Planar process for making high frequency ion implanted passivated semiconductor devices and microwave integrated circuits

摘要

The specification describes new high frequency ion implanted semiconductor devices, novel microwave integrated circuits employing same, and a planar fabrication process for both wherein initially an ion implantation and PN junction passivation mask is formed on one surface of a semiconductor substrate. Next, a heavily doped buried region is ion implanted through an opening in the mask and into the substrate to a preselected controlled depth. Thereafter, one or more additional ion implants are made through the mask opening to complete the active device regions and a PN junction therebetween, all of which are bounded by an annular, higher resistivity unimplanted region of the semiconductor substrate. The PN junction thus formed terminates beneath the implantation and passivation mask, and the semiconductor substrate is then annealed to remove ion implantation damage and to electrically activate the ion implanted regions, while simultaneously controlling the lateral movement of the PN junction beneath the passivation mask. Such annealing does not adversely affect the conductivity and passivation characteristics of either the higher resistivity region or the passivation mask. Openings to the heavily doped buried regions in the substrate are made both opposite and coaxial to the openings in the passivation mask. Precision in the area and depth of these contact openings is achieved by use of a chemical etchant that is preferential to the substrate crystallographic orientation and the impurity concentration levels. Ohmic contact metallization is deposited into the contact openings after which the heat sink metallization is applied to either or both of the metallized contact regions. A mesa is formed to provide discrete structures with the implanted device region surrounded by a ring of high-resistivity semiconductor and thick low-loss dielectric. The resultant device structure exhibits a small degradation in high frequency performance relative to comparable state of the art unpassivated devices.