Process Research Of Titanium Silicide Thin Films By APCVD

Due to low resistivity, high temperature resistant and good thermal stability,titanium silicide has been widely used in the field of integrated circuits andhigh-temperature materials. In this paper, titanium silicide thin films were preparedon glass substrates by atmospheric pressure chemical vapor deposition (APCVD)using TiCl4-SiH4-N2reaction system. The experiment through study the mole ratio ofSi/Ti, deposition temperature and deposition time, than discuss crystal phaseformation process and the growth mechanism of titanium silicide thin film, thussummed change rule with deposition conditions of the titanium silicide thin film. Theresults showed that:1. Ti5Si3films and TiSi2films were prepared successfully on glass substrates byAPCVD using TiCl4-SiH4-N2reaction system. Ti5Si3phase was the hexagonal structurewhile the TiSi2film was C54TiSi2phase with orthogonal face centered structure.2. The crystal phase composition of titanium silicide changed with Si/Ti molarratio. When the mole ratio of Si/Ti changed from1to3, the films presented mainlythe crystalline phase of Ti5Si3and the content firstly increased and then decreasedwith the increased mole ratio of Si/Ti. As the mole ratio of Si/Ti was2, the content ofthe Ti5Si3crystalline phase was the highest and the crystalline grain was full growthand nearly spherical shape. Ti5Si3films were optimally deposited in this mole ratio ofSi/Ti. The main reaction equation is:10SiH4(g)+5TiCl4(g)=Ti5Si3(s)+4SiCl4(g)+3SiH3Cl(g)+HCl(g)+15H2(g); When the mole ratio of Si/Ti changed from3to5, thefilms presented mainly the crystalline phase of TiSi2and the content firstly increasedand then decreased with the increased mole ratio of Si/Ti. As the mole ratio of Si/Tiwas4, the content of the TiSi2crystalline phase was the highest, the surfacemorphology was evenly distributed, orderly, and higher bulk density sheet structure.TiSi2films were optimally deposited in this mole ratio of Si/Ti. The main reactionequation is:4SiH4(g)+TiCl4(g)=TiSi2(s)+2SiH2Cl2(g)+6H2(g); When the mole ratioof Si/Ti was greater than5, the crystalline phase films changed into thepolycrystalline silicon and the surface morphology changed from dense orderedlamellar structure gradually into the group, eventually forming the lowest bulkdensity and flower-like structures with different sizes. The main reaction equation is: SiH4(g)=2H2(g)+Si(s)。3. The crystal phase growth of titanium silicide was significantly affected by thereaction temperature. When the deposition temperature was below700oC, the crystalphase growth rate was small, and the films were almost amorphous structure with fewand incomplete-developed particles. On the contrary, temperature was conducive tothe growth of the crystal phase of titanium silicide and titanium silicide phasesincreased significantly when synthesised above700oC. Particles became bigger insize and more uniform meanwhile. Once the reaction temperature is too high,although the crystalline phase grows fast, but the crystal nucleation rate decreases.And the content of titanium silicide phases decreased, and its bulk density was greatlyreduced. The best reaction temperature of Ti5Si3film is720oC. In this situation, thecontent of Ti5Si3film phases is the highest, and particles’ diameter reached400nmwith better morphology. While the best temperature of TiSi2film is700oC. Thecontent of TiSi2film is the highest every per unit volume, and the particles size wereabout200nm.4. Crystal phases grew less time if the deposition time was not enough. The thinfilm was amorphous deposited less than30s. With the increase of deposition time,titanium silicide crystal phase content gradually increased with larger particles andmore compact arrangement. The results showed the best deposition time of Ti5Si3thinfilms was120s with high Ti5Si3crystalline phase content and uniform surfaceparticle density. The best deposition time of TiSi2thin films was90s with high TiSi2crystalline phase content and orderly arranged particles. But, when the depositiontime is too long, its content and particles was almost unchanged and the surface of thefilm stacking disordered.5. As the depositon time increased, the electrical resisitivity oftitanium silicideflims presented steady after a reducing trend. When thedeposition time is120s andthe temperature is720oC, the resistance of Ti5Si3films is lowest and relatively stable,which measures about3.80/sq; as for the TiSi2films, When the deposition time is90s and the temperature is700oC, the resistance is also lowest and relatively stable,which measures about0.54/sq.