Importance

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Abstract

An interconnecting post for mounting a microelectronic device such as an integral circuit chip is fabricated with generally uniform cross-section, by forming a first layer of positive photoresist on a substrate, soft-baking that first layer and exposing it for a short time with a wide-apertured mask or simply a UV blank flood exposure. Without developing the first layer, a second layer of positive resist is then applied over the first layer, soft-baked, and then exposed with a narrow-apertured mask. During the soft-baking of the second layer, some of its activator in the photoresist compound diffuses into the exposed portion of the first layer and modifies its solubility in such a way that, when the layers are subsequently developed, the developer partially undercuts the unexposed portion of the first layer to form in the photoresist an opening of generally uniform cross-section. This opening can then be filled by plating to produce a strong, integral interconnect post.

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First Claim