Fast Etch Rate Research Articles

Metal-assisted chemical etching in HF/H2O2 produces porous silicon

A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d<10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface prior to immersion in a solution of HF and H2O2. Depending on the type of metal deposited and Si doping type and doping level, PSi with different morphologies and light-emitting properties is produced. PSi production occurs on the time scale of seconds, without electrical current, in the dark, on both p- and n-type Si. Thin metal coatings facilitate the etching in HF and H2O2, and of the metals investigated, Pt yields the fastest etch rates and produces PSi with the most intense luminescence. A reaction scheme involving local coupling of redox reactions with the metal is proposed to explain the metal-assisted etching process. The observation that some metal remains on the PSi surface after etching raises the possibility of fabricating in situ PSi contacts.

Inductively Coupled Plasma Etching of Doped GaN Films with Cl2 / Ar Discharges

The inductively coupled plasma etching of undoped n‐ and p‐type GaN films was carried out with discharges using different radio frequencies of 100 kHz and 13.56 MHz, in which the chuck power source operates. The etch rates with lower frequency of 100 kHz were greater than those with higher frequency of 13.56 MHz due to higher ion bombarding energy. The etch rates of the GaN films with 100 kHz frequency increased substantially with increasing pressure, while the etch rates with 13.56 MHz increased up to 20 mTorr and then decreased at higher pressures. The n‐GaN showed somewhat faster etch rates than undoped and p‐type GaN films. The surface of the etched GaN films showed quite smooth morphology, and the n‐GaN showed some depletion of nitrogen from the etched surface. © 2000 The Electrochemical Society. All rights reserved.

Structure of latent tracks created by swift heavy-ion bombardment of amorphousSiO2

The defect structure of ion irradiation damage localized in latent tracks in amorphous ${\mathrm{SiO}}_{2}$ and their role in the chemical etch rate of such tracks has been studied. A variety of light and heavy ions were used with energies ranging from 4 to 127 MeV. It was found that the frequency of the infrared absorption associated with the asymmetric stretch vibration of Si-O was significantly reduced following swift heavy-ion bombardment and that the shift correlated with the enhancement of the etching rate. In contrast, no correlation between the etching rate and either the ${E}^{\ensuremath{'}}$ center or the oxygen deficient center was observed. The IR peak shift has been related to the transition of ordinal six rings of ${\mathrm{SiO}}_{4}$ tetrahedra to planar three- and four-member rings, which were generated in the latent track due to the flash heating and quenching by bombardment. We propose that large numbers of planar three- and four-member rings in the latent track are responsible for the fast chemical etching rate.

High Etch Rate Gallium Nitride Processing Using an Inductively Coupled Plasma Source

The ongoing development of III-nitride laser diode and light emitting diode fabrication has been made possible by dry etching techniques. Conventional wet etching of these materials has proved difficult and while Reactive Ion Etch (RIE) plasma systems can be used as an alternative, the Inductively Coupled Plasma (ICP) offers an enhanced dry etch route. In this paper, high etch rate (>1.25 μm/min) gallium nitride (GaN) processing is reported using the Surface Technology Systems (STS) ICP system. This is the fastest etch rate published for an ICP system. The etched material exhibits smooth anisotropic profiles and is free from residues. The effect of plasma parameters such as power, pressure and flow of reactive and inert process gases are presented. The use of both chlorine (Cl2) and boron trichloride (BCl3) as reactive etch gases is also studied.

Patterning of thin film NiMnSb using inductively coupled plasma etching

Several plasma chemistries based on fluorine (SF6, NF3), Cl2/Ar, BI3/Ar, or BBr3/Ar were compared for etching NiMnSb under inductively coupled plasma (ICP) conditions. ICP source power, radio frequency chuck power, and plasma composition were found to have strong effects on the etch rate. SF6/Ar discharges provided the fastest etch rates for NiMnSb (>1 μm min−1) even with small amounts of source power (100 W) addition. On the other hand, NF3/Ar showed net deposition rather than etching at source powers >100 W or at high NF3 percentages. Cl2/Ar showed a similar trend, with net deposition at low dc self-bias (−100 V), but net etching above this threshold. BBr3/Ar discharges produced deposition under all the conditions investigated while relatively high etch rates (⩾3000 Å min−1) were obtained with BI3/Ar at halide percentages ⩾70%. In terms of etched surface morphology, SF6/Ar provided the best surfaces, with root-mean-square roughness of 2.5 nm and vertical etched profiles. Surfaces etched in plasma chemistries other than SF6/Ar revealed Mn enrichment, an indication of involatile Mn etch products. The SF6 chemistry has the further advantage of the absence of the corrosion noted with Cl2-based mixtures.

High-density, inductively coupled plasma etch of sub half-micron critical layers: Transistor polysilicon gate definition and contact formation

Sub-half-micron device design rules require precise control over two critical etch layers: transistor polysilicon gate definition and contact formation. The definition of the transistor polysilicon gate electrode is essential to the performance of the device. In addition, the small geometries and thin underlying gate oxide demand a high level of control over the gate dimensions. The design rules also require the formation of high-aspect-ratio contacts and vias with nearly vertical sidewalls and minimal critical dimension variation. To define these features, a deep-ultraviolet photolithography process was developed, incorporating a bottom antireflective coating (ARC). The etch processes used to translate these features into polysilicon (gates) and oxide (contacts) required an in situ ARC dry–develop step and a fast etch rate for high throughput with good uniformity while maintaining a high selectivity to any underlying layers. To achieve these stringent requirements, low-pressure, high-density-plasma reactors with independent substrate bias power control were needed.

Dry Etching of SrS Thin Films

Plasma chemistries based on fluorine, iodine, chlorine, bromine, or methane‐hydrogen have been investigated for use in the dry etching of SrS. The fastest etch rates were obtained with /Ar at high powers under electron cyclotron resonance conditions, where the ion density is much higher (1011 cm−3) than that of conventional reactive ion etching (∼109 cm−3). The etching is anisotropic for all of the chemistries studied, and a modest amount of surface smoothing may occur during etching under optimized conditions. In all cases, there was evidence of preferential loss of S from the near‐surface of the SrS due to the difference in volatilities of the respective etch products for strontium and sulfur.

Comparison of plasma chemistries for dry etching thin film electroluminescent display materials

Chlorine (Cl2 or BCl3, with additions of Ar or N2), fluorine (SF6/Ar) and methane/hydrogen (CH4/H2/Ar or CH4/H2/N2) based plasmas have been examined as a function of composition, source and sample chuck power, and pressure, for dry etching of the typical luminescent sulphide phosphors (ZnS, SrS), conductive electrode materials [indium tin oxide, (ITO) and TiW] and insulators (Al2O3, alumina/titania-ATO) used in thin film electroluminescent displays. It is necessary to have both a high ion flux and an ion energy above a particular threshold (typically ⩾125 eV) in order to achieve practical etch rates for the high bond strength materials such as Al2O3, alumina/titania and SrS. The fastest etch rates for ZnS, Al2O3 and aluminum tin oxide are obtained with Cl2/Ar for SrS with SF6/Ar and for ITO with CH4/H2/Ar.

Electron cyclotron resonance plasma etching of materials for magneto-resistive random access memory applications

Dry etching of multilayer magnetic thin film materials is necessary for the development of sensitive magnetic field sensors and memory devices. The use of high ion density electron cyclotron resonance (ECR) plasma etching for NiFe, NiFeCo, TaN, and CrSi in SF6/Ar, CH4/H2/Ar, and Cl2/Ar plasmas was investigated as a function of microwave source power, rf chuck power, and process pressure. All of the plasma chemistries are found to provide some enhancement in etch rates relative to pure Ar ion milling, while Cl2/Ar provided the fastest etch rate for all four materials. Typical etch rates of 3000A/min were found at high microwave source power. Etch rates of these metals were found to increase with rf chuck power and microwave source power, but to decrease with increasing pressure in SF6/Ar, CH4/H2/Ar, and Cl2/Ar. A significant issue with Cl2/Ar is that it produces significant metal-chlorine surface residues that lead to post-etch corrosion problems in NiFe and NiFeCo. However, the concentration of these residues may be significantly reduced by in-situ H2 or O2 plasma cleaning prior to removal of the samples from the etch reactor.

Comparison of dry etching of III-V semiconductors in ICl/Ar and IBr/Ar electron cyclotron resonance plasmas

ICl/Ar and IBr/Ar plasmas were found to be promising candidates for room temperature dry etching processing of the III-V semiconductors GaAs, AlGaAs, GaSb, InP, InGaAs, and InSb. Results showed fast etch rates (0.7 µm/min in ICl/Ar and −0.3 µm/min in IBr/Ar), and at high microwave power, 1000 W, good surface morphology (typical root mean square roughness ∼2 nm), while retaining the near-surface stoichiometry, especially in IBr/Ar plasmas. There was little change of surface smoothness over a wide range of plasma compositions for Gacontaining materials in both ICl/Ar and IBr/Ar plasmas, (e.g. GaAs), while there was a window region with about 25–50% of IBr in IBr/Ar plasmas to maintain good morphology of In-containing semiconductors like InP. Selectivities of 4–10 over mask materials such as SiO2, SiNx, and W were typical in ICl/Ar plasmas.

Performance of different etch chemistries on titanium nitride antireflective coating layers and related selectivity and microloading improvements for submicron geometries obtained with a high-density metal etcher

Different chemistries were evaluated in a metal etcher with a high-density plasma source that was used to etch a titanium nitride antireflective coating (ARC). A composite film structure consisting of aluminum (with 0.5%–1% Cu) as the underlying layer, a titanium nitride ARC layer, and titanium nitride as the barrier layer were used for the standard stack, while titanium nitride and aluminum layers alone were used for the initial characterizations of the process. Conventional BCl3/Cl2 chemistry was used initially to etch both the titanium nitride ARC layer and the underlying aluminum layer. The performance of BCl3/Cl2 chemistry on the titanium nitride ARC layer as well as on the composite stack was evaluated. Partial etch measurements were taken to calculate the composite microloading and resist selectivity values. Different etch chemistries were then employed for the ARC layer while keeping conventional BCl3/Cl2 chemistry for the aluminum layer, and the difference in process performances were evaluated. Fluorine additives along with chlorine as the main etchant gave very high etch rate values for the titanium nitride layer. CHF3 was added as the fluorine source for the current study. When the titanium nitride layer was etched with chemistries having faster etch rates, CHF3 added chemistries in the current study, a remarkable improvement in the composite microloading was observed, compared to the microloading values obtained with conventional chemistry. An improved etch rate uniformity was another noticeable performance improvement. Possible mechanisms for these trends are explained in this article. The experimental portion of this article will provide details relating to the etcher and the film structure used for the study. The results and discussion section will give details of the process performance and a comparative evaluation of different titanium nitride chemistries, as well as possible mechanism for the trends observed.

Dry etching of III-V semiconductors in IBr/Ar electron cyclotron resonance plasmas

IBr/Ar plasmas were found to be promising candidates for room temperature dry etch processing of the III-V semiconductors GaAs, AlGaAs, GaSb, InP, InGaAs, and InSb. Results showed fast etch rates (∼3,000A/min) at high microwave power (1000W) and good surface morphology (typical root mean square roughness ∼2 nm), while retaining the near-surface stoichiometry. There was little variation of surface smoothness over a wide range of plasma compositions for Gacontaining materials. By contrast, there was a plasma composition window of about 25–50% of IBr in IBr/Ar plasmas for maintaining good morphology of Incontaining semiconductors like InP. Etch rates of the semiconductors generally increased with microwave power (400-1000 W) and rf power (50-250 W), whereas there was little dependence of the rates on the increasing percentage of IBr in the IBr/Ar plasma composition above 30% IBr for In-based, and 50% IBr for Ga-based materials. Those results show the etch rates over 30% of IBr in IBr/ Ar are desorption-limited. Photoresist masks do not hold up well to the IBr under ECR conditions, resulting in poor profile control, whereas SiNx offers much better etch resistance.

Dry and Wet Etch Processes for NiMnSb, LaCaMnO3 and Related Materials

ABSTRACTA variety of plasma etching chemistries were examined for patterning NiMnSb Heusler thin films and associated A12O3 barrier layers. Chemistries based on SF6 and Cl2 were all found to provide faster etch rates than pure Ar sputtering. In all cases the etch rates were strongly dependent on both the ion flux and ion energy. Selectivities of ≥20 for NiMnSb over A12O3 were obtained in SF6-based discharges, while selectivities ≤5 were typical in Cl2 and CH4/H2 plasma chemistries. Wet etch solutions of HF/H2O and HNO3/H2SO4/H2O were found to provide reaction-limited etching of NiMnSb that was either non-selective or selective, respectively, to A12O3. In addition we have developed dry etch processes based on Cl2/Ar at high ion densities for patterning of LaCaMnO3 (and SmCo permanent magnet biasing films) for magnetic sensor devices. Highly anisotropie features are produced in both materials, with smooth surface morphologies. In all cases, SiO2 or other dielectric materials must be used for masking since photoresist does not retain its geometrical integrity upon exposure to the high ion density plasma.

In situ fiber optic thermometry of wafer surface etched with an electron cyclotron resonance source

The effect of plasma heating on wafer temperature during etching has been studied. Si and InP were etched using a high ion density discharge generated by an electron cyclotron resonance source. The wafer temperature was measured using fiber optic thermometry as microwave power, rf power, chamber pressure, and gas flow were varied. Wafer temperatures increased with both rf and microwave power, and decreased with chamber pressure. For a rf power of 50 W, chamber pressure of 1 mTorr, a source distance of 13 cm, and a 10 sccm Ar flow, an increase in microwave power from 50 to 500 W caused the temperature to increase from 62 to 186 °C. An increase in the rf power from 50 to 300 W increased the wafer temperature to 145 °C. Additionally, the effectiveness of using He flowing at the backside of the wafer for temperature control was analyzed. By setting the backside He pressure at 3 Torr, the temperature increased to only 29 °C. Time dependent etch characteristics of InP were studied and related to the in situ temperature measurements. At 100 W of microwave power, the InP etch rate increased from 100 to 400 nm/min as the wafer temperature rose from 20 to 150 °C. As the temperature increased above 150 °C, the profile became more undercut and the surface morphology improved. By setting the stage temperature to −100 °C and using 3 Torr of He pressure at the backside of the wafer, the InP etch rate remained constant during etching and undercutting was suppressed. For 500 W of microwave power, a fast InP etch rate of 2 μm/min was obtained when the wafer temperature was <110 °C, and it increased to over 4 μm/min when the temperature was ≳150 °C.

Comparison of Dry Etching Techniques for III‐V Semiconductors in CH 4 / H 2 / Ar Plasmas

Dry etching of III‐V semiconductors under reactive ion etching, magnetron, or electron cyclotron resonance (ECR) conditions has been performed in the same reactor using the plasma chemistry. The use of ECR conditions with additional RF‐biasing provides the fastest etch rates, although this produces rough surface morphologies for InP. Materials such as GaAs, AlGaAs, and GaP display smooth, stoichiometric surfaces even at the highest ECR powers employed. The etching is limited by sputter‐induced desorption of the etch products for all of the III‐Vs investigated.

High Aspect Ratio Deep Via Holes in InP Etched Using Cl2 / Ar Plasma

Dry etching of using a plasma generated by an electron cyclotron resonance source has been studied. A fast etch rate (2.7 μm/min) with vertical profile and smooth surface morphology was achieved at room temperature for via holes that are 30 μm wide and 110 μm deep. etch rate has been found to increase with microwave power, temperature, RF power, and pressure. The results indicate that high temperature is not necessary to etch using when the reactive species densities are high at high microwave power. Compared to other compound semiconductors, has the highest etch rate, followed by , , , and . In situ monitoring using mass spectrometry was used to provide precise control of the etch initiation time and the etch depth. Etch initiation time was found to decrease with ion energy. Since devices based on via holes usually have Ti/Au metallization layer on the front side, the and signals were used for end point detection. Etching can be controlled to stop with <50 nm Ti removed after reaching the bottom of the via holes.

Heterocyclic catalysts for enhanced silicon oxidation and wet chemical etching

Heterocyclic amine catalysts used to accelerate the wet oxidation of 〈100〉 silicon in gallate-complexed aqueous amine etchant formulations include pyrazines, pyridazines, and N -conjugated triazoles, tetrazoles, and triazines. Faster oxidation results in faster etch rates, where 2- and 2,3-disubstituted pyrazines produce aggressive etchants. Steric factors seem to control catalytic activity: large substituents in the 2- or 2,3- positions may enhance catalyst dissociation from the oxidized silicon surface, but 2,3,5,6-substitution may inhibit association of the catalyst with the bare substrate. Etch rates greater than 125 μm h −1 are obtained on 〈100〉 Si with quinoxaline, but unconjugated 1,2-diazines or diazoles do not show catalytic activity.

Heterocyclic catalysts for enhanced silicon oxidation and wet chemical etching

Heterocyclic amine catalysts used to accelerate the wet oxidation of 〈100〉 silicon in gallate-complexed aqueous amine etchant formulations include pyrazines, pyridazines, and N-conjugated triazoles, tetrazoles, and triazines. Faster oxidation results in faster etch rates, where 2- and 2,3-disubstituted pyrazines produce aggressive etchants. Steric factors seem to control catalytic activity: large substituents in the 2- or 2,3- positions may enhance catalyst dissociation from the oxidized silicon surface, but 2,3,5,6-substitution may inhibit association of the catalyst with the bare substrate. Etch rates greater than 125 μm h−1 are obtained on 〈100〉 Si with quinoxaline, but unconjugated 1,2-diazines or diazoles do not show catalytic activity.

In-Situ Fiberoptic Thermometry Measurements Of Wafer Temperature During Plasma Etching Using An Electron Cyclotron Resonance Source

AbstractThe increase in wafer temperature due to plasma heating during etching has been studied. Si and InP were etched using a high ion density discharge generated by an electron cyclotron resonance source. The wafer temperature was measured in-situ using fiberoptic thermometry as microwave power, rf power, chamber pressure, and gas flow were varied. Wafer temperatures increased with both microwave and rf power, and decreased with chamber pressure. For rf power of 50 W, chamber pressure of 1 mTorr, a source distance of 13 cm, and 10 sccm Ar flow, an increase in microwave power from 50 to 500 W caused the temperature to increase from 62 to 186 °C. Additionally, the use of He flowing at the backside of the wafer for temperature control was analyzed. By setting the backside He pressure at 3 Torr, the temperature increased from 20 °C at the beginning of the etch to only 29 °C after 12 min. Time dependent etch characteristics of InP were studied and related to the wafer temperature measurements. At 100 W microwave power, the InP etch rate increased from 100 to 400 nm/min as the wafer temperature rose from 20 to 150 °C. As the temperature increased above 150 °C, the profile became more undercut and the surface morphology improved. By setting the stage temperature to -100 °C and using 3 Torr He pressure at the backside of the wafer, the InP etch rate remained constant during etching and undercutting was suppressed. For 500 W microwave power, a fast InP etch rate of 2 μm/min was obtained when the wafer temperature was &lt;110 °C, and it increased to over 4 μm/min when the temperature was &gt;150 °C.

ECR plasma etching of GaN, AlN and InN using iodine or bromine chemistries

The dry etching characteristics of GaN, AlN and InN in HI-H/sub 2/-Ar and HBr-H/sub 2/-Ar were examined using electron cyclotron resonance discharges operating at high microwave power (1000 W) and low pressure (1 mtorr). For an RF-induced DC bias of -150 V, the HI chemistry provides approximately 20% faster etch rates for GaN and AlN than more conventional chlorine-based plasmas. For InN the rates were up to a factor of 5 faster. The HBr chemistry produced slower etch rates for all three nitrides compared to chlorine chemistries. Highly anisotropic etched features were obtained in the three materials with both iodine and bromine chemistries.