FABRICATING CMOS IMAGE SENSOR
A CMOS image sensor includes at least one of: A P-type semiconductor substrate. A P-type photodiode formed in the P-type semiconductor substrate and having a higher impurity concentration than the semiconductor substrate. An N-type photodiode disposed over the P-type photodiode at a depth less than approximately 0.15 μm from the surface of the semiconductor substrate. A depletion layer provided by junction of the P-type photodiode and the N-type photodiode.
1 . An apparatus comprising:
a P-type semiconductor substrate;
a P-type photodiode formed in the P-type semiconductor substrate; and
an N-type photodiode formed in the P-type semiconductor substrate over the P-type photodiode, wherein:
the junction of the P-type photodiode and the N-type photodiode form a depletion region, and
a depth of the depletion region configures the N-type photodiode to have a photoelectric effect in response to blue light.
2 . The apparatus of claim 1 , wherein the apparatus is a CMOS image sensor.
3 . The apparatus of claim 1 , wherein the P-type photodiode has a higher impurity concentration than the P-type semiconductor substrate.
4 . The apparatus of claim 1 , wherein the depth of the depletion region substantially prevents a photoelectric effect in response to light having a wavelength greater than the wavelength of blue light.
5 . The apparatus of claim 1 , wherein the depth of the depletion region is based on a depth of the N-type photodiode.
6 . The apparatus of claim 5 , wherein the depth of the N-type photodiode is between approximately 0.1 μm and approximately 0.2 μm from the surface of the semiconductor substrate.
7 . The apparatus of claim 6 , wherein the depth of the N-type photodiode is approximately 0.15 μm from the surface of the semiconductor substrate.
8 . The apparatus of claim 1 , wherein the P-type photodiode is formed by implanting at least one of boron ions and BF4 ions.
9 . The apparatus claim 1 , wherein the N-type photodiode is formed by implanting phosphorus ions.
10 . The apparatus of claim 1 , wherein the depletion region is at the junction of the N-type photodiode and the P-type photodiode when a bias voltage is applied.
11 . A method comprising:
forming a P-type photodiode in a P-type semiconductor substrate; and
forming an N-type photodiode in the P-type semiconductor substrate over the P-type photodiode, wherein:
the junction of the P-type photodiode and the N-type photodiode form a depletion region, and
a depth of the depletion region configures the N-type photodiode to have a photoelectric effect in response to blue light.
12 . The method of claim 11 , wherein the method is a method of forming a CMOS image sensor.
13 . The method of claim 11 , wherein the P-type photodiode has a higher impurity concentration than the P-type semiconductor substrate.
14 . The method of claim 1 , wherein the depth of the depletion region substantially prevents a photoelectric effect in response to light having a wavelength greater than the wavelength of blue light.
15 . The method of claim 11 , wherein the depth of the depletion region is based on a depth of the N-type photodiode.
16 . The method of claim 15 , wherein the depth of the N-type photodiode is between approximately 0.1 μm and approximately 0.2 μm from the surface of the semiconductor substrate.
17 . The method of claim 16 , wherein the depth of the N-type photodiode is approximately 0.15 μm from the surface of the semiconductor substrate.
18 . The method of claim 11 , wherein said forming the P-type photodiode comprises implanting at least one of boron ions and BF4 ions.
19 . The method claim 11 , wherein said forming the N-type photodiode comprises implanting phosphorus ions.
20 . The method of claim 11 , wherein the depletion region is at the junction of the N-type photodiode and the P-type photodiode when a bias voltage is applied.