Optical projection printing apparatus wherein wafer mark has a g

Details Optical projection printing apparatus wherein wafer mark has a g Optical projection printing apparatus wherein wafer mark has a g

1988-07-27

1989-08-15

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

356401, G01N 2186, G01B 1100

Patent

active

048577448

ABSTRACT:
An optical projection printing apparatus which can irradiate a mask with light from a first light source to focus the mask pattern on a resist of a semiconductor wafer in a highly accurate alignment by a first optical system including a projection lens. A wafer mark formed on the wafer to have a grating pattern shape is arranged to have its grating pitch direction located in the sagittal plane of the first optical system. The wafer mark is irradiated with the light coming from a second light source having a wavelength different from that of the first light source. Of the reflected light from the wafer mark, only the .+-. 1st order diffraction light is extracted by a filter and partially superposed on the mask in a transversely misaligned state so that the reflected light from the wafer mark may be focused by a second optical system. The aforementioned filter is disposed in the Fourier plane of the second optical system.

REFERENCES:
patent: 4592625 (1986-06-01), Uehara et al.
patent: 4780616 (1988-10-01), Nishi et al.
Bouwhuis et al., Automatic Alignment System for Optical Projection Printing; 11/78, IEEE Transactions on Electron Devices, vol. ED-26, No. 4, Apr. 1979.

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