Electrical Characterization and Doping Uniformity Measurement during Crystalline Silicon Solar Cell Fabrication Using Hot Probe Method

Abstract

The parameters of crystalline semiconductor such as types of semiconductor, uniformity of impurity concentration of doped wafer, majority charge carrier concentration, sheet resistivity of doped wafer surface play an important role in solar cell fabrication process during emitter diffusion, that is the most critical step. In this paper, we have used a low cost in house made hot probe measurement setup. A hot plate was used to heat up the wafer up to 100°C. Two k-type thermocouples were placed simultaneously in contact with the hot and cold surface of the wafer to measure the temperature in situ for both hot and cold probe. We have used two copper probes with a voltmeter connected to measure the potential difference (thermoelectric voltage) between two probes for various temperatures up to 100°C with an interval of 10°C. We have taken measurement for commercial silicon wafer (thickness 200 µm) and one side polished 4 inch diameter Si wafer (thickness 660 µm) to determine the wafer type (n-type or p-type). We also calculated thermopower or Seebeck coefficient from the voltage vs. time curve, that is constant for particular substrate. As a process monitoring tool for solar cell fabrication process, after n-type diffusion using POCl3 on p-type silicon wafer of thickness 200 µm, we have done wafer mapping that gives us the information of doping uniformity over the whole surface of wafer both front and back side

Evaluation of Majority Charge Carrier and Impurity Concentration Using Hot Probe Method for Mono Crystalline Silicon (100) Wafer

“…Negative voltage reading on the voltmeter determines that the material is p-type and the reverse is n-type. From the plotted characteristics curve, thermally excited charge carrier generation for a particular temperature can be calculated [5]. The characteristic curves are divided into three-step processes:…”

“…Experimental setup of hot probe measurement shows the graph of characteristic curves for p-type 200 micrometer thickness (100) commercial silicon wafer[5]. Characteristic curves for p-type commercial (100) silicon wafer.…”

The design multi-functional probe for determining the P-N electrical conductivity type of thermoelectric semiconductors

“…[1] harici ısıtıcı plaka, sıcaklık kontrolörü, termokupl ve voltmetre yardımıyla manuel olarak çalışan bir Hot-Probe ölçüm düzeneği oluşturarak, silisyum numunelerin elektrik özelliklerini araştırmışlardır. Benzer şekilde literatürde, yığın ve ince film yarıiletkenlerin elektriksel ve ısıl özelliklerinin araştırılması amacıyla, manuel olarak çalışan Hot-Probe ölçüm düzenekleri kurularak çeşitli çalışmalar yapılmıştır [2]- [6].…”