Low open-area endpoint detection using a PCA-based T2statistic and Q statistic on optical emission spectroscopy measurements

Examines an approach for automatically identifying endpoint (the completion in etch of a thin film) during plasma etching of low open area wafers. Because many end-pointing techniques use a few manually selected wavelengths or simply time the etch, the resulting endpoint detection determination may only be valid for a very short number of runs before process drift and noise render them ineffective. Only recently have researchers begun to examine methods to automatically select and weight spectral channels for estimation and diagnosis of process behavior. This paper will explore the use of principal component analysis (PCA)-based T² formulation to filter out noisy spectral channels and characterize spectral variation of optical emission spectroscopy (OES) correlated with endpoint. This approach is applied and demonstrated for patterned contact and via etching using digital semiconductor's CMOS6 (0.35-μm) production process     

GaInAs/InP quantum wires grown by metalorganic vapor phase epitaxy on V-grooved InP substrates

A single nominally lattice matched GaInAs quantum well (QW)/quantum wire (QWR) structure was grown by metalorganic vapor phase epitaxy (MOVPE) in V-grooved InP substrates. Different Si0₂ etch masks with opening widths from 2 μm down to 200 nm (for application as second order DFB grating) were defined by optical and electron beam lithography. A damage-reduced wet chemical etching process enables the growth of the GaInAs QWs/QWRs without any InP buffer layer. In low temperature photoluminescence we found improved intensity for all wire structures prepared by this etching technique. A reduction of the period and opening width of the V-groove etch mask resulted in a optimized luminescence intensity ratio between QW and QWR. Decay times from time resolved luminescence measurements were compared to the decay times of wet or dry etched mesa wires before and after regrowth. The good optical properties of the GaInAs QWRs are encouraging for future application as a QWR-laser device.     

Neural network modeling of reactive ion etching using optical emission spectroscopy data

Neural networks are employed to model reactive ion etching (RIE) using optical emission spectroscopy (OES) data. While OES is an excellent tool for monitoring plasma emission intensity, a primary issue with its use is the large dimensionality of the spectroscopic data. To alleviate this concern, principal component analysis (PCA) and autoencoder neural networks (AENNs) are implemented as mechanisms for feature extraction to reduce the dimensionality of the OES data. OES data are generated from a 2/sup 4/ factorial experiment designed to characterize RIE process variation during the etching of benzocyclobutene (BCB) in a SF/sub 6//O/sub 2/ plasma, with controllable input factors consisting of the two gas flows, RF power, and chamber pressure. The OES data, consisting of 226 wavelengths sampled every 20 s, are compressed into five principal components using PCA and seven features using AENNs. Each method is subsequently used to establish multilayer perceptron neural networks trained using error back-propagation to model etch rate, uniformity, selectivity, and anisotropy. The neural network models of the etch responses using both methods show excellent agreement, with root-mean-squared errors as low as 0.215% between model predictions and measured data.     

等离子体刻蚀工艺中的OES监控技术

采用光学发射光谱(OES)原位检测技术,对等离子体刻蚀机中的等离子体状态进行实时监控,讨论了其在故障诊断、分类、刻蚀终点的判断及控制方面的应用。实验平台为在新研发的高密度等离子体刻蚀机,采用化学气体HBr/Cl₂为刻蚀气体进行多晶硅刻蚀工艺实验,实验过程中所采集的OES数据通过PCA法进行分析,得到与刻蚀过程相关的特征谱线。实验结果表明：OES技术适合于深亚微米等离子体刻蚀工艺过程的终点检测及故障诊断。最后就OES技术未来发展面临的挑战进行了讨论。     

Uniform, high-gain AlGaAs/In0.05Ga0.95As/GaAsP-n-p heterojunction bipolar transistors by dual selective etch process

AlGaAs/InGaAs/GaAs P-n-p heterojunction bipolar transistors (HBTs) have been fabricated using a dual selective etch process. In this process, a thin AlGaAs surface passivation layer surrounding the emitter is defined by selective etching of the GaAs cap layer. The InGaAs base is then exposed by selective etching of the AlGaAs emitter. The resulting devices were very uniform, with current gain varying by less than ±10% for a given device size. Current gain at a given emitter current density was independent of device size, with gains of over 200 obtained at current densities above 5×10⁴ A/cm ²     

高密度等离子体刻蚀机中的终点检测技术

高密度等离子体刻蚀是当今超大规模集成电路制造过程中的关键步骤.目前已经开发出许多终点检测技术.文章讨论了终点检测技术的原理,综述了目前主流刻蚀机使用的两种终点检测技术-OES和IEP-的最新进展,讨论了终点检测技术在深亚微米等离子体刻蚀工艺中的应用,以及所面临的挑战.     

GSMBE生长In_(0.49)Ga_(0.51)P/GaAs HBT微结构材料及器件研究

采用 GSMBE技术 ,在材料表征和分析的基础上 ,通过优化生长条件 ,生长出高性能In0 .4 9Ga0 .51P/ Ga As异质结双极晶体管 (HBT)微结构材料 ,并制备出器件。材料结构中采用了厚度为 6 0 nm、掺杂浓度为 3× 10 19cm-3的掺 Be Ga As基区和 5nm非掺杂隔离层 ,器件流片中采用湿法化学腐蚀制作台面结构。测试结果表明该类器件具有良好的结特性 ,在集电极电流密度 2 80 A/cm2时其共发射极电流增益达 32 0。由此说明非掺杂隔离层的引入有效地抑制了由于基区 Be扩散导致的 pn结与异质结偏位及其所引起的器件性能劣化。     

Selectively etched tunnel junction for lateral current and optical confinement in InP-based vertical cavity lasers

We demonstrate a thin, selectively lateral-etched, AlIn(Ga)As tunnel-junction (TJ) layer as a current and optical confinement aperture in the InP-based long-wavelength vertical cavity surface-emitting lasers (VCSELs). A high etch selectivity was demonstrated by etching the aperture a distance of several microns without affecting the surrounding InP etch-resistant layer. Edgeemitting lasers enclosing the TJ aperture showed high injection efficiency and low current spreading underneath the aperature. Single-mode continuous-wave operation of a 1.55-μm VCSEL was demonstrated successfully with a room-temperature differential efficiency of 21% using a 6-μm-wide TJ aperature.     

RCLED的制作工艺与性能研究

设计并用MOCVD在GaAs衬底上分别生长了以34对AlAs/Al0.5Ga0.5As材料为下DBR,6对(Al0.3Ga0.7)0.5In0.5P/AlInP材料为上DBR,以及有源区为3个GaInP/(Al0.5Ga0.5)0.5In0.5P量子阱的外延片。设计了以SiO2做阻挡层,并且深腐蚀过有源区的台形RCLED的工艺结构,利用光刻、腐蚀、等离子化学气相沉淀(PECVD)以及溅射等工艺,成功制备了波长为650nm的谐振腔发光二极管(RCLED),并对其性能进行了测试。通过与普通LED相比较发现,RCLED不仅具备更强的轴向光强和更高的提取效率,而且具有更窄的光谱线宽、更小的发散角、更好的发射方向性,利于与塑料光纤进行耦合。     

Fault detection of plasma etchers using optical emission spectra

The objective of this paper is to investigate the suitability of using optical emission spectroscopy (OES) for the fault detection and classification of plasma etchers. The OES sensor system used in this study can collect spectra at up to 512 different wavelengths. Multiple scans of the spectra are taken from a wafer, and the spectra data are available for multiple wafers. As a result, the amount of the OES data is typically large. This poses a difficulty in extracting relevant information for fault detection and classification. In this paper, we propose the use of multiway principal component analysis (PCA) to analyze the sensitivity of the multiple scans within a wafer with respect to typical faults such as etch stop, which is a fault that occurs when the polymer deposition rate is larger than the etch rate. Several PCA-based schemes are tested for the purpose of fault detection and wavelength selection. A sphere criterion is proposed for wavelength selection and compared with an existing method in the literature. To construct the final monitoring model, the OES data of selected wavelengths are properly scaled to calculate fault detection indices. Reduction in the number of wavelengths implies reduced cost for implementing the fault detection system. All experiments are conducted on an Applied Materials 5300 oxide etcher at Advanced Micro Devices (AMD) in Austin, TX     

Selective etching of (Ba,Sr)TiO3 thin films over silicon in an inductively coupled plasma

In this work, we investigated etching characteristics of BST thin films and higher selectivity of BST over Si using inductive coupled O₂/Cl₂/Ar plasma (ICP) system. The maximum etch rate of BST thin films and selectivity of BST over Si were 61.5 nm/min at a O₂ addition of 1 sccm, 9.52 at a O₂ addition of 4 sccm into the Cl₂(30%)/Ar(70%) plasma, respectively. Plasma diagnostics was performed by Langmuir probe (LP), optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS). These results confirm that the increased etch rates at O₂ addition of 1 sccm is the result of the enhanced chemical reaction between BST and Cl radicals and an ion bombardment effect.     

Growth of InGaN HBTs by MOCVD

The design and growth of GaN/InGaN heterojunction bipolar transistors (HBTs) by metalorganic chemical vapor deposition (MOCVD) are studied. Atomic-force microscopy (AFM) images of p⁺InGaN base layers (∼100 nm) deposited under various growth conditions indicate that the optimal growth temperature is limited to the range between 810 and 830°C due to a trade-off between surface roughness and indium incorporation. At these temperatures, the growth pressure must be kept above 300 Torr in order to keep surface pit density under control. An InGaN graded-composition emitter is adopted in order to reduce the number of V-shaped defects, which appear at the interface between GaN emitter and InGaN base and render an abrupt emitter-base heterojunction nearly impossible. However, the device performance is severely limited by the high p-type base contact resistance due to surface etching damage, which resulted from the emitter mesa etch.     

High emitter efficiency in InP/GaInAs HBT's with ultra high basedoping levels

The emitter efficiency of InP/GaInAs heterojunction bipolar transistors is calculated taking into account bandgap narrowing in the base, quantum mechanical tunneling, and the exact doping profile in the base. It is found that the emitter efficiency is high and does not limit the current gain of practical devices, up to a base doping level of 1×10²⁰ cm^-3, and up to 400°K . It is shown that the base emitter junction saturation current can be controlled over two orders of magnitude by a proper small displacement of the doped layer in the base     

On the recombination currents effect of heterostructure-emitter bipolar transistors (HEBTs)

In this paper, we will demonstrate the effect of recombination current on the electrical properties of heterostructure-emitter bipolar transistors (HEBTs). For comparison, an AlGaAs/GaAs and an AlInAs/GaInAs HEBT are fabricated with the same layer structure. The theoretical analysis shows that the neutral-emitter recombination current in the neutral emitter regime is a significant factor for determining transistor characteristics. For the AlGaAs/GaAs HEBT, the hole diffusion length is larger than the emitter thickness, so that most of holes can be reflected back at the confinement layer due to the hole recombination current being low in the neuter-emitter region. Thus, the high emitter injection efficiency and current gain can be achieved simultaneously. On the other hand, for the AlInAs/GaInAs HEBT, the increase of recombination current at neutral emitter regime and the existence of potential spike could reduce the emitter injection efficiency at large V_BE voltage. Hence, the non-1KT component of collector current is enhanced and the characteristics of transistor are degraded. However, a lower offset voltage of 40 mV is obtained attributed to the low base surface recombination current for the AlInAs/GaInAs HEBT. All of these experimental results are consistent with the theoretical analysis.     

聚合物波导光栅耦合器的衍射场仿真

为了实现横截面尺寸为50 m50 m的聚硅氧烷聚合物光波导的耦合转向问题,设计了一种表面覆盖高折射率包层的多层蚀刻光栅耦合器。首先,分析了影响聚合物波导光栅耦合器耦合效率的结构因素;然后,采用在光栅表面蚀刻高折射率层的方法,提高了聚合物波导光栅耦合器的耦合效率;接着,对不同的周期（范围:100~4 000 nm）和不同的蚀刻深度（范围:0~50 000 nm）进行排列组合,形成不同的光栅结构,基于时域有限差分法编写程序,遍历所有情况,得到不同光栅结构下的光场情况以及其耦合效率,找到使耦合效率最大的周期以及蚀刻深度。最后,设计了多层蚀刻的光栅耦合器,进一步提高耦合效率。当蚀刻深度为5 000 nm,光栅周期为2 600 nm时,带高折射率层的聚硅氧烷聚合物光波导均匀光栅耦合器的耦合效率达到最大,为17.2%。采用多层蚀刻的方式,对结构进行优化,其耦合效率能达到37.4%。为聚硅氧烷聚合物光波导在光互连中的实际应用提供了理论依据。     

Etch characteristics of GaN and BN materials in chlorine-based plasmas

Reactive ion etching (RIE) was performed on GaN and BN thin films using chlorine-based plasmas. The optimum chemistry was found to be BCl₃/Cl₂/N₂/Ar and Cl₂/Ar at 30 and 40 mtorr for GaN and BN etching, respectively. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analysis of the GaN and BN etched surfaces show a decrease in the surface nitrogen atomic composition and an increase in chlorine impurity incorporation with increasing self-dc bias. A photo-assisted RIE (PA-PIE) process using an IR filtered Xe lamp beam was then used and resulted in improved etch rates and surface composition. Optical emission spectroscopy (OES) measurements have also shown photoenhancement of the etch process.     

InAlAs photovoltaic cell design for high device efficiency

This study presents a new design for a single‐junction InAlAs solar cell, which reduces parasitic absorption losses from the low band‐gap contact layer while maintaining a functional window layer by integrating a selective etch stop. The etch stop is then removed prior to depositing an anti‐reflective coating. The final cell had a 17.9% efficiency under 1‐sun AM1.5 with an anti‐reflective coating. Minority carrier diffusion lengths were extracted from external quantum efficiency data using physics‐based device simulation software yielding 170 nm in the n‐type emitter and 4.6 μm in the p‐type base, which is more than four times the diffusion length previously reported for a p‐type InAlAs base. This report represents significant progress towards a high‐performance InAlAs top cell for a triple‐junction design lattice‐matched to InP. Copyright © 2017 John Wiley & Sons, Ltd.     

Spatial characterization of wafer state using principal componentanalysis of optical emission spectra in plasma etch

Optical emission spectroscopy (OES) is often used to obtain in-situ estimates of process parameters and conditions in plasma etch processes. Two barriers must be overcome to enable the use of such information for real-time process diagnosis and control. The first barrier is the large number of measurements in wide-spectrum scans, which hinders real-time processing. The second barrier is the need to understand and estimate not only process conditions, but also what is happening on the surface of wafer, particularly the spatial uniformity of the etch. This paper presents a diagnostic method that utilizes multivariable OES data collected during plasma etch to estimate spatial asymmetries in commercially available reactor technology. Key elements of this method are: first, the use of principal component analysis (PCA) for dimensionality reduction, and second, regression and function approximation to correlate observed spatial wafer information (i.e., line width reduction) with these reduced measurements. Here we compare principal component regression (PCR), partial least squares (PLS), and principal components combined with multilayer perceptron neural networks (PCA/MLP) for this in-situ estimation of spatial uniformity. This approach has been verified for a 0.35-μm aluminum etch process using a Lam 9600 TCP etcher. Models of metal line width reduction across the wafer are constructed and compared: the root mean square prediction errors on a test set withheld from training are 0.0134 μm for PCR, 0.014 μm for PLS, and 0.016 μm for PCA/MLP. These results demonstrate that in-situ spatially resolved OES in conjunction with principal component analysis and linear or nonlinear function approximation can be effective in predicting important product characteristics across the wafer     

InGaAs-InP metamorphic DHBTs grown on GaAs with lattice-matched device performance and f/sub /spl tau//, f/sub max/>268 GHz

InP-In/sub 0.53/Ga/sub 0.47/As-InP double heterojunction bipolar transistors (DHBTs) were grown on a GaAs substrate using a metamorphic buffer layer and then fabricated. The metamorphic buffer layer is InP - employed because of its high thermal conductivity to minimize device heating. An f/sub /spl tau// and f/sub max/ of 268 and 339 GHz were measured, respectively - both records for metamorphic DHBTs. A 70-nm SiO/sub 2/ dielectric sidewall was deposited on the emitter contact to permit a longer InP emitter wet etch for increased device yield and reduced base leakage current. The dc current gain /spl beta/ is /spl ap/35 and V/sub BR,CEO/=5.7 V. The collector leakage current I/sub cbo/ is 90 pA at V/sub cb/=0.3 V. These values of f/sub /spl tau//, f/sub max/, I/sub cbo/, and /spl beta/ are consistent with InP based DHBTs of the same layer structure grown on a lattice-matched InP substrate.     

用X射线衍射研究缓冲层对GaInAs材料的影响

用分子束外延方法制备了具有GaInAs组分渐变缓冲层和不具有GaInAs组分渐变缓冲层的Ga0.9In0.1As/GaAs结构的外延材料。利用高分辨率X射线衍射法(HRXRD)对制备的两种样品分别进行了测试分析。实验结果表明,GaInAs组分渐变缓冲层对外延生长在GaAs衬底上的Ga0.9In0.1As外延材料的晶体质量具有显著的改善作用,极大降低了由于外延层与衬底晶格不匹配所带来的影响。从X射线倒易空间衍射(RSM)二维图谱结果来看,具有GaInAs组分渐变缓冲层结构的样品,其Ga0.9In0.1As外延层与GaInAs组分渐变缓冲层接近完全弛豫,Ga0.9In0.1As外延层的应变降低,表面残留应力小于0.06%,同时,GaAs衬底与Ga0.9In0.1As外延层之间的偏移夹角明显变小。