Multi-layered polysilicon and oxygen-doped polysilicon design for RF SOI trap-rich poly layer
In some embodiments, the present disclosure relates to a high-resistivity silicon-on-insulator (SOI) substrate, including a first polysilicon layer arranged over a semiconductor substrate. A second polysilicon layer is arranged over the first polysilicon layer, and a third polysilicon layer is arranged over the second polysilicon layer. An active semiconductor layer over an insulator layer may be arranged over the third polysilicon layer. The second polysilicon layer has an elevated concentration of oxygen compared to the first and third polysilicon layers.
1. A high-resistivity silicon-on-insulator (SOI) substrate, comprising:
a semiconductor substrate;
a first polysilicon layer arranged over the semiconductor substrate;
a second polysilicon layer arranged over the first polysilicon layer;
a third polysilicon layer arranged over the second polysilicon layer;
a fourth polysilicon layer arranged over the third polysilicon layer;
a cap polysilicon layer arranged over the fourth polysilicon layer;
an insulator layer arranged over the cap polysilicon layer; and
an active semiconductor layer arranged over the insulator layer,
wherein the second and fourth polysilicon layers have an elevated concentration of oxygen compared to the first, third, and cap polysilicon layers,
wherein the first polysilicon layer is a continuously connected layer completely covering the semiconductor substrate,
wherein the second polysilicon layer is a continuously connected layer completely covering the first polysilicon layer, and
wherein the third polysilicon layer is a continuously connected layer completely covering the second polysilicon layer.
2. The high-resistivity SOI substrate of claim 1 , further comprising:
a native oxide layer between the semiconductor substrate and the first polysilicon layer.
3. The high-resistivity SOI substrate of claim 1 , wherein the first polysilicon layer has a first thickness, and wherein the second polysilicon layer has a second thickness less than the first thickness.
4. The high-resistivity SOI substrate of claim 3 , wherein the cap polysilicon layer has a third thickness that is greater than the first thickness and is greater than the second thickness.
5. The high-resistivity SOI substrate of claim 1 , wherein the first polysilicon layer has a first average grain size, and wherein the second polysilicon layer has a second average grain size that is less than the first average grain size.
6. The high-resistivity SOI substrate of claim 1 , further comprising:
a transistor device arranged over the active semiconductor layer, and wherein source/drain regions of the transistor device are arranged within the active semiconductor layer.
7. The high-resistivity SOI substrate of claim 1 , wherein the second and fourth polysilicon layers have a higher number of dangling bonds and a smaller grain size than each of the first, third, and cap polysilicon layers.
8. A high-resistivity silicon-on-insulator (SOI) substrate, comprising:
a semiconductor substrate;
an insulator layer over the semiconductor substrate;
a trap-rich polysilicon structure arranged between the insulator layer and the semiconductor substrate, the trap-rich polysilicon structure comprising:
a first polysilicon layer having a first thickness and arranged over the semiconductor substrate;
a second polysilicon layer having a second thickness and arranged over the first polysilicon layer;
a third polysilicon layer having a third thickness and arranged over the second polysilicon layer;
a fourth polysilicon layer having a fourth thickness and arranged over the third polysilicon layer; and
a cap polysilicon layer having a fifth thickness and arranged over the fourth polysilicon layer, wherein the first thickness and the third thickness are each greater than the second thickness and the fourth thickness, wherein the fifth thickness is greater than the first thickness and the third thickness, and
wherein the second and fourth polysilicon layers each have a higher concentration of oxygen, a higher number of dangling bonds, and a smaller grain size than each of the first polysilicon layer, the third polysilicon layer, and the cap polysilicon layer.
9. The high-resistivity SOI substrate of claim 8 , further comprising:
a native oxide layer between the semiconductor substrate and the first polysilicon layer of the trap-rich polysilicon structure.
10. The high-resistivity SOI substrate of claim 9 , wherein the first polysilicon layer of the trap-rich polysilicon structure directly contacts the native oxide layer, wherein the fourth polysilicon layer directly contacts the cap polysilicon layer, and wherein the cap polysilicon layer directly contacts the insulator layer.
11. The high-resistivity SOI substrate of claim 8 , wherein the trap-rich polysilicon structure further comprises:
one or more intermediate polysilicon layers between the second polysilicon layer and the third polysilicon layer; and
one or more intermediate oxygen-doped polysilicon layers between the second polysilicon layer and the third polysilicon layer, wherein the one or more intermediate polysilicon layers are alternatingly stacked with the one or more intermediate polysilicon layers.
12. The high-resistivity SOI substrate of claim 8 , wherein an atomic percent of oxygen to polysilicon in each of the second and fourth polysilicon layers is between approximately 10 percent and approximately 20 percent.
13. The high-resistivity SOI substrate of claim 8 , wherein the second polysilicon layer has a first average grain size, and wherein the first polysilicon layer has a second average grain size that is greater than the first average grain size.
14. The high-resistivity SOI substrate of claim 13 , wherein the cap polysilicon layer has a third average grain size that is greater than the second average grain size.
15. A high-resistivity silicon-on-insulator (SOI) substrate, comprising:
a semiconductor substrate;
an insulator layer over the semiconductor substrate;
a trap-rich polysilicon structure arranged between the insulator layer and the semiconductor substrate, the trap-rich polysilicon structure comprising:
a lower polysilicon layer;
a lower oxygen-doped polysilicon layer arranged over the lower polysilicon layer;
an upper polysilicon layer arranged over the lower oxygen-doped polysilicon layer, wherein the lower oxygen-doped polysilicon layer has a smaller average grain size than the lower and upper polysilicon layers; and
an upper oxygen-doped polysilicon layer arranged over the upper polysilicon layer and having an elevated concentration of oxygen compared to the upper polysilicon layer;
a cap polysilicon layer arranged over the upper oxygen-doped polysilicon layer;
a semiconductor active layer arranged over the insulator layer and the trap-rich polysilicon structure; and
semiconductor devices arranged on and/or within the semiconductor active layer.
16. The high-resistivity SOI substrate of claim 15 , wherein the lower oxygen-doped polysilicon layer is thinner than the lower polysilicon layer and the upper polysilicon layer.
17. The high-resistivity SOI substrate of claim 15 , wherein the lower oxygen-doped polysilicon layer has an elevated concentration of oxygen compared to the lower and upper polysilicon layers.
18. The high-resistivity SOI substrate of claim 15 , further comprising:
a native oxide layer between the semiconductor substrate and the trap-rich polysilicon structure.
19. The high-resistivity SOI substrate of claim 15 , wherein the cap polysilicon layer has a larger average grain size than the upper and lower oxygen-doped polysilicon layers, and wherein the cap polysilicon layer is thicker than the upper oxygen-doped polysilicon layer, the lower oxygen-doped polysilicon layer, the lower polysilicon layer, and the upper polysilicon layer.
20. The high-resistivity SOI substrate of claim 15 , wherein the semiconductor devices comprise source/drain regions that are arranged completely over the trap-rich polysilicon structure.