Effects of resist strip and clean on USJ performance

Metrology for Implanted Si Substrate Loss Studies

“…Photoresist removal on the ultrashallow implanted substrates requires nonetching chemistries to meet the strict substrate and dopant loss requirements. 2,3 For such plasma processes, the main and very likely the only mechanism for substrate loss is oxidation, i.e., chemical conversion of Si substrate into SiO 2 . With the SE model, we monitor thickness changes in i-Si and SiO 2 films before and after plasma treatment.…”

“…1 Traditional processes used for post-ion implantation photoresist strip require careful optimization, with the ultimate goal of pioneering functional cleaning processes that would cause minimal modifications such as dopant and substrate losses on ultrashallow junctions. 2,3 Finding means to monitor the effect of these processes, i.e., developing a metrology with sufficient accuracy and sensitivity, presents a great challenge itself. This is even more so when in-line monitoring is required because most of the methods used for characterizing shallow implants, such as secondary-ion mass spectrometry ͑SIMS͒ [4][5][6] and transmission electron microscopy ͑TEM͒, 7 are destructive, time consuming, and require tedious manual preparation.…”

“…So far, most of the SE-based substrate loss studies have been conducted on silicon-on-insulator ͑SOI͒ wafers, where substrate loss is monitored by measuring the change in thickness of the Si layer on top of the buried oxide layer directly. 2 The use of SOI wafers is the most convenient way to study substrate loss ͑because SE cannot measure substrate thicknesses͒ but can be quite expensive because of SOI wafer costs. It has been shown previously that implantation induces damage, resulting in greatly modified optical properties of the ion-implanted portion of the substrate.…”

Optimization of cleanliness and oxidation in plasma doped photoresist strip

“…Conventional oxidizing chemistries have been shown to undercut the photoresist crust, causing residues to fall onto the hot substrate where they harden and cause defects [3]. Aggressive wet cleans can remove these defects but conventional oxygen based ash chemistries are not compatible with USJ applications due to Si and metal consumption in oxidation.…”

Effluent Management for Non-Oxidizing Plasma Strip Processes

“…Optimization of the PR and residue removal process step after high-dose-implantation has become essential in order to preserve proper dopant activation and to avoid substrate loss and/or gate stack material modifications (1,2). As a result the industry has started to utilize non-oxidizing strip chemistries for these critical PR and residue removal steps, in replacement of the traditional oxidizing chemistries (3,4). However, the non-oxidizing chemistries, such as Forming gas (N 2 :H 2 ), lack the oxidizing species to efficiently remove the long chain polymers of the PR.…”