Materials and Technologies for High-Mobility TFTs for Liquid Crystal Display-Bus Drivers

Información del proyecto

Identificador del acuerdo de subvención: 491

Proyecto cerrado

Fecha de inicio 1 Junio 1985

Fecha de finalización 1 Junio 1990

Financiado con arreglo a

• European programme (EEC) for research and development in information technologies (ESPRIT), 1984-1988

Coste total

Sin datos

Aportación de la UE

Sin datos

Coordinado por

AEG Olympia AG
Germany

Objetivo

The objective of this project was to develop polycrystalline silicon thin films and technologies for column bus drivers and line bus drivers to replace external chemical vapour deposition (IC) for peripheral driver circuits of active matrix liquid crystal displays (LCD). The main task was to develop a low temperature deposition process for the thin semiconductor films compatible with the glass substrates used for the LCD. The investigated deposition processes were plasma enhanced chemical vapour deposition (CVD) and electron gun evaporation, whereas low pressure CVD was used to establish the thin film transistors (TFT) process technology. Furthermore, elementary TFT circuits, suitable for bus driver shift registers, were investigated and developed. Driver prototypes of short length were also combined with LCD matrices and tested.
technologies can also affect other applications in large-area microelectronics, such as motionless scanners.
The objective of this project was to develop polycrystalline silicon(pSi) thin films and technologies for column-bus and line-bus drivers to replace external ICs for peripheral driver circuits of active matrix liquid crystal displays(LCDs).
The main task was to develop a low-temperature deposition process for the thin semiconductor films compatible with the glass substrates used for the LC display. The investigated deposition processes were Plasma Enhanced CVD and Egun evaporation, whereasLow Pressure CVD was used to establish the TFT process technology. Furthermore, elementary TFT circuits, suitable for bus driver shift registers, were investigated and developed. Driver prototypes of short length were also combined with LCD matrices and tested.
Progress and Results
The following results were achieved:
-Polycrystalline Si films prepared below 600 oC on borosilicate glasses were processed to produce TFTs.
-TFTs, prepared from Egun Si films deposited at 550 oC, used an atmospheric pressure CVD-deposited SiO2 layer. These TFTs showed field effect mobilities up to 16cm2/V and enabled a better yield than TFTs using plasma-processed gate insulators.
-With PECVD, the capability exists to prepare Si3N4 transistors with field effect mobilities up to 35 cm2/Vs in Silayers.
Using these deposition processes there is no need to use the costly process of ion implantation to obtain TFTs with the requested characteristics. Furthermore, at the above-mentioned deposition temperatures high-quality glass substrates can be used instead of the expensive quartz substrates needed for higher temperatures. Nevertheless, additional investigation will be necessary to reduce the deposition temperature to values where cheap soda lime glass substrates can be used.
A new TFT-equivalent circuit was inserted into the SPICE simulation programme, from which a five-level inverter with static TFTs could be simulated. Tests of the dynamic behaviour of this programme were performed, and good correlation with actual TFT was found.
Although the project was originally planned to last 5years, it stopped after in May1988, after only 3 years, by common agreement between the partners, following the decision of CNET to work on a production line in a competitive environment using some ofthe initial results (two-masks process for TFT manufactured with LPCVD-deposited pSifilms).
The goal expected for the end of the project (mid-1990), ie driver circuits on soda lime glass able to address a 300x300pixels LCD matrix with a resolution of 4pixels per millimetre, has obviously been not achieved. But the work scheduled for the lasttwo years in this project is now a part of the ongoing ESPRITproject on Active Matrix LCDs (number 2283). It is included in this new project as a specific task to be carried out by the same companies, AEG and CETIA.

Ámbito científico (EuroSciVoc)

• ingeniería y tecnología › ingeniería de materiales › recubrimiento y películas
• ciencias naturales › ciencias físicas › electromagnetismo y electrónica › dispositivo semiconductor
• ciencias naturales › ciencias físicas › electromagnetismo y electrónica › microelectrónica
• ciencias naturales › ciencias químicas › química inorgánica › metaloides
• ingeniería y tecnología › ingeniería de materiales › cristal líquido

Programa(s)

• FP1-ESPRIT 1 - European programme (EEC) for research and development in information technologies (ESPRIT), 1984-1988

Tema(s)

Datos no disponibles

Convocatoria de propuestas

Datos no disponibles

Régimen de financiación

Datos no disponibles

Coordinador

AEG Olympia AG

• Aportación de la UE: Sin datos
• Dirección: Goldsteinstraße 235 ; 60528 Frankfurt am Main ; Alemania
• Coste total: Sin datos

Participantes (3)

CNET France Télécom

Francia

• Aportación de la UE: Sin datos
• Dirección: 2 route de Tregastel ; 22300 Lannion
• Coste total: Sin datos

Compagnie de Signaux et d'Équipements Électroniques (CSEE)

Francia

• Aportación de la UE: Sin datos
• Dirección: Rue Marcelin Berthelot Zone Industrielle Toulon Est ; 83088 Toulon
• Coste total: Sin datos

THOMSON CETIA

Francia

• Aportación de la UE: Sin datos
• Dirección: RUE MARCELIN BERTHELOT ; 83078 TOULON
• Coste total: Sin datos