Chris Werkhoven

Ruthenium films by digital chemical vapor deposition: Selectivity, nanostructure, and work function

Ruthenium electrodes were selectively deposited on photoresist-patterned HfO2 surface [deposited on a SiOx/Si wafer by atomic layer deposition (ALD)] by a manufacturable, digital chemical vapor deposition (DCVD) technique. DCVD of Ru was carried out at 280–320 °C using an alternate delivery of Bis (2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)Ru (dissolved in tetrahydrofuran) and oxygen. The as-deposited Ru films were polycrystalline, dense, and conducting (resistivity ∼20.6 μΩ cm). However, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, and high-resolution electron microscopy results indicate the presence of an amorphous RuOx at the Ru grain boundaries and at the DCVD–Ru/ALD–HfO2 interface. The estimated work function of DCVD–Ru on ALD–HfO2 was ∼5.1 eV. Moreover, the equivalent oxide thickness, hysteresis in capacitance–voltage, and leakage current density at −2 V of the HfO2/SiOx dielectric, after forming gas (95% N2+5% H2) annealing at 450 °C for 30 min, were 1....

Atomic layer chemical vapor deposition of ZrO2-based dielectric films: Nanostructure and nanochemistry

A 4 nm layer of ZrOx (targeted x∼2) was deposited on an interfacial layer (IL) of native oxide (SiO, t∼1.2 nm) surface on 200 mm Si wafers by a manufacturable atomic layer chemical vapor deposition technique at 300 °C. Some as-deposited layers were subjected to a postdeposition, rapid thermal annealing at 700 °C for 5 min in flowing oxygen at atmospheric pressure. The experimental x-ray diffraction, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and high-resolution parallel electron energy loss spectroscopy results showed that a multiphase and heterogeneous structure evolved, which we call the Zr–O/IL/Si stack. The as-deposited Zr-O layer was amorphous ZrO2-rich Zr silicate containing about 15% by volume of embedded ZrO2 nanocrystals, which transformed to a glass nanoceramic (with over 90% by volume of predominantly tetragonal-ZrO2 (t-ZrO2) and monoclinic-ZrO2 (m−ZrO2) nanocrystals) upon annealing. The formation of disordered amorphous regions within some of the nanocr...

Relationships among equivalent oxide thickness, nanochemistry, and nanostructure in atomic layer chemical-vapor-deposited Hf–O films on Si

The relationships among the equivalent oxide thickness (EOT), nanochemistry, and nanostructure of atomic layer chemical-vapor-deposited (ALCVD) Hf–O-based films, with oxide and nitrided oxide interlayers on Si substrates, were studied using x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) in annular dark-field imaging (ADF), and parallel electron energy-loss spectroscopy (PEELS), capacitance–voltage, and leakage-current–voltage measurements. The XPS (Hf 4f binding energy shift) studies indicated the formation of Hf–O–Si bonds in as-deposited amorphous films, the amount of which was influenced by the interlayer composition and annealing conditions. After post-deposition annealing in N2 and O2, the Hf–O layers were nanocrystalline. Although HRTEM images showed a structurally sharp interface between the Hf–O layer and the interlayer, angle-resolved XPS, ADF imaging, and PEELS in the STEM revealed a chemically di...

Cluster-Tool Integrated HF Vapor Etching for Native Oxide Free Processing

Three regimes of HF-H 2 O vapor etching of oxide can be distinguished, viz. a gas phase, an adsorption and a condensation regime with gas phase etching behaving distinctily different in terms of etch rate and surface passivation properties. Integration of a vapor etch process in a vacuum-controlled, leak-tight cluster tool equipped with vertical reactor LPCVD and oxidation modules offers important thin film interface engineering capabilities; significant process control improvement is achievable in critical device technologies, such as formation of poly-contacts, poly-emitters and NO capacitors.

Process control improvements realized in a vertical reactor cluster tool

Advance cell structures present in high-density memories and logic devices require high quality, ultra thin dielectric and conductor films. By controlling the interface properties of such films, remarkable process control enhancements of manufacturing proven, vertical LPCVD and oxidation processes are realized. To this end, an HF/H2O vapor etch reactor is integrated in a vacuum cluster tool comprising vertical reactors for the various LPCVD and oxidation processes. Data of process control improvement are provided for polysilicon emitters, polysilicon contacts, polysilicon gates, and NO capacitors. Finally, the cost of ownership of cluster tool use is compared with that of stand-along equipment.

Influence of Pre and Post Process Conditions on the Composition of Thin Si3N4 Thin Films (3 nm) Studied by XPS and TOFSIMS

With the downscaling of the electronic devices and the increase in the frequency of the electronic circuits, a large search for new gate dielectric is ongoing. The exact composition and element distribution in the dielectric film have a large impact on the electrical characteristics of these films. We studied here the formation of ultrathin Si 3 N 4 films (3 nm) under different conditions and concentrated on their composition analysis. The Si substrates were cleaned using RCA and/or HF dip. The Si 3 N 4 films were subsequently fabricated either by RTCVD (SiH 4 /NH 3 ) either by remote plasma (SiH 4 /N 2 ) with or without a pre-anneal to form a 0.5 nm SiO 2 layer. Post annealing was made using NO, N 2 O or NH 3 at various temperatures and for various times. The quantification of the composition was realized using XPS and elemental distribution was analyzed using TOFSIMS with Ar + sputtering and positive ion detection mode. The results show that the fabrication method of the nitride film has only a very limited influence on the O/N content of the films. However, both the preparations of the substrate (HF last or RCA last) and the post-annealing influence strongly the film composition. The presence of an interfacial oxide increases significantly the oxygen content of the film. Post-annealing with N 2 O also increases the oxygen content of the film while the NH 3 post-annealing leads to a significant decrease. The results are compared with electrical characterization of the same films.

Single Wafer CVD of Silicon Nitride for Cmos Gate Applications

The MESC/CTMC compatible, Advance 2500 cluster tool made by ASM is evaluated for the manufacturing of CMOS gate stack structures based on CVD silicon nitride rather than thermally grown silicon oxide as the gate dielectric material, and polysilicon as the gate electrode material. With two different CVD chemistries excellent growth characteristics and thickness uniformity control of the silicon nitride is demonstrated. Electrical assessment reveals lower leakage current as compared to silicon oxide and minimal hysteresis in C-V curves, even for gates stacks that have an equivalent oxide thickness below 1.5nm. The best properties are for silicon nitride films that also have a low H 2 content.

Application of a cluster tool for control of bipolar polysilicon emitter transistor characteristics

A cluster tool technique featuring a vapor HF clean followed by controlled growth of a thin interfacial oxide prior to polysilicon deposition is described. The tool is used in the fabrication of polysilicon emitter contact bipolar transistors. Parametric data show that base current and beta vary systematically with oxide thickness but other device parameters remain unchanged. An initial assessment of run-to-run-process reproducibility is also described. The tool has significant potential for future BiCMOS processes which will require precision control of the interfacial layer and low- temperature processing.