PECVD法制备纳米晶硅薄膜的研究进展

简要介绍了纳米晶硅薄膜的微结构表征方法,重点讨论了PECVD制备方法中工艺参数对薄膜结构的影响,并探讨了氢在薄膜形成和生长中的作用。通过优化氢稀释率、衬底温度、反应气压、激励功率和激发频率等工艺参数可提高纳米晶硅薄膜的晶化率并改善薄膜质量。结合喇曼光谱、X射线衍射谱、傅里叶红外光谱和高分辨透射电镜等表征方法可深入研究薄膜形成机理,对进一步探索薄膜光电特性有重要意义。分析了等离子体化学气相沉积(PECVD)制备方法中各工艺参数对薄膜质量和沉积速率的影响,指出其存在的问题,并探寻了今后的研究方向。     

PECVD法沉积类金刚石膜的结构及其摩擦学性能

以C2H2为碳源,Ar气为辅助气体,利用射频等离子体化学气相沉积的方法在有机薄膜PET和载玻片上制备了类金刚石(diamond-like carbon,DLC)薄膜.通过红外光谱(FTIR)、拉曼光谱(Raman)分析了所制备DLC薄膜的结构;利用原子力显微镜(AFM)分析了薄膜的表面形貌;另外,还利用摩擦磨损仪对薄膜的机械性能进行了研究.实验得到:FTIR、Raman谱图分析发现碳氢膜主要由sp2和sp3杂化的碳氢化合物呈层状堆积而成,其组分与沉积参数密切相关;同时,sp2和sp3杂化比例影响所制备薄膜的致密性、均匀性和耐磨性能.     

氢在微晶硅薄膜低温沉积及退火过程中的影响

采用等离子体增强化学气相沉积(PECVD)法,在玻璃衬底上不同的氢稀释比下低温制备了微晶硅(μc-Si:H)薄膜.利用拉曼(Raman)散射谱研究显示当H2稀释比从95%升高到99%,所得硅膜晶粒大小从2.98 nm增加8.79 nm,晶化率从24%增加到91%;暗电导测试结果从1.32×10-6scm-1增加到7.24×10-3scm-1;沉积速率却大大降低.沉积出的薄膜在进行高温炉退火后,扫描电镜(SEM)显示样品表面孔洞变大增多,推测是氢逸出所致.     

Microwave plasma assisted preparation of disperse chromium oxide supported catalysts: Adsorption and decomposition of chromium acetylacetonate

Microwave plasma enhanced chemical vapour deposition (PECVD) is a promising method for the solvent free preparation of catalytic materials. In this work, microwave low temperature plasma technology has been used for the deposition of catalytic active chromia species on zirconia and lanthanum doped zirconia supports. The obtained materials were characterized by inductive coupled plasma-optical emissions spectroscopy (ICP-OES), Fourier-transform infrared spectroscopy (FTIR), thermo gravimetric analysis-difference thermo analysis (TG/DTA) investigations and transmission electron spectroscopy-energy dispersive X-ray analysis (TEM-EDX).The results reveal that the PECVD method is a solvent free one step method suitable for preparation of chromia containing catalysts. During the PECVD process the adsorption of Cr(acac)₃ probably takes place by cleavage of one ligand on both supports. The anchoring of the formed active component CrO_x is more stable on La_0.1Zr_0.9O_1.95 than on ZrO₂. Furthermore, the utilization of the PECVD method can inhibit the formation of large CrO_x agglomerates or α-Cr₂O₃ on both supports. After upscaling, this method can be used for the preparation of catalysts for fine chemicals in larger scale.     

PC树脂上沉积DLC薄膜耐磨性与透光性的研究

采用等离子体增强化学气相沉积(PECVD)技术,在聚碳酸酯(PC)树脂片上沉积类金刚石(DLC)薄膜,以获得耐磨性和透光性良好的光学镜片。研究了薄膜的沉积工艺对PC基体镀DLC薄膜耐磨性和透光性的影响。结果表明:PC树脂片上沉积DLC薄膜后,耐磨性有极大的提高,摩擦系数降低了70%左右,显微硬度增加了约30%且随着沉积时间增加而增加,但透光率由约90%降至80%～70%。薄膜样品的耐磨性和透光性与样品的粗糙度、形貌及组成有关。     

低介电常数含氟氧化硅薄膜的红外光谱分析

用等离子体化学气相淀积 (PECVD)制备了含氟氧化硅薄膜 (Si OF薄膜 )。通过傅里叶变换红外光谱 (FTIR)分析 ,研究了氟掺入后薄膜结构的变化 ,并进一步讨论了氟对薄膜介电常数及吸水性的影响。研究表明氟掺入后改变了 Si- O键上的电荷分布 ,降低了薄膜中 Si- O键的极性 ,导致 Si- O键伸缩振动吸收峰发生蓝移。同时氟的掺入抑制了强极性 Si- OH键的形成。这些变化有利于薄膜中离子极化和偶极子转向极化的降低 ,因而使薄膜介电常数减小。对 Si- F吸收峰的高斯拟合表明 ,在氟含量较高时 ,薄膜中掺入的氟一部分会以 Si F2 结构存在。由于 Si F2 结构稳定性较差 ,易与水汽发生作用 ,因而高氟掺杂的 Si OF薄膜易吸水 ,并使薄膜性能变差     

SiGe MOS器件SiO_2栅介质低温制备技术研究

为了获得电学性能良好的 Si Ge PMOS Si O2 栅介质薄膜 ,采用等离子体增强化学汽相淀积 (PECVD)工艺 ,对低温 30 0°C下薄膜制备技术进行了研究。实验表明 ,采用适当高温、短时间对PECVD薄膜退火有助于降低薄膜中正电荷密度和界面态密度。该技术用于 Si Ge PMOS研制 ,在30 0 K常温和 77K低温下 ,其跨导分别达到 45m S/mm和 92 .5m S/mm(W/L=2 0 μm/2 μm)     

用SiCl_4/O_2-PECVD技术低温沉积Si基厚SiO_2薄膜

选取不含 H2 的 Si Cl4 / O2 混合气体作为反应源气体 ,并利用普通的 PECVD技术来实现低温沉积 Si基微米厚度的 Si O2 薄膜 ,测试并分析薄膜的红外吸收谱以及工艺参数对沉积过程的影响。     

Si基富Ge含量Si1-x-yGexCy异质结构的热退火行为研究

研究了Si基富Ge含量的Si1-x-yGexCy异质结构的热退火地为,采用等离子体增强化学气相淀积（PECVD）法在Si(100）衬底上淀积一层厚度为170nm的Si1-x-yGexCy薄膜（x-0.7,y-0.15),并在其上覆盖－Ge层,将样品分别在650度和800度下进行N2氛围下热退火20min。用拉曼谱（Raman),俄歇电子能谱（AES）以及X射线光电子能谱XPS等方法对样品进行研究。研究结果表明,低温PECVD法生长的Si1-x-yGexCy薄膜是一种亚稳结构,Ge/Si1-x-yGexCy/Si异质结构在650度下呈现不稳定性,薄膜中的Ge,C相对含量下降,且在界面处出现Ge,C原子的堆积,经过800度下退火20min的样品中C 含量基本为0,Ge相对含量下降至约20％左右,且薄膜的组分比较均匀。     

Recent advances in very high frequency plasma enhanced CVD process for the fabrication of thin film silicon solar cells

We have deposited amorphous silicon (a-Si) and nanocrystalline silicon (nc-Si) materials and the total p-i-n configurations for solar cells in a high vacuum multichamber system ASTER using very high frequency plasma enhanced chemical vapour deposition (VHF PECVD) process. The deposition process is monitored and controlled by in-situ diagnostic tools to maintain reproducibility of the material quality. In this paper we show our recent results on single junction (amorphous silicon) and tandem (a-Si/nc-Si) cells on plastic foil using the Helianthos concept. The tandem cell efficiency on Asahi U-type SnO₂:F coated glass is ~ 12% and this is achieved by employing nc-Si deposited at high pressure (p) conditions of 5 mbar and a small inter-electrode distance (d) of 5 mm. The deposition scheme of this cell on glass was adapted for the SnO₂:F coated Al foil substrates from Helianthos b.v., especially taking into account the expansion of the foil during deposition. The inter-electrode distance d was one of the variables for this optimisation process. Depositions at four inter-electrode distances of 6 mm, 8 mm, 10 mm and 12 mm (keeping the pressure-distance product constant) revealed that the deposition rate increases at higher distances, reaching 0.6 nm/s at a d of 10 mm and pressure p of 3.0 mbar. The Raman crystalline ratio showed a monotonic increase with the combination of higher d and lower p. Tandem cells with an area of 2.5 cm² on plastic foil fabricated by the Helianthos concept and employing the above mentioned nc-Si made at 0.6 nm/s in the bottom cell and a-Si in the top cell, showed an efficiency of 8.12%, with a short circuit current density of 10 mA/cm². The combined deposition time of the photoactive silicon layers of the top and bottom cells amounted to only 85 min.