Optical system and laser processing apparatus having the same

Abstract

The optical system is used for modulating laser, and comprises a first optical element and a second optical element which are arranged in sequence along a laser propagation direction; the first optical element is provided with a first surface into which the laser is incident and which is perpendicular to the laser, and a second surface which is a conical surface and whose axis is coincident with an axis of the laser, so that a ring-shaped light beam is obtained; the second optical element comprises a correction unit for correcting aberration of the ring-shaped light beam and a focusing unit for focusing the ring-shaped light beam. The laser is modulated and processed by the optical element, so that a Bessel light beam with a long focal depth is obtained, and the quality of glass via hole modification is better.

Description

Technical Field

[0001] This disclosure relates to the technical field of laser processing, and more specifically to an optical system and laser processing equipment having the same. Background Technology

[0002] Due to its numerous superior properties, such as high-frequency characteristics (dielectric constant less than 5.0@10GHz), ultra-low loss factor, submicron-level surface flatness, and excellent thermal expansion matching, glass substrates are taking up an increasingly larger share of the packaging substrate market. Correspondingly, the process of modifying vias on glass substrates, as a key process for realizing three-dimensional interconnects, has a significant impact on the performance of glass substrates.

[0003] Currently, laser-induced etching technology is commonly used for glass through-hole modification. Ultrafast laser-induced glass modification, combined with wet etching, achieves through-hole fabrication through a synergistic mechanism. However, this current processing method has limitations in depth of focus, making it difficult to process thick substrates. When the substrate thickness is large, the processing quality is relatively low. Utility Model Content

[0004] In view of this, the present disclosure aims to provide an optical system and a laser processing apparatus having the same, in order to solve the problem of low quality in through-hole modification when the glass substrate is thick.

[0005] In a first aspect, this disclosure provides an optical system for modulating laser light. The optical system includes a first optical element and a second optical element, which are arranged sequentially along the propagation direction of the laser light. The first optical element has a first surface and a second surface, which are arranged opposite to each other along the propagation direction of the laser light. The first surface is perpendicular to the propagation direction of the laser light, and the laser light enters the first optical element through the first surface. The second surface is a conical surface, the axis of which coincides with the axis of the laser light, and the laser light is modulated by the conical surface to form a Bessel beam.

[0006] The second optical element includes a correction unit and a focusing unit, both positioned along the propagation path of the Bessel beam. The Bessel beam passes through the correction unit, which corrects its aberrations. Then, the Bessel beam passes through the focusing unit, which focuses it.

[0007] In the above technical solution, the laser beam is modulated by a first optical element to convert it from a Gaussian beam to a Bessel beam. Compared with a Gaussian beam, a Bessel beam has the characteristics of long focal depth and no diffraction, and its energy is more concentrated. The Bessel beam is corrected and focused by a second optical element, so that the energy distribution of the final Bessel beam is more concentrated and the adverse effects of chromatic aberration and spherical aberration on the controllability of the beam are reduced. The final through-hole has a higher aspect ratio, better perpendicularity, and lower surface roughness, thus improving the quality of the prepared through-hole.

[0008] In one specific feasible implementation, the laser is transmitted through the second surface.

[0009] In one specific implementation, the correction unit includes a cemented lens group. The cemented lens group includes a first planar convex lens, a second planar convex lens, and a planar concave lens, all arranged along the propagation direction of the Bessel beam. The first and second planar convex lenses are cemented together planarly. The curvature of the convex surface of the second planar convex lens is the same as the curvature of the concave surface of the planar concave lens. The convex surface of the second planar convex lens is cemented together with the concave surface of the planar concave lens.

[0010] In one specific implementation, the correction unit further includes a first meniscus lens, the convex and concave surfaces of which are arranged opposite each other along the propagation direction of the Bessel beam.

[0011] In one specific implementation, the correction unit further includes a cemented doublet lens assembly, comprising a biconvex lens and a second meniscus lens, both positioned along the propagation direction of the Bessel beam. The biconvex lens has a first convex surface and a second convex surface, the curvature of which is the same as the curvature of the concave surface of the second meniscus lens. The second convex surface is cemented together with the concave surface of the second meniscus lens.

[0012] In one specific implementation, when the correction unit includes a first meniscus lens, the first meniscus lens is located between the cemented triplet lens group and the cemented doublet lens group.

[0013] In one specific implementation, the focusing unit includes a focusing convex lens. The focusing convex lens is located on one side of the correction unit along the propagation direction of the Bessel beam. The Bessel beam, corrected by the correction unit, propagates to the focusing convex lens for focusing.

[0014] In one specific implementation, the focusing unit further includes a front convex lens. After the laser beam is generated by the first optical element into a Bessel beam, the Bessel beam propagates to the front convex lens for focusing.

[0015] In one specific implementation, the front convex lens is located between the correction unit and the first optical element.

[0016] Secondly, this disclosure also provides a laser processing apparatus, including a laser source and an optical system as described in any of the preceding claims. The optical system is used to modulate the laser emitted from the laser source.

[0017] In the above technical solution, the laser emitted by the laser source is modulated by the optical system, so that the laser beam to be processed is a Bessel beam with long focal depth and no diffraction characteristics. Its energy is more concentrated. At least in the stroke corresponding to the prepared through hole, the beam is not diffracted and is in a state of high energy concentration, thereby improving the quality of the through hole prepared by the laser processing equipment. Attached Figure Description

[0018] Figure 1 The diagram shown is a schematic representation of the overall structure of an optical system provided in an embodiment of this disclosure.

[0019] Figure 2 The diagram shown is a structural schematic of a correction unit provided in an embodiment of this disclosure.

[0020] Figure 3 The diagram shown is a schematic diagram of the light field distribution after laser modulation provided in an embodiment of this disclosure.

[0021] Figure 4 The diagram shown is a schematic diagram of a glass through-hole prepared according to an embodiment of this disclosure.

[0022] Figure 5 The image shown is a field curve diagram of laser modulation provided in an embodiment of this disclosure.

[0023] Figure 6 The image shown is a distortion diagram of laser modulation provided in an embodiment of this disclosure.

[0024] The attached figures are labeled as follows:

[0025] 1. First optical element; 11. First surface; 12. Second surface;

[0026] 2. Second optical element; 21. Correction unit; 211. Cemented triplet lens group; 2111. First planar convex lens; 2112. Second planar convex lens; 2113. Planar concave lens; 212. First meniscus lens; 213. Cemented doublet lens group; 2131. Double-sided convex lens; 2132. Second meniscus lens; 22. Focusing unit; 221. Focusing convex lens; 222. Front convex lens. Detailed Implementation

[0027] The technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments.

[0028] To facilitate understanding of the optical system for glass through-hole modification provided in this disclosure, a brief description is given first. In advanced packaging fields such as 2.5D / 3D ICs, radio frequency devices, MEMS (microelectromechanical systems), and optoelectronic integration, glass substrates are increasingly widely used due to their superior performance, becoming the mainstream choice for packaging substrates. Correspondingly, TGV (Through-Through-Vessel) technology (a technology for creating through-holes on glass substrates) is a core technology for realizing three-dimensional interconnects, and its hole-forming quality directly affects the quality of devices packaged using glass substrates.

[0029] Currently, laser-induced etching (LAI) is one of the mainstream choices for via fabrication using TGV (Through-Vessel Transformation). Its principle involves using an ultrafast laser (pulse width less than 10 ps) to induce glass modification, combined with a synergistic mechanism of wet etching, to fabricate vias on a glass substrate. In LAI, a Gaussian laser beam is used. The cross-sectional area of ​​the Gaussian beam changes along its propagation direction, and the energy density of the laser on the cross-section changes along the laser propagation axis. When modifying vias, if the substrate thickness is too large, such as exceeding 500 micrometers, the quality of the fabricated vias will decrease. Specifically, due to the energy density distribution characteristics and short depth-of-focus characteristics of the laser, the fabricated vias may exhibit defects such as a small aspect ratio, wide pitch, low perpendicularity, and high roughness of the via sidewalls.

[0030] To overcome the above problems, this disclosure provides an optical system and laser processing equipment. The optical system modulates the laser emitted from a laser source, improving the quality of through-hole modification on a glass substrate. This results in glass through-holes fabricated using this optical system exhibiting higher aspect ratios, narrower pitch, higher perpendicularity, and lower surface roughness. The following detailed description, in conjunction with specific drawings and embodiments, further illustrates these features.

[0031] This disclosure provides a laser etching processing apparatus, including a laser source and an optical system. The laser source emits a Gaussian beam that extends and propagates in a columnar shape. The optical system receives the laser and modulates it to obtain a Bessel beam with a long focal depth. The system also adjusts the focal depth and focusing position of the obtained Bessel beam to perform etching on a glass substrate.

[0032] refer to Figure 1The main structure of the optical system provided in this embodiment is shown, including a first optical element 1 and a second optical element 2 arranged sequentially along the propagation direction of the laser. The propagation direction of the laser refers to the direction of extension of the laser axis. In this embodiment, the propagation direction is unidirectional as an example. Correspondingly, in some other embodiments, the propagation direction of the laser can also be adjusted by setting components such as a reflector.

[0033] The first optical element 1 has a first surface 11 and a second surface 12 disposed opposite to each other along the propagation direction of the laser. The first surface 11 is configured as a plane and is perpendicular to the propagation direction of the laser, serving as the incident surface of the first optical element 1, through which the laser enters the first optical element 1. The second surface 12 is configured as a conical surface, with the apex of the conical surface protruding away from the first surface 11. The axis of the conical surface coincides with the axis of the laser. The second surface 12 is used to modulate the laser to form a Bessel beam.

[0034] In this embodiment, the second surface 12 is a transmissive surface, and the laser continues to propagate along the original direction after passing through the second surface 12; in other embodiments, the second surface 12 may also be a reflective surface to reflect the laser propagating to the position of the second surface 12.

[0035] As the laser beam propagates along the second surface 12, it is refracted, transforming from an approximately planar wavefront into a conical surface. During the propagation of the conical wavefront, different wavelets interfere with each other, causing the laser beam refracted by the second surface 12 to form a Bessel beam.

[0036] In addition, the second optical element 2 includes a correction unit 21 and a focusing unit 22 arranged on the propagation path of the Bessel beam. The correction unit 21 is used to allow the Bessel beam formed after modulation by the first optical element 1 to pass through and to correct the aberration of the Bessel beam. The focusing unit 22 is used to allow the Bessel beam to pass through and to perform a focusing redistribution processing on the energy distribution of the Bessel beam, so that the energy of the Bessel beam is concentrated towards the center, so that the energy is concentrated in the central bright spot area, and the subsequent etching of the via is mainly carried out through this part. Furthermore, the size of the central bright spot of the Bessel beam can be adjusted by the focusing unit 22 to match the size of the via to be processed.

[0037] In the technical solution of this embodiment, by setting a first optical element 1, the laser beam is modulated to form a Bessel beam. Compared with the Gaussian beam laser emitted by the laser source, the Bessel beam has a deeper depth of focus. In the direction of laser propagation, the Bessel beam can maintain non-diffraction characteristics over a longer distance, that is, it can maintain the concentration of energy in the propagation direction and has a higher energy density. During processing, by focusing, the laser energy can be concentrated on the glass substrate to be processed, and the laser energy can be maintained in a longer distance in the propagation direction. The prepared through hole has a higher aspect ratio, wider pitch, higher perpendicularity, and lower roughness of the through hole sidewall, thus improving the quality of the prepared through hole.

[0038] like Figure 3 and Figure 4 As shown, Figure 3 The optical field distribution after focusing a laser using this optical system is shown, with the focused light field distribution being more concentrated in the axial region. Here, X and Y represent the horizontal planes of space, and the vertical coordinate axis represents Intensity, which refers to the light field intensity, i.e., the amount of light energy per unit area. (See Appendix of this disclosure.) Figure 3 The vertical coordinate axis represents the distribution of light field intensity in the horizontal plane through relative light intensity. Figure 4 The diagram illustrates the structure of a through-hole fabricated on a glass substrate after laser modulation using this optical system. As shown, the energy of the Bessel beam used in the process is more concentrated in the central spot region, and the Bessel beam possesses the characteristics of long focal depth and no diffraction. This results in a through-hole with a higher aspect ratio and higher perpendicularity, thus improving the quality of the fabricated through-hole.

[0039] Specifically, Bessel beams exhibit non-diffraction characteristics over longer distances in the propagation direction, reducing laser beam diffraction and making it easier to maintain energy concentration. The resulting through-holes have higher aspect ratios, narrower pitches, higher perpendicularity, and lower surface roughness.

[0040] Although laser light differs from natural light and possesses strong monochromaticity, in practical applications, it inevitably contains light of different wavelengths. Therefore, during the modulation of the laser light through various lenses in the optical system, the different refractive indices of the lenses for different wavelengths can cause chromatic aberration, leading to a decrease in the precision of the fabricated through-hole. To address this, a second optical element 2, including a correction unit 21, is incorporated to eliminate chromatic aberration and improve the quality of the fabricated through-hole.

[0041] Specifically, refer to Figure 1 and Figure 2The correction unit 21 includes a three-cemented lens group 211, which is used to perform chromatic aberration correction. Specifically, the three-cemented lens group 211 includes a first planar convex lens 2111, a second planar convex lens 2112 and a planar concave lens 2113 arranged along the propagation direction of the Bessel beam, and the three are cemented together in sequence.

[0042] By employing a triple-cemented lens group 211 and using a corresponding combination of dispersive optical glass materials, high-order apochromatic correction of axial chromatic aberration and magnification chromatic aberration (transverse chromatic aberration) of the laser is achieved, thereby improving the optical system's ability to suppress laser chromatic aberration and enhancing the quality of laser-fabricated through-holes.

[0043] The first planar convex lens 2111 and the second planar convex lens 2112 are bonded together in planar cementation; the curvature of the convex surface of the second planar convex lens 2112 is the same as the curvature of the concave surface of the planar concave lens 2113, and the convex surface with the same curvature is bonded together with the curved surface.

[0044] This makes the three lenses that make up the triplex lens group 211 tightly connected to each other. When the three are combined, it is easier to ensure the stability of their relative positions, reduce the risk of deviations in their relative positions and angles due to assembly errors, and reduce the problem of deviations in the laser propagation path from the preset path.

[0045] In addition, the correction unit 21 also includes a first meniscus lens 212, which is disposed on one side of the cemented triplet lens group 211 along the propagation direction of the Bessel beam, and the convex and concave surfaces of the first meniscus lens 212 are arranged along the propagation direction of the Bessel beam. For example, the first meniscus lens 212 is a negative meniscus lens.

[0046] In this embodiment, B being positioned on one side of A along the propagation direction of the laser (Bessel beam) means that the laser propagates through A first, and then through B. All other similar expressions in this embodiment refer to the same meaning and will not be elaborated further. A and B refer to lenses in the optical system.

[0047] A negative field curvature is introduced by using the negative light angle corresponding to the first meniscus lens 212, which cancels out the positive field curvature generated by other positive lenses in the optical system. This is used to correct beam spherical aberration, reduce the deformation of the final focused spot and the problem of uneven energy distribution, improve the controllability of the spot obtained after the Bessel beam is finally focused, and enhance the uniformity of energy distribution, resulting in better quality of the prepared through-hole.

[0048] Furthermore, in this embodiment, the Bessel beam first propagates through the cemented triplet lens group 211 and then to the first meniscus lens 212. The cemented triplet lens group 211 corrects chromatic aberration and also focuses the Bessel beam to a certain extent, thus reducing its diameter. Correspondingly, the first meniscus lens 212 can compensate for spherical aberration of the laser beam through a smaller refraction angle. Compared to placing the first meniscus lens 212 on the side of the cemented triplet lens group 211 facing the laser source, this reduces the design size of the first meniscus lens 212, making the overall optical system structure more compact.

[0049] For example, the correction unit 21 further includes a cemented doublet lens group 213, which is disposed on one side of the cemented triplet lens group 211 along the propagation direction of the Bessel beam. By configuring the cemented doublet lens group 213 to cooperate with the cemented triplet lens group 211 to perform chromatic aberration correction on the laser, the performance of apochromatic correction can be further optimized, resulting in a better chromatic aberration correction effect.

[0050] The cemented doublet lens assembly 213 includes a double convex lens 2131 and a second meniscus lens 2132 arranged along the propagation direction of the Bessel beam. The concave surface of the second meniscus lens 2132 faces the double convex lens 2131, and the curvature of the convex surface of the double convex lens 2131 facing the second meniscus lens 2132 is the same as the curvature of the concave surface of the second meniscus lens 2132. This ensures that the double convex lens 2131 and the second meniscus lens 2132 are stably bonded together. The cementing of the two can ensure the stability of the connection, reduce the problem of deviation in their relative positions, and thus prevent the obtained laser from being inconsistent with expectations. It can also improve the compactness of the overall structure and reduce the space occupied.

[0051] For example, the second meniscus lens 2132 is a positive meniscus lens; of course, in some other embodiments, the second meniscus lens 2132 may also be configured as a negative meniscus lens.

[0052] Furthermore, the first meniscus lens 212 is located between the cemented triplet lens group 211 and the cemented doublet lens group 213.

[0053] With the above setup, the Bessel beam propagates sequentially through the cemented triplet lens group 211, the first meniscus lens 212, and the cemented doublet lens group 213. After the chromatic aberration is corrected by the cemented triplet lens group 211 and a certain degree of focusing is achieved, the beam propagates to the first meniscus lens 212. The spherical aberration is corrected by the first meniscus lens 212, which helps to reduce the design size of the first meniscus lens 212 and makes the overall structure more compact.

[0054] The Bessel beam propagates through the first meniscus lens 212 and then to the cemented doublet lens group 213. The cemented doublet lens group 213 works in conjunction with the triplet lens group 211 to improve apochromatic performance; it also compensates for and corrects any chromatic aberration that may occur when the Bessel beam passes through the first meniscus lens 212. This enhances the overall chromatic aberration correction capability of the optical system, resulting in higher quality through-holes fabricated by laser processing.

[0055] refer to Figure 5 and Figure 6 ,in, Figure 5 The field curvature diagram of the laser modulated by the optical system is shown. The vertical axis represents the field curvature of the optical system, and the horizontal axis represents the field curvature defocusing amount. As can be seen from the attached figure, the meridional field curvature value of the edge field of view is less than 0.0052 mm. Figure 6 The diagram shows the distortion of the laser after modulation by the optical system. The vertical axis represents the field of view of the optical system, and the horizontal axis represents the distortion percentage. As can be seen from the attached figure, the maximum distortion of the optical system is less than 3.9%.

[0056] refer to Figure 1 The focusing unit 22 includes a focusing convex lens 221, which is disposed on one side of the correction unit 21 along the propagation direction of the laser. The focusing convex lens 221 is configured to focus the Bessel beam after it has been corrected by the correction unit 21, so that the energy of the Bessel beam is more concentrated in the central bright spot area, and the size of the central bright spot of the Bessel beam can be adjusted to form a high-intensity processing area with a specific diameter. The glass substrate is located in the processing area, and the through hole is modified by the Bessel beam after focusing.

[0057] The Bessel beam is focused by a focusing convex lens 221 to form a high-intensity processing area of ​​a specific size, which is determined by the size of the through-hole to be prepared. This allows for the convenient acquisition of Bessel laser beams with the required focal depth and size, resulting in better quality through-hole fabrication.

[0058] For example, in this embodiment of the present disclosure, the focusing unit 22 further includes a front convex lens 222, which is located between the correction unit 21 and the first optical element 1, and is configured to converge the Bessel beam generated by the first optical element 1.

[0059] Specifically, the first optical element 1 modulates the laser beam emitted by the laser source to form a Bessel beam. The Bessel beam is initially focused by the front convex lens 22, making the Bessel beam more concentrated and reducing energy loss to a certain extent in the subsequent propagation path of the Bessel beam. Furthermore, the focusing unit 22, which includes a focusing convex lens 221 and a front convex lens 222, focuses the Bessel beam, resulting in a more concentrated energy distribution and improving the quality of the through-hole fabrication.

[0060] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Any modifications or equivalent substitutions made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. An optical system for modulating laser light, characterized in that, It includes a first optical element and a second optical element arranged sequentially along the direction of laser propagation; The first optical element has a first surface and a second surface disposed opposite to each other along the propagation direction of the laser, wherein, The first surface is configured perpendicular to the propagation direction of the laser, so that the laser enters the first optical element via the first surface; The second surface is configured as a conical surface, the axis of which coincides with the axis of the laser, and the laser is modulated via the second surface to form a Bessel beam; The second optical element includes a correction unit and a focusing unit arranged on the propagation path of the Bessel beam; The correction unit is configured to allow the Bessel beam to pass through and to correct the aberrations of the Bessel beam; The focusing unit is configured to allow the Bessel beam to pass through and to focus the Bessel beam.

2. The optical system according to claim 1, characterized in that, The second surface is configured to transmit the laser.

3. The optical system according to claim 1, characterized in that, The correction unit includes a three-cemented lens group, which includes a first planar convex lens, a second planar convex lens, and a planar concave lens arranged along the propagation direction of the Bessel beam. The first planar convex lens and the second planar convex lens are bonded together in planar cementation; The curvature of the convex surface of the second planar convex lens is the same as the curvature of the concave surface of the planar concave lens, and the convex surface of the second planar convex lens is bonded to the concave surface of the planar concave lens.

4. The optical system according to claim 3, characterized in that, The correction unit further includes a first meniscus lens, the convex and concave surfaces of which are arranged opposite to each other along the propagation direction of the Bessel beam.

5. The optical system according to claim 3 or 4, characterized in that, The correction unit further includes a cemented doublet lens group, which includes a double convex lens and a second meniscus lens arranged along the propagation direction of the Bessel beam. The double-sided convex lens has a first convex surface and a second convex surface. The curvature of the second convex surface is the same as the curvature of the concave surface of the second meniscus lens, and the second convex surface and the concave surface of the second meniscus lens are bonded together.

6. The optical system according to claim 5, characterized in that, When the correction unit includes a first meniscus lens, the first meniscus lens is located between the cemented triplet lens group and the cemented doublet lens group.

7. The optical system according to claim 1, characterized in that, The focusing unit includes a focusing convex lens, which is located on one side of the correction unit along the propagation direction of the Bessel beam; The focusing convex lens is configured to focus the Bessel beam corrected by the correction unit.

8. The optical system according to claim 7, characterized in that, The focusing unit further includes a front convex lens configured to focus the Bessel beam generated via the first optical element.

9. The optical system according to claim 8, characterized in that, The front convex lens is located between the correction unit and the first optical element.

10. A laser processing apparatus, comprising a laser source and an optical system as described in any one of claims 1-9; The optical system is used to modulate the laser emitted by the laser source.

Images