Micro-electro-mechanical system having movable element integrated into substrate-based package
Semiconductor-centered MEMS ( 100 ) integrates the movable MEMS parts, such as mechanical elements, flexible membranes, and sensors, with the low-cost device package, and leaving only the electronics and signal-processing parts in the integrated circuitry of the semiconductor chip. The package is substrate-based and has an opening through the thickness of the substrate. Substrate materials include polymer tapes with attached metal foil, and polymer-based and ceramic-based multi-metal-layer dielectric composites with attached metal foil. The movable part is formed from the metal foil attached to a substrate surface and extends at least partially across the opening. The chip is flip-assembled to span at least partially across the membrane, and is separated from the membrane by a gap.
1. A micro-electro-mechanical system (MEMS) comprising:
a flat substrate having a thickness, a first surface, an opposite second surface, and an opening through the thickness of the substrate, the opening extending from the first to the second surface;
a metal foil attached onto the first surface of the substrate, the foil including a plurality of pads and a membrane extending at least partially across the opening; and
an integrated circuit chip flip-assembled to the pads, the chip at least partially spanning across the opening, separated from the membrane by a gap.
2. The MEMS of claim 1 wherein the metal foil is attached by an adhesive onto the surface of the substrate.
3. The MEMS of claim 2 further including metal-filled via holes through the thickness of the substrate.
4. The MEMS of claim 1 wherein the substrate is a sheet-like multi-metal-layer plastic composite.
5. The MEMS of claim 1 wherein the substrate is a sheet-like multi-metal-layer ceramic composite.
6. The MEMS of claim 1 wherein the substrate is a polymeric tape.
7. The MEMS of claim 1 wherein the membrane is movable normal to the first surface in the space of the opening and of the gap.
8. The MEMS of claim 1 wherein the membrane seals the opening at the first substrate surface.
9. The MEMS of claim 1 wherein the membrane has the configuration of a suspension beam and a plate movable normal to the first substrate surface.
10. The MEMS of claim 9 further including an additional mass attached to the plate.
11. The MEMS of claim 1 wherein the metal pads include a first set and a second set, the pads of the first set enabling electrical interconnection between the membrane and the integrated circuit, the pads of the second set enabling contacts to external parts.
12. The MEMS of claim 11 wherein the metal pads further include a third set configured as a metal seal ring encircling the opening.
13. The MEMS of claim 1 further including a metal plate on the chip, the plate facing the first substrate surface and forming a capacitor with the membrane.
14. A method for fabricating a micro-electro-mechanical system (MEMS) comprising the steps of:
forming an opening from a first surface to an opposite second surface of a flat substrate;
laminating a metal foil onto the first substrate surface and at least partially across the opening so that the foil adheres to the substrate;
patterning the metal layer into a plurality of pads and a segment; and
flip-connecting a semiconductor chip having electronic circuitry onto the pads so that the chip spans at least partially across the opening, separated from the segment by a gap.
15. The method of claim 14 further including, before the step of laminating, the step of attaching a layer of adhesive material across the first surface of the substrate, including across the opening, the material being sticky to the substrate and to the metal foil.
16. The method of claim 14 wherein the metal foil has a thickness suitable for membranes of MEMS.
17. The method of claim 14 further including the step of forming the segment so that it extends at least partially across the opening and is operable as a membrane.
18. The method of claim 14 further including the step of strengthening the assembled substrate by depositing and hardening a polymeric compound while preserving the opening in the substrate.