ESD Protection Diode in RF pads

1 . A diode, comprising:

first and second diffusion layers formed in a substrate;

a first metal coupled to the first diffusion layer; and

a second metal coupled to the second diffusion layer that has width that is smaller than a width of the second diffusion layer.

2 . The diode of claim 1 , wherein the first diffusion layer is a n-type or a p-type diffusion layer.

3 . The diode of claim 1 , wherein the second diffusion layer is a n-type or a p-type diffusion layer.

4 . The diode of claim 1 , further comprising:

a first plurality of contacts coupled to the first diffusion layer and the first metal; and

a second plurality of contacts coupled to the second diffusion layer and the second metal.

5 . The diode of claim 1 , further comprising:

a third diffusion layer, wherein the third diffusion layer is adjacent to the second diffusion layer and wherein the third diffusion layer and the first diffusion layer are of the same type.

6 . The diode of claim 1 , wherein the diode comprises:

a first plurality of diffusion layers including the first diffusion layer;

a second plurality of diffusion layers including the second diffusion layer;

a first plurality of metals including the first metal, each metal of the first plurality of metals being coupled to a respective diffusion layer of the first plurality of diffusion layers;

a second plurality of metals including the second metal, each metal of the second plurality of metals being coupled to a respective diffusion layer of the second plurality of diffusion layers, wherein each metal of the second plurality of metals has a width that is smaller than a width of the respective diffusion layer of the second plurality of diffusion layers;

wherein diffusion layers of the first plurality of diffusion layers are of a first type and diffusion layers of the second plurality of diffusion layers are of a second type and wherein diffusion layers of the first plurality of diffusion layers are located between respective diffusion layers of the second plurality of diffusion layers.

7 . The diode of claim 1 , wherein a width of the first metal is substantially equal to a width of the first diffusion layer.

8 . The diode of claim 1 , wherein the width of the first metal is substantially equal to the width of the second metal.

9 . The diode of claim 1 , wherein the first and second diffusion layers are formed in a n-well or a p-well of the substrate.

10 . The diode of claim 1 , wherein the first and second diffusion layers have a substantially rectangular cross-section.

11 . The diode of claim 1 , wherein the width of the second diffusion layer is larger than a width of the first diffusion layer.

12 . A method of forming a diode, comprising:

(a) forming a first diffusion layer in a substrate;

(b) forming a second diffusion layer in the substrate;

(c) coupling a first metal to the first diffusion layer; and

(d) coupling a second metal to the second diffusion layer that has width that is smaller than a width of the second diffusion layer.

13 . The method of claim 12 , further comprising:

(e) forming a first plurality of contacts coupled to the first diffusion layer, wherein step (c) comprises coupling the first metal to the first plurality of contacts; and

(f) forming a second plurality of contacts coupled to the second diffusion layer, wherein step (d) comprises coupling the second metal to the second plurality of contacts.

14 . The method of claim 12 , further comprising:

(e) forming a third diffusion layer adjacent to the second diffusion layer, wherein the third diffusion layer and the first diffusion layer are of the same type.

15 . The method of claim 12 , wherein step (b) comprises:

forming the second diffusion layer such that the width of the second diffusion layer is larger than a width of the first diffusion layer.