SURFACEMETROLOGY
Solar cell surface inspection with 3D metrology
With the economy in its current tailspin and gas prices at record highs, the solar energy industry has been called upon to provide solutions for our energy crisis. Global concerns about the atmosphere and the effort to reduce greenhouse gas emissions are other reasons there has been a large acceleration of growth in the solar energy industry. By Benjamin Mell at Nanovea.
olar cell production is increasing at just under 50% yearly. The overall price tag for the buyer will be the most important factor for the solar energy industry to be successful. This task of decreasing the overall cost to the consumer can be achieved, thus producing higher profits for the solar cell manufacturer, only if the efficiency and quality of solar cell materials continues to improve.
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Importance of surface metrology inspection for quality control
Solar cell manufacturers are using profilometers for better control of trace line shape and surface roughness, in order to improve yields and efficiencies that will ultimately reduce costs and increase profits. Surface roughness is a vital parameter that influences the efficiency of solar cells. Accurate surface metrology used to monitor certain process steps, for quality control, will assist solar cell producers in amplifying yield and decreasing associated manufacturing costs. Also, thorough analysis of various surface roughness parameters allows an enhanced understanding of which characteristic of solar material topography indicates important variations in efficiency.
Solar cell material that is somewhat rough on the surface will absorb more light than a material with a very smooth surface, which will produce a higher efficiency and better performance. The negative aspect of a surface that is too rough, however, is that this material will scatter too much light, causing less absorption and a reduced efficiency. At the other end of the spectrum, plastic and glass solar materials are made to have an extremely
smooth surface, in order to scatter and absorb the smallest amount of light possible.
Measurement objective
In this application, the Nanovea HS1000 is used to measure two different types of solar material (photovoltaic material and glass) and calculate their respective surface roughness, surface features and wafer bow. The shape of trace lines on the photovoltaic material will also be measured. With a maximum stage speed of 1 meter per second, the HS1000, unlike stylus profilometers, can easily handle high production throughput applications, where many measurements are needed in quick fashion.
Measurement setup and tips For measuring this type of material, it is best to use a high-intensity Xenon light source. Our optional high-intensity Xenon source produces a very intense light, which is extremely useful when
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www.solar-pv-management.com Issue V 2010
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