(Invited) Proximity Gettering Design of Hydrocarbon Molecular Ion Implanted Silicon Wafers Using Direct Bonding Technique for Advanced CMOS Image Sensors: A Review

Abstract

We developed high gettering capability silicon wafers for advanced CMOS image sensors using hydrocarbon molecular ion implantation and surface activated direct wafer bonding (SAB). We found that this novel wafer has three unique characteristics for the improvement of CMOS image sensor device performance. The first is metallic impurity gettering capability in the hydrocarbon ion implantation projection range during CMOS device fabrication. The second is the oxygen out-diffusion barrier effect; this wafer can control out-diffusion to the device active region from the CZ grown silicon substrate during CMOS device heat treatment. The third is the hydrogen passivation effect; hydrogen passivates to the Si/SiO2 gate oxide interface state defects which out-diffuse to the device active region from the hydrocarbon ion implantation projection range during the CMOS device fabrication. Moreover, we demonstrated that this novel wafer can improve the pn-junction leakage current under the actual device fabrication.

Proximity Gettering Design of Hydrocarbon–Molecular–Ion–Implanted Silicon Wafers Using Dark Current Spectroscopy for CMOS Image Sensors

“…Second, our previous study demonstrated that pn-junction leakage current of pn-junction diode dramatically decreased by combination of both hydrocarbon–molecular implantation and surface activated wafer bonding (SAB) techniques compared to without SAB [65,66]. The pn-junction leakage current determined some factors such as metallic impurity contamination in space-charge region and interface state defect in device isolation region.…”

“…Third, we demonstrated that the hydrogen out-diffused to silicon epitaxial layer (device active region) from hydrogen storage in hydrocarbon–molecular–ion projection range during the heat treatment [35,65,66]. This hydrogen of out diffusion amount is 10 12 to 10 13 cm −2 measured by SIMS after heat treatment [70].…”

“…However, our wafer stores hydrogen in the hydrocarbon–molecular–ion implantation projection range of the epitaxial layer [35,65,66]. Hydrogen diffuses into the bonding interface region during the heat treatment [65,66]. This hydrogen diffuses to the wafer bonding interface during the BSI fabrication process.…”

Photoemission Spectroscopy Study on Hydrogen Termination Effect on SiO2/Si Structure Fabricated Using H+-Implanted Si Substrate

“…16,17 Such a method is expected to be an effective way to reduce D it 16,17 in advanced CIS, because hydrogen that diffused out from the Si bulk can be provided to the device active region without being trapped by multiple dielectric layers in advanced CIS. 18,19 On the basis of this concept, our group has been developing a hydrocarbon-molecularion-implanted epitaxial Si wafer 17,20 for CIS. The fabrication process for hydrocarbon-molecular-ion-implanted epitaxial Si wafer is very simple, that is, implantation of hydrocarbon molecular (C 3 H 5 or C 3 H 6 ) ions into a Si substrate followed by homoepitaxial growth on the substrate.…”