Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-03-01
2001-11-20
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S113000, C438S460000, C438S622000, C438S624000, C257S679000, C257S678000, C257S692000
Reexamination Certificate
active
06319827
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electronics, and, more particularly, to an electronic micromodule comprising a support wafer, an integrated circuit chip, and at least one flat winding forming an antenna coil.
BACKGROUND OF THE INVENTION
In recent years, contactless integrated circuits have been developed that operate through an antenna coil, including receiving or transmitting data by inductive coupling in the presence of a magnetic field transmitted by a data transmitting and/or receiving station. These integrated circuits, which are also called passive transponders, can be used to produce various contactless electronic portable objects such as smart cards, electronic tags and electronic tokens, for example.
The present invention concerns the production of such portable objects, and, more particularly, the production of the electronic part of such objects. The most frequently used method to produce the electronic part of a contactless portable object includes using a support wafer on which a coil and a silicon chip are arranged. The coil is then connected to the chip and the unit is covered with protective resin. Generally, the support wafer is a printed circuit board. The coil is a copper wire glued on or an etched copper strip. The coil and chip are connected by ultrasonically bonded metal wires. The assembly forms an electronic micromodule designed to be inserted into the body of a portable object (plastic card, token, land, key . . . ) or fixed onto the surface of such an object.
The inconvenience of this method is that it involves the micromodule components being handled at several steps and requires assembling, wiring and controlling steps which increases the cost of micromodules and restrict rates of output. Moreover, with this method it is not possible to produce very thin micromodules.
Generally, the printed circuit board is approximately 150 micrometers thick, the silicon chip is approximately 150 micrometers thick once the rear side has been chemically or mechanically abraded, and the height of the loops formed by the wiring cables is in the region of 120 micrometers. Finally, the thickness of the resin coating the wires is between 20 and 50 micrometers. In total, the thickness of a classic micromodule is in the region of 400 to 500 micrometers. In comparison, the thickness of a plastic card is approximately 760 micrometers. Contactless smart cards that contain this type of micromodule are often uneven.
Several methods are also known by which it is possible to collectively produce a plurality of coils on one silicon wafer comprising a plurality of integrated circuits, such as the method described in U.S. Pat. No. 4,857,893, for example. After cutting the silicon wafer, very thin integrated micromodules are obtained. The handling, assembly and connection phases of chips and coils are thus removed.
However, the surface area provided by a silicon chip, which is a few square millimeters, is insufficient to produce a high inductance coil. Integrated circuits fitted with an integrated coil are therefore reserved for so-called “proximity” applications. This is where the electromagnetic induction communication distance is short, and is on the order of one millimeter.
Moreover, it is also conceivable to produce larger scale coils on a silicon wafer, such as coils surrounding the areas where the integrated circuits are located, for example. However, this approach is inconvenient in that it reduces the number of integrated circuits that can be produced together on a single silicon wafer, and thus increases the cost. In the semiconductor industry, the cost of a silicon chip is determined by the production cost of the silicon wafer divided by the number of chips produced. Thus, for example, the production of 6 mm
2
coils on a silicon wafer comprising integrated circuits of a surface area of 2 mm
2
increases the cost price of each integrated circuit three-fold.
Finally, the methods that include integrating electronic circuits and coils in one silicon wafer do not seem to be advantageous despite the gain in labor due to the removal of the need to assemble and wire the coils and the integrated circuits. Several technological methods are already known, by which it is possible to produce integrated coils together and at a low cost, particularly the polyimide/silicon dioxide/copper multilayer method on a silicon wafer. Once separated, the coils are in the form of small chips that can be assembled and connected to integrated circuit chips. Nonetheless, the same problems of labor arise due to the need to handle, assemble and connect small individual components two at a time.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method to manufacture thin micromodules together that comprise an integrated coil and an integrated circuit, without increasing the cost price of integrated circuits and without the need to assemble individual components.
Another object of the present invention is to provide a hybrid micromodule with two operating modes, one conventional operating mode via contact pads and one contactless operating mode via an antenna coil that is small in size and easy to produce.
These and other objects, advantages and features are achieved by a collective manufacturing method for a plurality of electronic micromodules each comprising a support wafer, an integrated circuit chip with electric connector areas, and at least one coil. The method comprises assembling a plurality of integrated circuit chips onto a support wafer; depositing on the surface of the support wafer an electrically insulating layer covering all the chips; making several apertures in the insulating layer opposite the connector areas of the chips; jointly producing on the support wafer a plurality of flat windings forming coils; connecting each coil to a corresponding chip; and cutting out the support wafer to separate the micromodules.
Advantageously, the coils are connected to the chips by depositing a conducting material in the apertures made in the insulating layer. Advantageously, the conducting material deposited in the apertures is the conducting material forming the coils.
According to one embodiment, the coil is produced on several conducting levels separated by insulating layers.
According to another embodiment, the support wafer is made of silicon. The deposit of an insulating layer includes one step of depositing a layer of polyimide and one step of depositing a layer of silicon dioxide. The coils are produced by copper electroplating. According to yet another embodiment, a protective material is deposited on the entire support wafer before cutting the support wafer.
The present invention also concerns an electronic micromodule comprising a support wafer, an integrated circuit chip and at least one flat winding forming a coil. The chip is preferably embedded in at least one electrically insulating layer comprising at least one layer of at least one insulating material, and the coil is arranged on the insulating layer.
According to one embodiment, the coil is preferably connected to the chip through metal apertures passing through the insulating layer to reach the electric connector areas of the chip.
According to another embodiment, the chip is covered with at least two insulating layers, one of the two insulating layers is a support for the winding forming the coil. The other insulating layer is a support for a conductor linking one end of the coil to a connector area of the chip.
According to yet another embodiment, the chip is covered with at least two insulating layers and the coil comprises at least two flat windings arranged respectively on each of the insulating layers.
The present invention also concerns a hybrid micromodule comprising a support wafer with contact pads on its front side, and in which the support wafer has a micromodule according to the present invention on the rear side. The micromodule preferably comprises an integrated circuit chip with two operating modes, with or without contact, and an insulating layer with apertures to
Bertholio Frédéric
Kowalski Jacek
Serra Didier
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Inside Technologies
Niebling John F.
Zarneke David A.
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