<title>Self-aligned synthesis of titanium silicide by multipulse excimer laser irradiation</title>

Abstract

We present (report) a new type of titanium suicide self-aligned synthesis based upon excimer laser irradiation. This new process relaxes the requirements for ambient atmosphere control and suppresses the unwanted lateral growth of the silicide. . INTRODUCTIONThe development of the very large scale integration (VLSI) circuits requires new materials with improved performances and higher reliability to be used for gate electrodes or interconnection lines. The suicides of refractory metals were shown to be an appropriate choice for such applications1.One important advantage of these materials is the self-aligned manner of synthesis. The process called as SALICIDE is based upon a selective chemical etching causing the removal of the unreacted metal only, leaving unperturbed the suicide. However, several difficulties were found to be associated with the SAILICIDE process among which we mention the following ones: i) A strict control of the ambient atmosphere is required to the view of avoiding the reaction of the refractory metal with the oxygen2'3. ii) An important lateral growth6 or bridging of suicides is noticed.We report herewith a new method for the synthesis of self-aligned suicides which is based upon a mechanism differing of the SALICIDE process. To this pur pose we have exploited some peculiarities of the high power excimer laser irradiation which was showing to cause the vaporization of the metal deposited on 5102 only. This laser process also fulfils the requirements of a low thermal budget and of a high-purity of the synthesised layers, fundamental to VLSI technologies. As an illustrative examplification we refer to the titanium silicide synthesisthe compound the most intensively studied during recent years26. 2. EXPERIMENTAL DETAILS nrn-type (111)Si wafers with a resistivity of 5-8 flcm were employed in our experiments. The wafers were first oxidized to form a 250 nm thickness layer of Si02. Then, windows of 100 im or 1 mm diameter were opened through the oxide down to the single-crystalline Si substrate. A Ti layer of 150 nm thickness was then SPIE Vol. 1392 Advanced Techniques for Integrated Circuit Processing (1990) / 625 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/27/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx