| abstract |
A method for making frontside contact to a substrate through an SOI structure thereon is provided. An etching step is undertaken to form a trench in the SOI structure so as to expose and define a rough surface of the substrate. Then, a thin insulating layer, for example SiO 2 , is formed over the exposed surface of the substrate, this insulating layer being irregular because of its formation over the relatively rough etched surface. Contact material is provided in the trench, and electrical potential is applied across the contact and substrate sufficient to increase the conductivity of the insulating layer, i.e., to break down the insulating layer. Nitrogen may be implanted into the exposed surface of the substrate to slow subsequent growth of the insulating layer, resulting in an even thinner insulating layer, i.e., one even less resistant to breakdown upon application of electrical potential thereacross. If the insulating layer thereon is sufficiently thin or irregular, ohmic contact may be achieved between the contact and substrate without the application of such electrical potential. In yet another embodiment, prior to formation of the insulating layer, the exposed surface of the substrate and wall of the trench are fabricated such that meet at an abrupt angle. Insulating material formed in this area is of poor quality, readily lending itself to breakdown upon application of electrical potential across the contact material and substrate. |