Amplifier voltage limiting in radio-frequency devices
Disclosed herein are systems and method for voltage clamping in semiconductor circuits using through-silicon via (TSV) positioning. A semiconductor die is disclosed that includes a silicon substrate, a bipolar transistor having collector, emitter, base and sub-collector regions disposed on the substrate, and a through-silicon via (TSV) positioned within 35 μm of the sub-collector region in order to clamp a peak voltage of the bipolar transistor at a voltage limit level.
1. A radio-frequency device comprising:
a semiconductor substrate;
a bipolar transistor having collector, emitter, base and sub-collector regions disposed on the substrate;
an expitaxial layer of low-resistivity substrate formed at a top surface of the semiconductor substrate;
a through-silicon via positioned within 35 μm of the sub-collector region in order to clamp a peak voltage of the bipolar transistor at a voltage limit level;
a low-resistivity well implanted at the top surface of the semiconductor substrate; and
a high-resistivity implant region implanted at the top surface of the semiconductor substrate between the low-resistivity well and the through-silicon via.
2. The radio-frequency device of claim 1 wherein the through-silicon via is disposed a distance of between approximately 15-25 μm from the sub-collector region of the bipolar transistor.
3. The radio-frequency device of claim 1 wherein the through-silicon via is disposed a distance of approximately 20 μm from the sub-collector region of the bipolar transistor.
4. The radio-frequency device of claim 1 wherein the through-silicon via is disposed a distance of between approximately 10-15 μm from the sub-collector region of the bipolar transistor.
5. The radio-frequency device of claim 1 wherein the voltage limit level is between approximately 4-9 volts.
6. The radio-frequency device of claim 1 wherein the bipolar transistor is a bipolar transistor having a silicon or silicon-germanium alloy base.
7. The radio-frequency device of claim 1 wherein the semiconductor substrate has a resistivity greater than 50 Ohm*cm.
8. The radio-frequency device of claim 1 wherein the semiconductor substrate includes a high-resistivity portion and the bipolar transistor is disposed above the high-resistivity portion.
9. The radio-frequency device of claim 8 wherein the high-resistivity portion has a resistivity value greater than 500 Ohm*cm.
10. The radio-frequency device of claim 8 wherein the high-resistivity portion has a resistivity of at least approximately 1 kOhm*cm.
11. The radio-frequency device of claim 1 wherein the bipolar transistor is a component of a power amplifier.