Ayako Shimazaki

Total reflection x-ray fluorescence spectroscopy using synchrotron radiation for wafer surface trace impurity analysis (invited)

Trace impurity analysis is essential for the development of competitive silicon circuit technologies. Current best methods for chemically identifying and quantifying surface and near‐surface impurities include grazing incidence x‐ray fluorescence techniques using rotating anode x‐ray sources. To date, this method falls short of what is needed for future process generations. However, the work described here demonstrates that with the use of synchrotron radiation, total reflection x‐ray fluorescence methods can be extended to meet projected needs of the silicon circuit industry until, at least, the year 2000. The present results represent over an order of magnitude improvement in detection limit over what has been reported previously. A double multilayer monochromator on a high flux wiggler beam line resulted in a detection limit for Ni of 3×108 atoms/cm2. This is to be compared with a detection limit of 5×109 atoms/cm2 obtained with a rotating anode system. This is due to the greatly improved signal to bac...

Novel model of haze generation on photomask

ArF lithography sometimes generates the haze defects on the photomask substrate, resulting in serious yield deterioration in ULSI production. In order to solve this problem, experimental and theoretical studies have been carried out on the generated haze defects. In characterizing the haze defects, the composition and chemical structure of the haze defects were analyzed by focusing on 1.0 x 0.3μm sizes defects using Raman, ToF-SIMS and AES spectroscopy with their highest spatial and mass resolution level. To confirm the experimental analyses, theoretical ab initio molecular orbital calculations were carried out on the model compounds of the generated haze defects. These experimental and theoretical studies indicate that the haze defects on quartz surface consist of (NH4)2SO4 and that those on half-tone (HT) film surface, on the other hand, consist of (MoO3)x(SO4)y(NH4)z complex including Mo from HT film material. In the latter case, NH4 ion was observed only in surface region of the haze defects. Based on these results, we have proposed a novel model of haze generation mechanism on quartz and HT film surfaces of photomask substrate.

Metallic Contamination Control in Leading-Edge ULSI Manufacturing

Contamination control has become a high-centered issue for the fabrication yield, performance and reliability of leading-edge ULSI devices. With the progress of sizing down dimensions in higher-density devices, complicated device structures and various novel electronic materials have been introduced, particularly in the latest devices such as CMOS and nonvolatile memory LSIs (Table I). On the other hand, high productivity is a necessity when you consider QTAT (quick turnaround time) and cost-effective flexible ULSI manufacturing lines. Therefore, effective contamination control coupled with adequate protocol has become essential in such production lines. The point of the protocol is minimization of damage caused by impurity metals diffused from these novel electronic materials [1-5].

Analysis and Evaluation of Impurities on Wafer Surfaces

Figure 13.1 shows a classification of contamination on the silicon surface. As well as particles, impurities must be controlled on the surface of silicon wafers. The impurities are classified as various kinds of organic and inorganic materials [1]. The analysis methods and the aim of the observation differ depending on the contamination and have a wide range of macroscopic or microscopic, chemical or physical techniques. Generally speaking, chemical techniques are used for a macroscopic analysis, and physical techniques enable the analysis of the state of the contamination in the microscopic range. Table 13.1 lists various analytical methods for impurities on the silicon surface.