Phase-change material (pcm) radio frequency (rf) switching device with air gap

A method of fabricating a phase-change material (PCM) switching device, the method comprising:

• providing a base dielectric layer;
• forming a first heater element on the base dielectric layer, the first heater element comprising a first metal element characterized by a first coefficient of thermal expansion (CTE);
• forming a second heater element on the first heater element, the second heater element comprising a second metal element characterized by a second CTE larger than the first CTE;
• forming a first metal pad on the base dielectric layer, wherein the first metal pad is lateral to a first side, in a first horizontal direction, of the first heater element and the second heater element with a first air gap portion therebetween;
• forming a second metal pad on the base dielectric layer, wherein the second metal pad is lateral to a second side, in the first horizontal direction, of the first heater element and the second heater element with a second air gap portion therebetween;
• and
• forming a PCM region on the first metal pad and the second metal pad and above a top surface of the second heater element with a third air gap portion therebetween, wherein the PCM region comprises a PCM operable to switch between an amorphous state and a crystalline state in response to heat generated by the first heater element and the second heater element.

A phase-change material (PCM) switching device, comprising:

• a base dielectric layer over a semiconductor substrate;
• a first heater element disposed on the base dielectric layer, the first heater element comprising a first metal element characterized by a first coefficient of thermal expansion (CTE);
• a second heater element disposed on the first heater element, the second heater element comprising a second metal element characterized by a second CTE, wherein the second CTE is larger than the first CTE;
• a first metal pad and a second metal pad disposed on the base dielectric layer at two sides of the first heater element and the second heater element, respectively;
• and
• a PCM region comprising a PCM operable to switch between an amorphous state and a crystalline state in response to heat generated by the first heater element and the second heater element, wherein the PCM region is disposed on the first metal pad and the second metal pad and above a top surface of the second heater element, and an air gap surrounds the first heater element and the second heater element from three sides.