Creating high voltage FETs with low voltage process
View Patent ↗An integrated circuit (IC) includes a high voltage first-conductivity type field effect transistor (HV-first-conductivity FET) and a high voltage second-type field effect transistor (HV-second-conductivity FET). The HV first-conductivity FET has a second-conductivity-well and a field oxide formed over the second-conductivity-well to define an active area. A first-conductivity-well is formed in at least a portion of the active area, wherein the first-conductivity-well is formed to have the capability to operate as a first-conductivity-drift portion of the HV-first-conductivity FET. The HV second-conductivity FET has a first-conductivity-well and a field oxide formed over the first-conductivity-well to define an active area. A channel stop region I s formed in at least a portion of the active area, wherein the channel stop region is formed to have the capability to operate as second-conductivity− drift portions of the HV-second-conductivity FET.
1. A method of forming a high voltage first-conductivity-type metal oxide semiconductor field effect transistor, comprising:
forming one or more channel stop regions in an active area defined by an opening in field oxide over a second-conductivity-well, wherein the channel stop regions are formed to include first-conductivity− drift capabilities; and
forming a gate oxide region over the second-conductivity-well in the active area and a portion of one or more channel stop regions.
2. The method of claim 1 , further comprising:
applying a plurality of spacers on opposing sides of the gate oxide region, wherein one or more spacers define an opening to the channel stop regions; and
implanting first-conductivity+ dopant in the one or more openings of the spacers.
3. The method of claim 1 , and further comprising:
forming first-conductivity+ source regions in the active area of the second-conductivity-well, wherein the first-conductivity+ source regions are formed to span from beneath the gate oxide to an edge of the active area.
4. The method of claim 1 wherein the step of forming one or more channel stop regions further comprises performing a sequential chain implant of high energy to lower energy dose implants.