Method for forming ultra-shallow doping regions by solid phase diffusion

A method for forming ultra-shallow dopant regions in a substrate, the method comprising:

• forming a patterned layer on the substrate, a patterned cap layer on the patterned layer, and a sidewall spacer abutting the substrate, the patterned cap layer, and the patterned layer;
• depositing, by atomic layer deposition (ALD), a first dopant layer containing a first dopant in direct contact with the substrate adjacent the sidewall spacer;
• depositing a first cap layer on the first dopant layer;
• planarizing the first cap layer and the first dopant layer;
• removing the patterned cap layer and the patterned layer;
• depositing a second dopant layer containing a second dopant in direct contact with the substrate adjacent the sidewall spacer;
• depositing a second cap layer on the second dopant layer, the first and second dopant layers containing an oxide, a nitride, or an oxynitride, wherein the first and second dopant layers contain an n-type dopant or a p-type dopant with the proviso that the first or second dopant layer do not contain the same dopant, and wherein the n-type dopant and the p-type dopant are selected from boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), nitrogen (N), phosphorous (P), arsenic (As), antimony (Sb), and bismuth (Bi);
• and
• diffusing, by a thermal treatment, the first dopant from the first dopant layer into the substrate to form a first ultra-shallow dopant region in the substrate, and diffusing, by the thermal treatment, the second dopant from the second dopant layer into the substrate to form a second ultra-shallow dopant region in the substrate.