Si Nodule Formation in Al-Si Metallization

This paper describes the high electromigration resistance, absence of silicon nodule formation, and high surface specularity characteristics of sputtered magnesium-aluminum-silicon (Mg/A1-Si) metal systems. Stripe samples were tested at a current density of 4 • 106 A/cm 2, and the activation energy for 5.2% Mg/A1-Si alloy was 0.9 eV. Silicon nodule formation and hillock formation during heat-treatment were greatly suppressed at high Mg concentrations. Specular reflectance was 92% for alloys containing over 1.6% Mg.Aluminum and aluminum-silicon alloy (A1-Si) films are widely used for metallizing devices in IC processing. These metal systems have the advantages of low cost and low resistivity, but the disadvantages of low electromigration resistance and relatively high contact resistivity against n-type Si. To overcome these disadvantages, copper-aluminum (Cu/A1), and copper-aluminum-silicon (Cu/ A1-Si) metal systems have been developed and studied. Although Cu-containing metal systems have excellent electromigration resistance characteristics, contact resistivity for n-type Si is the same as for conventional A1-Si alloy. In addition, Si precipitation at the contact area has become a problem in recent fine-scale metallization processes, because of the low solubility of Si in A1 and Cu. This paper describes the high electromigration resistance and limited Si nodule formation of sputtered magnesium-aluminumsilicon (Mg/Al-Si) metal systems. Low contact resistivity and high specular reflectance characteristics of Mg/Al-Si are also reported.

Section: Silicon Nodule Formation On Sio2supporting

confidence: 77%

Electromigration and Nonformation of Silicon Nodules by Sputtered Magnesium‐Aluminum‐Silicon Alloys

Akiya¹,

Nakamura²,

Arita³

1990

“…The presence of copper can result in such problems as an increase in the aluminum film's susceptibility to corrosion by chlorine from a plasma etch process (5)(6)(7). An excess amount of silicon can cause aluminum metallization film cracking due to the precipitation of the excess silicon (8)(9)(10)(11), and wire bonding difficulty.…”

mentioning

confidence: 99%

Evaluation of Titanium as a Diffusion Barrier Between Aluminum and Silicon for 1.2 μm CMOS Integrated Circuits

Farahani¹,

Turner²,

Barnes³

1987

Metallurgical, electrical, and reliability evaluations of a Al‐0.5%Cu/Ti interconnect metallization system for use in 1.2 μm CMOS SRAM integrated circuit devices have been performed. The results indicate that the Al‐0.5%Cu/Ti metallization system is superior to both Al‐0.5%Cu and Al‐1%Si‐0.5%Cu metallization systems. It is shown that the presence of titanium has significantly improved the electromigration strength, reduced both the size and density of annealing hillocks, and improved the thermal and electrical stability of the metal‐silicon and metal‐metal contacts. The diffusion barrier behavior of titanium was studied electrically (via junction leakage current measurements) and analytically (via TEM examination of Al/Ti/Si interfaces). It is found that titanium is an effective diffusion barrier to aluminum and silicon as long as it is not completely consumed to produce TiAl3 .

“…The addition of copper is primarily to improve the electromigration strength of the aluminum film and suppress the formation of hillocks. The addition of these two alloying elements, however, can cause some severe reliability and processibility problems (1)(2)(3)(4)(5)(6)(7).…”

mentioning

confidence: 99%

Electrical and Metallurgical Characterization of Niobium as a Diffusion Barrier Between Aluminum and Silicon for Integrated Circuit Devices

Farahani

Turner

Barnes

1989

Electrical, metallurgical, electromigration, and functional characterizations of an (A1-0.5% Cu)/Nb interconnect metallization for use in 1.2 am SRAM integrated circuit devices have been performed. The results indicate that niobium is an excellent diffusion barrier to aluminum and silicon. It is shown that the presence of niobium has significantly improved the electromigration strength (at j = 1.0E7 A/cm 2) and the thermal and electrical stability of metal to silicon and metal to metal contacts. The barrier characteristics of the niobium were studied electrically (via junction leakage current and contact resistance measurements) and analytically (via TEM examination of aluminum-niobium-silicon interfaces). TEM and electron diffraction analyses show the formation of the NbA13 phase. It is found that the NbAI~ phase has a much slower rate of growth than TiA13 in the temperature range studied. Results do not indicate any significant increase in junction leakage current of contact resistance after 540 min of heat-treatment at 425~ The results further indicate that the niobium does not have any negative effects on the performance of 1.2 ~m CMOS SRAM devices. It appears, however, that the presence of niobium has an effect on the speed distribution of the devices.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120.3 Downloaded on 2015-06-04 to IP