Patent GB-1467521-A (GB)
Title: Method and apparatus for electron beam alignment with a member by detecting cathodoluminescence from oxide layers for fabricating circuit patterns
IPC: H01L21/027
Filed: 1974-06-03
Abstract: 1467521 Cathode-ray tubes WESTING- HOUSE ELECTRIC CORP 3 June 1974 [1 Oct 1973 13 June 1973] 24458/74 Heading H1D [Also in Division G3] For the fabrication of a circuit pattern, an electron beam is aligned with a member, by providing on the member at least one detection area whose cathodo-luminescence is differentiated from that of its surroundings, cathodoluminescence being generated by at least one oxide layer on the member, detected changes in the luminescence providing an electrical signal, dependent on the degree of overlap between the beam and detection area and used to control beam alignment. The member may be a single crystal of Si. The beam may be a patterned one, irradiating one of a sequence of electroresists on the member, or a scanning one, in which case a plurality of detection areas (105), Figs. 12, 13 (not shown), delineate areas (111) to be irradiated by the modulated scanning beam, the member being moved when an area has been irradiated. Cathode-luminescence arrangements, Figs. 3- 10 (not shown). The cathodo-luminescence is provided by an oxide layer arranged on the member to form a detection area which may be square, rectangular, circular, or triangular in shape. The emitted radiation is received by a photodetector, either after transmission through the member and a filter, or upon reflection at the upper surface of the member. The degree of cathodo-luminescence depends on the oxide layer thickness. Possible constructions comprise: (i) a local thickening or thinning of the oxide layer in the detection area (Figs. 3, 4). (ii) The presence or absence of the oxide layer in the detection area (Figs. 5, 6). (iii) The presence of a layer of material; either opaque, or having cathodo-luminescent character distinct from the oxide layer, either over or under the oxide layer and provided either within or without the detection area (Figs. 7, 8). (iv) The oxide layer may be formed on an epitaxially grown layer on a sapphire member (Figs. 8, 10). The detection areas may themselves form part of a fabricated circuit pattern. Alignment may be indicated by by maximum or minimum of photodetector output, when scanning beam or patterned beam alignment portions have the same shape, or the beam may oscillate over the detection areas, the beam being finally aligned at a rise or fall, or plateau region of photodetector output. Control of alignment, Figs. 11, 14 (not shown). A control circuit (Fig. 11), in which X Y error signals are generated, may be used, or, for the scanning electron beam, the photodetector output is fed to display (112, Fig. 14), computer (113), which controls the beam during circuit fabrication, indicating the desired alignment positions via the display. The two inputs are made coincident to align the beam, either manually or under computer control. For each field (111, Fig. 13), the beam scans between diagonally opposed detection areas, separate alignment procedures being used for each of the two pairs delineating the area.