Mask work is the arrangement on a chip of semiconductor devices such as transistors and passive electronic components such as resistors and interconnections. A mask work is a two or three-dimensional layout of an integrated circuit. A mask work also refers to the Intellectual Property Rights conferring time-limited exclusivity to reproduction of a particular layout. The layout is called a mask work because, in photolithographic processes, the multiple etched layers within actual ICs are each created using a mask, called the photomask, to permit or block the light at specific locations, sometimes for hundreds of chips on a wafer simultaneously.
Mask work exclusive rights were first granted in the US by the Semiconductor Chip Protection Act of 1984. In Canada these rights are protected under the Integrated Circuit Topography Act (1990, c. 37). Equivalent legislation exists in Australia and Hong Kong. Because of the functional nature of the mask geometry, the designs cannot be effectively protected under copyright law.
The United States Code defines a mask work as a series of related images, however fixed or encoded, having or representing the predetermined, three-dimensional pattern of metallic, insulating, or semiconductor material present or removed from the layers of a semiconductor chip product, and in which the relation of the images to one another is such that each image has the pattern of the surface of one form of the semiconductor chip product. (17 USC § 901 (a) (2)).
According to 17 USC § 904, rights in semiconductor mask work last only two years (if unregistered) or ten years (if registered). Contrast this with the effectively perpetual terms for modern copyrighted works and the fact that mask works are not subject to any statutory fair use defense, nor the typical backup copy exemptions that 17 USC § 117 provides for computer software. Nevertheless, as fair use in copyrighted works was originally recognized by the judiciary long before being codified in statute, it may one day be recognized in mask work protection as well.
The exclusive rights in a mask work are somewhat like those of copyright: the right to reproduce the mask work or distribute an IC made using the mask work.
Like the first sale doctrine, a lawful owner of an authorized IC containing a mask work may freely import, distribute or use, but not reproduce the chip (or the mask).
Mask work protection is characterized as a sui generis right, i.e., one created to protect specific rights where other laws were inadequate or inappropriate.
Mask work rights have more in common with copyrights than with other exclusive rights such as patents or trademarks. On the other hand, they are used alongside copyright to protect a read-only memory component that is encoded to contain computer software.