Advanced CMP Research Articles

Development of polystyrene/polyaniline/ceria (PS/PANI/CeO2) multi-component abrasives for photochemical mechanical polishing/planarization applications

Tri-layer nanostructured polystyrene/polyaniline/ceria (PS/PANI/CeO2) multi-component composites were developed as functionalized particle abrasives for improved photochemical mechanical polishing/planarization (PCMP) applications. The physicochemical characteristics of the PS/PANI/CeO2 and PS/CeO2 samples were examined by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Flourier-transform infrared spectroscopy, UV–visible spectrophotometer, photoluminescence spectroscopy, and thermogravimetric analysis. Ultra-smooth and defect-free surfaces with ultra-low roughness (0.12 nm Ra, 0.16 nm RMS) were achieved after PCMP with polymer/CeO2 hybrid abrasives. It might be attributed to the enlarged contact area and the decreased indention depth between the particle and the surface, possibly originating from the elastic polymer cores. The synergy of the PANI conductive polymer and the CeO2 particle photocatalyst contributed to improving the separation efficiency of photo-generated carriers, thereby enhancing the photochemical oxidation activity. As expected, the tri-layer PS/PANI/CeO2 abrasives achieved a ca. 69% increment of material removal rate compared to the PS/CeO2. The interfacial contact model and material modification/removal mechanism of the PS/PANI/CeO2 multi-component tri-layer abrasives during PCMP processes were also discussed. The aim of this work is expected to provide guidance for the design and promising applications of novel polymer/CeO2 composite abrasives in advanced CMP, PCMP, electrochemical mechanical polishing (ECMP), and photoelectrochemically combined mechanical polishing (PECMP).

Research on Si (100) crystal substrate CMP based on FA/O alkaline slurry

For the advanced IC technology nodes, the surface quality of the polished silicon substrate surface becomes more and more critical. Haze is used to characterize extremely small pits scatter light disproportionately at the angle of measurement (90°), and Haze collected on full wafer scale with high throughput is the key CMP output parameter in an advanced CMP process. In this study, the influence of surface defects especially scratch, particle contamination, and surface roughness on Haze was investigated. The results indicate scratch and particle contamination take some influence on Haze, and Haze increases quickly with the increasing of surface roughness. So it can be concluded that surface roughness is the key affecting factor of Haze. In addition, the influence of FA/O surfactant in the alkaline slurry on Haze was studied. The results show FA/O surfactant can effectively decrease Haze. Finally, the advantages of the FA/O alkaline slurry were exhibited by the contrast experiments. A much lower level of metallic ions residual and a much better WIWNU were gotten for silicon wafers polished by FA/O alkaline slurry than that by the commercial one. Hence, the FA/O alkaline slurry provides a high quality silicon wafer surface. The results are helpful for researching the silicon CMP as well as the other materials.

Ru Film Characterization Correlated to Advanced CMP Slurry Performance

Ruthenium has been considered as a barrier liner film for copper in advanced back-end-of-the-line (BEOL) metallization schemes in particular for the 10 nm and beyond technology nodes [1]. Ru shows a lower resistivity than traditionally used barrier films such as Ta or TaN [2] as well as negligible solubility with Cu [3] and Ru films can be deposited with a variety of techniques like CVD or PVD [4], which makes it an attractive candidate. However, new advanced BEOL barrier CMP slurries will have to be developed for this application and Ru is considered a very hard material and chemically inert. Hence it is a big challenge to develop advanced node Ru CMP slurries. Since Ru films can be deposited with various deposition techniques and onto different substrates the removal rate response of these different films to a given slurry can also be dramatically different. For example we found that the removal with a standard Cu-barrier slurry without any additional additives on Ru film type A was only 20 Å/min whereas it was 200 Å/min on the type B film even though both films had been deposited by PVD. Further investigation of the two films showed that the morphology and in particular the grain size was quite different as shown in the SEM images below. Interestingly, these two images correlate very well with images in [5] of two films which have been deposited at different plasma pressures and the difference in removal rate can be explained by different residual stresses in the two films as a result of the different plasma pressures. In this paper we will present the characterization of several different Ru films by XRF (film density), XRD (crystal structure), SEM (grain size and structure), AFM (surface roughness), XPS (atomic composition), contact angle (surface energy) and film hardness by micro/nano indentation. The analytical results will be correlated to CMP polishing performance and in particular on how the different films respond to rate boosting additives in the slurry. The goal is to be formulate a customized slurry by understanding the properties of individual Ru films.

OS0117 BTA-H_2O_2溶液中におけるCu表面のその場エリプソメトリ

During Cu CMP, Cu surface is oxidized by an oxidizer or a complexiation reagent. To inhibit oxidation, a corrosion inhibitor is co-added in the slurry. Balancing oxidation and surface passivation is of importance in advanced Cu CMP. Layer formation onto clean Cu surfaces in BTA (C_6H_5N_3)-H_2O_2 aqueous solutions was studied by using in-situ spectroscopic ellipsometry. Time changes in an ellipsometric parameter, Δ, which corresponds to the layer thickening, were discussed with respect to BTA and H_2O_2 concentrations. BTA forms a passivation layer and the oxidation from H_2O_2 precedes that. Too high addition of BTA accelerates the layer formation. Competition between oxidation and passivation is discussed.

Microreplicated Pad Conditioner for Advanced CMP Applications

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Novel Post Cleaning Solutions for Next Generation Cu CMP Application

An effective post CMP cleaning process has become a crucial technology to determine whether CMP technology can be successfully applied in semiconductor industry. As semiconductor fabrication technology advances and a variety of new applications emerge, there is an increase in demand on apply CMP and post-cleaning technology to new materials. It is challenging to develop a clean chemistry compatible with various applications. In this study, the cleaning solution design concept for advanced Cu CMP process is discussed and a novel alkali clean chemistry is proposed. The performance of the new clean chemistry was investigated and compared to industry benchmark products. Based on the data of inorganic particle removal, organic residue removal, Cu etching rate, roughness, Cu corrosion and defectivity on Cu/ULK wafers, the proposed clean chemistry showed promising performance in advanced applications.

Study on Effects of Slurry Key Factors on Advanced Oxide CMP Performance

With the advancement of technology nodes, the demands on oxide CMP have become more stringent. Defectivity, rate, profile, selectivity to various films (in special applications), planarization efficiency, process window, as well as costs, are the main considerations in an advanced oxide CMP process. Polishing rate and profile tuning by slurry formulations are challenging in certain silica based slurry systems. In this paper, various designed, novel additives are explored to enhance oxide CMP performance. The effects of key factors including abrasive types, chemistry, and pH range on within wafer non-uniformity, especially on the wafer edge rate drop, have been studied. The results indicated that a controlled removal rate and desired wafer edge profile can be achieved through the optimum combination of functional chemistry compositions, abrasive type and properties, and pH. A number of possible mechanisms will also be discussed.

Advanced Pad Conditioner Design for Oxide/Metal CMP

Advanced CMP conditioner design requires investigations of key conditioner manufacturing parameters and their effects on pad surface and then wafer performance. In the present investigation, diamond shape, concentration, distribution, and other key manufacturing parameters are considered to improve CMP process stability and conditioner life. Self avoiding random distribution () of diamond abrasives has been developed and both numerical simulation and experimental results show very stable and reliable polishing performance.

Characterizing STI CMP Processes with an STI Test Mask Having Realistic Geometric Shapes

AbstractChemical mechanical polishing (CMP) has become the enabling planarization method for shallow trench isolation (STI) of sub 0.25μm technology. CMP is able to reduce topography over longer lateral distances than earlier techniques; however, CMP still suffers from pattern dependencies that result in large variation in the post-polish profile across a chip. In the STI process, insufficient polish will leave residue nitride and cause device failure, while excess dishing and erosion degrade device performance.Our group has proposed several chip-scale CMP pattern density models [1], and a methodology using designed dielectric CMP test mask to characterize CMP processes [2]. The methodology has proven helpful in understanding STI CMP; however, it has several limitations as the existing test mask primarily consists of arrays of lines and spaces of large feature size varying from 10 to 100 μm. In this paper, we present a new STI characterization mask, which consists of various rectangular, L-shape, and X-shape structures of feature sizes down to submicron. The mask is designed to study advanced STI CMP processes better, as it is more representative of real STI structures. The small feature size amplifies the effects of edge acceleration and oxide deposition bias, and thus enables us to study their impact better. Experimental data from an STI CMP process is shown to verify the methodology, and these secondary effects are explored. The new mask and data guide ongoing development of improved pattern dependent STI CMP models.

Integration Challenges of Inorganic Low-K (K≤2.5) Materials with CU for Sub-0.25μm Multilevel Interconnects

AbstractThe recent introduction of dual inlaid Cu and oxide based interconnects within sub-0.25μm CMOS technology has delivered higher performance and lower power devices. Further speed improvements and power reduction may be achieved by reducing the interconnect parasitic capacitance through integration of low-k interlevel dielectric (ILD) materials with Cu. This paper demonstrates successful multi-level dual inlaid Cu/low-k interconnects with ILD permittivities ranging from 2.0 to 2.5. Integration challenges specific to inorganic low-k and Cu based structures are discussed. Through advanced CMP process development, multi-level integration of porous oxide materials with moduli less than 0.5 GPa is demonstrated. Parametric data and isothermal annealing of these Cu/ low-k structures show results with yield comparable to Cu/oxide based interconnects.

Integration Challenges of Inorganic Low-K (K≤2.5) Materials with Cu for Sub-0.25µm Multilevel Interconnects

AbstractThe recent introduction of dual inlaid Cu and oxide based interconnects within sub-0.25μm CMOS technology has delivered higher performance and lower power devices. Further speed improvements and power reduction may be achieved by reducing the interconnect parasitic capacitance through integration of low-k interlevel dielectric (ILD) materials with Cu. This paper demonstrates successful multi-level dual inlaid Cu/low-k interconnects with ILD permittivities ranging from 2.0 to 2.5. Integration challenges specific to inorganic low-k and Cu based structures are discussed. Through advanced CMP process development, multi-level integration of porous oxide materials with moduli less than 0.5 GPa is demonstrated. Parametric data and isothermal annealing of these Cu/ low-k structures show results with yield comparable to Cu/oxide based interconnects.