Optics: measuring and testing – By alignment in lateral direction – With light detector
Reexamination Certificate
2001-12-03
2003-09-09
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By alignment in lateral direction
With light detector
C356S399000, C356S401000, C356S138000, C356S153000, C356S508000, C356S237100, C359S565000, C359S839000
Reexamination Certificate
active
06618147
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention concerns a visualization device for alignment and positioning with respect to micro-mechanical and micro-optical devices, including micro-electronic (chips), and opto-electronic devices (laser diodes, photo-diodes), or others by component reversal method (alignment of two opposite surfaces). The assembly process is schematically represented in
FIGS. 1
a
and
1
b.
With respect to
FIG. 1
a
, the examined component transfer method consists of placing in accurate fashion, one or several components
1
on a substrate
2
. In general, component
1
and the substrate
2
are not transparent. In order to assure precise placement, alignment marks
3
and
4
can respectively be traced on the lower surface of component
1
and the upper surface of the substrate
2
. Final assembly of the device can be realized by means of gluing, welding or natural adhesion thanks to the possible presence of welding contacts
5
and
6
or glue, which are respectively present on component
1
and/or the substrate
2
. Any other assembly method can also be envisioned. This final assembly constitutes a new hybrid component—
FIG. 1
b.
PRIOR STATE OF THE ART
When the assembly involves small components (size on the order from 0.2 mm to 5 mm) for which high precision in placement is required (on the order from 0.5 &mgr;m to several &mgr;m) a number of different methods are usually utilized.
FIG. 2
a
and
FIG. 2
b
illustrate a method which consists of utilizing a dual sighting system comprising two microscope lenses
7
and
8
, one sighting the lower surface of component
1
, the other sighting the upper surface of substrate
2
. These microscopes permit visualizing the alignment designs
3
and
4
and allow for correction of placement defects.
Following correction, a movement of retraction
9
is applied to the sighting system, since a displacement program is applied to the component
1
through the intermediary of a mechanical device
11
in order to place same on the substrate
2
.
This method poses the following technical problems:
Utilization of two microscopic sighting systems requiring precisely the same characteristics (pairing).
Need to retract the microscopes before placement of component.
Significant placement distance of component, detrimental to large production output.
FIG. 3
a
and
FIG. 3
b
illustrate a variation of the preceding method, utilizing two fixed microscopes
7
and
8
and applying two displacements
10
and
12
to the component
This method poses the following technical problems:
Utilization of two microscopic sighting systems needing precisely the same characteristics (pairing).
Two significant placement distances of the component, detrimental to large production output.
Need for horizontal displacement
10
with absolute high precision.
FIG. 4
a
and
FIG. 4
b
illustrate a method utilizing a single microscopic sighting system
13
and a beam separator cube
14
permitting superposing the images of the component
1
and the substrate
2
at time of alignment. Following alignment, a retraction movement
15
of the separator cube
14
is performed in order to position the component
1
on the substrate
2
.
This method poses the following technical problems:
The final position of the component is sensitive to the thickness of the component (a very thin component will result in quite significant tilting and a very thick component will result in very weak tilting).
Need to retract the prism before placement of component.
Significant sighting distance, generally incompatible with utilization of high resolution and strong magnification microscopes.
Sighting through heavy glass, generally detrimental with the use of strong magnification microscopes.
FIG. 5
a
and
FIG. 5
b
illustrate a method utilizing a single microscopic sighting system
13
and a semi-reflecting plate
17
permitting superposing the images of the component
1
and the substrate
2
at time of alignment. After alignment, a displacement program
10
is applied to the component
1
through the intermediary of a mechanical device
11
in order to place same on the substrate
2
.
This method poses the following technical problems:
The final position of the component is sensitive to the thickness of the component, the system presenting a defect in parallax (absence of parallelism between the sighting axis
18
and the deposit axis
10
).
Significant sighting distance, generally incompatible with high resolution and strong magnification microscopes.
Sighting of substrate
2
through a semi-reflecting glass plate
17
inclined in relation to the median sighting axis
18
. Said configuration introduces optical aberrations such as coma and astigmatism, which reduces the resolution and enlargement capacities of the sighting system.
FIG. 6
a
and
FIG. 6
b
illustrate a method which is applicable when the component
1
is transparent over the length of the light wave utilized by the microscopic sighting system
13
. Sighting takes place through the transparent support
11
of the component
1
. When in alignment phase, the component
1
and the substrate
2
are separated by sufficient distance (d) so that the alignment movements can take place without contacts
5
and
6
touching each other. Following alignment, a transfer program
10
is applied to the component
1
through the intermediary of a mechanical device
11
in order to place same on the substrate
2
.
This method poses the following technical problems:
Component
1
must be transparent and its two surfaces must be perfectly polished in order to permit formation of images of the substrate
2
and the component
1
.
The component generally being semi-conductive, it is then necessary to resort to infra-red sighting systems.
The required separation distance (d) at time of alignment prevents perfect adjustment of the sighting system, simultaneously, as to the component
1
and the substrate
2
.
The metallizations which are present on the bottom surface of the component
1
act as a screen and do not permit the visualization of the totality of the surface of the substrate
2
.
It is impossible to differently illuminate the component
1
and the substrate
2
.
The present invention provides a new and improved method and apparatus that overcomes the above referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, an aligning device for microsystems is provided. The device includes a sighting system, a semi-reflective plate and a mechanical device for positioning a component. The reflective plate has a normal that merges with an optical axis of the sighting system.
One advantage of the present invention resides in utilization of a single microscopic sighting system for alignment of two components.
Another advantage resides in forming an enlarged image exactly united with the lower surface of component
1
.
Another advantage resides in the placement of component
1
on substrate
2
without having to displace the microscopic sighting system
22
.
Another advantage resides in minimizing the distance between the component
1
and the substrate
2
at time of alignment phase of the two components.
Another advantage resides in utilizing sighting devices
22
with high numerical apertures, compatible with high resolutions and strong magnifications, resulting in providing assurance of great precision in placement of the component
1
in relation to the substrate
2
.
Another advantage resides in visualization of the lower surface of the component
1
and of the upper surface of the substrate
2
without parallax effect.
Another advantage resides in alignment of non-transparent components.
Another advantage resides in utilization of a relative alignment principle which does not require absolute displacement precision
10
of the maintenance device
11
of the component
1
when the latter is placed on the substrate
2
.
Still further benefits and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding
Brown Khaled
Fay Sharpe Fagan Minnich & McKee LLP
Font Frank G.
Optiques et Microsystems SA
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