Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating selected area
Patent
1998-06-18
2000-03-14
Wong, Edna
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating selected area
205123, 205194, 377 57, 377 60, 365183, C25D 502, C23C 2800, G11C 1928, G11C 1134
Patent
active
060368349
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a process and devices for the electrolytic formation of a deposit on a chosen group of electrodes of a substrate.
The invention finds application, in particular, in the manufacture of sensors or other miniaturized sensing elements in which chips having a high number of electrodes must be made. For their adaptation to their specific function in the sensor or sensing element, these electrodes must be selectively coated with appropriate materials.
As an example, the invention applies to the production of miniaturized devices such as <<biochips>> which are chips comprising an electric circuit part fabricated on a substrate, and a biological part fabricated on the surface of the chip. In this example, chemical compounds that are compatible with the biological products must be selectively deposited on the electrodes. In this respect, reference may be made to document (3) cited at the end of this disclosure.
By electrolytic formation of a deposit is meant both conventional depositing of a metal such as copper or nickel for example, and the depositing of complex compounds obtained in particular from organic substances.
DISCUSSION OF THE BACKGROUND
To form a deposit on electrodes, recourse is currently made to known microelectronics processes, such as lithography processes.
With these processes it is possible to treat a great number of chips simultaneously on one same semiconductor section in order to selectively deposit a chemical compound on determined electrodes of each chip.
As is described by document (1) whose references are given at the end of this disclosure, said depositing process comprises the following successive stages: base in contact with the electrodes on which a deposit is to be made, the continuous base as an electrode, an independent counter-electrode being placed in an electrochemical bath with the semiconductor section,
This is a conventional process. It can be used to deposit locally on one section of the substrate, for example on determined electrodes, a metal or any other chemical compound.
However, for some applications, it is necessary to coat different electrodes of one same chip with different materials, these materials being dedicated to the specific function of each electrode.
With the above-mentioned electrochemical process, in order to deposit different materials on different sites or electrodes of a semiconductor section, it is necessary to form as many layers of resin as there are different materials to be deposited. To deposit each material it is necessary to expose the areas in which the material is to be deposited and to protect the areas where no deposit is to be made.
The succession of a great number of resin depositing stages and lithography operations to make the required number of openings in each resin layer, corresponding to the electrodes which are to be coated with a given material, means that this is a complex process.
According to another technique which can be used to avoid the lithography stages and resin depositing, an electrolysis support is used having individually addressable electrodes.
Depending upon the planned number of electrodes on the electrolysis support, a direct addressing system or a multiplex addressing system may be used in the support. In this respect, reference may be made to document (2) cited at the end of this disclosure.
In the case of multiplex addressing, integrated switches are associated with the electrodes. Therefore, to make a selective electrolytic deposit, it is merely required to selectively address a given group of electrodes by operating the closure of the appropriate switches and thus applying to them the electrolysis current.
This technique is less complex than the first technique mentioned but has the disadvantage of being costly.
In this case, an often complex and costly addressing system needs to be included in each electrolysis support. Also, this addressing system is of single use for each support and becomes unnecessary when the diffe
REFERENCES:
patent: 4198635 (1980-04-01), Gell, Jr.
patent: 5077762 (1991-12-01), Morimoto et al.
patent: 5776791 (1998-07-01), Caillat et al.
Patrice Caillat, et al., Leti (CEA-Technologies avancees-), pp. 12 to 5, "Fluxless Flip-Chip Technology"--date unavailable.
G. C. Fiaccabrino, et al., Sensors and Actuators B, vol. 18-19, pp. 675 to 677, "Array of Individually Addressable Microelectrodes", 1994--month unavailable.
Commissariat a l''Energie Atomique
Wong Edna
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