Electrical generator or motor structure – Non-dynamoelectric – Thermal or pyromagnetic
Reexamination Certificate
2002-01-24
2004-09-14
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Thermal or pyromagnetic
C251S011000
Reexamination Certificate
active
06791233
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to a semiconductor device made up of a semiconductor substrate, a flexible area isolated from the semiconductor substrate and displaced in response to temperature change, and a heat insulation area placed between the semiconductor substrate and the flexible area, a semiconductor microactuator using the semiconductor device, a semiconductor microvalve, a semiconductor microrelay, and a semiconductor microactuator manufacturing method.
2. Related Art
A semiconductor microactuator includes at least two materials having different thermal expansion coefficients in combination as a bimetal structure wherein the bimetal structure is heated and the difference between the thermal expansion coefficients is used to provide displacement is available as a mechanism using a semiconductor device made up of a semiconductor substrate, a flexible area isolated from the semiconductor substrate and displaced in response to temperature change, and a heat insulation area placed between the semiconductor substrate and the flexible area. The semiconductor microactuator is disclosed in U.S. Pat. No. 5,069,419 “Semiconductor microactuator.”
A semiconductor microactuator described in U.S. Pat. No. 5,069,419 is as shown in
FIG. 53
(top view) and
FIG. 54
(sectional view); it has a flexible area of a bimetal structure comprising an aluminum thin film
304
formed in a part of a silicon diaphragm
300
. If an electric current is made to flow into a heater
301
formed in the silicon diaphragm
300
, heat is generated and the temperature of the diaphragm
300
rises. Since silicon and aluminum differ largely in thermal expansion coefficient, a thermal stress occurs, bending the diaphragm
300
, producing displacement of a moving part
305
placed contiguous with the diaphragm
300
. To provide efficient displacement, a hinge
303
of a silicon dioxide thin film is placed between the periphery of the diaphragm
300
and a silicon frame
302
of a semiconductor substrate for preventing heat generated in the diaphragm
300
from escaping to the silicon frame
302
.
However, considering the current state of application, it is desired to furthermore decrease the heat loss. Specifically, the heat escape (heat loss) is thought of as power (consumption power) supplied all the time to maintain the diaphragm
300
at a predetermined temperature (for example, 150° C.).
Then, it is desired that the power consumption is 100 mW or less considering miniature, portable battery-driven applications.
Further, as examples of semiconductor microrelays in related arts, semiconductor microrelays are disclosed in JP-A-6-338244 and JP-A-7-14483. The semiconductor microrelays disclosed therein will be discussed with reference to the accompanying drawing.
FIG. 55
is a sectional view to show the structure of the semiconductor microrelay in the related art. As shown in
FIG. 55
, the semiconductor microrelay has a cantilever beam
313
having a first thermal expansion coefficient and made of a silicon monocrystalline substrate
312
with an opposite end supported so that one end can be moved. On the rear side of the cantilever beam
313
, the semiconductor microrelay has a metal layer
315
having a second thermal expansion coefficient larger than the first thermal expansion coefficient via a conductive layer
315
. On the main surface of the cantilever beam
313
, a contact circuit
317
is provided via an oxide film
314
on the one end side. Also, a heater circuit
318
is provided via the oxide film
314
on the roughly full face of the main surface of the cantilever beam
313
.
On the other hand, an opposed contact part
320
having a conductive layer
319
as an opposed surface is provided at a position facing the contract circuit
317
with a predetermined space above the contract circuit
317
. An electric current is made to flow into the heater circuit
318
, whereby the heater circuit
318
is heated. Thus, a flexible area consisting of the cantilever beam
313
and the metal layer
316
is heated. At this time, the thermal expansion coefficient of the metal layer
316
is set larger than that of the cantilever beam
313
, so that the cantilever beam
313
and the metal layer
316
are displaced upward. Therefore, the contact circuit
317
provided on the one end of the cantilever beam
313
is pressed against the opposed contact part
320
and is brought into conduction. Such a bimetal-driven relay enables an increase in the contact spacing and an increase in the contact load as compared with a conventional electrostatically driven relay. Thus, a relay with small contact resistance and good reliability with less welds, etc., can be provided.
However, the semiconductor microrelay in the related art also involves the following problem: To drive the relay, it is necessary to make an electric current flow into the heater circuit
318
provided on the main surface of the cantilever beam
313
for heating the cantilever beam
313
and the metal layer
316
. However, the silicon monocrystal forming the cantilever beam
313
is a material having very good thermal conductivity, the cantilever beam
313
is connected at the opposite end to the silicon monocrystalline substrate
312
, and large heat is escaped from the cantilever beam
313
to the silicon monocrystalline substrate
312
, so that it becomes extremely difficult to raise the temperature of the cantilever beam
313
with small power consumption.
That is, with the semiconductor microrelay in the related art, large power must be supplied all the time to maintain the conduction state. The value is extremely large as compared with a mechanical relay that can be driven with several ten mW. For practical use, realizing low power consumption is a large challenge.
SUMMARY OF INVENTION
As described above, the semiconductor microactuator using the semiconductor device, the semiconductor microvalve, and the semiconductor microrelay in the related arts require large power consumption and thus it becomes difficult to drive them with a battery and it is made impossible to miniaturize them for portable use.
It is therefore an object of the invention to provide a semiconductor device with small power consumption, manufactured by an easy manufacturing process, a semiconductor microactuator using the semiconductor device, a semiconductor microvalve, a semiconductor microrelay, and a semiconductor microactuator manufacturing method.
To the end, according to a first aspect of the present invention, there is provided a semiconductor device comprising a semiconductor substrate, a flexible area being isolated from the semiconductor substrate and displaced in response to temperature change, and a thermal insulation area being placed between the semiconductor substrate and the flexible area and made of a resin for joining the semiconductor substrate and the flexible area. The thermal insulation area made of a resin is placed between the semiconductor substrate and the flexible area, whereby heat escape when the temperature of the flexible area is changed is prevented, so that power consumption can be suppressed and further the manufacturing method is simple.
In a second aspect to the present invention, in the semiconductor device as first aspect of the present invention, the material of which the thermal insulation area is made has a thermal conductivity coefficient of about 0.4 W/(m° C.) or less. The heat insulation properties between the flexible area and the semiconductor substrate are enhanced.
In a third aspect of the present invention, in the semiconductor device as the second aspect of the present invention, the material of which the thermal insulation area is made is polyimide. The heat insulation properties between the flexible area and the semiconductor substrate are enhanced and manufacturing the semiconductor device is facilitated.
In a fourth aspect of the present invention, in the third aspect of the present invention, the material of which the thermal insulation area is made is a fluoridated resin. The heat in
Kamakura Masanao
Kawada Hiroshi
Nagao Shuichi
Nobutoki Kazuhiro
Ogihara Jun
Dougherty Thomas M.
Matsushita Electric & Works Ltd.
Nixon & Vanderhye P.C.
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