Lithography machine interferometer beam calibration apparatus and method

Abstract

The present application relates to the field of optical measurement, and provides a lithography machine interferometer light beam calibration device and method. The lithography machine interferometer light beam calibration device is used for calibrating a measurement light beam of an interferometric measurement system in a lithography machine, and comprises a reference optical element configured to establish an absolute angle reference in a calibration environment; a simulation target having at least one reflecting surface and configured to be detachably placed in the optical path of the measurement light beam during calibration; a reference transmission assembly configured to transmit the absolute angle reference defined by the reference optical element to the reflecting surface of the simulation target; and a diagnostic optical module configured to be detachably installed at the light beam outlet of the interferometric measurement system to receive the measurement light beam reflected by the reflecting surface of the simulation target; the diagnostic optical module interferes the received measurement light beam with an internal reference light beam of the diagnostic optical module, and uses the form of the formed interference fringes as a basis for judging the collimation state of the measurement light beam.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical measurement, and provides a lithography machine interferometer light beam calibration device and method. BACKGROUND

[0002] In the field of semiconductor manufacturing, the positioning accuracy of a lithography machine directly determines the feature size and overall performance of an integrated circuit. To achieve nanometer-level or even sub-nanometer-level displacement measurement, an interferometer is widely used in the position measurement system of a lithography machine workpiece table due to its high resolution and high reliability, and has become one of the key sensors for ensuring the precision of the lithography process.

[0003] However, the measurement performance of the interferometer is highly dependent on the calibration state of the optical path, and the angle of the interferometer measurement light beam will shift after long-term use. Even a slight shift can cause significant decline in the stability and accuracy of the displacement measurement result. SUMMARY

[0004] Embodiments of the present application provide a lithography machine interferometer light beam calibration device to solve the problem of low light beam calibration efficiency in related technologies.

[0005] Embodiments of the present application provide a lithography machine interferometer light beam calibration method.

[0006] In a first aspect, embodiments of the present application provide a lithography machine interferometer light beam calibration device for calibrating a measurement light beam of an interferometric measurement system in a lithography machine, comprising:

[0007] a reference optical element configured to establish an absolute angle reference in a calibration environment;

[0008] a simulation target having at least one reflective surface and configured to be detachably placed in the optical path of the measurement light beam during calibration;

[0009] a reference transfer assembly configured to transfer the absolute angle reference defined by the reference optical element to the reflective surface of the simulation target;

[0010] a diagnostic optical module configured to be detachably installed at the light beam exit of the interferometric measurement system to receive the measurement light beam reflected by the reflective surface of the simulation target;

[0011] wherein the diagnostic optical module interferes the received measurement light beam with an internal reference light beam of the diagnostic optical module, and uses the interference fringes formed thereby as a basis for judging the collimation state of the measurement light beam.

[0012] According to an embodiment of the present application, the reference optical element comprises a cubic reference prism, and the reference transfer assembly comprises a collimator.

[0013] According to an embodiment of the present application, the simulation target is a simulation worktable, and the simulation target comprises a plurality of reflecting mirrors respectively for reflecting X-axis, Y-axis and Z-axis measurement light beams.

[0014] According to an embodiment of the present application, the simulation target further comprises an adjusting mechanism for adjusting the overall pose of the simulation target in terms of pitch, yaw and roll.

[0015] According to an embodiment of the present application, the diagnostic optical module comprises:

[0016] a beam splitter for splitting an incident light beam into a measurement light beam and a reference light beam;

[0017] a reference mirror arranged in the light path of the internal reference light beam for returning the reference light beam along the original light path;

[0018] an image sensor for capturing the interference fringe pattern.

[0019] According to an embodiment of the present application, the diagnostic optical module further comprises a magnetic fixing member for attracting and fixing the diagnostic optical module to the housing of the interferometer measurement system.

[0020] According to an embodiment of the present application, the reference optical element is configured to be mounted on a reference surface of a metrology frame of a lithography machine to form an extended reference based on the absolute angle reference.

[0021] The second aspect embodiment of the present application provides a lithography machine interferometer light beam calibration method using the lithography machine interferometer light beam calibration device as described above, and the lithography machine interferometer light beam calibration method comprises:

[0022] transferring the absolute angle reference defined by the reference optical element to the reflecting surface of the simulation target by using the reference transfer assembly;

[0023] mounting the diagnostic optical module at the light beam exit of the interferometer measurement system to be calibrated;

[0024] adjusting the pointing of the exit light beam of the interferometer measurement system and observing the change of the interference fringe pattern generated by the diagnostic optical module in real time until the interference fringe pattern meets the preset collimation criterion.

[0025] According to an embodiment of the present application, the step of adjusting the pointing of the exit light beam of the interferometer measurement system and observing the change of the interference fringe pattern generated by the diagnostic optical module in real time until the interference fringe pattern meets the preset collimation criterion comprises:

[0026] observing the change of the interference fringe pattern from dense to sparse until it expands to a uniform light field, and determining that the measurement light beam is perpendicular to the reflecting surface of the simulation target.

[0027] According to one embodiment of the present application, the lithography interferometer beam calibration device further comprises a first beam and a second beam controlled by the same beam adjuster, the step of adjusting the pointing direction of the exit beam of the interferometric measurement system comprises:

[0028] adjusting the beam adjuster until the first beam is judged to be perpendicular to the reflective surface of the simulation target by the diagnostic optical module;

[0029] adjusting another optical component working with the second beam as a reference until another optical component is judged to be perpendicular to the second beam.

[0030] According to the lithography interferometer beam calibration device provided by the first aspect of the present application, a stable absolute angle reference is established by binding the reference optical element with the metrology frame, the reference accuracy is independent of external environment or other components, the reference scale is consistent every time the calibration is performed, the calibration error caused by reference drift is avoided from the root, and the nanometer level precision requirement of the lithography machine is met. From the angle accuracy of the reference optical element, the transmission accuracy of the reference transmission component, to the flatness of the reflective surface of the simulation target, the interference detection accuracy of the diagnostic module, the accuracy of the reference, transmission and detection is formed, and the problem of unreliable results caused by the lack of reference and record in traditional calibration is avoided. The simulation target and the diagnostic optical module are detachable structures, and the installation and disassembly do not need to disassemble the main body of the lithography machine, and the calibration can be completed during the downtime of the lithography machine, which greatly shortens the downtime time of traditional calibration and improves the utilization rate of the lithography machine. The state of the beam is directly reflected by the interference fringes, the operator does not need to perform complex calculations, and the calibration can be completed by observing the fringes, which reduces the human operation error and shortens the calibration operation time. If the simulation target integrates multiple reflective surfaces, the lithography interferometer beam calibration device can simultaneously or sequentially calibrate the measurement beams of X, Y, Z and other axes, without the need to design separate calibration devices for different axes, which meets the beam calibration requirement of multi-dimensional displacement measurement of the lithography machine and reduces the equipment investment cost. Through high-precision calibration, the beam collimation state is restored to the optimal state, the displacement data measured by the interferometer is accurate, and the positioning accuracy of the workpiece table of the lithography machine is indirectly improved, which provides protection for the nanometer level feature size manufacturing of semiconductor chips. By regularly calibrating the beam angle, the additional damage of the beam offset to the components is avoided, the service life of the interferometer is prolonged, and the component replacement frequency and maintenance cost are reduced.

[0031] According to the method for calibrating the light beam of the interferometer of the lithography machine provided by the second aspect of the present application, the absolute angle reference of the reference optical element is transmitted to the simulation target reflecting surface through the reference transmission assembly, a unified and stable calibration reference is established, the scale consistency of each calibration is ensured, the calibration error caused by the reference drift is avoided from the root, and the light beam calibration requirement of the nanometer level precision of the lithography machine is adapted. The interference fringe pattern generated by the diagnostic optical module can directly reflect the angle deviation of the measurement light beam. Even if the angle deviation is small, it can also be reflected through the density and curvature change of the fringe. The operator adjusts the light beam pointing based on the real-time observation of the fringe change, accurately captures the critical state of the light beam collimation, avoids the problem of blind adjustment or over-adjustment in the traditional method, ensures that the angle deviation of the measurement light beam after calibration is controlled in a very small range, and guarantees the displacement measurement precision of the interference measurement system. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0033] Figure 1 is a schematic structural diagram of the light beam calibration device of the lithography machine provided by the present application.

[0034] Figure 2 is a schematic connection mode diagram of the reference optical element and the reference transmission assembly provided by the present application.

[0035] Figure 3 is a schematic structural diagram of the simulation target and the reference transmission assembly provided by the present application.

[0036] Figure 4 is a schematic structural diagram of the diagnostic optical module provided by the present application.

[0037] Figure 5 is a schematic flow chart of the method for calibrating the light beam of the interferometer of the lithography machine provided by the present application.

[0038] Reference signs:

[0039] 100, reference optical element; 102, simulation target; 104, reference transmission assembly; 106, diagnostic optical module; 108, adjustment mechanism; 110, beam splitter; 112, reference mirror; 114, image sensor; 116, magnetic fixing part; 118, light beam adjuster. DETAILED DESCRIPTION

[0040] Embodiments of the present application will be further described below with reference to the drawings and examples. The following examples are intended to be illustrative of the present application and are not intended to limit the scope of the present application.

[0041] As shown in Figures 1 to 4 the first aspect of the present application provides an apparatus for calibrating a measurement beam of an interferometric measurement system in a lithography machine, comprising:

[0042] a reference optical element 100 configured to establish an absolute angular reference in a calibration environment;

[0043] a simulation target 102 having at least one reflective surface configured to be removably placed in the optical path of the measurement beam during calibration;

[0044] a reference transfer assembly 104 configured to transfer the absolute angular reference defined by the reference optical element 100 to the reflective surface of the simulation target 102;

[0045] a diagnostic optical module 106 configured to be removably mounted at the exit of the measurement beam of the interferometric measurement system for receiving the measurement beam after being reflected by the reflective surface of the simulation target 102;

[0046] wherein the diagnostic optical module 106 interferes the received measurement beam with an internal reference beam of the diagnostic optical module 106, and uses the interference fringes formed thereby as a basis for judging the collimation state of the measurement beam.

[0047] According to the embodiment of the first aspect of the present application, the lithography machine interferometer light beam calibration device is bound with the reference optical element 100 and the metering frame to establish a stable absolute angle reference, the reference precision is independent of the external environment or other components, and the reference scale is consistent every time the calibration is performed, thereby fundamentally avoiding the calibration error caused by the reference drift and adapting to the nanometer level precision requirement of the lithography machine. The precision of the reference, transmission and detection is closed looped to avoid the unreliable result caused by the traditional calibration without reference and record. The simulation target 102 and the diagnostic optical module 106 are detachable structures, and the installation and disassembly do not need to disassemble the main body of the lithography machine, so that the calibration can be completed during the downtime of the lithography machine, the downtime of the traditional calibration is greatly shortened, and the utilization rate of the lithography machine is improved. The simulation target 102 is integrated with multiple reflection surfaces, and the lithography machine interferometer light beam calibration device can simultaneously or sequentially calibrate the measurement light beams in X, Y and Z directions, without the need to design calibration devices for different directions, thereby adapting to the light beam calibration requirement of multi-dimensional displacement measurement of the lithography machine and reducing the equipment investment cost. The high-precision calibration restores the light beam collimation state to the optimal state, ensures the accuracy of the displacement data measured by the interferometer, indirectly improves the positioning precision of the workpiece table of the lithography machine, and provides protection for the nanometer level feature size manufacturing of the semiconductor chip. The regular calibration of the light beam angle avoids the additional damage of the light beam offset to the components, prolongs the service life of the interferometer, and reduces the component replacement frequency and maintenance cost.

[0048] Please continue to see Figures 1 to 4 The lithography machine interferometer light beam calibration device provided by the embodiment of the first aspect of the present application solves the problem of angle offset of the measurement light beam of the lithography machine interferometric measurement system through the closed loop design of absolute reference establishment, reference transmission and light beam diagnosis, and realizes the high-precision calibration of the measurement light beam.

[0049] The reference optical element 100 is an optical component with high angle precision, which is used to provide a stable and unique absolute angle reference in the calibration environment.

[0050] The reference optical element 100 is made of an optical material with low expansion coefficient, which avoids the angle reference drift caused by the change of the environmental temperature, and can define the absolute angle reference through its inherent geometric characteristics.

[0051] The reference optical element 100 is fixed on the metrology frame reference surface of the lithography machine by a special fixture, and a flexible gasket is arranged between the fixture and the reference surface to ensure firm installation of the element and avoid deformation of the element caused by vibration or stress of the frame, thereby realizing rigid binding of the absolute angle reference and the metrology frame and ensuring that the reference does not deviate with external environmental changes.

[0052] The simulation target 102 is of a detachable structure and is used to simulate the optical reflection characteristics of the workpiece table of the lithography machine to receive the measurement beam of the interferometric measurement system and reflect it to the diagnostic optical module 106, while the reflection surface attitude consistent with the absolute angle reference is obtained through reference transmission.

[0053] The simulation target 102 is provided with at least one reflection surface, the surface of which is treated with high reflectivity and precisely calibrated in flatness to ensure that the angle accuracy of the reflected beam is not affected by the error of the reflection surface; if it is necessary to calibrate multi-axial beams, the target can be integrated with multiple reflection surfaces, the angle relationship between which is consistent with that of the actual workpiece table, thereby meeting the multi-dimensional beam calibration requirements.

[0054] The simulation target 102 is detachably installed in the optical path of the measurement beam, and after installation, the reflection surface attitude is adjusted by the reference transmission assembly 104 to align the angle of the reflection surface with the absolute angle reference of the reference optical element 100, thereby ensuring that the reflection surface provides a reflection reference for the measurement beam and avoiding the influence of the attitude deviation of the target on the calibration results.

[0055] The reference transmission assembly 104 is a high-precision angle measurement and adjustment device used to transmit the absolute angle reference defined by the reference optical element 100 to the reflection surface of the simulation target 102 and establish the angle correlation therebetween.

[0056] The reference transmission assembly 104 first measures the absolute angle reference of the reference optical element 100 to obtain reference parameters; then aligns the measurement end with the reflection surface of the simulation target 102 and compares the deviation between the current angle of the reflection surface and the absolute angle reference through optical imaging or angle detection technology; finally, the reflection surface of the simulation target 102 is fine-tuned by the adjustment mechanism 108 of the device until the angle of the reflection surface is completely consistent with the absolute angle reference, thereby completing the reference transmission.

[0057] The reference transmission assembly 104 itself has high angle measurement accuracy and is provided with an error compensation function to ensure that the angle deviation in the reference transmission process is extremely small and to provide a reliable reflection reference for subsequent beam calibration.

[0058] The diagnostic optical module 106 is an integrated optical detection unit and is detachably installed at the beam exit of the interferometric measurement system to detect the collimation state of the reflected measurement beam through interference effect and intuitively reflect whether the beam angle deviates.

[0059] The diagnostic optical module 106 can include a beam splitter 110, a reference mirror 112, and an interference and imaging function, wherein the beam splitter 110 is used to receive the measurement light beam reflected by the simulated target 102 and divide it into two beams: one is a detection light beam, and the other is an internal reference light beam; the reference mirror 112 is fixed inside the module and receives the internal reference light beam and reflects it back to the beam splitter 110 along the original light path, and the angle and position of the reference mirror 112 are precisely calibrated to ensure the stability of the reference light beam; the interference and imaging function is used to combine the detection light beam and the internal reference light beam reflected back at the beam splitter 110, and interference fringes are generated due to the difference in optical path length or angle between the two light beams; the image sensor 114 in the module captures the interference fringe pattern and transmits the image signal to an external display device for observation by the operator;

[0060] The diagnostic optical module 106 is detachably fixed to the light beam outlet of the interferometric measurement system through a mechanical interface, and after installation, the optical axis of the module is aligned with the exit direction of the measurement light beam to ensure that the measurement light beam can enter the module completely; after disassembly, it does not affect the normal operation of the interferometric measurement system, and is suitable for online calibration requirements of the lithography machine.

[0061] The cooperation logic of the lithography machine interferometer light beam calibration device provided by the first aspect of the present application is roughly as follows:

[0062] Reference establishment: the reference optical element 100 establishes an absolute angle reference on the metrology frame;

[0063] Reference transmission: the reference transmission assembly 104 transmits the absolute angle reference to the reflecting surface of the simulated target 102 to standardize the attitude of the reflecting surface;

[0064] Light beam reflection and detection: the interferometric measurement system emits a measurement light beam, which enters the diagnostic optical module 106 after being reflected by the reflecting surface of the simulated target 102;

[0065] Interference judgment: the diagnostic optical module 106 judges the collimation state of the measurement light beam through the interference fringe pattern: if the light beam angle deviates, the interference fringes will present dense, curved, and other patterns; if the light beam is collimated, the interference fringes will be sparse or even uniform light field, which is used as a calibration basis.

[0066] The key calibration process of the lithography machine interferometer light beam calibration device provided by the first aspect of the present application is roughly as follows:

[0067] Reference initialization: install the reference optical element 100 on the reference surface of the metrology frame, and calibrate the angle of the element itself through the reference transmission assembly 104 to ensure the stability of the absolute angle reference;

[0068] Target installation and reference transmission: install the simulated target 102 in the light path, start the reference transmission assembly 104, adjust the angle of the target reflecting surface, and align it with the absolute angle reference;

[0069] Diagnosis module installation: fix the diagnosis optical module 106 at the light beam exit of the interferometric measurement system, ensure that the module optical axis is aligned with the measurement light beam exit direction;

[0070] Light beam calibration: start the interferometric measurement system, and exit the measurement light beam; the light beam enters the diagnosis module after being reflected by the target reflecting surface, and generates interference fringes; an operator observes the fringe pattern, adjusts the light beam pointing of the main interferometric system until the interference fringes meet the preset collimation criterion;

[0071] Calibration completion and disassembly: after calibration, sequentially disassemble the diagnosis optical module 106 and the simulation target 102, and the interferometric measurement system resumes normal operation.

[0072] According to one embodiment of the present application, the reference optical element 100 comprises a cubic reference prism, and the reference transmission assembly 104 comprises a self-collimator.

[0073] In one embodiment of the present application, the reference optical element 100 adopts a cubic reference prism, which is a regular hexahedron structure made of optical material with low expansion coefficient, and the included angle between two adjacent working surfaces thereof is super-precisely processed and has stable right-angle characteristics, and can be used as an absolute angle reference in the calibration environment. The cubic reference prism is installed on the metrology frame reference surface of the lithography machine through a special fixing clamp, and a flexible buffer layer is arranged at the position where the clamp contacts the prism, which can not only ensure that the prism is firmly installed, but also avoid the stress or vibration of the metrology frame being transmitted to the prism, so as to prevent the deformation of the prism structure from affecting the angle reference accuracy.

[0074] The reference transmission assembly 104 adopts a self-collimator, which has high-precision angle measurement function, and integrates a light source, a collimating objective lens, a beam splitter 110 and an imaging assembly inside. The measurement end of the self-collimator is first aligned with the working surface of the cubic reference prism, the light beam emitted by the light source is collimated by the collimating objective lens and then irradiates the working surface of the prism, the light beam returns along the original light path after being reflected by the working surface, enters the imaging assembly through the beam splitter 110, and forms a reference imaging point, and the self-collimator determines the absolute angle reference parameter of the cubic reference prism through the imaging point. Subsequently, the self-collimator is moved so that the measurement end is aligned with the reflecting surface of the simulation target 102, and the angle parameter of the reflecting surface is obtained through the same light beam emission and reflection imaging, and the angle parameter is compared with the absolute angle reference parameter of the cubic reference prism, and the angle deviation value is calculated. According to the deviation value, the adjusting mechanism 108 matched with the self-collimator drives the reflecting surface of the simulation target 102 to be finely adjusted until the angle parameter of the reflecting surface is completely consistent with the absolute angle reference parameter, and the reference transmission process is completed.

[0075] The low-expansion material of the cube reference prism and the ultra-precise processing working surface ensure that the angle reference is not affected by environmental temperature changes or external vibrations, provide a long-term stable reference scale for the calibration process, avoid the reference drift problem caused by the material characteristics or installation method of the traditional reference, and ensure the calibration accuracy from the root. The high-precision angle measurement capability of the autocollimator can accurately capture the small angle deviation between the cube reference prism and the reflection surface of the simulation target 102, and the fine adjustment function of the matching adjustment mechanism 108 can control the angle error in the reference transmission process to a very small range, ensuring that the posture of the reflection surface of the simulation target 102 is consistent with the absolute angle reference, and providing a precise reflection reference for subsequent measurement beam calibration.

[0076] According to one embodiment of the present application, the simulation target 102 is a simulation worktable, and the simulation target 102 includes a plurality of mirror surfaces for reflecting X-axis, Y-axis and Z-axis measurement beams respectively.

[0077] In one embodiment of the present application, the overall structure of the simulation target 102 is consistent with the size and installation interface of the actual worktable of the lithography machine, and can be directly adapted to the installation position of the worktable in the lithography machine to realize detachable installation. The simulation target 102 integrates a plurality of mirror surfaces, and the material, size and surface reflectivity of each mirror surface are consistent with the mirror surface on the actual worktable for reflecting the interference measurement beam, so as to ensure that there is no difference between the reflection characteristics of the measurement beam and the actual worktable.

[0078] Among them, the mirror surface for reflecting the X-axis measurement beam is arranged along the length direction of the simulation target 102, and the working surface faces the incident direction of the X-axis measurement beam; the mirror surface for reflecting the Y-axis measurement beam is arranged along the width direction of the simulation target 102, and the working surface faces the incident direction of the Y-axis measurement beam; the mirror surface for reflecting the Z-axis measurement beam is arranged along the height direction of the simulation target 102, and the working surface faces the incident direction of the Z-axis measurement beam. The relative angle relationship between each mirror surface is exactly the same as the angle relationship of the corresponding mirror surface on the actual worktable, and each mirror surface is installed on the main body of the simulation target 102 through an independent fixing structure, and the fixing structure has a certain rigidity to prevent the mirror surface from being deviated or deformed during installation or calibration.

[0079] When performing multi-axis beam calibration, the interference measurement system emits X, Y and Z axis measurement beams respectively, each axis measurement beam is incident on the corresponding mirror surface on the simulation target 102, and after reflection, it enters the corresponding diagnostic optical module 106 to realize simultaneous or sequential calibration of multi-axis beams.

[0080] By integrating multiple reflective surfaces, the simulation target 102 can simultaneously adapt to the reflection requirements of X, Y, and Z three-axis measurement light beams, without the need to design or replace the target for different axes, achieving efficient calibration of multi-axis light beams, adapting to the light beam calibration requirements of the multi-dimensional displacement measurement system of the lithography machine, and greatly reducing the calibration process interruption and time waste caused by replacing the target. The structure and reflective surface characteristics of the simulation target 102 are consistent with the actual workpiece table height, ensuring that the light path state and angle change of the measurement light beam during reflection are identical to the actual working scene, avoiding calibration deviation caused by the inconsistency between the target and the actual workpiece table characteristics, and making the calibration result directly reflect the light beam state of the interferometric measurement system in the actual work, thereby improving the reliability and practicality of the calibration result.

[0081] According to one embodiment of the present application, the simulation target 102 further comprises an adjusting mechanism 108 for adjusting the pitch, yaw, and rotation of the overall pose of the simulation target 102.

[0082] In one embodiment of the present application, the adjusting mechanism 108 is installed between the bottom of the simulation target 102 and the installation base, and is a multi-degree-of-freedom fine adjustment structure, mainly including a pitch adjusting assembly, a yaw adjusting assembly, and a rotation adjusting assembly, which are independent of each other and work cooperatively to achieve multi-dimensional adjustment of the overall pose of the simulation target 102.

[0083] The pitch adjusting assembly is composed of two symmetrically arranged micro-displacement tables, which are distributed along the length direction of the simulation target 102. By rotating the adjusting knobs on the micro-displacement tables, the simulation target 102 can be driven to rotate around the transverse axis, achieving pose adjustment in the pitch direction. The yaw adjusting assembly is also composed of two symmetrically arranged micro-displacement tables, which are distributed along the width direction of the simulation target 102. By adjusting the knobs, the simulation target 102 can be driven to rotate around the longitudinal axis, achieving pose adjustment in the yaw direction. The rotation adjusting assembly is a circular rotary table installed between the bottom of the simulation target 102 and the pitch and yaw adjusting assemblies. The central axis of the rotary table coincides with the vertical axis of the simulation target 102. By rotating the adjusting ring of the rotary table, the simulation target 102 can be driven to rotate around the vertical axis, achieving pose adjustment in the rotation direction.

[0084] The adjusting knobs of each adjusting assembly are provided with scale markings. The operator can judge the adjustment amount by observing the scale, and at the same time, cooperate with the angle measurement function of the reference transmission assembly 104 to obtain the angle parameters of the simulation target 102 after pose adjustment in real time, until the overall pose of the simulation target 102 meets the reference transmission requirements, i.e., the angles of each reflective surface are consistent with the absolute angle reference.

[0085] The multi-degree-of-freedom adjusting mechanism 108 can independently fine-tune the pitch, yaw and rotation poses of the simulation target 102 respectively, can accurately compensate for the pose deviation of the simulation target 102 caused by the installation base error and the positioning deviation during the installation process, and can ensure that each mirror surface of the simulation target 102 can accurately align with the absolute angle reference, thereby avoiding the influence of the pose deviation of the target itself on the reference transmission accuracy and the subsequent light beam calibration result. Even if the flatness and levelness of the installation base in the lithography machine has a slight error, or the simulation target 102 is slightly tilted during the installation process, the adjusting mechanism 108 can compensate through pose adjustment, so that the simulation target 102 is always in a pose state meeting the calibration requirements, the adaptation capability of the simulation target 102 to different installation environments is enhanced, and the complex flatness correction of the installation base is not required, thereby simplifying the preparation work in the early stage of calibration.

[0086] According to one embodiment of the present application, the diagnostic optical module 106 comprises:

[0087] A beam splitter 110 is configured to split the incident light beam into a measurement light beam and a reference light beam.

[0088] A reference mirror 112 is arranged in the optical path of the internal reference light beam and is configured to return the reference light beam along the original optical path.

[0089] An image sensor 114 is configured to capture the interference fringe pattern.

[0090] In one embodiment of the present application, the diagnostic optical module 106 is a closed integrated structure, and the beam splitter 110, the reference mirror 112 and the image sensor 114 are sequentially arranged in the optical path inside the module. Each component is fixed in the module housing through a precision support, thereby ensuring the stability of the optical path.

[0091] The beam splitter 110 is a semi-transparent and semi-reflective optical element, which is arranged in the optical path of the incident light beam at an angle. The working surface of the beam splitter 110 is at a preset angle with respect to the axis of the incident light beam. When the incident light beam reflected by the simulation target 102 enters the diagnostic optical module 106, the incident light beam is split into two beams by the beam splitter 110: one is the measurement light beam, which transmits through the beam splitter 110 and continues to propagate along the original optical path; the other is the internal reference light beam, which changes the propagation direction after being reflected by the beam splitter 110 and is directed to the reference mirror 112.

[0092] The reference mirror 112 is a high-flatness reflective element, which is fixed at a preset position in the module housing, and the reflecting surface of the reference mirror 112 is perpendicular to the axis of the internal reference light beam. After the internal reference light beam is directed to the reference mirror 112, the internal reference light beam is reflected along the original optical path and is directed to the beam splitter 110 again. At this time, the reference light beam changes the propagation direction after being reflected by the beam splitter 110, and the reference light beam is combined with the measurement light beam which transmits through the beam splitter 110.

[0093] The image sensor 114 is installed in the light path after the measurement light beam and the reference light beam are combined, the photosensitive surface of the image sensor 114 is perpendicular to the axis of the combined light beam, the image sensor 114 is used to receive the interference fringes formed after the two light beams are combined, and the interference fringes are converted into an electrical signal and transmitted to a display device outside the module for observation and judgment by an operator.

[0094] The housing of the diagnostic optical module 106 is also provided with a light path shielding structure, which can prevent external stray light from entering the module and interfering with the formation of interference fringes and the capture of the image sensor 114, and at the same time protect the internal optical components from being affected by dust, water vapor and other pollutants, to ensure the long-term stable operation of the diagnostic optical module 106.

[0095] The precise fixing and light path design of the beam splitter 110 and the reference mirror 112 ensure the stability of the light paths of the measurement light beam and the internal reference light beam, the optical path difference and the angle relationship of the two light beams are controllable, and clear interference fringes can be stably generated, which avoids the interference fringes from being blurred, flickering or deformed due to unstable light path, and provides a reliable visual basis for accurately judging the collimation state of the measurement light beam. The reference mirror 112 with high flatness can ensure the reflection accuracy of the internal reference light beam and reduce the angle deviation of the reference light beam itself; the image sensor 114 has high resolution and high sensitivity, and can accurately capture the subtle morphological changes of the interference fringes, accurately reflect the slight angle deviation of the measurement light beam, and meet the nanometer-level precision light beam calibration requirement of the lithography machine interferometer.

[0096] According to one embodiment of the present application, the diagnostic optical module 106 further comprises a magnetic fixing member 116 for adsorbing and fixing the diagnostic optical module 106 on the housing of the interferometric measurement system.

[0097] In one embodiment of the present application, the magnetic fixing member 116 is a plurality of permanent magnet blocks uniformly distributed on the bottom edge of the housing of the diagnostic optical module 106, the material of the magnet blocks is selected from high-magnetic-strength permanent magnet materials, the adsorption surface of the magnet blocks is flush with the bottom surface of the housing of the diagnostic optical module 106, and the adsorption surface is flat processed to ensure sufficient contact area with the housing of the interferometric measurement system.

[0098] The area of the housing of the interferometric measurement system corresponding to the installation position of the diagnostic optical module 106 is made of a magnetic material, when the diagnostic optical module 106 needs to be installed, the magnetic fixing member 116 at the bottom of the module is aligned with the installation area on the housing, the magnetic force generated by the magnetic fixing member 116 can quickly adsorb the module on the housing to achieve preliminary fixation.

[0099] If it is necessary to dismount the diagnostic optical module 106, only an external force greater than the magnetic force is needed to remove the module from the shell, and the dismounting process is simple and fast, and will not cause damage to the shell of the interferometric measurement system or the diagnostic optical module 106. The magnetic force of the magnetic fixing member 116 is calculated to ensure that the module is firmly installed and will not be loose, and to avoid excessive magnetic force that causes difficulty in dismounting or damage to the surface of the shell.

[0100] The adsorption type installation of the magnetic fixing member 116 does not need to use traditional fasteners such as bolts and buckles, and the operator can quickly complete the installation and dismounting of the diagnostic optical module 106, greatly shortening the installation and dismounting time, and especially suitable for the requirement of operation efficiency in the online calibration scene of the lithography machine, and reducing the equipment downtime caused by calibration operation.

[0101] According to one embodiment of the present application, the reference optical element 100 is configured to be installed on the reference surface of the metrology frame of the lithography machine to form an extended reference based on an absolute angle reference.

[0102] In one embodiment of the present application, the metrology frame of the lithography machine is a rigid frame with the highest stability in the overall structure, the reference surface thereof is super-precisely processed and has extremely high flatness and perpendicularity, and the frame material is selected from a low-expansion coefficient alloy material, which can effectively resist structural deformation caused by environmental temperature changes, vibration and other factors, and ensure the long-term stability of the reference surface.

[0103] The reference optical element 100 is fixed on the reference surface of the metrology frame by a special installation clamp, and the installation clamp is composed of a base and a pressing block: the base is a flat plate structure matched with the reference surface of the metrology frame, the lower surface of the base is closely attached to the reference surface, and a low-volatility and high-stability adhesive is applied between the attached surfaces to ensure the rigid connection of the base and the reference surface and avoid relative sliding; the pressing block is an L-shaped structure, and the number of the pressing blocks is multiple, which are uniformly distributed around the reference optical element 100, one end of the pressing block is fixed on the base by a bolt, and the other end is tightly pressed against the top surface edge of the reference optical element 100, which not only ensures the firm installation of the reference optical element 100, but also avoids excessive pressure of the pressing block that causes deformation of the element.

[0104] During the installation process, first, the reference surface of the metrology frame is cleaned to remove surface dust and impurities; then the base is placed on the reference surface, and the flatness and levelness of the base are detected by a laser interferometer to ensure that the base is installed flat; then the reference optical element 100 is placed on the base, and the position and angle of the element are adjusted by a precision positioning tool to make the angle relationship between the reference surface of the element and the reference surface of the metrology frame meet the design requirements; finally, the pressing block is installed and the bolt is tightened to complete the fixation of the reference optical element 100.

[0105] By the above installation mode, the reference optical element 100 can form an extended reference based on an absolute angle reference, and the stability of the absolute angle reference directly depends on the structural stability of the metrology frame and is not affected by the movement or deformation of other components of the lithography machine.

[0106] The high rigidity and low expansion characteristics of the metrology frame and the ultra-precise reference surface provide a stable installation basis for the reference optical element 100, so that the absolute angle reference can be kept stable for a long time and is not affected by environmental temperature fluctuations, equipment vibration or component aging, etc. The problem of reference drift caused by the instability of the installation carrier of the traditional reference is avoided, and the consistency and reliability of the reference scale in each calibration process are ensured, which provides a fundamental guarantee for high-precision beam calibration. The reference optical element 100 forms an extended reference based on the absolute angle reference, so that the reference can directly reflect the angle characteristics of the core structure of the lithography machine, and the angle of the calibrated measurement beam can be consistent with the reference of the metrology frame, thereby ensuring that the measurement accuracy of the interferometric measurement system matches the positioning accuracy of the lithography machine as a whole, and avoiding the problem that the calibration result cannot meet the actual work requirements due to the disconnection between the reference and the main body of the equipment.

[0107] As shown in Figure 5 The third aspect of the present application provides a lithography machine interferometer beam calibration method, which uses the lithography machine interferometer beam calibration device as described above. The lithography machine interferometer beam calibration method comprises the following steps:

[0108] Step 10: using the reference transmission assembly 104 to transmit the absolute angle reference defined by the reference optical element 100 to the reflecting surface of the simulation target 102;

[0109] Step 20: installing the diagnostic optical module 106 at the beam exit of the interferometric measurement system to be calibrated;

[0110] Step 30: adjusting the pointing direction of the outgoing beam of the interferometric measurement system, and observing the change of the interference fringe pattern generated by the diagnostic optical module 106 in real time until the interference fringe pattern meets the preset collimation criterion.

[0111] According to the method for calibrating the light beam of the interferometer of the lithography machine provided by the third aspect of the present application, the absolute angle reference of the reference optical element 100 is transmitted to the reflecting surface of the simulation target 102 through the reference transmission assembly 104, a unified and stable calibration reference is established, the scale of each calibration is ensured to be consistent, the calibration error caused by reference drift is avoided from the root, and the light beam calibration requirement of the nanometer level precision of the lithography machine is adapted. The interference fringe pattern generated by the diagnostic optical module 106 can directly reflect the angle deviation of the measurement light beam. Even if the angle deviation is small, it can also be reflected through the density and curvature change of the fringe. The operator adjusts the light beam direction based on the real-time observation of the fringe change, accurately captures the critical state of the light beam collimation, avoids the problem of blind adjustment or over-adjustment in the traditional method, ensures that the angle deviation of the measurement light beam after calibration is controlled in a very small range, and guarantees the displacement measurement precision of the interferometric measurement system.

[0112] Referring to Figure 5 The method for calibrating the light beam of the interferometer of the lithography machine provided by the third aspect of the present application is based on the above-mentioned light beam calibration device of the interferometer of the lithography machine, and the high-precision calibration of the measurement light beam of the interferometric measurement system is realized through the standardized process of reference transmission, module installation and light beam adjustment.

[0113] Specifically, in step 10, it is necessary to ensure that the reference optical element 100 has been stably installed on the reference surface of the metrology frame of the lithography machine, and the simulation target 102 has been detachably placed in the light path of the measurement light beam.

[0114] The reference transmission assembly 104 is started, and first, the measurement end of the device is aligned with the working surface of the reference optical element 100. The device obtains the absolute angle reference parameter defined by the reference optical element 100 through the internal optical system, and this parameter serves as the reference scale for subsequent transmission.

[0115] Subsequently, the measurement end of the reference transmission assembly 104 is moved to be aligned with the reflecting surface of the simulation target 102, and the current angle parameter of the reflecting surface is obtained through the same optical measurement method. The angle parameter of the reflecting surface is compared with the absolute angle reference parameter, and the angle deviation value between the two is calculated.

[0116] According to the deviation value, the adjustment mechanism 108 matched with the reference transmission assembly 104 is operated to drive the reflecting surface of the simulation target 102 to be finely adjusted. If there is a pitch deviation, the adjustment mechanism 108 drives the reflecting surface to rotate around the transverse axis; if there is a yaw deviation, the reflecting surface is driven to rotate around the longitudinal axis; and if there is a roll deviation, the reflecting surface is driven to rotate around the vertical axis. During the fine adjustment process, the reference transmission assembly 104 monitors the angle change of the reflecting surface in real time, until the angle parameter of the reflecting surface is completely consistent with the absolute angle reference parameter, the reference transmission is completed, and the reflecting surface of the simulation target 102 has a unified posture with the absolute angle reference, which can serve as the standard reflecting reference for the calibration of the measurement light beam.

[0117] In step 20, first clean the surface of the housing at the exit of the interferometric measurement system light beam to remove dust and impurities, and avoid affecting the stability and light path alignment after the module is installed.

[0118] Align the installation surface of the diagnostic optical module 106 with the preset installation area of the light beam exit housing, and precisely match the positioning structure at the bottom of the module with the positioning hole on the housing to ensure that the optical axis is consistent with the direction of the measurement light beam after the module is installed.

[0119] Firmly fix the diagnostic optical module 106 on the housing through the adsorption force of the magnetic fixing part 116, without the need for additional fasteners. After installation, check the fit of the module and the housing to ensure that there is no looseness or tilt, and at the same time confirm that the signal output end of the diagnostic optical module 106 has been connected with the external display device, ensuring that the subsequent interference fringe pattern can be normally transmitted and observed.

[0120] In step 30, start the interferometric measurement system to make it emit a measurement light beam, which is directed along a preset light path to the reflecting surface of the simulated target 102, and after being reflected by the reflecting surface, it returns along the original light path and enters the diagnostic optical module 106.

[0121] The diagnostic optical module 106 receives the reflected measurement light beam, which is split into a measurement light beam and an internal reference light beam by the internal beam splitter 110. The internal reference light beam is reflected by the reference mirror 112 and then converges with the measurement light beam to form an interference fringe. The interference fringe pattern is captured by the image sensor 114 inside the module and transmitted in real time to the external display device.

[0122] The operator observes the change of the interference fringe pattern, and at the same time adjusts the light beam adjustment components inside the interferometric measurement system: if the interference fringes are dense and curved, it indicates that the measurement light beam is not perpendicular to the reflecting surface of the simulated target 102, and the adjustment components need to be adjusted according to the curvature direction and density of the fringes to gradually reduce the angle deviation of the light beam. With the adjustment, the interference fringes gradually change from dense to sparse, and the curvature gradually decreases.

[0123] Continue to adjust and observe until the interference fringe pattern meets the preset collimation criterion, at which point it is determined that the measurement light beam is collimated and qualified, and the adjustment is stopped, completing the light beam calibration this time.

[0124] According to one embodiment of the present application, the step of adjusting the light beam until the interference fringe pattern meets the preset collimation criterion includes:

[0125] Observe the change of the interference fringe pattern from dense to sparse until it expands to a uniform light field, and determine that the measurement light beam is perpendicular to the reflecting surface of the simulated target 102.

[0126] In one embodiment of the present application, when the light beam collimation judgment is performed, the operator observes the morphological changes of the interference fringes in real time through the display device outside the diagnostic optical module 106, which is directly related to the angle relationship between the measurement light beam and the reflective surface of the simulation target 102.

[0127] When the measurement light beam emitted by the interferometric measurement system is not perpendicular to the reflective surface of the simulation target 102, the reflected measurement light beam will have an angle offset. After the offset light beam enters the diagnostic optical module 106, there is a significant angle difference between the internal reference light beam. When the two light beams converge, they form dense interference fringes, indicating that the measurement light beam does not meet the collimation requirements.

[0128] The operator adjusts the light beam adjustment components inside the interferometric measurement system according to the density and bending direction of the interference fringes. If the fringes are dense in a certain direction, the corresponding components are adjusted in the opposite direction to gradually reduce the angle deviation between the measurement light beam and the reflective surface. As the adjustment proceeds, the perpendicularity of the measurement light beam to the reflective surface gradually improves, the angle offset of the reflected light beam decreases, the angle difference between the measurement light beam and the reference light beam in the diagnostic optical module 106 decreases, the spacing of the interference fringes gradually increases, and the bending degree of the fringes gradually decreases.

[0129] When the measurement light beam is completely perpendicular to the reflective surface of the simulation target 102, the reflected light beam has no angle offset, and the angle difference between the internal reference light beam is zero. When the two light beams have uniform light path difference, the interference fringes completely disappear, forming a uniform light field. After the operator observes the uniform light field, it can be determined that the measurement light beam has met the preset collimation criterion, the measurement light beam is perpendicular to the reflective surface, and the light beam collimation is qualified.

[0130] During the entire judgment process, the change process of the interference fringes from dense to sparse to uniform light field can be recorded by the image sensor 114 to form a calibration record, which is convenient for subsequent tracing and verification.

[0131] The dense, sparse, and uniform light field change process of the interference fringes is a visual morphological change. The operator does not need to master complex optical calculations or data processing knowledge, but only needs to observe directly to judge the collimation state of the measurement light beam, which reduces the technical threshold of the calibration operation, reduces the judgment error caused by insufficient professional knowledge, shortens the judgment time, and improves the calibration efficiency. The morphological change of the interference fringes can accurately reflect the slight change of the perpendicularity of the measurement light beam to the reflective surface. Even if the corresponding angle deviation is nanoscale, it can also be reflected through the subtle change of the fringe spacing, ensuring that the operator can accurately capture the critical state of the light beam collimation, avoiding insufficient or excessive calibration caused by ambiguous criteria, and ensuring that the calibration accuracy meets the high precision requirements of the lithography machine interferometer.

[0132] According to one embodiment of the present application, the lithography interferometer beam alignment device further comprises a first beam and a second beam controlled by the same beam adjuster 118, and the step of adjusting the pointing of the exit beam of the interferometric measurement system comprises:

[0133] Adjusting the beam adjuster 118 until the first beam is judged to be perpendicular to the reflective surface of the dummy target 102 by the diagnostic optics module 106;

[0134] Adjusting another optical component working with the second beam as a reference until the other optical component is judged to be perpendicular to the second beam.

[0135] In one embodiment of the present application, the operator adjusts the beam adjuster 118. During this process, the pointing of the first beam is continuously monitored by the diagnostic optics module 106. The goal of the adjustment is to make the propagation direction of the first beam completely perpendicular to the reflective surface of the dummy target as a reference. When the diagnostic optics module 106 judges that the two are perpendicular, the adjustment of the beam adjuster 118 is stopped. After this step, not only the pointing of the first beam is precisely calibrated, but more importantly, since the second beam is also controlled by this beam adjuster 118, its pointing is also precisely fixed at the same time.

[0136] At this time, no further operation is performed on the beam adjuster 118. The operator adjusts another independent optical component working with the second beam, such as a Z-direction long mirror. By adjusting the attitude of this optical component itself, until the reflective surface of the component is perpendicular to the second beam as a reference.

[0137] In this way, by fixing the beam adjuster 118 first and then adjusting the independent component, the complex coupling problem is transformed into independent linear steps, making the calibration process direct and orderly, without iteration, thereby significantly shortening the equipment debugging time. It ensures that the relative position accuracy between each beam and optical component in the system is extremely high, effectively avoids the cumulative error introduced by multiple alignments, and finally improves the overall accuracy of the interferometer measurement and the consistency of the results.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A beam calibration device for an interferometer in a lithography machine, used to calibrate the measurement beam of an interferometric measurement system within a lithography machine, characterized in that, The method comprises: a reference optical element (100) configured to establish an absolute angle reference in a calibration environment; a simulation target (102) having at least one reflecting surface and configured to be detachably placed in the light path of the measurement beam during calibration; a reference transmission assembly (104) configured to transmit the absolute angle reference defined by the reference optical element (100) to the reflecting surface of the simulation target (102); a diagnostic optical module (106) configured to be detachably installed at the light beam exit of the interferometric measurement system to receive the measurement beam reflected by the reflecting surface of the simulation target (102); wherein the diagnostic optical module (106) interferes the received measurement beam with an internal reference beam of the diagnostic optical module (106), and the formed interference fringe pattern is used as a basis for judging the collimation state of the measurement beam.

2. The lithography interferometer beam calibration apparatus of claim 1, wherein, The reference optical element (100) comprises a cubic reference prism, and the reference transmission assembly (104) comprises a collimator.

3. The lithography interferometer beam calibration apparatus of claim 1, wherein, The simulation target (102) is a simulation workpiece table, and the simulation target (102) comprises a plurality of reflecting surfaces for reflecting X-axis, Y-axis and Z-axis measurement beams respectively.

4. The lithography interferometer beam calibration apparatus of claim 3, wherein, The simulation target (102) further comprises an adjusting mechanism (108) for adjusting the pitch, yaw and roll of the overall pose of the simulation target (102).

5. The lithography interferometer beam calibration apparatus of claim 1, wherein, The diagnostic optical module (106) comprises: a beam splitter (110) for splitting an incident beam into a measurement beam and a reference beam; a reference mirror (112) arranged in the light path of the internal reference beam for returning the reference beam along the original light path; an image sensor (114) for capturing the interference fringe pattern.

6. The lithography interferometer beam calibration apparatus of claim 5, wherein, The diagnostic optical module (106) further comprises a magnetic fixing member (116) for attracting and fixing the diagnostic optical module (106) to the housing of the interferometric measurement system.

7. The lithography interferometer beam calibration apparatus of claim 1, wherein, The reference optical element (100) is configured to be installed on a reference surface of a metrology frame of a lithography machine to form an extended reference based on the absolute angle reference.

8. A lithography interferometer beam calibration method using the lithography interferometer beam calibration apparatus of any one of claims 1 to 7, characterized by, The lithography machine interferometer beam calibration method comprises: transmitting, by a reference transmission assembly (104), an absolute angle reference defined by a reference optical element (100) to a reflecting surface of a simulation target (102); installing a diagnostic optical module (106) at the light beam exit of an interferometric measurement system to be calibrated; adjusting the pointing of the exit light beam of the interferometric measurement system and observing the change of the interference fringe pattern generated by the diagnostic optical module (106) in real time until the interference fringe pattern meets a preset collimation criterion.

9. The lithography interferometer beam calibration method of claim 8, wherein, The step of until the interference fringe pattern meets the preset collimation criterion comprises: observing the interference fringe pattern changing from dense to sparse until expanding into a uniform light field, and determining that the measurement beam is perpendicular to the reflecting surface of the simulation target (102).

10. The lithography interferometer beam calibration method of claim 8, wherein, The lithography interferometer beam alignment apparatus further comprises a first beam and a second beam controlled by the same beam adjuster (118), the step of adjusting the exit beam of the interferometric measurement system to point at comprises: adjusting the beam adjuster (118) until it is determined with the diagnostic optical module (106) that the first beam is perpendicular to the reflective surface of the simulated target (102); adjusting another optical component cooperating with the second beam as a reference until it is determined that the other optical component is perpendicular to the second beam.

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