Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Temperature
Reexamination Certificate
2003-05-23
2004-09-07
Eckert, George (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Temperature
C257S470000, C257S706000, C257S713000, C257S717000
Reexamination Certificate
active
06787870
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a semiconductor component having an integrated circuit and, thermally coupled thereto, a temperature sensor, whose resistance is dependent on temperature, and also having a cooling body as a heat sink.
The concept “integrated circuit” includes a semiconductor-based, integrated, electronic circuit (IC) encapsulated in a housing, while the concept “semiconductor component” mentioned at the beginning is directed to a complete component with a cooling body.
From European Patent EP 0 350 015 B1 a semiconductor component with a housing is known, which contains at least a power MOSFET and a sensor thermally connected thereto, wherein the sensor changes its resistance between two of its terminals in dependence on temperature. A thyristor is provided as the temperature sensor, but a bipolar transistor can be used instead. It is possible in this manner to develop a semiconductor component such that the MOSFET is not simply switched off upon reaching a critical temperature, but, for example, its power is reduced by reducing the conductivity.
From International Patent Publication WO 96/02942 a housing for a semiconductor component is known which has a cooling body or a heat sink. Here, an integrated semiconductor component is provided with a conventional lead frame using bonding wires, while it is thermally conductively connected on its underside or in the region of its floor to a plate-shaped heat sink or a cooling body by means of a polymer material. The material of the heat sink preferably consists of aluminum or copper.
Furthermore, from European Patent EP 0 578 411 B1 a semiconductor arrangement is known with a semiconductor device installed on a lead frame and provided in a plastic housing, wherein the surface of the housing over the semiconductor device has upwardly-directed, integrally formed heat dissipating elements, and these heat dissipating elements arc formed as conical projections, which extend within a region provided directly above the semiconductor device.
Still further, from European published patent application EP 0 723 293 A1, a semiconductor arrangement with a heat sink is known, in which a semiconductor element mounted in a lead frame borders directly on a heat sink, which provides for the removal of heat arising in the semiconductor component.
From U.S. Pat. No. 6,092,927 a method of determining the temperature of a power semiconductor is known, wherein an integrated analog switching circuit is co-packaged together with the power semiconductor on a heat sink. In this manner it is possible to determine the thermal resistance between the power semiconductor and the integrated circuit, the thermal resistance between the power semiconductor and the heat sink, and between the analog integrated circuit and the heat sink. Consequently, it is possible to determine the power loss in the power semiconductor, by determining the temperature of the integrated circuit, the temperature of the heat sink by use of thermal capacities, as well as the heat sink temperature and thermal resistance with regard to the voltage and current of the integrated circuit. An output signal is thereby created for an asymptotic display system of the temperature of the power semiconductor.
Moreover, from U.S. Pat. No. 5,596,231 a heat sink is known, which is selectively coated with electrically insulating material, and is provided for an integrated circuit, wherein the electrically insulating material comprises anodically oxidized aluminum, which has been produced by vapor deposition onto the heat sink. The heat sink itself is formed from copper or copper alloys, which are selected for their high thermal conductivity. The entire integrated circuit device can then be accommodated in a plastic housing.
Furthermore, from International Patent Publication WO 80/00878 a differential calorimeter is known, which operates on the heat sink principle. Here, a pair of heat capacity measurement points is symmetrically arranged within a middle section of the heat sink, wherein one of the measuring cells contains a reference substance and the other a so-called sample substance. Temperature measurements are made at different points in time during a temperature measurement period.
BRIEF SUMMARY OF THE INVENTION
The invention has as an object performing an accurate and rapid temperature determination during heat removal from integrated circuits in the region of a heat sink for a semiconductor circuit element; particularly where sensors having small thermal mass are to be used.
The object is achieved in that the temperature sensor has a thin film measuring resistor, which is applied on an electrically insulating surface of a foil-like substrate, wherein the total thickness of the temperature sensor lies in a range of about 10 &mgr;m to 100 &mgr;m, and wherein the temperature sensor is thermally coupled to the cooling body.
It has been found to be particularly advantageous for the thin film measuring resistor, as the temperature sensor, to have only a small thermal mass, because of its small thickness, and to thus make possible an integration into the heat sink region of semiconductor chips without changing the cooling structure. Advantageous embodiments of the invention are set forth below and in the dependent claims.
In a preferred embodiment of the temperature sensor, the thin film measuring resistor is formed as a planar component. The measuring resistor advantageously has a layer in the form of a meandering pattern and substantially comprises platinum or a platinum alloy; the thickness of the layer lies in a range of about 0.8 to 1.2 &mgr;m.
In an advantageous embodiment of the semiconductor component, the temperature sensor is arranged between the integrated circuit and the cooling body.
Furthermore, in an advantageous embodiment of the invention, the thin film measuring resistor is applied to a substrate having an electrically insulating surface, the substrate comprising metal, preferably nickel, a nickel alloy, or an iron alloy with a chromium and aluminum content. The chromium content of this iron alloy is preferably about 20 wt. %, while the aluminum content is about 5 wt. %. This iron alloy, is described in the book C. W. Wegst,
Stahlschlüssel
(“Steel Key”), 18th edition; ISBN 3-922599-14-1,Verlag Stahlschlüssel West GmbH, Marbach (1998), and is also given the material number 1.4767 and the short name (DIN) CrAl 20 5 (X8CrAl20-5).
It has been found to be particularly advantageous that platinum thin film measuring resistors can be applied on nickel foils or foils of a nickel alloy or of an iron alloy having a thickness in a range of about 30 to 80 &mgr;m, giving a substantially delay-free temperature measurement due to the small heat capacity.
In a preferred embodiment of the invention, the thin film measuring resistor is applied to an insulating layer having a thickness in a range of about 2 to 5 &mgr;m. The insulating layer advantageously comprises silicon oxide or aluminum oxide and is applied to the substrate by a physical vapor deposition (PVD) process.
Furthermore, in an advantageous embodiment of the invention, a passivation layer is applied to the thin film measuring resistor. This passivation layer preferably is preferably made of silicon oxide (SiO) or aluminum oxide (Al
2
O
3
). The passivation layer has a thickness of about 1 to 5 &mgr;m and is applied by a physical vapor deposition (PVD) process.
In a further preferred embodiment, the thin film measuring resistor is arranged in a plane. The measuring resistor or the passivation layer is covered on one side with a thermal coupling layer bordering on the cooling body, while on the other side the resistor has a substrate bordering on a heat distributor, which at least partially surrounds the integrated circuit.
In a still further preferred embodiment of the invention, a layer which is electrically insulating but of good thermal conductivity is arranged between at least a portion of the integrated circuit and the heat distributor.
REFERENCES:
patent: 4791398 (1988-12-01), Sittler et al.
patent:
Ullrich Karlheinz
Wienand Karl-Heinz
Akin Gump Strauss Hauer & Feld & LLP
Eckert George
Heraeus Sensor Technology GmbH
Warren Matthew E.
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