In order to produce dopings in semiconductor materials, in particular, implantation methods are suitable in which the implantation depth is determined for example by the kinetic energy of the, for example ionic, dopants to be implanted. As an alternative and, if appropriate, in addition, it is possible to cause an implanted dopant to diffuse further into the semiconductor material by setting suitable drive-in conditions, in particular by running a suitable temperature program. By precisely coordinating implantation methods and drive-in conditions, different doping profiles can be produced in this way. A further known possibility for supervising the implantation depth consists in supervising the quantity of implanted dopant.
In the case of electronic components suitable for a high-voltage use at 50 V, for example, setting optimum doping profiles is particularly important since electrical short circuits e.g. toward the substrate or toward other component structures can occur particularly easily under the influence of the high voltage present at the component. Moreover, such an unsuitable doping profile can likewise cause undesirable currents, e.g. on account of impact ionization.
For electrical insulation of transistor contacts, in particular in the case of high-voltage components, use is usually made of wells having opposite conductivities that are arranged one in another, so that at the junctions between the connection region doped with a dopant of a first connectivity type and the outer insulating well, which is doped with a dopant of a second conductivity type, and also at the junction between the insulating well and the substrate, which is in turn doped with a dopant of the first conductivity type, additional space charge zones arise, which constitute charge carrier barriers.
In order to produce different deep dopings alongside one another in a substrate, a plurality of doping steps with different doping masks have been used heretofore in order to be able to use either a different implantation dose or a thermal budget for driving in the implanted dopant that is different for the doping steps. With regard to the additional doping masks required and the additional method steps associated therewith, this requires an increased outlay compared with producing a doping region with a uniform doping depth.
In order to produce dopings of different types alongside one another in a substrate, use has also usually been made of a plurality of doping steps with different doping masks heretofore.
U.S. Pat. No. 5,300,454 A discloses a method which can produce different levels of doping of the same type in different regions in a single step. For this purpose, a mask is produced which has regions having different geometrical features. The different regions in the mask differ by virtue of different density of mask openings. The doping intensity that can thereby be obtained is a function of the density of the mask openings.
U.S. Pat. No. 5,512,498 A discloses a method by which two different dopings can be produced in two different regions in two main steps, but with the same mask. Firstly, an oblique implantation is carried out at a first angle to a rotating substrate. This is followed by an essentially vertical implantation. In the first region, the mask openings have such a small aspect ratio that the dopants do not reach the substrate during the oblique implantation. During the second main doping step, no distinction is made between first and second region. However, this method does not enable two opposite dopings to be produced with the same mask.
USPTO Backgrounds
USPTO Backgrounds