Ferroelectric capacitor of semiconductor device and method...

Details Ferroelectric capacitor of semiconductor device and method... Ferroelectric capacitor of semiconductor device and method...

1999-11-15

2002-01-15

Chaudhuri, Olik (Department: 2811)

Semiconductor device manufacturing: process

Having magnetic or ferroelectric component

C257S295000, C438S239000, C438S381000

Reexamination Certificate

active

06338970

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a semiconductor device; and, more particularly, to a ferroelectric capacitor of semiconductor device including ferroelectric thin film as a capacitor dielectric film. The present invention also relates to a method for fabricating the same.
DESCRIPTION OF THE PRIOR ART
Ferroelectric Random Access Memory (FeRAM) is a nonvolatile memory device using ferroelectric material such as (Sr,Bi)Ta
2
O
9
(SBT) and PbZr
x
Ti
x−1
O
3
(PZT), as capacitor dielectric material. It is promising because it memorizes its stored information even at the time of cutting off power supply and equals to the conventional Dynamic Random Access Memory (DRAM) in view of operating speed.
FIG. 1
is a sectional view showing a ferroelectric capacitor fabricated in accordance with the conventional method. A platinum film
11
for bottom electrode is formed with a thickness of 1500~3000 Å on a lower layer
10
formed by predetermined processes. 1500~3000 Å of a SBT thin film
12
and 1500~3000 Å of a platinum film
13
for upper electrode are then formed on the bottom electrode, in turn. The films are selectively etched to form a capacitor.
In the case of forming the SBT thin film
12
by sol-gel method or metallorganic material chemical vapor deposition, conventionally, spin coating or deposition, baking and rapid thermal process (RTP) of SBT precursor are performed, in turn, two or three times to form the SBT film with a desired thickness (1500~3000 Å ). The treated SBT film is furnace-annealed under oxygen atmosphere at 800° C. for 1 hour. Here, the RTP is to thermal-treat the SBT film under oxygen atmosphere at a temperature of 700~750° C. during short time (for example, 30 seconds to 2 minutes) in order to form fine crystalline nuclei of SBT from the amorphous SBT film
12
after the spin coating and baking. The furnace annealing process is to form the SBT film
12
with sufficient ferroelectric characteristics by growing the SBT crystalline grains to a size of 1000~2000 Å.
The crystalline structure of the SBT film
12
is a sandwich structure in which a (Sr,Bi)Ta
2
O
9
layer of perovskite structure is inserted between two Bi
2
O
3
layers. In the case of forming the SBT film
12
using the precursor such as metal 2-ethylhexanoate by sol-gel method or metallorganic chemical vapor deposition, the crystalline grain of the formed SBT film by a series of processes including spin coating or deposition, baking, RTP and furnace-annealing is rod-like crystal with 1000~2000 Å size. Therefore, there are some drawbacks that the surface of the SBT film
12
is very rough and the SBT film is not dense. Also, the roughness of the surface allows the SBT film to become thin locally, thereby, increasing leakage current and lowering breakdown voltage.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a ferroelectric capacitor of semiconductor device in which the surface roughness of the SBT thin film is lower and the film is denser (namely, the film quality is better) in comparison with the conventional SBT film.
It is another object of the present invention to provide a method for fabricating the same ferroelectric capacitor.
In accordance with an aspect of the present invention, there is provided a ferroelectric capacitor of semiconductor device, which comprises a conductive film for bottom electrode on a predetermined lower layer; a first (Sr,Bi)Ta
2
O
9
thin film made of crystalline grains of (Sr,Bi)Ta
2
O
9
, on the bottom electrode; a second (Sr,Bi)Ta
2
O
9
thin film made of crystalline nuclei of (Sr,Bi)Ta
2
O
9
, on the first (Sr,Bi)Ta
2
O
9
film; and a conductive film for upper electrode on the second (Sr,Bi)Ta
2
O
9
film.
In accordance with another aspect of the present invention, there is provided a method for fabricating a ferroelectric capacitor of semiconductor device, which comprises the steps of forming a conductive film for bottom electrode on a predetermined lower layer; forming a first (Sr,Bi)Ta
2
O
9
thin film made of crystalline grains on the bottom electrode; a second (Sr,Bi)Ta
2
O
9
thin film made of crystalline nuclei on the first (Sr,Bi)Ta
2
O
9
film; and forming a conductive film for upper electrode on the second (Sr,Bi)Ta
2
O
9
film.
The SBT thin film of the present invention has double layer structure, in which each layer is different in detail crystalline structure of the thin film from each other fabricated by the following method under different condition of thermal treatment. SBT precursor is spin-coated, baked, thermal-treated with RTP and furnace-annealed, in turn, to form a first SBT thin film made of conventional crystalline grain structure. On the first SBT film, SBT precursor with lower viscosity is then spin-coated, baked and thermal-treated with RTP, in turn, to form a second SBT thin film made of only crystalline nuclei. Therefore, the present invention can improve the surface roughness and quality of the SBT thin film.


REFERENCES:
patent: 5423285 (1995-06-01), Araujo et al.
patent: 5426075 (1995-06-01), Perino et al.
patent: 5519566 (1996-05-01), Perino et al.
patent: 5825057 (1998-10-01), Watanabe et al.
patent: 5831299 (1998-11-01), Yokoyama et al.
patent: 5877062 (1999-03-01), Horii
patent: 5902131 (1999-05-01), Argos et al.
patent: 6133051 (2000-10-01), Hintermaier et al.
patent: 6143597 (2000-11-01), Matsuda et al.
patent: 6150684 (2000-11-01), Sone
patent: 6172385 (2001-01-01), Duncombe et al.
patent: 6204158 (2001-03-01), Hendrix et al.
patent: 5-152962 (1993-06-01), None
patent: 08-340085 (1996-12-01), None
patent: 10-321809 (1998-04-01), None
patent: 10-172298 (1998-06-01), None
patent: 10-189886 (1998-07-01), None
patent: 10-1998-0058554 (2001-03-01), None

Affiliated with

Also associated with

Rating

Ferroelectric capacitor of semiconductor device and method... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Ferroelectric capacitor of semiconductor device and method..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ferroelectric capacitor of semiconductor device and method... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2872537