Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Patent
1996-01-18
1998-12-08
Picardat, Kevin
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
438667, 438668, 257 59, 257773, H01L 2184
Patent
active
058468544
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to electrical circuits with very high conductivity and high fineness, and to the processes used to fabricate them. The term "conductivity" essentially implies electrical conductivity, but circuits made according to the present invention can, if necessary, be used for their thermal conductivity and contribute to the transport of calories.
BACKGROUND OF THE INVENTION
The invention also relates to devices comprising these circuits, such as electrochromic devices, operated in matrices or in segments, for the modulation of light, such as devices for variable reflection or variable transmission of light, or for the display of signals and images, for example alphanumeric or graphic data, as well as electroluminescent or liquid crystal display devices; glazing having variable optical properties (windows, screens, windscreens), valves, variable -transparency spectacles, variable-reflection mirrors; electric heating devices using power current (radiators or convectors, panel heaters); and electronic power circuits, for example amplifier output circuits. In these devices, the electrical circuits frequently have to be very fine so that they can be transparent and/or have a high density of conducting elements on a given surface.
At the present time, these electrical circuits are fabricated by a wide range of processes, of which the best known are:
(a) the engraving, for example by acid etching, of conducting layers (of copper, for example) deposited on non-conducting substrates such as sheets of plastic material which may or may not be fibre-reinforced, or glass plates;
(b) the deposition, by appropriate printing processes, on various non-conducting substrates, of conducting tracks consisting of conducting inks or pastes, these tracks corresponding to the circuit design;
(c) the deposition, by various processes of spraying or deposition in the vapour phase, of a conducting layer on a surface on which a mask has previously been deposited; the mask covers the areas of the non-conducting surface on which the conducting layer is not to be deposited, and the circuit appears after the removal of the mask by a suitable process, for example by chemical etching; a process of this category, namely photolithography, is used in particular for the fabrication of very fine circuits.
However, these known processes do not enable a number of conditions necessary for making certain electrical circuits to be met simultaneously. For example, photolithography, which can be used to make circuits with a very low thickness and very high fineness, cannot simultaneously provide a high linear conduction for the conductors of the circuit, owing to their very low thickness. Other processes, such as printing processes (screen printing, offset, etc.) cannot provide a sufficient fineness of the printed lines; moreover, they cannot provide a very fine separation of each conducting line from the adjacent line. This difficulty becomes even greater if the conducting area is to be coated with a layer designed to protect it from contact with a corrosive or conducting medium which might attack or short-circuit it. In order to deposit the conductor and then cover it with one or more protective layers, a number of successive passes must be made, positioned correctly with respect to each other, and it is even more difficult to obtain the desired fineness.
In certain cases, it is desirable to obtain at the same time an excellent linear conductivity, a surface whose roughness is close to zero after installation of the circuit, and protection of the circuit. This objective is not attainable with printing processes which, in order to obtain high conductivity, must deposit a thick layer which then forms an unacceptable relief on the surface of the substrate.
Certain supplementary conditions are sometimes required, and further increase the difficulty of the problem: for example, the production of circuits with large dimensions (practically inaccessible to photolithography), or the provision of a contact betwee
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L. Berenbaum "Processing Technique For Gas Discharge Panels," IBM Technical Disclosure Bulletin, vol. 18, No. 5, Oct. 1975, New York US pp. 1527-1528.
Fremaux Jacques
Giraud Andre
Compagnie Generale D'Innovation Et De Developpement Cogidev
Picardat Kevin
Radomsky Leon
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