CN209860345U - Excimer laser dose stabilization control system - Google Patents
Excimer laser dose stabilization control system Download PDFInfo
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- CN209860345U CN209860345U CN201920428832.1U CN201920428832U CN209860345U CN 209860345 U CN209860345 U CN 209860345U CN 201920428832 U CN201920428832 U CN 201920428832U CN 209860345 U CN209860345 U CN 209860345U
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Abstract
The utility model discloses an excimer laser dose stability control system, wherein, control system includes: the high-voltage discharge assembly is used for receiving the trigger signal and generating pulse high voltage according to the trigger signal and a preset high-voltage set value; the laser is filled with working gas, and the working gas is used for receiving the pulse high voltage and generating laser pulses; the laser parameter measuring component is used for detecting the energy value of the laser pulse and outputting the laser pulse to the outside; the energy stability controller is electrically connected with the high-voltage discharge assembly and is used for acquiring an energy value; the utility model discloses a laser parameter measurement subassembly detects pulse laser's energy value, through the high pressure that discharges of energy stability controller control high-pressure discharge subassembly when energy value skew predetermines energy value, and then control laser pulse's energy value and predetermine energy value and be close or equal to prevent that the serious overshoot of several preceding laser pulse of every sequence has guaranteed every laser pulse's stability.
Description
Technical Field
The utility model relates to a precision instruments controls the field, especially relates to an excimer laser dose stability control system.
Background
The 193nmArF excimer laser is a pulse type gas laser applied to deep ultraviolet characteristics, has the characteristics of high repetition frequency, large energy, short wavelength and narrow line width, and is an excellent laser light source for a microelectronic photoetching system.
The laser emitted by the excimer laser is emitted in a pulse form, energy is different from pulse to pulse due to charge change or working gas deterioration, and meanwhile, the energy of the laser pulse has a certain deviation from the set expected pulse energy, so that the dose stability of the laser energy of the laser fluctuates greatly. In semiconductor lithography, the result of dose instability is represented by overexposure or underexposure during the lithography process, making the resulting lines rough. In order to keep the accuracy of the lithography within the allowable range, the stability of the excimer laser pulse dose must be well controlled. Therefore, the control for solving the dose stability is a key in the development process of the excimer laser.
During the operation of the laser, due to the influence of factors such as gas temperature, gas degradation or update, and operation time, the excimer laser always has fluctuation of single-pulse energy, drift of average pulse energy and overshoot of single-pulse energy. Both of these phenomena affect the dose stability and energy stability of the laser. The overshoot of energy means that in burst mode, the time interval between one group of pulses is much higher than that of other pulses in each group due to the non-discharge state of gas under the same discharge high voltage. The phenomena of single pulse energy fluctuation and energy value overshoot are inherent characteristics of an excimer laser, the phenomena are difficult to improve simply by changing the optical characteristics of the laser, and necessary control algorithms are required to be adopted, so that the dose stability is greatly improved.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing an excimer laser dose stability control system to solve among the prior art excimer laser under burst mode, in a set of pulse and a set of pulsed time interval, because the gas is in the state of not discharging and leads to under the same high pressure that discharges each a set of first several pulses will be than other pulse many more high problems.
In order to solve the above problem, the utility model provides an excimer laser dose stabilization control system, it includes:
the high-voltage discharge assembly is used for receiving a trigger signal from the outside and generating a pulse high voltage according to the trigger signal and a preset high-voltage set value;
the laser is filled with working gas, and the working gas is used for receiving the pulse high voltage and generating laser pulses;
a laser parameter measuring unit for detecting an energy value of the laser pulse and outputting the laser pulse to the outside;
the energy stability controller is electrically connected with the high-voltage discharge assembly and is used for acquiring the energy value of the laser pulse; when the energy value is smaller than the preset energy value, the energy stability controller controls the high-voltage discharge assembly to increase the discharge voltage according to the preset control algorithm, so that the energy value is close to or equal to the preset energy value.
As a further improvement of the present invention, the preset control algorithm includes a closed-loop control algorithm, which realizes the control of the energy value through the PI control algorithm and the formula (1):
wherein E isset(n +1) is the energy value, DK, required for the next laser pulsepDelta dose (n) is the proportional coefficient of PI control algorithm and is the deviation of the laser pulse dose stability at this time, DKiIs the integral coefficient of the PI control algorithm, DT is the period coefficient of the PI control algorithm,is the sum of the deviations in the dose stability of the historical laser pulses.
As a further improvement of the utility model, the preset control algorithm further comprises an error control algorithm separated from the closed-loop control algorithm, which is used for controlling the serious overshoot of the previous 20 laser pulses of the pulse sequence:
the error control algorithm calculates the error between the energy value of the nth laser pulse in the mth Burst sequence and the energy set value when the laser emits light according to the formula (2):
Eerror(m,n)＝Eset-Emeasured(m.n) (2)，
wherein E ismeasured(m, n) is the energy value of the nth laser pulse in the mth Burst sequence when the laser emits light, Eerror(m, n) is an error;
calculating the energy value required by the nth laser pulse in the next pulse sequence according to a PI control algorithm and a formula (3);
where HV (m +1, n) is the energy value required for the nth laser pulse in the next pulse sequence, PKpIs a proportional parameter, PK, of a PI control algorithmiIs the integral parameter of the PI control algorithm, T is the control period parameter of the PI control algorithm,is an integral of the historical error.
As the utility model discloses a further improvement, calculate the energy value of the nth laser pulse in the mth Burst sequence when the light-emitting according to formula (2) and the error of energy setting value, specifically include:
in the form of an incremental form by a PI feedback control algorithm, as shown in equation (4);
where Δ HV (m +1, n) represents a variation value of the preset discharge high voltage of the nth laser pulse in the next pulse train, and HV (m, n) represents an energy value required for the nth laser pulse in the present pulse train.
The utility model discloses a laser parameter measurement subassembly detects pulse laser's energy value, through the high pressure that discharges of energy stability controller control high-pressure discharge subassembly when energy value skew predetermines energy value, and then control laser pulse's energy value and predetermine energy value and be close or equal to prevent that the serious overshoot of several preceding laser pulse of every sequence has guaranteed every laser pulse's stability.
Drawings
FIG. 1 is a schematic block diagram illustrating the structure of an embodiment of the excimer laser dose stabilization control system of the present invention;
fig. 2 is a control effect diagram of an embodiment of the excimer laser dose stabilization control system of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Fig. 1 shows an embodiment of the excimer laser dose stabilizing control system of the present invention, referring to fig. 1, in this embodiment, the control system thereof includes a high voltage discharge assembly, a laser parameter measurement assembly and an energy stabilizing controller.
The high-voltage discharge assembly is used for receiving a trigger signal from the outside and generating a pulse high voltage according to the trigger signal and a preset high-voltage set value; the laser is filled with working gas, and the working gas is used for receiving pulse high voltage and generating laser pulse; the laser parameter measuring component is used for detecting the energy value of the laser pulse and outputting the laser pulse to the outside; the energy stability controller is electrically connected with the high-voltage discharge assembly and is used for collecting the energy value of the laser pulse; when the energy value is smaller than the preset energy value, the energy stability controller controls the high-voltage discharge assembly to increase the discharge voltage according to the preset control algorithm, so that the energy value is close to or equal to the preset energy value.
Specifically, when the laser works, when the high-voltage discharge assembly receives an external trigger signal, a pulse high voltage is generated according to a high-voltage setting signal (preset high-voltage setting value), working gas in a cavity of the laser is electrically shocked, the laser is triggered to generate a laser pulse, and the laser pulse is measured by the laser parameter measuring assembly and then outputs the laser pulse for working.
Furthermore, the laser pulse generated by the laser and the energy of the working laser are mainly controlled by the high voltage of the high-voltage discharge assembly, and the higher the discharge high voltage is, the larger the light-emitting energy of the laser is in the working voltage range of the high-voltage discharge assembly.
Further, the dose of the laser is defined as the sum of the energies of the N pulses, i.e.
Where j is the pulse number in each Burst sequence, EiIs the energy value of the ith pulse.
The dose stability of the laser is defined as:
wherein DosetargetIs the dose setting.
And (3) calculating the dose stability after each laser pulse (the serial number of the position where the pulse is located is greater than or equal to N) in the Burst sequence is sent, and measuring the dose stability of each Burst by using the maximum value and the minimum value of the dose stability in each Burst.
The energy value of the pulse laser is detected through the laser parameter measuring component, the discharge high voltage of the high-voltage discharge component is controlled through the energy stability controller when the energy value deviates from the preset energy value, and then the energy value of the laser pulse is controlled to be close to or equal to the preset energy value, so that the first laser pulses of each sequence are prevented from being excessively adjusted seriously, and the stability of each laser pulse is ensured.
In order to realize the control of the energy value, on the basis of the above embodiment, in this embodiment, the preset control algorithm includes a closed-loop control algorithm, which realizes the control of the energy value through the PI control algorithm and the formula (1):
wherein E isset(n +1) is the energy value, DK, required for the next laser pulsepDelta dose (n) is the proportional coefficient of PI control algorithm and is the deviation of the laser pulse dose stability at this time, DKiIs the integral coefficient of the PI control algorithm,DT is the cyclic coefficient of the PI control algorithm,is the sum of the deviations in the dose stability of the historical laser pulses.
Specifically, for the first laser pulse of each Burst, the energy setting is:
when the position number of the laser pulse in a Burst is smaller than the number N of the laser pulses required by the dose calculation, the dose calculation is in the form of the following formula, which shows that the laser pulse which is not emitted is calculated according to the dose which accords with the energy set value:
after the single pulse energy required to be set is calculated in a closed loop mode by a dose stability algorithm, the subsequent work is to ensure that the control algorithm of the system can ensure that the single pulse energy of the laser reaches the energy value required to be set.
In order to prevent serious overshoot of the first few laser pulses in a pulse train, in this embodiment, based on the above embodiment, the preset control algorithm further includes an error control algorithm, separate from the closed-loop control algorithm, for controlling serious overshoot of the first 20 laser pulses in the pulse train:
the error control algorithm calculates the error between the energy value of the nth laser pulse in the mth Burst sequence and the energy set value when the laser emits light according to the formula (2):
Eerror(m,n)＝Eset-Emeasured(m.n) (2)，
wherein E ismeasured(m, n) is the energy value of the nth laser pulse in the mth Burst sequence when the laser emits light, Eerror(m, n) is an error;
specifically, since the first several pulses are excessively overshot due to the same discharge high voltage in one pulse train, it is difficult to achieve the intended control effect if the same feedback algorithm as that of the subsequent pulses is used. In this embodiment, a control method in which a control algorithm of a front laser pulse is separated from an algorithm of a subsequent laser pulse is adopted.
Further, according to the pulse energy test experiments of a large number of lasers, the first 20 pulses of a pulse sequence are selected by the embodiment by adopting a single control method, and the following pulses adopt the same control method.
Further, for overshoot of the first 20 laser pulses in the laser pulse sequence, the method adopted in this embodiment considers both the number of the pulse sequence where the laser pulse is located and the position of the laser pulse in the pulse sequence, that is, the discharge high voltage set this time needs to be controlled with reference to the discharge high voltage and the light emission energy of the laser pulse with the same number in the pulse sequence where the laser pulse is located in the history pulse sequence.
Aiming at the error, calculating the energy value required by the nth laser pulse in the next pulse sequence according to a PI control algorithm and a formula (3);
where HV (m +1, n) is the energy value required for the nth laser pulse in the next pulse sequence, PKpIs a proportional parameter, PK, of a PI control algorithmiIs the integral parameter of the PI control algorithm, T is the control period parameter of the PI control algorithm,is an integral of the historical error.
In order to make the formula (2) easier to implement in engineering, on the basis of the above embodiment, in this embodiment, an error between an energy value of an nth laser pulse in an mth Burst sequence and an energy set value when the laser emits light is calculated according to the formula (2), which specifically includes:
in the form of an incremental form by a PI feedback control algorithm, as shown in equation (4);
where Δ HV (m +1, n) represents a variation value of the preset discharge high voltage of the nth laser pulse in the next pulse train, and HV (m, n) represents an energy value required for the nth laser pulse in the present pulse train.
In particular, in implementing the control algorithm, sinceThe existing method occupies a large amount of memory, and the integral saturation phenomenon is easy to occur. For easy implementation in engineering, the present embodiment is implemented in an incremental form of P I feedback control algorithm, and the implementation formula is shown in formula (4).
Further, in order to avoid calculating the integral term during implementation, the present embodiment still adopts an incremental representation of P I feedback control algorithm, as shown in the following formula:
in practical implementation, the discharge high voltage value of the laser pulse is limited by the inherent properties of the high voltage discharge device, and is limited to a maximum value and a minimum value, so that the discharge high voltage value HV (m +1, n) or HV (n +1) set for each pulse is set to a maximum value and a minimum value.
Under the control of the energy stabilizing controller in the above embodiment, the control effect is obtained as shown in fig. 2. One laser pulse sequence contains 375 pulses, the laser works under the light-emitting frequency of 4KHz, the number N of laser pulses for calculating the dose is set to be 30, and the controlled target dose value is set to be 300 mJ. In the graph 10, the dose stability of the laser without the algorithm is shown, and the dose accuracy is approximately 4% as can be seen from the graph; the dose stability data that produce when adopting that 20 shows in the picture the utility model discloses a dose stability control algorithm, its dose precision is about 0.6%, can see out from this and adopt the utility model discloses excimer laser's dose stability has obtained fine control.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the expanded contents of the method embodiment in this specification, since the expanded contents are similar to those of the apparatus embodiment, detailed description is not repeated, and for the relevant points, reference may be made to part of the description of the expanded contents of the apparatus embodiment.
The above detailed description of the embodiments of the present invention is only exemplary, and the present invention is not limited to the above described embodiments. It will be apparent to those skilled in the art that any equivalent modifications or substitutions can be made to the present invention without departing from the spirit and scope of the invention, and therefore, all equivalent changes, modifications, improvements, etc. made without departing from the spirit and scope of the invention are intended to be covered by the scope of the invention.
Claims (1)
1. An excimer laser dose stabilization control system, comprising:
the high-voltage discharge assembly is used for receiving a trigger signal from the outside and generating a pulse high voltage according to the trigger signal and a preset high-voltage set value;
a laser filled with working gas for receiving the pulse high voltage and generating laser pulses;
a laser parameter measuring component for detecting an energy value of the laser pulse and outputting the laser pulse to the outside;
the energy stability controller is electrically connected with the high-voltage discharge assembly and is used for acquiring the energy value of the laser pulse; when the energy value is larger than a preset energy value, the energy stability controller controls the high-voltage discharge assembly to reduce the discharge voltage according to a preset control algorithm, and when the energy value is smaller than the preset energy value, the energy stability controller controls the high-voltage discharge assembly to increase the discharge voltage according to the preset control algorithm.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109950786A (en) * | 2019-03-29 | 2019-06-28 | 北京科益虹源光电技术有限公司 | Excimer laser dosage stability control system and control method |
| CN112038267A (en) * | 2020-09-21 | 2020-12-04 | 京东方科技集团股份有限公司 | Laser energy adjusting device |
| CN109950786B (en) * | 2019-03-29 | 2024-04-19 | 北京科益虹源光电技术有限公司 | Excimer laser dose stabilization control system and control method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109950786A (en) * | 2019-03-29 | 2019-06-28 | 北京科益虹源光电技术有限公司 | Excimer laser dosage stability control system and control method |
| CN109950786B (en) * | 2019-03-29 | 2024-04-19 | 北京科益虹源光电技术有限公司 | Excimer laser dose stabilization control system and control method |
| CN112038267A (en) * | 2020-09-21 | 2020-12-04 | 京东方科技集团股份有限公司 | Laser energy adjusting device |
| CN112038267B (en) * | 2020-09-21 | 2024-02-20 | 京东方科技集团股份有限公司 | Laser energy adjusting device |
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