Laser ablation system for package fabrication

Abstract

To provide a system and a method for fabricating semiconductor packages, and more particularly, a system and a method for forming features in semiconductor packages by laser ablation.SOLUTION: A substrate is patterned, which is to be utilized as a package frame for a semiconductor package having one or more interconnections formed therethrough and / or one or more semiconductor dies disposed therein. A laser system produces tunable laser beams for forming features in the substrate or another package structure. Specifically, the frequency, pulse width, pulse shape, and pulse energy of the laser beams are tuned based on the desired sizes of patterned features and on the material in which the patterned features are formed, so that the features are rapidly and accurately formed in the semiconductor substrate and package with controlled depth and topography.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to systems and methods for manufacturing semiconductor packages, and more particularly, to systems and methods for forming features on a package by laser ablation. [Background technology]

[0002] The continuing goal of semiconductor manufacturers to increase the yield and performance of electronic devices and components has driven efforts to increase the density of semiconductor devices fabricated on a semiconductor substrate of a given size. One method for increasing the density of semiconductor devices in semiconductor assemblies is to stack semiconductor dies to create three-dimensional multi-chip modules (3D MCMs). To form a 3D MCM, vias (i.e., through holes) must typically be created in at least one semiconductor die that extend from the active surface of the die to the opposite back surface of the die. The vias are filled with an electrically conductive material that provides interconnections on the back surface of the semiconductor die to external electrical contacts of another semiconductor die or a carrier substrate of the 3D MCM.

[0003] Traditionally, etching and laser ablation or drilling are two methods frequently used to form vias in semiconductor substrates. Laser drilling of vias has the advantage of being significantly faster and more positionally and dimensionally accurate than etching of vias, but traditional laser drilling has yet to achieve precise control of the depth and topography of the drilled area. Furthermore, laser energy is often used inefficiently, which results in slow ablation rates.

[0004] Therefore, there is a need for a laser drilling system and method for rapidly forming vias in semiconductor substrates with controlled depth and topography. Summary of the Invention

[0005] SUMMARY This disclosure relates generally to systems and methods for forming features on a package by laser ablation.

[0006] In one embodiment, a system for laser patterning a semiconductor device is provided. The system includes a diode-pumped solid-state laser source having a slab gain medium and configured to generate a pulsed laser beam. The laser source is further characterized by a pulse energy between about 0.25 mJ and about 10 mJ, a pulse width between about 1 ns and about 4000 ns, and a pulse frequency between about 1 kHz and about 200 kHz. The system further includes a large-angle galvanometer optical scanner and a first telecentric lens having a field of view (FOV) with a lateral dimension substantially equal to or greater than about 137 mm, and a working distance between about 30 mm and about 500 mm.

[0007] In one embodiment, a system for laser patterning a semiconductor device is provided. The system includes a diode-pumped solid-state laser source having a slab gain medium and configured to generate a pulsed laser beam. The laser source is further characterized by a pulse energy between about 0.25 mJ and about 10 mJ, a pulse width between about 1 ns and about 4000 ns, and a pulse frequency between about 1 kHz and about 200 kHz. The system further includes a large-angle galvanometer optical scanner, a first telecentric lens having a field of view (FOV) with a lateral dimension substantially equal to or greater than about 137 mm, and a working distance between about 30 mm and about 500 mm, and an adjustable stage with bidirectional motion. The stage motion is synchronized with the motion of the galvanometer optical scanner.

[0008] In one embodiment, a system for laser patterning a semiconductor device is provided. The system includes a diode-pumped solid-state laser source having an infrared (IR) slab gain medium and configured to generate a pulsed laser beam. The laser source is further characterized by a pulse energy between about 0.25 mJ and about 10 mJ, a pulse width between about 1 ns and about 4000 ns, and a pulse frequency between about 1 kHz and about 200 kHz. The system further includes a large-angle galvanometer optical scanner, a first telecentric lens having a lateral dimension substantially equal to or larger than about 137 mm in field of view (FOV) and a working distance between about 30 mm and about 500 mm, and an adjustable stage having bidirectional movement and configured to translate from a loading position for laser patterning and an absolute position for calibrating the galvanometer optical scanner. A controller is in communication with the laser source, the galvanometer optical scanner, and the adjustable stage, and is configured to modulate the pulse energy, pulse width, and pulse frequency of the laser source.

[0009] In order that the above-mentioned features of the present disclosure may be understood in detail, a more detailed description of the present disclosure briefly summarized above may be made with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings merely illustrate exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, which may admit of other equally effective embodiments. [Brief description of the drawings]

[0010] [Figure 1A] 1 is a simplified top view of an exemplary structured substrate according to an embodiment of the present disclosure. [Figure 1B] 1 is a schematic cross-sectional side view of an exemplary packaging structure according to an embodiment of the present disclosure. [Diagram 2] 1 is a schematic diagram of an exemplary laser system according to an embodiment of the present disclosure. [Diagram 3] 1 is a graph illustrating a temporal profile of instantaneous laser power of a pulsed laser beam according to an embodiment of the present disclosure. [Figure 4] 3 is a simplified diagram of a field of view of the laser system of FIG. 2 in accordance with an embodiment of the present disclosure. [Figure 5A] 1 is a schematic diagram illustrating a physical profile of a laser beam according to an embodiment of the present disclosure. [Figure 5B] 1 is a schematic diagram illustrating a physical profile of a laser beam according to an embodiment of the present disclosure. [Figure 6] 3 is a schematic diagram of a calibration setup for the laser system of FIG. 2 in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] For ease of understanding, wherever possible, the same reference numerals have been used to designate identical elements that are common between the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further detail.

[0012] The present disclosure relates to systems and methods for manufacturing semiconductor packages, and more particularly, to systems and methods for forming features in semiconductor packages by laser ablation. In one embodiment, the laser system and method described herein can be utilized to pattern a substrate utilized as a package frame for a semiconductor package having one or more interconnects formed therethrough and / or having one or more semiconductor dies disposed therein. The laser system described herein can produce an adjustable laser beam for forming features in a substrate or other package structure. In particular, the frequency, pulse width, pulse shape, and pulse energy of the laser beam can be adjusted based on the desired size of the patterned feature and based on the material from which the patterned feature is formed. The adjustable laser beam allows for rapid and precise formation of features in semiconductor substrates and packages with controlled depth and topography.

[0013] As used herein, the term "about" refers to a + / - 10% variation from the nominal value, and it is understood that such a variation may be included in all values ​​provided herein.

[0014] 1A illustrates a simplified top view of an exemplary structured substrate 100 that may be formed by the laser system described herein and that may be utilized as a structural frame for a semiconductor package. Substrate 100 is shown as having a rectangular cavity 110 surrounded by a number of substantially cylindrical vias 120, collectively referred to as features 130. Cavity 110 is typically formed in substrate 100 for subsequent placement and encapsulation of one or more semiconductor devices, such as one or more active semiconductor dies, or passive components therein. Vias 120 provide channels or passageways for interconnects formed in and routed through substrate 100 so that interconnects may be electrically coupled directly to devices and / or connections may be redistributed on both sides of substrate 100.

[0015] The cavities 110 and vias 120 can be laser patterned in the substrate 100 in any desired size and shape and in any desired quantity and arrangement. In certain embodiments, the individual cavities 110 have lateral dimensions ranging between about 1 mm and about 50 mm, such as about 8.6 mm, depending on the size of the semiconductor device or devices to be sealed and embedded therein during the manufacture of the semiconductor package. In some embodiments, the cavities 110 are sized to have lateral dimensions substantially similar to the lateral dimensions of the semiconductor devices to be embedded therein. For example, the individual cavities 110 formed have lateral dimensions that are at most less than about 150 μm longer than the lateral dimensions of the semiconductor devices to be placed therein, such as less than about 120 μm, such as less than 100 μm. Reducing the variation in size of the cavities 110 and the semiconductor devices to be embedded therein reduces the amount of gap fill material utilized in subsequent package manufacturing operations.

[0016] In certain embodiments, the individual vias 120 have a diameter ranging between about 50 μm and about 200 μm, such as about 90 μm. The minimum pitch 125 between the individual vias 120 is between about 30 μm and about 170 μm, such as about 40 μm. Typically, the vias 120 have a substantially cylindrical shape, although other configurations are contemplated. For example, the individual vias 120 can have a tapered or frustoconical shape.

[0017] 1B shows a schematic cross-sectional side view of the substrate 100 after encapsulating the semiconductor device 140 in the cavity 110 and plating the interconnects 150 in the vias 120 to form the package 101. To embed the semiconductor device 140 in the cavity 110, the semiconductor device 140 is placed in the cavity 110 prior to encapsulation with an insulating layer 160 that is laminated and cured on top of the semiconductor device 140. The insulating layer 160 can have a thickness between about 20 μm and about 70 μm, such as about 30 μm, from the surface of the substrate 100 to the outer surface of the insulating layer 160. In some embodiments, the insulating layer 160 includes an organic dielectric material, such as Ajinomoto Build-up Film (ABF) and Mitsubishi BT Film. In a particular example, the insulating layer 160 is an epoxy resin containing a ceramic filler, such as an epoxy resin containing silica (SiO2) particles.

[0018] By laminating the insulating layer 160, the dielectric material flows and fills into the voids between the underlying semiconductor device 140 and the substrate 100, as well as into the vias 120. Thus, through vias 170 (another type of feature 130) are laser drilled through the dielectric material of the insulating layer 160 in the vias 120 to form channels or passages for the interconnects 150 through the entire package 101 after laminating the insulating layer 160. Typically, the through vias 170 have a narrower diameter than the vias 120, such that by laser drilling the through vias 170, they are circumferentially surrounded by the insulating layer 160 in the vias 120. In some embodiments, the through vias have a diameter between about 20 μm and about 70 μm, such as about 30 μm. By surrounding the through vias 170 and the subsequently plated interconnects 150 with a dielectric material, capacitive coupling between the conductive silicon-based substrate 100 and the interconnects 150 in the package 101 can be reduced or eliminated. It should be noted, however, that through vias 170 may be formed only partially through package 101, or may be formed in insulating layer 160 at locations outside vias 120 in substrate 100. For example, through vias 170 may be formed above or below embedded semiconductor device 140 to electrically couple subsequent plating of interconnects 150 to semiconductor device 140.

[0019] 2 illustrates a schematic diagram of an exemplary laser system 200 that may be utilized to form desired features 130 (e.g., vias 120, through vias 170, and cavities 110) in a sample 240, such as a semiconductor package structure. The laser system 200 is configured to precisely ablate high density, narrow profile features 130 in a variety of package structures and materials, such as silicon-based substrates and dielectric epoxies. The laser system 200 generally includes a laser source 202, an optical assembly 206, a camera 208, and a controller 210. In certain embodiments, the laser system 200 further includes a stage 212, an optical bench 214, a vacuum source 216, a debris collector 218, and a wafer nest 220.

[0020] Typically, the laser source 202 is a solid-state laser, such as a diode-pumped solid-state laser having a slab gain medium configured to generate a continuous or pulsed laser beam 230 to irradiate the sample 240 and form one or more features 130 therein. The laser slab can be formed of any suitable laser crystal material, including neodymium-doped yttrium aluminum garnet (Nd:YAG; Nd:Y3Al5O12), yttrium-doped YAG (Yb:YAG), neodymium-doped yttrium orthovanadate (Nd:YVO; Nd:YVO4), and alexandrite. In certain embodiments, the laser slab has a face-pumped geometry. In certain embodiments, the laser slab has an end-pumped geometry.

[0021] In certain embodiments, the laser source 202 operates at an infrared (IR) wavelength (e.g., 1064 nm) to form features 130 in a silicon-containing substrate, such as a silicon substrate having a thickness between about 100 μm and about 1500 μm. In certain other embodiments, the laser source 202 operates at an ultraviolet (UV) wavelength (e.g., 355 nm) to form features 130 in a dielectric material, such as a polymerized epoxy resin. The laser source 202 can generate a pulsed laser beam 230 having a frequency between 1 kHz and 200 kHz. In some examples, the laser source 202 is configured to deliver a pulsed laser beam with a pulse duration between about 1 ns and 5 μs and a pulse energy between about 0.10 millijoules (mJ) and about 10 mJ. In the embodiments described herein, the frequency, pulse width and pulse energy of the laser beam 230 generated by the laser source 202 are adjustable (e.g., tunable) depending on the material to be patterned, the desired lateral dimensions of the features 130 to be drilled, and the depth of the features 130 to be drilled. Additionally, the speed at which the laser beam 230 moves, the number of pulses, and the beam profile and size can be adjusted.

[0022] For example, to drill a through via 170 having a diameter of about 90 μm through a thin silicon-based substrate 100 having a thickness between about 100 μm and about 200 μm, the laser source 202 can be tuned to have a frequency between about 5 kHz and about 100 kHz, a pulse energy between about 0.5 mJ and about 4.5 mJ, e.g., a pulse energy between about 0.8 mJ and about 1.2 mJ at a frequency of about 100 kHz, and a pulse energy between about 3.5 mJ and about 4.5 mJ at a frequency of about 5 kHz, and a pulse width between about 100 ns and about 1200 ns. For example, a frequency of about 5 kHz and a pulse width of about 600 ns can provide a pulse energy of about 70,000 μm. 3 and approximately 110,000 μm 3 A volume of material between 18,000 μm is removed per laser pulse. At a frequency of about 100 kHz and a pulse width of about 600 ns, 3 and about 26,000 μm 3 A volume of material between is removed per laser pulse. The amount of energy delivered to the material per unit volume is approximately 35 J / mm 3 and 60 J / mm 3 It is between.

[0023] To drill a through via 170 with a diameter of about 90 μm through a thick silicon substrate 102 with a thickness between about 500 μm and about 1 mm, the laser source 202 can be tuned to have a frequency between about 5 kHz and about 30 kHz, a pulse energy between about 2 mJ and about 10 mJ, for example, a pulse energy between about 2 mJ and about 3.5 mJ at a frequency of about 30 kHz, and a pulse energy between about 7 mJ and about 10 mJ at a frequency of about 5 kHz, and a pulse width between about 1 μs and about 5 μs.

[0024] To drill a cavity 110 having a lateral dimension of about 8.6 mm and a depth of between about 50 μm and 200 μm, the laser source 202 can be tuned to have a frequency of between about 5 kHz and about 40 kHz, a pulse energy of between about 0.5 mJ and about 4.5 mJ, and a pulse width of between about 15 ns and about 600 ns. For example, at a frequency of about 5 kHz and a pulse width of about 600 ns, a cavity 110 having a lateral dimension of about 8.6 mm and a depth of between about 50 μm and 200 μm can be tuned to have a frequency of between about 5 kHz and about 40 kHz, a pulse energy of between about 0.5 mJ and about 4.5 mJ, and a pulse width of between about 15 ns and about 600 ns. 3and 50,000 μm 3 A volume of material is removed per pulse. At a frequency of about 5 kHz and a pulse width of about 2 μs, this is about 220,000 μm 3 and 400,000 μm 3 A volume of material is removed per pulse. At a frequency of about 30 kHz and a pulse width of about 2 μs, this is about 95,000 μm 3 and approximately 110,000 μm 3 of material volume is removed per laser pulse. The amount of energy delivered to the material per unit removed is approximately 60 J / mm 3 and 75 J / mm 3 It is between.

[0025] In either form, the laser beam 230 produced by the laser source 202 is projected (e.g., transmitted) toward the sample 240 through the optical assembly 206. The optical assembly 206 is optically coupled to the laser source 202 and includes any suitable image projection device, such as an F-theta lens, for directing the laser beam 230 toward the sample 240 to laser pattern the features 130. In certain embodiments, the optical assembly 206 includes a scanner 232, such as a single-axis or multi-axis large-angle galvanometer optical scanner (i.e., a galvo scanner). In certain embodiments, the scanner 232 is a three-axis galvo scanner with one or more lenses of the optical assembly 206 positioned upstream on the laser propagation path. In certain embodiments, the scanner 232 is a polygon scanner. The term "galvanometer scanner" refers to any device that changes the projection or reflection angle of the laser beam 230 in response to electronic signals from the controller 210 to cause the laser beam 230 to sweep across the sample 240. Typically, the scanner 232 includes one or more adjustable, electromechanically controlled mirrors for diverging (e.g., multiplying) and / or steering the laser beam 230 across the sample 240 during laser drilling. The scanner 232 can be utilized to simultaneously drill multiple features 130 in the sample 240 in addition to scanning the laser beam 230 across the surface of the sample 240 without mechanically translating the sample 240 itself. The scanner 232 can further include any suitable features, such as digital servo feedback, low drift, fast dynamic response, and precise calibration capabilities, to facilitate high density drilling of the materials and structures described herein.

[0026] In certain embodiments, the optical assembly 206 further includes one or more telecentric lenses 234 having a wide field of view that encompasses the entire sample 240. For example, the telecentric lens 234 of the optical assembly 206 can have a field of view with a lateral dimension substantially equal to or larger than about 137 mm for purposes of thermal management and lithography alignment (discussed below with reference to FIG. 4). The telecentric lens 234 can have a transparent aperture between about 30 mm and about 60 mm and is configured to receive a laser beam 230 having a spot size between about 5 mm and about 20 mm. The telecentric lens 234 can also have an extremely small degree of distortion (i.e., telecentric error) and a long working distance. For example, the telecentric lens 234 can have a telecentric error value of less than about 5°, such as a telecentric error value of less than about 3° or about 1°. In other examples, the telecentric lens 234 has a working distance between about 30 mm and about 500 mm, thereby allowing for a greater depth of focus between the optical assembly 206 and the sample 240 without requiring Z height adjustment.

[0027] In certain embodiments, two or more telecentric lenses 234 can be utilized to laser drill different types of materials, with each telecentric lens 234 specialized for the wavelength range of the laser source 202 utilized for each material type. In such embodiments, the two or more telecentric lenses 234 can have matching properties to allow for alignment of features 130 to be drilled through different material types. In one example, a first telecentric lens 234 can be utilized to IR drill through a silicon-based substrate, such as the via 120 in the substrate 100 described above. Then, when an insulating layer 160 is stacked above the substrate 100, a second telecentric lens 234 can be utilized to UV drill through the insulating layer, such as the through via 170 in the via 120 of the substrate 100. Matching the properties of the two telecentric lenses 234 thus allows for good alignment of the through vias 170 in the vias 120, thus allowing for proper isolation between them by the insulating layer 160, and reducing or eliminating the chance of exposing the substrate 100. Examples of properties that may be matched between different telecentric lenses 234 include focal length, field of view size, maximum telecentricity error, mechanical scan angle per mirror of the corresponding scanner 232, lens length, lens diameter, working distance, and nominal spot size, to name a few.

[0028] In operation, the laser beam 230 projected by the optical assembly 206 is directed towards a sample 240 disposed on the stage 212. Typically, the stage 212 provides a receiving surface for the sample 240, which may be a substrate having lateral dimensions of approximately 156 mm by 156 mm or greater. The stage 212 is coupled to an optical bench 214 and may be supported above the optical bench 214 by one or more pairs of tracks 222. In certain embodiments, the tracks 222 are arranged in linear pairs to allow translation of the stage 212 in the X and / or Y directions. For example, the tracks 222 may include magnetic channels that are linear and parallel to one another. In certain other embodiments, the tracks 222 may have a non-linear shape. In operation, the stage 212 moves in the X and / or Y directions from a loading position to a processing position. Loading and / or unloading of the sample 240 onto the stage 212 is performed by utilizing one or more transport devices (not shown) capable of automated handling of thin and / or fragile substrates. For example, the sample 240 can be loaded utilizing a robotic arm having a Bernoulli-type gripper, a walking beam, a soft lifting jack, and the like. A processing position can refer to one or more positions of the stage 212 as the stage 212 passes under the optical assembly 206 of the laser system 200 in a processing direction. In certain embodiments, the movement of the stage 212 is synchronized with the movement of the scanner 232 to allow efficient transition between loading and unloading of the sample 240 and scanning of the laser beam 230 for laser drilling the sample 240.

[0029] An encoder (not shown), such as a linear stage encoder, may further be coupled to the stage 212 to provide location information of the stage 212 and / or the wafer nest 220 to the controller 210 prior to and / or during the laser drilling process. Additionally, the sample 240 or calibration substrate (not shown) may include one or more physical markings or features 242, such as crosses, circles, grid markings, or through sample fiducials, formed on at least an upper surface of the sample 240 or calibration substrate for visual tracking of the sample 240 or calibration substrate and / or for calibration of the laser system 200 by the controller 210 and a camera 208 directed at the stage 212. For example, the camera 208 may continuously capture images of the sample 240 and stage 212 for real-time measurement by the controller 210 of X and Y lateral position coordinates of the sample 240 and stage 212, thus facilitating precise and accurate laser drilling of features 130 in the sample 240.

[0030] The stage 212 and / or wafer nest 220 are fluidly coupled to a vacuum source 216, such as a dedicated vacuum pump, that provides a vacuum thereto. The vacuum source 216 may include a throttle valve (not shown) for adjusting the amount of vacuum provided. In certain embodiments, the vacuum source 216 is utilized to chuck a sample 240, such as a silicon-based substrate or packaged structure, to the stage 212 and / or wafer nest 220 during laser drilling, and thereby provide a planar drilling surface. For example, the vacuum source 216 may chuck the sample 240 to the stage 212 and / or wafer nest 220 to prevent warping due to elevated temperatures from the laser drilling process. In certain embodiments, the vacuum source 216 provides a vacuum pressure of about 100 mbar or less to chuck the sample 240 to the stage 212.

[0031] The controller 210 may include a central processing unit (CPU) (not shown), memory (not shown) and supporting circuits (or I / O) (not shown). The CPU may be one of any form of computer processor used in industrial environments to control various processes and hardware (e.g., laser sources, optical assemblies, scanners, stage motors and other hardware) and to monitor processes (e.g., processing time, stage and / or wafer nest position, and substrate position). The memory (not shown) is connected to the CPU and may be one or more of a random access memory (RAM), a read only memory (ROM), a floppy disk, a hard disk, or any other form of digital storage, local or remote, or other readily available memory. Software instructions and data may be encoded and stored in the memory to instruct the CPU. The supporting circuits (not shown) are also connected to the CPU and support the processor in a conventional manner. The supporting circuits may include conventional caches, power supplies, clock circuits, input / output circuitry, subsystems, and the like. Programs (or computer instructions) readable by the controller determine tasks that may be performed on a sample 240, such as a silicon-based substrate. The program may be software readable by the controller and may include, for example, code for monitoring and controlling (e.g., switching) the laser beam 230 characteristics (frequency, pulse width, and pulse energy) and the movement of the stage 212 and / or scanner 204.

[0032] In certain embodiments, the laser system 200 further includes a debris collector 218 disposed within a processing region of the laser system 200 and fluidly coupled to a vacuum source, such as vacuum source 216. The debris collector 218 generates a cross-flow 224 of circulating gas to provide a vacuum to the processing region to remove debris formed during laser ablation of the sample 240. In certain embodiments, the cross-flow 224 provided by the debris collector 218 is anti-parallel to a processing direction 226 of the laser system 200 (e.g., a direction in which the stage 212 and / or scanner 204 move during processing).

[0033] FIG. 3 illustrates a temporal profile of the instantaneous laser power of a pulsed laser beam, such as laser beam 230, which can be programmed by controller 210. Without intending to be bound by theory, it is believed that during the laser ablation process of sample 240, the material to be drilled melts and a small portion of the molten liquid state material evaporates and develops a thermal plasma. This plasma plume tends to be opaque to the laser beam, and therefore the speed at which the laser beam can be delivered to the material to be drilled is limited by this "plasma screening effect." However, when the laser is pulsed and the pulse energy of the laser beam is distributed over a longer pulse duration, this plasma screening effect can be reduced. Thus, a significant amount of pulse energy can be used to melt the material to be drilled without evaporating the melted material, and therefore the speed of laser drilling can be increased by applying a pulsed laser with a longer pulse width compared to a laser pulse with a shorter pulse width.

[0034] In some embodiments, the pulsed laser beam 230 emitted from the laser source 202 is programmed by methods known in the art to have an instantaneous laser output with a rectangular temporal profile 302 as shown in FIG. 3. The instantaneous laser output with a rectangular temporal profile 302 ensures a gentle heating rate that avoids overheating (i.e., evaporating the molten material) and improves the efficiency of laser drilling. In some embodiments, the pulsed laser beam 230 emitted from the laser source 202 is programmed by methods known in the art to have an instantaneous laser output with a chair-shaped temporal profile 304 as shown in FIG. 3, which can further improve the efficiency of laser drilling. Features 130 drilled by the pulsed laser beam 230 with the rectangular temporal profile 302 generally have straighter and smoother inner walls compared to features 130 drilled by laser pulses with a typical Q-switched temporal profile 306 as shown in FIG. 3. It should be noted that the laser source 202 is programmed to produce a number of pulse widths and / or temporal shapes for the laser beam 230 , which can be selected (eg, switched) by the controller 210 .

[0035] As mentioned above, excess laser energy beyond the energy required to melt the material will cause partial evaporation. Therefore, programming the pulse of the laser beam 230 to have a weighted pulse energy content towards the trailing end of the laser pulse can also have an advantageous effect. In the early part of the pulse, a slow energy delivery with a moderate heating rate melts a larger amount of the material being drilled. This is in contrast to laser drilling using a laser pulse with a typical Q-switched temporal profile 306 that delivers high energy at one time, where the temporal profile peaks relatively early in the pulse and lower energy is required (early in the pulse). Thus, a significant portion of the laser pulse energy is wasted in over-evaporation and possible ionization of the ablation plume. By programming the laser pulse with the temporal profile 302 or the chair-shaped temporal profile 304, effective laser drilling can be achieved without wasting laser energy in the evaporation of the melted material being drilled early in the pulse. In certain embodiments, the ratio of the energy density of the first half of the laser pulse (A) compared to the total energy density of the laser pulse (B) is between about 0.2 and about 0.8 (A / (A+B)=0.2-0.8).

[0036] Furthermore, the inventors of the present disclosure have also found that the straightness and smoothness of the inner walls of features 130, such as vias 120 and / or through vias 170, are highly related to the ablation depth per laser pulse. The ablation depth deepens with the optical penetration depth, the thermal penetration depth and the laser fluence (i.e., energy per unit area). For a near-IR laser with a wavelength of about 1.0 μm used in the exemplary embodiment described herein, a long pulse width ensures that the optical penetration depth (proportional to the square root of the pulse width) is sufficiently large. Thus, the laser pulse energy is more uniformly distributed over a long distance penetrating the substrate, thereby simultaneously heating and melting the thick substrate material, resulting in more effective ablation. The ablated material has a large momentum (i.e., mass x velocity) and a more directional motion, which is advantageous for evacuating the hole without redepositing on the inner wall, making the inner wall of the drilled hole straighter and smoother. This is in contrast to focused ablation with lasers having shorter wavelengths (such as 355 nm UV lasers) and shorter pulse widths, where only the surface of the substrate is ablated. Furthermore, ablation with such short pulse width lasers ablates much less material, but it is ablated explosively as a mixture of superheated melt, vapor and plasma, has a much less directional ejection from the hole being drilled, and includes redeposition on the inner walls of the hole.

[0037] 4 shows a schematic diagram of the drilling field of view (FOV) 402 (shown in phantom) of the telecentric lens 234 in relation to a substrate 400 having lateral dimensions D1, D2 of about 156 mm or less. As previously explained, the drilling FOV 402 of the telecentric lens 234 is larger than the lateral area of ​​the sample to be laser drilled, such as the substrate 400. The larger drilling FOV 402 allows the entire substrate 400 to be scanned by the scanner 232 without requiring mechanical movement of the substrate 400, such as by the stage 212. Thus, stitching of multiple FOVs or sections of the substrate 400 is not required, thus allowing for more robust alignment and shorter cycle times for laser drilling, and all features 130 to be drilled in the substrate 400 can be formed in a perpendicular orientation to the surface of the telecentric lens 234.

[0038] 4 also illustrates the drilling FOV 402 of the telecentric lens 234 in relation to a number of smaller lithography FOVs 404 that are utilized in subsequent processing steps of the substrate 400 during package manufacturing. As shown, the drilling FOV 402 spans the entire lithography FOV 404, thus eliminating the occurrence of litho printing on any misaligned features 130 formed during laser drilling. In certain embodiments, the drilling FOV 402 is a quantitative multiple of the lithography FOV 404, thus facilitating proper alignment. As such, no alignment between the drilling FOV 402 and the lithography FOV 404 is required while processing the substrate 400.

[0039] The telecentric lens 234 further allows on-the-fly drilling cycles to be performed and repeated across the surface of the substrate 400 without requiring mechanical translation of the substrate 400. During on-the-fly drilling, the pulsed laser beam 230 is scanned across the surface of the substrate 400 by the scanner 232 to drill subsets of features 130 at different locations on the substrate 400. At each location and / or subset of features 130, one or more pulses of the laser beam 230 may be delivered for each feature 130 before the scanner 232 translates the laser beam 230 to the next location in the drilling cycle. Once the drilling cycle is complete (e.g., after delivery of one or more pulses for each feature 130 at each location in the drilling cycle), the laser beam 230 returns to the initial location of the drilling cycle to deliver one or more additional pulses for each feature 130, and the drilling cycle is repeated. Typically, two or more drilling cycles, such as five or more drilling cycles, are utilized to form a complete feature 130 through the thickness of a sample, such as a substrate 400. By cycling the laser pulse across the entire surface of the substrate 400, individual drilling locations can be cooled between laser pulses, thus avoiding drilling into an already heated surface of the substrate 400, which can cause overheating and reduce drilling efficiency due to the "plasma screening" effect described above. Using a telecentric lens 234 with a FOV 402 larger than the lateral area of ​​the substrate 400, the entire drilling cycle is performed without the need to mechanically move the substrate 400, which can increase the risk of sample misalignment or variation and can also dynamically lengthen drilling cycle times.

[0040] In some embodiments, in an on-the-fly drilling cycle process, the pulsed laser beam 230 is positioned synchronously with the scanning motion of the galvo scanner for fast beam positioning, for example at a speed of about 10 m / s, and is repeated over a subset of features 130. The effective drilling repetition rate for any one feature 130 is approximately the laser repetition rate divided by the total number of features 130 being drilled. In some embodiments, the subset of features 130 includes between about 1000 and about 2,500,000 features 130 that are drilled by synchronous drilling during an on-the-fly drilling cycle.

[0041] In addition to providing a wider field of view 402, the telecentric lens 234 also provides an enhanced (e.g., extended) depth of focus for the laser beam 230. Figures 5A and 5B show the physical profile (i.e., shape) of the laser beam 230 penetrating a substrate 400 having a first thickness T1 and a second thickness T2 as projected by the telecentric lens 234 and a standard relay lens 500, respectively. As shown in Figure 5A, the telecentric lens 234 minimizes the beam divergence of the laser beam 230 in the far-field and also increases the peak intensity of the laser beam 230 over a longer distance, thus enabling consistent drilling of features 130 having uniform dimensions LB1 through the respective thicknesses T1 and T2 of the substrate 400. This is particularly advantageous during drilling of large arrays of thin vias 120 and / or through vias 170 in samples with negligible thickness variation, as no focus adjustment is required between different samples, as well as during drilling processes in which features are patterned into different samples with different thicknesses. In FIG. 5B, the limited depth of focus of the relay lens 500 causes beam focusing and divergence, resulting in a peak intensity of the laser beam 230 that varies throughout its propagation path. The variations in beam profile and intensity result in dimensional non-uniformity of dimension LB2 between features 130 drilled in the respective thicknesses T1 and T2 of the substrate 400.

[0042] 6 shows a schematic diagram illustrating a closed-loop calibration mechanism utilized by laser system 200 to calibrate and align scanner 232 for laser drilling. As shown, laser system 200 can load calibration plate 600 onto stage 212 and / or wafer nest 220 and laser pattern the top surface of calibration plate 600 with grid or cross markings 602. The grid or cross markings 602 can have any suitable degree of fineness depending on the number and features 130 formed during laser patterning. Upon marking calibration plate 600, calibration plate 600 is mechanically translated via stage 212 to an absolute position and the X and Y lateral position coordinates of calibration plate 600 are measured by controller 210 using camera 208 and one or more linear stage encoders. The actual position of the marking 602 is compared (e.g., evaluated) to the nominal (e.g., desired) position 604, and the trajectory for the laser beam 230 updated by the scanner 232 is interpolated by the controller 210. The modified instructions can be autocoded and stored in the memory of the controller 210 for instructing the CPU in further calibration cycles and / or the laser drilling process. Upon auto-generation of the modified instructions, the calibration mechanism can be repeated until the degree of measurement error exceeds the degree of potential correction improvement, at which point the laser drilling process can be performed. In certain embodiments, the calibration mechanism described above allows alignment of the actual feature with the nominal position with a discrepancy of less than about 5 μm.

[0043] The systems and methods disclosed herein include laser ablation systems and methods for forming features such as vias and cavities in semiconductor packaged devices. The laser ablation systems described herein can create tunable laser beams with desired frequency, pulse width, pulse shape and pulse energy based on the desired size of the features to be patterned and based on the material the patterned features are formed from. The tunable laser beam provides rapid and accurate drilling of vast arrays of high density features in semiconductor packaged device structures with controlled depth and topography, thus forming thin form factor packages with high chip or die package volume ratios. Thus, the systems and methods described herein enable greater I / O scalability to meet the ever-increasing bandwidth and power efficiency demands of artificial intelligence (AI) and high performance computing (HPC).

[0044] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the following claims.

Claims

1. 1. A system for laser patterning a semiconductor device, comprising:

1. A diode-pumped solid-state laser source configured to generate a pulsed laser beam, the laser source comprising a slab gain medium; Pulse energy between about 0.25 mJ and about 10 mJ; a pulse width between about 1 ns and about 4000 ns, and Pulse frequencies between about 1 kHz and about 200 kHz a diode-pumped solid-state laser source further characterized by: a large angle galvanometer optical scanner; a first telecentric lens having a field of view (FOV) with a lateral dimension substantially equal to or greater than about 137 mm, the first telecentric lens having a working distance between about 30 mm and about 500 mm; A system comprising:

2. The system of claim 1 , wherein the laser source is an infrared (IR) laser source.

3. The system of claim 1 , wherein the first telecentric lens has a telecentric error value of less than about 5°.

4. 10. The system of claim 1, further comprising a second telecentric lens having a FOV with a lateral dimension substantially equal to or greater than about 137 mm and a working distance between about 30 mm and about 500 mm.

5. The system of claim 4 , wherein the first telecentric lens is specialized for IR wavelengths and the second telecentric lens is specialized for UV wavelengths.

6. The system of claim 5 , wherein the first telecentric lens and the second telecentric lens have substantially the same maximum telecentric error and nominal spot size.

7. 10. The system of claim 1, further comprising a controller in communication with the laser source and the galvanometric optical scanner, the controller configured to modulate the pulse energy, the pulse width, and the pulse frequency of the laser source.

8. The system of claim 7 , wherein the controller is further configured to modulate a pulse shape of the laser source.

9. The system of claim 8 , wherein the pulse shape of the laser source is rectangular or chair shaped.

10. The system of claim 7 further comprising an adjustable stage disposed on linear, parallel tracks.

11. The system of claim 10 , wherein the adjustable stage is configured to receive a substrate having a lateral dimension of about 156 mm or greater.

12. The system of claim 10 , wherein the adjustable stage is coupled to a linear stage encoder that provides position information of the stage to the controller.

13. The system of claim 12 further comprising a camera pointed at the adjustable stage and in communication with the controller.

14. The system of claim 13 , wherein the camera, the adjustable stage and the controller form a closed-loop calibration system for positional calibration of the galvanometer optical scanner.

15. The system of claim 1 further comprising a debris collector for creating a cross-flow of circulating gas in a treatment region of the system.

16. 1. A system for laser patterning a semiconductor device, comprising:

1. A diode-pumped solid-state laser source configured to generate a pulsed laser beam, the laser source comprising a slab gain medium; Pulse energy between about 0.25 mJ and about 10 mJ; a pulse width between about 1 ns and about 4000 ns, and Pulse frequencies between about 1 kHz and about 200 kHz a diode-pumped solid-state laser source further characterized by: a large angle galvanometer optical scanner; a first telecentric lens having a field of view (FOV) with a lateral dimension substantially equal to or greater than about 137 mm, the first telecentric lens having a working distance between about 30 mm and about 500 mm; an adjustable stage having bidirectional motion, the motion of the stage being synchronized with the motion of the galvanometer optical scanner; A system comprising:

17. 17. The system of claim 16, wherein the first telecentric lens has a telecentric error value of less than about 5°.

18. 20. The system of claim 17, further comprising a second telecentric lens having a FOV with a lateral dimension substantially equal to the first telecentric lens.

19. 20. The system of claim 18, wherein the first telecentric lens is specialized for IR wavelengths and the second telecentric lens is specialized for UV wavelengths.

20. 1. A system for laser patterning a semiconductor device, comprising:

1. A diode-pumped solid-state laser source configured to generate a pulsed laser beam, the laser source comprising an infrared (IR) slab gain medium; Pulse energy between about 0.25 mJ and about 10 mJ; a pulse width between about 1 ns and about 4000 ns, and Pulse frequencies between about 1 kHz and about 200 kHz a diode-pumped solid-state laser source further characterized by: a large angle galvanometer optical scanner; a first telecentric lens having a field of view (FOV) with a lateral dimension substantially equal to or greater than about 137 mm, the first telecentric lens having a working distance between about 30 mm and about 500 mm; an adjustable stage having bidirectional motion and configured to translate from a loading position to a processing position for laser patterning and to an absolute position for calibrating the galvanometer optical scanner; a controller in communication with the laser source, the galvanometer optical scanner, and the adjustable stage, the controller configured to modulate the pulse energy, the pulse width, and the pulse frequency of the laser source; A system comprising:

Images