Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Amorphous semiconductor
Reexamination Certificate
2001-08-30
2002-06-25
Lebentritt, Michael S. (Department: 2824)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Amorphous semiconductor
C438S485000, C438S487000, C438S715000
Reexamination Certificate
active
06410408
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CVD film formation method using high-density plasma.
2. Description of the Related Art
In addition to achieving a detailed pattern (hereinafter referred to as “micropattern”) for semiconductor integrated circuit elements, it has become essential to ensure that high-aspect ratio interwiring spaces are filled using interlayer insulating film without the generation of voids, or that interwiring capacitance is reduced using a low-dielectric constant film so that wiring delay is reduced. For this reason, a high-density plasma CVD (chemical vapor deposition) technique has become essential, by which method not only is it possible to perform film formation and Ar sputtering etching simultaneously, and to improve filling characteristics of the insulating film or the like, but an insulating film of high quality can also be formed which is doped with fluorine in order to obtain low dielectric constant.
FIG. 4
is a schematic cross-sectional view of a high-density plasma CVD device. This CVD device is a leaf-type CVD device in which semiconductor substrates are processed one at a time. An electrostatic chuck
3
is provided, whereon a semiconductor substrate
2
to be processed is placed, inside a reaction chamber
1
.
Components connected to this reaction chamber
1
are: a reactive gas supply line
4
; a cleaning gas supply line
5
; a main exhaust line
8
, which has a exhaust valve
6
placed thereon and which is connected to a dry pump
7
at one end; and a rough exhaust line
11
, which has a exhaust valve
9
and a throttle valve
10
placed thereon and which is connected to the dry pump
7
at one end on the side the throttle valve
10
is placed.
An applicator
12
, which changes cleaning gas to plasma, is placed on the cleaning gas supply line
5
. A throttle valve
13
, a gate valve
14
and a turbo pump
15
are placed on the main exhaust line
8
, between the reaction chamber
1
and the exhaust valve
6
, in this order from the reaction chamber
1
side. The turbo pump
15
is used since reactive gas can thus be exhausted in the course of the formation of a CVD film and, further, a considerable vacuum can thereby be achieved in the reaction chamber
1
, and also since a turbo pump currently constitutes the only means of fulfilling such conditions.
A process of forming a CVD film, which utilizes the above-mentioned high-density plasma CVD device, will be described hereinbelow with reference to the flow chart of FIG.
5
.
First of all, at #
400
, with the gate valve
14
of the main exhaust line
8
closed, while 1100 sccm of nitrogen trifluoride (NF
3
) is being introduced from the cleaning gas supply line
5
, the pressure in the reaction chamber
1
is controlled to be a high pressure of 3 Torr by way of exhaustion via the rough exhaust line
11
, which is at a low vacuum and is connected to the dry pump
7
, so that cleaning is performed inside the reaction chamber
1
. The path, along which NF
3
flows, runs in the following order; from the applicator
12
to the reaction chamber
1
, the exhaust valve
9
, the throttle valve
10
and the dry pump
7
.
Next, at #
401
a
, reactive gas, which is a mixture of monosilane (SiH
4
), oxygen (O
2
) and argon (Ar), is introduced from the reactive gas supply line
4
, and the pressure of the reaction chamber
1
is controlled to be 6 m Torr. In other words, with the exhaust valve
9
of the rough exhaust line
11
closed, reactive gas is introduced from the reactive gas supply line
4
, and, the gate valve
14
of the main exhaust line
8
is opened, the turbo pump
15
is driven, and by adjusting the speed of exhaustion by means of the throttle valve
13
and by way of exhaustion via the main exhaust line
8
, the above-mentioned pressure value is maintained. At this time, the rotation speed of the turbo pump
15
is 30000 rpm. Under these conditions, electrical power is applied to the reactive gas inside the reaction chamber
1
by a high-frequency power source (not shown in the figure) to produce high-density plasma, whereby a CVD film is formed on a semiconductor substrate
2
. The path, along which reactive gas flows, runs in the following order; from the reaction chamber
1
, the throttle valve
13
, the gate valve
14
, the turbo pump
15
, the exhaust valve
6
, and to the dry pump
7
.
Thereafter, at #
401
b
, similarly to #
400
, while 1100 sccm of NF
3
gas is being introduced from the cleaning gas supply line
5
, the pressure in the reaction chamber
1
is controlled to be 3 Torr by way of exhaustion to the rough exhaust line
11
, and cleaning is thus performed inside the reaction chamber
1
. The path, along which NF
3
flows, runs in the following order; from the applicator
12
to the reaction chamber
1
, the exhaust valve
9
, the throttle valve
10
and the dry pump
7
.
Further, steps #
401
a
and #
401
b
constitute one cycle for one semiconductor substrate
2
, therefore, by the repetition of 50 cycles, from #
402
a
, #
402
b
. . . to #
450
a
, #
450
b
, a CVD film is formed on fifty semiconductor substrates
2
.
However, a problem exists with the conventional CVD film formation method mentioned above in that, irrespective of whether cleaning of the reaction chamber
1
is performed using high-pressure NF
3
each time the formation of a film on one semiconductor substrate
2
is complete, a great many particles are produced that cause unsatisfactory formation of a micropattern on the semiconductor substrate
2
, and in that the yield of a semiconductor device is therefore dropped.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a CVD film formation method, as a means of resolving the above-mentioned problems, that is capable of reducing the production of particles which are the cause of unsatisfactory formation of a micropattern on a semiconductor, without causing a drop in productivity, and that is capable of improving the yield of a semiconductor device.
According to a research by the present inventor, et al., the production of particles is caused by the exhaustion of cleaning gas NF
3
via a rough exhaust line. This rough exhaust line is utilized to avoid a rise in temperature of a turbo pump as a result of flowing high-pressure cleaning gas in the main exhaust line that comprises this turbo pump, thereby to avoid deformation or the like of the blades of a turbo pump and occurrence of breakdowns thereof. However, because of this, no cleaning gas is made to flow in the main exhaust line, providing no opportunity to remove, by etching, reactants (mostly SiO
2
when the high-density plasma CVD film is an insulating film) which are accumulated within the gate valve and the turbo pump. This causes production of particles of the reactant which are then caused to adhere to the semiconductor substrate during the formation of a film.
For this reason, according to the present invention, in a state in which the cleaning-gas pressure is made low, or the rotation speed of the turbo pump is made low, cleaning gas is made to flow in the exhaust line that comprises the turbo pump such that the reactant adhered to this exhaust line may be removed.
In other words, the present invention is characterized in that upon forming a CVD film on a plurality of semiconductor substrates by using a CVD device that comprises a reaction chamber for forming a CVD film, a first exhaust line which is connected to the reaction chamber and does not include a turbo pump, and a second exhaust line which is connected to the reaction chamber separately from the first exhaust line and which includes a turbo pump, two processes are performed, namely, a first process, which is repeated a number of times that corresponds to a predetermined number of substrates, and which comprises: a step of introducing a semiconductor substrate into the above-mentioned reaction chamber to form a CVD film thereon and, removing the semiconductor substrate, whose film formation is completed, from the chamber, in
Lebentritt Michael S.
Parkhurst & Wendel L.L.P.
LandOfFree
CVD film formation method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with CVD film formation method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CVD film formation method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2920703