CVD Products - Materials

APPLICATIONS    MATERIALS    SYSTEMS

Tungsten silicide (WSi_x)
Genus' initial product offering was tungsten silicide. Tungsten silicide is used as a conductor, most frequently to shunt the polycrystalline silicon lines to produce a more conductive and hence faster line. Tungsten silicide films provide an advantage of withstanding additional high-temperature deposition steps as tungsten silicide will oxidize only slightly in an oxidizing ambience and will not be destroyed as other silicide films might. Actually, tungsten silicide oxidizes in a manner similar to the oxidation of polysilicon.

Tungsten silicide can be deposited by various means; one is using monosilane with tungsten hexafluoride (WF₆) as source gases. Later evolution of tungsten silicide CVD is the use of dichlorolsilane (DCS) as a reactant. The use of DCS eliminates much of the fluorine incorporation into the film and provides greater gate stability. Both of these methods deposit a non-stoichometric tungsten silicide that converts to a lower resistivity stoichometric film after normal anneals.

METAL FILMS
Tungsten (W)
Genus was one of the first companies to provide chemical vapor deposition of metallic Tungsten films. Tungsten was initially used as low resistance large area contacts for source/drain contacts and also for low conductivity poly shunts prior to the use of tungsten silicide.
Tungsten is commonly deposited through the reaction of tungsten hexafluoride and hydrogen (H₂). This reaction forms metallic tungsten of low resistivity. In tungsten depositions there is sometimes included an initial reaction of tungsten hexafluoride with silane to minimize or eliminate any attack of the silicon surface or of any initiating film surface most commonly titanium nitrate (TiN). Today, tungsten films are most commonly used to form tungsten plugs. These plugs are low conductivity connections between levels of conductor layers in the integrated circuit. Because tungsten's conductivity is higher than that of aluminum or copper, tungsten is not generally used for large scale interconnect circuits other than local interconnect circuits in the early levels of metalization. Usually it is used within a "Damascene Process" where the tungsten film is deposited into a hole or trench and then the "above ground" excess is removed through a process of Chemical Mechanical Planarization (CMP). The final result is a conductive tungsten filled trench.

Tungsten Nitride (WN)
Tungsten nitride (WN) is another film used for conductive layers or barrier layers within integrated circuit manufacturing. Its use is not as common as pure tungsten films or titanium nitride films but appears to have much promise in the future as geometries shrink. It provides compatibility for applications using barriers in layers of W/WN and WSi_x / WN.