Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – By reaction with substrate
Reexamination Certificate
1999-09-10
2001-03-20
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
By reaction with substrate
C438S758000, C438S785000, C257S632000
Reexamination Certificate
active
06204199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a film forming method in which a substrate is introduced into a reaction chamber having a gas feed port and a gas exhaust port, subjected to predetermined processing and taken out of the reaction chamber. More specifically, it relates to a film forming method in which nonuniformity or irregularities in a film formed on the substrate can be prevented by precluding film-forming gas components, which have been attached to the gas exhaust port and then evaporated therefrom as a film-forming gas, from flowing back to the reaction chamber.
Throughout the description which follows, the term “an exhaust port” refers to an exhaust port and its vicinity in which the exhaust port is connected with a reaction chamber or tube.
2. Description of the Prior Art
When thin layers or films are to be formed on a substrate, a film forming apparatus of a sheet-fed type has been used for example. The term “sheet-fed type”, used broadly herein, means that one or more sheets of substrates are simultaneously processed in a successive manner. As a concrete example of such a film forming apparatus, a description will be made of the formation of tantalum oxide (Ta
2
O
5
) films on a substrate. Generally, tantalum oxide films are formed by use of a chemical vapor deposition (CVD) process.
FIG. 5
is a schematic view showing an example of a conventional tantalum oxide film producing apparatus. Penta-ethoxy-tantalum in a liquid state is used as a raw material for tantalum oxide films. The penta-ethoxy-tantalum liquid is received in a tank
41
which is located in a thermostatic chamber
42
. The temperature of the tank
41
is controlled to a constant value such as, for example, 35 degrees C by means of the thermostatic chamber
42
. The interior of the tank
41
is pressurized by a nitrogen (N
2
) gas supplied thereto through a nitrogen feed pipe
48
to push out the penta-ethoxy-tantalum liquid into a material feed pipe
49
. The penta-ethoxy-tantalum liquid is then supplied from the material feed pipe
49
to a carburetor
43
, into which a nitrogen carrier gas is supplied from the nitrogen feed pipe
48
. The film-forming gas evaporated by the carburetor
43
is introduced, together with the nitrogen carrier gas, into a reaction chamber
45
through a feed pipe
44
. Simultaneously, an oxygen gas is also introduced from an oxygen tank (not shown) into the reaction chamber
45
, in which the penta-ethoxy-tantalum liquid is thermally decomposed to form a tantalum oxide film on the substrate. After the film formation, the atmosphere or gases in the reaction chamber
45
is exhausted by means of a discharge pump
46
through an exhaust pipe
47
.
In the prior art technology described above, in order to provide a uniform formation of a tantalum oxide film on a substrate, certain proposals have been made for the configuration of the reaction chamber
45
, an introduction recipe of the film-forming gas, an exhaust recipe thereof, etc.
For example, Japanese Patent Application Laid-Open No. Hei 7-94419 discloses a semiconductor processing apparatus in which a flat reaction tube is disposed in a heating space defined by a pair of parallel plate heaters, and a substrate to be processed is introduced into the flat reaction tube and subjected to a film forming processing therein. In this semiconductor processing apparatus, the flat reaction tube is provided at its opposite ends with gas feed ports and exhaust ports, so that during the film forming processing, the direction of flow of a reaction gas, which is supplied from the gas feed ports to the reaction tube and exhausted therefrom through the exhaust ports, can be changed arbitrarily.
FIG. 6
illustrates a reaction chamber or tube
51
and its related portions of the semiconductor processing apparatus as disclosed in the above reference. In this figure, an unillustrated substrate is horizontally disposed substantially in the center of the interior of the reaction tube
51
, and gas feed ports
52
,
53
and gas exhaust ports
54
,
55
are provided at opposite ends of the reaction tube
51
, the gas feed ports
52
,
53
being opposed with respect to the gas exhaust ports
54
,
55
, respectively, with the substrate being interposed therebetween. For example, a gas supplied from the gas feed port
52
passes through the reaction tube
51
substantially in parallel with the substrate to be exhausted from the gas exhaust port
55
, as indicated by an arrow in FIG.
6
. At this time, the gas feed port
53
and the gas exhaust port
54
are both closed by unillustrated valves, respectively, to interrupt the passage of the gas. With this conventional apparatus, the direction of the gas flow can be set reversely so that a gas is supplied from the gas feed port
53
to the reaction tube
51
and exhausted from the gas exhaust port
54
while closing the gas feed port
52
and the gas exhaust port
55
.
A conventional film-forming recipe for forming a tantalum oxide film on a substrate by use of the semiconductor processing apparatus as disclosed in the above-mentioned Japanese Patent Laid-Open No. Hei-94419 will now be described while referring to the accompanying drawings.
FIGS.
7
(
a
) through
7
(
c
) illustrate the various states of ventilation or gas flows in the reaction tube
51
from a stand-by state to the end of a substrate heating step. Here, note that the substrate heating step is to heat, prior to the formation of a film thereon, the substrate to a desired temperature by a heater (not shown) and to being a surface (i.e., film-forming surface) of the substrate into a uniform state. Preferably, the heater is an electric resistance heater, and it is preferred to employ a hot-wall type heating system in which the temperature of the reaction chamber is held at the desired temperature before the introduction of the substrate into the reaction chamber. The heater may, of course, be a lamp, a high frequency heater, and the like.
In these figures, note that the opening state and the closing state of each gas feed port and each gas exhaust port are indicated by a white circle (valve opening) and a black circle (valve closing), respectively; that the presence of two of white circles and/or black circles indicates the degree or extent of opening or closing of these ports; and that arrows with no symbols designate gas flows. Also, one of the gas feed ports and the gas exhaust ports provided at one end (e.g., at the left side of FIGS.
7
(
a
) through
7
(
c
)) of the reaction tube
51
is designated by the term “back-side”, and the other of the gas feed ports and the gas exhaust ports provided at the other end (e.g., at the right side of FIGS.
7
(
a
) through
7
(
c
)) of the reaction tube
51
is designated by the term “front-side”.
FIG.
7
(
a
) shows the flow of a gas in the apparatus of the stand-by state. In this stand-by state, valves
61
through
64
respectively opening and closing the ports
52
through
55
(see
FIG. 6
) are adjusted such that a nitrogen gas flows in a direction from the back-side feed port to the back-side exhaust port and further from front-side feed port to the front-side exhaust port. The gas passing the reaction tube
51
is discharged to the outside by means of a discharge pump (DP) through the exhaust pipe
47
. Here, note that the stand-by state means a state prior to the substrate introducing step in which a substrate is introduced into the reaction tube
51
. Also, though not illustrated, during the substrate introducing step, all the gas feed ports are closed by the corresponding valves
61
,
62
and all the gas exhaust ports are opened by the corresponding valves
63
,
64
so that the reaction tube
51
is exhausted or vacuum drawn by the discharge pump (DP) from the exhaust ports via the exhaust pipe
47
so as to keep the interior of the reaction tube
51
at a desired pressure.
FIG.
7
(
b
) shows the flow of a gas in the apparatus during the substrate heating step. In the substrate heating step, a nitrogen gas supplied from the back-side feed
Itatani Hideharu
Matsuyama Naoko
Nakamure Michihide
Sakai Masanori
Tsuneda Masayuki
Bowers Charles
Kilday Lisa
Kokusai Electric Co. Ltd.
McGinn & Gibb PLLC
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