自蔓延反应薄箔技术研究进展

简述自蔓延反应薄箔的基本结构、反应原理、制备方法以及应用于电子封装中的优势,结合目前的研究现状分析了该技术应用于电子封装需要考虑的因数、应用方向以及存在的问题.     

Al/Ag/Al复合薄膜电极的抗氧化性和电性能研究

为开发大尺寸场发射显示器需要的能承受高温热处理的薄膜电极,以Al作为Ag层的保护层和与玻璃衬底的粘附层,采用直流磁控溅射制备了Al/Ag/Al复合薄膜及其电极.采用XRD、AFM、光学显微镜和电性能测试系统,研究不同温度热处理对复合薄膜和电极结构、表面形貌和电性能的影响.由于表面致密的Al2O3膜的保护,使得加热退火(<600℃)不会对Al/Ag/Al薄膜和电极造成明显的氧化,然而Al层与Ag层发生的界面扩散和固相反应增大了电极的电阻率(从5.0×10~(-8) Ω·m 上升至23.6×10~(-8) Ω·m).另外热处理温度足够高时(500℃、600℃),Ag原子向表面的扩散一定程度上降低了电极的化学稳定性.尽管如此,与Cr/Cu/Cr薄膜电极相比Al/Ag/Al薄膜电极仍然是一种能够承受高温热处理并且保持较低电阻率的新型电极.     

Ni元素对激光诱导自蔓延反应合成Ti-Fe共晶合金组织性能的影响

采用激光诱导自蔓延反应合成制备了Ti-Fe-Ni三元合金。实验结果表明,当第三组元Ni含量介于12 at.%之内时,合成产物仍保持Ti70.5Fe29.5共晶合金的相组成,即是由β-Ti固溶体、TiFe和Ti2Fe金属间化合物所组成。但随着Ni含量的增加,合成产物中β-Ti固溶体的数量逐渐减少,而TiFe和Ti2Fe金属间化合物的数量逐渐增加。同时组织形态也由共晶组织逐渐转变为过共晶组织。随着Ni含量的增加,合成样品的致密度逐渐降低;由于受合成样品微观组织和致密性这两种因素的综合作用,致使Ni含量为9 at.%的合成样品具有高的硬度、强度及良好的塑性。     

激光自蔓延连接CFRTP/铝接头微观形貌及形成机理

为了研究碳纤维复合材料（CFRTP）与金属的高效焊接，采用激光诱导Al-Ti-C粉末中间层自蔓延反应的方法，对碳纤维复合材料与铝进行了异种连接实验，分析了中间层自蔓延反应形成焊缝的反应机理、CFRTP/铝连接接头的微观界面和形成机理。结果表明，激光照射使中间层温度升高至933K左右时自蔓延反应开始进行，铝元素熔化并包裹住固态Ti发生反应，生成Ti-Al系化合物，在高温下化合物继续和Ti元素反应生成TiC并释放热量；同时，单质Ti与C也发生反应生成TiC并释放热量，反应产生的热量继续维持下一层面的反应，直至整个中间层反应结束形成良好的"焊缝"；这些热量使得中间层左右两侧母材发生微融再次挤压成型形成质量良好的连接接头。激光诱导Al-Ti-C中间层自蔓延高温合成连接方法可以实现CFRTP/铝的高质量连接，对实现交通工具结构轻量化是有帮助的。     

Ni/C纤维提高Ni/Al球形颗粒导电硅橡胶性能研究

为减少球形Ni/Al填充量并提高Ni/Al填充导电硅橡胶屏蔽效能,选取Ni/C纤维加入到此种导电橡胶中,并从导电性、屏蔽性能方面对其进行评价。实验发现Ni/C纤维的掺杂可以提高导电橡胶的导电性及屏蔽性能。当总颗粒填充量为130 phr时,掺杂纤维使导电橡胶的体积电阻率从1010Ω·cm降至1.4Ω·cm;当总颗粒填充量为240 phr时,在1.0~2.5 GHz的频段内,其屏蔽效能在90 d B以上,而未经过掺杂的仅能超过60 d B。利用面心立方堆垛结构模型计算颗粒间最小距离,结果发现导电橡胶的渗流阈值与颗粒最小间距有较为明显的相关性。     

7050铝合金表面Al/Ti激光熔覆工艺实验及温度场模拟分析

在7050铝合金表面激光熔覆Al/Ti复合粉体,通过3因素3水平正交试验得知当激光功率为1.5 k W,扫描速度为150 mm/min,离焦量为50 mm时熔覆层质量最优。模拟计算得到正交试验工艺参数下的光斑中心最高温度值,并利用极差分析得到:正交试验因素对中心点最高温度值影响程度从大到小的顺序是扫描速度V,激光功率P和离焦量S。通过对9组试样熔池尺寸及不同位置点温度随时间变化趋势分析可以得到,试样前端结合较差是由于熔覆过程中基体熔池深度较小,不足以使基体与熔覆材料很好地结合;而后端都出现的不同程度的变形和烧蚀,是末端温度急剧积累引起的。通过分析Al/Ti熔覆层的金相组织可知,熔覆层组织以胞状树枝晶为主,且分布均匀细密。     

Cr/Cu/Al/Cr薄膜电极的防氧化性能

采用Al作为Cu导电层的主要防氧化保护层,在普通浮法玻璃上利用磁控溅射和湿法刻蚀技术制备Cr/Cu/Al/Cr复合薄膜及其电极,研究不同的热处理温度对复合薄膜及其电极的结构、表面形貌和导电性能的影响。由于有Al层作为保护层,在热处理过程中,Al先与穿过Cr保护层的氧进行反应,从而可以更有效地保护Cu膜层在较高的温度下不被氧化,所制备的薄膜在经过600℃的热处理之后仍然具有较好的导电性能。而对于Cr/Cu/Al/Cr电极,侧面裸露的金属层在热处理过程中的氧化是其导电性能逐渐下降的主要原因,退火温度超过500℃之后,电极侧面裸露部分的氧化范围不断往电极的中间扩散,导致了薄膜电极导电性能显著恶化。虽然如此,Cr/Cu/Al/Cr薄膜电极在430℃附近仍然具有较好的导电性能,电阻率为7.3×10-8Ω.m,符合FED薄膜电极的要求。以此薄膜电极构建FED显示屏,通过发光亮度均匀性的测试验证了Cr/Cu/Al/Cr电极的抗氧化性。     

激光诱导自蔓延反应合成Zr-Ti-Ni准晶合金

利用构成Zr-Ti-Ni稳态准晶合金体系组元间具有负的混合焓而能发生放热反应的热力学特征,进行了激光诱导自蔓延反应合成准晶的工艺研究.研究结果表明,激光诱导自蔓延反应合成Zr44Ti40Ni16,Ti41.5Zr41.5Ni17和Ti40Zr40Ni20产物皆是由准晶I相,7(Ti/Zr)固熔体及具有MgZn2晶体结构的Laves相所组成,但各组成相的含量有所不同.当反应体系成分由Zr44Ti40Ni16依次变为Ti41.5Zr415Ni17和Ti40Zr40Ni20时,产物中准晶相的相对含量逐渐降低.随着合成产物中准晶含量的增加,合成样品的显微硬度增加.     

Ti/Al/Ni/Au金属体系在N-polar GaN上的欧姆接触特性

利用金属有机化合物化学气相淀积(MOCVD)在SiC衬底上外延生长了N-polar GaN材料,采用传输线模型(TLM)分析了Ti/Al/Ni/Au金属体系在N-polar GaN上的欧姆接触特性.结果表明,Ti/Al/Ni/Au (20/60/10/50 nm)在N-polar GaN上可形成比接触电阻率为2.2×10-3Ω·cm2的非合金欧姆接触,当退火温度升至200℃,比接触电阻率降为1.44×10-3 Ω·cm2,随着退火温度的进一步上升,Ga原子外逸导致欧姆接触退化为肖特基接触.     

Effect of annealing temperature on Ti/Al/Ni/Au ohmic contacts on undoped AlN films

The Ti/Al/Ni/Au metals were deposited on undoped AlN films by electron beam evaporation. The influence of annealing temperature on the properties of contacts was investigated. When the annealing temperatures were between 800 and 950℃, the AlN-Ti/Al/Ni/Au contacts became ohmic contacts and the resistance decreased with the increase of annealing temperature. A lowest specific contacts resistance of 0.379 Ω·cm² was obtained for the sample annealed at 950℃. In this work, we confirmed that the formation mechanism of ohmic contacts on AlN was due to the formation of Al-Au, Au-Ti and Al-Ni alloys, and reduction of the specific contacts resistance could originate from the formation of Au₂Ti and AlAu₂ alloys. This result provided a possibility for the preparation of AlN-based high-frequency, high-power devices and deep ultraviolet devices.     

Ti/Al/Ni/Au在GaN N面上的欧姆接触

以Ti/Al/Ni/Au作为欧姆接触金属体系,通过电感耦合等离子体(ICP)刻蚀的预处理,在氢化物气相外延法生长的单晶氮化镓(GaN)材料的N面实现了良好的欧姆接触,其比接触电阻率为3.7×10-4 Ω·cm2.通过扫描电子显微镜、原子力显微镜、阴极荧光和光致发光谱对GaN N面的表面、光学特性进行了对比表征.结果表明:未刻蚀GaN衬底的N面表面存在一定的损伤层,导致近表面处含有大量缺陷,不利于欧姆接触的形成;而ICP刻蚀处理有效地去除了损伤层.X射线光电子能谱(XPS)分析显示刻蚀后样品的Ga 3d结合能比未刻蚀样品向高能方向移动了约0.3 eV,其肖特基势垒则相应降低,有利于欧姆接触的形成.同时对Fe掺杂半绝缘GaN的N面也进行了刻蚀处理,同样实现了良好的Ti/Al/Ni/Au欧姆接触,其比接触电阻率为0.12 Ω·cm2.     

The Al/Ni interfacial reactions under the influence of electric current

Electromigration has been observed and quite extensively investigated in the compositionally homogeneous conducting lines in the integrated circuit devices; however, the effect of electric current upon the interfacial reactions has not been discussed. This study investigated the effect of electric current upon the chemically driven interfacial reactions in the Al/Ni system. Al/Ni reaction couples annealed at 400°C with and without the passing of electric current were examined. Two intensities of electric currents, 5×10² A/cm² and 10³ A/cm², were used in this study. Same intermetallics, Al₃Ni and Al₃Ni₂, were formed at the interfaces; however, the thickness of the reaction layer in the reaction couples with the passing of electric current was much larger than those without electric current. This novel phenomenon has never been reported in the literature, and the understanding of its mechanism needs further investigation.     

电阻丝蒸镀Si/Al膜特性及分析

用电阻丝加热蒸发，可作出合Si量为1％左右的Si／Al膜，能防止“Al钉”对结的破坏，采用适当的合金条件可作出良好欧姆接触，本文着重介绍了这种Si／Al膜的特性。     

Simultaneous Formation of Ni/Al Ohmic Contacts to Both n- and p-Type 4H-SiC

The fabrication procedure for silicon carbide power metal oxide semiconductor field-effect transistors can be improved through simultaneous formation (i.e., using the same contact materials and a one-step annealing process) of ohmic contacts on both the n-source and p-well regions. We have succeeded in the simultaneous formation of Ni/Al ohmic contacts to n- and p-type SiC after annealing at 1000°C for 5 min in an ultrahigh vacuum. Ohmic contacts to n-type SiC were found when the Al-layer thickness was less than about 6 nm, while ohmic contacts to p-type SiC were observed for an Al-layer thickness greater than about 5 nm. Only the contacts with an Al-layer thickness in the range of 5 nm to 6 nm exhibited ohmic behavior to both n- and p-type SiC, with a specific contact resistance of 1.8 × 10⁻⁴ Ω cm² and 1.2 × 10⁻² Ω cm² for n- and p-type SiC, respectively. An about 100-nm-thick contact layer was uniformly formed on the SiC substrate, and polycrystalline δ-Ni₂Si(Al) grains were formed at the contact/SiC interface. In the samples that exhibited ohmic behavior to both n- and p-type SiC, the distribution of the Al/Ni ratios in the δ-Ni₂Si(Al) grains was larger than that observed for any of the samples that showed ohmic behavior to either n- or p-type SiC. Furthermore, the grain size of the δ-Ni₂Si(Al) grains in the samples showing ohmic behavior to both n- and p-type SiC was smaller than the grains in any of the samples that showed ohmic behavior to either n- or p-type SiC. Thus, the large distribution in the Al/Ni ratios and a fine microstructure were found to be characteristic of the ohmic contacts to both n- and p-type SiC. Grains with a low Al concentration correspond to ohmic contacts to n-type SiC, while grains with a high Al concentration correspond to ohmic contacts to p-type SiC.