Three-dimensional passive circuit technology for ultra-compact MMICs

• Published in: IEEE transactions on microwave theory and techniques 1995-12, Vol.43 (12), p.2845-2850
• Main Authors: Hirano, H., Nishikawa, K., Toyoda, I., Aoyama, S., Sugitani, S., Yamasaki, K.
• Format: Article
• Language: English
• Subjects: Coupling circuits; Gold; Insulation; Metal-insulator structures; Microstrip; MMICs; Nonhomogeneous media; Passive circuits; Polyimides
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/22.475644

A novel passive circuit technology of a three-dimensional (3-D) metal-insulator structure is developed for ultra-compact MMICs. By combining vertical passive elements, such as a wall-like microwire for shielding or coupling, and a pillar-like via connection with multilayer passive circuits, a 3-D passive circuit structure is formed to implement highly dense and more functional MMICs. O/sub 2//He RIE for forming trenches and holes in a thick polyimide insulator, low-current electroplating for forming gold metal sidewalls in the trenches or holes, and ion-milling with a WSiN stopper layer for patterning the gold metal are used to produce such a structure. The complete 3-D structure provides miniature microstrip lines effectively shielded with a vertical metal-wall, a miniature balun with low-loss vertical wall-like microwires, and inverted microstrip lines jointed with pillar-like vias through a thick polyimide layer. This technology stages next-generation ultra-compact MMICs by producing various functional passive circuits in a very small area.