Modular bipolar-CMOS-DMOS analog integrated circuit and power transistor technology
View Patent ↗A family of semiconductor devices is formed in a substrate that contains no epitaxial layer. In one embodiment the family includes a 5V CMOS pair, a 12V CMOS pair, a 5V NPN, a 5V PNP, several forms of a lateral trench MOSFET, and a 30V lateral N-channel DMOS. Each of the devices is extremely compact, both laterally and vertically, and can be fully isolated from all other devices in the substrate.
1. A CMOS arrangement of transistors formed in a semiconductor substrate, said substrate being doped with P-type impurity and not comprising an epitaxial layer, said CMOS arrangement comprising a CMOS pair, said CMOS pair comprising a PMOS and an NMOS,
said PMOS comprising:
an N well having a relatively deep central portion and relatively shallow side portions, said relatively shallow side portions underlying a field oxide layer, said relatively deep central portion underlying a first opening in said field oxide layer, said N well having a breakdown voltage relative to said substrate;
a first gate overlying a channel region of said N well and separated from said substrate by a first gate oxide layer;
a P-type source region located at the surface of said substrate on one side of said first gate; and
a P-type drain region located at the surface of said substrate on an opposite side of said first gate from said P-type source region; and
electrical contacts connected to said first gate, P-type source region, P-type drain region and N well of said PMOS;
wherein said N well comprises an implanted N layer, said N layer comprising a deep section in said central portion of said N well, shallow sections in said side portions of said N well, and transition sections connecting said deep section and said shallow sections of said N layer, each vertical cross-section of said N layer comprising a location of peak doping concentration; said locations of peak doping concentration being relatively deep in said substrate in said deep section of said N layer and being at a shallower level in said substrate in said shallow sections of said N layer, the doping concentration of said N well at said surface of said substrate in said side portions of said N well being higher than the doping concentration of said N well at said surface of said substrate in said central portion of said N well; said NMOS comprising:
a P well having a relatively deep central portion and relatively shallow side portions, said relatively shallow side portions of said P well underlying said field oxide layer, said relatively deep central portion of said P well underlying a second opening in said field oxide layer;
a second gate overlying a channel region of said P well and separated from said substrate by a second gate oxide layer;
an N-type source region located at the surface of said substrate on one side of said second gate; and
an N-type drain region located at the surface of said substrate on an opposite side of said second gate from said N-type source region; and
electrical contacts connected to said second gate, N-type source region, N-type drain region and P well of said NMOS;
wherein said P well comprises an implanted P layer, said P layer comprising a deep section in said central portion of said P well, shallow sections in said side portions of said P well, and transition sections connecting said deep sections and said shallow sections of said P layer, each vertical cross-section of said P layer comprising a location of peak doping concentration; said locations of peak doping concentration being relatively deep in said substrate in said deep section of said P layer and being at a shallower level in said substrate in said shallow sections of said P layer, the doping concentration of said P well at said surface of said substrate in said side portions of said P well being higher than the doping concentration of said P well at said surface of said substrate in said central portion of said P well.
2. The CMOS arrangement of claim 1 wherein said PMOS has a maximum operating voltage and a field region of said N well under said field oxide layer has a field threshold voltage substantially greater than said maximum operating voltage of said PMOS, and wherein said NMOS has a maximum operating voltage and a field region of said P well under said field oxide layer has a field threshold voltage substantially greater than said maximum operating voltage of said NMOS.
3. The CMOS arrangement of claim 2 wherein said maximum operating voltage of said PMOS is less than 7 volts and said field threshold voltage of said field region of said N well is greater than 13.2 volts.
4. The CMOS arrangement of claim 2 wherein said breakdown voltage of said N well to said substrate is greater than 13.2 volts.
5. The CMOS arrangement of claim 2 wherein said maximum operating voltage of said NMOS is less than 7 volts and said field threshold voltage of said field region of said P well is greater than 13.2 volts.
6. The CMOS arrangement of claim 2 wherein said maximum operating voltage of said PMOS is less than 4 volts and said field threshold voltage of said field region of said N well is greater than 7 volts.
7. The CMOS arrangement of claim 6 wherein said breakdown voltage of said N well to said substrate is greater than 6.5 volts.
8. The CMOS arrangement of claim 2 wherein said maximum operating voltage of said NMOS is less than 4 volts and said field threshold voltage of said P well is greater than 7 volts.
9. The CMOS arrangement of claim 2 wherein said maximum operating voltage of said PMOS is less than 4 volts and said field threshold voltage of said N well is greater than 13.2 volts.
10. The CMOS arrangement of claim 9 wherein said breakdown voltage of said N well to said substrate is greater than 13.2 volts.
11. The CMOS arrangement of claim 2 wherein NMOS said maximum operating voltage of said NMOS is less than 4 volts and said field threshold voltage of said P well is greater than 13.2 volts.
12. The CMOS arrangement of claim 2 wherein said maximum operating voltage of said PMOS is less than or equal to 13.2 volts and said field threshold voltage of said N well is greater than 18 volts.
13. The CMOS arrangement of claim 12 wherein said breakdown voltage of said N well to said substrate is greater than 18 volts.
14. The CMOS arrangement of claim 2 wherein said maximum operating voltage of said NMOS is less than or equal to 13.2 volts and said field threshold voltage of said P well is greater than 18 volts.
15. The CMOS arrangement of claim 2 wherein said locations of peak doping concentration are at the surface of said substrate in said shallow sections of said N layer.
16. The CMOS arrangement of claim 2 wherein said locations of peak doping concentration are at the surface of said substrate in said shallow sections of said P layer.
17. The CMOS arrangement of claim 2 wherein said N well is biased to a positive voltage with respect to said substrate, said field threshold voltage of said N well being higher than said positive voltage.
18. The CMOS arrangement of claim 1 further comprising an isolation structure, said isolation structure comprising:
an N layer located in said substrate and underlying said P well and at least a portion of said N well; and
said N well, said N well laterally surrounding said P well,
wherein said N layer extends laterally beyond said P well and said N well is sufficiently deep in said substrate such that said N well overlaps said N layer so as to form said isolation structure, said isolation structure isolating said P well from said P-type substrate.