Method for fabricating a low trigger voltage silicon controlled rectifier and thick field device

A method for fabricating a silicon controlled rectifier semiconductor device in a substrate comprising:

• forming an oxide layer on the substrate;
• forming a silicon nitride layer on the oxide layer;
• etching away portions of the silicon nitride layer, wherein portions of the oxide layer are exposed and wherein remaining portions of the silicon nitride layer on the oxide layer define active regions in the substrate;
• forming field oxide regions in the exposed portions of the oxide layer;
• removing the remaining portions of the silicon nitride layer and the oxide layer, wherein the active regions in the substrate are exposed;
• growing a sacrificial oxide layer in the exposed active regions;
• forming a first mask to define regions for N-well implantations;
• implanting a P+ buried layer;
• implanting N-well regions with N-type dopants using multiple implants to define a desired profile for the N-type dopants in the N-well regions;
• removing the first mask;
• forming a second mask to define regions for P-well implantations;
• and
• implanting P-well regions with P-type dopants using multiple implants to define a desired profile for the P-type dopants in the P-well regions;
• forming source drain regions for a field device and a transistor;
• and
• forming interconnections to connect the field device and the transistor to form the silicon controlled rectifier semiconductor device.

The method for fabricating a silicon controlled rectifier in a substrate comprising:

• defining active regions within the substrate;
• forming field oxide regions over regions other than the defined active regions, wherein surfaces of the active regions are located between the field oxide regions;
• implanting a buried layer using a first type of dopant and a first mask;
• implanting a first number of well regions using multiple implants of a second type of dopant and using the first mask, wherein the multiple implants are used to create a desired profile for the first number of well regions;
• implanting a second number of well regions using multiple implants of the first type of dopant and using a second mask in place of the first mask, wherein the multiple implants are used to create a desired profile for the second number of well regions;
• forming source and drain regions for a field device and a transistor;
• and
• forming interconnections between the field device and the transistor to form the silicon controlled rectifier.