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Frontiers of Chemical Science and Engineering

Front. Chem. Sci. Eng.    2019, Vol. 13 Issue (3) : 511-516
Low-k integration: Gas screening for cryogenic etching and plasma damage mitigation
Romain Chanson1(), Remi Dussart2, Thomas Tillocher2, P. Lefaucheux2, Christian Dussarrat3, Jean François de Marneffe1
1. IMEC v.z.w., 3001 Leuven, Belgium
2. GREMI/University of Orleans, Orleans, France
3. Air Liquide Laboratories, Tsukuba, Japan
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The integration of porous organo-silicate low-k materials has met a lot of technical challenges. One of the main issues is plasma-induced damage, occurring for all plasma steps involved during interconnects processing. In the present paper, we focus on porous SiOCH low-k damage mitigation using cryogenic temperature so as to enable micro-capillary condensation. The aim is to protect the porous low-k from plasma-induced damage and keep the k-value of the material unchanged, in order to limit the RC delay of interconnexion levels while shrinking the microchip dimension. The cryogenic temperature is used to condense a gas inside the porous low-k material. Then, the etching process is performed at the temperature of condensation in order to keep the condensate trapped inside the material during the etching. In the first part of this work, the condensation properties of several gases are screened, leading to a down selection of five gases. Then, their stability into the porous structure is evaluated at different temperature. Four of them are used for plasma damage mitigation comparison. Damage mitigation is effective and shows negligible damage for one of the gases at –50°C.

Keywords low-k      nanotechnology      micro-electronics      cryo-etching      plasma processing     
Corresponding Authors: Romain Chanson   
Just Accepted Date: 28 May 2019   Online First Date: 25 July 2019    Issue Date: 22 August 2019
 Cite this article:   
Romain Chanson,Remi Dussart,Thomas Tillocher, et al. Low-k integration: Gas screening for cryogenic etching and plasma damage mitigation[J]. Front. Chem. Sci. Eng., 2019, 13(3): 511-516.
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Romain Chanson
Remi Dussart
Thomas Tillocher
P. Lefaucheux
Christian Dussarrat
Jean François de Marneffe
Fig.1  Correlation of the evolution of ΔT, the difference between condensation temperature of different gases into SOG-2.2 and the temperature associated to the partial pressure of a gas, and contact angle of the different molecules on OSG-2.55
Fig.2  Stability of (a) HBPO and Sumida, (b) Mikado and Akita. Full symbol is the RI after condensation and before pumping out of gas, open symbols show the RI 5 min after pumping out the reagent
Fig.3  Full symbols: Average etch rate measured as a function of the substrate temperature with the different reagents. Open symbols correspond to the damage depth estimated by the method of EDL, plasma conditions were Q(SF6/X) = 30/4 sccm, p = 22.5 mTorr. Prf = 500 W, PDC = 150 W bias. The temperature is indicated in the figure (X still represents one of the reagent)
Fig.4  k-value of the SOG-2.2 films after etching at different temperatures with the different reagents
Reagent Condensation temperature/°C SA/°C Etch rate/nm·min–1 a) EDL/nm b) k value c)
HBPO –20 20 (–35 → –50) 78 0 2.55
Sumida –40 10 (–50 → –60) 58 13 2.71
Mikado –30 5 (–45 → –50) 55 19 2.59
Akita –50 0–5 (–65 → –70) 96 29 3.24
Tab.1  Bests reagents found for plasma etching damage mitigation in SOG-2.2 as low-k (average pores Ø = 2.8 nm)
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