Analyses of chamber wall coatings during the patterning of ultralow-k materials with a metal hard mask: Consequences on cleaning strategies

Abstract

Articles you may be interested inResidue growth on metallic-hard mask after dielectric etching in fluorocarbon-based plasmas. I. MechanismsLow temperature remote plasma cleaning of the fluorocarbon and polymerized residues formed during contact hole dry etching Changes in chamber wall conditions ͑e.g., chemical surface composition͒ are identified as one of the main causes of process drifts leading to changes in the process performance ͑etch rates, etch profiles, selectivity, uniformity, etc.͒. The impact of a metal hard mask on the coating formed on the chamber walls during the dielectric etching process and reactor dry cleaning procedure has been investigated. The authors have used a technique based on x-ray photoelectron spectroscopy to monitor the chemical composition of the layer deposited on an electrically floating sample placed on the top of a patterned wafer exposed to typical plasma processing conditions ͑coatings deposited on the floating sample are representative of those deposited on the chamber walls͒. They have patterned porous SiOCH damascene structures using a TiN hard mask. After hard mask opening in a silicon etcher using Cl 2 based plasmas, they have shown that the chamber walls are coated by a thin SiOCl coating containing small concentrations of Ti. After photoresist ashing in the same etcher ͑with an O 2 plasma͒, the chamber wall coating is oxidized leading to the formation of a mixed SiO x -TiO x deposit. The cleaning strategy to remove this coating from the chamber walls consists in using a two step cleaning procedure: ͑1͒ a Cl 2 based plasma ͑Ti removal͒, followed by ͑2͒ a SF 6 /O 2 plasma ͑SiOCl species removal͒. During low-k etching in an oxide etcher with a fluorocarbon based chemistry, the chamber walls are coated by a fluorocarbon layer containing a significant concentration of Ti. They have developed a two step cleaning procedure: ͑1͒ a SF 6 plasma to remove the fluorocarbon layer and Ti based species and ͑2͒ an O 2 flash plasma ͑for a short time͒ to clean up the chamber walls from the remaining carbon.

Impact of low-k structure and porosity on etch processes

“…This chamber was installed on an experimental cluster located in a class 10 cleanroom. 53 After etching, the 200 mm diameter wafer was transferred under vacuum environment to the XPS via a transfer chamber 54 and/or to the vacuum spectroscopic ellipsometer. 51 For all etch processes, the magnetic field was kept constant at 20 G. More information about the experimental setup is supplied in previous works.…”

Mechanisms of porous dielectric film modification induced by reducing and oxidizing ash plasmas

“…However, by using a simple technique developed by Joubert et al, we can get some interesting information on the respective roles of ions and neutrals on the film modification in the RIE chamber. 23 Since the ions bombarding the sample have an energy of e͑V p -V f ͒, where V p is the plasma potential and V f the floating potential, typically a few tens of eV, the raised hp-SiOCH coupon withstands identical plasma conditions as the stuck coupon, excepting that the ion energy is much lower. The piece of sample can then be stuck ͑directly on the wafer͒ or raised ͑surelevated͒ onto a 200 mm diameter SiO 2 wafer.…”

Patterning of narrow porous SiOCH trenches using a TiN hard mask

“…The TiN hard mask opening is carried out in the DPS TM plasma etcher at a cathode temperature of 50°C. Before each process, a cleaning process (a Cl 2 plasma followed by a SF 6 /O 2 plasma) and a conditioning process are performed on a blanket silicon wafer in order to get reproducible etching conditions from wafer to wafer [11]. After TiN opening, the remaining photoresist is removed in an oxygen-based plasma.…”

“…The fluorinated TiN surface results from the synergy between the fluorine reactive species and the ion bombardment, leading to the formation of TiF x etch by-products in the plasma. Depending on the volatility of TiF x species, they are either pumped out of the plasma chamber or redeposited on any surface exposed to the plasma (chamber walls and wafer [11]). The volatility of TiF x compounds depends on the wafer temperature and on the number of fluorine atoms into the TiF x molecule.…”