ESD protection device
An electrostatic discharge protection clamp includes a substrate and a first electrostatic discharge protection device over the substrate. The first electrostatic discharge protection device includes a buried layer over the substrate. The buried layer has a first region having a first doping concentration and a second region having a second doping concentration. The first doping concentration is greater than the second doping concentration. The first electrostatic discharge protection device includes a first transistor over the buried layer. The first transistor has an emitter coupled to a first cathode terminal of the electrostatic discharge protection clamp. The first electrostatic discharge protection device includes a second transistor over the buried layer. The second transistor has an emitter coupled to a first anode terminal of the electrostatic discharge protection clamp. A collector of the first transistor and a collector of the second transistor are over the first region of the buried layer.
1. A method, comprising:
providing a substrate including a buried layer, the buried layer having a first region having a first doping concentration and a second region having a second doping concentration, the first doping concentration being greater than the second doping concentration; and
forming a first electrostatic discharge protection device by:
forming an epitaxial layer over the buried layer, the epitaxial layer having a first conductivity type and including a first epitaxial region and a second epitaxial region,
forming a first transistor over the buried layer, the first transistor having an emitter and a base formed within the first epitaxial region, the emitter of the first transistor being configured to couple to a first cathode terminal of an electrostatic discharge protection clamp;
forming a second transistor over the buried layer, the second transistor having an emitter and a base formed within the second epitaxial region, the emitter of the second transistor being configured to couple to a first anode terminal of the electrostatic discharge protection clamp;
forming a well region having a second conductivity type opposite the first conductivity type between the first epitaxial region and the second epitaxial region; and
wherein a collector of the first transistor and a collector of the second transistor are formed within the well region directly over and overlap the first region of the buried layer, the emitter and the base of the first transistor and the emitter and the base of the second transistor are formed directly over and overlap the second region of the buried layer, and the emitter and the base of the first transistor and the emitter and the base of the second transistor do not overlap any portion of the buried layer having the first doping concentration.
2. The method of claim 1 , wherein the second doping concentration is between 1×10 16 cm −3 and 5×10 17 cm −3 .
3. The method of claim 2 , wherein the first doping concentration is between 1×10 18 cm −3 and 1×10 19 cm −3 .
4. The method of claim 1 , including forming a buried oxide layer on the substrate.
5. The method of claim 1 , wherein at least one of the first transistor and the second transistor includes a bipolar junction transistor.
6. The method of claim 1 , including forming a second electrostatic discharge protection device over the substrate, the second electrostatic discharge protection device being connected to the first electrostatic discharge protection device.
7. The method of claim 6 , including forming a deep trench isolation region between the first electrostatic discharge protection device and the second electrostatic discharge protection device.
8. The method of claim 1 , wherein the buried layer includes a third region having the first doping concentration and including forming a side wall over the third region of the buried layer.