John M. Drynan

A quarter-micrometer interconnection technology using a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer structure

An interconnection structure using a TiN/Al-1% Si-0.5% Cu/TiN/Al-1% Si-0.5% Cu/TiN/Ti multilayer conductor was investigated as a quarter-micrometer interconnection candidate for 256-Mb DRAMs. It was found that intermetallic compounds such as TiAl/sub x/ were formed at both grain boundaries of Al-Si-Cu and interfaces between Al-Si-Cu and TiN of the multilayer, resulting in both increase in Vickers hardness and suppression of stress relaxation. The multilayer conductor strip, which was covered with plasma-enhanced chemical vapor deposition silicon nitride (P-SiN), suppressed stress-induced voiding after heat treatment at 500 degrees C. Electromigration tests for quarter-micrometer wide multilayer strips indicated the improvement in the mean time to failure and the increase of the standard deviation. >

A quarter-micron interconnection technology using Al-Si-Cu/TiN alternated layers

A novel interconnection structure using Al-Si-Cu/TiN alternated layers has been investigated as a quarter-micron interconnection candidate for 256 MDRAM. A TiN/Al-1%Si-0.5%Cu/TiN/Al-1%Si-0.5%Cu/TiN/Ti layered film structure was designed for both electro- and stress-migration-resistant interconnections. This alternated layer structure has extremely high endurances in terms of mechanical hardness, tensile strength, and electromigration lifetime.<<ETX>>

Quarter-Micron Interconnection Technologies for 256-Mbit Dynamic Random Access Memories

Quarter-micron interconnection technologies for 256-Mbit dynamic random access memories (DRAMs) are reviewed. Since the density of memory capacity is increased, both decreasing feature size and increasing sophistication of cell structures are required, resulting in three-dimensional structures. This trend leads us to the introduction of new interconnection technologies which have good coverage, low resistivity and high reliability, because the three-dimensional device structure requires high aspect-ratio contact hole plugs and narrow-pitch metal lines on different surface levels. The state of the art and current problems are discussed for quarter-micron contact-hole filling and quarter-micron interconnection lines.

Shared tungsten structures for FEOL/BEOL compatibility in logic-friendly merged DRAM

Shared tungsten structures are proposed to replace the conventional Si-based structures of commodity DRAMs, thereby enabling alignment with the Logic frontand back-end-of-line processes to achieve full compatibility for sub-quarter-micron merged DRAM-Logic devices. W-based damascene bit lines, storage capacitors, and contact plugs used in the memory cells can be shared as local interconnect lines and stacked via plugs in the Logic circuitry. Adopting bilayer (PVD+CVD) W can realize a 40-65% reduction in interconnect resistance, in addition to its optimal use in Ta/sub 2/O/sub 5/-dielectric full metal capacitors.

Comparison of Cvd and Pvd Tungsten for Gigabit-Scale Dram Interconnections

The characteristics of blanket CVD-W and PVD-W films with and without TiN/Ti underlayers have been investigated in terms of both materials properties such as resistance, stress, morphology, crystallinity, and composition, and prospective applications such as for DRAM bit line interconnections. The presence of a TiN underlayer has been found to induce preferential growth of dominant W (110) crystal orientation for both CVD-W and PVD-W whereas absence of TiN results in a W film of mixed W (110), (200), and (211) crystallites. Sheet resistance measurements of both blank films and conductor lines have shown that a 200nm-thick PVD-W film yields a lower resistance than a similar film with TiN underlayer and hence larger total thickness. This correspondence of W (110) intensity with resistance implies that reduction of the (110) oriented crystallites within a W film can yield lower resistances. Thus, by elimination of the TiN/Ti underlayer, monolayer PVD-W or CVD-W with a PVD-W underlayer can be effectively adapted to quarter-micron conductors for bit line interconnections and related structures in DRAM memory and other ULSI devices.

Fabrication of polysilicon plugs for deep-submicron contact-holes

Summary form only given. Contact holes with diameters down to 150 nm have been successfully plugged with polysilicon using a double-deposition low-pressure chemical vapor deposition (LPCVD) and double-phosphorus diffusion process. A 510 degrees C poly-Si deposition temperature was found to yield films with better contact-hole step coverage and lower resistivity than higher-temperature films. The contact resistance of 200-nm-diameter contact holes was measured to be below 100 Omega . This polysilicon plug process has been used for 64-MDRAM bit-line contacts.<<ETX>>

Effect of Nitrogen Diffusion in Ti and TiTiN Films for Future DRAM Bit Line Interconnects and Plugs

The effects of nitrogen diffusion from both N 2 gas phase and TiN solid phase sources on the characteristics of Ti/TiN bilayer and TiN/Ti/TiN trilayer films have been investigated in terms of both materials properties such as resistance, coloration, composition, and crystallinity, and prospective applications such as for DRAM bit line interconnections and contact-hole plugs. Using blank films it has been found, in coincidence with other work, that at the onset of N diffusion and hence low N concentrations within a Ti film, the sheet resistance increases and the Ti layer becomes a solid solution of N in hexagonal Ti. As the concentration increases, the sheet resistance reaches a maximum, after which it decreases abruptly and the structure becomes primarily tetragonal Ti 2 N phase. At higher concentrations the resistance stabilizes or increases slightly and the structure becomes more cubic TiN phase. Sheet resistances calculated from resistance measurements of Ti and TiN mono- and multilayer conductor lines with and without RTN and RTAr thermal treatments have shown that the conductor lines exhibit similar behavior to the blank films. In comparison with the mon-olayer lines, the multilayer ones are generally lower in resistance and more stable over a wider range of post-deposition process temperatures.