ToF‐SIMS analysis of organic impurities in UPW

Abstract

We have investigated adsorption of organic impurities in ultrapure water (UPW) on hydrophilic silicon wafer surface. The primary and tertiary amine molecules used as model compounds of organic impurities were adsorbed on the clean wafer surface during soaking in UPW. It was found that adsorbed quantities of relatively large tertiary amines among water-soluble amines, such as (C 3 H 7 ) 3 N and (C 4 H 9 ) 3 N, were higher at relatively short soak time (two h in this experiment) than at longer one (24 h). Time-of-flight secondary-ion mass spectrometry (ToF-SIMS) is a very powerful tool for identification of trace organic contamination on wafer surface after UPW rinse from the studies of adsorption of the molecules present in UPW.

ToF-SIMS analysis of influence of alkylamine compounds in UPW on hydrogen-terminated Si surface

“…While adsorbed quantities on hydrophobic surface decreased except for tripropylamine, those on hydrophilic surface increased as the increase of the soaking time. The adsorption behaviors on the hydrophilic surface have been investigated in the previous paper [9] and we indicated that there seems to be a good relationship between the octanol-water partition coefficients and peak intensity ratios of 24 h soaked to 2 h soaked. It was considered that the amines with large octanol-water partition coefficient are likely to be adsorbed physically on wafer surface at short soaking time because being not stable in water and replaced with the amines which have small octanol-water partition coefficients and high adsorption energy on hydrophilic wafer surface in long soaking time.…”

“…• C in the He atmosphere in order to remove organic contamination [9]. the same atmosphere, the wafer was cut into 10 mm×10 mm small pieces in the clean bench.…”

“…We have established a new technique of ToF-SIMS analysis of trace organic adsorbent on the native oxide surface soaking in UPW after high temperature heat cleaning and have investigated peculiar adsorption behaviors of alkylamine compounds supposed as organic impurity in UPW in the previous report [9]. It has been found that the adsorption behaviors are definitely dependent on the numbers of carbon atoms and the water rinse process could result in the wafer surface being more contaminated from the organic point of view.…”

“…Another source of organic contamination is ultra pure water (UPW) widely used in wet cleaning processes. Organic impurities on wafer surface after rinsing in UPW at a final stage of wet cleaning have not been fully investigated because the surface after rinsing has been considered as a starting surface to airborne contamination and no analytical techniques have been developed for the investigation [6][7][8][9][10]. The maintenance of surface cleanness and defect control of hydrogen-terminated surface in wet cleaning processes are needless to say important and the understanding of the adsorption property and the influence of organic impurities in UPW have been required.…”

Investigations of semiconductor devices using SIMS; diffusion, contamination, process control

“…The cluster-ion or polyatomic analysis beam has been used in the imaging of bio tissues [8]. In the recent years, there has been explosive growth in the quantitative analysis of organic contaminants in the semiconductor process [9,10]. It is considered that SIMS has been wide spreading the powerful mass spectrometric and imaging technique into the various fields, such as semiconductor, organic, polymer, and bio, nevertheless, the portion of contributions in the semiconductor process development has partially been declined [11].…”