Ultra-thin wafer level stack packaging method

A method of forming an ultra-thin wafer level stack package and structure thereof are provided. The method includes providing a first wafer having a plurality of base chips thereon, selectively binding the first wafer to a second substrate, lapping the first wafer to reduce its thickness, dicing the lapped first wafer, bonding a plurality stack chips to each base chip and packaging the base chip with the bonded stack chips to form an IC package. Thus, each IC package comprises at least a base chip and a stack chip. The IC package has a size almost identical to the base chip and a thickness a little larger than the combined thickness of the base chip and the stack chip. If a known good die inspection of the base chips and stack chips are carried out prior to wafer level packaging, overall yield of the IC package is increased.