Coherent light generators – Particular beam control device – Optical output stabilization
Reexamination Certificate
2000-09-20
2003-02-18
Ip, Paul (Department: 2828)
Coherent light generators
Particular beam control device
Optical output stabilization
C372S029011, C372S033000, C372S055000, C372S057000
Reexamination Certificate
active
06522674
ABSTRACT:
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
Hayashi Hideyuki
Niwano Motoki
Okamoto Takeshi
Sakanishi Shoichi
Tanaka Hiroshi
Al-Nazer Leith
Ip Paul
Komatsu Ltd.
Varndell & Varndell PLLC
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