Physical and Barrier Properties of PECVD Amorphous Silicon-Oxycarbide from Trimethylsilane and CO[sub 2]

Abstract

This work investigates the thermal stability and physical and barrier properties of amorphous silicon-carbide ͑␣-SiC͒ and amorphous silicon-oxycarbide ͑␣-SiCO͒ dielectric barriers deposited by plasma-enhanced chemical vapor deposition ͑PECVD͒ using trimethylsilane ͑3MS͒ precursor and He carrier gas. Films were deposited without and with various CO 2 flow rates. The dielectric constant of the ␣-SiCO films decreased with increasing CO 2 flow rate. Increasing CO 2 flow rate also promotes better thermal stability, higher breakdown field, lower leakage current, and superior resistance to Cu diffusion through the films. The improved barrier property is attributed to the denser and less porous structure of the ␣-SiCO dielectric barrier upon CO 2 addition. The ␣-SiCO barrier films deposited with the large ͑1200 sccm͒ CO 2 flow rate exhibit the low k value of 3.7, thermal stability up to 550°C, room-temperature breakdown field of 8 MV/cm and leakage current densities of 10 Ϫ7 to 10 Ϫ6 A/cm 2 at 3 MV/cm, and a superb Cu barrier property.To reduce the interconnect resistance-capacitance ͑RC͒ timedelay, a dominant factor in determining the performance of ultralarge scale integrated ͑ULSI͒ circuits, it is inevitable to use copper ͑Cu͒ metal to replace aluminum ͑Al͒ and its alloys in integrated circuits as the multilevel interconnect material and low dielectric constant ͑low-k͒ dielectric materials instead of the conventional SiO 2 film. Cu is the most suitable interconnect metal because of its low electrical resistivity and excellent electromigration resistance, and the use of low-k materials as the inter-and intra-layer dielectrics ͑ILD͒ can reduce the signal-propagation delay, crosstalk-noise between metal lines, and power dissipation of integrated circuits. While many low-k (k Ͻ 3) dielectric materials have been used as ILDs, high dielectric constant (k Ͼ 7) silicon nitride is still the primary candidate for the Cu cap-barrier and etching stop layer required in the Cu damascene structure. It is desirable to replace silicon nitride with dielectric materials of lower k value (k Ͻ 5) to further reduce the effective dielectric constant of the Cu interconnect system. In recent years, amorphous silicon-carbide ͑␣-SiC͒ and amorphous silicon-nitricarbide ͑␣-SiCN͒ deposited by plasmaenhanced chemical vapor deposition ͑PECVD͒ using organosilicate gases are receiving extensive attention for applications as Cu capbarrier and etching stop layer in Cu damascene structures because of their lower k value, better etching selectivity with respect to organosilicate glass ͑OSG͒, excellent chemical mechanical polishing ͑CMP͒ strength, and superb property as Cu barrier and passivation layer in terms of electromigration resistance and Cu hillock density. 1,2 There are studies on 3MS-based ␣-SiC and ␣-SiCN barriers which show k values in the range of 4 to 5, 1-5 while the ␣-SiCO barriers deposited using tetramethylsilane ͑4MS͒, hexamethydisiloxane ͑HMDSO͒ or trimethoxysilane ͑TMOS͒ precursor exhibit an even lower k value of 3.9. 6-8 Moreover, it ...

Highly Stable Ultrathin Carbosiloxane Films by Molecular Layer Deposition

“…The atomic concentration of C, Si, and O is 16.6 ± 0.4%, 27.6 ± 0.2%, and 55.8 ± 0.6%, respectively. Compared to carbosiloxane films deposited using other techniques, the carbon concentration of the MLD film is within the typical range of 10–30%; it is also higher than that of films grown by inductively coupled plasma CVD (ICPCVD) using bistrimethylsilylmethane and oxygen but lower than those made by PECVD using trimethylsilane and CO 2 . To conclusively exclude the possibility of the underlying SiO 2 /Si substrate contributing to the total apparent Si signal, the MLD carbosiloxane films were also deposited on substrates precoated with 18 nm Al 2 O 3 films grown by ALD.…”

“…Compared to carbosiloxane films deposited using other techniques, the carbon concentration of the MLD film is within the typical range of 10−30%; 4 it is also higher than that of films grown by inductively coupled plasma CVD (ICPCVD) using bistrimethylsilylmethane and oxygen 40 but lower than those made by PECVD using trimethylsilane and CO 2 . 41 To conclusively exclude the possibility of the underlying SiO 2 /Si substrate contributing to the total apparent Si signal, the MLD carbosiloxane films were also deposited on substrates precoated with 18 nm Al 2 O 3 films grown by ALD. Figure 3b To further explore the effect of O 3 exposure time on film growth, a series of ultrathin carbosiloxane films were deposited on Al 2 O 3 -coated substrates for 100 MLD cycles using different O 3 exposure lengths.…”

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

“…276,277 Recent studies have also indicated that dense a-SiCO:H dielectrics can also serve as Cu diffusion barriers with k values as low as 3.5. [51][52][53]55 Given that rapid Cu diffusion through SiO 2 and low-k a-SiOC:H with k values as high ∼ 2.9 have been previously reported, 273,278,279 the break point ECS Journal of Solid State Science and Technology, 4 (1) N3029-N3047 (2015)…”

“…Therefore, low-k forms of these materials were also needed to reduce the impact of the relatively high-k of PECVD a-SiN:H (k = 6.5-7.0). [41][42][43] The low-k DB/CCL/ES materials implemented to date have been primarily carbon doped silicon nitrides (a-SiNC:H) with k values of 4.5-5.8, [44][45][46][47][48][49][50][51] dense oxygen doped silicon carbides (a-SiCO:H) with k values of 4.0-4.8, [52][53][54][55][56][57][58] and pure silicon carbides (a-SiC:H) with k values of 4.0-7.0. [59][60][61][62][63][64][65][66] Similar to low-k ILDs, these materials have proven equally difficult and challenging to integrate with Cu interconnect fabrication processes.…”

Review—Beyond the Highs and Lows: A Perspective on the Future of Dielectrics Research for Nanoelectronic Devices

“…92,207 Since then, lower-k SiCN, SiOC, and SiC films with k as low as 4 have been demonstrated and adopted in the industry. [208][209][210][211][212][213][214] Recent experiments have also shown that high carbon content SiCH films with k as low as 3.2 may be suitable as next generation ES/DB materials. [215][216][217] However, there are scaling limits in k due to the need to maintain a dense enough material that can still function as a Cu diffusion barrier (DB) material as well as ES.…”