Top process:
high performance
M.O.S. (Metal - Oxide - Silicon) chips and arrays capacitors feature small size and high Q performances. They are ideally suited for hybrid microwave circuits up to 30 GHz.
The dielectric (Silicon dioxide) thermally grown on a silicon wafer has a very low dielectric constant (є1 = 3.9 є0) and very stable temperature coefficient allowing a complete range of stable capacitance values (0.1 to 100 pF).
Dielectric thickness determines rated voltage for a given capacitance value:
- VR = 40 V e = 0.15 μm
- VR = 100 V e = 0.25 μm
- VR = 200 V e = 0.50 μm
- VR = 400 V e = 1.0 μm
- VR = 500 V e = 1.8 μm
Metallization areas, which are capacitors terminations, are obtained with photo-masking techniques and are made of sputtered titanium (700 Å) and gold (6000 Å).
An electrolytic gold layer of 1.5 μm is made on top termination to ensure the best contact with the external circuits:
Bottom termination attachment techniques:
Eutectic Au-Sn (80/20) Melting point 280° C
“ “ Au-Ge (88/12) Melting point 350° C
Conductive epoxy
Top termination:
Thermocompression, Thermosonic and wedge bonding may be used
- Multi-pad Capacitor
- Single-pad Capacitor