Patent ID: 6067306
Filing Date: 2000-05-23
Classification: G03F,H01S

Abstract:
A semiconductor wafer fabrication system comprising:a laser having a pulse power system for producing laser light pulses P.sub.1, P.sub.2, . . . P.sub.N-1, P.sub.N, said pulse power system having a high voltage charging system defining a charging voltage,a wafer exposing system which receives light pulses generated by said laser, said exposing system providing optical elements between said laser and a mask, wherein said optical elements cause said light pulses emitted by said laser to be attenuated prior to impinging upon said mask;a first light intensity detector positioned within said exposing system so as to receive at least a portion of laser light pulses exiting at least one of said optic elements and prior to said light pulses impinging upon said mask;a second light intensity detector positioned proximate to said laser so as to receive at least a portion of laser light pulses output from said laser,outputs of at least one of said first light intensity detector and said second light intensity detector, being used to control an exposure of a semiconductor wafer to laser light;a processor programmed with an algorithm for controlling pulse energy and integrated energy dose in a dose of pulses defining present burst pulses, P.sub.1, P.sub.2 . . . P.sub.N-1, P.sub.N, from said laser having a pulse power system including a high voltage charging system defining a charging voltage, said algorithm comprising the steps of:A) measuring the energy of each pulse in said burst of pulses,B) determining a rate of change of pulse energy with charging voltage, dE/dV,C) controlling the pulse energy of each pulse P.sub.N in at least one plurality of pulses in said burst of pulses by regulating the charging voltage of the laser utilizing a computer processor programmed with an algorithm which:1) determines for each P.sub.N a pulse energy error, .epsilon. based on a measured energy of at least one previous pulse in said burst and a predetermined target pulse energy value,2) determines for each P.sub.N+1 an integrated dose error, D, of all previous pulses, P.sub.1 through P.sub.N, in said burst,3) determines a charging voltage, V.sub.N+1, for each of said pulses, P.sub.N+1, in said first plurality of pulses using:i) said dE/dVii) said Eiii) said Div) at least one reference voltage.