Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1999-12-23
2001-01-23
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298070, C204S298330
Reexamination Certificate
active
06176980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sputtering method such as a magnetron sputtering method, which is one technique for forming thin films.
2. Description of Prior Art
The sputtering method is a method whereby a thin film is formed by generating a plasma, typically by creating a gaseous discharge in a low-vacuum atmosphere, making positive ions of the plasma collide with a target arranged on a negative electrode called a sputtering electrode, and thereby depositing sputtered particles produced by the collision on the substrate. This sputtering method is widely used in film deposition steps since it enables composition to be controlled and operation of the apparatus is comparatively simple.
FIG. 5
shows the layout of a prior art magnetron sputtering apparatus. In
FIG. 5
, a vacuum chamber
101
has an evacuation port
102
from which vacuum chamber
101
is evacuated by a vacuum pump (not shown). The evacuation port
102
has a main valve
104
, and a moveable valve
103
whereby the evacuation conductance can be adjusted. The vacuum chamber
101
further has a gas introduction pipe
105
and a gas flow rate controller
106
mounted on gas introduction pipe
105
. Electrical discharge gas
107
is introduced into vacuum chamber
101
from gas introduction pipe
105
; usually, argon gas is employed.
108
is a gas introduction valve.
A target
109
is held on a sputtering electrode
110
, that is connected to a discharge power source
111
and is provided with a magnet
112
arranged at the back face of target
109
. A substrate
114
on which a thin film is formed is placed on a substrate holder
113
opposite the substrate electrode
110
. An insulator
116
is mounted so as to isolate sputtering electrode
110
from vacuum chamber
101
.
Operation of the sputtering apparatus constructed as above will now be described. First of all, the interior of vacuum chamber
101
is evacuated to about 10
−7
Torr by means of a vacuum pump from evacuation port
102
. Next, discharge gas
107
is introduced into vacuum chamber
101
through gas introduction pipe
105
that is connected to one end of vacuum chamber
101
, while the pressure within vacuum chamber
101
is maintained at about 10
−3
to 10
−2
Torr. When negative voltage or high-frequency voltage is applied by DC or high-frequency discharge power source
111
to sputtering electrode
110
on which target
109
is mounted, by the action of the electric field produced by discharge power source
111
and the magnetic field produced by magnet
112
arranged at the back face of target
109
, a ring-shaped plasma is produced by the discharge in the vicinity of the front face of target
109
, giving rise to the sputtering phenomenon. The thin film is thus formed on substrate
114
arranged on substrate holder
113
by the sputtered particles that are discharged from target
109
.
However, in the conventional arrangement described above, since gas introduction into vacuum chamber
101
and evacuation from vacuum chamber
101
are both performed during the formation of the thin film, the pressure on the front face of target
109
becomes uneven. As a result, the distribution of sputtered particles discharged from target
109
is uneven, giving rise to the problem that the thickness of the thin film formed on substrate
114
cannot be made uniform.
SUMMARY OF THE INVENTION
The present invention was made in view of the above problems of the prior art, its object being to provide a sputtering method and apparatus whereby the film thickness on the surface of the substrate can be made uniform and symmetric.
In a sputtering method according to a first aspect of the present invention, a thin film is formed in a condition with the introduction of gas into the vacuum chamber cut off and evacuation of gas from the vacuum chamber cut off.
Thus, non-uniformity of pressure produced by gas currents within the vacuum chamber during thin film formation is eliminated, enabling the thin film deposited on the substrate to be made of uniform and symmetric film thickness.
In a sputtering method according to a second aspect of the present invention, a thin film is formed on a substrate whilst alternating between a condition in which deposition is effected with introduction of gas into the vacuum chamber cut off and evacuation from the vacuum chamber cut off and a condition in which gas is introduced into the vacuum chamber and evacuated from the vacuum chamber.
The same benefits as the first aspect of the invention can therefore be obtained and, in addition, symmetry of film thickness is ensured and stability of film properties is ensured even when the reactive sputtering method is employed or the film deposition time is long.
A sputtering apparatus according to the present invention comprises a controller for effecting opening and closing control of the main valve of the evacuation port and the gas introduction valve of the gas introduction pipe such that the main valve and the gas introduction valve are opened and closed at the same time during film deposition. The merits of the methods pertaining to the first and second aspects of the present invention can be made evident through the use of preferred embodiments.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.
REFERENCES:
patent: 5716500 (1998-02-01), Bardos et al.
patent: 5976334 (1999-11-01), Fu et al.
patent: 5997699 (1999-12-01), Leiphart
Posadowski et al., “Sustained self-sputtering using a direct current magnetron source”, J. Vac. Sci. Technol. A 11(6), 2980-2984, Dec. 1993.
Briesacher et al. “Advanced Semiconductor Manufacturing”, Nov. 1989.
Aokura Isamu
Hayata Hiroshi
Kimura Teiichi
Mori Nobuyuki
Yamamoto Masahiro
Matsushita Electric - Industrial Co., Ltd.
Nguyen Nam
Price and Gess
VerSteeg Steven H.
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