Esta Abelev

The Compatibility of Copper CMP Slurries with CMP Requirements

Cu is currently used as a replacement for aluminum in IC interconnections. One of the challenges of integrated circuit (IC) interconnection technology is the planarization process that involves fine copper lines patterning; the most perspective technique for Cu lines patterning is chemical mechanical planarization (CMP). CMP is applicable only once a given metal-slurry system can provide certain requirements. Different media, such as ammonium hydroxide (NH 4 OH), peroxide (H 2 O 2 ), ferric nitrite [Fe(NO 3 ) 3 ], and nitric acid (HNO 3 ), with and without the presence of inhibitors, were suggested as potential candidates for copper CMP slurries. In this work we studied the compatibility of these media with CMP requirements. Our work indicated that these slurry solutions (basic and acidic media) do not provide sufficient conditions for a conventional CMP application. The Cu is actively dissolved in all of these solutions and in some of them with high dissolution rate, without a rapid repassivation. The sharp acceleration in Cu etching rate under abrasive abrading can be attributed only to a mechanical Cu removal. It was found that the active dissolution of Cu is conducted through deep intergranular penetrations which may result in the deterioration of thin Cu connectors. This study also shows that the use of benzotriazole or other inhibitors commonly used for reducing the etching rate of the actively dissolved Cu cannot provide the needed conditions for a rapid passive film growth on the copper metal. The electrochemical behavior of Cu in these solutions, morphology of dissolved copper metal surface, and mechanism of copper CMP are discussed.

Electrochemical Behavior of Copper in Conductive Peroxide Solutions

Electrochemical studies of copper in peroxide solution for chemical mechanical planarization applications was conducted in a solution media containing Na 2 SO 4 as an inactive and highly conductive electrolyte salt. The low current values observed during anodic potentiodynamic polarization of copper in peroxide based solutions can be mistakenly interpreted as a development of passivity at the copper surface. Cathodic pretreatment of the copper surface followed by anodic potentiodynamic polarization reveals the formation of an anodic peak at potentials of 0.2-0.3 V SCE . The formation of a dense deposition film of copper oxides at potentials below 0.4 V is attributed to increase in the solution pH at the electrode-electrolyte interface to values above pH 5.5. However, further positive shift in the applied potential decreases the cathodic reduction rate of H 2 O 2 , leading to a decrease in the solution pH values at the electrode/electrolyte interface and consequently, decreases the deposit formation rates covering the copper surface. The addition of benzotriazole (BTA) to peroxide solutions was also studied, and it was revealed that BTA cannot provide the protection needed to the copper surface in this system.

Copper Repassivation Characteristics in Carbonate-Based Solutions

bMax-Planck-Institut fur Eisenforschung, D-40237 Dusseldorf, Germany The present work reports on carbonate-based solutions, which can provide copper passivity in a wide potential range. This report focuses mainly on the identification of copper repassivation features obtained subsequent to mechanical damage of copper passive films in carbonate-based solutions. The repassivation rate of copper in carbonate-based solutions was measured with the use of a slurryjet system. The measured repassivation rate of copper in a slurryjet system utilizing a carbonate-based solution was found to be in the range of 1‐2 ms. An increase in the concentration of carbonate ions leads to a decrease of the copper repassivation time at potentials ranging from 200 to 600 mVAg/AgCl. The impingement angle between the copper surface and the single abrasive particle has an insignificant impact on the repassivation time and characteristics. It is therefore recommended that the use of carbonate anions as a passivating component in a future chemical mechanical planarization slurry design should be considered.

Food Preservatives Serving as Nonselective Metal and Alloy Corrosion Inhibitors

In this short communication we provide a glimpse into the unexpected, intriguing nature of 2,4-hexadienoic acid potassium salt {potassium sorbate [K(CH 3 CH=CHCH=CHCO 2 )]}. namely, its high superiority over other corrosioninhibitors to protect metals and alloys (copper, carbon steel, aluminum, and stainless steel) from surface degradation processes in a wide range of potentials in the presence of corrosive environments.

An alternative isolation of tungsten tips for a scanning tunneling microscope

Experimental results obtained from electrochemical preparation of tungsten followed by a novel insulating technique are reported. An additional effective method for insulation of the electrochemically etched W tips based on cathophoretic paint deposition is described. The cathophoretic paint deposition isolation method was found to be highly reproducible, forming an isolated stable film in both aqueous and nonaqueous organic solvents.

Copper Passivity in Carbonate Base Solutions and its Application in Chemical Mechanical Planarization (CMP)

Abstract Copper is fully passivated in sulfate solutions containing potassium carbonate. The potential range of copper passivity strongly depends on the relationship between sulfate and carbonate concentrations. At potentials above the passivity range copper suffers from localized attack by pitting corrosion. Copper passivity is more pronounced in solutions containing higher carbonate content. The increase in carbonate concentration shifts the breakdown potential towards positive anodic potentials while decreasing the anodic currents values in the region of passivity. In a solution containing carbonate copper passivity was detected in a wide potential range between OCP (~0.15 V SCE ) and ~1.0 V SCE . Increasing the sulfate concentration has the opposite effect on copper passivity than carbonate does.