Nonvolatile semiconductor memory device

Details Nonvolatile semiconductor memory device Nonvolatile semiconductor memory device

2001-06-14

2003-07-22

Thomas, Tom (Department: 2811)

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

C257S532000

Reexamination Certificate

active

06597029

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a capacitor of a nonvolatile semiconductor memory device that includes a ferroelectric film and the capacitor.
2. Description of the Background Art
A ferroelectric memory device is generally nonvolatile. Accordingly, even when no power is supplied, previously stored data is maintained. In the case that the ferroelectric memory device is sufficiently thin, spontaneous polarization is rapidly inverted, and thus read and write operations can be performed at a high speed such as in a DRAM.
In addition, one transistor and one ferroelectric capacitor can form a one-bit memory cell, thereby obtaining large capacity. Sr
x
Bi
2+y
Ta
2
O
9
(SBT) film and Sr
x
Bi
2+y
(Ta
i
Nb
1−i
)
2
O
9
(SBTN) film are examples of ferroelectric films used to form the ferroelectric capacitor.
FIG. 1
illustrates a conventional method for forming a capacitor using the SBT or SBTN film as a dielectric film. As shown in
FIG. 1
, a first interlayer insulation film
12
is deposited on a semiconductor substrate
11
where a node (not shown) has been formed. Thereafter, a glue layer
13
and a conductive layer
14
, or a storage electrode, are sequentially formed on the interlayer insulation film
12
. Preferably, the glue layer
13
consists of a Ti, TiN or TiOx layer, and the conductive layer
14
for the storage electrode consists of a Pt layer.
An SBT film
15
is deposited on the conductive layer
14
. A conductive layer
16
for a plate electrode is deposited on the SBT film
15
. Although not illustrated, additional processes are consecutively performed, thereby finishing formation of the capacitor.
This conventional method suffers from several drawbacks. For instance, the Ti of the glue layer
13
is rapidly diffused into the SBT or SBTN film
15
on the lower electrode
14
during a crystallization annealing process carried out in forming the capacitor, thereby deteriorating an electrical property of the capacitor.
In addition, the glue layer
13
is oxidized by oxygen flowing through the lower electrode
14
during the crystallization annealing process, and thus gaps are generated due to an increased volume. Moreover, voids and interface lifting are generated at the lower electrode
14
interface due to the re-crystallization of the lower electrode
14
and the fluidity caused during annealing. As a result, it is more difficult to form the capacitor.
SUMMARY OF THE INVENTION
Accordingly, at least two objects of the present invention are to provide a method for forming a capacitor of a nonvolatile semiconductor memory device which can prevent deterioration of the capacitor and to provide the capacitor.
In order to achieve the above-described object of the present invention, there is provided a method for forming a capacitor of a nonvolatile semiconductor memory device including the steps of: forming a first interlayer insulation film on a semiconductor substrate; forming a TaON film for a glue layer on the first interlayer insulation film; forming a lower electrode on the TaON film; forming an SBT or SBTN film for a ferroelectric film on the lower electrode; and forming an upper electrode on the ferroelectric film. In subsequent processing a second interlayer insulation film having a contact hole for contacting the upper electrode is formed and a metal film to fill up the contact hole is formed.
These and other objects are also achieved by providing a semiconductor device, comprising: a semiconductor substrate; a TaON glue layer formed over the semiconductor substrate; a lower electrode formed on the TaON glue layer; a ferroelectric film formed on the lower electrode; and an upper electrode formed on the ferroelectric film.


REFERENCES:
patent: 5874770 (1999-02-01), Saia et al.
patent: 6130103 (2000-10-01), Cuchiaro et al.
patent: 6229211 (2001-05-01), Kawanoue et al.

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