Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Patent
1996-04-12
1999-01-05
Tsai, Jey
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
438543, 438931, 438403, H01L 21265
Patent
active
058562311
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
This application is a National Stage Application under Section 371 of PCT/EP94/02400, filed Jul. 21, 1994.
BACKGROUND OF THE INVENTION
The invention relates to a process for producing high-resistance silicon carbide (SiC) from a low-resistance silicon carbide starting material.
SiC in crystalline form has properties of a semiconducting material and is increasingly employed in various semiconductor structural elements. For many applications it is desirable that the substrate, i.e., the starting crystal, be a disk of a high-resistance material. This monocrystal then can serve as the: common substrate for a plurality of individual structural elements which are electrically insulated. Many processes which are performed with pure Si, for example, can be transferred to SiC, i.e., in detail, masking technique with a thermal oxide, ion implantation, dry etching of structures, epitaxia growth and contacting.
The understanding of defects with low levels in the energy gap of SiC is still very incomplete. For example, little is known about transition elements in SiC, either regarding their defect structure (substitutionally or interstitially) or their suspected electrical activity as interference locations with states energetically located far below the conductivity band. An important characteristic of SiC is its polytypicism, i.e., its occurrence in several modifications. Hexagonal 4H- and 6H-SiC with an energy gap of 3.0 eV, and cubic 3D-SiC with an energy gap of 2.4 eV are of interest in connection with electronic applications. Very little is known in particular about the level position of titanium impurities, which are practically unavoidable with deep-drawn SiC. The knowledge and control of impurities with low energy levels, however, is absolutely required in order to assure the quality of opto-electronic and electronic structural elements on the basis of SiC.
It is known from the publication by J. Schneider. H. D. Muller, K. Maier, W. Wilkening, F. Fuchs, A. Dornen, S. Leibenzeder and R. Stein, Appl. Phys. Lett., 56 (1990) p. 1184, that vanadium impurities can occur in SiC crystals in the form of amphoteric impurities with low energy levels. This means that at least three different charge states of vanadium occur in SiC. Two new levels are created in the energy gap by means of vanadium. Based on this it was suspected that vanadium can reduce the life of minority carriers in SiC. In a later publication by K. Maier, J. Schneider, K. Wilkening, S. Leibenzeder and R. Stein "Electron Spin Resonance Studies of Transition Metal Deep Level Impurities in SiC", Materials Science and Engineering B11 (1992), pp. 27 to 30, these levels are also researched. This also does not contain any suggestions for purposefully inserting impurities in p-doped 4H- and 6H-SiC in order to compensate them electrically and to produce high-resistance SiC.
From U.S. Pat. No. 3,344,071 it is known how it is possible to produce high-resistance material from GaAs crystals drawn from the melt by purposeful doping with chromium. In connection with the n-type GaAs it is necessary to additionally admix a substance acting as an acceptor.
It is unknown so far how, in the case of SiC, the effects of flat (shallow) interference locations can be canceled and high-resistance material generated.
SUMMARY OF THE INVENTION
It is the object of the invention to produce SiC with high resistance, wherein the effect of impurities is to be compensated.
This object is attained by a process for producing high-resistance silicon carbide from a low-resistance silicon carbide starting material, wherein the shallow donor levels of the prevailing nitrogen impurities in the starting material are overcompensated by the addition of a trivalent element with shallow acceptor levels introduced by doping in the SiC starting material in a concentration which changes the conductivity type from n- to p- conductivity, and a transition element which, in SiC, has donor levels approximately in the center of its energy gap is added, by doping
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Maier, deceased Karin
Maier, heiress Elke
Maier, heiress Hildegard Inge
Mueller Harald
Niemann Ekkehard
Daimler-Benz Aktiengesellschaft
Kunitz Norman N.
Mulpuri S.
Spencer George H.
Tsai Jey
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