Mechanisms for plasma etching of HfO2 gate stacks with Si selectivity and photoresist trimming

Abstract

Articles you may be interested inComparison of the effects of downstream H2-and O2-based plasmas on the removal of photoresist, silicon, and silicon nitride Effect of high-frequency variation on the etch characteristics of ArF photoresist and silicon nitride layers in dual frequency superimposed capacitively coupled plasmaa) Plasma enhanced chemical vapor deposition Si-rich silicon oxynitride films for advanced self-aligned contact oxide etching in sub-0.25 μm ultralarge scale integration technology and beyondTo minimize leakage currents resulting from the thinning of the insulator in the gate stack of field effect transistors, high-dielectric constant ͑high-k͒ metal oxides, and HfO 2 in particular, are being implemented as a replacement for SiO 2 . To speed the rate of processing, it is desirable to etch the gate stack ͑e.g., metal gate, antireflection layers, and dielectric͒ in a single process while having selectivity to the underlying Si. Plasma etching using Ar/ BCl 3 / Cl 2 mixtures effectively etches HfO 2 while having good selectivity to Si. In this article, results from integrated reactor and feature scale modeling of gate-stack etching in Ar/ BCl 3 / Cl 2 plasmas, preceded by photoresist trimming in Ar/ O 2 plasmas, are discussed. It was found that BCl n species react with HfO 2 , which under ion impact, form volatile etch products such as B m OCl n and HfCl n . Selectivity to Si is achieved by creating Si-B bonding as a precursor to the deposition of a BCl n polymer which slows the etch rate relative to HfO 2 . The low ion energies required to achieve this selectivity then challenge one to obtain highly anisotropic profiles in the metal gate portion of the stack. Validation was performed with data from literature. The effect of bias voltage and key reactant probabilities on etch rate, selectivity, and profile are discussed.

Review and future perspective of feature scale profile modeling for high-performance semiconductor devices

“…Their models were actively adopted to predict feature scale profiles of planar-type Si gate, Si fin of FinFET, trench, and hole etching for various kinds of films and plasmas such as Si (Cl 2 ∕Ar mixture), SiO 2 , SiN (C 2 F 6 , CHF 3 , and C 4 F 8 ∕O 2 ∕Ar mixtures), SiOCH (He∕H 2 and Ar∕O 2 mixtures), and HfO 2 (Ar∕BCl 3 ∕Cl 2 and Ar∕O 2 mixtures). [51][52][53][54][55][56][57][58][59] As for HARC etching, the mechanism of the 3D SiO 2 HARC feature distortion during C 4 F 8 ∕O 2 ∕Ar plasma etching with a CCP reactor was discussed in the cases of symmetric and asymmetric patterns (AR ¼ 40) considering the charging effect caused by ion scattering and charge mobility on the pattern surface with the polymer. 60 The radius and depth, including the photoresist mask of the HARC pattern, were 25 and 2670 nm, respectively.…”

“…Their models were actively adopted to predict feature scale profiles of planar-type Si gate, Si fin of FinFET, trench, and hole etching for various kinds of films and plasmas such as Si (Cl2/Ar mixture), SiO2, SiN (normalC2normalF6, CHF3, and normalC4normalF8/normalO2/Ar mixtures), SiOCH (He/normalH2 and Ar/normalO2 mixtures), and HfO2 (Ar/BCl3/Cl2 and Ar/normalO2 mixtures) 51 – 59 As for HARC etching, the mechanism of the 3D SiO2 HARC feature distortion during normalC4normalF8/normalO2/Ar plasma etching with a CCP reactor was discussed in the cases of symmetric and asymmetric patterns (…”

Advanced simulation technology for etching process design for CMOS device applications

“…They demonstrated surface roughening and rippling during Si etching by Cl plasmas by considering the surface reactions in detail and proposed a mechanism for these reactions that take into account the variations in ion incident angle and gas flux ratio. Kushner and coworkers [58][59][60][61][62][63][64] have developed 2D models, not only for Si and SiO 2 films, but also for other kinds of films such as low-k (SiOCH) and metal (TiN=HfO 2 ) films using the gas and vacuum ultraviolet (VUV) radiation fluxes that were derived from the HPEM and showed the etched profiles as functions of the etching parameters in detail. 3D simulations of contact etching by the Bosch process, in which the cycles of etching and deposition are repeated, have also been proposed using a voxel model by Ertl and Selberherr, 70) and Sun et al 71) There are several other researchers on 3D feature scale profile simulations for Si and SiO 2 etching, including Kawai, 72) Moroz, 73) and Zhang and Kushner.…”

Highly selective etching of LaAlSiOxto Si using C4F8/Ar/H2plasma

“…So far, many studies has been made on achieving high selectivity of high-k materials to SiO 2 and Si. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Among them, BCl 3 -based plasma has been extensively studied with various high-k materials such as HfO 2 4,7,[10][11][12] and ZrO 2 14,16,17) to obtain the high etch selectivity of high-k materials to SiO 2 and Si. The mechanism of highly selective etching of high-k materials to Si and SiO 2 using BCl 3 plasma is considered to be as follows.…”

“…As a consequence, high etch selectivity of high-k materials to Si and SiO 2 is achieved in BCl 3 plasma. 7,[10][11][12]16) Concerning Hf-or Zr-based conventional high-k materials, many studies have been reported, as mentioned above. However, for lanthanum compounds, only a few studies have so far been carried out, although it has been reported that lanthanum compounds are difficult-to-etch materials.…”