Study of copper silicide retardation effects on copper diffusion in silicon

Lee, C. S.; Gong, Hao; Liu, R.; Wee, Andrew Thye Shen; Ma, C. L.; See, A.; Chan, Lap

doi:10.1063/1.1343518

Cited by 22 publications

(12 citation statements)

References 5 publications

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“…It is reported that copper precipitates homogeneously forming copper silicides Cu 3 Si, which are positively charged with electroneutrality level at approximately E c Ϫ 0.2 eV. 20,22 Therefore, we measured the time constant with such a low intensity that the electron Fermi level was well below the electroneutrality level of copper silicides (E c Ϫ E fn ϭ 0.23 eV). We observed that the time constant was considerably higher, around 39000 s, which indicates a very low copper precipitation rate.…”

Section: Resultsmentioning

confidence: 99%

Sensitive Copper Detection in P-type CZ Silicon using μPCD

Väinölä

Yli-Koski

Haarahiltunen

et al. 2003

J. Electrochem. Soc.

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Conventional microwave photoconductive decay ͑PCD͒ method in conjunction with high intensity bias light has been used to study out-diffusion and precipitation of copper in p-type Czochralski ͑CZ͒ silicon. The high intensity light is used to activate the precipitation of interstitial copper, which follows Ham's kinetics and results in a distinctive decrease in the excess carrier lifetime. Results indicate that Cu concentration well below 10 12 cm Ϫ3 can be detected by this method. It is demonstrated that positive corona charge can be used to prevent out-diffusion of interstitial copper, while negative charge enables copper to freely diffuse to the wafer surfaces. It was observed that the precipitation rate of copper increased significantly when the bias-light intensity is raised above a certain critical level. In addition, the copper precipitation rate was discovered to be much higher in samples which have internal gettering sites. These findings suggest that (i) high intensity light reduces the electrostatic repulsion between positively charged interstitial copper ions and copper precipitates enabling copper to precipitate in the wafer bulk even at a low concentration level, and (ii) during high intensity illumination, oxygen precipitates provide effective heterogeneous nucleation sites for copper.

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Section: Resultsmentioning

confidence: 99%

Sensitive Copper Detection in P-type CZ Silicon using μPCD

Väinölä

Yli-Koski

Haarahiltunen

et al. 2003

J. Electrochem. Soc.

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“…The Cu particles did not disappear because the solubility limit of Cu in Si was very low and a Cu silicide layer was formed at the Cu particle/Si interfaces to suppress diffusion of Cu atoms to the Si substrate. 27 Next, the CAFM results in Fig. 2 and 3 indicate that the leakage current flow is difficult at the Cu particles, while dark points corresponding to the leaky positions were randomly distributed over the entire scan area except at the Cu particles.…”

Section: Discussionmentioning

confidence: 99%

Leakage Current Distribution and Dielectric Breakdown of Cu-Contaminated Thin SiO[sub 2]

Tokuda

Nishiguchi

Yamasaki

et al. 2004

J. Electrochem. Soc.

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Dielectric degradation of an intentionally Cu-contaminated SiO 2 film on a Si substrate was investigated using conducting atomic force microscopy and metal-oxide-semiconductor capacitors. Comparison of the results of both measurements clarified that local oxide leakage currents increased at random points except at the Cu particles. At the Cu particles, accelerated thermal oxidation leads to the formation of a thick SiO 2 layer at the interface with the Si substrate and suppression of the oxide leakage current. A combination of electrical evaluations and total reflection X-ray fluorescence analyses indicated that a high Cu concentration on a SiO 2 surface induced low-voltage dielectric breakdown, and a low Cu concentration inside the SiO 2 film induced high leakage current in a low electric field range.A continuous decrease in the gate oxide thickness of metaloxide-semiconductor ͑MOS͒ systems is inevitable in current ultralarge-scale integrated circuits ͑ULSIs͒. Ultrathin gate oxide with uniform thickness within a large-diameter wafer can be easily formed with either a low oxidation temperature or a short oxidation time. 1 However, it is difficult to establish an ultrathin gate oxide technology in the ULSI manufacturing process with high device yield and high reliability. 2,3 This is because both the yield and longterm reliability of the thin gate oxide are easily deteriorated by crystal originated particles 4 or bulk microdefects 5 in the Si wafer or by such phenomena as charge-up 6,7 and radiation 8 during ULSI manufacturing processes. In addition, one of the most problematic causes of reliability degradation in ULSI manufacturing is unintentional contamination such as by metal and organic matter. In particular, care should be taken to prevent contamination with metallic impurities with high diffusivity in all process steps. 2,3,9,10 The scaling of devices to submicrometer dimensions has constrained ULSI performance because of the RC (resistance ϫ capacitance) delay interconnection. The resistance of interconnection wiring can be lowered by choosing alternative conductor materials such as Cu, Ag, or other new materials. The purity of such materials is still low in comparison with those of other materials used in ULSIs. In adopting such materials, attention should be paid to not only the main elements but also the impurities. Cu with low resistivity and a cost advantage is profitable as a low-resistance interconnection material. However, the diffusivity of Cu is high in SiO 2 11 and Si. 12 For example, the diffusion length at 600°C for 60 min in Si is approximately 2 mm, 12 which is more than the Si wafer thickness. That is, even Cu atoms adsorbed at the back surface of the Si wafers during the manufacturing process may degrade the functions of ULSIs. In addition, the electronegativity of Cu is higher than that of Si. 13 Immersion in a diluted hydrofluoric acid ͑DHF͒ solution before the gate oxidation easily causes the adsorption of Cu on the bare Si surface. 14 In many of the previous studies, deterioration by t...

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“…However, it was reported that micro-oxygen might indeed improve the thermal stability and performance of the diffusion barriers, such as, TaeGe(O)eN [25], TaeSieNeO [26] and MnSiO 3 [27]. Moreover, indium tin oxide (ITO), Ta 2 O 5 and TiO 2 all demonstrated good diffusion barrier candidates [28,29]. It is widely accepted that the thickness of the diffusion barrier rather than the resistivity play a critical role in the continuous downscale ULSI.…”

Section: Introductionmentioning

confidence: 99%

“…However, the inter-diffusion and reaction between Cu thin films and the dielectric layers limit the reliability of Cu interconnects and become the crucial issue in the field of microelectronics [4,5]. Therefore, an effective barrier layer is essential to block the unwanted atomic diffusion between Cu thin films and the dielectric layers.…”

Section: Introductionmentioning

confidence: 99%