A proposed magnetically enhanced reactive ion etcher for ULSI

An ultraclean (UC) magnetically enhanced reactive ion etcher (MERIE) is proposed to overcome the limitations of the present-state MERIE available commercially. The sensitivity of gas compositions, pumping speed, substrate temperature and magnetic field intensity are discussed as examples of hardware-related process limitations. Five major configuration changes are proposed in the system: (1) improved effective pumping speed; (2) supplementary magnets for uniform and stable plasma distribution; (3) dual RF excitation for independent control of ion energy and flux; (4) DC-biased shield electrode for minimum chamber material contamination; and (5) DC-biased substrate. A study with a dual RF excitation system found that DC-baising the Si substrate in low-energy SiO₂ etching process can significantly reduce the Si etching rate by impeding positive ions from reaching the substrate. In addition, SiO₂ to Si etching rate selectivity can be significantly improved during the overetch step in SiO₂ etching of high-aspect-ratio contact holes     

Independent control of ion density and ion bombardment energy in adual RF excitation plasma

A dual RF excited discharge is described. The dual RF excitation system provides a method to control the substrate self-bias without affecting the state of the discharge. The substrate can be RF-biased utilizing an appropriate excitation frequency and power significantly less than the plasma generating RF power. The substrate self-bias dependence on various system parameters, including substrate excitation frequency, pressure, plasma generating upper electrode RF power, substrate material, and process gas compositions, is described. For a simplified model, a linear relationship between self-bias and RF power is derived using the space-charge limited assumption. The effect of substrate bias on the thermal-oxide etch rate has been studied. The results show good correlation between the ion bombardment energy, i.e., the potential difference across the substrate dark space, and the SiO ₂ etch rate. The SiO₂ etch rate in a CF₄ plasma increases linearly with the ion bombardment energy, having a threshold etch energy of ~19 V     

Minimizing damage and contamination in RIE processes byextracted-plasma-parameter analysis

It is reported that important plasma parameters for reactive ion etching (RIE) processes, such as ion energy and ion flux density, can be extracted from a simple RF waveform analysis at the excitation electrode in a conventional cathode-coupled, parallel-plate plasma RIE system. This analysis does not introduce any contamination or disturbances to the process. By using the extracted plasma parameters, surface damage and contamination in Si substrates induced by reactive ion etching in a SiCl₄ plasma were investigated. Optimum RIE conditions were then confirmed by studying the relationship between these parameters and the etching performance. It is shown using the experimental data that low-energy high-flux etching is the direction for high performance RIE in future ULSI fabrication     

高密度RF等离子体刻蚀工艺直流自我偏压的研究

直流自我偏压作为高密度射频(RF)等离子体刻蚀工艺中的重要电学参数,反映出具有高能量的离子对待刻蚀晶片的轰击效果,后者决定了刻蚀工艺的各向异性、刻蚀速率、选择比及形貌特征等工艺结果。该文以HBr作为刻蚀气体,采用电感耦合等离子体(ICP)金属刻蚀系统针对刻蚀工艺中的直流自我偏压进行研究。研究中分别改变离子源功率、衬底偏压功率、刻蚀压力及HBr气体流量,观察直流自我偏压及其峰值的相应变化规律。实验结果表明,随着离子源功率的升高,直流自我偏压将会轻度降低;升高偏压功率则会显著提升直流自我偏压。刻蚀压力与直流自我偏压呈正比例关系,HBr气体流量的变化及待刻蚀晶片的材质对直流自我偏压无显著影响。     

Harmonic balance simulation of RF injection effects in analogcircuits

RF noise immunity is becoming a serious problem for integrated circuits (ICs). We have found a frequency-domain simulator [harmonic balance (HB)] to be useful for analyzing the undesired IC behavior, especially the DC output shift under the large RF injection. The simulator has the following advantages in comparison with a conventional time-domain simulator such as SPICE: (1) DC output shifts can be simulated in a very short time using a conventional bipolar transistor model and (2) steady-state current or voltage waveforms at each node in an IC are directly and easily obtained. This paper describes the methods and results of the DC shifts analysis of a bipolar transistor or a differential amplifier using the HB simulator     

FBAR用高质量AlN薄膜制备

采用直流磁控反应溅射法,在基片表面引入RF偏置,在Si(111)衬底上成功制备了(002)向AlN薄膜。使用高分辨率X射线衍射仪(XRD)来表征薄膜质量。当RF偏置从0 W变化到20 W时,XRD测试(002)摇摆曲线的半高宽有着显著的变化。当RF偏置为15 W时,AlN薄膜表现出了良好的(002)生长取向。实验结果表明,适当的RF偏置能够提高Al原子和N原子反应时的活性,促进AlN薄膜的(002)择优生长。该溅射方案应用于薄膜体声波谐振器(FBAR)谐振器工艺加工,成功制作了Q值为300,机电耦合系数为5%的FBAR样品。     

Tuning of microstrip antenna on ferrite substrate

The permeability variation of a ferrite substrate with an axial DC magnetic bias field along with the RF excitation of a microstrip antenna leads to multiresonant behavior. A study of tuning the patch antenna on a ferrite substrate to exploit this feature is reported, along with the associated theoretical analysis and experimental findings     

ESD failure signature in capacitive RF MEMS switches

RF MEMS are commonly known as electrostatic devices using high electric field for their actuation. They can be exposed to transient voltages in any environment, and are very sensitive. According to this point of view, it is necessary to understand and analyze the degradations and failure criteria that can make them useless or reduce their lifetime. This paper deals with the investigation of ESD failure signature in capacitive RF MEMS. ESD experiments were carried out using a transmission line pulsing technique. It has been observed that electrical discharges give rise to sparks or electrical arcing and induced DC parameter shift, which can directly lead to changes in RF metrics. The contact-less dielectric charging effects of ESD pulses have been reported in this paper. It has been found that induced charges are predominant compared to injected ones through the trend of slope of the shift in the voltage corresponding to the minimum of capacitance.     

高低频复合基板研究

高低频复合基板技术是在同一块基板上同时实现低频信号和高频信号的传输.主要介绍了高低频复合基板制造面临的挑战以及高低频复合基板的主要特性.较为详细地介绍了高低频复合基板主要的三种实现方式,即FR4印制电路板与微波印制电路的复合结构、低温共烧陶瓷技术以及液晶聚合物基板.     

On the Use of Static Temperature Measurements as Process Variation Observable

In this paper we present the use of static temperature measurements as process variation observable. Contrary to previously published thermal testing methods, the proposed methodology does not need an excitation signal, thus reducing test cost and improving built-in capabilities of thermal monitoring. The feasibility of the technique and a complete test methodology is presented using a narrowband LNA as example. Finally, a complete electro-thermal co-simulation test bench between the LNA and a differential temperature sensor embedded in the same silicon die is presented in order to validate the results. Results prove that RF figures of merit can be extracted from DC temperature measurements done without loading or exciting the RF circuit under test.     

Method to extract MOSFET substrate resistance using DC data of base resistance in parasitic BJT

A new DC method is proposed to extract the substrate resistance in MOSFETs by using current-dependent base resistance of parasitic lateral bipolar junction transistor without a complex RF extraction method. The extracted substrate resistance values using the new method match well with those using the RF one, verifying the accuracy of the new method.     

Theoretical study of RF-breakdown in bulk GaN and GaN MESFETs

RF-breakdown was studied in bulk GaN and in GaN MESFETs using a full band Monte Carlo simulator. It was found that in bulk materials, increasing the frequency of an applied RF field would result in a lower overall impact ionization rate and consequently lead to higher breakdown fields. It was also found that the RF-breakdown voltage of devices increases with increasing frequency of the applied large signal RF excitation. The frequency dependence of RF-breakdown and the difference between RF and dc-breakdown is explained based on the time response of the particle energy to the change in the applied RF excitation     

Loss minimization in DC drives

A method for determining the optimal DC machine excitation for loss minimization is presented. The proposed method may be implemented by using either analog or digital techniques. The method is simple, and its implementation does not affect significantly the cost, the complexity, and the dynamics of the DC drive. Thus, energy can be saved without sacrificing the quality of the DC drive. Even though the conception of the proposed method is based on the loss model of the DC machine, it is shown that its realization does not require knowledge of the loss model     

Influence of dual-frequency plasma-enhanced chemical-vapor deposition Si<Subscript>3</Subscript>N<Subscript>4</Subscript> passivation on the electrical characteristics of AlGaN/GaN heterostructure field-effect transistors

The influence of dielectric stress on the direct current (DC) electrical characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs) has been investigated. Dual-frequency plasma deposition was used to vary the amount of stress induced by a passivating dielectric on the surface of the devices. Initial data suggested a strong influence from the induced dielectric stress, but the low-frequency, radio-frequency (RF) excitation of the plasma deposition process was found to induce a severe nonreversible damage to the exposed AlGaN surface through N ion bombardment. The consequence is a drastic reduction of the sheet carrier concentration and mobility of the two-dimensional electron gas (2DEG). Subsequently, an alternative damage-free technique using a helium precursor was used to obtain compressive films. Based on the results, uniform dielectric stress has a minimal impact on the polarization charges within the AlGaN barrier.     

宽带隙立方氮化硼薄膜制备

报道了用偏压调制射频溅射方法制备宽带隙立方氮化硼(c-BN)薄膜的实验结果.研究了衬底负偏压对制备c-BN薄膜的影响.c-BN薄膜沉积在p型Si(100)衬底上,溅射靶为六角氮化硼（h-BN）,工作气体为Ar气和N2气混合而成,薄膜的成分由傅里叶变换红外谱标识.结果表明,在射频功率和衬底温度一定时,衬底负偏压是影响c-BN薄膜生长的重要参数.在衬底负偏压为-200V时得到了立方相含量在90%以上的c-BN薄膜.还给出了薄膜中的立方相含量随衬底负偏压的变化,并对c-BN薄膜的生长机制进行了讨论.     

Advanced three-dimensional tailored RF pulse design in volume selective parallel excitation

Volume selective excitation has a variety of uses in clinical magnetic resonance imaging, but can suffer from insufficient excitation accuracy and impractically long pulse duration in ultra-high field applications. Based on recently-developed parallel transmission techniques, an optimized 3D tailored radio-frequency RF (TRF) pulse, designed with a novel 3D adaptive trajectory, is proposed to improve and accelerate volume selective excitation. The trajectory is designed to be regular-shaped and adaptively stretched according to the size of a 3D k-space "trajectory container." The container is designed to hold most of the RF energy deposition responsible for the desired pattern in the excitation k-space in the use of the blurring patterns caused by the multichannel sensitivity maps. The proposed method can also be used to reduce both global and peak RF energy required during excitation. The feasibility of this method is confirmed by simulations of ultra-high field cases.     

An investigation of the DC and RF performance of InP DHBTs transferred to RF CMOS wafer substrate

This paper investigated the DC and RF performance of the InP double heterojunction bipolar transistors (DHBTs) transferred to RF CMOS wafer substrate.The measurement results show that the maximum values of the DC current gain of a substrate transferred device had one emitter finger,of 0.8μm in width and 5μm in length,are changed unobviously,while the cut-off frequency and the maximum oscillation frequency are decreased from 220 to 171 GHz and from 204 to 154 GHz,respectively.In order to have a detailed insight on the degradation of the RF performance,small-signal models for the InP DHBT before and after substrate transferred are presented and comparably extracted.The extracted results show that the degradation of the RF performance of the device transferred to RF CMOS wafer substrate are mainly caused by the additional introduced substrate parasitics and the increase of the capacitive parasitics induced by the substrate transfer process itself.     

ANALYSIS OF DUAL FREQUENCY CONFINED CAPACITIVELY COUPLED PLASMA AT LOW POWER

Confined dual frequency hydrogen plasma discharge has been investigated with microwave interferometer method and radial profiles are taken by Abel inversion technique. Dual radio-frequency sources, operating at 27.12MHz and 1.94MHz, are coupled to each other through the plasma. 27.12MHz RF power is used to enhance plasma density and 1.94MHz power is used to enhance ion acceleration energy to the electrode. Radial density profiles has been taken for comparing the effects of low frequency source that the secondary RF source causes reduction in plasma density due to the sheath expansion. Instead radial density profile is assumed as flat by most of the models, there is about 2.5eV of potential drop occurs from centre to boundary at 40W of primary source power. It has been observed that increasing sheath width (increasing the secondary source power to primary source power) reduces the bulk plasma volume and makes potential profile flattening in y direction. While the high frequency power is dissipated by electrons in the bulk plasma; low frequency power is mostly dissipated by ions in the sheath region. Using both high and low frequency power, we may control plasma density and ion acceleration energy to the electrode simultaneously.     

VHF plasma deposition for thin-film solar cells

Fast deposition rates, typical for very high frequency (VHF) plasma deposition, up to now have mainly been attributed to a more efficient silane decomposition as the results of an enhanced density of high-energy electrons in the plasma. In this work a-Si:H was prepared at excitation frequencies in a wide frequency range between 25 and 250 MHz and at otherwise constant conditions. In order to understand the processes leading to the observed increase in deposition rate with frequency, the plasma was investigated by optical emission spectroscopy and mass spectrometry. Plasma-substrate interactions were studied by impedance analysis and ion flux measurements. the results show that the high deposition rates are mainly the result of an increased surface reactivity of film precursors resulting from the ions impinging on the growth surface. It is shown that variation of the excitation frequency allows a flexible control of ion flux and energies. Conditions were optimized for the preparation of a-Ge:H films, which require a flux of high-energy ions to the substrate. Material properties were obtained that were comparable to results from deposition on the cathode of a radio frequency (RF) discharge.     

Electrical characterization and reliability study of integrated GaN power amplifier in multi-layer thin-film technology

In this work, the degradation of a GaN power amplifier (PA) integrated in a thin film multi-chip module (MCM-D) interconnect technology is investigated by means of DC and RF measurements. Failure analysis has demonstrated that improper thermal contact may cause the PA module performance degradation. Moreover, we have experimentally studied the thermal effects on the RF performance of MCM-D and low-temperature co-fired ceramic (LTCC) PAs. It shows that the device exhibits a higher output power density on a thinned MCM-D substrate than on an LTCC substrate with thermal vias, and also that the output power density can be further improved by reducing the heat spread distance between active devices and heat sink.