Transfer arm

Details Transfer arm Transfer arm

2000-12-19

2002-11-19

Fenstermacher, David (Department: 3682)

Machine element or mechanism

Control lever and linkage systems

Multiple controlling elements for single controlled element

C414S917000, C901S019000

Reexamination Certificate

active

06481309

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transfer arm, employed in a semiconductor processing system or the like, which is capable of accurately transferring substrates and which has excellent durability and thus long life.
2. Description of the Prior Art
Generally employed in a semiconductor processing system is a substrate transfer apparatus for transferring target substrates such as semiconductor wafers by predetermined sequence control. Such a substrate transfer apparatus is required to operate with its high accurate movement in a clean operational environment where airborne particles such as dust do not exist.
FIG. 27
is a schematic structural view schematically showing the structure and the operation of conventional transfer arms of a substrate transfer apparatus (see Japanese Patent No. 2808826). In the transfer apparatus, transfer arms shown in
FIG. 27
each comprise two pairs of parallel link elements (two parallel links) connected by a common short link element allowing the folding and stretching of the arm. The folding and stretching of the arm achieves linear reciprocating motion of a substrate holder to transfer a substrate (not shown) in the longitudinal direction. To prevent occurrence of interference between the pairs of parallel link elements, one pair of parallel link elements are disposed at a level different from the level of the other pair of parallel link elements. The two transfer arms are arranged symmetrically relative to the center line. By this structure, continuous transfer is achieved.
As shown in
FIG. 27
, in a conventional mechanism of the transfer apparatus
500
, articulated arms
520
,
530
are arranged symmetrically relative to a center line C. Each of the arms
520
,
530
comprises a linkage in which a parallel link
540
has link elements
541
,
542
as long link elements, a parallel link
550
has link elements
551
,
552
as long link elements, and two gears
570
,
572
engaging each other compose a short link element common to both the parallel link
540
and the parallel link
550
. The gear
570
is fixed to the link element
542
and the gear
572
is fixed to the link element
552
.
A short link element
543
for the link elements
541
,
542
at the opposite side of the common short link element is mounted on a rotary stand
510
as a drive. A substrate holder
590
is disposed on a short link element
553
connected to the other ends of the link elements
551
,
552
.
In the transfer apparatus
500
structured as mentioned above, the arm
530
is shown in its initial state. As the parallel link
540
is swung by rotation of a rotary shaft R
50
. Because of the engagement of the gears
570
and
572
, the parallel link
550
is swung in a direction opposite to and at the same angle as the swing motion of the parallel link
540
. As a result, the arm
520
shown in the right half of
FIG. 27
linearly moves the substrate holder
590
in the direction of arrow A along the center line C, while increasing the angle of a V shape formed between the two parallel links after passing the position on the rotary shaft R
50
.
Instead of the two gears
570
,
572
composing the short link element, a pulley belt or a wire may be employed as a mechanism for the folding and stretching of the arm composed of the two parallel links.
However, since gears to be engaged should be designed to have a predetermined backlash between them, the linkage easily rattles during the movement. This reduces the precision of transfer, so there is a problem that high precision of positioning can not be expected. There is also another problem that powders are produced by the grinding between teeth of the gears. On the other hand, in a conventional example in which the synchronization in moving angle is achieved by pulleys and a steel belt or a wire wound around the pulleys, there is a possibility of early causing of fatigue failure because the folding of the belt or wire is frequently repeated for being wound onto the pulleys. The life of the belt or wire is defined by the tension and the fold radius when the belt or wire is wound. For this, increase in the diameter of the pulley to be employed is considered as one of solving means. However, in this case, increase of the diameter of the pulley makes it difficult to miniaturize the apparatus as a whole.
In case where substrates are processed under high temperature condition, the belt or wire should be early deformed and deteriorated, so there is also a problem of durability.
Therefore, the first object of the present invention is to provide a transfer arm which can solve the aforementioned problems of the prior art, which is capable of accurately transferring substrates, and which has excellent durability because the wearing of components can be minimized.
The second object of the present invention is to provide a transfer arm which can solve the aforementioned problems of the prior art, which is capable of accurately transferring substrates under high temperature condition, and which has excellent durability because the wearing of components can be minimized.
SUMMARY OF THE INVENTION
For achieving the above first object, the present invention provides, as a first embodiment (described later), a transfer arm having a first parallel link and a second parallel link which are connected to each other by a common short link element, a drive shaft at an end of a link element of said first parallel link, and a holding plate disposed on the free end of said second parallel link which is linearly moved according to the rotation of said drive shaft while deforming parallelograms formed by the link elements of said first parallel link and formed by the link elements of said second parallel link, said transfer arm being characterized by comprising a linear guide having a guide rail disposed on a base between said first parallel link and said second parallel link to extend in a direction perpendicular to said common short link, and a synchronous link for connecting a slider which is slidable on said guide rail, articular shafts supporting the ends of link elements of said first parallel link, and articular shafts supporting the ends of link elements of said second parallel link which are arranged symmetrically relative to said linear guide.
It is preferable that said slider of said linear guide is linearly moved by the swing motion of the link element(s) of the first parallel link, and the link elements of the second parallel link are swung in a direction opposite to and at the same angle as the swing motion of the link elements of said first parallel link via said synchronous link according to the linear movement of said slider, whereby the holding plate disposed on the free end of said second parallel link is linearly moved while varying the angle formed between the link elements of said first parallel link and the link elements of said second parallel link.
It is preferable that said transfer arms are arranged to be opposed to each other relative to a center line parallel to the direction of transferring said holding plate, whereby subject objects are continuously transferred by alternatively operating the folding and stretching of said transfer arms.
It is preferable that said pair of transfer arms comprise two drive shafts which are coaxially arranged to allow independent folding and stretching operation of the respective transfer arms.
The present invention provides a transfer arm comprising two drive shafts coaxially arranged one of which is connected to an end of a link element of a quadrate link and the other one of which is connected to an end of another link element of the quadrate link which is symmetrical relative to a center line, a linear guide which is positioned at a joint of the other ends of the link elements at a location opposite to the location of said drive shaft, and a synchronous link which is arranged between a slider of said linear guide and portions near the ends of said link elements which are opposite to the ends connected to said joint.
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