Semiconductor-on-insulator with back side 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 semiconductor-on-insulator structure comprising:
an electrically conductive layer located in an excavated insulator region that is excavated on a bottom side of the structure;
an insulator layer being located above the electrically conductive layer, and partially vertically coextensive with the electrically conductive layer in the excavated insulator region;
an active layer being located above the insulator layer, the active layer comprising an active device with a body and a gate, wherein the gate is located above the body;
a handle wafer formed above the active layer; and
a body contact physically connecting the electrically conductive layer and the body, the body contact being located in a first portion of the excavated insulator region;
wherein the electrically conductive layer couples the body contact to a contact in the active layer, the contact being located in a second portion of the excavated insulator region, the second portion being detached from the first portion.
2. The semiconductor-on-insulator structure of claim 1 , wherein at least a portion of the electrically conductive layer is a lower resistivity metal.
3. The semiconductor-on-insulator structure of claim 2 wherein the metal is selected from the group consisting of aluminum and copper.
4. The semiconductor-on-insulator structure of claim 1 , further comprising: a circuit branch comprising the body contact and the contact;
wherein the circuit branch connects a source of the active device to the body of the active device.
5. The semiconductor-on-insulator structure of claim 1 , further comprising;
a circuit branch comprising the body contact and the contact;
wherein the circuit branch connects the gate of the active device to the body of the active device.
6. The semiconductor-on-insulator structure of claim 1 , further comprising:
a variable impedance circuit branch comprising the body contact and the contact;
wherein the variable impedance circuit branch is configured to have a high impedance when the active device is in an on state, and the variable impedance circuit branch is configured to have a low impedance when the active device is not in the on state.
7. The semiconductor-on-insulator structure of claim 6 , the variable impedance circuit branch further comprising:
a gate region of the active device;
wherein the variable impedance circuit branch latches the body to the gate voltage when the active device is in an off state.
8. The semiconductor-on-insulator structure of claim 1 , wherein:
the body contact is ohmic;
the contact is directly below a diode formed in the active layer; and
the diode is reversed biased when the active device is in an on state.
9. The semiconductor-on-insulator structure of claim 1 , wherein the body contact is a hot-carrier diode junction.
10. The semiconductor-on-insulator structure comprising:
an electrically conductive layer;
an insulator layer being at least partially vertically coextensive with the electrically conductive layer in an excavated insulator region that is excavated on a bottom side of the structure;
an active layer being located above the insulator layer, the active layer comprising an active device with a body and a gate, wherein the gate is located above the body;
a handle wafer formed above the active layer; and
a body contact physically connecting the electrically conductive layer and the body;
wherein the electrically conductive layer couples the body contact to a contact in the active layer.
11. The semiconductor-on-insulator structure of claim 10 , wherein at least a portion of the electrically conductive layer is a lower resistivity metal.
12. The semiconductor-on-insulator structure of claim 10 , wherein the metal is selected from the group consisting of aluminum and copper.