S-contact for SOI
Systems, methods, and apparatus for an improved protection from charge injection into layers of a device using resistive structures are described. Such resistive structures, named s-contacts, can be made using simpler fabrication methods and less fabrication steps. In a case of metal-oxide-semiconductor (MOS) field effect transistors (FETs), s-contacts can be made with direct connection, or resistive connection, to all regions of the transistors, including the source region, the drain region and the gate.
1. A device comprising:
a semiconductor substrate which consists of a single layer high resistivity semiconductor substrate, the high resistivity based on a nominal doping of the semiconductor substrate;
a single layer trap rich layer overlying and in contact with the semiconductor substrate;
an insulation layer overlying and in contact with the trap rich layer;
an active layer overlying and in contact with the insulation layer, the active layer comprising active regions and isolation regions of the device;
a transistor formed in the active layer, active regions of the transistor comprising a drain region, a source region and a gate channel region; and
a first conductive structure resistively connecting one of: a) a drain contact or a source contact, or b) a gate contact, to the semiconductor substrate so that there can be a symmetrical flow of charges between the semiconductor substrate and the one of a) or b), the first conductive structure comprising:
a first conductive line connecting the one of a) or b) to a first conductive contact, the first conductive contact extending through the active layer at an isolation region of the device, further extending through the insulation layer to make a contact with the semiconductor substrate that is arranged immediately below the single layer trap rich layer according to one of:
i) a resistive contact by partially penetrating the trap rich layer, or
ii) a direct contact by fully penetrating the trap rich layer.
2. The device according to claim 1 , wherein an effective contact resistance between the first conductive contact and the high resistivity semiconductor substrate is in a range of 0.2 to 20 G-ohm.
3. The device according to claim 1 , wherein the first conductive contact penetrates the trap rich layer partially, at a depth corresponding to a desired resistance value coupled between the resistive contact and the semiconductor substrate.
4. The device according to claim 1 , wherein the resistive contact with the semiconductor region is through a thickness portion of the trap rich layer not penetrated by the first conductive contact.
5. The device according to claim 1 , wherein a resistivity value of the high resistivity substrate is in a range of 3,000 to 20,000 ohm-cm.
6. The device according to claim 1 , wherein a resistivity value of the high resistivity substrate is greater than 3,000 ohm-cm.
7. The device according to claim 1 , further comprising a second conductive structure that resistively connects the other of the one of a) or b) to the semiconductor substrate so that there can be a symmetrical flow of charges between the semiconductor substrate and the other one of a) or b).
8. The device according to claim 7 , wherein the second conductive structure comprises:
a second conductive line connecting the other of the one of a) or b) to a second conductive contact, the second conductive contact extending through the insulation layer and penetrating the trap rich layer to make resistive contact with the semiconductor substrate.
9. The device according to claim 7 , further comprising one or more additional first conductive structures and/or one or more additional second conductive structures.
10. The device according to claim 9 , wherein a number of the one or more additional first conductive structures is based on a desired equivalent resistance between the first conductive structures and the bottom surface of the semiconductor substrate away from the insulation layer.
11. The device according to claim 10 , wherein a number of the one or more additional second conductive structures is based on a desired equivalent resistance between the second conductive structures and the bottom surface of the semiconductor substrate away from the insulation layer.
12. The device according to claim 1 , wherein the transistor is one of: a) an N-type metal-oxide-semiconductor field effect transistor (NMOSFET), or b) a P-type metal-oxide-semiconductor field effect transistor (PMOSFET).
13. A method for providing a discharge path to a silicon-on-insulator (SOI) transistor device, the method comprising:
(i) forming an active layer on a semiconductor substrate consisting of a single layer high resistivity semiconductor substrate, the high resistivity based on a nominal doping of the semiconductor substrate, the active layer being isolated from the high resistivity substrate via an insulation layer overlying and contacting a single layer trap rich layer formed on and contacting the semiconductor substrate;
(ii) forming active regions of the transistor device in the active layer, the active regions comprising a source region, a drain region and a gate channel region;
(iii) forming a first conductive structure resistively connecting one of: a) a drain contact or a source contact, or b) a gate contact, of the transistor device to the semiconductor substrate thereby providing a symmetrical flow of charges between the semiconductor substrate and the one of a) or b), the first conducting structure being formed by:
forming a first conductive line connecting the one of a) or b) to a first conductive contact;
extending the first conductive contact through the active layer at an isolation region of the active layer and through the insulation layer to make a contact with the semiconductor substrate that is arranged immediately below the single layer trap rich layer according to one of:
iii-a) a resistive contact by partially penetrating the trap rich layer, or
iii-b) a direct contact by fully penetrating the trap rich layer, and
(iv) based on the forming of the first conductive structure, providing a first discharge path for symmetrical flow of charges to the transistor device.
14. The method according to claim 13 , wherein the isolation region is a shallow trench isolation (STI) region.
15. The method according to claim 13 , wherein an effective contact resistance between the first conductive contact and the semiconductor substrate is in a range of 0.2 to 20 G-ohm.
16. The method according to claim 13 , wherein a resistivity value of the semiconductor substrate is in a range of 3,000 to 20,000 ohm-cm.
17. The method of claim 13 , further comprising:
forming a second conductive structure; and
based on the forming, resistively connecting the other of the one of a) or b) to the semiconductor substrate.
18. The method of claim 17 , wherein the forming of the second conductive structure comprises:
forming a second conductive line connecting the other of the one of a) or b) to a second conductive contact;
extending the second conductive contact through the active layer at an isolation region of the active layer and through the insulation layer to make a contact with the semiconductor substrate that is arranged immediately below the single layer trap rich layer according to one of:
a) a resistive contact by partially penetrating the trap rich layer, and
b) a direct contact by fully penetrating the trap rich layer, and
based on the forming of the second conductive structure, providing a second discharge path for symmetrical flow of charges to the transistor device.
19. A device comprising:
a semiconductor substrate which consists of a single layer high resistivity semiconductor substrate;
a single layer trap rich layer overlying and in contact with the semiconductor substrate;
an insulation layer overlying and in contact with the trap rich layer;
an active layer overlying and in contact with the insulation layer, the active layer comprising active regions and isolation regions of the device;
a transistor formed in the active layer, active regions of the transistor comprising a drain region, a source region and a gate channel region; and
a first conductive structure resistively connecting one of: a) a drain contact or a source contact, or b) a gate contact, to the semiconductor substrate, the first conductive structure comprising:
a first conductive line connecting the one of a) or b) to a first conductive contact, the first conductive contact extending through the active layer at an isolation region of the device, further extending through the insulation layer to make a contact with the semiconductor substrate that is arranged immediately below the single layer trap rich layer according to one of:
i) a resistive contact by partially penetrating the trap rich layer, or
ii) a direct contact by fully penetrating the trap rich layer.