HVMOS transistor structure having offset distance and method for fabricating the same
An HVMOS transistor structure includes: a first ion well of a first conductivity type and a second ion well of a second conductivity type different from the first conductivity type formed over a substrate, wherein the first ion well and the second ion well have a junction at their interface; a gate overlying the first ion well and the second ion well; a drain region of the first conductivity type, in the first ion well, spaced apart from a first sidewall of the gate by an offset distance; and a source region of the first conductivity type in the second ion well. In addition, a method for fabricating the HVMOS transistor structure described above is also provided.
1. An HVMOS transistor structure comprising:
a first ion well of a first conductivity type and a second ion well of a second conductivity type different from the first conductivity type formed over a substrate, wherein the first ion well and the second ion well have a junction at their interface;
a gate overlying the first ion well and the second ion well, wherein the gate has a first overlapping length with the first ion well, from the junction of the first and the second ion wells to the first sidewall of the gate, wherein the first overlapping length is between about 0.1 μm and about 0.3 μm, wherein the gate has a second overlapping length with the second ion well, from the junction of the first and the second ion wells to a second sidewall opposite to the first sidewall, and wherein the second overlapping length is greater than the first overlapping length;
a drain region of the first conductivity type, in the first ion well, spaced apart from a first sidewall of the gate, which is proximate to the first ion well, by an offset distance; and
a source region of the first conductivity type in the second ion well.
2. The HVMOS transistor structure of claim 1 , wherein the offset distance is between about 0.2 and about 0.5 μm.
3. The HVMOS transistor structure of claim 1 , wherein the source and drain regions have a greater doping concentration that that of the first ion well and the second ion well.
4. The HVMOS transistor structure of claim 1 , further comprising a resist protect oxide layer covering the unsilicided region.
5. The HVMOS transistor structure of claim 1 , wherein the gate comprises polysilicon, metal or a combination thereof.
6. The HVMOS transistor structure of claim 1 , further comprising a deep well of the first conductivity type underlying the first and the second ion wells.
7. The HVMOS transistor structure of claim 1 , wherein the first conductivity type is N-type, and the second conductivity type is P-type.
8. The HVMOS transistor structure of claim 1 , wherein the first conductivity type is P-type, and the second conductivity type is N-type.
9. The HVMOS transistor structure of claim 1 , wherein the gate comprises a gate electrode formed on a gate dielectric layer.
10. The HVMOS transistor structure of claim 1 , wherein the second ion well has a first concentration of about 1E13-1E14 cm −2 .
11. The HVMOS transistor structure of claim 1 , wherein the drain region and the source region have a second doped concentration of about 3E15-3E16 cm −2 .
12. The HVMOS transistor structure claim 1 , further comprising:
gate spacers formed on the first and second sidewalls of the gate; and
a silicide layer over the gate, the source region and a portion of the drain region;
an unsilicide region not covered by the silicide layer extends from the spacer on the first sidewall to another portion of the drain region that is not covered by the silicide layer.
13. An HVMOS transistor structure comprising:
a first ion well of a first conductivity type and a second ion well of a second conductivity type different from the first conductivity type formed over a substrate, wherein the first ion well and the second ion well have a junction at their interface;
a gate overlying the first ion well and the second ion well, wherein the gate has a first overlapping length with the first ion well, from the junction of the first and the second ion wells to the first sidewall of the gate, wherein the first overlapping length is between about 0.1 μm an about 0.3 μm, wherein the gate has a second overlapping length with the second ion well, from the junction of the first and the second ion wells to a second sidewall opposite to the first sidewall, and wherein the second overlapping length is greater than the first overlapping length.
a drain region of the first conductivity type, in the first ion well, spaced apart from a first sidewall of the gate, which is proximate to the first ion well, by an offset distance;
a source region of the first conductivity type in the second ion well
gate spacers formed on the first and second sidewalls of the gate; and
a silicide layer over the gate, the source region and a portion of the drain region;
an unsilicide region not covered by the silicide layer extends from the space one the first sidewall to another portion of the drain region that is not covered by the silicide layer.
14. A method for fabricating a transistor HVMOS structure, the method comprising:
forming a first ion well of a first conductivity type and a second ion well of a second conductivity type different from the first conductivity type in a substrate, wherein the first ion well and the second ion well have a junction at their interface;
forming a gate overlying the first ion well and second ion well, wherein the gate has a first overlapping length with the first ion well, from the junction of the first and the second ion wells to the first sidewall of the gate, wherein the first overlapping length is between about 0.1 μm and about 0.3 μm, wherein the gate has a second overlapping length with the second ion well, from the junction of the first and the second ion wells to a second sidewall opposite to the first sidewall, and wherein the second overlapping length is greater that the first overlapping length; and
forming a drain region and a source region of the first conductivity type in the first ion well and in the second ion well, respectively, wherein the drain region is spaced apart from a first sidewall of the gate, which is proximate to the first ion well, by an offset distance.
15. The method according to claim 14 , wherein the offset distance is between about 0.2 and about 0.5 μm.
16. The method according to claim 14 , wherein the source and drain regions have a greater doping concentration that that of the first ion well and the second ion well.
17. The method according to claim 14 , further comprising forming an interlayer dielectric layer over the silicide layer and the resist protect oxide layer.
18. The method according to claim 14 , further comprising a deep well of the first conductivity type underlying the first and the second ion wells.
19. The method according to claim 14 , wherein the first conductivity type is N-type, and the second conductivity type is P-type.
20. The method according to claim 14 , wherein the first conductivity type is P-type, and the second conductivity type is N-type.
21. The method according to claim 14 , wherein the gate comprises a gate electrode formed on a gate dielectric layer.
22. The method according to claim 14 , wherein the second ion well has a first concentration of about 1E13-1E14 cm −2 .
23. The method according to claim 14 , wherein the drain region and the source region have a second doped concentration of about 3E15-3E16 cm −2 .
24. The method according to claim 14 , further comprising:
forming gate spacers on the first and second sidewalls of the gate;
forming a resist protect oxide layer over the spacer on the first sidewall and extending to a portion of the drain region;
forming a metal later over the gate, the source region and the drain region; and
performing a silicide process to the metal layer to form a silicide layer on the gate, the source region and another portion of the drain region that is not covered by the resist protect oxide layer.
25. A method for fabricating a transistor HVMOS structure, the method comprising:
forming a first ion well of a first conductivity type and a second ion well of a second conductivity type different from the first conductivity type in a substrate, wherein the first ion well and the second ion well have a junction at their interface;
forming a gate overlying the first ion well and second ion well, wherein the gate has a first overlapping length with the first ion well, from the junction of the first and the second ion wells to the first sidewall of the gate, wherein the first overlapping length is between about 0.1 μm and about 0.3 μm, wherein the gate has a second overlapping length with the second ion well, from the junction of the first and the second ion wells to a second sidewall opposite to the first sidewall, and wherein the second overlapping length is greater than the first overlapping length;
forming a drain region and a source region of the first conductivity type in the first ion well and in the second ion well, respectively, wherein the drain region is spaced apart from a first sidewall of the gate, which is proximate to the first ion well, by an offset distance;
forming gate spacers on the first and second sidewalls of the gate;
forming a resist protect oxide layer over the spacer on the first sidewall and extending to a portion of the drain region;
forming a metal layer over the gate, the source region and the drain region; and
performing a silicide process to the metal layer to form a silicide layer on the gate, the source region and another portion of the drain region that is not covered by the resist protect oxide layer.