Because of the high potential to prevent of known issues (precursor penetration, moisture absorption, materials modification, or even adhesion problems) of porous dielectrics, air gaps are very promising for a sufficient device performance of the 45 nm node CMOS technology and below. This paper introduces two air gap approaches using PECVD SiOx sacrificial dielectrics in copper damascene architectures. The removal of the dielectric is performed by buffered HF wet etch media. Depending on the kind of approach, the etch attack is mainly controlled by a patterned hard mask film and PECVD SiC stop layers. Additionally, it may be supported by a self aligned, well adjustable PECVD SiOx spacer for a slot-like etch window of sub lithographical dimensions. Both process flows, the main issues involved and selected process optimizations are specified. Successful preparation results for cavity manufacturing are presented. First electrical examinations show, that in comparison to test structures using conventional SiOx as dielectric, the measured capacitances of structures including air gaps could be reduced to less than 50%.

The target of our investigation is the evaluation of the effect of decreasing thickness on the relative permittivity of dielectric films for high advanced interconnects of IC's. Two kinds of SiCOH-films with similar chemical composition and thickness between 70 and 830nm were deposited by spin coating (''SOD'') or PECVD (''CVD'') on silicon wafers. The relative permittivity was determined by CV-measurement and its components of polarization response are deduced from ellipsometric and FTIR measurements.

Abstract The paper deals with the application of Pharr’s concept of the effectively shaped indenter as well as an extension of that concept – referred to as extrapolation method – on the determination of the yield strength of porous thin films. As an example, a 1066 nm thick porous SiO2 xerogel film having a porosity of about 50% and an average pore size in the range 3 – 4 nm was investigated. Three different spherical indenters with radii of 1.4, 3.11 and 110 lm were used in this investigation. Depending on the indenter radius and the applied load the physical nature of the sample deformation was different making the one or the other of the two methods more suitable for analysis. We found that the data received with the large indenter could be well analysed using Pharr’s concept, while for the two smaller indenters the extrapolation method had to be used. The yield strength values obtained with the two methods were in remarkable agreement (109 vs. 99 MPa).

The synthesis if the silver(I) salts [AgX] (3a, X = acetylacetonate, acac; 3b, X = 1,1,1,5,5,5-hexafluoroacetylacetonate, hfac; 3c, X = 1,3-diphenyl-1,3-propanedionate, dipa) by the reaction of [AgNO3] (1) with H-X (2a, X = acac; 2b, X = hfac; 2c, X = dipa), or [Ag2O] (4) with 2b is reported. The addition of (Bu3P)-Bu-n (5) to 3a - 3c inn the ratios of 1:1 and 2:1, respectively, affords the phosphane silver (I) beta-diketonates [((Bu3P)-Bu-n)(m)AgX] (m = 1: 6a, X = acac; 6b, X = hfac; 6c, X = dipa. m = 2: 7a, X = acac; 7b, X = hfac; 7c, X = dipa) in yield.The thermal behavior (thermogravimetry) and gas phase properties (temperature-programmed mass spectrometry) of selected species are discussed.Complex 7a can successfully be used in deposition of silver on titanium nitride coated oxidized silicon wafers by the CVD process (CVD = Chemical Vapour Deposition). SEM studies show that homogeneous and continous silver layers were obtained.

A cyclic MOCVD TiN deposition process of alternating deposition and plasma treatment steps was modified to deposit Si stabilized TiN barriers for copper metallisation schemes. SiH4 plasma or soak treatments were introduced at different points in the multistep process. In case of the SiH4 plasma treatments, the film thickness was drastically increased because of the deposition of Si interlayers. Furthermore, no densification effect of the TiN pyrolysis layer is detected for the SiH4 plasma treatment, compared to the H2/N2 plasma. The influence of the presence of Si to the following deposition cycle is evident. Only the silane soak led to moderate thickness and resistivity increase compared to the TiN films.

Ultra low-k materials for interconnects in chip manufacturing require new or adapted procedures for integration into copper damascene metallization, including patterning processes. This work deals with the impact H"2 containing stripping processes at elevated temperatures on porous ultra low-k materials and low-k hard mask/capping materials. Porous MSQ and SiO"2 and a low-k hard mask have been prepared by spin on deposition (SOD) and for comparison dense SiOCH by PECVD deposition. Resist stripping was done with a downstream microwave discharge in an advanced strip passivation chamber (ASP) of Applied Materials using mixtures of H"2/N"2 and H"2/He. Shrinkage (change of thickness) and electrical properties (k-value and field break down) were investigated. FTIR spectra were used to support the investigation. Ashing parameters, like time of plasma treatment, temperature and gas composition, have been characterized. It was found that the advantage of nitrogen admixture is the high rate of ashing, but shrinkage and impact on k-values will be higher than with He admixture. Helium admixture reduces shrinkage and k-values will be only slightly impacted, but stripping time has to be increased for resist removal.

Polycyanurate-based intermetal dielectrics with lowered relative permittivity in comparison to silicon oxide as well as good electrical, thermal and mechanical properties permitting an easy low-step processing were developed. A thin reference film with a k-value of 2.91 (at 0.1 MHz) consisting of a three-dimensional polycyanurate network was obtained by curing the fluorine containing difunctional cyanate ester monomer 2,2'-bis(4-cyanatophenyl)-1,1,1,3,3,3-hexafluoroisopropylidene (F10). By co-curing of F10 with a bulky trifunctional cyanate ester monomer the dielectric constant was increased. However, co-curing with monofunctional cyanate ester monomers reduces the dielectric constant and the lowest k-value of 2.54 (at 0.1 MHz) was found for a cyanurate copolymer with a high content of m-(trifluoromethyl)phenyl structural units. All films investigated had a leakage current <= 10(-10) A/cm(2) and thermal and mechanical properties suitable for industrial application.Finally, first patterning attempts showed good potential for producing Cu damascene structures. Patterning using a PECVD SiO2 hard mask with partial hard mask opening was developed using ICP etch with CHF3, CF4 and He. The achieved structures showed straight profiles and no significant defects. (c) 2005 Elsevier B.V. All rights reserved.

The ene-yne copper(I) beta-diketonates [(eta(2) -TMSMB)Cu(beta-diketonate)] (beta-diketonate = acetylacetonate/acac, 5; = 1,3-di-tertbutylacetonate/dbac, 6;=1,1,1,5,5,5-hexafluoroacetylacetonate/hfac, 7; TMSMB=4-TriMethylSilyl-2-Methyl-But-1-ene-3-yne, Me3SiC=C-CMe=CH2) are accessible by the reaction of [(eta(2) -TMSMB)Cu(mu-Cl)](2) (3) with [Na(beta-diketonate)] (beta-diketonate = acac, 4a; = dbac, 4b; = hfac, 4c) in a 1:2 molar ratio. Complexes 6 and 7 are also formed, when Cu2O (8) is reacted with H-hfac (9a) or H-dbac (9b), respectively.The solid state structure of 7 is reported. The copper(l) ion possesses a planar environment caused by the eta(2)-coordinated TMSMB ligand and the chelate-bound hfac group, while the CMe=CH2 entity stays free.The thermal properties of 5-7 were determined by applying ThermoGravimetry (TG) and Differential Scanning Calorimetry (DSC). All complexes decompose in a two-step process beginning at ca. 85 degrees C. Elimination of TMSMB produces [Cu(beta-diketonate)] which disproportionates to give [Cu(beta-diketonate)2] and elemental copper.Preliminary hot-wall Chemical Vapour Deposition experiments (CVD) were carried out with 7. Copper films were deposited onto TiN-coated oxidised silicon wafers at a precursor vaporisation temperature of 50 degrees C and a deposition temperature of 145 degrees C. The films were characterised by SEM and EDX. (c) 2005 Elsevier B.V. All rights reserved.

In this feasibility study, an ultra low-k (ULK) mesoporous SiO2 aerogel dielectric (SAGel, k=2.2) has been successfully integrated in selected levels of a Cu multilevel metallization of RF demonstrators. Several integration issues like ULK adhesion and patterning, resist stripping and metal CMP have been successfully addressed and corresponding process optimisations are reported. The development of an Ar plasma pretreatment of the ULK surface, a double hardmask approach, a mild H-2/N-2 stripping process and a metal CMP process with reduced downforce have been essential. Successful integration of the advanced ULK dielectric is shown by SEM investigations and by electrical evaluation of line and via resistances and leakage currents. The DC parameters compare well with a corresponding Cu/SiO2 reference. The impact of ULK integration in selected levels of a 20 nH RF inductor is investigated and an improvement of the quality factor Q by approx, 10 % and an increase of the resonant frequency by approx. 20 % have been found after replacing SiO2 by ULK in one metal level beneath the inductor.

A series of copper(I) beta-diketonate complexes of type [((Bu3P)-Bu-n)(m)CuL] [m=1 or 2. m=1: L=acac (4), acac=acetylacetonate; L=dbac (5), dbac=1,3-di-tert-butylacetonate; L=hfac (6), hfac=1, 1, 1, 5, 5, 5-hexafluoroacetylacetonate; m=2: L=acac (7); L=dbac (8); L=hfac (9)] with (Bu3P)-Bu-n as ancillary Lewis-base ligand is accessible by the reaction of [((Bu3P)-Bu-n)mCuCl] (1: m=1, 2: m=2) with the sodium-beta-diketonate salts NaL (3a: L=aeac; 3b: L=dbac; 3c: L=hfac) in a 1:1 molar ratio. Complexes 7similar to9 can also be prepared by treatment of 4similar to6 with one equivalent of (Bu3P)-Bu-n (10).Spectroscopic data (IR, H-1-, C-13{H-1}-NMR) of 4similar to9 reveal that the respective beta-diketonates are chelate-bound to copper(I), thus resulting In a tri- (4similar to6) or tetra-coordination (7-9) at the transition metal ion.The thermal proper-ties of 4similar to9 were studied by ThermoGravimetric analysis (TG) and Differential Scanning Calorometry (DSC).Hot-wall Chemical Vapour Deposition experiments (CVD) were carried-out by using, for example, complexes 4 and 7 as precursors for the deposition of copper onto TiN-coated SiO2 wafers. SEM and EDX studies were applied to characterize the obtained copper films.

In this work CVD TiN diffusion barriers were investigated for integration with porous ultra low-k (ULK) dielectrics. Sheet resistance measurements of thin CVD TiN films on capped porous ULK and a SiO2 reference were compared. The impact of different ULK material pore size (3 and 7 nm) on TiN diffusion barrier integrity was investigated for patterned structures by etch dip test and analytical methods. In addition a SiO2 CVD liner was used for pore sealing. It was detected that a smaller pore size facilitates a better CVD liner and TiN barrier formation which results in a better barrier integrity. Evaluation of barrier continuity by HF dip test showed no effect of the CVD liner for the ULK material with higher pore size. A remarkably decrease of the number of defects was observed compared to non-patterned samples. Also a reduced TiN penetration into the ULK compared to non-patterned samples was detected by EDX line scan. It is assumed, that a partial pore sealing during ULK etching using a photoresist mask occurred by formation of a passivation layer at the sidewall. Furthermore for lower pore size material the CVD liner improved the barrier performance.

Silica xerogel films with low dielectric constant were prepared by means of a sol–gel spin-coating method using different aging and hydrophobisation conditions. Non-destructive variable angle spectroscopic ellipsometry (VASE) studies allow a complete characterization of the xerogel films, in terms of thickness, optical constants and void fraction. The electronic and ionic contributions to the static dielectric constant of the xerogel films were calculated from the refractive index in the visible range and from infrared transmission spectra, respectively. The origin of the differences between the contributions to the static dielectric constant of the xerogel films produced with different preparation conditions is discussed.

The patterning of porous SiO2 aerogel as ultra low k dielectric has been investigated. Three different concepts were examined to etch this material without damage and to finally integrate it into a copper damascene metallization. Oxygen containing etching and resist stripping chemistry has to be strictly avoided, even for cap layer and hardmask patterning and for resist stripping on aerogel protected with a thin ∼50 nm layer. A conventional approach using a cap layer to prevent interactions between aerogel and resist but etching over a resist mask is currently only usable, if the resist can be removed without any residues, because effective wet cleaning chemicals compatible with the porous aerogel material are still not available. An H2/N2 microwave plasma strip was developed and found to be compatible with the aerogel. No damage could be detected by SEM and combined TEM/EDX analysis. The choice with best flexibility with respect to the process steps offers a dual hardmask approach using an H2/N2 strip. In this case the aerogel is protected during wet clean by a thin PECVD SiN film. Using this process flow trenches for copper damascene metallization could be patterned with acceptable profile, etch rate and selectivity as well as without any delamination, even after CMP processing.

Low k and ultra low k dielectrics will be integrated in the lower metal levels of sub-100nm technology nodes in order to reduce RC delay. Several product applications require on chip inductors of high quality, which are typically integrated in the top levels of such multilevel metal schemes. This paper provides experimental and simulation results for the impact of SiO2 substitution by low-k dielectrics on the quality factor Q and the resonant frequency f(res) of inductors ranging from 1 to 20 nH. Substitution of SiO2 by low k in one or more levels has a beneficial impact on Q and f(res), which depends upon the k value, dielectric thickness, low k location, but also upon the inductor design and inductivity. In good agreement of experimental and simulation results, maximum improvements of 25% for f(res) and 16% for Q are found for the investigated inductor designs, if complete substitution of SiO2 by k = 2.2 dielectric in the lower levels is assumed.

To an existing PECVD (plasma enhanced chemical vapor deposition) process for the deposition of WNx, silane is added to obtain a ternary barrier film for the copper metallization. The film composition is dependent on the point in time of the silane deposition. A too early addition resulted in a two layer system of SiOxNy and WNx. A later addition, after the incubation time of the binary process, led to amorphous films which are thermally more stable than WNx. First structural changes were observed after vacuum anneals at 650 degrees C/1h, and at 700 degrees C the films crystallize into W2N and W. According to GDOES only small amounts of Si are introduced in the upper barrier region, and the film composition is probably graded. The deposited films have electrical resistivities varying between 230 and 600 mu Omega cm as a function of the used SiH4/WF6 ratio.

In this work a study about the barrier properties of a 10 nm PECVD-WNx barrier layer against copper diffusion into SiO2 dielectrics was performed. To give a realistic estimation about the thermal stability of a diffusion barrier on a dielectric it is necessary to prove small amounts of copper migrating into the SiO2. Analytical methods and electrical measurements were compared with respect to their sensitivities for copper diffusion. With GI-XRD and cross sectional TEM no Cu diffusion was proved before and after the crystallisation of the amorphous WNx films. AAS investigations of the dissolved filrns were performed to give a quantitative estimation about the copper content in the barrier layer and the SiO2. As relevant device structures MIS capacitors were prepared. After different annealing steps the structures have been examined to find electrical irregularities using HF-capacitance-voltage (HF-CV), capacitance-time (Ct) and triangular voltage sweep (TVS) measurements. A maximum Copper content in the thenual oxide without a barrier of 2.2.10(11) cm(-2) could be observed after 550 degreesC using CV measurements. The WNx barrier on PECVD oxide is stable up to 450 degreesC. On thermal oxide no barrier failures in the analysed temperature range up to 550 degreesC could be observed. Using Ct measurements no copper in the silicon could be detected in this work.

This paper reports about examinations on mechanical integrity improvement which were done to enable the integration of aerogel as ultra low k (ULK) dielectric into copper damascene technology. Our work focussed on the increase of the adhesive strength between the dielectrics aerogel and the cap layer material PECVD silicon nitride and on ensuring successful CMP process and post-treatment to achieve optimum copper damascene architectures. An argon plasma pre-treatment showed best potential for improvement of adhesive strength. Investigations were performed to find optimum process conditions of this treatment and to verify the impact on the porous ULK material. Furthermore, compatibility of CMP and post-CMP-cleaning chemicals with the ULK material was shown and a ULK compatible CMP process was developed. Finally, complete and defect-free damascene structures were manufactured.

The so-called 3ω measurement technique (transient hot wire method) was established to determine the thermal conductivity of thin films. Measurements of standard substrates and films validate the found thermal conductivity values and agree with published, commonly accepted values. The method was successfully applied to determine the thermal conductivity of porous low- k dielectric materials using special test structure fabrication. The thermal conductivity of the porous low- k dielectrics thus measured is only between 7 and 13% of the thermal conductivity of thermally grown silicon dioxide.

The integration of ultra low k materials in copper damascene architecture is one of the main issues in finding microelectronic-process-compatible dielectric materials. The aim of this paper is to show the integration conformity with common equipment and process steps using a PECVD (plasma enhanced chemical vapor deposition) CF polymer ultra low k material in a Cu single damascene architecture (Proceedings of the Advanced Metallization Conference, 2002). The intermetal dielectric low k material used in the described structures has 2.1≤k≤2.3 (k depends on deposition process parameters [Microelectron. Eng. 50 (2000) 7–14]) and the copper was deposited by a metal organic chemical vapor deposition process. After chemical mechanical polishing the structures were characterized by scanning electron microscopy and electrical measurements.