Characteristics of PECVD grown tungsten nitride films as diffusion barrier layers for ULSI DRAM applications

Abstract

We have developed tungsten nitride (W-Nitride) films grown by plasma enhanced chemical vapor deposition (PECVD) for barrier material applications in ultra large scale integration DRAM devices. As-deposited W-Nitride films show an amorphous structure, which transforms into crystalline, ~-W2N and a-W phases upon annealing at 800~ The resistivity of the as-deposited films grown at the NH~v'F 6 gas flow ratio ofl is about 160 p~-cm, which decreases to 50 ~2cm after an rapid thermal annealing treatment at 800~ In the contact holes with the size of 0.35 pm and aspect ratio of 3.5, the bottom step coverage of the tungsten nitride films is about 60%, which is about three times higher than that of collimated-TiN films. We obtained contact resistance and leakage current with the tungsten nitride barrier layer comparable to those with conventional collimated TiN films. The contact resistance and leakage current are stable upon thermal stressing at 450~ up to 48 h.

Nanolayer CrNx/WNy coatings used on micro drills for machining of printed circuit boards

“…Between these two extremely different patterns, the five XRD patterns of nanolayer coatings, corresponding to value from 25 to 31 nm, showed apparently gradual change from strongly amorphous structure to nanocrystalline structure. For being widely used in optical and microelectronic applications, many researchers, such as Uekubo et al (1996), Park et al (1997) and Suh et al (1999), have extensively studied and characterized monolayer WNy coatings regarding crystal structure with respect to nitrogen content: Firstly, crystalline structure and nitrogen content of WNy are closely related to deposition conditions, such as nitrogen partial pressure, sputtering power (So et al, 1988), target dc bias voltage, and deposition and post-treating temperature (Volders et al, 2007), etc. For example, with target dc bias voltage varying from −100 to −500 V, Migita et al (2001) found that the sequential changes are achieved from the WN phase with (1 0 0) plane, W 2 N phase with (1 1 1) and (2 0 0) planes, and finally to the amorphous phase.…”

“…Tungsten nitride (WNx) coatings have been widely employed as optical and microelectronic parts, such as barrier layer (Park et al, 1997) and electrode (Uekubo et al, 1996). A great number of researches on the nature and synthesis of WNx coatings can be found in literatures.…”

Surface modification by multilayered W/W2N coating

“…Tungsten nitride films possess excellent hardness, chemical inertness, high melting point and high conductivity. It is used for various applications such as diffusion barriers in microelectronic devices, [19][20][21] and hard wear resistant protective films. 22 Hardness, wear and corrosion resistance of W/W 2 N films are improved by optimization process, such as substrate temperature, partial pressure of nitrogen and substrate bias.…”

Kinetic and Mechanistic Studies of the Chemical Vapor Deposition of Tungsten Nitride from Bis(Tertbutylimido)Bis(Tertbutylamido)Tungsten

“…Its proposed applications include use as a top electrode for capacitors in advanced dynamic random access memories, as a Schottky contact to GaAs, − and as an adhesive layer for blanket tungsten deposition . The predominant use of W x N in technology, though, is as a diffusion barrier material for ULSI devices. − For such applications, it is desirable to have materials with low resistivities and microstructures that prevent the interdiffusion of other layers in the device. Furthermore, the barrier layer material must be thermally stable in order to withstand the deposition and processing temperatures necessary for device fabrication. ,, Metal nitrides are particularly attractive toward this end because they tend to be chemically stable, can be highly conductive, and exhibit high hardness and melting points. − …”

“…Tungsten nitride is a suitable replacement for TiN as a ULSI barrier layer material, − one that can be deposited readily by both thermal and plasma-enhanced chemical vapor deposition processes. Its growth by these means generally favors a (111) orientation and dense columnar texture .…”