CMOS transistor junction regions formed by a CVD etching and deposition sequence
View Patent ↗This invention adds to the art of replacement source-drain cMOS transistors. Processes may involve etching a recess in the substrate material using one equipment set, then performing deposition in another. Disclosed is a method to perform the etch and subsequent deposition in the same reactor without atmospheric exposure. In-situ etching of the source-drain recess for replacement source-drain applications provides several advantages over state of the art ex-situ etching. Transistor drive current is improved by: (1) Eliminating contamination of the silicon-epilayer interface when the as-etched surface is exposed to atmosphere and (2) Precise control over the shape of the etch recess. Deposition may be done by a variety of techniques including selective and non-selective methods. In the case of blanket deposition, a measure to avoid amorphous deposition in performance critical regions is also presented.
1. A method comprising:
simultaneously forming a first epitaxial thickness of a crystalline material in a first junction region in a substrate, a second epitaxial thickness of a crystalline material in a different second junction region in the substrate, the first and second junction regions adjacent a gate electrode, and a conformal thickness of an amorphous material over the gate electrode, wherein a rate of forming the conformal thickness of an amorphous material is faster than a rate of forming the first and second epitaxial thickness of crystalline material; then
simultaneously removing a thickness of the amorphous material and a thickness of the crystalline material.
2. The method of claim 1 , wherein a rate of removing the thickness of crystalline material is slower than a rate of removing the thickness of an amorphous material.
3. The method of claim 1 , wherein simultaneously removing comprises removing a thickness of the amorphous material until a remaining horizontal thickness of the amorphous material is thinner than a remaining vertical thickness of the crystalline material.
4. The method of claim 1 , wherein simultaneously removing comprises removing a thickness of the amorphous material until a remaining vertical thickness of the amorphous material is thinner than a remaining vertical thickness of the crystalline material.
5. The method of claim 4 , further comprising removing the remaining thickness of the amorphous material.
6. The method of claim 1 , wherein a surface of the substrate defines a top surface of the substrate and further comprising repeating simultaneously forming and simultaneously removing until a surface of the first junction region and a surface of the second junction region are superior to the top surface.
7. The method of claim 1 , further comprising repeating simultaneously forming and simultaneously removing between five and 10 times to form a thickness of crystalline material of between 0.8 nano-meters and 1.4 nano-meters.
8. The method of claim 1 , wherein simultaneously forming and simultaneously removing occur in one of a chemical vapor deposition (CVD) chamber, an ultra high vacuum (UHV) CVD chamber, a rapid thermal (RT) CVD chanter, a reduced pressure (RP) CVD chamber, and without breaking a seal of the chamber.
9. The method of claim 1 , wherein simultaneously forming and simultaneously removing occur in the same chemical vapor deposition chamber, at a temperature of between 500 and 750 degrees Celsius and at a pressure of between 12 and 18 Torr.
10. The method of claim 1 , wherein simultaneously removing comprises etching with a hydrochloric acid gas; and wherein simultaneously forming comprises non-selective chemical vapor deposition of the crystalline and amorphous materials by introducing trisilane, introducing monomethyl silane.
11. The method of claim 1 , wherein simultaneously forming comprises depositing a sufficient epitaxial thickness of a crystalline material having a lattice spacing different than a lattice spacing of the substrate material to cause a strain in the substrate material.
12. The method of claim 1 , wherein simultaneously forming comprises depositing a sufficient epitaxial thickness of a crystalline phosphorous doped silicon-carbon alloy material to cause a tensile strain in the substrate.
13. The method of claim 1 , wherein the first and second epitaxial thickness of a crystalline material comprises a silicon material having a substitutional-carbon concentration of between 0.13 percent and 2.0 percent, and a phosphorous concentration of between 5E13 atoms per centimeter cubed (atoms/cm 3 ) and 5E20 atoms/cm 3 .
14. The method of claim 1 , wherein Simultaneously removing comprises removing the conformal thickness of an amorphous material from a first sidewall surface of the substrate proximate to the first junction region, and from a second sidewall surface of the substrate proximate to the second junction region, and wherein simultaneously forming comprises depositing a sufficient epitaxial thickness of a crystalline phosphorous silicon-carbon alloy material to fill a first tip region superadjacent to the first sidewall surface and a second tip region superadjacertt to the second sidewall surface.