Semiconductor device manufacturing: process – Gettering of substrate
Reexamination Certificate
2002-11-18
2004-10-26
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Gettering of substrate
C438S473000, C438S476000, C438S928000
Reexamination Certificate
active
06809011
ABSTRACT:
BACKGROUND OF THE INVENTION
The following invention relates to a method of producing defect profiles in a crystalline or crystalline-like structure, preferably in a semiconductor, during a thermal treatment in a process chamber.
During the manufacture of semiconductor components, for example based on silicon, it is known, by thermal treatment steps of the semiconductor in a suitable process gas environment, to influence the distribution of foreign atoms introduced (implanted) in the semiconductor or to influence the distribution of crystal defects. In general, the distribution of foreign atoms is essentially codetermined by the distribution of the defects.
For example, it is known from W. Lerch et al.; Mat. Res. Soc. Symp. Proc. (1998), Vol 525, pp 237-255 and D. F. Downey et al.: Mat Res. Soc. Symp. Proc. (1998), Vol 525, pp. 263-271, that by means of an oxygen-containing process gas at a constant thermal stressing of an implanted or doped silicon semiconductor, the doping profile of boron can be influenced, since the oxidation of silicon leads to an over saturation of self-interstitial atoms (EZG, a type of point defects with which Si atoms are disposed on interstitial positions), the concentration of which influences the diffusion property of the boron and thus the doping profile of boron.
With an oxygen-containing process gas environment during the thermal treatment of semiconductors, essentially only those foreign atom profiles or doping profiles can be influenced, the foreign atoms of which essentially reach a lattice position via the kick-out mechanism. In so doing, the foreign atom previously disposed in the interstitial region reaches a lattice position, whereby a silicon atom (or in general lattice atom) is given off from this lattice position into an interstitial position.
U.S. Pat. Nos. 5,401,669 and 5,403,406 describe a selective formation of defects via a nitrogen-containing process gas atmosphere, whereby these defects serve as nucleation centers for the precipitation of oxygen dissolved in silicon.
D. F. Downey et al.; Mat. Res. Soc. Symp. Proc. (1997), Vol 470, pp. 299-311 describes a reactive process gas during the rapid thermal treatment (RTP: Rapid Thermal Processing) of doped silicon wafers with regard to the doping profile for various reactive gases of different concentrations.
In the not yet published German application 199 27 962 of the applicant there is presented a method for the adjustment of the doping profile that is improved relative to D. F. Downey et al. (Mat. Res. Soc. Symp. Proc. (1997) Vol 470, pp 299-311). In this case, a semiconductor is essentially subjected to a rapid thermal treatment (in an RTP system) in a process gas atmosphere that includes a number of reactive gases in order, for example, via these reactive gases, to activate different inherent or self-point defects simultaneously and in different concentrations. In general, defect concentration and/or their spatial defect distributions, and hence also the distribution(s) of the activated doping atoms, can be controlled by the described method.
With the increasingly smaller structure sizes of semiconductor components, the requirements also increase with regard to the possibilities of the control of defect and doping profiles (here in the sense of the spatial distribution of activated foreign atoms). It is therefore the object of the present invention to further improve the above-described method.
The present invention realizes this object by the initially mentioned method, whereby a concentration and/or a density distribution of defects is controlled as a function of at least two process gases that have different compositions and each contain at least one reactive component, and whereby at least two of the process gases, essentially separated from one another, respectively act on at least two different surfaces of the substrate.
With the inventive method, for example the front and rear side of, for example, disk-shaped semiconductors, for example silicon wafers, are brought into contact with different reactive gases. This makes it possible during a thermal treatment of the wafer to control defect distributions and/or defect concentrations from both sides of the wafer, whereby as a result a maximum of possibilities are possible, especially with regard to the concentration and the spatial distribution of defects, but also with regard to the type of defects, for example point defects and/or volume defects. The inventive method can preferably be used in RTP- (Rapid Thermal Processing-), CVD- (Chemical Vapor Deposition-), RTCVD- (Rapid Thermal Chemical Vapor Deposition-) and epitaxial units, in which generally a “single wafer processing” is carried out, i.e. with which respectively only one wafer is subjected to a thermal treatment. However, a plurality of wafers could also be simultaneously subjected to a thermal treatment, as is effected, for example with many epitaxial or CVD units. In such a case, a plurality of wafers (for example two to six) are essentially disposed in a single plane. As a consequence of a thermal treatment of respectively only a single wafer or only few wafers, that are essentially disposed within a plane, there exists the possibility of respectively bringing the wafer or wafers, each with front and back sides, pursuant to the inventive method in contact with essentially only one process gas, whereby the composition of the process gases is different and each includes at least one reactive component.
Pursuant to the present invention, a process gas includes at least one reactive component i.e. a component that reacts with the substrate. The reaction can be a chemical reaction of the component (for example O2) with the substrate (for example Si) to form a new substance (for example Si+O2>SiO2), an adsorption (physical sorption and/or chemical sorption) of a component of the process gas, and etching (chemical reaction) or a desorption of an already present adsorbent by components of the process gas. The reaction can be effected at the substrate surface (for example, beginning of the oxidation of Si, or the oxidation of a copper layer applied to a substrate), on a portion of the substrate surface, or also within the substrate (for example the oxidation of Si of the already present silicon oxide layer). Furthermore, the reaction can also be effected on defects within the substrate, as is the case, for example, with the reduction of SiO2 by hydrogen, whereby the SiO2 is disposed on the inner surfaces of COPs (crystal originated particles). The process gas can include inert gases, i.e. gases that do not react with the wafer or the substrate. Whether a gas or a gas component behaves in an inert fashion can depend upon the process temperature, with an example for this being N2 during the processing of silicon. At temperatures of up to about 1100° C. N2 behaves nearly inert; only at temperatures over 1100° C. does any appreciable action with silicon in the form of a nitridation occur. Other inert gases are, for example, noble gases such as argon, helium, neon. For this connection, helium is characterized, for example, by a particularly high thermal conductivity, which can, for example, be advantageous during the rapid cooling of the substrate.
With the phrase “process gases that are essentially separated from one another” it is to be understood that the process gases taking part in the process at most mix with one another to such an extent that at a surface or in a region of this surface, reactions dominate that are generated by the process gas that predominantly acts upon the surface. Ideally, the process gases would be entirely separated by the substrate, so that a mixing of the process gases in the vicinity of the respective surface is not possible, and each process gas acts only on one surface of the substrate. However, the fulfillment of this ideal condition depends greatly on the technical design of the process chamber and upon the holding device of the substrate. However, the inventive method can also be carried out even if this ideal condition is not comple
Lerch Wilfried
Niess Jürgen
Becker R W
Mattson Thermal Products GmbH
Picardat Kevin M.
R W Becker & Associates
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