Improving hole circularity via electro-optic beam modulation

Abstract

To provide system and method for providing an electro-optic beam modulation to improve circularity in F-Theta applications.SOLUTION: A disclosed system uses an optical system, a Pockels cell and a polarization control device. The optical system focuses a laser beam, onto a workpiece, to generate a plurality of spots within an optical field. A fast axis of the Pockels cell is aligned orthogonally to corners of the optical field. The polarization control device reduces circularity inconsistencies in the plurality of spots by adjusting a polarization of the laser beam.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and benefit of U.S. Provisional Patent Application No. 63 / 552,493, filed February 12, 2024, entitled "ELECTRO-OPTIC BEAM MODULATION FOR IMPROVED CIRCULARITY IN F-THETA APPLICATIONS," which is hereby incorporated by reference in its entirety. [Background technology]

[0002]

[0002] The limitations and drawbacks of conventional electro-optic modulators (EOMs) will become apparent to those skilled in the art upon comparing such approaches with certain aspects of the present method and system described in the remainder of this disclosure with reference to the drawings. Summary of the Invention

[0003]

[0003] The system and method provide electro-optical beam modulation for improving circularity in F-theta applications substantially as shown by and / or described in connection with at least one of the figures and more fully as set forth in the claims. [Brief explanation of the drawings]

[0004] [Figure 1]

[0004] FIG. 1 illustrates an example EOM system for improved circularity in F-theta applications, according to various example embodiments of the present disclosure. [Figure 2]

[0005] FIG. 1 illustrates an example of pore distortion and pore refinement, according to various exemplary embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005]

[0007] The following description provides various examples of systems and methods for improving circularity in F-theta applications using electro-optical beam modulation. Such examples are non-limiting, and the scope of the appended claims should not be limited to the particular examples disclosed. In the following description, the terms "example" and "for example" are non-limiting.

[0006]

[0008] The figures show general schemes of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the present disclosure. Additionally, elements in the depicted figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the examples discussed in this disclosure. The same reference numbers in different figures represent the same elements.

[0007]

[0009] The term "or" means any one or more of the items in the list connected by "or." As an example, "x or y" means any element of the three element set {(x),(y),(x,y)}. As another example, "x, y, or z" means any element of the seven element set {(x),(y),(z),(x,y),(x,z),(y,z),(x,y,z)}.

[0008]

[0010] The terms "comprises," "comprising," "includes," and / or "including" are "open-ended" terms that specify the presence of stated features but do not exclude the presence or addition of one or more other features.

[0009]

[0011] Terms such as "first," "second," and the like may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are used only to distinguish one element from another. Thus, for example, a first element discussed in this disclosure could be referred to as a second element without departing from the teachings of the disclosure.

[0010]

[0012] Unless otherwise specified, the term "coupled" may be used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements. For example, if element A is coupled to element B, element A may be in direct contact with element B or indirectly connected to element B by an intervening element C. Similarly, the terms "over" or "on" may be used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements.

[0011]

[0013] Light is a fundamental phenomenon with diverse properties and applications that span the electromagnetic spectrum, from radio waves to gamma rays. While the human eye perceives only the visible spectrum, light extends beyond this range to include longer wavelengths, such as infrared, and shorter wavelengths, such as ultraviolet and X-rays. These wavelength differences correspond to changes in energy, provide unique interactions with materials, and enable specialized technologies. For example, long-wave infrared (LWIR) light is characterized by lower energy and longer wavelengths compared to visible light and plays a key role in areas such as imaging, industrial processing, and advanced optics.

[0012]

[0014] An important attribute of light is its polarization, the orientation of its electric field in space. Polarization can appear as linear, circular, or elliptical, depending on the light wave's interaction with materials or filters. This property is particularly important when dealing with coherent light sources such as lasers, which propagate in a fixed direction and exhibit consistent wavelengths and polarizations. Being able to manipulate polarization can enable precise control over light for applications such as optical switching and modulation.

[0013]

[0015] The electro-optic effect, specifically the Pockels effect, is central to the operation of electro-optic modulators (EOMs), which enable dynamic control of light polarization. This effect occurs in certain non-centrosymmetric crystals, where an applied electric field causes a change in the refractive index, altering the polarization state of the transmitted light. Materials such as cadmium telluride (CdTe), gallium arsenide (GaAs), zinc selenide (ZnSe), zinc sulfide (ZnS), and boron arsenides (BAs) are among the few materials capable of supporting this effect in the LWIR and mid-wave infrared (MWIR) spectra due to their unique optical and structural properties.

[0014]

[0016] Pockels cells, a key component of EOMs, utilize these electro-optic materials to modulate light at high speeds without moving parts. By applying a voltage across the crystal, the birefringence of the material can be controlled, which can enable phase modulation of a laser beam with nanosecond precision. This capability is important in advanced applications such as extreme ultraviolet (EUV) lithography, where precise timing and modulation of light is essential to creating cutting-edge microchips.

[0015]

[0017] The present disclosure relates to systems and methods for controlling the polarization of light to improve laser drilling accuracy, particularly for applications requiring consistent hole roundness, such as microchip substrate processing. The present disclosure utilizes electro-optic modulation to address laser beam spot ellipticity caused by optical aberrations in scanning systems, thereby enabling improved control and uniformity in laser-drilled features.

[0016]

[0018] F-theta lenses can be used in laser systems for precision drilling because they can maintain a constant focal length across the scan field. However, when a laser passes through such a lens, the resulting beam spot often exhibits elliptical distortions, especially at the edges of the scan field. These distortions result in inconsistencies in the drilled holes, which are unacceptable for high-precision applications such as microchip substrate processing. Traditional approaches use circularly polarized light to mitigate these distortions and thereby achieve uniformity, but they limit flexibility in compensating for material- or process-specific requirements.

[0017]

[0019] The disclosed electro-optic modulation (EOM) system dynamically controls the polarization state of a laser beam to correct for laser spot ellipticity. By adjusting the polarization to counteract elliptical distortions at different scan field positions, the system can achieve consistent hole circularity across the entire field. Unlike prior methods, this system allows for the use of linear or elliptical polarization specifically tailored to specific positions in the scan field, thereby enabling compensation without compromising beam quality or cutting efficiency.

[0018]

[0020] 1 illustrates an example EOM system 100 for improved circularity in F-theta applications, according to various exemplary embodiments of the present disclosure. Referring to FIG. 1, EOM system 100 includes a polarization control device 101, one or more Pockels cells 103, a galvo mirror 105, and an F-theta lens 107.

[0019]

[0021] The polarization control device 101 is operable for initial polarization adjustment and may include, for example, a thin film polarizer, a Fresnel rhombohedron, a Faraday rotator, a wire grid polarizer, and / or a polarization dependent chromatic dispersion (PCD) waveplate.

[0020]

[0022] One or more Pockels cells 103 can enable dynamic polarization change in response to an applied electric field. One or more Pockels cells 103 are configured so that their fast axes are aligned in a particular direction. The Pockels cells 103 can be configured to dynamically change the beam polarization (111, 113, 115) in response to voltage changes. This feature compensates for spot ellipticity at different scan field positions, as shown in Figure 2.

[0021]

[0023] To achieve optimal results, the polarization control device 101 and Pockels cell 103 may need to be aligned with the geometry of the scan field. Additional optical components, such as a Faraday rotator or Fresnel rhombohedron, may be integrated to extend the range of polarization adjustment. The system is compatible with CO2 lasers and other lasers operating in the long-wave infrared spectrum, providing flexibility for material processing.

[0022]

[0024] A galvo mirror 105 can enable beam steering across the scan field. An F-theta lens 107 can maintain focus consistency. The EOM system 100 can be used on workpieces 109, such as microchip substrates, that require precise hole drilling.

[0023]

[0025] FIG. 2 shows an example of hole distortion and hole refinement according to various exemplary embodiments of the present disclosure. FIG. 2 illustrates how system 100 (of FIG. 1) addresses spot distortion. Beam spot 203 at the edge of the scan field often exhibits an elliptical shape due to lens aberrations. System 100 (of FIG. 1) can be modified to align the beam's polarization axis perpendicular to the major axis of the ellipse, effectively circularizing the drilled hole 207. This process can be achieved by dynamically adjusting the voltage across Pockels cell 103 (of FIG. 1), which changes the polarization state of the light. The resulting circularized spot 205 can ensure uniform cutting across the entire scan field.

[0024]

[0026] The disclosed system and method can enable dynamic polarization control. Unlike static polarizers, the system can allow for continuous adjustment of the polarization, allowing for custom-tailored compensation for aberrations at different scan positions.

[0025]

[0027] The disclosed system and method can improve hole circularity: by aligning the polarization with the elliptical distortion, the system can produce consistently circular holes even at the edges of the scan field.

[0026]

[0028] The disclosed systems and methods can provide increased flexibility: the systems can support a variety of polarization states, including linear, elliptical, and circular, to accommodate a variety of materials and applications.

[0027]

[0029] The disclosed system requires no moving parts: the use of electro-optic modulation eliminates the need for mechanical components, ensuring high speed operation and reliability.

[0030] The disclosed systems and methods are suitable for drilling holes in microchip substrates where precision and consistency are important, however, the disclosed systems are also adaptable to any application requiring high precision laser drilling, such as, for example, industrial cutting, medical device fabrication, and optical component manufacturing.

[0028]

[0031] The disclosed systems and methods represent an advancement in laser drilling technology, providing control over polarization to correct spot ellipticity and improve hole roundness. By combining electro-optic modulation with advanced optics, the disclosed systems and methods address challenges in precision manufacturing, enabling performance and reliability.

[0029]

[0032] While the present method and / or system has been described with reference to specific embodiments, it will be understood by those skilled in the art that various modifications may be made and equivalents may be substituted without departing from the scope of the present method and / or system. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its scope. Therefore, it is not intended that the present method and / or system be limited to the particular embodiments disclosed, but rather that the present method and / or system will include all embodiments falling within the scope of the appended claims.

Claims

1. An optical system configured to focus a laser beam onto a workpiece and generate multiple spots within the optical field, A Pockels cell configured to align the phase advance axis perpendicular to the corner of the optical field and to reduce inconsistencies in the roundness of the plurality of spots by adjusting the polarization of the laser beam, A system that includes this.

2. A system according to claim 1, comprising a plurality of Pockels cells.

3. A system according to claim 1, wherein the polarization control device includes a thin-film polarizer.

4. A system according to claim 1, wherein the optical system includes an F-theta lens.

5. The system according to claim 1, wherein the parameters of the laser beam are adjusted according to the material absorption of the workpiece.

6. A system according to claim 1, wherein the wavelength of the laser beam is within the medium-wave infrared (MWIR) spectrum.

7. The system according to claim 1, configured to compensate for distortion in a rectangular scanning field.

8. A system according to claim 1, comprising a computer numerical control (CNC) machine.

9. A system according to claim 1, wherein the polarization control device includes a Faraday rotor.

10. The steps include directing a laser beam onto a workpiece to generate multiple spots within the optical field, The steps include aligning the phase advance axis of the Pockels cell perpendicular to the corner of the optical field, A step of adjusting the polarization of the laser beam in accordance with the inconsistencies in the plurality of spots, The steps include drilling holes according to the aforementioned multiple spots and A method that includes this.

11. A method according to claim 10, comprising the step of aligning the phase advance axes of a plurality of Pockels cells.

12. A method according to claim 10, wherein a thin-film polarizer is configured to adjust the polarization of the laser beam.

13. A method according to claim 10, wherein the F-theta lens is configured to direct the laser beam.

14. A method according to claim 10, comprising the step of adjusting the parameters of the laser beam in accordance with the material absorption of the workpiece.

15. A method according to claim 10, wherein the wavelength of the laser beam is within the medium-wave infrared (MWIR) spectrum.

16. A method according to claim 10, wherein the step of adjusting the polarization of the laser beam compensates for distortion in a rectangular scanning field.

17. A method according to claim 10, wherein a computer numerical control (CNC) machine is configured to drill the hole.

18. A method according to claim 10, wherein the Faraday rotor is configured to adjust the polarization of the laser beam.

Images