Optics: measuring and testing – By polarized light examination – With light attenuation
Reexamination Certificate
1999-02-22
2001-03-13
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By polarized light examination
With light attenuation
C250S341400, C250S559290, C250S559360
Reexamination Certificate
active
06201603
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus employed in a system for treating semiconductor devices, such as a manufacturing system or an examining or inspecting system, to detect a positional shift of a semiconductor wafer, i.e., the central position and the like of the wafer relative to a reference center for positioning the wafer.
In a system for treating semiconductor devices, such as a manufacturing system or an examining or inspection system, a wafer is subjected to a positioning operation with reference to an orientation flat or notch, before the wafer is processed or examined.
In an apparatus for performing such a positioning operation, a wafer is held on a worktable, which is rotated by a motor. Adjacent to the worktable, the light emitting and light receiving members of a photoelectric sensor are arranged to interpose the edge region of the wafer therebetween. Note that “the edge region of a wafer” means a region including the edge and part thereabouts of the wafer.
During rotation of the wafer, the light emitting member of the photoelectric sensor emits light rays, such that the optical axis crosses the wafer edge region. The light receiving member receives part of the light rays which have not been shaded by the wafer, and then outputs electric signals representing the received light rays.
A motor control section receives the output signals of the photoelectric sensor, and the orientation flat or notch of the wafer is detected on the basis of the output signal. Then, a motor is rotated, so that the orientation flat or notch of the wafer is moved to a predetermined position.
Further, the edge region of the wafer is pushed by a positioning pusher to move the wafer in a direction perpendicular to the rotational axis of the motor, so that the center of the wafer is aligned with the rotational axis of the motor. However, when the wafer edge region is pushed by the pusher to align the center of the wafer with the rotational axis of the motor, the wafer may be damaged or stained by an impact applied by the pusher or friction between the wafer and the worktable.
In order to counter such a problem, Jpn. Pat. Appln. KOKAI Publication No. 5-226459 discloses a technique of positioning a wafer without any contact therewith.
In this technique, there are arranged an X-directional-position detecting unit, a Y-directional-position detecting unit, and a mechanism for correcting these units, to observe the wafer edge region. These units and mechanism make the whole structure complicated and expensive. Besides, this technique can be applied to a wafer having an orientation flat, but not to a wafer having a notch.
As described above, positioning a wafer by pushing its edge region damages or stains the wafer. On the other hand, positioning a wafer without contact makes an apparatus complicated and costly.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a compact and inexpensive apparatus which can precisely detect the center of a semiconductor wafer.
It is another object of the present invention to provide a compact and inexpensive apparatus which can precisely position the center of a semiconductor wafer without contact.
According to a first aspect of the present invention, there is provided a position detecting apparatus for a semiconductor wafer comprising:
(a) a support for supporting the wafer such that a reference center for positioning the wafer is positioned in a contour of the wafer;
(b) an optical detecting mechanism arranged to correspond to an edge region of the wafer supported by the support, the optical detecting mechanism comprising,
a light emitter for emitting a parallel luminous flux to the edge region of the wafer supported by the support,
a light receiver for receiving the parallel luminous flux, arranged on an optical axis of the light emitter to face the light emitter through the edge region of the wafer supported by the support, the light receiver being arranged to output a signal having a level corresponding to a received light quantity, and
a light shielding slit plate having a slit arranged on an optical path of the parallel luminous flux, the slit having such a width in an angular direction relative to the reference center, that is set to be narrow enough to cause a degree of shading of the parallel luminous flux by the wafer to be a one-dimensional data in a radial direction relative to the reference center;
(c) a driver for selectively moving the wafer supported by the support and the optical detecting mechanism relative to each other in an angular direction relative to the reference center; and
(d) an arithmetic section for computing a central position of the wafer relative to the reference center, from output levels of the light receiver, which are obtained when at least three positions on the edge region of the wafer are placed between the light emitter and the light receiver, and the parallel luminous flux is partly shaded by the wafer.
According to a second aspect of the present invention, there is provided a position detecting apparatus for a semiconductor wafer comprising:
(a) a worktable for supporting the wafer, the worktable is rotatable about a rotational axis on a reference center for positioning the wafer;
(b) an optical detecting mechanism arranged to correspond to an edge region of the wafer supported by the worktable, the optical detecting mechanism comprising,
a light emitter for emitting a parallel luminous flux to the edge region of the wafer supported by the worktable,
a light receiver for receiving the parallel luminous flux, arranged on an optical axis of the light emitter to face the light emitter through the edge region of the wafer supported by the worktable, the light receiver being arranged to output a signal having a level corresponding to a received light quantity, and
a light shielding slit plate having a slit arranged on an optical path of the parallel luminous flux, the slit having such a width in an angular direction relative to the reference center, that is set to be narrow enough to cause a degree of shading of the parallel luminous flux by the wafer to be a one-dimensional data in a radial direction relative to the reference center;
(c) a driver for selectively rotating the worktable; and
(d) an arithmetic section for computing a central position of the wafer relative to the reference center, from output levels of the light receiver, which are obtained when at least three positions on the edge region of the wafer are placed between the light emitter and the light receiver, and the parallel luminous flux is partly shaded by the wafer.
According to a third aspect of the present invention, there is provided a position detecting apparatus for a semiconductor wafer comprising:
(a) a support for supporting the wafer such that a reference center for positioning the wafer is positioned in a contour of the wafer;
(b) optical detecting mechanisms arranged to correspond to at least three positions on an edge region of the wafer supported by the support, each of the optical detecting mechanisms comprising,
a light emitter for emitting a parallel luminous flux to the edge region of the wafer supported by the support,
a light receiver for receiving the parallel luminous flux, arranged on an optical axis of the light emitter to face the light emitter through the edge region of the wafer supported by the support, the light receiver being arranged to output a signal having a level corresponding to a received light quantity, and
a light shielding slit plate having a slit arranged on an optical path of the parallel luminous flux, the slit having such a width in an angular direction relative to the reference center, that is set to be narrow enough to cause a degree of shading of the parallel luminous flux by the wafer to be a one-dimensional data in a radial direction relative to the reference center;
(c) an arithmetic section for computing a central position of the wafer relative to the reference center, from output levels of the light receivers of the optical detecting mechan
Font Frank G.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Merlino Amanda
Olympus Optical Co,. Ltd.
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