The feasibility of integrating a low permittivity spin-on hardmask (SoHM) into a Cu dual damascene structure using SiLK* Semiconductor Resin (*trademark of The Dow Chemical Company) has been investigated. The study focussed on the replacement of the embedded etch stop deposited by chemical vapor deposition (CVD) by a low permittivity inorganic: film deposited by traditional spin coating. The evaluation was performed using an existing damascene test vehicle. The etch selectivity was evaluated by applying different SoHM thicknesses and etch times. The patterning chemistry used was O-2/N-2 based, in a high density TCP etch tool. The electrical data collected indicated no significant yield difference when using an embedded SoHM. The integrated k value of the SoHM film is 3.2, as compared to similar to4.0 for SiO2 films.

The development of TaSiN diffusion barriers for Cu/SiLK metallization schemes is reported. First-pass studies optimized the TaSiN deposition process and evaluated process compatibility with SiLK. TaSiN/SiO/sub 2/ stacks were used for baseline comparisons. Second-pass studies evaluated thermal stability of TaSiN/Cu/TaSiN/SiLK stacks against Cu diffusion and the stability of the TaSiN/SiLK interface. At temperatures up to 450/spl deg/C no variations in stack composition or interfacial morphology were observed. Subsequently, electrochemical deposition (ECD) of highly [111] textured Cu on TaSiN/SiLK stacks was also demonstrated with a 30 nm sputtered Cu seed layer.

La presente invention concerne un procede qui consiste a prendre un substrat, a former une premiere couche sur ce substrat, cette premiere couche possedant une constante dielectrique inferieure a 3,0 et comprenant un polymere organique, a appliquer une resine organosilicate sur cette premiere couche, a retirer une partie de cette resine organosilicate de facon a exposer une partie de la premiere couche, et a retirer les parties exposees de cette premiere couche. Cette invention concerne aussi un circuit integre comprenant un substrat actif contenant des transistors et une structure d'interconnexion electrique contenant un schema de traces metalliques separes, au moins partiellement, par des couches ou des regions d'un materiau polymere organique possedant une constante dielectrique inferieure a 3,0 et comprenant aussi une couche d'une resine organosilicate au dessus d'au moins une couche de ce materiau polymere organique.

Scanning probe microscopy (SPM) techniques are used to characterize surfaces related to the processing of benzocyclobutene (BCB) dielectric thin films. Thermally cured resins and photodefineable resins are sold under the trade name CYLCOTENETM1) for electronic applications. TappingMode AFM (TMAFM) imaging is used to follow changes in adhesion promoter morphology upon baking to help explain adhesion performance. Power spectral density (PSD) analysis of TMAFM images of plasma treated BCB surfaces are unique and can be used to 'fingerprint' processes. Selective oxidation of the BCB surface can be used to fabricate a phase imaging standard for TMAFM. Near surface modulus of the BCB materials is 3.6 +/- 0.2 GPa and the hardness is 0.38 +/- 0.2 GPa measured by depth-sensing nanoindentation. Creep recovery of indents can be used to qualitatively distinguish between thermal and photocureable materials. A heated tip in a scanning thermal microscope can induce the thermal curing of BCB over micron sized areas. Local thermal analysis with the same probe allows the measurement of the changes in the glass transition, T,, at the surface with cure temperature.

Results are presented from a proof-of-concept study that examined the integration of damascene-processed thermal chemical vapor deposited (TCVD) aluminum (Al) interconnects in a benzocyclobutene (BCB) polymer matrix. In a first phase, the study identified baseline deposition conditions for the formation of structurally and chemically compatible blanket Al/titanium nitride (TiN)/BCB stacks on two types of blanket BCB substrates utilized to simulate the actual surfaces encountered in typical damascene processing: (1) blanket BCB films capped with a silicon dioxide SiO2 layer (SiO2-BCB), and (2) plasma reactive ion etched blanket BCB films. The TiN diffusion barrier was grown in two stages. A first (bottom) layer was deposited by physical vapor deposition (PVD), followed by a CVD-grown top layer. The resulting TCVD Al/CVD TiN/PVD TiN/BCB stacks were stable under thermal stressing up to 325 °C for 1 h. In a second phase, an optimized TCVD Al process flow was developed for void-free filling of TiN-coated 320-nm-wide trenches etched in a BCB matrix. The process flow included the demonstration of a chemical mechanical polishing recipe for planarization of the patterned TCVD Al/CVD TiN/PVD TiN/BCB structures. The resulting findings were incorporated in the fabrication of electrically testable TCVD Al/CVD TiN/PVD TiN/BCB interconnect structures on 200 mm wafers. Electrical evaluation for shorting and leakage of the test dice produced an adequate yield for the feasibility study of ∼71% of screened test sites. The electrical tests also generated an upper-bound value of 4.2 μΩ cm for Al line resistivity, a number that did not include corrections for contact resistance and interfacial scattering. These findings demonstrate the feasibility of TCVD Al/BCB based metallization schemes, particularly in terms of chemical, structural, mechanical, and electrical performance.

This work examines the mechanical performance of thin film coatings from Photosensitive-benzocyclobutene (Photo-BCB) formulations (Cyclotene2 4024, 4026 and 7200), on various substrate surfaces such as Al, Cu, Si, and SiN. The adhesion promoter used was designated AP-3000 and was based on vinyltriacetoxysilane (VTAS), which had been properly hydrolyzed and advanced. Measurement of the interfacial adhesion was performed primarily using the modified Edge Liftoff Test m-ELT. It was found that, by applying the newly developed adhesion promoter, AP-3000, the interfacial energy of Photo-BCB to Al, Cu, Si, and SiN was significantly improved, often approaching the toughness of Photo-BCB, ca. 45 J/m2. The x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses of the delaminated surfaces of the Photo-BCB/Al structure revealed distinct differences in surface roughness and the chemical composition depending on whether or not adhesion promoter was used. Other parameters important for long term stability (e.g., moisture uptake and thermal stability) of Photo-BCB were also measured. The equilibrium moisture content at 84 percent RH in ambient temperature was low, 0.14 wt percent and the thermally induced weight loss at 330°C in helium atmosphere was less than 1 percent/h. The low moisture absorption and good thermal stability, together with the given mechanical toughness and adhesion, allow the Photo-BCB to be widely usable for various microelectronic packaging applications, for up to 40 μm thick build in the case of silicon substrate. [S1043-7398(00)00701-5]

The integration of low-temperature plasma-promoted chemical-vapor deposition (PPCVD) of aluminum, using dimethylethylamine-alane (DMEAA) as the source precursor, with benzocyclobutene (BCB) low-k polymers has been investigated to explore the feasibility of BCB-based Al metallization for sub-quarter-micron integrated circuitry. The study examined the thermal, chemical, and structural compatibility of PPCVD Al interconnects with the BCB polymer, including the feasibility of barrierless aluminum–BCB multilevel metallization stacks. Studies were conducted on a range of BCB surfaces, consisting of untreated (UNT), reactive-ion etched (RIE), and SiO2-capped BCB (SiO2–BCB) surfaces. The purpose was to mimic the actual BCB surfaces encountered during damascene processing. Each BCB surface was treated with argon or hydrogen plasma prior to aluminum processing to ensure reduction in the barrier to aluminum formation, leading potentially to enhanced Al nucleation mechanisms. In all cases, the direct deposition of Al on BCB films via PPCVD was successfully demonstrated, with the RIE-BCB substrate providing the best Al nucleation characteristics. Compositional analyses of the Al films indicated that carbon and nitrogen contaminants, which could have resulted from the dissociation reaction of the DMEAA molecule, were below the detection limits of the techniques used. Alternatively, oxygen inclusion was highly dependent on the chemical state and type of plasma treatment of the BCB surface, with only the PPCVD Al on plasma pretreated RIE BCB exhibiting bulk oxygen levels below the detection limits of x-ray photoelectron spectroscopy. Oxygen incorporation in the PPCVD Al films on UNT BCB and SiO2–BCB could be attributed to the diffusion of oxygen through intergranular voids upon air exposure, resulting in increased Al film resistivity. In all cases, the study indicated that an appropriate diffusion barrier/adhesion promoter is required to ensure viable BCB integration in Al metallization schemes.

Diffusion barrier optimization and compatibility studies were undertaken with respect to the integration of Cu/TiSiN stacks on SiLK low-k dielectric films. First-pass testing optimized TiSiN film composition and evaluated process compatibility with SiLK. TiSiN/SiO2 stacks were used for baseline comparisons. Second-pass testing evaluated thermal stability of TiSiN/Cu/TiSiN/SiLK stacks against Cu diffusion and the stability of the TiSiN/SiLK interface. At temperatures up to 450 degrees C no variations in stack composition or interfacial morphology were evidenced.

For faster, smaller, and higher performance integrated circuits, a low dielectric constant insulator is required to replace silicon dioxide. Here the properties of a new dielectric-SiLK resin, a solution of a low-molecular-weight aromatic thermosetting polymer-are reviewed and examples of its application in the fabrication of interconnect structures, such as the one shown in the Figure, are given.

A new characterization tool based on ultrasonic force microscopy (UFM) has been developed to image the nanoscale mechanical properties of metal/low-k polymer damascence test structures. Metal and polymer regions are differentiated on the basis of elastic modulus with a spatial resolution less than or equal to 10 nm. This technique reveals a RIE-induced hardening of the low-k polymer at the metal/polymer interface and offers new opportunities for metrological reliability evaluation of low-k integration processes.

A new characterization tool based on ultrasonic force microscopy (UFM) has been developed to image the nanometer scale mechanical properties of aluminum/low-k polymer damascence integrated circuit (IC) test structures. Aluminum and polymer regions are differentiated on the basis of elastic modulus with a spatial resolution ≤ 10 nm. This technique reveals a reactive-ion etch (RIE)-induced hardening of the low-k polymer that is manifested in the final IC test structure by a region of increased hardness at the aluminum/polymer interface. The ability to characterize nanometer scale mechanical properties of materials used for IC back-end-of-line (BEOL) manufacture offers new opportunities for metrological reliability evaluation of low-k integration processes.

Adherence to the prescript of Moore’s law continues to drive materials development for new and lower dielectric constant materials for use as back-end-of-line (BEOL) interlayer dielectric in advanced logic IC’s. As is the case for the current generation of low-K materials (<3.0), these ultra-low K materials (<2.2) will need to meet the variety of integration and reliability requirements for successful product development. Excluding the incorporation of fluorine to lower the material polarity, further reductions of dielectric constant can only be achieved by reduced density. Based upon the industry’s experience with the current class of full density dielectrics, process integration may be challenging for ultra-low K materials. This anticipated difficulty derives from the profound differences in material properties, e.g. mechanical integrity, as one lowers the material density, which in turn confounds existing manufacturing processes that have evolved over 35 years based on silicon dioxide. Minimizing these material and processing differences by extending leveraged learning from previous technology nodes is essential for timely and cost-efficient development cycles. As a result, material selection of a full density low-K is somewhat influenced by the ability of that material to be extended into future generations. Understanding how the material properties will change as its density is lowered is vital to this selection process. In this paper, we present a summary of models for calculating effective properties as a function of density and apply these to current low-K materials with emphasis on mechanical integrity. We will also review experimental methods for measuring the mechanical integrity of ultra-low K materials and compare the results to the various models described herein.

Adhesion performance of coatings from Photo-BCB were investigated using a new adhesion promoter, AP-3000, based ion vinyltriacetoxysilane (VTAS) chemistry. A modified Edge Liftoff Test (m-ELT) was employed to evaluate adhesion performance of Photo-BCB on various surfaces; Si, SiN, Cu, and Al. AP-3000 resulted in a large improvement of adhesion energies for these interfaces. Atomic force microscopy (AFM) and x-ray photoelecton spectroscopy (XPS) of the aforementioned interfaces showed cohesive interfacial failure into the Photo-BCB phase. Therefore, the interfacial fracture energies approached fracture toughness of Photo-BCB, ca. 45 J/m(2).

Aluminum/liner binary stacks have been deposited on blanket and patterned films of benzocyclobutene (BCB) polymer to investigate its integration into an all-aluminum multilevel wiring structure. Blanket stacks were characterized for structural properties and reliability. Metallized patterned films were analyzed for gap fill of 0.30 mu m trenches. Aluminum was deposited via chemical vapor deposition (CVD). Titanium nitride liners were deposited via collimated reactive sputtering.

Successful integration of a polymer as an interlayer dielectric requires mechanical reliability to be maintained through all back-end of line (BEOL) processes. In this paper we use an integration demonstration of PE-CVD SiO2 with Cyclotene(TM) 5021 (BCB). Blistering after high temperature thermal anneals was mitigated by improving the adhesion strength of the deposited oxide film. This was successful when the BCB layer was treated with N-2 plasma. Fracture mechanics combined with surface analysis is used to understand the mechanism of improved mechanical reliability.

Currently, the IC industry is researching the integration of a variety of materials to meet the low dielectric constant requirement for improved back-end of line (BEOL) interconnect performance. One critical dimension for successful ntegration of these new materials is maintaining mechanical integrity through multilayer processes. This includes both cohesive and adhesive fracture resistance. The latter adds additional complexity in that adhesive toughness is a function of the adherend materials and the processes used to join them. Hence, many good dielectric materials may be rematurely eliminated from further research not because of inherently poor adhesion but because of the necessity to optimize processing strategies. In this paper, we use the modified Edge Liftoff Test (m-ELT) to quantify the mechanical adhesion of multilayer blanket coatings. A specific example is used to demonstrate the utility of combining the m-ELT with surface analysis to optimize the reliability of low-K dielectric resins for use in ULSI applications. The system studied consists of a Cyclotene ™ 5021(BCB) low-K material integrated with CVD aluminum for single level, damascene structures. The effects of liner layer metallurgy and surface plasma treatments are measured. Surface analysis is done on the failed parts to understand the location of the failure. In this way recommendations for process optimization can be made.

A novel polymer has been developed for use as a thin film dielectric in the interconnect structure of high density integrated circuits. The coating is applied to the substrate as an oligomeric solution, SiLK, using conventional spin coating equipment and produces highly uniform films after curing at 400 °C to 450 °C. The oligomeric solution, with a viscosity of ca. 30 cPs, is readily handled on standard thin film coating equipment. Polymerization does not require a catalyst. There is no water evolved during the polymerization. The resulting polymer network is an aromatic hydrocarbon with an isotropie structure and contains no fluorine. The properties of the cured films are designed to permit integration with current ILD processes. In particular, the rate of weight-loss during isothermal exposures at 450 °C is ca. 0.7 wt.%/hour. The dielectric constant of cured SiLK has been measured at 2.65. The refractive index in both the in-plane and out-of-plane directions is 1.63. The flow characteristics of SiLK lead to broad topographic planarization and permit the filling of gaps at least as narrow as 0.1 fum. The glass transition temperature for the fully cured film is greater than 490 °C. The coefficient of thermal expansivity is 66 ppm/°C below the glass transition temperature. The stress in fully cured films on Si wafers is ca. 60 MPa at room temperature. The fracture toughness measured on thin films is 0.62 MPa m ½ . Thin coatings absorb less than 0.25 wt.% water when exposed to 80% relative humidity at room temperature.