Boron diffusion induced shunts

Various types of shunt occur in solar cells, including process errors, defects, tunnel shunts between adjacent opposing diffusions and pinholes in insulating dielectric layers used to separate opposite-polarity regions. We have found that boron diffusions into small windows in dielectric layers generate pinholes in the layers following the removal of borosilicate glass (BSG) after the diffusion. These “boron-spots” lie close to the edge of the diffusion windows. If a phosphorus diffused region underlies the dielectric then subsequent metallisation can short circuit the two regions.