快速光热退火法制备多晶硅薄膜的研究

为了制备应用于太阳电池的优质多晶硅薄膜,研究了非晶硅薄膜的快速光热退火技术。先利用 PECVD 设备沉积非晶硅薄膜,然后放入快速光热退火炉中进行退火。退火前后的薄膜利用 X 射线衍射仪(XRD)和扫描电子显微镜(SEM)测试其晶体结构及表面形貌,用电导率设备测试其暗电导率。研究表明退火温度、退火时间对非晶硅薄膜的晶化都有很大的影响,光热退火前先用常规高温炉预热有助于增大多晶硅薄膜的晶粒尺寸和暗电导率。     

Ge诱导晶化多晶Si薄膜的制备及结构表征

采用测控溅射,通过Ge诱导晶化法在Si衬底上制备多晶Si薄膜.采用Raman光谱、X射线衍射(XRD)、原子力显微镜(AFM)及场发射扫描电镜(FESEM)等对所制备的薄膜进行表征.结果表明,当生长温度为800℃时,Ge有诱导非晶Si(a-Si)薄膜晶化的作用,所制备的多晶Si薄膜在(200)方向具有择优取向,且在此方...     

Low-temperature crystallization of amorphous silicon using Cu field-aided lateral crystallization at 350°C

The crystallization of amorphous silicon (a-Si) was achieved by field-aided lateral crystallization (FALC). Under the influence of an electric field, Cu is found to drastically enhance the lateral crystallization velocity of a-Si. When an electric field of 30 V/cm was applied to selectively Cu-deposited a-Si films during heat treatment at 350°C, dendrite-shaped crystallization of a-Si progressed toward the Cu-free region, and the crystallization from the negative electrode side toward the positive electrode side was accelerated. The Cu-FALC polycrystalline-silicon (poly-Si) film has a crystalline volume fraction of 58% with 300-nm-long, rod-shaped grains. Low-temperature crystallization of a-Si in an electric field appears to be caused by enhanced migration of the Cu ions in the a-Si region.     

Microstructure evolution of amorphous silicon thin films upon annealing studied by positron annihilation

Amorphous silicon (a-Si) thin films were prepared on glass substrates by plasma enhanced chemical vapor deposition (PECVD). Influence of annealing temperature on the microstructure, surface morphology, and defects evolution of the films were studied by X-ray diffraction (XRD), atomic force microscope (AFM) and positron annihilation Doppler broadening spectroscopy (DBS) based on a slow positron beam, respectively. The S parameter of the as-deposited a-Si thin film is high, indicative of amorphous state of Si film with many defects. The a-Si gradually grows into polycrystalline silicon with increasing temperature to 650 °C. For the films annealed below ~450 °C, positron diffusion lengths are rather small because most positrons are trapped in the defects of the a-Si films and annihilated there. With further rising the temperature to 600 °C, the diffusion length of positrons increases significantly due to the removal of vacancy-type defects upon annealing at a high temperature. The results indicate that the coalescence of small vacancy-type defects in a-Si thin film and the crystallization of a-Si occur around 450 °C and 650 °C, respectively.     

Using Phosphorus-Doped α-Si Gettering Layers to Improve NILC Poly-Si TFT Performance

Ni-metal-induced lateral crystallization (NILC) has been utilized to fabricate polycrystalline silicon (poly-Si) thin-film transistors (TFTs). However, the current crystallization technology often leads to trapped Ni and NiSi₂ precipitates, thus degrading device performance. In this study, phosphorus-doped amorphous silicon (p-α-Si) and chemical oxide (chem-SiO₂) films were used as Ni-gettering layers. After a gettering process, the Ni impurity within the NILC poly-Si film and the leakage current were both reduced, while the on/off current ratio was increased. This gettering process is compatible with NILC TFT processes and suitable for large-area NILC poly-Si films.     

Understanding the Effects of Stress on the Crystallization of Amorphous Silicon

This paper presents the results of a systematic study on the effects of stress on aluminum-induced crystallization (AIC) of plasma-enhanced chemical-vapor-deposited (PECVD) amorphous silicon (a-Si:H). To decouple the impact of stress on the AIC of a-Si:H from other factors that may affect crystallization, such as a-Si:H and aluminum deposition conditions, identical thin film structures [Al (200 nm)/a-Si:H (200 nm)] were deposited on the front surface of all samples. On the back surfaces, various amorphous silicon films were deposited to adjust the curvature of the samples and, therefore, the stress in the a-Si:H film on the front surface. It was found that tensile stress in a-Si:H can retard the AIC of a-Si:H.     

The effects of hydrogen on aluminum-induced crystallization of sputtered hydrogenated amorphous silicon

The effects of hydrogen on aluminum-induced crystallization (AIC) of sputtered hydrogenated amorphous silicon (a-Si:H) were investigated by controlling the hydrogen content of a-SiH films. Nonhydrogenated (a-Si) and hydrogenated (a-Si:H) samples were deposited by sputtering and plasma-enhanced chemical vapor deposition (PECVD). All aluminum films were deposited by sputtering. Hydrogen was introduced into the sputter-deposited a-Si films during the deposition. After deposition, the samples were annealed at temperatures from 200°C to 400°C for different periods of time. X-ray diffraction (XRD) patterns were used to confirm the presence and degree of crystallization in the a-Si:H films. For nonhydrogenated films, crystallization initiates at a temperature of 350°C. The crystallization of sputter-deposited a-Si:H initiates at 225°C when 14% hydrogen is present in the film. As the hydrogen content is decreased, the crystallization temperature increases. On the other hand, the crystallization initiation temperature for PECVD a-Si:H containing 11at.%H is 200°C. Further study revealed that the crystallization initiation temperature is a function, not only of the total atomic percent hydrogen in the film, but also a function of the way in which the hydrogen is bonded in the film. Models are developed for crystallization initiation temperature dependence on hydrogen concentration in a-Si:H thin films.     

铝膜沉积温度对铝诱导结晶化多晶硅薄膜性能的影响

以超白玻璃为衬底,采用热丝化学气相沉积法沉积初始非晶硅膜,经自然氧化形成二氧化硅层,最后利用磁控溅射 法在不同衬底温度下沉积铝膜,制备了glass/Si/SiO/Al叠层结构并对其进行铝诱导晶化形成多晶硅薄膜.用X射线衍射,光学显微镜和拉曼光谱对样品进行了分析.结果表明,铝诱导晶化制备的多晶硅薄膜的晶粒大小随着铝膜沉积...     

Electric field-enhanced metal-induced lateral crystallization and P-channel poly-Si TFTs fabricated by it

The poly-Si thin film was obtained by electric field-enhanced metal-induced lateral crystallization technique at low temperature. Raman spectra, X-ray diffraction (XRD) and scan electron microscope (SEM) were used to analyze the crystallization state, crystal structure and surface morphology of the poly-Si thin film. Results show that the poly-Si has good crystallinity, and the electric field has the effect of enhancing the crystallization when DC electric voltage is added to the film during annealing. Secondary ion mass spectroscopy (SIMS) shows that the metal Ni improves the crystallization by diffusing into the a-Si thin film, so the crystallization of the lateral diffused region of Ni is the best. The p-channel poly-Si thin film transistors (TFTs) were fabricated by this large-size grain technique. The I_DS−V_DS and the transfer characteristics of the TFTs were measured, from which, the hole mobility of TFTs was 65 cm²/V s, the on and off current ratio was 5×10⁶. It is a promising method to fabricate high-performance poly-Si TFTs at low temperature for applications in AMLCD and AMOLED.     

Thin-film transistors fabricated with poly-Si films crystallized atlow temperature by microwave annealing

Solid phase crystallization of amorphous silicon films for poly-Si thin film transistors (TFTs) has advantages of low cost and excellent uniformity, but the crystallization temperature is too high. Using a microwave annealing method, we lowered the crystallization temperature and shortened the crystallization time. The complete crystallization time at 550°C was within 2 h. The device parameters of TFTs with the poly-Si films crystallized by microwave annealing were similar to those of TFTs with the poly-Si films crystallized by conventional furnace annealing. The new crystallization method seems attractive because of low crystallization temperature, short crystallization time, and comparable film properties     

Characterization and simulation analysis of laser-induced crystallization of amorphous silicon thin films

The effect of laser energy density on the crystallization of hydrogenated amorphous silicon (a-Si:H) thin films was studied theoretically and experimentally. The thin films were irritated with a frequency-doubled (λ=532 nm) Nd:YAG pulsed nanosecond laser. An effective finite element model was built to predict the melting threshold and the optimized laser energy density for crystallization of intrinsic amorphous silicon. Simulation analysis revealed variations in the temperature distribution with time and melting depth. The highest crystalline fraction measured by Raman spectroscopy (84.5%) agrees well with the optimized laser energy density (1000 mJ/cm²) in the transient-state simulation. The surface morphology of the thin films observed by optical microscopy is in fairly good agreement with the temperature distribution in the steady-state simulation.     

Surface treatment effect on the poly-Si TFTs fabricated by electric field enhanced crystallization of Ni/a-Si:H films

Self-aligned, p-channel polycrystalline silicon thin-film transistors (TFTs) were fabricated by electric field enhanced crystallization of a-Si:H in contact with the Ni catalyst, where a chemical solution of 97.5% H/sub 2/O:1% HF:1.5% H/sub 2/O/sub 2/ was used for a surface treatment on polycrystalline silicon films. The wet surface treatment was found to remarkably improve the electrical properties of TFTs, especially the leakage current and subthreshold slope. The enhanced performance was confirmed to be from the removal of the Ni impurity remaining as defect states at the surface and also from the ameliorated surface roughness of the polycrystalline silicon films.     

A high performance thin-film transistor using a low temperaturepoly-Si by silicide mediated crystallization

Electric field enhanced silicide mediated crystallization (SMC) was introduced for low-temperature polycrystalline silicon thin-film transistors (TFTs) on glass substrates. The amorphous silicon (a-Si) film having an average Ni thickness of 0.15 Å, was completely crystallized at a temperature of 480°C within 30 min in the presence of an electric field of 40 V/cm. The poly-Si is composed of needlelike crystallites with a few μm length and about 50 nm width. The poly-Si TFT using the SMC exhibited a field effect mobility of 86 cm²/Vs, a threshold voltage of -0.6 V, and a subthreshold slope of 0.6 V/dec     

a-SiH 热处理过程中纳米硅粒尺寸的控制(英文)

报道了控制热处理过程中含氢非晶硅中纳米硅颗粒大小的一种新方法。用喇曼散射、X射线衍射和计算机模拟,发现在非晶硅中所形成的纳米硅颗粒的大小,随着热退火过程中升温速率的变化而变化。在退火过程中,若非晶硅薄膜升温速率较高(～100℃/s),则所形成纳米硅粒的大小在1.6～15nm;若非晶硅薄膜升温速率较低(～1℃/s),则纳米硅粒大小在23～46nm。根据晶体生长理论,讨论了升温速率的高低与所形成的纳米硅颗粒大小的关系。     

Fabrication of high-mobility p-channel poly-Si thin filmtransistors by self-aligned metal-induced lateral crystallization

High-mobility p-channel poly-Si TFTs were fabricated using a new low-temperature process (⩽500°C): self-aligned metal-induced lateral crystallization (MILC). With a one-step annealing at 500°C, activation of dopants in source/drain/gate a-Si films as well as the crystallization of channel a-Si films was achieved. The TFTs showed a threshold voltage of -1.7 V, and an on/off current ratio of ~10⁷ without post-hydrogenation. The mobility was measured to be as high as 90 cm²/V·s, which is two to three times higher than that of the poly-Si TFTs fabricated by conventional solid-phase crystallization at around 600°C     

非晶硅薄膜激光晶化及其结构分析

以射频(频率为13.6MHz)磁控溅射系统制备的非晶硅薄膜为前驱物,采用激光晶化技术实现从非晶硅薄膜到纳米晶硅薄膜的相变过程。采用拉曼光谱仪和高分辨透射电镜对激光晶化薄膜的组织结构进行了研究。结果表明:薄膜由非晶硅结构转变为微晶硅结构,微晶硅晶粒尺寸在纳米级。激光晶化存在一个最佳工艺参数,功率太高或太低都不利于晶化。     

Polycrystalline silicon films and thin-film transistors using solution-based metal-induced crystallization

Polycrystalline silicon (poly-Si) films consisting of dish-like and wadding-like domains were obtained with solution-based metal-induced crystallization (SMIC) of amorphous silicon. The Hall mobility of poly-Si was much higher in dish-like domains than in wadding-like domains. Thin-film transistors (TFTs) have been prepared using those two kinds of poly-Si films as the active layer, followed by the phosphosilicate glass (PSG) nickel gettering. The field effect mobility of dish-like domain poly-Si TFTs and wadding-like poly-Si TFTs were 70/spl sim/80 cm/sup 2//V/spl middot/s and 40/spl sim/50 cm/sup 2//V/spl middot/s, respectively. With a multi-gate structure, the leakage current of poly-Si TFTs was reduced by 1 to 2 orders of magnitude. In addition, the gate-induced drain leakage current (GIDL) and uniformity of the drain current distribution were also improved. P-type TFTs fabricated using SMIC exhibited excellent reliability.     

A high-performance polycrystalline silicon thin film transistorwith a silicon nitride gate insulator

We have fabricated a high performance polycrystalline silicon (poly-Si) thin film transistor (TFT) with a silicon-nitride (SiN_x ) gate insulator using three stacked layers: very thin laser of hydrogenated amorphous silicon (a-Si:H), SiN_x and laser annealed poly-Si. After patterning thin a-Si:H/SiN_x layers, gate, and source/drain regions were ion-doped and then Ni layer was deposited. This structure was annealed at 250°C to form a NiSi silicide phase. The low resistive Ni silicides were introduced as gate/source/drain electrodes in order to reduce the process steps. The poly-Si with a grain size of 250 nm and low resistance n⁺ poly-Si for ohmic contact were introduced to achieve a high performance TFT. The fabricated poly-Si TFT exhibited a field effect mobility of 262 cm²/Vs and a threshold voltage of 1 V     

铝诱导晶化法制备多晶硅薄膜

多晶硅薄膜在微电子和能源科学领域有着广泛的应用。本文介绍了利用铝诱导晶化非晶硅制备多晶硅薄膜的方法,叙述了铝诱导晶化法制备多晶硅薄膜的一般过程,着重讨论了铝诱导晶化非晶硅的机理和在制备过程中各种参数对多晶硅薄膜质量的影响。     

非晶硅薄膜YAG激光微晶化晶粒生长研究

以单晶硅(111)为衬底,以等离子体增强化学气相沉积技术制备的非晶硅薄膜为前驱物,采用YAG激光晶化技术实现从非晶硅薄膜到纳米晶硅薄膜的相变过程。采用X射线衍射仪和原子力显微镜对YAG激光晶化薄膜进行了表征与分析。结果表明:薄膜的晶粒尺寸在纳米级;随着激光脉冲频率的增加,晶粒尺寸先变大后变小,其最佳结晶频率区间为10～12 Hz。