Real-World Applications of Laser Direct Writing
- PDF / 2,636,601 Bytes
- 6 Pages / 396 x 630 pts Page_size
- 67 Downloads / 209 Views
Introduction In research dating back to the early 1980's laser and focused ion beam (FIB) direct write deposition and etching have been developed with an eye to a variety of microelectronic needs. The two methods referenced share much in the way of capabilities. Over time the two approaches have specialized and have been integrated into a powerful set of methods uniquely important to the microelectronics industry. This paper will briefly summarize some of the established and emerging applications to more or less conventional circuit design debug; the elaboration of these methods to the particularly demanding testing and debug of packaged flip-chip parts, and the further evolution to package level debug. Surprisingly, the importance of this class of methods has been greatly intensified over the last several years. Leading microprocessor companies have begun to use FIB and laser direct writing methods to adjust designs to increase manufacturing yield and binning count at the factory as well as at the design center. This paper will emphasize the practical applications of laser direct write methods and the integration of laser and FIB methods. The microchemical writing speed of the laser techniques are 2 to 6 orders of magnitude greater than they are for the ion beam analogs. Additionally, the electronic material quality of the laser deposited thin films are much higher, e.g. resistivity is typically 2 orders of magnitude lower than for the best focused ion beam deposited films. In the best cases the resolution of the laser techniques equal that of the dominant production technology for integrated circuits (ICs), which is optical lithography, but it cannot match the resolution of focused ion beams. As a result, users combine the virtues of both direct writing methods in actual practice. The diverse microchemical process technology used in laser direct writing is reviewed in Ref. 1.
Figure 1: Conventional debug of a wire-bonded front-surface part requires penetration of a passivation layer. In this case a compound silicon nitride/silicon dioxide layer was removed by a laser technique. Laser methods for chip depassivation are generally chosen for their process speed. 9 Mat. Res. Soc. Symp. Proc. Vol. 624 © 2000 Materials Research Society
Design Modification of Conventional Wire-Bonded Circuits
The modification of conventionally bonded (circuit up) parts has been relatively straight forward as the electrical connection to individual transistors was possible through the passivation layer and the top of the part. Laser methods were chosen for long length discretionary interconnects over the passivation layer where the high conductivity and rate of laser deposited metal greatly exceeds FIB metal. Another application was removal of passivation, silicon dioxide, silicon nitride, polyimide, etc., where the rate of laser depassivation greatly exceeds the FIB (e.g., see Fig. 1). Two developments have complicated these applications; (1) the low accessibility of transistor connections due to multi-layer metallization, which now
Data Loading...
