Copper Bottom-up Deposition by Breakdown of PEG-Cl Inhibition

102

Chloride ions and polyethylene glycol ͑PEG͒ are used together as additives to copper damascene electroplating baths, in which they suppress deposition. When the Cl − concentration is lower than the order of 1 mM, suppression abruptly breaks down below a critical potential, around which hysteresis between active and inhibited deposition is observed. A mathematical model is presented which successfully predicts the observed Cl − concentration-dependent breakdown of PEG suppression and currentpotential hysteresis. The model assumes that adsorbed Cl − ions are involved in binding of PEG to the Cu surface, and that these ions are incorporated in the deposited film. The expressions for Cl − incorporation and adsorption are consistent with experimental measurements of Cl in deposits. Hysteresis was found to depend on the high sensitivity of polymer surface coverage to the concentration of adsorbed Cl − ions, possibly because each PEG molecule has a small number of binding sites to the surface.

Section: Part Of the Chemical Engineering Commonsmentioning

confidence: 99%

Section: Mathematical Modelmentioning

confidence: 99%

Section: Mathematical Modelmentioning

confidence: 99%

See 1 more Smart Citation

Role of Chloride Ions in Suppression of Copper Electrodeposition by Polyethylene Glycol

Hebert

2005

102

“…In addition, such suppression was not present on the reverse sweep of CV, a known fact that the suppressing species on the copper surface was being incorporated into copper deposit, mitigating the suppressing effects. 37 With the addition of more Cl − , this suppression continues to higher potentials. A full suppression effect was observed at 50 ppm Cl − .…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Formation of Free-Standing 3D Structures Using Injection of Additives

Huang

Gyorgak

Pak

2017

A new method of electrochemical formation of free-standing 3D structures based on the injection of additives that controls the deposition rate was demonstrated using copper-chloride-polyethylene glycol as an example. A densely-packed defect-free pillar was formed upon the injection of chloride-free electrolyte into a chloride-containing electrolyte, where copper deposition was fully suppressed. The effects of diffusion coefficient, injection rate and the distance between injection nozzle and pillar top were evaluated with numerical simulation. A fast diffusion species, a moderate injection rate and a small gap between injection and pillar were found beneficial to obtaining the best contrast in the growth rates between pillar and background. The demonstration of free-standing copper structure in this paper provides an alternative path for electrochemical 3D printing of various metallic materials. Free-standing metallic structures are of interest for various devices. The recently developed additive manufacturing enables the direct formation of such structures without the need of expensive lithography processes.1 Among them, the metal wire feed process 2 was directly adapted from the original extrusion version of polymer 3D printing. 3-5 Extrusion and sintering of metal paste 6 also allow the formation of metal structures. Selective laser melting or sintering [7][8][9] of metal particles can create free-standing or non-attached metallic structures embedded in metal powders.While most of the above processes were heat-based physical processes, chemical reaction based 3D printing processes have been developed typically for direct formation of smaller structures. Tip based electrochemical machining has been widely used in the past to subtractively machine metallic or non-metallic structures for microdevices.10,11 However, electrochemical deposition processes have not been used until more recently for additive formation of 3D metal [12][13][14][15] and conductive polymer [16][17][18] micro-structures. Metal electrodeposition typically involves the reduction of metal ions into metal atoms on a conductive substrate. Therefore, 3D electrodeposition methods taking advantage of a local electrical field, local metal ion or local conductive substrate have been developed. The traditional lithography based electroforming, for example, the through-mask plating and LIGA process are based on the local exposure of conductive substrate. 19 This through mask concept has also been extended to achieve direct formation of nanostructures through local deposition. [20][21][22] Another so-called local electrochemical deposition was invented relying on a locally positioned anode.12-14 Such an anode is typically surrounded by a large insulating material and is closely positioned in a vicinity of the cathode substrate, 23-26 creating a highly local electrical field that enables the deposition to occur only at the location closest to the anode. Recently, Hirt et al. 27 used a modified atomic force microscope tip with fluidic channel to introduc...

“…These super filling processes generally rely on the organic additives in the plating solution, particularly, the suppressor and accelerator. The additive behavior [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and the associated properties of the plated Cu films [19][20][21][22][23][24][25] have been extensively studied. As the dimensions of the state-of-the-art semiconductor devices scale, advanced plating chemistries are demanded to form the structures defect free.…”

mentioning

confidence: 99%

An Electrochemical Method of Suppressor Screening for Cu Plating in Sub-100 nm Lines

Huang¹,

Liu²,

Baker-O'Neal³

2014

A two-step transient method was developed to electrochemically screen suppressor molecules toward the applications in Cu plating chemistry for narrow trenches. The first potential transient with full amount of suppressor was acquired to simulate the potential applied on the wafer, which is largely determined by the plating of the field region on the wafer. A second current transient experiment with the potential controlled by the transients acquired in the first experiment is used to mimic the plating at different locations across the wafer. When different fractional amounts of suppressor are injected into the second experiment, the current transients acquired thereof simulate the plating rate in the trench structure. A slower super filling rate at higher plating current was well predicted by the transient method and was confirmed by filling experiments. A good qualitative correlation was also observed between the current transients and the filling performance of different suppressors. Cu electroplating has been one of the critical steps in the Cu interconnect technology, which has been used for over a decade in semiconductor and microelectronic devices.1,2 The Cu electroplating is a so called super-conformal filling or super filling process, where the deposition rate at the bottom of a structure is much faster than the rate at the top of the structure so that the structure is filled void free. These super filling processes generally rely on the organic additives in the plating solution, particularly, the suppressor and accelerator. The additive behavior 3-18 and the associated properties of the plated Cu films [19][20][21][22][23][24][25] have been extensively studied. As the dimensions of the state-of-the-art semiconductor devices scale, advanced plating chemistries are demanded to form the structures defect free.The mechanism of the super conformal filling has been studied extensively. A widely adopted mechanism was proposed by Moffat et al. [9][10][11][12] and West et al., 13 where an accumulation and crowding of the accelerator was proposed to occur on the Cu surface at the bottom of the structure due to a continuous shrinkage of the Cu growth front surface area during plating. This so-called curvature enhanced accelerator coverage (CEAC) hypothesis is in agreement with the observations that the accelerator floats on top of the Cu surface during plating 11 and that the plating rate suppressed by the suppressor is promoted by the accelerator due to a displacement or disruption of the surface passivation film. 12 The CEAC model therefore successfully explains a faster local plating rate at the bottom of the feature, resulting in the super filling. The CEAC mechanism also predicts a bump formation on top of dense patterns of small structures due to the locally high surface coverage of accelerator after the structures are filled. 10,13 In addition, the CEAC mechanism predicts that a pre-treatment of the Cu substrate in a more concentrated accelerator solution can provide a higher initial coverage of accelerator...