Radio frequency interference mitigation for silicon-on-insulator devices
Disclosed is a silicon on insulator (SOI) radio frequency (RF) module with noise reduction shielding to mitigate radio frequency interference (RFI) between active circuit devices within the module. The RF module includes various semiconductor active devices disposed upon an insulating substrate. The RF module can be a front-end module (FEM) with one or more charge pumps as active devices. A polysilicon web extends between and underneath the devices to create a network of ground paths across a surface of the insulating substrate. The ground paths effectively conduct RF noise to a circuit ground, causing the polysilicon ground web to eliminate or substantially attenuate RFI produced by the active devices without altering signal characteristics of the RF module. The disclosed solution also reduces RF noise leakage into the substrate, and can reduce RFI between neighboring RF modules.
1 . A radio frequency module comprising:
a semiconductor die including a silicon substrate, a polysilicon layer, and a plurality of metal layers above the polysilicon layer;
a first active device formed in the semiconductor die and a second active device formed in the semiconductor die; and
a polysilicon ground web formed within the polysilicon layer and connected from the polysilicon layer to a circuit ground via a path formed from the polysilicon layer through silicon substrate, the polysilicon ground web extending around at least a portion of a periphery of the first active device, at least a portion of a periphery of the second active device, and between the first active device and the second active device.
2 . The radio frequency module of claim 1 wherein the first active device includes a transistor and the second active device does not include a transistor.
3 . The radio frequency module of claim 2 wherein the first active device includes a metal oxide semiconductor silicon-on-insulator transistor.
4 . The radio frequency module of claim 2 wherein the second active device is a metal-insulator-metal (MIM) capacitor.
5 . The radio frequency module of claim 2 wherein the polysilicon ground web extends beneath the second active device and does not extend beneath the first active device.
6 . The radio frequency module of claim 2 wherein the radio frequency module is a radio frequency front-end module including one or more power amplifiers and one or more charge pumps.
7 . The radio frequency module of claim 1 further comprising a through wafer via extending from the polysilicon layer through the silicon substrate to form the path to the circuit ground.
8 . A semiconductor die comprising:
a silicon substrate, a polysilicon layer, and a plurality of metal layers above the polysilicon layer;
a first active device and a second active device; and
a polysilicon ground web formed within the polysilicon layer and connected from the polysilicon layer to a circuit ground via a path formed from the polysilicon layer through silicon substrate, the polysilicon ground web extending around at least a portion of a periphery of the first active device, at least a portion of a periphery of the second active device, and between the first active device and the second active device.
9 . The semiconductor die of claim 8 wherein the first active device includes a transistor and the second active device does not include a transistor.
10 . The semiconductor die of claim 9 wherein the first active device includes a metal oxide semiconductor silicon-on-insulator transistor.
11 . The semiconductor die of claim 9 wherein the second active device is a metal-insulator-metal (MIM) capacitor.
12 . The semiconductor die of claim 9 wherein the polysilicon ground web extends beneath the second active device and does not extend beneath the first active device.
13 . The semiconductor die of claim 9 wherein the semiconductor die is a component of a radio frequency front-end module including one or more power amplifiers and one or more charge pumps.
14 . The semiconductor die of claim 8 further comprising a through wafer via extending from the polysilicon layer through the silicon substrate to form the path to the circuit ground.
15 . A mobile device comprising:
a radio frequency module including a semiconductor die including a silicon substrate, a polysilicon layer, and a plurality of metal layers above the polysilicon layer; a first active device formed in the semiconductor die and a second active device formed in the semiconductor die; and a polysilicon ground web formed within the polysilicon layer and connected from the polysilicon layer to a circuit ground via a path formed from the polysilicon layer through silicon substrate, the polysilicon ground web extending around at least a portion of a periphery of the first active device, at least a portion of a periphery of the second active device, and between the first active device and the second active device; and
an antenna coupled to the radio frequency module.
16 . The mobile device of claim 15 wherein the first active device includes a transistor and the second active device does not include a transistor.
17 . The mobile device of claim 16 wherein the second active device is a metal-insulator-metal (MIM) capacitor.
18 . The mobile device of claim 16 wherein the polysilicon ground web extends beneath the second active device and does not extend beneath the first active device.
19 . The mobile device of claim 16 wherein the radio frequency module is a radio frequency front-end module including one or more power amplifiers and one or more charge pumps.
20 . The mobile device of claim 15 further comprising a through wafer via extending from the polysilicon layer through the silicon substrate to form the path to the circuit ground.