Plasma Etch Rate Research Articles

Tungsten: sputter deposition and plasma etching

The plasma etch behaviour of magnetron sputtered tungsten films has been studied. Structured experiments using orthogonal arrays have been conducted to study the effects of deposition pressure, magnetron power and heating on film properties. Films which have low resistivity, bulk-like density and low tensile stresses (100–500 MPa) required for integrated circuit metallization have been obtained by optimizing the deposition conditions. Density and plasma etch rate in SF 6 have been measured. Plasma etch rates of tungsten films depend significantly on deposition conditions. Previously, oxygen incorporated into the film was thought to be responsible for high etch rates. Because large etch rate differences have been measured for nearly oxygen-free films, it is postulated that density, rather than incorporated oxygen, should be used to explain the differences in plasma etch rates.

Statistical experimental design in plasma etch modeling

The objective of this work is to obtain a comprehensive set of empirical models for plasma etch rates, uniformity, selectivity, and anisotropy. These models accurately represent the behavior of a specific piece of equipment under a wide range of etch recipes, thus making them ideal for manufacturing and diagnostic purposes. The response characteristics of a CCl/sub 4/-based plasma process used to etch doped polysilicon were examined via a 2/sup 6-1/ fractional factorial experiment followed by a Box-Wilson design. The effects of variation in RF power, pressure, electrode spacing, CCl/sub 4/ flow, He flow and O/sub 2/ flow on several output variables, including etch rate, selectivity, and process uniformity, were investigated. Etch anisotropy was also measured by scanning electron microscopy analysis on a 2/sup 6-2/ fraction of the original experiment. The screening factorial experiment was designed to isolate the most significant input parameters. Using this information as a platform from which to proceed, the subsequent phase of the experiment allowed the development of empirical models of etch behavior using response surface methodology (G. E. P. Box and N. D. Draper, 1987). The models were subsequently used to optimize the etch process. >

Investigation of Gaas Deep Etching by Using Reactive Ion Etching Technique

ABSTRACTRIE is an important technique in obtaining anisotropie etch profile. This is a critical requirement for very deep etching which needs long etch duration. Among many factors which affect RIE characteristics in deep etching, the following are most concerned: (1) the etch mask: needs suitable plasma resistance without significant plasma attack for extended etch time; (2) Long time stability in etch rate and surface conditions for the sample; (3) Etch profile: should be anisotropie with tolerable undercut In this work, CCl2F2 and SiCl4 were used with CCl2F2 as the main etchant. Ar was used in the initial stage for sputtering away surface residues prior to actual etching was performed. Three types of etch masks were prepared and their performance such as plasma was investigated. Multilayer metal etch mask has very low etch rate in plasma and its etch rate selectivity is around 300. The etch selectivities of GaAs to Si3N4 and to photoresist are 35 and 23, respectively. Etch mask can be chosen depending on the thickness of etch mask and the required GaAs etch depth. The etch rate of GaAs was found significantly increased when metal mask was applied. While PR mask is easier for inducing surface coating.

Modeling of plasma etching in microelectronics

Computer simulation and experimental results are used to establish the possibility of efficient control of plasma etching rate and nonuniformities.

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.

Characterization of Polymer Dielectrics for High-Density Electronic Packaging

ABSTRACTBecause of rapid advances in semiconductor technology, polymer dielectrics are finding widespread use in high-density packaging to improve performance and processability. Notable among these materials are polyimides, benzocyclobutene resins, and fluoropolymer containing composites.Polyimides have been used extensively for chip passivation and first-level packaging. Benzocyclobutenes, processed as conventional thermosets, are being investigated as thin film dielectric for use in multichip modules. A silicon containing derivative can be used as a plasma etch stop. Polytetrafluoroethylene is used either as matrix or reinforcement in circuit boards to produce a low dielectric constant composite.Knowledge of materials properties is crucial to ensure the reliability and function of products incorporating these polymers. In this article, a few selected characterization techniques for the determination of important materials properties such as solvent diffusion, plasma etch rate, and thermomechanical characteristics will be discussed.

Plasma etching and modification of organic polymers

Abstract

The effect of aluminum masks on the plasma etch rates of polysilicon and silicon nitride

Plasma etch rates of both aluminum and photoresist masked polysilicon and silicon nitride are reported. Both thermally grown and plasma deposited substrates of both films were studied. It is shown that all aluminum masked substrates except thermal nitride exhibit enhanced etch rates relative to photoresist masked samples. Aluminum masked thermal nitride etches more slowly than does photoresist masked. These results are shown to be consistent with a metal catalyzed surface reaction which generates additional fluorine radicals at the surface of the wafer.

Effect of hydrogen plasma treatment on CF4 plasma etching characteristics of single-crystal, polycrystalline, and amorphous silicon

A systematic study of etching rates in CF4 plasma of single-crystal, polycrystalline, and amorphous silicon exposed to hydrogen plasma has been carried out. An order of magnitude reduction in the etch rates after H2 plasma treatment has been observed in all cases and has been explained on the basis of an overlayer formation. Electron spectroscopy for chemical analysis and wet etching studies suggest the formation of a C, O, F, and H based complex overlayer, which reduces the CF4 plasma etch rate.

The Effect of Metal Masks on the Plasma Etch Rate of Silicon

The etch rate of silicon in plasmas is a strong function of the masking material coated on the wafer to define etch patterns. Samples coated with several different metals (silver, copper, chromium, and aluminum) all exhibit a higher silicon etch rate compared to samples coated with a photoresist mask. For silver‐masked samples, the silicon etch rate can be enhanced by as much as a factor of five relative to a photoresist mask. These results can be explained in terms of a catalytic reaction occurring on the mask surface which gives rise to a local enhancement of the fluorine radical concentration leading to an increased etch rate of silicon. The validity of this explanation was confirmed by actinometry.

Selective Wet and Dry Etching of Hydrogenated Amorphous Silicon and Related Materials

The etch rate in aqueous solutions and in plasmas was measured for hydrogenated amorphous silicon (a‐Si:H) as a function of preparation conditions, and was compared to that of silicon in the hydrogen‐free amorphous, polycrystalline, and crystalline form. The rate depends strongly on hydrogen content in wet etching and moderately in plasma etching. In analogy to crystalline silicon, the plasma etch rate of a‐Si:H exhibits a strong dependence on the Fermi level.

Etching in a pulsed plasma

The etching of silicon in a pulsed plasma using SF6 gas is investigated. For short pulses the Si etch rate for a pulsed plasma is essentially the same as for the continuous plasma, in spite of the duty cycle being only 20%. An heuristic model of the etching has been developed which accurately predicts the pulsed plasma etch rates and sets limits on important parameters, such as the number of F atoms yielded by the SF6, the reaction probability of F with Si, and the overall efficiency of the etching process.

Mask Dependent Etch Rates II: The Effect of Aluminum vs. Photoresist Masking on the Etch Rates of Silicon and Silicon Dioxide in Fluorine Containing Plasmas

Plasma etch rates of silicon and silicon dioxide when masked with photoresist and aluminum are compared. It was observed that the aluminum masked silicon had an enhanced etch rate relative to photoresist masking with a variety of fluorocarbon (, , and ) and nonfluorocarbon ( and ) containing etch gases. It is also shown that the aluminum masked silicon dioxide etch rate is depressed relative to that of photoresist masked but that this effect is limited to the fluorocarbon etch gases. It is shown that the aluminum mask is responsible for affecting the etch rates and not the photoresist mask. Evidence is presented that favors a mechanism by which excess fluorine radicals are catalytically produced at the aluminum mask surface. The relative amount of silicon etch rate enhancement is strongly linked to the oxygen concentration present in the etch gas mixture. This is consistent with a competition between fluorine and oxygen for reaction with and attachment to the aluminum surface. It is postulated that is a catalyst for fluorine production and is not.

Role of sulfur atoms in microwave plasma etching of silicon

The Si etch rate in an (F2+O2) microwave plasma has been measured as a function of O2 mixing ratio at a fixed total pressure of 5.3×10−2 Pa. The etch rate significantly decreases with the mixing ratio. This etch rate decrease is due primarily to surface oxidation. When sulfur is added to the (F2+O2) plasma, the Si surface is much less oxidized and the etch rate increases by about a factor of 4. Such sulfur-containing species as S atoms react with O atoms or ions in the plasma and form O atom-containing species, such as SO2, SO+, SOF+, and SOF+2, thereby reducing the O atom and O+ ion concentrations in the plasma. As a result, the Si surface is scarcely oxidized, so that the etching reaction can easily proceed. Sulfur atoms inhibit surface oxidation and promote Si etching. Sulfur atoms contained in SF6, which is usually used in microwave plasma etching of Si, are expected to have the same role.

Cermet as an inorganic resist for ion lithography

Al/O cermet has been found to act as a high‐resolution resist for ion lithography. The change in chemical etching produced by the ions appears to be similar to that produced by excimer laser irradiation. Both a focused Ga‐ion beam and collimated Ar ion or proton beams with stencil masks have been used for exposure. Cermet films 500 Å thick were e‐beam evaporated in an atmosphere of O2 and were exposed to ion doses of 5×1014 to 1.6×1016 cm−2 at energies ranging from 800 eV to 75 keV. The etch rate in a phosphoric acid based, Al etch falls rapidly to about 1/2 of the rate for unexposed material after exposure to 70 keVAr+ ions with a dose of 1×1015 cm−2 and is near zero for doses above 8×1015 cm−2. The etch rate in BCl3 plasma is less sensitive to dose and decreases by 30% for a dose of 8×1015 cm−2. Although comparison of Auger analysis of exposed and unexposed cermet indicates that ion bombardment increases the concentration of Al bound in Al2O3 on the surface compared to Al in the metallic state, the mechanism of the ion induced etch resistance is at this point unclear. A film of SiO2 on Si was patterned using the exposed cermet as a mask to reactive ion etch in CHF3. Linewidths down to 0.1 μm were produced.

Hydrogen Diffusion Between Plasma-Deposited Silicon Nitridepolyimide Polymer Interfaces

ABSTRACTA Nuclear Reaction Analysis (NRA) for Hydrogen technique was used to analyze the hydrogen concentration near Plasma Enchanced Chemical Vapor Deposition (PECVD) silicon nitride-polyimide interfaces at various nitride-deposition and polyimide-polymer-curing temperatures. The CF4 + O2 (8% O2) plasma-etch-rate variation of PECVD silicon nitride films deposited on polyimide appeared to correlate well with the variation of hydrogen-depth profiles in the nitride films. The NRA data indicate that hydrogen-depth-profile fluctuation in the nitride films is due to hydrogen diffusion between the nitride-polyimide interfaces during deposition. Annealing treatment of polyimide films in a hydrogen atmosphere prior to the nitride film deposition tends to enhance the hydrogen-depth-profile uniformity in the nitride films, and thus substantially reduces or eliminates variation in the nitride plasma-etch rate.

A comparison of the electron beam sensitivities and relative oxygen plasma etch rates of various organosilicon polymers

A study of the electron beam sensitivities and oxygen plasma etch rates of a variety of organosilicon polymers is discussed. The particular structures investigated include polysiloxanes, polysilmethylenes, polysilazanes. polysilanes, polysilphenylenes, and organic polymers with side silyl groups.The influence of pendant organic groups and heteroatoms in the main polymer chain on the plasma etch rates and electron beam sensitivities is also addressed.

The Composition and Physical Properties of LPCVD Silicon Nitride Deposited with Different NH 3 / SiH2Cl2 Gas Ratios

The composition and physical properties of low pressure chemical vapor deposition (LPCVD) silicon nitride films were studied. The samples were deposited at 770°C with different reactant gas ratios ranging from 2 to 20. Auger electron spectroscopy (AES) showed that the Si/N ratio was about 0.75, and the compositional uniformity as a function of depth was good for all samples. No excess Si clusters were detected by TEM for the samples annealed at 1000°C in for 5h. Only N‒H bonds were observed by infrared (IR) analysis. The amount of N‒H bonds in the asdeposited samples was estimated to be about . The normalized N‒H absorption peak area was found to increase by increasing values, while the amount of N‒H bonds was found to decrease after annealing at 1000°C in for 30 min. The plasma etch rates were found to increase by increasing values and showed a good correspondence to the trend of increasing the N‒H bonds. The film stress for all samples was tensile and had a level of . No difference was observed in the film's ability to act as an oxidation barrier for samples deposited with different values.

The mechanism of ion implantation passivation of PMMA for lithography with dry etch development

Ion implantation of PMMA is known to modify its etch rate in an oxygen plasma. This effect can be used as the basis for a lithography system based on ion beam exposure and dry development (Kuwano 1980). In this work we have systematically investigated the role of the main implant parameters; species, dose and energy. Implantation reduces the film thickness, changes its chemistry and reduces its dry etch rate. We elucidate the mechanisms involved in the resist passivation effect and present a critical energy density model to explain the role of the implant parameters.

Polysiloxanes for deep UV lithography

The sensitivity of linear siloxane polymers has been increased in the deep uv by the addition of photoinitiators. The resist system discussed in this paper has a sensitivity of 20mJ/cm2 at 2537A., with a contrast (γ) of 2.6. When used as a thin imaging layer in a double layer system, 0.75um resolution has been achieved on the PE500 exposure tool. Data is presented on exposure linewidth variation, resist stability, and etch rate in an oxygen plasma.