Patent ID: 7648896

Claim:
A method of forming a microelectronic structure, the method comprising: forming a first layer comprising semiconductor material that is very heavily n-doped before being annealed, having a first-layer before-anneal dopant concentration, the first layer being between about 50 and 200 angstroms thick, wherein the first layer is formed above a substrate, and wherein the first layer is heavily n-doped after being annealed, having a first-layer after-anneal dopant concentration, the first-layer before-anneal dopant concentration exceeding the first-layer after-anneal concentration; forming a second layer comprising semiconductor material that is not heavily doped before being annealed, having a second-layer before-anneal dopant concentration, the second layer being about as thick as the first layer, wherein the second layer is formed above and in contact with the first layer, and wherein the second layer comprises heavily n-doped semiconductor material after being annealed, having a second-layer after-anneal dopant concentration, the second-layer after-anneal dopant concentration exceeding the second-layer before-anneal concentration; and forming a third layer comprising semiconductor material that is above and in contact with the second layer and that is not heavily n-doped before or after being annealed, the third layer having a third-layer dopant concentration.