Atomic Layer Deposited Ultrathin HfO[sub 2] and Al[sub 2]O[sub 3] Films as Diffusion Barriers in Copper Interconnects

Majumder, Prodyut; Katamreddy, Rajesh; Takoudis, Christos G.

doi:10.1149/1.2756633

Cited by 33 publications

(35 citation statements)

References 29 publications

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“…22 Due to exceptional thickness control and uniformity, atomic layer deposition (ALD) has become the preferred method for depositing most high-k dielectric materials in micro-/nano-electronic applications. 23 The low deposition temperature, 23 excellent surface topography coverage, [23][24][25] low pinhole/defect density, 26,27 high mass/atomic density, 28 and thermodynamic stability 29 of ALD high-k materials have further enabled these materials to serve additional roles in complex interference coatings 30 as well as in moisture, 31 oxygen, 32 and metal 33 diffusion barriers in hermetic packaging, 34 organic light emitting diode, 35 and metal interconnect 36 applications.…”

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confidence: 99%

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Gaskins

Hopkins

Merrill

et al. 2017

ECS J. Solid State Sci. Technol.

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Atomic layer deposited (ALD) high-dielectric-constant (high-k) materials have found extensive applications in a variety of electronic, optical, optoelectronic, and photovoltaic devices. While electrical, optical, and interfacial properties have been the primary consideration for such devices, thermal and mechanical properties are becoming an additional key consideration for many new and emerging applications of ALD high-k materials in electromechanical, energy storage, and organic light emitting diode devices. Unfortunately, a clear correspondence between thermal/mechanical and electrical/optical properties in ALD high-k materials has yet to be established, and a detailed comparison to conventional silicon-based dielectrics to facilitate optimal material selection is also lacking. In this regard, we have conducted a comprehensive investigation and review of the thermal, mechanical, electrical, optical, and structural properties for a series of prevalent and emerging ALD high-k materials including aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), hafnium oxide (HfO 2 ), and beryllium oxide (BeO). For comparison, more established silicon-based dielectrics were also examined, including thermally grown silicon dioxide (SiO 2 ) and plasma-enhanced chemically vapor deposited hydrogenated silicon nitride (SiN:H). We find that in addition to exhibiting high values of dielectric permittivity and electrical resistance that exceed those of SiO 2 and SiN:H, the ALD high-k materials exhibit equally exceptional thermal and mechanical properties with coefficients of thermal expansion ≤ 6 × 10 -6 / • C, thermal conductivites (κ) of 3-15 W/m K, and Young's modulus and hardness values exceeding 200 and 25 GPa, respectively. In many cases, the observed extreme thermal/mechanical properties correlate with the presence of crystallinity in the ALD high-k films. In contrast, some of the electrical and optical properties correlate more strongly with the percentage of ionic vs. covalent bonds present in the high-k film. Overall, the ALD high-k dielectrics investigated concurrently exhibit compelling thermal/mechanical and electrical/optical properties. The drive to reduce gate leakage currents in highly scaled complementary metal-oxide-semiconductor (CMOS) transistors has led to the exploration and development of a wide variety of high-dielectricconstant (high-k) materials to replace silicon dioxide (SiO 2 ) as the insulating gate dielectric material.1-8 Many of these same high-k materials have found additional applications in future non-CMOS logic and memory storage products such as solid-state electrolytes in resistive switching devices, 9,10 tunnel barriers in spin-transport devices, 11 and as a ferroelectric in magnetoelectric devices. While electrical, physical, and thermodynamic properties have clearly been a key consideration in all of the above applications, thermal properties have become an additional important consideration for higk-k dielectrics as aggressive dimensional scaling of devices has created the need to dissipate ...

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confidence: 99%

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Gaskins

Hopkins

Merrill

et al. 2017

ECS J. Solid State Sci. Technol.

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“…• C. 490 These encouraging results indicate that an aggressively scaled high-k material could in some cases serve as a metal interconnect DB with minimal capacitance penalty. With respect to the ITRS goal of <2 nm DB, these results are also encouraging and should justify additional studies of high-k dielectrics as DBs at <2 nm thickness targets.…”

Section: 15mentioning

confidence: 92%

“…In this regard, Majumder has recently evaluated the Cu diffusion barrier performance of 3 nm thick Al 2 O 3 and even higher k HfO 2 ALD films. 490 X-ray diffraction measurements of Cu-MIS structures annealed at various temperatures showed these films to prevent Cu diffusion up to temperatures as high as 650…”

Section: 15mentioning

confidence: 99%

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

King

2014

ECS J. Solid State Sci. Technol.

133

115

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Over the past decade, the primary focus for improving the performance of nano-electronic metal interconnect structures has been to reduce the impact of resistance-capacitance (RC) delays via utilizing insulating dielectrics with ever lower values of dielectric permittivity. The integration and implementation of such low dielectric constant (i.e. low-k) materials has been fraught with numerous challenges. For intermetal and interlayer (ILD) low-k dielectrics, these challenges have been largely associated to integration with metal interconnect fabrication processes and well documented and reviewed in the literature. Although equally important, less attention has been given to other low-k dielectrics utilized in metal interconnect structures that are commonly referred to as low-k dielectric barriers (DB), etch stops (ES), and/or Cu capping layers (CCL). These materials present numerous challenges as well for integration into metal interconnect fabrication processes. However, they also have more stringent integrated functionality requirements relative to low-k ILD materials that serve only a basic purpose of electrically isolating adjacent metal lines. In this article, we review the integration challenges and associated integrated functionality requirements for low-k DB/ES/CCL materials with a focus on the current status and future direction needed for these materials to facilitate both Moore's law (i.e. More Moore) and More than Moore scaling.

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“…ALD grown metals or nitrides , such as Ru [3][4], and TaN films [5,6], have been widely studied as Cu diffusion barriers or adhesion layers. ALD grown oxides, such as TiO 2 [7], Ta 2 O 5 [8] and Al 2 O 3 [9] have also been reported as Cu diffusion barriers due to their excellent uniformity and thermal stability. Qi Xie et.al reported the excellent thermal stability of ALD TiO 2 .…”

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confidence: 99%

“…al. reported that the ultrathin Al 2 O 3 layer deposited by thermal ALD as diffusion barrier between Cu and Si substrate had excellent thermal stability. [9] However, these oxide layers were all directly deposited onto Si and the very primary properties of diffusion barriers to Cu were measured.…”

mentioning

confidence: 99%

Investigation of ultra-thin Al<inf>2</inf>O<inf>3</inf> film as Cu diffusion barrier on low-k (k=2.5) dielectrics

Xie

Chen

et al. 2011

2011 IEEE International Interconnect Technology Conference

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Ultra thin Al 2 O 3 films were deposited by plasma enhanced atomic layer deposition (PEALD) as Cu diffusion barrier on low-k (k=2.5) material. The thermal stability and electrical properties of the Cu/low-k system with Ta, Ta/Al 2 O 3 and Ru/Ta layers with different thickness were compared after annealing. The TEM and EDX results reveal that the ultrathin Al 2 O 3 films are thermally stable and have excellent Cu diffusion barrier performance. The I-V and TDDB electrical measurements further confirm that the ultra thin Al 2 O 3 film is a potential Cu diffusion barrier in copper/low k interconnect.Corresponding Author:Xin-Ping Qu, Professor, With the continuing scaling down of the line pitch in very large scale integrated circuits, ultrathin Cu diffusion barriers are necessary to mitigate the increase in the effective resistivity of the Cu interconnects due to grain boundary scattering and interface scattering. Conformal deposition of thin films in high aspect ratio trenches using traditional physical vapor deposition (PVD) Systematic study of ALD oxide films as Cu diffusion barrier on the low-k dielectric has been rarely reported. In this work, ultra thin Al 2 O 3 films were deposited by plasma enhanced atomic layer deposition (PEALD) together with Ta adhesion layer, its properties as a Cu diffusion barrier on the low k dielectric (k=2.5) were studied.The low k films (Novellus CORAL, k=2.5) were deposited on the 12" p-type Si wafers with a thickness of 220 nm. The wafers were cut into small pieces and then were cleaned in an ultrasonic cleaner with 2-propanol solution before loading to the loadlock chamber. After in-situ annealing at 250 ° C for 20 minutes in the high vacuum ALD chamber, 11 or 21 cycles (~1.2 Å/cycle) Al 2 O 3 films were grown by plasma enhanced atomic layer deposition (PEALD) using trimethylaluminium (TMA) and remote O 2 plasma (200W) as precursors. The growth temperature was 250° C. After deposition, samples were taken out and sent into a PVD chamber. The details of the ALD growth can be seen elsewhere. [7] Then the Cu(50 nm)/Ta(5 nm) film stacks were deposited by DC magnetron sputtering. The thin Ta film was used as a glue layer to promote adhesion between the Cu and Al 2 O 3 barrier layers. To form the patterned metal-insulatorsemiconductor (MIS) structures, a shadow mask was used when depositing the Cu/Ta stacks. For comparison, the Cu/Ta stack was also directly deposited onto the low k substrates. A Ti(40 nm)/Pt(30 nm) bi-layer was deposited as backside electrode by sputtering. Furnace annealing was conducted in the N 2 atmosphere at 400 °C for 30 minutes. After annealing, energy dispersive X-ray (EDX) transmission electron microscope (TEM), time-dependent dielectric breakdown (TDDB), and dielectric breakdown measurements were used to characterize the thermal stability and electrical reliability of the Cu/barrier/low k/Si system. The capacitance-voltage (C-V) measurements were carried out using an HP 4192A impedance analyzer to evaluate the effective k value of the system. The XTE...

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Atomic Layer Deposited Ultrathin HfO[sub 2] and Al[sub 2]O[sub 3] Films as Diffusion Barriers in Copper Interconnects

Cited by 33 publications

References 29 publications

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

Investigation of ultra-thin Al<inf>2</inf>O<inf>3</inf> film as Cu diffusion barrier on low-k (k=2.5) dielectrics

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