Abstract

As the complexity of Integrated Circuit(IC) design modifications increase, the time to perform these modifications also increases. As a result, the turn-around-time for bug fixes becomes criticalto a product's success. The Focused Ion Beam(FIB) mill is one such tool which has been actively used by the Semiconductor Industry for making complex IC modifications. This paper provides both characterization data and case studies supporting the use of laser assisted deposition as a complementary technique to the FIB mill. The laser process provides fast deposition of long, lowresistance silver lines as compared to the FIB's slow deposition rate and high resistivity. The processuses a spun': on organometallic liquidthat is heated and then exposed with an Argon Ion laserto pattern a metaltrace. After rinsingthe unexposed organo metallic, the process is repeated to increase the line thickness and achieve a conductive low resistance trace.The deposition properties for organometallic silver have been optimized for both resistance and speed. Parameters include: chuck temperature, laser power, deposition speed, and organometallic liquid concentration. Through experimentation, the deposition process has been characterized for resistivity, thickness and adhesion properties. The deposition has been used in conjunction with UV laser ablation for via formation and also in conjunction with FIB modifications by the routing of inter connects across largedie. Three case studies presented with in the paper will illustrate the application of this technique. The first case involves the creation of a low resistance path between internal signal lines, using only laser techniques, the second case demonstrates laser deposition as it is used to route interconnects, millimeters in length, between two complex FIB modifications and the third case is an example of reproducing a charge build-up problem. Finally, more recent investigations into the use of gold as a deposition material will also be discussed.

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