Ultrananocrystalline Diamond Films With Optimized Dielectric Properties For Advanced RF MEMS Capacitive Switches

1 . A process for use in fabricating a radio frequency (RF) microelectromechanical systems (MEMS) capacitive switch, comprising the steps of:

providing a bottom electrode; and

layering ultrananocrystalline diamond (UNCD) on the bottom electrode to provide a multilayered UNCD dielectric film having electrical leaky characteristics on the bottom electrode for fast dielectric charging and discharging and rapid recovery of the RF MEMS capacitive switch.

2 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 1 wherein the layering comprises depositing layers of UNCD by microwave plasma chemical vapor deposition (CVD) with microwave CVD plasma.

3 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 2 including forming a layer of substantially continuous dielectric film with rapid nucleation of UNCD by decreasing hydrogen (H 2 ) content of the microwave CVD plasma.

4 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 2 including increasing hydrogen (H 2 ) content of the microwave CVD plasma to form a high resistivity layer of film with a hydrogen-enriched grain boundary.

5 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 4 including decreasing hydrogen (H 2 ) content of the microwave CVD plasma for dense renucleation of the UNCD for filing in gaps or pinholes between grains and forming a substantially uniform continuous layer.

6 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 2 wherein said microwave CVD plasma comprises argon (A R ), methane (CH 4 ) and hydrogen (H 2 ).

7 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 1 including reducing stress in the film.

8 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 1 including increasing hydrogen (H 2 ) concentration in a grain boundary of an intermediate layer of the dielectric film.

9 . A process for use in fabricating a RF MEMS capacitive switch in accordance with claim 1 including:

placing a membrane above the dielectric film;

positioning an upper electrode above the membrane; and

positioning the RF MEMS capacitive to operate for at least 45 million cycles when driven by a complementary metal-oxide-semiconductor (CMOS) electronic device.

10 - 16 . (canceled)

17 . A radio frequency (RF) microelectromechanical (MEMS) switch, comprising:

a RF MEMS capacitive switch moveable for a switching time from an off position in an off state to an on position in an on state, comprising;

a bottom electrode comprising metal providing a RF signal path and having an upwardly facing portion;

a top electrode comprising a RF ground and a direct current (DC) ground;

a moveable metallic membrane less than 0.4 μm thick, said membrane being spaced from said bottom electrode by an air gap ranging from about 2 microns to about 10 microns resulting in a substantially insignificant capacitance relative to an operating frequency of the switch;

a multi-layer dielectric film comprising ultrananocrystalline diamond (UNCD) including:

a bottom UNCD layer covering a substantial area of the upwardly facing portion of the bottom electrode;

an intermediate UNCD layer on said bottom UNCD layer for providing a high resistivity film, said intermediate UNCD layer having a hydrogen enriched grain boundary for enhanced charge conduction;

an upper UNCD layer on the intermediate UNCD layer; and

the dielectric film comprising a substantially continuous UNCD film substantially without pinholes;

said membrane contacting said multi-layer dielectric film when a voltage ranging from about 30 volts to about 50 volts is applied across the top and bottom electrodes in the on state; and

said multi-layer dielectric film discharging and leaking accumulated charges and said RF MEMS capacitive switch recovering within 80 μsec.

18 . An RF MEMS switch in accordance with claim 17 wherein said RF MEMS switch is designed to operate for over 100 billion cycles.

19 . An RF MEMS switch in accordance with claim 17 wherein said multi-layer dielectric comprises an ultra thin UNCD dielectric film ranging from 200 nm to 300 nm.

20 . An RF MEMS switch in accordance with claim 17 wherein:

the membrane comprises molybdenum (Mo);

the bottom electrode selected from the group consisting of bottom electrode comprising tungsten (W) and a stack comprising chromium (chrome) (Cr), tungsten and chromium;

the bottom electrode is positioned on a substrate selected from the group consisting of silicon on sapphire (SOS) and a silicon wafer; and

the RF MEMS capacitive switch is monolithically integrated with a complementary metal-oxide-semiconductor (CMOS) electronic device.