METHOD OF DEPOSITING SI CONTAINING CARDON OVERCOAT
Original Publication Date: 1999-Dec-01
Included in the Prior Art Database: 2003-Jun-19
A method of fabricating thin film containing Si, hydrogen and carbon is disclosed here. The thin film coating thus obtained combines both physical vapor of Si and chemical vapor of carbon and hydrogen to provide the best step coverage and durability for protective coating applications; in particular the head-disk interface (HDI in a hard disk drive (HDD) where the very thin coating thickness is demanded. In order to obtain a good protective coating by vacuum deposition technique, it is important to rely on chemical vapor for step coverage and physical vapor to provide mechanical strength of the coating. It is disclosed that the Si containing carbon overcoat can be obtained by either DC or RF sputtering of a Si target in a mixture of Ar and CH4 gases. The role of Si in the film is to provide adhesion to the under lying substrate and to enhance the mechanical strength of the film. Films deposited using 10% CH4 (balance of Ar) were fabricated. Depending on the sputtering target power levels, the resultant film could contain less than 1% Si to up to 35% Si. The hydrogen concentration is less sensitive to power level and is around 35-40%. The film stress also varies with film composition; higher Si content typically shows higher stress, implying harder films. 100 Angstrom thick films with four different compositions were tested against contact start stop (CSS) test for durability. Films with little Si show adhesion failure; however with 9% Si, 52% carbon and 39% hydrogen the coating performs much better than typical C:H film with Si adhesion layer. The higher Si containing (31%) shows frictional coefficient increase in the early stage of the test, likely due to insufficient carbon in the film. On the corrosion protection test, it was found that all four films behave similarly and much better than the C:H film. The pin-hole density count after the test was less than 10% compared to more than 30% of a typical C:H film on the same substrate. In summary, it is disclosed that Si containing carbon overcoat can be fabricated by combining Si physical vapor and CHx chemical vapor deposition. The resultant film can possess the best step coverage, thus corrosion protection, from the chemical vapor source and the best mechanical durability resulted from the physical vapor deposition.