Detection using semiconductor detector

1. A device comprising:

a semiconductor fin comprising a channel region and source/drain regions on opposite sides of the channel region;

an isolation structure laterally surrounding the semiconductor fin;

a gate structure over the channel region of the semiconductor fin;

source/drain structures respectively over the source/drain regions of the semiconductor fin;

a sensing contact directly on the isolation structure and adjacent to the gate structure;

a sensing pad structure connected to the sensing contact; and

a reading contact directly on the isolation structure and adjacent to the gate structure, wherein a distance between the gate structure and the reading contact is less than a width of one of the source/drain structures.

2. The device of claim 1 , wherein one of the source/drain structures is between the sensing contact and the reading contact.

3. The device of claim 1 , wherein the reading contact is spaced apart from the semiconductor fin.

4. The device of claim 1 , wherein the isolation structure is in contact with the reading contact and the semiconductor fin.

5. The device of claim 1 , further comprising a source/drain contact connected to one of the source/drain structures, and a top surface of the source/drain contact is substantially coplanar with a top surface of the reading contact.

6. The device of claim 1 , wherein the sensing contact is spaced apart from the semiconductor fin.

7. The device of claim 1 , wherein the isolation structure is in contact with the sensing contact and the semiconductor fin.

8. The device of claim 1 , further comprising a source/drain contact connected to one of the source/drain structures, and a top surface of the source/drain contact is substantially coplanar with a top surface of the sensing contact.

9. The device of claim 1 , further comprising a word line connected to the reading contact.

10. The device of claim 1 , wherein a bottom surface of the sensing contact is lower than a top surface of the gate structure.

11. The device of claim 1 , further comprising an interlayer dielectric (ILD) layer over the isolation structure and laterally surrounding the gate structure and the sensing contact.

12. The device of claim 1 , wherein a bottom surface of the sensing contact is lower than top surfaces of the source/drain structures.

13. A method comprising:

forming an isolation structure over a substrate to define an active region in the substrate;

forming a gate structure over the active region;

forming source/drain structures on the active region and on opposite sides of the gate structure;

depositing an interlayer dielectric (ILD) layer over the substrate and surrounding the gate structure;

forming a first opening, a second opening, and a third opening in the ILD layer, such that the first opening exposes the active region, and the second and third openings expose the isolation structure, and a depth of the first opening is greater than a depth of the second opening;

forming a source/drain contact in the first opening, a reading contact in the second opening, and a sensing contact in the third opening; and

forming an interconnection structure over the gate structure and the sensing contact, wherein the interconnection structure comprises a sensing pad connected to the sensing contact.

14. The method of claim 13 , wherein forming the source/drain contact in the first opening, the reading contact in the second opening, and the sensing contact in the third opening comprises:

filling conductive materials in the first opening, the second opening, and the third opening of the ILD layer such that the conductive materials is in contact with the isolation structure; and

removing excessive portions of the conductive materials outside the first opening, the second opening, and the third opening of the ILD layer to form the source/drain contact, the reading contact, and the sensing contact.

15. The method of claim 13 , wherein forming the interconnection structure over the gate structure and the sensing contact is such that there is no via interconnecting the interconnection structure and the gate structure.

16. The method of claim 13 , wherein the interconnection structure further comprises a word line connected to the reading contact and is electrically isolated from the gate structure.

17. A method, comprising:

initializing an electrical potential of a gate structure of a semiconductor detector, wherein the semiconductor detector comprises:

the gate structure over a semiconductor fin;

an isolation structure surrounding the semiconductor fin;

a reading contact over the isolation structure and adjacent to the gate structure;

a sensing contact over the isolation structure and adjacent to the gate structure; and

a sensing pad over and connected to the sensing contact;

performing a pre-exposure reading operation on the semiconductor detector;

projecting an e-beam light to the sensing pad of the semiconductor detector after initializing the electrical potential of the gate structure of the semiconductor detector;

performing a post-exposure reading operation on the semiconductor detector, comprising obtaining a current-versus-voltage curve between the reading contact and a drain of the semiconductor detector;

comparing data of the pre-exposure reading operation with the post-exposure reading operation; and

adjusting an intensity of the e-beam light based on the compared data of the pre-exposure reading operation and the post-exposure reading operation.

18. The method of claim 17 , wherein no power is applied to the semiconductor detector during projecting the e-beam light to the sensing pad of the semiconductor detector.

19. The method of claim 17 , wherein initializing the electrical potential of the gate structure of the semiconductor detector comprises:

applying a positive voltage to the reading contact; and

applying a negative voltage to a drain of the semiconductor detector, wherein the positive voltage has a value greater than a value of the negative voltage, and the gate structure is floating during initializing the electrical potential of the gate structure of the semiconductor detector.

20. The method of claim 17 , wherein initializing the electrical potential of the gate structure of the semiconductor detector comprises:

applying a negative voltage to the reading contact; and

applying a positive voltage to a drain of the semiconductor detector, wherein the negative voltage has a value greater than a value of the positive voltage, and the gate structure is floating during initializing the electrical potential of the gate structure of the semiconductor detector.