JPH09107146A - Output control device of laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately obtain a desired laser output. SOLUTION: By randomly giving a plurality of command voltages V1, V2,... for a laser power supply at different levels, a data table showing the relationship between a command voltage value and the energy value of a laser beam is created in advance. A voltage V0 with a constant level corresponding to the energy value P0 of the laser beam at the time of an actual laser operation is outputted to a laser power supply for a specific period of time ΔT immediately before outputting command voltages V1, V2,... with a plurality of different values used as the data of the data table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light output control device for controlling the output of laser light so that laser light of desired energy required for laser processing is output from a laser oscillator.

[0002]

2. Description of the Related Art In various types of fine processing such as semiconductor exposure, it is necessary to perform delicate control of laser output at high speed and accurately while correcting fluctuations in characteristics of the laser apparatus itself and aging.

The invention described in Japanese Patent Publication No. 7-14097 solves these problems as follows.

That is, as shown in FIG. 10, a voltage V which changes stepwise with time t is successively given as a command value to a laser power source in advance, and a laser output value (laser light (Energy) is associated with each command voltage value and stored as a data table as shown in FIG.

Therefore, when there is a laser output command to the laser device during laser processing, the output command value Pco
It is determined whether m exists in the data table of FIG. As a result, when it is determined that the laser output value Pcom exists in the data table, the laser output value Pcom
The command voltage corresponding to is read from the data table. However, if it is determined that the laser output value Pcom does not exist in the data table, the laser output values P1 and P2 that satisfy P1 <Pcom <P2 are selected from the data table, and the command corresponding to each laser output value P1 and P2 is selected. The voltages V1 and V2 are read and the proportional distribution shown in (1) below is calculated.

Vcom = (V1−V2) (Pcom−P2) / (P1−P2) + V2 (1) Thus, the command voltage value Vcom corresponding to the output command value Pcom is obtained, and this is commanded to the laser power source. Give as a value.

[0007]

As described above, by using the above equation (1), the command voltage to the power source corresponding to the laser output value which does not exist in the data table can be obtained.

However, when the above-mentioned data table is created, as shown in FIG.
Since one of the voltages, the value of which gradually increases stepwise with the passage of, is given as the command value, there is a problem that the data on the data table does not accurately reflect the output characteristics of the laser.

That is, it is known that when laser oscillation is performed, the characteristics of the medium for laser oscillation change and the reproducibility of the laser oscillation characteristics deteriorates.

For example, in a gas laser such as an excimer laser, the flow and temperature of the laser medium gas change due to laser oscillation. For this reason, even if the voltage of the power supply is repeatedly oscillated with the same voltage, the energy level of each pulsed light is not the same, and the energy level of the first pulse is high and gradually decreases, and the energy level of the pulse light is reduced to some extent. The energy level of each pulsed light fluctuates in such a manner that the energy level of the pulsed light stabilizes after the lapse of time and the energy level of the pulsed light stabilizes. This has been clarified in the research conducted by the inventor of the present application. Similar phenomena are well known in solid-state lasers.

This means that the input / output characteristics of laser light (relationship between power supply voltage and pulse energy) depend on the history of laser operation up to that point.

Due to such laser characteristics, FIG.
When the laser output corresponding to each voltage is detected by increasing the power supply voltage of the laser in a stepwise manner as shown in the above, and conversely when the laser output corresponding to each voltage is detected while decreasing the power supply voltage in a stepwise manner And, the contents of the resulting data table will be different.

Therefore, when the laser output is controlled by using the data table in which the data affected by the history of the laser operation is stored during the laser processing, the laser oscillation characteristic at that time is determined by the data table. Since it is different from that at the time of production, the desired output required for laser processing may not be obtained.

In particular, the above formula (1) is a formula used to accurately obtain the power supply voltage by proportional distribution. The relation between the voltages V1 and V2 and the laser output values P1 and P2 in the above formula (1). However, if it is not an accurate one that accurately reflects the characteristics of the laser, an accurate power supply voltage cannot be obtained, and accurate laser processing cannot be performed.

The present invention has been made in view of the above situation, and by creating a data table in which the influence of the history of laser operation is removed, the desired laser output value as instructed during actual laser operation. It is the first object of the present invention to make it possible to obtain accurately.

Further, the above-mentioned input / output characteristics are different when the laser output is taken out from the laser operation halt state and when the laser output is taken out after the laser operation is performed at a predetermined input.

FIG. 12 is a graph showing a comparison between a sampled input / output characteristic after the rated CW operation and a sampled input / output characteristic after the laser operation is stopped. It can be seen that the two are very different.

Since the actual laser operation is the rated CW operation, it is desirable to obtain accurate data when sampling is performed in a state close to the rated CW operation even when the data table is created before the actual laser operation.

The present invention eliminates the influence of the history of laser operation and creates a data table close to the actual laser operation state, so that the desired laser output value as instructed can be accurately obtained during actual laser operation. The second purpose is to be able to obtain.

[0020]

In order to achieve the above first object, in the main invention of the first invention, the energy value of the laser beam output from the laser oscillator is used as the output command value. A laser light output control device comprising output command value setting means for setting, and controlling the output of the laser light so that the laser light having the output command value set by the output command value setting means is output from the laser oscillator. A detecting means for detecting energy of laser light output from the laser oscillator, a laser power source for outputting laser light having energy corresponding to an input command voltage or command current from the laser oscillator, and before actual laser operation In advance, to the laser power source, a plurality of command voltages or command currents of different values are randomly output, and the detection means Enter the energy value to be issued,
Data table creating means for creating a data table showing the relationship between the value of the command voltage or the command current and the energy value of the laser beam, and the output command value set by the output command value setting means during the actual laser operation. A corresponding command voltage or command current is read from the data table and is output to the laser power source.

As described above, since a plurality of command voltages or command currents are randomly given to the laser power source at different levels, it is possible to average the influence of the past history of the laser oscillation operation, and the laser oscillation operation. The influence of the history of can be reduced. Therefore, the desired laser output value as instructed can be accurately obtained during the actual laser operation. Further, the data table creating means outputs a plurality of command voltages or command currents having different values to the laser power source as a function value of a predetermined function that cyclically increases and decreases, and detects it by the detecting means. It is also possible to input the energy value to be generated and to prepare in advance a data table showing the relationship between the value of the command voltage or the command current and the energy value of the laser light.

Also in this case, similarly, the influence of the history of the laser oscillation operation in the past can be averaged, and the influence of the history of the laser oscillation operation can be reduced. Therefore, the desired laser output value as instructed can be accurately obtained during the actual laser operation.

As the data table creating means,
A plurality of command voltages or command currents having different values are sequentially output to the laser power source in a stepwise increasing direction and a decreasing direction, and the energy value detected by the detecting means is input to increase the value. The average value of both energy values corresponding to both command values that are the same value in the direction to make and the direction to decrease, the average value as the energy value corresponding to the same command value, the value of the command voltage or command current and the laser A data table showing the relationship with the energy value of light may be created in advance.

In this case as well, similarly, the influence of the history of the laser oscillation operation in the past can be averaged, and the influence of the history of the laser oscillation operation can be reduced. Therefore, when the laser is actually operated, it is possible to accurately obtain the desired laser output value as instructed.

In order to achieve the above second object,
In the second invention, immediately before outputting a plurality of command voltages or command currents having different values used as data of the data table, a laser having a constant level voltage or current corresponding to the energy value of the laser light during the actual laser operation is output. The power is output for a predetermined time.

That is, since the sampling of the data table according to the first aspect of the present invention is started immediately after the operation is carried out for a certain period of time under the load normally used during the laser operation,
Not only is the influence of the history of laser operation removed,
A data table close to the actual laser operating state is created. Therefore, the desired laser output value as instructed can be accurately obtained during the actual laser operation.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a laser light output control apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the construction of the apparatus of the embodiment, which is roughly composed of a laser apparatus 1 and a processing apparatus 9 for processing using laser light, such as a reduction projection exposure apparatus. Has been done.

That is, a part of the laser light L emitted from the laser oscillator 2 in the laser device 1 is sampled by the beam splitter 3 and is incident on the output monitor 5 via the lens 4.

The energy P of the laser beam detected by the output monitor 5 is transmitted to the output control section 6 so that the output control section 6 can obtain a desired laser output (energy) based on the feedback amount P. , And outputs the command voltage value V to the laser power supply 8.

The control unit 10 of the processing device 9 and the output control unit 6 of the laser device 1 are connected by a signal line, and the output control unit 6 is a trigger sent from the control unit 10 of the processing device 9. The signal Tr is received and the timing of laser oscillation is controlled.

The output P of the output monitor 5 is also sent to the controller 7. The control unit 7 inputs the laser output P output from the output monitor 5 and the command voltage V output from the output control unit 6 to the power supply 8, and outputs the command value V to the laser power supply 8 and the laser output energy P. A data table showing the relationship is created and stored.

Now, the process of creating a data table will be described.

This data table is created before the actual laser operation, that is, before the processing by the processing device 9 is started.
It is done in advance. FIG. 2 is a time-series graph showing how to provide voltage data to be stored as a data table.

As shown in the figure, from the output control section 6,
Command voltages V1, V2, V3 ... Vi-1, Vi, Vi + 1 ... Vn whose levels randomly change with time t are output to the laser power source 8. At the same time, the command voltages V1, V2 ... Are also output to the control unit 7. The command voltages V1, V2 ... Are changed stepwise with a time width Δt.

Thus, each command voltage Vi (i = 1 to n)
Is input to the laser power source 8, the laser oscillator 2 outputs laser light L having energy Pi corresponding to each command voltage Vi. In the output monitor 5, the energy P of the laser light L
i is sequentially detected, and the detected value Pi is input to the control unit 7.

The control section 7 associates the input command voltage Vi with the input laser output Pi and stores the relationship between the command voltage Vi and the laser output Pi as a table as shown in FIG. .

Here, as shown in FIG. 2, the command voltage V
Since 1, V2, ... Are given such that their values are random in time series, the values are also randomly arranged in the voltage data strings V1, V2, ... Stored in the data table shown in FIG. The Rukoto.

Therefore, as shown in FIG. 4, the voltage data strings V1, V2, ... May be rearranged in ascending order of the values v1, v2. That is, in the data table of FIG. 4, the smallest voltage Vi in the data table of FIG.
Becomes v1 and the maximum voltage Vi becomes vn. The laser output values Pi are also rearranged into p1, p2, ... According to the rearranged command voltages v1, v2.

By rearranging the data in the ascending order as shown in FIG. 4, it is possible to efficiently perform processing such as data reading.

That is, according to the data table of FIG. 4, when the laser output command value Pcom is set, even if the value Pcom does not exist in the data table, pi-1 <
Data pi-1 having a size satisfying the relationship of Pcom <pi,
The process of searching pi from the data table can be easily performed.

The calculation for obtaining the command voltage value Vcom corresponding to the laser output command value Pcom may be performed by using the above proportional distribution equation (1), but the voltage V of the laser power source 8 and the laser output P may be used. If there is no proportional relation between the laser power source voltage V and the laser output P, a function P = f indicating the relation between the laser power source voltage V and the laser output P is obtained.
(V) is obtained by actual measurement, and this function is (1)
You may use it instead of a formula. For example, the function f ()
If is a quadratic function, the following equation (2) can be used.

P = aV2 + bV (2) However, "a" and "b" are constants.

Here, the unknowns a and b can be calculated using the numerical values on the data table. Note that P and V
Even when the relationship between and can be expressed by a function other than a quadratic function (a cubic function or the like), it can be similarly obtained.

As shown in FIG. 5, the relationship between the input and output of the laser changes from P = f (V) to P = αf (V) or P = β depending on the temperature characteristics of the laser and the secular change of the laser medium.
Even if it changes to (V), the data table is recreated periodically or as needed, and the function αf (), β
By newly obtaining f (), it becomes possible to always obtain the relationship between the power supply voltage V and the laser output P, which accurately reflects the characteristics of the laser. FIG. 8 is a flowchart showing the processing procedure for creating the data table.

As shown in the figure, first, i is initially set to 1 (step 101), and the command voltage value Vi to the power source 8 is set to Vi.
(I = 1, 2, ... N) are sequentially calculated by the random number generation function RND ().
To generate a random number (steps 102, 106,
107).

Then, the command voltage value Vi generated in random numbers in step 102 is sequentially output to the laser power source 8 (step 103). Then, the command voltage Vi
The laser output value (energy) Pi of the laser light L oscillated and output by the laser oscillator 2 is read (step 104). Next, the command voltage value Vi and the laser output value Pi are stored in association with each other (step 105).

When the desired number n of data are stored (YES at step 107), as shown in FIG.
The command voltage values V1, V2 ... Vn are rearranged in the order of decreasing value v1 (minimum value), v2 ... vn (maximum value), and the laser power source 8
To create a data table in which the command voltage value vi and the laser output value pi are arranged in ascending order (step 1).
08).

In this embodiment, a plurality of command voltages Vi having different values are randomly generated in step 102, but the command voltages Vi having a plurality of different values are periodically increased and decreased repeatedly. You may output as a function value of the function of.

For example, the voltage Vi can be generated by the equation Vi = sin (iπ / d) (where d is a constant).

Further, a plurality of command voltages having different values may be sequentially generated stepwise in the direction of increasing the value and the direction of decreasing the value.

That is, FIG. 6 is a diagram corresponding to FIG. 2 described above, in which a plurality of command voltages for the laser power source 8 are increased stepwise at different levels (voltage V1 in FIG. 6).
~ V (N + 1) / 2) and the decreasing direction (voltage V (N + 1) in FIG. 6)
/ 2 to VN). In this case, VN-i = Vi +
The condition of 1 (i = 0 to (N + 1) / 2−1) is satisfied.

Here, the laser output value P for the same command value VN-i and Vi + 1 is not always the same due to the influence of the history of laser oscillation, as described above.

Therefore, in order to remove the influence of the history of laser oscillation, the processing of the next step 105 'is performed instead of the processing of step 105 described above.

Data to be respectively associated with the command voltage VN-i and the command voltage Vi + 1 having the same value as the command voltage VN-i, the laser output PN-i and the command voltage Vi + 1 corresponding to the command voltage VN-i.
Average value (PN-i + Pi +) with the laser output Pi + 1 corresponding to
1) / 2 (step 105 ').

By creating the data table as described above, the influence of the history of the laser oscillation operation in the past can be averaged, and the influence of the history of the laser oscillation operation can be reduced. Therefore, when the laser is actually operated, it is possible to accurately obtain the desired laser output value as instructed.

Further, as described above, the command voltages V1, V2 ... Which are used as the data of the data table are not output, but the command voltages V1, V2.
Immediately before starting to output, the voltage V0 at a constant level corresponding to the energy value P0 of the laser light L during the actual laser operation may be output to the power supply 8 for a predetermined time.

That is, instead of the processing of steps 102 and 103, the following processing of steps 102 'and 103' is performed. FIG. 7B is a diagram corresponding to FIG. First, the voltage value V0 corresponding to the load P0 expected in normal laser operation is output to the power supply 8 in advance. Then, only when the data V1, V2, V3 ... On the data table is acquired, the voltage is increased or decreased with reference to the constant voltage V0. This increase / decrease can be performed randomly as in step 102. Further, as described above, it may be given by a function that repeatedly increases and decreases periodically as in the formula Vi = sin (iπ / d). Further, as shown in FIG. 6, it may be given as increasing and decreasing stepwise.

In any case, immediately before the command voltages V1, V2, V3 ... Are output, the constant voltage V0 may be already output to the power source 8 for at least the time ΔT (step 102 ', 103 ': see FIG. 7B).

As a result, as shown in FIG.
The laser output Pi corresponding to each command voltage value Vi (i = 1 to n) is sequentially obtained. As a method of storing in the data table, Vi and Pi may be stored as they are, and since the reference voltage value V0 and the reference energy value P0 are known in advance, the deviations Vi-V0 and Pi-P0 from the reference value.
May be stored.

As described above, according to the embodiment shown in FIGS. 7 (a) and 7 (b), the data table is sampled immediately after the load is normally used during the laser operation for a certain period of time. Since the operation is started, not only the influence of the history of laser operation can be removed, but also a data table close to the actual laser operation state can be created. Therefore, the desired laser output value as instructed can be accurately obtained during the actual laser operation.

Now, FIG. 9 is a flow chart showing a procedure of processing for causing laser oscillation during actual laser operation using the data table created as described above. In this process, it is assumed that a data table arranged in ascending order of command voltage as shown in FIG. 4 is used.

First, a desired laser output command value Pcom required for laser processing is set and input by a laser output power setting device (not shown) (step 201).

Then, after i is initialized to 1 (step 202), it is judged whether or not the laser output command value Pcom is smaller than the minimum value P1 on the data table (step 203). Here, if it is determined that it is smaller than the minimum value Pi (YES at step 203), an alarm signal is output, the laser output command value Pcom does not exist in the data table, and the command voltage value Vcom is accurately calculated. Notify the operator that he cannot do it (step 20).
4).

Next, it is judged whether or not the laser output command value Pcom matches the data Pi on the data table (step 205). As a result, when it is determined that they match, the corresponding command voltage value Vi is read from the data table, and this is set as the voltage Vcom to be output to the laser power source 8 (step 206), and this command voltage Vcom is set.
Is output to the laser power source 8 (step 209).

When it is determined in step 205 that the laser output command value Pcom does not match the data Pi on the data table, the process proceeds to step 207, where the laser output command value Pcom corresponds to the current i. It is determined whether the output value is larger than Pi. Here, if it is determined that it is larger than the laser output value Pi corresponding to the current i (determination YES in step 207), i is incremented by +1 (step 210), and then the procedure shifts to step 205 again. .

After i is incremented by +1 (step 210), if i reaches the final value n (YES at step 211), an alarm signal is output and the laser output command value Pcom is set in the data table. Does not exist on
The operator is informed that the command voltage value Vcom cannot be calculated accurately (step 212).

Further, as a result of the judgment in step 205, it becomes clear that the laser output command value Pcom does not match the data Pi on the data table, and the laser output command value Pcom is within the range of the data table. If it is determined that the answer is NO (determination NO in step 207), P1 <Pcom <
Under the condition of P2, two laser output values P1 and P2 are selected from the data table, and P1, P2 and P1,
Based on the command voltage values V1 and V2 corresponding to P2, respectively, the command voltage value V is proportionally distributed using the above equation (1).
ask com. At least two laser output values P
If 1 and P2 are acquired, a straight line showing the relationship between the command voltage V and the laser output P can be obtained, so P1 <P2 <
The command voltage Vco is calculated by the interpolation calculation based on the two laser output values P1 and P2 having the relation of Pcom or Pcom <P1 <P2.
You may ask for m.

If proportional distribution cannot be applied,
The command voltage value Vcom may be obtained by a required functional expression such as the functional expression of the above-mentioned expression (2) (step 20).
8).

Thereafter, this command voltage Vcom is output to the laser power source 8 (step 209).

Although the command voltage V is output to the laser power source 8 in the embodiment, the laser oscillation may be controlled by outputting the command current to the power source 8. In this case, the data table showing the relationship between the command current and the laser output value P is created in the same manner as the data table showing the relationship between the command voltage V and the laser output value P.

[Brief description of the drawings]

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

FIG. 2 is a graph showing how command voltages are randomly output.

FIG. 3 is a graph conceptually showing the contents of a data table.

FIG. 4 is a graph conceptually showing the contents of a data table.

FIG. 5 is a graph showing that the relationship between the command voltage and the laser output is represented by a curve.

FIG. 6 is a graph showing how the command voltage increases stepwise and is output while decreasing.

7 (b) is a graph showing a state in which a constant level voltage is output for a certain period of time immediately before the command voltage increases / decreases, and FIG. 7 (a) shows the command voltage of FIG. 7 (b). 7 is a graph showing how the laser output value changes in accordance with.

FIG. 8 is a flowchart showing a procedure of processing for creating a data table.

FIG. 9 is a flowchart showing a procedure of processing when laser oscillation is performed during actual laser operation using a data table.

FIG. 10 is a diagram used to describe a conventional technique.

FIG. 11 is a diagram used for explaining a conventional technique.

FIG. 12 is a diagram used to describe a conventional technique.

[Explanation of symbols]

 1 Laser Device 2 Laser Oscillator 6 Output Control Unit 7 Control Unit 8 Laser Power Supply

Claims (5)

[Claims] 1. An output command value setting means for setting an energy value of laser light output from a laser oscillator as an output command value, wherein the laser light having the output command value set by the output command value setting means is the above-mentioned. In a laser light output control device that controls the output of laser light so as to be output from a laser oscillator, a detection unit that detects energy of laser light output from the laser oscillator, and a command voltage or command current to be input A laser power source for outputting a laser beam of a corresponding energy from the laser oscillator, and before the actual laser operation, with respect to the laser power source,
A plurality of command voltages or command currents having different values are output at random, and the energy value detected by the detection means is input to indicate the relationship between the value of the command voltage or command current and the energy value of laser light. Data table creating means for creating a data table, and during actual laser operation, a command voltage or a command current corresponding to the output command value set by the output command value setting means is read from the data table, and the laser power supply is read. An output control device for laser light, comprising: 2. An output command value setting means for setting an energy value of laser light output from a laser oscillator as an output command value, and the laser light having the output command value set by the output command value setting means is the above-mentioned. In a laser light output control device that controls the output of laser light so as to be output from a laser oscillator, a detection unit that detects energy of laser light output from the laser oscillator, and a command voltage or command current to be input A laser power source for outputting a laser beam of a corresponding energy from the laser oscillator, and before the actual laser operation, with respect to the laser power source,
The command voltage or command current having a plurality of different values is output as a function value of a predetermined function that repeatedly increases and decreases cyclically, and the energy value detected by the detecting means is input to the command voltage or command current. And a command voltage or command corresponding to the output command value set by the output command value setting device during actual laser operation. An output control device for laser light, comprising: output control means for reading out a current from the data table and outputting it to the laser power supply. 3. An output command value setting means for setting an energy value of laser light output from a laser oscillator as an output command value, wherein the laser light having the output command value set by the output command value setting means is the above-mentioned. In a laser light output control device that controls the output of laser light so as to be output from a laser oscillator, a detection unit that detects energy of laser light output from the laser oscillator, and a command voltage or command current to be input A laser power source for outputting a laser beam of a corresponding energy from the laser oscillator, and before the actual laser operation, with respect to the laser power source,
A plurality of command voltages or command currents having different values are sequentially output in a stepwise manner in a direction of increasing the value and in a direction of decreasing the value, and the energy value detected by the detecting means is input, and the increasing direction and the The average value of both energy values corresponding to both command values that are the same value in the decreasing direction is obtained, and the average value is used as the energy value corresponding to the same command value, and the value of the command voltage or command current and the laser light Data table creating means for creating a data table showing a relationship with the energy value of the data, and at the time of actual laser operation, the command voltage or command current corresponding to the output command value set by the output command value setting means is used as the data. An output control device for laser light, comprising: output control means for reading from a table and outputting to the laser power source. 4. Immediately before outputting a plurality of command voltages or command currents of different values used as data of the data table, a voltage or current of a constant level corresponding to the energy value of laser light during actual laser operation is set. The laser light output control device according to claim 1, 2 or 3, wherein the laser power is output to the laser power source for a predetermined time. 5. The output control means determines whether or not the output command value set by the output command value setting means matches the laser light energy value on the data table, and as a result, it matches. In this case, the command voltage or command current on the data table corresponding to the coincident laser light energy value is output to the laser power source, and if the result of the judgment is that they do not coincide, the output command At least two laser light energy values in the vicinity of the output command value set by the value setting means are selected from the data table, and the command voltage on the data table corresponding to the selected at least two laser light energy values or A command voltage or command current corresponding to the output command value set by the output command value setting means is obtained by interpolation calculation based on the command current, and the obtained The command voltage or command current, the output control apparatus of a laser beam of claim 1 or 2, wherein the laser is intended to be output to the power supply.