日盲探测器高Al组分n-Al_(0.6)Ga_(0.4)N欧姆接触(英文)

研究了应用于日盲探测器的高Al组分Si掺杂n型Al0.6Ga0.4N与两层金属层Ti（20nm）/Al（100nm）之间的欧姆接触.在制作金属电极前用煮沸王水对样片进行表面预处理,金属制作后再在N2氛围中做快速热退火处理.使用高精度XRD测试样品表面特性,并对不同温度下的情况进行比较.样品的比接触电阻率是用环形传输线模型通过I-V测试得到.670℃下90s退火得到最优ρc为3.42×10-4Ω·cm^2.将该处理方法应用到实际的背照式AlGaN p-i-n日盲探测器中,探测器的光谱响应度和反向特性等参数得到很大的优化.     

日盲探测器高Al组分n-Al0.6Ga0.4N欧姆接触

研究了应用于日盲探测器的高Al组分Si掺杂n型Al0.6Ga0.4N与两层金属层Ti(20nm)/Al(100nm)之间的欧姆接触. 在制作金属电极前用煮沸王水对样片进行表面预处理,金属制作后再在N2氛围中做快速热退火处理. 使用高精度XRD测试样品表面特性,并对不同温度下的情况进行比较. 样品的比接触电阻率是用环形传输线模型通过I-V测试得到. 670℃下90s退火得到最优ρc为3.42E-4Ω·cm2. 将该处理方法应用到实际的背照式AlGaN p-i-n日盲探测器中,探测器的光谱响应度和反向特性等参数得到很大的优化.     

用于紫外探测器的AlGaN/GaN异质结构的Ti/Al/Ni/Au欧姆接触特性

采用Ti/Al/Ni/Au多层金属体系在Al0.27Ga0.73N/GaN异质结构上制备了欧姆接触.分别采用线性传输线方法(LTLM)和圆形传输线方法(CTLM)对其电阻率进行了测试.当Ti(10nm)/Al(100nm)/Ni(40nm)/Au(100nm)金属体系在650℃高纯N2气氛中退火30s时,测量得到的最小比接触电阻率为1.46×10-5Ω·cm2.并制备了Al0.27Ga0.73N/GaN光导型紫外探测器,通过测试发现探测器的暗电流.电压曲线呈线性分布.实验结果表明在Al0.27 Ga0.73N/GaN异质结构上获得了好的欧姆接触,能够满足制备高性能AlGaN/GaN紫外探测器的要求.     

用于紫外探测器的AlGaN/GaN异质结构的Ti/Al/Ni/Au欧姆接触特性

采用Ti/Al/Ni/Au多层金属体系在Al0.27Ga0.73N/GaN异质结构上制备了欧姆接触. 分别采用线性传输线方法(LTLM)和圆形传输线方法(CTLM)对其电阻率进行了测试. 当Ti(10nm)/Al(100nm)/Ni(40nm)/Au(100nm)金属体系在650℃高纯N2气氛中退火30s时,测量得到的最小比接触电阻率为1.46E-5Ω·cm2. 并制备了Al0.27Ga0.73N/GaN光导型紫外探测器,通过测试发现探测器的暗电流-电压曲线呈线性分布. 实验结果表明在Al0.27Ga0.73N/GaN异质结构上获得了好的欧姆接触,能够满足制备高性能AlGaN/GaN紫外探测器的要求.     

调制掺杂AlGaN/GaN异质结上的Pt肖特基接触

研究了调制掺杂 Alx Ga1 - x N/Ga N表面 Pt肖特基接触的制备工艺 ,并对其进行了 I-V测量。通过改变对样品表面的处理工艺 ,研究了表面处理对调制掺杂 Alx Ga1 - x N/Ga N表面 Pt肖特基结接触特性的影响 ,在 n型掺杂浓度为 7.5× 1 0 1 7cm- 3的 Al0 .2 2 Ga0 .78N样品表面 ,制备得到了势垒高度为 0 .94e V、理想因子为 1 .4的 Pt肖特基接触。这与国外报道的结果接近 (=1 .2 e V,n=1 .1 1 [1 ] )     

高Al组分N-AlxGa1-xN材料的欧姆接触

基于各层金属间在快速热退火时容易合金化及Ti,Al易被氧化的特点,在高Al组分N-AlxGa1-xN(x≥0.45)材料上溅射生长多层金属Ti/Al/Ti/Au,并且变化Ti,Al比例以及改变退火温度和时间,得到了金属与高Al组分N-AlxGa1-xN(x≥0.45)材料间的欧姆接触,由传输线模型方法测试得比接触电阻为4.9×10-2 Ω·cm2.实验中用到的样品为P(Al0.45Ga0.55N)/i(Al0.45Ga0.55N)/N-Al0.63Ga0.37N多层结构的材料.最后,利用伏安特性和俄歇电子能谱深度分布(AES)研究金属与高Al组分的材料之间形成欧姆接触的原因.     

金属/n型AlGaN欧姆接触

用传输线模型对n型AlGaN(n-AlGaN)上Au/Pt/Al/Ti多金属层欧姆接触进行了接触电阻率的测量.在850℃退火5min后,测得欧姆接触电阻率达1.6×10-4Ω·cm2.经X射线衍射分析,Au/Pt/Al/Ti/n-AlGaN界面固相反应得出在500℃以上退火过程中,AlGaN层中N原子向外扩散,在AlGaN表面附近形成n型重掺杂层,导致欧姆接触电阻率下降;随退火温度的升高,N原子外扩散加剧,到800℃以上退火在Au/Pt/Al/Ti/n-AlGaN界面形成Ti2N相,导致欧姆接触电阻率进一步下降.     

金属/n型AlGaN欧姆接触

用传输线模型对n型AlGaN(n-AlGaN)上Au/Pt/Al/Ti多金属层欧姆接触进行了接触电阻率的测量.在850℃退火5min后,测得欧姆接触电阻率达1.6×10-4Ω·cm2.经X射线衍射分析,Au/Pt/Al/Ti/n-AlGaN界面固相反应得出在500℃以上退火过程中,AlGaN层中N原子向外扩散,在AlGaN表面附近形成n型重掺杂层,导致欧姆接触电阻率下降;随退火温度的升高,N原子外扩散加剧,到800℃以上退火在Au/Pt/Al/Ti/n-AlGaN界面形成Ti2N相,导致欧姆接触电阻率进一步下降.     

氧化后退火技术对SiO2/4H-SiC界面态密度的影响

采用等离子体增强化学气相沉积(PECVD)低温处理和高温快速退火的技术,研究了退火条件对SiO2/4H-SiC界面态密度的影响.在n型4H-SiC外延片上高温干氧氧化50 nm厚的SiO2层并经N2原位退火,随后在PECVD炉中对样品进行350℃退火气氛为PH3,N2O,H2和N2的后退火处理,之后进行高温快速退火,最后制备Al电极4H-SiC MOS电容.I-V和C-V测试结果表明,各样品的氧化层击穿场强均大于9 MV/cm,PH3处理可以降低界面有效负电荷和近界面氧化层陷阱电荷,但PH3处理样品的界面态密度比N2O处理的结果要高.经N2O氛围PECVD后退火样品在距离导带0.2和0.4 eV处的界面态密度分别约为1.7× 1012和4×1011eV-1·cm-2,有望用于SiC MOSFET器件的栅氧处理.     

KOH溶液处理对AlGaN紫外探测器暗电流的影响

采用KOH溶液表面处理工艺制备得到了128×1线列日盲AlGaN紫外探测器,器件的反偏暗电流为6.88×10-9A(-8 V时),比未采用此项工艺制备得到的器件的暗电流减小近103倍。元素深度分布俄歇电子谱(AES)等测试结果分析表明,采用这种表面处理工艺可以有效地去除干法刻蚀后材料表面的N空位、刻蚀生成物及自然氧化物,减小了界面态密度,改善了电流-电压特性,减小了反偏暗电流。利用传输线模型TLM计算得到了Ti/Al/Ti/Au金属电极与高Al组分n-Al0.65Ga0.35N材料间的接触电阻率为8.35×10-3Ωcm2。     

Formation of Ta/Ti/Al/Mo/Au ohmic contacts to an AlGaN/AlN/GaN heterostructure grown on a silicon substrate

The features of the formation of Ta/Ti/Al/Mo/Au ohmic contacts to a Al_0.26Ga_0.74N/AlN/GaN heterostructure grown on semi-insulating Si(111) substrates are studied. The dependences of the contact resistance on the Al (90, 120, 150, 180 nm) and Ti (15, 30 nm) layer thickness and optimal temperature-time annealing conditions are determined for each studied metallization scheme. It is shown that the minimum achievable contact resistance monotonically increases from 0.43 to 0.58 Ω mm as the Al layer thickness increases from 90 to 180 nm at unchanged Ta, Ti, Mo, Au layer thicknesses. A change in the Ti layer thickness from 15 to 30 nm has no significant effect on the minimum contact resistance. The least contact resistance of 0.4 Ω mm is achieved for Ta/Ti/Al/Mo/Au layers with thicknesses of 10/15/90/40/25 nm, respectively. The optimal annealing temperature for this metallization variant is 825°C at a process duration of 30 s. The grown ohmic contacts have smooth contact-area edges and flat morphology of their surface.     

Low-resistance Ohmic contacts to digital alloys of n-AlGaN/AlN

Low contact resistance to digital alloys of n-type AlGaN/AlN with high average Al concentration is described. Low-energy electron diffraction was used to evaluate surface precleaning with HCl and buffered HF. The contact metallization consisting of a stack of Ti/Al/Ti/Au, 20/100/45/60 nm in thickness, was e-beam deposited and etch-patterned. The lowest specific contact resistance of 5.6/spl times/10/sup -5/ /spl Omega//spl middot/cm/sup 2/ was obtained after annealing in N/sub 2/ ambient at 700/spl deg/C.     

Mo/Al/Mo/Au-based ohmic contacts to AlGaN/GaN heterostructures

Mo/Al/Mo/Au metallization scheme as an ohmic contact to undoped AlGaN/GaN heterostructures was investigated. The optimal thicknesses of the metal layers were determined: Mo (10 nm)/Al (60 nm)/ Mo (50 nm)/Au (50 nm). The specific contact resistance of the fabricated ohmic contact is 4.7 × 10^–7 Ohm cm² (0.14 Ohm mm). The microstructure of the contact after annealing was investigated using scanning and transmission electron microscopy, X-ray diffractometry and energy-dispersive X-ray spectroscopy. It is shown that a noticeable alloying of metallization into semiconductor upon annealing does not occur, but strong mixing of metals takes place. X-ray diffraction analysis demonstrated the presence of interfacial compounds, namely, Al₂Au, Al_{3 + x} Mo_1–x , AlMo₃, Al₁₂Mo, GaMo₃ and GaAu₂. Investigations of the phase composition of films depending on the thickness ratio of the metallization layers have shown that the formation of Al₂Au phase has a negative effect on the contact surface morphology, and the formation of GaMo₃, Al _x Mo_y phases likely plays the most important role in the ohmic contact formation, which was also confirmed by the method of energy-dispersive analysis.     

The effect of metallization on the ohmic contact resistivity toheavily B-doped polycrystalline diamond films

Three metallization schemes, namely Al/Si, Ti-Au and TiWN-Au contacts on B-doped polycrystalline diamond films have been compared. After annealing at 450°C in nitrogen Al/Si contacts show the lowest contact resistivity in the order of ~10^-7 Ω cm² . TiWN-Au contacts were found to be the most stable contact system in view of interdiffusion and oxidation. Ti-Au contacts show a catastrophic interdiffusion at moderate annealing temperatures and strong oxidation at the very surface. High surface boron doping concentrations lead to low contact resistivities. At sufficient high doping levels current transport through the metal-diamond barrier is due to field emission     

Rapid low-resistance interconnects by selective tungsten deposition on laser-direct-written polysilicon

Polysilicon interconnections were locally deposited on oxide-covered silicon wafers by pyrolysis of silane using a scanned Ar+-laser spot. The 2-µm-wide interconnects, written at scan speeds of 2.5 mm/s, have a 500-µΩ.cm resistivity and exhibit low contact resistance to underlying Al and Al/Si structures. These films were subsequently reacted with WF6vapor to form a tungsten-silicon composite interconnect by the silicon reduction of WF6. Electrical tests show that the conductivity of 0.4-µm-thick conductors is enhanced up to 20-fold, by formation of a surface metallic layer having conductivity characteristic of pure thin-film tungsten. Auger and Rutherford backscattering spectra (RBS) confirm the purity and selectivity of the surface tungsten layer formed at temperatures compatible with preexisting aluminum metallization. The tungsten-polysilicon composite interconnects have applications as rapidly written discretionary metallization for prototyping and in situ analysis of integrated circuits.     

Contact resistance and adhesion performance of ACF interconnections to aluminum metallization

Flip chip joining technology using anisotropically conductive films (ACFs) has become an attractive technique for electronic packaging. However, several factors have hindered the wide spread use of this technology. Along with the reliability issue, these factors also include the low availability and high cost of the bumped wafers. This paper introduces the feasibilities of using unbumped die with respect to ACF joints for flip-chip-on-flex (FCOF) assemblies. The unbumped dies contain only bare aluminum pads. Untill now the performance of ACF to Al metallization is a controversial issue from the published reports. In this study, two different test vehicles were used to study contact resistance and adhesion performance. Reliability of contact resistance for ACF joints with the unbumped dies was investigated in terms of varying the thickness of the Al pads. Adhesion performance of ACF to the Al metallization was compared with the adhesion performance of ACF to a glass substrate using the same ACF and the same bonding parameters.FCOF assemblies containing dies with thinner aluminum pads showed lower initial contact resistance and a lower rate of increment during accelerated aging tests. Three factors were considered as the potential causes for the above results: (1) lower concentration of aluminum oxide on the thin Al pad, (2) larger contact area per deformed particle with Au/Ni/Cu electrode for the interconnection of thin Al pad and (3) lower concentration of the defects in the thin Al pad. Contact resistance was found to increase during accelerated testing because of aluminum oxide formation on top of the pads.Contrary to the usual expectation, adhesion strength of ACF with the Al metallization was increased during 60 °C/95% RH testing. After 500 h of such moisture-soak testing, the adhesion strength becomes 3 times the initial value. The change in chemical state on the aluminum surface is considered to be responsible for higher adhesion strength. It is proposed that oxidation of Al surface due to diffused moisture and the new chemical bond formation at the adhesives/aluminum interface are the key reasons for good adhesion reliability.     

Surface oxide films on Aluminum bondpads: Influence on thermosonic wire bonding behavior and hardness

Using indentation testing, wire bond tests and electron microscopy, the influence of increased oxide films on Al metallization surfaces on the wire bonding behavior and hardness was investigated. Oxide film thickness values larger than about 20 nm obstruct the bond contact and resulted in a poor bonding quality. The presence of such films causes also a hardness increase which can be detected by current sensitive indentation test methods. Therefore, an improved indentation testing technique can be applied during the quality control of bondpad metallizations prior to wire bonding.     

Ohmic contacts on diamond by B ion implantation and Ti-Aumetallization

Low-resistance ohmic contacts have been fabricated on a natural IIb semiconducting diamond crystal and on undoped polycrystalline diamond films by B ion implantation and subsequent metallization with a Ti-Au bilayer metallization. A high B concentration of ~7×10²⁰ cm^-3 at the surface was obtained by ion implantation, a post-implant anneal, and a subsequent chemical removal of the graphite layer that resulted from the radiation damage. A bilayer metallization of Ti followed by Au annealed at 850°C yielded a specific contact resistance value on the order of 10^-6 Ω-cm² for chemical-vapor-deposition-grown polycrystalline films and on the order of 10^-5 Ω-cm² for the semiconducting natural crystal     

Very low resistance ohmic contacts to n-GaN

Ohmic contacts with low resistance are fabricated on n-GaN films using Al/Ti bilayer metallization. GaN films used are 0.3 μm thick layers with carrier concentrations of 1 × 10¹⁹ cm⁻³ grown on the c-plane sapphire by ion-removed electron cyclotron resonance molecular beam epitaxy. The lowest value for the specific contact resistivity (ρ_c) of 1.2×10⁻⁸ Ω·cm² was obtained with furnace annealing at 500°C for 60 min. This result shows the effectiveness of high carrier concentration GaN layers and the low temperature annealing for the realization of low resistance ohmic contacts. Sputtering Auger electron spectroscopy analysis reveals that Al diffuses into Ti layer and comes into contact with the GaN surface.