Benjamin French

X-ray photoelectron spectroscopy measurement of the Schottky barrier at the SiC(N)/Cu interface

Electrical leakage in low-k dielectric/Cu interconnects is a continuing reliability concern for advanced <22 nm technologies. One leakage mechanism deserving increased attention is electron transport across the Cu/dielectric capping layer interface. The Schottky barrier formed at this interface is an important parameter for understanding charge transport across this interface. In this report, we have utilized x-ray photoelectron spectroscopy to investigate the Schottky barrier formed at the interface between polished Cu substrates and standard low-k a-SiC(N):H dielectric capping layers deposited by Plasma Enhanced Chemical Vapor Deposition. The authors find the Schottky Barrier at this interface to range from 1.45 to 2.15 eV depending on a-SiC(N):H composition and to be largely independent of various in situ plasma pretreatments.

X-ray photoelectron spectroscopy investigation of the Schottky barrier at low-k a-SiO(C):H/Cu interfaces

In order to understand the fundamental mechanisms involved in electrical leakage in low-k/Cu interconnects, we have utilized x-ray photoelectron spectroscopy to determine the Schottky barrier present at interfaces formed by plasma enhanced chemical vapor deposition of low-k a-SiOxCy:H thin films on polished Cu substrates. We find the Schottky Barrier at this interface to range widely from 1 to >4 eV and to be dependent on the amount of network carbon incorporated into the a-SiOC:H thin films.

Investigation of the impact of insulator material on the performance of dissimilar electrode metal-insulator-metal diodes

The performance of thin film metal-insulator-metal (MIM) diodes is investigated for a variety of large and small electron affinity insulators using ultrasmooth amorphous metal as the bottom electrode. Nb2O5, Ta2O5, ZrO2, HfO2, Al2O3, and SiO2 amorphous insulators are deposited via atomic layer deposition (ALD). Reflection electron energy loss spectroscopy (REELS) is utilized to measure the band-gap energy (EG) and energy position of intrinsic sub-gap defect states for each insulator. EG of as-deposited ALD insulators are found to be Nb2O5 = 3.8 eV, Ta2O5 = 4.4 eV, ZrO2 = 5.4 eV, HfO2 = 5.6 eV, Al2O3 = 6.4 eV, and SiO2 = 8.8 eV with uncertainty of ±0.2 eV. Current vs. voltage asymmetry, non-linearity, turn-on voltage, and dominant conduction mechanisms are compared. Al2O3 and SiO2 are found to operate based on Fowler-Nordheim tunneling. Al2O3 shows the highest asymmetry. ZrO2, Nb2O5, and Ta2O5 based diodes are found to be dominated by Frenkel-Poole emission at large biases and exhibit lower asymmetry. The ...

Valence band offset at the amorphous hydrogenated boron nitride-silicon (100) interface

In order to understand the fundamental behavior of various boron nitride heterostructure devices, we have utilized x-ray photoelectron spectroscopy to determine the valence band offset (VBO) present at interfaces formed by plasma enhanced chemical vapor deposition of hexagonal amorphous hydrogenated boron nitride (a-BN:H) on Si (100) substrates. For an a-BN:H/Si interface with some interfacial SiNx and SiBx bonding, we determined the valence band offset to be 1.9 ± 0.15 eV. The conduction band offset was likewise determined to be 2.2 ± 0.2 eV with a type I alignment.

Valence and conduction band offsets at amorphous hexagonal boron nitride interfaces with silicon network dielectrics

To facilitate the design of heterostructure devices employing hexagonal/sp2 boron nitride, x-ray photoelectron spectroscopy has been utilized in conjunction with prior reflection electron energy loss spectroscopy measurements to determine the valence and conduction band offsets (VBOs and CBOs) present at interfaces formed between amorphous hydrogenated sp2 boron nitride (a-BN:H) and various low- and high-dielectric-constant (k) amorphous hydrogenated silicon network dielectric materials (a-SiX:H, X = O, N, C). For a-BN:H interfaces formed with wide-band-gap a-SiO2 and low-k a-SiOC:H materials (Eg ≅ 8.2−8.8 eV), a type I band alignment was observed where the a-BN:H band gap (Eg = 5.5 ± 0.2 eV) was bracketed by a relatively large VBO and CBO of ∼1.9 and 1.2 eV, respectively. Similarly, a type I alignment was observed between a-BN:H and high-k a-SiC:H where the a-SiC:H band gap (Eg = 2.6 ± 0.2 eV) was bracketed by a-BN:H with VBO and CBO of 1.0 ± 0.1 and 1.9 ± 0.2 eV, respectively. The addition of O or N to ...

Investigation of atomic layer deposited beryllium oxide material properties for high-k dielectric applications

Beryllium oxide (BeO) is a wide band gap alkaline earth oxide material that has recently shown significant promise as a high-k dielectric material in Si and III-V metal–oxide–semiconductor field effect transistor devices. However, many of the basic material properties for BeO thin films utilized in these devices have not been reported or remain in question. In this regard, the authors report an investigation of the chemical, physical, electrical, and mechanical properties of BeO thin films formed via atomic layer deposition (ALD). Combined Rutherford backscattering and nuclear reaction analysis measurements show that ALD BeO thin films exhibit a low hydrogen content (<5%) and are nearly stoichiometric (Be/O ≅ 1.1 ± 0.05). Reflection electron energy loss spectroscopy measurements reveal a wide band gap of 8.0 ± 0.14 eV, and nanoindentation measurements show that ALD BeO has a high Youngs modulus and hardness of 330 ± 30 and 33 ± 5 GPa, respectively.

Band diagram for low-k/Cu interconnects: The starting point for understanding back-end-of-line (BEOL) electrical reliability

Abstract The starting point for describing the electrostatic operation of any semiconductor device begins with a band diagram illustrating changes in the semiconductor Fermi level and the alignment of the valence and conduction bands with other interfacing semiconductors, insulating dielectrics and metal contacts. Such diagrams are essential for understanding the behavior and reliability of any semiconductor device. For metal interconnects, the band alignment between the metal conductor and the insulating intermetal and interlayer dielectric (ILD) is equally important. However, relatively few investigations have been made. In this regard, we have investigated the band alignment at the most common interfaces present in traditional single and dual damascene low- k /Cu interconnect structures. We specifically report combined X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS) measurements of the Schottky barrier present at the ILD and dielectric Cu capping layer (CCL) interfaces with the Ta(N) via/trench Cu diffusion barrier. We also report similar measurements of the valence and conduction band offsets present at the interface between a-SiN(C):H dielectric CCLs and low- k a-SiOC:H ILDs (porous and non-porous). The combined results point to metal interfaces with the CCL having the lowest interfacial barrier for electron transport. As trap and defect states in low- k dielectrics are also important to understanding low- k /Cu interconnect reliability, we additionally present combined electron paramagnetic resonance (EPR) and electrically detected magnetic resonance (EDMR) measurements to determine the chemical identity and energy level of some electrically active trap/defect states in low- k dielectrics. Combined with the photoemission derived band diagrams, the EPR/EDMR measurements point to mid-gap carbon and silicon dangling bond defects in the low- k ILD and CCL, respectively, playing a role in electronic transport in these materials. We show that in many cases the combined band and defect state diagrams can explain and predict some of the observed reliability issues reported for low- k /Cu interconnects.

Valence and conduction band offsets at low-k a-SiOxCy:H/a-SiCxNy:H interfaces

In order to understand the fundamental electrical leakage and reliability failure mechanisms in nano-electronic low-k dielectric/metal interconnect structures, we have utilized x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy to determine the valence and conduction band offsets present at interfaces between non-porous and porous low-k a-SiOxCy:H interlayer dielectrics and a-SiCxNy:H metal capping layers. The valence band offset for such interfaces was determined to be 2.7 ± 0.2 eV and weakly dependent on the a-SiOC:H porosity. The corresponding conduction band offset was determined to be 2.1 ± 0.2 eV. The large band offsets indicate that intra metal layer leakage is likely dominated by defects and trap states in the a-SiOC:H and a-SiCN:H dielectrics.