Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Multiple layers
Reexamination Certificate
1998-10-27
2002-03-12
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Multiple layers
C438S048000, C438S052000, C438S758000, C257S254000, C257S417000, C257S419000, C257S420000
Reexamination Certificate
active
06355578
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a composite device, as well as its manufacturing method. It particularly concerns a method for a composite device equipped with a micromachine and a circuit element, with the thin metallic film at the circuit element being protected by a protective film during etching of the sacrifice layer during the formation of said micromachine.
BACKGROUND OF THE INVENTION
Silicon micromachining techniques have been widely used in recent years; they are applied to acceleration sensors and angular velocity sensors, for example, in which microscopic sensor elements are formed on top of a silicon semiconductor substrate.
An acceleration sensor is illustrated by the number
100
in
FIG. 3
as an example of such a silicon micromachine.
This acceleration sensor
100
has a box area
122
, arms
121
1
to
121
4
, and fixed parts
120
1
to
120
4
that are formed on top of a silicon substrate
103
. The box area
122
is formed into a rectangular shape and the arms
121
1
to
121
4
are connected to its four corners at one end, with each of the arms
121
1
to
121
4
being connected to each of the fixed parts
120
1
to
120
4
at the other end.
The fixed parts
120
1
to
120
4
are secured over the silicon substrate
103
; on the other hand, the box area
122
and the arms
121
1
to
121
4
are constructed so that they can freely move without making contact with the substrate
103
. It is constructed so that the arms
121
1
to
121
4
are bent vertically using the fixed parts
120
1
to
120
4
as support points when the acceleration sensor
100
is subjected to an acceleration force in the vertical direction. Resulting movement between the parallel and flat capacitor plates, consisting of the box area
122
and the substrate
103
causes the capacitance to change.
The simplified manufacturing processes of such an acceleration sensor
100
are illustrated in FIGS.
4
(
a
)-(
l
), which will be explained below.
With reference to FIGS.
4
(
a
)-(
e
), two monocrystalline silicon substrates, onto which a silicon oxide film is formed on the surface, are first prepared; they are bonded together by a direct bonding method while their silicon oxide films closely adhere to each other, with one silicon wafer being formed. Successively, the surface at one side, which is opposite from the side onto which a monocrystalline silicon thermal oxide film is formed, is polished into a structural layer
104
, and the monocrystalline silicon layer on the other side becomes a substrate
103
. The silicon oxide film, which was used for direct bonding, remains between said substrate
103
and the structural layer
104
as a sacrificial layer
101
(FIG.
4
(
a
)).
An oxide film
105
is formed onto the entire surface of such a silicon wafer structural layer
104
((
b
) of the same FIG.), with an opening
107
being formed through patterning by etching a specific region ((
c
) of the same FIG.).
The surface of the silicon structural layer
104
is exposed in opening
107
. The exposed structural layer
104
, in is removed with anisotropic dry etching by an RIE method using the oxide film
105
as a mask; so that the structural layer is formed in the same pattern as that of the oxide film
105
((
d
) of the same FIG.).
The sacrifice layer
101
, which is exposed at the bottom the opening
107
at the completion of said patterning, and the oxide film
105
, which was used for patterning the structural layer
104
, are removed by performing wet etching ((
e
) of the same FIG.)
Subsequently, ion implantation and thermal diffusion are performed, with ohmic layers
113
and
114
being respectively formed in the substrate
103
and the structural layer
104
(FIG.
10
(
f
)).
Next, a resist film
115
is formed onto the entire surface ((
g
)) of the same FIG.), windows are opened at specific sections above the ohmic layers
113
and
114
, then the decomposition of chromium and platinum occurs, with thin chromium and platinum films
116
,
117
, and
118
being respectively formed over the resist film
115
and the ohmic layers
113
and
114
((
h
) of the same FIG.).
When the resist film
115
is removed, the thin chromium and platinum film
116
formed over the resist film
115
is removed together with the resist film
115
(lift-off method). On the other hand, the thin chromium and platinum films
117
and
118
formed over the ohmic layers
113
and
114
are not removed but remain with metallic electrodes being respectively formed at the substrate
103
and the fixed part
1204
((
i
) of the same FIG.).
Furthermore, the entire [wafer] is soaked in a hydrofluoric buffer (BHF), the side faces of the sacrifice layer
101
are exposed, and the sacrifice layer
101
is etched from its side faces. During this procedure, in a region where the size of the structural layer area is large or where the width is wide, a portion of the sacrificial layer
101
remains. Accordingly, the structural layer
104
in that part is fixed to the substrate
103
by the sacrificial layer
101
, forming fixed parts
120
1
to
120
4
.
On the other hand, the sacrificial layer
101
underneath the of the structural layer
104
in a part where the area is small, or where the width is narrow, is completely removed. Accordingly, a space
72
is formed in the middle of the substrate
103
when the structural layer at that part is connected to the structural layer
54
which makes up the fixed part; a movable part, which does not make contact with the substrate
103
, is thus constructed. The arms
121
1
to
121
4
and the box area
122
are constructed from such movable parts.
In this manner, the box area
122
and the arms
121
1
to
121
4
are supported by the fixed parts
120
1
to
120
4
in a condition in which they do not make contact with the substrate
103
, the arms
121
1
to
121
4
are bent by the weight of the box area
122
when an acceleration is added, and the distance between the substrate
103
and the box area
122
changes.
Accordingly, thin metallic wires are connected to the electrodes
117
and
118
by wire-bonding, the box area
122
and the substrate
103
are connected to an external measuring circuit, not shown in the FIG., and it becomes possible to detect the change in the capacity between the box area
122
and the substrate
103
and to calculate the size of the acceleration.
However, as described above, a lift-off method is used for the formation of the thin chromium and platinum film
116
in the existing technology, and the processes are complicated. Moreover, the electrodes
117
and
118
could not be formed from a thin aluminum film, which forms a thin film wiring within an integrated circuit, when said lift-off method was used, which was becoming an obstacle when forming circuit elements and a micromachine on top of the same substrate.
The aim of this invention, which was created to solve the aforementioned inconveniences in the prior art, is to offer a technique that allows for the formation of electrodes in a composite device without using a lift-off method.
SUMMARY OF THE INVENTION
In solving the aforementioned problems, an embodiment in the invention is a manufacturing method for a composite device, consisting of: a process in which a mask film that has been patterned is formed over a structural layer which is formed over a substrate through a sacrificial layer; a process in which the aforementioned sacrificial layer is exposed through etching the aforementioned structural layer using said mask film as a mask; and a process in which the sacrificial layer is removed through the aforementioned exposed part by side etching, and in which movable parts are formed in parts of the aforementioned structural layer where the sacrificial layer underneath the bottom face is completely removed and fixed parts are formed in parts where the sacrificial layer underneath the bottom face remains. The invention is also characterized by consisting of: a process in which electrical elements are formed within the structural layer, which constructs the aforem
Kilday Lisa
Petersen Bret J.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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