Coating apparatus – Solid applicator contacting work – With work-handling or work-supporting
Reexamination Certificate
2000-03-02
2002-05-14
Nelms, David (Department: 2818)
Coating apparatus
Solid applicator contacting work
With work-handling or work-supporting
C118S063000, C118S259000, C118S266000, C427S349000, C427S428010, C427S432000, C438S003000
Reexamination Certificate
active
06387182
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for processing a substrate, and more particularly to an apparatus and a method for processing a substrate to form a thin film of high-dielectric or ferroelectric such as barium/strontium titanates, or a copper film for wiring on the substrate, or to etch the substrate.
2. Description of the Related Art
Recently, in the semiconductor manufacturing industry, the integration of integrated circuits has been improved remarkably, and the research and development activities of DRAM are being intensively carried out in anticipation of gigabit order DRAMs which will replace current megabit order DRAMs. The capacitor element having a large capacity per unit area is needed to produce such DRAMs. As a dielectric thin-film material for producing elements having such a large capacity per unit area, in place of silicon oxide or silicon nitride having a dielectric constant of less than 10, a metallic oxide film material such as tantalum pentaoxide (Ta
2
O
5
) having a dielectric constant of approximately 20, or barium titanate (BaTiO
3
) or strontium titanate (SrTiO
3
) or barium strontium titanate having a dielectric constant of approximately 300 is considered to be a promising thin-film material. Further, a ferroelectric material having a higher dielectric constant is also considered to be a promising thin-film material.
In addition to the above, as a wiring material, copper which has a value of resistance lower than aluminum and a superior resistance against electromigration is considered to be a promising material. As a material for gate insulating film, BiVO, Bi
4
Ti
4
O
12
, YMnO
3
, ZnO, ZnS, and CdS are considered to be promising materials. As an electrode material having a perovskite structure, SrRuO
3
, BaRuO
3
, IrO, and CaRuO
3
are considered to be promising materials. As a material for a barrier layer or a buffer layer, MgO, Y
2
O
3
, YSZ, and TaN are considered to be promising materials. As a superconductivity material, La—Ba—Cu—O, La—Sr—Cu—O, Y—Ba—Cu—O, Bi—Sr—Ca—Cu—O, Tl—Ba—Ca—Cu—O, and Hg—Ba—Ca—Cu—O are considered to be promising materials.
Processes for forming films of the above materials include plating, sputtering, chemical vapor deposition (CVD), and the like. The CVD process is expected to be most favorable for forming films as wiring having small widths.
FIG. 9
of the accompanying drawings shows a substrate processing apparatus (chemical vapor deposition apparatus) for forming a thin film of high-dielectric or ferroelectric such as barium/strontium titanates, on a substrate. The substrate processing apparatus (vapor deposition apparatus) comprises a vaporizer (gas generator)
120
for vaporizing a liquid material, a hermetically sealable reaction chamber (processing chamber)
124
disposed downstream of the vaporizer
120
and connected to the vaporizer
120
through a material gas passage
122
, and a vacuum pump
126
disposed downstream of the reaction chamber
124
and provided in an evacuation passage
128
. An oxidizing gas pipe
130
for supplying an oxidizing gas such as oxygen is connected to the reaction chamber
124
.
In the vapor deposition apparatus having the above structure, a substrate W is placed on a substrate holder
134
for holding and heating the substrate W, and a mixture of material gas and oxidizing gas is ejected over the substrate W from gas ejection ports
136
of a gas ejection head
138
while keeping the substrate W at a predetermined temperature, thereby depositing a thin film on a surface of the substrate W. In this case, it is necessary to supply the material gas stably to the substrate W in the reaction chamber
124
. The material gas is produced by liquidizing Ba(DPM)
2
, Sr(DPM)
2
or the like which is solid at room temperature, mixing the liquidized substance with organic solvent such as tetrahydrofuran (THF) for stabilizing vaporization characteristics, and vaporizing the obtained mixture by the vaporizer
120
.
When a plurality of organic metal materials are used to form a film, the substrate processing apparatus tends to suffer certain problems. Specifically, since the organic metal materials have their inherent vaporization temperatures and decomposition temperatures, a temperature range in which the organic metal materials can exist stably in their vapor phase is generally narrow. A simple organic metal material gas which is mixed with the organic solvent cannot vaporize if the organic solvent vaporizes earlier. Therefore, it is necessary to vaporize the organic metal material gas and the organic solvent at the same time. If the material gas is subjected to a temperature irregularity while it is being supplied to the substrate, then the material gas is liable to be condensed or decomposed, and the temperatures of some of the organic metal materials have to be controlled so as to be lower than the vaporization temperature of any one of the materials.
For example, it is assumed that an organic metal material A has a vaporization temperature T
KA
and a decomposition temperature T
DA
, and an organic metal material B has a vaporization temperature T
KB
and a decomposition temperature T
DB
. If T
KB
<T
KA
<T
DB
<T
DA
, then a temperature range in which the materials A, B can exist stably in their vapor phase is from T
KA
to T
DB
. If T
KB
<T
DB
<T
KA
<T
DA
, then in order to suppress decomposition of the organic metal material B, the process temperature needs to be controlled so as to be equal to or lower than the vaporization temperature of the organic metal material A.
The inventors of the present application have found that the film growth rate and the substrate temperature are related to each other as shown in
FIG. 10
of the accompanying drawings. As shown in
FIG. 10
, when the heater of the substrate holder heats the substrate W to a film growth temperature T
1
, the rate vs. temperature curve exhibits the reaction-limited in which the film growth rate increases in proportion to the substrate temperature until the film growth temperature T
1
is reached, and the supply-limited in which the film growth rate is substantially constant beyond the film growth temperature T
1
. The material gas is introduced into the reaction chamber at a low temperature that is substantially the same as the vaporization temperature in order to suppress reaction and decomposition of the material gas, and an oxidizing gas for reaction with the material gas is also introduced at the same low temperature. Therefore, the surface of the substrate is held at a temperature T
2
which is lower than the film growth temperature T
1
, with the result that the substrate processing apparatus cannot perform its maximum capability.
As semiconductor devices become more highly integrated, their structural details become finer, and a more uniform film needs to be deposited on their finer uneven surfaces. For example, as shown in
FIG. 11
of the accompanying drawings, when a thin film
142
of high-dielectric or ferroelectric is grown in a minute hole or trench
140
(in some case stack structure is also available) defined in the surface of a semiconductor substrate W, coverage characteristics including the ratio of a film thickness B on the bottom of the groove
140
to a film thickness A on the surface of the semiconductor substrate W, i.e., the ratio B/A (bottom coverage), the ratio of a film thickness C on a side of the groove
140
to the film thickness A, i.e., the ratio C/A (side coverage), and the ratio of a film thickness C
2
on an upper portion of the side of the groove
140
to a film thickness C
1
on a lower portion of the side of the groove
140
, i.e., C
2
/C
1
(side coverage uniformity), are required to be increased.
For increasing the above coverage characteristics, a film may be grown according to the reaction-limited of an Arrhenius' curve which represents the relation of the film growth rate and the reciprocal of the film growth temperature as shown in
FIG. 12
of the accompanying drawings. If a film wer
Abe Masahito
Araki Yuji
Fukunaga Yukio
Horie Kuniaki
Nakada Tsutomu
Berry Renee R.
Ebara Corporation
Nelms David
Wenderoth , Lind & Ponack, L.L.P.
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