Reduced pressure irradiation processing method and apparatus
A system and method for processing substrates, such as porous low-K semiconductor wafers, using ultraviolet (UV) radiation is disclosed. The substrates are first cleaned in a wet processing module and then dried in a UV module under reduced pressure and at a temperature below 100 C., preferably at or below 80 C. A robot module transfers the substrates from the wet processing module to the UV module. The UV module can include a pulse xenon excimer lamp providing incoherent vacuum ultraviolet (VUV) radiation at 172 nm.
1 . A method for cleaning a substrate comprising cleaning the substrate in a wet-cleaning module; drying the substrate in the wet-cleaning module; transferring the substrate from the wet-cleaning module to a UV module, the UV module having a source of UV radiation; and drying the substrate in the UV module using UV radiation at subatmospheric pressure and at a temperature below 100° C.; wherein the wet-cleaning module and the UV module are coupled to a substrate transferring module which transfers the substrate to and from the wet-cleaning module and the UV module.
2 . The method of claim 1 wherein the temperature does not exceed 80° C.
3 . The method of claim 1 wherein the substrate includes a low-K dielectric material having pores.
4 . The method of claim 1 wherein the substrate includes a low-K dielectric material having pores which have residual liquids and wherein the UV drying of the substrate in the UV module removes the residual liquids in the pores.
5 . The method of claim 1 wherein transferring the substrate from the wet-cleaning module to the UV drying module is preformed by a robot included in the substrate transferring module.
6 . The method of claim 1 wherein the drying in the UV module is carried out for 60 to 90 seconds.
7 . An apparatus for cleaning a substrate comprising a UV module having a source of UV radiation; a wet-cleaning module having drying means; a substrate transferring module having means to transfer a cleaned substrate from the wet-cleaning module to the UV module; means to reduce pressure in the UV module; and a source of UV radiation in the UV module capable of drying the substrate at sub-atmospheric pressure and at a temperature below 100° C.
8 . The apparatus of claim 7 wherein the source of UV radiation is a pulse xenon excimer lamp providing incoherent vacuum ultraviolet (VUV) radiation at 172 nm at a temperature not exceeding 80° C. without cooling.
9 . The apparatus of claim 7 wherein the UV module comprises a VUV light box having three UV light sources and a reflector which providing incoherent VUV radiation at 172 nm in a nitrogen atmosphere and a VUV processing module having gas distribution manifolds, a vacuum manifold, and sensor ports.
10 . The apparatus of claim 7 wherein the means to reduce the pressure can provide subatmospheric pressure below 10 Torr.
11 . The apparatus of claim 7 wherein the UV module includes a VUV light box having a UV light source, means for creating an inert gas atmosphere, and a ultraviolet transmissive window separating the light box and the UV module.
12 . The apparatus of claim 11 wherein the ultraviolet transmissive window is made of fluorinated glass or sapphire.
13 . The apparatus of claim 11 further comprising a reflector for providing uniform ultraviolet radiation transmission.
14 . The apparatus of claim 11 comprising a controller that activates the means for creating a cleaning gas atmosphere upon activating the means for reducing pressure, thereby backfilling the first module with cleaning gas as undesirable gases are removed.
15 . The apparatus of claim 11 further including a source of inert gas is selected from the group consisting of nitrogen and argon.
16 . The apparatus of claim 7 comprising two or more of the UV modules.