Plasma-enhanced chemical vapor deposition of a-SiC:H films from organosilicon precursors

Abstract

A study of the growth of a-SiC:H films by plasma-enhanced chemical vapor deposition (PECVD) from two organosilicon precursors, silacyclobutane (H2CH2SiCH2CH2 or SCB) and methylsilane (CH3SiH3), is described. A capacitively coupled, parallel plate PECVD system was used to grow films at 250 °C and deposition pressure of 2.0 Torr. Standard (13.56 MHz) and low frequency (0.125 MHz) rf sources were used to generate the deposition plasma. Depositions were performed with and without argon dilution (neat) of the precursor. We report some of the first process/property relationships for organosilicon based a-SiC:H films grown using a fixed, controlled set of deposition conditions. Included are data on film composition, structure, dielectric constant and stress. Films deposited from silacyclobutane had much higher carbon concentrations than those deposited from methylsilane, but in both cases the carbon fraction in the film was lower than that in the precursor. It is found that the plasma drive frequency has a stronger influence on film composition than argon dilution of the precursor during deposition. The low frequency plasma significantly increases the film growth rate for the neat precursor process. Depending on the growth process, the relative dielectric constants of the a-SiC:H films ranged from 3.6 to 8.7. The variation of the dielectric constant over the frequency range 0.1–1000 kHz was negligible. All measured film stress was compressive and ranged from 0.1 to 1.0 GPa depending on precursor and plasma frequency. Films deposited from a 10% organosilicon/90% argon mixture showed higher dielectric constants, higher refractive indices and less bound hydrogen when compared to neat organosilicon precursor depositions. The films exhibited excellent oxidation resistance and could not be etched in 6:1 buffered HF solutions. The properties of the a-SiC:H films are compared to PECVD hydrogenated silicon nitride and discussed in the context of applications requiring low temperature deposited protective dielectric coatings.

Properties of Amorphous Hydrogenated Silicon Carbide (a‐SiC:H) Films Formed by Remote Hydrogen Microwave Plasma CVD From a Triethylsilane Precursor: Part 2

“…Density (r), refractive index (n), hardness (H), and elastic modulus (E) of a-SiC:H films produced on c-Si substrates from various organosilicon precursors by different CVD techniques. 800 --33 250 [17] Trimethylsilane (TrMS) Me 3 SiH RHP-CVD 300 2.02 1.74 -- [16] Hexamethyldisilane (HMDS) (Me 3 Si) 2 RHP-CVD 300 1.80 1.84 22 - [12] (Dimethylsilyl)(trimethylsilyl)-methane (DTMSM) Me 2 HSiCH 2 SiMe 3 RHP-CVD 300 1.62 1.88 30 238 [14] Tetrakis(trimethylsilyl)silane (TMSS) (Me 3 Si) 4 Si RHP-CVD 300 -2.09 -- [8,9] Tetramethylsilane (TMS) Me 4 Si P-CVD 400 --18 147 [4] Silacyclobutane (SCB) P-CVD 175 1.71 2.18 18 146 [1,2] Silacyclobutane (SCB) P-CVD 600 2.37 -46 241 [1] Fig. 6.…”

“…These a-SiC:H thin film coatings can effectively be fabricated from a number of volatile organosilicon precursors by plasma CVD techniques which include conventional (or direct) plasma (P)CVD, [1][2][3][4][5][6] as well as remote hydrogen plasma (RHP)CVD. [7][8][9][10][11][12][13][14] In view of the results of our earlier studies [7][8][9][10][11][12][13][14] the latter technique is particularly beneficial for the formation of high quality aSiC:H films with unique properties.…”

Micro‐ and nanomechanical structures for silicon carbide MEMS and NEMS

“…From a practical standpoint, a lowered dielectric constant prohibits cross-talk and capacitive coupling between parallel circuits. In the case of PECVD a-SiC, most k values found in the literature are 5 or lower [111,126,127], although it has been reported to be as high as 8.7 [120] and 14 [119]. These values appear to depend on the parametric combination of precursor gas chemistry and RF plasma frequency (125-100 kHz in the studies).…”

“…Relatively low hardness values (4 GPa to 7 GPa) were reported for films deposited by high energy ion beam deposition [119]. By comparison, it has been reported that the hardness of a-SiC films deposited by PECVD at 175 °C using silacyclobutane (SiC 3 H 8 ) was ~17.5 GPa [120]. In contrast, films deposited at the same temperature using SiH 4 and methane (CH 4 ) as precursors had hardness values of 10 GPa, which could be increased by up to 25% by annealing [121].…”

“…Previously reported work in PECVD of a-SiC:H has focused on synthesis using the following precursors: SiH 4 and CH 4 [125,129,[139][140][141][142], SiH 4 and ethylene (C 2 H 4 ) [116], methylsilane ((CH 3 )SiH) [120], trimethylsilane ((CH 3 ) 3 SiH) [128,143], methyltrichorosilane (CH 3 SiCl 3 , MTS) [121,144], hexamethyldisilane (C 6 H 18 Si 12 , HMDS) [117,138,145], and silacyclobutane (SiC 3 H 8 , SCB) [120,142]. CVD-based deposition processes that have been used to deposit a-SiC films include high-density plasma CVD (HDPCVD) [126], electron cyclotron resonance CVD (ECRCVD) [146] …”