SLT integrated circuit capacitor structure and methods
FET IC structures that enable formation of integrated capacitors in a “flipped” SOI IC structure made using a back-side access process, such as a “single layer transfer” (SLT) process, and which eliminate or mitigate unwanted parasitic couplings to a handle wafer. In some embodiments, a conductive interconnect layer may be patterned, pre-SLT, to form an isolated first capacitor plate. In other embodiments, pre-SLT, a conductive region of the active layer of an IC may be patterned to form an isolated first capacitor plate, with one or more interconnect layers being fabricated in position to form an electrical contact to the first capacitor plate. In either case, a post-SLT top-side layer of conductive material may be patterned to form a second capacitor plate. Couplings to the resulting capacitor structures include only external connections, only internal connections, or both internal and external connections.
1. An inverted integrated circuit structure attached to a first surface of a handle wafer and including:
(a) a buried-oxide (BOX) insulator layer, an active layer, and at least one conductive interconnect layer, the at least one conductive interconnect layer being situated between the active layer and the handle wafer, and the active layer being situated between the at least one conductive interconnect layer and the BOX insulator layer;
(b) at least one first capacitor plate comprising an isolated portion of the active layer formed before application of a back-side access process; and
(c) at least one second capacitor plate formed from a top-side layer of conductive material after application of the back-side access process;
wherein the BOX insulator is situated between the active layer and the top-side layer of conductive material and wherein at least one first capacitor plate is capacitively coupled to at least one second capacitor plate.
2. The invention of claim 1 , further including:
(a) a conductive via connected to the first capacitor plate; and
(b) a lateral electrical connection in electrical contact with the conductive via and formed from a first conductive interconnect layer before application of a back-side access process.
3. The invention of claim 2 , further including an electrical connection formed between the top-side layer of conductive material and the lateral electrical connection.
4. The invention of claim 1 , further including an electrical connection formed between the first capacitor plate and a second conductive interconnect layer, and formed before application of the back-side access process.
5. The invention of claim 1 , further including an electrical connection formed between the second capacitor plate and a second conductive interconnect layer, and formed after application of the back-side access process.
6. The invention of claim 1 , wherein at least one first capacitor plate is capacitively coupled to at least two second capacitor plates.
7. The invention of claim 1 , wherein at least one second capacitor plate is capacitively coupled to at least two first capacitor plates.
8. The invention of claim 1 , wherein the integrated circuit structure includes at least one field effect transistor.
9. The invention of claim 1 , wherein the integrated circuit structure includes at least one field effect transistor having a conductive aligned supplemental gate.
10. The invention of claim 1 , wherein the integrated circuit structure is fabricated using a silicon-on-insulator process.
11. The invention of claim 1 , wherein the handle wafer is principally silicon.
12. The invention of claim 1 , wherein the handle wafer is principally silicon, and the first surface includes a bonding layer of silicon dioxide.
13. The invention of claim 1 , wherein the handle wafer includes a low resistivity silicon wafer.
14. The invention of claim 1 , wherein the separation between the first capacitor plate and the second capacitor plate is about 0.2 μm.
15. An inverted integrated circuit structure attached to a first surface of a handle wafer and including:
(a) a buried-oxide (BOX) insulator layer, an active layer, and at least one conductive interconnect layer, the at least one conductive interconnect layer being situated between the active layer and the handle wafer, and the active layer being situated between the at least one conductive interconnect layer and the BOX insulator layer;
(b) at least one first capacitor plate, each formed from a selected region of a first conductive interconnect layer before application of a back-side access process; and
(c) at least one second capacitor plate, each formed from a selected region of a top-side layer of conductive material after application of the back-side access process;
wherein the BOX insulator is situated between the active layer and the top-side layer of conductive material and wherein at least one first capacitor plate is capacitively coupled to at least one second capacitor plate.
16. The invention of claim 15 , wherein the handle wafer is principally silicon.
17. The invention of claim 15 , wherein the handle wafer is principally silicon, and the first surface includes a bonding layer of silicon dioxide.
18. The invention of claim 15 , wherein the handle wafer includes a low resistivity silicon wafer.
19. An inverted integrated circuit structure including:
(a) a handle wafer having at least a first surface;
(b) a first passivation layer having a first surface physically coupled to the first surface of the handle wafer, and having a second surface;
(c) at least one first capacitor plate formed from a first conductive interconnect layer formed spaced apart from the second surface of the first passivation layer;
(d) an inverted device region having a first surface formed spaced apart from the first conductive interconnect layer, and having a second surface;
(e) a second passivation layer having a first surface physically coupled to the second surface of the inverted device region, and having a second surface; and
(f) at least one second capacitor plate formed from a top-side layer of conductive material formed on the second surface of the second passivation layer;
wherein at least one first capacitor plate is capacitively coupled to at least one second capacitor plate.