CMOS TRANSISTORS HAVING DIFFERENTIALLY STRESSED SPACERS
CMOS transistors are formed incorporating a gate electrode having tensely stressed spacers on the gate sidewalls of an n channel field effect transistor and having compressively stressed spacers on the gate sidewalls of a p channel field effect transistor to provide differentially stressed channels in respective transistors to increase carrier mobility in the respective channels.
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This application is a divisional application of co-pending application Ser. No. 13/013,801 filed Jan. 25, 2011 of which the benefit of the earlier filing date is claimed.
BACKGROUNDThe present invention relates to CMOS transistors, and more specifically, to n and p channel metal oxide semiconductor (MOS) field effect transistors (FET's) having differentially stressed spacers and differentially stressed channels.
Stressor layers have been one of the techniques used to increase device performance. However, due to the location of the spacers for short channel effect control, the stressor layers are typically located a few hundred angstroms away from the channel over a spacer thereby limiting the extent of performance improvement in carrier mobility in the channel.
BRIEF SUMMARY OF THE INVENTIONIn accordance with the present invention, an n type field effect transistor comprising a substrate having a p region, a first gate dielectric, a first poly silicon gate electrode there over having sidewalls, a tensely stressed spacer on the sidewalls of the first poly silicon gate electrode, a n type halo region in the p region on opposite sides of the first poly silicon gate electrode, a n type source and drain extension overlapping the n type halo regions on opposite sides of the first poly silicon gate electrode, and electrical contacts to the source extension, drain extension and gate electrode.
The invention further provides a p type field effect transistor comprising a substrate having a n region, a first gate dielectric, a first poly silicon gate electrode there over having sidewalls, a compressively stressed spacer on the sidewalls of the first poly silicon gate electrode, a p type halo region in the n region on opposite sides of the first poly silicon gate electrode, a p type source and drain extension overlapping the p type halo regions on opposite sides of the first poly silicon gate electrode, and electrical contacts to the source extension, drain extension and gate electrode.
The invention further provides an n type and p type field effect transistor is described comprising a substrate having p and n regions for forming n and p type field effect transistors respectively therein, a first gate dielectric and a first poly silicon gate electrode having sidewalls there over on at least one p region, a second gate dielectric and a second poly silicon gate electrode having sidewalls there over on at least one n region, a tensely stressed spacer on the sidewalls of the first poly silicon gate electrode, an n type halo region in the p region on opposite sides of the first poly silicon gate electrode, an n type source and drain extension in the p region overlapping the n type halo regions on opposite sides of the first poly silicon gate electrode, a compressively stressed spacer on the sidewalls of the second poly silicon gate electrode, a p type halo region in the n region on opposite sides of the second poly silicon gate electrode, and a p type source and drain extension in the n region overlapping the p type halo regions on opposite sides of the second poly silicon gate electrode.
These and other features, objects, and advantages of the present invention will become apparent upon consideration of the following detailed description of the invention when read in conjunction with the drawing in which:
Referring now to the drawing,
A first gate dielectric 25 and first poly silicon gate electrode 26 are formed on p region 14. A second gate dielectric 27 and second poly silicon gate electrode 28 is formed on n region 17. First poly silicon gate electrode 26 and second poly silicon gate 28 may be doped n or p type up to 5×1021 atoms/cm3. For p type doping, BF2 or BF3 may be used. For n type doping, an As containing gas may be used.
A first hard mask 30 which may be for example an oxide, a nitride such as a silicon nitride or an oxide nitride is formed over n region 17, over second gate dielectric 27 and second poly silicon gate electrode 28. First hard mask 30 functions to protect n region 17, second gate dielectric 27 and second poly silicon gate electrode 28 from damage during processing in p region 14. As shown in
After tensely stressed spacers 36 and 38 are formed; n type halo regions 44 and 46 are formed on opposite sides of first poly silicon gate electrode 26. Halo regions 44 and 46 are positioned with respect to tensely stressed spacers 36 and 38. Next, n type source and drain extensions 48 and 50 are formed in p region 14 overlapping the halo regions on opposite sides of first poly silicon gate electrode 26. Next, hard mask 30 is removed by a chemical etch for example by a timed chemical etch. Tensely stressed spacers 40 and 42 on either side of mask 30 are removed when mask 30 is removed.
Compressively stressed spacers 68 and 70 are also formed on mask 56 at the same time compressively stressed spacers 64 and 66 are formed. Compressively stressed spacers 64 and 66 function to compress sidewalls 57 and 59 of second poly silicon gate electrode 28 and channel 72 below which improves the carrier mobility of channel 72 below shown in
After compressively stressed spacers 64 and 66 are formed, p type halo regions 74 and 76 are formed on opposite sides of second poly silicon gate electrode 28. Next, p type source and drain extensions 78 and 80 are formed overlapping halo regions 74 and 76 on opposite sides of second poly silicon gate electrode 28.
A self aligned silicide process may be used to form silicide regions 82-85 in source extension 48/halo region 44, drain extension 50/halo region 46, source extension 78/halo region 74 and drain extension 80/halo region 76, respectively, shown in
Openings 90, 92, 94 and 96 may be formed in dielectric layer 89 to source extension 48, drain extension 50, source extension 78, and drain extension 80, respectively. Openings 90, 92, 94 and 96 may be filled with a conductor such as W to form contacts 98 and 100 to source extension 48 and drain extension 50 respectively of NMOS FET 86 and form contacts 102 and 104 to source extension 78 and drain extension 80 respectively of PMOS FET 88.
In
While there has been described and illustrated n and p channel MOS FETs having differentially stressed spacers and transistor channels, it will be apparent to those skilled in the art that modifications and variations are possible without deviating from the broad scope of the invention which shall be limited solely by the scope of the claims appended hereto.
Claims
1. An n type field effect transistor comprising:
- a substrate having a p region,
- a first gate dielectric,
- a first poly silicon gate electrode having sidewalls over said first gate dielectric,
- a tensely stressed spacer on said sidewalls of said first poly silicon gate electrode,
- an n type halo region in said p region on opposite sides of said first poly silicon gate electrode,
- an n type source and drain extension overlapping said n type halo regions on opposite sides of said first poly silicon gate electrode, and
- electrical contacts to said source extension, drain extension and gate electrode.
2. The n type field effect transistor of claim 1 wherein said tensely stressed spacer is in direct contact to said sidewalls of said first poly silicon gate electrode.
3. The n type field effect transistor of claim 1 wherein said tensely stressed spacer on said first poly silicon gate electrode is at an interface of said first gate dielectric.
4. The n type field effect transistor of claim 1 wherein said tensely stressed spacer abuts said halo region.
5. The n type field effect transistor of claim 1 wherein said tensely stressed spacer is spaced from said sidewalls of said first poly silicon gate electrode by an oxide layer having a thickness in the range from 0.5 to 5 nm.
6. The n type field effect transistor of claim 1 wherein said first poly silicon gate electrode is selected from the group consisting of SiGe, SiC, Ge, GaAs, combinations thereof and in combination with poly silicon.
7. A p type field effect transistors comprising:
- a substrate having an n region,
- a first gate dielectric,
- a first poly silicon gate electrode having sidewalls over said first gate dielectric,
- a compressively stressed spacer on said sidewalls of said first poly silicon gate electrode,
- a p type halo region in said n region on opposite sides of said first poly silicon gate electrode,
- a p type source and drain extension overlapping said p type halo regions on opposite sides of said first poly silicon gate electrode, and
- electrical contacts to said source extension, drain extension and gate electrode.
8. The p type field effect transistor of claim 7 wherein said compressively stressed spacer is in direct contact to said sidewalls of said first poly silicon gate electrode.
9. The p type field effect transistor of claim 7 wherein said compressively stressed spacer on said first poly silicon gate electrode is at an interface of said first gate dielectric.
10. The p type field effect transistor of claim 7 wherein said compressively stressed spacer abuts said halo region.
11. The p type field effect transistor of claim 7 wherein said compressively stressed spacer is spaced from said sidewalls of said first poly silicon gate electrode by an oxide layer having a thickness in the range from 0.5 to 5 nm.
12. The p type field effect transistor of claim 7 wherein said first poly silicon gate electrode is selected from the group consisting of SiGe, SiC, Ge, GaAs, combinations thereof and in combination with poly silicon.
13. An n type field effect transistor and a p type field effect transistor comprising:
- a substrate having p and n regions for forming n and p type field effect transistors respectively therein,
- a first gate dielectric and a first poly silicon gate electrode having sidewalls there over on at least one p region,
- a second gate dielectric and a second poly silicon gate electrode having sidewalls there over on at least one n region,
- a tensely stressed spacer on said sidewalls of said first poly silicon gate electrode, an n type halo region in said p region on opposite sides of said first poly silicon gate electrode,
- an n type source and drain extension in said p region overlapping said n type halo regions on opposite sides of said first poly silicon gate electrode,
- a compressively stressed spacer on said sidewalls of said second poly silicon gate electrode,
- a p type halo region in said n region on opposite sides of said second poly silicon gate electrode, and
- a p type source and drain extension in said n region overlapping said p type halo regions on opposite sides of said second poly silicon gate electrode.
14. The n type field effect transistor and p type field effect transistor of claim 13 wherein said tensely stressed film is positioned directly on exposed sidewalls of said first poly silicon gate electrode.
15. The n type field effect transistor and p type field effect transistor of claim 13 wherein said tensely stressed film is positioned on said first poly silicon gate electrode at an interface of said first gate dielectric.
16. The n type field effect transistor and p type field effect transistor of claim 13 wherein said tensely stressed film is positioned on said first poly silicon gate electrode and abutting said p region.
17. The n type field effect transistor and p type field effect transistor of claim 13 further includes an oxide layer having a thickness in the range from 0.5 to 5 nm on sidewalls of said first poly silicon gate electrode.
18. The n type field effect transistor and p type field effect transistor of claim 13 wherein said first poly silicon gate electrode is selected from the group consisting of SiGe, SiC, Ge, GaAs, combinations thereof and in combination with poly silicon.
19. The n type field effect transistor and p type field effect transistor of claim 13 wherein said compressively stressed film is positioned directly on exposed sidewalls of said second poly silicon gate electrode.
20. The n type field effect transistor and p type field effect transistor of claim 13 wherein said compressively stressed film is positioned on said second poly silicon gate electrode at an interface of said second gate dielectric.
21. The n type field effect transistor and p type field effect transistor of claim 13 wherein said compressively stressed film is positioned on said second poly silicon gate electrode and abutting said p region.
22. The n type field effect transistor and p type field effect transistor of claim 13 further including an oxide layer having a thickness in the range from 0.5 to 5 nm on sidewalls of said second poly silicon gate electrode.
23. The n type field effect transistor and p type field effect transistor of claim 13 wherein said second poly silicon gate electrode is selected from the group consisting of SiGe, SiC, Ge, GaAs, combinations thereof and in combination with poly silicon.
24. The n type field effect transistor and p type field effect transistor of claim 13 further including:
- a dielectric layer positioned over and above said p and n regions including said first and second poly silicon gate electrodes,
- said dielectric layer planarized down to said first and second poly silicon gate electrodes, and
- contacts contacting said first and second gate electrodes and said source and drain extensions of said n and p type field effect transistors.
Type: Application
Filed: Jan 29, 2013
Publication Date: May 30, 2013
Applicant: INTERNATIONAL BUSINESS MACHINES CORPORATION (ARMONK, NY)
Inventor: International Business Machines Corporation (Armonk, NY)
Application Number: 13/752,388
International Classification: H01L 29/78 (20060101); H01L 27/092 (20060101);