Bipolar transistor on high-resistivity substrate
Systems and methods are disclosed for processing radio frequency (RF) signals using one or more bipolar transistors disposed on or above a high-resistivity region of a substrate. The substrate may include, for example, bulk silicon, at least a portion of which has high-resistivity characteristics. For example, the bulk substrate may have a resistivity greater than 500 Ohm*cm, such as around 1 kOhm*cm. In certain embodiments, one or more of the bipolar devices are surrounded by a low-resistivity implant configured to reduce effects of harmonic and other interference.
1. A semiconductor die comprising:
a plurality of elements of a front-end module integrated on the semiconductor die, the plurality of elements including a power amplifier, a switch, and a plurality of filters;
a bulk silicon substrate having a high-resistivity portion;
a silicon-germanium bipolar transistor disposed on the bulk silicon substrate above the high-resistivity portion of the bulk silicon substrate, the silicon-germanium bipolar transistor configured as the power amplifier, the bulk silicon substrate including a low-resistivity well at least partially surrounding the silicon-germanium bipolar transistor, the bulk silicon substrate further including a trench disposed adjacent to the low-resistivity well;
a complementary metal oxide semiconductor field-effect transistor device grown on the bulk silicon substrate; and
one or more capacitors disposed on the high-resistivity portion.
2. The semiconductor die of claim 1 wherein the silicon-germanium bipolar transistor conditions or creates electronic signals.
3. The semiconductor die of claim 1 wherein the silicon substrate includes a low-resistivity epitaxial layer adjacent to a first portion of a top surface of the substrate at least partially above the high-resistivity portion.
4. The semiconductor die of claim 3 wherein the low-resistivity epitaxial layer includes material from an implanted sub-collector region of the silicon-germanium bipolar transistor that has out-diffused during processing of the silicon-germanium bipolar transistor.
5. The semiconductor die of claim 3 wherein at least a second portion of the top surface of the substrate includes a high-resistivity crystal-lattice-destroying implant.
6. The semiconductor die of claim 5 wherein the second portion of the top surface of the substrate is greater than 1 μm from the silicon-germanium bipolar transistor.
7. The semiconductor die of claim 5 further comprising a passive device disposed above the high-resistivity crystal-lattice-destroying implant.
8. The semiconductor die of claim 1 wherein the bulk silicon substrate includes a counter-doped high-resistivity region.
9. The semiconductor die of claim 1 further comprising an active device and a passive device disposed on the substrate wherein the low-resistivity well is disposed at least partially between the silicon-germanium bipolar transistor device and both the active device and the passive device.
10. The semiconductor die of claim 1 wherein the high-resistivity portion has a resistivity value greater than 500 Ohm*cm.
11. The semiconductor die of claim 1 wherein the high-resistivity portion has a resistivity of approximately 1 kOhm*cm.
12. A radio-frequency module comprising:
a packaging substrate configured to receive a plurality of components;
a die mounted on the packaging substrate, the die having a plurality of elements of a front-end module integrated on the die, the plurality of elements including a power amplifier, a switch, and a plurality of filters, the die further having a high-resistivity substrate portion and one or more passive devices, the power amplifier including a silicon-germanium bipolar transistor disposed above the high resistivity substrate portion, the die including a low-resistivity well at least partially surrounding the silicon-germanium bipolar transistor, the die further including a trench disposed adjacent to the low-resistivity well, a complementary metal oxide semiconductor field-effect transistor device grown on the packaging substrate, and one or more capacitors disposed on the high-resistivity substrate portion; and
a plurality of connectors configured to provide electrical connections between the die and the packaging substrate.
13. The semiconductor die of claim 1 wherein the power amplifier is a dual band power amplifier that includes a low-band power amplifier and a high-band power amplifier.
14. The radio-frequency module of claim 12 wherein the high-resistivity substrate portion includes a low-resistivity epitaxial layer formed adjacent to a first portion of a top surface of the high-resistivity substrate portion at least partially above the high-resistivity portion.
15. The radio-frequency module of claim 14 wherein the low-resistivity epitaxial layer includes material from an implanted sub-collector region of the silicon-germanium bipolar transistor that has out-diffused during a device manufacturing process for the silicon-germanium bipolar transistor.
16. The radio-frequency module of claim 14 wherein the high-resistivity substrate portion includes a low-resistivity well at least partially surrounding the silicon-germanium bipolar transistor.
17. The semiconductor die of claim 8 further comprising a passive device disposed above the counter-doped high-resistivity region.