Ion implantation method
First Claim
1. A method of ion beam implanting ions containing a selected atomic specie through a surface of a semiconductor substrate to form a junction between regions of different conductivity type in the substrate at a desired depth below said surface, comprising the steps of selecting in accordance with said desired depth a maximum implant energy of said selected atomic specie and the total dose of said atomic specie to achieve a desired concentration of said specie implanted in the region in front of said junction, and ion beam implanting a part of said dose with said atomic specie at below said maximum implant energy before completing said dose at said maximum energy, said maximum energy being no greater than 10 keV.
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Abstract
In ion implantation processes for forming junctions in semiconductor devices, a proportion of ions implant into the semiconductor material beyond the desired junction depth due to channelling along axes and planes of symmetry in the crystal. A method is provided in which ions are implanted at a series of different energies starting with a lower energy than that required for the desired junction depth. The initial amorphising of the surface regions of the semiconductor during the lower energy implantation reduces the channelling probability when the ions are subsequently implanted at the full energy resulting in a more sharply defined junction.
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Citations
18 Claims
- 1. A method of ion beam implanting ions containing a selected atomic specie through a surface of a semiconductor substrate to form a junction between regions of different conductivity type in the substrate at a desired depth below said surface, comprising the steps of selecting in accordance with said desired depth a maximum implant energy of said selected atomic specie and the total dose of said atomic specie to achieve a desired concentration of said specie implanted in the region in front of said junction, and ion beam implanting a part of said dose with said atomic specie at below said maximum implant energy before completing said dose at said maximum energy, said maximum energy being no greater than 10 keV.
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12. A method of forming by ion beam implantation in a semiconductor substrate, a junction between region of different conductivity at a desired depth below a surface of said substrate comprising ion beam implanting ions through said substrate surface at a first energy to amorphise said semiconductor material beneath said surface in front of the desired junction depth and then ion beam implanting ions at a higher energy through said amorphised semiconductor, said higher energy being no greater than 10 keV.
- 15. A method of implanting ions containing atomic species of a selected conductivity doping type through a surface of a semiconductor substrate to form a junction at a desired depth below said surface between an upper region doped with said atomic species to have said selected conductivity type and a lower region of the opposite conductivity type, the method comprising a first step of implanting ions containing a first atomic specie of said selected conductivity doping type at a first implant energy less than the energy required for said first atomic specie to penetrate to said desired depth, and a subsequent step of implanting ions containing a second atomic specie of said selected conductivity doping type which has a lower atomic weight than said first specie at a second implant energy at which said second atomic specie will penetrate to form said junction at said desired depth, said second implant energy being no greater than 10 keV.
Specification