Method of manufacturing semiconductor device
A back alignment mark on a surface of a semiconductor substrate is detected and a resist mask patterned into a circuit pattern corresponding to a surface element structure is formed on a back of the semiconductor substrate. Detection of the back alignment mark is performed by using a detector opposing the back of the semiconductor substrate and measuring contrast based on the intensity of reflected infrared light irradiated from the back of the semiconductor substrate. The back alignment mark is configured by a step formed by the surface of the semiconductor substrate and bottoms of trenches formed from the surface of the semiconductor substrate. A polysilicon film is embedded in the trenches. The back alignment mark has, for example, a cross-shaped planar layout in which three or more trenches are disposed in a direction parallel to the surface of the semiconductor substrate.
1. A method of manufacturing a semiconductor device, the method comprising:
forming a surface element structure and a mark on a first main surface of a semiconductor substrate;
forming a resist film on a second main surface of the semiconductor substrate;
irradiating light on the semiconductor substrate from the second main surface of the semiconductor substrate, and identifying a position of the mark by detecting reflected light of the light;
performing alignment using the identified position of the mark as a reference, and exposing the resist film; and
performing etching or ion-implantation using the resist film as a mask, and forming a back element structure on the second main surface of the semiconductor substrate,
wherein
forming the surface element structure and the mark includes:
forming at least one trench by which two or more peaks are detected in the reflected light in each of a first direction and a second direction, the first direction and the second direction being perpendicular to each other,
forming a stacked film on the first main surface of the semiconductor substrate; and
forming a groove, which constitutes the mark, that penetrates the stacked film so that a part of the first main surface of the semiconductor substrate is exposed in the groove.
2. The method according to claim 1 , wherein
forming the surface element structure and the mark includes forming a plurality of trenches in the first direction and the second direction in the first main surface of the semiconductor substrate, and
at least one step formed on the first main surface of the semiconductor substrate by the plurality of trenches constitutes the mark.
3. The method according to claim 2 , wherein
the plurality of trenches are formed in a layout in which three or more of the plurality of trenches are disposed in the first direction, and three or more of the plurality of trenches are disposed in the second direction.
4. The method according to claim 2 , wherein
a first trench and a second trench are formed as the plurality of trenches, the first trench being disposed in a cross-shaped layout and the second trench being disposed separated from the first trench, in a layout along the first trench and surrounding the first trench in a form of a cross.
5. The method according to claim 4 , wherein
four trench segments having a straight planar shape are formed as the first trench, the four trench segments being disposed separated from each other in a cross-shaped layout having a center at a predetermined position and in which one end of each of the four trench segments is located at the center.
6. The method according to claim 1 , wherein
forming the surface element structure and the mark includes embedding a polysilicon film in the at least one trench.
7. The method according to claim 1 , wherein
the stacked film has a cross-shape, and
the groove has a cross-shape and is surrounded by the stacked film.
8. The method according to claim 1 , wherein
the stacked film is constituted by an oxide film, a polysilicon film, and an interlayer insulating film that are sequentially stacked.
9. The method according to claim 7 , wherein
a total width of the stacked film in the first direction is less than three times a width of an end part of the groove in the first direction.
10. The method according to claim 1 , wherein
forming the surface element structure and the mark includes forming the groove so that a portion of the stacked film remains having a cross-shaped planar shape and the groove surrounds the portion of the stacked film.
11. The method according to claim 1 , wherein
forming the surface element structure and the mark includes covering the mark by a metal film.
12. The method according to claim 1 , wherein
the light is infrared light.
13. The method according to claim 1 , further comprising:
separating the mark from the surface element structure.
14. A method of manufacturing a semiconductor device, the method comprising:
forming a surface element structure and a mark on a first main surface of a semiconductor substrate;
forming a resist film on a second main surface of the semiconductor substrate;
irradiating light on the semiconductor substrate from the second main surface of the semiconductor substrate, and identifying a position of the mark by detecting reflected light of the light;
performing alignment using the identified position of the mark as a reference, and exposing the resist film; and
performing etching or ion-implantation using the resist film as a mask, and forming a back element structure on the second main surface of the semiconductor substrate,
wherein
forming the surface element structure and the mark includes:
forming a plurality of trenches in the first main surface of the semiconductor substrate by which two or more peaks are detected in the reflected light in each of a first direction and a second direction, the first direction and the second direction being perpendicular to each other, and at least one step formed on the first main surface of the semiconductor substrate by the plurality of trenches constituting the mark, and
the plurality of trenches includes a first trench disposed in a cross-shaped layout and a second trench being disposed separated from the first trench, in a layout along the first trench and surrounding the first trench in a form of a cross.
15. A method of manufacturing a semiconductor device, the method comprising:
forming a surface element structure and a mark on a first main surface of a semiconductor substrate;
forming a resist film on a second main surface of the semiconductor substrate;
irradiating light on the semiconductor substrate from the second main surface of the semiconductor substrate, and identifying a position of the mark by detecting reflected light of the light;
performing alignment using the identified position of the mark as a reference, and exposing the resist film; and
performing etching or ion-implantation using the resist film as a mask, and forming a back element structure on the second main surface of the semiconductor substrate,
wherein
forming the surface element structure and the mark includes:
forming a plurality of trenches in the first main surface of the semiconductor substrate by which two or more peaks are detected in the reflected light in each of a first direction and a second direction, the first direction and the second direction being perpendicular to each other, and at least one step formed on the first main surface of the semiconductor substrate by the plurality of trenches constituting the mark, and
embedding a polysilicon film in the plurality of trenches.