Semiconductor device with isolation and/or protection structures

1. A packaged Doherty amplifier comprising:

a substrate of a semiconductor device enclosed in a package;

a main transistor formed on the substrate; a first edge seal structure formed on the substrate and completely surrounding the main transistor;

a peaking transistor formed on the substrate;

a second edge seal structure formed on the substrate and completely surrounding the peaking transistor; and

wherein the first and second edge seal structures are configured to protect the respective transistors from chips or cracks, formed during a singulation process, from propagating into the active area of the transistors;

wherein the main and peaking transistors are monolithically integrated and the substrate containing both transistors and the first and second edge seal structures are packaged into the amplifier; and

wherein the first and second edge seal structures each comprise at least a first metal layer formed continuously on a front side of the substrate, a second metal layer formed on the first metal layer intermittently along its length, and a plurality of through vias connecting the first metal layer to a grounded conductor on a back side of the substrate.

2. The packaged Doherty amplifier of claim 1 , further comprising on-die wire bonds on the substrate between the first and second edge seal structures.

3. The packaged Doherty amplifier of claim 1 , further comprising:

a third transistor formed on the substrate; and a third edge seal structure formed on the substrate and completely surrounding the third transistor;

wherein the third transistor is monolithically integrated with the first and second transistors and the substrate containing the main, peaking, and third transistors and first, second, and third edge seal structures is packaged into the amplifier;

wherein the third edge seal structure is configured to protect the third transistor from chips or cracks formed during a singulation process from propagating into the active area of the transistor; and

wherein the third edge seal structure comprises at least a first metal layer formed on a front side of the substrate, a second metal layer formed on the first metal layer intermittently along its length, and a plurality of through vias connecting the first metal layer to a grounded conductor on a back side of the substrate.

4. The packaged Doherty amplifier of claim 1 , wherein the main and peaking transistors are GaN-based High Electron Mobility Transistors (“HEMT”).

5. The packaged Doherty amplifier of claim 1 , wherein the first and second transistors are laterally diffused metal oxide semiconductor (“LDMOS”) transistors.

6. The packaged Doherty amplifier of claim 1 , wherein the amplifier operates at a frequency between 0.5 GHz and 1 GHz.

7. The packaged Doherty amplifier of claim 1 , wherein the amplifier operates at a frequency of approximately 3 GHz.

8. The packaged Doherty amplifier of claim 1 , wherein the amplifier operates at a frequency of approximately 10 GHz.

9. The packaged Doherty amplifier of claim 1 , wherein the amplifier operates at a frequency between 12 GHz and 18 GHz.

10. The packaged Doherty amplifier of claim 1 , wherein the amplifier operates at a frequency between 18 GHz and 27 GHz.

11. The packaged Doherty amplifier of claim 1 , wherein the amplifier operates at a frequency between 27 GHz and 40 GHz.

12. The packaged Doherty amplifier of claim 1 , further comprising an isolation structure formed on the substrate between the first and second edge seal structures.

13. The packaged Doherty amplifier of claim 12 , wherein the isolation structure is a recessed isolation structure.

14. The packaged Doherty amplifier of claim 13 , wherein the recessed isolation structure comprises at least two rows of recesses in the substrate.

15. The packaged Doherty amplifier of claim 14 , wherein the rows are staggered.

16. The packaged Doherty amplifier of claim 13 , wherein the recessed isolation structure is formed on one or both of the front side of the substrate and the back side of the substrate.

17. The packaged Doherty amplifier of claim 13 , further comprising a metal layer on one or both of the front side of the substrate and the back side of the substrate.

18. The packaged Doherty amplifier of claim 12 , wherein the isolation structure comprises a metal isolation structure and a recessed isolation structure.

19. The packaged Doherty amplifier of claim 12 , wherein the isolation structure comprises at least a first metal layer formed on a front side of the substrate and a plurality of through vias connecting the metal layer to a grounded conductor on a back side of the substrate.

20. The packaged Doherty amplifier of claim 19 , wherein the first metal layer of the isolation structure comprises a first row generally transverse to an axis between the main and peaking transistors.

21. The packaged Doherty amplifier of claim 20 , wherein the isolation structure further comprises a second row formed on front side of the substrate.

22. The packaged Doherty amplifier of claim 21 , wherein the through vias of the first and second rows are staggered.

23. The packaged Doherty amplifier of claim 20 , wherein the isolation structure covers a portion of the width of the substrate.

24. The packaged Doherty amplifier of claim 20 , wherein the isolation structure covers the width of the substrate.

25. The packaged Doherty amplifier of claim 19 , wherein the isolation structure further comprises on-die wire bonds.

26. The packaged Doherty amplifier of claim 1 , wherein the second metal layer is formed on the first metal layer in a serpentine pattern.