Semiconductor devices with gate electrodes and with monocrystalline silicon regions that contain atoms of nitrogen and one or more of chlorine, bromine, sulfur, fluorine, or phosphorus
View Patent ↗Performance of field effect transistors and other channel dependent devices formed on a monocrystalline substrate is improved by carrying out a high temperature anneal in a nitrogen releasing atmosphere while the substrate is coated by a sacrificial oxide coating containing easily diffusible atoms that can form negatively charged ions and can diffuse deep into the substrate. In one embodiment, the easily diffusible atoms comprise at least 5% by atomic concentration of chlorine atoms in the sacrificial oxide coating and the nitrogen releasing atmosphere includes NO. The high temperature anneal is carried out for less than 10 hours at a temperature less than 1100° C.
1. A semiconductor device comprising:
a monocrystalline silicon substrate; and
a gate electrode, disposed above and insulated from a surface of the monocrystalline silicon substrate, the gate electrode overlying a first region of the monocrystalline silicon substrate, wherein the first region extends laterally at least as far as the gate electrode;
wherein the monocrystalline silicon substrate has been subjected to a high temperature first anneal in a nitrogen releasing atmosphere while the substrate was coated by a doped sacrificial first oxide layer that was doped with diffusible atoms selected from the group consisting of CI, Br, S, F and P, where in the sacrificial first oxide layer, said diffusible atoms spread continuously over at least the entire first region, and where said diffusible atoms constituted at least 1% by atomic percentage of atoms in the sacrificial first oxide layer and where said high temperature of the first anneal allowed nitrogen atoms released from said atmosphere to penetrate into the substrate to a predetermined depth below the doped sacrificial first oxide layer;
where the diffusible atoms and the nitrogen atoms are present in the monocrystalline silicon substrate, and at least one of (A) and (B) is true:
(A) the nitrogen atoms spread continuously in the monocrystalline silicon substrate throughout at least the entire first region;
(B) the diffusible atoms spread continuously in the monocrystalline silicon substrate throughout at least the entire first region; and
where the gate electrode is coupled to drive circuitry for inducing a drift of minority charge carriers below said surface.
2. The semiconductor device of claim 1 wherein:
said diffusible atoms constituted at least 5% by atomic percentage of atoms in the sacrificial first oxide layer.
3. The semiconductor device of claim 1 wherein:
said diffusible atoms constituted at least 10% by atomic percentage of atoms in the sacrificial first oxide layer.
4. The semiconductor device of claim 1 wherein:
said diffusible atoms constituted at least 5% by atomic percentage of chlorine atoms in the sacrificial first oxide layer.
5. The semiconductor device of claim 1 wherein:
said nitrogen releasing atmosphere included NO.
6. The semiconductor device of claim 1 wherein:
said high temperature first anneal was carried out at a temperature of about 800° C. or more, but less than 1100° C.
7. The semiconductor device of claim 6 wherein:
said high temperature first anneal was carried out for more than 1 hour but less than 10 hours.
8. The semiconductor device of claim 1 and further comprising:
a source region disposed along a first side of a portion of the surface of the silicon substrate which has been subjected to the high temperature first anneal, where the source region is coupled to circuitry for inducing a drift of minority charge carriers below said portion of the surface; and
a drain region disposed along an opposed second side of the portion of the surface of the silicon substrate which has been subjected to the high temperature first anneal, where the drain region is coupled to circuitry for inducing a drift of minority charge carriers below said portion of the surface.
9. The semiconductor device of claim 1 and further wherein:
the monocrystalline silicon substrate which has been subjected to a high temperature second anneal in a nitrogen releasing atmosphere while the substrate was exposed so that shallow surface nitridation takes place after said first anneal in a nitrogen releasing atmosphere takes place.
10. The semiconductor device of claim 1 wherein (A) is true.
11. The semiconductor device of claim 1 wherein (B) is true.
12. The semiconductor device of claim 1 wherein (A) and (B) are true.
13. A semiconductor device comprising:
a monocrystalline silicon substrate which has been subjected to a high temperature first anneal in a nitrogen releasing atmosphere while the substrate was coated by a doped sacrificial first oxide layer that was doped with diffusible atoms selected from the group consisting of CI, Br, S, F and P, where said diffusible atoms constituted at least 1% by atomic percentage of atoms in the sacrificial first oxide layer and where said high temperature of the first anneal allowed nitrogen atoms released from said atmosphere to penetrate into the substrate to a predetermined depth below the doped sacrificial first oxide layer, the diffusible atoms being present in the substrate; and
a gate electrode, disposed above and insulated from a surface of the silicon substrate which has been subjected to the high temperature first anneal, where the gate electrode is coupled to drive circuitry for inducing a drift of minority charge carriers below said surface;
a source region disposed along a first side of a portion of the surface of the silicon substrate which has been subjected to the high temperature first anneal, where the source region is coupled to circuitry for inducing a drift of minority charge carriers below said portion of the surface; and
a drain region disposed along an opposed second side of the portion of the surface of the silicon substrate which has been subjected to the high temperature first anneal, where the drain region is coupled to circuitry for inducing a drift of minority charge carriers below said portion of the surface;
wherein said gate electrode, source region and drain region define a transistor having a transconductance that is approximately 10% greater than a hypothetical transconductance that would have been obtained if said high temperature first anneal had not been performed with the doped sacrificial first oxide layer.
14. A semiconductor device comprising:
a monocrystalline silicon region comprising a top surface, the monocrystalline silicon region comprising a channel region of the semiconductor device;
two source or drain regions bordering on the monocrystalline silicon region, the source or drain regions bordering on the channel region; and
a gate electrode adjacent to the top surface of the monocrystalline silicon region, for inducing changes in population of charge carriers in the monocrystalline silicon region;
wherein the monocrystalline silicon region comprises:
a plurality of first atoms each of which is an atom of chlorine, bromine, sulfur, fluorine, or phosphorus, the first atoms being present at a depth or depths greater than 0.1 μm below the top surface at which depth or depths the first atoms spread laterally continuously at least as far as the channel region; and
a plurality of nitrogen atoms being present at a depth or depths greater than 0.1 μm below the top surface at which depth or depths the nitrogen atoms spread laterally continuously at least as far as the channel region.
15. The semiconductor device of claim 14 wherein the gate electrode is insulated from the channel region.
16. The semiconductor device of claim 14 wherein the first atoms are present at a depth or depths at least as great as 1 μm below the top surface at which depth or depths the first atoms spread laterally continuously at least as far as the channel region.
17. The semiconductor device of claim 14 wherein the nitrogen atoms are present at a depth or depths at least as great as 1 μm below the top surface at which depth or depths the nitrogen atoms spread laterally continuously at least as far as the channel region.
18. The semiconductor device of claim 14 wherein the first atoms are chlorine atoms.
19. A semiconductor device comprising:
a monocrystalline silicon region comprising a top surface, the monocrystalline silicon region comprising a channel region of the semiconductor device;
two source or drain regions bordering on the monocrystalline silicon region, the source or drain regions being at opposite ends of the channel region; and
a gate electrode adjacent to the top surface of the monocrystalline silicon region, for inducing changes in population of charge carriers in the monocrystalline silicon region;
wherein the monocrystalline silicon region comprises:
a plurality of first atoms each of which is an atom of chlorine, bromine, sulfur, fluorine, or phosphorus, the first atoms being present at a depth or depths greater than 0.1 μm below the top surface at which depth or depths the first atoms spread laterally continuously between the two source or drain regions; and
a plurality of nitrogen atoms being present at a depth or depths greater than 0.1 μm below the top surface at which depth or depths the nitrogen atoms spread laterally continuously between the two source or drain regions.
20. The semiconductor device of claim 19 wherein the gate electrode is insulated from the channel region.
21. The semiconductor device of claim 20 wherein the first atoms are present at a depth or depths at least as great as 1 μm below the top surface at which depth or depths the first atoms spread laterally continuously at least as far as the channel region.
22. The semiconductor device of claim 19 wherein the nitrogen atoms are present at a depth or depths at least as great as 1 μm below the top surface at which depth or depths the nitrogen atoms spread laterally continuously at least as far as the channel region.
23. The semiconductor device of claim 19 wherein the first atoms are chlorine atoms.