JPH06169123A - Output controllor for laser device - Google Patents

Abstract

PURPOSE:To precisely control the prevention of spiking phenomenon in a laser device at all times. CONSTITUTION:Discharge voltage, with which the magnitude of energy of each continuous pulse is made equal, is stored in the memory of a laser device 1 in advance. A laser beam is pulse-oscillated under the prescribed condition during the prescribed time when no prescribed treatment is conducted by a stepper 9 using the laser beam L, the energy of the above-mentioned oscillated pulse is detected by a monitor 5, and the discharge voltage, which is stored on the basis of the detected energy magnitude based on the desired energy magnitude and the prescribed conditions, is corrected by an output control part 6. The output control part 6 controls the discharge voltage in such a manner that corrected discharge voltage is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used as a light source of a stepwise moving reduction projection exposure apparatus (hereinafter referred to as "stepper"), and an output control apparatus of a laser apparatus which oscillates a laser by being discharge-excited. Regarding

[0002]

2. Description of the Related Art In a stepper, strict exposure amount control is required to maintain the resolution of a circuit pattern at a certain level or higher. On the other hand, the excimer laser used as the light source of this stepper has a variation in pulse energy for each pulse because it is a so-called pulse discharge excitation gas laser, and it is necessary to reduce this variation in order to improve the accuracy of exposure amount control. is there. Moreover, since the light is intermittent light, it is necessary to control the amount of exposure differently from the conventional shutter control when a mercury lamp, which is continuous light, is used as the light source.

Therefore, for example, as seen in the literature (Miyaji et al., "Excimer Laser Lithography", International Laser / Application '91, Seminar L-5, P36-51), a plurality of pulses are continuously oscillated to perform exposure. Do,
There is an attempt to improve the accuracy of exposure amount control by so-called multiple pulse exposure.

In this method, since the variation in the energy of the oscillation pulse of the excimer laser can be approximated by a normal distribution, the variation in the integrated energy after exposure by oscillating the pulse n times is different from the variation in the energy of one pulse. The fact that it becomes 1 / (n) 1/2 is used.
That is, the variation in energy of one pulse is ΔP /
Assuming that P is P and the required exposure amount control accuracy is A, the number N of exposure pulses required for it is given by the following relationship.

N ≧ {(ΔP / P) / A} 2 For example, the energy variation ΔP / P of 1 pulse is 1
5% (3σ), the required exposure control accuracy A is 1.5% (3
σ), N ≧ 100, and the desired accuracy can be achieved by continuous pulse oscillation 100 times or more.

By the way, the stepper alternately repeats exposure and stage movement. Therefore, the operating state of the excimer laser, which is the light source, is inevitably the so-called burst mode. The burst mode means that the laser light is continuously pulse-oscillated a predetermined number of times and then the operation of suspending the pulse oscillation for a predetermined time is repeated. That is, the short continuous pulse oscillation period and the short oscillation quiescent period are alternately repeated.

In this specification, the terms "continuous pulse" and "continuous pulse oscillation" are used to mean that pulse discharge can be repeated and intermittent pulsed laser light can be repeated. Therefore, the term "continuous oscillation laser" and "CW oscillation" are generally used in different meanings.

As described above, since the excimer laser is a pulse discharge excitation gas laser, it is difficult to always oscillate with pulse energy of a certain magnitude. The cause of this is that the density disturbance of the laser gas occurs in the discharge space due to the discharge, which makes the next discharge non-uniform and unstable, and the non-uniform discharge causes local discharge on the surface of the discharge electrode. This is because a large temperature rise occurs and the next discharge is deteriorated to make the discharge uneven and unstable. In particular, the tendency is remarkable at the beginning of the continuous pulse oscillation period, and stable discharge is obtained and relatively high pulse energy is obtained in the first pulse after the oscillation pause period, but the discharge deteriorates thereafter. A so-called spiking phenomenon that the pulse energy gradually decreases appears. This phenomenon is shown by S in FIG.
That is, as shown in FIG.
This is a phenomenon in which the energy P1 of the first pulse actually becomes larger than Ps even if oscillation is performed at a predetermined discharge voltage corresponding to this energy in order to obtain s.

As described above, in the burst mode operation excimer laser device, the above-mentioned variation in energy for each pulse deteriorates the accuracy of the exposure amount control, and the spiking phenomenon causes the variation to be significantly increased, thereby increasing the accuracy of the exposure amount control. There is a problem of further lowering.

Moreover, in recent years, the sensitivity of the photosensitizer applied to the wafer has been improved, and exposure with a small number of continuous pulses has become possible, and the number of pulses tends to decrease.

However, when the number of pulses decreases, the variation in pulse energy increases accordingly, and it becomes difficult to maintain the accuracy of the exposure amount control only by the above-described multiple pulse exposure control. Therefore, it is desired to improve the variation in pulse energy and remove the influence of the spiking phenomenon in the burst mode.

Therefore, by utilizing the property that the energy of the pulse oscillated increases as the discharge voltage increases, the discharge voltage of the first pulse of the continuous pulse oscillation in the burst mode is reduced and the discharge voltage of the pulse is changed thereafter. Controls that prevent the initial increase in energy due to the spiking phenomenon by changing the discharge voltage for each pulse, such as gradually increasing it, that is, technology related to spiking prevention control have been adopted and implemented. There is. As a literature on this kind of technology, "T. Ishihara e
t.al. 'Advanced Krypton Fluoride Excimer Laser Fo
r Microlithography ', SPIE Proc.Optical / Laser Micro
Lithography V, vol. 1674, 473 (1992) ”.

According to such a technique, the influence of the spiking phenomenon is eliminated, so that the accuracy of exposure amount control can be improved even with a small number of continuous pulse oscillations.

[0014]

However, the above document does not disclose that the optimum control is performed according to the operating conditions of the laser. That is, in general, the content of the spiking prevention control is uniquely determined according to the operating conditions of the laser such as the composition of the laser medium gas, the partial pressure of each component gas, the shape of the discharge electrode, and the like. Optimal control will be performed. However, if the operating conditions of these lasers change even slightly, the optimal control is not performed and the accuracy of the spiking prevention control deteriorates. Here, for changes related to the laser medium gas,
It is possible to prevent the accuracy of spiking prevention control from being affected by accurately controlling the composition, partial pressure, etc. by a gas control device etc. so that the composition etc. becomes constant. Operating conditions that are difficult to manage, such as the amount of electrode wear and changes in the electrode shape due to wear, are difficult to predict and are difficult to manage.If the spiking prevention control is continued, the operating conditions will eventually change. Will reduce the accuracy.

The present invention has been made in view of the above situation, and spiking prevention control is always performed accurately even if the change in the operating conditions of the laser is difficult to predict and the management is difficult. It is an object of the present invention to provide a device capable of performing the above.

[0016]

Therefore, in the main invention of the present invention, the laser device is operated in a burst mode in which the laser light is continuously pulsed a predetermined number of times and then the pulse oscillation is stopped for a predetermined time. Along with, in the output control device of the laser device that controls the discharge voltage so that the energy of the pulse has a predetermined magnitude, and performs a predetermined process using the laser light, the magnitude of the energy of each pulse of the continuous pulse is changed. Storage means for storing the same discharge voltage in advance, detection means for detecting the energy of the oscillated pulse, during the time when the predetermined processing is not performed, pulse the laser light under a predetermined condition, The energy of the oscillated pulse is detected by the detection means, and the magnitude of the detected energy, the predetermined magnitude, and the A correction unit that corrects the stored discharge voltage based on a constant condition; and a unit that controls the discharge voltage so that the corrected discharge voltage is obtained during the time when the predetermined process is performed. I am.

[0017]

According to this structure, the discharge voltage for equalizing the magnitude of the energy of each pulse of the continuous pulse is stored in advance. Then, during the time when the predetermined processing using the laser light is not performed, the laser light is pulse-oscillated under the predetermined condition, the energy of the oscillated pulse is detected, and the magnitude of the detected energy and the desired energy are detected. The stored discharge voltage is corrected based on the predetermined magnitude and the predetermined condition. Then, the discharge voltage is controlled so that the corrected discharge voltage is obtained during the time when the predetermined process using the laser light is performed. Therefore, even if the change in the operating condition of the laser is difficult to predict and it is difficult to manage the change, the change in the operating condition of the laser is detected by detecting the energy of the pulse, and based on this, The stored discharge voltage is corrected to an optimum value, and the corrected discharge voltage allows control to always be performed accurately.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an output control device for a laser device according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the apparatus of the embodiment is roughly composed of an excimer laser device 1 which outputs an excimer laser beam L, and a stepper 9 which uses the excimer laser device 1 as a light source and performs reduction projection exposure with the output laser beam L. It consists of and.

The oscillator 2 of the laser device 1 comprises a laser chamber, an optical resonator, etc., and Kr and
The laser gas such as F2 is filled. And
Discharge is performed between the electrodes arranged in the laser chamber to excite the laser gas to cause laser oscillation. The oscillated laser light is resonated in the optical resonator, and is output as effective oscillated laser light L from the front mirror. The discharge is performed at a predetermined interval with a predetermined pulse width, and the laser light L is intermittently output.

The laser light thus oscillated from the oscillator 2 is partially sampled by the beam splitter 3 and is incident on the output monitor 5 through a lens (not shown). The output monitor 5 detects energy per pulse of the output laser light L, that is, pulse energy E.

The pulse energy E detected by the output monitor 5 is applied to the output control section 6 so that the desired pulse energy Ed can be obtained based on the input pulse energy E. , Voltage data is added to the laser power supply unit 8. In this case, power lock control is performed.

The power lock control is a control method for preventing the pulse energy E from decreasing even if the laser gas deteriorates and the same discharge voltage is applied, by increasing the discharge voltage according to the deterioration. Is one. In general,
Energy of multiple oscillated pulses is integrated and averaged,
This is feedback control that determines the discharge voltage after the next pulse by comparing with the desired energy Ed.
The determined discharge voltage (the discharge voltage for obtaining the desired energy Ed) is called the power lock voltage Vpl. In addition,
"POWERLOK" is a registered trademark of Questek Corporation in the United States. On the other hand, the spiking prevention control is
This is predictive control for predicting the pulse energy of one pulse to be oscillated next and determining the discharge voltage before oscillation.

The laser power supply unit 8 gives a potential difference V between the electrodes according to the applied voltage data, and discharges. Here, the voltage for discharging is the laser power supply unit 8
It is once charged by a charging circuit provided inside and is discharged by the operation of a switching element such as a thyratron.

The output control unit 6 is connected to the stepper control unit 10 in the stepper 9 by a signal line, and receives the trigger signal Tr sent from the stepper control unit 10. Upon receiving the transmitted trigger signal Tr, the output control unit 6 controls the laser power supply unit 8 so that oscillation of one pulse is performed.

The laser device 1 is provided with a laser beam emission port 1a, and the laser beam L oscillated through this emission port 1a is projected onto an external stepper 9 and the laser beam L is used by the stepper 9. The exposed exposure process is performed. The shutter 4 is provided to block the oscillated laser light L so that the laser light L is not projected to the outside from the emission port 1a, and the opening / closing control of the shutter 4 is performed by the output control unit 6. This is done via the driver 7. Shutter 4
When is opened, the laser light L is projected to the stepper 9 without being blocked, and the exposure process using the laser light is performed in the stepper 9. On the other hand, when the shutter 4 is closed, the laser light is blocked and the above process in the stepper 9 is not performed.

As will be described later, a memory (not shown) of the output control unit 6 has a discharge voltage that equalizes the energy levels of the continuous pulses in the burst mode according to the parameters contributing to the spiking phenomenon. V is stored in advance. Then, the output control unit 6 causes the laser light to pulse-oscillate under a predetermined condition during the time when the shutter 4 is closed and the above-described processing using the laser light is not performed. Hereinafter, this oscillation is referred to as “adjustment oscillation”. Then, the energy E of the adjusted and oscillated pulse is detected by the output monitor 5, and the stored discharge voltage V is corrected on the basis of the magnitude E of the detected energy.
Then, the output control unit 6 controls the discharge voltage so that the corrected discharge voltage V is obtained during the time when the above-described predetermined process using the laser light is performed.

The contents of various correction processes performed by the output control unit 6 will be described below. Note that the following various correction processes may be performed individually, or any of the various correction processes may be appropriately combined and performed.

Correction Process 1 By the way, the error that is most likely to occur in the spiking prevention control is the first pulse of continuous pulse oscillation (hereinafter referred to as "first pulse") as shown in PL1 of FIG. Is. Therefore, in the correction processing 1, only the first pulse is a correction target.

The energy E of the first pulse PL1 strongly depends on the oscillation quiescent time Tpp immediately before (see FIG. 10).
As shown in, the oscillation stop time Tpp, that is, the elapsed time t from the start of the oscillation stop gradually increases,
Eventually, a certain pulse energy is reached at time t3. After t3, it becomes constant regardless of the rest time Tpp. The relationship between the pulse energy E of the first pulse PL1 and the time t is substantially proportional, and the relationship can be approximated by a straight line. On the other hand, since the relationship between the discharge voltage V and the pulse energy E is also a substantially linear relationship, the optimum discharge voltage V of the first pulse for preventing the occurrence of spiking can also be approximated by a straight line as shown in FIG.

The contents shown in FIG. 6 are stored in advance in the memory of the output control unit 6, and the correction process is performed in the procedure as shown in FIG. The processing contents will be described below with reference to the timing chart shown in FIG.

As shown in FIG. 2, during the laser operation, the output control unit 6 adjusts to the external control device such as the stepper control unit 10 of the stepper 9 that the process using the laser light will not be performed thereafter. An oscillation start signal is output (see FIG. 7 (c)). As a result, it is understood that the processing using the laser light is not performed while the adjusted oscillation start signal is being output on the side of the external control device, and the corresponding predetermined measure is taken (step 101). Then, a control signal for closing the shutter 4 is output to the driver 7,
After that, the shutter 4 is closed and the laser light L is not projected onto the stepper 9 (step 102; see FIG. 7B).

Then, the procedure shifts to "adjustment oscillation routine 1" shown in FIG. 2 (b) (step 103). In the adjusted oscillation routine 1, first, the time t from the start of oscillation suspension is measured by a predetermined timer (step 10
9) When the counted time reaches t1 (see FIG. 6), the laser power supply unit 8 is controlled so as to oscillate the laser light L by one pulse. Note that this adjustment oscillation is performed by the trigger signal generated by the output control unit 6 itself, not by the trigger signal Tr sent from the stepper control unit 10 during normal oscillation (see FIG. 7A; step 110). . Then, the energy E of the oscillated pulse is detected by the output monitor 5, and the detected value is temporarily held in a predetermined memory (step 111).

The procedure is returned to step 104, and the process of the adjusted oscillation routine 1 is performed again.

In the same manner as described above, the time t is measured (step 109), and this time t2 (see FIG. 6).
1 pulse adjustment oscillation is carried out when it reaches (Fig. 7
See (a); step 110). It should be noted that the times t1 and t2 are different times, and they are preselected so that they are times t3 or less. The energy of the pulse oscillated at time t2 is detected by the output monitor 5, and the detected value is also stored in the memory (step 111).

Then, the procedure is returned to step 105, and the deviation between the detected energy value held in the memory and the desired energy Ed is taken. Depending on whether or not this deviation is equal to or more than a predetermined threshold value, It is determined whether the laser output is not proper or proper (step 105).
As a result of this determination, if it is determined that either one of the detected values is not appropriate and is deviated from Ed, it is determined that the accuracy of the spiking prevention control is decreased, and both detected values are detected. A process of correcting the straight line shown in FIG. 6 based on the value as shown by, for example, a two-dot chain line in the figure is performed.

In this case, since the pulse energy detection values corresponding to the elapsed times t1 and t2 are known, t
It is easy to calculate the appropriate discharge voltages v1 and v2 corresponding to 1 and t2, respectively, and the correction straight line has two points (t1, v2).
It is clear that it can be easily obtained as a line segment connecting 1) and (t2, v2). In this way, in this correction processing 1, since the straight line is corrected, it is understood that at least two detection values have to be acquired (step 106).

On the other hand, as a result of the judgment in step 105, if it is judged that all the detected values of both the detected values are proper and Ed is not deviated, the accuracy of the spiking prevention control is maintained. And step 106
Do not perform the correction process of.

Next, a control signal for opening the shutter 4 is output to the driver 7, and thereafter the shutter 4 is opened (step 107; see FIG. 7B). Then,
The adjusted oscillation start signal is released (see FIG. 7C), and it is understood that the external stepper controller 10 can perform the process using the laser light (step 108). As a result, the stepper control section 10 outputs the trigger signal Tr when the oscillation pause time Tpp is reached, and again performs continuous pulse oscillation in the burst mode (FIG. 7).
(See (a)). In this case, the first pulse of the continuous pulse oscillation is oscillated with the discharge voltage V corrected to an appropriate value in step 106. Therefore, the spiking phenomenon occurrence control is accurately performed, and the desired energy Ed is obtained in the first pulse (the same energy Ed is similarly obtained in the second and subsequent pulses).

In the correction process 1, the rest time Tpp
Although the relationship between and the energy E of the first pulse PL1 is described as a substantially proportional relationship or a linear relationship, this relationship depends on the device configuration and the like, and may be a relationship other than the proportional relationship. The point is to find the relationship between Tpp and E that are suitable for the device, and perform the correction process based on that. Therefore, the relationship between the pulse energy and the oscillation quiescent time, the power lock voltage, etc. in the following embodiments of the present invention does not necessarily have to be a proportional relationship or a linear relationship, but may be an arbitrary function or a combination of straight lines.

In the correction process 1, as shown in FIG. 6, the adjustment oscillation times t1 and t2 are set to t3 or less, and the linear portion in which the discharge voltage V increases as the elapsed time t increases is corrected. However, the adjustment oscillation is time t3
It is also possible to carry out in a time period that exceeds the time period and correct the linear portion where the discharge voltage V does not change. In short, it is sufficient to correct only the part actually used as data.

Further, in the correction processing 1, when the adjustment oscillation is performed, the output control section 6 inside the laser device 1 outputs a signal to that effect to an external control device. A control device, for example, the stepper control unit 10 may output a signal indicating that the adjustment oscillation may be performed to the output control unit 6, and the adjustment oscillation may be performed accordingly.

Correction process 2 As described above, the pattern of occurrence of the spiking phenomenon is
It also changes depending on the power lock voltage Vpl. Typical generation patterns thereof are shown in FIG. 8A (when the power lock voltage is small) and FIG. 8B (when the power lock voltage is large). From these figures, the change in pulse energy due to the change in power lock voltage is shown in FIG.
It is obvious that it appears in the part B in (b).

FIG. 9 shows the power lock voltage Vpl and the above B
The relationship with the energy E of each pulse included in the section is shown, and can be approximated by a substantially straight line as shown in the figure. Therefore, even if the vertical axis in FIG. 9 is the discharge voltage as shown in parentheses, the relationship between the power lock voltage Vpl and the discharge voltage can be approximated by a straight line as in FIG.

On the other hand, the discharge voltage of the first pulse of the continuous pulse oscillation is the oscillation pause time T as described in the correction processing 1 above.
It has a linear relationship with pp. Therefore, in this correction processing 2, 1) two different oscillation pause times T1 and T2 2) two different power lock voltages V1 and V2 are selected, and continuous pulse oscillation is performed at T1 and V1.
This is intended to correct the straight line shown in FIG. 6 and the straight line shown in FIG. 9 by causing continuous pulse oscillation at T2 and V2.

That is, as shown in FIG. 3, the output control unit 6 first causes the stepper control unit 10 of the stepper 9 and other external control devices to perform adjustment oscillation to the effect that processing using laser light will no longer be performed. Output the start signal. As a result, it is understood that the process using the laser light is not performed while the adjusted oscillation start signal is being output on the side of the external control device, and the corresponding predetermined measure is taken (step 201). Then, a control signal for closing the shutter 4 is output to the driver 7, the shutter 4 is closed thereafter, and the laser light L is not projected onto the stepper 9 (step 202).

Next, the oscillation pause time Tpp is set to T1 and the power lock voltage Vpl is set to V1 (step 203). Then, the procedure shifts to "adjustment oscillation routine 2" shown in FIG.
4). In the adjusted oscillation routine 2, first, the time from the start of the oscillation stop is measured by a predetermined timer, and when the measured time reaches the set oscillation stop time T1, the set power lock voltage V1 is reached. The laser power supply unit 8 is controlled so that continuous pulse oscillation (adjustment oscillation) of the corresponding laser light L is started. Note that this adjustment oscillation is performed by the trigger signal generated by the output control unit 6 itself, not by the trigger signal Tr sent from the stepper control unit 10 during normal oscillation (step 211). Then, the energy E of each pulse of the oscillated continuous pulse is detected by the output monitor 5, and the detected value is temporarily held in a predetermined memory (step 212).

The procedure returns to step 205, and the oscillation pause time Tpp is reset to T2 and the power lock voltage Vpl is reset to V2 (step 205). Then, the procedure shifts to "adjustment oscillation routine 2" shown in FIG. 3 (b) (step 206). Then, the time from the start of the oscillation stop measured in the same manner is set to the set oscillation stop time T2.
The laser power source unit 8 is controlled so that the continuous pulse oscillation (adjustment oscillation) of the laser light L according to the set power lock voltage V2 is started when the value reaches (step 21).
1). Then, the energy E of each pulse of the oscillated continuous pulse is detected by the output monitor 5, and the detected value is temporarily stored in the memory (step 212).

Then, the procedure returns to step 207, and the deviation between the detected energy value held in the memory and the desired energy Ed is calculated. Depending on whether or not this deviation is equal to or more than a predetermined threshold value, It is determined whether or not the laser output is proper (step 207).
As a result of this determination, if it is determined that any of the detected values is not appropriate and is out of the range of Ed, it is determined that the accuracy of the spiking prevention control is reduced, and based on each detected value Processing for correcting the straight line shown in FIG. 6 and the straight line shown in FIG. 9 is performed.

In this case, the straight line in FIG. 6 is the set time T1,
Based on T2 and the energy detection value of the first pulse when continuous pulse oscillation occurs at these times, correction is performed in the same manner as described above. Further, since FIG. 9 also has a proportional relationship similar to that of FIG. 6, similarly to the correction of FIG. 6, the power lock voltages V1 and V2 and the second and subsequent pulses when continuous pulse oscillation is performed with these power lock voltages. Correction is performed based on the detected energy value of the pulse (step 208).

On the other hand, as a result of the determination in step 207, if it is determined that any of the detected values is proper and that the difference from Ed is not exceeded, the accuracy of spiking prevention control is maintained. It is determined that the correction process in step 208 is not performed.

Then, a control signal for opening the shutter 4 is output to the driver 7, and thereafter the shutter 4 is opened (step 209). Then, the adjusted oscillation start signal is released, and it is understood that the external stepper control unit 10 can perform the process using the laser light (step 210). As a result, the stepper control section 10 outputs the trigger signal Tr when the oscillation pause time Tpp is reached, and again performs continuous pulse oscillation in the burst mode. In this case, each pulse of the continuous pulse oscillation has the discharge voltage V corrected to an appropriate value in step 208.
Is being oscillated. Therefore, the spiking phenomenon occurrence control is accurately performed, and the desired energy Ed is obtained in each pulse of the continuous pulse.

In the correction process 2, the correction is performed by performing continuous pulse oscillation twice with different values for the oscillation pause time and the power lock voltage. The correction may be performed based on the result of performing continuous pulse oscillation three or more times with different voltages, and in this case, the correction is performed more precisely and the spiking prevention control can be maintained more accurately. It will be possible.

By the way, as a method for performing the spiking generation prevention control with high accuracy, there is a method of preparing a functional expression for determining the optimum discharge voltage for each pulse in the portion where the spiking phenomenon occurs. For example, it is a method of preparing a function Vi () such that V (i) = Vi (Tpp, Vpl) and obtaining the discharge voltage V (i) of the i-th pulse of the continuous pulse by this function. In this correction processing 2, the optimum discharge voltage of each pulse included in the portion B of FIG. 8 is adjusted all at once, but when the functional expression Vi () is prepared for each pulse as described above. May be adjusted for each functional expression.

Also in this correction processing 2, as in the correction processing 1, when performing the adjustment oscillation, the output control section 6 inside the laser device 1 outputs a signal to that effect to an external control device. However, an external control device, for example, the stepper control unit 10 may output a signal indicating that the adjustment oscillation may be performed to the output control unit 6, and the adjustment oscillation may be performed accordingly. Is.

Correction process 3 By the way, when the adjustment oscillation is performed in the burst mode as in the correction process 2, it is desirable to perform the adjustment oscillation with the burst pattern used for the actual exposure process.
Therefore, in this correction processing 3, the laser device 1 of FIG.
During the operation of the laser device 1, a storage means for storing a burst pattern which is considered to be frequently used is provided. Then, before starting the operation of the laser, a burst pattern which is expected to be used frequently is stored in the storage means, and when the operation of the laser is started, the adjustment oscillation is performed in the burst pattern. Then, as a result of the adjusted oscillation, the laser device is operated thereafter with the corrected discharge voltage.

Further, after the operation of the laser device is started, the burst patterns used are successively stored in the storage means, and when the adjustment oscillation is performed, the burst patterns used based on the storage contents of the storage means. Of these, a burst pattern that is considered to be frequently used may be selected, and the adjusted oscillation may be performed using the selected burst pattern. To improve accuracy, a plurality of frequently used burst patterns may be selected and adjusted oscillation may be performed using these plurality of burst patterns.

Correction Process 4 By the way, the output monitor 5 shown in FIG. 1 constantly monitors the energy E of the laser light. From this, the output monitor 5 constantly monitors the spiking prevention control based on the output, and only when the accuracy of the control is lowered, the adjustment oscillation,
It is conceivable to perform a correction process. Figure 4
It is a flow chart which shows the contents of such processing.

That is, as shown in the figure, when the operation of the laser device 1 is started (step 301), burst patterns used thereafter are sequentially stored (step 302). Then, the output monitor 5 constantly detects the energy E of the oscillated pulse (step 3).
03). Then, it is judged whether or not the accuracy of the spiking prevention control is lowered based on the deviation between the detected energy E and the desired energy Ed (step 304), and as a result, the detected energy E is desired. If it is determined that the accuracy is reduced and the accuracy is reduced from the energy Ed, only in this case (determination YES in step 304), a burst pattern that is frequently used is selected based on the storage processing in step 302, and Adjustment oscillation is performed with the selected burst pattern to perform discharge voltage correction processing. It should be noted that the use of this burst pattern having a high frequency of use corresponds to the contents described in the correction process 3 (step 305).

In the embodiment described above, the discharge voltage is stored in correspondence with the oscillation pause time Tpp or the power lock voltage Vpl, and the case of correcting the stored content has been described. It is sufficient that the discharge voltage is stored in correspondence with the parameter that is considered to affect the spiking phenomenon generation pattern. For example, the elapsed time after the laser gas is newly enclosed in the laser chamber is used as the parameter. It is also possible to carry out.

In the embodiment, the case where the discharge voltage is stored in a proportional relationship with the parameter value has been described, but the present invention is not limited to this and the present invention can be applied even in a non-linear case. You can

[0062]

As described above, according to the present invention,
Even if the change in laser operating conditions is difficult to predict and difficult to manage, the change in laser operating conditions
The discharge voltage that is captured by detecting the energy of the pulse and is stored based on this is corrected to an optimum value, and the spiking prevention control is always performed accurately with this corrected discharge voltage.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an output control device of a laser device according to the present invention.

FIG. 2 is a flowchart showing a processing procedure of the embodiment.

FIG. 3 is a flowchart showing a processing procedure of the embodiment.

FIG. 4 is a flowchart showing a processing procedure of the embodiment.

FIG. 5 is a graph showing the relationship between the elapsed time from the start of oscillation pause and the pulse energy.

FIG. 6 is a graph showing the relationship between the elapsed time from the start of oscillation suspension and the discharge voltage.

FIG. 7 is a timing chart used to explain the embodiment shown in FIG.

FIG. 8 is a graph used to explain that a change in power lock voltage affects a pattern in which a spiking phenomenon occurs.

FIG. 9 is a graph showing the relationship between the power lock voltage and the energy of each pulse in a predetermined portion of continuous pulses.

FIG. 10 is a graph used to show the burst mode and the spiking phenomenon, and is a graph showing how the pulse energy changes with time.

[Explanation of symbols]

 1 Laser Device 6 Output Control Unit 10 Stepper Control Unit

Claims (11)

[Claims] 1. A laser device is operated in a burst mode in which pulsed laser light is continuously pulsed a predetermined number of times, and then pulsed oscillation is suspended for a predetermined time, and the pulse energy is set to a predetermined magnitude. In the output control device of the laser device that controls the discharge voltage to perform a predetermined process using the laser light, a storage unit that stores in advance the discharge voltage that makes the magnitude of the energy of each pulse of the continuous pulse the same, Detecting means for detecting the energy of the oscillated pulse, and pulsing the laser light under a predetermined condition during the time when the predetermined processing is not performed, and detecting the energy of the oscillated pulse by the detecting means. The stored discharge voltage is compensated based on the detected energy level, the predetermined level, and the predetermined condition. An output control device for a laser device, comprising: a correction means for correcting the discharge voltage; and a means for controlling the discharge voltage so that the corrected discharge voltage is obtained during the time when the predetermined processing is performed. 2. The correction means determines that correction is to be performed when a deviation between the detected energy magnitude and the predetermined magnitude is equal to or greater than a predetermined threshold value. Laser device output control device. 3. The output control device of a laser device according to claim 1, wherein the correction by the correction means is performed within a pause time immediately before continuous pulse oscillation. 4. The laser device emits laser light to the outside of the laser device so that the predetermined processing is performed by a predetermined device outside the laser device. 3. A light-projection blocking means for blocking the projection of light to the outside is provided, and the light-projection blocking means is turned on while the correction processing by the correction means is being performed.
An output control device for the laser device described. 5. The storage means stores the discharge voltage in a predetermined relationship with a parameter that contributes to a spiking phenomenon in which the energy of each pulse gradually decreases from the start of continuous pulse oscillation. During the time when the process is not performed, the value of the parameter is set to a different value and at least two pulses are oscillated, and the correction means sets a different value of the parameter and the magnitude of each energy of the detected two pulses. 2. The output control device for a laser device according to claim 1, wherein the predetermined relationship stored in the storage means is corrected based on the above. 6. The output control device of a laser device according to claim 5, wherein the parameter is a pause time immediately before continuous pulse oscillation. 7. The output control device of the laser apparatus according to claim 5, wherein the parameter is a power lock voltage for obtaining the energy of the predetermined magnitude according to the deterioration of the laser gas. 8. The output control device of a laser device according to claim 1, wherein the laser beam is pulse-oscillated in the burst mode during a time when the predetermined processing is not performed. 9. The storage means stores a power for obtaining a predetermined amount of energy as a discharge voltage corresponding to each pulse of continuous pulse oscillation in accordance with a pause time immediately before continuous pulse oscillation and deterioration of laser gas. Each pulse voltage is stored in a predetermined relationship with the lock voltage, and during the time when the predetermined process is not performed, the pause time and the power lock voltage are set to different values, and at least two continuous pulse oscillations are performed. The correction means stores the respective values stored in the storage means based on different values of the rest time and the power lock voltage and the magnitude of energy of each pulse of the detected two consecutive pulses. 9. The output control device of the laser device according to claim 8, which corrects a predetermined relationship. 10. The output control of the laser device according to claim 8, wherein the laser device is pulse-oscillated in advance in a burst mode according to a burst mode pattern used in the laser device when the operation of the laser device is started up. apparatus. 11. The correction means is always performed during the operation of the laser device by the detection means, and only when the deviation between the magnitude of the detected energy and the predetermined magnitude is a predetermined threshold value or more. The output control device for a laser device according to claim 1, wherein the correction process is performed by the method.