Method of fabricating CMOS image sensor
View Patent ↗A method of fabricating a CMOS image sensor can minimize a dark current by avoiding a dry etch process of a photodiode surface. The method can also reduce a contact resistance and variation of the contact resistance of a read-out circuit unit within a unit pixel. The method includes steps of forming an insulating layer on a semiconductor substrate divided into a photodiode area and a transistor area, removing the insulating layer on a gate electrode forming area, forming a gate insulating layer, forming a conductive layer, forming a gate electrode by planarizing the conductive layer, selectively removing the insulating layer to expose the semiconductor substrate, forming a lightly doped impurity region in the exposed semiconductor substrate, forming a spacer on a sidewall of the gate electrode, completely removing the insulating layer, and forming a heavily doped impurity region on the transistor area of the semiconductor substrate.
1. A method of fabricating a CMOS image sensor, comprising the steps of:
forming an insulating layer on a first conductive type semiconductor substrate divided into a photodiode area and a transistor area;
removing the insulating layer on a gate electrode forming area of the transistor area;
forming a gate insulating layer on the gate electrode forming area of the semiconductor substrate;
forming a conductive layer over the semiconductor substrate;
forming a gate electrode by planarizing the conductive layer to expose a surface of the insulating layer;
selectively removing the insulating layer to expose the semiconductor substrate;
forming a second conductive type lightly doped impurity region in the exposed semiconductor substrate;
forming a spacer on a sidewall of the gate electrode;
completely removing the insulating layer; and
forming a second conductive type heavily doped impurity region on the transistor area of the semiconductor substrate by ion implantation using a mask.
2. The method of claim 1 , wherein in the step of selectively removing the insulating layer, the insulating layer on the transistor area is selectively removed.
3. The method of claim 1 , wherein the insulating layer is formed of a TEOS based oxide layer.
4. The method of claim 1 , wherein the gate insulating layer is formed by oxidation.
5. The method of claim 1 , further comprising the step of forming a salicide on a surface of the gate electrode and an exposed epitaxial layer of an active area.
6. The method of claim 1 , further comprising the step of forming a second conductive type impurity region and a first conductive type impurity region in the photodiode area by ion implantation using a mask.
7. A method of fabricating a CMOS image sensor, comprising the steps of:
forming an insulating layer on a first conductive type semiconductor substrate divided into a photodiode area and a transistor area;
removing the insulating layer on a gate electrode forming area of the transistor area;
forming a gate insulating layer on the gate electrode forming area of the semiconductor substrate;
forming a conductive layer over the semiconductor substrate;
forming a gate electrode by planarizing the conductive layer to expose a surface of the insulating layer;
selectively removing the insulating layer to expose the semiconductor substrate;
forming a second conductive type lightly doped impurity region in the exposed semiconductor substrate;
forming a spacer on a sidewall of the gate electrode;
forming a second conductive type heavily doped impurity region on the semiconductor substrate using the gate electrode and the spacer as a mask;
forming a salicide on a surface of the gate electrode and an exposed epitaxial layer of an active area; and
completely removing the insulating layer.
8. The method of claim 7 , wherein in the step of selectively removing the insulating layer, the insulating layer on the transistor area is selectively removed.
9. The method of claim 7 , wherein the insulating layer is formed of a TEOS based oxide layer.
10. The method of claim 7 , wherein the gate insulating layer is formed by oxidation.
11. The method of claim 7 , further comprising the step of forming a second conductive type impurity region and a first conductive type impurity region in the photodiode area by ion implantation using a mask.
12. A method of fabricating a CMOS image sensor, comprising the steps of:
forming an insulating layer on a first conductive type semiconductor substrate divided into a photodiode area and a transistor area;
removing the insulating layer on a gate electrode forming area of the transistor area;
forming a gate insulating layer on the gate electrode forming area of the semiconductor substrate;
forming a conductive layer over the semiconductor substrate;
forming a gate electrode by planarizing the conductive layer to expose a surface of the insulating layer;
completely removing the insulating layer;
forming a second conductive type lightly doped impurity region on an exposed transistor area of the semiconductor substrate;
forming a spacer on a sidewall of the gate electrode;
forming a second conductive type heavily doped impurity region on the semiconductor substrate using the gate electrode and the spacer as a mask;
forming a salicide on a surface of the gate electrode and an exposed epitaxial layer of an active area; and
forming a second conductive type impurity region and a first conductive type impurity region in the photodiode area by ion implantation using a mask.