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Characterization of Backside Roughness of Silicon Wafers by Mid-Ir Spectrometry

IP.com Disclosure Number: IPCOM000046872D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Kelleher, KH: AUTHOR [+2]

Abstract

Control of backside damage of silicon wafers is important for both impurity gettering and oxygen measurement. The roughness can be quantitatively defined by the following method. The roughness of silicon wafer surfaces can be accurately characterized from the mid-infrared spectrum by determining the slope of a baseline arbitrarily defined through points having nearly no absorption (1046 and 700 cm-1 in our case) and off-set of a similar point (1107 cm-1) from its location in the spectrum of a sample with polished surfaces. Fig. 1 illustrates infrared spectra obtained on a silicon wafer after one of its polished surfaces was abraded with silicon carbide paper of increasing grit sizes to generate damage that increased both in scratch density and scratch size. Spectra S1 is of a polished backside surface.

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Characterization of Backside Roughness of Silicon Wafers by Mid-Ir Spectrometry

Control of backside damage of silicon wafers is important for both impurity gettering and oxygen measurement. The roughness can be quantitatively defined by the following method. The roughness of silicon wafer surfaces can be accurately characterized from the mid-infrared spectrum by determining the slope of a baseline arbitrarily defined through points having nearly no absorption (1046 and 700 cm-1 in our case) and off-set of a similar point (1107 cm-1) from its location in the spectrum of a sample with polished surfaces.

Fig. 1 illustrates infrared spectra obtained on a silicon wafer after one of its polished surfaces was abraded with silicon carbide paper of increasing grit sizes to generate damage that increased both in scratch density and scratch size. Spectra S1 is of a polished backside surface. Please note that all of the spectra (linear in absorbance and wavenumber) show that no-absorption baselines will pass through an approximately single point at 0 cm-1. The slopes of the line drawn between points located at 1046 and 700 cm-1 on these spectra and the shift in the baseline at 1107 cm-1 are presented in the table below and graphically represented in Fig. 2.

(Image Omitted)

The straight line nature of the relationship between the offset of the baseline at 1107 cm-1 and the slope indicates that the damage is random and the Mie scattering theory can be applied to uniquely descr...