Laser ablation system for package manufacturing

Abstract

The present disclosure relates to systems and methods for manufacturing semiconductor packages, and more particularly, systems and methods for forming features in semiconductor packages by laser ablation. In one embodiment, the laser systems and methods described herein can be used to pattern a substrate that serves as a package frame for a semiconductor package having one or more interconnects formed therethrough and / or one or more semiconductor dies placed therein. The laser systems described herein can produce a tunable laser beam for forming features in a substrate or other package structure. Specifically, the frequency, pulse width, pulse shape, and pulse energy of the laser beam can be adjusted based on the desired size of the patterned features and the material in which the patterned features are formed. The tunability of the laser beam enables the rapid and accurate formation of features in semiconductor substrates and packages having controlled depth and topography.

Description

BACKGROUND TECHNICAL FIELD

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

[0002] DESCRIPTION OF THE RELATED ART

[0003] Due to the semiconductor manufacturers' continuing purpose to increase yield and enhance the performance of electronic devices and components, efforts have been increased to increase the density of semiconductor devices manufactured on a given size of semiconductor substrate. One method for increasing the density of semiconductor devices in a semiconductor assembly is to stack semiconductor dies to create a three-dimensional multichip module (3-D MCM). Forming a 3-D MCM generally requires creating vias (i.e., through-holes) in at least one semiconductor die that extend from the active surface of the die to the opposing back surface of the die. The vias are filled with a conductive material that provides interconnection of the back surface of the semiconductor die to an external electrical contact of another semiconductor die or a carrier substrate of the 3-D MCM.

[0004] Conventionally, etching and laser ablation, or drilling, are two methods frequently used to form vias in semiconductor substrates. Although laser drilling of vias has the advantage of being much faster and more accurate in location and size compared to etching of vias, precise control of the depth and topography of the drilled region has not been achieved by conventional laser drilling. Furthermore, laser energy is typically used inefficiently, thus resulting in low ablation rates.

[0005] Thus, there is a need for a laser drilling system and method for rapidly forming vias in semiconductor substrates with controlled depth and topography. SUMMARY

[0006] The present disclosure generally relates to systems and methods for forming features on a package by laser ablation.

[0007] In one embodiment, a system for laser patterning of semiconductor devices 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 further has a pulse energy of between about 0.25 mJ to about 10 mJ, a pulse width of between about 1 ns to about 4000 ns, and a pulse frequency of between about 1 kHz to about 200 kHz. The system further includes a large angle galvanometer optical scanner and a first telecentric lens having a field of view (FOV) substantially equal to or greater than about 137 mm in lateral dimension and a working distance of between about 30 mm to about 500 mm.

[0008] In one embodiment, a system for laser patterning of semiconductor devices 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 further has a pulse energy of between about 0.25 mJ to about 10 mJ, a pulse width of between about 1 ns to about 4000 ns, and a pulse frequency of between about 1 kHz to about 200 kHz. The system further includes a large angle galvanometer optical scanner, a first telecentric lens having a field of view (FOV) substantially equal to or greater than about 137 mm in lateral dimension and a working distance of between about 30 mm to about 500 mm, and an adjustable stage having bidirectional movement. Movement of the stage is synchronized with movement of the galvanometer optical scanner.

[0009] In one embodiment, a system for laser patterning of semiconductor devices 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 further has a pulse energy of between about 0.25 mJ to about 10 mJ, a pulse width of between about 1 ns to about 4000 ns, and a pulse frequency of between about 1 kHz to about 200 kHz. The system further includes a large angle galvanometer optical scanner, a first telecentric lens having a field of view (FOV) substantially equal to or greater than about 137 mm in lateral dimension and a working distance of between about 30 mm to 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 calibration of the galvanometer optical scanner. A controller is in communication with the laser source, the galvanometer optical scanner, and the adjustable stage and configured to modulate the pulse energy, the pulse width, and the pulse frequency of the laser source. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, can be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only example embodiments and therefore are not to be considered as limiting the scope of the disclosure, and can admit other equally effective embodiments.

[0011] Figure 1A A schematic top view of an exemplary structured substrate according to embodiments of the present disclosure is shown.

[0012] Figure 1B A schematic cross-sectional side view of an exemplary packaging structure according to embodiments of the present disclosure is shown.

[0013] Figure 2 A schematic view of an exemplary laser system according to embodiments of the present disclosure is shown.

[0014] Figure 3 A time profile of the instantaneous laser power of a pulsed laser beam according to embodiments of the present disclosure is shown.

[0015] Figure 4 A schematic view of the field of view of a laser system according to embodiments of the present disclosure is shown. Figure 2

[0016] Figure 5A A physical profile of a laser beam according to embodiments of the present disclosure is schematically shown.

[0017] Figure 5B A physical profile of a laser beam according to embodiments of the present disclosure is schematically shown.

[0018] Figure 6 A schematic view of a calibration mechanism of a laser system according to embodiments of the present disclosure is shown. Figure 2

[0019] So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, can be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only example embodiments and therefore are not to be considered as limiting the scope of the disclosure, and can admit other equally effective embodiments. DETAILED DESCRIPTION

[0020] ​​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 systems and methods described herein can be used to pattern a substrate that will be used as a package frame for a semiconductor package having one or more interconnects formed therethrough and / or one or more semiconductor dies disposed therein. The laser systems described herein can produce a tunable laser beam for forming features in a substrate or other package structure. Specifically, the frequency, pulse width, pulse shape, and pulse energy of the laser beam can be adjusted based on the desired size of the patterned features and the material in which the patterned features are formed. The tunability of the laser beam enables the rapid and accurate formation of features in semiconductor substrates and packages having controlled depth and topography.

[0021] As used herein, the term "about" refers to a + / - 10% variation from the nominal value. It will be understood that such variation can be included in any value provided herein.

[0022] Figure 1A A schematic top view of an exemplary structured substrate 100 that can be formed by the laser systems described herein and used as a structural frame for a semiconductor package is shown. The substrate 100 is shown as having a quadrilateral shaped cavity 110 surrounded by a plurality of substantially cylindrical through-holes 120, collectively referred to as features 130. The cavity 110 is typically formed in the substrate 100 for subsequent placement and encapsulation of one or more semiconductor devices therein, such as one or more active semiconductor dies or passive components. The through-holes 120 are formed in the substrate 100 to provide a passage or pathway for interconnects to be routed therethrough, thus enabling direct electrical coupling of the interconnects to the devices and / or redistribution connections on both sides of the substrate 100.

[0023] The cavity 110 and the through-holes 120 can be laser patterned onto the substrate 100 having any desired size and shape and having any desired number and arrangement. In certain embodiments, depending on the size of the one or more semiconductor devices to be enclosed and embedded therein during the manufacture of the semiconductor package, each cavity 110 has a lateral dimension that varies between about 1 mm to about 50 mm, such as about 8.6 mm. In some embodiments, the size of the cavity 110 is adjusted to have a lateral dimension that is substantially similar to that of the semiconductor devices to be embedded therein. For example, each cavity 110 is formed to have a lateral dimension that exceeds the lateral dimension of the semiconductor devices placed therein by less than about 150 pm, such as less than about 120 pm, such as less than 100 pm. The variation in the size of the cavity 110 and the semiconductor devices to be embedded therein is reduced, thereby reducing the amount of gap fill material utilized in subsequent package manufacturing operations.

[0024] In certain embodiments, each via hole 120 has a diameter that varies between about 50 pm to about 200 pm, such as about 90 pm. The minimum pitch 125 between each via hole 120 is between about 30 pm to about 170 pm, such as about 40 pm. Typically, the via holes 120 have a substantially cylindrical shape, although other morphologies are also contemplated. For example, each via hole 120 can have a tapered shape or a frustoconical shape.

[0025] Figure 1B A schematic cross-sectional side view of the substrate 100 after the semiconductor device 140 is packaged within the cavity 110 and the interconnect 150 is electroplated within the via hole 120 thereby forming the package 101 is shown. To embed the semiconductor device 140 within the cavity 110, the semiconductor device 140 is placed within the cavity 110 prior to being encapsulated by the insulating layer 160 that is laminated and cured over the semiconductor device 140. The insulating layer 160 can have a thickness between about 20 pm to about 70 pm, such as about 30 pm, from the surface of the substrate 100 to the outer surface of the insulating layer 160. In some embodiments, the insulating layer 160 comprises an organic dielectric material, such as an Ajinomoto Build-up Film (ABF) and a Mitsubishi BT film. In certain examples, the insulating layer 160 is an epoxy resin containing ceramic fillers, such as an epoxy resin containing silica (Si02) particles.

[0026] Lamination of the insulating layer 160 causes its dielectric material to flow into and fill the voids between the placed semiconductor device 140 and the substrate 100, and into the via hole 120. Thus, to form a passage or pathway for the interconnect 150 through the entire package 101 after the insulating layer 160 is laminated, a via 170 (another type of feature 130) is laser drilled through the dielectric material of the insulating layer 160 within the via hole 120. Typically, the via 170 has a narrower dimension than the via hole 120, such that its laser drilling causes the via 170 to be circumferentially surrounded by the insulating layer 160 within the via hole 120. In some embodiments, the via has a diameter between about 20 pm and about 70 pm, such as about 30 pm. By surrounding the via 170 and the subsequently electroplated interconnect 150 with a dielectric material, capacitive coupling between the electrically conductive silicon-based substrate 100 and the interconnect 150 in the package 101 can be reduced or eliminated. It should be noted, however, that the via 170 can also be formed only partially through the package 101, or within the insulating layer 160 in a location outside of the via hole 120 in the substrate 100. For example, the via 170 can be formed above or below the embedded semiconductor device 140 for the subsequently electroplated interconnect 150 to be electrically coupled thereto.

[0027] Figure 2A schematic diagram of an exemplary laser system 200 that can be used to form desired features 130 (e.g., vias 120, vias 170, and cavities 110) in a sample 240, such as a semiconductor package structure, is shown. The laser system 200 is configured to accurately ablate high-density, narrow-distribution features 130 in various package structures and materials, such as silicon-based substrates and dielectric epoxy. 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 stage 214, a vacuum source 216, a debris collector 218, and a wafer nest 220.

[0028] Generally, the laser source 202 is a solid-state laser, such as a diode-pumped solid-state laser having a slab gain medium, that is configured to generate a continuous or pulsed laser beam 230 to irradiate the sample 240 for forming one or more features 130 in the sample 240. The laser slab can be formed of any suitable laser crystal material, including neodymium-doped yttrium aluminum garnet (Nd:YAG; Nd:Y3Al50i2), ytterbium-doped YAG (Yb:YAG), neodymium-doped yttrium orthovanadate (Nd:YVO; Nd:YVO4), and alexandrite. In certain embodiments, the laser slab has a face-pumping geometry. In certain embodiments, the laser slab has an edge-pumping geometry.

[0029] In certain embodiments, the laser source 202 operates at an infrared (IR) wavelength (e.g., 1064 nm) for forming features 130 in silicon-containing substrates, such as silicon substrates having a thickness between about 100 pm and about 1500 pm. In certain other embodiments, the laser source 202 operates at an ultraviolet (UV) wavelength (e.g., 355 nm) for forming features 130 in dielectric materials, such as polymeric epoxy. The laser source 202 can generate a pulsed laser beam 230 having a frequency between 1 kHz and 200 kHz. In some instances, the laser source 202 is configured to deliver a pulsed laser beam having a pulse energy between about 0.10 millijoule (mJ) and about 10 mJ at a pulse duration between about 1 ns and 5 ps. In the embodiments described herein, the frequency, pulse width, and pulse energy of the laser beam 230 generated by the laser source 202 are tunable (e.g., adjustable) depending on the material being patterned, the desired lateral dimension of the feature 130 being drilled, and the depth of the feature 130 being drilled. Additionally, the speed of movement of the laser beam 230, the number of pulses, and the beam profile and size are also tunable.

[0030] For example, for drilling a via 170 having a diameter of about 90 pm through a thin silicon-based substrate 100 having a thickness of between about 100 pm to about 200 pm, the laser source 202 can be tuned to have a frequency of between about 5 kHz to about 100 kHz, a pulse energy of between about 0.5 mJ to about 4.5 mJ (e.g., between about 0.8 mJ to about 1.2 mJ at a frequency of about 100 kHz, and between about 3.5 mJ to about 4.5 mJ at a frequency of about 5 kHz), and a pulse width of between about 100 ns to about 1200 ns. For example, at a frequency of about 5 kHz and a pulse width of about 600 ns, between about 70,000 pm 3 and about 110,000 pm 3 of material volume is removed per laser pulse. At a frequency of about 100 kHz and a pulse width of about 600 ns, between about 18,000 pm 3 and about 26,000 pm 3 of material volume is removed per laser pulse. The amount of energy supplied to each unit volume of material is between about 35 J / mm 3 and about 60 J / mm 3 .

[0031] For drilling a via 170 having a diameter of about 90 pm through a thick silicon-based substrate 500 having a thickness of between about 500 pm to about 1 mm, the laser source 202 can be tuned to have a frequency of between about 5 kHz to about 30 kHz, a pulse energy of between about 2 mJ to about 10 mJ (e.g., between about 2 mJ to about 3.5 mJ at a frequency of about 30 kHz, and between about 7 mJ to about 10 mJ at a frequency of about 5 kHz), and a pulse width of between about 1 ps and about 5 ps.

[0032] For drilling a cavity 110 having a lateral dimension of about 8.6 mm and a depth of between about 50 pm to 200 pm, the laser source 202 can be tuned to have a frequency of between about 5 kHz to about 40 kHz, a pulse energy of between about 0.5 mJ to about 4.5 mJ, and a pulse width of between about 15 ns to about 600 ns. For example, at a frequency of about 5 kHz and a pulse width of about 600 ns, between about 30,000 pm 3 and about 50,000 pm 3 of material volume is removed per pulse. At a frequency of about 5 kHz and a pulse width of about 2 ps, between about 220,000 pm 3 and about 400,000 pm 3 of material volume is removed per pulse. At a frequency of about 30 kHz and a pulse width of about 2 ps, between about 95,000 pm 3 and about 110,000 pm 3of the material volume. The energy supplied to each unit of material removed is about 60 J / mm 3 to 75 J / mm 3 .

[0033] In any form, the laser beam 230 generated by the laser source 202 is projected (e.g., delivered) via the optical assembly 206 toward the sample 240. The optical assembly 206 is optically coupled with 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 for laser patterning of the features 130. In certain embodiments, the optical assembly 206 includes a scanner 232, such as a single- or multi-axis large-angle galvanometer optical scanner (i.e., galvanometer scanner). In certain embodiments, the scanner 232 is a 3-axis galvanometer scanner having one or more lenses of the optical assembly 206 disposed upstream thereof on a laser propagation pathway. In certain embodiments, the scanner 232 is a polygon scanner. The term “galvanometer scanner” refers to any device that changes a projection or reflection angle of the laser beam 230 in response to an electronic signal from the controller 210 to cause the laser beam 230 to be swept across the sample 240. Typically, the scanner 232 includes one or more adjustable and electromechanically controlled mirrors to diverge (e.g., multiply) and / or steer the laser beam 230 across the sample 240 during laser drilling. In addition to causing the laser beam 230 to be swept across a surface of the sample 240 without mechanical translation of the sample 240 itself, the scanner 232 is simultaneously utilized to drill multiple features 130 in the sample 240. The scanner 232 can further include any suitable features for facilitating high-density drilling of the materials and structures described herein, such as digital servo feedback, low drift, fast dynamic response, and precise calibration capabilities.

[0034] In certain embodiments, the optical assembly 206 further includes one or more telecentric lenses 234 having a large field of view encompassing an entirety of the sample 240. For example, the telecentric lenses 234 of the optical assembly 206 can have a field of view substantially equal to or greater than about 137 mm in lateral dimension for thermal management and photolithography matching purposes, as described below with reference to FIG. 3. In certain embodiments, the telecentric lenses 234 of the optical assembly 206 are configured to have a field of view substantially equal to or greater than about 137 mm in lateral dimension for thermal management and photolithography matching purposes, as described below with reference to FIG. 3. Figure 4Discussed above). The telecentric lens 234 can have a clear aperture of between about 30 mm to about 60 mm and be configured to receive a laser beam 230 having a spot size of between about 5 mm to about 20 mm. The telecentric lens 234 can also have very low distortion (i.e., telecentric error) and a large working distance. For example, the telecentric lens 234 can have a telecentric error value of less than about 5°, such as less than about 3° or about 1°. In further examples, the telecentric lens 234 has a working distance of between about 30 mm to about 500 mm, thus enabling an added depth of focus between the optical assembly 206 and the sample 240 without requiring Z-direction height adjustment.

[0035] In certain embodiments, two or more telecentric lenses 234 can be used for laser drilling of different types of materials, each telecentric lens 234 specialized for a wavelength range of the laser source 202 utilized for each material type. In such embodiments, the two or more telecentric lenses 234 can have properties that match one another to enable alignment of the features 130 drilled through different material types. In one example, a first telecentric lens 234 can be used for IR drilling in a silicon-based substrate, such as for drilling the via 120 in the substrate 100 described above. Subsequently, after lamination of the insulating layer 160 over the substrate 100, a second telecentric lens 234 can be used for UV drilling in the insulating layer 160, such as for drilling the via 170 within the via 120 of the substrate 100. The properties of the two telecentric lenses 234 are matched, thus enabling good alignment of the via 170 within the via 120, thereby enabling it to be sufficiently isolated therebetween by the insulating layer 160 and reducing or eliminating the chance of exposure of the substrate 100. Examples of properties that can be matched between the different telecentric lenses 234 include focal length, field size, maximum telecentric error, mechanical scan angle of each mirror of the corresponding scanner 232, lens length, lens diameter, working distance, and nominal spot size, to name a few.

[0036] During operation, the laser beam 230 projected by the optical assembly 206 is directed toward a sample 240 disposed on the stage 212. Typically, the stage 212 provides a receiving surface for the sample 240, which can be a substrate having lateral dimensions of about 156 mm by 156 mm or greater. The stage 212 is coupled to the optical bench 214 and can be supported thereon by one or more pairs of rails 222. In certain embodiments, the rails 222 are arranged as linear pairs, enabling translation of the stage 212 in the X and / or Y directions. For example, the rails 222 can comprise linear and parallel magnetic tracks. In certain other embodiments, the rails 222 can have a non-linear shape. During operation, the stage 212 is moved from a loading position to a processing position in the X and / or Y directions. Automated processing of thin and / or fragile substrates is enabled by loading and / or unloading the sample 240 onto the stage 212 using one or more transfer devices (not shown). For example, the sample 240 can be loaded using a robotic arm having Bernoulli-type grippers, a walking beam, soft grippers, or the like. The processing position can refer to one or more positions of the stage 212 as it passes under the optical assembly 206 of the laser system 200 in the processing direction. In certain embodiments, movement of the stage 212 is synchronized with movement of the scanner 232 to enable efficient transfer between loading and unloading of the sample 240 and scanning of the laser beam 230 for laser drilling of the sample 240.

[0037] An encoder (not shown, such as a linear stage encoder) can be further coupled to the stage 212 to provide position information of the stage 212 and / or wafer nest 220 to the controller 210 prior to and / or during the laser drilling process. Additionally, the sample 240 or a calibration substrate (not shown) can include one or more physical markers or features 242, such as crosshairs, a circle, a grid-like marker, or a fiducial passing through the sample formed on at least its top surface for visual tracking of the sample 240 and / or calibration of the laser system 200 by the controller 210 and camera 208 directed at the stage 212. For example, the camera 208 can continuously capture images of the sample 240 and stage 212 for real-time measurement of its X and Y lateral position coordinates by the controller 210, thus facilitating precise and accurate laser drilling of features 130 in the sample 240.

[0038] The platform 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 can include a throttle valve (not shown) to adjust the amount of vacuum provided. In certain embodiments, the vacuum source 216 is used to chuck a sample 240, such as a silicon-based substrate or a package structure, to the platform 212 and / or wafer nest 220 and provide a flat drilling surface therefrom during laser drilling. For example, the vacuum source 216 can chuck the sample 240 to the platform 212 and / or wafer nest 220 and prevent warping caused by temperature increases 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 platform 212.

[0039] The controller 210 can include a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I / O) (not shown). The CPU can be one of any form of computer processors that are useful in an industrial setting for controlling various processes and hardware (e.g., laser source, optical components, scanner, platform motor, and other hardware) and monitoring processes (e.g., processing time, platform and / or substrate nest position, and substrate position). The memory (not shown) is connected to the CPU, and can be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage (local or remote). Software instructions and data can be coded and stored within the memory for instruction of the CPU. The support circuits (not shown) are also connected to the CPU for supporting the processor in a conventional manner. The support circuits can include conventional cache, power supplies, clock circuits, input / output circuitry, subsystems, and the like. A program (or computer instructions) readable by the controller determines which tasks to perform when, and where to perform tasks. The program can be software readable by the controller and can include code to monitor and control (e.g., switch between) characteristics of, for example, the laser beam 230 (frequency, pulse width, and pulse energy) and movement of the platform 212 and / or scanner 204.

[0040] In some embodiments, the laser system 200 further includes a debris collector 218 disposed within its processing area and fluidly coupled to a vacuum source (such as vacuum source 216). The debris collector 218 provides a vacuum to the processing area to generate a crossflow 224 of circulating gas for removing debris formed during the laser ablation of the sample 240. In some embodiments, the crossflow provided by the debris collector 218 is antiparallel to the processing direction 226 of the laser system 200 (e.g., the direction of movement of the platform 212 and / or scanner 204 during processing).

[0041] Figure 3 The temporal distribution of instantaneous laser power for a pulsed laser beam (such as laser beam 230) programmable by controller 210 is shown. While not intended to be theoretically limited, it is believed that during the laser ablation process of sample 240, the material being drilled melts, and a portion of the molten material evaporates to form a thermal plasma. This plasma plume tends to be opaque to the laser beam, and therefore the rate at which the laser beam can be directed to the material being drilled is limited by a "plasma shielding" effect. However, this plasma shielding effect can be reduced if the laser is pulsed and the pulse energy of the laser beam is distributed over a longer pulse duration. Thus, a large amount of pulse energy can be used to melt the material being drilled without evaporating the molten material, and therefore, the rate of laser drilling can be enhanced by applying a pulsed laser with a longer pulse width compared to a laser pulse with a shorter pulse width.

[0042] In some embodiments, such as Figure 3 As shown, the pulsed laser beam 230 emitted from the laser source 202 is programmed with a rectangular time distribution 302 having instantaneous laser power using methods known in the art. The rectangular time distribution 302 of instantaneous laser power ensures an appropriate heating rate to avoid overheating (i.e., evaporation of molten material) and enhances the efficiency of laser drilling. In some embodiments, such as Figure 3 As shown, using methods known in the art, the pulsed laser beam 230 emitted from the laser source 202 is programmed with a chair-shaped time distribution 304 having instantaneous laser power, which can further enhance the efficiency of laser drilling. Figure 3 As shown, feature 130 drilled by a pulsed laser beam 230 with a rectangular time distribution 302 typically has a straighter and smoother inner wall compared to feature 130 drilled by a laser pulse with a typical Q-switching time distribution 306. It should be noted that the laser source 202 is programmed to generate multiple pulse widths and / or timing shapes of the laser beam 230 that can be selected (e.g., switched between) by the controller 210.

[0043] As mentioned above, excess laser energy beyond that required to melt the material results in partial evaporation. Thus, programming the pulses of the laser beam 230 to have a pulse energy content that is weighted toward the back end of the laser pulse can also have beneficial effects. In the early portion of the pulse, a slow energy delivery due to a proper heating rate melts a larger volume of the material being drilled. This is in comparison and contrast to laser drilling with a laser pulse having a typical Q-switching time profile 306 in which the time profile peaks relatively early in the pulse, delivering high energy all at once when less energy is needed (early in the pulse). Thus, a large portion of the laser pulse energy is consumed in excess evaporation and possible ionization of the ablation plume. Programming the laser pulse with the time profile 302 or the chair-shaped time profile 304 allows for effective laser drilling without consuming laser energy early in the pulse where the molten material being drilled is evaporating. In certain embodiments, the ratio of the energy density in 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).

[0044] Further, the inventors of the present disclosure have also discovered that the straightness and smoothness of the inner walls of features 130, such as vias 120 and / or vias 170, are highly related to the ablation depth per laser pulse. Ablation depth increases with optical penetration depth, thermal penetration depth, and laser fluence (i.e., energy per unit area). With the use of near-IR lasers having a wavelength of about 1.0 pm in the example embodiments described herein, the long pulse width ensures that the optical penetration depth (proportional to the square root of the pulse width) is large enough. As such, the laser pulse can be more evenly distributed over a long distance through the substrate in order to heat and melt the thick substrate material simultaneously, resulting in more efficient ablation. The ablated material has a large momentum (i.e., mass times velocity) and a more directional motion that advantageously ejects from the hole without redeposition on the inner walls, resulting in a straighter and smoother inner wall of the hole being drilled. This is in contrast to intense ablation by lasers having a shorter wavelength, such as a 355 nm UV laser, and a shorter pulse width, in which only the surface of the substrate is ablated. With ablation using a laser having such a short pulse width, a very small amount of material is ablated, but is explosively ablated as a mixture of superheated melt, vapor, and plasma, such that there is very little directional ejection from the hole being drilled and redeposition on the inner walls of the hole.

[0045] Figure 4A schematic of the drilled field of view (FOV) 402 (illustrated in dashed lines) of the telecentric lens 234 is shown with respect to a substrate 400 that each have a lateral dimension D1, D2 of about 156 mm or less. As previously described, the drilled FOV 402 of the telecentric lens 234 is larger than the lateral area of a sample (such as the substrate 400) to be laser drilled. The larger drilled FOV 402 allows the entire substrate 400 to be scanned by the scanner 232 without mechanical movement (such as by the stage 212) of the substrate 400, thereby eliminating the need to stitch multiple FOVs or sections of the substrate 400, resulting in a more robust alignment and shorter laser drilling cycle time, and all features 130 drilled into the substrate 400 can be formed in an orientation normal to the surface of the telecentric lens 234.

[0046] Figure 4 The drilled FOV 402 of the telecentric lens 234 is also shown with respect to multiple smaller lithography FOVs 404 utilized in subsequent processing steps of the substrate 400 during package fabrication. As shown, the drilled FOV 402 extends across all of the lithography FOVs 404 and thus eliminates the occurrence of lithography printing over any mispositioned features 130 formed during laser drilling. In certain embodiments, the drilled FOV 402 is a quantitative multiple of the lithography FOVs 404, thus facilitating proper alignment. Accordingly, matching between the drilled FOV 402 and the lithography FOVs 404 is not required during processing of the substrate 400.

[0047] The telecentric lens 234 further enables performing and repeating an on-the-fly drilling cycle across the entire surface of the substrate 400 without mechanical translation of the substrate 400. During on-the-fly drilling, the pulsed laser beam 230 is scanned by the scanner 232 across the surface of the substrate 400 to drill out a subset of the features 130 at different locations thereon. At each location and / or subset of the features 130, one or more pulses of the laser beam 230 can be delivered per feature 130 before the scanner 232 translates the laser beam 230 to the next location in the drilling cycle. After completing the drilling cycle (e.g., delivering one or more pulses per feature 130 at each location thereof), the laser beam 230 returns to the initial location of the drilling cycle to deliver one or more additional pulses per feature 130 and repeats the drilling cycle. Typically, two or more drilling cycles, such as five or more drilling cycles, are used to form a complete feature 130 through the thickness of the sample, such as the substrate 400. The cycling of the laser pulses across the surface of the substrate 400 enables cooling of each drilled location between delivery of the laser pulses, thus avoiding drilling on a surface of the substrate 400 that has been heated, which can cause overheating and reduce drilling efficiency via the “plasma shielding” effect described above. With the telecentric lens 234 having a FOV 402 that is larger than the lateral area of the substrate 400, the entire drilling cycle is performed without having to mechanically move the substrate 400, which can increase the risk of sample misalignment or drift and significantly increase the drilling cycle time.

[0048] In some embodiments, in the on-the-fly drilling cycle process, the pulsed laser beam 230 is positioned and repeatedly positioned over a subset of the features 130 in synchronization with the scanning motion of a galvanometer scanner used for high speed (e.g., at speeds of about 10 m / s) beam positioning. The effective drilling repetition rate on 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 1,000 and about 2,500,000 features 130 drilled by the synchronized drilling during the on-the-fly drilling cycle.

[0049] In addition to providing a larger field of view 402, the telecentric lens 234 also provides an enhanced (e.g., extended) depth of focus of the laser beam 230. Figure 5A and Figure 5B The physical profile (i.e., shape) of the laser beam 230 as projected through the substrate 400 having a first thickness T 1和 The physical profile (i.e., shape) of the laser beam 230 as projected through the substrate 400 having a second thickness T2. As Figure 5AAs shown, the telecentric lens 234 minimizes beam divergence of the laser beam 230 in the far field and increases its peak intensity over larger distances, thus enabling consistent drilling of features 130 having uniform size LB1 through each thickness T1 and T2 of the substrate 400. This is particularly advantageous during drilling of narrow vias 120 and / or through vias 170 in large arrays of samples having even the slightest thickness variations, as well as during drilling processes that pattern features in different samples having different thicknesses, since no focusing adjustments are needed between different samples. Figure 5B In the middle, the finite depth of focus of the relay lens 500 causes beam convergence and divergence, resulting in a variation of the peak intensity of the laser beam 230 over its propagation path. The variation of the beam profile and intensity results in a non-uniformity of the size LB2 between features 130 drilled into each thickness T1 and T2 of the substrate 400.

[0050] Figure 6 A schematic diagram showing a closed-loop calibration mechanism used by the laser system 200 to calibrate and align the scanner 232 for laser drilling is illustrated. As shown, the laser system 200 can load a calibration plate 600 onto the stage 212 and / or wafer nest 200 and laser pattern the top surface of the calibration plate 600 with a grid-like or crosshair mark 602. The grid-like or crosshair mark 602 can have any suitable fineness depending on the number of features 130 to be formed during laser patterning. After marking the calibration plate 600, the calibration plate 600 is mechanically translated to an absolute position via the stage 212, and the X and Y lateral position coordinates of the calibration plate 600 are measured by the controller 210 using the camera 208 and one or more linear stage encoders. The actual positions of the marks 602 are compared (e.g., evaluated) to the nominal (e.g., expected) positions 604, and updated trajectories of the laser beam 230 by the scanner 232 are interpolated by the controller 210. The corrected instructions can be automatically encoded and stored within the memory of the controller 210 for instructing the CPU in subsequent calibration cycles and / or laser drilling processes. After the corrected instructions are automatically generated, the calibration mechanism can be repeated until the degree of metrology error exceeds the degree of potential correction improvement, after which the laser drilling process can be performed. In certain embodiments, the calibration mechanism described above enables alignment of actual features to nominal positions with a deviation of less than about 5 pm.

[0051] The systems and methods disclosed herein include laser ablation systems and methods for forming features, such as vias and cavities, in semiconductor package devices. The laser ablation systems described herein can produce a tunable laser beam having a desired frequency, pulse width, pulse shape, and pulse energy based on a desired size of the patterned features and the material in which the patterned features are formed. The tunability of the laser beam provides for fast and accurate drilling of a large array of high-density features in semiconductor package device structures having controlled depth and topography, thus enabling the formation of packages having a thin form factor with high chip or die to package volume ratios. As such, the systems and methods described herein enable greater I / O ratios to meet the ever-increasing bandwidth and efficiency demands of artificial intelligence (AI) and high performance computing (HPC).

[0052] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure can be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A system for laser patterning a semiconductor device substrate, comprising: A diode-pumped solid-state laser source, configured to generate a pulsed laser beam, the laser source comprising a planar gain medium, the laser source further having the following characteristics: Pulse energy, wherein the pulse energy is between 0.25 mJ and 10 mJ; The pulse width is between 1 ns and 4000 ns; as well as The pulse frequency is between 1 kHz and 200 kHz; Optical scanner for galvanometers; The first telecentric lens has a field of view (FOV) with a lateral dimension equal to or greater than 137 mm and a working distance between 30 mm and 500 mm. as well as The second telecentric lens has a FOV of 137 mm or greater and a working distance between 30 mm and 500 mm. The first telecentric lens and the second telecentric lens are configured to have matching properties to achieve alignment of features through boreholes of different material types.

2. The system as described in claim 1, characterized in that, The laser source is an infrared (IR) laser source.

3. The system as described in claim 1, characterized in that, The first telecentric lens has a telecentric error value of less than 5°.

4. The system as described in claim 1, characterized in that, The first telecentric lens is dedicated to IR wavelengths and the second telecentric lens is dedicated to UV wavelengths.

5. The system as described in claim 4, characterized in that, The maximum telecentric error and the nominal spot size are the same for the first telecentric lens and the second telecentric lens.

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

7. The system as described in claim 6, characterized in that, The controller is further configured to modulate the pulse shape of the laser source.

8. The system of claim 7, wherein the pulse shape of the laser source is rectangular or chair-shaped.

9. The system of claim 6, further comprising an adjustable platform disposed on linear and parallel tracks.

10. The system as described in claim 9, characterized in that, The adjustable platform is configured to receive a substrate with a lateral dimension of 156 mm or greater.

11. The system as described in claim 9, characterized in that, The adjustable platform is coupled to a linear platform encoder to provide the platform's position information to the controller.

12. The system of claim 11, further comprising a camera pointing toward the adjustable platform and communicating with the controller.

13. The system of claim 12, wherein the camera, the adjustable platform, and the controller form a closed-loop calibration system for position calibration of the galvanometer optical scanner.

14. The system of claim 1, further comprising a debris collector for generating a crossflow of circulating gas in the processing area of ​​the system.

15. A system for laser patterning a semiconductor device substrate, comprising: A diode-pumped solid-state laser source, configured to generate a pulsed laser beam, the laser source comprising a planar gain medium, the laser source further having the following characteristics: Pulse energy, wherein the pulse energy is between 0.25 mJ and 10 mJ; The pulse width is between 1 ns and 4000 ns; as well as The pulse frequency is between 1 kHz and 200 kHz; Optical scanner for galvanometers; A first telecentric lens, having a field of view (FOV) with a lateral dimension equal to or greater than 137 mm, and a working distance between 30 mm and 500 mm. The second telecentric lens has a lateral dimension equal to the FOV of the first telecentric lens; as well as An adjustable platform having bidirectional movement, the movement of the platform being synchronized with the movement of the galvanometer optical scanner; The first telecentric lens and the second telecentric lens are configured to have matching properties to achieve alignment of features through boreholes of different material types.

16. The system as described in claim 15, characterized in that, The first telecentric lens has a telecentric error value of less than 5°.

17. The system as claimed in claim 15, characterized in that, The first telecentric lens is dedicated to IR wavelengths and the second telecentric lens is dedicated to UV wavelengths.

18. A system for laser patterning a semiconductor device substrate, comprising: A diode-pumped solid-state laser source configured to generate a pulsed laser beam, the laser source comprising an infrared (IR) planar gain medium, the laser source further having the following characteristics: Pulse energy, wherein the pulse energy is between 0.25 mJ and 10 mJ; The pulse width is between 1 ns and 4000 ns; as well as The pulse frequency is between 1 kHz and 200 kHz; Optical scanner for galvanometers; A first telecentric lens, having a field of view (FOV) with a lateral dimension equal to or greater than 137 mm, and a working distance between 30 mm and 500 mm. The second telecentric lens has a FOV of 137 mm or greater and a working distance between 30 mm and 500 mm. An adjustable platform having bidirectional movement, the platform being configured to translate from a loading position to a processing position for laser patterning and an absolute position for calibrating the galvanometer optical scanner; as well as A controller that communicates with the laser source, the galvanometer optical scanner, and the adjustable platform, and is configured to modulate the pulse energy, the pulse width, and the pulse frequency of the laser source; The first telecentric lens and the second telecentric lens are configured to have matching properties to achieve alignment of features through boreholes of different material types.

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