Examination of Salicylaldehyde as a Surface Modifier of Manganese for Application in Chemical Mechanical Planarization

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Defect-control is a critical requirement for chemical mechanical planarization (CMP) of the ultrathin diffusion barriers considered for the new Cu-interconnects. The challenging task of developing advanced CMP slurries for such systems can be aided by electrochemical evaluations of model CMP schemes under tribological conditions. The present work uses this strategy to characterize an alkaline slurry formulation aimed at minimizing galvanic corrosion in the CMP systems involving Ru, Ta (barrier metals) and Cu (wiring metal). This slurry is based on percarbonate and guanidine additives, and the test metals are polycrystalline disc samples. A particular goal of this study is to explore the essential analytical aspects of evaluating CMP systems in the triboelectrochemical approach. The CMP specific surface reactions are characterized by potentiodynamic polarization and open circuit voltage measurements, performed both in the presence and in the absence of polishing, and by employing abrasive free as well as abrasive (colloidal SiO 2 ) added solutions. The findings of these experiments are further checked by using impedance spectroscopy. The electrochemical mixed potential steps of the CMP promoting reactions are analyzed, and the removable surface species formed by these reactions are discussed. The recent developments in the manufacturing of advanced interconnects have largely centered on the Cu/low-k technology, where the processing challenges are coupled with those of material selection. The introduction of mechanically fragile low-k dielectrics has set strict limits on the usable down-pressure of chemical mechanical planarization (CMP) used in the processing of Cu interconnects. This in turn has driven the strategies for material removal more toward the chemical considerations of CMP, and less reliant on mechanical abrasion.2,3 At the same time, the CMP chemistries of the relatively unconventional new barrier materials have presented other challenges, because in the slurry environment, they often have appeared chemically too inert 4 or too corrosive.5 If the CMP chemistries for these new materials are not properly controlled, the processed wafer can develop surface defects due to erosion and galvanic corrosion activated by the wet CMP process. Such defects are detrimental to device performance, and this issue is particularly relevant for the CMP of ultrathin (< 5 nm) barrier films, where defect-control is often more critical than achieving high rates of material removal. Due to these reasons, the tasks of designing the slurry chemistries for metal CMP have become progressively more complex during recent years. This specific aspect of CMP consumable challenges can be addressed to a large extent by employing laboratory scale evaluations of slurry compositions with electrochemical measurements. The present work is based on this approach.The role of electrochemical reactions (and hence the applicability of electro-analytical tests in this context) is integrated in the overall mechanism of chemically promoted metal-C...

Section: Resultsmentioning

confidence: 99%

Tribo-Electrochemical Characterization of Ru, Ta and Cu CMP Systems Using Percarbonate Based Solutions

Shi

Simpson

Roy

2015

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“…These differences between E corr and E oc originate from the different sample conditions operated in the OCP (zero electrode-current) and potentiodynamic (activated electrode current) measurements. 17,36 The shifts in the values of E corr (as well as those of E oc ) observed for each metal by switching between H and P conditions are caused by correspondingly activated selective changes in the metal's cathodic or anodic function. 18,35 To bring out these latter effects, the polarization plots from Fig.…”

Section: Results Of Ocp Transients and Potentiodynamic Polarization F...mentioning

confidence: 99%

An Alkaline Slurry Design for Co-Cu CMP Systems Evaluated in the Tribo-Electrochemical Approach

Johnson

Wei

Roy

2018

Self Cite

The sub-14 nm technology nodes of integrated circuits require metal components of ultrathin linewidths. The chemical mechanical planarization (CMP) protocols needed to process such structures are associated with several challenges, one of which is to design/screen slurry formulations required to address both the scaling and the nontraditional metal chemistries of these structures. Laboratory scale tribo-electrochemical techniques serve as a cost-effective yet comprehensive means to aid these tasks, and the present work focuses on further quantifying this approach with an alkaline slurry formulation designed to planarize Co diffusion barriers for Cu lines. The CMP strategy uses controlled corrosion in a (potentially abrasive-free) slurry of potassium acetate, hydrogen peroxide, and benzotriazole. The tribo-electrochemical experiments involve open circuit potential transients, current interruption, and potentiodynamic polarization. Material removal rates, normalized with respect to the polisher parameters are analyzed as specific wear rates to quantitatively probe the chemical aspects of CMP. The slurry functions necessary to control galvanic corrosion and CMP selectivity of Co are investigated. The necessity for incorporating tribo-control in these measurements is demonstrated by showing how the results obtained with stationary metal samples could result in misleading conclusions about the galvanic corrosion rates.

“…To eliminate this concern, we used the appropriate Ru/Mn stack in our experiments. While the polishing and corrosion rates of standalone Mn disks and the galvanic corrosion of Cu/Mn were reported recently by Chockalingam et al 24 and Turk et al, 25 there are no similar investigations of Ru/Mn. Since, Mn disks may be expected to behave very differently from very thin Mn films and the associated MnSi x O y it is necessary to work with the Ru/Mn film stack.…”

mentioning

confidence: 89%

Chemical Mechanical Polishing and Planarization of Mn-Based Barrier/Ru Liner Films in Cu Interconnects for Advanced Metallization Nodes

Sagi¹,

Teugels²,

Veen³

et al. 2017

Mn-based (referred to simply as Mn in the following) barrier/Ru liner stack has been proposed to replace TaN/Ta barrier-liner in Cu interconnects for 7 nm and 5 nm technology nodes. During chemical mechanical planarization (CMP) of the associated Cu/Ru/Mn/SiCOH pattern structures, the usual galvanic corrosion and removal rate selectivity issues need to be resolved. In this study, we investigated the polishing and electrochemical behavior of Cu, Mn, Ru and SiCOH films on the relevant substrates in the alkaline region using silica dispersions containing potassium permanganate (KMnO 4 ), guanidine carbonate (GC) and benzotriazole (BTA) and identified compositions that address these challenges. An XPS study of the as-deposited and annealed Mn films confirmed the formation of amorphous manganese silicate (MnSi x O y ), a self-forming dielectric layer, at the Mn/SiCOH interface. A crosssectional TEM analysis of the polished Cu/Ru/Mn/SiCOH patterned wafers (32 nm half pitch Cu lines) with our candidate slurry showed excellent post-polish performance with no corrosion and no post-CMP loss of either Cu or the Mn barrier/Ru liner film. As the node sizes continue to diminish, the 5∼7 nm thick Ta/TaN barrier-liner will occupy a significant portion of the Cu trench resulting in higher effective resistance and increased resistance-capacitance delay.1 Also, with the even smaller feature sizes and high-aspect-ratio trenches of these nodes, deposition of a conformal Cu seed layer on the Ta liner is a major challenge with any discontinuities in it leading to voids in the copper fill and limiting the yield.1 Hence, it has become necessary to replace these Ta/TaN barrier-liner films with thinner and more functional candidate materials. One such candidate is a Mn/Mnbased film since it can form a very thin (∼1 nm) self-forming and excellent Cu diffusion barrier layer of amorphous manganese silicate (MnSi x O y ) at the Mn/low-k (black diamond or SiCOH with k = 2.9 or lower) 1-10 interface. However, this MnSi x O y layer is not conductive enough and requires a thin conductive liner for the deposition of a Cu seed layer. A ∼2 nm thick Ru film with a resistivity of ∼7 μ cm, much lower than that of Ta's ∼13 μ cm, has been proposed 10,11 as such a liner. As always, these film stacks need to be planarized and for effective planarization, as shown in Figure 1, the removal rate (RR) selectivities among the Cu, Ru, Mn and SiCOH or BD layers and the galvanic corrosion between Cu/Ru and Ru/Mn couples need to be controlled. With that goal in mind, we investigated the polishing and electrochemical behavior of the relevant Mn-based barrier/Ru liner stack using silica based dispersions and various additives. For convenience, in the following the Mn-based films will be addressed simply as Mn films.Cu and Ru polishing behavior 12-18 and related corrosion issues [19][20][21][22][23] for barrier applications have been studied by several authors. Among these, Amanapu et al. 18 showed that the underlying substrate can modify the crystalline orientation o...