Proxy advisers oppose 3 Axcelis board directors

SAN FRANCISCO, April 18 (Reuters) - Proxy advisory firms Riskmetrics and Glass Lewis on Friday recommended that shareholders of Axcelis Technologies Inc (ACLS.O: Quote, Profile, Research, Stock Buzz) withhold votes to oppose election of three directors at an upcoming annual meeting.

Axcelis's corporate bylaws say that any nominee who has a greater number of votes withheld than voted in support must offer to resign. The board currently has seven directors.

Axcelis is trying to fend off a $615.6 million takeover bid from Japan's Sumitomo Heavy Industries (6302.T: Quote, Profile, Research, Stock Buzz). (Reporting by Anupreeta Das; Editing by Gary Hill)