Sung Gyu Pyo

Interconnect Fabrication by Superconformal Iodine-Catalyzed Chemical Vapor Deposition of Copper

The mechanism behind superconformal filling of fine features during surfactant catalyzed chemical vapor deposition (CVD) is described and the metrology required to predict it is identified and quantified. The impact of adsorbed iodine coverage on copper deposition rate during chemical vapor deposition of copper on planar substrates is determined first. These kinetic parameters are then used in a model based on the curvature-enhanced accelerator coverage mechanism to predict superconformal filling during iodine-catalyzed CVD. In this model, the coverage of the adsorbed catalyst is presumed to change with surface area during interface evolution. The surface area decreases along the bottoms of submicrometer dimension features, increasing the local coverage and deposition rates and thereby enabling superconformal filling. Experimental filling results are then described and shown to be consistent with the predictions.

Development of a Production-Ready, Back-Illuminated CMOS Image Sensor with Small Pixels

A back-illuminated 2 megapixel CMOS sensor utilizing mature wafer manufacturing operations is described. Sensitivity, dark current and other key pixel performance measures are compared against an equivalent conventional sensor. Aspects of the process integration that make the technology manufacturable are described. Simulations that predict the performance of a full color sensor are discussed.

Fabrication of multilayered titanium aluminide sheets by self-propagating high-temperature synthesis reaction using hot rolling and heat treatment

This study is concerned with the fabrication of multilayered and bulk Ti aluminide sheets by self-propagating high-temperature synthesis (SHS) reaction using hot rolling and heat treatment. A multilayered Ti/Al sheet was prepared by stacking thin Ti and Al sheets alternatively. When this sheet was hot-rolled and heat-treated at 1000°C, a multilayered sheet composed of Ti3Al and TiAl was made through the process of formation and growth of intermetallic phases at Ti/Al interfaces and porosity reduction. A bulk Ti aluminide sheet having a lamellar structure of TiAl and Ti3Al was also fabricated successfully by heat treatment at 1400°C.

An Approach to the Development of Organic Additives for Electrodeposition of Narrow Copper Interconnects

We have characterized the electrochemical properties and wetting effects of various organic materials, including selected accelerators, suppressors, and wetters, for the electrodeposition of submicrometer-wide copper interconnects. An additive composition consisting of the following organic chemicals was tested: bis(3-sulfopropyl)-disulfide, disodium salt as an accelerator, polyethylene glycol as a suppressor, and a cross-linked polyamide as a second suppressor (working also as a wetter). Copper films plated using this makeup exhibited a surface roughness of ∼35 nm after annealing, with grain sizes on the order of 0.1-0.5 μm, and an electrical resistivity of ∼ 1.9 μΩ cm. Using this made-up solution, 120 nm wide trenches were successfully gap-filled.

Transmission electron microscopy characterization of mechanically alloyed NiAl powder and hot-pressed product

Abstract NiAl intermetallic powder has been synthesized by mechanical alloying of elemental powders in an attritor mill using controlled atmospheres. The powders contain a bimodal distribution of dispersoids with sizes ranging from 5 to 200 nm. Analytical transmission electron microscopy has been used to establish the types of dispersoid phase present in the powder and the development of the microstructure with processing. In the finished powder the majority of the dispersoids present are either α-alumina or aluminum nitride depending on the process conditions. The grain size in the as-milled powder is nanocrystalline. Two types of hot pressing have been used for consolidation: a simple pressing using an argon cover gas and a vacuum hot pressing. After hot pressing to greater than 97% density, both grain and dispersoid growth are observed to have occurred and the larger dispersoids appear to coarsen in a coupled manner with the grains via a dragging mechanism. Hot-pressed materials show much improved yield strength and ductility compared with the ingot-cast NiAl, indicating the effectiveness of mechanical alloying in improving the mechanical properties.

Metalorganic Chemical Vapor Deposition of Copper Using (Hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) with a Liquid Delivery System.

From variable temperature (VT) 1H-nuclear magnetic resonance (NMR) and a heating test, it was found that (hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) [(hfac)Cu(I)(DMB)] was stable up to 65°C. The effects of various process conditions such as substrate temperature, liquid precursor flow rate and hydrogen carrier gas flow rate on the deposition rate, texture, microhardness, surface roughness and uniformity were studied using a direct liquid injection 200 mm metalorganic chemical vapor deposition (MOCVD) reactor with hollow-cathode magnetron (HCM) sputter-deposited Cu substrate on silicon wafer. The MOCVD Cu process with (hfac)Cu(I)(DMB) showed good conformality, continuous film morphology and low resistivity at a substrate temperature of 190°C, vaporizer temperature of 55°C, total pressure of 2.5 Torr and precursor flow rate of 0.5 cm3/min. X-ray diffraction (XRD) analyses demonstrated a strong (111) texture of the copper film. The higher (111) peak intensity and the narrower width at half maximum were obtained when the source feed rate was low. Also the higher (111) peak intensity was observed at higher substrate temperature. At temperature below about 200°C, the microhardness was increased with increasing substrate temperature. In the high temperature regime (>200°C), the hardness was decreased.

Seam-free fabrication of submicrometer copper interconnects by iodine-catalyzed chemical vapor deposition

Kinetic parameters from studies of deposition on planar deposits are used to predict superconformal filling of fine features during iodine-catalyzed chemical vapor deposition. The mechanism behind the superconformal filling is described and the metrology required to predict it is identified and quantified. The dominant effect is the change in coverage of adsorbed catalyst with the surface area during interface evolution. Experimental filling results are described and are shown to be consistent with the predictions. An associated effect on surface roughness of planar deposits is also described.

SnO2-graphene nanocomposite free-standing film as anode in lithium-ion batteries

SnO2-reduced graphene oxide nanocomposite in the form of a free-standing film was prepared by simple chemical synthesis. The homogeneous and compact formation of the nanocomposite of SnO2 and reduced graphene oxide was confirmed by various analysis methods. When incorporated as anode in lithium-ion batteries, a high capacity (503 mAh g-1) and very stable cycle life were observed. These favorable properties probably arise from the efficient relaxation of high mechanical stress by the reduced graphene-oxide layers during the lithiation-delithiation process within SnO2.

Microstructure and mechanical properties of duplex tiAl alloys containing Mn

A study has been made of the effect of Mn on the structure and compressive mechanical properties of duplex TiAl alloys. In order to clarify the separate effect of Mn and Al contents, the effect of Ti/Al ratio was also studied by analyzing the behavior of alloys with different Ti/Al ratios at the fixed Mn content. Addition of 3 at.% Mn to the binary Ti53Al47 alloy decreases the tetragonality and the unit cell volume of γ structure. It also promotes the formation of twin-related structure, the refinement of interlamellar spacing and grain size, and the increase in the volume fraction of lamellar grains. Increase in Ti/Al ratio at the fixed Mn content results in the further decrease in the tetragonality and unit cell volume and the refinement of grain size, while it decreases the volume fraction of lamellar grains. The modification of microstructure directly influences the compressive properties and deformation mode of duplex TiAl alloys. It has been found that Mn addition and increase in Ti/Al ratio enhance the plasticity of duplex alloys. Generation of mobile dislocations at the twin intersections has been found to occur in Mn containing alloys. Such dislocation generation at the twin intersections as well as the promotion of deformation twins in Mn containing alloys are all beneficial for improving the ductility of duplex TiAl alloys.

Effect of planarity on the 3D integration in 3-D integrated CMOS image sensor

In this work, some of the tradeoffs that need to be considered in optimizing a back-illuminated (BSI) sensor were described. The manufacturing feasibility of a BSI CMOS image sensor was demonstrated and compared between the front-illuminated (FSI) and back-illuminated (BSI) versions of the sensor with the same fabrication process. 3D integration processes were evaluated to get stable performance of BSI CMOS image sensor.The broadband quantum efficiency (81% for BSI) improved 2.7 times over FSI sensitivity.