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Method to Increase Surface Area for Microelectronic Applications Disclosure Number: IPCOM000015477D
Original Publication Date: 2002-Aug-17
Included in the Prior Art Database: 2003-Jun-20
Document File: 6 page(s) / 186K

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This article describes a method to increase surface area for microelectronic applications.

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Method to Increase Surface Area for Microelectronic Applications

  This article describes a method to increase surface area for microelectronic applications.

Object of the Invention :

    In this invention, a method to create a true three-dimensional surface area improvement is proposed. In other words, the method increases not only the exterior surface area of the structure, but also the interior surface area within the bulk of the structure. First, a porous insulating material is used as the skeleton. Then, a selective metal plating technique is used to deposit a high electrically and thermally conductive metal on the porous substrate. The drastically increased surface area can be used to improve on-chip thermal dissipation or to form ultra high density capacitors.

Background of Porous Oxide

    Porous structure can be fulfilled by many different approaches. For example, published by El-Bahar, et. al, titled " N-type Porous Silicon Doping Using Phosphorous Oxychloride ( POCl3)", IEEE Device Letters, Vol. 21, No. 9, Sept 2000, p 436 -438, is about how to dope a porous silicon substrate. Here, the porous silicon can be formed by electrochemical anodizing of lightly doped p-type crystalline silicon using an HF: ethanol 1:1 solution. The current density is 30 mA/cm2 and anodization time is 10 min. The porosity level is about 65%.

    Then, another paper teaches how to oxidize the porous silicon substrate, reported by Wu, et al titled, " Electrical Properties of Thermally Oxidized Porous Silicon", in J. Electrochem. Soc. (USA) Vol. 143, No.9, Sept 1996, p2972-2980.

    Another technique teaching a method to form porous oxide is reported by Lingchuan Li, titled, " Formation of ultrafine metal particles and metal oxide precursor on anodized aluminum by electrolysis deposition", J. Mater. Sci., Technol. ( China) Vol. 16, No.1, Jan 2000 p 50-54. In this report, the porous oxide film is formed by anodizing aluminum in phosphoric acid. After that, nickel was deposited by an electrolysis

deposition in the pores of the porous oxide film.

Description of the Invention: This invention introduces the novel concept to create a truly 3-dimensional increase in surface area by a) first forming selectively a porous body on a substrate , and b) selective metallization throughout the whole volume of the porous region. The key to improve the surface area comprises steps to selectively depositing metal on a porous insulating region and not on any place else. Such selective metal deposition will reduce integration cost and improve chip yield. A special metal plating technique is used to conformally coat the porous skeleton and thus increases the surface area per unit volume of space. The area increased is about an order of magnitude higher than that by HSG technique mentioned above. The same method can be used to form high-density capacitor elements for ultra high density DRAM arrays. Or, it can be used to fabricate various semiconductor sensing devices, such as pressure,...