WAFER-TO-WAFER OXIDE FUSION BONDING

摘要

Oxide-oxide fusion bonding of wafers that includes performing a van der Waals force bonding process with a chuck having at least a flat central zone and an outer annular zone lower than the central zone, an edge portion of a mounted wafer is biased towards the outer annular zone. The van der Waals bonding wave is disrupted at the outer annular zone, causing an edge gap. A thermocompression bonding process is performed that includes heating the bonded wafers to a temperature sufficient to initiate condensation of silanol groups between the bonding surfaces, reducing the atmospheric pressure to cause degassing from between the wafers, applying a compression force to the wafers with flat chucks so as to substantially eliminate the edge gap, and performing a permanent anneal bonding process.

主权项

1. A method for oxide-oxide fusion bonding of two wafers, a bonding surface of each wafer being prepared for oxide-oxide fusion bonding, the method comprising:
performing a van der Waals force bonding process between the bonding surfaces of the first and second wafers by at least:
mounting on a first chuck face of a first chuck a first wafer having a bonding surface facing away from the first chuck face;mounting on a second chuck face of a second chuck a second wafer having a bonding surface facing away from the second chuck face, the second chuck face including at least a flat central zone and an outer annular zone contiguous to the central zone, the outer annular zone being lower than the flat central zone such that an annular edge portion of the bonding surface of the second wafer that is mounted to the outer annular zone of the second chuck face is biased towards the outer annular zone;while the bonding surfaces of the first and second wafers are in opposed aligned close proximity to each other, biasing a center portion of the first wafer towards the second wafer such that a center portion of the bonding surface of the first wafer contacts a center portion of the bonding surface of the second wafer, andreleasing the first wafer from the first chuck, whereby the first wafer snaps against the second wafer forming a van der Waals bonding wave propagating radially outward from the center contact portions of the bonding surfaces that is disrupted upon reaching the annular edge portion of the bonding surface of the second wafer that is biased towards the outer annular zone of the second chuck face, the annular edge portion of the bonding surface of the second wafer and a corresponding annular edge portion of the bonding surface of the first wafer defining an edge gap between the annular edge portions; mounting the van der Waals force bonded first and second wafers between a third chuck having a flat chuck face, and a fourth chuck having a flat chuck face; in a process chamber, performing a thermocompression bonding process between the bonding surfaces of the first and second wafers by at least:
heating the first and second wafers to a temperature at least sufficient to initiate condensation of silanol groups between the bonding surfaces of the first and second wafers;reducing the pressure of the atmosphere in the process chamber;applying a compression force to the first and second wafers with the third and fourth chucks so as to substantially eliminating the edge gap; and performing a permanent anneal bonding process between the bonding surfaces of the first and second wafers.