Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-07-14
2004-01-13
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S598000, C438S050000, C438S739000, C438S619000, C257S499000, C156S345420
Reexamination Certificate
active
06677225
ABSTRACT:
TECHNICAL FIELD
The present invention relates in general to a system and method for constraining microcomponents in a desirable manner, and in specific to a method and system for handling microcomponents that are totally released from a substrate in a manner that enables such microcomponents to be constrained to a base and unconstrained as desired.
BACKGROUND
Extraordinary advances are being made in micromechanical devices and microelectronic devices. Further, advances are being made in MicroElectroMechanical System (“MEMS”) devices, which comprise integrated micromechanical and microelectronic devices. The terms “microcomponent” and “microdevice” will be used herein generically to encompass microelectronic components, micromechanical components, as well as MEMS components. Traditionally, microcomponents are fabricated on a substrate in a manner such that the microcomponents are fixed or anchored to such substrate. Thus, microcomponents are traditionally not totally released from a substrate, but instead are fixed to the substrate.
An example of a typical fabrication process of the prior art is described in conjunction with
FIGS. 1A-1E
. Turning to
FIG. 1A
, a substrate (e.g., a wafer)
102
is provided, on which a first layer of sacrificial release layer (e.g., silicon oxide)
106
is deposited. As shown in
FIG. 1B
, the sacrificial release layer
106
is then etched (or patterned) into a desired shape. Typically, the sacrificial release layer
106
is etched to form an opening therein to the substrate
102
, as shown in FIG.
1
B. Thereafter, a layer of polysilicon (“P1”)
108
is deposited, as shown in FIG.
1
C. Where the sacrificial release layer
106
was etched to form an opening to substrate
102
, P1
108
fills such opening to form an anchor
104
, which anchors the structure to substrate
102
. As shown in
FIG. 1D
, the P1 layer
108
is then etched (or patterned) into a desired shape. Further polysilicon and sacrificial release layers may be added in a similar manner. Additionally, electrical conducting layers (e.g., gold) and electrical insulating layers (e.g., silicon nitride) may be added to produce a microcomponent having electrical conductivity and/or insulation. Finally, the sacrificial release layers,
106
for example, may be released by exposing such sacrificial release layers to a releasing agent, such as hydrofluoric acid (HF), resulting in a microcomponent that is fixed (or “anchored”) to the wafer, as shown in FIG.
1
E.
In most respects it has been beneficial for a microcomponent to be fixed (or anchored) to its substrate, in the prior art. For example, if the microcomponent is not anchored to the substrate during the release of the sacrificial layers (e.g., layer
106
), the microcomponent may become lost, mis-positioned, or otherwise difficult to handle. For instance, to release the sacrificial layers, a substrate is commonly placed in an HF bath. Thus, if the microcomponent were not anchored to the substrate, the microcomponent might float around in the HF bath. Furthermore, the microcomponent may become mis-positioned (e.g., positioned in an undesirable manner on the substrate) and/or be difficult to handle in the HF bath. However, many situations arise in which it is desirable to totally release a microcomponent from its substrate. For example, it may be desirable to release a microcomponent from its substrate in order to perform assembly operations with such released microcomponent, e.g., assemble the released microcomponent to other microcomponents. Accordingly, relatively crude techniques have been developed in the prior art for removing a microcomponent from its substrate anchoring.
An example of a first prior art technique is described in conjunction with FIG.
2
. As shown, microcomponent
208
may be anchored to wafer
202
with anchor
204
. As described in the exemplary fabrication process above, the anchor
204
may be a polysilicon layer and the microcomponent
208
may comprise any number of additional layers. It can be seen that the microcomponent
208
may be removed from the wafer
202
by breaking anchor
204
. However, such a crude form of removing microcomponents is often undesirable for several reasons. First, such breaking of the anchor
204
presents difficulty in defining the shape of microcomponent
208
. For example, a portion of a broken anchor
204
may remain attached to microcomponent
208
. Additionally, such an attached portion of a broken anchor
204
may be in the form of a spur or spike, as examples, which may be an undesirable feature to be included within microcomponent
208
. Additionally, breaking of the anchor
204
may result in particles of silicon, the presence of which may be undesirable. For example, such particles may land on and interfere with the operation of microcomponent
208
or other microcomponents. Also, such particles may present a health hazard to persons that inhale such particles.
An example of a second prior art technique for removing microcomponents from a substrate is described in conjunction with FIG.
3
. As shown in
FIG. 3
, microcomponent
308
is fixed to a tether
304
which is anchored to wafer
302
with anchor
306
. As described in the exemplary fabrication process of
FIGS. 1A-1E
above, the anchor
306
may be a polysilicon layer and the microcomponent
308
may comprise any number of additional layers. Further, tether
304
may be in any layer that is fixed to the microcomponent
308
, for example. It can be seen that the microcomponent
308
may be removed from the wafer
302
by breaking tether
304
. An example of this technique is disclosed by Chris Keller in
Microfabricated High Aspect Ratio Silicon Flexures
, 1998. More specifically, Keller discloses a photoresist tether holding a polysilicon beam (microcomponent) to a polysilicon anchor, wherein the tether may then be broken to release the polysilicon beam component (see e.g., FIGS. 4.59 and 4.60 and discussion thereof). However, as discussed above, such a crude form of removing microcomponents is often undesirable and presents the same problems described above for breaking anchor
204
of FIG.
2
. More specifically, such breaking of the tether
304
presents difficulty in defining the shape of microcomponent
308
. For example, a portion of a broken tether
304
may remain attached to microcomponent
308
. Additionally, such an attached portion of a broken tether
304
may be in the form of a spur or spike, as examples, which may be an undesirable feature to be included within microcomponent
308
. Additionally, breaking of the tether
304
may result in particles, which may be undesirable. For example, such particles may land on and interfere with the operation of microcomponent
308
or other microcomponents, and such particles may present a health hazard to persons that inhale them.
Recent developments have allowed for fabrication of “totally released” microcomponents (e.g., stand-alone microcomponents that are totally released from the substrate). For example, the process as disclosed in U.S. Pat. No. 4,740,410 issued to Muller et al. entitled “MICROMECHANICAL ELEMENTS AND METHODS FOR THEIR FABRICATION,” U.S. Pat. No. 5,660,680 issued to Chris Keller entitled “METHOD FOR FABRICATION OF HIGH VERTICAL ASPECT RATIO THIN FILM STRUCTURES,” and U.S. Pat. No. 5,645,684 issued to Chris Keller entitled “MULTILAYER HIGH VERTICAL ASPECT RATIO THIN FILM STRUCTURES” may be utilized to fabricate totally released microcomponents. As a further example, the fabrication process disclosed in concurrently filed and commonly assigned U.S. patent application Ser. No. 09/569,330 entitled “METHOD AND SYSTEM FOR SELF-REPLICATING MANUFACTURING STATIONS” allows for fabrication of totally released microcomponents. Furthermore, such fabrication process also allows for the fabrication of electrically isolated microcomponents. Additionally, other fabrication processes may be developed in the future, which may also allow for totally released microcomponents.
However, difficulties with constraining (e.g., restricting or restraining) tota
Ellis Matthew D.
Parker Eric G.
Skidmore George D.
Haynes and Boone LLP
Lee Jr. Granvill D
Smith Matthew
Zyvex Corporation
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