A thermal interposer is provided for attachment to a surface of a
semiconductor device. In one embodiment, the thermal interposer includes
an upper plate having a bottom surface with a plurality of grooves and
made of a material having high thermal conductivity, and a lower plate
having a top surface with a plurality of grooves and made of a material
having a coefficient of thermal expansion that is substantially the same
as the coefficient of thermal expansion of the material of a
semiconductor device that is bonded to the bottom surface of the lower
plate. The bottom surface of the upper plate is hermetically bonded to
the top surface of the lower plate so that a vapor chamber is formed by
the upper and lower plates, and walls of the grooves on the top surface
of the lower plate extend to within less than 250 microns from walls of
the grooves on the bottom surface of the upper plate comprise a plurality
of second walls the first walls.