Electric resistance heating devices – Heating devices – Vaporizer
Reexamination Certificate
2000-09-08
2003-01-28
Paik, Sang (Department: 3742)
Electric resistance heating devices
Heating devices
Vaporizer
C118S724000
Reexamination Certificate
active
06512885
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vaporizer for vaporizing a liquid raw material, a semiconductor device manufactured by using the vaporizer, and a method of manufacturing the semiconductor device by using the vaporizer. More particularly, the vaporizer is to be used for a CVD (Chemical Vapor Deposition) apparatus in the field of a semiconductor manufacturing apparatus.
2. Description of the Background Art
In recent years, the integration of semiconductor memories and devices has rapidly been enhanced in order to increase the processing speed of the device, to reduce power consumption and to cut down costs. However, even if the integration is enhanced, a capacitor to be a component of a DRAM (Dynamic Random Access Memory) requires a prescribed capacity. For this reason, it is necessary to reduce the thickness of a capacitor dielectric layer.
However, reduction in the film thickness of silicon dioxide (SiO
2
) which has been used as the capacitor dielectric layer has almost reached the limit. Consequently, vigorous studies and developments have been made to utilize a material having a high dielectric constant as the material of the capacitor dielectric layer and a metal material as the material of a capacitor electrode, in order to change the material of the capacitor dielectric layer to increase the dielectric constant. More specifically, tantalum oxide, lead zircon titanate (PZT), lead lanthanum zircon titanate (PLZT), strontium titanate (ST), barium titanate (BT), barium strontium titanate ((Ba, Sr) TiO
3
which will be hereinafter referred to as “BST”) and the like have been studied as the material having a high dielectric constant, and platinum (Pt), ruthenium (Ru) and the like have been studied as the metal material.
In order to form the thin films of the material having a high dielectric constant and the metal material on the pattern of a semiconductor device having a difference in height, it is the most advantageous that the film formation should be carried out by a CVD method having excellent attachment properties to a substance having a complicated shape. However, there is a big problem in that no material has stable and excellent vaporization characteristic for a CVD raw material to form a thin film having a high dielectric constant and a metal thin film.
Under the circumstances, the present inventors have proposed a CVD raw material in Japanese Patent Laying—Open No. 7-268634 in which a conventional solid raw material is dissolved in an organic solvent, that is, tetrahydrofuran (C
4
H
8
O, hereinafter referred to as “THF”) to remarkably enhance vaporization properties. However, even if a thin film having a high dielectric constant is formed with this raw material by using a conventional CVD apparatus for a liquid raw material, for example, for the formation of a SiO
2
film, good results cannot be obtained. Therefore, the present inventors have further proposed a CVD apparatus for a liquid raw material which can fully vaporize a liquid raw material to be supplied stably to a reaction chamber (Japanese Patent Laying—Open No. 8-186103).
FIG. 8
is a typical view schematically showing a solution vaporizing CVD apparatus for forming a thin film having a high dielectric constant which has been described in Japanese Patent Laying—Open No. Hei 8-186103. With reference to
FIG. 8
, the conventional CVD apparatus mainly has a liquid raw material vaporizer
101
, liquid raw material vessels
102
to
105
, a pressure pipe
106
, liquid raw material flow controllers
107
to
110
, a carrier gas supply pipe
111
, a carrier gas flow controller
112
, a connecting pipe
113
, an oxidant supply pipe
114
, a raw material gas transport pipe
115
, a transport pipe heater
116
, a reaction chamber
117
and a substrate heater
118
.
Each of the four liquid raw material vessels
102
to
105
is connected to the pressure pipe
106
, and is connected to the connecting pipe
113
through each of the liquid raw material flow controllers
107
to
110
. The carrier gas supply pipe
111
is also connected to the connecting pipe
113
through the carrier gas flow controller
112
.
The connecting pipe
113
is connected to a raw material supply pipe
123
of the liquid raw material vaporizer
101
. The raw material gas transport pipe
115
extended toward the reaction chamber
117
is connected to the liquid raw material vaporizer
101
. Moreover, the oxidant supply pipe
114
is provided to be extended toward the reaction chamber
117
. There are provided the transport pipe heater
116
for heating the raw material gas transport pipe
115
and a heater for heating the oxidant supply pipe
114
.
The substrate heater
118
for heating and holding a semiconductor substrate
119
is held in the reaction chamber
117
.
Next, the operation of a conventional solution vaporizing CVD apparatus will be described.
A carrier gas flows from the carrier gas supply pipe
111
to the connecting pipe
113
with its a flow rate adjusted by the carrier gas flow controller
112
. A solution raw material in the liquid raw material vessels
102
to
105
is pressurized by the pressure pipe
106
and the flow rate thereof is adjusted by the liquid raw material flow controllers
107
to
110
. Then, the solution material is supplied to the connecting pipe
113
and is sprayed into the liquid raw material vaporizer
101
.
The liquid raw material sprayed into the liquid raw material vaporizer
101
is vaporized in the liquid raw material vaporizer
101
. The vaporized gas (raw material gas) is supplied into the reaction chamber
117
through the raw material gas transport pipe
115
heated by the transport pipe heater
116
. The raw material gas reacts, in the reaction chamber
117
, with an oxidant supplied from the oxidant supply pipe
114
, and a thin film having a high dielectric constant or a metal thin film is formed on the semiconductor substrate
119
heated by the substrate heater
118
.
An organic solvent THF and a solution raw material are provided in each of the liquid raw material vessels
102
to
105
. The reaction chamber
117
is set at a pressure of approximately 133 Pa to approximately 1330 Pa in the O
2
atmosphere. A film is formed, with the heater set temperature of 400 to 600° C.
However, it has been found that a thin film having a high dielectric constant and a metal thin film cannot always be formed stably by using the solution vaporizing CVD apparatus. Actually, there have been the following problems. More specifically, foreign matters fall onto a semiconductor substrate (wafer), and a film forming rate, film properties (film composition and crystallinity) and electrical characteristics vary for each film formation.
The present inventors have investigated the cause. As a result, it has been found that the above-mentioned drawbacks are caused by a solid component such as an organic metal compound deposited from a liquid raw material in the liquid raw material vaporizer
101
, which will be specifically described below with reference to the drawings.
FIG. 9
is a sectional view schematically showing the structure of a conventional liquid raw material vaporizer. With reference to
FIG. 9
, the liquid raw material vaporizer
101
includes a vaporizer body
120
, an upper vaporizer cover
121
, a rod heater
122
and a raw material supply pipe
123
. The vaporizer body
120
and the upper vaporizer cover
121
constitute a vaporizing chamber, in which the rod heater
122
is embedded. The raw material supply pipe
123
for supplying a mixture of a liquid raw material and a carrier gas into the vaporizing chamber is connected to the upper vaporizer cover
121
. Moreover, the vaporizer body
120
is provided with a vaporizing chamber outlet for discharging the vaporized raw material. A raw material gas transport pipe
115
for introducing the vaporized raw material to a reaction chamber is connected to the outlet of the vaporizing chamber. A transport pipe heater
116
is provided around the vaporizer outlet portion and the raw material ga
Horikawa Tsuyoshi
Kawahara Takaaki
Tarutani Masayoshi
Yamamuka Mikio
Mitsubishi Denki & Kabushiki Kaisha
Paik Sang
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