Method of surface processing

Details Method of surface processing Method of surface processing

1998-12-10

2001-01-09

Beck, Shrive (Department: 1762)

Coating processes

Direct application of electrical, magnetic, wave, or...

Electromagnetic or particulate radiation utilized

C427S099300, C427S255280, C438S706000, C438S707000

Reexamination Certificate

active

06171662

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface processing device and a method of processing a surface. It particularly relates to a surface processing device and a method of processing a surface which contemplate improvement in processing a surface of an object to be processed.
2. Description of the Background Art
Conventionally in the process for manufacturing semiconductor devices, various types of surface processing are performed, typically including film forming and etching. The film forming process includes the CVD method and sputtering.
An example of a conventional plasma CVD system will now be described with reference to FIG.
5
.
A conventional plasma CVD system
300
has an electrode
306
and a holder electrode
308
contained opposite to each other within an evacuated container
304
which is evacuated by an evacuating device
312
. Holder electrode
308
is grounded. Mounted on holder electrode
308
is a substrate
302
to the surface of which film forming process is applied. Substrate
302
is heated, for example, by a heater
310
within holder electrode
308
.
A raw material gas
320
is introduced into evacuated container
304
via gas introducing portion
314
communicating with electrode
306
. As raw material gas
320
, SiH
4
(silane) +H
2
O is used, and recently, TEOS (tetraethoxysilane) +H
2
O or the like has come to be used in view of processing at lower temperature and for planarization of silicon oxide films.
In plasma CVD system
300
, gas introducing portion
314
is supplied with TEOS from a gas source
322
and H
2
O from a gas source
324
. Furthermore, mass flow controllers
326
and
328
are provided at supplying passages of TEOS and H
2
O, respectively, and a heater
330
for vaporizing TEOS is also provided at the TEOS supplying passage.
Radio frequency (RF) power is supplied to the space between electrode
306
and holder electrode
308
from an RF generator
318
via a matching box
316
. A continuous sign wave is used for the RF power and its frequency is generally 13.56 MHz.
In such a plasma CVD system, when raw material gas
320
as described above is introduced into evacuated container
304
to obtain a degree of vacuum, for example, of several hundred mTorr within evacuated container
304
while RF power is supplied to electrode
306
from RF generator
318
, RF electric discharge is generated between electrodes
306
and
308
, causing plasma
332
therebetween.
At that time, electrons are trapped in a blocking capacitor, which is generally contained in matching box
316
, so that electrode
306
is negatively charged. This causes positive ions in plasma
332
to accelerate toward and collide against electrode
306
and electrons are thereby generated to maintain plasma
332
.
Thus, due to plasma
332
, raw material gas
320
is activated and chemical reactions proceed whereby a silicon oxide (SiO
2
) film is formed on a surface of substrate
302
.
The reaction between the TEOS and H
2
O described above can be expressed by the following chemical formulas:
i) Si(OC
2
H
5
)
4
+H
2
O→Si(OC
2
H
5
)
4-n
(OH)
n
+C
2
H
5
OH  (hydrolysis reaction)
ii) Si(OC
2
H
5
)
4-n
(OH)
n
→SiO
m
(OH)
j
(OC
2
H
5
)
k
+H
2
O  (dehydrating condensation reaction)
iii) SiO
2
+H
2
O+C
2
H
5
OH
TEOS=Si(OC
2
H
5
)
4
silanol=Si(OC
2
H
5
)
4-n
(OH)
n
silicon polymer=SiO
m
(OH)
j
(OC
2
H
5
)
k
In the system of reaction between TEOS and H
2
O, silanol is first produced by the hydrolysis reaction expressed by chemical formula (i). Then, by the dehydrating condensation reaction expressed by chemical formula (ii), silicon polymer having an appropriate molecular weight is produced from the silanol as an intermediate. The silicon polymer adheres to a surface of an object to be processed and is fluidized to realize a planarized film formed on the substrate surface. Thereafter, as expressed by chemical formula (iii), the silicon polymer also dehydrates to produce SiO
2
and thus SiO
2
film is formed on the substrate surface.
However, in the reactions in the above plasma CVD system, since a chemical reaction is caused by electrons of several eV, the molecules of the raw material gases are decomposed into many kinds of molecules. This practically makes it difficult to selectively cause only the above desired reactions.
In forming a SiO
2
film by reaction between TEOS and H
2
O, it is important to produce silanol by reacting TEOS, the molecular structure of which is kept intact, with H
2
O maintained at high temperature.
However, while the decomposition of the new material gases by plasma partially excites reaction (i), Si and SiO produced by decomposition of TEOS directly reacts with O produced by decomposition of H
2
O, for example, causing a reaction dominantly producing SiO
2
, rather than silanol, as the intermediate. Thus, it is not practically ensured that the films formed are adequately planarized by silicon polymer.
Furthermore, in the above plasma CVD system, since silanol is less produced and SiO
2
in gas phase dominantly adheres to the substrate surface, flatness of the films cannot be achieved without keeping the substrate at a low temperature of at most 120° C. and restraining the dehydrating condensation rate of the silanol.
Thus, since a SiO
2
film thus formed on a substrate maintained at low temperature has not experienced adequate reaction, it contains a large amount of OH group and has shortcomings such as large leakage current and low dielectric strength.
Furthermore, when heat treatment (300° C.-400° C.) is performed after the film formation to improve film quality, volumetric shrinkage is caused and thus tensile stress is caused, resulting in cracks or the like in the film.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a surface processing device and a method of processing a surface capable of precisely controlling CVD reaction to form thin films with good step coverage, which is required, for example, for manufacturing semiconductor devices.
Another object of the present invention is to provide a surface processing device and a method of processing a surface capable of precisely etching a surface of an object to be processed in manufacturing semiconductor devices.
A surface processing device according to the present invention processes a surface of an object to be processed in an atmosphere under the atmospheric pressure. It includes: a first gas supplying passage disposed near the surface of the object to be processed for supplying a first gas insusceptible to heating by electromagnetic wave; a second gas supplying passage disposed near the surface of the object to be processed for supplying a second gas susceptible to heating by electromagnetic wave; and an electromagnetic wave generating unit disposed near the surface of the object to be processed for irradiating the first gas supplied from the first gas supplying passage and the second gas supplied from the second gas supplying passage with electromagnetic wave and selectively heating only the second gas to cause reaction between the first gas and the second gas, thereby processing the surface of the object to be processed.
Preferably, a plurality of the first gas supplying passages and a plurality of the second gas supplying passages are alternately provided. Still preferably, the electromagnetic wave generating unit is a microwave generating unit.
When a gas containing TEOS is used as the first gas and a gas containing H
2
O is used as the second gas in the above surface processing device, for example, it is possible to selectively heat only the second gas, H
2
O, near the surface of the object to be processed by microwave generated from the electromagnetic wave generating unit.
Thus, since dissociation of molecules of the first gas, i.e., TEOS, is hardly caused, it is ensured that the following reactions are caused:
i) Si(OC
2
H
5
)
4
+H
2
O→Si(OC
2
H
5
)
4-n
(OH)
n
+C
2
H
5
OH  (hydrolysis reaction)
i

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