Miyuki Takenaka

Accurate SIMS depth profiling for ultra-shallow implants using backside SIMS

We studied accurate depth profiling for ultra-shallow implants using backside SIMS. In the case of measuring ultra-shallow profiles, the effects of surface transient and knock-on are not negligible. Therefore, we applied backside SIMS to analyze ultra-shallow doping to exclude these effects. Comparing the SIMS profiles of surface-side and those of backside, backside profiles show a sharper ion implantation tail than surface-side profiles. Furthermore, backside SIMS profiles show almost no dependence on primary ion energy. This indicates that backside SIMS provides sharp B profiles suitable for analyzing ultra-shallow implants, using higher primary ion energy in comparison with implantation energy. The backside SIMS technique has a good potential to be used for next generation devices.

Determination of Ultratrace Amounts of Metallic and Chloride Ion Impurities in Organic Materials for Microelectronics Devices After a Microwave Digestion Method

A digestion method was developed for the determination of ultratrace concentrations of sodium, potassium, magnesium, calcium and chloride ions. Using ETAAS and ion chromatography, the digestion method was applied successfully to the determination of ultratrace concentrations of these elements in organic materials for microelectronics devices such as photoresists, epoxy resins, and liquid crystals. Very low contamination levels were maintained throughout the procedure. The blank levels were 0.05 ng for sodium, 0.02 ng for potassium, 0.03 ng for magnesium and calcium, and 20 ng for chloride ion. The method is very effective in measuring the impurity distributions of organic materials whilst preventing their contamination from the surrounding environment and from the reagents used in the procedure.

Evaluation of a mirror-polishing technique for fluorocarbon polymer surfaces for reduction of contamination from containers used in ultratrace analysis.

A mirror-polishing technique for fluorocarbon polymer surfaces using high-precision diamond cutting tools was developed. The goal of this technique was the reduction of ultratrace elemental analysis contamination levels of containers fabricated from such mirror-polished materials. Remarkably smooth inner surfaces with degrees of flatness of 0.1 μm peak-to-valley (PTV) for containers fabricated from mirror-polished PTFE materials were obtained, in contrast to degrees of surface flatness of more than 30 μm PTV for commercially available PTFE containers. (Here, PTV denotes the difference between the highest peak and deepest valley in a scanned area of 10 × 10 μm.) Extractable impurity levels for mirror-polished PTFE container surfaces were reduced by more than 1 order of magnitude relative to those of unpolished PTFE containers. The surface conditions of the PTFE containers were observed by atomic force and scanning electron microscopy. The microphotographs so obtained suggest that the degree of surface smoothness of the containers is proportional to their ultratrace metallic contamination levels.

Rapid analysis of polybrominated diphenyl ethers by ion attachment mass spectrometry

Novel rapid analytical method was developed for evaluating polymers for the presence of polybrominated diphenyl ethers (PBDEs), which have been prohibited by the RoHS directive, using ion attachment mass spectrometry (IAMS). IAMS requires no chemical pretreatment or separation process for the individual organic compounds before analysis because of its “soft” ionization feature. When measurement was performed for a standard solution of decabromodiphenly ether (decaBDE), no fragment ions were detected. The optimum analysis conditions for polymers were determined using reference materials. When polymers containing decaBDE were analyzed by IAMS under the optimum conditions, a decaBDE concentration of approximately 300 ppm (in the case of 1-mg solid sample for analysis) could be detected with no fragmentation. Even if other brominated compounds, such as ethylene (bis-tetrabromophthal)imide (EBTBPI) and bis(pentabromophenyl)ethane (BPBPE) were present in the sample together with decaBDE, each compound could be identified successfully. In addition, with respect to the validation of IAMS, it was confirmed the limit of detection (LOD) and the limit of quantification (LOQ) for decaBDE were 13.5 and 45.0 ppm (in the case of 1-mg solid sample for analysis), respectively, and that the calibration curve showed good linearity (R2 = 0.9962) within the range of 0.04 to 2.00 μg. The recovery of the decaBDE from the certified reference materials was 81.4% for the 317-ppm sample and 85.4% for 886-ppm sample.

Determination of ultratrace metallic impurities in fluorocarbon polymers by electrothermal atomic absorption spectrometry after decomposition with a combustion system

A combustion system method for determining ultra-trace impurities in fluorocarbon polymers was developed. 200 mg polytetrafluoroethylene (PTFE) material samples were inserted into a quartz combustion system and decomposed for 30 min in air. Sodium-, potassium-, calcium-, copper-, and iron-concentrations in the raw PTFE materials ranged between 2–96, 1–35, 4–18, <1 and 12–97 ng g−1, respectively, with blank levels of 0.3, 0.2, 0.4, 0.2, and 0.5 ng/analysis, respectively. The impurity profiles of the fluorocarbon polymers indicated that the polymers were contaminated as a result of the polymer processing procedures. The technique reported herein gives low blank concentrations and is a rapid and safe analytical method for fluorocarbon polymers.

Application of X-ray Absorption Fine Structure Method for the Quantitative Analysis of Hexavalent Chromium in Chromate Conversion Coating and Plastic

The X-ray absorption fine structure method was applied for the quantitative analysis of hexavalent Cr in electronic products. The pre-edge peak intensity of the Cr K-edge increased according to the hexavalent Cr amount, and the hexavalent Cr ratio was calculated quantitatively by using the intensity. By combining with inductively coupled plasma atomic emission spectroscopy measurement results that gave the total Cr amount, the absolute amount of hexavalent Cr in chromate conversion coating and plastic samples could be evaluated. The results obtained by this method were in good agreement with those obtained by the chemical analysis method. This method can be successfully applied for the determination of hexavalent Cr amount in electronic products such as chromate conversion coating and plastic.

Evaluation of Ultratrace Metallic Impurities in Thin Copper Layers, Barrier Metals and Silicon Wafers for Copper Metallization Technology

An analytical method for the determination of ultratrace concentrations of metals in several semiconductor-related materials for copper metallization technology such as thin Cu layers, barrier metals and silicon wafers has been developed. Using this method, the concentration of Cu impurities in Si wafers resulting from diffusion of Cu from Cu metallization layers through barrier layers of TiN, TiSiN, or WSiN was found to be less than 1012 atoms/cm3.