Paper PS-TuP10
Stripe and Hole Shape Contacts Etch for Power Amplifier BICMOS Devices

Tuesday, October 16, 2007, 6:00 pm, Room 4C

Power amplifier applications of BICMOS devices need a specific contact module in order to support high current density and temperature. In order to achieve such performances, stripe-shaped contacts are designed for the bipolar transistor, while classic hole contacts are used for CMOS and the contact depth is increased to 1.5µm. Therefore, taking into account the topography of the bipolar and MOS structures, 5 different types of contacts must be opened. To fulfill these specifications, contacts etch process requires: - sharp profile to achieve high depth contacts; - high selectivity of oxide to nitride to safely land on emitter, gate and active areas; - low loading effects to achieve both stripe and hole contacts having the same critical dimension (CD). In this paper we focus on oxide etch process for contact opening developed on a MERIE industrial etcher using C5F8/ O2/ Ar chemistries. In a first time we characterize the oxide to nitride selectivity and the profile slope as a function of the C5F8/O2 ratio. Higher C5F8/O2 ratio favors selectivity, but degrades slope and CD, while lower C5F8/O2 ratio leads to sharp profile in the detriment of selectivity, therefore our approach consists in using a sequence of etching steps having different C5F8/O2 ratio. We demonstrate that this process solution enables us to achieve the above mentioned morphological constraints. Moreover, electrical tests performed on contact chains show that the resistivity and leakage results are in line with technology specifications.