The problem of tracking very small semiconductor products with a bar code is easily overcome by the use of the matrix symbol, which is a unique two-dimensional symbol that is the most space efficient method of packing binary data. It is both machine written and machine read to provide the utmost in accuracy and repeatability. The number of data cells can either be expanded or contracted to handle the required information and in addition can contain parity and error correcting codes. Semiconductor chips, wafers, substrates, modules and even masks can all be laser marked with this symbol and quickly read at any later stage of the manufacturing process. This unique symbol is computer generated by a software algorithm which creates the data cells and data frame which are laser etched on the product. On-line product identification yields immediate benefits in manufacturing such as inventory control, proper mating of parts, proper selection of test programs, quality control, etc. Use of a very small unique machine readable symbol now permits these benefits to be extended to miniature parts in an automated high speed manufacturing line.
James P. Martin,
"Unique symbol for marking and tracking very small semiconductor products", Proc. SPIE 1598, Lasers in Microelectronic Manufacturing, (1 December 1991); doi: 10.1117/12.51042; https://doi.org/10.1117/12.51042