Optics: measuring and testing – By alignment in lateral direction – With light detector
Reexamination Certificate
2001-12-05
2004-06-22
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
By alignment in lateral direction
With light detector
C356S614000
Reexamination Certificate
active
06753964
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an axis determination apparatus, a film-thickness measurement apparatus, a deposition apparatus, an axis determination method, and a film-thickness measurement method. More particularly, the present invention relates to an improvement of a technique that enables the determination of a film-thickness distribution by measuring the thickness of an electrically conductive film, at a plurality of points thereon, the film being deposited on a surface of a circular wafer.
2. Description of the Related Art
In many cases, it is customary to use generally circular wafers for the fabrication of semiconductor devices.
A wafer, designated by
150
in FIGS.
32
(
a
) and (
b
), has a thin film deposited on a surface thereof. FIG.
32
(
b
) is a cross-sectional view taken along line X—X of FIG.
32
(
a
). The wafer
150
, formed of silicon, having a circular shape, is provided with an electrically conductive thin film
152
deposited on a surface of a substrate
151
, on part of the circumferential portion of which there is formed a triangular cut-away portion (hereinafter referred to as the notch)
153
.
In order to determine whether the thin film
152
has been deposited in a constant thickness on the surface of the substrate
151
, it is necessary to measure the thickness of the thin film
152
at a plurality of points on the surface of the wafer
150
to thereby determine the film-thickness distribution and know the extent of variations in the film thickness measured at each point.
Now, referring to FIGS.
33
(
a
) and (
b
), a step height method as one of a prior-art method for determining a film-thickness distribution is described below. FIG.
33
(
b
) is a cross-sectional view taken along Y—Y of FIG.
33
(
a
). In the step height method, the thin film
152
is deposited on the surface of the wafer
150
, which is then taken out of the deposition apparatus. Subsequently, the thin film
152
is etched at predetermined positions on the surface of the wafer
150
(i.e., at the center of the wafer
150
and at both ends of center axis lines of the surface of the wafer). A plurality of openings
156
1
-
156
5
are thus formed to expose the surface of the substrate
151
, as shown in FIG.
33
(
a
). Thereafter, a stylus
171
is drawn near each of the openings
156
1
-
156
5
to measure the step height between each of the openings
156
1
-
156
5
and the electrically conductive thin film on a portion other than on the openings
156
1
-
156
5
, thereby determining the thickness of the thin film near each of the openings
156
1
-
156
5
and the film-thickness distribution.
In the step height method, it is necessary to take the wafer
150
once out of the deposition apparatus to etch the aforementioned predetermined position and thereby form an opening, and thereafter draw the measurement stylus near the opening. Accordingly, there existed a problem of making the process considerably complicated.
SUMMARY OF THE INVENTION
The present invention was developed to solve the aforementioned drawbacks of the prior art. It is therefore an object of the present invention to provide a technique, which enables the accurate determination of the center axis of a circular substrate in a short time and the precise determination of the film-thickness distribution of a thin film deposited on the substrate surface.
To solve the aforementioned problems, the present invention provides an axis determination apparatus for determining a center axis line of a surface of a circular substrate. The axis determination apparatus comprises a support mount for supporting the substrate placed on a surface thereof, a drive mechanism for rotating the support mount in a plane containing the surface of the support mount, a light-emitting device disposed near the circumferential portion of the support mount, and a light-receiving device disposed, opposite to the light-emitting device, near the circumferential portion of the support mount. The light-emitting device is adapted to emit a beam of light to the light-receiving device.
The axis determination apparatus according to the present invention is such that the light-receiving device is disposed so as to receive the beam of light emitted by the light-emitting device through a notch provided on the circumferential portion of the substrate when the notch stays between the light-emitting device and the light-receiving device.
The present invention also provides an axis determination apparatus, for determining a center axis line of a surface of a circular substrate, comprising a support mount for supporting the substrate placed on a surface thereof. The axis determination apparatus further comprises a lifter, including a support member formed generally in a shape of a cube arranged on a circumference with a center of the support mount and a projected member projected towards the center under the support member, for supporting the substrate with a circumferential portion of the substrate sitting on the projected member. The axis determination apparatus further comprises a lifting mechanism for hoisting and lowering the lifter near the support mount. The axis determination apparatus is such that the support member is provided with an inclined surface sloped towards the projected member, and the lifter, when lowered below the support mount while supporting the substrate, transfers the substrate onto the surface of the support mount.
Furthermore, the axis determination apparatus according to the present invention is such that the substrate is clamped against the support mount.
Furthermore, the present invention provides a film-thickness measurement apparatus comprising an axis determination apparatus for determining a center axis line of a surface of a circular substrate and a measurement apparatus for measuring a thickness of an electrically conductive thin film formed on the surface of the substrate. The axis determination apparatus includes a support mount for supporting the substrate placed on a surface thereof, a drive mechanism for rotating the support mount in a plane containing the surface of the support mount, a light-emitting device disposed near a circumferential portion of the support mount, and a light-receiving device disposed, opposite to the light-emitting device, near the circumferential portion of the support mount, the light-emitting device being designed to emit a beam of light to the light-receiving device. The measurement apparatus determines a measurement position on the surface of the substrate at the measurement position in accordance with the center axis line determined by the axis determination apparatus and measures the thickness of the electrically conductive thin film at the measurement position.
Furthermore, the film-thickness measurement apparatus of the present invention is such that the measurement apparatus comprises a film-thickness sensor, a power source, and a measurement device. The film-thickness sensor includes a measurement coil. The power source applies an AC voltage to the measurement coil when the substrate is in close proximity to the measurement coil to generate an eddy current in the electrically conductive thin film on the surface of the substrate. The measurement device is designed to measure a signal generated in the measurement coil by an effect of the eddy current.
Furthermore, the film-thickness measurement apparatus according to the present invention is such that the film-thickness sensor comprises a reference coil and two reference resistors. The reference coil is connected in series to the measurement coil and arranged to stay farther away from the substrate than the measurement coil when the measurement coil faces the substrate. The two reference resistors are connected in series to each other to form a serially-connected circuit, which is connected in parallel to the serially-connected circuit of the measurement coil and the reference coil. The measurement device is designed to measure the potential difference between the connection of the meas
Chen Kai
Minamitsu Akihito
Nakamura Shizuo
Omura Fumihiko
Armstrong Kratz Quintos Hanson & Brooks, LLP
Barth Vincent P.
Rosenberger Richard A.
Ulvac Inc.
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