METHOD AND APPARATUS FOR ELECTRON BEAM ALIGNMENT WITH A MEMBER BY DETECTING X-RAYS

摘要

1522372 Aligning semi-conductor wafers WESTINGHOUSE ELECTRIC CORP 1 Aug 1975 32300/75 Heading G1A [Also in Division G3] In a system in which it is necessary to accurately position an object with respect to an electron beam, the object is provided with regions which emit x-rays when struck by the beam; analysis of the x-rays by detectors placed close to the marks provides a measure of whether the marks are receiving the beam, i.e. whether alignment is correct. Any errors noted may be corrected by manual or automatic adjustment of the beam or object position. The object may be an integrated circuit or the like, with the beam being used to expose a photo-resist layer after alignment has been achieved. In Fig. 1, the object 10 has recessed x-ray generating marks 13, preferably of Mo, Hf, Ta, W or Au. A layer of material 14, such as a metal, which is to be etched is covered with photo-resist 15. Initially the beam 18 is scanned over object 10 to overlap the marks 13, and the x-rays are measured by silicon diodes 16 placed behind the marks. The beam scan or the object position is adjusted until each mark emits a predetermined level of x-rays, indicating alignment. The beam is then scanned over the photo-resist sufficiently slowly for the pattern subsequently to be etched in layer 14 to be recorded in the resist. Details are given of a suitable photo-cathode electron beam source which is fixed in a housing with beam scanning coils; the housing also contains the detectors and a holder for the object, Fig. 4 (not shown). Also detailed are a phase detector circuit for use with a swept beam to allow co-ordinate information, angular information and beam size to be determined and hence to permit automatic alignment by adjusting the sweep, Fig. 7 (not shown). The object may be provided with a series of marks, so that the resist can be exposed area by area, the beam being re-aligned with successive marks as each area is exposed.