Browse Prior Art Database

Hydraulic Electric Positioning System

IP.com Disclosure Number: IPCOM000076994D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 67K

Publishing Venue

IBM

Related People

Stuckert, PE: AUTHOR

Abstract

Step and repeat exposure systems require the successive positioning of a table (or carriage) on which a semiconductor wafer (or mask) which is to be exposed is mounted. Positioning, in the complete sense, requires orientation of the wafer area to be exposed relative to the exposing image in terms of six orientation parameters, i.e., X, Y, Z, alpha, beta, upsilon. The hydraulic-electric positioning (HEP) system described below is particularly suitable for, but not confined to, "closed-loop" positioning systems, i.e., systems in which the position of the wafer (in terms of the six orientation parameters, above) relative to the exposing image is known (or knowable) from position-error signals which, in turn, can be used to effect corrective operation of the positioning system.

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Hydraulic Electric Positioning System

Step and repeat exposure systems require the successive positioning of a table (or carriage) on which a semiconductor wafer (or mask) which is to be exposed is mounted. Positioning, in the complete sense, requires orientation of the wafer area to be exposed relative to the exposing image in terms of six orientation parameters, i.e., X, Y, Z, alpha, beta, upsilon. The hydraulic-electric positioning (HEP) system described below is particularly suitable for, but not confined to, "closed-loop" positioning systems, i.e., systems in which the position of the wafer (in terms of the six orientation parameters, above) relative to the exposing image is known (or knowable) from position-error signals which, in turn, can be used to effect corrective operation of the positioning system. The desirable characteristics of such a positioning system are: 1) Fast stepping (or slewing) between successive exposure positions. 2) Accurate positioning at each exposure position. 3) Absence of potential contaminants in the vicinity of the semiconductor wafer. 4) Minimization or absence of electric, magnetic, thermal, or sonic fields in the vicinity of the wafer. 5) Operable in diverse ambient atmospheres or in a vacuum. 6) Small size of system components which must be located in the vicinity of the wafer.

The following description is confined to a system for positioning in one orientation parameter only (specifically, X), it being obvious that the techniques applicable to one parameter can, by replication, be extended to any or all six parameters. Fig. 1 is a sketch showing the components of the system wherein, since the system is symmetrical, the subscripts "L" and "R" indicate identical left and right components: W - The semiconductor wafer, which is to be subjected to the step and repeat exposure process and which is affixed to T - The table (or carriage) which is mounted on ways or rails, wherein "X" indicates the directions of motion imparted by R - A rod or other suitable member, the lower end of which is held in compression between the movable faces of B - Bellows (or rams) with an effective diameter D2, which are filled with and actuated by a suitable hydraulic fluid under pressure, and where the volumetric content of the bellows is controlled by the remaining components of the system to position R, T, and W. A - Auxiliary bellows which may be included to prevent contamination in the event of leakage from B, and which may also function as a gas barrier if T is to be operated in a nonatmospheric or vacuum environment. C - A cylinder...