Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-03-29
2002-12-31
Wojciechowicz, Edward (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S296000, C257S300000, C257S301000, C257S306000, C257S379000
Reexamination Certificate
active
06501118
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device, a manufacturing method thereof and a method of forming a resist pattern used therein. More particularly, the present invention relates to a semiconductor device having a conducting material film formed in a trench, a manufacturing method thereof and a method of forming a resist pattern used therein.
2. Description of the Background Art
In the field of a DRAM (Dynamic Random Access Memory), which is conventionally known as one type of the semiconductor device, efforts have been made to increase capacity and miniaturize the device. Along with these efforts and achievements, to secure a capacity necessary for a capacitor cell, which is an element of a DRAM, within a limited area of a semiconductor substrate, three-dimensional cells such as a trench type cell or a stacked type cell have been developed. Among the stacked capacitor cells, those with vertically long shape such as a cylindrical type cell or a thick film type cell are mainly used.
FIGS. 17-19
show partial sectional views of a cylindrical stacked capacitor cell, on which the present invention is based and which is referenced for describing the manufacturing process of a lower electrode of a capacitor. With reference to
FIGS. 17-19
, the manufacturing process of the capacitor lower electrode of the cylindrical stacked capacitor cell will be described.
As shown in
FIG. 17
, a first interlayer insulation film
115
is formed on a semiconductor substrate (not shown). Openings
116
a
and
116
b
are formed in first interlayer insulation film
115
. Plugs
117
a
and
117
b
are formed respectively in openings
116
a
and
116
b
for electrically connecting the capacitor lower electrode and a conducting region in a main surface of the semiconductor substrate. A second interlayer insulation film
123
is formed on first interlayer insulation film
115
. Trenches
130
a
and
130
b
are formed in second interlayer insulation film
123
in regions above plugs
117
a
and
117
b
. Polycrystalline silicon film
119
is formed on second interlayer insulation film
123
as well as in trenches
130
a
and
130
b
. An HSG (Hemi Spherical Grained) polycrystalline silicon film
120
having a resist
127
formed thereon is formed on polycrystalline silicon film
119
. Here, HSG polysilicon film means a polysilicon film having roughened surface, and to roughen (roughening) refers to a process of generating hemispherical grains by growing crystal grains.
With etch back of resist
127
using Reactive Ion Etching (hereinafter referred to as RIE), portions
127
a
and
127
b
of resist are left in trenches
130
a
and
130
b
as shown in
FIG. 18
while resist
127
(see
FIG. 17
) is removed in other regions. Here, the level difference L
1
between an upper surface of HSG polycrystalline silicon film
120
on second interlayer insulation film
123
and an upper surfaces of resists
127
a
and
127
b
is called recess length. As will be described hereinafter, as portions
127
a
and
127
b
of resist are used as masks for removing polycrystalline silicon film
119
and HSG polycrystalline silicon film
120
on second interlayer insulation film
123
, the recess length L
1
must be controlled with a high precision. If the recess length L
1
is too small and the upper surfaces of resist portions
127
a
and
127
b
are higher than the upper surface of second interlayer insulation film
123
, problems arise. For example, upon etching for removing polycrystalline silicon film
119
and HSG polycrystalline silicon film
120
on the upper surface of second interlayer insulation film
123
, etching residue may be produced.
Then using resist portions
127
a
and
127
b
as masks, polycrystalline silicon film
119
and HSG polycrystalline silicon film
120
on the upper surface of second interlayer insulation film
123
are etched and removed. Thus a capacitor lower electrode of polycrystalline silicon film
119
a
and HSG polycrystalline silicon film
120
a
is formed in trench
130
a
and a capacitor lower electrode of polycrystalline silicon film
119
b
and HSG polycrystalline silicon film
120
b
is formed in trench
130
b
as shown in FIG.
19
.
Then resist portions
127
a
and
127
b
are removed and a dielectric film, a capacitor upper electrode and so on are formed on the capacitor lower electrode. The cylindrical stacked capacitor cell is thus formed.
The process shown in
FIGS. 17-19
has a following problem. When the resist is etched back by RIE to leave resist portions
127
a
and
127
b
only in trenches
130
a
and
130
b
as shown in
FIG. 18
, an oxide film or the like is sometimes partially formed on the surface of HSG polycrystalline silicon film
120
on the upper surface of second interlayer insulation film
123
. The oxide film thus formed through RIE serves as a mask upon etching of polycrystalline silicon film
119
and HSG polycrystalline silicon film
120
for isolating the capacitor lower electrode trench by trench. Therefore polycrystalline silicon film
119
of HSG polycrystalline silicon film
120
is sometimes partially left on the upper surface of second interlayer insulation film
123
.
When polycrystalline silicon film
119
or the like is left on the upper surface of second interlayer insulation film
123
, the capacitor lower electrode is not sufficiently isolated, and whereby a problem such as short circuit of the capacitor lower electrode is caused. As a result, operation failure and reliability degradation of the DRAM occur.
Alternatively, CMP (Chemical Mechanical Polishing) can be used for removing resist
127
(see
FIG. 17
) in the region outside trenches
130
a
and
130
b
for leaving resist portions
127
a
and
127
b
in trenches
130
a
and
130
b
. In this case, however, slurry used in CMP is left in the area such as an inner area of trenches
130
a
and
130
b
, and adversely affects the subsequent process steps. The slurry thus left in trenches
130
a
and
130
b
also causes operation failure and reliability degradation of the semiconductor device such as a DRAM.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a highly reliable semiconductor device having a conducting material film formed in a trench.
Another object of the present invention is to provide a method of manufacturing a highly reliable semiconductor device having a conducting material film formed in a trench.
Still another object of the present invention is to provide a method of forming a resist pattern which can be used in the method of manufacturing the highly reliable semiconductor device having the conducting material film formed in the trench.
In the method of manufacturing the semiconductor device according to one aspect of the present invention, an underlying film having an upper surface and a trench is formed. A conducting material film is formed on the upper surface and in the trench. A photo resist film is formed on the conducting material film which is located on the upper surface of the underlying film and in the trench. The photo resist film is left in the trench whereas in other region the photo resist film is developed and removed. With the photo resist film left in the trench used as a mask, the conducting material film on the upper surface of the underlying film is etched and removed.
Thus, an etching technique such as RIE which is used in a conventional manufacturing process is not employed in the step of leaving the photo resist film in the trench and removing the photo resist film in the region outside the trench. Therefore the formation of oxide film on the conducting material film caused by etching can be prevented. As a result, in the step of removing the conducting material film on the upper surface of the underlying film, the conducting material film is prevented from being partially left on the upper surface of the underlying film because of the existence of the oxide film. Thus, failure such as short circuit caused by the residual conducting material film can be avoided, w
Matsubara Hiroshi
Nakao Syuji
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