Shoji Kozuka

Estimation of ultra-shallow implants using SIMS, NRA and chemical analysis

Estimation methods for ultra-shallow implants (boron and arsenic) were investigated. SIMS analysis enables accurate junction depth estimation for ultra-shallow junctions, when concentration and depth calibration methods using bulk-doped samples and multi-delta-structure samples are used together. Even with this advanced SIMS measurement, accurate implant doses cannot be estimated for ultra-shallow implants. NRA and chemical analyses have been developed for accurate measurements of boron and arsenic doses, respectively. Using three analytical methods (SIMS, NRA and chemical analysis), junction depths and implant doses can be estimated accurately and precisely.

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.

Simultaneous determination of iron(II), iron(III), and titanium(IV) by flow injection analysis using kinetic spectrophotometry with Tiron

SummaryTwo flow injection analysis systems have been worked out for the simultaneous determination of Fe(III), Fe(II), and Ti(IV) based on the kinetic spectrophotometry with Tiron. The first system uses a silver reductor column and a single detector with two flow cells aligned in the same optical path to yield two peaks corresponding to (a) Ti(IV)-Tiron and (b) Ti(IV) plus total iron(III)-Tiron complexes. An another sample injection without the silver column yields a single peak which corresponds to Ti(IV) plus Fe(III)-Tiron complexes. With the two sample aliquot injections the system permits simultaneous determinations with throughput of 30 samples/h in the μg to several tens μg range of each species. The second system is a multidetection system with or without the silver reductor column using the same spectrophotometry with Tiron, in which the entrapment of the sample plug into a closed system allows its repetitive passage through a single detector. With the advantage of much simpler instrumentation, the system permits 6 samples/h to be analyzed for the three metal species with somewhat lower precisions than the first system.

Determination of impurities in strontium titanate ceramics by inductively coupled plasma mass spectrometry

The determination of impurities in SrTiO3 by ICPMS was investigated. The sample was decomposed with hydrochloric and hydrofluoric acids in a PTFE pressure vessel. The internal standard method using Au was selected to eliminate an ion count suppression by the Sr and Ti matrix. Impurities at sub μg/ml level in SrTiO3 were determined. The detection limits were in the range of 0.008 to 0.01 μg/g.

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.

Determination of Surface Impurities on a Gallium Arsenide Wafer by Inductively Coupled Plasma Mass Spectrometry

The surface impurities on a GaAs wafer were determined by inductively coupled plasma mass spectrometry to clarify the diffusion behavior which affected the layer construction. The sample was etched by hydrofluoric acid in a PTFE vessel at room temperature. Depth analysis of the wafer was performed by repeated etching as impurities were thought to exist near the wafer surface. Copper was difficult to dissolve by hydrofluoric acid due to an ionization tendency compared to the hydrogen ion. The method used in this study was demonstrated to be effective for determining surface impurities on a GaAs wafer for an impurity level of 1011 atoms/cm2 and for analyzing depth profiles from the surface.