SiGe SRAM butted contact resistance improvement
View Patent ↗The present disclosure relates to a method for fabricating a butted a contact arrangement configured to couple two transistors, wherein an active region of a first transistor is coupled to a gate of a second transistor. The gate of the second transistor is formed from a gate material which comprises a dummy gate of the first transistor, and is configured to straddle a boundary between the active region of the first transistor and an isolation layer formed about the first transistor. The butted a contact arrangement results in a decreased contact resistance for the butted contact as compared to previous methods.
1. A method, comprising:
forming a first gate structure over a first active region of a substrate to form a first transistor, wherein the first gate structure also extends at least partially over a second active region of the substrate to establish a dummy gate over the second active region;
forming a second gate structure over the second active region to form a second transistor;
forming a recess within the second active region between the dummy gate and the second gate structure;
forming a source/drain region within the recess; and
forming a butted contact to couple the source/drain region to the dummy gate.
2. The method of claim 1 , further comprising disposing sidewall spacers along opposite sidewalls of the dummy gate, wherein at least one of the sidewall spacers resides entirely over the second active region.
3. The method of claim 1 , wherein the recess is formed by a wet chemical etch, a dry chemical etch, or a combination thereof.
4. The method of claim 3 , wherein forming the source/drain region within the recess comprises using an epitaxial growth process to form a strain inducing layer within the recess.
5. The method of claim 1 , further comprising forming an isolation region that surrounds and abuts the second active region prior to forming the first gate structure, wherein a boundary of the second active region abuts the isolation region.
6. The method of claim 5 , wherein the first gate structure is arranged over the isolation region and wherein a top portion of the butted contact overhangs past the first gate structure, and wherein the butted contact does not touch the isolation region.
7. A method, comprising;
forming a first gate structure over a first active region of a substrate to form a first transistor, wherein the first gate structure also extends at least partially over a second active region to establish a first dummy gate over the second active region;
forming a second gate structure over the second active region to form a second transistor, wherein the second gate structure also extends at least partially over the first active region to establish a second dummy gate over the first active region; and
forming a butted contact to couple the second active region to the first dummy gate, thereby coupling the second active region to the first gate structure of the first transistor.
8. The method of claim 7 , further comprising:
forming a first isolation region, which surrounds and abuts the first active region;
forming a second isolation region, which surrounds and abuts the second active region;
disposing the second gate structure over a first boundary between the first active region and the first isolation region; and
disposing the first gate structure over a second boundary between the second active region and the second isolation region.
9. The method of claim 8 , further comprising:
disposing a first sidewall spacer along a first sidewall of the first gate structure, wherein the first sidewall spacer extends over the second active region; and
disposing a second sidewall spacer along a second sidewall of the first gate structure, which is opposite the first sidewall, wherein the second sidewall spacer extends over the second isolation region;
wherein the first sidewall spacer does not touch the second isolation region and the second sidewall spacer does not touch the second active region.
10. The method of claim 7 , wherein the butted contact connects a first p-type field-effect transistor (PFET) source or drain to a second PFET gate.
11. The method of claim 7 , further comprising:
forming recesses within the first and second active regions; and
disposing strain inducing or high mobility layers within the recesses to form source and drain regions prior to connecting the butted contact.
12. The method of claim 11 , wherein forming the recesses comprises an anisotropic etch configured to selectively etch along one of more lattice planes of the substrate.
13. The method of claim 11 , wherein the strain inducing or high mobility layers are grown epitaxially within the recesses.
14. The method of claim 11 , wherein the strain inducing or high mobility layers comprise SiGe, Ge, Si, or any combination thereof.
15. A method, comprising:
forming a first inverter on a substrate by connecting a first p-type field-effect transistor (PFET) in series with a first n-type field-effect transistor (NFET);
forming a second inverter on the substrate by connecting a second PFET in series with a second NFET; and
connecting a first drain region of the first PFET to a second gate of the second PFET with a first butted contact, wherein a second gate structure that forms the second gate of the second PFET straddles a first boundary between the first drain region of the first PFET and an inactive region of the substrate.
16. The method of claim 15 , further comprising connecting a second drain region of the second PFET to a first gate of the first PFET with a second butted contact, wherein a first gate structure that forms the first gate of the first PFET straddles a second boundary between the second drain region of the second PFET and the inactive region of the substrate.
17. The method of claim 16 , further comprising:
forming recesses within active regions of the first and second PFETs; and
disposing strain inducing or high mobility layers within the recesses to form source and drain regions prior to connecting the first and second butted contacts.
18. The method of claim 17 , wherein the strain inducing or high mobility layers comprise SiGe, Ge, Si, or any combination thereof, and are grown epitaxially within the recesses.
19. The method of claim 15 , wherein the inactive region of the substrate comprises an isolation region, which surrounds the first and second PFETs.
20. The method of claim 19 , wherein the isolation region comprises a shallow trench isolation (STI) region.