Semiconductor device manufacturing: process – Having magnetic or ferroelectric component
Reexamination Certificate
1998-12-28
2001-03-20
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Having magnetic or ferroelectric component
C438S238000
Reexamination Certificate
active
06204070
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, more particularly to a method for manufacturing a ferroelectric capacitor.
DESCRIPTION OF THE PRIOR ART
The ferroelectric material has a large permittivity at room temperature and has multiple polarization states. One of the multiple polarization states can be selected depending on the applied electric field to the ferroelectric material. When a particular polarization state is set in a ferroelectric material, it is retained even when no power is further applied to the material. It is, therefore, possible to store a particular state in a non-powered device and then read the state at later time. In other words, the ferroelectric material can be used for implementation of a non-volatile memory element. Generally, for the ferroelectric material, there are two stable polarization states one of which corresponds to data “0” and the other corresponds to data “1”. Also, the ferroelectric material is in general formed as thin film between a top and a bottom electrode layers, which corresponds to a ferroelectric capacitor.
In conventional ferroelectric capacitor, there is a problem in that hydrogen or oxygen generated in the subsequent-processes may be introduced into the underlying ferroelectric capacitor material film, thereby making the composition of the ferroelectric material uneven. Thus, the conventional ferroelectric capacitor has such problems as fatigue and/or aging.
SUMMARY OF THE INVENTION
Accordingly, the present invention is addressed to solve the above problems. The object of the present invention is to provide a method for manufacturing ferroelectric capacitor which is capable of preventing hydrogen or oxygen atoms from being diffused into the ferroelectric material film, thereby eliminating the degradation of the characteristics of the ferroelectric capacitor.
According to one aspect of the present invention to achieve the above object, there is provided a method for manufacturing ferroelectric capacitor comprising the steps of: forming a bottom electrode over a semiconductor substrate; forming a ferroelectric material film over the bottom electrode; forming a diffusion barrier film over the ferroelectric material film using silicon nitride; opening a contact hole exposing a part of the ferroelectric material film by patterning the diffusion barrier film; and forming a top electrode coupled to the ferroelectric material film through the contact hole.
In one preferred embodiment, the diffusion barrier film comprises Si
3
N
4
or SiO
x
N
y
. The method preferably further comprises the step of forming a stress buffer film using silicon dioxide (SiO
2
), prior to the step of forming the diffusion barrier film using silicon nitride. In this case, the contact hole is made by patterning the diffusion barrier film and the stress buffer film. The silicon dioxide stress buffer film is preferably formed by PECVD. It is also preferable that the ferroelectric material film comprises SrBi
2-x
Ta
2
O
9-x
. The SrBi
2-x
Ta
2
O
9-x
ferroelectric material film is formed by spin coating method, MOCVD (Metal Organic Chemical Vapor Deposition), or LSMCD (Liquid source mixed chemical deposition) and its thickness is preferably 1000 Å-2500 Å. In addition, the bottom electrode is preferably composed of sequentially deposited Ti/TiN/Pt.
According to another aspect of the present invention, there is provided a method for manufacturing ferroelectric capacitor comprising the steps of: forming a bottom electrode over a semiconductor substrate; forming a ferroelectric material film over the bottom electrode; forming a first diffusion barrier film over the ferroelectric material film using TiO
2
; forming a second diffusion barrier film over the first diffusion barrier film using silicon nitride; opening a contact hole exposing a part of the ferroelectric material film by patterning the first and second diffusion barrier films; and forming a top electrode coupled to the ferroelectric material film through the contact hole.
In preferred embodiments, the second diffusion barrier film is formed at the temperature between approximately 650° C. and 800° C. using Si
3
N
4
. It is also preferable that the second diffusion barrier film is approximately 50 Å-500 Å in thickness. Alternatively, the second diffusion barrier film comprises SiO
x
N
y
.
The method may further comprise the step of performing a thermal rapid process, after the step of forming the first diffusion barrier film. It is also preferable that the first diffusion barrier film is approximately 400 Å-600 Å in thickness and it is formed by CVD(Chemical Vapor Deposition) or PECVD(Plasma Enhanced Chemical Vapor Deposition). When the first diffusion barrier film is formed by PECVD, the applied power is preferably 80W-200W. Also, the ferroelectric material film is preferably formed using PZT. The method may further comprises the step of forming a stress buffer film between the first diffusion barrier film and the second diffusion barrier film using silicon dioxide (SiO
2
), and the step of forming the contact hole is made by patterning the second diffusion barrier film, the stress buffer film and the first diffusion barrier film.
According to still another aspect of the present invention, there is provided a method for manufacturing ferroelectric capacitor comprising the steps of: forming a bottom electrode over a semiconductor substrate; forming a ferroelectric material film over the bottom electrode; patterning the ferroelectric material film and the bottom electrode; forming a stress buffer film over the patterned ferroelectric material film using silicon dioxide; forming a diffusion barrier film over the stress buffer film using silicon nitride; forming a contact hole exposing a part of the ferroelectric material film by patterning the diffusion barrier film and the stress buffer film; and forming a top electrode coupled to the ferroelectric material film through the contact hole.
In summary, according to the present invention, a silicon nitride film such as Si
3
N
4
or SiON film is formed over the ferroelectric material film. Also, as a stress buffer film, silicon dioxide (SiO
2
) film is formed under the silicon nitride film. In preferred embodiments, a silicon dioxide (SiO
2
) film and a silicon nitride (e.g. Si
3
N
4
or SiON) film are sequentially formed over the ferroelectric material film for SBT, whereas a TiO
2
film, a silicon dioxide (SiO
2
) film and a silicon nitride (e.g. Si
3
N
4
or SiON) film are sequentially formed over the ferroelectric material film for PZT.
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Blakely & Sokoloff, Taylor & Zafman
Elms Richard
Hyundai Electronics Industries Co,. Ltd.
Smith Bradley
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