High density out-of-plane microprobe array

In this paper, the high density out-of-plane microprobe array is demonstrated. The fabrication processes of proposed device including bulk micromachining, thin film deposition and electroplating. By depositing the various thickness of thin film with residual tensile stress, the deflection of bending beam could be precisely controlled. The horizontal variation of bending beam array could also restrict in a few micrometer. The concept for the device fabrication is depositing the Ti thin film on a suspension SiO₂ cantilever to bring out-of-plane bending deformation, and then use electroplating process such as low stress Ni film to increase the stiffness of the probe structure without change the beampsilas bending profile. Through the different electroplating bath, the bending microprobe with different material, such as Ni and Cu, could be fabricated for IC testing and interconnection applications. According to the mask design, the high density probe array could easily achieve. The prototypes of the 40 times 40 microprobe array in pitch sizes of 50 mum, 80 mum and 100 mum were fabricated and characterized. Measurement result by the optical interferometer shown the mean bending height of twenty samples are about 3 mum, 9 mum and 26 mum in different beam length 25 mum, 55 mum and 85 mum, besides the maximum horizontal variations are less than plusmn0.8 mum, plusmn1.2 mum, plusmn2 mum that corresponded to the pitch size of 50 mum, 80 mum, and 100 mum, respectively.