Geometrical instruments – Gauge – Work support
Reexamination Certificate
1997-04-14
2001-04-10
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Gauge
Work support
C033S551000, C033SDIG002
Reexamination Certificate
active
06212786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a thin board holding device for holding a thin board in a plane state to measure the thickness of the thin board and also to a method of and an apparatus for the thin board thickness measurement on holding a thin board in a plane state.
2. Description of the Related Art
The thickness of a thin board, such as a film-like sheet or a silicon wafer, is usually measured with a micrometer.
To measure the thickness, the thin board is held with one hand, and the micrometer is operated with the other hand. Therefore, when the thin board is inserted into and pushed out from the space between micrometer measurement terminals, the thin board may strike or be distorted between the terminals, and this may result in its breakage.
Therefore, it is difficult to accurately measure the thickness of a thin board, particularly a large diameter and fragile thin board such as a silicon wafer.
FIG. 13
shows a related technique, in which displacement gauges
101
and
102
provided on a frame
100
over and under a thin board
1
under measurement measures the thickness of the thin board
1
.
In this system, the displacement gauges
101
and
102
should be such that their relative positions are not varied and that the thin board under measurement can be passed between them. Therefore, the system is inevitably rather elaborated, and a high technical level is necessary.
In addition, in this system it is necessary to move a silicon wafer to measure the thickness thereof at a plurality of designated points, so that greater caution and time are required to prevent breakage of the wafer, thus reducing the production rate and increasing the cost of manufacture. It has been desired to solve this problem.
OBJECT AND SUMMARY OF THE INVENTION
In view of the above circumstances, it is an object of the invention to provide a thin board holding device and a method of and an apparatus for measuring the thickness of a thin board, which can prevent breakage of large diameter and fragile thin boards such as silicon wafers and permit accurate measurement of the thin board thickness.
Another object of the invention is to provide a thin board holding device and a method of and an apparatus for measuring the thin board thickness, which permit the thin board thickness measurement with a simple construction.
A further object of the invention is to provide a method of and an apparatus for thin board thickness measurement, which permit accurate thickness measurement in a short period of time.
To attain the above objects of the invention, according to a first aspect of the invention, a thin board holding device for holding a thin board in a plane state to measure the thickness of said thin board is provided, which comprises an adsorption portion including a plurality of spot supports for receiving one surface of said thin board to hold said thin board in a multiple point support fashion such that said thin board is held attached by adsorption to said spot supports.
According to the invention, effectively the dimension between a reference surface with the thin board holding device placed thereon and the surface of the adsorption portion in contact with the thin board is set to a predetermined dimension as a computational constant.
According to the invention, effectively the adsorption portion has two or more different surfaces to be in contact with a thin board to be able to set two or more values as the predetermined dimension for holding a thin board having locally different thicknesses.
FIGS. 1 and 2
show a thin board holding device
2
A, which has a number of spot supports
3
each having an adsorption face
3
a
which is in contact with a thin board (or wafer)
1
.
As shown in
FIG. 3
, each spot support
3
has a exhausting port
3
A
b
such that the thin board
1
can be adsorbed under vacuum to the adsorption face
3
a
by suction from sucking means (not shown) through the exhausting port
3
A
b.
As shown in
FIG. 1
, the spot supports
3
are provided as many as corresponded to each of support points S
1
to S
9
in an arrangement of a cross. This arrangement, however, is merely an example, and it is possible to provide the spot supports in any arrangement.
The spot supports
3
may not all be capable of adsorption under vacuum; they may be incapable of sucking in a zone where the strain of the thin board poses no problem when the thickness of the thin board is not taken into consideration.
With the thin board supported at multiple spots or points, deterioration of the flatness of the thin board, by dust particles intruding into the space between the thin board and the supporting surface, is less liable compared to the case where the thin board is supported over the entire surface.
By moving a measuring terminal of a measuring instrument to a measuring point on the thin board, which has one surface set on the thin board holding device, the level of the other surface of the thin board from a reference surface supporting the thin board holding device at a reference position can be measured.
With the provision of data of the level of the adsorption attached surface of the thin board from the reference position, the thickness of the thin board can be determined by calculation from such data.
The thin board holding device thus can be used for the thin board thickness measurement. In this case, one surface of the thin board is held stationary, and the level of the other thin board surface is measured. Breakage of the thin board, which may even be very fragile such as a silicon wafer, is thus far less possible.
A stepped thin board
10
with a local stepped portion having a different thickness as shown in
FIG. 10
, may be held by providing a spot support
3
′ which is reduced by difference in level with corresponded to the stepped portion.
The reduced dimension spot support
3
′ may be intrinsically provided on the thin board holding device
2
B, but desirably the spot supports
3
and
3
′ can be selectively detachably installed by screwing.
The spot supports each include:
adsorbing means having an elastic skirt portion;
a spherical projection extending from the bottom of a space defined by the skirt portion to the top opening of the adsorbing means and having a lower level end portion than the level of the skirt portion; and
an air suction opening formed in the bottom;
the thin board being held in contact with an end portion of the spherical projection by suction through the opening.
As shown in
FIG. 5
, the spot support
3
B has an adsorbing means (i.e., an adsorbing pad)
5
with an elastic skirt portion. A thin board (or wafer)
1
, the surfaces of which are not mirror-finish surfaces but rough surfaces as shown in
FIG. 6
, thus can be attached by adsorption to the upper edge
5
a
of the adsorbing means
5
by exhausting air through an exhausting port
3
Bb without air leak, and it is possible to improve the state of holding of the thin board.
A spherical projection
4
is provided such that it extends from the bottom of the adsorbing pad (i.e., the top
3
B
f
of the spot support) to the top opening of the adsorbing pad. Its upper end
4
a
is lower in level than the level of the skirt and in contact with a very small surface area of the thin board
1
.
Dust particles in the adsorbing pad are exhausted together with air through the exhausting port
3
B
b
, thus preventing the presence of dust particles in the space between the thin board
1
and the end portion
4
a
of the spherical projection
4
as much as possible.
According to the first aspect of the invention, the sport supports are detachable from the thin board holding device. For example, the spot supports may each have a thread formed in a lower portion, and the holding device also has threads or threading screws. In this case, various spot supports may be detachable installed for use in dependence on the kind of the thin board.
According to the first aspect of the invention, effectively the thin board holding device further comprises the projection surfac
Evenson, McKeown, Edwards & Lenahan, P.L.L.C
Fulton Christopher W.
Kuroda Precision Industries Ltd.
LandOfFree
Thin board holding device and method of and apparatus for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thin board holding device and method of and apparatus for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thin board holding device and method of and apparatus for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2546990