the semiconductor substrate 11 is heated by a heater built in the mounting table 2 to raise the substrate temperature in a normal temperature state to 400 to 700 ° C.

Next, when hydrazine (N ₂ H ₄ ) gas is introduced into the chamber 1 through the gas introduction port 4 at a flow rate of 100 sccm and the upper surface of the semiconductor substrate 11 is exposed to N ₂ H ₄ , S exposed from the contact holes 17a and 17b. The native oxide film (SiO ₂ ) 50 having a thickness of about 10 mm formed on the surfaces of the / D region layers 15a and 15b is removed as shown in FIG.

Note that the natural oxide film 50 can be removed from the substrate even if the substrate temperature is set to 400 ° C. and a hydrazine alkyl compound such as methyl hydrazine (MH) is flowed at a flow rate of 100 sccm for 60 seconds instead of N ₂ H ₄ .

It is considered that the natural oxide film 50 is removed in this way because active hydrogen radicals dissociated from N ₂ H ₄ reduce SiO ₂ .

  Next, the process of growing TiSi as a contact metal is started.

The temperature of the semiconductor substrate 11 is heated to 400 ° C. to 700 ° C., TiCl ₄ gas is introduced at 10 sccm, MH gas is introduced at 5 sccm, and Si ₂ H ₆ gas is introduced into the chamber 1 at a flow rate of 200 sccm. Is set to several tens of mTorr.

  Under this condition, TiSix grows at a growth rate of about 100 Å / min. By maintaining this state for a predetermined time, the upper surfaces of the S / D region layers 15a and 15b are maintained as shown in FIG. A TiSix film 51 is formed to a thickness of 100 mm along the inner peripheral surfaces of the contact holes 17 a and 17 b and the upper surface of the interlayer insulating film 16. In this case, the TiSix film 51 contains several ppm of nitrogen.

In addition to Si ₂ H ₆ , polysilane gas such as SiH ₄ or Si ₃ H ₈ may be used.

  Next, the process proceeds to a process of growing TiN as a barrier metal for wiring.

The semiconductor substrate 11 is heated to 400 to 500 ° C., and TiCl ₄ is introduced into the chamber 1 at a flow rate of 10 sccm and MH at 10 sccm. At this time, the pressure in the chamber 1 is set to 100 m Torr. Note that 100 sccm of NH ₃ may be added as a carrier and a nitrogen source.

  According to this condition, as shown in FIG. 10A, the TiN film 52 having a specific resistance of 100 μΩ · cm or less is formed on the S / D region layers 15a and 15b and the inner peripheral surfaces of the contact holes 17a and 17b. , Formed on the interlayer insulating film 16.

The chlorine concentration remaining in the TiN film 52 was reduced to 1/40 compared with the case where NH ₃ was used as the reducing agent. When the density of chlorine increases, the chlorine dissolves in the water during washing and causes corrosion of the Al film laminated on the barrier metal, but if the chlorine concentration drops significantly as in this example, the corrosion will occur. The possibility of is almost gone.

  After laminating such a barrier metal, the semiconductor substrate 11 is taken out from the CVD apparatus, and then, as shown in FIG. 10B, an Al film 53 is laminated to a thickness of about 5000 mm by sputtering.

  Then, the layers from the Al film 53 to the contact metal 51 are patterned by photolithography to form S / D electrodes 54 and 55. Thereafter, an interlayer insulating film 21 is laminated by a CVD method. Next, as shown in FIG. 10 (C), upper wirings 24a and 24b made of TiN / Al are formed. Details thereof have already been described in the first embodiment, and will be omitted.

The reducing gas may be other hydrazine alkyl compounds of MH or N ₂ H ₄ .

  According to the process as described above, the process from the step of removing the natural oxide film 50 on the surface of the S / D region layers 15a and 15b to the process of forming the TiN film 52 as a barrier metal is performed in the chamber 1 of the same CVD apparatus. Since the process is performed without breaking the vacuum state, the natural oxide film does not re-grow, and the throughput is improved. In addition, since a series of steps from the removal of the natural oxide film to the formation of the contact metal is performed at a low temperature of 600 ° C. or lower using hydrazine or a hydrazine alkyl compound, thermal strain generated between layers is reduced.

  When Ti is 60% or more of TiN serving as a barrier metal, Ti-rich TiN is formed at the interface between the silicon surface of the S / D region layers 15a and 15b and the TiN film 52. When annealing is performed for 10 seconds at a temperature of 450 ° C. or higher, for example, 600 ° C. without forming, a TiSix layer is formed at the interface. This eliminates the need for flowing polysilane to form the contact metal.

  Further, as the reaction gas, a source gas and a reducing gas as shown in the first embodiment may be used.

  With respect to the film forming speed, specific resistance, chlorine concentration, and coverage in this example, the same results as in the first example are obtained, which is optimal as a barrier metal material for wiring of a semiconductor device.

  (E) Description of Fifth Embodiment of the Invention In the fourth embodiment, barrier metal formation is performed from the removal of the natural oxide film in one reaction chamber, but the removal of the natural oxide film and the metal growth are performed separately. An example of such an apparatus is shown in FIG.

  The apparatus has two reaction chambers 61 and 62, and a vacuum transfer chamber 63 for transferring a semiconductor substrate in a reduced-pressure atmosphere is provided between the reaction chambers 61 and 62. The vacuum transfer chamber 63 is connected to a load chamber 64 and an unload chamber 65 for taking in and out the semiconductor substrate, and cassette stations 66 and 67 for storing the semiconductor substrate are connected to them.

  Note that, between the reaction chambers 61 and 62 and the vacuum transfer chamber 63, between the vacuum transfer chamber 63 and the load chamber 64, between the vacuum transfer chamber 63 and the unload chamber 65, and between the load chamber 64 and the first cassette station 66. Gate valves 67 to 73 are attached between the unload chamber 65 and the second cassette station 67, respectively. These gate valves 67 to 73 are opened and closed when the semiconductor substrate is moved, and the opening and closing thereof is omitted in the following description.

  Next, the process from the removal of the natural oxide film to the process of forming the barrier metal using the above-described apparatus will be described. In this embodiment, the growth conditions such as the type of gas, the growth temperature, and the growth film thickness are the same as those in the fourth embodiment, and the change in the stacked structure on the semiconductor substrate is as shown in FIGS. become.

  First, the semiconductor substrate 11 taken out from the first cassette station 66 by a transport system (not shown) is transported to the load chamber 64 and placed in an atmosphere where the pressure is reduced. The reaction chamber 61 is attached. The vacuum transfer chamber 63 and the reaction chamber 61 are in a reduced pressure state.

  In the first reaction chamber 61, hydrazine or a hydrazine alkyl compound is introduced, and the substrate temperature is set to 400 ° C. to 700 ° C. while the internal pressure is set to 100 mTorr.

When this state is maintained for a predetermined time, the natural oxide film (SiO ₂ ) 50 formed on the surfaces of the S / D region layers 15a and 15b as shown in FIG. 9A is removed.

  Next, after the semiconductor substrate 11 is taken out from the first reaction chamber 61 by a transfer system (not shown), the semiconductor substrate 11 is transferred into the second reaction chamber 62 through the vacuum transfer chamber 63.

In the reaction chamber 62, TiCl ₄ , MH and Si ₂ H ₆ are introduced and the substrate temperature is set to 400 to 600 ° C. as in the fourth embodiment. Thus, as shown in FIG. 9C, the TiSix film 51 as the contact metal is formed along the inner peripheral surfaces of the contact holes 17a and 17b, the surfaces of the S / D region layers 15a and 15b, and the upper surface of the interlayer insulating film 16. Form.

Next, the gas introduced into the second reaction chamber 62 is changed, TiCl ₄ and MH are introduced, and the semiconductor substrate 11 is heated to 400 ° C. to 500 ° C., thereby, as shown in FIG. Then, a TiN film 52 is grown as a barrier metal.

  Thereafter, the semiconductor substrate 11 is transferred from the second reaction chamber 62 to the vacuum transfer chamber 63 by the transfer system (not shown), and then transferred from the vacuum transfer chamber 63 to the unload chamber 65 in a reduced pressure state. Further, after closing the gate valve 73 between the unload chamber 65 and the vacuum transfer chamber 63, the inside of the unload chamber 65 is brought to normal pressure, and then the semiconductor substrate 11 is stored in the second cassette station 67.

  Thereafter, in the same manner as in the fourth embodiment, as shown in FIG. 10B, an Al film 53 is laminated on the barrier metal film 52 by sputtering, and then contact metal is formed from the Al film 53 by lithography. Patterns up to the film 51 are formed to form S / D electrodes 54 and 55 as shown in FIG.

In this embodiment as well, when Si ₂ H ₆ is not introduced to form a contact metal, the Ti content in the TiN film 52 is set to 60% or more and annealing is performed at a temperature of 450 ° C. or higher. TiSi is formed between the silicon surfaces of the / D region layers 15a and 15b and the TiN film 52.

  The source gas and the reducing gas used in this embodiment may be the same as those in the first embodiment, and the same results as in the first embodiment can be obtained with respect to the film forming rate, specific resistance, chlorine concentration, and coverage.

  As described above, according to the present invention, when the wiring electrode in contact with the silicon layer is formed, the refractory metal silicide film is provided under the refractory metal barrier metal. I can improve my contacts.

Further, according to the present invention, when growing a refractory metal nitride serving as a barrier metal, not only NH ₃ as a reducing and nitriding gas, but also a gas containing an alkyl azide compound, an alkylamino compound, a hydrazine, and a hydrazine alkyl compound Is used. According to this, when forming an aluminum wiring, a refractory metal nitride can be grown at a low temperature that does not cause melting or hillocks. Further, when the refractory metal nitride is generated, a product that becomes a solid at normal temperature is not generated by the reaction, and deposition of a product causing particles on the inner wall of the chamber can be suppressed. Furthermore, when using NH ₃ chlorine content of the refractory metal nitride film is reduced as compared with a reducing gas, can suppress corrosion of the aluminum film laminated on wiring electrode thereon, the TiCl ₄ Ti When used as a source, its coverage can be improved and its specific resistance can be reduced.

  According to another aspect of the present invention, since a natural oxide film is removed by supplying hydrazine or a hydrazine alkyl compound to the surface of the silicon layer in a reduced pressure atmosphere, the CVD film is continuously formed. It is possible to prevent regrowth of the natural oxide film.

  Furthermore, the removal of the natural oxide film, the growth of the refractory metal silicide film as the contact metal, and the growth of the refractory metal nitride film as the barrier metal are performed without breaking the vacuum state. Throughput can be improved.

  Furthermore, as a method of forming a refractory metal silicide on the surface of the silicon layer, the content of the refractory metal in the refractory metal nitride film formed on the silicon layer is increased to 60% or more, and a high melting point is obtained by a subsequent heat treatment. Since the refractory metal silicide is grown between the metal nitride film and the silicon layer, it is not necessary to introduce polycide when growing the refractory metal silicide, and the throughput can be improved.

It is a block diagram of the CVD apparatus used for formation of the TiN film | membrane which concerns on the 1st, 4th Example of this invention. It is sectional drawing (the 1) explaining the manufacturing method of the semiconductor device of the 1st Example of this invention. FIG. 6 is a cross-sectional view (No. 2) for explaining the method of manufacturing the semiconductor device according to the first example of the invention. It is a characteristic view which shows the growth rate of the TiN film which concerns on 1st Example of this invention, and the growth rate of the TiN film by a conventional method. It is a characteristic view which shows the specific resistance of the TiN film | membrane which concerns on 1st Example of this invention, and the specific resistance of the TiN film | membrane by the conventional method. It is a characteristic view which shows Cl concentration of the TiN film | membrane concerning 1st Example of this invention, and Cl concentration of the TiN film | membrane by the conventional method. It is a block diagram of the CVD apparatus used for formation of the TiN film concerning the 2nd example of the present invention. It is a block diagram of the CVD apparatus used for formation of the TiN film | membrane concerning the 3rd Example of this invention. It is sectional drawing (the 1) explaining the manufacturing method of the semiconductor device of the 4th, 5th Example of this invention. It is sectional drawing (the 2) explaining the manufacturing method of the semiconductor device of the 4th, 5th Example of this invention. It is a block diagram of the apparatus used for the process from the removal of the natural oxide film concerning the 5th Example of this invention to barrier metal film formation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 2 Mounting base 3, 4 Gas inlet 5 Exhaust 11 Silicon substrate (semiconductor substrate)
12 Field insulating film 13 Gate insulating film 14 Gate electrodes 15a and 15b S / D region layer 16 Interlayer insulating films 17a and 17b Contact metal 18 TiN film (refractory metal nitride)
19 Al film 20a, 20b S / D electrode 21 Interlayer insulating film 21a, 21b Via hole 22 TiN film (refractory metal nitride film)
23 Al film 24a, 24b Wiring layer 31 Reaction chamber 32 Mounting table 33, 34 Gas inlet 35 Exhaust port 36 Plasma chamber 37 Ion trap 38a, 38b Electrode 39 AC power source 41 Chamber 42 Mounting table 43, 44 Gas inlet 45 Exhaust port 46 Mercury lamp 47 Transparent window 50 Natural oxide film 51 TiSix film (contact metal)
52 TiN film (barrier metal)
53 Al film 54, 55 S / D electrode 61, 62 Reaction chamber 63 Vacuum transfer chamber 64 Load chamber 65 Unload chamber 66, 67 Cassette station

Claims (6)

Refractory metal nitridation using a chemical vapor deposition method to form a refractory metal nitride film on a semiconductor substrate using a source gas containing a refractory metal alkylamino compound and a reducing gas containing hydrazine or a hydrazine alkyl compound A method for forming a film, comprising:
A method of forming a refractory metal nitride film comprising a step of activating the reducing gas. 2. The refractory metal nitriding according to claim 1 , wherein in the step of activating the reducing gas, the reducing gas is activated by bringing the semiconductor substrate to a temperature of 300 ° C. or more and 500 ° C. or less. Method for forming a film.   2. The method of forming a refractory metal nitride film according to claim 1, wherein, in the step of activating the reducing gas, the reducing gas is activated by plasma.   2. The method for forming a refractory metal nitride film according to claim 1, wherein, in the step of activating the reducing gas, the reducing gas is activated by ultraviolet rays. 2. The natural oxide film on the surface of the semiconductor substrate is removed by exposing the semiconductor substrate to hydrazine or a hydrazine alkyl compound gas before forming the refractory metal nitride film on the semiconductor substrate. The method for forming a refractory metal nitride film according to any one of claims 1 to 4 . High melting point metal nitride film is formed on a semiconductor substrate by chemical vapor deposition using a source gas containing a high melting point metal alkylamino compound and a reducing gas containing an alkylamino compound or an alkyl azide compound. A method of forming a metal nitride film,
A method of forming a refractory metal nitride film comprising a step of activating the reducing gas.

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