Silicon cryo-etching of deep holes

Thomas Tillocher (1) , Remi Dussart (1) , Xavier Mellhaoui (1) , Philippe Lefaucheux (1) , Mohamed Boufnichel (2) , Pierre Ranson (1)

1 GREMI - Groupe de recherches sur l'énergétique des milieux ionisés
2 ST-CROLLES - STMicroelectronics [Crolles]

The cryogenic process is used to drill 400 um thick silicon wafers. It is first studied on single side masked substrates. Holes of 14 um in diameter are 210 um deep after 30 min, representing an average etch rate as high as 7 um/min. This process enables the drilling of holes of 12 um in diameter within 1 h 06 min. We investigate the effect of the substrate temperature and show that the process is very sensitive to this parameter. It is the main issue in cryo-etching. We use a recent cryogenic chuck with a good temperature uniformity. This last point was characterized using a new method we developed. It is based on the dependencies of columnar microstructures dimensions on the temperature. We have shown that the maximum temperature variation is less than 2 C on the cryogenic chuck.

Domaines: Physique des plasmas [physics.plasm-ph]

Thomas Tillocher, Remi Dussart, Xavier Mellhaoui, Philippe Lefaucheux, Mohamed Boufnichel, et al.. Silicon cryo-etching of deep holes. Microelectronic Engineering, 2007, 84, pp.1120. ⟨10.1016/j.mee.2007.01.148⟩. ⟨hal-00365907⟩