Static random access memory and method of manufacturing the same

Patent metadata

Field	Value
Publication number	US-10083969-B2
Application number	US-201715437915-A
Country	US
Kind code	B2
Filing date	Feb 21, 2017
Priority date	Apr 28, 2016
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

A Static Random Access Memory (SRAM) cell includes a first pull-up transistor and a first pull-down transistor, a second pull-up transistor and a second pull-down transistor, and first and second pass-gate transistors. A first buried contact electrically connects a drain region of the first pull-up transistor and gate electrodes of the second pull-up transistor and the second pull-down transistor, and includes a first metal layer formed in a region confined by spacers of a first gate layer and a first electrically conductive path formed at a level below the spacers. A second buried contact electrically connects a drain region of the second pull-up transistor and gate electrodes of the first pull-up transistor and the first pull-down transistor, and includes a second metal layer formed in a region confined by spacers of a second gate layer and a second electrically conductive path formed at the level below the spacers.

First claim

What is claimed is:

1. A Static Random Access Memory (SRAM) cell, comprising:
a first pull-up transistor and a first pull-down transistor;
a second pull-up transistor and a second pull-down transistor;
first and second pass-gate transistors;
a first buried contact electrically connecting a drain region of the first pull-up transistor and gate electrodes of the second pull-up transistor and the second pull-down transistor, and including a first metal layer formed in a region confined by spacers of a first gate layer by which the gate electrodes of the second pull-up transistor and the second pull-down transistor are formed; and
a second buried contact electrically connecting a drain region of the second pull-up transistor and gate electrodes of the first pull-up transistor and the first pull-down transistor, and including a second metal layer formed in a region confined by spacers of a second gate layer by which the gate electrodes of the first pull-up transistor and the first pull-down transistor are formed.

2. The SRAM cell of claim 1 , wherein the first and second metal layers are formed of one selected from the group consisting of tungsten, cobalt, titanium, copper, and a combination thereof.

3. The SRAM cell of claim 1 , wherein the first metal layer penetrates through the first gate layer to electrically connected to a first electrically conductive material buried below the first gate layer, and the second metal layer penetrates through the second gate layer to electrically connected to a second electrically conductive material buried below the second gate layer.

4. The SRAM cell of claim 2 , further comprising:
a first metal contact electrically connecting the drain region of the first pull-up transistor and drains of the first pass-gate transistor and the first pull-down transistor;
a second metal contact electrically connecting the drain region of the second pull-up transistor and drains of the second pass-gate transistor and the second pull-down transistor;
third and fourth metal contacts electrically connecting source regions of the first and second pass-gate transistors and first and second bitlines, respectively;
fifth and sixth metal contacts electrically connecting source regions of the first and second pull-up transistors to a first power supply line; and
seventh and eighth metal contacts electrically connecting source regions of the first and second pull-down transistors to a second power supply line,
wherein the first through eight metal contacts, made of the same material, are formed at the same level with reference to a surface of the substrate on which the SRAM cell is formed.

5. The SRAM cell of claim 4 , wherein the first and second metal layers and the first through eight metal contacts are formed at the same level and are made of the same material.

6. The SRAM cell of claim 3 , wherein:
the first electrically conductive material includes a first doped semiconductor electrically connecting the first metal layer and the drain region of the first pull-up transistor to each other, and
the second electrically conductive material includes a second doped semiconductor electrically connecting the second metal layer and the drain region of the second pull-up transistor to each other.

7. The SRAM cell of claim 6 , wherein the first and second doped semiconductor regions having a doping concentration from about 5×10 19 cm −3 to about 1×10 20 cm −3 .

8. The SRAM cell of claim 6 , wherein:
the first electrically conductive material further includes a first silicide layer disposed between the first metal layer and the first doped semiconductor, and
the second doped semiconductor further includes a second silicide layer disposed between the second metal layer and the second doped semiconductor region.

9. The SRAM cell of clam 6 , wherein the first doped semiconductor directly contacts the drain region of the first pull-up transistor and the second doped semiconductor directly contacts the drain region of the second pull-up transistor.

10. The SRAM cell of claim 8 , wherein the first and second silicide layers are made of one selected from the group consisting of TiSi, TaSi, NiSi, CoSi, and a combination thereof.

11. A semiconductor device, comprising:
a first transistor, source, drain, and channel regions of which are formed of a first semiconductor fin protruding from a substrate;
a second transistor, source, drain, and channel regions of which are formed of a second semiconductor fin protruding from the substrate; and
a buried contact electrically connecting the drain region of the first transistor and a gate electrode of the second transistor, and including a metal layer formed in a region confined by spacers of the gate electrode of the second transistor.

12. The semiconductor device of claim 11 , wherein the metal layer is made of one selected from the group consisting of tungsten, cobalt, titanium, copper, and a combination thereof.

13. The semiconductor device of claim 11 , further includes a metal drain electrode disposed over the drain region of the first transistor and electrically connected to the metal layer of the buried contact at least through a portion of the first semiconductor fin doped with impurities.

14. The semiconductor device of claim 13 , wherein the buried contact further includes a silicide layer disposed between the metal layer and the portion of the first semiconductor fin.

15. The semiconductor device of claim 13 , wherein the portion of the first semiconductor fin directly contacts the drain region of the first transistor.

16. A method of manufacturing a semiconductor device, comprising steps of:
forming first and second transistors in first and second semiconductor fins, respectively;
forming a buried contact electrically connecting a drain region of the first transistor and a gate electrode of the second transistor and including a metal layer formed in a region confined by spacers of the gate electrode of the second transistor, the metal layer being in contact with the spacers of the gate electrode of the second transistor; and
forming a drain contact over the drain region of the first transistor and a source contact over a source region of the first transistor.

17. The method of claim 16 , wherein the metal layer is formed of one selected from the group consisting of tungsten, cobalt, titanium, copper, and a combination thereof.

18. The method of claim 16 , wherein the step of forming the buried contact comprises:
forming an opening in a portion of a gate electrode of the second transistor so as to expose a portion of the second semiconductor fin;
implanting impurities into the exposed portion of the second semiconductor fin; and
filling the opening with the metal layer.

19. The method of claim 16 , wherein the step of forming the buried contact comprises growing a doped epitaxy region electrically connecting the metal layer and the drain region of the first transistor.

20. The method of claim 18 , wherein the step of forming the buried contact further comprising:
after implanting the impurities and before filling the opening with the metal layer, forming a silicide layer on the exposed portion of the second semiconductor fin.

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Chen Ying-Yan
• Lai Jui-Yao
• Yeong Sai-Hooi
• Chen Yen-Ming

Classifications

• H10W20/069

  by forming self-aligned vias or self-aligned contact plugs · CPC title

• H10W20/021

  of interconnections within wafers or substrates · CPC title

• H10W20/0698 Primary

  Local interconnections · CPC title

• H01L29/0847

  Electricity · mapped topic

• H01L23/53228

  Electricity · mapped topic