Roger Palmans

Self-annealing characterization of electroplated copper films

Self-annealing of electro-chemically deposited copper films is described and studied, with a focus on the effect of process parameters like concentration of the organic additives, current density or thickness of plated copper. Sheet resistance and stress have been monitored and a non-correlated behavior has been observed for these two film characteristics, indicating that other phenomena than the grain growth typically associated with the room temperature recrystallization are likely to be involved. Diffusion/desorption of carbon containing molecules incorporated in the copper film from the bath additives could be a mechanism for stress release.

New plating bath for electroless copper deposition on sputtered barrier layers

A new copper plating bath for electroless deposition directly on conductive copper-diffusion barrier layers has been developed. This plating bath can be operated at temperatures between 20 and 50°C and has good stability. High temperature processing allows for increased deposition rates and decreased specific resistivity values for the deposited copper films. Electroless Cu films deposited from this bath showed a conformal step coverage in high aspect ratio trenches and, therefore, are promising as seed layers for copper electroplating. The effect of the bath composition, activation procedure and processing temperature on the plating rate and morphology of the deposited copper has been studied and is presented here.

Microstructure and resistivity characterization of CuAu I superlattice formed in Cu∕Au thin films

Stoichiometric AuCu alloy has been well studied in bulk form, but the resistivity of very thin films has rarely been reported. In fact, thin copper and gold films show a strong deviation from bulk resistivity due to the size effect, which motivates us to study CuAu I thin films and understand the properties of nanoscale metallization in more details. Very thin films of ordered CuAu I phase were formed by interdiffusion of Cu∕Au bilayers, in which the intermetallic phase formation was characterized by glancing angle x-ray diffraction and transmission electron microscopy. It was found that Kirkendall voids were created during the interdiffusion. Also, as it turned out, the resistivity of such thin CuAu I films changed only slightly with decreasing film thickness, which was different from pure copper and gold thin films.

Feasibility study of electroless copper deposition for VLSI

Abstract In this study the possibility of electroless deposition of copper has been investigated as an alternative metallization method in VLSI processing. The electroless deposition method involves the chemical reduction of a metal ion in solution on a catalytically active surface. As a consequence, this technique can be used to selectively deposit a very conductive metal such as copper in contact or via holes onto a catalytically active or activated metal surface. In order to optimize a standard electroless copper deposition bath containing tartrate as complexant and formaldehyde as reducing agent, the influence of several deposition parameters was investigated. With the resulting optimized copper deposition bath selective filling of submicron trenches and holes was performed with excellent surface planarity of the copper lines and plugs. Several characteristics of the deposited copper films will be discussed.

Electrical and mechanical characterization of chemical vapor deposition of tungsten on sputter‐deposited TiN layers

Tungsten (W) films are deposited from tungsten hexafluoride on sputter‐deposited TiN adhesion layers in a cold‐wall chemical vapor deposition reactor. The film resistivity of the W films is found to be thickness dependent. It decreases monotonically with increasing film thickness. Typical resistivity values of 40‐nm‐thick W films are about 19.3–23.4 μΩ cm, depending on the structure of the underlying TiN layer used. The resistivity of a 980‐nm‐thick W film is 9.8 μΩ cm. Oxygen and fluorine impurities, as well as structural difference in the W films are found to be the major causes for the resistivity variations. Lowering impurity level and/or increasing W crystallite size can decrease film resistivity. The stress of all the W films is found to be tensile, independent of the structure of the TiN layers. However, the absolute value of the stress is intimately associated with the structure of the TiN layers. The stress values can differ by a factor of more than 2 for the 40‐nm‐thick W films deposited on the ...

Influence of hydrogen on chemical vapor deposition of tungsten on sputter‐deposited TiN layers

Tungsten (W) films are deposited on sputter‐deposited TiN adhesion layers in a cold‐wall chemical vapor deposition reactor, initiated with the deposition of a W nucleation layer by SiH4 reduction of WF6. H2 is also introduced in the reactor for some depositions. The electrical resistivity and mechanical stress of the W films are found to be dependent on the underlying TiN layers as well as on the presence of H2 during W nucleation layer deposition. A higher resistivity is obtained when the W is deposited on the TiN prepared at 250 °C than on the TiN prepared at 450 °C. For the W deposited on the low‐temperature TiN, the resistivity is reduced by adding H2 to the reactants during W nucleation layer deposition; while for the W deposited on the high‐temperature TiN, the resistivity is almost insensitive to the H2 addition. More oxygen and fluorine are found at the W–TiN interface for the W deposited on the low‐temperature TiN than on the high‐temperature TiN. Introduction of H2 to the reactants during W nucl...

An experimental study of chemical vapour deposition of tungsten on Ti/TiN adhesion bilayers: mechanical properties

Abstract The mechanical properties of chemical vapour deposited tungsten (W-CVD) on Ti/TiN adhesion bilayers have been studied. Rapid thermal annealing (RTA) of the Ti/TiN bilayers has been found to strongly affect subsequently deposited W films. The stress in W is reduced as a consequence of the RTA treatment of Ti/TiN, and the stress reduction is especially pronounced for thin W films. However, the stress in the Ti/TiN bilayers deposited at 300 or 550 °C increases substantially after the RTA treatment at 650 °C, leading to appreciable increase in the total stress of the whole Ti/TiN/W stack. The nucleation deposition of W on the annealed Ti/TiN is somewhat hindered. The retardation of W growth on annealed Ti/TiN is discussed in terms of thermodynamics and classical nucleation theory in conjunction with the reduction of the interfacial impurities (i.e. fluorine and oxygen) as a result of the RTA of Ti/TiN [ A. Mouroux, R. Palmans, J. Keinonen, S.-L. Zhang, K. Maex, S. Petersson, in: Materials Research Society, MRS, San Francisco, CA, 1996 ], as well as the evolution of the W film texture with the W thickness.

Etch process development for FLARE/sup TM/ for dual damascene architecture using a N/sub 2//O/sub 2/ plasma

In this article, the feasibility of via and trench etch of FLARE/sup TM/, a low-k organic material product from AlliedSignal Inc. in dual damascene architectures for 0.25 /spl mu/m applications is described. The effects of O/sub 2/ concentration and flow rate on the etch rate and the etch profile of FLARE/sup TM/ during etching in oxygen reactive ion etch plasmas have been studied. Best via and trench profiles are obtained for a 25/5 nitrogen-to-oxygen ratio; no undercut of the hard mask is observed at a good etch rate. The feasibility of via filling with a low temperature W process and Cu fill of the trenches in a damascene structure has been demonstrated.

Impact of Rapid Thermal Annealing of Ti/Tin Bilayers On Subsequent Chemical Vapor Deposition Of Tungsten

The influence of rapid thermal annealing (RTA) of Ti/TiN on the stress in the subsequently deposited tungsten (W) films and on the impurity contents at the TiN-W interface was investigated for two types of Ti/TiN bilayers sputter-deposited at 300 °C and 550 °C. A post treatment of the Ti/TiN bilayers resulted in a substantially decreased stress in the W films. It also led to a considerable reduction of the fluorine contents at the TiN-W interface. Both effects were more pronounced for the W deposited on the low-temperature Ti/TiN bilayers and/or annealed in the NH 3 atmosphere, than on the high-temperature Ti/TiN bilayers and/or annealed in the N 2 atmosphere. Annealed in N 2 , the interfacial oxygen at the TiN-W interface increased slightly, which can be attributed to the presence of trace amounts of O 2 in the N 2 atmosphere. A slight increase in the W film resistivity was thus found for the W films deposited on the N 2 annealed Ti/TiN bilayers, while the resistivity decreased somewhat for the W films deposited on the NH 3 annealed Ti/TiN bilayers. After the post treatment, a large amount of nitrogen was found incorporated in the Ti layer forming TiN x (×