Theodore J Cosby

US Patent:

57739510, Jun 30, 1998

Filed:

Mar 25, 1996

Appl. No.:

8/621494

Inventors:

Paul S. Markowski - San Jose CA
Theodore J. Cosby - San Jose CA

Assignee:

Digital Test Corporation - San Jose CA

International Classification:

G05B 1132

US Classification:

318625

Abstract:

A wafer prober for testing uncut die of a semiconductor wafer has an alignment accuracy in the X-Y plane within the sub-micron range. The wafer, held by a chuck, is positioned in the X-Y plane by using a pair of linear servo motors each driven by a servo drive unit providing drive control, monitoring and diagnostic functions. Positional information is obtained from a pair of linear encoders, one along each drive axis. Positional information is also obtained from a pair of resolvers, one for the vertical axis and the other for rotational position about the vertical axis. Ways and runner blocks are used to provide substantial downforce capability and high speed translational movement. In addition, the present invention uses a general purpose computer providing for an on-board controller card interfacing with the servo drives via a fiber optic coupler. Wafers are automatically loaded onto the chuck by an on-board juke box-type loader capable of handling wafer sizes of between four (4) and twelve (12) inches in diameter.