Fabrication and Characterization of Hydrogenated Amorphous Silicon Bipolar Thin Film Transistor (B-TFT)

2004 ◽  
Vol 808 ◽  
Author(s):  
Yue Kuo ◽  
Yu Lei ◽  
Helinda Nominanda
Keyword(s):  
Thin Film ◽  
Thin Film Transistor ◽  
Chemical Vapor ◽  
Base Layer ◽  
Current Gain ◽  
Collector Current ◽  
Literature Report ◽  
Small Current ◽  
Operation Speed ◽  
Driving Capability

ABSTRACTThe conventional a-Si:H thin film transistor (TFT) is a field effect transistor (FET), which has disadvantages of a low operation speed and a small current driving capability. To achieve a higher speed and larger current driving capability, a potential solution is to fabricate the a-Si:H-based bipolar thin film transistor (B-TFT). In this study, a-Si:H p-i-n junctions were prepared and studied in order to determine the proper layer thickness for good junction behaviors. B-TFTs composed of a stacked structure of n+/i/p/i/n+ were then fabricated. The complete B-TFT was made using plasma enhanced chemical vapor deposition (PECVD) to deposit all doped and undoped a-Si:H layers and SiNx dielectrics at 250°C. Reactive ion etching (RIE) and wet etching methods were used to define base and emitter regions and contacts. The I-V characteristics of the complete B-TFT were investigated. The common-emitter current gain is 3∼6, which is larger than the literature report of 2∼3. In addition, a collector current larger than the literature value was obtained. A significant current noise was observed, which may be contributed to the high series resistance of the base layer and defective junction interfaces. In this paper, process and structure influences on the a-Si:H junction and B-TFT performances are discussed.

Potential of Hot Wire CVD for Active Matrix TFT Manufacturing

2009 ◽  
Vol 1153 ◽  
Author(s):  
Ruud E.I. Schropp ◽  
Zomer Silvester Houweling ◽  
Vasco Verlaan
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Mass Density ◽  
Thin Film Transistor ◽  
Chemical Vapor ◽  
High Mass ◽  
Hot Wire ◽  
Large Area ◽  
Active Matrix ◽  
Electrical Fields

AbstractHot Wire Chemical Vapor Deposition (HWCVD) is a fast deposition technique with high potential for homogeneous deposition of thin films on large area panels or on continuously moving substrates in an in-line manufacturing system. As there are no high-frequency electromagnetic fields, scaling up is not hampered by finite wavelength effects or the requirement to avoid inhomogeneous electrical fields. Since 1996 we have been investigating the application of the HWCVD process for thin film transistor manufacturing. It already appeared then that these Thin Film Transistors (TFTs) were electronically far more stable than those with Plasma Enhanced (PE) CVD amorphous silicon. Recently, we demonstrated that very compact SiNx layers can be deposited at high deposition rates, up to 7 nm/s. The utilization of source gases in HWCVD of a-Si3N4 films deposited at 3 nm/s is 75 % and 7 % for SiH4 and NH3, respectively. Thin films of stoichiometric a-Si3N4 deposited at this rate have a high mass-density of 3.0 g/cm3. The dielectric properties have been evaluated further in order to establish their suitability for incorporation in TFTs. Now that all TFT layers, namely, the SiNx insulator, the a-Si:H or μc Si:H layers, and the n-type doped thin film silicon can easily be manufactured by HWCVD, the prospect of “all HWCVD” TFTs for active matrix production is within reach. We tested the 3 nm/s SiNx material combined with our protocrystalline Si:H layers deposited at 1 nm/s in ‘all HW’ TFTs. Results show that the TFTs are state of the art with a field-effect mobility of 0.4 cm2/Vs. In order to assess the feasibility of large area deposition we are investigating in-line HWCVD for displays and solar cells.

Taper Angle of Silicon Nitride Thin Film Control by Laser Direct Pattern for Transistors Fabrication

2013 ◽  
Vol 284-287 ◽  
pp. 225-229 ◽  
Author(s):  
Chao Nan Chen ◽  
Jung Jie Huang ◽  
Gwo Mei Wu ◽  
How Wen Chien
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Silicon Nitride ◽  
Laser Irradiation ◽  
Vapor Deposition ◽  
Liquid Crystal Display ◽  
Thin Film Transistor ◽  
Chemical Vapor ◽  
Taper Angle ◽  
Shot Number

Silicon nitride (SiNx), an important material used as a dielectric layer and passivation layer in thin film transistor liquid crystal display (TFT LCD) was patterned by a non-lithographic process. SiNx was deposited by plasma enhanced chemical vapor deposition (PECVD) on glass substrate. Laser photoablation can effectively pattern 5 µm diameter with 200 nm depth hole in SiNx thin films with laser photoablation. The threshold remove fluence is 1350 mJ/cm2 with 1 laser irradiation shot. The contact-hole taper angle as a function of the laser irradiation shot number. The taper angle increased with increasing the laser irradiation shot number. The contact-hole taper angle etched profile was successfully controlled by vary the laser irradiation shot number.

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