No abstract

This paper presents experimental and analytical studies of AFM nanoindentation as a method to determine microhardness of hard thin films. Indentations are performed on Au, Si, and DLC using triangular pyramidal diamond probes to determine microhardness. We examined the effects of indentation force and three different methods to measure the indentation area (direct area measurement for a triangular indentation, size analysis of an inverted AFM image of the indentation, and prediction of area from indentation depth based on a tip shape function). The responses are indentation depth, projection area, and microhardness. Relationship of responses with indentation force is examined. At a low depth range, microhardness based on pyramidal shape function is erroneously higher than the other two methods. However, all three methods generally agree with each other when indentation force exceeds 16μN. Size analysis of inverted images gives more consistent microhardness with the least variability over the whole force (4∼30μN) or depth (0.5∼70 nm) range. Tip shape models are developed to predict microhardness. The ellipsoidal tip model is a good approximation at low depth ranges, while the pyramidal model works better for deeper indentations. The force vs area curves are also significantly nonlinear which can distort the hardness measurements.

Continuing demand for high performance microelectronic products propelled integrated circuit technology into 45 nm node and beyond. The shrinking device feature geometry created unprecedented challenges for dimension metrology in semiconductor manufacturing and research and development. Automated atomic force microscope (AFM) has been used to meet the challenge and characterize narrower lines, trenches and holes at 45nm technology node and beyond. AFM is indispensable metrology techniques capable of non-destructive full three-dimensional imaging, surface morphology characterization and accurate critical dimension (CD) measurements. While all available dimensional metrology techniques approach their limits, AFM continues to provide reliable information for development and control of processes in memory, logic, photomask, image sensor and data storage manufacturing. In this paper we review up-todate applications of automated AFM in every mentioned above semiconductor industry sector. To demonstrate benefits of AFM at 45 nm node and beyond we compare capability of automated AFM with established in-line and off-line metrologies like critical dimension scanning electron microscopy (CDSEM), optical scatterometry (OCD) and transmission electronic microscopy (TEM).

a Forming gas annealing (FGA) is an effective process to repair low efficiency crystalline silicon (c-Si) solar cells with overfired screen-printed paste electrodes. An experimental study was performed to investigate the effect and mechanism of FGA treatment on front silver electrodes of c-Si cells. To facilitate the FGA mechanistic study, special simulation samples were prepared to magnify the FGA effects on glass frit and overfired electrodes. The micro-morphology (from cross-sectional X-SEM) and elemental composition (from energy-dispersive X-ray spectroscopy) data revealed few Ag crystallites in the paste/Si interface because of the thick glass layer from the paste overfiring. The FGA treatment induced phase crystallization (from X-ray diffraction) in the paste and increased the glass wettability on both Si and Ag substrates, thus resulting in a thinner glass layer, which expedited the precipitation of more pyramidal Ag crystallites at the Ag/Si interface. The wetting angle data of glass samples measured before and after FGA confirmed the mechanism of FGA and concluded that the improvement of glass wettability benefited to reduce the glass layer thickness. As a result, more Ag crystallites diffused toward and precipitated at the Si interface contributing to a lower contact resistance between the paste electrode and the Si matrix and thus improved electrical properties for overfired c-Si cells.

No abstract