Increase In Etch Rate Research Articles

Use of CF3,Br/Al, discharges for reactive ion etching of III-V semiconductors

The reactive ion etching of GaAs, InP, InGaAs, and InAlAs in CF3Br/Ar discharges was investigated as a function of both plasma power density (0.56-1.3 W - cm−2) and total pressure (10-40 mTorr) The etch rate of GaAs in 19CF3Br:1Ar discharges at 10 m Torr increases linearly with power density, from 600 A min−1 at 0.56 W · cm−2, to 1550 A · min at 1.3 W · cm−2. The in-based materials show linear increases in etch rates only for power densities above − 1.0 W · cm−2. These etch rates are comparable to those obtained with CCI2F2:O2 mixtures under the same conditions. Smooth surface morphologies and vertical sidewalls are obtained over a wide range of plasma parameters. Reductions in the near-surface carrier concentration in n-type GaAs are evident for etching with power densities of >0.8 W cm−2, due to the introduction of deep level trapping centers. At 1.3 W· cm−2, the Schottky barrier height of TiPtAu contacts on GaAs is reduced from 0.74 to 0.53 eV as a result of this damage, and the photoluminescent intensity from the material is degraded. Alter RIE, we detect the presence of both F and Br on the surface of all of the semiconductors. This contamination is worse than with CCl2F2-based mixtures. High-power etching with CF3Br/Ar together with Al-containing electrodes can lead to the presence of a substantial layer of aluminum oxide on the samples if the moisture content in the reactor is appreciable.

Interactive effects in the reactive ion etching of SiGe alloys

Reactive ion etching (RIE) of epitaxial, strained Si1−xGex alloys, x≤0.20, in fluorine-, chlorine-, and bromine-based low-pressure plasmas has been investigated. The SiGe etch rates increase for each etchant with Ge concentration, e.g., for fluorine-based RIE (CF4 and SF6) the etch rate of a Si80Ge20 alloy is ≂2x that of elemental Si. Analysis shows that the etch rate increase is not accounted for by the greater rate of gasification of Ge atoms alone but that the presence of Ge atoms in the SiGe alloy increases the rate of Si etch product formation.

Studies of the reactive ion etching of SiGe alloys

Reactive-ion etching (RIE) of epitaxial, strained Si1−xGex alloys, x≤0.20, in fluorine-chlorine-, and bromine-based low-pressure plasmas has been investigated. The reactive-ion etch rates of the Si1−xGex alloys increase with the Ge content of the alloy for most etching gases. This effect is most pronounced for fluorine (CF4 and SF6) plasmas where the etch rate of a Si80Ge20 alloy is increased by a factor of ≂2 over that of Si. The etch rate enhancement is of reduced importance for chlorine (CF2Cl2) and bromine (HBr) plasmas, where the etch rate increases by less than 50% for a Si80Ge20 alloy relative to that of elemental Si. Analysis shows that the etch rate increase is not accounted for by the greater rate of gasification of Ge atoms alone but that the presence of Ge atoms in the SiGe alloy increases the Si etch product formation rate. Directional SiGe profiles are observed for CF2Cl2 and HBr plasmas which are identical to those obtained with Si. After etching in CF4 or SF6 plasmas the Ge surface concentration of the SiGe alloy is increased relative to its bulk value and both fluorinated Si and Ge are observed by in situ x-ray photoemission spectroscopy. On the other hand, for CF2Cl2 and HBr plasmas the SiGe surface is Si rich. The effect of band-gap narrowing, strain and plasma-induced surface modifications on the etching of the SiGe alloys is discussed.

Ion bombardment of X-ray multilayer coatings: Comparison of ion etching and ion assisted deposition

The effects of two forms of ion bombardment treatment on the reflectivity of multilayer X-ray coatings were compared: ion etching of the metal layers, taking place after deposition, and ion bombardment during deposition, the so-called ion assisted deposition. The ion beam was an Ar + beam of 200 eV, and the multilayer coatings studied were W-C, Ni-C and W-Si. Cu K α reflection measurements ( λ = 0.154 nm) of Ni-C and W-C multilayer coatings having ion etched metal layers showed considerably higher reflectivities than those of coatings having as-deposited layers; a factor 2.5 and 4, respectively. Ion etching of tungsten layers in W-Si coatings did not result in enhanced reflectivities. We applied ion assisted deposition to nickel in Ni-C multilayer coatings. We observed enhanced in-situ soft X-ray reflectivities of ion assisted deposited nickel layers with respect to as-deposited layers. However, the observed increases were less than those obtained by ion etching, which we ascribe to bombardment-induced intermixing at the underlying Ni-C interfaces. Finally we demonstrate that during ion assisted deposition the deposition and ion etch rates are not additive, but that the ion etch rate increases. This indicates that during deposition a number of atoms are temporarily loosely bound to the surface.

Experimental study of electron cyclotron resonance reactive ion beam etching of W and Mo thin film

A microwave electron cyclotron resonance ion source has been developed and studied for use in a reactive ion-beam system. The system has been tested and fully characterized for thin film etching. The CF4 reactive ion beam etching of W and Mo, have been investigated as a microfabrication technique for integrated semiconductor devices of submicron geometry. The etching rate has been characterized as a function of ion energy, ion-beam current density, and angle of beam incidence. It has been found that the etching rate increase linearly with current density and pressure. The rate also increases with ion energy, but the rate of increase drops as the ion energy increases. The maximum etching occurs at a beam angle of 35°.

Enhancement of Photoresist Etch Rates by Argon Metastables in a Plasma Afterglow Reactor

AbstractThe etching of a novolak-based positive photoresist was studied downstream of O2/CF4 and Ar/O2/CF4 plasmas. Gas phase electron resonance was used to quantitatively track the two primary etchant species, atomic oxygen and atomic fluorine. These species were then correlated to etch rates as determined by laser interferometry. In addition to being industrially relevant, the downstream reactor allows the influence of neutral chemistry and surface activation to be deconvoluted from that of ion bombardment and strong electric fields, which traditionally make processes occurring in the body of the plasma so difficult to understand. The maximum in etch rate with respect to CF4 addition to an oxygen plasma yields an optimum ratio of O/F of 20 at 150 °C. The addition of argon to the O2/CF4 gas mixture unexpectedly leads to an increase in etch rate by a factor of at least two. Moreover, the optimum O/F ratio decreases by a factor of three and, correspondingly, the optimum CF4 mole fraction decieases. Analysis of oxygen and fluorine densities suggests argon metastables alter the homogeneous chemistry for fluorine atom production as well as the heterogeneous chemistry of photoresist chain scission. Overall activation energies are 10.6, 10.8, 4.1 and 0.7 kcal/mole for O2, Ar/O2, O2/CF4 and Ar/O2/CF4 mixtures, respectively. The optimal CF4 mole fraction increases with increasing substrate temperature. A Hougen-Watson model for the heterogeneous chemistry on the wafer surface reproduces the data very well.

The Influence of HBr Discharge Ambience on Poly-Si/SiO2 Etching Selectivity

ABSTRACTThe influence of HBr discharge ambience on SiO2 etching is investigated. A batch type parallel-plate reactive ion etching (RIE) dry etcher was used. The discharge ambience was changed by changing the numbers of poly-Si and SiO2 wafers in the same chamber. It is found that as the number of poly-Si wafers increased, the poly-Si etch rate slightly decreased due to a loading effect and SiO2 etching rate drastically increased. The selectivity of poly-Si / SiO2 decreased with increasing the ratio of the loaded poly-Si number in the same chamber. When A12O3 wafers instead of poly-Si wafers were loaded with SiO2 substrates, SiO2 etching rate enhancement did not occur. Therefore, increase of SiO2 etch rate could not be explained using a loading effect. From the results of mass analysis during etching in Si contained HBr plasma, etching products SiBrx (x=1,2,3) peaks were observed. Namely, when the Si etching products were supplied to SiO2 surface, SiO2 etch rate increased. In order to suppress the enhancement of SiO2 etch rate, the etch temperature must be reduced.

Etching and annealing characteristics of different CR-39 track detectors: A comparative study

Abstract A comparative study of etching response of CR-39 (DOP) with dopant concentration 1% by weight and CR-39 (no additive) detectors for alpha particles indicates that, contrary to the findings of some earlier workers, doped CR-39 detectors are more sensitive than CR-39 (no additive). A possible explanation to interpret these apparently contradictory results has been attempted. The increase in bulk etch rate with annealing has been found to be more for CR-39 (no additive) than CR-39 doped. The annealing (pre- and post-irradiation), on the other hand, causes a decrease in sensitivity of both types of detectors.

Etching characteristics of Si1−xGex alloy in ammoniac wet cleaning

Etching characteristics of Si1−xGex alloys in ammoniac wet cleaning (RCA cleaning) were examined. The etching rate of Si1−xGex became larger with increasing Ge ratio (X). Temperature dependence of the etching rate was studied and the etching rate was large at high temperatures. However, no obvious difference was observed in the temperature dependence of Si1−xGex etching rate at different Ge ratio (X). A surface morhology degradation after RCA cleaning was observed at high Ge ratio (X). A stoichiometry change of Si1−xGex surface after RCA cleaning was observed by x-ray photoelectron spectroscopy (XPS). The etching rate increase and the surface morphology degradation are thought to be due to the rapid etching of Ge atoms at the top surface layer.

High‐Rate Anisotropic Etching of Silicon by Remote Microwave Plasma in Sulfur‐Hexafluoride

Microwave plasma is used to study the effects of metal catalysts and substrate temperature on the etching of single‐crystalline silicon wafers. Silicon etching without undercut has been achieved at elevated substrate temperatures without the use of ion bombardment of plasma with copper mask. The use of copper mask not only increases the silicon etch rate compared to that using photoresist mask but also leads to a vertical etching profile when the substrate temperature is around 335°C. The increase in etch rate is consistent with the increase of the concentration of atomic fluorine measured by optical emission spectroscopy. The anisotropic etching is found to be caused by the deposition on the sidewalls of etched holes with thin films containing mainly and some as confirmed by EDAX analysis.

Material-enhanced spatially dependent etch rate of SiO2 in CF4 reactive ion etching

We report on the spatially dependent enhanced etch rate of SiO2 in a CF4 planar reactive ion etcher due to the presence of the compounds GaAs or InP, or the single elements Ti, V, Nb, Ta, Cr, Mo, W, Ni, Pd, Pt, Cu, Ag, Au, Al, Ga, In, or Ge. The etch rate enhancement is maximum immediately adjacent to the source of the material and decreases nonlinearly with increasing distance away from the source of the material. Of the materials studied, the largest local etch rate increase was due to the element Ni (65% increase), followed closely by the elements In (57%) and Ga (43%) and the compounds InP (55%) and GaAs (40%). The lateral range of the effect extends 5 to 30 mm away from the material depending on the element or compound. Material interaction, possibly a catalized reaction, with the CF4 plasma reactants and lateral transport to provide an increased local concentration of fluorine at the SiO2 surface is a preliminary suggestion for the observed etch rate increase.

Role of native oxide layers in the patterning of InP by Ga ion beam writing and ion beam assisted Cl2 etching

We have studied the mechanism of increased etch rate induced in InP substrates by focused Ga ion implantation and Cl2 etching. We cannot account for the depth of surface steps formed in this process with a purely kinetic mechanism. The preferential etching of implanted areas is attributed instead to local modification or removal of native oxides from the surface of InP. The thin oxide layer effectively protects the substrate and inhibits Cl2 etching. Consistent with the thermodynamic prediction, a cleaned InP(100) surface is etched by Cl2 (5×10−4 Torr) with a rate of approximately 1000 Å/min at 200 °C. Surface steps as deep as 3 μm have been reproducibly prepared using an oxide mask believed to be approximately 20 Å thick. In the etching process, any substrate damage caused by the Ga beam writing is completely removed. The oxide mask, which can be patterned on a very fine scale by energetic particle bombardment, provides a new avenue for in situ processing of InP.

Plasma Etching of Polysiloxane Based SOG Films

We have studied the plasma etch behavior of four different SOG materials which range from 0 to 14% in their organic content (weight percent of -CH3). A number of gas chemistries were investigated, including SF6/He, CF4/He, C2F6, and CHF3/He. Etch rates of SOG films were determined relative to that of thermal SiO2 as a function of the partial pressure of the fluorine-containing gases. In general, at low partial pressures of the etch gas, where no polymer formation occurs, the SOG films etch faster than thermal oxide. Also, the etch rates increase with an increase in the overall organic content (Si-CH3) of the SOG. While higher SOG etch rates relative to that of thermal SiO2 are attributable to the lower SOG densities, the increase in SOG etch rates with increasing Si-CH3 content probably reflects the effect of decreasing Si-O bond density. Under conditions favoring polymer formation, the SOG etch rates are suppressed relative to that of oxide indicating enhanced polymerization rates on a siloxane SOG surface. Preliminary data obtained using gas chemistries with high F/C ratios suggest that the relative contributuion by F atoms to etching is larger in a siloxane SOG than in SiO2.

Chemically Assisted Ion Beam Etching of SiGe

ABSTRACTChemically assisted ion beam etching (CAIBE) of Si1−Gex films is reported. Ar+ ion sputtering in the presence of Cl2 background gas has been used to etch epitaxial films of Si1−xGex, with x ranging between 0 and 0.5. It is found that Si1−xGex, sputters more rapidly than Si, but less than Ge. The use of C12 gas enhances the sputter rates of SiGe as in the case of Si. Analysis of the etch rates indicates that the etch rate increase is due to an enhancement of the sputtering process, rather than a chemical effect.

Effect of reactor loading on atomic oxygen concentration as measured by no chemiluminescence

Summary It has previously been observed that the etch rate of polyethylene samples in the afterglow of an r.f. discharge in oxygen increases with reactor loading. This enhancement of the etch rate is attributed to reactive gas phase products of the polymer etching. In the present work, emission spectroscopy is employed to examine the species present in the gas phase during etching of polyethylene. In particular, the concentration of atomic oxygen downstream from the polyethylene samples is studied as a function of the reactor loading. It is found that the concentration of atomic oxygen increases as the reactor loading is increased. Since atomic oxygen is known to etch hydrocarbons, the increase of etch rate with increased reactor loading is attributed to the increase of atomic oxygen concentration in the vicinity of the sample.

Comparison of etch rates of silicon nitride, silicon dioxide, and polycrystalline silicon upon O2 dilution of CF4 plasmas

The etch rates of Si3N4, SiO2, and doped polycrystalline silicon with CF4 plasmas have been examined as a function of O2 dilution and radio frequency (rf) (13.56 MHz) power density at constant residence time (25 mTorr and 25 sccm total process gas flow rate) at 22±2 °C in a batch reactor. At fixed reactor pressure and process gas composition, the etch rates of these materials increase linearly, with different slopes, with increasing rf power density. Under the conditions studied, the etch rates of SiO2 are lower than those of the other two materials and are primarily a function of rf power for CF4 plasmas that are diluted with 0%–25% O2 by flow rate. In comparison, the etch rates of Si3N4 and doped polycrystalline silicon are functions of both rf power density and gas composition, although at each rf power level (200, 300, and 400 W) the Si3N4 etch rate reaches a plateau at an O2 dilution of ∼10%–15% by flow rate. Although the doped polycrystalline silicon etch rate exhibits similar behavior at 200 and 300 W, a steady increase in etch rate is noted at 400 W over the range of O2 dilution examined in this work. At low O2 dilutions, the Si3N4 etch rate is greater than the doped polycrystalline silicon etch rate. However, with increasing O2 dilution, the doped polycrystalline silicon etch rate exceeds the Si3N4 etch rate, with the intersections of these etch rate curves shifting to greater O2 dilution at higher rf power settings.

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.

Polymer Etching in the Oxygen Afterglow: Increased Etch Rates with Increased Reactor Loading

Reactor loading has an effect on the etch rate (rate of decrease of film thickness) of films of polyvinylfluoride (Tedlar) and polyethylene exposed in the afterglow of an RF discharge in oxygen. The etch rate is found to increase with the total surface area of the polymer exposed in the reactor. The etch rates of polypyromellitimide (Kapton H) and polystyrene under these conditions are very low. However, the etch rate of these polymers is greatly enhanced by adding either Tedlar or polyethylene to the reactor. A kinetic model is proposed based on the premise that the oxygen atoms [O(3P)] produced by the RF discharge react with Tedlar or polyethylene to produce a much more reactive species, which dominates the etching of the polymers studied.

液晶ディスプレイパネルの電極形成技術

Fine patterning technology of ITO and Ni on the Cr (Ni/Cr) bilayer film electrode for LCD panel was studied. Hl or HBr solution was found to be the most suitable etching solution for ITO because of small undercutting property.For preferential etching for Ni/Cr double bilayer electrode on ITO, mixed solution of CH3COOH-HNO3-H2SO4 H3PO4 was found to be most suitable for Ni film, while for Cr film, Ce (NO3) 4·2NH4NO3 solution was found most suitable. For Ni etching, HNO3 was the most effective component because it shifted the electrode potential to the nobler direction, resulting in an increased etching rate.

The role of chlorinated surface films in excimer laser etching of Cu at low Cl2 pressures

Mass spectroscopy combined with time of flight (TOF) is used to study the products ejected from a Cu surface exposed concurrently to nanosecond excimer laser pulses at 308 nm and a low Cl2 pressure (p). Starting with a clean surface the etch rate increases with the number of pulses (n) until a steady state level (S) is reached. For various values of the laser pulse fluence F (0.14–0.82 J cm−2), of p (3×10−4–10−2 Pa), at a pulse repetition rate (r) of 4 Hz, and for irradiation along the surface normal, the main products are Cu3Cl3 and CuCl. All TOF distributions can be simulated well with Maxwellians (MB). At each set of values of F, p, r, and n the temperature (T) corresponding to the MB’s of the different products is the same. Starting with a clean Cu surface, T increases with n until S is reached. In S, T increases with p, but the dependence on F shows a maximum. T values of up to 6000 K may be reached. Rutherford backscattering analysis of the etched Cu samples reveals that Cl is incorporated during etching up to several tens of atom percentages and to depths of a few hundred nm. The increase in etch rate with n in the buildup to S is correlated to the gradual laser-assisted formation of a chlorinated Cu surface film. In S the Cl profile remains constant. The magnitude of the Cl concentration in and the thickness of the chlorinated Cu surface film are correlated to T and the etch rate. It is proposed that this behavior can be related to the lower heat conductivity of the chlorinated surface film.