Copper micromoulding process for NMR microinductors realization

Micromoulding has been used to realize high quality factor microcoils operating at room temperature for NMR application. The mould is a positive thick resist (AZ 4562) and the electrodeposition process is optimized for copper structures. Two types of micromoulding processes were performed: conventional one using binary mask, and gray-tone lithography one in order to control the local thickness of the metallic device by controlling current density repartition. The copper growth is simulated with the two types of mould and the realization is consistent with expected results, i.e. the thickness of different structures can be modified using the second process. A variation of about 10% between the highest and the lowest thickness is obtained for a 200 mum device size with a mean thickness of 3.5 mum. Classical copper micromoulding is used to obtain nuclear magnetic resonance (NMR) imagery antennas in the range of 500 kHz-1 GHz. Five turns coils (line width 400 mum, space width 300 mum, thickness 7 mum) are realized on each side of glass and kapton(TM) substrates. First measurements at ambient temperature show, respectively resonant frequencies of 174 and 102 MHz, and Q factors of 74 and 60. (C) 2002 Elsevier Science B.V. All rights reserved.