Semiconductor device manufacturing: process – Making passive device – Stacked capacitor
Reexamination Certificate
1999-04-20
2001-03-13
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Making passive device
Stacked capacitor
C438S734000, C438S735000
Reexamination Certificate
active
06200877
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor manufacturing field, more particularly, to a process of forming a charge storage electrode to which a selective hemispherical grains (HSG) silicon film is applied.
2. Background of the Invention
In general, there exists a problem in that a capacitance of more than certain amount must be maintained to secure operational characteristics of a semiconductor device regardless of the fact that an area of unit cell is reduced as degree of integration of semiconductor device such as DRAM, etc. is increased.
To solve such problem, charge storage electrodes of a variety of 3-dimensional structures were proposed and attempts were made to secure a surface area of the charge storage electrode, however, there were problems in that the process of forming the charge storage electrode involves a high degree of difficulty and induces a large step after completion of the process so as to make subsequent processes difficult. In another scheme of solution, attempts were made to secure the capacitance by using a high dielectric material such as Ta
2
O
5
, (Ba
1-X
Sr
X
) T
1 O
3
(referred to as BST), etc., however, there was a problem in that mass production was difficult since there were many insufficiencies related with processes to be solved to be applied to actual devices.
Recently, a technology for applying the hemispherical grains silicon film to the charge storage electrode has been proposed. This technology can be applied to a high integration semiconductor device of more than 256 mega class since it can increase the surface area of film by more than twice by indenting the surface of film by using a fine structure characteristics. A conventional process for forming the charge storage electrode having the hemispherical grains silicon film includes a process of growing the hemispherical grains silicon film on top of the entire structure of wafer to which a charge storage electrode contact hole is formed, a doping process, deglaze process and etch back process, however, there is a problem in that the productivity is reduced due to the increase of the number of processes, the occurrence of particle, etc..
To solve such problem, a technology for applying a selective HSG process in which the HSG silicon film grows only in a charge storage electrode formation region were proposed. This technology inevitably requires a dry etching process in a patterning process for defining the charge storage electrode and it was confirmed that kind of gas used in the dry etching process acts as a critical parameter which determines a selectibility of subsequent selective HSG process and size of grain. In particular, in case of using carbon halide gas (for example, C
2
F
6
, CF
4
, CHF
3
, CCl
4
, etc.), there are problems in that the HSG silicon film is not formed, or even if formed, it can not obtain an effect of expanding the surface area of the charge storage electrode since the grain size of HSG is very small. This is because carbon(C) component, contained in the carbon halide gas which is the dry etching gas used in patterning the charge storage electrode, acts as an element which obstructs the formation of a necessary for formation of HSG silicon film by remaining after the etching process in an amorphous silicon film surface and an interlayer insulation film in which the HSG silicon film is to be selectively formed or obstructs surface migration of silicon atom after formation of seed.
The accompanying
FIGS. 6
a
and
6
b
show Scanning Electron Microscope(SEM) photographs of a charge storage electrode having a selective hemispherical grains silicon film of simple stack structure formed according to the conventional technology described above. Condition of HSG silicon film growth in the top surface of charge storage electrode can be seen in
FIG. 6
a
and that in the side surface of charge storage electrode in
FIG. 6
b
. As shown in
FIG. 6
b
, the side surface of charge storage electrode is less affected by carbon component during etching so as to show some degree of grain size of HSG silicon film, however, as shown in
FIG. 6
a
, the top surface of charge storage electrode is affected by carbon component contained in carbon halide gas which is the dry etching gas so as to show unsatisfactory growth of grain of HSG silicon film.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method of forming a charge storage electrode having a selective hemispherical grains silicon film in a semiconductor device which can secure a sufficient capacitor effective surface area by obtaining desired grain size at the time of selective HSG silicon film formation.
The present invention prevents remaining of carbon component which obstructs the growth of HSG silicon film after dry etching process by limiting the carbon halide gas used in dry etching process of amorphous silicon film for defining the charge storage electrode at the time of process of forming the charge storage electrode having a selective hemispherical grains silicon film. That is, the present invention is a technology of etching a part of amorphous silicon film by using general carbon halide gas at the time of dry etching process of the amorphous silicon film for defining the charge storage electrode, and then, finally etching the remaining part of amorphous silicon film by using silicon etching gas such as SF
6
gas, Cl
2+O
2
gas, HBr gas, etc. not containing carbon component during selective etching of amorphous silicon film.
A method of forming a charge storage electrode having a selective hemispherical grains silicon film in a semiconductor device provided by the technical principle of the present invention comprises the steps of:
a first step of forming an amorphous silicon film on top of the entire structure of wafer to which contact holes are formed;
a second step of selectively etching a part of said amorphous silicon film by using a carbon halide gas as a main etching gas;
a third step of selectively etching the remaining part of said amorphous silicon film by using a silicon etching gas not containing carbon component; and
a fourth step of selectively forming a hemisphere grains silicon film at surface portion of said amorphous silicon film after performing the third step.
Also, a method of forming a charge storage electrode having a selective hemispherical grains silicon film in a semiconductor device comprising provided by the technical principle of the present invention comprises the steps of:
a first step of forming an amorphous silicon film on top of the entire structure of wafer to which contact holes are formed;
a second step of selectively etching said amorphous silicon film by using a silicon etching gas not containing carbon component as a main etching gas; and
a third step of selectively forming a hemispherical grains silicon film at the surface portion of said amorphous silicon film after performance of said second step.
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Sakai and Tatsumi, “Novel seeding method for the growth of polycrystalline Si films with hemispherical grains”, Applied Physics Letters, pp. 159-161, Jul. 13, 1992.
Han Il Keoun
Jeon Kwang Seok
Mun Jung Yun
Oh Hoon Jung
Shin Seung Woo
Hyundai Electronics Industries Co,. Ltd.
Malsawma Lex H.
Pennie & Edmonds LLP
Smith Matthew
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