News Column

Patent Issued for Interconnect Line Selectively Isolated from an Underlying Contact Plug

August 19, 2014

By a News Reporter-Staff News Editor at Journal of Technology -- A patent by the inventor Drynan, John M. (Boise, ID), filed on January 24, 2011, was published online on August 5, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8796815 is assigned to Micron Technology, Inc. (Boise, ID).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Modern integrated circuit designers confront problems related to the need for increasingly smaller size and higher levels of integration. In the art of integrated circuit fabrication, and particularly when dealing with modern memory circuits, circuit manufacturers must design memory cells that are more densely constructed such that the basic elements making up the cell are closer together. This increasingly close proximity of the discrete electrical features within a memory cell, such as dynamic random access memory (DRAM) cells, becomes problematic in light of the increasing potential for shorting between adjacent electrical conductors. This shorting may cause a memory cell to function improperly or not at all.

"An additional concern in the manufacture of integrated circuits is the increasing complexity and cost related to the necessity for diminishing size of the memory devices. The desire to utilize fewer stages of fabrication has led designers of memory cells to strive to simultaneously perform, at a given stage of fabrication, as many necessary steps as possible. An example of this may be seen in the standard technology of fabricating capacitor-over-bit-line (COB) type DRAM cells, which typically employs a process wherein all contacts to the memory cell active area are formed simultaneously. Thus, both bit line and capacitor contacts to the semiconductor substrate are formed using a single layering and etching step (utilizing material such as polysilicon), which creates contact studs over which the additional features of the memory cell are fabricated.

"Specifically in a process such as described above, after the contact studs are formed in the memory cell, a dielectric layer is deposited and a bit line contact-hole pattern is lithographically delineated and subsequently etched down to the top of the stud corresponding to the bit line connection to the active area on the substrate below. A plug is next formed within each contact-hole, typically of doped polysilicon, and the conductive layers for the bit lines (typically silicide, polycide, or tungsten-based material) are deposited and subsequently delineated using lithographic-etching techniques. An interlayer dielectric is next deposited around the bit line and a capacitor contact-hole pattern is lithographically delineated and etched down between the formed bit lines to the tops of the studs corresponding to the capacitor bottom electrode connections to the active area on the substrate below. This fabrication step is completed when the capacitor contact-holes are then plugged with doped poly silicon or another conductor. Then the process of cell fabrication continues on to the formation of the capacitor features.

"This standard method of fabricating memory cells utilizes the single-step forming of contact studs for both capacitors and bit lines, and the forming of bit line contacts and bit lines. Though this method is useful in reducing the steps required to form contacts to active areas of a substrate, it is desirable that the contacts, and subsequently the fully formed features, be located in a more densely packed array. It is also desirable to have the electrical features and interconnects, exemplified by bit line and capacitor features, arranged in such a more densely packed array without increasing the probability of shorting."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "The present invention relates to integrated circuit fabrication and more particularly to selectively electrically connecting an electrical interconnect line with an associated contact to an active area and electrically isolating the interconnect line from other underlying contacts for other electrical features.

"More specifically, in this invention a first interconnect line is formed over two underlying contact holes such that it is electrically connected to a first polysilicon stud but is electrically isolated from a second stud. The line is essentially formed over the first stud and partially over the second stud, and is thereafter electrically isolated from the second studs, thereby allowing the electrical features to be formed in closer proximity to one another for higher levels of integration.

"The present invention also provides a method for efficiently connecting interconnect lines to a plurality of selected contact studs while maintaining electrical isolation from other non-selected plugs.

"The above-described and other advantages and features of the invention will be more clearly understood from the following detailed description which is provided in connection with the accompanying drawings."

URL and more information on this patent, see: Drynan, John M.. Interconnect Line Selectively Isolated from an Underlying Contact Plug. U.S. Patent Number 8796815, filed January 24, 2011, and published online on August 5, 2014. Patent URL:

Keywords for this news article include: Micron Technology Inc..

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Source: Journal of Technology

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