Maskless growth of patterned films

Details Maskless growth of patterned films Maskless growth of patterned films

1982-07-19

1986-08-26

Bernstein, Hiram H.

Adhesive bonding and miscellaneous chemical manufacture

Delaminating processes adapted for specified product

Delaminating in preparation for post processing recycling step

427 531, 430935, C30B 2502

Patent

active

046081178

DESCRIPTION:

BRIEF SUMMARY
This application is based upon, and claims the priority of International application PCT/US82/00745 filed June 1, 1982.


TECHNICAL FIELD

This invention relates to film processing and, in particular, to the manufacture of patterned thin films.


BACKGROUND OF THE INVENTION

Attention is directed to an article by three of the inventors herein entitled "Spatially delineated growth of metal films via photochemical prenucleation" in Vol. 38, No. 11 of Applied Physics Letters (June 1981), incorporated herein by reference. Attention is also directed to U.S. patent application Ser. No. 150,816 now U.S Pat. No. 4,340,617, filed July 20, 1982 by Deutsch et al. entitled "Method and Apparatus for Depositing a Material on a Surface" filed May 19, 1980, disclosing a technique fo depositing materials by laser-induced photo-disassociation of a fluid medium, also incorporated herein by reference.
Conventionally, the growth of patterned thin metallic films is accomplished by the use of photolithographic masks. For example, an etch resistant coating ("a resist") is laid down upon a semiconductor wafer. A pattern is created by further coating portions of the resist with an opaque material and then irradiating the material to break down the exposed resist. The exposed resist is then removed by developing and the wafer may then be etched and metallized to produce a patterned film. The above example illustrates positive resists, wherein the pattern which remains after development corresponds to the opaque regions. Negative resists are also known in the art.
Maskless growth of two dimensionally patterned thin films would be an important processing capability for both the microelectronics and photovoltaics industry. Elimination of the necessity of masking during thin-film growth would reduce the complexity and number of steps in, say, the metallization step in IC-chip formation or, even more important, in the metallization of contacts for photovoltaic solar cells. Further, it would make it economical to produce custom or one-of-a-kind designs--since the expensive mask production step is eliminated. Thus, there exists a need for methods and apparatus for growing patterned films without masks.


SUMMARY OF THE INVENTION

We have discovered that maskless film growth can be accomplished by first "prenucleating" the desired region of growth using photodissociation of a thin surface layer of absorbed molecules. Then a spatially uniform, high-fluence atom source can be used for film growth which will occur selectively in the prenucleated region where atoms have a higher sticking coefficient. This prenucleation technique allows one to separate the delineation phase of the film formation from the growth phase and, as a result, to use separate sources for production of the atom flux in the two phases. In fact, while the examples which follow demonstrate the prenucleation technique using laser photodissociation, it is clear that other nonoptical deposition methods can be used to achieve similar results. For example, delineation may be effected with a low-power, focused electron beam and film growth with conventional vacuum deposition.
In one preferred embodiment a ultraviolet laser beam is directed onto a substrate which is mounted in a 3-cm-path-length stainless-steel sample cell; this cell can be evacuated to 10.sup.-6 Torr. The beam is focused for the patterning phase of the process, writing of the pattern is accomplished by translating the quartz or silicon substrate and cell normal to the optical axis. For the film-growth phase, the laser beam is unfocused. In the latter phase, atoms are provided dominantly by direct photodissociation of the gas-phase organometallic molecules and in the patterning stage by photolysis of a layer of the same molecules absorbed on the substrate. The ultraviolet laser beam is from either a low-power, cw, 257.2-nm, frequency doubled Ar-ion laser (10.mu.-3 mW), or from a 193-nm, pulsed, ArF laser (10 mJ, 10 ns). Heating of the surface for cw irradiation is limited to several degrees centigrade. The gases wh

REFERENCES:
patent: 4260649 (1981-04-01), Dension et al.
patent: 4340617 (1982-07-01), Deutsch et al.
patent: 4359485 (1982-11-01), Donnelly et al.
App. Phys. Lett., Deutsch et al., 35(2), Jul. 15, '79.
Ehrlich et al., Appl. Phys. Lett. 38(11), 6/81.
Hanabusa et al., Appl. Phys. Lett. 35(8), 10/79, pp. 626-627.
Cali et al., Applied Optics, v. 15, No. 5, 5/70, pp. 1327-1330.
Ardreatta et al., J. Vac. Sci. Technol. 20(3), 3/82, pp. 740-741.

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