F.G. Kirscht

Recent advanced applications of AAS and ICP-MS in the semiconductor industry

Abstract We report on instrumentation-related challenges of applying graphite furnace atomic absorption spectroscopy (GF-AAS) and inductively coupled plasma mass spectrometry (ICP-MS). We show that a significant amount of polyatomic species derived from silicon sample solution in the plasma, such as SiO, SiOH, SiOH 2 ·SiOH 3 , SiO 2 , SiO 2 H, SiO 2 H 2 and SiO 2 H 3 , can hamper the detection limits of many elements of interest. This paper describes a method for eliminating these polyatomic ions. We discuss the advantages and disadvantages of vapor phase decomposition method (VPD), drop etching method (DE) and drop sandwich-etching method (DSE) for the recovery of metal impurities from a silicon wafer surface. We report the application of the DSE method for the evaluation of near-surface metal impurities, used for gettering studies. We describe the direct acid bulk decomposition (DABD) and the room temperature acid vapor phase decomposition method (RT-AVPD) for the determination of metal impurities in bulk silicon. Finally, we report concentration of trace metal contamination in several chemical reagent solutions.

Fine Structure of Dislocation Related PL Bands D1 and D2 in Silicon

The samples of p- and n-doped Fz Si were deformed in 3-point bending mode in the temperature range 800-950°C. The fine structure of dislocation related luminescence in the region of D1 and D2 bands was most pronounced at lowest rate of deformation. The temperature variation of intensity of individual lines did not reveal any thermalization effects. It implies that centers responsible for different individual lines are situated in diverse places. The most narrow lines with maximum positions of 802 meV and 807 meV (D1 band) and 869 meV and 873 meV (D2 band) are rapidly quenched with increase in temperature, while the broader background lines survive at higher temperature. The new line with maximum position at about 882 meV appears in the D2 band with enhanced carbon doping. It was found that at higher P-doping the low energy fine structure lines 802 meV and 869 meV are absent. Besides, the Fz samples with different P doping level from 6×1014 cm-3 to 1.2×1016 cm-3 demonstrate quite a different temperature variation of broad background lines. At lowest level of P-doping they move to low energy side at temperature above 30K, while at P-doping above 1015 cm-3 these lines move to higher energy in the same temperature range. A possible explanation of this observation can be related to distribution of electrons in the cband. It implies that the corresponding electronic transitions occur between the edge of conduction band and deep states.

Laser Scattering Tomography on Magnetic CZ-Si for Semiconductor Process Optimization

Laser scattering tomography (LST) and band-to-band photoluminescence (PL) are applied for supporting a MEMS process optimization. Process wafers are based on magnetic CZ grown silicon material. LST allows the characterization of number-size distributions of oxygen precipitates in various stages of the process flow. Precipitation is shown to be affected by the design of high-temperature anneal post initial oxidation. PL gives useful information on relative concentration level and radial distribution of recombination centers within process wafers. The initial oxidation leads to significant reduction of recombination centers. The combined LST/PL information enables valuable conclusions towards process optimization.

Model-based silicon wafer criteria for optimal integrated circuit performance

The Starting Materials requirements in the 1997 Semiconductor Industry Association (SIA) National Technology Roadmap for Semiconductors (NTRS) were developed by a fifty-nine member team comprised of industrial (e.g., silicon suppliers, equipment and IC manufacturers) and university personnel. The silicon wafer parameter values as-received by the IC manufacturers are generally derived from model-based analyses based on the technology generation critical dimension (CD), bits, wafer diameter, etc. The values represent the perceived critical material characteristics required to ensure that silicon materials support the continued growth of the IC industry while being cognizant of cost-of-ownership (CoO) considerations. The characteristics were developed via a modular approach of a core set of general characteristics applicable to all product wafers, plus specific recommendations for polished, epitaxial and silicon-on-insulator (SOI) wafers. The formulae utilized, assumptions made and the issues involved, as we...