Backside illuminated image sensor and method of manufacturing the same
A method of manufacturing a backside illuminated image sensor, including forming a first isolation layer in a first semiconductor layer, such that the first isolation layer defines pixels of a pixel array in the first semiconductor layer, forming a second semiconductor layer on a first surface of the first semiconductor layer, forming a second isolation layer in the second semiconductor layer, such that the second isolation layer defines active device regions in the second semiconductor layer, forming photo detectors and circuit devices by implanting impurities into a first surface of the second semiconductor layer, the first surface of the second semiconductor layer facing away from the first semiconductor layer, forming a wiring layer on the first surface of the second semiconductor layer, and forming a light filter layer on a second surface of the first semiconductor layer.
1. A method of manufacturing a backside illuminated image sensor having a pixel array, the method comprising:
forming a first isolation layer in a first semiconductor layer, such that the first isolation layer defines pixels of the pixel array in the first semiconductor layer;
forming a second semiconductor layer on a first surface of the first semiconductor layer;
forming a second isolation layer in the second semiconductor layer, such that the second isolation layer defines active device regions in the second semiconductor layer;
forming photo detectors and circuit devices by implanting impurities into a first surface of the second semiconductor layer, the first surface of the second semiconductor layer facing away from the first semiconductor layer;
forming a wiring layer on the first surface of the second semiconductor layer; and
forming a light filter layer on a second surface of the first semiconductor layer, the second surface of the first semiconductor layer being opposite the first surface of the first semiconductor layer, wherein the second isolation layer is between the first isolation layer and the wiring layer.
2. The method as claimed in claim 1 , wherein forming the second semiconductor layer includes using an epitaxial method.
3. The method as claimed in claim 2 , wherein the first semiconductor layer is formed by using an epitaxial method.
4. The method as claimed in claim 3 , wherein forming the light filter layer includes:
forming the first semiconductor layer on a first supporting substrate;
forming a second supporting substrate on a surface of the wiring layer facing away from the second semiconductor layer;
removing the first supporting substrate from the first semiconductor layer;
forming a color filter layer on the second surface of the first semiconductor layer; and
forming a lens layer on the color filter layer.
5. The method as claimed in claim 4 , wherein forming the first isolation layer includes forming a trench-type insulation layer.
6. The method as claimed in claim 5 , wherein forming the first isolation layer includes using a material having a refraction index lower than that of a material of the first semiconductor layer.
7. The method as claimed in claim 6 , wherein the first isolation layer is formed to extend from the first surface of the first semiconductor layer toward the second surface of the first semiconductor layer, a length of the first isolation layer being substantially equal a thickness of the first semiconductor layer.
8. The method as claimed in claim 6 , wherein the first isolation layer is formed to extend from the first surface of the first semiconductor layer toward the second surface of the first semiconductor layer, a length of the first isolation layer being shorter than a thickness of the first semiconductor layer.
9. The method as claimed in claim 6 , wherein the first isolation layer is formed to have a lattice structure surrounding each of the pixels of the pixel array.
10. The method as claimed in claim 4 , wherein the photo detectors are formed to be aligned with corresponding micro-lenses of the lens layer.
11. The method as claimed in claim 10 , wherein a center of each of the photo detectors is aligned with a center of each corresponding pixel of the pixel array.
12. The method as claimed in claim 11 , wherein each photo detector is a photo diode, a photo transistor, a photo gate, or a pinned photo diode (PPD).
13. The method as claimed in claim 11 , wherein active regions of the circuit devices are formed to be symmetric around an imaginary line extending from the first isolation layer.
14. The method as claimed in claim 13 , wherein a first part of the photo detector is formed in the first semiconductor layer and a second part of the photo detector is formed in the second semiconductor layer.
15. The method as claimed in claim 14 , wherein at least two of the pixels share a floating diffusion (FD) region.
16. The method as claimed in claim 15 , wherein the circuit devices include:
transmitting transistors for transmitting charges accumulated in the corresponding photo detectors to the corresponding FD regions;
resetting transistors for initializing potentials of the corresponding FD regions;
driving transistors for amplifying changes of potentials of the corresponding FD regions; and
selecting transistors for outputting output signals of the corresponding driving transistors in response to corresponding row selecting signals.
17. The method as claimed in claim 1 , wherein the first isolation layer is formed to have a side surface to reflect light passing through the light filter layer.
18. The method as claimed in claim 1 , wherein at least one of the circuit devices overlaps the first isolation layer.
19. The method as claimed in claim 1 , wherein the first isolation layer is longer than the second isolation layer.
20. The method as claimed in claim 1 , wherein the first isolation layer is between at least one of the active devices and the light filter layer.
21. The method as claimed in claim 1 , wherein the active devices and the first isolation layer are at different levels.