AVS 45th International Symposium
    Manufacturing Science and Technology Group Monday Sessions
       Session MS-MoA

Paper MS-MoA6
Influence of Wafer Back Surface Finish on Dry Etching Characteristics

Monday, November 2, 1998, 3:40 pm, Room 317

Session: Contamination Free Manufacturing
Presenter: S. Muramatsu, NEC Corporation, Japan
Authors: S. Muramatsu, NEC Corporation, Japan
K. Ando, NEC Corporation, Japan
H. Nanbu, NEC Corporation, Japan
H. Miyamoto, NEC Corporation, Japan
T. Kitano, NEC Corporation, Japan
Correspondent: Click to Email
Process tolerance and controllability have become more severe with the scaling down and integration of devices. Wafer back surface finish is a factor affecting the process conditions such as dry etching and rapid thermal annealing. In this study, the correlation between back surface roughness and dry etching characteristics was investigated. The back surface roughness was changed from Ra=0.41 nm to 50.1 nm by final back surface treatments (mechanochemical polishing or chemical etching). Contact-hole etching with CHF@sub 3@ gas was performed for interlayer CVD oxide deposited on the front surface of wafers. The etching rate for a smooth back surface (0.41 nm) was increased by 1.1 times over that for a rough back surface (50.1 nm). During contact-hole etching, the wafer temperature of the smooth back surface was10°C lower than that for the rough back surface. This is due to the difference in electrostatic chucking (Ra=80-120nm) force during contact-hole etching. When the smooth back surface wafer was used, the adhesion area between the dry-etching stage and the wafer back surface increased because the back surface roughness was small. Consequently, the wafer can be cooled down sufficiently and the etching rate dominated by gas absorption was increased. As well as the etching rate, the position where residual gas was deposited inside the contact hole was governed by the degree of the wafer back surface finish. These experimental results indicate that the roughness of the wafer back surface should be well controlled for fabricating advanced devices.