Browse Prior Art Database

Photomask Plate Sorting

IP.com Disclosure Number: IPCOM000076933D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Rottmann, HR: AUTHOR

Abstract

In photomask fabrication and wafer exposure systems, not only is the distortion of the wafer topography a key variable but the degree of flatness of the mask which is used is also an important variable. For example, most commercial precision flat plates have a surface waviness of between approximately 150 to 500 microinches. Presently the so-called precision flat plates are utilized indiscriminately for all masking levels fabrication. A system is described below for plate sorting so that the less wavy surfaces may be paired with critical mask levels.

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Photomask Plate Sorting

In photomask fabrication and wafer exposure systems, not only is the distortion of the wafer topography a key variable but the degree of flatness of the mask which is used is also an important variable. For example, most commercial precision flat plates have a surface waviness of between approximately 150 to 500 microinches. Presently the so-called precision flat plates are utilized indiscriminately for all masking levels fabrication. A system is described below for plate sorting so that the less wavy surfaces may be paired with critical mask levels.

As illustrated in the drawing, a plate 10 having a lower surface 11 (having an exaggerated waviness) is shown in the drawing as being mounted on supports 12 (preferably three adjustable supports) extending from a stable platform 13. A plurality of sensors, such as air sensors 14, project from the platform to indicate the distance from the end of the sensor 14 to the adjacent portion of the surface 11 of the plate 10. The sensors 14 may be connected to a processor 15 into which is placed a particular specification to be used as the reference, such as a suitable encoder 16, for dialing the specification into the system. The processor may include a numeric readout 17 which indicates, in microinches for example, the worst case of waviness on the plate 10 by the readout at 17A, the second worse case at 17B and the reference at 17C. Additionally, the processor may be connected to a television displa...