Plasma Etch Rate Research Articles

Examination of nonideal film growth in batch atomic layer deposition for plasma-resistant coatings

Atomic layer deposition (ALD) can be used to fabricate protective coatings including moisture barrier layers for organic light emitting diodes, anticorrosion layers for photoelectrodes, and plasma-resistant coating for semiconductor manufacturing equipment, which necessitates the deposition of large and thick ALD films via batch ALD. However, batch ALD for the fabrication of large-area and thick coatings exhibits nonideal film growth, a phenomenon that cannot solely be explained by transient concentration distribution within the deposition chamber. This paper describes the application of precursor “exposure” (in the unit of Langmuir, or Pa s), defined as the integral of concentration over time, as a metric to assess the growth per cycle (GPC) distribution under nonideal ALD conditions, demonstrating that the local GPC correlates well with the cumulative precursor exposure at that site. Consequently, this measure can effectively predict the nonuniformity (NU) distribution of film thickness and facilitate the determination of optimal operating conditions that ensure maximal uniformity of exposure. Under this condition, the intrafilm NU of ALD-grown Al2O3 film (nominal thickness 300 nm) was reduced to 1.2%, and the interfilm NU is diminished to as low as 3.3%. These values represent reductions of 40% and 45%, respectively, compared to the NU levels observed under nonideal conditions (insufficient trimethylaluminum, TMA exposure downstream). The plasma etch rate of ALD-deposited films is merely 4.3 nm/min, representing a reduction of one-half compared to films deposited under nonideal conditions (9.8 nm/min) with overload TMA exposure downstream leading to chemical vapor deposition-like reactions.

Optimization of plasma etch rate of deposited thin films by adaptive neuro fuzzy inference system

Optimization of plasma etch rate of deposited thin films by adaptive neuro fuzzy inference system

Correlation of SiO2 etch rate in CF4 plasma with electrical circuit parameter obtained from VI probe in inductively coupled plasma etcher

The plasma etch process has become more difficult and longer than other processes and the etch process engineers have tried to confirm whether the results of etch process were normal by monitoring the equipment. However, it is difficult for the engineers unfamiliar with plasma to discover the parameter correlated to the real etch results, so the intuitive parameter to easily estimate the etch results is required. In this study, we focused on analyzing the correlation of the etch rates of SiO2 in CF4 plasma with electrical circuit parameters closely related to genuine plasma, which were obtained by chamber modeling and VI probe. We also introduced the intuitive parameter by combining several electrical circuit parameters to estimate the etch rate more precisely. The proposed parameter was strongly correlated to the etch rates and the coefficient of determination between the etch rates and the proposed parameter was over 0.94. We expect that using the proposed parameter can contribute to maintaining the stability of etch process.

Surface characterization and resistance changes of silver-nanowire networks upon atmospheric plasma treatment

Highly conductive silver-nanowire (Ag-NW) networks are used in composite materials as conductive channels. Their resistance tuning can be accomplished by changing the Ag-NW concentration, and, therefore, changing the network structure. In this study, an alternative pathway to resistance engineering of conductive Ag-NW networks by local atmospheric plasma treatment is employed. The corresponding changes in nanowire network morphology and crystallinity as a function of plasma etching time are investigated by time-resolved grazing-incidence X-ray scattering, field-effect scanning electron microscopy, and X-ray photoelectron spectroscopy. Three characteristic etching phases are identified. The first two phases enable the controlled engineering of the electrical properties with different rates of resistance change, which results from changes in nanowire shape, network morphology, and different oxidation rates. Phase III is characterized by pronounced fragmentation and destruction of the Ag-NW networks. These results show the feasibility of atmospheric plasma treatments to tune the local electrical properties of conductive Ag-NW networks. Furthermore, we present a physical Monte Carlo model explaining the electrical network properties as a function of plasma etching time based on the network connectivity and a constant plasma etching rate of 570 ng s−1 cm−2.

Effect of CaF2 on fluorocarbon plasma resistance and thermal properties of CaO-Al2O3-SiO2 glasses

ABSTRACT The effect of CaF2 addition on plasma resistance and thermal properties of CaO-Al2O3-SiO2 (CAS) glasses was investigated. The amount of SiO2 and Al2O3 was fixed to 42.9 and 9.1 (in mol%), respectively, while total amount of CaO and CaF2 was 48 mol% and the ratios of CaO:CaF2 were changed from 10:0 to 8:2. As the amount of CaF2 of CAS glass increased, CF4/O2/Ar plasma etch rate of glass decreased proportionally. In case of sample with CaO:CaF2 = 8:2, its etch rate had 5.04 ± 0.14 ㎚/min, which was about 20 times lower than that of quartz glass and was improved by more than 25% compared to the glass without CaF2. All glass samples maintained the initial surface and roughness even after plasma etching. In addition, the glass transition (Tg), crystallization (Tc), and the first melting temperature (Tf1) temperatures decreased with the amount of increased CaF2. F− ion in CAS glasses not only enhances the plasma resistance but also facilitates glass melting and forming operations.

Flow control in fully enclosed microfluidics paper based analytical devices using plasma processes

Microfluidic paper based analytical devices (μ-PADs) have shown promising results for disease diagnostics in resource limited settings but they often lack effective fluid flow control in the hydrophilic channels. Flow control in μ-PADs is necessary to conduct multiple step assays with minimum user interference. Using fluorocarbon (pentafluoroethane) plasma deposition followed by O2 plasma etching with a metal mask, flow control functionality in fully enclosed channels was achieved. Channels with up to a 10-fold difference in wicking rate were fabricated by changing the O2 plasma etch time. Metal meshes were used to locally vary the O2 plasma etch rate and therefore fabricate channels with different wettability inside a single paper substrate in a single etch step. The channels in fully enclosed devices are isolated, thereby preventing contamination due to handling and environmental exposure. To gain additional reliability, channels were covered with non-porous adhesive tape to minimize the effect of evaporation on fluid flow to eliminate variation in device operation under different humidity conditions. Proof of concept was demonstrated by fabricating and operating a device with three channels that converged to a single reaction zone. Solutions of different pH values were sequentially transported to and reacted with an indicator deposited at the reaction zone. μ-PADs fabricated by this method are suitable for field use when conducting complex low-cost diagnostic tests.

Etching of Si3N4 induced by electron beam plasma from hollow cathode plasma in a downstream reactive environment

An etching system based on the interaction of electrons extracted from a direct current hollow cathode (HC) Ar plasma and injected toward an Si3N4 covered silicon substrate located in the downstream reactive environment created by an additional remote CF4/O2 plasma source was developed and evaluated. By controlling the properties of the injected beam electrons, this approach allows to deliver energy to a surface functionalized by exposure to reactive species and initiate surface etching. The energy of the primary beam electrons is controlled by the acceleration voltage relative to the HC discharge. Ar atoms flow from the high-pressure HC discharge into the low pressure downstream reactive environment in the process chamber. For an acceleration voltage greater than the ionization potential of Ar and/or process gas species, the energetic primary beam electrons produce a secondary plasma in the process chamber and can also cause additional dissociation. The authors have characterized the properties of the secondary plasma and also surface etching of Si3N4 as a function of process parameters, including acceleration voltage (0–80 V), discharge current of the HC discharge (1–2 A), pressure (3.5–20 mTorr), source to substrate distance (1.5–5 cm), and feed gas composition (20% and 80% O2 in CF4/O2). The electron energy probability function measured with a Langmuir probe about 2.5 cm below the extraction ring suggests several major groups of electrons for this situation, including high energy primary beam electrons with an energy that varies as the acceleration voltage is changed and low-energy electrons produced by beam electron-induced ionization of the Ar gas in the process chamber. When a remote CF4/O2 plasma is additionally coupled to the process chamber, Si3N4 surfaces can be functionalized, and by varying the energy of the beam electrons, Si3N4 etching can be induced by electron-neutral synergy effect with plasma-surface interaction. For conditions without beam electron injection, the remote plasma etching rate of Si3N4 depends strongly on the O2 concentration in the CF4/O2 processing gas mixture and can be suppressed for O2-rich process conditions by the formation of an SiONF passivation layer on the Si3N4 surface. The combination of the HC electron beam (HCEB) source with the remote plasma source makes it possible to induce Si3N4 etching for O2-rich remote plasma conditions where remote plasma by itself produces negligible Si3N4 etching. The electron enhanced etching of Si3N4 depends strongly on the O2/CF4 mixing ratio reflecting changing arrival rates of O and F species at the surface. Optical emission spectroscopy was used to estimate the ratio of gas phase F and O densities and found to be controlled by the gas mixing ratio and independent of HCEB operating conditions. At this time, the detailed sequence of events operative in the etching mechanism is unclear. While the increase of the electron energy is ultimately responsible for initiating surface etching, presently, the authors cannot rule out a role of ions from the simultaneously produced secondary plasma in plasma-surface interaction mechanisms.

Effect of terminal methyl group concentration on critical properties and plasma resistance of organosilicate low-k dielectrics

Surfactant-templated porous organosilicate glass low-k films have been deposited by using a tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) mixture with different ratios and Brij® 30 surfactant. The deposited films contain different concentrations of terminal methyl groups that are proportional to the MTEOS concentration. Increasing the methyl group concentration by changing the TEOS/MTEOS ratio decreases the open porosity, k-value, and Young's modulus and increases the mean pore radius, although the template concentration was kept constant. The plasma etch rate well correlates with the number of fluorine atoms penetrated into pores. Plasma damage by fluorine radicals depends on the carbon concentration in the films. It can be reduced by 60% when the carbon concentration in the films exceeds 10 at. % as measured by XPS (the films deposited with the TEOS/MTEOS ratio of 40/60). Damage to the dielectrics associated with exposure to vacuum ultraviolet photons is reduced by more than 70% for the same samples.

Optical Nanofabrication of Concave Microlens Arrays

AbstractFor the simple and versatile fabrication of nanosmooth finished microlens arrays on hard materials, an approach combining femtosecond laser modification with subsequent ion beam etching is demonstrated. This method is based on the dependence of the plasma etching rate on the laser fluence used to modify the surface. The fabricated microlenses exhibit a low surface roughness of approximately 2.5 nm, due to the high precision of the plasma etching and benefit from the smooth interface between the laser‐modified and pristine subsurface regions. Microlenses with focal lengths ranging from 60 to 100 µm are realized by controlling the laser fluence, exposure dose, and etching time. Uniform square and hexagonal microlens arrays are fabricated on both hard and ultrahard materials and glasses (fused silica, GaAs, SiC, diamond) by the same process and deliver high‐quality focusing and imaging.

A Study on the NF3 Plasma Etching Reaction with Cobalt Oxide Grown on Inconel Base Metal Surface

In this study, the reaction of NF3 gas plasma with cobalt oxide (Co3O4) film grown on the Inconel base metal surface was investigated. Experimental results showed the plasma etching rate as high as 3.36 μm/min at 350 °C under 220 W of plasma power with negative 300 DC bias voltage. AES and XPS analyses revealed that reaction product is CoF2, demonstrating that the plasma processing is a fluorination reaction. Based on the linear kinetics law, the activation energy of the etching reaction was derived to be 66.93 kJ/mol. This study demonstrates that the plasma decontamination technique can be applied to efficiently and effectively remove radioactive surface contaminants such as 60Co hiding in the oxide film on the surfaces of the metallic waste generated during decommissioning of old nuclear power plants.

Investigation of etching optimization in capacitively coupled SF6–O2 plasma

The selective etching process is widely used for achieving the desired etch rate in semiconductor fabrication. Parameters such as input power, operating pressure, gas mixture, chamber geometry, and amplitude of the radio-frequency voltage govern the etch rate and etch quality in plasma. In this work, we experimentally investigated the optimum plasma etching conditions required to achieve an anisotropic etch profile and analyzed how the optimum etching can be carried out using an appropriate operating pressure and oxygen concentration. Optical emission spectroscopy was used to measure the concentrations of oxygen and fluorine, and Langmuir probe was used to measure the electron density in the plasma. The oxygen concentration was varied from zero to 100 vol. % for pressures in the range of 20–600 mTorr. The optimum etch conditions are used to study the ion energy distribution given by Kawamura et al., Plasma Sources Sci. Technol. 8, R45 (1999). The results suggest that in addition to O2% and pressure, the DC bias is another crucial parameter for achieving the optimum etch conditions.

Elemental depth profiles and plasma etching rates of positive-tone electron beam resists after sequential infiltration synthesis of alumina

By scanning transmission electron microscopy and energy dispersive X-ray spectroscopy (STEM–EDS), we investigated the elemental depth profiles of organic electron beam resist films after the sequential infiltration synthesis (SIS) of inorganic alumina. Although a 40-nm-thick poly(methyl methacrylate) (PMMA) film was entirely hybridized with alumina, an uneven distribution was observed near the interface between the substrate and the resist as well as near the resist surface. The uneven distribution was observed around the center of a 100-nm-thick PMMA film. The thicknesses of the PMMA and CSAR62 resist films decreased almost linearly as functions of plasma etching period. The comparison of etching rate among oxygen reactive ion etching, C3F8 reactive ion beam etching (RIBE), and Ar ion beam milling suggested that the SIS treatment enhanced the etching resistance of the electron beam resists to chemical reactions rather than to ion collisions. We proposed oxygen- and Ar-assisted C3F8 RIBE for the fabrication of silica imprint molds by electron beam lithography.

Plasma Exposure Behavior of Yttrium Oxide Film Formed by Aerosol Deposition Method

Aerosol deposition (AD) method is technique for forming high density ceramic films on substrate material surface at room temperature. The yttrium oxide films formed by the AD method (AD-Y2O3 films) have been developed as plasma resistance coating used for the plasma etching equipment. In recent years, plasma eroded particles from chamber components of the etching devices are regarded as a serious issue that they reduce the semiconductor device yield rate. AD-Y2O3 films which have excellent plasma resistance can reduce the eroded particles in the plasma etching equipment and greatly have contributed to manufacturing high integrated semiconductor devices. In this paper, the plasma erosion behavior of AD-Y2O3 films were investigated compared with sintered Al2O3, sintered Y2O3 and thermal splayed Y2O3 in order to clarify the reason why AD Y2O3 films were superior as plasma resistance material. The plasma etching rates of AD-Y2O3 films were not significantly different from other samples. It was assumed that the etching rates were dependent on the chemical stability to fluorine plasma of material. On the other hand, the surface roughness difference before and after plasma exposure of AD-Y2O3 films were much smaller than other samples. It was assumed that the surface roughness difference is dependent on the crystalline size of material. The structure of AD-Y2O3 films, which had high density and nano-crystalline structure, were eroded homogeneously and smoothly. It suggests AD-Y2O3 films do not generate large eroded particles and are superior to reduce the eroded particles in the etching devices.

Correlation of III/V semiconductor etch results with physical parameters of high-density reactive plasmas excited by electron cyclotron resonance

Reactive ion etching is the interaction of reactive plasmas with surfaces. To obtain a detailed understanding of this process, significant properties of reactive composite low-pressure plasmas driven by electron cyclotron resonance (ECR) were investigated and compared with the radial uniformity of the etch rate. The determination of the electronic properties of chlorine- and hydrogen-containing plasmas enabled the understanding of the pressure-dependent behavior of the plasma density and provided better insights into the electronic parameters of reactive etch gases. From the electrical evaluation of I(V) characteristics obtained using a Langmuir probe, plasmas of different compositions were investigated. The standard method of Druyvesteyn to derive the electron energy distribution functions by the second derivative of the I(V) characteristics was replaced by a mathematical model which has been evolved to be more robust against noise, mainly, because the first derivative of the I(V) characteristics is used. Special attention was given to the power of the energy dependence in the exponent. In particular, for plasmas that are generated by ECR with EM modes, the existence of Maxwellian distribution functions is not to be taken as a self-evident fact, but the bi-Maxwellian distribution was proven for Ar- and Kr-stabilized plasmas. In addition to the electron temperature, the global uniform discharge model has been shown to be useful for calculating the neutral gas temperature. To what extent the invasive method of using a Langmuir probe could be replaced with the non-invasive optical method of emission spectroscopy, particularly actinometry, was investigated, and the resulting data exhibited the same relative behavior as the Langmuir data. The correlation with etchrate data reveals the large chemical part of the removal process—most striking when the data is compared with etching in pure argon. Although the relative amount of the radial variation of plasma density and etch rate is approximately , the etch rate shows a slightly concave shape in contrast to the plasma density.

Via Bottom Profile Optimization in All-in-One Etch with Double Patterning Scheme

—In advanced CMOS technology node with Cu/low-K interconnection, double patterning scheme with Metal Hard-Mask (MHM) All-In-One (AIO) etch is used to define smaller via and trench. The bottom profile of via is critical for via connectivity and RC delay. Tapered via bottom profile means smaller contact area with lower metal which means larger via contact resistance and degradation of chip interconnect performance. The bottom profile of via may probably become tapered when it enters Etch Stop Layer (ESL) or when the plasma touches lower Cu layer. In this paper, we will explain the reason of tapered via bottom profile and several ways to solve this problem. Keywords—AIO etch; Via bottom taper profile; ESL; Cu exposure; Metal capping layer; Introduction—In current LELE double patterning scheme, the partial via (PV) is firstly formed in 1st mask. Then the second PV is formed in 2nd mask, following by one in-situ ash which will remove PR tri-layer film. Then AIO etch will form via bottom and hard mask defined trench pattern at one etch process synchronously. MHM pattern is also defined by LELE double patterning before PV etch. The process sequence is briefly depicted in Fig.1. In our process, via is self-aligned by MHM for photo lithography reaches its limit on via. After photography critical dimension (CD) is quite large, via CD is shrunk during tri-layer etch process. After shrinking, Via CD is still larger than line CD. Therefore, we use self-aligned via (SAV) to confine via in MHM open area to ensure final VBD and TDDB performance acceptable. In this scheme, we should ensure MHM selectivity during whole etch process to let it not be etched through. Porous ultra-low-k (ULK) is introduced to reduce interconnect RC delay [1]. The etch stop layer (ESL) is introduced to balance different patterns’ loading after PV and trench etch. Then we used a LRM step to open ESL and touch lower Cu layer. However, we found the via bottom profile inside ESL is usually tapered. The tapered via profile into ESL could result in decreased contact area to lower metal Cu which is critical to final RC value. The plasma etch rate in ESL is always relatively slow to make sure the former PV and trench etch step can stop on it. For the practical ULK and ESL film thickness in advanced technology node, the selectivity ULK to ESL should be at least 5 to ensure 80-90% percentage of trench depth is etched by trench etch step, and the following ESL opening step just remove the little trench depth remaining [2]. In final Liner Remove (LRM) step, the etch rate cannot be so fast, meanwhile the etch rate (ER) will be slower after Cu exposure. In fluorocarbon plasma with oxygen, oxygen captures carbon to form C-O bond and control the polymer generation. Such ER change is induced by the reduction of oxygen ion after Cu exposure which will affect the total etch performance to form tapered via bottom profile. In this paper, tradition way to change plasma condition, the change of ESL and the introduction of lower metal capping layer will be used to solve via bottom tapered issue.

Pengaruh Laju Alir Gas CH2FCF3 Terhadap Laju Plasma Etching SiO2 Pada Quartz Crystal Microbalance

Effect of gas flow rate on the surface of quartz crystal SiO 2 during plasma etching was studied. The etching process was applied using the capacitively coupled plasma (CCP) reactor generated with 100 W power AC generator at low frequency of 40 kHz using a gas flow of CH 2 FCF 3. The main objective of this study was to determine the effect of changing gas flow rate on the plasma etching rate on the SiO 2 surfaces. Gas flow rate was varied between 20-40 mL/min, while keeping all other plasma parameters constant. The etched surface of SiO 2 was analyzed using white-light profilometer (Topography Measurement System (TMS 1200 Micro Lab)). The results show the physical etching processes influenced the rate of etching at a low gas flow rate, while the higher flow rate influence reactive ion etching (RIE) in the etching process. The maximum etching rate is found at 7.753 nm / min achieved in plasma etching process.

Orientation-dependent plasma etch rates of single crystal silicon for dry etcher parts

Abstract We have evaluated the orientation dependence of plasma etch rates for single crystal silicon using SF6/Ar and CF4/Ar/O2 chemical gases in an inductively coupled plasma dry etcher. Etch rates for different crystal orientations having various surface conditions were measured. The results indicate that the <111> crystal lattice orientation is etched at a lower rate than the <100> orientation. The dependence of the silicon etch rate on the crystal orientation is derived from differences in the local neighborhood of the exposed surface atoms, such as number of neighbors, dangling bond, and surface bond. Finishing the silicon parts with mirror-finish polishing results in surfaces with a very thin subsurface damage layer that exhibits a lower plasma etch rate. This compares to the much thicker damage layer caused by abrasive machining of the surface during grinding steps, and to the portion of this that remains after polishing.

Fabrication of PMMA nanofluidic electrochemical chips with integrated microelectrodes.

A novel method based on plasma etching was proposed for monolithically integrating planar nanochannels and microelectrodes on a poly (methyl methacrylate) (PMMA) plate, and complete PMMA nanofluidic electrochemical chips with integrated microelectrodes were constructed by bonding with another PMMA plate containing microchannels. The fabrication sequences of nanochannels and microelectrodes were optimized. The oxygen plasma etching rate of PMMA nanochannels was studied, and the average rate was 15 nm/min under optimal conditions. An UV-ozone assisted thermal bonding method was developed to realize a low-temperature chip bonding, and the variations in width and depth of nanochannels before and after bonding were 2% and 5%, respectively. As a demonstration, a nanoparticle crystal (NPC)-based nanofluidic biosensor with integrated Ag microelectrodes was designed and fabricated. Sub-microchannel arrays with a depth of 400 nm and a width of 30 μm on the biosensor functioned as filters, and trapped 540 nm silica nanoparticles modified with streptavidin inside the connected microchannel to assemble the NPC. The interspaces in the NPC formed a three-dimensional nanochannel network with an equivalent diameter of 81 nm. By measuring the conductance across the NPC, a high quality nanofluidic sensing of biotin was achieved. The limit of detection was 1 aM, and the detection range was from 1 aM to 0.1 nM.

Inductively coupled reactive ion etching studies on sputtered yttria stabilized zirconia thin films in SF6, Cl2, and BCl3 chemistries

Downscaling of yttria stabilized zirconia (YSZ) based electrochemical devices and gate oxide layers requires successful pattern transfer on YSZ thin films. Among a number of techniques available to transfer patterns to a material, reactive ion etching has the capability to offer high resolution, easily controllable, tunable anisotropic/isotropic pattern transfer for batch processing. This work reports inductively coupled reactive ion etching studies on sputtered YSZ thin films in fluorine and chlorine based plasmas and their etch chemistry analyses using x-ray photoelectron spectroscopy. Etching in SF6 plasma gives an etch rate of 7 nm/min chiefly through physical etching process. For same process parameters, in Cl2 and BCl3 plasmas, YSZ etch rate is 17 nm/min and 45 nm/min, respectively. Increased etch rate in BCl3 plasma is attributed to its oxygen scavenging property synergetic with other chemical and physical etch pathways. BCl3 etched YSZ films show residue-free and smooth surface. The surface atomic concentration ratio of Zr/Y in BCl3 etched films is closer to as-annealed YSZ thin films. On the other hand, Cl2 etched films show surface yttrium enrichment. Selectivity ratio of YSZ over silicon (Si), silicon dioxide (SiO2) and silicon nitride (Si3N4) are 1:2.7, 1:1, and 1:0.75, respectively, in BCl3 plasma. YSZ etch rate increases to 53 nm/min when nonoxygen supplying carrier wafer like Si3N4 is used.

Numerical investigation of HBr/He transformer coupled plasmas used for silicon etching

A two-dimensional hybrid Monte Carlo—fluid model is applied to study HBr/He inductively coupled plasmas used for etching of Si. Complete sets of gas-phase and surface reactions are presented and the effects of the gas mixing ratio on the plasma characteristics and on the etch rates are discussed. A comparison with experimentally measured etch rates is made to validate the modelling results. The etch rate in the HBr plasma is found to be quite low under the investigated conditions compared to typical etch rates of Si with F- or Cl-containing gases. This allows for a higher control and fine-tuning of the etch rate when creating ultra-small features. Our calculations predict a higher electron temperature at higher He fraction, because the electrons do not lose their energy so efficiently in vibrational and rotational excitations. As a consequence, electron impact ionization and dissociation become more important, yielding higher densities of ions, electrons and H atoms. This results in more pronounced sputtering of the surface. Nevertheless, the overall etch rate decreases upon increasing He fraction, suggesting that chemical etching is still the determining factor for the overall etch rate.