Patent•
Method employing UV laser pulses of varied energy density to form depthwise self-limiting blind vias in multilayered targets
17 May 1996-
TL;DR: In this article, the output of a continuously pumped, Q-switched, Nd:YAG laser is converted to provide ultraviolet light for forming vias in targets (40) having metallic layers (64,68) and a dielectric layer (66).
Abstract: The output of a continuously pumped, Q-switched, Nd:YAG laser (10) is frequency converted to provide ultraviolet light (62) for forming vias (72, 74) in targets (40) having metallic layers (64,68) and a dielectric layer (66) The invention employs a first laser output of high power density to ablate the metallic layer and a second laser output of a lower power density to ablate the dielectric layer The parameters of the output pulses (62) are selected to facilitate substantially clean, sequential drilling or via formation These parameters typically include at least two of the following criteria: power density first above and then below the ablation threshold of the conductor, wavelength less than 400 nm, a temporal pulse width shorter than about 100 nanoseconds, and a repetition rate of greater than about one kilohertz The ability to generate ultraviolet light output pulses at two power densities facilitates the formation of depthwise self-limiting blind vias in multilayer targets, such as a target composed of a layer dielectric material covered on either surface by a layer of metal
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Patent•
19 Dec 2000
TL;DR: In this article, an energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided.
Abstract: An energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided. The system includes a controller for generating a processing control signal and a signal generator for generating a modulated drive waveform based on the processing control signal. The waveform has a sub-nanosecond rise time. The system also includes a gain-switched, pulsed semiconductor seed laser for generating a laser pulse train at a repetition rate. The drive waveform pumps the laser so that each pulse of the pulse train has a predetermined shape. Further, the system includes a laser amplifier for optically amplifying the pulse train to obtain an amplified pulse train without significantly changing the predetermined shape of the pulses. The amplified pulses have little distortion and have substantially the same relative temporal power distribution as the original pulse train from the laser. Each of the amplified pulses has a substantially square temporal power density distribution, a sharp rise time, a pulse duration and a fall time. The system further includes a beam delivery and focusing subsystem for delivering and focusing at least a portion of the amplified pulse train onto the target material. The rise time (less than about 1 ns) is fast enough to efficiently couple laser energy to the target material, the pulse duration (typically 2-10 ns) is sufficient to process the target material, and the fall time (a few ns) is rapid enough to prevent the undesirable changes to the material surrounding the target material.
234 citations
Patent•
25 Jan 2006
TL;DR: In this paper, a laser beam processing machine comprising a path distribution means for distributing a pulse laser beam oscillated by pulse laserbeam oscillation means to a first path and a second path alternately, and one laser beam that passes through one of the paths and is converged by one condensing lens and the other laser beam is applied at different focusing points which have been displaced from each other in the direction of the optical axis.
Abstract: A laser beam processing machine comprising a path distribution means for distributing a pulse laser beam oscillated by pulse laser beam oscillation means to a first path and a second path alternately, and one laser beam that passes through one of the paths and is converged by one condensing lens and the other laser beam that passes through the other path and is converged by the condensing lens are applied at different focusing points which have been displaced from each other in the direction of the optical axis, alternately with a time lag between them.
212 citations
Patent•
07 Jun 2002TL;DR: In this paper, a long cut path is divided into short segments, from about 10 µm to 1 mm, and the laser output is scanned within a first short segment for a predetermined number of passes before being moved to and scanned within another short segment (122) for a certain time interval.
Abstract: UV laser cutting throughput through silicon and like materials is improved by dividing a long cut path (112) into short segments (122), from about 10 µm to 1 mm. The laser output (32) is scanned within a first short segment (122) for a predetermined number of passes before being moved to and scanned within a second short segment (122) for a predetermined number of passes. The bite size, segment size (126), and segment overlap (136) can be manipulated to minimize the amount and type of trench backfill. Real-time monitoring is employed to reduce rescanning portions of the cut path (112) where the cut is already completed. Polarization direction of the laser output (32) is also correlated with the cutting direction to further enhance throughput. This technique can be employed to cut a variety of materials with a variety of different lasers and wavelengths.
208 citations
Patent•
30 Mar 2001TL;DR: In this paper, a single pass actuator, such as a deformable mirror, quickly changes the focus and hence the spot size of ultraviolet or visible wavelength laser pulses to change the fluence of the laser output at the workpiece surface between at least two different fluence levels.
Abstract: A single pass actuator (70, 200), such as a deformable mirror (70), quickly changes, preferably in less than 1 ms, the focus and hence the spot size of ultraviolet or visible wavelength laser pulses to change the fluence of the laser output (66) at the workpiece surface between at least two different fluence levels to facilitate processing top metallic layers (264) at higher fluences and underlying dielectric layers (266) at lower fluences to protect bottom metallic layers (268). The focus change is accomplished without requiring Z-axis movement of the laser positioning system (62). In addition, the spot size can be changed advantageously during trepanning operations to decrease via taper, reduce lip formation, increase throughput, and/or minimize damage.
194 citations
Patent•
26 May 2000TL;DR: In this article, a diode-pumped solid-state laser (52) of a laser system (50) provides ultraviolet Gaussian output (54) that is converted by a diffractive optical element (90) into shaped output (94) having a uniform irradiance profile.
Abstract: A diode-pumped, solid-state laser (52) of a laser system (50) provides ultraviolet Gaussian output (54) that is converted by a diffractive optical element (90) into shaped output (94) having a uniform irradiance profile. A high percentage of the shaped output (94) is focused through an aperture of a mask (98) to provide imaged shaped output (118). The laser system (50) facilitates a method for increasing the throughput of a via drilling process over that available with an analogous clipped Gaussian laser system. This method is particularly advantageous for drilling blind vias (20b) that have better edge, bottom, and taper qualities than those produced by a clipped Gaussian laser system. An alternative laser system (150) employs a pair of beam diverting galvanometer mirrors (152, 154) that directs the Gaussian output around a shaped imaging system (70) that includes a diffractive optical element (90) and a mask (98). Laser system (150) provides a user with the option of using either a Gaussian output or an imaged shaped output (118).
191 citations
References
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IBM1
TL;DR: When a pulse (~ 14 nsec half width) of laser radiation of 193 nm wavelength with a fluence above a threshold value falls on a polymer film, the material at the irradiation site is spontaneously etched away to a depth of 1000 A or more.
Abstract: When a pulse (~ 14 nsec half-width) of laser radiation of 193 nm wavelength with a fluence above a threshold value falls on a polymer film, the material at the irradiation site is spontaneously etched away to a depth of 1000 A or more.[1,2] This process has been called Ablative Photo Decomposition’ [3]. The excimer laser which is the source of the 193 nm radiation is capable of providing radiation at other wavelengths such as 249 nm, 308 nm, and 351 nm. Spontaneous etching of the polymer films by the laser beam has been observed at all of these wavelengths [4–7].But there are quantitative differences in the etching process at different wavelengths and with different polymers.
269 citations
Patent•
06 Jul 1995TL;DR: In this paper, the output of a continuously pumped, Q-switched, Nd:YAG laser (10) is frequency converted to provide ultraviolet light for forming vias (72, 74) in multi-layered targets (40).
Abstract: The output of a continuously pumped, Q-switched, Nd:YAG laser (10) is frequency converted to provide ultraviolet light (62) for forming vias (72, 74) in multi-layered targets (40). The parameters of the output pulses (62) are selected to facilitate substantially clean, simultaneous or sequential drilling or via formation in a wide variety of materials such as metals, organic dielectrics, and reinforcement materials having different thermal absorption characteristics in response to ultraviolet light. These parameters typically include at least two of the following criteria: high average power of greater than about 100 milliwatts measured over the beam spot area, a temporal pulse width shorter than about 100 nanoseconds, a spot diameter of less than about 50 microns, and a repetition rate of greater than about one kilohertz. The laser system (10) and method circumvent conventional depth of cut saturation limitations and can achieve an increased depth of cut per pulse in a target (40) formed of either single- or multi-layered material.
258 citations
Patent•
14 Feb 1989TL;DR: In this article, the surface of a polymer dielectric layer is scanned repeatedly with a high energy continuous wave laser in a pattern to create via holes of desired size, shape and depth.
Abstract: The surface of a polymer dielectric layer is scanned repeatedly with a high energy continuous wave laser in a pattern to create via holes of desired size, shape and depth. This is followed by a short plasma etch. The via holes are produced at commercial production rates under direct computer control without use of masks and without damage to conductor material underlying the dielectric layer. A two-step technique usable to form a large hole to a partial depth in the dielectric layer and several smaller diameter holes within the large hole through the remainder of the dielectric layer depth allows formation of a large number of holes in a given area of a thick dielectric layer.
159 citations
Patent•
IBM1
TL;DR: In this article, a technique for the fabrication of devices and circuits using multiple layers of materials, where patterned layers of resists are required to make the device or circuit, is described by the selective removal of portions of the resist layer by ablative photodecomposition.
Abstract: A technique is described for the fabrication of devices and circuits using multiple layers of materials, where patterned layers of resists are required to make the device or circuit. The fabrication process is characterized by the selective removal of portions of the resist layer by ablative photodecomposition. This decomposition is caused by the incidence of ultraviolet radiation of wavelengths less than 220 nm, and power densities sufficient to cause fragmentation of resist polymer chains and the immediate escape of the fragmented portions from the resist layer. Energy fluences in excess of 10 mJ/cm2 /pulse are typically required. The deliverance of a large amount of energy in this wavelength range to the resist layer in a sufficiently short amount of time causes ablation of the polymer chain fragments. No subsequent development step is required for patterning the resist layer.
134 citations
TL;DR: The time dependence of the expansion for various environmental gas pressures has been studied in this way as discussed by the authors, showing that at low pressures (< 0.5 mb) the expansion approaches a free expansion into a vacuum, while at 15 mb the time dependence is close to that predicted by an ideal blast wave model, suggesting that a significant fraction of the luminous species detected spectroscopically may be created in the shock front at the plume/environmental gas interface.
Abstract: Spectroscopy and fast photography have been used to study the luminous plume produced by ablative etching of polyimide and polyethylene‐terephthalate polymer films with the XeCl laser. The time dependence of the expansion for various environmental gas pressures has been studied in this way. The results show that at low pressures (<0.5 mb) the expansion approaches a free expansion into a vacuum, while at 15 mb the time dependence is close to that predicted by an ideal blast wave model. It is suggested that a significant fraction of the luminous species detected spectroscopically may be created in the shock front at the plume/environmental gas interface.
129 citations