Material or article handling – Horizontally swinging load support – Swinging about pivot
Reexamination Certificate
2001-02-17
2002-12-31
Matecki, Kathy (Department: 3652)
Material or article handling
Horizontally swinging load support
Swinging about pivot
C901S015000, C901S021000
Reexamination Certificate
active
06499936
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a transfer system used for transfer of wafers in a semiconductor manufacturing line, or the like.
2. Description of the Prior Art
In the manufacture of semiconductors, for example, a transfer system is used to move an object being processed, such as a semiconductor wafer, from one process to another process. Examples of conventional transfer systems are discussed below.
First Conventional Transfer System
FIG. 1
shows a first example of a conventional transfer system, wherein two upper arms
11
,
12
are positioned on a drive shaft
13
. Drive shaft
13
is designed to be driven by rotation. Upper arms
11
,
12
are linked to drive shafts
14
,
15
. Upper arms
11
,
12
rotate on drive shaft
13
. To the tip of upper arm
11
, forearms
16
,
17
are rotatably mounted. To the tip of upper arm
12
, forearms
18
,
19
are rotatably mounted. Platform
20
is linked to the tips of forearms
16
,
18
. Platform
21
is linked to the tips of forearms
17
,
19
. The four forearms
16
-
19
are assembled to form a pair of frog-legs like structure. Platforms
20
,
21
are positioned depending on the rotated angles of upper arms
11
,
12
.
Operation of the system of
FIG. 1
is as follows. By turning two upper arms
11
,
12
in opposite directions, one platform (
20
or
21
) moves in a direction away from drive shaft
13
(i.e. the distance from drive shaft
13
is increased) and the other platform (
21
or
20
) is moved only slightly from its standby position. The other platform stays approximately at the same position as the standby position, wherein the standby position is a position disposed above drive shaft
13
.
In addition, by rotating drive shaft
13
, the orientation of the frog-legs like structure is changed. This makes the extending direction of platforms
20
and
21
change. From these operations, two wafers are transferred by (a) selecting either of platforms
20
and
21
, and (b) then extending or contracting that platform which is selected depending on the angle formed with the upper arms
11
and
12
. Drive shaft
13
is rotated when a wafer, upon which processing is completed, is removed from the process using a platform and then is transferred to another process.
However, the conventional system of
FIG. 1
has certain problems. For example, if the direction of extension of platforms
20
,
21
is to be changed, drive shaft
13
is rotated with the platforms
20
,
21
being placed in the standby position. In order to ensure that platforms
20
,
21
do not contact adjacent machines, equipment, etc, the turning radius of the platforms
20
,
21
must be small. In that case, platforms
20
,
21
must be made to move close to drive shaft
13
, which limits the thickness of the forearms
16
-
19
. Hence, the forearms must be made to be very thin, and suitable rigidity cannot be achieved. Accordingly, due to the weight of the wafers and platforms, the forearms are subjected to bending, and stable transfer is prevented from occurring and speed of transfer cannot be increased.
Second Conventional Transfer System
FIG. 2
shows a second conventional transfer system wherein first arm
32
is arranged rotatably around rotating shaft
31
; second arm
34
is arranged rotatably around rotating shaft
33
located on the tip of first arm
32
; and third arm
36
is arranged rotatably around rotating arm
35
located on the tip of second arm
34
. The center of rotation of third arm
36
is at the midpoint thereof. First arm
32
is rotated by being directly coupled to a first motor (not shown). Second arm
34
and third arm
36
are rotated by a second motor and a third motor (not shown) via pulleys and belts. The second conventional transfer system has Selective Compliance Assembly Robot Arm (also called “SCARAB”) types of arms. The test object mounting parts
37
,
38
, on which test objects are disposed, respectively, are provided at both ends of third arm
36
.
Operation of the
FIG. 2
system is as follows. The stand by position is a position whereat first arm
32
and second arm
34
overlap each other. Rotation of first arm
32
in one direction causes test object mounting part
37
or
38
disposed on either tip of third arm
36
to be placed in an extended position which is furthest from rotating shaft
31
. The other test object mounting part, located on the opposite side, is positioned in a place nearer to the rotating shaft
31
than the test object mounting part located furthest away. Rotation of first arm
32
in the opposite direction moves the test object mounting part on the opposite side to the furthest extended position via the stand by position. In addition, the extending direction of a test object mounting part is set at an arbitrary angle by turning the system around rotating shaft
31
. Accordingly, two wafers are transferred to other places by moving the two test object (e.g. wafers) mounting parts to the standby position or the furthest extended position.
However, the second conventional transfer system has the following problems. First arm
32
and second arm
34
are provided with a sealed barrier to exclude particles generated or provided by wear of the bearings that support the belts and pulleys used therein, in order to obtain the degree of cleanliness required for semiconductor manufacture. Also, the width of the belts depend on the strength required for transmitting power. Accordingly, thicker arms must be used to insure provision of the required width of the belts, and to provide barrier construction.
Moreover, in SEMI E21 and SEMI E22 standards, which are the standards generally followed in the industry to manufacture semiconductors, standard dimensions of the arms are provided. Specifically, the thickness of the hands in the interface zones for engaging test objects is defined to be 23 mm for wafers up to 8 inches; that is, a very thin dimension is required by the industry standards. In the
FIG. 2
system, the coupling part of the second arm
34
and third arm
36
correspond to this zone. Making the thickness of the coupling part to be 23 mm or less and providing barriers incorporating the belts and pulleys and bearings in the arms, result in fragile construction of the arms. Thus, in the prior art, the required arm thickness cannot be satisfied for such arm construction. Moreover, the arms are likely to become bent due to the weight of the wafers and the test object mounting parts, because the arms must be designed to be thin. Thus, stable transfer of wafers from one process to another cannot be assured.
Third Conventional Transfer System
FIG. 3
shows a third conventional transfer system, wherein two forearms
43
,
44
are rotatably mounted on the tips of rear arms
41
,
42
. Transfer base
45
is linked to the tips of forearms
43
,
44
using hinges
46
,
47
. The structure resulting from such construction is a frog-legs shaped structure. Rear arms
41
,
42
are rotated by gears
48
,
49
that rotate in opposite directions to each other and in synchronism. Forearms
43
,
44
are each rotated by pulleys
50
,
51
having an effective diameter ratio of 2 to 1, and tension belt
52
is stretched between both pulleys
50
,
51
. Pulley
50
is tightly fixed in a coaxial manner to gears
48
,
49
. Pulley
51
is tightly fixed in a coaxial manner to hinges
53
,
54
.
Operation of the
FIG. 3
system is as follows. Forearms
43
,
44
are rotated to an angle
2
&agr;, which is twice the deflection angle &agr; of each of rear arms
41
,
42
when the rear arms are rotated in opposite directions to each other and transfer base
45
is positioned. The rotating angles and rotating directions of the forearms, which are restricted by pulleys
50
,
51
and belt
52
, correspond to the rotating positions of the rear arms. Hence, transfer base
45
is positioned by the rotation of each rear arm in the range of ±90° in opposite directions starting at the condition where each of the forearms and rear arms overlap.
The
FIG. 3
system has the following problems, however. The arm cons
Kojima Moonray
Lowe Michael
Matecki Kathy
Yokogawa Electric Corporation
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