Solar cell and method for manufacturing the same

1. A method for manufacturing a solar cell, the method comprising:

injecting first impurity ions at a first surface of a substrate by using a first ion implantation method to form a first impurity region, the substrate having a first conductivity type and the first impurity ions having a second conductivity type opposite the first conductivity type, and the first impurity region having the second conductivity type;

first heating the substrate with the first impurity region to activate the first impurity region to form an emitter region from the first impurity region;

etching the emitter region from a surface of the emitter region to a predetermined depth to form an emitter part from the emitter region;

forming a first electrode on the emitter part to connect to the emitter part by using a screen printing method, and then being dried;

injecting second impurity ions at a second surface of the substrate by using a second ion implantation method to form a second impurity region of the first conductivity type, the second surface being opposite the first surface of the substrate;

second heating the substrate with the second impurity region to activate the second impurity region to form a surface field region from the second impurity region;

etching the surface field region from a surface of the surface field region to a predetermined depth to form a surface field part from the surface field region; and

forming a second electrode on the surface field part to connect to the surface field part by using a screen printing method, and then being dried,

wherein the emitter part comprises a first emitter portion having a first impurity doped thickness and a second emitter portion having a second impurity doped thickness greater than the first impurity doped thickness,

wherein the surface field part comprises a first surface field portion having a first impurity doped thickness and a second surface field portion having a second impurity doped thickness greater than the first impurity doped thickness,

wherein the first electrode is connected to the first surface of the substrate through the second emitter portion, and

wherein the second electrode is connected to the second surface of the substrate through the second surface field portion.

2. The method of claim 1 , wherein the first heating of the substrate heats the first impurity region at 800° C. to 1100° C. in a nitrogen atmosphere.

3. The method of claim 1 , wherein the etching of the emitter region removes a portion of the emitter region from the surface of the emitter region to a depth of 5 nm to 20 nm, and

wherein the emitter region is etched by an etchant composed of nitric acid HNO 3 , hydrofluoric acid HF and pure water.

4. The method of claim 1 , wherein the first heating of the substrate heats the first impurity region at 800° C. to 1100° C. in an oxygen atmosphere.

5. The method of claim 1 , wherein the etching of the emitter region removes a portion of the emitter region from the surface of the emitter region to a depth of 20 nm to 35 nm, and

wherein the emitter region is etched by an etchant composed of hydrofluoric acid HF and pure water.

6. The method of claim 1 , wherein the second heating of the substrate heats the second impurity region at 900° C. to 1100° C. in a nitrogen atmosphere.

7. The method of claim 1 , wherein the etching of the surface field region removes a portion of the surface field region from the surface of the surface field region to a depth of 5 nm to 20 nm.

8. The method of claim 7 , wherein the surface field region is etched by an etchant composed of nitric acid HNO 3 , hydrofluoric acid HF and pure water.

9. The method of claim 1 , wherein the second heating of the substrate heats the second impurity region at 900° C. to 1100° C. in an oxygen atmosphere.

10. The method of claim 1 , wherein the etching of the surface field region removes a portion of the surface field region from the surface of the surface field region to a depth of 20 nm to 35 nm.

11. The method of claim 10 , wherein the surface field region is etched by an etchant composed of hydrofluoric acid HF and pure water.

12. The method of claim 1 , wherein the etching of the emitter region comprises:

selectively forming an etch prevention layer on the emitter region to expose a portion of the emitter region and to cover a remaining portion of the emitter region;

etching the exposed portion of the emitter region from the surface of the emitter region to the predetermined depth using the etch prevention layer as a mask; and

removing the etch prevention layer,

wherein the etched exposed portion of the emitter region is formed as the first emitter portion and the remaining portion of the emitter region is formed as the second emitter portion.

13. The method of claim 1 , wherein the first impurity region comprises a first impurity portion having a first impurity doped thickness and a second impurity portion having a second impurity doped thickness greater than the first impurity doped thickness, and

wherein the injecting of the first impurity ions forms the first and second impurity portions by use of a mask positioned at the first surface of the substrate and use of the first ion implantation method.

14. The method of claim 13 , wherein the mask comprises a first portion having a first exposing area for forming the first impurity portion and a second portion having a second exposing area for forming the second impurity portion, the first and second exposing areas being areas exposing the substrate in a unit area thereof.

15. The method of claim 13 , further comprising forming the first impurity region not having the first and second impurity portions at an entire first surface of the substrate by injecting the first impurity ions of the second conductivity type at the entire first surface of the substrate without a mask, before forming the first and second impurity portions of the first impurity region,

wherein the forming of the first and second impurity portions of the first impurity region forms the first and second impurity portions by use of the mask positioned at the first impurity region not having the first and second impurity portions and use of the first ion implantation method.

16. The method of claim 1 , wherein the etching of the surface field region comprises:

selectively forming an etch prevention layer on the surface field region to expose a portion of the surface field region and to cover a remaining portion of the surface field region;

etching the exposed portion of the surface field region from the surface of the surface field region to the predetermined depth using the etch prevention layer as a mask; and

removing the etch prevention layer,

wherein the etched exposed portion of the surface field region is formed as the first surface field portion and the remaining portion is formed as the second surface field portion.

17. The method of claim 1 , wherein the second impurity region comprises a first impurity portion having a first impurity doped thickness and a second impurity portion having a second impurity doped thickness greater than the first impurity doped thickness, and

wherein the injecting of the second impurity ions forms the first and second impurity portions by use of a mask positioned at the second surface of the substrate and use of the second ion implantation method.

18. The method of claim 17 , wherein the mask comprises a first portion having a first exposing area for forming the first impurity portion and a second portion having a second exposing area for forming the second impurity portion, the first and second exposing areas being areas exposing the substrate in a unit area thereof.

19. The method of claim 17 , further comprising forming the second impurity region not having the first and second impurity portions at an entire second surface of the substrate by injecting the second impurity ions at the entire second surface of the substrate without a mask, before forming the first and second impurity portions of the second impurity region,

wherein the forming of the first and second impurity portions of the second impurity region forms the first and second impurity portions by use of the mask positioned at the second impurity part not having the first and second impurity portions and use of the second ion implantation method.

20. A method for manufacturing a solar cell, the method comprising:

injecting first impurity ions at a first surface of a substrate by using a first ion implantation method to form a first impurity region, the substrate having a first conductivity type and the first impurity ions having a second conductivity type opposite the first conductivity type, and the first impurity region having the second conductivity type;

heating the substrate with the first impurity region to activate the first impurity region to form an emitter region from the first impurity region;

forming a first electrode on the emitter region to connect to the emitter region by using a screen printing method, and then being dried;

injecting second impurity ions at a second surface of the substrate by using a second ion implantation method to form a second impurity region of the first conductivity type, the second surface being opposite the first surface of the substrate;

heating the substrate with the second impurity region to activate the second impurity region to form a surface field region from the second impurity region;

etching the surface field region from a surface of the surface field region to a predetermined depth to form a surface field part from the surface field region; and

forming a second electrode on the surface field part to connect to the surface field part by using a screen printing method, and then being dried,

wherein the surface field part comprises a first surface field portion having a first impurity doped thickness and a second surface field portion having a second impurity doped thickness greater than the first impurity doped thickness, and

wherein the second electrode is connected to the second surface of the substrate through the second surface field portion.