Quantitative Evaluation of Gate Oxide Damage during Plasma Processing Using Antenna-Structure Capacitors

Saitoh

et al. 2014

Jpn. J. Appl. Phys.

Self Cite

The annealing performance of an elongated inductively coupled plasma (ICP) torch that enables instantaneous thermal processing over a large area has been improved by using a ceramic chamber that ensures better mechanical and thermal properties than a quartz chamber, realizing a substrate temperature higher than 1,600 K. Si wafers damaged by the bombardment of ions from Ar plasma were irradiated by the ICP torch for recovery. The thickness of the damaged layer was monitored by spectroscopic ellipsometry (SE), and the changes in Si crystal structure were examined by transmission electron microscopy (TEM). Significant decreases in damaged layer thickness and TEM contrast, which corresponds to the degree of damage, were observed after the ICP torch irradiation.

Section: Introductionmentioning

confidence: 99%

Annealing performance improvement of elongated inductively coupled plasma torch and its application to recovery of plasma-induced Si substrate damage

Okumura

Saitoh

et al. 2014

Jpn. J. Appl. Phys.

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“…2 The first mechanism is damage induced by conduction current from plasma flowing into MOSFETs, resulting in degradation of the performance and increase in the parameter variability owing to plasma-induced electrical stress. 1,4,5 This electrical interaction has been discussed and is called plasma-induced charging damage. 2 The second mechanism is damage induced by incident photons on material surface.…”

mentioning

confidence: 99%

Characterization of Plasma Process-Induced Latent Defects in Surface and Interface Layer of Si Substrate

Nakakubo

ECS J. Solid State Sci. Technol.

Ono

2015

Self Cite

Characterization of plasma-induced Si substrate damage is demonstrated using an electrical capacitance-voltage (C-V) technique customized for the nano-scale analysis. Low resistive Si wafers are exposed to an inductively coupled plasma (ICP) or a capacitively coupled plasma (CCP). We focus on the effects of plasma parameters and wet-etching processes on plasma-induced physical damage (PPD) analyses. The optical thicknesses of surface and interfacial layers (d SL and d IL ) were characterized using spectroscopic ellipsometry (SE) and compared with the electrical oxide thicknesses (EOT) obtained by the C-V technique. In the case of asdamaged samples, the optical thickness d SL by SE is found to be smaller than the EOT by the C-V technique, while the sum of d SL and d IL was approximately equal to the EOT. A diluted hydrofluoric acid (DHF) wet-etch step is employed to address depth profile of defect density in damaged samples. We identify the latent defect density, d SL , and d IL after the DHF wet-etch, which are indispensible for practical device performance designs. It is found that, although the average energy of incident ions (Ē ion ) is larger for the case of CCP, the latent defect density of CCP-damaged samples is smaller than that of ICP even after the wet-etching. This finding is in sharp contrast to previous pictures-the largerĒ ion leads to the thicker damaged layer and the larger latent defect density. We propose a model for these conflicting results, where the profiles of defect density and the sensitivities of each analysis technique are taken into account. The present work highlights the importance of the nano-scale damage characterization using the C-V technique, allowing to understand the influence of latent defects and to enable better design of future electronic devices. Plasma processing plays an important role in manufacturing present-day microelectronics. Over the last two decades, plasma process-induced damage (PID) has been one of the crucial problems in fabricating metal-oxide-semiconductor field-effect transistors (MOSFETs) 1-3 in LSI (Large Scale Integration) circuits. PID consists of four major mechanisms.2 The first mechanism is damage induced by conduction current from plasma flowing into MOSFETs, resulting in degradation of the performance and increase in the parameter variability owing to plasma-induced electrical stress. 1,4,5 This electrical interaction has been discussed and is called plasma-induced charging damage.2 The second mechanism is damage induced by incident photons on material surface. Photons with high energy can interact with materials such as photoresist masks and low-k dielectrics, leading to bond breaking in the materials exposed to plasma, or in some cases, create an interface state between SiO 2 and Si substrate.6-8 The third mechanism is surface and bulk chemical reaction with fast diffusion reactions causing material modification such as surface defects and roughness. The fourth mechanism is damage induced by high-energy ion bombardment on Si substrates or oth...

“…Also it has been reported that the plasma processing degrades the transconductance of MOSFETs [8], [9] and accelerates the hot carrier degradation [8]. We found that Qbd is a good monitor for the antenna effect [2] as shown in Fig.9, while tbd is "not", as shown in Fig.10. In these results, the oxide damage is induced by the plasma process.…”

Section: Applications To Evaluation Of Process-induced Gate Oxide Degmentioning

confidence: 60%

“…The physical parameters in the calculation are listed in Table I. By the new method, tbd under various voltages are "calculated" using (2), which are demonstrated in Figs.5 and 6. By extrapolating the t,, versus applied voltage characteristics, the oxide lifetime under various applied voltages is determined.…”

Section: Resultsmentioning

confidence: 99%

“…J(t) for the large antenna ratio becomes small due to the plasma-induced electron trapping. The small value of J(t) induces the decrease in J(t)lQbAJ) in (2), which determines the oxide lifetime (tbd). This means that the tbd testing leads to overestimation of the oxide lifetime for the large antenna ratios.…”

Section: Applications To Evaluation Of Process-induced Gate Oxide Degmentioning

confidence: 99%

See 1 more Smart Citation

A new gate oxide lifetime prediction method using cumulative damage law and its applications to plasma-damaged oxides

Proceedings of International Electron Devices Meeting

Uraoka²,

Odanaka³

A Model for Cumulative Damage LawThe Cumulative Damage Law to the electrical stress, which correlates charge-to-breakdown with constant current injection (Q,,) to time-to-breakdown with constantvoltage stress (t,,), is theoretically derived from the defect generation model. Based on this law, we propose a new gate oxide lifetime prediction method. Although in some cases, the degradation of gate oxide induced by the plasma and ion implantation processes can not be distinguished by tbd measurement, the new method allows an accurate and relevant evaluation of process-induced gate oxide degradation.The gate oxide wearout is related to the generation of the defects such as the electron trapping in the oxide and the interface states [4]. In general, the defect generation model includes the generation rate as a function of "the electron energy, E" in the oxide [4]. Since the electron energy relaxation length in SiO, films is about 5 nm [5], the energy distribution is assumed to be in equilibrium at the interface in the case of the oxide thicker than 5 nm. Therefore, instead of E, we introduce the new generation rate a(J) as a function of "the current density J" (or "the electrical field E,,") into the conventional rate equation as follows: Introduction dnldt = MJ) J l e ( N -n)(1) Process-induced degradation of gate oxide becomes a key issue in the development for highly reliable MOSFET devices. Charge-to-breakdown with constant current injection (Q,) has been proposed to evaluate the gate oxide degradation induced by the antenna effect [1],[21. However, the Q, method has little impact on the "lifetime" prediction (time-to-breakdown with constant-voltage stress ; tbd) of the gate oxide degradation. Also, the plasmainduced damage has not so far been characterized by t,, measurement. It is needed to clarify the relationship between Qbd and tbd and to evaluate the process-induced oxide lifetime degradation.The purpose of this paper is to present a new lifetime prediction method based on Cumulative Damage Law to the electrical stress. The Cumulative Damage Law [3], which explicates the relationship between Qbd and t, , is theoretically derived from a new defect generation model. It is also found that the gate oxide degradation induced by the plasma and ion implantation processes can not be characterized by the tbd testing. The present prediction method gives an excellent explanation for this phenomenon and clearly characterizes the plasma-induced and ion implantation-induced oxide lifetime degradation.where n is the defect density, e is the elemental charge, and N is the precursor defect sites. As shown in Fig.1, Qbd measurement introduces J-dependence of Q, and the defect generation rate MJ,J for (I). In the case of t, , measurement, J is a function of time in (1).We postulate that the oxide breaks down when n reaches a critical value No which is independent of the stress type. Then, the two equations can be integrated until n=No for both Qbd and tbd measurements, respectively. By assuming that a(J) in tbd testing is equa...