Selective Etching Solutions Research Articles

Synthesis of Noble Metal M@YSiO2 Yolk-Shell Nanoparticles with Thin Organic/Inorganic Hybrid Outer Shells via an Aqueous Medium Phase.

A simple method is proposed for the synthesis of noble metal M@YSiO2 (M = Au, Pd, Ag) yolk-shell nanoparticles. The effects of synthesis conditions on the preparation of yolk-shell nanoparticles were discussed in detail. According to the different corrosion resistances between inorganic silica and organosilicone in a selective etching solution, yolk-shell nanoparticles with large cavity and thin shell were prepared using the same aqueous medium in a step-by-step synthesis process. Different from traditional methods, this method is facile and efficient because the main synthesis process is carried out in an aqueous phase. This extended method may benefit the synthesis and application of other nanomaterials with a similar yolk-shell structure.

Highly Selective Etching Solutions for Advanced Logic Technologies

As logic semiconductor moves to 65nm node and beyond, several process-enhancement technologies have come into prominence with the help of dry etch processes. In high-aspect ratio contact etch (CT) process, the sufficient over-etch during dielectric oxide etch without too much loss of SiN-based stop layer is required to maintain the enough process window for less silicide loss loading and leakage. Stress memorization technology (SMT) is designed to enhance the P-MOS performance. It removes the stressed nitride and stops on one thin oxide layer. The enough oxide remaining is also imperative to avoid silicon damage. Besides, the loading effect of nitride thickness in SRAM area has to be compensated. Highly selective etching process is indispensable to fulfill these tightening and newly-born process requirements. In this paper, we address the effect of etch parameters including pressure, chemistry, gas ratio and power on the etching selectivity between nitride and oxide film in the above two processes. Scanning Electron Microscope (SEM) is utilized to compare the final etched profile. Results demonstrate besides the etch chemistry and power ratio, the etcher selection also plays the vital role on etching selectivity and etch rate.

Defect imaging of SiGe strain relaxed buffers grown by LEPECVD

We compare four different selective etching solutions commonly used to highlight threading dislocations (TD), in SiGe hetero-epitaxial layers. The aim is to identify, amongst the many reported in the literature, an etching solution effective over the whole Ge concentration range. Etching experiments have been performed on Si 1− x Ge x linearly graded relaxed buffer layers with a final germanium concentration x varying from x = 0.2 to 0.9. All samples have been deposited on Si(1 0 0) by low-energy plasma-enhanced chemical vapour deposition (LEPECVD). The experimental results show that a variant of the so-called Schimmel-etch is successful in revealing TD over the Ge concentration range investigated.

Selective wet etching of GaAs on Al 0.24 Ga 0.76 Asfor GaAs/Al 0.24 Ga 0.76 As/In 0.22 Ga 0.78 AsPHEMT

A selective etching solution of GaAs over Al0.24Ga0.76As, composed of acid-buffer solution (citric acid monohydrate + potassium citrate) and H2O2, has been developed for GaAs/Al0.24Ga0.76As/In0.22Ga0.78As PHEMT applications. The best selectivity of 776 was achieved using the mixed solution (citric acid-buffer solution:H2O2 = 5:1). The etch rate of GaAs in the solution is as low as 46.6 A/s. Both the low etch rate of GaAs and the high selectivity exhibit the standard deviation of pinch-off voltage of 1.0 µm-gate PHEMTs as low as ±0.029 V across a 3 in wafer. This demonstrates the applicability of this solution to the gate recess process.

Sub-100 nm Patterning of Aluminum Film by AFM Local Oxidation

AbstractWe have investigated the local oxidation of an aluminum film to fabricate aluminum and aluminum oxide masks on Si and SiGe substrates. The local oxidation is made by negatively biasing the probe of an atomic force microscope operating in contact mode. The masks are defined by removing the unwanted material using highly selective etching solutions at room temperature. The produced aluminum-based masks can withstand reactive ion etching processes using fluorinated gases mixtures. We report examples of sub-100 nm pattern transfer on the substrate using the AFM fabricated masks. Preliminary observations suggest to use the sputtered aluminum films for which the anodization is found more efficient than for e-beam evaporated aluminum.

Selective wet etching of GaAs on AlxGa1−xAs for AlGaAs/InGaAs/AlGaAs pseudomorphic high electron mobility transistor

Selective wet etching of GaAs over AlxGa1−xAs (x=0.2, 0.23, 0.3, and 1.0) for AlGaAs/InGaAs/AlGaAs pseudomorphic high electron mobility transistor (PHEMT) was studied using current–voltage, etched step measurement, atomic force microscopy (AFM), and x-ray photoelectron spectroscopy. The volume ratio of 50% citric acid solution (citric acid:H2O=1:1) to H2O2 was changed from 0.7:1 to 3:1, and the etching selectivity of GaAs over AlxGa1−xAs was examined. In the solution with the ratio of 1.5:1 of the 50% citric acid/H2O2, the best selectivities for GaAs on AlxGa1−xAs with x=0.2, x=0.23, x=0.3, and x=1.0 are measured to be 137, 143, 159, and 2700, respectively. The AFM measurements show that the AlxGa1−xAs surface etched by the selective etching solution is much smoother than that by a nonselective one, consisting of H3PO4:H2O2:H2O=4:1:180. The amount of Al–O bond at the selectively etched surface of AlxGa1−xAs increases with the Al composition in the AlxGa1−xAs. This means that the insoluble Al2O3 mainly plays a role in suppressing the dissolution of the AlGaAs in the etching solution. The selective etching solution is applied to the fabrication of PHEMT. The PHEMT exhibits excellent and reliable performance, demonstrating the applicability of this solution to gate recess process.

Fabrication of flexible monocrystalline ZnSe-based foils and membranes

We report the successful fabrication of flexible single crystal semiconductor structures. A highly selective etching solution allowed us to obtain large area foils and membranes of good structural integrity, using films of indium and silicone as flexible substrates. Photoluminescence and transmission measurements verified that the optical properties of these structures were preserved.

A Selective Etching Solution for Use with Patterned Self-Assembled Monolayers of Alkanethiolates on Gold

Nl icrocontact pr int ing t r rCPtr is a technique that generates patterned self-assembled monolayers lSAtr{s t2 of' alkanethiolates t typically, hexadecanethiolate ) on the surfaces of goid,1 silver,l l and copper,l and of alkylsiloxanes on hydroxyl-terminated surf'aces.r' Patterned SAI{s of alkanethiolates serve as nanomc.ter-thick resists in certain etching solutions: the one we i.rave. used most extensively when gold is the underiving substrate has been aqueous KCN so lu t ion (p l l ' . 1 t . ICN ] . . ,0 .1 M) saturated with 0z.6 Llsing this etchant. t l-re patterns in the SAMs can be transf'erred faithfuih' into the thin fi lms of gold; the resulting patterns of gold can be used subsequently as secondarv masks for the etching (isotropic or anisotropic ) of' underlving la.vers of sil icon dioxide and si l icon; ' or i ls funct ional e lements ( for example, for microerlectrodese and diffraction gratingsi0). Microcontact printing is renrarkablv convenient fbr the fabrication of structures rvith feature sizes of 1 zrm and larger: it can be r-rsed. rvith more diff iculty and less reliabil itv. to fabricate f 'eatures with sizes down to 100

Two Selective Etching Solutions for GaAs on InGaAs and GaAs / AlGaAs on InGaAs

Two solutions for selectively etching on and on are presented. A solution of is shown to have a etch rate more than 50 times higher than the etch rate of . A solution of etches both and selectively relative to , with a selectivity of 8 or more for.

液晶表示パネル上へのＬＳＩチップ実装技術の開発

Mounting technologies with high reliability were investigated for flip chip bonding of LSI chips on glass substrate in chip on type liquid crystal displays.For metallic film conductor on glass substrate, four layered structure of Cr-Ni-Cu-Cr was found to be the best combination. Best selective etching solution for each metal was found and metal thicknesses were optimized.For protection material of metallic film, sputtered SiO2 film was chosen because of good reliability in operating life test. In order to obtain highly reliable LSI chips under thermal shock test condition, the thermal expansion coefficient of covering epoxy resin was taken to be nearlly equal to that of 95Pb-5Sn solder by controlling amount of added Si powder.

Etch rates for two material selective etches in the InGaAsP/InP system

Two material selective etching solutions have been evaluated for the InGaAsP/InP system. One of these solutions etches the InGaAsP-InGaAs alloys and stops at InP, while the other etches InP and stops on the ternary or quaternary alloys. Room-temperature etch rates were measured for both etches on bulk and liquid phase epitaxial materials.