The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 28, 1994
Filed:
Jul. 06, 1992
Masaaki Aoyama, Kanagawa, JP;
Keiichi Kimura, Kanagawa, JP;
Nikon Corporation, Tokyo, JP;
Abstract
A holder which cleanly holds an article such as a semiconductor wafer and which is high in rigidity, light in weight, high in dimensional stability and excellent in dust resistance. The wafer holder includes a vacuum holding surface formed with a plurality of concentric or helical annular projections and annular vacuum holding grooves which are arranged at a given pitch. A plurality of vacuum holes for vacuum holding purposes are formed in the respective annular grooves so as to be arranged radially and each of the vacuum holes is subjected to pressure reduction by a vacuum source through the interior of the holder, thereby correcting the flatness of a wafer to conform with the upper surfaces of the annular projections. At least the portions of the holder which contact with the wafer (preferably the holder on the whole) are made of a sintered ceramic containing covalent bond-type conductive material such as a TiC-containing sintered Al.sub.2 O.sub.3 so that the contact portions exhibit conductivity and also less pores are present in the surface, thereby practically preventing the occurrence and deposition of fine particles.