Browse Prior Art Database

TFT/LCD Damascene Scan Lines

IP.com Disclosure Number: IPCOM000035902D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Kuo, Y: AUTHOR [+2]

Abstract

Disclosed is a set of process steps for fabricating planarized metallic lines of arbitrary thickness to be used as the scan lines in thin film transistor/liquid crystal displays (TFT/LCDs).

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 81% of the total text.

Page 1 of 2

TFT/LCD Damascene Scan Lines

Disclosed is a set of process steps for fabricating planarized metallic lines of arbitrary thickness to be used as the scan lines in thin film transistor/liquid crystal displays (TFT/LCDs).

The RC time constant for the scan lines of a TFT/LCD array can impose a serious design constraint. Scan line delay can cause incomplete sampling of the data intended for cells at the far end of the line being scanned as well as erroneous sampling of the next line to be scanned. This problem is aggravated by larger displays (longer display lines), by video rates on the data lines (smaller error margins for the pulses being driven down the lines), and by gray scale data (smaller error margins for the charge stored in the cell).

Simply increasing the scan line thickness to reduce the RC time constant causes insulator step coverage problems in the inverted TFT structures commonly used. What is needed is a "buried gate" structure with a planar top surface. Basically this is accomplished by creating a trench to receive the scan line metal, depositing the metal, and then planarizing it.

The desired scan line pattern is etched into a blanket layer of transparent insulator deposited on a glass substrate. This etched pattern is then covered by a thin, deposited layer of metal, such as chrome or tantalum, which acts as an adhesion layer. This is followed by a layer of scan line metal, such as copper, some 20% to 30% thicker than the trench depth (Fig. 1). Che...