Copper Seed Layer Research Articles

Integration of Atomic Layer Deposition-Grown Copper Seed Layers for Cu Electroplating Applications

A plasma-enhanced atomic layer deposition (PEALD) copper process, using Cu(II) acetylacetonate and atomic hydrogen, was developed for Cu seed applications in nanoscale semiconductor processing. In this paper, the integration characteristics of PEALD Cu with electroplated Cu for advanced interconnect applications were investigated. Superconformal electroplated [electrochemical deposition (ECD)] copper was demonstrated on PEALD Cu-seeded high aspect ratio patterned structures. The filling characteristics of ECD/PEALD-grown Cu were compared with those of a conventional ECD/physical vapor deposition (PVD)-grown Cu stack. Void-free electroplated Cu was demonstrated on 60 and 35 nm patterned via structures using both atomic layer deposition Ru/TaN and conventional PVD Ta/TaN liner/barrier structures coupled with PEALD Cu seed layers. The resulting integration characteristics suggest that electroplated/PEALD Cu is a promising integration approach for emerging complementary metal oxide semiconductor metallization applications.

Atomic Layer Deposition of Copper Seed Layers from a (hfac)Cu(VTMOS) Precursor

Copper is an alternative material to aluminum that has been used as an interconnection material in metallization for large-scale integrated circuits because of its favorable electrical conductivity (1.67 -cm) and superior resistance to electro-migration. Cu metallization by ECD (electrochemical deposition) requires a seed layer of Cu, which should have a continuous and smooth lm surface, in order to achieve Cu superlling. High-quality Cu thin lms were deposited on TiN/Si substrates by using a radio-frequency plasma-enhanced atomic layer deposition (RF-PEALD) technique and a hexa uoroacetylacetonate copper vinyltrimethoxysilane [(hfac)Cu(VTMOS)] precursor. The variation in the lm's growth mode with the substrate temperature was investigated at temperatures between 150 { 350 C. As the vertical growth rate increase at the temperatures above 200 C, forming a continuous thin lm is di cult and the resistivity increases due to voids between grains and due to surface scattering.

ベンゾトリアゾール誘導体のマイクロコンタクトプリンティングを利用するＵＬＳＩ銅微細配線の形成

This report describes a new process for ULSI minute copper-wiring formation. It relies on microcontact printing [μCP] of polyethylene glycol bis(1,2,3-benzotriazolylether) [PBTA]—synthesized from polyethylene glycol and benzotriazole—to the surface of copper seed layer, with preferential copper electrodeposition in PBTA-free regions (contact hole and trench) using an acid copper sulfate bath. The copper electrodeposition was done using an insoluble anode in the basic bath without additives. The microcontact printed PBTA on the copper seed-layer surface strongly inhibits copper electrodeposition. Using this process, because of the effect of site-selective printing of PBTA, a minute contact hole can be filled completely with copper without causing voids and seams.

Barrier and Copper Seedlayer Wet Etching

This paper summarizes the process development of TiN barrier etching in presence of copper, for a thick copper level in BICMOS technology. In an industrial context, we have chosen to use a SC1 chemistry in a spin etch single wafer tool. The SC1 composition and therefore the pH level allows - the barrier to be etched with no metallic residues, ( if not clear this can be a source for shorts) - control of the selectivity between copper and TiN - control of lateral etching under copper lines, the possible source of open chains by W attack during TiN etch. The electrical results show a robust process according to current specifications, in terms of leakage and via resistance with a fresh chemistry approach. In fact, the recirculation of SC1 is not possible due to substantial concentration changes during processing, high evaporation rate of Ammonia and high decomposition rate of Peroxide in the presence of copper on surface wafer.

A Potential Novel Two-Step MOCVD of Copper Seed Layers

The feasibility of using a novel metallorganic chemical vapor deposition (MOCVD) technique to achieve the deposition of a thin and conformal copper film was examined. The deposition procedure consisted of two consecutive steps: an oxide deposition step followed by a reduction step. Copper(II)-1,1,1,5,5,5-hexafluoro-acetylacetonate hydrate was used as the copper precursor and water as the additive. The preformed copper oxide thin film was reduced to an elemental copper metal film through exposure to ethyl alcohol. The proposed two-step MOCVD method was found to succeed in forming smooth and continuous thin copper films.

New copper seed-layer enhancement process metrology for advanced dual-damascene interconnects

The extendibility of the physical vapor deposition (PVD), seed-layer deposition process for future devices needs to be enhanced with electrochemical techniques. Developing analytical techniques for the plating bath is a particular challenge because bath ingredients are often proprietary and difficult to ascertain. The feasibility of using an ion chromatography for an electrochemical copper, seed-layer enhancement (SLE) process metrology is studied. It is shown that the ion-chromatography method can be used to precisely determine the composition dynamics in a copper SLE plating bath. The bath concentration dynamics are found to be significant in influencing the electroplated Cu film properties, i.e., the resistivity and surface roughness. An excellent correlation exists between the ion chromatograms and the electroplated Cu film properties, suggesting that the ion-chromatography method is a powerful method.

Effects of Post-deposition Annealing on the Copper Films Electrodeposited on the ECR Plasma Cleaned Copper Seed Layer

Thin copper films were grown by electrodeposition on copper seed layers which were grown by sputtering of an ultra-pure copper target on tantalum nitride-coated silicon wafers and subsequently, cleaned in ECR plasma. The copper films were then subjected to ⅰ) vacuum annealing, ⅱ) rapid thermal annealing (RTA) and ⅲ) rapid thermal nitriding (RTN) at various temperatures over different periods of time. XRD, SEM, AFM and resistivity measurements were done to ascertain the optimum heat treatment condition for obtaining film with minimum resistivity, predominantly (111)-oriented and smoother surface morphology. The as-deposited film has a resistivity of ∼6.3 <TEX>$\mu$</TEX><TEX>$\Omega$</TEX>-cm and a relatively small intensity ratio of (111) and (200) peaks. With heat treatment, the resistivity decreases and the (111) peak becomes dominant, along with improved smoothness of the copper film. The optimum condition (with a resistivity of 1.98 <TEX>$\mu$</TEX><TEX>$\Omega$</TEX>-cm) is suggested as the rapid thermal nitriding at 400oC for 120 sec.

Selective Copper Deposition on Barrier Layer Ta and TaN in the Presence of a Copper Seed Layer

Electrochemical deposition of copper on exposed barrier layer (Ta and TaN) was carried out without deposition on an existing Cu seed layer on the same substrate. This was accomplished by immersing the sample in a solution of 1 mM 1-dodecanethiol (RSH) in ethanol, where preferential adsorption of a self-assembled monolayer of RSH deactivated the copper surface. The Cu seed layer could be reactivated again by applying a negative potential pulse. Such an externally controlled reversible change in surface chemistry toward copper deposition is potentially useful for a copper seed layer repair in the fabrication of contacts and interconnects for integrated circuits. © 2003 The Electrochemical Society. All rights reserved.

Electroplating of Copper Conductive Layer on the Electroless-Plating Copper Seed Layer

High resistivity and peeling have been problems with electroless copper layers preventing their use as a seed layer. Further, when copper is electroplated onto this seed layer, the resistivity is as high as 4.0 μΩ cm, much higher than the 2.2 μΩ cm value when plated on a physical vapor deposition (PVD) seed layer. This paper describes the deposition of low resistivity in copper conductive layer on the electroless-plating copper seed layer. The resistivity of the as-deposited layer decreases from 4.0 to 2.7 μΩ cm as the grain size increases from 33 to 42 nm. The grain size and resistivity of the copper layer correlate with the stress in the copper conductive layer and in seed layers. The grain growth can be enhanced by reducing the stress in the copper seed layer. A low stress and highly (111) oriented seed layer can be deposited with nucleation control. Stress reduction can also be achieved by employing the agglomeration process for the seed layer. A resistivity of 2.2 μΩ cm was attained in this conductive layer electroplated from copper hexafluorosilicate electrolytic solution on the low stress seed layer. This resistivity is comparable to the value obtained in a conventional electroplated copper layer on the PVD seed layer.

Effects of Post-Deposition Annealing on the Copper Films Electrodeposited on the ECR Plasma Cleaned Copper Seed Layer

Thin copper films were grown by electrodeposition on copper seed layers which were grown by sputtering of an ultra-pure copper target on tantalum nitride-coated silicon wafers and subsequently, cleaned in ECR plasma. The copper films were then subjected to i) vacuum annealing, ii) rapid thermal annealing (RTA) and iii) rapid thermal nitriding (RTN) at various temperatures over different periods of time. XRD, SEM, AFM and resistivity measurements were done to ascertain the optimum heat treatment condition for obtaining film with minimum resistivity, predominantly (111)-oriented and smoother surface morphology. The as-deposited film has a resistivity of ∼6.3 µΩ·cm and a relatively small intensity ratio of (111) and (200) peaks. With heat treatment, the resistivity decreases and the (111) peak becomes dominant, along with improved smoothness of the copper film. The optimum condition (with a resistivity of 1.98 µΩ·cm) is suggested as the rapid thermal nitriding at 400°C for 120 s.

Properties of Copper Layers Deposited by Electroplating on an Agglomerated Copper Seed Layer

This paper describes the properties and adhesion strength of electroplated copper layers deposited onto two different seed layers. In a thin (10 nm) seed layer, which we term seed layer A, agglomeration occurs across the full thickness of the layer and a stress free or lower stress seed layer is formed with an annealing at 400°C. A highly (111)-oriented copper conductive layer is the result of this electroplating strategy. The adhesion strength is so high (40 gf) that no peeling occurs during chemical mechanical planarization (CMP) in this layer. When the layer is electroplated onto a thick (100 nm) seed layer, which we term seed layer B, agglomeration only occurs at the interface with Ta barrier layer with this annealing. Although a smooth copper layer still remains at the surface, a weakly (111)-orientated copper layer is electroplated. The adhesion strength of this type of copper layer is as low as 10 gf so that peeling can easily occur both during annealing and CMP. Correlation is found between the critical pressure defined by the pressure occurring of the peeling in the copper layers during the CMP with adhesion strength. © 2002 The Electrochemical Society. All rights reserved.

Effects of Rapid Thermal Annealing after Plasma H2 Pretreatment of the Copper Seed Layer Surface on Copper Electroplating

In ULSI fabrication, copper is widely accepted as a new interconnect material to replace aluminum and its alloys due to its low resistivity and high electromigration resistance. Cu seed layers for copper electroplating were deposited by magnetron sputtering on silicon wafers using TaN as diffusion barriers between the seed layer and silicon. Effects of plasma H2 pretreatment and also the combined effects of plasma H2 pretreatment and rapid thermal annealing of the Cu seed layers have been investigated on the physical properties including the resistivity, the grain size and the surface roughness of the electroplated copper films. The best physical properties were obtained for the electroplated copper film on the TaN film the surface of which was given the plasma H2 treatment at the rf-power of 100 W for 10 min followed by rapid thermal annealing at 350°C for 30 s. The mechanism of the cleaning process has also been discussed.

Control of Agglomeration on Copper Seed Layer Employed in the Copper Interconnection

Control of Agglomeration on Copper Seed Layer Employed in the Copper Interconnection

Stress in Copper Seed Layer Employing in the Copper Interconnection

Stress of copper seed employing in the copper interconnection layer is studied. Since this stress affects largely the adhesion strength at the Cu/barrier layers and the Cu~111! orientation of copper layer, reduction of stress is important. Higher and high stresses are applied in the layer on TaN and Ta barrier layers. These layers can lead to poor adhesion strength. Much better adhesion strength can be accomplished in the layer on the TaSiN barrier layer. The surface changes to rough surfaces with annealing at 400°C in the layer deposited on TaN. The highly stressed layer changes to a low stress layer as a result of this agglomeration. However, a smooth surface is held in the low stress layer on the TaSiN barrier layer. © 2001 The Electrochemical Society. @DOI: 10.1149/1.1399876# All rights reserved.

Effects of copper seedlayer deposition method for electroplating

We have investigated copper seedlayer deposition using both ionized physical vapor deposition (IPVD) and collimation methods by depositing similar films into single and dual damascene structures. Step coverage measurements using transmission electron microscopy indicated that IPVD seedlayers exhibited better bottom and sidewall coverage as compared to collimated seedlayers. Subsequent electroplating of contact structures did not indicate differences in the quality of the filling when observed using scanning electron microscopy (SEM). However electrical testing of 68 000 link dual damascene via chains did show improved chain yield for the IPVD deposited films. Cross sections of the chains revealed small voids at the bottom of some of the vias deposited using collimated seedlayers, while no voiding was observed for the IPVD copper films. Finally SEM examinations of unfilled dual damascene cross sections indicated the IPVD copper seedlayer morphology to be rougher as compared to copper films sputtered using collimation.

Organic Solution Deposition of Copper Seed Layers onto Barrier Metals

AbstractSpontaneous deposition of copper seed layers from metal bearing organic based solutions onto sputter deposited titanium, titanium nitride, and tantalum diffusion barrier thin films has been demonstrated. Based on electrochemically driven cementation exchange reactions, the process was used to produce adherent, selectively deposited copper metal particulate films on blanket and patterned barrier metal thin films on silicon substrates. The organic solution deposited copper films were capable of acting as seed layers for subsequent electrolytic and electroless copper deposition processes using standard plating baths. Electroless and electrolytic copper films from 0.1µm to 1.0µm thick were produced on a variety of samples on which the organic solution copper acted as the initial catalytic seed layer. The feasibility of using organic solution deposited palladium as a seed layer followed by electroless copper deposition has also been demonstrated. In addition, experiments conducted on patterned barrier metal samples with exposed areas of dielectric such as polyimide indicated that no organic solution copper or palladium deposition occurred on the insulating materials.

Effects of collimator aspect ratio and deposition temperature on copper sputtered seedlayers

We have investigated the effects of collimator aspect ratio and deposition temperature of copper seedlayers to improve conformality in aggressive single and dual damascene structures. Collimation filters of various aspect ratios were used to deposit copper seedlayers which were then filled using electrodeposition. It was found that collimators of 1.0 aspect ratio resulted in the best seedlayer conformality, as evidenced by film structure coverage and quality of plating fill. Further, electrical testing using 68 000 via chains also showed the average via resistance to be lowest and the chain opens yield to be highest with the 1.0 aspect ratio condition. Finally, thermal effects on seedlayer conformality were examined by varying the wafer temperature during deposition. It was observed that deposition temperatures of 100 °C and lower resulted in smoother films as compared to seedlayers deposited at 200, 300, or even 400 °C.

Atomic Layer Deposition of Copper Seed Layers

Deposition of thin and conformal copper films has been examined using atomic layer deposition as possible seed layers for subsequent electrodeposition. For this investigation, the copper films were deposited on glass plates as well as on , , and films on silicon wafers. Typical resistivities of these films ranged from for thick copper films to for thick films. The adhesion of the copper films deposited on and at was excellent. These films were highly conformal over high aspect ratio trenches. ©2000 The Electrochemical Society