Method for cleaning PZT thin film

Details Method for cleaning PZT thin film Method for cleaning PZT thin film

1999-07-07

2002-05-21

Stinson, Frankie L. (Department: 1746)

Cleaning and liquid contact with solids

Processes

For metallic, siliceous, or calcareous basework, including...

C134S041000, C216S104000, C252S079300, C438S754000, C438S003000

Reexamination Certificate

active

06391119

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for cleaning a lead zirconate titanate (PZT) thin film using an etchant.
2. Description of the Related Art
A PZT thin film is a thin film having La, Sr, Ca, Sc, Nb, Ta, Ni, Fe or Er added to Pb(Zr
x
Ti
1−x
)O
3
. In manufacturing a semiconductor device such as a ferroelectric random access memory (FRAM) using the PZT thin film, the PZT thin film is degraded by various processes. According to the growth mechanism of a thin film, defects or components impediment to ferroelectric characteristics are concentrated on the surface of the PZT thin film. These materials are generally called a secondary phase materials, e.g., PbO or pyrochlore phase materials, which are paraelectric materials without ferroelectricity to thus degrade capacitor characteristics. Since the pyrochlore phase is thermodynamically weaker than a perovskite phase, it is liable to be damaged during integration, thereby accelerating degradation of capacitor characteristics. Also, during dry etching, layers damaged due to plasma are produced at the lateral surfaces of the PZT thin film. These layers directly connect an upper electrode and a lower electrode, and analysis thereof proves that they do not have crystallinity and the thicknesses thereof are 100 Å or less (please see Scanning Electron Micrograph (SEM) picture.) Also, they function as a leakage path due to their strong metallic characteristic.
FIG. 1
is a cross-sectional view of a ferroelectric capacitor manufactured by a conventional method without a cleaning process. As shown in
FIG. 1
, the conventional ferroelectric capacitor is constructed such that a PZT thin film
2
is formed on a lower electrode
1
and an upper electrode
3
is deposited on the PZT thin film
2
to then be etched in a predetermined dimension. Here, in the case of dry-etching the PZT thin film
2
, a thin etching damaged layer
4
due to plasma remains on lateral surfaces of the PZT thin film
2
, which increases leakage current.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a method for cleaning a PZT thin film, which improves ferroelectric capacitor characteristics by eliminating secondary phase crystals or etching damaged layers from the top surface or lateral surface of the PZT thin film generated during manufacturing of the same.
To achieve the first objective of the present invention, there is provided a method for cleaning a PZT thin film using an etchant comprising the step of submerging a PZT thin film in an etchant in combination of HF and acetic acid to etch the surface of the PZT thin film.
In the present invention, alcohol may be further added to the etchant in combination of HF and acetic acid. Preferably, the alcohol is at least one selected from the group consisting of methanol, ethanol and propanol. Instead of alcohol, a polar solvent which is at least one selected from the group consisting of DMSO, DMF, dioxane, THF, NMP, pyridine, CCl
3
H and CClH
3
may be used.


REFERENCES:
patent: 4181623 (1980-01-01), Dillarstone et al.
patent: 4759823 (1988-07-01), Asselanis et al.
patent: 5258093 (1993-11-01), Maniar
patent: 5418389 (1995-05-01), Watanabe
patent: 5496485 (1996-03-01), Maternagham
patent: 5714407 (1998-02-01), Maeno et al.
patent: 5976928 (1999-11-01), Kirlin et al.
Fabrication and Comparison of Ferroelectric Capacitor Structures for Memory Applications, Chee Won Chung, June Key Lee, et al., Integrated Ferroelectrics, 1997, vol. 16, pp. 139-147 (previously cited).
“Characterization and elimination of dry etching damaged layer in Pt/Pb(Zr0.53TI0.47)O3/Pt ferroelectric capacitor”, June Key Lee, et al., Applied Physics Letters, vol. 75, No. 3, Jul. 19, 1999, pp. 334-336.
Chee Won Chung, June Key Lee et al., Integrated Ferroelectrics, 1977, vol. 16, pp. 139-147 (to be provided).

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