a solar cell with such a doping structure may still be limited by the amount of dopant between the contacts 202 in an implant through the mask 104 the mask 104 must travel with the substrate 100 when the substrate 100 is scanned as mentioned above this movement increases the difficulty in cooling and grounding the mask 104 additionally a mask 104 with small apertures 105 will block much of the ion beam 103 which decreases productivity and device throughput a fixed mask 104 having a plurality of apertures 105 is configured to cover the height y direction of the ion beam 101 this may be for example the height of a ribbon ion beam 101 or the maximum and minimum vertical extent of a scanned ion beam 101 such a design provides positional definition in one dimension such as the dimension in which the ion beam 101 is scanned e g y direction or the long dimension of a ribbon ion beam 101 e g x direction positional definition in a second dimension such as the direction in which the substrate 100 is scanned is provided by changing the scan speed of the substrate 100 fig4 is a front perspective view of a shadow mask 404 having seven apertures 405 and is fixed i e does not translate or scan with respect to the ion beam 101 while seven apertures 405 are illustrated the mask 404 is not solely limited to seven apertures 405 and other numbers are possible.