射频激发热丝化学气相沉积制备硅薄膜过程中光发射谱的研究

采用射频(rf)激发,在热丝化学气相沉积(HWCVD)制备微晶硅薄膜的过程中产生发光基元,测量了rf激发HWCVD (rf-HWCVD)的光发射谱,比较了相同工艺条件下rf-HWCVD和等离子体增强CVD(PECVD)的光发射谱,分析了rf功率、热丝温度和沉积气压对rf-HWCVD光发射谱的影响.结果表明,在射频功率<0.1W/cm²时,rf-HWCVD发射光谱反映了HWCVD高的气体分解效率和高浓度原子氢的特点,能够解释气压变化与微晶硅薄膜微结构的关系,是研究HWCVD气相过程的有 关键词： HWCVD OES 微晶硅     

高速微晶硅薄膜沉积过程中的等离子体稳态研究

通过光发射光谱监测高速沉积微晶硅薄膜过程中I(H_α^*)/I(SiH^*) 随沉积时间的变化趋势, 分析高速率微晶硅薄膜纵向晶化率逐渐增大的原因. 通过氢稀释梯度法, 即硅烷浓度梯度和氢气流量梯度法来改善材料的纵向均匀性.结果表明: 硅烷浓度梯度法获得的材料晶化率从沉积300 s时的53%增加到沉积600 s时的62%, 相比于传统方式下纵向晶化率从55%到75%的变化有了明显的改善. 在硅烷耗尽的情况下, 增加氢气流量一方面增加了气体总流量, 使得电子碰撞概率增加, 电子温度降低, 从而降低氢气的分解, 抑制SiH_x基团的放氢反应, 同时背扩散现象也得到了一定的缓解, 使得I(H_α^*)/I(SiH^*) 在沉积过程中逐渐增加的趋势有所抑制, 所制备的材料的纵向晶化率在240 s 后维持在53%-60%范围内, 同样改善了薄膜的纵向结构. 关键词： 光发射光谱 高速沉积 微晶硅 纵向结构均匀性     

VHF-PECVD低温制备微晶硅薄膜的拉曼散射光谱和光发射谱研究

采用拉曼散射光谱和PR650光谱光度计对VHF-PECVD制备的微晶硅薄膜进行了结构表征和在线监测研究.结果表明：功率对材料的晶化率（χc）有一定的调节作用，硅烷浓度大，微调作用更明显；SiH*的强度只能在一定的范围内表征材料的沉积速率，功率大相应的速率反而下降；I［Hα*］/I［SiH*］强度比值反映了材料晶化程度，此结果和拉曼散射光谱测试结果显示出一致性；I［Hβ*］/I［Hα*］的强度比表明氢等离子体中的电子温度随功率的增大而逐渐降低. 关键词： 甚高频等离子体增强化学气相沉积 微晶硅 拉曼散射谱 光发射谱     

微晶硅薄膜沉积过程中的等离子体光学与电学特性研究

采用空间分辨光发射谱和傅里叶变换功率阻抗分析仪研究了衬底偏压和辉光功率对微晶硅薄膜沉积过程中的等离子体光学与电学特性的影响.研究表明：在交流偏压(AC)、悬浮(floating)、负直流加交流(-DC＋AC)偏压下,Hα发射强度空间分布规律相似,平均鞘层长度相等;正直流加交流(＋DC＋AC)偏压和接地(grounded)时Hα发射强度显著增强,并存在双峰(double layers)现象.增大功率,Hα发射强度也随着增大,并在17W与22W之间产生跳变.电学测试发现功率增大,等离子体电阻降低,电抗降低,电 关键词： 等离子体 光发射谱 衬底偏压 辉光功率     

椭圆偏振技术研究VHF-PECVD高速沉积微晶硅薄膜的异常标度行为

采用VHF-PECVD技术高速沉积了不同生长阶段的微晶硅薄膜,通过椭圆偏振技术研究了生长过程中微晶硅薄膜表面粗糙度的演化.实验结果表明,沉积气压P_g=300 Pa时,β=0.81,其超出标度理论中β最大值为0.5范围,出现异常标度行为.这表明微晶硅薄膜高速生长中还存在其他粗糙化增加的因素,此粗糙化增加的因素与阴影作用有关. 关键词： 微晶硅薄膜 椭偏光谱法 生长机制 表面粗糙度     

薄膜硅/晶体硅异质结电池中本征硅薄膜钝化层的性质及光发射谱研究

本文采用甚高频等离子体化学气相沉积技术 (VHF-PECVD) 制备薄膜硅/晶体硅异质结电池中的本征硅薄膜钝化层, 光发射谱 (OES) 测量技术研究了硅薄膜沉积过程中等离子体发光谱随时间的变化. 结果表明: 在实验优化条件下等离子体发光谱很快达到稳定 (大约25 s), 并且SiH^*/H_α^* 的比值随时间变化较小, 避免了生长过程中硅薄膜结构的不均匀性, 这主要是SiH₄没有完全耗尽避免了SiH₄的反向扩散. 进一步研究了沉积参数对稳态发光谱和硅薄膜性质的影响, 结果表明: 随着硅烷浓度增加, H_α^*峰强度减小, SiH^*峰强度增加, 薄膜从微晶转变成非晶, 非晶硅薄膜钝化效果好; 随着沉积气压增大, H_α^*和 SiH^*峰强度先增加后减小, 高气压下H_α^*和 SiH^*峰强度下降主要是反应前驱物的聚合形成高聚合物, 不利于形成高质量的硅薄膜, 因此钝化效果下降; 随着反应功率密度增加, H_α^*和 SiH^*峰强度增大, 当功率密度为150 mW/cm² 趋于饱和, 硅薄膜的致密度和钝化效果也开始下降, 50 mW/cm²的低功率密度下硅薄膜钝化效果差可能是由于原子H 浓度低, 不能完全钝化单晶硅表面的悬挂键. 关键词： 薄膜硅 异质结 光发射谱 钝化     

高压射频等离子体增强化学气相沉积制备高效率硅薄膜电池的若干关键问题研究

报道了采用高压射频等离子体增强化学气相沉积(RF-PECVD) 制备高效率单结微晶硅电池和非晶硅/微晶硅叠层电池时几个关键问题的研究结果, 主要包括: 1)器件质量级本征微晶硅材料工艺窗口的确定及其结构和光电性能表征; 2)孵化层的形成机理以及减小孵化层的有效方法; 3)氢稀释调制技术对本征层晶化率分布及其对提高电池性能的作用; 4)高电导、高晶化率的微晶硅p型窗口层材料的获得, 及其对减小微晶硅电池p/i界面孵化层厚度和提高电池性能的作用等. 在解决上述问题的基础上, 采用高压RF-PECVD制备的单结微晶硅电池效率达8.16%, 非晶硅/微晶硅叠层电池效率11.61%.     

甚高频高速沉积微晶硅薄膜的研究

采用甚高频化学气相沉积(VHF-PECVD)技术制备了系列微晶硅(μc-Si:H)薄膜样品,重点研究了硅烷浓度、功率密度、沉积气压和气体总流量对薄膜沉积速率和结晶状态的影响,绘制了沉积气压和功率密度双因素相图. 以0.75nm/s的高速沉积了器件质量级的微晶硅薄膜,并以该沉积速率制备出了效率为5.5%的单结微晶硅薄膜电池. 关键词： 微晶硅薄膜 高速沉积 甚高频化学气相沉积     

高速沉积微晶硅薄膜光发射谱的研究

采用PR650光谱光度计对高速沉积微晶硅薄膜的生长过程进行了在线监测研究,并对所对应的材料进行了Raman谱和红外吸收谱(FTIR)的测试.结果表明：能反映材料晶化程度的I_［SiH^*］/I_［Hβ^*］比值在沉积时间为100 s之内有下降的趋势,且反应气体总流量T_fl越小下降趋势越明显,这与拉曼散射光谱对材料的结构测试结果一致;沉积5 min时I 关键词： 高速沉积 微晶硅薄膜 电子温度     

沉积速率对甚高频等离子体增强化学气相沉积制备微晶硅薄膜生长标度行为的影响

本文采用甚高频等离子体增强化学气相沉积技术制备了沉积速率系列不同生长阶段的微晶硅薄膜,通过椭圆偏振技术研究了生长过程中微晶硅薄膜表面粗糙度的演化.实验结果表明:沉积速率为0.08和0.24nm/s的低速沉积时,硅薄膜表面粗糙度接近,生长指数分别为β=0.21和β=0.20,对应有限扩散生长模式,此时沉积速率对硅薄膜生长影响不大,原因是低速沉积时成膜先驱物有足够时间迁移到能量低的位置;当沉积速率增加到0.66nm/s时,硅薄膜表面粗糙度明显增加,生长指数β=0.81,大于0.5,出现了异常标度行为,与低速沉积的生长模式明显不同,原因是高速沉积时成膜前驱物来不及扩散就被下一层前驱物覆盖,降低了成膜前驱物在薄膜表面的扩散,使表面粗糙度增加和生长指数β增大.β大于0.5的异常标度行为与阴影效应有关.     

Optical emission spectroscopy study on depositionprocess of microcrystalline silicon

This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities (SiH\sj{*}, H微晶硅 VHF-PECVD 发射光谱学 薄膜物理学microcrystalline silicon, VHF-PECVD, optical emission spectroscopy2005-11-092005-11-092005-12-12This paper reports that the optical emission spectroscopy （OES） is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities （Sill^＊, H^＊ and H^＊β） are investigated by varying the deposition parameters. The result shows that the discharge power, silane concentrations and substrate temperature affect the OES intensities. When the discharge power at silane concentration of 4% increases, the OES intensities increase first and then are constant, the intensities increase with the discharge power monotonously at silane concentration of 6%. The SiH^＊ intensity increases with silane concentration, while the intensities of H^＊α and H^＊β increase first and then decrease. When the substrate temperature increases, the SiH^＊ intensity decreases and the intensities of H^＊α and H^＊β are constant. The correlation between the intensity ratio of IH^＊α/ISiH^＊ and the crystalline volume fraction （Xc） of films is confirmed.     

Formation mechanism of incubation layers in the initial stage of microcrystalline silicon growth by PECVD

The incubation layers in microcrystalline silicon films (\muc-Si:H) are studied in detail. The incubation layers in \muc-Si:H films are investigated by bifacial Raman spectra, and the results indicate that either decreasing silane concentration (SC) or increasing plasma power can reduce the thickness of incubation layer. The analysis of the in-situ diagnosis by plasma optical emission spectrum (OES) shows that the emission intensities of the SiH*(412\,nm) and H_\al (656nm) lines are time-dependent, thus SiH*/H_\al ratio is of temporal evolution. The variation of SiH*/H_\al ratio can indicate the variation in relative concentration of precursor and atomic hydrogen in the plasma. And the atomic hydrogen plays a crucial role in the formation of \muc-Si:H; thus, with the plasma excited, the temporal-evolution SiH*/H_\al ratio has a great influence on the formation of an incubation layer in the initial growth stage. The fact that decreasing the SC or increasing the plasma power can decrease the SiH*/H_\al ratio is used to explain why the thickness of incubation layer can reduce with decreasing the SC or increasing the plasma power.     

The role of hydrogen in hydrogenated microcrystalline silicon film and in deposition process with VHF-PECVD technique

The role of hydrogen in hydrogenated microcrystalline silicon ($\mu $c-Si:H) thin films in deposition processes with very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) technique have been investigated in this paper. With \textit{in situ} optical emission spectroscopy (OES) diagnosis during the fabrication of $\mu $c-Si:H thin films under different plasma excitation frequency $\nu _{\rm e }$ (60MHz--90MHz), the characteristic peak intensities ($I_{{\rm SiH}^*}$, $I_{{\rm H}\alpha^*}$ and $I_{{\rm H}\beta ^*}$) in SiHVHF-PECVD技术 氢化微晶硅 光发射光谱 薄膜学VHF-PECVD technique, hydrogenated microcrystalline silicon, role of hydrogen, optical emission spectroscopyProject supported by the Natural Science Foundation of Guangdong Province, China (Grant No 05300378), the State Key Development Program for Basic Research of China (Grant Nos G2000028202 and G2000028203) and the Program on Natural Science of Jinan University, Guangzhou, China (Grant No 51204056).2005-11-252005-11-252006-01-05The role of hydrogen in hydrogenated microcrystalline silicon （μc-Si：H） thin films in deposition processes with very high frequency plasma-enhanced chemical vapour deposition （VHF-PECVD） technique have been investigated in this paper. With in situ optical emission spectroscopy （OES） diagnosis during the fabrication of μc-Si：H thin films under different plasma excitation frequency Ve （60MHz-90MHz）, the characteristic peak intensities （IsiH＊, IHα＊ and IHβ＊ ） in SiH4＋H2 plasma and the ratio of （IHα＊ ＋ IHβ＊ ） to IsiH＊ were measured; all the characteristic peak intensities and the ratio （IHα＊ ＋ IHβ＊ ）/IsiH＊ are increased with plasma excitation frequency. It is identified that high plasma excitation frequency is favourable to promote the decomposition of SiH4＋H2 to produce atomic hydrogen and SiHx radicals. The influences of atomic hydrogen on structural properties and that of SiHx radicals on deposition rate of μc-Si：H thin films have been studied through Raman spectra and thickness measurements, respectively. It can be concluded that both the crystalline volume fraction and deposition rate are enhanced with the increase of plasma excitation frequency, which is in good accord with the OES results. By means of FTIR measurements, hydrogen contents of μc-Si：H thin films deposited at different plasma excitation frequency have been evaluated from the integrated intensity of wagging mode near 640 cm^-1. The hydrogen contents vary from 4% to 5%, which are much lower than those of μc-Si：H films deposited with RF-PECVD technique. This implies that μc-Si：H thin films deposited with VHF-PECVD technique usually have good stability under light-soaking.     

A fast method to diagnose phase transition from amorphous to microcrystalline silicon

A series of hydrogenated silicon thin films were prepared by the radio frequency plasma enhanced chemical vapor deposition method (RF-PECVD) with various silane concentrations. The influence of silane concentration on structural and electrical characteristics of these films was investigated to study the phase transition region from amorphous to microcrystalline phase. At the same time, optical emission spectra (OES) from the plasma during the deposition process were monitored to get information about the plasma properties, Raman spectra were measured to study the structural characteristics of the deposited films. The combinatorial analysis of OES and Raman spectra results demonstrated that the OES can be used as a fast method to diagnose phase transition from amorphous to microcrystalline silicon. At last the physical mechanism, why both OES and Raman can be used to diagnose the phase transition, was analyzed theoretically.     

Influence of ignition condition on the growth of silicon thin films using plasma enhanced chemical vapour deposition

The influences of the plasma ignition condition in plasma enhanced chemical vapour deposition (PECVD) on the interfaces and the microstructures of hydrogenated microcrystalline Si (μc-Si:H) thin films are investigated.The plasma ignition condition is modified by varying the ratio of SiH 4 to H 2 (R H).For plasma ignited with a constant gas ratio,the time-resolved optical emission spectroscopy presents a low value of the emission intensity ratio of Hα to SiH (I Hα /I SiH) at the initial stage,which leads to a thick amorphous incubation layer.For the ignition condition with a profiling R H,the higher I Hα /I SiH values are realized.By optimizing the R H modulation,a uniform crystallinity along the growth direction and a denser μc-Si:H film can be obtained.However,an excessively high I Hα /I SiH may damage the interface properties,which is indicated by capacitance-voltage (C-V) measurements.Well controlling the ignition condition is critically important for the applications of Si thin films.     

Influence of ignition condition on the growth of silicon thin films using plasma enhanced chemical vapour deposition

The influences of the plasma ignition condition in plasma enhanced chemical vapour deposition (PECVD) on the interfaces and the microstructures of hydrogenated microcrystalline Si (μc-Si:H) thin films are investigated. The plasma ignition condition is modified by varying the ratio of SiH₄ to H₂ (R_H). For plasma ignited with a constant gas ratio, the time-resolved optical emission spectroscopy presents a low value of the emission intensity ratio of Hα to SiH^* (I_Hα/I_SiH^*) at the initial stage, which leads to a thick amorphous incubation layer. For the ignition condition with a profiling R_H, the higher I_Hα/I_SiH^* values are realized. By optimizing the R_H modulation, a uniform crystallinity along the growth direction and a denser μ c-Si:H film can be obtained. However, an excessively high I_Hα/I_SiH^* may damage the interface properties, which is indicated by capacitance-voltage (C-V) measurements. Well controlling the ignition condition is critically important for the applications of Si thin films.     

硼对沉积本征微晶硅薄膜特性的影响

采用甚高频等离子体增强化学气相沉积(VHF-PECVD)技术制备了不同腔室环境下的微晶硅薄膜.对单室沉积掺杂层p材料后遗留在腔室中的硼对本征微晶i材料电学特性和结构特性的影响进行了详细研究.测试结果表明：单室沉积p层后的硼降低了微晶i层材料的暗电导,增加了材料的光敏性;由于硼对i层污染程度的不同,使得材料的激活能发生了变化;腔室中残余的硼也导致微晶硅薄膜的结晶状况恶化,同时弱化了材料的(220)择优取向.而在较高功率和较强氢稀释下制备的晶化率较高,(220)晶向明显择优的材料受硼污染影响相对减小. 关键词： 单室 甚高频等离子体增强化学气相沉积 微晶硅 硼