Three semiconductor manufacturers yesterday registered the first semiconductor chip designs at the Library of Congress under new legislation which protects the thumbnail-sized devices.

Intel Corp., Motorola Inc. and Harris Corp. registered their designs at the library's copyright office under the Semiconductor Chip Protection Act of 1984.

The chips are used in a wide variety of products such as personal computers, X-ray scanners and microwave ovens.

"The Semiconductor Chip Protection Act is the first new intellectual-property law passed by Congress in more than 100 years," said Rep. Robert W. Kastenmeier (D-Wis.), chairman of the House Judiciary Committee's subcommittee on patents, copyrights and trademarks and an architect of the legislation.

"Now, semiconductor companies will have protection from pirates copying their complicated designs," said Tom Dunlap, Intel's general counsel and secretary. "As a result, the Chip Protection Act will encourage the development of chips that were previously considered economically marginal."

Other products, such as computer and video software not clearly protected under the existing system of patents and copyrights, may be examined by members of Congress this year to determine whether new legislation is necessary for them as well, Kastenmeier said.

"By the middle of 1985, we will be fairly involved in computer software problems," he said. Despite "theoretical protection" under existing copyright laws, the current copyright law does not "wholly respond to all the problems that have arisen in the computer software area," Kastenmeier said.

Still other products, such as biological designs used in the field of biotechnology, may eventually be covered by legislation designed to protect rapidly advancing technologies that fall between the cracks of existing intellectual-property laws.

The Semiconductor Chip Protection Act was prompted by the semiconductor industry, which said that existing laws did not sufficiently protect its products from increasing amounts of piracy at home and abroad.

The new law, which is a hybrid of copyright and patent laws, protects the designs of semiconductor chips by making it illegal to reproduce any semiconductor pattern for 10 years after registration. It carries penalties of up to $250,000 for infringement.

Copyright laws generally apply to works of art, not utilitarian objects such as semiconductor-chip designs. Patent laws protect basic circuitry but not design work related to adapting circuits to particular industrial purposes.

Foreign companies will be able to register their works if their countries extend equivalent protection to U.S. designs by treaty or domestic laws. The Japanese are said to be drafting and reviewing a similar chip protection law.