PAA-based etchant, methods of using same, and resultant structures

1. A wet-etch composition comprising:

peracetic acid (PAA); and

a fluorinated acid;

a relative amount of the PAA in the composition being sufficient to ensure an etch rate ratio of SiGe:Si for NMOS transistors of a CMOS device that is substantially the same as an etch rate ratio of SiGe:Si for PMOS transistors of the CMOS device.

2. The wet-etch composition of claim 1 , wherein the relative amount of PAA is in a range of about 1.0 wt % to about 50 wt %.

3. The wet-etch composition of claim 2 , wherein the relative amount of PAA is about 3.0 wt %.

4. The wet-etch composition of claim 1 , further comprising:

a diluent.

5. The wet-etch composition of claim 4 , wherein the diluent includes deionized water.

6. The wet-etch composition of claim 4 , wherein the relative amount of PAA in the composition is sufficient to achieve a selectivity an etch rate ratio of SiGe:Si of at least about 20:1 for NMOS transistors of a CMOS device and an etch rate ratio of SiGe:Si of at least 20:1 for PMOS transistors of the CMOS device.

7. The wet-etch composition of claim 6 , wherein the relative amount of PAA in the composition is sufficient to achieve a selectivity of (P-doped-SiGe):( P-doped-Si) ≈(N-doped-SiGe):(N-doped-Si) of at least about 60:1.

8. The wet-etch composition of claim 4 , further comprising:

an additional component selected from a group consisting of surfactants, buffering agents; secondary oxidizers and polymers.

9. The wet-etch composition of claim 4 , further comprising:

a surfactant selected from a group consisting of cationic surfactants, anionic surfactants and non-ionic surfactants.

10. The wet-etch composition of claim 9 , further comprising:

a surfactant selected from a group consisting of cethyl trimethyl ammonium bromide (CTABr), ammonium lauryl sulfate (ALS), lauryl alcohol ethylene oxide, stearyl alcohol ethylene oxide, nonyl phenol ethylene oxide, tri-decyl alcohol ethylene oxide and oleyl alcohol ethylene oxide.

11. The wet-etch composition of claim 4 , further comprising:

a polymer selected from a group consisting of cationic polymers and anionic polymers.

12. The wet-etch composition of claim 11 , wherein:

the polymer is selected from a group consisting of polyethylene imine, polylysine, polyacrylic acid, polyacrylamide, poly(methacrylic acid), poly(diethylaminoethyl methacrylate) and poly(dimethylaminoethyl methacrylate).

13. The wet-etch composition of claim 1 ,

the fluorinated acid is selected from a group consisting of HF, NH 4 F and a mixture thereof.

14. The wet-etch composition of claim 1 , further comprising:

at least one secondary oxidizer selected from a group consisting of H 2 O 2 , H 3 PO 4 , HNO 3 , H 2 SO 4 , I 2 , NH 4 NO 3 , (NH 4 ) 2 SO 4 , NH 4 IO 3 , HClO 4 , HClO 2 , O 3 and H 5 IO 6 .

15. The wet-etch composition of claim 1 , wherein:

the wet-etch composition further includes at least one buffering agent selected from a group consisting of acetic acid, ammonium acetate, methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol and heptanol.

16. The wet-etch composition of claim 1 , wherein:

peracetic acid constitutes between about 0.05 and about 17.5 wt % of the wet-etch composition;

the fluorinated acid constitutes between about 0.05 and about 15 wt % of the wet-etch composition;

surfactants, if present, constitute up to about 10 wt % of the wet-etch composition;

buffering agents, if present, constitute up to about 30 wt % of the wet-etch composition;

secondary oxidizers, if present, constitute up to about 30 wt % of the wet-etch composition; and

polymers, if present, constitute up to about 5 wt % of the wet-etch composition.

17. The wet-etch composition of claim 16 , wherein the diluent is deionized water.