- SEMI MF1982 - Test Method for Analyzing Organic Contaminants on Silicon Wafer Surfaces by Thermal Desorption Gas Chromatography
This Standard was technically approved by the Silicon Wafer Global Technical Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on February 2, 2017. Available at www.semiviews.org and www.semi.org in March 2017; originally published by ASTM International as ASTM F1982-99; previously published July 2014.
Organics are present in many materials, such as plastics, lubricants, cleansers, soaps, and living tissues. Some of these compounds are volatile and others can become airborne through chemical reactions, heating, abrasion, or outgassing. Organic compounds are present in many materials such as parts and components for cleanrooms, carriers, FOUP, developers, and organic removers. Some of these organic compounds are volatile and some can be discharged into clean room environment through chemical reactions or by heating. Also they can transfer to wafers by direct contact or be left behind from solvent residues. Once present in clean facilities, they can deposit on wafer surfaces. The desorbed organic compounds can be transferred to wafers or reticles through the environment. Organics deposited on wafers can cause degradation haze, wafer surface tension changes, irregular oxidation rates, and other effects, such as counter-doping by organophosphorus compounds. Various organic compounds on wafer surfaces can cause a pseudo increase of the thickness of the native oxide film. Nonuniformity of the surface leads to nonuniform oxide on a wafer and causes degradation of the oxide breakdown voltage. It also causes not only wafers, but also the reticles or mirrors to haze. Identification of trace level organic contaminants is important in determining the source of the particular contamination. These test methods use the thermal desorption gas chromatography mass spectrometry (TD/GC-MS), technique to characterize and quantify organics deposited on wafer surfaces. This is one of the reasons that control of organic compounds is required in a cleanroom environment or on wafer surfaces. This mandates test methods of organic compounds on wafer surfaces. TD/GC-MS is useful for qualitative and quantitative analysis of trace-level organic compounds adsorbed on wafer surfaces.<br>Monitoring of organic contamination on wafer surfaces also can be used to measure material outgassing for proper selection of cleanroom, construction, and wafer packaging materials.
This Test Method covers the identification and quantification of organic compounds on wafer surfaces by using gas chromatography mass spectrometry (GC-MS).<br>This Test Method describes the procedures for sample preparation and analyses by thermal desorption gas chromatography (TD-GC).<br>The range of lower detection limits of this Test Method depends on the species of organic compound. However, generally for organic compounds, it ranges from subpicogram to nanogram per square centimeter of silicon-wafer surface (pg/cm2 to ng/cm2). The lower detection limit when the molecular weight is assumed as 300 and carbon numbers as from 10 to 20 is in the range of 5e10–5e11 molecules/cm2, 1e12-1e13 C atoms/cm2.<br>This Test Method can be used for various materials depending on the purposes, but mainly for bare silicon wafers.<br>When testing wafers, full wafers are basically used. However, cleaved wafers can be accepted as long as it does not cause a significant drop in the sensitivity (from a quarter to a half of a wafer).
Referenced SEMI Standards
SEMI M59 — Terminology for Silicon Technology