Method and device for measuring depth of ultra-shallow junction of double-sided solar cell

Abstract

The invention relates to a method for measuring a PN junction of a double-sided cell. The method comprises the steps of: adsorbing a silicon wafer to be measured in vacuum by a graphite tubular electrode, allowing a surface to be measured to be in contact with an electrolytic solution to perform oxidize and generate a silicon dioxide film, monitoring and measuring the thickness of the film in realtime by employing a fiber spectrometer, removing an oxide layer by using a hydrofluoric acid solution, employing four probes to measure the resistivity, repeating the steps of generation of the oxidelayer, the measurement of film thickness, corrosion of the oxide layer and measurement of the resistivity until the resistivity is equal to the resistance of a substrate. The silicon wafer is overturned to repeat the steps mentioned above to achieve measurement of the depth of the PN junction. The measurement method of the depth of the PN junction is suitable for the measurement of the depth of the double-sided cell, and is simple in step, low in cost and accurate in measurement.

Description

technical field [0001] The invention relates to the field of photovoltaic solar cells, in particular to a method for measuring the junction depth of double-sided solar cells. Background technique [0002] Environmental issues such as "smog weather", "global warming", "ozone layer destruction", "drinking water pollution" and "land desertification" have attracted more and more attention, and energy and environmental protection have become the world's themes. To this end, my country's energy science and technology master plan puts forward measures and suggestions to promote efficient and clean utilization of traditional energy, development and utilization of new energy, and guarantee of energy security. In terms of crystalline silicon cells, research is mainly on crystalline silicon cells and high-efficiency cells that are fully industrialized on a large scale. [0003] The double-sided battery forms NPP+ or PNN+ high-low junction battery structure by doping B or P at a high c...

AI Technical Summary

Problems solved by technology

However, the PN junction depth of traditional single-sided cells is several microns, while the preparation of double-sided cells usually adopts shallow junctions and heavy doping, and its junction depth is less than 1 micron

This method needs to prepare an electrode on the surface of the sample every time it is corroded, which makes the operation complicated and the test process takes a long time, and the corrosion depth is estimated by the corrosion rate, so the test results are difficult to be accurate

Although the traditional electrochemical ECV method is simple and has good resolution and accuracy, it is limited by the breakdown under reverse bias and is not easy to characterize highly doped samples and samples with a certain depth distribution and PN junctions.

In addition, the impurity concentration of the lightly doped n-type substrate in the lower layer of the ECV test is greatly affected by the high-concentration doping of the upper layer, and it is impossible to accurately measure the back junction of the double-sided battery.

Secondary ion mass spectrometry (SMIS) has better resolution and accuracy, and can also characterize the PN junction, but it requires complex and expensive equipment and the measured impurity concentration is the atomic concentration rather than the electrically active impurity concentration

However, due to the high energy of the laser, the impurity concentration of phosphorus element due to thermal action is reduced, thereby reducing the generation and redistribution of impurities, which interferes with the measurement accuracy

The traditional anodic oxidation method is a commonly used method for testing the depth of PN junctions. It uses silicon wafers as anodes and platinum wires as cathodes, and puts them in pure water for electro-oxidation to form a silicon dioxide oxide layer. Colorimetric method or weighing method To obtain the thickness of the silicon dioxide layer, it is necessary to fix the silicon wafer on the electrode with a binder such as paraffin wax or conductive glue. Although the operation is simple, the accuracy is not enough

[0005] In summary, the above-mentioned measurement method of PN junction depth is not fully applicable to the junction depth measurement of shallow junction heavily doped double-sided cells

Images