MEMS spring probe for non-destructive wafer level chip test

MEMS spring probes were fabricated for non-destructive testing of ultra-small pad-pitch chips. The probes had high suspension from the bottom planar surface, uniformity, high elastic spring constant and low contact resistivity. All contacts took place simultaneously. The contact area at the tip was 70 mu m(2). Fabricated probes showed great spring properties when compression force was applied from the top glass substrate. No noticeable physical markings were observed on the pads over a known range of compression. At the contact resistivity test, as the compression force was increased, the contact resistivity was decreased due to increase of contact surface area. Low RF signal loss was observed through metal probes due to low resistive loss and capacitive parasitics. Measured scattering parameter S-11 was approximately -50 dB and S-21 was -0.5 dB up to 30 GHz. Inductance and capacitance of the MEMS probe were negligible.