We investigated the diffusion behavior of hydrogen in a silicon wafer made by a carbon-cluster ion-implantation technique after heat treatment and silicon epitaxial growth. A hydrogen peak was observed after high-temperature heat treatment (>1000 °C) and silicon epitaxial growth by secondary ion mass spectrometry analysis. We also confirmed that the hydrogen peak concentration decreased after epitaxial growth upon additional heat treatment. Such a hydrogen diffusion behavior has not been reported. Thus, we derived the activation energy from the projected range of a carbon cluster, assuming only a dissociation reaction, and obtained an activation energy of 0.76 ± 0.04 eV. This value is extremely close to that for the diffusion of hydrogen molecules located at the tetrahedral interstitial site and hydrogen molecules dissociated from multivacancies. Therefore, we assume that the hydrogen in the carbon-cluster projected range diffuses in the molecular state, and hydrogen remaining in the projected range forms complexes of carbon, oxygen, and vacancies.

REGULAR PAPERS • OPEN ACCESSEffect of dose and size on defect engineering in carbon cluster implanted silicon wafers Carbon-cluster-ion-implanted defects were investigated by high-resolution cross-sectional transmission electron microscopy toward achieving high-performance CMOS image sensors. We revealed that implantation damage formation in the silicon wafer bulk significantly differs between carbon-cluster and monomer ions after implantation. After epitaxial growth, small and large defects were observed in the implanted region of carbon clusters. The electron diffraction pattern of both small and large defects exhibits that from bulk crystalline silicon in the implanted region. On the one hand, we assumed that the silicon carbide structure was not formed in the implanted region, and small defects formed because of the complex of carbon and interstitial silicon. On the other hand, large defects were hypothesized to originate from the recrystallization of the amorphous layer formed by high-dose carbon-cluster implantation. These defects are considered to contribute to the powerful gettering capability required for high-performance CMOS image sensors.

The trapping and diffusion behaviour of hydrogen in projection range of carbon‐cluster was investigated by using a technology computer aided design (TCAD) simulation for high performance complementary metal–oxide–semiconductor (CMOS) image sensors. The hydrogen behaviour seemingly contributes to passivating the interface state density of the isolation region and process‐induced defects during the CMOS image sensor fabrication process. This hydrogen behaviour was simulated by a TCAD simulation assuming a reaction model in which the cluster of carbon and silicon self‐interstitial (carbon‐interstitial cluster) binds to hydrogen. We found that the hydrogen profiles of TCAD agreed with the secondary ion mass spectrometry (SIMS) results after epitaxial growth and high‐temperature heat‐treatment, thus suggesting that the hydrogen in the projection range of the carbon cluster forms a binding state with the carbon‐interstitial cluster. In addition, hydrogen gradually diffused out from the projection range of the carbon‐cluster after high‐temperature heat‐treatment. Therefore, the hydrogen behaviour in projection range of the carbon‐cluster is considered to contribute to the CMOS image sensor fabrication process to achieve high electrical performance.

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Fundamental characteristics such as metal‐gettering capability and defect morphology of a cyanide‐related multielement molecular (CH4N) ion‐implanted epitaxial silicon (Si) wafer are investigated. It is found that the CH4N ion‐implanted epitaxial Si wafer has a higher gettering capability for transition metallic impurities than a hydrocarbon molecular (C3H5) ion‐implanted epitaxial Si wafer. This higher metal‐gettering capability of the CH4N ion‐implanted epitaxial Si wafer may be due to the formation of stacking faults as well as carbon (C) agglomeration defects in the CH4N ion‐implanted region during the epitaxial Si layer growth process. The formation of stacking faults may be a specific phenomenon in the case of the CH4N ion implantation. In addition, the CH4N ion‐implanted region can trap high concentrations of hydrogen (H) and nitrogen (N) atoms during the epitaxial Si growth. This fact suggests that the distribution of N atoms is strongly associated with the defect morphology and C distribution in the CH4N ion‐implanted region. The CH4N ion‐implanted epitaxial Si wafer with these characteristics has the potential to improve the performance of complementary metal‐oxide‐semiconductor (CMOS) image sensors.