Browse Prior Art Database

Measurement Method of Differential Overlay Accuracy

IP.com Disclosure Number: IPCOM000118556D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Odagiri, T: AUTHOR [+2]

Abstract

Disclosed is a program for an accurate measurement method of differential overlay for array process of liquid crystal display. A screen of a large display is exposed by step and repeat. The differential overlay consists of screen stitching (same layer) and layer-to-layer overlay. This method uses a square pattern in the test pattern area.

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Measurement Method of Differential Overlay Accuracy

      Disclosed is a program for an accurate measurement method of
differential overlay for array process of liquid crystal display.  A
screen of a large display is exposed by step and repeat.  The
differential overlay consists of screen stitching (same layer) and
layer-to-layer overlay.  This method uses a square pattern in the
test pattern area.

      As shown in Fig. 1, the square pattern is designed an upper
layer (1) smaller and a lower layer (2) larger.  The difference of
the center position of an upper layer (1) and a lower layer (2) is
detected as overlay.

      Fig. 2 shows the arrangement of the square pattern in a glass
substrate.  The difference of the overlay values of position (3) and
position (4) is detected as the differential overlay.

     Fig. 2 Example of Four Displays in a Glass Substrate and Four
Screens in a Display

This method has the following advantages:
  1.  The measurement error is decreased from 40% to under 10%.
  2.  The measurement accuracy is improved from 1.0um to 0.6um
       (3sigma).
  3.  This method is effective for larger display and for larger
       glass substrate.