Method of forming a charge-storage electrode of semiconductor device

This invention discloses a method of forming a charge-storage electrode of a semiconductor device by forming a platinum film at a side wall and top area of a polysilicon charge-storage electrode, in which the platinum film restrains a leakage current through a high dielectric film at the same time the capacitance can be increased.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method of forming a charge-storage electrode of 
a semiconductor device, and more particularly to a method of forming a 
charge-storage electrode, in which a leakage current through a high 
dielectric film can be restrained and capacitance can be increased by 
forming a platinum film at a side wall and top area of a polysilicon 
charge-storage electrode. 
2. Information Disclosure Statement 
As semiconductor devices are integrated, cell size is rapidly reduced 
accordingly. In spite of the reduction of the cell size, a certain amount 
of capacitance in a storage node is a necessity for the cell operation in 
a semiconductor device like a Dynamic Random Access Memory(DRAM). 
Therefore establishing an advanced process and high reliability in a 
device is needed to minimize the area which the capacitor occupies, while 
securing the minimum capacitance required for the cell operation. 
As a solution to fix this kind of problem, BST(Barium-Strontium Titanate) 
or PZT(Lead-Zirconium Titanate) is used for a high dielectric film. But in 
using these dielectric films having a high dielectric constant, stable 
metal like platinum which is non-reactive is required to maintain 
characteristics of low leakage current. References are made to FIG. 1 to 
show a prior art which uses to form a platinum charge-storage electrode of 
a semiconductor device. 
As shown in FIG. 1, a previous method of manufacturing a charge-storage 
electrode of a semiconductor device in a prior art, comprises: forming an 
insulating film(3) on a silicon substrate(1) having a junction region(2), 
etching the insulating film(3) so that the junction region(2) is exposed 
to form a contact hole for a charge-storage electrode, filling the inside 
of the contact hole with a polysilicon film(4), depositing a titanium film 
or a tantalum film as a barrier metal film(5) on the resulting structure, 
sequentially depositing a platinum film(6) on the barrier metal film(5), 
consecutively patterning a portion of the platinum film(6) and the barrier 
metal film(5) to form the charge-storage electrode, forming a high 
dielectric film(7) on the resulting structure. At this time, the high 
dielectric film(7) becomes in direct contact with the barrier metal film 
poor in electrical properties at the side wall of the charge-storage 
electrode so that it becomes the main reason for the leakage current. In 
addition, due to the fact that a thick platinum should be deposited to 
secure a high capacitance at a small charge-storage electrode on the 
plane, it may result in peeling problem of the platinum film or 
difficulties in etching process. 
SUMMARY OF THE INVENTION 
An object of the invention is that it provides a method of forming a 
charge-storage electrode of a semiconductor device to solve the above 
disadvantages by forming a platinum film at a side wall and top area of a 
polysilicon charge-storage electrode. To accomplish the object, the 
present invention, includes the steps of: forming an insulating film on a 
silicon substrate having a junction region; etching the insulating film so 
that the junction region is exposed to form a contact hole for a 
charge-storage electrode; sequentially depositing a polysilicon film, a 
first barrier metal film, and a first platinum film on the resulting 
structure; consecutively patterning a portion of the first platinum film 
and the first barrier metal film and the polysilicon film to form the 
charge-storage electrode; sequentially depositing a second barrier metal 
film and a second platinum film on the resulting film; sequentially 
blanket etching the second platinum film, the second barrier metal film to 
leave a spacer at the sidewall of the charge-storage electrode; and then 
etching the exposed area of the second barrier metal film to a 
pre-determined depth.

DETAILED DESCRIPTION OF THE INVENTION 
FIGS. 2A through 2F are cross-sectional views of the semiconductor device 
to illustrate the procedures of manufacturing a charge-storage electrode 
at successive steps in accordance with the present invention. 
In FIG. 2A, an insulating film(3) is formed on a silicon substrate(1) 
having a junction region(2) already made. Then to make a contact hole for 
a charge-storage electrode, the insulating film(3) is etched till the 
junction region(2) is exposed. After that, a polysilicon film(8) is 
deposited on the resulting structure, in which the polysilicon film(8) is 
in-situ phosphorus doped and its thickness should be fixed considering the 
total area of the side wall of the charge-storage electrode which effects 
the capacitance of the device. 
in FIG. 2B, a titanium film or a tantalum film is deposited to form a first 
barrier metal film(9) on the resulting structure. The first barrier metal 
film(9) is deposited of thickness of 100 through 300 .ANG.. And then a 
first platinum film(10) is sequentially deposited. After that, photo 
resist film(11) is coated and patterned using a mask for the 
charge-storage electrode. The first barrier metal film(9) restrains the 
diffusion between the first platinum film and the underlying polysilicon 
film(8) and used to promote the adhesion between the platinum film and the 
polysilicon film which has the property of poor adhesion. 
Sequentially etching a portion of the first platinum(10), the first barrier 
metal film(9) and the polysilicon film(8) using the photoresist film(11) 
as a mask, sequentially depositing a second barrier metal film(12) and a 
second platinum film(13) on the resulting structure after removing the 
photoresist film(11), in which argon sputtering may be done as a 
pre-treatment before depositing the second barrier metal film(12) to 
promote adhesion between films, are shown in FIG. 2C. Here the second 
barrier metal film(12) is deposited of thickness of 100 through 300 .ANG.. 
FIG. 2D illustrates that the second platinum film(13) and the second 
barrier metal film(12) are etched back using a blanket etch process, in 
which a portion of the second platinum(13) is left a thin spacer at the 
side wall of the charge-storage electrode. The role of the thin spacer is 
that it increases the effective area of the charge-storage electrode and 
promotes the step coverage in the following deposition step of a high 
dielectric film. 
FIG. 2E shows that a groove(indicated by "X" in FIG.) is formed at the both 
side walls of the first platinum film(10) and under the spacer of the 
second platinum film(13) formed by etching the exposed part of the second 
barrier metal film(12) of more than 500 .ANG. using a acidic or basic 
solution, in which the groove ("X") is used to prevent the electrical 
properties of a high dielectric film(14) from deteriorating due to the 
direct contact of the high dielectric film and the second barrier metal 
film(12) remaining between the first platinum film(10) and the second 
platinum film(13). 
In FIG. 2F, after forming the charge-storage electrode, the high dielectric 
film(14) and a plating polysilicon film(15) are sequentially deposited to 
form a capacitor. In depositing the high dielectric film(14), the inside 
of the groove is completely filled so that the deterioration of the 
electrical properties of the high dielectric film can be prevented. And 
also due to the first platinum film(10) formed on the top of the 
charge-storage electrode, and the thin spacer of the second platinum 
film(13) formed at the side wall of the charge-storage electrode, the high 
dielectric property and the low leakage current property can be 
maintained. Futhermore the use of the thin platinum film improves the 
peeling problem of the platinum film caused by stress and difficulty in 
etching. 
As described in detail, in accordance with the present invention, as 
platinum films are formed on the top and at the side wall of the 
polysilicon charge-storage electrode, the exposed area of the 
charge-storage electrode is increased and the effective surface area of 
the charge-storage electrode is also increased so that the resulting 
capacitance in the limited area can be maximized. And it has a dominant 
effect on the promotion of the electrical properties of the capacitor by 
preventing the deterioration of the high dielectric film. 
The foregoing description, although described in its preferred embodiment 
with a certain degree of particularity, is only illustration of the 
principle of the present invention. It is to be understood that the 
present invention is not to be limited to the preferred embodiments 
disclosed and illustrated herein. Accordingly, all expedient variations 
that may be made within the scope and spirit of the present invention are 
to be encompassed as further embodiments of the present invention.