GDOES

Patrick Chapon, HORIBA Scientific, 16 rue du Canal, 91160 Longjumeau, France

IntroductionRepeatability and Reproducibility are well known and extensively studied parameters in analytical chemistry. In order to evaluate the capability of an instrument to monitor and study changes in a process, the variations in the instrument response must be small compared to the observed changes.

However many studies dealing with surface and depth profile analysis do not provide statistical information on the obtained results though ISO standards do require such data. This fact is obviously explained by the long analysis time required to perform a single measurement with SIMS or XPS for instances.

On the opposite pulsed RF GDOES is extremely fast: therefore multiple measurements could be done simply and quickly on test samples to address the repeatability and reproducibility of the instrumentation assuring that the technique is suitable to monitor the process under scrutiny.

InstrumentationThe GD Profiler 2 couples an advanced Pulsed RF Glow Discharge Source to a high resolution, wide spectral range Optical Emission Spectrometer. The source permits a precise and fast sputtering of a representative part of the material investigated (typically 4mm in diameter).

Figure 1. GD Profiler 2

Figure 2. Typical GD crater (4mm diameter)

The QuantumTM software includes on line SPC functions first to monitor the instrument performance (Cp), detect possible drifts to identify root causes of variations and second to to evaluate the instrument capability (capability coefficient Cpk) to control and monitor a process.

Figure 3. On line SPC

Abstract: : This note describes the advantages of using a fast and reproducible analytical technique for process control.

Key wordsGDOES, pulsed RF operation, Repeatability, Reproducibility, Fast elemental depth profiling, Glow Discharge Optical Emission Spectroscopy

On the reproducibility of pulsed GDOES measurements

Application Note

Material ScienceGD30

ResultsWe are showing here 2 results published or presented by HORIBA Scientific GD users showing the excellent performance of the pulsed RF GDOES instrument.

The first result is extracted from ref 1. The reproducibility in radiofrequency glow discharge optical emission spectroscopy (r.f.-GDOES) depth profiling has been examined using a 360 nm thick anodic alumina film with a chromium-containing delta-function layer.

The time required to sputter through the film was constant, to within 1%, whereas the signal intensities of film species agreed to within 3%.

The comment made is that “this level of reproducibility together with high depth resolution makes the technique ideal for on-site quality control of various surface-enhanced industrial products, embracing electronics and protective surface treatments”.

Figure 4: Overlay of 5 mesurements and reference TEM cross section (from Ref 1)

The second measurement is extracted from the presentation given by S. Liang from Seagate at the 2012 GD day. The GDOES instrument is notably used at Seagate to address the uniformity in thickness of the different layers of the active part of hard disks.

Figure 5: Repeatability measurements at different locations on hard disk

Excellent gage is shown (0.07nm at 6 sigma !) using of course SPC functions.

Figure 6: Statistical results of the repeatability measurements

ConclusionsThe speed and ease of use of pulsed RF GDOES favor the implementation of statistical process controls that are crucial to optimize processes involving thin and thick films deposition and control.

References 1) J.Miller “Statistics and Chemometrics for Analytical chemistry”.

Pearson Education Limited.2) K. Shimizu,H. Habazaki, P. Skeldon and G. E. Thompson. “Reproducibility

in r.f.-GDOES depth profiling analysis of thin films”. Surf. Interface Anal. 2001; 31: 1085–1086

3) S. Liang. Seagate. Presentation at the 6th International GD day 2012.

info.sci@horiba.com www.horiba.com/scientificUSA: +1 732 494 8660 France: +33 (0)1 69 74 72 00 Germany: +49 (0)89 4623 17-0UK: +44 (0)20 8204 8142 Italy: +39 2 5760 3050 Japan: +81 (0)3 6206 4721China: +86 (0)21 6289 6060 Brazil: +55 (0)11 2923 5400 Other: +33 (0)1 69 74 72 00 Th

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