Atomic Layer Deposition of SrTiO₃ Thin Films with Highly Enhanced Growth Rate for Ultrahigh Density Capacitors

다국어 초록 (Multilingual Abstract)

<P>The ever-shrinking dimensions of dynamic random access memory (DRAM) require a high quality dielectric film for capacitors with a sufficiently high growth-per-cycle (GPC) by atomic layer deposition (ALD). SrTiO<SUB>3</SUB> (STO) films are considered to be the appropriate dielectric films for DRAMs with the design rule of ∼20 nm, and previous studies showed that STO films grown by ALD have promising electrical performance. However, the ALD of STO films still suffers from much too slow GPC to be used in mass-production. Here, we accomplished a mass-production compatible ALD process of STO films using Ti(O-<SUP><I>i</I></SUP>Pr)<SUB>2</SUB>(tmhd)<SUB>2</SUB> as a Ti-precursor for TiO<SUB>2</SUB> layers and Sr(<SUP><I>i</I></SUP>Pr<SUB>3</SUB>Cp)<SUB>2</SUB> as a Sr-precursor for SrO layers. O<SUB>3</SUB> and H<SUB>2</SUB>O were used as the oxygen sources for the TiO<SUB>2</SUB> and SrO layers, respectively. A highly improved GPC of 0.107 nm/unit-cycle (0.428 nm/supercycle) for stoichiometric STO films was obtained at a deposition temperature of 370 °C, which is ∼7 times higher than previously reported. The origin of such high GPC values in this STO films could be explained by the partial decomposition of the precursors used and the strong tendency of water adsorption onto the SrO layer in comparison to the TiO<SUB>2</SUB> layer. The STO film grown in this study also showed an excellent step coverage (∼95%) when deposited inside a deep capacitor hole with an aspect ratio of 10. Owing to the high bulk dielectric constant (∼ 146) of the STO film, an equivalent oxide thickness of 0.57 nm was achieved with a STO film of 10 nm. In addition, the leakage current density was sufficiently low (3 × 10<SUP>−8</SUP> Acm<SUP>−2</SUP> at +0.8 V). This process is extremely promising for fabrication of the next generation DRAMs.</P><P>Conformal SrTiO<SUB>3</SUB> (STO) thin films were grown at 370 °C with a high growth-per-cycle (0.107 nm/unit-cycle) by atomic layer deposition. An equivalent oxide thickness of 0.57 nm was achived with a STO film of 10 nm.</P><P><B>Graphic Abstract</B>
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