Laser Assisted CVD of Aluminum from a Novel Liquid Alane Precursor
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LASER ASSISTED CVD OF ALUMINUM FROM A NOVEL LIQUID ALANE PRECURSOR. Jaesung Han*, Yoshihide Senzaki**, Wayne L. Gladfelter**, and Klavs F. Jensen* *Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 **Department of Chemistry, University of Minnesota, Minneapolis, MN 55455
ABSTRACT We describe pyrolytic laser assisted chemical vapor deposition of Al from dimethylethylamine-alane with 514 nm radiation from an Ar+ laser. Results from deposition on different substrates, including Pt, Au, W, and Si, provide insight into to thermal and nucleation effects in the laser writing process. High purity Al lines with resistivity close to bulk Al are reported for a range of operating conditions. The relationship between operating parameters and the resulting properties of the deposited lines is investigated. We also demonstrate a two-step fast writing process based on fast laser nucleation of lines followed by selective chemical vapor deposition of Al on the nucleated pattern. INTRODUCTION Laser assisted CVD (LCVD) of high conductivity metals, such as Cu and Al, has potential applications for deposition of micron scale interconnection lines for multichip packaging as well as for device repair and customization. Recent studies have demonstrated that it is possible to obtain high purity Cu lines by using reagents designed to decompose cleanly to the metal [1]. Here we consider similar issues for the LCVD of Al. Conventional thermal CVD of Al has been studied extensively for a variety of organometallic reagents [2, and references within] and the results extend to pyrolytic LCVD. Early studies of aluminum LCVD used trimethylaluminum (TMA) [3], but the need to break Al-C bonds and the strong affinity of Al towards C typically meant significant C incorporation and correspondingly high resistivity Al deposits [4]. Substantial reduction in carbon contamination levels was achieved through the use of an aluminum reagent, triisobutylaluminum (TIBA), that decomposed via a 13-hydride-elimination mechanism [5, 6]. More recently, trimethylamine alane (TMAA), an aluminum reagent with Al-H bonds and no Al-C bonds, has been found to yield high purity Al in thermal CVD [7, 8] as well as LCVD [9]. The success of the alane reagent further demonstrates the advantages of using a precursor that is designed to decompose cleanly to the desired metal. Here we investigate LCVD with a new alane source, dimethylethylamine alane (DMEAA), that has the further advantage of being a liquid as opposed to the solid TMAA. The source being a liquid simplifies its delivery to the deposition chamber. Thermal CVD studies have shown that this reagent yield high purity Al analogous to other alanes [10]. In addition to suitable precursor chemistry, writing speed is an issue in LCVD. Laser writing is a serial process and a very fast scanning speed is then needed to compete with Applications of the technique are conventional photolithography, a parallel process. therefore mostly limited to mask or circuit repair. If LCVD is to be u
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