Ion implantation method using tilted ion beam

DETAILED DESCRIPTION Accordingly, an object of the present invention is to provide an ion implantation method that is able to improve the controllability of implanted dopant ions.
Another object of the present invention is to provide an ion implantation method that is able to improve the uniformity in concentration and profile of implanted dopant ions.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
An ion implantation method according to a first aspect of the present invention includes the following steps (a) to (c).
(a) A semiconductor substrate with a (100)-oriented crystal surface is prepared.
(b) An elongated mask with a specific pattern is formed on the surface of the substrate.
(c) A beam of dopant ions is irradiated to the surface of the substrate along a first direction, thereby selectively implanting the dopant ions into the substrate using the mask.
The first direction has a first angle with a normal of the surface of the substrate in a plane perpendicular to a longitudinal axis of the mask, where the first angle is in the range from 7.
degree.
C.
to 60.
degree.
C.
The first direction has a second angle with a lateral axis of the mask in a plane parallel to the surface of the substrate, where the second angle is in the range from 5.
degree.
C.
to 20.
degree.
C.
The longitudinal axis of the mask is parallel to one of the <011>-directions or one of the <011>-directions.
With the ion implantation method according to the first aspect of the present invention, since the crystal surface of the substrate is oriented to the (100)-direction, this surface corresponds to a (100)-plane of the substrate.
Therefore, the <011>- and <011>-directions, which are perpendicular to each other, are parallel to the surface of the substrate.
A beam of dopant ions is irradiated to the (100)-surface of the substrate along a first direction, thereby selectively implanting the dopant ions into the substrate using an elongated mask formed on the (100)-surface of the substrate