US 4,536,252 AGranted

Laser-induced production of nitrosyl fluoride for etching of semiconductor surfaces

AssigneeThe United States of America as represented by the Secretary of the Army

InventorsJoseph K. McDonald, James A. Merritt

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Abstract

Nitrosyl fluoride is prepared by laser-induced method wherein the nitrosyl luoride is produced in situ or in close proximity to where it is used to etch semiconductor surfaces. A reaction mixture of a catalyst compound and a fluoro compound, wherein the catalyst compound is an oxide of nitrogen selected from the group of nitrogen oxide compounds consisting of NO, N.sub.2 O, and NO.sub.2 and wherein the fluoro compound is selected from the group of fluoro compounds consisting of NF.sub.3 and N.sub.2 F.sub.4, is irradiated with CO.sub.2 laser radiation to produce FNO. FNO reacts with an exposed silicon material to produce SiF.sub.4 and nitrogen oxide. Since the oxide is regenerated, it can be regarded as a catalyst which can be recovered and recycled. A production scheme for producing nitrosyl fluoride for etching is disclosed wherein the nitrosyl fluoride is produced directly in the laser reaction chamber by passing a CO.sub.2 laser beam through the reaction mixture. Alternately, the nitrosyl fluoride can also be produced in a side chamber and the gas flowed into an etching chamber.

Claims5

Dependent claims

A method for laser-induced production of gaseous nitrosyl fluoride for the continuous etching of a semiconductor silicon wafer by gaseous nitrosyl fluoride, said method comprising:

(i) filling a laser reaction cell with a gaseous mixture of a catalyst compound of an oxide of nitrogen selected from the group of nitrogen oxide compounds consisting of NO, N.sub.2 O, and NO.sub.2 and a fluoro compound selected from the group of fluoro compounds consisting of NF.sub.3 and N.sub.2 F.sub.4, said catalyst compound introduced into said laser reaction cell in a ratio of about 60 torr to about 45 torr of said fluoro compound,
(ii) irradiating said gaseous mixture with a power level from about 25 to about 150 watts of a cw CO.sub.2 tunable laser, tuned to a radiation line that is resonant with an absorption band of said fluoro compound, said irradiating being carried out for a predetermined time period based on a predetermined power level of said laser to thereby achieve a continuous production of gaseous nitrosyl fluoride,
(iii) exposing a semiconductor silicon material to said gaseous nitrosyl fluoride to react said gaseous nitrosyl fluoride with the exposed semiconductor silicon material to achieve etching while producing SiF.sub.4 and NO from said reacting;
and,
(iv) recovering said etched semiconductor silicon material, said SiF.sub.4, and said NO.

2 more elements

Dependencies are inferred from the claim text.