Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Patent
1981-05-21
1983-04-12
Schilling, Richard L.
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
430273, 430325, 430326, 430327, 430396, 430950, 355 27, 355 30, G03C 504, G03C 500, G03B 2732, G03B 2752
Patent
active
043798314
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
In the production of integrated circuits, it is known to image a number of masks with different configurations onto a substrate whose surface is modified by exposure to light. The substrate is subjected to physical and chemical changes between successive images, such as a removal of the exposed or unexposed part of a photoresist applied to the substrate and the etching of underlying layers. The photoresist is conventionally termed "positive" in the first and "negative" in the second instance.
Whereas vertical structuring is readily possible today in the processing of integrated circuits by modern doping techniques and highly developed methods for the deposition of layers onto semiconductor surfaces, the possibilities for horizontal structuring are considerably more limited. A refinement of the lateral structuring of integrated circuits of the semiconductor disk is therefore the object of considerable present efforts.
While in the past it used to be the practice to contact the pattern-bearing mask directly with the substrate during the exposure step, the greater present-day requirements for accuracy have more recently led to imaging the mask onto the substrate with interposition of an objective (projection exposure). Moreover, there is also a tendency to simplify the production of several identical patterns on a single wafer by a stepwise shifting of the image instead of using a mask provided with a corresponding plurality of patterns.
OBJECT OF THE INVENTION
Since alternatives to optical lithography in the production of integrated circuits are not yet available or not yet sufficiently developed for practical applications, additional advances are to be expected mainly by the elimination of drawbacks which presently occur in projection exposure. My present invention, therefore, aims in particular at reducing the contamination problem along with elimination of a number of other present-day difficulties.
SUMMARY OF THE INVENTION
Impurities on a semiconductor disk can exist between the substrate and the photoresist as well as on the surface of the latter. Contaminating particles at the boundary layer between the semiconductor and the photoresist are less critical. If they are located fully in a bright or dark field they do not have any disadvantageous effect at all, since they can be considered as a filler of the photoresist. They remain during development in the photoresist and are either dissolved with the resist or flushed away. However, dust particles at the surface of the photoresist are critical since they act as mask defects and completely shield the underlying photoresist portions.
The accumulation of dust particles at the upper surface of the semiconductor disk already prepared for exposure is difficult to avoid even with greatest care for the reason that the time between the preparation and the exposure cannot be reduced to the extent desired from the point of view of keeping the surface clean. Between the individual process steps, however, substantial delays frequently occur on account of the production of semiconductor disks in lots of typically 50 to 100 pieces. This, accordingly, is not a continuous process where dwell times can be minimized. In operation, on the contrary, an equalization of the work load of the equipment is considered of principal importance.
On the assumption that contamination by minute dust particles is substantially unavoidable, my invention reduces its damaging effects by applying a planar, solid light-transmitting coating directly onto the photoresist before the exposure. This coating has a thickness where the spherical aberration defined by the formula ##EQU1## (d=thickness of the coating, n=index of refraction of the coating, .theta..sub.max =maximum angle of incidence of the light onto the coating) amounts to less than the Rayleigh depth, preferably to less than one third of that depth. This light-transmitting coating is fully removed after exposure and not later than upon the partial removal of the photoresist.
The contaminan
REFERENCES:
patent: 3458311 (1969-07-01), Alles
patent: 3573975 (1971-04-01), Dhaka et al.
patent: 3652273 (1972-03-01), Htoo
patent: 3719487 (1973-03-01), Schutze et al.
patent: 3895949 (1975-07-01), Aktamatsu et al.
patent: 4200463 (1980-04-01), Flowers
Moreau et al., "Topcoat for Prevention . . . Failure", IBM Techn. Disclosure Bull., vol. 12, No. 9, 2/1970, p. 1417.
Moreau, "Topcoat Formulation . . . Resists", IBM Techn. Disclosure Bull., vol. 12, No. 9, 2/1970, pp. 1418 & 1419.
Feng et al., "Fabrication of Devices . . . Method", IBM Techn. Disclosure Bull., vol. 21, No. 6, 11/1978, pp. 2325, 2326.
Censor Patent- und Versuchs-Anstalt
Ross Karl F.
Schilling Richard L.
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