Method for depositing a tungsten layer on silicon

A process for forming a tungsten metal layer on a polycrystalline silicon layer, said process comprising the steps of:

• providing a substrate having a polycrystalline silicon layer deposited thereon, said polycrystalline silicon layer having an exposed surface;
• longing a tungsten nitride layer via plasma chemical vapor deposition using, as precursor compounds, WF.sub.6 and a nitrogen-containing compound selected from the group consisting of N.sub.2 and NH.sub.3, said tungsten nitride layer covering said exposed surface, and acting to restrict an upward flow of mobile silicon atoms from said polycrystalline silicon layer;
• and
• depositing a tungsten metal layer on top of said tungsten nitride layer.

A process for forming a tungsten metal layer on a polycrystalline silicon layer, said process comprising the steps of:

• providing a substrate having a polycrystalline silicon layer deposited thereon, said polycrystalline silicon layer having an exposed surface;
• forming a titanium carbonitride barrier layer on said exposed surface by pyrolizing an organometallic compound genetically described as tetrakis-dialkylamido-titanium at a temperature within a range of 200.degree. to 600.degree. C. in a chemical vapor deposition chamber in which pressure has been reduced to less than 100 torr;
• reducing the carbon content of the deposited barrier film by performing a rapid thermal anneal step in the presence of ammonia;
• and
• depositing a tungsten metal layer on top of said barrier layer.

A process for forming a tungsten metal layer on a polycrystalline silicon layer, said process comprising the steps of:

• providing a substrate having a polycrystalline silicon layer deposited thereon, said polycrystalline silicon layer having an exposed surface;
• forming a titanium carbonitride barrier layer on said exposed surface by pyrolizing an organometallic compound generically described as tetrakis-dialkylamido-titanium at a temperature within a range of 200.degree. to 600.degree. C. in a chemical vapor deposition chamber in which pressure has been reduced to less than 100 torr;
• reducing the carbon content of the deposited barrier film by subjecting the barrier film to a plasma generated from one or more of the gases selected from the group consisting of nitrogen gas and ammonia gas;
• and
• depositing a tungsten metal layer on top of said barrier layer.

A process for forming on a silicon substrate partially covered by field isolation regions a conductive sandwich structure from which gate electrodes and interconnect lines can be patterned, said process comprising the steps of:

• forming a gate oxide layer on each portion of the substrate not covered by field isolation regions;
• depositing a polycrystalline silicon layer which completely covers the field isolation regions and the gate oxide layers, said polycrystalline silicon layer having an upper surface;
• forming a barrier layer over the entire upper surface of said polycrystalline silicon layer by depositing a preliminary tungsten metal layer on said upper surface and converting at least a portion of said preliminary tungsten metal layer to tungsten nitride, said barrier layer being impermeable to mobile silicon atoms within said polycrystalline layer;
• and
• depositing a final tungsten metal layer which completely covers said barrier layer.

A process for forming on a silicon substrate partially covered by field isolation regions a conductive sandwich structure from which gate electrodes and interconnect lines can be patterned, said process comprising the steps of:

• forming a gate oxide layer on each portion of the substrate not covered by field isolation regions;
• depositing a polycrystalline silicon layer which completely covers the field isolation regions and the gate oxide layers, said polycrystalline silicon layer having an upper surface;
• forming a barrier layer on top of the entire upper surface of said polycrystalline silicon layer via chemical vapor deposition, said barrier layer being selected from the group consisting of tungsten nitride, titanium nitride, titanium carbonitride, platinum nitride, palladium nitride, cobalt nitride, molybdenum nitride, nickel nitride, rhodium nitride and iridium nitride, said metal nitride layer being impermeable to mobile silicon atoms within said polycrystalline layer;
• and
• depositing a tungsten metal layer which completely covers said barrier layer.