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Thickness measurements of thin carbon overcoats on magnetic thin film media by Auger and X-ray photoelectron spectroscopy

IP.com Disclosure Number: IPCOM000013823D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 5 page(s) / 94K

Publishing Venue

IBM

Abstract

Disclosed are techniques used to measure the thickness of thin overcoats on magnetic thin film media by Auger and X-ray photoelectron spectroscopy. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) are similar techniques in that they measure the intensity of electrons ejected from the core levels of atoms near the surface of the sample. By measuring the electron intensity as a function of kinetic energy, peaks in the spectrum can be identified as originating from specific elements, for example cobalt, and for XPS, for specific oxidation states of the elements. For the thickness measurement technique disclosed here, the electron intensity from one or several elements in the magnetic layer are measured along with one or several elements of the overcoat layer. For measuring the thickness of a disk overcoat, it is usually sufficient to measure the electron intensity originating from the cobalt (Co) atoms in the magnetic layer and from the carbon atoms in the overcoat layer. The intrinsic physical property--Co electron escape depth for specific COC--is used to determine the COC thickness of 50 Å and below. There are several advantages for this technique: 1. No underlayer effect. Once the electron escape depth, which is the intrinsic physical property of the COC, and the electron energy are determined, this method can be used as an absolute scale to determine the COC thickness. No other parameters are required for the measurement. 2. This technique has high sensitivity with good measurement precision around 0.5 angstroms) for COC thicknesses range from 0 to 50 Å. The signal to noise ratio actually increases with decreasing COC thickness.

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  Thickness measurements of thin carbon overcoats on magnetic thin film media by Auger and X-ray photoelectron spectroscopy

      Disclosed are techniques used to measure the thickness of thin overcoats on magnetic thin film media by Auger and X-ray photoelectron spectroscopy.

      Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) are similar techniques in that they measure the intensity of electrons ejected from the core levels of atoms near the surface of the sample. By measuring the electron intensity as a function of kinetic energy, peaks in the spectrum can be identified as originating from specific elements, for example cobalt, and for XPS, for specific oxidation states of the elements. For the thickness measurement technique disclosed here, the electron intensity from one or several elements in the magnetic layer are measured along with one or several elements of the overcoat layer. For measuring the thickness of a disk overcoat, it is usually sufficient to measure the electron intensity originating from the cobalt (Co) atoms in the magnetic layer and from the carbon atoms in the overcoat layer. The intrinsic physical property--Co electron escape depth for specific COC--is used to determine the COC thickness of 50 Å and below. There are several advantages for this technique:

1. No underlayer effect. Once the electron escape depth, which is the intrinsic physical property of the COC, and the electron energy are determined, this method can be used as an absolute scale to determine the COC thickness. No other parameters are required for the measurement.

2. This technique has high sensitivity with good measurement precision ( around 0.5 angstroms) for COC thicknesses range from 0 to 50 Å. The signal to noise ratio actually increases with decreasing COC thickness.

3. The elemental dopant concentration in the COC (except for H and He) can be measured at the same time.

4. With XPS, the degree of oxidation of the magnetic layer after disk has been exposed to atmosphere can be used as a measure of overcoat coverage.

      For Auger, high energy electrons impinge on the sample which cause core-level electrons to be ejected into a vacuum where they are analyzed using an electron spectrometer. For XPS, x-rays rather than high energy electrons are used to cause the ejection of electrons. Those electrons ejected from atoms in the magnetic layer are attenuated by the overcoat before reaching the vacuum above the sample. Assuming a smooth homogeneous layer of COC lies on top of Co magnetic layer, then the normalized intensity of Co for a fixed angle q can be expressed, using Beer's law, as:

Ico/I o -t/ Lsinq co = e

1

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e-

Ico

e-

q

where t: COC thickness, L : effective escape depth for Co on particular COC. Then, the thickness can be derived as:

ot = - LSinq*ln(Ico/Ico)

Once the L is determined by a set of known thickness samples, the thickness can be determined by measuring the intensity of the Co peak. Following are some...