WO2023273392A1 - High-stability excimer laser apparatus - Google Patents

Abstract

A high-stability excimer laser apparatus, comprising a discharge resonant cavity, a line width narrowing module, a measurement module and a control module. The line width narrowing module comprises a beam expanding apparatus and an echelle grating, which are sequentially arranged in a laser emission direction of a first side of the discharge resonant cavity. The measurement module comprises a central wavelength fine measurement apparatus and a central wavelength coarse measurement apparatus, wherein the central wavelength coarse measurement apparatus comprises a reflection apparatus, a light beam convergence apparatus and a first photoelectric detection apparatus, and is used for performing central wavelength coarse measurement, and the central wavelength fine measurement apparatus is arranged on a second side opposite the first side of the discharge resonant cavity, and is used for receiving a laser beam which is emitted from the second side, and for performing central wavelength fine measurement. The control module is respectively connected to the discharge resonant cavity, the central wavelength fine measurement apparatus and the central wavelength coarse measurement apparatus, and is used for adjusting a parameter in the discharge resonant cavity according to measurement results of the central wavelength fine measurement apparatus and the central wavelength coarse measurement apparatus.

Description

High stability excimer laser device technical field

The present application relates to the field of lasers, in particular to a high-stability excimer laser device.

Background technique

The laser output by the excimer laser is widely used in the field of semiconductor chip processing because of its short wavelength, narrow line width, and high energy. For example, the laser output by the excimer laser is the most common light source in the field of lithography.

With the continuous development of chip processing technology, the size requirements for chips have reached 28nm, 14nm or even smaller. Therefore, the requirements for excimer lasers used to process chips are also increasing. Not only does the laser need to be able to release higher energy and have a narrower spectrum, but it also needs to have a central wavelength with high stability during the working process. Higher requirements are put forward for the on-line measurement of excimer laser energy and central wavelength, central wavelength and energy closed-loop device and closed-loop feedback control.

In the patents US6539046 and US6317448, the central wavelength measurement method using FP etalon and grating was proposed. The FP standard has extremely high wavelength sensitivity, but the measurement range is relatively small, which cannot meet the needs of full-scale measurement of excimer lasers. Therefore, , the center wavelength needs to be roughly measured by the grating method first, and then the FP etalon is used for fine measurement to achieve a wide range and high-precision measurement of the center wavelength.

In the patent CN109073463, two FP etalons are used to measure the center wavelength of the laser at the same time. One of the FP etalons has a relatively large free spectral path and is used for rough measurement of the center wavelength. The other FP etalon has a relatively small free spectral path and is used for the center The precise measurement of the wavelength, the combination of the two realizes the large-range and high-precision measurement of the central wavelength.

The generation of the narrow line width and the tuning of the central wavelength of the excimer laser are completed by the line width narrowing module. In the patents US6192064, US6560254, US10416471, CN1232010, CN102576974 and CN107534266, the beam expander unit and the echelle grating are used for the laser The spectral width is narrowed, and the central wavelength is controlled by adjusting the angle of the mirror, prism or echelle grating, which is used for tuning the central wavelength of the laser. Patents US6985508, CN100397732, CN107851958 and CN107925214 introduce the closed-loop feedback method of excimer laser energy and central wavelength. By real-time measurement of excimer energy and central wavelength and closed-loop feedback, the long-term stable output of excimer laser is guaranteed.

Therefore, how to design the excimer laser so that the excimer laser can have a relatively stable central wavelength during the working process has become a technical problem that needs to be solved urgently in this field.

Contents of the invention

The present application provides a high-stability excimer laser device to solve the problems existing in the prior art.

The application provides a high-stability excimer laser device, which includes: a discharge resonator, a line width narrowing module, a detection module, and a control module;

The line width narrowing module includes a beam expander and an echelle grating sequentially arranged along the laser emission direction from the first side of the discharge resonator;

The detection module includes a central wavelength precise measurement device and a central wavelength rough measurement device; wherein, the central wavelength rough measurement device includes a reflection device, a beam converging device and a first photoelectric detection device, and the reflection device is used to convert the discharge Part of the light beam emitted from the first side of the resonant cavity is transmitted to the echelle grating, and the beam converging device is arranged in the exit direction of the echelle grating for converging the part of the light beam that is emitted by the echelle grating transmitted to said first photodetection device;

The central wavelength precision measuring device is arranged on the second side opposite to the first side of the discharge resonant cavity, and is used to receive the laser beam emitted from the second side and perform precise central wavelength measurement;

The control module is respectively connected with the discharge resonant cavity, the central wavelength precise measurement device and the central wavelength rough measurement device, and is used to measure the The parameters in the discharge resonant cavity are adjusted.

Optionally, the beam expander is a beam expander prism group, and the echelle grating is a dispersion grating;

The reflection device is arranged on the incident side of the light beam of the beam expander prism group, and is located in the optical path after the incident light is reflected by the incident surface of the beam expander; the setting angle of the reflection device satisfies the requirement of receiving the After the light is reflected, it is reflected to the echelle grating twice.

Optionally, the converging device is a convex lens or a concave mirror; the first photodetection device is a charge-coupled device;

The beam converging device is used for converging the dispersed outgoing light so that the converging light is irradiated on the detection surface of the first photodetection device to form interference fringes;

The first photoelectric detection device is configured to receive the interference fringes, convert the interference fringes into corresponding interference fringe information, and send the interference fringe information to the control module.

Optionally, the reflecting device and the beam converging device are arranged inside the line width narrowing module.

Optionally, the central wavelength precise measurement device includes a first beam splitter, a homogenizer, a second beam splitter, a collimator, an FP etalon, a second converging mirror, and a second Photoelectric detection device;

The first beam splitter is used to receive the laser light emitted from the second side of the discharge resonator, split the laser light, and irradiate one of the split laser beams on the homogenizer superior;

The homogenizer is arranged between the first beam splitter and the second beam splitter, and is used to homogenize the laser light so that the homogenized laser light enters the second beam splitter;

The second beam splitter is used to split the laser beam emitted by the homogenizer, and irradiate one of the laser beams on the collimating mirror;

The collimating mirror is arranged between the second beam splitter and the FP etalon, and is used to collimate the laser light irradiated on the FP etalon;

The FP etalon is used to reflect the laser light passing through the FP etalon multiple times to form multi-level light interference, and converge the multi-level light interference to the second photoelectric through the second converging mirror detection means to form a second interference fringe.

Optionally, the detection module further includes an energy detection device, the energy detection device includes a third photodetection device, and the third photodetection device is arranged on another beam of light after splitting by the second beam splitter. In the outgoing direction of the laser, it is used to detect the laser energy information of the laser, and send the laser energy information to the control device.

Optionally, the control device includes: a central wavelength rough measurement board and a central wavelength fine measurement board;

The central wavelength coarse measurement board is connected to the first photoelectric detection device and the central wavelength fine measurement board respectively;

The central wavelength rough measurement board is used to obtain the interference fringe information sent by the first photoelectric detection device, and obtain the rough measurement value of the laser wavelength according to the interference fringe information sent by the first photoelectric detection device; The rough measurement value of the laser wavelength is sent to the central wavelength fine measurement board;

The central wavelength precision measurement board is also connected to the second photoelectric detection device;

The center wavelength precise measurement board is used to obtain the second interference fringe information sent by the second photoelectric detection device, and according to the second interference fringe information, obtain the center wavelength roughness information sent by the center wavelength rough measurement board. Measured value; according to the second interference fringe information and the rough measured value of the central wavelength, obtain the fine measured value of the central wavelength.

Optionally, the control device further includes a laser tuning controller connected to at least one device of the beam expander for adjusting the beam irradiated by the beam expander to the echelle grating Angle.

Optionally, the laser tuning controller is specifically configured to adjust the rotation of at least one component of the beam expander according to the difference between the obtained precise value of the central wavelength and the target value of the central wavelength, so as to adjust the radiation to the echelle grating angle of the beam.

Optionally, the control device includes: an energy measurement board, a high-voltage power supply controller;

The energy measurement board is respectively connected to the high-voltage power supply controller and the third photoelectric detection device;

The energy measurement board is configured to receive the laser energy information sent by the third photoelectric detection device; obtain the laser energy information output by the excimer laser device according to the laser energy information, and send the laser energy information to To the high-voltage power supply controller; the high-voltage power supply controller is connected to the discharge resonant cavity, and is used to receive the laser energy information, and control the laser energy released by the discharge resonant cavity according to the laser energy information.

Compared with the prior art, the present application has the following advantages:

The high-stability excimer laser device provided by the application includes: a discharge resonator, a line width narrowing module, a detection module, and a control module; A beam expander and an echelle grating arranged in sequence; the detection module includes a central wavelength precise measurement device and a central wavelength rough measurement device; wherein, the central wavelength rough measurement device includes a reflection device, a beam converging device and a first photoelectric detector device, the reflecting device is used to transmit part of the light beam emitted from the first side of the discharge resonator to the echelle grating, and the beam converging device is arranged in the outgoing direction of the echelle grating, and is used to transfer the aforementioned part to the echelle grating The light beam is converged by the outgoing light of the echelle grating and then transmitted to the first photodetection device; the central wavelength precise measurement device is arranged on the second side opposite to the first side of the discharge resonant cavity for receiving The laser beam emitted from the second side is used for precise measurement of the central wavelength; the control module is connected to the discharge resonator, the precise central wavelength measurement device and the rough central wavelength measurement device respectively, for The parameters in the discharge resonant cavity are adjusted according to the measurement results of the central wavelength precise measuring device and the central wavelength rough measuring device.

The high-stability excimer laser device provided by this application realizes the real-time accurate measurement of the central wavelength of the excimer laser through the line width narrowing module, the central wavelength rough measurement device, the detection module, and the central wavelength precise measurement device. When the central wavelength of the molecular laser does not meet the preset central wavelength, the driving adjustment module controls the line width narrowing module to adjust, so that the central wavelength of the excimer laser meets the preset central wavelength. The above-mentioned device realizes the closed-loop feedback of the central wavelength of the excimer laser, and improves the stability of the laser in the working process.

Description of drawings

Fig. 1 is the structural representation of the highly stable excimer laser device provided by the embodiment of the present application;

FIG. 2 is a schematic structural diagram of a discharge resonant cavity provided in an embodiment of the present application;

FIG. 3 is a schematic structural diagram of a linewidth narrowing module and a central wavelength rough measurement device provided in an embodiment of the present application;

Fig. 4 is a schematic structural diagram of the central wavelength precise measurement module provided by the embodiment of the present application;

5 is a schematic diagram of the second interference fringes produced by the FP etalon provided in the embodiment of the present application;

Fig. 6 is a flow chart of the closed-loop control of the energy released by the excimer laser device and the central wavelength provided by the embodiment of the present application.

detailed description

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the application. However, the present application can be implemented in many other ways different from those described here, and those skilled in the art can make similar promotions without violating the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below .

The terminology used in the present application is for the purpose of describing particular embodiments only, and is not intended to limit the present application. The descriptions used in this application and in the appended claims, such as: "a", "first", and "second", etc., are not limited to the number or sequence, but Used to distinguish information of the same type from one another.

The high-stability excimer laser device provided by this application realizes real-time accurate measurement of the central wavelength of the excimer laser through a line width narrowing module, a central wavelength rough measurement device, a detection module, and a central wavelength precise measurement device. When the central wavelength of the molecular laser deviates from the preset central wavelength, it can be adjusted through the line width narrowing module, so that the central wavelength of the excimer laser meets the preset central wavelength. The above-mentioned device realizes the closed-loop feedback of the central wavelength of the excimer laser, and improves the stability of the laser in the working process.

In order to facilitate the understanding of the high-stability excimer laser device provided by this application, the high-stability laser device provided by this application will be introduced below with reference to Figure 1, Figure 2, Figure 3, and Figure 4.

Wherein, FIG. 1 is a schematic structural diagram of a high-stability excimer laser device provided in an embodiment of the present application. FIG. 2 is a schematic structural diagram of a discharge resonant cavity provided by an embodiment of the present application. FIG. 3 is a schematic structural diagram of a linewidth narrowing module and a central wavelength rough measurement device provided in an embodiment of the present application. FIG. 4 is a schematic structural diagram of a central wavelength precise measurement module provided in an embodiment of the present application.

In this embodiment, the high-stability excimer laser includes: a discharge resonator 1 , a line width narrowing module 2 , a detection module 3 , and a control module 4 .

A pumping device 27 is arranged in the discharge resonator 1, and the discharge resonator 1 is filled with a mixture of inert gas and halogen gas, and an electrode (EL) connected to the pumping device 27, for example: for a laser with a wavelength of 193nm, its discharge Inside the cavity 1 is a mixed gas of fluorine (F ₂ ) and argon (Ar); another example: for a laser with a wavelength of 248nm, the inside of the discharge cavity 1 is a mixed gas of fluorine (F ₂ ) and krypton (Kr).

During the working process of the excimer laser, the mixed gas in the discharge resonator 1 generates laser light under the action of the electric pulse generated by the pump device 27, and the laser is reflected by the mirrors on both sides of the discharge resonator to realize resonance amplification. The laser light enters the linewidth narrowing module 2 from the first side of the discharge resonator 1 (in this embodiment, the right side of FIG. 1 , ie, the side facing the linewidth narrowing module 2, is the first side). However, the natural width of the laser light generated by the above-mentioned mixture of inert gas and halogen gas under the action of the electric pulse is about several hundred picometers. The narrowing process is performed to make the spectrum of the laser light released from the other side of the discharge resonator 1 meet the requirements.

The light outlets on both sides of the discharge resonator 1 are equipped with windows 10 made of _CaF2 or fused silica. The reflection between the outgoing lasers increases the energy and polarization of the lasers emitted by the laser.

The line width narrowing module 2 includes a beam expander 5 and an echelle grating 6 sequentially arranged along the laser emission direction of the first side of the discharge resonator 1 .

The beam expander 5 is composed of several right-angled triangular prisms, and is used to expand the laser beam entering the linewidth narrowing module 2 to reduce the divergence angle of the laser beam irradiated on the echelle grating 6 .

The beam expander 5 is a key component of the linewidth narrowing module 2, and is also an important element for obtaining a narrow linewidth laser. Each prism of the beam expander 5 expands the laser beam incident between the echelle gratings 6, and its beam expansion factor is usually 30 to 60 times. At the same time, the dispersion characteristics of the prism itself also have a certain divergence function for the incident spectrum, so that Prerequisites are provided for the subsequent light splitting of the echelle grating 6 . After being expanded by the beam expander 5, the divergence angle of the laser beam will be compressed to reduce the divergence angle of the beam shining on the surface of the echelle grating 6.

In addition, in order to increase the transmittance of each prism in the beam expander 5 , the surface of each prism in the beam expander 5 may also be coated with an anti-reflection film to increase the transmittance of the prism.

The echelle grating 6 is also called a reflective echelle grating, and the echelle grating has the characteristics of small size, strong dispersion ability and high diffraction efficiency. The echelle grating 6 is specifically used to disperse the laser light irradiated on the echelle grating 6 through the beam expander 5 so that the light of different wavelengths spreads along the direction of the exit angle. When the light beam is irradiated on the surface of the echelle grating 6, its incident light and diffracted light satisfy the following grating equation (1):

nd(sinθ+sinβ)=mλ (1)

Among them, λ is the central wavelength of the laser, θ is the incident angle of the beam on the echelle grating 6, β is the exit angle of the beam, d is the grating constant, n is the gas refractive index in the line width control device, and m is the interference level Second-rate.

According to the formula (1), it can be seen that the light of different wavelengths incident on the echelle grating 6 through the beam expander 5 will spread out along different angles, therefore, only a part of the light with a narrow wavelength range can return to the original path Discharge resonator 1. The other end of the discharge resonant cavity 1 opposite to the line width narrowing module 2 is also equipped with an output coupling mirror 11. The output coupling mirror 11 and the line width narrowing module 2 form a larger resonant cavity, which oscillates the light returned by the original path Amplified, resulting in a narrower linewidth laser output. At this time, because the incident angle and exit angle of the incident beam are equal, which is basically equal to the blaze angle θ _B of the echelle grating, when the magnification of the prism group of the beam expander 5 is M, the beam incident to the line width narrowing module 2 When the angle distribution is f(θ), the distribution of the spectrum emitted from the echelle grating along the angle is the following formula (2)

In order to achieve a narrower spectrum, the blaze angle of the echelle grating is generally greater than 75°. At the same time, slits are added at both ends of the discharge cavity DC to further compress the divergence angle of the laser. The laser spectrum passed through the line width narrowing module is greatly narrowed. Reaching about 0.15 to 0.5pm, this laser wavelength can meet the needs of lithography light sources in semiconductor manufacturing.

The high-stability excimer laser device of this embodiment further includes a detection module 3, and the detection module 3 includes: a central wavelength rough measurement device 3b and a central wavelength fine measurement device 3a. In this embodiment, the central wavelength rough measuring device includes: a reflecting device 7 , a beam converging device 8 , and a first photoelectric detection device 9 . The reflection device 7 is used to transmit the part of the light beam emitted from the first side of the discharge resonator 1 to the echelle grating 6, and the beam converging device 8 is arranged in the exit direction of the echelle grating 6, and is used to pass the aforementioned part of the light beam through the echelle grating 6 The emitted light is converged and transmitted to the first photodetection device 9;

As shown in Figure 1 and Figure 3, after the first prism in the beam expander 5 is irradiated by the laser light emitted from the first side of the discharge resonator 1, most of the light will pass through the first prism and flow to the second prism. The prisms propagate, but a small amount of light is still reflected off the first prism's incident surface. It should be noted that even if the surface of each prism in the prism group is coated with an anti-reflection coating, some light will still be reflected. This application uses this part of the reflected light to complete the rough measurement of the center wavelength of the excimer laser. process.

Please continue to refer to Fig. 1 and Fig. 3, the reflector 7 is arranged in the reflection optical path of the incident surface of the first prism, and the reflected light will shine on the reflector 7, and the reflector 7 can be a plane mirror or reflective prism. The placement angle of the reflecting device is set so that the reflecting device 7 re-reflects the reflected light onto the echelle grating 6 after receiving the reflected light. As mentioned above, in this embodiment, the echelle grating 6 is an echelle grating. This part of the light beam transmitted to the echelle grating by the reflection device 7 is different from the incident angle of the light irradiated on the echelle grating 6 by the beam expander 5, which will be smaller than the blaze angle θ _B of the echelle grating, and the incident angle is θ ₁ , this part of the light will still be dispersed by the échelle grating 6, and one order (m1) of the light beam emerges at the exit angle β ₁ , and its incident light and outgoing light still satisfy the grating equation of the above formula (1), that is :

nd(sinθ ₁ +sinβ ₁ )=m ₁ λ

The outgoing light passing through the echelle grating 6 is irradiated on the beam converging device 8, and is focused by the beam converging device 8 onto the surface of the photosensitive element of the first photodetection device 9 to generate first interference fringes. In this embodiment, the beam converging lens 8 can be a convex lens (group) or a concave mirror, the surface of the convex lens can be coated with an anti-reflection coating, and the surface of the working surface of the concave mirror can be coated with an anti-reflection coating. The first photodetection device 9 is specifically a charge-coupled device (charge-coupled device, CCD). In the embodiment of the present application, the first photodetection device 9 is used to convert the first interference fringes into corresponding first interference fringe information, and send the first interference fringe information to the following control module 4 . In an optional embodiment of the present application, the first photodetection device 9 adopts a linear array CCD,

When the wavelength of the laser in the discharge resonator ₁ changes, the exit angle β1 and the wavelength λ of the light (called the first light beam) irradiated on the surface of the echelle grating 6 after being reflected by the reflection device 7 satisfy the following formula (3):

Among them, Δλ is the change value of the central wavelength, n is the gas refractive index in the linewidth narrowing device, _Δβ1 is the change value _of the laser exit angle, m1 is the interference order, and d is the grating constant.

Further, if the focal length of the beam converging device 8 is set to f1, and the peak position of the _first interference fringe is x, then the peak change of the interference fringe and the change of the center wavelength of the laser satisfy the following formula (4):

Among them, Δλ is the change value of the central wavelength, Δx is the change value of the peak of the _first interference fringe, and β1 is the laser emission angle.

It can be seen from the above formula (4) that the change of the central wavelength of the excimer laser is proportional to the change of the peak position of the first interference fringe, and the first photodetection device 9 collects the first interference fringe information and sends it to the control module 4 to control The module 4 can calculate and obtain the peak position of the first interference fringe according to the information of the first interference fringe, so as to obtain a rough measurement value of the central wavelength change Δλ of the excimer laser. The central wavelength λ=λ ₀ +△λ, λ ₀ is the theoretical value of the central wavelength, so the rough measured value of the central wavelength is obtained.

In the above-mentioned embodiment, by sharing the prism and the echelle grating in the linewidth narrowing module, the linewidth narrowing and the rough measurement of the center wavelength of the laser are realized at the same time. As follows, the rough measurement of the center wavelength can be combined with the precise measurement of the center to realize the tuning of the center wavelength of the resonator. This scheme makes the overall structure of the laser compact, and the stability and accuracy are greatly improved. Therefore, the reflective device 7 (or the reflective device 7 and the beam converging device 8 ) can be arranged inside the line width narrowing module 2 to make the structure more compact. Of course, the above components can also be arranged outside the line width narrowing module 2, and those skilled in the art can make adjustments according to actual needs.

As mentioned above, in this embodiment, the reflected light of the first prism of the beam expander is used. In other embodiments, the beam used for rough measurement can also be obtained directly from the beam splitting output from the first side, or the beam expander can be used to The reflected light of the reflective surface of any prism in the prism group will not be repeated here. Any scheme that utilizes the partial beam of the first side output beam and combines the echelle grating 6 of the line width narrowing device to realize the rough measurement of the central wavelength Included within the protection scope of this application.

In addition, preferably, the first photodetection device 9 is installed outside the line width narrowing module 2 to prevent the circuit board and electronic components of the first photodetection device 9 from polluting the line width voltage control module 2 .

In addition, the line width narrowing module 2 provided by the embodiment of the present application can also realize the tuning of the central wavelength, and a part of the light with a narrow wavelength range that is incident on the echelle grating 6 through the beam expander 5 returns to the discharge resonator 1 through the original path, At this time, the outgoing angle of this part of the light beam is the same as the incident angle, assuming that the incident angle of the laser light entering the echelle grating 6 through the beam expander 5 is θ ₂ , according to the grating equation of formula (1), it can be known that the laser light at this time The wavelength λ satisfies the following formula (5):

Wherein, n is the refractive index of the gas in the line width narrowing module 2, m ₂ is the interference order, and d is the grating constant.

It can be seen that the central wavelength of the laser can be changed by changing the angle at which the light is incident on the echelle grating. As shown in Figure 1 and Figure 3, changing the angle of the last prism in the prism group will also change the angle of the refracted light passing through the prism, and the angle of incident on the echelle grating will also change, thus changing the central wavelength of the laser. Of course, In addition to rotating the last prism, any other prism in the prism group can also be used to tune the center wavelength. The rotation of the prism can be controlled by the control mechanism, which will be described in detail below.

In addition, it can be seen from the above formulas (4) and (5) that the rough measurement and tuning of the central wavelength of the laser are related to the gas refractive index n of the gas inside the linewidth narrowing module 2, and the change in the refractive index will cause the central wavelength of the laser to change. Changes will also cause changes in the rough wavelength. The rough measurement of the central wavelength of the excimer laser by using the beam split into the linewidth narrowing module 2 after exiting the laser means that the rough measurement of the central wavelength is consistent with the refractive index n of the gas during the tuning process. Therefore, the rough measurement device 3b of the wavelength of the excimer laser provided by the present application can eliminate the rough measurement error caused by the change of the refractive index of the gas, and improve the rough measurement accuracy of the central wavelength.

In addition, in the embodiment of the present application, the detection module 3 further includes a central wavelength precision measuring device 3a. In this embodiment, the central wavelength precision measuring device 3a is disposed on the second side opposite to the first side of the discharge resonant cavity 1 . As shown in Figure 1. The output coupling mirror 11 is disposed on the second side of the discharge resonant cavity 1 . The central wavelength precision measurement device 3a is specifically used to obtain the second interference fringe information of the narrow linewidth laser light emitted by the output coupling mirror 11 of the excimer laser.

As shown in Figures 1 and 4, the central wavelength precision measurement device 3a includes a first beam splitter 12, a homogenizer 13, a second beam splitter 14, a collimator 15, an FP etalon 16, and a second convergent mirror 17 , The second photodetection device 18 .

The first beam splitter 12 is used to receive the laser light emitted from the second side of the discharge resonator 1, and split the laser light emitted from the second side of the discharge resonator 1, and irradiate one of the split laser beams on the uniform light device 13. The homogenizer 13 can be an integrating rod, a microlens array or a diffractive optical element, or a combination of these elements. The purpose is to homogenize the incident beam.

The homogenized light is split by the second beam splitter 14 , part of it enters the collimating mirror 15 , is collimated by the collimating mirror 15 and enters the FP etalon 16 .

The FP etalon 16 is composed of two high-parallel high-reflection mirrors. After the light beam enters the FP etalon 16, it is reflected multiple times by the two high-reflection mirrors of the FP etalon 16 to form multi-level light interference, and finally passes through the second converging The mirror 17 converges to the surface of the second photodetection device 18 to form the second interference fringes. Wherein, the second converging lens 17 may be a plano-convex lens or a double-convex lens, or a group of lenses. In addition, in order to reduce the volume of the central wavelength precise measuring device 3a, a reflector 26 is installed between the second converging mirror 17 and the second photodetecting device 18 for reflecting light.

Please refer to FIG. 5 , which is a schematic diagram of the second interference fringes produced by the FP etalon provided in the embodiment of the present application. As shown in FIG. 5 , d _FP is the distance between two high reflection mirrors of the FP etalon, f ₂ is the focal length of the second converging mirror 17 , and r is the radius of the second interference fringe. The laser beam forms second interference fringes on the second photodetection device 18 after passing through the FP etalon 16 and the second converging mirror 17 .

Assume that λ is the central wavelength of the laser output from the laser, n ₂ is the refractive index of the gas inside the FP etalon, and m ₃ is the order of the interference fringes of the FP etalon. Then the second interference fringe satisfies the following formula (6):

It can be seen that after the second photodetection device 18 converts the second interference fringes into corresponding second interference fringes information, and sends the second interference fringes information to the following control module, the radius r of the second interference fringes can be calculated , the central wavelength of the excimer laser can be calculated according to the above formula. Further, since the order m ₃ of the interference fringe of the FP etalon 16 is an integer, different m ₃ can be selected to obtain a set of precise measurement values of the central wavelength of the excimer laser. At the same time, compare each fine value in the fine value group of the center wavelength of the excimer laser with the rough value of the center wavelength of the excimer laser, and obtain the fine value closest to the rough value of the center wavelength, as the quasi The final result of the center wavelength of the molecular laser.

In addition, in order to avoid the center wavelength calculated by the different interference orders of the FP etalon 16 and the roughly measured value of the central wavelength are relatively close, and it is difficult to determine the interference order, the accuracy of the roughly measured value of the central wavelength needs to be higher than that of the FP 1/2 of the free spectral range of the standard device 16.

After determining the final result of the central wavelength of the excimer laser, the control device 4 compares the final result of the central wavelength of the excimer laser with the target central wavelength, and if the calculated final result of the central wavelength of the excimer laser is consistent with the target center If the wavelength is different, the control device 4 can drive the prism in the beam expander 5 in the line width narrowing module 2 to rotate to change the incident angle on the echelle grating in the aforementioned Figure 1 to compensate for the deviation of the central wavelength . Specifically, in order to realize the above-mentioned control process, a rotating mechanism can be installed on at least one prism included in the beam expander 5, and the control module 4 is connected with the rotating mechanism 19, so that the prism can be controlled by the rotating mechanism under the control of the control module 4. rotate.

In addition, the detection module further includes an energy detection device for energy detection of the output of the laser. In this embodiment, the energy detection device is the third photoelectric detection device 20 as shown in FIG. 1 . The third photodetection device 20 may be a CCD. Specifically, the third photodetection device 20 receives another beam after splitting the light beam by the second beam splitter 14 to detect the energy of the laser beam, and the third photodetection device 20 also communicates with the following control The relevant control unit in the module 4 is connected to convert the light intensity signal of this part of the light into an electrical signal and send it to the control module 4, and the high voltage electrode in the discharge resonant cavity can be controlled by the control module 4.

Please continue to refer to FIG. 1 , the control module 4 of this embodiment includes a central wavelength rough measurement board 21 , a central wavelength precise measurement board 22 , a laser tuning controller 23 , an energy measurement board 24 and a high voltage power supply controller 25 . Of course, the control module 4 may also include some of the aforementioned components. For example, only the central wavelength rough measurement board 21 , the central wavelength fine measurement board 22 and the laser tuning controller 23 are included.

The central wavelength rough measurement board 21 is connected to the first photoelectric detection device 9 and the central wavelength precise measurement board 22 respectively, and the central wavelength precise measurement board 22 is also connected to the output end of the second photoelectric detection device 18 and the laser tuning controller 23 The input end is connected, and the laser tuning controller 23 is connected to the control mechanism of the prism group in the line width narrowing module 2, and the control mechanism can control the rotation of one or several prisms in the prism group, thereby changing the irradiation on the echelle grating. angle of incident light.

The central wavelength rough measurement board 21 receives the first interference fringe information output by the first photodetection device 9, and obtains a rough measurement value of the central wavelength according to the first interference fringe information, and then sends the rough measurement value of the central wavelength to the central wavelength Precision test board 22.

The central wavelength precision measurement board 22 receives the second interference fringe information output by the second photodetection device 18, and obtains the precise measurement value group of the central wavelength according to the second interference fringe information, and compares the precise measurement value group of the central wavelength with the central wavelength The rough measured value is obtained, and the fine measured value closest to the rough measured value of the center wavelength is obtained as the final result of the center wavelength of the excimer laser. Obtain the final result of the central wavelength, and send it to the laser tuning controller 23, the laser tuning controller 23 compares the final result of the central wavelength with the preset target central wavelength, obtains the corresponding adjustment parameter, and controls according to the corresponding adjustment parameter The line width narrowing module 2 adjusts the central wavelength. Specifically, the adjustment parameter can be the rotation angle of the prism, and then the laser tuning controller 23 drives the rotation mechanism of the prism to compensate the deviation value of the center wavelength, and realizes the closed-loop feedback of the center wavelength. By improving the measurement and feedback accuracy of the center wavelength and the closed-loop The speed of the feedback unit can effectively improve the stability of the central wavelength of the excimer laser, thereby meeting the requirements of the lithography machine for the stability of the wavelength of the light source.

In addition, the input end of the energy detection board 24 is connected with the output end of the third photoelectric detection device 20, and the output end of the energy detection board 24 is connected with the input end of the high voltage power controller 25; the output end of the high voltage power controller 25 is connected with the The pumping means 27 of the discharge resonator 1 are connected. The energy detection board 24 determines the energy information released by the excimer laser according to the electrical signal output by the third photodetection device 20, and calculates the difference between the energy information and the preset energy information, and then adjusts it through the high-voltage power supply controller 25 The voltage released by the pumping device 27 is used to adjust the energy released by the excimer laser.

The high-stability excimer laser device of the embodiment of the present application, by sharing the prism and the echelle grating 6 in the line width narrowing module 2, realizes laser spectral narrowing, rough measurement and tuning of the central wavelength, and rough measurement and tuning of the central wavelength. Tuning in the same environment can eliminate measurement errors and feedback errors caused by changes in the refractive index of gases, and improve the measurement accuracy of the center wavelength and the stability of the laser. At the same time, the central wavelength precision measurement device only has one FP etalon 16 and energy measurement components, which is compact in structure and small in size, which is conducive to improving the stability of the gas inside the detection module, improving the measurement accuracy and stability of laser energy and central wavelength, and ensuring performance and long-term stability of the laser.

The control module 4 obtains the central wavelength of the laser through calculation, compares it with the target value of the central wavelength, then calculates the rotation angle of the prism, and then drives the rotating mechanism 19 of the prism to compensate the deviation value of the central wavelength, thereby realizing the closed-loop feedback of the central wavelength, which can Effectively improve the central wavelength stability of the excimer laser. Through the energy feedback control link, the energy of the laser is calculated, and the voltage value that needs to be adjusted by the high-voltage power supply is calculated to control the pumping device 27 of the discharge resonator 1, to realize closed-loop energy feedback of the laser, and to realize the stability of the energy or dose of the laser.

Another embodiment of the present application also provides a high-stability excimer laser device, which includes: a discharge resonator 1, a line width narrowing module 2, a detection module, and a control module 4; the line width narrowing module 2 includes The beam expander 5 and the echelle grating 6 are arranged sequentially from the laser emission direction on the first side of the discharge resonator 1; the detection module includes a central wavelength precise measurement device 3a and a central wavelength rough measurement device 3b, which are respectively used to measure the discharge resonant cavity 1 The central wavelength of the outgoing light is finely measured and roughly measured; the control module 4 is connected with the discharge resonant cavity 1, the central wavelength fine measuring device 3a and the central wavelength rough measuring device 3b respectively, and is used to measure according to the central wavelength fine measuring device 3a and the central wavelength The measurement results of the rough measuring device 3b adjust the parameters in the discharge resonator 1; the control module 4 also includes a laser tuning controller 23, and the laser tuning controller 23 is connected with at least one device of the beam expanding device 5 for adjusting the The angle of the beam irradiated by the beam device 5 to the echelle grating.

In order to facilitate the understanding of the above-mentioned control of the energy released by the excimer laser device and the central wavelength, the above-mentioned control process will be introduced below with reference to FIG. 6 . Please refer to FIG. 6 , which is a flow chart of the closed-loop control of the energy released by the excimer laser device and the central wavelength provided in the embodiment of the present application.

The above process is based on the premise that the laser works normally, and the following steps are performed:

Step S601, measuring the central wavelength and energy of the excimer laser device.

Step S602, respectively calculate the difference between the center wavelength and the target center wavelength, and the difference between the energy and the target energy, according to the difference between the center wavelength and the target center wavelength, and the difference between the energy and the target energy value, the prism adjustment parameters for the line width narrowing module 5 and the voltage adjustment parameters for the pumping device 27 are obtained.

Step S603, respectively judging whether the prism adjustment parameter and the voltage adjustment parameter are greater than a preset parameter threshold;

Step S604, if the prism adjustment parameter and the voltage adjustment parameter are less than or equal to the preset parameter threshold, then continue to judge whether the excimer laser device is in the light emitting state.

Step S605, if the excimer laser device is in the state of emitting light, return to step S602. If the excimer laser device is not in the state of emitting light, the control process ends.

Step S606, if the prism adjustment parameter and the voltage adjustment parameter are greater than the preset parameter threshold, adjust the prism angle of the line width narrowing module 5 and the voltage released by the pumping device 27 according to the prism adjustment parameter and the voltage adjustment parameter, and perform the step S605.

In summary, the high-stability excimer laser device provided by the embodiment of the present application realizes the alignment of the excimer laser through the line width narrowing module 5, the central wavelength rough measurement device 3b, the control module 4, and the central wavelength precise measurement device 3a The central wavelength of the excimer laser is accurately measured in real time. When the central wavelength of the excimer laser does not meet the preset central wavelength, the control module 4 controls the line width narrowing module 2 to adjust so that the central wavelength of the excimer laser meets the preset center wavelength. The above-mentioned device realizes the closed-loop feedback of the central wavelength of the excimer laser, and improves the stability of the laser in the working process.

Although the present application is disclosed as above with preferred embodiments, it is not used to limit the present application. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, the present application The scope of protection should be based on the scope defined by the claims of this application.

Claims (10)

1. A high-stability excimer laser device, characterized in that it includes: a discharge resonant cavity (1), a line width narrowing module (2), a detection module and a control module (4);

   The line width narrowing module (2) includes a beam expander (5) and an echelle grating (6) sequentially arranged along the laser emission direction from the first side of the discharge resonator (1);

   The detection module includes a central wavelength precise measurement device (3a) and a central wavelength rough measurement device (3b); wherein, the central wavelength rough measurement device (3b) includes a reflection device (7), a beam converging device (8) and a first A photodetection device (9), the reflection device (7) is used to transmit the part of the beam emitted from the first side of the discharge resonator (1) to the echelle grating (6), and the beam converging device ( 8) set in the exit direction of the echelle grating (6), for converging the aforementioned part of the beam through the exit light of the echelle grating (6) and then transmitting it to the first photodetection device (9);

   The central wavelength precise measurement device (3a) is arranged on the second side opposite to the first side of the discharge resonator (1), and is used to receive the laser beam emitted from the second side and perform precise central wavelength measurement ;

   The control module (4) is respectively connected with the discharge resonant cavity (1), the center wavelength precision measurement device (3a) and the center wavelength rough measurement device (3b), for according to the center wavelength precision measurement device (3a) and the measurement results of the central wavelength rough measuring device (3b), adjust the parameters in the discharge resonant cavity (1).
2. The device according to claim 1, wherein the beam expander (5) is a beam expander prism group;

   The reflector (7) is arranged on the incident side of the light beam of the beam expander prism group, and is located in the optical path after the incident surface of the beam expander (5) reflects the incident light; the reflector (7) ) is set at an angle satisfying that after receiving the reflected light, it is reflected twice to the echelle grating (6).
3. The device according to claim 2, characterized in that, the beam converging device (8) is a convex lens or a concave mirror; the first photodetection device (9) is a charge-coupled device;

   The beam converging device (8) is used for converging the dispersed outgoing light so that the converging light is irradiated on the detection surface of the first photodetection device (9) to form interference fringes;

   The first photodetection device (9) is configured to receive the interference fringes, convert the interference fringes into corresponding interference fringe information, and send the interference fringe information to the control module (4).
4. The device according to any one of claims 1 to 3, characterized in that the reflecting device (7) and the beam converging device (8) are arranged inside the line width narrowing module (2).
5. The device according to claim 1, characterized in that, the central wavelength precise measurement device (3a) comprises a first beam splitter (12), a light homogenizer (13), a second beam splitter arranged in sequence along the beam exit direction Beam mirror (14), collimating mirror (15), FP etalon (16), second converging mirror (17) and second photoelectric detection device (18);

   The first beam splitter (12) is used to receive the laser light emitted from the second side of the discharge resonator (1), split the laser beam, and illuminate one of the split laser beams on the homogenizer (13);

   The homogenizer (13) is arranged between the first beam splitter (14) and the second beam splitter (17), for homogenizing the laser light so that the homogenized laser light enters the The second beam splitter (17);

   The second beam splitting mirror (14) is used to split the laser beam emitted by the homogenizer (13), and irradiate one of the laser beams on the collimating mirror (15);

   The collimator mirror (15) is arranged between the second beam splitter mirror (17) and the FP etalon (16), for collimating the laser light irradiated on the FP etalon;

   The FP etalon (16) is used to reflect the laser light passing through the FP etalon (16) multiple times to form multi-level light interference, and pass the multi-level light interference through the second converging mirror ( 17) Converging to said second photodetection device (18) to form second interference fringes.
6. The device according to claim 5, characterized in that, the detection module (4) further includes an energy detection device (20), and the energy detection device includes a third photodetection device (20), and the third photodetection device The device (20) is arranged in the outgoing direction of another beam of light after the beam splitting by the second beam splitter (14), and is used to detect the laser energy information of the laser, and send the laser energy information to the control device.
7. The device according to claim 1, 2, 3, 5 or 6, characterized in that the control device comprises: a central wavelength rough measurement board (21), a central wavelength fine measurement board (22);

   The central wavelength coarse measurement board (21) is respectively connected to the first photoelectric detection device (9) and the central wavelength fine measurement board (22);

   The central wavelength rough measurement board (21) is used to obtain the interference fringe information sent by the first photoelectric detection device (9), and obtain the interference fringe information sent by the first photoelectric detection device (9). The roughly measured value of the wavelength of the laser; the roughly measured value of the wavelength of the laser is sent to the precise measurement board (22) of the central wavelength;

   The central wavelength precise measurement board (22) is also connected to the second photoelectric detection device (18);

   The central wavelength fine measurement board (22) is used to obtain the second interference fringe information sent by the second photoelectric detection device (18), and obtain the central wavelength rough measurement board according to the second interference fringe information The rough measured value of the central wavelength sent by the card (21); according to the second interference fringe information and the roughly measured value of the central wavelength, the fine measured value of the central wavelength is obtained.
8. The device according to claim 7, characterized in that, the control device (4) further comprises a laser tuning controller (23), and at least the laser tuning controller (23) and the beam expander (5) A device is connected to adjust the angle of the beam irradiated by the beam expander (5) to the echelle grating (6).
9. The device according to claim 8, characterized in that the laser tuning controller (23) is specifically configured to adjust the beam expander (5) according to the difference between the obtained precise value of the central wavelength and the target value of the central wavelength. ) at least one device is rotated, thereby adjusting the angle of the light beam irradiated to the echelle grating (6).
10. The device according to claim 7, wherein the control device (4) comprises: an energy measurement board (24), a high-voltage power supply controller (25);

    The energy measurement board (24) is connected to the high-voltage power supply controller (25) and the third photoelectric detection device (20) respectively;

    The energy measurement board (24) is configured to receive the laser energy information sent by the third photoelectric detection device (20); obtain the laser energy information output by the excimer laser device according to the laser energy information, and The laser energy information is sent to the high voltage power supply controller (25);

    The high-voltage power supply controller (25), connected to the discharge resonator (1), is used to receive the laser energy information, and control the laser energy released by the discharge resonator (1) according to the laser energy information .

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