Edward J. Swenson

Laser micromachining in the microelectronics industry: a historical overview

The use of lasers in microelectronics is production for trimming, ablating, drilling and general micromachining continues to grow. As one example, traditional laser trimming techniques for passive and active microelectronic circuits have been used for nearly thirty years to improve yields and/or device performance. The majority of these processes have been accomplished using the fundamental wavelengths of the Nd:YAG laser source. However, recent technological advances in microelectronics laser processing, mainly for hybrid integrated circuits (HIC), dynamic random access memories (DRAM) and printed wiring boards (PWB) have resulted in new process techniques. Several new technologies, such as alternative wavelength processing and shaped, uniform laser spots have produced better processing quality, higher reliabiltiy, and greater yields. This paper will review the past, present and future of laser micromachining in microelectronics.

Optimization of memory redundancy laser link processing

Memory repair through the use of laser processing of redundant elements is an industry standard procedure for memory chip manufacturing. But, shrinking memory feature sizes and the industrys tendency to use metals as link materials rather than polysilicon imposes new challenges for laser processing. So far, the majority of the research on memory link laser processing has concentrated on: The vertical structure of a link (such as the multiple layers of passivation, link, field oxidation and silicon substrate); the laser beam absorption; and, the different temperature distribution within the structure as the result of laser beam heating. Until now, the emphasis in laser link processing optimization has been aimed at creating uniform temperature distribution while severing the link before exploding the passivation layer. Our study has shown that the link width plays an important roll in the processing as well. Analysis of the mechanical stress beneath the passivation layer using finite element modeling has been carried out. Different link width and passivation layer thicknesses vary the stress dramatically. The results of this simulation will be presented and their implication on link processing optimization will be discussed. To optimize the laser processing further, we have proven that absorption contrast of laser energy between the link material and the silicon substrate beneath the link must be maximized. Based upon the fact that while the absorption of most metal materials in the 1.3- to 2-micron range remains the same as that at 1 micron, it drops dramatically for silicon. By using laser wavelengths within the 1.3- to 2-micron range, a much wider laser processing window can be realized. Comparison analysis of link processing by different laser wavelengths will be discussed.

Improved microelectronics manufacturing using new laser technologies

The use of the 1.3 line and third harmonic of the diode pumped Nd:YAG laser provides a variety of new methods to address the continued advance towards smaller, lighter more complex microelectronics.

Recent advances in laser micromachining for semiconductor and microfluidic applications

Recent advances in fiber amplified lasers, modelocked technology, and harmonic conversion not only have enabled improvements in traditional micromachining applications but also have opened the door for laser processing in new areas. This paper will review recent work with UV diode-pumped solid state lasers, picosecond lasers and master oscillator fiber power amplifier systems in processing semiconductor, metal, dielectric and polymer materials for such diverse applications as memory repair, microfluidics, solar cells, and MEMS.Recent advances in fiber amplified lasers, modelocked technology, and harmonic conversion not only have enabled improvements in traditional micromachining applications but also have opened the door for laser processing in new areas. This paper will review recent work with UV diode-pumped solid state lasers, picosecond lasers and master oscillator fiber power amplifier systems in processing semiconductor, metal, dielectric and polymer materials for such diverse applications as memory repair, microfluidics, solar cells, and MEMS.

Present And Future Applications For Laser Processing Of Hybrids And Semiconductors

Present and future development of laser processing as a production technique for modifying semiconductor devices, improving yields, and decreasing developmbnt times are described. Current applications covered include thick-and thin-film resistor trimming, deposited film and polysilicon resistors on silicon trimming and redundant memory repair. Emerging applications include microcircuit mask making and capacitor trimming. Examples of processes still under development include selective annealing, minority-carrier lifetime doping, and device diagnostics by laser imaging.