U.S. patent application number 10/343210 was filed with the patent office on 2004-02-12 for production method for a thin-layer component, especially a thin-layer high pressure sensor, and corresponding thin-layer component.
Invention is credited to Gluck, Joachim, Goebel, Herbert, Henn, Ralf, Kretschmann, Andre, Muenzel, Horst, Wanka, Harald.
Application Number | 20040026367 10/343210 |
Document ID | / |
Family ID | 26006514 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040026367 |
Kind Code |
A1 |
Goebel, Herbert ; et
al. |
February 12, 2004 |
Production method for a thin-layer component, especially a
thin-layer high pressure sensor, and corresponding thin-layer
component
Abstract
Proposed is a method for manufacturing a thin-layer component,
in particular a thin-layer, high-pressure sensor, as well as a
thin-layer component, where a resistive layer for forming measuring
elements, in particular strain gauges (30), is deposited on an
electrically non-conductive surface of a diaphragm layer (10, 20),
a contact-layer system (41) for electrically contacting the
measuring elements being deposited on the measuring elements in
such a manner, that regions of the measuring elements (30) are
situated between each region of the contact-layer system and the
diaphragm layer (10, 20). This is used to provide, in particular, a
high-pressure sensor, in which the capacitances of the contacts of
the contact-layer system are designed to be symmetric.
Inventors: |
Goebel, Herbert;
(Reutlingen, DE) ; Wanka, Harald; (Reutlingen,
DE) ; Kretschmann, Andre; (Reutlingen, DE) ;
Henn, Ralf; (Stuttgart, DE) ; Gluck, Joachim;
(Renningen, DE) ; Muenzel, Horst; (Clayton,
AU) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
26006514 |
Appl. No.: |
10/343210 |
Filed: |
July 29, 2003 |
PCT Filed: |
July 25, 2001 |
PCT NO: |
PCT/DE01/02768 |
Current U.S.
Class: |
216/59 |
Current CPC
Class: |
G01L 9/0054
20130101 |
Class at
Publication: |
216/59 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 26, 2000 |
DE |
100-36-285.0 |
Jul 24, 2001 |
DE |
101-35-216.6 |
Claims
What is claimed is:
1. A method for manufacturing a thin-layer component, in particular
a thin-layer, high-pressure sensor, where a resistive layer for
forming measuring elements, in particular strain gauges (30), is
deposited on an electrically non-conductive surface of a diaphragm
layer (10, 20), wherein a contact-layer system (40, 41) for
electrically contacting the measuring elements is deposited on the
measuring elements in such manner, that no steps, or steps which
are small in comparison with the thickness of the contact layer,
are covered.
2. The method as recited in claim 1, wherein the contact-layer
system (41) is deposited on the measuring elements in such a
manner, that a region of the measuring elements (30) is situated
between each region of the contact-layer system and the diaphragm
layer (10, 20).
3. The method as recited in claim 2, wherein the contact-layer
system is deposited through the openings of a shadow mask, using a
sputtering process or a vapor-deposition process, the position of
the openings being selected such that deposition exclusively occurs
on the resistive layer.
4. The method as recited in claim 3, whereinn the resistive layer
is initially deposited over the entire surface, and, in a further
step, the resistive layer is patterned photolithographically or
with the aid of a laser method, so that the lateral expansion of
the patterned resistive layer or the measuring elements is greater,
at all locations, than that of the openings in the shadow mask
subsequently used for depositing the contact-layer system.
5. The method as recited in claim 3, wherein the resistive layer is
initially deposited over the entire surface, the contact-layer
system is deposited onto the resistive layer in a further step, and
the set-up is provided, in a further step, with a passivation layer
over the entire surface; the patterning of the resistive layer and
the passivation layer subsequently being accomplished, using only
one etching mask.
6. The method as recited in claim 5, wherein the etching mask is
produced by depositing, exposing, and developing a photoresist
layer on the passivation layer.
7. The method as recited in claim 6, wherein photosensitive BCB is
used as a material for the passivation layer, so that the
passivation layer is simultaneously exposed and developed with the
photoresist layer.
8. The method as recited in one of the preceding claims, wherein
nickel-chromium or nickel-chromium-silicon is used as a material
for the resistive layer (30).
9. The method as recited in claim 5, wherein nickel-chromium or
nickel-chromium-silicon is used as a material for the resistive
layer, and a layer of BCB material is used as a passivation layer
that is simultaneously used as an etching mask, without
additionally depositing a photoresist layer.
10. A thin-layer component, in particular a thin-layer,
high-pressure sensor, where a resistive layer for forming measuring
elements, in particular strain gauges (30), is deposited on an
electrically non-conductive surface of a diaphragm layer (10, 20),
wherein a contact-layer system (40, 41) for electrically contacting
the measuring elements is deposited on the measuring elements in
such manner, that no steps, or steps which are small in comparison
with the thickness of the contact layer, are covered.
11. The thin-layer component as recited in claim 10, wherein the
contact-layer system (41) for electrically contacting the measuring
elements is deposited on the measuring elements in such a manner,
that regions of the measuring elements (30) are situated between
each region of the contact-layer system and the diaphragm layer
(10, 20).
Description
BACKGROUND INFORMATION
[0001] The present invention relates to a method for manufacturing
a thin-layer component and a thin-layer component, in particular a
thin-layer, high-pressure sensor having a substrate on which at
least one functional layer to be provided with contacts is to be
deposited. Such high-pressure sensors are used in numerous systems
in a motor vehicle, for example in direct gasoline injection or
common-rail diesel injection. High-pressure sensors are also used
in the field of automation technology. The functioning of these
sensors is based on converting the pressure-induced mechanical
deformation of a diaphragm into an electrical signal with the aid
of a thin-layer system. DE 100 14 984 already describes such
high-pressure sensors, which have thin-layer systems, but can have,
in practice, slight layer-adhesion problems in the region of the
contact layers and instances of capacitive asymmetry as a result of
instances of surface asymmetry of the contact layers caused by
manufacturing.
SUMMARY OF THE INVENTION
[0002] The method of the present invention and the thin-layer
component of the present invention possessing the characterizing
features of the independent claims have the advantage over the
background art, that problems with edge coverings and edge tears
are prevented and the layer adhesion is improved, since the
contact-layer system is deposited on a uniform undersurface, i.e.
since no steps or only very small steps to be overcome by the
layers are present.
[0003] The measures indicated in the dependent claims render
possible advantageous further refinements and improvements of the
method and thin-layer component specified in the independent
claims.
[0004] It is particularly advantageous that, because a region of
the measuring elements is situated between each region of the
contact-layer system and the diaphragm layer, a capacitive symmetry
is ensured since the surface and therefore the capacitance of the
contacts (relative to the diaphragm layer) are determined by the
precisely etched resistive layer, not the less precise
contact-layer system deposited into a shadow mask. In addition, the
layer adhesion is improved since the contact-layer system is
deposited on a uniform undersurface, and not, as up to this point,
also at least partially on the insulating undersurface of the
diaphragm layer, on which residues deteriorating the adhesion to
the undersurface may remain during the etching process of the
resistive layer. In addition, there are no steps at all to be
overcome by the layers, so that problems with edge coverings or
edge tears are effectively prevented.
[0005] Furthermore, it is advantageous to etch the resistive layer
and a passivation layer jointly, since, in this manner, an
increased yield may be achieved by dispensing with a masking level.
In addition, the bondability is prevented from being disturbed by
residues, which may be formed when a passivation layer is applied
through a shadow mask.
[0006] In addition, is advantageous that nickel-chromium or
nickel-chromium-silicon is used as a material for the resistive
layer. This allows the PECVD process step for the deposition of
polysilicon as a resistive layer at over 500.degree. C. to be
dispensed with, and instead allows a sputtering process for the
deposition of the nickel-chromium or nickel-chromium-silicon to be
used, which may already be applied at 130.degree. C. and lower. In
this manner, the maximum process temperature may be reduced
markedly.
[0007] Further advantages are derived from the additional features
named in the dependent claims and the description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Exemplary embodiments of the present invention are shown in
the drawing and explained in detail in the following description.
The figures show:
[0009] FIG. 1 a first manufacturing method according to the present
invention;
[0010] FIG. 2 method steps of a second manufacturing method
according to the present invention;
[0011] FIG. 3 a third manufacturing method according to the present
invention;
[0012] FIG. 4 a method step of a fourth manufacturing method;
and
[0013] FIG. 5 method steps of a fifth manufacturing method.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0014] FIG. 1 shows a first method according to the present
invention for manufacturing high-pressure sensors. An insulating
layer 20 is first deposited onto the entire upper surface of a
steel diaphragm 10 to be coated (FIG. 1a). The actual functional
layer for strain gauges is then deposited over the entire surface;
in a further step, these strain gauges 30 are then fabricated with
the aid of a photolithographic patterning step (FIG. 1b). The
contact layer or contact layer system 40, which is usually
photolithographically patterned as well, is subsequently deposited
(FIG. 1c). Shadow-masking technology is also used as an alternative
to photolithographically patterning contact layer 40. In order to
set the desired electrical properties, a balancing operation is
then often performed, in particular for adjusting the symmetry of a
Wheatstone bridge formed by several patterned-out, piezoresistive
strain gauges or resistive elements. In a further step (FIG. 1d), a
passivation layer 50 is deposited, whose patterning is also
accomplished either photolithographically or through the use of the
shadow-mask technique. When a passivation layer is
photolithographically patterned, this is accomplished with the aid
of a photoresist mask and a plasma-etching step, in which a
CF.sub.4/0.sub.2 gas mixture is preferably used as an etching gas.
When the passivation layer is patterned, using the shadow-mask
technique, the position of the shadow-mask opening is selected in
such a manner, that deposition exclusively occurs at suitable
positions or locations.
[0015] In a first exemplary embodiment of the present invention, an
insulating layer 20 is deposited, as shown in FIGS. 1a and 1b, onto
steel diaphragm 10, and a resistive layer is then deposited onto
insulating layer 20, and, in a further step, the resistive layer is
patterned to form strain gauges or resistive elements 30. For
example, a 10 .mu.m thick silicon-oxide layer, which is deposited
in a PECVD process (PECVD=plasma enhanced chemical vapor
deposition), is used as an insulating layer. A 500 nanometer thick
polysilicon layer or a 50 nanometer thick nickel-chromium or
nickel-chromium-silicon layer is deposited as a resistive layer,
which, in the case of polysilicon, is patterned using a
photolithography step and a subsequent plasma-etching step, and, in
the case of nickel-chromium or nickel-chromium-silicon, is
patterned using a wet-etching step.
[0016] In order that, during the subsequent deposition of
contact-layer system 40, steps are covered that are small in
comparison with the thickness of the contact layer, the present
invention provides, in the method shown in FIG. 1, for the
resistive layer being formed as an approximately 50 nanometer thick
nickel-chromium or nickel-chromium-silicon layer. The contact
layer, which is denoted by reference numeral 40 in FIG. 1, is then
deposited with the aid of a sputtering or vapor-deposition process.
This is either accomplished with the aid of a shadow mask or done
over the entire surface with a subsequent photodelineation process,
using an ion-beam etching step.
[0017] For producing the contact-layer system, a second method of
the present invention provides for one to proceed as described in
FIG. 2, the contact-layer system being deposited on the measuring
elements in such a manner, that no steps are covered: To produce
contact-layer system 41, a 500 nanometer thick sequence of layers
made up of nickel-chromium, palladium, and then gold is initially
sputtered or vapor-deposited through a shadow mask onto strain
gauges 30 (FIG. 2a). In this case, the openings of the shadow mask
used here are all situated inside the region of the strain gauges
patterned beforehand, so that regions of strain gauge 30 are
situated at every point of contact-layer system 41 between contact
system 41 and steel diaphragm 10. In a further step (FIG. 2b), a
500 nanometer thick passivation layer 50, which is made of silicon
nitride (Si.sub.xNi.sub.y; x=3, y=4) and protects the
function-sensitive regions of strain gauges 30 between the contacts
of contact-layer system 41 from external influences, is deposited,
in a PECVD process, through an additional shadow mask, in order to
ensure trouble-free operation of the sensor element under the field
conditions in a motor vehicle.
[0018] FIG. 3 shows a third method according to the present
invention for manufacturing a high-pressure sensor, in which, in a
first step (FIG. 3a), a 10 micrometer thick silicon-oxide
insulating layer 20 is deposited, in a PECVD process, onto a steel
diaphragm 10 on which a resistive layer 32 made of polysilicon (500
nanometer thick) or NiCr (50 nanometer thick) or NiCrSi (50
nanometer thick) is subsequently deposited. In a second step (FIG.
3b), a 500 nanometer thick contact-layer system 41 is deposited,
using shadow-mask technology. Nickel or a layer sequence of
nickel-chromium, palladium, and then gold is used as a material for
this. To produce the contact-layer system, the contact material may
alternatively be deposited over the entire surface, and the
deposited contact material may then be patterned, using a
photolithography step and an etching step. As shown in FIG. 3c, a
silicon nitride layer 52 is subsequently deposited over the entire
surface, and a photoresist layer 60 is deposited onto it. In order
to pattern resistive layer 32 for producing the resistive elements
or strain gauges 30, the photoresist is exposed in such a manner,
that, during the subsequent development, both inner regions 43 of
contact-layer system 41 and edge regions of the sensor may also be
exposed or subjected to an etch attack. After the development of
photoresist layer 60, the etching-away of silicon-nitride layer 52
in inner regions 43, where inner regions 43 are used as an
etch-stopping layer, and the etching-away of both silicon-nitride
layer 52 and resistive layer 32 between the contacts of
contact-layer system 41 for forming the resistive elements, as well
as in the edge regions of the sensor element, the result is a
high-pressure sensor, which is still covered by the remaining parts
of the photoresist layer, and whose strain gauges 30 are covered by
a silicon-nitride passivation layer 50, and whose contact-layer
system is underlaid with unremoved regions of resistive layer 32
over the entire surface. In this connection, a plasma-etching
process employing a tetrafluoromethane-oxyge- n mixture is
preferably used as an etching method when polysilicon is the
resistive material, and a wet-chemical etching process is used as
an etching method when NiCr or NiCrSi is the resistive material. In
further steps, the contacts of the contact-layer system may be
provided with electrical connections, and the upper side of the
high-pressure sensor may still be covered, for example, by a
housing, after the rest of the photoresist layer is removed (FIG.
3e).
[0019] In a procedure (fourth method) that is an alternative to the
third specific embodiment represented in FIG. 3, photosensitive BCB
(=benzocyclobutene) may be deposited in place of silicon nitride
(FIG. 3c) as passivation layer 52. The exposure and development of
the photoresist layer and BCB layer may then occur simultaneously,
so that, subsequently, the passivation layer no longer has to be
etched, but rather just the resistive layer. As shown in FIG. 4,
the set-up may then be heated to a temperature of, e.g. 300.degree.
C. after the removal of the photoresist layer, in order to attain a
light reflow of the BCB layer and, thus, to also cover the outer
edges of strain gauges 30 with passivation layer 55 resulting from
the BCB layer.
[0020] In a fifth manufacturing method, which is a further
alternative to the specific embodiment represented in FIG. 3 and
employs nickel-chromium as the resistive material, the use of
photoresist is completely dispensed with, and, subsequently to a
procedure shown in partial FIGS. 3a and b, only a layer 57 of
photosensitive BCB material is sprayed or printed onto the entire
upper surface of resistive layer 32 or contact-layer system 41
(FIG. 5a). After exposure and development of BCB layer 57, the
resistive layer is laid bare in both the edge regions and the
region between the contacts, in such manner, that, first of all,
desired passivation layer 58 is already formed, and secondly,
subsequent, wet-chemical etching of the resistive layer at these
exposed locations results in the desired patterning of the
resistive layer to form strain gauges 30 (FIG. 5b). It is possible
to dispense with a photoresist layer in the case of using NiCr or
NiCrSi as a resistive material and in the case of using a
wet-chemical etching process, since the BCB layer is resistant to
the acid for etching the nickel-chromium or the
nickel-chromium-silicon. A subsequent "reflow bake" results, in
turn, in the rounding-off of the passivation-layer edges at the
contacts and, in particular, in the passivation of the edge regions
of strain gauges 30, because of reshaped passivation layer 59
forming.
[0021] As described in DE 100 14 984, the resistive layer may also
be patterned in an alternative manner, using a laser method.
[0022] The unit of (stainless) steel diaphragm 10 and insulating
layer 20 may optionally be replaced by a glass diaphragm.
[0023] In a further alternative, the insulating layer may be made
of other organic or inorganic layers, such as "HSQ" (hydrogen
silsesquioxane) from Dow Corning, "SiLK" from Dow Chemical, or
"Flare" from Allied Signal.
* * * * *