Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
1999-12-23
2002-04-09
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S398000, C438S964000
Reexamination Certificate
active
06368913
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method of manufacturing a semiconductor device and a semiconductor device manufactured by the method. More particularly, the present invention relates to an improved method of manufacturing a semiconductor device including capacitors, such as a DRAM (Dynamic Random Access Memory) device, and the like, in which each capacitor comprises a lower electrode having an HSG structure (Hemispherically Grained Structure) to increase electrostatic capacitance of the capacitor. The present invention also relates to a semiconductor device manufactured by such an improved method.
BACKGROUND OF THE INVENTION
In a semiconductor device including capacitors, such as a DRAM device and the like, it is required that each of the capacitors has relatively large capacitance while occupying a small area in the semiconductor device. In order to increase the capacitance of the capacitor, various structures of the capacitor and, especially, various structures and shapes of a capacitor electrode are devised.
FIG.
6
A through
FIG. 6C
are cross sectional views schematically showing various structures of a lower or inner electrode of a capacitor used in the DRAM device and the like. In each of
FIGS. 6A through 6C
, there is formed an interlayer insulating film
112
on a silicon substrate
111
. In the interlayer insulating film
112
, there is formed an opening
113
, and the opening
113
is filled with a contact plug portion
114
made of conductive material. The lower electrodes
101
through
103
, which have various shapes as shown in
FIGS. 6A through 6C
, respectively, are formed on the interlayer insulating film
112
such that the lower electrodes
101
through
103
are electrically coupled with the contact plug portion
114
. Although not shown in the drawings, an upper or outer capacitor electrode is formed via an insulating film on the surface of each of these lower electrodes
101
through
103
, thereby a capacitor is formed.
A box type or a simple stack type electrode
101
shown in
FIG. 6A
has a simple structure and is easy to manufacture. However, this structure has a disadvantage that the capacitance of the capacitor using the simple stack type electrode
101
is relatively small.
A cylinder type or a crown type electrode shown in
FIG. 6B
has a structure which is a little more complex than that of the simple stack type electrode
101
shown in FIG.
6
A. However, this electrode has a larger electrode area than that of the simple stack type electrode
101
shown in FIG.
6
A. Therefore, capacitance of the capacitor using the cylinder type electrode
102
can be approximately twice the capacitance of the capacitor using the simple stack type electrode
101
.
In order to further increase the capacitance of the capacitor, there is known an HSG cylinder (hemispherically grained cylinder) type electrode which is fabricated by forming HSG (hemispherical grain) or an HSG layer (hemispherically grained layer) on or at a surface of the cylinder type electrode.
FIG. 6C
illustrates an HSG cylinder type electrode
103
having an ideal HSG structure. In the HSG cylinder type electrode
103
, the area of the electrode is increased by the HSG layer formed at the surface thereof. The capacitance of the capacitor using the ideal HSG cylinder type electrode
103
is expected to become approximately 3.5 through 4 times of that of the capacitor using the simple stack type electrode
101
. A method of growing the HSG layer at a cylinder type structure is disclosed, for example, in Japanese patent laid-open publication No. 9-167833.
However, in the prior art method of fabricating an HSG cylinder type electrode
103
, it was difficult to properly grow the HSG both at an inner wall portion and at an outer wall portion of the cylinder type structure.
FIG.
7
A through
FIG. 7C
illustrate schematic cross sectional structures at various stages, in order of process steps, during a conventional process of fabricating an HSG cylinder type electrode.
As shown in
FIG. 7A
, an interlayer insulating film
112
, such as an oxide film and the like, is formed on a silicon substrate
111
. Thereafter, by using, for example, photolithography and etching, the interlayer insulating film
112
is selectively removed and a contact opening
113
is formed. The contact opening
113
is filled with doped polysilicon or doped amorphous silicon and thereby a contact plug
114
is formed.
Thereafter, on the contact plug
114
and on the interlayer insulating film
112
, a relatively thick silicon oxide film
115
is formed. Then, by using, for example, photolithography and etching, the silicon oxide film
115
is selectively removed and thereby an opening
116
is formed. In this condition, the top surface of the contact plug
114
is exposed via the opening
116
and at the bottom of the opening
116
. Next, a relatively thin phosphorus doped amorphous silicon film
117
is formed inside the opening
116
, i.e., on the inside bottom surface and on an inner side wall of the opening
116
, and on the silicon oxide film
115
, by using a thermal CVD method. Conventionally, taking the deposition rate or growth rate of a phosphorus doped amorphous silicon film into consideration, a deposition temperature or a growth temperature of the phosphorus doped amorphous silicon film of approximately
530
through
550
degrees Celsius is used in general. Thereby, the structure shown in
FIG. 7A
is obtained.
Thereafter, a recessed portion or trench
118
formed by the portion of the phosphorus doped amorphous silicon film
117
along the opening
116
is filled with coating glass not shown in the drawing. The phosphorus doped amorphous silicon film
117
is etched back. Then, the coating glass not shown in the drawing and the silicon oxide film
115
are removed by etching. Thereby, as shown in
FIG. 7B
, a cylinder structure
119
made of the remainder of the phosphorus doped amorphous silicon film
117
can be obtained.
The substrate having the structure of
FIG. 7B
is loaded into an HSG forming apparatus not shown in the drawing. The atmosphere around the substrate is depressurized, and silane gas is introduced around the substrate. Thereafter, the atmosphere around the substrate is evacuated and the substrate is heat treated. Thereby, HSG or an HSG layer
120
is grown at the surface of the cylinder
119
. As a result, an HSG cylinder type electrode
121
is fabricated as shown in FIG.
7
C.
However, as schematically shown in
FIG. 7C
, in the HSG cylinder type electrode
121
actually fabricated, at the inside wall surface, the HSG having an approximately expected shape is formed, but, at the outside wall surface, the HSG grows too much and unevenness becomes relatively small. Therefore, the outer wall surface of the HSG cylinder type electrode
121
actually fabricated by the conventional method becomes smoother than the inner wall surface.
The inventor of the present invention inspected the causes for such phenomenon, and found that the causes are as follows.
As shown schematically in
FIG. 7A
, when the phosphorus doped amorphous silicon film
117
is formed by using the thermal CVD method, crystalline nuclei
122
are produced in the phosphorus doped amorphous silicon film
117
near the interface between the phosphorus doped amorphous silicon film
117
and the silicon oxide film
112
and between the phosphorus doped amorphous silicon film
117
and the silicon oxide film
115
. Portions of the nuclei
122
are not removed at the etching process thereafter and are left in the phosphorus doped amorphous silicon oxide film
117
. Therefore, as shown schematically in
FIG. 7B
, the nuclei exist in the bottom surface portion and the outer wall portion
124
of the cylinder
119
, and do not exist in the inner wall portion
123
of the cylinder
119
. In the process of growing the HSG thereafter, the HSG grows preferentially from the nuclei
122
existing in the outer wall portion
124
of the cylinder
117
. Therefore, it is considered that, in the finally fabric
Kennedy Jennifer M.
Niebling John F.
Whitham Curtis & Christofferson, P.C.
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