Spectroscopic and Topographic Investigations of Nanoparticle Abrasive Retention in Polyurethane CMP Pads for Cu CMP
- PDF / 194,348 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 93 Downloads / 183 Views
0991-C02-02
Spectroscopic and Topographic Investigations of Nanoparticle Abrasive Retention in Polyurethane CMP Pads for Cu CMP Iftikhar Ul-hasan and Robert Geer College of Nanoscale Science & Engineering, University at Albany, SUNY, 255 Fuller Rd., Albany, NY, 12203 ABSTRACT A spectroscopic and topographic investigation of abrasive nanoparticle retention in polyurethane chemical mechanical planarization (CMP) pads has been carried out as a function of ex situ pad conditioning parameters for Cu CMP. X-ray photoelectron spectroscopy (XPS) and scanning electron microscope energy dispersive spectroscopy (SEM-EDS) were utilized to quantitatively characterize the presence of alumina nanoabrasive in the pad following Cu CMP. As expected, conditioning did not modify the overall pad morphology but did increase local asperity roughness with increasing conditioner downforce. As expected, the magnitude of the conditioner downforce reduced the overall average alumina nanoabrasive retention, albeit weakly, as determined via XPS. However, local EDS analysis revealed that increased downforce does significantly reduce nanoabrasive retention at pad asperities. In contrast, increased downforce increased the amount of nanoabrasive present in the polyurethane pad surface pores. Moreover, overall conditioning time was shown to be a more dominant parameter compared to conditioner downforce regarding removal of abrasive particles from both pad asperities and pores. INTRODUCTION The downward scaling of integrated circuit (IC) feature size has placed increased demands on defect reduction in chemical mechanical planarization (CMP) [1]. Examples include microscratching in Cu CMP whereby mechanical contact between the wafer, pad and large particles (e.g nanoabrasive agglomerates) results in linear regions of mechanical abrasion that can lead to electrical or reliability issues. Point-of-use slurry filtration is often used to prevent large particles or agglomerates reaching the CMP pad surface. However, little detailed information is available regarding the slurry abrasive retained at the polyurethane pad surface in direct contact with the Cu during the planarization process. Likewise, there is little known on the effects the CMP and ex situ conditioning processes have on the distribution of residual abrasive nanoparticles and agglomerates on pad asperities and in surface pores. This information is critical since pad asperities provide the primary mechanical contact force by which slurry nanoabrasive particles interact with the Cu surface during CMP [2, 3]. To address this issue and quantitatively elucidate the disposition of nanoabrasive particles we present spectroscopic and topographic investigations of abrasive nanoparticle retention in polyurethane CMP pads following Cu CMP with ex situ conditioning. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) were combined with profilometry and scanning electron microscopy to investigate the relative concentration of residual nanoparticle abrasive at the pad surface as
Data Loading...
