Deposition Method-Induced Stress Effect on Ultrathin Titanium Nitride Etch Characteristics

Abstract

A systematic study to investigate the fundamental cause for wet etch variation of ultrathin titanium nitride ͑TiN͒ film as a function of the deposition technique such as physical vapor deposition, chemical vapor deposition, and atomic layer deposition is presented. For this study, 10 nm TiN films were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, X-ray reflectometry, and absolute ellipsometry. It is shown that the deposition method plays an important role on the final TiN crystallography and properties. However, it is demonstrated that the dominating factor defining etch rate is the resulting film strain.Thermodynamic stability, 1 low diffusivity, and high conductivity make titanium nitride ͑TiN͒ a good candidate for several complementary metal oxide semiconductor ͑CMOS͒ applications. In fact, TiN is already used in several applications in semiconductor device technology, such as aluminum ͑Al͒ diffusion barriers, advanced metallization, and interconnects in ultralarge scale integration ͑ULSI͒ circuits and devices. 2 TiN provides an effective barrier layer in contact strucrures 3 with exceptional stability due to the low diffusivity of impurity atoms in TiN. 4 Additionally, the low resistivity of TiN permits its use as a local interconnect in very large scale integration ͑VLSI͒ CMOS technology. 5 Also, the barrier height of TiN on silicon ͑Si͒ is about one-half of the energy gap, allowing the use of TiN contacts equally well on both p-and n-type silicon. 6 This also makes TiN a good midgap metal gate electrode. In addition, TiN has also been used as a good contact etch stop layer 7 and as an adhesion layer. 8 As reported elsewhere, a metal/high permittivity ͑k͒ dielectric combination is likely to replace the conventional poly silicon/silicon dioxide ͑SiO 2 ͒ gate stack. 9 The metal gate/high-k combination eliminates poly depletion, boron penetration, and instability of poly silicon/high-k dielectric combinations. 10 During the screening phase of metal gate/high-k dielectrics, TiN drew attention because this material is already used in conventional CMOS fabrication. [11][12][13][14][15][16][17] In addition, the TiN has been used to integrate high-k/metal gate metal oxide semiconductor field-effect transistors ͑MOSFETs͒. [18][19][20][21][22] Wet etch is extensively used in CMOS technology; therefore, a controlled wet etch of TiN is very important. 23,24 TiN can be etched by standard cleaning agent 1 ͓SC1ϭdeionized water:H 2 O 2 :NH 4 OH͔. A challenging task in dual metal gate CMOS integration with metal wet etch is that the etch needs to be effective to remove the metal gate electrode and, at the same time, highly selective to stop at the ultra-thin ͑typically 2-3 mm͒ high-k dielectric layer. 25 Furthermore, an over etch is normally used which might also result in additional high-k degradation. 26 Depending on the application, TiN can be deposited by chemical vapor deposition ͑CVD͒, physical vapor deposition ͑PVD͒, or atomic layer deposition ͑ALD͒ methods. Therefore, understanding the impac...

Mechanisms of TiN Effective Workfunction Tuning at Interfaces with HfO2 and SiO2

“…As follows from these results, the PVD-TiN film shows a preferential growth in the (200) orientation while the ALD (450 °C)-TiN contains crystallites of two different orientations. Similar behavior was also reported earlier . Joint analysis of the angular position and shape of the (200) diffraction peak indicates the similar grain size in both types of deposited TiN films.…”

“…Similar behavior was also reported earlier. 30 Joint analysis of the angular position and shape of the (200) diffraction peak indicates the similar grain size in both types of deposited TiN films. At the same time the absence of the (111) diffraction peak in the spectrum of the PVD-TiN suggests better ordering with (200) preferential orientation in the PVD film.…”