Patent Application
20240010544
Substrates, such as glass substrates, may be utilized in a wide variety of applications. In some applications, it may be desirable to drill small features into the substrate. Representative features include through holes, blind vias, channels, grooves, slots, depressions, bevels, and chamfers. However, present methods for fabricating such features have disadvantages, such as long process times, low positional accuracy, and rough sidewalls. These disadvantages may be unacceptable when applications demand tight tolerances and high quality features.
Accordingly, alternative methods for fabricating features within substrates may be desired.
A method for forming features in transparent substrates is described. The method is a hybrid method that combines an initial step of forming a perforation contour and a subsequent step of ablation to remove material from the substrate to form a feature. The features exhibit low sidewall roughness and minimal chipping.
The present disclosure extends to:
A method of forming a feature in a substrate, the method comprising:
The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the representative embodiments.
Embodiments described herein relate to laser drilling through-features in substrates, such as glass substrates. The methods described herein may be utilized in applications where features with precise position, precise shape, small dimensions (e.g., diameters, widths, and/or lengths of less than 10 mm) with smooth sidewalls are desired. However, traditional methods of fabricating features are either too slow (and therefore costly), are not precise (e.g., positional accuracy greater than ±10 μm), produce low-quality edges (e.g., high surface roughness, cracking, or excessive chipping), or combinations thereof.
For example, a laser-based ablation method uses a 532 nm nanosecond laser to laser-drill a through hole. The typical hole diameters for this method range from 0.2 mm to 10 mm. However, although this laser-based ablation approach can create small holes in a short amount of time, this approach may result in holes with high surface roughness that may not be acceptable in demanding applications.
Another approach is a laser-based ablation method that uses a 532 nm picosecond laser to create small through-features (e.g., diameters in the range of 0.1 mm to 1 mm) having smooth sidewalls that cannot be achieved by the nanosecond laser-based ablation approach. However, the processing times for this approach are much longer than the nanosecond laser-based ablation approach, and result in tapered sidewalls that also may be undesirable in some applications.
Yet another approach is based on an initial laser-based modification of the substrate followed by an etching step. A laser beam (e.g., a nanosecond UV laser or a laser beam configured to induce non-linear absorption or a Kerr effect in the substrate) is used to create damage regions in or through the substrate. The damage regions are positioned along a pathway of the substrate to weaken the substrate along the pathway. A subsequent etching step is used to expand the damage regions to the desired diameter. Because the substrate is weakened along the damage pathway, etching occurs preferentially along the damage pathway to enable formation of a feature. However, this approach has long process times and results in tapered sidewalls.
Embodiments of the present disclosure address these problems through a hybrid approach that includes formation of damage regions through non-linear effects induced by a laser and ablation. In a first step, a perforation contour is formed in the substrate. The perforation contour consists of a plurality of damage regions formed through non-linear interaction of a laser beam with the substrate. The perforation contour defines a shape, perimeter, or outline of the feature. Configuration of a pulsed laser beam to induce non-linear absorption through formation of a laser beam focal line is a preferred non-linear interaction. A minimal amount of substrate material is removed during this step. The substrate with a perforation contour is ablated in a second step. Ablation is accomplished by directing a pulsed ablation laser beam along an ablation track. The ablation track is offset from the perforation contour. The ablation laser beam removes substrate material to complete formation of the feature. Formation of the perforation contour preconditions the substrate to facilitate removal of material by ablation to provides features having high positional accuracy (e.g., within 5 to 10 μm), small dimensions (e.g., as small as 0.5 mm) and smooth sidewalls (e.g., a surface roughness Ra less than 3 μm). In some embodiments, the sidewalls of the features are substantially straight and not tapered. Additionally, the processing times needed to form the features are short and enable high-throughput processing of substrates with demanding feature requirements.
Features may extend through the full thickness of the substrate or less than the full thickness of the substrate. Features that extend through the full thickness of the substrate are referred to herein as “through features” (e.g. through hole). Features that extend through less than the full thickness of the substrate are referred to herein as “blind features” (e.g. blind via). As used herein, “formation”, “forming” and the like when used in reference to a feature refers to a laser process for removing material from the substrate to create the feature. Representative laser processes include drilling and micromachining.
Referring now to
In embodiments, features formed by the hybrid method disclosed herein have a feature size greater than 0.5 mm, or greater than 1.0 mm, or greater than 3.0 mm, or greater than 5.0 mm, or greater than 10.0 mm, or greater than 25.0 mm, or less than 25.0 mm, or less than 20.0 mm, or less than 15.0 mm, or less than 10.0 mm, or less than 5.0 mm, or less than 3.0 mm, or less than 1.0 mm, or in a range from 0.5 mm to 100.0 mm, or in a range from 0.5 mm to 50.0 mm, or in a range from 0.5 mm to 25.0 mm, or in a range from 0.5 mm to 15.0 mm, or in a range from 0.5 mm to 5.0 mm, or in a range from 1.0 mm to 20.0 mm, or in a range from 1.0 mm to 10.0 mm, or in a range from 1.0 mm to 5.0 mm.
It is noted that the features described herein may be closed features on or within the substrate 100 as well as open features, such as a notch or a chamfer extending to or from one or more edges of the substrate 100.
In embodiments of the disclosure, a perforation contour outlining a perimeter of the feature 110 is first formed at least partially through the thickness of the substrate 100. The perforation contour, which is described in more detail below, comprises a plurality of damage regions (referred to herein as “perforations”) extending at least partially through the thickness of the substrate 100. The perforation contour is created by a pulsed laser beam focal line that is directed to the substrate 100. The pulsed laser beam focal line is positioned to extend at least through a portion of the thickness of the substrate 100. In some embodiments, the pulsed laser beam focal line is oriented orthogonal for first surface 102 or second surface 104. In other embodiments, the pulsed laser beam focal line is oriented at an angle to first surface 102 or second surface 104. The pulsed laser beam focal line and/or the substrate is translated to form the sequence of damage regions (perforations) that define the perforation contour.
In accordance with methods described below, a laser can be used to create highly controlled perforations through a substrate, with extremely little (<75 μm, often <50 μm) subsurface damage, no or negligible material removal, and no or negligible debris generation. As used herein, a “perforation” refers to a region of a substrate that has been structurally modified by a laser beam. For purposes of the present disclosure, structural modification means that the substrate has been weakened mechanically (and thus “damaged”) by the laser beam. Typical structural modifications include compaction (densification) and cleaving of chemical bonds. In addition to differing in mechanical strength from surrounding unmodified portions of the substrate, perforations may also differ in other properties (e.g. refractive index or density). Representative characteristics of perforations include cracks, scratches, flaws, holes, or other deformities in the substrate produced by a laser beam focal line. Formation of perforations is accompanied by little or no removal of material from the substrate. Instead, the perforations remain substantially occupied by structurally modified substrate material. Perforations may also be referred to, in various embodiments herein, as defects, defect lines or damage regions.
The laser pulses that form the perforations can be emitted at rates of several hundred kilohertz (several hundred thousand perforations per second, for example) using a pulsed laser beam. Thus, with relative motion between the source and the material the perforations can be placed adjacent to one another by selecting or triggering the required laser pulses (spatial separation varying from sub-micron to tens of microns as desired, such as a spacing between perforations of 0.1 μm to 30 μm, or 2.0 μm to 20 μm, or 4.0 μm to 15 μm, or 5.0 μm to 12 μm). This spatial separation is selected in order to optimize processing speed and to facilitate feature formation. As a non-limiting example, in the embodiments described herein the diameter of the perforations is <500 nm, for example ≤400 nm, or ≤300 nm, or in a range from 50 nm to 500 nm, or in a range from 100 nm to 400 nm, or in a range from 150 nm to 300 nm.
The wavelength of the laser is selected so that the substrate modified by the pulsed laser beam focal line is transparent to the laser wavelength. A substrate is transparent to the laser wavelength if it absorbs less than 10% of the intensity of the laser wavelength per mm of thickness of the substrate. In embodiments, the substrate absorbs less than 5%, or less than 2%, or less than 1% of the intensity of the laser wavelength per mm of thickness of the substrate.
The selection of the laser source is further predicated on the ability to induce multi-photon absorption (MPA) in the transparent material. MPA is a non-linear optical effect in the transparent substrate that involves the simultaneous absorption of multiple photons (e.g. two, three, four or more) of identical or different frequencies in order to excite the substrate from a lower energy state (usually the ground state) to a higher energy state (excited state). The excited state may be an excited electronic state or an ionized state. The energy difference between the higher and lower energy states of the material is equal to the sum of the energies of the two or more photons. MPA is a nonlinear process that is several orders of magnitude weaker than linear absorption. In the case of two-photon absorption, it differs from linear absorption in that the strength of absorption depends on the square of the light intensity, thus making it a nonlinear optical process. At ordinary light intensities, MPA is negligible. If the light intensity (energy density) is extremely high, such as in the region of focus of a laser source (particularly a pulsed laser source), MPA becomes appreciable and leads to measurable effects in the material within the region where the energy density of the light source is sufficiently high (i.e. above the non-linear threshold). Within the focal region, the energy density may be sufficiently high to result in structural modification of the substrate through, for example, ionization, breaking of molecular bonds, and vaporization of material.
At the atomic level, the ionization of individual atoms has discrete energy requirements. Several elements commonly used in glass (e.g., Si, Na, K) have relatively low ionization energies (˜5 eV). Without the phenomenon of MPA, a wavelength of about 248 nm would be required to create linear ionization at ˜5 eV. With MPA, ionization or excitation between states separated in energy by ˜5 eV can be accomplished with wavelengths longer than 248 nm. For example, photons with a wavelength of 1064 nm have an energy of ˜1.165 eV, so two photons with wavelength 1064 nm can induce a transition between states separated in energy by ˜2.33 eV in two-photon absorption (TPA), for example.
Thus, atoms and bonds can be selectively excited or ionized in the regions of a transparent material where the energy density of the laser beam is sufficiently high to induce nonlinear TPA of a laser wavelength having half the required excitation energy, for example. MPA can result in a local reconfiguration and separation of the excited atoms or bonds from adjacent atoms or bonds. The resulting modification in the bonding or configuration constitutes a structural modification corresponding to formation of a perforation. The structural modification associated with perforations mechanically weakens the transparent material and renders it more susceptible to cracking, fracturing, or material removal by ablation.
Perforations can be formed by operating a pulsed laser in burst mode. In burst mode, the pulsed laser emits a series of burst pulses at a high repetition rate. Perforations can be formed with one or more burst pulses. Each burst pulse constitutes an envelope of high energy, short duration sub-pulses spaced close together in time. The laser pulse duration, defined as the separation in time between consecutive burst pulses, may be 10−10 s or less, or 10−11 s or less, or 10−12 s or less, or 10−13 s or less. The separation in time of sub-pulses within a burst is much smaller than the laser pulse duration. The repetition rate of the burst pulses is in a range from about 1 kHz to 4 MHz, such as in a range from about 10 kHz to about 3 MHz, or from about 10 kHz to about 650 kHz). The perforations of a perforation contour may be spaced apart and precisely positioned by controlling the velocity of a substrate relative to the laser through control of the motion of the laser and/or the substrate. As an example, in a substrate moving at 200 mm/sec exposed to a 100 kHz series of burst pulses, the individual burst pulses would be spaced 2 microns apart and would create a perforation contour with a series of perforations separated by 2 μm. In some embodiments, the substrate is positioned on a translation table (not shown) capable of being translated along at least one axis. Any translation table or other device capable of translating either the glass substrate or the optical delivery head may be utilized.
Turning now to
The laser beam focal lines 2b described herein may be formed using a quasi-non-diffracting beam (e.g. Bessel beam, Gauss-Bessel beam, Airy beam). As used herein, the term “quasi-non-diffracting beam” is used to describe a laser beam having low beam divergence (large Rayleigh range). The laser beam 2a has an intensity distribution I(X,Y,Z), where Z is the beam propagation direction of the laser beam, and X and Y are directions orthogonal to the beam propagation direction. The X-direction and Y-direction may also be referred to as cross-sectional directions and the X-Y plane may be referred to as a cross-sectional plane. The coordinates and directions X, Y, and Z are also referred to herein as x, y, and z; respectively. The intensity distribution of the laser beam 2a in a cross-sectional plane may be referred to as a cross-sectional intensity distribution.
The quasi-non-diffracting laser beam may be formed by impinging a diffracting laser beam (such as a Gaussian beam) into, onto, and/or thorough a phase-altering optical element of an optical system 6, such as an adaptive phase-altering optical element (e.g., a spatial light modulator, an adaptive phase plate, a deformable mirror, or the like), a static phase-altering optical element (e.g., a static phase plate, an aspheric optical element, such as an axicon, or the like), to modify the phase of the beam, to reduce beam divergence, and to increase Rayleigh range. Example quasi-non-diffracting beams include Gauss-Bessel beams, Airy beams, Weber beams, and Bessel beams.
Without intending to be limited by theory, beam divergence refers to the rate of enlargement of the beam cross section in the direction of beam propagation (i.e., the Z direction). Laser beams for forming the perforations of the perforation contours described herein are formed from laser beam focal lines 2b as stated above. Laser beam focal lines 2b have low divergence and weak diffraction. The divergence of the laser beam is characterized by the Rayleigh range ZR, which is related to the variance σ2 of the intensify distribution and beam propagation factor M2 of the laser beam. Additional information on the formation of laser beam focal lines 2b using quasi-non-diffracting laser beams for forming perforation contours can be found in U.S. Pat. Publ. Nos. 2018/0221988 or 2020/0361037, the disclosures of which are hereby incorporated by reference in their entirety. A summary of Rayleigh range ZR and quasi-non-diffracting beams follows.
The Rayleigh range of a laser beam is the distance over which the spot size w of the laser beam increase by a factor of √{square root over (2)} relative to the minimum spot size w0. The spot size of the laser beam corresponds to the distance from the position of the peak intensity of the laser beam (typically defined to be the center of the beam (r=0)) to the position (r>0) at which the intensity of the laser beam has decreased to 1/e2 of the peak intensity. The minimum spot size w0 of a laser beam is corresponds to the beam waist (see ISO 11146-1:2005(E)). in a material of refractive index no at wavelength λ0. A criterion for quasi-non-diffracting beams based on Rayleigh range ZR can be defined. the spot size wo. can be defined More particularly, a quasi-non-diffracting laser beam is a laser beam that satisfies the condition set forth in Eq. (1):
where w0 is the spot size of the laser beam at the beam waist, λ is the wavelength of the laser beam, n is the refractive index of the medium in which the laser beam propagates, and FD is a dimensionless divergence factor having a value of at least 10, at least 50, at least 100, at least 250, at least 500, at least 1000, in the range from 10 to 2000, in the range from 50 to 1500, in the range from 100 to 1000. For purposes of comparison, the dimensionless divergence factor FD has a value of 1 for a Gaussian beam and the Rayleigh range ZR for a Gaussian beam is derived from Eq. (1) by setting FD to 1 and replacing the inequality (“>”) with equality (“=”). The dimensionless divergence factor FD provides a criterion for determining whether or not a laser beam is quasi-non-diffracting. As used herein, a laser beam is considered quasi-non-diffracting if the characteristics of the laser beam satisfy Eq. (1) with a value of FD≥10. As the value of FD increases, the laser beam approaches a more nearly perfectly non-diffracting state. In the method described herein, the laser beam focal line used to form the perforations of the perforation contour is formed from a quasi-non-diffracting beam. Preferably, the quasi-non-diffracting beam is a Bessel beam or a Gauss-Bessel beam.
Referring once again to
As
As
The laser beam 2a may be a pulsed laser beam, such as a picosecond pulsed laser beam. In some embodiments, the picosecond laser creates a burst pulse consisting of a plurality of sub-pulses. Each burst pulse contains multiple sub-pulses (such as at least 2 sub-pulses, at least 3 sub-pulses, at least 4 sub-pulses, at least 5 sub-pulses, at least 10 sub-pulses, at least 15 sub-pulses, at least 20 sub-pulses, or more) of very short duration (e.g., in a range of from about 1 femtosecond to about 200 picoseconds, such as from about 1 picosecond to about 100 picoseconds, 5 picoseconds to about 20 picoseconds, or the like). That is, a burst pulse is a packet of sub-pulses, and the burst pulses are separated from one another by a longer separation duration than the separation of individual adjacent pulses within each burst. The duration between sub-pulses within a burst pulse may be in a range from about 1 ns to about 50 ns, for example, from about 10 ns to about 30 ns, such as about 20 ns. In other embodiments, sub-pulses within the burst pulse may be separated by a duration of up to 100 picoseconds (e.g., 0.1 picoseconds, 5 picoseconds, 10 picosecond, 15 picoseconds, 18 picoseconds, 20 picoseconds, 22 picoseconds, 25 picoseconds, 30 picoseconds, 50 picoseconds, 75 picoseconds, or any range therebetween). The separation duration between burst pulses may be from about 0.25 ms to about 1000 ms, e.g., from about 1 ms to about 10 ms, or from about 3 ms to about 8 ms.
In other embodiments of the present disclosure, non-linear absorption is induced in a transparent laser using a tightly focused Gaussian laser beams. A tightly focused Gaussian laser beam has intensity to induce absorption through the Kerr effect and the Kerr effect can be used to form perforations through a filamentation process.
During filamentation, non-linear effects such as Kerr self-focusing and plasma formation can extend the focal region of a tight Gaussian focus to >100 μm to enable formation of perforations having an extended length. The central lobe of the filament can be quite small and thus produce a high-intensity beam capable of inducing non-linear effects. To further elongate the beam, a lens with multiple foci at various depths or multiple laser passes with varying focal depths may be used.
In general, the optical method of forming the laser focus can take multiple forms, such as, without limitation, spherical lenses, diffractive elements, or other methods to form the linear region of high intensity. The type of laser (picosecond, femtosecond, and the like) and wavelength (IR, visible, UV, and the like) may also be varied, as long as sufficient optical intensities are reached to create breakdown of the substrate material. As non-limiting examples, the wavelength may be 515 nm, 532 nm, 800 nm, 1030 nm, or 1064 nm.
It is noted that any laser process capable of creating the perforations may be utilized.
Referring now to
As shown in
Embodiments are not limited by the material of the substrate 100. Non-limiting examples of materials for the substrate include glass, glass-ceramic, and silicon.
Following the formation of perforation contour 120 to define the shape of the feature 110, an ablation laser is used to ablate the substrate material to form the feature 110. The ablation laser is directed along an ablation track that is offset from perforation contour 120 by a perforation-ablation offset ΔnP-Ablation (
Referring now to
The focus and intensity of the ablation laser beam 32 are such that substrate material is removed by ablation along the ablation track to form one or more ablation grooves. The wavelength of the ablation laser beam 32 may be less than 2000 nm, or less than 1500 nm, or less than 1200 nm, or in a range from 300 nm-1100 nm, (e.g., a Nd:YAG laser (1064 nm) or harmonics thereof (532 nm, 355 nm, 266 nm)), or in a range from 400 nm-1000 nm, or in a range from 500 nm-900 nm. The wavelength of the ablation laser beam 32 may be the same as or different from the wavelength of laser beam 2 that is used to form the perforations of the perforation contour. A repetition rate of the ablation laser may be greater than or equal to 10 kHz, the power of the ablation laser may be in a range from 5 W-50 W and the translation speed of the ablation laser beam relative to the substrate may be in a range from 0.5 to 10 m/s. The one or more focusing lenses 40 (e.g., having a focal length f between 50 mm and 300 mm) may focus the ablation laser beam 32 to a beam spot BS having a diameter of 10-50 μm.
The ablation laser 30 and/or the substrate 100 are translated relative to each other such that the ablation laser beam 32 is traversed multiple times (e.g., 10-30 times depending on substrate material and thickness) along the ablation track. With each traversal, the position of the beam spot BS may be adjusted closer to first surface 102 in a direction normal to the first surface 102. In some embodiments, the positioning of the beam spot BS in a traversal is positioned directly above (in a direction normal to the first surface 102) the position of the beam spot BS in the immediately preceding traversal. In other embodiments, the positioning of the beam spot BS in a traversal is positioned laterally offset (relative to a direction normal to the first surface 102) from the position of the beam spot BS in the immediately preceding traversal. Various placement patterns of beam spot BS relative to the direction normal to the first surface 102 are envisioned for a series of traversals of ablation laser beam 32 along the ablation track. Examples include spiral patterns or concentric shapes within the perforation contour.
An appropriately selected perforation-ablation offset ΔnP-Ablation reduces the roughness of the sidewall of the feature and reduces chipping. Particularly, an appropriately selected perforation-ablation offset ΔnP-Ablation may result in a side wall roughness Ra of less than or equal to 3 μm and/or chipping with chip size less than 50 μm. As defined herein, a “chip” is a defect wherein substrate material is removed from the sidewall of the feature and the size of a chip is the longest linear distance, as measured in the plane of the sidewall, connecting two points on the perimeter of the chip in the plane of the sidewall. The size of a chip may be measured using optical microscopy. In embodiments, a sidewall of a feature formed by the hybrid method described herein has an average chip size of less than 100 μm, or less than 75 μm, or less than 50 μm, or in a range from 5 μm to 100 μm, or in a range from 20 μm to 90 μm, or in a range from 40 μm to 80 μm. In embodiments, a sidewall of a feature formed by the hybrid method described herein lacks chips having a size greater than 50 μm, or greater than 75 μm, or greater than 100 μm.
It is noted that ablation processes in the absence of a perforation contour typically result in a sidewall roughness Ra greater than 5 μm and chips with sizes up to 100 μm. Furthermore, the placement of the ablation laser beam at points along the ablation track in a given traversal and between different traversals is typically only accurate to within about 25-50 μm range This leads to variability in the dimensions of features formed in the conventional ablation process and contributes to sidewall roughness. The positional accuracy of forming perforations (through focal lines or filamentation) is much improved, typically in the 5-10 μm range. Since the ablation track is offset from the perforation contour in the methods described herein, positional variability in the ablation step of the processes described herein has little effect on feature dimensions. The methods described herein provide features with precise boundaries, smooth sidewalls, and low chipping and are able to do so at high process speed.
Referring now to
ΔnP-Ablation≈0.5*WAblation˜dAblation Spot*E(b)*Ethreshold−1, Eq. (2)
where:
In embodiments, the diameter dAblation Spot of the ablation laser beam is in a range from 10 μm to 50 μm, or in a range from 15 μm to 45 μm, or in a range from 20 μm to 40 μm, and the width wAblation is in a range from 10 μm to less than 50 μm, or in a range from 15 μm to 45 μm, or in a range from 20 μm to 40 μm. In one embodiment, the beam spot BS of the ablation laser beam is positioned such that the diameter dAblation Spot overlaps perforation contour 120 and the width wAblation of the ablation groove does not overlap perforation contour 120. In embodiments, the ablation track is offset from the perforation contour by spacing in a range from 5 μm to 25 μm, or a spacing in a range from 8 μm to 22 μm, or in a range from 10 μm to 20 μm. In embodiments, the ablation laser beam forms an ablation groove without ablating the sidewall of the feature.
The edge quality (wall smoothness and low chipping) that can be achieved with the hybrid process is comparable to the edge quality of the perforation process itself. For an optimized perforation-ablation offset ΔnP-Ablation, the ablation step only removes material and does not change the properties of the edges (walls). Thus with a combination of perforation contour and ablation, the edge quality is determined by the perforation formation step
Referring now to
At block 204, a second laser process step includes directing a focused ablation laser beam 32 into the substrate 100 to ablate at least a portion of the substrate 100 along an ablation track that is offset from the perforation contour by a perforation-ablation offset ΔnP-Ablation. The focused ablation laser beam 32 removes substrate material along the ablation track to form an ablation groove within a shape defined by the perforation contour to fabricate the feature 110. As stated above the perforation-ablation offset ΔnP-Ablation is chosen such that a surface of a sidewall of the feature has a surface roughness Ra of less than or equal to 3 μm or a surface roughness obtained by controlling the parameters of the ablation laser beam to satisfy Equation (2).
At block 206, further substrate treatment steps may or may not be performed. For example, the substrate 100 may be chemically etched by an etching process to further improve the smoothness of the sidewall of the feature 110 as well as the smoothness of other edges of the substrate 100.
In some embodiments, both the first and second surfaces 102 and 104 of the substrate 100 are individually processed. In some cases, processing the substrate 100 from only one of the first and second surfaces 102 and 104 may cause the sidewall of the feature to be tapered such that an opening of the feature on the first surface 102 (i.e., the surface facing the laser beams) may be larger than an opening of the feature on the second surface 104 in embodiments in which the feature is a through feature. The tapered effect may be more pronounced with increasing thickness of the substrate, for example.
At block 302, a pulsed laser beam focal line 2b is directed into a first surface 402 of the substrate 400 at a plurality of first locations. As shown in
At block 304, a focused ablation laser beam 32 is directed into a first portion of the substrate 400 from the first surface 402 to ablate the substrate 400 from the first surface 402 along a first ablation track that is offset from the first perforation contour by a perforation-ablation offset ΔnP-Ablation. The focused ablation laser beam 32 is configured such that it partially removes substrate material to the depth D1 within the thickness of the substrate and within a shape defined by the first perforation contour 420A.
In yet another example, first and second perforation contours are formed on first and second surfaces of the substrate prior to any ablation step. After the first and second perforation contours are formed, ablation grooves are formed on the first surface and the second surface of the substrate.
Next, at block 306, a second perforation contour 420B is formed on the second surface 404 of the substrate 400 by directing the pulsed laser beam focal line 2b into the second surface 404 of the substrate 400 at a plurality of second locations. The pulsed laser beam focal line 2b generates an induced absorption within the substrate 400 such that the pulsed laser beam focal line 2b produces a second perforation contour 420B that at least partially extends into the thickness of the substrate from the second surface at each location of the plurality of second locations.
At block 308, the process includes directing the focused ablation laser beam 32 into a second portion of the substrate 400 from the second surface 404 and ablating the substrate 400 from the second surface 404 along a second ablation track that is offset from the second perforation contour 420B by a perforation-ablation offset ΔnP-Ablation. The ablation laser beam 32 removes substrate material to the depth D2 that reaches the first ablation groove 432A formed from the first surface and within the shape defined by the second perforation contour 420B. The ablation laser beam 32 thus forms a second ablation groove 432B that meets the first ablation groove 432A. The meeting of the first ablation groove 432A and the second ablation groove 432B cause an inner piece to drop out, which thereby forms the through-feature 410 (
At block 310, further substrate treatment steps may or may not be performed. For example, the substrate 400 may be chemically etched by an etching process to further improve the smoothness of the sidewall of the through-feature 410 as well as the smoothness of other edges of the substrate 100.
An inspection of the hole of
Next, an ablation groove with a width of 400 μm was formed to create the hole. The ablation laser beam parameters were the same as described above in Comparative Example 1.
An inspection of the hole of
Through-features and blind features other than features having a circular cross-section may be fabricated using the hybrid method described herein.
It should now be understood that embodiments described herein provide methods for forming features in a substrate that have sidewalls with low surface roughness (e.g., a surface roughness Ra of less than 3 μm), small diameters (e.g., less than 5 mm), limited chipping and small chip sizes (<100 μm, or <75 μm, or <50 μm). The methods described herein utilize a first laser process wherein individual perforations are formed within the bulk of the substrate by non-linear absorption to define a perforation contour that defines a shape of a feature. Next, an ablation groove is formed within the interior of the shape defined by the perforation contour by a second laser process to remove an inner piece of the substrate and form the feature. The ablation laser that creates the ablation groove follows an ablation track that is offset from the perforation contour by a perforation-ablation offset ΔnP-Ablation such that the surface roughness Ra of the sidewall of the feature is less than 3 μm.
It is noted that recitations herein of a component of the embodiments being “configured” in a particular way, “configured” to embody a particular property, or function in a particular manner, are structural recitations as opposed to recitations of intended use. More specifically, the references herein to the manner in which a component is “configured” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component.
It is noted that one or more of the following claims utilize the term “wherein” as a transitional phrase. For the purposes of defining the embodiments of the present disclosure, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.”
Although the disclosure has been illustrated and described herein with reference to explanatory embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples can perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the disclosure and are intended to be covered by the appended claims. It will also be apparent to those skilled in the art that various modifications and variations can be made to the concepts disclosed without departing from the spirit and scope of the same. Thus, it is intended that the present application cover the modifications and variations provided they come within the scope of the appended claims and their equivalents.
This application claims the benefit of priority under 35 U.S.C § 120 of U.S. Provisional Application Ser. No. 63/358,903 filed on Jul. 7, 2022, the content of which is relied upon and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63358903 | Jul 2022 | US |
