Etching a substrate: processes – Etching of semiconductor material to produce an article...
Reexamination Certificate
1997-12-19
2001-02-20
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Etching of semiconductor material to produce an article...
C438S510000, C073S504140
Reexamination Certificate
active
06190571
ABSTRACT:
INCORPORATION BY REFERENCE
The entire disclosure of each of Japanese Patent Applications No. HEI 08-355339 filed on Dec. 20, 1996, HEI 09-022037 filed on Jan. 20, 1997, and HEI 09-032963 filed on Jan. 31, 1997 including specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor micromachine applied to various microsensors and a manufacturing method thereof.
2. Description of the Related Art
Conventionally, there has been developed a micromachining technology that employs semiconductor materials such as silicon. This micromachining technology enables the manufacture of a minute sensor such as an angular velocity sensor (gyro sensor), an acceleration sensor, a microactuator and the like. In combination with a generally employed technology for manufacturing semiconductor circuits or the like, this technology enables the manufacture of the aforementioned minute sensors having a dimension of less than 1 mm, without making use of machining work.
As an example of a product of this technology, a semiconductor micromachine that operates as an angular velocity sensor will now be described with reference to
FIGS. 15 through 17
.
A semiconductor micromachine
9
as illustrated in
FIGS. 15 through 17
has a substrate
92
, a movable portion
93
and a pair of stationary portions
97
. The movable portion
93
is supported by acicular bodies
95
, and is arranged opposite the substrate
92
with a gap
91
provided therebetween. The movable portion
93
is arranged between the stationary portions
97
that are located opposite each other. As shown in
FIG. 16
, the movable portion
93
is arranged parallel to the substrate
92
.
The movable portion
93
is composed of a vibrating plate
96
and movable-side comb-shaped electrodes
961
integrally provided on both sides of the vibrating plate
96
.
Each acicular body
95
is connected at an end thereof with a supporting portion
94
secured to the substrate
92
. The supporting portions
94
are secured to the substrate
92
through securing layers
949
. Each supporting portion
94
is provided with an electrode pad
948
.
Furthermore, the substrate
92
has thereon a distance detecting electrode
98
, which is located opposite the vibrating plate
96
to detect the distance between the substrate
92
and the vibrating plate
96
. As shown in
FIG. 16
, the vibrating body
96
has on a back surface
962
thereof a detecting electrode section that cooperates with the distance detecting electrode
98
.
The distance detecting electrode
98
is connected with an electrode pad
988
through a lead portion
980
and a terminal portion
982
.
The stationary portions
97
are provided with stationary-side comb-shaped electrodes
971
for causing the vibrating plate
96
to vibrate. The stationary-side comb-shaped electrodes
971
and the movable-side comb-shaped electrodes
961
are arranged to be engaged with each other. A very narrow gap is formed between each movable-side electrode
961
and each stationary-side electrode
971
.
The stationary portions
97
are secured to the substrate
92
by securing layers
979
. The stationary portions
97
are provided with electrode pads
978
for applying a voltage to the stationary-side comb-shaped electrodes
971
.
In the aforementioned semiconductor micromachine
9
, the substrate
92
is made of monocrystal silicon, and the movable portion
93
is made of polycrystalline silicon doped with phosphorus, boron, antimony or the like. The stationary portions
97
, the supporting portions
94
, and the acicular bodies are also made of polycrystalline silicon doped with phosphorus, boron, antimony or the like.
The distance detecting electrode
98
provided on the substrate
92
is doped with a dopant whose characteristics are different from those of the substrate
92
. More specifically, a corresponding portion of the substrate
92
made of p-type monocrystal silicon is doped with phosphorus, boron, antimony or the like, so that the distance detecting electrode
98
is obtained.
The lead portion
980
and the terminal portion
982
are also formed on the substrate
92
substantially in the same manner as the distance detecting electrode
98
.
The securing layers
949
,
979
are made of a silicon nitridation film.
Furthermore, the electrode pads
948
,
978
and
988
are made of conductive materials such as gold, aluminium or the like.
It will be described hereinafter how the aforementioned semiconductor micromachine
9
detects an angular velocity.
First, an alternating-current voltage of a rectangular waveform ranging from 0 to V
0
(V) is applied between the movable-side and stationary-side comb-shaped electrodes
961
,
971
on one side. This alternating-current voltage has a resonance frequency for the case where the movable portion
93
resonates in a direction indicated by arrow &agr; of FIG.
15
. An alternating-current voltage having a phase shifted by 180 degrees is applied between the movable-side and stationary-side comb-shaped electrodes
961
,
971
on the other side.
There is thus generated an electrostatic force between the respective movable-side and stationary-side electrodes
961
,
971
. As indicated by arrow &agr; of
FIG. 15
, this electrostatic force causes the vibrating plate
96
to vibrate horizontally, that is, in a direction parallel to the substrate
92
.
Starting from this state, the semiconductor micromachine
9
is caused to rotate about the c-axis as illustrated in
FIG. 15
at an angular velocity &ohgr;.
Then, Corioli's forces F
1
, F
2
as illustrated in
FIG. 16
are alternately applied to the vibrating plate
96
, which is caused to vibrate in a direction perpendicular to the substrate
92
as indicated by arrow &bgr; of FIG.
15
.
The Corioli's forces F
1
, F
2
are represented as follows:
F
1
=
F
2
=2
m&ohgr;×A
(2
&pgr;f
)cos{(2
&pgr;f
)
t}
wherein “m” represents mass of the vibrating plate
96
, “&ohgr;” angular velocity of the semiconductor micromachine
9
, “A” amplitude of the vibrating plate
96
, “f” frequency of the alternating-current voltage, and “t” elapsed time.
When the vibrating body
96
vibrates vertically, the distance between the vibrating body
96
and the substrate
92
, that is, the thickness of the gap
91
changes in accordance with a frequency of the vibration. The change in the distance is detected as a change in the electrostatic capacity between the back surface
962
of the vibrating body
96
and the distance detecting electrode
98
. Based on the value thus detected, the angular velocity &ohgr; is detected by processing signals from a circuit not shown in the drawings.
As will be described hereinafter, the semiconductor micromachine
9
has been conventionally manufactured using a generally employed technology for manufacturing semiconductor circuits.
As shown in
FIGS. 18-22
, a distance electrode
98
or the like is formed in a substrate
92
by doping the substrate
92
with a dopant. This dopant has a conductivity different from that of the substrate
92
.
As shown in
FIGS. 18
a
and
20
a,
a silicon oxidation film
653
is provided on the substrate
92
, an etching stopper layer
654
is then provided on the silicon oxidation film
653
, and finally an etching layer
655
is provided on the etching stopper layer
654
.
After that, a resist pattern used as a mask is subsequently formed on the etching layer
655
by a photolithographic process. The etching layer
655
, the etching stopper layer
654
and the silicon oxidation film
653
are subjected to a RIE (reactive ion etching) process. This etching process allows the formation of contact holes
900
penetrating the silicon oxidation film
653
, the etching stopper layer
654
and the etching layer
655
as shown in
FIG. 20
b
(Note that the contact holes
900
can not be seen from a direction shown in
FIG. 18
b.
).
After the resist pattern has been removed, a semiconductor thin film
657
is provided on t
Aisin Seiki Kabushiki Kaisha
Gulakowski Randy
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Olsen Allan
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