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Complementary metal-oxide-semiconductor (CMOS) image sensors have widely been used in internet of thinking (IoT) devices such as smartphones, smart watch and personal computer tablets [1] . The consumer market strongly requires higher sensitivity and higher speed image data processing to realize high functional CMOS image sensors such as three dimensionally stacked back-side-illuminated CMOS image sensors (3D-CIS) [2] . However, there are some serious technological issues in the fabrication of advanced CMOS image sensors as shown in Fig. 1 .

The gettering behavior in a hydrocarbon molecular (C3H5) ion implanted region was investigated using atom probe tomography (APT) with the aim of improving electrical properties of CMOS image sensors (CISs) and stacked CISs. APT clarified the formation of carbon atom agglomerates with copper and oxygen gettering capability in the C3H5 ion implanted region. However, there were no oxygen atoms near the copper atoms in the C3H5 ion implanted region. In addition, the copper gettering capability of each carbon atom agglomerates decreased with increasing ratio of the number of oxygen atoms to that of carbon atoms in the carbon atom agglomerates. The copper and oxygen gettering mechanism was considered to involve the formation of a complex with carbon-containing gettering sites. Oxygen degrades the copper gettering capability of carbon atom agglomerates by the formation of stable complexes with carbon-containing gettering sites, which can also act as copper gettering sites. Consequently, the oxygen concentration in the C3H5 ion implanted regions is an important factor in improving the electrical properties of CISs and stacked CISs.

We present a miniature physical-contact optical connector featuring a novel magnetic attraction structure. The magnetic optical connectors we designed and fabricated yield low insertion and high return losses comparable to those of a conventional connector.

Three-dimensional (3D) stacked complementary metal oxide semiconductor (CMOS) image sensors require reduction in leakage current due to interface state defects at the SiO2/Si interface. Hydrocarbon molecular ion implanted silicon wafers have identified the hydrogen termination effect of such wafer, contributing to high performance of CMOS image sensors. However, recently, low-temperature heat treatment during a device process has been shown to reduce the concentration of hydrogen diffusing from the hydrocarbon-molecular-ion-implanted region. Thus, a new method of molecular ion implantation with phosphorus added has been developed. In this paper, we present the results of our analysis of the diffusion behavior of hydrogen in a hydrocarbon molecule with phosphorus (CH2P) by reaction kinetic analysis and TCAD simulation. The results of reaction kinetic analysis show binding energies of 0.76 eV (C–H2 binding state) and 0.45 eV (P–H binding state). TCAD simulation results show that the 0.76 eV binding energy indicates that hydrogen is adsorbed in a carbon and silicon self-interstitial cluster (C/I cluster). On the other hand, the binding energy of 0.45 eV indicates that hydrogen is trapped in phosphorus complexes. Hydrogen in the CH2P-implanted region diffuses owing to the difference in between these binding states. Thus, a reduction in the interface state density of Si/SiO2 can be expected.

Gettering sinks for metallic impurities formed by carbon-cluster ion implantation in epitaxial silicon wafers have been investigated using technology computer-aided design and atom probe tomography (APT). We found that the defects formed by carbon-cluster ion implantation consist of carbon and interstitial silicon clusters (carbon-interstitial clusters). Vacancy-type clusters are not dominant gettering sinks for metallic impurities in the carbon-cluster ion implanted region. APT data indicated that the distribution of oxygen atoms in the defects differs between Czochralski-grown silicon and epitaxial silicon wafers. The high gettering efficiency observed in carbon-cluster ion implanted epitaxial silicon wafers in comparison with Czochralski-grown silicon wafers is due to the distribution of oxygen atoms in the defects. Defects not containing O atoms provide strong gettering sinks for metallic impurities. These defects are formed by only carbon-interstitial clusters. Oxygen atoms inside the defects modify the amount of carbon-interstitial cluster formation on the defects. It is suggested that the gettering efficiency for metallic impurities in carbon-cluster ion implanted epitaxial silicon wafer is determined by the amount of carbon-interstitial clusters.

We developed silicon epitaxial wafers with high gettering capability by using hydrocarbon&ndash, molecular&ndash, ion implantation. These wafers also have the effect of hydrogen passivation on process-induced defects and a barrier to out-diffusion of oxygen of the Czochralski silicon (CZ) substrate bulk during Complementary metal-oxide-semiconductor (CMOS) device fabrication processes. We evaluated the electrical device performance of CMOS image sensor fabricated on this type of wafer by using dark current spectroscopy. We found fewer white spot defects compared with those of intrinsic gettering (IG) silicon wafers. We believe that these hydrocarbon&ndash, ion&ndash, implanted silicon epitaxial wafers will improve the device performance of CMOS image sensors.

In this paper, we make a summary report of our 5G RaD activities for "High Capacity Technologies with Ultra High-Density Multi-Band and Multi-Access Layered Cells", funded by the Ministry of Internal Affairs and Communications (MIC) in Japan. This national project consists of three research subjects: "Ultra high-density distributed antenna systems", "Optical access technologies accommodating highly densified small cells" and "Multi-RAT system technologies for multi-band and multi-access layered cells". We describe the research and development result for each subject.

The reduction in the density of SiO2/Si interface state (D it) in the isolation region and transfer transistor gate oxide is necessary to improve the performance of complementary metal-oxide semiconductor (CMOS) image sensors. In this study, we demonstrated that a hydrocarbon-molecular-ion-implanted epitaxial silicon wafer can reduce the D it and Pb0 center density in SiO2/Si interface regions analyzed by quasi-static capacitance–voltage and electron spin resonance measurements, respectively. The D it and Pb0 center density of wafers without hydrocarbon molecular ions increased after annealing at 700 °C. On the other hand, the D it and Pb0 center density of wafers implanted with hydrocarbon molecular ions decreased after annealing at 700 °C. We also estimated the activation energy to be 1.67 eV for the hydrogen termination reactions with hydrogen molecules and Si dangling bonds at the SiO2/Si interface. The termination effects of the hydrocarbon-molecular-ion-implanted epitaxial silicon wafers can contribute to the high electrical performance of CMOS image sensors.

We investigate the amorphous formation behavior on hydrocarbon molecular ion implantation conditions such as hydrocarbon molecular ion size by X-ray photoelectron spectroscopy (XPS). The cross-sectional radius of the amorphous region was obtained from the peak intensity of the amorphous component in Si 2p spectra analyzed by XPS, and using columnar formula for a model. We confirmed that the cross-sectional radius of the amorphous region formed by hydrocarbon molecular ions differs greatly from that formed by monomer carbon ions, and increases by 0.078 nm as the number of carbon atoms composing the hydrocarbon molecular ion increases. The dependence of amorphous formation on the hydrocarbon molecular size is related to the C–C binding distance, and the ratio of increase in the amorphous cross-sectional radius corresponds to half of the C–C binding distance. Therefore, the collision behavior of hydrocarbon molecular ions during implantation predominantly influence the size of hydrocarbon molecular ions.