Patent ID: 6253464
Filing Date: 2001-07-03
Classification: G03F

Abstract:
A method for protecting a surface from particle contamination in a low pressure environment, comprising:a) providing a thermophoretic pellicle contained within a system chamber, the thermophoretic pellicle having walls comprising a material having a high electrical and thermal conductivity, and provided with at least one gas inlet means and at least one aperture that controls the rate of outflow of a gas to maintain a region of locally high pressure within the thermophoretic pellicle relative to a lower and sub-atmospheric pressure maintained in the system chamber by pumping means;b) placing a substrate having a front and a back surface within the thermophoretic pellicle, the substrate having a surface to be protected from particle deposition, wherein the aperture provides line of sight access to the surface of the substrate from the system chamber, and wherein the gas inlet means and aperture are located to provide a flow of gas substantially parallel to and away from the surface of the substrate; andc) establishing and maintaining a temperature differential between the front surface of the substrate and the walls of the thermophoretic pellicle, wherein the front surface of the substrate is warmer than the walls of the thermophoretic pellicle; andd) eliminating the electric field between the front surface of the substrate and the walls of the thermophoretic pellicle.