Recent investigations of rapid thermal processing (RTP) of thin films using an in-situ optical process control in
conjunction with in-situ energy-dispersive X-ray diffraction (EDXRD) are presented. The growth of Cu(In,Ga)(S,Se)2
layers by sulfurization or selenization of sputtered Cu-In-Ga precursor layers was realized by a heating ramp from room
temperature to temperatures between 500 and 550°C during which elemental sulfur or elemental selenium was
evaporated by radiative heating. White light scattered at the surface of the growing Cu(In,Ga)(S,Se)2 layers was
monitored by a CCD camera in order to record in-situ the changing optical properties of the films. EDXRD was used to
monitor the evolving structural properties of the growing films simultaneously. During the sulfurization and selenization
process the growing films pass through various phase transition which could be correlated with the white-light scattering
Detailed analysis of the time evolution of both signals (EDXRD and WLS) allowed to determine specific signatures in
the WLS signals indicating the influence of the process parameters on the growth process of Cu(In,Ga)(S,Se)2.
A new method for optical process control of the three-stage co-evaporation of Cu(In,Ga)Se2 thin films is presented.
Precise control of the deposition process is desirable as the field of process parameters is rather complex. In an
enhancement to laser light scattering (LLS) with a single photo-detector, the diffuse part of the scattered laser light is
now used to a larger extent. In consequence, it is possible to deduce compositional information (e.g., the Ga/III-ratio) for
the deposited layer with high accuracy. This is demonstrated in a series of experiments on Mo-coated float glass and
titanium foil substrates where the final Ga content of the Cu(In,Ga)Se2 thin film has been intentionally varied. As an
additional benefit of the enhanced LLS system, the new system can also be used for process control, in cases where
previously the intensity of scattered component of light has not been sufficient for reliable interpretation. The
information from this new monitoring technique was used to set up an optical model for semitransparent, coevaporated
InxGaySez-layers of various compositions. Using this model, an evaluation of phases formed during the process and
adjustment of deposition parameters is possible. The knowledge of phases formed on glass and titanium substrates is
important since the Cu(In,Ga)Se2 formation depends on properties of the InxGaySez-layer evaporated in stage 1 of the
three-stage process. Break-off experiments at different points within stage 1 were carried out to test and improve the
model. Depth profiling by means of x-ray fluorescence (XRF) and microstructural studies by means of x-ray diffraction
(XRD) also deliver valuable information for the optical model.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.