Abstract:
The pulsed laser control system comprises a plurality of controllers ( 2 ) through ( 6 ) for controlling devices ( 21 ) through ( 30 ) constituting the pulsed laser apparatus ( 1 ); parallel communication lines (P 1 ) to (P 4 ) for parallel connection of the plurality of controllers ( 2 ) through ( 6 ); an Ethernet (S) for serial connection of the plurality of controllers ( 2 ) through ( 6 ); parallel communication line (PP) for parallel connection between the external apparatus ( 10 ) and the main controller ( 2 ); and an Ethernet (SS) for serial connection between the external apparatus ( 10 ) and the main controller ( 2 ); wherein the parallel communication lines (P 1 ) to (P 4 ) and (PP) transmit signals for which realtime performance is required. With this construction, even if design changes are frequently made to a pulsed laser apparatus, the changes can be made easily and with little expansion space. Moreover, management of the devices constituting the pulsed laser apparatus can be easily performed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     The present invention relates to a pulsed laser control system for controlling a highly repetitive pulsed laser, such as an excimer laser. 
     2. Description of the related art 
     Generally, reducing projection aligners (steppers) use laser beams in the ultraviolet range such as excimer laser beams and the like. When a pulsed laser apparatus such as excimer laser device is used in steppers, such apparatus must be controlled for each pulse because highly stabilized laser beam output is required for the steppers. 
     FIG. 9 shows a general configuration of the laser control system in a conventional pulsed laser apparatus. In FIG. 9, a main controller  102  effects centralized control of devices  121  through  130  constituting a pulsed laser apparatus  102 . 
     The main controller  102  comprises an interface  102   i  and is connected to an external apparatus  110 , such as a stepper, by means of the interface  102   i . The external apparatus  110  comprises a controller  111  for controlling the external apparatus  110 , and a management device  112  for managing the external apparatus  110  as well as the pulsed laser apparatus  101 . The external apparatus  110  and the pulsed laser apparatus  101  are connected by a parallel communication line  103  and a serial communication line  104  such as RS232C. 
     With reference to FIG. 10, a particular configuration of the laser control system is explained for the case where the external apparatus  110  is a stepper and the pulsed laser apparatus  201  is an excimer laser device. Laser chamber  202  comprises a laser discharge unit LD serving as discharge electrodes in which positive and negative electrodes are arranged in opposition to each other and perpendicularly to this drawing, and laser medium gas comprising halogen gas, noble gas, buffer gas or the like filling the laser chamber  202  is excited by discharge between the electrodes in the laser discharge unit LD so that laser oscillation is effected. 
     Windows  204  are provided in both laser radiation apertures of the laser chamber  202 . Also, a front mirror  205  is provided on the laser beam output side of the laser chamber  202 . Further, a band-narrowing module  206  is provided on the side facing a front mirror  205 . The band-narrowing module  206  comprises an optical beam-expanding system  20 , a mirror  208 , a grating  209  that is an angular distributed wavelength selecting element, and a mirror adjuster  210 . 
     An optical cavity is formed between the front mirror  205  and grating  209 . The mirror adjuster  210  adjusts the angle of incidence of the laser beam striking the grating  209  by adjusting the angle of the mirror  208 . The wavelength selection adjustment of the grating  209  including this mirror adjustment is effected under control by the main controller  230 . This control by the controller  230  is effected on the basis of the results of monitoring the laser output beam by a monitor module  220 , which will be discussed below. 
     Laser beam generated in the laser chamber  202  strikes the band-narrowing module  206 . More particularly, the laser beam strikes the optical beam-expanding system  207 , by which the beam width is expanded in the direction perpendicular to the discharge direction thereof. Furthermore, the laser beam strikes the grating  209  and is diffracted thereby. As a result, only the part of the laser beam with the prescribed wavelength is turned back in the same direction as the incident beam. The beam width of the laser beam turned around by the grating  209  is reduced by the optical beam-expanding system  207  and then the laser beam enters the laser chamber  202 . The laser beam is then passed through the laser chamber  202  and amplified. A part of such laser beam is extracted via the front mirror  205  as an output beam, while the remainder is again returned to the laser chamber  202  and amplified. 
     On the laser beam output side, a beam splitter  211  is provided for splitting a part of the laser beam output from the front mirror  205 , so that the laser beam extracted by the beam splitter  211  is input to a monitor module  220 . The monitor module  220  detects the beam width, output intensity, and, if necessary, beam profile of the input laser beam, and sends the detected data to the main controller  230 . The main controller  230  effects control of the band-narrowing module  206  and the pulsed laser power source device  240  on the basis of these detection results. 
     When the pulsed laser apparatus  201  actually effects highly repetitive pulsed oscillation continuously, a laser beam emission signal and energy signal are sent from a stepper controller  302 . The main controller  230  controls the mirror adjuster  210  and the pulsed laser power source device  240  to cause pulse oscillation based on these signals. This control is carried out for each pulse. 
     However, in the conventional pulsed laser control system discussed above, all the devices  121  through  130  within the pulsed laser apparatus  101  are controlled in a centralized manner by the main controller  102  only. Therefore, the load is too large for the main controller to effect control for each pulse. In the event that a design change or the like is to be made in the pulsed laser apparatus  101 , such load limitations and limitations to expansion hinder construction of an adequate pulsed laser control system and, in addition, considerable work and time are required for the design changes. 
     Also, in the conventional pulsed laser control system, although centralized control is carried out by the main controller  102 , the connections to each device are made by buses between the boards, and a harness is laid round for that purpose. The space within the housing of the pulsed laser apparatus  101  is therefore limited and it is not possible to ensure sufficient space required for the design changes. 
     Furthermore, because the status log of the pulsed laser apparatus  101  is captured by downloading directly from the pulsed laser apparatus  101 , time and efforts are required for the management processing for the pulsed laser apparatus  101 . 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a pulsed laser control system that resolves these problems, with which changes can be made easily and within a small expansion space, even if design changes are frequently made in the pulsed laser apparatus, and that can easily effect management of the devices constituting the pulsed laser apparatus. 
     The pulsed laser control system according to the present invention comprises: a plurality of controllers for controlling each of the devices constituting a pulsed laser apparatus; a main controller for controlling the abovementioned plurality of controllers and external apparatus; parallel communication means for parallel communication connections between the abovementioned plurality of controllers and the abovementioned main controller; and serial communication means for serial communication connections between the abovementioned plurality of controllers and the abovementioned main controller by means of a serial network; wherein the abovementioned parallel communication means transmit signals for which realtime performance is required. 
     With the present invention, the load for controlling the pulsed laser apparatus is distributed among the main controller and the plurality of controllers. Signals for which realtime performance is required are transmitted at a high speed using parallel communication means. The main controller and the plurality of controllers are connected on a network by serial communication means such as Ethernet, for example. As a result, changes involving increase or reduction in [the number of] devices can be handled flexibly and easily. 
     Also, the space used for the purpose of control within the pulsed laser apparatus is reduced. This can contribute to the realization of compact pulsed laser apparatus. 
     Furthermore, because the distances of connection from the main controller and plurality of controllers to the devices connected thereto becomes short, good communication can be realized without the need of worrying about the effects of noise or the like. 
     In the pulsed laser control system according to the second invention, the parallel communication means and the serial communication means are both connected to the external apparatus. 
     With the second invention, in addition to the operating effects of the first invention, it is made possible to transmit signals, for which real time performance is required, at a high speed from the external apparatus by the parallel connection to the external apparatus. Also, management of the pulsed laser apparatus can be performed remotely because the external apparatus can be connected to a network by serial communication means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the configuration of a pulsed laser control system according to an embodiment of the present invention; 
     FIG. 2 shows an example of communications processing among the controllers during laser emission; 
     FIG. 3 shows an example of communications processing among the controllers during laser emission; 
     FIG. 4 shows an example of communications processing among the controllers during laser emission; 
     FIG. 5 shows an example of communications processing among the controllers during laser emission; 
     FIG. 6 shows an example of communications processing among the controllers during error detection; 
     FIG. 7 shows an example of communications processing among the controllers relating to the acquisition of log data; 
     FIG. 8 shows an example of communications processing for realtime acquisition of the status of changes in beam quality during laser emission; 
     FIG. 9 is a drawing showing the configuration of a conventional pulsed laser control system; and 
     FIG. 10 is a drawing a showing a specific example to which the conventional pulsed laser control system is applied. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, an embodiment of the present invention is explained with reference to the accompanying drawings. 
     FIG. 1 is a drawing showing the configuration of a pulsed laser control system that is an embodiment of the present invention. In FIG. 1, the pulsed laser apparatus  1  realized by an excimer laser or the like is connected in serial communication to an external apparatus  10  realized by a stepper or the like by means of a serial communication line SS such as Ethernet which is a serial communications network. The pulsed laser apparatus is also connected in parallel communication to the external apparatus  10  by means of a parallel communication line PP. 
     The pulsed laser apparatus  1  comprises a main controller  2  connected to device  21 , a wavelength controller  3  connected to devices  22  through  24 , an energy controller connected to devices  25 ,  26 , a utility controller  5  connected to devices  27  through  29 , and an option controller  6  connected to device  30 . The devices are a pulsed power source device and so on constituting the pulsed laser apparatus  1 . The main controller  2  comprises an interface  2   i  for connecting the abovementioned serial communication line SS and parallel communication line PP. 
     An Ethernet S is constituted within the pulsed laser apparatus  1  and the controllers  2  through  6  are thereby connected in serial communication at a high speed. Also the controllers  2  through  6  are connected in parallel communication by means of parallel communication lines P 1  to P 4 . 
     The wavelength controller  3  monitors the wavelength, beam width, and so forth of the current laser beam, for example, and controls the wavelength based on these monitoring results. The energy controller  4  calculates the necessary energy for the pulsed laser power source device. The utility controller  5  monitors and controls the status of a prescribed device. The option controller  6  controls newly added optional functions. 
     On the other hand, the external apparatus  10  comprises a controller  11 , realized by a stepper controller or the like, and a management device  12  for controlling the pulsed laser apparatus  1  and external apparatus  10  itself. 
     An example of the procedure for controlling the pulsed laser apparatus  1  using Ethernets S and SS and parallel communication lines P 1  through P 4  and PP is explained here with reference to FIGS. 2 through 8. 
     In FIG. 2, the energy controller  4  comprises a parallel interface  4   a  for connecting the parallel communication line, an energy calculation unit  4   b , and a log storage unit  4   c . The wavelength controller  3  comprises a parallel interface  3   a  for connecting the parallel communication line, a wavelength calculation unit  3   b , and a log storage unit  3   c . The utility controller  5  comprises a parallel interface  5   a  for connecting the parallel communication line, a utility calculation unit  5   b , and a log storage unit  5   c . The main controller  2  comprises a parallel interface  2   a  for connecting the parallel communication line and a main calculation unit  2   b.    
     When a laser emission signal P 10  is input to the energy controller  4  from the device  25 , this laser emission signal P 10  is transmitted in parallel to the wavelength controller  3  by means of the parallel communication line, the utility controller  5 , and main controller  2 . At the same time, the parallel interfaces  4   a ,  3   a ,  5   a  and  2   a  transmit the laser emission signal P 10  to the energy calculation unit  4   b , the wavelength calculation unit  3   b , the utility calculation unit  5   b , and the main calculation unit  2   b  respectively. Furthermore, the main controller  2  outputs an emission signal P 14  indicating signal reception to the external apparatus  10  via a parallel communication line. The connections of the parallel communication line in this case are assigned to each specific signal by means of a one signal/one pair line. 
     In FIG. 3, the energy controller  4  captures an energy signal  41  from the connected device at the time when the laser emission signal P 10  is received, and stores the signal in the log storage unit  4   c . Similarly, the wavelength controller  3  captures the laser wavelength monitor signal  31  from the connected device at the time when the laser emission signal P 10  is received, and stores the signal in the log storage unit  3   c . Similarly, the utility controller  5  captures the device status signal  51  from the connected device at the time when the laser emission signal P 10  is received, and stores the signal in the log storage unit  5   c.    
     In FIG. 4, the energy calculation unit  4   b  then calculates an energy for the next pulse based on the captured energy signal  41  and outputs that value as an energy control signal  42  to an device such as the pulsed laser power source device. Also, the wavelength calculation unit  3   b  calculates adjustment data to be adjusted at the next pulse based on the laser wavelength monitor signal  31  and outputs that value as a wavelength control signal  32  to an device such as the mirror adjuster. 
     After that, as shown in FIG. 5, the main controller  2  uses the high-speed serial communication line of the Ethernet S to make a request for log data held in log storage units  3   c  through  5   c , and acquires the log data. 
     Next, error processing to be carried out when any of the controllers detects an error is explained with reference to FIG.  6 . In FIG. 6, when the energy controller  4  has detected an error, for example, the energy controller  4  uses the parallel communication line and sends error detection events P 41 , P 42  to the main controller  2  and other controllers  3 ,  5 ,  6 . The main controller  2  and other controllers  3 ,  5 ,  6  that have received these events P 41 , P 42  latch these events as log data. Meanwhile, the energy controller  4  that detected the error also latches the error detection as log data. 
     Thereafter, the main controller  2  uses the Ethernet S to send requests S 41 , S 42  for error details to the energy controller  4  and receives the error codes showing the error details from the energy controller  4 . Then, the main controller  2  confirms the error codes received, and notifies the main controller  2  and other controllers  2 ,  3 ,  5 ,  6 , meaning all the controllers, of error occurrence P 43 , P 44  using the parallel communication line. The energy controller  4  and other controllers  2 ,  3 ,  5 ,  6  stop the connected devices upon receiving this notification. 
     After that, the main controller  2  uses the Ethernet S and makes requests S 43 , S 44  for stored log data to the energy controller  4  and other controllers  2 ,  3 ,  5 ,  6 . The energy controller  4  and other controllers  3 ,  5 ,  6  effect transmissions S 45 , S 46  of log data to the main controller  2 , whereby the main controller  2  acquires the log data. The log data acquired in this way can be captured and managed by the management device  12  within the external apparatus  10  via the Ethernet SS, for example. 
     The retention and acquisition of those log data are carried out, as shown in FIG. 7, in such a way that the controllers  2  through  5  hold the log data in the respective source database in synchronization with the reception of the laser emission signal P 10 , in other words, in synchronization with each pulse via the parallel communication line, and then the main controller  2  requests and acquires the log data via the Ethernet S. In this case, because of acquisition of log data in synchronization with a pulse, the main controller  2  can acquire and manage the log data for each pulse. 
     On the other hand, the external apparatus  10  sometimes needs to acquire changes in beam quality on the pulsed laser apparatus  1  side in real time and effect control and management. For example, FIG. 8 shows the processing to be carried out when the beam quality on the pulsed laser apparatus  1  side is output to the external apparatus  10  side in real time. In FIG. 8, the wavelength controller  3  and energy controller  4  receive the laser emission signal P 10  via the parallel communication line, whereupon the wavelength calculation unit  3   b  calculates the wavelength and beam width at that time and sends the computation results to the main controller  2  using the parallel communication line; the energy calculation unit  4   b  calculates the mean value and dispersion of the energy and sends the computation results to the main controller  2  using the parallel communication line; and the main controller  2  sends these computation results to the external device  10  in real time. In this manner, the beam quality of the pulsed laser apparatus  1  can be monitored remotely and in real time. 
     With the present embodiment, the load of control in the pulsed laser apparatus  1  is divided and distributed among the plurality of controllers  2  through  6 ; the controllers  2  through  6  are connected by an Ethernet, as a high-speed serial line, so that expansion or the like involved by design changes or the like can be easily effected. Also, because the controllers  2  through  6  are connected by parallel communication lines, time critical signals, that cannot tolerate communication delays due to Ethernet communication speed or temporary increase of load, can be sent assuredly in real time. In other words, the hybrid system using serial communication lines and parallel communication lines ensures high speed communications among the controllers  2  through  6 . 
     Also, because the controllers  2  through  6  can be provided close to the devices connected thereto, the devices can be connected by short wiring without laying around a harness or the like. As a result, it is possible to construct a communication control system for which it is relatively unnecessary to consider the effects of noise or the like. 
     Furthermore, because the log held in each controller  2  through  6  can be acquired using the Ethernet S, subsequent maintenance and management become easy. In particular, because the external apparatus  10  and pulsed laser apparatus  1  are connected by Ethernet and parallel communication lines, control and management of the pulsed laser apparatus  1  can be performed remotely.