Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Reexamination Certificate
2000-03-13
2002-05-07
Christianson, Keith (Department: 2813)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
Reexamination Certificate
active
06383902
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for producing a microelectronic semiconductor component, in particular made of silicon carbide, wherein doped regions in the semiconductor are produced through ion implantation and irradiation damages in the semiconductor are subsequently annealed through irradiation with electromagnetic rays.
Following the implantation of dopants during the production of microelectronic semiconductor components, the semiconductor shows radiation damage in the region of the implanted volume, in the form of lattice defects and interstitial atoms. The semiconductor must be annealed at a high temperature to improve the crystalline order of the semiconductor once more and electrically activate the implanted dopants. The effect of high temperatures leads to considerable diffusion processes in the semiconductor, which is desirable in the case of doped areas and for annealing the radiation damage caused by the implantation. However, the mobility of all constituents of the semiconductor is strongly increased at high temperatures, so that undesirable diffusions of other components occur as well. Another problem is the possible loss of constituents with high partial pressures during the annealing temperatures, which has disadvantageous effects on electrical or other properties of the semiconductor. In particular semiconductors such as GaAs or SiC show a loss of constituents if increased temperatures effect the component.
It was previously suggested in an article by S. Ahmed et al., in the magazine Applied Physics Letters, Volume 66, Year 1995, page 71 and following, that silicon carbide be heated on the surface with a high-energy excimer laser. A laser beam with high energy and high intensity is guided over a silicon carbide element, whereby the surface is scanned. The disadvantage of this method is that it takes relatively long for the heating, particularly during the annealing of complete semiconductor wafers, and that the energy source for the irradiation is additionally very involved and expensive. Using an excimer laser for the production is particularly problematic since it is not suitable for continuous user and requires extremely expensive filling gases for its operation.
The object of the invention is to provide a simple, quick and inexpensive method for producing a microelectronic component from a semiconductor material, particularly silicon carbide. The method is designed to make possible a far-reaching annealing of the lattice defects and a high degree of dopant activation, without having to heat the complete semiconductor component volume to temperatures exceeding 1000° C. in an oven-type environment.
SUMMARY OF THE INVENTION
The above object is solved accuracy to the present invention by a method for producing a microelectronic semiconductor component, in particular made of silicon carbide, wherein doped regions in the semiconductor are produced through ion implantation and irradiation damages in the semiconductor are subsequently annealed through irradiation with electromagnetic rays, and wherein essentially the complete surface of the semiconductor is irradiated with optical rays and is heated at least in the doped region, and wherein each location on the surface, which is subjected to irradiation, is irradiated at the same time. Modifications and advantageous embodiments follow from the description.
The invention involves using optical rays for irradiating substantially the entire surface of the semiconductor and to anneal this surface at least in the doped area, wherein each location on the surface that is subjected to the rays is irradiated simultaneously. It is particularly favorable if a wavelength or a wavelength range is selected in this case, for which the semiconductor has an increased absorption capacity for the respective rays.
Suitable radiation sources are noble gas high-pressure lamps or metal vapor high-pressure lamps. A particularly suitable radiation source is a xenon high-pressure lamp, especially a Xe photoflash lamp. Favorable pulse lengths are in the range of milliseconds to seconds. The particular advantage here is that the surface region of the semiconductor that must be annealed can be annealed in a single step, in particular with a single light pulse.
With one preferred embodiment, an ion-implanted semiconductor material is irradiated in a protective gas atmosphere, particularly an argon-containing atmosphere. However, an ion-implanted semiconductor material can also be irradiated in a vacuum atmosphere. With this, an undesirable oxidation and/or contamination of the heated semiconductor material is advantageously avoided. In another preferred embodiment of the method according to the invention, ion-implanted semiconductor material is irradiated in an atmosphere with increased partial pressure for one or several volatile components of the semiconductor material, relative to the environmental conditions. This provides protection against degradation of the semiconductor characteristics due to loss of material or due to decomposition of the material.
The method is particularly suitable for semiconductors with increased absorption capacity for electromagnetic rays in a region following an ion-implantation, particularly silicon carbide, whereas the undisturbed semiconductor material does not exhibit an increased absorption in this region. In that case, non-implanted and thus non-disturbed areas of the semiconductor are not heated as strongly as the implanted regions, which are to be annealed. If the absorption capacity in an implanted region does not differ or differs only slightly from the absorption capacity in the undisturbed region, it is advantageous if the undisturbed region is covered, so as to limit the effect of heat to the desired, implanted region.
In one preferred embodiment, a semiconductor material is inserted into a radiation chamber, following an ion-implantation, and is irradiated there with light.
The semiconductor material of one preferred embodiment is treated with ion-implantation at an increased substrate temperature between the room temperature and 1200° C., preferably at about 800° C. and especially preferred at about 400° C. Immediately thereafter, the material is irradiated with light at the same temperature or nearly the implantation temperature and in the same radiation chamber.
The invention is explained with the aid of the exemplary embodiments shown in the Figures.
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Niemann Ekkehard
Panknin Dieter
Skorupa Wolfgang
Wirth Hans
Christianson Keith
Daimler-Chrysler AG
Kunitz Norman N.
Venable
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