Semiconductor-on-insulator with back side body connection
View Patent ↗Embodiments of the present invention provide for the removal of excess carriers from the body of active devices in semiconductor-on-insulator (SOI) structures. In one embodiment, a method of fabricating an integrated circuit is disclosed. In one step, an active device is formed in an active layer of a semiconductor-on-insulator wafer. In another step, substrate material is removed from a substrate layer disposed on a back side of the SOI wafer. In another step, an insulator material is removed from a back side of the SOI wafer to form an excavated insulator region. In another step, a conductive layer is deposited on the excavated insulator region. Depositing the conductive layer puts it in physical contact with a body of an active device in a first portion of the excavated insulator region. The conductive layer then couples the body to a contact in a second detached portion of the excavated insulator region.
1. A method of fabricating an integrated circuit, the method comprising the steps of:
forming an active device in an active layer of a semiconductor-on-insulator wafer;
removing a substrate material from a substrate layer disposed on a back side of the semiconductor-on-insulator wafer;
removing an insulator material from a back side of the semiconductor-on-insulator wafer to form an excavated insulator region; and
depositing an electrically conductive layer on the excavated insulator region;
wherein the depositing puts the electrically conductive layer in physical contact with a body of the active device in a first portion of the excavated insulator region, and couples the body to a contact, the contact being in a second detached portion of the excavated insulator region and being physically connected to another part of the active device.
2. The method of fabricating an integrated circuit from claim 1 , further comprising the step of forming a handle wafer above the active layer.
3. The method of fabricating an integrated circuit from claim 1 , further comprising the step of selecting a lower resistivity metal to form at least a portion of the electrically conductive layer.
4. The method of fabricating an integrated circuit from claim 1 , further comprising the step of forming a circuit branch from the contact to a source of the active device.
5. The method of fabricating an integrated circuit from claim 1 , wherein the depositing forms a segment of a variable impedance circuit branch having a high impedance when the active device is in an on state, and a low impedance when the active device is not in the on state.
6. The method of fabricating an integrated circuit from claim 5 , further comprising the step of forming a gate region of the active device and a second segment of a variable impedance circuit branch from the gate to the contact.
7. The method of fabricating an integrated circuit from claim 1 , further comprising the step of forming a diode in the active layer directly above the contact, the diode being reversed biased when the active device is in an on state.
8. The method of fabricating an integrated circuit from claim 1 , wherein the depositing forms a hot-carrier diode junction between the active layer and the electrically conductive layer.
9. The method of fabricating an integrated circuit from claim 1 , further comprising the step of depositing an assembly material, the assembly material being electrically coupled to the electrically conductive layer.
10. The method of fabricating an integrated circuit from claim 9 , wherein the assembly material comprises solder bumps or copper posts.
11. A method of fabricating an integrated circuit, the method comprising the steps of:
forming an active device in an active layer of a semiconductor-on-insulator wafer;
removing a substrate material from a substrate layer disposed on a back side of the semiconductor-on-insulator wafer;
removing an insulator material from a back side of the semiconductor-on-insulator wafer to form an excavated insulator region; and
depositing an electrically conductive layer on the excavated insulator region;
and wherein:
the depositing puts the electrically conductive layer in physical contact with a body of the active device in a first portion of the excavated insulator region, and couples the body to a contact, the contact being in a second detached portion of the excavated insulator region; and
the forming of the active device in the active layer further comprises forming a landing pad above a point where the body is contacted by the electrically conductive layer, the landing pad being comprised of a wider region of the body.
12. The method of fabricating an integrated circuit from claim 11 , further comprising the step of forming a handle wafer above the active layer.
13. The method of fabricating an integrated circuit from claim 11 , further comprising the step of selecting a lower resistivity metal to form at least a portion of the electrically conductive layer.
14. The method of fabricating an integrated circuit from claim 11 , further comprising the step of forming a circuit branch from the contact to a source of the active device.
15. The method of fabricating an integrated circuit from claim 11 , wherein the depositing forms a segment of a variable impedance circuit branch having a high impedance when the active device is in an on state, and a low impedance when the active device is not in the on state.
16. The method of fabricating an integrated circuit from claim 15 , further comprising the step of forming a gate region of the active device and a second segment of a variable impedance circuit branch from the gate to the contact.
17. The method of fabricating an integrated circuit from claim 11 , further comprising the step of forming a diode in the active layer directly above the contact, the diode being reversed biased when the active device is in an on state.
18. The method of fabricating an integrated circuit from claim 11 , wherein the depositing forms a hot-carrier diode junction between the active layer and the electrically conductive layer.
19. The method of fabricating an integrated circuit from claim 11 , further comprising the step of depositing an assembly material, the assembly material being electrically coupled to the electrically conductive layer.
20. The method of fabricating an integrated circuit from claim 19 , wherein the assembly material comprises solder bumps or copper posts.