Patent Number: 
Section: claims

1. A method of smoothing a solid surface with a gas cluster ion beam comprising:an irradiation step of directing the gas cluster ion beam onto the solid surface at an irradiation angle not smaller than a critical angle, where the irradiation angle, is between a normal to the solid surface and the gas cluster ion beam;whereinthe critical angle is an irradiation angle of 70 degrees at which a distance of interaction between the solid and a cluster colliding with the solid turns to an abrupt increase; andthe irradiating step comprises a process of directing the gas cluster ion beam while varying the irradiation angle in a range not smaller than the critical angle. 2. The method of smoothing a solid surface with a gas cluster ion beam according to claim 1, wherein the irradiation step comprises:a process of directing the gas cluster ion beam while varying a dose of the gas cluster ion beam. 3. The method of smoothing a solid surface with a gas cluster ion beam according to claim 1, wherein the irradiation step comprises a process of directing the gas cluster ion beam of a dose determined with reference to a database that allows a dose to be determined from at least a desired etching amount and the irradiation angle. 4. The method of smoothing a solid surface with a gas cluster ion beam according to claim 1, wherein, when a striped uneven pattern is present on the solid surface, the irradiation step comprises a process of directing the gas cluster ion beam in a direction nearly parallel to the direction in which the uneven pattern is repeatedly formed. 5. A solid surface smoothing apparatus that uses a gas cluster ion beam comprising:gas cluster ion beam emission means adapted to emit the gas cluster ion ea onto the solid surface; andan irradiation angle setting means adapted to set an irradiation angle to a critical angle or a greater angle, the irradiation angle being between a normal to the solid surface and the gas cluster ion beam,whereinthe critical angle is an irradiation angle of 70 degrees at which a distance of interaction between the solid and a cluster colliding with the solid turns to an abrupt increase; andthe irradiation angle setting means is adapted to vary the irradiation angle in a range not smaller than the critical angle. 6. The solid surface smoothing apparatus according to claim 5, further comprising:a database that allows a dose to be determined from at least a desired etching amount and the irradiation angle;wherein the gas cluster ion beam emission means emits the gas cluster ion beam of the dose determined with reference to the database in accordance with the desired etching amount and the irradiation angle specified by the irradiation angle setting means. 7. A method of smoothing a solid surface with a gas cluster ion beam comprising:an irradiation step of directing the gas cluster ion beam onto the solid surface at an irradiation angle not smaller than a critical angle, where the irradiation angle is between a normal to the solid surface and the gas cluster ion beam,whereinthe critical angle is an irradiation angle at which a distance of interaction between the solid and a cluster colliding with the solid turns to an abrupt increase; andthe irradiation step comprises, when a striped uneven pattern with interval within a range of 800 nm to 10 μm inclusive is present on the solid surface, a process of directing the gas cluster ion beam in a direction nearly parallel to the direction in which the uneven pattern is repeatedly formed. 8. The method of smoothing a solid surface with a gas cluster ion beam according to claim 7, wherein the critical angle is 70 degrees.