Methods for bonding semiconductor wafers
View Patent ↗A method of bonding a cap wafer to a device wafer includes heating the device wafer and the cap wafer in the chamber, cooling the device wafer and the cap wafer in the chamber, pressurizing the chamber, introducing gas into the chamber while the chamber is pressurized to accelerate a rate of one of a group consisting of the heating and the cooling, and applying pressure to the device wafer and the cap wafer while a bond is formed between the device wafer and the cap wafer.
1. A method of bonding, in a chamber, a cap wafer to a device wafer, comprising:
heating the device wafer and the cap wafer in the chamber;
cooling the device wafer and the cap wafer in the chamber;
pressurizing the chamber by introducing gas into the chamber to accelerate a rate of one of a group consisting of the heating and the cooling;
applying pressure to the device wafer and the cap wafer while a bond is formed between the device wafer and the cap wafer, and
after the cooling, raising a temperature of the chamber to enhance forming the bond, wherein the bond is a eutectic bond.
2. The method of claim 1 , wherein:
the heating causes outgassing from the cap wafer and the device wafer.
3. The method of claim 2 , wherein:
the heating causes the cap wafer and the device wafer to exceed a eutectic temperature.
4. The method of claim 3 , wherein:
the cooling causes the cap wafer and the device wafer to drop below the eutectic temperature.
5. The method of claim 1 , wherein:
the pressurizing by introducing gas into the chamber accelerates the heating and the cooling.
6. The method of claim 1 , further comprising:
establishing a strong vacuum level in the chamber to remove the gas and residual absorbed gases.
7. The method of claim 6 , further comprising:
establishing a vacuum in the chamber; and
before the applying pressure to the device wafer and the cap wafer, positioning a surface of the cap wafer including a plurality of cavities in alignment with a surface of the device wafer that includes a corresponding plurality of devices, wherein each of the cavities encloses a respective one of the devices and the cavities are vacuum-sealed after the bond if formed.
8. The method of claim 7 , further comprising:
after the positioning, changing a temperature in the bond chamber to a bond temperature while the pressure is applied to the device wafer and the cap wafer.
9. The method of claim 1 , wherein:
the introducing gas into the chamber comprises introducing an inert gas.
10. The method of claim 1 , wherein:
the gas comprises one of a group consisting of argon, helium, forming gas, and nitrogen.
11. The method of claim 1 , further comprising:
clamping the cap wafer and the device wafer together while separating the cap wafer and the device wafer with a plurality of spacers.
12. The method of claim 11 , further comprising, prior to the applying pressure, removing the spacers.
13. A method of bonding, in a chamber, a cap wafer that is paired with a device wafer spaced apart by a plurality of spacers, comprising:
pressurizing the chamber and heating the chamber to induce outgassing from the cap wafer and the device wafer;
evacuating the chamber to remove residual absorbed gases resulting from the outgassing;
pressurizing the chamber and cooling the cap wafer and the device wafer;
removing the plurality of spacers; and
forming a bond between the cap wafer and the device wafer.
14. The method of claim 13 , wherein:
the cooling the cap wafer and the device wafer is further characterized by the pressurizing the chamber causing a temperature differential between the cap wafer and the device wafer to be reduced.
15. The method of claim 14 , wherein:
the pressurizing the chamber to induce outgassing comprises introducing, into the chamber, a gas comprising one of group consisting of nitrogen, argon, helium, and forming gas.