Influence of Trench Width on III-V Nucleation during InP Selective Area Growth on Patterned Si(001) Substrate

The integration of III/V materials onto Si substrates is of significant interests for microelectronic and optoelectronic applications. The utilization of the selective epitaxial growth (SEG) on patterned Si substrates by metalorganic vapor phase epitaxy (MOVPE) is proved as a valuable solution for the heteroepitaxy of III-V semiconductors on Si thanks to the “defect trapping” by sidewalls. The demonstration of successful integration by the SEG in wide trenches (above 100nm) is extensively available in the literatures.[1-6] However, following scaling rules for Logic CMOS devices, new challenges are imposed on the heteroepitaxy inside nano-scaled trenches (i.e. sub-50nm trenches for FinFET devices). Therefore, in this study, the influence of trench width on nucleation behavior based on InP SEG in “V-groove” trenches[7,8] as an example, is discussed and analyzed via the proposal of a nucleation model according to the ex-situ morphology observation in the experiments.

      The evolution of morphology for the selective growth of InP in submicron “V-groove” trenches on on-axis Si(001) substrates is characterized by SEM and AFM. Due to the high lattice mismatch between InP and Si, the typical evolution of 3D islands growth mode in both wide and narrow trenches is identified. The comparison of nominally 40nm to both 150nm and 500nm wide trenches indicates that there is an evolution lag for islands coalescence in narrower trenches. This is the reason for discontinuous topology and highly defective layers obtained in sub-50nm trenches. We believe that one possible mechanism attributing to this lag is induced by greater inter-island distance in narrower trenches. Therefore, we propose a nucleation model to evaluate the influence of trench width on the inter-island distance, suggesting that the scaling relationship between the critical inter-island distance and trench width is theoretically predicted as L^* ~W^-1/(2i*+4) if W≤2L^*in the surface-diffusion limited regime. This understanding is of critical importance for the uniform growth inside nano-trenches for the heteroepitaxy of mismatched III/V compounds onto Si substrates, where the 3D island growth mode dominates in most cases.

ACKNOWLEDGMENTS

This work is supported by IMEC Industrial Affiliation Program. The present authors would like to thank the Logic Program and Management, partners.

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