ESD protection for high voltage applications
View Patent ↗An ESD device includes a low doped well connected to a first contact and a diffusion area connected to a second contact. A substrate between the low doped well and the diffusion area has a dopant polarity that is opposite a dopant polarity of the low doped well and the diffusion area. A distance between the low doped well and the diffusion area determines a triggering voltage of the ESD device. A depletion region is formed between the low doped well and the substrate when a reverse bias voltage is applied to the ESD device. A current discharging path is formed between the first contact and the second contact when the depletion region comes in to contact with the diffusion area. The substrate is biased by a connection to the second contact. Alternatively, an additional diffusion area with the same dopant polarity, connected to a third contact, biases the substrate.
1. An electrostatic discharge (ESD) device, comprising:
a substrate;
a low doped well formed in the substrate, and having a first contact; and
a diffusion area formed in the substrate, and having a second contact that is also in contact with the substrate;
wherein the substrate has a dopant polarity that is opposite a dopant polarity of the low doped well and a dopant polarity of the diffusion area;
wherein the second contact is positioned so as to prevent a reverse bias between said substrate and said diffusion area;
wherein a distance between the low doped well and the diffusion area determines a triggering voltage of the ESD device; and
wherein a periphery of the diffusion area has a lower concentration of a dopant relative to a center of the diffusion area.
2. The ESD device of claim 1 , wherein a depletion region is formed between the low doped well and the substrate when a reverse bias voltage is applied to the low doped well and the substrate.
3. The ESD device of claim 2 , wherein a width of the depletion region increases as the reverse bias voltage increases.
4. The ESD device of claim 3 , wherein a current discharging path is formed between the first contact and the second contact when the depletion region comes into contact with the diffusion area.
5. The ESD device of claim 4 , wherein the triggering voltage of the ESD device is equal to the reverse bias voltage that causes the depletion region to come into contact with the diffusion area.
6. The ESD device of claim 1 , wherein a periphery of the low doped well has a lower concentration of a dopant relative to a center of the low doped well.
7. The ESD device of claim 1 , wherein the diffusion area is a conventional doped well.
8. The ESD device of claim 1 , wherein the diffusion area is a conventional low doped well.
9. The ESD device of claim 1 , wherein the diffusion area is a conventional doped diffusion area.
10. The ESD device of claim 1 , wherein the dopant polarity of the low doped well and the diffusion area is n-type and the dopant polarity of the substrate is p-type.
11. The ESD device of claim 1 , wherein the dopant polarity of the low doped well and the diffusion area is p-type and the dopant polarity of the substrate is n-type.
12. An electrostatic discharge (ESD) device, comprising:
a substrate;
a low doped well formed in the substrate, and having a first contact;
a first diffusion area formed in the substrate, and having a second contact;
a second diffusion area formed in the substrate, and having a third contact;
wherein the substrate and the second diffusion area have dopant polarities that are opposite dopant polarities of the low doped well and the first diffusion area;
wherein the low doped well and the first diffusion area are configured to conduct an ESD current;
wherein a distance between the low doped well and the first diffusion area determines a triggering voltage of the ESD device.
13. The ESD device of claim 12 , wherein the third contact is between the first contact and the second contact.
14. The ESD device of claim 12 , wherein the dopant polarity of the low doped well and the first diffusion area is n-type and the dopant polarity of the substrate and the second diffusion area is p-type.
15. The ESD device of claim 12 , wherein the dopant polarity of the low doped well and the first diffusion area is p-type and the dopant polarity of the substrate and the second diffusion area is n-type.
16. The ESD device of claim 12 , wherein the second contact and the third contact are connected by a conductor.
17. A method of forming an electrostatic discharge (ESD) device, comprising:
forming a substrate;
forming a low doped well within the substrate connected to a first contact; and
forming a diffusion area within the substrate connected to a second contact, wherein the substrate is connected to the second contact and has a dopant polarity that is opposite a dopant polarity of the low doped well and a dopant polarity of the diffusion area;
wherein the second contact is positioned so as to prevent a reverse bias between said substrate and said diffusion area;
wherein a distance between the low doped well and the diffusion area determines a triggering voltage of the ESD device; and
wherein a periphery of the diffusion area has a lower concentration of a dopant relative to a center of the diffusion area.
18. A method of forming an electrostatic discharge (ESD) device comprising:
forming a substrate;
forming a low doped well within the substrate connected to a first contact;
forming a first diffusion area within the substrate connected to a second contact; and
forming a second diffusion area within the substrate connected to a third contact, wherein the substrate and the second diffusion area have dopant polarities that are opposite dopant polarities of the low doped well and the first diffusion area;
wherein the low doped well and the first diffusion area are configured to conduct an ESD current;
wherein a distance between the low doped well and the first diffusion area determines a triggering voltage of the ESD device.
19. The method of claim 18 , further comprising forming the second diffusion area between the low doped well and the first diffusion area.
20. The method of claim 18 , further comprising connecting the second contact to the third contact with a conductor.