Low-<i>k</i> integration: Gas screening for cryogenic etching and plasma damage mitigation

doi:10.1007/s11705-019-1820-5

Front. Chem. Sci. Eng.

2019, Vol. 13

Issue (3) : 511-516 https://doi.org/10.1007/s11705-019-1820-5

RESEARCH ARTICLE

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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Abstract

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 Author(s): 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.

URL:

https://academic.hep.com.cn/fcse/EN/10.1007/s11705-019-1820-5
https://academic.hep.com.cn/fcse/EN/Y2019/V13/I3/511

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. P_rf = 500 W, P_DC = 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

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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