Image sensor and fabrication method thereof
Example embodiments relate to an image sensor and a fabrication method thereof, capable of reducing dark current and a fabrication method thereof. The image sensor may include a semiconductor substrate including an active region defined by an isolation layer, a photoelectric-conversion region and a charge-movement-prevention region formed at an interface between the photoelectric-conversion region and the isolation layer.
1. A method of fabricating an image sensor comprising:
forming a trench having a bottom and sidewalls in a semiconductor substrate;
depositing an insulation layer including impurities along the trench;
forming a charge-movement-prevention region by spreading the impurities included in the insulation layer by a thermal process through the bottom and sidewalls of the trench to the semiconductor substrate around the trench;
removing the insulation layer including the impurities; and
completing an isolation layer composed of an undoped insulation material in the trench.
2. The method of claim 1 , wherein the insulation layer is formed to a thickness of about 300 Å to about 700 Å.
3. The method of claim 2 , wherein the insulation layer includes a boron silicate glass (BSG).
4. The method of claim 1 , wherein the impurities are p-type impurities.
5. The method of claim 4 , wherein the p-type impurities are Boron ions.
6. The method of claim 4 , wherein the density of the p-type impurities is about 1×10 14 to about 1×10 17 atoms/cm 3 .
7. The method of claim 1 , wherein the thermal process is executed for about 20 to about 100 minutes at the temperature in the range of about 700° C. to about 900° C. when forming the charge-movement-prevention region.
8. The method of claim 1 , wherein the insulation layer is removed by a dry etching process when removing the insulation layer.
9. The method of claim 1 , further comprising:
forming a transmission-gate electrode on the semiconductor substrate in which the isolation layer is formed to form a charge-transmission structure; and
implanting impurities on both sides of the transmission-gate electrode and at an interface between the charge-movement-prevention layer to form a photoelectric-conversion region and a charge-detection region, respectively.
10. The method of claim 9 , wherein when forming the photoelectric-conversion region a charge accumulates corresponding to incident light and forms an n-type photodiode overlapping with the transmission gate electrode.
11. The method of claim 10 , wherein forming the photoelectric-conversion region includes forming a p-type pinning layer on the photodiode.