JPH09283371A - Formation of thin film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the residual carbon concn. in a dielectric film by emitting a hydrogen plasma or that diluted with an inert gas e.g. Ar to a perovskite oxide thin film which forms a thin film capacitor. SOLUTION: An electron cyclotron resonance(ECR) generator 3 in a film- forming chamber 1 upper part generates an O2 plasma which reacts with other org. metal material fed from an injection nozzle 5 to form a perovskite oxide dielectric film on a substrate 2 heated at approximately 500 deg.C. A H plasma diluted with an inert gas e.g. Ar is irradiated on the substrate 2 held at approximately 50 deg.C to thereby reduce the residual C concn. in the dielectric film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film capacitor.

[0002]

2. Description of the Related Art Next-generation high-density DRAM of 1 Gbit or more
SrTiO ₃ , (Ba, Sr) Ti, which has excellent dielectric properties, insulating properties, and chemical stability for use as a capacitor film
Research and development of perovskite type oxide dielectric thin films such as O ₃ and (Pb, Zr) TiO ₃ have been conducted.

As a method for forming the oxide dielectric thin film, there are a sputtering method, a vapor phase growth method (CVD method), a sol-gel method and the like.
Since it is necessary to use the side area of the stack structure to realize a 1 Gbit DRAM, it is desired to establish a film forming technique by a CVD method having excellent step coverage.

Film formation of a perovskite type oxide dielectric by the CVD method, for example, (Ba, Sr) TiO ₃ (hereinafter, referred to as
In the case of BST), T. Kawahara et al., Material Research Society Symposium Proceedings, 361, 361, 1995 (TK
awahara et al. , Mat. Res. So
c. Symp. Proc. Vol. 361, 325 (1
995)) or Masaji Yoshida et al., Journal of Electrochemical Society, 142, 24.
P. 4, 1995 (Masaji Yoshida e
t al. , Journal of the Elec
trochemical Society Vol. 1
42, 244 (1995)). Generally, as a raw material for CVD film formation of BST, bis-dipivaloylmethanate barium (bis- (dipiva) is used.
loylmethanato) barium (Ba (D
PM) ₂ )), bis- (dipivaloylmethana)
to) trontium (Sr (DPM) ₂ )), tetraisopropoxytitanium (tetra-iso-
propoxytitanium (Ti (i-OC ₃ H
₇ ) ₄ )), titanyl bis dipialoy metalate (ti
tanyl bis (dipivaloylmetha
nato) (TiO (DPM) ₂ )) and O ₂ are used. The reports so far do not include a step of removing residual carbon in the film as a post-treatment after the BST film formation.

Although not by CVD film formation, in order to remove the residual carbon in the perovskite type oxide dielectric, it is particularly preferable to perform burnout in a hydrogen-containing atmosphere prior to firing the multilayer ceramic capacitor. Kaihei 4
-317309 and JP-A-5-90066.

[0006]

As described in the conventional example, a raw material containing an organic group is used in the CVD film formation of a perovskite type oxide dielectric thin film. Since a raw material containing such an organic group is used, there is a problem that carbon derived from the raw material remains in the formed film.

The first reason is that this causes an increase in the leak current of the dielectric film (Hisato Yabuta et al., Material Research Society Symposium Proceedings, 361, 325, 1995). Year (Hisato Yabuta et al., Ma
t. Res. Soc. Symp. Proc. Vol. 3
61, 325 (1995))).

Secondly, it has been reported that residual carbon in the BST film forms BaCO ₃ having high hygroscopicity, which increases the dielectric loss (tan δ) when operated as a capacitor ( Makita et al., Proceedings of 41st Joint Lecture on Applied Physics No. 2, 413 pages, 19
1994).

An object of the present invention is to remove residual carbon in a dielectric film, which causes increase of leakage current and dielectric loss, in a perovskite type oxide dielectric thin film formed by CVD to improve insulation and dielectric properties. An object is to provide an excellent perovskite type oxide dielectric thin film capacitor.

[0010]

A method of forming a thin film capacitor according to the present invention comprises a step of irradiating a perovskite type oxide thin film forming a thin film capacitor with hydrogen plasma or hydrogen plasma diluted with an inert gas such as argon. It is characterized by including.

As will be described in detail in the embodiments of the present invention, in the experiment by the author of the present invention, the CVD method (B
After the a, Sr) TiO ₃ film was formed, an experiment was conducted in which this wafer was exposed to a plasma atmosphere containing active hydrogen. As a result, the carbon concentration in the film was reduced to 1/10 of that in the case without plasma treatment. Was there. This is because a reaction occurs between active hydrogen and carbon in the film, and the carbon in the film is hydroca.
It is considered that it became an rbon and was detached.

From the viewpoint of mass productivity, it is desirable to obtain uniform characteristics on a large area substrate. From this experiment, it was found that the in-plane uniformity of the electrical characteristics when the plasma treatment was performed was improved as compared with the case where the plasma treatment was not performed. It is considered that this is because the reduction of the carbon concentration in the film by the plasma treatment was carried out uniformly in the plane.

By applying this method, the carbon concentration in the film is reduced, and as a result, it is possible to provide a thin film capacitor having high insulating and dielectric properties.

As mentioned in the prior art, CVD
Although not by film formation, it has been reported that burnout is performed in a hydrogen-containing atmosphere prior to firing of the multilayer ceramic capacitor in order to remove carbon residue in the perovskite oxide dielectric.

The first difference between this technique and the present invention is that the present invention is based on the CVD film formation, whereas the prior art is based on firing the raw material mixture.

The second difference is that, in the prior art, firing is performed in a hydrogen-containing gas, whereas irradiation with plasma containing hydrogen is performed. By irradiating with hydrogen plasma, compared to simply firing in a hydrogen-containing gas,
The following effects can be obtained. The first effect is that the efficiency of carbon concentration reduction is significantly improved. That is, a higher concentration of carbon can be removed with a lower hydrogen concentration than by firing in gas. The second effect is that the uniformity of carbon concentration removal in the plane is significantly improved. This is because the plasma containing hydrogen is uniformly irradiated in the plane.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION 【Example】

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS.

FIG. 1 shows an Electron Cyclotron Re used for explaining Example 1 of the present invention.
1 is a schematic view of a film forming chamber of a sonance (ECR) -CVD apparatus 1. FIG. O ₂ plasma 4 is generated from the ECR generation unit 3 in the upper part of the film forming chamber and reacts with another organometallic raw material introduced from the injection nozzle 5 to generate the substrate 2
A dielectric film is formed on top. The substrate temperature is controlled to 50 to 600 ° C. by radiant heating.

FIG. 2 is a sectional view of the same thin film capacitor. TiN on 6 inch Si substrate 9 by sputtering method
8 and RuO ₂ 7 were laminated to a film thickness of 50 and 200 nm, respectively. RuO ₂ is the lower electrode of the capacitor, TiN is Ru
This is a barrier layer that prevents the reaction between O ₂ and Si.

This wafer was introduced into the film forming chamber 1 of the (ECR) -CVD apparatus, and the perovskite type oxide dielectric (Ba, Sr) TiO ₃ 6 was heated to 500 ° C.
Of 30 nm was formed (Ba / (Ba + Sr) = 0.5).
Ba (DPM) ₂ , Sr (DPM) ₂ , T
i (i-OC ₃ H ₇ ) ₄ (hereinafter, TIP) and O ₂ were used. Ba (DPM) ₂ temperature is 200 ° C, flow rate is 70sc
cm, Sr (DPM) ₂ temperature is 190 ° C, flow rate is 70s
ccm, TIP temperature 36 ° C, flow rate 140 sccm
(Each carrier gas is argon), O ₂ flow rate is 1
40 sccm, plasma excitation microwave power is 750
W, deposition chamber pressure 1 Pa, deposition rate 1.0 nm / min
And

After forming the (Ba, Sr) TiO ₃ film, while maintaining the wafer temperature at 500 ° C., hydrogen plasma diluted with an inert gas such as argon (hydrogen flow rate: 10 sccm,
The wafer was irradiated with an argon flow rate of 130 sccm).
The plasma excitation microwave power was 750 W, and the plasma irradiation time was 5 to 10 minutes.

After plasma irradiation, the wafer is CVD
The film was taken out from the film forming chamber and annealed in an oxygen atmosphere (annealing temperature 400 ° C., annealing time 1 hour). This is done to compensate for oxygen deficiency in the film caused by the hydrogen plasma treatment.

After that, Ru10, which is an upper electrode, was deposited to a thickness of 300 nm by a sputtering method.

The thin film capacitor manufactured by the above steps has a relative dielectric constant of 160 and a leakage current density of 1 × 10.
^-8 (A / cm ² ) (at 1 V applied), tan δ = 1% or less, which is a good characteristic. SIMS (Ba, S
r) As a result of analyzing the carbon concentration in the TiO ₃ film, it was reduced to about 1/10 of that in the case where the plasma treatment was not performed.
In addition, when the in-plane distribution of the electrical characteristics of the 6-inch wafer was examined, the uniformity was within 3%, which was improved compared to the case where the plasma treatment was not performed (electricity when the plasma treatment was not performed). In-plane uniformity of characteristics is about 10
%).

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIGS. FIG. 3 is a sectional view of the thin film capacitor.

Thermally oxidized SiO ₂ (6
(00 nm) 9 in which a poly-Si plug 7 is formed, and TiN (50 nm) 4 and RuO are formed thereon by a sputtering method.
₂ (500 nm) 3 was laminated. The RuO ₂ / TiN structure was patterned by photolithography (pattern width was 0.4 μm) and processed into a stack electrode having a three-dimensional structure as shown by plasma etching.

This wafer was introduced into the film forming chamber 1 of the ECR-CVD apparatus, and the perovskite type oxide dielectric (Ba, Sr) TiO ₃ 6 was added to the film while heating the wafer to 500 ° C.
0 nm was formed (Ba / (Ba + Sr) = 0.5). Ba (DPM) ₂ , Sr (DPM) ₂ , TI
P and O ₂ were used. Ba (DPM) ₂ temperature is 200 ° C,
Flow rate is 70 sccm, Sr (DPM) ₂ temperature is 190
° C., the flow rate is 70 sccm, TIP temperature 36 ° C., the flow rate is 140 sccm (respectively, the carrier gas is argon), O ₂ flow rate 140 sccm, plasma excitation microwave power 750W, the deposition chamber pressure is 1 Pa, the deposition rate of 1. It was set to 0 nm / min.

Next, the wafer temperature is set to 80 ° C. and hydrogen plasma diluted with an inert gas such as argon (hydrogen flow rate: 1
The wafer was irradiated with 0 sccm and an argon flow rate of 130 sccm). Plasma excitation microwave power is 750
W and the plasma irradiation time were 5 to 10 minutes.

After plasma irradiation, the wafer is CVD
The film was taken out from the film forming chamber and annealed in an oxygen atmosphere (annealing temperature 400 ° C., annealing time 1 hour). This is done to compensate for oxygen deficiency in the film caused by the hydrogen plasma treatment.

After that, Ru (700 nm) 10 as the upper electrode was deposited by the sputtering method.

The thin film capacitor manufactured by the above method has a relative dielectric constant of 250 and a leakage current density of 1 × 10 ^-8 (A /
cm ² ) (at the time of applying 1 V) and tan δ was 1% or less, which is a good characteristic. (Ba, Sr) TiO by SIMS
As a result of analyzing the carbon concentration in the _three films, it was reduced to about 1/10 as compared with the case where the plasma treatment was not performed. In addition, when the in-plane distribution of the electrical characteristics of the 6-inch wafer was examined, the uniformity was within 3%, which was improved compared to the case where the plasma treatment was not performed (electricity when the plasma treatment was not performed). In-plane uniformity of properties is about 10%).

[0032]

According to the method of forming a thin film capacitor of the present invention, a step of irradiating a perovskite type oxide thin film forming a thin film capacitor with hydrogen plasma or hydrogen plasma diluted with an inert gas such as argon is included. As a result, the residual carbon concentration in the dielectric thin film is reduced.

As a result, the first effect is to provide a thin film capacitor excellent in insulation.

As a second effect, it is possible to provide a thin film capacitor having excellent dielectric characteristics.

As a third effect, the in-plane uniformity of electrical characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a film forming chamber of an ECR-CVD apparatus showing an embodiment of the present invention.

FIG. 2 is a sectional view of a thin film capacitor showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a thin film capacitor showing an embodiment of the present invention.

[Explanation of symbols]

1 Film-forming chamber of ECR-CVD apparatus 2 Substrate 3 ECR generation part 4 Plasma 5 Injection nozzle 6 Perovskite type oxide dielectric 7 Lower electrode 8 Barrier layer 9 Si substrate 10 Upper electrode 11 poly-Si plug 12 SiO ₂ layer

Claims (1)

[Claims] 1. A thin film comprising a step of irradiating a vapor-grown perovskite type oxide thin film forming a thin film capacitor with hydrogen plasma or hydrogen plasma diluted with an inert gas such as argon. Method of forming a capacitor.