Method for reducing line-end space in integrated circuit patterning

A method, comprising:

• forming a resist pattern over a structure, wherein the resist pattern includes elongated trenches surrounded by first resist walls oriented lengthwise substantially along a first direction and second resist walls oriented lengthwise substantially along a second direction perpendicular to the first direction, and the first and the second resist walls intersect, wherein each of the elongated trenches is longer along the first direction than along the second direction;
• loading the structure and the resist pattern into an ion implanter so that a top surface of the resist pattern faces an ion travel direction of the ion implanter;
• tilting the structure and the resist pattern so that the ion travel direction forms a tilt angle of at least 40 degrees with respect to an axis perpendicular to the top surface of the resist pattern;
• initially rotating the structure and the resist pattern around the axis to an initial position so that the ion travel direction is in an initial plane containing the first direction and the axis;
• first rotating the structure and the resist pattern around the axis from the initial position to a first position by a first angle that is less than 90 degrees;
• first implanting ions into the first and the second resist walls with the structure and the resist pattern at the first position;
• after the first implanting, second rotating the structure and the resist pattern around the axis from the first position to a second position by a second angle that is less than a sum of 90 degrees and a complementary angle of the first angle;
• and
• second implanting ions into the first and the second resist walls with the structure and the resist pattern at the second position.

A method, comprising:

• forming a resist pattern over a structure, the resist pattern having a trench surrounded by first resist walls extending lengthwise along a first direction and second resist walls extending lengthwise along a second direction perpendicular to the first direction, wherein the trench is longer along the first direction than along the second direction;
• loading the structure and the resist pattern into an ion implanter so that a top surface of the resist pattern faces an ion travel direction of the ion implanter;
• first implanting ions into the resist pattern using the ion implanter with a first recipe that includes applying a first ion dose to the resist pattern with the resist pattern being held at a first tilt angle and at multiple first twist angles one at a time;
• and
• second implanting ions into the resist pattern using the ion implanter with a second recipe that includes applying a second ion dose to the resist pattern with the resist pattern being held at a second tilt angle and at multiple second twist angles one at a time, wherein the first ion dose is different from the second ion dose, the first tilt angle is different from the second tilt angle, or the multiple first twist angles are different from the multiple second twist angles
• wherein each of the first and the second tilt angles is an angle between the ion travel direction and an axis perpendicular to the top surface of the resist pattern, and each of the first twist angles and the second twist angles is another angle formed between a plane containing the axis perpendicular to the top surface of the resist pattern and the first direction and another plane containing the axis perpendicular to the top surface of the resist pattern and the ion travel direction.