Plasma Phase Chemistry Research Articles

Oxygen-Based Reactive Ion Etching of Ruthenium Thin Film

Copper (Cu) is a popular interconnect material in ICs and other microelectronics. As the technology node is reduced, the performance of copper interconnect lines becomes challenging due to the CMP limitation and the reliability concern [1,2]. It has been suggested that Ruthenium (Ru) can replace Cu in the sub 10 nm node for better conductivity and reliability [3]. An effective plasma etching method for Ru is needed to meet the demand of the industry [4,5].O2 can be utilized in the plasma etch of Ru as it can form volatile RuO3 and RuO4 in the process [5-9]. However, the solid RuO2 can also be formed on the Ru surface, which decreases the overall etch rate of the film [9]. Gases, such as N2, Cl2, and CF4, can be added to the O2 plasma to enhance the removal of RuO2 [6,7]. In this study, authors investigated the RIE etch of Ru using the O2/Ar and O2/N2 feed gases.The TiW (10nm)/Ru (280 nm) stack was sputter deposited on a silicon dioxide (SiO2) coated silicon (Si) wafer [10]. TiW served as a barrier layer similar to the Cu case [10]. The etching experiment was done in a parallel reactor system (PlasmaTherm 700) under the RIE mode with a constant flow rate of 25 sccm at various O2/Ar and O2/ N2 ratios, 450W to 600W power, and 50 mTorr and 70 mTorr pressure. The photoresist and Ru etch rates were determined from the thickness change before and after the etch.Figure 1 (a) shows the Ru etch rate as a function of the Ar concentration in the Ar + O2 feed stream. As the increase of Ar concentration in the feed stream, the overall etch rate decreased, unlike in previous studies, where the addition of additive gases with an O2 mixture improved the etch rate of the thin films [5-7]. However, this phenomenon can be explained by changes in the ion bombardment energy and plasma phase chemistry, as shown in Fig. 1 (b) and (c).Fig. 1 (b) shows the slight change of the cathode self-bias voltage -Vdc with the increase of the Ar concentration in the feed stream over a large range of plasma power. Since ion bombardment enhances the removal of the reaction product, the very small change of the -Vdc indicates that the change of the etch rate is very slightly contributed by the removal of the RuOx product.Fig. 1(c) shows changes in two major radical components, i.e., O 777.5 nm and Ar 751 nm, with the increase of the Ar concentration in the feed stream. With the addition of Ar in the feed stream, the O radical concentration is reduced while the Ar radical concentration is increased. This result indicates that the Ru etch is more influenced by the O radical etchant concentration than the ion bombardment [5,7].A minimum ion bombardment energy may still be needed for the etch process, which will be discussed in the presentation. In addition, the influence of N2 on the Ru etch rate will be discussed with respect to the plasma phase chemistry and ion bombardment energy.[1] S. Paolillo, et al., J. Vac. Sci. Technol. B, 36(3), E103 (2018).[2] R. Chang, et al., IEEE TED, 51, 1577 (2004).[3] L. G. Wen, et al., ACS Appl. Mater. Int., 8(39), 26119 (2016).[4] SIA Roadmap for Semiconductors (2003).[5] C. C. Hsu, et al., J. Vac. Sci. Technol. A, 24(1), 1 (6006).[6] W. Pan and S. B. Desu, J. Vac. Sci. Technol. B, 12(6), 3208 (1994).[7] E. J. Lee, et al., Jpn. J. Appl. Phys., 37(5R), 2634 (1998).[8] S. M. Hwang, et al., Thin Solid Films, 587, 28 (2015).[9] M. Nakahara, et al., J. Vac. Sci. Technol. B, 19(6), 2133 (2001).[10] Y. Kuo, M. Li, J. Q. Su, ECS Transactions., 92(5), 9 (2019). Figure 1

Direct Observation of Plasma-Stimulated Activation of Surface Species Using Multimodal In Situ/Operando Spectroscopy Combining Polarization-Modulation Infrared Reflection-Absorption Spectroscopy, Optical Emission Spectroscopy, and Mass Spectrometry.

Nonthermal plasmas (NTPs) produce reactive chemical environments, including electrons, ions, radicals, and vibrationally excited molecules, that can drive chemistry at temperatures at which such species are thermally inaccessible. There has been growing interest in the integration of conventional catalysis with reactive NTPs to promote novel chemical transformations. Unveiling the full potential of plasma-catalytic processes requires a comprehensive understanding of plasma-catalytic synergies, including characterization of plasma-catalytic surface interactions. In this work, we report on a newly designed multimodal spectroscopic instrument combining polarization-modulation infrared reflection-absorption spectroscopy (PM-IRAS), mass spectrometry, and optical emission spectroscopy (OES) for the investigation of plasma-surface interactions such as those found in plasma catalysis. In particular, this tool has been utilized to correlate plasma-phase chemistry with both surface chemistry and gas-phase products in situ (1) during the deposition of carbonaceous surface species via NTP-promoted nonoxidative coupling of methane and (2) during subsequent activation of surface deposits with an atmospheric pressure and temperature argon plasma jet on both nickel (Ni) and silicon dioxide (SiO2) surfaces. For the first time, the activation of carbonaceous surface species by a NTP on Ni and SiO2 surfaces to form hydrogen gas and C2 hydrocarbons was directly observed, where both PM-IRAS and OES measurements suggest that they may form through different pathways. This unique tool for studying plasma-surface interactions could enable more rational design of plasma-stimulated catalytic processes.

Emission spectra study of plasma enhanced chemical vapor deposition of intrinsic,n+, andp+amorphous silicon thin films

ABSTRACTThe PECVD intrinsic,n+, andp+a-Si:H thin film deposition processes have been studied by the optical emission spectroscope to monitor the plasma phase chemistry. Process parameters, such as the plasma power, pressure, and gas flow rate, were correlated to SiH*, Hα*, and Hβ* optical intensities. For all films, the deposition rate increases with the increase of the SiH* intensity. For the doped films, the Hα*/SiH* ratio is a critical factor affecting the resistivity. The existence of PH3or B2H6in the feed stream enhances the deposition rate. Changes of the free radicals intensities can be used to explain variation of film characteristics under different deposition conditions.

Process effects of copper film over a step etched with a plasma-based process

The additive gas effect of a new plasma-based process for etching the copper film over a dielectric step has been investigated. The addition of different gases, such as Ar, N2, and CF4, affected the copper vertical and lateral conversion rates, which are critical to the attack of the cusp region and the sidewall as well as the residue formation. This is due to changes of plasma phase chemistry and ion bombardment energy. Excessive attacks of the cusp region and the sidewall were observed when the chlorine radical concentration was high except for the short plasma exposure time or the sidewall passivation condition. When the slope angle of the dielectric step was small, the cusp structure of the copper film was barely visible; therefore, the excessive plasma attack of the cusp region was negligible. A two step etch process that minimizes excessive attacks of the cusp region and the sidewall as well as the residue formation has been developed. This new process is critical to the practical application of copper in microelectronic products.

Plasma Etching of Copper Thin Film over a Dielectric Step and Electromigration Failure Mechanism

ABSTRACTProcess and electromigration issues of the copper line over a dielectric step etched with a new plasma-based process have been studied. The N2 and CF4 additive gas effects on the line profile, undercut, and “neck” formation at the cusp area were investigated with respect to changes of the plasma phase chemistry and ion bombardment energy. The sidewall passivation layer hindered the excessive attack of the cusp region. The undercut of the photoresist pattern caused the residue formation. The lifetime of the etched copper was related to the line shape and the film topography, which directly affected the local current density and stress. With the proper control the plasma phase chemistry and ion bombardment energy, the Cu film over a topographic surface can be etched into fine lines with a long electromigration lifetime.

Additive-Gas Effects on Cl2 Plasma-Based Copper-Etch Process and Sidewall Attack

The influence of the additive gas in plasma-based copper etch and sidewall attack was investigated. The additive gas, such as Ar, , and , drastically changed the plasma-phase chemistry, i.e., the Cl radical concentration, and the ion-bombardment energy, which resulted in changes of the copper chlorination rate and the sidewall roughness. The addition of Ar increased the Cl concentration, which increased the copper chlorination rate and the sidewall attack. The addition of enhanced ion bombardment, which increased the copper chlorination rate. Meanwhile, the addition of diluted the Cl concentration and formed a copper nitride passivation layer, which protected the sidewall and reduced roughness. The addition of induced a fluorocarbon passivation layer, which decreased the copper chlorination rate in the vertical direction but protected the sidewall from vigorous Cl attack and resulted in a smooth sidewall surface. Therefore, the additive gas not only affected the Cu chlorination rate but also influenced sidewall roughness.

Hydrogen bromide plasma–copper reaction in a new copper etching process

The hydrogen bromide (HBr) plasma–copper reaction, which is the base of a new copper etching process, has been studied. A high etch rate has been obtained with the reaction. Influences of process parameters, such as plasma exposure time, pressure, plasma power and substrate temperature, to the reaction process were explored. In addition to the reaction rate, we also investigated the relationship between the morphology and structure of the reaction product layer and the process condition. The results show that both the plasma-phase chemistry and the ion bombardment energy are important to the reaction. Mechanism for the HBr plasma–Cu reaction process was compared with that for the HCl or Cl 2 plasma–Cu reaction. The reaction product was characterized with X-ray photoemission spectroscopy and X-ray diffraction. These results are critical to the understanding of this new copper dry etching process.

A New Hydrogen Chloride Plasma-Based Copper Etching Process

The plasma–copper reaction that is based on the hydrogen chloride (HCl) feed gas has been studied. Copper line can be etched at a high rate with this process. The wall profile can also be controlled by the process condition. Influences of process parameters such as plasma exposure time, pressure, plasma power, and substrate temperature, to the reaction process were investigated. In addition to the reaction rate, the relationships between the structure of the reaction product and the process condition were investigated. The results show that both the plasma-phase chemistry and the ion bombardment energy play important roles in the reaction mechanism. The reaction product is a non-stoichiometric, non-homogeneous, and polycrystalline CuClx film. These results are critical to the fabrication of advanced microelectronic devices as well as to the understanding of this new copper dry etching process.

Chlorine Plasma/Copper Reaction in a New Copper Dry Etching Process

The chlorine plasma/copper reaction that is the base of a new copper (Cu) dry etching process was studied. The reaction product is a rough and porous Cu chloride compound film. Influences of process parameters such as plasma exposure time, pressure, plasma power, and substrate temperature, on the copper chlorination process, were explored. In addition to variations of morphology and reaction rate, we also investigated the relationship between the structure of the reaction product and the process condition. The result shows that both the plasma phase chemistry and the ion bombardment energy are critical to the reaction mechanism and the reaction product’s morphology. A simple model that describes the progress of the reaction through the Cu layer has been developed based on above results. This study result indicates that it is possible to etch Cu with a plasma process at room temperature. © 2001 The Electrochemical Society. All rights reserved.

RF plasma deposition of SiO 2-like films: plasma phase diagnostics and gas barrier film properties optimisation

Hexamethyldisiloxane/oxygen fed radiofrequency glow discharges have been utilised for the deposition onto polyethyleneterephtalate of transparent silicon dioxide-like films with barrier properties to oxygen. The complexity of such plasma phases and the increasing interest shown for the industrial deposition process of barrier films have led the authors to investigate Fourier transform infrared absorption spectroscopy as a plasma technique for better understanding of the deposition mechanism and the development of a process control useful for scaling up. The above mentioned technique has shown its potential in the correlation of plasma phase chemistry with the barrier properties of the SiO x coated polymer, especially when very good performances are required (OTR≤3 cm 3/m 2 day atm).

Room-temperature copper etching based on a plasma–copper reaction

A promising room-temperature copper etching process is described. The copper thin film can be etched into a vertical profile at a high rate using a parallel-plate reactor under mild conditions. The key factor for the success of this process is a copper swelling phenomenon from the plasma–copper reaction. The reaction product has been identified as a crystalline copper chloride. Key parameters that influence the reaction process and the final copper profile have been studied. In addition to the plasma phase chemistry, ion bombardment plays a critical role in the process. Although results reported in this letter are based on the chlorine plasma, similar results can be obtained with other halogen gases. This process is potentially important to the fabrication of advanced microelectronic, storage, display, and optical devices.

A Mass Spectral Investigation of the RF Plasmas of Small Organic Compounds: An Investigation of the Plasma-Phase Reactions in the Plasma Deposition from Allyl Amine

Inductively coupled, radiofrequency-induced plasmas of allyl amine, operated at low values of electrical power P/ monomer flow rate Φ (ΦP/Φ), have been investigated using mass spectrometry (MS) and deposition rate measurements. The solid, plasma deposit products were obtained as films and analyzed by X-ray photoelectron spectroscopy (XPS) and grazing angle infra-red (IR). The positiveion MS data indicate that species of the general types (nM − H)+, (nM+H)+, and nM+, where M represents a unit of the starting material (monomer), are present in the plasma. The relative abundance of these was monitored as a function of the electrical power supplied to the plasma. Mass spectrometry of the plasma neutrals revealed that only M and its fragments are present in the plasma: no neutral oligomeric species were detected. XPS analysis revealed that the plasma deposits contain at least three different nitrogen functional groups. The relative proportions of these were only marginally affected by plasma power. The deposition rate increased with P/Φ. The observation of three classes of species in the plasma-phase sets allyl amine apart from other compounds previously studied. We believe that the plasma-phase chemistry accounts for the low retention of amine in the solid-phase plasma product and for the weak dependence of deposit chemistry on P/Φ.

Effects of “processing parameters” in plasma deposition: Acrylic acid revisited

In this article we explore the relationship between the plasma-phase chemistry and deposit in the plasma deposition of acrylic acid. This is achieved through systematic variation of some of the plasma deposition variables, termed “processing parameters.” The surface chemical composition of deposits has been investigated by means of x-ray photoelectron spectroscopy. Changes in the surface chemical composition with the ratio of plasma power-to-monomer flow rate, P/φ, substrate position (in the reactor), nature of the substrate, and washing and aging (of the deposit) are examined. Based on these, we provide a qualitative description of the deposits’ molecular structure, and how this changes with P/φ. The plasma-phase chemistry has been probed by means of mass spectrometry and attention given to the effect of P/φ on the neutral and ionic components of the plasma. The major plasma-phase reactions are elucidated, and a knowledge of these help to explain how the molecular structure of plasma deposits are affected by P/φ and other processing parameters.

High Temperature Reactive Ion Etching of Indium‐Tin Oxide

Reactive ion etching of indium‐tin oxide at 250°C based on , and gases has been studied. An etch rate as high as 435 Å/min has been achieved. Depending on process parameters such as temperature, gas, power, and pressure, the etch rate can be controlled by ion bombardment energy alone or by plasma phase chemistry and ion bombardment energy. The bottleneck step of the surface reaction can be the reduction of the metal oxide or the removal of reaction products. These process results are consistent with the surface analysis data. Photoresist can be used as a masking layer in the 250°C plasma etching process when the mask is properly designed and the feeding gas includes .

Reactive Ion Etching of Sputter Deposited Tantalum with CF4, CF3Cl, and CHF3

This paper discusses the reactive ion etching of tantalum with Freon gases. Factors affecting the etch rate, such as the power, pressure, and temperature, were studied over a wide range of conditions. The chlorine component enhanced the etch rate and the hydrogen component hindered the etch rate. Activation energies of the CF4 and the CHF3 processes were measured. For CF4 and CF3Cl plasmas, both the plasma phase chemistry and the surface reaction affected the etch rate. For the CHF3 plasma, the ion bombardment energy controlled the etch rate. Electron spectroscopy for chemical analysis (ESCA) results on the etched surfaces revealed: 1) the tantalum etch mechanism included two steps, i.e., the oxidation step and the product formation step; 2) residues on the CHF3 etched surface were different from those on the CF4 etched surface; 3) the difference in residues could explain the etch rate difference. Secondary ion mass spectroscopy (SIMS) analysis results showed that the CHF3 etched surface contained hydrogen and fluorohydrocarbons, which may be responsible for its low oxygen absorption.

Effects of Oxygen Addition in the CCl4 Reactive Ion Etching of a-SiC:H Films

We have studied the effects of oxygen addition in the CCl4 reactive ion etching of hydrogenated amorphous silicon carbide (a-SiC:H) films. The effects of oxygen on the etching profile of a-SiC:H films, the etch rates of a-SiC:H and oxide, and the etching selectivity of a-SiC:H/oxide are examined. It is observed that the addition of oxygen into CCl4 plasma greatly increases the etch rate of a-SiC:H and the etching selectivity of a-SiC:H/oxide, while gradually changes the etching process from being anisotropic to isotropic. Experimental data are interpreted with the examining of the plasma phase chemistry and ion bombardment energy. An etch mechanism is proposed for explaining the observed effects.

Reactive Ion Etching of PECVD n+ a‐Si:H: Plasma Damage to PECVD Silicon Nitride Film and Application to Thin Film Transistor Preparation

Process parameters that affect the reactive ion etching of PECVD n+ a‐Si:H film have been studied. The n+ a‐Si:H etching mechanism is similar to that of a‐Si:H etching, e.g., both plasma phase chemistry and ion bombardment are contributing factors. The high chlorine‐containing plasma etches the film faster than the low chlorine‐containing plasma. The n+ a‐Si:H to a‐Si:H etch rate ratio is around 1.7 in either or plasma, independent of the pressure and the power when the power is higher than 500 W. A high etch ratio of n+ a‐Si:H to silicon nitride (e.g., between 3 and 30) has been obtained with these two gases. Plasma phase chemistry affects the etch rate ratio more than the ion bombardment does. The silicon nitride surface damage has been measured to be less than 60 Å by the Auger profile method. The EPR intensity of the plasma etched silicon nitride film increases with the increase of the etch time and power, but decreases with the increase of pressure. The film damage does not introduce current leakage through the silicon nitride layer, nor does it deteriorate the TFT characteristics.

The Role of Oxygen In the CF2Cl2 Reactive Ion Etching of Pecvd Films

ABSTRACTAn extensive study on 02 effects on RIE of PECVD a-Si:H and SiNx has been carried out. Mixtures of CF2Cl2/HCI and CF2Cl2/CF3Cl were used as base gases. The addition of O2 into these gases changed the film etch rate and etch selectivity in different ways. Process results were interpreted by examining the plasma phase chemistry, the ion bombardment energy, and ESCA surface chemical states.

Reactive ion etching of plasma enhanced chemical vapor deposition amorphous silicon and silicon nitride: Feeding gas effects

Reactive ion etching of PECVD a-Si:H and silicon nitride films was investigated using CF4, C2F6, CHF3, CF3Cl, and CF2Cl2 gases. Under the same power the a-Si:H etch rate decreases in the order of: CF4∼CF3Cl>CF2Cl2>C2F6>CHF3; and the nitride etch rate decreases in the order of: CF4>CF3Cl∼C2F6>CF2Cl2>CHF3. The etch selectivity is controlled by two competitive mechanisms: plasma chemistry and surface reactions. When no surface mass-transfer-limit layer is formed, the plasma phase chemistry dominates the etch rate of the film. For example, the silicon etch rate increases with the chlorine concentration in the plasma phase. When the surface is covered with a thin film, the etch rate is controlled by the ion bombardment energy. For example, the film etch rate in the C2F6 plasma depends on the self-bias voltage only. ESCA and emission spectra results support the above theory.

Thin films of a-Si1−xGex:H alloys by dual magnetron sputtering in a UHV chamber

This paper discusses the bonding of H atoms in a-Si1−xGex: H alloys that are deposited in a dual magnetron sputtering system. The relative numbers of SiH and GeH bonds, as a function of the Ge content are found to be qualitatively different than in films (a) grown by the glow discharge (GD) decomposition of germane, silane mixtures, or (b) deposited in diode sputtering (DS) systems with Ge/Si targets. The intrinsic films deposited by magnetron sputtering display higher concentrations of bonded H in monohydride arrangements and higher majority carrier photoconductivities than either the GD or DS alloy films. These differences are explained in terms of a model for H atom incorporation which emphasizes the relative importance of surface and plasma phase chemical interactions. In the magnetron films, H atom bonding is primarily determined by surface reactions, whereas in the other two techniques plasma phase chemistry is the dominant factor which favors precursors with SiH rather than GeH bonds.