Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Physical stress responsive
Reexamination Certificate
1999-01-26
2002-06-25
Zimmerman, John J. (Department: 1775)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Physical stress responsive
C029S622000, C029S874000, C029S825000
Reexamination Certificate
active
06410360
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
FEDERALLY SPONSORED RESEARCH
Not Applicable
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
The present invention relates to electromechanical devices having laminate structures and methods for fabricating such devices. More particularly, the present invention relates to laminate-based electromechanical relay devices and methods for fabricating such relays. However, the present laminate-based fabrication method may be suitably adapted for use in connection with the design and fabrication of a wide variety of laminate-based electromechanical devices. Accordingly, an example of a possible application of the laminate-based fabrication method and apparatus of the present invention includes the design and fabrication of high frequency range electromechanical relay devices.
DESCRIPTION OF THE INVENTION BACKGROUND
Conventional electromechanical devices, such as electromechanical relays, have traditionally been fabricated one individual device at a time, by either manual or automated processes. The individual devices produced by such an “assembly-line” type process generally have relatively complicated structures and exhibit high unit-to-unit variability. Such variability is undesirable because it limits the repeatability of performance from unit-to-unit. In particular, in the case of relays used to switch high frequency signals, such variances in physical geometry may result in changes in the device's inductance and capacitance, rendering such a device undesirable. While conventional electromechanical relays can be designed to reduce unit-to-unit variability, the resultant device is typically more costly to manufacture. Conventional electromechanical relays are also relatively large when compared to other electronic components. Size becomes an increasing concern as the packaging density of electronic devices continues to increase. Combined, these shortcomings render such conventional electromechanical relay devices undesirable.
A number of efforts at combating these and other shortcomings have focused on fabricating electromechanical devices, such as electromechanical relays, using silicon-based microfabrication techniques. Microfabrication, also known as micromachining, commonly refers to the use of known semiconductor processing techniques to fabricate devices known as microelectromechanical systems (MEMS) devices. Typical MEMS devices include motors, actuators and sensors. In general, known MEMS fabrication processes involve the sequential addition or removal of layers of material from a substrate layer through the use of thin film deposition and etching techniques until the desired structure has been achieved. Accordingly, MEMS devices typically function under the same principles as their macroscale counterparts. However, advantages in design, performance, and cost typically are also realized due to the great decrease in scale MEMS devices offer over their macroscale counterparts. In addition, due to the batch fabrication techniques employed to fabricate MEMS devices, significant reductions in unit-to-unit variation and per unit cost are also typically realized.
As noted above, MEMS fabrication techniques have been largely derived from the semiconductor industry. Accordingly, such techniques allow for the formation of a variety of micromechanical structures using adaptations of patterning, deposition, etching, and other processes that were originally developed for semiconductor fabrication. In general, these processes start with a wafer of silicon, glass, or other inorganic material. Multiple devices are then fabricated from the wafer through sequential addition and removal of layers of material using such techniques. Once complete, the wafer is sectioned (diced) to form the multiple individual MEMS devices (die). The individual devices are then fitted with external packaging to provide for electrical connection of the devices into larger systems and components. Again, the processes used for external packaging of the MEMS devices are analogous to those used in semiconductor manufacturing.
As an example, in the case of the moving contact of a MEMS relay, the moving contact may be formed using either surface micromachining techniques, bulk micromachining techniques, or a combination of the two techniques. In an example of surface micromachining techniques, an underlying layer, formed from an electrically conducting metal such as copper or gold, is defined, patterned, and deposited on the surface of a substrate typically formed from silicon, glass, or quartz. Through a photoresist process, a beam structure, typically formed from nickel or gold, is defined, patterned, and deposited on the surface of the underlying layer. The photoresist sheet is then removed, forming the actual structure of the beam. After the portion of the underlying layer that sits beneath the beam structure has been etched away, the resultant freestanding beam forms the moving contact of the relay. In an example of bulk micromachining, a free standing beam is formed from the layer of conducting material by deep etching of the underlying silicon, glass, or quartz substrate. The resulting beam structure is then plated with a layer of electrically conducting metal such as gold or copper. The resultant freestanding beam forms the moving contact of the relay.
MEMS devices have the desirable feature that multiple MEMS devices, or die, may be produced simultaneously in a single batch by processing many individual components on a single wafer. For example, using either surface or bulk micromachining, numerous individual relay devices may be formed on a single wafer of silicon. Once fabrication is complete, the substrate is typically diced to produce individual die. Each die typically contains a single relay. The individual relays may then be packaged in the same manner as semiconductor, for example, on a lead frame or chip carrier. Accordingly, the ability to produce numerous devices in a single batch results in a cost savings over the “one out” or “assembly line” style typically used by macro scale production techniques. The use of batch processing also increases the throughput of the MEMS fabrication process, while decreasing the overall variation between the individual die fabricated in each batch. In the specific example of electromechanical relays fabricated using MEMS fabrication techniques, batch processing has the advantage of increasing the uniformity of MEMS relay devices, decreasing the size of the devices, and reducing the cost associated with the fabrication and processing of the devices.
However, MEMS fabrication techniques are not without their drawbacks. In the example of electromechanical relays, the physical properties of the silicon, quartz, and glass substrates on which the MEMS relay devices are typically fabricated are not well suited in general to the demands placed on them by the design of an electromechanical relay. In particular, it is important to the operation of an electromechanical relay that the contacts on the relay be fully isolated when the relay is in the open position, such that no signal is carried across the relay, and that there be no isolation or resistance between the contacts when the relay is in the closed position, such that the signal is carried undistorted across the relay. Due to the reduced scale of MEMS devices, and the materials and processes used in MEMS fabrication, MEMS devices do not easily lend themselves to vertical processing. Accordingly, the physical spacing, and thus the signal isolation, between the contacts in a MEMS relay is often insufficient to fully isolate the contacts when the relay is in the open position. Thus, MEMS relays often exhibit an unacceptable flow of current across the contacts when the relays are in the open position. This problem is particularly apparent when the relays are used to switch high frequency signals. The ability of MEMS relays to operate at high frequencies may also be reduced by the dielectric properties of the material employed to fabricate the MEMS rel
Kirkpatrick & Lockhart LLP
Teledyne Industries Inc.
Zimmerman John J.
LandOfFree
Laminate-based apparatus and method of fabrication does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laminate-based apparatus and method of fabrication, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laminate-based apparatus and method of fabrication will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2979850