Title :
MEMS Vertical Probe Cards With Ultra Densely Arrayed Metal Probes for Wafer-Level IC Testing
Author :
Wang, Fei ; Cheng, Rong ; Li, Xinxin
Author_Institution :
State Key Lab. of Transducer Technol., Chinese Acad. of Sci., Shanghai, China
Abstract :
We have developed a MEMS probe-card technology for wafer-level testing ICs with 1-D line-arrayed or 2-D area-arrayed dense pads layouts. With a novel metal MEMS fabrication technique, an area-arrayed tip matrix is realized with an ultradense tip pitch of 90 mum times196 mum for testing 2-D pad layout, and a 50-mum minimum pitch is also achieved in line-arrayed probe cards for testing line-on-center or line-on-perimeter wafers. By using the anisotropic etching properties of single-crystalline silicon, novel oblique concave cavities are formed as electroplating moulds for the area-arrayed microprobes. With the micromachined cavity moulds, the probes are firstly electroplated in a silicon wafer and further flip-chip packaged onto a low-temperature cofired ceramic board for signal feeding to an automatic testing equipment. The microprobes can be efficiently released using a silicon-loss technique with a lateral underneath etching. The measured material properties of the electroplated nickel and the Sn-Ag solder bump are promising for IC testing applications. Mechanical tests have verified that the microprobes can withstand a 65-mN probing force, while the tip displacement is 25 mum, and can reliably work for more than 100 000 touchdowns. The electric test shows that the probe array can provide a low contact resistance of below 1 Omega, while the current leakage is only 150 pA at 3.3 V for adjacent probes.
Keywords :
contact resistance; electroplating; etching; flip-chip devices; integrated circuit testing; leakage currents; micromachining; micromechanical devices; probes; MEMS fabrication technique; MEMS probe-card technology; MEMS vertical probe cards; Sn-Ag solder bump; anisotropic etching property; area-arrayed microprobes; area-arrayed tip matrix; automatic testing equipment; contact resistance; current leakage; electroplated nickel; electroplating moulds; flip-chip packaged; lateral underneath etching; line-arrayed probe cards; line-on-center wafer; line-on-perimeter wafers; low-temperature cofired ceramic board; micromachined cavity moulds; oblique concave cavity; signal feeding; silicon wafer; single-crystalline silicon; ultra densely arrayed metal probes; ultradense tip pitch; wafer-level IC testing; Dense-arrayed vertical tips; IC testing; electroplating; micromachining; probe card;
Journal_Title :
Microelectromechanical Systems, Journal of
DOI :
10.1109/JMEMS.2009.2021815