Mei Chang

TiCN: A new chemical vapor deposited contact barrier metallization for submicron devices

High‐quality chemical vapor deposited TiCN films were produced in a single wafer reactor using a metallorganic (TDMAT) precursor. The films have excellent step coverage over high aspect‐ratio contacts as well as very low particle content. These properties are obtained because the films are deposited under surface‐reaction controlled conditions. The films show also excellent barrier properties against Al and WF6 attack. These properties make this material a superb contact barrier material for ultra‐large‐scale integrated devices.

Development of tungsten nitride film as barrier layer for copper metallization

A process has been developed to deposit tungsten nitride (WxN) film below 350 °C to be used as a barrier layer in copper metallization. The film is deposited using tungsten hexa-fluoride (WF6) as a precursor in a hydrogen (H2)–nitrogen (N2)–argon (Ar) radio-frequency plasma. The tungsten-to-nitrogen ratio (x) in the tungsten nitride film determines its effectiveness as a barrier film. The process described in this article allows one to vary x from 1.2 to 3.7 by a single parameter: H2/N2 ratio. The article describes the characteristics of the film such as resistivity, stress, and deposition rate for different processing conditions. Film properties and surface conditions that cause WxN film to fail adhesion on oxide are indicated, and methods to improve adhesion are also discussed. Thickness measurements by alpha-step and scanning electron microscopy were correlated with measurements by the Rudolph Metapulse™ equipment to develop a methodology of nondestructively measuring film thickness, uniformity, and ob...

Formation of compositionally uniform tungsten silicide films using dichlorosilane in a single‐wafer reactor

High quality chemical vapor deposited (CVD) WSix (2.2<x<2.6) films were deposited on 200 mm Si wafers using SiH2Cl2/WF6 chemistry. Earlier reported problems regarding silicide nucleation at the substrate interface were solved resulting in a highly uniform composition (vertically and laterally) regardless of the substrate type (SiO2 or polycrystalline Si). As‐deposited resistivities of ∼750 μΩ cm were obtained for WSix (x=2.4–2.5) films grown at 550–600 °C. The films were completely crystalline, consisting predominantly of the hexagonal WSi2 phase. The as‐deposited stress in the films was ∼1.3×1010 dyne/cm2 and after 900 °C anneal has reduced to ∼8×109 dyne/cm2. The films contained relatively low levels of impurities: F∼6×1016–2×1017 atoms/cm3, and Cl∼5×1017–5×1018 atoms/cm3.

Response surface modeling of high pressure chemical vapor deposited blanket tungsten

Chemical vapor deposited (CVD) blanket tungsten has been studied at high pressure (80 Torr) in a single‐wafer cold wall reactor using response surface modeling methods. Deposition factors studied include temperature (430–490 °C), H2 partial pressure (6–30 Torr), WF6 partial pressure (1–2 Torr), and the gas inlet to wafer surface separation (200–600 mils). Quadratic models were generated for deposition rate, resistivity, sheet resistance uniformity, film stress, step coverage, reflectance, and WF6 conversion. The models were examined for consistency with previously reported results for CVD tungsten films, and were used to construct contour plots that aided a deposition process optimization search for a plug application. Optimization requirements for step coverage and sheet resistance Rs uniformity resulted in significant constraints on the usable factor space, while requirements for deposition rate, resistivity, stress, WF6 conversion, and reflectance were largely met throughout the original factor space. ...

Control of bombardment energy and energetic species toward a superdense titanium nitride film

TiN deposited by dc magnetron sputtering has been widely used as a hard mask material for dielectric patterning in multilevel Cu interconnects. Typically inside a “poison-mode” regime, the film density is 4.5–4.9 g/cm3. The microstructure, varying from columnar structure to nanocrystalline, is controlled by both thermodynamics and surface kinetics through ionization, substrate bias, target voltage, etc. A relatively low density film can be correlated with a porous columnar structure, low mechanical robustness, and weak resistance to plasma etching. However, with controlled growth, an applied substrate bias does not create resputtering and crystal defects. Instead, the authors create film with a maximum density of 5.3 g/cm3. In this high density film, carrier scatterings through grain boundary are greatly suppressed and the film resistivity is as low as 95 μΩ cm, which brings additional benefits as a conductive capping layer. As it is deposited at room temperature, the process minimizes the thermal budget ...

Integrated deposition and etchback of tungsten in a multi-chamber, single-wafer system

An integrated deposition and etchback process to form tungsten plugs in submicron contacts and vias was developed using experimental design and response-surface methodology to characterize both the low-pressure chemical vapor deposition (LPCVD) chamber and the magnetron-enhanced etchback chamber for 150-mm-diameter wafer processing. Tungsten was deposited at 80 torr and 475 degrees C by the H/sub 2/ reduction of WF/sub 6/. Etchback was then carried out in two steps: bulk tungsten was etched with an Ar/SF/sub 6/ mixture until excited N/sub 2/ molecules from the underlying TiN adhesion layer were detected in the plasma, and residual TiN was then etched for a fixed time with an Ar/Cl/sub 2/ plasma. Both etching steps employ a rotating magnetic field. Although the use of the magnetic field has no pronounced effect on the etch rate of ether film, it provides broad regions of highly uniform etching. In addition, the DC bias voltage, which was measured as part of the TiN study, decreases with increasing magnetic field without reducing the etch rate of the film.<<ETX>>

Novel metal gates for high κ applications

The development of gate systems suitable for high κ dielectrics is critical to the advancement of complementary metal-oxide-semiconductor (CMOS) devices. Both the effective work function and material stability are key parameters to these systems. A systematic study of metal gates of the composition HfxSi1-x (0.25 ≤ x ≤ 1) is demonstrated here, including XPS, XRD and four point probe measurements. The effective work function of each material is evaluated and it is shown that it can be tuned from 4.5 to less than 4.0 eV. Suitable work functions for n-channel metal-oxide-semiconductor applications (4.05 ± 0.2 eV) were achieved using hafnium rich compositions; however, XPS and diffraction measurements confirmed that these materials demonstrated a high propensity to oxidise, causing the reduction of the underlying oxides, making them unsuitable for commercial application.