KR100853827B1 - Ultraviolet laser ablative patterning of microstructures in semiconductors - Google Patents

Abstract

Patterns with feature sizes smaller than 50 microns are rapidly formed directly on semiconductors, particularly silicon, using ultraviolet laser ablation. This pattern is characterized by a very high aspect ratio cylindrical through hole opening for integrated circuit connections, singulation of the processed die contained on the semiconductor wafer, and microtab cuts that separate the microcircuit workpiece from the parent semiconductor wafer. It includes. Laser output pulses 32 from diode-pumped, Q-switching frequency -3x Nd: YAG, Nd: YVO4 or Nd: YLF are directed to the workpiece 12 with high speed accuracy using a composite beam locator . The optical system produces a Gaussian spot size or top hat beam profile of about 10 microns. Using this concentrated spot size, the pulse energy used for the fast ablation treatment of silicon is greater than 5 kHz, and preferably greater than 200 μJ per pulse at PRF above 15 kHz. The laser pulse width measured at the maximum half point of the full width is preferably smaller than 80 ns.

Description

Ultraviolet Laser Ablation Patterning of Microstructures in Semiconductors {ULTRAVIOLET LASER ABLATIVE PATTERNING OF MICROSTRUCTURES IN SEMICONDUCTORS}

This patent application claims priority from Provisional Application No. 60 / 265,556, filed Jan. 31, 2001, and Patent Application No. 09 / 803,382, filed March 9, 2001.

The present invention relates to a method and / or apparatus for forming micron-scale features at high speed by ablation of a semiconductor, in particular silicon, using the pulsed output of an ultraviolet (UV) laser.

The semiconductor industry uses a variety of techniques to separate discrete electronic devices, often referred to as dies, from the semiconductor wafers on which they are manufactured. A common method for such separation is to use a diamond saw. There is an urgent need for a method for reducing the area on a semiconductor wafer that is needed to be allocated to a saw street to enable the use of more area of the wafer for useful dies to increase the yield of die per wafer. Laser technology offers such an opportunity to reduce street dimensions for dicing of semiconductor wafers.

It is well known to those skilled in the art to use an infrared laser such as a Q-switched 1064 nm Nd: YAG laser for laser processing of silicon. However, since silicon absorbs 1064 nm weakly, laser dicing methods operating at or near this wavelength face serious problems. Damage to cut quality is generally observed because silicon is redeposited along the wafer surface and along the walls of the cut.

US patents by Carlson et al. (NO. 4,541,035) and Anthony's US patents (NO. 4,589,190) are integrated into the ESI Model 25 Laser Scribing System. The fabrication of features in silicon devices using 1064 nm pulse output from -optic Q-switched), infrared (IR) Nd: YAG lasers. {See also "Diodes Formed by Laser Drilling and Diffusion" (TR Anthony, Journal of Applied Physics, Vol. 53, Dec. 1982, pp. 9154-9164). US patents (NO. 4,618,380) to Alcorn et al. We also describe a method of fabricating an imaging spectrometer by treating a silicon device with a laser.

In the US patent (NO. 5,543,365), Wills et al. Laser scribing apparatus for forming polysilicon streak on silicon wafers using 1064 nm pulse output from Nd: YAG lasers with pulse widths greater than 4 ns. Explain. Alternatively, they explain that they can use a frequency-multiplied wavelength of 532 nm.

In "Excimer VS Nd: YAG Laser Creation of Silicon Vias for 3D Interconnections" (1992 IEEE / CHMT Int'l Electronics Manufacturing Technology Symposium) Lee et al. (Lee) described the surface of silicon wafers to enable the fabrication of multichip modules. We report the use of Nd: YAG laser wavelengths of 1064nm and 532nm to generate vias. Lee reports that when a laser drills a hole in a silicon wafer at 1064 nm, the molten material often condenses on the wall of the hole when a significant depth is reached. This obvious redeposition of silicon makes the hole unsuitable for further processing. Lee reports the use of a dual drilling process at 1064 nm to improve hole quality. Lee is a 532nm from lamp-pumped, Q-switched Nd: YAG in a trepanning process that employs a rotating lens offset with respect to the incident laser to cut 4mil {approx. 100 micron (μm)) diameter holes in silicon. The use of frequency-multiplied pulsed laser output is described. He reports the process parameters used as 833 μJ per pulse at a pulse repetition frequency of 3 kHz with a pulse width of 70 ns. Redeposition of silicon along the periphery and along the walls of the laser drilled vias was observed and a chemical etching process was used to clean the holes.

Lee further reports on the use of excimer lasers at a wavelength of 248 nm to drill holes in silicon. Holes with very smooth sidewalls have been reported because of the very high pulse energy used. He reports the use of energy per pulse of 290 mJ at a concentrated spot size of 5 mils (approximately 125 μm) and pulse repetition frequency of 250 Hz to drill holes in silicon wafers for 30 seconds. He used the 532 nm Nd: YAG incision technology to compare the three seconds required to drill a hole to the drilling time. Lee proposes a method to reduce the drilling time required for silicon holes by the 248 nm excimer laser through the use of projection technology. As one of ordinary skill in the art will recognize, such techniques rely on the appropriate aperture masks for each pattern of holes formed using those techniques.

In the US patent (NO. 5,870,421) Dahm discusses the problem of using an infrared near laser to dice a silicon wafer. He explains that the main cause of poor cutting quality resulting from redeposition when using near infrared lasers is the use of laser pulse widths in excess of about 1 ns. Dahm mentions that short pulse widths create a surface plasma that acts as a high absorption layer, and describes the use of near-infrared lasers with short pulse widths of less than about 1 ns to solve the deep absorption thickness of near-infrared wavelengths in silicon. do. Dahm also claims that UV lasers do not generate enough power to process silicon at high speeds, and near-infrared lasers such as 1064nm Nd: YAG lasers are used for high-speed applications because of their ability to generate more power than UV lasers. To mention.

Owen et al. In US Pat. No. 5,593,606 describe the advantages of using a UV laser system to generate laser output pulses within desired parameters to form vias through at least two layers of a multilayer device. These parameters are typically nonexcimer outputs with instantaneous pulse widths shorter than 100 ns, spot areas with spot diameters less than 100 μm, and average intensity or irradiance greater than 100 mW over the spot area at repetition rates greater than 200 Hz. It includes a pulse.

In the US patent (NO. 5,841,099), Owen et al. Vary the UV laser power within parameters similar to those mentioned above to have different power densities while machining different materials. They change the intensity or change the spot size by changing the repetition rate of the laser to change the energy density of the laser spot incident on the workpiece.

In US Patent No. 5,751,585, Cutler et al. Describe a high speed, high precision multi-stage positioning system for accurately and quickly positioning a wide variety of tools, such as laser beams, against a target on a workpiece. They use a multi-rate locator system that processes the workpiece target positioning commands and translates them into commands that accelerate and decelerate the locator. Such locators move without necessarily stopping in response to the stream of positioning data. In one embodiment, this technique enables laser micromachining of patterns of small features across large workpieces, thereby increasing the yield of micromachining parts by the laser.

SUMMARY OF THE INVENTION An object of the present invention is to provide electronic and optoelectronic circuits useful for semiconductor substrates comprising gallium arsenide (GaAs), silicon carbide (SiC), silicon nitride (SiN), and / or Ge: Si, and / or comprising semiconductor wafers. Using lasers to create microfeatures in semiconductors that also include those semiconductors that are subsequently processed in semiconductor processes including, but not limited to, photolithography and etching well known to those skilled in the art to include additional layers to produce. To provide an improved method.

Another object of the present invention is to provide a method of using a high reliability nonexcimer UV laser that can operate at a high pulse energy output at a high pulse repetition frequency.

The present invention provides a method for rapidly and directly forming patterns with feature sizes smaller than 50 μm in semiconductor workpieces using ultraviolet laser ablation. Compound beam locators are used to quickly locate the concentrated output of a non-excimer UV laser on a workpiece that can emit high energy per pulse output at high pulse repetition frequencies. This pattern can be used to form very high-aspect cylindrical openings, such as through holes or blind vias for the connection of integrated circuits, curves or straight lines of the processed die contained on the silicon wafer. The formation of a singulation, the formation of microtabs that are cut to separate the microcircuits formed in the semiconductor workpiece from the parent wafer, the light of an array such as waveguide gratings (AWGs) or micromachine systems (MENS) Formation of curved or straight features in the waveguide, formation of scribing alignments, identifications or other features in the wafer surface.

The present invention uses a laser wavelength shorter than 390 nm with a light absorption coefficient of 1000 times greater than silicon at 1064 nm, as used in US Pat. Nos. 4,541,035, 4,589,190, 5,543,365. Nd: YAG, Nd: YVO ₄ or Nd: YLF diode-pumped lasers with Q-switching frequency threefold provide a preferred source of ablation ultraviolet output. The laser's optical system produces a Gaussian spot size of about 10 μm. Alternatively, an optical system can be used that creates a top hat beam profile. Exemplary pulse energy for a fast ablation process of silicon using this concentrated spot size is greater than 200 μJ per pulse at pulse repetition frequencies greater than 5 kHz, and preferably at pulse repetition frequencies above 15 kHz. The laser pulse width measured at the maximum half point of the full width is preferably less than 80 ns.

The advantage of using UV wavelengths is the ability to produce significantly smaller spot sizes than can be achieved by longer wavelength sources. This small spot size performance allows the formation of micron scale features in silicon. Also for fixed spot sizes achievable with conventional Gaussian focusing techniques, shorter wavelengths allow for the formation of features with improved aspect ratios by the deeper depth of focus given at ultraviolet wavelengths.

The invention also results from stray reflection of the ultraviolet treatment beam from a workpiece support structure, such as a wafer chuck, using a novel manufacturing technique of a structure that substantially supports antireflective materials and workpieces. A method of reducing damage or damage to a processed semiconductor workpiece is provided.

Further objects or advantages of the present invention will become apparent from the following detailed description of the preferred embodiments to be made with reference to the accompanying drawings.

1 is a graph showing the light absorption coefficient of silicon as a function of wavelength.

2 is a graph showing the light absorption coefficient of gallium arsenide (GaAs) as a function of wavelength.                 

3 is a simplified diagram of a preferred laser system for patterning microstructured ultraviolet laser ablation of a semiconductor according to the present invention.

4 is a simplified diagram of an alternative preferred laser system for microstructured ultraviolet laser ablation patterning of semiconductors.

5 is a simplified diagram of an optional imaging optical module that can be used in a laser system for microstructured ultraviolet laser ablation patterning of semiconductors.

6 is a graph showing the characteristic relationship between the pulse energy and pulse repetition frequency of a laser used during the practice of the present invention.

FIG. 7 is a representative illustration of ultraviolet ablation patterning of a cylindrical aperture of silicon. FIG.

8 is a representative illustration of ultraviolet ablation patterning of a trench pattern of silicon.

9 is a simplified representation of an exemplary segmented cut profile for making long cuts in semiconductor material.

10 shows a simplified representation of an alternative segmented cut profile for making long cuts in semiconductor material.

11 is a representative illustration of ultraviolet ablation patterning of a MEMS device on a semiconductor wafer.

12 is a representative illustration of ultraviolet ablation patterning of an AWG device fabricated on a semiconductor wafer.                 

13 is a representative illustration of an ultraviolet transparent chuck in which a semiconductor workpiece is positioned during the entire process using the ultraviolet ablation patterning method.

1 shows the optical absorption coefficient of silicon as a function of wavelength. Referring to FIG. 1, silicon exhibits a sharp increase in light absorption at ultraviolet wavelengths. The present invention advantageously forms various useful patterns or features in silicon using laser wavelengths shorter than 390 nm and using the increased absorption of silicon in the ultraviolet region to efficiently ablate the silicon. Absorption properties greatly facilitate ablation removal of silicon in the ultraviolet region, which significantly reduces the thermally affected area compared to features formed using either 532 nm or 1064 nm as described in the prior art.

2 shows the light absorption coefficient of GaAs as a function of wavelength. Referring to FIG. 2, GaAs shows that the light absorption rate increases rapidly at the wavelength of ultraviolet rays. The absorption coefficient at 355 nm for GaAs and silicon is very close. GaAs is a key material in optoelectronic devices such as diode lasers and detectors.

3 and 4 each laser using a compound beam positioning system 30 equipped with a wafer chuck assembly 140 that can be used to ultraviolet laser ablation patterning of microstructures in semiconductor workpieces 12 in accordance with the present invention. Alternative preferred embodiments of processing systems 10a and 10b (generally 10) are illustrated. Referring to Figures 3 and 4, a preferred embodiment of the laser system 10 is preferably a Q- containing solid-state lasant such as Nd: YAG, Nd: YLF, or Nd: YVO ₄ Switching, die-pumping (DP), solid-state (SS) UV laser 14. The laser 14 mainly comprises 355nm (Nd: YAG with tripled frequency), 266nm (Nd: YAG with quadrupled frequency), or 213nm (Nd: YAG with fivefold frequency) with a TEM ₀₀ spatial mode profile. It is desirable to provide a UV laser output 16 of one or more laser pulses generated harmonically at the same wavelength.

Although Gaussian may be used to describe the irradiance profile of laser output 16, those skilled in the art will appreciate that most lasers 14 do not emit a perfect Gaussian output 16 with a value of M ² = 1. Will understand. Although M ² values smaller than 1.3 or 1.2 are preferred, for the sake of convenience, Gaussian is used herein to include a profile where M ² is less than or equal to approximately 1.5.

In a preferred embodiment the laser 14 comprises a model 210-V06 Q-switching frequency -3x Nd: YAG laser, operating at about 355 nm and commercially available from Lightwave Electronics. This laser has been used in an ESI model 2700 microvia drilling system available from Electro Scientific Industries, Inc. of Oregon Portland. In an alternative embodiment, a Lightwave model 210-V09 Q-switching, frequency-multiplied Nd: YAG laser operating at about 355 nm may be used to utilize high energy per pulse at high pulse repetition frequency (PRF). Can be. Those skilled in the art will appreciate that other lasers may be used and other wavelengths are available from other listed larts. Although laser cavity arrangements, harmonic generation and Q-switch operations, and positioning systems are known to those skilled in the art, certain details of some of these components will be provided within the preferred embodiments.

The UV laser output 16 selectively passes through the well-known dilation and / or collimation optics 18 to propagate along the optical path 20 and at the desired laser target position 34 on the workpiece 12. The output pulse (s) 32 are guided by the beam positioning system 30 to be incident. The beam positioning system 30 supports, for example, the X, Y and / or Z positioning mirrors 42 and 44 and enables rapid movement between the target points 34 on the same or different workpiece 12. It is preferred to include a translation stage locator which preferably utilizes at least two transverse stages 36, 38.

In a preferred embodiment, the translational stage locator supports and moves the workpiece 12 by a Y stage 36, which is generally moved by a linear motor along the rail 46, by the linear motor along the rail 48. The X stage 38 that is generally moved is a scatter-axis system that supports and moves the high-speed positioner 50 and associated focal lens (s). The Z value between the X stage 38 and the Y stage 36 is also adjustable. The positioning mirrors 42, 44 align the optical path 20 through any turn between the high-speed locator 50 and the laser 14 positioned along the optical path 20. The high speed locator 50 may use, for example, a high resolution linear motor or a pair of galvanometer mirrors that may affect unique or repetitive processing operations based on provided test or design data. Stages 36 and 38 and locator 50 may be controlled or independently moved or moved together in response to predetermined or otherwise data.

The high speed locator 50 also preferably includes a vision system that can be aligned with one or more fiducials on the surface of the workpiece 12. The beam positioning system 30 may use a conventional vision or beam to work through an off axis with an objective lens 36 or a separate camera and to manipulate alignment systems well known to those skilled in the art. In one embodiment, an HRVX vision box that uses Freedom Library software in a positioning system 30 sold by Electro Scientific Industry, Inc., is located between the target position 34 on the workpiece 12 and the laser system 10. It is used to perform the sorting. Other suitable alignment systems are commercially available. Such an alignment system is particularly desirable to use bright-field, on-axis illumination to mirror-like a workpiece, such as a wrapped or polished wafer.

In addition, the beam positioning system 30 may also be driven by the pitch, yaw, or roll of stages 36 and 38 that are not dictated by an axial position indicator such as a linear scale encoder or laser interferometer. It is desirable to use a non-contact, urine level sensor to determine Abbe errors. Since the EVE error correction system can be collimated to precise existing standards, the correction only depends on detecting small changes in predecessor readings, and not on the absolute precision of the sensor readings. Such EVE error correction systems are described in detail in the international application published on July 19, 2001 (NO. WO 01/52004 A1) and in the US application published on October 18, 2001 (NO. 2001-0029674 A1). . The relevant disclosure portion of Cutler's corresponding US patent application (NO. 09 / 755,950) is incorporated herein by reference.

Many variations of the positioning system 30 are well known to those skilled in the art, and some embodiments of the positioning system 30 are described in detail in US Pat. No. 5,751,585 to Cutler et al. The ESI Model 5320 microvia drilling system, available from Electro Scientific Industries, Inc. of Oregon, Portland, is a preferred implementation of the positioning system 30 and has been used for laser drilling of resin coated copper packages for the electronics industry. Other preferred positioning systems such as model serial numbers 27xx, 43xx, 44xx, or 53xx manufactured by Electro Scientific Industries, Inc. of Oregon, Portland, may also be used. Some such systems that use an X-Y linear motor to move the workpiece 12 and an X-Y stage to move the scan lens are cost-effective positioning systems for making long straight cuts. Those skilled in the art will also appreciate that a system with a single X-Y stage that positions the workpiece with a fixed beam position and / or stationary galvanometer for beam positioning may alternatively be used. Those skilled in the art will appreciate that such systems may be programmed to use a toolpath file that dynamically positions the concentrated UV laser system output pulses 32 at high speed to produce a wide variety of useful patterns that may be periodic or aperiodic. You will recognize that you can. Those skilled in the art will also recognize that this capability has many advantages over Lee's proposal for creating vias in silicon through the use of projection imaging devices.

An optional laser power controller 52, such as a half wave plate polarizer, may be located along the optical path 20. In addition, one or more beam detection devices 54, such as photodiodes, are located downstream of the laser power controller 52 as aligned with a positioning mirror 44 adapted to partially transmit the wavelength of the laser output 16. can do. The beam detection device 54 preferably communicates with beam diagnostic electronics that transmit signals to alter the effect of the laser power controller 52.

Referring to FIG. 4, the laser system 10b emits respective laser outputs 16a, 16b linearly polarized in the transverse direction and respective optical paths 20a, 20b towards each reflecting device 42a, 42b. It is preferable to use at least two lasers 14a and 14b that propagate along An optional waveplate 56 may be located along the optical path 20b. Reflective device 42a is preferably a beam combiner that is sensitive to polarization and is located along two optical paths 20a and 20b to couple laser outputs 16a and 16b that propagate along common optical path 20.

The lasers 14a and 14b may be the same or different types of lasers and may produce laser outputs 16a and 16b having the same or different wavelengths. For example, laser output 16a may have a wavelength of about 266 nm, and laser output 16b may have a wavelength of about 355 nm. Those skilled in the art will appreciate that the lasers 14a, 14b can be mounted side by side or one on top of the other, all attached to either of the translational stages 36 or 38. The laser system 10b can generate very high energy laser output pulses 32b. A particular advantage of the apparatus shown in FIG. 4 is that it produces a combined laser output 32 incident on the working surface with increased energy per pulse that is difficult to produce from a conventional single laser head. This increased energy per pulse is particularly advantageous for ablation of deep trenches or deep cylindrical openings in thick silicon wafers.

Despite the substantially rounded profile of the laser system output pulses 32, improved beam shape quality can be achieved by the optional imaging optical module 62, whereby the residual astigmatism or elliptical or other shape characteristics The same undesirable beam artifacts are spatially filtered. Referring to FIG. 5, the imaging optics module 62 may detect any undesirable side lobes and peripheral portions such that the optical element 64, the lens 66 and the precisely shaped spot profile are subsequently imaged to the working surface. It is preferable to include a beam waist created by the optical element 64 for blocking, or an opening mask 68 located in the vicinity thereof. In a preferred embodiment the optical element 64 is a focusing lens and the lens 66 is a collimating lens that gives flexibility in the placement of the laser system 10.

By varying the size of the opening, the end sharpness of the spot profile can be controlled to create a smaller, sharper end profile of strength that promotes alignment accuracy. In addition, the shape of the opening with this device can be changed to a rectangular, elliptical, or other non-circular shape that can be exactly circular or can be aligned parallel or perpendicular to the cutting direction. The opening of the mask 68 may optionally be flared outwards at the light exit side. The mask 68 in the imaging optical module 62 may comprise a UV reflecting or UV absorbing material, but UV grade fused silica coated with a multilayer high UV reflecting coating or other UV resistive coating or It is preferred to be made of a dielectric material such as sapphire. Those skilled in the art will appreciate that the aperture mask 68 can be used without the optical elements 64, 66.

In an alternative preferred embodiment the optical element 64 is a semi-uniform " top hat " profile (a laser pulse having a raw Gaussian irradiance profile near the aperture mask 68 downstream of the optical element 64). near-uniform "top hat" profile), or one or more beam shaping components that convert to shaped (and focused) pulses having a specific super-Gaussian irradiance profile. Such beam shaping components may include aspheric optics or diffractive optics. In a preferred embodiment lens 66 includes imaging optics useful for controlling beam size and divergence. Those skilled in the art will appreciate that a single imaging lens component or multiple lens components may be used. Those skilled in the art will also appreciate that shaped laser output can be used without using the aperture mask 68.                 

In a preferred embodiment, the beam shaping component comprises a diffractive optical element (DOE) capable of performing composite beam shaping with high efficiency and precision. The beam shaping component can convert the Gaussian irradiance profile into a quasi-uniform irradiance profile as well as determine the shaped output or can focus on a defined spot size. Single element DOEs are preferred, but those skilled in the art will include multiple discrete elements such as phase plates and conversion elements as disclosed in the US patent (D. No. 5,864,430) to Dickey et al., Which also discloses techniques for designing DOEs for beam shaping. I will understand. The molding and imaging techniques discussed above are described in detail in International Application No. WO 00/73013, published December 7, 2000. The related disclosure portion of the corresponding US patent application (NO. 09 / 580,396) filed May 26, 2000, is incorporated herein by reference.

In order to provide increased flexibility in the dynamic range of energy per pulse, a fast response amplitude control mechanism such as an Acosto-Optic modulator or an electro-optic modulator can be used to modulate the pulse energy of successive pulses. Alternatively, or in combination with a fast response amplitude control mechanism, the pulse repetition frequency may be increased or decreased to change the pulse energy of successive pulses. 6 shows a characteristic relationship between pulse repetition frequency (PRF) and pulse energy of the laser 14 used during the practice of the present invention. As shown in FIG. 6, pulse energies greater than 200 μJ can be obtained from models 210-V06. In addition, the characteristic relationship between pulse energy and PRF for alternative lasers Lightwave 210-V09L and Lightwave 210-V09H is also shown. Those skilled in the art will understand that Figure 6 illustrates the principles described so that alternative embodiments of the laser system 10 may create other characteristic relationships between pulse energy and pulse repetition frequency.

The characteristic performance of the UV laser system 10 described above can be used to form micro-scale features at high speed by ablation of semiconductors and especially silicon. Such features include the formation of a very precisely shaped cylindrical opening 100 through or partially through a silicon wafer or other silicon workpiece 12, singulation of the die processed on the silicon wafer or silicon workpiece 12. Formation of through or partial through trenches of complex geometry, formation of microtab features to separate microcircuits formed in silicon from the parent wafer, formation of features on singulation of the AWG, And the formation of features in the MEMS. In addition, the present invention facilitates the formation of features without significant melt lip formation, significant slag formation and significant peel back of the feature ends.

7 is a cylindrical formed by ultraviolet ablation patterning on a silicon workpiece 12 such as a wafer having a 500 μm thick native silicon substrate 70 covered with a 0.5 μm thick SiO ₂ passivation layer (not shown). Representative illustration of the opening 100. Those skilled in the art will appreciate that the thickness of the silicon workpiece and the thickness of the passivation layer may vary.

The cylindrical opening 100 positions the target position 34 of the silicon workpiece 12 in the focal plane of the laser system 10 and sets a series of laser system output pulses 32 over the silicon workpiece 12. It is preferably patterned by directing it to position 34. In this embodiment, the laser system 10 guides the movement of the silicon workpiece 12 in the X and Y axes to a computer-programmed centriod target position 34 of the desired point of the cylindrical opening 100. do. The sequential laser system output pulses 32 each enter a programmed central target position 34.

Speaking of ablation patterning by sequential overlapping pulses, referred to herein as punching, of the cylindrical aperture 100 of the silicon workpiece, a combined including energy per pulse, pulse repetition frequency (PRF), and concentrated spot size The preferred range of processing parameters is particularly advantageous for the rapid punching of useful cylindrical openings 100.

In the punching process, the sequential laser system output pulses 32 enter the programmed central target position 34 while the workpiece 12 is held at the X and Y axis positions, respectively. For this exemplary ablation patterning of the silicon process, the preferred energy range per pulse is about 100 μJ to 1500 μJ, more preferably about 200 μJ to 1000 μJ energy per pulse, and even more preferably about 300 μJ to 800 μJ, most preferably about 360 μJ. The preferred PRF range is about 5 kHz to 100 kHz, more preferably the PRF range is 7 kHz to 50 kHz, most preferably the PRF range is 10 kHz to 30 kHz. Preferred concentrated spot size ranges from about 1 μm to 25 μm, more preferably concentrated spot size ranges from 3 μm to 20 μm, most preferably concentrated spot size is 8 μm to 15 μm. Those skilled in the art will appreciate that laser performance as shown in FIG. 6 can achieve energy per pulse output in the PRF within the most preferred range described above. In practice, the ESI model 2700 was programmed to operate with the most desirable process parameters, resulting in 100 cylindrical openings per second with 35 μm diameter punched through a 750 μm thick silicon wafer workpiece 12.

In another embodiment the Z-height of the laser focus position is simultaneously moved in line with each successive laser system output pulse 32 to position the laser focus sequentially into the deeper position of the silicon workpiece 12, thereby being concentrated. Keep the spot in a more consistent position with the remaining silicon surface.

In a preferred embodiment, about 100 sequential laser system output pulses 32 are used to fully penetrate the entire thickness 102 of the workpiece 12 using the output pulse energy from the laser 14 greater than 300 μJ. Cylindrical opening 100 is formed. The laser system output pulse 32 is incident on the working surface having a concentrated spot size (1 / e ² ) diameter of about 12 μm. The cylindrical opening 100 formed in this embodiment generally has a top surface opening diameter (d _t ) 104 of about 20 μm and an exit diameter (d _b ) 106 of about 13 μm, so about 30: 1. Creates an aspect ratio of the through-hole cylindrical aperture of and an opening taper angle of 0.4 degrees.

Those skilled in the art will appreciate that the exact value of the energy per pulse, the concentrated spot size, and the number of pulses needed to efficiently form a good quality cylindrical aperture 100 through silicon, the thickness 102 of the silicon workpiece 12, It will be further appreciated that the composition can vary depending on the composition and relative thickness of the top layer and the exact ultraviolet wavelength used. For example, for the formation of through-hole cylindrical openings 100 of silicon for use as integrated sites patterned on silicon die as sites for integrated conducting connections to printed circuits, for example, silicon may be do. In this example, about 10 pulses may be used to form the desired through hole cylindrical opening 100. Those skilled in the art will appreciate that a cylindrical opening (blind via) that does not fully penetrate the entire thickness 102 of silicon can be formed by accurately selecting the parameters described.

Those skilled in the art will appreciate that such cylindrical openings 100 through silicon with high aspect ratios and very low taper angles are very advantageous for electronic packaging and interconnect applications. In addition, one or more groups of such small through-hole cylindrical openings 100 may be on the upper side near the circuit of the workpiece 12 or the die, or scribing, slicing, or dicing streets or the like. Located within the intersection, the back or bottom side of the workpiece 12 can be precisely aligned with respect to the features on the top side. Such alignment facilitates backside treatment such as laser scribing or sawing to enhance processing speed or quality. Techniques for front and / or back wafer slicing or dicing are described in US patent applications filed March 9, 2001 entitled "UV Laser Cutting or Shape Modification of Brittle, High Melting Temperature Target Materials such as Ceramics or Glasses". (NO. 09 / 803,382) and US Provisional Application (NO. 60 / 301,701) filed June 28, 2001 entitled "Multistep Laser Processing for the Cutting or Drilling of Wafers with Surface Device Layers". .

8 is a representative illustration showing ultraviolet ablation patterning for trench 110 on silicon workpiece 12. The trench 110 positions the silicon workpiece 12 in the focal plane of the laser system 10 and the laser positioning system 30 moves the workpiece 12 along the X and / or Y axis of the workpiece 12. It is preferably patterned by directing a string of consecutive overlapping laser system output pulses 32 onto the silicon workpiece 12 when moving.

For the ablation patterning process of forming a trench in silicon, the preferred energy per pulse range is about 100 μJ to 1500 μJ, more preferably the energy range per pulse is about 200 μJ to 1000 μJ, more preferably about 300 μJ to 800 μJ, most preferably about 360 μJ. The preferred PRF range is about 5 kHz to 100 kHz, more preferably the PRF range is about 7 kHz to 50 kHz, and most preferably the PRF range is about 10 kHz to 30 kHz. Preferred concentrated spot size ranges are about 1 μm to 25 μm, more preferably concentrated spot size range is about 3 μm to 20 μm, most preferably concentrated spot size is 8 μm to 15 μm. Preferred byte size ranges from about 0.1 μm to 10 μm, more preferably byte size ranges from about 0.3 μm to 5 μm, most preferably byte size from 0.5 μm to 3 μm. The bite size can be adjusted by controlling the speed of one or both stages of the laser beam positioning system, adjusting the moving speed (s) at a repetition rate and firing the laser.

In a preferred embodiment the linear trench 110 has a pulse size of 1 μm and output pulse energy from the laser 14 of about 360 μJ at a stage speed of 10 mm / s at 180 passes on the workpiece 12. Using a 750 μm thick native silicon covered with a 2.0 μm SiO ₂ passivation layer. This laser pulse is incident on the working surface with a concentrated spot size (1 / e ² ) diameter of 12 μm. Those skilled in the art will appreciate that various patterns of varying geometric shapes, including but not limited to squares, rectangles, ellipses, spirals, and / or combinations thereof, may be used to control the X and Y axes during processing with tool path files used by the laser system 10. It will therefore be appreciated that it may be formed by programming the positioning system 30 to position the silicon workpiece 12. For laser cutting it is preferred that the beam positioning system 30 is aligned to a conventional typical saw cut or other fiducial or pattern on the wafer surface. If the wafer has already been mechanically notched, the alignment to the cut end is desirable to overcome saw tolerance and misalignment.

Laser cutting (the width of the traces is less than 50 μm and preferably less than 25 μm) damages the material considerably less than mechanical cutting (the slicing lane is about 300 μm and the dicing pass is about 150 μm) The devices can be manufactured very close to each other so that more devices can be formed on each wafer. Thus, the laser cutting process minimizes the pitch between rows and the pitch between devices.                 

The elimination of mechanical cutting can also simplify the manufacture of the device in the workpiece 12. In particular, mechanical cutting imposes significant mechanical stress on the device such that the device comes off the carrier. In order not to miss the furnace, the device manufacturer uses a strong adhesive or epoxy between the furnace and the carrier. All laser processes significantly reduce the mechanical strength requirements of the adhesive used to secure the furnace to the carrier. Therefore, laser cutting allows the removal of strong adhesives or epoxy used to secure the furnace to the carrier and the necessary harsh chemicals to remove them. Instead, the adhesive eases UV laser treatment, which improves yield by significantly reducing the likelihood of damage to the device and ease of debonding, such as reduced removal time and short exposure to potentially corrosive chemicals. Can be selected for

Laser row slicing reduces row bows because it does not have as much mechanical stress as mechanical slicing. However, since furnace warpage or other furnace defects are evident, the furnace can be laser diced (and re-sliced) to compensate for such defects regardless of the critical device and device alignment required between the furnaces for mechanical dicing. have. For convenience the term (penetration) cutting can be used to generally include slicing {often associated with wafer row separation} or dicing {often associated with partial singulation from wafer row}, slicing and die Singhs may be used interchangeably in accordance with the context of the present invention.

Since the positioning system 30 can be aligned with the through hole 100 or the standard point, the laser system 10 can process each furnace and / or each device independently. With respect to the inclined furnace, the laser spot is transverse across the inclined furnace at an appropriate position with respect to the outer end of the device with stage and / or beam translation between each cut to form a desired rectangular or curved wave pattern. Cleavage can be performed. Thus, laser dicing can compensate for furnace fixation defects and prevent the destruction of all furnaces of the device, which may be caused by mechanical dicing.

UV laser cutting throughput through silicon and similar materials can be improved by dividing long cutting paths into short segments. For example, for through cuts and trench cuts of thick silicon, these segments are preferably about 10 μm to 1 mm, more preferably about 100 μm to 1000 μm, most preferably about 200 μm to 500 μm. The laser beam is scanned in the first short segment for a predetermined number of passes before moving to the second short for a predetermined number of passes and scanning. The byte size, segment size and segment overlap can be adjusted to minimize the amount and shape of the trench backfill.

9 is a simplified representation of an exemplary segmented cut profile 112a. 9, the cutting profile (112a) is a separate cutting segments have a path to the cutting direction of from left to right are formed in the right to left in order to simplify (116k ₁ - 116r ₃₎ {In general, the cutting segment 116} It is shown to have. It has been shown to be parallel in Figure 9. In order to simplify the - (116r ₃ 116k _1), cut segments cut segments (116k ₁ - 116r ₃₎ are in a virtually straight line. 9 shows a multi-segment set 114a, each comprising an initial segment 116 and multiple progressively longer overlapping segments 116m-116r, each preferably processed in alphabetical order. Preferably each set 114a is processed to be a selected intermediate depth or complete through cut before the next set is processed. Although only five overlapping segments are shown for each set 114a, one of ordinary skill in the art will appreciate that substantially more overlapping segments 116 can be used to add smaller incremental lengths, particularly as needed to accommodate the thickness of the target material. I will understand. Those skilled in the art will also understand that all or any of the segments 116 used in the cutting profile 112a can be processed in both directions instead of a single direction as shown in FIG. 9.

10 is a simplified representation of an exemplary segmented cut profile 112b that is somewhat similar to profile 112a. Referring to FIG. 10, profile 112b starts with the same set of segments 114a where profile 112a begins. However, segment set 114b omits segment 116k and incrementally covers the previously processed segment set by 60%. In one example of this embodiment, the segment 116k ₁ is cut in 30 passes and has a length of 200 μm. The segment 116m ₁ is then cut in six passes (1/5 of 30 passes) and has a length of 240 μm (sum of 200 μm and 1/5 of the length of the segment 116k ₁ ). The segment 116n ₁ is then cut in six passes and has a length of 280 μm (the sum of 200 μm and 2/5 of the length of the segment 116k ₁ ). This sequence continues until the given set of segments 114b is complete. This example may exhibit a dicing speed greater than or equal to 8.5 mm / min.

Real-time monitoring may also be used to reduce the rescan portion of the cutting path where the cutting has already been completed. In addition, the polarization direction of the laser beam can be correlated with the cutting direction to further enhance throughput. Such segmented cutting techniques are discussed in detail in US Provisional Patent Application (NO. 60 / 297,218) filed June 8, 2001 entitled "Laser Segmented Slicing or Dicing."

Another application of the ultraviolet ablation patterning method of the present invention is to fabricate a microelectronic machine system (MEMS) device 120. 11 is a representative illustration of ultraviolet ablation patterning of MEMS device 120. In one preferred embodiment, the MEMS device 120 is patterned using the method described above to form trenches 122a, 122b, 122c, 122d, and 122e (generally trench 122) in silicon. Those skilled in the art will appreciate that the laser system output pulses 32, derived through computer control of the X and / or Y axis of the laser positioning system 30, direct to the work surface such that the superimposed pulses form a pattern representing any complex curved geometry. I will understand. This capability, combined with the UV ablation patterning method, can be used to create complex curved geometric patterns in silicon that are useful for the efficient manufacture of various MEMS devices 120.

Another application of the ultraviolet ablation patterning method of the present invention is to fabricate an optical integrated circuit such as an arrayed waveguide gratings (AWG) device 130 that is fabricated on a semiconductor wafer workpiece 12. 12 is a representative illustration of ultraviolet ablation patterning of AWG device 130. In one preferred embodiment the AWG 130 is patterned using the method described above to form a curved trench 132 in silicon, for example having portions 132a, 132b, 132c, 132d, and 132e. . Although the trench 132 is shown symmetrically, those skilled in the art will appreciate that the laser system output pulses 32, which are derived through computer control of the X and / or Y axis of the laser positioning system 30, may include any of the superimposed pulses 32. It will be appreciated that it may be directed to the working surface, to form a pattern representing a complex curved profile or geometrical shape. This capability, combined with the UV ablation patterning method, can be used to create complex curved geometric patterns in silicon that are useful for the efficient manufacture of various AWG devices 130.

The use of conventional metal chucks, such as made of aluminum, is not advantageous for the through processing of the silicon workpiece 12, because in the ultraviolet region the high reflectivity of this traditional metal material may damage the back of the silicon workpiece. Because. The experiment showed clear evidence of backside damage around the cylindrical through hole opening 100 or through trench 110 by the reflected energy from the top of the metal chuck after the through treatment was complete. However, no back damage was found near the through trench 110 or the cylindrical through hole opening 100 that was accidentally drilled over the tooling hole at the top of the chuck.

13 is a representative illustration of the chuck assembly 140 in which the silicon workpiece 12 is preferably positioned during the penetrating process using the ultraviolet ablation patterning method. The chuck assembly 140 preferably includes a vacuum chuck base 142, a chuck top 144 and an optional retention carrier 146. The base 142 is preferably made of a traditional metal material, preferably bolted to the additional plate 148. The plate 148 is adapted to be easily connected or disconnected to at least one of the stages 36 or 38. The engagement mechanism is preferably mechanical, and may include opposing groves and ridges, and may include a locking mechanism. Those skilled in the art will appreciate that many precise alignments and locks and key mechanisms are possible. Those skilled in the art will also appreciate that the base 142 may alternatively be adapted to be fixed directly to the stage 36 or 38.

The chuck top 144 is preferably made of a dielectric material having a low reflectance at the ultraviolet wavelength selected for a particular patterning application. In one preferred embodiment where 355 nm output from a Q-switching diode-pumped Nd: YAG laser is used, which is frequency-multiplied, the UV transparent chuck top 144 is UV-grade or excimer grade fused ( fused) silica, MgF ₂ or CaF ₂ . In other embodiments, the UV transparent chuck top 144 may alternatively or additionally be liquid-cooled to help maintain the temperature stability of the silicon workpiece 12. Those skilled in the art will appreciate that fused silica is a transparent material to ultraviolet light consisting of amorphous SiO ₂ and can be formed by chemical bonding of silicon and oxygen.

Referring again to FIG. 13, a retention carrier 146 can be positioned above the chuck top 144 to support the silicon workpiece 12 and to retain it after UV ablation patterning. The retaining carrier 146 is also preferably made of an ultraviolet transparent material to prevent damaging the workpiece 12 which is penetrated by backside reflection. The retaining carrier 146 is preferably made to include a low cavity in which the treated silicon workpiece 12 rests after the through processing operation.

In an alternative embodiment, the chuck top 144 or the retention carrier 146 may have the laser system 10 directed to the workpiece 12 to inscribe a corresponding pattern into the material of the chuck top 144 or the retention carrier 146. It can be made of an ultraviolet absorbing material, such as Al or Cu, to make use of the low cavity patterned tool path pile being drilled. For example, the cavity corresponds to the intended drill hole or end pattern and prevents backside damage of the workpiece 12 during the through cutting operation. In addition, any debris generated during the process can enter the cavity away from the back side of the workpiece 12. In one preferred embodiment, the pattern of low cavities is processed to have a slightly larger dimension than the corresponding workpiece 12 after treatment to allow the treated workpiece 12 to seat in the cavity of the holding carrier 146. do. In alternative embodiments, the retention carrier 146 is made of an ultraviolet transparent material by alternative means such as optical fabrication or etching, and subsequently aligned and secured to the chuck top 144. This embodiment of the chuck assembly 140 also has applications useful for UV via drilling of other materials, such as polyamide.

Those skilled in the art will appreciate that purge gases such as nitrogen, argon, helium and dry air are usefully used to remove waste fumes from work 12. Such purge gas may be supplied near the workpiece using a delivery nozzle attached to the laser system 10.

In order to improve the surface quality of the silicon workpiece 12 treated using the UV ablation patterning method, a ultrasonic bath with a liquid comprising water, acetone, methanol and ethanol, but not limited to this, may be used. Can be cleaned using. Those skilled in the art will appreciate that cleaning the silicon workpiece 12 treated with hydrofluoric acid may be advantageous for removing unwanted oxide layers.

Although the description provided above relates primarily to the treatment of silicon and GaAs, the described method also applies to other semiconductors that may be used as the substrate 70 of the workpiece 12, such as SiC, SiN, or indium phosphide. Generally applicable.

It will be apparent to those skilled in the art that many modifications may be made to the details of the above-described embodiments of the invention without departing from the principles of the invention. Therefore, the scope of the present invention should be determined by the following claims.

The present invention is applicable to methods and / or apparatuses and the like for rapidly forming micron-scale features by ablation of semiconductors, in particular silicon, using the pulsed output of ultraviolet lasers.

Claims (47)

A method of laser processing a substrate comprising at least one of silicon, GaAs, indium phosphide, silicon carbide, silicon nitride, silicon nitride, Ge: Si, or single crystal sapphire. Producing a first laser system output of wavelength shorter than 400 nm with an output pulse energy greater than 100 μJ at a pulse repetition frequency greater than 5 kHz, Directing the first laser system output to a target location of the substrate to ablate the substrate material at a target location to a first spot area of less than 25 μm across the surface of the substrate material; Generating a second laser system output having an output pulse energy of greater than 100 μJ at a pulse repetition frequency of greater than 5 kHz, Outputting the second laser system such that a second spot region at least partially overlaps the first spot region and enters a second target position into the second spot region smaller than 25 μm across the surface of the substrate material Steps to induce Including, A method of laser processing a substrate. The substrate material of claim 1, wherein the substrate material is chucked by a chuck having a surface material that does not reflect one or more outputs of the first or second laser system output proceeding through a cut in the substrate material. A method of laser processing a substrate that is supported. 3. The substrate material of claim 2, wherein the substrate material has a back surface, wherein the surface material of the chuck prevents laser damage to the back surface of the substrate material from laser system output proceeding through cuts in the substrate material. Method of laser processing a substrate. 3. The method of claim 2, wherein the surface material of the chuck is transparent to one or more outputs of the first or second laser system output proceeding through cuts in the substrate material. 3. The substrate processing of claim 2, wherein the surface material of the chuck absorbs wavelengths of a first laser system output or a second laser system output or first and second laser system outputs that proceed through cuts in the substrate material. How to. The method of claim 1, wherein the first and second laser system outputs are generated by different lasers. 7. The method of claim 6, wherein the first and second laser system outputs comprise different wavelengths. The method of claim 1, wherein the first and second laser system outputs are generated by the same laser. 3. The method of claim 2, wherein the first and second laser system outputs are generated by different lasers. 10. The method of claim 9, wherein the first and second laser system outputs comprise different wavelengths. The method of claim 1, wherein the substrate material has a substrate material depth of less than 100 μm and at least one of the first or second laser system outputs has a spot area of 1-25 μm and energy per pulse of 100-1500 μJ. Method of laser processing a substrate. The method of claim 1, wherein the substrate material has a substrate material depth greater than 100 μm and at least one of the first or second laser system outputs has a spot area of 1-25 μm and energy per pulse of 100-1500 μJ. A method of laser processing a substrate. The method of claim 12, wherein the substrate material has a substrate material depth greater than 300 μm. The method of claim 13, wherein the one or more outputs of the first or second laser system output have an output pulse energy greater than 360 μJ. The method of claim 13, wherein one or more outputs of the first or second laser system output are generated at a pulse repetition frequency greater than 10 kHz. The method according to any one of claims 1 to 15, Providing a low speed and high speed movement control signal from a positioning signal processor; Controlling a wide range of relative movement of the translation stage with a slow positioner driver in response to the slow movement control signal; Controlling a narrow range of relative movement of the fast positioner with a fast positioner driver in response to the fast movement control signal to form a cut profile on the surface of the substrate material Further comprising, A method of laser processing a substrate. The method according to any one of claims 1 to 15, Further comprising forming a through hole having an aspect ratio of greater than 20: 1 through a substrate material having a thickness greater than 50 μm, A method of laser processing a substrate. 18. The method of claim 17, wherein at least one output of the first or second laser system output comprises at least five laser system output pulses. 18. The method of claim 17, wherein the first or second laser system output is incident on a front surface of the substrate material and the through hole penetrates through a back surface of the substrate material. , Using a through hole on the back surface to align the device to perform a treatment on the back surface of the substrate material. 18. The method of claim 17, wherein at least two through holes are formed and the at least two through holes are used to align the back surface of the substrate material for further processing. 18. The method of claim 17, wherein the first or second laser system output is incident on the front surface of the substrate material, the through hole penetrates the back surface of the substrate material, and the substrate is a target location for through hole processing. A method of laser processing a substrate, supported by a chuck having a surface material having a cavity underneath. 16. The method of any of claims 1-15, further comprising forming a kerf having a lengthwise dimension that is greater than the first spot area or the second spot area. Method of laser processing a substrate. 23. The method of claim 22, wherein the characteristic of the first and second laser system outputs prevents the formation of melt lip. 23. The method of claim 22, wherein the characteristic of the first and second laser system outputs prevents the formation of slag. 23. The method of claim 22, wherein the characteristic of the first and second laser system outputs prevents peel back of the edge of the cutout. 23. The method of claim 22, wherein the characteristics of the first and second laser system outputs prevent damage along the ends of the cutout. The method of claim 22, Generating a continuous laser system output of wavelength shorter than 400 nm with an output pulse energy greater than 100 μJ at a pulse repetition frequency greater than 5 kHz, A continuous target position with a spot area of less than 25 μm across the surface of the substrate material such that a continuous spot area overlaps at least partially each of the leading spot areas to form the kerf Directing the continuous laser system output to enter Further comprising, A method of laser processing a substrate. The method of claim 22, wherein the cut comprises a curved profile. The method of claim 22, The substrate material has a deep kerf with bottoms, the deep cutout separating the microcircuit devices but connecting the substrate at the bottom of the deep cutout to connect the microcircuit devices. Keep the material at a sufficient thickness, and the method Using the first and second laser system outputs to separate the microcircuit device. 23. The opening of claim 22, wherein the substrate material is supported by a chuck, the substrate material has a substrate depth, the cutting portion extends through the substrate depth, and the chuck is an opening through which processing occurs. A method of laser processing a substrate having a. The method according to any one of claims 1 to 15, Identifying a first feature on the first surface of the workpiece including the substrate; Aligning a first target position of a laser system with respect to the first feature on the first surface such that a first target position is close to a cut that will penetrate the workpiece over the first surface; Inducing one or more first pulses of the first and second laser system outputs to linearly enter the first surface at the first target position and at the first target position to form the first cut to a depth of cut not deeper than the material depth To do that, The laser system with respect to the first surface or a second feature on the second surface such that a second target position is coplanar with the first target position proximate to a cut that will penetrate the workpiece over a second surface. Aligning a second target location of the; First and second lasers to be incident on the second surface linearly with the second target position to form a second cut in the same plane as the first cut to form a cut through the workpiece Inducing one or more second pulses of the system output Further comprising, A method of laser processing a substrate. 32. The method of claim 31, wherein the first and second features include respective through holes laser drilled through the material depth and transparent on the first and second surfaces. A laser system using the method of claim 16 to treat a workpiece substrate comprising at least one of silicon, GaAs, indium phosphide, silicon carbide, silicon nitride, Ge: Si, or single crystal sapphire. 16. The substrate material of any one of claims 3 to 8 or 11 to 15, wherein the substrate material is adapted to output one or more outputs of the first or second laser system output that proceed through cuts in the substrate material. A method of laser processing a substrate, supported by a chuck having a surface material that does not reflect. The method of claim 34, Providing a low speed and high speed movement control signal from a positioning signal processor; Controlling a wide range of relative movement of the translation stage with a low speed locator driver in response to the low speed movement control signal; Controlling a narrow range of relative movement of the high speed locator with a high speed locator driver in response to the high speed movement control signal to form a cut profile on the surface of the substrate material Further comprising a method of laser processing the substrate. 35. The method of claim 34, further comprising forming a through hole having an aspect ratio greater than 20: 1 through a substrate material having a thickness greater than 50 microns. 37. The method of claim 36, wherein one or more outputs of the first or second laser system outputs comprise five or more laser system output pulses. 37. The method of claim 36, wherein the first or second laser system output is incident on the front surface of the substrate material, the through holes penetrate the back surface of the substrate surface, and the method further comprises: Using a through hole on the back surface to align the device to perform a treatment on the back surface of the substrate material. 37. The method of claim 36, wherein at least two through holes are formed and the at least two through holes are used to align the back surface of the substrate material for further processing. 37. The substrate of claim 36, wherein the first or second laser system output is incident on the front surface of the substrate material, the through hole penetrates the back surface of the substrate surface, and the substrate is below a target position for through hole treatment. Wherein the substrate is supported by a chuck having a surface material having a cavity therein. The method of claim 1, wherein the first and second laser system outputs provide a bite size of 0.1 to 10 μm. The method of claim 1, wherein the first and second laser system outputs have an output pulse energy of less than 1500 μJ. The method of claim 2, wherein the chuck comprises MgF ₂ or CaF ₂ . The method of claim 17, wherein the substrate has a depth greater than 500 μm. 35. The method of claim 34, wherein the first and second laser system outputs provide a bite size of 0.1 to 10 microns. The method of claim 16, wherein the one or more outputs of the first or second laser system output have a spot area of 3-20 μm and an energy per pulse of 200-1000 μJ. The method of claim 16, wherein the one or more outputs of the first or second laser system outputs have a spot area of 8-15 μm and energy per pulse of 300-800 μJ.

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