Photomask and method for qualifying the same with a prototype specification

#The present invention relates in general to photolithography and, more particularly to a photomask and method for qualifying the same with a prototype specification.

#As semiconductor device manufacturers continue to produce smaller devices, the requirements for photomasks used in the fabrication of these devices continue to tighten. Photomasks, also known as reticles or masks, typically consist of substrates (e.g., high-purity quartz or glass) that have an absorber layer (e.g., chrome) formed on a substrate. The absorber layer includes a pattern representing a circuit image that may be transferred onto semiconductor wafers in a lithography system. As feature sizes of semiconductor devices decrease, the corresponding circuit images on the photomask also become smaller and more complex. Consequently, the quality of the mask has become one of the most crucial elements in establishing a robust and reliable semiconductor fabrication process.

#Before fabricating production quality integrated circuits (ICs), semiconductor manufacturers typically test the circuit design by using a prototype photomask. The cost of manufacturing prototypes that include advanced designs (e.g., feature sizes with a dimension less than 0.18 microns) has become a concern to photomask manufacturers since the cost of manufacturing photomasks is rapidly increasing. One factor that effects the cost of manufacturing a prototype photomask is the cycle time needed to print an image of the IC in a resist layer of a photomask blank. Currently, multiple instances of an IC are placed on a single photomask and each instance must meet standards in a production specification associated with a specific manufacturing process. For example, if a photomask contains twenty die and only nineteen die meet the standards in the production specification, the entire photomask is rejected and the process for manufacturing the photomask design starts from the beginning.

#A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:

#FIG. 1 illustrates a cross-sectional view of a photomask assembly manufactured with a prototype specification in accordance with teachings of the present invention;

#FIG. 2 illustrates a perspective view of a photomask including an array of die in accordance with teachings of the present invention; and

#Preferred embodiments of the present invention and their advantages are best understood by reference to FIGS. 1 through 3, where like numbers are used to indicate like and corresponding parts.

#A photomask is a crucial component of a lithography system because it serves as the template that images a complex geometry, such as an integrated circuit (IC), on a wafer. Each IC may be formed by a combination of patterns that include multiple design features. As the dimensions of the design features decrease, the complexity of the manufacturing process used to make the photomask increases. In some cases, the photomask may include multiple instances of the IC. In a conventional process, if one of the instances does not meet the criteria in a production specification, the photomask is discarded and the manufacturing process for the photomask starts from the beginning. The present invention provides a prototype specification that enables a photomask to be used in a semiconductor manufacturing process if one or less than all of the instances of the IC meets standards included in the prototype specification.

#FIG. 1 illustrates a cross-sectional view of photomask assembly 10 qualified with a prototype specification. Photomask assembly 10 includes photomask 12 coupled to pellicle assembly 14. Substrate 16 and patterned layer 18 form photomask 12, otherwise known as a mask or reticle, that may have a variety of sizes and shapes, including but not limited to round, rectangular, or square. Photomask 12 may also be any variety of photomask types, including, but not limited to, a one-time master, a five-inch reticle, a six-inch reticle, a nine-inch reticle or any other appropriately sized reticle that may be used to project an image of a circuit pattern onto a semiconductor wafer. Photomask 12 may further be a binary mask, a phase shift mask (PSM), an optical proximity correction (OPC) mask or any other type of mask suitable for use in a lithography system.