Capped ALD films for doping fin-shaped channel regions of 3-D IC transistors
Disclosed herein are methods of doping a fin-shaped channel region of a partially fabricated 3-D transistor on a semiconductor substrate. The methods may include forming a multi-layer dopant-containing film on the substrate, forming a capping film comprising a silicon carbide material, a silicon nitride material, a silicon carbonitride material, or a combination thereof, the capping film located such that the multi-layer dopant-containing film is located in between the substrate and the capping film, and driving dopant from the dopant-containing film into the fin-shaped channel region. Multiple dopant-containing layers of the film may be formed by an atomic layer deposition process which includes adsorbing a dopant-containing film precursor such that it forms an adsorption-limited layer on the substrate and reacting adsorbed dopant-containing film precursor. Also disclosed herein are multi-station substrate processing apparatuses for doping the fin-shaped channel regions of partially fabricated 3-D transistors.
1. A method of doping a channel region of a partially fabricated transistor on a semiconductor substrate, the method comprising:
(a) forming a dopant-containing film on the semiconductor substrate, wherein multiple dopant-containing layers of the dopant-containing film are formed by an atomic layer deposition process comprising:
(i) adsorbing a dopant-containing film precursor onto the semiconductor substrate such that the dopant-containing film precursor forms an adsorption-limited layer on the semiconductor substrate;
(ii) removing at least some unadsorbed dopant-containing film precursor from volume surrounding the adsorbed precursor;
(iii) reacting adsorbed dopant-containing film precursor, after removing the at least some unadsorbed precursor in (ii), to form a dopant-containing layer on the semiconductor substrate;
(iv) removing desorbed dopant-containing film precursor and/or reaction by-product from volume surrounding the dopant-containing layer when present after reacting the adsorbed precursor; and
(v) repeating (i) through (iv) to form the multiple dopant-containing layers of the dopant-containing film;
(b) forming a capping film comprising a silicon nitride material, the capping film located such that the dopant-containing film formed in (a) is located in between the semiconductor substrate and the capping film; and
(c) driving dopant from the dopant-containing film into the channel region,
wherein (a) further comprises forming multiple substantially dopant-free layers of the dopant-containing film, at least some of the substantially dopant-free layers formed by an atomic layer deposition process comprising:
(vi) adsorbing a dopant-free film precursor onto the semiconductor substrate such that the dopant-free film precursor forms an adsorption-limited layer on the semiconductor substrate;
(vii) removing unadsorbed dopant-free film precursor from volume surrounding the adsorbed dopant-free film precursor;
(viii) reacting the adsorbed dopant-free film precursor, after removing unadsorbed dopant-free film precursor in (vii), to form a substantially dopant-free layer on the semiconductor substrate;
(ix) removing desorbed dopant-free film precursor or reaction by-product or desorbed dopant-free film precursor and reaction by-product from volume surrounding the substantially dopant-free layer when present after reacting the adsorbed dopant-free film precursor; and
(x) repeating (vi) through (ix) to form the multiple substantially dopant-free layers of the dopant-containing film; and
wherein in (a):
a first dopant-rich portion of the dopant-containing film is formed by depositing the multiple dopant-containing layers in (i) through (v) sequentially, without intervening deposition of a substantially dopant-free layer; and
a first substantially dopant-free portion of the dopant-containing film is formed by depositing the multiple substantially dopant-free layers in (vi) through (x) sequentially, without intervening deposition of a dopant-containing layer.
2. The method of claim 1 , further comprising:
(d) after (c), removing (i) at least a portion of the dopant-containing film, or (ii) at least a portion of the capping film, or (iii) at least a portion of the dopant-containing film and at least a portion of the capping film from the semiconductor substrate.
3. The method of claim 1 , wherein the channel region is fin-shaped, and the dopant-containing film substantially conforms to the shape of the fin-shaped channel region.
4. The method of claim 1 , wherein the channel region is fin-shaped, and the driving in (c) comprises a thermal anneal which enhances diffusion of the dopant from the dopant-containing film to the fin-shaped channel region.
5. The method of claim 1 , wherein the dopant is boron.
6. The method of claim 5 , wherein at least some of the multiple dopant-containing layers comprise a borosilicate glass.
7. The method of claim 6 , wherein the dopant-containing film precursor is an alkyl borate.
8. The method of claim 7 , wherein the alkyl borate is trimethyl borate.
9. The method of claim 1 , wherein the dopant is phosphorous.
10. The method of claim 1 , wherein the dopant is arsenic.
11. The method of claim 1 , wherein the reacting in (a)(iii) comprises contacting the adsorbed dopant-containing film precursor with a plasma.
12. The method of claim 1 , wherein the reacting in (a)(iii) comprises reacting the adsorbed dopant-containing film precursor with another reactive chemical species which may or may not be first adsorbed onto the semiconductor substrate.
13. The method of claim 1 , wherein forming the capping film comprises a chemical vapor deposition process.
14. The method of claim 13 , wherein the chemical vapor deposition process is plasma enhanced.
15. The method of claim 1 , wherein forming the capping film comprises an atomic layer deposition process.
16. The method of claim 1 , wherein the channel region is fin-shaped having a width of less than about 12 nanometers.
17. The method of claim 1 , wherein an average thickness of the capping film is between about 10 and 100 Angstroms.
18. The method of claim 1 , wherein a relative standard deviation in thickness of the capping film is less than about 10%.
19. The method of claim 1 , wherein an average concentration of the silicon nitride in the capping film is between about 2 and 3 g/cm 3 .
20. The method of claim 1 , wherein at least some of the multiple substantially dopant-free layers comprise a dielectric material and the capping film comprises a dielectric material different than said dielectric material of the at least some of the multiple substantially dopant-free layers.
21. The method of claim 20 , wherein said dielectric material of the at least some of the multiple substantially dopant-free layers is a silicon dioxide.
22. The method of claim 1 , wherein in (a):
a second dopant-rich portion of the dopant-containing film is formed by depositing the multiple dopant-containing layers in (i) through (v) sequentially, without intervening deposition of a substantially dopant-free layer; and
a second substantially dopant-free portion of the dopant-containing film is formed by depositing the multiple substantially dopant-free layers in (vi) through (x) sequentially, without intervening deposition of a dopant-containing layer; and
wherein the first dopant-rich portion, the first substantially dopant-free portion, the second dopant-rich portion, and the second substantially dopant-free portion of the dopant-containing film are deposited in the following sequence: first dopant-rich portion, then first substantially dopant-free portion, then second dopant-rich portion, then second substantially dopant-free portion.