Deposition of BaHfO₃ Dielectric Layers for Microelectronic Applications by Pulsed Liquid Injection MOCVD

Abstract

Perovskite-type dielectrics exhibit a wide range of interesting properties and play an important role in many technological applications ranging from high energy nuclear medical applications and energy conversion to advanced microelectronic applications. [1,2] In microelectronics, thin dielectric layers (<50 nm) characterized by dielectric constants higher than that of SiO 2 (k $ 4) are of special interest for microprocessors, mass memory, and digital logic applications. The integration of these so-called high-k dielectrics would enable further miniaturization of the microelectronic devices and reduction in the static power dissipation. [3][4][5][6] In this context, HfO 2 -based materials are preferred due to their proven compatibility with semiconductor circuit-processing technology. [7] Current research on HfO 2 is concerned primarily with stabilizing its cubic and tetragonal phases which offer considerably higher dielectric constants than the monoclinic or amorphous HfO 2 . In a number of studies this stabilization and the associated increase in the dielectric constant was obtained by the addition of rare earth elements to HfO 2 . [4,[8][9][10] We have recently investigated properties of thin BaHfO 3 layers prepared using molecular beam deposition (MBD) for advanced dynamic random access memory (DRAM) cells.[11] As the first group investigating thin films of BaHfO 3 deposited by MBD, we obtained very promising results making BaHfO 3 a good candidate for this application. However, to enable technological applications, a chemical deposition process for this material must be available. To date, there are no reports in the literature concerning preparation of thin BaHfO 3 layers using chemical deposition techniques.In this paper, we present first results of BaHfO 3 deposition onto Si substrates using pulsed liquid injection metal-organic (MO)CVD.[12] Growth of pure BaHfO 3 was obtained at deposition temperatures of 600-700 8C using a combination of Ba(thd) 2 and Hf(thd) 4 precursors (thd -2,2,6,6-tetramethyl-3,5-heptanedionate). We show that the resulting layers crystallize in the cubic perovskite structure (c-BaHfO 3 ) and exhibit a high dielectric constant of $35. Furthermore, we address some surface quality issues related to the proposed deposition process. ). The growth rate increases rapidly with temperature and starts to saturate at about 700-750 8C. The growth rate of BaCO 3 from the Ba(thd) 2 precursor is clearly higher than that of HfO 2 from Hf(thd) 4 at the same temperature. Direct comparison of the growth rates of different materials (oxide and carbonate) is not very correct, however such big differences in the growth rates show that Hf(thd) 4 precursor has higher thermal stability than Ba(thd) 2 . This result suggests that an excess of Hf precursor should be used in solution for the growth of the complex oxide BaHfO 3 . Well-crystallized films of orthorhombic BaCO 3 (o-BaCO 3 ) and monoclinic HfO 2 were obtained on Si(100) substrates starting at 500 8C and 600 8C, respectively.Since polycrystalline hi...

Metal‐Organic Chemical Vapor Deposition of Oxide Perovskite Films: A Facile Route to Complex Functional Systems

“…For this type of applications, there has been a vast variety of high-k perovskite oxide thin films developed, including CaCu 3 Ti 4 O 12 , [108] (Ba,Sr)TiO 3 (BST), [109] (Pb,La)TiO 3 (PLT), [110][111][112][113] LaAlO 3 , [114] CeAlO 3 , [115] BaHfO 3 , [116] and BaHfTiO 3 . [117] Thin films of ferroelectric perovskite-based oxides such as BaTiO 3 , [52] PbTiO 3 , [118] PZT, [118] Pb(Mg 1/3 Nb 2/3 )O 3 (PMN), [119] (Pb 1−x La x )TiO 3 (PLT), [113,120] SrTiO 3 , [121,122] KNbO 3 , [123,124] SrBi 2 Ta 2 O 9 (SBT), [125] and (K x Na 1−x )NbO 3 (KNN) [126] have been successfully deposited on a variety of substrates, including Pt(111)/SiO 2 /Si, Pt(100)/MgO(100), Pt/Ti/SiO 2 /Si multilayers or simple (100)-Silicon wafers.…”

Chemical vapor deposition and characterization of high-k BaHf1−xTixO3 dielectric layers for microelectronic applications

“…6͑a͔͒, an initial evaluation of the dielectric constant indicates that k-values are around 14 ͓Fig. 8 Since carbon concentration within the layer is below the detection limit of sputter XPS measurements, we exclude carbon contamination as a possible reason for dielectric constant degradation. Extrapolation of the line in Fig.…”

“…In this context, HfO 2 -based materials are preferred due to their proven compatibility with semiconductor circuit-processing technology. 8 We obtained very promising results by MBD, making BaHfO 3 a good candidate for DRAM applications. [2][3][4][5][6] We have recently investigated the properties of thin BaHfO 3 layers prepared using molecular beam deposition 7 ͑MBD͒ and metal-organic chemical vapor deposition ͑MOCVD͒.…”

“…1 To fulfill requirements of future dynamic random access memory ͑DRAM͒ technologies, different material combinations including Al 2 O 3 / HfO 2 , Al 2 O 3 / ZrO 2 , and SrTiO 3 are investigated. 8 Furthermore, we studied the influence of partial substitution of Hf ions in BaHfO 3 by Ti ions on the dielectric constant. 8 We obtained very promising results by MBD, making BaHfO 3 a good candidate for DRAM applications.…”

First-principles study of thermodynamic stability and the electronic properties of intrinsic vacancy defects in barium hafnate

“…Barium hafnate, BaHfO 3 (BHO), has recently emerged as a potential candidate for utilization in important electronic technologies such as microprocessor and dynamic random access memory (DRAM) [1,2]. The environmental and health hazards of commercially dominant lead-based PbZr 1−x Ti x O 3 (PZT) have been driving the quest for identifying alternative piezoelectric materials for the electronics industry.…”