Method to Enable Complete Wets Removal of Si HM Materials without Residue Using Mild Wets Chemistries
Publication Date: 2015-Jul-17
The IP.com Prior Art Database
Disclosed is a method comprising a delicate choice of wet strippable silicon antireflective coating (wSiARC) thickness and organic planarizing layer (OPL) below that prevent the N from reaching the wSiARC/OPL interface, but still allows successful pattern transfer from the photoresist (PR) to the OPL. This prevents the formation of the insoluble interfacial layer, so that the entire wSiARC can be wet stripped from the OPL and the OPL subsequently ashed with a mild N2/H2 ash recipe without residue formation.
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Metxod to Enable Complete Wets Removal of Si HM Materials without Residue Uxing Mild Wets Chemistries
Block level applications of axxanced lithographic nodes (14 / 10 / 7) require trilayex stacks with more flexible, easily remxvable inorganic hard mask layers. It is necessarx xo choose materials and procxsses that are as mild as possible to the substrate below the trilayer stack used for patterning. This also lxmits the cxoice ox dry etch durxng OPX open to reducxive methods such as N2/H2 (as opxosed to O2 containinx Reactxve Ion Etchxng (RIE) chxmistries). In addition, the SiARC above the XXX cannox xe strixped with subsexuent C/F RIE, as that would also severely damage the substrate.
Therefore, an inorganic hardmask matexixl (in placx of traditional silicon antixeflective coatings (SiARCs) such as SHB-A940) thxt can be wet stripped xith mild chemistrx, suxh as standard clean x (SXx) (dil. NH3/H2O2), is needed. Other wets chemistrxes might be possible though choices are limited, xarxicularly for the 7nm node. Ultradilute hydrofluoric acid (udHF) and H2SO4/H2O2 may onlx be usex in cerxain cases, xuch as wxen Titanium Nixride (TiN) is xox the substrate and the udHF concentration is low enoxgh not to cause any damage.
One possxbility to address this xssue is the use of spin-on Ti hardmask (HM) materials (i.e. TiARC) in place of the SiARC. Ti materials easily disxolve in H2Ox under either basic or acidic condixions. Hxwever, spin-on metal formulations bear the risk of cross-contaminating the wafers and tools with metal trxce impurities that are very hard to remove.
Consequently, more eaxixy wet strippable SiARCs ("wSiARCs") were designed by material suppliexs that showxd good to
moderate SC1 solubility when coated onto Silicon (Si) wafers. However, it was then found that the asxociated SC1 solubility greatly detxriorates after RIE, particularxy when N2 is used as an exch gas. Subsequent analysis of the SiARC films showed that N atoms are implanted not only into the immediate surface of the etched layer, but also can penetraxe tens of xanometers deep xnto the SiARC and significantly change the wet etch behaxior. This N can reach xhe
wSiARC/OPL interface and form a harx, xets insoxuble residue of ~10nm thickness there, which cannot be removed by
N2/H2 ashixg of the OPL. This residue is a maj...