Wafer structure for electronic integrated circuit manufacturing
View Patent ↗A bonded wafer structure having a handle wafer, a device wafer, and an interface region with an abrupt transition between the conductivity profile of the device wafer and the handle wafer is used for making semiconductor devices. The improved doping profile of the bonded wafer structure is well suited for use in the manufacture of integrated circuits. The bonded wafer structure is especially suited for making radiation-hardened integrated circuits.
1. A method of forming a wafer structure comprising:
forming a first region in a device wafer having at least one major surface, a thickness, and a conductivity profile of a first conductivity type substantially parallel to said at least one major surface;
forming a second region in a separate handle wafer having a thickness, and a second conductivity profile of the first conductivity type of said first region, such second conductivity profile being substantially different than the conductivity profile of said first region, such that said second region is in electrical contact with said first region opposite the major surface of said first region;
bonding together said device and handle wafers;
forming an interface region formed between said first region and said second region; and
placing impurity sites in said first region, said second region, and said interface region, such impurity sites being substantially electrically inactive over a temperature range,
wherein the conductivity profile of said first region transitions abruptly to the conductivity profile of said second region within the interface region,
wherein said first region, said second region, and said interface region comprise the same semiconductor material, and
wherein said impurity sites are selected from the group of isotopes consisting of silicon, carbon, fluorine, sulfur, chlorine, nitrogen, or defects selected from the group consisting of lattice vacancies, interstitial defects, Frenkel defect pairs, crystal dislocations, or a combination of said isotopes and defects.
2. The method of claim 1 further comprising thinning one or both of said bonded device and handle wafers.
3. The method of claim 2 wherein thinning comprises grinding the device wafer.
4. The method of claim 2 wherein thinning comprises grinding the handle wafer.
5. The method of claim 2 wherein thinning comprises grinding to a predetermined thickness.
6. The method of claim 2 wherein thinning comprises polishing.