Patent ID: 7456721

Claim:
An on-chip transformer balun formed among N successive isolating layers from top to bottom on or over a semiconductor substrate, N being an integer larger than 4, said on-chip transformer balun comprising: a first winding, comprising: a plurality of first semi-turn coils formed on the first isolating layer among the isolating layers; a plurality of second semi-turn coils substantially symmetrical to the first semi-turn coils and formed on the first isolating layer among the isolating layers; a plurality of metal junctions formed on the first isolating layer among the isolating layers, each of the metal junctions connecting one of the first semi-turn coils with one of the second semi-turn coils; and a plurality of first conducting sections formed on the second isolating layer through the ith isolating layer among the isolating layers, i being an integer index ranging from 3 to (N−1), each of the first conducting sections, by use of a plurality of first vias formed among the first isolating layer through the (i−1)th isolating layer, connecting one of the first semi-turn coils with one of the second semi-turn coils; and a second winding, comprising: a plurality of third semi-turn coils interlaced with the first semi-turn coils and formed on the first isolating layer among the isolating layers; a plurality of fourth semi-turn coils substantially symmetrical to the third semi-turn coils, interlaced with the second semi-turn coils, and formed on the first isolating layer among the isolating layers; and a plurality of second conducting sections formed on the (i+1)th isolating layer among the isolating layers, each of the second conducting sections, by use of a plurality of second vias formed among the first isolating layer through the ith isolating layer, connecting one of the third semi-turn coils with one of the fourth semi-turn coils, or one of the third semi-turn coils with another of the third semi-turn coils, or one of the fourth semi-turn coils with another of the fourth semi-turn coils.