SEMI M85 - Guide for the Measurement of Trace Metal Contamination on Silicon Wafer Surface by Inductively Coupled Plasma Mass Spectrometry
Reduction of surface metal contamination below a concentration in accordance with the ITRS road map is a key issue for silicon wafer quality for most of the leading-edge technology applications. This Document provides a guide for a high-sensitivity measurement of trace metal contamination on the surface of a semiconductor grade silicon wafer by using inductively coupled plasma mass spectrometry (ICP-MS).
This Guide describes the procedure for trace metal measurement, including the metal impurity collection method from a silicon wafer surface, scanning solution composition, and its optimization. In particularly, the procedure of the collection method is described in detail because it influences the reliability of measurement data and reproducibility of each facility.
This Guide describes methods for the measurement of trace metal contamination on a silicon wafer surface. The decomposition of silicon oxide on silicon wafer, the collection of trace metal contamination from a wafer surface using mixture acid, measurements, and reports are described in this Guide.
This Guide covers an evaluated substrate wafer as a mirror-polished surface, annealed wafer, epitaxial growth wafer, diffusion wafer, and bonding wafer, which are nonpatterned surfaces. However, this Document also addresses the back side of a patterned wafer. Additionally, this Guide covers wafers that form native oxides and thermal oxides.
In the case of decomposition of silicon oxide on the silicon wafer and contamination collection from the wafer surface, a procedure with the recommended technique for the vapor phase decomposition (VPD) and the direct acid droplet decomposition (DADD) methods is presented (see ¶ 9.1).
In this Document, a scanning solution for collecting metal contamination from wafer surfaces is recommended for using the solution compositions optimized by ensuring recovery rate with 75%–125% (see ¶¶ 5.2.3 and 188.8.131.52). Here, the scanning solution consists of hydrofluoric acid and hydrogen peroxide or nitric acid.
This Guide uses only ICP-MS (see ¶ 7.1) for the measurement of contamination on the wafer surface. The target elements of this method are sodium, magnesium, aluminum, potassium, calcium, chromium, manganese, iron, cobalt, nickel, copper, and zinc.
Referenced SEMI Standards
SEMI C1 — Guide for Analysis of Liquid Chemicals
SEMI E45 — Test Method for the Determination of Inorganic Contamination from Minienvironments using Vapor Phase Decomposition-Total Reflection X-ray Spectroscopy (VPD/TXRF), VPD-Atomic Absorption Spectroscopy (VPD/AAS), or VPD/Inductively Coupled Plasma-Mass Spectrometry (VPD/ICP-MS)