多孔硅薄膜微结构的分形特性

用扫描电镜(SEM)对厚度不同的多孔硅膜的微结构进行了研究。对于23μm厚的多孔硅膜,其横截面微结构好似海底生长的海藻;而对于6μm厚的多孔硅膜,其表面微结构则像龟壳上的裂纹。通过对在不同放大倍数情况下拍摄的多孔硅的SEM图片进行分析,结果表明多孔硅薄膜的这两种微结构都具有分形特征,而且其分形维数为2.3～2.6。利用扩散限制凝聚模型(diffusion limited aggregation)对这两种微结构的形成过程进行了模拟。     

气相沉积法制备聚酰亚胺薄膜的光、电特性研究

以均苯四甲酸二酐 (PMDA)和二氨基二苯醚 (ODA)为单体原料 ,研究了在 3× 10 - 3Pa真空度下 ,通过控制双源单体的加入摩尔计量、加热时间和其沉积速率 ,在玻璃衬底上合成了聚酰亚胺的预聚体聚酰胺酸 ,再经 15 0～ 2 0 0℃真空加热亚胺化 1h后得到了成膜性良好的均匀聚酰亚胺薄膜。通过红外吸收、X射线衍射和扫描电镜等方法对样品的组织结构和特性进行了研究和探讨。结果表明 ,气相沉积法制备的聚酰亚胺薄膜具有良好的电学特性和热稳定性     

气相沉积法制备聚酰亚胺薄膜的光、电特性研究

以均苯四甲酸酐（ＰＭＤＡ）和二氨基二苯醚（ＯＤＡ）为单体原料,研究了在２×１０－５Ｔｏｒｒ真空度下,通过控制双源单体的加入摩尔计量、加热时间和其沉积速率,在玻璃衬底上合成了聚酰亚胺的预聚体聚酰胺酸,再经１５０～２００℃真空加热亚胺化,１小时后得到了成膜性良好的均匀聚酰亚胺薄膜。通过红外吸收、ｘ射线衍射、扫描电镜等方法对样品的组织结构和特性进行了研究和探讨。结果表明,气相沉积法制备的聚酰亚胺薄膜具有良好的电学特性和热稳定性,不失为聚合物合成的可能途径之一。     

气相沉积法制备含酞菁铜聚酰亚胺薄膜的光电性能

在2×10-3Pa真空度下,以酞菁铜、均苯四甲酸酐和二氨基二苯醚为原料,通过控制三源单体的加入摩尔计量、加热时间和沉积速率,在玻璃衬底上合成了含酞菁铜的聚酰胺酸,再经150℃～200℃真空加热亚胺化1 h后得到了成膜性良好的均匀含酞菁铜聚酰亚胺薄膜.红外谱图证实了所合成产物的结构,紫外-可见光吸收分析表明含酞菁铜聚酰亚胺薄膜在可见光区、近红外区具有较强的吸收,热失重分析表明所制备的含酞菁铜聚酰亚胺具有良好的热稳定性能;用简并四波混频方法测得薄膜的三阶非线性极化率为1.984×10-9esu,表现出良好的三阶非线性特性.     

异构化聚酰亚胺取向膜预倾角的研究

制备了一系列异构化的聚酰亚胺取向膜，并用晶体旋转法测定了它们的预倾角。发现由芳香类异构化二酐制得的聚酰亚脑膜对预倾角影响不大，而由环己烷类顺反异构化二酐制得的聚酰亚胺膜的预倾角变化较大，且顺式的比反式的大。     

二阶非线性光学聚酰亚胺的合成及性能

以1,2,4-苯三酸酐（TMA）、间氨基苯甲（ABA）为原料,经溶液聚合、化学亚胺化后,得到双羟基封端的聚酰亚胺（Ⅱ）,使其与分散红19（DR-19）发生酯化反应,制备了一种侧链上含DR-19结构的聚酰亚胺非线性光学材料。该聚合物的玻璃化温度（Tg）为155℃,耐热温度超过285℃,在室温下放置7d序列参数能保持初值的97．5％,具有良好的耐热性能与取向稳定性。     

聚乙二醇含量对纳米TiO2多孔薄膜性质的影响

以钛酸丁酯为无机原料、二乙醇胺作稳定剂,加入聚乙二醇（PEG）作模板制备前驱体溶胶,通过溶胶-凝胶工艺和浸渍提拉技术在玻璃基片上制备了孔径在10～1000nm范围内可调的纳米TiO2多孔薄膜．通过ESEM,AFM,UV-VIS,N2吸附,XPS和XRD等测试手段研究了PEG（1000）的加入量对薄膜结构及性能的影响．结果表明,当100mL溶胶中PEG的加入量在4.0g左右时,可以得到三维扩展的多孔结构,孔的形状规则且分布均匀,孔径为200～500nm,薄膜比表面积可达76.1m2／g,而过多的PEG加入量反而导致薄膜性能下降．     

Effect of porogen residue on electrical characteristics of ultra low-k materials

Porogen residue (sp² hybridized carbon) formed during UV curing of low-k materials increases leakage current and decreases breakdown voltage of low-k materials. The amount of porogen residue increases with increasing porosity of PECVD low-k films because of larger amount of co-deposited porogen. Electrical characteristics of PECVD ultra low-k films are significantly worse in comparison with CVD and SOG low-k film prepared without porogen. SOG low-k films prepared by self-assembling of nanocrystalline silica demonstrate very low leakage current. Removal of porogen residue significantly improves the electrical characteristics. Therefore, preparation of porogen residue free low-k films is an important challenge of future scaling of low-k materials.     

高可靠及军用PCB的选材与加工——聚酰亚胺

聚酰亚胺树脂由于高玻璃化温度,高分解温度,使之具有很高的耐高温性,制成的PCB也有较高的可靠性和耐高温性。文章从树脂的分析入手,介绍聚酰亚胺PCB的特点,同时介绍加工聚酰亚胺PCB的工艺要点。     

Analysis of Barrier Defects in Low-<Emphasis Type=Italic>k</Emphasis>/Cu Interconnects Based on Electrochemical Response and Simulation Cell

The electrochemical mechanism behind voltammograms produced by defective barriers in low-k/Cu interconnect structures is investigated using simulation cells which mimic various barrier conditions. The findings reveal that the Cu reaction peak current used as an indicator for barrier defects represents oxidation of Cu at the anodic electrode. When both electrodes have similar defect (Cu) fraction, the voltammogram is symmetric, but when the electrodes have different Cu fraction, the voltammogram is asymmetric and changes during repeated cycling until a stable form is reached.     

An investigation of ultra low-k dielectrics with high thermal stability for integration in memory devices

For the PMD in a next generation memory device, two kinds of newly developed ultra low-k MSQ materials (k < 2.0) are shown to have good thermal stability, up to 600 °C, while the investigated HSQ (k = 2.9) material degraded at temperatures >500 °C. The thermal stability of the low-k MSQ is correlated with the amount of Si-X (X = H or CH₃), the ratio of Si-X to Si-O, and the structure of the Si-O bonds. With PE-SiO₂ and PE-SiN capping on HSQ, the k-value of  < 3.0 can be maintained up to 800 °C due to Si-H remaining in the film. Similarly, PE-SiC and PE-SiO₂ capping increases the k-value degradation onset temperature of the MSQ materials by 50 °C.     

Etching characteristics of photoresist and low-k dielectrics by Ar/O2 ferrite-core inductively coupled plasmas

We have investigated the characteristics of Ar/O₂ plasmas in terms of the photoresist (PR) and low-k material etching using a ferrite-core inductively coupled plasma (ICP) etcher. We found that the O₂/(O₂+ Ar) gas flow ratio significantly affected the PR etching rate and the PR to low-k material etch selectivity. Fourier transform infrared spectroscopy (FTIR) and HF dipping test indicated that the etching damage to the low-k material decreased with decreasing O₂/(O₂ + Ar) gas flow ratio.     

Properties of low-k SiCOH films prepared by plasma-enhanced chemical vapor deposition using trimethylsilane

The properties of low-k SiCOH film deposited by plasma-enhanced chemical vapor deposition using trimethylsilane are reported here. The deposition process was performed at different temperatures from 200 to 400 °C. The influence of deposition temperature on the films were characterized using Fourier transform infrared spectroscopy (FTIR) to understand its impact on the studied properties. The films were annealed at ∼450 °C in an inert ambient after deposition in all the cases. The deposition rate decreases with increase in deposition temperature. The refractive index of the films increases as a function of deposition temperature. From FTIR spectra, OH-related bonds were not detected in films even when deposited at 200 °C. The Si-CH₃ bonds were detected in all the films and decreased monotonically from 200 to 400 °C. All deposition conditions studied resulted in films with dielectric constant less than 3, the lowest being ∼2.7 when deposited at 200 °C. All films exhibited good thermal stability.     

聚酰亚胺液晶垂直取向膜的制备与性质

虽然传统的平行取向技术已广泛应用于液晶显示器的生产,但其存在窄视角、低对比度和慢响应时间等问题,因此液晶分子的垂直取向技术在国外已经被广泛研究。在实验中,一种含有液晶结构侧链的聚酰亚胺通过均苯四羧酸二酐(PMDA),4,4′-二胺基二苯甲烷(MDA)和4-己氧基联苯酚-3′,5′-二胺基苯甲酸酯(C6BBDA,实验室自制)共聚被制备,并且被用作液晶取向膜,研究其取向性能。试验发现,该种聚酰亚胺作为取向膜可以诱导液晶分子垂直取向,即使在摩擦之后依然可以获得大于89°的预倾角;使用正交偏光显微镜观察所制得液晶盒中的液晶取向效果,发现垂直取向均匀良好;为了测试该垂直取向的热稳定性,将制备的液晶盒在120℃下烘烤12h后,偏光显微镜下观察发现垂直取向仍然良好均匀,表明该取向膜具有良好的热稳定性。     

The influence of N containing plasmas on low-k films

The use of low-k materials is essential for improving the quality of integrated circuits. Subsequent process steps may however modify this film to the extent that the final result is unacceptable. Organosilicate-based low-k films, with a nominal k-value of 2.3, were exposed to different post-CMP cleaning plasmas used for copper reduction. The resulting plasma damage was investigated and is reported in this paper. All the studied plasmas increased the density of the low-k film. TOFSIMS and FTIR analyses showed that they all removed CH₃ groups from the bulk, leading to water incorporation. The carbon depletion was more pronounced and deeper (100 nm) from a NH₃ plasma than from any other investigated plasma. N₂ + H₂ plasma removed somewhat less carbon from the low-k film (83 nm deep). The N₂ plasma removed carbon down to a depth of 60 nm into the film, while a pure H₂ plasma removed the least carbon of all the investigated plasmas, to a depth of only 35 nm. The combination of TOFSIMS and XPS indicated the incorporation of a significant amount of N in the films treated with the pure N₂ plasma. C-V measurements showed an increase of the dielectric constant, again mostly for the NH₃ plasmas. There was an intermediate and approximately equal increase of the dielectric constant for all N₂ containing plasmas, and the least increase was for the H₂ plasma. This increase of the dielectric constant was caused by the increase of density of the film, incorporation of water, and in the case of the N₂ plasma also the incorporation of N. This shows that the presence of N₂ in plasma may significantly damage low-k materials, and it should not therefore be treated as a mere carrier gas.     

Integrated monitoring of ULK dielectrics out-gassing and measurement of pore sealing efficiency by residual gas analysis technique

Residual gas analysis is a well-known technique used in the semi-conductor industry. This paper presents the RGA as an effective method to monitor wafer out-gassing during the degas process prior to barrier/copper seed deposition. The technique is easy to use, repeatable and very sensitive to the hydrophobic or hydrophilic nature of the surfaces. Moreover, it has been demonstrated that RGA is the technique of choice to evaluate the pore sealing efficiency of ultra low-k dielectric in high volume manufacturing environment.     

Reliability of copper low-k interconnects

For the implementation of copper and low-k materials into a tight pitch damascene interconnect architecture it is important to understand and correctly describe the underlying degradation mechanisms during reliability testing. Based on the understanding solutions can be proposed for avoiding fast degradation. While the physical understanding of electromigration mechanisms is less of a debate, technological challenges towards the fabrication of metal wires/vias able to carry the ever increasing current densities are enormous. Recently a number of novel metallization schemes including ruthenium and its alloys or self-forming barriers were proposed. As a consequence, some of the thermodynamic and kinetic behavior of the system can be modified when compared to the conventional Ta-based metallization. Another important component of the system is the insulating low-k dielectric. When scaling the critical dimensions into 50 nm ½ pitch and beyond, the impact of layout and line edge roughness becomes important. If a double patterning approach is used for printing a tight metal pitch, then misalignment between the different photos will exacerbate the layout induced effects. The choice of dielectric material, test structure design and damascene process steps will contribute on top of these effects. Based on recent understanding we review some aspects of novel metallization schemes and tight pitch copper/low-k interconnects from a reliability standpoint.     

Cracking energy estimation of ultra low-k package using novel prediction approach combined with global-local modeling technique

Interfacial crack/delamination, due to the presence of dissimilar material systems, is one of the major concerns of thermo-mechanical reliability for the development of next node technology in integrated circuits (IC) devices. The cracking energy results from many back end of line (BEOL) and packaging processes at various temperature differences is prone to drive the crack advance. To investigate the sensitivity of crack propagation in low-k dielectric materials, a robust estimation of J-integral approach combined with a rectangular path of integral contour is performed using finite element analysis (FEA). By means of the verification of 4-point bending test (4-PBT), excellent agreements are obtained as compared with the experimental data. Moreover, a multiscale modeling technique is proposed to resolve the difficulty of model construction as from bridge device level to packaging level. The sub-modeling procedures developed specifically for the impact prediction of interfacial crack in complicated Cu/low-k interconnects. The analytic results indicate the foregoing methodology is valuable to forecast the physical behavior and reliability of advanced IC devices in the nano scaled size. On the basis of the presented results in this research, an approximated criterion for determining the dimensions of sub-model is suggested and demonstrated as well.     

Development of capillaries for wire bonding of low-k ultra-fine-pitch devices

Although wire bonding has been a well-established technology for many years, the bonding tool design becomes more complex and the process is very sensitive for wire bonding of low-k ultra-fine-pitch microelectronics devices. In this study, two different types of external transition profile were considered in order to use lower ultrasonic-generator power for preventing pad damage. The ultrasonic vibration displacements of the capillaries were measured using a laser interferometer. The measurement results revealed that the amplification factor (the ratio of the vibration displacement at the capillary tip to that at the transducer point) of a capillary with a small radius transition between the bottleneck angle and the main taper angle was 37% higher than that of a capillary with a sharp transition, and this led to satisfactory results in terms of ball size, ball height, ball shear and stitch pull. To solve the ball lift problem for wire bonding of low-k ultra-fine-pitch devices, optimization of the capillary internal profile was attempted to improve bondability. Actual bonding responses were tested. Compared to a standard design, a capillary with a smaller chamfer angle, a larger inner chamfer and a larger chamfer diameter could increase the percentage of the intermetallic compound in the bond interface. Metal pad peeling and ball lift failures were not observed after an aging test.     

低介电常数多孔二氧化硅薄膜的制备与性能研究

利用Sol-Gel的方法制备了多孔二氧化硅薄膜。通过优化薄膜制备工艺,实现了多孔二氧化硅薄膜厚度在450nm～3000nm范围内可控,薄膜孔率为59%。用FTIR光谱分析了不同热处理温度下多孔二氧化硅薄膜的化学结构。研究了多孔二氧化硅薄膜的介电常数、介电损耗、漏电流等电学性能,结果表明多孔二氧化硅薄膜本征的介电常数为1.8左右,是典型的低介电常数材料。并通过原子力显微镜对薄膜的表面形貌进行了表征。