US 12,261,407 B2
Control method and system for stabilizing excimer laser pulse energy
Zebin Feng, Beijing (CN); Xiaoquan Han, Beijing (CN); Rui Jiang, Beijing (CN); Junhong Yang, Beijing (CN); Hua Zhang, Beijing (CN); Qin Zhang, Beijing (CN); Xiang Wang, Beijing (CN); and Mi Liao, Beijing (CN)
Assigned to Beijing Rslaser Opto-Electronics Technology Co., Ltd., Beijing (CN)
Filed by BEIJING RSLASER OPTO-ELECTRONICS TECHNOLOGY CO., LTD., Beijing (CN)
Filed on Jul. 30, 2021, as Appl. No. 17/389,400.
Application 17/389,400 is a continuation of application No. PCT/CN2019/076110, filed on Feb. 26, 2019.
Claims priority of application No. 201910122841.2 (CN), filed on Feb. 19, 2019.
Prior Publication US 2021/0359487 A1, Nov. 18, 2021
Int. Cl. H01S 3/134 (2006.01); H01S 3/13 (2006.01); H01S 3/225 (2006.01)
CPC H01S 3/134 (2013.01) [H01S 3/1305 (2013.01); H01S 3/225 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A control method for stabilizing excimer laser pulse energy, wherein an excimer laser is used to emit a plurality of pulse sequences, where each pulse sequence contains a plurality of pulses, and an energy level of each pulse is controlled by limiting a corresponding discharge voltage value of the pulse, where the discharge voltage value is calculated by a proportional-integral (PI) control algorithm, the control method comprising:
obtaining a measured energy value of an n-th pulse in an m-th pulse sequence;
calculating a difference between the measured energy value and a preset energy value;
when n is a positive integer less than z, estimating the discharge voltage value of an (n+1)th pulse in the m-th pulse sequence according to a first mathematical model, wherein the z is an integer that lies in the range of 10 to 100;
when n is an integer greater than (z−1), estimating the discharge voltage value of the (n+1)th pulse in the m-th pulse sequence according to a second mathematical model; and
generating the (n+1)th pulse in the m-th pulse sequence according to the discharge voltage value;
where m is an integer greater than 1;
wherein the first mathematical model is expressed in the following formula (1):

OG Complex Work Unit Math
where Eerror(m−1, n+1) represents the difference between the measured energy value and the preset energy value of the (n+1)th pulse in the (m−1)th pulse sequence, Σi=1m-1Eerror(i, n+1) represents a sum of the difference between the measured energy value and the preset energy value of each (n+1)th pulse in the 1st˜(m−1)th pulse sequences, PKp1 is a proportional parameter of the PI control algorithm, PK1 is an integral parameter of the PI control algorithm, and PT1 is a control period parameter of the PI control algorithm;
wherein an incremental form of the first mathematical model is expressed in the following formula (2):

OG Complex Work Unit Math
where ΔHV(m, n+1) represents an amount of change between the discharge voltage value of the (n+1)th pulse in the m-th pulse sequence and the (n+1)th pulse in the (m−1)th pulse sequence, Eerror(m−1, n+1) is the difference between the measured energy value and the preset energy value of the (n+1)th pulse in the (m−1)th pulse sequence, Eerror(m−2, n+1) is the difference between the measured energy value and the preset energy value of the (n+1)th pulse in the (m−2)th pulse sequence, PKp1 is the proportional parameter of the PI control algorithm, PK1 is the integral parameter of the PI control algorithm, and PT1 is the control period parameter of the PI control algorithm;
wherein the discharge voltage value of the (n+1)th pulse in the m-th pulse sequence is expressed in the following formula (3):
HV(m,n+1)=HV(m−1,n+1)+ΔHV(m,n+1)  (3)
where HV(m−1, n+1) is the discharge voltage value of the (n+1)th pulse in the (m−1)th pulse sequence.