Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2003-01-03
2004-11-09
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S309000, C310S026000
Reexamination Certificate
active
06815866
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application No. 2002-434 filed on Jan. 4, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro electro mechanical system (MEMS) driving device, and more particularly, to a cantilever having a step-up structure which reduces a deformation of a moving plate and a method of manufacturing the same.
2. Description of the Related Art
Generally, a MEMS driving device, such as a MEMS switch, is an application device used to route a signal and match impedance networks in a radio communication system which uses microwaves or millimeter waves.
Typical MEMS techniques used to produce a MEMS are a bulk micro-machining technique and a surface micro-machining technique. The bulk micro-machine technique enables a mechanical driving by forming an air gap through melting a portion of a substrate after forming a multiple-layer on the substrate, such as a silicon substrate. The surface micro-machining technique produces a predetermined structure according to a shape designed by depositing polycrystalline silicon, a silicon oxide layer, an oxide layer, and a metal layer on a substrate. The surface micro-machining technique is used to manufacture various micro machines including an atomic force microscope (AFM) tip, a barometer, and an RF resonator.
A micro multilayer thin film cantilever having a step-up structure is an example of a MEMS driving device produced by a surface micro-machining technique.
FIG. 1
shows a perspective view of a conventional cantilever, and
FIG. 2
shows a sectional perspective view of the cantilever of
FIG. 1
, along the cutting plane line
2
—
2
′.
Referring to
FIGS. 1 and 2
, the conventional cantilever
12
formed on a substrate
10
includes a rectangular anchor
12
a
fixed on the substrate
10
, and a moving plate
12
b
supported by the anchor
12
a
. An air gap
14
is formed between the moving plate
12
b
and the substrate
10
. In this case, the moving plate
12
b
is stepped up from the anchor
12
a
. Accordingly, the moving plate
12
b
and the anchor
12
a
are formed with a step having a thickness of the air gap
14
therebetween.
Since the cantilever
12
is manufactured at a high temperature and under a high pressure, a remaining bending stress after the manufacturing process thereof acts on the support structure. According to a slope of the remaining bending stress, deformations of the cantilever appear, performances of the cantilever deteriorate, and the cantilever cannot be used for micro and high-precision products.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a micro electro mechanical system (MEMS) driving device having a step-up structure which minimizes deformations due to a manufacturing process thereof.
Another object of the present invention to provide a method of manufacturing a MEMS driving device.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided a cantilever having a step-up structure, the cantilever comprising a substrate, an anchor formed on the substrate, and a moving plate connected to the anchor while maintaining a predetermined gap from the substrate, wherein the anchor includes a first anchor having a predetermined shape and a second anchor which is perpendicular to an edge of the first anchor while being formed along a longitudinal axis of the moving plate.
The anchor may further include a third anchor which is perpendicular to the edge of the first anchor and parallel with the second anchor. The first anchor may have a rectangular shape, and the second and third anchors may have predetermined lengths and widths, wherein a ratio of the respective widths to the respective lengths is larger than 0 and smaller than 1.
To achieve the above and/or other objects of the present invention, there is provided another cantilever having a step-up structure, the cantilever comprising a substrate, an anchor formed on the substrate, and a moving plate connected to the anchor while maintaining a predetermined gap from the substrate, wherein the anchor includes a first anchor of a predetermined shape and a second anchor formed near the first anchor. The first anchor may have a rectangular shape and the second anchor may have a slit shape perpendicular to a longitudinal axis of the moving plate.
To achieve the above and/or other objects of the present invention, there is also provided a manufacturing method for a cantilever of a step-up structure having a substrate on which a semiconductor device is formed, the method comprising forming a sacrificial layer on the substrate to cover the semiconductor device, forming an etch stop layer on the sacrificial layer, patterning the etch stop layer to expose the sacrificial layer in a predetermined shape, etching an exposed region of the sacrificial layer to expose a predetermined region which is connected to the semiconductor device, successively forming predetermined material layers on the etch stop layer to cover the exposed region so as to form the cantilever having the step-up structure, connecting a portion of the material layers on the exposed region with the substrate, and removing the sacrificial layer, wherein the patterning of the etch stop layer includes patterning first and second regions of the predetermined shape, the second region being formed along a longitudinal axis of the material layers and perpendicular to the first region.
The successively forming of the material layers may include forming a lower electrode layer on the sacrificial layer to cover the exposed region, forming a piezoelectric thin layer on the lower electrode layer, and forming an upper electrode layer on the piezoelectric thin layer. The patterning of the first and second regions may include patterning the second region having a length and a width with respect to the longitudinal axis and an axis perpendicular to the longitudinal axis of the material layers, respectively, and a ratio of the width to the length which is larger than 0 and smaller than 1.
The patterning of the etch stop layer may include patterning a third region of the predetermined shape along with the first and second regions, the third region being perpendicularly connected to the first region while being parallel with the second region along the longitudinal axis of the material layers. The third region may be patterned so as to have a predetermined length and width with respect to the longitudinal axis and an axis perpendicular to the longitudinal axis of the material layers, respectively, and a ratio of the width to the length which is larger than 0 and smaller than 1.
To achieve the above and/or other objects of the present invention, there is provided another manufacturing method for a cantilever of a step-up structure having a substrate on which a semiconductor device is formed, the method comprising forming a sacrificial layer on the substrate to cover the semiconductor device, forming an etch stop layer on the sacrificial layer, patterning the etch stop layer to expose the sacrificial layer in a predetermined shape, etching an exposed region of the sacrificial layer to expose a predetermined region which is connected to the semiconductor device, successively forming predetermined material layers on the etch stop layer to cover the exposed region so as to form the cantilever having the step-up structure, connecting a portion of the material layers on the exposed region with the substrate, and removing the sacrificial layer, wherein the patterning of the etch stop layer includes patterning first and second regions of the predetermined shape, the second region being parallel with and near the first region and perpe
Dougherty Thomas M.
Staas & Halsey , LLP
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