| AVS 58th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing Division | Wednesday Sessions |
| Session EM-WeM |
| Session: | Low-k Materials and Devices |
| Presenter: | Dimitri Kioussis, GLOBALFOUNDRIES |
| Authors: | D. Kioussis, GLOBALFOUNDRIES E.T. Ryan, GLOBALFOUNDRIES S.M. Gates, IBM T.J. Watson Res. Ctr. A. Madan, IBM N. Klymko, IBM C. Parks, IBM S. Molis, IBM R. Augur, GLOBALFOUNDRIES H. Masuda, Toshiba America D. Restaino, IBM Z. Sun, GLOBALFOUNDRIES S. Hosadurga, IBM S. Cohen, IBM T.J. Watson Res. Ctr. K. Virwani, IBM Almaden Res. Ctr. A. Grill, IBM T.J. Watson Res. Ctr. |
| Correspondent: | Click to Email |
In the demanding microelectronics industry there is a constant need to increase circuit density in multilevel Copper (Cu) back-end-of line (BEOL) interconnects to improve the operating speed and reduce power consumption. With successive nodeon- node scaling, one approach to meet the capacitance-resistance (RC) requirements for the BEOL is through the introduction of organo silicate glass (SiCOH) materials with low dielectric constants (κ-value) as interlevel dielectrics (ILD). At the 45 nm node, porosity was first introduced into the BEOL interconnect structures in the form of porous organo silicate glass films (p-SiCOH) with ultra low-κ (≤ 2.55) to further minimize the RC delay. These ULK materials incorporate a large number of methyl groups and pores into Si-O based network structures, although the initial precursors and final properties may vary. Both the SiCOH and pSiCOH ILD films are commonly deposited by plasma-enhanced chemical vapor deposition (PECVD). Since their introduction nanoporous ULK films have significantly increased the Cu BEOL fabrication complexity. For example, porous ULK films are mechanically weak and tend to crack as a result of elastic mismatch with the substrate. Meanwhile, pore collapse and carbon depletion occur when ULK is exposed to RF-plasma during etching or ashing. Subsequent moisture adsorption leads to the increase of effective κ-value in Cu interconnects degrading RC performance. Therefore, the integration challenges of ULK are significant, such as plasma damage, chip packaging interaction, and dielectric/metal barrier compatibility issues. Careful optimization of the ULK properties is crucial for successful process integration in the 28 nm BEOL node and beyond.
This presentation will report on the ability to tune the material properties of ULK films with κ ≤ 2.55 through the use of new chemical precursors and simple processing optimization steps to meet the specific integration requirements. Three ULK material classes were evaluated, optimized, and characterized to compare electrical and mechanical properties, pore characteristics, FTIR, XPS, and thermal stability. The effect of UV Cure dose on the ULK film properties and correlation of the degree of plasma damage to the ULK chemical, physical, and structural properties will be discussed. We will show that balancing composition of the film to minimize damage for successful integration needs to be coupled with improving electrical and mechanical integrity for packaging compatibility.