Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Optical Postcontact Alignment Method

IP.com Disclosure Number: IPCOM000088767D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Lin, BJ: AUTHOR

Abstract

In conformable lithography, after the mask and wafer are brought into contact, fine alignment correction is achieved by inclining the incident light from the normal such that the finite thickness of the photoresist between the mask and substrate displaces the image so as to correct alignment.

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 64% of the total text.

Page 1 of 2

Optical Postcontact Alignment Method

In conformable lithography, after the mask and wafer are brought into contact, fine alignment correction is achieved by inclining the incident light from the normal such that the finite thickness of the photoresist between the mask and substrate displaces the image so as to correct alignment.

After the mask and wafer are aligned to the best accuracy mechanically achievable at optimum separation without iteration or a servo mechanism, they are brought into contact and no more relative movement is required. The displacements between alignment marks are measured with a microscope o determine the amount of x and y translation and the amount of rotation ordinarily required for exact alignment. With knowledge of the photoresist thickness, the incident plane wave is then tilted from the vertical by an angle such that the required x and y translation of the image occurs.

Fig. 1 illustrates a translation in one direction. To move the image by 0.5 micron when the photoresist thickness is 1 micron, for example, requires the tilting of the mirror by slightly more than 13 degrees from the usual 45-degree orientation. This produces a 26-degree-from-vertical incident beam. The mirror must also be translated slightly to keep the wafer covered by the beam.

Rotational fine correction will not be required ordinarily. However, rotational fine correction also may be achieved optically by inserting a spiral prism in the optical beam. Such a prism h...