Bell Telephone Laboratories

Louis R Thibault

Leopoldo Dy Yau

Hyman J Levinstein

Arthur C Adams

Frank B Alexander, Jr

In a charged-particle-beam lithographic system, charge accumulation on the workpiece during alignment or writing can cause significant pattern placement errors. A film (16) formed directly under the resist layer (56) to be patterned is utilized as a charge-conducting medium during lithography. The pattern delineated in the resist layer (56) is transferred into the film (16) and subsequently into an underlying layer (20). The film (16) is highly compatible with standard lithographic and etching processes used to fabricate LSI and VLSI circuits.

Reducing charging effects in charged-particle-beam lithography

In one embodiment, a relatively thin layer of polysilicon is deposited on an underlying region to which spaced-apart electrical contacts are to be made through a subsequently formed relatively thick insulating layer. The polysilicon is selectively masked by a patterned silicon nitride layer in the regions where contact windows are to be formed. The unmasked polysilicon is then converted to a relatively thick insulating layer in an oxidizing step. Thereafter the silicon nitride portions are removed and the remaining polysilicon is utilized to provide conductive regions in the defined windows. In another embodiment, a relatively thick layer of polysilicon is selectively masked and partially converted to silicon dioxide to define both the insulating layer and the conductive regions. In still another embodiment, a relatively thin layer of polysilicon is patterned and then entirely converted to silicon dioxide to form an insulating layer having windows defined therein.

Fabrication of small contact openings in large-scale-integrated devices

A self-aligned technique for making metal-to-junction contacts in a shallow-junction large-scale-integrated device involves opening very small contact windows in the intermediate insulating layer of the device. These windows respectively overlie only limited central regions of the junctions. Impurities are then applied via the contact windows to provide deeper junction portions directly below the windows. As a result, metallic contact regions subsequently deposited in the windows are exactly aligned with respect to the deeper junction portions. Penetration or spiking of the junctions by the metallic regions is thereby significantly reduced.

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Piscataway, NJ, United States of America

Louis R Thibault