Claims
- 1. 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/dV
- ii) said E
- iii) said D
- iv) at least one reference voltage.
- 2. The system of claim 1 wherein said exposing system is a stepper.
- 3. The system of claim 1 wherein said exposing system is a scanner.
- 4. A system as in claim 3 wherein said algorithm contains a routine to calculate a dose value for each of a plurality of spaces on said wafer representing the integrated pulse energy of all pulses illuminating each of said plurality of spaces.
- 5. The system of claim 1 both said first detector and said second detector are used in conjunction with each other to control said exposure.
- 6. The system of claim 1 wherein said measured energy is energy measured by said first light intensity detector.
- 7. The system of claim 6 wherein said algorithm comprises the steps of using pulse energy measured with said second light intensity detector to determine if pulse energy as measured by said light detector is within a predetermined range.
- 8. The system of claim 1 wherein said at least one previous pulse is P.sub.N-1 and said reference voltage is a charging voltage specified for producing said P.sub.N-1 in the present burst.
- 9. The system of claim 1 wherein said present burst follows and defines a plurality of previous bursts and said at least one previous pulse is P.sub.N and said reference voltage is calculated based on charging voltage values determined for P.sub.N+1 in each of a plurality of previous bursts.
- 10. The system of claim 9 wherein said rate of change of pulse energy with charging voltage is determined by taking an average of a plurality of most recent values of said rate of change.
- 11. The system of claim 1 wherein said present burst follows and defines a plurality of previous bursts, said at least one previous pulse is P.sub.N and said at least one plurality of pulses is two pluralities of pulses, defining a first plurality of pulses and a second plurality of pulses, a first reference voltage and a second reference voltage, wherein said first reference voltage is a charging voltage determined using data from P.sub.N+1 of a previous burst and said second reference voltage is a charging voltage determined using data from P.sub.N of the present burst.
- 12. The system of claim 11 wherein said algorithm comprises at least three converging factors.
- 13. The system of claim 1 wherein said rate of change of pulse energy with charging voltage is determined periodically using at least two measured values of pulse energy obtained during bursts each of said at least two measured values corresponding to a different value of charging voltage.
- 14. The system of claim 1 wherein said rate of change of pulse energy with charging voltage is determined once during each of series of bursts.
- 15. The system of claim 1 wherein said rate of change of pulse energy with voltage is determined using a plurality of measured values of pulse energy and a specified value of charging voltage corresponding to each measured value of pulse energy in said plurality of measured values of pulse energy.
- 16. A process as in claim 15 wherein said algorithm further comprises at least three converging factors each having values between 0 and 1.
- 17. The system of claim 1 wherein said rate of change of pulse energy with voltage is determined using a plurality of measured values of pulse energy and a measured value of charging voltage corresponding to each measured value of pulse energy in said plurality of measured values of pulse energy.
- 18. The system of claim 1 wherein said algorithm comprises at least two converging factors.
- 19. The system for controlling pulse energy and integrated energy dose in a burst of pulses defining present burst pulses, P.sub.1, P.sub.2 . . . P.sub.N, P.sub.N+1 . . . P.sub.F from said excimer 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 the first K pulses, defining P.sub.k 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+1 a pulse energy error, E, 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/dV
- ii) said E
- iii) said D
- iv) a reference voltage based on specified voltages for P.sub.N+1 in a plurality of previous bursts,
- D) controlling the pulse energy of each pulse P.sub.N+1 in pulses following P.sub.k 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+1 a pulse energy error, E, 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/dV
- ii) said E
- iii) said D
- iv) a reference voltage based on a specified voltage for pulse P.sub.N.
Parent Case Info
This invention is a continuation-in-part of Ser. No. 09/034,870, Pulse Energy Control for Excimer Lasers, filed Mar. 4, 1998, now U.S. Pat. No. 6,005,879, and Ser. No. 08/908,862, Stepper or Scanner Having Two Energy Monitors for a Laser, filed Aug. 8, 1997.
Non-Patent Literature Citations (2)
Entry |
K. Suzuki, et al., "Dosage Control for Scanning Exposure with Pulsed Energy Fluctuation and Exposed Position Jitter",Jpn. J. Appl. Phys. vol. 34 (1995),pp. 6565-6572, no month. |
G. deZwart, et al., "Performance Of A Step And Scan System For DUV Lithography",SPIE Symposium on Optical Microlithography,Mar. 1997, pp. 1-19. |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
034870 |
Mar 1998 |
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