Integrated filter having ground plane structure
View Patent ↗In one embodiment, a filter structure includes first and second filter devices formed using a semiconductor substrate. A vertical ground plane structure prevents cross-coupling between the first and second filter devices.
1. A filter structure comprising:
a first filter device formed at least partially within a first conductivity type semiconductor substrate having a first major surface, wherein the first filter device provides a first channel of the filter structure;
a second filter device formed at least partially within the semiconductor substrate and spaced apart from the first filter device; wherein the second filter device provides a second channel of the filter structure; and
a first ground plane structure formed overlying the semiconductor substrate, wherein at least a portion of the first ground plane structure electrically contacts the semiconductor substrate, and wherein the first ground plane structure extends vertically above the semiconductor substrate, and is configured to reduce cross-channel coupling between the first and second channels when the filter structure is in operation.
2. The filter structure of claim 1 wherein the first ground plane structure is formed between the first and second filter devices, and wherein the filter structure further comprises a second ground plane structure surrounding the first and second filter devices, and wherein the second ground plane structure extends vertically above the semiconductor substrate to form a ground ring.
3. The filter structure of claim 2 wherein the first and second ground plane structures are electrically coupled together.
4. The filter structure of claim 2 , wherein the at least a portion of the second ground plane structure electrically contacts the semiconductor substrate.
5. The filter structure of claim 1 wherein the first ground plane structure electrically contacts the semiconductor substrate along the first ground plane structure's entire length.
6. The filter structure of claim 1 wherein the first ground plane structure comprises at least two layers of metal.
7. The filter structure of claim 6 wherein one of the two layers comprises copper and the other layer comprises a different metal.
8. The filter structure of claim 1 , wherein the first filter device comprises:
a first doped region of a second conductivity type opposite the first conductivity formed in the semiconductor substrate and extending from the first major surface, wherein the first doped region and the semiconductor substrate form a pn junction that provides both a first capacitance element for the filter structure and a transient voltage suppression element for the filter structure, and wherein the first capacitance element is other than a parasitic element;
a first conductive layer contacting a first portion of the first doped region;
a dielectric layer formed overlying a second portion of the first doped region, wherein the first doped region is continuous adjacent the dielectric layer; and
a second conductive layer formed overlying the dielectric layer, wherein the second conductive layer, the dielectric layer, and the first doped region form a second capacitive element for the filter structure, and wherein the first doped region has a dopant concentration that provides a substantially constant capacitance/voltage characteristic when a selected voltage range is applied between the second conductive layer and the first doped region.
9. The filter structure of claim 1 , wherein the semiconductor substrate has a first dopant concentration and a semiconductor layer of the first conductivity type formed overlying the semiconductor substrate, and wherein the semiconductor layer has a second dopant concentration less than the first dopant concentration, and wherein the first filter device comprises:
a first floating capacitor device formed adjacent the first major surface; and
a first transient voltage suppression device formed adjacent the first major surface, wherein the first floating capacitor device and the first transient voltage suppression device share a first doped region of a second conductivity type formed in the semiconductor layer, and wherein the first doped region terminates at the first major surface so that the first floating capacitor device overlies a portion of the semiconductor layer and a portion of the first doped region.
10. The filter structure of claim 8 , wherein the first filter device further comprises an inductor.
11. The filter structure of claim 10 wherein the inductor comprises a first multilayer inductor overlying at least a portion of the semiconductor substrate, the first multilayer inductor having a first terminal and a second terminal, the first multilayer inductor also having a first conductor overlying the portion of the semiconductor substrate, a second conductor overlying at least a portion of the first conductor, a first dielectric disposed between the first conductor and the second conductor.
12. The filter structure of claim 1 , wherein the semiconductor substrate has a first dopant concentration and a semiconductor layer of the first conductivity type formed overlying the semiconductor substrate, wherein the semiconductor layer has a second dopant concentration less than the first dopant concentration.
13. The filter structure of claim 12 further comprising a doped region of the first conductivity type formed in the semiconductor layer and having a higher dopant concentration than the semiconductor layer, wherein the doped region is further configured for improving contact between the first ground plane structure and the semiconductor substrate.
14. A filter structure including:
a semiconductor substrate of a first conductivity type having a first major surface;
a first filter device formed as part of the semiconductor substrate, the first filter device configured to provide a first channel of the filter structure and having first input and a first output;
a second filter devise formed as part of the semiconductor substrate, the second filter device configured to provide a second channel of the filter structure and having a second input and a second output; and
a first ground plane structure extending in a generally vertical direction from and above the first major surface and configured to reduce cross-channel coupling between the first and second channels when the filter structure is in operation, wherein the first ground plane structure laterally separates the first and second filter devices, and wherein at least a portion of the first ground plane structure is in contact with the semiconductor substrate.
15. The structure of claim 14 , wherein the first ground plane structure comprises at least two conductive layers.
16. The structure of claim 15 further comprising a second ground plane structure comprising a ground ring that surrounds both the first and second filter devices, and wherein the second ground plane structure extends in a generally vertical direction from and above the first major surface.
17. The structure of claim 16 , wherein at least a portion of the second ground plane structure contacts the semiconductor substrate.
18. The structure of claim 16 , wherein the second ground plane structure is isolated from the semiconductor substrate.
19. A filter structure comprising:
a semiconductor substrate having a first dopant concentration;
a semiconductor layer having a first conductivity type and a first major surface formed in spaced relationship with the semiconductor substrate, wherein the semiconductor layer has a second dopant concentration less than the first dopant concentration
a first filter device formed at least partially within the semiconductor layer, wherein the first filter device provides a first channel of the filter structure, and wherein the first filter device includes:
a first floating capacitor device formed adjacent the first major surface; and
a first transient voltage suppression device formed adjacent the first major surface wherein the first floating capacitor device and the first transient voltage suppression device share a first doped region of a second conductivity type opposite the first conductivity type formed in the semiconductor layer, and wherein the first doped region terminates at the first major surface so that the first floating capacitor device overlies a portion of the semiconductor layer and a portion of the first doped region;
a second filter device formed at least partially within the semiconductor layer and spaced apart from the first filter device; wherein the second filter device provides a second channel of the filter structure; and
a first ground plane structure formed overlying the semiconductor layer, wherein at least a portion of the first ground plane structure electrically contacts the semiconductor substrate, and wherein the first ground plane structure extends vertically above the semiconductor substrate, and is configured to reduce cross-channel coupling between the first and second channels when the filter structure is in operation.