FR2471119A1 - THIN-FILM ELECTRONIC CIRCUIT AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

A. THIN LAYER ELECTRONIC CIRCUIT AND METHOD FOR ITS MANUFACTURING. B. THIN LAYER ELECTRONIC CIRCUIT CHARACTERIZED IN THAT THE METAL OXIDE LAYER 4 DEPOSITED ON THE SUBSTRATE 5 DOES IN THE ZONE OF THE SECOND MODEL M A LAYER 8 MADE FROM THIS SAME METAL FROM WHICH THE METAL OXIDE IS FORMED OF THE METAL OXIDE LAYER 4. C. THE INVENTION APPLIES IN PARTICULAR TO THE REALIZATION OF DISPLAY ELEMENTS.

Description

The invention starts from a thin-film electronic circuit with a

substrate plate consisting of

  insulating material and with an electrically

  conductive layer partially covering the substrate plate, this layer constituting a first model and a second model, these two models being correlated at least in one

  point, and the first model defining elements

  of the thin-film electronic circuit while the second model defines the conductive pathways and / or contacts

connection.

  Thin-film electronic circuits of this type are already known, in which the metal oxide layer consists of tin dioxide or of indium oxide. Such thin-layer circuits are used for the construction of electronic components. such as, for example, liquid crystal display, gas discharge and electroluminescence display elements. In the case of these thin-film circuits, the metal oxide layer exhibits

  certain properties that have a detrimental effect on

  and the use of such display elements 1o in the plug contacts which must be provided within the second model for the alix.

  of operating voltages, there are

  high transmission rates; 20- and especially when a complex constitution is constrained to use a passage of narrow conduction, resistances too high take births in

  connecting conductors between the contact and the constituent element

  tutif that is to say inside the second model; 3.- Since the surface of the metal oxide layer inside the two models does not allow connection or soldering, semiconductor elements, for example control blocks, can not be integrated in

the display element.

  The object of the invention is to remedy these drawbacks and concerns for this purpose an electronic circuit in a thin layer, characterized in that the metal oxide layer carries in the zone of the second model a layer made from the same metal of which is constituted the metal oxide of the

metal oxide layer.

2.-

  The thin-film circuit conforms to the

  The invention having the above-defined characteristics provides a reduction in transmission resistance on the contacts compared to known solutions, an improvement in the conductivity in the supply conductors and the possibility of obtaining a surface allowing connections and connections. The invention will be explained in more detail with reference to exemplary embodiments of the thin film circuit according to the invention shown in the accompanying drawings in which: FIG. 1 shows the potentiodynamic characteristic U / I of a layer of In 203 with a surface resistance of about 20 S / mm in a 2 n H 2 SO 4 solution. FIGS. 2 a to 2 d show in section a thin-film electronic circuit according to the invention. FIG. 3 shows a first example of application of a thin-film electronic circuit that confers on the inve FIG. 4 shows a second example of application of a thin-film electronic circuit according to the invention; FIG. 5 shows a third example of application of a thin-film electronic circuit according to the invention;

to the invention.

  It has been found that a good adhesion of galvanically deposited metal layer (for example Au, Ni and In) can be obtained when the In203 or SnO2 layer has been electrochemically partially reduced in a partial manner. Diluted sulfuric acid or also buffer solutions are well adapted electrolytes. FIG. 1 shows the potentiodynamic characteristic curve iU / I of a layer of In 203 with a surface resistance of about 20-L per mm in a 2nH S0 solution. According to this characteristic, it can be seen that for a potential of about -600 mV, measured against a 3.5 n calomel electrode, the reduction of In 2 O 3 begins (see Part 1 of the characteristic curve). When going back, the indium thus formed is again oxidized (see part 2 of the characteristic curve). The flow

  returns to very small values when indium is complete.

  reoxidized (see Part 3 of the characteristic curve).

  In the case of the use according to the invention of this effect, the reduction reaction corresponding to the part 1 of the characteristic curve is used for

  convert a portion of the indium oxide layer to indium.

  By the partial reduction of the In 2 O 3 layer the surface is on the one hand roughened, and on the other hand the thin indium layer obtained constitutes a base layer facilitating the adhesion of the galvanic metal deposition which will follow. Good adhesion of the gold, nickel and indium layers can be obtained when the layers of In203 with a thickness of about

  nm are electrochemically reduced by about half.

  The application of the galvanic process thus described to the production of a thin-layer electronic circuit with gold and In205 structures on glass is shown schematically in FIG. 2. The glass substrate 5 coated on its entire surface is a layer of In203 is then first covered with a layer 6 of a photolac working positively By exposure to the light of a source of ultraviolet light and the development that follows, the locations M2 which must be reinforced with gold are cleared. In these M2 areas the In203 of the layer 4 is then partially electrochemically reduced and this with a cathode current density of 0.5 to 5 mA / cm 2. Thus is produced layer 8 (Figure 2b). The treatment time in an electrolyte which contains 5 g / l of (NH4) 2SO4 and 50 g / l

  hydrogenated diammonium citrate is from 30 to 240 seconds.

  The next step of the process is the galvanic deposition of the reinforcing metal bend 9 made of gold (FIG. 2c), pure gold having a thickness of 1 to 3 μm being deposited from a bath buffered with By a second exposure (to light and a second development, the photolayer layer 6 is then filled with all the zones which must not have transparent layers 4 of In203, that is to say of all the zones which do not belong In this way, the layer 4 of In20 3 is attacked with HCl at approximately 600 ° C. (Figure 2d) The layer system 8, 9 thus formed on the layer of In203-4 in 4 .- the zone of the second model M2 is well adapted to the application of

  ultrasonic welding technique.

  Other electrolytes suitable for the reduction of the In203 layer 4 are, for example, 2n sulfuric acid and 0.5% citric acid solutions. Referring to the following examples of applications, the method of embodiment and some possibilities for implementing thin film circuits will be described.

according to the invention.

EXAMPLE i

  In this example (see Figure 3) gilding 11 serves only to reduce the contact resistance in the supply conductors 12a to 12g of a 7-segment display. A glass plate coated with In 203 is covered with photolac and according to the process of exposure and development

  above mentioned, the zones which are to be gilded are released again.

  The thick In203 layer of 140 nm is first reduced by

  half, immersing the plate in a 2n solution of sulfuric acid

  furicating and cathodically treating it for 30 seconds with a current density of 2 mA / cm 2. The gilding is performed

  after an intermediate wash in a separate bath containing

  50 g / l of (NH4) 2SO4, 50 g / l of hydrogenated diammonium citrate, and 20 g / l of K Au (CN) 2. Then the structures of the supply conductors and the display elements are

  achieved by a photochemical etching process.

EXAMPLE 2

  Unlike the example lyce are not

  not only the contact surfaces but also the

  feeders 12a to 12g (FIG. 4) which must be gilded. Another difference lies in the reduction bath consisting here of 50 g / l of (NH 4) 2 SO 4 and of 50 g / l of hydrogenated diammonium citrate. As this bath contains components similar to the gilding bath, the intermediate wash can be

  deleted. Gilding and further processing of the electrical circuit

  thin-layer tronics are performed as in Example 1.

EXAMPLE 3

  The thin-film electronic circuit is prepared in a manner analogous to that described with reference to FIG. 2. It comprises a power supply conductor

  gold 9 and a non-gold feed conductor 13 (Figure 5).

5.- 2471119

  On the end of the supply conductor 13 not gilded is glued by means of a conductive glue a chip 14 of light emitting diode. A gold connection wire 15 conducts a conductive connection between the chip 14 LED and the gold power supply conductor 9. To protect the chip 14 LED and the lead wire 15,

  they are both covered by a drop of silicone resin 16

  cone. During the aforementioned mounting of the luminescent diode 14 there is furthermore the possibility of observing it through the glass plate 5, that is to say opposite to the usual observation mode. For this purpose the light must be reflected by a reflective layer 179 attached to the cover 16

  (silver plating, white lacquering, aluminum spraying).

  Instead of luminescent diodes, semiconductor components such as

  can be placed on the glass substrate and connected to

  A combination of all these examples ultimately results in a display element that is mounted on a common glass plate comprising a liquid crystal display, one or more light emitting diodes, and the associated control circuitry. As the gold layer is also suitable for soldering. ,

  other components such as, for example, incandescent bulbs

  can be introduced by welding in this arrangement.

  sition. The thin-film electronic circuit according to the invention allows a simple way of integrating semiconductor components into assemblies which moreover comprise only structures consisting of transparent resistant paths such as for example liquid crystal display elements or else the fields

  In addition, the thin-film circuit complies with the

  vention has the following advantages: a) during its production it does not involve high temperatures, b) the adhesion is so good that irreproachable connections and welds can be achieved

2471 1 1 9

6.-

Claims (9)

  1.- Thin film electronic circuit with a substrate plate (5) made of an insulating material   and with an electrically conductive metal oxide layer (4)   trice partially covering the substrate plate (5), this layer constituting a first model (Mj) and a second model (M2), these two models (M1, M2) being correlated at least at one point, and the first model (M1 ) defining constituent elements of the electronic circuit in a thin layer while the second model (M2) defines conductive paths and / or connection contacts, thin-layer electronic circuit characterized in that the metal oxide layer (4) carries in the zone of the second model (M2) a layer (8) produced from the same metal of which the metal oxide is constituted   the metal oxide layer (4).   2. A thin film electronic circuit according to claim 1, characterized in that, on the layer (8) thus produced is reported a metal layer (9) of reinforcement. 3.- Thin film electronic circuit   according to any one of claims 1 and 2, characterized   in that the layer (8) is obtained by reducing the metal oxide of the metal oxide layer (4) on the surface of this layer in the zone of the second model (M2), so that the layer of metal oxide (4) has in this area a thickness which is reduced with respect to the thickness of the   metal oxide layer (4) in the region of the first model (M1).   4.- Thin film electronic circuit   according to any one of claims 1 and 2, characterized   in that the layer (8) thus formed is a layer formed on the metal oxide layer (4), preferably deposited   galvanically on it, in the area of the second model (M2).   5.- Thin film electronic circuit   according to any one of claims 1 to 4, characterized   in that the metal oxide layer (4) consists of tin bi-oxide while the layer (8) thus produced is made of tin.   6.- Thin film electronic circuit   according to any one of claims 1 to 4, characterized   in that the metal oxide layer (4) consists of oxide 24 71119   indium while the layer (8) thus produced consists of indium. 7.- Thin film electronic circuit   according to any one of claims 2 to 6, 9, characterized   in that the reinforcing metal layer (9) is constituted by dtor. 8. = thin film electronic circuit according to any one of claims 2 to 6, characterized in that the metal reinforcing layer (9) is constituted ( of nickel.   9.- Thin film electronic circuit   according to any one of claims 2 to 6, characterized   in that the reinforcing metal layer (9) is made of indium. 10. A process for producing a thin-film electronic circuit according to any one of the   Claims 1 to 3, characterized in that on the plate   substrate (5) is firstly reported the alloy oxide layer, (4) in the form of a layer covering the entire substrate, then the metal oxide layer (4) is covered with a layer of photolac (6) over its entire surface, then this photolayer layer (6) is removed by exposure to light and developed in the region of the second model (M2), and the metal oxide layer is then partially electrochemically reduced ( 4) in the zone of the second model (M2) by elaborating the layer (8), then on this layer (8) thus elaborated galvanically depicting the metal reinforcing layer (9), then removing by a second exposure to light and a second development of the photolayer layer (6) of all the zones that do not belong to the first model (M1) and then the metal oxide layer is removed by etching (4)   in all locations thus discovered, and the final removal   parts of the remaining layer of photolac (6)   in the area of the first model (M1).   11. A process according to claim 10, characterized in that the layer (8) is produced by partial reduction o of the metal oxide of the metal oxide layer (4) in an electrolyte containing (NH4) 2SO4 and citrate of hydrogenated diammonium.   8, - 12.- Process according to claim 10, characterized in that the layer (8) is produced by partial reduction of the metal oxide of the metal oxide layer   (4) in dilute sulfuric acid.   13. A process according to claim 10, characterized in that the layer (8) is produced by partial reduction of the metal oxide of the metal oxide layer. (4) in citric acid.   14.- Process according to any one of   10 to 13, for the production of an electrical circuit   tronic-thin layer according to claim 7, characterized in that the metal reinforcing layer (9) is removed from a bath containing (NH 4) 2 SO 4,   hydrogenated diammonium citrate and KAu (CN) 2.   -15.- Process according to any one of   Claims 10 to 14, characterized in that for the attack   of the metal oxide layer (4) in the zone outside the first model (M1) and the second model (M2) on uses hydrochloric acid.