Takumi Nakahata

Formation of selective epitaxially grown silicon with a flat edge by ultra-high vacuum chemical vapor deposition

Abstract We studied the dependence of selective epitaxially grown silicon (SEG-Si) shape on the conditions of ultra-high vacuum chemical vapor deposition using disilane (Si 2 H 6 ) gas, which grew on Si (1xa00xa00) substrates patterned with SiO 2 stripes. SEG-Si edges typically formed two types of configurations: facets and bumps. It was confirmed that the shape of SEG-Si edge is strongly dependent on the growth mode of the (1xa00xa00) plane: facet configurations are formed in the mass transfer limited region, and bump configurations are formed in the kinetically limited region. Therefore, it was concluded that the surface migration length of adatoms resulting from the decomposition of Si 2 H 6 molecules is related to the formation of the shape of the SEG-Si. Moreover, it was confirmed that the flat shape of the SEG-Si is obtained by adjusting both the Si 2 H 6 flow rates and the growth temperature.

Optimization of process conditions of selective epitaxial growth for elevated source/drain CMOS transistor

Abstract We studied the dependence of selective epitaxially grown silicon (SEG-Si) morphology under the conditions of ultrahigh vacuum chemical vapor deposition (UHV-CVD) by using a mixture of disilane (Si 2 H 6 ) and chlorine (Cl 2 ) gases on Si(1xa00xa00) substrates patterned a complementary metal oxide semiconductor (CMOS) transistor. The SEG-Si surface became rougher with growth temperature, especially the SEG-Si in the p-MOS region, and there was a difference between p- and n-MOS regions in terms of SEG-Si thickness. It was revealed that an amorphous layer, which was induced by dry etching before SEG-Si growth, caused the roughness of the SEG-Si surface and difference in the thickness. Moreover, it was indicated that optimization of the growth conditions could sufficiently flatten the SEG-Si surface and correct the difference in thickness.

Low thermal budget surface cleaning after dry etching for selective silicon epitaxial growth

We studied the influence of plasma etching damage on epitaxial Si growth using ultrahigh vacuum chemical vapor deposition. The damaged layer induced on substrate surface had an amorphous structure that had some carbon, oxygen, and fluorine in its composition. The damaged layer was removed by in situ preheating above 850°C, before the growth, or by chemical dry etching (CDE). We found that CDE has the effect of decreasing the preheating temperature by 200°C as compared to the case without CDE. Furthermore, the dependence of the surface roughness of grown films on post-etching treatments is also discussed.

Epitaxial Si1−x Gex grown into fine contact hole by ultrahigh-vacuum chemical vapor deposition

Abstract An ultrahigh-vacuum chemical vapor deposition technique with disilane (Si 2 H 6 ) and germane (GeH 4 ) molecular flux is applied to Si 1− x Ge x ( x =0–0.15) selective growth into fine contact holes. The growth behavior of epitaxial Si 1− x Ge x layer is influenced by addition of GeH 4 with Si 2 H 6 flow rate kept at constant, which is interpreted by estimation of facet growth rates. The growth rates of (311) and (111) facets are drastically decreased by addition of a small amount of GeH 4 . As a result, in the fine holes, the epitaxial layer height of Si 1− x Ge x is limited by the (311) growth rate and decreased compared with pure Si.

Improvement of alignment tolerance against contact hole etching by growing of underlying silicon-selective epitaxial layer

Abstract We demonstrated that the influences of a contact hole overlapping a local oxidation of silicon (LOCOS) isolation can be reduced by using selective epitaxial growth, which is improved the alignment margin of the contact hole in the LOCOS region. The experimental results indicated that the epitaxial layer underlying the contact bottoms prevented the TiSi2 layer from penetrating into the Si substrate. Therefore, the leakage current at the overlapping region was drastically suppressed for a configuration where the contact hole and the LOCOS region overlapped. The breakdown voltage was improved compared with a case without an epitaxial layer.