Means and method for stabilizing polycrystalline semiconductor layers
First Claim
1. A method for controlling dopant migration in polycrystalline semiconductor layers, comprising:
- providing a substrate;
forming a polycrystalline semiconductor layer of a first thickness on said substrate, wherein said polycrystalline semiconductor layer has grains therein separated by grain boundaries;
implanting oxygen or nitrogen or mixtures thereof into a first zone of said polycrystalline semiconductor layer to a dose in the range from more than 1014 to less than 1017 ions/cm2, wherein said first zone has a second thickness less than said first thickness and a peak implant concentration located at a predetermined distance below the outward surface of said polycrystalline semiconductor layer and a implant concentration at said outward surface less than said peak concentration;
heating said polycrystalline semiconductor layer to migrate said oxygen or nitrogen or mixtures thereof to said grain boundaries;
thereafter implanting a conductivity enhancing dopant into a second zone of said polycrystalline semiconductor layer; and
heating said polycrystalline semiconductor layer to activate said dopant so that it is electrically active.
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Accused Products
Abstract
Implantation of oxygen or nitrogen in polysilicon layers to a dose above about 1015 ions/cm2 retards rapid grain boundary migration of conventional dopants such as B, P, As, Sb, and the like during dopant activation. Pre-annealing of the poly films to increase the grain size also decreases rapid grain boundary migration. The efffects can be combined by first pre-annealing and then implanting oxygen or nitrogen before introducing the dopant. It is desirable to anneal the oxygen implant before introducing the dopant to allow for oxygen diffusion to the grain surfaces where is precipitates and blocks the grain boundaries. Vertical and lateral migration of the dopants can be inhibited by placing the implanted oxygen or nitrogen between the dopant and the location desired to be kept comparatively free of dopants. When very high dopant activation temperatures are used the blocking effect of the oxygen on the grain boundaries is overwhelmed by dopant diffusion through the grains.
65 Citations
25 Claims
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1. A method for controlling dopant migration in polycrystalline semiconductor layers, comprising:
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providing a substrate; forming a polycrystalline semiconductor layer of a first thickness on said substrate, wherein said polycrystalline semiconductor layer has grains therein separated by grain boundaries; implanting oxygen or nitrogen or mixtures thereof into a first zone of said polycrystalline semiconductor layer to a dose in the range from more than 1014 to less than 1017 ions/cm2, wherein said first zone has a second thickness less than said first thickness and a peak implant concentration located at a predetermined distance below the outward surface of said polycrystalline semiconductor layer and a implant concentration at said outward surface less than said peak concentration; heating said polycrystalline semiconductor layer to migrate said oxygen or nitrogen or mixtures thereof to said grain boundaries; thereafter implanting a conductivity enhancing dopant into a second zone of said polycrystalline semiconductor layer; and heating said polycrystalline semiconductor layer to activate said dopant so that it is electrically active. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification