Device structures including backside contacts, and methods for forming same
View Patent ↗The present invention relates to device structures having backside contacts that extend from a back surface of a substrate through the substrate to electrically contact frontside semiconductor devices. The substrate preferably further includes one or more alignment structures located therein, each of which is sufficiently visible at the back surface of the substrate. In this manner, backside lithographic alignment can be carried out using such alignment structures to form at least one back contact opening in a patterned resist layer over the back surface of the substrate. The formed back contact opening is lithographically aligned with the front semiconductor device and can be etched to form a back contact via that extends from the back surface of the substrate onto the front semiconductor device. Filling of the back contact via with a conductive material results in a conductive back contact that electrically contacts the front semiconductor device.
1. A method comprising:
forming a substrate having a front surface and a back surface and one or more alignment structures that are visible at the back surface of the substrate for backside lithographic alignment, said substrate has a semiconductor-on-insulator (SOI) configuration and comprises a front semiconductor device layer, a buried insulator layer, and a back semiconductor substrate layer;
forming at least one front semiconductor device at the front surface of the substrate;
forming a passivation layer over the front surface of the substrate to cover the at least one front semiconductor device;
bonding a supporting wafer to the passivation layer to support the substrate at the front surface thereof;
completely removing the back semiconductor layer of the substrate to expose a back surface of the buried insulator layer;
forming a patterned resist layer on the back surface of the substrate by lithography, wherein the patterned resist layer defines at least one back contact opening therein that is lithographically aligned with at least one component of said at least one front semiconductor device;
etching the substrate through said at least one back contact opening to form at least one back contact via that extends from the back surface through the substrate onto the at least one component of the at least one front semiconductor device;
filling the at least one back contact via with a conductive material to form at least one back conductive contact; and
forming at least one back metal interconnect level over the exposed back surface of the buried insulator layer so that the at least one conductive back contact electrically connects the at least one front semiconductor device with the at least one back metal interconnect level.
2. A method comprising:
forming at least one front semiconductor device on a front surface of a substrate, said substrate further including a back surface opposing the front surface, and wherein the substrate comprises one or more alignment structures that are visible at the back surface of the substrate for backside lithographic alignment;
forming a patterned resist layer on the back surface of the substrate by lithography and by using said one or more alignment structures, wherein the patterned resist layer defines at least one back contact opening therein that is lithographically aligned with at least one component of said at least one front semiconductor device;
etching the substrate through said at least one back contact opening to form at least one back contact via that extends from the back surface through the substrate onto the at least one component of the at least one front semiconductor device; and
filling the at least one back contact via with a conductive material to form at least one back conductive contact.
3. The method of claim 2 , wherein before formation of the patterned resist layer on the back surface of the substrate, a passivation layer is deposited over the front surface of the substrate to cover the at least one front semiconductor device, and a supporting wafer is bonded to the passivation layer to support the substrate at the front surface thereof.
4. The method of claim 2 , wherein the substrate has a semiconductor-on-insulator (SOT) configuration and comprises a front semiconductor device layer, a buried insulator layer, and a back semiconductor substrate layer.
5. The method of claim 4 , wherein the back semiconductor substrate layer of the SOT substrate is completely removed to expose a back surface of the buried insulator layer before formation of the patterned resist layer thereover, and wherein at least one back metal interconnect level is formed over the exposed back surface of the buried insulator layer after formation of the at least one conductive back contact, so that the at least one conductive back contact electrically connects the at least one front semiconductor device with the at least one back metal interconnect level.
6. The method of claim 4 , wherein the back semiconductor substrate layer of the SOT substrate is thinned to form a back semiconductor device layer before formation of the patterned resist layer thereover, and wherein at least one back semiconductor device is formed in the back semiconductor device layer after formation of the at least one conductive back contact, so that the at least one conductive back contact electrically connects the at least one front semiconductor device with the at least one back semiconductor device.