Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1997-08-27
2001-01-23
Ng{circumflex over (o)}, Ng{circumflex over (a)}n V. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S352000, C257S353000
Reexamination Certificate
active
06177706
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a capable semiconductor device such as a micromachine, a solar battery having a high energy conversion efficiency, a volatile or a nonvolatile memory, a load of memory cell of an SRAM, a field effective thin film transistor (hereinafter referred to as “TFT”) which is used as a display device of a wide-screen, high-precision active-matrix type liquid crystal display and a liquid crystal display which comprises a pixel electrode and a thin film transistor. The present invention also relates to a method for manufacturing such a semiconductor device.
2. Background of the Invention
(Prior Art
1
)
A prototype of a micromachine, which is typically an apparatus of fine dimensions in the units of micrometers or less having a mechanical motion mechanism, is prepared by redeployment of a semiconductor technique mainly implementing simultaneous formation on a semiconductor wafer by transfer of a mask pattern or the like.
Micromachine Having Movable Part
FIG. 77
is a front sectional view showing a sectional structure of an electrostatic motor
3000
which is manufactured by a conventional method. In this electrostatic motor
3000
, a nitride film (Si
3
N
4
film)
3004
is formed on a single-crystalline Si substrate
3002
, and a rotary shaft
3014
and a stator
3010
of polycrystalline Si are fixedly formed on the nitride film
3004
, while a ring-shaped rotator
3008
of polycrystalline Si is stopped to the rotary shaft
3014
with a clearance. Thus, the rotator
3008
is rotatable about the rotary shaft
3014
.
The stator
3010
is formed by a plurality of members, being electrically isolated from each other, which are radially arranged at prescribed intervals to enclose the rotator
3008
. Alternating voltages which are out of phase with each other are independently applied to these members of the stator
3010
. Consequently, electrostatic attractive or repulsive force is generated between the stator
3010
and the rotator
3008
, and a bearer of such force is successively moved between the respective members, thereby rotating the rotator
3008
. It is reported that the rotator
3008
is 100 &mgr;m in diameter and 2.5 &mgr;m in thickness.
FIG. 78
is a process diagram showing a certain stage in a method of manufacturing the electrostatic motor
3000
. In manufacturing of the electrostatic motor
3000
, a technique of forming sacrifice layers and etching the same is employed in order to isolate the rotator
3008
, the stator
3010
, the rotary shaft
3014
and the nitride film
3004
serving as an underlayer from each other and defining clearances therebetween. In order to manufacture the electrostatic motor
3000
, an SiO
2
layer is first temporarily formed on an upper surface of the nitride film
3004
and selectively removed to form a first sacrifice layer
3006
, for selectively filling up spaces corresponding to clearances. A polycrystalline Si layer is stacked thereon by CVD (chemical vapor deposition) or the like. Thereafter this polycrystalline Si layer is selectively removed to be formed into the shapes of the rotator
3008
and the stator
3010
. Another sacrifice layer
3012
is newly formed so that another polycrystalline Si layer is newly stacked thereon, whereafter this polycrystalline Si layer is selectively removed to be formed into the shape of the rotary shaft
3014
. Finally, the two sacrifice layers
3006
and
3012
are entirely removed by etching, thereby completing the electrostatic motor
3000
shown in FIG.
77
.
<Micromachine Having Deformed Part>
FIG. 79
is a plan view showing an electrostatic linear actuator
3030
which is manufactured by a conventional method. In this actuator
3030
, fixed electrodes
3040
of polycrystalline Si and movable parts
3036
of polycrystalline Si are formed on a single-crystalline Si substrate
3032
. The comb-shaped fixed electrodes
3040
are fixed onto the single-crystalline Si substrate
3032
in base portions thereof, so that comb-shaped protrusions are upwardly raised from the single-crystalline Si substrate
3032
. On the other hand, the movable parts
3036
are fixed to the single-crystalline Si substrate
3032
only in support portions
3034
, so that other portions are entirely upwardly raised from the single-crystalline Si substrate
3032
. The movable parts
3036
have comb-shaped forward end portions
3038
, which are fitted with the fixed electrodes
3040
with no contact.
When voltage are applied to the fixed electrodes
3040
, electrostatic attractive or repulsive force acts across the same and the forward end portions
3038
, whereby the forward end portions
3038
are straightly displaced in a horizontal plane. At this time, members coupling the forward end portions
3038
with the support portions
3034
, which are elastic members serving as sources of restoring force for the displacement of the forward end portions
3038
, are elastically deformed following the displacement of the forward end portions
3038
.
A method of manufacturing the actuator
3030
also employs a step of forming a sacrifice layer and removing the same by etching, similarly to the method of manufacturing the electrostatic motor
3000
. Namely, a sacrifice layer is first formed on the single-crystalline Si substrate
3032
, so that a polycrystalline Si layer is formed thereon. Thereafter the polycrystalline Si layer is selectively removed, to be formed into the shapes of the movable parts
3036
and the fixed electrodes
3040
. Finally, the sacrifice layer is entirely removed by etching, to complete the actuator
3030
.
Micromachine Having Cavity
FIG. 80
is a fragmented perspective view showing a part of a pressure sensor
3100
which is manufactured by a conventional method. In this pressure sensor
3100
, a lower housing
3102
and an upper housing
3104
having grooves are joined with each other to form a hollow vessel defining a cavity
3106
in its interior. A plate-type oscillator
3108
is inserted in this cavity
3106
. All of the lower housing
3102
, the upper housing
3104
and the oscillator
3108
are made of single-crystalline Si.
Only an end portion of the oscillator
3108
is in contact with an inner wall portion defining the cavity
3106
to be supported by the hollow vessel, while all of the remaining portions are separated from the inner walls. Therefore, it is possible to excite natural oscillation in the oscillator
3108
by applying a stationary magnetic field and an oscillating current from the exterior. The lower housing
3102
is coupled with a diaphragm (not shown) which receives a pressure to be measured. The diaphragm is deformed upon application of the pressure, whereby the oscillator
3108
is also deformed. Upon such deformation of the oscillator
3108
, the natural frequency deviates in response to the degree of the displacement. The level of the pressure is measured by detecting the deviation of the natural frequency. This pressure sensor
3100
has an excellent elastic limit, excellent strength and the like, as well as uniform characteristics since all of the members
3102
,
3104
and
3108
are made of single-crystalline Si. Therefore, it is possible to provide these members with large deformation, while implementing a pressure sensor having high reliability.
In order to manufacture the pressure sensor
3100
, a technique of junction (also referred to as “cladding”) is employed as hereinabove described. After the two housings
3102
and
3104
having grooves and the oscillator
3108
are prepared from single-crystalline Si independently of each other, the two housing
3102
and
3104
are joined with each other at a junction plane
3110
while receiving the oscillator
3108
in the grooves. This junction step is carried out in a vacuum, whereby the cavity
3106
is maintained in a vacuum state also after completion of the apparatus.
Micromachine Having Diaphragm
FIG. 81
is a front elevational view showing another pressure sensor
3200
which is manufactured by a conventional method. Junction of single-c
Asakawa Toshifumi
Hikawa Tetsuo
Kosaka Daisuke
Sawada Takashi
Shindo Masahiro
Mega Chips Corporation
Ng{circumflex over (o)} Ng{circumflex over (a)}n V.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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