具有TiN扩散阻挡层的n-GaAs欧姆接触的可靠性

提出了金属-半导体欧姆接触退化的快速评估方法--温度斜坡快速评价法,并建立了自动评估系统,用该方法和系统测得的欧姆接触退化激活能,和传统方法相比,耗时少,所需样品少,所得结果和传统方法一致.针对传统AuGeNi/Au欧姆接触系统的缺点,提出了加TiN扩散阻挡层的新型欧姆接触系统.实验表明新型欧姆接触系统的可靠性远远优于传统AuGeNi/Au欧姆接触系统.     

具有TiN扩散阻挡层的n-GaAs欧姆接触的可靠性

提出了金属 -半导体欧姆接触退化的快速评估方法——温度斜坡快速评价法 ,并建立了自动评估系统 ,用该方法和系统测得的欧姆接触退化激活能 ,和传统方法相比 ,耗时少 ,所需样品少 ,所得结果和传统方法一致 .针对传统 Au Ge Ni/Au欧姆接触系统的缺点 ,提出了加 Ti N扩散阻挡层的新型欧姆接触系统 .实验表明新型欧姆接触系统的可靠性远远优于传统 Au Ge Ni/Au欧姆接触系统 .     

金属-半导体欧姆接触比接触电阻值的微机自动测定

本文描述了欧姆接触的测试原理和测定欧姆接触比接触电阻的微机自动测试系统,并用该系统对制备的欧姆接触进行了测量,其测量精度优1%,测试系统使用方便,操作简单,获得结果迅速、可靠,适合于半导体器件的欧姆接触工艺研究与监控中比接触电阻的测定.     

Ag/Au与n-ZnO的欧姆接触特性的研究

为了更好实现ZnO材料在光电器件方面的应用,研究了Ag/Au和n-ZnO薄膜的欧姆接触。通过半导体特性分析系统测出欧姆接触的I-V特性曲线和采用挖补圆盘法测试了欧姆接触的接触电阻率,研究了退火温度对接触特性的影响。利用俄歇电子能谱(AES)研究了欧姆接触的微观结构,比较了不同的金属电极的反射特性。结果表明,Ag(50nm)/Au(100nm)和n-ZnO薄膜的欧姆接触在退火温度为500℃时最好,欧姆接触电阻率仅为5.2×10-4Ω·cm-2,且其反射特性比其它金属电极好。     

p型SiC欧姆接触理论及研究进展

碳化硅(SiC)具有宽禁带、高临界击穿电场、高热导率等优异特性,是制备高温、高频、大功率器件最理想的半导体材料之一。然而,制备良好的SiC欧姆接触尤其是p型SiC欧姆接触仍然是SiC器件研制中亟需攻克的关键技术难题。首先对p型SiC欧姆接触的形成机制及金属/SiC接触势垒理论进行了深入分析。然后,对近年来p型SiC欧姆接触的重要研究进展进行了综述,包括形成欧姆接触的金属体系,制备工艺条件,获得的比接触电阻率等,并重点讨论了p型SiC欧姆接触的形成机理。最后,对未来p型SiC欧姆接触的研究方向进行了展望。     

PTC陶瓷欧姆接触银电极的研究

影响银电极欧姆接触的主要因素是:电极浆料的组成和形成过程。通过实验,获得了接触电阻小,表面光洁,附着力和焊接能力均好的欧姆接触银电极。探讨了PTC陶瓷欧姆接触电极材料的评价方法,认为采用接触电阻比ρ_c/ρ_0作为比较参数较为合适。     

n型GaAs上的欧姆接触

本文介绍了欧姆接触的原理及测试方法，着重概述了近几年来在ｎ型ＧａＡｓ上制备欧姆接触所做的研究工作，介绍了改善欧姆接触特性的途径和方法。     

P型GaN欧姆接触的比接触电阻率测量

采用多种传输线模型方法,测量了p型GaN上的欧姆接触的比接触电阻率.通过比较和分析不同测量方法所得的结果之间的差异,得出了一个准确、可靠测量p型GaN上的欧姆接触的比接触电阻率的方法--圆点传输线模型方法.利用该方法优化了p型GaN上欧姆接触的退火温度,在氧气气氛中650℃退火后获得了最优的欧姆接触,其比接触电阻率为5.12×10-4Ω·cm2.     

GaAs及InP半导体激光器欧姆接触技术的评述

欧姆接触技术在半导体激光器制作中占有十分重要的地位,按其理论分析了获得GaAs、InP激光器低欧姆接触方法,分析了影响欧姆接触电特性的主要因素。介绍了现今所采用的各种金属化系统,就近期在欧姆接触制作技术新动向、新工艺作了较详细介绍。     

n+多晶硅/n+ SiC异质结欧姆接触

采用器件仿真软件ISE TCAD模拟了n 多晶硅/n SiC异质结形成欧姆接触的新的SiC欧姆接触制造技术.模拟结果表明n 多晶硅/n SiC异质结接触可以形成良好的欧姆接触,具有工艺简单、性能优良的优点.     

Diamond transistor performance and fabrication

The author reviews some of the device properties of diamonds, as well as recently developed diamond device fabrication techniques for high-frequency, high-power transistors. Two advantages of diamond over other semiconductors used for high-frequency, high power devices are its high thermal conductivity and high electric-field breakdown. Homoepitaxial diamond has been grown by both plasma and hot-filament techniques. The device properties of homoepitaxial diamond produced by the hot-filament technique are reviewed. Much of the development necessary for the production of diamond devices already exists. Doping by homoepitaxy, diamond etching, device quality SiO₂-diamond interface, and ohmic contact technology are reviewed. The remaining problems are the development of large area single crystal diamond substrates, improvement of doping techniques, and refinement in ohmic contact technology     

自对准栅金刚石MESFET器件研究

基于表面氢化处理的金刚石材料,利用自对准栅工艺技术研制了p型金刚石肖特基栅场效应晶体管(MESFET)。利用AFM和Raman测试方法对材料的特性进行了测试及分析。同时,对研制的金刚石MESFET器件进行了TLM以及直流特性测试及性能分析。利用TLM方法测试获得的表面氢化处理金刚石材料的方阻和Au欧姆接触比接触电阻率分别为4kΩ/□和5.24×10-4Ω.cm2。研制的1μm栅长金刚石MESFET器件的最大电流在-5V偏压下达到10mA/mm以上。     

High-temperature Schottky diodes with thin-film diamond base

High-temperature (500-580°C) current-voltage (I-V ) characteristics of gold contacts to boron-doped homoepitaxial diamond films prepared using a plasma-enhanced chemical vapor deposition (CVD) method are described. Schottky diodes were formed using gold contacts to chemically cleaned boron-doped homoepitaxial diamond films. These devices incorporate ohmic contacts formed by annealing Au(70 nm)/Ti(10 nm) layers in air at 580°C. The experiments with homoepitaxial diamond films show that the leakage current density increases with the contact area. This implies that a nonuniform current distribution exists across the diode, presumably due to crystallographic defects in the diamond film. As a result, Au contacts with an area >1 mm² are essentially ohmic and can be used to form back contacts to Schottky diodes. Schottky diodes fabricated in this matter also show rectifying I-V characteristics in the 25-580°C temperature range     

Mechanisms of current flow in metal-semiconductor ohmic contacts

Published data on the properties of metal-semiconductor ohmic contacts and mechanisms of current flow in these contacts (thermionic emission, field emission, thermal-field emission, and also current flow through metal shunts) are reviewed. Theoretical dependences of the resistance of an ohmic contact on temperature and the charge-carrier concentration in a semiconductor were compared with experimental data on ohmic contacts to II–VI semiconductors (ZnSe, ZnO), III–V semiconductors (GaN, AlN, InN, GaAs, GaP, InP), Group IV semiconductors (SiC, diamond), and alloys of these semiconductors. In ohmic contacts based on lightly doped semiconductors, the main mechanism of current flow is thermionic emission with the metal-semiconductor potential barrier height equal to 0.1–0.2 eV. In ohmic contacts based on heavily doped semiconductors, the current flow is effected owing to the field emission, while the metal-semiconductor potential barrier height is equal to 0.3–0.5 eV. In alloyed In contacts to GaP and GaN, a mechanism of current flow that is not characteristic of Schottky diodes (current flow through metal shunts formed by deposition of metal atoms onto dislocations or other imperfections in semiconductors) is observed.     

金刚石薄膜高温器件

本文详细地论述了低压气相生长的金刚石薄膜作为一种新型半导体材料的研究进展,讨论了金刚石薄膜与金属的欧姆接触和整流接触,以及可以在高温区工作的金刚石薄膜Schottky二极管和MESFET器件。最后,讨论了目前金刚石薄膜作为半导体材料所遇到的两个尚无法实现的问题:n型掺杂和异质外延单晶膜的生长。     

PHEMT欧姆接触的双源共蒸技术

近年来,砷化镓器件的发展极为迅速。其中,欧姆接触的制作是器件研制的关键工艺之一。为了提高GaAsPHEMT器件欧姆接触的性能和可靠性水平,文章比较了三种常见的GaAsPHEMT器件欧姆接触制备技术的差异,分别是:分层蒸发、溅射+蒸发、双源共蒸。通过传输线模型(TLM)法测试数据以及微细形貌分析,得出双源共蒸工艺制备的欧姆接触的电阻率和均匀性综合特性最佳,因此认为双源共蒸技术在大尺寸GaAsPHEMT圆片工艺中具有最优的综合特性。     

The thermal stability of ohmic contact to n-type InGaAs layer

The thermal stability of ohmic contact to n-type InGaAs layer is investigated. When Ni/Ge/Au is used as the contact metal, the characteristics of the ohmic contact are degraded after thermal treatment. The specific contact resistance of (Ni/Ge/Au)-InGaAs ohmic contact after annealing at 450°C is about 15 times larger than that of as-deposited sample. This is due to the decomposition of InGaAs and the interdiffusion of Ga and Au. A new phase of Au₄ln appears after annealing at 300°C. While in the case of Ti/Pt/Au, Au does not penetrate into the InGaAs layer as revealed by secondary ion mass spectroscopy. The specific contact resistance of (Ti/Pt/Au)-InGaAs ohmic contact after annealing at 450°C is eight times larger than that of as-deposited sample. Therefore, the thermal stability of (Ti/Pt/Au)-InGaAs ohmic contact is better than that of (Ni/Ge/Au)InGaAs ohmic contact.     

The optimization of the double mask system to minimize the contact resistance of a Ti/Pt/Au contact

The fabrication of Ti/Pt/Au ohmic contacts on diamond using two transmission line model masks during the photolithography step was modified as a result of the adverse effects on the resistance from the rectifying lip created by the overlap of the two masks, and the possible inhibition of carbide formation due to the presence of oxygen on the diamond surface before metallization. The first modification consisted of decreasing the rectifying lip by diffusing a small amount of Ti from beneath the contact defined by the first mask, and decreasing the overlap of the two masks from 5 to 2 μm, which is close to the minimum allowable by our photolithography techniques. The second modification consisted of the desorption of oxygen from the diamond surface using a heat treatment in vacuum and cool down in purified hydrogen. As a result of these changes, the contact resistance was decreased by more than two orders of magnitude from 8.1 × 10^-2 Ω-cm² to 1.2 × 10^-4 Ω-cm².     

Low-thermal-budget Au-free ohmic contact to an ultrathin barrier AlGaN/GaN heterostructure utilizing a micro-patterned ohmic recess

A pre-ohmic micro-patterned recess process,is utilized to fabricate Ti/Al/Ti/TiN ohmic contact to an ultrathin-barrier(UTB) AlGaN/GaN heterostructure,featuring a significantly reduced ohmic contact resistivity of 0.56 Ω.mm at an alloy temperat-ure of 550 ℃.The sheet resistances increase with the temperature following a power law with the index of +2.58,while the spe-cific contact resistivity decreases with the temperature.The contact mechanism can be well described by thermionic field emis-sion (TFE).The extracted Schottky barrier height and electron concentration are 0.31 eV and 5.52 × 1018 cm-3,which suggests an intimate contact between ohmic metal and the UTB-AlGaN as well as GaN buffer.A good correlation between ohmic trans-fer length and the micro-pattern size is revealed,though in-depth investigation is needed.A preliminary CMOS-process-compat-ible metal-insulator-semiconductor high-mobility transistor (MIS-HEMT) was fabricated with the proposed Au-free ohmic con-tact technique.