| 摘要 |
1481099 Aligning objects photo-electrically INTERNATIONAL BUSINESS MACHINES CORP 19 Sept 1974 [11 Oct 1973] 40804/74 Heading G1A An object having an alignment pattern in relief to enable it to be photo-electrically aligned with another object is coated with a reflective layer to make the pattern more easily detected. In Fig. 1 a system is shown for aligning a semi-conductor wafer 11 with a mask 13. The system is described in detail in Specification 1414658. The wafer 11 has a relief alignment pattern in it, and it is found that due to multiple reflections in oxide and resist layers on the wafer the pattern can be obscured. For this reason the wafer is covered with a reflective layer which reflects light at an alignment wavelength but transmits at a wavelength which can expose the photo-resist layers beneath it. Suitable coatings are dyes such as Rhodamine B, Erythrosin, Wasser Blau or Sudan II, or metals such as aluminium, gold or silver, usable wavelengths being given in the description. The coatings are not wholly reflective at the alignment wavelengths, but are sufficiently absorbing to prevent any significant amount of light being passed through the coating, reflected off a lower layer and being transmitted back through the coating. |
