Melt through contact formation method
AssigneePacific Solar Pty Limited
InventorsZhengrong Shi, Paul Alan Basore, Stuart Ross Wenham, Guangchun Zhang, Shijun Cai
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Abstract
A thin film photovoltaic devices is described, having a glass substrate 11 over which is formed a thin film silicon device having an n++ layer 12, a p layer 13 and a dielectric layer 14 (typically silicon oxide or silicon nitride). To create a connection through the p layer 13 to the underlying n++ layer 12, a column of semi-conductor material is heated, the column passing through the various doped layers and the material in the column being heated or melted to allow migration of dopant between layer of the device in the region of the column.
Claims29
A method for forming a connection region for making electrical connection to a first doped semi-conductor region of a thin film semi-conductor device located beneath at least a second doped semi-conductor region of opposite dopant type, the method including the steps of:
- forming the first semi-conductor region with a predominant first dopant type of first dopant polarity, such that there is an excess number of dopant atoms of the first dopant type with respect to dopant atoms of a second dopant type of opposite dopant polarity in the first semi-conductor region;
- forming at least the second semi-conductor region over the first semi-conductor region with a predominant dopant type of the second dopant polarity, such that there is an excess number of dopant atoms of the second dopant polarity with respect to dopant atoms of the first dopant polarity in the second semiconductor region and where, in the connection region, the excess number of dopant atoms of the predominant second dopant polarity per unit area of the film in the second semi-conductor region is lower than the number of excess dopant atoms of the predominant first dopant type per unit area of the film in the corresponding first semi-conductor region;
- heating a column of semi-conductor material passing through the second semi-conductor region and into the first semi-conductor region in an area of the connection region of the semi-conductor device where a contact to the first semi-conductor region is required, the heating step causing the material in the first and second semi-conductor regions to increase in temperature whereby dopant mobility is increased and dopant atoms of the first dopant polarity migrate from the first semi-conductor region to the second semi-conductor region to locally change the dopant polarity of the predominant dopant type in the second semi-conductor region.
A method of forming an electrical connection to a first doped semi-conductor region of a thin film semi-conductor device located beneath at least a second doped semi-conductor region of opposite dopant type, the method including the steps of:
- forming the first semi-conductor region having a predominant first dopant type of first dopant polarity, such that there is an excess number of dopant atoms of the first dopant type with respect to dopant atoms of a second dopant type of opposite dopant polarity in the first semi-conductor region;
- forming at least the second semi-conductor region over the first semi-conductor region, the second semi-conductor region having a predominant second dopant type of opposite dopant polarity to the first dopant type, such that there is an excess number of dopant atoms of the second dopant polarity with respect to dopant atoms of the first dopant polarity in the second semi-conductor region;
- forming a metal layer over at least an area of the semi-conductor material in a contact region where a contact is required to the first semi-conductor region;
- heating the metal layer in the contact region whereby the metal and the underlying semi-conductor material melt at least down to the first semi-conductor region such that at least a part of the metal layer alloys with the underlying material to form a column of metal alloy between the first semi-conductor region and the top surface of the device and dopant mobility is increased whereby excess dopant molecules of the first dopant polarity occupy a shell around the alloy in the second semi-conductor region to locally change the dopant polarity of the predominant dopant type in the second semi-conductor region in the shell.
Dependencies are inferred from the claim text.