Method for local modification of etching resistance in a silicon layer, use of this method in the production of passivation contact solar cells and thus-created solar cell
Provided are a method for local structuring of a silicon layer, which method comprises a step of local modification of the etching resistance within said silicon layer and a subsequent step of removing unmodified regions of said silicon layer by etching and applications of this method for the production of solar cells.
1 . A method for local structuring of a silicon layer to produce locally structured polycrystalline layers ( 301 , 1301 , 1302 ),
characterized in that
the method comprises a step of local modification of the etching resistance within said silicon layer ( 301 , 1301 , 1302 ) and a subsequent step of removing unmodified regions of said silicon layer ( 301 , 1301 , 1302 ) by etching,
wherein the local modification of the etching resistance of the silicon layer ( 301 , 1301 , 1302 ) is brought about at least partly by application of a laser to those regions of the silicon layer ( 301 , 1301 , 1302 ) in which the etching resistance is increased,
wherein the local modification of the etching resistance is brought about at least partly by inducing a local increase in the crystallinity of the silicon layer ( 301 , 1301 , 1302 ) in the modified regions to produce locally structured polycrystalline layers, and
wherein the laser that is used is a short pulse ultraviolet light laser, and wherein the pulse energy is being selected such that a local increase in the crystallinity of the silicon layer ( 301 , 1301 , 1302 ) and diffusion or activation of dopants, in case dopants are present, occurs, but an underlying layer remains unaffected.
2 . The method according to claim 1 , wherein the silicon layer ( 301 , 1301 , 1302 ) as deposited is amorphous, partly crystalline or completely crystalline.
3 . The method according to claim 1 , wherein the pulse energy is being selected such that a local increase in the crystallinity of the silicon layer ( 301 , 1301 , 1302 ) and diffusion or activation of dopants, in case dopants are present, occurs, but an underlying layer remains unaffected.
4 . The method according to claim 1 , wherein the local modification of the etching resistance of the silicon layer ( 301 , 1301 , 1302 ) is brought about at least partly by local doping.
5 . The method according to claim 4 , wherein the doping source is a doping source layer ( 401 , 1401 , 1402 ) formed by a highly doped amorphous silicon layer or a dopant-containing a borosilicate glass layer.
6 . The method according to claim 1 , wherein the local modification of the etching resistance of the silicon layer ( 301 , 1301 , 1302 ) is brought about at least partly by local doping by implantation of boron.
7 . The method according to claim 4 , wherein the doping source is a doping source layer ( 401 , 1401 , 1402 ) formed by a highly doped amorphous silicon layer or a dopant-containing silicate glass layer.
8 . The method according to claim 7 , wherein the silicon layer ( 301 , 1301 , 1302 ) and the doping source layer ( 401 , 1401 , 1402 ) are successively created in the same process chamber.
9 . The method according to claim 4 , wherein local doping is obtained by ion implantation using a shadow mask.
10 . The method according to claim 1 , wherein the subsequent step of removing unmodified regions of said silicon layer ( 301 , 1301 , 1302 ) by etching takes place in alkaline solution.
11 . The method according to claim 1 , wherein the subsequent step of removing unmodified regions of said silicon layer ( 301 , 1301 , 1302 ) by etching takes place in alkaline solution in a concentration range between 1 and 40%.
12 . A method for the production of silicon solar cells, said method comprising at least one step of local structuring of the silicon layer ( 301 , 1301 , 1302 ) according to claim 1 .
13 . The method according to claim 12 , wherein as a starting substrate a silicon wafer ( 101 , 1101 ), the saw damage of which was removed and which was then cleaned, is provided.
14 . The method according to claim 13 , wherein a stack of layers is first deposited onto said silicon wafer ( 101 , 1101 ) which stack comprises an oxide layer ( 201 , 1201 , 1202 ), an undoped silicon layer ( 301 , 1301 , 1302 ) and a dopant layer ( 401 , 1401 , 1402 ) on top of the undoped silicon layer ( 301 , 1301 , 1302 ).
15 . The method according to claim 14 , wherein a laser is applied to produce a highly doped (p++) region ( 501 , 1501 , 1502 ) in the undoped silicon layer ( 301 , 1301 , 1302 ) and wherein at parts of the locations where the laser has been applied a metal contact for the extraction of positive charge carriers is created in a later process step.
16 . The method according to claim 1 , wherein the solar cell is a two side contacted solar cell, further comprising producing localized passivation layers for passivation the contacts on the front side of the solar cell.
17 . The method according to claim 16 , wherein the regions between places, at which local modification of the etching resistance within said silicon layer ( 301 , 1301 , 1302 ) has been performed, are homogenously doped with the same doping type as the passivation layer.
18 . The method according to claim 1 , wherein the solar cell is an IBC solar cell, further comprising producing localized passivation layers or passivation contacts in an interdigitated structure on the rear side, wherein the subsequent step of removing unmodified regions of said silicon layer ( 301 , 1301 , 1302 ) by etching takes place in alkaline solution.
19 . A method for local structuring of a silicon layer to produce locally structured polycrystalline layers ( 301 , 1301 , 1302 ),
characterized in that
the method comprises a step of local modification of the etching resistance within said silicon layer ( 301 , 1301 , 1302 ) and a subsequent step of removing unmodified regions of said silicon layer ( 301 , 1301 , 1302 ) by etching,
wherein the local modification of the etching resistance of the silicon layer ( 301 , 1301 , 1302 ) is brought about at least partly by application of a laser to those regions of the silicon layer ( 301 , 1301 , 1302 ) in which the etching resistance is increased,
wherein the local modification of the etching resistance is brought about at least partly by inducing a local increase in the crystallinity of the silicon layer ( 301 , 1301 , 1302 ) in the modified regions to produce locally structured polycrystalline layers, and
wherein the laser that is used is a short pulse ultraviolet light excimer laser, and wherein the pulse energy is being selected such that a local increase in the crystallinity of the silicon layer ( 301 , 1301 , 1302 ) and diffusion or activation of dopants, in case dopants are present, occurs, but an underlying layer remains unaffected.