International Business Machines Corporation

Hans A Protschka

Harish N Kotecha

Jake Theisen

Dave Stanasolovich

A method is disclosed for fabricating patterned conductive lines which are self-aligned with underlying contacts windows. A layer of a photosensitive material such photoresist is formed over a dielectric layer. The photoresist layer is processed to have fully developed areas corresponding to contact windows, partially developed areas corresponding to the patterned conductive lines and undeveloped areas which correspond to field areas where the entire dielectric layer is maintained. The dielectric layer is preferably a compound dielectric layer to reduce interlevel shorts. Through the use of selective etch steps, the compound dielectric layers aid in the formation of the patterned conductive line and contact window structure. A series of reactive ion etch (RIE) steps are performed. The first RIE step, highly selective to dielectric material as compared to photoresist, etches the fully developed areas at least partially through the dielectric thickness. In the second RIE step, the photoresist which protected dielectric in the conductive line areas is removed. The third RIE step is also selective to dielectric material as compared to photoresist and etches the dielectric to form channels where the conductive lines are formed, and completes the etching in the contact window areas. The remaining resist is then removed. The channels and contacts are overfilled with a deposition of a conductive material. This conductive material is then planarized by either a RIE process or a chemical-mechanical polishing step.

Method for fabricating high circuit density, self-aligned metal linens

The process is based upon applying a layer of release agent which is a solution of a polysulfone constituent and a dye, applied to the surface of a polysilicon layer. Thereafter, the photoresist layer can be applied on top of the release agent layer. Then, the photoresist can be optically exposed and developed and its alignment measured. If the alignment of the resultant photoresist structures is found to be incorrect, rework can be easily accomplished by dissolving the release agent in a suitable solvent. This allows the existing photoresist structures to be removed. Then the rework cycle can continue by applying a new layer of the release agent and dye solution and followed by a new photoresist layer. If the original photoresist layer or the reworked photoresist layer is found to have been properly aligned, then the normal processing steps can continue. The process also provides for an improved control over back reflected and diffracted light during the optical exposure step. The presence of a dye which is selected to have an absorption cross-section which peaks at an optical wavelength approximately equal to the emission peak for the wavelength of the exposure light, enables any portion of the exposure light which passes through the photoresist and into the release layer, to be absorbed before it has a chance to be reflected or diffracted back up into the photoresist layer. This enables the photoresist to be uniformly exposed even when it passes over structures which lie beneath the release layer and which might otherwise cause unwanted reflection or diffraction of the exposure light.

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Gaithersburg, MD, United States of America

Hans A Protschka