Doped well for semiconductor devices

A method of forming a semiconductor device, the method comprising:

• forming a first patterned mask over a substrate, wherein the first patterned mask has a first opening over a top surface of a first portion of the substrate;
• performing a first implantation to the first portion of the substrate with a first dopant, wherein a first ion beam of the first implantation is at a first acute angle relative to the top surface of the first portion of the substrate, the first ion beam being substantially parallel to a plane perpendicular to the top surface of the substrate, the plane including a longitudinal side of the first portion of the substrate;
• after performing the first implantation, rotating the substrate by 180 degrees;
• performing a second implantation to the first portion of the substrate with the first dopant, wherein a second ion beam of the second implantation is at a second acute angle relative to the top surface of the first portion of the substrate, the second ion beam being substantially parallel to the plane perpendicular to the top surface of the substrate, the plane including the longitudinal side of the first portion of the substrate;
• and
• etching the first portion of the substrate to form a first fin structure and a second fin structure and to define an upper surface of the substrate between the first fin structure and the second fin structure, wherein the first fin structure comprises a first sidewall and a second sidewall, wherein the second fin structure comprises a third sidewall and a fourth sidewall, wherein the second sidewall faces the third sidewall, wherein a maximum concentration region of the first dopant is underneath the first fin structure, the second fin structure, and the upper surface of the substrate, and wherein side borders of the maximum concentration region of the first dopant are laterally between the first sidewall and the fourth sidewall in a cross-sectional view.

A method of forming a semiconductor device, the method comprising:

• implanting a first dopant having a first conductivity type into a substrate with a first ion beam, wherein the first ion beam impacts a top surface of the substrate at a first angle relative to a line perpendicular to the top surface of the substrate;
• implanting the first dopant into the substrate with a second ion beam, wherein the second ion beam impacts the top surface of the substrate at a second angle relative to the line perpendicular to the top surface of the substrate, wherein the first ion beam and the second ion beam are on opposite sides of the line perpendicular to the top surface of the substrate, and wherein implanting with the first ion beam and implanting with the second ion beam forms a first well;
• forming a second well on a first side of the first well;
• forming a third well on a second side of the first well opposite the first side of the first well, wherein the first well is between the second well and the third well, wherein the first dopant has a first concentration at a first location along a first vertical line, wherein the first vertical line is positioned in the first well midway between the second well and the third well, wherein the first location is at a center of a peak of a dopant concentration profile of the first dopant along the first vertical line, wherein the first dopant has a second concentration at a second location, wherein a depth of the second location is 1.5 times a depth of the first location from the top surface of the substrate, and wherein the second concentration is 30% to 40% of the first concentration;
• and
• etching the substrate to form a plurality of fins in the first well, wherein a first lateral boundary is aligned with a first sidewall of the plurality of fins, wherein a second lateral boundary is aligned with a second sidewall of the plurality of fins, wherein the first sidewall is a sidewall of the plurality of fins closest to the second well, wherein the second sidewall is a sidewall of the plurality of fins closest to the third well, wherein an average concentration of the first dopant in a first region of the substrate below the plurality of fins and between the first lateral boundary and the second lateral boundary is in a range from 5×1017 atom/cm3 to 7×1017 atom/cm3.