Quantitative characterization of pore stuffing and unstuffing for postporosity plasma protection of low-k materials

Abstract

Residue growth on metallic hard mask after dielectric etching in fluorocarbon based plasmas. II. SolutionsThe problem of k-value degradation (plasma damage) is a key issue for the integration, and it is becoming more challenging as the dielectric constant of low-k materials scales down. One way to circumvent this issue is temporarily conversion of low-k material from a porous to a dense state by filling the pores with a sacrificial polymer after the deposition and curing of the low-k material. A detailed process scheme for the pore stuffing and postetch polymer removal of PMMA is described in this work. The filling temperature was optimized according to the molecular weight of the PMMA. To remove the polymer after plasma-etching in a purely thermal environment, a temperature of at least 430 C had to be applied. Annealing assisted by variable frequency microwaves could remove the polymer already at 380 C and with a He-H 2 afterglow plasma the polymer could be removed at 280 C. Laser annealing allowed the removal at a stage temperature of 200 C with an only surface-limited heating of about 500 C and higher to prevent the FEOL structures from damage. This work presents the results of the detailed study of stuffing and unstuffing processes, discusses mechanisms, and provides background for a robust stuffing and polymer removal process for the plasma damage reduction in porous low-k dielectrics.

Improved Plasma Resistance for Porous Low-k Dielectrics by Pore Stuffing Approach

“…5, confirming our previous conclusion based on FTIR characterization. For non-protected samples, the κ-value degrades faster with C-free plasmas (SF 6 and NF 3 gas discharges). With pore stuffing, the k value degradation is significantly reduced for all the recipes.…”

“…Evaluation details including spectrum and elemental analysis were discussed in complementary paper (Ref. 6). Table I shows the properties of pristine and PMMA stuffed samples, which will be used for plasma resistance tests.…”

Stuffing-enabled surface confinement of silanes used as sealing agents on CF4 plasma-exposed 2.0 p-OSG films

“…The pore stuffing process consists of (i) densification of the porous low-k film by wet stuffing with a sacrificial polymer filling agent (PMMA); (ii) CF 4 plasma etch; and (iii) a thermal burnout process at 450°C for 15 min in N 2 ambient to remove the PMMA. It has been observed that the plasma-induced Si-CH 3 depletion is significantly reduced via pore stuffing and that the silanol groups can be confined to the top surface of the porous film [14]. Afterwards, a wet cleaning procedure was applied in order to remove the post-etch polymer residues and to make the surface more hydrophilic.…”

“…Low-k etch was then performed using a CF 4 plasma. PMMA was selected as the pore stuffing chemistry because it decomposes thermally without leaving residues behind (no C@C sp2 formation) [14]. The pore stuffing process consists of (i) densification of the porous low-k film by wet stuffing with a sacrificial polymer filling agent (PMMA); (ii) CF 4 plasma etch; and (iii) a thermal burnout process at 450°C for 15 min in N 2 ambient to remove the PMMA.…”

“…In this work, we adapt a new pore stuffing approach during plasma etching which helps to limit the hydrophilic layer thickness [13,14]. With this approach, the SAMs distribution inside the pores is confined to the surface and the sealing ability against tetrakis(dimethylamino)titanium (TDMAT) ALD precursor has been demonstrated.…”