NOVELTY - Formation of a contact structure comprises forming an opening in the semiconductor material under an opening in a masking layer (101), to extend through an overlying semiconductor material layer to expose an underlying semiconductor material layer, and to extend under the edges of the opening in the masking layer to form an undercut region extending around the entire periphery of the opening in the masking layer. The undercut region extends entirely across the overlying semiconductor material layer. It defines a void (645) between a metal layer (644) and the overlying semiconductor material.    USE - The method is for formation of a contact structure, in a device including a first contact type for contacting an underlying layer of a semiconductor junction of a semiconductor structure in a manufacturing process of a bifacial solar cell useful for photovoltaic device. It is useful for devices formed on wafers and thin films.    ADVANTAGE - The metal does not bridge the semiconductor junction. The method achieves electrical isolation from the overlying semiconductor material of opposite polarity; and achieves higher efficiencies than currently achievable in commercial solar cell production, including zero front surface metal shading loss, lightly diffused surfaces to reduce surface recombination and avoid any regions of low collection probability for generated carriers, low metal/silicon interface area to minimize the contribution to the device dark saturation current, achievement of minority carrier diffusion lengths in the bulk much greater than the wafer thickness, and low resistive losses. Defects and damage to the silicon do not result and thus the p-n junction retains a very high shunt resistance and produces a floating junction of superior quality compared to those produced using laser scribing. By using inkjet printing based processes to facilitate all of the cell finishing processes, these can be performed without the use of sophisticated equipment that requires technical expertise for its operation and maintenance. Thus, it becomes feasible in regions such as developing countries to do the remaining processing that requires relatively low cost and unsophisticated equipment that is typical of equipment already found in such developing countries. This is not possible with commercial cell technologies, currently in use around the world, which require high temperature diffusions and oxidations and high temperature metal sintering, such as for the conventional screen printed solar cell.    DETAILED DESCRIPTION - Formation of a contact structure, in a device including a first contact type for contacting an underlying layer of a semiconductor junction, which comprises the underlying layer of a semiconductor material of a first dopant polarity, and an overlying layer of a semiconductor material oppositely doped to the underlying layer, comprises forming a masking layer (i.e. insulating layer) over the overlying layer of semiconductor material; forming an opening in the masking layer exposing the semiconductor material; forming an opening in the semiconductor material under the opening in the masking layer; and forming a metal layer extending into the opening in the semiconductor material to contact the underlying semiconductor layer, where metal layer is isolated from the overlying semiconductor material layer. The opening in the semiconductor material is formed to extend through the overlying semiconductor material layer to expose the underlying semiconductor material layer, and to extend under the edges of the opening in the masking layer to form an undercut region extending around the entire periphery of the opening in the masking layer. The undercut region extends entirely across the overlying semiconductor material layer. The insulating layer is silicon nitride or silicon dioxide. The metal layer is formed using an inkjet deposition technique. Lines and grooves are formed by printing of the processing agent in abutting or slightly overlapping dots.    INDEPENDENT CLAIMS are included for:    (a) a contact structure;    (b) a method of processing a semiconductor structure in a manufacturing process;    (c) a processing apparatus;    (d) a method of applying a processing agent to a surface of a semiconductor structure; and    (e) a method of forming an opening in an insulation layer.    DESCRIPTION OF DRAWING(S) - The figure diagrammatically illustrates the contact structure after a metallization step.    Masking layer (101)    Opposite polarity substrate (102)    N-type surface layer (633)    Metal layer (644)    Void (645)