Control of Etch Slope during Etching of Pt in Ar/Cl₂/O₂ Plasmas

Abstract

Pt patterns of the 0.25 µ m design rule were etched at 20° C using a magnetically enhanced reactive ion etcher. The main problem of this device integration process is the redeposition of the etch products onto the pattern sidewall, making it difficult to reduce the pattern size. In both cases using a photoresist mask and an oxide mask, the redeposits of the etch products onto the sidewall were reduced by the addition of Cl2 to Ar, although the etch slope was lowered to 45°. Using the oxide mask, by adding O2 to the Cl-containing gas, the etch slope was increased up to 70°, and the redeposits were removed by an HCl cleaning process.

(Ba,Sr)TiO3 Thin Films for Dram’s

“…Pt and Ir do not form any volatile halogens; therefore etching these materials is primarily physical. Dry etching Pt results in either Pt "ears" from redeposition of Pt on the mask which is subsequently removed, or sloped sidewalls [102][103][104][105]. In general, some slope is required to avoid the formation of "ears".…”

“…In general, some slope is required to avoid the formation of "ears". Efforts to control the geometry of etched Pt features have focused have focused on etch gas chemistry [103][104][105] and plasma parameters [102]. Even with sloped sidewalls some wet clean is required to remove redeposits and the ease of removal is sensitive to etch chemistry.…”

Investigation of the gas pressure influence on patterned platinum etching characteristics using a high-density plasma

“…In this context, the plasma etching of platinum has been studied over the last few years using either rf capacitive discharges 3-11 or high-density plasma sources. [12][13][14][15][16][17][18][19] When the etching process is performed below 210°C, the main etching mechanism is sputtering, 17 which results in poor selectivity over resist, in the formation of fences even on micrometric features, and in shallow sidewall angles when fence-free profiles can be achieved. Recall that ''fence'' is a common term relating to redeposition of material on the sidewalls of the resist, which are left standing after the resist is removed.…”

Aqueous Cleaning of Sidewall Redepositions Formed by Reactive Ion Etching of Platinum

“…1 This process invariably produces sidewall redepositions (SRDs) or "fences" on the features. 2,3 It is believed that these residues contain Pt, PtCl x , PtO y , TiO 2 , and organic material.…”

“…5 Higher Cl 2 content in the dry etch gas mix results in SRDs which are soluble in dilute HCl solutions or water after etching and are soluble in 12 M HCl after oxygen plasma ashing. 1,4,9 The goal of this paper is to explain the process by which these SRDs can be removed using either a wet or a dry clean process. Wafers etched in an 80/20 Ar/Cl 2 gas mix to form patterned bottom platinum electrodes for an embedded DRAM-type (dynamic random access memory) application were obtained from Motorola.…”