A Spin-on Dielectric Material for High Aspect Ratio Gap Fill
- PDF / 367,778 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 20 Downloads / 187 Views
B8.5.1
A SPIN-ON DIELECTRIC MATERIAL FOR HIGH ASPECT RATIO GAP FILL Wei Chen, Sheng Wang, Ather Ashraf, Edward Somerville, Gerard Nowaczyk, BK Hwang, JK Lee, and Eric S. Moyer Dow Corning Corporation, Midland, MI 48686 Carlo Waldfried, Orlando Escocia, and Qingyuan Han Axcelis Technologies, Inc, Rockville, MD 20855 ABSTRACT This communication describes the results of a potential spin-on glass (SOG) solution for narrow and high aspect ratio trench fill in both shallow trench isolation (STI) and premetal dielectric (PMD) applications. We have focused our development work on a hydrogen silsesquioxane (HSQ, (HSiO3/2)n) material, which offers the advantage of a carbon free gap fill solution. The main challenge for carbon-free SOG materials is to achieve material densification in the nano-scale gaps during thermal processing that of the gap filled material during the wet cleaning steps. This paper reports some approaches and findings on material densification in the nano-scale gaps and the results of subsequent wet etch tests. INTRODUCTION As the technology nodes in IC manufacturing shrink to 65 nm and beyond, the demands for gap filling of nano-scale trenches are ever increasing. The common trenches are 4070 nm wide with aspect ratios greater than seven. High density plasma chemical vapor deposition (HDP CVD) oxide has been the main technology used for the trench filling with aspect ratios around 3 [1]. The oxide films deposited from HDP CVD processes have shown good filling, and low HF etch rate. However, as the aspect ratio increases, the HDP CVD technology encounters major issues such as void formation during the gap filling process. SOG offers an attractive alternative for the high aspect ratio gaps with excellent gap filling capability [2]. Currently, SOG gap fill technology is still facing some obstacles. Among them, survival of certain wet steps is the key roadblock for potential SOG materials. After wet etch steps, the corners and less dense bottoms of the trenches are often etched away. The corner etch could be related to stress build-up at the corners of the trenches due to the high stress concentration in the corners [3]. For the narrow trenches, it was reported that HSQ materials form a dense skin layer on the top of a trench during the thermal processing step [4]. Also, the material densification was enhanced under oxidation environment. This “skin” layer on the top of a trench was observed to act as a diffusion barrier to prevent oxidants to penetrate into the bottoms of the trenches. Therefore, insufficient cure of HSQ was observed even after a complete oxidative cure. The capillary effect and the “skin” formation prevent effective densification of the HSQ material in a narrow gap filled trench. EXPERIMENTAL The HSQ films were spin coated using a DNS spin coater. After spin coating, the films went through a hot plate thermal treatment at 150 ˚C for one minute. For plasma and oxygen UV cure approaches, the cure steps were carried out on separate Axcelis plasma
B8.5.2
and UV curing systems. The steam cur
Data Loading...
