Low pressure chemical vapor deposition of titanium silicide

A system and a process have been developed for the low pressure chemical vapor deposition (LPCVD) of titanium sillcide. We report for the first time the optimization of LPCVD titanium silicide film properties against the deposition parameters, including the temperature, pressure, and SiHJTiC14 flow rate ratios. Smooth, reproducible, low resistivity (15-20 ~-cm) titanium silicide films have been deposited at a temperature of 730~ a pressure of 67 mtorr, and a SiH4/TiC14 flow rate ratio of 20/2. The as-deposited films did not require any post-deposition annealing to achieve this low resistivity. All the as-deposited films had a Si/Ti metal ratio of about 2 (determined by Rutherford backscattering spectroscopy). Within the Auger detection limit, no contamination was observed in the silicide films, and the films had uniform composition except for a transition region between the titanium silicide and the underlying polysilicon layers. During the experiments, it was observed that the SiH4/TiC14 flow rate ratio is the primary variable that affects the titanium silicide film properties. The rate of the silicon consumption during the silicide deposition has been determined and discussed in conjunction with the dependence of this rate on the TIC14 flow rate; increasing the TIC14 flow increases the polysilicon consumption rate. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 142.58.129.109 Downloaded on 2015-03-16 to IP Vol. 135, No. 10 TITANIUM SILICIDE 2591

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Optimized Deposition Parameters for Low Pressure Chemical Vapor Deposited Titanium Silicide

Ilderem

Reif

1988

“…4"~''J'~''~-:6 Titanium disilicide is formed in a reaction between titanium tetraehloride and elemental silicon, where both hydrogen as well as silicon itself can act as reducing agents. Consider the reaction with no hydrogen present TiC14(g) + (2 + x)Si(s) --~ TiSi2(s ) + xSiC14,~(g) [7] One part of the silicon consumed in the reaction forms the silicide. The other part is oxidized to volatile silicon chlorides in an etching process.…”

Section: Selectivity--inmentioning

confidence: 99%

Selective Deposition of TiSi2 from H 2 ‐ TiCl4 Gas Mixtures and Si: Aspects of Thermodynamics Including Critical Evaluation of Thermochemical Data in the Ti‐Si System

Engqvist

Myers

Carlsson

1992

Chemical vapor deposition (CVD) of TiSi2 from TIC14, H2, and substrate silicon has been investigated thermodynamically. From a critical evaluation of the thermochemical data, an assessment of the Ti-Si binary phase diagram has been performed. This is the basis of a new set of thermodynamic values for the titanium silicides, which have been used in the calculations. As a comparison, two other common data sets have also been used. The results from the calculations showed that the trends in selectivity as well as substrate etching were not affected by the choice of the silicide data. However, in the calculated CVD phase diagrams the stability regions for the various equilibria were strongly affected. The selectivity of the process was found to be very high and was favored by a low temperature and a low H2/TiC14 molar ratio. Moreover, improved selectivity can be expected for hot-wall reactor conditions. It was also shown that thermodynamics can be used for prediction of trends in substrate etching. The lowest etching yield was obtained at low pressures, at high temperatures, and at high H2/TiC14 molar ratios.With the decreasing feature sizes of the integrated circuits there is a need for new metallization schemes. Metals like W, Cu, and AI and disilicides of Ti, Mo, and W are here attractive candidates for various metallizatien applications. I Among the disilicides TiSi2 has the lowest resistivity and a low contact resistance to silicon.TiSi2 can be prepared by techniques like evaporation and sputtering. ~ However, chemical vapor deposition (CVD) offers several advantages like selectivity, excellent uniformity, and good step coverage. TiSi2 can be deposited from an H2-TiCI4 vapor and using substrate silicon 2-6 or from H~-TiCI4 vapor with a gaseous silicon-carrying precursor (SiHI4 or SIC14). s-17 The latter case has the advantage of less consumption of the substrate silicon. Cold-wall ~47 as well as hot-wall reactors are used for TiSi~ CVD. 2-4 Concerning the deposition pathways, the basic difference between these two reactor types is that the homogeneous reactions in the vapor are favored in the hot-wall reactor, while these reactions are suppressed in a cold-wall reactor.As mentioned above, TiSi2 can be deposited selectively onto silicon on a patterned Si/SiO2 substrate from a TIC14 carrying vapor. The selectivity is based on the difference in reactivity between the different substrate materials Si and SiO2. The Si is much more reactive towards the vapor than SiO2 and hence the Ti deposition with the subsequent TiSi2 formation is localized to the Si windows according to a reaction TiCl4(g) + 3St(s) --) TiSi~(s) + SiCl4(g)[I]With He in the reaction gas mixture, competing reactions involving HCI also occur. Thermodynamic calculations can be used for prediction of trends in selectivity as well as substrate etching when changing the experimental parameters. Calculated CVD phase diagrams are often used in order to select appropriate deposition parameters, such as temperature, total pressure and molar ratio between the ...

“…It has also been suggested that C49-C54 conversion occurs more readily for this process although this area still lacks an in-depth investigation. The CVD process was first introduced by Tedrow et al 7 in 1985, and it has attracted considerable interest from researchers in U.S., Japan, and France. [8][9][10][11][12][13][14][15][16] Silicides are formed on heavily doped source/drain regions and polycrystalline silicon gates.…”

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confidence: 99%

Effects of Arsenic Doping on Chemical Vapor Deposition of Titanium Silicide

Fang¹,

Öztürk²,

Seebauer

et al. 1999

Titanium silicide (TiSi 2 ) has long been used in complementary metal oxide silicon (CMOS) integrated circuits because of its low resistivity and compatibility with standard processes. 1 With the scaling of device dimensions into the deep submicron regime, two problems related to the conventional self-aligned silicide (SALICIDE) process have emerged. The first problem is the so-called narrow-line effect which describes the difficulty in conversion of TiSi 2 from the high resistivity C49 phase into the low resistivity C54 phase on narrow polysilicon lines. 2 Several new growth methods have been suggested to solve this problem, including the use of titanium alloys 3 and molybdenum implants. 4 The second problem is the silicon substrate consumption during silicide formation, which makes the SALICIDE process incompatible with ultrashallow junctions. Metal oxide semiconductor field effects transistor (MOSFETs) with elevated source/ drain structures have been proposed to address this problem. 5,6 Selective chemical vapor deposition (CVD) of TiSi 2 has been proposed as an alternative process to form contacts to ultrashallow junctions without silicon consumption. It has also been suggested that C49-C54 conversion occurs more readily for this process although this area still lacks an in-depth investigation. The CVD process was first introduced by Tedrow et al. 7 in 1985, and it has attracted considerable interest from researchers in U.S., Japan, and France. [8][9][10][11][12][13][14][15][16] Silicides are formed on heavily doped source/drain regions and polycrystalline silicon gates. For the conventional SALICIDE process, the effects of dopants on the formation and characteristics of silicides have been extensively studied. For TiSi 2 , several general remarks can be made: (i) TiSi 2 growth rate depends on dopant type and concentration. The growth rate is highest on undoped and borondoped substrates, lower on heavily phosphorous-doped substrates, and lowest on heavily arsenic-doped substrates 17,18 ; (ii) Ti reacts with boron and arsenic to form stable compounds such as TiAs and TiB 2 , which makes TiSi 2 unsuitable as a dopant out-diffusion source to form junctions [18][19][20] ; (iii) TiSi 2 films formed on arsenic-doped substrates are thermally less stable. 21 Most studies on CVD TiSi 2 have concentrated mainly on understanding the first principles of the process on undoped or moderately doped substrates, or on heavily doped silicon with an undoped silicon epitaxial interlayer. 22,23 Only a few studies exist concerning TiSi 2 deposition on heavily doped substrates. [24][25][26][27] It appears, however, that arsenic does effect deposition and consumption. 25 In a recent report, 28 this group presented experimental results on TiSi 2 deposition on heavily boron-doped substrates. It was conclud-ed that implanted boron does not have a strong influence on the deposition process. Shallow p ϩ -n junctions (X j ϭ 1000 Å) with 800 Å thick TiSi 2 contacts were successfully fabricated. It was also shown by a preliminary experiment...