CHF3/C6H6等离子体中的基团分析

在一个微波电子回旋共振等离子体化学气相沉积系统中，测量了CHF3、C6H6及其混合气体放电的质谱和发射光谱图，分析了等离子体中主要基团的分布及其产生的途径，研究了放电功率和流量对主要基团密度的影响，以及它们与氟化非晶碳薄膜沉积速率和键结构之间的关联。结果表明，提高微波功率会增加CHx、CFx等成膜基团的密度，有利于加大沉积速率；而增加CHF3的进气量则会加大F原子基团的密度，这是由于它控制了薄膜的氟化程度。     

微波ECR-CVD法制备a-C:F:H膜的红外吸收及其光学带隙

改变CHF3 CH4 流量比R =[CHF3] ([CHF3]+[CH4 ]) ,采用微波电子回旋共振等离子体化学气相沉积 (MWECR CVD)方法沉积a C :F :H薄膜。a C :F :H薄膜的结构和光学带隙使用傅立叶变换红外光谱和紫外 可见光谱来表征。红外结果表明 ,在低流量比R(R <6 4 % )下 ,薄膜的红外特征结构主要以 CF(10 6 0cm- 1 ) , CF2(112 0cm- 1 )以及 CHx(2 80 0～ 30 0 0cm- 1 )的伸缩振动为主 ;在高流量比R(R >6 4 % )下 ,薄膜表现为类聚四氟乙烯(PTFE)的结构特征 ,典型的红外特征峰是位于 12 2 0cm- 1 处的 -CF2 反对称伸缩振动。薄膜的光学带隙Eg 随流量比R的变化表现为先降后升。进一步研究表明 ,薄膜中的H和F浓度调制着薄膜的CC共轭双键结构 ,使光学带隙Eg 从 2 37到 3 3之间变化     

氟化非晶碳薄膜的低频介电性质分析

研究了电子回旋共振等离子体技术沉积的氟化非晶碳(α-C：F)薄膜的低频(10^2～10^6Hz)介电性质。发现α-C：F薄膜的低频介电色散随源气体CHF3／C6H6的比例、微波入射功率而改变。结合薄膜键结构的红外分析,发现薄膜中C=C相对含量的增大是导致低频介电色散增强的原因,而C—F相对含量的增大则使低频介电色散减弱。     

沉积温度对a-C:F薄膜结构与热稳定性的影响

在不同的沉积温度下，利用CHF3和C2H2为气体源，在微波电子回旋共振等离子体化学气相沉积(ECR-CVD)系统中制备了氟化非晶碳(-C：F)薄膜，为了研究其热稳定性，薄膜在500℃的真空中作了退火处理。测量了退火前后其电学、光学性质的变化，使用FFIR、Raman、XPS方法考察了其结构随沉积温度的变化，分析了性质同结构之间的关联。结果表明，在高的沉积温度下制备的薄膜中的F／C比较低，CF2和CF3键成分较少而以CF键成分为主，其交联程度高，因而具有较好的热稳定性。     

氟化类金刚石(F-DLC)薄膜的红外分析

以CF4和CH4为源气体,利用射频等离子体增强化学气相沉积法,在不同条件下制备了氟化类金刚石(F-DLC)薄膜,并进行了退火处理。红外分析表明,F-DLC薄膜中主要有C-Fx(x=1,2,3)、C-C、C-H2、C-H3和C=C化学键等。低功率下制备的薄膜主要由C-C、CF和CF2键构成,功率增加时,薄膜内C-C键含量相对增加;气体流量比R(R=CF4/[CF4 CH4])增大,薄膜内F的含量增加,C-C键相对减少;高温退火后,薄膜内部分F和几乎全部的H从膜内逸出,薄膜的稳定温度在300℃以上。低功率、高流量比下制备的薄膜,F含量相对较大,介电常数较低。     

功率和温度对a-C:F:H膜表面形貌和结构的影响

分析薄膜的表面形貌对其生长机理和光学性质研究有着十分重要的作用。本文使用CF4和CH4为源气体，利用射频等离子体增强化学气相沉积（RF—PECVD）法在不同射频功率和沉积温度下制备了掺氟氢化无定形碳（a—C：F：H）薄膜，并在N2气氛中进行了不同温度的退火处理。用原子力显微镜（AFM）和扫描电子显微镜（SEM）观察了薄膜表面形貌，发现低功率下沉积的薄膜表面均匀性好、缺陷少；在低温下沉积的薄膜表面光滑，而高温下粗糙；真空低温退火可使薄膜表面形貌得到改善，但薄膜内空洞增加，退火温度过高，薄膜的结构发生变化，且在薄膜表面发生皲裂现象。用Raman光谱对薄膜内的结构变化进行了进一步的分析。     

有机发光器件的低温氮化硅薄膜封装

利用等离子体化学气相沉积(PECVD)技术，采用不同的沉积条件(20—180℃的基板温度范围和10—30W的射频功率)制备了氮化硅薄膜，研究了沉积条件对氮化硅薄膜性质和防水性能的影响。实验发现随着基板温度的增加，氮化硅薄膜的密度、折射率和Si／N比相应增加，而沉积速率和H含量相应减少；随着射频功率的增加，氮化硅薄膜的沉积速率、密度、折射率和Si／N比相应增加，而H含量相应减少。水汽渗透实验发现即使基板温度降低为50℃，所沉积的氮化硅薄膜仍然具有良好的防水性能。实验结果表明低温氮化硅薄膜可以有效地应用于有机发光器件（OLED)的封装。     

源气体流量比对a_C:F:N薄膜的影响

以CF4、CH4和N2的混合气体为源气体,利用rf-PECVD沉积技术制备了氮掺杂氟化非晶碳(a_C:F:N)薄膜,研究了源气体流量比对a_C:F:N薄膜沉积速率和结构的影响.用椭圆偏振光谱测试仪测量了薄膜厚度,结合沉积时间计算了薄膜的沉积速率(在18～21nm/min之间),随流量比增大,薄膜的沉积速率先升高后降低.FTIR光谱分析表明,随流量比增大,薄膜中含F量降低,交联结构增强.Raman光谱分析发现,薄膜中的碳原子由sp2和sp3两种组态的混合结构组成,并进一步证明,随流量比增大,薄膜中sp2键含量增加,交联程度增强.     

ECR-CVD制备氟化非晶碳低k介质薄膜

采用电子回旋共振等离子体化学气相沉积(ECR-CVD)方法,以C4F8和CH4为源气体在不同气体流量比R(R=[CH4]/{[CH4] [C4F8]})条件下成功地沉积了氟化非晶碳(a-C:F)低介电常数(低k)材料.采用X光电子能谱和椭圆光谱方法分析了a-C:F薄膜的化学组分和光学性质.沉积的a-C:F薄膜介电常数约为2.1～2.4,热稳定性优于350℃.随着气体流量比的增大,沉积a-C:F薄膜中的碳含量增大,CF、CF2、CF3含量减少,C-C交链成分增加,从而使得π-π(*)吸收增强,并引起薄膜光学带隙下降.氮气气氛下350℃温度退火后应力释放引起a-C:F薄膜厚度变化,变化量小于4%.450℃温度退火后,由于热分解作用薄膜厚度变化量在30%左右.     

α-C:F薄膜的键合结构与电子极化研究

利用微波电子回旋共振等离子体化学气相沉积技术,通过改变微波输入功率的方法,沉积了具有不同有不同结构特征的氟化非晶碳（α-C:F薄膜。随着微波功率从140W升高到560W,薄膜的光频介电常数从2．26降至1．68,红外光谱（FT－IR）分析表明薄膜的刍结构由以CF基团为主变化到CF与CF2基团共存。由于CF2基团的极化比CF基团弱,薄膜中CF2基团的增加可能是导致光频介电常数减小的因素。     

Fluorohydrogenated amorphous carbon (a-C:H, F) films prepared by the r.f. plasma decomposition of 1,3-butadiene and carbon tetrafluoride

Amorphous fluorohydrogenated carbon films (a-C:H, F) were prepared by the r.f. glow discharge decomposition of a hydrocarbon (C₄H₆) diluted with a fluorocarbon (CF₄). An increase in the CF₄ content of the deposition gas mixture was accompanied by a corresponding increase in the fluorine content and a decrease in the hydrogen content of the films. The IR spectra indicate fluorine incorporation in the film primarily via the monofluoride mode. No absorption owing to CF₂ and CF₃ could be detected. The film density and optical bandgap stayed fairly constant until about 40–50% dilution with CF₄. Further dilution of the hydrocarbon with CF₄ resulted in a large drop in the deposition rate, film density, optical bandgap, oxygen plasma etch resistance and thermal stability. These film properties differ from those of a-C:H, F films obtained by the r.f. plasma decomposition of substituted benzenes (Sah et al., Appl. Phys. Lett., 46 (1992) 739).     

Effect of deposition temperature and thermal annealing on the dry etch rate of a-C: H films for the dry etch hard process of semiconductor devices

The effect of deposition and thermal annealing temperatures on the dry etch rate of a-C:H films was investigated to increase our fundamental understanding of the relationship between thermal annealing and dry etch rate and to obtain a low dry etch rate hard mask. The hydrocarbon contents and hydrogen concentration were decreased with increasing deposition and annealing temperatures. The I(D)/I(G) intensity ratio and extinction coefficient of the a-C:H films were increased with increasing deposition and annealing temperatures because of the increase of sp² bonds in the a-C:H films. There was no relationship between the density of the unpaired electrons and the deposition temperature, or between the density of the unpaired electrons and the annealing temperature. However, the thermally annealed a-C:H films had fewer unpaired electrons compared with the as-deposited ones. Transmission electron microscopy analysis showed the absence of any crystallographic change after thermal annealing. The density of the as-deposited films was increased with increasing deposition temperature. The density of the 600 °C annealed a-C:H films deposited under 450 °C was decreased but at 550 °C was increased, and the density of all 800 °C annealed films was increased. The dry etch rate of the as-deposited a-C:H films was negatively correlated with the deposition temperature. The dry etch rate of the 600 °C annealed a-C:H films deposited at 350 °C and 450 °C was faster than that of the as-deposited film and that of the 800 °C annealed a-C:H films deposited at 350 °C and 450 °C was 17% faster than that of the as-deposited film. However, the dry etch rate of the 550 °C deposited a-C:H film was decreased after annealing at 600 °C and 800 °C. The dry etch rate of the as-deposited films was decreased with increasing density but that of the annealed a-C:H films was not. These results indicated that the dry etch rate of a-C:H films for dry etch hard masks can be further decreased by thermal annealing of the high density, as-deposited a-C:H films. Furthermore, not only the density itself but also the variation of density with thermal annealing need to be elucidated in order to understand the dry etch properties of annealed a-C:H films.     

High aspect ratio contact hole etching using relatively transparent amorphous carbon hard mask deposited from propylene

In this study, a high aspect ratio contact pattern, beyond 70 nm technology, in a very-large-scale integrated circuit, was achieved using hydrogenated amorphous carbon (a-C:H) film as the dry etching hard mask. The effect of temperature on the a-C:H deposits prepared by plasma enhanced chemical vapor deposition was studied. The a-C:H films resulting from propylene (C₃H₆) decomposition exhibited high transparency incorporated rich hydrogen concentration with a decreasing deposition temperature. A matrix of dispersed cross-linked sp³ clusters in a-C:H films, which has an increasing optical band gap and higher hydrogen content, is attributed to reduce the defect density of status and obtain high transmittance rate. Moreover, the higher transparency of a-C:H films could afford lithographic aligned capability as well as compressive stress and dry etching resistance. These explorations provided insights into the role of hydrogen in a-C film and also into the practicality of its future nano-scale device applications.     

Stress reduction for hard amorphous hydrogenated carbon thin films deposited by the self-bias method

Hard amorphous hydrogenated carbon (a-C:H) thin films were deposited by the r.f. (13.56 MHz) self-bias method using 2-methyl-propane as the source gas. To achieve stress reduction, we used the periodic plasma deposition technique: repeated cycles of alternating 5 s of deposition (plasma on) with 180 s of cooling (plasma off). Substrate temperature changes during the plasma deposition were monitored by a fluorescent/ optical thermosensor. We investigated the film deposition rate, density, and internal stress as functions of the deposition temperature.

We found a linear relationship between the internal stress of a-C:H films and the deposition temperature over the range of 0 to 150 °C. The increase in internal film stress from 0.48 to 1.5 GPa, respectively, over this deposition temperature range is the result of the increase in deposition temperature. Within the range of deposition temperature and r.f. power parameters studied, the deposition temperature appeared to play a more significant role in determining the intrinsic film stress than the r.f. power.     

The influence of methane/argon plasma composition on the formation of the hydrogenated amorphous carbon films

The quality of the a-C:H films was particularly correlated with the mixed ratio of methane/argon plasma. For a constant supply of energy and flowing rate, the optical emission from H_α intensity linearly increased with the addition of methane in argon plasma, while that from intensities of radiation of diatmoic radicals (CH^?and C₂^?) exponentially decreased. For the a-C:H films, the added methane in argon plasma tended to raise the quantity of hydrogenated carbon or sp³ C-H structure, which exponentially decreased the nano-hardness and friction coefficient of the films. In contrast, the electric resistance of the films enlarged dramatically with the increase of the methane content in argon plasma. It is therefore advantageous to balance the mechanical properties and electrical resistance of the a-C:H film by adjusting plasma composition in the course of the film-growing process.     

Mechanical properties of a-C:H and a-C:H/SiOx nanocomposite thin films prepared by ion-assisted plasma-enhanced chemical vapor deposition

a-C:H and a-C:H/SiO_x nanocomposite thin films were deposited on silicon, aluminum and polyimide substrates at 25 °C in an asymmetric 13.56 MHz r.f.-driven plasma reactor under heavy ion bombardment. Fourier transform infrared spectra of the films indicate that the nanocomposite filmsappears to consist of an atomic scale random network of a-C:H and SiO_x. Raman spectroscopy revealed that the sp² carbon fraction in the nanocomposite film was reduced compared with the a-C:H film. The intrinsic stress of both films increased with increasing negative bias voltage (−V_dc) at the substrate. However, the nanocomposite films exhibited lower intrinsic stress compared w with a-C:H-only films. Especially, a thin SiO_x-rich interlayer was very effective in reducing the film stress and enhancing the bonding strength at the interface. The interlayer allowed deposition of thick films of up to 5 μm. Also, the nanocomposite films were stable in 0.1 M NaOH solution and showed good microhardness.     

On the chemistry at the Si,Ti-doped a-C:H/TiC interface

Silicon-titanium-doped a-C:H, deposited via plasma assisted chemical vapor deposition and its chemistry at the titanium carbide interface has been studied via X-ray photoelectron spectroscopy. In the a-C:H film, as well as at the interface, the carbide species TiSiC is formed. Thermal treatment of Si,Ti-a-C:H films on TiC causes an increase in TiSiC at the interface leading to a better adhesion performance.     

Annealing effects on structural and electrical properties of fluorinated amorphous carbon films deposited by plasma enhanced chemical vapor deposition

The annealing effects on the structural and electrical properties of fluorinated amorphous carbon (a-C:F) thin films prepared from C₆F₆ and Ar plasma are investigated in a N₂ environment at 200 mTorr. The a-C:F films deposited at room temperature are thermally stable up to 250 °C, but as the annealing temperature is increased beyond 300 °C, the fluorine incorporation in the film is reduced, and the degree of crosslinking and graphitization in the film appears to be enhanced. At the annealing temperature of 250 °C, the chemical bond structures of the film are unchanged noticeably, but the interface trapped charges between the film and the silicon substrate are reduced significantly. The increased annealing temperature contributes the decrease of both the interface charges and the effective charge density in the a-C:F film. Higher self-bias voltage is shown to reduce the charge density in the film.