Spiral planar inductor and manufacturing method thereof

1. An inductor, comprising an inductor wiring made of a metal layer and having a spiral planar shape,

wherein, in a cross-sectional shape in a width direction of the inductor wiring, the inductor wiring has a larger film thickness in its inner side end than in its middle part and its outer side end.

2. The inductor according to claim 1 , wherein:

the inductor wiring includes a first metal layer provided only in the inner side end, and a second metal layer provided in the inner side end, the middle part and the outer side end, and

in the inner side end, the first layer and the second layer are stacked, and are made of a same metal material.

3. The inductor according to claim 1 , wherein:

the inductor wiring includes a first metal layer provided only in the inner side end, and a second metal layer provided in the inner side end, the middle part and the outer side end, and

in the inner side end, the first layer and the second layer are stacked, and are made of different metal materials from each other.

4. A method for manufacturing an inductor, comprising the steps of:

(a) forming an insulating film on a semiconductor substrate;

(b) forming a first groove having a spiral planar shape in the insulating film;

(c) forming a first inductor pattern by embedding a first metal layer in the first groove; and

(d) forming on the insulating film a second inductor pattern made of a second metal layer, extending along a top surface of the first inductor pattern, and having a larger width than that of the first inductor pattern, wherein:

in the step (d), an inductor wiring formed by the first inductor pattern and the second inductor pattern is formed by positioning an inner side end of the second inductor pattern on the first inductor pattern, and

in a cross-sectional shape in a width direction of the inductor wiring, the inductor wiring has a larger film thickness in its inner side end than in its middle part and its outer side end.

5. The method according to claim 4 , wherein a second groove is further formed in the step (b) so as to have a spiral planar shape extending in parallel with the first groove, a third inductor pattern is further formed in the step (c) by embedding the first metal layer in the second groove, and an inductor wiring formed by the first inductor pattern, the second inductor pattern, and the third inductor pattern is formed in the step (d) by positioning an outer side end of the second inductor pattern on the third inductor pattern.

6. The method according to claim 4 , wherein the first metal layer and the second metal layer are made of a same metal material.

7. The method according to claim 4 , wherein

the first metal layer and the second metal layer are made of different metal materials from each other.

8. The method according to claim 5 , wherein the first metal layer and the second metal layer are made of a same metal material.