Patent•
Ultraviolet laser system and method for forming vias in multi-layered targets
06 Jul 1995-
TL;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.
Citations
More filters
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•
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
Patent•
25 Feb 2004
TL;DR: In this paper, a fundamental wave is used without putting laser light into a non linear optical element, and laser annealing is conducted by irradiating a semiconductor thin film with pulsed laser light having a high repetition rate.
Abstract: In conducting laser annealing using a CW laser or a quasi-CW laser, productivity is not high as compared with an excimer laser and thus, it is necessary to further enhance productivity. According to the present invention, a fundamental wave is used without putting laser light into a non linear optical element, and laser annealing is conducted by irradiating a semiconductor thin film with pulsed laser light having a high repetition rate. A laser oscillator having a high output power can be used for laser annealing, since a non linear optical element is not used and thus light is not converted to a harmonic. Therefore, the width of a region having large grain crystals that is formed by scanning once can be increased, and thus the productivity can be enhanced dramatically.
188 citations
References
More filters
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
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
Patent•
24 Jul 1989TL;DR: In this article, a method of ablating fluoropolymer composition materials is presented wherein it has been found that small holes (less than 100 νm) can be formed in fluoropolymers composition laminate materials using UV lasers to direct laser light through a mask and focusing lens.
Abstract: A method of ablating fluoropolymer composition materials is presented wherein it has been found that small holes (less than 100 νm) can be formed in fluoropolymer composition laminate materials using UV lasers (10) to direct laser light through a mask (12) focusing lens (14) and onto fluoropolymer laminate (16). The resulting holes can be used to produce vias and plated through-holes having smooth side walls with little or no debris or residue remaining in holes and minimal damage to the polymer. Thus, the vias and plated through-holes can be plated without further cleaning processes. In addition, the holes are formed at a relatively fast rate.
113 citations
Patent•
01 Aug 1991TL;DR: In this article, a method for rapidly forming a pattern of vias in multilayer electronic circuits in which each of the via holes is formed by drilling with a controlled number of Nd:YAG laser beam pulses is presented.
Abstract: The invention is directed to a method for rapidly forming a pattern of vias in multilayer electronic circuits in which each of the via holes is formed by drilling with a controlled number of Nd:YAG laser beam pulses. Beam positioning is controlled by means of a programmed galvanometric beam positioner. The drilling sequence is optionally controlled by application of an heuristic algorithm of the symmetric Traveling Salesman Problem.
95 citations
TL;DR: In this article, a new formula for the etch depth l per pulse of an excimer laser of fluence F was presented, and it was shown that l is proportional to F, rather than ln(F).
Abstract: A new formula is presented for the etch depth l per pulse of an excimer laser of fluence F. Incremental ablation is defined as the etch depth per pulse after many pulses. We show that l is proportional to F, rather than ln(F).
77 citations