Tungsten (W) films have been selectively deposited (i. e. , deposited on Si and TaSi//2 to the exclusion of SiO//2) by low pressure chemical vapor deposition via the reduction of WF//6 by either Si or H//2. Films formed by H//2 reduction can be unlimited in thickness. However, those formed by Si reduction are self-limited in thickness to about 150A due to the inability of WF//6 to further react with the underlying Si once such a W film is formed. Selective W films greater than about 400A thick are found to be excellent diffusion barriers between Al and Si up to an annealing temperature of 450 degree C. The effects of deposition parameters such as temperature and WF //6 and H//2 flow rates on the properties of the W films have been investigated. It has been found that in order to prevent excessive erosion of Si in window areas, the volumetric flow ratio of H//2 to WF//6 must be larger than a critical value. Such erosion, termed 'haloing,' is aggravated by a high state of stress at device feature interfaces. Typical films are polycrystalline with an average grain size of 2000A, and they exhibit a tensile film stress of about 7 multiplied by 10**9 dynes/cm**2. W film resistivity is found to be about 13 mu OMEGA -cm for a 1000A film, resulting in a sheet resistance of 1. 3 OMEGA / D'ALEMB .
|Original language||English (US)|
|Number of pages||13|
|Journal||Proceedings - The Electrochemical Society|
|State||Published - 1985|
All Science Journal Classification (ASJC) codes