EP-4742289-A1 - MEMS SWITCH, PACKAGED MEMS SWITCH PRODUCT AND METHOD OF OPERATING IT

EP4742289A1EP 4742289 A1EP4742289 A1EP 4742289A1EP-4742289-A1

Abstract

In accordance with an embodiment, a microelectromechanical system (MEMS) switch device includes: a substrate; a switching membrane disposed above the substrate; a pull-in electrode disposed above the switching membrane; a metal contact disposed on the switching membrane; and a pull-back electrode disposed below the switching membrane, wherein the switching membrane is movable between an open position and a closed position, and wherein in the closed position, the metal contact electrically connects two RF signal lines.

Inventors

TIMME, Hans-Jörg
LOHNINGER, GERHARD
AHRENS, CARSTEN

Assignees

Infineon Technologies AG

Dates

Publication Date: 20260513
Application Date: 20251111

Claims (15)

A microelectromechanical system switch device, comprising: a substrate; a switching membrane disposed above the substrate; a pull-in electrode disposed above the switching membrane; a metal contact disposed on the switching membrane; and a pull-back electrode disposed below the switching membrane, wherein the switching membrane is movable between an open position and a closed position, and wherein in the closed position, the metal contact electrically connects two RF signal lines.
The microelectromechanical system switch device of claim 1, wherein the pull-back electrode is integrated into the substrate as a highly-doped area.
The microelectromechanical system switch device of claim 2, further comprising pillar structures extending from the pull-back electrode to the pull-in electrode, wherein the pillar structures provide no electrical connection between electrodes.
The microelectromechanical system switch device of any one of claims 1 to 3, further comprising anti-sticking bumps disposed on a top surface or a bottom surface of the switching membrane.
The microelectromechanical system switch device of any one of claims 1 to 4, wherein the switching membrane is perforated.
The microelectromechanical system switch device of any one of claims 1 to 5, further comprising one or more of: - segmentation lines electrically isolating the metal contact from the switching membrane; - pillar structures extending from the substrate to the pull-in electrode, wherein the pillar structures provide no electrical connection between electrodes, - a sealed vacuum cavity between the pull-in electrode and the substrat, - a piezoelectric layer disposed on or below the switching membrane, wherein optionally the piezoelectric layer is configured to bend the switching membrane downwards to assist in opening the switch, or - a piezoelectric layer disposed on or below the pull-in electrode.
The microelectromechanical system switch device of any one of claims 1 to 6, wherein the metal contact is made of titanium tungsten.
A packaged microelectromechanical system switch product comprising: the microelectromechanical system switch device of any one of claims 1 to 7; and an integrated circuit coupled to the microelectromechanical system switch device, wherein the microelectromechanical system switch device and the integrated circuit are enclosed in a package.
The packaged microelectromechanical system switch product of claim 8, wherein the integrated circuit comprises a digital CMOS integrated circuit configured to provide control signals to the microelectromechanical system switch device.
The packaged microelectromechanical system switch product of claim 8 or 9, wherein the microelectromechanical system switch device and the integrated circuit are arranged side-by-side on a substrate, wherein optionally the substrate is a laminate or interposer.
The packaged microelectromechanical system switch product of any one of claims 8 to 10, wherein: - the microelectromechanical system switch device is stacked on the integrated circuit; and/or - the package is a chip scale package with solder balls.
A method of operating a microelectromechanical system switch device, comprising: applying a first voltage between a switching membrane and a pull-in electrode to move the switching membrane from an open position to a closed position, wherein in the closed position a metal contact on the switching membrane electrically connects two RF signal lines disposed on the pull-in electrode; and applying a second voltage between the switching membrane and a pull-back electrode to move a switch formed by the metal contact and the RF signal lines from the closed position to the open position.
The method of claim 12, further comprising applying a voltage to a piezoelectric layer disposed on the switching membrane or on the pull-in electrode to assist in moving the switch from the closed position to the open position.
The method of claim 12 or 13, wherein the switching membrane is perforated to reduce mass and increase switching speed.
The method of any one of claims 12 to 14, further comprising maintaining a sealed vacuum cavity between the pull-in electrode and a substrate to protect the switch from environmental contaminants, wherein optionally the sealed vacuum cavity is supported by pillar structures extending from the substrate to the pull-in electrode.

Description

TECHNICAL FIELD The present invention relates generally to electronic systems, and, in particular embodiments, to a microelectromechanical systems (MEMS) switch. BACKGROUND Radio frequency (RF) switches are common components in modern wireless communication systems, including smartphones, tablets, and other mobile devices. These switches enable the routing of RF signals between different components within a device, such as antennas, power amplifiers, and receivers. As wireless technologies continue to evolve and expand, there is an increasing demand for RF switches that can operate across a wide range of frequencies, handle higher power levels, and provide improved performance characteristics. Traditional RF switches have typically been implemented using semiconductor technologies, such as PIN diodes or field-effect transistors (FETs). While these solid-state switches have been widely used, they often face limitations in terms of insertion loss, isolation, and power handling capabilities, particularly at higher frequencies. In recent years, microelectromechanical systems (MEMS) technology has emerged as a promising alternative for implementing RF switches. MEMS-based RF switches offer several potential advantages over their solid-state counterparts, including lower insertion loss, higher isolation, and better linearity. These characteristics make MEMS switches particularly attractive for applications requiring high performance and low power consumption. However, the development and implementation of MEMS RF switches present several challenges. These include ensuring reliable and consistent switch operation over millions of cycles, managing issues related to stiction and wear of contact surfaces, and developing efficient manufacturing processes that can produce these devices at scale. Additionally, integrating MEMS switches into existing semiconductor manufacturing processes and packaging technologies poses further challenges that need to be addressed. As wireless devices continue to incorporate an increasing number of frequency bands and antennas, the need for compact, high-performance RF switching solutions becomes more critical. This drives the ongoing research and development efforts to create innovative MEMS switch designs that can meet the demanding requirements of next-generation wireless communication systems. SUMMARY According to some embodiments, a microelectromechanical system switch device as defined in claim 1, a packaged microelectromechanical system switch product as defined in claim 8 and a method as defined in claim 12 are provided. The dependent claims define further embodiments. The methods may be performed using the switch devices and switch products. In accordance with an embodiment, a microelectromechanical system (MEMS) switch device includes: a substrate; a switching membrane disposed above the substrate; a pull-in electrode disposed above the switching membrane; a metal contact disposed on the switching membrane; and a pull-back electrode disposed below the switching membrane, wherein the switching membrane is movable between an open position and a closed position, and wherein in the closed position, the metal contact electrically connects two RF signal lines. In accordance with another embodiment, a method of operating a microelectromechanical system (MEMS) switch device includes: applying a first voltage between a switching membrane and a pull-in electrode to move the switching membrane from an open position to a closed position, wherein in the closed position a metal contact on the switching membrane electrically connects two RF signal lines disposed on the pull-in electrode; and applying a second voltage between the switching membrane and a pull-back electrode to move a switch formed by the metal contact and the RF signal lines from the closed position to the open position. In accordance with another embodiment, a wafer-level encapsulated microelectromechanical system (MEMS) switch device includes: a substrate; a switching membrane disposed above the substrate; a pull-in electrode disposed above the switching membrane; a metal contact disposed on the switching membrane; a sealed cavity enclosing the switching membrane; and pillar structures extending from the substrate to support the pull-in electrode, wherein the switching membrane is movable between an open position and a closed position within the sealed cavity. In accordance with a further embodiment, a microelectromechanical system (MEMS) single pole double throw (SPDT) switch device includes: an upper pull-in electrode comprising a first electrical contact; a switching membrane disposed below the upper pull-in electrode and comprising a second electrical contact disposed on a first surface of the switching membrane facing the upper pull-in electrode, and a third electrical contact disposed on a second surface of the switching membrane opposite the first surface; and a lower pull-in electrode disposed below the switching mem