Radio frequency isolation cavity formation using sacrificial material

Patent metadata

Field	Value
Publication number	US-2016336990-A1
Application number	US-201615154646-A
Country	US
Kind code	A1
Filing date	May 13, 2016
Priority date	May 15, 2015
Publication date	Nov 17, 2016
Grant date	—

Abstract

Fabrication of radio-frequency (RF) devices involves providing a field-effect transistor (FET), forming one or more electrical connections to the FET, forming one or more dielectric layers over at least a portion of the electrical connections, and disposing an electrical element over the one or more dielectric layers, the electrical element being in electrical communication with the FET via the one or more electrical connections. RF device fabrication further involves covering at least a portion of the electrical element with a sacrificial material, applying an interface material over the one or more dielectric layers, the interface material at least partially covering the sacrificial material, and removing at least a portion of the sacrificial material to form a cavity at least partially covered by the interface layer.

First claim

1 . A method for fabricating a radio-frequency (RF) device, the method comprising:
providing a field-effect transistor (FET); forming one or more electrical connections to the FET; forming one or more dielectric layers over at least a portion of the electrical connections; disposing an electrical element over the one or more dielectric layers, the electrical element being in electrical communication with the FET via the one or more electrical connections; covering at least a portion of the electrical element with a sacrificial material; applying an interface material over the one or more dielectric layers, the interface material at least partially covering the sacrificial material; and removing at least a portion of the sacrificial material to form a cavity at least partially covered by the interface layer.

2 . The method of claim 1 wherein the electrical element is a surface acoustic wave (SAW) device.

3 . The method of claim 1 wherein the electrical element is a bulk acoustic wave (BAW) device.

4 . The method of claim 1 further comprising applying a handle wafer to a top surface of the interface layer to provide mechanical stability for the RF device.

5 . The method of claim 1 wherein the FET is formed over an oxide layer formed on a semiconductor substrate.

6 . The method of claim 5 further comprising at least partially removing the semiconductor substrate thereby exposing at least a portion of a backside of the oxide layer.

7 . The method of claim 6 further comprising disposing an electrical contact structure on the backside of the oxide layer to provide electrical contact to the one or more electrical connections via a through-oxide via.

8 . The method of claim 1 wherein said covering the at least a portion of the electrical element with the sacrificial material involves forming a channel of the sacrificial material leading to a die boundary associated with the RF device.

9 . The method of claim 8 wherein said removing the at least a portion of the sacrificial material is performed at least partially through the channel.

10 . The method of claim 1 wherein said removing the at least a portion of the sacrificial material involves evaporating the at least a portion of the sacrificial material.

11 . A radio-frequency (RF) device comprising:
a field-effect transistor (FET) implemented over an oxide layer; one or more electrical connections to the FET; one or more dielectric layers formed over at least a portion of the electrical connections; an electrical element disposed over the one or more dielectric layers, the electrical element being in electrical communication with the FET via the one or more electrical connections; a patterned form of sacrificial material covering at least a portion of the electrical element; and an interface layer covering at least a portion of the one or more dielectric layers and the sacrificial material.

12 . The RF device of claim 11 wherein the electrical element is a surface acoustic wave (SAW) device.

13 . The RF device of claim 11 wherein the electrical element is a bulk acoustic wave (BAW) device.

14 . The RF device of claim 11 further comprising a handle wafer applied to a top surface of the interface layer, the handle wafer providing mechanical stability for the RF device.

15 . The RF device of claim 11 wherein the FET is formed over an oxide layer.

16 . The RF device of claim 15 further comprising an electrical contact structure disposed on a backside of the oxide layer that provides electrical contact to the one or more electrical connections via a through-oxide via through the oxide layer.

17 . The RF device of claim 11 wherein the patterned form of sacrificial material includes a channel leading to a die boundary associated with the RF device.

18 . The RF device of claim 17 wherein the channel is designed such that the at least a portion of the sacrificial material may be removed at least partially through the channel.

19 . The RF device of claim 11 wherein the sacrificial material is configured to be evaporated to form a cavity.

20 . A wireless device comprising:
a transceiver configured to process radio-frequency (RF) signals; an RF module in communication with the transceiver, the RF module including a switching device having a field-effect transistor (FET) implemented over an oxide layer, the switching device further including one or more electrical connections to the FET, one or more dielectric layers formed over at least a portion of the electrical connections, an electrical element disposed over the one or more dielectric layers that is electrically coupled to the FET via the one or more electrical connections, a patterned form of sacrificial material covering at least a portion of the electrical element, and an interface layer covering at least a portion of the one or more dielectric layers and the sacrificial material; and an antenna in communication with the RF module, the antenna configured to facilitate transmitting and/or receiving of the RF signals.

Assignees

• Skyworks Solutions Inc

Inventors

• Petzold David T
• Whitefield David Scott

Classifications

• H10W20/0245

  comprising use of blind vias during the manufacture · CPC title

• H10W20/218

  in silicon-on-insulator [SOI] wafers · CPC title

• H10W70/63

  Vias, e.g. via plugs · CPC title

• H10W72/0198

  batch processes · CPC title

• H10W72/884

  Die-attach connectors and bond wires · CPC title