Browse Prior Art Database

Processes for Making Complete Self-Aligned, Tri-Layer Thin Film Transistors

IP.com Disclosure Number: IPCOM000102534D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Kuo, Y: AUTHOR

Abstract

Disclosed is a tri-layer thin film transistor (TFT) structure with its processing methods that need only two masks.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 70% of the total text.

Processes for Making Complete Self-Aligned, Tri-Layer Thin Film Transistors

       Disclosed is a tri-layer thin film transistor (TFT)
structure with its processing methods that need only two masks.

      Fig. 1 shows the structure of the tri-layer inverted, staggered
thin film transistors.  To manufacture this kind of transistor,
conventionally, it requires at least three masks: one for the gate
(GATE mask), one for the top dielectric (ETCH STOP mask), and one for
the N+ and the top metal (TOP METAL mask).  The alignment of the ETCH
STOP mask is critical, because it determines the source and drain
contact areas.  When the gate is narrow, e.g., equal to or less than
6 m, the ETCH STOP  mask is difficult to align and to define with
current commercial large area aligners.  That is because the sum of
1) the layer- to-layer alignment tolerance of the aligner, 2) the
source or drain opening width, and 3) the etch stop pattern width is
usually greater than 6 m.  Slight misalignments of the ETCH STOP mask
may cause the asymmetry of the source and the drain areas.  With the
process disclosed in Fig. 2, the whole TFT can be made with only two
masks: the GATE and the TOP METAL masks.  The source-drain mask (or
the ETCH STOP mask) is eliminated. The source and drain areas are
always symmetrical because of the self-alignment nature of this
process.  Since no alignment of the ETCH STOP mask is needed, the
layer-to-layer misalignment is zero and the gate size can be sm...