Semiconductor devices
Methods, devices, modules, and systems providing semiconductor devices in a stacked wafer system are described herein. One embodiment includes a first wafer for NMOS transistors in a CMOS architecture and a second wafer for PMOS transistors in the CMOS architecture, with the first wafer being bonded and electrically coupled to the second wafer to form at least one CMOS device. Another embodiment includes a number of DRAM capacitors formed on a first wafer and support circuitry associated with the DRAM capacitors formed on a second wafer, with the first wafer being bonded and electrically coupled to the second wafer to form a number of DRAM cells. Another embodiment includes a first wafer having a number of vertical transistors coupled to a data line and a second wafer having amplifier circuitry associated with the number of vertical transistors, with the first wafer being bonded and electrically coupled to the second wafer.
1. A method for forming a CMOS device, the method comprising:
forming a number of NMOS transistors on a first wafer using an NMOS process;
forming a number of bond pads on the first wafer, the number of bond pads coupled to at least one of the number of NMOS transistors;
forming a number of PMOS transistors on a second wafer using a PMOS process;
forming a number of bond pads on the second wafer, the number of bond pads coupled to at least one of the number of PMOS transistors;
bonding the first wafer and the second wafer to form at least one CMOS device; and
providing relative alignment of corresponding bond pads on the first and second wafers, during bonding of the first and second wafers, via an initial alignment scheme that includes complementary coarse alignment structures formed on a surface of the first wafer and on a surface of the second wafer;
wherein bonding the first wafer and the second wafer includes electrically coupling the first wafer to the second wafer with a number of reflowable interconnects.
2. The method of claim 1 , wherein bonding includes electrically coupling in a manner that enables signal processing CMOS logic between the first wafer and the second wafer.
3. The method of claim 1 , wherein the method includes bonding and electrically coupling the first wafer and the second wafer to form at least one static random access memory cell.
4. The method of claim 1 , wherein at least some of the number of reflowable interconnects are micro solder balls having a diameter of not more than 5 microns.
5. The method of claim 4 , wherein at least some of the number of reflowable interconnects are micro solder balls having a diameter of not more than 2 microns.
6. The method of claim 1 , wherein forming at least one of the CMOS devices includes forming a CMOS device that is a three input logic circuit.
7. The method of claim 6 , including forming the CMOS device that is a three input logic circuit by using at least three of the number of reflowable interconnects.
8. A method for forming a CMOS device, the method comprising:
forming a number of NMOS transistors on a first wafer using an NMOS process;
forming a number of bond pads on the first wafer, the number of bond pads coupled to at least one of the number of NMOS transistors;
forming a number of PMOS transistors on a second wafer using a PMOS process;
forming a number of bond pads on the second wafer, the number of bond pads coupled to at least one of the number of PMOS transistors;
bonding the first wafer and the second wafer to form at least one CMOS device;
forming a reflowable interconnect on at least one of the number of bond pads formed on the first wafer and the number of bond pads formed on the second wafer; and
providing relative alignment of corresponding bond pads on the first and second wafers, during bonding of the first and second wafers, via an initial alignment scheme that includes complementary coarse alignment structures formed on a surface of the first wafer and on a surface of the second wafer.
9. The method of claim 8 , wherein the method includes bonding a third wafer to the at least one of the first and the second wafer, wherein bonding the third wafer includes using a reflowable interconnect, the reflowable interconnect having different material properties from the reflowable interconnect formed on at least one of the number of bond pads formed on the first wafer and the number of bond pads formed on the second wafer.
10. The method of claim 8 , wherein the method includes forming the complementary coarse alignment structures on the surface of the first and second wafer prior to forming the number of bond pads on the first and second wafer and prior to forming the reflowable interconnect.
11. The method of claim 8 , wherein the method includes reflowing the reflowable interconnect to provide fine alignment of corresponding bond pads on the first and second wafers.
12. The method of claim 8 , wherein the method includes further aligning corresponding bond pads by forming at least one solder ball by heating at least one of the first and second wafer to a reflow temperature associated with the reflowable interconnect and thereby creating a meniscus surface tension force.
13. A method for forming a CMOS device, the method comprising:
forming a number of NMOS transistors on a first wafer using an NMOS process;
forming a number of bond pads on the first wafer, the number of bond pads coupled to at least one of the number of NMOS transistors;
forming a number of PMOS transistors on a second wafer using a PMOS process;
forming a number of bond pads on the second wafer, the number of bond pads coupled to at least one of the number of PMOS transistors;
bonding the first wafer and the second wafer to form at least one CMOS device; and
providing relative alignment of corresponding bond pads on the first and second wafers, during bonding of the first and second wafers, via an initial alignment scheme that includes complementary coarse alignment structures formed on a surface of the first wafer and on a surface of the second wafer;
wherein the complementary coarse alignment structures include a number of vertical depressions formed in the surface of one of the first and second wafer and a complementary number of vertical protrusions formed on the surface of one of the first and second wafer, and wherein the method includes;
forming the vertical depressions via an anisotropic etching process; and
forming the vertical protrusions via selective epitaxy.