Patent Publication Number: US-9412824-B2

Title: Semiconductor component having a dopant region formed by a dopant composed of an oxygen/vacancy complex

Description:
PRIORITY CLAIM 
     This application is a Divisional of U.S. application Ser. No. 13/613,985, filed on 13 Sep. 2012, which in turn claims priority to German Patent Application No. 10 2011 113 549.2, filed on 15 Sep. 2011, the content of said applications incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     Dopant regions within a semiconductor body are required in all semiconductor components. Dopant regions which extend deep into the semiconductor body or are situated deep in the semiconductor body are required for some applications. A field stop zone of an IGBT (insulated gate bipolar transistor) or of a diode serves as an example of this. The production of such a field stop zone, i.e. of a zone of increased doping deep in the semiconductor body, is described, for example, in DE 10 2004 047 749 A1. 
     A field stop zone is usually produced by diffusion, particularly in the case of semiconductor wafers having a relatively small diameter 6 inches) or thicknesses of above 200 μm. In this case, by way of example, for the production of an n-type dopant region as a field stop zone, either phosphorus or selenium atoms are indiffused into the semiconductor body. This usually results in doping profiles having a Gaussian distribution and a penetration depth into the semiconductor body of typically between 1 μm and 30 μm. 
     Field stop zones, which have to be produced at relatively low temperatures on account of the semiconductor wafer thickness and the wafer diameter, are usually produced by proton implantation. In this case, temperatures in the range of 400° C. are usually sufficient for producing the desired n-doped field stop zones. What is disadvantageous in this case, however, is that the resulting doping profile of the field stop zone has a considerable undulation. This can lead e.g. to an undesirable change in the gradient in the current and voltage profile during the turn-off operation of e.g. an IGBT. However, the undulation of the doping profile can in some cases adversely affect the softness of the turn-off operation. 
     SUMMARY 
     Exemplary embodiments of the invention relate to a semiconductor component comprising an extensive dopant region in a semiconductor body, which has a relatively small variation of the dopant concentration. In particular, exemplary embodiments relate to power semiconductor components comprising such a dopant region. Furthermore, exemplary embodiments of the invention relate to a method for producing such a dopant region in a semiconductor body. 
     It is an object of the invention to provide a semiconductor component comprising a dopant region, in particular a field stop zone, having a small variation of the dopant concentration. Moreover, the intention is to provide a method that makes it possible to produce such a dopant region in the semiconductor body. 
     Exemplary embodiments of the invention are explained in greater detail below. However, the invention is not restricted to the embodiments specifically described, but rather can be suitably modified and altered. It lies within the scope of the invention to combine individual features and feature combinations of one embodiment with features and feature combinations of another embodiment in a suitable manner, in order to arrive at further embodiments according to the invention. 
     In one embodiment, a semiconductor component comprises a semiconductor body having a first side and a second side situated opposite the first side, and a dopant region in the semiconductor body. In this case, the dopant region is formed by a dopant composed of an oxygen/vacancy complex over a section L having a length of at least 10 μm along a direction from the first side to the second side and has an oxygen concentration in the range of 1×10 17  cm −3  to 5×10 17  cm −3  over the section L. In a further embodiment, the dopant region has an oxygen concentration in the range of 2×10 17  cm −3  to 5×10 17  cm −3  over the section L. In yet another embodiment, the dopant region has an oxygen concentration in the range of 3×10 17  cm −3  to 5×10 17  cm −3  over the section L. 
     The specific oxygen concentration in the dopant region has the effect that dopants formed by an oxygen/vacancy complex can form. In this case, an oxygen/vacancy complex should be understood to mean a structure that comprises, inter alia, oxygen as a constituent without the oxygen in this case forming a chemical bond with other constituents of the complex. By virtue of the fact that the specific oxygen concentration extends over a section L, dopant formation can occur uniformly over the section L on account of the formation of oxygen/vacancy complexes. It is thus possible to provide a dopant region having a small variation of the dopant concentration. By way of example, the dopant region can have a dopant concentration that varies along the section L by maximally a factor of 15, furthermore for example by a factor of 10 and once again for example by a factor of 3. 
     One embodiment of the invention provides for the semiconductor body to be formed at least partly from a Czochralski semiconductor material and preferably from a magnetic Czochralski material. A Czochralski semiconductor material is a semiconductor material which is pulled from a melt according to the Czochralski method and which can be bought cost-effectively as a mass-produced product. In the case of magnetic Czochralski material, the oxygen concentration is reduced in a targeted manner by an external magnetic field being applied during the crystal growth. 
     In a further embodiment, the semiconductor body is formed at least partly from a float zone semiconductor material. A float zone semiconductor material is distinguished by the fact that a semiconductor material is briefly melted and then solidified again as a single crystal. A float zone semiconductor material has a very high purity. 
     In yet another embodiment, the semiconductor body comprises a semiconductor material epitaxial layer. The semiconductor material epitaxial layer can be produced on a monocrystalline substrate by arrangement of semiconductor material atoms from the gas phase onto the crystal lattice of the substrate. Through targeted control of the gas composition, it is possible to alter the epitaxial layer with regard to its composition in a desired manner. 
     In one exemplary embodiment, the semiconductor body has a basic doping with a basic dopant concentration, and the dopant region has a dopant concentration higher than the basic dopant concentration. 
     It is a further exemplary embodiment if the dopant is a thermal donor formed e.g. from a hydrogen-oxygen-lattice vacancy complex. 
     One embodiment of the invention is a power semiconductor component, comprising a semiconductor body having a first side and a second side situated opposite the first side. A first electrode is arranged at the first side and a second electrode is arranged at the second side of the semiconductor body. A pn junction in the semiconductor body is situated between the first electrode and the second electrode and a dopant region in the semiconductor body, which is formed by a dopant composed of an oxygen/vacancy complex over a section L having a length of at least 10 μm along a direction from the first side to the second side, has an oxygen concentration in the range of 1×10 17  cm −3  to 5×10 17  cm −3  over the section L. 
     In this case, a power semiconductor component should be understood to mean a semiconductor component in which voltages of more than 20 V, usually more than 500 V, are present between the first and second electrodes. In this case, a power semiconductor component is distinguished by the fact that a high voltage of more than 20 V present in the reverse direction across the pn junction does not lead to the destruction of the semiconductor component. In one exemplary embodiment, such a power semiconductor component comprises a so-called drift zone between the pn junction and one of the electrodes, in which drift zone a space charge zone can form over a wide section in order to avoid field strengths within the semiconductor body. In this case, the drift zone has a dopant concentration that is low relative to other dopant regions occurring in the semiconductor body. A power semiconductor component can be, for example, a diode, a MOSFET (metal oxide semiconductor field effect transistor) or an IGBT. 
     In one embodiment of such a power semiconductor component, the semiconductor body has a basic doping with a basic dopant concentration, and the dopant region has a dopant concentration higher than the basic dopant concentration. By way of example, in this case, a drift zone present in the semiconductor body can have the basic dopant concentration and the dopant region can be a field stop zone arranged in the drift zone and having a higher doping. The field stop zone prevents the punch-through of the electric field strength in the drift zone as far as the electrode. 
     For the so-called softness of the turn-off operation of the power semiconductor component, it can be advantageous if the dopant region has a dopant concentration that varies along the section L between adjacent doping maxima and doping minima for example by maximally a factor of 15, furthermore, for example, less than by a factor of 10 and once again, for example less than by a factor of 3. The fall in the doping concentration at the end of the section L toward the basic doping is not taken into account in the specification of these factors. This means, in particular, that the ratio of the height of adjacent doping peaks to directly adjacent doping minima varies by less than a factor of 15 or 10 or 3. 
     It is one exemplary embodiment of a method according to the invention for producing a dopant region in a semiconductor body if a semiconductor body having a first side and a second side situated opposite the first side is provided, wherein in the semiconductor body at least one partial region is formed over a section L of at least 10 μm in a direction from the first side to the second side, the at least one partial region having an oxygen concentration in the range of 1×10 17  cm −3  to 5×10 17  cm −3 . In the course of heat treating at least the partial region in a temperature range of between 350° C. and 450° C., a dopant region comprising a dopant composed of an oxygen/vacancy complex formed in the partial region over the section L. 
     In one embodiment, the partial region is formed by setting the oxygen supply during the crystal growth of the semiconductor body in a Czochralski method. 
     In another embodiment, the partial region is formed by setting the oxygen supply from the gas phase during an epitaxial deposition of the semiconductor body on a semiconductor substrate. 
     In a further embodiment, the partial region is formed by outdiffusion of oxygen from a substrate into an epitaxial layer deposited thereon. 
     A further exemplary embodiment provides for the partial region to be formed by indiffusion of oxygen via the first side or via the second side into the semiconductor body. 
     It is yet another exemplary embodiment if the partial region is formed by implantation of oxygen into the semiconductor body. 
     One development of the method provides for the oxygen concentration in the partial region to vary along the section L. By way of example, it can be advantageous if the oxygen concentration decreases in a direction toward the first side. This can lead to an effective smoothing of the dopant profile within the dopant region. 
     One exemplary embodiment provides for the semiconductor body to be thinned before the formation of the partial region at the second side. 
     Furthermore, one embodiment of the method provides for hydrogen to be introduced at least into the partial region before the heat treatment. This can firstly accelerate the diffusion of oxygen atoms and/or facilitate dopant formation. By way of example, the hydrogen is introduced by implantation of hydrogen ions. Moreover, the implantation or indiffusion can be effected with at least two different implantation energies, such that hydrogen accumulations are produced at different depths in the partial region. In conjunction with the increased oxygen concentration in the partial region this can lead to the formation of dopant concentration profiles in the partial region which vary spatially to a lesser extent than in a region having an oxygen concentration that is significantly less than 1×10 17  cm −3 . 
     In one exemplary embodiment of the method, the heat treatment is effected over a time period of 30 minutes to 5 hours and preferably between 1 hour and 4 hours. The annealing temperature is typically in the range of between 350° C. and 450° C. It is thereby possible to achieve, for example, a relatively weakly varying dopant distribution of the dopant concentration in the dopant region over the section L. 
     In one development of the method, the dopant region is predominantly formed by thermal donors formed from a hydrogen-oxygen-lattice vacancy complex. In one exemplary embodiment, for this purpose in the semiconductor body, lattice vacancies are produced at least in the partial region before the heat treatment. 
     A further embodiment of the method provides for the dopant region to acquire a dopant concentration that varies at least along the section L between adjacent doping maxima and doping minima by maximally a factor of 15, preferably 10 and particularly preferably 3. 
     Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the figures are not necessarily to scale, instead emphasis being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts. In the drawings: 
         FIG. 1  shows a semiconductor component comprising a dopant region in a semiconductor body; 
         FIG. 2  shows a power semiconductor component comprising electrodes on opposite sides of a semiconductor body and comprising a dopant region in the semiconductor body; 
         FIG. 3  shows a dopant profile in a semiconductor body of a semiconductor component; 
         FIG. 4 , which includes  FIG. 4 a    and  FIG. 4 b   , shows a method for producing a dopant region in a semiconductor body; 
         FIG. 5  shows the introduction of hydrogen into a partial region of a semiconductor body; and 
         FIG. 6  shows a dopant profile in a semiconductor body of a semiconductor component. 
     
    
    
     DETAILED DESCRIPTION 
     Before the exemplary embodiments of the present invention are explained in greater detail below with reference to the figures, it is pointed out that identical elements in the figures are provided with the same or similar reference signs and that a repeated description of these elements is omitted. Furthermore, the figures are not necessarily true to scale, rather the main emphasis is on elucidating the basic principle. 
       FIG. 1  illustrates a semiconductor component  10  comprising a semiconductor body  11  having a first side  12  and a second side  13  situated opposite the first side  12 . The semiconductor component  10  can be a diode or an IGBT, for example, wherein the possible embodiments of the invention are not restricted to these two types of semiconductor component. 
     In the exemplary embodiment shown, the semiconductor body  11  can be formed at least partly from either a Czochralski semiconductor material or magnetic Czochralski semiconductor material, or a float zone semiconductor material or a semiconductor material epitaxial layer. The semiconductor body  11  is generally present as a semiconductor wafer, from which one or more semiconductor components are then produced. The semiconductor wafer can have a wafer diameter which, in the present case, is for example&gt;200 mm. The diameter can be 300 mm, for example. The thickness of the semiconductor body  11  is normally approximately 750 μm, but can also be smaller. By way of example, the semiconductor body thickness can be less than 200 μm.  FIG. 1  furthermore illustrates a dopant region  14  in the semiconductor body  11 . The dopant region  14  is formed by a dopant composed of an oxygen/vacancy complex. The dopant can be formed, for example, from a hydrogen-oxygen-lattice vacancy complex. The dopant region  14  extends over a section L having a length of at least 10 μm along a direction X from the first side  12  to the second side  13 . In this case, the dopant region  14  has an oxygen concentration in the range of 1×10 17  cm −3  to 5×10 17  cm −3  over the section L. In one embodiment, the oxygen concentration can be in a range of 2×10 17  cm −3  to 5×10 17  cm −3 . In a further embodiment, the oxygen concentration can even just lie in a range of 3×10 17  cm −3  to 5×10 17  cm −3 . 
     The semiconductor body  11  has a basic doping with a basic dopant concentration. The dopant region  14  has a dopant concentration higher than the basic dopant concentration. In a development relative to the exemplary embodiment from  FIG. 1 , the semiconductor component is a power semiconductor component. 
       FIG. 2  shows an exemplary embodiment of a power semiconductor component  20 , comprising a semiconductor body  21  having a first side  22  and a second side  23  situated opposite the first side  22 . A first electrode  24  is mounted at the first side  22  of the semiconductor body  21 . At the second side  23 , a second electrode  25  is mounted on the semiconductor body  21 . In the semiconductor body  21 , a pn junction  26  is situated between the first electrode  24  and the second electrode  25 . The pn junction  26  is formed between a p-doped partial region of the semiconductor body  21  and an n-doped partial region of the semiconductor body  21 . Furthermore, a dopant region  27  is situated in the semiconductor body  21 . The dopant region  27  is formed by a dopant composed of an oxygen/vacancy complex. The dopant can be formed, for example, from a hydrogen-oxygen-lattice vacancy complex. The dopant region  27  extends over a section L having a length of at least 10 μm along a direction X from the first side  22  to the second side  23 . The dopant region  27  has an oxygen concentration in the range of 1×10 17  cm −3  to 5×10 17  cm −3  over the section L. 
     The semiconductor body  21  of the power semiconductor component  20  normally has a basic doping with a basic dopant concentration. The basic doping is often used in a drift zone or base zone  28  of the power semiconductor component  20 . The drift zone  28  lies between the pn junction  26  and the dopant region  27 . The dopant region  27  can be a field stop zone, for example. 
       FIG. 3  illustrates an example of a dopant profile within a semiconductor body having a dopant region. The semiconductor body has a basic doping with a basic dopant concentration  30 . In this case, the basic dopant concentration  30  is in the range of 1×10 13  cm −3  to 1×10 14  cm −3 . The basic dopant concentration can be used for forming a drift zone or base zone within a power semiconductor component. The semiconductor body furthermore has the dopant region of a section L, wherein the dopants are predominantly formed by an oxygen/vacancy complex and the dopant concentration is above the basic dopant concentration. This higher dopant concentration has values in the range of 1×10 14  cm −3  to 1×10 15  cm −3 . Moreover, the higher dopant concentration varies over the section L maximally by a factor of 3. 
       FIG. 6  shows a further example of a dopant profile within a semiconductor body having a dopant region.  FIG. 6  shows a dopant concentration in a dopant region in which the basic dopant concentration has a high undulation, with maxima  91  and minima  92 . In the case of an oxygen content, or in the case of an oxygen concentration of 1×10 17  cm −3  to 5×10 17  cm −3 , the undulation of the maxima  93  and minima  94  decreases greatly. With an oxygen concentration of 1×10 17  cm −3  to 5×10 17  cm −3 , the doping concentration varies in such a way that a doping concentration maximum and an adjacent doping concentration minimum differ maximally by a factor of 15, preferably by a factor of maximally 10. 
       FIG. 4 a    illustrates a first intermediate result of a method for producing a dopant region in a semiconductor body. For this purpose, a semiconductor body  11  having a first side  12  and a second side  13  situated opposite the first side  12  is provided. In the semiconductor body  11 , at least one partial region  15  is formed over a section L of at least 10 μm in a direction X from the first side  12  to the second side  13 . The at least one partial region  15  has an oxygen concentration in the range of 1×10 17  cm −3  to 5×10 17  cm −3 . The partial region  15  can be formed, for example, during the crystal growth of the semiconductor body  11 . Thus, the formation of the partial region  15  can be formed for example in a Czochralski method, e.g. a magnetic Czochralski method. In another example, the partial region  15  can also be formed by setting the oxygen supply from the gas phase during an epitaxial deposition of the semiconductor body  11  on a semiconductor substrate. Furthermore, the partial region  15  can be formed by outdiffusion of oxygen from a substrate into an epitaxial layer deposited thereon. An epitaxial layer can be used e.g. for producing drift zones or base zones in power semiconductor components. In a further example, the partial region  15  can be formed by indiffusion of oxygen via the first side  12  or via the second side  13  into the semiconductor body  11 . In the case of indiffusion via the first side  12 , e.g. during the processing of power semiconductor components the oxygen should be indiffused into the semiconductor body  11  already before a polishing of the first side  12  of the semiconductor body  11 , in order to ensure that the oxygen atoms are indiffused as deeply as possible. In yet another example, the partial region  15  can be formed by implantation of oxygen into the semiconductor body  11 , wherein suitable indiffusion steps are usually carried out after the implantation. 
     Depending on the way in which the oxygen is introduced, it is possible to set the oxygen concentration in the partial region  15  along the section L in such a way that the oxygen concentration in the partial region  15  decreases along the section L. In this case, the oxygen concentration can also be set such that it decreases in a direction toward the first side  12 . An embodiment that is not illustrated provides for the semiconductor body  11  to be thinned before the formation of the partial region  15  at the second side  13 . This can play an important part for example during the indiffusion of the oxygen via the second side  13  into the semiconductor body  11 . 
       FIG. 4 b    illustrates the semiconductor body  11 , in which, by means of heat treatment  40  (represented as arrows in  FIG. 4 b   ) at least of the partial region  15  in a temperature range of between 350° C. and 450° C., a dopant region  14  is formed by means of an oxygen/vacancy complex having a doping effect in the partial region  15  over the section L. In this case, hydrogen H can be introduced at least into the partial region  15  before the heat treatment  40 . This is shown in  FIG. 5 . The hydrogen can be introduced, for example, by implantation of hydrogen ions. In this case, the implantation can also be effected with at least two different implantation energies. This gives rise, in the partial region  15 , to hydrogen accumulations and also greatly increased vacancy densities at different depths. If, by way of example, the dopants in the dopant region  14  are formed from a hydrogen-oxygen-lattice vacancy complex, so-called thermal donors, the hydrogen accumulation at different depths of the partial region  15  makes it possible to achieve a very homogeneous distribution of the dopants in the dopant region  14  over the section L. Furthermore, lattice vacancies or additional lattice vacancies can be produced in the semiconductor body  11  before the heat treatment  40  at least in the partial region  15  preferably by means of hydrogen implantation. This can foster e.g. the formation of hydrogen-oxygen-lattice vacancy complexes. 
     Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper” and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description. 
     As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise. 
     With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.