Method for fabricating a Schottky diode including a guard ring overlapping an insolation layer
View Patent ↗A Schottky diode includes a deep well formed in a substrate, an isolation layer formed in the substrate, a first conductive type guard ring formed in the deep well along an outer sidewall of the isolation layer and located at a left side of the isolation layer, a second conductive type well formed in the deep well along the outer sidewall of the isolation layer and located at a right side of the isolation layer, an anode electrode formed over the substrate and coupled to the deep well and the guard ring, and a cathode electrode formed over the substrate and coupled to the well. A part of the guard ring overlaps the isolation layer.
1. A method for fabricating a Schottky diode, comprising:
forming an isolation layer in a substrate in which a deep well of a second conductive type is formed;
forming a well region of a second conductive type in the deep well along an outer sidewall of the isolation layer to be located at one side of the isolation layer;
forming a guard ring of a first conductive type in the deep well along the outer sidewall of the isolation layer to be located at an opposite side of the isolation layer in such a manner that a part of the guard ring overlaps the isolation layer; and
forming an anode electrode over the substrate to be coupled to the deep well and the guard ring and simultaneously forming a cathode electrode coupled to the well region over the substrate,
wherein an impurity doping concentration of the well region is reduced in a depth direction from a surface of the substrate,
wherein the forming of the well region comprises:
forming an ion implantation mask over the substrate to expose the deep well of an outer side of the isolation layer;
forming a first impurity region in the deep well by ion implanting a second conductive type impurity by using the ion implantation mask as an ion implantation barrier;
forming a second impurity region on an upper portion of the first impurity region by ion-implanting the second conductive type impurity by using the ion implantation mask as an ion implantation barrier, the second impurity region having an impurity doping concentration higher than an impurity doping concentration of the first impurity region; and forming a third impurity region on an upper portion of the second impurity region by ion-implanting the second conductive type impurity by using the ion implantation mask as an ion implantation barrier, the third impurity region having an impurity doping concentration higher than an impurity doping concentration of the second impurity region.
2. The method of claim 1 , wherein the isolation layer is formed to have a ring shape.
3. The method of claim 1 , wherein the guard ring has a depth smaller than a depth of the isolation layer.
4. The method of claim 1 , wherein the well region has a depth larger than a depth of the isolation layer.
5. The method of claim 4 , wherein a lower portion of the well region surrounds a part of a lower surface of the isolation layer.
6. The method of claim 1 , wherein the forming of the guard ring comprises:
forming an ion implantation mask over the substrate to expose the deep well of the opposite side of the isolation layer and a part of the isolation layer being in contact with the deep well; and
ion-implanting a first conductive type impurity by using the ion implantation mask as an ion implantation barrier.
7. The method of claim 1 , wherein the forming of the anode electrode and the cathode electrode comprises:
depositing a metal layer over a resultant structure including the substrate;
forming a metal silicide layer by reacting the substrate with the metal layer through a thermal treatment process; and
removing a metal layer which does not react in the thermal treatment process.
8. A method for fabricating a Schottky diode, comprising:
forming an isolation layer in a substrate in which a deep well of a second conductive type is formed;
forming a well region of a second conductive type in the deep well along an outer sidewall of the isolation layer to be located at one side of the isolation layer;
forming a guard ring of a first conductive type in the deep well along the outer sidewall of the isolation layer to be located at an opposite side of the isolation layer in such a manner that a part of the guard ring overlaps the isolation layer; and
forming an anode electrode over the substrate to be coupled to the deep well and the guard ring and simultaneously forming a cathode electrode coupled to the well region over the substrate,
wherein a first region of the guard ring overlaps with the isolation layer and a second region of the guard ring does not overlap with the isolation layer,
wherein a width of a top surface of the first region is different from a width of a top surface of the second region, and
wherein the width of a top surface of the second region is substantially the same as a width of a bottom surface of the second region.
9. The method of claim 8 , wherein a n overlapping width between the guard ring and the isolation layer is smaller than a width of the guard ring not overlapping the isolation layer.
10. The method of claim 8 , wherein the isolation layer has a ring shape.
11. The method of claim 8 , wherein the guard ring has a depth smaller than a depth of the isolation layer on a basis of an upper surface of the substrate.
12. The method of claim 8 , wherein the isolation layer has a depth smaller than a depth of the well region on the basis of the upper surface of the substrate.
13. The method of claim 12 , wherein a lower portion of the well region surrounds a portion of a lower surface of the isolation layer.
14. The method of claim 8 , wherein the forming of the well region comprises:
forming an ion implantation mask over the substrate to expose the deep well of an outer side of the isolation layer;
forming a first impurity region in the deep well by ion implanting a second conductive type impurity by using the ion implantation mask as an ion implantation barrier;
forming a second impurity region on an upper portion of the first impurity region by ion-implanting the second conductive type impurity by using the ion implantation mask as an ion implantation barrier, the second impurity region having an impurity doping concentration higher than an impurity doping concentration of the first impurity region; and forming a third impurity region on an upper portion of the second impurity region by ion-implanting the second conductive type impurity by using the ion implantation mask as an ion implantation barrier, the third impurity region having an impurity doping concentration higher than an impurity doping concentration of the second impurity region.
15. The method of claim 8 , wherein the forming of the anode electrode and the cathode electrode comprises:
depositing a metal layer over a resultant structure including the substrate;
forming a metal silicide layer by reacting the substrate with the metal layer through a thermal treatment process; and
removing a metal layer which does not react in the thermal treatment process.
16. The method of claim 8 , wherein the width of a top surface of the first region is smaller than the width of a top surface of the second region.
17. A method of claim 8 , wherein the width of a top surface of the first region is substantially the same as a width of a bottom surface of the first region.