Other

Julia Qiu

Cindy Xing Qiu

Yi-Chi Shih

Chunong Qiu

Ishiang Shih

Andy Shih

Lu Han

Kuang-Yu Yang

The present invention provides tunable film bulk acoustic resonators (FBARs) with the resonant frequency of the acoustic wave to be excited and to be transmitted tuned by digital to analog converters which convert an input digital signal to an output DC voltage and provide DC bias voltages to the FBARs through integrated thin film biasing resistors. The polarity and the value of the output DC voltage are controlled by the input digital signal to achieve selection and tuning of the resonant frequency of the FBARs. A plurality of the tunable FBARs are connected to form microwave filters with tunable bandpass frequencies and oscillators with selectable resonating frequencies by varying the input digital signals applied to the digital to analog converters.

Tunable film bulk acoustic resonators and FBAR filters with digital to analog converters

Due to strong needs to reduce the dimensions and the cost of the RF filters and to reduce the number of filters required in an mobile handsets and wireless system covering numbers of operation bands, tunable RF filters which can cover as many bands or frequency ranges as possible are needed so that the number of filters can be reduced in the mobile handsets and wireless systems. The present invention provides tunable surface acoustic wave (SAW) IDT structures with the resonant frequency of the acoustic wave to be excited and to be transmitted tuned by digital to analog converters (DACs). The DAC converts an input digital signal to an output DC voltage and provide DC bias voltages to the SAW IDTs through integrated thin film biasing resistors. The polarity and the value of the output DC voltage are controlled by the input digital signal to achieve selection and tuning of the resonant frequency of the SAW IDTs.

Tunable surface acoustic wave resonators and SAW filters with digital to analog converters

Structures of high electron mobility thin film transistors (HEM-TFTs) are provided in this invention. In one embodiment, HEM-TFTs with a single heterojunction structure are disclosed to have a substrate, a first metal oxide channel layer, a first spacer layer, a first doped layer, a first barrier layer, a source, a drain and a gate. In another embodiment, HEM-TFTs with a double heterojunction structure are provided to have a substrate, a second barrier layer, a second doped layer, a second spacer layer, a first metal oxide channel layer, a second spacer layer, a second doped layer, a second barrier layer, a source, a drain and a gate. In yet another embodiment, HEM-TFTs with a single heterojunction structure are disclosed to comprise a substrate, a first metal oxynitride channel layer, a first spacer layer, a first doped layer, a first barrier layer, a source, a drain and a gate. In still another embodiment, HEM-TFTs with a double heterojunction structure are provided to include a substrate, a first barrier layer, a first doped layer, a first spacer layer, a first metal oxynitride channel layer, a second spacer layer, a second doped layer, a second barrier layer, a source, a drain and a gate.

High electron mobility thin film transistors

In wireless communications, many radio frequency bands are used. For each frequency band, there are two frequencies, one for transmitting and the other for receiving. As the band widths are small and separation between adjacent bands is also small, many band pass filters with different band pass frequencies are required for each communication unit such as mobile handset. The invention provides tunable film bulk acoustic resonators TFBARs containing semiconducting piezoelectric layers and methods for tuning and adjusting the resonant properties. When a DC biasing voltage is varied, both the depletion region thickness and neutral region thickness associated in the semiconducting piezoelectric layers varies leading to changes in equivalent capacitances, inductance and resistances and hence the resonance properties and frequencies. A plurality of the present TFBARs are connected into a tunable oscillator or a tunable and selectable microwave filter for selecting and adjusting of the bandpass frequency by varying the biasing voltages.

Tunable film bulk acoustic resonators and filters

In wireless communications, many radio frequency bands are used. For each frequency band, there are two frequencies one for transmit and the other for receive. As the band widths are small and separation between adjacent bands is also small, many band pass filters with different band pass frequencies are required for each communication unit such as mobile handset. The present invention provides frequency tunable film bulk acoustic resonators (FBAR) with different structures. Thin film biasing resistors are integrated into the FBAR structure for DC biasing and RF isolation. A plurality of the present tunable FBARs are connected to form microwave filters with tunable bandpass frequencies and oscillators with selectable resonating frequencies by varying DC biasing voltages to the resonators.

Tunable film bulk acoustic resonators and filters with integrated biasing resistors

Due to strong needs to reduce the dimensions and the cost of the RF filters and to reduce the number of filters required in an mobile handsets and wireless system covering numbers of operation bands, tunable RF filters which can cover as many bands or frequency ranges as possible are needed so that the number of filters can be reduced in the mobile handsets and wireless systems. This invention provides tunable surface acoustic wave resonators and filters utilizing semiconducting piezoelectric layers having embedded or elevated electrode doped regions. Both metallization ratio and loading mass are changed by varying a DC biasing voltage to effect a change in the resonant frequency of the tunable SAW devices.

Tunable surface acoustic wave resonators and filters

A process for forming a T-gate with enhanced mechanical strength and a reduced gate length for high electron mobility transistors is provided. The process includes the steps of forming a stem portion cavity with rounded top edges to enhance the mechanical strength, creating an insoluble diffused feature shrinking layer to reduce the gate length, carrying out a thermal flow process to further reduce the gate length, and forming a head portion cavity with negative side wall slopes to facilitate lift-off of gate metal layers.

Process for forming gate of thin film transistor devices

Metal oxynitride diodes having at least a first metal oxynitride layer of a first conduction type and a second metal oxynitride layer of a second conduction type are provided. The first oxynitride layer is selectively doped or un-intentionally doped and have high carrier mobility. The second oxynitride layer is also selectively doped or un-intentionally doped and have high carrier mobility. A compensated oxynitride drift layer having a low carrier density may be adopted to increase the breakdown voltage of the device.

Metal oxynitride diode devices

In one embodiment of the invention, a high electron mobility thin film transistor with a plurality of gate insulating layers and a metal oxynitride active channel layer is provided for forming a backplane circuit for pixel switching in an electronic display, to reduce unwanted ON state series resistance in the metal oxynitride active channel layer and minimize unwanted power dissipation in the backplane circuit. Another embodiment of the invention provides a high electron mobility thin film transistor structure with a plurality of metal oxynitride active channel layers and a gate insulating layer for forming a backplane circuit for pixel switching in an electronic display, to reduce unwanted ON state series resistance in the metal oxynitride active channel layer and to minimize unwanted power dissipation in the backplane circuit. In yet another embodiment of the invention a high electron mobility thin film transistor structure with a plurality of gate insulating layers and a plurality of metal oxynitride active channel layers for forming a backplane circuit for pixel switching in an electronic display, to reduce unwanted ON state series resistance in the metal oxynitride active channel layers and to minimize unwanted power dissipation in the backplane circuit.

Thin film transistors with metal oxynitride active channels for electronic displays

In high frequency circuits, the switching speed of devices is often limited by the series resistance and capacitance across the input terminals. To reduce the resistance and capacitance, the cross-section of input electrodes is made into a T-shape or inverted L-shape through lithography. The prior art method for the formation of cavities for T-gate or inverted L-gate is achieved through several steps using multiple photomasks. Often, two or even three different photoresists with different sensitivity are required. In one embodiment of the present invention, an optical lithography method for the formation of T-gate or inverted L-gate structures using only one photomask is disclosed. In another embodiment, the structure for the T-gate or inverted L-gate is formed using the same type of photoresist material.

Fabrication methods for T-gate and inverted L-gate structure for high frequency devices and circuits

The prior art method for the formation of T-gate or inverted L-gate is achieved through several lift-off processes and requires at least two different photoresists and hence two different developers. In one embodiment of the present invention, an etching method for the formation of the source, the drain and the T-gate or inverted L-gate of a compound semiconductor HEMT device is disclosed. In such a method, only one type of photoresist and developer are needed. In one other embodiment, a fabrication process for a HEMT device is disclosed to have the stem of the T-gate or the inverted L-gate defined by a dielectric cavity and its mechanical strength enhanced by a dielectric layer. In another embodiment, a fabrication process for a HEMT device is disclosed to have the stems of the source and the drain defined by dielectric cavities and their mechanical strength enhanced by a dielectric layer. In yet another embodiment, a fabrication process for a HEMT device is revealed to have the stems of the source, the drain and the T-gate or inverted L-gate of a compound semiconductor HEMT strengthened by dielectric supporting pillars.

Growing community of inventors

Brossard, Canada

Julia Qiu