Atomic Layer Deposition of Lu Silicate Films Using [(Me[sub 3]Si)[sub 2]N][sub 3]Lu

Abstract

Rare-earth silicates are promising materials for future microelectronic devices based on high dielectric constant dielectrics. In this work, we report the investigation of Lu silicate films deposited using atomic layer deposition on Si͑100͒. The films were grown from tris͓bis͑trimethylsilyl͒amido͔lutetium-͓͑Me 3 Si͒ 2 N͔ 3 Lu ͑where Me = CH 3 ͒, which can supply both Lu and Si. Water or ozone were used as oxygen sources. The films deposited using the latter are shown to be richer in Si. The films are amorphous as grown, have a low physical roughness, an electronic density lower than expected for both crystalline and amorphous stoichiometric Lu silicates, and promote a SiO 2 -rich interfacial layer on Si͑100͒. Crystallization, observed only in films deposited using O 3 , has an onset temperature above 900°C. Annealing at 950°C induces film densification. Signs of crystallization are observed only in the electron diffraction patterns of the annealed film deposited using O 3 as oxygen source, but the resulting crystallographic phases cannot be unequivocally identified. The values of the dielectric stacks are between 5 and 7. The conduction band offset between the Lu silicate layer and Si͑100͒ measured for the film deposited using O 3 is 2.2 eV.High dielectric constant ͑͒ materials are proposed to substitute SiO 2 as insulating layer in complementary metal-oxidesemiconductor devices. 1 For this purpose, in addition to a high value, a large conduction band offset ͑CBO͒ and the thermodynamical stability on silicon are required. Rare-earth ͑RE͒ oxides and silicates are high-materials generally satisfying these requirements. [2][3][4][5] In addition, Lu silicates are expected to exhibit a high crystallization temperature, and high transverse optical ͑TO͒ mode frequencies ͑and therefore moderate remote phonon scattering 6 ͒. All these properties make these materials interesting for applications in microelectronics. 1 This work investigates Lu silicate films grown by atomic layer deposition ͑ALD͒, a technique employed in microelectronics because of the smoothness, conformality, 7 and good electrical characteristics 8 of the deposited films. For RE silicates, there are in general two approaches for their growth using ALD. One is to use Si-containing RE precursors; the other involves a precursor for Si and another one for the RE element. In both cases, oxygen sources such as O 2 , O 3 , or H 2 O are needed to form SiO 3 2− species. The first approach is appealing because it does not require Si precursors, often delivered as flammable, explosive, toxic, or even pyrophoric gases or liquids. Thus we are interested in the first approach 9 and therefore in molecular species in which a direct RE-Si bond exists. To date few such complexes are known. 10 Among them, the low coordinate RE bis͑trimethylsilyl͒amides complexes ͓͑Me 3 Si͒ 2 N͔ 3 RE ͓where RE = Sc, 11 Y, 12 Ce, 13 Nd, 14 Eu, 11 Dy, and Er, 15 Yb ͑Ref. 16͔͒ are worthy of mention because in some of them an agostic interaction of the central RE atom with the methyl groups and...

Synthesis of Doped, Ternary, and Quaternary Materials by Atomic Layer Deposition: A Review

“…34,40,44,48,106,173,174 A number of studies have successfully deposited Si-containing materials by ALD by using precursor strategies other than supercycles. These strategies include co-dosing multiple precursors simultaneously (Figure 3b), 34 combining Si with another element in a multiconstituent precursor (Figure 3c), 44,48,150,167,168 or using an alkoxide-containing precursor with no separate co-reactant (Figure 3d). 40,52,175−185 These approaches have allowed for the synthesis of Si-containing compounds that might have otherwise been very challenging to grow via ALD, illustrating that these strategies are worth exploring for other interesting but difficult chemistries.…”

“…In the majority of cases found in Tables –, the supercycle scheme is used to combine two separate binary ALD processes that share one element (e.g., O, N, S) into a single ternary process. Some studies implement deposition with multiconstituent precursors to introduce more than one atom into the film with a single precursor, ,,− ,,,,− and others eschew the supercycle pulsing strategy in other ways ,,,− ,− as discussed in Section ; however, these are far less common among the works shown in the tables. Regarding the use of these alternative approaches, Si-containing compounds are of particular note as SiO 2 itself is often difficult to grow on its own. ,,,,,, A number of studies have successfully deposited Si-containing materials by ALD by using precursor strategies other than supercycles.…”

“…Regarding the use of these alternative approaches, Si-containing compounds are of particular note as SiO 2 itself is often difficult to grow on its own. ,,,,,, A number of studies have successfully deposited Si-containing materials by ALD by using precursor strategies other than supercycles. These strategies include co-dosing multiple precursors simultaneously (Figure b), combining Si with another element in a multiconstituent precursor (Figure c), ,,,, or using an alkoxide-containing precursor with no separate co-reactant (Figure d). ,,− These approaches have allowed for the synthesis of Si-containing compounds that might have otherwise been very challenging to grow via ALD, illustrating that these strategies are worth exploring for other interesting but difficult chemistries. Because of contamination concerns, however, the vast majority of the ternary and quaternary processes outlined above avoid halogenated precursors or precursors containing elements other than C, N, H, and O, which can limit the options for precursor chemistries in multicomponent processes.…”

Lanthanide N,N-Dimethylaminodiboranates as a New Class of Highly Volatile Chemical Vapor Deposition Precursors

“…Polymerization can be prevented by incorporating additional Lewis bases into the metal coordination spheres, but heating often results in dissociation of the Lewis bases (and a return to a polymeric structure) rather than sublimation. Lanthanide precursors that do have sufficient volatility for CVD and ALD applications typically employ anionic ligands that either are sterically bulky, such as silylamides, − or are multidentate (or polyhapto), such as β-diketonates, − cyclopentadienyls, − amidinates, − and guanidinates. − Neutral chelating donors (such as glymes) are often employed to fill remaining vacancies in the coordination sphere, sometimes by grafting them onto the anionic ligands. Examples of these ligand types include ether-functionalized β-ketoiminates , and alkoxides. − Several reviews of lanthanide precursors and their use in CVD and ALD have been published. ,,,,− …”

High-Performance Amorphous InGaZnO Thin-Film Transistors With HfO₂/Lu₂O₃/HfO₂ Sandwich Gate Dielectrics

“…1(b) shows the O 1s XPS spectra of the Lu 2 O 3 and HLH dielectric films with their appropriate peak curve-fitting lines. In the two sets of spectra, the O 1s peaks at 529.6 and 531.8 eV for Lu 2 O 3 film represent the Lu 2 O 3 [14] and Lu(OH) x [15], while at 530.2 and 531.3 eV for HLH film is assigned to the HfO 2 [16] and nonlattice, respectively. The O 1s peak of the Lu 2 O 3 film has a large intensity peak corresponding to Lu(OH) x .…”