LAUSR

A transferable-tip technology has been developed that has applications for wafer-level fine-pitch probe and electrical test of semiconductor devices. The tips are made by filling a mold made in a (100)-oriented Si substrate wafer, with cavities created by anisotropic etch. The tips are very sharp and planar, with a precise cone angle of 70.5°. The metal tips are then transferred to any suitable substrate, using a solder and release process. The tips, used in a probe head, enable electrical contact to large-area microbump arrays at low force. Test structures were fabricated with as many as 250 000 tips at the 50- $\mu \text{m}$ pitch. This approach also enables test electronics to be incorporated into the probe head. In this way, high-speed functional tests can be performed that minimize difficulties normally encountered in wiring and shielding many high-frequency signals in the probe head and to external test electronics. This probe tip technology also has potential for improved chip-to-chip interconnections that ensure known-good-dies are added to a chip stack. As compared to other probe contact technologies, the transferable-tip approach is potentially low-cost and amenable to new modes of probing, particularly applicable to chip stacks made with 3-D Si integration and heterogeneous integration.