Coating processes – With stretching or tensioning – Running lengths
Reexamination Certificate
1999-01-11
2001-07-17
McDonald, Rodney (Department: 1753)
Coating processes
With stretching or tensioning
Running lengths
C427S171000, C427S255500, C427S248100, C427S249300, C427S536000, C427S562000, C204S298050, C204S298240, C118S7230ER, C118S718000
Reexamination Certificate
active
06261634
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method of forming a thin film having small residual stress and good adhesion to a substrate having the film thereon.
BACKGROUND OF THE INVENTION
It is conventionally known that as methods of forming a thin film, typically, a sputtering method, an ionized vapor deposition method, etc. are used in the PVD field and a plasma CVD method is employed in the CVD field.
FIG. 1
shows a CVD apparatus using a high-frequency glow discharge of a capacitive coupled type. A high-frequency power system (
5
), a high-frequency power supply electrode (
1
), an opposed ground electrode (
2
), a substrate (
3
) having a surface on which a thin film is formed, and a plasma region (
4
) generated between the flat electrodes (
1
) and (
2
) installed in parallel are designated. This manner as shown in
FIG. 1
is to form a film using a self bias acting in the side of the substrate (
3
) installed in the side of the high-frequency power supply electrode (
1
).
Also,
FIG. 2
shows an inductive coupled CVD apparatus. In this manner as shown in
FIG. 2
, a plasma region (
4
) is formed by applying an induction energy from a coil (
6
) for high-frequency excitation and ions of a material activated in the plasma region are introduced into a filmy substrate (
3
) by an electric field from an auxiliary electrode for applying an external bias and a thin film is formed on the flexible substrate (
3
). Also, this manner is to move the filmy substrate sequentially by a cylindrical roller and a guide roller and form a thin film sequentially on the substrate (
3
).
When a thin film having a large compressive residual stress, typically such as a thin film of diamond-like carbon, is formed using the CVD apparatus as shown in
FIG. 1
, force by which the formed film is warped with the surface upwardly curved to a protrusion shape is applied to the thin film since the diamond-like carbon thin film has a large compressive stress of the order of 10
10
dyne/cm
2
.
The above condition will be described in FIG.
5
. FIG.
5
(A) shows the condition in which a thin film (
13
) having a compressive residual internal stress is formed on a substrate (
3
). When the compressive residual internal stress acts on the thin film (
13
), the thin film (
13
) tends to warp as shown in the drawing. In this case, of course, a stress occurs between the thin film (
13
) and the substrate (
3
), and thereby problems such as the decrease in adhesion of the thin film (
13
) to the substrate (
3
) or the cracking or peeling of the film (
13
) occur.
When a flexible and filmy substrate is used as the substrate, particularly, the thin film will curl outwardly and the substrate will curl inwardly.
Also, when the CVD apparatus shown in
FIG. 2
is used, the compressive residual stress in the longitudinal direction of the movement of the substrate (
3
) is canceled by winding the substrate. Though any significant problem does not occur in this case, the substrate will still curl after forming the film thereon due to the compressive residual internal stress in the transverse direction of the substrate (
3
).
The compressive residual stress in the transverse direction of the substrate (
3
) cannot easily be restored to its original condition even if corrections are performed later. Even if the compressive residual stress be restored to its original condition, now the stress still remains in the interface between the thin film and the substrate, and cracking, peeling, etc. are induced due to the stress. Taking the long view, therefore, the CVD apparatus in
FIG. 2
is lacking in the reliability.
The above problems occur more or less in the thin film formed by the CVD (chemical vapor deposition) method.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to solve the problems of the residual stress of the thin film formed by the vapor phase method as described above.
The present invention is summarized in an apparatus of forming a thin film on a substrate by a vapor phase method, characterized in that the substrate is curved in the direction canceling of the internal stress remaining in the thin film after the formation.
In the present invention as above, the vapor phase method designates a sputtering method, an evaporation method and a CVD method. Also, all the well-known thin films such as diamond-like carbon thin film, semiconductor thin film, insulator thin film, a conductive film, etc. may be generally used as a kind of thin film.
Curving the substrate in the direction canceling the internal stress means that the substrate is previously warped in the direction opposite to the direction of the substrate itself warping due to the internal stress remaining in the thin film to be formed thereon. In this manner, when the substrate is warped due to the residual internal stress of the thin film, the previously applied warp of the substrate cancels out the warp of the thin film formed thereon and, as a result, an integrated article composed of the thin film and the substrate with no warp can be obtained.
The function of curving the substrate designates a substrate holding means or substrate carrying means for forcibly curving the substrate, and a means for curving the substrate by moving the substrate along a curved member. The present invention can be applied to all the thin films having a compressive or tensile residual internal stress.
An example of the procedures for carrying out the present invention will be described below.
(a) A residual internal stress of the thin film is formed previously measured or a degree of the curling of the substrate to be generated by forming a thin film thereon is quantitatively examined.
(b) A film is formed while providing the curvature corresponding to the deformation caused by the residual internal stress of the thin film to the substrate.
By adopting the above process, the substrate on which a flat thin film has been formed can be obtained.
The condition of the thin film obtained by utilizing the present invention will be simply indicated in FIG.
5
(B). When a thin film (
13
) having a compressive residual internal stress is formed on the surface of a flexible and filmy substrate (
3
), the substrate (
3
) tends to warp due to the compressive stress as shown in FIG.
5
(A). As illustrated here, warping the substrate in the direction reverse to the condition shown in FIG.
5
(A) during the filming, the stress caused by the warp of the substrate cancels out the compressive residual internal stress of the thin film formed, and the condition as indicated in FIG.
5
(B) can be realized. Further, it is important to use the radius of curvature not inducing wrinkles, flaws, etc. on the film, as the curvature to be previously applied to the substrate, during the filming.
Previously applying the stress capable of canceling the internal stress of the formed thin film to the substrate of which the surface is to be coated with the film, prior to the filming, the internal stress of the thin film can be canceled and thus the deformation of the substrate caused by forming the thin film thereon (that is, the curling phenomenon occurring in a flexible and filmy substrate) can be prevented or reduced beforehand.
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patent: 4920917 (1990-05-01), Nakatani et al.
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patent: 5140938 (1992-08-01), Kasanuki et al.
patent: 5224441 (1993-07-01), Felts et al.
patent: 5879741 (1999-03-01), Itoh
patent: 53-75179 (1978-07-01), None
patent: 60-239714 (1985-11-01), None
patent: 61-67765 (1986-04-01), None
patent: 63-9013 (1988-02-01), None
Costellia Jeffrey L.
McDonald Rodney
Nixon & Peabody LLP
Semiconductor Energy Laboratory Co,. Ltd.
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