| AVS 59th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuA |
| Session: | Materials and Processes for Advanced Interconnects |
| Presenter: | N. LiCausi, GLOBALFOUNDRIES |
| Authors: | N. LiCausi, GLOBALFOUNDRIES V. Kamineni, GLOBALFOUNDRIES S. Ohsiek, GLOBALFOUNDRIES, Germany H. Geisler, GLOBALFOUNDRIES, Germany M. Weisheit, GLOBALFOUNDRIES, Germany M. Majer, GLOBALFOUNDRIES, Germany E.T. Ryan, GLOBALFOUNDRIES |
| Correspondent: | Click to Email |
SiCOH films have been used in advanced semiconductor devices to enable continued scaling of interconnect integration. The further scaling of ultra low k-value (ULK) films has necessitated a move to porous SiCOH films. Porosity is intentionally introduced to decrease the dielectric k-value and therefore reduce interconnect RC delay. However, this porosity also leads to reduced mechanical strength and presents substantial challenges to integration and packaging.
Nanoporous thin films can be formed with PECVD of a SiCOH film with embedded porogen clusters. The porogen can either be supplied by a second porogen precursor or using a single precursor containing an embedded porogen fragment. The porogen is then removed with curing. Currently the industry favors UV assisted thermal curing to simultaneously drive out porogen (forming the porous structure) and enable cross-linking of the film matrix (Si-O-Si bond formation). However, prior investigation claims that this porogen is not completely removed, leaving porogen residue in the pores [1]. It is believe that cross-linking of the film matrix inhibits porogen removal and inversely, porogen residue prevents efficient cross-linking. Subsequently, this can lead to degraded electrical and mechanical performance.
A new approach under review uses a two-step curing procedure. First porogen is removed from the film with a novel film treatment. This step targets porogen removal, but does not cross-link the film’s matrix. An example of this is remote H2/He plasma (H radical exposure) [2]. After removing the porogen, a traditional UV assisted thermal cure strengthens the film and drives out any remaining porogen. We evaluated this and two similar approaches and observed the same qualitative trends. Generally speaking, when using conventional curing techniques there is an unavoidable tradeoff between k-value and mechanical performance. However, the two-step process results in films which have both increased mechanical strength and improved electrical performance.
Films have been evaluated electrically (k-value, breakdown voltage, leakage current). Film structure (porosity and pore size distribution), mechanical properties (Young’s modulus) and film composition were measured with ellipsometry porosimetry, nanoindentation and XPS/FTIR, respectively. The UV absorption peaks related to porogen residue have also been measured using vacuum ultraviolet spectroscopic ellipsometry.
[1] A.M. Urbanowicz, K. Vanstreels, D. Shamiryan, S.D. Gendt and M.R. Baklanova, Electrochem. Solid St.12 (2009).
[2] A.M. Urbanowicz, K. Vanstreels, P. Verdonck, D. Shamiryan, S. De Gendt and M.R. Baklanov, J. Appl. Phys.107 (2010).