Nanoporous materials show a large surface area and co-continuous topology, leading to a high sensitivity to chemically active components over macroscopic length scales. The processing of nanoporous systems can be complex, causing modifications of the original material, or appearance of unwanted contaminants. The present work report on a protection method based on temporary filling by a sacrificial template polymer, forming in-situ a reversible urea linkage. Microporous organo-silicate low-k dielectric thin films are used as demonstrators, exposed to aggressive plasma discharges. Depending on the studied material, the fraction of filled pore volume varies between 29 and 66 %, with a homogeneous spatial distribution. The filling component is formed by a blend of urea-linked polymer and isocyanate-terminated monomers, is stable during plasma processing and can be fully removed by annealing above 300°C. This sacrificial filler protect the internal structure of the porous dielectric from the plasma, leading to...

The integration of porous organo-silicate low-k materials has met a lot of technical challenges. One of the main issues is plasma-induced damage, occurring for all plasma steps involved during interconnects processing. In the present paper, we focus on porous SiOCH low-k damage mitigation using cryogenic temperature so as to enable micro-capillary condensation. The aim is to protect the porous low-k from plasma-induced damage and keep the k-value of the material unchanged, in order to limit the RC delay of interconnexion levels while shrinking the microchip dimension. The cryogenic temperature is used to condense a gas inside the porous low-k material. Then, the etching process is performed at the temperature of condensation in order to keep the condensate trapped inside the material during the etching. In the first part of this work, the condensation properties of several gases are screened, leading to a down selection of five gases. Then, their stability into the porous structure is evaluated at different temperature. Four of them are used for plasma damage mitigation comparison. Damage mitigation is effective and shows negligible damage for one of the gases at –50°C.

In back-end-of-the-line (BEOL) patterning process, porous low-k dielectrics are degraded by plasma reactive species during etching and resist stripping -this is so-called plasma induced damage (PID). PID increases the k-value of dielectrics and inter-line capacitance, which causes resistive-capacitive (RC) delay. In this paper, the authors introduce two approaches to suppress the PID, using a novel volatile organic film. The first approach is an improved Post Porosity Plasma Protection (P4, or pore stuffing), and the second approach is based on the use of a temporary plug. In the case of pore stuffing, the filling ability and protection effect are evaluated on various blanket low-k dielectric materials. For the plug approach, its effectiveness is demonstrated in terms of electrical characteristics and reliability using a patterned interconnect test vehicle.

Porous low-k dielectrics play an important role in lowering the circuit capacitance in nano-interconnects. However, these materials are damaged during plasma etching process and subsequent steps, leading to a degradation of their dielectric properties. Many methods have been suggested to solve this issue. The post porosity plasma protection (P4) from IBM [1] is a possible solution which protects the pores of low-k dielectrics by filling them with sacrificial polymers before the plasma process, which are removed later in the flow. In this paper, we suggest a new method to protect the pores, so-called Gas Phase Pore Stuffing (GPPS).

Plasma induced damage on porous low-k dielectrics is a critical issue for lowering the interconnect RC delay in densely packed CMOS transistors. In this paper, we propose a new approach to protect the pores on porous organo-silicate glasses (OSG) during plasma process, so-called Gas Phase Pore Stuffing (GPPS).

The plasma etching of a k = 2.3 periodic mesoporous ultra-low-k dielectric is studied, using a new gas mixture made of a high boiling point organic (HBPO) reagent and NF3. By decreasing the wafer temperature below 10 °C, the onset of micro-capillary condensation is observed, inducing pore wall passivation (∼10 °C < T < ∼ −20 °C, refractive index between 1.27 and 1.38) then complete pore filling (T < −20 °C, refractive index ∼1.38). The HBPO condensed phase is found to be stable for more than one minute for temperatures below −30 °C. The patterning capabilities of the discharge are studied on a 45 nm half pitch vehicle, leading to plasma etch conditions giving good morphological profiles and reduced sidewall damage. Due to HBPO condensation, the pristine carbon content of the film is maintained, preventing any drift in k-value. The absence of damage also prevents significant modifications of the mechanical properties of the ultra-porous low-k material. The present work shows that electrically and mechanically safe low-k etching can be achieved with an NF3/HBPO plasma, around −30 °C.

The micro-capillary condensation of a new high boiling point organic reagent (HBPO), is studied in a periodic mesoporous oxide (PMO) with ∼34 % porosity and k-value ∼2.3. At a partial pressure of 3 mT, the onset of micro-capillary condensation occurs around +20 °C and the low-k matrix is filled at −20 °C. The condensed phase shows high stability from −50 < T ≤−35 °C, and persists in the pores when the low-k is exposed to a SF6-based plasma discharge. The etching properties of a SF6-based 150W-biased plasma discharge, using as additive this new HBPO gas, shows that negligible damage can be achieved at −50 °C, with acceptable etch rates. The evolution of the damage depth as a function of time was studied without bias and indicates that Si-CH3 loss occurs principally through Si-C dissociation by VUV photons.

Porous low-k dielectrics play an important role in lowering the circuit capacitance in nano-interconnects. However, these materials are damaged during plasma etching process and subsequent steps, leading to a degradation of their dielectric properties. Many methods have been suggested to solve this issue. The post porosity plasma protection (P4) from IBM [1] is a possible solution which protects the pores of low-k dielectrics by filling them with sacrificial polymers before the plasma process, which are removed later in the flow. In this paper, we suggest a new method to protect the pores, so-called Gas Phase Pore Stuffing (GPPS).

Polymer grafting was studied in porous low-k SiCOH films as a protection against plasma damage. Pores of low-k films were covered by a plasma damage management polymer. A multistep deposition approach was applied to increase the polymer layer thickness that helped avoid pore stuffing, nonuniform deposition and polymer overburden. To study polymer protection, low-k films were exposed to F radicals and VUV photons, separately and simultaneously, at temperatures from -45 degrees C to +10 degrees C. Effective polymer protection at room temperatures was demonstrated. Lowering the temperature decreases degradation by F radicals while VUV damage, which is temperature independent, became dominant. Low-k damage protection was also significant under simultaneous exposure to F radicals and VUV photons. In the tested temperature range damage under simultaneous exposure to F radicals and VUV photons was higher than the sum of separate F and VUV damage due to a synergistic effect. To decrease the material k-value after etching, the polymer was removed from the pore walls using UV cure. It was shown that almost complete polymer removal was achieved after UV treatment. The described approach was applied to low-k etching in RF CCP CF4, CF4/Ar plasmas and exposure to Ar plasma. Significant improvement of the film k-value after the plasma treatment was confirmed.

Two x-ray photoelectron spectroscopy configurations are proposed to analyze the surface chemistry of micron-scale InP ridge structures etched in chlorine-based inductively coupled plasma (ICP). Either a classical or a grazing configuration allows to retrieve information about the surface chemistry of the bottom surface and sidewalls of the etched features. The procedure is used to study the stoichiometry of the etched surface as a function of ridge aspect ratio for Cl2/Ar and Cl2/H2 plasma chemistries. The results show that the bottom surface and the etched sidewalls are P-rich, and indicate that the P-enrichment mechanism is rather chemically driven. Results also evidence that adding H2 to Cl2 does not necessarily leads to a more balanced surface stoichiometry. This is in contrast with recent experimental results obtained with the HBr ICP chemistry for which fairly stoichiometric surfaces have been obtained.

The chemical composition of the surface of InP samples etched in Cl2 and Cl2/Ar inductively coupled plasma (ICP) is analyzed using ex-situ x-ray photoelectron spectroscopy (XPS). Comparison between ex-situ and in-situ XPS measurements shows that the stoichiometry of the etched surface can be retrieved from the ex-situ analysis provided that an adapted procedure is used. This allows for investigating the evolution of the surface stoichiometry as a function of etching parameters. The sample temperature is found to play a determining role in the top surface composition during etching. An abrupt switch from a rough and In-rich surface to a smooth and significantly P-rich surface is observed above a critical temperature and is found to depend only weakly upon the other etching parameters such as direct current bias or pressure. Ex-situ XPS measurements are used to estimate the thickness of the phosphorus layer identified on the top surface as ∼1 nm, which is consistent with the value previously derived using in-situ XPS. Finally, the stoichiometry of the InP etched sidewalls is analyzed selectively using dedicated microscale periodic patterns. The surface P-enrichment of the etched sidewalls is found to be very similar to that of the bottom etched surface. The presence of the phosphorus top layer may have an impact on the sidewall passivation mechanism during anisotropic ICP etching of InP-based heterostructures using Cl2-containing plasma chemistry.

A global kinetic model of Cl-2/Ar/N-2 plasma discharge has been developed, which allows calculation of the densities and fluxes of all neutral and charged species considered in the reaction scheme, as well as the electron temperature, as a function of the operating conditions. In this work, the results from the global model are first compared to the calculations given by other models. Our simulation results are focused on the effect of nitrogen adding to the Cl-2/Ar plasma mixture, which impacts both neutral and charged species transport phenomena. The N-2 percentage is varied to the detriment of Cl-2 by keeping the total flow rates of Cl-2 and N-2 constant. In order to better understand the impact of N-2 addition to the Cl-2/Ar gas mixture, the authors analyzed the output plasma parameters calculated from the model for different N-2 flow rate percentages. Indeed, the simulation results show a decrease in electron density and an increase in electron temperature with increasing percentage of N-2. Particular attention is paid to the analysis of electronegativity, Cl-2 and N-2 dissociation, and positive ion to neutral flux ratio evolution by varying percentage of N-2. Such parameters have a direct effect on the etching anisotropy of the materials during the etching process. (C) 2013 American Vacuum Society. [http://dx.doi.org/10.1116/1.4766681]

A 2D Monte-Carlo etching model of InP by a Cl2/Ar/N2 plasma discharge coupled to our kinetic plasma model and sheath model have been developed. It allows prediction of geometrical and chemical profile of etched trenches versus the operating conditions. The plasma kinetic model is performed to quantify reactive species densities and fluxes of Cl, N, and positive ions. The latter are introduced as input parameters in the etching model. Under Cl2/Ar plasma mixture, the mechanism of bowing development is attributed to chemical desorption of InClx sites. The addition of nitrogen into Cl2/Ar gas mixture outline the role of nitrogen in the formation of a passivated layer on the side wall.[GRAPHICS].

A multiscale approach has been developed in order to simulate the etch process of InP in an inductive coupled plasma (ICP) Cl-2/Ar plasma discharge. The model consists of three modules: a global kinetic model of the Cl-2/Ar plasma discharge, a sheath model, and a 2-D Monte-Carlo etching model. The densities and the fluxes of all neutral and charged species considered in the reaction scheme as well as the electron temperature are calculated from the global model. The angular and energy distribution functions of ions are computed from the sheath model. The output parameters of both the global kinetic model and the sheath model in terms of particle fluxes, ion angular distribution function and ion energy distribution function are used as input parameters in the 2-D etching model. The latter allows tracking in time the evolution of the etched surface. The ultimate goal of the multiscale approach is to predict the etch rate, the etched surface chemical composition, and the etch profile as a function of the operating conditions (power, pressure, gas flow rates, etc). In this paper, the results from the global model are first compared to the measurements carried out in the ICP etching tool, showing a satisfactory agreement. The etching model is then used to simulate the etching of narrow trench and small-diameter hole in InP. The mechanisms involved in the development of undercut below the mask and in the bowing effect are analyzed. The comparison between simulated and experimental etch profiles evidences the important role of Cl adsorption probability on the development of the undercut, and the significant impact of the redeposition of the etched species on the etch rate variation and on the narrowing in the bottom of the etched hole/trench.

A multiscale approach has been developed in order to simulate the etch process of InP in an inductive coupled plasma (ICP) Cl 2 /Ar plasma discharge. The model consists of three modules: a global kinetic model of the Cl 2 /Ar plasma discharge, a sheath model, and a 2-D Monte-Carlo etching model. The densities and the fluxes of all neutral and charged species considered in the reaction scheme as well as the electron temperature are calculated from the global model. The angular and energy distribution functions of ions are computed from the sheath model. The output parameters of both the global kinetic model and the sheath model in terms of particle fluxes, ion angular distribution function and ion energy distribution function are used as input parameters in the 2-D etching model. The latter allows tracking in time the evolution of the etched surface. The ultimate goal of the multiscale approach is to predict the etch rate, the etched surface chemical composition, and the etch profile as a function of the operating conditions (power, pressure, gas flow rates, etc). In this paper, the results from the global model are first compared to the measurements carried out in the ICP etching tool, showing a satisfactory agreement. The etching model is then used to simulate the etching of narrow trench and small-diameter hole in InP. The mechanisms involved in the development of undercut below the mask and in the bowing effect are analyzed. The comparison between simulated and experimental etch profiles evidences the important role of Cl adsorption probability on the development of the undercut, and the significant impact of the redeposition of the etched species on the etch rate variation and on the narrowing in the bottom of the etched hole/trench.

Submitted for the GEC12 Meeting of The American Physical Society A complete simulation of InP etching by Cl2/N2/Ar plasma mixture1 ROMAIN CHANSON, AHMED RHALLABI, MARIE CLAUDE FERNANDEZ, CHRISTOPHE CARDINAUD, Institut des Materiaux (IMN) University of Nantes, PLASMAS COUCHES MINCES TEAM — Deep anisotropic plasma etching of InP is an indispensable tool for the fabrication of a large variety of integrated optical devices. In this context, a 2D Monte Carlo etching model of InP by a Cl2/Ar/N2 plasma discharge coupled to a global kinetic plasma model and a sheath model have been developed. It allows the prediction of the geometrical and chemical profile of trenches etched through the mask versus the operating conditions. The plasma kinetic model is performed to quantify the reactive species densities and fluxes such as those of Cl, N and positive ions. The latter are introduced as the input parameters in the etching model. Under Cl2/Ar plasma mixture, the mechanism of the development of bowing defect is mainly attributed to the chemical etching of the adsorbed sites InClx. The impact of nitrogen addition into the Cl2/Ar gas mixture is studied. Both the simulations and the experiments show the role of the nitrogen on the disappearance of the bowing defect. This is attributed to the passivated layer due to the formation of InClxNy species. For a moderate nitrogen proportion, the passivated layer is mainly composed of InNCl2 and InNCl sites at the top of the InP etched trenches while at the bottom, the passivated layer is mainly composed by InN sites. 1This work is supported by French researcher agency (ANR) under INCLINE project. Ahmed Rhallabi Institut des Materiaux (IMN) University of Nantes Date submitted: 15 Jun 2012 Electronic form version 1.4