Schottky clamped radio frequency switch

• US 9,177,968 B1
• Filed: 09/19/2014
• Issued: 11/03/2015
• Est. Priority Date: 09/19/2014
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Silanna Semiconductor USA Inc
• Inventors: Nygaard, Paul A.
• Primary Examiner(s): Lee, Cheung
• Assistant Examiner(s): BRADLEY, STEPHEN M
• Application Number:
  US14/491,783
• Time in Patent Office: 410 Days
• Field of Search: 257/401
• US Class Current: 1/1
• CPC Class Codes: H01L 21/84 the substrate being other than a semiconductor body, e.g. being an insulating body
• CPC Class Codes: H01L 27/0629 in combination with diodes, or resistors, or capacitors
• CPC Class Codes: H01L 27/0727 in combination with diodes, or capacitors or resistors
• CPC Class Codes: H01L 27/1203 the substrate comprising an insulating body on a semiconductor body, e.g. SOI three-dimensional layout H01L27/0688
• CPC Class Codes: H01L 29/47 Schottky barrier electrodes H01L29/435 takes precedence
• CPC Class Codes: H01L 29/665 using self aligned silicidation, i.e. salicide formation of conductive layers comprising silicides H01L21/28518
• CPC Class Codes: H01L 29/7833 with lightly doped drain or source extension, e.g. LDD MOSFET's; DDD MOSFET's for thin film transistors H01L29/78618
• CPC Class Codes: H01L 29/7839 with Schottky drain or source contact
• CPC Class Codes: H01L 29/78615 with a body contact

Abstract

Various methods and devices that involve radio frequency (RF) switches with clamped bodies are provided. An exemplary RF switch with a clamped body comprises a channel that separates a source and a drain. The RF switch also comprises a clamp region that spans the channel, extends into the source and drain, and has a lower dopant concentration than both the source and drain. The RF switch also comprises a pair of matching silicide regions formed on either side of the channel and in contact with the clamp region. The clamp region forms a pair of Schottky diode barriers with the pair of matching silicide regions. The RF switch can operate in a plurality of operating modes. The pair of Schottky diode barriers provide a constant sink for accumulated charge in the clamped body that is independent of the operating mode in which the RF switch is operating.

Claims

1. A radio frequency switch with a clamped body comprising:

a channel that separates a source and a drain;

a clamp region that spans the channel, extends into the source and drain, and has a lower dopant concentration than both the source and drain; and

a pair of matching silicide regions formed on either side of the channel and in contact with the clamp region;

wherein the clamp region, the source, and the drain are all doped with a lightly doped drain implant that has a moderate implant concentration;

wherein the source and drain are also doped with a heavy implant that has a heavy implant concentration;

wherein the lower dopant concentration is less than a dopant concentration of the source and drain by at least the difference between the moderate implant concentration and the heavy implant concentration;

wherein the clamp region forms a pair of Schottky diode barriers with the pair of matching silicide regions;

wherein the radio frequency switch can operate in a plurality of operating modes; and

wherein the pair of Schottky diode barriers provide a constant sink for accumulated charge in the clamped body that is independent of the operating mode in which the radio frequency switch is operating.

2. The radio frequency switch of claim 1, comprising:

a matching clamp region that spans the channel;

wherein a lengthwise dimension vector of the matching clamp region is parallel with a lengthwise dimension vector of the clamp region; and

wherein the matching clamp region and the clamp region are spaced apart by at least 5 microns.

3. The radio frequency switch of claim 2, comprising:

a plurality of transistor fingers; and

a plurality of additional clamp regions;

wherein the plurality of transistor fingers comprise a plurality of finger widths that each contribute to an overall width of the channel; and

wherein each additional clamp region in the plurality of additional clamp regions is spaced apart from all other additional clamp regions in the plurality of clamp regions by less than 20 microns along a finger width in the plurality of finger widths.

4. The radio frequency switch of claim 3, wherein:

the clamp region and each of the plurality of additional clamp regions are at least 0.2 microns wide along the overall width of the channel.

5. The radio frequency switch of claim 1, wherein:

the clamp region comprises silicon; and

the source, drain, and clamped body are all in contact with a buried insulator layer of a silicon on insulator wafer.

6. A radio frequency switch with a clamped body comprising:

a channel separating a source and a drain of the radio frequency switch;

a first clamp region of a semiconductor material that;

(i) spans the channel;

(ii) comprises a first contact region extending into the source; and

(iii) comprises a second contact region extending into the drain;

a first silicide region formed on the first contact region; and

a second silicide region formed on the second contact region;

wherein the first clamp region of the semiconductor material has a lower dopant concentration than both the source and the drain;

wherein the first clamp region, the source, and the drain are all doped with a lightly doped drain implant that has a moderate implant concentration;

wherein the source and drain are also doped with a heavy implant that has a heavy implant concentration;

wherein the lower dopant concentration is less than a dopant concentration of the source and drain by at least the difference between the moderate implant concentration and the heavy implant concentration;

wherein the first contact region forms a first Schottky diode barrier with the first silicide region; and

wherein the second contact region forms a second Schottky diode barrier with the second silicide region.

7. The radio frequency switch of claim 6, comprising:

a matching clamp region of the semiconductor material that spans the channel;

wherein a lengthwise dimension vector of the matching clamp region of the semiconductor material is parallel with a lengthwise dimension vector of the first clamp region of the semiconductor material; and

wherein the first clamp region of the semiconductor material and the matching clamp region of the semiconductor material are spaced apart by less than 20 microns along a width of the channel.

8. The radio frequency switch of claim 7, comprising:

a plurality of transistor fingers; and

a plurality of additional clamp regions;

wherein the plurality of transistor fingers comprise a plurality of finger widths that each contribute to the width of the channel; and

wherein each additional clamp region in the plurality of clamp regions is spaced apart from all other additional clamp regions in the plurality of clamp regions by less than 20 microns but more than 5 microns along a finger width in the plurality of finger widths.

9. The radio frequency switch of claim 8, wherein:

the clamp region and each of the plurality of additional clamp regions are at least 0.2 microns wide along the width of the channel.

10. The radio frequency switch of claim 6, wherein:

the first clamp region comprises silicon; and

the source, the drain, and the clamped body are all in contact with a buried insulator layer of a silicon on insulator wafer.

11. The radio frequency switch of claim 6, wherein:

the first contact region extends into the source along a first portion of a width of the channel;

the second contact region extends into the drain along a second portion of the width of the channel; and

the first portion of the width is smaller than the second portion of the width.

12. The radio frequency switch of claim 11, wherein:

the second portion of the width of the channel spans a finger width of the channel.

13. The radio frequency switch of claim 12, wherein:

the source is doped with a halo implant; and

the drain is not doped with the halo implant.

14. A radio frequency switch comprising:

a gate that comprises a gate electrode and a gate insulator;

a channel that;

(i) is located in a body of the radio frequency switch; and

(ii) is insulated from the gate electrode by the gate insulator;

a first doped region located across the channel from a second doped region;

a third region that;

(i) spans the channel;

(ii) extends into the first and second doped regions; and

(iii) has a lower dopant concentration than the first and second doped regions;

a first silicide region that forms a first Schottky diode junction with the third region; and

a second silicide region that;

(i) is located across the channel from the first silicide region; and

(ii) forms a second Schottky diode with the third region;

wherein the third region extends into the first doped region along a first portion of a width of the channel;

wherein the third region extends into the second doped region along a second portion of the width of the channel; and

wherein the first portion of the width is larger than the second portion of the width.

15. The radio frequency switch of claim 14, comprising:

a fourth region that;

(i) spans the channel;

(ii) extends into the first and second doped regions; and

(iii) has a lower dopant concentration than the first and second doped regions;

wherein a lengthwise dimension vector of the third region is parallel with a lengthwise dimension vector of the fourth region; and

wherein the third region and the fourth region are spaced apart by at least 5 microns along a width of the channel.

16. The radio frequency switch of claim 15, wherein:

the third and fourth regions comprise a pair of matching clamp regions.

17. The radio frequency switch of claim 16, comprising:

a plurality of transistor fingers; and

a plurality of additional clamp regions;

wherein the plurality of transistor fingers comprise a plurality of finger widths that each contribute to the width of the channel; and

wherein each additional clamp region in the plurality of clamp regions is spaced apart from all other additional clamp regions in the plurality of clamp regions by less than 20 microns but more than 5 microns along a finger width in the plurality of finger widths.

18. The radio frequency switch of claim 17, wherein:

the pair of matching clamp regions and the plurality of additional clamp regions are each at least 0.2 microns wide along the width of the channel.

19. The radio frequency switch of claim 14, comprising:

the third region comprises silicon; and

the first doped region, the second doped region, and the body are all in contact with a buried insulator layer of a silicon on insulator wafer.

20. The radio frequency switch of claim 14, wherein:

the third region, first doped region, and the second doped region, are all doped with a lightly doped drain implant that has a moderate doping concentration;

the first doped region and the second dope region are also doped with a heavy implant that has a heavy implant concentration; and

the lower dopant concentration is less than the dopant concentration of the first doped region and the second doped region by at least a difference between the heavy implant concentration and the moderate doping concentration.