Mechanical pressure Schottky contact array

A Scottky diode arrangement comprises a metallically conducting plate and a semiconductive plate, one or both of which are provided with at least three raised portions which form electrically parallel Schottky contacts between the plates.

BACKGROUND OF THE INVENTION 
The invention describes a Schottky diode arrangement in which a number of 
small-area metal semiconductor contacts are combined to form a 
mechanically stable component. 
Besides some disadvantages, Schottky diodes, as is known, also have several 
advantages as compared to p/n diodes. They may be manufactured relatively 
easily, have small switching times and may be manufactured with relatively 
small gate voltages. In the last few years Schottky diodes have been 
manufactured as mixer diodes for higher and higher operating frequencies. 
With diode diameters of 5.multidot.10.sup.-5 cm, frequencies of up to more 
than 4 THz have been achieved. D. T. Hodges and M. McColl, "Extension of 
the Schottky barrier detector 70 um (4.3 THz) using submicron-dimensional 
contacts", Appl. Phys. Letters., 30, 5-7 (1977). These Schottky diodes are 
seriously competing with metal oxide metal (MOM) point contact diodes 
because they are constructed by the planar technique and consequently have 
greater mechanical stability. Their manufacture is therefore more costly. 
SUMMARY OF THE INVENTION 
The object underlying the invention is to provide a Schottky diode 
arrangement which is mechanically stable and which may be constructed for 
operation up to extremely high frequencies and for high power. According 
to a first aspect of the invention there is provided a Schottky diode 
arrangement comprising a plate, disc or chip of metallically conducting 
material having two main surfaces and a plate, disc or chip of 
semiconductor material having two main surfaces, wherein at least one of 
said plates, discs or chips has on at least one of its said surfaces at 
least three raised portions, and said plates, discs or chips are located 
adjacent each other to form electrically parallel contacts therebetween by 
means of said raised portions. According to a second aspect of the 
invention there is provided a Schottky diode arrangement comprising a 
plate, disc or chip made from metallically conducting material and a 
plate, disc or chip made from semiconductor material, wherein at least one 
plate, disc or chip has on one of its two sides a structure with at least 
three raised portions, the plates, discs or chips being put together under 
pressure so that electrically parallel, pressure contacts are formed 
between them by the raised portions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with the invention there is provided a plate, disc or chip 
made from metallically conductive material and a plate, disc or chip made 
from semiconductor material. The term `plate` as used hereinafter is 
intended to include discs and chips. At least one plate has on one side of 
its two sides a structure with at least three raised portions; and the 
plates are put together under pressure so that pressure contacts connected 
electrically in parallel are formed between them by the raised portions. 
These electrically parallel, pressure contacts are preferably of equal 
area. 
In a preferred embodiment of the invention the structure comprises parallel 
ridges. The two plates are put together under pressure applied between 
their structured surfaces so that the parallel rigdes in the structure of 
both plates intersect and form a regular distribution in terms of area of 
electrically parallel, pressure contacts. If N is the number of parallel 
rigdes in the structure of each plate, then N.sup.2 pressure contacts are 
formed between the two plates. The principle of intersecting parallel 
ridges has already been described in German Offenlegungsschrift No. P 25 
47 262. However, it is not disclosed in P 25 47 262 that Schottky diodes 
may be manufactured by this principle and a fortiori it is not disclosed 
how they may be so manufactured. 
The plate comprising metallically conductive material may comprise a metal, 
an alloy, a metallically conductive compound, or a degenerated doped 
semiconductor. 
The plate made from semiconductor material may comprise n- or p-conductive 
monocrystalline or polycrystalline elemental semiconductor or 
semiconductor compound. 
The plate made from semiconductor material may be coated in accordance with 
a preferred feature of the present invention with an insulating layer, the 
thickness of which is smaller than 1.multidot.10.sup.-6 cm. A chemical 
oxide, SiO.sub.2, an anodic oxide, a thermal oxide, an electrolytic oxide, 
a pyrolytic oxide or nitride, among others, may be used as the insulator 
material. 
The intermediate space between the elevations of the structure may be 
evacuated so that the two plates are pressed together by atmospheric 
pressure. 
Several Schottky diode arrangements may be connected in series 
electrically. 
Referring now to the drawing, five preferred embodiments of the present 
invention will be described. 
Embodiment 1 
In FIG. 1, 1 is a nickel chip and 2 is an n-silicon chip which has three 
conical raised portions 3, all of equal size, which are manufactured by 
means of an etching process. After putting together the two chips 1 and 2 
the three raised portions 3 form Schottky contacts between the chips 1 and 
2. 
Embodiment 2 
In FIG. 2, 1 is a tungsten plate on one side of which parallel ridges 3 are 
produced by means of an electrolytic etching process. The ridges 3 taper 
towards the upper surface and have a width there of 1.multidot.10.sup.-5 
cm. The ridges 3 are coated with a 5.multidot.10.sup.-6 cm thick layer of 
platinum. An n.sup.+ -GaAs plate 2 has a structure with parallel ridges 3 
also on one side. These ridges 3 also taper and have a width of 
1.multidot.10.sup.-5 cm at their upper surface. The plate 1 is placed and 
fixed on the plate 2 with a certain pressure. The plates 1 and 2 are 
rotated with respect to each other so that ridges of one plate are at a 
90.degree. angle with respect to the ridges of the other plate. The ridges 
which are in contact and intersect thus form small-area Schottky contacts 
on both plates. 
The seven parallel ridges on discs 1 and 2 thus produce forty-nine 
electrically parallel Schottky contacts having an individual area of 
approximately 1.multidot.10.sup.-10 cm.sup.2. This Schottky diode 
arrangement has very low parasitic impedances and may be used up to very 
high frequencies as a mixer. 
Embodiment 3 
In the sectional view of FIG. 3a, 1 is a copper plate which has a structure 
with tapering parallel riges 3 on one side as in FIG. 2. The outer face of 
the ridges 3 is 5.multidot.10.sup.-5 cm wide. The copper plate 1 is coated 
with a layer 5 of gold which is 2.multidot.10.sup.-5 cm thick. An 
aluminium plate 1* has the same structure of parallel ridges 3 on one side 
as 1. An n.sup.+ -GaAs plate 2 is located between the structured surfaces 
of the two metallic plates 1 and 1*, the plate 2 being doped 
3.multidot.10.sup.18 Sn atoms/cm.sup.3. This GaAs plate 2 has the same 
structure of parallel ridges 3 on both sides as the plates 1 and 1*. The 
n.sup.+ -GaAs plate is coated with a layer 6 of oxide by a chemical 
oxidation process and its thickness is approximately 1.multidot.10.sup.-7 
cm. The n.sup.+ -GaAs plate 2 is rotated by 90.degree. with respect to the 
structures in the plates 1 and 1* and placed between the structured sides 
of the plates 1 and 1* and is held together at a certain pressure. The 
Schottky contacts are formed bya the contact surfaces of the intersecting 
ridges on plates 1 and 2. Corresponding non-blocking/contacts are made 
between the plates 1* and 2. 
FIG. 3b shows the sixteen blocking Schottky contacts 4 between the plate 1 
and the GaAs plate 2 in a view of the plane of contact and corresponding 
to these are non-blocking contacts 4* (FIG. 3a) between the plate 1* and 
the GaAs plate 2. FIG. 3a shows a ceramic casing 7 containing the Schottky 
diode arrangement, which casing has two coaxial diode connections 8 to the 
metal plates 1 and 1*. 
Embodiment 4 
In the sectional view of FIG. 4, 1 is a copper plate which has a structure 
with parallel ridges 3 running in the direction of the picture plane on 
one side, as in the corresponding part of FIG. 2. Ridges 3 taper to a 
diameter of 5.multidot.10.sup.-4 cm at their outer face. The copper plate 
1 is coated with a nickel layer 5 having a thickness 2.multidot.10.sup.-4 
cm. An n+-silicon chip or plate 2 is provided with an epitaxial layer 9 of 
n.sup.- -silicon having a specific resistance of 20.OMEGA. cm and a 
thickness of 1.multidot.10.sup.-3 cm. An n-diffusion layer 10 with a 
surface concentration of 5.multidot.10.sup.17 /cm.sup.3 and a diffusion 
depth of 1.multidot.10.sup.-5 cm is inserted into this epitaxial layer 9. 
Thereafter a structure with parallel ridges 3 tapering towards the upper 
surface to 5.multidot.10.sup.-4 cm is inserted into the silicon chip 2. By 
placing the plates 1 and 2 on top of each other, and rotating them with 
respect to each other in the plane of the plates in the manner shown in 
relation to the ridge structures, a regular distribution, in terms of 
area, of electrically parallel Schottky contacts 4 is formed under a 
mechanical pressure acting on the plates. The gate voltage of this 
Schottky diode arrangement is reduced by the thin n-silicon layer 10. A 
metal contact 11 is provided on the silicon chip 2. 
In order to increase the blocking voltage several such Schottky diode 
arrangements may be connected electrically in series. 
Embodiment 5 
In the sectional view of FIG. 5 the n-silicon chip 2 has a structure of 
conical raised portions 3 of equal size on one side, these raised portions 
having a curve radius of 2.multidot.10.sup.-4 cm at their peak. A membrane 
or plate 1 made from spring steel and having a thickness of 
2.5.multidot.10.sup.-3 cm is disposed adjacent conical portions 3. It is 
fixed to the ceramics casing 7 containing the semiconductor arrangement by 
means of resilient folds 14 and at its lower surface rests on the peaks of 
the conical portions 3 with a light pressure. An n+-layer 12 is provided 
on the surface of the n-silicon chip 2 opposite the elevations and a 
metallic contact 11 on this n+-layer 2 provides the connection with a 
metallic baseplate 13 of the casing. The battery 16 produces a blocking or 
reverse voltage at the Schottky contacts 4 between the n-silicon chip 2 
and the membrane 1 via an electrical resistor 17 and connections 1 and 13. 
The diode blocking current 19 flowing through the arrangement is 
registered as a voltage fluctuation 18 across resistor 17, as a result of 
pressure fluctuations 15 action on the membrane 1. 
It will be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations.