Capped ALD films for doping fin-shaped channel regions of 3-D IC transistors

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.