Thin Solid Films 343-314 (1999) 199-301 LPCVD deposition of silicon nitride assisted by high density plasmas L.S. Zambomb, R.D. Mansanoa, R. Furlana”‘, P. Verdonck” Abstract A low pressure chemical vapour deposition (LPCVD) reactor nv~s transformed into an inductively coupled plasma like plasma enhanced chemical vapour &position reactor by placing a coil at the inIet side of the &be and applying 13.56 MHz power to it. Silicon nitride Btns were deposited at 300°C in the plasma region, or at 720°C at the center of the tube, either without plasma or with a remote plasma. The &ns deposited in the plasma region have a high deposition rate, more than 2.5 times that of the deposition rate of films deposited without plasma. Their refractive index ranges from 1.5-1.5, increasing with the ammonium to dichlorosilane ratio, indicating a nitrogen rich film. Fourier Transform tnfrarrd Spectroscopy shows that at the higher ammonium lo dichlorosilane ratios, the number of Si-H bonds is as low as for stoichiometrk silicon nitride. Etching these films in 2% HF results in high etch rates ,2-30 rim/s. The wafers deposited at ‘720°C with rerno[e plasma show an increased deposition rate, compared to films deposited without plasma, and refractive index of approsimakly 2.00. CD 1999 Elsevier Science S.4. AI1 rights reserved. Kqwol-&; Low pressure chemical vapour deposition; Sitieon nitride: High density plasma 1. Introduction Silicon nitride thin fi11ns deposited by chemical vapow deposition 633) have been used as dielectric layers of metal-nitride-oxide-semiconductor (MNOS) devices [l], passivarion or intermetallic layers in metal-oxide-semicon- ductor field-effect-transistors IMOSFETs) [2], and gate dielectric of thin film transistors (TFTsl [3]. The deposition of silicon nitride films by low pressure chemical vapour deposition (LPCVD) is generally performed by using different compositions of dichlorosiiane (SiH$3) and ammonia (NH?) mixtures 141. Although the stoichiometry and properties of these films are very depen- dent on deposition conditions, they normally present a good thickness uniformity [5] and also low hydrogen concentra- tions. PECVD silicon nitride films, present in the form of SiH bonds, different gas compositions have been used. in&ding SiHi and N2 (or NF3j [73 and SiF4 and N1 [Sj. The mixtures including W3present a lower deposition rate than those using NH,, because the N3 molecule has a higher bonding energy than the NH? molecule 191. This fact makes the dissociation of W2kto active species more difficult; this led to the use of alternative processes, for example. Electron Cyclotron Resonance (ECR) [IO]. Inductively Coupled Plasmas (ICP), using a helicoidal resonator, have been used to increase the plasma density [ll], obtaining plasmas with 10” ions/cm’ and deposition rates as high as 1 ~rn/min [ 121. * Corresponding author. Tel.: + 55-11-818-5657; fax: + 55-1141% 5665. E-t~aii address: furlan@lsi.usp.br (R. Furlann) 0030~6090/99/$ - see front matter Q 1999 Elsevier Science S.A. -MiuI rights reserved, Another important technological approach, the plasma enhanced chemical vapour deposition (PECVD) process. uses the reaction between silane (SiH4j and F,XA [q. Its main advantage is the low deposition temperature (<4OO”C). However, an inherent disadvantage is the high hydrogen concentration in the film [6]. In order to minimze the hydrogen concentration in In this work, a LPCVD reactor was modified into an ICP- CVD system in order to combine the advantages of a deposi- tion with SiHlC12 and NH, (resuiting in a low concentration of WI bonds) with the activation by a high density plasma. Fig. 1. Reactor schematics. PE SOO40-6090(95)01587-9