Patent Number: 
Section: claims

1. A drawing apparatus that performs drawing on a substrate with a plurality of charged particle beams, the drawing apparatus comprising:an electron lens positioned at a location facing opposite to the substrate and including a plurality of holes through which the charged particle beams pass; anda cleaning unit configured to release active species to a decomposition product that has adhered to the electron lens and reduce the decomposition product by the reaction of the active species and the decomposition product to thereby change the decomposition product to a volatile gas,wherein the cleaning unit has a plurality of openings formed such that the active species are released toward the plurality of holes of the electron lens, andwherein each opening of the cleaning unit is disposed opposite to each of the holes. 2. The drawing apparatus according to claim 1, wherein each opening of the cleaning unit is configured concentrically with the holes corresponding to the electron lens. 3. The drawing apparatus according to claim 1, wherein the cleaning unit comprises a main body that is opened such that a plane facing opposite to the electron lens is capable of being connected to a fixing unit for supporting the electron lens, and the main body comprises an opening array having the plurality of openings provided in the plane. 4. The drawing apparatus according to claim 3, wherein the cleaning unit comprises a drive mechanism that drives the opening array so as to align the position of the openings with the position of the holes. 5. The drawing apparatus according to claim 3, further comprising:a substrate holding unit configured to place the substrate to be treated and be movable based on the drawing position; anda controller configured to control the operation of the substrate holding unit and the cleaning unit,wherein the cleaning unit comprises a post unit that supports the main body and is capable of moving the main body toward the fixing unit, andwherein, when the active species are released, the controller moves the substrate holding unit from the drawing position, and then moves the post unit toward the fixing unit to thereby bring the main body into connection with the fixing unit. 6. The drawing apparatus according to claim 3, wherein, when the main body is brought into connection with the fixing unit, the distance from the opening to the deepest part of the electron lens is shorter than the mean free path of the active species at the maximum pressure in a region from the openings to the electron lens. 7. The drawing apparatus according to claim 1, wherein the number of openings is equal to the number of holes or is greater than the number of holes. 8. An article manufacturing method, comprising:performing, in a performing step, drawing on a substrate with a plurality of charged particle beams using a drawing apparatus; anddeveloping, in a developing step, the substrate on which the drawing has been performed in the drawing step,wherein the drawing apparatus comprises:an electron lens positioned at a location facing opposite to the substrate and including a plurality of holes through which the charged particle beams pass; anda cleaning unit configured to release active species to a decomposition product that has adhered to the electron lens and reduce the decomposition product by the reaction of the active species and the decomposition product to thereby change the decomposition product to a volatile gas,wherein the cleaning unit has a plurality of openings formed such that the active species are released toward the plurality of holes of the electron lens, andwherein each opening of the cleaning unit is disposed opposite to each of the holes.