Study of C49-TiSi2 and C54-TiSi2 formation on doped polycrystalline silicon using in situ resistance measurements during annealing

Abstract

la situ resistance versus temperature or time for reactions between 32 and 57.5 nm of titanium and undoped or doped polycrystalline silicon (boron, arsenic, or phosphorus, 7.9X1019-3.0X1020/cm3) has been measured and no clear correlation was found between the activation energy for the formation of the industrially important low-resistance C54-TiSia phase and its formation temperature. It is also demonstrated that with certain moderate doping levels typical of complementary metal-oxide-semiconductor manufacturing, boron or phosphorus-doped polycrystalline silicon can delay the formation of C5CTiSia more than arsenic-doped polycrystalline silicon. Finally, by using in situ resistance measurements, it is demonstrated that the "two-step" thermal annealing process similar to a salicide process requires less thermal annealing time at high temperatures to form C54-TiSi, than a single temperature.

Reduction of the C49-C54 TiSi 2 phase transformation temperature by reactive Ti deposition

“…Heterogeneous nucleation of C54 TiSi 2 occurs at the triple grain boundaries (grain edges) of the C49 phase [4], [8] while grain boundary nucleation has only been observed at the boundaries buried inside the film in thick titanium disilicide layers [4]. The values reported for the activation energy of the C49-C54 transformation are spread in the range between 3.3 and 6 eV depending on the details of the transformation [4], [6], [9]- [12] (single or double step annealing, substrate doping, blanket or patterned film, film thickness. .…”

Characteristics of the nanoscale titanium film deposited by plasma enhanced chemical vapor deposition and comparison of the film properties with the film by physical vapor deposition

“…In our experiment, however, C49 TiSi 2 grown by PECVD was not changed into C54 TiSi 2 after RTA at 900°C. It was already reported that the phase transition of C49 to C54 was incomplete on heavily doped Si substrate 9 and very narrow lines. 10 The Si substrate was heavily doped in our experiment, too.…”

Laser-induced titanium disilicide formation for submicron technologies

“…[1][2][3][4][5][6][7] Silicides can significantly reduce the contact resistance of the gate electrode and the source/drain regions as compared to nonsilicided structures. In particular, titanium disilicide (TiSi 2 ) has been used extensively as a contact material in ultra-large-scale integration technology because of its low electrical resistivity and good thermal stability.…”

“…2,3 TiSi 2 is a polymorphic material and may exist either as a high resistivity (ϳ60-90 ⍀cm) base-centered orthorhombic C49 phase or a low resistivity (ϳ15-20 ⍀cm) face-centered orthorhombic C54 phase. [2][3][4] When titanium reacts with silicon, the high resistivity C49 phase forms at temperatures ranging between 550 and 650°C and then transforms into the low resistivity C54 phase at annealing temperatures greater than 650°C. The C49 structure usually forms first due to a lower barrier to nucleation that has been attributed to a lower surface energy of this phase.…”