Devices and methods for layout-dependent voltage handling improvement in switch stacks
Devices and methods for layout-dependent voltage handling improvement in switch stacks. In some embodiments, a switching device can include a first terminal and a second terminal, a radio-frequency signal path implemented between the first terminal and the second terminal, and a plurality of switching elements connected in series to form a stack between the second terminal and ground. The stack can have an orientation relative to the radio-frequency signal path, and the switching elements can have a non-uniform distribution of a first parameter based in part on the orientation of the stack.
1. A radio-frequency switching module comprising:
a packaging substrate configured to receive a plurality of components; and
a die mounted on the packaging substrate, the die having a switching circuit that includes a plurality of switching elements in series to form a signal branch between a first terminal and a second terminal, and a plurality of switching elements in series to form a shunt branch between the second terminal and ground, the shunt branch having an orientation relative to the signal branch, the switching elements of the shunt branch having a non-uniform distribution of a first parameter determined based in part on the orientation of the shunt branch relative to the signal branch, the non-uniform distribution determined to decrease toward the second terminal based on the orientation of the shunt branch being 180° relative to the signal branch and determined to increase toward the second terminal based on the orientation of the shunt branch being 0° or 90° relative to the signal branch, the second terminal dimensioned to support the signal branch and the shunt branch.
2. The radio-frequency switching module of claim 1 wherein a first orientation of the shunt branch corresponds to a first non-uniform distribution of the first parameter.
3. The radio-frequency switching module of claim 2 wherein the first orientation of the shunt branch includes placement of the shunt branch at 180° relative to the placement of the signal branch.
4. The radio-frequency switching module of claim 2 wherein a second orientation of the shunt branch corresponds to a second non-uniform distribution of the first parameter.
5. The radio-frequency switching module of claim 4 wherein the second orientation of the shunt branch includes placement of the shunt branch at 0° or 90° relative to the placement of the signal branch.
6. The radio-frequency switching module of claim 1 wherein each of the plurality of switching elements of the shunt branch includes a field-effect transistor having a source, a drain, and a gate formed on an active region.
7. The radio-frequency switching module of claim 6 wherein the field-effect transistor is implemented as a finger configuration device such that the gate includes a number of rectangular shaped gate fingers, each gate finger implemented between a rectangular shaped source finger of the source contact and a rectangular shaped drain finger of the drain contact.
8. The radio-frequency switching module of claim 6 wherein the first parameter is of a set of one or more of a physical characteristic, an electrical characteristic, a chemical characteristic, and a mechanical characteristic of each field- effect transistor.
9. The radio-frequency switching module of claim 8 wherein the first parameter includes a length of the gate of each field-effect transistor.
10. The radio-frequency switching module of claim 9 wherein the non-uniform distribution of the gate length is further based in part on a non-uniform distribution of a second parameter associated with the field-effect transistors.
11. The radio-frequency switching module of claim 10 wherein the second parameter includes a distribution of voltage VDS across each field-effect transistor.
12. The radio-frequency switching module of claim 11 wherein the non-uniform distribution of the gate length is selected to yield a scaled version of the voltage VDS distribution.
13. The radio-frequency switching module of claim 12 wherein the scaled version of the voltage VDS distribution is based on scaling of the highest value of a voltage VDS distribution corresponding to a substantially uniform distribution of the gate length.
14. The radio-frequency switching module of claim 9 wherein a gate length of at least a first field-effect transistor of the shunt branch having a first orientation is less than a value of a uniform distribution of gate length of field-effect transistors of a corresponding shunt branch, and a gate length of at least the first field-effect transistor of the shunt branch having a second orientation is greater than the value of the uniform distribution of the gate length.
15. The radio-frequency switching module of claim 14 wherein at least some of the field-effect transistors of the shunt branch having the first orientation have gate lengths that are less than the value of the uniform distribution of the gate length and at least some of the field-effect transistors of the shunt branch having the second orientation have gate lengths that are less than the value of the uniform distribution of the gate length.
16. The radio-frequency switching module of claim 15 wherein the sum of the VDS values of the field-effect transistors for the non-uniform distribution of the gate length is greater than the sum of the VDS values of the field-effect transistors for the uniform distribution of the gate length.
17. The radio-frequency switching module of claim 15 wherein the sum of the gate lengths of the field-effect transistors for the non-uniform distribution of the gate length is greater than the sum of the gate length of the field-effect transistors for the uniform distribution of the gate length.
18. The radio-frequency switching module of claim 9 wherein the non-uniform distribution of the gate length includes a plurality of groups of gate length values, each group having a common value of the gate length.
19. The radio-frequency switching module of claim 1 wherein the non-uniform distribution of the first parameter is further based in part on the distance of the shunt branch from the signal branch.
20. A method for fabricating a radio-frequency switching device, the method comprising:
providing a semiconductor substrate;
forming a plurality of switching elements on the semiconductor substrate in series to form a signal branch between a first terminal and a second terminal, and a plurality of switching elements in series to form a shunt branch between the second terminal and ground, the shunt branch having an orientation relative to the signal branch, the switching elements of the shunt branch having a non-uniform distribution of a first parameter based at least in part on the orientation of the shunt branch relative to the signal branch, the non-uniform distribution determined to decrease toward the second terminal based on the orientation of the shunt branch being 180° relative to the signal branch and determined to increase toward the second terminal based on the orientation of the shunt branch being 0° or 90° relative to the signal branch; and
connecting the switching elements to form the shunt branch such that the non-uniform distribution of the shunt branch results in the shunt branch having a first voltage handling capacity that is greater than a second voltage handling capacity corresponding to a similar shunt branch having a substantially uniform distribution of the first parameter.