Radio frequency transistor amplifiers and other multi-cell transistors having isolation structures
View Patent ↗A multi-cell transistor includes a semiconductor structure, a plurality of unit cell transistors that are electrically connected in parallel, each unit cell transistor extending in a first direction in the semiconductor structure, wherein the unit cell transistors are spaced apart from each other along a second direction, and an isolation structure that is positioned between a first group of the unit cell transistors and a second group of the unit cell transistors and that extends above the semiconductor structure.
1. A multi-cell transistor, comprising:
a semiconductor structure;
a plurality of unit cell transistors that are electrically connected in parallel, each unit cell transistor extending in a first direction in the semiconductor structure, wherein the unit cell transistors are spaced apart from each other along a second direction; and
an isolation structure that is positioned between a first group of the unit cell transistors and a second group of the unit cell transistors,
wherein the isolation structure comprises an isolation element that extends vertically between the first group of the unit cell transistors and the second group of the unit cell transistors and is configured to reduce a mutual coupling between the first group of the unit cell transistors and the second group of the unit cell transistors.
2. The multi-cell transistor of claim 1 , wherein the isolation structure is above the semiconductor structure.
3. The multi-cell transistor of claim 1 , wherein a first distance in the second direction between two adjacent unit cell transistors in the first group of the unit cell transistors is less than a second distance in the second direction between a first unit cell transistor that is at one end of the first group of the unit cell transistors and a second unit cell transistor that is in the second group of the unit cell transistors, where the second unit cell transistor is adjacent the first unit cell transistor.
4. The multi-cell transistor of claim 1 , wherein the isolation structure is electrically connected to a reference signal, and
wherein the isolation structure further comprises a metal pad, and
wherein the isolation element is electrically connected to the metal pad.
5. The multi-cell transistor of claim 4 , wherein the isolation structure comprises a plurality of vias that are disposed between the metal pad and the semiconductor structure.
6. The multi-cell transistor of claim 1 , wherein the isolation element comprises a conductive isolation material, a magnetic isolation material, or a lossy dielectric isolation material.
7. A multi-cell transistor, comprising:
a semiconductor structure;
a plurality of unit cell transistors that are electrically connected in parallel, each unit cell transistor extending in a first direction in the semiconductor structure, wherein the unit cell transistors are spaced apart from each other along a second direction;
an isolation structure that is positioned between a first group of the unit cell transistors and a second group of the unit cell transistors;
an input bond wire electrically connected to a gate of a first unit cell transistor of the plurality of unit cell transistors;
an output bond wire electrically connected to a drain of the first unit cell transistor; and
a secondary isolation material between the input bond wire and the output bond wire.
8. The multi-cell transistor of claim 7 , wherein the isolation structure further comprises a wall structure, and
wherein the secondary isolation material is electrically connected to the wall structure.
9. The multi-cell transistor of claim 1 , wherein the isolation element comprises a bond wire that is electrically connected to a metal pad of the isolation structure, and
wherein the multi-cell transistor further comprises an isolation material electrically connected to the bond wire.
10. A multi-cell transistor, comprising:
a semiconductor structure;
a plurality of unit cell transistors that are electrically connected in parallel, each unit cell transistor including a gate finger that extends in a first direction on a top surface of the semiconductor structure, the gate fingers spaced apart from each other along a second direction and arranged on the top surface of the semiconductor structure in a plurality of groups; and
an isolation structure on the top surface of the semiconductor structure between a first group and a second group of the plurality of groups,
wherein the isolation structure is electrically connected to a ground signal.
11. The multi-cell transistor of claim 10 , wherein each isolation structure further includes a plurality of vias that physically and electrically connect each respective metal pad to a source region in the semiconductor structure.
12. The multi-cell transistor of claim 10 , wherein each respective isolation structure comprises a metal pad and a wall structure extending vertically from the metal pad.
13. The multi-cell transistor of claim 12 , wherein the wall structure comprises a plurality of wall segments extending vertically from the metal pad.
14. The multi-cell transistor of claim 10 , wherein each unit cell transistor comprises a drain finger that extends in the first direction on the top surface of the semiconductor structure, and
wherein the multi-cell transistor further comprises:
an input bond wire electrically connected to at least one of the gate fingers;
an output bond wire electrically connected to at least one of the drain fingers; and
a secondary isolation material extending in the second direction between the input bond wire and the output bond wire.
15. A transistor device, comprising:
a multi-cell transistor, comprising:
a plurality of unit cell transistors that are electrically connected in parallel and that are spaced apart along a second direction; and
a first isolation structure that is positioned between a first group of the unit cell transistors and a second group of the unit cell transistors and extends in a first direction;
an input bond wire electrically connected to a gate of a first unit cell transistor of the plurality of unit cell transistors;
an output bond wire electrically connected to a drain of the first unit cell transistor; and
a second isolation structure extending in the second direction between the input bond wire and the output bond wire.
16. The transistor device of claim 15 , further comprising a plurality of vias that that electrically connect a metal pad of the first isolation structure to at least one source region of the unit cell transistors.
17. The transistor device of claim 15 , wherein the first isolation structure comprises:
a metal pad that is electrically connected to a reference signal; and
a wall structure that is electrically connected to metal pad,
wherein the second isolation structure is electrically connected to the wall structure.
18. The transistor device of claim 17 , wherein the wall structure comprises a plurality of wall segments extending vertically from the metal pad.
19. The transistor device of claim 17 , wherein the wall structure comprises an isolation material configured to reduce a mutual coupling between the first group of the unit cell transistors and the second group of the unit cell transistors.