Method for estimating cathode lifetime of electron gun, and electron beam writing apparatus

A method for estimating a cathode lifetime of an electron gun comprising:

• recording a change amount, per unit temperature increase of a cathode of an electron gun which emits an electron beam, with respect to a bias voltage to be applied to a Wehnelt electrode of the electron gun, to be recorded in relation to a usage time of the cathode each time a temperature of the cathode is changed;
• and
• estimating a lifetime of the cathode by one of estimating a time obtained by adding a predetermined time to a time at which the change amount recorded a plurality of times becomes lower than a prescribed value as the lifetime of the cathode, and estimating, using an approximate line obtained by a line approximation function using a plurality of the change amounts recorded each time the temperature of the cathode was changed, a time at which the approximate line indicates that the change amount becomes zero as the lifetime of the cathode, and
• outputting an estimated lifetime.

A method for estimating a cathode lifetime of an electron gun comprising:

• recording a change amount, per unit temperature increase of a cathode of an electron gun which emits an electron beam, with respect to a sample surface current of the electron beam at a position on a sample surface irradiated with the electron beam, to be recorded in relation to a usage time of the cathode each time a temperature of the cathode is changed;
• and
• estimating a lifetime of the cathode by one of estimating a time obtained by adding a predetermined time to a time at which the change amount recorded a plurality of times becomes lower than a prescribed value as the lifetime of the cathode, and estimating, using an approximate line obtained by a line approximation function using a plurality of the change amounts recorded each time the temperature of the cathode was changed, a time at which the approximate line indicates that the change amount becomes zero as the lifetime of the cathode, and
• outputting an estimated lifetime.

A method for estimating a cathode lifetime of an electron gun comprising:

• recording a change amount, per unit temperature increase of a cathode of an electron gun which emits an electron beam, with respect to a current density of the electron beam at a position on a sample surface irradiated with the electron beam, to be recorded in relation to a usage time of the cathode each time a temperature of the cathode is changed;
• and
• estimating a lifetime of the cathode by one of estimating a time obtained by adding a predetermined time to a time at which the change amount recorded a plurality of times becomes lower than a prescribed value as the lifetime of the cathode, and estimating, using an approximate line obtained by a line approximation function using a plurality of the change amounts recorded each time the temperature of the cathode was changed, a time at which the approximate line indicates that the change amount becomes zero as the lifetime of the cathode, and
• outputting an estimated lifetime.