Electro Scientific Industries, Inc.

Other

Richard S Harris

Yunlong Sun

Brian W Baird

Edward J Swenson

Lian-Cheng Zou

Kevin P Fahey

Michael J Wolfe

Ho Wai Lo

James N O'Brien

Jay Johnson

Leon A Newman

Kelly Bruland

Hisashi Matsumoto

John T Kennedy

Vernon A Seguin

William J Jordens

David A Watt

Joel C Johnson

Robert Hainsey

Corey M Dunsky

Lei Sun

Thomas R McNeil

A set () of laser pulses () is employed to sever a conductive link () in a memory or other IC chip. The duration of the set () is preferably shorter than 1,000 ns; and the pulse width of each laser pulse () within the set () is preferably within a range of about 0.1 ps to 30 ns. The set () can be treated as a single 'pulse' by conventional laser positioning systems () to perform on-the-fly link removal without stopping whenever the laser system () fires a set () of laser pulses () at each link (). Conventional IR wavelengths or their harmonics can be employed.

Method for processing a memory link with a set of at least two laser pulses

UV laser cutting throughput through silicon and like materials is improved by dividing a long cut path () into short segments (), from about 10 &#x3bc;m to 1 mm. The laser output () is scanned within a first short segment () for a predetermined number of passes before being moved to and scanned within a second short segment () for a predetermined number of passes. The bite size, segment size (), and segment overlap () 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 () 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.A multi-step process can optimize the laser processes for each individual layer.

Laser segmented cutting, multi-step cutting, or both

Laser segmented cutting

Processing a memory link with a set of at least two laser pulses

Methods and systems use laser pulses to process a selected structure on or within a semiconductor substrate. The structure has a surface, a width, and a length. The laser pulses propagate along axes that move along a scan beam path relative to the substrate as the laser pulses process the selected structure. The method simultaneously generates on the selected structure first and second laser beam pulses that propagate along respective first and second laser beam axes intersecting the selected structure at distinct first and second locations. The first and second laser beam pulses impinge on the surface of the selected structure respective first and second beam spots. Each beam spot encompasses at least the width of the selected link. The first and second beam spots are spatially offset from one another along the length of the selected structure to define an overlapping region covered by both the first and the second beam spots and a total region covered by one or both of the first and second beam spots. The total region is larger than the first beam spot and also larger than the second beam spot. The method sets respective first and second energy values of the first and second laser beam pulses to cause complete depthwise processing of the selected structure across the width of the structure in at least a portion of the total region.

Semiconductor structure processing using multiple laser beam spots overlapping lengthwise on a structure

Systems and methods for scribing a semiconductor wafer with reduced or no damage or debris to or on individual integrated circuits caused by the scribing process. The semiconductor wafer is scribed from a back side thereof. In one embodiment, the back side of the wafer is scribed following a back side grinding process but prior to removal of back side grinding tape. Thus, debris generated from the scribing process is prevented from being deposited on a top surface of the wafer. To determine the location of dicing lanes or streets relative to the back side of the wafer, the top side of the wafer is illuminated with a light configured to pass through the grinding tape and the wafer. The light is detected from the back side of the wafer, and the streets are mapped relative to the back side. The back side of the wafer is then cut with a saw or laser.

Back side wafer dicing

A specially shaped laser pulse energy profile characterized by different laser wavelengths at different times of the profile provides reduced, controlled jitter to enable semiconductor device micromachining that achieves high quality processing and a smaller possible spot size.

Synchronization technique for forming a substantially stable laser output pulse profile having different wavelength peaks

A laser pulse with a specially tailored temporal power profile, instead of a conventional temporal shape or substantially square shape, severs an IC link. The specially tailored laser pulse preferably has either an overshoot at the beginning of the laser pulse or a spike peak within the duration of the laser pulse. The timing of the spike peak is preferably set ahead of the time when the link is mostly removed. A specially tailored laser pulse power profile allows the use of a wider laser pulse energy range and shorter laser wavelengths, such as the green and UV, to sever the links without appreciable damage to the substrate and passivation structure material located on either side of and underlying the links.

Methods of and laser systems for link processing using laser pulses with specially tailored power profiles

Patterns with feature sizes of less than 50 microns are rapidly formed directly in semiconductors, particularly silicon, GaAs, indium phosphide, or single crystalline sapphire, using ultraviolet laser ablation. These patterns include very high aspect ratio cylindrical through-hole openings for integrated circuit connections; singulation of processed die contained on semiconductor wafers; and microtab cutting to separate microcircuit workpieces from a parent semiconductor wafer. Laser output pulses () from a diode-pumped, Q-switched frequency-tripled Nd:YAG, Nd:YVO, or Nd:YLF is directed to the workpiece () with high speed precision using a compound beam positioner. The optical system produces a Gaussian spot size, or top hat beam profile, of about 10 microns. The pulse energy used for high-speed ablative processing of semiconductors using this focused spot size is greater than 200 &#x3bc;J per pulse at pulse repetition frequencies greater than 5 kHz and preferably above 15 kHz. The laser pulsewidth measured at the full width half-maximum points is preferably less than 80 ns.

Ultraviolet laser ablative patterning of microstructures in semiconductors

Digital control of frequency and/or amplitude modulation techniques of an intracavity and/or extracavity AOM () facilitate substantially full extinction of a laser beam () to prevent unwanted laser energy from impinging a workpiece (); facilitate laser pulse amplitude stability through closed-loop control of pulse-to-pulse laser energy; facilitate beam-positioning control including, but not limited to, closed-loop control for applications such as alignment error correction, beam walk rectification, or tertiary positioning; and facilitate employment of more than one transducer on an AOM () to perform any of the above-listed applications.

AOM frequency and amplitude modulation techniques for facilitating full beam extinction in laser systems

A quasi-CW diode- or lamp-pumped, A-O Q-switched solid-state UV laser system ( ) synchronizes timing of the quasi-CW pumping with movement of the positioning system ( ) to reduce pumping while the positioning system ( ) is moving from one target area ( ) to the next target area ( ) to form multiple vias in a substrate at a high throughput. Thus, the available UV power for via formation is higher even though the average pumping power to the laser medium ( ), and thermal loading of the laser pumping diodes ( ), remains the same as that currently available through conventional CW pumping with conventionally available laser pumping diodes ( ). The quasi-CW pumping current profile can be further modified to realize a preferred UV pulse amplitude profile.

Quasi-CW diode pumped, solid-state UV laser system and method employing same

An EOM Q-switched CO laser produces bursts of laser pulses delivered at a high PRF such as 20-140 kHz and having a short high-power spike of about 80-150 ns followed by a lower-power tail of about 0.05-12.0 &mgr;s. The bursts and/or laser pulses can be shaped by controlling the RF pumping duty cycle, the delay between the onset of RF pumping and the initiation of Q-switching, the pulse repetition frequency, and/or the duration of the tail. The bursts of laser pulses can be adapted to facilitate machining of metal layers and/or layers containing materials having disparate vaporization temperatures and/or disparate melting points, such as FR4 or green ceramics.

Micromachining with high-energy, intra-cavity Q-switched CO2  laser pulses

A quasi-CW diode-pumped, A-O Q-switched solid-state harmonic laser system ( ) synchronizes timing of the quasi-CW pumping with movement of the positioning system ( ) to reduce pumping while the positioning system ( ) is moving from one target area ( ) to the next target area ( ) to form multiple vias in a substrate at a high throughput. Thus, the available UV power for via formation is higher even though the loading to the laser pumping diodes ( ) remains the same as that currently available through conventional CW pumping with conventionally available laser pumping diodes ( ). The quasi-CW-pumping current profile can be further modified to realize a preferred UV pulse amplitude profile.

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Portland, OR, United States of America

Richard S Harris