Bromine-methanol etching of semiconductor crystals Cd1-xZnxTe1-ySey with different selenium concentrations

The apparent and steady-state etch rates of PECVD SiO2, HDP SiO2 and PECVD Si3N4 are measured both in a single thin film and a stacked film configuration. This is done for a HF:H2O/1:1, a HF:IPA/1:1 and a BHF solution. It is shown that etch rates vary with the used etch time, confirming the influence of both an incubation and a rinsing period on the average etch rate when performing typical ex situ etch rate experiments. Hence, this second part of a set of two papers provides the experimental evidence for part I where a general etch rate model was proposed. Furthermore this work shows that the etch rate varies whether it is determined on a single layer, in a stacked configuration or while under-etching a structural layer. This confirms the need of a straightforward characterization method for under-etching measurements at the sacrificial release stage of MEMS fabrication processes. Therefore, a new characterization method, using a suspended beam array and a surface profilometer, is proposed to determine the amount of under-etch after sacrificial release of surface micromachined devices.

A methodology for optimizing and characterizing processes for selectively etching Cu underbump metallurgy in the presence of Pb-Sn solder in spray acid tools is discussed. Wafers with the following UBM and bump structure were used in this study: sputtered TiW/sputtered Cu/electroplated Cu stud/electroplated Pb-Sn solder. The development of a manufacturable etch process is illustrated by discussing the method used to establish the process for selectively etching the sputtered Cu film using a commercial, two-component, ammoniacal Cu etch chemistry. The average etch rate on monitors with blanket sputtered Cu films, placed in all slots of the tool clamshell, was used to establish a non-uniformity factor (/spl eta/), which is defined as the ratio of the etch rate in the slot displaying the fastest etch rate to the etch rate in the slot displaying the slowest etch rate. Under ideal conditions the non-uniformity factor should be unity. Over the parameter space investigated it was found that the non-uniformity factor was minimized with the following conditions: temperature of 27/spl deg/C, RPM of 20, pump pressure of 52 psi, etchant flow rate of 6 liters/min, and a 25% solution of the two-component etch chemistry, with the two-components in a 1:3 proportion. Flip chip packages containing electroplated Cu stud and solder bump structures require selective etching of the underlying underbump metallurgy layers that serve as a diffusion barrier and as an electrical bus layer for the electroplating process. In this paper the characterization of a spray acid tool for selectively etching the sputtered Cu bus layer from multiple wafers simultaneously is discussed. The use of the non-uniformity parameter, /spl eta/, defined earlier, to establish the preliminary process is presented. /spl eta/ was also used to understand the parameters that controlled the uniformity of the spray pattern. In particular the effect of pump pressure, flow rate, and etchant composition on /spl eta/ was used to establish the levels of these variables for the Cu etch process. The preliminary Cu etch process was confirmed with a full lot containing 25 blanket Cu wafers. A maximum overetch of 39% was obtained for the full lot.

The interaction phenomena of nanosecond Q-switched diode-pumped solid state (DPSS) laser using 355nm radiation with 0.2mm thick 316L stainless steel foil was investigated at incident laser fluence range of 19 – 82Jcm−2. The characterization study was performed with and without the use of assist gas by utilizing micro supersonic minimum length nozzles (MLN), specifically designed for air at inlet chamber pressure of 8bar. MLN ranged in throat diameters of 200µm, 300µm, and 500µm respectively. Average etch rate per pulse under the influence of three micro supersonic impinging jets, for both oxygen and air showed the average etch rate was reduced when high-speed gas jets were utilized, compared to that without any gas jets, but significant variation was noticed between different jet sizes. Highest etch rate and quality was achieved with the smallest diameter nozzle, suggesting that micro nozzles can produce a viable process route for micro laser cutting.The interaction phenomena of nanosecond Q-switched diode-pumped solid state (DPSS) laser using 355nm radiation with 0.2mm thick 316L stainless steel foil was investigated at incident laser fluence range of 19 – 82Jcm−2. The characterization study was performed with and without the use of assist gas by utilizing micro supersonic minimum length nozzles (MLN), specifically designed for air at inlet chamber pressure of 8bar. MLN ranged in throat diameters of 200µm, 300µm, and 500µm respectively. Average etch rate per pulse under the influence of three micro supersonic impinging jets, for both oxygen and air showed the average etch rate was reduced when high-speed gas jets were utilized, compared to that without any gas jets, but significant variation was noticed between different jet sizes. Highest etch rate and quality was achieved with the smallest diameter nozzle, suggesting that micro nozzles can produce a viable process route for micro laser cutting.

The affect of varying a wide range of excimer laser parameters on the average etch rate per shot of aerospace alloys (Al, Ti and Ni) has been investigated. The parameters found to most profoundly influence the etch rate were, the laser fluence (up to 70 J/cm<SUP>2</SUP>), pulse length (20 - 160 nsec FWHM), gas environment, beam spot size (35 - 300 micrometers ) and material thickness (0.4 - 1.8 mm). Optimization of these parameters has produced an increase in average etch rate per shot from 0.05 to 1.5 micrometers with Ti alloy (2 TA - 10). Such increases in etch rate are seen to occur above a relatively well defined 'critical' fluence for thick samples which it is postulated corresponds to the transition from a largely vaporization dominated to a vaporization/melt expulsion regime. Information is also included on the quality of the processing and on the extent of the laser affected zone around the processed area. Potential aerospace application areas identified and discussed include drilling multiple hole arrays for producing porous surfaces for drag reduction on aircraft and the cutting and profiling of alloy/glass fiber composites (GLARE).

The characteristics of isotropic etching of silicon in a purely inductively coupled SF6 plasma are quantitatively studied. Since the etch results are strongly dependent on mask features, the authors investigated both large area and narrow trench etch characteristics. Circles of diameter 500 μm were used as a proxy for unpatterned surfaces and etched for different durations to establish the material etch rate and surface roughness. The average etch rate using the chosen recipe was found to be 2.27 μm/min. Arrays of narrow trenches ranging from 8 to 28 μm were also etched to analyze the effect of trench size on etch rate and degree of anisotropy. The etch rate of the trenches was found to strongly decrease with decreasing trench width. The results demonstrate that isotropic SF6 etch can be readily used as a replacement for more exotic silicon vapor phase etch chemistries such as XeF2.

The dependence of the etch depth of a contact hole or circular via on the diameter of the hole opening is derived for a simple model which includes the effect of the bombarding ions and the neutral radicals on the etching. The ion etch rate at the center of the contact hole is proportional to the ion energy flux and the neutral etch rate is proportional to the neutral flux expression for molecular flow in a pipe. The total etch rate expression is found by Langmuir kinetics. The linear experimental relation for the etch depth versus the inverse diameter holds in this model for etching in the near ion flux-limited regime. The dependence of the etch depth and average etch rate on the etch time is given for this model.

We have etched 700 nm thick silicon nitride (SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> ) on 370×235 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> substrate using a linear electron cyclotron resonance (ECR) plasma source with reciprocating substrate motion. A mixture of NF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and Ar gases was used as etch gas. The etching of SiN x was performed with and without reciprocating substrate motion and compared to each other. In the etching without reciprocating substrate motion, the etch rate was measured in 45 points, showed 17.5% uniformity and the average etch rate was 92 nm/min. For the etching with reciprocating substrate motion, 4% uniformity of etch rate and 72 nm/min etch rate were obtained in the same measuring points. Moreover, there were no stains left on 370×235 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> SiNx glass after the etching with reciprocating substrate motion. In this paper, the linear ECR plasma source with reciprocating substrate motion is proved to be suitable for large-sized substrates and is profitable due to high yield and low-cost manufacturing.

Analysis of data gathered during a experiment to demonstrate control of the polysilicon gate etch revealed the possible presence of a first wafer effect, i.e., a different response of the etch metrics for the first wafer run after a delay or pump down. In this paper, we investigate this first wafer effect on spatial etch rate and in situ ellipsometer metrics more thoroughly. The spatial metrics were standard deviation and Median Absolute Deviation from the Median, as well as contrasts (such as average etch rate of fast sites--average of slow sites). Ellipsometer metrics were Mean Etch Rate, initial etch rate, rate of change of the etch rate during etch, initial thickness--estimated initial thickness, and polysilicon loss during the deglaze step. Multivariate Statistical Quality Control statistics of the ellipsometer metrics were also examined. In addition, a comparison of the ellipsometer data with data measured ex situ on a site near the ellipsometer measurement die were made. This document demonstrates that data obtained in situ with an ellipsometer can indicate when the etch rate spatial pattern is different from that expected.

This paper describes the development of a novel technology that can form a dense and complex pattern on a polymer tube without thermal damage. We have developed an etching mask and equipment capable of processing the tubular material. We named this technology cylindrical RIE (reactive ion etching). In order to evaluate the fundamental processing characteristics of this technology, etching rate, side etching ratio and etching uniformities along the tube axis and circumferential directions are evaluated. As a result, a vertical wall caused by anisotropic etching could be observed, and the average etching rate was 1.0 µm min−1 and the average side etching ratio was 0.027. The maximum differences between etching rate along the axis and circumferential directions were 0.25 and 0.12 µm min−1, respectively. The cross-section of the etched through-groove (slit) processed in a PP (polypropylene) tube having wall thickness of 200 µm was evaluated. By the bowing phenomenon, pattern width decreased most at the middle of the thickness of the tube wall, and average width errors at the middle of the thickness was 22.4 µm. To demonstrate the usefulness of the cylindrical RIE, a stent made of PP tube was fabricated. It was possible to fabricate a stent with an outer diameter of 4.4 mm, length of 19 mm, main strut width of 300 µm, and connecting strut width of 80 µm.

1. Introduction Ge has been received much attention as the next generation semiconductor materials due to its attractive characteristics such as high carrier mobility[1] and narrow bandgap corresponding near infrared wavelength[2]. In order to utilize its characteristics for the applications, Ge-on-Insulator (GOI) structure is necessary. Several fabrication methods for GOI have been suggested such as wafer bonding and mechanical thinning[3], Smart-CutTM[4,5], and SiGe condensation[6]. It is well known Smart-CutTM is widely used for commercial Si-on-Insulator (SOI) fabrication. However, Ge is more sensitive to damages caused by ion implantation and difficult to recover damages completely. Therefore, the best way for GOI fabrication have not been developed.In early stage of SOI R&D, many approaches were proposed, too[7]. Wafer bonding and etchback is one of the simplest technique, and the advantage of this method is any damages due to ion implantation or mechanical stress are not induced to the top semiconductor layer. Therefore, we focused on etchback technique for GOI fabrication. It is necessary to develop appropriate Ge etching method with moderate etching rate and keeping or improving surface flatness. In this study, we aim to develop appropriate etching method of Ge for etchback GOI fabrication. 2. Experimental and results We used single side mirror polished Ge wafer with a thickness of 500 μm. Figure 1 shows the experimental procedure in this study. The original polished top surface was covered by photoresist to avoid etching from this side. Firstly, we confirmed HF + HNO3 mixture solution for Ge etching because it is widely known as etching solution for Si. Figure 2 shows optical microscope images for the back side (non-polished side) of (100)-oriented Ge wafer (a) before etching and (b) after etching by HF + HNO3 for 7 minutes. By etching, surface uniformity drastically improved. So, wet etching can be used for Ge thinning and planarization. However, this solution reacts handle Si substrate of GOI, too. As an alternative etching solution, we selected HF + H2O2 mixture[8]. Figure 3 shows the etching result of (100)-oriented Ge etched by HF + H2O2 + H2O (7:7:6) solution. Although Ge was etched similar to Fig. 2(b), surface uniformity was inferior to HF + HNO3 etching. To improve surface uniformity, CH3COOH was added as diluent instead of H2O because politic amount of CH3COOH into HF + HNO3 solution leads isotropic etching and mirror plane on Si surface[9]. Figures 4 shows the etching results of (100)-oriented Ge by HF + H2O2 + CH3COOH (1:1:1) solution. Surface uniformity improved than Fig. 3 and there is no orientation dependence (data not shown). Therefore, isotropic etching occurs on Ge surface. The average etching rate in the first 20 minutes calculated from the lost masses was 7.9 μm/min. It should be noted any agitation was not carried out during etching and longer etching time leads decreasing of etching rate. Possible etching reaction is expressed as[10]:2CH3COOH + 2H2O2 → 2CH3COOOH + 2H2O (1)Ge + 2CH3COOOH + 2e - → Ge2+ + 2CH3COO- + 2OH- (2)As further investigation of surface uniformity, atomic force microscope (AFM) observation was carried out. Figure 5 shows AFM images for backside of (100)-oriented Ge etched for 110 minutes. The RMS of 30×30 μm2 area is 0.48 nm. Compared with the RMS of original backside (> 5 μm), the surface flatness is improved drastically. In the conference, electrical characteristics of etched surface will be presented. 3. Conclusions For etchback GOI fabrication, we study isotropic etching for Ge. HF + H2O2 + CH3COOH mixture solution can etch Ge isotropic and improving surface uniformity. This solution has a potential as etching solution for etchback to make GOI structure. Acknowledgements This work was supported by JSPS KAKENHI Grant Numbers 19K15028 and 19H05616. Appendix Original concentrations of the chemicals in this study are HF: 49 wt%, HNO3: 69 wt%, H2O2: 30 wt%, and CH3COOH: 99.7 wt%. All compounding ratios in this article are volume rate.

Reactive ion etching of via holes for grounding of monolithic microwave integrated circuits has become the industry standard. It is well known that the via etch rate decreases as a function of decreasing via mask diameter as well as increasing etch depth. A model has been developed which relates the experimental etch rates in Cl2/BCl3/Ar plasmas to the ion and neutral fluxes incident on the wafer. This model provides a useful tool for designers and process engineers to predict etch depths and average etch rates as functions of via diameter and total etch time.

In this study we have investigated the reactive ion etching of 60 μm diam, 200 μm deep holes in 3 in. diam semi-insulating GaAs wafer using a combination of and gases for fabrication of through substrate via holes for grounding in monolithic microwave integrated circuits (MMICs). The effect of process parameters viz. pressure, ratio, and power on GaAs etch rate and resultant etch profile was investigated. Two kind of masks, photoresist and Ni, were used to etch GaAs and their performance was compared by investigating effect on etch rate, etch depth, etch profile, and surface morphology. The etch profile, etch depth, and surface morphology of as-etched samples were characterized by scanning electron microscopy. The desired 200 μm deep strawberry profile, with a top μm and bottom μm, was obtained at 40 mTorr process pressure with an average etch rate μm/min using Ni mask. The vias were then metallized by depositing a thin seed layer of Ti/Au (1000 Å) using radio frequency sputtering and Au (5 μm) electroplated to connect the front side pad and back side ground plane. The parasitic inductance offered by these vias was pH. The developed process was then integrated into the MMIC process line and a 16-18 GHz amplifier was fabricated using grounding vias with yield >90%. © 2003 The Electrochemical Society. All rights reserved.

The effects of process conditions and chamber geometry on the uniformity of Al etched by Cl2 were measured in a Lam TCP™ 9600 SE etch reactor. A computer simulation accurately predicted etch uniformity and aided in the explanation of uniformity trends. Parameters used in the experimental matrix included pressures between 6 and 24 mT, flow between 25 and 100 sccm, power supplied to the plasma between 0 and 350 W, and chamber heights ranging from 6 to 12 cm. The distinctive features of this study include the large number of input parameters studied in a commercial reactor and the accurate predictions obtained from a self-consistent simulation without free parameters. Reducing residence time in the experiments by adjusting chamber height or flow rate produces a more center-fast etch, as expected. The flow simulations were useful in corroborating intuitive arguments and in explaining anomalous results such as the effect of pressure on etch uniformity. More specifically, comparison of simulations and measurements demonstrated the quantitative connection between the Peclet number, the residence time, and the edge uniformity over a large range of process conditions. In addition to explaining general trends with residence time, Peclet number considerations also clarify the differing effects of pressure, flow rate, and chamber height change on uniformity. No attempt was made to impose plasma effects in the flow simulation because measurements of the neutral temperature and dissociation fraction were not available. Plasma power was observed experimentally to slightly improve uniformity without changing the average etch rate.

Most of the methods which are currently being used to obtain high depth resolution composition profiles in solids rely on the continuous removal of surface particles by sputter−etching as a microsectioning technique. Sputter−etching has the advantages of being able to microsection essentially all materials in a clean, controllable, relatively uniform manner, and of being compatible with the vacuum requirements of several elemental analysis procedures. There are two general methods by which the sputter−etch procedure can be used to determine composition profiles: (i) Analysis of the sputter−etched sample surface (Auger electron spectroscopy,1 x−ray photoelectron spectroscopy,2 appearance potential spectroscopy,3 low−energy ion scattering spectrometry4); and (ii) analysis of the sputtered particles following their ejection from the surface (secondary ion mass spectrometry,5 glow discharge mass spectrometry,6 analysis of impact radiation,7 glow discharge optical spectroscopy8). Each of these two general approaches to the problem has some advantages and disadvantages independent of the specific technique employed and these considerations will now be discussed. The methods which involve the detection of the emitted sputtered particles have an advantage in that the recorded data include information about the sputter−etch rate if all the major constituents of the sample are monitored. The data provided by surface analysis methods are independent of the sputter−etch rate and an independent measurement of the sputter−etch rate is needed to calibrate the depth scale. Furthermore, if the sputter−etch rate changes during the analysis, it is possible to extract the correct composition profile from the data provided by the sputtered species detection methods, whereas only an approximate profile can be obtained from surface analysis methods. A second basic difference between these two approaches to composition profiling arises from the fact that in general, the steady−state surface composition of a sputter−etched multiconstituent sample will be different from the bulk composition, whereas the composition of the steady state flux of sputtered species will be representative of the bulk composition. That is to say the data provided by the sputtered species detection methods are independent of the sputtering yields of the individual species, whereas the data provided by the surface analysis methods depend directly on the sputtering yields. Although this effect can be accounted for by a calibration factor for the surface analysis methods, the sputtered species detection methods have an advantage in quantitative analyses. The fact that the sensitivity of the surface analysis methods is independent of the sputter−etch rate, whereas the sensitivity of the sputtered species detection methods is proportional to the sputter−etch rate complicates a comparison of relative sensitivities. However, it is believed that the sputtered species detection methods have a somewhat higher sensitivity with the sputter−etch rates normally encountered in composition profiling work. Although some information about chemical bonding at a surface can be obtained from a study of the nature of molecular sputtered species with the sputtered species detection methods, most of the surface analysis methods are clearly more useful in obtaining information about chemical bonding and electronic structure. Whereas the molecular sputtered species do provide some information about surface chemistry, they also complicate the analysis for the sputtered species detection methods. The surface analysis methods are not influenced by molecular sputtered particles and consequently have an advantage in terms of the complexity of the data and calibration procedures. Finally, if the sputter−etching and the surface analysis can be performed simultaneously as opposed to sequentially in the surface analysis methods, it is suspected that the surface analysis methods will be somewhat less sensitive to the effects of residual gas in the vacuum system than the sputtered species detection methods. The reason for this statement is that two of the sputtered species detection methods (secondary ion mass spectrometry and analysis of impact radiation) are very sensitive to surface contamination, whereas in the other two methods (glow discharge mass spectrometry and glow discharge optical spectroscopy) the residual gas can contribute to the observed signal directly from the gas phase.

Crystallographic anisotropy of growth and etch rates of CVD diamond