Coating apparatus – Work holders – or handling devices – Gripper or clamped work type
Reexamination Certificate
1999-10-29
2001-09-11
Edwards, Laura (Department: 1734)
Coating apparatus
Work holders, or handling devices
Gripper or clamped work type
C118S728000, C269S2540DF
Reexamination Certificate
active
06287385
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to support structures for restraining substrates, such as semiconductor wafers, during processing. The invention further relates to a compound spring assembly that can be easily manipulated by an operator with forces that exceed the strength of the substrate while imparting forces for restraining the substrate without damage.
DESCRIPTION OF THE PRIOR ART
The deposition, or coating, of materials is a process that is widely used in the manufacturing of many semiconductor and optical components. An example of a batch processor
111
that can perform this type of process is shown schematically in FIG.
1
. Batch processor
111
includes a vacuum chamber
101
, an evaporative source
103
of coating material
105
, and a framework
107
generally positioned to uniformly coat a plurality of optical components, flat panel display panels, semiconductor wafers or other substrates
109
that are usually located approximately equidistant from source
103
. Using an evaporative source, coating materials may include many metals, semiconductors and refractory materials. Vacuum chamber
101
is opened, and substrates
109
are manually loaded onto framework
107
one at a time. The number of substrates that can be held by a framework varies with the substrate, chamber and framework size, with frameworks typically adapted to hold substrates of 25 mm to 200 mm in diameter or larger. Framework
107
is connected to a motor
113
, rotating the framework within the chamber to increase the uniformity of coating material
105
being deposited. Other systems, not shown, may have fixed frameworks, while others may incorporate multiple frameworks and planetary or other rotational systems for moving substrates about to produce a specific coating effect.
At the low pressures under which evaporative coating operations occur, typically 10
−6
to 10
−7
Torr, material
105
travels in a straight line from source
103
, coating surfaces with a direct line-of-sight to the source. In the configuration of
FIG. 1
, a framework front side
115
and substrate front side
119
both face source
103
and are coated, while a framework back side
117
and substrate back side
121
face away from source
103
and are generally not coated. Details of one of the many substrates which may be held in the prior art framework is shown in
FIGS. 2 and 3
. Substrate
109
is placed over one of the apertures
201
, which are located over much of the framework surface and have a shape roughly the same as the substrates they are meant to hold. Substrate
109
is supported on substrate front side
119
by a plurality of aperture tabs or an aperture lip
203
, which supports some or all of the edge of substrate
109
, and on substrate back side
121
by a prior art clip mechanism
205
. Some systems have more than one clip for each substrate, especially for larger substrates, with a 150 mm substrate having 2 to 4 clips holding it in place. A substrate restraining force
217
is transferred from a deflected coil spring
211
to a substrate contact point
209
by a clip
219
, which is rigid and metallic. Typical prior art clips are made of alloys such as stainless steel or Inconel, with a thickness and shape that allow them to be rigid. Clip
219
can be pulled away from substrate
109
by pinching a clip handle
207
between thumb
301
and forefinger
303
, and rotated clear of aperture
201
about a pivot pin
215
, as shown in FIG.
3
.
A second prior art clip mechanism
401
is shown in side and top view in
FIGS. 4 and 5
, respectively. In clip mechanism
205
, a combined clip spring
401
is made of a mildly flexible metal, producing less of a restraining force than prior art clip mechanism
205
. In addition, coil spring
211
of the first prior art clip has been incorporated directly into the clip through a bend
403
. For this configuration, clip materials and shapes are chosen to allow some spring force to be imparted by the clip.
The first and second prior are clips of
FIGS. 2 through 5
were designed primarily for substrates that can withstand the forces imparted by those clips, and the spring force acts to both restrain the clip and hold the substrate. These clips have wide utility, though not without problems, with silicon substrates. As galium-arsenide (Ga—As) substrates have become more common, several problems in using prior art clips to restrain the more fragile Ga—As substrates have become evident, mainly due to their imparting a large force over a small substrate area. Consider the first prior art clip of
FIGS. 2 and 3
. Rigid clip
219
can rotate about pivot pin
215
and is held in place by stiff coil spring
211
. This clip design has several drawbacks. Since the prior art clip is held in place against the substrate by a stiff spring, the force imparted by the clip has a limited lower value—it is difficult to design such a clip with a small force. If the operator accidentally releases clip handle
207
before placing it on substrate
109
, clip
219
is forced by stiff spring
211
onto substrate
109
, damaging more fragile substrate materials such as Ga—As. Another drawback of this design is that since stiff spring
211
also keeps the clip rigid, slight deformities due to mishandling the clip may result in a clip contact surface
209
smaller than the design area, with an increase in the substrate contact forces. Yet another drawback is that clip handle
207
is close to substrate back side
121
, and thus the operator must be very careful not to touch the substrate. The second prior art clip of
FIGS. 4 and 5
incorporates a less rigid, and slightly elastic material for a combined clip and stiff spring
403
. This design is slightly better at maintaining a maximum contact surface with substrate
109
, but suffers from many of the same limitations as the first clip design.
The limitations of prior art clips with fragile substrates has been noted, and have been partially addressed by the use of slotted restraining devices that hold the substrate by the application of forces primarily on the edge of the substrate. In U.S. Pat. No. 4,971,676, Doue et al. describe a framework in which a substrate is held in place by one edge spring and a plurality of edge abutments. Although that invention places less stress on a substrate once it is in place, other problems result from the sliding required in placing or removing the substrate. For example, inserting the substrate into the narrow slots defined by the edge abutments can result in breakage of fragile substrates. In addition the sliding required by that invention can scratch or create and deposit an unacceptable level of particulate matter on the substrate surface.
SUMMARY OF THE INVENTION
It is an advantage of the present invention that the substrate restraining force imparted by the clip is uncoupled from the force that holds the clip in place.
It is a further advantage of the present invention to impart restraining forces on a fragile substrate that will result in a lower incidence of substrate damage.
It is another advantage of the present invention that forces used by the operator in positioning the present invention on a fragile substrate are not imparted onto the substrate.
It is a further advantage of the present invention that the forces used by the operator with the present invention provide positive and firm control while imparting a much smaller force on a substrate.
It is yet a further advantage of the present invention that the force imparted onto the substrate occurs over a larger contact area and at multiple points by the use of multiple leaves.
It is a further advantage of the present invention that the operators fingers are kept way from the wafer during operation.
It is yet another advantage that the present invention be simple and inexpensive to manufacture and be easy to use.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon
Edwards Laura
Neida Philip H. Von
Pace Salvatore P.
The BOC Group Inc.
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