JP2611466B2 - Method of forming capacitive insulating film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a capacitive insulating film used for a semiconductor, and more particularly to a chemical vapor deposition method for forming a multilayer structure film including a capacitive insulating film and a conductive barrier film. About.

[Conventional technology]

As an important process technology in a VLSI memory of 64 Mbit DRAM or more, there is a method of forming a capacitor using a multilayer structure film of a high dielectric constant capacitance insulating film and a conductive barrier film. Conventionally, these high-dielectric-capacitance insulating films and conductive barrier films (hereinafter abbreviated as barrier films) are formed by using separate apparatuses and by the following method.

The tantalum oxide film, which is a high dielectric constant capacitance insulating film, is composed of tantalum pentaethoxide (Ta (OC ₂ H
₅ ) ₅ ) or tantalum pentamethoxide (Ta (OC
It is formed by a thermal chemical vapor deposition method using H ₃ ) ₅ ) and oxygen gas. FIG. 4 shows a schematic structural view of a chemical vapor deposition apparatus used in the conventional formation method.

Oxygen gas and argon gas for dilution are
6. The gas is introduced from the argon gas introduction pipe 5 into the quartz reactor 12a through the valves 15f and 15d. The organic tantalum gas is vaporized by the heater 7 in the vaporization chamber 6 by the heater 7, and the organic tantalum gas is introduced into the reaction furnace 12a through the valve 15g with the argon gas as the carrier gas. Argon gas as a carrier gas is introduced into the vaporization chamber 6 through a valve 15 from a carrier gas argon introduction pipe 1.
The reaction furnace 12a made of quartz is heated by the heater 8a,
The organic tantalum gas and oxygen gas introduced on the surface of the wafer 10 on the substrate holder 11 cause a chemical reaction to form a tantalum oxide film.

Here, as the conditions for the chemical vapor deposition of the tantalum oxide film, the heating temperature of the organic tantalum as a raw material by the heater 7 is 100 ° C.
The heating temperature in the reaction furnace 12a by the heater 8a is 200 to 600 ° C.
The flow rate of oxygen gas from the oxygen gas inlet pipe 16 is 0.1 to 5.0 SLM
(STD.LITER / MINUTE), flow rate of argon gas as carrier gas is 10 ~ 200sccm (std.cc/minute), pressure is 10 ~
Generally, it is performed at 10 ² Pa.

Unreacted gas not deposited on the wafer 10 is supplied to the reactor 12a.
Is exhausted to the exhaust port 14 by the vacuum pump 13.

On the other hand, as a method of forming a barrier film such as titanium nitride, a sputtering method is generally used.

[Problems to be solved by the invention]

In the above-described conventional method for forming a high dielectric constant capacitance insulating film by chemical vapor deposition and a barrier film by sputtering,
There are the following problems.

First, there is a problem in that the high dielectric constant capacitance insulating film and the barrier film are formed by different devices. After forming a high dielectric constant capacity insulating film by a chemical vapor deposition method, a wafer is carried in a process of forming a barrier film by a sputtering method. This transport contaminates the wafer surface with dust and particles. Therefore, a cleaning step for removing these contaminants is performed before the formation of the barrier film. However, there is a problem that a considerable amount of contaminants remains on the wafer surface.

In addition, as a conventional technology, a capacitive insulating film is formed on a polysilicon or silicon substrate, but a natural oxide film exists on the polysilicon or silicon substrate, and in a capacitive insulating film in a VLSI memory of 64 MDRAM or more, The existence of this natural oxide film cannot be ignored. Therefore, there is a problem that the natural oxide film must be removed.

Further, in the conventional method of forming a tantalum oxide film, for example, when an organic tantalum gas such as tantalum pentaethoxide or tantalum pentamethoxide and oxygen gas are used, a large amount of oxygen is taken into the tantalum oxide film as an impurity, A tantalum oxide film having many dangling bonds due to lack of oxygen other than stoichiometry and also having many pinholes is formed. A large amount of carbon is incorporated in these tantalum oxide films, and there are many dangling bonds due to lack of oxygen.Moreover, many tantalum oxide films have many pinholes. become.

On the other hand, the sputtering method, which is a conventional technique for forming a barrier film, has a problem that step coverage is poor. For this reason, it cannot be applied to an VLSI using fine design rules.

[Means for solving the problem]

The present invention provides a step of forming a tantalum oxide capacitance insulating film by a plasma chemical reaction, and a step of forming a conductive barrier film for suppressing a reaction due to a heat treatment between the substrate or the electrode and the tantalum oxide capacitance insulating film by a plasma chemical reaction. Are performed continuously in the same chamber to form a multilayer structure film including the tantalum oxide capacitance insulating film and the conductive barrier film.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic structural view of a chemical vapor deposition apparatus using a plasma chemical reaction according to one embodiment of the present invention. The procedure of a method for forming a two-layer structure film of a high dielectric constant capacitance insulating film and a barrier film using this apparatus is as follows.

First, an argon gas for dilution is supplied to an argon gas introduction pipe 5.
Then, the gas is introduced into the reaction chamber 12 through the valves 15d and 15e, and when the high-frequency power supply 9 is turned on, a plasma chemical reaction of the introduced argon gas occurs, and the natural oxide film on the substrate surface of each wafer 10 is removed.

Next, in the vaporization chamber 6 heated by the heater 7, the tantalum chloride (TaCl ₅ ) gas reacts through the valve 15e with the carrier gas argon gas introduced through the carrier gas argon introduction pipe 1 and the valve 15. The nitrous oxide (N ₂ O) gas is introduced into the chamber 12 and the nitrous oxide gas introduction pipe 2 and the valve 15
Introduced into the reaction chamber 12 through a and 15e. The substrate holder 11 is heated by the heater 8, and when the high frequency power supply 9 is turned on, a plasma chemical reaction of the introduced tantalum chloride gas and dinitrogen oxide gas occurs to form a tantalum film on each surface of the wafer 10. .

Unreacted gas not deposited on the wafer 10 is exhausted from the reaction chamber 12 to the exhaust port 14 by the vacuum pump 13.

In the above-described method of forming a tantalum oxide film, the film quality of the tantalum oxide film is improved by introducing a hydrogen (H ₂ ) gas into the reaction chamber 12 through the hydrogen gas introduction pipe 3 and the valves 15b and 15e during film formation. it can. This is because the introduced hydrogen gas causes a chemical reaction with the chlorine (Cl) in the tantalum chloride gas, which can reduce the amount of impurities such as chlorine contained in the tantalum oxide film as compared with the case where hydrogen is not used. is there.

As the growth conditions, the heating temperature of the vaporization chamber 6 and the tantalum chloride gas pipe by the heater 7 is 50 to 200 ° C., the heating temperature of the reaction chamber 12 by the heater 8 is 100 to 600 ° C., and the flow rate of the nitrous oxide gas is 0.1 to 5.0. SLM, the flow rate of argon gas as a carrier gas is 10 to 200 sccm, the pressure is 0.1 to 10.0 Torr, the flow rate of hydrogen gas is 0.1 to 3.0 SLM. 13.
It is suitable to operate at 56 MHz and power of 30 to 500 W, but other conditions may be used.

Note that tantalum fluoride (Ta) is used instead of tantalum chloride gas.
F ₅ ) Use oxygen (O ₂ ) gas instead of nitrous oxide gas
Nitrogen oxide (NO) gas may be used.

Next, a process of forming a tantalum oxide (Ta ₂ O ₅ ) film by the above-described method and then forming a barrier film in the same chamber will be described. Here, a procedure for forming a tantalum nitride film will be described.

First, tantalum chloride (TaCl ₅ ) gas in the vaporization chamber 6 heated by the heater 7 passes through the valve 15 e together with the carrier gas argon gas introduced through the introduction pipe 1 and the valve 15 of the carrier gas argon. Ammonia (NH ₃ ) gas is introduced into the ammonia gas introduction pipe 4, valve 15
It is introduced into the reaction chamber 12 through c and 15e. The substrate holder 11 is heated by the heater 8, and when the high-frequency power supply 9 is turned on, a plasma chemical reaction of the introduced tantalum chloride gas and ammonia gas occurs to form a tantalum nitride film on each surface of the wafer 10.

As the growth conditions, the heating temperature of the vaporization chamber 6 and the tantalum chloride gas pipe by the heater 7 is 50 to 200 ° C., the heating temperature of the reaction chamber 12 by the heater 8 is 100 to 600 ° C., the flow rate of the ammonia gas is 0.1 to 5.0 SLM, The flow rate of the argon gas as a carrier gas is 10 to 200 sccm, the pressure is 0.1 to 10.0 Torr.
It is suitable to operate at 50 kHz to 13.56 MHz and power of 30 to 500 W, but other conditions may be used.

Note that a tantalum fluoride gas may be used instead of the tantalum chloride gas, and a nitrogen (N ₂ ) gas may be used instead of the ammonia gas.

The tantalum nitride film formed by this method has significantly better step coverage than the conventional sputtering method.

When a titanium nitride film is formed by a plasma chemical reaction using titanium chloride (TiCl ₄ ) gas and ammonia gas as a barrier film, titanium chloride gas is used in place of tantalum chloride gas as a source gas, and the same method as described above is used. Formation is possible. Further, a titanium gas such as a titanium fluoride gas, a nitrogen (N ₂ ) gas, or the like may be used as a material gas.

FIG. 2 is a sectional view in the order of steps when this embodiment is applied to the production of a capacitance device.

First, as shown in FIG.
An O ₂ film 18 is formed, a contact hole is opened, and a capacitor polysilicon film 19 doped with phosphorus is deposited and formed.

Next, as shown in FIG. 2 (b), in the plasma enhanced chemical vapor deposition apparatus shown in FIG. 1, a natural oxide film existing on the capacitive polysilicon film 19 is removed using argon gas. A tantalum nitride film serving as the lower barrier film 20 is formed by a plasma chemical reaction using a tantalum chloride gas and an ammonia gas under the above-described growth conditions.

Next, as shown in FIG. 2C, following the formation of the lower barrier film 20, a plasma using a tantalum chloride gas and a nitrous oxide gas under the above-described growth conditions is formed on the lower barrier film 20. A tantalum oxide film to be the high dielectric constant capacity insulating film 21 is formed by a chemical reaction. Furthermore, the high dielectric constant capacitance insulating film 21
A tantalum nitride film serving as the upper barrier film 22 is formed thereon by a plasma chemical reaction using a tantalum chloride gas and an ammonia gas under the above-described growth conditions. Finally, a sample is taken out of the plasma enhanced chemical vapor deposition apparatus shown in FIG. 1, and a tungsten silicide film is formed as a plate electrode 23 on the upper phase barrier film 22.

Next, FIG. 3 shows a characteristic diagram relating to the TDDB of the device created based on this embodiment.

Here, the TD of a tantalum oxide film formed by a thermal chemical vapor deposition method using a conventional organic tantalum gas as a raw material is used.
DB characteristics are also shown. In the figure, the abscissa indicates the elapsed time (second), and the ordinate indicates the failure rate (%).

TDDB of capacitance device formed by applying this embodiment
The characteristics are superior to those of the capacitance device formed by the conventional method.

In the application example of the above-described embodiment, the high dielectric constant capacitance insulating film 21 is used.
Lower barrier film 20 and upper barrier film 2 of tantalum oxide film
Although a method of forming a tantalum nitride film as 2 was used, the same effect as shown in FIG. 3 can be obtained when a titanium nitride film is formed as a barrier film. Also plate electrode
23, a silicide film other than tungsten, a polysilicon film, a polycide film, a refractory metal film such as tungsten, or a laminated film of these may be used instead of the tungsten silicide film.

〔The invention's effect〕

As described above, in one embodiment of the present invention, a tantalum nitride film as a barrier film is formed by a plasma chemical reaction using a tantalum chloride gas and an ammonia gas. Forming a tantalum oxide film which is a high dielectric constant capacity insulating film by a plasma chemical reaction using nitrogen gas, or after forming the above dielectric constant capacity insulating film, subsequently, in the same chamber, titanium chloride gas and ammonia gas By forming a titanium nitride film which is a barrier film by a plasma chemical reaction using GaN, a multilayer structure film as a capacitance insulating film composed of a high dielectric constant capacitance insulating film and a barrier film is formed.

As a result, in the present invention, since the film formation method is performed in the same chamber, the contamination of the device surface by dust and particles accompanying the formation of the multilayer structure film as the conventional capacitor insulating film should be avoided. Can be. Further, in the present invention, a natural oxide film on the device surface can be removed by plasma chemical reaction of argon gas before film formation. Since the film formation method is a plasma chemical reaction, the step coverage of the barrier film and the like is good.

Furthermore, since carbon is not present in the components of the material gas used for the plasma chemical reaction, no carbon is present as a reaction product. Therefore, in the present invention, the occurrence of pinholes is reduced and the leakage current is prevented from increasing. Therefore, a highly reliable capacitance device having excellent TDDB characteristics can be realized.

From the above, it is clear that the present invention is a super LSI with fine design rules.
It becomes possible to apply to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic structural view of a plasma enhanced chemical vapor deposition apparatus used in one embodiment of the present invention, and FIGS. 2 (a) to (c) show one embodiment of the present invention. FIG. 3 is a characteristic view of a TDDB comparing a capacitance device according to an embodiment of the present invention with a capacitance device according to the prior art, and FIG. It is a schematic structure figure of a plasma chemical vapor deposition apparatus. DESCRIPTION OF SYMBOLS 1 ... Introduction pipe of carrier gas argon, 2 ... Nitrogen oxide gas introduction pipe, 3 ... Hydrogen gas introduction pipe, 4 ... Ammonia gas introduction pipe, 5 ... Dilution argon gas introduction pipe, 6
…… Vaporization chamber, 7,8,8a …… Heater, 9 …… High frequency power supply, 10
... wafer, 11 ... substrate holder, 12 ... reaction chamber, 12a ...
... Quartz reactor, 13 ... Vacuum pump, 14 ... Exhaust port,
15,15a, 15b, 15c, 15d, 15e, 15f, 15g ...... valves, 16 ...... oxygen gas introduction pipe, 17 ...... Si substrate, 18 ...... thermal SiO ₂ film, 19 ......
Capacitance polysilicon film, 20: Lower barrier film, 21: High dielectric constant capacitance insulating film, 22: Upper barrier film, 23: Plate electrode.

Claims (3)

(57) [Claims] 1. A step of forming a tantalum oxide capacitive insulating film by a plasma chemical reaction, and a step of forming a conductive barrier film by a plasma chemical reaction for suppressing a reaction between a substrate or an electrode and the tantalum oxide capacitive insulating film due to a heat treatment. And forming the multilayer structure film including the tantalum oxide capacitor insulating film and the conductive barrier film by performing the steps successively in the same chamber. 2. The method according to claim 1, wherein the plasma chemical reaction for forming the tantalum oxide capacitance insulating film is performed using a tantalum chloride (TaCl ₅ ) gas and a nitrous oxide (N ₂ O) gas. A method for forming a capacitive insulating film. 3. The method according to claim 1, wherein the conductive barrier film is formed of a tantalum nitride film, and a plasma chemical reaction for forming the tantalum nitride film is performed using a tantalum chloride ((TaCl ₅ ) gas and an ammonia (NH ₃ ) gas). 2. The method for forming a capacitive insulating film according to claim 1, wherein: