Electronic component

The invention relates to an electronic component manufactured in thick film technology, thin film technology or silicon technology and then provided with an electrically insulating layer which is covered by an amorphous metal layer. The amorphous metal layer protects the component, even with the smallest of layer thicknesses, from external influences and directly transmits heating and force effects.

BACKGROUND OF THE INVENTION 
The invention relates to an electronic component which is produced with 
thick film technology, thin film technology or silicon technology. 
Such electronic components are produced and applied in many different 
embodiments. In particular, when such an electronic component comprises or 
forms a sensor and is provided for measuring physical magnitudes, 
particular problems arise with regard to the encapsulation. On the one 
hand the component must be encapsulated as tightly as possible with regard 
to the surrounding medium, and on the other hand, the material covering 
the component must be applied as thinly as possible so that for example 
the temperature conduction to the component but also the forces affecting 
the component are transmitted as directly and as unadulterated as 
possible. 
The usual embedding in plastics is mostly sufficient when merely the 
surrounding air comes into contact with the component. If however the 
component comes into contact with fluid for example such as water, 
alcohol, oil or likewise, then this embedding in a plastics mass is not 
usually adequate, since such plastic is not sufficiently sealing with 
respect to such fluids. The fluid may be diffused through the plastic and 
thus can reach to the electronic component which may become damaged or 
even destroyed by this direct contact. A certain improvement may be 
achieved in that the embedding plastic layer is formed correspondingly 
thick, which however leads to those previously mentioned disadvantages 
such as lack of heat conduction or bad force transmission. A reliable 
encapsulation with respect to fluids is normally only made possible with 
metal encapsulation which is effected by incorporating the component in 
correspondingly formed sheeting. Although the heat conduction of such 
sheeting is good, a coupling of the component to the sheeting is required 
and besides, the force transmission onto the component through the 
sheeting is practically not possible. 
In order to have as good as possible transmission of force onto the 
component of the type mentioned, it is known for example from U.S. Pat No. 
4,686,764 and U.S. Pat. No. 4,732,042 to cover the component, which here 
is applied as a membrane of a differential pressure sensor, with a 
relatively thick layer of gel, which on the one hand is so flexible that 
it hardly inhibits either the transmission of force onto the membrane or 
the movement of the membrane, but is otherwise so resistant that it does 
not come off when subjected to flow. Although in this manner, pressure 
forces may be transmitted onto the membrane quite well, the transfer of 
heat from the prevailing fluid onto the component is effected with a 
notable time delay at the minimum, since the design for holding the gel 
layer onto the component as well as the gel layer itself prevent a fast 
transfer of heat. Such an arrangement is thus not so suitable for 
measuring temperatures or transferring of heat. 
SUMMARY OF THE INVENTION 
Proceeding from this it is the object of the invention to provide a 
component of the type previously mentioned which on the one hand is 
reliably protected against external influences, in particular 
environmental influences, water and likewise, and on the other hand has a 
good heat and force conducting connection with the surrounding medium. 
In one aspect, this invention comprises an electronic component which is 
manufactured by thick film technology, thin film technology or silicon 
technology comprising membrane comprising at least one electrical 
component, an insulating layer deposited on the membrane and at least one 
electrical component for insulating the at least one electrical component, 
and an amorphous metal layer deposited on the insulating layer protecting 
at least one electrical component from fluid and the insulating layer 
insulating the amorphous metal layer from the at least one electrical 
component in order to prevent the amorphous layer from providing an 
electrically conductive connection among the at least one electrical 
component. The invention thus provides for the electronic component to be 
provided with an amorphous metal layer. According to the type and 
embodiment of the electronic component, this amorphous metal layer, where 
appropriate, is firstly electrically separated from the component by 
depositing an electrically insulating layer. Since on the one hand the 
amorphous metal layer, also known by the expression metal glass, due to 
its amorphous structure, is completely fluid tight even with layer 
thicknesses of the order of .mu.m, and on the other hand has a high 
hardness, such a metal layer firstly provides good protection for the 
component, and secondly, with an appropriatly small as possible layer 
thickness, permits an almost perfect, practically undelayed thermal 
conductivity from the surrounding medium to the component and vice versa. 
Furthermore, forces, in particular pressure forces of the prevailing 
medium, are transmitted to the electronic component almost without loss 
and with a high accuracy. The latter is then particularly advantageous 
when the component is designed as a sensor for pressure or other forces or 
comprises such a sensor. 
The electronic component according to the invention offers a wide range of 
application possibilities. For example it may serve as a pressure and/or 
temperature sensor. It is however also conceivable to design the component 
according to the invention as a heat producing resistance as part of a 
measuring apparatus for measuring the flow velocity. In this case, a 
heating element as well as a temperature probe or probes may be formed as 
an electronic component according to the invention. The high thermal 
conductivity of the thin metal layer permits a very exact and quick 
measurement. Because of the small thickness of the layer, a good thermal 
conductivity transverse to the layer and a poor thermal conductivity along 
the layer is provided. This is particularly advantageous for the 
application of the component as part of a discharge measuring apparatus. 
In an analogous manner, the component according to the invention may also 
be provided for a cooling liquid or other cooling medium to be used for 
removing waste heat arising therein. Here the good thermal conductivity of 
the extremely thin layer is advantageous, whereby the component itself is 
reliably protected from outside influences by this layer. This is because 
the amorphous metal layer described in more detail hereinafter is 
considerably more corrosion and wear resistant than for example thin 
stainless steel sheeting, which in a thickness which is fluid tight, 
already has such a stiffness that it is suitable for transmitting forces 
onto the electronic component only under very limited circumstances. 
A further advantage of the component according to the invention lies in the 
fact that the amorphous metal layer is self-conducting, so that it can 
also serve as a shielding by connecting this layer to earth or any chosen 
potential. 
Finally such an amorphous metal layer may be cheaply manufactured, also 
particularly in large series production. The components may be 
manufactured in a known manner as several components arranged next to one 
another in the form of a wafer or oblate, then covered with an 
electrically insulating layer and finally vapor deposited with an 
amorphous metal layer. Only then is the separation of the individual 
components from one another effected. 
The electrically insulating layer may be extremely thin, since it merely 
has the job of ensuring that the amorphous metal layer does not cause a 
short circuiting of the electronic component located thereunder. On the 
other hand, the insulating layer is well protected by the amorphous metal 
layer. Due to the fact that the metal layer is not in a crystalline 
structure but an amorphous structure, on the one hand it is highly 
resistant to corrosion, and on the other it is fluid and also gas tight, 
even with the thinnest layer thicknesses. Such amorphous metal layers are 
for example known from EP-A-0537710, DE-A-4216150 and DE-A-3814444. In 
this respect the following publication is referred to: Palmstrom, C. J.; 
J. Gylai and J. W. Meyer in J. Vac. Sci. Technol. A1C21 April-June 1983, 
sides 452 ff. 
Preferably the component, particularly when designed as a membrane, is 
essentially made from silicon. The electrically insulating layer may then 
be composed of silicon oxide, silicon nitrite or polyimide. The covering 
amorphous metal layer is preferably chrome-tantalum based or 
chrome-titanium based, since these have a high resistance to wear and have 
good elastic characteristics over a wide composition range. 
In order to ensure that the amorphous metal layer is fluid tight, the layer 
thickness should be at least 0.1 .mu.m, this corresponds to about 700 atom 
layers. On the other hand the metal layer should be as thin as possible 
for those reasons cited earlier. Thus the maximum layer thickness should 
be approximately 5 .mu.m. Preferably the range is between 0.5 and 1.5 
.mu.m, with which on the one hand a reliable sealing of the amorphous 
metal layer is ensured, and on the other hand a high mobility of this 
amorphous metal layer is guaranteed, this being particularly advantageous 
when transmitting forces. 
If the component is to form part of a differential pressure sensor then it 
is useful when the membrane is part of a plate shaped substrate which 
forms the electronic component and is designed as one piece with the 
membrane. The membrane region is then so designed, that here the substrate 
has a smaller thickness such that a region for deflection is created. 
Moreover then the whole substrate may be covered, first with the 
electrically insulating layer and then the metal glass layer. This also 
has advantages with the gripping of the so designed sensor element. The 
amorphous metal layer then forms the protective layer with respect to the 
medium whose pressure is to be measured. With such an arrangement, such a 
previously mentioned layer of gel may be completely done away with. 
Temperature compensation of the measurement may be effected very exactly 
on account of the good heat conduction, in the case that this should still 
be required despite the direct arrangement of the sensor electronics.

DETAILED DESCRIPTION OF THE INVENTION 
The carrier 1, representated by way of FIGS. 1 and 2, in the plan view, has 
a roughly rectangular shape. It comprises a much reduced thickness in a 
middle, roughly quadratic region. This region 2 forms the membrane of a 
pressure or differential pressure sensor, whilst the remaining carrier is 
to be regarded as essentially rigid. The carrier 1 and the membrane 2 are 
formed from silicon. In the region of the membrane, four resistances 4 for 
determining the membrane deflection as well as a further resistance 5, 
directly neighbouring the membrane 2, for temperature compensation of the 
sensor, are deposited on the silicon base body 3. The electrical 
connection of the resistances 4 and 5 is effected via strip conductors 6 
made from aluminium, which are likewise deposited directly onto the 
carrier 1. The arrangement of the conductors to the resistances 4 is 
already preparedly formed as a bridge circuit which lays the contact 
points to the strip conductors 6 for further wiring all along one side of 
the carrier, this being distant to the membrane 2. 
The membrane 2 and carrier 1 are covered on both sides with a silicon oxide 
layer 7. This layer 7 is directly deposited onto the silicon base body 3 
or the resistances 4 and 5 as well as the strip conductors 6. The silicon 
oxide layers 7 on both sides of the carrier 1 are each covered by a metal 
glass layer 8. This amorphous metal layer is vapor deposited and comprises 
a thickness of about 1 .mu.m, which is about 7,000 atom layers. The metal 
glass layer 8 is impervious to fluid and gas. It has a considerably higher 
resistance to corrosion and greater hardness in comparison to crystalline 
stainless steels. It however practically does not inhibit the measuring 
characteristics of the membrane 2, since this layer deforms only 
elastically. Thus it protects the membrane from external influences in an 
almost optimal manner. In order to prevent a short circuit by the metal 
glass layer 8 of the resistances and strip conductors formed on the 
silicon base body 3, the electrically insulating silicon oxide layer 7 is 
provided. 
With the embodiment example described, the metal glass layer 8 is comprised 
from an amorphous metal alloy based on chrome-tantalum or chrome-titanium. 
In this respect the document EP-A-0537710 is referred to. 
As shown in FIG. 2, a strip 9 is provided running parallel to the narrow 
side of the carrier 1 and in which the strip conductors 6 are neither 
covered by a silicon oxide layer 7 nor by a metal glass layer 8. Here the 
strip conductors 6 run out for the purpose of contacting (bonding). 
The previously described carrier is incorporated in a pressure tight manner 
into a mounting 10, in an such a manner that the membrane 2 is impingable 
on both sides. This is shown schematically by way of FIG. 3. Here the 
mounting 10 (FIG. 3) comprises a plate shaped base body 11 and a cover 
plate 12 which are connected to one another under incorporation of the 
carrier. The plate shaped base body 11 comprises a plane recess 13, 
roughly the size of the carrier 1, for receiving this carrier. 
Furthermore, the base body 11 and the cover plate 12 comprise recesses 14 
and 15 which are flush with one another and through which the membrane 2 
can be impinged by fluid. Concentric to their recesses 14 and 15, the 
components 11 and 12 each comprise annular grooves 16 and 17, in which 
O-rings 18 lie, which grip the carrier between the components 11 and 12 in 
an airtight manner. The arrangement is chosen such that the membrane 2 is 
freely accessible within the recesses 14 and 15, whilst the strip 9 which 
is provided for contacting the ends of the strip conductors 6, lies on the 
other side of the seal within the mounting 10. Moreover, the mounting is 
so formed that only the region of the recesses 14 and 15 can be impinged 
by fluid, but the remaining part is sealed with respect to the fluid. 
Arranged on the base body 11 is a circuit board 19 which comprises further 
electronic components for processing the measuring signal. This circuit 
board 19 is electrically connected to the strip conductors 6 of the 
carrier 1 via a conductor 20. The contacting is effected by soldering or 
welding the conductor 20 onto the ends of the strip conductors 6 made 
freely accessible by way of the strips 9 (so-called bonding). 
The electronic, electrical and structural construction of the differential 
pressure sensor is accomplished in the usual way and is thus not descibed 
in detail here. The construction, as far as the mounting is concerned, is 
made clearer by way of FIGS. 5 and 6. Here, for connecting the plate 
shaped components 11 and 12, bores 21 are arranged next to the recess 13 
flush in the base body 11 and cover plate 12, through which a screw or 
rivet connection can be made between the two components. 
Such a designed sensor may be applied as a pressure sensor when the 
membrane 2 is only impinged on by pressure from one side. For application 
as a differential pressure sensor, the membrane is impinged on by fluid 
from both sides. 
By way of FIG. 4 and alternative gripping of the carrier 1 between the 
components 11 and 12 is represented. This embodiment example differs from 
that represented by way of FIG. 3 in that the annular grooves 16, 17 as 
well as the O-rings 18 are done away with and instead the carrier 1 is 
incorporated between the plate shaped base body 11 and the cover plate 12 
by way of an adhesive layer 22. This incorporation is advantageous 
inasmuch as the occurring stress in the carrier 1 and in the membrane is 
much less than with the previously described gripping. This is 
advantageous with regard to the measuring accuracy and linearity of the 
measurement. In any case, however, the gripping of the carriers 1 between 
the components 11 and 12 is effected before the contacting of the ends of 
the strip conductors 6, since the comparatively sensitive carrier 1 after 
incorporation into the holder 10 is much more simple and secure to 
operate.