Magnetic shielding devices and methods involving active cancellation of external magnetic fields at the column of a charged-particle-beam optical system

A method for magnetically shielding a charged-particle-beam optical system situated inside a column that extends along an optical axis, the method comprising:

• situating at least one active-canceler coil set on or near the column so as not to obstruct a trajectory of a charged particle beam propagating in the column, each coil set being configured, when electrically energized, to produce a respective magnetic field oriented in a prescribed direction;
• and
• electrically energizing the at least one coil set to cause the coil set to produce the respective magnetic field having a magnitude sufficient to cancel at least a portion of a target magnetic field, external to the column, that otherwise would penetrate through the column to the optical axis.

In a charged-particle-beam (CPB) optical system situated inside a column that extends along an optical axis, a device for reducing, by cancellation, a magnetic field external to the column that otherwise would extend to inside the column, so as to magnetically shield the CPB optical system from the external magnetic field, the device comprising an active-canceler coil set situated at an axial position relative to the column and adjacent a wall of the column so as not to obstruct a trajectory of a charged particle beam propagating in the column, the coil set comprising at least one electrically energizable coil that, when electrically energized, produces a respective magnetic field of a direction and magnitude sufficient for canceling at least a portion of the external magnetic field.

In a charged-particle-beam (CPB) optical system situated inside a column that extends along an optical axis, a device for reducing, by cancellation, a magnetic field external to the column that otherwise would extend to inside the column, so as to magnetically shield the CPB optical system from the external magnetic field, the device comprising:

• an active-canceler coil set situated at an axial position relative to the column and adjacent a wall of the column so as not to obstruct a trajectory of a charged particle beam propagating in the column, the coil set comprising at least one individual coil that, when electrically energized, produces a respective magnetic field of a direction and magnitude sufficient for canceling at least a portion of the external magnetic field;
• and
• a magnetic shield, made of an anisotropic magnetic material, situated outside the column.

In a charged-particle-beam (CPB) optical system situated inside a column that extends along an optical axis, a device for shielding the CPB optical system from a magnetic field external to the column that otherwise would extend to inside the column, the device comprising at least one active-canceler coil set situated on or near the column so as not to obstruct a trajectory of a charged particle beam propagating in the column, each coil set being configured to be electrically energized and, when electrically energized, to produce a respective magnetic field oriented in a prescribed direction and having a magnitude sufficient to cancel at least a portion of the external magnetic field.

A method for magnetically shielding a charged-particle-beam (CPB) system comprising a CPB column and at least one chamber situated relative to an optical axis, the method comprising:

• at an optical axial position relative to the system, disposing at least one active-canceler coil adjacent a wall of the system so as not to obstruct a trajectory of a charged particle beam propagating in the system, the at least one coil being electrically energizable;
• and
• electrically energizing the at least one coil so as to cause the coil to produce a magnetic field that cancels at least a portion of an external magnetic field or a magnetic flux, present externally to the system and that otherwise would extend from outside the system to the optical axis within the system, to a desired distribution.

In a charged-particle-beam (CPB) system including a CPB column and at least one chamber situated relative to an optical axis, a device for magnetically shielding the CPB system, comprising at least one active-canceler coil situated at an optical axial position adjacent a wall of the CPB system so as not to obstruct a trajectory of a charged particle beam propagating in the CPB system, the at least one coil being electrically energizable so as to cause the at least one coil to produce a magnetic field sufficient for canceling at least a portion of an external magnetic field or a magnetic flux, present externally to the CPB system and that otherwise would extend from outside the CPB system to the optical axis within the CPB system, to a desired distribution.

A charged-particle-beam (CPB) microlithography apparatus, comprising:

• a CPB system including a CPB column and at least one chamber situated relative to an optical axis;
• and
• a device for magnetically shielding the CPB system, comprising at least one active-canceler coil situated at an optical axial position adjacent a wall of the CPB system so as not to obstruct a trajectory of a charged particle beam propagating in the CPB system, the at least one coil being electrically energizable so as to cause the at least one coil to produce a magnetic field sufficient for canceling at least a portion of an external magnetic field or a magnetic flux, present externally to the CPB system and that otherwise would extend from outside the CPB system to the optical axis within the CPB system, to a desired distribution.