James A. Sellers

X-ray photoelectron spectroscopy characterization of the oxidation of electroplated and sputter deposited copper surfaces

X-ray photoelectron spectroscopy (XPS) was used to study the surface oxidation of sputtered and electroplated copper films following exposure to ambient air and chemical processing reagents used during the fabrication of interconnect structures. Exposure of both sputtered and electroplated copper films to ambient air and deionized (DI) water resulted in the formation of thin copper oxide layers. For ambient exposed copper films, the topmost layer contains Cu2+ oxide species, and the next Cu+ oxides. For DI water exposure, only Cu+ oxide species were observed. Oxidation was more rapid for the electroplated compared to the sputtered copper films as measured by copper oxide to copper metal concentration ratios calculated from XPS curve fitting results and photon-induced Auger peak height measurements. For the electroplated copper films, oxygen uptake was slower as a result of exposure to ambient compared to DI water treatments. Electroplated copper films exposed to common wet chemical etchants also show indications of oxidation of the copper surface region with evidence of mechanical instability between the formed oxide and underlying copper film, resulting in adhesion loss. A method for the removal of the oxide layer has also been investigated to improve adhesion to overlying passivation films.X-ray photoelectron spectroscopy (XPS) was used to study the surface oxidation of sputtered and electroplated copper films following exposure to ambient air and chemical processing reagents used during the fabrication of interconnect structures. Exposure of both sputtered and electroplated copper films to ambient air and deionized (DI) water resulted in the formation of thin copper oxide layers. For ambient exposed copper films, the topmost layer contains Cu2+ oxide species, and the next Cu+ oxides. For DI water exposure, only Cu+ oxide species were observed. Oxidation was more rapid for the electroplated compared to the sputtered copper films as measured by copper oxide to copper metal concentration ratios calculated from XPS curve fitting results and photon-induced Auger peak height measurements. For the electroplated copper films, oxygen uptake was slower as a result of exposure to ambient compared to DI water treatments. Electroplated copper films exposed to common wet chemical etchants also show indi...

OXIDATION OF TIN IN AN OXYGEN PLASMA ASHER

In previous work we have studied the thermal oxidation of titanium nitride. This involved temperatures of 350 °C and greater, and times of hours. In this work, we study the oxidation of titanium nitride in a downstream plasma asher, where the sample temperature is about 200 °C. For comparison to an older technology, we also include samples oxidized in a barrel asher where the sample temperature was about 100 °C. Oxidation times of 16 min and less were studied. Thickness and optical constants were measured using ellipsometry along with Auger electron spectroscopy with argon ion etching for depth profiles. The growth kinetics are shown to be logarithmic. In the down‐stream asher, films form in 90 s which would require 40 min at 450 °C if grown thermally. We show that only the thinner films can be etched off in 50:1 HF.

An inorganic anti-reflective coating for use in photolithography

In this work, we discuss the design of an inorganic anti‐reflective coating for use in photolithography at a wavelength of 3650 A (I line). We consider the effect of the optical constants on the reflectance and show that when the extinction coefficient, k, of the film has a value near 0.8, the reflectance will be very small for a range of values of the thickness and the index of refraction, n. We illustrate the principle with one example where we use a combination of TiW and the oxide of TiW. Reflectance is measured for a range of thicknesses of both the TiW and the oxide of TiW. Values less than 5% were obtained.

A comparison of a two layer metal system built with selective CVD W plugs and elevated temperature, sputtered Al(Cu)

Summary form only given. Advanced ULSI circuits require minimum features <or=1.0 mu m to maximize packing density. In addition, metal line pinches must be approximately 2.0 mu m and vias <or=1.0 mu m with straight walls. Thicker interlevel dielectrics for capacitance reduction mean that the aspect ratio (height/width) of vias must be approximately 1.0. These high aspect ratios greatly reduce the step coverage of sputtered metal causing two potential problems: (1) increased via resistance and (2) sources of reliability failure. To study these issues, the authors used a double-level metal vehicle with a range of metal 1 pitch of 1.75-3.0 mu m, a metal 2 pitch range of 3.0-4.5 mu m, and a range of via sizes from (0.75 mu m)/sup 2/ to (1.5 mu m)/sup 2/. The via chains using W to achieve an approximately 100% via fill had excellent results. All chains were continuous and the average resistance/via was 0.33, 0.19 and 0.13 Omega for the (0.75 mu m)/sup 2/, (1.0 mu m)/sup 2/, and (1.25 mu m)/sup 2/ via chains, respectively. The standard deviation across a wafer in each case was less than 2%. When the Wfills were 75% on the smallest vias the step coverage from 325 degrees C sputtered AlCu was poor; causing some opens and an increase in the mean and standard deviation of the Omega /via. On larger vias with same percent fill, the chains were continuous, but the resistance was greater than for the 100% fills. This is an issue when the vias have different depths due to underlying topography.<<ETX>>

Submicron two‐layer metal system of selective tungsten and TiW cap metallization

The processing options available to fabricate multilevel metal interconnects are becoming greatly reduced as circuit dimensions enter the submicron regime. Advanced lithography techniques are required, such as x ray, electron‐beam, or monochromatic steppers. The choice of metal materials is small, due to resistivity and interconnect dimension requirements. Sputter deposition equipment has difficulty in depositing the metal into the high aspect ratio vias and new processes with superior stepcoverage are required. Other processing technologies are also experiencing difficulties as dimensions shrink. This paper discusses the utilization of certain advanced processing technologies, namely: stepper lithography, TiW capped AlCu metallization, chemical vapor deposition (CVD) tungsten, plasma deposited oxide (tetraethylorthosilicate source), and etchback planarization to successfully fabricate a submicron two‐layer metal structure. The test vehicle had via chains increasing in length from 10–8000 vias with dimens...